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Thengius, Sandra. "Fault current injection from power electronic interfaced devices." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-287728.
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An increasing number of synchronous generators being replaced by renewable energy sources (RES) and HVDC links is expected in the future. HVDC links, some fast-growing renewable energy sources (RES) such as wind and solar photovoltaics, and system controllers such as STATCOM, have power- electronic interfaces to the grid. These are described here by the term power electronic interfaced devices (PEIDs). PEIDs have a different characteristic from synchronous generators. Therefore, having more synchronous generators replaced by PEIDs results in changed system behaviour, especially during a fault. Synchronous generators inject a fault current around 3 - 6 p.u. for low impedance faults. PEIDs inject a fault current around 1.1 p.u., but lower fault current injection is common. This thesis describes how PEIDs can contribute to voltage support during a low impedance fault in a grid that gets weaker due to a lower share of synchronous generators. The aim of the thesis is to increase the knowledge about fault current injection from PEIDs by firstly describing the differences between fault current injection from synchronous generators and PEIDs. Secondly, by describing some short circuit fault-related effects of increasing share PEIDs. Thirdly, by describing how the control system can influence the fault current injection. Lastly, by illustrating with simulations how potential consequences of decreased penetration of synchronous generators can be mitigated. The conclusion of the thesis is that the voltage support becomes less effective with an increasing share of PEIDs when the grid gets weaker during low impedance faults. However, PEID characteristics can be changed significantly by their controller settings. With well defined requirements in grid codes, controller settings suited for more effective voltage support. Well defined grid codes are important for minimizing some negative effects related to higher share of PEIDs in the power system.I framtiden förväntas mer kraftelektronikomriktare ersätta synkrongeneratorer. Kraftelektronikomriktare som exempelvis används till HVDC-förbindelser, STATCOM, och vind- och solkraft karakteriseras i hög grad av på omriktarens prestanda. Detta resulterar i förändringar av kraftsystemets beteende, bland annat under ett fel. Synkrongeneratorer injicerar en felström runt 3 - 6 p.u. under lågohmiga fel. Kraftelektronik injicerar en felström runt 1.1 p.u., men lägre felströmmar är vanligt. Detta arbete beskriver hur kraftelektroniken kan stötta spänningen under lågohmiga fel i ett nät som blir svagare på grund av minskad andel synkrongeneratorer. Syftet med arbetet är att öka kunskapen om felströmsinmatning från kraftelektronik. För att uppnå syftet har skillnaden mellan felströmsinmatning från synkrongeneratorer och kraftelektronik redogjorts. Därefter har effekterna av ökad andel kraftelektronik under ett fel beskrivits. Dessutom beskrivs hur kontrollsystemet kan påverka felströmsinmatningen. Slutligen har resultat från simuleringar presenterats för att illustrera effekterna av minskad andel synkrongeneratorer och hur de identifierade konsekvenserna kan minimeras. Rapportens slutsats är att spänningen stöttas mindre effektivt med ökande andel kraftelektronik samtidigt som nätet blir svagare under lågohmiga fel. Lämpliga kontrollinställningar medför att spänningen stöttas bättre. Tillräckligt detaljerade krav i nätkoderna krävs för att lämpliga kontrollinställningar ska appliceras. Detaljerade krav i nätkoderna är även av betydelse för att kunna minimera negativa konsekvenser relaterade till högre andel kraftelektronik i elnätet.
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Tse, Shing Chi. "Charge transport and injection in amorphous organic electronic materials." HKBU Institutional Repository, 2007. http://repository.hkbu.edu.hk/etd_ra/821.
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Jannapu, Reddy Ramya. "Preparation, characterization and properties of injection molded graphene nanocomposites." Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3726.
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The use of nanotechnology is rapidly growing in various fields for different applications such as aerospace, electronics, construction, biomedicine, cosmetics etc. Nanomaterials posses unique size dependent material properties and can manipulate the host material properties to a greater extent compared to the micron sized particles of the same composition, and make them suit the requirements. Various kinds of nanomaterials with different size and shapes such as particulate, fibrous, layered, tube and foam when added to the host matrix material in composites will tailor the properties of the matrix material to a greater extent making nanocomposites a good alternative to conventional composites.
In this research, more emphasis is made on improving mechanical and other physical properties of recycled high-density polyethylene (HDPE) polymer by adding graphene nanoplatelets at different concentrations. Recycled HDPE graphene nanocomposites were prepared using a solvent method assisted by a sonication method where samples are processed in to dog bone shaped specimens by using an injection molding process. For comparision, samples of plain recycled HDPE without graphene nanoplatelets were prepared. The samples were tested to evaluate the improvement in physical properties as function of the graphene concentrations in the polymer matrix. Physical properties of these samples were determined using different techniques: a) thermal conductivity which is found by using axial flow comparative cut bar method, b) dielectric constant is found by measuring capacitance of parallel plate capacitor setup using a capacitance bridge, c) water contact angle is found by optical angle goniometer, and d) tensile modulus is found by uniaxial tensile testing. The morphological characterization of PMN samples is performed using SEM technique to observe the type of distribution and dispersion of graphene nanoplatelets in the polymer matrix. The test results showed that adding graphene into recycled matrix drastically changed the physical properties of the materials. This may improve the value of the recycled materials for various applications.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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Alexander, Ashley II. "Analysis of Using Electronic Fuel Injection In Restricted FSAE Competition Engines." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1305893914.
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Walker, Ethan. "Injection, Transport, and Ionic Interactions of Carriers in Polyacetylene Ionomers as Probed by Near-Infrared Absorbance and Visible Photoresoponse." Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19331.
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While mixed ionic-electronic conductors (MIECs) show promise in a number of different device structures, their successful application has been inhibited by difficulties with characterization. The simultaneous influence of both ionic and electronic systems often foils attempts to quantify material parameters important for rational device design. In many cases, even general models of MIEC function can prove uncertain or controversial.
This dissertation addresses the broader issue of ambiguity in MIEC characterization by exploring near-infrared absorbance as a method of gaining further insight into these systems. In combination with a traditional suite of techniques, this method enables determination of parameters not otherwise accessible. The determination of a concentration-dependant carrier mobility in an MIEC material will be demonstrated, and MIEC conduction in the unipolar regime will be broadly described as a system of electrochemically-supported charge injection. This model will be subsequently expanded to describe an unusual and previously unreported phenomenon of rectification when MIECs are interfaced with otherwise appropriate semiconducting contacts. A model labeled as extracting-electrode space-charge limited current will be described and experimentally demonstrated. Finally, the unique photovoltaic properties of an ionic heterojunction system comprising two MIECs will be examined. The results will be used to gain insight into the role of ionic asymmetry in the behavior of MIEC interfaces.
This dissertation contains coauthored, previously published, and unpublished work.
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Abad, Garcia Carlos. "Error Injection Study for a SpaceFibre In-Orbit Demonstrator." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-289527.
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The space electronics sector is shifting towards the New-Space paradigm, in which traditional space-quali_ed and expensive components and payloads are replaced by commercial o_-the-shelf (COTS) alternatives. This change in mentality is accompanied by the development of inexpensive cubesats, lowering the entry barrie in terms of cost, enabling an increase in scienti_c research in space. However, also well-established and resourceful spacecraft manufacturers are adopting this trend that allows them to become more competitive in the market. Following this trend, Thales Alenia Space is developing R&D activities using COTS components. One example is the SpaceFibre In-Orbit Demonstrator, a digital board integrated in a cubesat payload that aims to test two Intellectual Property blocks implementing the new ECSS standard for high-speed onboard communication. This thesis presents the necessary steps that were taken to integrate the _rmware for the demonstrator's Field-Programmable Gate Array (FPGA) that constitutes the main processing and control unit for the board. The activity is centered around the development of a Leon3 System-on-Chip in VHDL used to manage the components in the board and test the SpaceFibre technology. Moreover, it also addresses the main problem of using COTS components in the space environment: their sensitivity to radiation, that, for a FPGA results in Single-Event Upsets causing the implementation to malfunction, and a potential failure of the mission if they are not addressed. To accomplish the task, a SEU-emulation methodology based in partial recon_guration and integrating the state of the art techniques is elaborated and applied to test the reliability of the SpaceFibre technology. Finally, results show that the mean time between failures of the SpaceFibre Intellectual Property Block using a COTS FPGA is of 170 days for Low Earth Orbit (LEO) and 2278 days for Geostationary Orbit (GEO) if con_guration memory scrubbing is included in the design, enabling its usage in short LEO missions for data transmission. Moreover, tailored mitigation techniques based on the information gathered from applying the proposed methodology are presented to improve the gures.Rymdsektorn börjar luta mot \the New-Space paradigm", i vilken traditionella och dyrarymd-kvalificerade komponenter och laster börjar bytas ut kommerciella-från-hyllan (eng. Commercial-o -the-Shelf - COTS) alternativ. Denna förändring i mentalitet ackompanjeras av utvecklingen av billiga CubeSats som sänker entre-kostnaden för vetenskaplig forskning i rymden. Även väletablerade och resursstarka rymdfarkost-tillverkare har anammat denna trend vilket låter dem bli mer konkurrenskraftiga på marknaden. För att följa trenden så utför Thales Alenia Space R&D utecklingsaktiviteter med COTS komponenter. Ett exempel är SpaceFibre In-Orbit Demonstrator, a digitalt kort integrerat i en CubeSat payload som ämnar testa två s.k. Intellectual Property (IP) konstruktioner som implementerar den nya ECSS standarde for hog-hastighets kommunikation ombord. Denna avhandling presenterar de nödvandiga stegen for att integrera firmware för demonstratorns programmerbara FPGA-krets (eng. Field-Programmable Gate Array - FPGA) som fungerar som kortets huvudsakliga beräknings- och styrenheten. Aktiviteten är centrerad kring utvecklingen av ett Leon3 System-on-Chip i VHDL för att hantera och managera komponenterna på kortet och testa SpaceFibre-teknologin. Vidare adresserar den också huvudproblemet med att använda COTS-komponenter i rymdmiljö: deras kanslighet för strålning, vilket i en FPGA kan resultera i s.k. Single-Event-Upsets, vilket orsakar fel i implementeringen och ett potentiellt misslyckande av uppdraget om de inte adresseras. För att åstadkomma detta, utarbetas och appliceras en SEU-emuleringsmetodik baserad på partiell rekonfigurering för att testa tillförlitligheten hos SpaceFibre-tekniken. Slutligen visar resultaten att den genomsnittliga tiden mellan fel (eng. Mean-Time BetweenFailure - MTBF) for SpaceFibre IP blocken i en COTS FPGA är 170 dagar för låg omloppsbana och 2278 dagar for Geostationär omloppsbana om scrubbing-tekniker implementeras. Skräddarsydda mitigations-tekniker, baserade på den insamlade informationen av tillämpningen av den föreslagna metoden, föreslås för att förbättra siffrorna.
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Westling, Joel, and Haris Subasic. "Effects and Models of Water Injection in an SI Engine." Thesis, Linköpings universitet, Fordonssystem, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-148952.
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Downsizing and turbocharging is a popular combination nowadays in cars inorder to decrease the fuel consumption. However, the boost pressure increasesthe risk of engine knock, limiting the engine in high-load operating points. Inthe current engines, fuel is used to cool the engine in these operating points,leading to a higher fuel consumption. Water injection is an effective method tomitigate knock and enable a more aggressive ignition. It enables the engine toproduce more power and cools the exhaust, thereby protecting the turbochargerand the catalyst from wear. In this thesis, the effects of injecting water in anengine is investigated and a further development of a cylinder pressure model,with a model that takes the water into account, is presented and validated. Themodel can be used to estimate the cylinder pressure in several operating points.
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Li, Zhi. "Electronic Structure Characterization of Hybrid Materials." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5060.
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In this dissertation, the studies aim to characterize the electronic structure at the internal interface of hybrid materials. The characterization challenge is originating from the spectral superposition of hybrid constituents. A characterization protocol based on photoemission spectroscopy (PES) was developed and applied to investigate the orbital alignment at the internal interface of the oligothiophene-TiO2 and ArS-CdSe hybrid materials by characterizing the individual constituents and the assembly hybrids respectively. Electrospray deposition technique was used to deposit targeting materials which enabled preparation of thin films in vacuum minimizing ambient contaminations while transmission electron microscopy (TEM) was used to investigate the morphology and the particle size of the pure nanoparticles and the hybrids. Ultraviolet-visible (UV-vis) spectroscopy was also used in the estimation of the optical band gap of the pure nanoparticles and the HOMO-LUMO gap of the organic ligands.
One of the hybrid materials studied in this dissertation is oligothiophene-TiO2 nanoparticle hybrids in which the oligothiophene ligands are bonded to the surface of TiO2 nanoparticles covalently. This hybrid system was used to develop and demonstrate a measurement protocol to characterize the orbital alignment at the internal interface. Low intensity X-ray photoemission spectroscopy (LIXPS) was used to determine the work function of the oligothiophene ligands and the TiO2 nanoparticles. In combination with the highest occupied molecular orbital (HOMO) cutoff and the valence band maximum (VBM) measured by ultraviolet photoemission spectroscopy (UPS), the ionization energies (IE) of these two constituents were determined. X-ray photoemission spectroscopy (XPS) was used to characterize the core level emissions of the constituents and the hybrid assembly, which were used to determine the charge injection barriers at the internal interface.
The results showed that there was an interface dipole at the internal interface between organic and inorganic constituents of the hybrid. The dipole was determined to be 0.61 eV and the hole injection barrier at the internal interface amounted to 0.73 eV. The electron injection barrier was estimated by taking into account the gap between highest occupied and lowest unoccupied molecular orbitals (HOMO, LUMO). The procedure followed only suggested the presence of an insignificant barrier in the oligothiophene-TiO2 nanoparticle hybrids.
Arylthiol functionalized Cadmium Selenide (ArS-CdSe) is a novel hybrid material which can be used in hetero-junction solar cells. The ArSH ligands are bonded on the surface of the CdSe nanoparticles covalently through sulfur atoms serving as anchors. The internal interface in the ArS-CdSe hybrids between the organic constituent and the inorganic constituent was studied by the same characterization protocol developed in this dissertation. Furthermore, a physisorbed interface between the ArSH ligands and the CdSe nanoparticles was created through multi-step in-vacuum deposition procedure. The electrospray deposition technique enabled the formation of a well-defined physisorbed interface which was characterized by LIXPS, UPS and XPS for each deposition step. Accordingly, the orbital alignment at the physisorbed interface was determined.
Based on the results obtained, detailed orbital alignments at the ArSH/CdSe physisorbed interface and the internal interface in the ArS-CdSe hybrid materials were delineated and discussed. The hole injection and electron injection barrier at the physisorbed ArSH/CdSe interface are 0.7 eV and 1.0 eV respectively. An interface dipole of 0.4 eV was observed at the interface. In the ArS-CdSe hybrid materials, the electronic system of the ArSH component shifts down due to the charge transfer induced by the covalent hybridization. The hybridization also shifts the electronic system of the CdSe constituent to a lower energy level due to saturation of the unoccupied bonds of the Cd atoms on the surface. The hole injection barrier and electron injection barrier were determined to be 0.5 eV and 1.2 eV respectively. A small interface dipole (0.2 eV) was observed at the internal interface as a result of the presence of covalent bonds.
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Hoy, Daniel R. "Gallium Nitride and Aluminum Gallium Nitride Heterojunctions for Electronic Spin Injection and Magnetic Gadolinium Doping." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331855661.
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Balachandran, Ganesh Kumar. "A switched-current filter in digital-CMOS technology with low charge-injection errors." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/15405.
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Sarker, Biddut. "Electronic and Optoelectronic Transport Properties of Carbon Nanotube/Organic Semiconductor Devices." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5482.
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Organic field effect transistors (OFETs) are of significant research interest due to their promising applications in large area, low-cost electronic devices such as flexible displays, sensor arrays, and radio-frequency identification tags. A major bottleneck in fabricating high-performance OFET is the large interfacial barrier between the metal electrodes and organic semiconductors (OSC) which results in an inefficient charge injection. Carbon nanotubes (CNTs) are considered to be a promising electrode material which can address this challenge. In this dissertation, we demonstrate fabrication of high-performance OFETs using aligned array CNT electrodes and investigate the detailed electronic transport properties of the fabricated devices. The OFETs with CNT electrodes show a remarkable enhancement in the device performance such as high mobility, high current on-off ratio, higher cutoff frequency, absence of short channel effect and better charge carrier injection than those OFETs with metal electrodes. From the low temperature transport measurements, we show that the charge injection barrier at CNT/OSC interface is smaller than that of the metal/OSC interface. A transition from direct tunneling to Fowler-Nordheim tunneling observed in CNT/OSC system shows further evidence of low injection barrier. A lower activation energy measured for the OFETs with CNT electrodes gives evidence of lower interfacial trap states. Finally, OFETs are demonstrated by directly growing crystalline organic nanowires on aligned array CNT electrodes. In addition to investigating the interfacial barrier at CNT/OSC interface, we also studied photoconduction mechanism of the CNT and CNT/OSC nanocomposite thin film devices. We found that the photoconduction is due to the exciton dissociations and charge carrier separation caused by a Schottky barrier at the metallic electrode/CNT interface and diffusion of the charge carrier through percolating CNT networks. In addition, it is found that photoresponse of the CNT/organic semiconductor can be tuned by changing the weight percentage of CNT into the organic semiconductors.Ph.D.
Doctorate
Physics
Sciences
Physics
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Fuchs, Heinrich Daniel. "Development and implementation of a 1.5 MW inverter and active power filter system for the injection of regenerated energy in a Spoornet traction substation." Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/1751.
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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005.Spoornet is one of South-Africa’s largest railway companies. It is very important to operate the railway system as cost effectively as possible. A large portion of the railway operates from 3 kV DC traction supplies. One method of cost saving is to utilise the regenerative braking mechanism of the electric trains.
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Wolak, Matthaeus Anton. "The Electronic Structure of Biomolecular Self-Assembled Monolayers." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4258.
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The studies presented here address the characterization of the electronic structure of various self-assembled monolayers (SAMs) of peptide nucleic acid (PNA) and tetraphenylporphyrin (TPP) SAMs and arrays, formed on gold substrates.
PNA is a promising alternative to DNA for bio-sensing applications, as well as for strategies for self-assembly based on nucleic acid hybridization. In recent years charge transfer through PNA molecules was a focus of research due to possible applications in self-assembled molecular circuits and molecular tools. In light of this research it is interesting to investigate the electronic structure of PNA interfaces to gold, a potential electrode material.
TPP is, due to its electronic structure, an organic p-type molecular semiconductor. Such a material can provide an alternative to standard micro- and optoelectronic devices and in recent years more attention was paid to semiconducting polymers and organic compounds offering these low-cost and flexible alternatives. Therefore, it is of high importance to investigate the prospect of using modified TPP molecules for the formation of interconnected molecular networks on metallic surfaces.
All investigated monolayers were formed from solution in a nitrogen atmosphere inside a homemade glove box. This process allowed for PNA SAM and TPP SAM and array formation on clean Au substrates without the exposure to the ambient atmosphere. Ultraviolet and X-ray photoemission spectroscopy (UPS and XPS) measurements on the resulting PNA SAMs and TPP SAMs and arrays, which were performed in a to the glove box attached vacuum chamber containing a photoemission spectrometer, revealed the hole injection barriers at the interfaces and the interface dipoles.
In addition to the UPS and XPS measurements on PNA, electronic structure calculations based on molecular dynamics sampling of the PNA structure were obtained, yielding the HOMO-LUMO gap and the electronic density of states for PNA. Combined with the UPS data, the theoretical calculations enabled estimation of the charge injection barriers for the PNA SAMs at the interface, as well as the assignment of individual UP-spectral features to specific molecular orbitals.
The orbital line-up at the interface between the Au substrate and the PNA indicated a significant interface dipole resulting in the alignment of the Au Fermi level near the center of the PNA HOMO-LUMO gap. This alignment causes large charge injection barriers for both holes and electrons, and thus impedes charge transfer from Au into the PNA SAM. The study of PNA molecules with ferrocene termini showed that this hole injection barrier is shifted to lower energies at the PNA/ferrocene interface. This shift was explained with a molecular orbital reconfiguration through the presence of the ferrocene terminus. The further investigation of the dependence of the electronic structure of PNA SAMs, based on their orientation, showed that incomplete films containing flat lying molecules can have a significant impact on the charge injection barriers. The close proximity of the nucleobases to the Au surface offers new ways for charge transfer between the substrate and the PNA molecule through its nitrogen sites, leading to a lowering of the hole injection barrier at the interface.
The TPP arrays were formed by depositing AgNO3 on the Au substrate prior to TPP incubation using the electrospray technique. The interaction of AgNO3 with the TPP promoted the formation of an interconnected thin film forming a network on the Au substrate. The line-up at the Au/TPP interface without AgNO3 exposure showed an interface dipole formation with injection barriers that would potentially obstruct charge injection into the molecule. However, the addition of AgNO3 to the process resulted in the formation of fine structures, and lead to a lower hole injection barrier due to an induced dipole, which would ultimately improve charge transfer between the substrate and the thin film. A separate thiolated TPP derivative was used to form SAMs on a gold substrate. The SAM exhibited an even lower injection barrier than the mentioned TPP thin film with AgNO3 exposure, leading to the conclusion that a mix of both TPP derivatives could potentially lead to a SAM with long range interconnectivity and a low hole injection barrier towards the substrate.
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Senthil, Kumar Sathiya Lingam. "Condition monitoring of induction machines using a signal injection technique." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-289354.
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Condition monitoring techniques can be employed to enhance reliability of electric machinery. The stator winding fault is one of the dominant causes for the failure of induction machines. In this work, the condition monitoring of an inverter-fed induction machine using high-frequency signal injection based technique is investigated. Initially, an analytical model of the induction machine with a stator inter-turn fault is developed. Subsequently, the behaviour of the induction machine in the presence of stator inter-turn fault is analyzed using the symmetrical component theory. Because of their use for fault diagnosis purposes, the analytical expressions for the fundamental and high-frequency symmetrical component currents are derived. The high-frequency signal injection is performed by adding a balanced three-phase high-frequency low-magnitude voltage to the fundamental excitation voltage. The resulting high-frequency negative-sequence current component can be used as reliable fault indicator to detect stator inter-turn faults. The effectiveness of the high-frequency negative-sequence current as a fault indicator is compared with the fundamental negative-sequence current, which is one of the traditionally used fault indicators for detecting these faults. The high-frequency signal injection technique proposed in this work is tested experimentally on a prototype machine in a laboratory set-up. The use of the proposed fault indicator is found to be advantageous when compared to the use of the traditional fault indicator for variable-frequency drives. In particular, it is shown that the proposed fault indicator is less dependent from the drive operating conditions than the traditional fault indicator.Tillståndsövervakning är en teknik som kan användas för att förbättra tillförlitligheten hos elektriska maskiner. För asynkronmaskiner är fel i statorlindningen en av de dominerande orsakerna som leder till problem. I detta arbete undersöks tillståndsövervakning av en omriktarmatad asynkronmotor med hjälp av en högfrekvent signalinjektionsbaserad teknik. Inledningsvis utvecklas en analytisk modell av en asynkronmaskin med korsslutningsfel mellan varven i statorn. Därefter analyseras beteendet hos maskinen med hjälp av teorin för symmetriska komponenter. Analytiska uttryck för både grund- och övertoner härleds för de symmetriska komponenterna. Den högfrekventa signalinjektionen utförs genom att addera en liten högfrekvent trefasspänning till den matningsspänningen. Den resulterande högfrekventa negativa strömkomponenten kan användas som en tillförlitlig indikator för att upptäcka eventuella kortslutningar i statorlindningen. Förmågan som felindikator hos den högfrekventa negativa sekvensströmmen jämförs med den grundläggande negativa strömkomponentens förmåga, vilken är den traditionella indikatorn för att detektera dessa fel. Den högfrekventa signalinjiceringsmetoden som föreslås i detta arbete undersöks experimentellt på en prototypmaskin. Den föreslagna felindikatorn har visat sig vara fördelaktig jämfört med användningen av den traditionella felindikatorn för frekvensomriktare. I synnerhet visas att den föreslagna felindikatorn är mindre beroende av frekvensomriktarens driftsförhållanden än den traditionella felindikatorn.
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Uwagbole, Solomon. "A pattern-driven corpus to predictive analytics in mitigating SQL injection attack." Thesis, Edinburgh Napier University, 2018. http://researchrepository.napier.ac.uk/Output/1538260.
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The back-end database provides accessible and structured storage for each web application's big data internet web traffic exchanges stemming from cloud-hosted web applications to the Internet of Things (IoT) smart devices in emerging computing. Structured Query Language Injection Attack (SQLIA) remains an intruder's exploit of choice to steal confidential information from the database of vulnerable front-end web applications with potentially damaging security ramifications. Existing solutions to SQLIA still follows the on-premise web applications server hosting concept which were primarily developed before the recent challenges of the big data mining and as such lack the functionality and ability to cope with new attack signatures concealed in a large volume of web requests. Also, most organisations' databases and services infrastructure no longer reside on-premise as internet cloud-hosted applications and services are increasingly used which limit existing Structured Query Language Injection (SQLI) detection and prevention approaches that rely on source code scanning. A bio-inspired approach such as Machine Learning (ML) predictive analytics provides functional and scalable mining for big data in the detection and prevention of SQLI in intercepting large volumes of web requests. Unfortunately, lack of availability of robust ready-made data set with patterns and historical data items to train a classifier are issues well known in SQLIA research applying ML in the field of Artificial Intelligence (AI). The purpose-built competition-driven test case data sets are antiquated and not pattern-driven to train a classifier for real-world application. Also, the web application types are so diverse to have an all-purpose generic data set for ML SQLIA mitigation. This thesis addresses the lack of pattern-driven data set by deriving one to predict SQLIA of any size and proposing a technique to obtain a data set on the fly and break the circle of relying on few outdated competitions-driven data sets which exist are not meant to benchmark real-world SQLIA mitigation. The thesis in its contributions derived pattern-driven data set of related member strings that are used in training a supervised learning model with validation through Receiver Operating Characteristic (ROC) curve and Confusion Matrix (CM) with results of low false positives and negatives. We further the evaluations with cross-validation to have obtained a low variance in accuracy that indicates of a successful trained model using the derived pattern-driven data set capable of generalisation of unknown data in the real-world with reduced biases. Also, we demonstrated a proof of concept with a test application by implementing an ML Predictive Analytics to SQLIA detection and prevention using this pattern-driven data set in a test web application. We observed in the experiments carried out in the course of this thesis, a data set of related member strings can be generated from a web expected input data and SQL tokens, including known SQLI signatures. The data set extraction ontology proposed in this thesis for applied ML in SQLIA mitigation in the context of emerging computing of big data internet, and cloud-hosted services set our proposal apart from existing approaches that were mostly on-premise source code scanning and queries structure comparisons of some sort.
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Barnard, Francois Jacobus Wessels. "Position sensorless control of a transverse-laminated reluctance synchronous machine." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95904.
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Thesis (MEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: The focus of this thesis is position sensorless control of a transverse-laminated reluctance synchronous machine. Rotor position information is required for high-performance closedloop control of the reluctance synchronous machine and is conventionally supplied by unreliable hardware position resolvers. In addition a FPGA-based rapid prototyping system is completed as part of the research term for control of the machine drive system. For the first time the unified active- ux (AF) method is investigated and implemented for position sensorless control of the transverse-laminated reluctance synchronous machine in this study. The method is based on the torque equation of the machine and is basically the same for any AC machine. The estimation scheme is implemented for closed-loop position sensorless control from low- to rated speed in the entire rated load range with simulation and measured results confirming its capabilities. A number of characteristics of the machine (including generator operation) have implications for implementation of the active- ux (AF) method and are therefore investigated. Another position estimation method investigated is the arbitrary injection (AI) scheme which is derived to be completely machine parameter independent. The method simply requires a current progression at each calculation step allowing use of a smaller injection voltage. This method is implemented again on the reluctance synchronous machine and is shown to be capable of position sensorless current and speed control of the drive from standstill to rated speed with simulation and measured results. However, when the machine is operating above low speeds it is shown that this technique is only capable of position sensorless control at low loads. To deliver position sensorless control in the entire rated speed and load range a new hybrid controller scheme is designed and implemented. The hybrid scheme is speed and load dependent with hysteresis regions for stability at specific working points. The active- ux (AF) method is implemented in the low to rated speed range at medium to rated loads while the arbitrary injection (AI) method is implemented elsewhere. Measured results show that the scheme is capable of position sensorless control in the entire rated speed and load range with some limitations on dynamics. Because of the limitations on dynamics of the hybrid scheme an assisted fundamental model position estimation scheme was investigated. Simulation results show that this controller requires further investigation.
AFRIKAANSE OPSOMMING: Die fokus in hierdie tesis is die posisie-sensorlose beheer van 'n transvers-gelamineerde reluktansie sinchroonmasjien. Rotor posisie inligting word benodig vir geslote-lus beheer van die reluktansie sinchroonmasjien met ho e-werkverrigting, en word normaalweg deur onbetroubare hardeware sensors verskaf. As deel van die navorsings-termyn is 'n FPGAgebaseerde beheerstelsel vir die masjien stelsel voltooi. Die \aktiewe-vloed" posisie-afskattings metode is ondersoek en vir die eerste keer ge mplementeer vir posisie-sensorlose beheer van die transvers-gelamineerde reluktansie sinchroonmasjien. Die metode is dieselfde in konsep vir alle WS masjiene en word basseer op die vergelyking vir wringkrag van die masjien. Vollas geslote-lus posisie-sensorlose beheer van die masjien in die lae tot ho e spoedbereik is suksesvol ge mplementeer met simulasie en gemete resultate. Verkskeie inherente eienskappe van die masjien het implikasies vir gebruik van die \aktiewe-vloed" metode (insluitend generator werking) en is dus ondersoek. Die \arbitr^ere injeksie" metode wat afgelei is om onafhanklik van masjien parameters te wees is ook odersoek. Hierdie metode verlang slegs 'n stroom-afgeleide by elke tydstip en benodig dus 'n kleiner injeksie-spanning. Hierdie metode is weer ge mplementeer op die reluktansie sinchroon masjien met suksesvolle posisie-sensorlose beheer in die hele spoed bereik getoon in simulasie en praktiese resultate. Dit word egter getoon dat hierdie metode slegs onder lae-las toestande posisie sensorlose beheer bo lae-spoed kan bewerkstellig. Ten einde posisie-sensorlose beheer in die hele spoed en wringkrag bereik te verkry is 'n nuwe hibriede beheerskema ontwerp en ge mplementeer. Die skema is spoed en las afhanklik met histerese vir stabiliteit by 'n spesi eke werkpunt. Die \aktiewe-vloed" metode word gebruik bo lae spoed teen 'n minimum las terwyl die \arbitr^ere injeksie" andersins ge mplementeer word. Gemete resultate toon dat die skema posisie-sensorlose beheer van die masjien in die hele spoed en las bereik toelaat met sommige beperkings op dinamika. Met inagneming van die beperkings op die hibriede metode is 'n ondersteunde fundamentele model afskattingskema ondersoek. Simulasie resulate toon dat hierdie beheerder verdere ondersoek benodig.
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Ciampa, Paulo Fracalossi. "Projeto e desenvolvimento de um sensor MAP de pressão e temperatura em LTCC para aplicações automotivas." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-26082011-144842/.
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Este trabalho apresenta um módulo sensor de pressão absoluta do duto de admissão (MAP) para aplicações automotivas desenvolvido em substrato cerâmico LTCC. Em um veículo com sistema de injeção eletrônica de combustível, o sensor MAP informa a unidade de controle do motor sobre a pressão no duto de admissão permitindo o cálculo da vazão de ar e o ajuste da injeção de combustível. O sensor desenvolvido possui circuitos eletrônicos para a aquisição de sinais analógicos e digitais, realiza o condicionamento de sinal, a calibração e compensação de temperatura através de processamento digital, que permitem a indicação de pressões de 0 a 100kPa na faixa de temperaturas de -40 a +125ºC. Utilizou-se um elemento sensor de pressão piezorresistivo com membrana micro fabricada em silício e um sensor resistivo de temperatura. São apresentadas: a topologia do circuito, a construção, caracterização e testes. O protótipo apresenta precisão melhor do que 1,5% FE em pressão e 0,5% em temperatura. O teste de diferentes sensores de pressão e diferentes funções de transferência é facilmente realizado através de um circuito versátil que permite a alteração via programa. A montagem em cerâmica LTCC é realizada e é desenvolvida uma técnica de montagem do sensor de pressão MEMS em flip-chip, com excelentes resultados. Finalmente, é apresentado o teste em operação real em um veículo.This paper presents a manifold absolute pressure (MAP) sensor module developed on LTCC substrate. In electronic fuel injection systems, a MAP sensor measures the vacuum at the engine intake manifold, allowing the electronic control unit to calculate mass flow and control the fuel injection. The sensor developed is composed by electronic circuits for analog signal acquisition and generation, digital signal processing and features software calibration and temperature-compensated pressure indications from 0 to 100kPa in the -40 to +125ºC temperature range. It is presented the assembly of a MEMS silicon pressure sensor and a thermistor on ceramic substrate and also the circuit topology, construction, characterization and tests. The prototype exhibits full scale accuracy better than 1.5% for pressure and 0.5% for temperature measurements. Tests are easily performed with different pressure sensors and different transfer functions due to a versatile circuit which enables software updates. The assembly on LTCC ceramic substrate is performed and an innovative flip-chip assembly technique is developed for MEMS pressure sensors, with excellent results. Finally, it is presented the test on a real vehicle.
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Williams, Charles. "Injection Locking of Semiconductor Mode-Locked Lasers for Long-Term Stability of Widely Tunable Frequency Combs." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5726.
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Harmonically mode-locked semiconductor lasers with external ring cavities offer high repetition rate pulse trains while maintaining low optical linewidth via long cavity storage times. Single frequency injection locking generates widely-spaced and tunable frequency combs from these harmonically mode-locked lasers, while stabilizing the optical frequencies. The output is stabilized long-term with the help of a feedback loop utilizing either a novel technique based on Pound-Drever-Hall stabilization or by polarization spectroscopy. Error signals of both techniques are simulated and compared to experimentally obtained signals. Frequency combs spaced by 2.5 GHz and ~10 GHz are generated, with demonstrated optical sidemode suppression of unwanted modes of 36 dB, as well as RF supermode noise suppression of 14 dB for longer than 1 hour. In addition to the injection locking of actively harmonically mode-locked lasers, the injection locking technique for regeneratively mode-locked lasers, or Coupled Opto-Electronic Oscillators (COEOs), is also demonstrated and characterized extensively.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
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Nilsing, Mattias. "Computational Investigation of Dye-Sensitized Solar Cells." Doctoral thesis, Uppsala universitet, Avdelningen för kvantkemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7673.
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Interfaces between semiconductors and adsorbed molecules form a central area of research in surface science, occurring in many different contexts. One such application is the so-called Dye-Sensitized Solar Cell (DSSC) where the nanostructured dye-semiconductor interface is of special interest, as this is where the most important ultrafast electron transfer process takes place. In this thesis, structural and electronic aspects of these interfaces have been studied theoretically using quantum chemical computations applied to realistic dye-semiconductor systems. Periodic boundary conditions and large cluster models have been employed together with hybrid HF-DFT functionals in the modeling of nanostructured titanium dioxide. A study of the adsorption of a pyridine molecule via phosphonic and carboxylic acid anchor groups to an anatase (101) surface showed that the choice of anchor group affects the strength of the bindings as well as the electronic interaction at the dye-TiO2 interface. The calculated interfacial electronic coupling was found to be stronger for carboxylic acid than for phosphonic acid, while phosphonic acid binds significantly stronger than carboxylic acid to the TiO2 surface. Atomistic and electronic structure of realistic dye-semiconductor interfaces were reported for RuII-bis-terpyridine dyes on a large anatase TiO2 cluster and perylene dyes on a periodic rutile (110) TiO2 surface. The results show strong influence of anchor and inserted spacer groups on adsorption and electronic properties. Also in these cases, the phosphonic acid anchor group was found to bind the dyes significantly stronger to the surface than the carboxylic acid anchor, while the interfacial electronic coupling was stronger for the carboxylic anchor. The estimated electron injection times were twice as fast for the carboxylic anchor compared to the phosphonic anchor. Moreover, the electronic coupling was affected by the choice of spacer group, where unsaturated spacer groups were found to mediate electron transfer more efficiently than saturated ones.
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Yèche, Adrien. "Caractérisation par courant induit sous faisceau électronique (EBIC) à basse température de détecteurs infrarouges de 3ème génération." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY086.
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Des études de caractérisation par courant induit sous faisceau électronique (EBIC) ont été menées sur des photodétecteurs infrarouges (IR) principalement à base de CdHgTe (CMT). Le banc de mesure a été développé pour améliorer le rapport signal à bruit de la mesure et adresser l’ensemble du spectre IR. Des simulations Monte Carlo et des mesures expérimentales sur un motif technologique dédié ont permis de quantifier la résolution spatiale de l’EBIC. Contrairement à une observation à travers de la passivation qui nécessite une énergie suffisante pour injecter des électrons dans la couche active, typiquement 15 keV pour une résolution spatiale d’environ 1,4 µm, une étude en tranche permet de réduire la résolution à environ 40 nm à 2 keV. A forte énergie, le faisceau sonde préférentiellement le matériau massif et les porteurs sont peu influencés par les états d’interface. Une modification de la diffusion des porteurs a été observée avec une augmentation de la longueur de diffusion à fort courant de sonde pour du CMT en technologie p/n dans la gamme MWIR à 300 K et LWIR à 145 K. Les propriétés du semiconducteur sont respectées en faible injection mais la détermination de la longueur de diffusion est d’autant plus précise que le rapport signal à bruit du courant EBIC est élevé, c’est-à-dire à fort courant de sonde et/ou forte énergie. L’influence de la surface coupée a été qualifiée pour les filières n/p intrinsèque et p/n du CMT grâce à la comparaison d’observations en vue de dessus et en tranche. Finalement, la fonction de transfert de modulation a été mesurée pour des photodiodes CMT en milieu matriciel. Contrairement aux mesures optiques, la bonne résolution spatiale de l’EBIC permet d’investiguer les détecteurs IR futurs pour des pas pixel inférieurs à 10 µmElectron beam induced current (EBIC) characterizations have been performed on infrared (IR) photodetectors mainly based on HgCdTe (MCT). The EBIC setup has been developed to improve the signal to noise ratio and to address the whole IR spectrum. Monte Carlo simulations and experiments on a dedicated pattern have allowed quantifying the EBIC spatial resolution. In contrary to observations through a passivation requesting an energy high enough to inject electrons in the active layer, typically 15 keV for a spatial resolution of around 1.4 µm, a cross section study allows to reduce the resolution to 40 nm at 2 keV. At high energy, the beam investigates the bulk material and carriers are less influenced by interface states. A change in the carrier diffusion has been observed with a diffusion length increase with increasing the probe current for MWIR and LWIR p/n MCT at 300 and 145 K respectively. Even if the semiconductor properties are kept at low injection, a precise diffusion length determination can be obtained by a high signal to noise ratio enhanced by whether a strong probe current or a high energy. The cross section surface influence has been compared for intrinsic n/p and p/n MCT technologies thanks to top view and cross section observations. Finally, the modulation transfer function has been measured for MCT photodiodes in a matrix environment. Unlike optical measurements, the very good EBIC spatial resolution allows to investigate the future IR detectors for pixel pitches below 10 µm
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Vallini, Felipe 1985. "Nanolasers de semicondutor metálico-dielétrico com bombeio eletrônico = a influência do meio de ganho." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278504.
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Orientador: Newton Cesario FrateschiTese (doutorado) - Universidade Estaual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Neste trabalho são investigados os nanolasers de semicondutor do tipo metálico-dielétrico com injeção eletrônica. Com o uso de softwares robustos otimizamos as propriedades eletromagnéticas das cavidades propostas através da solução das equações de Maxwell em um meio material. Também resolvemos auto-consistentemente as equações de Poisson, de continuidade, de transporte e de Schroedinger para obter as propriedades eletrônicas da cavidade. Tal otimização, considerando a parte de confinamento do modo em conjunto com a parte da injeção eletrônica nunca havia sido proposta ou realizada para nanolasers. Estudamos o efeito do meio de ganho em um nanolaser desse tipo através da comparação do desempenho de um nanolaser com meio de ganho bulk e outro com meio de ganho de múltiplos poços quânticos. Essa análise foi feita inserindo um modelo de reservatório de portadores às equações de taxa convencionais para nanolasers. Fabricamos dois nanolasers, um com cada meio de ganho. Os nanolasers foram caracterizados e demonstramos que um meio de ganho bulk é mais adequado ao desenvolvimento de nanolasers de semicondutor metálico-dielétrico com bombeio eletrônico. Por fim, medimos um nanolaser com meio de ganho bulk a 77 K, o qual apresentou uma corrente de limiar da ordem de 2 mA, emissão em 1567 nm e largura de linha de 0.4 nm
Abstract: In this work we have investigated metallo-dielectric semiconductor nanolasers with electronic pumping. We have optimized the electromagnetic properties of the proposed cavities through the solution of Maxwell equations in a material media using robust software. We also solved self-consistently Poisson, continuity, transport and Schrodinger equations to obtain the electronic properties of the cavities. Such optimization, which considers the optical mode confinement together with the electronic injection, had not been proposed or realized for nanolasers yet. We have studied the effect of the gain media in this class of nanolaser comparing the performance of a nanolaser with bulk gain media and a nanolaser with multiple quantum wells gain media. This analysis was done inserting a reservoir model for carriers into conventional laser rate equations. We have fabricated two nanolasers, each one with one of the proposed gain media. The nanolasers were measured and we demonstrated that a bulk gain media is more suitable for the development of metallo-dielectric semiconductor nanolasers with electronic pumping. Finally, we have measured a bulk gain media nanolaser at 77 K, with a threshold current of 2 mA, emission at 1567 nm and a linewidth of 0.4 nm
Doutorado
Física
Doutor em Ciências
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Gouveia, Filipe Rocha. "Análise da injeção de gás natural veicular em motores de ignição por compressão com uso de biodiesel em diferentes proporções." Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/8968.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In search for greater energy efficiency there is the application of new technologies and renewable fuels. Due to the expected shortage of oil coupled with environmental awareness, has high potential research for new energy sources and more efficient combustion processes and less polluting. Among the less polluting fuels is natural gas that has an increased consumption year on year. This paper analyzes the injection of compressed natural gas (CNG) in an internal combustion engine compression ignition, evaluating the pollutant emissions, opacity and performance. The engine under study, the energy comes from the combustion of natural gas and biodiesel, where biodiesel serves to ignite the natural gas, being possible to replace up to 80% of biodiesel injection. Thus, there is a partial substitution of biodiesel natural gas in order to increase the combustion efficiency. Engine MWM 4:07 TEC has developed an electronic injection system adapted to reduce the biodiesel injection time per cycle and compensate with CNG injection. Based on a survey of injected cycle mass flow to calculate the energy value equivalent to reducing biodiesel injection proportions to compensate with CNG injection. There was a reduction in the torque according to the increase of the proportion of biodiesel in the diesel fuel and a higher specific consumption with the use of B7 fuel (7% biodiesel). It has been found the need for injection of a larger amount of mass CNG instead of B7 fuel. Regarding the emission of pollutants in the exhaust measured at a range of engine working speed smaller carbon monoxide level (CO), carbon dioxide (CO2), hydrocarbons (HC), nitrogen oxides (NOx) were checked respectively in the application of B7 fuels, B20, B50 and B50. The lowest levels of opacity were investigated in tests using the B10 fuel.
Em busca por maior eficiência energética há a aplicação de novas tecnologias e combustíveis renováveis. Devido a previsível escassez de petróleo aliada a uma consciência ambiental, tem-se elevado potencialmente pesquisas por novas fontes de energia e processos de combustão mais eficientes e menos poluentes. Entre os combustíveis menos poluentes está o gás natural, que tem um consumo aumentado ano a ano. O presente trabalho analisa a injeção de gás natural veicular (GNV) em um motor de combustão interna de ignição por compressão, avaliando os níveis de emissões de poluentes, opacidade e o rendimento. No motor em estudo, a energia provém da combustão do gás natural e do biodiesel, onde o biodiesel tem a função de produzir a ignição do gás natural, sendo possível a substituição de até 80% da injeção do biodiesel. Assim, haverá uma substituição parcial de biodiesel por gás natural, a fim de aumentar o rendimento da combustão. No motor MWM 4.07 TCE foi desenvolvido um sistema de injeção eletrônico adaptado para reduzir o tempo de injeção do biodiesel por ciclo e compensar com injeção de GNV. Baseando-se em um levantamento do fluxo de massa injetada por ciclo para calcular o valor energético equivalente a redução das proporções de injeção de biodiesel a compensar com injeção de GNV. Houve um redução do torque de acordo com o aumento da proporção de biodiesel no óleo diesel e um maior consumo específico com a utilização do combustível B7 (7% de biodiesel). Foi constatada a necessidade de injeção de maior quantidade de massa de GNV em substituição do combustível B7. Em relação as emissões de gases poluentes na exaustão medidos na faixa de rotação de trabalho do motor os menores níveis de monóxido de carbono (CO), dióxido de carbono (CO2), hidrocarbonetos (HC), óxidos de nitrogênio (NOx), foram verificados respectivamente na aplicação dos combustíveis B7, B20, B50 e B50. Os menores níveis de opacidade foram averiguados em testes com utilização do combustível B10.
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Apicella, Fernandez Sergio. "Surface energy modification of metal oxide to enhance electron injection in light-emitting devices : charge balance in hybrid OLEDs and OLETs." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-25097.
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Organic semiconductors (OSCs) present an electron mobility lower by several orders of magnitude than the hole mobility, giving rise to an electron-hole charge imbalance in organic devices such as organic light-emitting diodes (OLEDs) and organic light-emitting transistors (OLETs). In this thesis project, I tried to achieve an efficient electron transport and injection properties in opto-electronic devices, using inorganic n-type metal oxides (MOs) instead of organic n-type materials and a polyethyleneimine ethoxylated (PEIE) thin layer as electron transport (ETLs) and injection layers (EILs), respectively. In the first part of this thesis, inverted OLEDs were fabricated in order to study the effect of the PEIE layer in-between ZnO and two different emissive layers (EMLs): poly(9,9-dioctylfluorene-alt-benzothiadiazole) polymer (F8BT) and tris(8-hydroxyquinolinato) aluminum small molecule (Alq3), based on a solution and thermal evaporation processes, respectively. Different concentrations (0.80 %, 0.40 %) of PEIE layers were used to further study electron injection capability in OLEDs. After a series of optimizations in the fabrication process, the opto-electrical characterization showed high-performance of devices. The inverted OLEDs reported a maximum luminance over 104 cd m-2 and a maximum external quantum efficiency (EQE) around 1.11 %. The results were attributed to the additional PEIE layer which provided a good electron injection from MOs into EMLs. In the last part of the thesis, OLETs were fabricated and discussed by directly transferring the energy modification layer from OLEDs to OLETs. As metal oxide layer, ZnO:N was employed for OLETs since ZnO:N-based thin film transistors (TFTs) showed better performance than ZnO-based TFTs. Finally, due to their short life-time, OLETs were characterized electrically but not optically.
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Milhor, Carlos Eduardo. "Sistema de desenvolvimento para controle eletrônico dos motores de combustão interna ciclo Otto." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/18/18135/tde-12032003-092253/.
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O sistema de gerenciamento dos motores automotivos tem se tornado um avançado sistema de controle. Seu objetivo é fazer com que o nível de emissões de gases poluentes gerados esteja dentro dos padrões exigidos pela legislação de cada país e ao mesmo tempo manter os níveis de desempenho e dirigibilidade. Apresenta as principais características de um típico sistema de gerenciamento de motores a combustão interna, descreve os modos de controle e aponta tendências futuras. Descreve o sistema de controle desenvolvido, o qual servirá de ferramenta de pesquisa para trabalhos que envolvam o estudo de técnicas de controle aplicadas neste contexto e pesquisas envolvendo otimização do rendimento dos motores automotivosThe automotive engine management system has become an advanced control system. Its objective is to maintain the pollutants gas emissions according to legislations and to maintain the performance and driveability, at the same time. It presents the main features of a tipical internal combustion engine management system, it describes the control modes and it point out the future tendencies. It describes the control system developed, which one will be usefull as a tool for research involving control applied in this context and engine automotive efficiency optimization researchs
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Chhun, Labo. "Modes d'Alimentation et de Commande des lampes sodium haute pression en vue d’éviter les résonances acoustiques." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0009/document.
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Grâce au développement de la technologie des semi-conducteurs, les ballasts électroniques fonctionnant en haute fréquence offrent des avantages considérables par rapport aux ballasts électromagnétiques conventionnels. Il en résulte une augmentation de la durée de vie de la lampe, une diminution du volume et du poids du système et surtout un meilleur contrôle de son fonctionnement afin de réduire notamment la consommation électrique. Parmi des lampes à décharge, la lampe sodium haute pression a une excellente efficacité lumineuse et une longue durée de vie. Pourtant, quand la lampe fonctionne en haut fréquence, des perturbations de type « résonance acoustique (RA) » peuvent entraîner l’instabilité de la décharge, son extinction ou pire, la destruction de la lampe. Cette thèse, intitulée « Modes d’Alimentation et de Commande des lampes sodium haute pression en vue d’éviter les résonances acoustiques », traite de plusieurs problèmes. Les caractéristiques de la décharge haute pression, le phénomène de RA, ses conditions d’excitation (notamment au travers d’un phénomène d’hystérésis original) et la variation des paramètres électriques due à la présence de résonances acoustiques dans la lampe, ont été étudiés. Les résultats sont issus de travaux de simulation et expérimentaux menés au sein du laboratoire LAPLACE. Grâce à ces acquis fondamentaux, plusieurs nouvelles méthodes d’alimentation par l’injection de signaux à fréquences proches ont été proposées dans nos travaux. Il s’agit d’éviter la résonance acoustique dans la lampe alimentée par un ballast de structure très réduite par rapport aux solutions classiques. Cette méthode est basée sur le choix judicieux des signaux injectés dans la lampe et leur répartition, (alimentation par deux, trois ou cinq signaux, répartition symétrique, asymétrique totale ou partielle). Le résultat est un meilleur étalement du spectre et donc une réduction de puissances harmoniques sélectionnées permettant de s’adapter, à terme aux conditions d’excitation des RA, mais aussi les limitations de ces méthodes compte tenu du facteur crête. Enfin, différents types de commande en boucle fermée sont proposés, ils permettent d’assurer la stabilité de la décharge et le contrôle des puissances imposées dans la lampe. Les études théoriques, en simulation et expérimentales qui ont été conduites nous ont permis d’aboutir à des résultats concluantsFor high pressure sodium (HPS) lamps, the progress of semi-conductor technology has provided considerable advantages in the design of high frequency operated electronic ballasts, compared to conventional electromagnetic ballasts. The advantages deal with lamp lifetime improvement, ballast volume and mass reduction, and particularly with a better control of lamp operation for optimized power consumption. Among discharge lamps, high pressure sodium (HPS) lamp has excellent efficacy and long lifetime. However, when it is operated at high frequency, discharge perturbation namely “acoustic resonances (AR)” can provoke some lamp arc instabilities, extinction or, even worst, lamp destruction. The present thesis, entitled “Supply and control methods for acoustic resonances avoidance in high intensity discharge lamps” deals with several matters. High intensity discharge (HID) characteristics, AR phenomenon, its excitation conditions (including the original features of AR hysteresis) and lamp electrical parameters variation due to AR presence, will be studied. The obtained results were provided by simulations and experimentations carried out in LAPLACE laboratory. Thanks to the acquired results of previous studies, several novel lamp supply strategies via adjacent frequency signals injection were proposed. The main concepts here consist in the avoidance of AR presented in a lamp supplied by designed electronic ballast with reduced structure, compared to classical solutions. Otherwise, the presented methods are based on pertinent choices of injected signals applied to the lamp and their frequency distributions (two, three or five signals and symmetric, partial asymmetric or total asymmetric signals). The studies actually showed better spreading of signal spectrum and power harmonic amplitudes reduction adapted to AR excitation conditions, while taking into account crest factor limitation. Finally, different control laws (PI, Hysteresis, Self-oscillation, Resonant controllers) were also proposed in order to guarantee lamp discharge stabilization and power controls. The theoretical and experimental studies including simulations were conducted to reach concluding results of our works
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Andreoli, Alexandre Giordani. "Análise e simulação de mapas base de injeção eletrônica de combustível para motores de ignição a centelha." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/75756.
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Uma nova metodologia para a criação de mapas base de injeção eletrônica de combustível para motores de combustão interna de ignição a centelha é apresentada e seu comportamento é comparado com os resultados fornecidos pela metodologia MVEM. A partir da utilização de equacionamentos da literatura, é feita uma modelagem do ciclo ideal Otto para um motor genérico alternativo monocilíndrico de 500 cm³ de volume deslocado. É modelada também uma válvula do tipo borboleta genérica de 0,06 m³ de diâmetro que opera tanto em regime subsônico quanto sônico. A pressão à jusante da borboleta é calculada para aberturas de 5° a 88,64°. Os modelos são acoplados a partir da vazão mássica de ar admitida, que é o parâmetro principal, sendo programados e simulados usando o programa comercial EES. O mapa base de pressão por abertura de borboleta por rotação resultante mostra o detalhe de descontinuidade pelo uso das equações de vazão mássica juntamente com a imposta pelas equações de coeficiente de descarga, implicando na mudança brusca de valores de pressão calculados para a região de abertura menor que 20%. O mapa de vazão mássica de combustível por rotação e por abertura de borboleta para uma razão estequiométrica de 14,67 também é gerado. Nele é possível observar a demanda por vazão mássica de combustível para cada rotação e abertura da válvula borboleta mostrando o caminho a ser seguido pelo motor para que seja atingida a vazão mássica necessária para obter-se a relação ar/combustível desejada. A metodologia proposta gera mapas base de combustível para módulos de injeção eletrônica. Os resultados são apresentados na forma de gráficos. O modelo produz resultados satisfatórios, reproduzindo o comportamento da válvula borboleta, comparado com a literatura.A new methodology for EMS base maps to the internal combustion spark ignition engines is presented. Its behavior is compared with results from the MVEM methodology. From the technical literature an ideal Otto cycle for a generic reciprocating single cylinder engine with 500 cm³ of displaced volume. Also, throttle valve with a diameter of 0.06 m of diameter operating in subsonic and sonic flow regime is modeled. The downstream pressure is calculated for throttle openings of 5° to 88.64°. The models are coupled using the engine air mass flow rate as the main parameter, being programmed and simulated using a commercial EES software. The base map of pressure versus throttle opening and engine speed shows the discontinuity detail imposed from the mass flow and discharge coefficient equations, resulting into a abrupt change of pressure values calculated for an opening region less than 20%. The fuel mass flow versus revolutions per minute versus throttle valve opening for stoichiometric air fuel ratio of 14.67 is also generated. In such map it is possible to show the fuel mass flow demand for each rotation and throttle opening showing the path to be followed by the engine to reach the mass air flow needed to reach the target air fuel ratio. This methodology generates base fuel maps for electronic fuel injection modules. The results are presented in graph forms. The model presents satisfactory results that reproduce the throttle valve behavior, compared to the literature.
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Arias, Olivares David. "Relation Among Localization, Delocalization and Physicochemical Properties. From Electron Density Databases to Magnetic Properties Effects of the acceptor unit in dyes with acceptor–bridge–donor architecture on the electron photo-injection mechanism and aggregation in DSSCs The role of Cr, Mo and W in the electronic delocalization and the metal–ring interaction in metallocene complexes." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS015.
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Tout d'abord, nous évoquerons un aperçu général de l'analyse topologique basée sur la densité d'électronique, le trou d'échange-corrélation et la densité de paires. Une fois la densité électronique rappelée, l'analyse topologique de la densité électronique est expliquée, ainsi que la procédure de calcul des points critiques de la densité électronique, le calcul de la matrice hessienne de la densité électronique et la définition des points critiques à la surface. Tous ces outils topologiques permettent de caractériser la nature des liaisons chimiques parallèlement à l'indice basé sur la délocalisation. Afin de comprendre la nature des énergies et des interactions dans les systèmes, l'analyse d'interaction non covalente est expliquée et combinée à l'analyse de décomposition d?énergie. De plus, les états de transition seront étudiés en appliquant les orbitales naturelles pour la valence chimique (ETS-NOCV). Les concepts clés du magnétisme moléculaire sont abordés. Nous nous concentrons sur l'aimantation et la susceptibilité magnétique, les composants diamagnétiques et paramagnétiques provenant de toute réponse magnétique dans les systèmes. Les propriétés de champs magnétiques induits sont étudiés dans le but de comprendre l'aromaticité à travers de deux descripteurs, les déplacements chimiques indépendants du noyau et les densités de courant induit. En annexe à la théorie, l'interaction isotrope dans les composés dinucléaires est introduite pour expliquer et mesurer certaines erreurs trouvées dans la théorie de la fonctionnelle de densité (TFD). [...]The first property here analysed and related with electronic localization/delocalization is the aromaticity. Aromaticity is an important concept introduced by Kekulé; since then, theoreticians and experimentalist have tried to understand it in different groups of molecules analogues to benzene. The importance of this concept and how the aromaticity is affected by the chemical environment is important to understand and link some physicochemical properties. i.e., reactivity, stability, magnetic response. The physicochemical properties of interest are the electronic structure, the nature of bonds and organometallic interactions(differentiation between metallocenes and metallabencenes). Furthermore, the magnetic response and the study of building blocks as possible candidates to make nano-wires or new low-dimension magnetic materials. Finally, we try to understand the interaction and the errors involved in some properties theoretically computed like, the isotropic coupling between metals through aromatic (or organic) units that have become important benchmark molecules to study magnetic properties in inorganic as well as metal-organic systems [...]
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Kabiri, Isfahani Yasin. "Injection matching of antenna." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7136/.
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One of the most important modules of the current and next generation of the wireless communications is the antenna. The coexistence of the machine and human in the next communication system will open-up a vast range of new applications and communication services which need to be supported by the antenna. Moreover, the forthcoming 5G technology vision is prognosticated on the use of multiple communication bands and standards in a seamless fashion. This can force the mobile devices to have multiple antennas on a single device which will add significant complexity or using an antenna with wideband reconfiguration capability. On the other hand, switched-off analogue communications provides the opportunity for re-using prime spectrum in UHF bands. Considering the size of hand-held devices, this will need strong miniaturization. To address these requirements, electrically small, tunable, wideband and highly efficient antenna technology is strongly desired. In this thesis a new area of research in antenna design is introduced which has been unexplored by the other researchers. A new theory called Injection Matching Theory (IMT) is proposed which uses multi-port configuration. This will enable to control current distribution on the antenna structure at its extremities and couple a wave length, much larger than what the antenna dimensions naturally allow. Apart from electrically small operation this can be used for improving band width and efficiency, and providing reconfiguration capability. To illustrate the versatility of the proposed theory, for every feature mentioned above a chapter is provided which demonstrates the potential capability of the proposed theory via simulation and fabrication of the prototyped examples.
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Koops, Sara. "Electron injection in dye sensitised solar cells." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/5656.
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In this thesis, the dynamics and quantum yields of electron injection occurring in liquid and solid state dye sensitised solar cells (DSSCs) based on titanium dioxide (TiO2) anodes sensitised with Ru – polypyridyl or organic dyes have been measured. The electron injection process is investigated through both experimental and modelling studies. A transient emission technique based on time correlated single photon counting (TCSPC) has been developed to measure the kinetics and yields of injection occurring in both films and devices. Other processes occurring in the device are probed using a range of experimental techniques, including transient absorption spectroscopy and transient photovoltage. Initially the principles of the TCSPC measurement technique are introduced and the procedure for measuring the injection in samples is outlined. Comparison of appropriate control sample measurements, which show transient emission decay dynamics in the absence of electron injection, with the TiO2 sample traces enables the quantification of injection occurring in each experimental sample. TCSPC emission decays associated with each sample are then fitted using stretch exponential functions constrained by two degrees of freedom. This TCSPC technique for measuring electron injection dynamics is validated by showing agreement with previously published kinetics for an analogous system as measured by a well established ultrafast transient absorption technique. The fits to the TCSPC decay dynamics are also shown to be accurately replicated by Monte Carlo integrations based on a previously published model of the active dye / TiO2 interface in the DSSCs. The technique is extended to probing DSSCs employing a range of different sensitisers and measuring the kinetics under different operating conditions occurring within the DSSCs where injection is found to only depend strongly on the concentration of potential determining additives. The first results chapter describes the TCSPC technique and gives examples of the data analysis procedures associated with each transient emission decay measurement. The agreement between injection kinetics measured using TCSPC with those measured using ultrafast transient absorption technique is highlighted. The model of 5 the active dye / TiO2 DSSC interface is introduced and Monte Carlo integrations based on this physical model are shown to agree well with the experimental data. The second results chapter extends the measurement of injection kinetics to different Ru – polypyridyl based sensitisers. Injection kinetics are measured for a structure – function dye series and the observed variations in the kinetics and yields are explained with reference to the dye / TiO2 interface. The measurements are extended to completely solid state DSSCs and successful fitting of the TCSPC data with integrations based on the physical model show dispersive injection kinetics observed in solid state DSSCs are controlled by the same parameters as the liquid cells. The third chapter looks at a variety of factors which may affect injection in complete, operating DSSCs. The factors addressed include presence of the commonly used iodide / triiodide redox couple, residual effects of acid versus base film synthesis procedures, effect of increasing the Fermi level in the DSSC and changing the concentration of potential determining ions in the redox electrolyte. The major controlling factor is found to be the concentration of the potential determining, commonly used tert – butyl pyridine device additive and implications of this on DSSC performance are discussed. The last chapter compares device parameters for DSSCs based on successful organic sensitiser with DSSCs based on the commonly used Ru – polypyridyl N719. Features which control the performance of organic dyes in general are outlined and the reduced performance of DSSCs employing these dyes is explained.
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Middleton, Bethany. "Injection moulding electroluminescent devices." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/56133/.
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Electroluminescence is a developing area of research in the fields of display technology and lighting. Solution based processing of organic materials offers the opportunity to manufacture large area, low cost illuminating surfaces but current processes are limited to two dimensions. The ability to apply electroluminescent materials onto three dimensional contoured surfaces would incorporate the illuminating function into objects, enhancing usability and removing the need for an additional light source. Furthermore, the integration directly into the manufacturing process, such as injection moulding, would have the added benefits of reducing manufacturing time, handling and have environmental and economic savings. Incorporating electronics manufacturing in-mould offers considerable potential for novel research and commercial applications. Electroluminescent multi-layer structures were constructed on 3D surfaces, applying materials using an airbrush. Novel injection moulded electroluminescent devices were successfully made using insert moulding and in-mould layer application techniques, then characterised and compared to a bought device. Electroluminescent layers were also applied to injection moulded plastic parts as a post mould treatment for further comparison. In the current state of development, insert moulding using a PTFE carrier film is the most successful method of injection moulding EL parts, producing devices that light up with an average illuminance of 210.2 39.2 lx when operated at 300 V and 400 Hz. A multi-layer thermal model developed in this project confirms that the injected plastic does not transfer enough heat energy to cure materials that are applied directly in-mould. It was also found that, after 10 weeks, the airbrush made devices maintained 27.3 % points more relative illuminance compared to devices made using a conventional method. Problems associated with all of the new processes have been identified and solutions suggested, but with further research these methods could be used to routinely mould plastic parts with the ability to illuminate.
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Mesgarzadeh, Behzad. "Low-Power Low-Jitter Clock Generation and Distribution." Doctoral thesis, Linköpings universitet, Elektroniska komponenter, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-14896.
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Today’s microprocessors with millions of transistors perform high-complexitycomputing at multi-gigahertz clock frequencies. Clock generation and clockdistribution are crucial tasks which determine the overall performance of amicroprocessor. The ever-increasing power density and speed call for newmethodologies in clocking circuitry, as the conventional techniques exhibit manydrawbacks in the advanced VLSI chips. A significant percentage of the total dynamicpower consumption in a microprocessor is dissipated in the clock distributionnetwork. Also since the chip dimensions increase, clock jitter and skew managementbecome very challenging in the framework of conventional methodologies. In such asituation, new alternative techniques to overcome these limitations are demanded. The main focus in this thesis is on new circuit techniques, which treat thedrawbacks of the conventional clocking methodologies. The presented research in thisthesis can be divided into two main parts. In the first part, challenges in design ofclock generators have been investigated. Research on oscillators as central elements inclock generation is the starting point to enter into this part. A thorough analysis andmodeling of the injection-locking phenomenon for on-chip applications show greatpotential of this phenomenon in noise reduction and jitter suppression. In thepresented analysis, phase noise of an injection-locked oscillator has been formulated.The first part also includes a discussion on DLL-based clock generators. DLLs haverecently become popular in design of clock generators due to ensured stability,superior jitter performance, multiphase clock generation capability and simple designprocedure. In the presented discussion, an open-loop DLL structure has beenproposed to overcome the limitations introduced by DLL dithering around the averagelock point. Experimental results reveals that significant jitter reduction can beachieved by eliminating the DLL dithering. Furthermore, the proposed structuredissipates less power compared to the traditional DLL-based clock generators.Measurement results on two different clock generators implemented in 90-nm CMOSshow more than 10% power savings at frequencies up to 2.5 GHz. In the second part of this thesis, resonant clock distribution networks have beendiscussed as low-power alternatives for the conventional clocking schemes. In amicroprocessor, as clock frequency increases, clock power is going to be thedominant contributor to the total power dissipation. Since the power-hungry bufferstages are the main source of the clock power dissipation in the conventional clock distribution networks, it has been shown that the bufferless solution is the mosteffective resonant clocking method. Although resonant clock distribution shows greatpotential in significant clock power savings, several challenging issues have to besolved in order to make such a clocking strategy a sufficiently feasible alternative tothe power-hungry, but well-understood, conventional clocking schemes. In this part,some of these issues such as jitter characteristics and impact of tank quality factor onoverall performance have been discussed. In addition, the effectiveness of theinjection-locking phenomenon in jitter suppression has been utilized to solve the jitterpeaking problem. The presented discussion in this part is supported by experimentalresults on a test chip implemented in 130-nm CMOS at clock frequencies up to 1.8GHz.Mikroprocessorer till dagens datorer innehåller hundratals miljoner transistorersom utför åtskilliga miljarder komplexa databeräkningar per sekund. I stort settalla operationer i dagens mikroprocessorer ordnas genom att synkronisera demmed en eller flera klocksignaler. Dessa signaler behöver ofta distribueras överhela chippet och driva alla synkroniseringskretsar med klockfrekvenser pååtskilliga miljarder svängningar per sekund. Detta utgör en stor utmaning förkretsdesigners på grund av att klocksignalerna behöver ha en extremt högtidsnoggranhet, vilket blir svårare och svårare att uppnå då chippen blir större.Idealt ska samma klocksignal nå alla synkroniseringskretsar exakt samtidigt föratt uppnå optimal prestanda, avvikelser ifrån denna ideala funktionalitet innebärlägre prestanda. Ytterliggare utmaningar inom klockning av digitala chip, är atten betydande andel av processorns totala effekt förbrukas i klockdistributionen.Därför krävs nya innovativa kretslösningar för att lösa problemen med bådeonoggrannheten och den växande effektförbrukningen i klockdistributionen. att lösa de problem som finns i dagens konventionella kretslösningar förklocksignaler på chip. I den första delen av denna avhandling presenterasforskningsresultat på oscillatorer vilka utgör mycket viktiga komponenter igeneringen av klocksignalerna på chippen. Teoretiska studier avfaslåsningsfenomen i integrerade klockoscillatorer har presenterats. Studiernahar visat att det finns stor potential för reducering av tidsonoggrannhet iklocksignalerna med hjälp av faslåsning till en annan signal. I avhandlingensförsta del presenteras även en diskussion om klockgeneratorer baserade påfördröjningslåsta element. Dessa fördröjningslåsta elementen, kända som DLLkretsar, har egenskapen att de kan fördröja en klocksignal med en bestämdfördröjning, vilket möjliggör skapandet av multipla klockfaser. En nykretsteknik har introducerats för klockgenerering av multipla klockfaser vilken reducerar effektförbrukningen och onoggranheten i DLL-baseradeklockgeneratorer. I denna teknik används en övervakningskrets vilken ser till attalla delar i klockgeneratorn utnyttjas effektivt och att oanvända kretsarinaktiveras. Baserat på experimentalla mätresultat från tillverkade testkretsar ikisel har en effektbesparing på mer än 10% uppvisats vid klockfrekvenser påupp till 2.5 GHz tillsammans med en betydande ökning av klocknoggranheten. I avhandlingens andra del diskuteras en klockdistributionsteknik som baseraspå resonans, vilken har visat sig vara ett lovande alternativ till konventionllabufferdrivna klockningstekniker när det gäller minskande effektförbrukning.Principen bakom tekniken är att återanvända den energi som utnyttjas till attladda upp klocklasten. Teoretiska resonemang har visat att storaenergibesparingar är möjliga, och praktiska mätningar på tillverkadeexperimentchip har visat att effektförbrukingen kan mer än halveras. Ettproblem med den föreslagna klockningstekniken är att data som används iberäkningarna kretsen direkt påverkar klocklasten, vilket även påverkarnoggranheten på klocksignalen. För att komma till rätta med detta problemetpresenteras en teknik, baserad på forskning inom ovan nämndafaslåsningsfenomen, som kan minska onoggrannheten på klocksignalen medöver 50%. Både effektbesparingen och förbättringen av tidsnoggranheten harverifierats med hjälp av mätningar på tillverkade chip vid frekvenser upp mot1.8 GHz.
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Hinds, Sean O'Reilly. "Negative differentiated optical injection of semiconductor lasers." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26336.
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In this thesis, we present a new technique of semiconductor modulation that maintains simplicity of design and overcomes many deficiencies of current direct modulation technologies. This technique of negative differentiated optical injection locking, makes it possible to equal or improve the Q factor and reduce the chirp penalty of a directly modulated laser source. Using this new structure we stabilize the dielectric properties of the slave laser, beyond the performance of standard optical injection locking, by reducing the refractive index excursion in the active layer and minimizing optical frequency chirp. This enables more reliable bandwidth efficient communication without compromising linearity or demanding prohibitive control complexity. We contrast this technique with direct, standard injection locking, electro absorption and Mach-Zehnder modulators at various speeds and find that our particular technique demonstrates desirable trade-offs between performance, control flexibility and simplicity.
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Fajgenbaum, Renata 1985. "Influência da temperatura do combustível nos parâmetros de atomização de um atomizador utilizado em bicos injetores automotivos." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265254.
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Orientador: Rogério Gonçalves dos SantosDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: A motivação em se estudar os fenômenos que acontecem em cada subsistema de um motor de combustão interna ciclo Otto reside na possibilidade de se prever e otimizar seu funcionamento, em especial com os diferentes combustíveis de nova geração que estão sendo inseridos no mercado. O processo de atomização que ocorre nos bicos injetores de combustível, dispositivos integrantes do sistema de injeção eletrônica do motor, apresenta forte relação com a posterior reação de combustão e, por conseguinte, com a eficiência térmica do motor. No presente trabalho, experimentos foram conduzidos para investigar o efeito da temperatura do líquido em parâmetros de atomização de um atomizador do tipo mecânico-centrífugo utilizado em bicos injetores de combustível automotivos. O aparato experimental consistiu de uma bancada de injeção de combustível conectada a um sistema de controle de calor, este com objetivo de variar a temperatura do combustível. Os parâmetros de atomização foram avaliados por meio da técnica de Shadowgraphy, a fim de se medir diâmetro de gotas, distribuição de partículas e campo de velocidades. Gasolina e etanol em diferentes temperaturas foram usados para fornecer variação nas propriedades do líquido, ambos com a mesma pressão de injeção. Os resultados de tamanho de gota foram dados, principalmente, em termos de Sauter Mean Diameter (SMD) e outros diâmetros representativos que se mostraram pertinentes. Todas as medições foram realizadas em duas diferentes distâncias axiais do orifício de descarga. Para as duas distâncias escolhidas, 25 mm e 100 mm, o SMD e a velocidade se mostraram insensíveis à faixa de temperatura testada, devido à baixa variação das propriedades dos combustíveis. Por outro lado, a distribuição das partículas permitiu visualizar o efeito da temperatura nos diâmetros das gotas, mostrando que o aumento da temperatura proporciona diminuição no tamanho das gotas, e o comparativo entre os parâmetros nas duas distâncias axiais permitiu visualizar o efeito da primeira e segunda atomização sobre o spray
Abstract: The motivation in studying the phenomena that happen in each internal combustion engine subsystem lies in the possibility to predict and optimize its operation. The atomization process that occurs in fuel injectors, devices that belong to engine injection system, has a strong relation with the subsequent combustion reaction and thus with the engine thermal efficiency. Experiments were performed to investigate the liquid temperature effect on atomization parameters in an internal combustion engine pressure-swirl atomizer. The experimental apparatus consisted of a flow control rig connected with a heat control system. The flow rig, which is an injection system, was built specifically for that purpose and the heat system goal was to vary the liquid temperature. The atomization parameters were evaluated by means of Shadowgraphy technique in order to measure drop mean diameter, particle size distribution and drop velocity field. Gasoline and ethanol in different temperatures were used to provide variation in liquid properties and the same injection pressure was used for both fuels. The results for drop sizing were expressed in terms of Sauter Mean Diameter (SMD) and the velocity field as well as the particle size distribution measurements were taken in two different axial distances from the nozzle exit. At both distances, 25 mm and 100 mm, SMD and velocity seemed to be insensitive to the range of temperature used because it provided low variation in fuel properties. On the other hand, particle size distribution allowed the visualization of temperature effect on drop diameters, showing that increasing temperatures decrease droplet sizes, and the comparison between two axial distances allowed seeing the effects of first and second atomization on the spray
Mestrado
Termica e Fluidos
Mestra em Engenharia Mecânica
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Ramos, Diego Berlezi. "Controlador nebuloso para motor de ignição por compressão operando com gás natural e óleo diesel." Universidade Federal de Santa Maria, 2006. http://repositorio.ufsm.br/handle/1/8607.
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A foreseeable shortage of petroleum, associated to a growing ecological conscience, demand for alternative sources of energy and more efficient and less pollutant combustion processes. Among the few pollutant fuels this work approaches the combination of natural gas, whose consumption has been increasing year to year, and
diesel. It is known that the internal combustion engines convert energy with low efficiency. Based on that, this
work evaluates a bi-fuel Diesel engine, power by Diesel and natural gas as means of improving its efficiency.
In the engine used as a prototype, the main energy comes from the combustion of natural gas. Being the gas the
main fuel, the Diesel is used only to generate the pilot explosion for the combustion process. In this way, the
diesel oil is partially substituted by natural gas, increasing the combustion efficiency. Initially it was made a study on the use of the natural gas in Diesel engine through a bibliographical revision. Therefore after, they were certain the parameters that should be monitored to develop an appropriate controller. It was verified that should be appraised the engine rotation and the injection angle. The performance aimed for the action of the loop control should be the rotation of the engine. The more appropriate control techniques were investigated for the management of the natural gas injection. When analyzing the traditional techniques it observed that they present some disadvantages as the mathematical complexity, difficulties in adapt the motor to the everchanging conditions of the motor with time/temperature, limitations in the grade of controller performance and complications for practical implementation on the part of non-specialized operators. To optimize the volume of natural gas supplied to the engine an electronic manager was developed for injection of this fuel. This electronic controller is based on an adaptive fuzzy algorithm to regulate the rate of injection of fuel, which was implemented through a microcontroller. The electronic injection system controls the timing of fuel injection, so managing the volume of gas supplied to each injection cycle. The injection angle is also accurately monitored by the control system. This topology, with few alterations, can be used in any Diesel engine operating in the bifuel mode. Results of this dissertation should contribute to increase the efficiency of Diesel engine as well as reduce the consumption of fuel and emission of pollutants.Uma previsível escassez de petróleo, aliada a uma crescente consciência ecológica, tem levado pesquisadores a procurar fontes alternativas de energia e processos de combustão mais eficientes e menos poluentes. Entre os combustíveis pouco poluentes este trabalho aborda o uso do gás natural, cujo consumo tem aumentado ano a ano. É sabido que os motores de combustão interna convertem energia com baixa eficiência. Com base nisto, este trabalho avalia um motor Diesel, bi-combustível, movido a Diesel e gás natural como forma de encontrar meios de melhorar sua eficiência. No motor usado como protótipo, nessa dissertação a energia origina-se da combustão do gás natural. Sendo o gás o combustível principal, o Diesel presta-se apenas à geração da chama piloto para o processo de combustão. Assim, substitui-se parcialmente o óleo Diesel por gás natural, aumentando o rendimento da combustão. Inicialmente procurou-se estudar o uso do gás natural em motores Diesel através de uma revisão bibliográfica. Em seguida, determinaram-se quais os parâmetros que seriam monitorados a fim de se desenvolver um controlador adequado. Verificou-se que deveriam ser avaliados a rotação do motor e o ângulo de injeção. A performance almejada para a ação da malha de controle deve ser a rotação do motor. Investigaram-se as técnicas de controle mais apropriadas para o gerenciamento da injeção de gás natural. Ao se analisarem as técnicas tradicionais observou-se que estas apresentam algumas desvantagens como a complexidade matemática, limitações na faixa de atuação do controlador, dificuldades de adaptação às condições do motor sempre variáveis com o tempo/temperatura e complicações para implementação prática por parte de operadores não-especializados. Para otimizar o volume de gás natural fornecido ao motor foi desenvolvido um gerenciador eletrônico para injeção deste combustível. Este controlador eletrônico baseia-se em um algoritmo nebuloso para regular a taxa de injeção de combustível implementado através de um microcontrolador. O sistema de injeção eletrônica controla o tempo de injeção do combustível, gerenciando assim o volume de gás fornecido a cada ciclo de injeção. O ângulo de injeção, também monitorado com precisão pelo sistema, é sincronizado com o eixo de comando de válvulas e, tomando-se como referência de posição angular o ponto morto superior do primeiro cilindro. Com poucas alterações, esta topologia, pode ser usada em qualquer motor Diesel que opere no regime bi-combustível. Os resultados desta dissertação devem contribuir para o aumento da eficiência do motor bem como redução do consumo de combustível e emissão de poluentes.
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Duffy, Christopher James. "Modeling hot-electron injection and impact ionization in pFET's." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/14796.
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Moorsom, Timothy. "Electron transfer and spin injection in C60-ferromagnetic composites." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15569/.
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The magnetic properties of spin doped fullerenes are investigated in hybrid organic/inorganic structures with the aim of establishing the extent to which magnetic states can be induced and controlled in these materials. Volume magnetometry is used to measure a reduction of net magnetization and an increase in coercivity in cobalt which can be understood in terms of a transfer of majority spin electrons from the transition metal d-band into spin polarized hybrid interface states. This is supported by PNR and XAS studies of Co/C60 which reveal AF coupling between Co metal films and a hybrid interfacial region where magnetic ground states are induced in fullerenes through charge transfer. Investigations of hybridization between C60 and the RE-TM alloy CoGd show that the compensation temperature of the ferrimagnet is altered by the presence of C60. PNR measurements of CoGd/C60 MLs reveal interfacial coupling which creates an AF region 1.5 $\pm$ 0.1 nm thick. Magnetometry of Gd/C60 bilayers indicates that hybridization between the metal conduction bands and the C60 LUMO modifies magnetic ordering in Gd. This is supported by the observation of novel features in the temperature dependence of magnetization and resistivity in the composite. XAS of Gd/C60 bilayers shows a large peak in the carbon K-edge at 282 eV which is attributed to interfacial hybridization. It is shown that PL quenching in C60 is greater over Co than Au which is attributed to the greater electron transfer between Co and C60. PL quenching is proposed as an effective way to measure magnetic coupling and electron transfer in interfaces. Raman spectra are recorded in C60 junctions during spin polarised transport. The Ag(2) peak splitting is shown to depend on the polarisation of injected current acting as an effective probe of triplet formation in C60. Finally, XAS at the carbon K-edge is recorded during spin transport. A suppression of the LUMO to zero and increase in the intensity of the 282 eV peak occurs after removal of external bias and is shown to be reversible and repeatable under cycles of grounding and charge injection. A proposed mechanism involving the redistribution of charge following the removal of bias which causes electrons to become trapped in interfacial states is suggested.
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Martorell, Alexandre. "Détection à distance d’électroniques par l’intermodulation." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS019/document.
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Électromagnétisme, sécurité et guerre électronique sont étroitement liés depuis des décennies. Leur association rassemble des applications de surveillance radar, de neutralisation de systèmes électroniques ou de détection d’électroniques cachées. Aujourd’hui, la multiplication des EEI (Engins Explosifs Improvisés) aussi bien sur les théâtres d’opération que dans les milieux urbains conduit à la nécessité de leur détection. Les travaux de cette thèse peuvent entrer dans cette thématique et proposent une nouvelle alternative qui permet de mettre en évidence la présence de récepteurs RF cachés. Le radar non-linéaire est particulièrement adapté à la détection de dispositifs contenant des métaux et des semi-conducteurs (électroniques). Une technique populaire consiste à transmettre une seule fréquence f1 et à recevoir la seconde harmonique générée par la cible. Une autre technique, moins courante, consiste à transmettre deux fréquences, f1 et f2, et à recevoir les produits d'intermodulation d’ordre 3 (2f1 - f2 et 2f2 - f1). Un état de l’art approfondi des systèmes radars non-linéaires est effectué dans un premier chapitre avec une comparaison de leurs caractéristiques. Dans un second chapitre, un banc de test en mode conduit est développé permettant la mesure de l’IM3 réfléchi d’une cible RF. Ainsi des analyses et des ordres de grandeurs seront connus aidant au développement du radar. Dans le chapitre 3, Le démonstrateur du radar à IM3 est développé. Un large panel de systèmes RF, commerciaux ou non, susceptibles d’être trouvé dans des milieux opérationnels est mis sous test. Leur détection va permettre de valider la technique de récupération de l’IM3. Un nouveau bilan de liaison réaliste du radar IM3 est mis en place afin d’estimer la portée de détection réelle du radar, pour différentes cibles RF. Dans le dernier chapitre les travaux s’orientent sur l’identification et la classification d’une cible RF. L’étude porte sur la possibilité d’extraire tous paramètres pouvant aider à une classification (évaluation du danger) de récepteurs RF dans un milieu opérationnel. Le travail de recherche présenté dans ce manuscrit contribue à l’amélioration des techniques de détection d’électroniques cachées. Un protocole de détection a été proposé décrivant les faits et gestes du radar IM3. Il inclut un balayage en fréquence puis en puissance. Les premiers tests ont été effectués sur un Talkie-Walkie démontrant la possibilité de détecter sa bande passante via la réémission d’IM3, à plus de 2 m. La répétabilité des tests sur un panel élargi de récepteurs RF valide le protocole de détection et l’intérêt du radar IM3. Une puissance d’émission du radar IM3 de 40 dBm, à une fréquence d’IM3 de 400 MHz, peut potentiellement détecter un récepteur à 80 m. Enfin dans un dernier travail exploratoire nous avons démontré que, par l’observation de la réponse de l’IM3 réfléchi suite à un balayage en puissance, le radar IM3 peut ajouter de nouveaux critères d’identification discriminant les récepteurs détectés entre euxElectromagnetism, security and electronic warfare have been closely linked for decades. Their association gathers applications of radar surveillance, neutralization of electronic systems or detection of hidden electronics. Today, the multiplication of IEDs (Improvised Explosive Devices) both in theatres of operation and in urban environments leads to the need for their detection. The works of this thesis can enter into this theme and propose a new alternative that allows to highlight the presence of hidden RF receivers. The nonlinear radar is particularly suitable for detecting devices containing metals and (electronic) semiconductors. A popular technique is to transmit a single frequency f1 and receive the second harmonic generated by the target. Another less common technique consists of transmitting two frequencies, f1 and f2, and receiving intermodulation products of order 3 (2f1 - f2 and 2f2 - f1). An in-depth state of the art of nonlinear radar systems is made in a first chapter with a comparison of their characteristics. In a second chapter, an inductive test bench is developed to measure the reflected IM3 of an RF target. Thus analyses and orders of magnitude will be known helping the development of radar. In chapter 3, the IM3 radar demonstrator is developed. A wide range of RF systems, commercial and non-commercial, that may be found in operational environments are being tested. Their detection will validate the IM3 recovery technique. A new realistic IM3 radar link budget is implemented to estimate the actual radar detection range for different RF targets. In the last chapter the work focuses on the identification and classification of an RF target. The study focuses on the possibility of extracting all parameters to assist in a classification (hazard assessment) of RF receptors in an operational environment. The research work presented in this manuscript contributes to the improvement of hidden electronic detection techniques. A detection protocol was proposed describing the actions of the IM3 radar. It includes a frequency scan and then a power scan. The first tests were carried out on a walkie-talkie demonstrating the possibility of detecting its bandwidth via IM3 retransmission, at more than 2 m. The repeatability of the tests on an extended panel of RF receivers validates the detection protocol and the interest of the IM3 radar. An IM3 radar transmission power of 40 dBm, at an IM3 frequency of 400 MHz, can potentially detect a receiver at 80 m. Finally in a final exploratory work, we demonstrated that by observing the IM3 response reflected following a power scan the IM3 radar can add new identification criteria that discriminate the hidden receivers detected between them
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Teske, Nikolas. "Sensorless position control of induction machines using high frequency signal injection." Thesis, University of Nottingham, 2001. http://eprints.nottingham.ac.uk/13117/.
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The aim of this research project was to develop a position controlled induction machine vector drive operating without a speed or position sensor but having a dynamic performance comparable to that of a sensored position vector drive. The methodology relies on the detection of a rotor saliency in the machine by persistent high-frequency voltage injection. The rotor position is then estimated from the resulting stator current harmonics that are modulated by the spatial rotor saliency. This can be a built-in rotor saliency (a designed asymmetry) or the natural saliency due to rotor slotting. This project investigates the demodulation of the extracted high-frequency current spectrum and different topologies for the estimation of rotor position. The tracking of rotor position through rotor saliencies helps to overcome the limitations of model-based approaches that are restricted to speeds above 30rpm on a 4-pole machine and are sensitive to parameter mismatches. The project addresses the difficult problem of separating the modulation effects due to the rotor saliency from distorting modulations due to the saturation saliency and inverter effects. In previous research it had been found that the saturation saliency causes a deterioration of the position estimate that can result in a loss of position and eventually causes the drive to fail. The application of filters to remove the interfering saturation harmonics is not possible. In this research a new approach was developed that compensates online for the saturation effect using pre-commissioned information about the machine. This harmonic compensation scheme was utilized for a 30kW, 4-pole induction machine with asymmetric rotor and enabled the operation from zero to full load and from standstill up to about ±150rpm (±5Hz). The steady-state performance and accuracy of the resulting sensorless drive has been found to operate similarly to a sensored drive fitted with a medium resolution encoder of 600ppr. The project involved studies of the inverter switching deadtime and its distorting effect on the position estimation. A second compensation strategy was therefore developed that is better suited if a large interfering modulation due to the inverter deadtime is present in the machine. The new compensation method was implemented for a second 30kW machine that utilizes the rotor slotting saliency. Good tracking results were obtained with a mean error of less than ±0.5° mechanical under steady-state. The derivation of the position signal for higher speeds introduces an additional speed-dependent error of about 4° mechanical at 170rpm. Sensorless position control was realized for operation from zero to full load for the fully fluxed machine. The performance allowed low and zero speed operation including position transients reaching a speed of 50rpm. The high-frequency modulation introduced by the fundamental currents during transient operation was examined and identified as the main factor limiting the dynamics of the sensorless drive. Two rigs were used for the research. The first rig is build around a network of Transputers, the second rig uses state-of-the-art TMS320C40 and TMS320F240 digital signal processors for the control and was designed and constructed as part of the research.
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Burdett, William Charles. "ELECTRON INJECTION-INDUCED EFFECTS IN III-NITRIDES: PHYSICS AND APPLICATIONS." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4417.
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This research investigated the effect of electron injection in III-Nitrides. The combination of electron beam induced current and cathodoluminescence measurements was used to understand the impact of electron injection on the minority carrier transport and optical properties. In addition, the application of the electron injection effect in optoelectronic devices was investigated. The impact of electron injection on the minority carrier diffusion length was studied at various temperatures in Mg-doped p-GaN, p-Al[subscript x]Ga[subscript 1-x]N, and p-Al[subscript x]Ga[subscript 1-x] N/GaN superlattices. It was found that Lsubscript n] experienced a multi-fold linear increase and that the rate of change of L[subscript n] decreased exponentially with increasing temperature. The effect was attributed to a temperature-activated release of the electrons, which were trapped by the Mg levels. The activation energies, E[subscript a], for the electron injection effect in the Mg-doped (Al)GaN samples were found to range from 178 to 267 meV, which is close to the thermal ionization energy of the Mg acceptor. The E[subscript a] observed for Al[subscript 0.15]Ga[subscript 0.85]N and Al[subscript 0.2]Ga[subscript 0.8]N was consistent with the deepening of the Mg acceptor level due to the incorporation of Al into the GaN lattice. The E[subscript a] in the homogeneously doped Al[subscript 0.2]Ga[subscript 0.8]N/GaN superlattice indicates that the main contribution to the electron injection effect comes from the capture of injected electrons by the wells (GaN). The electron injection effect was successfully applied to GaN doped with an impurity (Mn) other than Mg. Electron injection into Mn-doped GaN resulted in a multi-fold increase of the L[subscript n] and a pronounced decrease in the band-to-band cathodoluminescence intensity. The E[subscript a] due to the electron injection effect was estimated from temperature-dependent cathodoluminescence measurements to be 360 meV. The decrease in the band-to-band cathodoluminescence is consistent with an increase in L[subscript n] and these results are attributed to an increase in the minority carrier lifetime due to the trapping of injected electrons by the Mn levels. A forward bias was applied to inject electrons into commercially built p-i-n and Schottky barrier photodetectors. Up to an order of magnitude increase in the peak (360 nm) responsivity was observed. The enhanced photoresponse lasted for over four weeks and was attributed to an electron injection-induced increase of L[subscript n] and the lifetime.Ph.D.
Department of Physics
Arts and Sciences
Physics
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Uythoven, Jan Arie. "An investigation of low-energy injection for electron storage rings." Thesis, University of Oxford, 1991. http://ora.ox.ac.uk/objects/uuid:6c399187-4845-4f6a-9b33-3ad93133b141.
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This thesis reports on low-energy injection studies, considering a multi-shot and multiturn injection method in radial phase space, using only one kicker magnet. A new model is presented in which the coupling between the radial and longitudinal phase space significantly increases the injection efficiency at low energies. Coupling with the longitudinal phase space takes place if the energy of the injected beam is different from the equilibrium ring energy and if there is dispersion at the septum position. Coupling with the vertical phase space, introduced by skew quadrupole fields, also increases the injection efficiency. A computer program, MCIS, has been written in order to make quantitative predictions from the new model. Calculations are presented for HELIOS, a superconducting synchrotron with a final electron energy of 700 MeV. The present injection energy is 200 MeV. The calculations show that if injection were to take place off-energy by δ m ≈ 1 %, then the injection energy could be lowered to a minimum of about 35 MeV. This prediction only takes into account single particle beam dynamics. The effect of most other parameters on the injection efficiency is also calculated. Experimental studies of the injection process were performed during the commissioning period of Helios, which was carried out by a team under the author's direction. Data obtained at an injection energy of 100 MeV are compared with calculations. A precise measurement of the relative energy deviation of the injected beam δm has been made. The agreement with the model is good and it proves the presence of longitudinal coupling for the optimum injection conditions. The measurement of the optimum kicker strength also agrees with the model, as does the general behaviour of injection as a function of several parameters. The measurements lead to a high level of confidence in the model presented. The belief in the general validity of the model is reinforced by its agreement with the overall injection behaviour of accelerators other than HELIOS, which inject successfully at low energies.
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Guillaume, Emilien. "Control of electron injection and acceleration in Laser-Wakefield Accelerators." Palaiseau, Ecole polytechnique, 2015. https://tel.archives-ouvertes.fr/tel-01249964v2/document.
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Les accélérateurs laser-plasma, plus compacts, constituent une alternative prometteuse aux accélérateurs conventionnels. Quand un laser ultra-intense est focalisé dans une cible de gaz sous-dense, des ondes plasma présentant des champs électriques de grande amplitude sont générées. Les électrons qui sont piégés dans ces ondes plasmas peuvent être accélérés jusqu’à des énergies de plusieurs GeV. Malgré leur fort potentiel, les accélérateurs laser-plasma font face à plusieurs difficultés, notamment en ce qui concerne la stabilité et la reproductibilité du faisceau au moment de l’injection dans la structure accélératrice. Dans ce manuscript, plusieurs techniques d’injection d’électrons sont présentées et comparées, notamment les méthodes d’injection dans un gradient raide de densité et d’injection par ionisation. Nous montrons qu’il est possible d’obtenir des faisceaux d’électrons stables et contrôlables en combinant ces deux techniques. Nous étudions également un moyen de manipuler le paquet d’électrons dans l’espace des phases afin de s’affranchir de la limite de déphasage et d’accélérer un peu plus les électrons. Cette technique est utilisée pour augmenter l’énergie de faisceaux d’électrons quasi-monoénergétiques. Par ailleurs, nous analysons l’origine de l’évolution du moment angulaire des électrons, précédemment observé expérimentalement. Enfin, nous présentons la démonstration expérimentale d’une nouvelle méthode permettant de réduire fortement la divergence du faisceau d’électron, la lentille laser-plasmaLaser-plasma accelerators provide a promising compact alternative to conventional accelerators. Plasma waves with extremely strong electric fields are generated when a high intensity laser is focused into an underdense gas target. Electrons that are trapped in these laser-driven plasma waves can be accelerated up to energies of a few GeVs. Despite their great potential, laser-wakefield accelerators face some issues, regarding notably the stability and reproducibility of the beam when electrons are injected in the accelerating structure. In this manuscript, different techniques of electron injection are presented and compared, notably injection in a sharp density gradient and ionization injection. It is shown that combining these two methods allows for the generation of stable and tunable electron beams. We also studied a way to manipulate the electron bunch in the phase-space in order to accelerate the bunch beyond the dephasing limit. Such a technique was used with quasi-monoenergetic electron beams to enhance their energy. Moreover, the origin of the evolution of the angular momentum of electrons observed experimentally was investigated. Finally, we demonstrated experimentally a new method – the laser-plasma lens – to strongly reduce the divergence of the electron beam
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Zhao, Si Ping. "Hot electron induced degradation in VLSI MOS devices." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320607.
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Richter, Thiago. "Arquitetura de sistema inteligente para sensoriamento virtual de oxigênio em veículos bicombustíveis com injeção eletrônica." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-08092009-162813/.
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A indústria automobilística é um dos mais importantes setores da economia no Brasil e no mundo. Nos últimos anos viu-se praticamente obrigada a melhorar o desempenho de seus veículos produzidos e reduzir seus custos. Um dos marcos desta transformação foi o desenvolvimento do sensor de oxigênio, sendo este um dos principais elementos dos sistemas gerenciadores de motor. Esta dissertação propõe o estudo de arquiteturas de sistemas inteligentes para sensoriamento virtual de oxigênio em veículos bicombustíveis, utilizando-se redes neurais artificiais supervisionadas, com arquitetura Perceptron multicamadas. As topologias implementadas atingiram resultados com erros relativos médios menores que 1% em centenas de topologias. Verificou-se também que para o sensoriamento virtual de oxigênio em veículos bicombustíveis, a abordagem de se realizar treinamentos com todos os tipos de combustíveis, segmentando conjuntos de todo o universo de dados, mostra-se a mais adequada.The automotive industry is one of the most important sectors in Brazilians economy and in the world. In recent years, this industry has been forced to improve the performance of their produced vehicles and to reduce their costs. One of the landmarks of this transformation was the development of the oxygen sensor, which is one of the main elements of the engine management systems. This dissertation proposes the use of intelligent systems architectures for virtual oxygen sensing of bi-fuel vehicles, using multilayer Perceptron artificial neural networks. The implemented topologies reach results with mean relative errors less than 1% in hundreds of topologies. It was also noted that the approach to train the neural network with all types of fuels, using subsets of data universe, it is the most appropriate to have a virtual sensing of oxygen in bi-fuel vehicles.
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Jaksic, Marko Dragoljub. "Identification of small-signal dq impedances of power electronics converters via single-phase wide-bandwidth injection." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51222.
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AC and DC impedances of switching power converters are used for the stability analysis of modern power electronics systems at three-phase AC and single-phase DC interfaces. Therefore, a small-signal characterization algorithm for switching power converter, which is based on FFT, will be presented and explained. The presented extraction algorithm is general and can be used to obtain other small-signal transfer functions of arbitrary power converter switching simulation models. Furthermore, FFT algorithm is improved by using cross power spectral density functions for identification, resulting in an algorithm, which is more noise immune. Both small-signal identification algorithms are validated in simulations, and CPSD algorithm is used in experimental measurement procedure. Several wide bandwidth injection signals, among which are chirp, multi-tone, pulse and white noise, are compared and theoretically analyzed. Several hardware examples are included in the analysis.
The second part of the dissertation will focus on the modeling of small-signal input dq admittance of multi-pulse diode rectifiers, providing comparison between well-known averaged value models (AVMs), parametric averaged value models (PAVM), the switching simulation model and hardware measurements. Analytical expressions for all four admittances present in the dq matrix are derived and analyzed in depth, revealing the accuracy range of the averaged models. Furthermore, a hardware set-up is built, measured and modeled, showing that the switching simulation model captures nonlinear sideband effects accurately. In the end, a multi-pulse diode rectifier feeding a constant power load is analyzed with modified AVM and through detailed simulations of switching model, proving effectiveness of the proposed modifications.
The third part describes implementation and design of a single-phase multi-level single-phase shunt current injection converter based on cascaded H-bridge topology. Special attention is given toward the selection of inductors and capacitors, trying to optimize the selected component values and fully utilize operating range of the converter. The proposed control is extensively treated, including inner current, outer voltage loop and voltage balancing loops. The designed converter is constructed and integrated with measurement system, providing experimental verification. The proposed multi-level single-phase converter is a natural solution for single-phase shunt current injection with the following properties: modular design, capacitor energy distribution, reactive element minimization, higher equivalent switching frequency, capability to inject higher frequency signals, suitable to perturb higher voltage power systems and capable of generating cleaner injection signals.
Finally, a modular interleaved single-phase series voltage injection converter, consisting of multiple paralleled H-bridges is designed and presented. The decoupling control is proposed to regulate ac injection voltage, providing robust and reliable strategy for series voltage injection. The designed converter is simulated using detailed switching simulation model and excellent agreement between theory and simulation results are obtained. The presented control analysis treats different loads, examining robustness of the circuit to load variations. Simulation model and hardware prototype results verify the effectiveness of the proposed wide-bandwidth identification of small-signal dq impedances via single-phase injections.Ph. D.
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Wen, Szu-sheng 1971. "Advances in on-line ultrasonic monitoring of injection molding process." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29784.
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On-line ultrasonic monitoring of conventional and gas-assisted injection molding processes, and temperature measurement using ultrasound, are carried out. A technique utilizing reflection coefficients obtained by a pulse/echo technique is established to monitor the local polymer melt arrival, end of filling, pressure overshoot, solidification, part detachment, plunger retraction, and part ejection in conventional injection molding. The same technique is applied to monitor additional process parameters such as the local gas arrival, start and end of gas injection, gas penetration, and gas blow-through in gas assisted injection molding. During solidification monitoring of a high-density polyethylene part, the solidification front is observed. Also the thickness of solidified layers is determined, and its application in obtaining temperature within the molded part is demonstrated. An approach to determine the local flow front speed of the molten polymer is also proposed.A high-performance buffer rod is fabricated and calibrated as a new type of ultrasonic temperature probe to measure temperature during the extrusion process. The temperature obtained using the ultrasonic technique is comparable with calibrated conventional thermocouples. Comparison between ultrasonic sensors and conventional pressure and temperature probes is also discussed in this study.
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Bai, Gang. "Modeling and experiments on injection into University of Maryland electron ring." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3262.
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Thesis (M.S.) -- University of Maryland, College Park, 2005.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Juozapavicius, Mindaugas. "Mechanisms and kinetics of electron injection in dye-sensitized solar cells." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/50291.
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Electron injection in dye-sensitized solar cells (DSSC) has been extensively studied in the present thesis. Many transient and steady-state experimental techniques were utilized: ultrafast transient absorption spectroscopy in the visible, near-IR and mid-IR regions; time-correlated single photon counting; incident photon to current conversion measurement; temperature dependence of luminescence and device efficiency; determination of energy conversion efficiency parameters. All these methods were collated and analysed as a whole, providing a very detailed picture of the electron injection. It was found that in devices utilizing the most efficient Ru-bipyridyl dyes and commercially viable, performance optimized iodine/triiodide electrolytes, electron injection kinetics are multiphasic, with significant components in the femtosecond, tens of picoseconds and in nanosecond regimes. The broad non-exponential kinetics gave rise to non-100% efficient injection. A fraction of the dyes manage to decay giving rise to luminescence. All of these observations were fully quantified and validated by performing measurements on different systems. The huge length of the delay lines in TAS measurements and very broad probe wavelengths used in the current work gave a very detailed picture of the injection process. Along the way, some very basic experiments were done, which added confidence to the results obtained in the thesis. In addition, interesting phenomena occurring in the ultrafast timescales were found and spectra of transient species such as the dye excited states were recorded. Finally, relevance of the current work to the practical aspects of the solar cells was described and future work discussed.
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Yakymenko, Ivan. "Modelling of injection of electrons by low-dimensional nanowire into a reservoir." Thesis, Linköpings universitet, Teoretisk Fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-145659.
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High-mobility two-dimensional electron gas (2DEG) which resides at the interface between GaAs and AlGaAs layered semiconductors has been used experimentally and theoretically to study ballistic electron transport. The present project is motivated by recent experiments in magnetic electron focusing. The proposed device consists of two quantum point contacts (QPCs) serving as electron injector and detector which are placed in the same semiconductor GaAs/AlGaAs heterostructure. This thesis is focused on the theoretical study of electron flow coming from the injector QPC (a short quantum wire) and going into an open two-dimensional (2D) reservoir. The transport is considered for non-interacting electrons at different transmission regimes using the mode-matching technique. The proposed mode-matching technique has been implemented numerically using Matlab software. Electron flow through the quantum wire with rectangular, conical and rounded openings has been studied with and without an applied electric bias. We have found that the geometry of the opening does not play a crucial role for the electron flow propagation while the conical opening allows the electrons to travel longer distances into the 2D reservoir. When electric bias is applied, the electron flow also penetrates farther into the 2D region. The results of this study can be applied in designing magnetic focusing devices.
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Jiang, Chen. "MB-FICA: An ADL framework for multi-bit fault injection and coverage analysis." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123312.
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Safety-critical systems (SCS) may experience soft errors due to upsets caused by externalevents such as cosmic rays, packaging radiation and thermal neutrons. Traditional errormodeling techniques often only address single bit corruptions and analysis based on populartechniques such as architectural vulnerability factor (AVF) treat each bit as independent.However recent studies have shown a dramatic increase in multi-bit upset (MBU) wherethe failure of a single bit is highly correlated with its neighboring bits. This phenomenon isdue to shrinking transistors and resulting increases in transistor density, making a particlestrike capable of corrupting multiple bits at a time. To assist designers with MBU mitigation in microprocessor register les (RF), we havedeveloped a novel framework (available at http://bhm.ece.mcgill.ca/~mb-fica) to simulate and analyze the eect of MBU and the eectiveness of fault tolerance techniques.Unlike the prior work, our approach performs fault injection in microarchitecture includingmitigation technologies and simulates the consequent behavior of the system running various benchmarks. In this framework, we consider (a) the eect of SRAM layout on MBUpatterns, (b) the data-dependent nature of transient upsets, and (c) runs benchmarks tocompletion to accurately evaluate fault coverage under dierent mitigation techniques. Fault injection is computationally expensive, especially in the context of MBU; consequently, we propose a suite of fault injection acceleration techniques that reduce theexecution time of individual trials by only simulating mitigation techniques when faults arepresent, and stopping simulation entirely when all errors have been detected or corrected.When evaluating parity, SECDED, and 2-bit 2D ECC, our results demonstrate a speedupin the fault injection performance of 14x on average, and up to nearly 60x in one case.Les systemes de securite critiques (SCS) peuvent rencontrer des erreurs doux en raison deperturbations causees par des evenements exterieurs tels que les rayons cosmiques, rayonnement de l'emballage et de neutrons thermiques. Les techniques traditionnelles demodelisation d'erreur souvent ne traitent que des corruptions et d'analyse uniques bitsbases sur des techniques populaires tels que le facteur de vulnerabilite architecturale (AVF)traiter chaque bit comme independant. Toutefois, des etudes rcentes ont montre une augmentation spectaculaire renversement multi-bits (MBU) ou la defaillance d'un seul bit estfortement correlee avec ses bits voisins. Ce phenomene est dû a la diminution des transistors et l'augmentation de la densite des transistors resultant, faisant une gresve de laparticule capable de corrompre plusieurs bits a la fois. Pour aider les concepteurs a MBU attenuation dans les chiers du registre du microprocesseur, nous avons developpe une structure original (disponible sur le site http://bhm.ece.mcgill.ca/~mb-fica) pour simuler et analyser l'eet de MBU et l'ecacite des techniques de tolerance aux pannes. Contrairement au travail avant, notre approche eectuel'injection de fautes dans la microarchitecture qui est integre avec les technologies fauted'attenuation et presente le comportement decoule du systeme executant divers criteres.Dans ce cadre , nous considerons (a) l'eet de la SRAM mise sur les modeles MBU ,(b) la nature des donnees dependant de troubles transitoires , et (c) execute des reperespour l'achevement d'evaluer avec precision la couverture de faute en vertu de dierentestechniques d'attenuation . Injection d'erreur est co^uteuse en ressources informatiques, en particulier dans le contexte de la MBU, par consequent, nous proposons une gamme de techniques d'accelerationde l'injection de fautes qui reduisent le temps d'execution des essais individuels que desimuler des techniques d'attenuation en cas de defauts sont presents, et l'arrêt de la simulation tout quand tout erreurs ont ete detectees ou corrigees. Lors de l'evaluation parite,SECDED, et 2 bits 2D ECC, nos resultats montrent une acceleration de la performance del'injection de fautes de 14x en moyenne, et jusqu'a pres de 60x dans un cas.
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Thangaraj, Jayakar Charles Tobin. "Beam injection and matching studies in the University of Maryland Electron Ring." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3851.
Full textAbstract:
Thesis (M.S.) -- University of Maryland, College Park, 2006.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.