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1
Røstelien, Tonette. "Functional characterisation of olfactory receptor neurone types in heliothine moths : Identification of molecular receptive ranges by the use of single cell recordings linked to gas chromatography and mass spectrometry." Doctoral thesis, Norwegian University of Science and Technology, Department of Biology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-570.
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<p>When the study of this thesis was initiated, hardly any work had been carried out on how plant odour information was encoded by the olfactory RNs in heliothine moths. The method of gas chromatography linked to single cell recordings (GC-SCR) was employed and improved for identifying naturally occurring plant odorants that are detected by single RNs and can be considered as biologically relevant. Three species of the subfamily Heliothinae were included in this work, the two polyphagous <i>H. virescens </i>and <i>H. armigera</i> and the oligophagous <i>H. assulta</i>. The American <i>H. virescens</i> is geographically separated from the other two species. <i>H. armigera</i> and <i>H. assulta</i> are partly sympatric in Asia and Australia.</p><p>The aims of the thesis elucidated in Papers I-IV were as follows:</p><p>1. To identify plant produced volatiles detected by antennal RNs in the three species of the subfamily Heliothinae.</p><p>2. To elucidate whether the single RNs can be classified into distinct types according to their specificity.</p><p>3. To characterise the plant odour RN types by their molecular receptive ranges, sensitivity and specificity.</p><p>4. To compare the specificity of plant odour RN types across the three related species of Heliothinae, with the aim to reveal any differences in the peripheral olfactory system that may have evolved through evolution.</p>
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Savage, Lydia Yvonne. "A buyer's guide for range cooktops and microwave ovens." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39131.
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Orsini, Martin Cesar Daniel. "Geological reservoir modelling for Whicher Range Field tight gas sand." Thesis, Curtin University, 2013. http://hdl.handle.net/20.500.11937/571.
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A poor understanding of the reservoir properties within the Whicher Range area has led to unsuccessful exploration and appraisal strategies. A key driver for this research is to develop a geological reservoir model on the tight gas sand Permian section in the southern Perth Basin that contribute to the development and production of the field by integrating core, well logs and analogue data within a sequence stratigraphic framework and generating a plausible depositional model that constrained the reservoir architecture and facies distribution over the field.
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Meanley, Peter. "The evolution of a range of salt glaze teapots." Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342412.
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Sasaki, Hironobu, Toshio Fukuda, Masashi Satomi, and Naoyuki Kubota. "Growing neural gas for intelligent robot vision with range imaging camera." IEEE, 2009. http://hdl.handle.net/2237/13913.
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Schäfer, Robert [Verfasser], and Oskar von der [Akademischer Betreuer] Lühe. "Characterization of gas-based absolute detectors for the EUV energy range." Freiburg : Universität, 2017. http://d-nb.info/1200352734/34.
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Kihlberg, David, and Amir Ebrahimi. "Wireless Gas Sensor Nodes : With focus on Long Range (LoRa) communication." Thesis, Linköpings universitet, Elektroniska Kretsar och System, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-168669.
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Greenhouse gas emissions in indoor or outdoor areas are dangerous and can have short- or long-term effects on people’s health. There are several methods to monitor the air quality in such environments. This thesis project attempts to design and evaluate a wireless sensor network with two main characteristics such as long range and low power consumption. The sensor network is built upon Long Range Wide Area Network (LoRaWAN) protocol and is composed of sensor nodes and gateways. The sensor nodes are built upon a Raspberry Pi model 3B, a LoRa SX1276 transceiver and gas sensors. The sensors are intended to measure CO2, CH4, temperature, pressure and relative humidity. The collected data is then logged and sent to The Things Network (TTN) via a backhaul connection.
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Tabasso, Alberto. "Spatially resolved measurement of photon fluxes from the JET divertor on the visible range." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286688.
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Abdullah, Abu Hasan. "The application of high inlet swirl angles for broad operating range turbocharger compressor." Thesis, University of Bath, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320555.
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Eshghi, Hosein. "Electron and hole transport in GaN and InGaN." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/2237/.
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Batet, Torrell Óscar. "Investigation of continuous-wave range-resolved lidar systems for gas detection and concentration measurement." Doctoral thesis, Universitat Politècnica de Catalunya, 2011. http://hdl.handle.net/10803/471533.
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The techniques for detection of the atmosphere constituents and their distribution in the space have evolved in the last years driven by needs in the environmental, meteorological and climate science fields and backed by technological developments. The study of the atmosphere behavior, the health risks provoked either by natural or man-made phenomena or the study of the climate change are examples of applications of optical remote sensing techniques that tend to increase as time goes by.
This thesis presents an innovative lidar system for gas detection with range resolution and moderate cost. We study a frequency-modulated continuous-wave lidar system (FMCW) for gas detection in the atmosphere. As a previous step a system for aerosol detection has been studied, which has led to the development of a phase switching technique in the modulating signal to make possible the retrieval of the low-spatial-frequency components of the atmosphere optical parameters. This technique has been tested with an experiment of discrimination of targets close to each other. Then the system has been extended to gas detection either with topographical targets or with aerosols as backscattering medium and a preliminary experiment for the first case has been performed. An analysis of the uncertainty in the gas-concentration retrieval as a function of the signal-to-noise ratio (SNR) has been developed and the extension of the `phase-hop¿ technique for gas-detection FMCW-lidar systems has been proposed.
Previous to this system, a wavelength modulation spectroscopy (WMS) system has been developed as an intermediate step to achieve some degree of expertise in gas detection by means of absorption spectroscopy techniques. Different experiments with gas cells and open-path environments have been carried out.
Finally an optical amplifier which can be used in WMS systems as well as in FMCW-lidar systems is studied, designed, developed and tested. The analysis of the fiber-amplifier behavior for conditions of temperature and pressure change has been performed with a certain dependence of the background with temperature.<br>Les tècniques per a la detecció dels constituents de l’atmosfera i la seva distribució en l’espai ha evolucionat en els últims anys degut a les necessitats en els camps del medi ambient, la meteorologia i les ciències del clima i amb el suport del desenvolupament tecnològic. L’estudi del comportament atmosfèric, els riscos per la salut provocats per fenòmens tant naturals com artificials o l’estudi del canvi climàtic són exemples d’aplicacions de tècniques de teledetecció òptica que tendeixen a incrementar amb el temps. Aquesta tesi presenta un sistema lidar innovador per a la detecció de gasos amb resolució en distancia i amb un cost moderat. S’estudia un sistema lidar d’ona continua i modulat en freqüència FMCW (frequency-modulated continuous-wave) per a la detecció de gasos a l’atmosfera. Com a pas previ, s’ha estudiat un sistema per a detecció d’aerosols que ha portat al desenvolupament d’una tècnica de salts de fase en el senyal modulador per tal de fer possible la recuperació dels components de baixa freqüència espacial dels paràmetres òptics atmosfèrics. Aquesta tècnica s’ha testejat amb un experiment de discriminació de blancs propers entre ells. Llavors el sistema s’ha estès a la detecció de gasos utilitzant com a medi de retrodispersió tant els blancs topogràfics com els aerosols i s’ha fet un experiment preliminar per al primer cas de blancs topogràfics. S’ha analitzat també la incertesa en la recuperació de la concentració de gas com a funció de la relació senyal-soroll (SNR) i s’ha proposat l’extensió de la tècnica phase-hop per a sistemes lidar FMCW per a la detecció de gasos. Previ a aquest sistema, s’ha desenvolupat un sistema WMS (wavelength modulation spectroscopy) com a pas intermedi per tal d’assolir un cert grau d’expertesa en la detecció de gasos per mitjà de tècniques d’absorció espectroscòpica. S’han desenvolupat diferents experiments amb cel·les de gas i també en espais oberts. Finalment s’ha estudiat, dissenyat, desenvolupat i testejat un amplificador òptic que es pot fer servir en sistemes WMS així com en sistemes lidar FMCW. L’anàlisi del comportament de l’amplificador de fibra per a condicions de canvi de pressió i temperatura s’ha realitzat obtenint com a resultat una certa dependència del senyal de background amb la temperatura.
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Allsford, K. V. "Gas-Liquid Dispersion and Mixing in Mechanically Agitated Vessels with a Range of Fluids." Thesis, University of Birmingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512063.
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This study aims at understanding the effect of fluid rheology on gas dispersion and mixing in mechanically agitated vessels. Bulk flow is linked with the two-phase flow in the impeller region and the power drawn by the rotating agitator(s). A base case study using a Rushton Disc Turbine in water is initially reported. Model Newtonian, viscoelastic and shear-thinning fluids (corn syrup, Boger fluids and Carbopol solutions respectively) and a typical fluid (CMC solution) were then used to determine the effects of fluid rheology on flow phenomena and power consumption for single agitators (Disc Turbines and Angle-Bladed Impellersl dual combinations thereof, and InterMIGs under gassed and ungassed conditions in a 0.61 m diameter vessel. Similar experiments were performed in smaller vessels. The relative effectiveness of all the agitator configurations studied at achieving bulk liquid mixing was also determined using a redox reaction technique. The most energy efficient configuration proved to be a large Disc Turbine combined with an equisized Angle-Bladed Impeller (pumping upwards) in both the gassed and ungassed cases. The results presented in this thesis are also related to process design considerations and a technique which predicts the agitator rotational speed and diameter required for achieving optimal mass transfer is developed.
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Masson, Christian. "Numerical prediction of gas-solid particle flows over a wide range of concentration in irregular geometries." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41710.
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The formulation of a co-located equal-order Control-Volume-based Finite Element Method (CVFEM) for the solution of two-fluid models of two-dimensional, planar or axisymmetric, incompressible, gas-solid particle flows is presented in this thesis. The main focus is on the development of a numerical method that allows computer simulation of gas-solid particle flows over a wide range of solid-phase volume concentration in complex irregular geometries.<br>A general two-fluid mathematical model is presented. This model is essentially borrowed from published works in the area of granular flows. It is established here that this model is applicable to gas-solid flows over a wide range of solid-phase concentration. The governing equations of the fluid phase are obtained by volume averaging the Navier-Stokes equations for an incompressible fluid. The solid-phase macroscopic equations are derived using an approach that has been successfully used earlier for the description of granular materials, and is based on the kinetic theory of dense gases. This approach accounts for particle/particle collisions, and permits the determination of the solid-phase macroscopic properties such as viscosity and pressure.<br>The proposed CVFEM is formulated by borrowing and extending ideas put forward in earlier CVFEMs for single-phase flows. In axisymmetric problems, the calculation domain is discretized into torus-shaped elements and control volumes: in a longitudinal cross-sectional plane, or in planar problems, these elements are three-node triangles, and the control volumes are polygons obtained by joining the centroids of the three-node triangles to the midpoints of the sides. In each element, mass-weighted skew upwind functions are used to interpolate the volume concentrations. An iterative variable adjustment algorithm is used to solve the discretized equations.<br>The chosen mathematical model, along with its specializations to single-phase flows and dilute gas-solid flows, and the proposed CVFEM have been applied to several test problems and some demonstration problems. These test and demonstration problems include single-phase flows, dilute-concentration gas-solid particle flows and dense-concentration gas-solid particle flows. The CVFEM results have been compared with results of independent numerical and experimental investigations whenever possible. These comparisons and the results of the demonstration problems are quite encouraging.
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Albusaidi, Waleed. "Techno-economic assessment of radial turbomachinery in process gas applications." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/9872.
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This research aims to assess the causes of inefficient and unstable operation of centrifugal compressors and turboexpanders in process gas applications in order to provide a solution for performance restoration and enhancement. It encompasses thermodynamic and flow evaluations to examine the efficiency and operating range improvement options of new units. Besides, this work is complemented by a technoeconomic analysis to provide a rounded outcome from these studies. In order to achieve the desired objectives, a novel integrated approach has been developed to assess the design and performance of multi-stage centrifugal compressors. The proposed systematic methodology involves five basic elements including evaluation of compressor selection, compressor sizing and casing structure, performance prediction at the design and off-design conditions, modelling of efficiency and head deterioration causes; and stage design evaluation. This will contribute towards evaluating the geometrical parameters of the new units’ designs at the early preliminary design phase, and thus, will be useful to identify the options for efficiency and operating range enhancements. For installed units, this approach can be implemented to assess the cause of inefficient and unstable operation by assessing the available operation data. A method was developed to predict the performance curve of multi-stage centrifugal compressor based on a stage stacking technique. This approach considers the advantages of Lüdtke and Casey-Robinson methods with an incorporation of a methodology for compressor selection and sizing to generate more accurate results. To emphasize the validity of the developed model, it has been evaluated for both low and high flow coefficient applications. The obtained results show a significant improvement in the estimated efficiency, pressure ratio, shaft power and operating range as compared with the existing methods. The centrifugal compressor is designed to run under various operating conditions and different gas compositions with the primary objective of high efficiency and reliability. Therefore, a new iterative method has been developed to predict the equivalent compressor performance at off-design conditions. This technique uses the performance parameters at design conditions as a reference point to derive the corresponding performance characteristics at numerous suction conditions with less dependency on the geometrical features. Through a case study on a gas transport centrifugal compressor, it was found that the developed approach can be applied for design evaluation on the expected variation of working conditions, and for the operation diagnosis of installed units as well. Furthermore, a parametric study has been conducted to investigate the effect of gas properties on the stage efficiency, surge margin, and compressor structure. The obtained results support the need for considering the gas properties variation when the off-design performance is derived. To evaluate the impact of internal blockage on the performance parameters, this study proposed an approach to model the effect of non-reactive deposits, which has been qualified using four operation cases and the obtained results are compared with the internal inspection findings from the stage overhauling process. This also covers the influential aspects of flow blockage on the technical and economic values. Since the main challenge here is to analyze the process gas composition in real time, the influences of the non-reactive deposits have been compared with the effect of the unanticipated gas composition change. Subsequently, it has turned out that the pressureratio parameter is not enough to assess the possibility of flow blockage and unexpected gas properties change. Moreover, it was observed that the stage discharge pressure was more sensitive to the fouled aftercooler comparing with suction and internal blockage. However, the effect of contaminated aftercooler on the surge point and discharge pressure and temperature of the upstream stage was found greater than its impact on the shaft power. Thus, a substantial surge margin reduction was detected when the first stage was operating with a fouled aftercooler comparing with the measured reduction as a result of unanticipated gas properties change. Furthermore, a larger pressure ratio drop was measured in the case of liquid carryover which revealed a more significant impact of the two phases densities difference comparing with the gas volume fraction (GVF) effect. The possibility of hydrate formation has been assessed using hydrate formation temperature (HFT) criteria. Additionally, this research highlights a number of challenges facing the selection of typical centrifugal stage design by assessing the contribution of design characteristics on the operating efficiency and stable flow range. Besides, an empirical-based-model was established to select the optimum impeller and diffuser configurations in order to make a compromise decision based on technical and economic perspective. It was concluded that there is no absolute answer to the question of optimum rotor and stator configuration. The preliminary aerothermodynamic evaluation exposed that the selection of the optimum impeller structure is governed by several variables: stage efficiency, pressure loss coefficient, manufacturing cost, required power cost, resonance frequency and stable operating range. Hence, an evaluation is required to compromise between these parameters to ensure better performance. Furthermore, it was argued throughout this study that the decision-making process of the typical stage geometrical features has to be based upon the long-term economic performance optimization. Thus, for higher long-term economic performance, it is not sufficient to select the characteristics of the impeller and diffuser geometry based on the low manufacturing cost or efficiency improvement criterion only. For turboexpanders, a simple and low cost tool has been developed to determine the optimum turboexpander characteristics by analysing the generated design alternatives. This approach was used in designing a turboexpander for hydrocarbon liquefaction process. Moreover, since the turboexpanders are expected to run continuously at severe gas conditions, the performance of the selected turboexpander was evaluated at different inlet flow rates and gas temperatures. It has turned out that designing a turboexpander with the maximum isentropic efficiency is not always possible due to the limitations of the aerodynamic parameters for each component. Therefore, it is necessary to assess the stage geometrical features prior the construction process to compromise between the high capital cost and the high energetic efficiency.
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Wickramaratne, Chatura. "Experimental Study of High-Temperature Range Latent Heat Thermal Energy Storage." Scholar Commons, 2017. https://scholarcommons.usf.edu/etd/7451.
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Among all thermal energy storage (TES) systems, latent heat thermal energy storage (LHTES) attracts high interest due to its high energy density and high exergetic efficiency. Due to the high enthalpy of fusion and low cost, inorganic salts are becoming popular as phase change materials and are used as the storage media in LHTES systems. The main drawbacks for the inorganic salts are their low thermal conductivity and high reactivity above 500°C. Therefore, designing a cost-effective containment at these conditions with longevity is a challenge. Macro-encapsulation of the PCM is one way to solve both the PCM containment issue as well as the low thermal conductivity problem. However, finding a practically viable encapsulation technique is a challenge especially for temperatures above 500°C.
In the present study, encapsulation techniques were investigated for two temperature ranges; 500°C – 600°C and 600°C above. Metallic encapsulation was adopted for the 500°C – 600°C temperature. Commercially available, low-cost carbon-steel tubes were used, and the encapsulation shape was cylindrical. A 200µm coating of Ni was applied to strengthen the corrosion resistance. For temperatures above 600°C, a novel approach involving the use of ceramic materials was investigated for encapsulating chloride based PCMs. Low-cost ceramics with excellent thermal and chemical stability under molten-salt conditions were identified as the encapsulants. The influence of sintering temperature on the reactivity of feldspar, ball clay, kaolin and the mixture thereof with molten sodium chloride was investigated. The results were used to develop an optimum ceramic capsule fabrication procedure, using a green ceramic body followed by sintering at 1190°C. An innovative sealing process of in-situ layered eutectic formation was introduced. Sealing was performed at a temperature above the eutectic melting point of the salt mixture but below the individual melting points of each salt. The fabricated capsule survived more than 500 thermal cycles without showing degradation in its thermo-physical properties. Alumina (99%) based capsule containing NaCl-KCl was tested successfully for 1000 thermal cycles with a PCM weight loss of less than 5%.
A lab-scale setup was designed and constructed to test an industry scalable LHTES system suitable for supplementing heat to a steam-powered cycle. Metallic cylindrical capsules were used with a eutectic of sodium sulfate (Na2SO4) and potassium chloride (KCl), which melts at 515°C, as the PCM for energy storage. This system was modeled and validated with experimental measurements. The calculated ratio of exergy to energy efficiency was around 89% (for 380-535°C). Flow irregularities were found due to a bend in the flow channel. Therefore, flow conditioners were investigated. A modified system with the flow conditioners and radiation shields showed 98% exergy to energy efficiency ratio (for 495-535°C). The overall efficiency of the system, however, was found to be low due to the heat losses from the storage tank.
Finally, a novel design of a TES system using spherical capsules is proposed with additional enhancement gained from the experimental work on the lab-scale LHTES system. The innovation of this design lies in the manufacturing process to forms multiple spherical capsules using sheet metals. The adoptability of this technique for higher or lower temperature LHTES applications depends on the properties of the selected sheet metal. Any formable sheet metal can be used depending on the compatibility with PCM and HTF.
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Kucheruk, V. Yu, I. A. Dudatiev, В. Ю. Кучерук, and І. А. Дудатьєв. "Physical nature metrological select of range of infrared waves to optical absorbtion methods of control flue gas boilers." Thesis, ВНТУ, 2013. http://ir.lib.vntu.edu.ua/handle/123456789/8105.
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Gaj, Anita [Verfasser]. "Ultralong-range Rydberg molecules in external electric and magnetic fields / Anita Gaj." München : Verlag Dr. Hut, 2017. http://d-nb.info/1149579536/34.
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Sciacca, Francesco G. P. "Analogue readout and signal processing for micro strip gas chambers of the compact muon solenoid at LHC." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391719.
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Gutierrez, Carlos Eduardo. "DYNAMIC SIMULATION OF TURBINE ENGINE USED WITH MOLTEN CARBONATE FUEL CELL FOR POWER GENERATION IN THE MEGAWATT RANGE." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1389268833.
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Krall, Kerstin Ellen [Verfasser], and Bernd [Akademischer Betreuer] Jähne. "Laboratory Investigations of Air-Sea Gas Transfer under a Wide Range of Water Surface Conditions / Kerstin Ellen Krall ; Betreuer: Bernd Jähne." Heidelberg : Universitätsbibliothek Heidelberg, 2013. http://d-nb.info/117704076X/34.
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Pasieka, Lucian. "The applicability of the mass-flow-model according to iso 6358 with the parameter critical conductance c and critical pressure ratio b for gases in high-pressure range up to 300 bar." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71162.
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Mass flow models for gaseous media describe the relationship between gas flow through throttle elements depending on pressure, temperature and type of medium. These models are used to calculate pneumatic components, to simulate pneumatic systems or to plan facilities. The known flow models are verified for ideal gases, such those as according to ISO 6358-1 (International Standard ISO 6358- 1: pneumatic fluid power – Determination of flow-rate characteristics of components using compressible fluids: General rules and test methods for steady-state flow, 2013). But they fail with real gases, especially at higher pressures. The objective of this contribution is to recommend a simple-touse model for the mass flow calculation of real gases. The advantage of the C and b model is the use of only two parameters. A testbench for high pressure up to 300 bar was used for model verification with air and hydrogen. The Library for standard dry air and hydrogen up to 1000 bar was used for the state variables of the real gases. The parameters C and b are obtained, applied and verified in the state space of real gas. With the C and b parameter it is possible to simulate not only the single component (valve, throttle, nozzle and so on) but also the whole system with a complete system simulation, like such as hydrogen filling stations.
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Hedlund, Emma. "Studies of Heavy Ion Induced Desorption in the Energy Range 5-100 MeV/u." Doctoral thesis, Uppsala University, Division of Nuclear and Particle Physics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8654.
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<p>During operation of heavy ion accelerators a significant pressure rise has been observed when the intensity of the high energy beam was increased. The cause for this pressure rise is ion induced desorption, which is the result when beam ions collide with residual gas molecules in the accelerator, whereby they undergo charge exchange. Since the change in charge state will affect the bending radius of the particles after they have passed a bending magnet, they will not follow the required trajectory but instead collide with the vacuum chamber wall and gas are released. For the Future GSI project FAIR (Facility for Antiproton and Ion Research) there is a need to upgrade the SIS18 synchrotron in order to meet the requirements of the increased intensity. The aim of this work was to measure the desorption yields, η, (released molecules per incident ion) from materials commonly used in accelerators: 316LN stainless steel, Cu, Etched Cu, gold coated Cu, Ta and TiZrV coated stainless steel with argon and uranium beams at the energies 5-100 MeV/u. The measurements were performed at GSI and at The Svedberg Laboratory where a new dedicated teststand was built. It was found that the desorption yield scales with the electronic energy loss to the second power, decreasing for increasing impact energy above the Bragg Maximum. A feasibility study on the possibility to use laser refractometry to improve the accuracy of a specific throughput system was performed. The result was an improvement by up to 3 orders of magnitude, depending on pressure range.</p>
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Dann, Martin Richard. "Experimental study of two dimensional fluid and solid '3He adsorbed on preplated graphite." Thesis, Royal Holloway, University of London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325525.
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The heat capacity of 3He adsorbed on Grafoil (exfoilated graphite) preplated with four layers of 4He was measured between 1 and 50mK. The heat capacity was found to be linear up to 4OmK. At 3He surface densities below 4nm-2 two dimensional Fermi liquid behaviour was found and values of the hydrodynamic effective mass and Landau parameter Ff inferred. Subsequent steps in the heat capacity as a function of coverage were taken as evidence of independent 2D Fermi fluids. A low field DC SQUID pulsed NMR spectrometer was developed for future studies of magnetic order in 2D solid 3He films at ultralow temperatures
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Mularcik, Bradley S. "Virtual Moving Air Gap for the Speed Range Improvement of a Dual Stator Axial Flux Motor." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1340404856.
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Sando, Brett G. "The geology, petrology and geochemistry of the Tommys Gap area in the Giles Creek Synform, MacDonnell Ranges, South-Eastern Arunta Block, Northern Territory /." Adelaide, 1987. http://web4.library.adelaide.edu.au/theses/09SB/09sbs218.pdf.
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Ali, Imad. "CFD prediction of stratified and intermittent gas-liquid two-phase turbulent pipe flow using RANS." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/cfd-prediction-of-stratified-and-intermittent-gasliquid-twophase-turbulent-pipe-flow-using-rans(4fa69a04-51b9-4b5e-8bef-76cc93135407).html.
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The transport of multi-phase flow in pipelines can be met in a wide range of industrial applications, including the oil and gas industry, showing great savings in developments. In addition, as the exploration of new fields in oil and gas expands to harsh environments, such as ocean or polar, the multi-phase flow transport sometimes becomes the only feasible option. The important features of such multi-phase flow applications include flow regimes, pressure drop and liquid holdup. The precise estimation of these parameters has significant technical and economical impacts on the design and operation of an oil and gas pipelines. Many prediction correlations and methods have been developed; computational fluid dynamics (CFD) being one of them. This type of modelling approach has many advantages over the conventional approaches such as its ability to solve 3D transient problems; offering access to a wealth of information which with conventional techniques is extremely difficult to obtain. Therefore, interest in applying CFD for multi-phase flow transport in pipelines has been on the rise. This thesis is aimed at presenting CFD simulations based on the use of the Volume of Fluid model (VOF) approach for various conditions of gas-liquid turbulent flow in a horizontal circular pipe. In the current VOF formulation in addition to the secondary phase transport equation, a geometric reconstruction technique based on a piecewise-linear interface construction approach is used for reconstructing the interface. A number of multi-phase studies using different turbulence models to the current one have recently appeared in the open literature for simple flow geometries such as rectangular channels. However, most of them assume specific boundary conditions (such as fully-separated phases for stratified flows, the use of square wave at the inlet to represent slug flow or imposing an interfacial disturbance to initiate slugging). These require case-by-case empirical information such as, interfacial roughness for stratified- or slug frequency for intermittent-flow. However, most of them have not presented any detailed validation of their results. The former two points are very crucial for the design of transport pipelines as a pre-knowledge of the operative flow regime and empirical information are not available at the design stage. The predictive accuracy of the present simulations is tested against most common mechanistic approaches and detailed measurements of stratified two-phase flow in a horizontal pipe of Strand (1993) and have been found to be in reasonable quantitative agreement. For the intermittent flow type cases, the numerical results are qualitatively compared against experiments in a horizontal pipe of Al-alweet (2008). The computed flow data of intermittent flow type are further tested against some empirical and mechanistic correlations; the numerical results are qualitatively in a reasonable agreement. Gas compressibility effects on the simulations of slug flow are also explored and are found to bring about some positive benefit. Overall, the predictive accuracy of the present approach is reasonable and promising, demonstrating the ability of the model to predict different types of flow regimes found in two-phase pipe flows. Furthermore, the proposed model shows potential for general applicability to the design of two-phase pipeline systems as it does not require pre-knowledge of the flow regime or any case-by-case empirical information.
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Ceballos, Cesar Augusto Celis. "Modelo computacional da camada ganglionar da retina para estudo de mecanismos responsáveis por sua faixa dinâmica." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-23102013-150346/.
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Teoricamente, conexões por sinapses elétricas entre neurônios poderiam levar ao aumento da faixa de resposta dinâmica da rede neural. A faixa de resposta dinâmica de uma rede de neurônios pode ser definida como a faixa de valores de intensidade dos estímulos de entrada para a qual o conjunto de neurônios produz resposta antes de atingir a saturação. Em um cenário biológico, propôs-se que junções gap entre células ganglionares da retina aumentariam a faixa dinâmica da retina. O teste experimental dessa proposta apresenta várias dificuldades, o que torna a modelagem computacional uma alternativa metodológica para o estudo do papel das sinapses elétricas na faixa dinâmica da camada ganglionar da retina. O objetivo deste trabalho foi a construção de um modelo biologicamente plausível da camada ganglionar da retina da salamandra, submetida a sinais de entrada realísticos conforme evidências experimentais e com a inclusão de sinapses elétricas conectando suas células, para estudar in silico os possíveis efeitos dessas sinapses elétricas sobre a faixa dinâmica da camada ganglionar. A camada ganglionar foi modelada como uma rede bidimensional cujos neurônios foram modelados pelo formalismo de Hodgkin-Huxley. Cada neurônio recebeu um de dois tipos de entrada sináptica, transiente ou sustentada. Avaliou-se o efeito da inibição pré-sináptica das células ganglionares e o efeito de diferentes padrões de conectividade mediados pelas sinapses elétricas. Os resultados sugerem que o acoplamento elétrico aumenta a sensibilidade do sistema e altera o ponto de saturação, mas não necessariamente aumenta a faixa dinâmica.<br>Theoretically, connections by electrical synapses between neurons could lead to an increase in their dynamic range. The dynamic range of a network of neurons can be defined as the range of input stimuli values for which the network responds before saturation. In a biological scenario, it is hypothesized that gap junctions between retinal ganglion cells may increase the dynamic range of the retina. However, the experimental testing of this hypothesis presents several difficulties, which makes computational modeling a methodological alternative to study the role of electrical synapses on the dynamic range of the ganglion cell layer of the retina. In this work we constructed a biologically plausible computational model of the ganglion cell layer of the salamander retina. A bidimensional network was built with cells modeled by the Hodgkin-Huxley formalism connected via gap junctions and subject to realistic inputs constrained by experimental evidence, to study in silico the effects of gap junctions on the dynamic range of the model. We studied the effect of different gap junction-mediated connectivity patterns, input type combinations (transient, sustained and mixed between the two) and presynaptic inhibition on the dynamic range. Our results suggest that gap junction coupling increases the network\'s sensitivity and alters the saturation point but not necessarily increases the dynamic range.
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Schmidt-Grund, Rüdiger, Hannes Krauß, Christian Kranert, Michael Bonholzer, and Marius Grundmann. "Temperature dependence of the dielectric function in the spectral range (0.5–8.5) eV of an In2O3 thin film." American Institute of Physics, 2014. https://ul.qucosa.de/id/qucosa%3A31187.
Full textAbstract:
We present the dielectric function of a bcc-In2O3 thin film in the wide spectral range from nearinfrared
to vacuum-ultraviolet and for temperatures 10 K–300K, determined by spectroscopic
ellipsometry. From the temperature dependence of electronic transition energies, we derive
electron-phonon coupling properties and found hints that the direct parabolic band-band transitions
involve In-d states. Further we discuss possible excitonic contributions to the dielectric
function.
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Djerfi, Kheireddine. "Non-linear magnetoconductivity of the two-dimensional electron fluid and solid on liquid helium." Thesis, Royal Holloway, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325526.
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Schmidt-Grund, Rüdiger, Christian Kranert, Wenckstern Holger von, Vitaly Zviagin, Michael Lorenz, and Marius Grundmann. "Dielectric function in the spectral range (0.5–8.5)eV of an (Alx Ga1−x )2O3 thin film with continuous composition spread." American Institute of Physics, 2015. https://ul.qucosa.de/id/qucosa%3A31190.
Full textAbstract:
We determined the dielectric function of the alloy system (AlxGa1−x)2O3 by spectroscopic
ellipsometry in the wide spectral range from 0.5 eV to 8.5 eV and for Al contents ranging from
x = 0.11 to x = 0.55. For the composition range x<0.4, we observe single phase material in the
b-modification and for larger Al content also the occurrence of γ-(Al,Ga)2O3. We derived spectra of
the refractive index and the absorption coefficient as well as energy parameters of electronic bandband
transitions by model analysis of the dielectric function. The dependence of the dielectric functions
lineshape and the energy parameters on x is highly continuous, reflecting theoretical expectations.
The data presented here provide a basis for a deeper understanding of the electronic properties
of this material system and may be useful for device engineering.
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SANDOVAL, VELASQUEZ Andres Libardo. "Noble gas and CO2 isotopic signatures of the lithospheric mantle underneath Mexico and the Canary Islands: clues from mantle xenoliths and arc lavas." Doctoral thesis, Università degli Studi di Palermo, 2022. http://hdl.handle.net/10447/533636.
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Studying the isotopic composition of fluids trapped in mantle xenoliths opens avenues to understand the origin and cycling of volatiles in the Earth’s upper mantle. In this PhD dissertation, new and in most cases the very first data regarding the isotopic (noble gases and CO2) characterization of the lithospheric mantle portions of three different geodynamic environments are presented: (i) Central and NW Mexico, a continental setting dominated by extension; (ii) the Transmexican Volcanic Belt (TMVB) a subduction setting, and (iii) the Canary Islands, particularly El Hierro and Lanzarote, two oceanic islands formed by mantle plume-derived intraplate volcanism. In total 32 peridotites (including spinel lherzolites, spinel harzburgites, 1 pyroxenite and 1 dunite) and four arc lavas (from the TMVB) were investigated.
To characterize the isotopic signature of the Mexican lithospheric mantle, the present work was focused on the analysis of fluid inclusions entrapped in mantle xenoliths found in pyroclastic deposits of the Ventura Espiritu Santo Volcanic Field (VESVF), the Durango Volcanic Field (DVF), the San Quintin Volcanic Field (SQVF) (three Quaternary monogenetic volcanic fields formed in the Basin and Range extensional province). Fluid inclusions in olivine phenocrysts found in arc lavas from the Sierra Chichinautzin Volcanic Field (SCN) (a Quaternary monogenetic field located in the Transmexican Volcanic Belt (TMVB)) were also analyzed. According to the petrographic analysis, all xenoliths exhibit similar mineralogy (Ol> Opx> Cpx >> Sp). The VESVF xenoliths, in particular, bring textural evidence of interstitial glass veins bearing dendritic trails of secondary melt and fluid inclusions related to pervasive mantle metasomatism driven by carbonate-rich silicate melts. Inclusions are composed of silicate glass ± CO2 ± Mg-Ca carbonates ± pyrite as indicated by Raman microspectroscopy. Excluding samples possibly affected by secondary processes, the averages Rc/Ra ratios (3He/4He ratios corrected for atmospheric contamination) measured in Mexican localities are within the MORB-like range: VESVF = 7.39 ± 0.14 Ra (1SD, n = 30), DVF= 8.39 ± 0.24 Ra (1SD, n = 10), SQVF = 7.43 ± 0.19 Ra (1SD, n = 1) and SCN lavas = 7.24 ± 0.33 Ra (1SD, n = 4). This noble gas similarity between the VESVF and SCN samples supports the existence of a homogeneous mantle in central Mexico. The 3He/4He signatures observed in xenoliths suggest that (i) either the mantle He budget was scarcely modified by the Farallon plate subduction, and/or (ii) that any (large) crustal contribution was masked by a later metasomatism/refertilization episode, possibly driven by the upwelling mantle from the asthenosphere and the subsequent Basin and Range extension. The association between glass veins and fluid inclusions in VESVF xenoliths revealed that the metasomatism/ refertilization was driven by a silicate-rich melt which is consistent with a calculated helium residence time in the VESVF mantle (20 to 60 Ma) that overlaps the timing of the above geodynamic events. It is proposed that, after the refertilization event (e.g., over the last ~20 Ma), the lithospheric mantle has evolved in a steady-state, becoming slightly more radiogenic. The relative proximity between the DVF and the VESVF suggests a similar process should have happened beneath Durango, and that the difference in 3He/4He ratios with the VESVF is likely to be associated with different ages of mantle refertilization and He residence times (more recent for the DVF mantle; 4 to 10Ma). The Ar and Ne systematics reflect a mixing between MORB-like upper mantle and atmosphere-derived fluids. The mantle beneath the SQVF and the DVF seems to be more impacted by the interaction with atmospheric fluids, as proved by a systematic decrease in 40Ar/36Ar and 4He/20Ne ratios from central (VESVF) to western Mexico (DVF, SQVF) It is proposed that these atmospheric components were likely air-derived fluids recycled by the Farallon plate subduction. 3He fluxes (0.027 - 0.080 mol/g), 4He production rates (340 - 1000 mol/yr), and mantle CO2 fluxes (3.93 x 107 mol/yr to 1.18 x 108 mol/yr) were also estimated using the helium isotopic values measured in VESVF mantle xenoliths. Finally, DVF and VESVF nodules exhibit CO2/3He ratios comparable to those of the upper mantle (from 3.38 x 108 to 3.82 x 109) but more positive δ13C values (between -1.0 and -4.0‰), supporting the involvement of a recycled crustal carbonate component likely inherited by the Farallon plate subduction. Conversely, the SCN samples exhibit δ13C values within the MORB range (comparable to other values previously reported in fluid inclusions and fumaroles from Popocatépetl, Colima and Ceboruco volcanoes) and unlike the mantle beneath VESVF-DVF, indicate a negligible mantle contamination by subduction-related crustal carbon.
The Canary Islands, in the central-eastern Atlantic, are among the most enigmatic Oceanic Island provinces on Earth, as the mantle source feeding their volcanism is spatially heterogeneous and with a multiplicity of involved components. Multi-isotope whole-rock studies have long revealed the presence of a recycled oceanic crust/lithosphere in the mantle. However, noble gas systematics have been more challenging to interpret, and carbon isotope data have remained sparse and incomplete. Our very first fluid inclusion data for El Hierro and Lanzarote nodules indicate carbon isotopic compositions of CO2 (δ13C) range from –2.38 to –1.23‰ in pyroxenes and from –0.19 to +0.96‰ in olivines. These unusually positive δ13C values, well above the typical upper mantle range (–8‰<–4‰), prove, for the first time, the presence of a regional recycled crustal carbon component in mantle beneath the Canary Islands. We interpret this 13C-rich component as inherited from a mantle metasomatism event(s) driven by fluids carrying carbon from subducted altered oceanic crust (AOC) and/or oceanic lithosphere (OL). Regarding noble gas isotopes, El Hierro xenoliths identify a depleted mantle source with MORB-like He signature. The average Rc/Ra ratio (3He/4He normalized to air ratio and corrected for atmospheric contamination) of 7.45±0.26 Ra (2SD, n = 14) overall indicates a marginal role played by past subduction events in modifying the local mantle He budget. Instead, Lanzarote xenoliths point to a more radiogenic mantle with an average of 5.97±0.44 Ra (2SD, n = 13) which we interpret as reflecting the involvement of an EM component. When put in the context of previous 3He/4He measurements in fluid inclusions and surface gases along the Canary archipelago, these results confirm an overall west-to-east decrease of Rc/Ra ratios (from El Hierro to Lanzarote), which may reflect a combination of i) increasing contributions of the African continental lithosphere, ii) the addition of radiogenic 4He during magma migration in the oceanic crust (whose thickness increases eastward) and/or iii) magma ageing. Finally, as proposed for Mexico, the involvement of depleted mantle-like fluids, variably admixed with air-derived components (possibly recycled via paleo-subduction event(s)), is corroborated by Ne-Ar isotopic compositions.
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Lanz, B. (Brigitte). "Compact current pulse-pumped GaAs–AlGaAs laser diode structures for generating high peak-power (1–50 watt) picosecond-range single optical pulses." Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526213569.
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Abstract Although gain-switching is a simple, well-established technique for obtaining ultrashort optical pulses generated with laser diodes, the optical energy in a pulse achievable from commercial structures using this technique is no more than moderate and the ‘spiking’ behaviour seen at turn-on is likely to evolve into trailing oscillations. This thesis investigates, develops and improves laser diodes in order to offer experimentally verified solutions for maximizing the optical energy so as to achieve a peak power of several watts in a single optical pulse of picosecond-range duration in the gain-switching operation regime, and for suppressing the energy located in any trailing pulses to a negligible level relative to the total optical pulse energy. This was addressed by means of either (i) an ultrashort pump current pulse with an amplitude range ~(1–10) A or (ii) custom laser diode structures, both options being capable of operating uncooled at room temperature (23±3°C). For the first solution a unique superfast gallium arsenide (GaAs) avalanche transistor was utilized as a switch in order to achieve an injection current pulse with a duration of < 1 ns, which is short enough to generate only a first optical ‘spike’ when pumping a commercial laser diode. The most promising structure with regard to the second solution was an edge-emitting semiconductor laser having a strongly asymmetric broadened double heterostructure with a relatively thick active layer. Laser pulses with full width at half maximum (FWHM) of ~100 ps and an optical energy of >3 nJ but with some trailing oscillations were achieved in experiments employing injection current pulses in the nanosecond range with an amplitude of ≤17 A, generated using inexpensive silicon (Si) electronics. The performance was improved by introducing a saturable absorber (SA) into the laser cavity, which suppressed the formation of trailing oscillations, resulting in a single optical pulse<br>Tiivistelmä ”Gain switching” (vahvistuskytkentä) on tunnettu tekniikka lyhyiden (<100 ps) optisten pulssien generoimiseen laserdiodeilla. Kaupallisia laserdiodirakenteita käyttäen optinen energia rajoittuu kuitenkin 10…100 pJ:n tasolle. Tällöinkin, erityisesti suurilla energiatasoilla, optisessa pulssissa ilmenee voimakkaita jälkioskillaatioita. Tässä väitöskirjassa tutkittiin ja kehitettiin kokeellisesti varmennettuja laserdiodilähetinrakenteita tavoitteena saavuttaa >1 nJ:n optisen pulssin energia ja ~100 ps:n pulssinpituus gain-switching -toimintamoodissa. Tavoitteena oli myös minimoida jälkipulssien energia. Tutkimuksen pääsisältönä on kaksi toimintaperiaatetta: Toisessa tekniikassa päähuomio kohdistuu laseridiodin virta-ajuriin, johon kehitettiin elektroniikka, joka kykenee tuottamaan nopeita virtapulsseja laajalla pulssivirta-alueella. Virtapulssin nopeuden kasvattamisen (<1 ns) osoitettiin edistävän gain switching -ilmiötä. Toisena tekniikkana tutkittiin räätälöityä laserdiodirakennetta, joka sisäisen toimintansa perusteella tuottaa dynaamisessa ohjaustilanteessa tehokkaan ja nopean laserpulssin. Kummankin periaatteen osoitettiin toimivan huonelämpötilassa (23±3°C) ilman erillistä jäähdytystä. Ensimmäisessä ratkaisussa käytettiin nopeaa gallium-arsenidi (GaAs) -avalanchetransistoria virtakytkimenä, jolla saavutettiin <1 ns FWHM injektiovirtapulssi 10 A:n virtatasolla. Tällainen virtapulssi on riittävän lyhyt virittämään ”gain switching” -ilmiön nJ-energiatasolla. Lupaavin rakenne toiseksi ratkaisuksi oli reunaemittoiva puolijohdelaseri, jossa epäsymmetrinen aaltoputki ja aktiivinen alue ovat sijoitettu normaalista laserdiodirakenteesta poiketen rinnakkain. Tällä rakenteella voitiin tuottaa ~100 ps levyisiä (FWHM) ja >3 nJ optisen kokonaisenergian omavia laserpulsseja edullisella pii-pohjaisella (Si) elektroniikalla luoduilla 1.5–2 ns:n (FWHM) ≤17 A injektiovirtapulsseilla. Suorituskykyä saatiin edelleen parannettua istuttamalla saturoiva absorbaattori (SA) laserin optiseen onteloon. Tämän osoitettiin vähentävän jälkioskillaatioiden muodostumista
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Arenas, Buendia Cristina. "Enhanced fluid characterization in the millimeter-wave band using Gap Waveguide Technology." Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/62781.
Full textAbstract:
[EN] Microfluidic systems have been emerged as a promising technology for molecular analysis, biodefence and microelectronics. The properties of the microfluidic devices, such as rapid sample processing and the precise control of fluids, have made them attractive candidates to replace traditional experimental approaches. Microfluidic devices are characterized by fluidic channels with dimensions on the order of tens to hundreds of micrometers. Structures with this size enable the integration of lab-on-chip technology, which allows processing miniaturized devices for fluid control and manipulation.
Fluid sensing by microwave sensors based on the RF analysis offers new possibilities for the characterization of mediums by non-invasive methods. Dielectric measurement of fluids is important because it can provide the electric or magnetic characteristics of the materials, which proved useful in many research and development fields, such as molecular biology and medical diagnosis.
Several techniques are available in the frequency domain for analyzing the dielectric properties of liquids and their composition. We are focused in resonant cavity techniques for fluid characterization in the millimeter-wave range. However, these techniques are incompatible with lab-on-chip process due its dimensions in this frequency range. In this context, a new structure called gap waveguide appears as a good candidate to overcome the principal drawbacks of the classical resonant cavities.
This thesis presents the development of the gap waveguide technology in the millimeter-wave band. Other conventional technologies are discussed as well, to compare them with the performance in terms of losses of the gap waveguide. We also present the resonator design based on gap waveguide with the purpose of making the gap waveguide a technology capable of working in the microfluidic sensing domain. In this context, we propose a comparative study between gap waveguide and Substrate Integrated Cavity (SIC) with the aim to characterize the fluid permittivity at 60 GHz. With this purpose, several prototypes have been manufactured with PCB ("Printed Circuit Board") and Low Temperature Co-fired Ceramic (LTCC) technologies. A work in the LTCC laboratory has been done with the purpose of validating some steps in the LTCC process which are key in the gap waveguide manufacturing, especially those related with the creation of cavities (external and internal) using LTCC materials.<br>[ES] Los sistemas microfluídicos han emergido como una tecnología prometedora para el análisis molecular, biodefensa y microelectrónica. Las propiedades de los dispositivos microfluídicos tales como el procesamiento rápido de las muestras y el control de los fluidos, les han hecho atractivos candidatos para reemplazar los tradicionales métodos experimentales. Los dispositivos microfluídcos están caracterizados por canales fluídicos con dimensiones del orden de decenas a centenares de micrómetros. Las estructuras con estos tamaños permiten la integración de la tecnología "lab-on-chip", la cual permite el procesamiento de dispositivos miniaturizados para el control y la manipulación de fluidos.
La detección de fluidos a través de sensores de microondas basados en el análisis de radiofrecuencia ofrece nuevas posibilidades para la caracterización de medios a través de métodos no invasivos. Las medidas dieléctricas de los fluidos son importantes debido a que pueden proporcionar información las características eléctricas o magnéticas de los materiales, siendo útil en muchos campos de investigación y desarrollo tales como biología molecular o para realizar diagnósticos médicos.
En el dominio frecuencial, varias tecnologías están disponibles en el mercado para analizar las propiedades dieléctricas y la composición de los líquidos. En esta tesis, estamos enfocados en las técnicas basadas en cavidades resonantes para la caracterización de fluidos en el rango de las ondas milimétricas. Sin embargo, estas técnicas son incompatibles con los procesos "lab-on-chip" debido a sus dimensiones en esta banda de frecuencia. En este contexto, una nueva estructura guía onda denominada "gap waveguide" aparece como un buen candidato para solventar los principales inconvenientes de las clásicas cavidades resonantes.
En esta tesis se ha desarrollado la tecnología "gap waveguide" en la banda de ondas milimétricas. Otras tecnologías convencionales serán estudiadas para comparar el rendimiento de todas ellas en términos de pérdidas. También se presenta en esta tesis, el diseño de resonadores basados en la tecnología "gap waveguide" con el propósito de hacer esta tecnología compatible con la detección microfluídica. En este contexto, proponemos un estudio comparativo entre las tecnologías "gap waveguide" y "Substrate Integrated Cavity" (SIC) con el objetivo de caracterizar la permitividad de los fluidos a 60 GHz. Con este propósito, varios prototipos han sido fabricados usando las tecnologías PCB ("Printed Circuit Board") y LTCC ("Low Temperature Co-fired Ceramic". Un importante trabajo en el laboratorio LTCC se realizó para validar algunas de las etapas del proceso LTCC que eran la clave para la fabricación de prototipos basados en "gap waveguide", como la creación de cavidades (externas e internas) usando materiales LTCC.<br>[CAT] Els sistemes microfluídics han emergit com una tecnologia prometedora per a l'anàlisi molecular, biodefensa i microelectrònica. Les propietats dels dispositius microfluídics com el processament ràpid de les mostres i control dels fluids, els han fet atractius candidats per a reemplaçar les tradicionals aproximacions experimentals. Els dispositius microfluídcs estan caracteritzats per canals fluídics amb dimensions de l'orde de desenes a centenars de micròmetres. Les estructures amb estes grandàries permeten la integració de la tecnologia "lab-on-chip", la qual permet el processament de dispositius miniaturitzats per al control i la manipulació de fluids.
La detecció de fluids a través de sensors de microones basats en l'anàlisi de radiofreqüència oferix noves possibilitats per a la caracterització de sistemes a través de mètodes no invasius. Les mesures dielèctriques dels fluids són importants pel fet que poden proporcionar informació sobre les característiques elèctriques o magnètiques dels materials, sent útil en molts camps d'investigació i desenvolupament com biologia molecular o per a realitzar diagnòstics.
En el domini freqüencial, diverses tecnologies estan disponibles en el mercat per analitzar les propietats dielèctriques i la composició dels líquids. En aquesta tesi, estem enfocats en les tècniques basades en cavitats ressonants per a la caracterització de fluids en el rang de les ones mil·limètriques. No obstant això, aquestes tècniques són incompatibles amb els processos "lab-on-chip" a causa de les seues dimensions en aquesta banda de freqüència. En aquest context, una nova estructura guia onda denominada "gap waveguide" apareix com un bon candidat per a resoldre els principals inconvenients de les clàssiques cavitats ressonants.
En aquesta tesi s'ha desenvolupat la tecnologia "gap waveguide" en la banda d'ones mil·limètriques. Altres tecnologies convencionals seran estudiades per a comparar el rendiment de totes elles en termes de pèrdues.També es presenta en esta tesi el disseny de ressonadors basats en la tecnologia "gap waveguide" amb el propòsit de fer esta tecnologia compatible amb la detecció microfluídica. En aquest context, proposem un estudi comparatiu entre les tecnologies "gap waveguide" i "Substrate Integrated Cavity" (SIC) amb l'objectiu de caracteritzar la permitivitat dels fluids a 60 GHz. Amb aquest propòsit, diversos prototips han sigut fabricats usant les tecnologies PCB ("Printed Circuit Board") i LTCC ("Low Temperature Co-fired Ceramic". Un important treball en el laboratori LTCC es va realitzar per a validar algunes de les etapes del procés LTCC que eren la clau per a la fabricació de prototips basats en "gap waveguide", com la creació de cavitats (externes i internes) usant materials LTCC.<br>Arenas Buendia, C. (2016). Enhanced fluid characterization in the millimeter-wave band using Gap Waveguide Technology [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62781<br>TESIS
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Iker, Theresa M. "Gals Getting "Reno-Vated": Individual Transformation and National Change During the Rise and Fall of the Reno Divorce Ranches." Scholarship @ Claremont, 2014. http://scholarship.claremont.edu/scripps_theses/365.
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Divorces in the United States during the twentieth century were, to say the least, extremely difficult to obtain. Most states had few grounds for divorce, and some, like New York, only allowed divorce in the instance of proven adultery. Waiting periods could stretch from one to three years. But for some hopeful divorcees, there was another way. Nevada had nine broad grounds for divorce, among them “mental cruelty.” After 1931, anyone could become a Nevada citizen and divorce within the state after a mere six weeks of residency.
Before the widespread liberalization of divorce law in the early to mid-1970s, Reno, Nevada became the divorce capital of America. Divorcees, usually women, from all over the country poured into Reno to “get Reno-vated” and quickly part with their spouses. Subsequently, a complex local economy developed to accommodate the “six-weekers” during while they established residency. For the wealthy divorce-seeking elite, luxurious “divorce ranches” offered a relaxing six-week stay complete with catered meals, horseback riding, and trips to Lake Tahoe.
The ranches brought together a substantial number of women who were overtly there for the same reason: to obtain a divorce. The simple fact of this mutual understanding provided a level of closeness and openness that was very unusual for the time, facilitating commiseration, camaraderie, and friendship. The closeness of ranch relationships was amplified by their demographics; the ranches were overwhelmingly female spaces, as the majority of their guests, proprietors, and staff were women. The Reno divorce industry demonstrates that women were willing to go to great lengths, measured in miles, days, and dollars, to obtain divorces. Affirming the existence of these Reno divorcees and examining their experiences during their quickie divorces illustrates substantial shifts in marital expectations throughout the twentieth century and contextualizes the 1970s expansion of divorce rights.
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RIGONI, FEDERICA. "EXPLORING DETECTION LIMITS AND RESPONSE TIME SCALES OF CHEMIRESISTOR GAS SENSORS BASED ON CARBON NANOTUBE AND HYBRID LAYERS." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/262413.
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Crucial features in gas sensors for environmental monitoring are the gas sensitivity in the low ppb range and the ability to discriminate variations of a certain polluting gas from other interfering gases.
Monitoring of ammonia gas concentrations is mandatory to reduce the hazard for human health and vegetation determined by the widespread use of ammonia derivatives as agricultural nitrogen fertilizers, industrial production and traffic. In particular, ammonia, besides being a toxic molecule is one of the main precursors of secondary fine particulate matter (PM10, PM2.5). Ammonia could hence be used as a local marker of secondary fine particulate formation, allowing indirect control of particulate emission sources. In spite of this urgency, the detection of NH3 concentrations in urban areas with chemiresistor gas sensors (CGSs) has been so far widely overlooked, since the average levels are usually low, i.e. in the 20-30 ppb range, while the CGSs are generally tested by exposure to ammonia in the ppm range.
Carbon nanotubes (CNTs), discovered more than 20 years ago, are well known and studied systems for many applications, among which (of course) gas sensing. With respect to commercial electrochemical sensors (mostly based on metal oxide materials), CNTs show a higher physical and chemical stability, better transport of charge to the electrodes and a wide range of possible hybrid architectures and operational features, among which the operation at room temperature, that make them unique materials for gas detection.
The main goal of this thesis is to increase the sensitivity to [NH3] and to lower the detection limit (DL), exploring sample preparation strategies of low-cost single walled carbon nanotubes (SWCNT)-based gas sensors operating at room temperature, considering also the response to other interfering gases. Furthermore, effects of metal oxide nanoparticles functionalization and gas response of hybrid layers have been also investigated.
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Lovett, Brendon. "Three molecular materials studied by positive muons and magnetometry." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365360.
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Publio, Rodrigo. "Estudo computacional sobre a influência de sinapses elétricas entre bastonetes na faixa dinâmica escotópica da retina de vertebrados." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-25092008-105120/.
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Recentes estudos sugerem a existência de sinapses elétricas mediadas por junções gap entre fotorreceptores na retina de vertebrados. Neste trabalho, descrevemos um modelo computacional dos circuitos primário e secundário mediados pelos bastonetes da retina de vertebrados. O modelo é composto pelas seguintes populações de células: bastonetes, cones, células bipolares dos bastonetes, células bipolares dos cones, células amácrinas do tipo AII e células ganglionares. As células do modelo estão acopladas entre si por sinapses químicas e elétricas segundo padrões realísticos de convergência e divergência. As sinapses elétricas ocorrem entre os bastonetes, entre os bastonetes e os cones, entre as células amácrinas AII e entre as células bipolares dos cones e a células amácrinas AII. O modelo assume que um estímulo luminoso de baixa intensidade, simulando condições escotópicas, atinge todos os bastonetes da camada receptora, porém menos da metade deles é excitada. A resposta dos bastonetes excitados é controlada por uma fotocorrente cuja amplitude pode ser alterada para simular estímulos de diferentes intensidades dentro da faixa escotópica. O modelo é utilizado para investigar os efeitos dos diferentes graus de acoplamento elétrico entre as células receptoras e entre as células amácrinas AII, além do efeito de diferentes valores de condutância do canal Ih ativado pela hiperpolarização nos bastonetes, sobre a faixa dinâmica da retina. Os resultados das simulações mostram que, para valores realísticos da condutância do canal Ih, a faixa dinâmica medida na camada receptora é maximizada para o índice de conectividade crítico para que haja percolação de ligação. No entanto, quando a faixa dinâmica é medida para as células bipolares ou ganglionares o valor máximo é obtido para um índice de conectividade subcrítico. Este resultado é conseqüência da alta convergência de sinapses químicas entre os bastonetes e células bipolares.<br>Recent studies suggest the existence of electrical synapses (gap junctions) connecting photoreceptors in the vertebrate retina. In this work we describe a computer model of the primary and secondary rod pathways in the vertebrate retina. The model is composed of the following cell populations: rods, cones, rod bipolar cells, cone bipolar cells, AII amacrine cells and ganglion cells. Cells of the model are connected via chemical as well as electrical synapses according to realistic convergence and divergence factors. There are electrical synapses between rods, rods and cones, AII amacrine cells, and cone bipolar cells and AII amacrine cells. The model assumes that low intensity stimuli simulating scotopic conditions reach all rods in the receptor array but less than half of them are excited. The excited rods response is controlled by a photocurrent waveform whose amplitude can be manipulated to simulate stimuli of different intensities within the scotopic range. The model is used to investigate the effects of different degrees of coupling among photoreceptors and among AII amacrine cells, as well as values of rod hyperpolarization activated current Ih on the dynamic range of the retina. Results show that for realistic values of Ih conductance the dynamic range of the rod array is maximized at the critical connectivity degree for bond percolation. However, the dynamic range of the rod bipolar and ganglion cells is maximized for a photoreceptor connectivity degree below the critical value. The latter result is a consequence of the high convergence of chemical synapses from rods to rod bipolar cells.
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Battistini, Lorenzo. "Impact of future EU7 regulations on high performance gasoline-ICEs and possible innovative technologies for extension of lambda 1 operating range." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25674/.
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The aim of pollutant emissions legislation is to bring environmental benefit by helping reduce, for what road transport is responsible, the concentration of pollutants where levels are too high and endanger human health.
Europe is considering several changes in “post Euro 6d” regulation from 2025. Several measures have been proposed for Euro 7, most of which introduce new challenges in the development of high-performance turbocharged gasoline engine such as the extension of lambda 1 in the whole engine map.
In this Master Thesis, possible technologies to expand the engine operating range with lambda 1 in the entire engine map, without widely reducing the engine performances are analyzed. In particular the focus is on the Pre-Chamber Spark Ignition (PCSI), the Exhaust Gas Recirculation (EGR), the Miller Cylce, the Water Injection and the Ultra High Pressure Injection.
Subsequently, the modeling and validation in Simulink/Matlab of thermal models to analyze and monitor the exhaust gas temperature in the entire exhaust system is presented and explained. The aim of the modeling is integrating the modules into the Model-in-the-Loop environment and co-simulating with GT-Power/Simulink for a virtual pre-calibration of exhaust gas temperature control.
Finally, homologation cycles are run to obtain a first analysis feedback regarding the pre-calibration and to understand which are the cycle zones where the fuel enrichement will be necessary to reach the desired temperature.
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Frevert, Carlo [Verfasser], Günther [Akademischer Betreuer] Tränkle, Günther [Gutachter] Tränkle, Stephen [Gutachter] Sweeney, and Michael [Gutachter] Kneissl. "Optimization of broad-area GaAs diode lasers for high powers and high efficiencies in the temperature range 200-220 K / Carlo Frevert ; Gutachter: Günther Tränkle, Stephen Sweeney, Michael Kneissl ; Betreuer: Günther Tränkle." Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1174990643/34.
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Tran, Hong Quan. "Cutoff phenomenon for some interacting particle systems." Electronic Thesis or Diss., Université Paris sciences et lettres, 2024. http://www.theses.fr/2024UPSLD007.
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Sur un espace d’états fini, une chaîne de Markov irréductible à temps continu converge vers sa mesure stationnaire unique, ou en d’autres termes, se mélange. La convergence est mesurée par rapport à la distance en variation totale. Dans la théorie moderne des chaînes de Markov, nous nous intéressons aux chaînes où l’espace d’états devient grand. En étudiant certains modèles de mélange de cartes, Aldous, Diaconis et Shashahani ont découvert le phénomène remarquable maintenant connu sous le nom de cutoff : lorsque l’espace d’états devient grand, la distance entre la chaîne et l’équilibre reste proche de sa valeur maximale pendant une longue période, puis chute soudainement vers zéro sur une échelle de temps beaucoup plus courte. Depuis, le phénomène de cutoff a été observé dans de nombreux contextes différents, tels que les chaînes de naissance et de mort, les systèmes de spin à haute température, les systèmes de particules en interaction, etc. Malgré l’accumulation de modèles, il n’existe pas encore de théorie générale permettant de prédire efficacement cutoff. Au lieu de cela, le cutoff est montré modèle par modèle. Dans cette thèse, nous étudions trois systèmes de particules en interaction: le processus d’exclusion unidimensionnel avec réservoirs, le processus de Glauber-Exclusion dans le régime à haut température, et le processus de Zero-Range à champ-moyen avec potentiel croissant sous-linéairement. Pour chaque modèle, nous établissons cutoff et fournissons une estimation fine pour le trou spectral. Nous nous concentrons particulièrement sur le cadre de la percolation de l’information introduit par Lubetzky et Sly, qui nous permet de montrer le cutoff même sans connaître la formule explicite de la mesure invariante<br>On a finite state space, an irreducible continuous-time Markov chain converges to its unique stationary measure, or in other words, mixes. The convergence is often measured by the total variation distance. In the modern theory of Markov Chains, we are interested in the case where the state space becomes large. When studying some models of card shuffling, Aldous, Diaconis, and Shashahani discovered a remarkable phenomenon now known as cutoff: as the state space becomes large, the distance between the chain and equilibrium stays close to its maximal value for a long time and then suddenly drops to near zero in a much shorter time scale. Since then, the cutoff phenomenon has been observed in many different contexts, such as birth and death chains, high-temperature spin systems, interacting particle systems, etc. Despite the accumulation of models, there is not yet a general theory to effectively predict cutoff. Instead, cutoff is proved model by model.In this thesis, we study three models : the one-dimensional Exclusion process with reservoirs, the Glauber-Exclusion process in the high-temperature regime, and the mean-field Zero-Range process with increasing sublinear potential. These three models all fall under the category of interacting particle systems. For each model, we establish cutoff and provide a sharp estimate on the spectral gap. We particularly focus on the information percolation framework introduced by Lubetzky and Sly, which allows us to show cutoff even without knowing the explicit formula of the invariant measure
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PANTINI, SARA. "Analysis and modelling of leachate and gas generation at landfill sites focused on mechanically-biologically treated waste." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2013. http://hdl.handle.net/2108/203393.
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Despite significant efforts have been directed toward reducing waste generation and encouraging alternative waste management strategies, landfills still remain the main option for Municipal Solid Waste (MSW) disposal in many countries. Hence, landfills and related impacts on the surroundings are still current issues throughout the world. Actually, the major concerns are related to the potential emissions of leachate and landfill gas into the environment, that pose a threat to public health, surface and groundwater pollution, soil contamination and global warming effects. To ensure environmental protection and enhance landfill sustainability, modern sanitary landfills are equipped with several engineered systems with different functions. For instance, the installation of containment systems, such as bottom liner and multi-layers capping systems, is aimed at reducing leachate seepage and water infiltration into the landfill body as well as gas migration, while eventually mitigating methane emissions through the placement of active oxidation layers (biocovers). Leachate collection and removal systems are designed to minimize water head forming on the bottom section of the landfill and consequent seepages through the liner system. Finally, gas extraction and utilization systems, allow to recover energy from landfill gas while reducing explosion and fire risks associated with methane accumulation, even though much depends on gas collection efficiency achieved in the field (range: 60-90% Spokas et al., 2006; Huitric and Kong, 2006). Hence, impacts on the surrounding environment caused by the polluting substances released from the deposited waste through liquid and gas emissions can be potentially mitigated by a proper design of technical barriers and collection/extraction systems at the landfill site. Nevertheless, the long-term performance of containment systems to limit the landfill emissions is highly uncertain and is strongly dependent on site-specific conditions such as climate, vegetative covers, containment systems, leachate quality and applied stress. Furthermore, the design and operation of leachate collection and treatment systems, of landfill gas extraction and utilization projects, as well as the assessment of appropriate methane reduction
strategies (biocovers), require reliable emission forecasts for the assessment of system feasibility and to ensure environmental compliance. To this end, landfill simulation models can represent an useful supporting tool for a better design of leachate/gas collection and treatment systems and can provide valuable information for the evaluation of best options for containment systems depending on their performances under the site-specific conditions. The capability in predicting future emissions levels at a landfill site can also be improved by combining simulation models with field observations at full-scale landfills and/or with experimental studies resembling landfill conditions. Indeed, this kind of data may allow to identify the main parameters and processes governing leachate and gas generation and can provide useful information for model refinement.
In view of such need, the present research study was initially addressed to develop a new landfill screening model that, based on simplified mathematical and empirical equations, provides quantitative estimation of leachate and gas production over time, taking into account for site-specific conditions, waste properties and main landfill characteristics and processes. In order to evaluate the applicability of the developed model and the accuracy of emissions forecast, several simulations on four full-scale landfills, currently in operative management stage, were carried out. The results of these case studies showed a good correspondence of leachate estimations with monthly trend observed in the field and revealed that the reliability of model predictions is strongly influenced by the quality of input data. In particular, the initial waste moisture content and the waste compression index, which are usually data not available from a standard characterisation, were identified as the key unknown parameters affecting leachate production. Furthermore, the applicability of the model to closed landfills was evaluated by simulating different alternative capping systems and by comparing the results with those returned by the Hydrological Evaluation of Landfill Performance (HELP), which is the most worldwide used model for comparative analysis of composite liner systems. Despite the simplified approach of the developed model, simulated values of infiltration and leakage rates through the analysed cover systems were in line with those of HELP.
However, it should be highlighted that the developed model provides an assessment of leachate and biogas production only from a quantitative point of view. The leachate and biogas composition was indeed not included in the forecast model, as strongly linked to the type of waste that makes the prediction in a screening phase poorly representative of what could be expected in the field. Hence, for a qualitative analysis of leachate and gas emissions over time, a laboratory methodology including different type of lab-scale tests was applied to a particular waste material. Specifically, the research was focused on mechanically biologically treated (MBT) wastes which, after the introduction of the European Landfill Directive 1999/31/EC (European Commission, 1999) that imposes member states to dispose of in landfills only wastes that have been preliminary subjected to treatment, are becoming the main flow waste landfilled in new Italian facilities. However, due to the relatively recent introduction of the MBT plants within the waste management system, very few data on leachate and gas emissions from MBT waste in landfills are available and, hence, the current knowledge mainly results from laboratory studies. Nevertheless, the assessment of the leaching characteristics of MBT materials and the evaluation of how the environmental conditions may affect the heavy metals mobility are still poorly investigated in literature. To gain deeper insight on the fundamental mechanisms governing the constituents release from MBT wastes, several leaching experiments were performed on MBT samples collected from an Italian MBT plant and the experimental results were modelled to obtain information on the long-term leachate emissions. Namely, a combination of experimental leaching tests were performed on fully-characterized MBT waste samples and the effect of different parameters, mainly pH and liquid to solid ratio (L/S,) on the compounds release was investigated by combining pH static-batch test, pH dependent tests and dynamic up-flow column percolation experiments. The obtained results showed that, even though MBT wastes were characterized by relatively high heavy metals content, only a limited amount was actually soluble and thus bioavailable. Furthermore, the information provided by the different tests highlighted the existence of a strong linear correlation between the release pattern of dissolved organic carbon (DOC) and several metals (Co, Cr, Cu, Ni, V, Zn), suggesting that complexation to DOC is the leaching controlling mechanism of these elements. Thus, combining the results of batch and up-flow column percolation tests, partition coefficients between DOC and metals concentration were derived. These data, coupled with a simplified screening model for DOC release, allowed to get a very good prediction of metal release during the experiments and may
provide useful indications for the evaluation of long-term emissions from this type of waste in a landfill disposal scenario.
In order to complete the study on the MBT waste environmental behaviour, gas emissions from MBT waste were examined by performing different anaerobic tests. The main purpose of this study was to evaluate the potential gas generation capacity of wastes and to assess possible implications on gas generation resulting from the different environmental conditions expected in the field. To this end, anaerobic batch tests were performed at a wide range of water contents (26-43 %w/w up to 75 %w/w on wet weight) and temperatures (from 20-25 °C up to 55 °C) in order to simulate different landfill management options (dry tomb or bioreactor landfills). In nearly all test conditions, a quite long lag-phase was observed (several months) due to the inhibition effects resulting from high concentrations of volatile fatty acids (VFAs) and ammonia that highlighted a poor stability degree of the analysed material. Furthermore, experimental results showed that the initial waste water content is the key factor limiting the anaerobic biological process. Indeed, when the waste moisture was lower than 32 %w/w the methanogenic microbial activity was completely inhibited. Overall, the obtained results indicated that the operative conditions drastically affect the gas generation from MBT waste, in terms of both gas yield and generation rate. This suggests that particular caution should be paid when using the results of lab-scale tests for the evaluation of long-term behaviour expected in the field, where the boundary conditions change continuously and vary significantly depending on the climate, the landfill operative management strategies in place (e.g. leachate recirculation, waste disposal methods), the hydraulic characteristics of buried waste, the presence and type of temporary and final cover systems.
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Shawcross, Mark. "Breakup reactions populating cluster states in 28Si and 24Mg." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/843397/.
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The 12C+16O breakup of 28Si and the 12C+12C breakup of 24Mg have been studied following the interaction of a 170 MeV 24Mg beam with 7Li, 9Be,12C and 16O target nuclei. The measurements were performed at the Australian National University in Canberra, using the technique of Resonant Particle Spectroscopy. The breakup fragments from the decay of the resonant nuclei were detected in two Gas-Si-CsI telescopes positioned on opposite sides of the beam axis. The data suggest that the same states in 28Si are populated via the 7Li(24Mg, 12C 16O)3H, 9Be(24Mg,12C 16O)5He and 12c(24Mg,12C 16O)8Be reactions. This implies that the cluster decaying states are populated by direct a-transfer. Breakup has been observed from states in 28Si at excitation energies (spins) of (26.15), 28.17 (13-, 29.51, 29.95, 30.45, 30.76, (31.3), 31.65, 31.90, 32.51, 33.14, 33.41, 33.77, 34.45 (12+,14+) and 35.13 MeV. A consistent theoretical interpretation of the 28Si molecular structures has been given, taking into account the predictions of Nilsson-Strutinsky, a-cluster model and two centre shell model calculations. The present results for the 12C(24Mg,12C 12C)12C reaction agree with previous measurements. In addition, new spin assignments have been proposed for several of the breakup states in 24Mg. States have been observed at excitation energies (spins) of 20.54 (2+), 21.07 (4+), 21.88 (4+), 22.33 (4+), 22.90 (6+), 23.80 (6+,(8+)), 24.56 (8+), 25.14 (6+), 25.72, 26.41 (8+) and 27.12 MeV. Evidence for the population of many of these states via the 16O(24Mg,12C 12C)16O reaction has also been observed. However, the data gave no evidence for either the 7Li(24Mg,12C 12C)7Li or 9Be(24Mg,12C 12C)9Be reactions. The presently available information did not allow an unambiguous determination of the reaction mechanism responsible for the population of the 24Mg breakup states. The performance of the Gas-Si-Csl telescopes has been investigated. For multiplicity 2 events in the silicon strip detectors, a crosstalk has been observed between the two active strips. The energy calibration of the silicon strip detectors for penetrating particles has also been found to differ to that for stopped particles. Empirical corrections for both of these effects have been deduced allowing the simultaneous detection and identification of heavy and light ions within a single telescope. These techniques have been extended to the detection of 8Be → alpha+alpha events over a wide range of alpha-particle energies.
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Le, Helloco Jean-Guy. "Étude de poudres électrocatalytiques pour le dégagement d'hydrogène en milieu alcalin." Grenoble INPG, 1994. http://www.theses.fr/1994INPG0021.
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Afin d'ameliorer les performances des electrodes a degagement d'hydrogene, les materiaux electrocatalytiques pouvant etre mis en uvre sous forme de poudre sont etudies en milieu alcalin. Les electrocatalyseurs sont prepares par mecanosynthese, et la voltamperometrie est associee aux mesures stationnaires pour comparer, voire determiner, les aires reelles des electrodes. La premiere conclusion de ce travail montre que vingt-quatre pour cent de l'aire reelle developpee par les catalyseurs de raney sont effectivement inondes par l'electrolyte, et sous degagement d'hydrogene, le gaz produit bloque certains pores, abaissant a douze pour cent le taux d'utilisation du catalyseur. Il ressort d'autre part que l'oxyde de ruthenium presente une bonne activite electrocatalytique, associee a une excellente resistance aux impuretes metalliques. Une technique permettant de deposer l'oxyde de ruthenium sur des poudres est developpee. Les catalyseurs, d'abord etudies sous forme de pastilles compactes, sont disperses dans une structure volumique. Le gain apporte par la dispersion du catalyseur est evalue, et un modele mathematique decrit le fonctionnement d'une telle electrode
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Pistikopoulos, Panayotis. "Comportement physiochimique des hydrocarbures aromatiques polycycliques, particulaires et gazeux, dans l'atmosphere : mode de formation des aerosols, transport a meso-echelle, adaptation d'un modele-recepteur a des composes reactifs." Paris 7, 1988. http://www.theses.fr/1988PA077140.
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Garet, Frédéric. "Génération optoélectronique d'impulsions électromagnétiques ultra-courtes : application à la spectroscopie THz." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0175.
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Nous presentons la construction et l'utilisation d'une experience de spectroscopie terahertz pour la caracterisation de materiaux dans le domaine sub-millimetrique, les mesures etant realisees dans le domaine temporel. Dans une premiere partie, nous decrivons tout d'abord l'experience dediee a la generation et a la mesure d'impulsions electromagnetiques (em) ultracourtes. Nous employons des photocommutateurs sur substrat de lt-gaas excites par une impulsion laser de 100 fs de duree, et utilises comme dipole de hertz. Nous obtenons ainsi des impulsions em de durees voisines de la picoseconde et dont les spectres s'etendent de quelques dizaines de ghz a plus de 2 thz. Pour caracteriser un materiau, ce dernier est positionne entre les antennes emettrice et receptrice. On mesure ainsi sa fonction de transfert temporelle. Par transformee de fourier numerique, on calcule son coefficient de transmission frequentiel, dont on deduit l'indice de refraction et l'absorption intrinseque du materiau. Nous presentons des resultats de caracterisation pour differents cas rencontres en pratique : echantillons optiquement epais, fins (dont les films minces sur un substrat), materiaux anisotropes. Pour traiter tous ces cas, nous proposons une methode originale d'extraction des parametres materiaux. Nous montrons aussi que l'epaisseur precise des echantillons peut etre simultanement deduite de ces mesures. Cette technique peut aussi etre utilisee pour une etude dynamique de materiaux. Nous avons construit une experience pompe (optique) - sonde (thz). Nous avons teste plusieurs materiaux semi-conducteurs, et compare les resultats avec ceux obtenus avec une experience pompe - sonde tout optique. Nous analysons ces resultats, en particulier pour des echantillons de semi-conducteurs iii-v.
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Chen, Jun-Yu, and 陳俊諭. "Gap Solitons in an Ultracold Bose Gas with Long-Range Interaction." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/44086261579084700410.
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Liao, Tsung-Jen, and 廖崇任. "short-range exchange free energy for electron-gas systems." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/00894628271534731331.
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碩士<br>國立臺灣大學<br>應用物理所<br>100<br>We propose an analytic representation of the short-range exchange free energy for a homogeneous electron system at various temperatures and densities. This short-range exchange free energy is needed for the development of Mermin-Kohn-Sham finite temperature density functional theory (FT-DFT), which is increasingly important in electronic structure and thermochemistry. Our resulting short-range exchange free energy, based on LDA allows the range-separated hybrid functionals, such as the widely used LC hybrids to be available in FT-DFT. We also provide the theoretical calculations of heat of reactions with various temperatures and the range-separated parameter omega.
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Wang, Wei-Cheng, and 王偉丞. "Chaos Differential Absorption Lidar for High-Resolution Range-Resolved Gas Concentration Detection." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/k4c5r8.
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BASTI, GIULIA. "Low energy behavior in few-particle quantum systems: Efimov effect and zero-range interactions." Doctoral thesis, 2018. http://hdl.handle.net/11573/1642732.
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We investigate the emergence of a universal behavior in certain few-particle quantum sys- tems at low-energy.
First we consider a system composed by two identical fermions of mass one and a dif- ferent particle of mass m in dimension three. Under the assumption that the two-particle Hamiltonians composed by one of the fermions and the third particle have a resonance at zero-energy, and for m less than a mass threshold m∗, we prove the occurrence of the Efimov effect, i. e., the existence of an infinite number of three-body bound states accumulating at zero. Then we study three-particle systems with zero-range interactions. In dimension one we give a rigorous definition of the Hamiltonian for three identical bosons and we prove that it is the limit of suitably rescaled regular Hamiltonians. In dimension three we write the expression of the quadratic form associated to the STM extension for a generic three-particle system. Then we focus on a system of three identical bosons proving stability outside the s-wave subspace. As a third example of universal behavior in few-particle system we con- sider a quantum Lorentz gas in dimension three: a particle moving through N obstacles whose positions are independently chosen according to a given common probability density. We assume that the particle interact with each obstacle via a Gross Pitaevskii potential. We prove the convergence, as N → ∞, to a Hamiltonian depending on the common distribution density of the obstacles and such that the only dependence on the interaction potential is through its scattering length.
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CHEN, YU-CHOU, and 陳宥州. "Estimation and Management of Tug Gas Emission in Kaohsiung Port- Take the second port as the range." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/a6v3p7.
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碩士<br>國立高雄海洋科技大學<br>輪機工程研究所<br>105<br>Shipping is the most reliable means of transportation in global industrial trade. Due to frequent shipping trade, the resulting air pollutions will seriously impact the marine environment and ecosystems. Kaohsiung Port is the largest international commercial port in Taiwan, in both import quantity and export This is the total number of tugboats in Kaohsiung port area is insufficient, their workload and duty time are very high. In addition, their emissions of waste air pollutions are substantial . This research investigates the fuel consumption and air pollution emissions of tugboats in Kaohsiung port area in 2015, during the period for all types of ships landing in the case of the Kaohsiung port. The results of this research can be used in the port pollution control strategy. Compared to ocean-going ships, port tugboat emissions are not too serious, however, because the tugboat emissions are Concentrated in the port area, the impact of emissions in port area must be stickly controlled.