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1
Le, Gros Mark. "NMRON studies of insulating magnetic materials." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30569.
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Selective excitation pulsed NMRON, CW-NMRON and Thermal NMR methods have been used to study the low temperature ⁵⁴Mn nuclear spin-lattice relaxation mechanisms in magnetic insulators.
The selective single and double quantum excitation sequences have been used for the first time in NMRON to obtain single and double quantum rotation patterns, Free Induction Decays, Hahn spin echoes and pulsed T₁ measurements.
Two insulating magnets have been studied; MnCl₂.4H₂O and Mn(COOCH₃ )₂ .4H₂O. In the ⁵⁴Mn-MnCl₂ .4H₂O system the temperature dependence of the ⁵⁴Mn spin-lattice relaxation time at zero field was measured between 35 mK and 90 mK and it was found that the dominant relaxation process between 65 mK and 90 mK is an electronic magnon Raman process and below 65 mK a direct relaxation process dominates.
Single and double quantum Free Induction Decays and Hahn spin echoes have been used to determine the magnitude and nature of the spin-spin relaxation mechanism for ⁵⁴Mn oriented in MnCl₂.4H₂O at zero applied field.
NMRON was observed for the first time in the paramagnetic phase of MnCl₂.4H₂O. The resonance lines are inhomogeneously broadened and 300 kHz wide. A value of <⁵⁴AS>/h=-513.6(3) MHz has been determined for the paramagnetic phase hyperfine coupling constant, and this value has been used to determine the zero point spin deviation of the antiferromagnetic phase.
The field and temperature dependence of the ⁵⁴Mn T₁ was measured for values of field above the spin flop paramagnetic phase transition and a field dependent T₁ minimum was discovered at Ba=2.64 T.
For the ⁵⁴Mn-Mn(COOCH₃) .4H₂O system two ⁵⁴Mn resonances have been observed and the value of the hyper fine coupling constants for the two sites were found to be <⁵⁴AS>/h=-435 (1) MHz for the ⁵⁴Mn1 site and <⁵⁴AS>/h=-478(1) MHz for the ⁵⁴Mn2 site. The high field spin-lattice relaxation behavior has also been investigated and a T₁ minimum at Ba =2.74 T analogous to that observed in MnCl₂ .4H₂O was discovered.
A Hahn echo study of the low field single quantum spin-spin relaxation processes has been performed and anomalous behavior of the spin echo amplitude revealed.Science, Faculty of
Physics and Astronomy, Department of
Graduate
2
Meletse, Thabo Frans. "Development of low cost thermal insulating materials." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/8724.
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Includes bibliographical references.The disadvantaged people in South Africa are unfortunate by virtue of their financial status. It was estimated in 1992 that 20 % of the South African population live in informal settlements. The houses in these settlements are found to be very energy inefficient. This study was aimed at developing low cost thermal insulating materials that can be used to increase energy efficiency of the houses in these informal settlements. This was done by firstly studying the properties of thermal insulation materials. Furthermore, common thermal insulating materials in South Africa were studied and evaluated. Only recycled polymeric based materials were examined for selecting the raw materials that were used to investigate the feasibility of the thermal insulating materials from waste material. The experimental work was extended to construct a thermal conductivity rig that was to be used in measuring the thermal conductivity of both the developed and existing thermal insulating materials. The expanded polystyrene obtained from Sagex (Pty) Ltd and polyester obtained from Isotherm (Pty) Ltd. were evaluated and compared to the manufactured recycled polymer slabs and expanded polyethylene foams (EPEF). Expanded polyethylene foam and recycled polymer slab samples were subjected to mechanical and physical testing. A temperature comparison test and thermal conductivity determination were conducted on both the expanded polyethylene foam (EPEF) and recycled polymer slab (RPS) samples. The scanning electron microscope (SEM) was used to reveal the micro-structures of all the developed thermal insulating material samples. The expanded polystyrene and polyester thermal insulating materials were also examined using the SEM. Optical microscopy was only used on RPS samples. It was found in this research, that the properties that govern the viability of thermal insulating materials are: thermal conductivity (k-value), thermal resistance (R-value), combustibility, moisture absorption and the presence of hazardous gases during burning. The temperature comparison test showed that the recycled polymer slab (RPS) and expanded polyethylene foam (EPEF) retards the flow of heat to levels comparable to that of the locally obtained thermal insulation. The comparative cut bar method was found to be relatively cheap to design and it was ideal for the measurement of the thermal conductivity of polymeric based materials. The k-value of all the EPEF samples was measured to be around 0.04 W.m-¹K-¹ and the RPS k-value was found to be 0.05 W.m-¹K-¹. This is attributed to air pockets with lower conductivities values, found within the structure of the polymeric thermal insulating materials. The porous structure is evident from the SEM micrographs of both the EPEF and RPS samples. One grade of expanded polyethylene foam, the SPX80, had accumulated less moisture when moisture absorption was compared with other EPEF samples. The RPS material did have a propensity for absorption of water. The flammability retardant tests have showed that gypsum board has to be incorporated during service for the RPS and SPX80. The mechanical testing results also suggest that both the EPEF and RPS need to be supported when installed in a ceiling, for example.
3
Hoffmann, Ryan Carl. "Electron-Induced Electron Yields of Uncharged Insulating Materials." DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/749.
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Presented here are electron-induced electron yield measurements from high-resistivity, high-yield materials to support a model for the yield of uncharged insulators. These measurements are made using a low-fluence, pulsed electron beam and charge neutralization to minimize charge accumulation. They show charging induced changes in the total yield, as much as 75%, even for incident electron fluences of <3 fC/mm2, when compared to an uncharged yield. The evolution of the yield as charge accumulates in the material is described in terms of electron recapture, based on the extended Chung and Everhart model of the electron emission spectrum and the dual dynamic layer model for internal charge distribution. This model is used to explain charge-induced total yield modification measured in high-yield ceramics, and to provide a method for determining electron yield of uncharged, highly insulating, high-yield materials. A sequence of materials with progressively greater charge susceptibility is presented. This series starts with low-yield Kapton derivative called CP1, then considers a moderate-yield material, Kapton HN, and ends with a high-yield ceramic, polycrystalline aluminum oxide. Applicability of conductivity (both radiation induced conductivity (RIC) and dark current conductivity) to the yield is addressed. Relevance of these results to spacecraft charging is also discussed.
4
Suebthawilkul, Somkeat. "Application of hollow spheres in insulating castables." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/19164.
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Zhang, Lei. "Electrical tracking over solid insulating materials for aerospace applications." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/electrical-tracking-over-solid-insulating-materials-for-aerospace-applications(94086fc5-0ca2-4d12-aa6d-97452d3169d1).html.
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The concept of More Electric Aircraft, where is to utilize the electrical power to drive more or all aircraft subsystem instead of conventional combination of pneumatic, hydraulic, mechanical and electrical power, can be recalled to World War II. It has been proven to have more advantages for decades in terms of energy efficiency, environmental issues, logistics and operational maintenance. It can also enhance aircraft weight, volume and battle damage reconfigurability.Thanks to the new electronics technologies and the emergence of new materials, It becomes feasible for high power density electrical power components to drive the majority of aircraft subsystem. However, sustaining the transmission of hundreds of kilowatts of electrical power at low voltages is not feasible owing to the penalties incurred due to high cable weights and voltage drop may become critical. It is very easy to come up with the solution of the increase of voltage. However, higher voltage will introduce other problems such as the reliability of insulation coordination on the aircraft due to the increased probability of electrical discharge. For aircraft designers, it is very important to understand the rules of insulation coordination on the aircraft including determining clearance and creepage distances, and also have a clear investigation of the phenomena and mechanism of electrical discharges. Past research has identified a number of the concerns of operating electrical systems at higher voltages in an aerospace environment, especially for dimensioning of clearances. However, there is little study on dimensioning of creepage distances and relevantly flashover and electrical tracking on solid insulating material surfaces. This thesis firstly discusses the rules for determining clearances and creepage distances. The experimental validation work was done for breakdown in air gap and on the solid insulating material surfaces under dry condition so that some standard recommended values can be evaluated not only with theoretical values such Paschen's law. Suggestions of application of those standards were provided. Secondly, the complex electrical discharge under wet condition on solid insulating material surfaces was discussed. A mathematical model to predict this type of electrical failure -electrical tracking (the electrical discharges on solid insulation materials which will lead to physical damage in the materials) with the consideration of different environmental conditions including air pressure, ambient temperature, and pollution degrees was developed. A series of electrical tracking tests were carried out on organic materials to find out the mechanism of electrical tracking and validate the finding by the mathematic model. Finite element analysis simulations were also conducted to find out the background thermal transfer mechanism to support our explanation of those phenomena of electrical tracking. Different test techniques have ben developed for specific impact factors. Finally, the suggestions for utilization of the standards and feasible test techniques for electrical tracking under wet conditions were provided.
6
Sim, Alec. "Unified model of charge transport in insulating polymeric materials." Thesis, Utah State University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3606878.
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Presented here is a detailed study of electron transport in highly disordered insulating materials (HDIM). Since HDIMs do not lend themselves to a lattice construct, the question arises: How can we describe their electron transport behavior in a consistent theoretical framework? In this work, a large group of experiments, theories, and physical models are coalesced into a single formalism to better address this difficult question. We find that a simple set of macroscopic transport equations--cast in a new formalism--provides an excellent framework in which to consider a wide array of experimentally observed behaviors. It is shown that carrier transport in HDIMs is governed by the transport equations that relate the density of localized states (DOS) within the band gap and the occupation of these states through thermal and quantum interactions. The discussion is facilitated by considering a small set of simple DOS models. This microscopic picture gives rise to a clear understanding of the macroscopic carrier transport in HDIMs. We conclude with a discussion of the application of this theoretical formalism to four specific types of experimental measurements employed by the Utah State University space environments effects Materials Physics Group.
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Sim, Alec. "Unified Model of Charge Transport in Insulating Polymeric Materials." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/2044.
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Charge transport, charging, and subsequent electrostatic discharge due to interactions with the space environment are primary concerns of spacecraft designers. Developing a physical understanding of the interactions of charge with the multitude of materials that spacecraft are composed of is a critical step in understanding and mitigating both short-term and long-term spacecraft degradation. In particular, the study of charge transport in highly insulating materials is critical as they store charge longer, with higher capacity, and with greater destructive capability than other materials.The Utah State University Materials Physics Group, with the funding of the NASA James Webb Space Telescope project and Rocky Mountain Space Consortium, have developed a complete and consistent theoretical model that predicts short-term and long-term storage capabilities based on physical material parameters. This model is applicable across a wide range of experimental systems designed to test specific behaviors that characterize charging phenomena.Modeling and understanding the complex relationships between the spacecraft and its surroundings are fundamentally based on detailed knowledge of how individual materials store and transport charge. The ability to better understand these effects will help make exploring the edges of the universe more stable, reliable, and economic.
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Rux, Lorelynn Mary. "The physical phenomena associated with stator winding insulation condition as detected by the ramped direct high-voltage method." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-04042004-112949.
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Valentini, Francesco. "Development of insulating materials with thermal energy storage/release capability." Doctoral thesis, Università degli studi di Trento, 2022. https://hdl.handle.net/11572/335644.
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Nowadays the environmental sustainability and the limitation of the energy consumption of buildings is of substantial importance in order to reduce greenhouse gases emissions and mitigate the consequences of climate change. Thermal energy storage (TES) allows to store thermal energy when available in order to use it when and where necessary. The use of insulating materials with TES capability may results in the compensation of energy absorption peaks caused by air conditioning or by space heating with a consequent reduction of energy consumption and related CO2 emissions. This work aims at the development and characterization of composite materials based on polymeric foams and containing a phase change material providing the TES capability. The production procedures were optimized in order to maximize the quality of the samples and the main properties of the resulting materials were then investigated. Different matrices were considered in this work: thermosetting, thermoplastic and elastomeric ones. As thermosetting matrix, a polyurethane foam was considered: this foam was filled, during the production process, with increasing amounts (from 10 to 40 wt%) of a microencapsulated PCM with a melting point of 24 °C. The addition of the PCM caused the disruption of the regular close cell morphology of the foams with a consequent increase of the thermal conductivity and a reduction of the mechanical properties. On the other hand, the addition of the PCM led to interesting TES properties, measured both through differential scanning calorimetry and infrared thermography (up to 54 J/g). Polyethylene was chosen as thermoplastic matrix and the technology of salt leaching was used to obtain foams without the use of chemical foaming agents. Foams containing different amounts (up to 56 wt%) of a microencapsulated PCM with a melting point of 24 °C were prepared. The addition of the PCM led to a decrease of the connectivity and porosity values of the prepared foams with a consequent decrease of the mechanical properties and increase of the thermal conductivity. Despite the rupture of a certain part of the PCM capsules due to the production process, good TES properties (up to 50 J/g) were measured. Elastomeric foams were prepared using an EPDM rubber as matrix and different foaming agents for the expansion process: foams obtained using two different commercial foaming agents were compared with foams obtained using the salt leaching technique. In the first case, a shape-stabilized PCM was added during the production process, while in the second one the foams were impregnated with a liquid PCM without the necessity of a shape stabilization. Salt leaching foams were able to retain higher PCM loads with respect to foams produced using commercial foaming agents and were therefore characterized by higher TES capability (up to 129 J/g). Infrared thermography tests highlighted that the time required to reach a reference temperature during heating/cooling cycles was three times
longer for samples with a PCM amount of about 55 wt%. These foams evidenced a general decrease of the mechanical properties upon PCM addition. Moreover, a strong influence of the temperature on the mechanical behaviour of these foams was highlighted, with the PCM acting as softener above its melting point and as hardener below. In order to consider practical applications, elastomeric panels made of an ethylene propylene diene monomer (EPDM) rubber filled with a shape stabilized PCM and covered with a nitrile-butadiene rubber (NBR) envelope were prepared. It was possible to verify the absence of leakage, the uniform distribution of the PCM and the influence of temperature on the mechanical properties of the samples. From rheological tests it was also possible to observe the plasticizing effect of the PCM that hindered the vulcanization process of the EPDM/PCM compound. In the second part of this work larger samples were prepared and used for the internal insulation of wood boxes that were subjected to heating/cooling cycles, simulating thus real summer conditions in north Italy. The beneficial effect of the PCM resulted in a consistent reduction of the temperature peak with respect to a reference box insulated with elastomeric panels without PCM. Moreover, the fire behaviour of the produced samples was studied and the effect of the addition of different flame retardants was deeply investigated. The addition of a flame retardant based on ammonium polyphosphate and aluminium diethyl phosphinate as synergistic agents allowed a strong reduction of the peak of heat release rate measured through cone calorimeter tests, with a significant improvement of the fire behaviour. Fire tests allowed also to point out the significant role, in improving the fire performances of the samples, of the interactions between ammonium polyphosphate and the mineral fillers present in the EPDM/PCM compound (clay) and in the envelope (talc, kaolin and silica). A better comprehension of the combustion mechanisms and of the flame retardant efficacy was achieved through the analysis of the combustion residues. Finally, the specific enthalpy of the different systems was evaluated with respect to the cost of the raw materials used in the production stages in order to classify them on the basis of their melting enthalpy and on the economical aspects.
10
Söderström, David. "Expitaxy, analysis and application of semi-insulating III-V materials /." Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3096.
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Dinkins, Walter Russell. "Electrical characterization of insulating materials using spectral and spatial measurements." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/19416.
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Widenor, Ross. "An Investigation of Contact Electrification and Triboelectric Charging in Insulating Materials." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1364229648.
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Abdul, Karim Aniza. "The interaction of keV cluster and MeV ions with insulating materials." Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/808312/.
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Secondary ion mass spectrometry (SIMS) is a well-known surface analysis technique with numerous applications in materials science. In recent years various types of primary ion beams have emerged to improve SIMS for analysing polymers, organic semiconductors and biological materials. keV cluster ions have given an improvement in producing higher secondary ion yields, reduced topography and reduced interface mixing while MeV SIMS has proven to be better in certain cases especially at desorbing higher mass molecules and has the ability to perform measurements at ambient pressure. This has generally driven the study to understand the interaction between keV cluster ions and MeV ions with insulating materials from both a modelling and an experimental perspective. A simple Monte Carlo model describing the desorption of a molecular solid under keV cluster and MeV ion bombardment is described. The model employs a conical ejection pattern, which has been suggested to be applicable for keV cluster and MeV ions impinging on molecular solids. The conical ejection region is combined with a cylindrical fragmentation region to predict the sputtering behaviour of molecular materials. Molecular dynamics simulations are used to back up this model. The model provides information about surface roughness induced by the process as well as the fragmentation build up during a prolonged sputtering process. This model is expanded to multi-layered systems and has produced some insight on the depth resolution of the analysis. Comparison studies between the model and experiments are also presented with polymer films analysed by a 10keV C60+ time-of-flight (TOF) SIMS. These results are found to compare favourably with each other.
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Mahmood, Salih Qasim. "Behavior of Lap Shear Connections with Thermally Insulating Filler Plates." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/4159.
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This research consists of experimental load tests and numerical simulations of structural steel connections with various filler materials to study the effect of non-steel fillers on the connection strength. Non-steel fillers are used in the steel connections to provide thermal insulation by reducing thermal bridging. Eight specimens having steel and polypropylene filler plates of various thicknesses were tested in the laboratory. The collected data were compared to a Finite Element Analysis (FEA) using ABAQUS to validate the numerical results. After validation, three parametric studies were conducted using ABAQUS to provide insight into general behavior of connections with a variety of fillers that could be used as thermal breaks. In addition, an extreme case of having air gaps instead of alternative fillers was also considered.
The Research Council on Structural Connections (RCSC 2014) suggests a reduction in the bolt shear strength when undeveloped fillers with a thickness of more than 0.25 inch are used while using any non-steel material is prohibited due the limited research available.
Most research studies have investigated the mechanical behavior of thermal breaks in either end-plate moment connections or slip-critical connections. No data is available for thermal breaks in bearing-type connections up to failure.
This research aims to study the effects of filler material properties such as modulus of elasticity and strength on bolt strength, as well as investigate whether the current equation in RCSC 2014 is applicable for alternative filler materials like polypropylene that has less than 0.5% of the steel modulus of elasticity and less than 10% of steel strength.
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Sokotun, Zh, and O. Koshelieva. "Evaluation durability of polymeric insulating material of electric cables." Thesis, Київський національний університет технологій та дизайну, 2017. https://er.knutd.edu.ua/handle/123456789/6714.
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Condò, Marco. "Electrical characterization of innovative insulating materials for HVDC energy transmission cable systems." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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La tesi si è svolta nel corso di uno stage di quasi nove mesi all'interno del laboratorio elettrico di alta tensione del reparto R&D di Prysmian, leader mondiale dei sistemi elettrici in cavo. La tesi si è articolata nelle fasi seguenti:
1) analisi dei fondamenti teorici dei sistemi elettrici in cavo ad alta tensione in corrente continua (HVDC);
2) caratterizzazione elettrica di materiali isolanti innovativi per lo sviluppo di sistemi in cavo HVDC. Più in dettaglio tale caratterizzazione è consistita nelle fasi seguenti:
a) progettazione e/o realizzazione dei set-up di prova;
b) esecuzione delle prove di conducibilità elettrica su provini piani di materiale isolante costituiti da diverse mescole candidate per la realizzazione di cavi modello nella seconda parte della caratterizzazione (vedi seguito);
c) elaborazione dei dati delle prove di cui al punto b) per ricavare i parametri σ0, α e β della conducibilità di ogni mescola isolante testata - e quindi l’andamento della conducibilità delle mescole in funzione della temperatura e del gradiente elettrico – così da selezionare le mescole migliori per la realizzazione dei cavi modello (cavi in scala ridotta con dimensioni standardizzate realizzati ai fini di prove di sviluppo);
d) esecuzione delle prove di tenuta in AC sui cavi modello selezionati;
e) esecuzione delle prove di rigidità ad impulso atmosferico su cavi modello;
f) esecuzione delle prove di stabilità termica su cavi modello.
I risultati di tutte le prove condotte hanno consentito di determinare quali fossero, tra tutte le mescole prese in esame, le più performanti dal punto di vista elettrico.
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Castrovilli, Matteo. "Characterization of the dipole processes of insulating materials used in aeronautical cables." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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The studies of this thesis are focused on aeronautic Polymers materials and their dielectric properties, in order to analyze the relaxation times for the materials of interest under an applied electric field, and in order to increase the work operations of the Novocontrol dielectric spectroscopy measurement machine available in the LAPLACE laboratory. In this context, the research team DSF in collaboration with MDCE, from LAPLACE laboratory, has developed in 2019 a numerical model taking into account the polar mechanisms of the polymer insulators used in the aeronautic industry. However, this theoretical model, is not yet validated. Therefore the aim of this thesis, is to make it possible to validate this theoretical model, then by a series of measurements with dielectric spectroscopy(D.S.) for different materials of interest, different frequencies and temperatures; the measurements consist on the measuration of the phase difference between current and voltage applied to the samples, in order to calculate the permittivity values under different working conditions. The permittivity trend is therefore analyzed to find the polar relaxation under thermoelectrical stresses, and the model will then have to calculate the current density (and from the current density is directly calculated the dissipated energy) of the measured data with dielectry spectroscopy, and the validation will be done if the future measurement values of the current density correspond to the calculated one by the model. For this reasons, the main part of the work for this thesis consist in measurements trought the dielectric spectroscopy (using the following polar materials: Polyimide(PI) and PTFE ) under different working conditions and analyze the results in order to evidence polarization phenomena, because the purpose of this part of the validation process is to have the better polar relaxation data for the future work.
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LORENZATI, ALICE. "Super Insulating Materials for energy efficient buildings: thermal performance and experimental uncertainty." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2711530.
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In a global energy-saving policy, Super Insulating Materials (SIMs) represent an effective solution, especially in a world almost saturated with old buildings for which energy refurbishments are needed. Given their extremely low thermal conductivity, they allow reaching an excellent insulation level, with reduced thicknesses. Anyway, they are recent materials or at least recent insulation solutions for the building sector. And as all the new technologies, they bring with them some critical issues to be solved. For example, what is the accuracy of their available thermal conductivity, what are the criteria for their optimal laboratory characterisation, what are their actual thermal performances in situ and how long is their durability and what is their practical convenience still remain open questions.
The aim of this research was to provide an answer to these questions, although sometimes in a preliminary way.
Therefore, the thermal properties of SIMs (and in particular of the Vacuum Insulation Panels, since, between the SIMs they are the most performing and the most critical solution) were explored at different levels, from the material/panel scale to the building scale.
SIMs are actually laboratory tested using traditional experimental apparatuses, such as the Heat Flow Meter (HFM) and the Guarded Hot Plate (GHP), and in accordance with as traditional standard, developed for the most common insulating material. Indeed, at the first stage of this research, the applicability of the current methodologies was extensively verified, with an in-depth analysis of the obtainable measurement uncertainties. The uncertainty assessment was performed in three different ways, to analyse the various scenarios that may occur: a theoretical standard based uncertainty evaluation, and both the Type A and Type B experimental uncertainty assessment.
Once defined the best criteria for a proper evaluation of the SIMs thermal properties, they were experimentally characterised, considering the different parameters which could have some effects on their thermal behaviour (different thicknesses, average testing temperature, temperature difference, ageing conditions and so on).
In practical applications of the VIPs, they must be assembled one to each other: innovatively, both the HFM and GHP apparatuses were also used for the evaluation of the linear thermal transmittance of the thermal bridges that occur in case of VIPs assemblies. The investigation performed at the material/panel level were then repeated at the component scale, to evaluate the variability and the measurement uncertainty of the linear thermal transmittance.
The so defined thermal performances represented a reliable pool of input data for the dynamic hygrothermal simulations at the building scale. The goals were the evaluation of the energy efficiency of building insulated with SIMs and the prediction of the durability of these materials (considering different severities of the building envelope component boundary conditions).
The outputs of the numerical simulations were then coupled with an economic analysis, to evaluate the convenience of VIP insulation, in terms of discounted pay-back period.
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Hirschberger, Maximilian Anton. "Quasiparticle Excitations with Berry Curvature in Insulating Magnets and Weyl Semimetals." Thesis, Princeton University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10286472.
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The concept of the geometric Berry phase of the quantum mechanical wave function has led to a better theoretical understanding of natural phenomena in all fields of fundamental physics research. In condensed matter physics, the impact of this theoretical discovery has been particularly profound: The quantum Hall effect, the anomalous Hall effect, the quantum spin Hall effect, magnetic skyrmions, topological insulators, and topological semimetals are but a few subfields that have witnessed rapid developments over the three decades since Michael Berry's landmark paper. In this thesis, I will present and discuss the results of three experiments where Berry's phase leads to qualitatively new transport behavior of electrons or magnetic spin excitations in solids.
We introduce the theoretical framework that leads to the prediction of a thermal Hall effect of magnons in Cu(1,3-bdc), a simple two-dimensional layered ferromagnet on a Kagomé net of spin S = 1/2 copper atoms. Combining our experimental results measured down to very low temperatures T = 0.3 K with published data from inelastic neutron scattering, we report a quantitative comparison with the theory. This confirms the expected net Berry curvature of the magnon band dispersion in this material.
Secondly, we have studied the thermal Hall effect in the frustrated pyrochlore magnet Tb2Ti2O7, where the thermal Hall effect is large in the absence of long-range magnetic order. We establish the magnetic nature of the thermal Hall effect in Tb2Ti2O7, introducing this material as the first example of a paramagnet with non-trivial low-lying spin excitations. Comparing our results to other materials with zero thermal Hall effect such as the classical spin ice Dy2Ti 2O7 and the non-magnetic analogue Y2Ti2O 7, we carefully discuss the experimental limitations of our setup and rule out spurious background signals.
The third and final chapter of this thesis is dedicated to electrical transport and thermopower experiments on the half-Heusler material GdPtBi. A careful doping study of the negative longitudinal magnetoresistance (LMR) establishes GdPtBi as a new material platform to study the physical properties of a simple Weyl metal with only two Weyl points (for magnetic field along the crystallographic ⟨111⟩ direction). The negative LMR is associated with the theory of the chiral anomaly in solids, and a direct consequence of the nonzero Berry curvature of the energy band structure of a Weyl semimetal. We compare our results to detailed calculations of the electronic band structure. Moving beyond the negative LMR, we report for the first time the effect of the chiral anomaly on the longitudinal thermopower in a Weyl semimetal.
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Elsayad, Kareem. "Understanding the insulating phases of disordered materials through crosstalk and Coulomb drag experiments." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3290773.
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Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2007.Title from dissertation home page (viewed May 28, 2008). Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7391. Adviser: John P. Carini.
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Angulo, Barrios Carlos. "Gallium arsenide based buried heterostructure laser diodes with aluminium-free semi-insulating materials regrowth." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3305.
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Semiconductor lasers based on gallium arsenide and relatedmaterials are widely used in applications such as opticalcommunication systems, sensing, compact disc players, distancemeasurement, etc. The performance of these lasers can beimproved using a buried heterostructure offering lateralcarrier and optical confinement. In particular, if theconfinement (burying) layer is implemented by epitaxialregrowth of an appropriate aluminium-free semi-insulating (SI)material, passivation of etched surfaces, reduced tendency tooxidation, low capacitance and integration feasibility areadditional advantages.
The major impediment in the fabrication of GaAs/AlGaAsburied-heterostructure lasers is the spontaneous oxidation ofaluminium on the etched walls of the structure. Al-oxide actsas a mask and makes the regrowth process extremely challenging.In this work, a HCl gas-basedin-situcleaning technique is employed successfully toremove Al-oxide prior to regrowth of SI-GaInP:Fe and SI-GaAs:Fearound Al-containing laser mesas by Hydride Vapour PhaseEpitaxy. Excellent regrowth interfaces, without voids, areobtained, even around AlAs layers. Consequences of usinginadequate cleaning treatments are also presented. Regrowthmorphology aspects are discussed in terms of different growthmechanisms.
Time-resolved photoluminescence characterisation indicates auniform Fe trap distribution throughout the regrown GaInP:Fe.Scanning capacitance microscopy measurements demonstrate thesemi-insulating nature of the regrown GaInP:Fe layer. Thepresence of EL2 defects in regrown GaAs:Fe makes more difficultthe interpretation of the characterisation results in the nearvicinity of the laser mesa.
GaAs/AlGaAs buried-heterostructure lasers, both in-planelasers and vertical-cavity surface-emitting lasers, withGaInP:Fe as burying layer are demonstrated for the first time.The lasers exhibit good performance demonstrating thatSI-GaInP:Fe is an appropriate material to be used for thispurpose and the suitability of our cleaning and regrowth methodfor the fabrication of this type of semiconductor lasers.Device characterisation indicates negligible leakage currentalong the etched mesa sidewalls confirming a smooth regrowthinterface. Nevertheless, experimental and simulation resultsreveal that a significant part of the injected current is lostas leakage through the burying material. This is attributed todouble carrier injection into the SI-GaInP:Fe layer.Simulations also predict that the function of GaInP:Fe ascurrent blocking layer should be markedly improved in the caseof GaAs-based longer wavelength lasers.
Keywords:semiconductor lasers, in-plane lasers, VCSELs,GaAs, GaInP, semi-insulating materials, hydride vapour phaseepitaxy, regrowth, buried heterostructure, leakage current,simulation.
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Henriquez, Guerrero Jorge Recarte. "Estudo numerico e experimental sobre vidros termicos." [s.n.], 1996. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263522.
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Orientador: Kamal Abdel Radi IsmailDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Este trabalho apresenta uma abordagem diferente em relação ao conceito de janelas termicamente efetivas, isto é, janelas que reduzem a energia transmitida para dentro ou fora de uma sala. A idéia é usar um painel de vidro duplo preenchido com material de mudança de fase (pcm), cuja temperatura de fusão é determinada por critérios de conforto térmico. A investigação inclui modelamento dos mecanismo de transferência de calor e radiação através do painel, caracterização ótica de janelas convencionais e compostas, e simulação numérica. As amostras incluem vidros comerciais simples de diferentes espessuras e painéis de vidro duplo de diferentes espessuras e espaçamento entre vidros, preenchidos com ar, pcm e finalmente pcm colorido. O modelo é unidimensional transiente e a simulação numérica foi implementada através do método de diferenças finitas na sua forma explícita. Dos resultados da simulação numérica e dos testes de caracterização óticos foram levantadas curvas de ganho térmico, distribuição de temperatura através do painel e evolução da temperaturas da superfícies interna e externas do painel ao longo de um período de 24 horas de forma a verificar o efeito do pcm no desempenho térmico da janela composta
Abstract: This work present a new concept for thermally effective windows, that is windows which reduce the energy transfer to and fIom the internal ambient. This idea behind this concept is to use a pcm fill in the gap between the two glass panels. The fusion temperature of the pcm is selected according to the thermal cornfort criterion. The investigation includes modeling of the mechanisms of heat transfer relevant to the window problem, the thermal radiation through the glass panels, the optical characterization of conventional and composite window configurations and finally the numerical simulation of these configurations. Because of the lack of information on the thermal and optical properties of national gla~s and specially on the composite configuration optical tests were realized to determine the transmittance and reflectivity of simple glass panels of different thicknesses and spacings, air and pcm filled glass panels and finally coloured pcm filled glass panels. The model is a transient one dimensional and the numerical solution is based upon explicit finite difference scheme. the numerical simulations and the optical tests realized allow the determination of the heat gain, the temperature distribution across the glass panels, the outlet and the inlet instantaneous surface temperatures and finally the overall thermal performance of any glass panels including the proposed system
Mestrado
Termica e Fluidos
Mestre em Engenharia Mecânica
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Kuse, Ronald J. (Ronald John). "Development of lightweight insulating refractories for steelmaking and other high-temperature process industries." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/29113.
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Thesis (M.S.)--Massachusetts Institute of Technology, Sloan School of Management, 1996, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science & Engineering, 1996.Includes bibliographical references (p. 105-113).
by Ronald J. Kuse.
M.S.
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Hergert, Alexander [Verfasser]. "Test methods for evaluating the dynamic properties of hydrophobicity of polymeric insulating materials / Alexander Hergert." München : Verlag Dr. Hut, 2017. http://d-nb.info/1135597049/34.
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Garcia, Roberto Linan. "SFâ†6 decomposition under power arc and its degradation effects on superficial properties of insulating materials." Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238773.
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Andersen, Allen. "The Role of Recoverable and Non-Recoverable Defects in DC Electrical Aging of Highly Disordered Insulating Materials." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7047.
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Electrical insulation under high voltage can eventually fail, causing critical damage to electronics. Such electrostatic discharge (ESD) is the primary source of anomalies or failures on spacecraft due to charged particles from the Sun or planetary radiation belts accumulating in spacecraft insulators. Highvoltage direct current power distribution is another example of a growing industry that needs to estimate the operational lifetime of electrical insulation. My research compares laboratory tests of ESD events in common insulating materials to a physics-based model of breakdown. This model of breakdown is based on the approximation that there are two primary types of defects in structurally amorphous insulators. One of the two defect modes can switch on and off depending on the material temperature. This dual-defect model can be used to explain both ESD and less-destructive transient partial discharges. I show that the results of ESD tests agree reasonably well with the dual defect model. I also show that transient partial discharges, which are usually ignored during ESD tests, are closely related to the probability of catastrophic ESD occurring. Since many partial discharges are typically seen during one ESD test, this relationship suggests that the measurements of partial discharges could accelerate the testing needed to characterize the likelihood of ESD in insulating materials.
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Christensen, Justin. "Electron Yield Measurements of High-Yield, Low-Conductivity Dielectric Materials." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6694.
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Materials exposed to the space plasma environment acquire electric charge, which can have harmful effects if it leads to arcing or electrostatic breakdown of important spacecraft components. In fact, spacecraft charging is the leading environmentally induced cause of spacecraft anomalies. This study focuses on measuring electron yield, a property of materials that describes how many electrons are ejected from a material under energetic electron bombardment, which can vary depending on the energy of incident electrons. Intrinsic electron yield is defined as the average number of electrons emitted per incident electron from an electrically neutral material. The specific aim of this work is to improve yield measurements for insulator materials, which can be difficult to test using conventional methods due to charge accumulation in insulators.Most studies of electron yield use a steady current electron beam in a vacuum chamber to irradiate materials to be tested. By comparing the amount of current deposited in the material to the total incident current, the emitted current can be calculated. This works well for conductors; however, insulators charge up quickly, which either repel incident electrons or reattract emitted electrons producing erroneous yield measurements. This study improves on methods that use a pulsed electron beam to measure yield with small amounts of charge per pulse, as well as neutralization methods to dissipate stored charge between pulse measurements.The improvements to instrumentation and data analysis techniques are quantified to demonstrate their validity. These improvements will allow for continued studies on extreme insulator materials. Future studies will provide new understanding of interactions between electron radiation and materials, which will allow for better modeling of spacecraft charging and the development of materials that meet desired electron emission specifications.
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Gentilini, Jean Carlos. "O comportamento de dielétricos na presença de campos elétricos e a sua descrição em termos da função resposta dielétrica." Universidade Tecnológica Federal do Paraná, 2012. http://repositorio.utfpr.edu.br/jspui/handle/1/411.
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CAPESCom o avanço da miniaturização de componentes e dispositivos eletrônicos ocorrida nos últimos anos, a utilização de materiais dielétricos e a necessidade de informações precisas sobre o comportamento dielétrico apresentado por estes materiais aumentou consideravelmente. Neste trabalho é apresentado inicialmente as motivações para o estudo do comportamento dielétrico e da modelagem da função resposta dielétrica. A partir da teoria proposta por Debye e identificando suas peculiaridades, são exploradas algumas extensões deste modelo e analisada a interpretação da função resposta proposta por estes. Muitos modelos assumiam a existência de múltiplas interações envolvendo os dipolos com o meio dielétrico, as quais contribuíam para a dinâmica do comportamento dielétrico, somente mais tarde é que estas múltiplas interações ganharam uma conexão entre a resposta dielétrica observada com as propriedades intrínsecas do material. Por meio do modelo proposto por Dissado e Hill e assumindo dados experimentais disponíveis na literatura para alguns materiais, foi testada a validade da função resposta resultante do modelo, na qual veri cou-se a capacidade da mesma em ajustar as curvas para as componentes real e imaginária da permissividade para uma grande variedade de materiais dielétricos. A partir das simulações e análises realizadas, ficou evidente a dependência do comportamento dielétrico com a temperatura, fato este que deverá ser abordado em trabalhos futuros.
With the improvement of miniaturization of electronic components and devices occurred in recent years, the use of dielectric materials and the need for accurate information about the dielectric behavior displayed by these materials has increased considerably. In this work is initially presented the motivations for the study of dielectric behavior and the modeling of the dielectric response function. From the theory proposed by Debye and identifying its peculiarities, are exploited some extensions of this model and analyzed the interpretation of response function proposed by these. Many models used to assume the existence of multiple interactions involving the dipoles with the dielectric medium, which contributed to the dynamics of the dielectric behavior, only later the multiple interactions won a connection between the dielectric response observed with the intrinsic properties of the materials. Through the model proposed by Dissado and Hill and assuming experimental data available in bibliography for some materials, was tested the validity of the response function resulting from the model, in which was veri ed the ability of the same to adjust the curves for the real and imaginary components of permittivity to a wide variety of dielectric materials. From the simulations and analyzes performed, was evident the dependence of dielectric behavior with temperature, a fact that should be discussed in future works.
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Kalyankar, Rahul R. "Natural fiber reinforced structural insulated panels for panelized construction." Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2010r/kalyankar.pdf.
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Kashfipour, Marjan Alsadat. "Thermal Conductivity Enhancement Of Polymer Based Materials." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron156415885613422.
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Moretti, João Paulo [UNESP]. "Reciclagem de isolantes térmicos presentes em defletores de calor automotivo." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/98302.
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moretti_jp_me_bauru.pdf: 623430 bytes, checksum: 8a8b037467da86497bd4f13030b6c3d1 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Os defletores de calor automotivos são constituídos de uma carcaça de aço aluminizado que envolve um isolante térmico, fisicamente bastante semelhante ao papel, entrentanto com uma composição elevada de partes inorgânicas, chegando a cerca de 80% do material seco. Esses materiais são utilizados para a proteção de vários componentes fundamentais nos veículos presentes em locais de temperaturas extremamentes elevadas, tais como o bloco do motor e o sistema de exaustão de gases. Essa proteção garantes a integridade de peças vitais sensíveis ao calor, como por exemplo, os circuitos eletro-eletrônicos. Neste trabalho, recortes do elemento defletor de calor foram reciclados em sistema manual e em escala industrial e propriedades como espessura, densidade, compreensibilidade, retorno, teor de cinzas, efetividade da deflexão de calor, além da análise por termogravimetria e microscopia eletrônica de varredura com acoplamento de sistema de energia dispersiva (EDS) foram realizados. Os produtos reciclados demonstraram resultados positivos quanto aos ensaios de deflexão de calor, teor de cinzas, ensaio termogravimétrica e visualmente dos espectros de energia dispersiva, indicando a manutenção da composição geral do material após os processos de reciclagem realizados. Os resultados dos ensaios físicos, como espessura, densidade, resistência à tração após quatro horas a sem graus Celsius, resistência à tração após 22 horas a 200 graus Celsius, compreessibilidade e retorno, compressibilidade e retorno após 22 horas a 200 graus Celsius, apontaram variações de acordo com a prensagem exercida no material, indicando a necessidade de melhorias nos processos de reciclagem utilizados
The automotive heat shields are made of an aluminized steel housing that surrounds a thermal insulator, physically quite similar to paper, though with a composition of inorganic parts high, reaching about 80% of dry material. These materials are used to protect several key components in vehicles sites present in extremely high temperatures, such as the engine block and the exhaust gas system. This protetion ensures the integrity of vital parts sensitive to heat, such as electric and electronic circuits. In this paper, clippings element baffe heat were recycled in manual in industrial scale and properties such as thickness, density, compressibility, recovery, ignition loss, effectiveness of heat deflection, and thermogravimetric analysis and scanning electron microscopy with coupling energy dispersive system (EDS) were performed. The recycled product showed positive results regarding heat deflection tests, ash content, thermogravimetric test and visually energy dispersive spectra, indicating maintaining the overall composition of the material after recycling processes performed. The results of the physical tests such as thickness, density, tensile strengh after four hours at one hundred degrees Celsius tensile strength after twenty-two hours to two hundred degrees Celsius, and recovery, compressibility, compressibility and recovery after twenty-two hours to two hundred degrees Celsius, showed variations according to the press exerted on the material, pointing to the need for improvements in recycling processes used
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Moretti, João Paulo. "Reciclagem de isolantes térmicos presentes em defletores de calor automotivo /." Bauru : [s.n.], 2012. http://hdl.handle.net/11449/98302.
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Orientador: Sandro Donnini ManciniBanca: Jane Maria Faulstich de Paiva
Banca: Maria Lucia Pereira Antunes
Resumo: Os defletores de calor automotivos são constituídos de uma carcaça de aço aluminizado que envolve um isolante térmico, fisicamente bastante semelhante ao papel, entrentanto com uma composição elevada de partes inorgânicas, chegando a cerca de 80% do material seco. Esses materiais são utilizados para a proteção de vários componentes fundamentais nos veículos presentes em locais de temperaturas extremamentes elevadas, tais como o bloco do motor e o sistema de exaustão de gases. Essa proteção garantes a integridade de peças vitais sensíveis ao calor, como por exemplo, os circuitos eletro-eletrônicos. Neste trabalho, recortes do elemento defletor de calor foram reciclados em sistema manual e em escala industrial e propriedades como espessura, densidade, compreensibilidade, retorno, teor de cinzas, efetividade da deflexão de calor, além da análise por termogravimetria e microscopia eletrônica de varredura com acoplamento de sistema de energia dispersiva (EDS) foram realizados. Os produtos reciclados demonstraram resultados positivos quanto aos ensaios de deflexão de calor, teor de cinzas, ensaio termogravimétrica e visualmente dos espectros de energia dispersiva, indicando a manutenção da composição geral do material após os processos de reciclagem realizados. Os resultados dos ensaios físicos, como espessura, densidade, resistência à tração após quatro horas a sem graus Celsius, resistência à tração após 22 horas a 200 graus Celsius, compreessibilidade e retorno, compressibilidade e retorno após 22 horas a 200 graus Celsius, apontaram variações de acordo com a prensagem exercida no material, indicando a necessidade de melhorias nos processos de reciclagem utilizados
Abstract: The automotive heat shields are made of an aluminized steel housing that surrounds a thermal insulator, physically quite similar to paper, though with a composition of inorganic parts high, reaching about 80% of dry material. These materials are used to protect several key components in vehicles sites present in extremely high temperatures, such as the engine block and the exhaust gas system. This protetion ensures the integrity of vital parts sensitive to heat, such as electric and electronic circuits. In this paper, clippings element baffe heat were recycled in manual in industrial scale and properties such as thickness, density, compressibility, recovery, ignition loss, effectiveness of heat deflection, and thermogravimetric analysis and scanning electron microscopy with coupling energy dispersive system (EDS) were performed. The recycled product showed positive results regarding heat deflection tests, ash content, thermogravimetric test and visually energy dispersive spectra, indicating maintaining the overall composition of the material after recycling processes performed. The results of the physical tests such as thickness, density, tensile strengh after four hours at one hundred degrees Celsius tensile strength after twenty-two hours to two hundred degrees Celsius, and recovery, compressibility, compressibility and recovery after twenty-two hours to two hundred degrees Celsius, showed variations according to the press exerted on the material, pointing to the need for improvements in recycling processes used
Mestre
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Xpамченко, А. С., Т. Ю. Таранова, and В. Т. Тверезовський. "Дослідження теплоізоляційних властивостей пінопласту та пінополістиролу." Thesis, Сумський державний університет, 2018. http://essuir.sumdu.edu.ua/handle/123456789/67681.
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Теплоізоляційні матеріали – матеріали, які мають невелику теплопровідність.
Застосування теплоізоляційних матеріалів призводить до економії основних
будівельних матеріалів (цементу, металу, деревини, кераміки), до зменшення товщини і маси стін і інших захисних конструкцій, скорочення витрат праці, тpанспоpтниx витрат і, врешті, до зниження вартості будівництва.
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Neumann, Andreas C. "Electronic transport in highly resistive materials in strong magnetic fields :nonlinear dynamics in semi-insulating GaAs and magnetoresistance of carbon-black polymer composites." Doctoral thesis, Universite Libre de Bruxelles, 1997. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212185.
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Nagashima, Haroldo Naoyuki. "Migração de carga espacial em copolímeros P(VDF/TrFE)." Universidade de São Paulo, 1992. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-14012009-102720/.
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Este trabalho apresenta um modelo teórico que procura explicar a origem de um pico anômalo de corrente, observado na fase faraeletrica do copolímero P(VDF/TrFE), nos processos de descarga. Quando uma voltagem tipo V(t) = Vo S(t) é aplicado em materiais isolantes, correntes elétricas observadas em medidas, de carga-descarga decaem aproximadamente com T-n e obedecem ao principio da superposição linear (PSL). Esse comportamento e também observado em polímeros dielétricos. Entretanto, nos processos de descarga, acima da temperatura de Curie do copolímero p (VDF/TrFE), surge um pico anomalo de corrente que viola, aparentemente, o (PSL). Apresentamos um modelo de migração de cargas de espaço em presença de armadilhas, que pode ser responsável pelo pico de corrente e que estaria superposta a corrente de descarga da absorção dielétrica, conforme o modelo, durante os processos de carga, impurezas extrínsecas seriam varridas, pelo campo, do volume da amostra e ficariam, preferencialmente, presas em armadilhas de superfície. Nos processos de descarga, essas cargas se deslocariam em direção ao interior da amostra, devido a repulsão Coulombiana. Esse mecanismo de condução gera um pico de corrente. A aplicação do modelo, permitiu-nos inferir valores de parâmetros como a mobilidade dos portadores de carga e o tempo de transito.A model based on space charge migration to explain an anomalous electric current peak on films of P (VDF/TrFE) copolymer in its paraelectric phase is presented. In general step-voltage current measurements of insulating polymeric materials obey the Principle of Linear Super-position. However, an unexpected anomalous peak was observed in discharge currents in measurements performed with P (VDF/TrFE) above the Curie temperature. We have assumed that space charges were dragged from the bulk of the sample by the external field during the charge measurement, and trapped close to the surface of the sample in a region where the concentration of traps would be very high. Two methods were developed to calculate the magnitude of the current peak: I) assuming a given space charge distribution during the discharge measurement, and II) considering the movement of thin discrete layers of charge under the influence of the internal field.
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Elsafi, Bassem. "Etude de l’effet de la température sur les courants induits des matériaux isolants soumis à l’irradiation électronique dans un microscope électronique à balayage." Thesis, Reims, 2013. http://www.theses.fr/2013REIMS010.
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Les phénomènes de charge des isolants ont été étudiés à l'aide d'un MEB (Microscope Electronique à Balayage). L'effet de la température sur ces phénomènes a été également discuté. Cette étude concernera, plus particulièrement, la mesure des courants induits sous irradiation électronique (courants de conduction et de déplacement) et la détermination du rendement d'émission électronique secondaire. Notre travail est porté en premier lieu sur des échantillons de verre à base de silice. Nous avons prouvé que l'augmentation de la température fait diminuer la capacité de charge du verre. Les résultats sont expliqués par l'augmentation de la conductivité activée par la température qui tend à réduire la formation de la charge d'espace négative grâce à l'augmentation de la mobilité de porteurs de charge. Cette explication est confirmée par une augmentation dans le courant de fuite mesuré sur le verre en fonction de la température.La seconde partie de ce travail a été consacrée à l'étude de l'effet de la température sur le comportement du polyéthylène téréphtalate (PET) irradié avec les électrons. Nous avons montré que la température joue un rôle important dans la grande rétention de la charge accumulée à cause du un phénomène de repiégeage rapide qui se produit dans le volume de l'échantillon dans le cas de la relaxation de la charge. Nos résultats indiquent que le phénomène de «flashover» a lieu aussi bien en volume qu'au niveau de la surface de l'échantillon. L'émission électronique secondaire de ce polymère devient de moins en moins faible avec l'augmentation de la températureThe charging phenomena of insulators have been studied using a SEM (Scanning Electron Microscope). The temperature effect on these phenomena was also discussed. The study will cover, in particular, the measurement of the induced currents under electron irradiation (conduction current and displacement current) and determining the secondary electron emission yield. Our work is focused primarily on silica glass samples. We have shown that increasing of the temperature decreases the capacity of the glass. The results are explained by the increase in conductivity activated by temperature, which tends to reduce the formation of the negative space charge due to the increased mobility of charge carriers. This explanation is confirmed by an increase in the conduction current measured on the glass as a function of temperature.The second part of this work was devoted to the study of the temperature effect on the behavior of polyethylene terephthalate (PET) irradiated with electrons. We have shown that temperature plays an important role in the high retention of accumulated charge due to a rapid trapping phenomenon that occurs in the bulk sample in the case of the charges relaxation. Our results indicate that the "flashover" phenomenon occurs both in bulk and to the surface of sample. The secondary electron emission of the polymer becomes less weak with increasing temperature
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Sedlačík, Martin. "Anorganický tepelněizolační materiál pro zdící prvky." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2020. http://www.nusl.cz/ntk/nusl-414139.
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This master’s thesis deals with preparation of foam glass and explores the possibilies of utilization of this material as an inorganic thermal insulating filler of fired hollow bricks. Foam glass was prepared via powder sintering method from waste packaging glass, using limestone and graphite as foaming agents. After inital analysis of raw materials, the effect of mixture composition and different processing parameters on bulk density, pore size and morphology of foam glass was investigated. Last but not least, different ways of manufacturing thermal insulating bricks, by preparation of foam glass directly in the cavities of fired hollow bricks, were tested.
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Yahyaoui, Hanen. "Matériaux isolants pour appareillages haute tension dans le domaine du courant continu : comportement et vieillissement." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS267.
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Les projets de mise en place dans les prochaines décennies de « super réseaux intelligents », qui prévoient la construction de centrales de production à des milliers de kms des centres de consommation, nécessite le développement à large échelle du transport de très fortes puissances par câbles à courant continu. Les principaux verrous à ce développement se situent au niveau du câble et des appareillages adéquats, qui doivent être conçus sur des critères spécifiques et comporter des matériaux isolants ayant des propriétés particulières. Outre la variation de la résistivité qui dépend fortement du champ électrique et de la température, il est établi que des charges sont injectées dans la matière isolante, donnant lieu à une charge d'espace modifiant la répartition du champ électrique. Dans le cas d'un renforcement du champ électrique, la présence de charges d'espace peut conduire à une accélération du vieillissement électrique et, par suite, à un phénomène auto-accélérant pour la rupture diélectrique. Le comportement de ces matériaux sous fortes contraintes continues et en particulier leur vieillissement reste aujourd'hui mal connu.Ce travail de thèse concerne ainsi l'étude du comportement diélectrique de résines époxydes chargées d'alumine utilisées comme supports isolants dans les disjoncteurs à isolation gazeuse en vue d'évaluer leur aptitude à être utilisées dans des appareillages de coupure haute tension continue. Les différentes propriétés diélectriques de ce matériau à l'état initial (facteur de pertes, résistivité volumique, seuils et coefficients de non linéarité, résistivité surfacique, rigidité diélectrique, évolution des charges d'espace) sont déterminées et étudiées sous contrainte électrique continue et à différentes températures.Afin de mieux évaluer l'effet à long terme de la charge d'espace sur le matériau et d'en tirer des informations approfondies pour la conception des futurs composants pour la haute tension à courant continu, une étude de vieillissement accéléré sous contraintes électriques (champs continus) et thermiques (différentes températures) est réalisée. En plus de la charge d'espace, les autres paramètres analysés (permittivité, pertes diélectriques) constituent également des marqueurs potentiels du vieillissement du matériau. L'analyse de l'évolution de ces marqueurs constitue une phase nécessaire dans la compréhension du comportement du matériau pour une utilisation en haute tension à courant continuThe development of high voltage dc equipment requires design according to specific criteria and including materials with appropriate properties. Indeed, while in ac the dielectric behaviour is mainly determined by permittivity, which varies little for the used materials with field and temperature at power frequency, the dc behavior is determined by highly non-linear volume and surface conductivity-related phenomena. Thus, it is well known that, in dc conditions, electric charge is injected and trapped in the bulk and on the surface, affecting the distribution of the electric field. Space charge accumulation is able to increase significantly the values of the field, thus accelerating ageing and increasing the risk of breakdown. The electrode nature, the field and temperature dependence of the electrical conductivity of the insulating material are key factors involved in the high dc field phenomena.Epoxy resins form an important category of polymeric insulating materials used in a wide range of electric power installations and equipment. In particular, they have been used especially as insulating supports for ac Gas Insulated Switchgear (GIS), because of their electrical and mechanical properties. However, the behaviour of these materials under high dc stress is less known and needs thorough investigation in view of dc applications.The purpose of this thesis is to investigate dielectric behavior of epoxy resins in order to assess their suitability for use in high DC voltage switchgear and define actions and criteria support for the design of such devices.We start by presenting the most important chemical thermal and dielectric properties of polymers as well as the various properties of the epoxy resin.Dielectric properties of the material at initial state with continuous temperature and electrical stress (loss factor, volume resistivity, thresholds and nonlinearity coefficients, surface resistivity, breakdown, evolution of space charge) are determined and investigated under dc fields at different temperatures
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Ратушняк, Г. С., and О. Ю. Горюн. "Використання теплоізоляційних матеріалів на основі аерогелю для зменшення тепловтрат будівель." Thesis, ВНТУ, 2018. http://ir.lib.vntu.edu.ua//handle/123456789/23932.
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Доповідь присвячена аналізу підвищення теплоізоляційних показників будівель при
використанні інноваційних теплоізоляційних матеріалів. Сьогодні вже розроблені різні види нано - або
аерогелей, використання яких дозволяє створювати матеріали з новими властивостями. Аерогелі
можуть ефективно застосовуватися в склопакетах, світлопрозорих покрівельних конструкціях
Теплоізолюючі матеріали на їх основі можуть використовуватись для утеплення зовнішніх стін будинку
та вузлів примикання. Застосування інноваційних теплоізоляційних матеріалів дозволить підвищити
енергоефективність багатоповерхових житлових будинків та зменшити затрати коштів на оплату
спожитих енергоносіїв на опалення в холодний період року.The report is devoted to the analysis of increase of insulation parameters of buildings using innovative insulation materials. Today, different types of nano - or aerogels have been developed, the use of which allows the creation of materials with new properties. Aerogels can be effectively applied in fiberglass, translucent roofing structures. Thermal insulation materials on their basis can be used for insulation of external walls of the house and adjacent units. The use of innovative thermal insulation materials will increase the energy efficiency of multi-storey residential buildings and reduce the cost of consuming energy for heating in the cold season.
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Naldi, Matteo. "The effect of the temperature dependency of building insulation conductivity in continental and humid temperate climate." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
Find full textAbstract:
Constant conductivity values of insulating materials are typically used in building design and assessment. However, the thermal conductivity of insulating materials changes with temperature. Linear temperature-dependent law exist for many inorganic fibrous materials such as fiberglass or rockwool, that exhibit a decreased thermal conductivity (better performance) at low temperatures, and a higher thermal conductivity (weaker performance) at high temperatures. However some insulating materials, especially the petrochemical-foamed insulation such as the polyisocyanurate (PIR), exhibit less regular behavior with poorer performance at cold temperatures.
In this scenario, using constant thermal resistance values results in actual building are different from the design predictions, with increasing building energy consumptions, greater risks of condensation issues, and decreased occupant comfort.
This thesis aims to understand the impact of the thermal conductivity change due to temperature when the insulation is used for exterior walls and flat roofs. Experimental results were used in detailed building energy simulations in the continental and humid temperate climates of Toronto and Milan respectively.
Common rigid insulating materials boards were taken into account, such as fiberglass, rock- wool, polyisocyanurate, extruded polystyrene, and a hybrid insulation system, that is constituted by two different materials, polyisocyanurate and rockwool.
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Přikrylová, Pavlína. "Vývoj tepelně izolačních materiálů na bázi odpadních textilních vláken." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265439.
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The increasing quantity of waste represents serious environmental, social and economic problem. Wastes produced from industry and households. A large part of the economy transforms a certain amount of raw materials to waste in their production, because it is currently emphasis is placed on finding sustainable sources of raw materials. One of the suitable secondary raw materials can be discarded textiles or waste from the textile industry. These kinds of textile waste often ends up in landfills or incinerators, so it is from an ecological and environmentally advantageous to their further use. The diploma thesis deals with the study and development of thermal and acoustic insulation materials based on textile fibers. It focuses on the legislative requirements for waste management for the sorting of textile wastes and their subsequent modification before reuse. Further it contains kinds of textile fibers and bonding technologies thermal and acoustic insulation materials. Finally, an evaluation of thermal insulation, acoustic and mechanical properties of fibrous insulation materials.
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Bugla, Marek. "Virtuální laboratoř na bázi JAVA a LABVIEW." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217510.
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Dielektrické materiály jsou použivány v elektronice i v elektrotechnice. Jako jejich základní vlastnost může považovat změnu jejich charakteristik během jejich životnosti. Změny jsou způsobeny namáhaním materiálu vyvolané elektrickými či teplotími vlivy. Možnost jak určit průběh jejich charakteristik v závislosti na čase je měření proudu během aplikování elektrického napětí na materiál. Tyto experimenty vědci z LEMD provaděli ručně, tento postup ale není přílíš učinný pro vysokofrekvenční signály nebo pro experimenty s dlouhou periodou. Hlavním cílem této práce bylo vytvořit aplikaci v LabVIEW k ovládaní měřícího přístroje Keithley (generátor napětí) a k automatickému získavání měřených hodnot v pikoampérech. Tato aplikace nabízí uživateli různé funkce: - Zadání vystupního napětí. - Vyběr typu průběhu. - Definování délky periody. - Ovládaní přístroje. - Měření proudu, ukládaní dat do souboru vhodného pro jiné aplikace (textový soubor). - Analýzu naměřených dat.
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FANTUCCI, STEFANO. "Advanced materials for the energy retrofit of opaque building envelopes. From laboratory thermal characterisation to the application on the building components." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2711559.
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In EU almost 40% of the final energy use is consumed by the building sector. In particular, ~ 83% of existing buildings were built before 1991 when poor or no-energy regulations were applied. For this reason, pushing towards deep renovations of the existing building stock, which has an important energy saving potential, can be one of the best solutions to address the next targets of 40% reduction of the emissions until 2030 (Paris Agreement). Among the retrofit interventions, the renovation of building envelopes seems to be one of the most effective practice. Nevertheless, the intervention on building envelope presents several issues, since space saving, technological and historical compatibility represent important barriers which limit the large diffusion of envelope retrofit intervention. In the thesis four different advanced materials were deeply investigated: Super Insulating Materials, Advanced Thermal Plasters, Phase Change Materials, and Low Emittance Materials. These materials start to be attractive since they seem to be particularly suitable for all the cases in which usual envelope retrofit techniques cannot be adopted. Their high potential is mainly related to the high thermal performance (thermal insulation or storage capability) they are able to provide with lower thickness and less use of space if compared to traditional materials. Unfortunately, the building sector is a conservative market, and as a consequence, despite the great potentials of advanced materials, they are still poorly adopted, because of the high costs, the short durability (concerning the building lifetime) and the lack of knowledge about their actual thermal behaviour. The aim of the thesis is to overcome the barriers that limit the use of these advanced materials in buildings, providing methodologies, tools, data and guidelines related to their application in energy retrofit interventions on opaque building envelope components. For this reasons the research activities were focused on experimental (in lab and in-field) analyses and on numerical modelling. For each Advanced Material, the investigations were carried out at different scales: material, component and building scale. At material scale, laboratory assessment of the thermal performance and development of new testing procedures were carried out by using a Heat Flow Meter Apparatus. At building component scale, laboratory experiments using a double climatic chamber (Building Envelope Test cell) were performed. Moreover, each presented technology was installed in a real case study (demonstration buildings) and its performance was monitored under actual operating conditions. The results of the in-lab and in-field experimental activities were used for the empirical validation of different simulation software. Moreover, the validated models were used to test different design alternatives that allow defining new guidelines for the proper design of envelope retrofit making use of advanced materials. In the last phase, the analyses allowed to scale up from the component level to the building/room level, so to identify and to demonstrate the effects/benefits achievable through the adoption of the proposed advanced materials on IEQ and energy demand, in comparison to usual and conventional solutions.
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Garth, John Stuart. "Experimental Investigation of Lateral Cyclic Behavior of Wood-Based Screen-Grid Insulated Concrete Form Walls." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1857.
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Insulated concrete forms (ICFs) are green building components that are primarily used for residential wall construction. Unlike most polystyrene based ICF variants, the Faswall ICFs used in these experiments were significantly denser because they were made from recycled wood particles and cement. The current design approach for structures constructed with this type of wall form only allows the designer to consider the contribution of the reinforced concrete cores. Previous research has shown that this approach may be conservative. This project experimentally evaluated the lateral structural response of these types of grid ICF walls under increasing amplitude of in-plane cyclic loading. Two different height-to-length (aspect) ratios (approximately 2:1 and 1:1) were investigated, as was the effect of simultaneous gravity load. Furthermore, the reinforced concrete grid was exposed for each aspect ratio in order to examine the contribution of the ICF blocks to the lateral response. Analyses of hysteretic behaviors and failure modes indicated conservatism in the current design approach for estimating lateral strength and ignoring the beneficial contribution of the ICF blocks to overall performance. The presence of the wall forms increased the lateral shear capacity of the walls by an average of 42% (compared to the walls with forms removed), while also increasing the deformation capacity by an average of 102%. Furthermore, by considering an additional gravity load of 10 kips-per-lineal-foot (klf), the shear resistance of the walls increased by 32% (versus walls only subjected to self-weight), on average, and the deformation capacity of the walls increased by an average of 19%. Comparisons of the experimental results to several design equations led to the recommendation of a design equation that was previously accepted for another type of ICF system.
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Koutný, Ondřej. "Příprava pórobetonu pro tepelně izolační účely." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2014. http://www.nusl.cz/ntk/nusl-217095.
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In these days of economic crisis subsiding, in the civil engineering the attention is pointed especially to the systems, which effectively reduce energy and decrease costs associated with using of residential or industrial premises. Especially the heat-insulating systems are mentioned, because of their characteristics and construction which will be applied economical solutions. It is possible to use the materials based on aerated concrete which excel within construction materials due to its heat-insulating properties. The use of this material for clearly heat-insulations seems to be fully-fledged alternative to standard heat-insulating systems also due to combination of nature character and sufficient strength. This work deals with possibility of preparation non-bearing, heat-insulating material based on autoclaved aerated concrete with volume weight under 200 kg/m3.
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Freye, Claudius [Verfasser], Frank [Akademischer Betreuer] Jenau, and Thomas [Gutachter] Leibfried. "Methoden und Aspekte zur Leitfähigkeitsanalyse von Isolationsmaterialien der Kabeltechnologie und zur Isolationskoordination für Systeme der Hochspannungsgleichstromübertragung (HGÜ) : Methods and aspects for conductivity analysis of insulating materials in cable technology and for insulation coordination in high-voltage direct current transmission (HVDC) systems / Claudius Freye ; Gutachter: Thomas Leibfried ; Betreuer: Frank Jenau." Dortmund : Universitätsbibliothek Dortmund, 2020. http://d-nb.info/1214887627/34.
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Adetunji, Oludurotimi Oluwaseun. "The nature of electronic states in conducting polymer nano-networks." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1206218304.
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Suetake, Graziela Yumi. "Avaliação do desempenho térmico de mantas isolantes em guaritas de fibra de vidro." Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2780.
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Tratando-se de construções leves, para as condições climáticas de Curitiba, é recomendável o uso de materiais de cobertura que minimizem a transferência de calor no verão, porém evitando perdas de calor no inverno. A utilização de materiais isolantes como barreiras radiantes, formadas, por exemplo, por folhas de alumínio justapostas, pode trazer vantagens térmicas nessas duas situações. Uma opção de baixo custo para exercer a função de uma barreira radiante baseia-se no uso de embalagens Tetra Pak® , as quais têm uma de suas faces aluminizada. A pesquisa teve por objetivo avaliar o desempenho térmico das seguintes mantas isolantes: placas de 50 mm de Isopor® , foil dupla face e mantas Tetra Pak® em coberturas de guaritas de fibra de vidro, em condições reais de exposição aos elementos do clima e nos períodos de transição outono-inverno e primavera-verão. Os procedimentos metodológicos no período de transição outono-inverno compreenderam a comparação das temperaturas do ar e superficiais da cobertura. No período de transição primavera-verão, realizou-se a comparação das temperaturas do ar, superficiais da cobertura e das paredes face leste e face sul e da medição do fluxo de calor, para cálculo da resistência térmica. A utilização das mantas Tetra Pak® com a face aluminizada voltada para a cobertura ou com revestimento em dupla face (duas mantas Tetra Pak® coladas - ambas as faces aluminizadas expostas) apresentaram uma redução na temperatura superficial máxima de 9,8°C e 9,3°C, respectivamente e um aumento na temperatura superficial mínima de 2,7°C e 2,0°C, respectivamente. Para o período de transição primavera-verão os resultados para as mantas Tetra Pak® mostraram-se superiores aos das placas de Isopor® e do foil dupla face.In light-weight buildings under the climatic conditions of Curitiba, it is recommended the use of roofing materials that minimize heat gains in summer while avoiding heat losses in winter. The use of insulating materials such as radiant barriers, formed, for example, by juxtaposed aluminum sheets, can bring thermal advantages in such situations. A low-cost option to perform the function of a radiant barrier is based on the use of open Tetra Pak® packages, which have one of their aluminized sides exposed. The aim of the study was to evaluate the thermal performance of the following insulation sheets: 50mm Styropor® , double-sided foil and Tetra Pak® sheets for fiberglass enclosures, in conditions of natural exposure to weather elements and in transitional periods in fall-winter and spring-summer. The methodological procedures in the autumn-winter transitional period comprised the comparison of air and surface temperatures of the roof elements. In spring-summer, air and surface temperatures of roof and walls (east- and south-facing) were compared and the measurement of the heat flow, to calculate the thermal resistance. The use of Tetra Pak® sheets with an upward-facing aluminized side or with double-sided coating (two glued, open Tetra Pak® packages - aluminized faces exposed) showed a reduction in the maximum surface temperature of 9.8°C and 9.3°C, respectively, and an increase in the minimum surface temperature of 2.7°C and 2.0°C, respectively. For the spring-summer transitional period, results for Tetra Pak® sheets were superior to those of Styropor® and double-sided foils.
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Desmars, Loriane. "Etude des propriétés électriques et thermiques de matériaux composites à matrice époxy-anhydride pour l'isolation haute tension." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI021.
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L’avènement des énergies renouvelables, notamment offshore, et la nécessité de transporter l’électricité sur des distances toujours plus grandes tout en réduisant les pertes en ligne requièrent la mise en place d’un nouveau réseau électrique plus performant, le supergrid. L’amélioration des sous-stations ultra haute tension en courant alternatif (UHVAC) de type poste sous enveloppe métallique (PSEM), i.e. la réduction de leur empreinte au sol ou leur montée en tension, s’inscrit parmi les défis engendrés par le développement du supergrid. L’amélioration de la tenue aux contraintes électrothermiques des isolants solides employés dans les PSEM a été identifiée comme le principal verrou technologique pour le perfectionnement de ces appareillages, déjà pleinement maîtrisés en HVAC. Les travaux présentés dans ce manuscrit ont été motivés par la nécessité de développer un matériau isolant électrique plus performant que les matériaux existant actuellement sur le marché. L’un des matériaux couramment employés pour la fabrication d’isolants solides pour PSEM, une matrice époxy-anhydride chargée d’alumine micrométrique, a servi de référence commerciale à notre étude. Suite à une étude bibliographique, nous avons choisi de conserver la matrice époxy du système commercial de référence et de jouer sur les charges inorganiques employées pour optimiser les propriétés du matériau isolant. Les travaux présentés mettent en évidence l’influence de la nature des charges inorganiques (alumine ou nitrure de bore hexagonal), de leur facteur de forme (quasi sphérique ou lamellaire) et de leur fraction volumique sur la conductivité thermique, le coefficient d’expansion thermique, les propriétés mécaniques dynamiques, les propriétés diélectriques, la conductivité électrique à haute tension (DC) et la rigidité diélectrique (AC) des matériaux composites. L’étude expérimentale des relations structure-propriétés est complétée par un travail de modélisation des propriétés diélectriques et de la conductivité thermique des matériaux compositesThe integration of renewable energies to the power grid requires its modification in order to ensure its stability, security and efficiency. Improving ultra-high voltage alternative current (UHVAC) gas insulated substations (GIS), e.g. reducing their size or increasing their voltage, is one of the challenges induced by the development of the future power grid, the supergrid. Increasing the ability of solid insulators used in such equipment to withstand electro-thermal stress has been identified as the main obstacle to overcome. The work presented in this manuscript has been motivated by the necessity to develop more efficient electrical insulating materials compared to commercially available ones. An epoxy-anhydride matrix filled with micron sized alumina, often used to produce GIS solid insulators, has been used as a reference for this study. We decided to keep the matrix of the reference material throughout our work and to concentrate on the filler influence in order to optimize the properties of the composites. The impact of the nature of the filler (alumina or hexagonal boron nitride), its shape factor (platelets or almost spherical particles) and its volume fraction upon thermal conductivity, coefficient of thermal expansion, dynamic mechanical properties, dielectric properties, high voltage direct current (DC) conductivity and AC breakdown strength have been highlighted. The experimental study of structure-property relationships is completed by dielectric properties and thermal conductivity modelling using the effective medium theory
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Figueiredo, Mariangela Tassinari de. "Resolução numérica de equações de transporte de cargas elétricas através de isolantes." Universidade de São Paulo, 1988. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-18052007-164709/.
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Apresentamos alguns métodos numéricos para a resolução das equações hiperbólicas que regem problemas de transporte de cargas elétricas em isolantes, aplicando-os a quatro problemas específicos: injeção de corrente por um contato ôhmico em uma amostra com voltagem constante aplicada; transporte de um pulso de cargas através de uma amostra em circuito aberto; transporte de um pulso de cargas através de uma amostra submetida a uma diferença de potencial constante (tempo de vôo); e, finalmente, descarga termo-estimulada em circuito aberto. Empregamos, basicamente, dois tipos de métodos: características e diferenças finitas. Concluímos que, quando as descontinuidades são importantes, é mais conveniente usar o método das características; porém, quando não houver descontinuidades ou se estas não forem importantes, alguns métodos de diferenças finitas podem ser utilizados com boa precisão e menores tempos de computação do que aqueles gastos pelos métodos das características.Numeral methods for solving partial differential equations of the hiperbolic type, governing some problems of transport of electric charge in dielectrics are presented and then applied to four specific problems: injection of charge via an ohmic contact into a sample with a constant applied voltage; transport of a pulse of charge through a sample in the open circuit mode; transport of a pulse of charge through a sample subjected to a constant voltage; and finally, thermally stimulated discharge in open circuit. Essentially two kinds of methods are employed: the method of characteristics and finite-difference methods. It is concluded that when discontinuities are important, the method of characteristics is the most convenient; otherwise, appropriate finite-difference schemes can be used with sufficient precision and less time expenses in computers.