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Tesi sul tema "Electric conductivity"

Autore: Grafiati
Pubblicato: 4 giugno 2021
Ultima modifica: 1 agosto 2024

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1

Shegelski, Mark Raymond Alphonse. "Hopping conductivity in lightly doped semiconductors". Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/27529.

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In lightly doped semiconductors (LDSs), electrons can exist in localized states around impurities and dc electronic conduction can occur by electrons hopping between localized states. Such hopping is the dominant mechanism for conduction if the temperature is so low that the contribution from band electrons is negligible. According to theories of hopping conduction, at low enough temperature T, the conductivity σ will be o=σ₀e⁻(T₀/T)¼ where T₀ is a temperature which depends on the material. Experimental work on doped semiconductors which exhibits this form of σ is scarce. Recently, however, conductivities which were clearly of this form were reported for lightly doped n-GaAs and lightly doped n-InP. The experimental results were surprising in that the temperature ranges were well above, and the T₀ values well below, the limits set by the theories. To understand these experimental results, hopping in LDSs is modelled in this dissertation using a resistor network. This dissertation is unique in that the conductivity of the unabridged resistor network is examined in a temperature range (called "the high temperature regime") where kT is comparable to the spread ∆ε in the energies of localized electrons. A numerical simulation is performed and an analytic theory based on percolation methods is presented. In this dissertation, an analytic approach is developed for the first time for studying how, in the high temperature regime, the conductivity of the unabridged resistor network depends on the density of localized states. It is found that, in either two or three dimensions, if the density of states is flat, σ is of the activated form o=σ₀e ⁻εa/kt. The activation energies are found to be εa=0.28∆ε in two dimensions and εa =0.20∆ε in three dimensions. These values are considerable improvements over the estimates of previous workers, who used the low temperature asymptotic form of the resistance in the high temperature regime. It is also revealed that σ can be o=µσ₀e ⁻(T₀/T)¼ in the high temperature regime if the density of states decreases with |ε⁻µ₀| for energy e far enough away from the zero temperature chemical potential µ₀, These results are in accord with the experimental results described above.
Science, Faculty of
Physics and Astronomy, Department of
Graduate
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2

Fung, Sing Chor. "Conductivity fluctuations in yttrium barium cooper oxides". HKBU Institutional Repository, 1994. http://repository.hkbu.edu.hk/etd_ra/34.

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3

Li, Haiying. "Study of thermally reworkable epoxy materials and thermal conductivity enhancement using carbon fiber for electronics packaging". Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04062004-164718/unrestricted/li%5Fhaiying%5F200312%5Fphd.pdf.

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4

Oh, Tae-il. "Electrical conductivity and related defect structures in reduced rutile". Full text open access at:, 1985. http://content.ohsu.edu/u?/etd,90.

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5

Allen, David Andrew. "Electrical conductivity imaging of aquifers connected to watercourses : a thesis focused on the Murray Darling Basin, Australia". University of Technology, Sydney. Faculty of Science, 2007. http://hdl.handle.net/2100/428.

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Electrical imaging of groundwater that interacts with surface watercourses provides detail on the extent of intervention needed to accurately manage both resources. It is particularly important where one resource is saline or otherwise polluted, where spatial quantification of the interacting resources is critical to water use planning and where losses from surface waterways need to be minimized in order to transport water long distances. Geo-electric arrays or transient electromagnetic devices can be towed along watercourses to image electrical conductivity (EC) at multiple depths within and beneath those watercourses. It has been found that in such environments, EC is typically related primarily to groundwater salinity and secondarily to clay content. Submerged geo-electric arrays can detect detailed canal-bottom variations if correctly designed. Floating arrays pass obstacles easily and are good for surveying constricted rivers and canals. Transient electromagnetic devices detect saline features clearly but have inferior ability to detect fine changes just below beds of watercourses. All require that water depth be measured by sonar or pressure sensors for successful elimination of effects of the water layer on the data. The meandering paths of rivers and canals, combined with the sheer volume of data typically acquired in waterborne surveys, results in a geo-referencing dilemma that cannot be accommodated using either 2D imaging or 3D voxel imaging. Because of this, software was developed by the author which allows users to view vertical section images wrapped along meandering paths in 3D space so that they resemble ribbons. Geo-electric arrays suitable for simultaneous imaging of both shallow and deep strata need exponentially spread receiver electrodes and elongated transmitter electrodes. In order to design and facilitate such arrays, signed monopole notation for arrays with iv segmented elongated electrodes was developed. The new notation greatly simplified generalized geo-electric array equations and led to processing efficiency. It was used in the development of new array design software and automated inversion software including a new technique for stable inversion of datasets including data with values below noise level. The Allen Exponential Bipole (AXB) array configuration was defined as a collinear arrangement of 2 elongated transmitter electrodes followed by receiver electrodes spaced exponentially from the end of the second transmitter electrode. A method for constructing such geo-electric arrays for use in rivers and canals was developed and the resulting equipment was refined during the creation of an extensive set of EC imaging case studies distributed across canals and rivers of the Australian Murray- Darling Basin. Man made and natural variations in aquifers connected to those canals and rivers have been clearly and precisely identified in more than 1000 kilometres of EC imagery.
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6

Santiago, Claudia. "Resistivity and conductivity studies of the Rattlesnake Springs, New Mexico watershed". To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.

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7

Ray, Nicolas [Verfasser], e Oleg [Gutachter] Pankratov. "Phonon-induced electron scattering and electric conductivity in twisted bilayer graphene / Nicolas Ray ; Gutachter: Oleg Pankratov". Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2018. http://d-nb.info/1152078976/34.

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8

Crawford, Charles. "Transverse Thermoelectric Effect". ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1866.

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Anisotropic thermoelectric effects can be measured in certain materials. Anisotropy can also be simulated using a repeated, layered structure of two materials cut at an angle. Various aspect ratios and angles of inclination are investigated in device geometry in order to maximize the thermopower. Eddy currents have been shown to occur in thermoelectric devices, and evidence of these currents are revealed in finite element analysis of the artificially synthesized anisotropic Peltier effect.
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9

FIGUEROA, FRANCISCO RAMON. "MONOMERS, POLYMERS AND CHARGE-TRANSFER COMPLEXES OF DITHIAFULVENES AND POLYMERS FROM 4,4'-SULFONYL DIPHENOL (2-BENZYLIDENE, 1,3-DITHIOLES, 1,3-DITHIOLIUM)". Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183817.

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Monomers, polymers, charge-transfer complexes of 2-benzylidene-1,3-dithioles (Dithiafulvenes), and 1,3-dithiolium (Dithiafulvenium) salts of dithioesters and poly(dithioesters) were synthesized. The infrared, nuclear magnetic resonance (NMR) and ultra violet spectra of these materials were also reported. Condensation polymerization of piperidinium tetrathio terephthalate with α-halocarbonyl compounds using phase-transfer techniques yielded poly(dithioesters) that upon dehydrative cyclization with sulfuric acid gave poly(1,3-dithiafulvenium) salts. Polymerization of substituted dithiafulvenes with diacid chlorides, p-phenylene diisocyanate or terephthalaldehyde yielded polymers with inherent viscosities of 0.10 dL/g to 0.21 dL/g. The electric resistivity of the charge-transfer complexes of several dithiafulvenes and the electron donors TCNQ and TNF measured by the two-probe method was found to be >10⁶ Ω.cm at room temperature, hence behaving like insulators. Polyesters and polyesterimides of 4,4'-sulfonyl diphenol were synthesized. The low molecular weight polymers had viscosities of 0.12 to 0.20 dL/g. The polymers formed brittle films and their IR and NMR spectra were reported.
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10

Miller, Darren A. "The ionic conductivity of p(2-hydroxyethyl methacrylate) hydrogels /". Title page, contents and summary only, 1995. http://web4.library.adelaide.edu.au/theses/09PH/09phm6483.pdf.

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11

Simpson, Joycelyn Ovetta. "Modeling viscosity and ionic conductivity of epoxy resins using free volume concepts". Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/10258.

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12

Richter, Reinhart. "Quantum corrections to the conductivity in simple metallic glasses". Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75757.

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The validity of the theories of quantum corrections to the electrical conductivity, namely weak localization and enhanced electron-electron interaction, has been tested quantitatively in well characterized, free-electron-like Mg-Cu and Mg-Zn metallic glasses containing various amounts of Ag and Au through measurement of the electrical resistivity between 1.5K and 20K in magnetic fields up to 5.6T. It is found that the theories give an excellent description of the magnetoresistance at low fields, in both the weak and strong spin-orbit scattering limit but that at higher fields they break down. The electron spin-orbit scattering and dephasing rates have been deduced. Above 4K the dephasing rate is controlled by inelastic electron-phonon scattering, below 4K it saturates to a value consistent with a new model of dephasing of the quantum back scattering interference by ionic zero-point motion. The first direct measurement of the effect of superconductivity on the magnetoresistance in bulk amorphous metals is also presented. The temperature dependence of the resistivity between 1.5 and 6K is in qualitative but not quantitative agreement with the quantum correction theories.
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13

Edwards, Thomas Raymond. "Empirical Ionospheric Models: The Road To Conductivity". Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/100284.

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The Earth's polar ionosphere is a highly dynamic region of the upper atmosphere, and acts as the closure of the greater magnetospheric current system. This region plays host to many electrodynamic effects that impact terrestrial systems, such as power grids, railroads, and pipelines. These effects are fundamentally related to the currents, electric fields, and conductivity present in the polar ionosphere. Understanding and predicting the electrodynamics of this region is vital to being able to determine the physical impacts on terrestrial systems and provide predictions to government and commercial entities. Empirical models play a key role in the research and forecasting of the solar wind and interplanetary magnetic field's impact on the polar ionosphere, and is an active area of development and research. Recent interest in polar ionospheric conductivity has led to a community-wide campaign to develop our understanding of this portion of the electrodynamic system. Characterizing the interactions between the solar wind and the polar ionosphere is a difficult task, as the region of interest is highly data starved in many respects. In particular, satellite based data products are scarce due to being costly and logistically difficult. Recent advancements in data sources (such as the Swarm and CHAMP satellite missions) as well as continued research into the physical relationships between solar wind and interplanetary magnetic field drivers have provided the opportunity to develop new, novel tools to study this region of interest. In this dissertation, two polar ionosphere models are described in Chapters 3 and 4, along with the original research that their construction has produced in Chapter 1. These two models are combined to provide a foundation for future research in this area, which is described in Chapter 5.
Doctor of Philosophy
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14

Manna, Tapan K. "Impulse impedance of grounding systems and its effect on tower crossarm voltage : a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /". Click to access online version, 2006. http://proquest.umi.com/pqdweb?index=97&did=1208141981&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1256323226&clientId=28564.

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15

Su, Bin. "Electrical, thermomechanical and reliability modeling of electrically conductive adhesives". Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-12192005-124641/.

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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2006.
Qu, Jianmin, Committee Chair ; Baldwin, Daniel, Committee Member ; Wong, C. P., Committee Member ; Sitaraman, Suresh, Committee Member ; Jacob, Karl, Committee Member.
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16

Cao, Jingnan, e 曹靖楠. "Thermoelectric transport properties in nanoscale systems". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49799708.

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As the fast development of nanotechnology and further industrial applications, theoretical investigations upon nanoscale devices are in urgent need. Until now several formalisms have been well established in quantum transport of mesoscopic areas, including of tight-binding and first principle calculations. In this dissertation those methods were partly explored to explore transport and thermoelectric features in various models and actual devices. The density functional theory plus non-equilibrium Green’s function serves well in the probing process of transport properties like conductance in mesoscopic systems. Atoms’ positions were treated as the only input parameters and one computation package based on NEGF-DFT loop was utilized to get the numerical results, then the corresponding thermal quantities were analysed. The coherent transport exhibits an obvious character in transmission spectrum called transmission node, whose existence relies on the asymmetric structure of molecular junctions. In the main body of the thesis, firstly two types of model simulation were tested, and the following thermoelectric quantities showed that there’s one interesting signature in the thermopower performance, which was its temperature independence around transmission node. Through comparisons between different system parameters a rough regular pattern was obtained, that the degree of zero transmission and the energy difference around it influenced this temperature invariance feature at the same time. While these two properties were mainly determined by the natural structure of devices. Besides model simulations the ab initio investigations were also carried out. Although the actual device was not easily altered as ideal models, some similar behaviours in the transmission and thermal curves were still found out. The temperature insensitivity was considered to appear more often in a π electron dominated molecular structure rather than ones with σ electron interactions.
published_or_final_version
Physics
Master
Master of Philosophy
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17

Yoon, Im T. (Im Taek). "Anisotropy of conduction electrons in n-InSb and extrinsic and intrinsic properties of HgCdTe". Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc332803/.

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The anistropy of the orbital and spin properties of conduction electrons in InSb has been measured simultaneously using a cyclotron-resonance type experiment. This represents the first time that the anistropy of effective mass in InSb has been directly measured using an optical method.
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18

Li, Qi. "Competing orders in s-wave and p-wave superconductors /". Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2008. http://hdl.handle.net/1794/8285.

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Thesis (Ph. D.)--University of Oregon, 2008.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 107-110). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.
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19

Nartey, Emmanuel Akuffo. "Oil/ Paper Insulation for HVDC: Conductivity of Oil". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13264.

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The work begins with a theoretical description of conductivity and the importance of this material property in the electrical power industry. The various theories describing high voltage conduction in highly insulating dielectric liquids are analysed to ascertain their propensity to explain the exponential rise in the conductivity of the insulating liquid at high fields.The work goes further to analyse the various methods and standards that are presently utilised in the measurement of conductivity of highly insulating oils. The short-comings of the present methods particularly the IEC 61620 and 60247 are identified. The physics behind the peculiar behaviour of the conductivity when stressed under high electric fields is described and analysed.Measurements carries out according to a standard, may not lead to useful results. Therefore, it is preferable to determine the conductivity under practical aspects and also to measure the different parameters on which the conductivity depends (1). A new method of carrying out conductivity measurements based on the use of triangular and sinusoidal input high voltage is used in this work.Conductivity analysis is carried out based on this method while time dependency, frequency dependency and field dependencies are studied.The results of the various results show a strong dependency of the resistance of the oil on the input electric field up to two powers of ten; when the electric field is varied from zero to 10 kV/mm for all frequencies. The frequency of input voltage has a minimum effect of the results of the conductivity up to 0.1 Hz; the only observable change is the increasing values of the capacitive current component of the measured total current.The time dependency of the resistance values shows a very remarkable variation of conductivity. There is an average of 3 times in the conductivity when the oil is stressed over a 24 hour period.Finally Comsol Multiphysics simulation is carried out to compare to the results of the experimental results obtained in the laboratory. The results of the current as well as the resistance values obtained using the comsol simulation bears great similarity to that of the laboratory experiments.
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Su, Bin. "Electrical, thermomechanical and reliability modeling of electrically conductive adhesives". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/10425.

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The first part of the dissertation focuses on understanding and modeling the conduction mechanism of conductive adhesives. The contact resistance is measured between silver rods with different coating materials, and the relationship between tunnel resistivity and contact pressure is obtained based on the experimental results. Three dimensional microstructure models and resistor networks are built to simulate electrical conduction in conductive adhesives. The bulk resistivity of conductive adhesives is calculated from the computer-simulated model. The effects of the geometric properties of filler particles, such as size, shape and distribution, on electrical conductivity are studied by the method of factorial design. The second part of the dissertation evaluates the reliability and investigates the failure mechanism of conductive adhesives subjected to fatigue loading, moisture conditioning and drop impacts. In fatigue tests it is found that electrical conduction failure occurs prior to mechanical failure. The experimental data show that electrical fatigue life can be described well by the power law equation. The electrical failure of conductive adhesives in fatigue is due to the impaired epoxy-silver interfacial adhesion. Moisture uptake in conductive adhesives is measured after moisture conditioning and moisture recovery. The fatigue life of conductive adhesives is significantly shortened after moisture conditioning and moisture recovery. The moisture accelerates the debonding of silver flakes from epoxy resin, which results in a reduced fatigue life. Drop tests are performed on test vehicles with conductive adhesive joints. The electrical conduction failure happens at the same time as joint breakage. The drop failure life is found to be correlated with the strain energy caused by the drop impact, and a power law life model is proposed for drop tests. The fracture is found to be interfacial between the conductive adhesive joints and components/substrates. This research provides a comprehensive understanding of the conduction mechanism of conductive adhesives. The computer-simulated modeling approach presents a useful design tool for the conductive adhesive industry. The reliability tests and proposed failure mechanisms are helpful to prevent failure of conductive adhesives in electronic packages. Moreover, the fatigue and impact life models provide tools in product design and failure prediction of conductive adhesives.
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21

Fraser, Iain Stuart. "Electrical conduction in macroscopic carbon nanotube assemblies". Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609756.

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Ringer, Eric. "The energetis, dynamics and transport properties of CaF₂ : surface superionic conductivity". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/31029.

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23

Whittall, Kenneth Patrick. "Exploring magnetotelluric nonuniqueness using inverse scattering methods". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27563.

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I present two algorithms which solve the one-dimensional magnetotelluric (MT) problem of finding the electrical conductivity σ(z) as a function of depth in the earth. Together, these algorithms restrict and explore the nonuniqueness of the nonlinear MT inverse problem. They accept constraints which limit the space of acceptable conductivity models and they construct diverse classes of σ(z) in order to explore this space. To avoid pitfalls during interpretation, it is essential to investigate the extent of the nonuniqueness permitted by the MT data. Algorithm 1 is a two-stage process based on the inverse scattering theory of Weidelt. The first stage uses the MT frequency-domain data to construct an impulse response analogous to a deconvolved seismogram. Since this is a linear problem (a Laplace transform), numerous impulse responses may be generated by linear inverse techniques which handle data errors robustly. I minimize four norms of the impulse response in order to construct varied classes of limited structure models. Two least-squares norms minimize the energy in the impulse response or the energy in its derivative with respect to depth. Two least absolute value norms minimize the magnitudes of the response or its derivative. It is possible to use other norms. The different classes sample the range of acceptable models and the minimum structure criterion is unlikely to allow models with spurious features. The second stage of Algorithm 1 constructs the conductivity model from the impulse response using any of four Fredholm integral equations of the second kind. I evaluate the performance of each of the four mappings and recommend the Burridge and Gopinath-Sondhi formulations. I also evaluate three approximations to the second-stage equations. One of these is equivalent to the Born approximation which assumes the impulse response has negligible multiple reflections. The approximation that includes first-order multiple reflections is the most accurate and gives conductivity models similar to those given by the integral equations. Algorithm 2 solves an integral form of a nonlinear Riccati equation relating the measured frequency-domain data to a function of the conductivity. The iterative solution scheme sacrifices the efficiency of a direct inversion process such as Algorithm 1 for the advantages of incorporating localized conductivity constraints. The linear programming formulation readily accepts a wide variety of equality and inequality constraints on σ(z). I use these constraints in two ways to combat the nonuniqueness of this nonlinear inverse problem. First, I impose physical constraints derived from external sources to restrict the nonuniqueness and construct σ(z) models that are closer to reality. Second, I impose constraints specifically designed to estimate the extent ofthe nonuniqueness and explore the range of acceptable σ(z) profiles. The first technique enhances the reliability of an interpretation and the second assesses the plausibility of particular conductivity features. The convergence of Algorithm 2 is good because Algorithm 1 provides varied initial σ(z) which already fit the data well.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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24

Ywata, Ricardo Sussumu [UNESP]. "Caracterização de filmes finos de polímeros entrecruzáveis como camada dielétrica em dispositivos de eletrônica orgânica". Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/99691.

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Made available in DSpace on 2014-06-11T19:30:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-06-11Bitstream added on 2014-06-13T20:40:12Z : No. of bitstreams: 1 ywata_rs_me_bauru.pdf: 1172780 bytes, checksum: 9144da0c9124443e6313263e76ce6fbd (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O objetivo deste trabalho é a caracterização de polímeros isolantes elétricos para seu uso na fabricação de dispositivos eletrônicos orgânicos. Os polímeros estudados foram: a poli(amida-imida), PAI, poli(fenil-metilsilsesquioxano), PSQ, e o fotoresiste SU8. O processo de fabricação dos filmes poliméricos foi realizado pela técnica de spin-coating e eles foram submetidos a um processo de cura apropriado para o entrecruzamento das cadeias poliméricas. Os filmes foram caracterizados espectroscopia de impedância e microscopia de força atômica (AFM). Curvas de capacitância e tan'delta' também foram analisadas e valores menores de 10-2 foram encontradas para a tn'delta' indicando que os polímeros são bons isolantes elétricos. Curvas características de corrente versus diferença de potencial elétrico (ddp) em diferentes temperaturas foram obtidas para todos os filmes. A condução elétrica foi analisada e conclui-se que o processo de condução predominantes nos filmes poliméricos é por injeção de cargas por efeito Schottky. A altura da barreira de injeção polímero/metal calculada foi da ordem de 1,1 eV para o PSQ e 1,2 eV para o SU8 e PAI
This work aims the films characterization of electric insulating polymers for the fabrication of organic electronic devides: the poly(amide-imide), PAI, poly(phenylmethylsilsesquioxane), PSQ, and the SU8 photoresist. The manufacturing process of the polymer films was performed by spin-coating and they were submitted to the appropriated curing process in order to promote the cross-linking of polymeric chains. The thin films were characterized by using electric impedance technique and scanning atomic force microscopy (AFM). Curves of capacitance and tan'delta' were also analyzed and values smaller than 10-2 were found for tan'delta' indicating that the polymers are good electrical insulators. Current versus voltage characteristics curves at different temperatures were obtained for all films. The electrical conduction was analyzed and it was concluded that the conduction process on polymeric films are dominated by Schottky charge injection. The injection barrier height of polymer/metal was found to be of the order of 1,1 eV for PSQ and 1,2 eV for SU8 and PAI
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Lu, Daoqiang. "Fundamental understanding of electrically conductive adhesives (ECA's)". Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19911.

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Laughlin, Paul Jonathan. "The effect of uniaxial orientation upon the structural properties of polvaniline films". Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5237/.

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The effects of elongation upon the structural and electronic properties of the conducting polymer polyaniline have been investigated. In particular, the properties of high molecular weight (ca. 150 000 Daltons) polyaniline have been examined, and the effects of increased molecular weight assessed. A method has been found to elongate the emeraldine base (EB) form up to 700% (l/l(_o)=8). This induces partial molecular alignment in the polymer which, upon doping, exhibits electrical conductivity of up to 700 Scm(_-1) and electrical anisotropy of almost 4.The mechanical properties of high molecular weight emeraldine base have been investigated as a function of elongation. The breaking stress has been observed to increase by almost one order of magnitude for a 500% elongated film compared with its unoriented counterpart. The breaking strain is found to decrease initially with increasing elongation, though no noticeable change is evident for samples elongated to more than 300%. Similarly, Young's modulus increases by a factor of 2 with increased elongation, but above 300% remains approximately constant. The behaviour has been interpreted in terms of the crystalline fraction of the samples. X-ray diffraction experiments have enabled the crystalline fraction of emeraldine base and emeraldine salt (ES) to be assessed. 300% elongated EB samples exhibit increased crystalhnity compared with as-cast samples. However, no further increase in crystallmity is evident for 600% elongated samples. Unoriented ES samples have a crystalline fraction of approximately 0.3. The crystallinity of 300% and 600% elongated ES samples is slightly less than for unoriented ES. The polarised reflectance spectra of EB and ES have been measured in the region 0.5- 5.6 eV. The results show increased optical anisotropy with increasing elongation for EB samples, but no change in anisotropy for ES samples above 300% elongation. A Kramers-Kronig analysis of the reflectance data reveals near metallic behaviour parallel to the dkection of elongation, and a high degree of localisation perpendicular to this direction.
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Öztürk, Serdar Balköse Devrim. "Preparation and characterization of metal soap nanofilms/". [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezler/master/kimyamuh/T000379.pdf.

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Thesis (Master)--İzmir Institute of Technology, İzmir, 2005.
Keywords: Electrical conductivity, langmuir blodgett technique, metal soaps, nanofilms, moisture adsorption. Includes bibliographical references (leaves. 127-132).
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28

Ruiz, Trejo David Enrique. "A study of conductivity and diffusion in Sr-doped LaYo (209)". Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299723.

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Song, Yi. "AC conductivity and dielectric constant of systems near the percolation threshold /". The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726754698361.

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30

Lilly, Jonathan Patrick. "One-dimensional computer modeling of electrical conductivity through methane and synthesis gas flames". Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4898.

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Thesis (M.S.)--West Virginia University, 2006.
Title from document title page. Document formatted into pages; contains xvi, 291 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 289-291).
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31

VIVALDINI, TULIO C. "Medidas de velocidade de arrastamento de elétrons em gases inibidores de descargas pelo método de townsend pulsado". reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10629.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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32

Bai, Jing. "Percolation study of nano-composite conductivity using Monte Carlo simulation". Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002644.

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33

Mülazımoğlu, Mehmet Hașim. "Electrical conductivity studies of cast Al-Si and Al-Si-Mg alloys". Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75785.

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Cast Al-Si and Al-Si-Mg alloys containing up to 12.6 wt. pct. silicon and 1.0 wt. pct. magnesium were prepared. The changes in electrical conductivity/resistivity of these alloys due to strontium additions have been investigated and explained in terms of variations in microstructure. The conductivity behaviour of strontium-containing and strontium-free alloys was found to exhibit marked differences, depending on the silicon and magnesium contents and the rate of solidification. The electrical conductivity of single phase alloys containing less than 1.60 wt. pct. Si decreased with increasing silicon and magnesium levels. However, strontium had no effect on the conductivity of these solid solution alloys since it does not dissolve appreciably in the aluminum matrix or change the solid solubility of silicon and magnesium in aluminum. Silicon precipitation processes in the supersaturated solid solution alloys of Al-Si and Al-Si-Sr have been examined using the Johnson-Mehl-Avrami equation and found to be isokinetic. Strontium, however, retarded the growth rate of silicon precipitates. Strontium did not affect the kinetics of G.P. zone formation in Al-Si-Mg alloys but it suppressed the formation of stable Mg$ sb2$Si precipitates during subsequent aging at 175$ sp circ$C. Unlike the single phase alloys, two phase Al-Si and Al-Si-Sr alloys, in the range of 2.0 to 12.6 wt. pct. Si, exhibited different electrical conductivity behaviour. The strontium-containing alloys showed a higher conductivity than alloys with no strontium, and this conductivity difference increased as the silicon and magnesium contents were increased and the solidification rate was decreased. It has been demonstrated this difference is due to changes in the silicon morphology. Electron scattering at the interface between the aluminum matrix and the eutectic silicon phase contributes significantly more to the resistivity of unmodified alloys than that of modified alloys. In addition, the resistivity of
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34

Wood, Sandra Jean. "Determination of effective thermal conductivity of media surrounding underground transmission cables". Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/17390.

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35

Goad, Stephen D. "The theory and design of switched-mode power transformers for minimum conductor loss". Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/52290.

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A comprehensive and general analysis of the electromagnetic fields, power dissipation, and energy storage within transformer windings is presented. Emphasis is placed on applications in switched-mode power conversion. One-dimensional radial variation of the field quantities is assumed. The first phase of the investigation is for sinusoidal excitation; solutions for the current density and magnetic field intensity are derived and studied in order to develop a fundamental understanding of the basic phenomena. Expressions for the power dissipation and energy storage in both single- and multi-layer windings are then derived which, upon investigation, yield a technique for minimizing the power dissipation by choosing an optimum conductor thickness. Several levels of accuracy, ranging from exact solutions to very simple and physically meaningful series approximations, are defined and examined to determine their usefulness and range of validity. The time-harmonic treatment is generalized to arbitrary periodic exoitation by means of Fourier analysis, resulting in a powerful extension of its applicability to any possible converter topology. Results for several representative waveshapes are presented from which a fundamental dependence cn the waveform bandwidth is discovered. Practical application of the theoretical analysis is considered by developing models for several couon winding types: single and multi-filar round wire, litz wire, and sheet conductors. Experimental results are presented and compared with the theoretical results for each of these cases. Finally, a design procedure is outlined for switched—mode pour transformers which is based on this work.
Ph. D.
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36

Nuttall, Kevin. "The on-line determination of underground cable conductor temperatures". Thesis, Queensland University of Technology, 1986. https://eprints.qut.edu.au/36458/1/36458_Nuttall_1986.pdf.

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The criterion determining the maximum load able to be sustained by an underground cable is its maximum allowable conductor temperature. Above this value, degradation of insulation will commence and lead to ultimate failure of the cable. Methods using a digital computer program are available for calculating cable conductor temperature given the thermal characteristics of the cable and its environment and the loads at whlch the cable will be operated. Such methods invariably assume a 24 hourly load cycle to which the cable is subjected continuously and a maximum ground ambient temperature which conservatively occurs at the time of peak load. The thesis describes the development of an electronic device which can be installed in a substation, reading cable loading and ambient temperature in real time, and calculating in an on-line capacity, the cable conductor temperature. The device overcomes the limitations of the use of assumed variables. It calculates cable operating temperature which is continuously updated as loading and ambient conditions change. The algorithm used relies on a modification of the CIGRE Method (circa 1974) and a long term load test on a buried cable installation has confirmed its accuracy. All storage and calculation functions required are processed by a microcomputer developed specifically for the task using a proprietary line 16-bit processor. Software development was aided by the use of a high level language facilitated by the compatibility of the device processor and computer development systems already possessed by SEQEB. The device can be installed in a normal substation environment (5°c - 35°c ambient) without the need for a controlled atmosphere and will operate from normal 240V mains supply. Ten cable groups each consisting of one or two circuits may be processed from the one device and updated temperatures are calculated at hourlyIn the normal mode, continuous conductor temperature monitoring is provided which is able to accommodate any load or ground ambient temperature change. The SEQEB substation automated control system, a microprocessor based supervisory and control facility, can relay conductor temperature information from the device to remote system operators at VDU terminals via normal telecommunication lines. Alarm initiation is incorporated into software for operator attention in the case of conductor temperature exceeding allowable limits. Furthermore, the device may be used to predict conductor temperature response to a contingency situation known in advance. In the event of a power supply failure to the device and consequent memory loss, a cassette drive backup system has been employed. This system re-loads stored data and program instructions into memory upon power restoration and instructs the microcomputer to recommence operation. It is concluded that although devices of this type are new to the electricity supply industry in Australia, they can provide additional benefits for the planning and operation of a supply system. The added economic benefit to the supply authority, and ultimately the consumer, is evident in the more effective utilisation of the system with deferment of capital expenditure on new circuits while the existing system is operated nearer its full capacity. intervals.
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37

BATISTA, RAFAEL M. "Efeitos da adicao do NiO na densificacao, na microestrutura e na condutividade eletrica da zirconia totalmente estabilizada com itria". reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9499.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
FAPESP:07/56298-7
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38

Milošević, Borka. "On voltage stability monitoring and control using multiagent systems". Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/16355.

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39

Tipirneni, Raja Ram. "Characterization of thermal and electrical properties of fiber reinforced polymer (FRP) composites". Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5932.

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Abstract (sommario):
Thesis (M.S.)--West Virginia University, 2008.
Title from document title page. Document formatted into pages; contains xii, 117 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 116-117).
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40

Daniels-Hafer, Carrie Lynn. "Electrochemical tuning of charge transport at inorganic semiconductor doped conjugated polymer interfaces through manipulation of electrochemical potential /". view abstract or download file of text, 2004.

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Thesis (Ph. D.)--University of Oregon, 2004.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 185-196). Also available for download via the World Wide Web; free to University of Oregon users.
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41

Yamaguchi, T., T. Matsuoka e S. Koda. "A theoretical study on the frequency-dependent electric conductivity of electrolyte solutions. II. Effect of hydrodynamic interaction". American Institite of Physics, 2009. http://hdl.handle.net/2237/12627.

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42

Emelyanenko, Artyom. "Measurements and interpretation of lateral electromagnetic waves on the surface of low conductivity media". Thesis, Griffith University, 2020. http://hdl.handle.net/10072/393637.

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Measurements of electromagnetic fields are used for a wide range of applications. Often such measurements provide a non-destructive and non-intrusive way of obtaining information about the internal structure and other properties of the medium. Observations may be conducted across a very broad frequency range. Depending on the application domain, the frequency bands may range from the UHF band in biomedical engineering to the ULF band in geophysics. This thesis reports on several experiments where the electric and magnetic fields were measured on the surface of different media for the purpose of determining the electric properties of the material (electric conductivity and relative permittivity). A series of interference nulls were observed while measuring the electric field at UHF frequencies on the surface of a large, uniform sand dune. The source of the field was a transmitter buried in sand. The same pattern was observed after substituting the active transmitter with a passive scatterer exposed to a surface located electromagnetic transmitter. The scatterer then became a source of the electromagnetic field producing the interference pattern identical to the pattern observed in case of the active transmitter. Modelling of the surface electric field was done using known closed-form solutions for a uniform halfspace and by using an FDTD EM solver. Both approaches showed a close match with the measured fields. By varying the resistivity and the electric permittivity in the constructed models, it is demonstrated that the observed pattern (position of the nulls, nulls depth) depend on these electric properties. The inverse problem is posed with the goal of determining the electric properties of the material using the observed field. The inverse problem was solved, and the conductivity and relative permittivity of sand were determined. Two experiments conducted in different conditions showed the following results: conductivity 1×10-6 S/m and relative permittivity of 2.13 in dry conditions and conductivity 3×10-3 S/m and relative permittivity of 2.86 in wet conditions. Another experiment reports the measurements of the surface electric field on the top surface of a small three-dimensional concrete block at microwave frequencies (1 – 5 GHz). A copper rod was placed in concrete during sample manufacturing to serve as a scatterer. The FDTD solver was used for modelling and determining the inverse problem solution. At VLF frequencies, several experiments were conducted using surface impedance measurement equipment TranSIM. TranSIM allows registering amplitude of the electric and magnetic field in the time domain in the frequency range between 100 Hz – 50 kHz. The equipment was used to measure the EM fields produced by lightning strikes. Data collection was conducted on a site where the geology is known. The short-time Fourier transform was used to obtain the spectra of the electric and magnetic fields and the surface impedance was determined in the frequency range 0.5-20 kHz. Frequency sections of apparent resistivity were constructed along the measurement profiles and can be interpreted in terms of the geological sections. These experiments and subsequent data interpretation techniques represent a novel approach of determining electric properties of the material by observing the electromagnetic field on the surface of the media. Experiments conducted at UHF and microwave (S-band) frequencies utilize the innovative approach of using the field reradiated by a passive scatterer embedded in the material. Potential applications allow using that approach for non-intrusive data collection when a passive conductor is already present or can be put in the material during manufacturing. Experiments conducted at VLF frequency range utilize the data collection equipment developed at Griffith University by Mogensen and Thiel. Novel data collection and data processing approach of registering solitary short samples of electric and magnetic fields produced by lightning strikes is discussed. It is shown that the EM field observed in that way can be used consistently for creating a reliable geoelectric model of the media.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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43

Blood, Arabella M. "A study of the electrical properties of defects in silicon". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298320.

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44

TADOKORO, SANDRA K. "Obtencao e caracterizacao de ceramicas de ceria com dupla dopagem". reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11243.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:00/08908-1
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45

Eriksson, Björn. "In-line application of electric fields in capillary separation systems". Doctoral thesis, Karlstad University, Division for Chemistry, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1197.

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The magnitude of an electric field possible to apply in a capillary separation system is limited, because a high electric field causes a too high current through the capillary. Application of the electric field in-line will give an increased conductivity in the column, further increasing the risk of too high currents. The conductivity changes were found to result from an overall increase in ionic strength within the electric field. The increase in ionic strength is caused by the increase in mobile phase ions with electrophoretic velocity against the flow, together with OH- or H3O+ ions (depending on polarity) formed at the inlet electrode. Further it was found that the use of a pressurized reservoir or splitting of the flow at the inlet electrode could significantly limit the conductivity changes and thereby the maximum applicable electric field strengths could be increased.

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46

Watkins, Bobby Gene II. "Materials selection and evaluation of Cu-W particulate composites for extreme electrical contacts". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39494.

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Materials for extreme electrical contacts need to have high electrical conductivity coupled with good structural properties. Potential applications include motor contacts, high power switches, and the components of electromagnetic launch (EML) systems. In particular, the lack of durability of these materials in rail components limits practical EML implementation. These rails experience significant amounts of Joule heating, due to extreme current densities, and subsequent thermally-assisted wear. New more durable materials solutions are needed for these components. A systematic materials selection study was executed to identify and compare candidate materials solutions. Several possible candidate non-dominated materials as well as hybrid materials that could potential fill the "white spaces" on the Ashby charts were identified. A couple potential candidate materials were obtained and evaluated. These included copper-tungsten W-Cu, "self-lubricating" graphite-impregnated Cu, and Gr-W-Cu composites with different volume fractions of the constituents. The structure-property relations were determined through mechanical and electrical resistivity testing. A unique test protocol for exposing mechanical test specimens to extreme current densities up to 1.2 GA/m2 was developed and used to evaluate these candidate materials. The systematic design of multi-functional materials for these extreme electrical contacts requires more than an empirical approach. Without a good understanding of both the tribological and structural performance, the optimization of the microstructure will not be quickly realized. By using micromechanics modeling and other materials design modeling tools coupled with systematic mechanical and tribological experiments, the design of materials for these applications can potentially be accelerated. In addition, using these tools, more complex functionally-graded materials tailored to the application can be systematically designed. In this study, physics- and micromechanics-based models were used to correlate properties to the volume fraction of the constituents of the evaluated candidate materials. Properties correlated included density, elastic modulus, hardness, strength, and electrical resistivity of the W-Cu materials.
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47

Ywata, Ricardo Sussumu. "Caracterização de filmes finos de polímeros entrecruzáveis como camada dielétrica em dispositivos de eletrônica orgânica /". Presidente Prudente : [s.n.], 2012. http://hdl.handle.net/11449/99691.

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Orientador: José Alberto Giacometti
Banca: Antonio José Felix de Carvalho
Banca: Nilson Cristino da Cruz
Resumo: O objetivo deste trabalho é a caracterização de polímeros isolantes elétricos para seu uso na fabricação de dispositivos eletrônicos orgânicos. Os polímeros estudados foram: a poli(amida-imida), PAI, poli(fenil-metilsilsesquioxano), PSQ, e o fotoresiste SU8. O processo de fabricação dos filmes poliméricos foi realizado pela técnica de spin-coating e eles foram submetidos a um processo de cura apropriado para o entrecruzamento das cadeias poliméricas. Os filmes foram caracterizados espectroscopia de impedância e microscopia de força atômica (AFM). Curvas de capacitância e tan'delta' também foram analisadas e valores menores de 10-2 foram encontradas para a tn'delta' indicando que os polímeros são bons isolantes elétricos. Curvas características de corrente versus diferença de potencial elétrico (ddp) em diferentes temperaturas foram obtidas para todos os filmes. A condução elétrica foi analisada e conclui-se que o processo de condução predominantes nos filmes poliméricos é por injeção de cargas por efeito Schottky. A altura da barreira de injeção polímero/metal calculada foi da ordem de 1,1 eV para o PSQ e 1,2 eV para o SU8 e PAI
Abstract: This work aims the films characterization of electric insulating polymers for the fabrication of organic electronic devides: the poly(amide-imide), PAI, poly(phenylmethylsilsesquioxane), PSQ, and the SU8 photoresist. The manufacturing process of the polymer films was performed by spin-coating and they were submitted to the appropriated curing process in order to promote the cross-linking of polymeric chains. The thin films were characterized by using electric impedance technique and scanning atomic force microscopy (AFM). Curves of capacitance and tan'delta' were also analyzed and values smaller than 10-2 were found for tan'delta' indicating that the polymers are good electrical insulators. Current versus voltage characteristics curves at different temperatures were obtained for all films. The electrical conduction was analyzed and it was concluded that the conduction process on polymeric films are dominated by Schottky charge injection. The injection barrier height of polymer/metal was found to be of the order of 1,1 eV for PSQ and 1,2 eV for SU8 and PAI
Mestre
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48

Leuenberger, Georg H. W. "Electrostatic density measurements in green-state P/M parts". Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0429103-125812/.

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Thesis (Ph. D.)--Worcester Polytechnic Institute.
Keywords: green-state P/M parts; inverse algorithm; conductivity-density relationship; nondestructive testing. Includes bibliographical references (p. 142-148).
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49

VIVALDINI, TULIO C. "Medidas de velocidade de arrastamento de eletrons no isobutano puro". reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9525.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
FAPESP:07/06771-8
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50

Khan, Saima N. "Electrospinning Polymer Nanofibers-Electrical and Optical Characterization". Ohio : Ohio University, 2007. http://www.ohiolink.edu/etd/view.cgi?ohiou1200600595.

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