Dissertations / Theses on the topic 'Electrical resistance'
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Dhu, Tania. "Environmental monitoring using electrical resistance tomography (ERT) /." Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09SB/09sbd534.pdf.
Full textGeorgakopoulos, Dimitrios. "Spectroscopic electrical capacitance and resistance tomography systems." Thesis, University of Manchester, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488162.
Full textAkram, Shakeel. "High temperature and high electrical resistance multilayer polyimide nanodielectrics for electric motors insulation." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTS028.
Full textIn this thesis, the multilayer PI/nanocomposite films were prepared using an optimized synthesis process. The synthesized samples are characterized by experiments and simulations. First, the samples degradation mechanism was explored using pulse power source. Second, dielectric constant, dielectric loss, insulation lifetime, dielectric strength, conduction current, space charge and thermal stimulated current (TSC) were investigated. Third, trap levels were calculated using total charge decay data and TSC data. In the end, multilayer PI/nanocomposite 3D models based on actual boundary conditions obtained from SEM/TEM images of synthesized samples were constructed in COMSOL Multiphysics software. The impact of nanoparticle dispersion on the electric field enhancement is explicitly described in this model. Our results demonstrate that the chances of nanoparticles agglomeration are reduced by using multilayer structure. In consequence, less space charge and low electrical fields are observed in multilayer films. Using multilayer insulations would ensure reliable operation for electric motors and increase its lifetime
Cookson, Edward James. "Development of the Metal Foam Electrical Resistance Heater." NCSU, 2003. http://www.lib.ncsu.edu/theses/available/etd-04112003-105028/.
Full textRicard, Francois-Xavier. "Application of electrical resistance tomography to pharmaceutical processes." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417797.
Full textCovington, Brett A. "Activated carbon cloth regeneration with electrical resistance heating." Thesis, Monterey, California. Naval Postgraduate School, 1995. http://hdl.handle.net/10945/25649.
Full textRicketts, David. "Diagnosis of occlusal caries by electrical resistance measurement." Thesis, King's College London (University of London), 1995. https://kclpure.kcl.ac.uk/portal/en/theses/diagnosis-of-occlusal-caries-by-electrical-resistance-measurement(1bbd1235-84ef-427f-ae04-65591cc71d66).html.
Full textNaidoo, Thoneshan. "Signal and image processing for electrical resistance tomography." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/5140.
Full textElectrical Resistance Tomography (ERT) is in essence an imaging technique.In ERT current is injected into and removed from a vessel via paired electrodes. The resulting voltage measurements are captured between the remaining electrode pairs. The principle behind ERT is to map these boundary voltages into a conductivity distribution that represents the domain of the vessel. The author has coded a versatile reconstruction algorithm based on the Newton-Raphson algorithm. The knowledge gained by implementing the algorithm is documented in this thesis. The literature covers the basic aspects of two-dimensional and three-dimensional ERT. It is hoped that this thesis will create a greater interest in ERT at the University of Cape Town (UCT) and also act as a building block for further developments. The thesis starts by presenting the basic concepts of ERT such as the underlying equations, the various boundary measurement strategies and a global perspective of ERT. The nature of this thesis is on software reconstruction and in so doing information on the incorporation of the Finite Element Method in ERT is provided. The thesis goes on to provide information about the reconstruction algorithms, which incorporate regularization. A novel aspect of this thesis involves the calibration and pre-processing of boundary voltages. These concepts were conceptualised and developed during formal communications with Dr. Wilkinson (2002) and Randal (2002). The calibration schemes try to eliminate the potential errors that can arise inthe captured data thus allowing for a clearer image to be reconstructed, Electrical Resistance Tomography. This thesis further develops the idea of parallelizing the Newton-Raphson algorithm to increase the speed of the algorithm. Various schemes on how this parallelization is achievable are put forward.
Martin, Eric John. "Laboratory study evaluating electrical resistance heating of pooled trichloroethylene." Thesis, Kingston, Ont. : [s.n.], 2009. http://hdl.handle.net/1974/1723.
Full textPereira, Paulo J. S. "An approximation method for electrical impedance tomography." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/1536.
Full textElliott, Jeremy. "Monitoring an air core by means of electrical resistance tomography." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/5279.
Full textGregory, Peter. "Analysis of sedimenting Kaolin suspensions by miniaturised Electrical Resistance Tomography." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302456.
Full textRusso, Analisa. "Variation of electrical resistance in superelastic NiTi for sensor applications." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/57875.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (p. 32).
Nickel-Titanium (NiTi) is a most commonly known as a heat-activated shape memory alloy. However, the material sometimes displays a constant-temperature property called "superelasticity." A superelastic material is one which can undergo very high reversible strains due to stress-induced change in crystal structure. In the case of Superelastic NiTi, Martensitic transformation occurs. The two crystal structures differ to the extent that the gradual phase transformation is coupled to a gradual change in resistivity. In fact, resistive sensing is a common characterization technique for shape memory alloys. The unique material properties of superelastic NiTi could also be the basis for creating a resistive sensor that is sensitive enough to measure small displacements, and robust enough to measures large displacements. This study focuses on NiTi which displays superelastic behavior above room temperature. To assess the material's potential as a strain sensing medium, the NiTi wire is shape-set into coil springs which amplify the sensor's net deformation. The relationship between strain and resistance is measured. The study shows that various aspects of the strain-resistance response, including non-linear hysteretic behavior and temperature dependence of electrical resistivity, pose challenges to sensor design. Though the accuracy of the spring sensors is still under development, several recommendations are made with regard to effective device design. In addition, the design of a one-axis strain rate sensor, which differentiates between only two modes of behavior, is explored.
by Analisa Russo.
S.B.
Wisung, Grete. "Method evaluation : Electrical surface resistance measurements on coated conductive textiles." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-14769.
Full textFaraj, Yousef. "Measurement and visualisation of slurry flow using electrical resistance tomography." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/4604/.
Full textXiao, Lianzhen. "Interpretation of hydration process of concrete based on electrical resistivity measurement /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202007%20XIAO.
Full textSmith, Stewart. "Sheet resistance and electrical linewidth test structures for semiconductor process characterisation." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/11416.
Full textSunesson, Fredric. "Real-time stator resistance estimation for electrical drives : a control perspective." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-286793.
Full textFordonsindustrin är mitt i en omsträllning mot elektriska motorer. Detta leder till ett ökat intresse i kontroll av elektriska motorer. I detta arbete föreslås en statorresistans estimering för elektriska motorer med fältorienterings reglering (FOC). Estimeringen testas både i simuleringar och experiment. Den föreslagna estimeringen utgår från att likström (DC) injiceras i en stationär referensram. Med hjälp av Ohms lag estimeras statorresistansen. Estimeringen av likströmmen kommer från en nollövergångs detekterings algoritm som räknar ut medelvärdet över en elektrisk period. Likströmmen elimineras därefter från feedbacken till övriga regulatorer för att minimera störningar i övriga regulatorer. Injektionen kontrolleras av enklar PI-regulatorer i både α och β för att kompensera för tvärkopplingen mellan dessa. Simuleringarna visar att noggrannheten ökar och estimerings tiden minskar när likströmmen kontrolleras i både α och β. Att kontinuerligt implementera Ohms lag är ostabilt. För att stabilisera estimeringen inför en ackumulator som räknar ut medelvärdet för estimering över flera elektriska perioder. Avvägning står dock mellan högre noggrannhet i estimeringen och längre tid för estimeringen. Vridmomentssvägnignar är oundvikliga när likström injiceras i motorn. Dock är vridmomentssvägnignarna endast beroende på hur stör likström som injiceras. Experimenten visar lovande initiala resultat i både likströms estimeringen och injicerings regleringen. Fler tester är dock nödvändiga för att ytterligare förbättra estimeringen.
Herholdt, Siegfried. "Image reconstruction on electrical resistance tomography measurements in a settling process." Thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/6768.
Full textThis thesis uses Electrical Resistance Tomography (ERT) to measure a settling process. The measurement hardware for this system was developed during previous work carried out by the author. This research is the continuation of this work by focusing on image reconstruction from the measured data. The reconstruction algorithm attempts to find the conductivity distribution of the interior of a rig from measurements made on its boundary. The method used in this thesis is the Newton-Raphson (NR) Algorithm, which employs iterative solutions of the Finite Element Method (FEM) in order to converge to a solution for conductivity. FEM is a numerical simulation method that discretises a region into elements and performs a global optimisation or minimisation in order to arrive at a solution. The NR-method is similar in principle to Newton's method, but is designed to operate on complex data and matrix equations in multiple dimensions. This thesis discusses the methods in reasonable detail and highlights several issues, including ill-conditioning, and regularisation as a method to improve the conditioning of the data. The results contain images of successful reconstruction of a settling process.
Loh, Weng Wah. "Real-time monitoring of drilling cuttings transport using electrical resistance tomography." Thesis, University of Manchester, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501704.
Full textWeemees, Ilmar Andrew. "Development of an electrical resistivity cone for groundwater contamination studies." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28730.
Full textApplied Science, Faculty of
Civil Engineering, Department of
Graduate
Jia, Joey Zong-yi. "Voltage controlled resistance model for MOS transistors." PDXScholar, 1988. https://pdxscholar.library.pdx.edu/open_access_etds/3802.
Full textTsappi, Philip. "Resistance heating of steel conductors of circular cross-section." Thesis, Aston University, 1987. http://publications.aston.ac.uk/8047/.
Full textHenry-Poulter, Siobhan. "An investigation of transport properties in natural soils using electrical resistance tomography." Thesis, Lancaster University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389933.
Full textTan, Jin Chong. "Thermo-electrical properties of metallic sandwich sheets and their resistance welding characteristics." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615008.
Full textShirhatti, Vijay Shamrao. "Characterisation and visualisation of particulate solid-liquid mixing using electrical resistance tomography." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441347.
Full textClements, Randy Allen. "Development of an ohmic thawing apparatus for accurate measurement of electrical resistance." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013034.
Full textChen, Zhangjing. "Measurement of wood moisture content above fiber saturation point by electrical resistance." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-11102009-020203/.
Full textForrest, Andrew E. "Gas-liquid mixing in stirred vessels imaged using electrical resistance tomography (ERT)." Thesis, University of Manchester, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488332.
Full textSmith, Craig Edward. "Monitoring Damage Accumulation In SiC/SiC Ceramic Matrix Composites Using Electrical Resistance." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1249917100.
Full textDeshpande, Pranav K. "Wear Resistance and Electrical Property of Infrared Processed Copper/Tungsten Carbide Composites." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1147536455.
Full textChung, Hye Won. "An energy efficient AES engine with DPA-resistance." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55146.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (p. 73-75).
The advent of portable electronics which transmit and receive sensitive data via wireless communication have led to interest in the design of energy-efficient security engines. The hardware implementation of cryptographic algorithms, however, leaks side-channel information about the operations they process. Differential Power Analysis (DPA) is one of the most powerful attacks to disclose secret key of the engine. This thesis proposes an energy efficient AES-128 engine which is resilient to DPA attacks. A proposed design adopts extensive parallelism and voltage scaling to simultaneously achieve energy efficiency and throughput requirement. Optimized 128-bit architecture and 16 S-boxes placed in the encryption datapath allow the parallel operation of 16 bytes of encryption data at supply voltages in the subthreshold region while maintaining more than tens of Mbps throughput rate. The energy efficient AES core, which does not incorporate techniques to mitigate DPA attack, can operate at 0.35V with 54.12pJ/encrypt. and 64.6Mbps. Before developing countermeasures against DPA, a previously suggested DPA attack methodology in [1] is studied and modified to disclose secret key of our system. The transition power of register is estimated by using the byte-oriented reverse algorithm of AES with the knowledge of a ciphertext and a guess of a secret key. Correlation between the power estimate and the power measurement discloses 12 key bytes (among 16) within 20K encryption runs. A newly proposed AES architecture which balances the Hamming weight of register input can protect the system from DPA attacks.
(cont.) The secured core has been subjected to 100K encryptions, 33x more than the number of runs at which attack can disclose a secret key of the unprotected core, but none of its secret key have yet been disclosed. When running the encryption core at 0.4V and 10IMHz, power increases by 2x compared to the unprotected core. Maximum throughput at 1.OV is reduced by 2/3 for protected core compared with the unprotected core. This IC performance overhead comes at the cost of the increased security.
by Hye Won Chung.
S.M.
Homer, Hannah S. "Stability Analysis of Negative Resistance-Based Source Combining Power Amplifiers." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1466.
Full textDeba, Charlie Nindjou. "Evaluation and verification of five different image reconstruction algorithms for electrical resistance tomography applications." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2465.
Full textTomography is the ability to internally visualise an opaque medium or a body, using different imaging techniques. Electrical Resistance Tomography (ERT) technique is a method commonly used in process tomography. It uses a non-intrusive resistance measurement between a set of electrodes attached on the circumference of a fixed cross-section with a given conductivity and permittivity distribution. ERT appears to be simple, low cost, safe and non-invasive. Despite the advantages of ERT, the reconstruction of the internal conductivity of the pipe still face a crucial challenges such as noise, a relatively low spatial resolution, as well as ill-posedness of the inverse problem when doing the image reconstruction using reconstruction algorithms. Although previous work showed the potential of various algorithms for the reconstruction of ERT tomograms, no full characterisation and comparison of different algorithms could be found for real flow situations. The ERT system was tested in the identification of different objects and fluid beds in a real time situation. The data collected from the measurements were then used for the image reconstruction using an algorithm developed by Time Long (One-step algorithm) and four EIDORS-based algorithms namely: Gauss-Newton algorithm with Laplace Prior (LP) and Gaussian prior (Automatic Hyper Parameter Selection (AHSP)), the Total Variation (TV) algorithm and the Conjugate Gradient (CG) algorithm. The performance of each algorithm was tested in different scenarios. The results obtained were then compared based on the quality and the accuracy of the images as well as the computational time of each algorithm. Firstly, reconstructed images were obtained using objects placed inside the ERT pipe test. Secondly, the algorithm performances were put to test in a level bed setup experiment and finally, the algorithm reconstructions were applied to the real flow situation, where different flow rates were applied. The results obtained were then analysed and compared.
Scholtz, J. P. "Improved transient earth fault clearing on solid and resistance earthed MV netwworks." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11151.
Full textThe aim of this thesis is to endeavour to develop, through a literature study, a method or methods whereby transient earth faults on neutral earthed MV networks may be cleared without customer supply interruptions, without compromising public safety and without compromising network integrity. In order to propose such a method, or methods, it is important to understand the various earthing practices employed in MV networks in terms of network behaviour under earth fault conditions, as this may influence network component insulation rating requirements, as well as the way in which such a system may function.
Martin, Elizabeth E. M. Eng Massachusetts Institute of Technology. "Determining patterns of cancer drug resistance from autopsy patients." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129922.
Full textCataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 97-102).
Determining patterns of drug resistance is fundamentally required for improving clinical outcome of cancer treatment. The ability to study multiple samples from different metastatic sites of the same patient is a clinically and analytically challenging task, which has become possible with the advent of "rapid" autopsy procedures (<10 hours from death) conducted on cancer patients through the Massachusetts General Hospital (MGH) Rapid Autopsy Program. The dataset of whole-exome, whole genome and transcriptome sequencing data from advanced cancer samples uniquely captures genomic and transcriptomic information from multiple lesions of the same patient for advanced study of how resistance develops on the systemic level. Additionally, previously collected cell-free DNA samples enable the establishment of both a spatial and temporal picture of cancer drug resistance and progression.
Using RNA expression and pathway analysis, we can also identify unique transcriptional programs and differentially expressed genes between distinct clones within one patient as well as compare genetically similar clones across patents. This thesis integrates genomic and transcriptomic data through advanced clonal reconstruction methods, as well as clinical information such as cancer type, treatment history, and lesion location and response to investigate how the patient developed resistance to anti-cancer therapy. This thesis concentrates on findings in two cohorts of rapid autopsy patients: ER+ metastatic breast cancer, with a focus on patients treated with a CDK4/6 inhibitor, and cholangiocarcinoma, with a focus on patients with FGFR2-fusions treated with an FGFR-inhibitor.
In the ER+ breast cancer cohort, we identified multiple known and potentially novel resistance mechanisms in separate branches of the phylogenetic tree, often converging on distinct mutations in the same resistance genes. In cholangiocarcinoma, we found high levels of inter- and intra-tumoral heterogeneity in several patients, with a convergence on FGFR2 activating mutations as a form of resistance to FGFR-inhibitor therapy. The richness of the rapid autopsy dataset allows us to develop a fuller picture of convergent resistance mechanisms to therapy in cancer.
by Elizabeth E. Martin.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
Hart, Robert James. "Electrical resistance based damage modeling of multifunctional carbon fiber reinforced polymer matrix composites." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5493.
Full textButler, Ivan Charles. "AN ANALYSIS OF RESISTANCE SPOT WELD QUALITY BASED ON ACOUSTIC AND ELECTRICAL SIGNATURES." UKnowledge, 2019. https://uknowledge.uky.edu/ms_etds/8.
Full textVithayathil, Anne M. (Anne Marie) 1978. "Substrate resistance extraction using a multi-domain surface integral formulation." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28543.
Full textIncludes bibliographical references (p. 65-66).
In recent years, mixed-signal designs have become more pervasive, due to their efficient use of area and power. Unfortunately, with sensitive analog and fast digital circuits sharing a common, non-ideal substrate, such designs carry the additional design burden of electromagnetic coupling between contacts. This thesis presents a method that quickly extracts the electroquasistatic coupling resistances between contacts on a planar, rectangular, two-layer lossy substrate, using an FFT-accelerated multi-domain surface integral formulation. The multi-domain surface integral formulation allows for multi-layered substrates, without meshing the volume. This method has the advantages of easy meshing, simple implementation, and FFT-accelerated iterative methods. Also, a three-dimensional variant of this method allows for more complex substrate geometries than some other surface integral techniques, such as multilayered Green's functions; this three-dimensional problem and its solution are presented in parallel with the planar substrate problem and solution. Results from a C++ implementation are presented for the planar problem.
by Anne M. Vithayathil.
S.M.
Jin, Donghyun. "Dynamic ON-resistance in high voltage GaN field-effect-transistors." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91108.
Full textCataloged from PDF version of thesis.
Includes bibliographical references.
Recently, the development of energy efficient electrical power management systems has received considerable interest due to its potential to realize significant energy savings for the world. With current Si-based power electronics system being matured, GaN Field-Effect-Transistors have emerged as a disruptive technology with great potential that arises from the outstanding material properties of GaN. However, in spite of great progress in GaN device fabrication, electrical reliability and a number of unique anomalies of GaN remain key challenges that prevent the wide deployment of this technology. In particular, the dynamic ON-resistance (RON), in which the RON of the transistor remains high for a certain period of time after a high-voltage OFF-ON switching event, is a critical concern. This phenomenon greatly affects the efficiency of electrical power management circuits based on GaN power transistors. This thesis investigates in depth this important issue. Firstly, we have developed a new dynamic RON measurement methodology which can observe dynamic RON transients after OFF-to-ON switching events over many decades in time. We have experimentally demonstrated this technique on GaN-on-SiC high-voltage HEMTs (High-Electron- Mobility-Transistors). The possible origin of the mechanisms responsible for dynamic RON in these devices has been postulated. Through our new technique, the impact of high-power stress on dynamic RON has been investigated as well. The results emphasize the importance of studying dynamic RON characteristics over very short time scale when conducting reliability studies of GaN transistors. Secondly, high-voltage GaN-on-Si MIS (Metal-Insulator-Semiconductor) HEMTs designed for > 600 V switching operation have been investigated. Excessive electron trapping leading to total current collapse has been observed. We have carried out an extensive characterization of this phenomenon and we have proposed "Zener trapping" as the responsible mechanism. In this view, electron trapping takes place inside the AlGaN/GaN heterostructure through a tunneling process under high-electric-field. The understanding derived here suggests that this effect can be mitigated through attention to defect control during epitaxial growth and appropriate design of the field plate structure of the device. Our findings in this thesis provide a path to achieve high performance GaN power transistors with minimum dynamic RON effects.
by Donghyun Jin.
Ph. D.
Yenjaichon, Wisarn. "Characterization of in-line mixing of pulp fibre suspensions based on electrical resistance tomography." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43718.
Full textChandler, James Henry. "Direct current electrical resistance measurement techniques for assessment of colorectal cancer during laparoscopic surgery." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/12434/.
Full textChuang, Eugene (Eugene Yu) 1975. "Cyclic load resistance of reinforced concrete beams retrofitted with composite laminates." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/47496.
Full textBrand, Vitali. "Contamination- induced Interfacial Resistance in Ohmic Microswitch Contacts." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/448.
Full textGrönström, Niclas. "Optimal Demagnetization of Transformer After Winding Resistance Measurements." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291560.
Full textI detta examensarbete undersöks avmagnetisering av transformatorer i samband med lindningsresistansprovning. Vid transformatorprovning är mätning av lindningsresistans ett viktigt test som används för att upptäcka lindningseller kopplingsfel. Vanligtvis mäts resistansen genom att en likström injiceras i transformatorns lindningar. Processen magnetiserar kärnan, vilket leder till att transformatorn förblir magnetiserad även efter testet. En magnetiserad transformator kan orsaka olika problem med diagnostiska tester och leda till inkopplingsströmmar som är flera gånger högre än märkströmmen. Vidare kan restmagnetism påverka AC-tester, såsom SFRA-testet (Sweep Frequency Response Analysis) och exciteringsströmstestet. Därför rekommenderas det att transformatorer avmagnetiseras efter lindningsresistanstest. Kärntyp och lindningskonfiguration kan ha påverkan på avmagnetiseringsprocessen. Det gör det intressant att undersöka olika avmagnetiseringsmetoder, så att den mest effektiva metoden kan användas. Detta arbete demonstrerar avmagnetiseringsexperiment på flera krafttransformatorer med olika kärntyper och lindningskonfigurationer. Transformatorerna magnetiserades genom lindningsresistansmätning och sedan användes en TRAX (transformer and substation test system) för att avmagnetisera transformatorerna med olika tillvägagångssätt. Flera mätningar utfördes på trebenta och fembenta krafttransformatorer. Avmagnetiseringsmetodernas effektivitet mättes genom att jämföra exciteringsströmmen i magnetiserat och avmagnetiserat tillstånd. Det visas att avmagnetiseringsmetoden för den trebenta kärnan hade liten inverkan på magnetiseringsresultatet. Exciteringsströmmarna vid avmagnetiserat tillstånd för de olika kombinationerna var ungefär lika. Den fembenta transformatorn avmagnetiserades först på mittbenet och sedan på de yttre benen för att se om resultaten förbättrades. För den fembenta transformatorn visade mätningarna att avmagnetiseringsmetoden påverkade resultaten. Olika Yy-konfigurationer testades och resultatet visade att remanensen avlägsnades efter den första avmagnetiseringen med fas till fas tillvägagångssättet. Men om Yy-konfigurationen avmagnetiserades med fas till neutral, då krävdes det att transformatorn avmagnetiseras två gånger för att få bort remanensen. Resultatet för Yd-konfigurationen visade ingen förbättring genom fas till fas tillvägagångssättet. Den fas som magnetiserades hade i allmänhet en något större exciteringsström än övriga faser, även efter avmagnetisering.
Nygren, Kristian. "Magnetron Sputtering of Nanocomposite Carbide Coatings for Electrical Contacts." Doctoral thesis, Uppsala universitet, Oorganisk kemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302063.
Full textSmith, Jacob A. "Electrical Performance of Copper-Graphene Nano-Alloys." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1550675878730599.
Full textImashuku, Susumu. "Electrical Conductivity of Grain Boundary in Accepter Doped Barium Zirconate." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/78014.
Full textNoman, Mohammad N. "Investigation of electroforming characteristics of TiO2 based resistance switching devices." Research Showcase @ CMU, 2013. http://repository.cmu.edu/dissertations/213.
Full textFromknecht, Conner(Conner M. ). "LOKI : a lease-oriented key infrastructure with instant updates and seizure-resistance." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112914.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (pages 69-70).
Most of the secure communication protocols that power the Internet of today rely on a robust and frictionless mechanism for digital identity attestation. Authentication is typically achieved using a Public Key Infrastructure (PKI) that enables users to verify a counterparty's public key binding. Unfortunately, the structure of many existing PKIs present vulnerabilities and usability issues that stem from a lack of consistency, inefficient updates, or a dependence on centralized entities. In this work we present a decentralized marketplace for digital identities that autonomously leases the verification state of a globally-consistent PKI. Users express ownership of an identity through a sequence of leases, which incrementally defines the conditions under which ownership can be renewed and the identity's bindings can be updated. A careful structuring of the lease semantics, economic incentives and architectural design enables a fast update protocol, which permits clients to verify and accept a fresher binding without needing to wait for confirmation from the underlying consensus layer. The task of registration accuracy is extended naturally through the structure of the DNS namespace, after which the state of the system at any particular time acts as the root of trust during authentication. We discuss a novel seizure-resistance mechamism called dormancy, which in turn gives the existing owner of an identity substantial preference during the renewal process. Finally, we show how the system could be used to efficiently and unobtrusively secure today's communication protocols.
by Conner Fromknecht.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science