Tesi: "Ids and devices"

1

Li, Fudong. "Behaviour profiling for mobile devices". Thesis, University of Plymouth, 2012. http://hdl.handle.net/10026.1/1025.

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With more than 5 billion users globally, mobile devices have become ubiquitous in our daily life. The modern mobile handheld device is capable of providing many multimedia services through a wide range of applications over multiple networks as well as on the handheld device itself. These services are predominantly driven by data, which is increasingly associated with sensitive information. Such a trend raises the security requirement for reliable and robust verification techniques of users.This thesis explores the end-user verification requirements of mobile devices and proposes a novel Behaviour Profiling security framework for mobile devices. The research starts with a critical review of existing mobile technologies, security threats and mechanisms, and highlights a broad range of weaknesses. Therefore, attention is given to biometric verification techniques which have the ability to offer better security. Despite a large number of biometric works carried out in the area of transparent authentication systems (TAS) and Intrusion Detection Systems (IDS), each have a set of weaknesses that fail to provide a comprehensive solution. They are either reliant upon a specific behaviour to enable the system to function or only capable of providing security for network based services. To this end, the behaviour profiling technique is identified as a potential candidate to provide high level security from both authentication and IDS aspects, operating in a continuous and transparent manner within the mobile host environment.This research examines the feasibility of a behaviour profiling technique through mobile users general applications usage, telephone, text message and multi-instance application usage with the best experimental results Equal Error Rates (EER) of 13.5%, 5.4%, 2.2% and 10% respectively. Based upon this information, a novel architecture of Behaviour Profiling on mobile devices is proposed. The framework is able to provide a robust, continuous and non-intrusive verification mechanism in standalone, TAS or IDS modes, regardless of device hardware configuration. The framework is able to utilise user behaviour to continuously evaluate the system security status of the device. With a high system security level, users are granted with instant access to sensitive services and data, while with lower system security levels, users are required to reassure their identity before accessing sensitive services.The core functions of the novel framework are validated through the implementation of a simulation system. A series of security scenarios are designed to demonstrate the effectiveness of the novel framework to verify legitimate and imposter activities. By employing the smoothing function of three applications, verification time of 3 minutes and a time period of 60 minutes of the degradation function, the Behaviour Profiling framework achieved the best performance with False Rejection Rate (FRR) rates of 7.57%, 77% and 11.24% for the normal, protected and overall applications respectively and with False Acceptance Rate (FAR) rates of 3.42%, 15.29% and 4.09% for their counterparts.

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2

SILVA, Aline Lopes da. "MODELO DE IDS PARA USUÁRIOS DE DISPOSITIVOS MÓVEIS". Universidade Federal do Maranhão, 2008. http://tedebc.ufma.br:8080/jspui/handle/tede/335.

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Made available in DSpace on 2016-08-17T14:52:48Z (GMT). No. of bitstreams: 1 Aline lopes.pdf: 2261944 bytes, checksum: 0cbbb27a7a17ab362f4fce42298c4b45 (MD5) Previous issue date: 2008-06-26
Mobile devices are increasing common reality in wireless networks and have integrated the wireless environment, helping to ease and to make available information. Meanwhile, the wireless environment is subject to vulnerabilities because of the way of spreading information that is given through the air, and is subject to interception or even information theft. Mobile Devices in addition of its vulnerability to these vulnerabilities common in wireless environments, are devices with some physical limitations such as lack of processing capacity and memory, beyond the limited battery life. These limitations become critical in this kind of environment, when unidentified threats attack are directed mobile devices. It is necessary to develop an intrusion detection system dedicated to these devices to identify intrusive behaviour, taking into account their physical limitations. This work proposes an intrusion detection system (IDS, Intrusion Detection System) for wireless networks and mobile devices. This is an adaptation and extension of NIDIA-IDS (Intrusion Detection System-Network Intrusion Detection System based on Intelligent Agents). The system acts with two processes: the first one is an information tracking on the device performance and the second one is a wireless network traffic monitoring, analyzing both the traffic of monitored devices. As proof of concepts a prototype was developed and some experiments were carried to validate this solution.
Os dispositivos móveis são uma realidade cada vez mais comum em redes wireless e se integraram ao ambiente wireless, contribuindo para facilidade e disponibilidade da informação. Entretanto, o ambiente wireless está sujeito a vulnerabilidades, devido à forma de propagação da informação que se dá através do ar, estando sujeito a intercepção ou até mesmo roubo das informações. Dispositivos móveis além de estarem sujeitos a essas vulnerabilidades comuns em ambientes wireless, são dispositivos com algumas limitações físicas, como pouca capacidade de processamento e memória, além da vida útil de bateria limitada. Estas limitações tornam-se críticas neste tipo ambiente, quando ameaças não identificadas são direcionadas a dispositivos móveis. Torna-se necessário a implementação de sistema de detecção de intrusão voltado para estes dispositivos a fim de identificar comportamentos intrusivos, levando em consideração suas limitações físicas. Este trabalho propõe um sistema de detecção de intrusão (IDS, Intrusion Detection System) em redes wireless destinados a dispositivos móveis como adaptação e extensão do IDS-NIDIA (Intrusion Detection System- Network Intrusion Detection System based on Intelligent Agents). O mecanismo utiliza dois processos: o primeiro faz o monitoramento de informações sobre o comportamento do dispositivo e o segundo através do monitoramento de tráfego da rede wireless, analisando o tráfego destinado e originado aos dispositivos monitorados. A implementação da arquitetura e os testes realizados demonstram a viabilidade da solução.

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3

Shea, Patrick. "DESIGN AND MODELING OF RADIATION HARDENED LDMOSFET FOR SPACE CRAFT POWER SYSTEMS". Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2822.

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NASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching performance, development and manufacturing costs, and total mass of power electronics systems. Availability of a hardened fast-switching power MOSFET will allow space-borne power electronics to approach the current level of terrestrial technology, thereby facilitating the use of more modern digital electronic systems in space. It is believed that the use of a p+/p-epi starting material for the LDMOS will offer better hardness against single-event burnout (SEB) and single-event gate rupture (SEGR) when compared to vertical devices fabricated on an n+/n-epi material. By placing a source contact on the bottom-side of the p+ substrate, much of the hole current generated by a heavy ion strike will flow away from the dielectric gate, thereby reducing electrical stress on the gate and decreasing the likelihood of SEGR. Similarly, the device is hardened against SEB by the redirection of hole current away from the base of the device's parasitic bipolar transistor. Total dose hardness is achieved by the use of a standard complementary metal-oxide semiconductor (CMOS) process that has shown proven hardness against total dose radiation effects.
M.S.E.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering MSEE

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4

Alemayehu, Andargachew Desta. "Microwave Frequency Thin BST Film Based Tunable Shunt and Series Interdigital Capacitor Device Design". University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1304558851.

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5

Chang, David Wei-Péng. "ST. JUDE MEDICAL: PULMONARY EDEMA MONITORING IN PACEMAKERS AND ICDS". DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1112.

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Pulmonary edema occurs when fluid leaks from the pulmonary capillary network into the lung interstitium and alveoli. When the heart is not able to pump blood to the body efficiently, fluid can back up into the veins that take blood through the lungs to the left atrium. This then builds up the pressure in the blood vessels and fluid is pushed into the alveoli in the lungs. The fluid reduces normal oxygen movement through the lungs and can cause impaired gas exchange and respiratory failure. There are many causes of congestive heart failure that may lead to pulmonary edema such as heart attack, any diseases of the heart that weaken or stiffen the heart muscle, a leaking or narrowed heart valve, and sudden, severe high blood pressure. Pulmonary edema is a strong indicator of congestive heart failure in patients and therefore can be used as a gauge for congestive heart failure. One way to diagnose cardiogenic pulmonary edema constantly is through the continuous monitoring of the transthoracic impedance throughout the day. One method to achieve this constant monitoring is through the use of a cardiac pacemaker or an implantable cardioverter defibrillator (ICD). Many patients who are at risk of heart failure have these medical devices implanted already. In these implantable cardiac devices, the connected cardiac leads can be utilized to continually screen several impedance vectors for decreases in impedance in the thoracic cavity. A pacemaker or ICD that implements Pulmonary Edema Monitoring is designed to continuously monitor these impedance vectors and alert the patient to seek medical attention. This thesis will discuss the implementation of Pulmonary Edema Monitoring via screening of multiple impedance vectors in a pacemaker or implantable cardioverter defibrillator and the effectiveness of this monitoring method. Furthermore, the design, implementation, and testing of this feature will be explored in greater detail.

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6

Liu, Haitao. "Novel 3-D CMOS and BiCMOS devices for high-density and high-speed ICs /". View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20LIU.

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7

Andersson, Dorothea. "Simulation of industrial control system field devices for cyber security". Thesis, KTH, Elkraftteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202405.

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Industrial Control Systems (ICS) are an integral part of modernsociety, not least when it comes to controlling and protecting criticalinfrastructure such as power grids and water supply. There is a need to testthese systems for vulnerabilities, but it is often difficult if not impossible to doso in operational real time systems since they have been shown to be sensitiveeven to disturbances caused by benign diagnostic tools. This thesis exploreshow ICS field devices can be simulated in order to fool potential antagonists,and how they can be used in virtualized ICS for cyber security research. 8different field devices were simulated using the honeypot daemon Honeyd,and a generally applicable simulation methodology was developed. It was alsoexplored how these simulations can be further developed in order to functionlike real field devices in virtualized environments.
Industriella informations- och styrsystem utgör en viktig delav vårt moderna samhälle, inte minst när det gäller kontroll och skydd avkritisk infrastruktur som elnät och vattenförsörjning. Det finns stora behov avatt säkerhetstesta dessa typer av system, vilket ofta är omöjligt iproduktionsmiljöer med realtidskrav som är erkänt känsliga för störningar, tilloch med från vanligt förekommande analysverktyg. Denna rapport presenterarhur vanliga komponenter i industriella informations- och styrsystem kansimuleras för att lura potentiella antagonister, och hur de kan användas ivirtualiserade styrsystem för cybersäkerhetsforskning. 8 olika komponentersimulerades med hjälp av Honeyd, och en generellt applicerbarsimuleringsmetodik utvecklades. Hur dessa simuleringar kan vidareutvecklasför att fungera som riktiga styrsystemskomponenter i virtualiserade miljöer harockså undersökts.

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8

Seidel, Robert Viktor. "Carbon Nanotube Devices". Doctoral thesis, Technische Universität Dresden, 2004. https://tud.qucosa.de/id/qucosa%3A24460.

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Eine Reihe wichtiger Wachstums- und Integrationsaspekte von Kohlenstoff-Nanoröhren wurde im Rahmen dieser Arbeit untersucht. Der Schwerpunkt der experimentellen Arbeit lag dabei hauptsächlich bei einschaligen Kohlenstoffnanoröhren (SWCNT). Das große Potential dieser Nanoröhren für Transistor-Anwendungen wurde durch die Herstellung einer Vielzahl funktionierender Bauelemente aus diesen Kohlenstoffnanoröhren mittels relativ einfacher Herstellungsprozesse demonstriert. Ein fundiertes Verständnis für die Abhängigkeiten des Nanoröhrenwachstums von einer Vielzahl an Parametern wurde mit Hilfe mehrerer tausend Wachstumsexperimente gesammelt. Verschiedene Katalysatormetalle, Kohlenstoffquellen und Katalysatorunterlagen wurden detailliert untersucht. Ein Hauptaugenmerk wurde dabei auf eine Reduzierung der Wachstumstemperatur gerichtet. Die niedrige Wachstumstemperatur spielt eine große Rolle für eine möglichst hohe Kompatibilität mit konventionellen Herstellungsverfahren der Silizium-Halbleitertechnik. Ein einfaches phänomenologisches Wachstumsmodell wurde für die Synthese von Nanoröhren mittels katalytisch-chemischer Gasphasen-Abscheidung (CCVD) formuliert. Dieses Modell basiert hauptsächlich auf der Oberflächendiffusion von adsorbierten Kohlenstoffverbindungen entlang der Seitenwände der Nanoröhren sowie auf der Oberfläche der Katalysatorunterlage. Das Modell ist eine wichtige Ergänzung zu dem VLS-Mechanismus. Ein Wachstumsverfahren zur Herstellung von Nanoröhren für niedrigere Temperaturen bis zu 600 °C wurde entwickelt. Experimentell wurde nachgewiesen, dass der Durchmesser des Katalysatorteilchens fast ausschließlich bestimmt, wie viele Schalen eine wachsende Nanoröhre bei geeigneten Wachstumsbedingungen hat. Es wurde zum ersten Mal gezeigt, dass einschalige Kohlenstoffnanoröhren auf Metallelektroden wachsen werden können, insofern eine dünne Aluminiumschicht als Trennschicht verwendet wird. Dadurch können in-situ kontaktierte Nanoröhren einfach hergestellt werden, was deren elektrische Charakterisierung weitaus erleichtert. Mittels stromloser Abscheidung von Nickel oder Palladium aus einer Lösung konnte eine deutliche Verbesserung der Kontaktwiderstände der in-situ-kontaktierten Nanoröhren erreicht werden. Durch Einbettung von Nanoröhren in eine Tantaloxidschicht konnten Transistoren mit einem Dielektrikum mit hoher relativer Dielektrizitätskonstante hergestellt werden. Die Tantaloxidschicht wurde mit einem neu entwickelten Tauchprozess abgeschieden. Erstmalig wurden Transistoren basierend auf Kohlenstoffnanoröhren hergestellt, die relativ hohe Ströme (Milliampere) mit einer Modulation bis zu einem Faktor 500 schalten können. Diese Transistoren beruhen auf einer Parallelschaltung einer großen Anzahl an Nanoröhren. Mit Hilfe der hergestellten Transistoren konnten die Eigenschaften einer großen Zahl von Nanoröhren untersucht werden, wobei große Unterschiede in den elektronischen Eigenschaften von metallischen Nanoröhren, halbleitenden Nanoröhren und Nanoröhren mit einer kleinen Bandlücke beobachtet wurden.
A number of very important growth and integration aspects of carbon nanotubes have been investigated during the course of this thesis. The focus was mainly on single-walled carbon nanotubes. Their potential for transistor applications was demonstrated by the successful fabrication of a variety of devices using rather simple processes. A detailed understanding of the dependence of SWCNT growth on a variety of parameters was obtained as the result of several thousand growth experiments. Various catalyst materials, gaseous carbon sources, and catalyst supports have been investigated. Special attention was paid to a considerable reduction of the growth temperature. A simple phenomenological growth model could be derived for CCVD of SWCNTs taking into account a number of effects observed during the various growth experiments. The model presented is mainly based on the surface diffusion of carbon species along the sidewalls of the carbon nanotubes or on the catalyst support and is an addition to the vapor-liquid-solid (VLS) mechanism. Growth methods for the CCVD synthesis of SWCNTs were developed for temperatures as low as 600 °C. It has been found that the size of the catalyst particle alone determines whether a SWCNT, DWCNT, or MWCNT will nucleate from a specific particle under suitable growth conditions. It could be demonstrated for the first time that SWCNTs can be grown on a variety of conducting materials if the catalyst is separated from the electrode by a thin Al layer. In-situ contacted SWCNTs can be easily obtained that way, largely facilitating the electronic characterization of as-grown SWCNTs. A tremendous improvement of the contacts of in-situ contacted SWCNTs could be achieved by electroless deposition. SWCNT growth on appropriate electrodes allowed the encapsulation of the nanotubes by electroless deposition of Ni and Pd, yielding good and reliable contacts. SWCNT transistors with a high-k dielectric could be fabricated by encapsulation of the nanotube with a tantalum oxide layer. The tantalum oxide was deposited by a newly developed dip-coat process. High-current SWCNT transistors consisting of a large number of SWCNTs in parallel were demonstrated for the first time during this work. Finally, the properties of a large number of CCVD grown SWCNTs have been investigated by electronic transport measurement. Large differences in the electronic transport have been observed for metallic, small band gap semiconducting (SGS), and semiconducting SWCNTs with small diameters.

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9

Rajan, Parthiban. "Novel Capacitive Sensors for Chemical and Physical Monitoring in Microfluidic Devices". Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1549449776383119.

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10

Wu, Yudong. "Simulation of graphene electronic devices". Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1554/.

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Since the publication of research in the mid-1980s describing the formation of freeform graphene there has been an enormous growth in interest in the material. Graphene is of interest to the semiconductor industry because of the high electron mobility exhibited by the material and, as it is planar, it is compatible with silicon technology. When patterned into nanoribbons graphene can be made into regions that are semiconducting or conducting and even into entire circuits. Graphene nanoribbons can also be used to form the channel of a MOSFET. This thesis describes numerical simulations undertaken on devices formed from graphene. The energy band structure of graphene and graphene nanoribbons is obtained using nearest-neighbour and third nearest-neighbour interactions within a tight binding model. A comparison of the current-voltage characteristics of MOS structures formed on graphene nanoribbons and carbon nanotubes suggests that the nanoribbon devices may be better for switching applications. Conductivities of graphene nanoribbons and junctions formed from them were obtained using a nonequilibrium Green’s function formulation. The effects of defects and strain on these systems were also studied using this technique. Advancements were made when the self-energies used within the nonequilibrium Green’s function were obtained from an iterative scheme including third nearestneighbour interactions. An important result of this work is that accurate simulations of graphene based devices should include third nearest-neighbour interactions within the tight binding model of the energy band structure.

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11

Wells, Gary George. "Voltage programmable liquid optical devices". Thesis, Nottingham Trent University, 2009. http://irep.ntu.ac.uk/id/eprint/168/.

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In this study I have looked at two types of voltage programmable liquid optical device. The first is a rotatable liquid crystal waveplate and the second is an amplitude programmable liquid phase grating. The rotatable waveplate was created by confining a droplet of E7 nematic liquid crystal between two glass substrates in a photolithographically produced square well of 60x60x15µm dimensions. The droplet forms a circular disc shape with two nematic defects at opposite edges of the disc. The optical texture has been examined and the most likely n-director orientation is shown to be Bipolar. Electrodes etched into the sandwiching substrate allow an in-plane electric field to be applied and because of the E7's positive dielectric anisotropy the n-director of the droplet aligns itself with the field. The speed at which this rotation occurs is shown to follow the relationship Ø = 0.0472гV 2 and rotation speeds of 450° /s have been achieved. The droplet is multistable and can be rotated to any arbitrary angle. The temperature of the droplet affects its switching ability by changing the shape and size of the droplet within the well. The switching time with voltage at different temperatures has been investigated and shows that at higher temperatures switching is faster. Rounded square droplets have also been seen which exhibit six stable states which can be switched from one state to another by applying various electric fields. The switching speed of these states has been investigated for several different switching regimes. A voltage programmable phase grating has also been demonstrated by inducing an undulation in the surface of a thin film of either hexadecane or 1-decanol oil. The thin film of oil is the result of a dielectrophoretic force created by a non-uniform electric field above a set of interdigitated electrodes. The thickness of the film is almost independent of the applied voltage. At higher voltages, an undulation in the oil air interface occurs which is static and stable with the same period as the electrode pitch. Measurements of hexadecane and 1-decanol oil for a variety of layer thickness on several different electrode pitches show that the amplitude of the undulation is proportional to the voltage squared. This scaling relationship and the exponential dependence on the ratio of oil thickness and the electrode pitch can be explained in terms of the balance between the dielectrophoretic forces created by the non-uniform electric field and the increase in surface energy associated with the surface deformation. For a thin layer of oil with low dielectric constant the higher order spatial harmonics in the electric field cause the undulation to become non-sinusoidal. The extent to which these harmonics shape the surface of the oil is explored and their relationship to oil thickness is shown. The relative contributions of these higher order harmonics are also shown to be independent from the applied voltage. As an example of the devices applications it has been shown to operate as an amplitude programmable phase grating and diffracts the energy of an incoming 543nm laser from the zero straight through order into the higher orders. The diffraction efficiency of 32.8% is very close to that predicted by theory. The device is polarization insensitive and switching times in excess of 40µs have been achieved in switching the first diffraction order from its minimum intensity to its maximum.

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12

Kumar, Sandeep S. "Elliptic curve cryptography for constrained devices". [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=982216998.

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13

Alzubi, Feras. "Planar Organic Photovoltaic Devices". Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5756.

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Organic Photovoltaic devices (OPV) are considered to be attractive candidates for clean and renewable energy source because of their potential for low cost of fabrication, easy processing, and their mechanical flexibility. The device efficiency of OPV cells are limited by several factors. Among them are: (i) donor-acceptor interface, (ii) morphology of the materials, (iii) electrode-organic semiconductor (OSC) interface and (iv) device architecture such as active material thickness and electrode separation. Although, the donor-acceptor interface has been studied in detail, the commonly prevalent vertical OPV device structure does not allow a good understanding of the other key issues as the vertical structure limits one of the electrode to be a transparent electrode as well as introducing inseparable relation between the electrodes separation and the active material thickness. In addition, it is also well known that the charge transport in OSC is anisotropic and the charge mobility is better in lateral direction rather than vertical direction. In order to address some of these issues, we fabricated OPV devices in a planar device structure where cathode and anode of dissimilar metals are in-plane with each other and their photovoltaic behaviors were studied. We used poly(3-hexylthiophene) and [6,6]-pheny1 C61-butyric acid methy1 ester (P3HT:PCBM) blend as an active material. In particular, we present a detailed study about the effects of the structural parameters such as the channel length, the active layer thickness, and the work function of the electrodes on the open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and the power conversion efficiency (PCE). In order to determine the suitable anode and cathode for the planar organic photovoltaic (P-OPV) structure, we first fabricated and measured organic field effect transistor (OFET) devices with different contacts and studied the effect of barrier height at the P3HT:PCBM/electrode interface on the device output and transport properties. The study showed a clear effect of varying the contact material on the charge injection mechanism and on the carriers mobilities. The results have also shown that Au with high hole mobility and on current in the p-channel can be used as an anode (holes extractor) in the P-OPV device while In, Cr, and Ti that showed a reasonable value of electron mobility can be good candidates for cathode (electron extractor). We also found that, Ag, Al, and Mg showed large barrier which resulted in large threshold voltage in the I-V curve making them undesired cathode materials in the P-OPV device. We then fabricated P-OPV devices with Au as an anode material and varied the cathode material to study the effect of the interface between the P3HT:PCBM layer and the cathode material. When Al, Mg, or Ag used as a cathode material no PV behavior was observed, while PV behavior was observed for In, Cr, and Ti cathode materials. The PV behavior and the characteristic parameters including Voc, Isc, FF and PCE were affected by varying the cathode material. The results have shown that the P-OPV device performance can be affected by the cathode material depending on the properties and the work function of the metal. We have also studied the effect of varying the P3HT:PCBM layer thickness at a fixed channel length for Cr and Ti cathode materials and Au as anode. While Voc and FF values do not change, Isc and PCE increase with increasing the layer thickness due to the increase of the light absorption and charges generation. Moreover, we studied the effect of varying the channel length at a fixed film thickness; and showed that the values of Isc and PCE increase with decreasing channel length while Voc and FF maintain the same value. In this thesis we will also present the results on experimentally defining and testing the illuminated area in the P-OPV device by using different measurement set-ups and different electrodes patterns. The results prove that the illuminated area in the P-OPV device is the area enclosed between the two electrodes. Lastly, we will present the effect of the P3HT:PCBM ratio on the P-OPV device performance. We show that 1:2 ratio is the optimized ratio for the P-OPV device. The detailed results in this thesis show a potential opportunity to help improving and understanding the design of OPV device by understanding the effects of the device structural parameters.
Ph.D.
Doctorate
Physics
Sciences
Physics

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14

Zhang, Panpan, Faxing Wang, Minghao Yu, Xiaodong Zhuang e Xinliang Feng. "Two-dimensional materials for miniaturized energy storage devices: from individual devices to smart integrated systems". Royal Society of Chemistry, 2018. https://tud.qucosa.de/id/qucosa%3A34566.

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Nowadays, the increasing requirements of portable, implantable, and wearable electronics have greatly stimulated the development of miniaturized energy storage devices (MESDs). Electrochemically active materials and microfabrication techniques are two indispensable parts in MESDs. Particularly, the architecture design of microelectrode arrays is beneficial to the accessibility of two-dimensional (2D) active materials. Therefore, this study reviews the recent advancements in microbatteries and microsupercapacitors based on electrochemically active 2D materials. Emerging microfabrication strategies enable the precise control over the thickness, homogeneity, structure, and dimension in miniaturized devices, which offer tremendous opportunities for achieving both high energy and power densities. Furthermore, smart functions and integrated systems are discussed in detail in light of the emergence of intelligent and interactive modes. Finally, future developments, opportunities, and urgent challenges related to 2D materials, device fabrications, smart responsive designs, and microdevice integrations are provided.

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15

Bhuwalka, Krishna K. "Novel tunneling devices for future CMOS technologies". [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980688434.

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16

Thomas, Sam Lloyd. "Backdoor detection systems for embedded devices". Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8365/.

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A system is said to contain a backdoor when it intentionally includes a means to trigger the execution of functionality that serves to subvert its expected security. Unfortunately, such constructs are pervasive in software and systems today, particularly in the firmware of commodity embedded systems and “Internet of Things” devices. The work presented in this thesis concerns itself with the problem of detecting backdoor-like constructs, specifically those present in embedded device firmware, which, as we show, presents additional challenges in devising detection methodologies. The term “backdoor”, while used throughout the academic literature, by industry, and in the media, lacks a rigorous definition, which exacerbates the challenges in their detection. To this end, we present such a definition, as well as a framework, which serves as a basis for their discovery, devising new detection techniques and evaluating the current state-of-the-art. Further, we present two backdoor detection methodologies, as well as corresponding tools which implement those approaches. Both of these methods serve to automate many of the currently manual aspects of backdoor identification and discovery. And, in both cases, we demonstrate that our approaches are capable of analysing device firmware at scale and can be used to discover previously undocumented real-world backdoors.

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17

Ranjan, Nitesh. "Dielectrophoretic formation of nanowires and devices". Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23832.

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We report the self assembly of nanostructures via. the bottom-up approach by dielectrophoresis. Dielectrophoresis deals with the force on an electric dipole placed in an external in-homogenous field. The force depends on the geometry and volume of the dielectric material and on the frequency and gradient of the electric field. We report the self-assembly of metallic palladium nanowires from the aqueous solution by dielectrophoresis. The metal cations with the surrounding hydration shell and counter-ion cloud results in the formation of a dipole which responds to the local dielectrophoretic forces. Structural properties and morphology of the palladium nanowires are listed. Depending on the experimental conditions two different types of nanowires were grown. Some of them were extremely thin (5 nm diameter) and branched while the others were thick (25 nm diameter) and dendritic. The wire formation can be divided into the nucleation and growth process. For the particle assembly, a minimum threshold force is needed to overcome the random Brownian motion. The nucleation depends on the asperities on the electrode surface and the growth depends on the tip of the growing wires where exists extremely high field magnitude and in-homogeneties and so the force overcomes the threshold at these locations. We showed that wire growth depends a lot on the formation of the double layer at the electrode/solution interface and potential drop within the double layer. Carbon nanotubes (CNT) were also deposited between the electrodes leading to the formation of field-effect transistors (FETs). We produced CNTFETs having extremely high on/off ratio, in a single step without the requirement of any intermediate burning process of the metallic tubes. Besides these inorganic systems, we also investigated the dielectrophoretic experimental conditions required for self assembly of bio-molecules like microtubules between the electrodes. Hybrid structures were also formed by mixing these materials in combination of two. In conclusion, we report in this work the possibility to assemble a large variety of particles (ions, neutral particles and bio-molecules) between the electrodes leading to the device formation. The thesis was mainly devoted to the task for the synthesis and assembly of the nanostructures via. the bottom-up approach.

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18

Myint, Cho Zin. "A new electronic device for measuring pulse and oxygen concentration". Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1788.

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Abstract (sommario):

Sensor devices such as pulse oximetry are practical tools used by most healthcare professionals, and even patients. An electronic sensor device that has the capability to measure physiological signs of saturation of arterial oxygen (SpO2) and heart beat rate of the human body has been developed in this study.The hardware design of the sensor device consists of a microcontroller PIC18F452, an external flash memory, and a transceiver unit. The most suitable sensors of red and infra red LEDs are installed on the arms of the plastic clip and functioned with the right resistor values. The red and infra red lights are detected by the photo diode and converted to digital numbers by the Assembly Language software program embedded into the microcontroller PIC18LF452. Those digital numbers are converted to SpO2 value in percentage level. A low power dual operational amplifier LM358 is used to amplify the current signal of the two lights, which depends on the intensity and visibility of the two lights. The output signals are displayed in 16 characters and 2 lines on Hitachi HD44870 compatible liquid crystal display (LCD). In order to display this data on personal computer (PC) monitor, the data is also transmitted via Universal Synchronous Asynchronous Receiver Transmitter (USART) ports of microcontroller to a PC. A Visual Basic 6 programming language is installed in the PC to display the wave forms, the percentage of the SpO2 level, and the pulse rate.Pulse oximetry has a promising future in the healthcare industry. This research enables a more efficient and economical means for managing the healthcare of the growing population.

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19

Wu, Yung-Hsun. "FAST RESPONSE LIQUID CRYSTAL DEVICES". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3111.

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Abstract (sommario):

Liquid crystal (LC) has been widely used for displays, spatial light modulators, variable optical attenuators (VOAs) and other tunable photonic devices. The response time of these devices is mainly determined by the employed liquid crystal material. How to obtain fast response for the LC devices is a fundamentally important and technically challenging task. In this dissertation, we investigate several methods to improve liquid crystal response time, for examples, using dual-frequency liquid crystals, polymer stabilized liquid crystals, and sheared polymer network liquid crystals. We discover a new class of material, denoted as sheared polymer network liquid crystal (SPNLC) which exhibits a submillisecond response time. First, dual-frequency liquid crystals and polymer network methods are demonstrated as examples for the variable optical attenuators. Variable optical attenuator (VOA) is a key component in optical communications. Especially, the sheared PNLC VOA shows the best result; its dynamic range reaches 43 dB while the response time is in the submillisecond range at 1550 nm wavelength, which is 50 times faster than the commercial LC-based VOA. Second, we report a new device called axially-symmetric sheared polymer network liquid crystals (AS-SPNLC) and use it as LC devices. An axially-symmetric sheared polymer network liquid crystal has several attractive features: 1) it is polarization independent, 2) it has gradient phase change, and 3) its response time is fast. It can be used for polarization converter and divergent LC lens. In addition, a new method for simultaneously measuring the phase retardation and optic axis of a compensation film is demonstrated using an axially-symmetric sheared polymer network liquid crystal. This simple technique can be used for simultaneously measuring the optic axis and phase retardations of both A- and C-plates. These compensation films have been used extensively in wide-view LCD industry. Therefore, this method will make an important impact to the LCD industry.
Ph.D.
Optics and Photonics
Optics

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20

Fan, Yun-Hsing. "TUNABLE LIQUID CRYSTAL PHOTONIC DEVICES". Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3926.

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Abstract (sommario):

Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices and their fabrication methods. The devices presented include inhomogeneous polymer-dispersed liquid crystal (PDLC), polymer network liquid crystals (PNLC) and phase-separated composite film (PSCOF). Liquid crystal/polymer composites could exist in different forms depending on the fabrication conditions. In Chap. 3, we demonstrate a novel nanoscale PDLC device that has inhomogeneous droplet size distribution. In such a PDLC, the inhomogeneous droplet size distribution is obtained by exposing the LC/monomer with a non-uniform ultraviolet (UV) light. An electrically tunable-efficiency Fresnel lens is devised for the first time using nanoscale PDLC. The tunable Fresnel lens is very desirable to eliminate the need of external spatial light modulator. Different gradient profiles are obtained by using different photomasks. The nanoscale LC droplets are randomly distributed within the polymer matrix, so that the devices are polarization independent and exhibit a fast response time. Because of the small droplet sizes, the operating voltage is higher than 100 Vrms. To lower the driving voltage, in Chap. 2 and Chap. 3, we have investigated a polymer-network liquid crystal (PNLC) using a rod-like monomer structure. Since the monomer concentration is only about 5%, the operating voltage is below 10 Vrms. The PNLC devices are polarization dependent. To overcome this shortcoming, stacking two cells with orthogonal alignment directions is a possibility. In Chap. 3, another approach to lower the operating voltage is to use phase-separated composite film (PSCOF) where the LC and polymer are separated completely to form two layers. Without multi-domain formed in the LC cell, PSCOF is free from light scattering. Using PNLC and PSCOF, we also demonstrated LC blazed grating and Fresnel lens. The diffraction efficiency of these devices is continuously controlled by the electric field. Besides Fresnel lens, another critical need for imaging and display is to develop a system with continuously tunable focal length. A conventional zooming system controls the lens distance by mechanical motion along the optical axis. This mechanical zooming system is bulky and power hungry. To overcome the bulkiness, in Chap. 4 we developed an electrically tunable-focus flat LC spherical lens which consists of a spherical electrode imbedded in the top flat substrates while a planar electrode on the bottom substrate. The electric field from the spherical and planar electrodes induces a centrosymmetric gradient refractive index distribution within the LC layer which, in turn, causes the focusing effect. The focal length is tunable by the applied voltage. A tunable range from 0.6 m to infinity is achieved. Microlens array is an attractive device for optical communications and projection displays. In Chap. 5, we describe a LC microlens array whose focal length can be switched from positive to negative or vise versa by the applied voltage. The top spherical electrode glass substrate is flattened with a polymer layer. The top convex substrate and LC layer work together like a zoom lens. By tuning the refractive index profile of the LC layer, the focal length of the microlens array can be switched from positive to negative or vise versa. The tunable LC microlens array would be a great replacement of a conventional microlens array which can be moved by mechanical elements. The fast response time feature of our LC microlens array will be very helpful in developing 3-D animated images. A special feature for LC/polymer composites is light scattering. The concept is analogous to the light scattering of clouds which consist of water droplets. In Chap. 6, we demonstrate polymer network liquid crystals for switchable polarizers and optical shutters. The PNLC can present anisotropic or isotropic light scattering behavior depending on the fabrication methods. The use of dual-frequency liquid crystal and special driving scheme leads to a sub-millisecond response time. The applications for display, light shutters, and switchable windows are emphasized. Although polymer networks help to reduce liquid crystal response time, they tend to scatter light. In Chap. 7, for the first time, we demonstrate a fast-response and scattering-free homogeneously-aligned PNLC light modulator. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. As a result, the PNLC response time is ~300X faster than that of a pure LC mixture except that the threshold voltage is increased by ~25X. The PNLC cell also holds promise for mid and long infrared applications where response time is a critical issue.
Ph.D.
Other
Optics and Photonics
Optics

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21

Lin, Yi-Hsin. "POLARIZATION-INDEPENDENT LIQUID CRYSTAL DEVICES". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4199.

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Abstract (sommario):

Liquid crystal (LC) devices can be operated as amplitude modulators and phase modulators. LC amplitude modulation is commonly used in liquid crystal display (LCD) while phase-only modulation is useful for laser beam steering, tunable grating, prism, lens, and other photonic devices. Most LC devices are polarization dependent and require at least one polarizer. As a result, the optical efficiency is low. To enhance display brightness, a power hungry backlight has to be used leading to a high power consumption and short battery life. In a LC phase modulator, the polarization dependent property complicates the laser beam steering system. It is highly desirable to develop new operating mechanisms that are independent of the incident light polarization. In this dissertation, we have developed eight polarization-independent liquid crystal operation principles: three of them are aimed for displays and the other five are for phase modulators. For amplitude modulations, a new polymer-dispersed liquid crystal (PDLC) and two new dye-doped LC gels are polarizer-free by combining light scattering with dye-absorption effects. In phase modulation, we explore five device concepts: PDLC and Polymer-Stabilized Cholesteric Texture (PSCT), homeotropic LC gels, thin polymer film separated double-layered structure, and double-layered LC gels. In the low voltage regime, both PDLC and PSCT have a strong light scattering. However, as the voltage exceeds a certain level, the phase modulation is scattering-free and is independent of polarization. The homeotropic LC gels do not require any biased voltage and the response time is still fast. Although the remaining phase in these devices is small, they are still useful for micro-photonic device applications. To increase the phase change, thin polymer film separated double-layered structure is a solution. The orthogonal arrangement of top and bottom LC directors results in polarization independence. However, the response time is slow. Similarly, double-layered LC gels are not only polarization independent but also fast response due to the established polymer network.
Ph.D.
Optics and Photonics
Optics

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22

Wetzler, Reinhard. "Spatial Coulomb effects in semiconductor quantum dot devices". [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971082073.

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23

Denzel, Michael. "Malware tolerance : distributing trust over multiple devices". Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8422/.

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Abstract (sommario):

Current security solutions try to keep the adversary out of the computer infrastructure. However, with zero-day exploits and certain rootkit attacks, the assumption that attacks can be blocked does not hold any more. This work presents the concept of malware tolerance accepting that every device might be compromised at some point in time. The concept aims to distribute trust over several devices so that no single device is able to compromise security features by itself. I create three malware-tolerant techniques to demonstrate the feasibility of the concept. This thesis introduces a trusted input system which delivers keystrokes securely from the keyboard to a recipient even if one of its components is compromised. The second approach is the design of a self-healing Industrial Control System, a sensor-actuator network to securely control a physical system. If an adversary manages to compromise one of the components, it remains secure and can even recover from attacks. Lastly, this thesis proposes a mesh network architecture aimed at smart-home networks without assuming any device in the network invulnerable to attacks applying isolation mechanisms to otherwise flat mesh networks. This thesis gives formal security proofs with protocol verifier ProVerif. The proof scripts are open-source.

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24

Qureshi, Omar Osman. "The modelling of ferrite-loaded helical devices". Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/2918/.

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Abstract (sommario):

Helical devices are employed in the area of microwave technology. Applications such as filters and travelling-wave tubes are some of these in which helical devices are used. Ferrite loaded helical devices have been of interest to scientists and engineers throughout the last half century. The structure that is considered in this thesis is of a helix surrounded by a ferrite tube, both of which are enclosed in a cylindrical waveguide. Maxwell's equations for electromagnetism are employed in order to derive the expressions for the electric and magnetic fields. The parameters of the structure are varied in order to observe how certain factors will affect the dispersiveness, loss and phase shift of the structure. The investigation considers the effect of varying the applied magnetic field. The investigation also incorporates an air gap between the ferrite and helix and between the ferrite and metal waveguide. For the first time, the affects of these air gaps are analysed.

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25

Sampara, N. "Voltage induced spreading and liquid optical devices". Thesis, Nottingham Trent University, 2013. http://irep.ntu.ac.uk/id/eprint/83/.

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Abstract (sommario):

An experimental investigation has been carried out into Liquid dielectrophoresis (LDEP), in which dielectric forces are used to actuate bulk liquid spreading and to imprint a deformation pattern at a liquid air surface. Our basic conguration uses a set of co-planar stripe interdigital electrodes to create a non-uniform A.C. electric field that exponentially decays in amplitude and penetrates above the structure into a dielectric liquid droplet. Dielectric forces drive a voltage-induced spreading of the droplet into a low contact angle droplet/film, an effect which will be referred to here as "dielectrowetting". Further application of the A.C. voltage to the electrodes results in a static sinusoidal wrinkle forming at the oil-air interface on the spread film. Three main areas of investigations are reported, the first of which is a study of the statics and dynamics of the voltage induced spreading of a stripe of the material 1,2 propylene glycol. In the limit of thick droplets, a theoretical prediction has been derived that the cosine of the static equilibrium contact angle is proportional to the square of the amplitude of the voltage applied to the inter-digital electrodes. This relationship is analogous to that found for electrowetting-on-dielectric (EWOD). Experimental observations confirm this predicted dielectrowetting behavior for the advancing static contact angle of the voltage induced spreading of a stripe of the material 1,2 propylene glycol. The predicted scaling relationship with the electrode dimensions has been confirmed for electrodes of linewidth 20 um, 40 um and 80 um. It is also shown that with an appropriate surface treatment the induced wetting is made reversible. The dynamic contact angle ( o) of the liquid droplet was also measured as a function of voltage during spreading and the results are found to agree with the predictions of the Hoffman-de-Gennes macroscopic viscous dissipation approach extended to account for the electric field. Three distinct regimes have been investigated experimentally and theoretically: partial wetting and exponential approach to equilibrium shape, spreading to complete wetting obeying a Tanner's law relationship, and super-spreading towards a complete wetting film. The second area is the fabrication of the solid phase transmission grating with a minimized zeroth order using LDEP and a UV curable liquid resin. A new electric-field assisted approach to fabricate solid diffractive optical devices is demonstrated in which the optical properties of the device can be tuned by adjusting the applied voltage whilst the optical medium is in its liquid phase. Continuous adjustment of the voltage, and hence the optical diffraction pattern, during UV curing can produce a solid grating with suppressed intensity of the transmitted zero order. The third area is a study of the dynamics of the formation of a periodic wrinkle deformation at the oil-air interface on a spread dielectric liquid film. An experimental study of how the switch on time ton and the switch off/relaxation time toff of the wrinkle scales as a function of the applied voltage V is presented. The amplitude A(V, t) of the wrinkle as a function of time was obtained from fitting the time dependent intensities of the positive zeroth, first and second diffracted orders of laser light transmitted through the oil film assuming that it acts as a thin sinusoidal phase grating. The results for relaxation have been compared with an analytical expression for toff that has been derived by considering the LaPlace pressure restoring force at the oil-air interface under a creeping flow approximation.

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26

Zulkifli, Muhammad. "Microalgae derived carbon for energy storage devices". Thesis, Zulkifli, Muhammad (2017) Microalgae derived carbon for energy storage devices. Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/41924/.

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Abstract (sommario):

In this study, the electrochemical properties and sample characterization of activated carbon have been analysed to gain a clear understanding of its behaviour reflecting the energy storage performance. When tested in a three-electrode configuration for electrochemical characterization working with 2M NaOH electrolyte solution, the activated carbon exhibits excellent capacitance and energy density value which is 124.436 F g-1 and 62.218 Wh kg-1, respectively. The activated carbon showed large BET surface area and large pores area, which are 1133.8038 m2 g-1 and 891.909 m2 g-1, respectively, ascribed to micropores. Besides, 2h holding time at 200oC by hydrothermal carbonisation of solid hydrochar from Chlorella algae species was used as precursor material. It is for the preparation of microalgae derived carbon by chemical activation method with KOH. An approach has been made to test the influences of the activation temperature on the pore structure and the energy storage performance. The macroalgal hydrochar is synthesized at two different temperatures, 800oC and 900oC, for 60 min under same impregnation ratio of KOH/hydrochar is being 4:1. Two samples thus synthesized present low capacitance and thus low energy density value which sample 1 (AC1-4:1-800) exhibited 10.679 F g-1 and 5.34 Wh kg-1, respectively, while sample 2 (AC2-4:1-900) exhibit 0.939 F g-1 and 0.47 Wh kg-1, respectively. From the BET and porosity analysis, it is concluded that both samples have low BET surface area, pores volume and low pores area. The conclusion from this experiment is that a high activation temperature, (i.e., 900oC), may degrade the pore structure of electrode materials.

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27

Korzetz, Mandy, Romina Kühn, Karl Kegel, Franz-Wilhelm Schumann, Leon Georgi e Thomas Schlegel. "MilkyWay: A Toolbox for Prototyping Collaborative Mobile-Based Interaction Techniques". Springer, 2019. https://tud.qucosa.de/id/qucosa%3A71301.

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Abstract (sommario):

Beside traditional multitouch input, mobile devices provide various possibilities to interact in a physical, device-based manner due to their built-in hardware. Applying such interaction techniques allows for sharing content easily, e.g. by literally pouring content from one device into another, or accessing device functions quickly, e.g. by facing down the device to mute incoming calls. So-called mobile-based interaction techniques are characterized by movements and concrete positions in real spaces. Even though such interactions may provide many advantages in everyday life, they have limited visibility in interaction design due to the complexity of sensor processing. Hence, mobile-based interactions are often integrated, if any, at late design stages. To support testing interactive ideas in early design stages, we propose MilkyWay, a toolbox for prototyping collocated collaborative mobile-based interaction techniques. MilkyWay includes an API and a mobile application. It enables easily building up mobile interactive spaces between multiple collocated devices as well as prototyping interactions based on device sensors by a programming-by-demonstration approach. Appropriate sensors are selected and combined automatically to increase tool support. We demonstrate our approach using a proof of concept implementation of a collaborative Business Model Canvas (BMC) application.

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28

Lehmann, Thomas. "Towards device driver synthesis". [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=968551009.

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29

Galan, Elias Jason. "Magnesium Diboride Superconducting Devices and Circuits". Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/353715.

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Abstract (sommario):

Physics
Ph.D.
While magnesium diboride (MgB2) was first synthesized in the 1950s, MgB2’s superconductive properties were not discovered until 2001. It has the highest superconducting transition temperature of all the metallic superconductors at ~39 K at atmospheric pressure. MgB2 is also unique in that it has a two superconductive gaps, a pi gap at 2 meV and a sigma gap at 7.1 meV. There are a theoretical models discussing the inter- and intra- gap scattering of the superconductivity of MgB2 and the Josephson transport of MgB2 Josephson Junctions. The focus of this work is to further the study of all-MgB2 Josephson junctions and quantum interference device technology. This work discusses the transport in all-MgB2 Josephson junctions and designing, fabricating, and measuring multi-junction devices. The junctions studied include all-MgB2 sandwich-type Josephson junctions (one with TiB2 normal conducting barrier and another with an MgO insulating barrier). The junction MgB2 films were deposited by hyprid physical-vapor deposition and the junction barrier were deposited by sputtering. The junctions were patterned and etched with UV photolithography and argon ion milling. With the TiB2 barrier we studied Josephson transport by the proximity effect. With these junctions, we also observed complete suppression of the critical current by an applied magnetic field showing for the first time a leakage free barrier in an all-MgB2 Josephson junction with a single ultrathin barrier. We also studied junctions utilizing MgO barrier deposited by reactive sputtering which gave a larger characteristic voltage of 1-3 mV compared to TiB2 barriers. By connecting several SQUIDs with varying loop areas we developed of two types of superconducting quantum interference filters (SQIFs). The first SQIF designed with 21 SQUIDs connected in parallel and the SQUID loops are sensitive to magnetic fields applied parallel to the substrate. The SQUID loop areas were designed to vary in such a way that the voltage modulation gave a unique peak corresponding to the absolute value of the applied magnetic field. The SQIF shows an antipeak height of 0.25 mV with a transfer function of 16 V/T at 3 K. The lowest noise measured for this SQIF is 110 pT/Hz1/2. The second SQIF is designed with 17 SQUIDs in parallel and the SQUID loops are sensitive to magnetic field perpendicular to the substrate. This SQIF has shown improved voltage modulation with a peak height of 1 mV and a transfer function of 7800 V/T. The noise sensitivity was measured at 70 pT/Hz1/2. The sensitivity of the SQIF shows MgB2 potential superconductor to improve performance of current superconductive electronics. Utilizing known all-MgB2 junctions and SQUID parameters two rapid single flux quantum (RSFQ) circuits were designed and tested. A toggle flip flop (TFF) operating as a frequency divider was developed. The TFF design consisted of a Josephson transmission line, a splitter, and an interferometer (a DC SQUID). The TFF utilized an improved designed, compared to previous all-MgB2 TFFs, and showed operation up to 335 GHz at 7 K and operation up to 30 K. A low frequency set-reset flip flop (SRFF) was also developed to demonstrate RSFQ digital logic. The SRFF design includes a DC-SFQ converter, a Josephson transmission line, and an inductively coupled readout SQUID. The SRFF demonstrates proper digital logic by toggling between a high and low voltage state with a sequential set and reset input. While these developed devices are not close to the potential that MgB2 allows, they do show the promise MgB2 based devices have in making more sensitive and faster superconductive logic devices.
Temple University--Theses

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30

Kunets, Vasyl. "Micro Hall devices based on high electron velocity semiconductors". Doctoral thesis, [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=973088672.

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31

Rodríguez, Sanmartín Daniel. "Smart piezoelectric devices for X-ray optics applications". Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/3193/.

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Abstract (sommario):

The development of active/adaptive X-ray optics, utilising piezoelectric actuation for the focussing of X-rays in large and small scale applications, has been studied as part of the UK Smart X-Ray Optics (SXO) consortium. For laboratory based X-ray sources utilising micro structured optical arrays (MOAs), a novel spider actuator structure, compatible with silicon wet etching of MOAs, has been developed. Test spider samples (20x20x0.100mm) have been bent to a 6.5cm radius using unimorph actuators, and to a 3cm radius without failure. FEA models predicted that a 4.5cm radius and +/-3mrad tip/tilt control of the MOAs could be obtained using unimorph actuators with segmented electrodes and optimized thickness, which would enable a tandem pair MOA configuration of suitable focal length. A first generation prototype Wolter I optic for future high resolution X-ray telescopes exhibited kinks in the reflecting surface corresponding to the gaps between piezoelectric devices. FEA models have been used to develop second generation prototypes in which the gaps have been minimised or filled. These incorporate a brick wall arrangement of curved unimorph piezoelectric actuators (32x75x0.190mm) with radii from 160-200mm +/-6mm, manufactured using a VPP technique and laser machining for precise dimensional control. Keywords: Smart X-ray optics (SXO), micro-structured optical arrays (MOAs), Wolter I X-ray optics, piezoelectric actuators, finite element analysis (FEA), viscous plastic processing (VPP).

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32

Deng, Sunan. "Nanophotonic devices based on graphene and carbon nanotubes". Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7041/.

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Abstract (sommario):

The research presented in the thesis includes the modelling and characterization of the novel devices based on graphene and carbon nanotube (CNT)-based buckypaper. The devices have great potential to be used in applications such as photovoltaics, optical communications/imaging and sensors for oil and gas industry. Graphene is a promising material with excellent optical and electrical properties. Research was carried out in utilizing graphene for photonic and plasmonic devices, including ultra-thin flat lens, plasmonic lens, and oil sensor. Buckypaper extends the applications of CNTs’ excellent properties from nanoscale to microscale. This opportunity was explored in the development of ultra-thin flat lens.

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33

Xu, Su. "Optical Fluid-based Photonic and Display Devices". Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5585.

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Abstract (sommario):

Conventional solid-state photonic devices exhibit an ultra-high optical performance and durability, but minimal adaptability. Recently, optical fluid-based photonic and display devices are emerging. By dynamically manipulating the optical interface formed by liquids, the optical output can be reconfigured or adaptively tuned in real time. Such devices exhibit some unique characteristics that are not achievable in conventional solid-state photonic devices. Therefore, they open a gateway for new applications, such as image and signal processing, optical communication, sensing, and lab-on-a-chip, etc. Different operation principles of optical fluid-based photonic devices have been proposed, for instance fluidic pressure, electrochemistry, thermal effect, environmentally adaptive hydrogel, electro-wetting and dielectrophoresis. In this dissertation, several novel optical fluid-based photonic and display devices are demonstrated. Their working principles are described and electro-optic properties investigated. The first part involves photonic devices based on fluidic pressure. Here, we present a membrane-encapsulated liquid lens actuated by a photo-activated polymer. This approach paves a way to achieve non-mechanical driving and easy integration with other photonic devices. Next, we develop a mechanical-wetting lens for visible and short-wavelength infrared applications. Such a device concept can be extended to longer wavelength if proper liquids are employed. In the second part, we reveal some new photonic and display devices based on dielectrophoretic effects. We conceive a dielectric liquid microlens with well-shaped electrode for fixing the droplet position and lowering the operating voltage. To widen the dynamic range, we demonstrate an approach to enable focus tuning from negative to positive or vice versa in a single dielectric lens without any moving part. The possibility of fabricating microlens arrays with different aperture and density using a simple method is also proposed. Furthermore, the fundamental electro-optic characteristics of dielectric liquid droplets are studied from the aspects of operating voltage, frequency and droplet size. In addition to dielectric liquid lenses, we also demonstrate some new optical switches based on dielectrophoretic effect, e.g., optical switch based on voltage-stretchable liquid crystal droplet, variable aperture or position-shifting droplet. These devices work well in the visible and near infrared spectral ranges. We also extend this approach to display and show a polarizer-free and color filter-free display. Simple fabrication, low power consumption, polarization independence, relatively low operating voltage as well as reasonably fast switching time are their key features.
Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics

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34

Jollivet, Clemence. "Specialty Fiber Lasers and Novel Fiber Devices". Doctoral diss., University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6295.

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At the Dawn of the 21st century, the field of specialty optical fibers experienced a scientific revolution with the introduction of the stack-and-draw technique, a multi-steps and advanced fiber fabrication method, which enabled the creation of well-controlled micro-structured designs. Since then, an extremely wide variety of finely tuned fiber structures have been demonstrated including novel materials and novel designs. As the complexity of the fiber design increased, highly-controlled fabrication processes became critical. To determine the ability of a novel fiber design to deliver light with properties tailored according to a specific application, several mode analysis techniques were reported, addressing the recurring needs for in-depth fiber characterization. The first part of this dissertation details a novel experiment that was demonstrated to achieve modal decomposition with extended capabilities, reaching beyond the limits set by the existing mode analysis techniques. As a result, individual transverse modes carrying between ~0.01% and ~30% of the total light were resolved with unmatched accuracy. Furthermore, this approach was employed to decompose the light guided in Large-Mode Area (LMA) fiber, Photonic Crystal Fiber (PCF) and Leakage Channel Fiber (LCF). The single-mode performances were evaluated and compared. As a result, the suitability of each specialty fiber design to be implemented for power-scaling applications of fiber laser systems was experimentally determined. The second part of this dissertation is dedicated to novel specialty fiber laser systems. First, challenges related to the monolithic integration of novel and complex specialty fiber designs in all-fiber systems were addressed. The poor design and size compatibility between specialty fibers and conventional fiber-based components limits their monolithic integration due to high coupling loss and unstable performances. Here, novel all-fiber Mode-Field Adapter (MFA) devices made of selected segments of Graded Index Multimode Fiber (GIMF) were implemented to mitigate the coupling losses between a LMA PCF and a conventional Single-Mode Fiber (SMF), presenting an initial 18-fold mode-field area mismatch. It was experimentally demonstrated that the overall transmission in the mode-matched fiber chain was increased by more than 11 dB (the MFA was a 250 ?m piece of 50 ?m core diameter GIMF). This approach was further employed to assemble monolithic fiber laser cavities combining an active LMA PCF and fiber Bragg gratings (FBG) in conventional SMF. It was demonstrated that intra-cavity mode-matching results in an efficient (60%) and narrow-linewidth (200 pm) laser emission at the FBG wavelength. In the last section of this dissertation, monolithic Multi-Core Fiber (MCF) laser cavities were reported for the first time. Compared to existing MCF lasers, renown for high-brightness beam delivery after selection of the in-phase supermode, the present new generation of 7-coupled-cores Yb-doped fiber laser uses the gain from several supermodes simultaneously. In order to uncover mode competition mechanisms during amplification and the complex dynamics of multi-supermode lasing, novel diagnostic approaches were demonstrated. After characterizing the laser behavior, the first observations of self-mode-locking in linear MCF laser cavities were discovered.
Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics and Photonics

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35

Van, Tien Pham. "Proactive ad hoc devices for relaying real-time video packets". [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983780226.

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36

Jakobi, Martin. "Laser speckle based surface measurement techniques relevant to fusion devices". [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=960674144.

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37

Devlin, Sean M. "Improving Degradable Biomaterials for Orthopedic Fixation Devices". Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/394989.

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Bioengineering
Ph.D.
Current degradable orthopedic ﬁxation devices do not typically facilitate tissue integration during healing. Proposed here is a novel combination of processing methods to enhance the tissue integration capability of degradable thermoplastics used in temporary orthopedic ﬁxation devices. The provision of open pores in devices used to aﬃx reconstructed hard tissues would allow for local cells to inﬁltrate during the healing process. Any openly porous structure is inherently weakened in comparison to its monolithic peers (i.e. decreased relative bulk modulus), such that the matrix materials must be made more resilient in keep the device from becoming friable. These processing methods aim to improve degradable surgical ﬁxation devices at multiple levels of design: both through the inclusion of porous morphology, processing changes, and additives to regain mechanical integrity. Biomimetic pores are added for cellular inﬁltration by dissolving a porogen’s interpenetrating polymer network. The addition of open pores signiﬁcantly reduces the bulk stiﬀness. More uniform phase separation has led to better pores, but the objects still need more resilience. Carbon nanomaterials are used to improve on the mechanics and surface chemistry of the polymer matrix material, composites of polylactide/nanodiamond are produced through cryogenic milling and solid state polycondensation. The addition of minute amounts of functionalized nanodiamond has remedied the brittle failure of the material, by cryogenic milling and solid state polycondensation of poly((D,L)lactide-co-glycolide) and hydroxyl functionalized detonation nanodiamonds. This composite has also demonstrated increased cytocompatability with 7F2 osteoblasts, as analyzed by cellular adhesion through ﬂuorescence microscopy and alamar blue assay.
Temple University--Theses

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38

Pinkney, Thomas David. "Wound-edge protection devices to reduce surgical site infection". Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7588/.

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This thesis provides an overview of the design, conduct and analysis of a multicentre phase III trial exploring the clinical effectiveness of a novel in-theatre intervention to try to reduce rates of post-operative surgical site infection (SSI). The pitfalls inherent in the conduct of research into SSI are discussed, along with measures to try and overcome these. The wound-edge protection device (WEPD) intervention is defined and the published evidence assessing its clinical effectiveness systematically appraised. Clinical surgical research and its difficulties are described, and the paradigm-shift bought about by the new trainee-led research collaborative model introduced. The design considerations involved creating a pragmatic and simple trial within the complex intervention that is surgery are explored in the context of the creation of the ROSSINI trial. This trial successfully recruited ahead of time and target and robustly proved that WEPDs are not clinically effective in reducing SSI. It also demonstrated the power and ability of this new collaborative model, as witnessed by both the citations of the results paper and the exponential growth in similar collaborative ventures. Finally, lessons learned about SSI research and clinical surgical research are summarised, and plans for future research presented.

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39

Doy, Nicola. "Characterising room temperature ionic liquids with acoustic wave devices". Thesis, Nottingham Trent University, 2010. http://irep.ntu.ac.uk/id/eprint/107/.

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Data for the physical properties of Room Temperature Ionic Liquids (RTILs) as a function of chemical composition is limited due to the expense and difficulty of producing large volumes of pure samples for characterization. RTILs comprise solely of ions and are liquid at room temperature. These are becoming of increasing interest for an extensive range of applications. This thesis looks at developing small scale characterization processes to find low cost and efficient methods for processing smaller sample volumes. Quartz crystal impedance analysis has been used to assess whether room temperature ionic liquids behave in a Newtonian manner to determine the values of their square root viscosity-density product using small volumes. Values are compared to traditional viscometer and densitometer measurements. A range of harmonics were studied for a 5 MHz fundamental crystal. The frequency shift of the third harmonic was found to provide the closest agreement between the two measurement methods with a limit seen at a square root viscosity-density product value of approximately 18 kg m⁻² s⁻⁰.⁵. Further characterisation of the liquid was performed to separate values of density and viscosity using dual Quartz Crystal Microbalance (QCM) with fabricated surface features on one QCM; this required a total sample volume of only 240 L. Values were corroborated with standard measurement techniques demonstrating good agreement. A QCM was then incorporated into a microfluidic glass chip system to measure the square root of the viscosity-density product of RTILs. The QCM covers a central recess on the glass chip, with a seal formed by tightly clamping from above outside the sensing region. The change in resonant frequency of an 8 MHz QCM operating on the 3rd harmonic was shown to allow determination of the square root viscosity-density product of RTILs to a maximum limit of square root viscosity-density product of approximately 10 kg m⁻² s⁻⁰.⁵. This microfluidic technique reduced the sample size needed for characterisation from 1.5 ml to only 30 μL and allowed the measurement to be made in an enclosed system reducing the risk of water contamination. In the final part of this work surface acoustic wave devices were studied. The most promising device, a Shear Horizontal Surface Acoustic Wave (SH-SAW) device with silicon dioxide guiding layer, provided good correlation between phase, insertion loss and the square root viscosity-density product. A maximum square root viscosity-density product limit was observed at approximately 10 kg m⁻² s⁻⁰.⁵ at which point the acoustic response becomes too damped for accurate results to be determined. This work provides a basis for further miniaturisation and characterisation which could develop a surface acoustic wave device based system for high throughput microfluidic characterisation of many properties of ionic liquids within a single chip.

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40

Zeng, Guang. "Some aspects in lifetime prediction of power semiconductor devices". Universitätsverlag Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A34891.

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Power electronics, which fully covers the generation, conversion, transmission and usage of electrical energy, is a key technology for human welfare. With the development of technologies, the requirements on the reliability of power electronic systems are keep increasing. Long term operation under harsh environments is often accompanied by higher switching frequency and higher power density. To allow a reliable and sustainable performance of the power electronic systems, precise lifetime estimation of the power semiconductor devices is of significant importance. This work covers some aspects in the lifetime prediction of power semiconductor devices, especially IGBT and diode, in power module and transfer-molded discrete package. Difference in device temperature determination was illustrated using analytical calculation, simulation and measurement. In addition, temperature calculation in the frequency domain was demonstrated which gives benefits in the application with several hundred devices. Furthermore, different control strategies in the power cycling test were compared. The linear cumulative damage theory was validated by using the power cycling test. For the high power IGBT module used in the MMC HVDC application, power cycling lifetime with 50 Hz heating processes was investigated. For the transfer-molded discrete package, the first lifetime model with comparable scope like the lifetime model of power modules was proposed.
Leistungselektronik, welche direkt relevant für die Erzeugung, Umwandlung, Übertragung und Nutzung elektrischer Energie ist, ist eine Schlüsseltechnologie für das Wohl der Menschen. Mit der Entwicklung von Technologien steigen die Anforderungen an die Zuverlässigkeit leistungselektronischer Systeme. Der Langzeitbetrieb unter rauen Umgebungsbedingungen geht häufig mit einer höheren Schaltfrequenz und einer höheren Leistungsdichte einher. Um eine zuverlässige und nachhaltige Operation der leistungselektronischen Systeme zu ermöglichen, ist die genaue Lebensdauerabschätzung der Halbleiter-Leistungsbauelemente von großer Bedeutung. Diese Arbeit befasst sich mit einigen Aspekten der Lebensdauerabschätzung von den Halbleiter-Leistungsbauelementen. Unterschied in der Temperaturabstimmung der Halbleiter-Leistungsbauelemente wird anhand von Berechnung, Simulation und Messung veranschaulicht. Darüber hinaus bietet die Temperaturberechnung im Frequenzbereich Vorteile bei der Anwendung mit mehreren hundert Bauelementen. Darüber hinaus wurden verschiedene Regelstrategien im Lastwechseltest verglichen. Die lineare kumulative Alterungstheorie wurde unter Verwendung des Lastwechseltests validiert. Für das in der MMC-HGÜ-Anwendung verwendete Hochleistungs-IGBT-Modul wurden Alterungsprozesse bei 50 Hz Erwärmung untersucht. Für das Diskrete-Gehäuse wird das erste Lebensdauermodell vorgestellt, welches ein vergleichbares Anwendungsbereich wie das Lebensdauermodell von Leistungsmodulen hat.

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41

Hansen, Sinclair D. "An intrusion detection system for supervisory control and data acquisition systems". Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/16636/1/Sinclair_Hansen_Thesis.pdf.

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Despite increased awareness of threats against Critical Infrastructure (CI), securing of Supervisory Control and Data Acquisition (SCADA) systems remains incomplete. The majority of research focuses on preventative measures such as improving communication protocols and implementing security policies. New attempts are being made to use commercial Intrusion Detection System (IDS) software to protect SCADA systems. These have limited effectiveness because the ability to detect specific threats requires the context of the SCADA system. SCADA context is defined as any information that can be used to characterise the current status and function of the SCADA system. In this thesis the standard IDS model will be used with the varying SCADA data sources to provide SCADA context to a signature and anomaly detection engine. A novel addition to enhance the IDS model will be to use the SCADA data sources to simulate the remote SCADA site. The data resulting from the simulation is used by the IDS to make behavioural comparison between the real and simulated SCADA site. To evaluate the enhanced IDS model the specific context of a water and wastewater system is used to develop a prototype. Using this context it was found that the inflow between sites has similar diurnal characteristic to network traffic. This introduced the idea of using inflow data to detect abnormal behaviour for a remote wastewater site. Several experiments are proposed to validate the prototype using data from a real SCADA site. Initial results show good promise for detecting abnormal behaviour and specific threats against water and wastewater SCADA systems.

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42

Hansen, Sinclair D. "An intrusion detection system for supervisory control and data acquisition systems". Queensland University of Technology, 2008. http://eprints.qut.edu.au/16636/.

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Abstract (sommario):

Despite increased awareness of threats against Critical Infrastructure (CI), securing of Supervisory Control and Data Acquisition (SCADA) systems remains incomplete. The majority of research focuses on preventative measures such as improving communication protocols and implementing security policies. New attempts are being made to use commercial Intrusion Detection System (IDS) software to protect SCADA systems. These have limited effectiveness because the ability to detect specific threats requires the context of the SCADA system. SCADA context is defined as any information that can be used to characterise the current status and function of the SCADA system. In this thesis the standard IDS model will be used with the varying SCADA data sources to provide SCADA context to a signature and anomaly detection engine. A novel addition to enhance the IDS model will be to use the SCADA data sources to simulate the remote SCADA site. The data resulting from the simulation is used by the IDS to make behavioural comparison between the real and simulated SCADA site. To evaluate the enhanced IDS model the specific context of a water and wastewater system is used to develop a prototype. Using this context it was found that the inflow between sites has similar diurnal characteristic to network traffic. This introduced the idea of using inflow data to detect abnormal behaviour for a remote wastewater site. Several experiments are proposed to validate the prototype using data from a real SCADA site. Initial results show good promise for detecting abnormal behaviour and specific threats against water and wastewater SCADA systems.

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43

Moore, Lamar. "The application of the capacitive division technique to wide-field time-resolved fluorescence microscopy". Thesis, University of Sussex, 2018. http://sro.sussex.ac.uk/id/eprint/80448/.

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Capacitive division and other charge-sharing techniques have become ubiquitous within modern technology. Almost all touchscreen devices depend on some form of charge sharing mechanism. The Capacitive-Division Imaging Readout, C-DIR, scheme developed for space/astronomy applications, is a proven concept which has benefited from widespread publication and several iterations of prototyping. In this study, we borrowed this idea and assessed its application in the field of life sciences, specifically, fluorescence lifetime imaging microscopy (FLIM). Firstly, the composite C-DIR camera system was developed using a prototype anode developed by Lapington et al in combination with advanced photomultiplier tube technology developed by Photek Limited, and ultra-fast NINO ASIC and high performance time-to-digital converter, HPTDC, readout electronics developed by CERN. Several issues like signal noise, timing jitter and image distortion required special attention to successfully tune the C-DIR system for obtaining FLIM measurements. The C-DIR was characterized in the context of current detector technologies used for time-resolved applications. The maximum achievable global event rate was determined to be a USB 2.0 hard limit of about 1MHz. The spatial resolution and timing performance were identified as 0.5 line-pairs/mm and 200ps FWHM, respectively, which was comparable to other wide-field fluorescence lifetime cameras. These results provided the basis for using the system in a real situation. Before this was possible, however, it was necessary to engineer a bespoke software platform for data acquisition which could cope with the data rates and reduce raw data emerging from the C-DIR system, producing a format compatible with widely used fitting software. The final stage of the project involved using the C-DIR for real science by reproducing real world experiments which allow for a fitness test of the system in the field. The first experiment involved a calcium calibration where the C-DIR system was calibrated using FLIM on a series of calcium buffers of known concentrations. This C-DIR was able accurately recover the lifetime values from the calcium buffers. The second shorter experiment involved using the calibrated system for the quantification of calcium within living tissue samples using fluorescence lifetime imaging. Results were consistent with those published in the literature which solidified the position of the C-DIR as a viable option for time-resolved fluorescence microscopy.

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44

Chen, Yupeng. "FINITE ELEMENT METHOD MODELING OF ADVANCED ELECTRONIC DEVICES". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3115.

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In this dissertation, we use finite element method together with other numerical techniques to study advanced electron devices. We study the radiation properties in electron waveguide structure with multi-step discontinuities and soft wall lateral confinement. Radiation mechanism and conditions are examined by numerical simulation of dispersion relations and transport properties. The study of geometry variations shows its significant impact on the radiation intensity and direction. In particular, the periodic corrugation structure exhibits strong directional radiation. This interesting feature may be useful to design a nano-scale transmitter, a communication device for future nano-scale system. Non-quasi-static effects in AC characteristics of carbon nanotube field-effect transistors are examined by solving a full time-dependent, open-boundary Schrödinger equation. The non-quasi-static characteristics, such as the finite channel charging time, and the dependence of small signal transconductance and gate capacitance on the frequency, are explored. The validity of the widely used quasi-static approximation is examined. The results show that the quasi-static approximation overestimates the transconductance and gate capacitance at high frequencies, but gives a more accurate value for the intrinsic cut-off frequency over a wide range of bias conditions. The influence of metal interconnect resistance on the performance of vertical and lateral power MOSFETs is studied. Vertical MOSFETs in a D2PAK and DirectFET package, and lateral MOSFETs in power IC and flip chip are investigated as the case studies. The impact of various layout patterns and material properties on RDS(on) will provide useful guidelines for practical vertical and lateral power MOSFETs design.
Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering

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45

Grummel, Brian. "HIGH TEMPERATURE PACKAGING FOR WIDE BANDGAP SEMICONDUCTOR DEVICES". Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3200.

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Currently, wide bandgap semiconductor devices feature increased efficiency, higher current handling capabilities, and higher reverse blocking voltages than silicon devices while recent fabrication advances have them drawing near to the marketplace. However these new semiconductors are in need of new packaging that will allow for their application in several important uses including hybrid electrical vehicles, new and existing energy sources, and increased efficiency in multiple new and existing technologies. Also, current power module designs for silicon devices are rife with problems that must be enhanced to improve reliability. This thesis introduces new packaging that is thermally resilient and has reduced mechanical stress from temperature rise that also provides increased circuit lifetime and greater reliability for continued use to 300°C which is within operation ratings of these new semiconductors. The new module is also without problematic wirebonds that lead to a majority of traditional module failures which also introduce parasitic inductance and increase thermal resistance. Resultantly, the module also features a severely reduced form factor in mass and volume.
M.S.E.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering MSEE

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46

Ge, Zhibing. "MODELING OF LIQUID CRYSTAL DISPLAY AND PHOTONIC DEVICES". Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3867.

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Liquid crystal (LC) materials have been widely applied in electro-optical devices, among which display is the most successful playground and numerous new applications in photonic areas (such as laser beam steering devices) are also emerging. To well guide the device design for optimum performance, accurate modeling is of prior and practical importance. Generally, the modeling of LC devices includes two parts in sequence: accurate LC molecule deformation extraction under external electric fields and optical calculation thereafter for the corresponding electro-optical behaviors. In this dissertation, first, hybrid finite element method and finite difference method are developed to minimize the free energy of the LC systems. In this part of study, with computer-aided derivation, the full forms of the LC free energy equations without any simplification can be obtained. Besides, Galerkin's method and weak form technique are further introduced to successfully degrade the high order nonlinear derivative terms associated with the free energy equations into ones that can be treated by first order interpolation functions for high accuracy. The developed modeling methods for LC deformation are further employed to study display structures, such as 2D and 3D in-plane switching LC cells, and provides accurate results. Followed is the optical modeling using extended Jones matrix and beam propagation method to calculate the electro-optical performances of different devices, according to their amplitude modulation property or diffractive one. The developed methods are further taken to assist the understanding, development, and optimization of the display and photonic devices. For their application in the display area, sunlight readable transflective LCDs for mobile devices and the related optical films for wide viewing angle are developed and studied. New cell structure using vertically aligned liquid crystal mode is developed and studied to obtain a single cell gap, high light efficiency transflective LCD that can be driven by one gray scale control circuit for both transmissive and reflective modes. And employing an internal wire grid polarizer into a fringe field switching cell produces a single cell gap and wide viewing angle display with workable reflective mode under merely two linear polarizers. To solve the limited viewing angle of conventional circular polarizers, Poincaré sphere as an effective tool is taken to trace and understand the polarization change of the incident light throughout the whole LC system. This study further guides the design of high performance circular polarizers that can consist of purely uniaxial plates or a combination of uniaxial and biaxial plates. The developed circular polarizers greatly enhance the viewing angle of transflective LCDs. Especially, the circular polarizer design using a biaxial film can even provide comparable wide viewing angle performance for the same vertically aligned cell as it is used between merely two linear polarizers, while using circular polarizers can greatly boost the display brightness. As for the beam steering device modeling, the developed LC deformation method is taken to accurately calculate the associated LC director distribution in the spatial light modulator, while beam propagation method and Fourier transformation technique are combined to calculate the near and far fields from such devices. The modeling helps to better understand the origins and formations of the disclinations associated with the fringe fields, which further result in reduced steering efficiency and output asymmetric polarizations between positive and negative diffractions. Optimization in both voltage profile and driving methods is conducted to well tune the LC deformation under strong fringe fields and improve the light efficiency.
Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD

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47

Lades, Martin. "Modeling and simulation of wide bandgap semiconductor devices 4H/6H-SiC /". [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=962057827.

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48

Thalhammer, Robert. "Internal laser probing techniques for power devices analysis, modeling and simulation /". [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=962057959.

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49

Meisel, Andreas. "Alignment, characterization and application of polyfluorene in polarized light-emitting devices". [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963670441.

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50

Rosenstrauch, Doreen. "Use of autologous auricular chondrocytes for lining left ventricular assist devices". Doctoral thesis, [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972610480.

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