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Forss, Henrik, and David Asteberg. "Att prata i politik : En diskurspsykologisk undersökning av positionering i kommunfullmäktige." Thesis, Uppsala universitet, Sociologiska institutionen, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-254576.
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Lokal politik har en viktig roll i samhället och dess faktakonstruktion kan ha en påverkan på individen. Lokalpolitikern konstruerar i sina anföranden beskrivningar av verkligheten som görs trovärdiga genom retoriskt arbete. Arbetet använder en diskurspsykologisk metod för att undersöka kommunpolitikers anförande i debatten rörande kommunens styrdokument, Inriktning, verksamhet och ekonomi (förkortat IVE) för åren 2015 till 2018. Studien kommer fram till att problem och lösningar görs till fakta genom användandet av offensiv och defensiv retorik. I konstruerandet av problemet finns också ett konstruerande av en politisk motståndare som föranlett problemet. Producerandet görs trovärdigt genom retoriska resurser som främst är av offensiv karaktär. I konstruerandet av lösningar positionerar kommunpolitiker sig nära lösningen och som kapabla och ansvarsfulla aktörer. I producerandet nyttjas retoriska resurser som främst är av defensiv karaktär.Local government has an important role in society and their facts construction can have an impact on the individual citizen. In their speeches, local politicians construct descriptions of reality that are made credible by their rhetorical work. This study utilizes a discourse psychological method to investigate municipal politicians’ speech in the debate on the municipal policy regarding Orientation, Services and Economics (abbreviated IVE) for the years of 2015 throughout 2018. The study concludes that problems and solutions become facts through utilization of offensive and defensive rhetorical techniques. In the construction of the problem there is also a construction of the political opponent that has prompted the problem. The production is made credible through rhetorical resources of primarily offensive characteristics. In constructing the solution the municipal politicians position themselves close to the solution and as capable and responsible actors. In the production they use rhetorical resources that are mainly in defensive form.
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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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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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Brimicombe, Paul. "Fast-switching nematic liquid crystal devices." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443597.
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Erezzaghi, M. "The effects of FACTS devices on distance relay." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426704.
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Sellahewa, Harin. "Wavelet based automatic face recognition for constrained devices." Thesis, University of Buckingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436888.
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del, Valle Yamille E. "Optimization of power system performance using facts devices." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29612.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.Committee Chair: Dr. Ronald G. Harley; Committee Member: Dr. Bonnie Heck; Committee Member: Dr. Deepak Divan; Committee Member: Dr. Ganesh K. Venayagamoorthy; Committee Member: Dr. Miroslav Begovic. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Liu, Deyun. "Advances in beam propagation method for facet reflectivity analysis." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13491/.
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Waveguide discontinuities are frequently encountered in modern photonic structures. It is important to characterize the reflection and transmission that occurs at the discontinuous during the design and analysis process of these structures. Significant effort has been focused upon the development of accurate modelling tools, and a variety of modelling techniques have been applied to solve this kind of problem. Throughout this work, a Transmission matrix based Bidirectional Beam Propagation Method (T-Bi-BPM) is proposed and applied on the uncoated facet and the single coating layer reflection problems, including both normal and angled incident situations. The T-Bi-BPM method is developed on the basis of an overview of Finite Difference Beam Propagation Method (FD-BPM) schemes frequently used in photonic modelling including paraxial FD-BPM, Imaginary Distance (ID) BPM, Wide Angle (WA) BPM and existing Bidirectional (Bi) BPM methods. The T-Bi-BPM establishes the connection between the total fields on either side of the coating layer and the incident field at the input of a single layer coated structure by a matrix system on the basis of a transmission matrix equation used in a transmission line approach. The matrix system can be algebraically preconditioned and then solved by sparse matrix multiplications. The attraction of the T-Bi-BPM method is the potential for more rapid evaluation without iterative approach. The accuracy of the T-Bi-BPM is verified by simulations and the factors that affect the accuracy are investigated.
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Xuan, Qing-Yun. "Adaptive protection and control systems for controllable series compensated EHV transmission using neural networks." Thesis, Liverpool John Moores University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337860.
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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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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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Westerlund, Rickard. "Interactive Advertisements for Smart TV Devices Using Face Detection." Thesis, Umeå universitet, Institutionen för datavetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-56471.
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This thesis report details a project to extend the AdGateway product developed at Dohi Sweden with a framework that allows advertisers to create interactive advertisements. The key feature of this framework is to provide augmented reality capabilities by taking advantage of face recognition and webcams on smart TV systems. The interactive advertisements are created as applications in JavaScripts which get downloaded on the fly when a user clicks on a banner for that type of advertisement. This implementation will both extend the back-end system to support the distribution of this new type of advertisement as well as the front-end for the supported devices in order to set up the environment and run the JavaScript application. The Sony Google TV is the primary focus for the implementation but an extensive study is also included in the report to gather information about other possible platforms that could be supported. This report also studies in detail how the performance of face recognition can be improved by performing illumination normalization on input images. The project could not be completed on time due to limitations in both hardware and software regarding face detection. Nevertheless a framework has been implemented, and solutions for the impediments are discussed in the report
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Zeraatzade, Mahbube. "Transmission congestion management by optimal placement of FACTS devices." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4710.
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This thesis describes the implementation of the Flexible AC Transmission Systems (FACTS) devices to develop a market-based approach to the problem of transmission congestion management in a Balancing Market. The causes, remedies and pricing methods of transmission congestion are briefly reviewed. Balancing Market exists in markets in which most of the trading is done via decentralized bilateral contracts. In these markets only final adjustments necessary to ensure secure system operation is carried out at a centralized Balancing Market. Each market player can participate in the Balancing Market by submitting offers and bids to increase and decrease its initially submitted active generation output. In this research a method is proposed to reduce costs associated with congestion re-dispatch in a Balancing Market by optimal placement of FACTS devices, and in particular Thyristor Controlled Phase Shifter Transformers (TCPST). The proposed technique is applicable to both Mixed Integer Linear Programming (MILP) and Mixed Integer Non-Linear Programming (MINLP). In the MILP a power system network is represented by a simplified DC power flow under a MILP structure and the Market participants' offers and bids are also represented by linear models. Results show that applications of FACTS devices can significantly reduce costs of congestion re-dispatch. The application of the method based on the MINLP creates a nonlinear and non-convex AC OPF problem that might be trapped in local sub-optima solutions. The reliability of the solution that determines the optimal placement of FACTS devices is an important issue and is carried out by investigation of alternative solvers. The behavior of the MINLP solvers is presented and finally the best solvers for this particular optimization problem are introduced. The application of DC OPF is very common in industry. The accuracy of the DC OPF results is investigated and a comparison between the DC and AC OPF is presented.
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Yoon, Yong Tae. "Enhancement of electric power systems operation using FACTS devices." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10269.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 76-77).
by Yong Tae Yoon.
M.Eng.
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Villaroman, Norman. "Face Tracking User Interfaces Using Vision-Based Consumer Devices." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3941.
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Some individuals have difficulty using standard hand-manipulated input devices such as a mouse and a keyboard effectively. For such users who at the same time have sufficient control over face and head movement, a robust perceptual or vision-based user interface that can track face movement can significantly help them. Using vision-based consumer devices makes such a user interface readily available and allows its use to be non-intrusive. Designing this type of user interface presents some significant challenges particularly with accuracy and usability. This research investigates such problems and proposes solutions to create a usable and robust face tracking user interface using currently available state-of-the-art technology. In particular, the input control in such an interface is divided into its logical components and studied one by one, namely, user input, capture technology, feature retrieval, feature processing, and pointer behavior. Different options for these components are studied and evaluated to see if they contribute to more efficient use of the interface. The evaluation is done using standard tests created for this purpose. The tests were done by a single user. The results can serve as a precursor to a full-scale usability study, various improvements, and eventual deployment for actual use. The primary contributions of this research include a logical organization and evaluation of the input process and its different components in face tracking user interfaces, a common library for computer control that can be used by various face tracking engines, an adaptive pointing input style that makes pointing using natural movement easier, and a test suite that can be used to measure performance of various user interfaces for desktop systems.
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Oh, Sang Joon. "Electromagnetics of inertial energy storage systems with fast electromechanical energy conversion /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Collins, Christopher Donald. "FACTS device modelling in the harmonic domain." Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1103.
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This thesis describes a novel harmonic domain approach for assessing the steady state performance of Flexible AC Transmission System (FACTS) devices. Existing harmonic analysis techniques are reviewed and used as the basis for a novel iterative harmonic domain model for PWM FACTS devices. The unified Newton formulation adopted uses a combination of positive frequency real valued harmonic and three-phase fundamental frequency power-flow mismatches to characterise a PWM converter system. A dc side mismatch formulation is employed in order to reduce the solution size, something only possible because of the hard switched nature of PWM converters. This computationally efficient formulation permits the study of generalised systems containing multiple FACTS devices. This modular PWM converter block is applied to series, shunt and multi-converter FACTS topologies, with a variety of basic control schemes. Using a three-phase power-flow initialisation and a fixed harmonic Jacobian provides robust convergence to a solution consistent with time domain simulation. By including the power-flow variables in the full harmonic solution the model avoids unnecessary assumptions regarding a fixed (or linearised) operating point, fully modelling system imbalance and the associated non-characteristic harmonics. The capability of the proposed technique is illustrated by considering a range of harmonic interaction mechanisms, both within and between FACTS devices. In particular, the impact of transmission network modelling and operating point variation is investigated with reference to ac and dc side harmonic interaction. The minor role harmonic distortion and over-modulation play in the PWM switching process is finally considered with reference to the associated reduction in system linearity.
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Athanasiadis, Nikolaos P. "Modelling, control and design of Flexible AC Transmission Systems (FACTS), custom power devices and variable speed drives for transmission and distribution architectures." Thesis, University of Strathclyde, 1999. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21441.
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The main tasks of power electronics in power transmission and distribution systems is to process and control the flow of electric energy by supplying voltages and currents in a form that is suitable for user loads. In recent years, the field of power electronics has experienced a large growth. Electric utilities expected that by the year 2000 over half of the electrical load may be supplied through power electronic systems. In order to take advantage of this highly developed technology a number of detailed modelling procedures and simulation facilities are needed. The work in this thesis is concentrated on modelling, control and design of various power electronic based models for use within transmission and distribution systems. The overall objective is to provide effective methods and tools for assessing the impact of the latest technology based on power electronic devices in the reinforcement of power system networks. The thesis clarifies modelling and control of various variable speed drive models, such as the six-step, PWM and vector control and gives a detailed account of the systematic derivation of equations that are necessary for the dynamic and transient analysis of a multi-machine multi-node power system with associated adjustable speed drives. Simulation of Flexible AC Transmission Systems (FACTS) models has also been developed for a number of devices including: the SVC (Static Var Compensator), the STATCON (Static Condenser) and the UPFC (Unified Power Flow Controller). The methodologies for development of the models are described and a number of case studies are included in order to give a broad overview of the applications and to prove the usefulness of the results. The last part of the thesis includes simulation, control and design of Custom Power Devices for use within distribution system architectures. It starts with a complete control system strategy for the modelling of a solid-state switch and continues with the modelling of a Dynamic Voltage Restorer model, using an innovative control system. The creation of the power electronics models library provides several opportunities for future developments, which are discussed in the concluding sections of the thesis.
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Thompson, Michael Thomas. "Fast amplitude and delay measurement for characterization of optical devices." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4440.
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A fast measurement technique based on the modulation phase-shift technique is
developed to measure the wavelength-dependent magnitude and phase responses of
optical devices. The measured phase response is in the form of group delay, which is
used to determine the chromatic dispersion in the device under test by taking the
derivative of the group delay with respect to optical wavelength. The measurement
setup allows both step-tunable and sweeping laser sources. A modulation frequency of
up to 2.7 GHz is accommodated. An alternate method for the phase measurement that
overcomes non-linearities in the measurement setup is also presented. The speed of the
measurement setup is limited by the sweeping speed of the laser source, which for the
Agilent 81682A is 40 nm/sec. The magnitude accuracy is determined by taking a
comparison to the commercially available Micron Finisar measurement system, where
an error of 0.125 dB is noted. The phase accuracy of the measurement setup is tested
by taking the Hilbert transform of the measured magnitude response of an Acetylene
gas cell and comparing it to the integral of the measured group delay. The average
deviation between the two methods is 0.1 radians. An Acetylene gas cell, fiber Bragg
grating, and chirped Bragg grating are tested with the measurement setup and the
Agilent 8168The characterization of the setup leads to the conclusion that the measurement setup
developed in this paper is fast and accurate. The speed of the technique is on the order
of microseconds for a single measurement and excels beyond the speed of the standard
modulation phase-shift technique, which includes measurement times on the order of
minutes. The accuracy of the technique is within 0.125 dB for magnitude
measurements and 0.1 radians for phase measurements when compared to
commercially available measurement systems.2A laser source at 40 nm/sec and the measurement plots are presented.
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Cyrus, Sam. "Fast Computation on Processing Data Warehousing Queries on GPU Devices." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6214.
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Current database management systems use Graphic Processing Units (GPUs) as dedicated accelerators to process each individual query, which results in underutilization of GPU. When a single query data warehousing workload was run on an open source GPU query engine, the utilization of main GPU resources was found to be less than 25%. The low utilization then leads to low system throughput. To resolve this problem, this paper suggests a way to transfer all of the desired data into the global memory of GPU and keep it until all queries are executed as one batch. The PCIe transfer time from CPU to GPU is minimized, which results in better performance in less time of overall query processing. The execution time was improved by up to 40% when running multiple queries, compared to dedicated processing.
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Smith, Mark Alan. "Improved dynamic stability using FACTS devices with phasor measurement feedback." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/42417.
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With an increasing number of regulatory and economic factors making the
operation of power systems more challenging, utilities must take full advantage of
technological advances which allow more flexibility for operation. One of these advances
is the combination of power electronic controllers and compensation devices known as
F1exible AC Transmission Systems (FACTS) technology. This thesis will examine the
ability of FACTS technology to improve dynamic stability when controlled with data
obtained from another recent advancement, phasor measurement units (PMUs). Based on
an overview of the relative capabilities of presently available FACTS devices, a specific
device will be chosen to be modeled in a dynamic stability study. Eigenvalue sensitivity
analysis will be used to determine the optimal placement for this FACTS device in regards
to stability for a test power system. Then a state space model will be developed for the
FACTS compensated test system, and eigenvalue sensitivity and time-domain methods will
be used to determine the optimal controller characteristics for the modeled FACTS device.
Stability results will be verified using eigenvalue analysis and time simulation techniques.Master of Science
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Bhardwaj, Shubhendu. "Hybrid Numerical Models for Fast Design of Terahertz Plasmonic Devices." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1500336630858748.
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Smith, Mark Allen. "Improved dynamic stability using FACTS devices with phasor measurement feedback /." This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-05022009-040702/.
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Barnsley, Peter E. "Two-contact semiconductor devices for ultra-fast switching and synchronisation." Thesis, University of St Andrews, 1993. http://hdl.handle.net/10023/14159.
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The information contained within this document is a study of the properties of two-contact semiconductor laser devices. The emphasis of this study was on understanding the behaviour and properties of semiconductor laser devices where regions of saturable absorption are introduced into the Fabry-Perot cavity, and to demonstrate that the inherent nonlinearity of such a device can be harnessed to provide all-optical switching and routing functions that could be incorporated within future multi-gigabit optical telecommunications networks. Important advances in the field are presented in the assessment and performance of such two-contact functional components when operated both below threshold, as nonlinear optical amplifiers, and above threshold, as self-pulsating lasers. Detailed measurements on the nonlinear optical amplifiers are presented defining the dependence of both the steady state and dynamic characteristics on optical input power and wavelength. These results are compared with theoretical predictions from a model incorporating material gain calculations based on strict momentum conservation. It is shown that such devices can be used to convert the wavelength of Gb/s data between the 1.3mum and 1.55mum telecommunications window of silica fibre, and that fast all-optical switching of gigabit/s data packets with sub-ns rise and fall times is achievable. Detailed system data Bit-Error-Ratio (BER) measurements are used to highlight the systems potential of such functions. Also presented are significant advances in the field of self-pulsating laser devices and their use in multi-gigabit all-optical clock recovery circuits. The pulsation behaviour is investigated in detail and a detailed study of the locking behaviour of these devices for Return-to-Zero-'soliton' data format made. Some of the properties investigated are: tuning and locking range, clock purity, data pattern dependence, clock lock-up time, pulse spectral variation (chirp). In addition BER measurements using the clock recovery circuit in a 20 Gb/s OTDM system has demonstrated their potential application. Operation with Non-Return-to-Zero format data is also demonstrated in combination with the nonlinear amplifier devices. In summary the results contained within this thesis show that two-contact devices have characteristics and functionality suitable for use in many application areas consistent with the development of future synchronous gigabit all-optical telecommunication networks.
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Chen, Wei. "Fast switching low power loss devices for high voltage integrated circuits." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262863.
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Bliss, Martin. "Measurement system for fast power and energy rating of photovoltaic devices." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8336.
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This thesis presents a new type of solar simulator and new measurement methods that allow for fast power rating of photovoltaic devices and for fast performance measurements for energy rating and energy yield predictions indoors under controlled, and more realistically simulated outdoor conditions. A novel indoor measurement system for photovoltaic device characterisation based on light emitting diodes (LEDs) as the light sources is described. The solar simulator is capable of reproducing spectral changes seen in natural sunlight, with its intricacies of variable air mass and weather conditions, to a better match than previously possible. Furthermore, it allows measurements under varying light intensity and device temperature. The prototype LED-based solar simulator developed is characterised and its measurement quality is analysed. The system achieves a class BAA solar simulator classification with a class B spectral match, class A light intensity uniformity and a class A temporal stability. It is the first system of its kind that meets the standards of a solar simulator in spectral match to the standard sunlight spectrum and in terms of minimum light intensity. An uncertainty analysis shows that calibration uncertainty for crystalline silicon solar cells is 5% in maximum power with a 95.45% level of confidence. Recommendations for further versions of the solar simulator are given and show potential of reducing this uncertainty down to 2.9% across all measurement spectra (1.8% with a primary calibrated reference cell). A new method for automated power-rating of single- and multi-junction devices is developed. The method uses a unique spectral response measurement and fitting method. It eliminates the need of external measurement equipment for determining spectral response. A simulated characterisation of an amorphous silicon single- and double-junction solar cell show accuracy of better than 0.5% in maximum power. First measurements on the LED-based solar simulator show a measurement error of 4.5% in maximum power, which is due to a lack of measurement feedback of spectral output and measurement irradiance. The first three-dimensional performance matrix for use in photovoltaic energy rating is reported, utilising the LED-based solar simulator. Device characteristics are measured indoors under varying irradiance, temperature and spectrum. A measurement method is detailed and utilised on a crystalline and amorphous silicon solar cell. It allows for the first time a direct investigation of spectral effects on photovoltaic devices under controlled conditions. Results show that amorphous silicon devices are very sensitive to changes in spectrum. Thus, spectral effects should not be neglected in energy yield predictions for such devices.
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Ghasemi, Zarir. "Stacking of IGBT devices for fast high-voltage high-current applications." Thesis, University of Strathclyde, 2007. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21731.
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The development of solid-state switches for pulsed power applications has been of considerable interest since high-power semiconductor devices became available. However, the use of solid-state devices in the pulsed power environment has usually been restricted by device limitations in either their voltage/current ratings or their switching speed. The stacking of fast medium-voltage devices, such as IGBTs, to improve the voltage rating, makes solid-state switches a potential substitute for conventional switches such as hard glass tubes, thyratrons and spark gaps. Previous studies into stacking IGBTs have been concerned with specific devices, designed or modified particularly for a specific application. The present study is concerned with stacking fast and commercially available IGBTs and their application to the generation of pulsed electric field and the switching of a high intensity Xenon flashlamp. The aim of the first section of the present study was to investigate different solid-state switching devices with a stacking capability and this led to the choice of the Insulated Gate Bipolar Transistor (IGBT). It was found that the collector-emitter voltage decreases in two stages in most of the available IGBTs. Experiments and simulation showed that a reason for this behaviour could be fast variations in device parasitic parameters particularly gate-collector capacitance. Choosing the proper IGBT, as well as dealing with problems such as unbalanced voltage and current sharing, are important aspects of stacking and these were reported in this study. Dynamic and steady state voltage imbalances caused by gate driver delay was controlled using an array of synchronised pulses, isolated with magnetic and optical coupling. The design procedure for pulse transformers, optical modules, the drive circuits required to minimise possible jitter and time delays, and over-voltage protection of IGBTmodules are also important aspects of stacking, and were reported in this study. The second purpose of this study was to investigate the switching performance of both magnetically coupled stacks, in pulse power applications such as Pulse Electric Field (PEF) inactivation of microrganisms and UV light inactivation of food-related pathogenic bacteria. The stack, consisting of 50 1.2 kV IGBTs with the voltage and current capabilities of 10 kV, 400 A, was incorporated into a coaxial cable Blumlein type pulse - generator and its performance was successfully tested with both magnetic and optical coupling. As a second application of the switch, a fully integrated solid-state Marx generator was designed and assembled to drive a UV flashlamp for the purpose of microbiological inactivation. The generator has an output voltage rating of 3 kV and a peak current rating of 2 kA, although the modular approach taken allows for a number of voltage and current ratings to be achieved. The performance of the switch was successfully tested over a period of more than 10⁶ pulses when it was applied to pulse a xenon flashlamp.
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Oukati, Sadegh Mahmoud. "Control of power electronic devices (FACTS) to enhance power system stability." Thesis, University of Strathclyde, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275177.
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Mekelburg, Alexander (Alexander Mark). "Ergonomic, adaptable keyboard for fast data entry on mobile computing devices." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32956.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (leaves 22-24).
The usefulness of modem portable computational devices such as cellular phones and portable digital assistants (PDAs) is currently limited by the lack of an effective method for text entry. The currently available input options (such as the 12-key phone pad and PDA touch screens) are a quarter to a third of the speed of the standard desktop QWERTY keyboards. Therefore, it is slow and frustrating for people to use these systems for any significant text input, such as writing emails, taking notes in a meeting, or writing down thoughts while on-the-go. The proposed solution is a one-handed, hand-held, wireless, portable keyboard that would allow the mobile device user to achieve speeds closer to the desktop standard while performing text-entry tasks. Previously developed handheld input devices employ unfamiliar typing systems, are too large, or are not ergonomically comfortable, which may be the reasons they have not been widely adopted by the public. The device described in this paper is small enough to store in one's pocket, is inconspicuous during use, and is adjustable so that the keys reach the fingers in their natural curved position. One interface point allows each finger to control multiple buttons thereby preventing the fingers from, needing to move into uncomfortable positions.
(cont.) These features were incorporated into a prototype that proves the feasibility of a compact and comfortable hand-held keyboard. The device also has potential as an ergonomic replacement to the standard desktop keyboard. Unlike traditional keyboards it allows the typist to be relaxed and mobile eliminating some risk factors for repetitive strain injury.
by Alexander Mekelburg.
S.B.
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Lakkireddy, Jahnavi. "Steady State Voltage Stability Enhancement Using Shunt and Series FACTS Devices." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1881.
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It is specifically important to focus on voltage stability analysis of the power system to avoid worst case scenarios such as voltage collapse. The purpose of this thesis is to identify methods for enhancing the steady-state voltage stability using FACTS devices and determining their impact on real and reactive power losses, improvement of bus voltage magnitude, and transmission line loadability. To achieve this, FACTS devices such as Static VAR Compensator (SVC), Static Synchronous Compensator (STATCOM), and Thyristor Controlled Series Capacitor (TCSC) are used in the test system as three separate test cases. The results obtained assist in drawing conclusions on the effectiveness of each FACTS devices at generator, load and swing buses, on lines between two load buses, and between a load bus and a generator bus, in terms of metrics such as voltage magnitude profile, PV curves, and active and reactive power losses.
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Wu, Xiaofeng. "Fast spatially-resolved electrical modelling and quantitative characterisation of photovoltaic devices." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18018.
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An efficient and flexible modelling and simulation toolset for solving spatially-resolved models of photovoltaic (PV) devices is developed, and its application towards a quantitative description of localised electrical behaviour is given. A method for the extraction of local electrical device parameters is developed as a complementary approach to the conventional characterisation techniques based on lumped models to meet the emerging demands of quantitative spatially-resolved characterisation in the PV community. It allows better understanding of the effects of inhomogeneities on performance of PV devices. The simulation tool is named PV-Oriented Nodal Analysis (PVONA). This is achieved by integrating a specifically designed sparse data structure and a graphics processing unit (GPU)-based parallel conjugate gradient algorithm into a PV-oriented numerical solver. It allows more efficient high-resolution spatially-resolved modelling and simulations of PV devices than conventional approaches based on SPICE (Simulation Program with Integrated Circuit Emphasis) tools in terms of computation time and memory usage. In tests, mega-sub-cell level test cases failed in the latest LTSpice version (v4.22) and a PSpice version (v16.6) on desktop PCs with mainstream hardware due to a memory shortage. PVONA efficiently managed to solve the models. Moreover, it required up to only 5% of the time comparing the two SPICE counterparts. This allows the investigation of inhomogeneities and fault mechanisms in PV devices with high resolution on common computing platforms. The PVONA-based spatially-resolved modelling and simulation is used in various purposes. As an example, it is utilised to evaluate the impacts of nonuniform illumination profiles in a concentrator PV unit. A joint optical and electrical modelling framework is presented. Simulation results suggest that uncertainties introduced during the manufacturing and assembly of the optical components can significantly affect the performance of the system in terms of local voltage and current distribution and global current-voltage characteristics. Significant series resistance and shunt resistance effects are found to be caused by non-uniformity irradiance profiles and design parameters of PV cells. The potential of utilising PVONA as a quality assessment tool for system design is discussed. To achieve quantitative characterisation, the PVONA toolset is then used for developing a 2-D iterative method for the extraction of local electrical parameters of spatially-resolved models of thin-film devices. The method employs PVONA to implement 2-D fitting to reproduce the lateral variations in electroluminescence (EL) images, and to match the dark current-voltage characteristic simultaneously to compensate the calibration factor in EL characterisations. It managed to separate the lateral resistance from the overall series resistance effects. The method is verified by simulations. Experimental results show that pixellation of EL images can be achieved. Effects of local shunts are accurately reproduced by a fitting algorithm. The outcomes of this thesis provide valuable tools that can be used as a complementary means of performance evaluation of PV devices. After proper optimisation, these tools can be used to assist various analysis tasks during the whole lifecycle of PV products.
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Rehman, Shaikh Muhammad Asim. "Investigation of FACTS devices to improve power quality in distribution networks." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6197.
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Flexible AC transmission system (FACTS) technologies are power electronic solutions that improve power transmission through enhanced power transfer volume and stability, and resolve quality and reliability issues in distribution networks carrying sensitive equipment and non-linear loads. The use of FACTS in distribution systems is still in its infancy. Voltages and power ratings in distribution networks are at a level where realistic FACTS devices can be deployed. Efficient power converters and therefore loss minimisation are crucial prerequisites for deployment of FACTS devices. This thesis investigates high power semiconductor device losses in detail. Analytical closed form equations are developed for conduction loss in power devices as a function of device ratings and operating conditions. These formulae have been shown to predict losses very accurately, in line with manufacturer data. The developed formulae enable circuit designers to quickly estimate circuit losses and determine the sensitivity of those losses to device voltage and current ratings, and thus select the optimal semiconductor device for a specific application. It is shown that in the case of majority carrier devices (such as power MOSFETs), the conduction power loss (at rated current) increases linearly in relation to the varying rated current (at constant blocking voltage), but is a square root of the variable blocking voltage when rated current is fixed. For minority carrier devices (such as a pin diode or IGBT), a similar relationship is observed for varying current, however where the blocking voltage is altered, power losses are derived as a square root with an offset (from the origin). Finally, this thesis conducts a power loss-oriented evaluation of cascade type multilevel converters suited to reactive power compensation in 11kV and 33kV systems. The cascade cell converter is constructed from a series arrangement of cell modules. Two prospective structures of cascade type converters were compared as a case study: the traditional type which uses equal-sized cells in its chain, and a second with a ternary relationship between its dc-link voltages. Modelling (at 81 and 27 levels) was carried out under steady state conditions, with simplified models based on the switching function and using standard circuit simulators. A detailed survey of non punch through (NPT) and punch through (PT) IGBTs was completed for the purpose of designing the two cascaded converters. Results show that conduction losses are dominant in both types of converters in NPT and PT IGBTs for 11kV and 33kV systems. The equal-sized converter is only likely to be useful in one case (27-levels in the 33kV system). The ternary-sequence converter produces lower losses in all other cases, and this is especially noticeable for the 81-level converter operating in an 11kV network.
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Chen, Zengjun Williams John R. "Electrical properties of MOS devices fabricated on 4H carbon-face SiC." Auburn, Ala, 2009. http://hdl.handle.net/10415/1858.
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Silvestrini, Simone. "Microfluidic Devices: Compact Laboratories from Design to Application." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422061.
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This doctoral thesis resumes the most interesting experimental results achieved between 2009 and 2011 by the author, during his stay in the laboratories of the department of chemical sciences of the university of Padova, under the supervision of prof. M. Maggini. The main theme behind this work is microfluidics, an ensemble of techniques for the manipulation of fluids on the micrometer scale. Such manipulation is carried out inside microchannels, confined environments whose geometries can be exploited to optimize unit operations – such as mixing and heat transfer – of profound interest for chemists.
Microfabrication is the first theme treated, and one that has been constantly developed during this internship. The fast prototyping of microfluidic chips is described thoroughly, from the fabrication of chip-external world interfaces, to that of microchannels and electrodes, in order to allow for their easy reproduction. Two techniques widely employed were soft photolithography and embossing. The former makes use of photocurable resins, in particular thiol-ene ones, employing masks to copy a design to the resin bulk in order to make the channels. The latter is based on the use of a cutting plotter to work directly on the materials the microchannels are made of, such as biadhesive tapes and Parafilm M laboratory film.
A commercial thiol-ene resin, NOA, was the object of two experimental works: one aimed at increasing its solvent resistance and the other at achieving wettability control for its surfaces. Solvent resistance is possibly the foremost requirement for a chemical reactor; while NOA displays better chemical compatibility towards organic solvents than other materials commonly used for microfluidic applications, such as poly(dimethylsiloxane), its scarce resistance towards halogenated solvents is a drawback for its employment. The deposition of a silica layer proved to ease this problem, even though it did not solve it, by extending the working life of microchannels made in polymeric material when aggressive solvents were used.
Another interesting characteristic is wettability, which controls the interaction between solvent and the reactor’s inner surfaces, playing an important role in the flow characteristics of the device. To control this feature, NOA was functionalized by silanizing the hydroxide groups on its surface by condensation with trichlorosilane derivatives. A demonstrator device consisting in a passive valve that can discriminate between aqueous and organic liquids was fabricated in a few hours thanks to this method.
Being able to quickly produce microfluidic devices led to the development of various applications, the most interesting of which are reported in the third part of the thesis. As a first example, a very common laboratory material such as Parafilm M was used to fabricate an elegant microreactor capable of producing two diazo dyes in parallel, in a multistep synthesis whose first step relies on the production in confined environment of an intermediate (diazonium salt) which is potentially explosive.
Next, a flow cell interfaced with a spectrophotometer is described, which was used for the study of adsorption kinetics of organic dyes (photosensitizers) on porous titanium dioxide. Such process is of general interest, being a fundamental step in the fabrication of dye sensitized solar cells.
The optical transparency of NOA resins is exploited in the third application presented: a microreactor that was used to carry out photochemical reactions. Light emitting diodes were used as cold, highly efficient light sources to direct the growth phenomena of metal nanostructures, to produce silver nanoparticles with controlled sizes and shapes.
The same masking technology developed for photocurable materials was also exploited to produce gold electrodes. A microfluidic device for electrochemical impedance spectroscopy was then developed and a description of its design, production and electronic characterization is reported at the end of the third section.
Finally, the last part of the thesis report two kinetic studies carried out on important processes for fullerene chemistry: a 1,3-dipolar cycloaddition of azomethyne ylides (the Prato-Maggini reaction) and a cyclopropanation reaction to the fullerene cage with bromomalonate derivatives (the Bingel-Hirsch reaction). The interest behind these studies is two-fold: i) they allow a critical comparison between batch and flow chemistry and ii) notwithstanding the widespread employment of these two reactions in chemical laboratories, few kinetic studies are available on the subject.Questa tesi è un riassunto delle più rappresentative attività sperimentali svolte dall’autore nel triennio 2009-2011 presso i laboratori del dipartimento di scienze chimiche dell’università di Padova, sotto la supervisione del prof. M. Maggini. Il filo conduttore che lega le tematiche toccate dal presente lavoro è la tecnologia microfluidica, intesa come insieme di tecniche per la manipolazione dei fluidi su scala micrometrica. Tale manipolazione avviene all’interno di microcanali, ambienti confinati nello spazio la cui geometria può essere sfruttata per ottimizzare operazioni unitarie – quali il mescolamento e il trasferimento di calore – di profondo interesse dal punto di vista chimico. Una porzione importante di questo elaborato è dedicata alle tecniche di microfabbricazione per la prototipizzazione rapida di chips microfluidici, un tema sviluppato costantemente durante tutto l’internato di tesi. I protocolli sviluppati per la fabbricazione di interfacce con l’ambiente esterno, di microcanali e di elettrodi, sono riportati punto per punto e commentati in modo da permetterne una fedele riproduzione. Due tecniche largamente sfruttate sono la fotolitografia “soft” e l’embossing. La prima si basa sulla fotopolimerizzazione di resine commerciali (in particolare di tipo tiolenico), utilizzando una maschera disegnata al computer e stampata su acetato per imprimere un disegno sul materiale polimerico e ricavarne quindi dei canali. La seconda prevede l’uso di un plotter da taglio per lavorare materiali quali nastri biadesivi o film di cera dai quali ricavare direttamente le microstrutture desiderate. La resina tiolenica commerciale NOA è anche al centro di due lavori sperimentali riguardanti gli aspetti più chimici della prototipizzazione: la resistenza ai solventi e la bagnabilità. Fra i requisiti principali di un materiale per la fabbricazione di reattori chimici, c’è senz’altro la resistenza ai solventi utilizzati nelle sintesi per cui il reattore stesso deve essere utilizzato. Nonostante la resina in oggetto presenti caratteristiche di compatibilità interessanti, soprattutto se confrontata con altri materiali tipicamente usati in microfluidica, quali il poli(dimetilsilossano), la sua resistenza verso i solventi alogenati non ne consente un ampio uso in ambito sintetico. La deposizione di uno strato di silice, ad ogni modo, ha permesso di aumentare la sua resistenza, pur non rendendola completamente resistente. Altra caratteristica importante, in quanto controlla l’interazione fra solvente e superficie interna del reattore è la bagnabilità. Nel caso del NOA, si dimostra come essa possa essere controllata derivatizzando la resina grazie alla condensazione dei gruppi idrossili superficiali con derivati triclorosilani. La possibilità di produrre rapidamente dispositivi microfluidici ha portato allo sviluppo di varie applicazioni, le più interessanti delle quali sono descritte nella terza parte della tesi. Innanzitutto viene dimostrato come un elegante dispositivo fabbricato con un materiale ceroso molto comune come il Parafilm, possa essere utilizzato per la sintesi parallela di diversi coloranti diazoici attraverso una sintesi multistep che prevede la produzione in ambiente confinato di un intermedio potenzialmente esplosivo come un sale di diazonio. In seguito viene descritta l’applicazione di una cella a flusso interfacciata a uno spettrofotometro, con cui si possono ricavare interessanti informazioni sulle cinetiche di adsorbimento di sensibilizzatori sulla superficie dell’ossido di titanio. Tale processo è di interesse generale, essendo alla base della produzione delle celle fotovoltaiche a colorante organico. La trasparenza ottica della resina tiolenica NOA viene poi sfruttata per condurre reazioni fotochimica all’interno di canali microfluidici fabbricati in questo materiale. Luci monocromatiche “fredde” LED vengono qui usate per direzionare il fenomeno di crescita di nanostrutture metalliche, producendo nanoparticelle di forma e dimensioni controllate. La possibilità di fabbricare elettrodi direttamente all’interno di canali ha avuto come sbocco naturale la costruzione di dispositivi per elettrochimica. Quello presentato in questa tesi è stato progettato per compiere misure di spettroscopia elettrochimica di impedenza e ne viene presentata la fabbricazione e la caratterizzazione elettronica di base. L’ultima parte della tesi riporta gli studi cinetici relativi a due importanti reazioni nell’ambito della chimica dei fullereni: la cicloaddizione di speci 1,3-dipolari alla gabbia fullerenica (reazione di Prato-Maggini) e la reazione di ciclopropanazione con derivati bromomalonati (reazione di Bingel-Hirsch). L’interesse dietro a questi studi è duplice: da un lato studiare queste reazioni fornisce dati interessanti per un confronto critico fra la chimica condotta in flusso e quella condotta con tecniche tradizionali, d’altra parte studi di tipo cinetico su queste due reazioni non sono presenti in letteratura nonostante l’indiscussa utilità delle reazioni suddette.
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Kim, Sang Hwa. "Fast Switching Polymer Stabilized Liquid Crystal Devices: Morphological and Electro-Optical Properties." [Kent, Ohio] : Kent State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1101220722.
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von, dem Knesebeck Matthias. "Fast motion estimation methods for H.264 video coding on mobile devices." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/28761.
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Digital video is becoming an increasingly widespread application on a multitude of devices ranging from mobile devices to digital cinema. Technological advancements in processing speed and available bandwidth along with substantial improvements in compression techniques enable completely new applications and services for digital video content.
The most demanding task in video encoding is the motion estimation process which aims to identify similarities to previously transmitted video frames. Up to 90% of the processing requirements are attributable to this element.
In this thesis, we present three methods for encoding new and transcoding existing video content with significantly reduced computational complexity while maintaining both quality and bitrate.
The first method reduces the number of steps required to perform motion estimation by adaptively adjusting the search accuracy needed in distortion measurement.
The second method addresses the topic of mode decision in video encoding and provides an algorithm that allows an early decision about the most probable modes without the need to evaluate all 259 different combinations of block sizes.
The third method provides a multi-dimensional measure that facilitates evaluating only the most likely modes for efficiently transcoding existing pre-encoded content to lower resolutions with an arbitrary downscaling ratio. This is an important factor for the ever-growing number of devices and application scenarios that access existing pre-encoded content. Our method supplements existing fast transcoding schemes that primarily focus on efficiently determining motion vectors in transcoding.
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Vujatovic, Davor. "Power Quality Improvement using FACTS Devices with Particular Emphasis on Electric Traction." Thesis, City University London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.524710.
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Petricca, Marco <1984>. "Face recognition on embedded devices: a proof of concept for residential application." Master's Degree Thesis, Università Ca' Foscari Venezia, 2020. http://hdl.handle.net/10579/16226.
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Face recognition is a well-known technique with a wide range of existing real world applications. Residential systems, like video intercom or security alarm, are instead nearly unfamiliar terrain to such methods with few commercial solutions available today in the market. A leading company in the sector has called for a research, with the purpose of assessing the feasibility of equipping their embedded video intercom systems with a feature for automatic identification and authorization of the calling subject. In this paper a combination of face detection and recognition methods on such system has been studied and evaluated, leading to a proof of concept in order to verify the feasibility assumptions, and support the claimant company decision process on investing for prototype development and final product extensions and adjustments. Early promising results suggest that the proposed system could prove usable, complying with constraints such as providing a reasonable recognition rate and execution time, running on embedded hardware and being user-friendly.
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Gu, X. M., J. P. Wang, S. J. Yuan, W. S. Li, and Y. J. Zhang. "A DIGITAL DEVICE FOR FAST ACQUISITION OF PSEUDO-RANDOM CODE." International Foundation for Telemetering, 1991. http://hdl.handle.net/10150/612904.
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International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, NevadaA digital device for rapid acquisition of the initial phase of PN code has been implemented. The principles and results of the experiment are introduced in this paper. The m PN code is modulated on IF with BPSK type. The cycle of PN code P=255 chips. The rate of PN code R=5.1 × 10 chips /s. The IF is not acquired. The shift in Doppler 6 frequency f is within l-4KHz. In these conditions, the phase of PN code can be acquired d within 3 ms and the error of sychronization is less than 0.5 chip.
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Sookananta, Bongkoj. "The optimal placement of FACTS devices considering renewable generation and the electricity market." Thesis, University of Strathclyde, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501833.
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In modem electrical power systems there is trend towards an increase of renewable generation being present on the main electrical grid and energy transmission is generally operated under a deregulated environment where electricity is bought and sold in a market. This thesis investigates the effects of renewable generation intermittency and electricity market operations on optimal placement of FACTS devices. Two techniques based on the MC simulation associated with an evolutionary optimization technique are proposed for determination of the optimal placement of the FACTS device considering uncertainty of demand and renewable generation output. These techniques can be useful to support practical industrial and research activities on FACTS planning for future networks where there is a significant presence of intermittent renewables as there is no sufficient planning with respect to FACTS deployment in its current form. These methods, established in this thesis, collectively are called Renewable Uncertainty based optimal FACTS Allocation (RUF A) techniques. This is a key outcome of the research reported in this thesis. This thesis considers the operation under Power Exchange (PX) and a simplified mixed power pool with bilateral transactions as they are commonly used models and as such they provide good domain coverage in terms of their applicability. Under the PX only model, the influence of changes in price elasticity of demand on the optimal F ACTS allocation is determined. It is found that there is no strong influence on the optimal placement and only a little influence on the operational rate.
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Shahrazad, Mohammad. "Optimal allocation of FACTS devices in power networks using imperialist competitive algorithm (ICA)." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/11445.
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Due to the high energy consumption demand and restrictions in the installation of new transmission lines, using Flexible AC Transmission System (FACTS) devices is inevitable. In power system analysis, transferring high-quality power is essential. In fact, one of the important factors that has a special role in terms of efficiency and operation is maximum power transfer capability. FACTS devices are used for controlling the voltage, stability, power flow and security of transmission lines. However, it is necessary to find the optimal location for these devices in power networks. Many optimization techniques have been deployed to find the optimal location for FACTS devices in power networks. There are several varieties of FACTS devices with different characteristics that are used for different purposes. The imperialist competitive algorithm (ICA) is a recently developed optimization technique that is used widely in power systems. This study presents an approach to find the optimal location and size of FACTS devices in power networks using the imperialist competitive algorithm technique. This technique is based on human social evolution. ICA technique is a new heuristic algorithm for global optimization searches that is based on the concept of imperialistic competition. This algorithm is used for mathematical issues; it can be categorized on the same level as Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) techniques. Also, in this study, the enhancement of voltage profile, stability and loss reduction and increasing of load-ability were investigated and carried out. In this case, to apply FACTS devices in power networks, the MATLAB program was used. Indeed, in this program all power network parameters were defined and analysed. IEEE 30-bus and IEEE 68-bus with 16 machine systems are used as a case study. All the simulation results, including voltage profile improvement and convergence characteristics, have been illustrated. The results show the advantages of the imperialist competitive algorithm technique over the conventional approaches.
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Lundberg, Martin. "Implementation of Fast Real-Time Control of Unstable Modes in Fusion Plasma Devices." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-329243.
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In recent years, multi-core graphics processing units (GPUs) have been increasingly used by researchers for other purposes than rendering graphics. This thesis presents the implementation of GPU computing for real-time control of plasma instabilities known as resistive wall modes at the EXTRAP T2R fusion plasma device. A NVIDIA GPU is installed in the device plasma control system. Using the CUDA parallel computing platform, PID and LQG control algorithms are developed for the GPU. It is shown that computation times decrease with up to 80 % for the LQG algorithm and 33 % for the PID algorithm if computations in the control system are shifted from the central processing unit (CPU) to the GPU. The gains of GPU utilization are limited by latencies introduced by the CPU-GPU interaction. To better exploit the potential of the GPU, a zero-copy method is proposed, in which the GPU is allowed to perform read and write operations on CPU memory.
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Kasala, Sinduri. "Value of Fast Switching Devices to Electric Distribution Networks : An Approach to Reduce Voltage Sags and Interruptions in Distribution Networks." Thesis, KTH, Elektroteknisk teori och konstruktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160543.
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Power Quality (PQ) has gained a lot of importance in the last decade. Several solutions to power quality problems have been proposed and developed. With the advent of solid state technology and power electronics in the power system protection devices, faster switching is achievable. In order to control and minimize the power quality problems which occur in extremely short times of less than 100ms, the need arises for a selection of devices that can switch faster than today. Also, the economic losses that occur in the network due to the power quality problems increase the incentive to transform the existing devices into faster and e fficient devices. This transformation can be seen as valuable from both a technical and economical point of view to the distribution networks today where a large number of customers are connected. However, in order to interpret the value these fast switching devices render to the distribution network a prior study is required. This thesis presents a picture of the devices that can be suitable for fast switching in today’s distribution network, and how to determine their value to the distribution network. Further it summarizes the research work related to this field. The description of the devices and technical aspects is presented first. A literature review of proposed devices is given. The technical aspects of power quality and its problems is described. An approach to estimate the value of the fast switching devices is detailed from different literature. The study shows that fast switching devices can be worthy to invest in when seen from a distribution network’s perspective provided that different technical aspects are taken into account.
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Alabduljabbar, Ayman A. "Optimal placement of FACTS devices for the improvement of technoeconomic performance of power networks." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490127.
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In contemporary power system studies, the optimal allocation and utilisation of Flexible AC Transmission System (FACTS) devices are imp0l1ant issues primarily due to their cost as well as their multifunctional capabilities. In this thesis, a depth literature review regarding the technical contribution of FACTS devices along with their allocation methods in power systems is presented. Four types of FACTS devices (Static Var compensator (SVC), Thyristor-Controlled Series Capacitor (TCSC), Thyristor-Controlled Voltage Regulator (TCVR), and Thyristor-Controlled Phase Shifting Transformer (TCPST)) are considered for optimal placement in a multi-machine power system to reduce the overall costs of power generation. The placement methodology simultaneously considers the cost of generated active and reactive powers and the cost of selected FACTS devices for a range of operating conditions. The annual Load Duration Curve (LDC) has been used in the selection of the operating conditions in order to make the proposed allocation beneficial over the year and to remove any bias in the device selection. Two global optimisation techniques: the Genetic Algorithm (GA) and a new method based on the Low Discrepancy Sequences (LOS), are employed to solve the allocation task. The Optimal Power Flow (OPF) is integrated into the proposed optimisation methods in order to solve for the cheapest generation dispatch. The Net Present Value( NPV) method is then utilised to assess the economic value of the solution. The NPV evaluation study includes a detail discussion of the uncel1ainties involved in the NPV main parameters. The system steady state propel1ies in terms of voltage profile and power transfer are investigated after the allocation of the devices in order to avoid any adverse effects of such allocations. The Voltage Security Margin (VSM) is used in the voltage profiles assessment which measures the relative voltage strength. In addition to the steady state performance assessment, the system dynamics has been examined as well after the placement of the devices in order to find out the devices impact on the system stability, both small signal and transient, as the contribution of such devices to damping the electromechanical oscillation represents a crucial benefit. In this assessment, a systematic explanation of the FACTS devices incorporation in the muItimachine power system is presented in addition to a method of coordinated tuning of the system damping controllers. Furthermore, an observability study is performed for the selection of the FACTS devices damping controllers input signals.
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Heider, Samuel A. "An MCNP study of fast neutron interrogation for standoff detection of improvised explosive devices." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/13939.
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Master of ScienceDepartment of Mechanical and Nuclear Engineering
William L. Dunn
The signature-based radiation-scanning (SBRS) technique relies on radiation detector responses, called “signatures,” and compares them to “templates”, to differentiate targets containing nitrogen-rich explosives from those that do not. This investigation utilizes nine signatures due to inelastic-scatter and prompt-capture gamma rays from hydrogen, carbon, nitrogen, and oxygen (HCNO) as well as two neutron signatures, produced when a target is interrogated with a 14.1 MeV neutron source beam. One hundred and forty three simulated experiments were conducted using MCNP5. Signatures of 42 targets containing explosive samples (21 of RDX and 21 of Urea Nitrate), and 21 containing inert samples were compared with the signatures of 80 artificial templates through figure-of-merit analysis. A density filter, comparing targets with templates of similar average density was investigated. Both high and low-density explosives (RDX-1.8 g cm-3 and Urea Nitrate-0.69 g cm-3) were shown to be differentiated from inert materials through use of neutron and gamma-ray signature templates with sensitivity of 90.5% and specificity of 76.2%. Density Groups were identified, in which neutron signature templates, gamma-ray signature templates or the combination of neutron and gamma-ray signature templates were capable of improving inert-explosive differentiation. figure-of -merit analysis, employing the best Density Group specific templates, differentiated explosive from inert targets with 90.5% sensitivity and specificity of over 85%.
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Ghazal, Omar M. S. "Low reflectivity facet realization in GaAs-based optoelectronic devices using self-aligned stripe process." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/13316/.
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This thesis explores the realization of low facet reflectivity using self-aligned stripe buried waveguide configuration and its implementation in optoelectronic devices such as superluminescent diodes (SLDs) and semiconductor optical amplifiers (SOAs). I explored the development of the buried waveguide in AlGaAs/GaAs material system ,since its first presentation in 1974 by Tsukada, in order to identify the problems associated with this technology. A novel window-faceted structure is demonstrated. The experimental measurements demonstrated effective reflectivity <10-14 as a result of both divergence and absorption within these window-like regions (i.e. not transparent). Its implementation to suppress lasing in tilted and normal-to-facet waveguide SLDs was thoroughly investigated in chapters 3 and 4. In the tilted devices, ~40mW output power with spectral modulation depth < 2% is demonstrated. In the latter types of SLDs, up to 16mW output power with <5% spectral modulation depth was recorded, which is the highest power demonstrated for such configurations. The performance of the two types of devices was measured without the application of anti-reflective coatings on the rear facet, which makes them inherently broadband. By incorporating a windowed facet at each end of a waveguide I could realize an SOA with window structured facet. Promising results were demonstrated in this configuration including 33dB gain and <6dB noise figure, which are comparable to the state-of-the-art. A trial was held to extend the concept of absorptive rear window to visible wavelengths available in the GaInP/AlGaInP material system. Problems associated with such devices were explored briefly and two solutions are suggested. Simulations were performed to realize design of an optimized device. Unfortunately, the experimental implementation of the design was not successful but suggestions for strategies to overcome these problems are discussed.
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Pourbeik, Pouyan. "Design and coordination of stabilisers for generators and FACTS devices in multimachine power systems /." Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09php877.pdf.
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Anderson, Margaret B. "Music as a mnemonic device in the teaching of multiplication facts /." View abstract, 2000. http://library.ctstateu.edu/ccsu%5Ftheses/1579.html.
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Thesis (M.S.)--Central Connecticut State University, 2000.Thesis advisor: Philip Halloran. " ... in partial fulfillment of the requirements for the degree of Master of Science [in Mathematical Sciences]." Includes bibliographical references (leaves 28-32).
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Pedersen, Jan Egedal. "Fast ions in tokamaks and their collective measurement by collective Thomson scattering." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298419.
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Liu, Chengjian. "ESetStore: an erasure-coding based distributed storage system with fast data recovery." HKBU Institutional Repository, 2018. https://repository.hkbu.edu.hk/etd_oa/507.
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The past decade has witnessed the rapid growth of data in large-scale distributed storage systems. Triplication, a reliability mechanism with 3x storage overhead and adopted by large-scale distributed storage systems, introduces heavy storage cost as data amount in storage systems keep growing. Consequently, erasure codes have been introduced in many storage systems because they can provide a higher storage efficiency and fault tolerance than data replication. However, erasure coding has many performance degradation factors in both I/O and computation operations, resulting in great performance degradation in large-scale erasure-coded storage systems. In this thesis, we investigate how to eliminate some key performance issues in I/O and computation operations for applying erasure coding in large-scale storage systems. We also propose a prototype named ESetStore to improve the recovery performance of erasure-coded storage systems. We introduce our studies as follows. First, we study the encoding and decoding performance of the erasure coding, which can be a key bottleneck with the state-of-the-art disk I/O throughput and network bandwidth. We propose a graphics processing unit (GPU)-based implementation of erasure coding named G-CRS, which employs the Cauchy Reed-Solomon (CRS) code, to improve the encoding and decoding performance. To maximize the coding performance of G-CRS by fully utilizing the GPU computational power, we designed and implemented a set of optimization strategies. Our evaluation results demonstrated that G-CRS is 10 times faster than most of the other coding libraries. Second, we investigate the performance degradation introduced by intensive I/O operations in recovery for large-scale erasure-coded storage systems. To improve the recovery performance, we propose a data placement algorithm named ESet. We define a configurable parameter named overlapping factor for system administrators to easily achieve desirable recovery I/O parallelism. Our simulation results show that ESet can significantly improve the data recovery performance without violating the reliability requirement by distributing data and code blocks across different failure domains. Third, we take a look at the performance of applying coding techniques to in-memory storage. A reliable in-memory cache for key-value stores named R-Memcached is designed and proposed. This work can be served as a prelude of applying erasure coding to in-memory metadata storage. R-Memcached exploits coding techniques to achieve reliability, and can tolerate up to two node failures. Our experimental results show that R-Memcached can maintain very good latency and throughput performance even during the period of node failures. At last, we design and implement a prototype named ESetStore for erasure-coded storage systems. The ESetStore integrates our data placement algorithm ESet to bring fast data recovery for storage systems.
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Johnson, Kelly Eugene. "A Validation of a Handheld Ultrasound Device to Assess Body Composition in College-Aged Adults." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1362846764.
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Nguyen, Van Liem. "Modeling and control coordination of power systems with FACTS devices in steady-state operating mode." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0036.
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This thesis is devoted to the development of new models for a recently-implemented FACTS (flexible alternating current transmission system) device, the unified power flow controller (UPFC), and the control coordination of power systems with FACTS devices in steady-state operating mode. The key objectives of the research reported in the thesis are, through online control coordination based on the models of power systems having FACTS devices, those of maximising the network operational benefit and restoring system static security following a disturbance or contingency. Based on the novel concept of interpreting the updated voltage solutions at each iteration in the Newton-Raphson (NR) power-flow analysis as dynamic variables, the thesis first develops a procedure for representing the unified power flow controllers (UPFCs) in the steady-state evaluation. Both the shunt converter and series converter control systems of a UPFC are modeled in their dynamical form with the discrete time variable replaced by the NR iterative step in the power-flow analysis. The key advantage of the model developed is that of facilitating the process of UPFC constraint resolution during the NR solution sequence. Any relative priority in control functions pre-set in the UPFC controllers is automatically represented in the power-flow formulation. Although the developed UPFC model based on the dynamic simulation of series and shunt converter controllers is flexible and general, the number of NR iterations required for convergence can be large. Therefore, the model is suitable mainly for power system planning and design studies. For online control coordination, the thesis develops the second UPFC model based on nodal voltages. The model retains all of the flexibility and generality of the dynamic simulation-based approach while the number of iterations required for solution convergence is independent of the UPFC controller dynamic responses. Drawing on the constrained optimisation based on Newtons method together with the new UPFC model expressed in terms of nodal voltages, a systematic and general method for determining optimal reference inputs to UPFCs in steady-state operation is developed. The method is directly applicable to UPFCs operation with a high-level line optimisation control (LOC) for maximising the network operational benefit. By using a new continuation technique with adaptive parameter, the algorithm for solving the constrained optimisation problem extends substantially the region of convergence achieved with the conventional Newtons method. Having established the foundation provided by the comprehensive models developed for representing power systems with FACTS devices including the UPFC, the research, in the second part, focuses on real-time control coordination of power system controllers, with the main purpose of restoring power system static security following a disturbance or contingency. At present, as the cost of phasor measurement units (PMUs) and wide-area communication network is on the decrease, the research proposes and develops a new secondary voltage control where voltages at all of the load nodes are directly controlled, using measured voltages.