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1
Mbabele, Modeste. "Intermodulation distortion performance enhancement of microwave power amplifiers." Thesis, Brunel University, 2000. http://bura.brunel.ac.uk/handle/2438/5440.
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This thesis reports the author's investigation of the effects of the injection of specific signals on the intermodulation distortion performance of microwave power amplifiers. Theory, simulation and practical results are presented, analysed and compared. The thesis gives the reader background knowledge of power amplifiers and their nonlinearities and go on to analyse the phenomena of intermodulation distortion product generation in power amplifiers. The analysis is based on a three-tone test since this highlights a second kind of third order intermodulation distortion (IMD3), which are in general higher in amplitude than the first kind of IMD3 found in a two-tone test. A mathematical analysis and a simulation of a MESFET amplifier are performed. It enables the comparison of the performance of IMD cancellation by injection of signals whose frequencies are chosen to be first, the second harmonic of the fundamental signals, second, the sum of the fundamental signal frequencies and finally the difference frequencies of the fundamental signals. A practical implementation of the difference frequency technique is then presented and practical results are compared to the other two techniques of second harmonic injection and the injection of the sum of fundamental frequencies. It is further shown that in practise these two techniques may be considered as a single technique.
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Papamarkos, Ioannis. "Inlet distortion generation for a transonic compressor." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Sep%5FPapamarkos.pdf.
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Lucas, James Redmond. "Effect of BLI-Type Inlet Distortion on Turbofan Engine Performance." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23272.
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Boundary Layer Ingestion (BLI) is currently being researched as a potential method to improve efficiency and decrease emissions for the next generation of commercial aircraft. While re-energizing the boundary layer formed over the fuselage of an aircraft has many system level benefits, ingesting the low velocity boundary layer flow through a serpentine inlet into a turbofan engine adversely affects the performance of the engine. The available literature has only yielded studies of the effects of this specific type of inlet distortion on engine performance in the form of numerical simulations. This work seeks to provide an experimental analysis of the effects of BLI-type distortion on a turbofan engine\'s performance. A modified JT15D-1 turbofan engine was investigated in this study. Inlet flow distortion was created by a layered wire mesh distortion screen designed to create a total pressure distortion profile at the aerodynamic interface plane (AIP) similar to NASA\'s Inlet A boundary layer ingesting inlet flow profile. Results of this investigation showed a 15.5% decrease in stream thrust and a 14% increase in TSFC in the presence of BLI-type distortion. <br /><br />Flow measurements at the AIP and the bypass nozzle exit plane provided information about the losses throughout the fan flow path. The presence of the distortion screen resulted in a 24% increase in mass-averaged entropy production along the entire fan flow path compared to the non-distorted test. A mass-averaged fan flow path efficiency was also calculated assuming an isentropic process as ideal. The non-distorted fan flow path efficiency was computed to be 60%, while the distorted fan flow path efficiency was computed to be 50.5%, a reduction in efficiency of 9.5%. The entropy generation between ambient conditions and the AIP was compared to the entropy production along the entire fan flow path. It was found that the majority of entropy generation occurred between the AIP and bypass nozzle exit. Based on flow measurements at the bypass nozzle exit plane, it was concluded that inlet flow distortion should be located away from the tip region of the fan in order to minimize losses in a very lossy region. It was also determined that the fan and bypass duct process the different regions of the total pressure distortion in different ways. In some regions the entropy production decreased for the distorted test compared to the clean test, while in other regions the entropy production increased for the distorted test compared to the clean test. Finally, it was found that small improvements in total pressure and total temperature variation at the bypass nozzle exit plane will greatly improve the fan flow path efficiency and entropy generation, thereby decreasing performance losses.<br /><br>Master of Science
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McGuinness, Christopher. "Characterizing Remote Sensing Data Compression Distortion for Improved Automated Exploitation Performance." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1524844209730534.
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MacLeod, Brenda Brennan 1971. "Effect of a sinusoidal three-lobe total pressure distortion on a transonic compressor : distortion propagation, compressor performance, and blade passage events." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/82772.
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O'Brien, Daniel Gerard, and n/a. "Broadband matching and distortion performance relating to multiple subcarrier multiplexed photonic systems." University of Canberra. Information Sciences & Engineering, 1992. http://erl.canberra.edu.au./public/adt-AUC20060821.095055.
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This thesis describes the outcome of study to investigate methods of
broadband matching to photonic devices such as lasers and high speed detectors.
The thesis is divided into two areas of interest relating to the design of
broadband fiber optic links.
The first area is the application of numerical methods and commensurate
line methods to the design of compact equalisers which allow an improved
transducer power gain over a wide band. It is shown that physically small
equalisers can yield an improvement of 4 dB over a 2 GHz bandwidth.
The second area considered is the distortion inherent in a laser diode.
Detailed measurements of the second order and intermodulation products
are given. A small signal perturbation analysis is presented which helps to
explain the observed distortion products. The results of numerical
simulation of the distortion using a state variable implementation of the full
rate equations and related first, second and intermodulation equations is
presented and possible methods of reducing the distortion are explored. It is
shown that in principle the distortion could be reduced by pre-generating
the distortion and adding an inverted form of the distortion to the
transmitted signal. The distortion can then be corrected in the fiber and
simulation studies suggest that an improvement of 13 dB optical or 26 dB
electrical may be possible.
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Firm, Richard. "Mechanical distortion and performance associated with cylindrical components in diesel injector systems." Thesis, University of Bath, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392055.
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As European and US vehicle emissions regulations tighten, more effective methods of reducing diesel engines pollutants must be devised. Increasing the injection pressure results in smaller fuel droplets and consequently more efficient combustion with a reduction in emissions output. However, to gain acceptable levels of NO. and particulates, required pressures must be of the order of 1800 to 2400 bar. At this level the components within the diesel injector and pump experience an appreciable level of distortion, that can, in severe cases, lead to leakage and a loss in pumping efficiency. It is therefore critical that an accurate means of determining the distortion and associated leakage is established. An efficient analytical method of solution for the problem of mechanical distortion of a diesel pump is presented. Both the EUI (Electronic Unit Injector) and CR (Common Rail) injection systems use essentially in-line pumps for which this technique allows the individual components (principally the plunger and barrel) to be analysed. Also, combined fluid-elastic systems are considered in both CR and EUI cases. An elastic integral equation formulation is optimised for a cylindrical geometry and this is used to evaluate key features of the system such as pressure distributions and variations in film thickness during the pumping stroke. It is then straightforward to evaluate other parameters such as leakage and both magnitude and direction of fluid flow within the film thickness. Simplification of elastic models is not required and as such this thesis also considers the effect of ports on the fluid flow and pressure distribution and also the relative orientation and axial position of the plunger within the barrel. This allows a detailed description and explanation to be made of the behaviour of the diesel pump. A key advantage of the method is that the fluid and elastic solvers may be decoupled and developed separately. This provides a means of extending the scope of the method beyond that presented here.
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Smurzynski, Jacek. "Frequency Modulated Distortion-product Otoacoustic Emission (FMDPOAE) Tests Aimed for Improving Diagnostic Performance." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/2220.
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Guerreiro, João Francisco Martinho Lêdo. "Maximum likelihood detection for OFDM signals with strong nonlinear distortion effects." Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/7983.
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Häger, Emil. "Performance Evaluation of Medium-Power Voltage Inverters." Thesis, Linköpings universitet, Elektroniska Kretsar och System, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-118568.
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Power inverters, used to convert DC power to AC, are often used in e.g. solar power applications. However, they tend to be impractically large and expensive; as such, power miniaturization is an active research area. In this thesis, several classes of modern power inverters are evaluated and compared with regards to size, efficiency and output quality in order to identify areas of potential improvement. Methods for estimation of THD, power losses and input ripple are created and verified against a simulation of a five-level neutral-point-clamped inverter with SPWM control. Finally, this design is implemented physically and is found to achieve 94.5% efficiency and 7% THD under low voltage laboratory conditions, while remaining smaller than an average textbook.
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Filipkowski, Jenna Noelle. "Impression Management across Applicant and Incumbent Contexts: The Effect on Job Performance." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1334170063.
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Gray, Ashley A. "An investigation of the effects of perceived feedback accuracy on performance." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001719.
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Sujudi, David D. (David Dewantara). "An experimental investigation of the effects of inlet circumferential temperature distortion on the aerodynamic performance of a single stage turbine." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11912.
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Tian, Yunjia. "Theory based on device current clipping to explain and predict performance including distortion of power amplifiers for wireless communication systems." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/1414.
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Power amplifiers are critical components in wireless communication systems that need to have high efficiency, in order to conserve battery life and minimise heat generation, and at the same time low distortion, in order to prevent increase of bit error rate due to constellation errors and adjacent channel interference. This thesis is aimed at meeting a need for greater understanding of distortion generated by power amplifiers of any technology, in order to help designers manage better the trade-off between obtaining high efficiency and low distortion. The theory proposed in this thesis to explain and predict the performance of power amplifiers, including distortion, is based on analysis of clipping of the power amplifier device current, and it is a major extension of previous clipping analyses, that introduces many key definitions and concepts. Distortion and other power amplifier metrics are determined in the form of 3-D surfaces that are plotted against PA class, which is determined by bias voltage, and input signal power level. It is shown that the surface of distortion exhibits very high levels due to clipping in the region where efficiency is high. This area of high distortion is intersected by a valley that is ‘L’-shaped. The 'L'-shaped valley is subject to a rotation that depends on the softness of the cut-off of the power amplifier device transfer characteristic. The distortion surface with rotated 'L'-shaped valley leads to predicted curves for distortion versus input signal power that match published measured curves for power amplifiers even using very simple device models. The distortion versus input signal power curves have types that are independent of technology. In class C, there is a single deep null. In the class AB range, that is divided into three sub-ranges, there may be two deep nulls (sub-range AB(B)), a ledge (sub-range AB(A)) or a shallow null with varying depth (sub-range AB(AB)).
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Leung, Raymond Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Scalable video compression with optimized visual performance and random accessibility." Awarded by:University of New South Wales. Electrical Engineering and Telecommunications, 2006. http://handle.unsw.edu.au/1959.4/24192.
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This thesis is concerned with maximizing the coding efficiency, random accessibility and visual performance of scalable compressed video. The unifying theme behind this work is the use of finely embedded localized coding structures, which govern the extent to which these goals may be jointly achieved. The first part focuses on scalable volumetric image compression. We investigate 3D transform and coding techniques which exploit inter-slice statistical redundancies without compromising slice accessibility. Our study shows that the motion-compensated temporal discrete wavelet transform (MC-TDWT) practically achieves an upper bound to the compression efficiency of slice transforms. From a video coding perspective, we find that most of the coding gain is attributed to offsetting the learning penalty in adaptive arithmetic coding through 3D code-block extension, rather than inter-frame context modelling. The second aspect of this thesis examines random accessibility. Accessibility refers to the ease with which a region of interest is accessed (subband samples needed for reconstruction are retrieved) from a compressed video bitstream, subject to spatiotemporal code-block constraints. We investigate the fundamental implications of motion compensation for random access efficiency and the compression performance of scalable interactive video. We demonstrate that inclusion of motion compensation operators within the lifting steps of a temporal subband transform incurs a random access penalty which depends on the characteristics of the motion field. The final aspect of this thesis aims to minimize the perceptual impact of visible distortion in scalable reconstructed video. We present a visual optimization strategy based on distortion scaling which raises the distortion-length slope of perceptually significant samples. This alters the codestream embedding order during post-compression rate-distortion optimization, thus allowing visually sensitive sites to be encoded with higher fidelity at a given bit-rate. For visual sensitivity analysis, we propose a contrast perception model that incorporates an adaptive masking slope. This versatile feature provides a context which models perceptual significance. It enables scene structures that otherwise suffer significant degradation to be preserved at lower bit-rates. The novelty in our approach derives from a set of "perceptual mappings" which account for quantization noise shaping effects induced by motion-compensated temporal synthesis. The proposed technique reduces wavelet compression artefacts and improves the perceptual quality of video.
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Ozkilic, Sibel. "Performance Improvement Of A 3-d Configuration Reconstruction Algorithm For An Object Using A Single Camera Image." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/1095793/index.pdf.
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Performance improvement of a 3-D configuration reconstruction algorithm using a passive secondary target has been focused in this study. In earlier studies, a theoretical development of the 3-D configuration reconstruction algorithm was achieved and it was implemented by a computer program on a system consisting of an optical bench and a digital imaging system. The passive secondary target used was a circle with two internal spots.
In order to use this reconstruction algorithm in autonomous systems, an automatic target recognition algorithm has been developed in this study. Starting from a pre-captured and stored 8-bit gray-level image, the algorithm automatically detects the elliptical image of a circular target and determines its contour in the scene. It was shown that the algorithm can also be used for partially captured elliptical images.
Another improvement achieved in this study is the determination of internal camera parameters of the vision system.
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Novikov, Yaroslav. "Development Of A High-fidelity Transient Aerothermal Model For A Helicopter Turboshaft Engine For Inlet Distortion And Engine Deterioration Simulations." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614389/index.pdf.
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Presented in this thesis is the development of a high-fidelity aerothermal model for GE T700 turboshaft engine. The model was constructed using thermodynamic relations governing change of flow properties across engine components, and by applying real component maps for the compressor and turbines as well as empirical relations for specific heats. Included in the model were bleed flows, turbine cooling and heat sink effects. Transient dynamics were modeled using inter-component volumes method in which mass imbalance between two engine components was used to calculate the inter-component pressure. This method allowed fast, high-accuracy and iteration-free calculation of engine states. Developed simulation model was successfully validated against previously published simulation results, and was applied in the simulation of inlet distortion and engine deterioration. Former included simulation of steady state and transient hot gas ingestion as well as transient decrease in the inlet total pressure. Engine deterioration simulations were performed for four different cases of component deterioration with parameters defining engine degradation taken from the literature. Real time capability of the model was achieved by applying time scaling of plenum volumes which allowed for larger simulation time steps at very little cost of numerical accuracy. Finally, T700 model was used to develop a generic model by replacing empirical relations for specific heats with temperature and FAR dependent curve fits, and scaling T700 turbine maps. Developed generic aerothermal model was applied to simulate steady state performance of the Lycoming T53 turboshaft engine.
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Seth, Sachin. "Using complementary silicon-germanium transistors for design of high-performance rf front-ends." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44721.
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The objective of the research presented in this dissertation is to explore the achievable dynamic range limits in high-performance RF front-ends designed using SiGe HBTs, with a focus on complementary (npn + pnp) SiGe technologies. The performance requirements of RF front-ends are high gain, high linearity, low dc power consumption, very low noise figure, and compactness. The research presented in this dissertation shows that all of these requirements can easily be met by using complementary SiGe HBTs. Thus, a strong case is made in favor of using SiGe technologies for designing high dynamic range RF front-ends. The contributions from this research are summarized as follows:
1. The first-ever comparison study and comprehensive analysis of small-signal linearity (IIP3) for npn and pnp SiGe HBTs on SOI.
2. A novel comparison of large-signal robustness of npn and pnp SiGe HBTs for use in high-performance RF front-ends.
3. A systematic and rigorous comparison of SiGe HBT compact models for high-fidelity distortion modeling.
4. The first-ever feasibility study of using weakly-saturated SiGe HBTs for use in severely power constrained RF front-ends.
5. A novel X-band Low Noise Amplifier (LNA) using weakly-saturated SiGe HBTs.
6. Design and comprehensive analysis of RF switches with enhanced large-signal linearity.
7. Development of novel methods to reduce crosstalk noise in mixed-signal circuits and the first-ever analysis of crosstalk noise across temperature.
8. Design of a very high-linearity cellular band quadrature modulator for use in base-station applications using first-generation complementary SiGe HBTs.
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Zhao, Zhanlue. "Performance Appraisal of Estimation Algorithms and Application of Estimation Algorithms to Target Tracking." ScholarWorks@UNO, 2006. http://scholarworks.uno.edu/td/394.
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This dissertation consists of two parts. The first part deals with the performance appraisal of estimation algorithms. The second part focuses on the application of estimation algorithms to target tracking. Performance appraisal is crucial for understanding, developing and comparing various estimation algorithms. In particular, with the evolvement of estimation theory and the increase of problem complexity, performance appraisal is getting more and more challenging for engineers to make comprehensive conclusions. However, the existing theoretical results are inadequate for practical reference. The first part of this dissertation is dedicated to performance measures which include local performance measures, global performance measures and model distortion measure. The second part focuses on application of the recursive best linear unbiased estimation (BLUE) or lineae minimum mean square error (LMMSE) estimation to nonlinear measurement problem in target tracking. Kalman filter has been the dominant basis for dynamic state filtering for several decades. Beyond Kalman filter, a more fundamental basis for the recursive best linear unbiased filtering has been thoroughly investigated in a series of papers by Dr. X. Rong Li. Based on the so-called quasirecursive best linear unbiased filtering technique, the constraints of the Kalman filter Linear-Gaussian assumptions can be relaxed such that a general linear filtering technique for nonlinear systems can be achieved. An approximate optimal BLUE filter is implemented for nonlinear measurements in target tracking which outperforms the existing method significantly in terms of accuracy, credibility and robustness.
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Kilic, Varlik. "Performance Improvement Of A 3d Reconstruction Algorithm Using Single Camera Images." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606259/index.pdf.
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In this study, it is aimed to improve a set of image processing techniques used in a previously developed method for reconstructing 3D parameters of a secondary passive target using single camera images. This 3D reconstruction method was developed and implemented on a setup consisting of a digital camera, a computer, and a positioning unit. Some automatic target recognition techniques were also included in the method. The passive secondary target used is a circle with two internal spots.
In order to achieve a real time target detection, the existing binarization, edge detection, and ellipse detection algorithms are debugged, modified, or replaced to increase the speed, to eliminate the run time errors, and to become compatible for target tracking. The overall speed of 20 Hz is achieved for 640x480 pixel resolution 8 bit grayscale images on a 2.8 GHz computer
A novel target tracking method with various tracking strategies is introduced to reduce the search area for target detection and to achieve a detection and reconstruction speed at the maximum frame rate of the hardware.
Based on the previously suggested lens distortion model, distortion measurement, distortion parameters determination, and distortion correction methods for both radial and tangential distortions are developed. By the implementation of this distortion correction method, the accuracy of the 3D reconstruction method is enhanced.
The overall 3D reconstruction method is implemented in an integrated software and hardware environment as a combination of the methods with the best performance among their alternatives. This autonomous and real time system is able to detect the secondary passive target and reconstruct its 3D configuration parameters at a rate of 25 Hz. Even for extreme conditions, in which it is difficult or impossible to detect the target, no runtime failures are observed.
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Clark, Adam. "Predicting the Crosswind Performance of High Bypass Ratio Turbofan Engine Inlets." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1476265135449178.
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Mollén, Christopher. "High-End Performance with Low-End Hardware : Analysis of Massive MIMO Base Station Transceivers." Doctoral thesis, Linköpings universitet, Kommunikationssystem, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-143455.
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Massive MIMO (multiple-input–multiple-output) is a multi-antenna technology for cellular wireless communication, where the base station uses a large number of individually controllable antennas to multiplex users spatially. This technology can provide a high spectral efficiency. One of its main challenges is the immense hardware complexity and cost of all the radio chains in the base station. To make massive MIMO commercially viable, inexpensive, low-complexity hardware with low linearity has to be used, which inherently leads to more signal distortion. This thesis investigates how the degenerated linearity of some of the main components—power amplifiers, analog-to-digital converters (ADCs) and low-noise amplifiers—affects the performance of the system, with respect to data rate, power consumption and out-of-band radiation. The main results are: Spatial processing can reduce PAR (peak-to-average ratio) of the transmit signals in the downlink to as low as 0B; this, however, does not necessarily reduce power consumption. In environments with isotropic fading, one-bit ADCs lead to a reduction in effective signal-to-interference-and-noise ratio (SINR) of 4dB in the uplink and four-bit ADCs give a performance close to that of an unquantized system. An analytical expression for the radiation pattern of the distortion from nonlinear power amplifiers is derived. It shows how the distortion is beamformed to some extent, that its gain never is greater than that of the desired signal, and that the gain of the distortion is reduced with a higher number of served users and a higher number of channel taps. Nonlinear low-noise amplifiers give rise to distortion that partly combines coherently and limits the possible SINR. It is concluded that spatial processing with a large number of antennas reduces the impact of hardware distortion in most cases. As long as proper attention is paid to the few sources of coherent distortion, the hardware complexity can be reduced in massive MIMO base stations to overcome the hardware challenge and make massive MIMO commercial reality.<br>Massiv MIMO (eng: multiple-input–multiple-output) är en flerantennsteknologi för cellulär trådlös kommunikation, där basstationen använder ett stort antal individuellt styrbara antenner för att multiplexa användare i rummet. Denna teknologi kan tillhandahålla en hög spektral effektivitet. En av dess främsta utmaningar är den enorma hårdvarukomplexiteten och kostnaden hos basstationens alla radiokedjor. För att massiv MIMO skall bli kommersiellt attraktivt, måste billiga, enkla hårdvarukomponenter med låg linjäritet användas, vilket oundvikligen leder till mer signaldistorsion. Denna avhandling undersöker hur den försämrade linjäriteten hos några av huvudkomponenterna – effektförstärkare, analog-digital-omvandlare (AD-omvandlare) och lågbrusförstärkare – påverkar systemets prestanda, i termer av datatakt, effektförbrukning och utombandsstrålning. Huvudresultaten är: Rumslig signalbehandling kan reducera sändsignalernas toppvärde i nerlänken ända ner till 0dB, vilket dock inte nödvändigtvis minskar effektförbrukningen. I miljöer med isotrop fädning leder enbits-AD-omvandlare till 4dB lägre signal-till-interferens-och-brus-förhållande i upplänken, och fyrabits-AD-omvandlare ger en prestanda nära den ett system utan kvantisering kan uppnå. Ett analytiskt uttryck för strålningsmönstret för distorsionen från icke-linjära effektförstärkare härleds. Det visar hur distorsionen till viss del lobformas, att dess förstärkning aldrig är starkare än förstärkningen för den önskade signalen och att distorsionens förstärkning minskar med ett högre antal betjänade användare och ett högre antal kanaltappar. Icke-linjära lågbrusförstärkare ger upphov distorsion som delvis kombinerar koherent och begränsar det möjliga signal-till-brus-och-interferens-förhållandet. Slutsatsen är att rumslig signalbehandling med ett stort antal antenner reducerar hårdvarudistorsionens inverkan i de flesta fall. Så länge som de få källorna till koherent distorsion ges tillbörlig uppmärksamhet, kan hårdvarukomplexiteten minskas i basstationer för massiv MIMO för att övervinna hårdvaruutmaningen och göra massiv MIMO kommersiell verklighet.<br>蜂窩無線通訊領域中的大規模多天線技術以多個單獨可控的天線通過空間複用的方式服務多個用戶。如是可以大幅提高頻譜效率。實現此技術的主要難題在於基站所用射頻單元的極大複雜度及成本。爲使大規模多天線技術適用在商業系統中，需使用導致失真的低複雜度低成本的非線性硬件。本文探討若將一些主要部件——功放、模數轉換器、低噪聲放大器——的線性程度降低，系統性能是如何受到影響的，即系統的速率、功耗、帶外泄露等指標。主要的結果爲：空間信號處理可以降低下行信號的峯均比，直至０分貝；然而低峯均比不一定能夠降低功耗。用一比特模數轉換器使上行的信干噪比減少４分貝；用四比特模數轉換器可在各向同性衰落的環境裏實現接近無量化系統的性能。本文推導出非線性功放失真輻射方向的解析公式。該公式展示失真在某種程度上會被波束成形的；具體而言，失真的波束成形增益不大於有效信號的增益，波束成形增益會根據服務用戶數量和信道階數的增長而降低。非線性低噪聲放大器引起的失真，一部分會相干地合併，因此會限制信干噪比的增長。結論爲多天線的空間信號處理可以減少硬件失真的影響。只要適當地處理少數相干失真的來源，大規模多天線基站可以降低硬件複雜度，解決硬件難題，使大規模多天線技術成功地應用在商業系統中成爲現實。
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Souza, Lafranckia Saraiva Paz de. "O ensino médio regular noturno em Manaus: indicadores do rendimento escolar." Universidade Federal de Juiz de Fora (UFJF), 2016. https://repositorio.ufjf.br/jspui/handle/ufjf/4658.
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Previous issue date: 2016-11-29<br>A presente dissertação, desenvolvida no âmbito do Mestrado Profissional em Gestão e Avaliação da Educação (PPGP) do Centro de Políticas Públicas e Avaliação da Educação da Universidade Federal de Juiz de Fora (CAEd/UFJF), apresenta em seu conteúdo uma análise dos indicadores de rendimento escolar do Ensino Médio Noturno das Escolas Estaduais da Coordenadoria Distrital de Educação 02 (CDE02) de Manaus. O texto está organizado em três capítulos. No primeiro capítulo descrevemos o caso de gestão estudado, subsidiando a escrita com textos que abordam contextos sócio-políticos e expressam a forma de organização atual do Ensino Médio, como um todo, e do Ensino Médio Noturno, em particular. Evidenciamos também, no capítulo 1, através dos dados do rendimento escolar, os resultados de aprendizagem das Escolas de Ensino Médio da CDE02. No segundo capítulo expomos os quatro eixos que integraram a pesquisa, gestão escolar, docência, organização curricular, fluxo e distorção idade/série, dialogando com os autores do ramo educacional que trouxeram fundamento teórico tais como: Luck (2009) e Machado (2011). Togni e Carvalho (2007) e Hagemeyer (2004). Tavares ( 2014). Por meio do estudo dos eixos foi possível identificar a importância de um gerenciamento participativo para a integração do aluno, a influência da docência na motivação e aprendizagem do educando, a necessidade de uma organização curricular mais próxima da realidade do educando e os percalços de um fluxo escolar interrompido. A metodologia de natureza qualitativa e o instrumento de coleta de dados, entrevista semiestruturada, realizado com a equipe gestora, a análise de dados secundários e documental integram o capítulo 2. No terceiro e último capítulo propomos ações de melhoria descritas no Plano de Ação Educacional parametrizadas pelos resultados encontrados na pesquisa. Os resultados apontam que, é preciso saber lidar com as diferenças e lacunas de aprendizagem do educando para a permanência do mesmo. O docente ainda é referência para o estudante do Ensino Médio, a relação entre educando e professor interfere no seu aprendizado e desempenho. A escola precisa proporcionar um espaço educativo que amplie a aprendizagem por meio da articulação do ensino dos componentes curriculares das áreas afins em prol de garantir não somente o acesso, mas o sucesso e permanência do educando. A expansão das matrículas não garante a permanência nem a conclusão dos estudos por parte do estudante apesar da igualdade de condições de acesso, para que haja equidade de permanência é necessário que o estudante do Ensino Médio Noturno tenha oportunidade igual para concluir seus estudos no tempo certo.<br>This dissertation, developed within Professional Master in Management and Education Assessment (PPGP) of the Public Policy Center and Education Assessment of the Juiz de Fora Federal University (CAEd/UFJF), presents in its content an analysis of the High School income indicators for the night shift of the State school of Coodenadoria Distrital da Educação 02 (CDE02) in Manaus. The text is organized in three chapters. In the first chapter we describe the case of studied management, subdisizing the writing with texts that approach contexts politicalpartner and express the way of current organization of the High School, as a whole, and the High School night shift, in private. We also evidence, in the chapter 1, through the school performances data, the results of the learning in High School levels of CDE02. In the chapter 2 we expose four axis that integrate the research, school management, teaching, curricular organization, flow and age distortion/grade, dialoguing with the writes of the education career who brought theorical foundation such as: Luck (2009) and Machado (2011). Togni and Carvalho (2007) and Hagemeyer (2004). Tavares (2014). By means of study it was possible to identify the importance of the participatory management for the integration for the student´s integration, the influence of teaching in the motivation and the student´s learning process, the need of a curricular organization closer to the reality of the student and the mishaps of a school flow interrupted. In the third chapter we suggest improvement actions described in the educational action plan parameterized by the results achieved in the research. The results aim that, it´s necessary to know how to deal with diferences and gaps of the student´s learning himself. The teacher is still a reference for the high school student, the relation between the studnet and the teacher.The school needs to provide an educational environment that enlarges the learning by means of articulation of the curricular componentes of the related area so that it can guarantee not only access, but the succeess and permanence of the student. The expansion of registrations does not guarantee the permanence neither the conclusion of the studies by the students, although the iguality of access conditions, so that there is equity of permanence is necessary that the night high school student has the same opportunity to accomplish his or her studies in time.
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Svanberg, J. Magnus. "Predictions of manufacturing induced shape distortions : high performance thermoset composites." Doctoral thesis, Luleå tekniska universitet, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25822.
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High performance composites usually consist of continuous fibres and a thermoset matrix. A well-known example is carbon fibre epoxy composites. When this kind of material is cured residual stresses and/or shape distortions are produced owing to thermally and chemically induced volumetric strains. The cure means the manufacturing step where the thermoset matrix is transformed from a liquid to a solid material. It is a quite complex thermal- chemical- mechanical process that in addition to volumetric strains, involves heat generation and dramatic changes in mechanical properties. For manufacturing of parts with high shape tolerances, such as aircraft components, the geometry of the mould is compensated to accommodate for shape distortions. Today this is made based on thumb rules and experience followed by trials. This is time consuming and expensive. Development of a tool for prediction of shape distortions and residual stresses is therefore an important step towards more optimised manufacturing of composites. The present thesis, consisting of five papers, describes the development and validation of a simulation tool for prediction of shape distortion and residual stresses. In the first paper a typical material and manufacturing process for high performance composites was used to experimentally investigate the effects from the cure temperature on spring-in of angle sections. The experimental results were interpreted in terms of mechanisms responsible for shape distortions. Based on the observations, a process model including a new mechanical constitutive model for predictions of residual stresses and shape distortions was proposed and implemented in a general purpose FE-program, as presented in the second paper. In the third paper, the model was validated by comparing spring-in predictions with the experimental results of the first paper complemented by same new experiments. The third paper also embraces a numerical investigation of the effect from the mechanical boundary conditions during cure. So far (in the three first papers), the curing conditions were kept isothermal. When a thick component is cured, the conditions are no longer isothermal owing to heat generated by the exothermal cure reaction. Hence, in the fourth paper the process model was validated against experimental results for a non-isothermally cured component. Finally, in the last paper shape distortions of a complex aircraft component was studied. This was made to both get further validation of the process model as well as investigate the feasibility to simulate large parts of complex shape.<br>Godkänd; 2002; 20061109 (haneit)
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Alberto, Rita Sofia Grácio. "Gender distorting genre distorting gender : exploring women's rock musicking practices in contemporary Portugal." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/33397.
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This work explores the everyday uses of rock music by women rock musicians, fans and DJs (amateurs), in a specific place (Portugal) and time (1990s-2014). Drawing on the work in the two main fields of music sociology and gender studies and its performative perspective to both gender and music (but also taking contributions from techno-feminist studies, science and technology studies, sociology of work, leisure and sports), this research takes a ‘music-in-action’ approach. This approach understands music as a social activity, as a network of connections between people, materials, discourses and activities. Rock music is best understood as a genre-in-action (not just as a semiotic text or reflection), as socio-material practice, in its collective, relational, performative, situated contexts of use - as rock musicking. As such, there are socio-material processes that constrain and enable women (as a minority group) doing and being in a masculinist rock music world. Taking a ‘mutual shaping’ approach to genre and gender, this research also takes into account how people use aesthetic materials in the processes of performative gendered identity making and relationship with others, as well as world building. The data consists of sixty in-depth interviews with Portuguese rockers (between 2012 and 2014), and supplementary field observations and follow-up interviews. The research found that girls and women’s musical opportunities are more restricted, but that they are also actively negotiated. Parental support and the presence of rock fathers in early years, as well as participation in male networks – whether or not a woman is romantically involved with ‘one of the boys’ – throughout the life course are pathways into rock musicking, as documented in other studies. Adding to the literature, this research highlights how not only in early years, but throughout the life course, rock musicking practices are dependent upon specific aesthetic (musical and visual) gender performances. From female masculinity to alternative femininities, rock music and its visual and material cultures are ‘active ingredients’ in doing and undoing gender. In Portugal, the absence of a strong riot grrrl movement and the lack of female/feminist networks, turns membership in male bands the norm. Consequently, either the “girl in the band’ or girl/female bands have to deal with their ‘novelty’ value. These rockers negotiate the labels of riot grrrl, feminist and grunge within a ‘girl power’ discourse, but mostly, struggling not to let their musical skills and value be obscured by their sex/ualization – developing high standards of musicianship, managing on-stage bodily disclosure, naming and praising their peers, aligning with an Anglo-Saxon rock female canon, but also othering female fans. In male bands, due to male skill ascription, women are segregated into traditional female musical roles, the singer, the bass player. On the other hand, women drummers get token value. At the expenses of instrument specialization, women undertake multi-instrumental pathways. Becoming musical agile selves and re-valuing (traditionally female) musical roles, playing conventions and body techniques. Women also appropriate mixers to spread their love for rock music. These women creatively expand rock music’s material culture, crafting it with clothes, acessories and even food. For rockers who are mothers, rock musicking becomes a technology of mothering. Taking Portuguese women rockers and their socio-musical practices, at both the everyday level and on the “spectacular” rock stage, this research adds to the international and growing body of work on gender and (rock) music across different disciplinary fields (sociology, popular music studies, feminist studies). It extends the traditional focus within popular music scholarship on Anglo-American rock culture, feminist mo(ve)ments, and subcultures, to place emphasis instead on an age group and place that has otherwise been overlooked.
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Thiele, Veikko. "Essays on incongruent preferences for effort allocations in multi-task agency relations." Doctoral thesis, Humboldt-Universität zu Berlin, Wirtschaftswissenschaftliche Fakultät, 2006. http://www.gbv.de/dms/zbw/523228546.pdf.
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Xu, Xiao. "Harmonic modelling and characterisation of modern power electronic devices in low voltage networks." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33106.
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Although the overall levels of harmonics in modern power supply systems are in most of the practical cases still below the prescribed tolerance limits and thresholds (e.g. these stipulated in [IEC 61000-3-2 and 61000-3-12]), the sources of harmonics are constantly increasing in numbers and are expected to increase even more in the future. Some of the examples of modern non-linear power electronic (PE) devices that are expected to be employed on a much wider scale in LV networks in the future include: light-emitting diode (LED) lamps, switched-mode power supplies (SMPS'), electric vehicle battery chargers (EVBCs) and photovoltaic inverters (PVIs), which are all analysed in this thesis. The thesis first reviews the conventional harmonic analysis methods, investigating their applicability to modern PE devices. After that, the two most widely used forms of harmonic models, i.e. component-based models (CBMs) and frequency-domain models (FDMs), are applied for modelling of the four abovementioned types of modern PE devices and their models are fully validated by measurements. The thesis next investigates the impact of supply voltage conditions and operating modes (e.g. low vs high operating powers) on the device characteristics and performance, using both measurements and developed CBMs and FDMs. The obtained results confirm that both supply conditions and operating modes have an impact on the characteristics of most of the considered PE devices, which is taken into account in the developed models and demonstrated on a number of case studies. As the next contribution, the thesis proposes new indices for the evaluation of current waveform distortions, allowing for a separate analysis of contributions of low and high frequency harmonics and interharmonics to the total waveform distortion of PE devices. As the modern PE devices are normally based on high-frequency switching converters or inverters, the impact of circuit topologies and control algorithms on their harmonic emission characteristics and performance is also investigated. Special attention is given to the operation of PE devices at low powers, when there is a significant increase of current waveform distortion, a substantial decrease of efficiency and power factors and when input ac current might lose its periodicity with the supply voltage frequency. This is analysed in detail for SMPS', resulting in the proposal of a new methodology ("operating cycle based method") for evaluating overall performance of PE devices across the entire range of operating powers. Finally, a novel and simple hybrid harmonic modelling technique, allowing for the use of both time-domain and frequency-domain models in the same simulation environment, is proposed and illustrated on the selected case studies. This is accompanied with a frequency-domain aggregation approach, which is applied in the thesis to investigate the impact of increasing numbers of different types of modern PE devices on the LV network. The implementation of the developed hybrid harmonic modelling approach and frequency-domain aggregation technique is demonstrated on the example of a typical (UK) urban generic LV distribution network and used for the analysis of different deployment levels of EVs and PVIs. The presented harmonic modelling framework for individual PE devices and, particularly, for their aggregate models, fills the gap in the existing literature on harmonic modelling and characterisation of modern PE devices, which is important for the correct evaluation of their harmonic interactions and analysis of the impact of their large-scale deployment on the overall network performance.
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Shahosseini, Iman. "Vers des micro-haut-parleurs à hautes performances électroacoustiques en technologie silicium." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00856591.
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Ce mémoire présente la conception, la réalisation et la caractérisation d'un micro-haut-parleur en silicium destiné à des applications électroniques portables, telles que les tablettes et les téléphones cellulaires. L'objectif est d'évaluer le potentiel des microtechnologies pour améliorer la qualité sonore et le rendement électroacoustique, qui sont deux points faibles majeurs des micro-haut-parleurs actuels.En analysant les paramètres dont dépendent le rendement et la qualité sonore, nous montrons que le silicium monocristallin présente des propriétés particulièrement intéressantes pour réaliser la surface émissive et la suspension du transducteur. Une microstructure de la partie mobile est proposée pour satisfaire la double exigence d'une surface émissive très rigide, nécessaire à la qualité sonore, et d'une masse très faible, permettant d'augmenter le rendement. Les aimants et la bobine, qui constituent le moteur électrodynamique, sont également optimisés en utilisant conjointement des modèles analytiques et à éléments finis. La microfabrication du transducteur MEMS est étudiée, étape par étape. Elle repose sur l'utilisation d'un substrat SOI (silicium sur isolant), qui sert de base à la structuration des différents composants, et sur lequel sont rapportés des aimants massifs. La caractérisation électroacoustique des échantillons réalisés montre une très bonne qualité de reproduction sonore. Un niveau sonore de 80 dB à 10 cm est obtenu pour une puissance électrique de 0,5 W, ce qui place le rendement au niveau des micro-haut-parleurs du marché. Ces travaux montrent en outre que les technologies MEMS offrent des possibilités d'augmenter très largement le rendement.
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Khouz, Boujemaa. "Etude de la réduction de l'usure dans un lubrifiant contaminé par des particules." Ecully, Ecole centrale de Lyon, 1987. http://www.theses.fr/1987ECDL0004.
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Datsiou, Kyriaki Corinna. "Design and performance of cold bent glass." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/269408.
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The demand for flat glass is high and increasing significantly in the building industry as a direct result of architectural requirements for lightness, transparency and natural light. Current architectural trends require glass in curvilinear forms for smooth free-form façades. Two principal challenges arise from this: to cost-effectively produce the desired curvature and; to ensure its safe performance after exposure to ageing. The recent availability of high strength glass provides an opportunity to address the first challenge by developing cold bent glass. Cold bending involves the straining of relatively thin glass components, at ambient temperatures, and is a low energy and cost effective manner of creating curvilinear forms. However, cold bending is not yet widely established as a reliable method. The aim of this thesis is to develop the understanding of cold bent glass during the bending process and to evaluate its post-ageing performance. This thesis, firstly, investigates the mechanical response of monolithic glass plates during the cold bending process. The stability of cold bent glass is investigated experimentally by bending it in double curved anticlastic shapes. A parametric numerical analysis involves different boundary conditions, geometrical plate characteristics and bending parameters. The principal outcome is that a local instability, now termed cold bending distortion, occurs when certain displacement limits are exceeded and could degrade the optical quality of the glass. An evaluation procedure is also formulated to set limits and aid designers/manufacturers to predict the mechanical response and the optical quality of the glass. Cold bent glass is subjected to permanent bending stresses throughout its service life and therefore, its strength degradation after ageing needs to be quantified. Analytical, experimental and numerical investigations are undertaken in this thesis to identify the most effective method for estimating glass strength (evaluation of destructive tests, required number of specimens, statistical analysis methods and sub-critical crack growth). The limited availability of naturally aged toughened glass and the absence of a reliable ageing standard impede the evaluation of its aged performance. Therefore, a parametric experimental investigation of artificial ageing methods on glass is undertaken in this thesis. A procedure for the evaluation of the strength of aged glass is finally, formulated to allow the selection of artificial ageing parameters that correspond to a target level of erosion. The knowledge on artificial ageing and strength prediction acquired above is finally implemented on different types of glass to determine their strength after ageing and assess their safe use in cold bending / load bearing applications. The investigation showed that fully toughened glass has a superior performance to chemically toughened or annealed glass. Overall, the research presented in this thesis demonstrates that high quality cold bent toughened glass can be created when certain applied displacement limits are respected. These can be used as a safe, cost-effective and energy efficient replacement to the more conventional hot bent glass. However, cold bending / load bearing applications in which the stressed glass surface is exposed to ageing, require glass with a relatively high case depth such as fully toughened or bi-tempered glass.
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Cheng, Shanshan. "Fire performance of cold-formed steel sections." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3316.
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Thin-walled cold-formed steel (CFS) has exhibited inherent structural and architectural advantages over other constructional materials, for example, high strength-to-weight ratio, ease of fabrication, economy in transportation and the flexibility of sectional profiles, which make CFS ideal for modern residential and industrial buildings. They have been increasingly used as purlins as the intermediate members in a roof system, or load-bearing components in low- and mid-rise buildings. However, using CFS members in building structures has been facing challenges due to the lack of knowledge to the fire performance of CFS at elevated temperatures and the lack of fire design guidelines. Among all available design specifications of CFS, EN1993-1-2 is the only one which provided design guidelines for CFS at elevated temperatures, which, however, is based on the same theory and material properties of hot-rolled steel. Since the material properties of CFS are found to be considerably different from those of hot-rolled steel, the applicability of hot-rolled steel design guidelines into CFS needs to be verified. Besides, the effect of non-uniform temperature distribution on the failure of CFS members is not properly addressed in literature and has not been specified in the existing design guidelines. Therefore, a better understanding of fire performance of CFS members is of great significance to further explore the potential application of CFS. Since CFS members are always with thin thickness (normally from 0.9 to 8 mm), open cross-section, and great flexural rigidity about one axis at the expense of low flexural rigidity about a perpendicular axis, the members are usually susceptible to various buckling modes which often govern the ultimate failure of CFS members. When CFS members are exposed to a fire, not only the reduced mechanical properties will influence the buckling capacity of CFS members, but also the thermal strains which can lead additional stresses in loaded members. The buckling behaviour of the member can be analysed based on uniformly reduced material properties when the member is unprotected or uniformly protected surrounded by a fire that the temperature distribution within the member is uniform. However if the temperature distribution in a member is not uniform, which usually happens in walls and/or roof panels when CFS members are protected by plaster boards and exposed to fire on one side, the analysis of the member becomes very complicated since the mechanical properties such as Young’s modulus and yield strength and thermal strains vary within the member. This project has the aim of providing better understanding of the buckling performance of CFS channel members under non-uniform temperatures. The primary objective is to investigate the fire performance of plasterboard protected CFS members exposed to fire on one side, in the aspects of pre-buckling stress distribution, elastic buckling behaviour and nonlinear failure models. Heat transfer analyses of one-side protected CFS members have been conducted firstly to investigate the temperature distributions within the cross-section, which have been applied to the analytical study for the prediction of flexural buckling loads of CFS columns at elevated temperatures. A simplified numerical method based on the second order elastic – plastic analysis has also been proposed for the calculation of the flexural buckling load of CFS columns under non-uniform temperature distributions. The effects of temperature distributions and stress-strain relationships on the flexure buckling of CFS columns are discussed. Afterwards a modified finite strip method combined with the classical Fourier series solutions have been presented to investigate the elastic buckling behaviour of CFS members at elevated temperatures, in which the effects of temperatures on both strain and mechanical properties have been considered. The variations of the elastic buckling loads/moments, buckling modes and slenderness of CFS columns/beams with increasing temperatures have been examined. The finite element method is also used to carry out the failure analysis of one-side protected beams at elevated temperatures. The effects of geometric imperfection, stress-strain relationships and temperature distributions on the ultimate moment capacities of CFS beams under uniform and non-uniform temperature distributions are examined. At the end the direct strength method based design methods have been discussed and corresponding recommendations for the designing of CFS beams at elevated temperatures are presented. This thesis has contributed to improve the knowledge of the buckling and failure behaviour of CFS members at elevated temperatures, and the essential data provided in the numerical studies has laid the foundation for further design-oriented studies.
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Chatterjee, Saikat. "Rate-Distortion Performance And Complexity Optimized Structured Vector Quantization." Thesis, 2008. http://hdl.handle.net/2005/1056.
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Although vector quantization (VQ) is an established topic in communication, its practical utility has been limited due to (i) prohibitive complexity for higher quality and bit-rate, (ii) structured VQ methods which are not analyzed for optimum performance, (iii) difficulty of mapping theoretical performance of mean square error (MSE) to perceptual measures. However, an ever increasing demand for various source signal compression, points to VQ as the inevitable choice for high efficiency. This thesis addresses all the three above issues, utilizing the power of parametric stochastic modeling of the signal source, viz., Gaussian mixture model (GMM) and proposes new solutions. Addressing some of the new requirements of source coding in network applications, the thesis also presents solutions for scalable bit-rate, rate-independent complexity and decoder scalability.
While structured VQ is a necessity to reduce the complexity, we have developed, analyzed and compared three different schemes of compensation for the loss due to structured VQ. Focusing on the widely used methods of split VQ (SVQ) and KLT based transform domain scalar quantization (TrSQ), we develop expressions for their optimum performance using high rate quantization theory. We propose the use of conditional PDF based SVQ (CSVQ) to compensate for the split loss in SVQ and analytically show that it achieves coding gain over SVQ. Using the analytical expressions of complexity, an algorithm to choose the optimum splits is proposed. We analyze these techniques for their complexity as well as perceptual distortion measure, considering the specific case of quantizing the wide band speech line spectrum frequency (LSF) parameters. Using natural speech data, it is shown that the new conditional PDF based methods provide better perceptual distortion performance than the traditional methods.
Exploring the use of GMMs for the source, we take the approach of separately estimating the GMM parameters and then use the high rate quantization theory in a simplified manner to derive closed form expressions for optimum MSE performance. This has led to the development of non-linear prediction for compensating the split loss (in contrast to the linear prediction using a Gaussian model). We show that the GMM approach can improve the recently proposed adaptive VQ scheme of switched SVQ (SSVQ). We derive the optimum performance expressions for SSVQ, in both variable bit rate and fixed bit rate formats, using the simplified approach of GMM in high rate theory.
As a third scheme for recovering the split loss in SVQ and reduce the complexity, we propose a two stage SVQ (TsSVQ), which is analyzed for minimum complexity as well as perceptual distortion. Utilizing the low complexity of transform domain SVQ (TrSVQ) as well as the two stage approach in a universal coding framework, it is shown that we can achieve low complexity as well as better performance than SSVQ. Further, the combination of GMM and universal coding led to the development of a highly scalable coder which can provide both bit-rate scalability, decoder scalability and rate-independent low complexity. Also, the perceptual distortion performance is comparable to that of SSVQ.
Since GMM is a generic source model, we develop a new method of predicting the performance bound for perceptual distortion using VQ. Applying this method to LSF quantization, the minimum bit rates for quantizing telephone band LSF (TB-LSF) and wideband LSF (WB-LSF) are derived.
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Yu, Hao-jun, and 游豪俊. "《DISTORTION》－Improving Visual Performance of Animation Creation by Rotoscoping." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/94061224116238409134.
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碩士<br>國立臺南大學<br>動畫媒體設計研究所<br>99<br>The goal of the animation is to make roles come alive in the eyes of the audience and let people feel its reality and existence. In order to achieve the results, we have to depend on various factors to constitute it, such as the appearance of roles, dialogue, action, plot, etc.
The technology of Rotoscoping was developed in 1914, and it allowed animators to draw the movements and appearance of roles more similar with actual human beings. Thus animators can capture dynamic images of real people and transfer into animated characters by this technique. Nowadays there are still many animation directors use this technology to draw the animation. It is thus clear that Rotoscoping provide the animators the significant control of the role performance.
The topic of our research is analyzing the animated works which were created by Rotoscoping. By the simulation of appearance, character modeling and lens movement, we try to find the subtle connection and diversity between the real visual images and the animated images. We also created an animation, in which Rotoscoping is applied to make the line shape, shot compositions and the sense of speed. We try to present a fully rhythmic and highly dynamic hand-drawn animated film.
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"Rate-distortion performance for joint source and channel coding of images." Massachusetts Institute of Technology, Laboratory for Information and Decision Systems], 1996. http://hdl.handle.net/1721.1/3432.
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Michael J. Ruf, James W. Modestino.<br>Caption title.<br>Includes bibliographical references (p. 31-32).<br>Supported by the German Educational Exchange Service (DAAD) as part of the HSP II-program, and in part by ARPA. F30602-92-C-0030 Supported by the Laboratory for Information and Decision Systems, Massachusetts Institute of Technology. DAAH04-95-1-0103
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Gannon, Liam. "Effect of Welding Residual Stress and Distortion on Ship Hull Structural Performance." 2011. http://hdl.handle.net/10222/13367.
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The finite element method is used to investigate the effects of welding-induced residual stress and distortion on the strength and behaviour of ship hull structures. A finite element welding simulation consisting of sequentially coupled transient thermal and nonlinear structural analyses is used to predict the three-dimensional residual stress and distortion fields in welded stiffened plates. Three types of stiffener commonly used in commercial and naval applications are considered. The welding simulation is followed by a 'shakedown' analysis to study the possibility of residual stress relief caused by cyclic loads. The strength and behaviour of stiffened plates under axial load is characterized by normalized plots of average axial stress versus axial strain, commonly referred to as load-shortening curves. These curves are used to evaluate the effects of welding-induced residual stress and distortion on stiffened plate behaviour with and without considering stress relief by shakedown. Load-shortening curves generated by finite element analysis are also compared with load-shortening curves produced using analytical methods including those prescribed in ship structural design standards published by the International Association of Classification Societies (IACS). To conclude, a hull girder ultimate strength analysis is carried out using Smith's method with load-shortening curves generated by several different methods.
Results indicate that welding-induced residual stress and distortion decrease the ultimate strength of flat-bar, angle, and tee-stiffened plates investigated in this study by as much as 17%, 15% and 13%, respectively. Stiffened plate ultimate strength values calculated using IACS common structural rules agreed reasonably well with results from numerical models in most cases. There was however, a significant discrepancy between the numerical load-shortening curves and the IACS curves in the post-ultimate regime, where the IACS curves overestimated the post-ultimate strength of stiffened plates by as much as 30%. To investigate stress relief by shakedown, axial stresses of 25% and 50% of the yield stress were applied and residual stresses were reduced by approximately 20% and 40%, respectively. In some cases, these reductions in residual stress led to increases in stiffened plate ultimate strength as high as 7%. Analysis of a box girder using load-shortening curves from a finite element model including residual stresses and distortions predicted by welding simulation predicted a bending moment capacity within 2.7% of the experimentally measured value. Using load-shortening curves from the IACS common structural rules, the ultimate strength was overestimated by 17%.<br>Thesis .pdf/A
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Awuor, Frederick Mzee. "Distributed joint power and rate adaption in ad hoc networks." 2011. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000287.
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M. Tech. Electrical Engineering.<br>This study proposes a distributive joint power and rate adaptation algorithm (JRPA) in ad hoc networks based on coupled interference minimisation. In the proposed method, the influence of coupled interference was controlled by dynamically adjusting network users' transmit power choices. The users are therefore aware of the current link status while determining their data rates. In addition, every maximize utility of other users as it maximizes its utility due to the inevitable cooperation, hence, improving a collective network performance. Solving this network utility maximization problem results in a supermodular game equivalence where users cooperate to maximise both local and global utility, hence the supermodular game theory concept was used to analyse the optimality and convergence of the proposed solution.
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"An Analysis of the Memory Bottleneck and Cache Performance of Most Apparent Distortion Image Quality Assessment Algorithm on GPU." Master's thesis, 2016. http://hdl.handle.net/2286/R.I.41229.
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abstract: As digital images are transmitted over the network or stored on a disk, image processing is done as part of the standard for efficient storage and bandwidth. This causes some amount of distortion or artifacts in the image which demands the need for quality assessment. Subjective image quality assessment is expensive, time consuming and influenced by the subject's perception. Hence, there is a need for developing mathematical models that are capable of predicting the quality evaluation. With the advent of the information era and an exponential growth in image/video generation and consumption, the requirement for automated quality assessment has become mandatory to assess the degradation. The last few decades have seen research on automated image quality assessment (IQA) algorithms gaining prominence. However, the focus has been on achieving better predication accuracy, and not on improving computational performance. As a result, existing serial implementations require a lot of time in processing a single frame. In the last 5 years, research on general-purpose graphic processing unit (GPGPU) based image quality assessment (IQA) algorithm implementation has shown promising results for single images. Still, the implementations are not efficient enough for deployment in real world applications, especially for live videos at high resolution. Hence, in this thesis, it is proposed that microarchitecture-conscious coding on a graphics processing unit (GPU) combined with detailed understanding of the image quality assessment (IQA) algorithm can result in non-trivial speedups without compromising quality prediction accuracy. This document focusses on the microarchitectural analysis of the most apparent distortion (MAD) algorithm. The results are analyzed in-depth and one of the major bottlenecks is identified. With the knowledge of underlying microarchitecture, the implementation is restructured thereby resolving the bottleneck and improving the performance.<br>Dissertation/Thesis<br>Masters Thesis Computer Science 2016
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Oliveira, Beatriz Manata de. "Performance analysis of radio over fiber system employing digital predistortion." Master's thesis, 2017. http://hdl.handle.net/10316/83405.
Full textAbstract:
Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia<br>Actualmente, as comunicações sem fios (wireless) estão a entrar numa nova fase, as redes de 5ª geração (5G), onde se espera o aumento de serviços que necessitam de grande largura de banda, nomeadamente, serviços interactivos e multimédia. Para suportar estas exigências, uma vertente da investigação em comunicações wireless estuda a operação na gama das microondas/ondas milimétricas para assim evitar o congestionamento espectral nas baixas frequências. Esta estratégia implica uma redução do tamanho da célula e, consequentemente, um aumento do número de células necessárias para cobrir uma determinada área. Tais redes exigem um número elevado de Estações de Base (BSs-Base Stations) para fazer a cobertura de uma área de serviço; assim, uma BS de baixo custo é a chave de sucesso no mercado. Esta exigência levou ao desenvolvimento de uma arquitectura de um sistema onde funções tais como o encaminhamento (routing)/processamento são tratadas numa Unidade Central (CU-Central Unit), mais do que na BS, tornando as BSs em unidade rádio remotas simples (RRHs-Remote Radio Head). A arquitectura de rede centralizada permite a equipamento sensível de ser localizado num ambiente mais seguro, para além de permitir a partilha dos componentes mais dispendiosos pelas várias RRHs. Uma estratégia atractiva para ligar uma CU com as RRHs é através de uma rede de fibra óptica, pois a fibra óptica tem baixas perdas e tem uma grande largura de banda. No entanto, os sinais de rádio são severamente distorcidos por estas ligações. A distorção, introduzida pelo sistema de transmissão ótico, será um fator limitante, uma vez que a potência dos sinais tem de ser reduzida para que os componentes operem na zona linear, diminuindo, assim, o alcance das ligações.O espectro disponível torna-se uma limitação do aumento da taxa de transmissão, uma vez que a largura de banda não será suficiente para as redes de próxima geração. Uma banda que se encontra em estudo para responder a este desafio é a banda não licenciada nos 60 GHz, apesar das suas elevadas atenuações limitarem significativamente o alcance das ligações.Nesta dissertação é implementado um modelo de simulação de um sistema rádio sobre fibra. As distorções sofridas pelos sinais rádio são identificadas, analisadas e compensadas com um bloco de pré-distorção digital baseado em polinómios de memória. A conversão eletro-ótica do sinal rádio multiplexado por divisão em frequências ortogonais (OFDM – Orthogonal Frequency Division Multiplexing) através do modulador Mach-Zehnder é destacada, uma vez que é a principal causa da distorção do sistema ótico.Ao longo desta dissertação, os componentes e a arquitetura da rede são discutidos; modelos para o modulador Mach-Zehnder, fotodetector e fibra são apresentados. O ponto de polarização DC do Mach-Zehnder é estudado, assim como a sua influência no desempenho do sistema; o número de símbolos e o débito binário são otimizados e o impacto do comprimento da fibra e a largura espetral do laser são também discutidos.<br>Wireless communications are currently entering a new stage, 5th generation networks (5G), where an increase of services requiring high bandwidth is expected; namely, interactive services and multimedia. To support such demands, investigation in wireless communications has a strand studying operation at microwaves/millimeter waves to avoid spectral congestion in lower frequencies. This strategy implies a reduction in size of the cells, consequently leading to higher numbers of cells needed to provide coverage to a certain area. Such networks require a high number of Base Stations (BSs); thus, low cost BSs are the key to success in the market. This demand led to the development of an architecture of a system where functions such as routing/processing are dealt with at the Central Unit (CU), making BSs simple Remote Radio Heads (RRHs). This centralized network architecture allows sensible equipment to be localized at a safer environment while allowing resource sharing of the high cost components between RRHS. This strategy is attractive to connect a CU to RRHs trough optical fiber, since optical fiber has low losses and high bandwidth. However, radio signals are highly distorted by these connections. The distortion, introduced by the optical transmission system, will be a limiting factor, since the power of the signals must be reduced so the components operate at a linear zone, thus decreasing the range of the connections.Available spectrum becomes a restraint in the increase of transmission rate, since the bandwidth will not be sufficient for next generation networks. The unlicensed 60 GHz band is being studied to meet this challenges, despite its high attenuation significantly limiting the range of the connections.In this dissertation, a simulation model of a Radio over Fiber system is implemented. The distortions suffered by radio signals are identified, analyzed and compensated with a digital predistortion block based on memory polynomials. Electro-optic conversion of the Orthogonal Frequency Division Multiplexing (OFDM) radio signal is highlighted, since it is the main cause of distortion in the optical system.Throughout this work, the components and architecture of the network are presented and discussed; the models for the Mach-Zehnder, optical fiber, photodetector and predistorter are shown. The impact on the performance of the bias point of the MZM is analyzed, the number of symbols and bit rate are optimized and the impact of the fiber’s length and laser’s linewidth are discussed.<br>FCT
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Guerreiro, João Francisco Martinho Lêdo. "Analytical Characterization and Optimum Detection of Nonlinear Multicarrier Schemes." Doctoral thesis, 2016. http://hdl.handle.net/10362/19916.
Full textAbstract:
It is widely recognized that multicarrier systems such as orthogonal frequency division
multiplexing (OFDM) are suitable for severely time-dispersive channels. However, it is
also recognized that multicarrier signals have high envelope fluctuations which make them especially sensitive to nonlinear distortion effects. In fact, it is almost unavoidable to have nonlinear distortion effects in the transmission chain. For this reason, it is essential to have a theoretical, accurate characterization of nonlinearly distorted signals not only to evaluate the corresponding impact of these distortion effects on the system’s performance, but also to develop mechanisms to combat them. One of the goals of this thesis is to address these challenges and involves a theoretical characterization of nonlinearly distorted multicarrier signals in a simple, accurate way.
The other goal of this thesis is to study the optimum detection of nonlinearly distorted,
multicarrier signals. Conventionally, nonlinear distortion is seen as a noise term
that degrades the system’s performance, leading even to irreducible error floors. Even
receivers that try to estimate and cancel it have a poor performance, comparatively to the performance associated to a linear transmission, even with perfect cancellation of nonlinear distortion effects. It is shown that the nonlinear distortion should not be considered as a noise term, but instead as something that contains useful information for detection purposes. The adequate receiver to take advantage of this information is the optimum receiver, since it makes a block-by-block detection, allowing us to exploit the nonlinear distortion which is spread along the signal’s band. Although the optimum receiver for nonlinear multicarrier schemes is too complex, due to its necessity to compare the received signal with all possible transmitted sequences, it is important to study its potential performance gains. In this thesis, it is shown that the optimum receiver outperforms the conventional detection, presenting gains not only relatively to conventional receivers that deal with nonlinear multicarrier signals, but also relatively to conventional receivers that deal with linear, multicarrier signals. We also present sub-optimum receivers which are able to approach the performance gains associated to the optimum detection and that can even outperform the conventional linear, multicarrier schemes.
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Zhang, Heng. "High Performance RF and Basdband Analog-to-Digital Interface for Multi-standard/Wideband Applications." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8609.
Full textAbstract:
The prevalence of wireless standards and the introduction of dynamic
standards/applications, such as software-defined radio, necessitate the next generation
wireless devices that integrate multiple standards in a single chip-set to support a variety
of services. To reduce the cost and area of such multi-standard handheld devices,
reconfigurability is desirable, and the hardware should be shared/reused as much as
possible. This research proposes several novel circuit topologies that can meet various
specifications with minimum cost, which are suited for multi-standard applications. This
doctoral study has two separate contributions: 1. The low noise amplifier (LNA) for the
RF front-end; and 2. The analog-to-digital converter (ADC).
The first part of this dissertation focuses on LNA noise reduction and linearization
techniques where two novel LNAs are designed, taped out, and measured. The first LNA,
implemented in TSMC (Taiwan Semiconductor Manufacturing Company) 0.35Cm
CMOS (Complementary metal-oxide-semiconductor) process, strategically combined an
inductor connected at the gate of the cascode transistor and the capacitive cross-coupling
to reduce the noise and nonlinearity contributions of the cascode transistors. The proposed technique reduces LNA NF by 0.35 dB at 2.2 GHz and increases its IIP3 and
voltage gain by 2.35 dBm and 2dB respectively, without a compromise on power
consumption. The second LNA, implemented in UMC (United Microelectronics
Corporation) 0.13Cm CMOS process, features a practical linearization technique for
high-frequency wideband applications using an active nonlinear resistor, which obtains a
robust linearity improvement over process and temperature variations. The proposed
linearization method is experimentally demonstrated to improve the IIP3 by 3.5 to 9 dB
over a 2.5–10 GHz frequency range. A comparison of measurement results with the prior
published state-of-art Ultra-Wideband (UWB) LNAs shows that the proposed linearized
UWB LNA achieves excellent linearity with much less power than previously published
works.
The second part of this dissertation developed a reconfigurable ADC for multistandard
receiver and video processors. Typical ADCs are power optimized for only one
operating speed, while a reconfigurable ADC can scale its power at different speeds,
enabling minimal power consumption over a broad range of sampling rates. A novel
ADC architecture is proposed for programming the sampling rate with constant biasing
current and single clock. The ADC was designed and fabricated using UMC 90nm
CMOS process and featured good power scalability and simplified system design. The
programmable speed range covers all the video formats and most of the wireless
communication standards, while achieving comparable Figure-of-Merit with customized
ADCs at each performance node. Since bias current is kept constant, the reconfigurable
ADC is more robust and reliable than the previous published works.