No description available.

No description available.

The goals of this thesis are to modify a full-scale personal hovercraft to perform autonomous maneuvers on flat ground, develop a first principles of the craft, and present data on the vehicle behavior in field trials. The hovercraft, initially designed for manual control by a rider, was modified both physically and with software to allow for remote and autonomous operation. The design leverages the actuator control solutions that are already implemented on the hovercraft for ease of installation and control. A key modification made in the design is the addition of auxiliary fans to increase overall thrust. Controller designs are presented to manage the rotation rate of the added fans. The purpose of the dynamic model is to assist in the design and evaluation of model-based controllers for the vehicle speed and heading. A first principles model was developed to give an approximate understanding of the vehicle's behavior. Data collected during field trials was used to challenge the assumptions made in the first principles model. Based on the field data, the model was updated to provide a better basis to evaluate model based controllers. Additionally, several key observations about the hovercraft performance were noted during the field trials. Controlling the vehicle heading is a nontrivial task and will require a responsive and authoritative controller / Master of Science / Hovercraft are useful vehicles because they can travel over many terrains, including water and land, without being impacted severely by friction. However, they also have several drawbacks including being difficult to steer and having insufficient thrust to scale a steep incline. To address these concerns, we present a design for a modified hovercraft that is capable of being steered with a remote control or with autonomy software. Additionally, eight fans were added to increase the overall thrust of the vehicle to allow it to drive uphill. A model of the hovercraft dynamics was made to allow us to study its behavior. Field trials were conducted to collect data on the hovercraft's performance from the onboard sensors. This data was used to improve the dynamic model so that it can be used in the future to decide the best control design for the hovercraft steering.

Visualization of large amounts of simulation data is important for the understanding of most physical phenomena. The limited capabilities of desktop machines make them unsuitable for handling excessive amounts of simulation data. The present day high speed networks have made it possible to remotely visualize the data being generated by a supercomputer in real time. In order for such a system to be reliable, a robust communication protocol and an efficient compression mechanism are needed. This work presents a remote visualization system that addresses these issues, and emphasizes the design and implementation of the application level network protocol. A control theory based adaptive rate control algorithm is presented for UDP streams that maximizes the effective throughout experienced by the stream while minimizing the packet loss. The algorithm is shown to make the system responsive to changing network conditions. This makes the system deployable over any network, including the Internet. / Master of Science

Yes

This thesis dwells on two important problems in the field of video coding; namely rate control and spatial domain intra prediction. While the former is applicable generally to most video compression standards, the latter applies to recent advanced video compression standards such as H.264, VC1 and AVS. Rate control regulates the instantaneous video bit-rate to maximize a picture quality metric while satisfying channel rate and buffer size constraints. Rate control has an important bearing on the picture quality of encoded video. Typically, a quality metric such as Peak Signal-to-Noise ratio (PSNR) or weighted signal-to-noise ratio (WSNR) is chosen out of convenience. However neither metric is a true measure of perceived video quality. A few researchers have attempted to derive rate control algorithms with the combination of standard PSNR and ad-hoc perceptual metrics of video quality. The concept of using perceptual criterion for video coding was introduced in [7] within the context of perceptual adaptive quantization. In this work, quantization noise levels were adjusted such that more noise was allowed where it was less visible (busy and textured areas) while sensitive areas (typically flat and low detail regions) were finely quantized. Macro–blocks were classified into low detail, texture and edge areas depending on a classifier that studied the variance of sub-blocks within a macro-block (MB). The Rate models were trained from training sets of pre -classified video. One drawback of the above scheme as with standard PSNR was that neither accounts for the perceptual effect of motion. The work in [8] achieved this by assigning higher weights to the regions of the image that were experiencing the highest motion. Also, the center of the image and objects in the foreground are perceived as more important than the sides. However, attempts to use perceptual metrics for video quality have been limited by the accuracy of the video quality metrics chosen. In the recent years, new and improved metrics of subjective quality have been invented and their statistical accuracy has been studied in a formal manner. Particularly interesting is the work undertaken by ITU and the Video quality experts group (VQEG). VQEG conducted two phases of testing; in the first pha se, several algorithms were tested but they were not found to be very accurate, in fact none were found to be any more accurate than PSNR based metric. In the second phase of testing a few years later, a few new algorithms were experimented with, and it wa s concluded that four of these did achieve results good enough to warrant their standardization as a part of ITU –T Recommendation J.144. These experiments are referred to as the FR-TV (Full Reference Television) phase-II evaluations. ITU-T J.144 does not explicitly identify a single algorithm but provides guidelines on the selection of appropriate techniques to objectively measure subjective video quality. It describes four reference algorithms as well as PSNR. Amongst the four, the NTIA General Video Quality Model (VQM), [11] is the best performing and has been adopted by American National Standards Institute (ANSI) as a North American standard T1.801.03. NTIA’s approach has been to focus on defining parameters that model how humans perceive video quality. These parameters have been combined using linear models to produce estimates of video quality that closely approximate subjective test results. NTIA General Video Quality Model (VQM) has been proven to have strong correlation with subjective quality. In the first part of the thesis, we apply metrics motivated by NTIA-VQM model within a rate control algorithm to maximize perceptual video quality. We derive perceptual weights using key NTIA parameters to influence QP value used to decide degree of quantization. Our experiments demonstrate that a perceptual quality motivated standard TMN8 rate control in an H.263 encoder results in perceivable quality improvements over a baseline TMN8 rate control algorithm that uses a PSNR metric. Our experimental results on a set of 11 sequences show on an average reduction of 6% in bitrate using the proposed algorithm for the same perceptual quality as standard TMN-8. The second part of our thesis work deals with spatial domain intra prediction used in advance video coding standard such as H.264. The H.264 Advanced Video coding standard [36] has been shown to achieve video quality similar to older standards such as MPEG2 and H.263 at nearly half the bit-rate. Generally, this compression improvement is attributed to several new tools that were introduced in H.264 – including spatial intra prediction, adaptive block size for motion compensation, in-loop de-blocking filter, context adaptive binary arithmetic coding (CABAC), and multiple reference frames. While the new tools allow better coding efficiency, they also introduce additi onal computational complexity at both encoder and decoder ends. We are especially concerned here on the impact of Intra prediction on the computational complexity of the encoder. H.264 reference implementations such as JM [29] search through all allowed intra-rediction “modes” in order to find the optimal mode. While this approach yields the optimal prediction mode, it comes at an extremely heavy computational cost. Hence there is a lot of interest into well -motivated algorithms that reduce the computational complexity of the search for the best prediction mode, while retaining the quality advantages of full-search Intra4x4. We propose a novel algorithm to reduce the complexity of full search by exploiting our knowledge of the source statistics. Specifically, we analyze the transform domain energy distribution of the original 4x4 block in different directions and use the results of our analysis to eliminate unlikely modes and reduce the search space for the optimal I ntra mode. Experimental results show that the proposed algorithm achieves quality metrics (PSNR) similar to full search at nearly a third of the complexity. This thesis has four chapters and is organized as follows, in the first chapter we introduce basics of video encoding and subsequently present exiting work in the area of perceptual rate control and introduce TMN-8 rate control algorithm in brief. At the end we introduce spatial domain intra prediction. In the second chapter we explain the challenges present in combining NTIA perceptual parameters with TMN8 rate control algorithm. We examine perceptual features used by NTIA from a video compression perspective and explain how the perceptual metrics capture typical compression artifacts. We next present a two pass perceptual rate control (PRCII) algorithm. Finally, we list experimental results on set of video sequences showing on an average of 6% bit-rate reduction by using PRC-II rate control over standard TMN-8 rate control. Chapter 3 contains part-II of our thesis work on, spatial domain intra prediction . We start by reviewing existing work in intra prediction and then present the details of our proposed intra prediction algorithm and experimental results. We finally conclude this thesis in chapter 4 and discuss direction for the future work on both our proposed algorithms.

Every runner faces changes in speed and slope while exercising. While running faster or on a steepier surface represent different stimuli, both conditions lead to an increase in metabolic demand and therefore in heart rate (HR). The control of HR is given by both neural and non-neural components and can be accessed analyzing the heart rate variability (HRV). During exercise, HRV is known to be influenced by both sympathetic and parasympathetic branches of the autonomic nervous system, by breathing frequency, cadence, amongst other components. Hence, the present study sought to address how changes in speed and slope during running impact HR and HRV and whether the patterns observed for a restricted population were applicable to a broader group. We collected ECG records from volunteers divided into 2 groups: Experiment 1 (N = 12, with a broader range of ages and fitness level) and Experiment 2 (N = 9, composed of a more homogeneous population). Subjects ran on 9 (Experiment 1) or 16 (Experiment 2) combinations of speed and slope for a few minutes. Our data shows that the relationship between slope (%), relative speed (v) and relative HR is HR = 0.36 + 0.643 * v + 0.033 * s * v . HR behaved as predicted by a general equation of cost of locomotion in mammals and avians when it comes to the proportional impact of speed and slope, but not regarding the magnitude of such responses. This must reflect the loss of linearity between metabolic demand and HR at very high exercise intensities. Changes in HR could explain the behavior of most HRV estimators. However, one estimator (a1ApEn) could better be explained by changes in speed and slope. This indicates that HRV responds primarily to metabolic demand. The same general pattern of response of HRV to the different running conditions was observed in both groups, although, likely due to age-associated changes in cardiac control, how much a given HRV estimators changes differ between groups / Todo corredor se depara com mudanças de velocidade (v) e inclinação (i) durante o exercício. Correr mais rápido ou em uma superfície mais íngreme representam estímulos diferentes, porém ambos levam a um aumento na demanda metabólica e, portanto, na freqüência cardíaca (FC). O controle da FC é dado por componentes neurais e não neurais e pode ser acessado analisando-se a variabilidade da frequência cardíaca (VFC). Durante o exercício a VFC é influenciada pelos ramos simpático e parassimpático, freqüência ventilatória, cadência, dentre outros componentes. Assim, buscamos abordar como mudanças de velocidade e inclinação durante a corrida impactam a FC e a VFC e se os padrões observados para uma população restrita aplicam-se à um grupo mais amplo. Foram coletados registros de ECG de voluntários divididos em 2 grupos: Experimento 1 (N = 12, com faixa etária e nível de condicionamento físico mais amplos) e Experimento 2 (N = 9, composto por uma população mais homogênea). Os voluntários correram em 9 (Experimento 1) ou 16 (Experimento 2) combinações de velocidade e inclinação por alguns minutos. Nossos dados mostram que a relação entre inclinação (%), velocidade relativa (v) e FC relativa é FC = 0.36 + 0.643 * v + 0.033 * s * v . A FC se comportou como previsto por uma equação geral do custo de locomoção em mamíferos e aves quando se trata do impacto proporcional de velocidade e inclinação, mas não em relação à magnitude de tais respostas. Isso deve refletir a perda de linearidade entre a demanda metabólica e a FC em intensidades de exercício muito altas. Mudanças na FC explicam o comportamento da maioria dos estimadores de VFC. No entanto, um estimador (a1ApEn) foi melhor explicado por mudanças de velocidade e inclinação. Isso indica que a VFC responde principalmente à FC. O mesmo padrão de resposta da VFC às diferentes condições de corrida foi observado em ambos os grupos, embora, possivelmente devido à mudanças no controle cardíaco associadas à idade, o quanto um determinado estimadores se altera difere entre os grupos

" Three dimensional travel in immersive virtual environments (IVE) has been a difficult problem since the beginning of virtual reality (VR), basically due to the difficulty of designing an intuitive, efficient, and precise three degrees of freedom (DOF) interface which can map the user's finite local movements in the real world to a potentially infinite virtual space. Inspired by the Silver Surfer Sci-Fi movie and the popularity of the Nintendo Wii Balance Board interface, a surfboard interface appears to be a good solution to this problem. Based on this idea, I designed and developed a VR Silver Surfer system which allows a user to surf in the sky of an infinite virtual environment, using either an isometric balance board or an elastic tilt board. Although the balance board is the industrial standard of board interface, the tilt board seems to provide the user more intuitive, realistic and enjoyable experiences, without any sacrifice of efficiency or precision. To validate this hypothesis we designed and conducted a user study that compared the two board interfaces in three independent experiments that break the travel procedure into separate DOFs. The results showed that in all experiments, the tilt board was not only as efficient and precise as the balance board, but also more intuitive, realistic and fun. In addition, despite the popularity of the balance board in the game industry, most subjects in the study preferred the tilt board in general, and in fact complained that the balance board could have been the cause of possible motion sickness. "

<p>The packing and coding of digital video is a part of science where much innovation has taken place during the last few decades. The MPEG standards of video encoding are some of the most well-known and used video coding standards today. Since MPEG defines exact requirements for the decoder, but not the encoder, encoders can be made in many different ways and levels of complexity, as long as they produce legal MPEG streams that can be viewed on any MPEG-conformant decoder. This thesis will examine the possible performance of MPEG, in particular MPEG-1/MPEG-2 full TV resolution (720*576), for coding video at bitrates significantly lower than the 2-15 Mb/s MPEG-2 originally was designed for. For this purpose, encoding methods previously proposed by various researchers are presented. Furthermore a few new algorithms, which can be used for MPEG coding in general, but was constructed with a low-bitrate encoder in mind, were developed. Finally objective video quality benchmarks were conducted and the results evaluated.</p>

The packing and coding of digital video is a part of science where much innovation has taken place during the last few decades. The MPEG standards of video encoding are some of the most well-known and used video coding standards today. Since MPEG defines exact requirements for the decoder, but not the encoder, encoders can be made in many different ways and levels of complexity, as long as they produce legal MPEG streams that can be viewed on any MPEG-conformant decoder. This thesis will examine the possible performance of MPEG, in particular MPEG-1/MPEG-2 full TV resolution (720*576), for coding video at bitrates significantly lower than the 2-15 Mb/s MPEG-2 originally was designed for. For this purpose, encoding methods previously proposed by various researchers are presented. Furthermore a few new algorithms, which can be used for MPEG coding in general, but was constructed with a low-bitrate encoder in mind, were developed. Finally objective video quality benchmarks were conducted and the results evaluated.