This thesis investigates lattice compression of polynomial matrices over finite fields. For an m x n matrix, the goal of lattice compression is to find an m x (m+k) matrix, for some relatively small k, such that the lattice span of two matrices are equivalent. For any m x n polynomial matrix with degree bound d, it can be compressed by multiplying by a random n x (m+k) matrix B with degree bound s. In this thesis, we prove that there is a positive probability that L(A)=L(AB) with k(s+1)=\Theta(\log(md)). This is shown to hold even when s=0 (i.e., where B is a matrix of constants). We also design a competitive probabilistic lattice compression algorithm of the Las Vegas type that has a positive probability of success on any input and requires O~(nm^{\theta-1}B(d)) field operations.

L’utilisation et la mise au point de polymères renforcés sont des activités déjà anciennes et de nombreuses études leur ont déjà été consacrées. Parallèlement à l’utilisation des matières plastiques la question de leur recyclage se pose avec de plus en plus d’acuité. Le travail présenté cherche à comprendre le rôle d’un renfort constitué d’écorce de riz sur le comportement mécanique d’un mélange de polyoléfines. Un plan d’expérience est construit sur la base 1) de mélanges de polyoléfines recyclés 2) d’ajout d’écorce de riz et 3) d’ajout d’agent compatibilisant et 4) sur le mode d’élaboration par injection ou compression. L’adhérence de l’écorce de riz avec la matrice polymère a été examinée en relation avec sa microstructure et sa composition. Il est mis en évidence que l’addition d’écorce de riz seule réduit les propriétés de traction mais que l’addition d’agent compatibilisant favorise la déformation du polymère. La différence est notable entre les valeurs des propriétés de traction des éprouvettes élaborées par injection ou par compression. Cependant, les résultats peuvent être comparés valablement à l’aide d’un paramètre « capacité de charge » que nous proposons comme le rapport entre la tension maximale et la déformation maximale qui renseigne sur la capacité globale de résistance et de déformation aux conditions à rupture. Du point de vue du processus physico-chimique on peut conclure que l’addition de compatibilisant améliore l’adhérence entre les composants polymères et de l’écorce de riz, et par voie de conséquence la surface de rupture. L’indice de « capacité de charge » que nous proposons pourrait être considéré comme un facteur de conception pertinent. / The use and development of reinforced polymers are long-standing activities and many studies have already been done on the subject. With the development of the use of plasticsthe question of recycling becomes more and more acute. The work presented here reflects these concerns by seeking to understand the role of a reinforcement consisting of rice husk on the mechanical behavior of a mixture of polyolefins. The experimental design which was used was built on the base 1) of polyolefin blends 2) the addition of rice wheat and 3) the addition of compatibilizer and 4) the mode of preparation by injection or compression. The adhesion of rice husk with the polymer matrix has been examined in relation to its microstructure and composition. It was also revealed that the addition of rice wheat alone reduces the tensile properties but that the addition of compatibilizer promotes the deformation of the polymer blend. A noticeable difference was found between tensile properties of specimens prepared by injection or compression. However, the results can be validly compared if we introduce a parameter called "load capacity" that we propose as the ratio between the maximum voltage and maximum strain which provides information on the overall ability of strength and deformation conditions at fracture. From the standpoint of physical-chemical process it can be concluded that the addition of compatibilizer improves the adhesion between the polymer components and rice wheat and consequently the fracture surface. The index of "load capacity" that we propose could be considered a relevant design factor. / El uso y desarrollo de plásticos reforzados son actividades sobre las cuales se han publicado muchos estudios y con ello, la cuestión del reciclaje se vuelve cada vez un tema mas critico. El trabajo aquí presentado refleja esta preocupacion al tratar deentender el papel de la cáscara de arroz como elemento reforzante en el comportamiento mecánico de una mezcla de poliolefinas. El diseño experimental que se utilizó fue construido en la base 1) de mezclas de poliolefinas con reciclado depolietileno de baja densidad 30%, 40% de polietileno de alta densidad y polipropileno 30% correspondiente a la composición de los plásticos reciclados en Arequipa, Perú, 2) la adición de cáscara de arroz y 3) la adición de compatibilizante y 4) el modo depreparación, por inyección o compresión. Los resultados confirman que la cáscara de arroz es térmicamente estable hasta 250 º C. Su adhesión con la matriz polimérica se ha examinado en relación con su microestructura y composición. También se reveló que la adición de cáscara de arroz solo reduce las propiedades de tracción, pero que la adición de compatibilizante promueve la deformación de la mezcla del polímero. Una notable diferencia se encontró entre las propiedades de tracción de las muestras preparadas por inyección o compresión. Sin embargo, los resultados pueden ser validados por comparación si se introduce un parámetro llamado "capacidad de carga" que se propone como la relación entre la resistencia máxima y la deformación máxima hasta la ruptura que puede soportar. Desde el punto de vista del proceso físico-químico, se puede concluir que la adición de compatibilizante mejora la adhesión entre los componentes de polímero y la cáscara de arroz y por ende la calidad de la superficie de fractura. Los compuestos preparados puede ser una alternativa para la recuperación de residuos plásticos y agrícolas. El índice de "capacidad de carga" que proponemos podría ser considerado un factor de diseño pertinente para este tipo de materiales.

Images are forming an increasingly large part of modern communications, bringing the need for efficient and effective compression. Many techniques developed for this purpose include transform coding, vector quantization and neural networks. In this thesis, a new neural network method is used to achieve image compression. This work extends the use of 2-layer neural networks to a combination of cascaded networks with one node in the hidden layer. A redistribution of the gray levels in the training phase is implemented in a random fashion to make the minimization of the mean square error applicable to a broad range of images. The computational complexity of this approach is analyzed in terms of overall number of weights and overall convergence. Image quality is measured objectively, using peak signal-to-noise ratio and subjectively, using perception. The effects of different image contents and compression ratios are assessed. Results show the performance superiority of cascaded neural networks compared to that of fixedarchitecture training paradigms especially at high compression ratios. The proposed new method is implemented in MATLAB. The results obtained, such as compression ratio and computing time of the compressed images, are presented.

During hot days, gas turbine power output deteriorates significantly. Among various means to augment gas turbine output, inlet air fog cooling is considered as the simplest and most costeffective method. During fog cooling, water is atomized to micro-scaled droplets and introduced into the inlet airflow. In addition to cooling the inlet air, overspray can further enhance output power by intercooling the compressor. However, there are concerns that the water droplets might damage the compressor blades and increased mass might cause potential compressor operation instability due to reduced safety margin. Furthermore, the two-phase flow thermodynamics during wet compression in a rotating system has not been fully established, so continued research and development in wet compression theory and prediction model are required. The objective of this research is to improve existing wet compression theory and associated models to accurately predict the compressor and the entire gas turbine system performance for the application of gas turbine inlet fog cooling. The following achievements have been accomplished: (a) At the system level, a global gas turbine inlet fog cooling theory and algorithm have been developed and a system performance code, FogGT, has been written according to the developed theory. (b) At the component level, a stage-stacking wet compression theory in the compressor has been developed with known airfoil configurations. (c) Both equilibrium and non-equilibrium water droplet thermal-fluid dynamic models have been developed including droplet drag forces, evaporation rate, breakup and coalescence. A liquid erosion model has also been developed and incorporated. (d) Model for using computational fluid dynamics (CFD) code has been developed to simulate multiphase wet compression in the rotating compressor stage. In addition, with the continued increase in volatility of natural gas prices as well as concerns regarding national energy security, this research has also investigated employing inlet fogging to gas turbine system fired with alternative fuels such as low calorific value synthetic gases. The key results include discovering that the saturated fogging can reduce compressor power consumption, but overspray, against conventional intuition, actually increases compressor power. Nevertheless, inlet fogging does increase overall net power output.

Image-related communications are forming an increasingly large part of modern communications, bringing the need for efficient and effective compression. Image compression is important for effective storage and transmission of images. Many techniques have been developed in the past, including transform coding, vector quantization and neural networks. In this thesis, a novel adaptive compression technique is introduced based on adaptive rather than fixed transforms for image compression. The proposed technique is similar to Neural Network (NN)-based image compression and its superiority over other techniques is presented It is shown that the proposed algorithm results in higher image quality for a given compression ratio than existing Neural Network algorithms and that the training of this algorithm is significantly faster than the NN based algorithms. This is also compared to the JPEG in terms of Peak Signal to Noise Ratio (PSNR) for a given compression ratio and computational complexity. Advantages of this idea over JPEG are also presented in this thesis.

"Liquid piston gas compression utilizes a liquid to directly compress gas. The benefit of this approach is that liquid can conform to irregular compression chamber volume. The compression chamber is divided into many small little bores in order to increases the surface area to volume ratio. The heat transfer rate increases with increasing surface area to volume ratio. However, as the bore diameter becomes smaller, the viscous force increases. In order to maximize the heat transfer rate and to minimize the viscous force, computational fluid dynamics is used. ANSYS Fluent is used to simulate the liquid piston gas compression cycle. Having created the model in Fluent, different factors, including diameter, length, liquid temperature, and the acceleration are varied in order to understand how each factor affects the heat transfer and viscous energy loss. The results show that both viscous force and heat transfer rate increase as the diameter decreases. The viscous force increases and the heat transfer decreases as the length increases. Both the viscous force and heat transfer increase as the acceleration increases. The viscous force decreases as the liquid temperature increases. Results show that the highest compression efficiency of 86.4% is found with a 3mm bore radius and a short cylinder. The piston acceleration is advised to be below 0.5g in order to avoid surface instability problem."

No description available.

The regular representation of the symmetric group Sn is a vector space of dimension n! with many interesting invariant subspaces. The projections of a vector onto these subspaces may be computed by first considering projections onto certain basis elements in the subspace and then recombining later. If all of these projections are kept, it creates an explosion in the size of the data, making it difficult to store and work with. This is a study of techniques to compress this computed data such that it is of the same dimmension as the original vector.

When a structural element is acted upon by axial compressive force simultaneously with bending, the design must consider the effect of combined bending and compression. Hence, the structure should be designed with the consideration of bending moment in order to provide the enough design strength to the member. The main objective of this thesis is to compare the effect of interaction of flexural moment and axial compressive force on the regular column of the steel moment frame with the same column when cantilever section is introduced into the frame as the loading is kept constant in all three cases. In this work, STAAD is used to determine the required variables such as axial forces, bending moments and deformations in all the cases, and those values are used in approximate second order analysis for the further analysis of special steel moment frame. The calculated values are then plugged into the design interaction equation for combined flexure and compression as given by AISC Steel Construction Manual (2011) to check the criticality of the moment frame. The result of the analysis indicates that the regular frame model has higher demand of capacity ratio in design of columns than the one with cantilever projection.

In this work we investigate adaptive techniques which can be used to improve the performance of highly scalable video compression schemes under resolution scaling. We propose novel content adaptive methods for motion compensated 3D discrete wavelet transformation (MC 3D-DWT) of video. The proposed methods overcome problems of ghosting and non-aligned aliasing artifacts, which can arise in regions of motion model failure, when the video is reconstructed at reduced temporal or spatial resolutions. We also study schemes which facilitate simultaneous scaling of compressed video bitstreams based on both constant bit-rate and constant distortion criteria, using simple and generic scaling operations. In regions where the motion model fails, the motion compensated temporal discrete wavelet transform (MC TDWT) causes ghosting artifacts under frame-rate scaling, due to temporal lowpass filtering along invalid motion trajectories. To avoid ghosting artifacts, we adaptively select between different lowpass filters, based on a local estimate of the motion modelling accuracy. Experimental results indicate that the proposed adaptive transform substantially removes ghosting artifacts while also preserving the high compression efficiency of the original MC TDWT. We also study the impact of various MC 3D-DWT structures on spatial scalability. Investigating the interaction between spatial aliasing, scalability and energy compaction shows that the t+2D structure essentially has higher compression efficiency. However, where the motion model fails, structures of this form cause non-aligned aliasing artifacts under spatial scaling. We propose novel adaptive schemes to continuously adapt the structure of MC 3D-DWT based on information available within the compressed bitstream. Experimental results indicate that the proposed adaptive structure preserves the high compression efficiency of the t+2D structure while also avoiding the appearance of non-aligned aliasing artifacts under spatial scaling. To provide simultaneous rate and distortion scaling, we study ???layered substream structure. Scaling based on distortion generates variable bit-rate traffic which satisfies the desired average bit-rate and is consistent with the requirements of leaky-bucket traffic models. We propose a novel method which also satisfies constraints on instantaneous bit-rate. This method overcomes the weakness of previous methods with small leaky-bucket buffer sizes. Simulation results indicate promising performance with both MC 3D-DWT interframe and JPEG2000 intraframe compression.