In recent years, the engineering community has focused attention on selecting durable and low maintenance materials. As a result of recent advances in steel fabrication technologies, stainless steel has risen as a valuable alternative to regular carbon steel for heavy structural elements in addition to the traditional light gage structural elements of common use. The objective of this investigation is to summarize the existing literature concerning on the behavior of cold formed and hot rolled, annealed stainless steel members undergoing axial compression forces. Research related to the subject will be summarized as well as available design practice codes, from where applicable expressions will be investigated and used to perform practical examples.

The design of non-classical materials, such as multifunctional energetic materials and/or the synthesis of high pressure phases rely on the understanding of the mechanisms responsible for shock-induced reactions in powder mixtures. The critical reactant powder configurational changes and mechanical mixing processes necessary for reaction initiation have yet to be determined. Consequently, shock-induced reactions have only been observed in select material systems under certain conditions, and remain an uncontrolled phenomenon. Shock-induced reactions in nickel and aluminum powder mixtures are investigated in this work through the use of instrumented gas-gun experiments performing time-resolved pressure and shock velocity measurements to determine the pressure-volume (P-V) shock compressibility (Hugoniot) of the mixture, from which evidence of reaction is inferred through deviations from the inert shock response calculated on the basis of mixture theory. The role of particle size and morphology on non-diffusional mixing and chemical reactivity is explored by conducting similar tests on micron-scale powders of spherical and plate-like (flake) shape. Recovery experiments performed just below the reaction threshold provide information about the densification and mixing behavior between reactants. Discrete-component numerical simulations of the shock-compression of powder mixtures are performed to reveal the micromechanics of particle deformation, and mechanisms of mass-flow and mixing that can lead to the formation of reaction products. The results obtained from time-resolved measurements, recovery experiments, and numerical simulations are coupled to model the linkages between starting powder configuration, mechanically-driven mixing, and chemical reactivity. The knowledge gained from this investigation will lead to understanding of reaction mechanisms, and the control over reaction initiation threshold, time and exothermicity, in addition to characteristics of reaction products formed. The scientific understanding attained will advance the design and application of multifunctional materials for next generation energetic applications, and/or the synthesis of novel materials.

This thesis presents an efficient buffer management scheme for 3-D graphic rendering systems. The purpose of this scheme is to reduce the off-chip memory accesses, which have become a valuable resource, and very often a performance bottleneck of embedded 3-D applications. The 3-D buffers, including depth and color frame buffers, will be divided into rectangular blocks. The proposed scheme can first provide the management of buffer clear operation. For most of time, the rendering of each 3-D frame starts from the buffer clear command to clear the data remaining in buffers from the previous frame. Instead of clearing the buffers residing in the off-chip memory immediately, our scheme will just set the clear flag in an on-chip buffer management table which provides a control information entry for each of the blocks in the buffer. When the blocks have to be accessed later during rendering process, they won¡¦t be brought in from on-chip memory; instead, they are cleared directly in the corresponding cache location. When the cache blocks are replaced, the corresponding off-chip buffer blocks will be updated. Only those blocks in the off-chip color buffer which are not visited will be actually cleared when the color frame is swapped for display. The second contribution of the propose management scheme is to compress and decompress the depth blocks to save the transfer data amount of these blocks. Since the difference of the depth values of the neighboring pixels belonging to the same triangle plane will be the same, this difference value can be stored and encoded along with the run-length information which can lead to significant saving of the storage space. The actual reduction ratio depends on the relative object complexity to the output screen size, the block size, and the degree of the anti-aliasing considered. However, our experimental results show that the compression ratio of 17-28% can be achieved for the moderate block size. The entire buffer management has been implemented, and the entire gate count is 65k, which is about 10% of the entire 3-D systems. The proposed management chip is very suitable for embedded 3D graphic rendering systems where the memory bandwidth budget is very tightly restricted.

Compression tests along the rolling and normal direction of AZ31B plate materials under 10 s strain rate were performed at room temperature to understand the effect of grain size on the formation of deformation twins. When compressed along the rolling direction, tension twins were formed in bands. Within the twin bands, nearly all grains contained tension twins, irrespective of grain size. And outside the bands, no twin was found. Under this deformation condition, grain size has no effect on the formation of tension twins. The reason for this is due to the fact that the formation of a tension twin can trigger the formation of tension twin in the neighboring grain, irrespective of the neighboring grain size. When compressed along the normal direction, no twin band was formed, and compression twins were formed evenly in the specimens. Under this deformation condition, it was found that the larger the grain size, the higher the fraction of grains which contained compression twins. This result indicates that compression twins are easier to be formed in the large grains.

Twin-screw multiphase pumps experience a severe decrease in efficiency, even the breakdown of pumping function, when operating under wet gas conditions. Additionally, field operations have revealed significant vibration and thermal issues which can lead to damage of the pump internals and expensive repairs and maintenance. There are limited models simulating the performance of twin-screw pump under these conditions. This project develops a pump-user oriented simulator to model the performance of twin-screw pumps under wet gas conditions. Experimental testing is conducted to verify the simulation results. Based on the simulations, an innovative solution is presented to improve the efficiency and prevent the breakdown of pumping function. A new model is developed based upon a previous Texas A&M twin-screw pump model. In this model, both the gas slip and liquid slip in the pump clearances are simulated. The mechanical model is coupled with a thermodynamic model to predict the pressure and temperature distribution along the screws. The comparison of experimental data and the predictions of both isothermal and non-isothermal models show a better match than previous models with Gas Volume Fraction (GVF) 95% and 98%. Compatible with the previous Texas A&M twin-screw pump model, this model can be used to simulate the twin-screw pump performance with GVF from 0% to 99%. Based on the effect of liquid viscosity, a novel solution is investigated with the newly developed model to improve the efficiency and reliability of twin-screw pump performance with GVF higher than 94%. The solution is to inject high viscosity liquid directly into the twin-screw pump. After the simulations of several different scenarios with various liquid injection rates and injection positions, we conclude that the volumetric efficiency increases with increasing liquid viscosity and injecting liquid in the suction is suggested.

This study investigates the changes due to crosslinking treatment in stiffness, permeability, and glycosaminoglycan (GAG) content of bovine intervertebral discs. The objective of this study was to determine the mechanical and biochemical effects of crosslinking treatment on lumbar bovine tissue. Previous studies have found that crosslinking can increase stiffness and permeability in the intervertebral disc. These changes have not yet been investigated by confined compression, stress-relaxation tests of young bovine tissue. Eleven lumbar motion segments were harvested from calf spines and soaked in a saline solution or one of four crosslinking treatments (genipin, methylglyoxal, proanthrocyanidin, and EDC). Five mm diameter samples were removed from the midannulus region at anterior / anterior-lateral locations, confined in a saline bath, swelled to equilibrium, and tested in confined compression stress-relaxation to 15% strain in 5% increments. Radial samples were also harvested, treated with saline solution and EDC, and tested in the same manner. The aggregate modulus and hydraulic permeability were calculated using the nonlinear biphasic theory. Swelling pressure was calculated as the load at swelling equilibrium. GAG content was measured using the dimethylmethylene blue assay. Differences with P value < 0.05 were considered significant. In the axial orientation, all crosslinking treatments except methyglyoxal at least doubled the aggregate modulus relative to soaked controls (P less than 0.05). Genipin treatment resulted in 78% lower axial permeability, proanthrocyanidin (PA) 50% lower, and EDC treatment 84% lower relative to soaked controls (P &lt; 0.05). GAG content measured in the methyglyoxal treatment group was 25% lower than in soaked control group. Genipin (G), proanthrocyanidin (PA), and EDC treatment increased the swelling pressure by at least 65% (P less than 0.05). In the radial orientation, EDC treatment increased the stiffness by 75%, and did not significantly affect the permeability or swelling pressure. Some crosslinking treatments proved effective in increasing the stiffness and swelling pressure of the disc. The increased swelling pressure in G, PA, and EDC treatment groups relative to soaked controls suggests reduced GAG leaching during soaking treatment, further confirmed by the reduction in permeability in these groups.

In an attempt to slow the exhaustion of the Internet Protocol (IP) address space, Class-less Inter-Domain Routing (CIDR) was proposed and adopted. However, the decision to utilize CIDR also increases the size of the routing table, since it allows an arbitrary partitioning of the routing space. We propose a scheme to reduce the size of routing table in the CIDR context. Our approach utilizes a well-known and highly efficient heuristic to perform 2-level logic minimization in order to compress the routing table. By considering the IP routing table as a set of completely specified logic functions, we demonstrate that our technique can achieve about 25% reduction in the size of IP routing tables, while ensuring that our approach can handle routing table updates in real-time. The resulting routing table can be used with existing routers without needing any change in architecture. However, by realizing the IP routing table as proposed in this thesis, the implementation requires less complex hardware than Ternary CAM (TCAM) which are traditionally used to implement IP routing tables. The proposed architecture also reduces lookup latency by about 46%, hardware area by 9% and power consumed by 15% in contrast to a TCAM based implementation.

In our research, aluminum (1050) was deformed by plane strain compression (PSC) up to 65% reduction. The total deformation conditions include four temperatures (from 150oC to 300oC) and two strain rates (5¡Ñ10-2s-1 and 5¡Ñ10-4s-1). After the deformation, the specimens were examined by TEM for observing the morphology of the microstructures and measuring various parameters, which includes the sizes and aspect ratios of dislocation cells, as well as the distribution of misorientation angles for dislocation walls. At last, the proportions of GNBs and IDBs were tried to be determined.

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In this dissertation, several GA-based approaches for fractal image compression and active contour model are proposed. The main drawback of the classical fractal image compression is the long encoding time. Two methods are proposed in this dissertation to solve this problem. First, a schema genetic algorithm (SGA), in which the Schema Theorem is embedded in GA, is proposed to reduce the encoding time. In SGA, the genetic operators are adapted according to the Schema Theorem in the evolutionary process performed on the range blocks. We find that such a method can indeed speedup the encoder and also preserve the image quality. Moreover, based on the self-similarity characteristic of the natural image, a spatial correlation genetic algorithm (SC-GA) is proposed to further reduce the encoding time. There are two stages in the SC-GA method. The first stage makes use of spatial correlations in images for both the domain pool and the range pool to exploit local optima. The second stage is operated on the whole image to explore more adequate similarities if the local optima are not satisfactory. Thus not only the encoding speed is accelerated further, but also the higher compression ratio is achieved, because the search space is limited relative to the positions of the previously matched blocks, fewer bits are required to record the offset of the domain block instead of the absolute position. The experimental results of comparing the two methods with the full search, traditional GA, and other GA search methods are provided to demonstrate that they can indeed reduce the encoding time substantially. The main drawback of the traditional active contour model (ACM) for extracting the contour of a given object is that the snake cannot converge to the concave region of the object under consideration. An improved ACM algorithm is proposed in this dissertation to solve this problem. The algorithm is composed of two stages. In the first stage, the ACM with traditional energy function guides the snake to converge to the object boundary except the concave regions. In the second stage, for the control points which stay outside the concave regions, a proper energy template are chosen and are added in the external energy. The modified energy function is applied so as to move the snake toward the concave regions. Therefore, the object of interest can be completely extracted. The experimental results show that, by using this method, the snake can indeed completely extract the boundary of the given object, while the extra cost is very low. In addition, for the problem that the snake cannot precisely extract the object contour when the number of the control points on the snake is not enough, a GA-based ACM algorithm is presented to deal with such a problem. First the improved ACM algorithm is used to guide the snake to approximately extract the object boundary. By utilizing the evolutionary strategy of GA, we attempt to extract precisely the object boundary by adding a few control points into the snake. Similarly, some experimental results are provided to show the performance of the method.