Browsing by Subject "Compression"
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Item Compression of a context-based marshalling methodology in Java(2016-12) Harrod, Ryan William; Khurshid, SarfrazThis report focuses on a method for serializing messages in Java which is somewhere between a customized solution and Java’s built-in serialization. Customized serialization will lead to the fastest, most optimized code, but will require more development time. Java’s built in serialization, on the other hand, requires almost no effort to use but is slow, and uses more than is strictly necessary. This project gives a third option which requires a little more effort than Java’s built in serialization, but still provides fast serialization speed, and low message sizes. The tool presented here can take in requirements for a message to transmit, which includes numbers, strings, booleans, and enumerations, and the output is a collection of Java classes which will serialize and deserialize that message. In turn, this generated library can be shared between projects within an organization, or even with third parties. The original message definition becomes a sort of interface control document, while the resulting code becomes a library which can be used to communicate with the defined messages, without requiring users of that message to develop their own code.Item Dynamic Response Of Complex Materials Under Shock Loading(2012-10-19) Arman, BedriWe investigated dynamic response of Cu46Zr54 metallic glass under adiabatic planar shock wave loading (one-dimensional strain) with molecular dynamics simulations, including Hugoniot (shock) states, shock-induced plasticity, and spallation. The Hugoniot states are obtained up to 60 GPa along with the von Mises shear flow strengths, and the dynamic spall strengths, at different strain rates and temperatures. For the steady shock states, a clear elastic-plastic transition is identified. The local von Mises shear strain analysis is used to characterize local deformation, and the Voronoi tessellation analysis, the corresponding local structures at various stages of shock, release, tension and spallation. The plasticity in this glass, manifested as localized shear transformation zones, is of local structure rather than thermal origin, and void nucleation occurs preferentially at the highly shear-deformed regions. The Voronoi and shear strain analyses show that the atoms with different local structures are of different shear resistances that lead to shear localization. Additionally, we performed large-scale molecular dynamics simulations to investigate plasticity in Cu/Cu46Zr54 glass nanolaminates under uniaxial compression. Partial and full dislocations are observed in the Cu layers, and screw dislocations, near the amorphous?crystalline interfaces (ACIs). Shear bands are directly induced by the dislocations in the crystalline Cu layer through ACIs, and grow from the ACIs into the glass layers and absorb ambient shear transformation zones. Plasticity in the glass layers is realized via pronounced, stable shear banding. As the last part of the dissertation, we investigated with nonreactive molecular dynamics simulations, the dynamic response of phenolic resin and its carbon-nanotube (CNT) composites to shock wave compression. For phenolic resin, our simulations yielded shock states in agreement with experiments on similar polymers, except the "phase change" observed in experiments, indicating that such phase change is chemical in nature. The elastic?plastic transition is characterized by shear stress relaxation and atomic-level slip, and phenolic resin shows strong strain hardening. Shock loading of the CNT-resin composites was applied parallel or perpendicular to the CNT axis, and the composites demonstrated anisotropy in wave propagation, yield and CNT deformation. Our simulations suggested that the bulk shock response of the composites depends on the volume fraction, length ratio, impact cross-section, and geometry of the CNT components; the short CNTs in current simulations had insignificant effect on the bulk response of resin polymer.Item Foveated video compression for lossy packet networks(2010-12) Larcom, Ronald Craig; Bovik, Alan C. (Alan Conrad), 1958-; Caramanis, ConstantineUnreliable networks can severely hamper transmission of video data. In applications requiring minimal latency, video frames must be compressed using intraframe techniques. We develop a video codec suitable for robot teleoperation over unreliable networks with high packet loss rates. The codec combines a foveated image compression algorithm, Embedded Foveation Image enCoding (EFIC), with a Forward Error Correction (FEC) code tuned to network performance. Foveation, or spatially variant image resolution, allows very high compression levels while preserving the most important image characteristics. By tightly integrating an FEC within the codec we are able to virtually eliminate dropped frames independent of the network protocol. We find that the new codec supports much higher video quality than another intraframe compression technique, Motion JPEG (M-JPEG).Item Implementation and analysis of eidochromatic transform for color image compression(Texas Tech University, 2005-05) Shrivastava, Prateek; Mitra, Sunanda; Karp, Tanja; Nutter, BrianWith increasing use of color images for various applications, transmitting them quickly and with high fidelity has been possibly the greatest challenge today. In order to achieve this objective, the image has to be compressed to the greatest extent with the loss of as little image information as possible. Many current popular color image coding formats enhance the compression by the use of a color component transform, which reduces the redundancy across the three color channels and a subsequent transform, which relates the values of pixels in a single color channel at proximate but different locations. The objective of this thesis work has been to reduce the redundancies in all the color planes using a recent transform which translates into a better compression performance for a color image compression codec. The emphasis has been to optimize the novel Hybrid Vector Scalar Quantizer (HVSQ). To achieve this objective, a spatio-chromatic transform called Eidochromatic transform has been studied and implemented. This transform step is performed after the color transform to luminance-chrominance plane and their subsequent wavelet transform. The tests performed have shown that eidochromatic transform concentrates the energy in particular bands in the chrominance channels. Also discussed are classes of images on which this algorithm shows significant Peak Signal to Noise Ratio (PSNR) improvement and some of its limitations.Item Implementation and analysis of eidochromatic transform for color image compression(2005-05) Shrivastava, Prateek; Mitra, Sunanda; Karp, Tanja; Nutter, BrianWith increasing use of color images for various applications, transmitting them quickly and with high fidelity has been possibly the greatest challenge today. In order to achieve this objective, the image has to be compressed to the greatest extent with the loss of as little image information as possible. Many current popular color image coding formats enhance the compression by the use of a color component transform, which reduces the redundancy across the three color channels and a subsequent transform, which relates the values of pixels in a single color channel at proximate but different locations. The objective of this thesis work has been to reduce the redundancies in all the color planes using a recent transform which translates into a better compression performance for a color image compression codec. The emphasis has been to optimize the novel Hybrid Vector Scalar Quantizer (HVSQ). To achieve this objective, a spatio-chromatic transform called Eidochromatic transform has been studied and implemented. This transform step is performed after the color transform to luminance-chrominance plane and their subsequent wavelet transform. The tests performed have shown that eidochromatic transform concentrates the energy in particular bands in the chrominance channels. Also discussed are classes of images on which this algorithm shows significant Peak Signal to Noise Ratio (PSNR) improvement and some of its limitations.Item Investigation of fixation of the disrupted pubic symphysis using multiple prosthetics in cadaveric models(Texas Tech University, 2005-05) Francis, Nathan R.; Hashemi, Javad; Dabezies, Eugene J.; Burton, Thomas D.This thesis presents the results from a research project involved with the development of new prosthetics used to stabilize disrupted pubic symphysis. This work has been performed and documented to set the foundation for future developments in the area. The focus of the research was on developing a method for testing the human cadaveric pelvis under static conditions, which includes the design and manufacturing of a test setup, assembling of precision measurement tools, and a data acquisition system. The initial phase of the project dealt with the analysis of the intact pelvis and a commonly used prosthetic. The static testing of the intact and stabilized pelves are then compared to published results, which tested for the displacement at a load of 300 N. The second phase of the project dealt with the testing of a newly developed prosthetic device used for stabilization. The mean compliance was determined for all fixation devices as well as the intact symphysis in order to determine whether the locking plate was able to limit the motion per force better than the compression plate. The displacement data and the compliance coefficient data provided evidence that the locking plate assembly is more apt to limit motion in the pubic symphysis. The compliance coefficients were compared using the cadaver information. The weight of a specimen played a role in the compliance coefficient. The heavier a specimen was, the lower the compliance coefficient for the inferior pubic symphysis. There was a gender based difference in the compliance ratios of the intact pubic symphysis. The male pelves had a mean inferior compliance of -.5308 microns/N, where the female pelvis was -.0921 microns/N. The sex based difference was not statistically significant but shows a direction for future research.Item Investigation of fixation of the disrupted pubic symphysis using multiple prosthetics in cadaveric models(2005-05) Francis, Nathan R.; Hashemi, Javad; Dabezies, Eugene J.; Burton, Thomas D.This thesis presents the results from a research project involved with the development of new prosthetics used to stabilize disrupted pubic symphysis. This work has been performed and documented to set the foundation for future developments in the area. The focus of the research was on developing a method for testing the human cadaveric pelvis under static conditions, which includes the design and manufacturing of a test setup, assembling of precision measurement tools, and a data acquisition system. The initial phase of the project dealt with the analysis of the intact pelvis and a commonly used prosthetic. The static testing of the intact and stabilized pelves are then compared to published results, which tested for the displacement at a load of 300 N. The second phase of the project dealt with the testing of a newly developed prosthetic device used for stabilization. The mean compliance was determined for all fixation devices as well as the intact symphysis in order to determine whether the locking plate was able to limit the motion per force better than the compression plate. The displacement data and the compliance coefficient data provided evidence that the locking plate assembly is more apt to limit motion in the pubic symphysis. The compliance coefficients were compared using the cadaver information. The weight of a specimen played a role in the compliance coefficient. The heavier a specimen was, the lower the compliance coefficient for the inferior pubic symphysis. There was a gender based difference in the compliance ratios of the intact pubic symphysis. The male pelves had a mean inferior compliance of -.5308 microns/N, where the female pelvis was -.0921 microns/N. The sex based difference was not statistically significant but shows a direction for future research.Item IP Routing Table Compression Using TCAM and Distance-one Merge(2011-02-22) Bollapalli, Kalyana ChakravarthyIn 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.Item On the crushing of honeycomb under axial compression(2010-12) Wilbert, Adrien; Kyriakides, S.; Ravi-Chandar, KrishnaswamyThis thesis presents a comprehensive study of the compressive response of hexagonal honeycomb panels from the initial elastic regime to a fully crushed state. Expanded aluminum alloy honeycomb panels with a cell size of 0.375 in (9.53 mm), a relative density of 0.026, and a height of 0.625 in (15.9 mm) are laterally compressed quasi statically between rigid platens under displacement control. The cells buckle elastically and collapse at a higher stress due to inelastic action. Deformation then first localizes at mid-height and the cells crush by progressive formation of folds; associated with each fold family is a stress undulation. The response densifies when the whole panel height is consumed by folds. The buckling, collapse, and crushing events are simulated numerically using finite element models involving periodic domains of a single or several characteristic cells. The models idealize the microstructure as hexagonal, with double walls in one direction. The nonlinear behavior is initiated by elastic buckling while inelastic collapse that leads to the localization observed in the experiments occurs at a significantly higher load. The collapse stress is found to be mildly sensitive to various problem imperfections. For the particular honeycomb studied, the collapse stress is 67% higher than the buckling stress. It was also shown that all aspects of the compressive behavior can be reproduced numerically using periodic domains with a fine mesh capable of capturing the complexity of the folds. The calculated buckling stress is reduced when considering periodic square domains as the compatibility of the buckles between neighboring cells tends to make the structure more compliant. The mode consisting of three half waves is observed in every simulation but its amplitude is seen to be accented at the center of the domains. The calculated crushing response is shown to better resemble measured ones when a 4x4 cell domain is used, which is smoother and reproduces decays in the amplitude of load peaks. However, the average crushing stress can be captured with engineering accuracy even from a single cell domain.Item Pressure Drop and Filtration through Fibrous Porous Media on the Sump Strainer of Light Water Reactors(2014-12-15) Lee, SayaFibrous porous media has been found in a variety of industrial applications including filters and insulation materials. In nuclear power plants, fibrous media are found as insulation materials to prevent heat loss and protect the containment structures and other components from thermal effects. However, in spite of efficient thermal insulation, fibrous media have been focused on as a hazard in the Emergency Core Cooling Systems (ECCSs). Fibrous debris generated from fiberglass insulation materials during a Loss of Coolant Accident (LOCA) might accumulate on the containment sump strainer causing loss of Net Positive Suction Head (NPSH), called the upstream effect, or it might penetrate through the strainer becoming a source of clogging for flow channels in the core (downstream effect). In the present work, head loss through fibrous porous media made of the same fiberglass insulation material used in pressurized water reactors (PWRs) were experimentally investigated to study upstream effects. Porosity of fibrous porous media was also considered by measuring build-up of debris beds. In order to study downstream effects, quantity of debris bypass was examined by changing the type of water, concentration of debris, fluid approach velocity, and temperature. As results, a head loss model, a compression model, and a debris bypass model were proposed for the given conditions in this study. Additionally, a microscope system was developed to characterize size distribution of irregular-shaped fibrous debris. The methodology was applied to three samples and the maximum fraction of debris bypass was found in the size range of 10 to 250 ?m.Item Viscoelastic characterization of polyurea based polymers(2007-05) Chakkarapani, Venkatasubbarao; Liechti, K.M.; Ravi-Chandar, K.Several formulations of sprayed polyurea were considered as an alternative to cast polyurea. Based on results from confined compression experiments on these materials, TRI – 25 was selected as the best alternative material on account of its good flow characteristics at lower stresses. The constitutive behavior of this formulation has been determined using confined relaxation and Arcan relaxation experiments. Bulk relaxation modulus and shear relaxation modulus were obtained in the form of Prony series. The thermal shift factor for bulk relaxation was fitted with the Arrhenius equation while for shear relaxation, the trend was fitted with the WLF equation. The nonlinear response at ambient conditions was predicted using the modified free volume model (Park et al., 2004). Calibration factors for the nonlinear model were obtained using bulk data from confined compression under ramp loading and Arcan shear. The prediction of uniaxial tensile test followed the experimental response closely while the compressive response followed it with stress and strain shifts, suggesting that the voids in the material could shift the compressive response of the material.