Engineering Commons^™

Kinetic Characterization For Pretreatment Of Timber Varieties And Switchgrass Using Diluted Acid Hydrolysis, Shu Chiang Yat

Dissertations, Master's Theses and Master's Reports - Open

In recent years, growing attention has been devoted to the use of lignocellulosic biomass as a feedstock to produce renewable carbohydrates as a source of energy products, including liquid alternatives to fossil fuels. The benefits of developing woody biomass to ethanol technology are to increase the long-term national energy security, reduce fossil energy consumption, lower greenhouse gas emissions, use renewable rather than depletable resources, and create local jobs. Currently, research is driven by the need to reduce the cost of biomass-ethanol production. One of the preferred methods is to thermochemically pretreat the biomass material and subsequently, enzymatically hydrolyze the pretreated …

Enzyme Engineering Of Aminotransferases For Improved Activity And Thermostability, Abraham Rogelio Mártin García

Dissertations, Master's Theses and Master's Reports - Open

The production by biosynthesis of optically active amino acids and amines satisfies the pharmaceutical industry in its demand for chiral building blocks for the synthesis of various pharmaceuticals. Among several enzymatic methods that allow the synthesis of optically active aminoacids and amines, the use of minotransferase is a promising one due to its broad substrate specificity and no requirement for external cofactor regeneration. The synthesis of chiral compounds by aminotransferases can be done either by asymmetric synthesis starting from keto acids or ketones, and by kinetic resolution starting from racemic aminoacids or amines.

The asymmetric synthesis of substituted (S)-aminotetralin, an …

Development And Modeling Of Thermally Conductive Resins For Fuel Cell Bipolar Plate Applications, Michael G. Miller

Dissertations, Master's Theses and Master's Reports - Open

Thermally conductive resins are a class of material that show promise in many different applications. One growing field for their use is in the area of bipolar plate technology for fuel cell applications. In this work, a LCP was mixed with different types of carbon fillers to determine the effects of the individual carbon fillers on the thermal conductivity of the composite resin. In addition, mathematical modeling was performed on the thermal conductivity data with the goal of developing predictive models for the thermal conductivity of highly filled composite resins.

Shear Band Evolution In Zr/Hf-Based Bulk Metallic Glasses Under Static And Dynamic Indentations, Hongwen Zhang

Dissertations, Master's Theses and Master's Reports - Open

Bulk metallic glasses (BMGs) exhibit superior mechanical properties as compared with other conventional materials and have been proposed for numerous engineering and technological applications. Zr/Hf-based BMGs or tungsten reinforced BMG composites are considered as a potential replacement for depleted uranium armor-piercing projectiles because of their ability to form localized shear bands during impact, which has been known to be the dominant plastic deformation mechanism in BMGs. However, in conventional tensile, compressive and bending tests, limited ductility has been observed because of fracture initiation immediately following the shear band formation. To fully investigate shear band characteristics, indentation tests that can confine …

Time-Domain Models For Power System Stability And Unbalance, Ramanathan Arunachalam

Dissertations, Master's Theses and Master's Reports - Open

It is an important and difficult challenge to protect modern interconnected power system from blackouts. Applying advanced power system protection techniques and increasing power system stability are ways to improve the reliability and security of power systems. Phasor-domain software packages such as Power System Simulator for Engineers (PSS/E) can be used to study large power systems but cannot be used for transient analysis. In order to observe both power system stability and transient behavior of the system during disturbances, modeling has to be done in the time-domain. This work focuses on modeling of power systems and various control systems in …

Study Of And Design Procedure For Dual Circularly Polarized Waveguide Slot Arrays, Lee M. Paulsen

Dissertations, Master's Theses and Master's Reports - Open

For the past sixty years, waveguide slot radiator arrays have played a critical role in microwave radar and communication systems. They feature a well-characterized antenna element capable of direct integration into a low-loss feed structure with highly developed and inexpensive manufacturing processes. Waveguide slot radiators comprise some of the highest performance—in terms of side-lobe-level, efficiency, etc. — antenna arrays ever constructed.

A wealth of information is available in the open literature regarding design procedures for linearly polarized waveguide slots. By contrast, despite their presence in some of the earliest published reports, little has been presented to date on array designs …

Reducing Main Memory Access Latency Through Sdram Address Mapping Techniques And Access Reordering Mechanisms, Jun Shao

Dissertations, Master's Theses and Master's Reports - Open

As the performance gap between microprocessors and memory continues to increase, main memory accesses result in long latencies which become a factor limiting system performance. Previous studies show that main memory access streams contain significant localities and SDRAM devices provide parallelism through multiple banks and channels. These locality and parallelism have not been exploited thoroughly by conventional memory controllers. In this thesis, SDRAM address mapping techniques and memory access reordering mechanisms are studied and applied to memory controller design with the goal of reducing observed main memory access latency.

The proposed bit-reversal address mapping attempts to distribute main memory accesses …

Optimal Beam Forming For Laser Beam Propagation Through Random Media, Baoyong Liu

Dissertations, Master's Theses and Master's Reports - Open

Focusing optical beams on a target through random propagation media is very important in many applications such as free space optical communica- tions and laser weapons. Random media effects such as beam spread and scintillation can degrade the optical system's performance severely. Compensation schemes are needed in these applications to overcome these random media effcts. In this research, we investigated the optimal beams for two different optimization criteria: one is to maximize the concentrated received intensity and the other is to minimize the scintillation index at the target plane. In the study of the optimal beam to maximize the weighted …

Porous Silicon Technology For Integrated Microsystems, Jin Zheng Wallner

Dissertations, Master's Theses and Master's Reports - Open

With the development of micro systems, there is an increasing demand for integrable porous materials. In addition to those conventional applications, such as filtration, wicking, and insulating, many new micro devices, including micro reactors, sensors, actuators, and optical components, can benefit from porous materials. Conventional porous materials, such as ceramics and polymers, however, cannot meet the challenges posed by micro systems, due to their incompatibility with standard micro-fabrication processes. In an effort to produce porous materials that can be used in micro systems, porous silicon (PS) generated by anodization of single crystalline silicon has been investigated.

In this work, the …

Integrated Solar Energy And Absorption Cooling Model For Hvac (Heating, Ventilating, And Air Conditioning) Applications In Buildings, Sharizal Shaik Ahmedullah

Dissertations, Master's Theses and Master's Reports - Open

The demands in production and associate costs at power generation through non renewable resources are increasing at an alarming rate. Solar energy is one of the renewable resource that has the potential to minimize this increase. Utilization of solar energy have been concentrated mainly on heating application. The use of solar energy in cooling systems in building would benefit greatly achieving the goal of non-renewable energy minimization.

The approaches of solar energy heating system research done by initiation such as University of Wisconsin at Madison and building heat flow model research conducted by Oklahoma State University can be used to …

Flow Simulation For Optimized Performance Of Displacement Pumps Manufactured By Engineered Machined Products, Jordan D. Bilyeu

Dissertations, Master's Theses and Master's Reports - Open

No abstract provided.

Experimental And Modeling Study Of The Filtration And Oxidation Characteristics Of A Diesel Oxidation Catalyst And A Catalyzed Particulate Filter, Kiran C. Premchand

Dissertations, Master's Theses and Master's Reports - Open

A diesel oxidation catalyst (DOC) with a catalyzed diesel particulate filter (CPF) is an effective exhaust aftertreatment device that reduces particulate emissions from diesel engines, and properly designed DOC-CPF systems provide passive regeneration of the filter by the oxidation of PM via thermal and NO₂/temperature-assisted means under various vehicle duty cycles. However, controlling the backpressure on engines caused by the addition of the CPF to the exhaust system requires a good understanding of the filtration and oxidation processes taking place inside the filter as the deposition and oxidation of solid particulate matter (PM) change as functions of loading …

Aerothermodynamic Cycle Analysis Of A Dual-Spool, Separate-Exhaust Turbofan Engine With An Interstage Turbine Burner, Ka Heng Liew

Dissertations, Master's Theses and Master's Reports - Open

This study focuses on a specific engine, i.e., a dual-spool, separate-flow turbofan engine with an Interstage Turbine Burner (ITB). This conventional turbofan engine has been modified to include a secondary isobaric burner, i.e., ITB, in a transition duct between the high-pressure turbine and the low-pressure turbine. The preliminary design phase for this modified engine starts with the aerothermodynamics cycle analysis is consisting of parametric (i.e., on-design) and performance (i.e., off-design) cycle analyses.

In parametric analysis, the modified engine performance parameters are evaluated and compared with baseline engine in terms of design limitation (maximum turbine inlet temperature), flight conditions (such as …

Fluidic Oscillator Design For Water Removal Enhancement In A Pem Fuel Cell, Sheng Han Tseng

Dissertations, Master's Theses and Master's Reports - Open

This research initiative was triggered by the problems of water management of Polymer Electrolyte Membrane Fuel Cell (PEMFC). In low temperature fuel cells such as PEMFC, some of the water produced after the chemical reaction remains in its liquid state. Excess water produced by the fuel cell must be removed from the system to avoid flooding of the gas diffusion layers (GDL). The GDL is responsible for the transport of reactant gas to the active sites and remove the water produced from the sites. If the GDL is flooded, the supply gas will not be able to reach the reactive …

Emission Cross Sections For Neutral Xenon Impacted By Xe+ And Xe2+, Jason D. Sommerville

Dissertations, Master's Theses and Master's Reports - Open

Ion impact emission cross sections for eleven transitions from the 5p⁵6p configuration to the 5p⁵6s configuration of neutral xenon occurring in the spectral region between 700 nm and 1000 nm have been measured experimentally. Collisions between both singly- and doublyionized xenon and neutral xenon have been studied. These cross sections are of primary use in the development of a spectrographic diagnostic for Hall effect thruster plasma. A detailed discussion of the experimental methods and the subsequent data reduction is included. The results are presented and the importance of these data for spectrographic emission models of Hall …