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Articles 1 - 11 of 11
Full-Text Articles in Engineering
Technical Evaluation Of Hardwood Biorefinery Using The "Near-Neutral" Hemicellulose Extraction Process, Haibo Mao
Electronic Theses and Dissertations
A technical analysis was performed for a new process that produces ethanol and acetic acid from hardwood in addition to bleached hardwood Kraft pulp. The new process, termed the "near neutral" hemicellulose extraction process, involves the extraction of wood hemicellulose using green liquor prior to conventional Kraft pulping. This thesis assumes that the new process is located at an existing kraft pulp mill. Ancillary unit operations in the process include hydrolysis of the extracted carbohydrates using sulfuric acid, filtration of the extract to remove lignin that was extracted with the carbohydrates, liquid-liquid extraction of acetic acid and by-product furfural, liming …
Sub-Femtomolar Isothermal Desoprtion And Reaction Kinetics On Microhotplate Sensor Platforms, Amol G. Shirke
Sub-Femtomolar Isothermal Desoprtion And Reaction Kinetics On Microhotplate Sensor Platforms, Amol G. Shirke
Electronic Theses and Dissertations
The population of adsorbates on a semiconductor surface directly influences the physical and chemical properties of the semiconductor. In the case of a metal-oxide semiconductor, the adsorbing species can change its electrical conductivity, a phenomenon which forms the operating principle of gas sensors. The interaction of adsorbed oxygen species on a metaloxide surface with reducing or oxidizing gases leads to an increase or decrease in electrical conductivity respectively. Miniature gas sensors called microhotplates (developed at the National Institute of Standards and Technology) are excellent surface science tools to explore surface reactions on semiconducting metal-oxide films. This thesis outlines how the …
Kinetics And Mechanism Of Oxygen Delignification, Yun Ji
Kinetics And Mechanism Of Oxygen Delignification, Yun Ji
Electronic Theses and Dissertations
Considerable research has been conducted into the kinetics and selectivity of the oxygen delignification process to overcome limitation in its use. However most studies were performed in a batch reactor whereby the hydroxide and dissolved oxygen concentrations are changing during the reaction time in an effort to simulate tower performance in pulp mills. This makes it difficult to determine the reaction order of the different reactants in the rate expressions. Also the lignin content and cellulose degradation of the pulp are only established at the end of the experiment when the sample is removed from the batch reactor. To overcome …
Modification Of Semi-Metal Oxide And Metal Oxide Powders By Atomic Layer Deposition Of Thin Films, Mark Q. Snyder
Modification Of Semi-Metal Oxide And Metal Oxide Powders By Atomic Layer Deposition Of Thin Films, Mark Q. Snyder
Electronic Theses and Dissertations
This work describes two methods of modifying, and the subsequent characterizing of, oxide nanopowders. The first method, atomic layer deposition, or ALD, is a series of surface-limited reactions that are repeated to deposit a thin, inorganic film on the surface of the nanopowder. Deposition of a thin film is a useful method to alter the surface properties of a material while retaining its bulk properties. Part of this thesis concerns the understanding of the growth mechanism of thin film titanium nitride (a material known for thermal and chemical stability as well as electronic conductivity) on silica through the ALD process. …
Thermal Shock Fracture Behaviors Of Functionally Graded Ceramics, Wenjin Luo
Thermal Shock Fracture Behaviors Of Functionally Graded Ceramics, Wenjin Luo
Electronic Theses and Dissertations
This thesis uses a thermal fracture mechanics model to study the thermal shock fracture behavior of functionally graded ceramics (FGC). The specimen used in this study is a FGC strip with an edge crack on one surface. A severe thermal shock is applied on the cracked surface. The temperature field in a thermally shocked FGC strip is evaluated first using a closed form solution. Thermal stresses, thermal stress intensity factors (TSIF) and critical thermal shocks are evaluated using a thermomechanics and fracture mechanics approach. The effective thermal properties of the FGC specimens are estimated using micromechanics models for conventional composites. …
Seasonal Variations Of Pavement Layer Moduli Determined Using In Situ Measurements Of Pavement Stress And Strain, Lauren J. Swett
Seasonal Variations Of Pavement Layer Moduli Determined Using In Situ Measurements Of Pavement Stress And Strain, Lauren J. Swett
Electronic Theses and Dissertations
Pavement design procedures have advanced a great deal in recent years, changing from empirical equations based on road tests in the 1950s to mechanistic-empirical design procedures developed in the past few years. The resilient moduli for the asphalt and soil layers of pavement sections are important properties necessary for pavement design, and an accurate method for determining moduli under different conditions is necessary. The stiffness of pavement section layers changes with the season, and typically, a road section will be the weakest during spring thaw due to loss of frozen soil stiffness, and increases in water content. This is critical …
Mobilization Of Metals And Phosphorous From Intact Forest Soil Cores By Dissolved Inorganic Carbon: A Laboratory Column Study, Brett Holmes
Mobilization Of Metals And Phosphorous From Intact Forest Soil Cores By Dissolved Inorganic Carbon: A Laboratory Column Study, Brett Holmes
Electronic Theses and Dissertations
Dissolved inorganic carbon (DIC) causes increased mobilization of dissolved, organically bound and particulate aluminum (Al), calcium (Ca), iron (Fe), and phosphorus (P) from the soils. Our objective was to examine whether increased metal solubility is attributed to increased DIC concentration in solution. Intact soil cores of 16.35 - 24.10 cm were taken from the O and B horizons from the East and West Bear Brook Watershed in Maine (BBWM) to conduct seven soil column transport experiments. DIC concentrations ranging from approximately 20 to 600 ppm with a background electrolyte solution of 0.1 M NaCl were introduced into the soil columns. …
Developing Dns Tools To Study Channel Flow Over Realistic Plaque Morphology, Ryan M. Beaumont
Developing Dns Tools To Study Channel Flow Over Realistic Plaque Morphology, Ryan M. Beaumont
Electronic Theses and Dissertations
In a normal coronary artery, the flow is laminar and the velocity is parabolic in nature. Over time, plaques deposit along the artery wall, narrowing the artery and creating an obstruction, a stenosis. As the stenosis grows, the characteristics of the flow change and transition occurs, resulting in turbulent flow distal to the stenosis. To date, direct numerical simulation (DNS) of turbulent flow has been performed in a number of studies to understand how stenosis modifies flow dynamics. However, the effect of the actual shape and size of the obstruction has been disregarded in these DNS studies. An ideal approach …
High Temperature Compression Testing Of Monolithic Silicon Carbide (Sic), Adam L. Mcnaughton
High Temperature Compression Testing Of Monolithic Silicon Carbide (Sic), Adam L. Mcnaughton
Electronic Theses and Dissertations
High temperature compression tests were administered in an oxidizing atmosphere on a commercially available monolithic (un-reinforced) reaction bonded silicon carbide (RBSiC) and an in-house processed silicon carbide based on a pre-ceramic polymer precursor. Ceramics such as silicon carbide have exceptional mechanical properties for both structural and thermal load applications. High tolerance specimen preparation via diamond wheel cutting and grinding to allow for compression testing on both types of silicon carbide ceramic at temperatures ranging from 20°C (68°F) to 1000°C (1832°F) is also addressed. Two types of specimen geometry were chosen due to the high strength and high stiffness of silicon …
Photocatalytic Oxidation Of Carbon Monoxide Using Sputter Deposited Molybdenum Oxide Thin Films On A Silicon Dioxide Substrate, Donald Bragg
Photocatalytic Oxidation Of Carbon Monoxide Using Sputter Deposited Molybdenum Oxide Thin Films On A Silicon Dioxide Substrate, Donald Bragg
Electronic Theses and Dissertations
CO contamination is common in hydrogen extraction processes. Proton exchange membrane fuel cells need a source of hydrogen containing less than 10ppm of CO to avoid the irreversible poisoning of the fuel cell’s platinum anode. Platinum metal is commonly used as a catalyst for the purification of hydrogen gas. An effort has been put forth to replace the expensive platinum catalyst with a less expensive alternative. Photocatalytically active metal oxide semiconductors have shown promise as less expensive alternatives to platinum for redox reactions such as the oxidation of CO. This research studies a MoO3 sputter deposited thin film on a …
Mercury Dynamics In Sulfide-Rich Sediments: Geochemical Influence On Contaminant Mobilization And Methylation Within The Penobscot River Estuary, Maine, Usa, Karen A. Merritt
Mercury Dynamics In Sulfide-Rich Sediments: Geochemical Influence On Contaminant Mobilization And Methylation Within The Penobscot River Estuary, Maine, Usa, Karen A. Merritt
Electronic Theses and Dissertations
Research concerning the fate and biogeochemical cycling of mercury (Hg) within coastal ecosystems has suggested that microbially-mediated diagenetic processes control Hg mobilization and that ligands with strong affinity for Hg control Hg partitioning between the dissolved and particulate phases. Of specific further concern is the likelihood that Hg sequestered in coastal marine sediments may be efficiently methylated to highly toxic methylmercury (MeHg), thereby placing exposed organisms at significant risk of MeHg bioaccumulation. We have studied total dissolved Hg (HgT) and methylmercury (MeHg) cycling in the sediments of the Penobscot River estuary in Maine, USA using a combination of equilibrium porewater …