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Non-evaporable getters (NEG) are widely used in ultra high vacuum (UHV) systems for particle accelerators to assure distributed pumping speed. By heating the NEG to an activation temperature, the oxide layer on the surface dissolves into the material, leaving a clean (activated) surface. The activated NEG surface is capable of chemisorbing most of the residual gases present in a UHV system and will act as a vacuum pump. NEG can be sputter deposited on the inner wall of vacuum chambers, turning the whole wall from a source of gas into a pump. At the largest particle accelerator in the world, the Large Hadron Collider, more than 6 km of beam pipe has been NEG coated. In this work, a DC magnetron sputtering system dedicated for coating cylindrical vacuum chambers with NEG has been assembled, installed and commissioned. The system has been used to do NEG depositions on inner walls of vacuum chambers. The vacuum performance of the coating has been measured in terms of pumping speed, electron stimulated desorption and activation temperature. In addition, the thin film composition and morphology has been investigated by scanning electron microscopy (SEM). The work has resulted in an operational DC magnetron sputtering system, which can be used for further studies of NEG materials and compositions.

Title: The anthopometric relation to bench press performance and sticking region Objectives: The aim of the thesis is to determine the influence of anthropometric parameters on the performance in bench press and its critical phase of motion. Another objective of this work is to determine the differences of influence anthropometry between 1 RM, 4 RM, 8 RM and 12 RM as well as anthropometric impact on the area occurring before the critical phase of motion and on the area after the critical phase of motion. Methods: This is a quantitative research based on the comparison of measured anthropometric parameters with performance and kinematics by bench press analysis. For experimental methods it was used laboratory conditions and it was used methods of analysis to evaluate the acquired data. Results: The results of the work show that anthropometric parameters affect the performance especially at 1 RM and 12 RM. Overall, the forearm has the greatest impact, reaching a strong negative correlation r = -0.69. Lower arm abduction at 12 RM has a large correlation coefficient r = 0.68, and the chest ratio with upper limb length has a mean positive correlation r = 0.55 for 1 RM and 12 RM. The influence of anthropometry on the critical phase of motion has not been confirmed. Only the correlation between...

It is estimated that there are 5x1030 microorganisms on Earth and that approximately 50% live in unconsolidated sediment on the terrestrial subsurface. Subsurface disturbances caused by the constant search for natural resources and our dependence on groundwater make the abundance and diversity of these organisms a global concern. It is vital to many environmental fields, including bioremediation, water purification, and contaminant transport, that we understand how microorganisms and other colloidal particles attach to and detach from natural sediments and ultimately how they travel through porous media. Sticking efficiency (alpha) is a major component of most particle transport theories. It is defined as the ratio of particles that adhere to a collector surface compared to the total number of particles that collide with that surface. In this study, the Interaction Force Boundary Layer (IFBL) model was used to determine the sticking efficiencies of inorganic colloidal particles and Enterococcus faecalis cells against a silica glass collector surface. Sticking efficiencies were derived from intersurface potential energies that were determined from integrated force-distance data measured by Atomic Force Microscopy (AFM). Force data were measured in buffered aqueous solutions of varying pH and ionic strength to determine the influence of solution chemistry on particle removal from solution. Zeta-potentials were measured to determine the impact of particle and collector surface charge on force measurements. The results of this study indicate that alpha is strongly influenced by solution chemistry. The response of alpha to small changes in solution pH and ionic strength may be several orders of magnitude. Zeta-potential measurements imply that sticking efficiencies are strongly influenced by the electrical charges on both the particle and collector surfaces. Zeta-potentials of bacteria did not vary significantly with changing solution pH, but did respond to changing solution ionic strength. Historically, alpha has been very difficult to predict. This study is the first to report sticking efficiencies measured using AFM and the first to successfully apply the IFBL model to colloidal particles. Æ nThe incorporation of empirical nanoscale interactions into the measurement of alpha promises to more successfully describe particle adhesion and, thus, particle transport. / Ph. D.

Increasing commercial and military aircraft operations in arid environments are increasing the likelihood of sand and dust ingestion. Turbine engines are particularly susceptible to the ingestion of sand and dust, which can erode cold-section components and deposit onto hot-section components. Ultimately, the erosion and deposits will shorten the operational lifespan of these engines and limit their availability thereby increasing maintenance costs and risking safety. Mitigating these risks has become more prevalent in recent years due to increasing combustion temperatures in effort to increase fuel efficiency. Increasing combustion temperatures directly increases deposit formation onto hot-section components. Monitoring deposit formation on existing turbine engine platforms and improving deposit resilience on new designs has been the industry focus for the last two decades. This study focused on statistically modeling the initial onset of microparticle deposits onto an analogous hot-section surface. Generally, as deposits accumulate onto a hot-section surface, the existing deposit formation is more likely to bond with incoming particulate at a faster rate than an exposed bare surface. Predicting the initial deposits onto a bare surface can determine the accelerated deposition rate depending on subsequent particulate impinging onto the surface. To emulate the initial deposits, a HASTELLOY® X test coupon was exposed to 20 μm to 40 μm samples of Arizona Road Test Dust (ARD) at varying loadings and aerosol densities. The Virginia Tech Aerothermal Rig was used for all test scenarios at flow-particle temperatures between 1000°C to 1100°C. Several statistical models were developed as a function of many independent variables, culminating with a final sticking probability (SP) model. Overall, the SP of individual ARD particulate is a primary function of flow-particle temperature and normal impact momentum. Tangential impact momentum of a particle will decrease the SP, while surface temperatures reaching isothermal conditions with the flow will increase SP. However, there are specific cases where lower surface temperatures and high particle temperatures result in a high SP. Particle size was a strong predictor of SP where particles between 10 μm to 19 μm were 5 to 10 times greater than the 19 μm to 40 μm range. Additional studies will be necessary to examine some additional parameters that become more prominent with smaller particle sizes. Ultimately, the intention of the models is to assist turbine engine designers to improve resilience to deposit formation on hot-section components. / PHD / Dust ingestion by propulsion turbine engines can have severe negative implications on the operational safety of an aircraft. Recently, increased air traffic, both military and commercial, in desert regions has caused many aircraft engine designers to improve the resilience to dust ingestion effects. One of the detrimental mechanisms is hot particle deposits in the combustion and exhaust sections. This dissertation evaluates deposit formation using carefully developed high temperature experiments. In general, deposit formation can negatively change flow characteristics inside the engine that can limit available power and safety margins. Likewise, deposits can reduce or stop cooling needed for hot-section parts inside a jet engine. Hot-section components need cooling since the main gas path operation temperatures of a jet engine typically exceed the melting points of common high temperature metals. During dust ingestion events, deposits will initially adhere to a hot metallic or ceramic surface inside the engine. Subsequent deposit accumulation will occur at a faster rate since incoming particles will more readily adhere to existing deposits than to a metallic or ceramic surface. The experimental work in this dissertation focused only on quantifying the initial individual particle deposits on a HASTELLOY®-X surface between 1000°C to 1100°C. Arizona Road Dust was the particulate selected for all testing. The dust has sizes ranging between 10 µm to 40 µm. The sticking probability or the likelihood a particle would deposit per an impact was less than 5% for all tests performed. Particles smaller than 19 µm had a sticking probability up to 5% while larger particles were generally less than 3%. Effectively, this implies that the initial deposits onto a hot engine surface are strongly dependent on the smallest particles. Propulsion turbine engine designers can utilize this information to develop mitigation methods against deposit formation of the smallest particles that are ingested. Ultimately, the research presented in this work is intended to improve operational safety of current and future aircraft.

We use the first-principles molecular-dynamics¡@simulation method (MD), which is based on the density functional theory (DFT) with local-density approximation (LDA), to calculate the sticking property of a carbon atom on hydrogen covered C(100) surface. We focused on trajectories and kinetic energy transfer of the gas-phase C atom for four incident angles of =0, £k/8, £k/6 and £k/4. We find that the calculated trajectories and the kinetic energy transfer of the gas-phase atom, Cn, overall are not very sensitive to the change of the incident angle. The insensitivity of the sticking property on the incident angle may be due to a large chemisorption energy, which bends the trajectory of Cn toward the surface, so that Cn is confined to move within a small range.

The objective of this study uses the plasticity theory of the slab method and the numerical analysis of the finite difference method to construct a mathematical model. And a computer program will be developed to evaluate the quality of the tubes formed by hydraulic expansion. Considering sticking and sliding modes, a mathematical model is proposed to predict the forming pressure needed to hydroform a circular tube into square and rectangular cross-sections and the thickness distribution of the product. In the sticking friction mode, it is assumed that the elements after contact with the die do not move or slide. Whereas, in the sliding friction mode, the element in contact with the die will continue to deform with the stress variation in the subsequent forming process. A series of FE simulations on tube expansion by a commercial FE code¡§DEFORM¡¨have been carried out. In addition, the experiment employing aluminum alloy AA 6063 that has been annealed to proceed the hydraulic expansion experiment. The comparisons between analysis and the result of forming pressure, corner radius and thickness distribution by experiment are verified the validity of this mathematical model. The effects of the forming parameters such as the die geometry, the material property of the tube, friction coefficient between the die and tube, etc., upon the expansion results, such as the forming pressure, corner radius, the tube contact distance with the die, thickness distribution after expansion, etc., are systematically discussed.

Title: The effect of breathing technique on intra-thoracic pressure, kinematics of barbell, and muscle activity during bench press exercise. Objectives: The main aim of this study is to determine relationship between breathing technique and bench press exercise. Furthermore, determine which breathing modification leads to overcoming highest resistance and how each individual breathing techniques (Valsalva maneuver (VM), Hold breath (HB), Lung packing (PAC), "reversed breathing" (REVB)) affects kinematics of barbell, and muscle activity, during different intensity (1 RM, 4RM, 8RM, 12RM). Methods: Experiment of cross-sectional character, with usage of our-calibrated sensor, for intrathoracic pressure measurements, 3D kinematics with passive markers and surface electromyography. For measuring anthropometric measurements was further used goniometer, digital scale, and measuring tape. Comparisons of the breathing techniques was done by analysis of covariance ANOVA, while particular parameters were compared by Pearson correlation. Results: Except of REVB technique, which indicated significantly lower load, there was no significant difference between techniques in lifted resistance. Similar effect was observed at results of intrathoracic pressure, where REVB technique showed significantly lower pressure,...

Atomic Layer Deposition (ALD) of Al2O3 on tall multiwalled carbon nanotube forests shows concentration variation with the depth in the form of discrete steps. While ALD is capable of extremely conformal deposition in high aspect ratio structures, decreasing penetration depth has been observed over multiple thermal ALD cycles on 1.3 mm tall multiwalled carbon nanotube forests. SEM imaging with Energy Dispersive X-ray Spectroscopy elemental analysis shows steps of decreasing intensity corresponding to decreasing concentrations of Al2O3. A study of these steps suggests that they are produced by a combination of diffusion limited delivery of precursors with increasing precursor adsorption site density as discrete nuclei grow during the ALD process. This conceptual model has been applied to modify literature models for ALD penetration on high aspect ratio structures, allowing several parameters to be extracted from the experimental data. The Knudsen diffusion constant for trimethylaluminum (TMA) in these carbon nanotube forests has been found to be 0.3 cm2s-1. From the profile of the Al2O3 concentration at the steps, the sticking coefficient of TMA on Al2O3 was found to be 0.003.

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