The best estimate codes are used for licensing of Nuclear Power Plants (NPP), but with conservative assumptions. It is claimed that the uncertainties are covered by the conservatism of the calculation. Nowadays, it is possible to estimate certain parameters using non-conservative data with the complement of uncertainty evaluation, and these calculations can also be used for licensing. As NPPs are applying for power up-rates and life extension, new licensing calculations need to be performed. In this case, evaluation of the uncertainties could help improve the performance, while staying below the limit of the safety margins. Given the problem of unstable behavior of Boiling Water Reactors (BWR), which is known to occur at certain power and flow conditions, it could cause SCRAM and decrease the economic performance of the plant. Performing an uncertainty analysis for BWR stability would give better understating of the phenomenon and it would help to verify and validate (V&amp;V) the codes used to predict the NPP behavior. This thesis, reports a sensitivity/uncertainty study of numerical, neutronics, and thermal-hydraulics parameters on the prediction of the BWR stability within the framework of OECD Ringhals-1 (R1 stable reactor) and OECD Oskarshamn-2 (O2 unstable reactor) stability benchmarks. The time domain code TRACE/PARCS was used in the analyses. This thesis is divided in three parts: space-time convergence; uncertainty; sensitivity. A space-time convergence study was done for the numerical parameters (nodalization and time step). This was done by refining nodalization of all components and time step until obtaining space-time converged solution, i.e. further refinement doesn’t change the solution. When the space-time converged solutions were compared to the initial models, much better solution accuracy has been obtained for the stability measures (decay ratio and frequency), for both stable (R1) and unstable (O2) reactors with the space-time converged models. Further on, important neutronics and thermal-hydraulics parameters were identified and an uncertainty calculation was performed using the Propagation of Input Errors (PIE) methodology. This methodology, also known as the GRS method, has been used because it has been extensively tested and verified by the industry, and because it allows identifying the most influential parameters using the spearman rank correlation method. Using the uncertainty method’s results, an attempt has been done to identify the most influential parameters affecting the stability. A methodology using the spearman rank correlation coefficient has been implemented, which helps to identify the most influential parameters on the stability (decay ratio and frequency). Additional sensitivity calculations have been performed for better understanding of BWR stability and parameters that affect it. / <p>This work has been preformed thanks to the support of the Swedish Radiation Safety Authority (SSM) and EU project NURISP. QC 20121129</p>

Copper is a widely used conductor in the manufacture of printed wiring boards (PWB). The trends in miniaturization of electronic devices create increasing challenges to all electronic industries. In particular PWB manufacturers face great challenges because the increasing demands in greater performance and device miniaturization pose enormous difficulties in manufacturing and product reliability. Nanocrystalline and ultrafine grain copper can potentially offer increased reliability and functionality of the PWB due to the increases in strength and achievable wiring density by reduction in grain size. The first part of this thesis is concerned with the synthesis and characterization of nanocrystalline and ultra-fine grain-sized copper for potential applications in the PWB industry. Nanocrystalline copper with different amounts of sulfur impurities (25- 230ppm) and grain sizes (31-49nm) were produced and their hardness, electrical resistivity and etchability were determined. To study the thermal stability of nanocrystalline copper, differential scanning calorimetry and isothermal heat treatments combined with electron microscopy techniques for microstructural analysis were used. Differential scanning calorimetry was chosen to continuously monitor the grain growth process in the temperature range from 40C to 400C. During isothermal annealing experiments samples were annealed at 23C, 100C and 300C to study various potential thermal issues for these materials in PWB applications such as the long-term room temperature thermal stability as well as for temperature excursions above the operation temperature and peak temperature exposure during the PWB manufacturing process. From all annealing experiments the various grain growth events and the overall stability of these materials were analyzed in terms of driving and dragging forces. Experimental evidence is presented which shows that the overall thermal stability, grain boundary character and texture evolution of copper is greatly related to changes in driving and dragging forces, which in turn, are strongly depended on parameters such as annealing temperature and time, total sulfur impurity content and the distribution of the impurities within the material. It was shown that a simple increase in the sulfur impurity level does not necessarily improve the thermal stability of nanocrystalline copper.

A research program was undertaken to quantify the effect of flow induced erosion on the stability of natural river banks along the Red River in Winnipeg, Manitoba. The study correlated the percent decrease in factor of safety to intensity of river flow and duration. Two methods to quantify flow induced erosion were assessed, the first method based on observed erosion and the second on theoretically calculated erosion. The first method involved aligning annual historical river bank cross-sections and measuring the distance between cross-sections to represent the erosion induced from the flow year between successive cross-sections. Due to the fact there are no sites along the Red River regularly surveyed, the analysis did not provide for a correlation between erosion from a specific flow event to percent decrease in factor of safety. The second part involved the use of theoretical equations to quantify erosion given the river elevation of a specific flow year. The study showed a 1% to 8% decrease in factor of safety from low to high intensity flows and as high as 14.5% for high intensity flows of long duration. Additionally, the evolutionary stability of the riverbank was generated showing the percent decrease each year in factor of safety due to erosion and the years during which failure occurs. The results correlated well to the previous analysis showing a 1% to 5% decrease for low to high intensity flows respectively and as high as 10% for high intensities of long duration. / October 2007

Approximately 50% - 80% of the population will experience disabling low back pain at some point in their life. Assessing and developing interventions based on “lumbar stability” and/or joint stiffness to reduce low back pain has been a common research focus. Specific focus has been on identifying which muscles influence lumbar stability/stiffness, with one argument being between focusing training on the transverse abdominis and lumbar multifidus muscles versus broader training approaches involving the entire abdominal wall and erector spinae muscles. However, there has not been research on whether pain reduction was due to increased stability/stiffness or another mechanism. The main goals of this thesis were to determine the effect of individual muscles on stability/stiffness through a two phase process. In the first phase, a model sensitivity analysis was performed to assess the interactions of variables that influence the quantification of stability. Stability was quantified via the eigenvalues (EV) of the Hessian matrix of potential energies at each lumbar level and axis of rotation, for a total of 15 EVs (3 axes of rotation x 5 joints). In phase 2, assessment of clinical interventions on patients with low back pain designed to alter biomechanics was conducted to assess factors in stability/stiffness quantification and mechanisms of action in pain modulation. More detail of the study phases are described below, in order to test the following hypotheses: 1) It was hypothesized that individual muscles affect specific EVs, but no one muscle can be associated with one EV level. 2) It was hypothesized that specific muscles do affect specific planes of stability/stiffness. 3) It was hypothesized that EVs are affected by posture. 4) It was hypothesized that overactivating muscles by increasing muscle activation to 100% MVC negatively affects the EVs. 5) It was hypothesized that the relationship between muscles and specific EVs obtained during simulation remains with real subjects performing loaded tasks. 6) It was hypothesized that coaching and cueing specific movement patterns and motor patterns would alter pain in low back pain patients. 7) If hypothesis 6 is true, then it was hypothesized that changes in pain would be reflected in changes in EVs. Methods for Phase 1 The first phase involved a sensitivity analysis using an anatomically detailed spine model. Theoretical data including posture, motion and muscle activity were synthesized to include 23 static spine postures, including neutral, 0° - 50° flexion, 0° - 30° extension, 0° - 30° right and left lateral bend, and 0° - 40° right and left axial twist, all in increments of 10°. For each posture, all eleven muscles included in the model, some with several fascicles, were artificially activated to 50% MVC. A knockout approach ensued whereby activity in single muscles were systematically reduced to 0% MVC or increased to 100% MVC. The relationships between the 15 EVs and the changes in muscle activity and posture were assessed. This muscle knockout model was repeated with actual muscle activity values obtained from electromyographic (EMG) signals and postures obtained from four subjects who performed a walking task with a 15 kg load in each hand. Results for Phase 1 The sensitivity analysis showed that the abdominal muscles contribute a greater stabilizing effect on the L4 and L5 EVs, while the multifidus and erector spinae muscles contribute a greater effect on the L1, L2 and L3 EVs. When examining the effect of muscles on a specific plane in terms of influencing stability/stiffness, it was found that the abdominal muscles contribute a greater effect on the bend axis and twist axis EVs than the flexion axis EVs, while the erector spinae muscles contribute the greatest effect on the flexion axis EVs. Posture was found to have a biologically significant effect on EVs, with the 50° flexion and 30° extension postures having the most detrimental effect in terms of compromising stability/stiffness. In addition, when there was a 10° excursion in any axis, there was little change in the EVs, while postures at angles greater than this were often associated with decreases in stability/stiffness in some EVs. Increasing the muscle activation from 50% MVC to 100% MVC did not have a large effect on most EVs, but when there was a meaningful change, as defined by a change of 10% or greater in the EV, the 100% MVC activation level always resulted in more stability/stiffness at that particular EV. Finally, using actual EMG and lumbar angle patterns resulted in similar results as the theoretical data, as expected. Interpretation of these findings is limited by the following. Even though EVs changed, there is no guarantee that the magnitude of change in one EV could be interpreted to equal a similar magnitude of change in another EV, nor may it be assumed that EVs have a linear relationship with stability/stiffness. These results suggest that when the goal is to increase lumbar stability, a neutral spine should be maintained and activating the larger abdominal muscles is more important than activating the transverse abdominis or multifidus, as proposed by some clinical groups. Methods for Phase 2 Four case studies of individuals with chronic low back pain were recruited from whom kinematic, kinetic and EMG data were collected in addition to a measure of pain intensity using an 11-point verbal numerical rating scale. Pain provocation tests were performed by a clinician (professor Stuart McGill) to identify the motions, postures and loads that exacerbated their pain. Then these tasks were repeated while the motion and EMG data was collected. This was followed by interventions coached by the clinician that could include the abdominal brace (stiffening the abdominal wall), latissimus dorsi stiffening, incorporating a hip-hinge motion rather than spine bending, or any combination of these. The intention of the intervention was to immediately reduce pain intensity. These tasks arranged in a repeated measures design were assessed with the anatomically detailed spine model to calculate stability/stiffness from evaluation of the 15 EVs, lumbar compression and lumbar shear forces. Results for Phase 2 The results from phase 2 suggest that pain was sometimes reduced by altering motions, postures and load, but the mechanism of what proved effective and the degree of success was variable from patient to patient. In most situations, the EVs, lumbar compression forces and lumbar shear forces increased due to the intervention that was chosen. In addition, the lumbar flexion angle typically trended to a more neutral posture and in tasks where spine motion occurred, there was less spine motion when using the suggested intervention. Further, the biomechanical variable that would be expected to change based on clinical assessment did not always react in the expected way (i.e. a compression intolerant individual would be expected to have decreased compression linked with decreased pain, but this did not occur). While the stability/stiffness increased, the associated compression was tolerated suggesting that the increase in concomitant stiffness enhanced the compression load bearing tolerance. Overall Conclusions This thesis showed that careful examination of the EVs did not offer substantial insight into links between changes in individual EVs and individual muscles, as muscle activity was not reflected in the EVs. Specifically, single muscles contributions were not reflected in specific EVs as was hypothesized. Further, it was difficult to interpret the EVs collectively because of the inherent non-linearity between EV magnitude and changes in muscle activation/stiffness; it can only be said that there was more or less stability/stiffness with each change in an EV, not how much. In addition, pain reduction appeared to be due to a combination of altered motions, postures and loads, but this did not result in systematic EV changes. Globally, the present work provides evidence supporting the idea that maintaining a neutral posture and activating the abdominal muscles results in less pain and larger EVs, suggesting an increase in stability/stiffness. This work has potential for informing clinicians on possible options for immediate reduction in low back pain.

The somatosensory system has been implicated in the compensatory response of the nervous system to postural perturbations in humans and cats. The approach elicited - dubbed the Force Constraint Strategy - through a possible combined action of proprioceptive and cutaneous feedback, determines, and adjusts for, horizontal disturbances in various directions of a supporting surface. To understand the mechanisms underlying this strategy, we asked whether the response patterns of muscle proprioceptors correspond to those of electromyographic recordings (EMG) in the aforementioned Force Constraint experiments. The mechanical properties of the musculoskeletal system may also play a role in the restoration of stability. Thus, we also hypothesize that a proximal muscle would be relatively tightly tuned spatially whereas the distal muscle would exhibit a more diffuse spatial response distribution. To this end we selected the medial gastrocnemius (MG) and biceps femoris (BF) muscles to serve as our proximal and distal models respectively. Cats anesthetized using pentobarbital were set in a stereotaxic frame with the right leg positioned on a servo-controlled platform. The platform was shifted horizontally in 16 different directions according to a ramp-and-hold waveform. Intra-axonal recordings of activity from Ia afferents of BF and MG muscles were taken. Results indicate that the strategy makes use of information from the muscle proprioceptors. However, there is no differential response in tuning breadth with respect to muscle architecture. By characterizing the role of muscle proprioceptors in the mediation of corrective responses to perturbations of balance and stability, the results from this experiment can be used to verify biomechanical models, as well as further elucidate the underlying mechanisms of motor control.

This dissertation analyzes the effect of periodic roughness elements on the stability of a flat plate boundary layer. Receptivity data is extracted from direct numerical simulations and experimental data and the results are compared to theoretical predictions. This analysis shows that flow in the immediate vicinity of roughness elements is non-linear; however, the evolution of roughness-induced perturbations is a linear phenomena. New techniques are developed to calculate receptivity information for cases where direct numerical simulations are not yet possible. Additionally, the stability behavior of the roughness wake is analyzed. New instability modes are found, and the effect of boundary layer complexity, perturbation amplitude and other factors are examined. It is shown that the wake is much less stable than optimal perturbation theory predicts, and highlights the importance of receptivity studies. The implication of these results on transition-to-turbulence is discussed, and future work is proposed. T

ABSTRACT In this dissertation, the stability analysis and stabilization problems of neutral systems are investigated. Firstly, the stability analysis of various classes of neutral systems, including discrete and distributed time-delay systems, are investigated by using Lyapunov functional approach. Delay-dependent and delay-independent criteria are proposed. Secondly, we consider the stability problems of neutral systems by using the powerful LMI tools. In this part, we also provide delay-dependent and delay-independent criteria for the stability of neutral systems under consideration. Finally, the stabilization problems of neutral systems are considered. We will propose stabilizability criteria for neutral systems with multiple time delays and with input delay, respectively. We will provide an observer-based controller design method. The improvements of our results over those results recently published in related literature are illustrated if the comparisons are possible. Examples are given in appropriate places to illustrate our main results.

It is critical to consider the balance between the catalytic capabilities of an enzyme and the inherent structural stability of the protein when developing enzymes for specific applications. Rational site directed mutagenesis has been used to explore the role of residues 254 and 257 in the global stability and catalytic specificities of organophosphorus hydrolase (OPH, EC 3.1.8.1). Substitution of residues H254 and H257, which are located near the active site, had a marked effect on both the global stability and substrate specificity of the enzyme. For example, the for the double mutation CoTGΔ2+ H254R H257L (RL) enzyme variant was 19.6 kcal/mol, 5.7 kcal/mol less than that of the wild type enzyme. At the same time, the altered enzyme was catalytically more effective against VX and VR (Russian VX), as compared to the wild type enzyme. Limited proteolysis verified the importance of residues 254 and 257 for functional stability, evidenced by enhanced resistance to irreversible unfolding associated with thermal denaturation. It has been possible to construct third generation OPH variants, which are more stable than the wild type enzyme, with a 10 °C increase in the apparent melting temperature (TM app), yet retained desirable catalytic properties. It appeared that aromatic stacking and cation-π interactions involving near active site residues not only affected activity but significantly contributed to the chemical and thermal stability of OPH. Rational design was used to develop an enzyme with an optimized orientation on a catalytically active biosensor surface. In these studies, lysine side chains located on the surface of OPH were used to create attachment sites to a surface plasmon resonance sensor resulting in an ensemble of enzyme orientations. Some of these orientations could be functionally restrictive if the active site is oriented toward the sensor surface. Substitution of a lysine near the active site resulted in 20% more activity with 53% less enzyme immobilized, thus increasing the specific activity of the decorated surface 2.5 fold.

Fort Hood Military Reservation is a 900 km2 military installation located between Killeen, Copperas Cove, and Gatesville in central Texas. It supports two full armored divisions which require year-round, live-fire maneuvers and training (Ft. Hood, 2003). As a result of the constant foot traffic and use of heavy equipment, the soils on the training ranges have become increasingly compacted, eroded, and stripped of vegetation. This study evaluated the impact that selected soil amendments would have on soil aggregation, infiltration, and levels of glomalin. A field study was done on plots located inside Fort Hood on a Nuff silty clay (fine-silty, carbonatic, thermic Udic Calciustoll). The plots were amended with composted dairy manure, inorganic fertilizers, and native grass seed. Aggregate stability was determined using a wet sieving procedure and total glomalin values were quantified using a Bradford assay. Field measurements of infiltration rates were taken using a drip-type rainfall simulator. Aggregate stability exhibited decreased values over time for all treatments but two (Site Prep / No Seed and Site Prep / Compost / Seed). In addition, three treatments changed significantly over time (from before treatment application to after treatment application). These treatments were the Site Prep / Compost / No Seed, No Prep / No Seed, and No Prep / Seed treatments. Levels of glomalin increased significantly over time for all treatments (p-value <0.001). Glomalin was correlated to aggregate stability after treatments were applied (p-value <0.01) but not before (p-value 0.89). In addition, infiltration rates were not related to glomalin (p-value 0.9) or aggregate stability (p-value 0.09). Additional sampling of Fort Hood beyond the plot study demonstrates significant differences in aggregate stability, infiltration rates, and levels of glomalin. Measurements taken from ten sites showed no correlations between aggregate stability, infiltration rates, or glomalin. Organic C was correlated to percent water stable aggregates (%WSA) and levels of glomalin. These results illustrate the relationship between organic C and aggregate stability as well as glomalin levels in maintaining infiltration rates and reducing soil loss by erosion.

Thesis (doctoral)--Technische Hochschule Fridericiana zu Karlsruhe, 1911. / "Sonderabdruck aus dem 61. Bande der "Zeitschrift für Mathematik und Physik""--P. following t.p. Vita. Includes bibliographical references (p. 319-320).