No description available.

La simulation directe des ondes de souffle générées par une explosion maîtrisée, ou accidentelle, est un problème délicat du fait des différentes échelles spatiales en jeu. De plus, en environnement réel (topographie, zone urbaine, …), l’onde de souffle interagit avec les obstacles géométriques en se réfléchissant, se diffractant et se recombinant. La forme du front devient complexe, rendant difficile voire impossible une estimation a priori des effets des explosions.Ce travail de thèse contribue à la mise au point d’une méthode de calcul rapide des ondes de souffle en présence d’obstacles. Il repose sur des modèles hyperboliques simplifiés de propagation d'ondes de choc extraits de la littérature, où seul le front incident est modélisé. Ceci permet une réduction significative du coût des simulations : les 5 équations d'Euler 3D sont réduites à un problème 2D à 2 équations. L’analyse du problème de Riemann met en évidence l’absence de solution de ces modèles lors de la diffraction sur un coin convexe dans certaines configurations fréquemment rencontrées en pratique. L’extension des modèles aux ordres supérieurs ne permet pas de corriger ce défaut. Nous levons cette limitation au travers d'une modification ad hoc. L’effet de souffle consécutif à une explosion est ensuite introduit à partir d’une loi expérimentale pression/distance. Du point de vue numérique, un algorithme Lagrangien conservatif de suivi de front est développé en 2D. Les tests montrent que ce nouveau modèle se compare favorablement à l’expérience, avec une réduction de plusieurs ordres de grandeur du temps de calcul en comparaison des méthodes de résolution directe des équations d’Euler. / The direct numerical simulation of blast waves (accidental or industrial explosions) is a challenging task due to the wide range of spatial and temporal scales involved. Moreover, in a real environment (topography, urban area …), the blast wave interacts with the geometrical obstacles resulting in reflection, diffraction and waves recombination phenomena. The shape of the front becomes complex, which limits the efficiency of simple empirical methods.This thesis aims at contributing to the development of a fast running method for blast waves propagation in presence of obstacles. This is achieved through the use of simplified hyperbolic models for shock waves propagation such as Geometrical Shock Dynamics (GSD) or Kinematic models. These models describe only the leading shock front. This leads to a drastic reduction of the computational cost, from 5 Euler equations at 3D to a 2D problem with 2 equations. However, the study of the Riemann problem shows that the solution of these models does not always exist in the case of the diffraction over a convex corner. We propose an ad-hoc extension of GSD in order to remove this limitation. The blast effects are also recovered through an empirical law available in free field. From a numerical point of view, a 2D conservative Lagrangian algorithm has been implemented and validated. First comparisons with experimental data show the good behaviour of this new model at nearly free computational cost compared to direct Euler methods.

In the flying field of space transportation domain, the increased efforts involving design and development of hypersonic flight for space missions is on toe to provide the optimum aerothermodynamic design data to satisfy mission requirements. Aerothermodynamics is the basis for designing and development of hypersonic space transportation flight vehicles such as X 51 a, and other programmes like planetary probes for Moon and Mars, and Earth re-entry vehicles such as SRE and space shuttle. It enables safe flying of aerospace vehicles, keeping other parameters optimum for structural and materials with thermal protection systems. In this context, the experimental investigations on hypersonic waverider are carried out at design Mach 6. The hypersonic waverider has high lift to drag ratio at design Mach number even at zero degree angle of incidence, and this seems to be one of the special characteristics for its shape at hypersonic flight regime. The heat transfer rates are measured using 30 thin film platinum gauges sputtered on a Macor material that are embedded on the test model. The waverider has 16 sensors on top surface and 14 on bottom surface of a model. The surface temperature history is directly converted to heat transfer rates. The heat transfer data are measured for design (Mach 6) and off-design Mach numbers (8) in the hypersonic shock tunnel, HST2. The results are obtained at stagnation enthalpy of ~ 2 MJ/kg, and Reynolds number range from 0.578 x 106 m-1 to 1.461 x 106 m-1. In addition, flow visualization is carried out by using Schlieren technique to obtain the shock structures and flow evolution around the Waverider. Some preliminary computational analyses are conducted using FLUENT 6.3 and HiFUN, which gave quantitative results. Experimentally measured surface heat flux data are compared with the computed one and both the data agree well. These detailed results are presented in the thesis.

Shock-tube experiments are typically performed at high temperatures (≥1200K) due to test-time constraints. These test times are usually ~1 ms in duration and the source of this short, test-time constraint is loss of temperature due to heat transfer. At short test times, there is very little appreciable heat transfer between the hot gas and the cold walls of the shock tube and a high test temperature can be maintained. However, some experiments are using lower temperatures (approx. 800K) to achieve ignition and require much longer test times (up to 15 ms) to fully study the chemical kinetics and combustion chemistry of a reaction in a shock-tube experiment. Using mathematical models, analysis was performed studying the effects of temperature, pressure, shock-tube inner diameter, and test-port location at various test times (from 1 - 20 ms) on temperature maintenance. Three models, each more complex than the previous, were used to simulate test conditions in the endwall region behind the reflected shock wave with Ar and N2 as bath gases. Temperature profile, thermal BL thickness, and other parametric results are presented herein. It was observed that higher temperatures and lower pressures contributed to a thicker thermal boundary layer, as did shrinking inner diameter. Thus it was found that a test case such as 800K and 50 atm in a 16.2-cm-diameter shock tube in Argon maintained thermal integrity much better than other cases - pronounced by a thermal boundary layer ≤ 1 mm thick and an average temperature ≥ 799.9 K from 1-20 ms.

Call number: LD2668 .T4 1984 A43 / Master of Science

Despite their name, a number of the cold shock proteins are expressed during normal growth, and not just during cold shock, in several species. The function of these constitutively expressed CspA paralogues is unclear. In Salmonella Typhimurium (a major worldwide cause of gastrointestinal disease) they have been linked to various stress responses and the establishment of virulence. Study of the cold shock proteins as gene regulators is therefore of great interest, and they also have potential as targets for antimicrobial development. CspE in Salmonella Typhimurium is constitutively expressed during normal growth. In order to determine its function, attempts were made to identify the interactions it forms with other cellular proteins. Initially, a proteomic investigation attempted to identify proteins which complex with CspE by in vivo cross-linking and affinity purification followed by mass spectrometry. Although no defined complex was consistently identified, the results suggested a handful of proteins which might interact with CspE in a weak or transient manner. These proteins included many from the nucleoid and ribosomal entry site, hinting at CspE’s cellular localisation. In order to investigate these transient interactions, a bacterial two-hybrid system was employed. Interactions between CspE and HupA, a nucleoid protein identified in the proteomic analysis, were probed, as were interactions between CspE and CsdA, an RNA helicase thought to function co-operatively with CspE. The twohybrid system also allowed investigation of CspE dimerisation, which has been reported in vitro but not investigated in vivo until this study. CspE appears not to interact significantly with either HupA, CsdA, or itself at 37oC. Finally in a further attempt to identify interactions of CspE, a genomic library was created to test CspE interactions by two-hybrid assay with random peptides derived from the whole Salmonella genome. The library was successfully created and screened for evidence of interaction, and revealed an association between CspE and a transcriptional repressor, DeoT. DeoT is a repressor of several genes for catabolic processes, suggesting a role for CspE in the regulation of central metabolism. The findings of this work present a number of novel discoveries and several interesting opportunities for further studies.

Injury is a global health problem and in the United States is the leading cause of death for persons aged 1 – 44 years. The primary causes of trauma related death are head injury and hemorrhage; hemorrhagic shock is difficult to recognize in the first hours after trauma. Identification of specific and optimal criteria upon which to base effective triage decisions for trauma patients has been an elusive goal for decades. The purpose of this dissertation was to identify measures available in the prehospital phase of care and in the Emergency Department that should be included for a more comprehensive definition of the trauma patient who will require trauma center care to better allocate trauma care and resources available. The first paper is a critical review of early physiologic markers of occult tissue hypoperfuson in which we examine markers of cardiovascular function and markers of tissue perfusion. In this review, we found surrogate measures of tissue perfusion include shock index as a measure of hemodynamic stability and acid-base indicators as measures of tissue oxygenation. This review guides the variable selection for the research study. The second paper is a report of a study conducted to examine shock index calculated from the first available prehospital vital signs and first available emergency department vital signs as a predictor of mortality within 48-hours in trauma compared to the Injury Severity Score. Shock index can be calculated in real-time during the course of treatment and provides continuous input into the ever changing condition of the patient. Injury severity score is calculated once, at the time of hospital discharge and is used primarily as a marker for comparison of injury severity in research and quality measures of trauma care. The study consisted of 516,156 trauma patient data reported to the National Trauma Data Bank (NTDB) in 2009. The results revealed SI as calculated in both the pre-hospital phase of care by Emergency Medical Services and in the Emergency Department to be significant independent predictors of mortality within forty-eight hours from trauma injuries. The third paper is a report of a study conducted to examine potential markers of occult tissue hypoperfusion within forty-eight hours of injury. The variables included four major variable categories, physiologic measures, anatomic measures, injury severity and presence of reported comorbid illness. The variable most predictive of death from trauma related injuries within forty-eight hours was the need for intubation. The findings from this dissertation provide further evidence of the value of multiple physiologic markers in early recognition of occult tissue hypoperfusion. Data from neither the review of the literature nor the two data-based studies are sufficient to identify a brief, accurate, easily used clinical instrument. Further work is needed to develop a clinically useful instrument to identify the occult tissue hypoperfusion in the trauma patient.

International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, California / Aydin Vector Division has developed and manufactured an airborne, high shock, wideband FM/FM telemetry system for Saab Missiles AB in Sweden. This system was presented in the ITC Proceedings of 1988, Volume XXIV, pp 71-84 (Ref [1]). Three such systems were supplied. Saab Missiles AB also awarded Aydin Vector Division with an additional order for a larger number of high shock, computer based, specially designed, miniature PCM/FM airborne telemetry systems. These systems were developed, manufactured and supplied to Saab Missiles AB, and have been extensively and successfully used in the Swedish program. The PCM/FM telemetry package described in this paper was used for the system testing and the firing trials program of a mortar projectile, where the measurement requirements included micro processor interfaces, as well as a high amount of analog and bi-level data channels. The paper covers the specifications of the PCM/FM system mentioned above, the concept that was used to meet these specifications, the system’s mechanical and electrical design, the packaging technique and some of the test results.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The accurate measurement of shock and vibration data via flight telemetry is necessary to validate structural models, indicate off-nominal system performance, and/or generate environmental qualification criteria for airborne systems. Digital telemetry systems require anti-aliasing filters designed into them. If not properly selected and located, these filters can distort recorded time histories and modify their spectral content. This paper provides filter design guidance to optimize the quality of recorded flight structural dynamics data. It is based on the anticipated end use of the data. Examples of filtered shock data are included.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Today’s telemetry specifications are requiring electronic systems to not only survive, but operate through severe dynamic environments. Pyrotechnic shock and Random Vibration are among these environments and have proven to be a challenge for systems that rely on highly stable, low phase noise signal sources. This paper will mathematically analyze how Pyrotechnic shock and Random Vibration events deteriorate the phase noise of crystal oscillators (XO).