Dissertations / Theses on the topic 'High temperature shock'

Cette thèse vise à déterminer l’influence de deux traitements mécaniques, le grenaillage SMAT effectué avec plusieurs types de billes (en WC, en alumine et en verre) et le choc laser, sur la résistance à l’oxydation haute température de deux alliages de titane : un alliage alpha commercialement « pur » (Grade 1) et un alliage aéronautique béta métastable (TIMETAL-21S).Une fois traitées, les pièces sont oxydées avec différentes conditions : de durée (entre 5 heures pour étudier les premier instants de l’oxydation et 3000h pour se rapprocher d’un essai type en aéronautique), de température (600°C à 700°C) et d’atmosphère (air sec et oxygène).Les pièces sont analysées avant et après oxydation à l’aide de plusieurs techniques d’analyses : mécaniques (dureté, mesures de contraintes), chimiques (DRX, microsonde nucléaire, …) ou structurales (EBSD, texture).Les résultats obtenus montrent que les traitements perturbent fortement les pièces avant leur exposition à haute température d’un point de vue morphologique, structural, mécanique et chimique. Ces traitements mécaniques amènent une réduction de l’oxydation des pièces étudiées. Il semble qu’ils modifient la vitesse de diffusion des espèces (azote, oxygène, aluminium, molybdène) mais aussi la microstructure (recristallisation, morphologie de grain ou texturation) au cours de la mise en température. L’azote joue un rôle essentiel dans les phénomènes observés.Néanmoins, la détermination des conséquences de ces traitements sur la résistance à l’oxydation reste encore complexe de par les observations de ce travail, qui révèlent une contribution simultanée de plusieurs facteurs : chimiques, mécaniques et structuraux
The aim of this thesis is to determine the influence of two mechanical surface treatments, the shot- peening performed with several type of balls (WC, alumina and glass) and the laser shock peening, on the high temperature oxidation resistance of two titanium alloys : alpha alloy with commercially purity (Grade 1) and aeronautical beta metastable alloy (TIMETAL-21S).After different treatments, the pieces are oxidized with different conditions: of time (between 5 hours to study the firsts times of oxidation and 3000 hours to compare with a classical aeronautical test), of temperature (600°C to 700°C) and atmosphere (dry air or oxygen).The pieces are analyzed before and after oxidation exposure with several mechanical (micro-hardness, strain measurements), chemicals (XRD, nuclear microprobe) and structural (EBSD, texture) techniques. The results show a large surface perturbation before the high temperature exposure in term of morphological, mechanical, structural and chemical point of view.This mechanical treatments lead up to an oxidation rate reduction for all the different titanium alloys. This treatments modified the diffusion rate of several elements (nitrogen, oxygen, molybdenum or aluminum) but also the microstructure (recrystallization, grain morphology or texturing) during high temperature exposure. Nitrogen element plays an important role in the observed phenomena.However, the determination of consequences after mechanical treatment on the titanium oxidation resistance is again difficult with the observations noted in this work. Actually, there is a simultaneous contributions of several factors: chemical, mechanical and structural

The dynamic response of filled corrugated steel sandwich panels was investigated under combined extremes of blast loading and high temperature heating. The objective of this project was to study blast mitigation and the thermo-mechanical response of panels using a polymer based syntactic foam and mortar as a filler material. These materials were selected due to their thermal resistivity. In this study, silicone resin (with an operating temperature range between -53°C to 232°C) and two types of glass bubbles were selected as materials to develop a heat resistive syntactic foam. The mechanical properties of the foam were investigated, in ambient temperatures, before and after high-temperature heat treatment (of 500°C), by quasi-static compression experiments. It was observed that plateau stress increases after introduction of glass bubbles in silicone, enhancing the energy absorption properties for both specimens with and without heat treatment. To produce repeatable blast loading, a shock tube was utilized. Pressure history was recorded using pressure transducers located in the shock tube muzzle. High speed photo-optical methods utilizing Digital Image Correlation (DIC) coupled with optical band-pass filters and high-intensity light source, were utilized to obtain the real-time deformation at high temperature while a third camera captured side-view deformation images. The shock pressure profiles and DIC analysis were used to obtain the impulse imparted to the specimen, transient deflection, in plane strain and out-of-plane velocity of the back face sheet. Shock tube experiments were performed to investigate the blast response of corrugated steel sandwich panels filled with a silicone based syntactic foam filler at room and high temperature. It was observed that using the syntactic foam as a filler material, decreased the front face and back face deflections by 42% and 27%, respectively, compared to an empty panel. The highest impulse was imparted on the specimen at room temperature and subsequently lower impulses with increasing temperature. Due to increasing ductility in steel with high temperature, the specimens demonstrated an increase in back face deflection, in-plane strain and out-of-plane velocity with increasing temperatures with weld failure being the primary form of core damage. High temperature blast experiments were also performed on mortar filled corrugated steel sandwich panels. Mortar is a common building material that can withstand extreme temperatures. It was observed cement based mortars are thermally resilient enough to be used as a filler material for high temperature applications. The highest impulse was imparted on the specimen at room temperature and subsequently lower impulses with increasing temperature. A temperature difference of at least 300ºC was observed across the thickness of the specimen for all heating conditions. Due to increasing ductility in steel with high temperature, the specimens demonstrated an increase in back face deflection, in-plane strain and out-of-plane velocity with increasing temperatures with weld failure being the primary form of core damage.

Chemiluminescence from the OH(A-X) transition near 307 nm is a commonly used diagnostic in combustion applications such as flame chemistry, shock-tube experiments, and reacting-flow visualization. Measurements of the chemiluminescent intensity provide a simple, cost-effective, non-intrusive look at the combustion environment. The presence of the ultra-violet emission is often used as an indicator of the flame zone in practical combustion systems, and its intensity may be correlated to the temperature distribution or other parameters of interest. While absolute measurements of the ground-state OH(X) concentrations are well-defined, there is no elementary relation between emission from the electronically excited state (OH*) and its absolute concentration. Thus, to enable quantitative emission measurements, a kinetics model has been assembled and optimized to predict OH* formation and quenching at combustion conditions. Shock-tube experiments were conducted in mixtures of H2/O2/Ar, CH4/O2/Ar and CH4/H2/O2/Ar with high levels of argon dilution (> 98%). Elementary reactions to model OH*, along with initial estimates of their rate coefficients, were taken from the literature. The important formation steps follow. CH + O2 = OH* + CO (R0) H + O + M = OH* + M (R1) H + OH + OH = OH* + H2O (R2) Sensitivity analyses were performed to design experiments at conditions most sensitive to the formation reactions. A fitting routine was developed to express the key rate parameters as a function of a single rate, k1 at the reference temperature (1490 K). With all rates so expressed, H2/CH4 mixtures were designed to uniquely determine the value of k1 at the reference temperature, from which the remaining rate parameters were calculated. Quenching rates were fixed at their literature values. Comparisons to predictions of previously available models show marked improvement relative to the new shock-tube data. An approach for using this work in the calibration of further measurements is outlined taking examples from a recent ethane oxidation study. The new model qualitatively matches the experimental data over the range of conditions studied and provides quantitative results applicable to real combustion environments, containing higher-order hydrocarbon fuels and lower levels of dilution in air.
M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering

Ignition and oxidation characteristics of CO/H2, H2/O2 and CO/H2/CH4/CO2/Ar fuel blends in air were studied using both experimental and computer simulation methods. Shock-tube experiments were conducted behind reflected shock waves at intermediate temperatures (825 < T < 1400 K) for a wide range of pressures (1 < P < 45 atm). Results of this study provide the first undiluted fuel-air ignition delay time experiments to cover such a wide range of syngas mixture compositions over the stated temperature range. Emission in the form of chemiluminescence from the hydroxyl radical (OH*) transition near 307 nm and the pressure behind the reflected shock wave were used to monitor reaction progress from which ignition delay times were determined. In addition to the experimental analysis, chemical kinetics calculations were completed to compare several chemical kinetics mechanisms to the new experimental results. Overall, the models were in good agreement with the shock-tube data, especially at higher temperatures and lower pressures, yet there were some differences between the models at higher pressures and the lowest temperatures, in some cases by as much as a factor of five. In order to discern additional information from the chemical kinetics mechanisms regarding their response to a wide range of experimental conditions, ignition delay time and reaction rate sensitivity analyses were completed at higher and lower temperatures and higher and lower pressures. These two sensitivity analyses allow for the identification of the key reactions responsible for ignition. The results of the sensitivity analysis indicate that the ignition-enhancing reaction H + O2 = O + OH and hydrogen oxidation kinetics in general were most important regardless of mixture composition, temperature or pressure. However, lower-temperature, higher-pressure ignition delay time results indicate additional influence from HO2- and CO- containing reactions, particularly the well-known H + O + M = HO2 + M reaction and also the CO + O + M = CO2 + M and CO + HO2 = CO2 + OH reactions. Differences in the rates of the CO-related reactions are shown to be the cause of some of the discrepancies amongst the various models at elevated pressures. However, the deviation between the models and the experimental data at the lowest temperatures could not be entirely explained by discrepancies in the current rates of the reactions contained within the mechanisms. Additional calculations were therefore performed to gain further understanding regarding the opposing ignition behavior for calculated and measured ignition delay time results. Impurities, friction induced ionization, static charge accumulation, boundary layer effects, wall reaction effects, and revised chemical kinetics were all considered to be possible mechanisms for the model and measured data disparity. For the case of wall-reaction effects, additional shock-tube experiments were conducted. For the remaining effects listed above, only detailed calculations were conducted. Results from this preliminary anomaly study are at this time inconclusive, but likely avenues for future study were identified. Additional kinetics calculations showed that the large difference between the experimental data and the chemical kinetics models predictions at low temperatures can be explained by at least one missing reaction relevant to low-temperature and high-pressure experimental conditions involving the formation of H2O2, although further study beyond the scope of this thesis is required to prove this hypothesis both theoretically and experimentally.
Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering PhD

Die vorliegende Arbeit beschreibt einen neuartigen Fügeprozess, das sogenannte reaktive Fügen bzw. Bonden. Hierbei werden sich selbsterhaltene exotherme Reaktionen in nanoskaligen Schichtsystemen als lokale Wärmequelle für das Fügen unterschiedlichster Substrate der Mikrosystemtechnik verwendet. Das Bonden mit den reaktiven Systemen unterscheidet sich von herkömmlichen Verfahren der Aufbau- und Verbindungstechnik primär dadurch, dass durch die rasche Reaktionsausbreitung bei gleichzeitig kleinem Reaktionsvolumen die Fügetemperaturen unmittelbar auf die Fügefläche beschränkt bleiben. Entgegen den herkömmlichen Fügeverfahren mit Wärmeeintrag im Volumen, schont das neue Verfahren empfindliche Bauteile und Materialien mit unterschiedlichsten thermischen Ausdehnungskoeffizienten lassen sich besser verbinden. In der vorliegenden Arbeit werden die Grundlagen zur Dimensionierung, Prozessierung und Integration der gesputterten reaktiven Materialsysteme beschrieben. Diese Systeme werden verwendet, um heterogene Materialien mit unterschiedlichen Durchmessern innerhalb kürzester Zeit auf Wafer-Ebene und bei Raumtemperatur zu bonden. Die so erzeugten Verbindungen werden hinsichtlich der Mikrostruktur, der Zuverlässigkeit sowie der Dichtheit untersucht und bewertet. Zusätzlich wird die Temperaturverteilung in der Fügezone während des Fügeprozesses mit numerischen Methoden vorhergesagt.

The re-entry space vehicles encounter high temperatures when they enter the earth atmosphere and the high temperature air in the shock layer around the body undergoes partial dissociation. Also, the gas molecules injected into the shock layer from the ablative thermal protection system (TPS) undergo pyrolysis which helps in reducing the net heat flux to the vehicle surface. The chemical species due to the pyrolysis add complexity to the stagnation flow chemistry (52 chemical reactions) models which include species like NOx, CO and hydrocarbons (HCs). Although the ablative TPS is responsible for the safety of re-entry space vehicle, the induced chemical species result in variety of adverse effects on environment such as global warming, acid rain, green house effect etc. The well known three-way-catalyst (TWC) involves simultaneous removal of all the three gases (i.e, NOx, CO, Hydrocarbons) present in the shock layer. Interaction of such three-way-catalyst on the heat shield materials or on the wall of the re-entry space vehicle is to reduce the heat flux and to remove the gases in the shock layer, which is an important issue. For the re-entry vehicle the maximum aerodynamic heating occurs at an altitude ranging about 68 to 45 km during which the vehicle is surrounded by high temperature dissociated air. Then the simplest real gas model of air is the five species model which is based on N2, O2, O, NO and N. This five species model assumes no ionization and no pyrolysis gases are emitted from the heat shield materials. The experimental research work presented in this thesis is directed towards the understanding of catalytic and non-catalytic surface reactions on high temperature materials in presence of strong shock heated test gas. We have also explored the possibility of using shock tube as a high enthalpy device for synthesis of new materials. In the first Chapter, we have presented an overview of re-entry space vehicles, thermal protection system (TPS) and importance of real gas effects in the shock layer. Literature survey on TPS, ablative materials and aerothermochemistry at the stagnation point of reentry capsule, in addition to catalytic and non-catalytic surface reactions between the wall and dissociated air in the shock layer are presented. In Chapters 2 and 3, we present the experimental techniques used to study surface reactions on high temperature materials. A brief description of HST2 shock tunnel is presented and this shock tunnel is capable of generating flow stagnation enthalpies ranging from 0.7 to 5 MJ/kg and has an effective test time of ~ 800 µs. High speed data acquisition system (National Instruments and Yokogawa) used to acquire data from shock tube experiments. The experimental methods like X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Raman and FTIR spectroscopy have been used to characterize the shock-exposed materials. Preliminary research work on surface nitridation of pure metals with shock heated nitrogen gas is discussed in Chapter 2. Surface nitridation of pure Al thin film with shock heated N2 is presented in Chapter 3. An XPS study shows that Al 2p peak at 74.2 eV is due to the formation AlN on the surface of Al thin film due to heterogeneous non-catalytic surface reaction. SEM results show changes in surface morphology of AlN film due to shock wave interaction. Thickness of AlN film on the surface increased with the increase in temperature of the shock heated nitrogen gas. However, HST2 did not produce sufficient temperature and pressure to carry out real conditions of re-entry. Therefore design and development of a new high enthalpy shock tunnel was taken up. In Chapter 4, we present the details of design and fabrication of free piston driven shock tunnel (FPST) to generate high enthalpy test gas along with the development of platinum (Pt) and thermocouple sensors for heat transfer measurement. A free piston driven shock tunnel consists of a high pressure gas reservoir, compression tube, shock tube, nozzle, test section and dump tank connected to a vacuum pumping system. Compression tube has a provision to fill helium gas and four ports, used to mount optical sensors to monitor the piston speed and pressure transducer to record pressure at the end of the compression tube when the piston is launched. Piston can attain a maximum speed of 150 m/s and compress the gas inside the compression tube. The compressed gas bursts the metal diaphragm and generates strong shock wave in the shock tube. This tunnel produces total pressure of about 300 bar and temperature of about 6000 K and is capable of producing a stagnation enthalpy up to 45 MJ/kg. The calibration of nozzle was carried out by measuring the pitot tube pressure in the dump tank. Experimentally recorded P5 pressure at end of the shock tube is compared with Numerical codes. Calibrated pressure P5 values are used to calculate the temperature T5 of the reflected shock waves. This high pressure and high temperature shock heated test gas interacts with the surface of the high temperature test materials. For the measurement of heat transfer rate, platinum thin film sensors are developed using DC magnetron sputtering unit. Hard protective layer of aluminum nitride (AlN) on Pt thin film was deposited by reactive DC magnetron sputtering to measure heat transfer rate in high enthalpy tunnel. After the calibration studies, FPST is used to study the heat transfer rate and to investigate catalytic/non-catalytic surface reaction on high temperature materials. In Chapter 5, an experimental investigation of non-catalytic surface reactions on pure carbon material is presented. The pure carbon C60 films and conducting carbon films are deposited on Macor substrate in the laboratory to perform shock tube experiments. These carbon films were exposed to strong shock heated N2 gas in the shock tube portion of the FPST tunnel. The typical shock Mach number obtained is about 7 with the corresponding pressure and temperature jumps of about 110 bar and 5400 K after reflection at end of the shock tube. Shock exposed carbon films were examined by different experimental techniques. XPS spectra of C(1s) peak at 285.8 eV is attributed to sp2 (C=N) and 287.3 eV peak is attributed to sp3 (C-N) bond in CNx due to carbon nitride. Similarly, N(1s) core level peak at 398.6 eV and 400.1 eV observed are attributed to sp3-C-N and sp2-C=N of carbon nitride, respectively. SEM study shows the formation of carbon nitride crystals. Carbon C60 had melted and undergone non-catalytic surface reaction with N2 while forming carbon nitride. Similar observations were made with conducting carbon films but the crystals were spherical in shape. Micro Raman and FTIR study gave further evidence on the formation of carbon nitride film. This experimental investigation confirms the formation of carbon nitride in presence of shock-heated nitrogen gas by non-catalytic surface reaction. In Chapters 6 and 7, we present a novel method to understand fully catalytic surface reactions after exposure to shock heated N2, O2 and Ar test gas with high temperature materials. We have employed nano ZrO2 and nano Ce0.5Zr0.5O2 ceramic high temperature materials to investigate surface catalytic reactions in presence of shock heated test gases. These nano crystalline oxides are synthesized by a single step solution combustion method. Catalytic reaction was confirmed for both powder and film samples of ZrO2. As per the theoretical model, it is known that the catalytic recombination reaction produces maximum heating on the surface of re-entry space vehicles. This was demonstrated in this experiment when a metastable cubic ZrO2 changed to stable monoclinic ZrO2 phase after exposure to shock waves. The change of crystal structure was seen using XRD studies and needle type monoclinic crystal growth with aspect ratio (L/D) more than 15 was confirmed by SEM studies. XPS of Zr(3d) core level spectra show no change in binding energy before and after exposure to shock waves, confirming that ZrO2 does not change its chemical nature, which is the signature of catalytic surface reaction. When a shock heated argon gas interacted with Ce0.5Zr0.5O2 compound, there was a change in colour from pale yellow to black due to reduction of the compound, which is the effect of heat transfer from the shock wave to the compound in presence of argon gas. The reduction reaction shows the release of oxygen from the compound due to high temperature interaction. The XPS of Ce(3d) and Zr(3d) spectra confirm the reduction of both Ce and Zr to lower valent states. The oxygen storage and release capacity of the Ce0.5Zr0.5O2 compound was confirmed by analyzing the reduction of Ce4+ and Zr4+ with high temperature gas interaction. When Ce0.5Zr0.5O2 (which is same as Ce2Zr2O8) in cubic fluorite structure was subjected to strong shock, it changed to pyrochlore (Ce2Zr2O7) structure by releasing oxygen and on further heating it changed to Ce2Zr2O6.3 which is also crystallized in pyrochlore structure by further releasing oxygen. If this heating is carried out in presence of argon test gas, fluorite structure can easily change to pyrochlore Ce2Zr2O6.3 structure, which is a good electrical conductor. Due to its oxygen storage capability (OSC) and redox (Ce4+/Ce3+) properties, Ce0.5Zr0.5O2 had been used as oxygen storage material in three-way-catalyst. Importance of these reactions is that the O2 gas released from the compound will react with gas released from the heat shield materials, like NOx, CO and hydrocarbon (HCs) species which results in reduction of temperature in the shock layer of the re-entry space vehicle. The compound Ce0.5Zr0.5O2 changes its crystal structure from fluorite to pyrochlore phase in presence of shock heated test gas. The results presented in these two Chapters are first of their kind, which demonstrates the surface catalytic reactions. In Chapter 8, we present preliminary results of the oxygen recombination on the surface of heat shield material procured from Indian Space Research Organization (ISRO) used as TPS in re-entry space capsule (Space capsule Recovery Experiment SRE-1) and on thin film SiO2 deposited on silicon substrate. The formation of SiO between the junctions of SiO2/Si was confirmed using XPS study when shock exposed oxygen reacted on these materials. The surface morphology of the ablated SiO2 film was studied using SEM. The damage induced due to impact of shock wave in presence of oxygen gas was analyzed using Focused Ion Beam (FIB) microscope. The results reveal the damage on the surface of SiO2 film and also in the cross-section of the film. We are further investigating use of FIB, particularly related to residual stress developed on thin films due to high pressure and high temperature shock wave interaction. In Chapter 9, conclusions on the performance of FPST, synthesis of high temperature materials, catalytic and non-catalytic surface reactions on the high temperature material due to shock-heated test gases are presented. Possible scope for future studies is also addressed in this Chapter.

abstract: Shock metamorphism in meteorites constrains the impact histories of asteroids and planets. Shock-induced high-pressure (HP) minerals can provide more precise estimates of shock conditions than shock-induced deformation effects. In this research, I use shock features, particularly HP minerals, in ordinary-chondrite samples to constrain not only shock pressures but also the pressure-temperature-time (P-T-t) paths they experienced. Highly shocked L5/6 chondrites Acfer 040, Mbale, NWA 091 and Chico and LL6 chondrite NWA 757 were used to investigate a variety of shock pressures and post-shock annealing histories. NWA 757 is the only highly shocked LL chondrite that includes abundant HP minerals. The assemblage of ringwoodite and majoritic garnet indicates an equilibration shock pressure of ~20 GPa, similar to many strongly shocked L chondrites. Acfer 040 is one of the only two chondrite samples with bridgmanite (silicate perovskite), suggesting equilibration pressure >25 GPa. The bridgmanite, which is unstable at low-pressure, was mostly vitrified during post-shock cooling. Mbale demonstrates an example of elevated post-shock temperature resulting in back-transformation of ringwoodite to olivine. In contrast, majoritic garnet in Mbale survives as unambiguous evidence of strong shock. In these two samples, HP minerals are exclusively associated with shock melt, indicating that elevated shock temperatures are required for rapid mineral transformations during the transient shock pulse. However, elevated post-shock temperatures can destroy HP minerals: in temperature sequence from bridgmanite to ringwoodite then garnet. NWA 091 and Chico are impact melt breccias with pervasive melting, blackening of silicates, recrystallization of host rock but no HP minerals. These features indicate near whole-rock-melting conditions. However, the elevated post-shock temperatures of these samples has annealed out HP signatures. The observed shock features result from a complex P-T-t path and may not directly reflect the peak shock pressure. Although HP minerals provide robust evidence of high pressure, their occurrence also requires high shock temperatures and rapid cooling during the shock pulse. The most highly shocked samples lack HP signatures but have abundant high-temperature features formed after pressure release.
Dissertation/Thesis
Doctoral Dissertation Geological Sciences 2016

碩士
逢甲大學
機械工程學系
88
Heat Resistant Cast Irons have been used in high temperature environment, so it must have excellent high temperature properties, such as high temperature tensile strength, high temperature fatigue strength and thermal shock resistance . The objective of this study is to investigate the high temperature strength property and thermal shock resistance of the heat resistant cast irons. The effects of matrix structure (ferrite, pearlite and austenite) , graphite morphology (flake, compacted / vermicular , spheroidal) and alloying element (Cr,Ni) on the high temperature tensile strength, the high temperature fatigue strength, and thermal shock resistant at different temperatures(1073 K, 873 K and 673 K) of cast irons have been evaluated in this study. We expect to find the quality index apply to themal shock resistance. According to the results of study know that , as a whole , the order of high temperature tensile strength for alloying element is that 0.5%Cr＞20%Ni-2%Cr＞none alloy addition at R.T., 673K, and 873K ; but the order is that 20%Ni-2%Cr＞0.5%Cr＞none alloy addition at 1073K. The order of high temperature tensile strength for the matrix strcutures is that pearlite＞austenite＞ferrite; but the order is that austenite＞pearlite＞ferrite at 1073K. The order of high temperature tensile strength for various graphite morphology is that spheroidal＞c / v＞flake at vaious test temperature. The order of high temperature fatigue strength for Heat Resistant Cast Irons of austenite matrix strcutures is that spheroidal＞c / v＞flake at 673K. For thermal shock resistance of cast irons , the order of thermal shock resistance for graphite morphology of cast iron is that spheroidal＞c / v＞flake.The order of thermal shock resistance for matrix is austenite＞pearlite＞ferrite . The order of thermal shock resistance for alloying element is that 20%Ni-2%Cr＞0.5%Cr＞none alloy addition. Quality Index of High Temperature Strength Property (QHTSP) is obtained for evaluating the high temperature property of the heat resistant cast iron by analysis and evaluation. It is showed has high accurcy and can be used as an important index and reference.

博士
國立臺灣大學
植物學系研究所
86
Promoter region of Oshsp16.9A from -721 to -1 (F31) contained several alone and overlapping HSE-like sequences. DNA fragments contained the TATA box proximal HSEs (F33 and F35) in Oshsp16.9A promoter were specifically bound with nuclear proteins extracted from heat-shocked rice seedlings. The specific binding was competed with HSE-containing DNA fragments, including HSE sequences from Drosophila. The distal HSEs-containing fragment, F7, revealed the minor binding specificity. Modification of control nuclear proteins by adding 1mM calcium chloride, heating, phosphorylation and phosphorylation with heating did not change the binding property of control nuclear proteins. In contrast, dephosphorylation of heat-shocked nuclear proteins removed the HSE binding activity. Southwestern assay indicated that molecular weight of the nuclear protein involved the HSE binding activity was 70-80 kDa. Oshsp16.9A promoter (F31) contained proximal and distal HSEs was heat-induced in tobacco protoplasts detected by reporter gene - CAT(Chloramphenicol acetyl transferase). Six class I low molecular weight heat shock protein genes were characterized in rice. They are Oshsp16.9A, Oshsp16.9B, Oshsp16.9C, Oshsp17.0, Oshsp18.0 and Oshsp17.7. They showed 80-90% similarity in their coding region. Especially, Oshsp16.9A and Oshsp16.9B shared 99.3% similarity in coding region. However, six 3''UTRs revealed 45-61% similarity and showed the gene specificity. The onset of transcription of rice class I lmw hsp genes at 41℃ was fast and reached the maximal level in 1h. Continuous 41℃ treatment did not keep the high transcription rate. The hs mRNAs accumulated at 41℃ for 2h were stable at 41℃ and 45℃, but not at 28℃. Half-life of individual class I lmw hsp gene was determined by calculating the declination rate of mRNA at 28℃.

碩士
逢甲大學
機械工程學所
90
The objective of this study is to investigate the effects of various graphite morphologies ( flake , compacted/vermicular , spheroidal ) and aluminum contents on the high temperature tensile strength and thermal shock property at different test temperatures of aluminum-based heat resistant cast irons. According to the results of this study , the high temperature tensile strength of aluminum-based heat resistant cast irons with 2.5%Al is greater than with 8%Al at RT、673K、873K、1073K. The order of high temperature tensile strength for different graphite morphologies is spheroidal graphite cast iron＞c / v graphite cast iron＞flake graphite cast iron at any test temperature. As a whole , the thermal shock resistant property of aluminum-based heat resistant cast irons with 2.5%Al is better than with 8%Al. The order of thermal shock resistant property for different graphite morphologies is spheroidal graphite cast iron＞c / v graphite cast iron＞flake graphite cast iron. The order of thermal shock resistant property for the matrix structures is pearlite＞ferrite. Moreover, the order of crack number after rupture for different graphite morphologies is flake graphite cast iron＞c / v graphite cast iron＞spheroidal graphite cast iron. Quality Index of High Temperature Strength Property(QHTSP) is used for evaluating the heat resistance of aluminum-based heat resistant cast iron in this study. Experimental results showed that QHTSP has high accuracy and can be used as important index and reference.

Pre-harvest sprouting (PHS) is the germination of seed under wet environmental conditions whilst still on the mother plant prior to harvest. In wheat, PHS causes farmers substantial economic losses due to quality downgrading. A high level of dormancy is regarded as an important mechanism of resistance to PHS in cereal species, such as wheat (Triticum aestivum L.). Many dormancy quantitative trait loci (QTL) have been identified and the corresponding genes that impart tolerance to PHS are actively being sought. Besides genetic factors, environmental conditions during grain maturation have been shown to have profound effects on dormancy. These environmental factors include temperature, light, drought and nutrients. This project aimed to determine the role of high temperature shock during wheat seed maturation on its dormancy at harvest-ripeness. The results of these experiments showed that seed of dormant or intermediate dormant wheat genotypes may have lower dormancy levels after experiencing a high temperature shock (5 days of 40°C). The highest sensitivity towards high temperature shock is limited to a short “window” of approximately five days starting around 25 dpa. The sensitivity increases and reaches a peak at 25 to 30 days post anthesis (dpa), causing an effective and quicker release of dormancy. The sensitivity later decreases and high temperature becomes less influential on dormancy. For the dormant genotype SUN325B, release from dormancy occurred 35 days earlier if treated with temperature shock. There was no significant correlation between the timing of the peak of sensitivity and factors such as daily temperatures before temperature shock, humidity or subsequent grain moisture losses. However, the stronger the intensity (40°C versus 35°C) and longer duration (5 days versus <5 days) of temperature shock seem to influence dormancy more significantly. Changes in embryonic and endospermic abscisic acid (ABA) concentration following temperature shock could not explain the change in dormancy levels in genotype SUN325B. Instead, the change in dormancy levels following the temperature shock could potentially be ascribed to the loss of ABA sensitivity. A comparison of the dormancy response to temperature shock of 23 genotypes that harbour different combinations of known dormancy QTL was performed. Strongly dormant genotypes, P07.683, 50213/Cunn798 and DM1073 #31, did not show an increased germination index at 65 dpa. Other genotypes, ranging from dormant to intermediate dormant phenotype under control conditions, i.e. displaying germination index less than 0.6 at 65 dpa, responded strongly to temperature shock. Dormancy levels significantly decreased, reflected by increases of germination index ranging from 0.4 to 0.9. It is highly likely that a temperature-shock-induced decrease in dormancy is a common response of these genotypes, and a higher number of combinations of QTL are required to resist dormancy changes. The identification of Delay of Germination 1 (DOG1) as the gene underlying a major dormancy QTL in Arabidopsis thaliana has led to stronger understanding of the mechanism of dormancy. Based on results of studies of the AtDOG1 and TaDOG1-like genes in Arabidopsis and cereal species respectively, and their functional conservation and responsiveness towards temperature changes during seed development, it seems likely that the TaDOG1-like genes in wheat might play a role in temperature shock-regulated dormancy levels. A search of publicly available bioinformatics databases revealed three expressed sequence tags (ESTs) with accession numbers AK336217, X56782 and D12921 that could be TaDOG1-like genes in wheat additional to the five previously reported by Ashikawa et al. (2010, 2014). Protein motif analysis showed that the orthologs of DOG1 possess combinations of protein motifs specific to each clade. Promoter analysis revealed RY repeats (CATGCAT) and (ACGTG)-core-containing ABA-responsive elements-like sequences in the promoters of these genes. Comparative mapping analysis also showed that one TaDOG1-like gene (accession: X56782, could reside in dormancy QTL regions in wheat and similarly, two rice putative orthologs (Os01g0159000 and Os05g0560200) reside in dormancy QTL regions in rice. In a reverse transcription quantitative PCR (RT-qPCR) analysis, no significant expression of two TaDOG1-like genes (accession: AB555729 and AK332921 or TaDOG1-L1 and TaDOG1-L2 respectively) were detected in either embryos or de-embryonated wheat grains of SUN325B at 45 and 60 dpa. However, both genes were detected to be expressed at 25 dpa and 30 dpa in the excised embryo tissues, signifying the mRNA to be short-lived. TaDOG1-L1 showed a non-significant increase following temperature shock, hence failed to explain the increase in germination index. TaDOG1-L2 was significantly down-regulated at 30 dpa following temperature shock, which could cause a lower protein accumulation towards 65 dpa. Further investigation could focus on the role of TaDOG1-L2 in dormancy in white wheat genotypes to better explain the effect of temperature shock during the sensitive “window” on dormancy in general.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2015.

Hsp22 has been implicated in stress tolerance and longevity in various organisms though its role in Drosophila melanogaster larval thermal tolerance has not yet been investigated. I undertook this project to determine if over-expression of hsp22 in either muscle or motor neurons could alter locomotor ability at high temperature in third instar larvae of D. melanogaster. A combination of the UAS-gal4 and tet-On promoter systems was used to over-express transgenic hsp22 in the larvae. A β-galactosidase assay was used to determine the level of gene expression following administration of different amounts of tetracycline. A concentration of 100 μg/ml of tetracycline was found to elicit appreciably higher expression of the reporter gene than 0 and 0.1 μg/ml of tetracycline. Locomotor ability of larvae was assessed at a temperature of approximately 400C by measuring the time to movement failure (TMF). Larvae that were fed 100 μg/ml of tetracycline showed a significant decline in the TMF, which could be attributed to the presence of tetracycline at a concentration of 100 μg/ml. Possible reasons behind the lack of a noticeable effect of hsp22 over-expression on the TMF are discussed. The detrimental effect of tetracycline could be attributed to the decline in mitochondrial translation or a decline in the population of endogenous bacteria, which are known to exert positive effects on the development and function of Drosophila larvae.
Thesis (Master, Biology) -- Queen's University, 2007-10-01 14:24:15.801

碩士
國立中正大學
化學工程研究所
105
In industry, simultaneous saccharification and fermentation (SSF) is considered to be an important process for the production of alcohol. Because it can efficiently reduce the cost of the production of cellulosic bioethanol. Unfortunately, the temperature for cellulose saccharification is higher than that for yeast fermentation. Therefore, it is desirable to develop a thermotolerance yeast strain to be adopted in the SSF process. When exposed to a variety of environmental stresses such as high temperature, alcoholic or oxidative stress, yeasts rapidly produces trehalose and heat shock proteins (HSPs). In the case of high temperature stress, the hydrogen bonding and Van der Waals force inside proteins can be destroyed then leading their denaturation. The increased misfolding proteins then induced expression of HSPs to help protein refolding and the survival of the cells. Among HSPs, HSP104 is essential for cell survival under high temperature. However, the induction of HSP104 is only transient by which the cells would not be able to survive after a long period of high-temperature fermentation. To prolong the expression of HSP104 at high temperature, plasmid pTEF1-2μ ori HSP26P ISA1 40homo was constructed and the NDA fragment 40homo-FRT-HSP26p-40homo amplified using polymerase chain reaction transformed to Saccharomyces cerevisiae for substituting the HSP104 promoter for the HSP26 promoter using homologous recombination.

Die vorliegende Arbeit beschreibt einen neuartigen Fügeprozess, das sogenannte reaktive Fügen bzw. Bonden. Hierbei werden sich selbsterhaltene exotherme Reaktionen in nanoskaligen Schichtsystemen als lokale Wärmequelle für das Fügen unterschiedlichster Substrate der Mikrosystemtechnik verwendet. Das Bonden mit den reaktiven Systemen unterscheidet sich von herkömmlichen Verfahren der Aufbau- und Verbindungstechnik primär dadurch, dass durch die rasche Reaktionsausbreitung bei gleichzeitig kleinem Reaktionsvolumen die Fügetemperaturen unmittelbar auf die Fügefläche beschränkt bleiben. Entgegen den herkömmlichen Fügeverfahren mit Wärmeeintrag im Volumen, schont das neue Verfahren empfindliche Bauteile und Materialien mit unterschiedlichsten thermischen Ausdehnungskoeffizienten lassen sich besser verbinden. In der vorliegenden Arbeit werden die Grundlagen zur Dimensionierung, Prozessierung und Integration der gesputterten reaktiven Materialsysteme beschrieben. Diese Systeme werden verwendet, um heterogene Materialien mit unterschiedlichen Durchmessern innerhalb kürzester Zeit auf Wafer-Ebene und bei Raumtemperatur zu bonden. Die so erzeugten Verbindungen werden hinsichtlich der Mikrostruktur, der Zuverlässigkeit sowie der Dichtheit untersucht und bewertet. Zusätzlich wird die Temperaturverteilung in der Fügezone während des Fügeprozesses mit numerischen Methoden vorhergesagt.