Aerospace Performances of IPDiA −250°C up to 250°C Grade Silicon Capacitors

2016 ◽  
Vol 2016 (HiTEC) ◽  
pp. 000284-000289
Author(s):  
Laurent Lengignon ◽  
Sebastien Leruez
Keyword(s):  
Thermal Stress ◽  
High Temperatures ◽  
Frequency Data ◽  
Aerospace Applications ◽  
Grade Silicon

Abstract This paper covers technological results achieved with silicon capacitors for Aerospace applications, including stability, reliability and frequency data at high temperatures, as well as thermal stress, vibration & shock tests and radiations stress, according to ESA TRP reference (n° T723-325QT).

Thermoelectric properties and thermal stress simulation of pressureless sintered SiC/AlN ceramic composites at high temperatures

2018 ◽  
Vol 182 ◽  
pp. 302-313 ◽  
Author(s):  
Dina H.A. Besisa ◽  
Emad M.M. Ewais ◽  
Essam A.M. Shalaby ◽  
Andrey Usenko ◽  
Denis V. Kuznetsov
Keyword(s):  
Thermal Stress ◽  
High Temperatures ◽  
Thermoelectric Properties ◽  
Ceramic Composites ◽  
Stress Simulation

Influence of Distinct Manufacturing Processes on the Microstructure of Ni-Based Metal Matrix Composites Submitted to Long Thermal Exposure

2019 ◽  
Vol 809 ◽  
pp. 79-86
Author(s):  
Georges Lemos ◽  
Márcio C. Fredel ◽  
Florian Pyczak ◽  
Ulrich Tetzlaff
Keyword(s):  
Metal Matrix Composites ◽  
High Temperatures ◽  
Metal Matrix ◽  
Thermal Exposure ◽  
High Energy ◽  
Matrix Composites ◽  
Microstructural Stability ◽  
Aerospace Applications ◽  
Plasma Sintering ◽  
Energy Processes

Metal Matrix Composites (MMCs) are known for their remarkable properties, by combining materials from different classes. Ni-based MMCs are a promising group of heat-resistant materials, targeting aerospace applications. A discontinuously reinforced Inconel X-750/TiC 15 vol.% MMC was proposed for use in lighter, creep resistant turbine elements, with the aim to endure service temperatures up to 1073 K (800 °C). However, their microstructural stability at high temperatures for long periods of time remained to be further investigated. To address this need, specimens were produced by both conventional hot pressing and spark plasma sintering, using powders milled by low and high energy processes, followed by long isothermal aging. The treatments were conducted at 973 and 1073 K, for times between 50 and 1000 hours. The resulting samples were investigated with XRD and EDS techniques for phase analysis. In addition, measurements of hardness were made to monitor changes in mechanical behavior. It was found that, for each different manufacturing process, the amount, distribution and size of γ’ and other precipitates notably vary during the overaging process. Consequently, the amount of elements kept in solid solution also shifted with time. Furthermore, the study shows how distinct initial microstructures, resulting from diverse fabrication processes, differently impact the microstructural stability over long times of exposure to high temperatures.

scholarly journals Thermal stress estimation in relation to spalling of HSC restrained with steel rings at high temperatures

2013 ◽  
Vol 6 ◽  
pp. 01004 ◽  
Author(s):  
T. Tanibe ◽  
M. Ozawa ◽  
R. Kamata ◽  
R. Sato ◽  
K. Rokugo
Keyword(s):  
Thermal Stress ◽  
High Temperatures ◽  
Stress Estimation

scholarly journals Antioxidant Enzymes and Heat Shock Protein Genes from Liposcelis bostrychophila Are Involved in Stress Defense upon Heat Shock

Insects ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 839
Author(s):  
Ze Qing Miao ◽  
Yan Qing Tu ◽  
Peng Yu Guo ◽  
Wang He ◽  
Tian Xing Jing ◽  
...  
Keyword(s):  
Antioxidant Enzymes ◽  
Heat Stress ◽  
Thermal Stress ◽  
Heat Shock ◽  
Oxidative Damage ◽  
High Temperatures ◽  
Defense Mechanisms ◽  
Molecular Mechanisms ◽  
Instar Nymph ◽  
Liposcelis Bostrychophila

Psocids are a new risk for global food security and safety because they are significant worldwide pests of stored products. Among these psocids, Liposcelis bostrychophila has developed high levels of resistance or tolerance to heat treatment in grain storage systems, and thus has led to investigation of molecular mechanisms underlying heat tolerance in this pest. In this study, the time-related effects of thermal stress treatments at relatively high temperatures on the activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidases (POD), glutathione-S-transferases (GST) and malondialdehyde (MDA), of L. bostrychophila were determined. Thermal stress resulted that L. bostrychophila had a significantly higher MDA concentration at 42.5 °C, which indicated that the heat stress increased lipid peroxidation (LPO) contents and oxidative stress in this psocid pest. Heat stress also resulted in significant elevation of SOD, CAT and GST activities but decreased POD activity. Our data indicates that different antioxidant enzymes contribute to defense mechanisms, counteracting oxidative damage in varying levels. POD play minor roles in scavenging deleterious LPO, while enhanced SOD, CAT and GST activities in response to thermal stress likely play a more important role against oxidative damage. Here, we firstly identified five LbHsps (four LbHsp70s and one LbHsp110) from psocids, and most of these LbHsps (except LbHsp70-1) are highly expressed at fourth instar nymph and adults, and LbHsp70-1 likely presents as a cognate form of HSP due to its non-significant changes of expression. Most LbHsp70s (except LbHsp70-4) are significantly induced at moderate high temperatures (<40 °C) and decreased at extreme high temperatures (40–45 °C), but LbHsp110-1 can be significantly induced at all high temperatures. Results of this study suggest that the LbHsp70s and LbHsp110 genes are involved in tolerance to thermal stress in L. bostrychophila, and antioxidant enzymes and heat shock proteins may be coordinately involved in the tolerance to thermal stress in psocids.

Analysis of Post-Combustion High-Strength Concrete Compressive Strength Using Polypropylene Fibers

2020 ◽  
Vol 26 (1) ◽  
pp. 118-127
Author(s):  
Teuku Budi Aulia ◽  
Muttaqin Muttaqin ◽  
Mochammad Afifuddin ◽  
Zahra Amalia
Keyword(s):  
Compressive Strength ◽  
Thermal Stress ◽  
Silica Fume ◽  
High Temperatures ◽  
High Strength Concrete ◽  
High Strength ◽  
Polypropylene Fibers ◽  
Concrete Compressive Strength ◽  
Strength Concrete ◽  
Maximum Value

High-strength concrete is vulnerable to high temperatures due to its high density. The use of polypropylene fibers could prevent structure explosion by forming canals due to melted fibers during fire, thus release its thermal stress. This study aims to determine the effect of polypropylene fibers on compressive strength of high-strength concrete after combustion at 400ºC for five hours. High-strength concrete was made by w/c-ratio 0.3 with cement amount 550 kg/m3 and added with silica fume 8% and superplasticizer 4% by cement weight. The variations of polypropylene fibers were 0%, 0.2% and 0.4% of concrete volume. The compression test was carried out on standard cylinders Ø15/30 cm of combustion and without combustion specimens at 7 and 28 days. The results showed that compressive strength of high-strength concretes without using polypropylene fibers decreased in post-combustion compared with specimens without combustion, i.e., 0.81% at 7 days and 23.42% at 28 days. Conversely, the use of polypropylene fibers can increase post-combustion compressive strength with a maximum value resulted in adding 0.2% which are 25.52% and 10.44% at 7 and 28 days respectively. It can be concluded that the use of polypropylene fibers is effective to prevent reduction of high-strength concrete compressive strength that are burned at high temperatures.

Response of antioxidant enzymes in Mythimna separata (Lepidoptera: Noctuidae) exposed to thermal stress

2016 ◽  
Vol 107 (3) ◽  
pp. 382-390 ◽  
Author(s):  
A. Ali ◽  
M. A. Rashid ◽  
Q. Y. Huang ◽  
C. Wong ◽  
C.-L. Lei
Keyword(s):  
Antioxidant Enzymes ◽  
Thermal Stress ◽  
Oxidative Damage ◽  
High Temperatures ◽  
Stress Responses ◽  
Physiological Stress ◽  
Southern China ◽  
Northern China ◽  
Mythimna Separata ◽  
Lepidoptera Noctuidae

AbstractThe oriental army worm Mythimna separata (Lepidoptera: Noctuidae) is a migratory pest in Eastern Asia and China. Seasonal high temperatures in Southern China and low temperatures in Northern China are pressures favouring the annual migration of this species, while cold tolerance determines the northern limit of its overwintering range. A number of physiological stress responses occur in insects as a result of variations in temperature. One reaction to thermal stress is the generation of reactive oxygen species (ROS), which can be harmful by causing oxidative damage. The time-related effects (durations of 1, 4 and 7 h) of thermal stress treatments of M. separata at comparatively low (5, 10, 15 and 20°C) and high (30, 35, 40 and 45°C) temperatures on the activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POX) and glutathione S-transferases (GSTs), and total antioxidant capacity (T-AOC) were determined. Thermal stress resulted in significant elevation of the activities of SOD, CAT and GSTs, indicating that these enzymes contribute to defence mechanisms counteracting oxidative damage caused by an increase in ROS. However, at high-temperatures, POX and T-AOC were also found to contribute to scavenging ROS. Our results also indicate that extreme temperatures lead to elevated ROS production in M. separata. The present study confirms that thermal stress can be responsible for oxidative damage. To overcome such stress, antioxidant enzymes play key roles in diminishing oxidative damage in M. separata.

scholarly journals Irreversible impacts of heat on the emissions of monoterpenes, sesquiterpenes, phenolic BVOC and green leaf volatiles from several tree species

2012 ◽  
Vol 9 (12) ◽  
pp. 5111-5123 ◽  
Author(s):  
E. Kleist ◽  
T. F. Mentel ◽  
S. Andres ◽  
A. Bohne ◽  
A. Folkers ◽  
...  
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
High Temperatures ◽  
Tree Species ◽  
De Novo ◽  
Heat Waves ◽  
Green Leaf Volatiles ◽  
Leaf Volatiles ◽  
Resin Ducts ◽  
As Stress

Abstract. Climate change will induce extended heat waves to parts of the vegetation more frequently. High temperatures may act as stress (thermal stress) on plants changing emissions of biogenic volatile organic compounds (BVOCs). As BVOCs impact the atmospheric oxidation cycle and aerosol formation, it is important to explore possible alterations of BVOC emissions under high temperature conditions. Applying heat to European beech, Palestine oak, Scots pine, and Norway spruce in a laboratory setup either caused the well-known exponential increases of BVOC emissions or induced irreversible changes of BVOC emissions. Considering only irreversible changes of BVOC emissions as stress impacts, we found that high temperatures decreased the de novo emissions of monoterpenes, sesquiterpenes and phenolic BVOC. This behaviour was independent of the tree species and whether the de novo emissions were constitutive or induced by biotic stress. In contrast, application of thermal stress to conifers amplified the release of monoterpenes stored in resin ducts of conifers and induced emissions of green leaf volatiles. In particular during insect attack on conifers, the plants showed de novo emissions of sesquiterpenes and phenolic BVOCs, which exceeded constitutive monoterpene emissions from pools. The heat-induced decrease of de novo emissions was larger than the increased monoterpene release caused by damage of resin ducts. For insect-infested conifers the net effect of thermal stress on BVOC emissions could be an overall decrease. Global change-induced heat waves may put hard thermal stress on plants. If so, we project that BVOC emissions increase is more than predicted by models only in areas predominantly covered with conifers that do not emit high amounts of sesquiterpenes and phenolic BVOCs. Otherwise overall effects of high temperature stress will be lower increases of BVOC emissions than predicted by algorithms that do not consider stress impacts.

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