• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.872-875
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• 2004

In this paper, thermal response analysis of a temperature controlled three-axis accelerometer for high temperature environments with integrated micro-heaters and temperature sensors is investigated with finite element method (FEM) program, ANSYS and infrared thermal measurement systems. And availability to application fields from a viewpoint about short thermal response time is discussed. In this paper, the time of three-axis accelerometer for high temperatures becoming $300^{\circ}C$ by integrated micro-heaters and temperature sensors to reduce thermal drift characteristics was analyzed as a thermal response time of this device. The simulated thermal response time (time until SOI piezoresistors actually becomes $300^{\circ}C$) of three-axis accelerometer for high temperatures with ANSYS is about 0.6s, and measured result with infrared temperature measurement systems is about 0.64s. Experimental results using infrared thermal measurement systems agreed well with these theoretical results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.567-573
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• 2015

This paper aims to evaluate the variation in the mechanical properties of carbon/epoxy composites under in situ low- and high-temperature environments. In situ low- and high-temperature environments were simulated with temperature ranging from $-40^{\circ}C$ to $220^{\circ}C$ using an environmental chamber and furnace. The variation in the mechanical properties of the composites was measured for longitudinal and transverse tensile properties, in-plane shear properties and interlaminar shear strength. Under the low temperature of $-40^{\circ}C$, all mechanical properties increased moderately compared to the baseline properties measured at room temperature. The changes in the longitudinal tensile properties decreased moderately with increasing temperature. However, transverse tensile properties, in-plane shear properties and interlaminar shear strength each showed a significant drop due to the glass transition behavior of the matrix after $140^{\circ}C$. Notably, the tensile property value near $100^{\circ}C$ increased compared to baseline property value, which was an unusual occurrence. This behavior was a direct result of post-curing of the epoxy resin due to its exposure to high temperature.

• Corrosion Science and Technology
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• v.17 no.5
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• pp.218-224
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• 2018

Alloy 617 is a candidate Ni-based superalloy for intermediate heat exchanger (IHX) of a high-temperature gas reactor (VHTR), because of its good creep strength and corrosion resistance at high temperature. Small amount of impurities such as $H_2O$, $H_2$, CO and $CH_4$ are introduced inevitably in helium, as a coolant during operation of a VHTR. Reactions of material and impurities are accelerated with increase of temperature to $950^{\circ}C$ of operating temperature of a VHTR, leading to material corrosion aggravation. In this circumstance, high-temperature corrosion tests were performed at $950^{\circ}C$ in air and impure helium environments, up to 250 hours in this study. Oxidation rate of $950^{\circ}C$ in an air environment was higher than that of impure helium, explained by difference in outer oxide morphology and microstructure as a function of oxygen partial pressure. An equiaxed Cr-rich surface oxide layer was formed in an air environment, and a columnar Cr-rich oxide was formed in an impure helium environment.

• Journal of Sensor Science and Technology
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• v.19 no.3
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• pp.197-201
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• 2010

This paper describes the fabrication and characteristics of a NO sensor using ZnO thin film integrated 3C-SiC micro heater based on polycrystalline 3C-SiC thin film of operation in harsh environments. The sensitivity, response time, and operating properties in high temperature and voltages of NO sensors based SiC MEMS are measured and analyzed. The sensitivity of device with pure ZnO thin film at the heater operating power of 13.5 mW ($300^{\circ}C$) is 0.875 in NO gas concentration of 0.046 ppm. In the case of Pt doping, the sensitivity of at power consumption of 5.9 mW ($250^{\circ}C$) was 1.92 at same gas flow rate. The ZnO with doped Pt was showed higher sensitivity, lower working temperature and faster adsorption characteristics to NO gas than pure ZnO thin film. The NO gas sensor integrated SiC micro heater is more strength than others in high voltage and temperature environments.

• Journal of Power System Engineering
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• v.21 no.2
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• pp.14-19
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• 2017

The corrosion characteristics of Al-Si-Mg alloy were investigated in $O_2$ and $H_2S/H_2$ environments at high temperature. The weight gain and the reaction rate constant of the Al-Si-Mg alloy were measured in the oxygen and hydrogen sulfide environments at 773K. The weight gain of Al-Si-Mg alloy was showed parabolic increase in the oxygen and hydrogen sulfide environments. The reaction rate constants were confirmed to be $1.45{\times}10^{-4}mg^2cm^{-4}sec^{-2}$ in the oxygen environment and $6.19{\times}10^{-4}mg^2cm^{-4}sec^{-2}$ in the hydrogen sulfide environment respectively. As a result of XPS analysis on the specimen surface, $Al_2O_3$ and MgO compounds were detected in oxygen environment and $Al_2(SO_4)_3$ sulfate was detected in the hydrogen sulfide environment. Corrosion rate of Al-Si-Mg alloy was about 4.3 times faster in hydrogen sulfide environment than oxygen environment.

• Corrosion Science and Technology
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• v.12 no.2
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• pp.102-112
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• 2013

A very high-temperature gas reactor (VHTR) is one of the next generation nuclear reactors owing to its safety, high energy efficiency, and proliferation-resistance. Heat is transferred from the primary helium loop to the secondary helium loop through an intermediate heat exchanger (IHX). Under VHTR environment Alloy 617 is being considered a candidate Ni-based superalloy for the IHX of a VHTR, owing to its good creep resistance, phase stability and corrosion resistance at high temperature. In this study, high-temperature corrosion tests were carried out at 850 - $950^{\circ}C$ in air and impure helium environments. Alloy 617 specimens showed a parabolic oxidation behavior for all temperatures and environments. The activation energy for oxidation was 154 kJ/mol in helium environment, and 261 kJ/mol in an air environment. The scanning electron microscope (SEM) and energy-dispersive x-ray spectroscopy (EDS) results revealed that there were a Cr-rich surface oxide layer, Al-rich internal oxides and depletion of grain boundary carbide after corrosion test. The thickness and depths of degraded layers also showed a parabolic relationship with the time. A corrosion rate of $950^{\circ}C$ in impure helium was higher than that in an air environment, caused by difference in the outer oxide morphology.

• Proceedings of the Korea Contents Association Conference
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• 2010.05a
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• pp.31-33
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• 2010

The image communication system based on power line communication(PLC) that manages the status of workers in deteriorated. work environments such as high temperature and pressures as realtime is designed and implemented in this paper. The major design considerations for system design are such that the adaptation of simple architecture, simplicity of installation and movement, tolerances about high temperature and pressures, transmission of high quality image under various noise environments.

• Journal of Internet of Things and Convergence
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• v.10 no.2
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• pp.125-130
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• 2024

With the rapid growth of mobility technology, the industrial sector is demanding storage devices that can reliably process data from various equipment and sensors in vehicles. NAND flash memory is being utilized as a storage device in mobility environments because it has the advantages of low power and fast data processing speed as well as strong external shock resistance. However, flash memory is characterized by data corruption due to long-term exposure to high temperatures. Therefore, a dedicated system for temperature management is required in mobility environments where high temperature exposure due to weather or external heat sources such as solar radiation is frequent. This paper designs a dedicated temperature management system for managing storage device temperature in a mobility environment. The designed temperature management system is a hybrid of traditional air cooling and water cooling technologies. The cooling method is designed to operate adaptively according to the temperature of the storage device, and it is designed not to operate when the temperature step is low to improve energy efficiency. Finally, experiments were conducted to analyze the temperature difference between each cooling method and different heat dissipation materials, proving that the temperature management policy is effective in maintaining performance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.191-192
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• 2023

In recent years, the use of high-strength grout has gained popularity in offshore wind power generation complexes for facility foundations and bridges. These marine wind farms require support for horizontal loads from wind and waves. To ensure the strength of the grout produced in environments similar to the actual placing site, this study investigated the curing of high-strength grout discharged through pump pressure in various environments, and examined the difference in strength according to different variables. Compressive strength measurements revealed that the core specimen collected from the bottom (3cm) and uppermost (50cm) of the specimen exhibited lower strength compared to other height specimens, while the core specimen obtained from the corner exhibited lower strength compared to the center. These findings suggest that the strength difference between the center and the corner is more pronounced when curing at low temperatures. This effect is greater than the strength reduction that typically occurs during low-temperature curing, and thus, necessitates careful attention in similar construction environments.

• Journal of the Korean Ceramic Society
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• v.55 no.6
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• pp.527-555
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• 2018

High-temperature thermal insulation materials challenge extensive oxide candidates such as porus $SiO_2$, $Al_2O_3$, yttria-stabilized zirconia, and mullite, due to the needs of good mechanical, thermal, and chemical reliabilities at high temperatures simultaneously. Recently, porous rare earth (RE) silicates have been revealed to be excellent thermal insulators in harsh environments. These materials display attractive properties, including high porosity, moderately high compressive strength, low processing shrinkage (near-net-shaping), and very low thermal conductivity. The current critical challenge is to balance the excellent thermal insulation property (extremely high porosity) with their good mechanical properties, especially at high temperatures. Herein, we review the recent developments in processing techniques to achieve extremely high porosity and multiscale strengthening strategy, including solid solution strengthening and fiber reinforcement methods, for enhancing the mechanical properties of porous RE silicate ceramics. Highly porous RE silicates are highlighted as emerging high-temperature thermal insulators for extreme environments.