• Journal of Welding and Joining
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• v.27 no.3
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• pp.92-96
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• 2009

Metallic sandwich plate has many good properties such as high specific stiffness, high specific strength, good impact absorptivity, effective thermal insulation and soundproofing. In our study, a new bonding method, 3-layer roll projection welding, is introduced to fabricate the metallic sandwich plate. The new method uses a pair of roll electrodes like the seam welding, and projection welding is made at two internal interfaces of the 3-layer weldment consisting of a structured inner sheet and a pair of skin sheets. During the welding process, skin sheet temperature are measured to produce metallic sandwich plate with uniform and good quality. But it is difficult to observe or measure the temperature at the welding points during welding process because the welding points exist at the internal interfaces. Therefore FEM numerical analysis using ABAQUS is conducted to estimate the generated heat at the welding points with different welding conditions.

• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2259-2264
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• 2009

A new high-energy organic potassium salt, 2-(dinitromethylene)-1,3-diazepentane potassium salt K(DNDZ), was synthesized by reacting of 2-(dinitromethylene)-1,3-diazepentane (DNDZ) and potassium hydroxide. The thermal behavior and non-isothermal decomposition kinetics of K(DNDZ) were studied with DSC, TG/DTG methods. The kinetic equation is $\frac{d{\alpha}}{dT}$ = $\frac{10^{13.92}}{\beta}$3(1 - $\alpha$[-ln(1 - $\alpha$)]$^{\frac{2}{3}}$ exp(-1.52 ${\times}\;10^5$ / RT). The critical temperature of thermal explosion of K(DNDZ) is $208.63\;{^{\circ}C}$. The specific heat capacity of K(DNDZ) was determined with a micro-DSC method, and the molar heat capacity is 224.63 J $mol^{-1}\;K^{-1}$ at 298.15 K. Adiabatic time-to-explosion of K(DNDZ) obtained is 157.96 s.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.6
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• pp.896-902
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• 2009

EGR is applied in order to lower temperature of combustion chamber by using the specific heat of carbon dioxide in engine exhaust gas. However, the problem of EGR system in diesel engine is high PM concentration. Combined EGR system can be reduced it by mixing exhaust gas of gas engine into the intake air of diesel engine. This experimental study was designed for EGR system for both engines use. The results of EGR experimental study by using diesel engine and gas engine are as follows. 1) The pressure of combustion and rate of heat release decreased. 2) The specific fuel consumption increased. But, up to middle load, it little increased. 3) NO concentration has decreased up to 50% in almost all combustion area. 4) The variation of the PM concentration at low load is not so seen. But at high load, PM increased rapidly when concentration of oxygen is decreased and most of it caused the increasing of Dry Soot.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.1
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• pp.13-26
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• 2006

When the stagnation temperature of a perfect gas increases, the specific heat for constant pressure and ratio of the specefic heats do not remain constant any more and start to vary with this temperature. The gas remains perfect: its state equation remains always valid, with exception that it will be named by calorically imperfect gas. The aim of this research is to develop the relations of the necessary thermodynamics and geometrical ratios. and to study the supersonic flow at high temperature. lower than the threshold of dissociation. The results are found by the resolution of nonlinear algebraic equations and integration of complex analytical functions where the exact calculation is impossible. The dichotomy method is used to solve the nonlinear equation. and the Simpson algorithm for the numerical integration of the found integrals. A condensation of the nodes is used. Since. the functions to be integrated have a high gradient at the extremity of the interval of integration. The comparison is made with the calorifcally perfect gas to determine the error made by this last. The application is made for the air in a supersonic nozzle.

• Composites Research
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• v.16 no.6
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• pp.41-47
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• 2003

Composites are widely used for aircraft, satellite and other structures due to its good mechanical and thermal characteristics such as low coefficient of thermal expansion(CTE), heat-resistance, high specific stiffness and specific strength. In order to use composites under condition of high temperature, however, material properties of composites at high temperatures must be measured and verified. In this paper, material properties of T700/Epoxy were measured through tension tests of composite specimens with an embedded FBG sensor in the thermal chamber at the temperatures of RT, $100^{\circ}$, $200^{\circ}$, $300^{\circ}$, $300^{\circ}$. Through the pre-test of an embedded optical fiber, we confirmed the embedding effects of an optical fiber on material properties of the composites. Two kinds of specimens of which stacking sequences are [0/｛0｝/0]$_{T}$. and [$90_2$/｛0｝/$90_2$]. were fabricated. From the experimental results, material property changes of composites were successfully shown according to temperatures and we confirmed that fiber Bragg grating sensor is very appropriate to strain measurement of composites under high temperature.

• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.777-786
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• 2005

The Solid Oxide Fuel Cell (SOFC) is an electrochemical device to convert chemical energy of a fuel into electricity at temperatures from about 600 to $1000^{\circ}C$. The SOFC offers certain advantages over lower temperature fuel cells, notably its ability to use CO as a fuel rather than being poisoned by it, and high grade exhaust heat for combined heat and power, or combined cycle gas turbine applications. This paper reviews the operating principle, materials for different cell and stack components, cell designs, and applications of SOFCs. Among all designs of Solid Oxide Fuel Cells (SOFCs), the most progress has been achieved with the tubular design. However, the electrical resistance of tubular SOFCs is high, and specific power output $(W/cm^2)$ and volumetric power density $(W/cm^3)$ low. Planar SOFCs, in contrast, are capable of achieving very high power densities.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.66-70
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• 2005

Structural components for aerospace, electronics and automobile industry are the main applications for magnesium alloys due to their lightweight and high specific strength. The adoption of magnesium alloys in sheet forming processes is still limited, due to their low formability at room temperature caused by the hexagonal crystal structure. In this paper, the authors aim to improve the formability of AZ31 magnesium alloy. For this, experiment and finite element analysis on used warm deep drawing process with a local heating and cooling technique were done. Both die and blank holder were heated at various warm temperature while the punch was kept at room temperature by cooling water.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.3
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• pp.199-206
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• 2017

A geological repository for the disposal of high-level radioactive waste is generally constructed in host rock at depths of 500~1,000 meters below the ground surface. A geological repository system consists of a disposal canister with packed spent fuel, buffer material, backfill material, and intact rock. The buffer is indispensable to assure the disposal safety of high-level radioactive waste, and it can restrain the release of radionuclides and protect the canister from the inflow of groundwater. Since high temperature in a disposal canister is released to the surrounding buffer material, the thermal properties of the buffer material are very important in determining the entire disposal safety. Even though there have been many studies on thermal conductivity, there have been only few studies that have investigates the specific heat capacity of the bentonite buffer. Therefore, this paper presents a specific heat capacity prediction model for compacted Gyeongju bentonite buffer material, which is a Ca-bentonite produced in Korea. Specific heat capacity of the compacted bentonite buffer was measured using a dual probe method according to various degrees of saturation and dry density. A regression model to predict the specific heat capacity of the compacted bentonite buffer was suggested and fitted using 33 sets of data obtained by the dual probe method.

• Korean Journal of Environmental Agriculture
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• v.37 no.4
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• pp.324-332
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• 2018

BACKGROUND: Insects are ectothermic organisms in terrestrial ecosystems and play various roles such as controlling plant biomass and maintaining species diversity. Because insects are ectothermic, their physiological responses are very sensitive to environmental temperature which determines survival and distribution of insect population and that affects climate change. This study aimed to identification of genes contributing to fitness under high temperature. METHODS AND RESULTS: To identify genes contributing to fitness under high temperature, the transcriptomes of fat body in Plutella xyostella larva have been analyzed via next generation sequencing. From the fat body transcriptomes, structure-related proteins, heat shock proteins, antioxidant enzymes and detoxification proteins were identified. Genes encoding proteins such as structural proteins (cuticular proteins, chitin synthase and actin), stress-related protein (cytochrome P450), heat shock protein and antioxidant enzyme (catalase) were up-regulated at high temperature. In contrast expression of glutathione S transferase was down-regulated. CONCLUSION: Identifications of temperature-specific up- or down-regulated genes can be useful for detecting temperature adaptation and understanding physiological responses in insect pests.

• Journal of Mechanical Science and Technology
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• v.19 no.10
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• pp.1932-1938
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• 2005

Graphite foams consist of a network of interconnected graphite ligaments and are beginning to be applied to thermal management of electronics. The thermal conductivity of the bulk graphite foam is similar to aluminum, but graphite foam has one-fifth the density of aluminum. This combination of high thermal conductivity and low density results in a specific thermal conductivity about five times higher than that of aluminum, allowing heat to rapidly propagate into the foam. This heat is spread out over the very large surface area within the foam, enabling large amounts of energy to be transferred with relatively low temperature difference. For the purpose of graphite foam thermosyphon design in electronics cooling, various effects such as graphite foam geometry, sub-cooling, working fluid effect, and liquid level were investigated in this study. The best thermal performance was achieved with the large graphite foam, working fluid with the lowest boiling point, a liquid level with the exact height of the graphite foam, and at the lowest sub-cooling temperature.