• 태양에너지
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• 제9권1호
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• pp.70-77
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• 1989

Sodium pyrophosphate that melting point is $79-80^{\circ}C$ have been Studied on heat storage and heat discharge. In heat storage process, sodium pyrophosphate was kept up initial temperature $50^{\circ}C,\;60^{\circ}C,\;70^{\circ}C$ which melt by heated water at temperature $85^{\circ}C,\;90^{\circ}C,\;95^{\circ}C$. In heat discharge process, initial temperature of sodium pyrophosphate was maintained at temperature $85^{\circ}C,\;90^{\circ}C,\;95^{\circ}C$ which varied cooling temperature $50^{\circ}C,\;60^{\circ}C,\;70^{\circ}C$. The experiment has been reached conclusions as follows. 1) Heat transfer properties of phase change material is controlled by conduction during heating and cooling process. 2) The temperature increased rapidly at initial stage and transient region increase slowly because of characteristic of latent heat. 3) The lower cooling water temperature is the less the time that get to thermal equivalent state take during discharge process. 4) The higher cooling water temperature is the less temperature difference between top and bottom in P.C.M during discharge process.

• 한국군사과학기술학회지
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• 제3권1호
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• pp.207-217
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• 2000

A fire fighting characteristic by a single evaporating droplet in the case of a fire of military enclosure space was studied experimentally. Transient cooling of solid surface by water droplet evaporation has been investigated through controlled experiments using a heated brass cylinder. Quantitative predictions of droplet evaporation time and in-depth transient temperature distribution in solid have been made. The particular interest was in the removal of thermal energy from the heated cylinder by evaporative cooling. A $10{\mu}1$ single droplet is deposited on a horizontal brass surface with initial temperatures in the range of $90^{\circ}C{\sim}130^{\circ}C.$ The results can be summarized as follows; Evaporating droplet was divided into three different configuration. Evaporation time was predicted as a function of initial surface temperature ($t_c=492.62-6.89T_{s0}+0.0248T_{s0}^2).$ The contact temperature was predicted as a function of initial surface temperature( $T_{i}$=0.94 $T_{s0}$+1.4), The parameter ${\beta}_o$ was predicted as a function of initial surface temperature( ${\beta}_0$ : 0.O0312 $T_{s0}+0.932$)>)>)

• 소성∙가공
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• 제17권8호
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• pp.558-563
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• 2008

The initial strain, the applied stress exponent, the activation energy, and rupture time in AZ31 magnesium alloy have been measured in order to predict the deformation mechanism and rupture life of creep over the temperature range of 423-443K. Creep tests were carried out under constant applied stress and temperature, and the lever type tester and automatic temperature controller was used for it, respectively. The experimental results showed that the applied stress exponent was about 9.74, and the activation energy for creep, 113.6KJ/mol was less than that of the self diffusion of Mg alloy including aluminum. From the results, the mechanism for creep deformation seems to be controlled by cross slip at the temperature range of 423-443K. Also the higher the applied stress and temperature, the higher the initial strain. And the rupture time for creep decreased as quadratic function with increasing the initial strain in double logarithmic axis.

• Journal of Mechanical Science and Technology
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• 제17권4호
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• pp.469-476
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• 2003

Despite of considerable research results or uniaxial tension creep available for superalloys, few studies have been made on high temperature creep using the Initial Stram Method (ISM) In this paper, the real-time prediction of high temperature creep strength and creep lift for the nickel-based superalloy Udimet 720 (high-temperature and high-pressure gas turbine engine materials) was performed on round-bar type specimens under pure static load at the temperatures of 538$^{\circ}C$. 649$^{\circ}C$, and 704$^{\circ}C$. The predictive equation derived from the ISM in creep tests showed better reliability than those from LMP (Larson-Miller Parameter) and LMP-lSM (Larson Miller Parameter-Initial Strain Method) specially for long time creep prediction (10$^3$∼10$\^$5/h).

• 한국해양공학회지
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• 제11권4호
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• pp.40-48
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• 1997

There are many research results as individual uni-axial tension creep test of heat-resisting materials. However, there are very few about the study on the high temperature creep test for the Initial Strain Method, and especially any study on it about the friction welded joints of SUH3 to SUH35. One of the important concerns is a reliable method of evaluating static creep properties. No reliable method seems available at present to evaluate or predict static creep properties. So, the reliable method to evaluate and predict them by the ISM and AE techniques was made.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 센서 박막재료
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• pp.18-22
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• 2001

Spinel $LiMn_{2-y}Mn_{y}O_4$ powder was prepared solid-state method by calcining the mixture of $LiOH{\cdot}H_2O$, $MnO_2$ and MgO at $800^{\circ}C$ for 36h. To investigate the effect of temperature for cycle behaviour of cathode material during cycling, charge-discharge experiments and initial impedance spectroscopy performed by the condition of the charge-discharge temperature. Initial charge-discharge capacity was gradually increased by rising charge-discharge temperature. However, capacity was suddenly decreased at high temperature during cycling. Capacity at low temperature was almost constant during cycling. It confirmed because Mn dissolution is more serious at high temperature than at low temperature.

• Earthquakes and Structures
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• 제8권6호
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• pp.1299-1323
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• 2015

A model for reflection and refraction of magneto-thermoelastic SV-waves at the interface of two transversely isotropic and homogeneous solid half spaces under initial stress by applying classical dynamical theory of thermoelasticity is purposed. The reflection and refraction coefficients of SV-waves are obtained with ideal boundary conditions for SV-wave incident on the solid-solid interface. The effects of magnetic field, temperature and initial stress on the amplitude ratios after numerical computations are shown graphically with MATLAB software for the particular model.

• 생명과학회지
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• 제5권4호
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• pp.155-161
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• 1995

The effects of substrate concentration, enzyme concentration, reaction temperature, and water content were investigated in intramolecular esterification. This study used cyclohexane as organic solvent, power lipase as enzyme, and benzyl alcohol and octanoic acid as substrate. The initial reaction rate was found to be proportional to enzyme concentration; followed Michaelis-Menten equation for octanoic acid; and was inhibited by benzyl alcohol . The observed initial reaction rate first increased, then decreased with increasing reaction temperature, giving rise to the maximum rate at 20$\circ$. The drop in the reaction rate at higher temperature was to partition equilibrium change of substrate between organic solvent and hydration layer of enzyme molecule in addition to the deactivation by enzyme denaturation. Water layer surrounding enzyme molecule seemed to activate in organic solvent and the realistic reaction was done in the water layer. In the enzymatic reaction in organic solvent, the initial reaction rate was influenced by partition quilibrium of substrate, so the optimum condition of substrate concentration, enzyme concentration, reaction temperature, and water content would give a good design tool.

• Steel and Composite Structures
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• 제11권4호
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• pp.341-358
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• 2011

This paper presents the effects of thermal environment and temperature-dependence of the material properties on axisymmetric bending of functionally graded (FG) circular and annular plates. The material properties are assumed to be temperature-dependent and graded in the thickness direction. In order to accurately evaluate the effect of thermal environment, the initial thermal stresses are obtained by solving the thermoelastic equilibrium equations. Governing equations and the related boundary conditions, which include the effects of initial thermal stresses, are derived using the virtual work principle based on the elasticity theory. The differential quadrature method (DQM) as an efficient and robust numerical tool is used to obtain the initial thermal stresses and response of the plate. Comparison studies with some available results for FG plates are performed. The influences of temperature rise, temperature-dependence of material properties, material graded index and different geometrical parameters are carried out.

• 한국연소학회지
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• 제4권1호
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• pp.95-103
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• 1999

Experimental study on combustion characteristics of a regenerative combustor has performed. High-temperature air combustion in the regenerative combustor is obtained through heat recovery from exhaust gas flow by porous ceramic materials and through alternation of air flow direction through the combustor. Temperature field, CO and NOx emission with respect to the frequency of alternation are measured. It is found that at initial stage of the alternation, temperature of inlet section of main combustion chamber is increased sharply since both high temperature air preheated by the ceramics and prompt fuel injection results in rapid combustion. Following this initial stage, combustion temperature is reduced as the preheated air temperature is reduced. However peak temperature in the chamber and exhaust gas temperature are decreased as the alternation period is reduced, increased temperature of ceramic is observed. CO and NOx emission with respect to the alternation period is also examined. It is found that there exists a range of optimum alternating period for CO and NOx emission characteristics.