• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 하계학술대회 논문집 D
• /
• pp.880-882
• /
• 1997

The secondary arcing phenomenon can be hardly modeled for computer simulation due to its particularly-nonlinear characteristics. This paper describes a new computer modeling technique for the secondary arc which can be implemented with the EMTP MODELS. The computer model proposed is based on realistic arc conduction behaviors through newly designed variable resistor modules which can be supported in the EMTP. In this Paper, for the variable resister modules, a new variable arc resistance formula is proposed. Simulation results using the proposed technique are compared with some previous studies.

• 한국세라믹학회지
• /
• 제35권12호
• /
• pp.1323-1328
• /
• 1998

The electrical conductivities of the yttria (8mol%) stabilizedzirconia-ceria solid solutions were measured as a function of oxygen partial between 80$0^{\circ}C$ and 100$0^{\circ}C$ using 4-probe d.c. method Under pure oxygen atmosphere the oxygen ionic conductivity of CeO2-ZrO2 decreased with the concentration of CeO2 Under reducing condition electronic conduction due to the redox equilibrium of Ce ion was observed. Total ionic and electronic conductivities fitted by a defect model enabled to determine the electronic transference number(tei) which increased with the concentration of CeO2 and with the degree of reduction.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2008년도 하계학술발표대회 논문집
• /
• pp.643-649
• /
• 2008

The purpose of this study is to establish a standard for unit cooling load in central control type apartment applied district cooling. The model of unit household was selected. And the standard of coefficient of overall heat transmission, location of unit household, indoor air temperature, solar radiation & thermal conduction at window and interior load was selected, and region, expansion or non-expansion of balcony, pyeong type, azimuth, rate of window area was applied as parameter. And then cooling load simulation was performed. Based on the result of simulation, the synthetic district cooling load was presented for selecting heat source of apartment applied district cooling, and unit cooling load was analyzed according to design parameter.

• 설비공학논문집
• /
• 제10권5호
• /
• pp.600-609
• /
• 1998

The experimental investigation of thermal response characteristics by the air flow through the porous media has been carried out. The packed spheres of steel or glass were considered as the porous media in the present study. Temperature distributions of the fluid in the porous media as well as pressure drops through the porous media were measured. The transient temperature variations in the porous media are compared favorably with the analytical results in the high Reynolds number ranges. However, in the low Reynolds number ranges, the experimental data deviate from the analytical results, due to the dominant heat conduction penetration to the upstream direction, which is not considered in the analytical model. The cool-down response of porous media is found to be dependent upon the specific dimensionless time considering the material property and air velocity. The heat discharge process is recommended to be operated until a certain time, considering the cost efficiency.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제17권2호
• /
• pp.74-79
• /
• 2009

The performance of cryogenic refrigerator greatly depends on the effectiveness of heat exchanger, which generates major entropy at low temperature. There are numerous types of heat exchanger available, but it is not easy to apply most of them to cryogenic application because the cryogenic heat exchanger must have high effectiveness value as well as small conduction loss in the environment of considerable temperature difference. In this paper, two kinds of heat exchanger are noticeably introduced for high-effectiveness miniature cryogenic recuperator(recuperative heat ex-changer). Also, the flow mal-distribution problem, which is a critical issue of performance deterioration in a high-effectiveness recuperator, is addressed with simplified model, and its alleviation method is discussed.

• 전자공학회논문지B
• /
• 제33B권10호
• /
• pp.148-156
• /
• 1996

Increasing the switching frquency is essential to achieve the high density of switched mode power supplies, but this leads to the increase of switching losses. A number of new soft switching converters have been presented ot reduce switching losses, but most of them may have some demerits, such as the increase of voltage/current stresses and high conduction losses. To overcome these problems, the ZVT-PWM converter has recently been presented. in this paper, the operation characteristics of the ZVT-PWM boost converter is analyzed, and the steady-states (DC) and small-signal model of this converter are derived and analyzed, and then the transfer functions of this converter are derived. The transfer functions of ZVT-PWM boost converter are similar to those of the conventional PWM boost converter, but the transfer characteristics are affecsted by te duty ratio and the switching frequency.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
• /
• pp.1055-1055
• /
• 2009

The mobility of charge carriers has been investigated in the pristine and phosphorescent materials doped host materials using time-of-flight photoconductivity technique. The field and temperature dependences of the mobility were analyzed with the Gaussian disorder model. Based on these results, we optimized white organic light emitting diodes (WOLEDs) consisting of multi-emitting layers doped with phosphorescent and fluorescent dopants. Especially, we studied the effect of each emitter position and an interlayer on the device characteristics of WOLEDs.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2014년도 추계 학술논문 발표대회
• /
• pp.169-170
• /
• 2014

In this study, a general strength concrete member is produced and its hydrothermal temperature is measured. It is intended to present the basic data for establishment of fire resistance performance assessment and review of safety against fire by comparing the data values of slab fire resistance experiment and the numerical analysis model. The value obtained by measuring the hydrothermal temperature of the concrete after heating the concrete designed to have general strength (30 Mpa) for 3 hours in accordance with the ISO 834 Heating Curve is compared with the value obtained from a thermal conduction analysis. As a result of the comparison, though there is a little difference, it is thought that fire behaviors can be predicted in the future if the movement of moisture and the added evaporation speed are taken into account.

• 복식문화연구
• /
• 제10권6호
• /
• pp.793-801
• /
• 2002

The effects of ambient air temperature on the clothing ventilation were investigated numerically by a finite difference method. Numerical analysis using a 2-dimensional model comprising the air space between the skin and the clothing was conducted under the assumption that the clothing ventilation occurred only through the openings not through the fabric. The larger the temperature difference between the skin and the surroundings, the more apparent the thermal boundary layer As the ambient air temperature decreased, the air flow and the rate of the return of oxygen concentration to the atmosphere level in the clothing increased. Convection was dominant under low ambient air temperature, whereas conduction was dominant under high ambient air temperature. The ventilation rate was faster in the clothing microenvironment of the body part than that of the arm part.

• 한국자동차공학회논문집
• /
• 제9권3호
• /
• pp.173-180
• /
• 2001

In the case of axisymmetric thermal analysis of drum brakes, the distribution of frictional heat produced on the interface and temperature difference between mating frictional faces are very interesting problems to computational researchers. In the first part, the influence of the s-cam load angles and elastic modulus of the pad on the contact pressure distribution between pad and drum was checked by a three dimensional model. In the second part heat conduction from the interface to the pad and the drum was modeled by using a thin interface element, so artificial division of the generated frictional heat between pad and drum is not necessary. Temperature difference between mating frictional faces is successfully modeled by using the interface element. The influence of some parameters on the thermal distribution is checked. The analysis was performed by ABAQUS/Standard code.