• Structural Monitoring and Maintenance
• /
• 제6권3호
• /
• pp.191-218
• /
• 2019

The aim of the present investigation is to examine the propagation of plane waves in transversely isotropic homogeneous magneto thermoelastic rotating medium with fractional order heat transfer. It is found that, for two dimensional assumed model, there exist three types of coupled longitudinal waves (quasi-longitudinal, quasi-transverse and quasi-thermal waves). The wave characteristics such as phase velocity, attenuation coefficients, specific loss, penetration depths, energy ratios and amplitude ratios of various reflected and transmitted waves are computed and depicted graphically. The conservation of energy at the free surface is verified. The effects of rotation and fractional order parameter by varying different values are represented graphically.

• 열처리공학회지
• /
• 제22권2호
• /
• pp.80-87
• /
• 2009

Effects of retained austenite contents on ductility of medium carbon spring steels according to steel alloy compositions and heat treatment conditions were studied. Contents of retained austenite varied with steel compositions and heat treatment conditions, and some retained austenite were found to transform to martensite on stress. Reduction of area (RA) increased with contents of retained austenite, then saturated through its maximum, and subsequently decreased. Increase in RA with retained austenite contents could be due to crack blunting effect by retained austenite on stress, however, more contents of martensite transformed from retained austenite in its higher contents could cause decrease in RA.

• 한국태양에너지학회 논문집
• /
• 제22권1호
• /
• pp.43-53
• /
• 2002

This study has been carried out to study the thermal performance of an all-glass type solar collector tube when a heat transfer medium is used with a heat storage unit capable of preventing pressure build-up within the tube. The heat storage unit is devised such that it performs the dual function of relieving excessive pressure and storing solar thermal energy. Different types of heat storage medium are tested under heat-up phase of a collector tube. It is found that the proposed unit could be used quite effectively if one wishes to capitalize more aggressively in harnessing the solar energy.

• 한국수정란이식학회지
• /
• 제16권1호
• /
• pp.41-46
• /
• 2001

This study was carried out to evaluate the effect of culture methods on development of embryos with each developmental stage after heat shock in bovine oocytes. The results obtained were as fellows. 1. The culture method after heat shock on development of embryos was better drop-culture than co-culture. 2. The medium without amino acids were not effect of heat sock on development of embryos but it was in need of amino acid during formation of blastocyst.

• Nuclear Engineering and Technology
• /
• 제56권2호
• /
• pp.636-643
• /
• 2024

The coolability of the debris bed with a simulant of solidified corium is experimentally studied, focusing on the effects of the structure of the axial stratified debris bed on the dryout heat flux (DHF). DHF was obtained for the four structures with different particle sizes for the axial stratified debris bed under top flooding. The experimental results show that the dryout position of the axial stratified debris bed is formed at the stratified interface indicated by the temperature rise, and the DHF of the axial stratified bed is much lower than that of the homogeneous bed packed with the upper small particles. To predict the dryout heat flux of the stratified debris beds, by considering the properties of the mixed area, a one-dimensional dryout heat flux model of the porous medium is derived from a water and vapor momentum equation for porous medium, two-phase permeability modifications, interfacial drag, and the correlation between capillary pressure and liquid saturation and verified with the experimental data. The modified model can give reasonable results under different structures.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2004년도 춘계 학술대회논문집
• /
• pp.183-189
• /
• 2004

The flow and the heat transfer about the cross-flow fin-tube heat exchanger in an out-door unit of a heat pump system has been numerically Investigated. Using the general purpose analysis code, FLUENT, the Navier-Stokes equations and the energy equation are solved for the three dimensional computation domain that encompasses multiple rows of the fin-tube. The temperature on the fin and tube surface is assumed constant but compensated later through the fin efficiency when predicting the heat-transfer rate. The contact resistance is also taken into consideration. The flow and temperature fields for a wide range of inlet velocity and fin-tube arrangements are examined and the results are presented in the paper. The details of the flow are very well captured and the heat transfer rate for a range of inlet velocity is in excellent agreement with the measured data. The flow solution provides the effective permeability and the inertial resistance factor of the heat exchanger if the exchanger were to be approximated by the porous medium. This information is essential in carrying out the global flow field calculation which, in turn, provides the inlet velocity lot the microscopic temperature-field calculation of the heat exchanger unit.

• 한국자원식물학회:학술대회논문집
• /
• 한국자원식물학회 1999년도 The 6th International Symposium on the Development of Anti-Cancer Resource from Plants
• /
• pp.46-57
• /
• 1999

Ginseng(Panax ginseng C.A. Meyer) is important medicinal plant but requires 4-year cultivation for root harvest because of slow growth. In contrast, ginseng callus and hairy roots grow vigorously and may Produce the same or more biologically active compounds for human health than natural ginseng roots. Therefore, ginseng callus and hairy roots can be used for commercial purposes. Polyacetylene, one of anti-cancer compounds in ginseng, was not detected in the callus cultured on the medium containing 2, 4-B, but cells derived from the callus growth was excellent, The ginseng calli cultured on the medium containing 2mg11 CPA and 0.05mg/1 BA was grown vigorously and produced panaxydol, one of ginseng polyacetylene. The biosynthesis of polyacetylene in callus was not affected by addition of NAA and sucrose in media. The SH medium was better than the MS medium for ginseng callus growth and biosynthesis of panaxydol. Another ginseng anti-cancer compounds, ginsenoside-Rg$_3$, Rh$_1$and Rh$_2$ were detected in ginseng hairy roots by heat treatment. Those of Panax ginseng were obtained after root disks of three-year old roots were infected with Agrobacterium rhizogenes Rl000 $A_4$T in dark condition after one month of culture. The optimum growth of hairy roots was achieved in the culture of 1/2 MS liquid medium in dark(22$^{\circ}C$) under 60 rpm gyratory shaking. Hairy roots grew well in 5 ι Erlenmeyer flasks, 1ι roller drums, 10ι jar-fermenters, and especially in 20ι air-lift .culture vessels. All heat treatments had remarkably different ginsenoside contents. Eleven ginsenosides were determined in heat treatment, eight in freeze dried hairy roots. Contents of ginsenoside-Rbl , Rb2, Rc, Rd. Re, Rf, and Rg$_1$tested in all heat treatments were less than those of freeze dried hairy roots. Contents of glnsenoside-Rg$_2$ in heat treatment for 1 hour at 105$^{\circ}C$ was 4.92mg/g dry wt, 3.9 times higher than 1.27 mg/g dry wt of freeze dried hairy roots. The optimum condition of heat treatment for the production of ginsenoside-Rg$_3$and Rhl was 2 hours at 105$^{\circ}C$, and ginsenoside content was 2.58mg/g dry wt and 3.62mg/g dry wt, respectively. The production of ginsenoside-Rh2 was the highest in heat treatment for 2 hours at 105$^{\circ}C$ among treatments examined, and ginsenoside-Rh$_2$content was 1.08mg/g dry wt.

• 한국재료학회지
• /
• 제30권1호
• /
• pp.8-13
• /
• 2020

Effect of heat treatment on microstructure and mechanical properties of an Fe-6.5Mn-0.08C medium-manganese steel is investigated in this study. Three kinds of medium-manganese steel specimens are fabricated by varying heat treatments of intermediate quenching (IQ), step quenching (SQ), and intercritical annealing (IA). Hardness and tensile tests are performed to examine the correlation of microstructure and mechanical properties for the Fe-6.5Mn-0.08C medium-manganese steel specimens. The IQ and SQ specimens have microstructures of martensite matrix with ferrite, whereas IA specimen exhibits microstructure of acicular ferrite matrix with martensite. The tensile test results show that the SQ specimen with martensite matrix has the highest yield strength and the lowest elongation. On the other hand, the SQ specimen has the highest hardness due to the relatively lower reduction of carbon content in martensite during intercritical annealing. According to the fractography of tensile tested specimens, the SQ specimen exhibits a dimple and quasi-cleavage fracture appearance while the IQ and IA specimens have fully ductile fracture appearance with fine-sized dimples caused by microvoid coalescence at ferrite and martensite interface.

• 한국초전도ㆍ저온공학회논문지
• /
• 제23권1호
• /
• pp.7-11
• /
• 2021

Cryogenic vessels are special equipment that requires periodic evaluation of their thermal insulation performance. At the current standard, the test is considered as the loss product or heat leakage of cryogenic vessel, which takes over 72 h to evaluate; consequently, a large amount of working medium is discharged to the environment in the process. However, hydrogen is flammable and explosive, and the discharged gas may be dangerous. If liquid hydrogen is replaced with liquid nitrogen before testing, the operation then becomes complicated, and the loss product or heat leakage cannot respond to the thermal insulation performance of cryogenic vessels for liquid hydrogen. Therefore, a novel method is proposed to evaluate the heat leakage of cryogenic vessels for liquid hydrogen in self-pressurization. In contrast to the current testing methods, the method proposed in this study does not require discharge or exchange of working medium in all test processes. The proposed method is based on one-dimensional heat transfer analysis of cryogenic vessels, which is verified by experiment. When this method is used to predict the heat leakage, the comparison with the experimental data of the standard method shows that the maximum error of heat leakage is less than 5.0%.

• 한국전산구조공학회논문집
• /
• 제17권4호
• /
• pp.451-458
• /
• 2004

본 연구는 동결토의 동결심도 및 매설된 파이프라인의 온도분포를 예측하기 위하여 유효열용량 개념 반영한 수치해석 모델의 개발에 초점이 맞추어져 있다. 이를 위하여 저자는 사용코드인 ANAQUS를 활용하여 파이프라인이 매설된 폐쇄형 시스템의 화강 동결토에 대하여 비정상 열전달 수치해석을 수행하였다. 제안된 수치해석 모델은 Frozen Fringe에서 간극수의 상변화 효과가 반영되었다. 제안된 수치해석 모델과 실내 실험으로부터 얻어진 결과들을 비교함으로써 유효열용량 모델의 적용성을 검증하였다.