• 소성∙가공
• /
• 제12권4호
• /
• pp.302-307
• /
• 2003

Hot rolled strip is cooled by air and water in Run-Out-Table. In this process, phase transformation and shape deformation occurs due to temperature drop. Because of un-ideal cooling condition of ROT, irregular shape deformation and phase transformation arise in the strip. which affect the strip property and lead to the residual stress of strip. And these exert effects on the following processes, coiling process, coil cooling process, and re-coiling process. Through these processes, the residual stress becomes higher and severe. For the prediction of residual stress distribution and shape deformation of final product, Finite element(FE) based model was used. It consists of non-steady state heat transfer analysis, elasto-plastic analysis. thermodynamic analysis and phase transformation kinetics. Successive FEM simulation were applied from ROT process to coil cooling process. In each process simulation, previous process simulation results were used for the next process simulation. The simulation results were matched well with the experimental results.

• Animal Bioscience
• /
• 제37권6호
• /
• pp.1130-1139
• /
• 2024

Objective: The daily maximum temperature and seawater level continuously increase as global warming continues. We examined the adaptability and production performance of heat-stressed goats with a supply of low-saline drinking water. Methods: Twelve Kacang and Kacang Etawah cross goats were exposed to two climatic conditions (control, 25℃ to 33℃, 83% relative humidity [RH], temperature humidity index [THI]: 76 to 86; and hot environment, 26℃ to 39℃, 81% RH, THI: 77 to 94) and two salt levels in drinking water (0% and 0.4% NaCl). The experimental design was a Latin Square (4×4) with four treatments and four periods (28 days each). Results: Temperature of the rectal, skin, and udder, and respiration rate rose, reached a maximum level on the first day of heat exposures, and then recovered. Plasma sodium rose at 0.4% NaCl level, while the hot environment and salinity treatments increased the drinking water to dry matter (DM) intake ratio. Water excretion was elevated in the hot environment but lowered by the increase in salinity. Total lying time increased, whereas change position frequency decreased in the hot condition. Lying and ruminating and total ruminating time increased and explained the enhanced DM digestibility in the hot conditions. Conclusion: The goats exhibited a high level of plasma sodium as salinity increased, and they demonstrated physiological and behavioral alterations while maintaining their production performances under increasing daily maximum temperatures.

• 한국작물학회:학술대회논문집
• /
• 한국작물학회 2022년도 추계학술대회
• /
• pp.14-14
• /
• 2022

Greenhouse gas emissions are one of the critical factors that drive change in rice cropping systems. Within this changing system, less water irrigation and chemical fertilizer are seriously considered, as well combining precision farming technologies with irrigation control. Water and phosphorus (P) fertilizer are two of the most critical inputs in rice cultivation. Due to the lack of water availability in the system, P fertilizer is not available, especially in acidic soil conditions. Moreover, the various types of abiotic stresses, such as drought, high temperature, salinity, submergence, and limited fertilizer result in significant yield loss in the system. Even in the late stage of growth, the waves caused by diseases and insects make the field more unfruitful. Therefore, agronomists and breeders need to identify the secondary phenotypes to estimate the yield loss of when stress appears. The prediction will be clearer if we have a set of markers tagging the causal variation and the associated precise phenotype indices. Although there have been various studies for abiotic stress tolerance, we still lack functional molecular markers and phenotype indices. This is due to the underlying challenges caused by environmental factors in highly unpredictable regional and yearly environmental conditions in the field system. Pupl (phosphorus uptake 1) is still known as the first QTL associated with phosphorus uptake and have been validated in different field crops. Interestingly, some pyramiding lines of Pupl and other QTLs for other stress tolerances showed preferable phenotypes in the yield. Precise physiological studies with the help of genomics are on-going and some results will be discussed.

• 대한기계학회논문집A
• /
• 제34권2호
• /
• pp.129-138
• /
• 2010

공업용 세라믹은 자체의 특이한 물리적 특성으로 인하여 극한의 열 및 화학적 환경에서도 적용할 수 있는 우수한 고온 재료이다. 세라믹은 고온에서 저온으로 빠르게 이동되면 열충격을 받는다. 본 연구에서는 열충격에 대한 매개변수로 임계온도차이를 제안한다. 세라믹 부품에 대한 임계온도차이는 부품 크기와 대류열전달계수 등에 의해 영향을 받는다. 부품의 열충격 특성은 비정상 열응력에 의해 평가된다. 비정상 열응력이 파단계수를 초과한다면 열충격 균열이 표면에서 시작된다고 가정할 수 있다. 물에 대한 임계온도차이는 공기에 대한 임계온도차이보다 적다. 본 연구에서 사용된 국내 승용차용 삼원 촉매 담체는 반경 및 축방향 온도차이가 임계온도차이 아래에 존재하므로 충분한 열충격 성능을 가지고 있었다.

• 콘크리트학회지
• /
• 제10권4호
• /
• pp.195-204
• /
• 1998

콘크리트가 고강도를 확보하기 위해서는 일반적으로 큰 단위시멘트량 및 낮은 물-시멘트비를 유지해야 하므로 콘크리트 타설후 내부온도 상승은 필연적이며, 구조물의 위치와 온도응력차에 의하여 콘크리트 구조물에 균열이 발생하게 된다. 그러므로 고강도용 콘크리트의온도상승 억제대책의 한 방안으로 고로슬래그미분말 3종류와 혼합률 4단계로 변화시킨 콘크리트를 제조하여 온도상승량과 최고온도 도달시간 및 강도를 측정하였으며, 고로슬래그미분말을 5단계로 혼합한 페이스트의 수화발열량 및 수화속도를 측정한 값에 대하여 고찰하였다. 본 연구결과 고로슬래그미분말의 분말도 6,000$\textrm{cm}^2$/g, 혼합률 50% 정도인 고강도용 콘크리트가 온도상승 억제효과 뿐만 아니라 조기재령에서의 강도도 비교적 잘 만족하였다.

• Journal of Biosystems Engineering
• /
• 제24권5호
• /
• pp.439-444
• /
• 1999

Automated greenhouse production systems often require crop growth monitoring involving accurate quantification of plant physiological properties. Conventional methods are usually burdensome, inaccurate, and harmful to crops. A thermal image analysis system can accomplish rapid and accurate measurements of physiological-property changes of stressed crops. In this research a thermal imaging system was used to measure the leaf-temperature changes of several crops according to water deficit. Thermal images were obtained from lettuce, cucumber, pepper, and chinese cabbage plants. Results showed that there were significant differences in the temperature of stressed plants and non-stressed plants. The temperature differences between these two group of plants were 0.7 to 3$^{\circ}C$ according to species.

• 한국발생생물학회지:발생과생식
• /
• 제19권1호
• /
• pp.19-24
• /
• 2015

This study was conducted to determine the stress response [ethological (operculum movement number (OMN)), hematological (hematocrit and hemoglobin), biochemical (glucose, cortisol and glutamic oxaloacetic transaminase (GOT))] in red spotted grouper, Epinephelus akaara during exposure of different water temperature in winter season. This species (Total length, $18.56{\pm}0.34cm$) previously maintained in water temperature of $15^{\circ}C$ were transferred to 15, 20 and $25^{\circ}C$. During experimental period (7 days), OMN, hematocrit (Ht), glucose and GOT values were significantly high in $15^{\circ}C$ when compared to 20 and $25^{\circ}C$. Hemoglobin value was also increased at $15^{\circ}C$, but no significant differences. There was no differences in cortisol levels among the temperature groups. No fish mortality was observed during the experimental period. From these results, $15^{\circ}C$ is likely more stressful to red spotted grouper than $20^{\circ}C$ and $25^{\circ}C$. These observations confirm that red spotted grouper adapts better to temperatures between 20 and $25^{\circ}C$ during the winter season.

• Journal of the Korean Wood Science and Technology
• /
• 제22권2호
• /
• pp.61-70
• /
• 1994

This study was executed to find the applicability of press drying of tree disk by investigating the shrinkage and drying defect and to form appropriate model by comparing the actual moisture content(MC) and internal temperature in respect of drying time with calculated values based computer simulation to which was applied finite difference method. In press drying disk, heating period, constant drying rate period maintained plateau temperature at 100$^{\circ}C$ and falling drying rate period were significantly distinguished. Actual MC and internal temperature were analogous to those calculated at comparing points. Heat transfer model formed by Fourier's law using specific heat of moist wood and conduction coefficient considering fractional volume of each element of wood cell wall, bound water, free water and air showed applicability as basic data to developing heat expansion, shrinkage and drying stress during press drying. Also mass transfer model formed by Fick's diffusion law using water vapor diffusion coefficient showed applicability. Longitudinal shrinkage was developed by pressure of hot press and tangential shrinkage was restrained by hygrothermal recovery. The heart check, surface check and ring failure were occurred differently in species, but V-shaped crack didn't develop.

• 한국환경과학회지
• /
• 제20권12호
• /
• pp.1599-1605
• /
• 2011

To evaluate heat environment surrounding plants diurnal change of leaf temperature in the broad-leaved deciduous and evergreen trees was measured with microclimatic environmental factors including global solar radiation, and upward and downward long wave radiation. Maximum daily solar radiation was 961.2 and 976.3 w/$m^2$ in August 9 and 23, respectively. Upward long wave radiation was slightly higher than downward long wave radiation, showing 404.2 w/$m^2$ in August 9 and 394.5 w/$m^2$ in August 23. In addition, daily maximum vapor pressure deficit was 5.42 and 6.84 kPa in August 9 and 23, respectively, indicating high evaporative demand. Quercus glauca and Acer mono was differently responded to changing light regimes. On August 9, leaf temperature at the top-positioned leaves of Acer plants was higher than air temperature as well as those of Quercus plants in the morning. This indicates that stomata in Acer plants were closed by heat stress or water stress in the morning, while Quercus plant maintained active transpiration by opening stomata. These results indicated that improved light regimes such as gap opening in the closed forest may not always affect positively in the physiology of understory plants.

• 한국표면공학회지
• /
• 제56권6호
• /
• pp.401-411
• /
• 2023

This study investigates the synthesis, characterization, and application of zinc oxide (ZnO) nanoparticles for corrosion resistance and stress corrosion cracking (SCC) mitigation in high-temperature and high-pressure environments. The ZnO nanoparticles are synthesized using plasma discharge in water, resulting in rod-shaped particles with a hexagonal crystal structure. The ZnO nanoparticles are applied to Alloy 600 tubes in simulated nuclear power plant atmospheres to evaluate their effectiveness. X-ray diffraction and X-ray photoelectron spectroscopy analysis reveals the formation of thermodynamically stable ZnCr₂O₄and ZnFe₂O₄ spinel phases with a depth of approximately 35 nm on the surface after 240 hours of treatment. Stress corrosion cracking (SCC) mitigation experiments reveal that ZnO treatment enhances thermal and mechanical stability. The ZnO-treated specimens exhibit increased maximum temperature tolerance up to 310 ℃ and higher-pressure resistance up to 60 bar compared to non-treated ZnO samples. Measurements of crack length indicate reduced crack propagation in ZnO-treated specimens. The formation of thermodynamically stable Zn spinel structures on the surface of Alloy 600 and the subsequent improvements in surface properties contribute to the enhanced durability and performance of the material in challenging high-temperature and high-pressure environments. These findings have significant implications for the development of corrosion-resistant materials and the mitigation of stress corrosion cracking in various industries.