• 제목/요약/키워드: heat variations

검색결과 673건 처리시간 0.035초

《상한론(傷寒論)》 궐음병의 병리본질과 삼음삼양(三陰三陽) 개념과의 관계 (Pathological Entity of Jueyin Disease and the Relationship between the Concept of Three-Yin-Three-Yang in 《Shanghanlun》)

  • 지규용;박신형
    • 동의생리병리학회지
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    • 제33권2호
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    • pp.75-81
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    • 2019
  • In order to research the pathological entity of Jueyin disease in ${\ll}Shanghanlun{\gg}$, some sharing concept of three-yin-three-yang used in ${\ll}Neijing{\gg}$ and ${\ll}Shanghanlun{\gg}$ were investigated first, and then the meaning of jueyin and jueyin disease were analyzed. In cold damage disease, time-space factor is important because the pathological change is rapid and the symptoms along path are similar, therefore three-yin-three-yang having complex meaning of time and space can be used as an appropriate pathological concept. So to speak, it is able to be interpreted as various modes like variations of yin-yang, qi-blood, change of pulse condition, theories of opening, closing, pivot or exuberance and debilitation of form and qi manifested in the six districts of the human body following disease process. Jueyin is between front taiyin and rear shaoyin, and it's attribution is inherent in qi stagnation and yin exuberance in relative to the location of flank and liver. Putting together above descriptions, pathological entity of jueyin disease is that the symptoms mingled with cold and stagnant heat competing each other when a subject having qi stagnation in flank with cold in extremities and lower abdomen in particular is seized with cold influenza.

일교차가 당뇨병성 창상의 치유에 미치는 영향: 동물 실험 연구 (Relationship between the Diurnal Temperature Range and Wound Healing of Diabetic Foot: Animal Study)

  • 원성훈;천동일;조재호;박인근;이영
    • 대한족부족관절학회지
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    • 제24권4호
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    • pp.142-147
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    • 2020
  • Purpose: Diabetic foot ulcers are closely related to body surface heat, which can be affected easily by temperature differences. This study examined the correlation between the healing process of diabetic wounds and abnormal diurnal temperature through an animal study. Materials and Methods: Rats in the abnormal diurnal temperature group and control group were given a 10 mm sized full-thickness skin ulcer. Wound size progression was observed in both groups. H&E and Masson's trichrome staining was performed at 14 days after wound formation, and the number of vessels per unit area and histology analysis were performed. The changes in the ulcer were measured through three dimensional cross-section area using INSIGHT® devices. Results: The wound recovery period (granulation ingrowing) was 24 days in the abnormal diurnal temperature model and 20 days in the control group. The thickness of scar tissue was 402±23.19 ㎛ in the control group and 424.5±36.94 ㎛ in the diurnal temperature model. Neovascular formation was counted as 5.1±0.97 for the control group and 4.16±0.94 for the diurnal temperature model group. Conclusion: Delayed and inferior diabetic wound healing was observed in the abnormal diurnal temperature group, which was characterized by greater diurnal variations than the typical growth environment.

A Systems Engineering Approach to Predict the Success Window of FLEX Strategy under Extended SBO Using Artificial Intelligence

  • Alketbi, Salama Obaid;Diab, Aya
    • 시스템엔지니어링학술지
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    • 제16권2호
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    • pp.97-109
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    • 2020
  • On March 11, 2011, an earthquake followed by a tsunami caused an extended station blackout (SBO) at the Fukushima Dai-ichi NPP Units. The accident was initiated by a total loss of both onsite and offsite electrical power resulting in the loss of the ultimate heat sink for several days, and a consequent core melt in some units where proper mitigation strategies could not be implemented in a timely fashion. To enhance the plant's coping capability, the Diverse and Flexible Strategies (FLEX) were proposed to append the Emergency Operation Procedures (EOPs) by relying on portable equipment as an additional line of defense. To assess the success window of FLEX strategies, all sources of uncertainties need to be considered, using a physics-based model or system code. This necessitates conducting a large number of simulations to reflect all potential variations in initial, boundary, and design conditions as well as thermophysical properties, empirical models, and scenario uncertainties. Alternatively, data-driven models may provide a fast tool to predict the success window of FLEX strategies given the underlying uncertainties. This paper explores the applicability of Artificial Intelligence (AI) to identify the success window of FLEX strategy for extended SBO. The developed model can be trained and validated using data produced by the lumped parameter thermal-hydraulic code, MARS-KS, as best estimate system code loosely coupled with Dakota for uncertainty quantification. A Systems Engineering (SE) approach is used to plan and manage the process of using AI to predict the success window of FLEX strategies under extended SBO conditions.

오스테나이타이징 온도와 냉각 속도가 SCM415 저탄소강의 미세조직과 경도에 미치는 영향 (Effect of Austenitizing Temperature and Cooling Rate on Microstructure and Hardness of Low-carbon SCM415 Steel)

  • 이종언;이교명;차재원;박성혁
    • 소성∙가공
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    • 제31권4호
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    • pp.207-213
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    • 2022
  • In this study, variations in the microstructure and hardness of a low-carbon SCM415 steel with austenitizing temperature and cooling rate are investigated. When the austenitizing temperature is lower than the A1 temperature (738.8 ℃) of the SCM415 steel, the microstructures of both the air-cooled and water-cooled specimens consist of ferrite and pearlite, which are similar to the microstructure of the initial specimen. When heat treatment is conducted at temperatures ranging from the A1 temperature to the A3 temperature (822.4 ℃), the microstructure of the specimen changes depending on the temperature and cooling rate. The specimens air- and water-cooled from 750 ℃ consist of ferrite and pearlite, whereas the specimen water-cooled from 800 ℃ consists of ferrite and martensite. At a temperature higher than the A3 temperature, the air-cooled specimens consist of ferrite and pearlite, whereas the water-cooled specimens consist of martensite. At 650 ℃ and 700 ℃, which are lower than the A1 temperature, the hardness decreases irrespective of the cooling rate due to the ferrite coarsening and pearlite spheroidization. At 750 ℃ or higher, the air-cooled specimens have smaller grain sizes than the initial specimen, but they have lower hardness than the initial specimen owing to the increased interlamellar spacing of pearlite. At 800 ℃ or higher, martensitic transformation occurs during water cooling, which results in a significant increase in hardness. The specimens water-cooled from 850 ℃ and 950 ℃ have a complete martensite structure, and the specimen water-cooled from 850 ℃ has a higher hardness than that water-cooled from 950 ℃ because of the smaller size of prior austenite grains.

열-수리-역학적 연계해석을 위한 OGS-FLAC 시뮬레이터의 성능 평가 (Performance Evaluation of OGS-FLAC Simulator for Coupled Thermal-Hydrological-Mechanical Analysis)

  • 박도현;박찬희
    • 터널과지하공간
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    • 제32권2호
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    • pp.144-159
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    • 2022
  • 본 연구에서는 지반의 열-수리-역학적 복합거동을 모델링하기 위한 순차적 접근법 기반의 시뮬레이터를 개발하고 적용된 연계해석 알고리즘의 계산성능을 분석하였다. 본 연구의 순차적 연계해석에서는 다공성 매질의 열 및 유체거동 분석을 위한 오픈소스 기반의 OpenGeoSys 수치코드와 역학해석을 위한 상용 소프트웨어 FLAC3D가 연동되었다. 해석해가 주어진 열-수리-역학적 복합거동 문제를 토대로 개발된 시뮬레이터에 대한 벤치마크 테스트가 수행되었다. 적용된 벤치마크 문제는 완전포화된 지반 내 점열원 작용 시 지반거동(시간에 따른 온도, 간극수압, 응력, 변형 변화)과 관계된다. 해석해와 수치해석 시뮬레이션 결과를 비교 분석하고 연계해석 시뮬레이터의 적정성을 조사하였다.

사각형 그루브로 Surface Texturing한 평행 스러스트 베어링의 열유체윤활 해석: 제1보 - 유막온도경계조건의 영향 (THD Lubrication Analysis of a Surface-Textured Parallel Thrust Bearing with Rectangular Grooves: Part 1 - Effect of Film-Temperature Boundary Condition)

  • 박태조;강정국
    • Tribology and Lubricants
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    • 제38권6호
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    • pp.267-273
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    • 2022
  • Surface texturing is the latest technology for processing grooves or dimples on the friction surface of a machine. When appropriately applied, it can reduce friction and significantly increase durability. Despite many studies over the past 20 years, most are isothermal (ISO) analyses in which the viscosity of the lubricant is constant. In practice, the viscosity changes significantly owing to the heat generated by the viscous shear of the lubricant and film-temperature boundary condition (FTBC). Although many thermohydrodynamic (THD) analyses have been performed on various sliding bearings, only few results for surface-textured bearings have been reported. This study investigates the effects of the FTBC and groove number on the THD lubrication characteristics of a surface-textured parallel thrust bearing with multiple rectangular grooves. The continuity, Navier-Stokes, and energy equations with temperature-viscosity-density relations are numerically analyzed using a commercial computational fluid dynamics code, FLUENT. The results show the pressure and temperature distributions, variations of load-carrying capacity (LCC), and friction force with four FTBCs. The FTBCs greatly influence the lubrication characteristics of surface-textured parallel thrust bearings. A groove number that maximizes the LCC exists, which depends on the FTBC. ISO analysis overestimates the LCC but underestimates friction reduction. Additional analysis of various temperature boundary conditions is required for practical applications.

극저온 액화가스 누출에 의한 선체 구조용 강재의 샤르피 충격성능에 관한 연구 (A Study on the Charpy Impact Performance of Structural Steel Considering the Leakage of Cryogenic Liquefied Gas)

  • 강동혁;김정현;김슬기;김태욱;박두환;박기범;이제명
    • 한국산업융합학회 논문집
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    • 제26권2_2호
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    • pp.333-340
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    • 2023
  • Environmental regulations are being strengthened worldwide to solve global warming. For this reason, interest in eco-friendly gas fuels such as LNG and hydrogen is continuously increasing. However, when adopting eco-friendly gas fuel, liquefying at a cryogenic temperature is essential to ensure economic feasibility in storage and transportation. Although austenitic stainless steel is typically applied to store cryogenic liquefied gas, structural steel can experience sudden heat shrinkage in the case of leakage in the loading and unloading process of LNG. In severe cases, the phase of the steel may change, so care is required. This study conducted Charpy impact tests on steel material in nine different temperature ranges, from room to cryogenic temperatures, to analyze the effects of cryogenic liquefied gas leaks. As a result of the study, it was not easy to find variations in ductile to brittle transition temperature (DBTT) due to the leakage of cryogenic liquefied gas. Still, the overall impact toughness tended to decrease, and these results were verified through fracture surface analysis. In summary, brittle fracture of the steel plate may occur when a secondary load is applied to steel for hull structural use exposed to a cryogenic environment of -40 ℃ or lower. Therefore, it needs to be considered in the ship design and operating conditions.

Analysis of DC insulation and properties of epoxy/ceramic composites with nanosized ZnO/TiO2 fillers

  • Kwon, Jung-Hun;Kim, Yu-Min;Kang, Seong-Hwa;Kim, Pyung-Jung;Jung, Jong-Hoon;Lim, Kee-Joe
    • Journal of Ceramic Processing Research
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    • 제13권spc2호
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    • pp.332-335
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    • 2012
  • A molded transformer is maintenance-free, which makes it unnecessary to replace the insulating material, like in an oil-filled transformer, because the epoxy, which is a molded insulating resin, does not suffer variations in its insulating performance for heat cycles over a long time, as compared to insulating oil. In spite of these advantages, a molded transformer may still be accessed by the user, which is not good in regards to reliability or noise compared to the oil transformers. In particular, a distrust exists regarding reliability due to the long-term insulating performance. These properties have been studied in regards to the improvement of epoxy composites and molded transformer insulation. There have nevertheless been insufficient investigations into the insulation properties of epoxy composites. In this study, it is a researching of the epoxy for insulating material. In order to prepare the specimens, a main resin, a hardener, an accelerator, and a nano/micro filler were used. Varying amounts of TiO2 and ZnO nano fillers were added to the epoxy mixture along with a fixed amount of micro silica. This paper presents the DC insulation breakdown test, thermal expansion coefficient, and thermal conductivity results for the manufactured specimens. From these results, it has been found that the insulating performance of nano/micro epoxy composites is improved as compared to plain molded transformer insulation, and that nano/micro epoxy composites contribute to the reliability and compactness of molded transformers.

건물에너지시뮬레이션 기법을 이용한 육계사 표준설계모델의 에너지 부하 산출 (Evaluation of Energy Loads for Broiler-Standard Design Models Using a Building Energy Simulation Method)

  • 권경석;양가영;김종복;장동화;하태환;전소라
    • 한국농공학회논문집
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    • 제65권1호
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    • pp.27-39
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    • 2023
  • This study was to quantitatively evaluate periodic and maximum energy loads for broiler-standard design models by the Ministry of Agriculture, Food and Rural Affairs (2016). Building energy simulation method was used to compute heating and cooling loads of the designed broiler houses according to regional locations and insulation characteristics of wall and roof. It considered sensible and latent heat generation from broilers, dynamic operation of ventilation system according to environment variations. It was found that variation of periodic heating loads was relatively higher than that of periodic cooling loads according to thickness changes of wall and roof. Assuming that broiler was raised at every even-month, periodic heating and cooling loads were 6 and 18% lower, respectively than odd-month raising condition. When recommendation rules of insulation characteristics (wall and roof thickness) by the Ministry of Land, Infrastructure and Transport was adopted, periodic heating load of Jeju-si was 20.3% higher than national average values. Based on the BES computed periodic and maximum energy loads under the designed experimental condition, these results can contribute to reestablishing standard design of broiler houses, especially for insulation characteristics, and designing management strategies for efficient energy uses.

폴리올법으로 제조된 Pt/C 촉매의 연료전지 적용을 위한 나노 입자 크기제어 (Nano particle size control of Pt/C catalysts manufactured by the polyol process for fuel cell application)

  • 허준;윤혁준;최지훈;문채린;최순목
    • 한국표면공학회지
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    • 제56권6호
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    • pp.437-442
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    • 2023
  • This research aims to enhance the efficiency of Pt/C catalysts due to the limited availability and high cost of platinum in contemporary fuel cell catalysts. Nano-sized platinum particles were distributed onto a carbon-based support via the polyol process, utilizing the metal precursor H2PtCl6·6H2O. Key parameters such as pH, temperature, and RPM were carefully regulated. The findings revealed variations in the particle size, distribution, and dispersion of nano-sized Pt particles, influenced by temperature and pH. Following sodium hydroxide treatment, heat treatment procedures were systematically executed at diverse temperatures, specifically 120, 140, and 160 ℃. Notably, the thermal treatment at 140 ℃ facilitated the production of Pt/C catalysts characterized by the smallest platinum particle size, measuring at 1.49 nm. Comparative evaluations between the commercially available Pt/C catalysts and those synthesized in this study were meticulously conducted through cyclic voltammetry, X-ray diffraction (XRD), and field-emission scanning electron microscopy-energy dispersive X-ray spectroscopy (FE-SEM EDS) methodologies. The catalyst synthesized at 160 ℃ demonstrated superior electrochemical performance; however, it is imperative to underscore the necessity for further optimization studies to refine its efficacy.