• 제목/요약/키워드: Thermal changes

검색결과 1,938건 처리시간 0.031초

Immune Based 2-DOF PID Controller Design for Complex Process Control

  • Kim, Dong-Hwa
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2002년도 ICCAS
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    • pp.70.2-70
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    • 2002
  • In the thermal power plant, it is difficult to maintain strict control of the steam temperature in order to avoid thermal stress, because of variation of the heating value according to the fuel source, the time delay of changes in main steam temperature versus changes in fuel flow rate, difficulty of control on the main steam temperature control and the reheater steam temperature control system owing to the dynamic response characteristics of changes in steam temperature and the reheater steam temperature, fluctuation of inner fluid water and steam flow rates widely during load-following operation. Up to the present time, the PID controller has been used to operate this system...

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도시 확장에 따른 온열환경의 변화 (Change of Thermal Environment with Urban Expansion)

  • 김상진
    • 한국태양에너지학회 논문집
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    • 제27권2호
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    • pp.95-101
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    • 2007
  • The surface changes due to urban expansion and the increase of artificial heat releases have brought significant climate changes such as heat island phenomenon in urban area. Furthermore, these changes also have brought serious problems such as air temperature increase, wind changes, and air pollution in urban area. Comprehensive analytical technologies considering various effects are required to analyse complicated mechanism of climate changes, and review the efficient measures. In this research, the effect of the urban expansion in Tokyo and Bangkok area on urban environment will be discussed. By using CFD, urban development and the mechanism of global warming and wind change are studied in those two cities. As a result of numerical research, the surface changes of city could bring the environmental changes in urban area.

기후변화 대응 건축물 기화냉각시스템 적용에 따른 외부 열환경 변화 연구 (Changes in the External Heat Environment of Building Evaporative Cooling Systems in Response to Climate Change)

  • 윤용한;권기욱
    • 한국환경과학회지
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    • 제27권12호
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    • pp.1261-1269
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    • 2018
  • The purpose of this study was to investigate changes in the external thermal environment, following the application of evaporative cooling systems in buildings, in response to climate change. In order to verify changes in the external thermal environment, a T-test was performed on the microclimate, Thermal Comfort Index (TCI), and building surface temperature. Differences in microclimate, following the application of the evaporative cooling system in the building, were significant in terms of temperature and relative humidity. In particular, temperature decreased by more than 7% when the evaporative cooling system was applied. According to the results of the Thermal Comfort Index analysis, the Wet-Bulb Globe Temperature (WBGT) was below the limit of outdoor activities, indicating that outdoor activities were possible. The Universal Thermal Climate Index (UTCI) values were within the very strong heat stress range when the evaporative cooling system was not applied, When the system was applied, the UTCI values were within the strong heat stress range, indicating that they were lowered by one level. The building surface temperature decreased by ~10% or more when the evaporative cooling system was applied, compared to when it was not applied. Finally, the outside surface temperature of the building decreased by ~12% or more when the system was applied, compared to when it was not applied. We conclude that the energy saving effect of the building was significant.

몇가지 천연 산화방지물의 첨가가 가열 팜유에 미치는 영향 (Influence of some Natural Antioxidants Effect on Thermal Oxidation in Palm Oil)

  • 장영상;이영수;강우석;신재익
    • 한국응용과학기술학회지
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    • 제6권1호
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    • pp.9-14
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    • 1989
  • Effectiveness of some natural antioxidants were investigated by measuring the physico-chemical charcteristics and fatty acid composition during thermal oxidation in palm oil. Tocopherol showed most enhanced thermal oxidation stabilities compared to the other natural antioxidants. AR spice was no good AOM stability and changes of acid value but the other parameters were obtained desirable results. The changes of linoleic aicd content was slightly decreased during thermal oxidation. Addition of rosemary and glycyrriza extract increased the stabilities of oil less than tocopherol and AR spice. Order of antioxdative effects was tocopherol, AR spice and others. There was no significiant difference in stability of rosemary and glycyrriza extract.

Monitoring the Degradation Process of Inconel 600 and its Aluminide Coatings under Molten Sulfate Film with Thermal Cycles by Electrochemical Measurements

  • Take, S.;Yoshinaga, S.;Yanagita, M.;Itoi, Y.
    • Corrosion Science and Technology
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    • 제15권6호
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    • pp.259-264
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    • 2016
  • With a specially designed electrochemical cell, the changes in impedance behavior for Inconel 600 and aluminide diffusion coatings under molten sulfate film with thermal cycles (from $800^{\circ}C$ to $350^{\circ}C$) were monitored with electrochemical impedance measurements. It was found that corrosion resistance for both materials increased with lower temperatures. At the same time, the state of molten salt was also monitored successfully by measuring the changes in impedance at high frequency, which generally represents the resistance of molten salt itself. After two thermal cycles, both Inconel 600 and aluminide diffusion coatings showed excellent corrosion resistance. The results from SEM observation and EDS analysis correlated well with the results obtained by electrochemical impedance measurements. It is concluded that electrochemical impedance is very useful for monitoring the corrosion resistance of materials under molten salt film conditions even with thermal cycles.

정지궤도 통신위성의 원격측정명령처리기 기술모델 열해석 (Thermal Analysis on the Engineering Model of Command and Telemetry Unit for a Geostationary Communications Satellite)

  • 김정훈;구자춘
    • 한국항공우주학회지
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    • 제32권9호
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    • pp.114-121
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    • 2004
  • 정지궤도 통신위성 원격측정명령처리기의 기술인증모델 개발을 위하여 기술모델의 열 설계변경 및 해석을 수행하였다. 보드레벨의 소모전력량 측정치와 열주기시험의 결과를 활용하여 기술모텔에 대한 열해석모델을 개발하였다. 발열소자의 열소산 모델링은 인쇄회로기판에 투영된 소자의 footprint를 생성하고 그 표면의 전 영역에 균일하게 열소산량을 가하였다. 열설계변경(안)에 따라 설계변경 후 기술인증수준의 열진공환경에서 소자온도를 예측한 결과, CTU의 모든 소자들의 접합온도는 허용온도 이내로 존재하였다.

열 경계 조건이 다른 틸팅패드저널베어링의 성능 (Performance of Tilting Pad Journal Bearings with Different Thermal Boundary Conditions)

  • 서준호;황철호
    • Tribology and Lubricants
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    • 제37권1호
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    • pp.14-24
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    • 2021
  • This study shows the effect of the thermal boundary condition around the tilting pad journal bearing on the static and dynamic characteristics of the bearing through a high-precision numerical model. In many cases, it is very difficult to predict or measure the exact thermal boundary conditions around bearings at the operating site of a turbomachine, not even in a laboratory. The purpose of this study is not to predict the thermal boundary conditions around the bearing, but to find out how the performance of the bearing changes under different thermal boundary conditions. Lubricating oil, bearing pads and shafts were modeled in three dimensions using the finite element method, and the heat transfer between these three elements and the resulting thermal deformation were considered. The Generalized Reynolds equation and three-dimensional energy equation that can take into account the viscosity change in the direction of the film thickness are connected and analyzed by the relationship between viscosity and temperature. The numerical model was written in in-house code using MATLAB, and a parallel processing algorithm was used to improve the analysis speed. Constant temperature and convection temperature conditions are used as the thermal boundary conditions. Notably, the conditions around the bearing pad, rather than the temperature boundary conditions around the shaft, have a greater influence on the performance changes of the bearing.

가교 시스템이 다른 NR 가황물의 열노화 특성 (Thermal Aging Properties of NR Vulcanizates with Different Cure Systems)

  • 최성신;박병호
    • Elastomers and Composites
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    • 제40권3호
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    • pp.181-187
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    • 2005
  • 가교 시스템이 다른 NR 가황물의 열노화에 의한 물성 변화를 연구하였다. 두 가지 황가교 시스템과 한 가지 레졸 가교 시스템을 도입하였으며, 가교제 함량을 변화시켰다. 황 가교시스템으로 만든 NR 가황물의 경우, $90^{\circ}C$에서 3일간 노화 후 경도와 모듈러스는 증가한 반면 신율과 인장강도는 감소하였다. 레졸 가교 시스템으로 만든 NR 가황물의 경우에는 노화 후 전반적으로 물성이 하락하였다. 열노화에 의한 물성 변화를 가교밀도의 변화로 설명하였다. 노화 후, 황 가교 시스템으로 만든 NR 가황물의 가교밀도는 증가한 반면, 레졸 가교 시스템으로 만든 NR 가황물의 가교밀도는 감소하였다. 노화방지제의 이동이 물성에 미치는 영향에 대해서도 조사하였다. 그러나 노화방지제의 이동으로는 노화에 의한 물성의 변화를 충분히 설명할 수 없었다.

합곡(合谷)$(LI_4)$ 자침(刺鍼)이 구순부(口脣部)의 온도변화(溫度變化)에 미치는 영향(影響) (Effects of Acupuncture at Hap-Kok$(LI_4)$ on the Thermal Changes of Labia Oris Surface in Man)

  • 박귀종;안성훈;구성태;이문호;김경식;손인철
    • 대한한의학회지
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    • 제20권2호
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    • pp.75-87
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    • 1999
  • We reported that acupuncture on $LI_4$ effected thermal change on $LI_4$ and ST25 area, And this study was performed on 100 healthy students to observe the effects of acupuncture at Hap-kok ($LI_4$) according to the meridian and qi-xue(氣血) phenomenon of oriental medicine's theory, The results was 1. In healthy man, mean skin temperatures of $LI_4$, ST25, CV12 areas(Control) were decreased, 2. In left $LI_4$ acupuncture group, the temperature of abdominal skin and $LI_4$ area had the tendency of increase, both right and left $LI_4$ acupuncture group, the temperature of abdominal skin and $LI_4$ area had not significant tendency. 3. In the research of thermal difference which eliminate a special region temperature, in the control group, the thermal changes had not significant tendency, in the left $LI_4$ acupuncture group and both right and left $LI_4$ acupuncture group, the thermal changes had tendency to be increased, 4. In the deviation analysis which mean of each group is excluded, in the control group, it turned out that deviation is regular for 10 minutes; in the left $LI_4$ acupuncture group and both right and left $LI_4$ acupuncture group, it turned out that deviation is more larger than the control group for 10 minutes. The above results indicates that Digital Thermography is a useful method to observe effects and changes by acupuncture stimulation on objective evaluation of phenomenon for the meridian system. Thus, acupuncture on $LI_4$ affects to thermal changes of the abdominal skin and $LI_4$ area, but exact examination of thermal changes on abdominal skin will have to be done.

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Kinetic Data for Texture Changes of Foods During Thermal Processing

  • Lee, Seung Hwan
    • 산업식품공학
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    • 제21권4호
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    • pp.303-311
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    • 2017
  • To automate cooking processes, quantitative descriptions are needed on how quality parameters, such as texture change during heating. Understanding mechanical property changes in foods during thermal treatment due to changes in chemical composition or physical structure is important in the context of engineering models and in precise control of quality in general. Texture degradation of food materials has been studied widely and softening kinetic parameters have been reported in many studies. For a better understanding of kinetic parameters, applied kinetic models were investigated, then rate constants at $100^{\circ}C$ and activation energy from previous kinetic studies were compared. The food materials are hardly classified into similar softening kinetics. The range of parameters is wide regardless of food types due to the complexity of food material, different testing methods, sample size, and geometry. Kinetic parameters are essential for optimal process design. For broad and reliable applications, kinetic parameters should be generated by a more consistent manner so that those of foods could be compared or grouped.