• 제목/요약/키워드: freezing analysis model

검색결과 85건 처리시간 0.029초

Thermal Analysis of Spacecraft Propulsion System and its Validation

  • Han, Cho-Young;Park, Joon-Min
    • Journal of Mechanical Science and Technology
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    • 제18권5호
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    • pp.847-856
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    • 2004
  • Heaters for the spacecraft propulsion system are sized to prevent propellant from catastrophic freezing. For this purpose, thermal mathematical model (TMM) of the propulsion system is developed. Calculation output is compared with the results obtained from thermal vacuum test in order to check the validity of TMM. Despite a little discrepancy between the two types of results, both of them are qualitatively compatible. It is concluded that the propulsion system heaters are correctly sized and TMM can be used as a thermal design tool for the spacecraft propulsion system.

기하구조 및 지형적 요소를 고려한 융설시스템 설치 기준 정립에 관한 연구 (Study about the Standard of Anti-icing System Based on Geography and Geometric Designs)

  • 이동현;정원석;김지원;고석범
    • 한국도로학회논문집
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    • 제13권2호
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    • pp.95-102
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    • 2011
  • 융설액 분사 시스템은 강설이 예상되거나 진행 중인 상황에서 즉시 대응이 가능하며, 강설 초기에 효율적인 처리로 강설로 인해 발생 가능한 교통사고와 교통 지정체를 감소시킬 수 있는 장점을 가지고 있다. 그러나 시스템의 설치비용이 고가이고, 설치되는 장비의 종류에 따라 운영 및 유지관리 비용이 지속적으로 소요되기 때문에 모든 도로 구간에 설치하는 것은 현실적으로 불가능하다. 최근 국내에서는 결빙 위험 구간을 파악할 수 있는 프로그램들이 개발되어 턴키 및 대안 설계에 활용되고 있다. 그러나 프로그램 개발 업체들마다 분석 방식이 상이하고 객관적인 기준이 없는 실정이다. 이에 따라 융설시스템 적용구간에 대한 기준 마련도 시급하다고 볼 수 있다. 본 연구에서는 선형, 기상조건, 일조조건 등을 다양한 도로 조건을 정량화하여 어떤 구간에 우선적으로 융설시스템을 적용하여야 하는지 판단할 수 있는 기준을 제시한다. 이를 위해 국내 지역별 기상 조사, 지형지물에 의해 음지 발생 여부 분석, 선형과 미끄럼 저항성을 고려한 차량 시뮬레이션 등을 수행하고 이론적 검토를 통해 설치 기준 방법론을 정립하는데 중점을 둔다.

A Numerical Model for the Freeze-Thaw Damages in Concrete Structures

  • Cho Tae-Jun
    • 콘크리트학회논문집
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    • 제17권5호
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    • pp.857-868
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    • 2005
  • This paper deals with the accumulated damage in concrete structures due to the cyclic freeze-thaw as an environmental load. The cyclic ice body nucleation and growth processes in porous systems are affected by the thermo-physical and mass transport properties, and gradients of temperature and chemical potentials. Furthermore, the diffusivity of deicing chemicals shows significantly higher value under cyclic freeze-thaw conditions. Consequently, the disintegration of concrete structures is aggravated at marine environments, higher altitudes, and northern areas. However, the properties of cyclic freeze-thaw with crack growth and diffusion of chloride ion effects are hard to be identified in tests, and there has been no analytic model for the combined degradations. The main objective is to determine the driving force and evaluate the reduced strength and stiffness by freeze-thaw. For the development of computational model of those coupled deterioration, micro-pore structure characterization, pore pressure based on the thermodynamic equilibrium, time and temperature dependent super-cooling with or without deicing salts, nonlinear-fracture constitutive relation for the evaluation of internal damage, and the effect of entrained air pores (EA) has been modeled numerically. As a result, the amount of ice volume with temperature dependent surface tensions, freezing pressure and resulting deformations, and cycle and temperature dependent pore volume has been calculated and compared with available test results. The developed computational program can be combined with DuCOM, which can calculate the early aged strength, heat of hydration, micro-pore volume, shrinkage, transportation of free water in concrete. Therefore, the developed model can be applied to evaluate those various practical degradation cases as well.

Evaluation of Therapeutic Monitoring of Prostate Cancer (PCa) using [18F]Florastamin, Diagnostic Radiopharmaceutical for PCa: Non-clinical Ex vivo Whole-body Autoradiographic Analysis

  • Min Hwan Kim;Kyongkyu Lee;Hee Seup Kil;Soon Jeong Kwon;Yong Jin Lee;Kyo Chul Lee;Dae Yoon Chi
    • 대한방사성의약품학회지
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    • 제9권1호
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    • pp.17-21
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    • 2023
  • In this study, we evaluated the targeting of prostate cancer (PCa) using [18F]Florastamin in non-clinical study, for the purpose of therapeutic monitoring of [177Lu]Ludotadipep, a therapeutic radiopharmaceutical for PCa, [18F]Florastamin/[177Lu]Ludotadipep was co-administered to a single-individual prostate tumor bearing mouse model, mimicking clinical condition. Considering the difference in half-life of the two isotopes (18F or 177Lu), image scan of whole-body autoradiography was performed at 24 or 48 h after preparation of frozen section, respectively. Then, it was confirmed whether they showed the same targeting efficiency for the area of tumor. A tumor xenograft model was prepared using PSMA-overexpressing PC3-PIP prostate cancer cells. [18F]Florastamin [111 MBq (3 mCi) in 100 µL]/177Lu]Ludotadipep [3.7 MBq (100 µCi) in 100 µL] was co-administered through the tail vein, and 2 hours after administration, the mice were frozen, and after freezing for 24 hours, whole-body cryosection was performed at 24 h after freezing. Image scanning using cryosection was performed after 24 or 48 hours after freezing, respectively. In the scan image after 24 hours, tumor uptake of [18F] Florastamin/[177Lu]Ludotadipep were simultaneously observed specific uptake in the tumor. In the scan image after 48 hours in the same section, signal of 18F was lost by decay of radioisotope, and specific uptake image for [177Lu]Ludotadipep was observed in the tumor. Uptake of [177Lu]Ludotadipep was specific to the same tumor region where [18F]Florastamin/[177Lu]Ludotadipep was uptake. These results suggested that [18F]Florastamin showed the same tumor uptake efficiency to PCa as [177Lu]Ludotadipep, and effective therapeutic monitoring is expected to be enable using [18F]Florastamin during [177Lu]Ludotadipep therapy for PCa.

냉장고 설계의 인간요소와 인간공학적 평가방법 (Human Factors and Evaluation methods of Refrigerator Design)

  • 박재희;황민철;박세진;김명석;안영진
    • 대한인간공학회:학술대회논문집
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    • 대한인간공학회 1998년도 춘계학술대회논문집
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    • pp.19.1-24
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    • 1998
  • Designers often hesitate to decide the shape, size, and layout of a product. Though ergonomic principles and data are absolutely needed in this process, they don't have enough guidelines to refer. For the refrigerator designers, they also are not convinced of their decision: the vertical position of the freezing and refrigerating rooms, the height of shelves, the shape of door-handle, and etc. To support the refrigerator design, we applied several ergonomic methods to the evaluation of a refrigerator. EMG measurement was used to evaluate the load of user's lumbar muscle. Based upon the experimental EMG data, we developed a model to predict the relative load according to the height of refrigerator shelves. Two different layouts of a refrigerator, R/F and F/R style, were compared with the model. A three-dimenaional motion analysis method was used to evaluate the user's motion of using a refrigerator. Ten door-handles with the different shapes and positions were evaluated by tracking the rotations of the user's arm. Video protocol analysis was used to evaluate the user interface of a control panel in a refrigerator. Finally, we made several ergonomic design guidelines based on the facts found in this research and the anthropometric data of the Korean adults. The results of this study can be applied to the ergonomic design of a refrigerator.

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캐비닛-도어 통합모델을 이용한 빌트인 양문형 냉장고의 도어 상하단차와 앞뒤단차 해석 (Analysis of Door Height Difference and Door Flatness Difference of Built-in Side-by-Side Refrigerator Using Cabinet-Door Integrated Model)

  • 이부윤
    • 한국기계가공학회지
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    • 제17권5호
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    • pp.76-83
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    • 2018
  • A cabinet-door integrated finite element model was constructed for a built-in side-by-side refrigerator with an ice dispenser, and its deformation was analyzed using the ANSYS finite element software. As loads, the food load needed to fill in the cabinet and doors and the thermal load occurring during normal operation conditions were taken into consideration. The door height difference (DHD) and door flatness difference (DFD) between the two doors of the freezing and refrigerating compartments were derived. The DHD and DFD under the assembled condition without applied loads satisfied the acceptance criteria specified by the refrigerator manufacturer. It appeared that the food load increases the DFD slightly. The thermal load tends to increase the differences because of the thermal deformation, especially the DFD, of the cabinet and doors.

고속도로 줄눈 콘크리트 포장의 평탄성 모델 개발 (Development of Roughness-Model for Jointed Plain Concrete Pavements in Express Highway)

  • 박영훈;전범준;김영규;이승우
    • 한국도로학회논문집
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    • 제12권2호
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    • pp.9-16
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    • 2010
  • 평탄성은 도로 공용성을 확보하기 위한 중요한 인자이며, 줄눈콘크리트 포장에서 수명에 큰 영향을 미친다. 포장의 공용성을 평가하는 요소로는 크게 기능성 평가, 안정성 평가 및 구조적 성능 평가가 있다. 기능성 평가 가운데 가장 대표적인 평탄성은 유지보수를 위한 중요한 기준으로 이용되고 있으나 체계적인 연구를 통해 포장 설계시에 적용하기 위한 연구는 미흡한 실정이다. 따라서 신뢰성 있는 평탄성 모델의 개발이 필요하다. 본 연구에서는 국내 콘크리트포장의 노선별 총 연장 280.93km를 일정기준으로 나누어 238개의 섹션으로 선별하였다. 또한, 현재 국내 평탄성 모델에서 고려하고 있는 영향인자인 스폴링, 균열, 재령뿐만 아니라 동결지수, 연평균강수량, 기층조건, 교통량 등에 대한 검토가 이루어졌으며, 재령의 다양화를 위하여 추가적인 노선을 선별하여 평탄성에 영향을 미치는 인자들에 대한 분석이 이루어졌다. 분석결과는 스폴링(%), 균열(%), 재령(년), 기층이 평탄성에 영향을 미치는 것으로 나타났다. 이를 통해 평탄성과의 상관관계를 분석한 결과 신뢰성 있는 평탄성 모델이 도출되었으며, 평탄성를 설명할 수 있는 비율은 68.8%로 나타나 통계적으로 유의한 것으로 판단된다. 본 연구에서는 소입경 골재노출콘크리트포장의 시험시공을 실시하여 초기 공용성을 평가하였으며, 이를 통하여 적정 강도, 저소음 및 적정 미끄럼저항을 확보함을 확인하였다.

등축 유로를 가진 이중진공관형 태양열 집열기의 열성능에 관한 시뮬레이션 연구 (The Performance Simulation of All-Glass Vacuum Tubes with Coaxial Fluid Conduit)

  • 이상진;현명택;박윤철;천원기;이정호
    • 한국태양에너지학회 논문집
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    • 제24권3호
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    • pp.27-38
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    • 2004
  • A numerical investigation has been carried out for a solar system, which consists of all glass solar vacuum tubes Water is heated as it flows through the coaxial fluid conduit inserted in each tube. The space between the exterior of the fluid conduit and the glass tube is filled with antifreeze solution. This is to facilitate heat transfer from the solar heated absorber surface to water and to prevent the functional problems due to freezing in frigid weather conditions. A one-dimensional steady state model is fully described which will be used to develop three-dimensional model using STAR-CD. These models could be used efficiently in designing all-glass solar collector tubes with different geometrical parameters other than those considered in the present analysis. Results show good agreement when compared with other experimental data demonstrating the reliability of the present model.

등축 유로 장착 이중 태양열 진공관의 열적 특성에 관한 수치해석적 연구 (A Numerical Study on the Thermal Characteristics of Double Skin Vacuum Tubes with Coaxial Fluid Conduit)

  • 현준호;박윤철;천원기;이상진
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2006년도 춘계학술대회
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    • pp.567-570
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    • 2006
  • A numerical study has been carried out for a solar water heater which consists of double skin solar vacuum tubes. Water is heated as it flows through the coaxial fluid conduit inserted in each tube. The space between the exterior of the fluid conduit and the glass tube is tilled with antifreeze solution. This is to facilitate heat transfer from the solar heated absorber surface to water and to prevent the functional problems due to freezing in frigid weather conditions. A one-dimensional steady state model is fully described which will be used to develop three-dimensional model using STAR-CD. These models could be used efficiently in designing double skin solar collector tubes with different geometrical parameters other than those considered in the present analysis. Results show a good agreement when compared with other experimental data demonstrating the reliability of the one-dimensional model employed.

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단일추진제 로켓 엔진 어셈블리를 위한 우주 공간에서의 과실 방지 설계 (Faultproof Design in Space for Monopropellant Rocket Engine Assembly)

  • 한조영;김정수
    • 대한기계학회논문집B
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    • 제27권10호
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    • pp.1377-1384
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    • 2003
  • An analysis has been performed for active thermal control of the KOMPSAT monopropellant rocket engine assembly, i.e., dual thruster module(DTM). The main efforts of this work have been directed at determining proper heater sizes for propellant valves and catalyst beds necessary to maintain their temperatures within specified temperature ranges under KOMPSAT environment and operational conditions. The TAS incorporated with TRASYS thermal radiation analyzer was used to establish a complete heat transfer model which allows to predict the DTM temperature as a function of time. The thermal analysis has been performed in transient mode to verify the appropriate power for catalyst bed heaters necessary to increase catalyst bed temperature to the required value within a specified period of time. Similar analysis has been executed to validate the heater power for the thermostatically controlled primary and redundant heater circuits used to prevent hydrazine freezing, i.e., single fault. Moreover the effect of the radiative property of thermal control coating of heat shield was examined. Thruster firing condition was also simulated for the heat soakback condition. As a consequence, all thermal analysis results for DTM satisfactorily met the thermal requirements for the KOMPSAT DTM under the worst case average voltage, i.e. 25 volt.