• Computers and Concrete
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• 제23권4호
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• pp.281-294
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• 2019

The post-fire behavior of structural elements and the cooling process has always been one of the main concerns of the structural engineers. The structures can be cooled at different rates, where they affect the structure's behavior. In the present study, a numerical model has been developed using the Abaqus program to investigate the effect of cooling rate on the post-fire behavior of the CFST column. To verify the model, results of an experimental study performed on CFST columns within a full heating and cooling cycle have been used. In this model, coMParison of the residual strength has been employed in order to examine the behavior of CFST column under different cooling rates. Furthermore, a parametric study was carried out on the strength of steel and concrete, the height of the specimens, the axial load ratio and the cross-sectional shape of the specimen through the proposed model. It was observed that the cooling rate affects the behavior of the column after the fire, and thus the higher the specimen's temperature is, the more effect it has on the behavior. It was also noticed that water cooling had slightly more residual strength than natural cooling. Furthermore, it was recognized from the parametric study, that by increasing the strength of steel and concrete and the load ratio, as well as modifying the cross-sectional shape from circular to square, residual strength of column at the cooling phase was less than that of the heating phase. In addition, with reducing column height, no change was witnessed in the column behavior after the cooling phase.

• Advances in aircraft and spacecraft science
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• 제9권1호
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• pp.59-68
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• 2022

The physical and mathematical foundations of the heat-shielding composite materials functioning under the conditions of aerodynamic heating of aircraft, as well as under the conditions of the point effect of high-energy radiation are considered. The problem of deformation of a thin shallow shell under the action of a local temperature field is approximately solved. Such problems arise, for example, in the case of local destruction of heat-protective coatings of aircraft shells. Then the aerodynamic heating acts directly on the load-bearing shell of the structure. Its destruction inevitably leads to the death of the entire aircraft. A methodology has been developed for the numerical solution of the entire complex problem on the basis of economical absolutely stable numerical methods. Multiple results of numerical simulation of the thermal state of the locally heated shallow shell under conditions of its thermal destruction at high temperatures have been obtained.

• 산업기술연구
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• 제43권1호
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• pp.15-23
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• 2023

Lithium-ion batteries are predominantly employed in electric vehicles and energy storage devices, offering the advantage of high energy density. However, they are susceptible to efficiency degradation when operated at high temperatures due to their sensitivity to the external environment. In this study, we conducted experiments using an indirect cooling method to prevent thermal runaway and explosions in lithium-ion batteries. The results were validated by comparing them with heat transfer simulations conducted through a commercial finite element analysis program. The experiments included single-cell exothermic tests and cooling experiments on a battery pack with 10 cells connected in series, utilizing 21700 lithium-ion batteries. To block external temperature influences, the experimental environment featured an extrusion method insulation in the environmental chamber. The cooling system, suitable for indirect cooling, was constructed with copper tubes and pins. The heat transfer analysis began by presenting a single-cell heating model using commercial software, which was then employed to analyze the heating and cooling of the battery pack.

• 한국산학기술학회논문지
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• 제14권2호
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• pp.955-961
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• 2013

본 연구는 친환경 건축의 대안으로 부각되고 있는 한옥의 열환경 평가를 수행하기 위하여 한옥을 구성하고 있는 건축요소의 전열 메카니즘을 규명하기 한옥건축부재의 규격화와 모델링을 통하여 열환경을 평가하였다. 최근 친환경 건축, 생태건축의 모델로 일반의 한옥 선호도는 높아지고 있으나, 한옥의 우수성이 정성적으로만 평가되고 있다. 이에 한옥의 건축재료 및 형태와 같은 건축요소를 고려, 한옥 건축요소의 Geometry를 작성하여 솔리드 모델을 구축하고, 열환경 평가의 도구로써 CFD를 적용하여 한옥의 실내 열환경을 평가하고자 하였다. 본 연구에서는 복잡한 형태의 Geometry 작성이 가능한 CATIA와 환경 시물레이션 Code인 FLUENT 등의 상용 Code를 활용함으로써 연구의 신뢰성을 높이고자 하였다. 본 연구는 일차적으로 서울지방에 건축된 한옥의 기준모델을 설정하여 벽, 천정, 바닥, 창호 등 건축요소의 부위별 형태를 고찰하고, Geometry작성의 입력자료로 사용하기 위하여 각 부위별 치수체계를 구축하였다. 건축요소의 부위별 각각의 형태를 솔리드 모델로 구축하기 위하여 단계별로 벽, 천정, 바닥, 창호 등에 관한 건축요소의 Geometry를 모델링하여 CFD 입력자료로 활용하여 열환경 시물레이션을 수행하였다.

• 대한토목학회논문집
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• 제37권2호
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• pp.507-512
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• 2017

유인 행성 탐사를 위해 인류는 행성에서 반영구적으로 거주할 수 있는 기술을 개발하고 있으며, 이에 거주에 기본적인 3대 요소인 의식주(衣食住)는 건설 분야의 필수적인 기술의 뒷받침이 요구된다. 국제적으로 인프라 구축 기술을 개발하기 위해 현지 시멘트화, 황, 알루미늄 등의 다양한 재료와 방법으로 시도되고 있다. 본 연구에서는 폴리머를 이용한 건설 인프라 재료 기술을 개발하기 위해 유인 탐사에 요구되는 조건에 부합하는 폴리머 콘크리트 시공성 검증 기술을 제안하고자 한다. 하부에서 가열하는 방식으로 제작된 중량비 10%의 폴리머를 사용한 콘크리트 시험체는 가열 후 2시간이 지났을 때 안정화 되었으며, 상부 가열 방식에 비해 강도는 낮았지만 고착속도가 2배 빠른 것으로 나타났다. 이러한 결과는 향후 유인 탐사를 위한 달 시설물 의 건설에 적용할 수 있을 뿐만 아니라 먼지방지를 위한 도로나 제방과 같은 인프라 시설의 시공성 향상에도 활용 가능하다고 기대된다.

• 유기물자원화
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• 제17권2호
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• pp.101-111
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• 2009

본 연구에서는 강원지역의 도시 생활 쓰레기의 성상 및 물리 화학적 조성을 연구하였다. 생활 쓰레기 자원화시설 설치 및 자료확보 차원, 매립장 관리차원에서 본 연구는 필요한 연구이다. 폐기물의 평균 밀도는 $101.8{\sim}199.8kg/m^3$ 범위내의 결과를 얻었다. 생활 쓰레기는 30.7%의 음식물류, 36.3% 의 종이류, 15.８%의 플라스틱 및 비닐류, 1.9%의 섬유류, 3.2%의 목재류 1.５%의 고무 및 가죽류 등으로 구성되어 있다. 생활쓰레기의 대부분은 음식물, 종이류, 플라스틱류 등으로 이루어져 있으며 9０% 정도가 가연 성분이다. 삼성분 분석에서는 44.6%의 수분 및 47.4%의 가연분 그리고 7.7% 의 회분으로 이루어져 있었다. 원소분석결과는 탄소, 산소, 수소 순으로 많았다. 생활쓰레기의 저위 발열량은 2,631kcal/kg 이며 고위 발열량은 3,310 kcal/kg 이었다.

• 대한환경공학회지
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• 제37권8호
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• pp.458-464
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• 2015

본 연구에서는 사산화삼철과 활성탄을 발열체로 하여 벙커C유 오염토양에 마이크로파를 조사한 후 온도변화 양상 및 TPH 제거효율을 살펴보았다. 사산화삼철 및 활성탄 함유 오염토양에 100~500 Watt로 마이크로파를 조사하였을 때 승온율은 $1.4{\sim}1.6^{\circ}C/Watt$로 나타났다. 조사시간에 따른 온도의 변화는 활성탄보다 사산화삼철 함유토양에서 민감하게 나타났으며, 사산화삼철과 활성탄의 경우 발열체 함량이 각각 10% 이상과 25%에서 열탈착을 위한 충분한 온도가 확보될 수 있음을 관찰하였다. 사산화삼철은 평균 44.1%, 활성탄은 평균 89.4%의 TPH 제거 효율을 나타났으며, 벙커C유의 제거 양상은 활성탄이 함유되었을 때 사산화삼철 보다 고분자탄화수소의 휘발이 더욱 원활하게 진행되고 있음을 확인하였다.

• 센서학회지
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• 제18권5호
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• pp.377-384
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• 2009

The ultrasonic hyperthermia for oncology has been developed and studied. The HIFU(high intensity focused ultrasound) is the most recent method to treat the tumor by using ultrasound. In this study, an insertion-type transducer for treating a prostate cancer, which can focus the ultrasonic beam mechanically and electrically, was designed and developed. The developed transducer was composed of three arrays, and each array has 32 elements. For the purpose of the mechanical focusing, both side arrays are slanted to the center array by $15^{\circ}$. With this structure, NFL(near field length) was set up as 30 mm. The PZT-4 and two matching layers were used, and the backing layer was excepted to prevent energy losses. The acoustic field analysis and the heating test were performed to evaluate the performance of developed transducer. The shape of an acoustic field, peak pressure, and acoustic pressure distribution were compared with numerical simulation. The NFL was 32 mm, the beam width was 5 mm, focal area was $40\;mm^2$, and peak pressure was 5.5 MPa. With heating by using developed transducer, the temperature increased up to $33^{\circ}C$ at focal zone. As a result of this study, the usefulness of suggested transducer for prostate cancer hyperthermia was confirmed by the acoustic field analysis and the heating test with TMM(tissue mimicking) phantom.

• 한국실내디자인학회논문집
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• 제25권1호
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• pp.132-141
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• 2016

For those with disabilities, the residential area is the primary place to adapt the disabilities. Since the quality of the area gives a critical impact on their quality of life, it is essential to finding the measures to create the residential environment that supports their independence. In this regard, this study aimed to compare and analyze the interior elements of the houses that hinder the independence of the physically handicapped in the rural and urban areas, and conducted a survey on a total of 80 physically challenged in Seoul and Yeongwol (40 for each area). As a result, the respondents answered that the houses where they are currently living are hindering their independence regardless of area, and there were regional differences in the level of inconvenience with the size of living room, size of utility room, location of room, lighting and heating environment, ventilation system, deteriorated wallpapers and finishing materials, threshold and floor level difference and humidity control. This study has significance by providing the realistic measures to improve the housing environment of the physically challenged living in the rural and urban areas to be customized to them to increase their quality of life.

• Architectural research
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• 제18권4호
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• pp.151-155
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• 2016

It is necessary to improve the performance of buildings with respect to the energy efficiency while improving the quality of occupants' lives through a sustainable built environment. During the design and development process, building projects must have a comprehensive, integrated perspective that seeks to reduce heating, cooling and lighting loads through climate-responsive designs. The aim of this study is to find an optimal thermal transmittance (U-values) for building envelope elements for low energy multi-rise residential buildings in the early design phase in Korea. The study found that using small U-values of $0.15w/m^2K$ for exterior walls, ceilings and floors and $1.0w/m^2K$ for south and north facing windows has resulted in energy reduction of 22.1%-59.4% in the south facing rooms and 43%-77.6% of the north facing rooms. It has also found the energy load reduction potential of using small U-values are higher on the north facing rooms. The findings of this study can be suggested to be used as a baseline case for low energy consumption studies. It can also be used to determine appropriate envelope materials and insulation values.