• Korean Journal of Environment and Ecology
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• v.3 no.1
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• pp.81-94
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• 1989

Use impacts to trail and campground deteriorations and their changes of natural environment were studied in Mt. Kaya National Park in 1989. The entire width, bare width and maximum depth of trail as the trail condition were significantly greater on the more heavily used trail. Deteriorations of trail which were surveyed at the total of 51 were significantly different from those of non-deteriorated points. The changes of soil and vegetation of trailsides were not found at a uniform tendency but could be more clearly grouped by the types of user's disturbance, and use impact on trailside had reached 15m inside of forest. Percentage of area for Class 5 in campsite was about 36% and about 69% of campsite area was more severe than Class 3. Recreational activities retarded the diameter growth of trees in campsite and accelerated the different composition of species. Soil and vegetative factors adapted to understand the difference of use amount and the realm of use impact could be sorted. The realm influenced by user's disturbance was about 50m from the core of campsite. Fraxinus rhynchophylla, Rhus trichocarpa, Symplocos chinensis for. pilosa and Stephanandra incisa were considered as the tolerant species to user's impact.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.10
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• pp.1188-1194
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• 2019

Among the many ways to measure the flow of fluid the hot air wind speed sensor is a device for measuring the speed or temperature by heat transfer of a fluid. However, the hot wire wind speed sensor is sensitive to external environmental factors, and has a disadvantage of inaccuracy due to ambient temperature, humidity, and signal noise. In order to compensate for this disadvantage, advanced technology has been introduced by adding temperature compensation circuits, but it is expensive. In order to solve this problem, this paper studies the wind speed sensor that does not need temperature compensation. Heated wind speed sensors are very vulnerable to the ambient temperature, which is generated by electronic circuits, even among external environmental factors. in order to improve this, the auxiliary heating element is additionally installed in the heating element to control a constant temperature difference between the auxiliary heating element and the heating element.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.3
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• pp.189-199
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• 2010

In a high-level waste (HLW) repository, heat is generated by the radioactive decay of the waste. This can affect the safety of the repository because the surrounding environment can be changed by the heat transfer through the rock. Thus, it is important to determine the heat transfer coefficient of the atmosphere in the underground repository. In this study, the heat transfer coefficient was estimated by measuring the indoor environmental factors in the Korea Atomic Energy Research Institute Underground Research Tunnel (KURT) under forced convection. For the experiment, a heater of 5 kw capacity, 2 meters long, was inserted through the tunnel wall in the heating section of KURT in order to heat up the inside of the rock to $90^{\circ}C$, and fresh air was provided by an air supply fan connected to the outside of the tunnel. The results showed that the average air velocity in the heating section after the provision of the air from outside of the tunnel was 0.81 m/s with the Reynolds number of 310,000~340,000. The seasonal heat transfer coefficient in the heating section under forced convection was $7.68\;W/m^2{\cdot}K$ in the summer and $7.24\;W/m^2{\cdot}K$ in the winter.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.167.2-167.2
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• 2010

본 연구에서는 지열 에너지원으로써 터널 내부 벽면의 항온성을 이용하여 터널 외벽에 텍스타일 형태의 열교환기를 설치하고 열적 거동을 평가하였다. 터널의 라이닝 부분에서는 여러 가지 요인에 의해 지하수가 터널 내부로 유입하게 되므로 지하수의 유무에 대한 열적 거동 및 유동액의 순환 속도에 따른 영향, 열교환 파이프 배열 형태에 따른 영향을 현장 시험 시공과 현장 열응답시험을 통하여 평가하고자 하였다. 또한 3-D 유한체적해석 프로그램(FLUENT)을 이용하여 숏크리트와 라이닝의 열전도도를 고려한 열교환기의 성능을 분석하였다. 수치해석 결과 열교환 파이프 주변에 지하수의 흐름이 존재할 경우 열전달이 상대적으로 더 원활히 이루어졌으며 순환속도가 빠를 때 보다 느릴수록 효율이 높게 나타났다. 또한, 파이프의 간격이 넓을수록, 파이프의 길이가 길수록 효율이 높게 나타났다. 라이닝 및 숏크리트의 열전도도가 증가함에 따라 에너지 텍스타일의 열전달 효율이 높게 나타났다. 현장 시험을 통해 비슷한 길이의 파이프가 사용된 경우, 파이프 배열 형태에 따라 수평형보다는 수직형 배열의 효율이 높게 측정되었다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.12
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• pp.996-1003
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• 2002

Heat transfer characteristics were investigated for the falling film flowing down the outside of an electrically heated vertical tube. Water was used for the falling film, and its Reynolds number was varied in the range of 70～500. Because water is heated and evaporated as it flows down, both sensible and latent heat transfer should be considered. The effect of the surrounding air movement was investigated by changing the direction of the air injection; without air injection, parallel-flow, and counter-flow. For all cases, sensible teat transfer rate was almost linearly increased with the increasing film flow rate. It was found that the film heat transfer coefficient was hardly influenced by the parallel air flow. However, the counter-flow of air reduced the heat transfer coefficient, which might be caused by the uneven distribution or flooding of the film. At high heat flux, a sudden change of the film heat transfer coefficient was detected as the film flow rate reached the transition value. It is supposed that this phenomenon was caused by the change in the film flow pattern.

• Bulletin of Food Technology
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• v.25 no.3
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• pp.276-281
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• 2012

우수 외식업지구 지정 및 지원 사업은 정부주도로 2012년부터 4년동안 전국 20개 주요 외식업 지구를 지정해서 매년 국비 20억원 씩 지원(5개소 4년간)하게 된다. 총 4년간 소요예산이 국비만도 400억에 달하며 각 지자체에서 지원되는 지방비를 합하면 800억원에 달하는 규모다. 식품산업이나 제조산업에 비하면 큰 예산이 아닐 수도 있으나 외식업에 대한 정부 차원에서 추진되는 첫 대규모 사업인 만큼 그 기대 또한 크다. 하지만 이러한 지구단위 외식업 육성의 문제점 또한 많다. 일례로 전남 지역 중 가장 많은 연간 650만명의 외지 관광객이 찾는 담양군의 경우 전체 600여개의 외식업소 중 죽녹원 인구 '남도음식 푸드필리지'에 속하는 외식업소는 20여개에 불과해 그 형평성에 대해 지역내 사업자들간에도 불만의 목소리가 터져 나올 수 밖에 없다. 또한 기존 유명관광지 주변에 위치한 외식업 지구에 지정되어 상대적으로 유리한 영업환경에 있었던 사업자들이 여타 불리한 조건하에서 노력하는 외식사업자들에 비해 경영의식이나, 친절도 및 부족한 부분에 대한 개선의지나 노력이 부족하다는 평은 많은 사람들의 입을 통해 회자되어 왔던 터다. 지자체별 그리고 전국 단위의 국제 경쟁력을 갖춘 유명외식업 지구를 육성한다는 취지는 나쁘다고 할 수 없지만, 가장 우선적으로 해당 외식업지구내 사업자들의 경영의식 개선 및 외식업 자체에 대해 공부하고 연구하는 풍토가 선결되어야 할 것이다. 또한 지역사회의 연계도 중요한 성공요인이다.

• Journal of the Korean Magnetics Society
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• v.23 no.5
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• pp.166-172
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• 2013

This article is to numerically investigate the temperature and heat transfer characteristics of the voice coil in the woofer speaker using ferrofluid with the input currents. The temperature and heat transfer of the major components of the woofer speakers with and without ferrofluid are calculated and analyzed with the increase of the input currents from 10 W to 50 W at an interval of 10W. As results, the temperature of voice coil is linearly increased with an increase of input currents. The temperature of the woofer speaker with ferrofluid is lower 51.0 % than that of the woofer speaker without ferrofluid at the condition of input current 40W and the required input current of the woofer speaker with ferrofluid is lower 42.5 % than that of the woofer speaker without ferrofluid at the condition of voice coil temperature 490 K. In addition, the heat transfer from voice coil to other components for woofer speaker with ferrofluid is higher 51.7 % than that for woofer speaker without ferrofluid.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.427-436
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• 2014

The goal of this paper is to estimate proper hardfacing material and thickness of STD61 hot-working tool steel through three-dimensional heat transfer and thermal stress analyses. Stellite6, Stellite21 and 19-9DL superalloys are chosen as alternative hardfacing materials. The influence of hardfacing materials and thicknesses on temperature, thermal stress and thermal strain distributions of the hardfaced part are investigated using the results of the analyses. From the results of the investigation, it has been noted that a hardfacing material with a high conductivity and a thinner hardfaced layer are desired to create an effective hardfacing layer in terms of heat transfer characteristics. In addition, it has been revealed that the deviation of effective stress and principal strain in the vicinity of the joined region are minimized when the Stellite21 hardfaced layer with the thickness of 2 mm is created on the STD61. Based on the above results, a proper hardfacing material and thickness for STD61 tool steel have been estimated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.27-33
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• 2013

To ensure proper functioning of electrical and mechanical systems, cooling devices are of great importance. A heat sink is the most common cooling device used in many industries such as the semiconductor, electronic instrument, LED lighting, and automotive industries. To design an optimal heat sink, the required surface area for heat radiation should be calculated based on an accurate expectation of the heat flow rate in the target environment. In this study, the convective heat flow characteristics were numerically investigated for a vertically installed typical heat sink and a horizontally installed one in free convection using ANSYS CFX. Comparative experiments were carried out to reveal the quantitative effect of the installation direction on the cooling performance. Moreover, the result was analyzed using the dimensionless correlation with the Nusselt number and Rayleigh number and compared with well-known theories. Finally, it was observed that the cooling performance of the vertically installed heat sink is approximately 10~15% better than that of the one in natural convection.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.692-698
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• 2015

This paper represents a trajectory design and analysis technique which uses invariant manifolds of the circular restricted three body problem. Instead of the classical patched conic method based on 2-body problem, the equation of motion and dynamical behavior of spacecraft in the circular restricted 3-body problem are introduced, and the characteristics of Lyapunov orbits near libration points and their invariant manifolds are covered in this paper. The trajectories from/to Lyapunov orbits are numerically generated with invariant manifolds in the Earth-moon system. The trajectories in the Sun-Jupiter system are also analyzed with various initial conditions in the boundary surface. These methods can be effectively applied to interplanetary trajectory designs.