• 한국분말재료학회지
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• 제27권5호
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• pp.388-393
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• 2020

The enamel powders used traditionally in Korea are produced by a ball-milling process. Because of their irregular shapes, enamel powders exhibit poor flowability. Therefore, polygonal enamel powders are only used for handmade cloisonné crafts. In order to industrialize or automate the process of cloisonné crafts, it is essential to control the size and shape of the powder. In this study, the flowability of the enamel powders was improved using the spheroidization process, which employs the RF plasma treatment. In addition, a simple grid structure and logo were successfully produced using the additive manufacturing process (powder bed fusion), which utilizes spherical enamel powders. The additive manufacturing technology of spherical enamel powders is expected to be widely used in the field of cloisonné crafting in the future.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권9호
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• pp.4180-4196
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• 2017

In this paper, we analyze average capacity of an amplify-and-forward (AF) cooperative communication system model in multi-relay multiuser networks. In contrast to conventional cooperative networks, relays in the considered network have no embedded energy supply. They need to rely on the energy harvested from the signals broadcasted by the source for their cooperative information transmission. Based on this structure, a two-step selection scheme is proposed considering both channel state information (CSI) and battery status of relays. Assuming each relay has infinite or finite energy storage for accumulating the energy, we use the infinite or finite Markov chain to capture the evolution of relay batteries and certain simplified assumptions to reduce computational complexity of the Markov chain analysis. The approximate closed-form expressions for the average capacity of the proposed scheme are derived. All theoretical results are validated by numerical simulations. The impacts of the system parameters, such as relay or user number, energy harvesting threshold and battery size, on the capacity performance are extensively investigated. Results show that although the performance of our scheme is inferior to the optimal joint selection scheme, it is still a practical scheme because its complexity is much lower than that of the optimal scheme.

• 대한공간정보학회지
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• 제17권4호
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• pp.61-66
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• 2009

본 연구는 넓은 지역의 DEM 생성 시 하드웨어 성능에 따라 자료를 부분적으로 처리해야 하는 불편을 개선하고 DEM의 정밀도를 개선하는 것에 그 목적이 있다. 본 연구에서 개발된 DEM Generator 프로그램은 대용량 LiDAR 자료, 수치지형도 자료에 스트리밍 방식을 적용하여 인덱싱 및 델로니 삼각망 생성을 수행하고, Natural Neighborhood 또는 TIN 보간법을 적용한 가상 파일을 생성하여 특정한 해상도로 대규모 지역의 DEM 및 음영기 복도를 효율적으로 생성하도록 설계되었다. 최종적으로 생성된 DEM 및 음영기복도는 GeoTIFF 포맷으로 제공된다. DEM Generator 프로그램은 GIS, 기상, 환경 분석 등 넓은 지역의 DEM 생성이 필요한 분야에서 기존의 부분적인 DEM 생성 및 인접 처리 과정에 의해 발생했던 시간적 경제적 손실을 절감시킬 수 있을 것으로 판단되며, 추가적인 인접 및 수정 작업이 불필요하여 DEM의 정밀도를 높일 수 있을 것으로 판단된다.

• International Journal of Aeronautical and Space Sciences
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• 제16권4호
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• pp.560-570
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• 2015

We present a simulation of a hybrid Reynolds-averaged Navier Stokes / Large Eddy Simulation (RANS/LES) based on detached eddy simulation (DES) for a Burrows and Kurkov supersonic planar mixing experiment. The preliminary simulation results are checked in order to validate the numerical computing capability of the current code. Mesh refinement studies are performed to identify the minimum grid size required to accurately capture the flow physics. A detailed investigation of the turbulence/chemistry interaction is carried out for a nine species 19-step hydrogen-air reaction mechanism. In contrast to the instantaneous value, the simulated time-averaged result inside the reactive shear layer underpredicts the maximum rise in $H_2O$ concentration and total temperature relative to the experimental data. The reason for the discrepancy is described in detail. Combustion parameters such as OH mass fraction, flame index, scalar dissipation rate, and mixture fraction are analyzed in order to study the flame structure.

• 한국화재소방학회논문지
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• 제21권2호
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• pp.98-104
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• 2007

본 연구는 원자력발전소의 방화지역에 대한 화재위험을 전산유체역학모델인 FDS를 이용하여 평가한 내용이다. 원자로 안전정지를 유지하기 위한 스위치기어실이 화재지역으로 선정되었으며, 화재 시나리오는 가상 화재조건을 기준으로 구성되었다. 본 연구의 주요 목적은 화재 모델링의 주요 입력항목인 열 발생율과 분석 모델 격자 크기를 변경한 경우 프로그램에 의하여 나타나는 결과값의 민감도를 분석하는 것이다. 그 결과는 전산유체역학모델에서 개선이 필요한 항목과 함께 결론에 제시되었다.

• 한국세라믹학회지
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• 제38권3호
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• pp.218-224
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• 2001

Yttria-stabilized zirconia (YSZ) films were deposited with varying temperatures of ZrCl$_4$between 250~55$0^{\circ}C$ with YCl$_3$and the substrate at 100$0^{\circ}C$. Nanoamperes per square centimeter of the electric current were measured in the reactor during deposition and the current increased with increasing evaporation temperature of ZrCl$_4$. The zirconia nanometer size clusters were captured on the grid membrane near the substrate during the CVD process and observed by transmission electron microscopy (TEM). The deposition rate decreased with increasing evaporation temperature of ZrCl$_4$. A cauliflower-shaped structure was developed at 25$0^{\circ}C$ then gradually changed to a faceted-grain structure above 35$0^{\circ}C$. Dependence of the growth rate and the morphological evolution on the evaporation temperature of ZrCl$_4$was approached by the charged cluster model.

• 한국전문물리치료학회지
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• 제16권2호
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• pp.41-49
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• 2009

This study was designed to investigate the effects of treadmill exercise of low-intensity and moderate- intensity on the functional recovery and histological change in spinal cord injury (SCI) rats. SCI was induced by the spinal cord impactor dropped after laminectomy. Experimental groups were divided into the Group I (normal control), Group II (non-treatment after SCI induction), Group III (low-intensity treadmill exercise after SCI induction), Group IV (moderate-intensity treadmill exercise after SCI induction). After operation, rats were tested at modified Tarlov scale at 2 days with divided into 4 groups, and motor behavior test (BBB locomotor rating scale, Grid walk test) was examined at 3, 7, 14, and 21 days. For the observation of damage change and size of the organized surface in spinal cord, histopathological studies were performed at 21 days by H & E, and BDNF(brain-derived neutrophic factor) & Trk-b immunohistochemistry studies were performed at 1, 3, 7, 14, 21 days. According to the results, treadmill exercise can play a role in facilitating recovery of locomotion following spinal cord injury. Specially, moderate-intensity treadmill exercise after SCI induction was most improvement in functional recovery and histological change.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 추계학술대회
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• pp.73-76
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• 2013

본 논문은 입 영역의 픽셀 분포의 비교를 통해 혀의 방향 인식 알고리즘을 제안한다. 스마트폰의 크기가 커짐에 따라 얼굴의 제스쳐를 이용한 스마트폰 제어 기술이 요구되고 있다. 처음 코의 영역을 먼저 검출한 뒤 코와 입 부분의 비율로 입의 영역을 검출한다. 입의 영역을 검출한 뒤 방향별 영역을 나누고 혀와 유사한 색의 픽셀분포를 파악해 가리키는 방향을 인지한다. 본 알고리즘은 연구실 연구원 5명을 대상으로 한 실험에서 인식률이 80%에 육박하였다.

• 한국물환경학회지
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• 제31권5호
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• pp.491-506
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• 2015

Distributed models represent watersheds using a network of numerous, uniform calculation units to provide spatially detailed and consistent evaluations across the watershed. However, these models have a disadvantage in general requiring a high computing cost. Semi-distributed models, on the other hand, delineate watersheds using a simplified network of non-uniform calculation units requiring a much lower computing cost than distributed models. Employing a simplified network of non-uniform units, however, semi-distributed models cannot but have limitations in spatially-consistent simulations of hydrogeochemical processes and are often not favoured for such a task as identifying critical source areas within a watershed. Aiming to overcome these shortcomings of both groups of models, a hybrid watershed model STREAM (Spatio-Temporal River-basin Ecohydrology Analysis Model) was developed in this study. Like a distributed model, STREAM divides a watershed into square grid cells of a same size each of which may have a different set of hydrogeochemical parameters reflecting the spatial heterogeneity. Like many semi-distributed models, STREAM groups individual cells of similar hydrogeochemical properties into representative cells for which real computations of the model are carried out. With this hybrid structure, STREAM requires a relatively small computational cost although it still keeps the critical advantage of distributed models.

• 한국추진공학회지
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• 제10권2호
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• pp.53-61
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• 2006

3차원 냉각 채널을 가지는 재생 냉각 시스템에 대하여 축대칭 열유속 모델을 이용한 축대칭 열해석을 수행하고자 하였다. 연소실 벽면에서의 급격한 온도 분포 및 열전달량을 정확히 모사하기 위한 격자 테스트 수행하고, 냉각재와 연소 가스의 온도에 따른 물성치 변화가 냉각 성능 예측에 미치는 영향들을 살펴보았다. 핀효율을 이용한 축대칭 열유속 모델이 3차원 냉각 채널에서의 열전달량과 동일한 열전달량을 나타낼 수 있도록 정의하였다. 제안된 모델을 이용한 축대칭 해석 결과가 1차원 해석 모델보다 우수하며 3차원 해석 결과에 근접한 온도 분포를 보임을 확인하였다.