• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.344-349
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• 2006

A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce thick SiC epitaxial layers for power device applications. We aimed to systematically investigate the dependence of SiC epilayer quality and growth rate during the sublimation growth using the CST method on various process parameters such as the growth temperature and working pressure. The etched surface of a SiC epitaxial layer grown with low growth rate $(30{\mu}m/h)$ exhibited low etch pit density (EPD) of ${\sim}2000/cm^2$ and a low micropipe density (MPD) of $2/cm^2$. The etched surface of a SiC epitaxial layer grown with high growth rate (above $100{\mu}m/h$) contained a high EPD of ${\sim}3500/cm^2$ and a high MPD of ${\sim}500/cm^2$, which indicates that high growth rate aids the formation of dislocations and micropipes in the epitaxial layer. We also investigated the Schottky barrier diode (SBD) characteristics including a carrier density and depletion layer for Ni/SiC structure and finally proposed a MESFET device fabricated by using selective epilayer process.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.183.1-183.1
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• 2013

70 MeV 사이클로트론의 인젝션 빔 라인은 Multi-CUSP 이온원에서 인출된 H- 빔을 펄스 또는 번칭하여 인플렉터를 통해 사이클로트론의 가속영역인 Dee로 전송하는 역할을 한다. 이 때, 빔을 번칭 시킴으로써 가속효율을 높이고, 손실을 줄여 높은 전류의 빔을 공급할 수 있도록 해야한다. 인젝션 시스템은 einzel lens, chopper, buncher, solenoid 등으로 구성된다. Einzel lens는 빔을 buncher의 중심으로 집속시켜 buncher의 번칭 효율을 높이고, buncher는 전기장을 이용하여 빔을 진행방향으로 집속시키는 기능을 갖는다. Chopper는 번칭된 빔을 일정 주기로 편향을 시켜 펄스 빔의 형태로 전송하는 역할을 한다. 솔레노이드는 적절한 자기장을 이용하여 빔을 집속시켜 인플렉터로 전송한다. 본 연구에서는 사이클로트론의 고전류 인젝션 시스템을 구축하고 각각의 구성요소에서 빔 envelope를 계산하고 비교하였다. SIMION code는 user가 지정한 특성을 가진 개별 입자의 궤도를 추적하는 프로그램으로 인젝션 시스템을 구성하는 각각의 컴포넌트에서의 입자의 진행모습과 buncher를 이용하여 빔의 전송 밀도가 향상됨을 확인하였다. 아울러 TRANSPORT 및 TURTLE 프로그램을 이용하여 SIMION을 통해 계산된 빔의 envelope과 비교하였다.

• 대한금속재료학회지
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• 제47권1호
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• pp.32-37
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• 2009

Molecular dynamic simulations on the structural evolution of the Si(001) vicinal surfaces, which are tilted with respect to [100] and [110] directions were performed by using the empirical Tersoff potential. Tersoff potential was implemented at LAMMPS code and confirmed to describe the properties of Si. When the steps are generated along [100] direction, symmetric dimer rows formed with respect to the step edges. On the other hand, when the steps are generated along [110] direction, alternating dimer rows form with respect to the step edges. The configurational differences between the two vicinal surfaces were discussed in terms of the surface diffusion and the possibility of preventing step bunching for the (001) vicinal surface tilted along [100] direction was suggested.

• International journal of advanced smart convergence
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• 제4권1호
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• pp.137-144
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• 2015

Development of the yarn sorting equipment (khonhook) by slide way due to the principle of engineering that cause of workers on the long of motion time. The data was collected from the weaving group Ban Nongkok village, Nakornratchasima Province, THAILAND. According to the study, the step of yarn sorting (konhook) was one of the steps that affect long of motion time. The problem was the inadequate capacity equipment. The objective of research was to study and develop the yarn sorting equipment (konhook). The fabric used in the study was 64 meters in length and 1 meter in width. Researchers studied the processes the yarn sorting (konhook) which it consists of seven sub steps, 1) the thread tube setting, 2) yarn bunching, 3) tying a knot at the end of yarn, 4) looping the yarn into a pillar, 5) sorting the yarn (konhook), 6) crossing pillars and 7) taking out the yarn. Researchers focused on studying yarn sorting process (konhook) by designing and creating a device for yarn sorting (konhook) for reducing yarn sorting (konhook) time by the original method performance indicators. The results found that the developed yarn sorting equipment (konhook) ) by slide way could reduce working time from 7.24 minutes to 6.08 minutes of the original equipment yarn sorting (konhook). This means it could make the process 16.02 % faster. This also helps reducing the distance of workers' movement from 2,234 meters to 8 meters. This is 99.64 % shorter.

• 유통과학연구
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• 제14권12호
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• pp.79-87
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• 2016

Purpose - Since 1990, the sudden stop in capital flows has caused the economic crisis. The purpose of this research is to suggest the policy measures to mitigate the risk of the sudden stop in capital flows. To this end, we examine the theoretical framework and analyze the case study for countries which are faced with the sudden stop. Also we examine the structural problems of the foreign exchange market in Korea and derive the policy implications to prevent the sudden stop. Research design, data, and methodology - The criteria of whether the sudden stop in capital flows occurs are based upon Calvo et al. (2008). In case the proxy variable for the balance of capital account decreases from the average by over twice standard deviation, we determine that the sudden stop occurs for that country. The sample period is from January 1990 to December 2008, as in Calvo (2014). The sample countries are 17 developed countries and 19 emerging market countries, which are different from those of the previous papers as Agosin and Huaita (2012), and Calvo (2014). When the exchange market pressure index(EMPI) is deviated from the average by over three times standard deviation, we determine that the foreign exchange market is unstable for that country. Results - We find that the characteristics of the sudden stop in capital flows are the bunching or contagion among countries, the rapid drop in real effective exchange rate, and the huge decrease in foreign exchange reserves. Many countries tried to increase foreign exchange reserves and regulate capital flows. Also the foreign exchange market in Korea are found to be the volatile exchange rate, the vulnerable external debt and careless management of the foreign exchange derivatives transaction risk. Conclusions - To lessen the risk in the sudden stop of capital flows, this research suggests the some useful policy measures. To enhance the foreign exchange and distribution market stability, we should improve the price mechanism of exchange rate, hold the appropriate level of foreign exchange reserves, prevent excessive inflows of foreign exchange and promote sound transactions of foreign exchange derivatives.

• 복식
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• 제62권7호
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• pp.205-219
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• 2012

The purpose of this study is to develop comfortable patient gown for spinal surgery patients. The results of the survey confirmed inconveniences and problems with the current gown, and a new gown style was recommended. The recommended changes addressed design, pattern, and materials. The final experimental design for the top of the new patient gown is a wrap style that moves the center opening of the gown to the side and enables patients to control the length of the sleeves by attaching two snaps. The cutting line is aligned with the back brace location, and the issue of repeated bunching of the gown material by the brace was solved by substituting 100% knitted structure fiber. The sleeve length can be adjusted with snaps on the sleeve cap and hem. When lifting up the gown for treatment on specific areas of the body, doctors open the edge of the right side of the gown in order to lift up the top. The bottom of the new patient gown was made from 100% cotton knitted structure fiber, and it enables patients to control the length of pants by attaching two snaps on the side. The results of an on-site dressing suitability evaluation and a flexibility evaluation with respect to dressing/undressing indicated that the new patient gown was much better received than the existing gowns (A and B). Our hypothesis regarding new patient gowns was supported in both the fit and design categories.

• 대한치과보철학회지
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• 제45권3호
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• pp.310-320
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• 2007

Statement of the problem. The fracture of acrylic resin dentures remains an unsolved problem. Therefore, many investigations have been performed and various approaches to strengthening acrylic resin, for example, the reinforcement of heat-cured acrylic resin using glass fibers, have been suggested over the years. But problems such as poor workability, rough surface, poor adhesion of glass fiber resin complex are not solved yet. Purpose. The aim of the present study was to investigate the effect of short glass fibers on the transverse strength of heat-polymerized denture base acrylic resin and roughness of resin complex after abrasion test. Material and methods. To avoid fiber bunching and achieve even fiber distribution, glass fiber bundles were mixed with acrylic resin powder in conventional mixer with a non-cutting blade, to produce the glass fiber($10{\mu}m$ diameter, 3mm length, silane treated) resin composite. Glass fibers were incorporated at 0%, 3%, 6% and 9% by weight. Transverse strength were measured. After abrasion test, surface roughness was evaluated and scanning electron microscope view was taken for clinical application. Results. 1. 6% and 9% incorporation of 3mm glass fibers in the acrylic resin enhanced the transverse strength of the test specimens(p<0.05). 2. Before abrasion test, incorporation of 0%, 3%, 9% glass fiber in the resin showed no dirrerence in roughness statisticaly(p>0.05). 3. After abrasion test, incorporation of 0%, 3%, 6% glass fiber in the resin showed same surface roughness value statistically(p>0.05). 4. In SEM, surface roughness increased as the percentage of the fibers increased. 5. In the areas where glass fiber bunchings are formated, a remarkably high roughness was noticed. Conclusion. 6% and 9% addition of silane-treated short glass fibers into denture base acrylic resin increased transverse strength significantly. Before and after abrasion test, incorporation of 0%, 3%, 6% glass fiber in the resin showed same surface roughness value statistically.

• 한국컴퓨터정보학회논문지
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• 제28권10호
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• pp.77-84
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• 2023

물리 기반 시뮬레이션에서 젖은 머리카락이나 털의 응집력과 뻣뻣함을 시뮬레이션 하는 것은 어려운 문제 중 하나이다. 젖은 머리카락이나 털은 끝부분이 뭉치고 뻣뻣해지는 것이 특징이며, 이는 젖은 동물의 털이나 머리카락에서 볼 수 있는 현상이다. 또한 젖은 머리카락은 고체와 상호작용을 하면 접착력이 발생하지만, 이 문제는 곱슬머리에서 힘의 분산과 균형이 달라지기 때문에 해결하기 어려워진다. 기존 방법에서는 수작업을 통해 젖은 머리를 표현하거나 정적인 헤어스타일로 젖은 곱슬머리 및 털을 표현한다. 그러나 젖은 곱슬머리의 디테일을 묘사하는 방법에 대한 연구는 아직 활발히 연구되지 않았다. 따라서 본 논문에서는 젖은 곱슬머리의 컬 과장, 응집력, 접착력 그리고 강성을 효율적으로 모델링하는 새로운 알고리즘을 제안한다. 제안하는 방법은 응집력을 효율적으로 시뮬레이션하고 강성 제약 조건을 곱슬머리 역학과 통합하여 안정적으로 모발의 탄성을 제어한다.

• 대한교통학회지
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• 제35권4호
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• pp.348-359
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• 2017

최근 국내에서는 대도시권의 교통혼잡 완화를 위하여 다양한 대중교통 활성화 정책을 시행중에 있다. 특히 대도시권역에서는 버스정보시스템이 도입되어 버스의 현재위치, 도착예정시간 등에 대한 정보를 제공하고 있다. 하지만 복잡한 도시부를 지나는 버스들의 경우 반복적인 교통혼잡과 버스몰림으로 인하여 정확한 통행시간 정보제공 시 정확도를 확보하는데 어려움이 있다. 기존 버스 통행시간 연구는 링크별 소통정보 제공방식으로 인하여 버스 이용자의 경로 통행시간 정보 제공 시 어려움이 있고, 데이터 기반의 단기 통행방식으로 중장기 정보 제공이 어렵다는 한계가 있다. 이에 본 연구에서는 경로기반의 중장기 버스통행시간 예측 방법론에 대한 연구를 실시한다. 이를 위하여 2015년 버스통행정보로 학습데이터, 2016년 자료로 검증데이터를 구성하였다. 학습데이터를 이용하여 버스통행정보를 분석하여 버스통행시간에 영향을 미치는 요인들을 출발시각, 요일, 그리고 기상요인 등으로 분류하고, 이들의 특성 값을 자기조직화지도를 활용하여 비슷한 통행 패턴을 가지는 군집으로 분류하였다. 도출된 군집들을 바탕으로 맑음과 우천시에 대한 요일/출발시각 별 버스통행시간 참조 테이블을 구성하였다. 검증데이터를 이용하여 본 연구에서 도출한 버스통행시간의 정확도를 검증하였다. 본 연구의 중장기 예측 알고리즘을 활용하여 기존의 직관적이고 경험적인 접근법의 한계를 극복할 수 있으며, 예측의 정확도 개선을 통한 버스이용자 만족도 향상 및 탄력적인 대중교통 정책 수립이 가능할 것으로 판단된다.