• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.193-193
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• 2012

In thin film silicon solar cells, p-i-n structure is adopted instead of p/n junction structure as in wafer-based Si solar cells. PECVD is the most widely used thin film deposition process for a-Si:H or ${\mu}c$-Si:H solar cells. Single-chamber PECVD system for a-Si:H solar cell manufacturing has the advantage of lower initial investment and maintenance cost for the equipment. However, in single-chamber PECVD system, doped and intrinsic layers are deposited in one plasma chamber, which inevitably impedes sharp dopant profiles at the interfaces due to the contamination from previous deposition process. The cross-contamination between layers is a serious drawback of single-chamber PECVD system. In this study, a new plasma process to solve the cross-contamination problem in a single-chamber PECVD system was suggested. In order to remove the deposited B inside of the plasma chamber during p-layer deposition, a high RF power was applied right after p-layer deposition with SiH4 gas off, which is then followed by i-layer, n-layer, and Ag top-electrode deposition without vacuum break. In addition to the p-i interface control, various interface control techniques such as FTO-glass pre-annealing in O2 environment to further reduce sheet resistance of FTO-glass, thin layer of TiO2 deposition to prevent H2 plasma reduction of FTO layer, and hydrogen plasma treatment prior to n-layer deposition, etc. were developed. The best initial solar cell efficiency using single-chamber PECVD system of 10.5% for test cell area of 0.2 $cm^2$ could be achieved by adopting various interface control methods.

• 대한기계학회논문집B
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• 제40권9호
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• pp.597-604
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• 2016

본 연구에서는 GPU를 이용한 비압축성 유동장의 병렬연산을 위하여, P2P1 유한요소를 이용한 분리 알고리즘 내의 행렬 해법인 이중공액구배법(Bi-Conjugate Gradient)의 CUDA 기반 알고리즘을 개발하였다. 개발된 알고리즘을 이용해 비대칭 협착관 유동을 해석하고, 단일 CPU와의 계산시간을 비교하여 GPU 병렬 연산의 성능 향상을 측정하였다. 또한, 비대칭 협착관 유동 문제와 다른 행렬 패턴을 가지는 유체구조 상호작용 문제에 대하여 이중공액구배법 내의 희소 행렬과 벡터의 곱에 대한 GPU의 병렬성능을 확인하였다. 개발된 코드는 희소 행렬의 1개의 행과 벡터의 내적을 병렬 연산하는 커널(Kernel)로 구성되며, 최적화는 병렬 감소 연산(Parallel Reduction), 메모리 코얼레싱(Coalescing) 효과를 이용하여 구현하였다. 또한, 커널 생성 시 워프(Warp)의 크기에 따른 성능 차이를 확인하였다. 표준예제들에 대한 GPU 병렬연산속도는 CPU 대비 약 7배 이상 향상됨을 확인하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.392-399
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• 2005

Shear modulus (or rigidity) of dam material is an important parameter which can be directly associated with the deformation of dam. Seepage or leakage of water can cause the defects or cracks of dam body. The existence of cracks and rigidity of dam body are decisive information for the estimation of dam safety. Rigidity of material is mainly determined from S-wave velocity and the defects of dam body can be detected by seismic reflection survey. Therefore, seismic reflection survey will be a desirable method which can give a solution about dam safety problem. Among various physical properties of dam body, S-wave velocity is the most important information but it is not easy to get the information. In this study, diverse measuring techniques of S-wave reflection survey were attempted to get the information about S-wave velocity of dam body. Ultimately, S-wave velocity could be estimated by the analysis of SH reflection events which can be easily observed in shot gather data obtained from SH measuring technique. Meanwhile, P-wave reflection survey was also performed at the same profile. P-beam radiation technique which can reduce the surface waves and reinforce the P-wave reflection events was applied for giving a help to analyse P-wave velocity. In the end, P-and S-wave velocity, Vs/Vp, Poisson's ratio distribution of the vertical section under the profile could be acquired.

• 공학교육연구
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• 제12권4호
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• pp.30-37
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• 2009

연구의 목적은 학생들의 자기효능감 수준에 따른 문제해결능력의 차이를 검증해 보는 것이었다. 즉, 자기효능감이 높은 학습자와 낮은 학습자의 PBL수업 후 문제해결능력의 차이를 살펴봄으로써 PBL 수업에서의 자기효능감의 중요성을 파악해 보고자 했다. 본 연구는 환경공학과 '환경기기분석'을 수강했던 3학년 72명의 학생들을 대상으로 진행되었다. PBL 활동을 시작하기 전 자기효능감 검사를 통해 나온 점수를 기준으로 상위 30%와 하위 30%의 학생들을 각각 선정하였고, 이들에게 문제해결 능력 사전검사를 실시하였다. 12주간의 PBL활동이 마무리 된 후 같은 학생들에게 사후 문제해결검사를 배포하고 완성하도록 요구하였다. 교정된 문제해결 능력 성취 수준이 자기효능감 상집단과 하집단에 따라 차이가 있는지를 확인하기 위하여 공분산분석을 실시한 결과, 두 집단은 유의 확률 .002로 유의수준 .01에서 유의미한 것으로 나타났다 (F=.11303, p<.01). 즉, 자기효능감 상집단의 평균(3.817)이 자기효능감 하집단의 평균(3.496)보다 높아 자기효능감은 문제해결 능력과 밀접한 관련이 있는 것으로 나타났다. 따라서 PBL 수업과정에서 학습자의 자기효능감 수준을 향상시켜 효과적인 문제해결을 할 수 있도록 도울 필요가 있다.

• 대한간호학회지
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• 제29권5호
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• pp.1155-1166
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• 1999

The purpose of this study was to investigate the residents' opinions about community mental health in the Taegu-Kyungpuk area for the future development of a community mental health program and model appropriate for Korea, The subjects were 152 residents in the Taegu - Kyungpuk area. In July 1999, the data was collected using a convenience sample technique. Mental health status was significantly different for the level of occupational advantage(x$^2$＝15.684, p＜.05) and physical health(x$^2$＝39.262, p＜.000). Factor structure for mental health problems with the percentage of variance was as follows. optimistic view(27.518), dark view(10.758), mastery(6.200), discomfiture(6.101) and life style(5.641). Most of the respondents(92.1%) took the mental health problems seriously. The serious aspects of the mental health problem were found to be epilepsy, mental retardation, neurosis and schizophrenia respectively. Concerning about the view of community mental health, most of the respondents answered that the a C.M.H.C. was ‘useful and urgent’ concerning the need for C.M.H,(77.6%). They answered positively on the utilization of C.M.H.C(75.7% ) and preferred the separately new community mental heath center. A psychiatrist was preferred as the key person in charge(44.1%). If community mental health centers were established in a community health center, they answered that the expected major problem would be quality control of care(44.7%). They preferred the psychiatrist's office as the recommended agency for the insane(44.7%). Opinions of the asylum system were found very negative in respect to psychiatric therapy and humanitarianism. The results of this study will help establish a relevant model for this community as the primary site for a community-based mental health model.

• 농촌의학ㆍ지역보건
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• 제27권1호
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• pp.143-153
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• 2002

경상북도 일개면 지역에 거주하는 65세 이상 재가노인 355명을 대상으로 방문보건의료 요구도를 알아봄으로써 향후 보건기관의 효율적이고 효과적인 방문보건의료서비스 제공방안의 기초자료를 제시하고자 하였다. 주관적 건강상태는 64.5%가 허약하다고 하였고, 저ADL과 저IADL이 각각 14.1%, 14.9%였다. 의료인의 도움을 받아야할 건강문제가 있다고 응답한 노인이 73.5%이었는데, 성, 연령, 결혼상태, 의료보장상태, 직업유무, 경제적 상태, 치료여건, 주관적 건강상태, 일상생활수행정도, 수단적 일상생활수행정도에 따라 차이가 있었다(p<0.05). 의료인의 도움을 받아야 할 건강문제가 있다고 느끼는 노인의 주관적인 방문보건의료 요구도는 19.5%였다. 방문보건의료 요구도는 75세 이상인 경우(p<0.05), 직업이 없는 경우(p<0.01) 유의하게 높았고, 가족이 화목하지 않을수록, 주관적 건강상태가 허약한 경우, 저 IADL인 경우 유의하게 높았다(p<0.01). 방문보건의료를 받기를 원하는 경우 이유는 돌봐줄 사람이 없어서가 64.7%로 가장 높았고, 거리가 너무 멀어서(지역적 문제)가 23.5%로 그 다음이었다. 제일원하는 방문보건의료서비스는 투약이 82.3%로 가장 높았다. 방문보건의료를 원하지 않는 경우 이유는 거동이 가능하므로 60.0%, 의사와 직접 만나기를 원하므로 25.7%의 순이었다. 방문보건의료 요구여부를 종속변수로 한 다중 로지스틱 회귀분석 결과, 가족이 화목하지 않을수록, 주관적 건강상태가 허약할수록 방문요구도가 높았다(p<0.05).

• Nuclear Engineering and Technology
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• 제49권2호
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• pp.395-403
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• 2017

An efficient evaluation method for the probability of a tornado missile strike without using the Monte Carlo method is proposed in this paper. A major part of the proposed probability evaluation is based on numerical results computed using an in-house code, Tornado-borne missile analysis code, which enables us to evaluate the liftoff and flight behaviors of unconstrained objects on the ground driven by a tornado. Using the Tornado-borne missile analysis code, we can obtain a stochastic correlation between local wind speed and flight distance of each object, and this stochastic correlation is used to evaluate the conditional strike probability, $Q_V(r)$, of a missile located at position r, where the local wind speed is V. In contrast, the annual exceedance probability of local wind speed, which can be computed using a tornado hazard analysis code, is used to derive the probability density function, p(V). Then, we finally obtain the annual probability of tornado missile strike on a structure with the convolutional integration of product of $Q_V(r)$ and p(V) over V. The evaluation method is applied to a simple problem to qualitatively confirm the validity, and to quantitatively verify the results for two extreme cases in which an object is located just in the vicinity of or far away from the structure.

• Journal of Preventive Medicine and Public Health
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• 제40권2호
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• pp.145-149
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• 2007

Objectives : This study characterized the extent to which youth depressive symptoms, parental alcohol problems, and parental drinking account for differences in alcohol-related problems among a large sample of adolescent females. Methods : The stratified sample consists of 2077 adolescent females from twelve female-only high schools located in a large metropolitan city in the Republic of Korea. Students completed a questionnaire about alcohol use and alcohol problems, their parents' alcohol problems, and a number of risk and protective factors. Data were analyzed using tobit regression analyses to better characterize the associations among variables. Results : Almost two-thirds of students who consume alcohol had experienced at least one to two alcohol-related problems in their lives and 54.6% reported at least one current symptom of depression, with nearly one-third reporting two depressive symptoms. Two-thirds of the students indicated that at least one parent had an alcohol-related problem, and that approximately 29% had experienced several problems. Results of tobit regression analyses indicate that youth alcohol-related problems are positively associated with depressive symptoms (p<0.01) and parent drinking problems (p<0.05). Parental drinking is no longer significant when the variable parental attention is added to the model. Decomposition of the tobit parameters shows that for every unit of increase in depressive symptoms and in parent drinking problems, the probability of a youth experiencing alcohol problems increases by 6% and 1%, respectively. For every unit of increase in parental attention, the probability of youth experiencing drinking problems decreases by 5%. Conclusions : This study presents evidence that alcohol-related problems and depressive symptoms are highly prevalent among adolescent females. Although a comprehensive public health approach is needed to address drinking and mental health problems, different interventions are needed to target factors associated with initiation of alcohol problems and those associated with increased alcohol problems among those who already began experiencing such problems.

• Composites Research
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• 제29권4호
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• pp.216-222
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• 2016

폴리디싸이클로팬타디엔 (p-DCPD) 수지를 경화하기 위해 개환반응이 사용된다. 이 반응은 텅스텐계 촉매를 이용한 반응이기 때문에 질소 조건에서 반응이 진행되어야 한다. 왜냐하면, 텅스텐계 수지는 촉매독 현상이 발생될 수 있기 때문에 대기조건에서는 사용이 어려운 것으로 알려져 있다. 이러한 문제를 개선하기 위해 본 연구에서는 대기 조건에서 텅스턴 (W)을 촉매로한 p-DCPD 대해 프레스 성형법을 이용하여 수지를 경화시켰다. 프레스 성형을 통해 p-DCPD (W) 수지를 경화시킬 경우 기계적 강도가 향상되는 결과를 얻었으며, 이는 DCPD 성형 단계에서 발생되는 기체를 압으로 눌러 미세 기공의 발생을 줄였기 때문이다. 촉매 독 현상이 발생되는 것은 반응시간이 길 때에 발생되지만, 짧은 성형을 시도하는 프레스 성형에서는 촉매 자체로 인한 물성 저하가 발생되지 않았다. 궁극적으로 p-DCPD 성형을 위해 대기 조건에서 성형이 가능하였으며, 경화 시간, 압력 변수를 조절할 경우 기계적 물성이 향상을 확인하였다.

• Wind and Structures
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• 제29권3호
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• pp.149-161
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• 2019

When a railway vehicle runs in crosswinds, the unsteady aerodynamic forces acting on the train induced by the vehicle speed, crosswind velocity and local landforms are a common problem. To investigate the dynamic performance of a railway vehicle due to the influence of unsteady aerodynamic forces caused by local landforms, a vehicle aerodynamic model and vehicle dynamic model were established. Then, a wind-loaded vehicle system model was presented and validated. Based on the wind-loaded vehicle system model, the dynamic response performance of the vehicle, including safety indexes and vibration characteristics, was examined in detail. Finally, the effects of the crosswind velocity and vehicle speed on the dynamic response performance of the vehicle system were analyzed and compared.