• 한국컴퓨터정보학회논문지
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• 제21권11호
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• pp.121-126
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• 2016

In recommender systems based on collaborative filtering, measuring similarity is very critical for determining the range of recommenders. Data sparsity problem is fundamental in collaborative filtering systems, which is partly solved by Jaccard coefficient combined with traditional similarity measures. This study proposes a new coefficient for improving performance of Jaccard coefficient by compensating for its drawbacks. We conducted experiments using datasets of various characteristics for performance analysis. As a result of comparison between the proposed and the similarity metric of Pearson correlation widely used up to date, it is found that the two metrics yielded competitive performance on a dense dataset while the proposed showed much better performance on a sparser dataset. Also, the result of comparing the proposed with Jaccard coefficient showed that the proposed yielded far better performance as the dataset is denser. Overall, the proposed coefficient demonstrated the best prediction and recommendation performance among the experimented metrics.

• 한국안전학회지
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• 제27권5호
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• pp.30-34
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• 2012

A safety helmet is a personal protective equipment to protect the head from falling and flying objects. A safety helmet has the maximum delivered impact force as shock absorption performance, the lower delivered impact force the better performance, which was not a controlled variety during manufacturing safety helmet. Accordingly there were some difficulties in establishing the standard for improved performance as there was not a clear controllable impact force for improved performance. In this study the shock absorption performance was intended to be found as coefficient of restitution related to impulse. As a research method, a coefficient of restitution during the absorption of shock was calculated using the impulse transferred to pharynx utilizing the safety helmet shock absorption performance testing device based on the theory of momentum and impulse. The estimated impulsive force curve was derived assuming that shock was not absorbed using the measured data. The sample was selected as tested goods of ABS material for safety certification available mainly in the market. As a result of study, the maximum delivered impact force of safety helmet made by a domestic safety certified a company was 735 N, and its coefficient of restitution proved to be 0.64. The smaller coefficient of restitution is, the lower maximum delivered impact force and the higher shock absorption performance. The coefficient of restitution can be used as a performance index of safety helmet.

• Journal of Biosystems Engineering
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• 제24권6호
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• pp.501-512
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• 1999

In this study, the coefficient of performance of a vapour compression heat pump system was analyzed for the evaluation of the heat pump performance. A water-to-air heat pump was assembled and tested by changing the level of the compressor driving speed and the air mass flow rate during air heating process. The coefficient of performance for air heating was 2.6~3.8 and that for water cooling was 1.0~1.4. The coefficient of performance was not depending on the levels of the compressor driving speed or levels of the air mass flow rate, but on the temperature of the air and water. The coefficient of performance for air heating increased by about 0.2 with the water temperature increasing by 1$^{\circ}C$.

• 동력기계공학회지
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• 제18권6호
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• pp.13-20
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• 2014

The steady-state, incompressible and three-dimensional numerical analysis was carried out to evaluate turbulent models on the aerodynamic performance of a small-size axial fan(SSAF). The prediction performance on the static pressure of all turbulent models is going downhill at the high static pressure and low flowrate region, but has improved at the axial flow region. In consequence, all turbulent models predict the static pressure coefficient with an error performance less than about 4% after the region of the flowrate coefficient of about 0.14. Especially, the turbulent model of SST $k-{\omega}$ shows the best prediction performance equivalent to an error performance less than about 2% on the static pressure.

• 한국콘텐츠학회논문지
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• 제13권1호
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• pp.147-155
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• 2013

본 연구의 목적은 공연산업의 경제적 파급 효과를 분석하는데 있다. 연구분석을 위해 한국은행의 2009년 산업연관표를 이용하여 연극, 음악 및 기타 예술(390 부문)만을 공연산업으로 한정하고 새로이 공연 산업연관표를 작성하여 공연산업의 경제적 파급효과를 분석하였다. 연구 결과, 공연산업의 총생산유발액은 391.6조원, 소득유발액은 65.1조원, 생산세유발액은 총 16.3조원으로 나타났다. 특히 공연산업의 생산유발계수는 1,387, 감응도 계수 0.020, 영향력계수 0.025, 부가가치유발계수 0.662, 소득유발계수 0.455, 생산세유발계수 0.046 그리고 노동유발계수 0.010 등으로 나타났다.

• 동력기계공학회지
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• 제17권6호
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• pp.73-78
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• 2013

A Small-size axial fan(SSAF) has widely been utilized to circulate a cooling air in a refrigerator, etc. Generally, the aerodynamic performance of SSAF is strongly dependent upon the depth between SSAF and bellmouth, and it includes axial, partially stalled, mostly stalled and radial flow regions according to the flow coefficient. In this study, four kinds of bellmouth depths were considered to analyze the aerodynamic performance of SSAF. As a bellmouth depth increases, a maximum flowrate decreases, but a maximum static pressure increases. Also, stall region includes an inflection point in all aerodynamic performance curves. Finally, a static pressure efficiency shows the maximum value of 37%.

• 한국유체기계학회 논문집
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• 제2권2호
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• pp.46-56
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• 1999

This study is on the performance prediction and design of a sirocco fan. Slip coefficient is very important factor for the performance analysis of a centrifugal-type fan. Because generally used slip coefficient equations of backward curved centrifugal fan are not appropriate for forward curved sirocco fan, in this study a proper slip coefficient equation for a sirocco fan is suggested. Using this equation performance prediction program for sirocco fan is composed of and also included the total noise prediction that include the turbulent noise at the fan inlet and boundary layer noise. A comparison between the values obtained from performance prediction program and experimental values shows that the program predicts the sirocco fan performance in a practical rate.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 강연회 및 연구개발 발표회 논문집
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• pp.63-72
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• 1998

This study Is on the performance prediction and design of sirocco fan. Slip coefficient is very important factor for the performance analysis of centrifugal-type fan. Because generally used slip coefficient equations of backward curved centrifugal fan are not appropriate for forward curved sirocco fan, in this study a proper slip coefficient equation for sirocco fan is suggested. Using this equation performance prediction program for sirocco fan is composed and also included the total noise prediction that include turbulent noise at the fan Inlet and boundary layer noise. A comparison between the values obtained from performance prediction program and experimental values shows that the program predicts the sirocco fan performance in a practical rate.

• 한국방재학회 논문집
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• 제10권5호
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• pp.135-141
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• 2010

본 연구에서는 우수관의 조도계수의 변화에 따른 성능불능확률을 산정할 수 있는 신뢰성 모형이 개발되었다. 조도계수는 우수관의 토사의 적체에 따라 다시 산정되었으며 새로운 조도계수를 이용하여 신뢰성 해석이 수행되었다. 해석결과, 우수관에 적체되는 토사의 깊이가 증가함에 따라 우수관의 용량은 크게 감소하고 성능불능확률은 크게 증가함을 알 수 있었다. 본 연구에서는 우수관에 적체되는 토사의 깊이에 따라 산정된 조도계수를 사용한 신뢰성 모형을 대구와 전주에 적용하였다. 원형 우수관에 적체된 토사의 깊이가 증가할수록 우수관의 조도계수는 커지고 성능불능확률도 역시 크게 증가 하는 것을 알 수 있었다.

• 한국지진공학회논문집
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• 제7권5호
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• pp.1-9
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• 2003

국내 콘크리트댐의 경우 내진설계는 관성력을 고려한 진도법을 적용하여 설계를 하고 있으나, 보수적인 설계 방법으로 동적특성을 반영하지 못하는 단점이 있어, 동적특성을 고려한 댐 내진설계가 필요하다. 또한 콘크리트댐 내진성능평가는 동적해석으로 평가해야 하지만, 국내의 경우 대부분 진도법으로 평가를 하고 있어 현행 기준을 적용하기에는 어려운 점이 있다. 이에 본 연구에서는 진도법, 수정진도법, 동적해석 방법을 수행하여 내진설계 및 내진성능평가 결과에 대해서 비교 분석하였다.