• Title, Summary, Keyword: Coefficient of Performance

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Improving Performance of Jaccard Coefficient for Collaborative Filtering

  • Lee, Soojung
    • Journal of the Korea Society of Computer and Information
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    • v.21 no.11
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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.

A Study on the Shock Absorption Performance of the Safety Helmet using Coefficient of Restitution (반발계수를 이용한 안전모의 충격 흡수 성능에 관한 연구)

  • Shin, Woon-Chul
    • Journal of the Korean Society of Safety
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    • v.27 no.5
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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.

Performance Analysis of an Earth Coupled Heat Pump System Operated by an Engine(II) - Performance Analysis of a Vapour Compression type Compact Heat Pump - (엔진구동 지열 열펌프의 성능 분석(II) - 소형 증기압축식 열펌프의 성능 분석 -)

  • 김영복;송대빈;손재길
    • Journal of Biosystems Engineering
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    • v.24 no.6
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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$^{\circ}C$.

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Evaluation of the Turbulence Models on the Aerodynamic Performance of Three-Dimensional Small-Size Axial Fan (3차원 소형축류홴의 공력특성에 대한 난류모델평가)

  • Kim, Jang-Kweon;Oh, Seok-Hyung
    • Journal of the Korea Society For Power System Engineering
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    • v.18 no.6
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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.

Estimation of Economic Value of the Performance Industry (공연산업의 경제적 파급효과 분석)

  • Bae, Ki-Hyung
    • The Journal of the Korea Contents Association
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    • v.13 no.1
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    • pp.147-155
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    • 2013
  • The purpose of this study is to analyze how much performance industry contribute to national economy by measuring economic effects of performance industry. To achieve the purpose of the study, the study uses an performance industry(theater, music and other arts, 390 sectors) Input-Output Table of yaer 2009 of korea bank. The results shows that performance industry induce 391.6 trillion won in the national production, 65.1 trillion won in the income inducement, 16.3 trillion won in the tax inducement. Especially the performance industry shows that production inducement coefficient is 1,387, Index of the power of dispersion is 0.020, index of the sensitivity of dispersion is 0.025, value-added inducement coefficient is 0.662, income inducement coefficient is 0.455, tax inducement coefficient is 0.046 and employment inducement coefficient is 0.010.

Experimental Study on the Aerodynamic Performance Characteristics of a Small-Size Axial Fan with the Different Depths of Bellmouth (벨마우스 깊이가 다른 소형축류홴의 공력특성에 대한 실험적 연구)

  • Kim, Jang-Kweon;Oh, Seok-Hyung
    • Journal of the Korea Society For Power System Engineering
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    • v.17 no.6
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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%.

A study on Low-Noise and High-Efficiency Sirocco Fan Development (저소음 고효율 시로코 홴 개발에 관한 연구)

  • Park, Kwang-Jin;Lee, Sang-Hwan;Son, Byung-Jin
    • The KSFM Journal of Fluid Machinery
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    • v.2 no.2
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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.

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A study on low-noise and high-efficiency sirocco fan development (저소음 고효율 시로코 팬 개발에 관한 연구)

  • Park, K.J.;Lee, S.H.;Son, B.J.
    • 유체기계공업학회:학술대회논문집
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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.

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Probability of Performance Failure and Change of Roughness Coefficient According to Accumulation of Debris in Storm Sewer (토사적체에 따른 우수관의 조도계수 변화와 성능불능확률)

  • Kwon, Hyuk-Jae
    • Journal of Korean Society of Hazard Mitigation
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    • v.10 no.5
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    • pp.135-141
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    • 2010
  • Reliability model which can calculate the probability of performance failure of storm sewer was developed considering change of roughness coefficient in this study. Roughness coefficient should be re-evaluated due to accumulations of debris in sewer pipe. Therefore, roughness coefficient according to depth of debris in circular sewer pipe was determined for the present study. Reliability analysis was performed with the new roughness coefficient. After the analysis, it was found that capacity of storm sewer can be significantly decreased and probability of performance failure of storm sewer can be significantly increased by increasing the depth of debris in storm sewer. In this study, reliability model was applied for the Daegu and Jeonju using new roughness coefficient which was determined according to accumulation of debris in circular storm sewer. It was observed that if the depth of debris is increased, roughness coefficient is increased simultaneously and probability of performance failure of storm sewer is significantly increased.

The Evaluation of Seismic Performance on the Concrete Dam of Analysis Method (해석방법에 따른 콘크리트댐의 내진성능평가)

  • 임정열;이종욱;오병현
    • Journal of the Earthquake Engineering Society of Korea
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    • v.7 no.5
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    • pp.1-9
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    • 2003
  • The seismic design of the domestic concrete dams has done by seismic coefficient method considering inertia force, but this method has defect not reflect dynamic properties, as a conservative design method. Therefore, it is necessary for seismic design of dam to consider dynamic properties. Also, concrete dam evaluation of seismic performance has done by seismic coefficient method - in fact, it may done by dynamic analysis - that has many problems when applied to the domestic criteria. This study make a comparative analysis for result from seismic design and evaluation of seismic performance by seismic coefficient method, modified seismic coefficient method, and dynamic analysis method.