• 설비공학논문집
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• 제16권12호
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• pp.1197-1203
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• 2004

This study investigates the air leakage and heat transfer characteristics of a rotary-type air-to-air heat exchanger with a fiber polyester matrix. The leakage airflow rate is measured using a tracer gas method for various ventilation rates and rotational speeds of the matrix wheel. A correlation equation for air leakage is obtained by combining the pressure leakage and the carryover leakage. The pressure leakage is observed to be a function of ventilation airflow rate only, and the carryover leakage is found to be a linear function of rotational speed. The real efficiency of the heat exchanger can be obtained from its apparent efficiencies by taking into account the air leakage ratio. As the ventilation rate increases, the heat recovery efficiency decreases. As the rotational speed of the matrix increases, the efficiency increases initially but reaches a constant value for the rotational speeds over 10 rpm.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1232-1240
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• 2002

Recently, linear motors are applied to many small precision products. Thus high generating power with small size is required of it. In order to increase the motor efficiency, the design variables need to be optimized. In this study, Vector Fields FEM software, OPERA-3d, was used for simulating linear motor. The thrust and magnetic flux density at the air-gap center were simulated and compared with the experimental results. Taguchi method was applied to investigate the effects of each variables. As a result, the thickness of conductor and magnet was important for the thrust but the thickness of the yoke. The temperature of the conductor was determined by finding the thermal conductivity that was determined by experimentation. Correlation equation relating to the thrust and temperature was proposed by Latin square and Least Square method. The optimum design variables were determined by correlation equation, and compared with simulation results. According to this analysis, thrust force of linear motor was improved about 7% comparing with conventional model.

• 상하수도학회지
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• 제19권6호
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• pp.827-837
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• 2005

In this study, we derived a new non-dimensional variable including bubble size and air diffusing area by Buckingham's theorem for making a practical correlation with experimental results. Firstly, we drew a relationship between a non-dimensional variable, $NH/u_s$, which has a form of Froude number and destratification efficiency with a simple theoretical consideration. Then we derived two non-dimensional variables by Buckingham's ${\pi}$-theorem and equating them with a form of $Fr_N$ for making single parameter to correlate overall destratification efficiency. As the result, the single parameter Be number shows a correlations with destratification efficiencies obtained from laboratory and pilot experiments. Also, for the practical applications, we conducted multiple regression analysis using Be and tank area to make predictive equations about destratification efficiency. The result also shows a successful correlations with destratification efficiency ($R^2$>0.9, p<0.001). Using this equation, we proposed a new design methodology with respect to bubble diffusing area.

• 한국농공학회논문집
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• 제52권5호
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• pp.27-35
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• 2010

The characteristics of delivered nutrient loads were analyzed and the regression equations to estimate delivery ratios of nutrients (TN and TP) were developed using HSPF simulation results at six subwatersheds within the Bochung A unit watershed during 1998-2007. TN delivery ratio was higher than TP delivery ratio because significant amounts of TP was considered to be attached at soil as ${PO_4}^-$ during delivery process from discharged point of nutrient source to main stream. As a results of correlation analysis, factors related to geomorphic characteristics had not statistical correlation with TN and TP delivery ratios. TN loading rate from living and specific stream flow had statistical negative and positive correlation, respectively, with TN delivery ratio. TP loading rates from all sources and from land cover and specific stream flow had statistical negative, negative and positive correlation, respectively. The specific stream flow represents the most strong correlation with nutrient delivery ratios. The regression equations to estimate delivery ratios for TN and TP were developed by including statistical correlated factors and showed high efficiency of 0.98 and 0.95 of coefficient of determination for TN and TP, respectively.

• 수산해양교육연구
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• 제27권5호
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• pp.1436-1446
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• 2015

This study aims to understand how scuba diving instructors' expertise, instructor reliability and instruction efficiency are related to each other. In order to achieve the research goal, the study used a multi-stage stratified cluster sampling method and collected valid samples from 400 individuals at age of 20 and older who were scuba diving in scuba diving clubs in Busan, Gyeongnam, Gyeongbuk, Jeonnam and Jeonbuk. The 400 valid samples were applied to the data analysis. The study used SPSS 21.0 for processing the gathered data via a frequency analysis, a reliability analysis and a correlation analysis and in order to verify the hypotheses, the study applied AMOS 21.0 and conducted a confirmatory factor analysis and a structure equation model analysis. Findings that the study had extracted are summarized as follows. First, the study confirmed that the scuba diving instructors' expertise has a positive effect on the instructor reliability. Second, the scuba diving instructors' expertise was reported to positively influence the instruction efficiency. Third, the results revealed that the scuba diving club members' reliability in the instructors has a positive influence on the instruction efficiency.

• 한국토양비료학회지
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• 제33권6호
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• pp.384-392
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• 2000

토양중 질산태 질소 함량이 $14{\sim}225mg\;kg^{-1}$의 범위를 갖는 시설재배지 9개 토양에서 배추를 공시작물로 하여 무비구, 3요소 표준시비량의 50%구, 100%구 및 150%구의 4개 시비수준에서 포트재배로 수량반응, 비료효과 및 시비효율 등을 검토하였다. 무비구 배추 건물중과 토양의 질산태 질소 함량은 유의성 있는 정의 상관을 나타냈고 시비구와 무비구의 건물중, 질소흡수량 및 질산태 질소흡수량의 차이로 평가한 비료효과 및 시비효율과는 유의성 있는 부의 상관을 보였다. 질산태 질소함량에 따른 시비수준별 건물중 반응의 관계로부터 표준시비량이 적용되는 질산태 질소의 하한기준은 $50mg\;kg^{-1}$ 미만으로 추정되었고, 질산태질소 함량과 비료효과 및 시비효율과의 회귀관계로부터 평가된 무비 재배를 위한 질산태 질소 함량은 $200mg\;kg^{-1}$ 이상으로 추정되었다. 따라서 시설재배지 토양중 질산태 질소 함량 $50mg\;kg^{-1}$에서 $200mg\;kg^{-1}$ 범위는 질소 표준시비량에 대한 비율로서 추천식은 $Y=-0.6667{\chi}+133.33$ 이었다 (Y:질소 표준시비량에 대한 %, ${\chi}$: 시험전 토양의 $NO_3-Nmg\;kg^{-1}$).

• 한국작물학회지
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• 제41권3호
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• pp.354-361
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• 1996

신속하고 정확한 근적외선 분광분석법으로 품질분석의 효율성을 증대하기 위하여 화학성분의 변이분포가 검량식 작성과정에 미치는 영향과 측정 정확성에 미치는 관계를 구명하여, 근적외선 분광광도계의 이용 효율성 제고를 위한 기초자료를 얻고자 실시한 실험의 결과는 다음과 같다. 1. 보리 전분에 대한추정치 표준오차는 변이폭이 증대될수록 증가하는 경향을 보였으며, 상관계수도 변이폭이 증대될수록 0.872에서 0.883으로 다소 높아지는 경향을 나타내었다. 2. $eta$-glucan과 단백질은 변이폭이 증대될수록 추정치 표준오차는 낮아지고 상관계수는 높아지는 결과를 보여, 근적외선 분광분석법의 이용성 향상을 위하여서는 이들 성분의 함량변이 확대가 필요할 것으로 생각되었다. 3. 회분은 첫번째와 두번째 group에서는 유의성이 인정되지 않았으나, 세번째 group에서는 상관계수가 0.743으로 유의성이 인정되어 회분함량의 경우에는 어느 정도의 변이폭이 있어야만 근적외선 분광분석법이 가능할 것으로 생각되었다. 4. 겉보리 성분 중 전분과 회분은 재검토가 이루어져야 할 것으로 생각되었으며, $\beta$-glucan과 단백질은 근적외선 분광분석법의 적용이 가능하여 분석의 효율성이 증대될 것으로 생각되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1175-1182
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• 2005

Using KUCCS, which enables real-time monitoring and controlling, the various boundary condition and in-situ field stress condition was simulated, to derive the correlation among ${{\sigma}_v}'-Dr-N$in domestic sandy soils. Soil specimens, having various relative density and confined stress, were formulated to evaluate N-value from the SPT. and Pile Driving Analyzer, PDA, was employed as a measuring device for the energy transfer efficiency in the rod. From the quantitative analysis of N-value, the correlating equation, $N_{60}/{D_r}^2=16.35+14.45{{\sigma}_v}'$ was obtained on the basis of Skempton's method(1986). More reliable soil parameters can be obtained from the N-value by using this study which considered regional characters and the correlation among ${{\sigma}_v}'-Dr-N$.

• Journal of Astronomy and Space Sciences
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• 제36권2호
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• pp.97-103
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• 2019

An automated signal-acquisition method for the NASA's space geodesy satellite laser ranging (SGSLR) system is described as a selection of two system parameters with specified probabilities. These parameters are the correlation parameter: the minimum received pulse number for a signal-acquisition and the frame time: the minimum time for the correlation parameter. The probabilities specified are the signal-detection and false-acquisition probabilities to distinguish signals from background noise. The steps of parameter selection are finding the minimum set of values by fitting a curve and performing a graph-domain approximation. However, this selection method is inefficient, not only because of repetition of the entire process if any performance values change, such as the signal and noise count rate, but also because this method is dependent upon system specifications and environmental conditions. Moreover, computation is complicated and graph-domain approximation can introduce inaccuracy. In this study, a new method is proposed to select the parameters via a conditional equation derived from characteristics of the signal-detection and false-acquisition probabilities. The results show that this method yields better efficiency and robustness against changing performance values with simplicity and accuracy and can be easily applied to other satellite laser ranging (SLR) systems.

• 융합경영연구
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• 제3권4호
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• pp.13-20
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• 2015

This study examined the relationship between working capital management and performance of listed companies Stock Exchange in Tehran. A total of 40 companies from the cement industry for the period 2007 to 2010 of which only 25 were selected for this study had the condition. In order to achieve the objectives, this study surveys the exploration of correlation regression analysis and used the curve obtained, the regression equation. To test the hypothesis, quantitative analysis was used as a method. The results showed a negative relationship between the variables of working capital management and the company's performance and the only variable cash conversion cycle did not show a significant relationship. There is often a negative correlation between the variables studied. This study is based on five assumptions impact of working capital management on corporate profitability is examined. Therefore, the results suggest that the variables in working capital (average collection of receivables, average inventory turnover period, the average net debt and average transaction cycle) and net operating profit is significant negative correlation Net cash conversion cycle and only illustrates the relationship is not significant. Thus, it showed that in debt collection and debt payment period, the turnover of inventory and net trade cycle to reduce the profitability of companies will increase.