• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.824-831
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• 2013

Lightning electromagnetic fields are important issues for the evaluation of lightning induced overvoltage on power lines and for setting the appropriate protection level for power networks. Such electromagnetic fields are strongly dependent on lightning return stroke currents at different heights along the lightning channel. On the other hand, the ground reflection factor due to the difference between the return stroke channel impedance and the equivalent ground impedance at channel base can have an effect on the shape of the return stroke currents by entering additional reflected currents into the channel. In this paper, the effect of the ground reflection factor on the return stroke currents at different heights along a channel and the electromagnetic fields associated with the lightning channel at close distances are considered. Moreover, the behavior of the electromagnetic fields versus the reflection factor changes and the radial distance changes are considered and the results are discussed accordingly. The results illustrate that the reflection factor has a direct relationship with the values of the electromagnetic fields while this is usually ignored in earlier studies.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.565-570
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• 2001

Base shear and roof drift relation was acquired from experiment of 3 story ordinary moment resisting frame which was designed using gravity loads. To evaluate the dynamic behavior of the frame, analytical model was generated from experimental result. Dynamic analysis was performed using the analytical model subjected to earthquake ground motions with 500, 1000, and 2400 years of return period. And capacity spectrum method was adopted to find the performance points of the frame. Both dynamic analysis and CSM showed that the performance of the frame meet the life safety objectives suggested by FEMA 273 and ATC 40.

• 한국산학기술학회논문지
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• 제20권12호
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• pp.125-130
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• 2019

가스스프링은 그 사용 목적에 따라 다양한 설계가 가능하여 많은 분야에서 사용되고 있고 그 사용량도 계속하여 증가하고 있다. 본 연구에서는 가스스프링을 압축할 경우 반발력을 감소시키고 피스톤이 복귀할 때 저속으로 복귀할 수 있도록 설계된, 오리피스 홀을 갖는 피스톤의 가스스프링 실린더 내부에서의 거동을 전산유체해석을 이용하여 예측해 보았다. 해석결과 가스스프링 내의 초기 가스압을 일정 수준 이상으로 증가시키면 피스톤의 복귀속도가 시간에 따라 감소하지 않고 일정하게 유지됨을 알 수 있었다. 오리피스 홀 사이즈가 피스톤 복귀속도에 미치는 영향을 해석을 통해 알아보았다. 오리피스 홀 사이즈를 줄이게 되면 피스톤 양단의 압력 차가 증가하여 피스톤 전진속도가 감소하게 되고 보다 등속으로 운동하게 됨을 알 수 있었다. 마지막으로 피스톤의 속도가 일정하다는 가정에서 초기 가스압에 따른 피스톤의 복귀속도를 이론적인 방법으로 도출하였고, 여러 초기 가스압에 대한 해석 결과와 비교하였다. 비교결과 이론적으로 도출한 해와 해석결과로부터 얻어진 결과 값이 거의 일치함을 알 수 있었다.

• 아태비즈니스연구
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• 제13권1호
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• pp.167-183
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• 2022

Purpose - The purpose of this study is to show the need to use the past long-term returns for investment decisions in U.S. equity funds and to suggest an investment strategy using long-term returns. Design/methodology/approach - This study solves the problem of high return volatility in long-term returns and proposes new investment portfolios based on the behavior of fund investors according to past returns. For the investment portfolio of this study, 60 months are divided into several periods and the average of the performance ranks for each period is used. Findings - First, funds with high average returns over multiple periods have lower future outflows and higher future returns than funds with high 60-month cumulative returns. Second, funds with low average returns over multiple periods have lower future inflows and lower future returns than funds with low 60-month cumulative returns. The findings mean that when making decisions based on past long-term returns, it is a smarter investment choice to buy funds with high average returns over multiple periods and sell funds with low average returns over multiple periods. Research implications or Originality - This study shows that it is necessary to use long-term returns in fund investment by analyzing the characteristics of the portfolio based on past returns. In addition, the study is meaningful in that it suggests a way to use long-term returns more efficiently based on the behavior of fund investors and shows that such investments lead to higher returns in the future.

• 한국지역지리학회지
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• 제12권6호
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• pp.748-756
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• 2006

본연구는 생산과 수요 양면을 고려한 농업입지모델에서 농작물 시장가격의 단기 및 장기적 변화를 고찰한다. 농작물 가격과 생산량의 단기적 변화 상황은 생산량의 연간 변화량에 의해서 결정되는 것으로 파악하면서 수리적 모형을 제시한다. 장기적 모형에서 농작물의 가격은 여러 가지 농업을 둘러싼 환경 및 변수(수요, 생산량, 생산비용, 운송률)의 변화를 고려하였다. 또한 예상 수익 모델(expected return model)과 보장 수익 모델(guaranteed return model)을 각각 제시하면서, 농작물의 생산량과 가격의 장기적 변화를 조사한다. 농작물 가격 하락은 지대 및 토지 가격의 하락과 관련된다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2010년도 학술발표회
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• pp.571-575
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• 2010

Drought is a natural hazard with different properties that are usually dependent to each other. Therefore, a multivariate model is often used for drought frequency analysis. The Copula based bivariate drought severity and duration frequency analysis is applied in the current study in order to show the effect of tail behavior of drought severity and duration on the selection of a copula function for drought bivariate frequency analysis. Four copula functions, namely Clayton, Gumbel, Frank and Gaussian, were fitted to drought data of four stations in Iran and Canada in different climate regions. The drought data are calculated based on standardized precipitation index time series. The performance of different copula functions is evaluated by estimating drought bivariate return periods in two cases, [$D{\geq}d$ and $S{\geq}s$] and [$D{\geq}d$ or $S{\geq}s$]. The bivariate return period analysis indicates the behavior of the tail of the copula functions on the selection of the best bivariate model for drought analysis.

• 소성∙가공
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• 제28권2호
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• pp.98-104
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• 2019

The present study numerically simulates the deformation heterogeneity developed in AA1100 during multi-axial diagonal forging (MADF) using finite element analysis (FEA). Diagonal forging type consisting of diagonal forging (DF) and return-diagonal forging (R-DF) proved to be relatively beneficial compared to plane forging type which includes plane forging (PF) and return-plane forging (R-PF) for minimizing the non-uniformity of deformation developed in workpieces. Simulation of the effective strain generated in workpieces during the two types of forging was done using 3-D FEA. FEA shows the effect of friction coefficient on the deformation behavior on workpieces. The simulation of 2 types forging with different friction coefficients revealed that the magnitude of barreling effect and strain heterogeneity in workpieces increases with an increase in the friction coefficient.

• The Journal of Asian Finance, Economics and Business
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• 제3권3호
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• pp.79-91
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• 2016

This paper is the first of its kind using a non-linear approach based on cross-correlation function (CCF) to investigate the information arrival hypothesis in crude palm oil (CPO) futures market. Based on daily data from 1986 to 2010, our empirical results reveal that: First, the volume of volatility is not a proxy of information flow. Second, dependence causality running from current return to future volume in conditional variance exhibit an asymmetric pattern of time span with different signs of correlation between price and volume series. This finding indicates the presence of noise traders' hypothesis of price-volume interaction in CPO futures market. Both findings suggest that this futures market is weak-form inefficiency. In terms of investors' behavior, they tend to change their expectations on current return based on errors made in previous trade in generating abnormal volume in the subsequent period. As implied, it is advisable for the investors devise their future trading strategies according to time span and changes of return.

• 한국의류학회지
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• 제25권6호
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• pp.1143-1154
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• 2001

This research aimed to examine consumer's expectancy disconformation related to purchase satisfaction/dissatisfaction and post-purchase behavior in cable TV home shopping. A total of 700 questionnaires were randomly sent to cable TV home shoppers and 172 copies were used in final analysis. Frequency analysis. correlation analysis, analysis of variance, regression analysis, path analysis, and multinominal logit were used. The expectancy discoformation on \"fitting\" and \"how well the clothes suits oneself\" were significantly related to the complaint behavior of return and refund. TV home shoppers tended to express their complaints by requesting the home shopping company or the manufacture company for a compensation rather than express privately such as warning friends, stop buying and boycotting the item. The significant variables that would influence consumers to seek refund rather than exchange were purchase satisfaction, request of compensation to the company, overall expectancy disconformation and expectancy disconformation on decoration and details and suiting oneself.

• Natural Product Sciences
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• 제5권3호
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• pp.138-141
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• 1999

The effects of Eurycoma longifolia Jack were studied in maintaining mating behavior of sexually experienced castrated male rats after dosing them with 500 mg/kg daily of E. longifolia Jack for 10 days prior to test and later continued for two weeks where the rats were then castrated. The similar dosage was then continued for 12 weeks post-castration. However, $400\;{\mu}g/day$ of testosterone was administered subcutaneously on the day of castration and lasted for 6 weeks post-castration but later raised to $800\;{\mu}g/day$ until 12 week post-castration. Tests were conducted weekly from 2-6 weeks and 8-12 weeks post-castration. Results showed that all the experimental male rats exhibited mating behavior before castration. Further results also indicated that E. longifolia Jack successfully maintained mating behavior but less than precastration level from 2-6 weeks and later increased from 8-12 weeks post-castration. Similarly, $400\;{\mu}g/day$ of testosterone was effective in maintaining mating behavior from 2-6 weeks post-castration. However, $800\;{\mu}g/day$ of testosterone managed to return the male rats to the precastration level with all male rats exhibited mating behavior from 8-12 weeks post-castration. Further results also indicated that testosterone significantly increased the penis weights (p < 0.05) as compared to the E. longifolia Jack. In conclusion, this study shows that E. longifolia Jack continued to maintain mating behavior of sexually experienced castrated male rats, giving further evidence of the folkuse of this plant as aphrodisiac.