• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.53-63
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• 2017

The increasing of wind power penetration level presents challenges in classical optimal reactive power dispatch (ORPD) which is usually formulated as a deterministic optimization problem. This paper proposes a two-stage stochastic programming model for ORPD by considering the uncertainties of wind speed and load in a specified time interval. To avoid the excessive operation, the schedule of compensators will be determined in the first-stage while accounting for the costs of adjusting the compensators (CACs). Under uncertainty effects, on-load tap changer (OLTC) and generator in the second-stage will compensate the mismatch caused by the first-stage decision. The objective of the proposed model is to minimize the sum of CACs and the expected energy loss. The stochastic behavior is formulated by three-point estimate method (TPEM) to convert the stochastic programming into equivalent deterministic problem. A hybrid Genetic Algorithm-Interior Point Method is utilized to solve this large-scale mixed-integer nonlinear stochastic problem. Two case studies on IEEE 14-bus and IEEE 118-bus system are provided to illustrate the effectiveness of the proposed method.

• 한국산학기술학회논문지
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• 제19권9호
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• pp.100-107
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• 2018

본 연구는 기업의 국제다각화가 하방경직적인 원가행태에 미치는 영향을 실증적으로 분석하였다. 기업의 활동수준을 나타내는 척도로서 매출액이 증가할 때의 원가증가율보다 매출액이 감소할 때의 원가감소율이 낮게 나타나는 원가행태를 하방경직적인 원가행태라고 부른다. 이러한 원가행태는 경영자의 조정비용을 고려한 의사결정으로 인해 발생하는데 국제다각화 기업의 경우, 발생액 상쇄가설에 따라 경영자의 조정비용에 대한 재량적 의사결정 판단개입이 줄어들 것이라고 판단하였다. 실증분석 결과, 국제다각화 기업이 그렇지 않은 기업보다 원가의 하방경직성이 완화되었음이 관찰되었다. 본 연구는 기업의 국제다각화가 경영자의 원가에 관련된 의사결정에 유의한 영향을 줄 수 있는 가를 검증함으로서 자본시장과 학계에 공헌할 것으로 기대된다.

• Journal of Preventive Medicine and Public Health
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• 제37권2호
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• pp.141-149
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• 2004

Objectives : To evaluate the cost and proportion of complementary and alternative medicines (CAM) in the total healthcare costs among the elderly in the last 6 months of life. Methods : The care-giving families of 301 persons older than 65 years, who died between July 1st and December 31st of 2001, and were also registered in Self-Employed Health Insurance Programs in Seoul, were interviewed. Results : The cost of CAM was 1.09 million Won, which as a proportion of the total healthcare cost was 38.1%. The elderly aged between 65 and 69 year-old, male, living with their spouse, Buddhist and having cancers had higher CAM costs in an ANOVA and simple regression analysis. After controlling of various factors, age was the only significant factor associated with the cost of CAM. The elderly above 80 years old, female, bereaved and Buddhist had higher proportional CAM costs, and the elderly having cancers or cardiovascular diseases had lower proportional CAM costs in an ANOVA and simple regression analysis. After adjusting for various factors, the elderly above 85 years old, female and Buddhist had higher proportional CAM costs, and the elderly having cancers had lower proportional CAM costs. Conclusion : The very old and Buddhist, and/or the ill with no clear diagnosis, may depend more on CAM. Further research will be needed on the meaning and impact of CAM and their costs to public health and the total healthcare system.

• 한국전산응용수학회:학술대회논문집
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• 한국전산응용수학회 2003년도 KSCAM 학술발표회 프로그램 및 초록집
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• pp.10-10
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• 2003

Option pricing theory developed by Black and Sholes depends on an arbitrage opportunity argument. An investor can exactly replicate the returns to any option on that stock by continuously adjusting a portfolio consisting of a stock and a riskless bond. The value of the option equal the value of the replicating portfolio. However, transactions costs invalidate the Black-Sholes arbitrage argument for option pricing, since continuous revision implies infinite trading, Discrete revision using Black-Sholes deltas generates errors which are correlated with the market, and do not approach zero with more frequent revision when transactions costs are included. Stochastic calculus serves as a fundamental tool in the mathematical finance. We closely look at the utility maximization theory which is one of the main option valuation methods. We also see that how the stochastic optimal control problems and their solution methods are applied to the theory.

• 산업공학
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• 제8권2호
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• pp.151-159
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• 1995

Two-dimensional cutting stock problem is to find a waste-minimizing method of cutting a single rectangular plane into a number of smaller pieces of known dimensions. In practice, besides wastes, setup cost taken during adjusting is of an important concern. We suggest 2-phased guillotine cutting method as a solution to the problem which minimize wastes and setup costs. Also, in order to reduce the computing time we apply techniques of discretization, cutoff, median. Experimental results show good performance of our algorithm.

• Journal of Korea Trade
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• 제26권5호
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• pp.23-38
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• 2022

Purpose - This research intends to find out whether R&D cost stickiness shows differentiated aspects depending on exports in Korea. A cost behavior that indicates a lower rate of costs decrease when sales decrease than the rate of costs increase when sales increase is called cost stickiness. This sticky cost behavior is caused by considering the adjusting costs. This study aims to empirically verify that R&D cost stickiness is greater in export firms than in non-export firms. We also investigate the effect of exports on R&D cost stickiness is nonlinear. Design/methodology - We obtain data for the analysis from Kis-Value and TS2000 from 2012 to 2020. This study tests for R&D cost stickiness of exports using the cost stickiness model developed by Anderson et al. (2003) that is used in a lot of prior literature. To explore the nonlinear behavior of R&D cost stickiness we include a quadratic term of exports in our model. Findings - The results of our analysis are as follows. First, we observed that R&D costs of export firms are more sticky than that of non-export firms. Our result indicated that export firms are less likely to reduce R&D costs in decreasing sales periods in preparation for future sales recovery. Second, our empirical evidence shows that export firms view R&D costs much favorably. However, we hypothesize that the effect of export intensity on R&D costs may not necessarily be linear. Our result shows the effect of exports intensity on R&D stickiness is thus nonlinear, forming a reverse U-shaped curve. When export intensity exceeds a certain threshold, the growth rate of R&D costs appears to be viewed negatively. Firms with relatively high export intensity do not support R&D costs, viewing them as taking away firms' resources from other more productive costs. On the contrary, those with export intensity under the threshold view R&D costs as beneficial and therefore promote further R&D costs when revenue decreases. Originality/value - The results of this research can contribute academically to the expansion of empirical research on R&D cost stickiness. R&D cost stickiness varies by industry. As a result of our research, the managers of export firms recognize the importance of R&D to lead innovation. We expected that this research contributes to further studies on R&D costs and cost stickiness. Second, this research has implications from a business perspectives. Our findings of export firms' R&D stickiness suggest that export firms' managers should consider keeping the stickiness of R&D when revenue decreases because it is essential for exporting firms to maintain their R&D stickiness to secure long-term competitiveness. R&D stickiness can be used on a practical basis to emphasize the need for continuous investment in exporting firms' R&D activities.

• 한국산업보건학회지
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• 제31권4호
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• pp.353-366
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• 2021

Objectives: An appropriate level of cost support is being proposed to maximize the participation rate. In addition, as the amount of support is highly concentrated at the level of the limit under the current level of supports, the level of cost support is low when the actual level of cost of measuring the working environment exceeds the limit. This paper describes the adjustment of an appropriate cost support rate. Methods: First, this paper analyzes the current cost support status using data from the KOSHA. Second, an alternative for adjusting the cost support rate is presented in consideration of the incentive aspect. Third, we present simulation results for the average cost support rate, the impact of each alternative on finance, and more. Fourth, the most desirable adjustment method is presented after comparing and analyzing the results of various alternatives. Results: In this paper, we present a new scale model. This model is a mixture of flat-rate, fixed rate, and subside cap. It is expected that the new model will not only facilitate participation in businesses with low measurement costs, but also have the effect of controlling measurement costs for institutions that incur greater costs. It is also expected that setting a cap will have the effect of considering government finances and inducing excessively costly institutions to reduce costs. Thus, the new model is likely to be superior to others. If the fourth plan is applied to new businesses and the fifth plan is applied to sustainable businesses, the average cost support rates will be 87.68 percent and 65.18 percent, respectively, and the needed finances will be 2.5 billion won, 18.8 billion won, and 21.3 billion won in total. Conclusions: It seems most desirable to introduce a new model that combines flat-rate, fixed-rate, and subsidy cap systems and achieve an appropriate cost support rate through this model.

• Nutrition Research and Practice
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• 제17권5호
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• pp.984-996
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• 2023

BACKGROUND/OBJECTIVES: Prior studies, mostly conducted in Western countries, have suggested that the low cost of energy-dense foods is associated with an increased risk of obesity. This study aimed to investigate the association between food costs and obesity risk among Koreans who may have different food cost and dietary patterns than those of Western populations. SUBJECTS/METHODS: We used baseline data from a cohort of 45,193 men and 83,172 women aged 40-79 years (in 2006-2013). Dietary intake information was collected using a validated food frequency questionnaire. Prudent and Western dietary patterns extracted via principal component analysis. Food cost was calculated based on Korean government data and market prices. Logistic regression analyses were performed to investigate the association of daily total, prudent, and Western food cost per calorie with obesity. RESULTS: Men in the highest total food cost quintile had 15% higher odds of obesity, after adjusting for demographic characteristics and lifestyle factors (adjusted odds ratio, 1.15; 95% confidence interval, 1.08-1.22; P-trend < 0.001); however, this association was not clear in women (P-trend = 0.765). While both men and women showed positive associations between prudent food cost and obesity (P-trends < 0.001), the association between Western food cost and obesity was only significant in men (P-trend < 0.001). CONCLUSIONS: In countries in which consumption of Western foods is associated with higher food costs, higher food costs are associated with an increased risk of obesity; however, this association differs between men and women.

• 한국IT서비스학회지
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• 제14권2호
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• pp.129-142
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• 2015

The purpose of this study is to suggest an effective regression testing method in order to minimize the scope of test resulting from the modification of software and to prevent mismatch of test case and test objects. As a way to improve the efficiency of regression testing which uses a change-centric testing technique, the method flow is analyzed and grasped through a static analysis based on source code in order to identify modified parts. After the order of priority is set according to the results of user action log-based dynamic analysis on identified regression testing objects, test effect can be raised by adjusting the order of priority using code complexity. Quality assurance coverage can be checked using the user action log suggested in this study, and the progress of test and whether or not each function has been verified can be checked, too. In addition, by minimizing test parts and adjusting the order of test, costs and time can be saved, making it possible to conduct regression testing effectively.

• 대한전자공학회논문지TC
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• 제48권6호
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• pp.22-27
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• 2011

본 논문은 직접 대역 확산(Direct sequence spread spectrum : DS-SS) 시스템에서 적응형 임계값을 적용하여 초기 동기 성능을 향상 시키는 알고리즘을 제안한다. 제안된 알고리즘은 탐색 모드(search mode) 이전에 프리덤프 모드(pre-dump mode)를 추가하고, 상관 에너지를 이용해 탐색 모드와 확인 모드(verification mode)의 임계값을 결정한다. 이를 통해 확인 모드뿐만 아니라 탐색 모드에서까지 거부 성능(rejection performance)을 향상시킬 수 있다. 제안된 방법은 기존 기술과 비교할 때 하드웨어 증가 없이 평균 코드 획득 시간(mean code acquisition time)을 약 40% 단축시킬 수 있다.