Multi-Objective Optimization of Powertrain Components for Electric Vehicles Using a Two-Stage Analysis Model

권기한,서민식,민승재 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.6

An electric vehicle (EV) powertrain is comprised of a motor and reduction gear. Thus, it must be designed by considering both components to improve its dynamic and economic performances. To obtain the optimal design of powertrain components for an EV, this study employs a two-stage analysis model focusing on the motor and vehicle at each stage for accuracy and efficiency. In the first stage, a motor system model analyzes the motor characteristics, such as the maximum and minimum torque and motor losses. Using the motor design parameters, these characteristics are converted to torque curves and an efficiency map. In the second stage, a vehicle system model analyzes the target performance using converted motor data for efficient analysis of the performance. An optimization problem is formulated to minimize the maximum motor power, acceleration time, and energy consumption with dynamic constraints, including the maximum vehicle speed and ascendable gradient. To reduce the excessive computational effort when conducting the multi-objective optimization, surrogate models with respect to performance are effectively constructed by using the adaptive sampling method. From the optimization results, a Pareto front having various solutions among the objective functions is obtained.

Determinant of Hedging and Its Impact on Firm Value : After Controlling Endogeneity Problem Using a Two-Stage Analysis

Sang Ik Seok,Tae Hyun Kim,Hoon Cho,Tae Joong Kim 한국유통과학회 2017 KODISA ICBE (International Conference on Business Vol.2017 No.-

A derivative market in Korea was used to be one of the biggest markets in the world, but it has dramatically decreased after 2011, and now, trading volume of Korea Exchange becomes 1/3 compared to that in 2011. Given that the unprecedented change in the derivative market in Korea, in this study, we suggest that it is caused by the inefficient use of derivatives by Korean firms which led to significant financial loss by analyzing the relation between hedging and firm value. To avoid endogeniety problem between these two variables, we use a two-stage analysis. At a first stage, we regress hedging on several control variables which are known to affect hedging theoretically or empirically, and we calculate the predicted value of hedging. Then we put this predicted value into a second stage model as an independent variable. The result of the first stage analysis also provides information about the determinant of hedging. The result of a second stage analysis shows that the use of derivatives itself significantly reduces firm value, but if a firm has decided to use derivative, then the extent of hedging increases its value. Thus, we conclude that a decision to use derivatives for hedging is, in fact, harmful for firm value in Korea because Korean firms may use them inefficiently. However, extensive users utilize derivative more efficiently than moderate users do.

Integrated hydrogen supply networks for waste biogas upgrading and hybrid carbon-hydrogen pinch analysis under hydrogen demand uncertainty

Hwangbo, Soonho,Nam, KiJeon,Han, Jeehoon,Lee, In-Beum,Yoo, ChangKyoo Elsevier 2018 Applied Thermal Engineering Vol.140 No.-

<P><B>Abstract</B></P> <P>This study aims to develop integrated hydrogen supply networks (IHSNs) by combining a natural gas hydrogen supply network and a sludge-biogas-biomethane-hydrogen supply network which is an environmentally benign hydrogen production system. Sludge from wastewater treatment plants is converted into biogas by anaerobic digestion, biomethane is generated using amine technology, which is one of the biogas upgrading technologies, and finally, hydrogen is produced by steam reforming. Multi-objective two-stage stochastic mixed integer linear programming is used to simultaneously optimize the total annual cost and the total environmental cost under hydrogen demand uncertainty. An ɛ-constraint method is employed to solve the multi-objective function, and Pareto analysis is performed to compare the results from the economic cost and the environmental cost. Then, hybrid carbon-hydrogen pinch analysis is suggested to investigate two distinct hydrogen supply networks in IHSNs, and is verified by the results and a sensitivity analysis based on supplementary wind power. Gyeongsang-do where is one of the five provinces in the Republic of Korea is applied for a case study to validate the proposed model and the results illustrate the feasibility of IHSNs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Integrated hydrogen supply networks (IHSNs) are developed. </LI> <LI> The environmental impact and demand uncertainty are considered. </LI> <LI> Multi-stage two-stage stochastic model is designed to solve the IHSNs model. </LI> <LI> Hybrid carbon-hydrogen pinch analysis is suggested to investigate the IHSNs model. </LI> <LI> A case study of Gyeongsang-do in Korea is applied for the IHSNs model. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

주요 작물의 생산성 결정요인 분석 - 한국 미작농가를 중심으로 Two-stage DEA 모형을 이용해서

소남호,최종산,고현석 한국농식품정책학회 2017 한국농식품정책학회 학술대회 논문집 Vol.2017 No.2

This study aims to measure the agricultural productivity of rice farmers and empirically analyze determinants on the productivity changes at the farm household level using Two-stage DEA model. In the first-stage, the productivity is calculated by Malmquist productivity index. In the second-stage, it is considered as the dependent variable in the two-way error component fixed effect panel model to define its determinants. The research results revealed: 1) The productivity shrinked over the analysis period, and it is attributed to retrogressive technical change. 2) In the panel analysis, the planted size is the only variable among the farm owner properties having a statistically significant effect and positively influencing on the productivity. It means that the larger the rice farming land, the higher the productivity. The improved productivity would lead to increase the rice revenues. Therefore, the policy and the effort making the arable land enlarged would be required to enhance productivity at the farm level.

경영과학적 관점에서 살펴본 호텔의 운영 효율성과 수익 효율성 분석

김현정 한국호텔리조트학회 2019 호텔리조트연구 Vol.18 No.4

This study classifies management efficiency into operational efficiency and profitability efficiency by using two-stage DEA (data envelopment analysis) for domestic hotels from first grade to fifth grade. For this purpose, a total of 25 hotels were selected, and the 2018 audit report and company profile data of the Financial Supervisory Service's DART (data analysis, retrieval and transfer system) were used. The results are as follows. Overall, domestic hotels are more urgent to improve profitability efficiency than operational efficiency. Specifically, this study compared how much utilization should be improved by hotel class in terms of operational efficiency. In terms of profitability efficiency, this study analyzed how much sales and net income should be improved by hotel class. This study expands the scope of previous studies by dividing management efficiency into operational efficiency and profitability efficiency of domestic hotels using two-stage DEA. In addition, this study suggests various management strategies for improving the efficiency of the hotel industry by analyzing all the hotels from first grade to fifth grade, not limited to the luxury hotels. Finally, the managers of each hotel can use the analysis results of this study to find out what to focus on between operational efficiency and profitability efficiency.

한국군 병력 규모에 관한 실증연구: 예비전력 규모를 중심으로

심형보 광운대학교 방위사업연구소 2023 선진국방연구 Vol.6 No.2

This study focuses on the size of reserve forces and the factors affecting their size. As a result of analyzing theory and prior research, we identified the relations between standing and reserve forces. To minimize the problem of relations, we used a two-stage least squares estimate with simultaneous equations as the analytical method used. We utilized the 2022 cross-sectional data points and analyzed the sample by dividing it into 69 countries and 38 countries with reserve forces. In 38 countries, the reserve force size derived from regression analysis was 2.2 million people, and the standing force size was 470,000 people. The empirical analysis shows that 2.2 million reserve forces solved the single-equation estimation problem caused by the two-way causal relationship between reserve force size and standing force size through simultaneous equations, which further improved the consistency of the estimated coefficients. In terms of size, it was smaller than the 2.75 million presented in Defense Reform 2.0, which seems to be due to the analysis of countries with relatively capital-intensive military structures compared with Korea. Various factors are expected to further increase the size of future reserve forces: the rapid decline in the nation’s birth population; the proportion of defense spending to the government’s budget; the reserve forces, which have been further expanded by Defense Reform 2.0; and the prospect of a reduction in standing forces expected by Defense Innovation 4.0. Therefore, the size of future appropriate reserve forces will increase further than the current appropriate level, making it necessary to determine policies related to reserve forces and develop appropriate measures for procurement.

An analysis of different types of advertising media and their influence on consumer preferences and purchase intentions for digital cameras

안중하,이창원,이종수,Michael Paik 한국마케팅과학회 2012 마케팅과학연구 Vol.22 No.4

This study analyzes consumer preferences for different types of advertising media: print media, the Internet, salespersons, and a new type of media1– an innovative information delivery device based on Microsoft’s multi-touch screen and a single-touch sensor bar. We chose three kinds of digital cameras for our study and analyzed how different types of advertising media influence purchase intention. We used mixed logit model and multinomial logit–OLS two-stage estimation method for this analysis. Our results show that the Internet had the highest influence on consumers’ purchase intentions. The new type of media had the second highest influence. This study reveals that advertisements which use new types of media can positively influence consumers. These findings can inspire companies to use new types of advertising media to develop their advertising strategy portfolios. This proposed model is applicable to other products and types of advertising media in order to analyze consumer preferences and purchase intentions.

Determinants of Hedging and their Impact on Firm Value and Risk: After Controlling for Endogeneity Using a Two-stage Analysis

Sang-Ik Seok,Tae-Hyun Kim,Hoon Cho,Tae-Joong Kim 한국무역학회 2020 Journal of Korea trade Vol.24 No.1

Purpose – In this study, we investigate determinants of hedging with derivatives and its effect on firm value and firm risk for Korean firms. Design/methodology – To avoid the endogeneity problem pointed out in previous studies, we use a two-stage analysis by using gains and losses from derivatives as instrument variable for hedging with derivatives. Findings – Our analysis on the determinants of hedging shows that firms that are more leveraged and less profitable, and with more growth opportunities are likely to hedge through derivatives. Additionally, large firms, firms less diversified into industry, and firms more diversified geographically are likely to use derivatives. Our two-stage analysis shows that indicators of hedging with derivatives have an insignificant effect on firm value, and the indicator of futures/forwards use and of swaps use have significant negative effect on firm value. Whereas, the extent of hedging with derivatives has positive effect on firm value for all types of foreign currency derivatives, which suggests that moderately low hedgers use derivatives inefficiently, but extensive hedgers use derivatives properly. With regard to firm risk, hedging with derivatives increases market-based risk, but decreases accounting-based risk. Thus, we conclude that Korean firms use derivatives to manage operational volatility rather than to manage market risk, and accounting-based risk reduction through hedging is not directly translated into higher firm value. Originality/value – This is not the first study to investigate hedging behavior of Korean firms, but the sample period that that this study analyzed is the longest and various method are used to control the endogeneity problem. We investigate not only total foreign currency derivatives but also by types of derivatives, including futures/forwards, options, and swaps.

Relationship of the Big Five Personality Traits and Risk Aversion with Investment Intention of Individual Investors

SARWAR, Danish,SARWAR, Bilal,RAZ, Muhammad Asif,KHAN, Hadi Hassan,MUHAMMAD, Noor,AZHAR, Usman,ZAMAN, Nadeem uz,KASI, Mumraiz Khan Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.12

This empirical research is aimed at testing the relationship of the big five personality traits namely openness to experience, extraversion, consciousness, agreeableness, neuroticism, and risk aversion with the investment intention of individual investors belonging to Balochistan, Pakistan. The primary data is collected through a self-administered questionnaire (a structured form that consists of a series of closed-ended and open-ended questions) from a sample of 397 active individual investors belonging to different districts of the province. The data is empirically analyzed by applying the Partial Least Square (PLS) path modeling technique by using the estimation package available in Smart-PLS. The findings of this study suggest that all the variables are statistically significant with investors' investment intention with risk aversion as the strongest predictor. Moreover, openness to experience, extraversion, consciousness, agreeableness, and risk are significantly and positively related to an investor's investment intention, whereas neuroticism is negatively related to an investor's investment intention. The results extended by this study can be used by financial planners and investment bankers to channelize the available financial resources in diversified portfolios. The results will help financial planners to make available diverse investment alternatives for investors in Balochistan, thus catering to their unique needs. Academia must offer courses on contemporary finance paradigm based on behavioral finance to enable future business graduates to make wise financial decisions.

KOSPI200 지수옵션 수익률의 결정요인

강병진 ( Byung Jin Kang ) 한국파생상품학회(구 한국선물학회) 2016 선물연구 Vol.24 No.1

본 연구는 요인모형(factor model)에 근거하여 KOSPI200 지수옵션 시장에서 위기 관련 요인(crisis related factor)들이 가격결정에 어떠한 영향을 미치는지를 분석하고, 이를 고려하였을 때 초과수익이 존재하는지의 여부를 실증분석 하였다. 주가 급락과 관련된 점프 요인, 변동성의 변화와 관련된 변동성 요인, 변동성의 폭등과 관련된 변동성점프 요인 등 총 3가지 위기 관련 요인을 고려하였으며, 요인모형의 적용을 용이하게 하기 위해 Constantinides, Jackwerth, and Savov(2013)가 제안한 “레버리지 조정 옵션 포트폴리오” 개념을 활용하였다. 이는 각 가격도(moneyness)별 옵션 포트폴리오의 이론적 베타(beta)가 1이 되도록 주기적으로 재조정(rebalancing)함으로써, 실증분석의 가장 큰 난관중 하나인 옵션 수익률의 비정규성(non-normality)을 완화할 수 있는 효과적인 방법이다. 2004년 1월부터 2015년 2월까지 KOSPI200 지수옵션시장을 분석한 결과, 우리는 다음과 같은 사실들을 발견하였다. 첫째, 본 연구에서 상정한 3가지 위기 요인들에 대한 위험프리미엄이 대부분 통계적으로 유의하게 관찰되며, 부호 또한 일반적인 예상과 일치한다. 둘째, 단일요인으로써 시장위험 요인만을 고려하였을 때에는 외가격 풋옵션 및 콜옵션이 고평가되는 경향이 강하게 관찰되지만, 위기 요인들을 추가로 고려하게 되면 이러한 이상현상(anomaly)이 사라지거나 대폭 완화된다. 셋째, 글로벌 금융위기 이전과 이후를 구분하여 살펴보면, 전술한 3가지 위기 요인들에 대한 위험 프리미엄은 금융위기 이전에는 통계적으로 유의하지 않은 반면 금융위기 이후에 본격적으로 나타나기 시작한다. 이에 특히 금융위기 이후에 관찰되는 외가격 콜옵션과 풋옵션의 고평가 경향은 전적으로 위기 요인에 대한 위험 프리미엄에서 기인하며, 이들을 고려하게 되면 옵션시장에서 초과수익의 가능성은 사라진다. 마지막으로 넷째, 위험 프리미엄을 옵션시장이 아닌 주식시장에서 추정하거나 장기(long-term) 및 내가격(in-the-money) 옵션과 같이 유동성이 부족한 옵션들의 영향을 고려하더라도, 위 실증결과에 본질적인 차이는 없음이 확인된다. This study examines the effects of crisis-related factors on the returns of KOSPI200 index options using a factor model, which was introduced by Constantinides, Jackwerth and Savov (2013). Three factors incorporating price jumps, changes in volatility, and volatility jumps are considered as the crisis-related factors. With the data for the period from 2004 to 2015, we find followings : First, most of the crisis-related factor premia are statistically significant, and their signs are consistent with those expected. Second, these crisis-related factors contribute to improve the understanding of the cross-sectional variation in KOSPI200 index option returns. Third, the crisis-related factor premia became much more significant after the global financial crisis in 2008. Finally, our empirical findings are robust to whether the long options and the in-the-money options are included in the sample or not, and to whether the factor premia are constrained to equal the corresponding premia estimated from the cross-section of equities.