• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.366-375
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• 2006

In this paper, it is intended to introduce a method to solve multi-objective optimization problems and to evaluate its performance. In order to verify the performance of this method it is applied for a vertical roller mill for Portland cement. A design process is defined with the compromise decision support problem concept and a design process consists of two steps: the design of experiments and mathematical programming. In this process, a designer decides an object that the objective function is going to pursuit and a non-linear optimization is performed composing objective constraints with practical constraints. In this method, response surfaces are used to model objectives (stress, deflection and weight) and the optimization is performed for each of the objectives while handling the remaining ones as constraints. The response surfaces are constructed using orthogonal polynomials, and orthogonal array as design of experiment, with analysis of variance for variable selection. In addition, it establishes the relative influence of the design variables in the objectives variability. The constrained optimization problems are solved using sequential quadratic programming. From the results, it is found that the method in this paper is a very effective and powerful for the multi-objective optimization of various practical design problems. It provides, moreover, a reference of design to judge the amount of excess or shortage from the final object.

• Smart Structures and Systems
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• 제21권2호
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• pp.249-255
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• 2018

Many studies in risk management have been focused on management process, contract relation, and risk analysis in the past decade, but very few studies have addressed project risks from the perspective of risk efficiency. This study started with using Fault Tree Analysis to develop a framework for the decision-making support system of risk management from the perspective of risk efficiency, in order for the support system to find risk strategies of optimal combination for the project manager by the trade-off between project risk and cost of project strategies. Comprehensive and realistic risk strategies must strive for optimal decisions that minimize project risks and risk strategies cost while addressing important data such as risk causes, risk probability, risk impact and risk strategies cost. The risk management in the construction phase of building projects in Taiwan upon important data has been analyzed, that provided the data for support system to include 247 risk causes. Then, 17 risk causes were extracted to demonstrates the decision-making support system of risk management from the perspective of risk efficiency in building project of Taiwan which could reach better combination type of risk strategies for the project manager by the trade-off between risk cost and project risk.

• 전기학회논문지
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• 제67권2호
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• pp.255-260
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• 2018

This study is focusing on the trade-offs between the passband ripples and transition bands of the Chebyshev BPF, which is converted by using the Chebyshev LPF that is well known as a proto-type analog filter. It is also focusing on the trade-offs between the passband ripples and transition bands of the cascading Chebyshev BPF, as well as, the trade-offs between the two BPFs. The study finds the frequency responses of the proto-type analog LPF, the Chebyshev BPF and the cascading Chebyshev BPF. The study shows the results as comparative analysis tables. The study designs the 10th Chebyshev BPF in order to analyze it easily. The simulation results show that the Chebyshev BPF decreases about 55% of the transition band for the -2.5[dB] passband ripple comparing to the -0.5[dB] passband ripple. This study shows the effectiveness and economic feasibility in the restricted frequency communication environment for the decrease of the transition band as providing the passband ripple margin.

• 한국항공운항학회지
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• 제22권2호
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• pp.27-33
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• 2014

There are several methods to improve the flight efficiency of HALE(High Altitude Long Endurance) UAV(Unmaned Aerial Vehicle). Airframe structural point of view, weight reduction of the airframe structure is the most important method to improve the flight efficiency. In order to reduce the weight of airframe structures, new concepts which are different from traditional airframe structure design such as the mylar wing skin should be introduced. The spar is the most important component in a mylar skin wing structure, so the spar weight reduction is the key point for reduction of the wing structural weight. In this study, design trade-off study for the front spar of the HALE UAV wing is conducted in order to reduce the weight. Design and analysis procedure of high aspect ratio wing spar are introduced. Several front spar structures are designed and trade-off study regarding the weight and strength for the each spar are performed. Spar design configurations are verified by the static strength test. Finally, optimal front spar design is decided and applied to the HALE UAV wing design.

• 에너지공학
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• 제6권2호
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• pp.129-136
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• 1997

본 연구는 전력계통의 화력발전소로부터 배출되는 NOx및 SO$_2$같은 대기환경오염물질을 고려한 새로운 경제부하배분법을 제시한다. 제안된 방법은 총배출량 제약, 지역별 배출랑 제약 그리고 이들의 동시제약을 만족하면서 화력발전기의 출력을 계획하는 것에 대해 설명되어진다. 또한, 모든 부하배분의 대체안이며 배출량과 총연료비 사이의 상호상충관계를 나타내는 Trade-Off곡선에 의해 배출량과 총연료비 사이의 감도해석이 이 알고리즘에 적용된다. 한편, 이 제안된 방법은 개별적 환경피해(NOx, SO$_2$등)의 상대적 가중치와 총환경비용의 함수로써 경제부하배분이 이것에 의해 어떻게 변화되는지를 해석한다. 본 연구에서 제안된 방법을 시험계통에 적용하여 그 유용성을 검증하였다.

• The Journal of Asian Finance, Economics and Business
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• 제8권4호
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• pp.263-276
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• 2021

This study examines the effect of international capital flows on corporate capital structures in Vietnam by analyzing panel data from all non-financial listed firms from 2005 to 2014 using pooled ordinary least square (OLS) with a variance estimator. The analysis includes a comparison of the signs and significance of the variable coefficients from the perking order and static trade-off theories to the empirical results to determine the optimum approach to the corporate capital structure given Vietnam's high-inflation environment. The results indicate that international capital flows have a positive relation to the debt ratio in the long term, and the relationship is more robust for 2005-2009 than for 2010-2014. Corporate capital structures adjusted to changes in the business environment in different sub-periods (2005-2009 and 2010-2014). When the economic environment became more favorable, the pecking order theory's predictive power increased, and that of trade-off theory lessened. Manufacturing and non-manufacturing firms required different capital structure decisions to fuel their operations and grow under foreign competition. The analysis demonstrates that firms should intensify their use of long-term debt relative to the availability of capital, which is an implication not only for firms in particular but also for industrial innovation overall.

• Journal of Positioning, Navigation, and Timing
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• 제9권4호
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• pp.293-304
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• 2020

In this paper, various modulation techniques, including the legacy Global Navigation Satellite System (GNSS) signal modulation techniques, are introduced and the spectral characteristics and correlation characteristics of signals with various modulation techniques are analyzed based on numerical simulation. With the development of various GNSS services, the limited frequency band has become increasingly saturated, and issues of interoperability and compatibility have emerged in the new GNSS design. Since the efficient allocation of frequency resources is closely related to spectrum design, modulation techniques are one of the important signal design parameters of new signal design. Signal modulation techniques are closely related to various figure of merits (FoMs) as well as spectrum characteristic, and in some cases there is a complicated trade-off between FoMs. Thus, the FoMs associated with modulation technology should be analyzed and the best signal candidates should be chosen carefully via the trade-off analysis for FoMs. In this paper, we define the modulation technique based on Phase Shift Keying (PSK), Binary Offset Carrier (BOC) and Continuous Phase Modulation (CPM) for the design of KPS signals, and the FoMs of signals in terms of spectrum and correlation function are evaluated. Signals with various modulation techniques are implemented through a numerical simulation, and the relevant FoMs are analyzed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
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• pp.299-306
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• 1998

Design sensitivity analysis of a mechanical system is an essential tool for design optimization and trade-off studies. This paper presents an efficient algorithm for the design sensitivity analysis of railway vehicle systems, using the direct differentiation method. The cartesian coordinate is employed as the generalized coordinate. The governing equations of the design sensitivity analysis are formulated as the differential equations. Design sensitivity analysis of railway vehicle systems is performed to show the validity and efficiency of the proposed method.

• 대한기계학회논문집A
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• 제39권12호
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• pp.1199-1206
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• 2015

본 연구는 경유와 바이오디젤(대두유) 혼합연료의 디젤엔진 배기특성을 조사하였고, 연료 혼합비는 BD(biodiesel)3, BD5, BD20, BD50 및 BD100이며, 분사압력 조건을 400 bar, 600 bar, 800 bar, 1000 bar 및 1200 bar로 변화시켰다. 그리고 연료 혼합비 및 분사압력에 따른 엔진배출물인 NOx와 Soot의 정량적인 분석을 위해 통계학에 기초한 피어슨 상관계수와 스피어만 상관계수를 이하였다. 본 연구의 결과로서 실험변수인 혼합비와 분사압력에 대한 NOx 및 Soot 발생량의 피어슨 상관계수는 -0.811이며, 스피어만 상관계수는 -0.884로 NOx와 Soot 발생량 관계가 선형적이며, 이것은 trade-off관계를 나타낸다. 또한 각각의 분사압력 조건에서 피어슨 상관계수가 음의 상관 관계를 나타내며 이것은 NOx와 Soot 배출관계가 반비례적인 것을 나타낸다.

• East Asian Economic Review
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• 제22권2호
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• pp.177-215
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• 2018

Trump's withdrawal from the Trans-Pacific Partnership (TPP) and his "America First" trade agenda ignite a second round of interest in mega-free trade agreements in the Asia-Pacific. Countries are evaluating alternative trade policy actions in a post-TPP era. Using national real GDP gains estimated by a modified GTAP model to construct "preference ordering" for 10 Association of Southeast Asian Nations members and their six regional dialogue partners, this paper comes up with several policy-oriented findings. First, when multilateral agreements are not possible, countries are better off with a regional trading agreement than without one. Second, the Regional Comprehensive Economic Partnership is likely to have higher beneficial impacts than the Comprehensive and Progressive Agreement for Trans-Pacific Partnership. Third, for dual-track countries, implementing both agreements is better than each separately. Fourth, impacts of open regionalism are likely to be higher than those of a closed and reciprocal one. Going forward, this paper argues that countries should adopt a "multi-track, multi-stage" approach to trade policy.