• 한국항공우주학회지
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• 제41권12호
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• pp.940-949
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• 2013

본 논문에서는 삼각형 태양돛의 주름저감설계 방안에 대한 연구를 수행하였다. 태양돛 멤브레인에 부분적으로 발생하는 주름으로 인하여 구조물의 추력성능과 제어성능에 영향을 받을 수 있으므로 멤브레인에 발생하는 주름을 감소시키거나 제거하는 것은 매우 중요하다. 주름을 저감하는 방법으로 태양돛 멤브레인과 붐을 연결하는 케이블의 하중의 각도를 조정하는 방식, 현수선 방식 및 현수선-와이어 방식을 고려하였으며 매개변수 연구를 통하여 주름저감효과에 대해 체계적으로 조사하였다.

• 한국생산제조학회지
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• 제20권3호
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• pp.310-315
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• 2011

General portal machine represents a distinct weak spot concerning their structural behavior because of long protruding structure components, such as saddles and rams. The weak point causes the deformation of the machine tool and consequently rises a severe machining error. The purpose of this study is to improve the structural design of crossrail in order to minimize it's distortion. Tool Center Point (TCP) was chosen as a reference point for evaluating the distortion effect of a crossrail and topological optimization was adopted as a method of structural design improvement. The displacements of TCP according to the machining positions were investigated by structural analyses for both of original crossrail design and the improved one. The comparing results showed that the displacement of TCP could be reduced about 55% maximum.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.321-322
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• 2015

The aim of this paper is to propose a design method for the double-sided LCC compensation circuit for 6.6kW electric vehicle (EVs) wireless charger. The analysis and comparison with several compensation topologies such as SS, SP, PS, PP and the hybrid LCC compensation is presented. It has been found that the hybrid LCC compensation has superior performance in comparison with other topologies. The design procedure for the EV charger is presented and the PSIM simulation results are provided.

• 한국추진공학회지
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• 제13권1호
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• pp.51-57
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• 2009

이 연구 논문에서는 위상최적화 방법을 사용하여 강제대류를 이용한 열소산하는 구조물을 설계하는 방법을 개발한다. 전기 부품이나 기계구조물에서 발생하는 열을 낮추기 위해서 자연 대류와 강제 대류가 넓게 사용되고 있다. 또한 현재에는 화학전지(Fuel cell)나 로켓의 추진기관 등에서 발생한 열을 낮추기 위해서 강제 대류를 사용하고 있다. 현재에 이런 시스템을 효과적으로 열을 소산시키기 위해서 유동의 채널을 설계하는 것이 아주 중요한 이슈로 다루어지고 있다. 따라서 이 논문에서는 위상최적화 기법을 사용하여 최적의 채널을 설계하는 연구를 수행한다. 대류 현상을 고려하기 위해서 비압축성 N-S 방정식의 해석을 수행하였다. 이 논문에서는 열과 유체가 연계되어 있는 시스템을 수치적으로 연구하고 강제대류를 고려하는 최적의 채널 설계 결과를 제시한다.

• 한국전산구조공학회논문집
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• 제31권1호
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• pp.47-52
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• 2018

본 연구에서는 페이즈필드 설계법을 통한 다중 유전체로 구성된 콜리메이터 구조를 설계하였다. 제작 가능성을 고려하여 폴리프로필렌과 파라핀을 유전체 재질로 선정하였고, 측정영역의 전기장의 세기의 면적분으로 계산하여 이를 최대화하는 것으로 설계의 목적 함수를 설정하였다. 두 가지 유전체 재질을 이용하여 설계영역 내의 중공영역이 배제된 구조를 도출하였으며 컷오프를 통해 최종 형상을 모델링하였다. 수치해석을 통하여 설계된 다중 유전체 구조의 콜리메이터를 이용하는 경우 자유공간 내의 원형 전자기파 대비 측정영역에서 105%의 전기장 세기가 증가된 평행파를 생성하는 콜리메이터의 성능을 확인하였다. 설계된 모델의 수치해석을 통하여 콜리메이터의 역변환 가능성과 구조적 내구성의 증가를 확인하였고, X밴드 대역 전체에서의 성능을 평가하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.622-624
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• 2008

This investigation studies the effects of material properties and corresponding propagation wave types on optimal configurations of sound absorbing porous materials in maximizing the absorption performance by topology optimization. The acoustic behavior of porous materials is characterized by their material properties which determine motions of the frame and the air. When the frame has a motion, two types of compressional wave propagate in the porous material. Because each wave in the material make different influence on the absorption performance, it is important to understand the relative contribution of each wave to the sound absorption. The relative contribution of the propagating waves in a porous material is determined by the material properties, therefore, an optimal configuration of a porous material to maximize the absorption performance is apparently affected by the material properties. In fact, virtually different optimal configurations were obtained for absorption coefficient maximization when the topology optimization method developed by the authors was applied to porous materials having different material properties. In this investigation, some preliminary results to explain the findings are presented. Although several factors should be considered, the present investigation is focused on the effects of the material properties and corresponding propagation waves on the optimized configurations.

• Journal of Power Electronics
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• 제16권5호
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• pp.1629-1638
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• 2016

Differential power processing (DPP) systems are among the most effective architectures for photovoltaic (PV) power systems because they are highly efficient as a result of their distributed local maximum power point tracking ability, which allows the fractional processing of the total generated power. However, DPP systems require a high-efficiency, high step-up/down bidirectional converter with broad operating ranges and galvanic isolation. This study proposes a single, magnetic, high-efficiency, high step-up/down bidirectional DC-DC converter. The proposed converter is composed of a bidirectional flyback and a bidirectional isolated switched-capacitor cell, which are competitively cheap. The output terminals of the flyback converter and switched-capacitor cell are connected in series to obtain the voltage step-up. In the reverse power flow, the converter reciprocally operates with high efficiency across a broad operating range because it uses hard switching instead of soft switching. The proposed topology achieves a genuine on-off interleaved energy transfer at the transformer core and windings, thus providing an excellent utilization ratio. The dynamic characteristics of the converter are analyzed for the controller design. Finally, a 240 W hardware prototype is constructed to demonstrate the operation of the bidirectional converter under a current feedback control loop. To improve the efficiency of a PV system, the maximum power point tracking method is applied to the proposed converter.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권8호
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• pp.2875-2893
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• 2015

Existing coding aware routing algorithms focused on novel routing metric design that captures the characteristics of network coding. However, in packet coding algorithm, they use opportunistic coding scheme which didn't consider the queue state of the coding node and are equivalent to the conventional store-and-forward method in light traffic load condition because they never delay packets and there are no packets in the output queue of coding node, which results in no coding opportunity. In addition, most of the existing algorithms assume that all flows participating in the network have equal rate. This is unrealistic since multi-rate environments are often appeared. To overcome above problem and expand network coding to light traffic load scenarios, we present an enhanced coding-aware routing algorithm based on queue state and local topology (OQMCAR), which consider the queue state of coding node in packet coding algorithm where the control policy is of threshold-type. OQMCAR is a unified framework to merge single rate case and multiple rate case, including the light traffic load scenarios. Simulations results show that our scheme can achieve higher throughput and lower end-to-end delay than the current mechanisms using COPE-type opportunistic coding policy in different cases.

• 전산구조공학
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• 제9권3호
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• pp.179-186
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• 1996

본 연구에서는 구조체의 위상학적 최적화를 위한 비선형 formulation(NLP)가 개발, 검토되었다. 이 NLP는 multiple-loading하에서 임의의 오브젝티브 함수, 응력, 변위 제약조건들을 쉽게 다룰 수가 있다. 또한 이 NLP는 해석과 최적화 디자인을 동시에 실시함으로써 요소 사이즈가 영으로 접근함에 따른 강성 매트릭스의 singularity를 피할 수 있다. 즉, 평형 방정식을 등제약조건으로 치환함으로써 강성 매트릭스 그 자체나 그의 역매트릭스를 구할 필요도 없어진다. 이 NLP는 multiple-loading conditon하에서 테스트되었으며, 이를 통해 이 NLP가 다양한 제약조건하에서 강력하게 작용함이 입증되었다.

• Tribology and Lubricants
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• 제32권6호
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• pp.207-211
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• 2016

To interpret the perception that originates from tactile sensibility during people touch and recognize the object surfaces, this study focuses on the development of a friction model that can describe the interaction of a stylus pen sliding over the counter surfaces. In addition, the study includes several other experimental factors such as the pressure, temperature, and topology of surface, which can have an effect on the emotional user experience concerning various surfaces; this research aims to suggest a method to quantitatively evaluate the relation between these experimental parameters and emotional user experience. Accordingly, the objective of research comprises the friction characteristic technology for measurement of fine tribological behavior and a standard to quantify the emotional feedback. Existing panels or input devices that provide interaction feedback about user actions simply operate with a single frequency vibration or sound response. On the contrary, this research investigates various interaction characteristics including friction force, frequency, and surface topology synthetically. Using the developed model, which can explain the relation between the friction parameters and emotional user experience, developers can design their product in order to provide the user with expected emotional sensibility. Consequently, it can contribute to reduce the development cost about sensitivity model.