• 한국전자파학회논문지
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• 제15권2호
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• pp.165-171
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• 2004

본 논문에서는 안테나 스위치 모듈 내에서 GSM/DCS 대역을 분리하는 적층형 다이플렉서를 설계하였고, LTCC 기술을 이용하여 제작한 후 그 특성을 고찰하였다. 다이플렉서를 구현하기 위해 소형의 L, C 집중 수동 소자를 사용하였으며, 또한 적층형 집중 수동 소자의 구조 모델링 및 등가 회로 모델을 제안함으로써 접지면 상에서 최적의 주파수 특성을 갖는 집중 수동 소자를 얻을 수 있었다. 이를 이용하여 RF 모듈에 적용 가능한 고품질의 다이플렉서를 구현하였다. GSM 저역 통과 필터는 0.55 dB 이하의 삽입 손실, 12 dB 이상의 반사 손실 그리고 DCS 통과 대역에서 26 dB 이상의 저지 특성을 나타내었다. DCS 고역 통과 필터는 0.82 dB 이하의 삽입 손실, 11 dB 이상의 반사손실 그리고 GSM 통과 대역에서 38 dB 이상의 저지 특성을 나타내었다.

• 한국정보통신학회논문지
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• 제24권11호
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• pp.1500-1506
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• 2020

본 논문에서는 오버레이 단말 간 직접 (Device-to-Device : D2D) 통신 네트워크를 위한 강화학습 기반 스케쥴링 문제를 연구한다. 강화학습 모델 중 하나인 Q-learning을 이용한 D2D 통신 기술들이 연구되었지만, Q-learning은 상태와 행동의 개수가 증가함에 따라서 높은 복잡도를 유발한다. 이러한 문제를 해결하기 위하여 Deep Q Network (DQN) 기반 D2D 통신 기술들이 연구되었다. 본 논문에서는 무선 통신 시스템 특성을 고려한 DQN 모델을 디자인하고, 피드백 및 시그널링 오버헤드를 줄일 수 있는 DQN 기반 분산적 스케쥴링 방식을 제안한다. 제안 방식은 중앙집중식으로 변수들을 학습시키고, 최종 학습된 파라미터를 모든 단말들에게 전달한다. 모든 단말들은 최종 학습된 파라미터를 이용하여 각자의 행동을 개별적으로 결정한다. 제안 방식의 성능을 컴퓨터 시뮬레이션을 통하여 분석하고, 최적방식, 기회주의적 선택 방식, 전체 전송 방식과 비교한다.

• 조명전기설비학회논문지
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• 제27권12호
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• pp.93-100
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• 2013

This paper propose a method to design the rotor of synchronous reluctance motors(SynRM) for maximum torque and power factor by using DOE(design of experiment) with the design variables which are parameters of barriers and segments. In this process, there are problems that require lots of simulation time and number of simulations when calculating the both torque and power factor using the finite element method in order to find load angle, core loss per speed. In order to improve this problem, we calculate only value of flux linkage by finite element method, and can decrease analysis and the number of analysis time by applying steady state expression of the power factor and torque. Finally, in order to verify the characteristics of optimal model, we make prototype motor and compare with the conventional SynRM. In this experiment, we use the DC current decay test for calculating d-and q-axis inductance.

• Geomechanics and Engineering
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• 제8권5호
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• pp.631-647
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• 2015

Engineers may encounter unpredictable cavities, sinkholes and karst conduits while tunneling in karst area, and water inrush disaster frequently occurs and endanger the construction safety, resulting in huge casualties and economic loss. Therefore, an optimal classification method based on grey system theory (GST) is established and applied to accurately predict the occurrence probability of water inrush. Considering the weights of evaluation indices, an improved formula is applied to calculate the grey relational grade. Two evaluation indices systems are proposed for risk assessment of water inrush in design stage and construction stage, respectively, and the evaluation indices are quantitatively graded according to four risk grades. To verify the accuracy and feasibility of optimal classification method, comparisons of the evaluation results derived from the aforementioned method and attribute synthetic evaluation system are made. Furthermore, evaluation of engineering practice is carried through with the Xiakou Tunnel as a case study, and the evaluation result is generally in good agreement with the field-observed result. This risk assessment methodology provides a powerful tool with which engineers can systematically evaluate the risk of water inrush in karst tunnels.

• 산업경영시스템학회지
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• 제38권2호
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• pp.120-128
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• 2015

Quality function deployment (QFD) is a useful method in product design and development to maximize customer satisfaction. In the QFD, the technical attributes (TAs) affecting the product performance are identified, and product performance is improved to optimize customer requirements (CRs). For product development, determining the optimal levels of TAs is crucial during QFD optimization. Many optimization methods have been proposed to obtain the optimal levels of TAs in QFD. In these studies, the levels of TAs are assumed to be continuous while they are often taken as discrete in real world application. Another assumption in QFD optimization is that the requirements of the heterogeneous customers can be generalized and hence only one house of quality (HoQ) is used to connect with CRs. However, customers often have various requirements and preferences on a product. Therefore, a product market can be partitioned into several market segments, each of which contains a number of customers with homogeneous preferences. To overcome these problems, this paper proposes an optimization approach to find the optimal set of TAs under multi-segment market. Dynamic Programming (DP) methodology is developed to maximize the overall customer satisfaction for the market considering the weights of importance of different segments. Finally, a case study is provided for illustrating the proposed optimization approach.

• 품질경영학회지
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• 제43권2호
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• pp.169-184
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• 2015

Purpose: This paper is concerned with optimally designing accelerated degradation test (ADT) plans based on a gamma process for the degradation model. Methods: By minimizing the asymptotic variance of the MLE of the q-th quantile of the lifetime distribution at the use condition, the test stress levels and the proportion of test units allocated to each stress level are optimally determined. Results: The optimal plans of ADT are developed for various combination of parameters. In addition, a method for determining the sample size is developed, and sensitivity analysis procedures are illustrated with an example. Conclusion: It is important to optimally design ADT based on a gamma process under the condition that a degradation process should be always nonnegative and strictly increasing over time.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.186-189
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• 2003

This paper presents an optimal tuning method of the decentralized PI controller of two-input, two-output(TITO) second order system to be formulated as LQR. The tuning method of proposed decentralized PI controller is developed by establishing the relationships between the closed-loop state equation including decentralized PI control factors and the closed-loop state equation of LQR, which can be guaranteed the performance and stability-robustness by selecting the weighting factors Q and R of the cost function in order to satisfy design specifications in frequency domain.

• Steel and Composite Structures
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• 제32권4호
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• pp.455-466
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• 2019

Despite the rapid advancement in computing resources, many real-life design and optimization problems in structural engineering involve huge computation costs. To counter such challenges, approximate models are often used as surrogates for the highly accurate but time intensive finite element models. In this paper, surrogates for first-order shear deformation based finite element models are built using a polynomial regression approach. Using statistical techniques like Box-Cox transformation and ANOVA, the effectiveness of the surrogates is enhanced. The accuracy of the surrogate models is evaluated using statistical metrics like $R^2$, $R^2{_{adj}}$, $R^2{_{pred}}$ and $Q^2{_{F3}}$. By combining these surrogates with nature-inspired multi-criteria decision-making algorithms, namely multi-objective genetic algorithm (MOGA) and multi-objective particle swarm optimization (MOPSO), the optimal combination of various design variables to simultaneously maximize fundamental frequency and frequency separation is predicted. It is seen that the proposed approach is simple, effective and good at inexpensively producing a host of optimal solutions.

• 한국항행학회논문지
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• 제11권4호
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• pp.437-446
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• 2007

$16{\times}40$ Gb/s WDM 전송 시스템에서 비트 에러율 (BER ; bit error rate)의 효과적 보상과 융통적 WDM 전송 시스템의 설계를 위한 광 위상 공액기 (OPC ; optical phase conjugator)의 최적 위치 값과 광섬유 구간의 최적 분산 계수 값들을 10 dB와 20 dB의 소광비(ER ; extinction ratio)에 따라 도출하였다. 모든 WDM 채널들의 BER의 효과적 보상을 위한 최적 파라미터 값들은 기존 연구들에서 살펴보았던 변조 파형 형식, 전송 채널수와 마찬가지로 신호의 소광비에 의존하는 것을 확인하였다. 그리고 최적 파라미터 값들을 이용한 융통적인 WDM 시스템 설계가 ER이 10 dB인 경우보다 ER이 20 dB인 경우가 더욱 유리한 것을 확인하였다.

• 정보저장시스템학회논문집
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• 제1권1호
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• pp.58-66
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• 2005

Pseudo-Near Field Recording (Pseudo-NFR) system is proposed to prevent contamination and oxidation of media surface occurred in conventional NFR systems. To solve these critical problems of the NFR systems, we investigate the optimal thickness of cover layer for Pseudo NFR. This paper presents the theoretical analysis for cover layer thickness based on the measured length of dust particle and numerical simulation for the temperature distribution using Finite Difference Time Domain (FDTD) method and heat conduction equation. To verify the simulation results, we conduct and compare simulation results in case of far field MO recording and near field MO recording. A measured dust particle length in general environment was mostly less than $20{\mu}m$, and the optimal thickness of cover layer is $30{\mu}m$ in this case. Based on the designed optimal cover layer thickness, temperature distribution is simulated to have $800{\~}850^{\circ}C$.