• 한국음향학회지
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• 제23권5호
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• pp.420-427
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• 2004

본 논문에서는 선형예측 잔여신호에 대한 하모닉 벡터 여기 코딩과 시간 대역 분리 혼합 코딩을 결합한 4kbps EHSX (Enhanced Harmonic Stochastic Excitation) 음성부호화기 실시간 구현한 내용을 기술한다. 유성음 구간에서는 하모닉 여기 코딩에 무성음 구간에 대해서는 분석-합성 구조의 벡터 여기 코딩을 사용하였으며, 유/무성음이 혼재하는 전이구간에서는 시간 분리 전이 코딩을 사용하였다. 이 음성부호화기 구현을 위해 부동소수점과 고정소수점을 모두 지원하는 DSP인 TMS320C6701을 사용하였고, 연산량을 줄이기 위해 IFFT를 사용한 저 복잡도 정현파 합성법을 사용하여 알고리즘의 최적화를 이루었으며, 복잡도의 문제가 되는 부분을 고정소수점으로 변환한 후 파이프라인을 적용한 핸드 어셈블리 코딩을 하여 구현에서의 최적화를 이루었다. 또한, 메모리의 효율성을 극대화하기 위해 캐쉬 메모리 할당과 데이터를 내부 메모리에 할당하였고 수학 연산의 최적화를 위해 FastRTS67x 라이브러리를 사용하였다. 개발 환경은 DSP EVM 보드를 사용하였으며 음성 신호의 입·출력 확인으로 동작 및 기능을 검증하여 실시간 구현하였다.

• Journal of Electrical Engineering and Technology
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• 제4권4호
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• pp.492-498
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• 2009

The placement of the UPFC is the major concern to ensure the full potential of utilization in the transmission network. Voltage stability enhancement with the optimal placement of UPFC using stability index such as modal analysis, Voltage Phasor method is made and the loss minimization including UPFC is formulated as an optimization problem. This paper proposes particle swarm optimization for the exact real power loss minimization including UPFC. The implementation of loss minimization for the optimal location of UPFC was tested with IEEE-14 and IEEE-57 bus system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.360-365
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• 2007

This work is concerned with the topology optimization of three-dimensional cooling fins or heat sinks. Motivated by earlier success of the Internal Element Connectivity Method (I-ECP) method in two-dimensional problems, the extension of I-ECP to three-dimensional problems is carried out. The main efforts were made to maintain the numerical trouble-free characteristics of I-ECP for full three-dimensional problems; a serious numerical problem appearing in thermal topology optimization is erroneous temperature undershooting. The effectiveness of the present implementation was checked through the design optimization of three-dimensional fins.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.50.1-50
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• 2001

Dynamic optimization with partially structured model in a slurry-phase HDPE reactor is implemented by the modified hierarchical dynamic optimization. Optimal trajectories of MI and density of HDPE are calculated as controlled variables and optimal profiles of the concentrations of ethylene, hydrogen and comonomer are calculated as manipulated variables in dynamic optimization. MI, density, the concentrations of ethylene, hydrogen and comonomer are used as controlled variables and flow rates of ethylene, hydrogen and comonomer are sued as manipulated variables in control implementation. Two-level hierarchical method is applied in dynamic optimization to reduce computation time. In the upper level formulation ...

• Journal of Mechanical Science and Technology
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• 제20권8호
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• pp.1169-1182
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• 2006

Robust design technology has been applied to versatile engineering problems to ensure consistency in product performance. Since 1980s, the concept of robust design has been introduced to numerical optimization field, which is called the robust optimization. The robustness in the robust optimization is determined by a measure of insensitiveness with respect to the variation of a response. However, there are significant difficulties associated with the calculation of variations represented as its mean and variance. To overcome the current limitation, this research presents an implementation of the approximate statistical moment method based on kriging metamodel. Two sampling methods are simultaneously utilized to obtain the sequential surrogate model of a response. The statistics such as mean and variance are obtained based on the reliable kriging model and the second-order statistical approximation method. Then, the simulated annealing algorithm of global optimization methods is adopted to find the global robust optimum. The mathematical problem and the two-bar design problem are investigated to show the validity of the proposed method.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2017년도 학술발표회
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• pp.184-184
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• 2017

A nation-wide water-energy-food (WEF) nexus simulation model has been developed by the authors and successfully applied to South Korea to predict the sustainability of those three resources in the next 30 years. The model was also capable of simulating future scenarios of resources allocation based on priority rules aiming to maximize resources sustainability. However, the process was still relying on several assumptions and trial-and-error approach, which sometimes resulted in non-optimal solutions of resources allocation. In this study, an optimization module was introduced to enhance the model in generating optimal resources management rules. The objective of the optimization was to maximize the reliability index of resources by determining the resources' allocation and/or priority rules for each demand type that accordingly reflect the resources management policies. Implementation of the optimization module would result in balanced allocation and management of limited resources and assist the stakeholders in deciding resources' management plans, either by fulfilling the domestic production or by global trading.

• Kyungpook Mathematical Journal
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• 제64권1호
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• pp.95-111
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• 2024

The filled function method is useful in solving unconstrained global optimization problems. However, depending on the type of function, and parameters used, there are limitations that cause difficultiies in implemenations. Exponential and logarithmic functions lead to the overflow effect, requiring iterative adjustment of the parameters. This paper proposes a polynomial-filled function that has a general form, is non-exponential, nonlogarithmic, non-parameteric, and continuously differentiable. With this newly proposed filled function, the aforementioned shortcomings of the filled function method can be overcome. To confirm the superiority of the proposed filled function algorithm, we apply it to a set of unconstrained global optimization problems. The data derived by numerical implementation shows that the proposed filled function can be used as an alternative algorithm when solving unconstrained global optimization problems.

• Structural Engineering and Mechanics
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• 제72권2호
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• pp.181-190
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• 2019

Topology optimization of structures seeking the best distribution of mass in a design space to improve the structural performance and reduce the weight of a structure is one of the most comprehensive issues in the field of structural optimization. In addition to structures stiffness as the most common objective function, frequency optimization is of great importance in variety of applications too. In this paper, an efficient multi-objective Bi-directional Evolutionary Structural Optimization (BESO) method is developed for topology optimization of frequency and stiffness in continuum structures simultaneously. A software package including a Matlab code and Abaqus FE solver has been created for the numerical implementation of multi-objective BESO utilizing the weighted function method. At the same time, by considering the weaknesses of the optimized structure in single-objective optimizations for stiffness or frequency problems, slight modifications have been done on the numerical algorithm of developed multi-objective BESO in order to overcome challenges due to artificial localized modes, checker boarding and geometrical symmetry constraint during the progressive iterations of optimization. Numerical results show that the proposed Multiobjective BESO method is efficient and optimal solutions can be obtained for continuum structures based on an existent finite element model of the structures.

• 전자공학회논문지CI
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• 제43권3호
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• pp.50-58
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• 2006

본 논문은 JPEG2000의 비율 제어과정의 성능을 향상시키기 위해 효율적인 비율-왜곡 최적화 알고리즘 구현에 대해 기술한다. 기존의 비율-왜곡 최적화 알고리즘에서는 전체 코드 블록들의 최대 비율-왜곡 기울기와 최소 비율-왜곡 기울기를 참조하여 그 평균을 비율 제한상수로 설정하는 반면 제안된 알고리즘 구현에서는 절단점 인접의 비율-왜곡 기울기를 참조하여 비율 제한상수를 설정하고, 이전의 비율 할당과정에서 배제된 코딩 패스에 대해서만 비율 할당과정을 수행함으로서 비율-왜곡 최적화를 위한 연산수를 감소하도록 하였다. 비율-왜곡 최적화 알고리즘은 C 언어를 통해 구현되었으며, Altera Excalibur(EPXA4)개발 보드를 통해 실험되었다.

• 한국정보통신학회논문지
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• 제7권3호
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• pp.423-436
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• 2003

해저 광케이블 공사는 해양조사, PLGR(Pre Lay Grapnel Run), 천해부공사, 포설/매설 순서로 이루어진다. PLGR은 해저 광케이블 매설전에 루트상의 해양 오염물(로프, 와이어, 그물, 어망 등)을 사전에 제거하는 작업이다. 이러한 PLGR은 케이블의 해저면 안착을 용이하게 하고, Plough 및 ROV(Remotely-Operated Vehicle) 매설작업의 성능을 향상시키며, 매설장비를 보호하기 위한 작업이다. 본 논문은 해양조사, PLGR 작업을 효율적으로 관리하기 위한 항해 누적 거리(KP Kilometer Post)와 경로 이탈 오차(XTE : Cross Track Error)의 최적화 알고리즘 구현에 대해서 논한다. 본 논문에서는 이를 위하여 전체적인 PLGR 작업을 구성하고, 항해 누적 거리와 경로 이탈 오차의 최적화 알고리즘을 제안하였다. 그리고 현재 진행중인 PLGR 작업의 일부 루트를 따라서 KP와 XTE 결정 알고리즘을 실험하였다.