• 한국정보과학회논문지:소프트웨어및응용
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• 제28권12호
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• pp.955-965
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• 2001

본 논문에서는 함수형 언어 Haskell 을 Java언어로 변환하여 Java Virtual Machine 에 수행하는 컴파일 방법을 제안한다. 이 컴파일 방법은 추상 기계 Spineless Tageless G-machine(STGM)을 수행 모델로 삼는다 L-code로 명명한 중간 언어를 도입하여 추상기계의 각각의 세부 동작을 이 언어의 명령어로 표현하고, 일견의 세부 동작들을 이 언어의 바인딩을 통해 표현한다. 각 명령어는 Java의 문장으로 변환하기 쉽도록 정의하였다. Java에서의 표현 방법을 결정하고. STS 프로그램의 L-code 프로그램으로의 컴파일 규칙과 Java 프로그램으로의 컴파일 규칙을 세안한다. 실험을 통해 제안한 컴파일러에 의해 Haskell 프로그램으로부터 생성된 Java 프로그램의 수행 성능은 Glasgow Haskell 컴파일러의 최적화 변환을 적용했을 때 기존의 Haskell 인터프리터인 Hugs와 대등함을 보인다

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.474-486
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• 2015

This paper proposes a multi-objective optimal placement method of Phasor Measurement Units (PMUs) in large electric transmission systems. It is proposed for minimizing the number of PMUs for complete system observability and maximizing measurement redundancy of the buses, simultaneously. The measurement redundancy of the bus indicates that number of times a bus is able to monitor more than once by PMUs set. A high level of measurement redundancy can maximize the system observability and it is required for a reliable power system state estimation. Therefore, simultaneous optimizations of the two conflicting objectives are performed using a binary coded firefly algorithm. The complete observability of the power system is first prepared and then, single line loss contingency condition is added to the main model. The practical measurement limitation of PMUs is also considered. The efficiency of the proposed method is validated on IEEE 14, 30, 57 and 118 bus test systems and a real and large- scale Polish 2383 bus system. The valuable approach of firefly algorithm is demonstrated in finding the optimal number of PMUs and their locations by comparing its performance with earlier works.

• 대한기계학회논문집A
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• 제31권11호
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• pp.1059-1068
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• 2007

Nonlinear response structural optimization is performed using equivalent loads (NROEL). Nonlinear response optimization is extremely cost because many nonlinear analyses are required. In NROEL, the external loads are transformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response field of linear analysis as that of nonlinear analysis. The primitive from of theory has been published. In this research, the theory is investigated with large scale example problems. Four examples are solved by using NROEL. Conventional optimization with sensitivity analysis using the finite difference method (FDM) is also applied to the same examples. Moreover, response surface optimization method is applied to the last two examples. The results of the optimizations are compared. In nonlinear response optimization of large scale problems, hundreds (or even thousands) of nonlinear analyses are expected to satisfy the convergence criteria. However, in nonlinear response optimization using equivalent loads, only tens of nonlinear analyses are required. The results are discussed and the usefulness of NROEL is presented.

• 소음진동
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• 제8권2호
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• pp.267-273
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• 1998

This study aims at performing sensitivity analysis of piezoelectric smart structure for minimizing radiated noise from the structure, The structure consists of a flat plate on which disk shaped piezoelectric actuator is mounted, and finite element modeling is used for the structure. The finite element modeling uses a combination of three dimensional piezoelectric, flat shell and transition elements so thus it can take into account the coupling effects of the piezoelectric device precisely and it can also reduce the degrees of freedom of the finite element model. Electric potential on the piezoelectric actuator is taken as a design variable and total radiated power of the structure is chosen as an objective function. The objective function can be represented as Rayleigh's integral equation and is a function of normal displacements of the structure. For the convenience of computation, all degrees of freedom of the finite element equation is condensed out except the normal displacements of the structure. To perform the design sensitivity analysis, the derivative of the objective function with respect to the normal displacements is found, and the derivative of the norma displacements with respect to the design variable is calculated from the finite element equation by using so called the adjoint variable method. The analysis results are compared with those of the finite difference method, and shows a good agreement. This sensitivity analysis is faster and more accurate than the finite difference method. Once the sensitivity analysis program is used for gradient-based optimizations, one could achieve a better convergence rate than non-derivative methods for optimal design of piezoelectric smart structures.

• 한국자동차공학회논문집
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• 제11권5호
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• pp.210-218
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• 2003

MDO (multidisciplinary design optimization) technology has been proposed and applied to solve large and complex optimization problems where multiple disciplinaries are involved. In this research. an MDO problem is defined for automobile design which has crashworthiness analyses. Crash model which are consisted of airbag, belt integrated seat (BIS), energy absorbing steering system .and safety belt is selected as a practical example for MDO application to vehicle system. Through disciplinary analysis, vehicle system is decomposed into structure subspace and occupant subspace, and coupling variables are identified. Before subspace optimization, values of coupling variables at given design point must be determined with system analysis. The system analysis in MDO is very important in that the coupling between disciplines can be temporary disconnected through the system analysis. As a result of system analysis, subspace optimizations are independently conducted. However, in vehicle crash, system analysis methods such as Newton method and fixed-point iteration can not be applied to one. Therefore, new system analysis algorithm is developed to apply to crashworthiness. It is conducted for system analysis to determine values of coupling variables. MDO algorithm which is applied to vehicle crash is MDOIS (Multidisciplinary Design Optimization Based on Independent Subspaces). Then, structure and occupant subspaces are independently optimized by using MDOIS.

• 한국항공우주학회지
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• 제32권6호
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• pp.72-80
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• 2004

본 논문에서는 추력중단 후 무유도방식 유도탄의 추력비행단계 유도알고리듬의 설계과정을 다룬다. 유도의 목적은 추력중단 시점에서 요구속도벡터를 성취하기 위한 것이다. 구현 가능한 피치평면 비행궤적을 조사하기 위해 네 가지 성능지수에 대한 비행궤적 최적화를 수행하였다. 궤적최적화 결과로부터 구속조건들을 만족시키기 위해서는 비행초기에 고앙각 기동이 필요함을 알 수 있다. 제안된 유도알고리듬은 개루프 피치자세각 명령 산출기인 피치프로그램과 증가요구속도벡터를 0으로 만들기 위한 요자세각 명령 산출기로 구성된다. 피치프로그램은 궤적최적화 결과 얻어진 피치자세각 선도를 이용하여 구성되었다.

• 대한의용생체공학회:의공학회지
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• 제28권4호
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• pp.455-460
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• 2007

Flow mismatch between blood and dialysate is invariably encountered during conventional hemodialysis, and this deteriorates diffusive mass transfer. A modification of a conventional dialyzer was conceived to prevent this mismatch. The modified dialyzer includes two independent blood flow regions (central and peripheral regions), which were achieved by redesigning the dialyzer cap. Resultantly, the blood stream was divided into two concentric dialyzer regions. Solutes clearances obtained using the modified dialyzers were compared with those of conventional dialyzers. Solutes clearances by conventional dialyzers were uniform, but solutes clearances by modified dialyzers were found to be dependent on the simulated blood split into dialyzer central and peripheral regions. Maximal clearances using the modified dialyzer were improved by up to approximately 7.6% for urea and 7.3% for creatinine, as compared with those of conventional dialyzers. More optimizations are required for clinical applications, but the finding that blood flowrates through central and peripheral fiber bundles can be easily regulated is encouraging.

• 정보과학회 컴퓨팅의 실제 논문지
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• 제23권3호
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• pp.165-170
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• 2017

GPGPU의 높은 연산 처리 능력을 활용하여 길고 복잡한 계산을 하려는 시도가 많이 있다. GPGPU 프로그램의 특성상 host와 device 사이에 메모리 복사가 필요하다. 해당 메모리 복사 latency가 길 경우 프로그램의 성능에 많은 영향을 준다. 그래서 GPGPU를 활용한 프로그래밍은 최적화에 따른 성능 차이가 크다. 여러 개의 GPGPU 프로그램을 동시에 실행시키면 메모리 복사와 GPGPU 컴퓨팅이 중첩이 되어 메모리 복사 latency hiding 효과를 기대할 수 있다. 이 논문에서는 메모리 복사 latency hiding을 분석한다. 또 메모리 복사의 성능을 높이기 위해 pinned memory를 사용했을 경우의 제약 조건에 따른 성능 예측 모델링 및 알고리즘을 제안하고 이를 바탕으로 실행할 워크로드를 선택하면 41%의 성능 향상을 보인다.

• 한국항행학회논문지
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• 제13권5호
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• pp.736-741
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• 2009

본 논문은 분할된 선형배열안테나를 사용하는 다중 사용자 MIMO 기술에서 코드북(codebook)을 운용 환경에 따라 최적화 하는 기술을 제안한다. 제안하는 기술은 공간상관도가 없는 MIMO 채널을 가정하여 디자인된 코드북을 각 순방향 링크의 송신 공간상관행렬을 이용하여 컬러링(coloring)하는 기술이며, 이를 위해 필요한 각 링크의 송신 상관행렬을 제한된 양의 long-term 피드백을 통해 피드백하는 기술을 제안한다. Zero-forcing maximum eigenmode transmission 기술을 사용하는 다중 사용자 MIMO 시스템에서, 제안하는 코드북 최적화 기술의 성능을 분석하였으며, 제안하는 기술이 적은양의 추가 피드백 정보량으로 다양한 운용 환경에 적응적으로 코드북을 최적화함을 보인다.

• Steel and Composite Structures
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• 제28권4호
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• pp.427-438
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• 2018

Static stability is a decisive factor in the design of domes. Stability-related external factors, such as load and supports, are incorporated into structural vulnerability theory by the definition of a relative rate of joint well-formedness ($r_r$). Hence, the instability mechanism of domes can be revealed. To improve stability, an optimization model against instability, which takes the maximization of the lowest $r_r$ ($r_{r,min}$) as the objective and the discrete member sections as the variables, is established with constraints on the design requirements and steel consumption. Optimizations are performed on two real-life Kiewitt-6 model domes with a span of 23.4 m and rise of 11.7 m, which are initially constructed for shaking table collapse test. Well-formedness analyses and stability calculation (via arc-length method) of the models throughout the optimization history demonstrate that this proposed method can effectively enhance $r_{r,min}$ and optimize the static stability of shell-like structures. Additionally, seismic performance of the optimum models subjected to the same earthquake as in the shaking table test is checked. The supplemental simulations prove that the optimum models are superior to the original models under earthquake load as well.