• 대한기계학회논문집A
• /
• 제30권11호
• /
• pp.1358-1368
• /
• 2006

This paper proposes a Pareto artificial life algorithm for solving multi-objective optimization problems. The artificial life algorithm for optimization problem with a single objective function is improved to handle Pareto optimization problem through incorporating the new method to estimate the fitness value for a solution and the Pareto list to memorize and to improve the Pareto optimal set. The proposed algorithm was applied to the optimum design of a journal bearing which has two objective functions. The Pareto front and the optimal solution set for the application were presented to give the possible solutions to a decision maker or a designer. Furthermore, the relation between linearly combined single-objective optimization problem and Pareto optimization problem has been studied.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.637-642
• /
• 2004

This paper presents a new shape design method for the multi-mode sensor that can detect selected multiple modes for the active vibration control of mechanical structures. The structure used for this study is an isotropic cantilever beam type with a PVDF(polyvinylidene fluoride) which is bonded onto the structure as a sensor. Characteristic behaviors of the sensor are related with the electrode shapes of PVDF. The shape optimization problem is solved by defining a new multi-objective function and using the genetic algorithm. Resulting electrode shape functions have good performances to detect the multiple vibration modes. The results of analytical simulations are compared with those of experiment works. The results agree well each other. Hence, the obtained experimental results give evidence for the validity of the presented theoretical analysis of the electrode shape design problem.

• Steel and Composite Structures
• /
• 제48권5호
• /
• pp.583-597
• /
• 2023

This paper introduces a novel approach to multi-material topology optimization (MTO) targeting in-plane bi-directional functionally graded (IBFG) non-uniform thickness Reissner-Mindlin plates, employing an alternative active phase approach. The mathematical formulation integrates a first shear deformation theory (FSDT) to address compliance minimization as the objective function. Through an alternating active-phase algorithm in conjunction with the block Gauss-Seidel method, the study transforms a multi-phase topology optimization challenge with multi-volume fraction constraints into multiple binary phase sub-problems, each with a single volume fraction constraint. The investigation focuses on IBFG materials that incorporate adequate local bulk and shear moduli to enhance the precision of material interactions. Furthermore, the well-established mixed interpolation of tensorial components 4-node elements (MITC4) is harnessed to tackle shear-locking issues inherent in thin plate models. The study meticulously presents detailed mathematical formulations for IBFG plates in the MTO framework, underscored by numerous numerical examples demonstrating the method's efficiency and reliability.

• Industrial Engineering and Management Systems
• /
• 제10권2호
• /
• pp.134-139
• /
• 2011

The problem of scheduling in permutation flowshops has been extensively investigated by many researchers. Recently, attempts are being made to consider more than one objective simultaneously and develop algorithms to obtain a set of Pareto-optimal solutions. Varadharajan et al. (2005) presented a multi-objective simulated-annealing algorithm (MOSA) for the problem of permutation-flowshop scheduling with the objectives of minimizing the makespan and the total flowtime of jobs. The MOSA uses two initial sequences obtained using heuristics, and seeks to obtain non-dominated solutions through the implementation of a probability function, which probabilistically selects the objective of minimizing either the makespan or the total flowtime of jobs. In this paper, the same problem of heuristically developing non-dominated sequences is considered. We propose an effective heuristics based on simulated annealing (SA), in which the weighted sum of the makespan and the total flowtime is used. The essences of the heuristics are in selecting the initial sequence, setting the weight and generating a solution in the search process. Using a benchmark problem provided by Taillard (1993), which was used in the MOSA, these conditions are extracted in a large-scale experiment. The non-dominated sets obtained from the existing algorithms and the proposed heuristics are compared. It was found that the proposed heuristics drastically improved the performance of finding the non-dominated frontier.

• International Journal of Fluid Machinery and Systems
• /
• 제9권3호
• /
• pp.265-276
• /
• 2016

Energy systems working coherently in different conditions may not have a specific design which can provide optimal performance. A system working for a longer period at lower efficiency implies higher energy consumption. In this effort, a methodology demonstrated by a jet pump design and optimization via numerical modeling for fluid dynamics and implementation of an evolutionary algorithm for the optimization shows a reduction in computational costs. The jet pump inherently has a low efficiency because of improper mixing of primary and secondary fluids, and multiple momentum and energy transfer phenomena associated with it. The high fidelity solutions were obtained through a validated numerical model to construct an approximate function through surrogate analysis. Pareto-optimal solutions for two objective functions, i.e., secondary fluid pressure head and primary fluid pressure-drop, were generated through a multi-objective genetic algorithm. For the jet pump geometry, a design space of several design variables was discretized using the Latin hypercube sampling method for the optimization. The performance analysis of the surrogate models shows that the combined surrogates perform better than a single surrogate and the optimized jet pump shows a higher performance. The approach can be implemented in other energy systems to find a better design.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1058-1063
• /
• 2004

This paper presents a new approach regarding thermal characteristics associated with a design of the high efficiency motor. Electrical conduction materials, such as coil and aluminum embedded in the core generate high heat exerting negative influence on both lifetime and performance of machine. Thus, it is necessary to design high efficiency motor considering heat transfer in order to improve motor performance and to be protected against overheating. In this paper, firstly, numerical analysis of electromagnetic field is carried out by the nonlinear transient finite element method (FEM). Secondly, the linear static FEA of magneto-thermal field is implemented by applying source current computed by the nonlinear transient analysis. FE results are validated in terms of electromagnetics and heat transfer by experiments. And then, the pseudo-transient topology optimization using a multi-objective function is performed. The proposed method is applied to a squirrel cage single-phase induction motor of the scroll compressor.

• Structural Engineering and Mechanics
• /
• 제70권4호
• /
• pp.395-405
• /
• 2019

In the present work, the effects of cutting parameters on surface roughness parameters (Ra), tool wear parameters (VBmax), tool vibration (Vy) and material removal rate (MRR) during hard turning of AISI 4140 steel using coated carbide tool have been evaluated. The relationships between machining parameters and output variables were modeled using response surface methodology (RSM). Analysis of variance (ANOVA) was performed to quantify the effect of cutting parameters on the studied machining parameters and to check the adequacy of the mathematical model. Additionally, Multi-objective optimization based desirability function was performed to find optimal cutting parameters to minimize surface roughness, and maximize productivity. The experiments were planned as Box Behnken Design (BBD). The results show that feed rate influenced the surface roughness; the cutting speed influenced the tool wear; the feed rate influenced the tool vibration predominantly. According to the microscopic imagery, it was observed that adhesion and abrasion as the major wear mechanism.

• 소성∙가공
• /
• 제30권3호
• /
• pp.125-133
• /
• 2021

In this study, response surface method (RSM), back propagation neural network (BPNN), and genetic algorithm (GA) were used for modeling and multi-objective optimization of the parameters of AA5052-H32 in incremental sheet forming (ISF). The goal of optimization is to determine the maximum forming angle and minimum surface roughness, while varying the production process parameters, such as tool diameter, tool spindle speed, step depth, and tool feed rate. A Box-Behnken experimental design (BBD) was used to develop an RSM model and BPNN model to model the variations in the forming angle and surface roughness based on variations in process parameters. Subsequently, the RSM model was used as the fitness function for multi-objective optimization of the ISF process the GA. The results showed that RSM and BPNN can be effectively used to control the forming angle and surface roughness. The optimized Pareto front produced by the GA can be utilized as a rational design guide for practical applications of AA5052 in the ISF process

• 한국산업정보학회논문지
• /
• 제25권2호
• /
• pp.115-127
• /
• 2020

본 연구에서는 모바일폰의 생산, 유통 및 사용 후 처리과정을 효율적으로 관리하기 위한 지속가능한 폐쇄루프 공급망 (Sustainable close-loop supply chain: SCLSC) 모델을 제안한다. 제안된 SCLSC모델의 지속가능성 (Sustainability)을 강화하기 위해 경제적 요인인 총이익 최대화, 환경적 요인인 총 CO2 방출량 최소화, 사회적 요인인 사회적 영향력 최대화를 각각 고려하였다. 이들 세 가지의 요인은 제안된 SCLSC모델의 수리화 모델링 과정에서 목적함수로 표현된다. 따라서 제안된 SCLSC모델은 다목적 최적화 (Multi-objective optimization) 문제로 고려될 수 있으며, 이를 해결하기 위해 혼합유전알고리즘 (Hybrid genetic algorithm: HGA) 접근법을 사용하였다. 수치실험에서는 세가지 상이한 규모의 SCLSC모델을 제시하고, 이를 다양한 수행도 척도들을 사용하여 HGA 접근법의 우수성을 확인하였다.

• 한국음향학회지
• /
• 제35권2호
• /
• pp.102-109
• /
• 2016

본 논문은 밀접한 간격의 두 개의 마이크 배열 환경에서 SNR(Signal-to-Noise Ratio) 추정을 통한 잡음 억제 방법을 제안한다. 기존의 방법은 전 밴드에서 간섭 함수 기반의 SNR 추정을 통해 이득 함수를 얻는 잡음 억제 방법을 사용한다. 그러나 이 방법은 잡음으로 인한 손상이 모든 특징 벡터 성분에 영향을 미쳐 성능을 저하시키는 문제점을 가지고 있다. 따라서 주파수 영역의 신호를 N개의 다중 주파수 밴드로 구분하고 각 밴드별로 간섭 함수 기반의 SNR 추정을 통한 이득 함수를 얻는 잡음 억제 방법을 제안한다. 제안하는 방법의 성능평가는 ITU-T(International Telecommunications Union Telecommunication)에서 제공되는 객관적인 품질 평가 방법인 PESQ(Perceptual Evaluation of Speech Quality)로 비교하여 나타내었다.