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Multi-station Fixture Layout Design Using Simulated Annealing
Kim, Pansoo,Sun, Ji Ung 한국경영과학회 2004 Management Science and Financial Engineering Vol.10 No.2
Automotive and aircraft assembly process rely on fixtures to support and coordinate parts and subassemblies. Fixture layout in multi-station panel assemblies has a direct dimensional effect on final products and thus presents a quality problem. This paper describes a methodology for fixture layout design in multi-station assembly processes. An optimal fixture layout improves the robustness of a fixture system against environmental noises. reduces product variability, and eventually leads to manufacturing cost reduction. One of the difficulties raised by multi-station fixture layout design is the overwhelmingly large number of design alternatives. This makes it difficult to find a global optimality and, if an inefficient algorithm is used, may require prohibitive computing time. In this paper, simulated annealing is adopted and appropriate parameters are selected to find good fixture layouts. A four-station assembly process for a sport utility vehicle (SUV) side frame is used throughout the paper to illustrate the efficiency and effectiveness of this methodology.
Kim, Heungseob,Kim, Pansoo Elsevier 2017 Reliability engineering & system safety Vol.159 No.-
<P><B>Abstract</B></P> <P>To maximize the reliability of a system, the traditional reliability–redundancy allocation problem (RRAP) determines the component reliability and level of redundancy for each subsystem. This paper proposes an advanced RRAP that also considers the optimal redundancy strategy, either active or cold standby. In addition, new examples are presented for it. Furthermore, the exact reliability function for a cold standby redundant subsystem with an imperfect detector/switch is suggested, and is expected to replace the previous approximating model that has been used in most related studies. A parallel genetic algorithm for solving the RRAP as a mixed-integer nonlinear programming model is presented, and its performance is compared with those of previous studies by using numerical examples on three benchmark problems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Optimal strategy is proposed to solve reliability redundancy allocation problem. </LI> <LI> The redundancy strategy uses parallel genetic algorithm. </LI> <LI> Improved reliability function for a cold standby subsystem is suggested. </LI> <LI> Proposed redundancy strategy enhances the system reliability. </LI> </UL> </P>
Kim, Heungseob,Kim, Pansoo Elsevier 2017 Reliability engineering & system safety Vol.159 No.-
<P><B>Abstract</B></P> <P>This research paper presents practical stochastic models for designing and analyzing the time-dependent reliability of nonrepairable systems. The models are formulated for nonrepairable systems with heterogeneous components having phase-type time-to-failure distributions by a structured continuous time Markov chain (CTMC). The versatility of the phase-type distributions enhances the flexibility and practicality of the systems. By virtue of these benefits, studies in reliability engineering can be more advanced than the previous studies. This study attempts to solve a redundancy allocation problem (RAP) by using these new models. The implications of mixing components, redundancy levels, and redundancy strategies are simultaneously considered to maximize the reliability of a system. An imperfect switching case in a standby redundant system is also considered. Furthermore, the experimental results for a well-known RAP benchmark problem are presented to demonstrate the approximating error of the previous reliability function for a standby redundant system and the usefulness of the current research.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Phase-type time-to-failure distribution is used for components. </LI> <LI> Reliability model for nonrepairable system is developed using Markov chain. </LI> <LI> System is composed of heterogeneous components. </LI> <LI> Model provides the real value of standby system reliability not an approximation. </LI> <LI> Redundancy allocation problem is used to show usefulness of this model. </LI> </UL> </P>
Analysis of the mobile DVB-S2 applicability to broadband mobile services
Pansoo Kim,Dae-Ig Chang,Ho-Jin Lee 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
This paper is shown to perform the DVB-S2 standard applicability for mobile services. First of all, it describes how current DVB-S2 standard has an effect as the different channel conditions caused by a high mobility or channel characteristics variation. In addition, it shows the promising countermeasures with a slight modification in the current DVB-S2 standard. Eventually, we intend to contribute on some parts of diversity reception, of mapping and of physical layer timing interleaving within technical report on DVB-S2 evolutions towards mobility, especially.
Kim, Pansoo,Vanelli-Coralli, Alessandro,Villanti, Marco,Pedone, Raffaella,Cioni, Stefano,Neri, Massimo,Palestini, Claudio,Papaleo, Marco,Lee, Ho-Jin,Corazza, Giovanni E. John Wiley Sons, Ltd. 2010 International journal of satellite communications Vol.28 No.3
<P>The recently approved mobile version of the Digital Video Broadcasting Return Channel via Satellite (DVB-RCS+M) foresees the use of direct sequence spectrum spreading (DS-SS) in the forward link. The addition of a spreading mode, on top of the conventional time division signaling structure of the fixed DVB-S2, allows in fact for the efficient extension of DVB-S2 to mobile terminals with small aperture antennas operating in Ku (11–14 GHz) and Ka (20–30 GHz) bands. Spectrum spreading has been introduced to augment the received energy without increasing the transmitted power density, which is limited by regulatory constraints, and to enhance the waveform resilience to co-channel interference. In this paper, we report on the design and assessment of the DS-SS technique that we carried out for its inclusion in the DVB-RCS+M standard. In particular, by comparing the physical layer performance of the spread and nonspread modes in the specific DVB-RCS+M mobile scenarios, we show that the proposed DS-SS technique has no impact on the DVB-RCS+M data detection performance, while satisfying the requirements on interference resilience and received energy augmentation. In order to deal with the acquisition issues raised by the introduction of the DS-SS technique, we then propose and evaluate several synchronization sub-systems able to deal with the specific impairments of the mobile satellite scenarios, that is, large frequency offsets, phase noise, link obstructions, etc. Finally, a possible implementation of the DS-SS technique that fully accommodates the reuse of the specific hardware compatible with conventional DVB-S2 is also reported. Copyright © 2009 John Wiley & Sons, Ltd.</P>
Design Optimization of Multistage Assembly Processes
Kim, Pansoo 경북대학교 경제경영연구소 2007 經商論集 Vol.34 No.2
다중조립공정의 품질에 가장 많은 영향을 주는 요소 중의 하나는 고정구의 위치라고 할 수 있다. 본 연구에서는 다중조립공정에서 가장 적절한 고정구의 위치를 선정하는 하나의 방법을 제공한다. 만약 가장 좋은 위치에 고정구가 조립공정의 판넬을 고정할 수 있다면 고정구는 외부의 충격에도 항상 일정한 정도의 품질특성치 변화만을 허용할 수 있고 이러한 성질은 결국 최종적인 비용을 줄이는 효과를 가져올 수 있다. 이러한 문제가 가치가 있는 이유는 가능한 고정구의 후보군이 엄청나게 많기 때문이며 제안된 알고리즘을 통한다면 글로벌 최적해는 아니지만 어느 정도 받아들일 수 있는 정도의 충분히 좋은 위치를 찾을 수 있을 것이다. 목적함수는 전체적인 민감도를 줄일 수 있 는 목적함수를 선택하였다. This paper presents a near design optimization algorithm in multistage assembly process. The developed algorithm is employed in designing an optimal multi-station fixture layout. An optimal fixture layout Improves the robustness of a fixture system against environmental noises, reduces product variability, and eventually leads to manufacturing cost reduction. One of the difficulties raised by multi-station fixture layout design is the overwhelmingly large number of design alternatives. This makes it difficult to find a global optimality and, if an inefficient algorithm is used, may require prohibitive computing time. The objective of the algorithm is to minimize the sensitivity function subject to geometric constraints.