• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 추계 학술대회논문집
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• pp.77-84
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• 1999

Numerical design optimization techniques are implemented for the improvement of the ram accelerator performance. The design object is to find the minimum ram tube length required to accelerate projectile from initial velocity $V_0$ to target velocity $V_e$. The premixture is composed of $H_2,\;O_2,\;N_2$ and the mole numbers of these species are selected as design variables. The objective function and the constraints are linearized during the optimization process and gradient-based Simplex method and SLP(Sequential Linear Programming) have been employed. With the assumption of two dimensional inviscid flow for internal flow field, the analyses of the nonequilibrium chemical reactions for 8 steps 7 species lave been performed. To determined the tube length, ram tube internal flow field is assumed to be in a quasi-steady state and the flow velocity is divided into several subregions with equal interval. Hence the thrust coefficients and accelerations for corresponding subregions are obtained and integrated for the whole velocity region. With the proposed design optimization techniques, the total ram tube length had been reduced $19\%$ within 7 design iterations. This optimization procedure can be directly applied to the multi-stage, multi-premixture ram accelerator design optimization problems.

• Geomechanics and Engineering
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• 제16권5호
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• pp.527-538
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• 2018

The study on the performance of the nonlinear friction tuned mass dampers (FTMD) for the mitigation of the seismic responses of the structures is a topic that still inspires the efforts of researchers. The present paper aims to carry out a numerical study on the optimum tuning of TMD and FTMD parameters using a multi-objective particle swarm optimization (MOPSO) algorithm including soil-structure interaction (SSI) effects for seismic applications. Considering a 3-story structure, the performances of the optimized TMD and FTMD are compared with the uncontrolled structure for three types of soils and the fixed base state. The simulation results indicate that, unlike TMDs, optimum tuning of FTMD parameters for a large preselected mass ratio may not provide a best and optimum design. For low mass ratios, optimal selection of friction coefficient has an important key to enhance the performance of FTMDs. Consequently, a free parameter search of all FTMD parameters provides a better performance in comparison with considering a preselected mass ratio for FTMD in the optimum design stage of the FTMD. Furthermore, the SSI significant effects on the optimum design of the TMD and FTMD. The simulation results also show that the FTMD provides a better performance in reducing the maximum top floor displacement and acceleration of the building in different soil types. Moreover, the performance of the TMD and FTMD decrease with increasing soil softness, so that ignoring the SSI effects in the design process may give an incorrect and unrealistic estimation of their performance.

• International Journal of Advanced Culture Technology
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• 제9권1호
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• pp.121-128
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• 2021

In this study, we aim to suggest direction for landscape design of residential complex in Korea by studying target areas to understand how landscape urbanism was applied to residential landscape design as it is the majority of landscape design in Korea and by closely examining design elements to be considered for design of residential complex based on landscape urbanism theory. For the purpose of the study, some of public multifamily housing complex were selected as target areas and a survey was first conducted to understand how landscape urbanism was applied to design of these target areas. Then, by analyzing the survey results, we identified which elements were of importance to designing of multifamily housing complexes in Korea and how practical design of landscape urbanism works. From this study, we concluded that landscape urbanism theory is not just about design strategies, but more of comprehensive design methodology covering both operation and management and that such theory can be appropriately applied to design of multi-housing complexes in Korea. We also discovered that in order to apply landscape urbanism in design stage for multi-housing complex, selecting which design strategy/words in the previous study is not what's important, but comprehensive understanding and interpretation of design languages is key.

• 한국인터넷방송통신학회논문지
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• 제16권4호
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• pp.133-137
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• 2016

IoT정보중 영상과 음성 정보가 많은 부분을 차지한다. 더 정확한 상황 인식과 주 정보의 부재에서 사용할 수 있는 다양한 센서가 요구되고 있다. 다양한 센서 사용에 따른 자원 관리의 증가로 이어진다. 여러 센서의 정보 전달에서 소요되는 자원을 줄이는 방법으로서 센서정보를 가공하여 다른 센서를 대신할 수 있는 가능성을 찾아본다. 본 논문에서는 LIS302 DL MEMS 모션센서를 사용하여 탁구대로 낙하하는 탁구공, 셔틀콕, 테니스공의 데이터를 측정하였다. 3가지 대상체에서 측정한 데이터는 충격량에 비례하는 함을 확인하였다. 이 실험은 가속도 센서를 사용하여 충격량으로 변경될 수 있음을 확인하였다. 이 결과 단일 센서를 사용하여 다기능구현이 가능함을 보였다. 또한, 센서의 초기 개발단계에서 다기능센서 고려 상황을 인식하게 한다.

• 천문학논총
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• 제28권1호
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• pp.7-13
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• 2013

We present a multi-dimensional reduction method of the surveyed cube database obtained using a single- dish radio telescope in Taeduk Radio Astronomy Observatory (TRAO). The multibeam receiver system installed at the 14 m telescope in TRAO was not optimized at the initial stage, though it became more stabilized in the following season. We conducted a Galactic Plane survey using the multibeam receiver system. We show that the noise level of the first part of the survey was higher than expected, and a special reduction process seemed to be definitely required. Along with a brief review of classical methods, a multi-dimensional method of reduction is introduced; It is found that the 'background' task within IRAF (Image Reduction and Analysis Facility) can be applied to all three directions of the cube database. Various statistics of reduction results is tested using several IRAF tasks. The rms value of raw survey data is 0.241 K, and after primitive baseline subtraction and elimination of bad channel sections, the rms value turned out to be 0.210 K. After the one-dimensional reduction using 'background' task, the rms value is estimated to be 0.176 K. The average rms of the final reduced image is 0.137 K. Thus, the image quality is found to be improved about 43% using the new reduction method.

• 한국정보시스템학회지:정보시스템연구
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• 제29권2호
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• pp.27-50
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• 2020

Purpose The research on the effective use of IS needs to embrace the alignment to organization learning process, which expands the limited focus on dynamic capability of IS use. In addition, it should be done in multi-level analysis with system, user, task, and organization. The current study suggests the inclusion of multi-level analysis of effective use of IS in the perspective of exploration and exploitation. Design/methodology/approach This review selected the representative studies in IS discipline which have investigated the effective use of IS, dynamic capability, operational capability, exploration, exploitation, or organizational learning. In the search of academic archives with those keywords, seventeen papers which have been most cited were chosen and validated whether the focus constructs are directly theorized or validated the suggested keywords. In addition, the level of analysis was verified whether it includes one or more levels of system, individual, task, or organization. Based on the initial analysis of dynamic capability, the further review of research on explorational and exploitational capabilities was implemented. Findings The present review study on previous literature on effective use of IS presented that it is largely implemented in the level of individual but few of them has included organization level. Similarly, the direct investigation of explorational and exploitational use of IS has not been done so much. The needs of study on effective use of IS in depth have been inquired for a decade. However, the review presented that it still lacks profound theories and empirical validations compared to those of adoption stage of IS. Based on the review, future research on the transition between explorational and exploitational use of IS is suggested.

• 멤브레인
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• 제23권1호
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• pp.1-11
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• 2013

혼합가스에서 $CO_2$를 선택적으로 분리할 수 있는 poly (etherimide) (PEI)-poly (dimethylsioxane) (PDMS) 재질의 복합막 및 모듈을 제조하여 $CO_2/H_2$ 분리특성을 확인하였다. 제조된 중공사 복합막 모듈은 모듈의 단수에 따라 $25^{\circ}C$, 일정 압력에서 stage-cut별로 분리된 가스의 유량, 농도, $H_2$ 회수율, $CO_2$ 제거율 등의 성능을 측정하였으며, $H_2$ 회수율을 높이기 위해 1단 시험에서 2단 직렬시험과 3단 직렬 + 병렬 시험으로 단수를 증가시켜 시험하였다. 각각의 운전조건에 대한 결과들을 확인한 결과 3단 운전조건에서 stage-cut을 0.32로 하였을 때 Product가스의 $H_2$ 농도는 97%이었으며 그때의 $H_2$ 회수율은 85%이었다. 또한, $CO_2$ 제거율은 약 90%의 결과를 얻을 수 있었으며 재순환 가스의 농도는 공급 가스와 유사하게 얻을 수 있었다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.49-54
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• 1998

The flow inside an axial turbomachinery with multi-stage can be characterized as unsteady phenomena. In order to predict accurately these complex unsteady flow patterns including rotor-stator interaction effects, enormous computer resources are required. So it is not compatible in preliminary design process. In this study, steady coupled blade row flow with rotor-stator interaction solver is developed using interrow mixing model and used to predict the performance of the axial fan. To verify the computational method, the calculations are compared with experimental results and show satisfactory agreement with them. The interaction effects on the performance of the axial fan have also been studied by comparing the results of steady coupled blade row and steady single blade row flow calculation.

• 대한산업공학회지
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• 제16권2호
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• pp.109-117
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• 1990

In this paper we study a mathematical programming model for the single-card KANBAN system in a multi-stage capacitated general-type-structure production. Until now this production type setting has not been studied. The modeling of this problem results in a complex integer programming which can be modified to the more simple integer programming model. We present a heuristic method and some numerical examples. Though the presented method doesn't always find an optimal solution, this method guarantees to find a feasible solution. We expect this work to be practised in the real fields.

• 산업공학
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• 제17권2호
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• pp.242-248
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• 2004

Lot-streaming is the process of splitting a job (lot) into a number of smaller sublots to allow the overlapping of operations between successive machines in a multi-stage production system. A new genetic algorithm (NGA) is proposed for minimizing the mean weighted absolute deviation of job completion times from due dates when jobs are scheduled in a no-wait lot-streaming flow shop. In a no-wait flow shop, each sublot must be processed continuously from its start in the first machine to its completion in the last machine without any interruption on machines and without any waiting in between the machines. NGA replaces selection and mating operators of genetic algorithms (GAs), which often lead to premature convergence, by new operators (marriage and pregnancy operators) and adopts the idea of inter-chromosomal dominance. The performance of NGA is compared with that of GA and the results of computational experiments show that NGA works well for this type of problem.