• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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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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• v.16 no.5
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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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• v.9 no.1
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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.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.4
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• pp.133-137
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• 2016

The video and audio information occupies a large portion of the IoT information. Various sensors can be used in a more accurate situation awareness and the absence of the main information has been required. Increasing in resource management in accordance with the use of various sensors. As a method to reduce the resources required in the communication of the various sensors and find the possibility to process the sensor information that can take the place of the other sensor. In this paper, using the LIS302 DL MEMS motion sensor to measure the data in the ping-pong ball, shuttlecock, tennis ball falling into table tennis. Data measured in the three object was confirmed that in proportion to the amount of impact. This experiment using the accelerometer can be confirmed that changes in the amount of impact. The results using a single multi-function sensor showed a possible implementation. In addition, the recognized in consideration of the situation in the early development stage of the multi-function sensor.

• Publications of The Korean Astronomical Society
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• v.28 no.1
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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.

• The Journal of Information Systems
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• v.29 no.2
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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.

• Membrane Journal
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• v.23 no.1
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• pp.1-11
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• 2013

Poly(ether imide) (PEI)-poly(dimethylsioxane) (PDMS) composite membranes and their modules were prepared, which are capable of selective $CO_2$ separation from the mixture gas. The gas flow rate, concentration, recovery ratio of $H_2$ and removal ratio of $CO_2$ outflowing by stage-cut were characterized at $25^{\circ}C$ and the constant pressure. In addition, to increase the recovery ratio of $H_2$, one stage, two stage series connection, and three stages series + parallel connection tests were carried out. When the stage-cut was 0.32 for the three stages connection operation, the concentration $H_2$ of the produced gas and the recovery ratio of $H_2$ was 97% and 85%, respectively. And also the removal ratio of $CO_2$ was 90% was obtained and the recycled gas concentration was similar with that of the feed gases.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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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.

• Journal of Korean Institute of Industrial Engineers
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• v.16 no.2
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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.

• IE interfaces
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• v.17 no.2
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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.