• 천문학회지
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• 제34권4호
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• pp.181-190
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• 2001

The advent of robust, reliable and accurate higher order Godunov schemes for many of the systems of equations of interest in computational astrophysics has made it important to understand how to solve them in multi-scale fashion. This is so because the physics associated with astrophysical phenomena evolves in multi-scale fashion and we wish to arrive at a multi-scale simulational capability to represent the physics. Because astrophysical systems have magnetic fields, multi-scale magnetohydrodynamics (MHD) is of especial interest. In this paper we first discuss general issues in adaptive mesh refinement (AMR), We then focus on the important issues in carrying out divergence-free AMR-MHD and catalogue the progress we have made in that area. We show that AMR methods lend themselves to easy parallelization. We then discuss applications of the RIEMANN framework for AMR-MHD to problems in computational astophysics.

• 한국위성정보통신학회논문지
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• 제5권1호
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• pp.54-57
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• 2010

위성 기반 측위 시스템은 위치 기반 기술의 핵심 기술로서, CDMA 시스템을 사용한다. CDMA 시스템에서 원활한 위치 측위를 하기 위해서는 확산 부호의 정확한 동기가 이루어져야 한다. 본 논문은 확산 부호의 동기 기법 가운데 부호 추적 기법에 초점을 맞춘다. 특히 다중 경로 환경에서 기존의 부호 추적 기법인 DLL 방법은 적합하지 않다. 본 논문은 수신 신호에서 다중 경로 신호를 축출하여 이를 부호 추적 기법에 사용하는 방법을 제안한다. Spirent simulator를 이용하여 제안 기법을 검증하고 성능 평가를 보인다.

• Transactions on Electrical and Electronic Materials
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• 제12권6호
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• pp.245-248
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• 2011

The scaling down of metal oxide semiconductor field-effect transistors (MOSFETs) for the last several years has contributed to the reduction of the scaling variables and device parameters as well as the operating voltage of the MOSFET. At the same time, the variation in the electrical characteristics of MOSFETs is one of the major issues that need to be solved. Especially because the issue with variation is magnified as the drive voltage is decreased. Therefore, this paper will focus on the variations between electrical characteristics and drain voltage. In order to do this, the test patterned multi-finger MOSFETs using 90-nm process is used to investigate the characteristic variations, such as the threshold voltage, DIBL, subthreshold swing, transconductance and mobility via parasitic resistance extraction method. These characteristics can be analyzed by varying the gate width and length, and the number of fingers. Through this modeling scheme, the characteristic variations of multi-finger MOSFETs can be analyzed.

• Journal of Positioning, Navigation, and Timing
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• 제10권1호
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• pp.49-54
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• 2021

Indoor positioning system becomes of increasing interests due to the demands for accurate indoor location information where Global Navigation Satellite System signal does not approach. Wi-Fi access points (APs) built in many construction in advance helps developing a Wi-Fi Received Signal Strength Indicator (RSSI) based indoor localization. This localization method first collects pairs of position and RSSI measurement set, which is called fingerprint database, and then estimates a user's position when given a query measurement set by comparing the fingerprint database. The challenge arises from nonlinearity and noise on Wi-Fi RSSI measurements and complexity of handling a large amount of the fingerprint data. In this paper, machine learning techniques have been applied to implement Wi-Fi based localization. However, most of existing indoor localizations focus on single position estimation. The main contribution of this paper is to develop multi-target localization by using deep neural, which is beneficial when a massive crowd requests positioning service. This paper evaluates the proposed multilocalization based on deep learning from a multi-story building, and analyses its learning effect as increasing number of target positions.

• 한국실내디자인학회논문집
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• 제22권3호
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• pp.174-182
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• 2013

The purpose of this research is to find applicable design characteristics of communal spaces in multi-family houses. With this goal, international multi-family housing projects are selected and their communal spaces are identified. The purpose of study lies in analyzing on recent 10 years trends of shared space of multi-family houses in Europe, Japan, central America. The design characteristics of the communal spaces are analyzed with a special focus on the four Aspects such as Organization of space, access roads, parking, pedestrian movement In terms of the framework for analysis, community, rest, separability, rambling, territory, distribution, entrance, openness, view, prospect and aesthetic characteristics are reviewed. As a result, the communal space of the analysis are integrated in plans and sections throughout the multi-family houses. Openness and connection with surrounding urban environments are articulated by communal spaces. Communal identities and aesthetics are emphasized by various space for dweller and the other inhabitant. For a further research, it is necessary to combine a design method study with new multi-family houses for the future.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.249-254
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• 2001

Abstract In this paper, we propose a method of cooperative control based on artifical intelligent system in distributed autonomous robotic system. In general, multi-agent behavior algorithm is simple and effective for small number of robots. And multi-robot behavior control is a simple reactive navigation strategy by combining repulsion from obstacles with attraction to a goal. However when the number of robot goes on increasing, this becomes difficult to be realized because multi-robot behavior algorithm provide on multiple constraints and goals in mobile robot navigation problems. As the solution of above problem, we propose an architecture of fuzzy system for each multi-robot speed control and fuzzy-neural network for obstacle avoidance. Here, we propose an architecture of fuzzy system for each multi-robot speed control and fuzzy-neural network for their direction to avoid obstacle. Our focus is on system of cooperative autonomous robots in environment with obstacle. For simulation, we divide experiment into two method. One method is motor schema-based formation control in previous and the other method is proposed by this paper. Simulation results are given in an obstacle environment and in an dynamic environment.

• KIEAE Journal
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• 제12권6호
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• pp.113-121
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• 2012

A hospital is the most important infra-facility of the places which take care of people's body in social environment. There exist several environmental factors in the ways to heal the human body in hospital ward, but this study tried to look into the improvable pleasant sickroom environment with focus on light environment among the factors. In other words, this study aims at the research on proper daylight inflow into sickroom space as basic data for understanding the link between healing environment and natural lighting. In the simulation analysis through this research, this study completed the initial simulation using Autodesk Revit 2011 with focus on two types of individual multi-bed room units of the two general hospitals located in Gwangju City. This study made a simulation analysis of The two multi-bed rooms looking to the west using the weather data on Gwangju district, which is the strong point of ECOTECT2011. Conclusively, looking into the analysis of the simulation model in time of attaching the length of in & outside light shelf, the angle controlling of light shelf, the daylight factor and DA were found to show the tendency to decrease in the numerical value due to the decrease in sunlight inflow as the simulation model moved more toward the room from the window in comparison with the existing analysis of multi-bed rooms. Particularly, this study was able to read that the daylight factor and DA were more decreasing to improve at the light shelf than the existing bedrooms; conclusively, this study judges that the natural lighting simulation analysis could be helpful in improving the healing environment as basic data.

• 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.

• 한국산학기술학회논문지
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• 제16권9호
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• pp.6368-6375
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• 2015

본 연구는 스마트 그린시티의 목표를 충족시켜 줄 수 있는 에너지 측면의 계획기법과 적용기술을 정리하고, 국내에서 가장 먼저 스마트 그린시티 계획을 수립한 행복도시를 분석함으로서 스마트 그린시티 계획의 실현방안을 정립하는 데 목적을 두고 있다. 이를 위해 첫째, 선행연구 고찰을 통해 스마트 그린시티의 개념을 정의하고, 3개 목표, 3개 부문, 6개 기본방향을 설정하였다. 둘째, 선행연구 분석과 스마트 그린시티 목표와 계획기법의 기대효과의 연관성을 고려한 전문가 브레인스토밍을 통하여 18개 계획기법을 도출하였다. 셋째, 행복도시를 대상으로 도출된 계획기법의 적용실태를 기반여건 조성과 기술 및 시스템 도입 측면으로 파악하였다. 그 결과, 스마트 그린시티 조성을 위한 주요 계획기법은 '도시 에너지 통합관리 센터 구축', '건축물 에너지 관리 시스템', '빌딩 자동화 시스템', '녹색교통 체계 구축', '지능형 교통 시스템', '친환경 교통수단 보급', 등 건축물 에너지 소비 절감과 지능형 녹색 교통 시스템 구축에 관련된 계획기법으로 도출되었으며 향후 개선 방안을 확인할 수 있었다.

• Nuclear Engineering and Technology
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• 제42권6호
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• pp.620-635
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• 2010

In this paper we describe current activities on the project Multi-Scale Modeling and Analysis of convective boiling (MSMA), conducted jointly by the Paul Scherrer Institute (PSI) and the Swiss Nuclear Utilities (Swissnuclear). The long-term aim of the MSMA project is to formulate improved closure laws for Computational Fluid Dynamics (CFD) simulations for prediction of convective boiling and eventually of the Critical Heat Flux (CHF). As boiling is controlled by the competition of numerous phenomena at various length and time scales, a multi-scale approach is employed to tackle the problem at different scales. In the MSMA project, the scales on which we focus range from the CFD scale (macro-scale), bubble size scale (meso-scale), liquid micro-layer and triple interline scale (micro-scale), and molecular scale (nano-scale). The current focus of the project is on micro- and meso-scales modeling. The numerical framework comprises a highly efficient, parallel DNS solver, the PSI-BOIL code. The code has incorporated an Immersed Boundary Method (IBM) to tackle complex geometries. For simulation of meso-scales (bubbles), we use the Constrained Interpolation Profile method: Conservative Semi-Lagrangian $2^{nd}$ order (CIP-CSL2). The phase change is described either by applying conventional jump conditions at the interface, or by using the Phase Field (PF) approach. In this work, we present selected results for flows in complex geometry using the IBM, selected bubbly flow simulations using the CIP-CSL2 method and results for phase change using the PF approach. In the subsequent stage of the project, the importance of effects of nano-scale processes on the global boiling heat transfer will be evaluated. To validate the models, more experimental information will be needed in the future, so it is expected that the MSMA project will become the seed for a long-term, combined theoretical and experimental program.