• 한국습지학회지
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• 제6권3호
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• pp.47-54
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• 2004

본 연구에서는 수리 수문학적인 이론을 근거로 수질모델링을 위한 유달 오염부하량 산정방법을 제안하고자 한다. 본 연구에서 제안하는 방법은 격자기반으로 구성되어 있으며, 최대 경사 방향으로 일어나는 지표면 유출을 추적함으로써 유달부하량을 계산하게 된다. 또한 GIS 및 DEM 자료를 이용함으로써 공간적으로 분포된 배출 오염부하량, 지형, 경사, 토양특성, 토지이용 등을 고려할 수 있다. 이를 통하여 수질에 영향을 미치는 다양한 토지이용방법 및 유역관리방식의 대안에 대한 평가가 가능할 것으로 기대된다.

• Journal of information and communication convergence engineering
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• 제14권4호
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• pp.207-214
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• 2016

In this paper, we propose a radial reference map-based location fingerprinting technique with constant spacing from an access point (AP) to all reference points by considering the minimum dynamic range of the received signal strength indicator (RSSI) obtained through an experiment conducted in an indoor environment. Because the minimum dynamic range, 12 dBm, of the RSSI appeared every 20 cm during the training stage, a cell spacing of 80 cm was applied. Furthermore, by considering the minimum dynamic range of an RSSI in the location estimation stage, when an RSSI exceeding the cumulative average by ${\pm}6dBm$ was received, a previously estimated location was provided. We also compared the location estimation accuracy of the proposed method with that of a conventional fingerprinting technique that uses a grid reference map, and found that the average location estimation accuracy of the conventional method was 21.8%, whereas that of the proposed technique was 90.9%.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.235-235
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• 2009

본 연구는 친환경 신새생 에너지를 이용한 전력 시스템을 개발함으로써 전력 IT인 Smart Grid 기술 활용과 더불어 예기치 못한 정전으로부터 중요한 전자 장비를 보호하는 UPS 기능을 갖는 친환경 3.0kW급 하이브리드 연료전지 UPS 시스템을 개발하는 것이다. 이를 위하여 시뮬레이션 기법을 이용하여 소형 경량화에 따른 구성 부품 배치 합리화 및 발생열 최적화 설계를 도출하였으며, 연료전지용 장수명 밀폐형 Ni-MH전지, 고효율 전력변환기, 하이브리드 PMS의 설계 및 제작과 개발된 3kW급 하이브리드 연료전지 UPS 시스템 기능 및 성능 평가를 공인 기관에서 검증받았다. 본 연구를 통하여 개발된 연료전지용 장수명 100Ah급 밀폐형 Ni-MH전지는 밀폐화와 더불어 장수명화 및 저온 방전 특성이 우수한 뿐만 아니라 KS규격을 모두 만족하였으며, 내구성도 DOD100%에서 1,093cycle의 결과를 얻을 수 있었다. 또한, 전지 설계 및 제작 기술뿐만 아니라 양산화 관련 기술들이 개발되어 향후 고용량, 고출력, 장수명의 축전지가 필요로 하는 분야에 적용될 수 있는 기반이 마련되었다. 또한 고효율 전력 변환기 및 연료전지과 축전지를 조절하는 PMS을 탑재한 소형 경량화 된 친환경 IT제품의 이미지를 구현하였다.

• 한국측량학회지
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• 제9권2호
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• pp.127-138
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• 1991

본 연구는 지형정보시스템을 활용한 최적 노선선정에 관한 연구이다. 일반적으로 노선의 선정은 후보노선대, 최적노선대, 최적노선의 선정 순으로 이루어지는데 본 연구에서는 노선선정계획의 마지막 부분인 최적노선선정부분을 고려하였다. 최적노선의 선정은 연구대상지역을 일정한 크기의 정규형격자로 구분하고, 각 정규형격자에 토지이용현황, 지가, 경상도 등을 고려하여 얻어진 가중치를 적용하였다. 이를 지형 정보시스템의 속성 데이타로 활용하여 노선선정에 적용되는 가중치의 특정부분으로 고려하고, 세개의 노선을 선정하였다. 이들 세개의 노선을 비교ㆍ분석하여 실제노선의 선정과정에서 지형정보시스템의 활용 가능성을 제시하고자 하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.948-951
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• 2014

Road traffic noise is closely related with urban forms and urban components, such as population, building, traffic and land-use, etc. Hence, it is possible to minimize the noise exposure problem depending on how to plan new town or urban planning alteration. This paper provides ways to apply for urban planning in consideration of noise through exposed noise estimation for urban planning alteration. Spatial autoregressive model which explains about 81.4% of road traffic noise from the former paper is used. The simulation results by the spatial statistical model are compared with those by the engineering program-based modeling for 5 small-scaled scenarios of urban planning alteration. The error from the limitation of containing informations inside the grid cell and the difficulties of reflecting acoustic phenomena is existed. Nevertheless, in the stage of preliminary design, the use of the statistical models that have been estimated well is useful in time and economically.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2006년도 한국컴퓨터종합학술대회 논문집 Vol.33 No.1 (C)
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• pp.46-48
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• 2006

This paper addresses the problem of monitoring continuous k-nearest neighbor (k-NN) queries. Given a set of moving (or static) objects and a set of moving (or static) query points, monitoring continuous k-NN query retrieves and updates the closest k objects to a query point continually. In order to support location based services (LBSs) in highly dynamic environments, where objects and/or queries are frequently moving, monitoring continuous queries require real-time updated results when objects and/or queries change their locations. Thus, it is important to minimize time delay for maintaining up to date the results. In this paper, we present monitoring method to shorten time delay for updating continuous k-NN queries based on the notion of result region and the minimum bounding rectangle enclosing all objects in each cell, referred to as c-MBR, in the grid index structure. Simulations are conducted to show the efficiency of the proposed method.

• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1347-1360
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• 2009

A multi-dimensional component for the thermal-hydraulic system analysis code, MARS, was developed for a more realistic three-dimensional analysis of nuclear systems. A three-dimensional and two-fluid model for a two-phase flow in Cartesian and cylindrical coordinates was employed. The governing equations and physical constitutive relationships were extended from those of a one-dimensional version. The numerical solution method adopted a semi-implicit and finite-difference method based on a staggered-grid mesh and a donor-cell scheme. The relevant length scale was very coarse compared to commercial computational fluid dynamics tools. Thus a simple Prandtl's mixing length turbulence model was applied to interpret the turbulent induced momentum and energy diffusivity. Non drag interfacial forces were not considered as in the general nuclear system codes. Several conceptual cases with analytic solutions were chosen and analyzed to assess the fundamental terms. RPI air-water and UPTF 7 tests were simulated and compared to the experimental data. The simulation results for the RPI air-water two-phase flow experiment showed good agreement with the measured void fraction. The simulation results for the UPTF downcomer test 7 were compared to the experiment data and the results from other multi-dimensional system codes for the ECC delivery flow.

• Nuclear Engineering and Technology
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• 제46권5호
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• pp.641-654
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• 2014

A new computer code, named CORONA (Core Reliable Optimization and thermo-fluid Network Analysis), was developed for the core thermo-fluid analysis of a prismatic gas cooled reactor. The CORONA code is targeted for whole-core thermo-fluid analysis of a prismatic gas cooled reactor, with fast computation and reasonable accuracy. In order to achieve this target, the development of CORONA focused on (1) an efficient numerical method, (2) efficient grid generation, and (3) parallel computation. The key idea for the efficient numerical method of CORONA is to solve a three-dimensional solid heat conduction equation combined with one-dimensional fluid flow network equations. The typical difficulties in generating computational grids for a whole core analysis were overcome by using a basic unit cell concept. A fast calculation was finally achieved by a block-wise parallel computation method. The objective of the present paper is to summarize the motivation and strategy, numerical approaches, verification and validation, parallel computation, and perspective of the CORONA code.

• Journal of Power Electronics
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• 제16권6호
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• pp.2272-2283
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• 2016

This paper proposes a power conditioning system (PCS) for distributed photovoltaic (PV) applications using an asymmetric cascaded multilevel inverter with a single PV source. One of the main disadvantages of the cascaded multilevel inverters in PV systems is the requirement of multiple isolated DC sources. Using multiple PV strings leads to a compromise in either the voltage balance of individual H-bridge cells or the maximum power point tracking (MPPT) operation due to localized variations in atmospheric conditions. The proposed PCS uses a single PV source with a flyback DC-DC converter to facilitate a reduction of the required DC sources and to maintain the voltage balance during MPPT operation. The flyback converter is used to provide input for low-voltage H-bridge cells which processes only 20% of the total power. This helps to minimize the losses occurring in the proposed PCS. Furthermore, transient analyses and controller design for the proposed PCS in both the stand-alone mode and the grid-connection mode are presented. The feasibility of the proposed PCS and its control scheme have been tested using a 1kW hardware prototype and the obtained results are presented.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.188-192
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• 2004

A Numerical analysis method is developed in order to compute the flaw and wave field for 2-dimensional floating body in the free roll motion with 3 degrees of freedom. Navier-Stokes and continuity equations are gaverning equations in tire present study. Finite Difference method is introduced to discretize the governing equation. The free surface is traced by the interface tracking method and the grid system is fitted to boundaries including free surface and body surface, which is moving in the flow field. The numerical scheme is based on Maker and Cell method. For the sake of validation of the numerical method, the computed roll decay factors according to tire midship section shapes are compared with measured results. The numerical results are discussed in order to understand the effect of midship section shape on roll motion.