• 전력전자학회논문지
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• 제17권4호
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• pp.337-344
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• 2012

A matrix converter is used for converting AC/AC power directly. In order to generate sinusoidal input/output waveform in matrix converter, it uses nine bidirectional switches and PWM modulation. This paper presents an analytical averaged loss model of matrix converter with DDPWM(direct duty ratio PWM) and proposes a new switching method for reducing switching losses. A Mathematical loss models with average magnitude of voltage/current are classed as conduction and switching loss. The proposed switching pattern is improved with existing DDPWM. To prove improved efficiency with proposed DDPWM, this paper compares losses between suggested switching pattern and conventional switching pattern using mathematical and simulation method. Each loss types are influenced by environmental factors such as temperature, switching frequency, output current and modulation method.

• 자원ㆍ환경경제연구
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• 제10권4호
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• pp.495-513
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• 2001

We investigate a practical method of calculating the impact of multiple domestic energy price change on the final demand, production, the export and import change, the change in the balance of payment of Korean economy. By combining an existing computable general equilibrium (CGE) model with the traditional input-output analysis with two additional assumptions on the price behavior, we provide a cost-effective method of analyzing the impact of multiple energy price changes on the domestic economy. The energy price shock we used in this paper is 0.127% increase weighted by the sectoral productions. The total impacts on price level and GDP are 1.258% and -0.940%, respectively. The impact on the total output (GDP and intermediate goods) is about -1.580%.

• 소음진동
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• 제5권4호
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• pp.555-563
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• 1995

This paper proposes the method of antiresonance frequency analysis of multi-input multi-output system. The structural dynamic modification techniques by antiresonance frequency analysis are also applied to reduce the undertest at specimen attachment points on the fixture in environmental vibration test, which is resulted from the inconsistency of antiresonance frequencies at any specified points. Several computer simulations show that the proposed method can remove the undertest problem which is not removed in conventional vibration test control. And the effectiveness of the method is verified with the impact hammer excitation of aluminium fixture model.

• Advances in Energy Research
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• 제5권4호
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• pp.321-339
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• 2017

Energy simulation tools can provide information on the amount of heat transfer through building envelope components, which are considered the main sources of heat loss in buildings. Therefore, it is important to improve the quality of outputs from energy simulation tools and also the process of obtaining them. In this paper, a new Building Energy Performance Assessment Tool (BEPAT) is introduced, which provides users with granular data related to heat transfer through every single wall, window, door, roof, and floor in a building and automatically saves all the related data in text files. This information can be used to identify the envelope components for thermal improvement through energy retrofit or during the design phase. The generated data can also be adopted in the design of energy smart homes, building design tools, and energy retrofit tools as a supplementary dataset. BEPAT is developed by modifying EnergyPlus source code as the energy simulation engine using C++, which only requires Input Data File (IDF) and weather file to perform the energy simulation and automatically provide detailed output. To validate the BEPAT results, a computer model is developed in Revit for use in BEPAT. Validating BEPAT's output with EnergyPlus "advanced output" shows a difference of less than 2% and thus establishing the capability of this tool to facilitate the provision of detailed output on the quantity of heat transfer through walls, fenestrations, roofs, and floors.

• Steel and Composite Structures
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• 제35권3호
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• pp.415-437
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• 2020

Circular concrete filled steel tube (CFST) columns have an advantage over all other sections when they are used in compression members. This paper proposes a new approach for deriving a new empirical equation to predict the axial compressive capacity of circular CFST columns using the Artificial Neural Network (ANN). The developed ANN model uses 5 input parameters that include the diameter of circular steel tube, the length of the column, the thickness of steel tube, the steel yield strength and the compressive strength of concrete. The only output parameter is the axial compressive capacity. Training and testing the developed ANN model was carried out using 219 available sets of data collected from the experimental results in the literature. An empirical equation is then proposed as an important result of this study, which is practically used to predict the axial compressive capacity of a circular CFST column. To evaluate the performance of the developed ANN model and the proposed equation, the predicted results are compared with those of the empirical equations stated in the current design codes and other models. It is shown that the proposed equation can predict the axial compressive capacity of circular CFST columns more accurately than other methods. This is confirmed by the high accuracy of a large number of existing test results. Finally, the parametric study result is analyzed for the proposed ANN equation to consider the effect of the input parameters on axial compressive strength.

• 한국지하수토양환경학회지:지하수토양환경
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• 제17권1호
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• pp.1-7
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• 2012

Selection of appropriate liner type would be the most important factor to prevent groundwater contamination by leachate from waste management site. This report introduces the IWEM (Industrial Waste Management Evaluation Model) developed by US EPA to evaluate the potential pollution of groundwater under the waste management unit and to suggest an appropriate type of liner, and provides with the results of IWEM application to a coal-ash landfill site in Korea as a case study. IWEM uses a standard method using a database, a decision-making process based on site characteristics, and the user-friendly input-and-output system. Authors evaluate this model to be applicable in Korea provided that the database is replaced into local data.

• 한국지구과학회지
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• 제32권2호
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• pp.190-199
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• 2011

지형 효과가 포함된 태양복사 모델(GWNU)을 이용한 한반도의 태양광 자원지도를 개발하였다. 태양복사 모델의 입력 자료는 위성 관측 자료(MODIS, OMI, MTSAT-1R)와 수치 모델(RDAPS) 자료를 사용하였으며 특히 고해상도 지형 자료를 이용하여 지형 효과에 따른 한반도의 지표면 태양광 변화를 계산하였다. 계산 결과를 월 및 연 누적하여 분석하였을 때 여름철은 태양 고도각이 높아 지형 효과에 영향이 10% 이하로 적은 반면 겨울철은 20% 이상의 큰 차이가 나타났다. 또한 4 km 해상도의 지표면 태양광의 경우보다 1 km 해상도의 경우 지형 효과 포함에 따른 태양광 차이가 약 2배 정도 크게 나타났다. 즉 지표면에 도달하는 태양광을 정확히 모델링하기 위해서는 입력 자료뿐만 아니라 정확하고 고해상도의 지형 자료가 필연적이며 지형효과는 더욱 뚜렷이 나타나 실제와 유사할 것이다.

• 한국지리정보학회지
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• 제4권4호
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• pp.21-28
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• 2001

본 연구에서는 기존에 개발된 상수도 관련 GIS(geographic information system)에서 관로해석을 위한 자료를 자동으로 입력할 수 있고, 사용자를 위한 GUI(geographic user interface)를 제공하는 GNLP(GIS linked non-linear pipe network analysis program)프로그램을 개발하였다. 관로시스템의 수리해석은 Hazen-Williams의 손실수두방정식을 기초로 한 비선형 해석기법을 이용하여 시행하였으며, 데이터베이스 응용 프로그램을 작성하기 위해서 관계형 데이터베이스 관리시스템(RDBMS ; relational database management system)인 Microsoft사의 Microsoft Access를 사용하였다. 이 GNLP 프로그램은 실제 관망설계자가 관로시스템의 수리해석에 필요한 자료의 입력을 용이하게 할 수 있도록 시스템환경을 개선하였다. 그리고 압력 및 유량 등 관로시스템의 수리적 해석 결과를 표 및 챠트 형태로 출력이 가능하고, Excel 파일로 변환이 가능하다. 또한 GIS의 중요 요소인 질의(query) 기능이나 분석된 자료를 확인하고자 할 때 이를 효과적으로 디스플레이가 가능하도록 개발되었다.

• 환경영향평가
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• 제9권3호
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• pp.185-202
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• 2000

Uncertainty and variability in Life Cycle Assessment(LCA) have been significant key issues in LCA methodology with techniques in other research area such as social and political science. Variability is understood as stemming from inherent variations in the real world, while uncertainty comes from inaccurate measurements, lack of data, model assumptions, etc. Related articles in this issues were reviewed for classification, distinguish and elaboration of probabilistic/stochastic health risk analysis application in LCA. Concept of focal zone, streamlining technique, scenario modelling and Monte Carlo/Latin Hypercube risk analysis were applied to the uncertainty/variability analysis of health risk in LCA. These results show that this general framework of multi-disciplinary methodology between probabilistic health risk assessment and LCA was of benefit to decision making process by suppling information about input/output data sensitivity, health effect priority and health risk distribution. There should be further research needs for case study using this methodology.

• 한국산업보건학회지
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• 제28권2호
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• pp.190-199
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• 2018

Objectives: The purpose of this case study is to assess the current airflow and find the ideal ventilation conditions in tank reactors for minimizing the possibility of exposure respiratory dusts(size of $2.5{\mu}m$, $10{\mu}m$) when workers exchange catalysts in the tank reactors. Methods: A Numerical study was performed to determine ideal ventilation conditions, We considered two sizes of airborne respiratory particles($2.5{\mu}m$, $10{\mu}m$) at 12points from the bottom of tank reactor. We changed input & output ventilation conditions and analyzed the particle motion in the tank reactor. The star-ccm+, computational fluid dynamics tool was used to predict air & particle flow patterns in the tank reactor and a numerical simulation was achieved by applying the realized ${\kappa}-{\varepsilon}$ turbulence model and the Lagrangian particle tracking method. Results: From the results, the increase of recirculation air had a significant impact on removing dusts because they are removed by HEPA filter. To the contrary, Increasing the clean air quantity or changing the input position of clean air is not good for workers because it causes the exit of respiratory dusts through workers' entrance or cause it to remail suspended in the air in the workplace tank.