• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.8
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• pp.24-32
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• 2005

Micro-source units having power ratings in thousands of watts can provide power quality with higher reliability and efficiency than the conventional large scale units. Since these units are small and easy to install, they are clustered with loads creating micro-grid services to customer sites such as office buildings, industrial parks and homes. Micro-sources adopt voltage source inverter to ensure the power quality of sensitive loads. This paper deals with the connection of micro-sources into the system grid EMTDC modeling of the grid connected micro-sources at the power frequency range are proposed and the characteristics of the control system parameters are investigated. Simulation results show that the micro-grid system with two micro-sources has good dynamic characteristics.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.87-100
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• 2006

A kinematically constrained microplane constitutive model is developed for intact granite. The model is verified by fitting the experimented data of Westerly granite and Bonnet granite. Using the model with the standard finite element method, the behavior of the intact granite subjected blasting impact is studied. What is studied includes the attenuation of the blasting waves, the size of the fractured zone and the effect of the charge condition to avoid overbreak of the rock mass. The model developed captures the energy loss due to the inelastic behavior and the microcracking of granite during blasting very well. The attenuation of the blasting waves calculated based on the model is much more than that based on the linear-elastic constitutive law. The size of damaged (or fractured) zone is calculated directly from the principal strain as blasting impact is spreading, not like in the case with the linear elasticity model.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.2
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• pp.66-74
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• 1985

An idea is presented in this paper that control panel be implemented with a ${\mu}$-processor instead of interrupt based logic circuits. To prove that the idea is reasonable, a ${\mu}$-computer controlled traffic light control system is chosen as a model, and its control panel is imple-mented witll a f-processor. The result is that the microprocessor-based control panel performs its function very well.

• Journal of the Korean Geotechnical Society
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• v.22 no.2
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• pp.41-53
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• 2006

The brittle materials like rocks show complicated strain-softening behavior after the peak which is hard to model using the classical constitutive models based on the relation between strain and stress tensors. A kinematically constrained three-dimensional microplane constitutive model is developed for granite. The model is verified by fitting the experimented data of Westerly granite and Bonnet granite. The triaxial behavior of granite is well reproduced by the model as well as the uniaxial behavior. We studied the development of the fracture zone in granite during blasting impact using the model with the standard finite element method. All the results obtained from the microplane model developed are compared to those from the linear elasticity model which is commonly used in many researches and practices. It is found that the nonlinearity of rocks sigificantly affects the results of analysis.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.3
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• pp.12-19
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• 2006

Micro-source units having power ratings in thousands of watts can provide power quality with higher reliability and efficiency than the conventional large scale units. This paper develops switching level model of micro-source and studies the characteristics of the micro-grid consisting of multiple micro-sources and interfaced with electric power system. The developed model adopts the space vector PWM to fully utilize the capacity of inverter. The interaction of the grid connected micro-sources and the characteristics of the control system parameters are investigated. Micro-sources and micro-grid are implemented using PSCAD/EMTDC. Simulation results show that the proposed model is efficient for studying micro-grid system.

• Information and Communications Magazine
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• v.34 no.5
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• pp.61-67
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• 2017

CES(Community Energy System) 마이크로그리드 기술은 에너지 생산/공급 및 소비가 일정 지역에 구역화하여 공급하는 집단에너지사업 중 구역전기사업이 이루어지는 커뮤니티에너지공급(CES) 시설 환경을 기반으로 이루어지는 마이크로그리드 시스템 기술이다. 마이크로그리드 환경을 위하여 CES 시설 환경을 기반으로 신재생발전, ESS 등 분산자원을 추가하고, 내부 전력시스템 개선 및 신규 에너지 서비스 인프라가 추가로 구축된다. 아울러, 이를 기반으로 마이크로그리드 환경에서 제공될 수 있는 에너지 서비스를 제공한다. 본고에서는 이러한 CES 마이크로그리드 기술에 대해 기술하고 최근 이루어지고 있는 CES 마이크로그리드 기술 개발의 사례를 통해 새로운 비즈니스 모델을 찾아보고자 한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.8
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• pp.1422-1427
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• 2006

In order to estimate the power consumed by an embedded microprocessor during an execution of software, we measure and utilize the current consumed by the processor during the execution of each instruction. In this paper, we measure and analyse the current consumed by the microprocessor adc16s310 during the execution of arithmetic and logic instructions, and propose a power estimation model which estimates the current for all instruction executions precisely by using a small numbers of current measurements. The proposed model can estimate the current with an average 0.34% error by using only 5.84% of total current measurements for arithmetic and logic instructions of the processor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.9-18
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• 2010

There are two kinds of models in two-phase pressured drop; homogeneous flow model and separated flow model. Many previous researchers have developed correlations for two-phase pressure drop in a microchannel. Most correlations were modified Lockhart and Martinelli's correlation, which was based on the separated flow model. In this study, experiments for adiabatic liquid water and nitrogen gas flow in rectangular microchannels were conducted to investigate two-phase pressure drop in the rectangular microchannels. Two-phase frictional pressure drop in the rectangular microchannels is highly related with flow regime. Homogeneous model with six two-phase viscosity models: $Owen^{(21)}$'s, $MacAdams^{(22)}$'s, Cicchitti et ${al.}^{(23)}$'s, Dukler et ${al.}^{(24)}$'s, Beattie and ${Whalley}^{(25)}$'s, Lin et ${al.}^{(26)}$'s models and six separated flow models: Lockhart and $Martinelli^{(27)}$'s, ${Chisholm}^{(31)}$'s, Zhang et ${al.,}^{(15)}$'s, Lee and ${Lee}^{(5)}$'s, Moriyama and ${Inue}^{(4)}$'s, Qu and $Mudawar^{(8)}$'s models were assessed with our experimental data. The best two-phase viscosity model is Beattie and Whalley's model. The best separated flow model is Qu and Mudawar's correlation. Flow regime dependency in both homogeneous and separated flow models was observed. Therefore, new flow pattern based correlations for both homogeneous and separated flow models were individually proposed.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.351-355
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• 1999

서비스 반경이 1이내인 마이크로셀 방식은 기지국의 송신출력을 가능한 작게 하고 안테나의 위치를 주변 건물의 높이보다 낮게 설치하기 때문에 셀 반경내에 있는 지형과 구조물들은 전파특성에 매우 큰 영향을 주므로 셀 내 지형지물의 특성에 따라 기지국의 최적 출력을 구할 수 있는 전파예측 모델이 필요하다. 본 연구에서는 이동국이 가시거리 영역의 전파 음영지역 또는 가시거리 영역과 일정 경사각으로 기울어져 있는 비가시거리 영역에 위치한 경우로 구분하고, 기지국으로부터 송신된 신호가 이동국까지 일정 직진경로를 전파하는 동안, 전파의 반사첫수와 전파경로를 계산할 수있는 연산처리 알고리즘을 개발하여, 이를 웅용하므로써 임의 지점에 위치한 이동국에 도래하는 수신전력을 예측할수 있는 모델을 제안한다. 그리고, 마이크로셀 이동통신 전파환경에서 개발 알고리즘과 제안 전파예측 모델을 시뮬레이션하여, 그 결과를 분석함으로써 마이크로셀 기지국의 최적 위치선정 조건과 기지국 출력에 따른 가입자 서비스 조건을 제시한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.823-829
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• 2014

In the present study, simple models were proposed to predict the capillary-driven flow length in a surfactant-added poly(dimethylsiloxane) (PDMS) rectangular microchannel. Owing to the hydrophobic nature of PDMS, it is difficult to transport water in a conventional PDMS microchannel by means of the capillary force alone. To overcome this problem, microchannels with a hydrophilic surface were fabricated using surfactant-added PDMS. By measuring the contact angle change on the surfactant-added PDMS surface, the behavior was investigated to establish a simple model. In order to predict the filling length induced by the capillary force, the Washburn equation was modified in the present study. From the investigation, it was found that the initial rate-of-change of the contact angle affected the filling length. Simple models were developed for three representative cases, and these can be useful tools in designing microfluidic manufacturing techniques including MIcroMolding In Capillaries (MIMIC).