• Journal of Electrical Engineering and Technology
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• 제6권2호
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• pp.147-153
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• 2011

This paper proposes a methodology using a tool based on the branch-parameter continuation power flow (BCPF) in order to restore the power flow solvability in unsolvable contingencies. A specified contingency from a set of transmission line contingencies is modeled, considering the transient analysis and practice in the Korean power system. This tool traces a solution path that satisfies the power flow equations with respect to the variation of the branch parameter. At a critical point, in which the branch parameter can move on to a maximum value, a sensitivity analysis with a normal vector is performed to identify the most effective compensation. With the sensitivity information, the location of the reactive power compensation is determined and the effectiveness of the sensitivity information is verified to restore the solvability. In the simulation, the proposed framework is then applied to the Korean power system.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.111-116
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• 2004

어구는 어획을 효과적으로 달성하기 위해서 사용되는 도구이다. 연승어업은 모릿줄에 일정한 간격으로 아릿줄을 연결하고 아릿줄 끝에 낚시 1개씩을 매달은 어업 방법이다. 본 논문은 연승어업의 어구 투승을 효율적으로 관리할 수 있는 어구 유형 설정 시스템의 설계 및 구현에 대해서 논한다. 본 논문에서는 이를 위하여 전체적인 어구 유형 설정 시스템을 설계하고, 시스템 사용자 및 통신환경 설정, 어구 유형 설계, 어구 투승의 모형 모듈을 구현하였다. 본 논문의 타당성 검토를 위하여 어구 유형 설계 및 투승 과정을 실험하였다.

• Advances in Energy Research
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• 제4권1호
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• pp.87-106
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• 2016

In this research, optimum design of the combined solar collector, geothermal heat pump and thermal seasonal storage system for heating and cooling a sample greenhouse is studied. In order to optimize the system from technical point of view some new control strategies and functions resulting from important TRNSYS output diagrams are presented. Temperatures of ground, rock bed storage, outlet ground heat exchanger fluid and entering fluid to the evaporator specify our strategies. Optimal heat storage is done with maximum efficiency and minimum loss. Mean seasonal heating and cooling COPs of 4.92 and 7.14 are achieved in series mode as there is no need to start the heat pump sometimes. Furthermore, optimal parallel operation of the storage and the heat pump is studied by applying the same control strategies. Although the aforementioned system has higher mean seasonal heating and cooling COPs (4.96 and 7.18 respectively) and lower initial cost, it requires higher amounts of auxiliary energy either. Soil temperature around ground heat exchanger will also increase up to $1.5^{\circ}C$ after 2 years of operation as a result of seasonal storage. At the end, the optimum combined system is chosen by trade-off between technical and economic issues.

• Smart Structures and Systems
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• 제21권5호
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• pp.537-548
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• 2018

A tunnel deformation monitoring system is developed with the use of fiber Bragg grating (FBG) sensing technique, aiming at providing continuous monitoring of railway tunnel deformation in the long term, and early warning for the rail service maintainers and authorities to avoid catastrophic consequences when significant deformation occurs. Specifically, a set of FBG bending gauges with the ability of angle measurement and temperature compensation is designed and manufactured for the purpose of online monitoring of tunnel deformation. An overall profile of lateral tunnel displacement along the longitudinal direction can be obtained by implementing an array of the FBG bending gauges interconnected by rigid rods, in conjunction with a proper algorithm. The devised system is verified in laboratory experiments with a test setup enabling to imitate various patterns of tunnel deformation before the implementation of this system in an in-service high-speed railway (HSR) tunnel.

• Asian Journal of Business Environment
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• 제7권4호
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• pp.17-25
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• 2017

Purpose - The purpose of this study is to present a framework for determining the most appropriate business model for e-learning. Research design, data, and methodology - The Electronics Branch of Azad University has been elected as a case study in this research. This study conducted using a descriptive method. The information was obtained using interviews with experts including managers, faculty and students at the Electronics Branch of Azad University. Results - Three service-product system (product oriented system, use an oriented and result oriented system) approaches determined a framework for the formation of a portfolio. This portfolio is including three types of e-learning business models. Examining the relevant characteristics, correspondence of behaviorism learning theory with a product-oriented approach, correspondence of cognitivism theory with a user-oriented approach and in finally match correspondence of constructivist learning theory with a results-oriented approach which is evident. Conclusions - After reviewing the literature on the fields of e-learning, business model and product - service systems, we have achieved three types of e-learning business models. Then the variables in any of the business models were defined by using business model canvas tool and thus a portfolio consisting of three types of e-learning business model canvas was obtained.

• 설비공학논문집
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• 제15권3호
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• pp.239-245
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• 2003

In the nuclear power plant, emergency core coolant system (ECCS) is furnished at reactor coolant system (RCS) in order to cool down high temperature water in case of emergency. However, in this coolant system, thermal stratification phenomenon can occur due to coolant leaking in the check valve. The thermal stratification produces excessive thermal stresses at the pipe wall so as to yield thermal fatigue crack (TFC) accident. In the present study, effects of turbulence penetration on the thermal stratification into T-branches with square cross-section in the modeled ECCS are analysed numerically. $textsc{k}$-$\varepsilon$ model is employed to calculate the Reynolds stresses in momentum equations. Results show that the length and strength of thermal stratification are primarily affected by the leak flow rate of coolant and the Reynolds number of the main flow in the duct. Turbulence penetration into the T-branch of ECCS shows two counteracting effects on the thermal stratification. Heat transport by turbulence penetration from the main duct to leaking flow region may enhance thermal stratification while the turbulent diffusion may weaken it.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 추계학술대회 논문집
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• pp.380-384
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• 2010

A disturbance flow at piping bands and discontinuous regions such as a valve, a header has a intense broadband internal pressure field and a sound field which are propagated through the piping system The fields becomes the source of a vibration of this piping system. Intense broadband disturbance flow at a discontinuous region such as elbows, valves or headers generates an acoustical pulsation. The pulsation becomes the source of structural vibration at the piping system. If it coincides with the natural frequency of the pipe system, excessive vibration results. High-level vibration due to the pressure pulsation affects the reliability of the plant piping system. This paper discusses the high vibration and the branch vent pipe's failure of condensate-water supply piping system due to the effect of acoustical pulsations by flow turbulence from the flow control valves of globe type in a power site.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 Asia Navigation Conference
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• pp.56-62
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• 2006

This thesis researches on the application of computer, modern communication, GIS, GPS, AIS and World-Wide-Web in the field of navigation-aids information system, and has realized an integrated system consisted of navigation-aids information GIS platform, navigation-aids monitoring system and navigation-aids information distribution system. This system has strong integration capability, and has realized navigation-aids information distribution based on WEBGIS at the first time. It strongly promotes navigation-aids daily management and maintenance, and this system provides technique guarantee fur ships and marine departments to acquire navigation-aids information in time, by rule and line expediently.

• 한국정보통신학회논문지
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• 제5권4호
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• pp.699-705
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• 2001

본 논문에서는 DPSK변조 방식을 고려하여 나카가미-m 페이딩채널로 다중경로 페이딩을 모델화 하였으며, 각 브랜치에서의 나카가미 페이딩 지수(m)는 전파 환경에 따라 일정하지 않을 것이며 각 MRC 다이버시티의 브랜치에서 나카가미 페이딩 지수가 낮은 값을 가지는 브랜치를 제거할 경우 성능이 좋아질 수 있을 것이다. 따라서 본 논문에서는 나카가미 페이딩 지수를 임의의 값으로 주었을 경우 광대역 DS/ /CDMA 시스템에서 각각의 경로로 수신된 신호의 평균 SNR(signal to Noise Ratio)이 시스템의 BER에 미치는 영향을 컴퓨터 시뮬레이션을 통해 분석하고 나카가미 페이딩 지수(m)값이 낮은 브랜치를 제거한 경우의 광대역 DS/CDMA 셀룰라 시스템에서 각각의 경로로 수신된 신호의 평균 SNR(signal to Noise Ratio)이 시스템의 BER에 미치는 영향을 컴퓨터 시뮬레이션을 통해 분석하였다.

• International Journal of Computer Science & Network Security
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• 제21권1호
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• pp.12-18
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• 2021

This paper proposes a framework for the development of the health recommender system, designed to cater COVID-19 symptoms' self-assessment and monitoring as well as to provide recommendations for self-care and medical treatments. The aim is to provide an online platform for Patient Under Investigation (PUI) and close contacts with positive COVID-19 cases in Malaysia who are under home quarantine to perform daily self-assessment in order to monitor their own symptoms' development. To achieve this, three main phases of research methods have been conducted where interviews have been done to thirty former COVID-19 patients in order to investigate the symptoms and practices conducted by the Malaysia Ministry of Health (MOH) in assessing and monitoring COVID-19 patients who were under home quarantine. From the interviews, an algorithm using user-based collaborative filtering technique with Pearson correlation coefficient similarity measure is designed to cater the self-assessment and symptoms monitoring as well as providing recommendations for self-care treatments as well as medical interventions if the symptoms worsen during the 14-days quarantine. The proposed framework will involve the development of the health recommender system for COVID-19 self-assessment and treatments using the progressive web application method with cloud database and PHP codes.