• 전력전자학회논문지
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• 제7권4호
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• pp.339-345
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• 2002

본 논문에서는 입력 전압 DC 24 [V]로 출력 전압 AC 220 [V] 정현파 출력을 낼 수 있는 인버터 기능과 충전 전압 및 충전 전류를 조정할 수 있는 DC 24 [V]용 자동 충전기 기능을 동시에 가지는 전원 장치의 시작품을 제작하고 실험을 통해서 타당성을 검증하였다. 본 논문에서 제안하는 전원장치는 두 기능을 동시에 가지면서도 전력 수수의 라인을 하나의 라인으로 회로 구성을 실현하여 스위치 소자 및 고주파 트랜스를 인버터 동작이나 충전기 동작 시에 겸용으로 사용함으로서 인버터나 충전기 각각의 제품을 구성하는데 사용된 제품 구성품에 비하여 매우 경제적이며, 저가의 마이크로 프로세스 (PIC16C74)를 사용하여 스위칭 동작 및 시？스 회로의 동작을 제어함으로서 전 체적인 제품의 구성을 간략화 하였다.

• 동력기계공학회지
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• 제20권2호
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• pp.32-42
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• 2016

Under part load condition of spark-ignition engine, pumping loss had great effect on engine efficiency. To reduce pumping loss, the study designed spark-ignited engines to make direct spray of gasoline to combustion chamber. In spark-ignited direct-injection engines, ignition probability is important for successful combustion and flame propagation characteristics are also different from pre-mixed combustion. This study designed a visualization testing device to study ignition probability of spark-ignited direct-injection LPG fuel and combustion flame characteristics. This visualization device consists of combustion chamber, fuel supply system, air supply system, electronic control system and data acquisition system. Ambient pressure, ambient temperature and ambient air flow velocity are important parameters on ignition probability of LPG-air mixture and flame propagation characteristics, and the study also found that sprayed LPG fuel can be directly ignited by spark-plug under proper ambient conditions. To all successful cases of ignition, the study recorded flame propagation image in digital method through ICCD camera and its flame propagation characteristics were analyzed.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.1254-1259
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• 2009

The purpose of this study is to analyze elemental maintenance costs for educational buildings. The adapted research method selected three school buildings in Seoul as BTL projects. On the basis of the selected case, the study suggested a model to establish a system for each parts and to estimate analyzed maintenance costs through that system. According to the analysis, the study proposed a partial maintenance costs standard and analyzed proper maintenance costs. The results of this study are as follows 1) The system is divided into 8 large-groups and 24 small-groups for the analysis elemental maintenance costs. 2) The average rations followed by analysis of partial maintenance costs of the three school buildings are as followings, the total maintenance costs are analyzed 3,992 million won and each part of average rations is exterior of building 10.9%, interior of building 41.58%, electricity & fire fighting facility 14.22%, water supply & healthy facility 11.39%, heating & water supply facility 12.93%, landscape 6.3%, civil engineering works 2.69%.

• 현장농수산연구지
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• 제18권1호
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• pp.3-12
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• 2016

Vitamin D plays a vital role in maintaining blood concentrations of Ca and P. In lipid metabolism, vitamin D is also known to negatively affect the development of adipocytes, but it has received little attention with regard to improve marbling score in beef cattle via restricting its supply. Recently, the method of feeding fat soluble vitamins(including vitamin D)-deficient diets in Korean native cattle (Hanwoo) has been spread by feed companies and TMR plants. But proper guidelines in feeding vitamin D-deficient diets should be provided, otherwise it can adversely affect the health of cattle. To maximize marbling score, a controlled level of vitamin D in blood needs to be maintained and the proper period for feeding vitamin D-deficient diets should be provided. This review was conducted to highlight the regulatory effects of vitamins D on adipocyte differentiation, and provide information on improving beef quality grades in relation to feeding vitamin D-deficient diets in beef cattle.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2008년도 정기학술발표대회 논문집
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• pp.851-854
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• 2008

본 연구는 군관사 건축물의 적정 유지관리비용의 산정을 위하여 수행하였다. 이를 위해 BTL방식으로 발주된 5개의 군관사 건축물을 사례대상으로 선정하였으며, 사례대상 건축물의 초기투자비용을 공종별로 분류한 후 장기 수선비용을 산정하였다. 또한 이렇게 산정된 공종별 장기수선비용을 공동주택 장기수선충당금 산정방법과 현가분석 산정방법을 준용하여 비교 분석하였다. 상기 같은 목적과 방법에 따라 진행된 본 연구의 결론을 요약하면 다음과 같다. 첫째, 초기투자비는 $m^2$당 건축 13,331,712원(79%), 토목 588,125원 (3%), 조경 285,658원(2%), 전기소화설비 760,549원(5%), 난방급탕설비 906,059원(5%), 급수위생설비 960,759원(6%)이며 초기투자비의 총 합계는 16,832,862천원으로 분석되었다. 둘째, 산정된 공종별 초기투자비를 바탕으로 공동주택의 장기수선비용을 산정한 후 공동주택 장기수선충당금 산정방법과 현가분석 산정방법을 각각 준용하여 적정 유지관리비용을 산정하였다.

• 한국산학기술학회논문지
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• 제15권9호
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• pp.5893-5898
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• 2014

본 논문은 연료비를 최소화 할 수 있는 2차전지 전력저장장치(BESS: Battery Energy Storage System)와 풍력-디젤 복합발전시스템으로 구성되는 독립형 마이크로그리드을 모델링하는 방법과 그 운전제어 알고리즘을 제안하였다. 먼저, 부하변동 및 풍속변동에 따른 주파수와 전압을 일정하게 제어할 수 있는 양방향 DC/AC 컨버터의 BESS를 모델링하고, 디젤발전기는 공급전력의 부족 및 BESS의 충전시에만 가동하도록 하는 운전제어알고리즘을 제안한다. 그리고, 제안된 모델링 방법과 운전제어알고리즘을 독립형 마이크로그리드에 적용한 결과, 풍속 및 부하변화에 대하여 주파수와 전압변동이 적정범위내로 유지할 수 있음을 증명할 수 있었다.

• 한국농공학회논문집
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• 제50권1호
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• pp.95-106
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• 2008

Eco-friendly material and implementation methods have become important along with the existing standardized maintenance concept for the irrigation and flood control. However, the intrinsic function of the hydraulic structure is water supply and disaster prevention. Therefore, the material and work methods should be considered both eco-friendliness, durability and safety which are prerequisite elements to maintain the engineering function. In this study eco-friendly material and work methods would be classified into the vegetation based system, eco-friendly concrete system and stone-material system according to the characteristics of material. The quality standard for durability followed KS specification and related regulations. The quality standard for safety and eco-friendliness was set after literature review, and the database was developed using the standard. The structure applicable to onsite - the eco-friendly material and work method were classified based on the function and material of the hydraulic structure. Finally, database has been established for convenient management and selection of the proper material and work method. The eco-friendly material and work method could be searched easily for the convenience of the users, and the web-based data system has been developed for continuous registration of the material and work methods to be developed in the future.

• Journal of Power Electronics
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• 제19권1호
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• pp.234-243
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• 2019

Studying the control strategy of a microgrid under the load unbalanced state helps to improve the stability of the system. The magnitude of the power fluctuation, which occurs between the power supply and the load, is generated in a microgrid under the load unbalanced state is called negative sequence reactive power $Q^-$. Traditional power distribution methods such as P-f, Q-E droop control can only distribute power with positive sequence current information. However, they have no effect on $Q^-$ with negative sequence current information. In this paper, a stationary-frame control method for power sharing and voltage unbalance compensation in islanded microgrids is proposed. This method is based on the proper output impedance control of distributed generation unit (DG unit) interface converters. The control system of a DG unit mainly consists of an active-power-frequency and reactive-power-voltage droop controller, an output impedance controller, and voltage and current controllers. The proposed method allows for the sharing of imbalance current among the DG unit and it can compensate voltage unbalance at the same time. The design approach of the control system is discussed in detail. Simulation and experimental results are presented. These results demonstrate that the proposed method is effective in the compensation of voltage unbalance and the power distribution.

• Korean Journal of Geomatics
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• 제3권2호
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• pp.107-114
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• 2004

The National Geographic Information Institute (NGII) in korea, through the National Geographic Information System (NGIS) Program, has prepared to generate and disseminate digital elevation data for Korea. This is a pilot research to propose a policy for production, maintenance, and supply of Korea Digital Elevation Data(KDED). Customer demands for accuracy and resolution of DEM was surveyed through a questionnaire. In order to investigate the quality, the technical efficiency and the production cost, a tentative DEM in a small test site was generated based on digital topographic maps (original paper map scale 1:5,000), analytical plotter, and LIDAR. The Accuracy standard for KDED was derived based on source data generation methods. As a result of this research, a uniformly spaced grid model was recommended for KDED. Its preferable grid space is 5m in urban areas and its vicinity, and 10m in field and mountainous area. LIDAR has been valuated as a proper KDED generation method fulfilling customers' demands for the accuracy.

• 한국공작기계학회논문집
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• 제13권6호
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• pp.74-80
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• 2004

An internal finishing process by the application of magnetic abrasive machining has been developed as a new technology to obtain a fine inner surface of pipe. In this paper, the finishing process of a non-ferromagnetic pipe by a static magnetic field method is introduced and its finishing characteristics is discussed with effective factors by various experiments. From these experimental results, it is found that the magnetic abrasives inserted in the pipe are arranged according to the magnetic force line. Through the experimental, it is possible to estimate the proper supply volume of the abrasive, which in proportional to the diameter of pipe.