• 대한토목학회논문집
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• 제9권1호
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• pp.11-23
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• 1989

본 논문에서는 guyed tower의 mooring system에 관한 수치해석결과를 제시하였다. 가상일의 원리와 유한요소법을 사용하여 기본식을 유도하였으며 케이블의 기하학적 비선형성을 고려하였다. 유체의 항력과 관성력은 Morrison식을 사용하여 고려하였으며 비선형 운동방정식의 해는 Newton-Raphson방법과 Newmark-${\beta}$ 방법을 사용하여 구하였다. Tower와 mooring line의 부착점에서의 초기경사각, 인장력, clump weight를 집중하중으로 이상화 시키는 종래의 해석방법의 문제점도 아울러 고찰하였다. 수치해석 예를 통하여 본 논문에서의 해석방법의 정당성을 입증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.707-710
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• 2002

A 120kV/70A high voltage switch has been installed at Korea Atomic Energy Research Institute in Taejon to supply power with Korea Superconducting Tokamak Advanced Research (KSTAR) Neutral Beam Injection (NBI) system. NBI system requires fast cutoff of the power supply voltage for protection of the grid when arc detected and fast turn-on the voltage for sustaining the beam current. Therefore the high voltage switch and arc current detection circuit are important part of the NBI power supply and there are much need for high voltage solid state switches in NBI system and a broad area of applications. This switch consisted of 100 series connected MOSFETs and adopted the proposed simple and reliable gate drive circuit without bias supply, Various results taken during the commissioning phase with a 100kW resistive load and NBI source are shown. This paper presents the detailed design of 120kV/70A high voltage MOSFETs switch and simple gate drive circuit. Problems with the high voltage switch and gate driver and solutions are also presented.

• 한국정밀공학회지
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• 제32권7호
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• pp.611-617
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• 2015

In the development of a vibration-based condition monitoring system in gearbox, one of the most important research topics is a quantitative analysis and test of the effect of gear damage on vibration of gearbox. This paper presents the evaluation result of vibration condition indicator according to the gear tooth damage through the vibration test of gearbox. The dynamic load test was performed with high speed railway (KTX)'s gearbox. The vibration of gearbox was measured according to a rotational speed change with the common gear fault modes, such as pitting and tooth breakage. The characteristics and the possibility of applying of vibration condition indicator on condition monitoring system were analyzed. As a result, the value of most condition indicator is gradually increased with the severity of gear faults. The NA6 indicator shows a low variation with the rotational speed change and high sensitivity in accordance with the gear fault.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.776-781
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• 2008

A ground heat exchanger in a GSHP system is an important unit that determines the thermal performance of a system and its initial cost. The Size and performance of this heat exchanger is highly dependent on the thermal properties. A proper design requires certain site-specific parameters, most importantly the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. This paper is part of a research project aiming at constructing a database of these site-specific properties, especially ground effective thermal conductivity. The objective was to develop and evaluation method, and to provide this knowledge to design engineers. To achieve these goals, thermal response tests were conducted using a testing device at nearly 150 locations in Korea. The in-situ thermal response is the temperature development over time when a known heating load imposed, e.g. by circulating a heat carrier fluid through the test exchangers. The line-source model was then applied to the response test data because of its simplicity. From the data analysis, the range of ground effective thermal conductivity at various sites is $1.5{\sim}4.0\;W$/mK. The results also show that the ground effective thermal conductivity varies with grouting materials as well as regional geological conditions and groundwater flow.

• 대한간호학회지
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• 제24권2호
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• pp.216-225
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• 1994

The cost of hospice care should be covered by the insurance system if it is to be promoted in our country and this, in turn, requires a proper method to the estimate of this cost. The purpose of this study was to set up the method to estimate the cost of hospice care. First the cost effectiveness of hospice care were studied. By tracing the activities of hospice nurses for a given period, all the relevant data such as the scope and load of activities as well as the cost were collected. Then these were analysed and compared with the data obtained from hospice and home care. The results showed that the cost of hospice care was the most economic, and indicate its qualification as .1n in-dependent system. The main part of the cost of hospice care was found to be the labor cost which was up to 83% of the total. Therefore a method to estimate the cost should reflect the real labor cost. Several methods have been proposed in the study in terms of unit labor cost, service time, material cost, and the weight of the labor cost. All variables, including the service time surveyed in this study, can easily be translated into numerical values and it would not difficult to estmate the cost of hospice care. Hence by letting the hospice care be insured, hospice care can be expected to function as a good alternative to the present medical system.

• 한국생산제조학회지
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• 제18권6호
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• pp.565-575
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• 2009

A forklift (also called a lift truck) is a powered industrial truck that is used to lift and transport materials. It has become an indispensable piece of equipment in manufacturing and warehousing operations. The modem forklift is equipped with automatic transmission to meet the requirement of loading and easy operation of the vehicle. This paper proposes the design of TECU(Transmission Electronic Control Unit) which is applied to PSD322-Axle transmission. Garofalo's control technique is generally used to the automatic transmission. We consider the work quality and market requirement that does not want to control engine throttle. This paper proposes new controller system which guarantees efficient speed changes with simple system. This new system does not control the engine throttle spontaneously. But it has the load of engine and vehicle as a maximum disturbance. The scope of the disturbance is limited to the stoll area of the torque converter. This paper proposes a ideal control commander that converges relative velocity of the input and ouput of a clutch into a zero. We design linear controller to execute the idea control commander. We applied the control algorithm to the forklift of PSD322-Axle type and the performance of this controller was verified.

• 설비공학논문집
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• 제21권9호
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• pp.496-504
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• 2009

In order to investigate the feasibility of a direct ice slurry transporting system for the purpose of district cooling, a case study of field application is performed. The research aims include the field measurement of ice packing factor, the performance of coldness delivery, and the branching characteristics of ice slurry. Two representative types of pipe branch are dealt with in this work. For the slurry flow with ice volume fraction of 0.16 or less, the pipe blocking due to aggregation is not observed. Based on the time-wise variation of temperature in the storage tank, a calculating method of ice packing factor is newly developed, which seems to be useful when the brine concentration is unknown. It is confirmed that the mass flow rate of ice slurry per unit cooling load is markedly reduced with increasing the ice content. The pumping power also decreases, but remains unchanged for high ice fractions. The distribution of ice particle before and after branching shows a good uniformity within the range of 5% difference, but yields a unique trend depending on the flow rate.

• 설비공학논문집
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• 제21권9호
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• pp.527-535
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• 2009

The aim of this study is to investigate the daily heating performance of ground source multi-heat pump system with vertical single U-tube type GLHXs, which were installed in a school building located in Cheonan. Daily average COP of heat pump unit on Jan. 12th, 2009 at heating mode was lower than it on Nov. 10th, 2008 and Dec. 15th, 2008, because of lower EWT of the outdoor heat exchanger and relatively smaller size of condenser and evaporator. But, the system COP on the former was higher than it on the latter because ground loop circulating pump was operated in rated speed. It is suggested that the new algorithms to control the flow rate of secondary fluid for GLHX according to load change have to be developed in order to enhance the performance of the system COP.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.285-290
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• 2009

The main thrust of this paper is to investigate acceptable supply air conditions of a dedicated outdoor air system (DOAS) for highrise apartment buildings. As for a typical $132-m^2$ apartment unit, it was assumed that centralized DOAS-Ceiling Radiant Cooling Panel was installed. Transient behavior and control characteristics of each system were modeled numerically using a commercial equation solver program. The optimized dew point temperature of the DOAS was discussed on the basis of the ASHRAE standard 62.1-2007 and the current Korean ventilation standard for apartments. It was found that the optimized dew point temperature of the DOAS supply air accommodating total latent load of a space is $11-12^{\circ}C$ and the appropriate supply air temperature of the DOAS is $11-12^{\circ}C$ in cooling period and neutral temperature of $18-20^{\circ}C$ in intermediate period.

• 전력전자학회논문지
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• 제19권4호
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• pp.303-311
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• 2014

This paper shows the test result of 2MVA BESS(Battery Energy Storage System) with wind-turbine in micro-grid of the Gapado. To implement of micro-grid with BESS, characteristics of generator and customer load in grid are considered. Also, to operate of 2-parallel PCU(Power Conversion Unit) in BESS, the droop control is adopted with operating mode of grid independent. Performances of BESS with wind-turbine were verified by analysis of power quality such as voltage harmonics, ratio of voltage and frequency regulation, and by measurement of waveform such as output voltage and current.