• 한국농공학회논문집
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• 제60권6호
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• pp.97-109
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• 2018

The LDC (Load Duration Curve) method can analyze river water quality changes according to flow rate and seasonal conditions. It is also possible to visually recognize whether the target water quality is exceeded or the size of the reduction load. For this reason, it is used for the optimal reduction of TPLCs and analysis of the cause of water pollution. At this time, the flow duration curve should be representative of the water body hydrologic curve, but if not, the uncertainty of the interpretation becomes big because the damaged flow condition is changed. The purpose of this study is to estimate the daily mean flow of the unit watershed using the HSPF model and to analyze the difference of the flow duration curves according to the cumulative daily mean flow rate using the NSE technique. The results show that it is desirable to construct the flow duration curve by using the daily average flow rate of at least 5 years although there is a difference by unit watershed. However, this is the result of the water bodies at the end of Han River basin watershed, so further study on various water bodies will be necessary in the future.

• 대한기계학회논문집A
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• 제26권3호
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• pp.537-543
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• 2002

This paper examines a new in-process measurement system for the measurement of micro-defects on the surfaces of brittle materials by using the AFM (Atomic Force Microscopy). A new AFM scanning stage that can also perform nano-scale bending of the sample was developed by adding a bending unit to a commercially available AFM scanner. The bending unit consists of a PZT actuator and sample holder, and can perform static and cyclic three-point bending. The true bending displacement of the bending unit is approximately 1.8mm when 80 volts are applied to the PZT actuator. The frequency response of the bending unit and the stress on the sample were also analyzed, both theoretically and experimentally. Potential surface defects of the sample were successfully detected by this measurement system. It was confirmed that the number of micro-defects on a scratched surface increases when the surface is subjected to a cyclic bending load.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.541-545
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• 2008

Particulate matter (PM) is one of the major indoor air pollutants especially in the subway station in Korea. In order to remove PM in the subway station, several kinds of PM removal system such as roll-filter, auto-washable air filter, demister, and electrostatic precipitator re used in the air handling unit (AHU) of subway station. However, those systems are faced to operation and maintenance problems since the filter-regeneration unit consisting of electrical or water jet parts is malfunctioned due to the high load of particulates and the filter material needs periodic replacement. In this study, we surveyed the particle removal systems in order to develop the new system of particle removing can be adopted in the current AHU of subway station.

• Steel and Composite Structures
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• 제20권4호
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• pp.869-887
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• 2016

The socket-spigot template supporting system is widely used in engineering applications in China. As a newer type of support structure, there has been growing research interest in its bearing capacity. In this paper, four vertical bearing capacity tests were carried out on the basic mechanical unit frame of a socket-spigot template supporting system. The first goal was to explore the influence of the node semi-rigid degree and the longitudinal spacing of the upright tube on the vertical bearing capacity. The second objective was to analyze the displacement trend and the failure mode during the loading process. This paper presents numerical analysis of the vertical bearing capacity of the unit frames using the finite element software ANSYS. It revealed the relationship between the node semi-rigid degree and the vertical bearing capacity, that the two-linear reinforcement model of elastic-plastic material can be used to analyze the socket-spigot template supporting system, and, through node entity model analysis, that the load transfer direction greatly influences the node bearing area. Finally, this paper indicates the results of on-site application performance experiments, shows that the supporting system has adequate bearing capacity and stability, and comments on the common work performance of a socket and fastener scaffold.

• Journal of Biosystems Engineering
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• 제43권1호
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• pp.1-13
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• 2018

Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission's power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission's gear, bearing, and oil seal. The motor's power was input in the transmission's input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and transmission. Results: The loss of power in the transmission efficiency test of the driving power unit was 6.0-9.7 kW based on all gear steps. This loss of horsepower was equal to 11-18% of the input power (52 kW). The transmission efficiency of the driving power unit was 81.5-89.0%. The noise of the driving power unit was 50-57 dB at 800 rpm, 70-77 dB at 1600 rpm, and 76-83 dB at 2400 rpm. The axle load test verified that the input torque and axle revolutions were constant. The results of the forward-reverse clutch performance test revealed that hydraulic pressure and torque changes were stably maintained when moving forward or backward, and its operation met the hydraulic design standards. Conclusions: When comprehensively examined, these research results were similar to the main driving power transmission systems from USA and Japan in terms of performance. Based on these results, tractor prototypes are expected to be created and supplied to farmhouses after going through sufficient in-situ adaptability tests.

• 환경영향평가
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• 제27권6호
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• pp.704-716
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• 2018

본 연구는 진위천 단위유역의 수질오염총량제도에 따른 유량 및 수질 특성을 정확히 파악하고 목표 수질을 달성하기 위하여 수질 개선이 우선적으로 필요한 총량 지점을 선정하여 관리 방안을 제시하는 것이다. 진위천 단위유역의 2014년부터 2016년까지 14개 총량 지점을 대상으로 유량 및 수질 특성, 통계 분석, 유달부하량 및 유달부하 밀도 산정, 하천 등급화 등을 평가하였다. 진위천 단위유역의 유량은 평균 $22.411m^3/s$이고 황구지천의 유량이 32.8%를 차지하였으며 지류 하천에 따른 공간적으로 수질특성이 뚜렷하게 나타났다. 주성분 분석 결과 오산천과 황구지천은 유기오염 간접지표 및 계절적 요인, 성은천은 유기오염 간접지표 요인, 관리천은 계절적 요인이 수질에 영향을 미치는 것으로 분석되었다. 유달부하량 산정 결과 HG-3 지점에서 6,470.4 BOD kg/day, 6,846.7 TN kg/day로 높게 나타났으며 유달부하 밀도는 HG-4 지점에서 $220.9BOD\;kg/day/km^2$, $22.4TP\;kg/day/km^2$로 높게 나타났다. 하천 등급화 방법을 이용한 진위천 단위유역의 수질 개선이 우선으로 필요한 총량 지점은 HG-3 지점으로 나타났다.

• Journal of Electrical Engineering and Technology
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• 제4권4호
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• pp.443-450
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• 2009

This paper deals with the design of decentralized controller for load-frequency control of interconnected power systems with superconducting magnetic energy storage units and Governor Dead Band Nonlinearity using Multi-Objective Evolutionary Algorithm. The superconducting magnetic energy storage unit exhibits favourable damping effects by suppressing the frequency oscillations as well as stabilizing the inter-area oscillations effectively. The proposed control strategy is mainly based on a compromise between Integral Squared Error and Maximum Stability Margin criteria. Analysis on a two-area interconnected thermal power system reveals that the proposed controller improves the dynamic performance of the system and guarantees good closed-loop stability even in the presence of nonlinearities and with parameter changes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.354-356
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• 2000

This paper describes the strategy of a daily optimal operational scheduling on cogeneration systems with each other generation mode. The cogeneration systems consists of three generators. auxiiiary devices which are three auxiliary boilers, two waste boilers and three sludge incinerators. One unit that using the back pressure turbin generates the electrical and the thermal energy. The other two units that using the extraction condensing turbine generate the energy. Auxiliary devices operate to supplement the thermal energy to the thermal load with three units. The cogeneration system has a large capacity which is able to supply enough the thermal energy to the thermal load, however the electric power generated is insufficient to satisfy the electrical load. Therefore the insufficient electric energy is supplemented by buying electrical energy from the utility. Simulation was carried out using optimization toolbox. The result reveals that the proposed modeling and strategy can be effectively applied to cogeneration systems with each other generation mode.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.210-213
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• 1999

A battery is the device that transforms the chemical energy into the direct-current electrical energy directly without a mechanical process. Unit cells are connected in series to obtain the necessary voltage, while being connected in parallel to organize capacity for load current and to decrease the internal resistance for corresponding the sudden shift of the load current. The circular-current, however, could be occurred when the system is driven in parallel. As a result, the new batteries are heated by over-change and discharge, and the over charge current makes to increase the rust of the positive grid and consequently the shortened life of the new batteris would be shown. In this paper, the internal resistance of charge and discharge will be balanced, through inserting the resistance into the system by way of calculation of the changed amount of internal resistance.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 춘계학술대회 논문집
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• pp.107-112
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• 1997

In this study of made Autmation system is moving linear transfer system for mainly forming of small electronic unit and other at press line. This system for loading and unloading a workpiece has been installed in a press in order to load and unload a workpiece from a press die. Main Control method be used PLC. It took data of input from each sensor and send signal of output to actuator by sequence program also, we try to Characteristics test of this system has good condition when operating with raser measurmant.