• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.11
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• pp.20-24
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• 1997

We have successfully fabricated high power (~20W) laser diode array, which are useful for pumping Nd:YAG lasers. The laser diode aray has 20 100.mu.m-wide cahnnels of which space was adjusted to 350.mu.m to improve thermal characteristics. And channel width is 100.mu.m. For an uncoated LD array, the output power of 15.66W has been obtained at 41A under quasi-CW operation, which results in about 0.42W/A slope efficiency. After aR(5%) and HR (95%) coatings on both facets, the output power was improved up to 21.18W at 40A under the same operation as above and the slope efficiency was 0.795W/A. On the other hand, by using a near field measurement system consisting of objective lens, eyepiece, CCD camera and image processing board, the typical near field patten of 1*20 LD array was observed.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.289-293
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• 1993

A Nd:YLF laser pumped by a CW GaAlAs laser diode(LD) at 792 nm has been designed and fabricated. The output power was investigated as a function of LD spectrum and pump power. A folded laser resonator was desinged to compensate for the astigmatism produced at the Brewster surface of Nd:YLF rod. We obtained output power of CW 1.1 Watt when the pumping power was 2.8 Watt and the output wavelength of LD was temperature tuned to the peak absorption line of Nd:YLF. The overall efficiency was 39 % and slope efficiency was 41 %.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.5
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• pp.50-57
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• 2008

In this paper, a high-efficiency charge pump for use in CMOS image sensor(CIS) is proposed. The proposed charge pump pursues high pumping efficiency by minimizing the switching and reversion losses by taking advantage of operation characteristics of CIS. That is, the proposed charge pump minimizes the switching loss by dynamically controlling the size of clock driver, pumping capacitor, and charge transfer switch based on the operation phase of CIS pixel sensor. The charge pump also minimizes the reversion loss by guaranteeing a sufficient non-overlapping period of local clocks using a tri-state local clock driver adapting the schmitt trigger. Comparison results using a 0.13-um CMOS process technology indicate that the proposed charge pump achieves up to 49.1% reduction on power consumption under no loading current condition as compared to conventional charge pump. They also indicate that the charge pump provides 19.0% reduction on power consumption under the maximum loading current condition.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.10a
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• pp.95-104
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• 2006

A floating-type wave power pump is a device which sends air into water by using wave power. The floating-type wave power pump has the new configuration composed of a curved surface reflection board, a slope, and phase plates. As a result of a water-tank experiment it turned out that the floating-type wave power pump with a curved surface reflection board and a slope raised power and efficiency in the wide wavelength waves. The result of a marine experiment was also preferable. The floating-type wave power pump sends air into the sea by using wave power, so it can be used for the improvement of marine environment. In addition, the floating body constituted of a curved surface reflection board, a slope, and phase plates, is effective as a device to utilize the energy of a wave. Therefore, it can be widely used for a wave power generation, pumping up deep seawater.

• Journal of Korea Water Resources Association
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• v.52 no.12
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• pp.975-984
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• 2019

As an essential prerequisite for systematic and integrated management of river water, it is necessary to secure the basic data such as discharge supplied to the river and released from the river. Under the current permit system for river water use, 59.1% of licensed facilities were found to have no discharge meters in 2017, especially for agricultural water, which makes it difficult to secure reliable data as a large portion of the reports are voluntarily reported by users. In this study, the indirect discharge measurement method of calculating the discharge through the power usage of the pumping station was applied to secure reliable discharge data. In particular, focusing on the fact that the discharge calculated by the power usage method differed with the actual discharge according to the level of the river, the study was conducted on improving the power usage method reflecting the river water level and improving the accuracy of discharge data. Analysis of the discharge calculated using the power usage method considering river water level using the correlation analysis method such as regression analysis, percent difference, root mean square error etc. confirmed that the results are not high compared to the conventional power usage method, but are slightly more approximated to the actual discharge. Therefore, although reliable discharge data can be obtained from the existing power usage method, it is expected that more accurate data on intaking water of river water can be obtained if the improved power usage method is used at points where the variation in the water level of the river is large.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1304-1310
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• 2015

In remote islands, due to expense of existing generation systems, installation of photovoltaic cells (PVs) and wind turbines has a chance of reducing generation costs. However, in island power systems, even short-term power fluctuations change the frequency of grids because of their small inertia constant. In order to compensate power fluctuations, the authors proposed the power consumption control of pumps which send water to tanks. The power control doesn’t affect water users’ convenience as long as tanks hold water. Based on experimental characteristics of a pump system, this paper shows methods to determine reference power consumption of the system with compensation for short-term PV fluctuations while satisfying water demand. One method uses a PI controller and the other method calculates reference power consumption from water flow reference. Simulations with a PV and a pump system are carried out to find optimum parameters and to compare the methods. Results show that both PI control method and water flow calculation method are useful for satisfying the water demand constraint. The water demand constraint has a little impact to suppression of the short-term power fluctuation in this condition.

• Journal of Biosystems Engineering
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• v.4 no.1
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• pp.67-74
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• 1979

This survey was carried out to grasp the actual condition of a power tiller utilization . Now, the power tiller has become the leading machinery in the field of agriculture throughout the country . Two hundred farm houses, located in the provincial districts of Kimcheon and kum0rung, hav etaken part in the survey from October 1, 1976 to September 30, 1977. The results are summarized as follows . 1. The average size of cultivated land of a farm household in the districts surveyed was 1.77ha which was bigger than that of whole country. And the average age of power tiller drivers was analyzed in which only 105 of total drivers was on their 30's. 2. Distribution of a power tiller utilization was appeared to be 34.4% for transporting , 24% for tilling , 23% for pumping , 11.5% for threshing and 6.6% for spraying. 3. Frequency of a power tiller utilization was high during the month of June, July and October while it was low during February and December . 4. Distribution of repairing cost was 8.5% for trailer, 7.1% for throttle lever and 6.7% for casket, respectively. The annual cost for repairing was 5,290 won.5. The annual cost for using a power tiller was composed of 51.5% of fixed cost and 48.5% of operating cost. 6. Economic analysis showed that it was not economically practical for individual ownership of a power tiller on the farm surveyed. Therefore, custom operation and joint ownership by a few farmers were recommended.

• Korean Journal of Metals and Materials
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• v.49 no.9
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• pp.708-714
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• 2011

The premature failure of a servovalve used for six months in a thermal power plant has been analyzed. The servovalve was made of stainless steel, containing 16Cr-0.44Mo, along with other elements. An overload of oil-supply pumping and an abnormal increase in the oil flux were observed during operation. A study revealed that erosion and corrosion could be the main causes of the failure. The visual examination of the servovalve did not show any appreciable damage. However, corrosion and erosion of the servovalve were observed using scanning electron microscopy (SEM). Upon examination of the servovalve, the corrosion was found to have occurred throughout the bushing and spool; however, erosion occurred at only the edge-side. In addition, the condition of the electrohydraulic control system (EHC) oil was investigated with respect to its satisfaction of the management standard.

• Journal of the Korean Society of Groundwater Environment
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• v.2 no.1
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• pp.30-37
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• 1995

In the tidal compartment, the hydraulic head is affected by the stage of tidal rivers. For groundwater or construct works, head variation of groundwater should be considered in zone of this aquifer. A numerical analysis is performed which has an 1-dimemsional explicit finite difference scheme to show the head variation of groundwater with tidal stage and hydraulic conductivity, etc. The stability of the numerical scheme is validated by using the analytic solution. The head variation of groundwater is observed for various tidal amplititude and hydraulic conductivity, mean hydraulic gradient and pumping at any point. The range of influence corresponding to the parameters used in this study is about 60m. This value is not beyond a wave length (equation omitted). There was a pumping at a constant rate out of aquifers affected by tide and not affected by tide. Because pumping head in aquifer affected by tide is short, the expense of electric power is economized in this zone. These results are applicable to trace of contaminant transport, efficient operation of groundwater, and examination of the safety and stability of works in the tidal compartment.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.159-164
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• 2001

An extensive range of pumping facilities are employed in the regional water supply system in metropolitan areas, and optimization and the systematic combination of the pump facilities have direct bearing on the stability and economy of the water supply system concerned. These systems must be able to guarantee stability, efficiency and offer high reliability. Preparation of metropolitan area regional water supply system construction project must include a basic plan which takes into account the suitability of pumping facilities to be used, the environment in which facilities will be installed, man-power requirements and basic operational and management policies. This paper contains over-all analysis of the management of metropolitan area regional water supply systems and highlights the cause of Inefficiency and energy waste and puts forward a remedial plan of action. In addition, pump/motor specification programs were developed using Visual Basic to assist selection of the same.