• Nuclear Engineering and Technology
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• 제40권6호
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• pp.467-476
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• 2008

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (RRS) with an exergetic equivalent cooling power of 9 kW at 4.5 K without liquid nitrogen ($LN_2$) pre-cooling has been manufactured and installed. The main components of the KST AR helium refrigeration system (HRS) can be classified into the warm compression system (WCS) and the cryogenic devices according to the operating temperature levels. The process helium is compressed from 1 bar to 22 bar passing through the WCS and is supplied to cryogenic devices. The main components of cryogenic devices are consist of cold box (C/B) and distribution box (D/B). The C/B cool-down and make the various cryogenic helium for the KSTAR Tokamak and the various cryogenic helium is distributed by the D/B as per the KSTAR requirement. In this proceeding, we will present the commissioning results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• Journal of Biosystems Engineering
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• 제6권1호
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• pp.60-72
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• 1981

This study was carried out to find out the effects of the sheaf size of paddy harvested by the binders on the threshing performance, load characteristics and power requirement of an auto-feed thresher. The results of the study are summarized as follows: 1. The seperating performance of the thresher appeared to be satisfactory for all the sheaf sizes although the amount of rubbishes and empty grains slightly increased with the sheaf size of paddy. 2. There was no significant difference in grain output quality of the thresher among the three sheaf sizes. However, the amount of grains left unthreshed increased with the sheaf size. In the case of the largest sheaf size with the feed rate of 780kg/h, it exceeded the limit set by the national inspection regulations. 3. The position of the feed-chain rail gave a significant effect on the power requirement of the thresher. At the feed rate of 780kg/h, the net power required to convey sheafs through the feed chain was in the range of 0.37 to 0.50 PS for the middle and lowest position of feed-chain rail, and there was no significant difference among the sheaf sizes. At the highest position, however, it appeared that the smallest sheaf required more power than the others. The net power requirements at this position were 1.03, 0.59. 0.65 PS for the smallest, medium and largest sheafs respectively. 4. The torques of both the thresher and the engine shaft increased with the feed rate and were not affected by the sheaf size for the lower two feed rates of 520 and 780kg/h. At the highest feed rate of 1,040 kg/h, however, they were affected by the sheaf size. In this case, the medium sheaf size gave lower values than the others. 5. The variations in the thresher and the engine torque increased with the feed rate and were not affected by the sheaf size for the feed rate of 520kg/h. At the feed rate of 780kg/h, however, they increased with sheaf size. And at the feed rate of 1,040 kg/h, the torque variations increased greatly for all the sheaf sizes due to an over-load operating condition. 6. It appeared that the average and maximum power requirements of the thresher increased with the feed rate. But, there was no significant difference in power requirement among the sheaf sizes for the lower two feed rates. 7. The threshing efficiency of the thresher was in the range of 214-249 kg/ps.h with the feed rates of 520 and 780 kg/h, and it was not affected by both the sheaf size and the feed rate. At the feed rate of 1,040 kg/h, however, it decreased to as low as 171-174 kg/ps.h because of a sudden increase in power requirement. 8. The average power requirements of the engine were slightly higher than those of the thresher due to the slippage of flat belt between the thresher and engine. It appeared that power transmission from the engine to the thresher was maintained properly since slippages were moderately low with the range of 2.78 to 6.51% throughout the tests. 9. The specific fuel consumption of the engine (diesel 8PS) decreased as the feed rate increased. However, there was no significant reduction in specific fuel consumption as the feed rate increased above 780 kg/h.

• Journal of Biosystems Engineering
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• 제9권2호
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• pp.1-7
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• 1984

The engines mounted on power-tillers are used as power source in various kinds of works such as plowing, harrowing, transporting, spraying, water pumping and threshing, etc. But the engines have not been used effectively from a standpoint of fuel consumption because of lack of proper power transmission system and lack of understanding of fuel consumption characteristics of the engines. Therefore, this study was attempted to establish proper power transmission system between the power-tiller engines and various implements. In order to accomplish the above objective, firstly, power requirement and pulley sizes for various implements, which are driven by the power-tiller engines, were investigated to find out whether the power transmission system is proper. Secondly, partload variable engine-speed test was conducted for 3 different sizes of diesel engines to measure to specific fuel consumption. Thirdly, the present power transmission systems were analyzed in terms of specific fuel consumption, and proper power transmission systems were suggested for various implements. The results of this study are summarized as follows: 1. Power requirement for each fixed-type implement of power-tiller varied from 1.5 ps to 11 ps according to its type and operating conditions, but generally in the range of 2.5 ps to 7 ps. 2. Each power tiller and implement were equipped with only one size of pully with few exeptions. With the present power transmission systems, the engines can't be utilized effectively in terms of fuel economy. The pulley size of engine or implement should be diversified to provide the optimum engine speed for different implements. 3. For a diesel eninge with the rated power output of 6 ps, the optimum engine speed to minimize specific fuel consumption was 2200 rpm for the power reguirement in the range of 6 ps or more, 1700 rpm in the range of 4 to 6 ps, and 1200 rpm in the range of 4 ps or less. 4. For a diesel engine with the rated power output of 8 ps, the optimum engine speed was 2200 rpm for the power requirement in the range of 7 ps or more, 1700 rpm in the range of 4.8 to 7 ps, and 1200 rpm in the range of 4.8 ps or less. 5. For a diesel engine with the rated power output of 10 ps, the optimum engine speed was 2200 rpm for the power requirement in the range of 8.4 ps or more, 1700 rpm in the range of 5.4 ps to 8.4 ps, and 1200 rpm in thr range of 5.4 ps or less. 6. Provided the existing implements are dirven by 8 ps diesel engines, the optimum size of engine pulley should be larger than 120mm for the works of requiring less than 4 ps and 90-110mm for the works requiring 4.5-6.5 ps in order to minimize fuel consumption.

• 한국IT서비스학회지
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• 제18권5호
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• pp.53-70
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• 2019

As information security becomes more important as the fourth industrial revolution gradually emerges, an efficient and effective way to find vulnerabilities in information systems is becoming an essential requirement of information security. As the point of the protection of current information and the protection of the future industry, the Korean government has paid attention to the bug bounty, which has been recognized for its efficiency and effectiveness and has implemented through the Korea Internet Security Agency's S/W vulnerability bug bounty program. However, there are growing problems about the S/W vulnerability bug bounty program of the Korea Internet Security Agency, which has been operating for about 7 years. The purpose of this study is to identify the problems in Korean bug bounty policies through the characteristics of the bug bounty program, and to suggest the direction of the government's policy to activate the bug bounty like changes in the government's approach utilizing the market.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.375-379
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• 1990

A microprocessor-based multi-function switchgear for the protection, measurement and control of the power system is presented. For the extraction of the RMS values of the fundamental components of current and voltage signals, a simple digital filter based on cross-correlation of the distorted signal with even and odd heptagonal waves is used. The frequency response of this filter is almost identical to that of the filter based on the discrete fourier transform, while its computational requirement is far less. For the time delay element relaying, a new log-table based relaying algorithm is suggested. The suggested use of the heptagonal wave cross-correlation digital filter algorithm and a new relaying algorithm reduce the computational needs so drastically that all functions of the switchgear can be implemented on the microprocessor system. Real time testing of the implemented daboratory prototype show good practical response under different operating conditions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1920-1923
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• 1991

An online RF power measurement is needed for the full-bridged MOS-FET RF power inverter because the output current and/or voltage waveform is other than sinusoidal. In order to satisfy the requirement, the online measurement of the output power of this type of RF power inverter by the use of the PC-98 personal computer has been presented. The current and voltage waveforms are sensed by the digital oscilloscope probes so as to obtain the instantaeous power and they are entered into the PC98 personal computer so as to average the instantaneous powers. The RF power of up to 1 kw at 1 MHz measured for the power inverter at the output transformer. This method was confirmed to be applied to evaluate the load resistance change with temperature.

• 항공우주기술
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• 제7권2호
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• pp.196-204
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• 2008

현대의 민간용 회전익 항공기는 모든 기상조건에서 비행할 수 있는 운용 능력이 요구되고 있으며 이에 따라 결빙 환경에서의 회전익 항공기 운항 안전과 인증에 대한 관심이 대두되고 있다. 또한, 항공기의 결빙은 항공기 운항 안전에 있어 가장 다루기 어렵고 위험한 요인 중에 하나이며 실제 사고의 원인이 되기도 한다. 본 연구에서는 회전익 항공기의 결빙 인증 요구조건에 대한 고찰을 수행함으로써 회전익 항공기 형식증명 시 어떻게 결빙을 입증할 것인가에 대한 제시와 함께 결빙에 대해 고려하여야 할 사항들에 대해 논하였다.

• Asia pacific journal of information systems
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• 제11권1호
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• pp.155-173
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• 2001

Assessing user information requirements is one of the most important issues in building Executive Information Systems. Application of the Balanced Score Card method as a tool for strategic planning and performance measurement has been increasing recently in various fields. However there has been meager attempt to apply the method to user requirement analysis, in particular, for small and medium sized companies. This study surveyed 79 executives of small and medium sized companies in Korea. The study founds the applicability of BSC for analyzing user requirements of EIS, in terms of financial, customer, internal process, learning and growth perspectives. The paper also suggested several guidelines for using BSC to improve user satisfaction to the practitioners who are operating or planning to build EIS in the small and medium sized companies.

• Asia pacific journal of information systems
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• 제4권2호
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• pp.83-130
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• 1994

Software development of large scale program such as Operating System or University Total Information System is lengthy and costly process. In order to reduce cost, time and risk, there is currentry general acceptance of the need for Software Reuse System during the whole development cycles. In this paper, (from a practical point of view), the problem of existing reuse system methodology is analyzed and an implement method of software reuse system is presented. Also using this method Application Program Reuse System(APRS) which supports all phase of software life cycles is designed and implemented. This application program reuse system which is based on common language is considerably shown to reduce communication Error of requirement specification between systems analyst and end-user.

• 비파괴검사학회지
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• 제31권3호
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• pp.246-259
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• 2011

This study presents a structural health monitoring (SHM) method for bolted connections by using multi-channel wireless impedance sensor nodes and multiple PZT-interfaces. To achieve the objective, the following approaches are implemented. Firstly, a PZT-interface is designed to monitor bolt loosening in bolted connection based on variation of electro-mechanical(EM) impedance signatures. Secondly, a wireless impedance sensor node is designed for autonomous, cost-efficient and multi-channel monitoring. For the sensor platform, Imote2 is selected on the basis of its high operating speed, low power requirement and large storage memory. Finally, the performance of the wireless sensor node and the PZT-interfaces is experimentally evaluated for a bolt-connection model Damage monitoring method using root mean square deviation(RMSD) index of EM impedance signatures is utilized to estimate the strength of the bolted joint.