• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1149-1154
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• 2007

Fluctuation of control rod was experienced when plant was operating in normal operation mode in WH type NPPs. In order to cope with increased control rod fluctuation, the lead-lag controller setpoint for rod control system was optimized and resulted in increasing the margin of operation and minimizing unnecessary control rod movement. By optimization of the time constant, the margin of operation was increased by $1.5^{\circ}F$ and the control rod movement was not occurred due to mitigation of temperature fluctuation in loop. According to the mitigation of time constant, the margin of operation was increased but safety margin can be affected badly, so that the influences to FSAR design reference was evaluated. As the result of this evaluation, it satisfied the design reference of the existing safety analysis and was applied to NPP after obtaining the approval.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.1
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• pp.31-38
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• 2016

A novel self-reference sense amplifier with parallel reading during writing operation is proposed. Read access time is improved compared to conventional self-reference scheme with fast operation speed by reducing operation steps to 1 for read operation cycle using parallel reading scheme, while large sense margin competitive to conventional destructive scheme is obtained by using self-reference scheme. The simulation was performed using standard $0.18{\mu}m$ CMOS process. The proposed self-reference sense amplifier improved not only the operation speed of less than 20 ns which is comparable to non-destructive sense amplifier, but also sense margin over 150 mV which is larger than conventional sensing schemes. The proposed scheme is expected to be very helpful for engineers for developing MRAM technology.

• The KSFM Journal of Fluid Machinery
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• v.15 no.6
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• pp.18-24
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• 2012

This study simulated the operation of a steam injected gas turbine combined heat and power (CHP) system. A full off-design analysis was carried out to examine the change in the turbine blade temperature caused by steam injection. The prediction of turbine blade temperature was performed for the operating modes suggested in the previous study where the limitation of compressor surge margin reduction was analyzed in the steam injected gas turbine. It was found that both the fully injected and partially injected operations suggested in the previous study would cause the blade temperature to exceed that of the pure CHP operation and the under-firing operation would provide too low blade temperature. An optimal operation was proposed where both the turbine inlet temperature and the injection amount were modulated to keep both the reference turbine blade temperature and the minimum compressor surge margin. The modulation was intended to maintain a stable compressor operation and turbine life. It was shown that the optimal operation would provide a larger power output than the under-firing operation and a higher efficiency than the original partially injected operation.

• Journal of Power System Engineering
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• v.14 no.4
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• pp.43-49
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• 2010

In the present study, optimization of throttle margin for high pressure turbine to be retrofitted or partially modified for power uprating or life extension in nuclear power plant, has been performed to increase the electrical output. Throttle margin for high pressure turbine is required to maintain all the time the rated power by opening more of governor valves whenever inlet pressure is decreased due to the tube plugging of steam generator. If throttle margin of high pressure turbine is too much compared to remaining lifetime, loss of electrical output due to pressure drop of governor valves is inevitable. On the contrary, if it is too little, the rated power operation can not be accomplished when inlet pressure of high pressure turbine is dropped after many years operation. So, throttle margin for high pressure turbine in nuclear power plant is compromised considering for the degradation of steam generator, governor valve capacity, manufacturing tolerance of high pressure turbine, future plan of power uprating, and remaining lifetime of power plant.

• The Journal of the Korean bone and joint tumor society
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• v.1 no.1
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• pp.30-37
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• 1995

The prognosis of parosteal osteosarcoma is better than any other malignant bone tumors, but there are many controversies in its treatment. We tried to evaluate the prognosis and the effectiveness of limb-salvage operation in the treatment of the parosteal osteosarcoma. We experienced 12 patients of conventional parosteal osteosarcoma(2 males and 10 females) from 1981 to 1991. The limb-salvage operations with wide resection margin were done in 8 patients(5 tumer prosthesis, 2 resection arthrodesis and 1 vascularized fibular transplantation), marginal en-bloc resection and amputation in 2 patients, respectively. The duration of mean follow up was 5 years and 9 months, ranging from 2 year-3 months to 11 years, except of the patient who died with metastasis 1 year 8 months after. The disease-free survival rate(DFSR) of all patients was 68% and that of the patients treated with limb-salvage operation was 88% at 7 years. The DFSR was 33% with marginal margin(3 cases) and 89% with wide margin(9 cases) at 7 years. The results were unsatisfactory in the conventional parosteal osteosarcoma treated with marginal resection. The limb-salvage operation with wide surgical margin was thought to be the treatment of choice.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1086-1090
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• 2011

This paper presents a method to evaluate generation rescheduling priority using transient energy margin sensitivity for power system operation. A change in any of the functional parameters obviously causes a change in the energy margin. Especially the energy margin sensitivity is evaluated for change with respect to generation. For a given contingency, the energy margin is computed and the respective sensitivities are also computed. It is possible to rank the sensitivities and thereby determine the generators which will affect the energy margin most and hence affect the stability (instability) of the system. The sign of the sensitivity indicates the direction of change in generation for a given change in energy margin.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1132-1137
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• 2008

Automatic Operation based on ATO (Automatic Train Operation) is necessary for driverless Light Rail Transit business. When this kind of driverless LRT operation plan is made, TPS (Train Performance Simulation) is traditionally simulated at all-out mode and coasting mode based on manual operation. Commercial schedule speed equals to all-out speed minus $9{\sim}15%$ make-up margin. Coasting mode TPS simulation is also run at commercial schedule speed to calculate run time and energy consumption. But TPS based on manual operation should make an improvement on accuracy in case of driverless LRT operation Plan. In this paper, new fast mode TPS simulation using ATO pattern is proposed and show near actual ATO result. The actual ATO pattern can be accurately simulated with the introduction of 4 parameters such as commercial braking rate, jerk, station stop profile and grade converted distance. Normal mode TPS simulation for commercial schedule speed can be designed to have fast mode trip time plus 3 seconds/km margin recommended by korean standard LRT specification.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.239-249
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• 2002

The Turbine Building of nuclear power plant is classified as non safety-related structure. During the operation, there may be possibility the original licensing basis would be changed, which makes non safety-related structure safety-related. Such a change in regulation requires utility to perform seismic qualification for the existing structure and their facilities. Thus it is meaningful to evaluate seismic margin of the existing non-qualified building structure. In addition, in this paper it is shown that a modification to the structure can enhance their seismic capacity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1011-1016
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• 2010

It is an important issue to electric power system operations that it can reliably supply large-capacity power to consumption area as due to increasing power demand growth. For this purpose, The FACTS equipment based on Power IT technology with the existing mechanical compensators has been applied to power system. Therefore we suggest on this paper that a plan for coordination control of multiple power compensation equipment in order to increase the utilization of each facility and secure operation margin capacity. As the result of simulation, it is possible to cope actively with a suddenly changed power system. This helps greatly for the voltage stability and supply reliability in a suddenly changed power system.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.6
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• pp.267-273
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• 2003

The plasma display panel with the electrode structure of new discharge AND gate and its driving scheme were proposed and the driving system for experiment was developed. And operation of these discharge AND gate was verified by the experiment of PDP addressing with floating electrode. This discharge AND gate operated by the operation speed of 8$mutextrm{s}$ and the operation margin of 100V. The address operation margin of 10V also obtained. It was known to be able to control the discharge of the adjoining scan electrode accurately. Because proposed method uses the DC discharge the control of the discharge can be facilitated compared with conventional discharge AND gate. Moreover, because the input discharge and the output discharge of discharge gate are separate, the display discharge can be prevented from passing discharge gates. Therefore, it is possible to apply to the large screen plasma display panel. And the decrease of contrast ratio does not occur because the scanning discharge does not influence the picture quality.