• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.136-139
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• 2005

On-line dynamic security assessment is becoming more and more important for the stable operation of power systems as load level increases. The necessity is getting apparent under Electricity Market environments due to more various operating conditions. Fast transient stability analysis tool is required for contingency selection. The TEF(Transient Energy Function) method is a good candidate for this purpose. The clustering of critical generators is crucial for the precise and fast calculation of energy margin. In this paper, we propose a new method for fast decision of mode of instability by using stability indices. Case study shows very promising results.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.149-151
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• 2005

A new approach considering CO2 air pollution constraints in the long-term generation mix is proposed under uncertain circumstances. A characteristic feature of the presented approach in this paper is what effects give the air pollution constraints in long term best generation mix. Best generation mix problem is formulated by linear programming with fuel and construction cost minimization with load growth, reliability (reserve margin rate) and air pollutionconstraints. The proposed method accommodates the operation of pumped-storage generator. It was assumed in this study that the construction planning of the hydro power plants is given separately from the other generation plans. The effectiveness of the proposed approach is demonstrated by applying to the best generation mix problem of KEPCO-system, which contains nuclear, coal, LNG, oil and pumped-storage hydro plant multi-years.

• Proceedings of the KSRS Conference
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• v.1
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• pp.290-293
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• 2006

COMS (Communication, Ocean and Meteorological Satellite) shall be operated with two remote sensing payloads, MI (Meteorological Imager) and GOCI (Geostationary Ocean Color Imager). Since both payloads have rotating mechanisms, the dynamic coupling between two payloads is very important considering the pointing stability during GOCI operation. In addition, COMS adopts a single solar wing to improve the image quality, which leads to the unbalanced solar pressure torque in COMS. As a result, the off-loading of the wheel momentum needs to be performed regularly (2 times per day). Since the frequent off-loading could affect MI/GOCI imaging performance, another suboptimal off-loading time needs to be considered to meet the AOCS design requirements of COMS while having margin enough in the number of thruster actuations. In this paper, preliminary analysis results on the pointing stability and the wheel off-loading time selection with respect to MI/GOCI operations are presented.

• Journal of Chest Surgery
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• v.20 no.2
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• pp.411-415
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• 1987

We have experienced a rare case of traumatic ventricular septal defect caused by fall down injury. The patient suffered from congestive heart failure after trauma and represented new developing typical murmur. Cardiac catheterization revealed a large left-to-right shunt at the ventricular level and a 4.4:1 ratio of pulmonary to systemic flow. Left ventricular angiogram also showed ventricular septal defect low in the muscular septum. At operation, the right ventricle and pulmonary artery were found to be moderately dilated. A marked systolic thrill was palpable over the right ventricle near the apex. Through a small left ventriculotomy an oval defect, 2x.3 cm with a firm scarred margin, was found in the lower muscular ventricular septum. This defect was repaired using Dacron patch and ventriculotomy was closed with long strip of Teflon felt. Postoperative course was uneventful and discharged in good condition.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.223-226
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• 1998

The control objective of steam generator water level in the secondary circuit of a nuclear power plant is to regulate the water level at the desired set point. The dynamics of steam generators is non-linear in nature. The task of modelling such plant is very difficult and especially so when plant operating conditions change frequently. In these reasons, conventional PI gains over all pover range will not work efficiently and a manual control is generally used in low power operation. Therefore the robust H$\infty$ controller design method should be required. In this paper, we design the robust H$\infty$ controller for water level control of steam generator using a mixed H$\infty$ optimization with model-matching method. Firstly we choose the desired model that has good disturbance rejection performance. Secondly we design a stabilizing controller to keep the model-matching error small and also provide sufficiently large stability margin against additive perturbations of the nominal plant.

• Proceedings of the KIEE Conference
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• summer
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• pp.245-247
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• 2004

Stability is an important constraint in powr system operation. A new methodolgy that reduces the need for repeated simulation to determine a transiently secure operating point is presented. at cntingency , critical generator is limited generation to prevent rotor accelation until system is secured. when energy margin is zero, generation is degermined Implementation issues and simulation results are discussed in th context of a 23-bus system

• Journal of Korean Foot and Ankle Society
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• v.21 no.4
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• pp.170-173
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• 2017

Soft tissue tumors of the foot have a low incidence rate, and most of them are symptom free, thus it is difficult to diagnose accurately. Herein, we report a 15-year-old male patient who had swelling without pain on the lateral margin of both feet. We performed excisional biopsy of the abductor digiti minimi via subtotal resection, following radiograph and magnetic resonance imaging. According to the histological analysis, hypertrophy of abductor digiti minimi was positive, and other soft tissue tumors were negative. Six months after the operation, normal appearance of both feet was maintained and the patient was satisfied with the result.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.593-598
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• 2009

In this study we present results for the design of ground test system for 4 degree of freedom(DOF) control test is one of the smart UAV ground test. This system is equipped with real smart UAV and Z direction DOF and 3 direction rotation DOF, Ensuring safe operation of the Smart UAV is a top priority. To this end, it is required to do structure analysis and test verification to confirm the design margin and safety. Based on the analysis, the ground test system has been redesigned to meet the structural conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.397.1-397
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• 2002

For high density optical storage, there should be a high NA objective lens and a shorter wavelength laser diode. To secure the disc tilt margin related to the coma aberration, moreover, it's difficult to apply the tilt compensation mechanism into the portable PC. In this paper, we proposed the 3-axis asymmetry pickup actuator with high efficiency symmetric magnetic circuit, which consisted of the top cover type inner yoke for high magnetic flux density, the coil stack unit for the 3-axis independent operation and vertically polarized magnets. (omitted)

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2001.04a
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• pp.17-20
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• 2001

Combustion characteristics of KSR-III liquid rocket engine are investigated numerically in the standpoints of engine performance and acoustic instability. In the present calculation, engine performance for design and off-design conditions is estimated effectively with reasonable error. Numerical results of acoustic instability show that engine operation for the design condition has sufficient stability margin, but for a certain off-design condition, acoustic instability can be triggered by artificial pressure perturbation. The present results are in a good agreement with the available experimental results and can be adopted for the prediction of engine performance and stability, depending on the specific operating condition.