• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.2
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• pp.179-185
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• 2008

Simulating combustion tests have been performed to elucidate the effect of baffle gaps on the optimal damping characteristics in liquid rocket combustors where coaxial injectors are installed. Amplitude of pressure oscillation in model combustion chamber and the combustion stability margin are used to quantify the damping capacitance of baffles. Satisfactory agreement has been achieved with the results of cold acoustic tests. Present results have shown that the optimal gap for high acoustic damping capacity has also the large combustion stability margin in simulating combustion tests. Therefore, the present results can be utilized to determine the baffle length and optimal gap in full-scaled rocket combustors.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.48 no.5
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• pp.249-258
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• 2022

The specific muscular structure of the tongue greatly affects margin shrinkage and tumor invasion, making the optimal surgical margin controversial. This study investigated surgical margin correlated prognosis of TSCC (tongue squamous cell carcinoma) according to margin location and its value, and the histopathologic factors which are suggestive of tumor invasion. And we would like to propose defining of the surgical margin for TSCC via prognosis according to location and margin values. We reviewed 45 patients diagnosed with TSCC who visited Seoul National University Dental Hospital (SNUDH) (Seoul, Republic of Korea) from 2010 to 2019, who were managed by a single surgical team. Patient clinical and pathological data of patients were retrospectively reviewed, and in 36 out of 45 patients, the pathologic parameters including the worst pattern of invasion (WPOI) and tumor budding were investigated via diagnostic histopathology slide reading. When standardized with as 0.25 cm anterior margins, as 0.35 cm deep margin, there was no significant difference in disease specific survival (DSS) or loco-regional recurrence-free survival (LRFS). Additionally, there was a non-significant difference in DSS and LRFS at the nearest margin of 0.35 cm (P_DSS=0.276, P_LRFS=0.162). Aggressive WPOI and high tumor budding showed lower survival and recurrence-free survival, and there were significant differences in close margin and involved margin frequencies. In TSCC, the value and location of the surgical margin did not have a significant relationship with prognosis, but WPOI and tumor budding suggesting the pattern of muscle invasion affected survival and recurrence-free survival. WPOI and tumor budding should be considered when setting an optimal surgical margin.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.188-196
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• 2003

In order to increase competitiveness and to gain economic benefit, companies ask more and more how to recycle their products in a efficient way. So far, to answer this question, companies are not sufficiently supported by suitable methods specially in the area of disassembly process planning. For this reason, we develop in collaboration with an industrial partner a new method for generating an optimal disassembly sequence. In the presented paper this method will be described in detail by considering the exiting assembly information, disassembly method and disassembly depth. PLM (Profit-Loss Margin) curve that is used to determine disassembly depth consists of profit value, disassembly cost and disassembly effect. Using assessment parameters, generated alternative disassembly sequences are evaluated and optimal disassembly sequence is proposed. This method is applied to generate the optimal disassembly sequence of Door Trim as an example.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.412-413
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• 2011

This paper presents a new generation rescheduling approach for preventive control of power systems, which can optimally reallocate power generations for unstable contingencies. The transient stability constraints used in the optimal rescheduling model are described by energy margin sensitivity. 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.

• 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.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.8
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• pp.388-394
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• 2001

This paper presents how to determine the optimal operating points of Unified Power Flow controllers (UPFC) the line flow control of which can enhance system security level. In order to analyze the effect of these devices on the power system, the decoupled model has been employed as a mathematical model of UPFC for power flow analysis. The security index that indicates the level of congestion of transmission line has been proposed and minimized by iterative method. The sensitivity of objective function for control variables of and UPFC has been derived, and it represents the change in the security index for a given set of changes in real power outputs of UPFC. The proposed algorithm with sensitivity analysis gives the optimal set of operating points of multiple UPECs that reduces the index or increases the security margin and Marquart method has been adopted as an optimization method because of stable convergence. The algorithm is verified by the 10-unit 39-bus New England system that includes multiple FACTS devices. The simulation results show that the power flow congestion can be relieved in normal state and the security margin can be guaranteed even in a fault condition by the cooperative operation of multiple UPECs.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.1
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• pp.42-50
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• 2005

In order to increase competitiveness and to gain economic benefit, companies ask more and more how to recycle their products in an efficient way. So far, to answer this question, companies are not sufficiently supported by suitable methods specially in the area of disassembly process planning. For this reason, we develop in collaboration with an industrial partner a new method for generating an optimal disassembly sequence. In this paper this method will be described in detail by considering the exiting assembly information, disassembly method and disassembly depth. PLM(Profit-Loss Margin) curve that is used to determine disassembly depth consists of profit value, disassembly cost and disassembly effect. Using assessment parameters, generated alternative disassembly sequences are evaluated and an optimal disassembly sequence is proposed. This method is applied to generate the optimal disassembly sequence of Door Trim as an example.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.177-182
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• 2010

The forward convener is one of power supplies used widely. This paper presents parameter tuning methods to obtain optimal circuit element values for the forward converter to minimize the output voltage variation under various load changing environments. The conventional method using the concept of the phase margin is extended to have optimal phase margin that gives slightly improved performance in the output voltage response. For this, the phase margin becomes the tuning parameter and is optimized with the genetic algorithm. Next, the circuit element values are directly chosen as the tuning parameters and also optimized using the genetic algorithm to have very improved performance in the output voltage control of the forward converter.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.2
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• pp.142-150
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• 2002

This paper presents a systematic method of the zigzag gait planning for quadruped walking robots. When a robot walks with a zigzag gait, its body is allowed to move from side to side, while the body movement is restricted along a moving direction in conventional continuous gaits. The zigzag movement of the body is effective to improve the gait stability margin. To plan a zigzag gait in a systematic way, the relationship between the center of gravity(COG) and the stability margin is firstly investigated. Then, new geometrical method is introduced to plan a sequence of the body movement which guarantees a maximum stability margin as well as monotonicity along a moving direction. Finally, an optimal swing-leg sequence is chosen for a given arbitrary configuration of the robot. To verify the proposed method, computer simulations have been performed for both cases of a periodic gait and a non-periodic gait.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.116-118
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• 2004

This paper gives a measurement data of the feeder demand factor in small size apartments. The power load measurement data of the feeder shows that the feeders have $10{\sim}30[%]$ margin in capacity. But this margin is not enough to keep up with the trend of power consumption increase from long term standpoint. So it is necessary to measure the feeder power load periodically for the purpose of optimal feeder capacity estimation