• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.808-815
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• 2001

The three-phase diode rectifier with a capacitive filter is highly sensitive to line voltage unbalance, and may cause significantly unbalanced line currents even under slightly unbalanced voltage condition. This paper presents an analysis of this 'unbalance amplification' effect for an ideal rectifier circuit without ac-and dc-side inductors. The voltage unbalance is modeled by introducing a deviation voltage superimposed on balanced three-phase line voltages. With proper approximations, closed-form expressions for symmetrical components of the line current and current unbalance factor are derived in terms of the voltage unbalance factor, filter reactance, and load current. The validity of analytical predictions is confirmed by simulation.

• Journal of applied mathematics & informatics
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• v.34 no.5_6
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• pp.435-441
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• 2016

Let G be a graph, and let g, f be two nonnegative integer-valued functions defined on V (G) with g(x) ≤ f(x) for each x ∈ V (G). A graph G is called a fractional (g, f, n)-critical graph if after deleting any n vertices of G the remaining graph of G admits a fractional (g, f)-factor. In this paper, we obtain a binding number condition for a graph to be a fractional (g, f, n)-critical graph, which is an extension of Zhou and Shen's previous result (S. Zhou, Q. Shen, On fractional (f, n)-critical graphs, Inform. Process. Lett. 109(2009)811-815). Furthermore, it is shown that the lower bound on the binding number condition is sharp.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.2
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• pp.121-132
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• 1982

Engine torque, specific fuel consumption and MBT spark advance of a domestic automotive engine fueled with methanal-gasoline blends or straight methanal were studied under steady state condition and compared to those obtained with gasoline. The effects of adding methanal to gasoline on engine performance were studied with or without any carburetor modification. At first, the engine was operated without any modification. Next, the diameters of metering orifices in carburetor were modified to give the same excess air factor regardless of fuel type under each fixed engine operating condition. Finally, the diameters of metering orifices in carburetor were modified to give the same excess air factor for 15% mixture of methanal in gasoline by volume as for gasoline with standard metering orifices in carburetor. The effects of adding methanal to gasoline on engine torque, specific energy consumption and MBT spark advance can be explained on the basis of change in stoichiometry caused by the addition of methanal to gasoline.

• International Journal of Automotive Technology
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• v.6 no.4
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• pp.367-374
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• 2005

This paper proposes a sound quality index to evaluate the vehicle interior noise. The index was developed using a correlation analysis of an objective measurement and a subjective evaluation data. First, the objective set of measurements was obtained at two specified driving conditions. One is from a wide-open test condition and the other is from a constant-speed test condition. At the same time, subjective evaluation was carried out using a score of ten scale where 17 test engineers participated in the experiment. The correlation analysis between the psycho-acoustic parameters derived from the objective measurement and the subjective evaluation was performed. The most critical factors at both test conditions were determined, and the corresponding equations for the sound quality were obtained from the multiple factor regression method. Finally, a comparative work between previous index and present index was performed to validate the effectiveness of the proposed index.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.569-572
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• 1995

In this study, a hydraulic modulator of solenoid-flow type ABS, the master sylinder, and the wheel cylinder are modeled and simulated for increasing pressure characteristics of the brake. Response can be predicted by external force of the the master sylinder and pulses to the solenoid valve as input. For a demonstration of simulation result, experiment is done under the same condition as simulation condition after experimental apparatus of 1/4 car model is constructed. When factors of flow control valve are changed, the effect of each factor to response, how to improve response, and the most critical factors are considered from simulated result of time constant.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.416-417
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• 2006

The recent movement to deregulated and competitive electricity market requires new concepts against existing central dispatch in the system operation and planning. As power systems tend to be operated more closely to their ultimate ratings, the role of SCOPF(Security Constrained Optimal Power Flow) is changed. This paper deals with the proper Unit Commitment condition changed according to the conditions or configuration of power system. This goal of is paper is to obtain proper security and Optimal UC condition through the efficient usage of the sensitivity Factor against critical contingencies. The proposed mechanism has been tested on a sample system and results show more secure conditions against critical contingencies.

• Proceedings of the KIEE Conference
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• 2006.05a
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• pp.71-73
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• 2006

Our company(KOWACO) has periodically performed off-line diagnostic test for 14 hydro generators (rated 11 kV over) for 15 years. In this paper, we summarized results of dissipation factor tip-up test and partial discharge test about these generators. Among these, we chose two generators and performed insulation reinforcement (cleaning and varnish Painting). We compared change of insulation condition for the stator winding based upon off-line diagnostic test result before and after repair. Test result shows that insulation condition was improved after insulation reinforcement. This insulation reinforcement has a function to reduce cause of deterioration, so we can know that it extends lifetime of generator and it is a very important factor for stable operation of facilities.

• The Journal of Korean Academy of Prosthodontics
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• v.9 no.1
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• pp.59-62
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• 1969

The causes of periodontal disease have been descried as malocclusion, trauma from occlusion, local irritants and poor oral hygien. The systemic factor has also been considered as a etiologic factor of periodontal disease. On the other aspect systemic condition could be affected by periodontal disease. For the study of relationships between periodontal disease and systemic condition, twenty patients with periodontal disease and twenty persons with no periodontal involvement were evaluated for inorganic elements and organic materials in the blood. The results of the blood analysis of the two groups were as follows. : Phosphorus and alkline-phoshatase in the group with periodontal disease showed slightly increased phenomenon compared to the control group, and on the other hand calcium and calcium-phosphorus ratio decreased phenomenon. But there is no any significant alteration in the content of each element between the two groups.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.727-730
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• 2001

In many structures a common method of construction is to make use of bolted or riveted joints. With this type of joint the load is transmitted through a pin from one section of the structure to another. Fatigue cracks often start from the edges of holes, due to local stress concentration. In order to predict the fatigue crack growth, the stress intensity factor K for hole-edge cracks should be available. In this paper the stress intensity factors are computed for cracks in bolt-joint region considering the contact condition.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1108-1113
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• 2000

A condition monitoring methodology for rotating machinery is proposed based on multivariate statistical analysis. The CMS usually are using the vibration signal amplitude such as acceleration RMS, peak and velocity RMS to detect machine faults but the information is not so enough that CMS cannot perform reliable monitoring. So new parameters are added such as shape factor, crest factor, kurtosis and skewness as time domain parameters and spectrum amplitude of rotating frequency, $2^{nd}$ harmonics and gear mesh frequency etc. as frequency domain parameters. Many parameters are combined to represent the machine state using the Hotelling's $T^2$ statistics. The proposed methodology is tested in laboratory and the on-line experiment has shown that the proposed methodology offers a reliable monitoring for rotating machinery.