• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.4
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• pp.261-268
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• 1989

A novel current controlled PWM voltage source type converter and control strategy is proposed that is able to draw nearly sinusoidal current at unity power factor from three phase power lines. Current error vector control scheme is used which has two operating states : low harmonic current content state and quick current response state. The state is changed according to the current error to optimize the steady state and transient state performances. To regulate the dc oupput voltage, the magnitude of the reference current is determined by a controller dc voltage error. The ac input power factor can be controlled with unity, and even leading or lagging by adjusting the relative position of the reference current with respect to the supply voltage.

• Electrical & Electronic Materials
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• v.10 no.8
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• pp.756-762
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• 1997

In this paper the change of electrical properties of transformer oil due to electron beam irradiation is investigated. The specimens are produced with a some different dose of 0.5[Mrad], 1[Mrad] and 2[Mard] except for original specimen. The physical properties of each specimen is analyzed by using the FT-IR spectrum. So it is confirmed that carbonyl groups are increased according to the increase of electron beam dose and also that the nitric compounds are disappeared. The magnitude of dielectric dissipation factor appears maximum value by the contribution of dipoles and ions in the low temperature low voltage region and it is stable due to the saturation of carriers in the high temperature high voltage region in the electric conduction characteristics. Volume resistivity is also measured one of original specimen is larger than irradiated specimen.

• Water for future
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• v.25 no.2
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• pp.79-87
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• 1992

This study is a model on the Migration Characteristics which developed by using the equations for conservation of mass, momentum and for lateral stability of the streambed, an the model can be examined for magnitude and location of near-bank bed scour as well as rates and direction of meander migration in which sine-Wave type rivers(SWR) of the small sinuosity. It is evident from this study that the transverse bed slope factor B' and transverse mass flux factor $ play significient roles, and show reasonable that the values are B'=4.0 and $=0.4 respectively . It will be a useful guide in planning, design, construction, and development of SWR river-basin projects.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.239-241
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• 2004

Stress intensity factor of semi-circular crack front was calculated by FEM, and also allowable crack size which doesn‘t break out the fracture by SCC in residual stress field of STS materials. Allowable crack size was increased with compressive residual stress provided by shot peening on material surface, and with magnitude of compressive residual stress for depth direction.

• Korean Journal of Health Education and Promotion
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• v.3 no.1
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• pp.99-111
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• 2001

Adolescent psychosocial smoking prevention programs have been successful, but limited in the magnitude of program effects on the reduction of smoking behaviors. This is primarily due to the mixed results of independent studies with program variations. This systematic, quantitative research synthesis is designed to identify program key factors that are likely to increase program effects. The present study examined school-based psychosocial smoking prevention programs (1978-1997)among students in grades 6 to 12 in the United States. Theoretical formulations in this analysis of mediating effects posit that program impact on knowledge and/ or skills is associated with less smoking behaviors among program participants. Knowledge factors investigated in this study included health effects, social consequences, social influences, and social norms. Skill factors included affective skill, self-efficacy, assertiveness, self-control, problem solving, and refusal skill. The findings from this study highlight the importance of social consequences knowledge factor and assertive communication skill factor in decreasing adolescent smoking behaviors.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1062-1064
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• 2005

3 phase 4-wire system has been widely used in the customer's application due to merit of 1 bank construction of loads such as 1-phase lighting, heat and 3-phase motor. But if the load distribution is not uniformed by the operation conditions, voltage unbalance is highly appeared by the difference of each phase current value. Especially, if the linear load such as resistance or inductive load has different power factor value, voltage unbalance factor is not the same due to the phase angle and magnitude of each phase voltage. In this paper, we composed the measurement device and analyzed by varying of load pattern.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.185-187
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• 1995

A boost converter proposed in this paper operates with high power factor due to input current of sinusoidal waveform. If there were no input LPF, the current is got to be discontinuos form in proportion to AC input voltage magnitude under the constant duty factor switching. Thereupon, the harmonics of input current waveform is reduced and the LPF is made with few elaboration and the control circuit is simple. The switching devices in proposed circuit are operated with soft switching by the partial resonant method. The patial resonant circuit makes use of a reactor using step-up and a capacitor of loss-less snubber. The result is that switching loss is very low and efficiency of system is high.

• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.8-16
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• 2003

A major concern in Gas Metal Arc (GMA) welding process is the determination of welding process variables such as wire diameter, gas flow rate, welding speed, arc current and welding voltage and their effects on the desired weld bead dimensions and shape. To successfully accomplish this objective, 81 welded samples from mild steel AS 1204 flats adopting the bead-on-plate technique were employed in the experiment. The experimental results were used to develop a mathematical model to predict the magnitude of bead geometry as follows; weld bead width, weld bead height, weld bead penetration depth, weld penetration shape factor, weld reinforcement shape factor, weld bead total area, weld bead penetration area, weld bead reinforcement area, weld bead dilution, length of weld bead penetration boundary and length of weld bead reinforcement boundary, and to establish the relationships between weld process parameters and bead geomery. Multiple regression analysis was employed for investigating and modeling the GMA process and significance test techniques were applied for the interpretation of the experimental data.

• Journal of Preventive Medicine and Public Health
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• v.20 no.1 s.21
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• pp.67-83
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• 1987

This study relates to the problems of organizational performance in the Christian hospitals. In this study, quality of working life (QOWL), which harmonizes individual as well as organizational goals, was used as an indicator of organizational performance from the open systems view. In order to identify the behavioral factors influencing QOWL in hospitals, self-administered questionnaires were distributed to 1,926 employees who were randomly selected from fifteen Christian hospitals from August 1 to August 30, 1986. The following results were obtained: 1) All correlation coefficients between QOWL and behavioral variables were statistically significant even though their magnitude varied according to hospital size. 2) Using factor analysis, 32 variables were parsimoniously grouped into four factors: individual conflicts, group behavior, organizational characteristics and situation, and job characteristics. The proportion of variance explained by these factors ranged from 33.5% to 38.6% according to hospital size. 3) The overall effects of the four factors in the multiple logistic models ranged from 0.85 to 3.12 according to hospital size. Among three hospital models, the model for small hospitals showed the best statistical fit. 4) The most influential factor was organizational characteristics and situation with an odds ratio ranging from 1.99 to 3.02. Again, the odds ratio was the highest for small hospitals. 5) For large hospitals, the two main factor effects were statistically significant: organizational characteristics and situation, and job characteristics. For medium hospitals, all main factor effects except job characteristics were statistically significant. For small hospitals, all main factor effects except group behavior were statistically significant. However, a factor interaction effect was shown only for large hospitals where it was statistically significant. 6) To examine whether the four factors influence financial performance, the four factor scores from the two financial performance groups were compared using Mann-Whitney test. The test results showed that the organizational characteristics and situation factor score was significantly different only for small hospitals.

• International Journal of Highway Engineering
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• v.10 no.1
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• pp.135-144
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• 2008

The dynamic loads imposed by moving vehicles have variations in the magnitude due to the surface roughness of the pavement systems and the larger dynamic loads than the design loads may affect the pavement performance. This paper presents variations of the moving dynamic vehicle loads due to the pavement surface roughness. This study was performed as a basic study to apply the pay factor to the surface roughness for the improvement of pavement quality and performance. The profile data was obtained from the old and new pavements and the analysis was performed to investigate the dynamic loads when vehicles move on the pavements having those profiles. The artificial profiles were also developed to find the effects of the vehicle speed, wavelength and amplitude of the surface roughness on the dynamic vehicle loads. The increase in the load magnitude due to the surface roughness affects the stresses and strains of pavements and finally reduces the pavement life. The methodology to obtain the relationship between the surface roughness and the pavement performance was proposed in this study.