• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.49-53
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• 2006

This paper specifies the new power supply paradigm converting 154kV voltage level into 22.9kV class with equivalent capacity using superconducting rower facilities and analyze the fault current characteristics with and without HTS-FCL (High Temperature Superconducting-Fault Current Limiter). Superconducting new power system is the power system to which applies the 22.9kV HTS cable in parallel to HTS transformer and HTS-FCL with low-voltage and mass-capacity characteristics replacing 154kV conventional cable and transformer. The fault current of superconducting new power system will increase greatly because of the mass capacity and low impedance of HTS transformer and cable. This means that the HTS-FCL is necessary to reduce the fault current below the breaking current of circuit breaker. This paper analyze the fault current and suggests the parallel HTS-FCL scheme complementing the inherent problem of HTS-FCL, that is recovery after quenching is impossible within shorter than a few seconds.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.6
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• pp.972-981
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• 2008

A New ZVS(Zero Voltage Switching) and ZVZCS(Zero Voltage and Zero Current Switching) Three-Level Converter is proposed. The proposed converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the all switch. A primary auxiliary circuit, which consists of one coupled inductor, is added in the primary to provide ZVZCS conditions to primary switches. Many advantages including simple circuit topology high efficiency, and low cost make this converter attractive for high power applications. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 2kW(27V, 74A) 40 kHz IGBT based experimental circuit.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.99-102
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• 2006

This paper proposes a DITC(Direct Instantaneous Torque Control of SRM (Switched Reluctance Motor) using a novel 4-level converter for smooth torque control and high efficiency. DITC of SRM is very useful for smooth torque control, but the driving efficiency is low due to advanced current that does not produce torque. For the high efficiency control of SRM, fast excitation and demagnetization of phase current are required. A novel 4-level converter and a new control scheme are present to improve the driving efficiency. The proposed DITC of SRM using 4-level converter is verified by computer simulation.

• International Journal of Contents
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• v.6 no.4
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• pp.57-61
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• 2010

This paper designed and developed internet based competency developing system for small IT (Information & Technology) companies. The purpose of this system was to provide career development opportunities to small IT business workers for their longstanding employment and self-improvement job skills. This study analyzed job competencies based on job descriptions from two IT companies. The survey was conducted to analyze employees' self-assessed current job competency level and effective ways of improving their current level of competencies. From the results of survey, most of subjects indicated their job competencies were in between mid-level to low level, and they required the need of training programs to improve their job knowledge and experience. Based on the interview from field experts about job competency development, this study designed and developed the internet based competency development system to provide effective and efficient way of improving job competencies and needed training programs for small IT business employees.

• Asia Marketing Journal
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• v.23 no.1
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• pp.29-62
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• 2021

The current research develops and tests the theory that beliefs in economic mobility are affected by social capital at the community level, especially for low-income individuals. Integrating concepts from social capital and perceived economic mobility (PEM), this research hypothesizes that members of disadvantaged groups (vs. members of advantaged groups) are more likely to adjust their PEM depending on the social capital at the community level. Using archival data, multilevel analysis is employed to examine whether individual- or community-level social capital increases PEM and the extent to which income moderates this relationship. Consistent with our hypotheses, social capital at the community level is significantly associated with PEM and this relationship is stronger for low-income (vs. high-income) earners. Study 1 shows that individuals in communities with high levels of social relations and participation are more likely to have higher PEM than those in communities with lower levels. Study 2 replicates this finding with a similar dependent variable: negative prospects. Further, the PEM-enhancing and negative prospects-decreasing effects of community-level social capital are consistently stronger for low-income (vs. high-income) earners. This study extends the investigation of PEM and social capital by suggesting social capital as a possible antecedent of PEM.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.451-454
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• 2015

This paper introduces 3 type of OTAs with $0.35-{\mu}m$ standard CMOS technology for Low-Power, Low-Voltage. The first type is a two-stage OTA designed to operate with a 1-V VDD and it has $1.774{\mu}W$ low power consumption. All transistors are operating in strong inversion. It takes Gm-Enhancement techniques to compensate gm, which is lowered by Bulk-Driven technique and has an Wide swing current mirror for low voltage operation and a Class-A output. The second type is a Two-stage OTA designed to operate with a 0.8-V VDD and It has 52nW low power consumption and 112dB high gain. The current mirror uses Composite Transistor binding Gates of two MOSFET to raise Rout which is similar with cascode structure. The third type is a Two-stage OTA designed to operate with a 0.6-V VDD and It has 160nW low power consumption and 72dB high gain. It takes Level Shift technique by Common Gate structure to amplify signals without additional bias voltage at second stage.

• Journal of Environmental Science International
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• v.2 no.3
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• pp.179-191
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• 1993

This paper aims to know the characteristics of occurrence of the anomaly level and variability of the monthly precipitation in Kyeongnam, Korea. For this study, it was investigated 주e distribution of the annual and cont비y mean precipitation, the precipitation variability and its annual change, and the characteristics of occurrence of the anomaly level in Kyeongnam area the results were summarized as follows : 1) she mean of annual total precipitation averaged over Kyeongnam area is 1433.3mm. I'he spatial distribution of the annual total precipitation shows that in Kyeongnam area, the high rainfall area locates in the southwest area and south coast and the low rainfall area in an inland area. 2) Monthly mean precipitation in llyeongnam area was the highest in July(266.4mm) 각lowed by August(238.0mm), June(210.2mm) in descending order. In summer season, rainfall was concentrated and accounted for 49.9 percent of the annual total precipitation. Because convergence of the warm and humid southwest current which was influenced by Changma and typhoon took place well in this area. 3) The patterns of annual change of precipitaion variability can be divided into two types; One is a coast type and the other an inland type. The variability of precipitation generally appears low in spring and summer season and high in autumn and winter season. This is in accord with the large and small of precipitation. 4) The high frequency of anomaly level was N( Normal)-level and the next was LN( Low Informal) -level and 25(Extremely Subnormal)-level was not appeared in all stations. The occurrence frequency of N level was high in high rainfall area and distinguish성 in spring and summer season but the low rainfall area was not. hey Words : anomaly level, variability, precipitation, coast type, inland type.

• Journal of the Optical Society of Korea
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• v.15 no.4
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• pp.373-379
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• 2011

Current therapeutic methods for suppressing muscle spasticity are intensive functional training, surgery, or pharmacological interventions. However, these methods have not been fully supported by confirmed efficacy due to the aggravation of the muscle spasticity in some patients. In this study, a combined system was developed to treat with a low-level laser and to monitor the region of the treatment using an optical spectroscopic probe that measures oxygen saturation and deoxygenation during low-level laser therapy (LLLT). The evaluation of the wavelength dependence for LLLT was performed using a Monte Carlo simulation and the results showed that the greatest amount of heat generation was seen in the deep tissue at ${\lambda}$ = 830 nm. In the oxy- and deoxygenation measurements during and after the treatment, oxygen-Hb concentration was significantly increased in the laser-irradiated group when compared to the control group. These findings suggest that LLLT using ${\lambda}$ = 830 nm may be of benefit in accelerating recovery of muscle spasticity. The combined system that we have developed can monitor the physiological condition of muscle spasticity during the laser treatment in real time and may also be applied to various myotonia conditions such as muscle fatigue, back-pain treatment/monitoring, and ulcer due to paralysis.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.2 no.3
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• pp.1-9
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• 1999

This paper described the results of the characteristics of the near-bottom flow and field analysis of the tidal flats sediment. It was the aim of this paper to grasp current flow of tidal flat's environment and influence factor for environmental change forecast of tidal flats. Field measurement of water velocity, water elevation, bed materials test, and temperature distribution of tidal flat were conducted. Thereafter, current flow, turbidity and temperature distribution of tidal flat sediment have been discussed. The field research results showed that the fluctuating velocity near the seabed before and after its appearance at low tide was strongly affected by the wind wave. The resuspension of the sea-bottom sediment took place with great intensity before and after the appearance of the seabed at low tide. Both the sea water level and the weather condition were a significant influential factors. Such as, temperature and turbidity just on the surface and the shallow layer of seabed sediments were varied largely with time and weather conditions, but that its deeper layers was almost constant. Temperature on the seabed sediments was strongly influenced by irradiance and water depth. The temperature variation of the tidal flat and the variation characteristics of the current flow and turbidity depend greatly on the inhabiting environment of the tidal flat benthic organism.

• Journal of Power Electronics
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• v.3 no.4
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• pp.205-214
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• 2003

This paper proposes a simple control strategy based on the discontinuous PWM (DPWM) to balance the DC-link voltage of three-level neutral-point-clamped (NPC) inverter at low modulation index. It introduces new DPWM methods in multi-level inverter and one of them is used for balancing the DC-link voltage. The current flowing in the neutral point of the DC-link causes the fluctuation of the DC-link voltage of the NPC inverter. The proposed DPWM method changes the path and duration time of the neutral point current, which makes the overall fluctuation of the DC-link voltage zero during a sampling time of the reference voltage vector. Therefore, by using the proposed strategy, the voltage of the DC-link can be balanced fairly well and the voltage ripple of the DC-link is also reduced significantly. Moreover, comparing with conventional methods which have to perform the complicated calculation, the proposed strategy is very simple. The validity of the proposed DPWM method is verified by the experiment.