• Journal of IKEEE
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• v.22 no.2
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• pp.258-265
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• 2018

This paper proposes an algorithm for reducing the starting current when the single-phase induction motor starts and analyzes its operation. Generally, the single-phase induction motors require several starters to generate the starting torque due to their structural characteristics. In this paper, a capacitor-start / capacitor-run method of the single-phase induction motor is basically adopted. This conventional method is efficient and has a large starting torque, but it generates about 5 ~ 6 times of inrush current at startup. As a result, the freezer starting device and peripheral devices are damaged and life time may be reduced. To reduce the inrush current, the current control algorithm based on the virtual dq model is presented to control the starting current. In addition, it validates the proposed algorithm through experiments to smooth transit from start-up operation to the rated operating region.

• The korean journal of orthodontics
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• v.21 no.1 s.33
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• pp.113-130
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• 1991

This study was undertaken to investigate soft tissue profile changes by orthodontic treatment in female patients. Traditional cephalometric appraisal yields data of dubious scientific value, the soft tissue profile forms were evaluated by finite element method. The subject was divided into three groups according to Angle's classification and each group was composed of 25 female patients averaged aged 12-14 years at the start of treatment. The changes in soft tissue form were evaluated by computing the degree of distortion in each triangle after treatment compared with the triangle before treatment. The conclusions were as follows; 1. The soft tissue profile forms were evaluated by finite element method and independent evaluation of each element by local changes was possible. 2. Maximum and minimum principal strains showed marked variability depending on the particular finite element and each group and Class II, III sample was greater than Class I sample. 3. Soft tissue size changes as a result of orthodontic treatment was not related to those of shape. 4. Soft tissue changes by orthodontic treatment were variable in individual patient, and were not related to Angle's classification.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.2
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• pp.312-320
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• 2005

The purpose of this study was to evaluate the polymerization contraction and the microhardness of compostie resin($Supreme^{(R)}$, Filtek $Flow^{(R)}$, 3M-ESPE, USA) according to irradiation modes of LED curing unit(Elipar $Freelight^{(R)}$, 3M-ESPE, USA). The strain guage method was used for determination of polymerization contraction. Sample were divided by 6 groups according to curing modes and filling method. Group A: $Supreme^{(R)}$, Filtek $Flow^{(R)}$ lining, 10seconds curing, Group B: $Supreme^{(R)}$, Filtek $Flow^{(R)}$ lining, 15seconds curing, Group C: $Supreme^{(R)}$, Filtek $Flow^{(R)}$ lining, 15seconds soft start curing, Group D: $Supreme^{(R)}$ only, 10seconds curing, Group E: $Supreme^{(R)}$ only, 15seconds curing, Group F: $Supreme^{(R)}$ only, 15seconds soft start curing. Preparations of acrylic molds were followed by filling and curing. Strain guage attached to each sample were connected to a strainmeter. Measurements were recorded at each second for the total of 10 minutes including the periods of light application. And microhardness of each group after 24hours from light irradiation were measured. Obtained data were analyzed statistically using Repeated measures ANOVA and Tukey test. The results of the present study are as follows: 1. In flowable resin liner group, soft start curing group was not found decrease of polymerization contraction. But, In Supreme only filling group, the lowest polymeriation contraction was found in soft start curing group. 2. 10 seconds curing group showed statistically significant reduction of polymerization contraction compared with 15 seconds curing group(p<0.05). 3. The microhardness values of each group not revealed significant difference(p>0.05). But, lower surface microhardness was not reached 80% of upper surface microhardness.

• Journal of Power Electronics
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• v.16 no.3
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• pp.915-924
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• 2016

A digital self-sustained phase shift modulation (DSSPSM) strategy that allows for good soft switching and dynamic response performance in the presence of step variations is presented in this paper. The working principle, soft switching characteristics, and voltage gain formulae of a LLC converter with DSSPSM have been provided separately. Furthermore, the method for realizing DSSPSM is proposed. Specifically, some key components of the proposed DSSPSM are carefully investigated, including a parameter variation analysis, the start-up process, and the zero-crossing capture of the resonant current. The simulation and experiment results verify the feasibility of the proposed control method. It is observed that the zero voltage switching of the switches and the zero current switching of the rectifier diodes can be easily realized in presence of step load variations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7A
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• pp.568-573
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• 2009

This paper presents a step-down DC-DC converter with On-chip Compensation for battery-operated portable electronic devices which are designed in O.13um CMOS standard process. In an effort to decrease system volume, this paper proposes the on chip compensation circuit using capacitor multiplier method. Capacitor multiplier method can minimize error amplifier's compensation capacitor size by 10%. It allows the compensation block of DC-DC converter be easily integrated on a chip and occupy less layout area. But capacitor multiplier operation reduces DC-DC converter efficiency. As a result, this converter shows maximum efficiency over 87.2% for the output voltage of 1.2V (input voltage : 3.3V), maximum load current 500mA, and 25mA output ripple current. This voltage mode controled buck converter has 1MHz switching frequency.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.96-108
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• 2015

his study deals with a power conversion unit of an anti-start air conditioner compressor system for the commercial vehicle. In case of converter, to reduce the switching losses and current stresses of the device, applies LLC resonant topology. Transformer leakage inductance in the full-bridge converter is used for making the resonance with the capacitor of the voltage-doubler. Through this method we can increase power and decrease volume of system. Both circuit analysis and design guideline are described. So in this paper, power conversion unit is designed. 2.5kW anti-start air conditioner compressor system was implemented, and system operation and stability was verified through experiment.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.43-45
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• 2006

대부분의 컨버터들은 초기 기동시에 MOSFET 전류와 전압의 과도한 상승을 막아주기 위해서 Soft Start 기능을 갖고 있다. 하지만 제어기 내부의 지연시간이나 LEB(Leading Edge Blanking) 시간 등으로 인해 MOSFET은 무시할 수 없는 상당한 기간의 최소 턴온 시간(Minimum Turn-on Time)을 갖게 되고, 이로 인해 드레인 전류가 과도하게 상승하는 현상을 보이게 된다. 본 논문에서는 이런 현상이 발생할 수 있는 초기 기동이나 출력단 단락시에 과도한 드레인 전류의 상승을 막아주는 방법을 제시하고자 한다.

• Journal of Power Electronics
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• v.4 no.2
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• pp.96-101
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• 2004

This paper presents an application of SRM drive for LSEV(Low Speed Electric Vehicle). In this paper, a 5〔㎾〕 SRM for a traction of a LSEV is to design and investigate the characteristics of the drive system. The main design parameters and control strategy are given. In the control method, a current control, for the soft-starting technique at a starting operation, is adopted. In the high speed range, an angle control technique is implemented, for a high efficiency drive of SRM. Some experimental tests are executed to find the drive performances.

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.613-613
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• 2003

The purpose of this study was to compare the effect of exponential curing method with conventional curing and two step soft start curing method on polymerization shrinkage of composite resins. Three brands of composite resins (Synergy Duo Shade, Z-250, Supreme) and three brands of light curing units (Spectrum 800, Elipar Highlight, Elipar Trillight) were used. In this study, the diameter of specimen was 5.5mm and height 1.6mm and the specimen was cured for 40 seconds. The shrinkage was measured by custom made linometer. The amount of linear polymerization shrinkage recorded in the computer every 0.5 second for 90 seconds. Each group was measured 10 times.(omitted)

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.165-166
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• 2011

양방향 AC/DC 컨버터를 이용하여 EV배터리를 충전하거나 계통으로 전력을 보낼 때 PI제어기를 사용하면 임피던스를 예측할 수 없으므로 초기 구동시 오버슈트가 발생하여 회로에 스트레스가 발생한다. 본 논문에서는 Sliding Mode Controller (SMC)를 이용하여 계통으로 전력을 전달하는 알고리즘으로 소프트 스타트를 하는 알고리즘을 제안하였다. 시뮬레이션을 통하여 회로를 구성하고 제안한 제어 방법의 성능을 확인하였다.