• Journal of Power Electronics
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• v.14 no.2
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• pp.203-216
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• 2014

In the conventional dc-dc converter, a pair of additional diode and the adjacent passive component capacitor/inductor can be added to the circuit with an X-shape connection, which generates a family of new topologies. The novel circuits, also called diode-assisted dc-dc converter, enhance the voltage boost/buck capability and have a great potential for high step-up/step-down power conversions. This paper mainly investigates and compares conventional dc-dc converter and diode-assisted dc-dc converter in wide range power conversion from the aspects of silicon devices, passive components requirements, electro-magnetic interference (EMI) and efficiency. Then, a comprehensive comparison example of a high step-up power conversion system was carried out. The two kinds of boost dc-dc converters operate under the same operation conditions. Mathematical analysis and experiment results verify that diode-assisted dc-dc converters are very promising for simultaneous high efficiency and high step-up/step-down power conversion in distributed power supply systems.

• Journal of the Korean Society of Physical Medicine
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• v.12 no.3
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• pp.99-104
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• 2017

PURPOSE: Gait disturbances in patients with hemiplegic stroke involve asymmetry of stance time. Step box training is used to supplement the limitations of stair walking training and increasing the torque value of the paralyzed lower leg's strength. This study aimed to investigate whether step-up training on unstable support could change walking ability in patients with chronic stroke. METHODS: Thirty stroke patients were randomly assigned to the step-up training group (experimental group), that performed training on an unstable surface, and the control group, that performed training on a stable surface. Walking speed, step length, and cadence were measured before and after training. Paired t-tests were used to compare pre- and post-intervention data, while the independent samples t-test was used to determine intergroup differences. Values of p < .05 were considered statistically significant. RESULTS: There was a significant difference in walking ability before versus after the intervention in both groups, although the experimental group showed greater differences than the control group (walking velocity by 8.1%; step length of the non-paralyzed side by 6.9%, respectively; p<.05). CONCLUSION: Step-up training might be more effective on an unstable surface than on a stable surface for increasing walking speed and step length of the non-paralyzed side.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1424-1425
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• 2006

A four-step rapid thermal annealing (RTA) process is proposed in order to improve the throughput and stabilize the process, compared to the six-step RTA process. Effects of annealing on the properties of a structure mode of CMOS process in both cases were investigated. The implanted dopant(As, $BF_2$ and Ti/TiN) movement in silicon during different rapid thermal annealing conditions was studied using secondary ion mass spectroscopy (SIMS) technique. These results show that the four-step RTA process significantly improves time effect and throughput (15%) by the condition of ramping up compared to the six-step RTA process.

• Atmosphere
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• v.25 no.3
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• pp.473-482
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• 2015

In this study, street canyons with a higher downwind building (so called, step-up street canyons) are considered for understanding characteristics of flow and reactive pollutants' dispersion as a basic step to understand the characteristics in wider urban areas. This study used a CFD_NIMR_SNU coupled to a chemistry module just including simple $NO_X-O_3$ photochemical reactions. First, flow characteristics are analyzed in step-up street canyons with four aspect ratios (0.33, 0.47, 0.6, 0.73) defined as ratios of upwind building heights to downwind building height. The CFD_NIMR_SNU reproduced very well the main features (that is, vortices in the street canyons) which appeared in the wind-tunnel experiment. Wind speed within the street canyons became weak as the aspect ratio increased, because volume of flow incoming over the upwind building decreased. For each step-up street canyon, chemistry transport model was integrated up to 3600 s with the time step of 0.5 s. The distribution patterns of $NO_X$ and $O_3$ were largely dependent on the mean flow patterns, however, $NO_X$ and $O_3$ concentrations were partly affected by photochemical reactions. $O_3$ concentration near the upwind lower region of the street canyons was much lower than background concentration, because there was much reduction in $O_3$ concentration due to NO titration there. Total amount of $NO_X$ in the street canyons increased with the aspect ratio, resulting from the decrease of mean wind intensity.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.708-712
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• 2001

A new phase-shifted parallel-input/series-output (PI SO) dual inductor-fed push-pull converter for high-power step­up applications is proposed. This converter is operated at a constant duty cycle and employs an auxiliary circuit to control the output voltage with a phase-shift between the two modules. It features a voltage conversion characteristic which is linear to changes in the control input, and high step-up ratio with a greatly reduced switch turn-off stress resulting in a significant increase in the converter efficiency. It also shows a low ripple content and low root-mean-square (RMS) current in the output capacitor. The operational principle is analyzed and a comparative analysis with the conventional pulse-width-modulated (PWM) PISO dual inductor-fed push-pull converter is presented. A 50kHz, 800W, 350Vdc prototype with an input of 20-32Vdc has also been constructed to validate the proposed converter. The proposed converter compares favorably with the conventional counterpart and is considered well suited to high-power step-up applications.

• Journal of The Korean Society of Integrative Medicine
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• v.2 no.3
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• pp.49-55
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• 2014

Purpose : The purpose of this study was to investigate the effect of cross bag weight and carrying bag position type on vastus medialis oblique and vastus lateralis muscle activity ratio during step up. Method : Twenty healthy subjects participated in this study. subjects randomized performed step up with bag weight less than 15%, more than 15% of totalbody weight and without bag and carrying bag position ipsilateral and contralateral. muscle activity was measured with surface electromyography. One-way analysis of variance with repeated measures was used with a significance level of 0.05 Result : The results of this study were as follows: 1. The muscle activity ratio decreased significantly ipsilateral bag position more than 15% of body weight(p<.05). Also, the muscle activity ratio increased significantly contra lateral bag position more than 15% of body weight(p<.05). Conclusion : In conclusion, it was found that applied carrying bag position with weight on VMO,VL muscle activity ratio during step up down. Therefore carrying bag position can be used to selective activate vastus medialis oblique muscle in subjects with patellofemoral pain syndrome.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1187-1194
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• 2017

In this paper, a high step-up DC-DC PWM converter with continuous input current and low voltage stress is presented for renewable energy application. The proposed converter is composed of a boost converter integrated with an auxiliary step-up circuit. The auxiliary circuit uses an additional coupled inductor and a balancing capacitor with voltage doubler and switching capacitor technique to achieve high step-up voltage gain with an appropriate switch duty cycle. The switched capacitors are charged in parallel and discharged in series by the coupled inductor, stacking on the output capacitor. In the proposed converter, the voltage stress on the main switch is clamped, so a low voltage switch with low ON resistance can be used to reduce the conduction loss which results in the efficiency improvement. A detailed discussion on the operating principle and steady-state analyses are presented in the paper. To justify the theoretical analysis, experimental results of a 200W 40/400V prototype is presented. In addition, the conducted electromagnetic emissions are measured which shows a good EMC performance.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1566-1577
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• 2015

A novel high step-up converter is presented herein, which combines the conventional buck-boost converter, the charge pump capacitor and the coupling inductor. By doing so, a quite high voltage conversion ratio due to not only the turns ratio but also the duty cycle, so as to increase design feasibility. It is noted that the denominator of the voltage conversion ratio is the square of one minus duty cycle. Above all, there is no voltage spike across the switch due to the leakage inductance and hence no passive or active snubber is needed, and furthermore, the used switch is driven without isolation and hence the gate driving circuit is relatively simple, thereby upgrading the industrial application capability of this converter. In this paper, the basic operating principles and the associated mathematical deductions are firstly described in detail, and finally some experimental results are provided to demonstrate the effectiveness of the proposed high step-up converter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.183-186
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• 2004

Unipoled piezoelectric transformers were designed with different input and output area ratios. The voltage step-up ratio increased proportionally with increasing the input area. The piezoelectric transformers operated in each transformer's resonance vibration mode. In this paper, ANSYS(FEM program) was used for analysing piezoelectric transformers. We compared with analysis and experimental results. The voltage step-up ratio showed maximum value in output area of small size. Output characteristics of piezoelectric transformers with various size were simulated. The result of analysis showed 2~7 times higher voltage step-up ratio than a experiment result.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.12
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• pp.515-519
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• 2005

We have developed shell type 765kV transformers for generator step-up. Our research and development for shell type 765kV transformers have been continued since 1990. The shell type 765kV transformers of single phase 3MVA for step-up and 500MVA for power transmission were developed in Dec. 1992 and Oct. 1996, respectively. 204MVA 765kV transformer for generator step-up was also developed with the basis of technique and experience to the present. Total 12 phases of 204MVA 765kV transformers will be delivered at Tangjin thermal power plant by 2006. This paper describes electrical and structural features of the shell type 204MVA 765kV transformer.