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

• Archives of Plastic Surgery
• /
• v.32 no.4
• /
• pp.496-502
• /
• 2005

This study was performed to compare the effect of external ultrasound assisted PAL(power assisted liposuction) with that of PAL alone. We performed 17 cases of liposuction from January 2003 to June 2003. For comparing both systems, we treated the right side(study group) with external ultrasound assisted PAL and the left side(control group) with PAL alone. To evaluate the difference in results between two groups, we surveyed three objective and four subjective items. Objectives were categorized as "Reduction rate of postoperative swelling", "Efficiency of suction" and "Histologic finding of aspirated fat tissue". Subjectives were also filed as "Degree of postoperative bruising", "Cannula resistance that operator felt", "Degree of postoperative pain" and "Patient's satisfaction". We assessed by questionnaire three times at 1day, 7 days and 30 days after operation. There were statistically significant differences in two of the subjective items; "Degree of postoperative pain at postoperative 1 day" and "Cannula resistance that operator felt". This study concludes that external ultrasound PAL is more effective high mobility of fat tissue and low tension of surrounding tissue. External ultrasound PAL will be more useful in case of large volume liposuction and revision procedures.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.3
• /
• pp.1296-1301
• /
• 2012

This paper deals with development of the driving-will control system in power-assisted electric wheelchair. Nowadays, population of elderly people has been increased rapidly, and also an electric wheelchair has been considered as the device for the elderly. Especially, power-assisted electric wheelchair can overcome problems that a conventional electric wheelchair holds, such as lack of movement of wheelchair user. In this paper, we propose the sensors system to measure the driving-will force and perform the control action for a power-assisted electric wheelchair. And motion performance of the proposed system is verified through the experiment.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2003.11a
• /
• pp.126-130
• /
• 2003

The optical power transfer of TM modes in grating-assisted directional couplers (GADCs) with three-guiding channels is rigorously evaluated by defining a novel coupling efficiency amenable to the rigorous analytical solutions of modal transmission-line theory (MTLT). The results reveal that the incident power is sensitively partitioned through three output channels in terms of such grating parameters as the period, the duty cycle, and wavelength.

• Journal of Power Electronics
• /
• v.3 no.1
• /
• pp.1-9
• /
• 2003

This paper presents a performance analysis of typical Auxiliary Resonant Commutation Snubber-assisted three phase voltage source soft switching inverter which can operate under a condition of Zero Voltage Switching (ZVS) using a digital control scheme which is suitable for high power applications compared with resonant DC link snubber assisted soft switching inverter. The system performances of this inverter are illustrated and evaluated on the basis of experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.8
• /
• pp.3360-3365
• /
• 2011

This paper deals with method to measure the user's driving-will force and to control the power-assisted wheelchair. To solve this problem, we extract the user's driving-will by using the mathematical motor model. And then, we get the linear and angular velocity at the center of the vehicle. Wheel velocities are also measured from center velocity. Finally, power-assisted electric wheelchairs are controlled by these data. Here all processes are verified by simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.339-339
• /
• 2010

Photo-assisted wet chemical etching of GaN thin film was studied using KOH based solutions. A $2{\mu}m-2{\mu}m$ titanium line-and-space pattern was used as a etching mask. It is found that the etching characteristics of the GaN thin film is strongly dependent on the pattern direction by unisotropic property of KOH based solution. When the pattern was aligned to the [$11\bar{2}0$] directions, ($10\bar{1}n$)-facet is revealed constructing V-shaped sidewalls.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.5B no.2
• /
• pp.111-117
• /
• 2005

Several of the conventional hydraulic systems in an automobile are now being replaced by more reliable and energy efficient electromechanical systems. Developments in the brushless permanent magnet machine and in the power and control electronics are the key factors responsible for this transformation. These applications brought out some performance challenges associated with the brushless machines. This paper will focus on these challenges to be able to use these machines in such applications. In terms of replacing hydraulic systems with electromechanical systems, steering system is leading the way in automobiles. Currently, steering systems using Electro-hydraulically assisted systems and Electrically assisted (Electromechanical) systems are in the market. Though the Electrically assisted power steering has several advantages over other systems, certain performance and cost challenges delayed the penetration of such systems in to the market.

• Journal of the Korean Society of Safety
• /
• v.33 no.5
• /
• pp.164-169
• /
• 2018

A detailed fatigue evaluation procedure was developed to mitigate the excessive conservativeness of the conventional environmental fatigue evaluation method for the pressurizer spray line elbow of domestic new nuclear power plants. The pressurizer spray line is made of austenitic stainless steel, which is relatively sensitive to the environmentally assisted fatigue, and has a low degree of design margin in terms of environmentally assisted fatigue due to the thermal stratification phenomenon on the pipe cross section as a whole or locally. In this study, to meet the environmental fatigue design requirements of the pressurizer spray line elbow, the new environmental fatigue evaluation has been performed, which used the ASME Code NB-3200-based detailed fatigue analysis and the environmental fatigue correction factor instead of the existing NB-3600 evaluation method. As a result, the design requirements for environmentally assisted fatigue were met in all parts of the pressurizer spray line elbow including the fatigue weakened zones by thermal stratification.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.7 no.1
• /
• pp.11-19
• /
• 2010

A gas-assisted hydraulic breaker uses both hydraulic and pneumatic energies and the appropriate balance between them mostly effects its performance. Mathematical modeling of the breaker is established and verified by experiment. Through sensitivity analysis using AMESim, the key design parameters are selected, which mostly affect the performance of the breaker. Taguchi method is used to optimize the key design parameters to maximize the output power for long and short strokes through simulation. As the result, the output power as well as the impact energy are increased significantly compared with the existing design. The pressure pulsation in the supply line is reduced to a tolerable level and the dynamic characteristics of the piston displacement is also improved by the optimization.