• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.229-230
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• 2015

This paper presents practical details about control-loop design and dynamic analysis for a voltage-mode controlled isolated double step-down DC-DC converter. Graphical loop gain method is used to design the feedback compensation and analyze the closed-loop performance of isolated double step-down DC-DC converter. The results of the control design and closed-loop analysis are validated by experiments on a prototype converter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.10
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• pp.1474-1480
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• 2017

This paper presents a new LED current balancing scheme using double-step-down dc-dc converter. With the proposed structure, the two channel LED currents are automatically balanced without using any dedicated control or auxiliary circuit. In addition, switching loss of the switching devices in the proposed LED driver is lower than that of the conventional buck LED driver. To verify the operation of the proposed LED driver, a hardware prototype is built and tested with different number of LED.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.347-348
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• 2017

This paper presents a new current balancing operation for LED using double-step-down dc-dc converter. The two output currents of the proposed converter can be balanced by charge balance condition although the two output resistances are different. In addition, voltage stresses of the switches of the proposed converter are lower than those of interleaved buck converter. To verify the operation of the proposed converter, simulation program is used.

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.371-376
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• 2005

Relative contributions of lower extremity joints on the support moment were investigated in this study. Three-dimensional gait analyses were performed in normal walking and in unexpected step-down walking. For both gait studies, inverse dynamics were performed to obtain each joint moment of the lower extremity, which was applied to the forward dynamics simulation to determine the contributions on the support moment at different phases of walking. The forward dynamic simulation results showed that, in normal walking, the ankle plantar flexors contributed significantly during single-limb-support. However, the ankle plantar flexors, knee extensors and hip extensors worked together during double-limb-support. In unexpected step-down walking, the important contributors on the support of the body during single-limb-support were not only ankle plantar flexors but also knee extensors. This study, analyzing the relative contributions of the lower limb joint moments for the body support, would be helpful to understand different unexpected walking conditions and compensatory mechanisms for various pathological gaits.

• Journal of the Korean Society of Physical Medicine
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• v.7 no.1
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• pp.21-28
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• 2012

Purpose : The purpose of this study was to examine the gait parameter and plantar foot pressure of adults with Down syndrome(DS) during walking in order to provide data for developing evidence-based deficit or common rehabilitation strategies. Method : 15 participants with DS(12 men, 3 women; age $26.06{\pm}4.47$) and 15 healthy subjects(12 men, 3 women; age $25.33{\pm}3.43$) were matched age. They walked at self selected speeds on a GAITRite system and RS-scan system, and had the following measurements done: cadence, stride length, step width, foot angle, percent stance, percent double support, and plantar foot pressure in 10 areas of the foot. Results : In comparison of gait parameter(cadence, stride length, step width, foot angle, percent stance, and percent double support) between adults with DS and healthy subjects, there was significant differences(p<.05). Regarding plantar foot pressure during gait with or without DS, there were statisically significant differences in the area of Toes 1-5, Metatasal 1-4, Midfoot, and Heel(Medial and lateral)(p<.05). Conclusion : Our data show that DS walk with a less physiolosical gait pattern and plantar foot pressure than healthy subjects. Based on our results, DS patients need targeted rehabilitation and exercise strategies.

• Journal of Power Electronics
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• v.18 no.2
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• pp.343-355
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• 2018

A wide-voltage-conversion range bidirectional DC-DC converter is proposed in this paper. The topology is comprised of one typical LC energy storage component and a special common grounded asymmetric H-bridge with four active power switches/anti-parallel diodes. The narrow output PWM voltage is generated from the voltage difference between two normal (wider) output PWM voltages from the asymmetric H-bridge with duty cycles close to 0.5. The equivalent switching frequency of the output PWM voltage is double the actual switching frequency, and a wide step-down/step-up ratio range is achieved. A 300W prototype has been constructed to validate the feasibility and effectiveness of the proposed bidirectional converter between the variable low voltage side (24V~48V) and the constant high voltage side (200V). The slave active power switches allow ZVS turn-on and turn-off without requiring any extra hardware. The maximum conversion efficiency is 94.7% in the step-down mode and 93.5% in the step-up mode. Therefore, the proposed bidirectional topology with a common ground is suitable for energy storage systems such as renewable power generation systems and electric vehicles with a hybrid energy source.

• Journal of the Korean Institute of Landscape Architecture
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• v.23 no.2
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• pp.157-166
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• 1995

To investigate walkability of ramps, walking patterns of 18 healthy adults,12 aged 20 to 26 and 6 aged 68 to 76,were studied at free,rhythm constrained walking up or down ramp using goniometer and footswitch Ramp inclinations were set 4,8,12,16,20 degrees. The results were as follows. 1)The step length of subjects were decreased significantly in12$^{\circ}C$′or 16′free downramp walking. With regard to step length, some subject groups walked abnormally in 16" or 20" ramp walking 2) The step width of subjects were increased significantly in 12" or 16" ramp walking. 3) The cadence duration of some subject groups were increased in 12" upramp walking. 4) The double stance duration and double stance ratio of some subject groups were increased significantly in 8",12", or 16"upramp walking. 5) The maximum knee flexion angle of stance phase were increased in 12" ramp walking. 6)Most temporal parameters and spatial parameters of gait were increased or decreassd greatly between 4" ramp and 8" ramp or between 8′ramp and 12′ramp. But statistics significancy were not recognized 7) The results suggest that ramp inclination less than 8′(14%) -12′(21%) is desirable for the normal gait the ramp inclination must not exceed 16" -20" in unavoidable circumstances.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.43-48
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• 2016

3-Dimensional System in Package (3-D SiP) structure (Amkor calls it mPossum-molded Possum) using double side Surface Mount Technology (SMT) and double side molding was evaluated in order to achieve small/thin form factor as well as good functionality by integration and double side layout. As the new platform on laminate substrate basis, molding process was challenge in mold flow balance at top and bottom side and package warpage control over the overall assembly process. There were two types of different molding process evaluated with 1) 1-step molding which was done at both side at the same time and 2) 2-step molding which was done at the conventional molding process twice. Mold simulation helped to narrow down the material selections and parameters available before actual sample build. There were many challenges for this first trial in design/ parameter and material types but optimized them to enable this structure.

• Toxicological Research
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• v.17
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• pp.257-261
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• 2001

Recently, a traditional medicine called Gouteng-san, which consists of eleven herbs, was reported to be effective in treating vascular dementia with a double-blind, placebo-controlled study. Gout-eng-san is also used for patients with vascular dementia in combination with Si-Wu-Tang. The effect of Gouteng-san and Si-Wu-Tang on deficit of learning behavior was investigated using step-down passive avoidance task in mice. Hot-water extract of Gouteng-san (1.5 and 6 g/kg, p.o.) significantly prolonged the step-down latency shortened by scopolamine. The extract of Uncaria hook (150 mg/kg, p.o.), one of the component herb of Gouteng-san, significantly prevented the decrease in the latency after scopolamine. Hot-water extract of Si-Wu-Tang (1.5 and 6 g/kg of dried herbs, p.o.) prevented dose-dependently scopola-mine-induced disruption qf learning behavior. Si-Wu-Tang also prevented the ischemia-induced deficit of learning behavior. Both hot water extract of peony and angelica (1.5 g/kg, p.o.), which are component herbs qf Si-Wu-Tang, prevented the scopolamine-induced learning behavior deficit. Scopolamine (10 uM) suppressed long-term potentiation (LTP) of population spike in the CA1 region of the rat hippocampal slices. Peoniflorin (0.1~ 1uM) extracted from paeony root significantly ameliorated scopolamine-induced inhibition of LTR These results suggest that improvement of deficit of learning behavior by Gouteng-san and Si-Wu-Tang is mediated by direct and/or indirect activation of the cholinergic system in the brain.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.1
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• pp.67-76
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• 2012

Due to the increasing amount of applications of power electronic ac-dc converters, it is necessary to design a single-stage converter that can reliably perform both buck and boost operations. Traditionally, this can be achieved by double-stage conversion (ac/dc-dc/dc) which ultimately leads to less efficiency and a more complex control system. This paper discusses two types of modern ac-dc converters. First, the novel impedance-source ac-dc converter, abbreviated as custom Z-source rectifier, is analyzed; and then, switched inductor (SL) Z-source ac-dc converter is proposed. This paper describes the Z-source rectifiers' operating principles, the concepts behind them, and their superiorities. Analysis and simulation results show that the proposed custom Z-source rectifier can step up and step down voltage; and the main advantage of the SL Z-source ac-dc converter is its high step-up capability. Low ripple of the output dc voltage is the other advantage of the proposed converters. Finally, the SL Z-source ac-dc converter is compared with the custom Z-source ac-dc converter.