• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.2
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• pp.59-64
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• 2001

The distribution of current in the conductors influenced by the armature geometry and velocity is an important parameter for determining performance of an electromagnetic launcher(EML). the electric current in the early launching stage tends to flow on the outer surfaces of the conductors, resulting in very high local electric current density. However, the tendency for current to concentrate on the surface is driven by the velocity skin effect later in launching stage. The high current density produces high local heating and, consequently, increases armature wear which causes several defects on EML system. This paper investigates the effects of rail/armature geometry on current density distribution, launcher inductance gradient (L'), and contact force. Three geometrical parameters are used here to characterize the railgun system. These are the ratio of contact length to root length, relative position of contact leading edge to root trailing edge, and the ratio of rail overhang to the rail height. The distribution of current density, L', contact force between various configurations of the armature and the rail are analyzed and compared by using the EMAP3D program.

• Journal of the Korean Society of Physical Medicine
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• v.14 no.1
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• pp.1-5
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• 2019

Purpose: In chronic stroke patients, muscle tone and stiffness increase due to ankle spasticity. Electrotherapy may control the spasticity of patients with central nerve system damage via neurophysiological mechanisms. Therefore, this study was conducted to determine the immediate effects of interferential current therapy on gastrocnemius (GCM) muscle. Methods: This study was a one-group pretest-posttest design and 20 stroke patients participated. The experimental group underwent interferential current therapy for GCM for 30 minutes. Muscle tone (MT) and stiffness were assessed using MYOTONE(R) PRO. After 30 minutes of interferential current therapy, MT and stiffness of the affected side and unaffected side by GCM were measured. Results: After interferential current therapy, the medial GCM MT (Hz) was significantly reduced in stroke patients. There was a significant difference in MT between affected GCM muscles and unaffected side medial GCM muscles before intervention, but there was no significant difference after interferential current therapy. Conclusion: This study demonstrated that interferential current therapy had a positive effect, producing an immediate decrease in the medial GCM muscles tone of stroke patients. However, this study employed a one-group pretest-posttest design. Future studies will show differences in muscle tone compared to a control group or other electrical stimulation treatments.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.487-494
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• 2020

In this paper, we propose a current memory circuit design that reduces static power consumption and maximizes the advantages of current mode signal processing. The proposed current memory circuit minimizes the problem in which the current transfer error increases as the data transfer time increases due to clock-feedthrough and charge-injection of the existing current memory circuit. The proposed circuit is designed to insert a support MOS capacitor that maximizes the Miller effect in the current transfer structure capable of low-power operation. As a result, it shows the improved current transfer error according to the memory time. From the experimental results of the chip, manufactured with MagnaChip / SK Hynix 0.35 process, it was verified that the current transfer error, according to the memory time, reduced to 5% or less.

• Physical Therapy Korea
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• v.3 no.1
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• pp.12-23
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• 1996

High Voltage Pulsed Current Stimulation(HVPCS) and Microcurrent Electrical Neuromuscular Stimulation(MENS) have been used to promote the healing of decubitus ulcer and surgical wounds. The benefits of HVPCS and MENS are thought to include an inhibitive effect on bacterial growth. The purpose of this study was to compare the inhibitive effect of two different electrical stimulation techniques growth in vitro. Using agarose-based media, the two bacterial species Staphylococcus aureus, Esherichia coli - which are commonly isolated from open wounds were incubated in an incubator for 24 hours following exposure to HVPCS(400 V, 120 pps, $70{\mu}s$) and MENS($100{\mu}A$, 0.3 Hz). We then measured the zone of inhibition around each electrode. Both HVPCS and MENS produced an inhibitive effect on bacterial growth in this vitro study. However MENS was more effective than HVPCS.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.20 no.3
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• pp.203-224
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• 2016

The heat and mass transfer characteristics of the unsteady hydromagnetic natural convection flow with Hall current and Soret effect of an incompressible, viscous, electrically conducting, heat absorbing and optically thin radiating fluid flow past a suddenly started vertical infinite plate through fluid saturated porous medium in a rotating environment are taken into account in this paper. Derivations of exact analytical solutions are aimed under different physical properties. The velocity, concentration and temperature profiles, Sherwood number and Nusselt number are easily examined and discussed via the closed forms obtained. Soret effect and permeability parameter tends to accelerate primary and secondary fluid velocities whereas hall current, radiation and heat absorption have reverse effect on it. Radiation and heat absorption have tendency to enhance rate of heat transfer at the plate. The results obtained here may be further used to verify the validity of obtained numerical solutions for more complicated transient free convection fluid flow problems.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.49-56
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• 2008

This paper introduces a compact analytical current conduction model of long-channel depletion-mode n-type nanowire field-effect transistors (NWFETs). The NWFET used in this work was fabricated with the bottom-up process and it has a bottom-gate structure. The model includes all current conduction mechanisms of the NWFET operating at various bias conditions. The results simulated from the newly developed NWFET model reproduce a reported experimental results within a 10% error.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.259-266
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• 2004

In this paper. a new two types of EST(Emitter Switched Thyristor) structures are proposed to improve the electrical characteristics including the current saturation capability. Besides, the two dimensional numerical simulations were carried out using MEDICI to verify the validity of the device and examine the electrical characteristics. First, a vortical trench electrode EST device is proposed to improve snap-back effect and its blocking voltage. Second, a dual trench gate EST device is proposed to obtain high voltage current saturation characteristics and high blocking voltage and to eliminate snap-back effect. The two proposed devices have superior electrical characteristics when compared to conventional devices. In the vertical trench electrode EST, the snap-back effect is considerably improved by using the vertical trench gate and cathode electrode and the blocking voltage is one times better than that of the conventional EST. And in the dual trench gate EST, the snap-back effect is completely removed by using the series turn-on and turn-off MOSFET and the blocking voltage is one times better than that of the conventional EST. Especially current saturation capability is three times better than that of the other EST.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.769-774
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• 2003

In this paper, we report on the DC characteristics of the AlGaN/GaN HFETs using physical models on piezoelectric and thermal effects. Employing the models was found to be essential for a realistic prediction of the DC current-voltage characteristics of the AlGaN/GaN HFETs. Though use of the implementation of the physical models, peak drain current, transconductance, pinch-off voltage, and most importantly, the negative slope in the current were accurately predicted. The importance of the heat sink effect was demonstrated by the comparison of the DC characteristics of AlGaN/GaN HFETs fabricated from different substrates including sapphire, Si and SiC. Highest peak current was achieved from the device with SiC by an effective suppression of heat sink effect.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.897-900
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• 2005

This paper presents temperature control of aluminum plate using Peltier module. As one of the thermoelectric effect, Peltier effect is heat pumping phenomena by electric energy. So if current is charged to Peltier module, it absorbs heat from low temperature side and emits heat to high temperature side. In this experiment, Peltier module is used to control the temperature of small aluminum plate with heating and cooling ability of Peltier module with current control and fan On/OFF control. And current control of Peltier module was accomplished by PWM method. As a results of experiments, it takes about 125sec to control temperature of aluminium plate between $30^{\circ}C\;and\;70^{\circ}C$ and about 70sec between $40^{\circ}C\;and\;60^{\circ}C$, in ambient temperature $29^{\circ}C$ while operating cooling fan only while cooling duration. Future aim is to realize more rapid temperature control and develop SMHA(special metal hydride actuator) by using Peltier module as a heating and cooling source.

• Smart Structures and Systems
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• v.29 no.3
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• pp.457-473
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• 2022

A high-frequency vibration control method is proposed in this paper for Pumped Storage Power Plants (PSPPs) using Eddy Current Tuned Mass Damper (EC-TMD), based on which a new type of EC-TMD device is designed. The eddy current damper parameters are optimized by numerical simulation. On this basis, physical simulation model tests are conducted to compare and study the effect of structural performance with and without damping, different control strategies, and different arrangement positions of TMD. The test results show that EC-TMD can effectively reduce the control effect under high-frequency vibration of the plant structure, and after the additional damping device forms EC-TMD, the energy dissipation is further realized due to the intervention of eddy current damping, and the control effect is subsequently improved. The Multi-Tuned Mass Damper (MTMD) control strategy broadens the tuning band to improve the robustness of the system, and the vibration advantage is more obvious. Also, some suggestions are made for the placement of the dampers to promote their application.