• Journal of Advanced Marine Engineering and Technology
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• 제27권7호
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• pp.930-936
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• 2003

A new method of direct current motor drive, which requires neither shaft encoder nor speed estimator, is presented. The proposed scheme is based on decreasing current gap between a numerical model and an actual motor. By supplying the identical instantaneous voltage to both model and motor in the direction of reducing the current difference, the rotor approaches to the model speed, that is, reference value. The performance of direct current motor drives without speed sensor is generally poor at very low speed. However, in this system, it is possible to obtain good speed performance in the low speed range.

• 대한임상전기생리학회지
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• 제10권2호
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• pp.37-42
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• 2012

Purpose : This study is to examine the effect of electrode size during transcranial direct current stimulation on hand function. Methods : By randomly assigning 26 right hand dominant subjects to two groups (I: carbon rubber electrode / II: disposable circular self-adhesive electrodes) with 13 subjects in each group depending on the electrode size, a positive electrodeof transcranial direct current stimulation was placed on the primary motor area (C4) and a negative electrode was placed on the left primary motor area (C3) and the stimulation was applied for 20 minutes.Hand function assessment before and after transcranial direct current stimulation were measured with JTT (Jebsen-Taylor hand function test). Results : According to hand function assessment by JTT, there were no interactions on both hands, and statistically significant differences according to time appeared in the main effect test. Conclusion : Regardless of the electrode size, it appears that transcranial direct current stimulation on the primary motor area activated hand function affected.

• Corrosion Science and Technology
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• 제8권3호
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• pp.93-102
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• 2009

The direct-current electroetching of high purity aluminum in hot aqueous-chloride solution produces a high density of micrometer-wide tunnels whose walls are made up of the {100} planes and penetrate aluminum in the <100> directions at rates of micrometer per second. In the process of the alternating-current pitting of aluminum, cathodic polarization plays an important role in the nucleation and growth of the pits during the subsequent polarization. The direct-current tunnel etching and alternating-current etching of aluminum are basically related to the formation of poorly crystallized or amorphous passive films. If the passive film forms on the wall, a natural misfit exists between the film and the aluminum substrate, which in turn gives rise to stress in both the film and the substrate. Even though the amorphous films do not have directed properties, their stresses are influenced by the substrate orientation. The films on elastically soft substrate are likely to be less stressed and more stable than those on elastically hard substrate. The hardest and softest planes of aluminum are the {111} and {100} planes, respectively. Therefore, the films on the {111} substrates are most likely to be attacked, and those on the {100} substrates are least likely to be attacked. For the tunnel etching, it follows that the tunnel walls tend to consist of the {100} planes. Meanwhile, the tunnel tip, where active corrosion takes place, tend to be made of four closely packed {111} planes in order to minimize the surface energy, which gives rise to the <100> tunnel etching.

• Journal of Electrical Engineering and Technology
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• 제4권3호
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• pp.370-376
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• 2009

The influence of magnetic saturation on electromagnetic field distribution in both a permanent-magnet direct-current (PMDC) motor and a field-winding (wound-field) direct-current (FWDC) motor, with the same output mechanical power, has been studied. In this paper, an approximate analytical method and time-stepping Finite Element Method (FEM) are used for prediction of Back-EMF and electromagnetic torque. No-load and rotor-lucked conditions, according to experimental measurements, and the FEM and analytical method studies of the motors have been considered. A sensitivity analysis has also been successfully accomplished on the major design parameters that affect motor performance. At last, these two DC motors are compared, in spite of their differences, on the basis of measured output characteristics.

• Journal of Medicine and Life Science
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• 제19권3호
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• pp.134-136
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• 2022

• 생물정신의학
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• 제24권4호
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• pp.175-187
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• 2017

Transcranial direct current stimulation (TDCS) is a clinically safe and effective method of delivering weak electric current to modulate cortical activities. And based on the cumulating scientific evidences, the method is recommended to treat major depressive disorder (MDD) and other psychiatric disorders. In this paper, we review the development of TDCS in the rising field of neuromodulation. Then with suggested biochemical and physical mechanism of TDCS, we summarize the reported cases of using TDCS to alleviate major neuropsychiatric disorders. And, in particular, the treatment of MDD is highlighted as an illustrative example of using TDCS. We discuss here the therapeutic potentials of this method in psychiatry. And in closing remarks, we evaluate the current technical limitations and suggest the future directions of this method in both the clinical and research aspects.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권5호
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• pp.283-294
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• 2004

This paper introduces the new Direct Torque Control(DTC) method based on the estimated torque in Switched Reluctance Motor(SRM) and applies the proposed DTC to SRM for the instantaneous torque ripple reduction. The nonlinear characteristics of SRM is considered in the calculation of the estimated torque and the theory is described in this paper. Current control is one of the kernel elements of torque controller and the performance of the current control should be high for this work. But the conventional PI current control has a weak point in SRM application because of motional EMF. Consequently, this paper makes up for the weakness of PI controller through present of new current controller, that is termed the non-interference current control. The ability of proposed torque and current controller is verified through simulation and experiment.

• 한국초전도ㆍ저온공학회논문지
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• 제18권4호
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• pp.30-34
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• 2016

In this study, a SFCL-combined DC circuit breaker system was proposed by applying the current-limiting technology for DC circuit breaking. The SFCL-combined circuit breaker system consists of a mechanical DC circuit breaker combined with superconductors. To ensure the reliable structure and operation of the SFCL-combined circuit breaker system, a simulation grid was designed using the EMTDC/PSCAD program, and simulation was conducted. The results showed that the SFCL-combined DC circuit breaker system with superconductors limited the maximum fault current by 37%. In addition, the burden on the DC circuit breaker was decreased by 87%.

• JSTS:Journal of Semiconductor Technology and Science
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• 제3권3호
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• pp.139-144
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• 2003

We report the results of extensive mixed mode simulations and theoretical analysis to quantify the contribution of the edge direct tunneling (EDT) current on the total gate leakage current of 80nm NMOSFET with SiO2 gate dielectric. It is shown that EDT has a profound impact on basic analog circuit building blocks such as sample-hold (S/H) circuit and the current mirror circuit. A transistor design methodology with zero gate-source/drain overlap is proposed to mitigate the EDT effect. This results in lower voltage droop in S/H application and better current matching in current mirror application. It is demonstrated that decreasing the overlap length also improves the basic analog circuit performance metrics of the transistor. The transistor with zero gate-source/drain overlap, results in better transconductance, input resistance, output resistance, intrinsic gain and unity gain transition frequency.

• 전력전자학회논문지
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• 제25권2호
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• pp.152-155
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• 2020

This study proposes an input filter for a gallium-nitride-based direct matrix converter with a stepless current commutation technique. Various current commutation strategies have been adopted for reliable operation of switches. These strategies are complex to be implemented and require additional components. The stepless current commutation technique is simple to operate but causes overcurrent issues due to the occurrence of short circuit on input sources. In this study, to restrict the short circuit current, we utilized GaN devices with fast switching properties and modified the input filter. The proposed input filter was verified by experimental results of induction motor drive.