• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.4
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• pp.72-79
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• 1997

A study is a experiment which is figure out to optimum discharge cutting condition of the surface roughness, electronic discharging speed and electrode wear ration with Ton , Toff and V(voltage) as an input condition according to the current(Ip) in an electric spark machine : 1) Electrode is utilized Cu and Graphite. 2) Work piece is used the material of carbon steel. The condition of experiment is : 1) Current is varied 0.7(A) to 50(A) and the time of electric discharging to work piece in each time is 30(min) to 60(min). 2) After the upper side of work piece was measured in radius(5$\mu$m) of stylus analyzed the surface roughness to ade the table and graph of Rmax by yielding data. 3) Electro wear ratio is : \circled1Cooper was measured ex-machining and post-machining by the electronic balance. \circled2The ex-machining of graphite measured by it, the post-machining was found the data from volume $\times$specific gravity and analyzed to made its table and graph on ground the data. 4) In order to keep the accuracy of voltage affected to the work piece was equipped with the A.V. R and the memory scope was sticked to the electric spark machine. 5) In order to preserve the precision of current, to get rid of the noise occured by internal resistance of electric spark machine and to force injecting for the discharge fluid , it made the fixed table for a work piece to minimize the work error by means of one's failure during the electric discharging.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.12
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• pp.1115-1120
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• 2007

This paper presents a novel mechanism of electro-spray micro-thruster featured by a nozzle with a conductive pole inside, referred to here as a pole type nozzle. And the effects of the pole type nozzle on the efficiency of the jetting are numerically and experimentally investigated. The electric voltage signal applied to the upper electrode plate, against the pole as the ground, allows a ejection of spray to take place. It is verified experimentally that the use of the pole type nozzle allows a stable and sustainable jetting mode of ejection for a wider range of applied voltages because it can concentrate the electric field more on the centre of the meniscus. According to results about size effect, experiments indicates that the proposed mechanism allows that operation of micro thruster at less than 500 volts through nanoscale nozzle.

• Journal of information and communication convergence engineering
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• v.3 no.4
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• pp.179-183
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• 2005

A photodiode capable of obtaining a sufficient photo/ dark current ratio at both forward bias state and reverse bias state is proposed. The photodiode includes a glass substrate, an aluminum film formed as a lower electrode over the glass substrate, an alumina film formed as an insulator barrier over the aluminum film, a hydrogenated amorphous silicon film formed as a photo conduction layer over a portion of the alumina film, and a transparent conduction film formed as an upper electrode over the hydro-generated amorphous silicon film. A good quality alumina $(Al_2O_3)$ film is formed by oxidation of aluminum film using electrolyte solution of succinic acid. Alumina is used as a potential barrier between amorphous silicon and aluminum. It controls dark-current restriction. In case of photodiodes made by changing the formation condition of alumina, we can obtain a stable dark current $(\~10^{-12}A)$ in alumina thickness below $1000{\AA}$. At the reverse bias state of the negative voltage in ITO (Indium Tin Oxide), the photo current has substantially constant value of $5{\times}10^{-9}$ A at light scan of 100 1x. On the other hand, the photo/dark current ratios become higher at smaller thicknesses of the alumina film. Therefore, the alumina film is used as a thin insulator barrier, which is distinct from the conventional concept of forming the insulator barrier layer near the transparent conduction film. Also, the structure with the insulator thin barrier layer formed near the lower electrode, opposed to the ITO film, solves the interface problem of the ITO film because it provides an improved photo current/dark current ratio.

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.151-156
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• 2004

The purpose of this study was to develop EMG triggered FES system for restoration of upper extremity function in chronic hemiplegic patients and to identify the optimal location of electrode application for the EMG triggered FES system which produces effective muscle contraction and detects EMG activity for extension in the wrist and finger joints. The stimulus system was composed of EMG measuring component, constant current component and the program for muscle contraction by EMG triggered FES and passive FES. Parameter of electrical stimulation was 35 ㎐ in frequency, 150 ${\mu}\textrm{s}$ in pulse width and symmetric bi-phasic wave. In 15 hemiplegic patients, EMG triggered FES was applied to the proximal half of forearm which was divided into 12 areas. The most sensitive area for measuring EMG activities during extension of the wrist and fingers was area 4, 5 and the optimal location of electrical stimulation for producing extension of the wrist and fingers was area 4, 5, 7, 8. These results suggest that the area 4 and 5 was considered as the most optimal location of electrode application for measuring EMG activities as well as producing extension of the wrist and fingers by EMG triggered FES system.

• Journal of Korean Neurosurgical Society
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• v.30 no.7
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• pp.831-841
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• 2001

Objective : Somatosensory evoked potentials(SSEPs) have been used widely both experimentally and clinically to monitor the function of central nervous system and peripheral nervous system. Studies of SSEPs have reported the various recording techniques and patterns of SSEP. The previous SSEP studies used scalp recording electrodes, showed mean vector potentials which included relatively constant brainstem potentials(far-field potentials) and unstable thalamocortical pathway potentials(near-field potentials). Even in invasive SSEP recording methods, thalamocortical potentials were variable according to the kinds, depths, and distance of two electrodes. So they were regarded improper method for monitoring of upper level of brainstem. The present study was conducted to investigate the characteristics of somatosensory evoked field potentials(SSEFPs) of the cerebral cortex that evoked by hindlimb stimulation using ball electrode and the pathways of SSEFP by recording the potentials simultaneously in the cortex, VPL nucleus of thalamus, and nucleus gracilis. Methods : In the first experiment, a specially designed recording electrode was inserted into the cerebral cortex perpendicular to the cortical surface in order to recording the constant cortical field potentials and SSEFPs mapped from different areas of somatosensory cortex were analyzed. In the second experiment, SSEPs were recorded in the ipsilateral nucleus gracilis, the contralateral ventroposterolateral thalamic nucleus(VPL), and the cerebral cortex along the conduction pathway of somatosensory information. Results : In the first experiment, we could constantly obtain the SSEFPs in cerebral cortex following the transcutaneous electrical stimulation of the hind limb, and it revealed that the first large positive and following negative waves were largest at the 2mm posterior and 2mm lateral to the bregma in the contralateral somatosensory cortex. The second experiment showed that the SSEPs were conducted by way of posterior column somatosensory pathway and thalamocortical pathway and that specific patterns of the SSEPs were recorded from the nucleus gracilis, VPL, and cerebral cortex. Conclusion : The specially designed recording electrode was found to be very useful in recording the localized SSEFPs and the transcutaneous electrical stimulation using ball electrode was effective in evoking SSEPs. The characteristic shapes, latencies, and conduction velocities of each potentials are expected to be used the fundamental data for the future study of brain functions, including the hydrocephalus model, middle cerebral artery ischemia model, and so forth.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1061-1065
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• 1995

To improve dielectric and mechanical properties of insulating composite by plasma surface treatment, new plasma surface treatment process is designed with concentric and hemi-circle electrodes system, the plasma, which is generated between anode and cathode, is induced to the upper side of the electrode system and treats the surface of the insulators. The optimal surface treatment condition is that pressure : 0.5[torr], flux density 100[gauss], discharge current : 500[mA] and treatment time : 3 minutes. The composite filled with glass cloth surface-treated by plasma shows the improvement in electric and mechanical properties, comparing non- and coupling agent-treated samples.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.147-148
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• 2008

In this paper, we calculated the axial magnetic field at mid-gap plane between upper and lower electrode in vacuum interrupter by means of commercial finite element method Maxwell 3D and compared on the basis of "effective area" criterion. The models used in this paper are coil type(axial magnetic field) vacuum interrupter electrodes which have different numbers of coil segment. We used Dr. Schulmann's experimental equation which indicates minimum critical value of axial magnetic field to diffuse arc.

• Electrical & Electronic Materials
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• v.8 no.4
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• pp.434-442
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• 1995

To improve dielectric and mechanical properties of insulating composite by plasma surface treatment, new plasma surface treatment process is designed with concentric and hemi-circle electrodes system. the plasma, which is generated between anode and cathode, is induced to the upper side of the electrode system and treats the surface of the insulators. The optimal surface treatment condition is that pressure : 0.5[torr], flux density : 100[gauss], discharge current : 500[mA] and treatment time : 3 minutes. The composite filled with glass cloth surface-treated by plasma shows the improvement in electric and mechanical properties, comparing non- and coupling agent treated samples.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1728-1731
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• 1996

To develop more sensitive humidity sensor on high temperature region, in this paper, we prepared polyimide humidity sensor by electrophoretic method. Sensing properties of be sensor in high temprature region were studied and compared with that prepared by solution casting method. From the result, the thiner film thickness, the more sensitive. however, It is difficult to make he thickness optimal because of short between electrodes, and the thickness of upper electrode is one of most important parameters affecting pefomance of the sensor.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.259-262
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• 2008

This paper describes the ground surface potential profiles near the object to be grounded. The hemisphere water tank was used to simulate the. scale model. As a result, the ground surface potential near the ground electrode was considerably raised. In particular the ground surface potential at the just upper part of ground rod was higher than other part. The ground surface potential was lowered with increasing the buried depth of ground rod.