• Journal of the Korean institute of surface engineering
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• v.36 no.1
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• pp.27-33
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• 2003

Pulsed magnetron sputtering of graphite target was employed for deposition of diamond-like carbon (DLC) films. Time-resolved probe measurements of magnetron discharge plasma have been performed. It was shown that the pulsed magnetron discharge plasma density ($∼10^{17}$ $m^{-3}$ ) is close to that of vacuum arc cathode sputtering of graphite. Raman spectroscopy was sed to examine DLC films produced at low ( $U_{sub}$ / < 1 kV) pulsed bias voltages applied to the substrate. It has been shown that maximum content of diamond-like carbon in the coating (50-60%) is achieved at energy per deposited carbon atom of $E_{c}$ =100 eV. In spite of rather high percentage of $sp^3$-bonded carbon atoms and good scratch-resistance, the films showed poor adhesion because of absence of ion mixing between the film and the substrates. Electric breakdowns occurring during the deposition of the insulating DLC film also thought to decrease its adhesion.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.13-13
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• 2010

Switching an elementary excitation by injecting a single carrier would offer the exciting opportunity for the ultra-high data storage technologies. However, there has been no methodology available to investigate the interaction of low energy discrete carriers with nano-structures. In order to map out the spatial dependency of such single carrier level interactions, we developed a pulse-and-probe algorithm, combining with low temperature scanning tunneling microscopy. The new tool, which we call single carrier spectroscopy, allows us to track the interaction with the target macrostructure with tunneling carriers on a single carrier basis. Using this tool, we demonstrate that it is possible not only to locally write and erase individual bi-solitons, reliably and reversibly, but also to track of creation yields of single and multiple bi-solitons. Bi-solitons are pairs of solitons that are elementary out-of-phase excitations on anti-ferromagnetically ordered pseudo-spin system of Si dimers on Si(001)-c(42) surfaces. We found that at low energy tunneling the single bisoliton creation mechanism is not correlated with the number of carriers tunneling, but with the production of a potential hole under the tip. An electric field at the surface determines the density of the local charge density under the tip, and band-bending. However a rapid, dynamic change of a field produces a potential hole that can be filled by energetic carriers, and the amount of energy released during filling process is responsible for the creation of bi-solitons. Our model based on the field-induced local hole gives excellent explanation for bi-soliton yield behaviors. Scanning tunneling spectroscopy data supports the existence of such a potential hole. The mechanism also explains the site-dependency of bi-soliton yields, which is highest at the trough, not on the dimer rows. Our study demonstrates that we can manipulate not just single atoms and molecules, but also single pseudo-spin excitations as well.

• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1097-1102
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• 2010

Silver coated copper powders were prepared by a chemical reduction method with controlling the deposition process variables such as the feeding rate of the silver ionic solution and concentration of the reductants at room temperature. The characteristics of the products were evaluated by scanning electron microscope (SEM), X-ray diffractometer (XRD), atomic absorption spectrophotometer (AA) and a 4 probe resistivity measurement system. The optimum condition of the preparation of Ag coated Cu powders was at 0.05 M of potassium sodium tartrate and 2 ml/min of the feeding rate of the silver ionic solution. Our method successfully produced dense, uniform, and well-dispersed Ag coated Cu powder of $2{\sim}2.5{\mu}m$ witha silver layer of 100~200 nm. Additionally, we found that thespecific resistivity of the 30 wt.% Ag coated Cu powder was similar to that of pure silver, so that the composite powder could be used as an alternative electromagnetic shielding material for silver.

• Korean Journal of Metals and Materials
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• v.47 no.4
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• pp.256-260
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• 2009

This study examined the effects of plated temperature on the surface morphology and property of an electrodeposited copper foil. The morphology, crystal structure and electric characteristics of the electrodeposited copper foil were examined by scanning electron microscopy, X-ray diffraction, and a four-point probe, respectively. The surface roughness, crystal growth orientation and resistivity could be controlled using various temperature of electrolyte. Large particles were observed on the surface of the copper layer electroplated onto the $30^{\circ}C$. However, a uniform surface, lower resistivity and high flexibility were obtained when a $50^{\circ}C$ electrolyte was used.

• Journal of Biomedical Engineering Research
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• v.43 no.6
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• pp.409-416
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• 2022

Since the detection of cervical intraepithelial neoplasia (CIN) is increasing due to regular cervical cancer screening, there is a high demand for simpler tools to diagnose and treat CIN in the clinic. In this study, we proposed an electric property of cervical tissue to verify treatment using a laser. At first, we observed the depth and width of ablated cervical tissues for 29 samples according to four different pulse energy of the fractional CO₂ laser to find enough pulse energy to reach the basement layer for initiated CIN. And then, the relative frequency differences in impedance spectrum before and after laser irradiation for ten non-CIN samples were collected using bioimpedance spectroscopy with a multi-electrode probe. As a result, the laser ablated the cervical tissues with a depth of more than 300 ㎛ at 100 mJ pulse energy. Also, we confirmed that the relative changes of electrical property for cervical tissue increased as the pulse energy of laser output increased, and the variation between samples decreased. Since the relative change in electrical properties of cervical tissue can be easily and quickly measured, the proposed technique paves the way for further verification and follow-up study of laser treatment for CIN.

• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.10-14
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• 2008

Differently from BSCCO tapes which are fabricated by powder-in-tube method, the coated conductors are made by the evaporation of YBCO on metal substrate. Due to this structural merit, although the coated conductors are generally used for large current transportation, they are expected to be favorable to the purpose of the fault current limitation as well. In this study, using YBCO coated conductor having copper stabilizer formed by plating technique(produced by Superpower Co.), we investigated the over-current characteristics of the coated conductor. The coated conductors had 85 A $I_c$ and 90 K $T_c$. The resistance of the conductor was 0.93 $m{\Omega}/cm$ at 300 K and 0.17 $m{\Omega}/cm$ at the temperature right above $T_c$. To the coated conductors, we applied the voltages of the range from 150 $V_{rms}$ to 230 $V_{rms}$ and measured the V-I curves using four probe method. From the results, we could analyze the electric behavior of the coated conductor in flux flow state. As the current exceed $I_c$, the currents were distributed into the superconductor and metal stabilizer. The amounts of the currents shared through both current paths were calculated under the assumption that the ,Joule heating was perfectly eliminated by $LN_2$ surrounding the conductor. Finally, the condition for the stable current flowing state which does not affect the conductor was established from the analysis on the over-current characteristics.

• Clinical Pain
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• v.18 no.2
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• pp.65-69
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• 2019

Objective: This study aims to evaluate the efficacy of high-voltage microcurrent therapy in patients with herniated lumbar disc (HLD) presenting radicular or back pain. Method: This is a retrospective study with 33 patients who are complaining pain with HLD findings on magnetic resonance image. Microcurrent therapy was applied to leg or paralumbar area. Treatment was conducted for seven minutes with 250~1000 uA intensity as high as the patients could tolerate via stimulating probe with roller type and the frequency was 60 Hz with a sine wave pulse. The visual analogue scale (VAS) was measured just before and after the treatment. Results: The degree of pain reduction (△VAS) was 1.6 points after treatment on average. The △VAS according to the diagnosis, stenosis, dermatome area, medication, pain site and caudal epidural block was not statistically significant. However, the △VAS according to the number of treatments (< 3, ≥ 3 times) showed a statistically significant difference (p=0.04). Conclusion: High-voltage microcurrent therapy may help reduce lumbar or lumbosacral radiating pain after the procedure. The effect was better when microcurrent was applied three times or more. This result suggests that the microcurrent would have cumulative effect on reducing radicular or back pain in patients with HLD.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.1
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• pp.101-107
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• 2012

When wireless devises for MICS(Medical Implant Communication Service) or ISM(Industrial Scientific and Medical) bands are designed, it is necessary to verify the performance by using a human body flat phantom. However, most of studies on the phantom are limited to the biological effects of mobile-phone EMF. In this paper, semi-solid phantoms having the electric properties suggested by FCC at MICS and ISM bands are fabricated. The manufactured phantoms satisfy the electric properties($\varepsilon_r=56.7$ and $\sigma=0.94$ at MICS band, $\varepsilon_r=52.7$ and $\sigma=1.95$ at ISM band) at each band. All the composing materials for phantoms are commercially available in domestic market. Two methods using both polyethylene powder and TX-151 and glycerin at each band are proposed for diverse purpose. The electrical properties of the fabricated phantoms are measured by a dielectric probe kit and network analyzer after the lapse of one day (24 hours).

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.312-319
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• 1997

The magnetometer is one of the most important payloads for scientific satellite to monitor the near-earth space environment. The electromagnetic variations of the space environment can be observed with the electric and magnetic field measurements. In practice, it is well known that the measurement of magnetic fields needs less technical complexities than that of electric fields in space. Therefore the magnetometer has long been recognized as one of the basic payloads for the scientific satellites. In this paper, we discuss the scientific fluxgate magnetometer which will be on board the KITSAT-3. The main circuit design of the present magnetometer is based on that of KITSAT-1 and -2 but its facilities have been re-designed to improve the resolution to about 5nT for scientific purpose. The calibration and noise level test of this circuit have been performed at the laboratory of the Tierra Tecnica company in Japan.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.672-678
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• 2011

In this work, carbon fibers were electrolessly Ni-plated in order to investigate the effect of metal plating on the electromagnetic shielding effectiveness (EMI-SE) of Ni-coated carbon fibers-reinforced epoxy matrix composites. The surfaces of carbon fibers were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Electric resistance of the composites was tested using a 4-point-probe electric resistivity tester. The EMI-SE of the composites was evaluated by means of the reflection and adsorption methods. From the results, it was found that the EMI-SE of the composites enhanced with increasing Ni plating time and content. In high frequency region, the EMI-SE didn't show further increasing with high Ni content (Ni-CF 10 min) compared to the Ni-CF 5 min sample. In conclusion, Ni content on the carbon fibers can be a key factor to determine the EMI-SE of the composites, but there can be an optimized metal content at a specific electromagnetic frequency region in this system.