• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.117-120
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• 1998

It is analyzed the erosing process of the polymeric insulator for outdoor use with the inclined plane method. Materials used are the different type of silicone rubber, they have the content of filler and component each other. As the content of filler added to improve the tracking and erosion resistance. It has the difference of electrical performance and erosion rate. The dry-band arc is also the parameter of accelerating erosion, and appear in the form of leakage current, and the activities of leakage current has a close relationship with the surface hydrophobicity. In this paper, the erosion growth is observed by measuring the time from the voltage application to the whole breakdown, and the erosion depth. In addition, it is measured the hydrophobicity and leakage current to be a cause of erosion by the erosion steps, studied SEM, EDX for observing the transformation of surface structure by erosing.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.1010-1013
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• 1998

In micromechanical system (MEMS) such as microactuators. thin film has been widely used as structural material. MEMS materials have difference with bulk in terms of mechanical properties. So, we design the advanced test structure for micromechanical properties of MEMS. The designed structure includes the newly developed pre-crack and it is driven by electrostatic force. To measure the fracture toughness, the pre-crack formation in the test structure is developed with conventional etching process. The advanced test structure is fabricated by application of semiconductor technology. After this, we propose analytical methodology to evaluate the fracture toughness and fatigue properties through a prediction of crack behavior from the variations of stiffness and frequency. Additionally, life time of a mirror plane used in DVD(Digital Video Disk) is measured as a function of capacitance and applied voltage under the accelerated conditions. Ultimately, we propose the method to evaluate the micromechanical reliabilities of the MEMS materials using the advanced test structure.

• ETRI Journal
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• v.38 no.2
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• pp.244-251
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• 2016

In this paper, we investigate the electrical characteristics of two trench-gate-type super-barrier rectifiers (TSBRs) under different p-body implantation conditions (low and high). Also, design considerations for the TSBRs are discussed in this paper. The TSBRs' electrical properties depend strongly on their respective p-body implantation conditions. In the case of the TSBR with a low p-body implantation condition, it exhibits MOSFET-like properties, such as a low forward voltage ($V_F$) drop, high reverse leakage current, and a low peak reverse recovery current owing to a majority carrier operation. However, in the case of the TSBR with a high p-body implantation condition, it exhibits pn junction diode.like properties, such as a high $V_F$, low reverse leakage current, and high peak reverse recovery current owing to a minority carrier operation. As a result, the TSBR with a low p-body implantation condition is capable of operating as a MOSFET, and the TSBR with a high p-body implantation condition is capable of operating as either a pn junction diode or a MOSFET, but not both at the same time.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.1
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• pp.3-6
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• 2008

Electrical discharge machining (EDM) is one of the most widespread nonconventional machining processes. Recently, a low-power micro-EDM process was introduced using a cylindrical electrode. Since its development, micro-EDM has been applied effectively to micromachining, and because the device setup for this process is simple, it is suitable for a microfactory that minimizes machines to fabricate small products economically in one system. In the EDM process, however, the electrode is also removed along with the workpiece. Therefore, the electrode shape and length vary as machining progresses. In this paper, a control method using a high speed realtime voltage measurement is proposed to regulate the rate and amount of material removed. The proposed method is based on the assumption that the volume of the workpiece removed in a single discharge pulses is nearly constant. The discharge pulses are monitored and controlled to regulate the amount of material removed. For this purpose, we developed an algorithm and apparatus for counting the number of discharge pulses. Electrode wear compensation using pulse number information was applied to EDM milling in a microfactory, in which a slight tilt of the workpiece may occur. The proposed control method improves the machining quality and efficiency by eliminating the inaccuracies caused by electrode wear and workpiece tilt.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.12
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• pp.1071-1079
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• 2002

This paper reports a methodology and application lot calculating distribution of the director in a liquid crystal cell by a numerical technique. To calculate distribution of the director, we applied a three dimensional finite element method (FEM) and calculated the distributions of electric potential and director in the liquid crystal cell. We have considered the free-energy density in the bulk of liquid crystal cell and calculated the switching property by the Ericksen-Leslie equation and the Laplace equation. We have calculated the optical transmission with distribution of the director by Berreman's method and confirmed the threshold voltage and the response time.

• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.397-402
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• 2007

Restenosis after percutaneous coronary intervention (PCI) continues to be a serious problem in clinical cardiology. To solve this problem, drug eluting stents (DES) with antiproliferative agents have been developed. Variable local drug delivery systems in the context of stenting require the development of stent manufacture, drug pharmacology and coating technology. We have worked on a system that integrates electrophoretic deposition (EPD) technology with the polymeric nanoparticles in DES for local drug delivery and a controlled release system. The surface morphology and drug loading amount of DES by EPD have been investigated under different operational conditions, such as operation time, voltage and the composition of media. We prepared poly-D,L-lactide-co-glycolic acid (PLGA) nanoparticles embedded with curcumin, which was done by a modified spontaneous emulsification method and used polyacrylic acid (PAA) as a surfactant because its carboxylic group contribute negative charge to the surface of CPNPs (?53.5 ± 5.8 mV). In the process of ‘trial and error' endeavors, we found that it is easy to control the drug loading amount deposited onto the stent while keeping uniform surface morphology. Accordingly, stent coating by EPD has a wide application to the modification of DES using various kinds of nanoparticles and drugs.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.554-560
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• 2009

We investigate a method for the electrochemical preparation of titanium dioxide/carbon nanotube ($TiO_2$/CNT) composites involving the electroplating of Ti in a titanium n-butoxide (TNB) electrolyte into a CNT matrix. The Brunauer-Emmett-Teller (BET) surface areas of $TiO_2$/CNT composites decrease as the electrochemical operating time increases. Changes in XRD patterns show a typical anatase type on the $TiO_2$/CNT composite prepared with a CNT matrix by the electroplating method in a TNB solution. In SEM micrographs, the titanium complex particles are uniformly distributed on the CNT surface. The results of chemical elemental analysis for the $TiO_2$/CNT composites show that most of the spectra for these samples produce stronger peaks for carbon and Ti metal than for any other element. Finally, the prominent photoelectrocatalytic activities of the $TiO_2$/CNT composites can be attributed to the combined effects of photodegradation of $TiO_2$, electron assistance of CNT, and the application of a sufficient voltage.

• Journal of the Korean Ceramic Society
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• v.46 no.4
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• pp.357-364
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• 2009

We investigate a method for the electrochemical preparation of titanium dioxide/carbon nanotube ($TiO_2$/CNT) composites involving the electroplating of Ti in a titanium n-butoxide (TNB) electrolyte into a CNT matrix. The BET surface areas of $TiO_2$/CNT composites decreased as electrochemical operating time increased. Changes in XRD patterns showed a typical anatase type on the $TiO_2$/CNT composite prepared with a CNT matrix by the electroplating method in the TNB solution. In SEM micrographs, the titanium complex particles were uniformly distributed on the CNT surface. The results of chemical elemental analysis for the $TiO_2$/CNT composites showed that most of the spectra for these samples produced stronger peaks for carbon and Ti metal than those of any other element. Finally, the prominent photoelectrocatalytic (PEC) activities of the $TiO_2$/CNT composites could be attributed to the combined effects of photodegradation of $TiO_2$, electron assistance of CNT and the application of a sufficient voltage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.5
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• pp.430-435
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• 2007

This paper describes the results of electrical characteristics assessment for organic insulations of polyethylene(PE) series insulations and acrylonitrile butadiene styrene copolymer(ABS). In the experiment, 4 kinds of specimens by composition density were tested in relative permittivity, specific resistance and tracking duration. A WinDETA system and a tracking test set manufactured for this assessment were used to measure the dielectric parameters and tracking duration, respectively. In measuring the tracking duration, the time from testing voltage application to testing circuit breaking due to the tracking current was measured. As a result, dielectric dispersion was observed in measuring the relative permittivity of ABS. It was confirmed that the relative permittivity decreased with the density of the PE series insulations and it depends rather on the temperature than frequency. In most specimens, specific resistance exponentially decreased with frequency and the result for each specimen was almost similar. By the way, in the tracking test, all the PE series insulations showed more excellent performance than ABS and especially in the case of HDPE, its tracking withstand performance was the best.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.683-689
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• 2016

Most outdoor solid insulators may suffer from surface degradations due to non-stationary currents that flow on the insulator surface. These currents may be classified as leakage, discharge and tracking currents due to their disturbing potencies respectively. The magnitude of these currents depends on the degree of the contamination of surface. The leakage signals are followed by discharge signals and tracking signals which are capable of forming carbonized tracking paths on the surface between high voltage and earth contacts (surface tracking). Surface tracking is one of the most breakdown mechanisms observed on the solid insulators, especially polymers which may cause severely reduced lifetime. In this study the degradations observed on polyester resin based insulators are investigated according to the IEC 587 Inclined Plane Test Standard. The signals are monitored and recorded during tests until surface tracking initiated. In order to prevent total breakdown of an insulator, early detection of tracking signals is vital. Continuous Wavelet Transform (CWT) is proposed for classification of signals and their energy levels observed on the surface. The application of CWT for processing and classification of the surface signals which are prone to display high frequency oscillations can facilitate real time monitoring of the system for diagnosis.