• Journal of the Korean institute of surface engineering
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• v.42 no.4
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• pp.179-185
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• 2009

Diamond-like carbon(DLC) films were deposited by linear ion source(LIS)-physical vapor deposition method changing the anode voltages from 800 V to 1800 V, and characteristics of the films were investigated using residual stress tester, nano-indentation, micro raman spectroscopy, scratch tester and Field Emission Scanning Electron Microscope(FE-SEM). The results showed that the residual stress and hardness increased with increasing the ion energy up to anode voltage of 1400 V. It was also found that the content of $SP^3$ carbon increased with increasing the anode voltage $SP^3/SP^2$ ratio through investigation of $SP^3/SP^2$ ratio by the micro-raman analysis. From these results, it can be concluded that the physical properties of DLC films such as residual stress and hardness are increased with increasing the anode voltage. These results can be explained that 3-dimensional cross-links between carbon atoms and Dangling bond are enhanced and the internal compressive stress also increased with increasing the anode voltage. The optimal anode voltage is considered to be around 1400 V in these experimental conditions.

• International Journal of Reliability and Applications
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• v.18 no.2
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• pp.21-44
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• 2017

Accelerated life tests (ALTs) are frequently used in manufacturing industries to evaluate the reliability of products within a reasonable amount of time and cost. Test units are subjected to elevated stresses which yield quick failures. Most of the previous works on designing ALT plans are focused on tests that involve a single stress. Many times more than one stress factor influence the product's functioning. This paper deals with the design of optimum modified ramp-stress ALT plan for Burr type XII distribution with Type-I censoring under two stress factors, viz., voltage and switching rate each at two levels- low and high. It is assumed that usage time to failure is power law function of switching rate, and voltage increases linearly with time according to modified ramp-stress scheme. The cumulative exposure model is used to incorporate the effect of changing stresses. The optimum plan is devised using D-optimality criterion wherein the ${\log}_{10}$ of the determinant of Fisher information matrix is maximized. The method developed has been explained using a numerical example and sensitivity carried out.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.7
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• pp.1250-1254
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• 2007

The multi-resonant(MR) converter has a characteristics that the parasitic components existing in the converter are absorbed into the resonant circuits. The designed MR converter could be got a high efficiency and a high power density because the switching power losses are reduced effectively due to resonant switching circuit. However, the high resonant voltage stress of switching power devices leads to the conduction loss. In this paper, it is proposed the novel alternated(AT) flyback multi-resonant converter to overcome such a drawback. The suggested converter dc input is divided by two series input filter capacitors. The resonant stress voltage is reduced to 2-3 times the input voltage without any complexity and it provides the various circuit schemes in lots of applications. The proposed flyback MR converter is verified through simulation and experiment.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2042-2044
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• 1998

In this paper, we proposed the alternated forward multi-resonant converter. It can reduce the voltage stress due to the operation of two multi resonant switches and also provides a high frequency applications. The proposed circuit is verified through the PSpice simulation and the 50W experimental set with 2MHz maximum frequency. The measured voltage stress is up to 170V of 2.9 times the input voltage and the efficiency is about 81.66% at low line.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.557-558
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• 2006

In this paper, the hysteresis characteristics by bias stress in organic thin film transistors using inkjet printing were investigated. Electron trapping increased threshold voltage for positive gate bias stress and hole trapping decreased threshold voltage for negative gate bias stress. From these phenomena, highly reproducible measurement method which minimized threshold voltage shift by choosing the proper range of gate voltage was suggested. Using this measurement method, we found that electron trapping as well as hole trapping had important influence on hysteresis characteristics.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1380-1382
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• 2005

The multi-resonant converter minimizes a parasitic oscillation by using the resonant tank circuit absorbed parasitic reactance existing in a converter circuit. So it is possible that the converter operated at a high frequency has a high efficiency because the losses are reduced. However, the resonant voltage stress across a switch is four or five times a input voltage. This high voltage stress increases the conduction loss. In this paper, we proposed the AT flyback multi-resonant converter. The proposed converter can reduce the voltage stress to two or three times by using two series input capacitors. The operational principle of the proposed converter was verified through the experimental converter.

• Journal of electromagnetic engineering and science
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• v.6 no.2
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• pp.135-145
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• 2006

This paper presents the theory, design, fabrication and characterization of the novel low actuation voltage capacitive shunt RF-MEMS switch using a corrugated membrane with HRS MEMS packaging. Analytical analyses and experimental results have been carried out to derive algebraic expressions for the mechanical actuation mechanics of corrugated membrane for a low residual stress. It is shown that the residual stress of both types of corrugated and flat membranes can be modeled with the help of a mechanics theory. The residual stress in corrugated membranes is calculated using a geometrical model and is confirmed by finite element method(FEM) analysis and experimental results. The corrugated electrostatic actuated bridge is suspended over a concave structure of CPW, with sputtered nickel(Ni) as the structural material for the bridge and gold for CPW line, fabricated on high-resistivity silicon(HRS) substrate. The corrugated switch on concave structure requires lower actuation voltage than the flat switch on planar structure in various thickness bridges. The residual stress is very low by corrugating both ends of the bridge on concave structure. The residual stress of the bridge material and structure is critical to lower the actuation voltage. The Self-alignment HRS MEMS package of the RF-MEMS switch with a $15{\Omega}{\cdot}cm$ lightly-doped Si chip carrier also shows no parasitic leakage resonances and is verified as an effective packaging solution for the low cost and high performance coplanar MMICs.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.285-291
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• 2013

In this paper, MOS-Capacitor and MOSFET devices with a Low Level Leakage Current of oxide thickness, channel width and length respectively were to investigate the reliability characterizations mechanism of ultra thin gate oxide films. These stress induced leakage current means leakage current caused by stress voltage. The low level leakage current in stress and transient current of thin silicon oxide films during and after low voltage has been studied from strss bias condition respectively. The stress channel currents through an oxide measured during application of constant gate voltage and the transient channel currents through the oxide measured after application of constant gate voltage. The study have been the determination of the physical processes taking place in the oxides during the low level leakage current in stress and transient current by stress bias and the use of the knowledge of the physical processes for driving operation reliability.

• Journal of Magnetics
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• v.16 no.4
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• pp.427-430
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• 2011

The rolled steels for welded structure applied tensile stress have been examined by means of magnetic Barkhausen noise (MBN) method and of a physical parameter obtained from a hysteresis loop. The behaviors of MBN parameters and coercive force with tensile stress were discussed in relation to microstructure changes. There is no change in MBN parameters and coercive force below yield strength. The coercive force rises rapidly with tensile stress above yield strength. On the other hand, the rms voltage and the peak in averaged rms voltage take a maximum around yield strength and then decreases. The magnetomotive force at peak in the averaged rms voltage shows a minimum around yield strength. These phenomena are attributed to the combined effects of cell texture and dislocation density. In addition, the behaviors of MBN parameters around yield strength may be reflected by the localized changes in strain field due to the formation of dislocation tangles.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.4
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• pp.439-442
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• 2004

In this study, we investigated about electrooptics characteristic of three kinds of TN cell on the polyimide surface. Monodomain alignments of thermal stressed TN cell over temperature of liquid crystal isotropic phase were almost the same as that of no thermal stressed TN cells. However, the thermal stressed TN cells have many defects. Also, threshold voltage and response time of thermal stressed TN cells show the same performances as no thermal stressed TN cells. There were little changes of value in these TN cells. However, transmittances of TN cells on the polyimide surface decrease with increasing thermal stress time. Finally, the residual DC voltage of the thermal stressed TN cell on the polyimide surface shows decrease of characteristics as increasing thermal stress time. Therefore, the thermal stability of TN cell was decreased by high thermal stress for the long times.