• The Journal of the Korea Contents Association
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• v.20 no.1
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• pp.356-363
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• 2020

As a becoming era of Internet-of-Things, various devices are connected via wire or wirless networks. Although every day life is more convenient, security problems are also increasing such as privacy, information leak, denial of services. Since ECC, a kind of public key cryptosystem, has a smaller key size compared to RSA, it is widely used for environmentally constrained devices. The key of ECC in constrained devices can be exposed to power analysis attacks during scalar multiplication operation. In this paper, a key-randomization method is suggested for scalar multiplication on SECG parameters. It is against differential power analysis and has operational efficiency. In order to increase of operational efficiency, the proposed method uses the property 2^lP=∓cP where the constant c is small compared to the order n of SECG parameters and n=2^l±c. The number of operation for the Coron's key-randomization scalar multiplication algorithm is 21, but the number of operation for the proposed method in this paper is (3/2)l. It has efficiency about 25% compared to the Coron's method using full random numbers.

• Journal of the Korean Chemical Society
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• v.18 no.1
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• pp.8-11
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• 1974

The solvolysis of p-substituted benzenesulfonyl chlorides $(substituents:p-H, p-Br, p-NO_2, p-OCH_3)$ in acetonitrile-water mixtures below 50 % of water content has been studied kinetically. Results show that Hammett plots give concaved curves but the mechanism is predominantly $S_N2$ and water acts both as nucleophile and general-base.

• Analytical Science and Technology
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• v.21 no.1
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• pp.20-24
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• 2008

A chemiluminescence method has been developed to determine vitamin $P_1$ in aqueous solution which is based on the enhancement of the intensity of lucigenin using lucigenin-$H_2O_2$ as chemiluminogenic system. The effects of experimental parameters such as concentrations of lucigenin, pH and concentrations of $H_2O_2$ were studied. The present method allows the determination of vitamin $P_1$ over the range $7.5{\times}10^{-6}{\sim}5.0{\times}10^{-4}mol/L$. The detection limit was $5.7{\times}10^{-7}mol/L$. The relative standard deviation was 0.75 % for 10 determinations of $7.5{\times}10^{-5}mol/L$ vitamin $P_1$. The correlation coefficient of the working curve was 0.9984 (S/N=3).

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.201-206
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• 2003

This study is test for STS304 specimen using bending and torsion state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed If summarize STS304 torsion result of fatigue test, is as following. Fatigue life prediction was available by Weibull statistics distribution, and 50% breakdown probability correlation equation was appeared as following.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.199-204
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• 2001

Big accidents of flyings, vessel, subways, gas equipments, buildings and bridge happens frenquently. Therefore many people are suffering harm of property. The destruction cause of macaine components is almost accused by fatigue. This study is test for STS304 specimen using pure and cantilever bending state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1691-1694
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• 2005

The fatigue characteristic of a material or a structure is derived from fatigue tests of standard specimens. However test results of standard specimens are very different from those of real structures or components. Therefore, to calculate more accurate fatigue life, the geometrical effect and surface condition must be considered by comparing test results of standard specimens with those of real structures or components. Thus the object of this paper is to evaluate the fatigue characteristic of a real waterwork pipe by conducting fatigue tests with standard specimens and non-standard(plate-shaped) specimens of base metal and weld metal. Also, to evaluate fatigue characteristic based on life distribution, statistical fatigue characteristic was analyzed by the normal distribution and related data of P-S-N curve.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.2
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• pp.71-82
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• 1984

A programme, called BIPOLE, for the numerical analysis of twotimensional n-p-n bipolar transistors was developed. It has included the SRH and Auger recolnbination processes, the mobility dependence on the impurity density and the electric field, and the band-gap narrowing effect. The finite difference equations of the fundamental semiconductor equations are formulated using Newton's method for Poisson's equation and the divergence theorem for the hole and electron continuity equations without physical restrictions. The matrix of the linearized equations is sparse, symmetric M-matrix. For the solution of the linearized equations ICCG method and Gummel's algorithm have been employed. The programme BIPOLE has been applied to various kinds of the steady-state problems of n-p-n transistors. For the examples of applications the variations of common emitter current gain, emitter and diffusion capacitances, and input and output characteristics are calculated. Three-dimensional representations of some D.C. physical quantities such as potential and charge carrier distributions were displayed. This programme will be used for the nome,rical analysis of the distortion phenom ana of two-dimensional n-p-n transistors. The BIPOLE programme is available for everyone.

• Clinical and Experimental Pediatrics
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• v.52 no.9
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• pp.984-990
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• 2009

Purpose : Being small for gestational age (SGA) is a risk factor of short stature in children. Genetic background such as mid-parental height (MPH) is known to influence growth of children born SGA. We studied the relationship between growth of children born SGA and MPH and studied the effects of insulin-like growth factor (IGF-I) and insulin-like growth factor binding protein 3 (IGFBP-3) on postnatal growth in children born SGA according to MPH. Methods : Forty-nine neonates born SGA were included in this study. We defined corrected height standard deviation score (cHtSDS) by modified height SDS (HtSDS) based on their MPH. We categorized subjects into group 1 consisting of children with cHtSDS ${\geq}0$ (n=35) and group 2 consisting of children with cHtSDS <0 (n=14), and compared IGF-I and IGFBP-3 between the two groups. Results : The HtSDSs and cHtSDSs in groups 1 and 2 were $0.06{\pm}1.05$ vs. $-0.95{\pm}0.85$ (P=0.000) and $0.78{\pm}0.93$ vs. $-0.46{\pm}0.67$ (P=0.000), respectively. IGF-I SDS was higher in group 1 than in group 2 ($2.82{\pm}3.69$ vs. $0.23{\pm}2.42$, P=0.012). Total cHtSDS ($0.42{\pm}1.03$) was significantly higher than HtSDS ($-0.22{\pm}1.10$) (P=0.000). Conclusion : Our results show that cHtSDS differs significantly from HtSDS. Growth assessment by standardized growth curve does not uniformly show effects of genetic factors. A more accurate assessment of growth uses a personalized corrected growth curve that considers the genetic factor measured by MPH.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.33-33
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• 2000

일반적으로 GaN-based light emitting diodes(LEDs)는 Top layer위에 금속박막으로 contact을 형성하고 있으며 광소자 구성에 있어 빛은 이러한 금속 contact을 통과할 수 없다. 그러나 만약 이러한 contact이 투명전도막으로 구성될 수 있다면 보다 효율적인 광소자의 구성이 기대되어진다. 특히 GaN photodetector, GaN-based LEDs, GaN vertical cavity surface emitting lasers(VCSELs)등의 소자형성에 있어 투명전도막 contact은 매우 중요하며 그 응용에 앞서 기본적인 구조적, 전기적, 광학적 특성에 대한 연구가 반드시 선행되어져야 한다. 따라서 본 실험에서는 이러한 투명전도막으로써 Indium Tin Oxide(ITO)를 사용하였으며 박막형태의 contact으로 제조하여 n-GaN, p-GaN와 corning glass위에 e-beam evaporation법로써 제조하였다. 또한 각 n-, p-type과 corning glass위에 증착된 ITO박막의 구조적 특성을 분석하기 위하여 x-ray diffractometry(XRD)와 Auger electron spectroscopy(AES)등을 사용하였으며 전기적 특성을 측정하기 위하여 four point probe를 사용하였고 그들의 I-V 곡선을 측정하였다. 또한 UV spectrometry를 사용하여 그들의 광학적 특성을 측정하고자 하였다. ITO 박막의 제조에 있어 기판은 초음파 유기세정 후 HCl과 H2O2(1:1)의 혼합용액을 사용하여 GaO2를 제거하고자 하였으며 이후 초순수로 세척하여 사용하였다. 초기 진공도는 3$\times$10-5 Torr이하였으며 기판온도 50$0^{\circ}C$에서 0.6 /s의 증착속도로 약 2000 증착하였다. 이렇게 제조된 ITO 박막은 5$\times$10-5 Torr이하의 진공분위기에서 $600^{\circ}C$로 열처리를 실시하였으며 열처리 시간의 변화에 따른 그들의 전기적, 구조적, 광학적 특성을 측정하였다. 열처리 과정을 통한 ITO박막은 투과도는 420nm의 영역에서 80%이상을 나타내었으며 이때의 면저항은 약 50ohm/ 이었다. 또한 I-V 곡선 측정에 의한 contact특성의 측정결과 열처리 전의 ITO contact은 n-GaN와 n-GaN에 대해 각각 ohmic과 schottky contact의 일반적인 contact 특성을 나타내었다. 그러나 이러한 contact 특성은 열처리 시간의 변화에 따라 변화하는 것을 확인할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1119-1129
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• 2011

Shot-peening effects on the fatigue behavior of bearing steel were investigated under the high cyclic loading. Hourglass shape specimens were made of bearing steel(JIS-SUJ2) for rotary bending fatigue tests. Two kinds of treatments were performed : a heat treatment and a shot-peened surface treatment after the heat treatment. The fracture surfaces of specimens were classified into two types of fracture mode : the surface fracture mode induced by a surface defect and the internal fracture mode induced by a nonmetallic inclusion. Inclusion depth and shape affected considerably the fatigue life. Shot-peening treatment improved much the fatigue life of the bearing steel under low and high levels of cyclic loads. Probabilistic-stress-life (P-S-N) curves were suggested for the reliable fatigue life estimation of the improved bearing steel.