• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.2
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• pp.61-65
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• 1987

In this study, the characteristics of TRC (tensile restraint crack) critical stress in the gravity type underwater wet welding process and in the in-air welding have been investigated for Y, y and 45$^{\circ}$r grooves using the KR Grade A-3 steel plates and the E4303 covered electrodes. The following results were obtained: (1) In the TRC tests, the initial critical stress of Y groove is higher than those of the 45$^{\circ}$r single bebel grooves in both in-air and underwater weldings, and the cold fracture sensitivity is higher in the underwater welding than in the in-air welding. (2) The hardness of underwater weld metal is the highest in heat affected zone is about Hk 365 in the in-air weld but Hk 670 in the underwater weld which is higher for cooling speed is more rapid, resulting in the lower critical stress by increase of fracture sensitivity. (3) The diffusible hydrogen quantity for 48 hours is about 18cc/100g-weld-metal in the in-air welding but 48cc/100g-weld-metal in the underwater welding. So that, in the case of underwater welding the diffusible hydrogen penetrates about 3 times more than that in the in-air welding.

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.287-294
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• 1989

The optimum condition for the separation of priority pollutant phenols using isocratic elution has been determined. The elution behavior of eleven phenols has been also studied to interpret the retention. The reversed phase liquid chromatographic methods were performed on a ${\mu}$-Bondapak $C_{18}$ column with methanol-water, acetonitrile-water, and THF water mixtures as mobile phases. The COF method, where Snyder's solvent triangle concept was combined with a mixture-design statistical technique, was used to optimize the strength and selectivity of solvents for the separation of phenols. The optimum solvent composition, which gives a complete separation of eleven phenols, was found to be $MeOH:ACN:H_2O$ = 7:40:53. The plots of ln k' vs. -${\Delta}H^{\circ}$ and ${\Sigma}{\pi}$ of phenols showed relatively good linearities. Effect of van der Waals volume, pi-energy and hydrogen bonding on the retention of phenols were investigated. The following equation with the correlation coefficient of 0.9927 for ACN-water solvent system was obtained; $log^{k'}=2.515{\times}10^{-2}VWV-1.301{\times}10^{-1}E-3.674{\times}10^{-1}$

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.273-276
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• 2006

CMM/CMMI 와 같은 프로세스 모델의 등장으로 소프트웨어 프로세스 개선에 대한 원리와 방법은 인식하였으나 현실에 적용하여 성과를 창출하기에는 상당한 어려움을 겪어왔다. 이러한 문제를 해결하고 개발자와 개발팀 차원에서 CMM/CMMI 의 목표와 프렉티스를 구현하기 위해 SEI(Software Engineering Institute)에 의해 PSP/TSP 가 개발되었다. 이렇게 PSP/TSP 가 개인과 팀차원에서 소프트웨어 개발에 사용될 수 있는 구체적인 기법들을 기술하고 있지만 일반적으로 PSP/TSP 에서 수집되는 메트릭에 대한 분석기법은 여전히 부족하다. 따라서 PSP/TSP 수행시 발생할 수 있는 문제를 방지하고 프로세스가 변경되고 유지 관리될 수 있도록 하기 위해서는 6 시그마의 다양한 통계 기법과 의사 결정도구의 사용이 필요하다. PSP/TSP 는 6 시그마가 성공적으로 적용될 수 있는 정량적인 기반을 개인과 프로젝트 차원에서 제공한다. 이에 대해 6 시그마는 PSP/TSP 에서 식별된 문제의 원인을 파악하고 분석하기 위해 필요한 분석도구와 통계적 기법을 제공하고, 문제를 방지하기 위해 프로세스가 변경되고 유지 관리될 수 있는 프로세스 관리 방법론을 제공한다. 따라서 본 논문에서는 PSP 의 각 프로세스에서 활용될 수 있는 6 시그마 도구를 식별하고 활용 가이드라인을 제시함으로써 개인과 팀 차원에서의 프로세스 개선의 수행을 지원하며 팀 차원에서 발생할 수 있는 이슈를 6 시그마의 분석, 정량화 도구를 사용하여 개인 또는 팀의 성과를 향상할 수 있는 방법을 모색해본다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.63-73
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• 1987

This study is a part of the research on the coupled vibration of train wheel with the stepped thickness and rail. The research was conducted for the purpose of examining the dynamic characteristics of train wheel at the running state and preventing the vibrations of the high speed railway. The stress at the boundary surface of web and rim, .sigma.$_{c}$, was analyzed in consideration of the uniform In-plane compressive stress depending on the conditions of rolling and the In-plane compressive stress depending on the rotation of train wheel. Then the equation of transverse vibration of the annular plate with the stepped thickness was analyzed by Rayleigh-Ritz's method. As a result of study, it was known that the rotational speed increase the natural frequency slightly and the acceleration level highly while the reaction force between train wheel and rail decrease the natural frequency linearly and the critical buckling is generated at n=1.

• The Korean Journal of Applied Statistics
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• v.22 no.4
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• pp.759-770
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• 2009

A problem of separating signals from noises is considered, when they are randomly mixed in the observation. It is assumed that the noise follows a Gaussian distribution and the signal follows a Gamma distribution, thus the underlying distribution of an observation will be a mixture of Gaussian and Gamma distributions. The parameters of the mixture model will be estimated from the EM algorithm. Then the signals and noises will be classified by a fixed threshold approach based on multiple testing using positive false discovery rate and Bayes error. The proposed method is applied to a real optical emission spectroscopy data for the quantitative analysis of inclusions. A simulation is carried out to compare the performance with the existing method using 3 sigma rule.

• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.95-98
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• 1997

The Gaussian diffraction pattern initially assumed in the diffraction inverse problem is further sharply defined by multiplying $e^{-q{\omega}_0$\mid${\chi}$\mid$}$. The modified pupil function is obtained and the diffraction intensity distribution for the finite aperture ($-{\omega}_0~{\times}{\omega}_0$ is obtained, and then the OTF is derived analytically. It is found the OTF is equal to or less than the $(OTF)_{q=0}$, namely the modulation is not useful. It is shown that the narrowing down the initial Gaussian diffraction pattern does not give the anticipated improvement in OTF and the reason is clarified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1349-1356
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• 1994

The results of laboratory experiments on the clear-water scour of cohesionless bed sediment for three types of pier shape were presented. According to the experimental data, the local scouring around the pier was initiated at $V/V_c=0.4{\sim}0.5$ and $Fr_p{\fallingdotseq}0.2$, and the relative local scour depths linearly increased with respect to the velocity ratio and the pier Froude number. The relative scour depth had the linear relationship with ${\tau}_r$ for ${\tau}_r$ < $10^{-4}$, but it tends to become constant for ${\tau}_r$ > $10^{-4}$, irrespective of ${\tau}_r$. And also the relative scour depths showed the close relationship with both the geometric standard deviation and the pier shape.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.1
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• pp.1-9
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• 1985

In-plane tension fatigue tests (R = 0.05) were carried out to investigate the initiation and propagation behaviors of micro-surface-fatigue cracks on smooth surfaces of a mild steel. Also, the investigations of saturated cyclic strain which can be obtained by the fatigue tests have been made via the cyclic strain intensity factor, .DELTA. $K_{\epsilon}$/, for the purpose of unifying two approaches of the study of fatigue; the one approach is based on the fracture mechanics concept and the other on lowcycle fatigue concept. Some of the results are as follows; The growth rate, d(2a)/dN, of small cracks cannot be represented by one straight line as a function of .DELTA.K for various of the nominal stress range, .DELTA..sigma., and is higher than that of a larger through crack. The rearrangement of the d(2a)/dN by .DELTA..epsilon..root..pi.s( = .DELTA. $K_{\epsilon}$/) with the stress range .DELTA..epsilon. in .DELTA.K replaced by .DELTA..epsilon., strain range, gives one straight line of the .DELTA. $K_{\epsilon}$-d(2a)/dN relation for various values of stress range .DELTA.$_{\epsilon}$../.X>../.

• 한국벤처창업학회:학술대회논문집
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• 2018.11a
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• pp.277-281
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• 2018

Information system has been at center of economic development in several developed countries, and as Africa envision to improve its global economic competitiveness it is important to assess penetration rate the digital divide and catch-up effect over the years. This paper examined whether there exists digital divide and if so, is it narrowing over time and whether the ICT is converging with time in the African countries. Three technologies namely mobile-cellular, internet and fixed broadband were used to measure the digital divide and the catch-up effect. Gamma and sigma convergence methodology together with averaged penetration ratios were used to assess the cross-country performance of each technology. This study confirms both the narrowing of digital divide and convergence of ICT in all three technologies for both total group and subgroups. The digital gap was narrowing over time and the low-income countries were catching up faster to the middle-income countries in all three technologies. However, there are marked differences exhibited in the speed of narrowing digital divide and the speed of convergence between the total groups and the subgroups of countries. Some policy implications were discussed in the conclusion and they can be utilized in designing developmental ICT policies in each technology case for individual countries.

• Journal of the Korean Chemical Society
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• v.39 no.9
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• pp.715-721
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• 1995

Reaction between trans-$[Co(py)_4/Ci_2]^+(py=pyridine)$ and L-proline and diimine (=2,2'-bipyridine, 1,10-phenanthroline) gives two products, $[Co(L-pro)_2/(bipy)]^+$ and $[Co(L-pro)_2(phen)]^+$ complexes, respectively. On column chromatography, $[Co(L-pro)_2(bipy)]^+$ was obtained only as $Lambda$-trans(N) and $[Co(L-pro)_2(phen)]^+$ was obtained both as ${\Delta}$-trans(N) and $Lambda$-cis(O)cis(N) due to the stereoselectivity of L-prolinato which was stereospecific. Crystal data are as follows: $Lambda$-trans(N)-$[Co(L-pro)_2(bipy)]CIO_4{\cdot}2H_2O$ (1): monoclinic, space group $P2_1(#4)$, a=9.807(3), b=10.421(1), c=12.778(2) ${\AA}$, ${\beta}=109.90(2)^{\circ}$, V=1227.8(5) ${\AA}^3$, Z=2; 1571 data with I > 3.0${\sigma}$(I) were refined to R=0.060, $R_W = 0.067$; ${\Delta}$-trans(N)-$[Co(L-pro)_2(phen)]Cl{\cdot}_3H_2O$(2): monoclinic, space group $P2_1(#4)$, a=9.838(2), b=12.892(2), c=10.747(2)${\AA}$, ${\beta}=113.79(2)^{\circ}$, V=1247.2(4) ${\AA}^3$, Z=2; 2433 data with I > 3.0${\sigma}$(I) were refined to R=0.043, $R_W = 0.050$.