• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1300-1302
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• 1998

Residual resistance ratio ( RRR ) of Cu/Nb-Ti Superconductor wire was evaluated by fixed point method. Our measured value of RRR showed good consistency with the average value obtained from round robin test conducted by IEC/TC 90. Our test results showed that the coefficient of variation ( COV ) was kept within 2 %

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09c
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• pp.31-36
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• 2010

This paper introduces a practical determination method for soil parameters adopted in the new performance based design code for port and harbour facilities in Japan. In the new port-design code, the depth profile of the derived values is modeled as the profile of the estimated values so as to be either the mean value or the regression line, then the correction factors are multiplied to the estimated value according to the coefficient of variation (if COV > 0.1) and the number of the data entries (if n < 10). The new port-design code is applied to the unconfined compression test results for the Hiroshima Port clay in order to evaluate the undrained shear strengths. From the discussion, it is emphasized that not only the statistic treatment but also the engineering judgment are required in the procedure of the soil parameter determination for the reliability design.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.4
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• pp.15-21
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• 2003

LPG is considered as one of the most prominent alternative automotive fuels in worldwide. However, conventional mixer system can not meet the emission regulations as the mileage accumulation increased. Recently, much attention is focused on the development of LPG liquid injection fuel systems to increase the engine performance and reduce the exhaust emissions. This study evaluates the LPLi(Liquid Phase LPG injection) engine performance and exhaust emission characteristics using a 3.0 liter LPG engine. The fuel supply system and engine management system were changed from FBM into LPLi to control the precise mixture ratio and optimized spark advance.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.125-132
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• 2007

The oedometer, radial CRS and Rowe cell tests, composite discharge capacity tests and smear effect tests are carried out to estimate the parameters for the reliability-based design of vertical drain method. Also the sensitivity analysis, the probabilistic and deterministic solutions of radial consolidation theory are presented. The result of probabilistic analysis was compared to that of deterministic analysis using the tested and estimated parameters. The results indicated that the drain spacing in the deterministic method is larger than that in the probabilistic method because the former does not consider the uncertainties in the geotechnical property. The divergence of two methods is dependent on the probability of achieving target degree of consolidation by a given time and the coefficient of variation (COV) of the coefficient of horizontal consolidation ($c_h$).

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.104-109
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• 2002

In this paper, a statistical analysis of fatigue crack growth behavior under constant amplitude loads has been carried out. Fatigue crack growth tests were conducted on sixteen pre-cracked compact tension (CT) specimens of the pressure vessel (SPV50) steel in controlled identical load and environmental conditions. The assessment of the statistical distribution of fatigue crack growth experimental data obtained from SPV50 steel was studied and also the correlation of the parameter C and m in the Paris-Erdogan law was discussed. The probability distribution function of fatigue crack growth life seems to follow the 3-parameter Weibull. The fatigue crack growth rate seems to follow the 3-parameter Weibull and the log-normal distribution. The coefficient of variation (COV) of fatigue crack growth life was observed to decrease as the crack grows. A strong negative linear correlation exists between the coefficient C and the exponent m in Paris model. Fatigue crack growth rate data shows a normal distribution for both m and logC.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.923-929
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• 2003

In this paper, an analysis of fatigue crack growth behavior from a statistical point of view has been carried out. Fatigue crack growth tests were conducted on sixteen pre-cracked compact tension (CT) specimens of the pressure vessel (SPV50) steel in controlled identical load and environmental conditions. The assessment of the statistical distribution of fatigue crack growth experimental data obtained from SPV50 steel was studied and also the correlation of the parameter C and m in the Paris-Erdogan law was discussed. The probability distribution function of fatigue crack growth life seems to follow the 3-parameter Weibull. The fatigue crack growth rate seems to follow the 3-parameter Weibull and the log-normal distribution. The coefficient of variation (COV) of fatigue crack growth life was observed to decrease as the crack grows. Fatigue crack growth rate data shows a normal distribution for both m and logC. A strong negative linear correlation exists between the coefficient C and the exponent m.

• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.105-110
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• 2009

The objective of this paper is to investigate the statistical properties of Vickers hardness (HV) for friction welded parts in a Ni-based super alloy (Alloy718). In the case of post weld heat treatment (PWHT) parts, hardness tests were repeated for three different applied loads, 100, 200, and 300 g, with a duration time of 10 seconds. The arithmetic means of the Vickers hardness in heat affected zone (HAZ) materials were smaller than those of the base metal (BM) in all of the applied loads. The coefficient of variation (COV) for the BM and HAZ decreased by increasing the applied load. The probability distribution of the Vickers hardness followed the Weibull distribution well. The distribution of the Vickers hardness was not found to be symmetric. The shape parameter and scale parameter increased by increasing the applied load at both the BM and HAZ.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.76-88
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• 1997

Constant .DELTA.K fatigue crack growth rate experiments were performed by applying an intermediate single and multiple overload for structural steel, SM45C. The purpose of the present study is to investigate the influence of multiple overloads at various stress intensity factor ranges and the effect of statistical variability of crack retardation behavior. The normalized delayed load cycle, delayed crack length and the minimum crack growth rate are increased with increasing baseline stress intensity factor range when the overload ratio and the number of overload application were constant. The crack retardation under low baseline stress intensity factor range increases by increasing the number of overload application, but the minimum crack growth rate decreases by increasing the number of overload application. A strong linear correlation exists between the minimum crack growth rate and the number of overload applications. And, it was observed that the variability in the crack growth retardation behavior are presented, the probability distribution functions of delayed load cycle, delayed crack length and crack growth life are 2-parameter Weibull. The coefficient of variation of delayed load cycle and delayed crack length for the number of 10 overload applications data are 14.8 and 9.2%, respectively.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.23-30
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• 2007

Round piles of Korean larch were excavated from the foundation of ex-Chosunchongdokbu (ex-Chosun Governer-General Building), which was constructed in 1916 and dismantled later in 1996. By the record (Huh, 1996), the Korean larch logs were logged from the Yalu river area near Mt. Baekdu in North Korea. At present, however, Korean larch is not so popular in South Korea. The latewood ratio profiles and strength properties (longitudinal compression, shear, longitudinal tensile, and bending) were obtained. The ratio of latewood from pith to bark increased up to 25 years, and then it showed constant tendency at 40% with some variances. From the microscopic observation, however, the latewood ratio decreased from the heartwood to the sapwood. Compression strength was greater and bending strength was a little lower than the previous reports (references 13~15), which might be attributed to the strength reduction of old structural members by aging or damage in the compression specimens than the bending ones. The flat-grained specimens for the shear and tension test showed higher coefficient of variation (COV) than the edge-grained ones. For the better comparison of results, in case of shear and tensile strength tests, the strength values of the edge-grained specimens were thought to be adopted rather than those of flat-grained ones.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.3
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• pp.191-198
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• 2013

In this paper, the effects of uncertain material constant on the nonlinear behavior of steel frames with semi-rigid joints are examined. As to the probabilistic model, a normal distribution is assumed to simulate the uncertain elastic modulus of steel material. A nonlinear structural analysis program, which can consider both semi-rigidity in joints of the steel frames and uncertainty in the material constant, is developed. Including the geometric, material and connection nonlinearites which are the parameters of nonlinear behavior of steel frames, probabilistic analysis is conducted based on the Monte-Carlo simulation. In the probabilistic analyses, we consider the three different cases for random variables. The deterministic analysis results are shown to be in good agreement with those of the previous research results in the literature. As to the probabilistic analyses, it is observed that the coefficient of variation(COV) of displacements increases as the loading increases, and that the values of COV are dependent on the structural features of the frames.