• Journal of the Korean Data and Information Science Society
• /
• v.17 no.3
• /
• pp.861-869
• /
• 2006

Burn-in is a widely used method to improve the quality of products or systems after they have been produced. In this paper, the problem of determining optimal burn-in time for a system which performs given mission is considered. It is assumed that the given mission time is not a fixed constant but a random variable which follows an exponential distribution. Assuming that the underlying lifetime distribution of a system has an eventually increasing failure rate function, an upper bound for the optimal burn-in time which maximizes the probability of performing given mission is derived. The obtained result is also applied to an illustrative example.

• Bulletin of the Korean Chemical Society
• /
• v.22 no.12
• /
• pp.1375-1379
• /
• 2001

Monte Carlo simulations of hard-spheres confined in parallel hard walls have been carried out extensively at various densities and for various wall distances. The compressibility factors in the directions parallel and normal to the wall have been calculated from the radial free space distribution function (RFSDF) with the results showing that the compressibility factors normal to the wall are smaller than those in parallel direction and that a solid phase is formed in the direction normal to the wall while a fluid phase remains in the parallel direction. An order parameter is found to classify the phases whether a system (or a molecule) is in a fluid or a solid state. The compressibility factors of narrow wall are very small compared to those when the wall is put away. A plausible mechanism of the rise of sap in xylem vessel has been proposed.

• Progress in Superconductivity and Cryogenics
• /
• v.12 no.3
• /
• pp.39-43
• /
• 2010

In Korea, 22.9kV hybrid SFCL (Superconducting Fault Current Limiter) has been developed and carried out long-term field tests in Gochagn power test center of KEPCO through DAPAS program. The SFCL will be installed at a distribution line of Icheon substation in Korea. For the successful application, we have to design the specifications considering real power system operation. This paper proposes a concept of the operating current based rms value for the protection coordination with protective delays and studies a proper range of the current in Korean distribution power system.

• Tribology and Lubricants
• /
• v.22 no.6
• /
• pp.307-313
• /
• 2006

In this paper, a theoretical analysis is carried out to study the effect of viscosity variation with pressure in multiply grooved moving hydraulic spool valves. Analytical expressions for pressure distribution in the clearance and leakage flowrate are obtained solving one-dimensional Reynolds. For constant viscosity, an analytical expression for lateral force is also presented. The results showed that variation of viscosity with pressure affect highly on pressure distribution, leakage flowrate and lateral forces in hydraulic spool valves. Therefore additional intensive studies, including numerical analysis for two-dimensional Reynolds, should be required to investigate detailed lubrication characteristics of spool valves for high pressure.

• The Korean Journal of Soil Zoology
• /
• v.3 no.2
• /
• pp.58-62
• /
• 1998

To find out ant fauna in the Mt. Chiak, collection tours were taken in three courses for two years. As a result, The ant fauna of Mt. Chiak were confirmed to be 45 species belonging to 23 genera under 4 subfamilies. Among them, ten species were new to Gangweon-province and Myrmica sp. 6 was new to Korea. Ants fauna of Gangweon-province at together became 74 species under 28 genera. In Ponerinae, ants fauna have become 5 species under 4 genera, in Myrmicinae, 20 species under 13 genera, in Dolichoderinae 1 species under 1 genera and in Formicinae 19 species under 5 genera.

• Journal of Korean Society for Quality Management
• /
• v.42 no.2
• /
• pp.209-219
• /
• 2014

Purpose: The purpose of this study is to develop the statistical test for process capability index $C_p$ based on mixture normal process. Methods: This study uses Bootstrap method to calculate the approximate P-value for various simulation conditions under mixture normal process. Results: This study indicates that our proposed method is effective way to test for process capability index $C_p$ based on mixture normal process. Conclusion: This study finds out that statistical test for process capability index $C_p$ based on mixture normal process is useful for real application.

• Journal of Korea Technology Innovation Society
• /
• v.8 no.spc1
• /
• pp.433-450
• /
• 2005

This paper empirically traces out the determinants of Information and Communication Technologies (ICT) progress. Using cross-national evidence, it is found that a country's income level and its distribution affect the ICT progress, through their influences on home market demand pattern. This result holds even when controlling for other variables that affects ICT progress and a sub-sample of less developed countries. Based on the findings, it is possible to conjecture that ICT progress can be a plausible reason for the income polarization in the world. In addition, a country with higher levels of human capital accumulation and financial development is positively associated with the ICT progress, although the effects depend on the sample and model specifications. However, these results are based on crude theoretical backgrounds and estimations, which require for further studies in the future.

• Journal of Korean Society for Atmospheric Environment
• /
• v.18 no.5
• /
• pp.345-353
• /
• 2002

A study of polydispersed aerosol dynamics by Electrostatic Precipitator (ESP) was carried out. The log-normal particle size distribution was assumed and moment method was considered. In order to apply moment method in Deutsch-Anderson equation, Cunningham slip correction factor and Cochet's charge equation were simplified for certain range of particle size. The three parameters, which explain the particle size distribution, such as total number concentration, geometric mean diameter, and geometric standard deviation were considered to derive the analytic solution. The obtained solution was compared with available numerical results (Bai et al., 1995). The comparison of the numerical and analytic results showed a good agreement.

• Tribology and Lubricants
• /
• v.14 no.1
• /
• pp.64-69
• /
• 1998

A numerical analysis is carried out to study the effect of piston shape on the lubrication characteristics between the cylinder and piston in hydraulic piston pumps. The results showed that the shape of piston affect significantly the pressure distribution in the clearance, the lateral force acting on the piston and leakage flow through the clearance. Partially tapered piston is more effective than any other piston shapes because it reduces the possibility of hydraulic locking and improves the volumetric efficiency of the pump.

• Journal of Positioning, Navigation, and Timing
• /
• v.9 no.1
• /
• pp.23-31
• /
• 2020

It is essential to estimate the vehicle localization for an autonomous safety driving. In particular, since LIDAR provides precise scan data, many studies carried out to estimate the vehicle localization using LIDAR and pre-generated map. The road marking always exists on the road because of provides driving information. Therefore, it is often used for map information. In this paper, we propose to generate the Gaussian mixture map based on road-marking information and localization method using this map. Generally, the probability distributions map stores the single Gaussian distribution for each grid. However, single resolution probability distributions map cannot express complex shapes when grid resolution is large. In addition, when grid resolution is small, map size is bigger and process time is longer. Therefore, it is difficult to apply the road marking. On the other hand, Gaussian mixture distribution can effectively express the road marking by several probability distributions. In this paper, we generate Gaussian mixture map and perform vehicle localization using Gaussian mixture map. Localization performance is analyzed through the experimental result.