• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.116-122
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• 2003

Monte Carlo method is one of the powerful engineering tools especially to solve the complex non-linear problems. The Monte Carlo method gives approximate solution to a variety of mathematical problems by performing statistical sampling experiments on a computer. One of the methods to predict the time dependent failure probability of one of the bridge components or the bridge system is a lifetime function. In this paper, FORTRAN program is developed to predict the failure probability of bridge components or bridge system by using both system reliability and lifetime function. Monte Carlo method is used to generate the parameters of the lifetime function. As a case study, the program is applied to the concrete-steel bridge to predict the failure probability.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.319-324
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• 2011

Recently, development of app for smartphone is much and many apps provide information by reproduced with achieved information from internet site. There is a need of method dependent on reproduced data by app. For solving these requirements, this paper first identifies problems such as lower hardware performance and limited bandwidth when legacy web pages are accessed by smart phones. This paper suggests three methods, "real time," "cache," and "static" to develop application programs for smart phones by considering identified problems.

• Communications for Statistical Applications and Methods
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• v.23 no.2
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• pp.131-146
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• 2016

In research on behavioral studies, significant attention has been paid to the stage-sequential process for longitudinal data. Latent class profile analysis (LCPA) is an useful method to study sequential patterns of the behavioral development by the two-step identification process: identifying a small number of latent classes at each measurement occasion and two or more homogeneous subgroups in which individuals exhibit a similar sequence of latent class membership over time. Maximum likelihood (ML) estimates for LCPA are easily obtained by expectation-maximization (EM) algorithm, and Bayesian inference can be implemented via Markov chain Monte Carlo (MCMC). However, unusual properties in the likelihood of LCPA can cause difficulties in ML and Bayesian inference as well as estimation in small samples. This article describes and addresses erratic problems that involve conventional ML and Bayesian estimates for LCPA with small samples. We argue that these problems can be alleviated with a small amount of prior input. This study evaluates the performance of likelihood and MCMC-based estimates with the proposed prior in drawing inference over repeated sampling. Our simulation shows that estimates from the proposed methods perform better than those from the conventional ML and Bayesian method.

• Nuclear Engineering and Technology
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• v.37 no.2
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• pp.201-206
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• 2005

Fretting, which is a special type of wear, is defined as small amplitude relative motion along the contacting interface between two materials. The structural integrity of steam generators in nuclear power plants is very much dependent upon the fretting wear characteristics of Inconel 690 U-tubes. In this study, a finite element model that can simulate fretting wear on the secondary side of the steam generator was developed and used for a quantitative investigation of the fretting wear phenomenon. Finite element modeling of elastic contact wear problems was performed to demonstrate the feasibility of applying the finite element method to fretting wear problems. The elastic beam problem, with existing solutions, is treated as a numerical example. By introducing a control parameter s, which scaled up the wear constant and scaled down the cycle numbers, the algorithm was shown to greatly reduce the time required for the analysis. The work rate model was adopted in the wear model. In the three-dimensional finite element analysis, a quarterly symmetric model was used to simulate cross tubes contacting at right angles. The wear constant of Inconel 690 in the work rate model was taken as $K=26.7{\times}10^{-15}\;Pa^{-1}$ from experimental data obtained using a fretting wear test rig with a piezoelectric actuator. The analyses revealed donut-shaped wear along the contacting boundary, which is a typical feature of fretting wear.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.940-945
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• 2004

Recently, the trend in architectural forms has been toward taller and larger building. The building materials, therefore, are getting larger and heavier as wall. Most of the construction projects are, however, dependent on outdated equipment and human resources. Construction processes up to now face a number of problems, including dangerous work, high construction cost and heterogeneous construction quality. In various construction sites, automation in construction has been introduced to address these problems. This paper proposes a human-machine cooperative system in the construction site; the system utilizes construction of a curtain wall in tall buildings. The use of automation system at construction sites can reduce the need of human involvement. Construction time and cost can be reduced as well. The most important aspect of the use of automation system at construction sites is prevention of accidents.

• Journal of the Korean Solar Energy Society
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• v.24 no.3
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• pp.47-54
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• 2004

Photovoltaic energy and wind energy are highly dependent on the season, time and extremely intermittent energy sources. Because of these reasons, in view of the reliability the photovoltaic and the wind power generation system have many problems(energy conversion, energy storage, load control etc.) comparing with conventional power plant. In order to solve these existing problems, hybrid generation system composed of photovoltaic(500W) and wind power system(400W) was suggested. But, hybrid generation system cannot always generate stable output due to the varying weather condition. So, the auxiliary power compensation unit that uses elastic energy of spiral spring was added to hybrid generation system for the present study. It was partly confirmed that hybrid generation system was generated a stable outputs by spiral spring was continuously provided to load.

• Tunnel and Underground Space
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• v.9 no.4
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• pp.288-295
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• 1999

Concentrated stresses due to the underground tunnel excavation easily cause many problems such as yielding, popping, and failure at the immediate roof, wall and floor of tunnel. Therefore, it is very important to predict the possibility of these problems when a tunnel is excavated underground. There are two typical methods to predict these problems. The one is to predict problems from the analysis of field monitoring data and the other is to predict them from computer simulations using good site investment data. Using the second method, this study attempted to describe the time-dependent or progressive manner of immediate roof and wall due to the underground tunnel excavation. An iterative technique was used to represent progressive failure of rockmass with the Hoek and Brown theory. By developing and simulating three different shapes of twin tunnels, this research estimated the proper size of critical pillar width between tunnels, distributed stresses on the tunnel walls, and convergences of tunnel crowns. Moreover, results out of progressive failure technique based on the Hoek and Brown theory were compared with the results out of Mohr-Coulomb theory.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.2
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• pp.138-149
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• 2000

Various modeling techniques for ultrasonic wave propagation and scattering problems in finite solid media are presented. Elastodynamic boundary value problems in inhomogeneous multi-layered plate-like structures are set up for modal analysis of guided wave propagation and numerically solved to obtain dispersion curves which show propagation characteristics of guided waves. As a powerful modeling tool to overcome such numerical difficulties in wave scattering problems as the geometrical complexity and mode conversion, the Boundary Element Method(BEM) is introduced and is combined with the normal mode expansion technique to develop the hybrid BEM, an efficient technique for modeling multi mode conversion of guided wave scattering problems. Time dependent wave forms are obtained through the inverse Fourier transformation of the numerical solutions in the frequency domain. 3D BEM program development is underway to model more practical ultrasonic wave signals. Some encouraging numerical results have recently been obtained in comparison with the analytical solutions for wave propagation in a bar subjected to time harmonic longitudinal excitation. It is expected that the presented modeling techniques for elastic wave propagation and scattering can be applied to establish quantitative nondestructive evaluation techniques in various ways.

• Journal of Korean Academy of Nursing
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• v.27 no.2
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• pp.389-400
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• 1997

This study examined the effects of group social support on the reduction of burden and increase in well-being of mothers of developmentally delayed children. The research used a one group pre-pose experimental design. The independent variable in the experiment was group social support. Two series of 4-weekly meetings for group social support were conducted by the researcher with the intention of developing a self-help group. The dependent variables were burden and well-being. Well-being was operationalized as physical symptoms and quality of life. Thirty mothers of developmentally delayed infants from the rehabilitation center of a medical center participated in the study. Data were collected by interviews and a self-administered questionnaire. The mean age of the subjects was 29.9 years. Changes of the dependent variables between pre and post tests were compared using the t-test. Even though there was a slight improvement in the scores for the dependent variables, they were not statistically significant. The items, "I resent my baby". "I feel angry about my interactions with my baby", "I feel guilty in my relationship with my baby" showed a significant decrease in burden score and were statistically significant. Symptoms of loneliness, constipation, anxiety, restlessness were less and feeling of happiness was greater after participation in the group social support, than on the pretest. The mothers showed emotional instability and frustrations during the group sessions but their reactions in general were positive. Emotional support, stress management and information provided were identified as the most valuable content of the sessions. However, participation was not active due to the mother's denial, delayed acceptance and /or avoidance of their infants' problems. It can be seen that group social support for the mothers with developmentally delayed children should be provided after infancy when the mothers have time to accept their children's conditions and are ready to receive support. The use of comprehensive instruments which measure burden in both families and mothers needs to be developed for future research.

• The Journal of the Korea Contents Association
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• v.13 no.11
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• pp.665-676
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• 2013

The present study analyzed the KOCCA's Game Immersion data to explore the relationship between psychological traits and game immersion. Psychological traits were classified into four categories; emotional stability, self-esteem, willpower, and happiness. These were put into the multiple regression analysis as the dependent variables with age, sex (dummy), economic status of the homes, variety of leisure activities, friend and family relationship, and time to play games. Four types of immersion (psychological unstability, bad relationship, interrupted daily lives, and failure to control game time and desire) were put into the multiple regression analysis as the independent variables. The multiple regression analysis indicated that the dependent variables predicted the game immersion. Among the psychological traits emotional stability was the strongest factor (negative) that influences the game immersion. Next powerful indicator (negative) among the psychological traits was self-esteem. Based on the findings, measures to alleviate the problems of game immersion and ideas for further research were suggested.