• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.158-169
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• 2019

A probabilistic model that can predict the residual useful lifetime of structure is formulated by using the gamma process which is one of the stochastic processes. The formulated stochastic model can take into account both the sampling uncertainty associated with damages measured up to now and the temporal uncertainty of cumulative damage over time. A method estimating several parameters of stochastic model is additionally proposed by introducing of the least square method and the method of moments, so that the age of a structure, the operational environment, and the evolution of damage with time can be considered. Some features related to the residual useful lifetime are firstly investigated into through the sensitivity analysis on parameters under a simple setting of single damage data measured at the current age. The stochastic model are then applied to the rubble-mound breakwater straightforwardly. The parameters of gamma process can be estimated for several experimental data on the damage processes of armor rocks of rubble-mound breakwater. The expected damage levels over time, which are numerically simulated with the estimated parameters, are in very good agreement with those from the flume testing. It has been found from various numerical calculations that the probabilities exceeding the failure limit are converged to the constraint that the model must be satisfied after lasting for a long time from now. Meanwhile, the expected residual useful lifetimes evaluated from the failure probabilities are seen to be different with respect to the behavior of damage history. As the coefficient of variation of cumulative damage is becoming large, in particular, it has been shown that the expected residual useful lifetimes have significant discrepancies from those of the deterministic regression model. This is mainly due to the effect of sampling and temporal uncertainties associated with damage, by which the first time to failure tends to be widely distributed. Therefore, the stochastic model presented in this paper for predicting the residual useful lifetime of structure can properly implement the probabilistic assessment on current damage state of structure as well as take account of the temporal uncertainty of future cumulative damage.

• Journal of Labour Economics
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• v.24 no.1
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• pp.67-96
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• 2001

The recent economic crisis started at the end of 1997 has brought about changes in labor market practices. One of them is rapid increase in the ratio of workers with alternative employment arrangement, so-called contingent workers. This type of arrangement, unlike traditional employment arrangement, makes employers properly adjust employment to business cycles and it also makes it possible for employees to solve time and spatial constraints related to labor supply. However, recent experience has revealed its negative characteristics such as lower wage rate, deficient fringe benefits, insufficient job security. Using the data from the first and the second wave of the Korea Labor and Income Panel Survey, this study focuses on change in the tendency of being contingent workers and decomposition of the wage differentials among regular and contingent workers by estimating the switching regression model. Results show that the recent crisis significantly contributed to probabilities of being contingent workers, especially for women, the young, the older, and the lowly educated. Decomposition shows that one quarter or one third of 35% of wage differentials are due to the price effect that the same productive characteristics are differently paid by the types of employment arrangements.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.7
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• pp.956-962
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• 2018

As the study of the object feature detection from image, we explain methods to identify the species of the tree in forest using the picture taken from dron. Generally there are three kinds of methods, which are GLCM (Gray Level Co-occurrence Matrix) and Gabor filters, in order to extract the object features. We proposed the object extraction method using the statistical properties of trees in this research because of the similarity of the leaves. After we extract the sample images from the original images, we detect the objects using cross correlation techniques between the original image and sample images. Through this experiment, we realized the mean value and standard deviation of the sample images is very important factor to identify the object. The analysis of the color component of the RGB model and HSV model is also used to identify the object.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.2
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• pp.63-72
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• 2016

An expected-discounted cost model based on RRP(Renewal Reward Process), referred to as a stochastic decision model, has been developed to estimate the optimal period of in-depth inspection which is one of critical issues in the life-cycle maintenance management of harbor structures such as rubble-mound breakwaters. A mathematical model, which is a function of the probability distribution of the service-life, has been formulated by simultaneously adopting PIM(Periodic Inspection and Maintenance) and CBIM(Condition-Based Inspection and Maintenance) policies so as to resolve limitations of other models, also all the costs in the model associated with monitoring and repair have been discounted with time. From both an analytical solution derived in this paper under the condition in which a failure rate function is a constant and the sensitivity analyses for the variety of different distribution functions and conditions, it has been confirmed that the present solution is more versatile than the existing solution suggested in a very simplified setting. Additionally, even in that case which the probability distribution of the service-life is estimated through the stochastic process, the present model is of course also well suited to interpret the nonlinearity of deterioration process. In particular, a MCS(Monte-Carlo Simulation)-based sample path method has been used to evaluate the parameters of a damage intensity function in stochastic process. Finally, the present stochastic decision model can satisfactorily be applied to armor units of rubble mound breakwaters. The optimal periods of in-depth inspection of rubble-mound breakwaters can be determined by minimizing the expected total cost rate with respect to the behavioral feature of damage process, the level of serviceability limit, and the consequence of that structure.

• Journal of Cadastre & Land InformatiX
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• v.47 no.2
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• pp.91-105
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• 2017

It is important to identify new apartment buyers with the object of investment and owner-occupation because it may determine the scope of marketing and marketing strategies. Establishing an more effective marketing scope and strategies should result in maximizing profits and reducing expenses. In this study, we split the participants in the new apartment market depending on the buyers' intent - investment and owner-occupation - and then examine their characteristics. We employ condominium buyers' information from 2011 to 2016, which is provided by the one of the largest construction companies in South Korea. The sites of the condominium samples locate in Gyeongnam and Busan areas and the number of household sample is 5,549. The results show that investors are approaching at a greater distance than actual buyers. The higher the age and the lower the price, the higher the probability of participation of investors. We also find that the samples of Busan have different results from the others, which may imply that the area has more demand due to its attractiveness.

• Korean Security Journal
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• no.37
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• pp.7-28
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• 2013

Based on the status of which the research is not active and the analysis is not progressed, the purpose of this study life up pride, value and professional ethic of private security guard. Also, through this research, it offers the effect on professional ethic, organizational trust and job satisfaction. The data collection and survey are taken by the private security business members who work staff member or manager. They are surveyed with convenience sampling that among 500 data, 46 data which are thought to be answered insincerely or lack are excluded, so the total of 454 answered data are included in the final analysis. After coding and input process, the data is analyzed by factor analysis, reliability analysis, correlation analysis and multiple regression analysis using window SPSS 19.0 version. Significance level is 0.05. The conclusion that has been made based on the statistical analysis results are the followings. Professional ethic has a positive impact on organizational trust, job satisfaction. The educational training of the company is connected job satisfaction resultantly. Also the professional ethics education will improve the ability of the individual. Finally, the professional ethics raises a job satisfaction. Also, Organizational trust has a positive impact on job satisfaction. This the while to agree with a research result about the other type of business worker who is researched. In order raising the job satisfaction, the effort for raising a organizational trust is necessary.

• 한국노년학
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• v.36 no.4
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• pp.1003-1024
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• 2016

The human rights of older people have gotten more attention recently in South Korea, a country that is in transition to a super-aged society. This study aimed to systematically review studies on elder abuse and related factors among community-dwelling older adults in South Korea over twenty years (1994-2016). We searched major databases (Riss, DBpia, KISS, KMbase, and PubMed) and identified published studies relevant to the topic. Based on inclusion and exclusion criteria related to study quality, a total of 31 studies were selected for this review. We examined types, measurements, and risk factors of elder abuse as well as study designs in the selected studies, guided by Johannesen's theoretical framework on elder abuse. All of the reviewed studies on elder abuse in Korea were cross-sectional studies, most of which focused on older people living in urban areas, using a non-random sampling method. All of the studies focused on certain types of elder abuse only. Some adopted elder-abuse instruments that were not validated, and others used self-developed instruments without psychometric tests. As for the risk factors of elder abuse in South Korea, the physical and mental health of the victims and aggressors impacted the risk of elder abuse, but general sociodemographic factors such as age, sex, and education were less likely to be related to the risk. In addition, decreasing caregiver burden and building elder-friendly communities are important for the prevention of elder abuse. Needed are further empirical studies on elder abuse with a theoretical framework that gives consideration to the unique sociocultural contexts of Korea. It is also recommended to develop instruments to measure elder abuse reflecting the sociocultural contexts of Korea, and to examine the multi-dimensional risk factors of elder abuse.