• Wind and Structures
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• v.36 no.2
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• pp.133-147
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• 2023

The random vibration of saddle membrane structures under wind load is studied theoretically and experimentally. First, the nonlinear random vibration differential equations of saddle membrane structures under wind loads are established based on von Karman's large deflection theory, thin shell theory and potential flow theory. The probabilistic density function (PDF) and its corresponding statistical parameters of the displacement response of membrane structure are obtained by using the diffusion process theory and the Fokker Planck Kolmogorov equation method (FPK) to solve the equation. Furthermore, a wind tunnel test is carried out to obtain the displacement time history data of the test model under wind load, and the statistical characteristics of the displacement time history of the prototype model are obtained by similarity theory and probability statistics method. Finally, the rationality of the theoretical model is verified by comparing the experimental model with the theoretical model. The results show that the theoretical model agrees with the experimental model, and the random vibration response can be effectively reduced by increasing the initial pretension force and the rise-span ratio within a certain range. The research methods can provide a theoretical reference for the random vibration of the membrane structure, and also be the foundation of structural reliability of membrane structure based on wind-induced response.

• Communications for Statistical Applications and Methods
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• v.27 no.3
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• pp.385-395
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• 2020

We present a new maximum likelihood approach to estimate demographic history using genomic data sampled from two populations. A demographic model such as an isolation-with-migration (IM) model explains the genetic divergence of two populations split away from their common ancestral population. The standard probability model for an IM model contains a latent variable called genealogy that represents gene-specific evolutionary paths and links the genetic data to the IM model. Under an IM model, a genealogy consists of two kinds of evolutionary paths of genetic data: vertical inheritance paths (coalescent events) through generations and horizontal paths (migration events) between populations. The computational complexity of the IM model inference is one of the major limitations to analyze genomic data. We propose a fast maximum likelihood approach to estimate IM models from genomic data. The first step analyzes genomic data and maximizes the likelihood of a coalescent tree that contains vertical paths of genealogy. The second step analyzes the estimated coalescent trees and finds the parameter values of an IM model, which maximizes the distribution of the coalescent trees after taking account of possible migration events. We evaluate the performance of the new method by analyses of simulated data and genomic data from two subspecies of common chimpanzees in Africa.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.4
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• pp.113-127
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• 2021

Topic modeling has been receiving much attention in academic disciplines in recent years. Topic modeling is one of the applications in machine learning and natural language processing. It is a statistical modeling procedure to discover topics in the collection of documents. Recently, there have been many attempts to find out topics in diverse fields of academic research. Although the first Department of Industrial Engineering (I.E.) was established in Hanyang university in 1958, Korean Institute of Industrial Engineers (KIIE) which is truly the most academic society was first founded to contribute to research for I.E. and promote industrial techniques in 1974. Korean Society of Industrial and Systems Engineering (KSIE) was established four years later. However, the research topics for KSIE journal have not been deeply examined up until now. Using topic modeling algorithms, we cautiously aim to detect the research topics of KSIE journal for the first half of the society history, from 1978 to 1999. We made use of titles and abstracts in research papers to find out topics in KSIE journal by conducting four algorithms, LSA, HDP, LDA, and LDA Mallet. Topic analysis results obtained by the algorithms were compared. We tried to show the whole procedure of topic analysis in detail for further practical use in future. We employed visualization techniques by using analysis result obtained from LDA. As a result of thorough analysis of topic modeling, eight major research topics were discovered including Production/Logistics/Inventory, Reliability, Quality, Probability/Statistics, Management Engineering/Industry, Engineering Economy, Human Factor/Safety/Computer/Information Technology, and Heuristics/Optimization.

• The Mathematical Education
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• v.52 no.2
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• pp.149-161
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• 2013

This study was to focus on analyzing about the composition of storytelling in the first graders' math textbooks of the middle school, which were recently implemented. The textbooks published by three well known publishing companies were chosen and three graduate students had scored the frequency of the problems according to three types of storytelling. As the results, in areas of mathematics, Number & Operation(44.23%), Letters & Formula(44.53%), Function(46.53%), Probability(41.67%), Geometry(46.23%) showed to have storytelling in balance. The type of 'explosion of mathematical history(EMH)' was shown in geometry most, the type of 'connection to daily life(CDL)' in statistics most, and the type of integration of disciplines(ID)' in geometry most in 5 math areas. Among three types of storytelling, the type of EMH was shown fewer that other 2 types. If we develop more problems in this type, students would study mathematics in-depth according to Freudenthal's principle of historical reinvention.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1695-1705
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• 2014

In the present study, a total of 275 tested specimens (149 of non-seismically designed and 126 of seismically designed) for reinforced concrete bridge piers with circular section have been investigated in order to suggest drift limits probabilistically according to damage states in seismic fragility analysis. Thus, quantitative damage states of the piers have been evaluated depending on details of the piers. Nonlinear time-history analyses have been conducted for a damaged bridge in terms of using the suggested drift limits. Then, seismic fragility analysis for a reinforced concrete bridge structure has been conducted using both suggested and existing drift limits. Comparative analyses have revealed that median values by the suggested limits is smaller than those by the existing limits. This implies that seismic performance of the structure can be overestimated when the existing limits are used.

• 한국노년학
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• v.31 no.1
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• pp.15-31
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• 2011

The purpose of this study is to explore the transition to retirement of the middle-aged in Korea according to the notion of "the career job" and "the bridge job". In order to scrutinize basic elements for the transition, three aspects such as the job history of the middle-aged, the characteristics of the demographic and economic status were investigated through the one to three wave of Korean Retirement and Income Study(KReIS). In addition, the characteristics of the career job and the bridge job were analyzed by both descriptive statistics and the conditional transition probability. Moreover, the influential factors to the job status of the middle-aged were examined by the multi-nominal logistic regression. The results of the study are as followed: first, gradual retirement is increasing in the transition to retirement of the middle-aged in Korea. Over time, the career job is decreasing whilst bridge job is increasing. However, the quality of the bridge job is poorer than the career job in terms of wage, employment status, industry, and occupation. Lastly, the middle-aged who work in the bridge job have vulnerable characteristics, so they work in the bridge job to supplement their economic needs. The results can be influential in the adjustment of the labor policies for the middle-aged in Korea. Moreover, the partial pension system could be a good alternative since the pension system is needed to protect the vulnerable situation of the middle-aged in Korea.