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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Operations Research and Management Science Society
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The Korean Operations and Management Science Society
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Volume & Issues
Volume 39, Issue 4 - Nov 2014
Volume 39, Issue 3 - Sep 2014
Volume 39, Issue 2 - Jun 2014
Volume 39, Issue 1 - Mar 2014
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Analysis and Improvement of Stocking and Releasing Processes in Logistics Warehouse Using Process Mining Approach
Kim, Hyun-Kyoung ; Shin, KwangSup ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 1~17
DOI : 10.7737/JKORMS.2014.39.4.001
The functions of stocking and releasing in logistics center consist of three major procedure such as receiving, shipping and stock managements. Each process includes various sub-processes which are complicatedly connected with each other. Furthermore, lots of operators execute various tasks in the different sub-processes, simultaneously. It makes difficult to standardize, monitor, and analyze the processes. This paper proposed the quantitative methodology using process mining approach to discover and analyze receiving and shipping processes. For this purpose, the PDA operation log data is analyzed to build a realistic process model. The deduced model has been compared with official process model. In addition, task assignment and social networks analysises are carried out by utilizing process mining tools. Also, it has been proposed how to improve the processes with the analytical simulation model based on the results of process mining.
Parallel Computing Environment for R with on Supercomputer Systems
Lee, Sang Yeol ; Won, Joong Ho ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 19~31
DOI : 10.7737/JKORMS.2014.39.4.019
We study parallel processing techniques for the R programming language of high performance computing technology. In this study, we used massively parallel computing system which has 25,408 cpu cores. We conducted a performance evaluation of a distributed memory system using MPI and of a the shared memory system using OpenMP. Our findings are summarized as follows. First, For some particular algorithms, parallel processing is about 150 times faster than serial processing in R. Second, the distributed memory system gets faster as the number of nodes increases while shared memory system is limited in the improvement of performance, due to the limit of the number of cpus in a single system.
The Impact of Firms' Environmental, Social, and Governancial Factors for Sustainability on Their Stock Returns and Values
Min, Jae H. ; Kim, Bumseok ; Ha, Seungyin ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 33~49
DOI : 10.7737/JKORMS.2014.39.4.033
This study empirically examines the impact of firms' environmental (E), social (S), and governancial (G) factors on their short-term and long-term values. To measure firms' non-financial performance, we use ESG performance grades published by KCGS (Korea Corporate Governance Service). We employ stock log return as the proxy of each firm's short-term value, and Tobin's Q ratio as that of its long-term value. From a series of regression analyses, we find each of the ESG factors generally has a negative impact on stock return while it has a positive impact on the Tobin's Q ratio. These results imply that firms' effort for enhancing their non-financial performance may adversely affect their financial performance in a short term; but in the long-term point of view, firms' values increase through their good images engraved by their respective social, environmental and governancial efforts. In addition, we compare the relative strength of impact among E, S, G, the three non-financial factors on the firms' value measured in Tobin's Q ratio, and find that S (social factor) and G (governancial factor) give statistically significant impact on the firms' value respectively. This result tells us it would be advised to strategically embed CSV (creating shared value) pursuing both of profits and social responsibility in the firms' future agenda. While E (environmental factor) is shown to be an insignificant factor for the firms' value, it should be emphasized as a major concern by all the stakeholders in order to form a sound business ecosystem.
A Bayesian Approach for the Analysis of Times to Multiple Events : An Application on Healthcare Data
Seok, Junhee ; Kang, Yeong Seon ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 51~69
DOI : 10.7737/JKORMS.2014.39.4.051
Times to multiple events (TMEs) are a major data type in large-scale business and medical data. Despite its importance, the analysis of TME data has not been well studied because of the analysis difficulty from censoring of observation. To address this difficulty, we have developed a Bayesian-based multivariate survival analysis method, which can successfully estimate the joint probability density of survival times. In this work, we extended this method for the analysis of precedence, dependency and causality among multiple events. We applied this method to the electronic health records of 2,111 patients in a children's hospital in the US and the proposed analysis successfully shows the relation between times to two types of hospital visits for different medical issues. The overall result implies the usefulness of the multivariate survival analysis method in large-scale big data in a variety of areas including marketing, human resources, and e-commerce. Lastly, we suggest our future research directions based multivariate survival analysis method.
Short Note on Optimizing Feature Selection to Improve Medical Diagnosis
Guo, Cui ; Ryoo, Hong Seo ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 71~74
DOI : 10.7737/JKORMS.2014.39.4.071
A new classification framework called 'support feature machine' was introduced in  for analyzing medical data. Contrary to authors' claim, however, the proposed method is not designed to guarantee minimizing the use of the spatial feature variables. This paper mathematically remedies this drawback and provides comments on models from .
Set Covering-based Feature Selection of Large-scale Omics Data
Ma, Zhengyu ; Yan, Kedong ; Kim, Kwangsoo ; Ryoo, Hong Seo ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 75~84
DOI : 10.7737/JKORMS.2014.39.4.075
In this paper, we dealt with feature selection problem of large-scale and high-dimensional biological data such as omics data. For this problem, most of the previous approaches used simple score function to reduce the number of original variables and selected features from the small number of remained variables. In the case of methods that do not rely on filtering techniques, they do not consider the interactions between the variables, or generate approximate solutions to the simplified problem. Unlike them, by combining set covering and clustering techniques, we developed a new method that could deal with total number of variables and consider the combinatorial effects of variables for selecting good features. To demonstrate the efficacy and effectiveness of the method, we downloaded gene expression datasets from TCGA (The Cancer Genome Atlas) and compared our method with other algorithms including WEKA embeded feature selection algorithms. In the experimental results, we showed that our method could select high quality features for constructing more accurate classifiers than other feature selection algorithms.
The Dynamic Research of Mobile and PC Online Media Visit Activities Effects on The E-Commerce Site Visit
Lee, Dong Il ; Kim, Hyun Gyo ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 85~95
DOI : 10.7737/JKORMS.2014.39.4.085
In the e-commerce, the conversion into the multi-media is the important issue. According to the research by Nielsen Korea, the 83% of customers who purchase the products in the e-commerce utilize multi-channel to buy the products such as mobile and online . Thus, to effectively implement online advertising, marketers should understand the customers' path  in the multi-channel. The study of the multi-site activities plays an important role to predict customers' purchase . To explain the e-commerce site visit activities of customers, we have developed research model in terms of the online advertising. This research model is based on the study of Moe and Fader . There are two types of composition in the research model. First, general site visit as an exploratory search have net effect on the shopping site visit because customers could acquire or develop information on the e-commerce site via online advertising. Secondly, the e-commerce site visit as a goal-directed search cause threshold of the e-commerce site visit because customers could achieve their goal. When the threshold is increased, the probability of a shopping site visit is decreased and vice versa. Thus, we have investigated the impact of customers' previous visit activities (general site visit and shopping site visit) on the next e-commerce site visit in terms of dynamic view. Research data was provided by Cheil World Wide. This panel data include mobile and online log data of panelists from Jan. 2013 to March 2013. As the results, the customers' e-commerce site visit on the online media would decrease the probability of e-commerce site visit because these visit activities increase the threshold of e-commerce site visit. This result is similar with the previous study . Otherwise, since e-commerce site visit on the mobile media decrease the threshold, the customers' probability of e-commerce site visit would increase In summary, the site visit activities on the mobile could improve the probability of e-commerce site visits.
A Heuristic Method for Resolving Circular Shareholding with the Objective of Voting Rights Maximization
Park, Chan-Kyoo ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 97~113
DOI : 10.7737/JKORMS.2014.39.4.097
Circular shareholding refers to a situation where at least three member firms in a business group have stock in other member firms and establish a series of ownership in a circular way. Although many studies have focused on the ultimate effect of circular shareholding on firm's value and profitability, there have been few studies which address how to resolve circular shareholding from the perspective of optimization theory. This paper proposes a heuristic method for identifying shareholdings which need to be cleared in order to settle the problem of circular shareholding in a business group. The proposed heuristic tries to maximize the sum of voting rights the controlling family has in its business group firms. The applications results confirm that the heuristic provides near-optimal solutions for most of 16 Korean large business groups involving circular shareholding.
The Drivers of Customer Defection in Online Games across Customer Types : Evidence from Novice and Experienced Customers
Son, Jungmin ; Jo, Wooyong ; Choi, Jeonghye ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 115~136
DOI : 10.7737/JKORMS.2014.39.4.115
The game industry has grown steadily and the online game has become one of the most attractive game segments for its remarkable growth. Customer management in the online game industry, however, has received little attention from the academic field. The purpose of this study is to analyze the drivers of customer defection in the online game setting and suggest not only theoretical but also managerial insights into increasing customer retention rates. Prior to empirical analysis, the authors hypothesized that 3 variables of interests (Learning, Playing, Achievement) would explain the customer defection according to preceeding researches. To demonstrate these hypotheses, the authors obtained data from one of the biggest game publishers in Korea, and the empirical analysis model was developed considering context of research settings. The results of analyses provide the following insights. First, the key behavioral variables of Learning, Playing, and Achievement play substantial roles in explaining the customer defection. Next, the effects of these variables vary between customer types: novice and experienced customers. The defection decisions by novice customers are predicted by all key behavioral variables and Playing serves as the most influential indicator of the defection decisions. However, experienced customers are influenced by Playing and Achievement, while Learning has no impact on the defection decisions. Finally, the authors investigated hypothetical customer retention strategies, using the empirical results. The market outcomes indicate that the customer retention strategies work well with novice customers and it is hard-to-impossible to prevent experienced customers from defection using their behavioral data. These findings together deliver several meaningful insights to management as follow. First, the management should support customers to get involved in Learning activities at the very first stage. Second, customer's Achievement and appropriate compensation for it would work as defection barriers. Last, to optimize the outcomes of firm's marketing investments, it is better to focus on retention of novice users not experienced ones.
Covariance Estimation and the Effect on the Performance of the Optimal Portfolio
Lee, Soonhee ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 137~152
DOI : 10.7737/JKORMS.2014.39.4.137
In this paper, I suggest several techniques to estimate covariance matrix and compare the performance of the global minimum variance portfolio (GMVP) in terms of out of sample mean standard deviation and return. As a result, the return differences among the GMVPs are insignificant. The mean standard deviation of the GMVP using historical covariance is sensitive to the estimation window and the number of assets in the portfolio. Among the model covariance, the GMVP using constant systematic risk ratio model or using short sale restriction shows the best performance. The performance difference between the GMVPs using historical covariance and model covariance becomes insignificant as the historical covariance is estimated with longer estimation window. Lastly, the implied volatilities from ELW prices do not lead to superior performance to the historical variance.
The Impact of Capacity Flexibility in a Rental Operation on the Financial Performance
Kim, Eungab ;
Journal of the Korean Operations Research and Management Science Society, volume 39, issue 4, 2014, Pages 153~165
DOI : 10.7737/JKORMS.2014.39.4.153
We present a new framework for rental capacity management in which rental capacity is dynamically managed by means of temporary inventory addition/return. While serving customers with its own (native) capacity, the rental firm rents additional rental capacity from an upper echelon rental company so that it can avoid lost sales which may occur when stock is not sufficient, and returns it when stock becomes sufficiently large enough to cope with demands. Formulating the model as a Markov decision process, we investigate a flexible capacity addition/return policy that maximizes the firm's profit with respect to system costs. Numerical study indicates that rental operation with capacity addition/return can be economically favorable over rental operation without capacity expansion/return and can contribute the reduction in the size of native rental capacity.