• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.3
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• pp.135-142
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• 2006

Engineers are always concerned with life cycle costs for making important economic decisions through engineering action like reliability of products. Decisions during the reliability growth development of products involve trade-offs between invested costs and its returns. In order to find minimal LCC containing the reliability improvement cost, production cost, repair and replacement costs, and holding cost of spare parts for failure items we suggest in this paper relationship between development cost and sustaining cost in values of growth parameter $\beta$ of AMSAA model. This model is applied to the reliability growth program based on AMSAA model during R&D phase, the warranty activities of items and the block replacement policy for maintenance of items in avionic equipment.

• Journal of Communications and Networks
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• v.4 no.4
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• pp.282-291
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• 2002

3GPP (Third Generation Partnership Project) is defining UMTS (Universal Mobile Telecommunication System) releases which span the transition from GSM/UMTS coexistence to All-IP UMTS networks. The deployment of an UMTS network depends, in the first place, on the intended service offerings and the release an operator chooses to start service with. Other key decisions in-fluencing UMTS deployment relate to the timing of the functional enhancements and capacity increases along the economic life of the network. This paper gives an overview on the architectural and technical options for UMTS deployment. It also outlines the methodology underlying the business plan aimed at estimating the returns from investments in the UMTS infrastructure, thus helping to tune operators’ strategies for UMTS deployment.

• Journal of Navigation and Port Research
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• v.30 no.4
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• pp.267-275
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• 2006

Due to the growth of container traffic and port competition, ports have increasingly been under pressure to improve their efficiency in port operation and port management for competitive edge. The purpose of this study is to compare the technical efficiency among major container terminals in China, Korea and Singapore using Data Envelopment Analysis (DEA). This paper analyses the returns-to-scale using the output orientation of VRS and CRS model. The benefits of this study examining the relative performance of container terminals will enable container terminal operating companies or port policy makers in those countries to identify current slacks and to set up a proper port management and operation plan to improve their productivity.

• East Asian Economic Review
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• v.19 no.2
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• pp.167-188
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• 2015

The objective of this study is to obtain a better understanding of the current rice production condition in Myanmar through efficiency analysis, especially, to examine the impact of farm mechanization on Myanmar rice production efficiency. For representation of efficiency and the determinants, this paper uses both the data envelopment analysis (DEA) and the stochastic frontier approach (SFA) with variable returns to scale on Myanmar rice production. The efficiency of the rice production was estimated and subsequently the determinants factors were investigated based on the estimated efficiency level of these sample farmers. The empirical evidence finds that farm mechanical tools significantly improve the Myanmar rice production efficiency.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.9
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• pp.1356-1365
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• 2008

As Korean retailers are expanding their return policies, customer abuse and fraud behaviors are increasing. This study attempts to understand customers' unethical return behaviors in the Korean retailing. As an exploratory approach, the study identifies behavioral patterns of unethical returns from retail employees' perspectives. A total of 168 cases collected from 112 individual interviews with retail employees are qualitatively analyzed. Unethical return behaviors are categorized into five groups: lenting/deshopping, product defects with customer faults, unreasonable compensation demands, selfish behaviors, and problem behaviors in the service encounter. The study indicates that a variety of unethical return behaviors are observed despite a short history of return policy in Korea, and renting/deshopping and product defects with customer faults are the most prevalent return abuse behaviors.

• East Asian Economic Review
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• v.18 no.4
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• pp.367-394
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• 2014

In this study, we examined the fractal structure of the Nikkei225, HangSeng, Shanghai Stock Exchange and Straits Times Index of Singapore. Empirical analysis was performed via non-parametric, semi-parametric long memory tests and also fractal dimension calculations. In order to avoid spurious long memory features, besides the Detrended Fluctuations Analysis (DFA), we also used Smith's (2005) modified GPH method. As for fractal dimension calculations, they were conducted via Box-Counting and Variation (p=1) tests. According to the results, while there is no long memory property in log returns of any index, we found evidence for long memory properties in the volatility of the HangSeng, the Shanghai Stock Exchange and the Straits Times Index. However, we could not find any sign of long memory in the volatility of Nikkei225 index using either the DFA or modified GPH test. Fractal dimension analysis also demonstrated that all raw index prices have fractal structure properties except for the Nikkei225 index. These findings showed that the Nikkei225 index has the most efficient market properties among these markets.

• 사회경제평론
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• no.38
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• pp.241-259
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• 2012

This paper reviews four different kinds of currency crisis models proposed to explain the Korean crisis of 1997 to examine which model is more relevant to explain the Korean crisis of 2008. According to the author's investigation, the 'Frenkel-Neftci' cycle is more relevant model to interpret the Korean crisis of 2008. In 2008, spreads opened due to, first, high interest rate policy by the Korean government aimed to suppress real estate price increase, and, second, the expectation about exchange rate appreciation, and thirdly stock market returns after recovering the crisis. Then the international capital market catastrophe due to the subprime crises produced the sudden change of expectation of the market participants. Huge capital outflows resulted from the credit crunch in the international capital markets, and the possibility of exchange rate depreciation by the Korean government to promote exports in the course of the global recession.

• ETRI Journal
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• v.43 no.6
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• pp.1004-1012
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• 2021

The collaboration productively interacting between multi-agents has become an emerging issue in real-world applications. In reinforcement learning, multi-agent environments present challenges beyond tractable issues in single-agent settings. This collaborative environment has the following highly complex attributes: sparse rewards for task completion, limited communications between each other, and only partial observations. In particular, adjustments in an agent's action policy result in a nonstationary environment from the other agent's perspective, which causes high variance in the learned policies and prevents the direct use of reinforcement learning approaches. Unexpected social loafing caused by high dispersion makes it difficult for all agents to succeed in collaborative tasks. Therefore, we address a paradox caused by the social loafing to significantly reduce total returns after a certain timestep of multi-agent reinforcement learning. We further demonstrate that the collaborative paradox in multi-agent environments can be avoided by our proposed effective early stop method leveraging a metric for social loafing.

• KDI Journal of Economic Policy
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• v.41 no.2
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• pp.59-79
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• 2019

This study analyzes whether mutual fund distributors are more likely to recommend products with higher sales compensation to maximize their profit. The lists of the 'fund of the month' on their webpages are utilized from April of 2015 to August of 2015. A simple comparative analysis shows that the average sales fees and the average front-end load are significantly higher in the recommended funds among the A share class of domestic equity funds. The results of a regression analysis confirm that funds with high sales compensation levels are more likely to be recommended. This holds true for both domestic equity funds and hybrid bond funds even after controlling for fund age, fund size, and past returns.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.4
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• pp.1-7
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• 2022

Explainable AI (XAI) is an approach that leverages artificial intelligence to support human decision-making. Recently, governments of several countries including Korea are attempting objective evidence-based analyses of R&D investments with returns by analyzing quantitative data. Over the past decade, governments have invested in relevant researches, allowing government officials to gain insights to help them evaluate past performances and discuss future policy directions. Compared to the size that has not been used yet, the utilization of the text information (accumulated in national DBs) so far is low level. The current study utilizes a text mining strategy for monitoring innovations along with a case study of smart-farms in the Honam region.