• 한국경영정보학회:학술대회논문집
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• 2007.06a
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• pp.661-666
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• 2007

MMORPG, massively multi-players in online role-playing game, is the most popular genre in online games. Because large number of players interacts with each other, virtual worlds in MMORPG are alike communities of real worlds. Moreover, players in virtual worlds trade game items with real money. This paper is to find impacts of real-money trading into real worlds, and game operators, by using two-period model between players of the game and the game operator. It was found that real-money trading benefits game operators, and there exists optimal supply of game items to maximize the profit of game operator. Moreover we found that the income disparity in real worlds could be decreased when real-money trading is allowed To support the analytical model, we used an empirical analysis using real-money trading data, and find the relationship among play time of MMORPG, transaction volume of real-money trading, and price of game items. In empirical analysis, it was found that real-money trading benefits game operators. Moreover, it was found that play time and price have positive relationship.

• ETRI Journal
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• v.31 no.2
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• pp.140-150
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• 2009

Although mutation testing is potentially powerful, it is a computationally expensive testing method. To investigate how we can reduce the cost of object-oriented mutation testing, we have conducted empirical studies on class mutation operators. We applied class mutation operators to 866 classes contained in six open-source programs. An analysis of the number and the distribution of class mutants generated and preliminary data on the effectiveness of some operators are provided. Our study shows that the overall number of class mutants is smaller than for traditional mutants, which offers the possibility that class mutation can be made practically affordable.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.1330-1333
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• 1993

In this paper, first, the fuzzy Petri net inference mechanism with learning function is proposed by using the extended fuzzy Petri nets. Secondly, a control system with this new inference engine is proposed. This system can do automatically and easily the knowledge acquisition from the operator's empirical data and can also be controller adaptively under the big parameter change.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.503-509
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• 2004

With modem computational fluid dynamics method (CFD), air-charging models of the air brake pipe system and auxiliary reservoir are built. Compared with one-dimension model, no empirical formula is introduced to solve branch pipe fields for two-dimension model. A modified operator-splitting method is presented to solve the coupled equations of pressure and velocity, and numerical simulation shows that it is very stable. Compare the numerical results with empirical data of heavy haul trains in home and abroad so as to prove the correctness of the theory and algorithm presented. This paper gives theoretic reference to the experiments of braking effects of heavy haul trains, and forms a basis for development of complete freight train air brake system simulation.

• Journal of the Korean Institute of Navigation
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• v.23 no.4
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• pp.77-88
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• 1999

Container terminal productivity is a critical factor for both the terminal operator and liner companies. For the former it is a determinant factor of the competitiveness and profit of terminal, and for the later it is one that determines ships' tern round time and hence ships' operation costs. The concept and measures of productivity are however not well defined and unified throughout terminals in the world. This paper therefore deals with the empirical study on the evaluation of container terminal productivity. It first clarifies the concept of terminal productivity, and secondly based on the actual data on container terminals in and outside Korea, productivity is evaluated and compared. Finally, problems hampered efficient operation of Korean terminals are derived, and several comments are suggested for solving them.

• Journal of Korea Trade
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• v.27 no.1
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• pp.101-118
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• 2023

Purpose - Korea became a trillion-dollar trading country in 2011. With the exponential increase in Korea's trade volume over the past decades, trade-related administrative burdens per capita for Korea Customs became enormous, for which the government established the Single Window, a trade-facilitating system, in 2004 to enhance the efficiency of customs-clearing procedures for traders. This paper focuses on finding whether the Korean Single Window system affects the country's trade facilitation positively through an empirical methodology. Design/methodology - To find empirical evidence that Single Window affects trade facilitation for the customs-clearing procedure, this study assumes that a time-efficient environment enables the handling of the increase in trade volume, under which four independent variables related to import customs-clearing procedures and two dependent variables to import were adopted for empirical analysis. The import customs procedures are classified into four steps from port entry to declaration acceptance. To understand the relationship between variables, scattered plots and correlation coefficients were calculated. Eight hypotheses were set and underwent simple linear regression. The data for analysis were collected by Korea Customs, and were about the lead time of import, the volume of imports in million USD, and the number of import declarations reported to customs offices on a monthly basis from 2005 to 2013. Findings - Six of the eight hypotheses showed the statistically significant result that lead time in the import customs-clearing procedure positively affects the number of import declaration reports and import volume. Specifically, Hypothesis 1, Hypothesis 2, and Hypothesis 3 strongly support the assumption lead time in import customs declaration has an inverse relationship with the number of import declarations, which means that the shorter the import lead time, the more import declaration increases. Research Limitations/Implications - With limited data accessibility to the government's custom-sclearing procedures, only the import lead time for customs clearance were adopted as independent variables. This paper, however, successfully found that the Single Window system contributed to trade facilitation. Originality/value - This study found that the time-saving Single Window system of Korea Customs enables itself to manage an exponentially-increasing trade volume by creating a trade-facilitating environment for customs personnel and traders, which may be a unique implication found through quantitative methodology.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2296-2298
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• 2000

Fuzzy control has been researched for application of industrial processes which have no accurate mathematical model and could not controlled by conventional methods because of a lack of quantitative input-output data. Intelligent control approach based on fuzzy logic could directly reflex human thinking and natural language to controller comparing with conventional methods. In this paper, fuzzy controller is implemented to acquire operator's knowledge. The tested system is constructed for sending a ball to the goal position using wind from two DC motors in the path. This system contains non-linearity and uncertainty because of the characteristic of aerodynamics inside the path. Ball position is measured by a vision camera. The system used in this experiment could be hardly modeled by mathematic methods and could not be easily controlled by linear control manners. The controller, in this paper is designed based on the input-output data and experimental knowledge obtained by trials.

• Journal of the Korean Society for Library and Information Science
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• v.44 no.3
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• pp.81-102
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• 2010

The purpose of this study was to investigate college students' preferences of Web-based OPAC retrieval techniques and their ABO blood types as an empirical survey. Data was collected through a self-designed questionnaire with a total of 101 undergraduate students from the College of Social Sciences responding. The collected data was analyzed using descriptive statistics, and One-way ANOVA. The results show that 'title' was most preferred among the access points, 'AND' was the most preferred Boolean operator, 'publication year' and 'subject' were the most favored techniques in limiting the scope of retrieval, and 'record number limit per page' was the most frequently used for displaying retrieval results. The results also show that there were little(3 out of 22, i.e. 13.6%) statistically significant differences between the college students' preferences of Web-based OPAC techniques and their blood type.

• Electronics and Telecommunications Trends
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• v.37 no.3
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• pp.74-84
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• 2022

The Korean mobile service market has persistently grown with the number of subscribers and volume of mobile traffic. It shows the slow diffusion of 5G subscribers, and rapid growth of both the MVNO(Mobile Virtual Network Operator) market and unlocked mobile phones. Therefore, this study derives the direction of telcos' strategies and policy implications by empirically analyzing the usage and attitude of LTE and 5G subscribers. Our major findings are as follows: First, our current mobile service subscription market constitutes most long-term customers for their incumbent carriers only by device change from lock-in with bundle services. Mobile tariffs, data speed, and benefits of bundle services are important factors affecting choices and customers' satisfaction with a provider and intentions of churning to another. Second, demand and satisfaction for using 5G are less because speeds and service tariffs act as pain points for 5G services. Third, the users' high preferences for MVNOs and unlocked mobile phones are linked to their subscription to MVNOs' low-cost plans with unlocked mobile phones on online channels. These streams lead to a big change in the market competition that MNO(Mobile Network Operator)s' market shares are expected to decrease and MVNOs' shares will be increased by two times, in the near future. Therefore, MNOs need to change their distribution strategies from offline to online channels and try to resolve the stereotype, "mobile tariffs are expensive," by enhancing their service values. Finally, as consumers prefer one-stop service in the same channel regardless of the distribution channel, policies should focus on the consumers' needs for convenience rather than on the channel separation for perfectly unlocked mobile phones.

• Journal of Welding and Joining
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• v.14 no.4
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• pp.33-42
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• 1996

In recent years there has been a significant growth in the use of the automated and/or robotic welding system, carried out as a means of improving productivity and quality, reducing product costs and removing the operator from tedious and potentially hazardous environments. One of the major difficulties with the automated and/or robotic welding process is the inherent lack of mathematical models for determination of suitable welding process parameters. Partial-penetration, single-pass bead-on-plate welds were fabricated in 12mm AS 1204 mild steel flats employing five different welding process parameters. The experimental results were used to develop three empirical equations: curvilinear; polynomial; and linear equations. The results were also employed to find the best mathematical equation under weld bend width to assist in the process control algorithms for the Gas Metal Arc Welding(GMAW) process and to correlate welding process parameters with weld bead width of bead-on-plates deposited. With the help of a standard statistical package program. SAS, multipe regression analysis was undertaken for investigating and modeling the GMAW process, and significance test techniques were applied for the interpretation of the experimental data.