• Journal of Internet Computing and Services
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• v.9 no.5
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• pp.141-151
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• 2008

In the paper, we analyze the performance of random access channels in multi-service multi-user OFDMA systems. The resource of the random access channels in OFDMA systems are available sub-channels and PN-codes. For given available sub-channels and PN-codes,' we analyze the performance of the random access channels of OFDMA systems in terms of the access success probability, the blocking probability, the access delay and the throughput per each service class. Further, we find the feasible region of the access probability of each service class in which the allowable minimum access success probability, the allowable maximum blocking probability and the allowable maximum access delay are satisfied. The results also can be used to find proper region of the access probabilities of each service class for differentiated quality of service(QoS)s, and for the system operations in multi-service multi-user OFDMA systems.

• Journal of the Korea Society of Computer and Information
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• v.17 no.7
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• pp.45-52
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• 2012

In this paper, an crowd density in elevator estimation method based on multi-class Adaboost classifier is proposed. The SOM (Self-Organizing Map) based conventional methods have shown insufficient performance in practical scenarios and have weakness for low reproducibility. The proposed method estimates the crowd density using multi-class Adaboost classifier with texture features, namely, GLDM(Grey-Level Dependency Matrix) or GGDM(Grey-Gradient Dependency Matrix). In order to classify into multi-label, weak classifier which have better performance is generated by modifying a weight update equation of general Adaboost algorithm. The crowd density is classified into four categories depending on the number of persons in the crowd, which can be 0 person, 1-2 people, 3-4 people, and 5 or more people. The experimental results under indoor environment show the proposed method improves detection rate by about 20% compared to that of the conventional method.

• Journal of the Korean Operations Research and Management Science Society
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• v.38 no.4
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• pp.11-33
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• 2013

We analyzed the structures and properties of the global financial market networks using social network analysis approach. The Minimum Spanning Tree (MST) lengths and networks of the global financial markets based on the correlation coefficients have been analyzed. Firstly, similar to the previous studies on the global stock indices using MST length, the diversification effects in the global multi-asset portfolio can disappear during the crisis as the correlations among the asset class and within the asset class increase due to the system risks. Second, through the network visualization, we found the clustering of the asset class in the global financial markets network, which confirms the possible diversification effect in the global multi-asset portfolio. Meanwhile, we found the changes in the structure of the network during the crisis. For the last one, in terms of the degree centrality, the stock indices were the most influential to other assets in the global financial markets network, while in terms of the betweenness centrality, Gold, Silver and AUD. In the practical perspective, we propose the methods such as MST length and network visualization to monitor the change of the correlation risk for the risk management of the multi-asset portfolio.

• Computers and Concrete
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• v.8 no.5
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• pp.583-595
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• 2011

This paper studied the cement efficiency factor (k factor) of high calcium Class F fly ash. This k factor represents a unit of fly ash with efficiency equivalent to k unit of cement. The high calcium Class F fly ash was used to replace cement in concrete. The modified Bolomey's law with linear relationship was used for the analysis of the result of compressive strength, cement to water ratio (c/w) and fly ash to water ratio (f/w) by using the multi-linear regression to determine the k factor and other constants in the equations. The results of analysis were compared with the results from other researcher and showed that the k factor of high calcium Class F fly ash depends on the fineness of fly ash, replacement level and curing age. While the amount of CaO content in Class F fly ash not evident. Furthermore, necessary criteria and variables for the determination of the k factor including the use of the k factor in concrete mix design containing fly ash were proposed.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.863-870
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• 2002

The current class scheduling has difficulties in reflecting students' preferences for the classes that they want to take and forecasting the demands of classes. Also, it is usually a repetitive and tedious work to allocate classes to limited time and cesourres Although many research studios in task allocation and meeting scheduling intend to solve similar problems, they have limitations to be directly applied to the class-scheduling problem. In this paper. a class scheduling system using multi agents-based negotiation is suggested. This system consists of student agents, professor agents and negotiation agents each agent arts in accordance with its respective human user's preference and performs the repetitive and tedious process instead of the user The suggested system utilizes negotiation cost concept to derive coalition in the agent's negotiation. The negotiation cost is derived from users' bidding prices on classes, where each biding price represents a user's preference on a selected class. The experiments were performed to verify the negotiation model in the scheduling system. The result of the experiment showed that it could produce a feasible scheduling solution minimizing the negotiation cost and reflecting the users' performance. The performance of the experiments was evaluated by a class success ratio.

• Journal of Power Electronics
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• v.18 no.1
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• pp.277-288
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• 2018

Wireless inductive power transfer (IPT) technology is used in many applications today. A compact and high-frequency primary side inverter is one of the most important parts of a WPT system. In this study, a modified class EF-type voltage-fed multi-resonant inverter has been proposed for WPT application at a frequency range of 85-100 kHz. Instead of an infinite input choke inductor, a resonant inductor is used to reduce loss and power density. The peak voltage stress across the MOSFET has been reduced to almost 60% from a class-E inverter using a passive clamping circuit. A simple yet effective design procedure has been presented to calculate the various component values of the proposed inverter. The overall system is simulated using MATLAB/SimPowerSystem to verify the theoretical concepts. A 500-W prototype was built and tested to validate the simulated results. The inverter exhibited 90% efficiency at nearly perfect alignment condition, and efficiency reduced gradually with the misalignment of WPT coils. The proposed inverter maintains zero-voltage switching (ZVS) during considerable load changes and possesses all the inherent advantages of class E-type inverters.

• Journal of Korean Society of Transportation
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• v.21 no.6
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• pp.77-88
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• 2003

This paper proposes a solution algorithm for solving a multi-class analytical DTA model. In the DTA model, three traveler classes are classified according to different assumptions of traveler's route choice behavior: including fixed route, Stochastic Dynamic User Optimum(SDUO), and Dynamic User Optimum(DUO). To solve this DTA model, variables of link flow and exit flow are represented solely by inflow. The resulting Linear Program(LP) subproblem in the inner iteration is solved as a typical time-dependent shortest route problem over a physical network. Accordingly, the required time-space network expansion in solving DTA models is no longer needed.

• The Journal of the Korea Contents Association
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• v.22 no.4
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• pp.365-378
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• 2022

This study attempted to understand the effect of subjective class consciousness on the quality of life of female elderly people and to verify the multi-mediated effect of expectation of living standards and depression. To this end, an analysis was conducted using the SPSS Process Macro for 8,070 female elderly people aged 55 or older in the data of the "2018 Aging Research Panel Survey 7" of the Korea Employment Information Service. As a result of the analysis, first, it was found that the higher the subjective class consciousness of the elderly women, the higher the quality of life. Second, the higher the subjective class consciousness of the elderly women, the higher the expectation of living standards and the lower the depression. Third, in the relationship between the subjective class consciousness and quality of life of female elderly, when expectations and depression of living standards were simultaneously put into the regression equation, both variables were found to have significant mediating effects. Based on these research results, practical and policy implications for improving the quality of life of the elderly women were discussed together.

• Journal of the Korean Data and Information Science Society
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• v.17 no.2
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• pp.437-447
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• 2006

Error Correcting Output Coding(ECOC) is used to solve multi-class problem. It is known that it improves the classification accuracy. In this paper, we compared various criteria to design code matrix while encoding. In addition. we prorpose an ensemble which uses the ability of each classifier while decoding. We investigate the justification of the proposed method through real data and synthetic data.

• Proceedings of the Korea Information Assurance Society Conference
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• 2004.05a
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• pp.43-50
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• 2004

Diffserv Network DSCP(Differentiated Service Code Point)는 8bit로 구성되어 있고, 그 중 6bit만 사용되고, 나머지 2bit는 비워져 있는 상태로 있다. 이 2bit를 사용하여, DF(Default Forwarding), EF(Expedited Forwarding), AF(Assured Forwarding)의 DSCP 에 각각의 Service Class Code Point를 부여해서 사용자의 패킷을 구분하여 서비스하는 DiffServ 같은 경우 상용화가 되었을 때, DiffServ를 서비스하는 망에서 동일한 DiffServ 정책을 설정해서 사용할 수 있는 기법을 제안한다.