• Journal of the Korean Operations Research and Management Science Society
• /
• v.16 no.2
• /
• pp.128-147
• /
• 1991

We propose a dynamic incidence matrix (DIM) for reflecting states and time conditions of a timed Petri net (TPN) explicitly. Since a DIM consists of a conventional incidence matrix, two time-related vectors and two state-related vectors, we can get the advantages inherent in the conventional incidence matrix of describing a static structure of a system as well as another advantage of expressing time dependent state transitions. We introduce an algorithm providing the DIM with a state transition mechanism. Because the algorithm is, in fact, an algorithmic model for discrete event simulation of TPN models, we provide a theoretical basis of model transformation of a TPN model into a DEVS(Discrete Event system Specification) model. By executing the algorithm we can carry out performance analysis of computer communication protocols which are represented TPN models.

• The Korean Journal of Food & Health Convergence
• /
• v.4 no.2
• /
• pp.17-23
• /
• 2018

Carica papaya is an important medicinal plant used in the management of different disease conditions. Phytochemical screening was carried out using different chemical test, Percentage yield and total phenolic content was evaluated using Folin Ciocalteu method in different solvent system; methanol, ethanol, ethyl acetate, n-butanol and n-hexane respectively. The phytochemical screening of the studies showed the presence of flavonoids, saponins, tannins, terpenoids, glycosides, steroids, carbonhydrate, anthraquinone and alkaloids. The percentage yield of crude extract and total polyphenol content was high in methanol, ethanol and ethyl acetate when compared with n-butanol and n-hexane. The studies show that Carica papaya leave extracts is a potent source of secondary metabolites. The use of the plant in the management of diseases is justified.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.5 no.3
• /
• pp.542-559
• /
• 2011

Most game-theoretic works of Aloha have emphasized investigating Nash equilibria according to the system state represented by the number of network users and their decisions. In contrast, we focus on the possible change of nodes' utility state represented by delay constraint and decreasing utility over time. These foregone changes of nodes' state are more likely to instigate selfish behaviors in networking environments. For such environment, in this paper, we propose a repeated Bayesian slotted Aloha game model to analyze the selfish behavior of impatient users. We prove the existence of Nash equilibrium mathematically and empirically. The proposed model enables any type of transmission probability sequence to achieve Nash equilibrium without degrading its optimal throughput. Those Nash equilibria can be used as a solution concept to thwart the selfish behaviors of nodes and ensure the system stability.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.9B
• /
• pp.823-833
• /
• 2003

To satisfy the requirements of the real-time Internet services, queue management and scheduling schemes should be enhanced to accommodate the delay and jitter characteristic of them. Although the existing queue management schemes can address the congestion problems of TCP flows, they have some problems in supporting real-time services. That is, they show performance degradation when burst traffics are continuously going into the system after the queue is occupied at a predefined threshold level. In addition, under the congestion state, they show large jitter, which is not a desirable phenomenon for real-time transmissions. To resolve these problems, we propose a SDRED (State Dependent Random Early Detection) and dynamic scheduling scheme that can improve delay and jitter performances by adjusting RED parameters such as ma $x_{th}$ and $w_{q}$ according to the queue status. The SDRED is designed to adapt to the current traffic situation by adjusting the max,$_{th}$ and $w_{q}$ to four different levels. From the simulation results, we show that the SDRED decreases packet delays in a queue and has more stable jitter characteristics than the existing RED, BLUE, ARED and DSRED schemes.mes.mes.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2008.10a
• /
• pp.121-121
• /
• 2008

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1989.10a
• /
• pp.52-52
• /
• 1989

• Journal of the Korean Society of School Health
• /
• v.21 no.1
• /
• pp.43-51
• /
• 2008

Background: Although school footpaths must guarantee pedestrians’ safety and pleasantness, even facilities installed according to standards provided in “Rules on the Designation and Management of School Zones” are not maintained and managed properly and as a result they are not effective for securing the safety of school footpaths. Purpose: The present study surveyed the physical environment of elementary school footpaths and investigated problems posed by the absence of facilities. Methods: First, the current state of street structure was investigated using maps as well as field surveys, and the current state of street furniture was surveyed by checking if it has been installed and photographing it. In addition, traffic characteristics were investigated by measuring traffic safety while children’s going to school and home, and children’s behaviors on school footpaths were surveyed by observing their behaviors when going to school and home. Result: This study surveyed the installation and state of safety facilities on school footpaths around elementary schools in B City, analyzed items to be improved, and presented materials for reducing accidents among elementary students.

• Journal of Korean Library and Information Science Society
• /
• v.48 no.1
• /
• pp.21-42
• /
• 2017

This study reports the result of the survey on collection management from 154 school libraries in Korea. The questionnaire is consisted of three section: state of collection, state of book use, and collection management system. Results reveal that (1) elementary schools and middle schools have many books for each student compared to the KLA's School Library Standards; (2) the component ratio of literature books is the biggest in school library collections; (3) the ratio of library book use is overwhelmingly higher in elementary schools than middle schools and high schools; (4) 64.6 percent of library books in the sample are never used during 2013-2015; (5) 74 percent of libraries have its own collection management document; (6) Almost all schools compose its own committee for library management, the committee plays an important roles in the communication among school members, collection development and promotion.

• Fashion, Industry and Education
• /
• v.14 no.1
• /
• pp.1-9
• /
• 2016

This study examined the comparative advantage of manmade textile (MMT) industries in the United States (US) and South Korea (SK). The Revealed Comparative Advantage (RCA) framework was used to assess the MMT industries' performance in both countries from 2004 to 2013. With the recent ratification of the United States-South Korea Free Trade Agreement (KORUS FTA), it is important to understand the current state of these industries. Using UN Comtrade export data, the RCA index values were calculated and analyzed for 27 MMT commodities, three aggregate groups, and the whole industry. It was found that SK had a consistent comparative advantage for the whole industry. Furthermore, SK had a larger number of products with a comparative advantage. The research findings indicate that the MMT industry in SK is likely to outperform the US following the complete ratification of the KORUS FTA.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.20 no.4
• /
• pp.344-350
• /
• 2015

A battery management system requires accurate information on the battery state of charge (SOC) to achieve efficient energy management of electric vehicle and renewable energy systems. Although correct SOC estimation is difficult because of the changes in the electrical characteristics of the battery attributed to ambient temperature, service life, and operating point, various methods for accurate SOC estimation have been reported. On the basis of piecewise linear (PWL) modeling technique, this paper proposes a simple SOC observer for lithium-polymer batteries. For performance evaluation, the SOC estimated by the PWL SOC observer, the SOC measured by the battery-discharging experiment and the SOC estimated by the extended Kalman filter (EKF) estimator were compared through a PSIM simulation study.