• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11B
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• pp.1030-1037
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• 2008

This paper presents an algorithm for the path-finding problem in unknown environments with cooperative and commutative multi-robots. To verify the algorithm, we investigate the problem of escaping through the exit of a randomly generated maze by muti-robots. For the purpose, we adopt the so called frontier cells and cell utility functions, which were used in the exploration problem for the multi-robots. For the wireless communications among the mobile robots, we modify and utilize the so called the random basket routing, a kind of hop-by-hop opportunistic routing. A mobile robot, once it finds the exit, will choose its next action, either escape immediately or stay-and-relay the exit information for the others, where the robot takes one action based on a given probability. We investigate the optimal probability that minimizes the average escaping time (out of the maze to the exit) of a mobile robot.

• Journal of KIISE:Databases
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• v.35 no.4
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• pp.307-318
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• 2008

One of the primary issues confronting XML message brokers is the difficulty associated with processing a large set of continuous XPath queries over incoming XML seams. This paper proposes a novel system designed to present an effective solution to this problem. The proposed system transforms multiple XPath queries before their run-time into a new region-based data structure, called an XP-table, by sharing their common constraints. An XP-table is matched with a stream relation (SR) transformed from a target XML stream by a SAX parser. This arrangement is intended to minimize the runtime workload of continuous query processing. Also, system performance is estimated and verified through a variety of experiments, including comparisons with previous approaches such as YFilter and LazyDFA. The proposed system is practically linear- scalable and stable for evaluating a set of XPath queries in a continuous and timely fashion.

• Smart Media Journal
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• v.5 no.4
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• pp.131-137
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• 2016

Since the phenomenon that the consumers slip important calls since they do not know the receiving information of the smart phone in spaces which smart phones can not be carried, the development of technology to solve this problem is urgent and the cases of burglary and losses of smart phones during hobby and recreation life are increasing and especially since burglary behaviors are occurring much in places such as bathing resort, swimming pool, Korean dry sauna, sauna and spa etc, the schemes to protect smart phones during hobbies and recreation life is needed. Since the smart watch, the conventional wearable device are high price machines and due to the burden about A/S costs for the damage or failure of the machine during exercise, hobbies and recreation activities, the burden about the use is high, development of products which can reduce such burden and emphasize the usefulness is urgent and in order to solve this problem, the added value and psychological repercussion effect will be very high in areas of smart phone users and utilizing them by developing the system which can know if the smart phone has received calls at least in places where smart phones can not be carried.

• Journal of Embryo Transfer
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• v.11 no.1
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• pp.41-50
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• 1996

This experiment was carried out to investigate the ovarian responses of the ovulation point, ovarian weight and size, the number of ovarian follicles and collected embryos, and to study the effects of the developmental stages (oocytes, 2-4 cell. 8-16 cell and morulae), additional levels of Ficoll (0, 15, 30%) on the survival rate (FDA-test) of rat embryos frozen in vitrification solution (20% glycerol + 10% ethylene glycol + 10% sucrose). Sunanarized results was as follows; 1. The mean ovulation point per head was 7, and the weight of ovaries was 0.03g. The size of ovary was 5.9 mm(L) and 4.6 mm(W), and the number of ovarian follicles over and below 2 mm was 4.7 and 8.7, respectively. The number of the collected embryos per head was 5.5 (79%). 2. 2. The FDA score of embryos frozen in 20 G 10 E 10 S without Ficoll was 2.8 (oocyte), 2.6 (2-4 cell), 3.9 (8-16 cell) and 3.6 (morula), respectively. However, there were no significant differences among treatments. 3. The FDA score of embryos frozen in 20 G 10 E 10 S with 15% Ficoll was 3.4 (oocyte), 4.0 (2-4 cell), 4.7 (8-16 cell) and 4.8 (morulae), respectively (P>0.05). 4. The FDA score of embryos frozen in 20 G 10 E 10 S with 30 % Ficoll was 3.7 (oocyte), 3.2 (2-4 cell), 4.4 (8-16 cell) and 4.4 (morulae), respectively (P>0.05). 5. As shown in the above results, the higher survival rate was obtained in the treatment of 15% Ficoll than that of 30%. And the survival rate (FDA-test)of the oocytes and 2-4 cell stages of the rat embryos was lower than that of 8~16 cell and morulae stages. It was considered that 8-16 cell and morulae could be available for the successful freezing by vitrification of rat embryos with 15% Ficoll except for oocytes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10B
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• pp.1043-1049
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• 2009

Broadcast of sink node is used for network management, data collection by query and synchronization in wireless sensor networks. Simple flooding scheme induces the broadcast storm problem. The MPR based broadcast schemes reduce redundant retransmission of broadcast packets. MPR is a set of one hop neighbor nodes which have to relay broadcast message to cover all two hop neighbors. Though MPR can reduce redundant retransmission remarkably, it still suffers from energy waste problem caused by collision and duplicate packets reception. This paper proposes a new MPR based sink broadcast scheme using 3-channel. The proposed scheme reduces energy consumption by avoiding duplicate packet reception, while increases reliability by reducing collision probability remarkably. The results of analysis and simulation show that the proposed scheme is more efficient in energy consumption compared to the MPR based scheme. The result also shows that the proposed scheme reduces delivery latency by evading a contention with other relay nodes and improves reliability of broadcast message delivery by reducing collision probability.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.920-928
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• 2000

In this paper, using newly proposed size reduction technique, the aperture coupled microstrip patch antenna for a repeater system in a mobile communication cellular band (824~849 MHz) is developed with a wide bandwidth, small size, light weight, and low cost. The resonant frequency of microstrip antennas is related to the electric field distribution of the radiating patch. The field strength of $TM_{01}$ mode of a rectangular patch antenna is strongest at each of the extremities of the radiating patch, but negligible at center. Therefore, the size of a patch antenna can be effectively minimized by inserting the narrow rectangular dielectric into just under the edges of the resonant Patch. This Paper also proposes the bandwidth improvement technique by using under-coupling technique with a tuning stub. The VSWR is less than 1.5 : 1 for the whole cellular band. The simulation tool was HFSS, Agilent Technologies, Inc.

• The Journal of the Korea Contents Association
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• v.18 no.6
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• pp.608-616
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• 2018

The significance of leisure activities is highlighted, and professional baseball games, which featured the 2008 Beijing Olympics gold medal, are very popular. In recent years, along with the revenue from broadcasting, the club has been trying to gain revenue by developing various licensing products and merchandising products. However, sports related products are more advanced than Japanese professional baseball teams in Korea, and there is a lot of revenue from product sales. We want to compare the difference between the two countries sales of their products.

• Journal of Digital Convergence
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• v.18 no.1
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• pp.111-119
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• 2020

This study takes Chinese independent tourists to South Korea as the research object, mines the data of tourists' digital footprints from online travel notes, and analyzes the characteristics of the tourism flow of Chinese independent tourists to South Korea by using the method of quantitative statistics and social network analysis(SNA). The results show that Seoul, Jeju Island, Busan and Daegu are the important tourist destinations for Chinese independent tourists entering South Korea. In addition, Qingdao, Tianjin, Shenyang, Hong Kong, Foshan and Macao are crucial hubs for Chinese independent tourists to visit South Korea. In future studies, the number of sample data should be increased. The time span of data collection should be extended for studying the annual variation characteristics of tourism flow and the trend of tourism hot spots.

• Journal of Digital Convergence
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• v.9 no.3
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• pp.95-104
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• 2011

This study explored how political figures build their image using twitters. To examine the research question, this study analyzed twitter messages in five political figures: Si-Min, Yu, Jung-hee, Lee, Mun-soo, Kim, and Young-gil, Song. The findings showed that except for Mrs. Lee, the other political figures presented more one-way messages than two-way messages in twitters. Even though twitter has benefits of communicating instantly and two-way communication between followers and followings, most messages in their twitters were limited to informative message. The study also classified the messages into social-oriented and individual-oriented in each politician' s twitter. The result presented that Mrs. Lee twitter included individual-oriented messages, but the other three political figures had more social-oriented messages.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.572-584
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• 1993

In this paper, we propose an efficient method to allocate carrier frequencies so as to minimize intermodulation products in two-level SCPC systems in which Hub station and many Remote stations communicate each other through the satellite transponder. Also we present a very efficient method to evaluate intermodulation products with highly reduced CPU time in two-level SCPC systems. We study and analyze the performance of some possible methods to extend the Deletion and Insertion operation, which is proposed by Okinaka and applied to only one-level SCPC systems, to two-level SCPC systems. The proposed algorithm is carefully selected out of these methods and is optimized, which shows superior performance to any other published strategies, especially in that it has very excellent characteristics in terms of generality for practical application. Considering the fact that most published strategies are seldom applicable to actual two-level SCPC systems, we can say that the proposed algorithm in this paper is quite meaningful.