• Journal of KIISE:Information Networking
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• v.30 no.3
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• pp.407-415
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• 2003

As services requesting data transfer from a sender to a multiple number of receivers become popular, efficient group communication mechanisms like multicast get much attention. Since multicast is more efficient than unicast in terms of bandwidth usage and group management for group communication, many multicast protocols providing scalability and reliability have been proposed. Recently, router-supported reliable multicast protocols have been proposed because routers have the knowledge of the physical multicast tree structure and, in this scheme, repliers which retransmit lost packets are selected by routers. Repliers are selected dynamically based on the network situation, therefore, any receiver within a multicast group can become a replier Hence, all receivers within a group maintains a buffer for loss recovery within which received packets are stored. It is an overhead for all group receivers to store unnecessary packets. Therefore, in this paper, we propose a new scheme which reduces resource usage by discarding packets unnecessary for loss recovery from the receiver buffer. Our scheme performs the replier selection and the loss recovery of lost packets based on the LSM [1] model, and discards unnecessary packets determined by ACKs from erasers which represent local groups.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.1
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• pp.85-95
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• 1998

The broadband ultrasonic transducers have been designed to use in obtaining the broadband echo signals from fish schools in relation to the identification of fish species. The broadening of bandwidth was achieved by attaching double acoustic matching layers on the front face of a Tonpilz transducer consisted of an aluminum head, a piezoelectric ring, a brass tail and to evaluate the performance characteristics, such as the transmitting voltage response(TVR) of transducers. The constructed transducers were tested experimentally and numerically by changing the parameters such as impedances and thicknesses of the head, tail and matching layers, in the water tank. Also, the developed transducer was excited by a chirp signal and the received chirp waveforms were analyzed. According to the measured TVR results, the available 3 dB bandwidth of the transducer with double matching layers of an $Al_O_3/epoxy$ composite of 7 mm thick and a polyurethane window of 18 mm thick was 7.3 kHz with a center frequency of 38.8 kHz, and the maximum and the minimum values of the TVR in this frequency region were 135.7 dB and 132.7 dB re $1\;{\mu}Pa/V$ at 1 m, respectively. Also, the available 3 dB bandwidth of the transducer with double matching layers of an $Al_O_3/epoxy$ composite of 11 mm thick and a polyurethane window of 15 mm thick was 6.2 kHz with a center frequency of 38.6 kHz, and the maximum TVR value in the frequency region was 136.3 dB re $1\;{\mu}Pa/V$ at 1 m. Reasonable agreement between the experimental results and the numerical results for the TVR of the developed transducers was achieved. The frequency dependant characteristics of experimentally observed chirp signals closely matched to the measured TVR results. These results suggest that there is potential for increasing the bandwidth by varying other parameters in the transducer design and the material of the acoustic matching layers.

• (The) Research of the performance art and culture
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• no.19
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• pp.88-123
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• 2009

Gyeongsanjain Dano Festival is a local festival of Yeongnam that was initially designated as Intangible Cultural Heritage No. 44 "Hanjanggun Nori" in 1971 and finally became Gyeongsanjain Dano Festival in 2007. At first, few parts of it were designated for preservation and it was succeeded as a whole without connections between each part. Problems also rise from the fact that it has not been closely studied. Gyeongsanjain Dano Festival is mostly classified into five parts: Keungut, Yeowonmu, Hojanggut, Hanmyoje, and Jainpalgwangdae. This study has closely discussed each part as follows: 1. Keungut 1) Process and Contents of Keungut - Characteristics of Gut in Daegu and Gyeongsan 2) Presence of Performers that can Execute Traditional Gut of Local Area 3) Problems with the Name of Keungut - Ex: 'Hanjanggungut' or 'Keungut' 4) Problems of Dano Festival without Parts to Summon and Send off Spirits before and After Keungut and Restoration Measures 2. Yeowonmu 1) Essence of Yeowonmu and Yeowonhwa 2) Problems with the Mass Game of Hundreds of High School Girls 3) Origin and Succession of Yeowonmu 3. Hojanggut 1) Changes in Characters of Hojanggut 2) Composition and Characteristics of Hojanggut 3) Problems with the Name and Characteristics of Hojanggut 4. Jainpalgwangdae Nori 1) Similarity with Newly Created Shows 2) Problems with the Name of Palgwangdae 3) Difference with the Composition of Other Mask Dances 4) Dances and Movements Distinguished from Other Mask Dances in Yeongnam The following are the solutions suggested for Gyeongsan Jain Dano Festival. First, for the restoration of Gyeongsanjain Dano Festival, Dano festivals and Byeolsinje of nearby areas with clear traditions could be benchmarked. Second, the major content of Gyeongsanjain Dano Festival is 'Hanjanggungut,' and it has to be the leading content of the festival. Third, the structural principle of Korean festival must be adopted and the process and principle must correspond to those of other traditional shows. Fourth, as Gyeongsanjain Dano Festival is the comprehensive form of art, folk, and festival, each part must be closely related in a well-planned scenario. Fifth, Intangible talents and successful training must be widely acknowledged for successful transmission and responsible performances. Sixth, traditional festivals must be restored along with the discovery and development of various festival repertories and spectacles such as tour programs and experiential tours that contribute to local economy.