• 자연과학논문집
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• 제4권
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• pp.11-22
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• 1991

Early studies on Korean Sargassum subjenus Bactrophycus were partly started by Kyetzubg(1843,1849), J. Agardh(1889), Cotton(1906), Yendo(1907) and Okamura(1913, 1914, 1915, 1917). Kang(1966) reported 15 species and 4 subspecies of Sargassum subgenus Bactrophycus and their wide distribution on the Korean coasts in his paper [On the geographical distribution of marine algae in Korea], a foundation stone of Korean phycology. In fact, all the Korean coasts and subtidal zone are inhabited by Sargassum plants. They constitute the most part of the primary production and dominant species of benthic algal vegetation. In 1974, L.K. Lee began to study Sargassum monographically as seaweed resources in Korea. The Koreans eat some species of Sargassum (including Hizikia fusiformis) or use them as fertilizer of the farm near the coast. Among the reported 17 species of Korean Fucales, 12 species belong to Bactrophycus. Yoo(1976) dealt with the descriptions, figures, and a key of 24 species of Korean Fucales plants in her M.S. thesis paper. Among them 16 species belonged to Bactrophycus. Even though the above two works were done with thorough observation of the dry specimens kept in the Pusan Fisheries University Herbarium (most of them were identified by Kang, J.W.) and nation-wide collections, great morphological varieties of these taxa made Lee and Yoo hesitate to publish the paper. Instead, the serial chemotaxonomic studies on the geographical variations of Korean Fucales plants(Yoo and Lee, 1988a, 1988b ; Yoo, et al., 1988) were held to solve the problem, while foreign papers (especially both Drs Tseng's and Yoshida's serial works on Bactrophycus). and authenthic specimens that foreign scholors sent to Korean phycologists induced them to find that several species of Sargassum had been misidentified from the beginning. We introduce here Korean Sargassum subgenus Bactrophycus according to Tseng et al. (1985), mentioning briefly the characteristics of the species, key, and distribution on the Korean coasts.

• 정보처리학회논문지C
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• 제18C권4호
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• pp.227-236
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• 2011

IPTV는 대표적인 방송통신융합 산업으로 IP망의 양방향성을 이용한 서비스의 차별화를 내세우며 여러 사업자에 의해 서비스가 이루어지고 있다. 최근에는 모바일 환경 등으로 그 영역을 확대하기 위한 연구가 진행되고 있으며 다른 한편으로는 IPTV 서비스를 위한 플랫폼 등을 개방하여 사업자가 아닌 일반인도 IPTV를 통한 방송을 할 수 있는 구조인 개방형 IPTV에 대한 연구가 활발하다. 이러한 개방형 IPTV 환경에서는 다수의 콘텐츠 제공자가 존재하기 때문에 기존 IPTV에서 사용되는 특정 기기 혹은 스마트카드를 통한 사용자 인증 및 키 분배가 어려운 실정이다. 본 논문에서는 기존 분산 네트워크에서의 인증 메커니즘인 Kerberos를 기반으로 하여 분산 환경에서 안전한 사용자 인증과 키 분배를 위한 메커니즘을 제안하였다. 제안 메커니즘은 콘텐츠의 안전한 전송을 보장하며 기존 제안된 IPTV 사용자 인증 관련 연구보다 인증 시간 오버 헤드에 있어 우위에 있음을 시뮬레이션을 통해 증명하였고 다양한 관점에서 제안 메커니즘을 다른 관련 연구와 비교하여 개방형 IPTV 환경에서 제안 메커니즘이 갖는 효율성을 증명하였으며 IPTV가 갖는 보안 요구 사항을 제안 메커니즘이 만족한다는 것을 보였다.

• Geomechanics and Engineering
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• 제23권2호
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• pp.151-163
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• 2020

Grouting method is an effective way of reinforcing cracked rock masses and plugging water gushing. Current grouting diffusion models are generally developed for horizontal cracks, which is contradictory to the fact that the crack generally occurs in rock masses with irregular spatial distribution characteristics in real underground environments. To solve this problem, this study selected a cement-sodium silicate slurry (C-S slurry) generally used in engineering as a fast-curing grouting material and regarded the C-S slurry as a Bingham fluid with time-varying viscosity for analysis. Based on the theory of fluid mechanics, and by simultaneously considering the deadweight of slurry and characteristics of non-uniform spatial distribution of viscosity of fast-curing grouts, a theoretical model of slurry diffusion in an oblique crack in rock masses at constant grouting rate was established. Moreover, the viscosity and pressure distribution equations in the slurry diffusion zone were deduced, thus quantifying the relationship between grouting pressure, grouting time, and slurry diffusion distance. On this basis, by using a 3-d finite element program in multi-field coupled software Comsol, the numerical simulation results were compared with theoretical calculation values, further verifying the effectiveness of the theoretical model. In addition, through the analysis of two engineering case studies, the theoretical calculations and measured slurry diffusion radius were compared, to evaluate the application effects of the model in engineering practice. Finally, by using the established theoretical model, the influence of cracking in rock masses on the diffusion characteristics of slurry was analysed. The results demonstrate that the inclination angle of the crack in rock masses and azimuth angle of slurry diffusion affect slurry diffusion characteristics. More attention should be paid to the actual grouting process. The results can provide references for determining grouting parameters of fast-curing grouts in engineering practice.

• Geomechanics and Engineering
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• 제19권5호
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• pp.421-434
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• 2019

It is of great significance to study the mechanical properties and failure mechanism of the defected rock for geological engineering. The defected sandstone modeling with power-law distribution of pre-cracks was built in this paper by Particle Flow Code software. Then the mechanical properties of sandstone and the corresponding failure process were meticulously analyzed by changing the power-law index (PLI) and the number of pre-cracks (NPC). The results show that (1) With the increase of the PLI, the proportion of prefabricated long cracks gradually decreases. (2) When the NPC is the same, the uniaxial compressive strength (UCS) of sandstone increases with the PLI; while when the PLI is the same, the UCS decreases with the NPC. (3) The damage model of rock strength is established based on the Mori-Tanaka method, which can be used to better describe the strength evolution of damaged rock. (4) The failure mode of the specimen is closely related to the total length of the pre-crack. As the total length of the pre-crack increases, the failure intensity of the specimen gradually becomes weaker. In addition, for the specimens with the total pre-crack length between 0.2-0.55 m, significant lateral expansion occurred during their failure process. (5) For the specimens with smaller PLI in the pre-peak loading process, the concentration of the force field inside is more serious than that of the specimens with larger PLI.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권3호
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• pp.1144-1156
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• 2014

In Internet, IP multicast has been used successfully to provide an efficient, best-effort delivery service for group communication applications. However, applications such as multiparty private conference, distribution of stock market information, pay per view and other subscriber services may require secure multicast to protect integrity and confidentiality of the group traffic, and validate message authenticity. Providing secure multicast for group communication is problematic without a robust group key management. In this paper, we propose a group key management scheme based on the secret sharing technology to require each member by itself to generate the group key when receiving a rekeying message multicast by the group key distributor. The proposed scheme enforces mutual authentication between a member and the group key distributor while executing the rekeying process, and provides forward secrecy and backward secrecy properties, and resists replay attack, impersonating attack, group key disclosing attack and malicious insider attack.

• 인터넷정보학회논문지
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• 제3권5호
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• pp.87-94
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• 2002

본 논문에서는 PIM-SM 멀티캐스트 그룹 통신에서 사용자의 정보 보호를 위한 그룹 키 관리 프로토콜을 제안한다. 이는 PR에 멀티캐스트 그룹 키를 관리하는 키 관리자를 두어 송신사 고유의 그룹 키를 부여하고 데이터를 수신자에게 전송하기 이전에 RP는 인증된 수신자에게 송신자의 그룹 키를 전달한다. 송신자가 그룹 키로 암호화한 후 RP에게 전송을 하면 RP는 각 수신자에게 전송하고, 수신자는 미리 받은 송신자의 그룹 키로 데이터를 복호화 할 수 있다. 따라서 그룹 키에 의한 데이터 변환 작업이 불필요하여 데이터 전송 시간이 단축되며, 최소거리경로로의 변화에도 새로운 키 분배 없이 데이터 전송이 가능하다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권11호
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• pp.2874-2892
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• 2013

Since security plays an important role in several ZigBee applications, such as Smart Energy and medical sensor applications, ZigBee Specification includes various security mechanisms to protect ZigBee frames and infrastructure. Among them, the Join and Leave operations of ZigBee are investigated in this paper. The current Join-Leave operation is protected by the network key (a kind of group key). We claim it is not adequate to employ the network key for such purpose, and propose a new Join-Leave operation protected by the application link key (a kind of pairwise key), which is based on a more efficient key management scheme than that of ZigBee. Hence, the original Join operation consists of a total of 12 command frames, while the new Join operation consists of only 6 command frames. In particular, the security of the proposed Join-Leave operation is equivalent to or better than that of the original Join-Leave operation. The new Join-Leave operation is extensively analyzed in terms of security and efficiency, and compared with the original Join-Leave operation of ZigBee.

• 정보보호학회논문지
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• 제25권4호
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• pp.759-766
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• 2015

본 논문에서는 WSN을 위한 위치 기반의 키 관리 기법에 대해서 제고한다. 기존의 위치 기반의 키 관리 기법들에 대해 알아보고 그 중 LDK (Location Dependent Key management) 기법을 집중적으로 파악하였다. 이를 통해 LDK 기법에서 고려하지 못한 통신 간섭 문제를 개선하기 위하여 그리드 정보를 활용한 키 생성 기법과 키 보정과정을 활용하는 기법을 제안하였다. 시뮬레이션을 통하여 보안성이 높은 환경에서 제안 기법이 기존의 LDK보다 접속율은 향상하였고 절충율은 감소하였음을 확인하였다. 또한, 육면체 형태의 AN 배치를 통해 네트워크 비용을 줄일 수 있음을 시뮬레이션을 통해 확인하였다.

• 융합보안논문지
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• 제2권2호
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• pp.19-27
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• 2002

본 논문에서는 멀티캐스트 그룹 통신에서 사용자의 정보 보호를 위한 동적 그룹 키 관리 프로토콜을 제안한다. 이는 서브그룹의 단위인 RP에 멀티캐스트 그룹 키를 관리하는 키 관리자를 두어 송신자 고유의 그룹 키를 부여하고 데이터를 수신자에게 전송하기 이전에 RP는 인증된 수신자에게 송신자의 그룹 키를 전달한다. 송신자가 그룹 키로 암호화한 후 RP에게 전송을 하면 RP는 각 수신자에게 전송하고, 수신자는 미리 받은 송신자의 그룹 키로 데이터를 복호화 할 수 있다. 따라서 그룹 키에 의한 데이터 변환 작업이 불필요하여 데이터 전송 시간이 단축되며, 최소거리 경로로의 변경에도 새로운 키 분배 없이 데이터 전송이 가능하다.

• The Journal of Asian Finance, Economics and Business
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• 제5권4호
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• pp.57-65
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• 2018

With the paramount importance of key account management in business-to-business relationship, today companies are using this approach as a strategic weapon in their selling efforts targeted at the most important customers to solve their complex requirements with special treatment that eventually ensures both parties' financial and nonfinancial objectives. The aim of this paper is to investigate the level of key account management performance among the export-oriented readymade garments companies in Bangladesh with regards to company's experience in business, size of the company and key account serving capacity of the company. Using a questionnaire, data from 112 readymade garments companies in Bangladesh were collected and analyzed using descriptive analysis and ANOVA to test the level of key account management performance. Results show that the level of key account management performance by the garments companies did not vary by the company's experience in business and size of the company respectively. In contrast, the level of key account management performance was found to be different concerning high, medium, and low customer service capacity. Apparently, companies with big number of customers show better performance than companies with small number of customer. Implications for this study are discussed along with suggestions for future research avenues.