• The KIPS Transactions:PartA
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• v.17A no.5
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• pp.229-236
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• 2010

With an increasing number of documents in the Internet or enterprises, it becomes crucial to efficiently support users' queries on those documents. In that situation, the full-text search technique is accepted in general, because it can answer uncontrolled ad-hoc queries by automatically indexing all the keywords found in the documents. The size of index files made for full-text searches grows with the increasing number of indexed documents, and thus the disk cost may be too large to process multi-keyword queries against those enlarged index files. To solve the problem, we propose both of the index file structure and its management scheme suitable to the processing of multi-keyword queries against a large volume of index files. For this, we adopt the structure of inverted-files, which are widely used in the multi-keyword searches, as a basic index structure and modify it to a hierarchical structure for join operations and ranking operations performed during the query processing. In order to save disk costs based on that index structure, we dynamically store in the main memory the results of join operations between two keywords, if they are highly expected to be entered in users' queries. We also do performance comparisons using a cost model of the disk to show the performance advantage of the proposed scheme.

• 한국벤처창업학회:학술대회논문집
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• 2010.08a
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• pp.71-89
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• 2010

It is strongly believed that multicast will become one of the most promising services on internet for the next generation. Multicast service can be deployed either on network-layer or application-layer. IP multicast (network-layer multicast) is implemented by network nodes (i.e., routers) and avoids multiple copies of the same datagram on the same link. Despite the conceptual simplicity of IP multicast and its obvious benefits, it has not been widely deployed since there remain many unresolved issues. As an alternative to IP multicast, overlay multicast (application-layer multicast) implements the multicast functionality at end hosts rather than routers. This may require more overall bandwidth than IP multicast because duplicate packets travel the same physical links multiple times, but it provides an inexpensive, deployable method of providing point-to-multipoint group communication. In this paper we develop an efficient method applied greedy algorithm for solving two models of overlay multicast tree building problem that is aimed to construct MDST (Minimum Diameter Spanning Tree : minimum cost path from a source node to all its receivers) and MST (Minimum Spanning Tree : minimum total cost spanning all the members). We also simulate and analyze MDST and MST.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.483-488
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• 2015

This paper implements a long-term monitoring system (LMS) for ship's engine performance analysis (SEPA) based on the web, for the purpose of the communication speed and engine maintenance. This system is composed of a simulator, monitoring module with a multi channel A/D converter, monitoring computer, network attached storage (NAS), RS485 serial and wireless internet communication system. The existing products monitor the information transmitted from pressure sensors installed in the upper parts of each of engines in the local or web computer, but have a delay in the communication speed and errors in long-term monitoring due to the large volume of sampling pressure data. To improve these problems, the monitoring computer saves the sampling pressure data received from the pressure sensors in NAS, monitors the long-term sampling data generated by the sectional down sampling method on a local computer, and transmits them to the web for long-term monitoring. Because this method has one tenth of the original sampling data, it will use memory with small capacity, save communication cost, monitor the long-term sampling data for 30 days, and as a result, make a great contribution to engine maintenance.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.7 s.361
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• pp.71-80
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• 2007

This paper describes an efficient hardware design of WiBro security processor (WBSec) supporting for the security sub-layer of WiBro wireless internet system. The WBSec processor, which is based on AES (Advanced Encryption Standard) block cipher algorithm, performs data oncryption/decryption, authentication/integrity, and key encryption/decryption for packet data protection of wireless network. It carries out the modes of ECB, CTR, CBC, CCM and key wrap/unwrap with two AES cores working in parallel. In order to achieve an area-efficient implementation, two design techniques are considered; First, round transformation block within AES core is designed using a shared structure for encryption/decryption. Secondly, SubByte/InvSubByte blocks that require the largest hardware in AES core are implemented using field transformation technique. It results that the gate count of WBSec is reduced by about 25% compared with conventional LUT (Look-Up Table)-based design. The WBSec processor designed in Verilog-HDL has about 22,350 gates, and the estimated throughput is about 16-Mbps at key wrap mode and maximum 213-Mbps at CCM mode, thus it can be used for hardware design of WiBro security system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.9
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• pp.73-80
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• 2004

In this paper, we present the cell resequencing buffer to solve the cell sequence integrity problem of the Cyclic banyan network that is a high-performance fault-tolerant cell switch. By offering multiple paths between input ports and output ports, using the deflection self-routing, the Cyclic banyan switch offer high reliability, and it also solves congestion problem for the internal links of the switch. By the way, these multiple paths can be different lengths for each other. Therefore, the cells departing from an identical source port and arriving at an identical destination port can reach to the output port as the order that is different from the order arriving at input port. The proposed cell resequencing buffer is a hardware sliding window mechanism. to solve such cell sequence integrity problem. To calculate the size of sliding window that cause the prime cost of the presented device, we analyzed the distribution of the cell delay through the simulation analyses under traffic load that have a nonuniform address distribution that express tile Property of traffic of the Internet. Through these analyses, we found out that we can make a cell resequencing buffer by which the cell sequence integrity is to be secured, by using a, few of ordinary memory and control logic. The cell resequencing buffer presented in this paper can be used for other multiple paths switching networks.

• Child Health Nursing Research
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• v.20 no.1
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• pp.49-57
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• 2014

Purpose: The purpose of this qualitative study was to explore how adolescent survivors of childhood cancer grieve the death of cancer peers. Methods: Data were obtained from Korean adolescents with cancer between the ages of 13 and 18 (N=12) through semi-structured interviews (face-to-face, telephone, and Internet chatting), observations of the social dynamics of participants in self-help groups, and retrieval of personal Web journals. Based on the grounded theory methodology, data collection and analysis were conducted simultaneously, and constant comparative methods were used. Clarke's situational analysis was adopted, and this paper focused on presenting "how to" and "what we can learn" from this analytic strategy. Results: Mapping examples were visualized using of three modes of maps. Adolescent cancer survivors coped with reminders of the "darkness" that ultimately featured their overall grief. Additionally, adolescents' encounters and avoidance of grief were triggered by introspection and interactions with family and friends. Conclusion: Situational analysis provided an efficient way to analyze the experiences of adolescent survivors of childhood cancer by systematizing possible information within the relational social contexts of the research phenomenon.

• Informatization Policy
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• v.20 no.3
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• pp.3-17
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• 2013

As electronic marketplaces grow and a large number of consumers exchange their opinions on products and services on the Internet, many studies have been conducted in the area of online consumer reviews. This paper analyzes the research trend of the online consumer reviews by investigating those studies in an attempt to provide future research directions. Many researchers have focused on the effects of online reviews on consumer behaviors as well as the usefulness of the online reviews. In particular, review contents, characteristics of reviewers/consumers and features of products/services have been identified as influencing factors on the effects of the online consumer reviews. For the review contents, the number and the volume of the contents have increasing effects on the online reviews, while the direction (positive vs. negative) of the contents has resulted in conflicting effects of the review. The reputation and trustfulness of reviewers, consumers' prior knowledge on the products, consumers' product involvement, and types of the products were investigated as these factors influence the effectiveness of the online consumer reviews. Social media (such as Facebook and Twitter) nowadays play an important role to disseminate online reviews among consumers. Thus, it is necessary to study how social media influence the effects of online reviews on consumers. Since some firms abuse the online reviews for their own sakes, we recognize the necessity for empirical studies on the side effects of the online reviews.

• Communications of Mathematical Education
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• v.22 no.4
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• pp.533-543
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• 2008

Recently, many advanced countries have used original ICT tools in their educational courses. But Korea didn't have any effective origin ICT tools in our mathematical education, compared with other countries which have developed various tools, for examples, Web-Mathematica and HP Calculator. Although we have the advanced IT environment, the educational environments in mathematics using ICT seems to be not promising. In this paper, we suggest a new mathematics education tools in ICT and the internet environments in Korea, and a teaching and studyingmodel for the teachers, students and classrooms. It is based on the Sage-Math and RPG. Sage-Math which is the software based on the web and RPG(Random Problem Generator) will give a good answer for the future of Korean mathematics ICT education.

• Convergence Security Journal
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• v.14 no.1
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• pp.23-32
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• 2014

Quantitative rise and This study carried out qualitative research by utilizing NVivo 10 focusing on the contents of mass media such as newspaper or internet on the presidential security service up to the Park Geun-hye government from the 3rd Republic of Korea, which was established the presidential security service. The aim is to present opinion so that the presidential security organization can strengthen capability and function within the governmental organization down the road based on the contents of categories, which were elicited through this. First, there is a need of solidifying the internal stability with the expansion in the activity sphere of organization and of externally approaching the public with removing sense of difference caused by offering personal protection only to some of the privileged class in the meantime. Second, it is the foundation of a reason related to crime in a cause for Discharge by Authority pertinent to "law on security for president and others" in Article 10 in order to prevent a criminal act of having abused the task characteristic and the position superiority or an external pressure act related to intervention in rights. Third, there is a need of making it recognized as very important organization with putting differentiation from other organizations of the government by providing the disciplinary level more strictly than "disciplinary order on public officials" based on particularity and importance dubbed presidential security service along with correspondingly applying "disciplinary order on public officials" in Article 31 in accordance with "enforcement ordinance of law on security for president and others" in terms of service negligence and false-information report in relation to task performance.

• The KIPS Transactions:PartC
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• v.16C no.2
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• pp.165-182
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• 2009

Mobile IPv6 spends considerable bandwidth considering that its signal volume is proportional to the mobile and also it should be strengthened to support the binding signal volume, the traffic, and effective mobility. So, the study in NEMO(Network Mobility), an extended version of Mobile IPv6, has been conducted. NEMO provides its mobility by putting several mobiles and more than one portable router into one unit called as mobile network. Because nodes access Internet via the portable router at this time, it receives transparency without any additional work and that much reduces binding signal while solving binding storm. By supporting mobility, NEMO is able to have various mobile structures which realize several networks hierarchically and it is necessary to improve its safety and security by authenticating among the upper networks or the lower ones while moving. Also, it is extremely required to begin a study in the device to improve efficiency accompanied with mobility, which is executed by the fast hand-off as well as the safe authentication. For those reasons, this paper not only classifies various NEMO mobile scenarios into 7 ways, but also provides AAA authentication of each scenario, the authentication through the safety authentication and fast handoff authentication using F+HMIPv6 and the way to reduce both signaling volume and packet delays efficiently during the handoff.