• Journal of Korea Multimedia Society
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• v.8 no.4
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• pp.502-508
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• 2005

This paper proposes a dynamic hybrid patching technique that can improve the performance of VOD systems by adopting the advantages of both greedy patching and grace patching to use a VOD server's limited network-I/O bandwidth. The proposed technique uses grace patching to the requests for the videos, arrival intervals of which are smaller than the size of patching window, and uses greedy patching to the rest requests. In addition, proposed patching technique expands the latest particular patching multicast into a regular multicast for a new request. In result, the patching multicast data for the new request can be the data from the beginning to the skew point of the video and the holding time of a dispatched channel can exceedingly decrease. Simulation results confirm that the proposed technique is better than grace patching in terms of defection rate and average service latency.

• Journal of Korea Multimedia Society
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• v.2 no.4
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• pp.459-467
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• 1999

With fully harnessing the functions provided by Windows NT, we suggest the generating method of RPL profile and the RPL protocol for remote booting on DL-NCS(Network Computing System for Diskless client PCs). This system can offer clients, without having hard disk, boot remotely Window 9x stored in server's hard disk and can share peripheral devices and application programs in the server side. For booting Window 9x from DL-NCS, twenty-five clients' PCs were set for simultaneous on and finally the PCs were booted in similar time interval compared to that from a desktop PC having local disk. This system was also experimented to the application programs. And this system can yield excellent networking environments. In sum, with using this DL-NCS, we can reduce the installing costs of peripheral device, recycle the lower grade PCs such as 486SX/DX, and save the budgets for software purchase.

• Journal of KIISE:Databases
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• v.27 no.2
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• pp.227-237
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• 2000

A Web database System is a large-scaled multimedia application system that has multimedia processing facilities and cooperates with relational/Object-Oriented DBMS. Conventional hypertext modeling methods and DB gateway have limitations for Web database because of their restricted versatile presentation abilities and inefficient concurrency control caused by bottleneck in cooperation processing. Thus, we suggest a Dynamic Navigation Model & Virtual Graph Structure. The Dynamic Navigation Model supports implicit query processing and dynamic creation of navigation spaces, and introduce node-link creation rule considering navigation styles. We propose a mapping methodology between the suggested hypertext model and the relational data model, and suggest a dynamic allocation scheduling technique for query processing server based on weighted value. We show that the proposed technique enhances the retrieval performance of Web database systems in processing complex queries concurrently.

• Journal of Korea Multimedia Society
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• v.4 no.5
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• pp.430-438
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• 2001

In this paper, we present the design and implementation of a web-based distance learning system supporting the collaborative browsing. Our system consists of an education affair management system, a video conferencing server/client, a white-board server/client, a session manager and a web browser sharing system. Among other things, our collaborative web browser is unique and not found in any other system. The web browser shows synchronously the same web pages as the lecturer moves through them. Therefore, it allows the student to feel real-time surfing gust as the lecturer would. The session manager supports multi-user and multi-group, and integrates various synchronous collaborative component into one distance learning system by providing the same session data and information of users in a session group. Our collaborative browsing system can increase the efficiency of distance learning and provides the effect of learning in the same classroom by supporting various synchronous functionalities, such as collaborative browsing.

• Journal of Korea Multimedia Society
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• v.4 no.5
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• pp.377-389
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• 2001

It has a tendency to build Workflow Systems based on the web with the spread of web environment. The important function in Workflow Systems are to automatize job flow according to the predefined regulations, procedures or conditions. Hence, there needs to consider excluding passive jobs, supporting GUI and a migratory information processing for information flow. Distributed Workflow System for workflow of a distributed service system should perform transfer control and Fault-Tolerance between tasks based on process logic, and real time processing. However, the existing mail systems being used are just for transmission and it doesn't fit to automatize job flow. To solve the matter, there needs a Distributed Workflow Engine to design workflow and automatize its control. In this paper, we design a web browser with graphic interface using web mail, a browser creating a script code for a procedural performance. Also, we design a Process-engine has a Preprocessor which tolerates process scheduler for task transaction or server node's faults on distributed environment. The proposed system enhances the reliability and usability of a system reduces the cost rather than a workflow system based on database, for they execute as proxy for a server's fault or suers' absence.

• Journal of Korea Multimedia Society
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• v.14 no.3
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• pp.392-402
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• 2011

Snow fall and icing on traffic roads in the winter season cause not only inconvenience but unexpected traffic accidents, so the proper measures are needed. The existing road information system is being installed for steep slope roads in mountain areas, however, it is not widely adopted because it is too expensive. In this paper, a novel and cost-effective road weather information system especially for snow fall and icing on roads is proposed. The system consists of digital temperature and relative humidity sensor, infrared temperature sensor, ultrasonic sensor, CMOS camera, and two types of control/communication board for ubiquitous sensor network to send the data to server. The server program including the decision making method with received data is also described. Experimental results are provided to prove the feasibility of the proposed system.

• Journal of Korea Multimedia Society
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• v.11 no.10
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• pp.1338-1346
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• 2008

In this paper, we propose a new P2P-based music recommendation system. In comparison with previous system in client-server environment, the proposed system shows higher quality of music recommendation through real-time sharing of music preference information between peers. A collaborative filtering is implemented as a recommendation algorithm. As a user preference profile, we use the inherit KID music genre index contained in all legitimate music file instead of music feature vectors as in previous research so that the proposed system can mitigate the performance degradation and high computational load caused by feature inaccuracy and feature extraction. The performance of the proposed system is evaluated in various ways with real 16-weeks transaction data provided by Korean music portal, 5 company and it shows comparative quality of recommendation with only small amount of computational load.

• Journal of the Korea Convergence Society
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• v.8 no.11
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• pp.7-13
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• 2017

In recent years, cloud computing technology has been socially emerged that provides services remotely as various devices are used. However, there are increasing attempts by some users to provide cloud computing services with malicious intent. In this paper, we propose a property - based multi - level hierarchical approach to facilitate authentication access for users accessing servers in cloud environment. The proposed method improves the security efficiency as well as the server efficiency by hierarchically distributing a set of attribute values by replacing the order of the user 's attribute values in the form of bits according to a certain rule. In the performance evaluation, the proposed method shows that the accuracy of authentication according to the number of attributes is higher than that of the existing method by an average of 15.8% or more, and the authentication delay time of the server is decreased by 10.7% on average. As the number of attributes increases, the average overhead change is 8.5% lower than that of the conventional method.

• The Journal of Korean Association of Computer Education
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• v.7 no.2
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• pp.25-34
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• 2004

Sixteen provincial Research Institute of Education and Science(RISE) in the country have provided good qualified multimedia educational materials that was produced by some special skilled teachers to elementary, middle and high school teachers using web services. And moreover KERIS and KICE have also produced educational materials and have a plan to integrate distributed multimedia educational materials that RISE produced. The development of KERIS's KEM metadata in 2001 and the making of educational material metadata of RISE is the first step of integration plan. These metadata can be used to make integration plan possible. But before taking integration plan, the study of how to integrate and manage it should be performed. Therefore, this paper introduces the technique of XML web service and JDBC with 3-tier system as the method of integrate distributed educational material metadata. The evaluation shows these two methods have similar response time with MS SQL Server 2000 and Oracle 9i. Thus, we conclude that JDBC and XML web service can be the proper solution to search XML-formatted metadata.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.81-88
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• 2012

As the performance of the next-generation broadband wireless networks is dramatically enhanced, various services (i.e., education, Live video streaming, Live video conferencing, online games, etc.) have been provided to users through a smart mobile platform. Those services are usually provided by using the centralized communication server. However, since all multimedia traffic is exchanged through a communication server, it often has the scalability problem with regard to traffic management. Our main purpose is for group smart users to provide scalable live multimedia streaming service based on P2P network. To do this, we have designed an architecture of P2P-based service management for mobile group communication management and service management protocol. In order to verify the performance of the proposed scheme, we have mathematically analyzed the performance in terms of the average transmission delay and bandwid th utilization.