• Journal of the Korea Society of Computer and Information
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• v.13 no.4
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• pp.115-126
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• 2008

VNC(Virtual Network Computing) is a desktop sharing system based on the RFB(Remote Framebuffer) protocol which allows you to control a remote computer running a VNC server through a VNC client(or viewer) on a local computer. To exchange information between the two computers, VNC provides the functionality of sharing the clipboard contents. Unfortunately, the current VNC softwares support only the clipboard text contents, not providing methods for sharing the clipboard multimedia contents such as images. In this paper, we extend the RFB protocol to share the clipboard contents composed of text and images. Also, to support the developed protocol. we extend both the UltraVNC server and the JavaViewer VNC client which are free open-source softwares. Through the developed VNC softwares, users can exchange the clipboard contents including texts and images between the remote computer and the local computer.

• Journal of the Korea Society of Computer and Information
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• v.11 no.2 s.40
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• pp.145-151
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• 2006

In conjunction with the rapid progress of IT(information technology) an increasing amount of data are being generated. The amount of new data is so big and the type of new data generated from clients or sensor devices needed to be in ubiquitous environment is so various that it is hard to manage and control them. Especially data to be occurred in ubiquitous environment are generated through PDA(personal digital assistant) smart phone, mobile device or sensor units etc. Therefore, to manage and control them generated from ubiquitous devices for decision making, we can use data warehouse as an integrated storage. A data warehouse integrates and aggregates data of several different DBMS into one DBMS. Also the updated data from source data have to be effectively propagated to the data warehouse. Therefore, in this paper, we proposed a mode) for an exact and efficient data management methodology in new IT paradigm environment, ubiquitous computing environment, to apply updated data on the warehouse to make decision. We also show brief result compared to conventional methodology.

• Journal of KIISE:Computing Practices and Letters
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• v.10 no.6
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• pp.435-447
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• 2004

For VOD systems, it is important to provide QoS to more users under the limited resources. To analyze QoS issues in real environment, we implement clustered VOD server and embedded client system based on the Linux open source platform. The parallel processing of MPEG data, load balancing for nodes and VCR like functions are implemented in the server side. To provide more user friendly interface, the general TV is used for a VOD client's terminal and the embedded board is used supporting for VCR functions. In this paper, we measure the performance of the implemented VOD system under the various user requirement features and evaluate the sources of performance limitations. From these analyses, we propose the dynamic admission control method based on the availability memory and network bandwidth. The proposed method enhances the utilization of the system resource for the more QoS media streams.

• Journal of Platform Technology
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• v.9 no.4
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• pp.42-50
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• 2021

Recently, the need to introduce smart farms is increasing in order to solve the problems of intensifying competition such as a decrease in rural population due to aging, a decrease in production, and the inflow of foreign agricultural products, and accordingly, the need for education is increasing. This paper is a study on the implementation of an Android-based IoT smart farm for education so that it can be used in a real environment by reducing the farm's smart farm system. To confirm that Android-based education can be applied in a real environment using the IoT smart farm for education, experiments were performed in automatic mode and manual mode using Bluetooth, Wi-Fi, and server/client communication methods. In the automatic mode, the current status can be checked in real time by receiving all data, and in the manual mode, commands are transmitted in real time using the received sensor data and remote control is performed. As a result of the experiment, it was possible to understand the characteristics of each communication method, and it was confirmed that remote monitoring and remote control of the smart farm using the Android App was possible.

• Journal of the Korea Society of Computer and Information
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• v.14 no.2
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• pp.79-89
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• 2009

As an IETF standard protocol, WebDAV provides infrastructure for managing and authoring resources and supports asynchronous collaborative authoring on the Web. The CoSlide server is an extension of the Jakarta Slide WebDAV server, providing various workspaces and collaborative services through the WebDAV protocol. The CoSlide server supports workspaces for storing and sharing information of various users, and provides environment for effective collaborative authoring. Actual collaboration activities are performed through a collaboration client software which provides collaboration services along with the CoSlide server. In this paper, we describe the development of the CoSpace client which operates in association with the CoSlide server, presenting effective collaborative environment. The CoSpace client provides user interfaces for accessing and controlling the resources of each workspace on the CoSlide server. In particular, CoSpace provides the facility to launch an authoring application from its workspace view, automatic locking, and downloading the content to be edited, and resource movement using mouse drag & drop.

• The KIPS Transactions:PartB
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• v.15B no.6
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• pp.575-584
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• 2008

According to the network condition, the communication network overload could be occurred when media transmitting. Many researches are being carried out to lessen the network overload, such as the filtering, load distributing, frame dropping and many other methods. Among these methods, one of effective method is frame dropping that reduces specified video frames for bandwidth diminution. B frames are dropped and then I, P frames are dropped according to dependency among the frames in frame dropping. This paper proposes a scheme for protecting copyrights by encryption, when we apply frame dropping to reduce bandwidth of media following MPEG-4 file format. We designed two kinds of frame dropping: first one stores and then sends the dropped files and the other drops frames in real-time when transmitting. We designed three kinds of encryption methods in which DES algorithm is used to encrypt MPEG-4 data: macro block encryption in I-VOP, macro block and motion vector encryption in P-VOP, and macro block and motion vector encryption in I, P-VOP. Based on these three methods, we implemented a digital right management solution for MPEG-4 data streaming. We compared the results of dropping, encryption, decryption and quality of video sequences to select an optimal method, and there is no noticeable difference between the video sequences recovered after frame dropping and the ones recovered without frame dropping. The best performance in encryption and decryption of frames was obtained when we apply the macro block and motion vector encryption in I, P-VOP.

• The Journal of the Korea Contents Association
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• v.5 no.5
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• pp.159-171
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• 2005

It has been increased to use the SAN with increasing the size of storage device. In this paper, we design and implement a backup system to support the tape and disk based backup with devices and media in SAN cluster. Our backup system provides device and media management for efficiently managing a number of devices and media in SAN cluster. It also supports script management to process an additional tasks requested by clients and monitoring to control and manage tasks in execution. In addition, it supports reporting to offer backup and restore information to clients.

• Journal of the Korea Society of Computer and Information
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• v.13 no.1
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• pp.153-160
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• 2008

This paper shows the maximum data flow utilizing the Weight Bipartite Graph Matching system. The Weight Bipartite Graph Matching system sets the data transmission as edges and guides the maximum data flow on the set server and the client. The proposed Weight Bipartite Graph Matching system implements the multi-user interface video conference system. By sending max data to the server and having the client receive the max data, the non-continuance of the motion image frame, the bottleneck phenomenon, and the broken images are prevented due to the excellent capacity. The experiment shows a two-times better excellency than that of the previous flow control.

• Journal of KIISE:Databases
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• v.31 no.2
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• pp.140-149
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• 2004

Data broadcast has received much attention as a very efficient method for disseminating data items in mobile environment with large number of mobile clients. In this approach, a database server periodically and continuously broadcasts data items through wireless channels and clients perform read-only transactions by accessing necessary data items from the air. While broadcasting, the server must also process update transactions on the database, which raises an obstacle for client's accessing consistent data. In this research, we propose a new algorithm SCDSC(Serialization Checking with DirtySet on Commit) which is an alternative for solving the concurrency control problem efficiently. The SCDSC is a kind of optimistic concurrency control in that a client checks the consistency of data using a DirtySet as a part of data broadcast when it commits its transaction. In each broadcast cycle, the server updates and disseminates the DirtySet with newly changed data items for last few cycles in the sliding window approach. We perform an analysis and a simulation study to evaluate the performance of our SCDSC algorithm in terms of data consistency and data currency.

• Journal of Korea Multimedia Society
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• v.12 no.8
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• pp.1142-1154
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• 2009

The brand new type of mobile terminal services are kept being introduced in accordance with the development of mobile communication technology. Among many kinds of mobile application services, the PoC application standard which is using instant messaging service and group calls method with the existing walkie-talkie technology has been finished as the version 1.0 after tremendously active discussion and is being continued to be confirmed as 2.0 and 2.1. The PoC Box, which is discussed for replacing the PoC client and intermediate object as a voice messaging box, is currently being introduced and the biggest issues for PoC Box technology topics include the part of saved informations' processing and effective multimedia contents' transmission in the PoC Box system. In this research, we propose that the PaC client could effectively transmit the media to the end-user by specifying the playback location or range, focusing on the contents and the methods of dynamic controlling for saved media in PoC Box. This paper deals with the way of dynamic controlling method using the RTSP which is appropriate for PoC Box and the effective method for generation, expression, processing of various multimedia contents including audio and video objects.