• Journal of KIISE:Databases
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• v.36 no.5
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• pp.352-365
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• 2009

Recently, data access control policies have not been applied for authorized or unauthorized persons properly and information leakage incidents have occurred due to database security vulnerabilities. In the traditional database access control methods, administrators grant permissions for accessing database objects to users. However, these methods couldn't be applied for diverse access control policies to the database. In addition, another database security method which uses data encryption is difficult to utilize data indexing. Thus, this paper proposes an enhanced database access control system via a packet analysis method between client and database server in network to apply diverse security policies. The proposed security system can be applied the applications with access control policies related to specific factors such as date, time, SQL string, the number of result data and etc. And it also assures integrity via a public key certificate and MAC (Message Authentication Code) to prevent modification of user information and query sentences.

• Journal of Internet Computing and Services
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• v.11 no.4
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• pp.119-128
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• 2010

Computing environment in these days aim for user-oriented development called RIA (Rich Internet Application). As a representative development method of RIA, Flex Framework overcomes the weaknesses of the Mainframe and C/S (Client/Server). However, the issues, such as, difficulties in memory management, complexity of the binding structure and large capacities of the compile outputs are left to be solved. The purpose of this paper is to implement the framework which enables the fast and accurate development of user-oriented web application on the Flex platform. DDX (Dynamic Data eXchange) framework proposes standardized and efficient development environment in a Flex platform. And by using scalability-prepared library that is applicable for various job areas, the framework enhances the performance, increase development productivity and help construct stable system.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.259-261
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• 2003

This paper suggests wireless diagnosis and monitoring system using SMS mode of mobile communication network for distribution transformer which could prevent electrical accident in the near future. Data are acquired by measuring the temperature of insulator oil in the distribution transformer and load current. Data acquisition of sensor using mobile communication network carried out filtering of sensor's output to optimize the size of send data Merit of this inspection method is that management, control and monitoring some transformers can be carried out using only one server. This inspection method will be the way of inspection to be worth spotlight in the near future because it is able to solve easily with the minimum facility inspection about state of transformer which is operating, to wide coverage about machine's wrong operation in other field.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1998.06b
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• pp.105-110
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• 1998

This paper proposes a method to manage individual information on large scale distributed geographic information systems. On such system, ordinary users usually cannot alter the contents of the server. The method proposed in this paper makes possible to alter the contents or add individual data onto such kinds of non-write-permitted data onto set. We call the method as GDSF, ‘geographic differential script file’. In this method, a client user makes a GDSF which contains the private information to be added onto the served data. Then, the client keeps the file on a local disk. After this, when the user uses the data, he applies the differential data sequence onto the down loaded data to restore the information. The GDSF is a collection of picture commands which tell pictures insertions, deletions, and modification operations. The GDSF also can contain the modification. The GDSF also can contain the modification of the attribute information of geographic entities. The method also applicable to modify data on a ROM device, for example CD-ROM or DVD-ROM. This paper describes the method and experimental results.

• Journal of KIISE:Computer Systems and Theory
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• v.37 no.3
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• pp.147-160
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• 2010

The system virtualization shows interest in the consolidation of servers for the efficient utilization of system resources. There are many various researches to utilize a server machine more efficiently through the system virtualization technique, and improve performance of the virtualization software. These researches have studied with the activity to control the resource allocation of virtual machines dynamically focused on CPU, or to manage resources in the cross-machine using the migration. However, the researches of the memory management have been wholly lacking. In this respect, the use of memory is limited to allocate the memory statically to virtual machine in server consolidation. Unfortunately, the static allocation of the memory causes a great quantity of the idle memory and decreases the memory utilization. The underutilization of the memory makes other side effects such as the load of other system resources or the performance degradation of services in virtual machines. In this paper, we suggest the dynamic allocation of the memory in Xen to control the memory allocation of virtual machines for the utilization without the performance degradation. Using AR model for the prediction of the memory usage and ACO (Ant Colony Optimization) algorithm for optimizing the memory utilization, the system operates more virtual machines without the performance degradation of servers. Accordingly, we have obtained 1.4 times better utilization than the static allocation.

• Journal of Intelligence and Information Systems
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• v.11 no.1
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• pp.53-63
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• 2005

Adaptive services need to become as mobile as their users and be extended to take advantage of the constantly changing context in which they are accessed. Context-awareness is a technology to facilitate information acquisition and execution by supporting interoperability between users and devices based on users' context. The objective of this study is to develop a middleware fer dealing with context-awareness in ubiquitous computing. To achieve it, our middleware plays an important role in recognizing a moving node with mobility by using a bluetooth wireless communication technology as well as in executing an appropriate execution module according to the context acquired from a context server. In addition, for verifying the usefulness of the Proposed middleware, we develop an application system which Provides a music playing service based on context information by using our context middleware.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.2
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• pp.354-359
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• 2016

Power plants maintenance data is to be sent to management server system via a communication network. In this case, reliable communication network is required. Transmission of the power plants maintenance data is used in the wired communication network or wireless communication network. PLC communication network is a kind of wired communication network. However PLC communication network is easily affected by noise. On the vulnerable areas in power line system, such as a mountain or rural areas, it is difficult to form a power line communication network. For a wireless communication, environment are also influenced factors in wireless communication. Harsh environmental factors are bring the communication characteristic degradation. In such areas it can be used a combination of two networks and in this way the complementary function can be achieved. Power plants are distributed in various regions across the country. The appropriate communication network is needed to maintain the power plant.This study investigated the effect of environment on the wired communication and wireless communication. It would examine a variable factor which is affect to the communication characteristic. We used PLC communication for wired communication network and ZigBee communication for wireless communication network. We investigated the characteristics of a single communication network and it raised the need for a complex communication technology to complement a single communication network.

• Journal of Korea Multimedia Society
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• v.13 no.8
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• pp.1212-1220
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• 2010

The technologies of domestic user programs are not enough to convert address convert information, which was collected via port redirection server, to user traffic. Generally traffic redirection technology is a special purpose technology for I/O traffic via network device. L4 switch needs various additional costs and devices to achieve this special purpose. To solve this problem, there appears need for a central management of control and monitoring by centralizing traffic at one position regardless of network structure and it is necessary to realize redirection function of switch at network layer. Therefore this study offer development of traffic central control system through protocol redirection of client-side.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.6
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• pp.1075-1081
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• 2008

The growth of digital content market inducted to develope consuming device of various content. And through this, digital content consuming is more Promoted. But digital content cryption tool need to handle to protect and consume digital content safely. Also, interoperability of cryption tool management is impossible, because of not standardized transfer protocol between device. In this paper, we defined transfer protocol of cryption tool for protecting and consuming digital content. And in this base, we designed and implemented transfer server/client system.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.1
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• pp.14-26
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• 2022

Recently, according to the severity of air pollution, interest in air pollution is increasing. The IoT based fine dust monitoring system proposed in this paper allows the measurement and monitoring of fine dust, volatile organic compounds, carbon dioxide, etc., which are the biggest causes affecting the human body among air environmental pollution. The proposed system consisted of a device that measures atmospheric environment information, a server system for storing and analyzing measured information, an integrated monitoring management system for administrators and smart phone applications for users to enable visualization analysis of atmospheric environment information in real time. In addition, the effectiveness of the proposed fine dust monitoring system based on the Internet of Things was verified by using the response speed of the system, the transmission speed of the sensor data, and the measurement error of the sensor. The fine dust monitoring system based on the Internet of Things proposed in this paper is expected to increase user convenience and efficiency of the system by visualizing the air pollution condition after measuring the air environment information with portable fine dust measuring device.