• Journal of Advanced Marine Engineering and Technology
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• v.35 no.6
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• pp.765-772
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• 2011

In this research, the fuel cell system model capable of generating codes in real time was developed to construct of a HIL (Hardware-In-the-Loop) for a SOFC-powered ship. Moreover, the effects of the distribution of the exhaust gas flow rates in a stack, the flow rates of fuels and temperature of air supplied on the temperature characteristics of fuels supplied to the cathode and the anode, the output power of the stack and system efficiency are examined to minimize the temperature difference between fuels supplied to the stack used in a 500kW SOFC system using methane as a fuel. As a result, the temperatures of fuels supplied to the cathode and the anode maintain at 830K when the opening factor of three-way valve located at outlet of turbine is 0.839. Also the process for optimization of methane flow rate considering the fuel cell stack and system efficiency is required to increase the temperatures of fuels supplied to the stack.

• The KIPS Transactions:PartC
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• v.14C no.3 s.113
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• pp.239-254
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• 2007

Ubiquitous computing supports environment to freely connect to network without restrictions of place and time. This environment enables easy access and sharing of information, but because of easy unauthorized accesses, specified security policy is needed. Especially, ubiquitous sensor network devices use limited power and are small in size, so, many restrictions on policies are bound to happen. This paper proposes double-key based light weight security protocol, independent to specific sensor OS, platform and routing protocol in ubiquitous sensor network. The proposed protocol supports safe symmetric key distribution, and allows security manager to change and manage security levels and keys. This had a strong merit by which small process can make large security measures. In the performance evaluation, the proposed light weight security protocol using double-key in ubiquitous sensor network allows relatively efficient low power security policy. It will be efficient to ubiquitous sensor network, such as smart of ace and smart home.

• Journal of Korea Multimedia Society
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• v.12 no.9
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• pp.1242-1251
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• 2009

A DSMS(Data Stream Management System) in ubiquitous environment processes huge data that input from a number of sensor. The existed system is used with a load shedding method that is eliminated with a part of huge data stream when it doesn't process the huge data stream. The Load shedding method has to filter a part of input data. This is because, data completeness or reliability is decreased. In this paper, we proposed the overload prediction load balancing to maintain data completeness when the system has an overload. The proposed method predicts the overload time. and than it is decreased with data loss when achieves the prediction overload time. The performance evaluation shows that the proposed method performs better than the existed method.

• Journal of the Korean Society for information Management
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• v.23 no.2
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• pp.229-243
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• 2006

This study aims to suggest an effective way to enhance question-answer(QA) document retrieval performance by reconstructing queries based on the structural features in the QA documents. QA documents are a structured document which consists of three components : question from a questioner, short description on the question, answers chosen by the questioner. The study proposes the methods to reconstruct a new query using by two major structural parts, question and answer, and examines which component of a QA document could contribute to improve query performance. The major finding in this study is that to use answer document set is the most effective for reconstructing a new query. That is, queries reconstructed based on terms appeared on the answer document set provide the most relevant search results with reducing redundancy of retrieved documents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2702-2706
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• 2012

In plants, factory automation systems, although most of the growth of plants by the state workforce is the restaurant to check manually. In this paper, we use two cameras to measure the plant's developmental state has been studied. Plant measurement algorithm, the camera only affordable, reliable and simple system to get the data you can build a system. In this paper, the size of plants that plant growth in the plant to measure the efficient monitoring system has been developed. By utilizing this system, the size of the plant measured data required to maintain and manage accordingly, saving time and reducing costs and improving operational efficiency of plants, plant managers, the effect could be obtained by building the actual system the performance of the proposed system was confirmed.

• The Journal of the Korea Contents Association
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• v.15 no.4
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• pp.17-28
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• 2015

The applications program that running on Operating System has high dependence. Because environment of OS and standard libraries that supports are different. For those reason, Applications that perform the same function should be implemented in accordance with the new operating system. This results in a temporal and economic waste not only in subsequent maintenance of application but also in management. Even though, to solve this problem Cygwin or MinGW has been distributed, they do not support the portability of the application but provide a virtual environment and the tool. Therefore, in this paper, we design the wrapper format interface middleware using the POSIX and standard C library to support the application performing the same function on virtual environment and without code modification. The middleware can be selectively loading the API that is classified by basic and extend. This allows to managing the application size efficiently. Also, perform the comparative experiments and performance evaluation for application, on equipped with the Interface Middleware Linux, Unix, Windows and on Cygwin.

• The KIPS Transactions:PartC
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• v.16C no.5
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• pp.605-614
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• 2009

Despite its graceful bandwidth saving nature, IP multicast has not been successful in widely spreading and using. Challenging includes policy and technological issues such as inter-domain routing, multicast availability and reachability. Properly detecting and isolating the faults would be the first step to stabilize IP multicast. In this paper, we introduce a scalable multicast monitoring framework. To efficiently cope with multicast network and networking problems, it enlarges its monitoring scopes from collecting delivery statistics to verifying end-to-end multicast availability, reachability and interactivity. We carry out various networking experiments to verify the scalability and feasibility of the proposed framework.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.187-192
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• 2007

Conference focus maintains and manages SIP(Session Initiation Protocol) signal connections with total conference participants, and it plays core functions of conference server. When the number of conference participants increases, conference focus restricts scalability of conference as increasing quantify of messages for processing. In this paper, to solve this problem. we propose a user system(conference information agent), which receives conference information from the conference focus and transfers them to the participants it manages. And we design and implement the total system including conference focus. When the conference information agent subscribe to the conference focus, it shows its possession of agent capability and capacity by using SIP SUBSCRIBE message. The conference focus informs to the other party by SIP response message that it was chosen as a conference information agent, and after that the conference focus sends all conference notification messages to it. So load of the conference focus can be reduced by this method. Finally, we have analyzed the performance of our system by experiments.

• Journal of Korea Multimedia Society
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• v.9 no.11
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• pp.1395-1409
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• 2006

A spatial data warehouse has spatial data cube composed of multi-dimensional data for efficient OLAP(On-Line Analytical Processing) operations. A spatial data cube supporting concept hierarchies holds huge amount of data so that many researches have studied a incremental update method for minimum modification of a spatial data cube. The Cube, however, compressed by eliminating prefix and suffix redundancy has coalescing paths that cause update inconsistencies for some updates can affect the aggregate value of coalesced cell that has no relationship with the update. In this paper, we propose incremental batch update method of a spatial data cube. The proposed method uses duplicated nodes and extended node structure to avoid update inconsistencies. If any collision is detected during update procedure, the shared node is duplicated and the duplicate is updated. As a result, compressed spatial data cube that includes concept hierarchies can be updated incrementally with no inconsistency. In performance evaluation, we show the proposed method is more efficient than other naive update methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.6
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• pp.929-934
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• 2018

The Internet of Things (IoT) is the network of devices embedded with electronics, software, sensors, actuators, and connectivity which enables these objects to connect and exchange data without any human intervention. The importance of time information is increased in order to impose order on scattered sensor data streams, resolving conflicts through time stamp information and so on. Time information and time synchronization are critical building blocks in the IoT. They allow devices to share a consistent notion of time and it is easier to build efficient and robust collaborative services. This paper proposes a standard time management scheme in the Internet of Things. Many IoT applications involve collection and forwarding of event data. It is useful to know when an event occurs for the purposes of triggering an action. In order to verify the feasibility of the proposed scheme, it is implemented and evaluated in the Arduino development environment.