• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.233-234
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• 2009

증착된 silicon nitride (Sin) 박막의 수명 시간을 예측하는 신경망 모델을 개발하였다. SiN 박막은 플라즈마 화학기상 증착방식을 이용하여 증착되었다. 증착 공정은 통계적인 실험계획표를 이용하여 수행되었고, 신경망 모델의 예측 성능은 유전자 알고리즘을 이용하여 최적화하였다. 수명시간은 다른 박막특성 (굴절률, 증착률, 전하밀도)의 영향을 상당히 받았으며, 특히 굴절률과 전하밀도는 높은 증착률에서 증가시킬 때 수명시간을 최대화할 수 있었다.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.5
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• pp.380-384
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• 2009

The log data collected on a mobile device contain diverse and continuous information about the user. From the log data, the location, pictures, running functions and services of the user can be obtained. It has interested in the research inferring the contexts and understanding the everyday-life of mobile users. In this paper, we have studied the methods for real-time collection of log data from mobile devices, analysis of the data, map based visualization and effective management of the personal everyday-life information. We have developed an application for sharing the contexts. The proposed application infers the personal contexts with Bayesian network probabilistic model. In the experiments, we confirm that the usability of visualization and information sharing functions based on the real world log data.

• Journal of Korea Multimedia Society
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• v.12 no.9
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• pp.1297-1308
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• 2009

The life time of a wireless sensor network composed of numerous sensor nodes depend on ones of its sensor nodes. The energy efficiency operation of nodes, therefore, is one of the crucial factors to design the network. Researches based on the hierarchical network topology have been proposed and evolved in terms of energy efficiency. However, in existing researches, application layer data obtained from sensor nodes are not considered properly to compose cluster, including issue that nodes communicate with their cluster heads in TDMA scheduling. In this paper, we suggest an energy-efficient topology control scheme based on application layer data in wireless sensor networks. By using application layer data, sensor nodes form a section which is defined as the area of adjacent nodes that retain similar characteristics of application environments. These sections are further organized into clusters. We suggest an algorithm for selecting a cluster head as well as a way of scheduling to reduce the number of unnecessary transmissions from each node to its cluster head, which based on the degree and the duration of similarity between the node's data and its head's data in each cluster without seriously damaging the integrity of application data. The results show that the suggested scheme can save the energy of nodes and increase the life time of the entire network.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5227-5237
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• 2011

Technology roadmap is a powerful tool that considers relationships of technology, product and market and referred as a supporting technology strategy and planning. There are numerous studies that have attempted to develop technology roadmap and case studies on specific technology areas. However, a number of studies have been dependant on brainstorming and discussion of expert group, delphi technique as qualitative analysis rather than systemic and quantitative analysis. To overcome the limitation, patent analysis considered as quite quantitative analysis is employed in this paper. Therefore, this paper proposes new technology roadmapping based on patent citation network considering technology life cycle and suggests planning for undeveloped technology but considered as promising. At first, patent data and citation information are collected and patent citation network is developed on the basis of collected patent information. Secondly, we investigate a stage of technology in the life cycle by considering patent application year and the technology life cycle, and duration of technology development is estimated. In addition, subsequent technologies are grouped as nodes of a super-level technology to show the evolution of the technology for the period. Finally, a technology roadmap is drawn by linking these technology nodes in a technology layer and estimating the duration of development time. Based on technology roadmap, technology planning is conducted to identify undeveloped technology through text mining and this paper suggests characteristics of technology that needs to be developed in the future. In order to illustrate the process of the proposed approach, technology for hydrogen storage is selected in this paper.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.27-30
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• 2005

Because of unreplenishable power resources, reducing node energy consumption to extend network lifetime is an important requirement in wireless sensor networks. In addition both path length and path cost are important metrics affecting sensor lifetime. We propose a dynamic clustering scheme based on location in wireless sensor networks. Our scheme can localize the effects of route failures, reduce control traffic overhead, and thus enhance the reachability to the destination. We have evaluated the performance of our clustering scheme through a simulation and analysis. We provide simulation results showing a good performance in terms of approximation ratios.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.325-327
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• 2012

배터리를 기반으로 동작하는 무선센서네트워크 환경에서는 전력이 가장 중요한 자원이다. 본고는 무선센서네트워크 환경에서 무선전력전송을 이용하여 센서 네트워크의 생명(Network Life Time)을 최대화하는 네트워크 환경을 제안하였다. 또한 전력을 전송하는 각 소스가 네트워크 생명을 최대화하기 위해 스케줄링을 결정짓는 메트릭을 제시하였다. 제안 모델은 지향성 안테나가 가지는 전송 범위의 구역을 나누고 각 영역에 대해서 그 영역의 전력 수급, 배터리 소모량, 구역의 면적당 센서 수를 이용하여 효과적으로 전력을 전달할 수 있는 메트릭을 도출하였다.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.8
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• pp.416-426
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• 2001

This paper deals with the impact of an inverter station on the torsional dynamics of turbine-generator which is located at the inverter side of a HVDC-AC network power system. The studies show that the torsional stress of turbine-generator depends on the AC network fault locations because of the commutation failures of inverter station. And the torsional stress induce fatigue in the shaft material and reduce the shaft life-time. So, the purpose of this paper is to analysis the torsional stress of turbine-generator shaft at inverter side, to find the checked points of turbine-generator. The EMTDC program is used for the simulation studies.

• Journal of Computing Science and Engineering
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• v.5 no.4
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• pp.346-353
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• 2011

With the advent of ubiquitous computing, a massive amount of trajectory data has been published and shared in many websites. This type of computing also provides motivation for online mining of trajectory data, to fit user-specific preferences or context (e.g., time of the day). While many trajectory clustering algorithms have been proposed, they have typically focused on offline mining and do not consider the restrictions of the underlying road network and selection conditions representing user contexts. In clear contrast, we study an efficient clustering algorithm for Boolean + Clustering queries using a pre-materialized and summarized data structure. Our experimental results demonstrate the efficiency and effectiveness of our proposed method using real-life trajectory data.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.3
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• pp.14-17
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• 2006

To diagnosis abnormal compressor conditions in an air-conditioner, the acoustic emission (AE) signal, which is derived from wear condition, compressed air, and assembly error, was analyzed experimentally. Burst and continuous type AE signals resulted from metal contact and compressed air, and the raw AE signal of compressors was acquired in the production line. After extracting samples using waveforms, the Early Life Test (ELT) was conducted and the waveform was classified as normal or abnormal. Efficient parameters in the waveform pattern were investigated in time and frequency domains and a diagnosis algorithm for air-conditioners using Neural Network estimation is suggested.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.10
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• pp.782-790
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• 1991

In this paper, we implement the function of the IEEE802.2LLC(logical link control) sublayer one of the 7layers in MAP(manufacturing automation protocol), a standard communication protocol for manufacturing automation. With the assembly language we designed the class 3 function based on the IEEE standards and verified on the network adaptor hardware. In this experiment, we tested the function using the simplified variables considering that the retransmission value was chosen to be 1 and the life-time of the transmission variable infinite. According to the result of the service procedures, we confirmed that user data were transmitted to the corresponding station without any error.