• The Journal of Information Systems
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• v.22 no.1
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• pp.225-248
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• 2013

Korean government has been implementing a smart grid testbed in Jeju Island for the low-carbon green growth. As smart grids are in the early stage of their diffusion, strategic guidelines and related measures are needed to spread them successfully. In general, the successful diffusion of new technologies or new products are mostly determined in its early stages. With the introduction of smart grids, the electricity market paradigm will be transformed into user-oriented from provider-oriented. Thus, a study on the diffusion of smart grids from the perspective of users is necessary. This paper examines factors affecting the adoption and diffusion of smart grids from users' perspectives and provide strategic guidelines for diffusing the smart grid. Researchers conducted in-depth interviews with 41 people who have been already using smart grids in the Jeju testbed. Semi-structured interviews were used to collect data. The interviews were recorded on a digital voice recorder memory and subsequently transcribed verbatim. A total of 133 pages of transcripts were obtained from about 10 hours interviews. 97 concepts, 47 sub-categories and 19 categories were identified through open coding of grounded theory. We suggested a paradigm model for diffusing smart grids and total of seven propositions as strategic guidelines.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.9
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• pp.747-756
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• 2002

The automatic steering system for unmanned vehicle was developed. The magnet and MR (Magnetoresistive) sensors are used for the tue detecting system. The lateral distance between sensor and the center line of the road is determined by the linearization of the distance according to the output. The PD control theory is used for the design of the controller to compare with $H_\infty$ control theory. The $H_\infty$ control theory is used for the design of the controller to reduce the disturbance. The performance of the PD controller and $H_\infty$ controller is compared in simulations and tests. The PD controller is easy to tune in the test site. The $H_\infty$ controller is robust far the disturbances in the test results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.6
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• pp.1379-1397
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• 2013

We consider a system where a licensed radio spectrum is shared by multiple primary users(PUs) and secondary users(SUs). As the spectrum of interest is licensed to primary network, power and channel allocation must be carried out within the cognitive radio network so that no excessive interference is caused to PUs. For this system, we study the joint beamforming and power allocation problem via game theory in this paper. The problem is formulated as a non-cooperative beamforming and power allocation game, subject to the interference constraints of PUs as well as the peak transmission power constraints of SUs. We design a joint beamforming and power allocation algorithm for maximizing the total throughput of SUs, which is implemented by alternating iteration of minimum mean square error based decision feedback beamforming and a best response based iterative power allocation algorithm. Simulation results show that the algorithm has better performance than an existing algorithm and can converge to a locally optimal sum utility.

• The Journal of Information Systems
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• v.16 no.1
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• pp.159-178
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• 2007

As generalization of using PC and the Internet information technology (IT) users in organizations are not passive clients but active producers of information services. One of the reasons for the change of users' role is social interactions with other users and IT department staffs. That is, users can find and develop new functions and usefulness of IT, especially, Web-based ones through communication with other users or IT department staffs. The objective of this study is to investigate the relationship between IT department service quality and social interactions with other users. For this purpose, we suggest a research model based on adaptive structuration theory (AST), which is to explain the changes in social structure (rules and resources) of IT by social interactions, as well as service quality theory. Our model's exogenous variable is service quality which is a second-order factor consisting of reliability, responsiveness, assurance, and empathy. As endogenous variables, we adopt two variables for appropriateness of using IT, faithfulness of appropriation and consensus on appropriation. Finally, dependent variables of ow model are usefulness and ease of use which can be considered as attitude on IT as well as other variables for appropriateness. For empirical test our model is applied to users of groupware and ERP in organizations and analyzed by partial least square. In result, all hypotheses suggested in our model are supported statistically.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2007.04a
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• pp.473-476
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• 2007

본 논문에서는 LBT(Listen Before Talk) 방식을 사용하는 ZigBee와 FH(Frequency Hopping) 방식을 사용하는 DCP, RFID, Bluetooth 등의 소출력 무선기기가 공유주파수대역에 공존할 경우 요구되는 적정 채널수를 산출하고 전체 공유주파수대역폭 산출법을 제시하였다. 한정된 주파수 대역에서 LBT 및 FH 방식을 사용하는 총 User 수가 포용되는 공유주파수대역폭 산출은 중요한 작업이다. 소출력 무선기기 시스템의 간섭 회피 기술로 사용되는 FH 방식과 LBT 방식에 대기행렬이론(Queueing Theory)을 적용하였으며, 주위의 전파환경을 감지하여 유휴 주파수대역을 찾아 데이터전송을 시도하는 LBT 방식은 random하게 주파수채널을 이동하며 통신을 시도하는 FH 방식과는 구별된다. 채널수 별 User의 통신시도 시간간격을 통계적으로 처리하여 Throughput을 분석한 결과, Throughput 70% 조건에서 FH 방식과 LBT 방식을 사용하는 250mW 소출력 무선기기들이 공존하는 공유주파수대역의 적정 채널수는 30개를 가지며, 전체 공유주파수대역폭은 채널수에 채널당 대역폭의 곱으로 산출이 가능하다.

• The Journal of Information Systems
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• v.21 no.3
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• pp.163-186
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• 2012

With the development of Internet and transition to information society, social capital is expanding to online from the traditional offline context. Especially with the widespread of social network service(SNS) the number of SNS users is increasing sharply and the importance of online social capital has been more and more significant. Most studies on social capital focused on organizational aspects but few studies have payed attention to personal aspect. Empirical studies on the relation between SNS and social capital were seldom conducted in previous studies. Based on the theory of social capital this study targets on the relationship formed through SNS and analyzes on how the relationship affects the perceived social capital. In this study 'self-presentation', 'playfulness' and 'critical mass' are posited as the antecedent factors of 'SNS usage'. This study proposes a research model to examine the effect of 'SNS usage' on 'relationship reinforcement', 'relationship building' and 'perceived social capital'. According to the results of empirical analysis, 'self-presentation', 'playfulness' and 'critical mass' can generate significant positive influence on 'SNS usage'. It also confirms not only the effect of 'relationship reinforcement' and 'relationship building' formed through SNS on 'perceived social capital' but also relationship between the social capital formation and SNS usage. The outcome obtained in this study can be applied in developing SNS services.

• Asia pacific journal of information systems
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• v.14 no.3
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• pp.93-120
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• 2004

The current study investigates major factors which influence the acceptance of mobile internet services based on the theoretical backgrounds of the technology acceptance model(TAM) and the flow theory. This research extended the Davis' TAM model(1989) by including the flow concept as another major factor towards the intention to use the mobile device in order to explain the acceptance of divers mobile services. According to the marketing studies(Ghani & Desphande, 1994; Novak, Hoffman & Yung, 2000), flow is regarded a psychological state in which one is absorbed in something he or she is doing, and is known to be widely adopted in explaining one's acceptance in the area of game, sports, and even hobby. This study developed a research model to explain the use of mobile services employing usefulness, ease of use and flow as major research variables, and collected 221 survey responses from the high school students who had experiences with such mobile services as game and audio file download. The results of the current research indicates that usefulness and flow influence the intension to use mobile services, but the effect of ease of use did not appear significant to the intention to use. It was also found that flow affects both usefulness and ease of use, and then ease of use next influences usefulness.

• The Journal of Information Systems
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• v.19 no.4
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• pp.111-136
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• 2010

This study examined the difference in the usage of internet banking users between Korea and China. This model tests various theoretical research hypotheses relating to internet banking, The Unified Theory of Acceptance and Use of Technology(UTAUT). The factors influencing on the use intention of Internet banking have been classified as performance expectancy, effort expectancy, social influence and facilitating conditions. The proposed model was empirically tested using data collected from a survey of internet banking users in Korea and China. The model is used by SPSS 15.0 and AMOS 7.0 for analysis on the sample collected from 272 respondents. The result of hypothesis testing are as follows. First, performance expectancy and social influence positively influence use intention of internet banking user both Korea and China. Second, facilitating conditions only positively influence on the usage of internet banking users in Korea. On the other side, effort expectancy do not influence the use intention of internet banking users in both two countries. The results of study will provide practical implications on the internet banking in Korea and China.

• Smart Structures and Systems
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• v.8 no.1
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• pp.69-92
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• 2011

This paper presents an emergent pattern recognition approach based on the immune network theory and hierarchical clustering algorithms. The immune network allows its components to change and learn patterns by changing the strength of connections between individual components. The presented immune-network-based approach achieves emergent pattern recognition by dynamically generating an internal image for the input data patterns. The members (feature vectors for each data pattern) of the internal image are produced by an immune network model to form a network of antibody memory cells. To classify antibody memory cells to different data patterns, hierarchical clustering algorithms are used to create an antibody memory cell clustering. In addition, evaluation graphs and L method are used to determine the best number of clusters for the antibody memory cell clustering. The presented immune-network-based emergent pattern recognition (INEPR) algorithm can automatically generate an internal image mapping to the input data patterns without the need of specifying the number of patterns in advance. The INEPR algorithm has been tested using a benchmark civil structure. The test results show that the INEPR algorithm is able to recognize new structural damage patterns.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.11
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• pp.997-1004
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• 2012

In enterprise software projects, performance issues have become more critical during recent decades. While developing software products, many performance tests are executed in the earlier development phase against the newly added code pieces to detect possible performance regressions. In our previous research, we introduced the framework to enable automated performance anomaly detection and reduce the analysis overhead for identifying the root causes, and showed Statistical Process Control (SPC) can be successfully applied to anomaly detection. In this paper, we explain the special performance trend in which the existing anomaly detection system can hardly detect the noticeable performance change especially when a performance regression is introduced and recovered again a while later. Within the fixed number of sampling period, the fluctuation gets aggravated and the lower and upper control limit get relaxed so that sometimes the existing system hardly detect the noticeable performance change. To resolve the issue, we apply dynamically tuned sampling window size based on the performance trend, and Fuzzy theory to find an appropriate size of the moving window.