• Journal of Communications and Networks
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• v.11 no.2
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• pp.157-165
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• 2009

In this paper, we investigate a dynamic spectrum sharing problem for the centralized uplink cognitive radio networks using orthogonal frequency division multiple access. We formulate a large-scale joint rate and power allocation as an optimization problem under quality of service constraint for secondary users and interference constraint for primary users. We also suggest admission control to nd a feasible solution to the optimization problem. To implement the resource allocation on a large-scale, we introduce a notion of using the conservative factors $\alpha$ and $\beta$ depending on the outage and violation probabilities. Since estimating instantaneous channel gains is costly and requires high complexity, the proposed algorithm pursues a practical and implementation-friendly resource allocation. Simulation results demonstrate that the large-scale joint rate and power allocation incurs a slight loss in system throughput over the instantaneous one, but it achieves lower complexity with less sensitivity to variations in shadowing statistics.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.6
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• pp.110-120
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• 2008

Cognitive Radio (CR) technology is proposed for using the unused spectrum band efficiently because of the spectrum scarcity problems. Spectrum sensing technology is one of the key challenge issues in cognitive radio technologies, which enables unlicensed users to identify and utilize vacant spectrum resource allocated to primary users. In this paper, the cooperative spectrum sensing technologies apply the ITS(Intelligent Transport System) and performance of signal detection analyzes. Then, we utilize the OR-rule and AND-rule for the cooperative signal detection. These data fusion rules improve the performance and reliability of the signal detection.

• Journal of Environmental Science International
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• v.24 no.5
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• pp.689-697
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• 2015

Based on the survey of 4 universities in Tai' an by questionnaire survey and interviews, this study acquired and analyzed the college student users' activity type, utilization frequency, retention time, companion, preference for landscape design style, the importance of the courtyard space's environment and landscape, as well as correlations between primary attributes and activity characteristics of student users. The weight of the university teaching area's courtyard space evaluation index was obtained by Analytical Hierarchy Process. The results indicated that nearly 60% college students select to study and to rest alone as the main activity type, 80% students' utilization frequency is at least two times or more a week. In addition, the relative weight of plant landscape is the highest in the 2nd class indexes of space garden landscape, and its value is 0.113; the relative weight of cleanliness is the highest in the 3rd class indexes of space environment quality, and its value is 0.143. Therefore, it should be attached much importance to constructing the environment and landscape for studying and relaxing, and the factors of cleanliness and plant landscape etc in the further design of courtyard space are taken into full consideration.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.11
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• pp.2426-2432
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• 2011

In this study, we evaluated web usability for hospital web sites in Korea and analyzed the evaluation results of web usability. Estimators investigated twelve hospital web sites and answered a questionnaire. They also performed predefined tasks which were frequently used services in hospital web sites. We had an interview with the estimator for finding what happened in process of evaluating usability. The evaluation results showed that university hospital provided comparatively better web usability for users. But ambiguous and complicated user interface caused confusion among users. The simplifications of service processes and interfaces were necessary to improve web usability. Some hospitals did not offer primary web services and their services related to the tasks were not systematic.

• Journal of the Ergonomics Society of Korea
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• v.24 no.3
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• pp.1-10
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• 2005

The primary objective of this study is to design input methods for assisting button selection tasks on a PDA screen. Familiar methods in the existing computing environments were investigated to develop aiding methods. Factors manipulated in the experiment included aiding method, button size, and users' prior experience with PDAs. A total of sixteen participants examined the usability of button selection tasks. Two types of button selection tasks were used as experimental tasks; one was selecting a target button, and the other was selecting multiple target buttons consecutively. The results showed that the aiding method and the button size had significant effects on the subjective satisfaction as well as the performance. In addition, users' prior experience with PDAs affected the performance significantly. The interaction between the aiding method and the button size was found to have significant effects on the performance. However, the interaction effect between the button size and the PDA experience was significant on the task performance time only for the multiple button selection tasks. Design considerations were proposed based on the experimental results. These can be applied to the PDA interaction design to make the PDAs more usable.

• Asia pacific journal of information systems
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• v.15 no.4
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• pp.61-87
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• 2005

This paper has two primary objectives: (1) to propose a comprehensive theoretical model that incorporates valuable insights from two complementary streams of research, and (2) to empirically test the model that explain the task-media fit and satisfaction of customer contact center users. The comprehensive model was tested using LISREL analysis on the sample of 232 users who have experience with the customer contact center. The model was supported in customer contact center context, accounting for 29% of the variance in the task-media fit, 53% of the variance in the perceived ease of use, 61% of the variance in the perceived usefulness, and 52% of the variance in the user satisfaction. The results showed that the task-media fit, the perceived ease of use, and the perceived usefulness play a significant role in influencing the user satisfaction of the customer contact center. In addition, task analyzability, media richness, media interactivity, and self-efficacy were found to influence the task-media fit. The paper concludes with discussions and implications for researchers and practitioners.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.839-844
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• 2011

Various technologies such as infrared light, ultrasonic waves, RFID, GPS, UWB, and signal indicators have been incorporated in the location tracking system. However, such pre-existing systems require location recognition in shadow areas. This study proposes a location tracking system that utilizes Cooperative Spectrum Sensing. Cooperative Spectrum Sensing is not only able to track the location and path of moving objects but also recognize when objects breakaway from the path set by sensors and guide them back. In addition, it has the advantage of being more efficient in terms of frequency usage. It is able to automatically fix power transmission and frequency modulation for transmission cognitive users to an optimum level within the range that does not cause interference for primary users.

• Journal of information and communication convergence engineering
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• v.8 no.1
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• pp.40-44
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• 2010

opportunistic spectrum access (OSA) allows unlicensed users to share licensed spectrum in space and time with no or little interference to primary users, with bring new research challenges in MAC design. We propose a cognitive MAC protocol using statistical channel information and selecting appropriate idle channel for transmission. The protocol based on the CSMA/CA, exploits statistics of spectrum usage for decision making on channel access. Idle channel availability, spectrum hole sufficiency and available channel condition will be included in algorithm statistical information. The model include the control channel and data channel, the transmitter negotiates with receiver on transmission parameters through control channel, statistical decision results (successful rate of transmission) from exchanged transmission parameters of control channel should pass the threshold and decide the data transmission with spectrum hole on data channel. A dynamical sensing range as a important parameter introduced to maintain the our protocol performance. The proposed protocol's simulation will show that proposed protocol does improve the throughput performance via traditional opportunistic spectrum access MAC protocol.

• Journal of Preventive Medicine and Public Health
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• v.50 no.5
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• pp.336-346
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• 2017

Objectives: To characterize the usage patterns of new types of tobacco products (NTTPs) to develop effective strategies for the regulation of NTTPs in Korea. Methods: We conducted focus group interviews to identify the NTTP usage patterns of research subjects. The NTTPs were limited to electronic cigarettes (e-cigarettes), waterpipe tobacco, and rolling tobacco. We categorized 30 research subjects into 4 groups. The ecigarette group was divided into adult and adolescent groups. Each group contained 7-8 subjects. An interview lasting approximately 2 hours was conducted with each group. Results: Ninety percent of NTTP users used an NTTP in combination with conventional cigarettes. Subjects mostly bought NTTPs online, unlike how they bought cigarettes. Additionally, a great deal of information, such as how to use NTTPs and descriptions of NTTP products, was exchanged through online or offline societies. The primary reason why the subjects used NTTPs was that NTTPs offer a greater range of flavors and aromas than cigarettes. Moreover, NTTPs were felt to be less repulsive than cigarettes. NTTPs were not used as a cigarette substitute; rather, they were mostly used in places and situations where traditional cigarette smoking was not allowed. Conclusions: Based on the results of this study, the government should conduct studies on the effects of the combined use of NTTPs and cigarettes on the human body, obtain and provide accurate data regarding NTTP use, and develop and implement polices to ban NTTP advertising, which may arouse adolescents' curiosity, and the addition of flavoring substances to tobacco products.

• Knowledge Management Research
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• v.14 no.5
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• pp.35-53
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• 2013

This paper aims to describe how knowledge management could be put into practice in a voluntary way. From a practice-based standpoint, this study focused closely on the linkage between knowledge and practice. It is because knowledge management could fail if not put into practice. Using its own information system, iCOOP, a federation of consumers' co-operatives in Korea has been practised successful knowledge management voluntarily with its members. Based on the exploratory case study on iCOOP, this study conducted focused interviews with 5 member co-operatives of iCOOP. Main findings are as follows. First, an NoP emerges within a corporate information system when corporate work processes are concentrated in the information system. Second, corporate information system facilitates CoPs and the NoP when its information and information about its users are opened to all of the information system users. In conclusion, this study points out that it is not the matter of primary importance to build a knowledge management system. Rather, practice has the key to the successful knowledge management.