• Journal of Communications and Networks
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• v.18 no.5
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• pp.744-761
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• 2016

For about the past decade and a half research efforts into cognitive radio networks (CRNs) have increased dramatically. This is because CRN is recognized as a technology that has the potential to squeeze the most out of the existing spectrum and hence virtually increase the effective capacity of a wireless communication system. The resulting increased capacity is still a limited resource and its optimal allocation is a critical requirement in order to realize its full benefits. Allocating these additional resources to the secondary users (SUs) in a CRN is an extremely challenging task and integer programming based optimization tools have to be employed to achieve the goals which include, among several aspects, increasing SUs throughput without interfering with the activities of primary users. The theory of the optimization tools that can be used for resource allocations (RA) in CRN have been well established in the literature; convex programming is one of them, in fact the major one. However when it comes to application and implementation, it is noticed that the practical problems do not fit exactly into the format of well established tools and researchers have to apply approximations of different forms to assist in the process. In this survey paper, the optimization tools that have been applied to RA in CRNs are reviewed. In some instances the limitations of techniques used are pointed out and creative tools developed by researchers to solve the problems are identified. Some ideas of tools to be considered by researchers are suggested, and direction for future research in this area in order to improve on the existing tools are presented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.7
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• pp.1533-1546
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• 2013

Wireless multicast is considered as an effective transmission mode for the future mobile social contact services supported by Long Time Evolution (LTE). Though wireless multicast has an excellent resource efficiency, its performance suffers deterioration from the channel condition and wireless resource availability. Cognitive Radio (CR) and Device to Device (D2D) are two solutions to provide potential resource. However, resource allocation for cognitive wireless multicast based on D2D is still a great challenge for LTE social networks. In this paper, a joint sub-carriers and power allocation model based on D2D for general cognitive radio multicast (CR-D2D-MC) is proposed for Orthogonal Frequency-Division Multiplexing (OFDM) LTE systems. By opportunistically accessing the licensed spectrum, the maximized capacity for multiple cognitive multicast groups is achieved with the condition of the general scenario of imperfect spectrum sensing, the constrains of interference to primary users (PUs) and an upper-bound power of secondary users (SUs) acting as multicast source nodes. Furthermore, the fairness for multicast groups or unicast terminals is guaranteed by setting a lower-bound number of the subcarriers allocated to cognitive multicast groups. Lagrange duality algorithm is adopted to obtain the optimal solution to the proposed CR-D2D-MC model. The simulation results show that the proposed algorithm improves the performance of cognitive multicast groups and achieves a good balance between capacity and fairness.

• Journal of Korean Library and Information Science Society
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• v.37 no.2
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• pp.317-343
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• 2006

The purpose of this study is to analyze the characteristics of OPAC displays of three children's libraries in Korea: Seoul Children's Library, Cheongju Miracle Library, and Yongsan Public Library. 'OPAC Display Guidelines( Draft)' Published by IFLA is used to examine the details of OPAC displays, and to suggest their improvement. Discussed are such topics as the features of basic and detailed search screens, the brief display of search results, the arrangement and full display of bibliographic records, and the use of terms and labels. All three libraries offer their users the same KOLAS' OPAC, only designed to serve general users rather than children, i.e., their primary user group. They show some weakness, and much improvement is urgently required to satisfy specifically the needs and information seeking behavior of children.

• Journal of the Korean Society for information Management
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• v.25 no.2
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• pp.127-141
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• 2008

In this study, we investigated the information users' needs and information seeking behavior in the field of science and technology. We found that the science and technology researchers most frequently needed information while conducting the research & development related tasks and drafting research papers. The researchers attributed the main sources of research ideas to be the communication among colleagues and the literature review. The researchers's most preferred information sources were digital libraries, web search engines, and academic information portal. In conclusion, the science and technology researchers regarded the online use of electronic materials as the primary source of information. We hope that this investigation reported herein to be the foundation for developing user-centered information services for the science and technology discipline.

• Journal of The Korean Association of Information Education
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• v.2 no.2
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• pp.278-285
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• 1998

Computer users frequently request large scale multimedia data such as images. voice, video rather than conventional formal data. Data in virtual fossil museum are represented as points, shape, location in multidimensional space and interrelation with other spatial object. Informations in virtual fossil museum should be maintained to manipulate spatial object and non-spatial object. In this report we propose virtual fossil museum which is consisted of two parts. In the first step, basic system is implemented in internet for non-specialist such as primary students. This system is implemented based on visual multimedia information system so that non-specialist about computer can access easily. In the second step, expert system is designed which allows computer users can store, magnify, reduce, and retrieve the spatial data. This expert system uses animation, spatial query and VRML.

• Journal of Digital Convergence
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• v.15 no.6
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• pp.353-359
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• 2017

Diverse public institutions from Republic of Korea currently hold various policies regarding public design with close attentions. Thus, the primary goal of this study relies on analyzing relation between public design and user experience. In accordance with comprehensive understanding from literature researches, and the evaluation criteria of public design could be identified through diverse pilot researches and existing relative researches. Analysis regarding Shedroff's experiential elements and user-experience factors had been conducted based on an instance mentioned by Korea Association of Public Design. The field test was conducted among experienced users (100 individuals) through survey. The research could detect significant correlation between public design(accessibility, regionalism) and user experience(pleasurable, meaningful). The overall user satisfaction level has been remarked as 2.64 out of 5.0 despite vigorous policies. Even though the importance of esthetic aspects should not be disregarded, the priority of study should rely on identifying 'who' are the actual users and 'the way' they understand.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.79-86
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• 2015

Cognitive radio networks (CRNs) offer the promise of intelligent radios that can learn from and adapt to their environment. CRN permits unlicensed users to utilize the idle spectrum as long as it does not introduce interference to the primary users due to the Federal Communications Commission's recent regulatory policies. Thereby, the security aspects in CRNs should be different with the other networks. The purpose of this paper is to devise a new delegation-based authentication protocol (NDAP) by extracting out the security aspects for unlicensed user authentication over CRNs from Tsai et al's delegation-based authentication protocol (TDAP). First of all, we will provide security analyses on the TDAP and set design goal for unlicensed user authentication. Then, we will propose a NDAP as a remedy mechanism for the TDAP and a new protocol for CRNs. The NDAP could be used as a security building block for the CRNs and various convergence applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.371-376
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• 2008

In this paper, we explain the unified inter-cell interference avoidance and cancellation in OFDM mobile cellular systems. Interference avoidance is used for cell-interior or two-cell-edge users, and interference cancellation is applied to three-cell-edge users. The performance of the unified scheme is evaluated by simplified system simulation. Link simulation results are used in the interpretation of system simulation output. We compare three schemes which are "no interference management," "only interference avoidance," "both avoidance and cancellation." Primary performance measures are the data rate of the 5th percentile user and the mean data rate. Simulation results show that interference management schemes greatly improve the cell edge performance, but slightly reduce the mean data rate. Use of both avoidance and cancelaltion is better than that of only avoidance in terms of the cell edge throughput and the mean data rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.1
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• pp.19-27
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• 2014

As frequency resource has taken on greater importance, Cognitive Radio(CR) technology has been considered as the solution to improve spectrum utilization by allowing a secondary user to utilize a licensed band when the primary user is absent. So spectrum sensing is significant part of CR for high performance. Recently, cooperative spectrum sensing that secondary users share each sensing results is proposed to improve spectrum sensing accuracy. In this paper, OR rule based cooperative spectrum sensing scheme using reporting error probability which occurs in user to fusion center(FC) channel The simulation results show that proposed scheme mitigates false alarm probability limitation which appears in existing cooperative spectrum sensing scheme by restricting the number of cooperating users using reporting error probability.

• Asia pacific journal of information systems
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• v.20 no.3
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• pp.51-72
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• 2010

Given the extensive role of IS in everyday life and the increasing presence of women in IS users, understanding gender differences in individual technology continuance usage decisions is an important issue. Nevertheless, much of the large body of research on gender differences has just examined mean differences between women and men in terms of abilities, usage habit, and traits. Even though lots of psychology studies have shown that women, more than men, were influenced by affective factors, gender-affection-continuance use linkage has not been examined in the context of on-line shopping services. Therefore, the primary purpose of this paper is to seek to examine gender differences in terms of influence of affective factor in the context of IS continuance use. Meanwhile, IS continuance has been an important subject of study in the IT research area. To date, to explain why and how users are motivated to continue to use on-line shopping services, lots of theory-based research such as expectation-confirmation model (ECM) has been proposed. In particular, various affective factors have been proposed to explain continuance use of on-line shopping services recently. Affective factors have been regarded as essential factors for increasing relational strength and satisfaction. Several affective factors have been studied by prior IS adoption and continuance studies. Among them are enjoyment and anxiety. In IS continuance research, positive affect has been commonly and narrowly conceptualized and measured as the enjoyment which a person derives from using computers. Hence, in this study, we introduced intimacy factor, which was conceptually related to the quality of interactions and relationships in previous research. It also has been regarded as essential factors for strengthening human relationships. As a result, we have observed gender effect while examining intimacy-continuance bond. As expected based on the previous literatures, women seem to be more sensitive in affective factors. The contribution point here is that we find evidence in the context of on-line shopping services.