• Journal of Korea Spatial Information System Society
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• v.10 no.4
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• pp.1-10
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• 2008

In wireless internet, the location information of the user is one of the important resources for many applications. One of these applications is Location-Based Services (LBSs) which are being popular. Because, in the LBS system, users request a location-based query to LBS servers by sending their exact location, the location information of the users can be misused by adversaries. In this regard, there must be a mechanism which can deal with privacy protection of the users. In this paper, we propose a cloaking method considering both features of K-anonymity and L-diversity. Our cloaking method creates a minimum cloaking region by finding L number of buildings (L-diversity) and then finding number of users (K-anonymity). To support this, we use a R*-tree based index structure and use filtering methods especially for the m inimum cloaking region. Finally, we show from a performance analysis that our method outperforms the existing grid based cloaking method.

• The Journal of Information Systems
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• v.10 no.1
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• pp.217-241
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• 2001

Groupware technologies have become an important part of the business computing infrastructure in many organizations, but many groupware applications, especially those requiring significant collaboration among users, are still nut adequately used. The purpose of the paper is to explore the impact of groupware on the job performance. Recently, utilization of new information technology such as groupware can increase office productivity, but often this potential is not realized. Results of most studies indicate that groupware could increase the productivity of knowledge workers, who compose the majority of the labor force in the organization. The study on the impact of job characteristics on groupware and job performance is not sufficient. This study examines the influence of job characteristics such as job diversity, autonomy, and feedback on the use of groupware and job performance. In addition to that, this study examines the influence of the use of groupware on job performance. The results of regression analyses revealed that feedback was the major predictor of job performance, while autonomy and job diversity were the Haler predictors of the use of groupware. Also, the use of groupware were found to be important predictors of job performance.

• Journal of Information Technology Services
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• v.8 no.1
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• pp.11-27
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• 2009

Recently, IPTV attracts great attention along with the digital convergence of communication and media technologies. This study examined critical factors on the consumer's continued use of the IPTV service. Based on the expectation-confirmation theory and the innovation diffusion theory, we derived nine key factors in the research model-relative advantage, compatibility, ease of use, image, diversity of contents, interactivity, monetary value, social influence, and user satisfaction. Using the partial least square method, we found that content diversity and compatibility have a significant indirect effect on the continued use of the IPTV service via user satisfaction, and user satisfaction and social influence also have a significant direct impact on the IPTV use. These findings not only provide practical insights on the consumer acceptance of new technology-converging services, but also help managers to plan their marketing strategies better.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.8
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• pp.437-444
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• 2014

In this paper, we propose a path loss model with the multiple antennas and doppler shift for high speed railroad communication. Path loss model is very important in order to design consider diverse characteristic in high-speed train communication. Currently wireless communication systems use the multiple antennas in order to improve the channel capacity or diversity gain. However, until recently, many researches on path loss model only consider geographical environment between the transmitter and the receiver. There is no study about path loss model considering diversity effect and doppler shift. In order to make average residuals considering doppler shift we use tuned free space path loss model which is utilized for measurement results at high speed railroad. The environment of high speed rail is mostly at viaduct and flatland over than 50 percent. And in order to make average residuals considering multiple antenna we use theoretical estimation of diversity gain with MRC scheme. proposed model predict loss of received signal by estimating average residuals between diversity effect and doppler shift.

• Journal of Communications and Networks
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• v.10 no.2
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• pp.175-185
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• 2008

In this paper, we investigate the effect of cooperative and selection relaying schemes on multiuser diversity in downlink cellular systems with fixed relay stations (RSs). Each mobile station (MS) is either directly connected to a base station (BS) and/or connected to a relay station. We first derive closed-form solutions or upper-bound of the ergodic and outage capacities of four different downlink data relaying schemes: A direct scheme, a relay scheme, a selection scheme, and a cooperative scheme. The selection scheme selects the best access link between the BS and an MS. For all schemes, the capacity of the BS-RS link is assumed to be always larger than that of RS-MS link. Half-duplex channel use and repetition based relaying schemes are assumed for relaying operations. We also analyze the system capacity in a multiuser diversity environment in which a maximum signal-to-noise ratio (SNR) scheduler is used at a base station. The result shows that the selection scheme outperforms the other three schemes in terms of link ergodic capacity, link outage capacity, and system ergodic capacity. Furthermore, our results show that cooperative and selection diversity techniques limit the performance gain that could have been achieved by the multiuser diversity technique.

• Journal of Forest and Environmental Science
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• v.32 no.3
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• pp.291-301
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• 2016

One of the most concerned topics in ecology is the relationship between biodiversity and ecosystem functioning. However, there are few field studies, carried out in forests, although many studies have been done in controlled experiments in grasslands. In this paper, we describe the relationship pattern between three facets of diversity and productivity at Ratargul Fresh Water Swamp Forest (RFWSF) in Bangladesh, which is the only remaining fresh water swamp forest of the country. Sixty sample plots were selected from RFWSF and included six functional traits including leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), tree height, bark thickness and wood density. In analyzing TD, we used Shannon diversity and richness indices, functional diversity was measured by Rao's quadratic entropy (Rao 1982) and Faith's (1992) index was used for phylogenetic diversity (PD). It was found that, TD, FD and PD were positively related with productivity (basal area) due to resource use complementarity but surprisingly the best predictor of tree productivity was FD. The results contribute to the understanding the effects of biodiversity loss and it is essential for conservation decision-making and policy-making of Ratargul Fresh Water Swamp Forest.

• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.170-176
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• 2007

In this paper, we improve performance for system when the carrier recovery signal is not perfect in the multipath mobile wireless communication fast fading channel based on DS-CDMA system. In the case, we use the phase estimation, diversity and adaptive FEC code technique in order to overcome this carrier phase error and mobile wireless fading. As a results in DS-CDMA system, we know that the appropriate use of diversity and adaptive FEC code technique reduced considerably performance degradation due to phase error.

• The Journal of the Korea Contents Association
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• v.13 no.5
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• pp.443-450
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• 2013

This study is about that how accessibility or norm influence to use diversity or usage of internet contents. Two hypotheses tested by statistic analysis. The major finding of this study are as follows. First, the greater the physical accessibility or intellectual accessibility, the greater the use diversity of internet contents. Second, the greater the physical accessibility or intellectual accessibility, the greater the usage of internet contents. Third, the greater the subject norm, the smaller the usage of internet contents. This study provides some implications that subject norm can influence to reduce usage of internet contents. The limitations, and future direction are discussed.

• ETRI Journal
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• v.25 no.4
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• pp.231-237
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• 2003

We derive and analyze the exact closed-form expression for the average bit error probability (BEP) of M-ary square quadrature amplitude modulation (QAM) for diversity reception in frequency-nonselective Nakagami fading. A maximal ratio combining (MRC) diversity technique with independent or correlated fading cases are considered. Numerical results demonstrate error performance improvement with the use of MRC diversity reception. The presented new expressions offer a convenient way to evaluate the performance of M-ary square QAM with an MRC diversity combiner for various cases of practical interest.

• ETRI Journal
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• v.21 no.4
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• pp.29-40
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• 1999

In this paper, we show the robustness of a proposed system using both a frequency diversity and a time diversity effect when the channel assumptions are relaxed such that all sub-bands are not independent fading. We take time-repetition coding with interleaving such that the repetition code symbols are spaced sufficiently far apart to guarantee time diversity. We also incorporate offset multicarriers into a proposed multicarrier DS-CDMA system in a different way compared to that of [10] to reduce the total multiple access interference. When we take a convolutional encoder instead of a time-repetition encoder, and again use both time diversity and frequency offset, then we can obtain the significant performance gain.