• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.6-10
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• 2015

RF energy harvesting technology is a promising technology for generating the electrical power from ambient RF signal to operate low-power consumption devices(eg. sensor) in wireless communication networks. This paper, motivated by this and building upon existing CR(Cognitive Radio) network model, proposes a optimal control policy for RF energy harvesting CR networks model where secondary users that have low power consumption harvest ambient RF energy from transmission by nearby active primary users, while periodically sensing and opportunistically accessing the licensed spectrum to the primary user's network. We consider that primary users and secondary users are distributed as Poisson point processes and contact with their intended receivers at fixed distances. Finally we can derive the optimal frame duration, transmission power and density of secondary user from the proposed model that can maximize the secondary users's throughput under the given several conditions and suggest future directions of research.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.1-5
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• 2015

Recently, RF energy harvesting technology is a promising technology for small-size IoT(Internet of Things) devices such as sensor to resolve battery scarcity problem. When applied to existing cognitive radio networks, this technology can be expected to increase network throughput through the increase of cognitive user's operating time. This paper proposes a optimal channel-selection policy for RF energy harvesting CR networks model where cognitive users in harvesting zone harvest ambient RF energy from transmission by nearby active primary users and the others in non-harvesting zone choose the channel and communicate with their receiver. We consider that primary users and secondary users are distributed as Poisson point processes and contact with their intended receivers at fixed distances. Finally we can derive the optimal frame duration, transmission power and density of secondary user from the proposed model that can maximize the secondary users's throughput under the given several conditions and suggest future directions of research.

• Journal of The Korea Institute of Healthcare Architecture
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• v.22 no.3
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• pp.35-44
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• 2016

Purpose: This study is focus on investigation of user's spontaneous behavior in the public space of ward where chronic patients are hospitalized. Methods: The notion and necessity of social healing environment is analyzed by literature review. User's location and behaviour are investigated for analyzing behavior by visiting the six wards. Results: The result 1) Stay is main behavior of users. 2) The frequency of stay is high in the place where are planned as the dayroom, the program room and the balcony. 3) In the corridor, the users are staying around court and single side corridor. And the users who are staying in the ward planned middle corridor and double corridor are spreaded all over the corridor. As the result of the analysis of correlation between frequency of user for stay and area of public space, 4) The area of the dayroom, the program room and the balcony is bigger, the frequency of users are higher. 5) There is no correlation between area of corridor and frequency of users. 6) When the density of user is highest in the place for stay, one person occupied $1.96m^2$. Implications: Hereafter the public space, which social healing environment is considered, is planned, this study could suggest the directions of architectural planning about area.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.11
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• pp.3026-3045
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• 2012

In this paper, diversity-multiplexing tradeoff (DMT) of three-user wireless multiple-antenna cooperative systems is investigated in general fading channels when half-duplex and decode-and-forward relay is employed. Three protocols, i.e., adaptive protocol, receive diversity protocol, and dual-hop relaying protocol, are considered. The general fading channels may include transmit and/or receive correlation and nonzero channel means, and are extensions of independent and identically distributed Rayleigh or Rician fading channels. Firstly, simple DMT expressions are derived for general fading channels with zero channel means and no correlation when users employ arbitrary number of antennas. Explicit DMT expressions are also obtained when all users employ the same number of antennas and the channels between any two users are of the same fading statistics. Finally, the impact of nonzero channel means and/or correlation on DMT is evaluated. It is revealed theoretically that the DMTs depend on the number of antennas at each user, channel means (except for Rayleigh and Rician fading statistics), transmit and/or receive correlation, and the polynomial behavior near zero of the channel gain probability density function. Examples are also provided to illustrate the analysis and results.

• Journal of the Korean Society for information Management
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• v.28 no.3
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• pp.163-178
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• 2011

Using the library users' data in Lake County Public Library Systems, Florida, US, this study discussed how geographic information systems can be applied in LIS fields. These data were analyzed with such GIS functions as geocoding, Thiessen polygon, density, buffer, and distance measurement. Results indicate that findings from a study of these functions allowed for, not only a better understanding of the geographic locations of library users and user's library activity patterns, but also for the ability to identify library market areas for future library service planning. Additionally, results from a study of the Thiesen polygon and buffer functions indicated the distance impact on library use. Regarding the travel distance of library users, the measurement of distance using road networks was suggested.

• Journal of Information Processing Systems
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• v.10 no.4
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• pp.602-617
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• 2014

The performance of a cognitive radio network (CRN) solely depends on how precisely the secondary users can sense the presence or absence of primary users. The incorporation of a spatial false alarm makes deriving the probability of a correct decision a cumbersome task. Previous literature performed this task for the case of a received signal under a Normal probability density function case. In this paper we enhance the previous work, including the impact of carrier frequency, the gain of antennas on both sides, and antenna heights so as to observe the robustness against noise and interference and to make the correct decision of detection. Three small scale fading channels: Rayleigh, Normal, and Weibull were considered to get the real scenario of a CRN in an urban area. The incorporation of a maximal-ratio combining and selection combing with a variation of the number of received antennas have also been studied in order to achieve the correct decision of spectral sensing, so as to serve the cognitive users. Finally, we applied the above concept to a traffic model of the CRN, which we based on a two-dimensional state transition chain.

• The Journal of Industrial Distribution & Business
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• v.9 no.1
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• pp.51-65
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• 2018

Purpose - This paper aims to identify factors that influence the users' word-of-mouth intention (WOMI) regarding mobile apps, focussing on the impacts of technology acceptance model (TAM) and social network theory. Research design, data and methodology - Based on TAM, this study integrates social network theory into the research model. The 317 sets of data collected in a survey were tested against the model using SmartPLS. Results - Our findings suggest the following: 1) Personal innovativeness positively influences perceived usefulness (PU), perceived ease of use (PEU) and perceived enjoyment (PE); 2) PEU affects PU and PE; 3) Both PU and Satisfaction are directly correlated with WOMI. Although PEU and PE has no direct impact on WOMI, they may indirectly affect WOMI via Satisfaction, as PU, PEU and PE all positively influence satisfaction; 4) Network density and network centrality both play a mediating role in the relation between PEU and WOMI. Referral Reward Program have a positive moderating effect on the relation between PU and WOMI. Conclusions - The findings of this study illustrate the traits of Apps that can promote users' WOMI, as well as the characteristics of people who are more likely to participate in the word-of-mouth process. The findings provide a theoretical basis for app developers to make word-of-mouth a marketing strategy.

• Journal of the military operations research society of Korea
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• v.16 no.2
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• pp.118-134
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• 1990

This paper considers the mutual interference problem of several users employing the same FH systems in selected multiple user environments. The environment consists of a desired transmitter-receiver pair located in an area where there are M interfering users distributed in accordance with a specified probability density function. Both coherent Phase-Shift-Keyed and incoherent Frequencey-Shift-Keyed modulations are considered. The general formulas of the average bit error probability are derived. The calculation results are summarized and analyzed. The average bit error probability is highly dependent on the relative location of interferences to the desired link, the time duty factor of the hopping and the number of available channels.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.05a
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• pp.81-84
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• 2018

Recently, many researchers claim that mobile data offloading is a key solution to alleviating overloaded cellular traffic by dividing the overloaded traffic with femtocells, WiFi networks or users. In this paper, we propose an idea to select a group of users, known as VIPs, that is able to effectively transfer the data to others using Density-Based Spatial Clustering of Application with Noise, also known as DBSCAN algorithm. We conducted our experiments using NCCU real trace dataset. The results show that our proposed idea offload about 70~77% of the network with VIP set size of four, which is better than the compared methods.

• Asian Journal of Turfgrass Science
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• v.10 no.1
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• pp.13-20
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• 1996

This study was carried out to investigate the characteristics of spatial distributon patterns of users by each type of recreational activities at lawn areas in the parks. Study sites were lawn areas at Kyungju World and Seorabul Plaza in Bomun Resort Complex in Kyungju, Korea. Space types by each recreation activities are Repose Type, Sports Type, Play Type and Strolling Type. Main results are as follows ; 1. Sport Type activities were mainly distributed at the central areas of each lawn areas. 2.The density of Sports Type activities were affected by the form of lawn areas. For natural control of excess dynamic activities, Complex Form has more advantage in the distribution of dynamic activities. So, as the form of lawn areas in the parks, complex form is more desirable. 3.Repose Typo activities were distributed at marginal areas of lawns and surrounding woods. These, the static activities, were affected by Edge Effect in spatial distribution of activities. 4.Play Typo activities also were distributed at marginal areas of lawns. It was also affected by Edge Effect in spatial distribution. 5.Strolling Type activities were distributed evenly over all lawn areas.