the objective followed in this descriptive-survey research was to investigate factors influencing farmers’ attitudes toward participation in water users’ associations. the statistical population of the study consisted of 1435 farmers of markazi district of zanjan county out of whom 329 were selected as sample using cochran formula. random sampling technique was used for the study. a questionnai...

Under the contemporary spectrum usage regulations, radio frequency bands are allocated statically to licensed users in a large geographical area and over a long period of time. Recent investigations revealed that such static spectrum allocation has led to very poor spectrum utilization. Cognitive radio has emerged as a new communication paradigm to improve spectrum utilization. It is defined as...

In GPS-denied indoor environments, localization and tracking of people can be achieved with a mobile device such as a smartphone by processing the received signal strength (RSS) of RF signals emitted from known location beacons (anchor nodes), combined with Pedestrian Dead Reckoning (PDR) estimates of the user motion. An enhacement of this localization technique is feasible if the users themsel...

This paper describes an approach for motivating participation in a peer-to-peer file sharing system through rewarding cooperative users with better quality of service. User modeling and modeling user relationships with other users is applied. Two forms of evaluation through simulation and through user experiment show that the user and relationship modeling approach provides cooperative users wi...

Cognitive radio (CR) has recently been identified as a promising technology to solve the spectrum inefficiency problem. CR users or secondary users (SUs) need to sense the presence of primary users (PUs) constantly and rapidly to utilize their unused spectrum. However, detection is compromised when a user experiences shadowing or fading effects. In such cases, the user cannot distinguish betwee...

Spectrum sensing is a fundamental function in cognitive radio networks for detecting the presence of primary users in licensed bands. The detection performance may be considerably compromised due to multipath fading and shadowing. To resolve this issue, cooperative sensing is an effective approach to combat channel impairments by cooperation of secondary users. This approach, however, incurs ov...

Cooperative communication has been proposed to improve the disadvantages of the multiple-input multiple-output (MIMO) technique without using extra multiple antennas. In an orthogonal frequency division multiple access (OFDMA) system, a cooperative communication that each user shares their allocated sub-channels instead of the MIMO system has been proposed to improve the throughput. But the coo...

Multiple secondary users can cooperate to increase the reliability of spectrum sensing in cognitive radio networks. However, the total transmission power grows approximately linearly with the number of cooperative secondary users. This paper proposes a new approach to optimize the trade-off between sensing reliability and power efficiency in cooperative cognitive radio networks over fading chan...

Conventional water use and management models have mostly emulated purposefully designed systems where centralized governance rule-based cooperation of agents are assumed. However, systems, whether actively governed or not, involve multiple, independent decision makers with diverse often conflicting interests. In the absence adequate institutions to effectively coordinate processes on use, users...

VIEW Media is a cooperative hypermedia system, which supports cooperative work utilizing hypermedia documents. It provides fundamental functions for cooperative work support system and enables developers to construct various groupware such as distributed presentation systems, education systems, conference systems, and so forth. This system provides a powerful and flexible mechanism of customiza...