m. najimi

Energy consumption and throughput optimization in cognitive radio networks (CRNs) are two critical issues that have attracted more attention in recent years. In this paper, we consider maximization of the energy efficiency and improvement of the throughput as optimization metrics for jointly optimizing sensing times and energy detection thresholds in each sub-channel and selecting the spectrum sensing (SS) and data transmitting multi-antenna secondary users (SUs) in multi-channel multi-antenna CRN under constraints on the probabilities of false alarm and detection. The considered problem is solved based on the convex optimization method and the algorithm having less computational complexity compared to baseline approaches is proposed to achieve the optimal parameters and goals of the problem. The performance of the proposed scheme is evaluated by simulations and compared with the other methods. The results indicate that the proposed approach can achieve less energy consumption while the minimum required throughput is guaranteed.

Brucellosis is an anthropozoonotic disease. Infection of livestock with Brucella is endemic in most parts of Iran. Sistan-Baluchestan is bordered on the east by the countries of Afghanistan and Pakistan. The high prevalence of brucellosis in livestock in the eastern neighboring countries results in transmission of the disease to this province. The present research aimed to determine the prevalence of brucellosis in small ruminants in the Sistan region of Iran and to compare serological and molecular tests for the detection of brucellosis. Blood samples were taken from 150 randomly selected sheep and goats, and sera were separated. All sera were analyzed by serological (Wright and 2-ME) and molecular (Polymerase Chain Reaction (PCR)) tests. Serological tests were carried out according to the instructions of the Iranian Veterinary Organization The degree of agreement between serological tests and PCR was determined by kappa value. In this study, 17 cases (11.3%) were identified as positive by the PCR method. Wright and 2-ME tests had the highest agreement with PCR in titers ≥2/80 and ≥2/40, respectively. The results of this study show that the brucellosis in sheep and goats has a greater prevalence in the Sistan region than in most other parts of Iran, and this is important in terms of public health. It is suggested that brucellosis vaccination coverage in livestock be increased in this area and that the people in Sistan region must be notified about methods for preventing brucellosis. Also, further studies to compare conventional serologic tests with the gold standard test are recommended.

Many performance evaluations for IEEE 802.11distributed coordination function (DCF) have been previouslyreported in the literature. Some of them have clearly indicatedthat 802.11 MAC protocol has poor performance in multi-hopwireless ad hoc networks due to exposed and hidden nodeproblems. Although RTS/CTS transmission scheme mitigatesthese phenomena, it has not been successful in thoroughlyomitting these drawbacks. We argue that when eliminatinghidden node effect with a given protocol is not feasible, onemay sometimes earn more throughput by controlling or evenwisely creating this phenomenon. In this paper we propose anovel solution to improve the performance of IEEE 802.11MAC protocol in multi-hop networks through modifying NAVtimer. We may call this method Dynamic NAV (DNAV) sincethe NAV timer operation changes dynamically with the changeof environment variables. Simulation results show that ourapproach noticeably increases the throughput in multi-hopwireless ad-hoc networks.