Broadcasting plays an important role in the communication protocol design and it acts as a fundamental operation in wireless sensor network (WSN). This paper investigates the Minimum Latency Broadcast Scheduling in Duty Cycled (MLBSDC) problem in WSN. The MLBSDC problem aims to find a broadcast scheduling that minimizes the time in which the last node receives the broadcast message with minimum collision. The focus is mainly on providing minimum collision and finding the lower bound of broadcast latency. In this paper, a novel algorithm Collision Optimized Broadcast Scheduling (COBS) is proposed which is a refinement of Effective Broadcast Scheduling with Optimized Latency (EBSOL) [9] algorithm. COBS allow nodes in different layers of the broadcast tree to transmit the message simultaneously. In EBSOL, the latency is efficiently reduced by layer by layer approach and the broadcast tree is constructed. It is proved that COBS produces a latency of at most 12 |T|, where T denotes the number of time slots in a scheduling period. To prevent collision, each node maintains an effective routing table and only one parent node transmits the message to the child node. The results from extensive simulation show that COBS has a better performance than the existing One To All Broadcast (OTAB) algorithm in terms of reduction in latency, number of transmission and collision.

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In the past, a large part of security requirements of wireless sensor networks (WSN) were fulfilled by symmetric cryptography systems. But, today by introduction of new needs in these networks and their security development, researchers of security and cryptography try to find new ways to increase efficiency and security of wireless sensor networks. Improving computational power of sensors used in wireless sensor networks made application of public key cryptography in WSN possible. Identity based cryptography is one important type of public key cryptography which using some bilinear functions called pairingfunctions was seriously applied. In this paper we will look at some researches done to find how to use pairings in wireless sensor networks.

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Background:The coronavirus disease 2019 (COVID-19) is transmitted through saliva and respiratory aerosols. Concerns among dental clinicians over cross-contamination are among the main challenges currently present in the dental profession. This study aimed to assess dental students' distress level and attitude towards their professional future following the emergence of the COVID-19 pandemic. Materials & Methods: This descriptive study was carried out recruiting 369 dental students of the Guilan University of Medical Sciences (a census sampling method) using an online questionnaire consisted of the three main topics of students' academic status, distress level, and attitude towards their professional future. The students received the link to the questionnaire via instant messaging applications. The Mann-Whitney U test, the Kruskal-Wallis test, the Spearman's correlation, the chi-squared test, the Fisher's exact test, the binomial test, as well as the backward multiple logistic regression model were used for data analysis. Results: The dental students had a low level of distress and a negative attitude towards their professional future. Accordingly, the distress level was significantly higher in females (P < 0.001) than in males. Besides, it had a positive correlation with the academic level. In addition, the attitude of the females and those attending the Rasht Dental School was more significantly negative than that of the males and those attending the Anzali Private Dental School (P = 0.01 and P = 0.009, respectively). Furthermore, attitude had a positive correlation with distress. Conclusion:The subjects showed little distress over the pandemic. However, this level of distress showed a significant correlation with the negative attitude towards the professional future. In fact, this negative attitude stemmed from structural changes in the dental profession as well as the threats posed to financial conditions following the transmission of the disease and concerns over it.