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Wireless sensor networks (WSNs) have many potential applications [1,2] and unique challenges. They usually consist of hundreds or thousands of small sensor nodes such as MICA2, which operate autonomously; conditions such as cost, invisible deployment and many application domains, lead to small size and resource limited sensors [3]. WSNs are susceptible to many types of link layer attacks [1] and most of traditional network security techniques are unusable on WSNs [3]; This is due to wireless and shared nature of communication channel, untrusted transmissions, deployment in open environments, unattended nature and limited resources [1]. Therefore security is a vital requirement for these networks; but we have to design a proper security mechanism that attends to WSN's constraints and requirements. In this paper, we focus on security of WSNs, divide it (the WSNs security) into four categories and will consider them, include: an overview of WSNs, security in WSNs, the threat model on WSNs, a wide variety of WSNs' link layer attacks and a comparison of them. This work enables us to identify the purpose and capabilities of the attackers; furthermore, the goal and effects of the link layer attacks on WSNs are introduced. Also, this paper discusses known approaches of security detection and defensive mechanisms against the link layer attacks; this would enable IT security managers to manage the link layer attacks of WSNs more effectively.

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The COVID-19 pandemic brought about many critical issues in all aspects such as economy, environment, health, and lifestyle, but people always try to find some response to crisis in different conditions. E-learning is defined as an elaborate response aiming at continuing education during the COVID-19 pandemic. It seems that developed countries have established and adjusted their technological infrastructures for the transition from a face-to-face education to a digital one. In contrast, developing countries were not completely prepared for this transition. Improper and deficient technological and practical fundamentals have been causing problems for all students, instructors, and other involved individuals. Therefore, we reviewed the challenges that have arisen from e-learning during the COVID-19 outbreak in different parts of tertiary education focusing on underprivileged countries.

There is a growing consensus among citizens and members of local government that citizen participation is desirable for local government. However in practice, there are differing perceptions between them regarding the level and extent of citizen participation. As citizen participation is a multi faceted concept, its meaning is construed differently by both the members of local government and the citizen groups. This paper attempts to describe the conflicts that arise from participation. The paper is based on the study of the process of citizen participation in local government carried out in Torbat-Heydarieh city, Iran. A qualitative research method is seen as the most suitable approach of collecting and analyzing the data. The method employed for data collection in this research is in-depth interviews. In-depth interviews were conducted to gauge the existence of conflicts regarding participation. The findings reveal four areas that give rise to conflicts. This study also attempts to highlight two different views regarding citizen participation; the people-centered view and authority-centered view.

Wireless sensor networks (WSNs) have many potential applications [1,5]

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