A Reliable Communication Model Based on IEEE802.15.4 for WSANs in Smart Grids

Creating cyber-physical systems (CPSs) based on wireless sensor and actuator networks (WSANs) has great potential to improve the performance of Smart Grid. In addition, IEEE802.15.4 has widely been regarded as an appropriate standard for WSANs, due to some striking and unique features. WSANs require provisioning strict quality of service (QoS) due to noisy harsh environments in Smart Grid applications. Although analytical models have been studied in the literature, they have not provided a full-fledged model for Smart Grid. In this paper, we have added a MAC-level buffer, and a novel Markov chain model has been also proposed. By comparison with previous studies, retransmission confines, acknowledgment, packet length variation, saturated traffic, and degenerate distribution of packet generation are accounted for. The algorithm has been experimentally implemented and appraised on a platform with self-designed WSAN. The analytical model predicts well our exhaustive experiments. Further, Monte Carlo simulations validate mathematical results

Is Atopic Dermatitis More Severe in Children with Lower Levels of 25-Hydroxy Vitamin D?

Background: Atopic Dermatitis (AD) is the most common chronic skin disease, which can lead to some complications in adulthood. According to the possibility that some environmental factors like vitamin D are effective in AD, this study was conducted to clarify the effect of serum level of vitamin D on it.Methods: This study was performed as a case-control study, in Hamadan University of Medical Science, comparing the serum level of vitamin D in 20 children with and 20 children without atopic dermatitis. Atopic dermatitis was confirmed by standard criteria of Hanfin Verajka and the severity score was assessed using the SCORAD scoring system. Data was analyzed using SPSS software.Results: In this study, no significant differences were found in age, gender and place of residence between two groups.  And, there was no significant difference in serum level of vitamin D between two groups (P-value: 0.394) but a significant, direct relationship was observed between disease severity and serum levels of vitamin D (P-value: 0.0431).Conclusion: The results of this study showed that vitamin D deficiency alone may not trigger atopic dermatitis, but it can worsen the disease, so it seems that the serum level of vitamin D in children with atopic dermatitis should be checked and in case of deficiency, a supplement should be prescribed