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Abstract-The problem considered in the present article is optimal design of network topologies in multi-agent systems in order to make communication on the network as efficient as possible for the continuous-time average-consensus protocol. The network design problem can be posed in two different ways.(1) Assuming that the maximum communication cost, i.e. the maximum number of communication links, is known, the goal is to find the network topology which results in the fastest convergence to the consensus (in presence of communication time delays on the links). (2) If a minimum performance of the protocol is required, the design problem can be posed as finding the network with lowest possible communication cost which fulfills the required performance. In both approaches, we formulate the problem of finding the optimal communication graph among a class of directed graphs, strongly balanced digraphs, as a Mixed Integer Semidefinite Program (MISDP). By solving this MISDP, the optimal graph and the weights on communication links are obtained. The average-consensus algorithm mainly developed in [5] has received tremendous attention in recent years due to its applicability and elegance. Authors in [5] have studied the convergence and performance of the average-consensus algorithm under different conditions. It is shown that the convergence speed of the average-consensus protocol is determined by the second smallest eigenvalue of the Laplacian matrix of the mirror graph of the network which is itself determined by the topology of the network. A natural question that arises is how to choose the weights on communication links, the entries of the adjacency matrix of the graph, in order to achieve the best performance. In most cases, the network designer can also determine which agents communicate with each other. Therefore, one can go even further and investigate the best communication topology, i.e. the communication graph as well as the weights on the links, so that the performance of the consensus algorithm is optimized.Since the development of the average-consensus algorithm, extensive efforts have been made to improve the

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Cultivation environment can be effective on the degree of limitations in crop evapotranspiration and yield, as a result of water shortage and salinity. The purpose of this study was to determine and compare the impact of different irrigation regimes (daily, weekly and every two weeks) combined with different water salinities (0.8, 2.5, 5.0 and, 7.0 dS m -1 ) on eggplant yield (Y) and evapotranspiration (ETc) in outdoor and greenhouse cultivation. Daily ETc values were measured by diurnal weighting of microlysimeters throughout the growing season (from May 19th to September 5th, 2012 and June 1st to September 22nd, 2013) placed in a plastic greenhouse and outdoor basins. Measurements showed apparent variations between different irrigation regimes×water salinity treatments, during the early growing season in both years. Both water deficit and salinity factors had significant effects on ETc, ECe, Y, fruit diameter and shoot dry weight in both environments. The applicability of Doorenbos-Kassam linear crop-water production function along with Maas-Hoffman salt tolerance model was investigated in the greenhouse and outdoor conditions. The Ky coefficient obtained for outdoor and greenhouse eggplants treatments were 0.97 and 1.03 in the first year and 0.91 and 0.93 in the second year, respectively. Higher sensitivity of greenhouse eggplants to salinity was later demonstrated for both years, obtaining higher values of b and lower values of ECe threshold in the greenhouse eggplants.

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Although a number of studies have been conducted on extreme precipitation trends in different parts of the world including Iran, a great number of such studies have reported only the total amount of daily precipitation greater than a certain percentage (e.g., 95%) of the long term data (R95p), ignoring other useful indices. To address this research gap, we used other modified indices, namely R95tot (fractional contribution of very wet days to annual total amounts), R95tt (fractional contribution of very wet days to the total annual obtained from fitted gamma probability distribution), and RS95 (same as R95tt except that it uses Weibull distribution and very wet days defined by 95 percentage of an individual year) by which the spatial and temporal changes of very wet days across Iran was assessed, 1985–2013. In addition, to evaluate the effect of the selected distribution on the results, a new index‐(RS95gm)—was introduced and reported. This index is similar to RS95, except that it uses gamma distribution instead of Weibull. According to trend analysis of R95p, R95tot, and R95tt, reduced frequency of extreme precipitation events was detected in some northwest, west and northeast parts of Iran. On the contrary, RS95 (RS95gm) results showed a higher frequency of extreme events across Iran. It was also demonstrated that while R95p, R95tot, and R95tt were unequivocally affected by changes in the mean wet‐day/ annual total precipitation, RS95 (RS95gm) was more influenced by changes in the distributional shape, showing more stable trends. Although RS95 and RS95gm were highly correlated with only 19% difference on average, their trend analysis results were not completely consistent (70% agreement). Thus, it may be concluded that any changes in statistical distribution in the calculation of the RS95 would have a considerable effect on whether the obtained trend is significant or not.

The improved systems of biogas production usually increase the energy consumption of biogas plants. Therefore, it is very important to determine an appropriate improvement system to increase plant efficiency. For this purpose, a biogas plant with a biological self-purification system was energetically and exergetically analyzed, and its performance was compared with that of a base plant. To keep the temperature of digesters up to 310.2 K, a solar water heater was used. It was able to maintain a high level of efficiency for both plants. The energy analysis of the plants indicated that the overall energetic efficiency of both plants was very close. The exergy analysis of the plants showed that the overall exergetic efficiency of the self-purification biogas plant (76.24%) was higher than that of the base plant (66.78%). This is due to the fact that the total exergy destruction rate of the self-purification plant was lower than that of the base plant and the exergy rate of biogas output of the self-purification plant was higher than that of the base plant. The exergy analyses of both plant components showed that although the highest exergy destruction rates were attributed to the principle digester and separation unit, they showed the highest exergetic improvement potential rates. These results confirm that the digesters in biogas plants have a great potential to be improved exergetically, and the self-purification system is a suitable improvement system to increase the plant efficiency exergetically.