This study was conducted during summer and winter of 2018- 2019 in the agricultural research field of Shahid Chamran University. Experimental design was split- plot based on RCBD with three replications. The main plot was the type of agricultural system in three levels including conventional (Conv), organic (Org) and sustainable (Sust) (integrated between Conv and Org) and sup- plot was the type of pre- cultivated crop in sequence with wheat including cultivation of mung bean (M- W), corn (C- W), sesame (S- W) and fallow (F- W). Yield quantity (yield and its component) and quality (grain protein), an estimate of photosynthesis matter transfer index of wheat and soil organic carbon (SOC) after one double-cropping were measured. The result showed that the highest (545.04 g/m2) and the lowest (409.28 g/m2) seed yields were obtained in Conv and Org respectively. In contract, with the changing type of system from Conv to Org, grain protein was increased significantly (from 8.3 to 9.6 %). In addition, the highest (535.47 g/m2) yield of wheat was obtained from M- W double cropping. On the other hands the highest remobilization and current photosynthesis matter were obtained in the organic agricultural system with M- W and conventional with M- W double cropping. The situation of SOC showed that the highest (33.18 mg/g) SOC was obtained in the organic agricultural system with C- W double cropping. The reason for improving SOC in the organic and sustainable agricultural system was application of organic matter (compost and vermicompost) and crop residue management. Totally, from the crop ecology point of view, sustainable agricultural method with a sequence of M- W was the most desirable system.

Wind turbines, because of their height and localization, are frequently subject to direct lightning strikes. Thus, the investigation on the performance of their grounding system is of paramount interest for the prediction of the potential threats either for people working in (or animals passing through) the wind farm area and for the power and control units installed in close proximity of the turbine towers. In this paper, we perform a comprensive study of the transient behavior of the earthing systems of wind turbines. The analysis is conducted in the frequency domain and an hybrid approach, based on circuit theory and Method of Moments, is adopted to fully account for resistive, inductive and capacitive couplings between elements of the ground system. The actual transient behavior is obtained by means of an Inverse Fourier Transform. The results, computed considering a typical wind turbine grounding system configuration, provide more insight on the nature of the early-time transient response of grounding systems and allow to draw up useful design guidelines.

This paper applies the Markov models, optimal control theory, eigen vectors and eigen values concepts to propose a methodology to analyze the transient behavior of Exponential queuing systems. We propose a procedure to calculate the transient probability, the average queue length and the duration of the system to reach the steady state. The method is implemented through an algorithm which is developed and tested in MATLAB software environment. The new method enjoys a stronger mathematical foundation and more flexibility to analyze the transient behavior of Exponential queuing systems.

With the rapid progress of semiconductors in the level of voltage and power of the power system as well as the progress of control systems, compensators with high flexibility and performance range have been designed and built to increase the flexibility of energy transmission systems. to be These compensators installed in power systems are called flexible ac transmission systems (FACTS). One of the most important advantages of FACTS devices in the transmission system is to increase the transient stability margin of the power system by controlling the active and reactive power of the line during the occurrence of a fault in the system. In this article, the effect of one FACTS device with parallel connection, i. e. static compensator, on transient stability is investigated. The studied system is a two-machine power system including a hydropower plant and a local power plant. The simulation results show the effect of the compensator on the damping of electric power angle fluctuations. Also, the simulation results show the lack of influence of the compensator on the transmission active power in the transmission line. The simulation results have been obtained using Simulink MATLAB software.