r. asghari

Using a conservative stability analysis to design a time delay system controller usually cause a devaluation on the actuator performance. In addition, the results obtained considering deterministic stability criteria may not be reliable due to the existence of random delays. Whenever the feedback loop of a power system oscillation damping control system receives remote signals through communication networks, we face a POD system with random delays namely POD-RD system.  In this paper, a new design approach to promote the performance of a POD-RD control system is proposed based on the delay scheduling control signal method. This is a two-step method for implementation. In the first step assuming the average value of the communication random delays, the controller''''s parameters and also delay parameter of the control signal are determined as initial values by minimizing sperctral abscissa of the closed loop system. In the next step, to include impact of the communication random delays, a repetitive procedure is proposed to determine the optimal value of the delay parameter of the control signal and also the controller''''s parameters. The objective of the optimization model is to minimize the spectral abscissa and the defined second order moment. The feasibility of the proposed method is evaluated by doing a number of simulations on the standard four-machine test system.The results reveal that the method can make a robust performance in the studied system.

In order to identify the plant parasitic nematodes in Alborz Province, some soil and root tissues of plants samples were collected from different crops in various regions of the Province during 2017 and 2018. After transferring the samples to the laboratory, soil and root washing operations, nematode extraction, transferring and fixing in pure glycerin were performed. Permanent microscopic slides and incisions were made from different parts of the body of some species. After microscopic observations, the extracted species were identified using different keys. During the survey and morphological studies, 6 nematode species belonging to 5 genera were identified as follows:Ditylenchus triformis, Nothotylenchus affinis, Nothotylenchus medians, Helicotylenchus pseudodigonicus, Rotylenchus agnetis, Pratylenchus mediterraneus Among the identified nematodes, species Helicotylenchus pseudodigonicus, Nothotylenchus affinis, Nothotylenchchus medians and Rotylenchus agnetis were reported for the first time in Alborz province.

German chamomile (Matricaria chamomilla L.) is one of the most important medicinal plants that its essential oils used in different medicinal industries. In this study which was carried out in 2013 growing season at the Faculty of Agricultural Sciences of the University of Mohaghegh Ardabili, the in vitro response of leaf and hypocotyl explants of German Chamomile in B5 medium supplemented with different levels of plant growth regulators including 2,4-D, naphthalene acetic acid (NAA), kinetin and 6-benzylaminopurine (BAP) were investigated in a factorial experiment based on completely randomized design (CRD).In addition, cell suspension cultures were established and characterized. Hypocotyl and leaf explants exhibited cell proliferation and produced callus within 1-2 weeks. The highest fresh weight of the callus (264.1 mg) was produced by leaf explants in the medium supplemented with 0.5 mg/l 2,4-D and 1 mg/l BAP. However, the leaf explants cultured on medium containing 1.5 mg/l 2,4-D showed the lowest cell proliferation and callus yield (40.42 mg). The highest percentage of root induction from leaf explants (58.73%) was observed on the medium containing 4 mg/l 2,4-D and 1 mg/l Kin, and from hypocotyl explants (48.61%) was observed on medium supplemented with 1.5 mg/l NAA. The 42.22% of calli derived from hypocotyl explants on B5 medium supplemented with 4 mg/l NAA and 3 mg/l BAP, were friable. Cell suspension cultures of German chamomile were established by transferring of hypocotyl-derived friable calli into the MS medium supplemented with 1.5 mg/l 2,4-D and 1 mg/l kinetin. The growth curve of cell proliferations started 4 days after culture and continued to grow until day 13th, where the cells entered stationary phase.

In order to evaluate the effect of feeding different levels of wheat bran on fattening performance as well as carcass characteristics، an experiment was conducted on fifteen Baluchi male lambs. The experiment was done using three treatments with five replicates each. in completely randomized design manner. The treatments consisting 10،20and 30% wheat bran. In the last two treatments، wheat bran was substitute with barley and corn. The experiment was run for 90 days. The results indicated that carcass componentsas well as، average daily gain، final live weight and feed conversion ratio were not affected by the treatments. Feed intake as well as nutrient consumption were not significantly affected by the treatments. Wheat bran consumption was affected by the treatments significantly (P<0. 05). Although pH was not significantly affected by the treatments، ammonia nitrogen concentration was different among the treatments (P<0. 05) and increased as wheat bran percentage increaded. It can be therefore concluded that levels higher than 30% DM of wheat bran could be used in replace of cereals.