Vazin F.,Islamic Azad University at Gonabad
Scientia Horticulturae | Year: 2013
The effects of water deficit on yield, fatty acids and essential oil yield and composition of Cumin (Cuminum cyminum L.) were investigated. Plants were treated with different levels of water deficit (I100, I50 and I0). Plant growth (height and dry matter weight) was significantly reduced by I0. This last caused also important reductions of the seed yield and yield components. Drought decreased significantly the fatty acid content and the double bond index (DBI) degree. This later was provoked mainly by a strong reduction of oleic, linolenic and petroselinic acid proportions and the disappearance of palmitoleic and arachidinic acid. Besides, moderate water deficit increased the essential oil yield (expressed as g/100g on the basis of dry matter weight). The main essential oil constituents were p-Menta-1,3-diene-7-al, cuminaldehyde, γ-Terpinene, p-Cymene and β-Pinene which showed a decreasing of their contents under I0. © 2012 Elsevier B.V.
Azari A.,Islamic Azad University at Gonabad
IEEE Transactions on Antennas and Propagation | Year: 2011
The commercial and military telecommunication systems require ultrawideband antennas. The small physical size and multi-band capability are very important in the design of ultrawideband antennas. Fractals have unique properties such as self-similarity and space-filling. The use of fractal geometry in antenna design provides a good method for achieving the desired miniaturization and multi-band properties. In this communication, a multi-band and broad-band microstrip antenna based on a new fractal geometry is presented. The proposed design is an octagonal fractal microstrip patch antenna. The simulation and optimization are performed using CST Microwave Studio simulator. The results show that the proposed microstrip antenna can be used for 10 GHz 50 GHz frequency range, i.e., it is a super wideband microstrip antenna with 40 GHz bandwidth. Radiation patterns and gains are also studied. © 2011 IEEE.
Rakhshani E.,Islamic Azad University at Gonabad |
Sadeh J.,Ferdowsi University of Mashhad
Energy Conversion and Management | Year: 2010
An attempt is made in this paper to present feasible and practical methods to improve dynamic response of load frequency control problem in a deregulated power system. In the practical environment, access to all of the state variables of system is limited and measuring all of them is also impossible. Access and also measuring the state variable is one of the most problems on application of control methods in real world. To solve this problem, in this paper, two methods with pragmatic viewpoint are proposed. The first method is optimal output feedback control and the second is based on state observer method. In the output feedback method, only the measurable state variables within each control area are required to use for feedback. But when we have fewer sensors available than the number of states or it may be undesirable, expensive, or impossible to directly measure all of the states, using a reduced-order observer is proposed. These proposed designs, which are presented in this paper, have been developed in order to over-come this problem and are tested on a two-area power system considering different contracted scenarios. The results show that when the power demands change, the output feedback method is the most rational technique with the best dynamic response. Also, with using a reduced-order observer, the dynamic response of system is improved. In fact, using these methods is necessary for load frequency control problem in a practical environment. © 2009 Elsevier Ltd. All rights reserved.
Balochian S.,Islamic Azad University at Gonabad
Evolving Systems | Year: 2013
In this paper, variable structure control is utilized for stabilization of a particular class of nonlinear polytopic differential inclusion systems with fractional-order-0 < q < 1. By defining a sliding surface with fractional integral formula and obtaining sufficient conditions for stability of the sliding surface, a special feedback law is presented which enables the system states to reach the sliding surface and consequently creates a sliding mode control. Finally, the performance of the proposed method is illustrated with examples and related numerical simulations results. © 2012 Springer-Verlag.
Seyed Javan D.,Ferdowsi University of Mashhad |
Rajabi Mashhadi H.,Ferdowsi University of Mashhad |
Rouhani M.,Islamic Azad University at Gonabad
International Journal of Electrical Power and Energy Systems | Year: 2013
Power system security is one of the major concerns in recent years due to the deregulation of power systems which are forced to operate under stressed operating conditions. This paper presents an enhanced radial basis function neural network (ERBFNN) and winner-take-all neural network (WTANN) to examine whether the power system is secure under steady-state operating conditions. Hidden layer units have been selected with the proposed algorithm which has the advantage of being able to automatically choose optimal unit centers and distances. The proposed approach to contingency analysis was found to be suitable for fast voltage and line-flow contingency screening. The generalization capability of the proposed method was able to identify unknown contingencies with large range of operating conditions and changes in network topology. A feature extraction technique based on class separability index and correlation coefficient has been employed to identify the inputs and dimensional reduction for the ERBFNN and WTANN networks. The advantages of this method are simplicity of algorithm and high accuracy in classification. Case studies with IEEE 14-bus, IEEE 30-bus and IEEE 118-bus power systems are used to illustrate the good performance of the proposed method. © 2012 Elsevier Ltd. All rights reserved.