In recent years, power system islanding is considered as the last resort to prevent network instability. The purpose of controlled islanding is to establish self-sustaining electrical islands to prevent a blackout and lead to ease of restoration. In this regard, an appropriate decision-making algorithm is required to determine the best separation points in a short time. This paper proposes a novel methodology by developing the hierarchical Spectral clustering algorithm. This method is computationally very efficient and determines an islanding solution with minimal power flow disruption while ensuring that each island contains only coherent generators. The proposed method also enables operators to constrain any branch to be excluded from the islanding solution. The method is tested using the models of the IEEE 39 and IEEE 118-bus test systems and comparative analysis with existing methods have been performed. The simulation results demonstrate that the methodology is more efficient than another existing approach and could be utilized in the real-time application of the power grid.

Plasma impurities are one of the loss factors of confined energy in tokamaks, so from this regard their study in order to maintain the stability of tokamak plasma and improve the confinement quality is essential. In this research, in order to study the impurities of Damavand tokamak plasma, a monochromator along with a Line Scan CCD array in the assembly of a visible light spectrometer was used. The modified spectrometer system was calibrated by the characteristic wavelengths of a mercury-vapor lamp and was used in the normal plasma regime of Damavand tokamak to record and analyze the radiation in the wavelength range of 3000-7000A°, . The finest instrumental resolution of the spectrometer was about 0. 9A°,at entrance slit width of 50μ, m, which was used for intensive hydrogen plasma radiation lines such as Hα,and Hβ, . To study the radiation from the impurities, due to their low intensity, the entrance slit width of 100 μ, m and the resolution of 1. 8A°,were selected. The results showed that the predominant impurities in Damavand tokamak plasma are oxygen, nitrogen and carbon, which are generally originated from air molecules trapped in the wall of the vacuum chamber and the plasma facing components, also iron impurities are produced as a result of hot plasma interaction with the limiter and other components inside the vacuum chamber.

The paper presents a Fast Fourier Transform (FFT) based power Spectral Density (PSD) filter for denoising the PMU signal received from the smart power system network to identify the low frequency Oscillation modes (LFO). Small disturbances are introduced during normal operation of power system causes low frequency oscillations and may hinder the power system transfer capabilities of a system. The traditional signal processing method cannot extract the information from ambient signals effectively during noisy measurement. In this paper, the performance of the Prony analysis with reduced sampling rate is analysed for the PMU data with noiseless and noise environment. It is observed that, the performance of the Prony approach is not satisfactory under noisy measurement data.  In the present work FFT-PSD is used to denoise the noisy measurement signal and identify the nature of the decrement factor of the low frequency oscillatory modes. The accuracy of the estimated decrement factors of modes are verified with eigenvalues to validate the proposed method. The performance of proposed method is compared with signal processing method for IEEE New England power system and found effective and suitable during noisy PMU measurements.

In this paper, a novel risk-based, two-objective (technical and economical) optimal reactive power dispatch method in a wind-integrated power system is proposed which is more consistent with operational criteria.  The technical objective includes the minimization of the new voltage instability risk index. The economical objective includes cost minimization of reactive power generation and active power loss. The proposed voltage instability risk employs a hybrid possibilistic (Delphi-Fuzzy)-probabilistic approach that takes into consideration the operator’s experience, the wind speed and demand forecast uncertainties when quantifying the risk index. The decision variables are the reactive power resources of the system. To solve the problem, the modified multi-objective particle swarm optimization algorithm with sine and cosine acceleration coefficients is utilized. The method is implemented on the modified IEEE 30-bus system. The proposed method is compared with those in the previously published literature, and the results confirm that the proposed risk index is better at estimating the voltage instability risk of the system, especially in cases with severe impact and low probability. In addition, according to the simulation results compared to typical security-based planning, the proposed risk-based planning may increase the security and economy of the system due to better utilization of system resources.

DC microgrids have gained extensive attention in the recent years. In the islanded mode of operation power sharing between sources is required. The power sharing usually is provided by employing P-V droop characteristics while the voltage local property results in power sharing error. In this paper two decentralized approaches for resolving power sharing error are studied and compared. In the first approach, sources employ proper virtual resistance. In second approach, droop characteristics are realized in the Point of Common Coupling (PCC). It is shown that by using second approach, the voltage drop is reduced and equally the voltage quality is improved. It is discussed that the reason is bypassing the voltage drop associated with the sources output resistance in the second approach. Time domain simulations of a test DC microgrid are provided to verify the results.

This paper describes the power Spectral density matrix of manipulator tip displacement to stochastic excitation of the base. The dynamic equations for an articulated manipulator subjected to a vertically stochastic excitation are derived by Lagrangian method. Then the equations are linearized with respect to a small displacement in a fixed configuration.Sensitivity of the power Spectral density of tip motion to the manipulator configuration and structural damping are investigated. Finally, simulation results are presented for a 2R Planner robot manipulator under vertical base excitation

Introduction: Lead intoxication in children has been associated with neurodevelopment disabilities that may result in motor and cognitive impairment. The aim of the present study is to evaluate in long term effects of prenatal exposure to low-level Pb2+ on learning, memory and EEG.Materials & Methods: Rat pregnant were exposed to distilled water or=0.05, 0.1, 0.2% of Pb-acetate in the drinking water during of pregnancy. Behavioral analysis was carried out in male offspring by using one way active avoidance. The numbers of electric shock was detected as an index of learning and memory of rats. At 60 days of age (active avoidance learning) and at 90 days of age (memory) behavioral assessment was measured. Then the rats were implanted with electrodes in sensorimotor regain. After a recovery period, EEG was also recorded.Findings: Lead acetate was no affected on learning but dose of 0.1% which was affected on memory of rats (No. of shocks 5.185±0.98%) compared to the control (No. of, shocks 1.667± 0.62%). This finding also showed that lead acetate (p<0.05) only decreases of memory ability.Except an increase in the delta waves, there was no any statistical significant on EEG Spectral power between test and control groups.Conclusion: In this research the lead acetate was no affected on EEG. The results showed that using dose of 0.1% lead acetate was affected on behavior and decrease of memory ability of tested rats.

Background: Standing on an unstable platform needs more effort from neuro-musculoskeletal system. This study was about to highlight the joint regulations in keeping balance, while standing on an unstable platform using Spectral analysis. Methods: Thirteen healthy young males were participated in this cross-sectional study to stand on an unstable platform with two levels of support stiffness, two visual, and three cognitive dual-task conditions. Motion analysis was utilized to measure postural regulations at the lower extremity joints. power Spectral analysis was applied on the joint rotations to discriminate the joint behaviors in different standing conditions. Results: Results showed that the body used higher levels of postural adjustment by more joint regulations as the standing conditions became more difficult. Support stiffness of the platform and vision were effective in keeping balance (P<0. 05), while the dual cognitive tasks had no significant effect (P>0. 05). In simpler standing conditions, the ankle-hip strategy was responsible for body stabilization in lower frequencies. However, increasing the standing difficulty by eliminating the vision or use of looser support of the platform was led to the predominance of ankle strategy. Conclusion: Standing in different conditions prevailingly relied on the ankle strategy. The enhancement of postural difficulty may revert to dominantly use the ankle strategy.

Topological indices are graph invariants most suitable for underlined structures of chemical compounds. Most of the topological indices are defined on the well-known graph concepts such as degree of a vertex, distances, eccentricity of a vertex etc. In this paper, new type of degree of a vertex is defined with the aid of resolving property of the graph as the minimum cardinality of a resolving set containing that vertex. The mathematical properties of this newly defined degree is established with the help of standard graphs and an attempt to analyze its applicability in chemical compounds are carried by taking silicate structures.