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Jakarta, Indonesia

Ansarizadeh F.,Sahid University | Movahhedi M.,University of Yazd
Applied Computational Electromagnetics Society Journal | Year: 2013

In this paper, new unconditionally-stable meshless methods based on different split-step methods are proposed. Moreover, comparison of the phase velocities of two different split-step meshless methods and that of alternative-direction-implicit meshless (ADI-ML) method is presented. Here we show how employing split-step (SS) technique using radial point interpolation meshless (RPIM) method results in an unconditionally stable scheme. Symmetric operators and uniform splitting are utilized simultaneously to split the classical Maxwell's matrix into four and six submatrices. Also, for more accurate approximations Crank-Nicolson (CM) scheme that is a fully implicit scheme has been applied for implementation of these schemes. It has been demonstrated, these proposed methods produce even more effective unconditionally stable responses than those of alternating-direction-implicit meshless time-domain ADIMLTD methods. Eventually, in order to prove the advantage of the proposed method, a comparison has been made between these novel meshless methods and their finite-difference counterparts. More smoothed phase velocities in proposed meshless methods imply a reduction in dispersion error in comparison with their analogous cases in finite-difference time-domain (FDTD) method. © 2013 ACES. Source

Utami R.,Bogor Agricultural University | Utami R.,Sahid University | Wijaya C.H.,Bogor Agricultural University | Lioe H.N.,Bogor Agricultural University
International Journal of Food Properties | Year: 2016

Over-fermented tempe, known as tempe semangit, is popular in Indonesian culture, especially in Java, as an umami seasoning in traditional foods. The objective of this study was to characterize taste-active compounds in water soluble extracts of over-fermented tempe. Over-fermented tempe was prepared from fresh tempe in which the fermentation was prolonged (0 to 96 h). Free amino acids in the water soluble extract were analyzed and characterized for their taste activity values. Water soluble extracts contained umami and bitter tasting free amino acids at relatively high concentrations. Their umami and bitter taste activity values were higher than the taste threshold concentration. Water soluble extract from 72 h over-fermentation had a higher umami taste activity value than bitter taste activity, exhibiting the highest umami taste dilution factor. The high-performance liquid chromatography profile of water soluble extract fractions obtained using Sephadex G-25 gel filtration chromatography demonstrated that fractions having higher umami taste intensity had more hydrophilic components than hydrophobic components. Copyright © 2016 Taylor & Francis Group, LLC Source

Estabragh M.R.,Sahid University | Mohammadian M.,Sahid University | Shafiee M.,University of Tehran
Turkish Journal of Electrical Engineering and Computer Sciences | Year: 2012

This paper presents a newly developed approach to find the optimal location of distributed generations (DGs) to improve power system voltage stability margin and reduce losses incorporating the constraints. The loadability limit index is used to assess the static voltage stability security margin, which is associated with the point of voltage collapse limit. Based on this, a toolbox is developed to recognize the loadability margin in power networks. Finally, the mentioned problem is modeled as a nonlinear and multiobjective optimization problem. The proposed method establishes a tradeoff between the security index and power losses in DG placement using the hybrid particle swarm optimization (HPSO) algorithm method to reach the best performance and acceptable operation. The simulations are performed on IEEE 14- and IEEE 30-bus test systems to find the optimal location of the DGs. The results are compared with the particle swarm optimization (PSO) algorithm to ascertain the effectiveness. © TÜBITAK. Source

Rezaie Estabragh M.,Sahid University | Mohammadian M.,Sahid University
ICEE 2012 - 20th Iranian Conference on Electrical Engineering | Year: 2012

A novel approach to find optimal real power generation pattern will be introduced in this study. This has been achieved by maximizing the power system voltage stability margin and minimizing generation cost. The loadability limit index is used to assess static voltage stability security margin. Based on proposed algorithm, a Toolbox has been developed to recognize the loadability limit by using Lagrangian method. The mentioned problem has been modeled as a non-linear and multi objective optimization problem along with Hybrid Genetic Algorithm Particle Swarm Optimization (HGAPSO) method to reach the optimal generation pattern. The method has been performed as a hierarchical optimization problem. In the first stage, HGAPSO method has been used to reach the securest pattern of real power. Also, mentioned voltage stability toolbox has been executed to evaluate the voltage stability margin respectively each real power generation pattern during HGAPSO search. These simulations are performed on IEEE 30 bus test system. To validation of proposed method, obtained results have been compared with Particle Swarm Optimization (PSO) results. © 2012 IEEE. Source

Habibi M.R.,Kerman Graduate University of Technology | Rashidinejad M.,Sahid University | Zeinaddini-Meymand M.,Sahid University | Fadainejad R.,Kerman Graduate University of Technology
International Transactions on Electrical Energy Systems | Year: 2014

Transmission network expansion planning (TNEP) is one of the most important parts of power system studies. An optimal expansion of a transmission system should also capable of facilitating forecasted load patterns as well as future generation. Mathematically, TNEP is a mixed integer nonlinear programming as a non convex problem that can be solved by either conventional or heuristic optimization algorithms. This paper proposes a methodology for choosing the optimal transmission expansion plan considering less computational effort. The proposed methodology is composed from combination of Modified Scatter Search Algorithm and Constructive Heuristic Algorithm (CHA) considering New Load Shedding Index (NLSI). The proposed NLSI is implemented without generation rescheduling in order to decrease the number of linear programming obtaining an optimal solution. The algorithm is applied to different cases: Garver, 24-Bus IEEE systems and Southern Brazilian System of 46 Buses system. The simulation result shows a significant performance of the proposed method in comparison with some studies addressed in literature. © 2012 John Wiley & Sons, Ltd. Source

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