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Time Domain Simulation (time + domain_simulation)
Selected AbstractsBandgap properties of low-index contrast aperiodically ordered photonic quasicrystalsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2009Gianluigi Zito Abstract We numerically analyze, using Finite Difference Time Domain simulations, the bandgap properties of photonic quasicrystals with a low-index contrast. We compared 8-, 10-, and 12-fold symmetry aperiodically ordered lattices with different spatial tiling. Our results show that tiling design, more than symmetry, determines the transmission properties of these structures. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2732,2737, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24724 [source] Analyzing dynamic performance of stressed power systems in vicinity of instability by modal series methodEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 8 2009Ali H. Naghshbandy Abstract Highly stressed power systems exhibit complex dynamic behaviors such as inter-area oscillations when subjected to large disturbances. In such conditions, nonlinear effects have dominant role in determining dynamic response of the systems. In this paper by using modal series method, dynamic behaviors of the stressed power systems in severe conditions and near instability have been studied. Also two measures, mode dominance measure (MDM) and most perturbed machine factor (MPF) have been introduced. They determine the most dominant modes and identify the most perturbed generators when the system is subjected to a given fault. Contribution factors have been used to show the links between identified modes and machines from the analysis. Time domain simulation has been helped for validation of the results. By using similarity transformation, state variables have been represented in modal space and utilized to check the results. The studies are carried out on the IEEE 50-generator test system which demonstrates a wide range of dynamic characteristics at different loading levels and fault scenarios. Copyright © 2008 John Wiley & Sons, Ltd. [source] Proper Splitting of Interconnected Power SystemsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2010S. Najafi Non-member Abstract Power system islanding is the last defense line to protect power grids from incidence of wide-area blackout. As a wide-area control action, power system splitting is a comprehensive decision making problem that includes different subproblems. This paper introduces a novel approach for separation of the entire power system into several stable islands in different loading levels. The proposed method combines both the dynamic and the static characteristics of interconnected power network and determines the proper splitting schemes. The presented algorithm searches for proper islanding strategy in the boundary of primary determined coherent machines using Krylov subspace method and finds the proper splitting points by transferring some of the buses in one island to another island such that total load shedding is minimized. A spanning tree-based depth first search algorithm is used to find all possible combination of transferred buses. The presented method reduces the huge initial search space of islanding strategy considering dynamic characteristics of integrated power system and reduction of search space to only boundary network. The speed of the proposed algorithm is remarkably high and can be applied for islanding the power system in real-time. The presented algorithm is applied to IEEE 118 BUS test system. Results show the robustness, effectiveness, and capability of the algorithm to determine fast and accurate proper islanding strategy. Time domain simulation of the islanding strategies confirms that all the islands which are specified by the proposed method are stable. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Use of Reversal Nanoimprinting of Nanoparticles to Prepare Flexible Waveguide Sensors Exhibiting Enhanced Scattering of the Surface Plasmon ResonanceADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Dehui Wan Abstract A flexible surface plasmon resonance (SPR)-based scattering waveguide sensor is prepared by directly imprinting hollow gold nanoparticles (NPs) and solid gold NPs onto flexible polycarbonate (PC) plates,without any surface modification,using a modified reversal nanoimprint lithography technology. Controlling the imprinting conditions, including temperature and pressure, allows for the fine adjustment of the depths of the embedded metal NPs and their SPR properties. This patterning approach exhibits a resolution down to the submicrometer level. A 3D finite-difference time domain simulation is used to examine the optical behavior of light propagating parallel to the air/substrate interface within the near-field regime. Consistent with the simulations, almost an order of magnitude enhancement in the scattering signal after transferring the metal NPs from the glass mold to the PC substrate is obtained experimentally. The enhanced signal is attributed to the particles' strong scattering of the guiding-mode waves (within the waveguide) and the evanescent wave (above the waveguide) simultaneously. Finally, the imprinting conditions are optimized to obtain a strongly scattering bio/chemical waveguide sensor. [source] Tailored Plasmonic Gratings for Enhanced Fluorescence Detection and Microscopic ImagingADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Xiaoqiang Cui Abstract The ability to precisely control the pattern of metallic structures at the micro- and nanoscale for surface plasmon coupling has been demonstrated to be essential for signal enhancement in fields such as fluorescence and surface-enhanced Raman scattering. In the present study, a series of silver coated gratings with tailored duty ratio and depth and a periodical pitch of 400,nm are designed and implemented. The influence of the grating profile on plasmonic properties and the corresponding enhancement factor are investigated by angular scanning measurement of reflectivity and fluorescence intensity and by finite difference time domain simulation. The application of the substrate in the enhanced fluorescence imaging detection of labeled protein is also investigated. This substrate has a wide range of potential applications in areas including biodiagnostics, imaging, sensing, and photovoltaic cells. [source] A global time domain circuit simulation of a microwave rectennaINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1-2 2007Brahim Essakhi Abstract The paper presents a global time domain simulation of a microwave rectenna studied for wireless energy transfer. The novelty of the work is to take into account both distributed electromagnetic parts of the antenna and the rectifier circuit including lumped elements. From a 3D finite element time domain electromagnetic modelling of the structure an equivalent circuit of the antenna is deduced: the input impedance is obtained as a function of frequency over a broad band. Then a rational approximation gives a corresponding PSPICE representation. The electromotive force induced between the ports of the antenna during the microwave illumination is directly computed from the 3D transient scattering problem. The resulting equivalent circuit of the antenna is finally incorporated into the electronic simulator PSPICE, together with the lumped components of the rectenna (ideal diodes and load). Thus a global non-linear time domain analysis of the whole structure becomes available. The results obtained with the methods presented in the paper are compared with those resulting from other techniques. The approach developed in the work could efficiently improve the design stage of rectennas devoted to microwave power transfer. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||