A Novel Eigenvalue Algorithm for the Complex Band Structure and Eigenmodes of Plasmonic Crystals

published_or_final_versio

Optimized operator-splitting methods in numerical integration of Maxwell's equations

Optimized operator splitting methods for numerical integration of the time domain Maxwell's equations in computational electromagnetics (CEM) are proposed for the first time. The methods are based on splitting the time domain evolution operator of Maxwell's equations into suboperators, and corresponding time coefficients are obtained by reducing the norm of truncation terms to a minimum. The general high-order staggered finite difference is introduced for discretizing the three-dimensional curl operator in the spatial domain. The detail of the schemes and explicit iterated formulas are also included. Furthermore, new high-order Padé approximations are adopted to improve the efficiency of the proposed methods. Theoretical proof of the stability is also included. Numerical results are presented to demonstrate the effectiveness and efficiency of the schemes. It is found that the optimized schemes with coarse discretized grid and large Courant-Friedrichs-Lewy (CFL) number can obtain satisfactory numerical results, which in turn proves to be a promising method, with advantages of high accuracy, low computational resources and facility of large domain and long-time simulation. In addition, due to the generality, our optimized schemes can be extended to other science and engineering areas directly. © 2012 Z. X. Huang et al.published_or_final_versio

Fast computation of radar cross-section by fast multipole method in conjunction with lifting wavelet-like transform

The fast multipole method (FMM) in conjunction with the lifting wavelet-like transform scheme is proposed for the scattering analysis of differently shaped three-dimensional perfectly electrical conducting objects. As a flexible and efficient matrix compression technique, the proposed method can sparsify the aggregation matrix and disaggregation matrix in real time with compression ratio about 30%. The computational complexity and choice of proper wavelet are also discussed. Numerical simulation and complexity analysis have shown that the proposed method can speed up the aggregation and disaggregation steps of the FMM with lower memory requirements. © 2010 The Institution of Engineering and Technology.postprin

Adaptive frequency sweep analysis for electromagnetic problems using the Thiele interpolating continued fractions

A direct rational approximation method based on Thiele interpolating continued fractions theory is proposed for fast frequency sweep analysis of electromagnetic problems. And an adaptive algorithm is also formed. Compared with the conventional rational approximation method, the proposed method can get a rational approximation directly without a great number of matrix inverse computations and doesn't need to allocate much memory for high derivatives of the dense impedance matrix. Meanwhile, the computation of surface currents by continued fractions can be sped up as compared with the traditional rational approximation. Numerical simulations for broad band scattering analysis of different shaped objects are discussed to shown the effectiveness of the present method. © 2010 IEEE.published_or_final_versionThe 2nd International Conference on Education Technology and Computer (ICETC 2010), Shanghai, China, 22-24 June 2010. In Proceedings of 2nd ICETC, 2010, v. 5, p. 126-12

Excitonic quantum confinement modified optical conductivity of monolayer and few-layered MoS2

2016-2017 > Academic research: refereed > Publication in refereed journal201804_a bcmaVersion of RecordPublishe

Flexible and Accurate Simulation of Radiation Cooling with FETD Method

Thermal management and simulation are becoming increasingly important in many areas of engineering applications. There are three cooling routes for thermal management, namely thermal conduction, thermal convection and thermal radiation, among which the first two approaches have been widely studied and applied, while the radiation cooling has not yet attracted much attention in terrestrial environment because it usually contributes less to the total amount of thermal dissipation. Thus the simulation method for radiation cooling was also seldom noticed. The traditional way to simulate the radiation cooling is to solve the thermal conduction equation with an approximate radiation boundary condition, which neglects the wavelength and angular dependence of the emissivity of the object surface. In this paper, we combine the heat conduction equation with a rigorous radiation boundary condition discretized by the finite-element time-domain method to simulate the radiation cooling accurately and flexibly. Numerical results are given to demonstrate the accuracy, flexibilities and potential applications of the proposed method. The proposed numerical model can provide a powerful tool to gain deep physical insight and optimize the physical design of radiation cooling

Supercapacitor and supercapattery as emerging electrochemical energy stores

This article reviews critically selected recent literature on electrochemical energy storage (EES) technologies, focusing on supercapacitor and also supercapattery which is a generic term for various hybrid devices combining the merits of rechargeable battery and supercapacitor. Fundamentals of EES are explained, aiming at clarification of some literature confusions such as the differences between capacitive and non-capacitive Faradaic charge storage mechanisms, and between cathode and positive electrode (positrode), and between anode and negative electrode (negatrode). In particular, the concept and origin of pseudocapacitance are qualitatively correlated with the band model for semiconductors. Strategies for design and construction of supercapattery are discussed in terms of both the materials structures and device engineering. Selection of materials, including electrolytes, is another topic reviewed selectively. Graphenes and carbon nanotubes are the favourable choice to composite with both capacitive and non-capacitive redox materials for improved kinetics of charge storage processes and charge-discharge cycling stability. Organoaqueous electrolytes show a great potential to enable EES to work at sub-zero temperatures, whilst solid ion conducting membranes and ionic liquids can help develop high voltage (> 4.0 V) and hence high energy supercapatteries

Influence of reconstruction on the structure of self-assembled normal-alkane monolayers on Au(111) surfaces

Ordered normal-alkane monolayers of lamellar structures are found to form in the interface between alkane solutions and the reconstructed Au (111) surfaces. The boundaries of the lamellae may exhibit a zigzag shape. In the alkane monolayers, two kinds of packing of the alkane molecules are observed. The packing patterns are correlated to the structure of the gold surface and the molecular lengths of the alkanes. The orientation of alkane molecules is gently disturbed by the reconstructed gold ridges. Furthermore, the lamellar boundaries are located on the elbow positions of the reconstructed gold surfaces for long-chain alkanes. These results demonstrate that the structures of self-assembled monolayers of normal alkanes are sensitive to the structures of the Au (111) surfaces

Momentum-resolved resonant inelastic soft X-ray scattering (qRIXS) endstation at the ALS

A momentum resolved resonant inelastic X-ray scattering (qRIXS) experimental station with continuously rotatable spectrometers and parallel detection is designed to operate at different beamlines at synchrotron and free electron laser (FEL) facilities. This endstation, currently located at the Advanced Light Source (ALS), has five emission ports on the experimental chamber for mounting the high-throughput modular soft X-ray spectrometers (MXS) [24]. Coupled to the rotation from the supporting hexapod, the scattered X-rays from 27.5° (forward scattering) to 152.5° (backward scattering) relative to the incident photon beam can be recorded, enabling the momentum-resolved RIXS spectroscopy. The components of this endstation are described in details, and the preliminary RIXS measurements on highly oriented pyrolytic graphite (HOPG) reveal the low energy vibronic excitations from the strong electron-phonon coupling at C K edge around σ* band. The grating upgrade option to enhance the performance at low photon energies is presented and the potential of this spectroscopy is discussed in summary