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Modulation of a trapezoidal signal: improving signal quality and reducing costs in power inverters

IET POWER ELECTRONICS 2017年第5期10卷 568-576页

作者： Juan Sotorrio-Ruiz, Pedro Sanchez-Pacheco, Francisco J. Perez-Hidalgo, Francisco M. Heredia-Larrubia, Juan Ramon Univ Malaga Elect Technol Dept Escuela Ingn C Dr Ortiz Ramos S-N Malaga Spain Univ Malaga Elect Engn Dept Escuela Ingn C Dr Ortiz Ramos S-N Malaga Spain

Power inverters applied in industries have seen a growth in modulation techniques over recent years. The aim of modulation techniques is to improve the quality of the inverter output signal and to reduce inverter losses. To improve an output signal, the amplitude of the fundamental frequency should be increased and the harmonics should be reduced. If a modulation technique can achieve these two objectives, a much smaller output filter is required to reduce hardware cost and filter losses. In this study, a technique is proposed where the obtained modulated signal can be directly used without the need of filtering. The resulting frequency profile fulfils the EN50160 standard, which sets the limits for harmonic components to ensure the quality in public low-voltage and medium-voltage power supplies. In addition, the proposed scheme requires a low computational algorithm allowing the use of low-cost microprocessors or Digital Signal Processor (DSPs). The proposed algorithm is based on a simple vector seed, making it possible to obtain all the patterns of Pulse Width Modulation (PWM).

关键词： PWM invertors cost reduction power harmonic filters power supply quality digital signal processing chips trapezoidal signal modulation signal quality improvement cost reduction power inverters inverter loss reduction filter losses hardware cost reduction frequency profile EN50160 standard harmonic components public low-voltage power supply quality public medium-voltage power supply quality computational algorithm low-cost microprocessors DSP PWM patterns

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algorithms for solving inverse problems in the optics of layered media based on comparing the extrema of spectral characteristics

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computational MATHEMATICS AND MATHEMATICAL PHYSICS 2017年第5期57卷 867-875页

作者： Isaev, T. F. Lukyanenko, D. V. Tikhonravov, A. V. Yagola, A. G. Moscow MV Lomonosov State Univ Fac Phys Moscow 119991 Russia Moscow MV Lomonosov State Univ Ctr Res Comp Moscow 119991 Russia

A new algorithm for determining the optical parameters of deposited multilayer optical coatings based on comparing the positions of the extrema of the optical characteristics of multilayer optical coatings is proposed. Two versions of this algorithm are compared. Using a series of numerical simulation experiments, the advantage of one of these versions is demonstrated. It is shown that this version decreases the influence of systematic errors in the spectral data.

关键词： inverse problems of optics spectral characteristics computational algorithm

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A Self-consistent Approach Applied to the Ferro and Antiferromagnetism of Nanotubes

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JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 2017年第9期30卷 2523-2534页

作者： Liu, Zhaosen Zhou, Ri-Gui Ian, Hou Nanjing Univ Informat Sci & Technol Dept Appl Phys Nanjing 210044 Jiangsu Peoples R China Univ Macau FST Inst Appl Phys & Mat Engn Macau Peoples R China UMacau Res Inst Zhuhai Guangdong Peoples R China Shanghai Maritime Univ Coll Informat Engn Shanghai 201306 Peoples R China

We employ a self-consistent simulation approach based on mean field theory to investigate the physical properties of both ferromagnetic and antiferromagnetic nanotubes. At the beginning, dipole-dipole interaction is neglected to facilitate theoretical analysis. Due to the geometric shape of the nanotubes and the magnetic uniaxial anisotropy, the spins are found always ordering parallel to the longitudinal axis of the nanotubes, no matter the external magnetic field is absent or applied along the axis, showing a typical ferromagnetic and antiferromagnetic characters. This peculiar feature allows us to build the one-dimensional magnetic chain models. Consequently, the results obtained with our theoretical models and numerical approach are exactly identical, manifesting the correctness of the new simulation approach. Finally, the dipole-dipole interaction is taken into account. It is very interesting to find that a very weak dipole-dipole interaction is able to make the spins align mainly along the longitudinal axis, though they tilt inwards or outwards slightly and symmetrically.

关键词： Magnetic nanotubes Quantum models Simulation computational algorithm

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Efficient computation of Laguerre polynomials

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COMPUTER PHYSICS COMMUNICATIONS 2017年 210卷 124-131页

作者： Gil, Amparo Segura, Javier Temme, Nico M. Univ Cantabria Dept Matemat Aplicada & Ciencias Comput E-39005 Santander Spain Univ Cantabria Dept Matemat Estadist & Comput E-39005 Santander Spain San Diego State Univ Dept Math & Stat 5500 Campanile Dr San Diego CA 92182 USA IAA NL-1825 BD Alkmaar 25 Netherlands CWI NL-1098 XG Amsterdam Netherlands

An efficient algorithm and a Fortran 90 module (LaguerrePol) for computing Laguerre polynomials L-n((alpha)) (z) are presented. The standard three-term recurrence relation satisfied by the polynomials and different types of asymptotic expansions valid for n large and a small, are used depending on the parameter region. Based on tests of contiguous relations in the parameter a and the degree n satisfied by the polynomials, we claim that a relative accuracy close to or better than 10(-12) can be obtained using the module LaguerrePol for computing the functions L-n((a))(z) in the parameter range z >= 0,-1 < alpha <= 5, n >= 0. Program summary Program Title: Module LaguerrePol Program Files doi: http://***/10.17632/3jkk659cn8.1 Licensing provisions: CC by 4.0 Programming language: Fortran 90 Nature of problem: Laguerre polynomials L-n((a))(z) appear in a vast number of applications in physics, such as quantum mechanics, plasma physics, etc. Solution method: The algorithm uses asymptotic expansions or recurrence relations for computing the function values depending on the range of parameters. Restrictions: The admissible input parameter ranges for computing the Laguerre L-n((a))(z) are z >= 0, -1 < alpha <= 5, n >= 0. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Laguerre polynomials computational algorithm Asymptotic expansions Recurrence relations

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Coupled elastoplasticity and plastic strain-induced phase transformation under high pressure and large strains: Formulation and application to BN sample compressed in a diamond anvil cell

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INTERNATIONAL JOURNAL OF PLASTICITY 2017年 96卷 156-181页

作者： Feng, Biao Levitas, Valery I. Iowa State Univ Dept Aerosp Engn Ames IA 50011 USA Los Alamos Natl Lab Los Alamos NM 87545 USA Iowa State Univ Dept Aerosp Engn Ames IA 50011 USA Iowa State Univ Dept Mech Engn Ames IA 50011 USA Iowa State Univ Dept Mat Sci & Engn Ames IA 50011 USA Ames Lab Div Mat Sci & Engn Ames IA 50011 USA

In order to study high-pressure phase transformations (PTs), high static pressure is produced by compressing a thin sample within a high strength gasket in a diamond anvil cell (DAC). However, since a PT occurs during plastic flow, it is classified and treated here as a plastic strain-induced PT. A thermodynamically consistent system of equations for combined plastic flow and plastic strain-induced PTs is formulated for large elastic, plastic, and transformation strains. The Murnaghan elasticity law, pressure-dependent J(2) plasticity (both dependent of the concentration of a high-pressure phase), and plastic strain-induced and pressure-dependent PT kinetics are utilized. A computational algorithm within finite element method (FEM) is presented and implemented in a user material subroutine (UMAT) in the FEM code ABAQUS. Combined plastic flow and strain-induced PT from the highly disordered hexagonal boron nitride (hBN) sample to a superhard wurtzitic wBN is simulated within the rhenium gasket for pressures up to 50 GPa. The evolution of the fields of stresses and plastic strains, as well as the concentration of phases in a sample is obtained and discussed in detail. Stress-strain fields in a gasket and diamond are presented as well. An unexpected shape of the deformed sample with almost complete PT in the external part of the sample that penetrated the gasket was found. Obtained results demonstrated the difference between material and system behavior which are often confused by experimentalists. Thus, while plastic strain-induced PT may start (and end) at plastic straining slightly above 6.7 GPa, it is not visible below 12 GPa. It becomes detectable at 21 GPa and is not completed everywhere in a sample even at a maximum pressure of 50 GPa. Due to a strong gasket the gradient of pressure is much smaller than the gradient of plastic strain, and therefore the distribution of the high pressure phase is mostly determined by the plastic strain field instead of the pressur

关键词： Large deformation Plasticity Plastic strain-induced phase transformation High pressure Diamond anvil cell computational algorithm

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SWPhylo - A Novel Tool for Phylogenomic Inferences by Comparison of Oligonucleotide Patterns and Integration of Genome-Based and Gene-Based Phylogenetic Trees

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EVOLUTIONARY BIOINFORMATICS 2018年第14期14卷 1176934318759299-1176934318759299页

作者： Yu, Xiaoyu Reva, Oleg N. Univ Pretoria Dept Biochem Ctr Bioinformat & Computat Biol Pretoria South Africa

Modern phylogenetic studies may benefit from the analysis of complete genome sequences of various microorganisms. Evolutionary inferences based on genome-scale analysis are believed to be more accurate than the gene-based alternative. However, the computational complexity of current phylogenomic procedures, inappropriateness of standard phylogenetic tools to process genome-wide data, and lack of reliable substitution models which correlates with alignment-free phylogenomic approaches deter microbiologists from using these opportunities. For example, the super-matrix and super-tree approaches of phylogenomics use multiple integrated genomic loci or individual gene-based trees to infer an overall consensus tree. However, these approaches potentially multiply errors of gene annotation and sequence alignment not mentioning the computational complexity and laboriousness of the methods. In this article, we demonstrate that the annotationand alignment-free comparison of genome-wide tetranucleotide frequencies, termed oligonucleotide usage patterns (OUPs), allowed a fast and reliable inference of phylogenetic trees. These were congruent to the corresponding whole genome super-matrix trees in terms of tree topology when compared with other known approaches including 16S ribosomal RNA and GyrA protein sequence comparison, complete genome-based MAUVE, and CVTree methods. A Web-based program to perform the alignment-free OUP-based phylogenomic inferences was implemented at http://***/. Applicabilityof the tool was tested on different taxa from subspecies to intergeneric levels. Distinguishing between closely related taxonomic units may be enforced by providing the program with alignments of marker protein sequences, eg, GyrA.

关键词： Phylogenomics oligonucleotide usage pattern evolutionary model bacterial evolution computational algorithm

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On the Numerical Analysis of Fan-Shaped Waves 6th

On the Numerical Analysis of Fan-Shaped Waves

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6th International Conference on Numerical Analysis and Applications (NAA)

作者： Tarasov, Boris G. Sadovskii, Vladimir M. Sadovskaya, Oxana V. Univ Western Australia Ctr Offshore Fdn Syst Stirling Highway 35 Perth WA 6009 Australia Inst Computat Modeling SB RAS Akademgorodok 50-44 Krasnoyarsk 660036 Russia

ISBN: (纸本)9783319570990;9783319570983

The fan-shaped mechanism of rotational motion transmission in a system of elastically bonded slabs on flat surface is studied. This mechanism governs the propagation of shear ruptures in super brittle rocks at stress conditions of seismogenic depths. The current paper analyzes a built laboratory physical model, which demonstrates the process of fan waves propagation. Equations of the dynamics of the fan-structure as a mechanical system with a finite number of degrees of freedom are obtained. computational algorithm, taking into account contact interaction of slabs, is worked out. The computations, showing the incomplete disclosure of fans with different opening angles due to fast or slow change in the velocity of rotation of the first slab, are performed. Comparison of the results of computations of length and velocity of a fan by means of a discrete model with laboratory measurements and observations shows good correspondence between the results.

关键词： Shear rupture Fan-shaped wave Discrete model Lagrange equations computational algorithm

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A new method to measure complexity in binary or weighted networks and applications to functional connectivity in the human brain

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BMC BIOINFORMATICS 2016年第1期17卷 1-18页

作者： Hahn, Klaus Massopust, Peter R. Prigarin, Sergei HMGU German Res Ctr Environm Hlth Inst Computat Biol Ingolstadter Landstr 1 D-85764 Neuherberg Germany Tech Univ Munich Ctr Math Res Unit M6 D-85747 Garching Germany Novosibirsk State Univ Inst Computat Math & Math Geophys Siberian Branch Russian Acad Sci Novosibirsk 630090 Russia

Background: Networks or graphs play an important role in the biological sciences. Protein interaction networks and metabolic networks support the understanding of basic cellular mechanisms. In the human brain, networks of functional or structural connectivity model the information-flow between cortex regions. In this context, measures of network properties are needed. We propose a new measure, Ndim, estimating the complexity of arbitrary networks. This measure is based on a fractal dimension, which is similar to recently introduced box-covering dimensions. However, box-covering dimensions are only applicable to fractal networks. The construction of these network-dimensions relies on concepts proposed to measure fractality or complexity of irregular sets in R-n. Results: The network measure Ndim grows with the proliferation of increasing network connectivity and is essentially determined by the cardinality of a maximum k-clique, where k is the characteristic path length of the network. Numerical applications to lattice-graphs and to fractal and non-fractal graph models, together with formal proofs show, that Ndim estimates a dimension of complexity for arbitrary graphs. Box-covering dimensions for fractal graphs rely on a linear log-log plot of minimum numbers of covering subgraph boxes versus the box sizes. We demonstrate the affinity between Ndim and the fractal box-covering dimensions but also that Ndim extends the concept of a fractal dimension to networks with non-linear log-log plots. Comparisons of Ndim with topological measures of complexity ( cost and efficiency) show that Ndim has larger informative power. Three different methods to apply Ndim to weighted networks are finally presented and exemplified by comparisons of functional brain connectivity of healthy and depressed subjects. Conclusion: We introduce a new measure of complexity for networks. We show that Ndim has the properties of a dimension and overcomes several limitations of presently used topolo

关键词： Network analysis Complexity measure computational algorithm Fractal dimension Human brain application Functional connectivity

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Analysis and computation of the stationary distribution in a special class of Markov chains of level-dependent M/G/1-type and its application to BMAP/M/∞ and BMAP/M/c plus M queues

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QUEUEING SYSTEMS 2016年第1-2期84卷 49-77页

作者： Takine, Tetsuya Osaka Univ Grad Sch Engn Dept Informat & Commun Technol Suita Osaka 5650871 Japan

This paper considers a special class of continuous-time Markov chains of level-dependent M/G/1-type, where block matrices representing downward jumps in the infinitesimal generator are nonsingular. This special class naturally arises in the analysis of BMAP/M/infinity queues and BMAP/M/c queues with exponential impatience times (BMAP/M/c+M). We first formulate the boundary probability vector in terms of a solution of a system of infinitely many linear inequalities. We then reveal that in the above special class, this infinite system is regarded as a nested sequence of simplices, and we identify their vertices. Based on these results, we develop a simple yet efficient computational algorithm for the stationary distribution conditioned that the level is not greater than a predefined N. Note that for a large N, the conditional distribution will provide a good approximation to the stationary distribution. Some numerical examples for BMAP/M/infinity and BMAP/M/c+M queues are shown.

关键词： Markov chain of M/G/1-type Level dependence Stationary distribution computational algorithm BMAP/M/infinity BMAP/M/c plus M

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Effects of external magnetic field and magnetic anisotropy on chiral spin structures of square nanodisks investigated with a quantum simulation approach

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SUPERLATTICES AND MICROSTRUCTURES 2016年 92卷 174-180页

作者： Liu, Zhaosen Ian, Hou Nanjing Univ Informat Sci & Technol Dept Appl Phys Nanjing 210044 Jiangsu Peoples R China Univ Macau FST Inst Appl Phys & Mat Engn Macau Peoples R China

We employed a quantum simulation approach to investigate the magnetic properties of monolayer square nanodisks with Dzyaloshinsky-Moriya (DM) interaction. The computational program converged very quickly, and generated chiral spin structures on the disk planes with good symmetry. When the DM interaction is sufficiently strong, multi-domain structures appears, their sizes or average distance between each pair of domains can be approximately described by a modified grid theory. We further found that the external magnetic field and uniaxial magnetic anisotropy both normal to the disk plane lead to reductions of the total free energy and total energy of the nanosystems, thus are able to stabilize and/or induce the vortical structures, however, the chirality of the vortex is still determined by the sign of the DM interaction parameter. Moreover, the geometric shape of the nanodisk affects the spin configuration on the disk plane as well. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Dzyaloshinsky-Moriya interaction Magnetic vortex computational algorithm Quantum theory

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