Can Electron Propagator Methods Be Used To Improve Polarization Propagator Methods?
DEFF Research Database (Denmark)
Jensen, Hans Jørgen Aagaard
2008-01-01
Calculations of Rydberg excitation energies with the second-order polarization propagator approximation (SOPPA) often produce results which are more in error than the random phase approximation (RPA), which formally is the first-order model. This is obviously because of cancellation of errors...... at the RPA level. On the other hand, valence excitation energies behave as expected, and they are systematically improved in SOPPA compared to RPA. Note that a Rydberg series is related to one of the ionization thresholds of the molecule, and it is thus obvious that a good description of the ionization...
Sagawara, H
1999-01-01
A simulation technique for the analysis of the transverse evolution of electron swarms in gases was developed based on moment equations derived from the Boltzmann equation. A numerical calculation of the moment equations for an electron swarm was performed using a propagator method and it was demonstrated that the propagator method can be used to calculate the higher-order transverse diffusion coefficients stably. Applying a Hermite expansion technique, the electron distribution in real space and other electron swarm parameters were derived as functions of the transverse position. The calculation result was verified by comparisons with those by a Monte Carlo simulation and other methods. Features of the transverse electron swarm evolution were presented. (author)
Corzo, H. H.; Velasco, A. M.; Lavín, C.; Ortiz, J. V.
2018-02-01
Vertical excitation energies belonging to several Rydberg series of MgH have been inferred from 3+ electron-propagator calculations of the electron affinities of MgH+ and are in close agreement with experiment. Many electronically excited states with n > 3 are reported for the first time and new insight is given on the assignment of several Rydberg series. Valence and Rydberg excited states of MgH are distinguished respectively by high and low pole strengths corresponding to Dyson orbitals of electron attachment to the cation. By applying the Molecular Quantum Defect Orbital method, oscillator strengths for electronic transitions involving Rydberg states also have been determined.
Observations of Obliquely Propagating Electron Bernstein Waves
DEFF Research Database (Denmark)
Armstrong, R. J.; Juul Rasmussen, Jens; Stenzel, R. L.
1981-01-01
Plane electron Bernstein waves propagating obliquely to the magnetic field are investigated. The waves are excited by a plane grid antenna in a large volume magnetoplasma. The observations compare favorably with the predictions of the linear dispersion relation.......Plane electron Bernstein waves propagating obliquely to the magnetic field are investigated. The waves are excited by a plane grid antenna in a large volume magnetoplasma. The observations compare favorably with the predictions of the linear dispersion relation....
International Nuclear Information System (INIS)
Abdolsalami, F.; Abdolsalami, M.; Perez, L.; Gomez, P.
1995-01-01
The authors have applied the finite-element method to electron-molecule collision with the exchange effect implemented rigorously. All the calculations are done in the body-frame within the fixed-nuclei approximation, where the exact treatment of exchange as a nonlocal effect results in a set of coupled integro-differential equations. The method is applied to e-H 2 and e-N 2 scatterings and the cross sections obtained are in very good agreement with the corresponding results the authors have generated from the linear-algebraic approach. This confirms the significant difference observed between their results generated by linear-algebraic method and the previously published e-N 2 cross sections. Their studies show that the finite-element method is clearly superior to the linear-algebraic approach in both memory usage and CPU time especially for large systems such as e-N 2 . The system coefficient matrix obtained from the finite-element method is often sparse and smaller in size by a factor of 12 to 16, compared to the linear-algebraic technique. Moreover, the CPU time required to obtain stable results with the finite-element method is significantly smaller than the linear-algebraic approach for one incident electron energy. The usage of computer resources in the finite-element method can even be reduced much further when (1) scattering calculations involving multiple electron energies are performed in one computer run and (2) exchange, which is a short range effect, is approximated by a sparse matrix. 17 refs., 7 figs., 5 tabs
Efficient Solution of the Electronic Eigenvalue Problem Using Wavepacket Propagation.
Neville, Simon P; Schuurman, Michael S
2018-02-15
We report how imaginary time wavepacket propagation may be used to efficiently calculate the lowest-lying eigenstates of the electronic Hamiltonian. This approach, known as the relaxation method in the quantum dynamics community, represents a fundamentally different approach to the solution of the electronic eigenvalue problem in comparison to traditional iterative subspace diagonalization schemes such as the Davidson and Lanczos methods. In order to render the relaxation method computationally competitive with existing iterative subspace methods, an extended short iterative Lanczos wavepacket propagation scheme is proposed and implemented. In the examples presented here, we show that by using an efficient wavepacket propagation algorithm the relaxation method is, at worst, as computationally expensive as the commonly used block Davidson-Liu algorithm, and in certain cases, significantly less so.
Intense relativistic electron beam: generation and propagation
International Nuclear Information System (INIS)
Mittal, K.C.; Mondal, J.
2010-01-01
A general review of relativistic electron beam extracted from explosive field emission diode has been presented here. The beam current in the diode gap taking into account cathode and anode plasma expansion velocity and excluding the self magnetic field effect is directly proportional to gap voltage V 3/2 and inversely proportional to the square of the effective diode gap (d-vt). In the limit of high current, self magnetic field focusing effect comes into play and results in a critical current at which pinching will take place. When the diode current exceeds the critical current, the electron flow is in the para-potential regime. Different diode geometries such as planner, coaxial, rod-pinched, reflex triode are discussed qualitatively. When the beam is injected into a vacuum drift tube the propagation of the beam is only possible in presence of a strong axial magnetic field which prevents the beam expansion in the radial direction. If the beam is injected in the drift tube filled with dense plasma, then the redistribution of the plasma electrons effectively neutralizes the beam space charge, resulting subsequent propagation of the beam along the drift tube. The beam propagation through neutral gas is similar to the plasma filled drift tube. In this case both the neutral gas pressure and the beam current regulate the transmission of the REB. (author)
Method and apparatus for charged particle propagation
Hershcovitch, A.
1996-11-26
A method and apparatus are provided for propagating charged particles from a vacuum to a higher pressure region. A generator includes an evacuated chamber having a gun for discharging a beam of charged particles such as an electron beam or ion beam. The beam is discharged through a beam exit in the chamber into a higher pressure region. A plasma interface is disposed at the beam exit and includes a plasma channel for bounding a plasma maintainable between a cathode and an anode disposed at opposite ends thereof. The plasma channel is coaxially aligned with the beam exit for propagating the beam from the chamber, through the plasma, and into the higher pressure region. The plasma is effective for pumping down the beam exit for preventing pressure increase in the chamber and provides magnetic focusing of the beam discharged into the higher pressure region 24. 7 figs.
Electron Beam Propagation in a Plasma
Directory of Open Access Journals (Sweden)
Kyoung W. Min
1988-06-01
Full Text Available Electron beam propagation in a fully ionized plasma has been studied using a one-dimensional particle simulation model. We compare the results of electrostatic simulations to those of electromagnetic simulations. The electrostatic results show the essential features of beam-plasma instability which accelerates ambient plasmas. The results also show the heating of ambient plasmas and the trapping of plasmas due to the locally generated electric field. The level of the radiation generated by the same non-relativistic beam is slightly higher than the noise level. We discuss the results in context of the heating of coronal plasma during solar flares.
Propagating Class and Method Combination
DEFF Research Database (Denmark)
Ernst, Erik
1999-01-01
number of implicit combinations. For example, it is possible to specify separate aspects of a family of classes, and then combine several aspects into a full-fledged class family. The combination expressions would explicitly combine whole-family aspects, and by propagation implicitly combine the aspects...
Modeling paraxial wave propagation in free-electron laser oscillators
Karssenberg, J.G.; van der Slot, Petrus J.M.; Volokhine, I.; Verschuur, Jeroen W.J.; Boller, Klaus J.
2006-01-01
Modeling free-electron laser (FEL) oscillators requires calculation of both the light-beam interaction within the undulator and the light propagation outside the undulator. We have developed a paraxial optical propagation code that can be combined with various existing models of gain media, for
Wave propagation retrieval method for chiral metamaterials
DEFF Research Database (Denmark)
Andryieuski, Andrei; Malureanu, Radu; Lavrinenko, Andrei
2010-01-01
In this paper we present the wave propagation method for the retrieving of effective properties of media with circularly polarized eigenwaves, in particularly for chiral metamaterials. The method is applied for thick slabs and provides bulk effective parameters. Its strong sides are the absence...... of artificial branches of the refractive index and simplicity in implementation. We prove the validity of the method on three case studies of homogeneous magnetized plasma, bi-cross and U-shaped metamaterials....
Pulsed electron beam propagation in argon and nitrogen gas mixture
Kholodnaya, G. E.; Sazonov, R. V.; Ponomarev, D. V.; Remnev, G. E.; Zhirkov, I. S.
2015-10-01
The paper presents the results of current measurements for the electron beam, propagating inside a drift tube filled in with a gas mixture (Ar and N2). The experiments were performed using the TEA-500 pulsed electron accelerator. The main characteristics of electron beam were as follows: 60 ns pulse duration, up to 200 J energy, and 5 cm diameter. The electron beam propagated inside the drift tube assembled of three sections. Gas pressures inside the drift tube were 760 ± 3, 300 ± 3, and 50 ± 1 Torr. The studies were performed in argon, nitrogen, and their mixtures of 33%, 50%, and 66% volume concentrations, respectively.
Propagation and oblique collision of electron-acoustic solitons in ...
Indian Academy of Sciences (India)
temperature-electron (2Te) plasmas (plasmas populated with two different electron species) ... plasmas [22–24]. The propagation of ion acoustic solitary waves (IASWs) in quantum 2Te plasma has been recently studied in refs [25,26]. However, to the best ..... Thus, their coefficients must vanish to eliminate the secularities.
Ab initio electron propagator theory of molecular wires. I. Formalism.
Dahnovsky, Yu; Zakrzewski, V G; Kletsov, A; Ortiz, J V
2005-11-08
Ab initio electron propagator methodology may be applied to the calculation of electrical current through a molecular wire. A new theoretical approach is developed for the calculation of the retarded and advanced Green functions in terms of the electron propagator matrix for the bridge molecule. The calculation of the current requires integration in a complex half plane for a trace that involves terminal and Green's-function matrices. Because the Green's-function matrices have complex poles represented by matrices, a special scheme is developed to express these "matrix poles" in terms of ordinary poles. An expression for the current is derived for a terminal matrix of arbitrary rank. For a single terminal orbital, the analytical expression for the current is given in terms of pole strengths, poles, and terminal matrix elements of the electron propagator. It is shown that Dyson orbitals with high pole strengths and overlaps with terminal orbitals are most responsible for the conduction of electrical current.
Experimental study of fast electron propagation in compressed matter
Vauzour, B.; Santos, J. J.; Batani, D.; Baton, S. D.; Koenig, M.; Nicolaï, Ph.; Perez, F.; Beg, F. N.; Benedetti, C.; Benocci, R.; Brambrink, E.; Chawla, S.; Coury, M.; Dorchies, F.; Fourment, C.; Galimberti, M.; Gizzi, L. A.; Heathcote, R.; Higginson, D. P.; Honrubia, J. J.; Hulin, S.; Jafer, R.; Jarrot, L. C.; Labate, L.; Lancaster, K.; Köster, P.; MacKinnon, A. J.; McKenna, P.; McPhee, A. G.; Nazarov, W.; Pasley, J.; Ramis, R.; Rhee, Y.; Regan, C.; Ribeyre, X.; Richetta, M.; Serres, F.; Schlenvoigt, H.-P.; Schurtz, G.; Sgattoni, A.; Spindloe, C.; Vaisseau, X.; Volpe, L.; Yahia, V.
2011-10-01
We report on experimental results of the fast electron transport in compressed plasmas, created by laser-induced shock propagation in both cylindrical and planar geometry. Two experiments were carried out. The first one was based on the compression of a polyimide cylinder filled with foams of three different initial densities ( ρ0). X-ray and proton radiographies of the target during the compression coupled with hydrodynamic simulations show that the obtained core densities and temperatures range from 2 to 11 g/cm 3 and from 30 to 120 eV, respectively. By studying the K-shell fluorescence from dopant atoms inside the target and from tracer layers situated at both front and rear side of the target it has been possible to investigate the fast electron propagation. The results show that Cu Kα yield emitted by the target rear side foil decreases with increasing compression, independently of ρ0. An electron collimation can also be observed for certain experimental conditions where a convergent resistivity gradient interacts with the fast electron beam. The second experiment was performed in a planar geometry with a compressing shock counter-propagative to the fast electron beam. In this case the areal density ρz seen by the electrons is constant during the compression in such a way that changes in the fast electron range should be ascribed to collective mechanisms. The study of the Kα fluorescence, from buried fluorescent layers of different atomic numbers, shows that the electrons with energy HiPER project.
Propagation of three-dimensional electron-acoustic solitary waves
Shalaby, M.; El-Labany, S. K.; Sabry, R.; El-Sherif, L. S.
2011-06-01
Theoretical investigation is carried out for understanding the properties of three-dimensional electron-acoustic waves propagating in magnetized plasma whose constituents are cold magnetized electron fluid, hot electrons obeying nonthermal distribution, and stationary ions. For this purpose, the hydrodynamic equations for the cold magnetized electron fluid, nonthermal electron density distribution, and the Poisson equation are used to derive the corresponding nonlinear evolution equation, Zkharov-Kuznetsov (ZK) equation, in the small- but finite- amplitude regime. The ZK equation is solved analytically and it is found that it supports both solitary and blow-up solutions. It is found that rarefactive electron-acoustic solitary waves strongly depend on the density and temperature ratios of the hot-to-cold electron species as well as the nonthermal electron parameter. Furthermore, there is a critical value for the nonthermal electron parameter, which decides whether the electron-acoustic solitary wave's amplitude is decreased or increased by changing various plasma parameters. Importantly, the change of the propagation angles leads to miss the balance between the nonlinearity and dispersion; hence, the localized pulses convert to explosive/blow-up pulses. The relevance of this study to the nonlinear electron-acoustic structures in the dayside auroral zone in the light of Viking satellite observations is discussed.
Propagation of three-dimensional electron-acoustic solitary waves
International Nuclear Information System (INIS)
Shalaby, M.; El-Sherif, L. S.; El-Labany, S. K.; Sabry, R.
2011-01-01
Theoretical investigation is carried out for understanding the properties of three-dimensional electron-acoustic waves propagating in magnetized plasma whose constituents are cold magnetized electron fluid, hot electrons obeying nonthermal distribution, and stationary ions. For this purpose, the hydrodynamic equations for the cold magnetized electron fluid, nonthermal electron density distribution, and the Poisson equation are used to derive the corresponding nonlinear evolution equation, Zkharov-Kuznetsov (ZK) equation, in the small- but finite- amplitude regime. The ZK equation is solved analytically and it is found that it supports both solitary and blow-up solutions. It is found that rarefactive electron-acoustic solitary waves strongly depend on the density and temperature ratios of the hot-to-cold electron species as well as the nonthermal electron parameter. Furthermore, there is a critical value for the nonthermal electron parameter, which decides whether the electron-acoustic solitary wave's amplitude is decreased or increased by changing various plasma parameters. Importantly, the change of the propagation angles leads to miss the balance between the nonlinearity and dispersion; hence, the localized pulses convert to explosive/blow-up pulses. The relevance of this study to the nonlinear electron-acoustic structures in the dayside auroral zone in the light of Viking satellite observations is discussed.
The electron-propagator approach to conceptual density-functional ...
Indian Academy of Sciences (India)
Unknown
Abstract. Both electron propagator theory and density-functional theory provide conceptually useful information about chemical reactivity and, most especially, charge transfer. This paper elucidates the qualitative and quantitative links between the two theories, with emphasis on how the reactivity indica- tors of conceptual ...
The electron-propagator approach to conceptual density-functional ...
Indian Academy of Sciences (India)
Both electron propagator theory and density-functional theory provide conceptually useful information about chemical reactivity and, most especially, charge transfer. This paper elucidates thequalitative and quantitative links between the two theories, with emphasis on how the reactivity indicators of conceptual ...
New mixed quantum/semiclassical propagation method
International Nuclear Information System (INIS)
Antoniou, Dimitri; Gelman, David; Schwartz, Steven D.
2007-01-01
The authors developed a new method for calculating the quantum evolution of multidimensional systems, for cases in which the system can be assumed to consist of a quantum subsystem and a bath subsystem of heavier atoms. The method combines two ideas: starting from a simple frozen Gaussian description of the bath subsystem, then calculate quantum corrections to the propagation of the quantum subsystem. This follows from recent work by one of them, showing how one can calculate corrections to approximate evolution schemes, even when the Hamiltonian that corresponds to these approximate schemes is unknown. Then, they take the limit in which the width of the frozen Gaussians approaches zero, which makes the corrections to the evolution of the quantum subsystem depend only on classical bath coordinates. The test calculations they present use low-dimensional systems, in which comparison to exact quantum dynamics is feasible
Experimental study of fast electron propagation in compressed matter
Energy Technology Data Exchange (ETDEWEB)
Vauzour, B. [Universite de Bordeaux - CNRS - CEA, Centre Lasers Intenses et Applications (CELIA), Talence (France); Santos, J.J., E-mail: Santos.Joao@celia.u-bordeaux1.fr [Universite de Bordeaux - CNRS - CEA, Centre Lasers Intenses et Applications (CELIA), Talence (France); Batani, D. [Dipartimento di Fisica, Universita di Milano-Bicocca, Milano (Italy); Baton, S.D.; Koenig, M. [Laboratoire pour l' Utilisation des Lasers Intenses, UMR 7605 CNRS-CEA-Ecole Polytechnique-Univ. Paris VI, Palaiseau (France); Nicolai, Ph. [Universite de Bordeaux - CNRS - CEA, Centre Lasers Intenses et Applications (CELIA), Talence (France); Perez, F. [Laboratoire pour l' Utilisation des Lasers Intenses, UMR 7605 CNRS-CEA-Ecole Polytechnique-Univ. Paris VI, Palaiseau (France); Beg, F.N. [University of California, San Diego, La Jolla (United States); Benedetti, C. [Dipartimento di Fisica, Universita di Bologna, Bologna (Italy); Benocci, R. [Dipartimento di Fisica, Universita di Milano-Bicocca, Milano (Italy); Brambrink, E. [Laboratoire pour l' Utilisation des Lasers Intenses, UMR 7605 CNRS-CEA-Ecole Polytechnique-Univ. Paris VI, Palaiseau (France); Chawla, S. [University of California, San Diego, La Jolla (United States); Coury, M. [SUPA, Department of Physics, University of Strathclyde, Glasgow (United Kingdom); Dorchies, F.; Fourment, C. [Universite de Bordeaux - CNRS - CEA, Centre Lasers Intenses et Applications (CELIA), Talence (France); Galimberti, M. [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Gizzi, L.A. [Intense Laser Irradiation Laboratory at INO-CNR, Pisa (Italy); Heathcote, R. [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Higginson, D.P. [University of California, San Diego, La Jolla (United States); Honrubia, J.J. [ETSI Aeronauticos, Universidad Politecnica de Madrid, Madrid (Spain); and others
2011-10-11
We report on experimental results of the fast electron transport in compressed plasmas, created by laser-induced shock propagation in both cylindrical and planar geometry. Two experiments were carried out. The first one was based on the compression of a polyimide cylinder filled with foams of three different initial densities ({rho}{sub 0}). X-ray and proton radiographies of the target during the compression coupled with hydrodynamic simulations show that the obtained core densities and temperatures range from 2 to 11 g/cm{sup 3} and from 30 to 120 eV, respectively. By studying the K-shell fluorescence from dopant atoms inside the target and from tracer layers situated at both front and rear side of the target it has been possible to investigate the fast electron propagation. The results show that Cu K{sub {alpha}} yield emitted by the target rear side foil decreases with increasing compression, independently of {rho}{sub 0}. An electron collimation can also be observed for certain experimental conditions where a convergent resistivity gradient interacts with the fast electron beam. The second experiment was performed in a planar geometry with a compressing shock counter-propagative to the fast electron beam. In this case the areal density {rho}z seen by the electrons is constant during the compression in such a way that changes in the fast electron range should be ascribed to collective mechanisms. The study of the K{sub {alpha}} fluorescence, from buried fluorescent layers of different atomic numbers, shows that the electrons with energy <75keV are more affected by resistive losses in compressed compared to non-compressed targets. These two experiments were part of the Experimental Fusion Validation Program of the HiPER project.
Nanosecond air breakdown parameters for electron and microwave beam propagation
International Nuclear Information System (INIS)
Ali, A.W.
1988-01-01
Air breakdown by avalanche ionization plays an important role in the electron beam and microwave propagations. For high electric fields and short pulse applications one needs avalanche ionization parameters for modeling and scaling of experimental devices. However, the breakdown parameters, i.e., the ionization frequency vs E/p (volt. cm -1 . Torr -1 ) in air is uncertain for very high values of E/P. A review is given of the experimental data for the electron drift velocity, the Townsend ionization coefficient in N 2 and O 2 and the ionization frequency and the collision frequency for momentum transfer in air are developed. (author)
GPU Accelerated Ultrasonic Tomography Using Propagation and Back Propagation Method
2015-09-28
tomographic imaging algorithm using Graphic Processing Units ( GPUs ). The Compute Unified Device Architecture (CUDA) programming model is used to develop...our parallelized algorithm since the CUDA model allows the user to interact with the GPU resources more efficiently than traditional Shader methods...3. DATES COVERED (From - To) - UU UU UU UU 28-09-2015 Approved for public release; distribution is unlimited. GPU accelerated ultrasonic tomography
Measurements on wave propagation characteristics of spiraling electron beams
Singh, A.; Getty, W. D.
1976-01-01
Dispersion characteristics of cyclotron-harmonic waves propagating on a neutralized spiraling electron beam immersed in a uniform axial magnetic field are studied experimentally. The experimental setup consisted of a vacuum system, an electron-gun corkscrew assembly which produces a 110-eV beam with the desired delta-function velocity distribution, a measurement region where a microwave signal is injected onto the beam to measure wavelengths, and a velocity analyzer for measuring the axial electron velocity. Results of wavelength measurements made at beam currents of 0.15, 1.0, and 2.0 mA are compared with calculated values, and undesirable effects produced by increasing the beam current are discussed. It is concluded that a suitable electron beam for studies of cyclotron-harmonic waves can be generated by the corkscrew device.
Laundy, D.; Sutter, J. P.; Wagner, U. H.; Rau, C.; Thomas, C. A.; Sawhney, K. J. S.; Chubar, O.
2013-03-01
Hard X-ray undulator radiation at 3rd generation storage rings falls between the geometrical and the fully coherent limit. This is a result of the small but finite emittance of the electron beam source and means that the radiation cannot be completely modelled by incoherent ray tracing or by fully coherent wave propagation. We have developed using the wavefront propagation code Synchrotron Radiation Workshop (SRW) running in a Python environment, a parallel computer program using the Monte Carlo method for modelling the partially coherent emission from electron beam sources taking into account the finite emittance of the source. Using a parallel computing cluster with in excess of 500 cores and each core calculating the wavefront from in excess of a 1000 electrons, a source containing millions of electrons could be simulated. We have applied this method to the Diamond X-ray Imaging and Coherence beamline (113).
The propagation of high power CW scanning electron beam in air
International Nuclear Information System (INIS)
Korenev, Sergey; Korenev, Ivan
2002-01-01
The question of propagation of high power electron beam in air presents the scientific and applied interests. The high power (80 kW) CW electron accelerator 'Rhodotron' with kinetic energy of electrons 5 and 10 MeV was used in the experiments. The experimental results for propagation of scanning electron beams in air are presented and discussed
Proton radiography and fast electron propagation through cyliderically compressed targets
Energy Technology Data Exchange (ETDEWEB)
Jafer, R.; Volpe, L.; Batani, D. [Universita di Milano-Bicocca (Italy); and others
2010-08-15
The paper describes the key points contained in the short term HiPER (High Power laser Energy Research) experimental road map, as well as the results of two phases of the experiment performed in HiPER dedicated time slots. Experimental and theoretical results of relativistic electron transport in cylindrically compressed matter are presented. This experiment was achieved at the VULCAN laser facility (UK) by using four long pulse beams ({approx}4 x 50 J, 1 ns, at 0.53 {mu}m) to compress a hollow plastic cylinder filled with plastic foam of three different densities (0.1, 0.3, and 1 g cm{sup -3}). In the first phase of the experiment, protons accelerated by a picosecond laser pulse were used to radiograph a cylinder filled with 0.1 g/cc foam. Point projection proton backlighting was used to measure the degree of compression as well as the stagnation time. Results were compared to those from hard X-ray radiography. Finally, Monte Carlo simulations of proton propagation in cold and compressed targets allowed a detailed comparison with 2D numerical hydro simulations. 2D simulations predict a density of 2-5 g cm{sup -3} and a plasma temperature up to 100 eV at maximum compression. In the second phase of the experiment, a short pulse (10 ps, 160 J) beam generated fast electrons that propagated through the compressed matter by irradiating a nickel foil at an intensity of 5 x 10{sup 18} Wcm{sup -2}. X-ray spectrometer and imagers were implemented in order to estimate the compressed plasma conditions and to infer the hot electron characteristics. Results are discussed and compared with simulations.
Comparative study of three methods of propagation of Jatropha ...
African Journals Online (AJOL)
Objective: Jatropha curcas L. is an Euphorbiaceae known for its oleaginous seed characters. Its propagation following a specific technical route is not yet established. This study aimed at comparing the growth of seedlings through three methods of propagation in southeastern of Gabon. Methodology and Results: This study ...
The parabolic equation method for outdoor sound propagation
DEFF Research Database (Denmark)
Arranz, Marta Galindo
of the ground in a homogeneous atmosphere. Propagation of sound above a mixed impedance ground and up-slope sound propagation is investigated. In the third application the influence of the atmosphere is studied, characterized and implemented in the CNPE-model. The refraction of the sound due to the wind......The parabolic equation method is a versatile tool for outdoor sound propagation. The present study has focused on the Cranck-Nicolson type Parabolic Equation method (CNPE). Three different applications of the CNPE method have been investigated. The first two applications study variations...
Clear-Air Propagation Modeling using Parabolic Equation Method
Directory of Open Access Journals (Sweden)
V. Kvicera
2003-12-01
Full Text Available Propagation of radio waves under clear-air conditions is affected bythe distribution of atmospheric refractivity between the transmitterand the receiver. The measurement of refractivity was carried out onthe TV Tower Prague to access evolution of a refractivity profile. Inthis paper, the parabolic equation method is used in modelingpropagation of microwaves when using the measured data. This paperbriefly describes the method and shows some practical results ofsimulation of microwave propagation using real vertical profiles ofatmospheric refractivity.
A wave propagation matrix method in semiclassical theory
International Nuclear Information System (INIS)
Lee, S.Y.; Takigawa, N.
1977-05-01
A wave propagation matrix method is used to derive the semiclassical formulae of the multiturning point problem. A phase shift matrix and a barrier transformation matrix are introduced to describe the processes of a particle travelling through a potential well and crossing a potential barrier respectively. The wave propagation matrix is given by the products of phase shift matrices and barrier transformation matrices. The method to study scattering by surface transparent potentials and the Bloch wave in solids is then applied
Does propagation method affect the field performance of peach trees?
Directory of Open Access Journals (Sweden)
André Luiz Kulkamp de Souza
2017-08-01
Full Text Available Worldwide, peach propagation has been performed mainly by grafting scions of desirable cultivars on rootstocks obtained from seeds. There are, however, other potential propagation methods not widely adopted due to the limited reports on the field performance of the resultant trees. This study addressed this knowledge gap and investigated the field performance of peach trees of the cultivar Maciel that were established in an orchard (5.0 m × 1.4 m spacing in 2011. The trees were trained in a "Y" system, with seedlings from three propagation techniques: 1 Conventional System (CS - vegetative bud grafting of the scion on the rootstock of the Okinawa cultivar obtained from seed; 2 Rootstock by Minicutting (RM - vegetative bud grafting of the scion on the rootstock of the Okinawa cultivar obtained by minicutting in a semi-hydroponic system; 3 Self-Rooting (SR - self-rooting of the scion in a semi-hydroponic system. The vegetative, productive, and fruit quality parameters were assessed during 2012 and 2013. The Maciel peach trees that were propagated by the SR technique were found to have similar or even superior field performance to those propagated by the CS. The RM propagation method was also found to be an important potential alternative to peach propagation, since this it combines two techniques (cutting and grafting to reduce tree vigor, especially if the goal is high-density planting.
Electron beam propagation in the ion-focused and resistive regimes
International Nuclear Information System (INIS)
Hubbard, R.F.; Lampe, M.; Fernsler, R.; Slinker, S.P.
1993-01-01
Pinched propagation of intense relativistic electron beams occurs in several distinct pressure regimes. In low density gases (∼ 1-100 mtorr), the beam propagates in the ion-focused regime (IFR). The beam ionizes the neutral gas, and plasma electrons are ejected, leaving behind a positive ion column which pinches the beam electrostatically. At gas densities near 1 atm, the beam-generated plasma is resistive and the pinch effect is provided by the self-magnetic field of the beam. Beam transport experiments in both regimes have been performed on the Advanced Test Accelerator (ATA) at Lawrence Livermore National Lab. and on SuperIBEX at the Naval Research Lab. IFR methods have been employed in both experiments to transport the beam prior to injection into the air and to introduce a head-to-tail taper in the beam radius. IFR simulations have shown how the resulting beam radius and emittance profiles are influenced by gas density, chamber dimensions and entrance and exit foils. Beam propagation in dense gas is subject to disruption by the resistive hose instability. However, both experiments and simulations have shown that the emittance variation introduced by IFR transport can substantially reduce the growth of the hose instability. Both experiments have also propagated beams in reduced-density channels. Simulations predict that the channel may in some cases produce a moderate stabilizing and tracking effect arising from plasma currents flowing at the edge of the channel
Spectral element method for wave propagation on irregular domains
Indian Academy of Sciences (India)
A spectral element approximation of acoustic propagation problems combined with a new mapping method on irregular domains is proposed. Following this method, the Gauss–Lobatto–Chebyshev nodes in the standard space are applied to the spectral element method (SEM). The nodes in the physical space are ...
Spectral element method for wave propagation on irregular domains
Indian Academy of Sciences (India)
Yan Hui Geng
2018-03-14
Mar 14, 2018 ... A spectral element approximation of acoustic propagation problems combined with a new mapping method on irregular ... Spectral element method; curved quadrilateral element; isoparametric element; Chebyshev polynomial ... overcome this problem, such as meshless local strong form method [9], the ...
Anton, Steven M.
2008-04-01
While graphene has been studied by theoreticians for over half a century, the two dimensional crystal lattice has only recently been realized experimentally. As such, theoretical work in the properties of graphene has exploded. A variety of these properties, which are truly exceptional and unique, have engendered much research into carbon based electronics, of which graphene is generally the most fundamental unit. In this thesis, we seek to characterize basic electronic properties of graphene nanoribbons. We begin with a tight-binding model of graphene and an analysis of the electronic band structure of the infinite sheet and semi-infinite nanoribbons. Also employing the spectral method, we create, inject, and propagate various types of wave packets infinite wires. A key effect that is expected is the so called Zitterbewegung oscillation of the wave packet center. Results are compared to theoretical predictions based on analytical methods rather than numerical simulations.
Chiral metamaterials characterisation using the wave propagation retrieval method
DEFF Research Database (Denmark)
Andryieuski, Andrei; Lavrinenko, Andrei; Malureanu, Radu
2010-01-01
In this presentation we extend the wave propagation method for the retrieval of the effective properties to the case of chiral metamaterials with circularly polarised eigenwaves. The method is unambiguous, simple and provides bulk effective parameters. Advantages and constraints are discussed...
Propagation of high-current fast electron beam in a dielectric target
International Nuclear Information System (INIS)
Klimo, O.; Debayle, A.; Tikhonchuk, V.T.
2006-01-01
Complete test of publication follows. A relativistic electron beam with very high current density may be produced during the interaction of a short high intensity laser pulse with a solid target. In Fast Ignition approach to Inertial Confinement Fusion, such beam is supposed to heat a part of the precompressed DT fuel pellet to the conditions of an efficient ignition. For successful implementation of Fast Ignition understanding the propagation and energy deposition of the beam is crucial. A number of processes, mostly associated with the return current, are dissipating the energy of the beam or inhibiting its collimated transport, namely the filamentation. Weibel, two-stream or the recently proposed ionization instability. Ionization instability may develop in a solid dielectric target due to the dependence of the propagation velocity of the beam on the beam density. To study the propagation of high current electron beam in dielectric target, we use a one-dimensional relativistic electrostatic simulation code based on the Particle in Cell method. The code includes ionization processes in dielectric material and collisions of newly generated cold electrons. The current density of the relativistic electron beam used in this work is in the range 3-300 GA/cm 2 , while its length roughly corresponds to the beam, produced by a 40 fs laser pulse. Propagation of the beam in the polyethylene target is studied. The code is complemented by an analytical model, which is applicable og a wider range of beam parameters that are currently beyond our computational possibilities. When the head of the beam enters the plastic target, electric field grows rapidly in consequence of the charge separation and it starts to ionize atoms. In the maximum of the field, which is less than 10% of the atomic field, the density of new free electrons is two orders of magnitude higher than the beam density, which is enough for the current neutralization. Cold electrons are accelerated by the field
Internal Error Propagation in Explicit Runge--Kutta Methods
Ketcheson, David I.
2014-09-11
In practical computation with Runge--Kutta methods, the stage equations are not satisfied exactly, due to roundoff errors, algebraic solver errors, and so forth. We show by example that propagation of such errors within a single step can have catastrophic effects for otherwise practical and well-known methods. We perform a general analysis of internal error propagation, emphasizing that it depends significantly on how the method is implemented. We show that for a fixed method, essentially any set of internal stability polynomials can be obtained by modifying the implementation details. We provide bounds on the internal error amplification constants for some classes of methods with many stages, including strong stability preserving methods and extrapolation methods. These results are used to prove error bounds in the presence of roundoff or other internal errors.
Simulation of the acoustic wave propagation using a meshless method
Directory of Open Access Journals (Sweden)
Bajko J.
2017-01-01
Full Text Available This paper presents numerical simulations of the acoustic wave propagation phenomenon modelled via Linearized Euler equations. A meshless method based on collocation of the strong form of the equation system is adopted. Moreover, the Weighted least squares method is used for local approximation of derivatives as well as stabilization technique in a form of spatial ltering. The accuracy and robustness of the method is examined on several benchmark problems.
Transplantation and direct sowing as methods of propagation of ...
African Journals Online (AJOL)
The establishment of Cordeauxia edulis Hemsley (yeheb) was assessed using two methods of propagation in glasshouse and in the field in 2006 and 2007 at Haramaya University, Ethiopia. In experiment 1, seedlings were transplanted into the field, with and without shade, 10, 20, 30, 40 and 50 days after germination.
Multigrid methods for the computation of propagators in gauge fields
International Nuclear Information System (INIS)
Kalkreuter, T.
1992-11-01
In the present work generalizations of multigrid methods for propagators in gauge fields are investigated. We discuss proper averaging operations for bosons and for staggered fermions. An efficient algorithm for computing C numerically is presented. The averaging kernels C can be used not only in deterministic multigrid computations, but also in multigrid Monte Carlo simulations, and for the definition of block spins and blocked gauge fields in Monte Carlo renormalization group studies of gauge theories. Actual numerical computations of kernels and propagators are performed in compact four-dimensional SU(2) gauge fields. (orig./HSI)
Manufacturing Data Uncertainties Propagation Method in Burn-Up Problems
Directory of Open Access Journals (Sweden)
Thomas Frosio
2017-01-01
Full Text Available A nuclear data-based uncertainty propagation methodology is extended to enable propagation of manufacturing/technological data (TD uncertainties in a burn-up calculation problem, taking into account correlation terms between Boltzmann and Bateman terms. The methodology is applied to reactivity and power distributions in a Material Testing Reactor benchmark. Due to the inherent statistical behavior of manufacturing tolerances, Monte Carlo sampling method is used for determining output perturbations on integral quantities. A global sensitivity analysis (GSA is performed for each manufacturing parameter and allows identifying and ranking the influential parameters whose tolerances need to be better controlled. We show that the overall impact of some TD uncertainties, such as uranium enrichment, or fuel plate thickness, on the reactivity is negligible because the different core areas induce compensating effects on the global quantity. However, local quantities, such as power distributions, are strongly impacted by TD uncertainty propagations. For isotopic concentrations, no clear trends appear on the results.
Singh, Nagendra; Hwang, K. S.
1988-01-01
One-dimensional Vlasov simulations are used to study the propagation of electron beams injected from a spacecraft into an ambient plasma and the associated potential structures. It is shown that, for a given beam velocity, the propagation velocity and the potential structure depends on the beam density. In the case of moderate beams, a double layer forms near the beam head which propagates into the ambient plasma much more slowly than the initial beam velocity.
MIMO nonlinear ultrasonic tomography by propagation and backpropagation method.
Dong, Chengdong; Jin, Yuanwei
2013-03-01
This paper develops a fast ultrasonic tomographic imaging method in a multiple-input multiple-output (MIMO) configuration using the propagation and backpropagation (PBP) method. By this method, ultrasonic excitation signals from multiple sources are transmitted simultaneously to probe the objects immersed in the medium. The scattering signals are recorded by multiple receivers. Utilizing the nonlinear ultrasonic wave propagation equation and the received time domain scattered signals, the objects are to be reconstructed iteratively in three steps. First, the propagation step calculates the predicted acoustic potential data at the receivers using an initial guess. Second, the difference signal between the predicted value and the measured data is calculated. Third, the backpropagation step computes updated acoustical potential data by backpropagating the difference signal to the same medium computationally. Unlike the conventional PBP method for tomographic imaging where each source takes turns to excite the acoustical field until all the sources are used, the developed MIMO-PBP method achieves faster image reconstruction by utilizing multiple source simultaneous excitation. Furthermore, we develop an orthogonal waveform signaling method using a waveform delay scheme to reduce the impact of speckle patterns in the reconstructed images. By numerical experiments we demonstrate that the proposed MIMO-PBP tomographic imaging method results in faster convergence and achieves superior imaging quality.
Energy Technology Data Exchange (ETDEWEB)
Deleuze, M.S.; Pickup, B.T.; Wilton, D.J.
2000-04-05
The authors present the theory of the electron propagator perturbed by an external electric field and show how it can be used to calculate a variety of one-electron linear response properties that are accurate through second order in electron correlation. Some illustrative calculations are discussed.
Propagation of Dirac electrons in Cantor graphene multilayers
Energy Technology Data Exchange (ETDEWEB)
Rodríguez-González, R.; Martínez-Orozco, J. C.; Madrigal-Melchor, J.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad Esquina Con Paseo La Bufa S/N, 98060 Zacatecas, Zac. (Mexico)
2014-05-15
In this work we use the standard T-matrix method to study the tunneling of Dirac electrons through graphene multilayers. A graphene sheet is deposited on top of slabs of Silicon-Oxide (SiO{sub 2}) and Silicon-Carbide (SiC) substrates, in which we applied the Cantor’s series. We calculate the transmittance as a function of energy for different incident angles and different generations of the Cantor’s series. Comparing the transmittance, we found three types of self-similarity: (a) local - into generations, (b) between incident angles and (c) between generations. We also compute the angular distribution of the transmittance for fixed energies finding a self-similar pattern between generations. To our knowledge is the first time that four different self-similar patterns are presented in Cantor-based multilayers.
Propagation of attosecond electron bunches along the cone-and-channel target
International Nuclear Information System (INIS)
Yang, X. H.; Shao, F. Q.; Yin, Y.; Tian, C. L.; Xu, H.; Ma, Y. Y.; Zhuo, H. B.; Yu, M. Y.
2011-01-01
Generation and propagation of attosecond electron bunches along a cone-and-channel target are investigated by particle-in-cell simulation. The target electrons are pulled out by the oscillating electric field of an intense laser pulse irradiating a cone target and accelerated forward along the cone walls. It is shown that the energetic electrons can be further guided and confined by a channel attached to the cone tip. The propagation of these electrons along the channel induces a strong quasistatic magnetic field as well as a sheath electric field since a part of the energetic electrons expands into the surrounding vacuum. The electromagnetic field in turn confines the surface currents. With the cone-and-channel target the energetic electrons can be much better collimated and propagate much farther than that from the classical cone target.
Wijnands, F.H.G.M.; Wijnands, Frank; Hoekstra, Hugo; Krijnen, Gijsbertus J.M.; de Ridder, R.M.
A method to construct modal fields for an arbitrary one- or two-dimensional intensity dependent refractive index structure is described. An arbitrary starting field is propagated along an imaginary axis using the Finite Difference Beam Propagation Method (FDBPM) based upon the Slowly Varying
Propagation of a nonrelativistic electron beam in a plasma in a magnetic field
International Nuclear Information System (INIS)
Okuda, H.; Horton, R.; Ono, M.; Ashour-Abdalla, M.
1986-10-01
Propagation of a nonrelativistic electron beam in a plasma in a strong magnetic field has been studied using electrostatic one-dimensional particle simulation models. Electron beams of finite pulse length and of continuous injection are followed in time to study the effects of beam-plasma interaction on the beam propagation. For the case of pulsed beam propagation, it is found that the beam distribution rapidly spreads in velocity space generating a plateaulike distribution with a high energy tail extending beyond the initial beam velocity
New methods for electron tomography
Ziese, Ulrike
2002-01-01
Electron tomography is a method for obtaining three-dimensional structural information from electron micrographs. It can be applied to a wide range of samples that can be prepared for transmission electron microscopy (TEM)may they be of biological origin like e.g. cryo or thin plastic sections of
Sunward-propagating Solar Energetic Electrons inside Multiple Interplanetary Flux Ropes
Energy Technology Data Exchange (ETDEWEB)
Gómez-Herrero, Raúl; Hidalgo, Miguel A.; Carcaboso, Fernando; Blanco, Juan J. [Dpto. de Física y Matemáticas, Universidad de Alcalá, E-28871 Alcalá de Henares, Madrid (Spain); Dresing, Nina; Klassen, Andreas; Heber, Bernd [Institut für Experimentelle und Angewandte Physik, University of Kiel, D-24118, Kiel (Germany); Temmer, Manuela; Veronig, Astrid [Institute of Physics/Kanzelhöhe Observatory, University of Graz, A-8010 Graz (Austria); Bučík, Radoslav [Institut für Astrophysik, Georg-August-Universität Göttingen, D-37077, Göttingen (Germany); Lario, David, E-mail: raul.gomezh@uah.es [The Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723 (United States)
2017-05-10
On 2013 December 2 and 3, the SEPT and STE instruments on board STEREO-A observed two solar energetic electron events with unusual sunward-directed fluxes. Both events occurred during a time interval showing typical signatures of interplanetary coronal mass ejections (ICMEs). The electron timing and anisotropies, combined with extreme-ultraviolet solar imaging and radio wave spectral observations, are used to confirm the solar origin and the injection times of the energetic electrons. The solar source of the ICME is investigated using remote-sensing observations and a three-dimensional reconstruction technique. In situ plasma and magnetic field data combined with energetic electron observations and a flux-rope model are used to determine the ICME magnetic topology and the interplanetary electron propagation path from the Sun to 1 au. Two consecutive flux ropes crossed the STEREO-A location and each electron event occurred inside a different flux rope. In both cases, the electrons traveled from the solar source to 1 au along the longest legs of the flux ropes still connected to the Sun. During the December 2 event, energetic electrons propagated along the magnetic field, while during the December 3 event they were propagating against the field. As found by previous studies, the energetic electron propagation times are consistent with a low number of field line rotations N < 5 of the flux rope between the Sun and 1 au. The flux rope model used in this work suggests an even lower number of rotations.
Lateral propagation of fast electrons at the laser-irradiated target surfaces
International Nuclear Information System (INIS)
Li, Y T; Lin, X X; Liu, B C; Du, F; Wang, S J; Li, C; Zhou, M L; Zhang, L; Liu, X; Wang, J; Liu, X L; Chen, L M; Wang, Z H; Ma, J L; Wei, Z Y; Zhang, J; Liu, F; Liu, F
2010-01-01
Lateral propagation of fast electrons at the target surfaces irradiated by femtosecond intense laser pulses is measured by k α x-ray imaging technique when a preplasma is presented. An annular halo surrounding a bright spot is observed in the x-ray images when the scale length of the electron density is large. For an incidence angle of 70 0 the x-ray images show a non-symmetrical distribution peaked to the laser propagation direction. The x-ray photons in the halo are mainly excited by the fast electrons that flow in the preplasma when their paths intersect the high density regions near the target surface.
Community Mining Method of Label Propagation Based on Dense Pairs
Directory of Open Access Journals (Sweden)
WENG Wei
2014-03-01
Full Text Available In recent years, with the popularity of handheld Internet equipments like mobile phones, increasing numbers of people are becoming involved in the virtual social network. Because of its large amount of data and complex structure, the network faces new challenges of community mining. A label propagation algorithm with low time complexity and without prior parameters deals easily with a large networks. This study explored a new method of community mining, based on label propagation with two stages. The first stage involved identifying closely linked nodes according to their local adjacency relations that gave rise to a micro-community. The second stage involved expanding and adjusting this community through a label propagation algorithm (LPA to finally obtain the community structure of the entire social network. This algorithm reduced the number of initial labels and avoided the merging of small communities in general LPAs. Thus, the quality of community discovery was improved, and the linear time complexity of the LPA was maintained.
Regional wave propagation using the discontinuous Galerkin method
Directory of Open Access Journals (Sweden)
S. Wenk
2013-01-01
Full Text Available We present an application of the discontinuous Galerkin (DG method to regional wave propagation. The method makes use of unstructured tetrahedral meshes, combined with a time integration scheme solving the arbitrary high-order derivative (ADER Riemann problem. This ADER-DG method is high-order accurate in space and time, beneficial for reliable simulations of high-frequency wavefields over long propagation distances. Due to the ease with which tetrahedral grids can be adapted to complex geometries, undulating topography of the Earth's surface and interior interfaces can be readily implemented in the computational domain. The ADER-DG method is benchmarked for the accurate radiation of elastic waves excited by an explosive and a shear dislocation source. We compare real data measurements with synthetics of the 2009 L'Aquila event (central Italy. We take advantage of the geometrical flexibility of the approach to generate a European model composed of the 3-D EPcrust model, combined with the depth-dependent ak135 velocity model in the upper mantle. The results confirm the applicability of the ADER-DG method for regional scale earthquake simulations, which provides an alternative to existing methodologies.
An accelerated training method for back propagation networks
Shelton, Robert O. (Inventor)
1993-01-01
The principal objective is to provide a training procedure for a feed forward, back propagation neural network which greatly accelerates the training process. A set of orthogonal singular vectors are determined from the input matrix such that the standard deviations of the projections of the input vectors along these singular vectors, as a set, are substantially maximized, thus providing an optimal means of presenting the input data. Novelty exists in the method of extracting from the set of input data, a set of features which can serve to represent the input data in a simplified manner, thus greatly reducing the time/expense to training the system.
Ab initio electron propagator theory of molecular wires. II. Multiorbital terminal description.
Dahnovsky, Yu; Ortiz, J V
2006-04-14
Correlated, ab initio electron propagator methodology may be applied to the calculation of electrical current through a molecular wire. A new theoretical formalism is developed for the calculation of retarded and advanced Green functions in terms of the electron propagator matrix for a bridge molecule. The calculation of the current requires integration in a complex half-plane for a trace that involves terminal and Green function matrices that may have any rank. Because the latter arrays have poles represented by matrices, an alternative expression is developed in terms of ordinary poles which are (n-1)-fold degenerate or nondegenerate. For an arbitrary number of terminal orbitals, the analytical expression for the current is given in terms of pole strengths, poles, and terminal matrix elements of the electron propagator, i.e., the parameters that are found in the output of numerical calculations.
Energy Technology Data Exchange (ETDEWEB)
Mahmood, S., E-mail: shahzadm100@gmail.com; Sadiq, Safeer; Haque, Q. [Theoretical Physics Division, PINSTECH, P. O. Nilore, Islamabad 44000 (Pakistan); Ali, Munazza Z. [Department of Physics, University of the Punjab, Lahore 54590 (Pakistan)
2016-06-15
The obliquely propagating arbitrary amplitude electrostatic wave is studied in a dense magnetized plasma having singly and doubly charged helium ions with nonrelativistic and ultrarelativistic degenerate electrons pressures. The Fermi temperature for ultrarelativistic degenerate electrons described by N. M. Vernet [(Cambridge University Press, Cambridge, 2007), p. 57] is used to define ion acoustic speed in ultra-dense plasmas. The pseudo-potential approach is used to solve the fully nonlinear set of dynamic equations for obliquely propagating electrostatic waves in a dense magnetized plasma containing helium ions. The upper and lower Mach number ranges for the existence of electrostatic solitons are found which depends on the obliqueness of the wave propagation with respect to applied magnetic field and charge number of the helium ions. It is found that only compressive (hump) soliton structures are formed in all the cases and only subsonic solitons are formed for a singly charged helium ions plasma case with nonrelativistic degenerate electrons. Both subsonic and supersonic soliton hump structures are formed for doubly charged helium ions with nonrelativistic degenerate electrons and ultrarelativistic degenerate electrons plasma case containing singly as well as doubly charged helium ions. The effect of propagation direction on the soliton amplitude and width of the electrostatic waves is also presented. The numerical plots are also shown for illustration using dense plasma parameters of a compact star (white dwarf) from literature.
DEFF Research Database (Denmark)
Bertelli, N.; Balakin, A.A.; Westerhof, E.
2010-01-01
A numerical analysis of the electron cyclotron (EC) wave beam propagation in the presence of edge density fluctuations by means of a quasi-optical code [Balakin A. A. et al, Nucl. Fusion 48 (2008) 065003] is presented. The effects of the density fluctuations on the wave beam propagation...... are estimated in a vacuum beam propagation between the edge density layer and the EC resonance absorption layer. Consequences on the EC beam propagation are investigated by using a simplified model in which the density fluctuations are described by a single harmonic oscillation. In addition, quasi......-optical calculations are shown by using edge density fluctuations as calculated by two-dimensional interchange turbulence simulations and validated with the experimental data [O. E. Garcia et al, Nucl. Fusion 47 (2007) 667]...
Uncertainty propagation for systems of conservation laws, stochastic spectral methods
International Nuclear Information System (INIS)
Poette, G.
2009-09-01
Uncertainty quantification through stochastic spectral methods has been recently applied to several kinds of stochastic PDEs. This thesis deals with stochastic systems of conservation laws. These systems are non linear and develop discontinuities in finite times: these difficulties can trigger the loss of hyperbolicity of the truncated system resulting of the application of sG-gPC (stochastic Galerkin-generalized Polynomial Chaos). We introduce a formalism based on both kinetic theory and moments theory in order to close the truncated system in such a way that the hyperbolicity of the latter is ensured. The idea is to close the truncated system obtained by Galerkin projection via the introduction of an entropy - strictly convex function on the definition domain of our unknowns. In the case this entropy is the mathematical entropy of the non truncated system, the hyperbolicity is ensured. We state several properties of this truncated system from a general non truncated system of conservation laws. We then apply the method to the case of the stochastic inviscid Burgers' equation with random initial conditions and to the stochastic Euler system in one and two space dimensions. In the vicinity of discontinuities, the new method bounds the oscillations due to Gibbs phenomenon to a certain range through the entropy of the system without the use of any adaptative random space discretizations. It is found to be more precise than the stochastic Galerkin method for several test problems. In a last chapter, we present two prospective outlooks: we first suggest an uncertainty propagation method based on the coupling of intrusive and non intrusive methods. We finally emphasize the modelling possibilities of the intrusive Polynomial Chaos methods in order to take into account three dimensional perturbations of a mean one dimensional flow. (author)
Wave propagation and absorption in the electron cyclotron frequency range for TCA and TCV machines
International Nuclear Information System (INIS)
Cardinali, A.
1990-01-01
The main theoretical aspects of the propagation and absorption of electron cyclotron frequency waves are reviewed and applied to TCA and TCV tokamak plasmas. In particular the electromagnetic cold dispersion relation is solved analytically and numerically in order to recall the basic properties of mode propagation and to calculate the ray-trajectories by means of geometric optics. A numerical code which integrates the coupled first order differential ray-equations, has been developed and applied to the cases of interest. (author) 4 figs., 23 refs
Optical guiding in an FEL with full account of electron wiggling and 3D propagation
International Nuclear Information System (INIS)
Chen Yujiuan; Solimeno, S.; Carlomusto, L.
1988-01-01
The driving current of a free electron laser is calculated by including terms, generally neglected, which represent the effect of the e-beam bending due to the electron wiggling. The 3D wave equation is solved by representing the field as a superposition of space harmonics. The transverse distribution of the field is accounted for by expanding it in a series of Gauss-Laguerre modes. A simple expression of the correction on the complex propagation constant caused by the electron wiggling is obtained. (orig.)
DEFF Research Database (Denmark)
Eriksen, Janus Juul; Solanko, Lukasz Michal; Nåbo, Lina J.
2014-01-01
We present an implementation of the Polarizable Continuum Model (PCM) in combination with the Second–Order Polarization Propagator Approximation (SOPPA) electronic structure method. In analogy with the most common way of designing ground state calculations based on a Second–Order Møller-Plesset (MP......2) wave function coupled to PCM, we introduce dynamical PCM solvent effects only in the Random Phase Approximation (RPA) part of the SOPPA response equations while the static solvent contribution is kept in both the RPA terms as well as in the higher order correlation matrix components of the SOPPA...... response equations. By dynamic terms, we refer to contributions that describe a change in environmental polarization which, in turn, reflects a change in the core molecular charge distribution upon an electronic excitation. This new combination of methods is termed PCM-SOPPA/RPA. We apply this newly...
Electron propagator and surface Green's function calculations in transport molecular junctions
Kletsov, Aleksey
A new theoretical approach to the calculation of electrical current through a molecular wire, based on ab initio electron propagator methodology, is proposed. The analytical expression for electric current is derived for an arbitrary number of terminal transport orbitals, which is given in terms of Dyson poles, Dyson pole strengths, overlap matrix elements, and expansion coefficients of atomic wavefunctions. The proposed approach is applied to calculations of the current-voltage characteristics of the transport molecular junction with a 1,4-benzene dithiol (BDT) molecule as a bridge. The obtained current-voltage characteristics exhibit negative differential resistance, that can be used in practical electronic devices. From the analysis of the output data, the origin of negative differential resistance in BDT molecular wire is explained. The observation of negative differential resistance in transport molecular devices based on a BDT molecule is predicted for certain Fermi energies. To discover the predicted effect, experimentalists should search for the appropriate Fermi energy by varying metal electrodes, coated by a gold monolayer. In addition, a novel computational method for non-recursive calculations of the surface Green's function matrices, using an infinite number of principal layers, is proposed. This method is employed to calculate the spectral function of the gold and aluminum surfaces. It is shown that the surface spectral function of the metal electrode dependence on applied voltage and this dependence can significantly change the electric current through a molecular wire. The new ab initio methods and computational results presented in this work allow for the prediction of novel devices with unusual properties that can be used in nanotechnology applications.
Energy Technology Data Exchange (ETDEWEB)
Light, Max Eugene [Los Alamos National Laboratory
2017-04-13
This report outlines the theory underlying electromagnetic (EM) wave propagation in an unmagnetized, inhomogeneous plasma. The inhomogeneity is given by a spatially nonuniform plasma electron density n_{e}(r), which will modify the wave propagation in the direction of the gradient rn_{e}(r).
Sakamoto, Moritsugu; Hizatsuki, Takuya; Noda, Kohei; Sasaki, Tomoyuki; Kawatsuki, Nobuhiro; Goto, Kohei; Ono, Hiroshi
2018-01-01
We propose and demonstrate a photolithography method for fine metal structure fabrication based on laser drawing that uses the interference pattern generated by co-propagating optical vortices. A tiny dark core region of the optical vortex allows us to overcome the diffraction limit for Gaussian beams. This means that the proposed method can be used to fabricate finer structures than those produced by the conventional laser drawing method while using a Gaussian beam, even under low numerical aperture conditions. The feasibility of the proposed method was demonstrated experimentally using a system that included an axially symmetrical polarization element that can generate the co-propagating optical vortices using a common path optical system. Our method has potential to fabricate few tens of nanometer scale metal line structures by increasing numerical aperture conditions and should be applicable to the development of nanometer scale electronic and optical devices and structures, such as integrated circuits and metamaterials, without using electron beam lithography.
International Nuclear Information System (INIS)
Uhm, H.S.
1997-01-01
Influence of the initial energy modulation caused by the self-potential depression on the premodulated electron-beam propagation through a drift tube is investigated. The potential depression κ can significantly vary because of the initial current modulation. Thus, beam close-quote s kinetic energy at the injection varies accordingly. A self-consistent nonlinear theory of current modulation of the premodulated electron beam is developed. It is shown that the initial energy modulation caused by the self-potential depression at injection plays a significant role in the current modulation for long range propagation. It is also found from a small signal theory that reduction of the beam close-quote s kinetic energy due to its potential depression accelerates debunching process of the initial current modulation. Although the initial current modulation is debunched quickly for high current beam, amplitude of the current modulation never becomes zero because of the initial energy modulation. copyright 1997 American Institute of Physics
Kinetic description of the oblique propagating spin-electron acoustic waves in degenerate plasmas
Andreev, Pavel A.
2018-03-01
An oblique propagation of the spin-electron acoustic waves in degenerate magnetized plasmas is considered in terms of quantum kinetics with the separate spin evolution, where the spin-up electrons and the spin-down electrons are considered as two different species with different equilibrium distributions. It is considered in the electrostatic limit. The corresponding dispersion equation is derived. Analysis of the dispersion equation is performed in the long-wavelength limit to find an approximate dispersion equation describing the spin-electron acoustic wave. The approximate dispersion equation is solved numerically. Real and imaginary parts of the spin-electron acoustic wave frequency are calculated for different values of the parameters describing the system. It is found that the increase in the angle between the direction of wave propagation and the external magnetic field reduces the real and imaginary parts of spin-electron acoustic wave frequency. The increase in the spin polarization decreases the real and imaginary parts of frequency either. The imaginary part of frequency has a nonmonotonic dependence on the wave vector which shows a single maximum. The imaginary part of frequency is small in comparison with the real part for all parameters in the area of applicability of the obtained dispersion equation.
Propagation of a laser-driven relativistic electron beam inside a solid dielectric.
Sarkisov, G S; Ivanov, V V; Leblanc, P; Sentoku, Y; Yates, K; Wiewior, P; Chalyy, O; Astanovitskiy, A; Bychenkov, V Yu; Jobe, D; Spielman, R B
2012-09-01
Laser probe diagnostics: shadowgraphy, interferometry, and polarimetry were used for a comprehensive characterization of ionization wave dynamics inside a glass target induced by a laser-driven, relativistic electron beam. Experiments were done using the 50-TW Leopard laser at the University of Nevada, Reno. We show that for a laser flux of ∼2 × 10(18) W/cm2 a hemispherical ionization wave propagates at c/3 for 10 ps and has a smooth electron-density distribution. The maximum free-electron density inside the glass target is ∼2 × 10(19) cm-3, which corresponds to an ionization level of ∼0.1%. Magnetic fields and electric fields do not exceed ∼15 kG and ∼1 MV/cm, respectively. The electron temperature has a hot, ringlike structure with a maximum of ∼0.7 eV. The topology of the interference phase shift shows the signature of the "fountain effect", a narrow electron beam that fans out from the propagation axis and heads back to the target surface. Two-dimensional particle-in-cell (PIC) computer simulations demonstrate radial spreading of fast electrons by self-consistent electrostatic fields driven by laser. The very low ionization observed after the laser heating pulse suggests a fast recombination on the sub-ps time scale.
Salmanpoor, H.; Sharifian, M.; Gholipour, S.; Borhani Zarandi, M.; Shokri, B.
2018-03-01
The oblique propagation of nonlinear ion acoustic solitary waves (solitons) in magnetized collisionless and weakly relativistic plasma with positive and negative ions and super thermal electrons has been examined by using reduced perturbation method to obtain the Korteweg-de Vries equation that admits an obliquely propagating soliton solution. We have investigated the effects of plasma parameters like negative ion density, electrons temperature, angle between wave vector and magnetic field, ions velocity, and k (spectral index in kappa distribution) on the amplitude and width of solitary waves. It has been found out that four modes exist in our plasma model, but the analysis of the results showed that only two types of ion acoustic modes (fast and slow) exist in the plasma and in special cases only one mode could be propagated. The parameters of plasma for these two modes (or one mode) determine which one is rarefactive and which one is compressive. The main parameter is negative ions density (β) indicating which mode is compressive or rarefactive. The effects of the other plasma parameters on amplitude and width of the ion acoustic solitary waves have been studied. The main conclusion is that the effects of the plasma parameters on amplitude and width of the solitary wave strongly depend on the value of the negative ion density.
Theoretical Studies of TE-Wave Propagation as a Diagnostic for Electron Cloud
International Nuclear Information System (INIS)
Penn, Gregory E.; Vay, Jean-Luc
2010-01-01
The propagation of TE waves is sensitive to the presence of an electron cloud primarily through phase shifts generated by the altered dielectric function, but can also lead to polarization changes and other effects, especially in the presence of magnetic fields. These effects are studied theoretically and also through simulations using WARP. Examples are shown related to CesrTA parameters, and used to observe different regimes of operation as well as to validate estimates of the phase shift.
Propagation of Threatened Nepenthes khasiana: Methods and Precautions
Directory of Open Access Journals (Sweden)
Jibankumar S. KHURAIJAM
2015-09-01
Full Text Available Ex-situ conservation is an important key in the management of rare, endangered and threatened (RET plant species and its effectiveness depends on several factors. Maintenance of viable germplasm and its subsequent propagation plays an important role in long term conservation of many RET species. Nepenthes khasiana is a rare and gravely threatened species in the wild due to over-collection and other threats. The species needs urgent in-situ and ex-situ conservation. Development of easy to propagate techniques would pave faster multiplication for its use of educational, medicinal and horticultural purpose. In the present paper, successful propagation technique of Nepenthes khasiana through seeds is demonstrated along with detailed information on precautions to be taken during the adoption of the techniques.
Obliquely propagating electron acoustic solitons in magnetized plasmas with nonextensive electrons
Directory of Open Access Journals (Sweden)
H. R. Pakzad
2013-04-01
Full Text Available The problem of small amplitude electron-acoustic solitary waves (EASWs is discussed using the reductive perturbation theory in magnetized plasmas consisting of cold electrons, hot electrons obeying nonextensive distribution and stationary ions. The presented investigation shows that the presence of nonextensive distributed hot electrons (due to the effects of long-range interactions causes a reduction in the soliton amplitude while its width increases. The effects of the population ratio of hot to cold electrons and also the effects of the presence of magnetic field in this situation are also discussed.
A high-repetition rate LWFA for studies of laser propagation and electron generation
He, Zhaohan; Easter, James; Hou, Bixue; Krushelnick, Karl; Nees, John; Thomas, Alec
2010-11-01
Advances in ultrafast optics today have enabled laser systems to deliver ever shorter and more intense pulses. When focused, such laser pulses can easily exceed relativistic intensities where the wakefield created by the strong laser electric field can be used to accelerate electrons. Laser wakefield acceleration of electrons holds promise for future compact electron accelerators or drivers of other radiation sources in many scientific, medical and engineering applications. We present experimental studies of laser wakefield acceleration using the λ-cubed laser at the University of Michigan -- a table-top high-power laser system operating at 500 Hz repetition rate. The high repetition rate allows statistical studies of laser propagation and electron acceleration which are not accessible with typical sub-0.1 Hz repetition rate systems. In addition, we compare the experiments with particle-in-cell simulations using the code OSIRIS.
Propagation of a surface electromagnetic wave in a plasma with allowance for electron heating
International Nuclear Information System (INIS)
Boev, A.G.; Prokopov, A.V.
1978-01-01
Considered is propagation of a surface high-frequency wave in a semibounded plasma, which electron component is heated within the wave field. Dissipative effects are considered small, that is possible if wave frequency is much higher than the collision frequency and phase velocity of wave considerably exceeds electron heat velocity. Under conditions of anomalous skin-effect the distributions of electron temperature and wave damping have been found. It is established, that higher electron temperature on the boundary results in a higher decrease of temperature inside a plasma, far from the boundary temperature decreases exponentially; damping coefficient under anomalous skin-effect conditions is characterized by a stronger dependence not only on the wave amplitude, but as well as on gas pressure and wave frequency in comparison with normal conditions
Bonds, Marta Anna
Self-propagating high temperature synthesis (SHS) in reactive multilayer foils (RMLFs) has been systematically studied in situ and ex situ. RMLFs are layered materials comprised of two constituents with a high enthalpy of mixing. The two constituents are deposited in an alternating fashion. The 10s--100s nanometer-thick layers produce short diffusion distances to enhance mixing. When initiated by an external heat source, the foils react in a self-propagating fashion driven by exothermic mixing. The propagation characteristics, namely velocity and maximum temperature, depend on the chemistries involved as well as the foil architecture. The Al/Ni 3:1 system was chosen because of its potential application in microelectronics and its lower reaction temperature. The foils were grown by magnetron sputtering with bilayers measuring 25 or 27nm and a final thickness of 125 and 189nm. In situ and ex situ experiments have yielded significant cumulative trends about RMLF behavior. Ex situ experiments rely on reaction quenching and post mortem examination with XRD to reveal intermetallic phase evolution. Quenching can introduce intermediate phases not necessarily native to the original process. In situ optical observation yield temperature and velocity information, but not necessarily phase information. In situ x-ray microdiffraction has been applied to study phase evolution but samples a large portion of the foil. The dynamic TEM (DTEM) has the spatial and temporal resolution to study these reactions in situ to better our understanding of the reaction process, which tends to be rather uncontrollable and occurs at very high temperatures. Using SHS of RMLFs as a novel method for intermetallic formation will be benefited by a more thorough understanding of the thermodynamics and kinetics involved, especially for heat-sensitive application. The dynamic transmission electron microscope (DTEM) has been a unique instrument allowing for in situ examination of RMLFs during the
Energy Technology Data Exchange (ETDEWEB)
Wang, Jian-Yong; Cheng, Xue-Ping; Tang, Xiao-Yan, E-mail: xytang@sjtu.edu.cn [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Yang, Jian-Rong [Department of Physics and Electronics, Shangrao Normal University, Jiangxi, Shangrao 334001 (China); Ren, Bo [Institute of Nonlinear Science, Shaoxing University, Shaoxing 312000 (China)
2014-03-15
The oblique propagation of ion-acoustic soliton-cnoidal waves in a magnetized electron-positron-ion plasma with superthermal electrons is studied. Linear dispersion relations of the fast and slow ion-acoustic modes are discussed under the weak and strong magnetic field situations. By means of the reductive perturbation approach, Korteweg-de Vries equations governing ion-acoustic waves of fast and slow modes are derived, respectively. Explicit interacting soliton-cnoidal wave solutions are obtained by the generalized truncated Painlevé expansion. It is found that every peak of a cnoidal wave elastically interacts with a usual soliton except for some phase shifts. The influence of the electron superthermality, positron concentration, and magnetic field obliqueness on the soliton-cnoidal wave are investigated in detail.
Maxwell+TDDFT multiscale method for light propagation in thin-film semiconductor
Uemoto, Mitsuharu; Yabana, Kazuhiro
First-principles time-dependent density functional theory (TDDFT) has been a powerful tool to describe light-matter interactions and widely used to describe electronic excitations and linear and nonlinear optical properties of molecules and solids. We have been developing a novel multiscale modeling to describe a propagation of light pulse in a macroscopic medium combining TDDFT and Maxwell equations. In the method, the finite-difference time-domain (FDTD)-like electromagnetism (EM) calculation is carried out in a macroscopic grid. At each grid point, the time-dependent Kohn-Sham equation is solved in real time. In the presentation, we show applications of this method to the 1D/2D propagations of femtosecond laser pulses through a thin-film semiconductor. This work was supported in part by MEXT as a social and scientific priority issue (Creation of new functional devices and high-performance materials to support next-generation industries; CDMSI) to be tackled by using post-K computer.
Singular value decomposition methods for wave propagation analysis
Czech Academy of Sciences Publication Activity Database
Santolík, Ondřej; Parrot, M.; Lefeuvre, F.
2003-01-01
Roč. 38, č. 1 (2003), s. 10-1-10-13 ISSN 0048-6604 R&D Projects: GA ČR GA205/01/1064 Grant - others:Barrande(CZ) 98039/98055 Institutional research plan: CEZ:AV0Z3042911; CEZ:MSM 113200004 Keywords : wave propagation * singular value decomposition Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.832, year: 2003
International Nuclear Information System (INIS)
Moir, D.C.; Faehl, R.J.; Newberger, B.S.; Thode, L.E.
1981-01-01
Near-term development of the existing PHERMEX standing-wave linac would provide a 40 to 60 MeV electron beam with a current of 3 kA capable of answering a number of fundamental issues concerning endoatmospheric, ultra-relativistic electron beam propagation. Inherent high-repetition rate and multiple-pulse capability would allow alternative propagation scenarios to be investigated. Much of the theoretical expertise required to support the technology development and time-resolved beam propagation experiments presently resides within the Theoretical Applications Division
Measurement of fatigue crack propagation at -700C with the d.c. potential probe method
International Nuclear Information System (INIS)
Siekmann, G.; Berns, H.
1983-01-01
Measurement of fatigue crack propagation by means of the d.c. potential probe on 1/2''CT specimens at 20 0 C and -70 0 C is described. The method proves to be a useful tool for the determination of fatigue crack propagation if the experiments have to be carried out in temperature baths or temperature chambers. At 20 deg C the comparison of the optical method of crack growth measurement with the d.c. potential probe method gives calibration curves which, accounting for several parameters of influence, from the basis of crack propagation measurements with the d.c. potential probe method at -70 0 C. (orig.) [de
DEFF Research Database (Denmark)
Rasmussen, Christian Jørgen
2001-01-01
Presents a simple and fast method for determination of the step size that exactly leads to a prescribed accuracy when signal propagation through nonlinear optical fibres is computed using the split-step Fourier method.......Presents a simple and fast method for determination of the step size that exactly leads to a prescribed accuracy when signal propagation through nonlinear optical fibres is computed using the split-step Fourier method....
Omura, Y.; Hsieh, Y. K.; Foster, J. C.; Erickson, P. J.; Kletzing, C.; Baker, D. N.
2017-12-01
A recent test particle simulation of obliquely propagating whistler mode wave-particle interaction [Hsieh and Omura, 2017] shows that the perpendicular wave electric field can play a significant role in trapping and accelerating relativistic electrons through Landau resonance. A further theoretical and numerical investigation verifies that there occurs nonlinear wave trapping of relativistic electrons by the nonlinear Lorentz force of the perpendicular wave magnetic field. An electron moving with a parallel velocity equal to the parallel phase velocity of an obliquely propagating wave basically see a stationary wave phase. Since the electron position is displaced from its gyrocenter by a distance ρ*sin(φ), where ρ is the gyroradius and φ is the gyrophase, the wave phase is modulated with the gyromotion, and the stationary wave fields as seen by the electron are expanded as series of Bessel functions Jn with phase variations n*φ. The J1 components of the wave electric and magnetic fields rotate in the right-hand direction with the gyrofrequency, and they can be in resonance with the electron undergoing the gyromotion, resulting in effective electron acceleration and pitch angle scattering. We have performed a subpacket analysis of chorus waveforms observed by the Van Allen Probes [Foster et al., 2017], and calculated the energy gain by the cyclotron acceleration through Landau resonance. We compare the efficiencies of accelerations by cyclotron and Landau resonances in typical events of rapid electron acceleration observed by the Van Allen Probes.References:[1] Hsieh, Y.-K., and Y. Omura (2017), Nonlinear dynamics of electrons interacting with oblique whistler mode chorus in the magnetosphere, J. Geophys. Res. Space Physics, 122, 675-694, doi:10.1002/2016JA023255.[2] Foster, J. C., P. J. Erickson, Y. Omura, D. N. Baker, C. A. Kletzing, and S. G. Claudepierre (2017), Van Allen Probes observations of prompt MeV radiation belt electron acceleration in nonlinear
Erosion of a relativistic electron beam propagating in a plasma channel
International Nuclear Information System (INIS)
Werner, P.W.; Schamiloglu, E.; Smith, J.R.; Struve, K.W.; Lipinski, R.J.
1994-01-01
A relativistic electron beam has propagated 91 m in a laser-ionized plasma channel across applied magnetic fields much larger than the geomagnetic field. Beam currents ranged from 0.3 to 1.0 kA and transverse magnetic field from 0.1 to 4.0 G. Beam degradation in the form of a shortening of the current pulse (erosion) was observed. The erosion processes were inductive and magnetic erosion. Observed total erosion rates are in agreement with the summation of the theoretical inductive and magnetic erosion rates. Magnetic erosion was enhanced when the beam radius was larger than the channel
Storage ring free electron laser, pulse propagation effects and microwave type instabilities
International Nuclear Information System (INIS)
Dattoli, G.; Mezi, L.; Renieri, A.; Migliorati, M.
2000-01-01
It has been developed a dynamical model accounting for the storage Ring Free Electron Laser evolution including pulse propagation effects and e-beam instabilities of microwave type. It has been analyzed the general conditions under which the on set of the laser may switch off the instability and focus everybody attention on the interplay between cavity mismatch, laser pulsed behavior and e-beam instability dynamics. Particular attention is also devoted to the laser operation in near threshold conditions, namely at an intracavity level just enough to counteract the instability, that show in this region new and interesting effects arises [it
Space-charge effects on the propagation of hollow electron beams
International Nuclear Information System (INIS)
Barroso, J.J.; Stellati, C.
1994-01-01
The dynamics of hollow electron beams with gyro motion propagating down a cylindrical drift tube is analysed on the basis of a non-adiabatic-gun-generated laminar beam. Due to the action of beam's self-space charge field, the transverse velocity spread has an oscillatory behavior along the drift tube wherein the spatial auto modulation period shortens with increasing current. Numerical simulation results indicate that even at a 10 A beam current, the resulting transverse velocity spread is still less than the spread for a zero beam current. (author). 5 refs, 3 figs
Seabra, G M; Kaplan, I G; Ortiz, J V
2005-09-15
Corrections to dipole approximation results for angular distributions in photoionization of first-row hydrides have determined by using Dyson orbitals calculated with ab initio electron propagator theory and by considering the full multipole expansion for the incident photon representation. The relative importance of first-order corrections which consist of electric quadrupole and magnetic dipole terms and of higher-order terms has been estimated as a function of photon energy. Multipole corrections to the dipole approximation depend on photon energy and on the characteristics of the Dyson orbitals.
Directory of Open Access Journals (Sweden)
Radi Radi
2011-08-01
Full Text Available Constructive Back Propagation Neural Network (CBPNN is a kind of back propagation neural network trained with constructive algorithm. Training of CBPNN is mainly conducted by developing the network’s architecture which commonly done by adding a number of new neuron units on learning process. Training of the network usually implements fixed method to develop its structure gradually by adding new units constantly. Although this method is simple and able to create an adaptive network for data pattern complexity, but it is wasteful and inefficient for computing. New unit addition affects directly to the computational load of training, speed of convergence, and structure of the final neural network. While increases training load significantly, excessive addition of units also tends to generate a large size of final network. Moreover, addition pattern with small unit number tends to drop off the adaptability of the network and extends time of training. Therefore, there is important to design an adaptive structure development pattern for CBPNN in order to minimize computing load of training. This study proposes Fuzzy Logic (FL algorithm to manage and develop structure of CBPNN. FL method was implemented on two models of CBPNN, i.e. designed with one and two hidden layers, used to recognize aroma patterns on an electronic nose system. The results showed that this method is effective to be applied due to its capability to minimize time of training, to reduce load of computational learning, and generate small size of network.
Physics-based statistical model and simulation method of RF propagation in urban environments
Pao, Hsueh-Yuan; Dvorak, Steven L.
2010-09-14
A physics-based statistical model and simulation/modeling method and system of electromagnetic wave propagation (wireless communication) in urban environments. In particular, the model is a computationally efficient close-formed parametric model of RF propagation in an urban environment which is extracted from a physics-based statistical wireless channel simulation method and system. The simulation divides the complex urban environment into a network of interconnected urban canyon waveguides which can be analyzed individually; calculates spectral coefficients of modal fields in the waveguides excited by the propagation using a database of statistical impedance boundary conditions which incorporates the complexity of building walls in the propagation model; determines statistical parameters of the calculated modal fields; and determines a parametric propagation model based on the statistical parameters of the calculated modal fields from which predictions of communications capability may be made.
Effects of buried high-Z layers on fast electron propagation
International Nuclear Information System (INIS)
Yang, Xiaohu; Zhuo, Hongbin; Ma, Yanyun; Shao, Fuqiu; Xu, Han; Yin Yan; Borghesi, M.
2014-01-01
The transport through high density plasmas of relativistic electron beams generated by ultra-intense laser-plasma interaction has potential applications in laser-driven ion acceleration and in the fast igniter scheme for inertial confinement fusion. By extending a prior model [A.R. Bell, J.R. Davies, S.M. Guerin, Phys. Rev. E 58, 2471 (1998)], the magnetic field generated during the transport of a fast electron beam driven by an ultra-intense laser in a solid target is derived analytically and applied to estimate the effect of such field on fast electron propagation through a buried high-Z layer in a lower-Z target. It is found that the effect gets weaker with the increase of the depth of the buried layer, the divergence of the fast electrons, and the laser intensity, indicating that magnetic field effects on the fast electron divergence as measured from K a X-ray emission may need to be considered for moderate laser intensities. On the basis of the calculations, some considerations are made on how one can mitigate the effect of the magnetic field generated at the interface. (authors)
International Nuclear Information System (INIS)
Struve, K.W.; Lauer, E.J.; Chambers, F.W.
1983-01-01
The IFR is a well-known stable, low pressure (0.10 to 0.120 torr in air) propagation window. Secondary electrons created by collisions of beam electrons with gas atoms are rapidly expelled by the strong radial electric field of the beam charge. The ions that remain inside the beam partially neutralize the electric field, allowing magnetic pinch forces to focus the beam. Experiments with the ETA beam have re-verified this stable window and are reported. Image forces from a close wall IFR propagation tank are also experimentally shown to center the beam and damp transverse oscillations. Results of experiments using 5 and 15 cm dia beam tubes are reported. For p tau > 2 torr-nsec (gas pressure x time into pulse the beam charge becomes completely neutralized by the ions, allowing a build up of plasma and resultant beam-plasma instabilities. The onset of these instabilities has been measured using rf pickup loops (0 to 2 GHz) and microwave detectors (6 to 40 GHz), and are also reported
Ai, Fei; Qian, Jianqiang; Shi, Junfeng; Zhang, Machi
2017-10-10
The transmission properties of beams in gain fibers are studied with the complex refractive index beam propagation method (CRI-BPM). The method is checked by comparison with an analytic method. The behavior of a gain-guided, index antiguided (GG-IAG) fiber with different gain coefficients is studied. The simulation results show that the signal can transfer in the fiber with almost no loss when the gain coefficient reaches the threshold of the fundamental mode, and the shape of output spot will have no major changes when the gain coefficient is over the thresholds of high-order modes, even when the mode competition is not obvious. The CRI-BPM can predict the changes in light power and light mode at the same time, and will be very useful in the designing of fiber amplifiers and lasers with complex structures. More factors will be considered in this method to provide reference for practical application in our further research.
Energy Technology Data Exchange (ETDEWEB)
Neudatchin, S.V.; Cordey, J.G.; Muir, D.G. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking
1993-12-31
Previous methods for the analysis of electron transport during sawtooth induced heat pulse propagation (HPP) are valid at radii greater than the mixing radius r{sub mix}. This report describes a new numerical technique for the analysis of the decay rate of sawteeth perturbed T{sub e} profiles between the inversion radius r{sub inv} and r{sub mix} and demonstrates the technique through its application to JET data. The method is a development of the `two-boundaries` method. It was suggested that the electron heat diffusivity, {chi}{sub e}, immediately after a crash is strongly enhanced and subsequently relaxes to its original level and that previous heat pulse data could have been distorted by this effect. For this radial zone the influence of {chi}{sub e} relaxation can be minimised by beginning the analysis a few milliseconds after the crash. Confinement mode transitions are also investigated. It is shown that during L-H-L transitions the change in {chi}{sub e} across most of the plasma occurs on a millisecond timescale and is well correlated with the change in the dynamic electron diffusivity {chi}{sub e}{sup HP}. (author) 4 refs., 4 figs.
A finite element beam propagation method for simulation of liquid crystal devices.
Vanbrabant, Pieter J M; Beeckman, Jeroen; Neyts, Kristiaan; James, Richard; Fernandez, F Anibal
2009-06-22
An efficient full-vectorial finite element beam propagation method is presented that uses higher order vector elements to calculate the wide angle propagation of an optical field through inhomogeneous, anisotropic optical materials such as liquid crystals. The full dielectric permittivity tensor is considered in solving Maxwell's equations. The wide applicability of the method is illustrated with different examples: the propagation of a laser beam in a uniaxial medium, the tunability of a directional coupler based on liquid crystals and the near-field diffraction of a plane wave in a structure containing micrometer scale variations in the transverse refractive index, similar to the pixels of a spatial light modulator.
Modeling laser beam diffraction and propagation by the mode-expansion method.
Snyder, James J
2007-08-01
In the mode-expansion method for modeling propagation of a diffracted beam, the beam at the aperture can be expanded as a weighted set of orthogonal modes. The parameters of the expansion modes are chosen to maximize the weighting coefficient of the lowest-order mode. As the beam propagates, its field distribution can be reconstructed from the set of weighting coefficients and the Gouy phase of the lowest-order mode. We have developed a simple procedure to implement the mode-expansion method for propagation through an arbitrary ABCD matrix, and we have demonstrated that it is accurate in comparison with direct calculations of diffraction integrals and much faster.
Propagation and Loss-Cone Properties of Relativistic Electron Beams in the Magnetosphere
Sanchez, E. R.; Powis, A.; Greklek, M.; Porazik, P.; Kaganovich, I.
2017-12-01
One of the main obstacles for achieving closure of several key outstanding questions in magnetospheric physics has been the lack of accurate magnetic field mapping between processes or regions in the magnetosphere and their ionospheric foot-points. Accurate correspondence between magnetospheric processes or regions and their ionospheric foot-points can be achieved with beams of MeV electrons that propagate along magnetic-field lines in fractions of a second, emitted by compact linear accelerators under controlled conditions at specified points in the magnetosphere, while the atmospheric imprint created by their precipitation is detected by an array of ground-based optical imagers, radars, riometers or X-ray detectors. To prove that successful magnetic field mapping is possible, we must ensure that the beam can be injected into the loss cone, that the spacecraft potentials induced by the beam emission are manageable, that the beam propagates all the way into the topside ionosphere, and that the beam produces a signature detectable from the ground or from low altitude. In this work, we present the latest results of calculations of beam injection and propagation for a wide range of injection distances in the magnetotail equator and geomagnetic conditions to determine under what conditions beams emitted from the magnetosphere would be able to propagate to the topside ionosphere with enough intensity to be detected by ground-based or low-altitude instrumentation. Using ballistic simulations of charged particle motion, we demonstrate that relativistic electron beams can be successfully injected into the loss cone under both ideal (analytic dipole) and realistic (MHD modeled) magnetosphere conditions from a wide range of injection positions. For identical injection coordinates, the impact location on the top of the atmosphere is dependent on the current magnetosphere conditions, demonstrating that this technique can distinguish between the phases of a geomagnetic storm
Sabry, R.; Omran, M. A.
2013-04-01
Investigation of nonlinear wave modulation of electron-acoustic solitary wave packets in planar as well as nonplanar geometry is carried out for an unmagnetized two temperature plasma composed of cold and hot (featuring q-nonextensive distribution) electrons with stationary ions. It is shown that in such plasma, propagation of EA wave packets is governed by a modified NLSE which accounts for the geometrical effect and the nonextensivity of the hot electron species. It is found that the nature of the modulational instabilities would be significantly modified due to the geometrical effects, density ratio α of the hot-to-cold electrons species as well as their temperature ratio θ. Also, there exists a modulation instability period for the cylindrical and spherical envelope excitations, which does not exist in the one-dimensional case. Furthermore, spherical EA solitary wave packets are more structurally stable to perturbations than the cylindrical ones. The relevance of the current study to EA wave modulation in auroral zone plasma is highlighted.
Electron Spectroscopic Methods in Teaching.
Allan, Michael
1987-01-01
Discusses electron-loss spectroscopy and the experimentally observed excitation energies in terms of qualitative MO theory. Reviews information on photoelectron spectroscopy and electron transmission spectroscopy and their relation to the occupied and unoccupied orbital levels. Focuses on teaching applications. (ML)
Propagation of energetic electrons in the solar corona observed with LOFAR
Breitling, F.
2017-06-01
This work reports about new high-resolution imaging and spectroscopic observations of solar type III radio bursts at low radio frequencies in the range from 30 to 80 MHz. Solar type III radio bursts are understood as result of the beam-plasma interaction of electron beams in the corona. The Sun provides a unique opportunity to study these plasma processes of an active star. Its activity appears in eruptive events like flares, coronal mass ejections and radio bursts which are all accompanied by enhanced radio emission. Therefore solar radio emission carries important information about plasma processes associated with the Sun's activity. Moreover, the Sun's atmosphere is a unique plasma laboratory with plasma processes under conditions not found in terrestrial laboratories. Because of the Sun's proximity to Earth, it can be studied in greater detail than any other star but new knowledge about the Sun can be transfer to them. This "solar stellar connection" is important for the understanding of processes on other stars. The novel radio interferometer LOFAR provides imaging and spectroscopic capabilities to study these processes at low frequencies. Here it was used for solar observations. LOFAR, the characteristics of its solar data and the processing and analysis of the latter with the Solar Imaging Pipeline and Solar Data Center are described. The Solar Imaging Pipeline is the central software that allows using LOFAR for solar observations. So its development was necessary for the analysis of solar LOFAR data and realized here. Moreover a new density model with heat conduction and Alfvén waves was developed that provides the distance of radio bursts to the Sun from dynamic radio spectra. Its application to the dynamic spectrum of a type III burst observed on March 16, 2016 by LOFAR shows a nonuniform radial propagation velocity of the radio emission. The analysis of an imaging observation of type III bursts on June 23, 2012 resolves a burst as bright, compact region
Modeling of high-frequency wave propagation in the heterogenous Earth using screen method
Ding, Y.; Zheng, Y.
2017-12-01
High-frequency (1Hz) wave propagation modeling in the heterogenous Earth is difficult due to computation cost. We have developed one alternative method to do high-frequency wave propagation locally in the Earth. First, we divide the heterogeneous Earth model into two parts: the background gradient velocity model, and the velocity perturbation. Then we trace rays from the source to the Earth surface and make screens perpendicular to the rays. We propagate the wavefield in each screen by Kirchhoff surface integral and account for the velocity perturbations with a phase shift. Recursively, the algorithm will propagate the wavefield locally from the source to the surface. The result is compared with that from the finite difference method.
Coherent-wave Monte Carlo method for simulating light propagation in tissue
Kraszewski, Maciej; Pluciński, Jerzy
2016-03-01
Simulating propagation and scattering of coherent light in turbid media, such as biological tissues, is a complex problem. Numerical methods for solving Helmholtz or wave equation (e.g. finite-difference or finite-element methods) require large amount of computer memory and long computation time. This makes them impractical for simulating laser beam propagation into deep layers of tissue. Other group of methods, based on radiative transfer equation, allows to simulate only propagation of light averaged over the ensemble of turbid medium realizations. This makes them unuseful for simulating phenomena connected to coherence properties of light. We propose a new method for simulating propagation of coherent light (e.g. laser beam) in biological tissue, that we called Coherent-Wave Monte Carlo method. This method is based on direct computation of optical interaction between scatterers inside the random medium, what allows to reduce amount of memory and computation time required for simulation. We present the theoretical basis of the proposed method and its comparison with finite-difference methods for simulating light propagation in scattering media in Rayleigh approximation regime.
Research on Band-limited Local Plane Wave Propagator and Imaging Method in TI Medium
Han, B.; Gu, H.; Liu, S.
2017-12-01
Traditional ray-based seismic wave propagators, under the infinite frequency assumption, are widely used in seismic wave propagation and imaging due to its efficiency and flexibility. Seismic wave is a typical band-limited signal; consequently, the high-frequency ray theory is difficult to accurately describe the propagation characteristics of the band-limited signals, and it cannot avoid ray shading zones and caustics. As for wave equation based operators, even though they can propagate band-limited waves accurately, they are computationally demanding. In this study, under the framework of traditional ray theory, a seismic wave propagator applicable to transverse anisotropic medium is proposed, which is based on the local plane wave assumption. The proposed band-limited local plane wave propagator not only preserves the advantages of conventional ray-based propagators but also propagates band-limited waves accurately. To be detailed, a band-limited Snell's Law is constructed by solving the Kirchhoff boundary integral in a local plane, which is perpendicular to the central ray. Then band-limited rays are traced following the band-limited Snell's Law, and equivalent ray parameters are calculated by averaging local plane wave parameters. Physically, band-limited Snell's Law depicts that the directions of band-limited wavefields with maximum energy rays in the first Fresnel zone. Finally, the band-limited beam migration method in TI medium is developed by combining the paraxial beams with the band-limited central rays. Numerical experiments show that the local plane wave propagator can enhance the illumination in shadow zone and the imaging qualities of complex structures, such as rugose salt boundaries. Compared to conventional beam migration, our method generates better angle domain common imaging gathers (ADCIGs).
METHOD OF ELECTRON BEAM PROCESSING
DEFF Research Database (Denmark)
2003-01-01
As a rule, electron beam welding takes place in a vacuum. However, this means that the workpieces in question have to be placed in a vacuum chamber and have to be removed therefrom after welding. This is time−consuming and a serious limitation of a process the greatest advantage of which is the o......As a rule, electron beam welding takes place in a vacuum. However, this means that the workpieces in question have to be placed in a vacuum chamber and have to be removed therefrom after welding. This is time−consuming and a serious limitation of a process the greatest advantage of which...... is the option of welding workpieces of large thicknesses. Therefore the idea is to guide the electron beam (2) to the workpiece via a hollow wire, said wire thereby acting as a prolongation of the vacuum chamber (4) down to workpiece. Thus, a workpiece need not be placed inside the vacuum chamber, thereby...... exploiting the potential of electron beam processing to a greater degree than previously possible, for example by means of electron beam welding...
An efficient method for studying and analysing the propagation ...
African Journals Online (AJOL)
The paper describes a method, based on the solution of travelling-wave phenomena in polyphase systems by the use of matrix methods, of deriving the basic matrices of the conductor system taking into account the effect of conductor geometry, conductor internal impedance and the earth-return path. It is then shown how ...
Symplectic Hamiltonian HDG methods for wave propagation phenomena
Sánchez, M. A.; Ciuca, C.; Nguyen, N. C.; Peraire, J.; Cockburn, B.
2017-12-01
We devise the first symplectic Hamiltonian hybridizable discontinuous Galerkin (HDG) methods for the acoustic wave equation. We discretize in space by using a Hamiltonian HDG scheme, that is, an HDG method which preserves the Hamiltonian structure of the wave equation, and in time by using symplectic, diagonally implicit and explicit partitioned Runge-Kutta methods. The fundamental feature of the resulting scheme is that the conservation of a discrete energy, which is nothing but a discrete version of the original Hamiltonian, is guaranteed. We present numerical experiments which indicate that the method achieves optimal approximations of order k + 1 in the L2-norm when polynomials of degree k ≥ 0 and Runge-Kutta time-marching methods of order k + 1 are used. In addition, by means of post-processing techniques and by increasing the order of the Runge-Kutta method to k + 2, we obtain superconvergent approximations of order k + 2 in the L2-norm for the displacement and the velocity. We also present numerical examples that corroborate that the methods conserve energy and that they compare favorably with dissipative HDG schemes, of similar accuracy properties, for long-time simulations.
Producing accurate wave propagation time histories using the global matrix method
International Nuclear Information System (INIS)
Obenchain, Matthew B; Cesnik, Carlos E S
2013-01-01
This paper presents a reliable method for producing accurate displacement time histories for wave propagation in laminated plates using the global matrix method. The existence of inward and outward propagating waves in the general solution is highlighted while examining the axisymmetric case of a circular actuator on an aluminum plate. Problems with previous attempts to isolate the outward wave for anisotropic laminates are shown. The updated method develops a correction signal that can be added to the original time history solution to cancel the inward wave and leave only the outward propagating wave. The paper demonstrates the effectiveness of the new method for circular and square actuators bonded to the surface of isotropic laminates, and these results are compared with exact solutions. Results for circular actuators on cross-ply laminates are also presented and compared with experimental results, showing the ability of the new method to successfully capture the displacement time histories for composite laminates. (paper)
Accurate finite difference beam propagation method for complex integrated optical structures
DEFF Research Database (Denmark)
Rasmussen, Thomas; Povlsen, Jørn Hedegaard; Bjarklev, Anders Overgaard
1993-01-01
A simple and effective finite-difference beam propagation method in a z-varying nonuniform mesh is developed. The accuracy and computation time for this method are compared with a standard finite-difference method for both the 3-D and 2-D versions...
International Nuclear Information System (INIS)
Sabouri, Pouya
2013-01-01
This thesis presents a comprehensive study of sensitivity/uncertainty analysis for reactor performance parameters (e.g. the k-effective) to the base nuclear data from which they are computed. The analysis starts at the fundamental step, the Evaluated Nuclear Data File and the uncertainties inherently associated with the data they contain, available in the form of variance/covariance matrices. We show that when a methodical and consistent computation of sensitivity is performed, conventional deterministic formalisms can be sufficient to propagate nuclear data uncertainties with the level of accuracy obtained by the most advanced tools, such as state-of-the-art Monte Carlo codes. By applying our developed methodology to three exercises proposed by the OECD (Uncertainty Analysis for Criticality Safety Assessment Benchmarks), we provide insights of the underlying physical phenomena associated with the used formalisms. (author)
Electron-capture Isotopes Could Constrain Cosmic-Ray Propagation Models
Benyamin, David; Shaviv, Nir J.; Piran, Tsvi
2017-12-01
Electron capture (EC) isotopes are known to provide constraints on the low-energy behavior of cosmic rays (CRs), such as reacceleration. Here, we study the EC isotopes within the framework of the dynamic spiral-arms CR propagation model in which most of the CR sources reside in the galactic spiral arms. The model was previously used to explain the B/C and sub-Fe/Fe ratios. We show that the known inconsistency between the 49Ti/49V and 51V/51Cr ratios remains also in the spiral-arms model. On the other hand, unlike the general wisdom that says the isotope ratios depend primarily on reacceleration, we find here that the ratio also depends on the halo size (Z h) and, in spiral-arms models, also on the time since the last spiral-arm passage ({τ }{arm}). Namely, EC isotopes can, in principle, provide interesting constraints on the diffusion geometry. However, with the present uncertainties in the lab measurements of both the electron attachment rate and the fragmentation cross sections, no meaningful constraint can be placed.
Directory of Open Access Journals (Sweden)
Avi Karsenty
2017-01-01
Full Text Available Phase measurements obtained by high-coherence interferometry are restricted by the 2π ambiguity, to height differences smaller than λ/2. A further restriction in most interferometric systems is for focusing the system on the measured object. We present two methods that overcome these restrictions. In the first method, different segments of a measured wavefront are digitally propagated and focused locally after measurement. The divergent distances, by which the diverse segments of the wavefront are propagated in order to achieve a focused image, provide enough information so as to resolve the 2π ambiguity. The second method employs an interferogram obtained by a spectrum constituting a small number of wavelengths. The magnitude of the interferogram’s modulations is utilized to resolve the 2π ambiguity. Such methods of wavefront propagation enable several applications such as focusing and resolving the 2π ambiguity, as described in the article.
Effective preconditioning methods for in vitro propagation of Uapaca ...
African Journals Online (AJOL)
The objective of the study was to determine efficient preconditioning methods for in vitro multiplication of Uapaca kirkiana plant materials from mature stock plants. The efficacy of sodium hypochlorite (NaOCl), calcium hypochlorite {Ca(OCl2)2} or mercuric chloride (HgCl2) as surface sterilant was evaluated in ...
A Survey of Symplectic and Collocation Integration Methods for Orbit Propagation
Jones, Brandon A.; Anderson, Rodney L.
2012-01-01
Demands on numerical integration algorithms for astrodynamics applications continue to increase. Common methods, like explicit Runge-Kutta, meet the orbit propagation needs of most scenarios, but more specialized scenarios require new techniques to meet both computational efficiency and accuracy needs. This paper provides an extensive survey on the application of symplectic and collocation methods to astrodynamics. Both of these methods benefit from relatively recent theoretical developments, which improve their applicability to artificial satellite orbit propagation. This paper also details their implementation, with several tests demonstrating their advantages and disadvantages.
CSIR Research Space (South Africa)
Mokotedi, O
2011-11-01
Full Text Available The purpose of this study was to deepen our understanding of the field performance of micro- and macro-propagated Eucalyptus grandis x nitens (GN), in comparison with seed-propagated E. grandis and E. nitens. The emphasis was on the relationship...
Wave propagation retrieval method for metamaterials: Unambiguous restoration of effective parameters
DEFF Research Database (Denmark)
Andryieuski, Andrei; Malureanu, Radu; Lavrinenko, Andrei
2009-01-01
In this brief report we propose a direct method of effective-parameters restoration that is based on the wave propagation phenomenon. It is easy in implementation, has no unambiguity in retrieving effective properties and is applicable to thick metamaterial (MTM) slabs. The method is validated...
Modeling of crack propagation in weak snowpack layers using the discrete element method
Gaume, J.; van Herwijnen, A.; Chambon, G.; Birkeland, K. W.; Schweizer, J.
2015-10-01
Dry-snow slab avalanches are generally caused by a sequence of fracture processes including (1) failure initiation in a weak snow layer underlying a cohesive slab, (2) crack propagation within the weak layer and (3) tensile fracture through the slab which leads to its detachment. During the past decades, theoretical and experimental work has gradually led to a better understanding of the fracture process in snow involving the collapse of the structure in the weak layer during fracture. This now allows us to better model failure initiation and the onset of crack propagation, i.e., to estimate the critical length required for crack propagation. On the other hand, our understanding of dynamic crack propagation and fracture arrest propensity is still very limited. To shed more light on this issue, we performed numerical propagation saw test (PST) experiments applying the discrete element (DE) method and compared the numerical results with field measurements based on particle tracking. The goal is to investigate the influence of weak layer failure and the mechanical properties of the slab on crack propagation and fracture arrest propensity. Crack propagation speeds and distances before fracture arrest were derived from the DE simulations for different snowpack configurations and mechanical properties. Then, in order to compare the numerical and experimental results, the slab mechanical properties (Young's modulus and strength) which are not measured in the field were derived from density. The simulations nicely reproduced the process of crack propagation observed in field PSTs. Finally, the mechanical processes at play were analyzed in depth which led to suggestions for minimum column length in field PSTs.
Salomons, E.M.; Lohman, W.J.A.; Zhou, H.
2016-01-01
Propagation of sound waves in air can be considered as a special case of fluid dynamics. Consequently, the lattice Boltzmann method (LBM) for fluid flow can be used for simulating sound propagation. In this article application of the LBM to sound propagation is illustrated for various cases:
Richardson, A. S.; Swanekamp, S. B.; Jackson, S. L.; Mosher, D.; Ottinger, P. F.
2018-01-01
Plasma density gradients are known to drive magnetic shocks in electron-magnetohydrodynamics. Previous slab modeling has been extended to cylindrical modeling of radially imploding shocks. The main new effect of the cylindrical geometry is found to be a radial dependence in the speed of shock propagation. This is shown here analytically and in numerical simulations. Ion acceleration by the magnetic shock is shown to possibly become substantial, especially in the peaked structures that develop in the shock because of electron inertia.
Direct determination of scattering time delays using the R-matrix propagation method
International Nuclear Information System (INIS)
Walker, R.B.; Hayes, E.F.
1989-01-01
A direct method for determining time delays for scattering processes is developed using the R-matrix propagation method. The procedure involves the simultaneous generation of the global R matrix and its energy derivative. The necessary expressions to obtain the energy derivative of the S matrix are relatively simple and involve many of the same matrix elements required for the R-matrix propagation method. This method is applied to a simple model for a chemical reaction that displays sharp resonance features. The test results of the direct method are shown to be in excellent agreement with the traditional numerical differentiation method for scattering energies near the resonance energy. However, for sharp resonances the numerical differentiation method requires calculation of the S-matrix elements at many closely spaced energies. Since the direct method presented here involves calculations at only a single energy, one is able to generate accurate energy derivatives and time delays much more efficiently and reliably
International Nuclear Information System (INIS)
Wang, Jilin; Gu, Yunle; Li, Zili; Wang, Weimin; Fu, Zhengyi
2013-01-01
Graphical abstract: Nano-sized amorphous boron powders were synthesized by active dilution self-propagating high-temperature synthesis (SHS) method. The effects of endothermic reaction rate, the possible chemical reaction mechanism and active dilution model for synthesis of the product were also discussed. Highlights: ► Nano-sized amorphous boron powders were synthesized by active dilution self-propagating high-temperature synthesis method. ► The morphology, particle size and purity of the samples could be effectively controlled via changing the endothermic rate. ► The diluter KBH 4 played an important role in active dilution synthesis of amorphous nano-sized boron powders. ► The active dilution method could be further popularized and become a common approach to prepare various inorganic materials. - Abstract: Nano-sized amorphous boron powders were synthesized by active dilution self-propagating high-temperature synthesis (SHS) method at temperatures ranging from 700 °C to 850 °C in a SHS furnace using Mg, B 2 O 3 and KBH 4 as raw materials. Samples were characterized by X-ray powder diffraction (XRD), Laser particle size analyzer, Fourier transform infrared spectra (FTIR), X-ray energy dispersive spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission TEM (HRTEM). The boron powders demonstrated an average particle size of 50 nm with a purity of 95.64 wt.%. The diluter KBH 4 played an important role in the active dilution synthesis of amorphous nano-sized boron powders. The effects of endothermic reaction rate, the possible chemical reaction mechanism and active dilution model for synthesis of the product were also discussed
Directory of Open Access Journals (Sweden)
L. S. Konev
2015-09-01
Full Text Available Numerical method for calculation of forward and backward waves of intense few-cycle laser pulses propagating in an optical waveguide with dispersion and cubic nonlinearity of electronic and electronic-vibration nature is described. Simulations made with the implemented algorithm show that accounting for Raman nonlinearity does not lead to qualitative changes in behavior of the backward wave. Speaking about quantitative changes, the increase of efficiency of energy transfer from the forward wave to the backward wave is observed. Presented method can be also used to simulate interaction of counterpropagating pulses.
International Nuclear Information System (INIS)
Weidman, D.J.; Murphy, D.P.; Myers, M.C.; Meger, R.A.
1994-01-01
The expansion of the radius of a 5 MeV, 20 kA, 40 ns electron beam from SuperIBEX during propagation through gas is being measured. The beam is generated, conditions, equilibrated, and then passed through a thin foil that produces Cherenkov light, which is recorded by a streak camera. At a second location, the beam hits another Cherenkov emitter, which is viewed by a framing camera. Measurements at these two locations can provide a time-resolved measure of the beam expansion. The two measurements, however, must be synchronized with each other, because the beam radius is not constant throughout the pulse due to variations in beam current and energy. To correlate the timing of the two diagnostics, several shots have been taken with both diagnostics viewing Cherenkov light from the same foil. Experimental measurements of the Cherenkov light from one foil viewed by both diagnostics will be presented to demonstrate the feasibility of correlating the diagnostics with each other. Streak camera data showing the optical fiducial, as well as the final correlation of the two diagnostics, will also be presented. Preliminary beam radius measurements from Cherenkov light measured at two locations will be shown
Survey of electronic payment methods and systems
Havinga, Paul J.M.; Smit, Gerardus Johannes Maria; Helme, A.; Verbraeck, A.
1996-01-01
In this paper an overview of electronic payment methods and systems is given. This survey is done as part of the Moby Dick project. Electronic payment systems can be grouped into three broad classes: traditional money transactions, digital currency and creditdebit payments. Such payment systems have
Energy Technology Data Exchange (ETDEWEB)
Kim, S. [Purdue Univ., West Lafayette, IN (United States)
1994-12-31
Parallel iterative procedures based on domain decomposition techniques are defined and analyzed for the numerical solution of wave propagation by finite element and finite difference methods. For finite element methods, in a Lagrangian framework, an efficient way for choosing the algorithm parameter as well as the algorithm convergence are indicated. Some heuristic arguments for finding the algorithm parameter for finite difference schemes are addressed. Numerical results are presented to indicate the effectiveness of the methods.
Methods for Isolation, Purification, and Propagation of Bacteriophages of Campylobacter jejuni
DEFF Research Database (Denmark)
Gencay, Yilmaz Emre; Birk, Tina; Sørensen, Martine Camilla Holst
2017-01-01
Here, we describe the methods for isolation, purification, and propagation of Campylobacter jejuni bacteriophages from samples expected to contain high number of phages such as chicken feces. The overall steps are (1) liberation of phages from the sample material; (2) observation of plaque-formin...
Stress Wave Propagation in Soils Modelled by the Boundary Element Method
DEFF Research Database (Denmark)
Rasmussen, K. M.
This thesis deals with different aspects of the boundary element method (BEM) applied to stress wave propagation problems in soils. Among other things BEM formulations for coupled FEM and BEM, moving loads, direct BEM and indirect BEM are presented. For all the formulations both analytical...
Directory of Open Access Journals (Sweden)
Mahmood Falah
2015-01-01
Full Text Available In this paper, we implement real irregular terrain model in computer program by using image processing. We show how this approach can be used in simulation of E.M. wave propagation on irregular earth’s surface in a realistic manner. Some simulations are performed for implementation of longitudinal height differences over the propagation path as PEC surface .We also describe that how this approach can be used for any boundary condition in computational space. The results observed in Snapshots of the field profiles taken at different simulation times, validates capability of this method.
Parallel Implicit Runge-Kutta Methods Applied to Coupled Orbit/Attitude Propagation
Hatten, Noble; Russell, Ryan P.
2017-12-01
A variable-step Gauss-Legendre implicit Runge-Kutta (GLIRK) propagator is applied to coupled orbit/attitude propagation. Concepts previously shown to improve efficiency in 3DOF propagation are modified and extended to the 6DOF problem, including the use of variable-fidelity dynamics models. The impact of computing the stage dynamics of a single step in parallel is examined using up to 23 threads and 22 associated GLIRK stages; one thread is reserved for an extra dynamics function evaluation used in the estimation of the local truncation error. Efficiency is found to peak for typical examples when using approximately 8 to 12 stages for both serial and parallel implementations. Accuracy and efficiency compare favorably to explicit Runge-Kutta and linear-multistep solvers for representative scenarios. However, linear-multistep methods are found to be more efficient for some applications, particularly in a serial computing environment, or when parallelism can be applied across multiple trajectories.
Hussain, S.; Brennan, C.
2017-07-01
This paper presents an efficient ray tracing algorithm for propagation prediction in urban environments. The work presented in this paper builds upon previous work in which the maximum coverage area where rays can propagate after interaction with a wall or vertical edge is described by a lit polygon. The shadow regions formed by buildings within the lit polygon are described by shadow polygons. In this paper, the lit polygons of images are mapped to a coarse grid superimposed over the coverage area. This mapping reduces the active image tree significantly for a given receiver point to accelerate the ray finding process. The algorithm also presents an efficient method of quickly determining the valid ray segments for a mobile receiver moving along a linear trajectory. The validation results show considerable computation time reduction with good agreement between the simulated and measured data for propagation prediction in large urban environments.
Effect of relative humidity on crack propagation in barrier films for flexible electronics
Vellinga, W. P.; De Hosson, J. Th M.; Bouten, P. C. P.
2012-01-01
A set of propagating cracks in a SiN barrier film on poly ethylene naphthalate (PEN) were subjected to differing levels of relative humidity. It was observed that the propagation speed of the cracks increased for increasing levels of relative humidity. This was shown using two independent,
International Nuclear Information System (INIS)
López, Rodrigo A.; Muñoz, Víctor; Viñas, Adolfo F.; Valdivia, Juan A.
2015-01-01
We use a particle-in-cell simulation to study the propagation of localized structures in a magnetized electron-positron plasma with relativistic finite temperature. We use as initial condition for the simulation an envelope soliton solution of the nonlinear Schrödinger equation, derived from the relativistic two fluid equations in the strongly magnetized limit. This envelope soliton turns out not to be a stable solution for the simulation and splits in two localized structures propagating in opposite directions. However, these two localized structures exhibit a soliton-like behavior, as they keep their profile after they collide with each other due to the periodic boundary conditions. We also observe the formation of localized structures in the evolution of a spatially uniform circularly polarized Alfvén wave. In both cases, the localized structures propagate with an amplitude independent velocity
Ketcheson, David I.
2014-04-11
In practical computation with Runge--Kutta methods, the stage equations are not satisfied exactly, due to roundoff errors, algebraic solver errors, and so forth. We show by example that propagation of such errors within a single step can have catastrophic effects for otherwise practical and well-known methods. We perform a general analysis of internal error propagation, emphasizing that it depends significantly on how the method is implemented. We show that for a fixed method, essentially any set of internal stability polynomials can be obtained by modifying the implementation details. We provide bounds on the internal error amplification constants for some classes of methods with many stages, including strong stability preserving methods and extrapolation methods. These results are used to prove error bounds in the presence of roundoff or other internal errors.
A high-order accurate, collocated boundary element method for wave propagation in layered media
Sundkvist, Elena
2011-01-01
The ultimate goal of this research is to construct a hybrid model for sound propagation in layered underwater environments with curved boundaries by employing a differential formulation for inhomogeneous layers and a boundary integral formulation for homogeneous layers. The discretization of the new hybrid model is a combination of a finite difference method for the Helmholtz equation for inhomogeneous media and a collocated boundary element method (BEM) for the integral equation for homogene...
An algorithm to improve sampling efficiency for uncertainty propagation using sampling based method
International Nuclear Information System (INIS)
Campolina, Daniel; Lima, Paulo Rubens I.; Pereira, Claubia; Veloso, Maria Auxiliadora F.
2015-01-01
Sample size and computational uncertainty were varied in order to investigate sample efficiency and convergence of the sampling based method for uncertainty propagation. Transport code MCNPX was used to simulate a LWR model and allow the mapping, from uncertain inputs of the benchmark experiment, to uncertain outputs. Random sampling efficiency was improved through the use of an algorithm for selecting distributions. Mean range, standard deviation range and skewness were verified in order to obtain a better representation of uncertainty figures. Standard deviation of 5 pcm in the propagated uncertainties for 10 n-samples replicates was adopted as convergence criterion to the method. Estimation of 75 pcm uncertainty on reactor k eff was accomplished by using sample of size 93 and computational uncertainty of 28 pcm to propagate 1σ uncertainty of burnable poison radius. For a fixed computational time, in order to reduce the variance of the uncertainty propagated, it was found, for the example under investigation, it is preferable double the sample size than double the amount of particles followed by Monte Carlo process in MCNPX code. (author)
An algorithm to improve sampling efficiency for uncertainty propagation using sampling based method
Energy Technology Data Exchange (ETDEWEB)
Campolina, Daniel; Lima, Paulo Rubens I., E-mail: campolina@cdtn.br, E-mail: pauloinacio@cpejr.com.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil). Servico de Tecnologia de Reatores; Pereira, Claubia; Veloso, Maria Auxiliadora F., E-mail: claubia@nuclear.ufmg.br, E-mail: dora@nuclear.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Nuclear
2015-07-01
Sample size and computational uncertainty were varied in order to investigate sample efficiency and convergence of the sampling based method for uncertainty propagation. Transport code MCNPX was used to simulate a LWR model and allow the mapping, from uncertain inputs of the benchmark experiment, to uncertain outputs. Random sampling efficiency was improved through the use of an algorithm for selecting distributions. Mean range, standard deviation range and skewness were verified in order to obtain a better representation of uncertainty figures. Standard deviation of 5 pcm in the propagated uncertainties for 10 n-samples replicates was adopted as convergence criterion to the method. Estimation of 75 pcm uncertainty on reactor k{sub eff} was accomplished by using sample of size 93 and computational uncertainty of 28 pcm to propagate 1σ uncertainty of burnable poison radius. For a fixed computational time, in order to reduce the variance of the uncertainty propagated, it was found, for the example under investigation, it is preferable double the sample size than double the amount of particles followed by Monte Carlo process in MCNPX code. (author)
Free Vibration Characteristics of Cylindrical Shells Using a Wave Propagation Method
Directory of Open Access Journals (Sweden)
A. Ghoshal
2001-01-01
Full Text Available In the present paper, concept of a periodic structure is used to study the characteristics of the natural frequencies of a complete unstiffened cylindrical shell. A segment of the shell between two consecutive nodal points is chosen to be a periodic structural element. The present effort is to modify Mead and Bardell's approach to study the free vibration characteristics of unstiffened cylindrical shell. The Love-Timoshenko formulation for the strain energy is used in conjunction with Hamilton's principle to compute the natural propagation constants for two shell geometries and different circumferential nodal patterns employing Floquet's principle. The natural frequencies were obtained using Sengupta's method and were compared with those obtained from classical Arnold-Warburton's method. The results from the wave propagation method were found to compare identically with the classical methods, since both the methods lead to the exact solution of the same problem. Thus consideration of the shell segment between two consecutive nodal points as a periodic structure is validated. The variations of the phase constants at the lower bounding frequency for the first propagation band for different nodal patterns have been computed. The method is highly computationally efficient.
Andreev, Pavel A.; Iqbal, Z.
2016-03-01
We consider the separate spin evolution of electrons and positrons in electron-positron and electron-positron-ion plasmas. We consider the oblique propagating longitudinal waves in these systems. Working in a regime of high-density n0˜1027cm-3 and high-magnetic-field B0=1010 G, we report the presence of the spin-electron acoustic waves and their dispersion dependencies. In electron-positron plasmas, similarly to the electron-ion plasmas, we find one spin-electron acoustic wave (SEAW) at the propagation parallel or perpendicular to the external field and two spin-electron acoustic waves at the oblique propagation. At the parallel or perpendicular propagation of the longitudinal waves in electron-positron-ion plasmas, we find four branches: the Langmuir wave, the positron-acoustic wave, and a pair of waves having spin nature, they are the SEAW and the wave discovered in this paper, called the spin-electron-positron acoustic wave (SEPAW). At the oblique propagation we find eight longitudinal waves: the Langmuir wave, the Trivelpiece--Gould wave, a pair of positron-acoustic waves, a pair of SEAWs, and a pair of SEPAWs. Thus, for the first time, we report the existence of the second positron-acoustic wave existing at the oblique propagation and the existence of SEPAWs.
Electronic filters, hearing aids and methods
Engebretson, A. Maynard (Inventor); O'Connell, Michael P. (Inventor); Zheng, Baohua (Inventor)
1991-01-01
An electronic filter for an electroacoustic system. The system has a microphone for generating an electrical output from external sounds and an electrically driven transducer for emitting sound. Some of the sound emitted by the transducer returns to the microphone means to add a feedback contribution to its electical output. The electronic filter includes a first circuit for electronic processing of the electrical output of the microphone to produce a filtered signal. An adaptive filter, interconnected with the first circuit, performs electronic processing of the filtered signal to produce an adaptive output to the first circuit to substantially offset the feedback contribution in the electrical output of the microphone, and the adaptive filter includes means for adapting only in response to polarities of signals supplied to and from the first circuit. Other electronic filters for hearing aids, public address systems and other electroacoustic systems, as well as such systems, and methods of operating them are also disclosed.
DEFF Research Database (Denmark)
Baltser, Jana; Bergbäck Knudsen, Erik; Vickery, Anette
2011-01-01
of X-ray beamline designs for particular user experiments. In this work we used the newly developed McXtrace ray-tracing package and the SRW wave-optics code to simulate the beam propagation of X-ray undulator radiation through such a "transfocator" as implemented at ID- 11 at ESRF. By applying two...
Method of fabricating a cooled electronic system
Chainer, Timothy J; Gaynes, Michael A; Graybill, David P; Iyengar, Madhusudan K; Kamath, Vinod; Kochuparambil, Bejoy J; Schmidt, Roger R; Schultz, Mark D; Simco, Daniel P; Steinke, Mark E
2014-02-11
A method of fabricating a liquid-cooled electronic system is provided which includes an electronic assembly having an electronics card and a socket with a latch at one end. The latch facilitates securing of the card within the socket. The method includes providing a liquid-cooled cold rail at the one end of the socket, and a thermal spreader to couple the electronics card to the cold rail. The thermal spreader includes first and second thermal transfer plates coupled to first and second surfaces on opposite sides of the card, and thermally conductive extensions extending from end edges of the plates, which couple the respective transfer plates to the liquid-cooled cold rail. The extensions are disposed to the sides of the latch, and the card is securable within or removable from the socket using the latch without removing the cold rail or the thermal spreader.
Computational methods of electron/photon transport
International Nuclear Information System (INIS)
Mack, J.M.
1983-01-01
A review of computational methods simulating the non-plasma transport of electrons and their attendant cascades is presented. Remarks are mainly restricted to linearized formalisms at electron energies above 1 keV. The effectiveness of various metods is discussed including moments, point-kernel, invariant imbedding, discrete-ordinates, and Monte Carlo. Future research directions and the potential impact on various aspects of science and engineering are indicated
Maupin, Valerie; Näsholm, Sven Peter; Schweitzer, Johannes; Gibbons, Steven J.
2016-04-01
We recently advocated using the reflectivity method, also known as the wavenumber integration method or fast-field program, to model atmospheric infrasound propagation at regional distances. The advantage of the reflectivity method is its ability to model the full wavefield, including diffractive effects with head waves and shadow zone arrivals, in a broad frequency range but still at a relatively low computational cost. Attenuation can easily be included, giving the possibility to analyse relative amplitudes and frequency content of the different arrivals. It has clear advantages compared with ray theory in terms of predicting phases considering the particular frequent occurrence of shadow zone arrivals in infrasound observations. Its main limitation, at least in the traditional form of the method, lies in the fact that it can only handle range-independent models. We presented earlier some reflectivity method simulations of an observed accidental explosion in Norway. Wind intensity and direction are non-negligible parameters for infrasound propagation and these are appropriately taken into account in most infrasound ray-tracing codes. On the other hand, in the previous reflectivity simulations wind was taken into account only through the effective sound speed approximation where the horizontal projection of the wind field is added to the adiabatic sound speed profiles. This approximation is appropriate for dominantly horizontal propagation but can give incorrect arrival times and shadow zone locations for waves which have a significant portion of their propagation path at more vertical incidence, like thermospheric arrivals. We present here how we have modified the original reflectivity algorithm in order to take the wind into account in a more correct fashion, and how this improvement influences the synthetics.
Extension of the noise propagation matrix method for higher mode solutions
Zhang, Peng; Lee, Hyunsuk; Lee, Deokjung
2017-09-01
The noise propagation matrix method (NPMM) has been extended to get higher mode solutions. Previous studies show that the NPMM can be used to compute the dominance ratio of a system. It is essentially the same as the Coarse Mesh Projection Method (CMPM), both of which use the noise propagation matrix (NPM) to determine the dominance ratio, either after finishing the Monte Carlo simulation or on-the-fly during the simulation. Since only the fundamental fission source information is explicitly utilized while the higher mode information is implicitly contained in the statistical noises, the NPMM can usually only give an approximate estimation of the dominance ratio after thousands of cycles. In this study, the NPMM is extended by simulating the higher modes explicitly, so that the dominance ratio estimation can be more accurate and efficient. Besides, the higher mode solutions can be obtained at the same time with good accuracy and efficiency.
Particle Discrete Method Based on Manifold Cover for Crack Propagation of Jointed Rock Mass
Directory of Open Access Journals (Sweden)
Yang Ping
2014-01-01
Full Text Available The rock mass can be assumed to be homogeneous material from a macroscopic view; however, it is the heterogeneous material in mesoscopic scale and its physicomechanical properties are discontinuous in space. The failure of jointed rock mass was usually caused by the initiation, propagation, and coalescence of new wing cracks derived from primary joint. In order to further study the rock fracture instability, we need to study the expansion of rock cracks under external loads from the macro-meso perspective. This paper, based on the manifold cover concept, proposes a new discrete element numerical method, manifold particle discrete (MPD, combined with the particle contact model and the introduced concept of stress boundary. The proposed method can easily simulate the crack generation, propagation, and coalescence of jointed rock mass from the macro-meso perspective. The whole process of rock fragmentation is thereafter reproduced. By analyzing the manifold cover and sphere particle model, this paper constitutes the sphere unit cover function of three-dimensional manifold cover, establishes tetrahedron units, and obtains the equilibrium equation and compatible equation of the MPD model. For rock-like brittle material, crack propagation process can be simulated, and it also verifies the accuracy of the proposed numerical method.
Methods for fabrication of flexible hybrid electronics
Street, Robert A.; Mei, Ping; Krusor, Brent; Ready, Steve E.; Zhang, Yong; Schwartz, David E.; Pierre, Adrien; Doris, Sean E.; Russo, Beverly; Kor, Siv; Veres, Janos
2017-08-01
Printed and flexible hybrid electronics is an emerging technology with potential applications in smart labels, wearable electronics, soft robotics, and prosthetics. Printed solution-based materials are compatible with plastic film substrates that are flexible, soft, and stretchable, thus enabling conformal integration with non-planar objects. In addition, manufacturing by printing is scalable to large areas and is amenable to low-cost sheet-fed and roll-to-roll processes. FHE includes display and sensory components to interface with users and environments. On the system level, devices also require electronic circuits for power, memory, signal conditioning, and communications. Those electronic components can be integrated onto a flexible substrate by either assembly or printing. PARC has developed systems and processes for realizing both approaches. This talk presents fabrication methods with an emphasis on techniques recently developed for the assembly of off-the-shelf chips. A few examples of systems fabricated with this approach are also described.
Liu, Xin; Liu, De-ming; Wu, Wei
2008-11-01
Finite-Difference Beam Propagation Method (FD-BPM) in conventional is modified, according to more accurate Helmholtz equation, a new arithmetic is advanced. By using the new arithmetic and the old arithmetic in calculating slab waveguide and calculate the parameter which scales the precision of the method and the calculating time, we prove that the accuracy of the new arithmetic is improved without affecting time performance. At last we calculate the transmission mode in the AWG by the new method to show the practical value of the modified arithmetic.
Grosse, Ralf
1990-01-01
Propagation of sound through the turbulent atmosphere is a statistical problem. The randomness of the refractive index field causes sound pressure fluctuations. Although no general theory to predict sound pressure statistics from given refractive index statistics exists, there are several approximate solutions to the problem. The most common approximation is the parabolic equation method. Results obtained by this method are restricted to small refractive index fluctuations and to small wave lengths. While the first condition is generally met in the atmosphere, it is desirable to overcome the second. A generalization of the parabolic equation method with respect to the small wave length restriction is presented.
Van Gorder, Robert A
2010-11-01
We apply the δ-expansion method to nonlinear stochastic differential equations describing wave propagation in a random medium. In particular, we focus our attention on a model describing a nonlinear wave propagating in a turbulent atmosphere which has random variations in the refractive index (we take these variations to be stochastic). The method allows us to construct much more reasonable perturbation solutions with relatively few terms (compared to standard "small-parameter" perturbation methods) due to more accurate linearization used in constructing the initial approximation. We demonstrate that the method allows one to compute effective wave numbers more precisely than other methods applied to the problem in the literature. The method also picks up on the stochastic damping of the solutions quickly, holding all of the relevant data in the initial term. These properties allow for both a qualitative and a quantitative construction of physically meaningful solutions. In particular, we show that the method allows one to retain higher-order harmonics which are hard to capture with standard perturbation methods based on small parameters.
Numerical methods in electron magnetic resonance
International Nuclear Information System (INIS)
Soernes, A.R.
1998-01-01
The focal point of the thesis is the development and use of numerical methods in the analysis, simulation and interpretation of Electron Magnetic Resonance experiments on free radicals in solids to uncover the structure, the dynamics and the environment of the system
Numerical methods in electron magnetic resonance
Energy Technology Data Exchange (ETDEWEB)
Soernes, A.R
1998-07-01
The focal point of the thesis is the development and use of numerical methods in the analysis, simulation and interpretation of Electron Magnetic Resonance experiments on free radicals in solids to uncover the structure, the dynamics and the environment of the system.
Directory of Open Access Journals (Sweden)
Xueqiang Chen
2015-01-01
Full Text Available We consider the computationally efficient direction-of-arrival (DOA and noncircular (NC phase estimation problem of noncircular signal for uniform linear array. The key idea is to apply the noncircular propagator method (NC-PM which does not require eigenvalue decomposition (EVD of the covariance matrix or singular value decomposition (SVD of the received data. Noncircular rotational invariance propagator method (NC-RI-PM avoids spectral peak searching in PM and can obtain the closed-form solution of DOA, so it has lower computational complexity. An improved NC-RI-PM algorithm of noncircular signal for uniform linear array is proposed to estimate the elevation angles and noncircular phases with automatic pairing. We reconstruct the extended array output by combining the array output and its conjugated counterpart. Our algorithm fully uses the extended array elements in the improved propagator matrix to estimate the elevation angles and noncircular phases by utilizing the rotational invariance property between subarrays. Compared with NC-RI-PM, the proposed algorithm has better angle estimation performance and much lower computational load. The computational complexity of the proposed algorithm is analyzed. We also derive the variance of estimation error and Cramer-Rao bound (CRB of noncircular signal for uniform linear array. Finally, simulation results are presented to demonstrate the effectiveness of our algorithm.
Directory of Open Access Journals (Sweden)
JERFFSON LUCAS SANTOS
2016-01-01
Full Text Available The passion fruit (Passiflora cincinnata Mast. is a perennial and drought resistant species that represents a new alternative crop for small farmers in rainfed conditions. This study aimed to evaluate the vegetative and physiological development of passion fruit plants derived from two propagation methods and grown at varied planting spacing. The experiment was conducted from January to June of 2012, in the Universidade Estadual do Sudoeste da Bahia (State University from Southwestern Bahia, in Brazil. It was carried out in a randomized block design under a 2 x 3 factorial scheme, which consisted of two propagation methods (cutting and seeds and three planting spacing distances within a row (1.5; 3.0 and 4.0 m, however, at same distance between rows (3.0 m, with four replicates and four plants per plot. Cuttings and seeds were sampled from adult plants pre-selected in native areas from Vitória da Conquista - BA, Brazil. Growth (stem diameter and leaf area and physiological parameters (leaf chlorophyll content, leaf water potential before dawn, relative water content and leaf gas exchange were assessed on the 90th, 120th and 150th day after transplanting of seedlings into the field (DAT. Based on our results, we concluded that despite plants propagated via cuttings showed most favorable water status, vegetative growth and photosynthetic capacity were lower whether compared to plants obtained from seeds.
An Entropy-Based Propagation Speed Estimation Method for Near-Field Subsurface Radar Imaging
Directory of Open Access Journals (Sweden)
Pistorius Stephen
2010-01-01
Full Text Available During the last forty years, Subsurface Radar (SR has been used in an increasing number of noninvasive/nondestructive imaging applications, ranging from landmine detection to breast imaging. To properly assess the dimensions and locations of the targets within the scan area, SR data sets have to be reconstructed. This process usually requires the knowledge of the propagation speed in the medium, which is usually obtained by performing an offline measurement from a representative sample of the materials that form the scan region. Nevertheless, in some novel near-field SR scenarios, such as Microwave Wood Inspection (MWI and Breast Microwave Radar (BMR, the extraction of a representative sample is not an option due to the noninvasive requirements of the application. A novel technique to determine the propagation speed of the medium based on the use of an information theory metric is proposed in this paper. The proposed method uses the Shannon entropy of the reconstructed images as the focal quality metric to generate an estimate of the propagation speed in a given scan region. The performance of the proposed algorithm was assessed using data sets collected from experimental setups that mimic the dielectric contrast found in BMI and MWI scenarios. The proposed method yielded accurate results and exhibited an execution time in the order of seconds.
An Entropy-Based Propagation Speed Estimation Method for Near-Field Subsurface Radar Imaging
Flores-Tapia, Daniel; Pistorius, Stephen
2010-12-01
During the last forty years, Subsurface Radar (SR) has been used in an increasing number of noninvasive/nondestructive imaging applications, ranging from landmine detection to breast imaging. To properly assess the dimensions and locations of the targets within the scan area, SR data sets have to be reconstructed. This process usually requires the knowledge of the propagation speed in the medium, which is usually obtained by performing an offline measurement from a representative sample of the materials that form the scan region. Nevertheless, in some novel near-field SR scenarios, such as Microwave Wood Inspection (MWI) and Breast Microwave Radar (BMR), the extraction of a representative sample is not an option due to the noninvasive requirements of the application. A novel technique to determine the propagation speed of the medium based on the use of an information theory metric is proposed in this paper. The proposed method uses the Shannon entropy of the reconstructed images as the focal quality metric to generate an estimate of the propagation speed in a given scan region. The performance of the proposed algorithm was assessed using data sets collected from experimental setups that mimic the dielectric contrast found in BMI and MWI scenarios. The proposed method yielded accurate results and exhibited an execution time in the order of seconds.
On the calculation of crack propagation behavior in disks and plates using a mixed finite method
International Nuclear Information System (INIS)
Fischer, W.
1991-01-01
According to the linear theory of elasticity, infinitely high stresses occur in the crack tips of cracked components. Plastic flow initiation or previous damage, however, will limit these stress singularities to an upper maximum stress for all real materials. To permit acquisition of this highly localized material behavior, while avoiding a very high physical nonlinear calculation effort for the evaluation of crack propagation behavior in disks and plates, models essentially based on Dugdale and Barenblatt are used. This involves determining the stress and displacement conditions required for the simulation of crack propagation by means of a mixed finite method introducing the disk cutting forces and plate curvatures or moments as unknown quantities. In addition to pure disk and plate problems, also coupled disk-plate problems are covered, where the coupling, on one hand, is due to the consideration of high deformations. (orig.) With 66 figs., 8 tabs [de
Rosenbaum, Joyce E.
2011-12-01
Commercial air traffic is anticipated to increase rapidly in the coming years. The impact of aviation noise on communities surrounding airports is, therefore, a growing concern. Accurate prediction of noise can help to mitigate the impact on communities and foster smoother integration of aerospace engineering advances. The problem of accurate sound level prediction requires careful inclusion of all mechanisms that affect propagation, in addition to correct source characterization. Terrain, ground type, meteorological effects, and source directivity can have a substantial influence on the noise level. Because they are difficult to model, these effects are often included only by rough approximation. This dissertation presents a model designed for sound propagation over uneven terrain, with mixed ground type and realistic meteorological conditions. The model is a hybrid of two numerical techniques: the parabolic equation (PE) and fast field program (FFP) methods, which allow for physics-based inclusion of propagation effects and ensure the low frequency content, a factor in community impact, is predicted accurately. Extension of the hybrid model to a pseudo-three-dimensional representation allows it to produce aviation noise contour maps in the standard form. In order for the model to correctly characterize aviation noise sources, a method of representing arbitrary source directivity patterns was developed for the unique form of the parabolic equation starting field. With this advancement, the model can represent broadband, directional moving sound sources, traveling along user-specified paths. This work was prepared for possible use in the research version of the sound propagation module in the Federal Aviation Administration's new standard predictive tool.
Energy Technology Data Exchange (ETDEWEB)
Tondu, Thomas; Belhaj, Mohamed; Inguimbert, Virginie [Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse (France); Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse, France and Fondation STAE, 4 allee Emile Monso, BP 84234-31432, Toulouse Cedex 4 (France); Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse (France)
2010-09-15
Secondary electron emission yield of gold under electron impact at normal incidence below 50 eV was investigated by the classical collector method and by the Kelvin probe method. The authors show that biasing a collector to ensure secondary electron collection while keeping the target grounded can lead to primary electron beam perturbations. Thus reliable secondary electron emission yield at low primary electron energy cannot be obtained with a biased collector. The authors present two collector-free methods based on current measurement and on electron pulse surface potential buildup (Kelvin probe method). These methods are consistent, but at very low energy, measurements become sensitive to the earth magnetic field (below 10 eV). For gold, the authors can extrapolate total emission yield at 0 eV to 0.5, while a total electron emission yield of 1 is obtained at 40{+-}1 eV.
International Nuclear Information System (INIS)
Tondu, Thomas; Belhaj, Mohamed; Inguimbert, Virginie
2010-01-01
Secondary electron emission yield of gold under electron impact at normal incidence below 50 eV was investigated by the classical collector method and by the Kelvin probe method. The authors show that biasing a collector to ensure secondary electron collection while keeping the target grounded can lead to primary electron beam perturbations. Thus reliable secondary electron emission yield at low primary electron energy cannot be obtained with a biased collector. The authors present two collector-free methods based on current measurement and on electron pulse surface potential buildup (Kelvin probe method). These methods are consistent, but at very low energy, measurements become sensitive to the earth magnetic field (below 10 eV). For gold, the authors can extrapolate total emission yield at 0 eV to 0.5, while a total electron emission yield of 1 is obtained at 40±1 eV.
International Nuclear Information System (INIS)
Hoffman, Adam J.; Lee, John C.
2016-01-01
A new time-dependent Method of Characteristics (MOC) formulation for nuclear reactor kinetics was developed utilizing angular flux time-derivative propagation. This method avoids the requirement of storing the angular flux at previous points in time to represent a discretized time derivative; instead, an equation for the angular flux time derivative along 1D spatial characteristics is derived and solved concurrently with the 1D transport characteristic equation. This approach allows the angular flux time derivative to be recast principally in terms of the neutron source time derivatives, which are approximated to high-order accuracy using the backward differentiation formula (BDF). This approach, called Source Derivative Propagation (SDP), drastically reduces the memory requirements of time-dependent MOC relative to methods that require storing the angular flux. An SDP method was developed for 2D and 3D applications and implemented in the computer code DeCART in 2D. DeCART was used to model two reactor transient benchmarks: a modified TWIGL problem and a C5G7 transient. The SDP method accurately and efficiently replicated the solution of the conventional time-dependent MOC method using two orders of magnitude less memory.
A comparison of attitude propagation and parameterization methods for low-cost UAVs
Casey, Robert Taylor
Unmanned aerial vehicles (UAVs) represent an increasingly important and prolific technology in today's world, finding use in myriad applications across multiple domains, including civil, commercial, military, and research environments. Control of these aircraft requires fundamental information on the vehicle's position and orientation in space. Attitude determination algorithms calculate this spatial orientation by propagating the attitude kinematic equations that estimate the current attitude based on previous estimates along with information about the vehicle's angular velocities. Within the domain of low-cost UAVs, numerous options exist for the choice of 1) propagation algorithms, 2) attitude representation, and 3) the assumptions about the behavior of the angular velocity vector between samples within the discrete-time hardware of the embedded system typically running the estimation algorithms. This thesis examines the impact of these three variables upon propagated attitude estimates with respect to accuracy, computational efficiency, and noise response. Noise response is evaluated in terms of the algorithm's ability to track an underlying clean signal in spite of inputs corrupted by additive Gaussian noise. Various propagation methods are evaluated across four attitude representations: the direction cosine matrix, Euler angles, quaternions, and the angle-axis or eigen-axis parameterization. Lastly, the nature of angular velocity (constant, linear, and quadratic) is evaluated in terms of accuracy, computational efficiency, and noise resilience. The algorithms were tested using simulated angular velocity inputs from analytic functions as well as flight test data from low-cost, fixed wing UAVs. Implementation was done in Matlab as well as Simulink-based test modules to evaluate algorithm performance. The quaternion parameterization proved most beneficial across all three test metrics, though the DCM representation was only slightly deficient in terms of
High-throughput methods for electron crystallography.
Stokes, David L; Ubarretxena-Belandia, Iban; Gonen, Tamir; Engel, Andreas
2013-01-01
Membrane proteins play a tremendously important role in cell physiology and serve as a target for an increasing number of drugs. Structural information is key to understanding their function and for developing new strategies for combating disease. However, the complex physical chemistry associated with membrane proteins has made them more difficult to study than their soluble cousins. Electron crystallography has historically been a successful method for solving membrane protein structures and has the advantage of providing a native lipid environment for these proteins. Specifically, when membrane proteins form two-dimensional arrays within a lipid bilayer, electron microscopy can be used to collect images and diffraction and the corresponding data can be combined to produce a three-dimensional reconstruction, which under favorable conditions can extend to atomic resolution. Like X-ray crystallography, the quality of the structures are very much dependent on the order and size of the crystals. However, unlike X-ray crystallography, high-throughput methods for screening crystallization trials for electron crystallography are not in general use. In this chapter, we describe two alternative methods for high-throughput screening of membrane protein crystallization within the lipid bilayer. The first method relies on the conventional use of dialysis for removing detergent and thus reconstituting the bilayer; an array of dialysis wells in the standard 96-well format allows the use of a liquid-handling robot and greatly increases throughput. The second method relies on titration of cyclodextrin as a chelating agent for detergent; a specialized pipetting robot has been designed not only to add cyclodextrin in a systematic way, but to use light scattering to monitor the reconstitution process. In addition, the use of liquid-handling robots for making negatively stained grids and methods for automatically imaging samples in the electron microscope are described.
International Nuclear Information System (INIS)
Campolina, Daniel de Almeida Magalhães
2015-01-01
There is an uncertainty for all the components that comprise the model of a nuclear system. Assessing the impact of uncertainties in the simulation of fissionable material systems is essential for a realistic calculation that has been replacing conservative model calculations as the computational power increases. The propagation of uncertainty in a simulation using a Monte Carlo code by sampling the input parameters is recent because of the huge computational effort required. By analyzing the propagated uncertainty to the effective neutron multiplication factor (k eff ), the effects of the sample size, computational uncertainty and efficiency of a random number generator to represent the distributions that characterize physical uncertainty in a light water reactor was investigated. A program entitled GB s ample was implemented to enable the application of the random sampling method, which requires an automated process and robust statistical tools. The program was based on the black box model and the MCNPX code was used in and parallel processing for the calculation of particle transport. The uncertainties considered were taken from a benchmark experiment in which the effects in k eff due to physical uncertainties is done through a conservative method. In this work a script called GB s ample was implemented to automate the sampling based method, use multiprocessing and assure the necessary robustness. It has been found the possibility of improving the efficiency of the random sampling method by selecting distributions obtained from a random number generator in order to obtain a better representation of uncertainty figures. After the convergence of the method is achieved, in order to reduce the variance of the uncertainty propagated without increase in computational time, it was found the best number o components to be sampled. It was also observed that if the sampling method is used to calculate the effect on k eff due to physical uncertainties reported by
Directory of Open Access Journals (Sweden)
Hosein Ghaffarzadeh
Full Text Available Abstract This paper investigates the numerical modeling of the flexural wave propagation in Euler-Bernoulli beams using the Hermite-type radial point interpolation method (HRPIM under the damage quantification approach. HRPIM employs radial basis functions (RBFs and their derivatives for shape function construction as a meshfree technique. The performance of Multiquadric(MQ RBF to the assessment of the reflection ratio was evaluated. HRPIM signals were compared with the theoretical and finite element responses. Results represent that MQ is a suitable RBF for HRPIM and wave propagation. However, the range of the proper shape parameters is notable. The number of field nodes is the main parameter for accurate wave propagation modeling using HRPIM. The size of support domain should be less thanan upper bound in order to prevent high error. With regard to the number of quadrature points, providing the minimum numbers of points are adequate for the stable solution, but the existence of more points in damage region does not leads to necessarily the accurate responses. It is concluded that the pure HRPIM, without any polynomial terms, is acceptable but considering a few terms will improve the accuracy; even though more terms make the problem unstable and inaccurate.
Kim, Jongsu; Kwon, Seung-Gab; Back, Seunghyun; Kang, Bongchul
2018-03-01
We present a novel laser-induced surface treatment process to rapidly control the spatial wettabilities of various functional solutions with submicron to micron resolutions. Ultrathin hydrophobic self-assembled monolayers (SAMs) that little absorb typical laser lights due to short penetration depth were selectively deactivated by instantaneous interaction with laser-induced metallic plasmas. The spatial region of the deactivated SAM, which corresponds to process resolution, is adjustable by controlling the spatial propagation of the plasma. This method leads to the parallel formation of hydrophilic functional solutions on glass substrates with a minimum resolution on the submicron scale. To show its feasibility in device engineering fields, this method was applied to the cost-effective fabrication of electronics and biosensors. Rapid self-patterning of electronic and biological functional solutions (silver nanoparticle solution and streptavidin protein solution) was successfully realized by selective deactivation of two different SAMs (tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS) for electronics and the hetero-hybrid SAM (octadecyltrichlorosilane (OTS)/2-[methoxy(polyethyleneoxy)propyl] trichlorosilane (PEG)) for biosensors). As a result, this method can be exploited for the rapid and low-cost fabrication of various thin film devices such as electronics, biosensors, energy, displays, and photonics.
Spin-wave propagation and spin-polarized electron transport in single-crystal iron films
Gladii, O.; Halley, D.; Henry, Y.; Bailleul, M.
2017-11-01
The techniques of propagating spin-wave spectroscopy and current-induced spin-wave Doppler shift are applied to a 20-nm-thick Fe/MgO(001) film. The magnetic parameters extracted from the position of the spin-wave resonance peaks are very close to those tabulated for bulk iron. From the zero-current propagating wave forms, a group velocity of 4 km/s and an attenuation length of about 6 μ m are extracted for 1.6-μ m -wavelength spin wave at 18 GHz. From the measured current-induced spin-wave Doppler shift, we extract a surprisingly high degree of spin polarization of the current of 83 % , which constitutes the main finding of this work. This set of results makes single-crystalline iron a promising candidate for building devices utilizing high-frequency spin waves and spin-polarized currents.
In-situ transmission electron microscopy observation of slip propagation in ä3 bicrystals
Czech Academy of Sciences Publication Activity Database
Gemperlová, Juliana; Jacques, A.; Gemperle, Antonín; Vystavěl, Tomáš; Zárubová, Niva; Janecek, M.
2002-01-01
Roč. 324, - (2002), s. 183-189 ISSN 0921-5093 R&D Projects: GA ČR GA202/98/1281 Institutional research plan: CEZ:AV0Z1010914 Keywords : in- situ TEM deformation * propagation of slip * plastic deformation * grain boundary * symmetrical ä3 bicrystal Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.107, year: 2002
EDM 1.0: electron direct methods.
Kilaas, R; Marks, L D; Own, C S
2005-02-01
A computer program designed to provide a number of quantitative analysis tools for high-resolution imaging and electron diffraction data is described. The program includes basic image manipulation, both real space and reciprocal space image processing, Wiener-filtering, symmetry averaging, methods for quantification of electron diffraction patterns and two-dimensional direct methods. The program consists of a number of sub-programs written in a combination of C++, C and Fortran. It can be downloaded either as GNU source code or as binaries and has been compiled and verified on a wide range of platforms, both Unix based and PC's. Elements of the design philosophy as well as future possible extensions are described.
A generalized multiscale finite element method for elastic wave propagation in fractured media
Chung, Eric T.
2016-02-26
In this paper, we consider elastic wave propagation in fractured media applying a linear-slip model to represent the effects of fractures on the wavefield. Fractured media, typically, are highly heterogeneous due to multiple length scales. Direct numerical simulations for wave propagation in highly heterogeneous fractured media can be computationally expensive and require some type of model reduction. We develop a multiscale model reduction technique that captures the complex nature of the media (heterogeneities and fractures) in the coarse scale system. The proposed method is based on the generalized multiscale finite element method, where the multiscale basis functions are constructed to capture the fine-scale information of the heterogeneous, fractured media and effectively reduce the degrees of freedom. These multiscale basis functions are coupled via the interior penalty discontinuous Galerkin method, which provides a block-diagonal mass matrix. The latter is needed for fast computation in an explicit time discretization, which is used in our simulations. Numerical results are presented to show the performance of the presented multiscale method for fractured media. We consider several cases where fractured media contain fractures of multiple lengths. Our numerical results show that the proposed reduced-order models can provide accurate approximations for the fine-scale solution.
The finite element method for micro-scale modeling of ultrasound propagation in cancellous bone.
Vafaeian, B; El-Rich, M; El-Bialy, T; Adeeb, S
2014-08-01
Quantitative ultrasound for bone assessment is based on the correlations between ultrasonic parameters and the properties (mechanical and physical) of cancellous bone. To elucidate the correlations, understanding the physics of ultrasound in cancellous bone is demanded. Micro-scale modeling of ultrasound propagation in cancellous bone using the finite-difference time-domain (FDTD) method has been so far utilized as one of the approaches in this regard. However, the FDTD method accompanies two disadvantages: staircase sampling of cancellous bone by finite difference grids leads to generation of wave artifacts at the solid-fluid interface inside the bone; additionally, this method cannot explicitly satisfy the needed perfect-slip conditions at the interface. To overcome these disadvantages, the finite element method (FEM) is proposed in this study. Three-dimensional finite element models of six water-saturated cancellous bone samples with different bone volume were created. The values of speed of sound (SOS) and broadband ultrasound attenuation (BUA) were calculated through the finite element simulations of ultrasound propagation in each sample. Comparing the results with other experimental and simulation studies demonstrated the capabilities of the FEM for micro-scale modeling of ultrasound in water-saturated cancellous bone. Copyright © 2014 Elsevier B.V. All rights reserved.
Shi, Hang; Tarabara, Volodymyr V
2018-02-10
Two virus propagation methods (in broth and on double agar overlay) and three purification procedures (PEG precipitation, centrifugal diafiltration and CsCl density gradient centrifugation) were comparatively evaluated using MS2 and P22 bacteriophages as model viruses. The prepared stocks were characterized in terms of electrophoretic mobility as a function of pH, particle size distribution, surface tension components and overall hydrophobicity of the virus, as well as the percentage of infectious and total virus recovered. The obtained data were used to rank the purification methods according to six criteria of likely practical relevance. Regardless of the purification method applied, virus propagation in broth media resulted in higher purity virus stocks as the growth on double agar overlay introduced difficult-to-remove residual agar. CsCl density gradient centrifugation gave the highest quality bacteriophage suspensions, recovered infectious P22 at least as efficiently as the other two purification methods and selected for intact P22 virions over damaged ones. The impurities remaining in the virus suspension after PEG precipitation and centrifugal diafiltration broadened the size distribution and interfered with electrophoretic mobility measurements. The residual impurities had a major impact on the free energy of virus-virus interfacial interaction (the quantitative measure of virus hydrophobicity/hydrophilicity) leading to an incorrect determination of P22 bacteriophage as hydrophilic. The trends in measured physicochemical properties can be rationalized by considering impurity-coated virions as permeable soft particles. Copyright © 2018 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Menouillard, T.
2007-09-01
Computerized simulation is nowadays an integrating part of design and validation processes of mechanical structures. Simulation tools are more and more performing allowing a very acute description of the phenomena. Moreover, these tools are not limited to linear mechanics but are developed to describe more difficult behaviours as for instance structures damage which interests the safety domain. A dynamic or static load can thus lead to a damage, a crack and then a rupture of the structure. The fast dynamics allows to simulate 'fast' phenomena such as explosions, shocks and impacts on structure. The application domain is various. It concerns for instance the study of the lifetime and the accidents scenario of the nuclear reactor vessel. It is then very interesting, for fast dynamics codes, to be able to anticipate in a robust and stable way such phenomena: the assessment of damage in the structure and the simulation of crack propagation form an essential stake. The extended finite element method has the advantage to break away from mesh generation and from fields projection during the crack propagation. Effectively, crack is described kinematically by an appropriate strategy of enrichment of supplementary freedom degrees. Difficulties connecting the spatial discretization of this method with the temporal discretization of an explicit calculation scheme has then been revealed; these difficulties are the diagonal writing of the mass matrix and the associated stability time step. Here are presented two methods of mass matrix diagonalization based on the kinetic energy conservation, and studies of critical time steps for various enriched finite elements. The interest revealed here is that the time step is not more penalizing than those of the standard finite elements problem. Comparisons with numerical simulations on another code allow to validate the theoretical works. A crack propagation test in mixed mode has been exploited in order to verify the simulation
Innovative electron transport methods in EGS5
International Nuclear Information System (INIS)
Bielajew, A.F.; Wilderman, S.J.
2000-01-01
The initial formulation of a Monte Carlo scheme for the transport of high-energy (>≅ 100 keV) electrons was established by Berger in 1963. Calling his method the 'condensed history theory', Berger combined the theoretical results of the previous generation of research into developing approximate solutions of the Boltzmann transport equation with numerical algorithms for exploiting the power of computers to permit iterative, piece-wise solution of the transport equation in a computationally intensive but much less approximate fashion. The methods devised by Berger, with comparatively little modification, provide the foundation of all present day Monte Carlo electron transport simulation algorithms. Only in the last 15 years, beginning with the development and publication of the PRESTA algorithm, has there been a significant revisitation of the problem of simulating electron transport within the condensed history framework. Research in this area is ongoing, highly active, and far from complete. It presents an enormous challenge, demanding derivation of new analytical transport solutions based on underlying fundamental interaction mechanisms, intuitive insight in the development of computer algorithms, and state of the art computer science skills in order to permit deployment of these techniques in an efficient manner. The EGS5 project, a modern ground-up rewrite of the EGS4 code, is now in the design phase. EGS5 will take modern photon and electron transport algorithms and deploy them in an easy-to-maintain, modern computer language-ANSI-standard C ++. Moreover, the well-known difficulties of applying EGS4 to practical geometries (geometry code development, tally routine design) should be made easier and more intuitive through the use of a visual user interface being designed by Quantum Research, Inc., work that is presented elsewhere in this conference. This report commences with a historical review of electron transport models culminating with the proposal of a
An Efficient Method for the Solution of Schwinger-Dyson Equations for Propagators
Bellon, Marc P.
2010-10-01
Efficient computation methods are devised for the perturbative solution of Schwinger-Dyson equations for propagators. I show how a simple computation allows to obtain the dominant contribution in the sum of many parts of previous computations. This allows for an easy study of the asymptotic behavior of the perturbative series. In the cases of the four-dimensional supersymmetric Wess-Zumino model and the {φ_6^3} complex scalar field, the singularities of the Borel transform for both positive and negative values of the parameter are obtained and compared.
International Nuclear Information System (INIS)
Appert, K.; Vaclavik, J.; Villard, L.; Hellsten, T.
1986-01-01
A system of two second-order ordinary differential equations describing wave propagation in a hot plasma is solved numerically by the finite element method involving standard linear and cubic elements. Evanescent short-wavelength modes do not constitute a problem because of the variational nature of the method. It is straightforward to generalize the method to systems of equations with more than two equations. The performance of the method is demonstrated on known physical situations and is measured by investigating the convergence properties. Cubic elements perform much better than linear ones. In an application it is shown that global plasma oscillations might have an importance for the linear wave conversion in the ion-cyclotron range of frequency. (orig.)
Transport and diffusion of material quantities on propagating interfaces via level set methods
Adalsteinsson, D
2003-01-01
We develop theory and numerical algorithms to apply level set methods to problems involving the transport and diffusion of material quantities in a level set framework. Level set methods are computational techniques for tracking moving interfaces; they work by embedding the propagating interface as the zero level set of a higher dimensional function, and then approximate the solution of the resulting initial value partial differential equation using upwind finite difference schemes. The traditional level set method works in the trace space of the evolving interface, and hence disregards any parameterization in the interface description. Consequently, material quantities on the interface which themselves are transported under the interface motion are not easily handled in this framework. We develop model equations and algorithmic techniques to extend the level set method to include these problems. We demonstrate the accuracy of our approach through a series of test examples and convergence studies.
Transport and diffusion of material quantities on propagating interfaces via level set methods
International Nuclear Information System (INIS)
Adalsteinsson, David; Sethian, J.A.
2003-01-01
We develop theory and numerical algorithms to apply level set methods to problems involving the transport and diffusion of material quantities in a level set framework. Level set methods are computational techniques for tracking moving interfaces; they work by embedding the propagating interface as the zero level set of a higher dimensional function, and then approximate the solution of the resulting initial value partial differential equation using upwind finite difference schemes. The traditional level set method works in the trace space of the evolving interface, and hence disregards any parameterization in the interface description. Consequently, material quantities on the interface which themselves are transported under the interface motion are not easily handled in this framework. We develop model equations and algorithmic techniques to extend the level set method to include these problems. We demonstrate the accuracy of our approach through a series of test examples and convergence studies
Czech Academy of Sciences Publication Activity Database
Berezovski, A.; Kolman, Radek; Blažek, Jiří; Kopačka, Ján; Gabriel, Dušan; Plešek, Jiří
2014-01-01
Roč. 19, č. 12 (2014) ISSN 1435-4934. [European Conference on Non-Destructive Testing (ECNDT 2014) /11./. Praha, 06.10.2014-10.10.2014] R&D Projects: GA ČR(CZ) GAP101/11/0288; GA ČR(CZ) GAP101/12/2315 Institutional support: RVO:61388998 Keywords : elastic wave propagation * finite element method * isogeometric analysis * finite volume method * stress discontinuities * spurious oscillations Subject RIV: JR - Other Machinery http://www.ndt.net/events/ECNDT2014/app/content/Paper/25_Berezovski_Rev1.pdf
Generalized Multiscale Finite Element Methods for Wave Propagation in Heterogeneous Media
Chung, Eric T.
2014-11-13
Numerical modeling of wave propagation in heterogeneous media is important in many applications. Due to their complex nature, direct numerical simulations on the fine grid are prohibitively expensive. It is therefore important to develop efficient and accurate methods that allow the use of coarse grids. In this paper, we present a multiscale finite element method for wave propagation on a coarse grid. The proposed method is based on the generalized multiscale finite element method (GMsFEM) (see [Y. Efendiev, J. Galvis, and T. Hou, J. Comput. Phys., 251 (2012), pp. 116--135]). To construct multiscale basis functions, we start with two snapshot spaces in each coarse-grid block, where one represents the degrees of freedom on the boundary and the other represents the degrees of freedom in the interior. We use local spectral problems to identify important modes in each snapshot space. These local spectral problems are different from each other and their formulations are based on the analysis. To the best of knowledge, this is the first time that multiple snapshot spaces and multiple spectral problems are used and necessary for efficient computations. Using the dominant modes from local spectral problems, multiscale basis functions are constructed to represent the solution space locally within each coarse block. These multiscale basis functions are coupled via the symmetric interior penalty discontinuous Galerkin method which provides a block diagonal mass matrix and, consequently, results in fast computations in an explicit time discretization. Our methods\\' stability and spectral convergence are rigorously analyzed. Numerical examples are presented to show our methods\\' performance. We also test oversampling strategies. In particular, we discuss how the modes from different snapshot spaces can affect the proposed methods\\' accuracy.
Methods and apparatus for cooling electronics
Hall, Shawn Anthony; Kopcsay, Gerard Vincent
2014-12-02
Methods and apparatus are provided for choosing an energy-efficient coolant temperature for electronics by considering the temperature dependence of the electronics' power dissipation. This dependence is explicitly considered in selecting the coolant temperature T.sub.0 that is sent to the equipment. To minimize power consumption P.sub.Total for the entire system, where P.sub.Total=P.sub.0+P.sub.Cool is the sum of the electronic equipment's power consumption P.sub.0 plus the cooling equipment's power consumption P.sub.Cool, P.sub.Total is obtained experimentally, by measuring P.sub.0 and P.sub.Cool, as a function of three parameters: coolant temperature T.sub.0; weather-related temperature T.sub.3 that affects the performance of free-cooling equipment; and computational state C of the electronic equipment, which affects the temperature dependence of its power consumption. This experiment provides, for each possible combination of T.sub.3 and C, the value T.sub.0* of T.sub.0 that minimizes P.sub.Total. During operation, for any combination of T.sub.3 and C that occurs, the corresponding optimal coolant temperature T.sub.0* is selected, and the cooling equipment is commanded to produce it.
International Nuclear Information System (INIS)
Foroutan, G.; Khalilpour, H.; Moslehi-Fard, M.; Li, B.; Robinson, P. A.
2008-01-01
The effects of plasma inhomogeneities on the propagation of a cloud of hot electrons through a cold background plasma and generation of Langmuir waves are investigated using numerical simulations of the quasilinear equations. It is found that in a plasma with decreasing density the quasilinear relaxation of the electron distribution in velocity space is accelerated and the levels of the generated Langmuir waves are enhanced. The magnitude of the induced emission rate is increased and its maximum value moves to lower velocities. Due to density gradient the height of plateau shows an increase at small distances and a corresponding decrease at large distances. It is also found that in a plasma with decreasing temperature, the relaxation of the beam is retarded, the spectral density of Langmuir waves is broadened, and the height of the plateau decreases below its value in a uniform plasma. In the presence of both density and temperature gradients, at given position, the height and upper boundary of the plateau and the level of Langmuir waves are all increased at small velocities. The spatial expansion of the beam is increased by the plasma inhomogeneities, but its average velocity of propagation decreases. Initially, at a given position, the velocity at the upper boundary of the plateau is smaller in the presence of the density gradient than in the uniform plasma but the reverse is true at longer times. Due to temperature gradient, at large times and small distances, the upper boundary of the plateau is increased above its value in the uniform plasma. Because of fast relaxation, the value of the lower boundary of the plateau in the plasma with decreasing density is always less than its value in the uniform plasma. It is found that the local velocity of the beam decreases when the density gradient is present. The local velocity spread of the beam remains unchanged during the propagation of the beam in the uniform plasma, but increases in the presence of inhomogeneities.
International Nuclear Information System (INIS)
Shokair, I.R.
1991-01-01
Phase mixing of transverse oscillations changes the nature of the ion hose instability from an absolute to a convective instability. The stronger the phase mixing, the faster an electron beam reaches equilibrium with the guiding ion channel. This is important for long distance propagation of relativistic electron beams where it is desired that transverse oscillations phase mix within a few betatron wavelengths of injection and subsequently an equilibrium is reached with no further beam emittance growth. In the linear regime phase mixing is well understood and results in asymptotic decay of transverse oscillations as 1/Z 2 for a Gaussian beam and channel system, Z being the axial distance measured in betatron wavelengths. In the nonlinear regime (which is likely mode of propagation for long pulse beams) results of the spread mass model indicate that phase mixing is considerably weaker than in the regime. In this paper we consider this problem of phase mixing in the nonlinear regime. Results of the spread mass model will be shown along with a simple analysis of phase mixing for multiple oscillator models. Particle simulations also indicate that phase mixing is weaker in nonlinear regime than in the linear regime. These results will also be shown. 3 refs., 4 figs
Gopalakrishnan, Srinivasan; Roy Mahapatra, Debiprosad
2008-01-01
The use of composites and Functionally Graded Materials (FGMs) in structural applications has increased. FGMs allow the user to design materials for a specified functionality and have many uses in structural engineering. However, the behaviour of these structures under high-impact loading is not well understood. This book is the first to apply the Spectral Finite Element Method (SFEM) to inhomogeneous and anisotropic structures in a unified and systematic manner. It focuses on some of the problems with this media which were previously thought unmanageable. Types of SFEM for regular and damaged 1-D and 2-D waveguides, solution techniques, methods of detecting the presence of damages and their locations, and methods for controlling the wave propagation responses are discussed. Tables, figures and graphs support the theory and case studies are included. This book is of value to senior undergraduates and postgraduates studying in this field, and researchers and practicing engineers in structural integrity.
Directory of Open Access Journals (Sweden)
Tao Zhang
2016-03-01
Full Text Available This paper researches an AUV (Autonomous Underwater Vehicle positioning method based on SINS (Strapdown Inertial Navigation System/LBL (Long Base Line tightly coupled algorithm. This algorithm mainly includes SINS-assisted searching method of optimum slant-range of underwater acoustic propagation multipath, SINS/LBL tightly coupled model and multi-sensor information fusion algorithm. Fuzzy correlation peak problem of underwater LBL acoustic propagation multipath could be solved based on SINS positional information, thus improving LBL positional accuracy. Moreover, introduction of SINS-centered LBL locating information could compensate accumulative AUV position error effectively and regularly. Compared to loosely coupled algorithm, this tightly coupled algorithm can still provide accurate location information when there are fewer than four available hydrophones (or within the signal receiving range. Therefore, effective positional calibration area of tightly coupled system based on LBL array is wider and has higher reliability and fault tolerance than loosely coupled. It is more applicable to AUV positioning based on SINS/LBL.
International Nuclear Information System (INIS)
Mullor, R.; Sanchez, A.; Martorell, S.; Martinez-Alzamora, N.
2011-01-01
Safety related systems performance optimization is classically based on quantifying the effects that testing and maintenance activities have on reliability and cost (R+C). However, R+C quantification is often incomplete in the sense that important uncertainties may not be considered. An important number of studies have been published in the last decade in the field of R+C based optimization considering uncertainties. They have demonstrated that inclusion of uncertainties in the optimization brings the decision maker insights concerning how uncertain the R+C results are and how this uncertainty does matter as it can result in differences in the outcome of the decision making process. Several methods of uncertainty propagation based on the theory of tolerance regions have been proposed in the literature depending on the particular characteristics of the variables in the output and their relations. In this context, the objective of this paper focuses on the application of non-parametric and parametric methods to analyze uncertainty propagation, which will be implemented on a multi-objective optimization problem where reliability and cost act as decision criteria and maintenance intervals act as decision variables. Finally, a comparison of results of these applications and the conclusions obtained are presented.
Energy Technology Data Exchange (ETDEWEB)
Mullor, R. [Dpto. Estadistica e Investigacion Operativa, Universidad Alicante (Spain); Sanchez, A., E-mail: aisanche@eio.upv.e [Dpto. Estadistica e Investigacion Operativa Aplicadas y Calidad, Universidad Politecnica Valencia, Camino de Vera s/n 46022 (Spain); Martorell, S. [Dpto. Ingenieria Quimica y Nuclear, Universidad Politecnica Valencia (Spain); Martinez-Alzamora, N. [Dpto. Estadistica e Investigacion Operativa Aplicadas y Calidad, Universidad Politecnica Valencia, Camino de Vera s/n 46022 (Spain)
2011-06-15
Safety related systems performance optimization is classically based on quantifying the effects that testing and maintenance activities have on reliability and cost (R+C). However, R+C quantification is often incomplete in the sense that important uncertainties may not be considered. An important number of studies have been published in the last decade in the field of R+C based optimization considering uncertainties. They have demonstrated that inclusion of uncertainties in the optimization brings the decision maker insights concerning how uncertain the R+C results are and how this uncertainty does matter as it can result in differences in the outcome of the decision making process. Several methods of uncertainty propagation based on the theory of tolerance regions have been proposed in the literature depending on the particular characteristics of the variables in the output and their relations. In this context, the objective of this paper focuses on the application of non-parametric and parametric methods to analyze uncertainty propagation, which will be implemented on a multi-objective optimization problem where reliability and cost act as decision criteria and maintenance intervals act as decision variables. Finally, a comparison of results of these applications and the conclusions obtained are presented.
Electronic Nose Feature Extraction Methods: A Review.
Yan, Jia; Guo, Xiuzhen; Duan, Shukai; Jia, Pengfei; Wang, Lidan; Peng, Chao; Zhang, Songlin
2015-11-02
Many research groups in academia and industry are focusing on the performance improvement of electronic nose (E-nose) systems mainly involving three optimizations, which are sensitive material selection and sensor array optimization, enhanced feature extraction methods and pattern recognition method selection. For a specific application, the feature extraction method is a basic part of these three optimizations and a key point in E-nose system performance improvement. The aim of a feature extraction method is to extract robust information from the sensor response with less redundancy to ensure the effectiveness of the subsequent pattern recognition algorithm. Many kinds of feature extraction methods have been used in E-nose applications, such as extraction from the original response curves, curve fitting parameters, transform domains, phase space (PS) and dynamic moments (DM), parallel factor analysis (PARAFAC), energy vector (EV), power density spectrum (PSD), window time slicing (WTS) and moving window time slicing (MWTS), moving window function capture (MWFC), etc. The object of this review is to provide a summary of the various feature extraction methods used in E-noses in recent years, as well as to give some suggestions and new inspiration to propose more effective feature extraction methods for the development of E-nose technology.
Propagation of ion-acoustic waves in a warm dusty plasma with electron inertia
Barman, S. N.; Talukdar, A.
2011-08-01
The KdV equation is derived for weakly nonlinear ion-acoustic waves in an unmagnetized warm dusty plasma with electron inertia. It has been shown that the inclusion of electron inertia and pressure variation of the species not only significantly modifies the basic features (width and amplitude) of dust ion-acoustic solitions, but also introduces a new parametric regime for the existence of positive and negative solitons.
Wave propagation in ducts using the finite element method. [for aircraft noise reduction
Majjigi, R. K.; Sigman, R. K.; Zinn, B. T.
1979-01-01
The paper outlines a comparative study designed to assess and compare the accuracy of the finite element method (FEM) for linear and quadratic elements as applied to problems in duct acoustics. The acoustic disturbances are assumed to be irrotational and isentropic so that the problem can be formulated in terms of the acoustic velocity potential. It is shown that for the case of plane wave propagation in a hard-walled annular cylinder, the accuracy of the FEM solution can be increased at higher frequencies by using quadratic triangular elements instead of linear triangular elements. Evidence is presented to enhance the confidence in applying the developed FEM by comparing results with those obtained by other independently developed numerical approaches such as an integral equation technique and a finite difference method.
Standardless quantification methods in electron probe microanalysis
Energy Technology Data Exchange (ETDEWEB)
Trincavelli, Jorge, E-mail: trincavelli@famaf.unc.edu.ar [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); Instituto de Física Enrique Gaviola, Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, Medina Allende s/n, Ciudad Universitaria, 5000 Córdoba (Argentina); Limandri, Silvina, E-mail: s.limandri@conicet.gov.ar [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); Instituto de Física Enrique Gaviola, Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, Medina Allende s/n, Ciudad Universitaria, 5000 Córdoba (Argentina); Bonetto, Rita, E-mail: bonetto@quimica.unlp.edu.ar [Centro de Investigación y Desarrollo en Ciencias Aplicadas Dr. Jorge Ronco, Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, Facultad de Ciencias Exactas, de la Universidad Nacional de La Plata, Calle 47 N° 257, 1900 La Plata (Argentina)
2014-11-01
The elemental composition of a solid sample can be determined by electron probe microanalysis with or without the use of standards. The standardless algorithms are quite faster than the methods that require standards; they are useful when a suitable set of standards is not available or for rough samples, and also they help to solve the problem of current variation, for example, in equipments with cold field emission gun. Due to significant advances in the accuracy achieved during the last years, product of the successive efforts made to improve the description of generation, absorption and detection of X-rays, the standardless methods have increasingly become an interesting option for the user. Nevertheless, up to now, algorithms that use standards are still more precise than standardless methods. It is important to remark, that care must be taken with results provided by standardless methods that normalize the calculated concentration values to 100%, unless an estimate of the errors is reported. In this work, a comprehensive discussion of the key features of the main standardless quantification methods, as well as the level of accuracy achieved by them is presented. - Highlights: • Standardless methods are a good alternative when no suitable standards are available. • Their accuracy reaches 10% for 95% of the analyses when traces are excluded. • Some of them are suitable for the analysis of rough samples.
1986-06-01
plus rapproch~es. Cette question, qui constitue en elle-mgme un domaine de recherche, d~ borde du cadre du present rapport. * Il est possible d’gtendre...par la commande JCL "PROPEX:T.’ qui produit le module ex~cutable "PROPAG:EX". TABLEAU I Bloc principal PROPAK *NOM DES ROUTINES FONCTION PROPAG...alise la r &mission des rayons r~fl~chis e77 SANS CLASSIFICATION 22 TABLEAU II Bloc utilitaire UTILPAK NOM DES ROUTINES FONCTION H - Calcule r la
Pelat, Adrien; Felix, Simon; Pagneux, Vincent
2011-03-01
In modeling the wave propagation within a street canyon, particular attention must be paid to the description of both the multiple reflections of the wave on the building facades and the radiation in the free space above the street. The street canyon being considered as an open waveguide with a discontinuously varying cross-section, a coupled modal-finite element formulation is proposed to solve the three-dimensional wave equation within. The originally open configuration-the street canyon open in the sky above-is artificially turned into a close waveguiding structure by using perfectly matched layers that truncate the infinite sky without introducing numerical reflection. Then the eigenmodes of the resulting waveguide are determined by a finite element method computation in the cross-section. The eigensolutions can finally be used in a multimodal formulation of the wave propagation along the canyon, given its geometry and the end conditions at its extremities: initial field condition at the entrance and radiation condition at the output. © 2011 Acoustical Society of America
Research on a Lamb Wave and Particle Filter-Based On-Line Crack Propagation Prognosis Method
Chen, Jian; Yuan, Shenfang; Qiu, Lei; Cai, Jian; Yang, Weibo
2016-01-01
Prognostics and health management techniques have drawn widespread attention due to their ability to facilitate maintenance activities based on need. On-line prognosis of fatigue crack propagation can offer information for optimizing operation and maintenance strategies in real-time. This paper proposes a Lamb wave-particle filter (LW-PF)-based method for on-line prognosis of fatigue crack propagation which takes advantages of the possibility of on-line monitoring to evaluate the actual crack...
Energetic electron propagation in the decay phase of non-thermal flare emission
Energy Technology Data Exchange (ETDEWEB)
Huang, Jing; Yan, Yihua [Key Laboratory of Solar Activities, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Tsap, Yuri T., E-mail: huangj@nao.cas.cn [Crimean Astrophysical Observatory of Kyiv National Taras Shevchenko University, 98409 Crimea, Nauchny (Ukraine)
2014-06-01
On the basis of the trap-plus-precipitation model, the peculiarities of non-thermal emission in the decay phase of solar flares have been considered. The calculation formulas for the escape rate of trapped electrons into the loss cone in terms of time profiles of hard X-ray (HXR) and microwave (MW) emission have been obtained. It has been found that the evolution of the spectral indices of non-thermal emission depend on the regimes of the pitch angle diffusion of trapped particles into the loss cone. The properties of non-thermal electrons related to the HXR and MW emission of the solar flare on 2004 November 3 are studied with Nobeyama Radioheliograph, Nobeyama Radio Polarimeters, RHESSI, and Geostationary Operational Environmental Satellite observations. The spectral indices of non-thermal electrons related to MW and HXR emission remained constant or decreased, while the MW escape rate as distinguished from that of the HXRs increased. This may be associated with different diffusion regimes of trapped electrons into the loss cone. New arguments in favor of an important role of the superstrong diffusion for high-energy electrons in flare coronal loops have been obtained.
Salomons, Erik M; Lohman, Walter J A; Zhou, Han
2016-01-01
Propagation of sound waves in air can be considered as a special case of fluid dynamics. Consequently, the lattice Boltzmann method (LBM) for fluid flow can be used for simulating sound propagation. In this article application of the LBM to sound propagation is illustrated for various cases: free-field propagation, propagation over porous and non-porous ground, propagation over a noise barrier, and propagation in an atmosphere with wind. LBM results are compared with solutions of the equations of acoustics. It is found that the LBM works well for sound waves, but dissipation of sound waves with the LBM is generally much larger than real dissipation of sound waves in air. To circumvent this problem it is proposed here to use the LBM for assessing the excess sound level, i.e. the difference between the sound level and the free-field sound level. The effect of dissipation on the excess sound level is much smaller than the effect on the sound level, so the LBM can be used to estimate the excess sound level for a non-dissipative atmosphere, which is a useful quantity in atmospheric acoustics. To reduce dissipation in an LBM simulation two approaches are considered: i) reduction of the kinematic viscosity and ii) reduction of the lattice spacing.
Production of advanced materials by methods of self-propagating high-temperature synthesis
Tavadze, Giorgi F
2013-01-01
This translation from the original Russian book outlines the production of a variety of materials by methods of self-propagating high-temperature synthesis (SHS). The types of materials discussed include: hard, refractory, corrosion and wear-resistant materials, as well as other advanced and speciality materials. The authors address the issue of optimal parameters for SHS reactions occurring during processes involving a preliminary metallothermic reduction stage, and they calculate this using thermodynamic approaches. In order to confirm the effectiveness of this approach, the authors describe experiments focussing on the synthesis of elemental crysalline boron, boron carbides and nitrides. Other parts of this brief include theoretical and experimental results on single-stage production of hard alloys on the basis of titanium and zirconium borides, as well as macrokinetics of degassing and compaciton of SHS-products.This brief is suitable for academics, as well as those working in industrial manufacturing com...
B-spline based finite element method in one-dimensional discontinuous elastic wave propagation
Czech Academy of Sciences Publication Activity Database
Kolman, Radek; Okrouhlík, Miloslav; Berezovski, A.; Gabriel, Dušan; Kopačka, Ján; Plešek, Jiří
2017-01-01
Roč. 46, June (2017), s. 382-395 ISSN 0307-904X R&D Projects: GA ČR(CZ) GAP101/12/2315; GA MŠk(CZ) EF15_003/0000493 Grant - others:AV ČR(CZ) DAAD-16-12; AV ČR(CZ) ETA-15-03 Program:Bilaterální spolupráce; Bilaterální spolupráce Institutional support: RVO:61388998 Keywords : discontinuous elastic wave propagation * B-spline finite element method * isogeometric analysis * implicit and explicit time integration * dispersion * spurious oscillations Subject RIV: BI - Acoustics OBOR OECD: Acoustics Impact factor: 2.350, year: 2016 http://www.sciencedirect.com/science/article/pii/S0307904X17300835
Domínguez, Macarena; Muñoz, Víctor; Valdivia, Juan Alejandro
2012-05-01
The propagation of circularly polarized electromagnetic waves along a constant background magnetic field in an electron-positron plasma is calculated by means of both a fluid and a kinetic theory treatment. In the fluid theory, relativistic effects are included in the particle motion, the wave field, and in the thermal motion by means of a function f, which depends only on the plasma temperature. In this work we analyze the consistency of the fluid results with those obtained from a kinetic treatment, based on the relativistic Vlasov equation. The corresponding kinetic dispersion relation is numerically studied for various temperatures, and results are compared with the fluid treatment. Analytic expressions for the Alfvén velocity are obtained for the fluid and kinetic models, and it is shown that, in the kinetic treatment, the Alfvén branch is suppressed for large temperatures.
Kletsov, Aleksey A; Glukhovskoy, Evgeny G; Chumakov, Aleksey S; Ortiz, Joseph V
2016-01-01
The conduction properties of DNA molecule, particularly its transverse conductance (electron transfer through nucleotide bridges), represent a point of interest for DNA chemistry community, especially for DNA sequencing. However, there is no fully developed first-principles theory for molecular conductance and current that allows one to analyze the transverse flow of electrical charge through a nucleotide base. We theoretically investigate the transverse electron transport through all four DNA nucleotide bases by implementing an unbiased ab initio theoretical approach, namely, the electron propagator theory. The electrical conductance and current through DNA nucleobases (guanine [G], cytosine [C], adenine [A] and thymine [T]) inserted into a model 1-nm Ag-Ag nanogap are calculated. The magnitudes of the calculated conductance and current are ordered in the following hierarchies: gA>gG>gC>gT and IG>IA>IT>IC correspondingly. The new distinguishing parameter for the nucleobase identification is proposed, namely, the onset bias magnitude. Nucleobases exhibit the following hierarchy with respect to this parameter: Vonset(A)DNA translocation through an electrode-equipped nanopore. The results represent interest for the theorists and practitioners in the field of third generation sequencing techniques as well as in the field of DNA chemistry. Copyright © 2015 Elsevier B.V. All rights reserved.
Couillaud, C
2002-01-01
This paper is concerned with the production of X-ray transition radiation when a relativistic electron crosses the interface between two media of different permittivities at the grazing incidence. The production yields are derived analytically when a thick interface is considered and are compared with those obtained when the electron crosses the interface at normal incidence. The production of X-ray photons having an energy between two photoabsorption edges or close to a photoabsorption edge is also investigated. The main features of the transition radiation produced are then exhibited and it is shown that the intensity can be increased by many orders of magnitude. We also show that, at grazing incidence, the backward transition radiation has an intensity close to the forward emission one, contrary to the normal incidence case. The production of quasi-monochromatic radiation is also presented. Finally, the production of X-ray transition radiation using a multilayer radiator is considered and compared in both ...
A nodal discontinuous Galerkin finite element method for nonlinear elastic wave propagation.
Bou Matar, Olivier; Guerder, Pierre-Yves; Li, YiFeng; Vandewoestyne, Bart; Van Den Abeele, Koen
2012-05-01
A nodal discontinuous Galerkin finite element method (DG-FEM) to solve the linear and nonlinear elastic wave equation in heterogeneous media with arbitrary high order accuracy in space on unstructured triangular or quadrilateral meshes is presented. This DG-FEM method combines the geometrical flexibility of the finite element method, and the high parallelization potentiality and strongly nonlinear wave phenomena simulation capability of the finite volume method, required for nonlinear elastodynamics simulations. In order to facilitate the implementation based on a numerical scheme developed for electromagnetic applications, the equations of nonlinear elastodynamics have been written in a conservative form. The adopted formalism allows the introduction of different kinds of elastic nonlinearities, such as the classical quadratic and cubic nonlinearities, or the quadratic hysteretic nonlinearities. Absorbing layers perfectly matched to the calculation domain of the nearly perfectly matched layers type have been introduced to simulate, when needed, semi-infinite or infinite media. The developed DG-FEM scheme has been verified by means of a comparison with analytical solutions and numerical results already published in the literature for simple geometrical configurations: Lamb's problem and plane wave nonlinear propagation.
Energy Technology Data Exchange (ETDEWEB)
Ueda, Y.; Murakawa, H. [Osaka Univ., Osaka (Japan). Welding Research Inst.; Tanigawa, M. [Hitachi Zosen Corp., Osaka (Japan)
1996-12-31
In order to investigate an effect of the plastic deformation, which was generated on ship side outer platings subjected to collision load before crack initiation, on the crack propagation behavior, crack propagation experiments using pre-strained specimens and simulation analysis by means of FEM method were carried out, to discuss about the practical simulation analysis method. As a result of the crack propagation experiments using pre-strained center notched plate specimens, a phenomenon where the crack is apt to propagate due to the pre-strains was confirmed, and measured data of crack tip opening angles were obtained. A method was proposed, in which the critical crack tip opening angle values are corrected by considering the difference between the crack shapes obtained from the FEM analysis model and actually measured, and its effectiveness was confirmed. The finite element size effect was also examined. A method using an equivalent plastic strain as the crack propagation condition was shown to determine the relationship between the element size and the critical value of equivalent plastic strain. 5 refs., 21 figs., 4 tabs.
International Nuclear Information System (INIS)
Lin, S.; Fukutomi, H.; Ogata, T.
2006-01-01
Wave propagation in an austenitic stainless steel specimen with a slit open to the lower surface is modeled using finite element method, with consideration of the effects of scattering at grain boundaries. The distribution of energy of a diffracted longitudinal wave shows that this wave has the strongest energy directly above the slit. As a consequence of this result, a new testing method is proposed. The new method is verified using austenitic stainless steel specimens. Experimental results show that the new method is applicable to austenitic stainless steel with high accuracy, to which the time of flight diffraction method (TOFD) is not applicable
Khalil, Shahid Akbar; Zamir, Roshan; Ahmad, Nisar
2014-01-01
Stevia rebaudiana (Bert.) is an emerging sugar alternative and anti-diabetic plant in Pakistan. That is why people did not know the exact time of propagation. The main objective of the present study was to establish feasible propagation methods for healthy biomass production. In the present study, seed germination, stem cuttings and micropropagation were investigated for higher productivity. Fresh seeds showed better germination (25.51–40%) but lost viability after a few days of storage. In order to improve the germination percentage, seeds were irradiated with 2.5, 5.0, 7.5 and 10 Gy gamma doses. But gamma irradiation did not show any significant change in seed germination. A great variation in survival of stem cutting was observed in each month of 2012. October and November were found the most suitable months for stem cutting survival (60%). In order to enhance survival, stem cuttings were also dipped in different plant growth regulators (PGRs) solution. Only indole butyric acid (IBA; 1000 ppm) treated cutting showed a higher survival (33%) than control (11.1%). Furthermore, simple and feasible indirect regeneration system was established from leaf explants. Best callus induction (84.6%) was observed on MS-medium augmented with 6-benzyladenine (BA) and 2,4-dichlorophenoxyacetic acid (2,4-D; 2.0 mg l−1). For the first time, we obtained the highest number of shoots (106) on a medium containing BA (1.5 mg l−1) and gibberellic acid (GA3; 0.5 mg l−1). Plantlets were successfully acclimatized in plastic pots. The current results preferred micropropagation (85%) over seed germination (25.51–40%) and stem cutting (60%). PMID:25473365
Effects of buried high-Z layers on fast electron propagation
Czech Academy of Sciences Publication Activity Database
Yang, X.; Xu, H.; Zhuo, H.; Ma, Y.; Shao, F.; Yin, Y.; Borghesi, Marco
2014-01-01
Roč. 68, č. 2 (2014), s. 1-7 ISSN 1434-6060 R&D Projects: GA MŠk ED1.1.00/02.0061; GA MŠk EE2.3.20.0279 Grant - others:ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061; LaserZdroj (OP VK 3)(XE) CZ.1.07/2.3.00/20.0279 Institutional support: RVO:68378271 Keywords : laser-plasma interactions * short-pulse * hot-electrons * solid targets * transport * field Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.228, year: 2014
Dósa, M.; Opitz, A.; Szegő, K.
2017-09-01
Concerning the increasing number of heliospheric space missions it is a key issue to foresee space weather conditions in the spacecraft's and the target object's neighborhood. Solar wind parameters are propagated to outer orbits by several ballistic and magnetohydrodynamic (MHD) methods. The ballistic model presented here is enhanced by adjusting for the target movement during the propagation time through a two-step method. First, the magnetic field line connecting the Sun and the target has to be found. Once the proper magnetic field line is found, solar wind bulk velocity, density and magnetic field polarity is propagated assuming no change during travel time. The method was tested successfully during the Rosetta mission. While the spacecraft was investigating the close environment of the comet Churyumov-Gerasimenko it was necessary to know the properties of the ambient solar wind in order to evaluate data and account for the dynamic changes.
International Nuclear Information System (INIS)
Gelman, David; Schwartz, Steven D.
2010-01-01
The recently developed quantum-classical method has been applied to the study of dissipative dynamics in multidimensional systems. The method is designed to treat many-body systems consisting of a low dimensional quantum part coupled to a classical bath. Assuming the approximate zeroth order evolution rule, the corrections to the quantum propagator are defined in terms of the total Hamiltonian and the zeroth order propagator. Then the corrections are taken to the classical limit by introducing the frozen Gaussian approximation for the bath degrees of freedom. The evolution of the primary part is governed by the corrected propagator yielding the exact quantum dynamics. The method has been tested on two model systems coupled to a harmonic bath: (i) an anharmonic (Morse) oscillator and (ii) a double-well potential. The simulations have been performed at zero temperature. The results have been compared to the exact quantum simulations using the surrogate Hamiltonian approach.
Peña-Ramírez, Yuri; Juárez-Gómez, Juan; González-Rodríguez, José Antonio; Robert, Manuel L
2012-01-01
The choice of a method to culture red cedar tissues depends on the final objectives pursued. If homogeneous clonal material is required for experimental purposes, the easiest way is to generate the lines through adventitious shoot induction from seedlings germinated from seeds. If the objective is to generate high yielding material for plantation purposes, the choice will be the same method but starting from mature vegetative tissues from selected elite plants. Most of the process are the same, but the initial steps are less efficient and much more elaborate. If the purpose is to generate lines with new genetic characteristics through somaclonal variation, mutagenesis, or genetic transformation, somatic embryogenesis will be required. No single method in its present form is suitable for all purposes. Eventually, the efficient production of somatic embryos from rejuvenated shoots collected from mature selected plants is the ideal way to culture this species, but for the time being we have to choose one or the other. In this chapter, we present a grafting procedure to rejuvenate and maintain mother plants in the greenhouse and the in vitro culture systems we have developed for the production of Cedrela odorata propagules using explants from both young seedlings and mature tissues from selected old trees. Using a modified TY17 medium and the BioMINT(®) temporary immersion system, we obtained high multiplication and ex vitro transplantation rates for efficient large-scale propagation of this species.
An Extended Affinity Propagation Clustering Method Based on Different Data Density Types
Directory of Open Access Journals (Sweden)
XiuLi Zhao
2015-01-01
Full Text Available Affinity propagation (AP algorithm, as a novel clustering method, does not require the users to specify the initial cluster centers in advance, which regards all data points as potential exemplars (cluster centers equally and groups the clusters totally by the similar degree among the data points. But in many cases there exist some different intensive areas within the same data set, which means that the data set does not distribute homogeneously. In such situation the AP algorithm cannot group the data points into ideal clusters. In this paper, we proposed an extended AP clustering algorithm to deal with such a problem. There are two steps in our method: firstly the data set is partitioned into several data density types according to the nearest distances of each data point; and then the AP clustering method is, respectively, used to group the data points into clusters in each data density type. Two experiments are carried out to evaluate the performance of our algorithm: one utilizes an artificial data set and the other uses a real seismic data set. The experiment results show that groups are obtained more accurately by our algorithm than OPTICS and AP clustering algorithm itself.
Ultrasound viscoelasticity assessment using an adaptive torsional shear wave propagation method
Energy Technology Data Exchange (ETDEWEB)
Ouared, Abderrahmane [Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9, Canada and Institute of Biomedical Engineering, University of Montréal, Montréal, Québec H3T 1J4 (Canada); Kazemirad, Siavash; Montagnon, Emmanuel [Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9 (Canada); Cloutier, Guy, E-mail: guy.cloutier@umontreal.ca [Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9 (Canada); Department of Radiology, Radio-Oncology and Nuclear Medicine, University of Montréal, Montréal, Québec H3T 1J4 (Canada); Institute of Biomedical Engineering, University of Montréal, Montréal, Québec H3T 1J4 (Canada)
2016-04-15
Purpose: Different approaches have been used in dynamic elastography to assess mechanical properties of biological tissues. Most techniques are based on a simple inversion based on the measurement of the shear wave speed to assess elasticity, whereas some recent strategies use more elaborated analytical or finite element method (FEM) models. In this study, a new method is proposed for the quantification of both shear storage and loss moduli of confined lesions, in the context of breast imaging, using adaptive torsional shear waves (ATSWs) generated remotely with radiation pressure. Methods: A FEM model was developed to solve the inverse wave propagation problem and obtain viscoelastic properties of interrogated media. The inverse problem was formulated and solved in the frequency domain and its robustness to noise and geometric constraints was evaluated. The proposed model was validated in vitro with two independent rheology methods on several homogeneous and heterogeneous breast tissue-mimicking phantoms over a broad range of frequencies (up to 400 Hz). Results: Viscoelastic properties matched benchmark rheology methods with discrepancies of 8%–38% for the shear modulus G′ and 9%–67% for the loss modulus G″. The robustness study indicated good estimations of storage and loss moduli (maximum mean errors of 19% on G′ and 32% on G″) for signal-to-noise ratios between 19.5 and 8.5 dB. Larger errors were noticed in the case of biases in lesion dimension and position. Conclusions: The ATSW method revealed that it is possible to estimate the viscoelasticity of biological tissues with torsional shear waves when small biases in lesion geometry exist.
Roelof, E. C.
2017-12-01
Voyager 1/2 LECP observations at the termination shock (TS) crossings established that energetic ions (40keV-1MeV) appeared to be locally accelerated "termination shock particles", and since then have exhibited remarkably steady and similar intensities at both spacecraft throughout the heliosheath (HS). On the other hand, the anomalous cosmic rays (ACRs, 4-80 MeV total energy H, He, and O ions) increased more or less steadily across the shock and then gradually peaked years later. All the time in the HS, the ACRs at each spacecraft exhibited a striking "common spectrum", i.e., closely similar intensity histories when ordered by total energy. Near-relativistic electrons (30 keV-1 MeV) exhibited seemingly mutually inconsistent behavior while the two Voyagers transited the shock and HS, with the VGR2 electrons peaking at the shock, but later disappearing for a year (in 2010) and then slowly recovering, as opposed to the less variable VGR1 electrons whose remarkably smooth time history (2008-2012) was very similar to the VGR1 ACRs. Consequently, shock acceleration seems to be operating locally at the TS along with another spatially distributed acceleration/transport mechanism within the HS. The "reservoir" equation (Roelof, AIP Conf. Proc., 1500, 174-179 and 180-184, 2012) offers quantitative explanations for many of these apparently disparate observations. Meso-scale gradients and curvatures in the magnetic field produce transverse transport of energetic particles and (in direct consequence) "transverse compressive" acceleration that relates the fractional rate of momentum d(lnp)/dt=-(1/3)div(Vperp) to the divergence of the component of the plasma velocity transverse to the magnetic field. However, this acceleration rate must compete with the extinction rate of singly-charged ions due to charge exchange with the cold interstellar neutral H-atoms that permeate the HS. The agreement of the Voyager 1/2 LECP observations with the acceleration/extinction processes has
Rolla, L. Barrera; Rice, H. J.
2006-09-01
In this paper a "forward-advancing" field discretization method suitable for solving the Helmholtz equation in large-scale problems is proposed. The forward wave expansion method (FWEM) is derived from a highly efficient discretization procedure based on interpolation of wave functions known as the wave expansion method (WEM). The FWEM computes the propagated sound field by means of an exclusively forward advancing solution, neglecting the backscattered field. It is thus analogous to methods such as the (one way) parabolic equation method (PEM) (usually discretized using standard finite difference or finite element methods). These techniques do not require the inversion of large system matrices and thus enable the solution of large-scale acoustic problems where backscatter is not of interest. Calculations using FWEM are presented for two propagation problems and comparisons to data computed with analytical and theoretical solutions and show this forward approximation to be highly accurate. Examples of sound propagation over a screen in upwind and downwind refracting atmospheric conditions at low nodal spacings (0.2 per wavelength in the propagation direction) are also included to demonstrate the flexibility and efficiency of the method.
International Nuclear Information System (INIS)
Levin, B.N.
1984-01-01
The propagation of an inhomogeneous stream of fast electrons through the corona - the type III radio burst source - is considered. It is shown, that the angular spectrum width of plasma waves excited by the stream is defined both by Landau damping by particles of the diffuse component and by damping (in the region of large phase velocities) by particles of the stream itself having large pitch angles. The regime of quasi-one-dimensional diffusion in the velocity space is realized only in the presence of a sufficiently dense diffuse component of super-thermal particles and only for a sufficiently large inhomogeneity scale of the stream. A large scale of the stream space profile is formed, evidently, close to the region of injection of super-thermal particles. It is the result of 'stripping' of part of the electrons from the stream front to its slower part due to essential non-one-dimensionality of the particle diffusion in velocity space. Results obtained may explain, in particular, the evolution of a stream particle angular spectrum in the generation region of type III radio bursts observed by spacecrafts (Lin et al., 1981). For the relatively low energetic part of the stream, the oblique plasma wave stabilization by a diffuse component results in a quasi-one-dimensional regime of diffusion. The latter conserves the beam-like structure of this part of the stream. (orig.)
openPSTD: The open source pseudospectral time-domain method for acoustic propagation
Hornikx, Maarten; Krijnen, Thomas; van Harten, Louis
2016-06-01
An open source implementation of the Fourier pseudospectral time-domain (PSTD) method for computing the propagation of sound is presented, which is geared towards applications in the built environment. Being a wave-based method, PSTD captures phenomena like diffraction, but maintains efficiency in processing time and memory usage as it allows to spatially sample close to the Nyquist criterion, thus keeping both the required spatial and temporal resolution coarse. In the implementation it has been opted to model the physical geometry as a composition of rectangular two-dimensional subdomains, hence initially restricting the implementation to orthogonal and two-dimensional situations. The strategy of using subdomains divides the problem domain into local subsets, which enables the simulation software to be built according to Object-Oriented Programming best practices and allows room for further computational parallelization. The software is built using the open source components, Blender, Numpy and Python, and has been published under an open source license itself as well. For accelerating the software, an option has been included to accelerate the calculations by a partial implementation of the code on the Graphical Processing Unit (GPU), which increases the throughput by up to fifteen times. The details of the implementation are reported, as well as the accuracy of the code.
Directory of Open Access Journals (Sweden)
Junfang Li
2016-01-01
Full Text Available Direct forecasting method for Urban Rail Transit (URT ridership at the station level is not able to reflect nonlinear relationship between ridership and its predictors. Also, population is inappropriately expressed in this method since it is not uniformly distributed by area. In this paper, a new variable, population per distance band, is considered and a back propagation neural network (BPNN model which can reflect nonlinear relationship between ridership and its predictors is proposed to forecast ridership. Key predictors are obtained through partial correlation analysis. The performance of the proposed model is compared with three other benchmark models, which are linear model with population per distance band, BPNN model with total population, and linear model with total population, using four measures of effectiveness (MOEs, maximum relative error (MRE, smallest relative error (SRE, average relative error (ARE, and mean square root of relative error (MSRRE. Also, another model for contribution rate of population per distance band to ridership is formulated based on the BPNN model with nonpopulation variables fixed. Case studies with Japanese data show that BPNN model with population per distance band outperforms other three models and the contribution rate of population within special distance band to ridership calculated through the contribution rate model is 70%~92.9% close to actual statistical value. The result confirms the effectiveness of models proposed in this paper.
Application of distributed point source method (DPSM) to wave propagation in anisotropic media
Fooladi, Samaneh; Kundu, Tribikram
2017-04-01
Distributed Point Source Method (DPSM) was developed by Placko and Kundu1, as a technique for modeling electromagnetic and elastic wave propagation problems. DPSM has been used for modeling ultrasonic, electrostatic and electromagnetic fields scattered by defects and anomalies in a structure. The modeling of such scattered field helps to extract valuable information about the location and type of defects. Therefore, DPSM can be used as an effective tool for Non-Destructive Testing (NDT). Anisotropy adds to the complexity of the problem, both mathematically and computationally. Computation of the Green's function which is used as the fundamental solution in DPSM is considerably more challenging for anisotropic media, and it cannot be reduced to a closed-form solution as is done for isotropic materials. The purpose of this study is to investigate and implement DPSM for an anisotropic medium. While the mathematical formulation and the numerical algorithm will be considered for general anisotropic media, more emphasis will be placed on transversely isotropic materials in the numerical example presented in this paper. The unidirectional fiber-reinforced composites which are widely used in today's industry are good examples of transversely isotropic materials. Development of an effective and accurate NDT method based on these modeling results can be of paramount importance for in-service monitoring of damage in composite structures.
[SciELO: method for electronic publishing].
Laerte Packer, A; Rocha Biojone, M; Antonio, I; Mayumi Takemaka, R; Pedroso García, A; Costa da Silva, A; Toshiyuki Murasaki, R; Mylek, C; Carvalho Reisl, O; Rocha F Delbucio, H C
2001-01-01
It describes the SciELO Methodology Scientific Electronic Library Online for electronic publishing of scientific periodicals, examining issues such as the transition from traditional printed publication to electronic publishing, the scientific communication process, the principles which founded the methodology development, its application in the building of the SciELO site, its modules and components, the tools use for its construction etc. The article also discusses the potentialities and trends for the area in Brazil and Latin America, pointing out questions and proposals which should be investigated and solved by the methodology. It concludes that the SciELO Methodology is an efficient, flexible and wide solution for the scientific electronic publishing.
International Nuclear Information System (INIS)
Choi, C.-R.; Dokgo, K.; Min, K.-W.; Woo, M.-H.; Choi, E.-J.; Hwang, J.; Park, Y.-D.; Lee, D.-Y.
2015-01-01
The diffusion of electrons via a linearly polarized, growing electromagnetic (EM) wave propagating along a uniform magnetic field is investigated. The diffusion of electrons that interact with the growing EM wave is investigated through the autocorrelation function of the parallel electron acceleration in several tens of electron gyration timescales, which is a relatively short time compared with the bounce time of electrons between two mirror points in Earth's radiation belts. Furthermore, the pitch-angle diffusion coefficient is derived for the resonant and non-resonant electrons, and the effect of the wave growth on the electron diffusion is discussed. The results can be applied to other problems related to local acceleration or the heating of electrons in space plasmas, such as in the radiation belts
Energy Technology Data Exchange (ETDEWEB)
Damiano, P. A. [Princeton Center for Heliophysics, Princeton Plasma Physics Laboratory, Princeton University, Princeton New Jersey USA; Johnson, J. R. [Princeton Center for Heliophysics, Princeton Plasma Physics Laboratory, Princeton University, Princeton New Jersey USA; Chaston, C. C. [Space Sciences Laboratory, University of California, Berkeley California USA; School of Physics, University of Sydney, Sydney New South Wales Australia
2015-07-01
A new 2-D self-consistent hybrid gyrofluid-kinetic electron model in dipolar coordinates is presented and used to simulate dispersive-scale Alfvén wave pulse propagation from the equator to the ionosphere along an L = 10 magnetic field line. The model is an extension of the hybrid MHD-kinetic electron model that incorporates ion Larmor radius corrections via the kinetic fluid model of Cheng and Johnson (1999). It is found that consideration of a realistic ion to electron temperature ratio decreases the propagation time of the wave from the plasma sheet to the ionosphere by several seconds relative to a ρi=0 case (which also implies shorter timing for a substorm onset signal) and leads to significant dispersion of wave energy perpendicular to the ambient magnetic field. Additionally, ion temperature effects reduce the parallel current and electron energization all along the field line for the same magnitude perpendicular electric field perturbation.
Kolesnikov, E. K.; Manuilov, A. S.; Petrov, V. S.; Klyushnikov, G. N.; Chernov, S. V.
2017-06-01
The influence of the current neutralization process, the phase mixing of the trajectories of electrons and multiple Coulomb scattering of electrons beam on the atoms of the background medium on the spatial increment of the growth of sausage instability of a relativistic electron beam propagating in ohmic plasma channel has been considered. It has been shown that the amplification of the current neutralization leads to a significant increase in this instability, and phase mixing and the process of multiple scattering of electrons beam on the atoms of the background medium are the stabilizing factor.
Theoretical methods for describing electronic states
International Nuclear Information System (INIS)
Buslaeva, T.M.; Umrejko, D.S.; Novitskij, G.G.; Sinitsyn, N.M.; Kovrikov, A.B.
1990-01-01
Theoretical description of electron states of ruthenium halogenocomplexes is presented. Properties of external electrons in ruthenium complexes, formation of chemical bonds, are considered. The main types of hybridization and corresponding spatial structures of the complexes with coordination number 2-6 are given. 5 figs.; 4 tabs
National Research Council Canada - National Science Library
Whalen, John
1998-01-01
A study was performed to compare shipboard measurements of atmospheric parameters that impact the evaporation duct and its effect on the propagation of electromagnetic energy from the AEGIS AN/SPY-1 radars...
Statistical analysis tolerance using jacobian torsor model based on uncertainty propagation method
Directory of Open Access Journals (Sweden)
W Ghie
2016-04-01
Full Text Available One risk inherent in the use of assembly components is that the behaviourof these components is discovered only at the moment an assembly isbeing carried out. The objective of our work is to enable designers to useknown component tolerances as parameters in models that can be usedto predict properties at the assembly level. In this paper we present astatistical approach to assemblability evaluation, based on tolerance andclearance propagations. This new statistical analysis method for toleranceis based on the Jacobian-Torsor model and the uncertainty measurementapproach. We show how this can be accomplished by modeling thedistribution of manufactured dimensions through applying a probabilitydensity function. By presenting an example we show how statisticaltolerance analysis should be used in the Jacobian-Torsor model. This workis supported by previous efforts aimed at developing a new generation ofcomputational tools for tolerance analysis and synthesis, using theJacobian-Torsor approach. This approach is illustrated on a simple threepartassembly, demonstrating the method’s capability in handling threedimensionalgeometry.
Mixed finite element-based fully conservative methods for simulating wormhole propagation
Kou, Jisheng
2015-10-11
Wormhole propagation during reactive dissolution of carbonates plays a very important role in the product enhancement of oil and gas reservoir. Because of high velocity and nonuniform porosity, the Darcy–Forchheimer model is applicable for this problem instead of conventional Darcy framework. We develop a mixed finite element scheme for numerical simulation of this problem, in which mixed finite element methods are used not only for the Darcy–Forchheimer flow equations but also for the solute transport equation by introducing an auxiliary flux variable to guarantee full mass conservation. In theoretical analysis aspects, based on the cut-off operator of solute concentration, we construct an analytical function to control and handle the change of porosity with time; we treat the auxiliary flux variable as a function of velocity and establish its properties; we employ the coupled analysis approach to deal with the fully coupling relation of multivariables. From this, the stability analysis and a priori error estimates for velocity, pressure, concentration and porosity are established in different norms. Numerical results are also given to verify theoretical analysis and effectiveness of the proposed scheme.
Sabouri, P.; Bidaud, A.; Dabiran, S.; Lecarpentier, D.; Ferragut, F.
2014-04-01
The development of tools for nuclear data uncertainty propagation in lattice calculations are presented. The Total Monte Carlo method and the Generalized Perturbation Theory method are used with the code DRAGON to allow propagation of nuclear data uncertainties in transport calculations. Both methods begin the propagation of uncertainties at the most elementary level of the transport calculation - the Evaluated Nuclear Data File. The developed tools are applied to provide estimates for response uncertainties of a PWR cell as a function of burnup.
A spectral hybridizable discontinuous Galerkin method for elastic-acoustic wave propagation
Terrana, S.; Vilotte, J. P.; Guillot, L.
2018-04-01
, when element polynomials of order k are used, and to exhibit the classical spectral convergence of SEM. Additional inexpensive local post-processing in both the elastic and the acoustic case allow to achieve higher convergence orders. The HDG scheme provides a natural framework for coupling classical, continuous Galerkin SEM with HDG-SEM in the same simulation, and it is shown numerically in this paper. As such, the proposed HDG-SEM can combine the efficiency of the continuous SEM with the flexibility of the HDG approaches. Finally, more complex numerical results, inspired from real geophysical applications, are presented to illustrate the capabilities of the method for wave propagation in heterogeneous elastic-acoustic media with complex geometries.
Belhadj, H; Taik, A; Ouazar, D
2006-01-01
International audience; This study is devoted to the flood wave propagation modelling corresponding to a realistic situation. The equations that governs the propagation of a flood wave, in natural rivers, corresponds to the free surface flow equations in the Shallow Water case. The obtained two dimensional system, known as Saint Venant's system, is derived from the three-dimensional incompressible Navier Stokes equations by depth-averaging of the state variables. This system is written in a c...
Shabir, Z.; Van der Giessen, E.; Duarte, C.A.; Simone, A.
2009-01-01
Two different approaches to intergranular crack propagation in brittle polycrystals are contrasted. Crack paths resulting from a method that allows a detailed description of the stress field within a polycrystal are compared to cracks dictated by topological considerations. In the first approach, a
Directory of Open Access Journals (Sweden)
Wenwan Ding
2016-01-01
Full Text Available An improved fractal sea surface model, which can describe the capillary waves very well, is introduced to simulate the one-dimension rough sea surface. In this model, the propagation of electromagnetic waves (EWs is computed by the parabolic equation (PE method using the finite-difference (FD algorithm. The numerical simulation results of the introduced model are compared with those of the Miller-Brown model and the Elfouhaily spectrum inversion model. It has been shown that the effects of the fine structure of the sea surface on the EWs propagation in the introduced model are more apparent than those in the other two models.
Nasawasd, T.; Simantathammakul, T.; Herold, C.; Stockmanns, T.; Ritman, J.; Kobdaj, C.
2018-02-01
To classify clusters of hits in the electromagnetic calorimeter (EMC) of bar PANDA (antiProton ANnihilation at DArmstadt), one has to match these EMC clusters with tracks of charged particles reconstructed from hits in the tracking system. Therefore the tracks are propagated to the surface of the EMC and associated with EMC clusters which are nearby and below a cut parameter. In this work, we propose a helix propagator to extrapolate the track from the Straw Tube Tracker (STT) to the inner surface of the EMC instead of the GEANE propagator which is already embedded within the PandaRoot computational framework. The results for both propagation methods show a similar quality, with a 30% gain in CPU time when using the helix propagator. We use Monte-Carlo truth information to compare the particle ID of the EMC clusters with the ID of the extrapolated points, thus deciding upon the correctness of the matches. By varying the cut parameter as a function of transverse momentum and particle type, our simulations show that the purity can be increased by 3-5% compared to the default value which is a constant cut in the bar PANDA simulation framework PandaRoot.
Method for surface treatment by electron beams
International Nuclear Information System (INIS)
Panzer, S.; Doehler, H.; Bartel, R.; Ardenne, T. von.
1985-01-01
The invention has been aimed at simplifying the technology and saving energy in modifying surfaces with the aid of electron beams. The described beam-object geometry allows to abandon additional heat treatments. It can be used for surface hardening
Gao, Kai
2015-04-14
It is important to develop fast yet accurate numerical methods for seismic wave propagation to characterize complex geological structures and oil and gas reservoirs. However, the computational cost of conventional numerical modeling methods, such as finite-difference method and finite-element method, becomes prohibitively expensive when applied to very large models. We propose a Generalized Multiscale Generalized Multiscale Finite-Element Method (GMsFEM) for elastic wave propagation in heterogeneous, anisotropic media, where we construct basis functions from multiple local problems for both boundaries and the interior of a coarse node support or coarse element. The application of multiscale basis functions can capture the fine scale medium property variations, and allows us to greatly reduce the degrees of freedom that are required to implement the modeling compared with conventional finite-element method for wave equation, while restricting the error to low values. We formulate the continuous Galerkin and discontinuous Galerkin formulation of the multiscale method, both of which have pros and cons. Applications of the multiscale method to three heterogeneous models show that our multiscale method can effectively model the elastic wave propagation in anisotropic media with a significant reduction in the degrees of freedom in the modeling system.
International Nuclear Information System (INIS)
Gao, Kai; Fu, Shubin; Gibson, Richard L.; Chung, Eric T.; Efendiev, Yalchin
2015-01-01
It is important to develop fast yet accurate numerical methods for seismic wave propagation to characterize complex geological structures and oil and gas reservoirs. However, the computational cost of conventional numerical modeling methods, such as finite-difference method and finite-element method, becomes prohibitively expensive when applied to very large models. We propose a Generalized Multiscale Finite-Element Method (GMsFEM) for elastic wave propagation in heterogeneous, anisotropic media, where we construct basis functions from multiple local problems for both the boundaries and interior of a coarse node support or coarse element. The application of multiscale basis functions can capture the fine scale medium property variations, and allows us to greatly reduce the degrees of freedom that are required to implement the modeling compared with conventional finite-element method for wave equation, while restricting the error to low values. We formulate the continuous Galerkin and discontinuous Galerkin formulation of the multiscale method, both of which have pros and cons. Applications of the multiscale method to three heterogeneous models show that our multiscale method can effectively model the elastic wave propagation in anisotropic media with a significant reduction in the degrees of freedom in the modeling system
International Nuclear Information System (INIS)
Ishida, Hitoshi; Meshii, Toshiyuki
2010-01-01
This study proposes an element size selection method named the 'Impact-Meshing (IM) method' for a finite element waves propagation analysis model, which is characterized by (1) determination of element division of the model with strain energy in the whole model, (2) static analysis (dynamic analysis in a single time step) with boundary conditions which gives a maximum change of displacement in the time increment and inertial (impact) force caused by the displacement change. In this paper, an example of application of the IM method to 3D ultrasonic wave propagation problem in an elastic solid is described. These examples showed an analysis result with a model determined by the IM method was convergence and calculation time for determination of element subdivision was reduced to about 1/6 by the IM Method which did not need determination of element subdivision by a dynamic transient analysis with 100 time steps. (author)
Zong, Q.
2016-12-01
When substorm injections are observed simultaneously with multiple spacecraft, they help elucidate potential mechanisms for particle transport and energization, a topic of great importance for understanding and modeling the magnetosphere. In the present paper, by using the data return from the BeiDa- IES (BD-IES) instrument onboard an inclined (55°) geosynchronous orbit (IGSO) satellite together with geo-transfer orbit (GTO) Van Allen Probe A&B satellite, we analysis a substorm injection event occurred on Oct 16, 2015. During the substorm injection, the IES onboard IGSO is outbound while both Van Allen Probe A&B satellites are inbound. This configuration of multiple satellite trajectories provides a unique opportunity to investigate the inward and outward radial propagation of the substorm injection simultaneously. This substorm as indicated by AE/AL indices is closely related an IMF/solar wind discontinuity with a sharp change in the IMF Bz direction (northward turning). The innermost signature of this substorm injection has been detected by the Van Allen Probes A & B at L 3.7. The outermost signature, observed by the BD-IES, is found to be at L 10. This indicated that this substorm have a rather global effect rather than just a local effect. Further, we suggest that the electric fields carried by fast-mode compressional waves around the substorm injection are the most likely mechanism candidate for the injection signatures of electrons observed in the innermost and outermost inner magnetosphere.
International Nuclear Information System (INIS)
Pisani, F.
2000-02-01
In the fast igniter scheme, a recent approach proposed for the inertial confinement fusion, the idea is to dissociate the fuel ignition phase from its compression. The ignition phase would be then achieved by means of an external energy source: a fast electron beam generated by the interaction with an ultra-intense laser. The main goal of this work is to study the mechanisms of the hot electron energy transfer to the compressed fuel. We intent in particular to study the role of the electric and collisional effects involved in the hot electron propagation in a medium with properties similar to the compressed fuel. We carried out two experiments, one at the Vulcan laser facility (England) and the second one at the new LULI 100 TW laser (France). During the first experiment, we obtained the first results on the hot electron propagation in a dense and hot plasma. The innovating aspect of this work was in particular the use of the laser-shock technique to generate high pressures, allowing the strongly correlated and degenerated plasma to be created. The role of the electric and magnetic effects due to the space charge associated with the fast electron beam has been investigated in the second experiment. Here we studied the propagation in materials with different electrical characteristics: an insulator and a conductor. The analysis of the results showed that only by taking into account simultaneously the two propagation mechanisms (collisions and electric effects) a correct treatment of the energy deposition is possible. We also showed the importance of taking into account the induced modifications due to the electrons beam crossing the target, especially the induced heating. (author)
New methods for trigger electronics development
Energy Technology Data Exchange (ETDEWEB)
Cleland, W.E.; Stern, E.G. [Univ. of Pittsburgh, PA (United States)
1991-12-31
The large and complex nature of RHIC experiments and the tight time schedule for their construction requires that new techniques for designing the electronics should be employed. This is particularly true of the trigger and data acquisition electronics which has to be ready for turn-on of the experiment. We describe the use of the Workview package from VIEWlogic Inc. for design, simulation, and verification of a flash ADC readout system. We also show how field-programmable gate arrays such as the Xilinx 4000 might be employed to construct or prototype circuits with a large number of gates while preserving flexibility.
Electronics design office organization, methods and tools
Van der Bij, E
2004-01-01
The group TS-DEM offers a global service for the design, manufacturing and assembly of electronics modules for several hundreds of electronics engineers at CERN and its collaborating institutes. The Design Office in DEM determines and controls an overall planning, defines the resources required, solves the technical aspects and invoices the whole project. This involves technical resources provided by service contracts and supply contracts, but also negotiations with clients to be able to provide realistic plannings while still being able to handle urgent cases and high-workload periods.
Axelberg, Peter; Bollen, Math; Gu, Irene Y.H.
2005-01-01
This paper describes a new and highly efficient measurement method (algorithm) that determines how flicker propagates throughout the network and also traces the dominant flicker source. The fundamental principle of the method is to use the fact that a flicker source produces an amplitude modulation in the voltage and current waveforms. The low frequency variations in voltage and current that cause flicker are retrieved in a demodulation and filtering process. By first multiplying the low fre...
Propagation of Threatened Nepenthes khasiana: Methods and Precautions
Directory of Open Access Journals (Sweden)
Jibankumar S. KHURAIJAM
2015-09-01
Full Text Available Ex-situ conservation is an important key in the management of rare, endangered and threatened (RET plant species and its effectiveness depends on several factors. Maintenance of viable germplasm and its subsequent propagation plays an important role in long term conservation of many RET species. Nepenthes khasiana is a rare and gravely threatened species in the wild due to over-collection and other threats. The species needs urgent in-situ and ex-situ conservation. Development of easy to propagate techniques would pave faster multiplication for its use of educational, medicinal and horticultural purpose. In the present paper, successful propagation technique of Nepenthes khasiana through seeds is demonstrated along with detailed information on precautions to be taken during the adoption of the techniques.
Directory of Open Access Journals (Sweden)
Baso Maruddani
2015-01-01
Full Text Available This paper deals with the prediction method using hidden Markov model (HMM for rain rate and rain propagation attenuation for K-band satellite communication link at tropical area. As is well known, the K-band frequency is susceptible of being affected by atmospheric condition, especially in rainy condition. The wavelength of K-band frequency which approaches to the size of rain droplet causes the signal strength is easily attenuated and absorbed by the rain droplet. In order to keep the quality of system performance for K-band satellite communication link, therefore a special attention has to be paid for rain rate and rain propagation attenuation. Thus, a prediction method for rain rate and rain propagation attenuation based on HMM is developed to process the measurement data. The measured and predicted data are then compared with the ITU-R recommendation. From the result, it is shown that the measured and predicted data show similarity with the model of ITU-R P.837-5 recommendation for rain rate and the model of ITU-R P.618-10 recommendation for rain propagation attenuation. Meanwhile, statistical data for measured and predicted data such as fade duration and interfade duration have insignificant discrepancy with the model of ITU-R P.1623-1 recommendation.
de Jonge, Niels [Oak Ridge, TN
2010-08-17
A confocal scanning transmission electron microscope which includes an electron illumination device providing an incident electron beam propagating in a direction defining a propagation axis, and a precision specimen scanning stage positioned along the propagation axis and movable in at least one direction transverse to the propagation axis. The precision specimen scanning stage is configured for positioning a specimen relative to the incident electron beam. A projector lens receives a transmitted electron beam transmitted through at least part of the specimen and focuses this transmitted beam onto an image plane, where the transmitted beam results from the specimen being illuminated by the incident electron beam. A detection system is placed approximately in the image plane.
Yıldız, Fehmiye; Kurt, Hamza
2017-09-01
It is well known that atmospheric turbulence severely limits the applications based on the laser propagation though the atmosphere. The most common disturbances occurring due to the atmospheric turbulence are beam spreading, beam wandering, and scintillation. These effects are continuously changing in response to atmospheric conditions. In this study, we create a Non-Kolmogorov turbulence model which is based on the geometrical optics approximation and the property of Gamma function and integrate with in Gaussian beam analytically. This approach helps us to understand the propagation of the laser beam at different wavelengths in the atmospheric turbulence.
Shorokhov, V. V.
2017-05-01
Solitary dopants in semiconductors and dielectrics that possess stable electron structures and interesting physical properties may be used as building blocks of quantum computers and sensor systems that operate based on new physical principles. This study proposes a phenomenological method of parameterization for a single-particle energy spectrum of dopant valence electrons in crystalline semiconductors and dielectrics that takes electron-electron interactions into account. It is proposed to take electron-electron interactions in the framework of the outer electron shell model into account. The proposed method is applied to construct the procedure for the determination of the effective dopant outer shell capacity and the method for calculation of the tunneling current in a single-electron device with one or several active dopants-charge centers.
Wang, Rui; Hu, Zhiping; Zhang, Dan; Wang, Qiyao
2017-12-01
The dynamic behavior of filled joints is mostly controlled by the filled medium. In addition to nonlinear elastic behavior, viscoelastic behavior of filled joints is also of great significance. Here, a theoretical study of stress wave propagation through a filled rock joint with linear viscoelastic deformation behavior has been carried out using a modified time-domain recursive method (TDRM). A displacement discontinuity model was extended to form a displacement and stress discontinuity model, and the differential constitutive relationship of viscoelastic model was adopted to introduce the mass and viscoelastic behavior of filled medium. A standard linear solid model, which can be degenerated into the Kelvin and Maxwell models, was adopted in deriving this method. Transmission and reflection coefficients were adopted to verify this method. Besides, the effects of some parameters on wave propagation across a filled rock joint with linear viscoelastic deformation behavior were discussed. Then, a comparison of the time-history curves calculated by the present method with those by frequency-domain method (FDM) was performed. The results indicated that change tendencies of the transmission and reflection coefficients for these viscoelastic models versus incident angle were the same as each other but not frequency. The mass and viscosity coupling of filled medium did not fundamentally change wave propagation. The modified TDRM was found to be more efficient than the FDM.
Relaxation time measurements by an electronic method.
Brousseau, R.; Vanier, J.
1973-01-01
Description of a simple electronic system that permits the direct measurement of time constants of decaying signals. The system was used in connection with relaxation experiments on hydrogen and rubidium masers and was found to operate well. The use of a computing counter in the systems gives the possibility of making averages on several experiments and obtaining the standard deviation of the results from the mean. The program for the computing counter is given.
Geometric reconstruction methods for electron tomography
DEFF Research Database (Denmark)
Alpers, Andreas; Gardner, Richard J.; König, Stefan
2013-01-01
Electron tomography is becoming an increasingly important tool in materials science for studying the three-dimensional morphologies and chemical compositions of nanostructures. The image quality obtained by many current algorithms is seriously affected by the problems of missing wedge artefacts...... and discuss several algorithms from the mathematical fields of geometric and discrete tomography. The algorithms incorporate geometric prior knowledge (mainly convexity and homogeneity), which also in principle considerably reduces the number of tilt angles required. Results are discussed...
Energy Technology Data Exchange (ETDEWEB)
Fiorina, D
1998-01-29
Some systems for the control and the surveillance of fast reactors are based on the characteristics of the ultrasonic wave propagation. We present here the results of a numerical and experimental study of ultrasonic propagation in a thermal turbulent medium. A numerical model, based on the technique of superposition of discrete Fourier modes for representing isotropic and homogeneous turbulence and on the Gaussian beam summation method for calculating the acoustic field, has been implemented in order to study the propagation of a point source wave in a bidimensional turbulent medium. Our model is based on the following principle: the medium is represented by a great number of independent realizations of a turbulent field and for each of them we calculate the acoustic field in a deterministic way. Statistics over a great number of realizations enable us to access to the different quantities of the distorted acoustic field: variance of the time of flight fluctuations, scintillation index and intensity probability density function. In the case of small fluctuations, the results for these three quantities are in a good agreement with analytical solutions. When the level of the fluctuations grows, the model predicts correct evolutions. However, a great sensitivity to the location of a receiver in the vicinity of a caustic has been proved. Calculations in the temporal domain have also been performed. They give an illustration of the possible effects of the turbulence on an impulsion signal. An experimental device, fitted with thermocouples and acoustic transducers, has been used to study the ultrasonic propagation in turbulent water. The different measures permitted to characterize the turbulent field and to get aware of the effect of the turbulence on the acoustic propagation. The acoustical measures agree well with the analytical solution of Chernov and Rytov. They are show the importance of the knowledge of the real spectrum of the fluctuations and the limitations of
Chabot, S.; Glinsky, N.; Mercerat, E. D.; Bonilla Hidalgo, L. F.
2018-02-01
We propose a nodal high-order discontinuous Galerkin method for 1D wave propagation in nonlinear media. We solve the elastodynamic equations written in the velocity-strain formulation and apply an upwind flux adapted to heterogeneous media with nonlinear constitutive behavior coupling stress and strain. Accuracy, convergence and stability of the method are studied through several numerical applications. Hysteresis loops distinguishing loading and unloading-reloading paths are also taken into account. We investigate several effects of nonlinearity in wave propagation, such as the generation of high frequencies and the frequency shift of resonant peaks to lower frequencies. Finally, we compare the results for both nonlinear models, with and without hysteresis, and highlight the effects of the former on the stabilization of the numerical scheme.
Chan, Jesse
2018-03-01
Weight-adjusted inner products are easily invertible approximations to weighted $L^2$ inner products. These approximations can be paired with a discontinuous Galerkin (DG) discretization to produce a time-domain method for wave propagation which is low storage, energy stable, and high order accurate for arbitrary heterogeneous media and curvilinear meshes. In this work, we extend weight-adjusted DG (WADG) methods to the case of matrix-valued weights, with the linear elastic wave equation as an application. We present a DG formulation of the symmetric form of the linear elastic wave equation, with upwind-like dissipation incorporated through simple penalty fluxes. A semi-discrete convergence analysis is given, and numerical results confirm the stability and high order accuracy of WADG for several problems in elastic wave propagation.
Non-parametric order statistics method applied to uncertainty propagation in fuel rod calculations
International Nuclear Information System (INIS)
Arimescu, V.E.; Heins, L.
2001-01-01
Advances in modeling fuel rod behavior and accumulations of adequate experimental data have made possible the introduction of quantitative methods to estimate the uncertainty of predictions made with best-estimate fuel rod codes. The uncertainty range of the input variables is characterized by a truncated distribution which is typically a normal, lognormal, or uniform distribution. While the distribution for fabrication parameters is defined to cover the design or fabrication tolerances, the distribution of modeling parameters is inferred from the experimental database consisting of separate effects tests and global tests. The final step of the methodology uses a Monte Carlo type of random sampling of all relevant input variables and performs best-estimate code calculations to propagate these uncertainties in order to evaluate the uncertainty range of outputs of interest for design analysis, such as internal rod pressure and fuel centerline temperature. The statistical method underlying this Monte Carlo sampling is non-parametric order statistics, which is perfectly suited to evaluate quantiles of populations with unknown distribution. The application of this method is straightforward in the case of one single fuel rod, when a 95/95 statement is applicable: 'with a probability of 95% and confidence level of 95% the values of output of interest are below a certain value'. Therefore, the 0.95-quantile is estimated for the distribution of all possible values of one fuel rod with a statistical confidence of 95%. On the other hand, a more elaborate procedure is required if all the fuel rods in the core are being analyzed. In this case, the aim is to evaluate the following global statement: with 95% confidence level, the expected number of fuel rods which are not exceeding a certain value is all the fuel rods in the core except only a few fuel rods. In both cases, the thresholds determined by the analysis should be below the safety acceptable design limit. An indirect
A Mnemonic Method for Assigning the Electronic Configurations of Atoms
Iza, Nerea; Gil, Manuel
1995-11-01
A simple mnemonic method for predicting electronic configurations of the majority of the elements of the Periodic Table is shown. With this device it is necessary only to draw a linear diagram for "building up" the electronic configurations of atoms. The advantages and limitations of the method are considered.
Geometric reconstruction methods for electron tomography
International Nuclear Information System (INIS)
Alpers, Andreas; Gardner, Richard J.; König, Stefan; Pennington, Robert S.; Boothroyd, Chris B.; Houben, Lothar; Dunin-Borkowski, Rafal E.; Joost Batenburg, Kees
2013-01-01
Electron tomography is becoming an increasingly important tool in materials science for studying the three-dimensional morphologies and chemical compositions of nanostructures. The image quality obtained by many current algorithms is seriously affected by the problems of missing wedge artefacts and non-linear projection intensities due to diffraction effects. The former refers to the fact that data cannot be acquired over the full 180° tilt range; the latter implies that for some orientations, crystalline structures can show strong contrast changes. To overcome these problems we introduce and discuss several algorithms from the mathematical fields of geometric and discrete tomography. The algorithms incorporate geometric prior knowledge (mainly convexity and homogeneity), which also in principle considerably reduces the number of tilt angles required. Results are discussed for the reconstruction of an InAs nanowire. - Highlights: ► Four algorithms for electron tomography are introduced that utilize prior knowledge. ► Objects are assumed to be homogeneous; convexity and regularity is also discussed. ► We are able to reconstruct slices of a nanowire from as few as four projections. ► Algorithms should be selected based on the specific reconstruction task at hand
Quantitative voltage contrast method for electron irradiated insulators in SEM
Energy Technology Data Exchange (ETDEWEB)
Belhaj, M [UR MMA INSAT Centre Urbain Nord, BP 676-1080, Tunis (Tunisia); Jbara, O [LASSI/GRESPI, Faculte des Sciences, BP 1039, 51687 Reims Cedex 2 (France); Fakhfakh, S [LaMaCop, Faculte des sciences de SFAX, Route Soukra Km 3, BP 802, CP 3018 Sfax (Tunisia)], E-mail: mohamed.belhaj@free.fr
2008-09-07
A surface potential mapping method for electron irradiated insulators in the scanning electron microscope (SEM) is proposed. This method, based on the use of a highly compact electrostatic toroidal spectrometer specially adapted to SEM applications, is able to monitor the spatial variation of surface potentials of strongly negatively charged materials. The capabilities of this method are tested on a made-up heterogeneous sample. First results prove that the method is particularly appropriate for the reconstitution of the surface potential distribution.
Quantitative voltage contrast method for electron irradiated insulators in SEM
International Nuclear Information System (INIS)
Belhaj, M; Jbara, O; Fakhfakh, S
2008-01-01
A surface potential mapping method for electron irradiated insulators in the scanning electron microscope (SEM) is proposed. This method, based on the use of a highly compact electrostatic toroidal spectrometer specially adapted to SEM applications, is able to monitor the spatial variation of surface potentials of strongly negatively charged materials. The capabilities of this method are tested on a made-up heterogeneous sample. First results prove that the method is particularly appropriate for the reconstitution of the surface potential distribution
International Nuclear Information System (INIS)
Ishida, Hitoshi; Meshii, Toshiyuki
2008-01-01
This paper proposes a guideline for selection of element size and time increment by 3-D finite element method, which is applied to elastic wave propagation analysis for a long distance of a large structure. An element size and a time increment are determined by quantitative evaluation of strain, which must be 0 on the analysis model with a uniform motion, caused by spatial and time discretization. (author)
Energy Technology Data Exchange (ETDEWEB)
Sebelin, E
1997-12-15
Full-wave calculations based on trial functions are carried out for solving the lower hybrid current drive problem in tokamaks. A variational method is developed and provides an efficient system to describe in a global manner both the propagation and the absorption of the electromagnetic waves in plasmas. The calculation is fully carried out in the case of circular and concentric flux surfaces. The existence and uniqueness of the solution of the wave propagation equation is mathematically proved. The first realistic simulations are performed for the high aspect ratio tokamak TRIAM-1M. It is checked that the main features of the lower-hybrid wave dynamics are well described numerically. (A.C.) 81 refs.
Energy Technology Data Exchange (ETDEWEB)
Faggiano, E; Scalco, E; Rizzo, G [Istituto di Bioimmagini e Fisiologia Molecolare (IBFM), CNR, Milan (Italy); Fiorino, C; Broggi, S; Cattaneo, M; Maggiulli, E; Calandrino, R [Department of Medical Physics, San Raffaele Scientific Institute, Milan (Italy); Dell' Oca, I; Di Muzio, N, E-mail: fiorino.claudio@hsr.it [Department of Radiotherapy, San Raffaele Scientific Institute, Milan (Italy)
2011-02-07
We developed an efficient technique to auto-propagate parotid gland contours from planning kVCT to daily MVCT images of head-and-neck cancer patients treated with helical tomotherapy. The method deformed a 3D surface mesh constructed from manual kVCT contours by B-spline free-form deformation to generate optimal and smooth contours. Deformation was calculated by elastic image registration between kVCT and MVCT images. Data from ten head-and-neck cancer patients were considered and manual contours by three observers were included in both kVCT and MVCT images. A preliminary inter-observer variability analysis demonstrated the importance of contour propagation in tomotherapy application: a high variability was reported in MVCT parotid volume estimation (p = 0.0176, ANOVA test) and a larger uncertainty of MVCT contouring compared with kVCT was demonstrated by DICE and volume variability indices (Wilcoxon signed rank test, p < 10{sup -4} for both indices). The performance analysis of our method showed no significant differences between automatic and manual contours in terms of volumes (p > 0.05, in a multiple comparison Tukey test), center-of-mass distances (p = 0.3043, ANOVA test), DICE values (p = 0.1672, Wilcoxon signed rank test) and average and maximum symmetric distances (p = 0.2043, p = 0.8228 Wilcoxon signed rank tests). Results suggested that our contour propagation method could successfully substitute human contouring on MVCT images.
Study of the propagation of fast neutrons in water, by Monte-Carlo methods
International Nuclear Information System (INIS)
Lafore, P.; Lattes, R.; Millot, J.P.
1958-01-01
We have studied the propagation in water of neutrons from mono-directional plane sources with energies ranging from 300 keV to 19,66 MeV, placed in an infinite water medium. The exact paths of a number of neutrons are determined, taking into account the microscopic sections, assuming that inelastic collisions of the neutrons on oxygen are absorptions, and neglecting the loss of energy by elastic collisions on oxygen. The neutron lifetimes have been made use of to study the propagation of neutrons from fission sources, Po-Be, Po-B and Ra-Be, as well as the reflection of fast neutrons on a semi-infinite water medium. We have taken complete account of the first collision in order to improve the precision of the results. The calculations were carried out by Mrs J. VASSEUR and Mr A. GUILLOU. (author) [fr
Investigation on electrical tree propagation in polyethylene based on etching method
Directory of Open Access Journals (Sweden)
Zexiang Shi
2017-11-01
Full Text Available To investigate the characteristic of electrical tree propagation in semi-crystalline polymers, the low-density polyethylene (LDPE samples containing electrical trees are cut into slices by using ultramicrotome. Then the slice samples are etched by potassium permanganate etchant. Finally, the crystalline structure and the electrical tree propagation path in samples are observed by polarized light microscopy (PLM. According to the observation, the LDPE spherocrystal structure model is established on the basis of crystallization kinetics and morphology of polymers. And the electrical tree growth process in LDPE is discussed based on the free volume breakdown theory, the molecular chain relaxation theory, the electromechanical force theory, the thermal expansion effect and the space charge shielding effect.
Splitting methods for time-independent wave propagation in random media
International Nuclear Information System (INIS)
Evans, J.W.
1985-01-01
Time-independent wave propagation is treated in media where the index of refraction contains a random component, but its mean is invariant with respect to translation in some direction distinguishing the wave propagation. Abstract splitting operators are used to decompose the wave field into forward and backward traveling components satisfying a coupled pair of equations. Mode-coupled equations follow directly from these after implementing a specific representation for the abstract splitting operators. Here we indicate a formal solution to these equations, concentrating on the diffusion regime, where we estimate the forward- and backscattering contributions to the mode specific diffusion coefficients. We consider, in detail, random media with uniform (random atmosphere) and square law (stochastic lense) mean refractive indices
Energy Technology Data Exchange (ETDEWEB)
Crestaux, Th. [CEA Saclay, Dept. Modelisation de Systemes et Structures (DEN/DANS/DM2S/SFME), 91 - Gif sur Yvette (France)
2008-07-01
The context of this thesis is the development of the numerical simulation in industrial processes. It aims to study and develop methods allowing a decrease of the numerical cost of calculi of Chaos Polynomials development. The implementing concerns problems of high stochastic dimension and more particularly the transport model of radionuclides in radioactive wastes disposal. (A.L.B.)
Energy Technology Data Exchange (ETDEWEB)
Etemadpour, R.; Dorranian, D., E-mail: doran@srbiau.ac.ir [Laser Laboratory, Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Sepehri Javan, N. [Department of Physics, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil (Iran, Islamic Republic of)
2016-05-15
The nonlinear dynamics of a circularly polarized laser pulse propagating in the magnetized plasmas whose constituents are superthermal ions and mixed nonthermal high-energy tail electrons is studied theoretically. A nonlinear equation which describes the dynamics of the slowly varying amplitude is obtained using a relativistic two-fluid model. Based on this nonlinear equation and taking into account some nonlinear phenomena such as modulational instability, self-focusing and soliton formation are investigated. Effect of the magnetized plasma with superthermal ions and mixed nonthermal high-energy tail electrons on these phenomena is considered. It is shown that the nonthermality and superthermality of particles can substantially change the nonlinearity of medium.
Taguchi methods in electronics: A case study
Kissel, R.
1992-05-01
Total Quality Management (TQM) is becoming more important as a way to improve productivity. One of the technical aspects of TQM is a system called the Taguchi method. This is an optimization method that, with a few precautions, can reduce test effort by an order of magnitude over conventional techniques. The Taguchi method is specifically designed to minimize a product's sensitivity to uncontrollable system disturbances such as aging, temperature, voltage variations, etc., by simultaneously varying both design and disturbance parameters. The analysis produces an optimum set of design parameters. A 3-day class on the Taguchi method was held at the Marshall Space Flight Center (MSFC) in May 1991. A project was needed as a follow-up after the class was over, and the motor controller was selected at that time. Exactly how to proceed was the subject of discussion for some months. It was not clear exactly what to measure, and design kept getting mixed with optimization. There was even some discussion about why the Taguchi method should be used at all.
Periodicity-Free Unfolding Method of Electronic Energy Spectra
Kosugi, Taichi; Nishi, Hirofumi; Kato, Yasuyuki; Matsushita, Yu-ichiro
2017-12-01
We propose a novel periodicity-free unfolding method of electronic energy spectra. Our new method solves the serious problem that a calculated electronic band structure strongly depends on the choice of the simulation cell, i.e., primitive cell or supercell. The present method projects the electronic states onto the free-electron states, giving rise to plane-wave unfolded spectra. Using the method, the energy spectra can be calculated as a quantity independent of the choice of the simulation cell. We examine the unfolded energy spectra in detail for the following three models and clarify the validity of our method: a one-dimensional two-chain model, monolayer graphene, and twisted bilayer graphene. We also discuss the relation between our present method and the spectra observed in angle-resolved photoemission spectroscopy (ARPES) experiments.
Faggiano, E.; Fiorino, C.; Scalco, E.; Broggi, S.; Cattaneo, M.; Maggiulli, E.; Dell'Oca, I.; Di Muzio, N.; Calandrino, R.; Rizzo, G.
2011-02-01
We developed an efficient technique to auto-propagate parotid gland contours from planning kVCT to daily MVCT images of head-and-neck cancer patients treated with helical tomotherapy. The method deformed a 3D surface mesh constructed from manual kVCT contours by B-spline free-form deformation to generate optimal and smooth contours. Deformation was calculated by elastic image registration between kVCT and MVCT images. Data from ten head-and-neck cancer patients were considered and manual contours by three observers were included in both kVCT and MVCT images. A preliminary inter-observer variability analysis demonstrated the importance of contour propagation in tomotherapy application: a high variability was reported in MVCT parotid volume estimation (p = 0.0176, ANOVA test) and a larger uncertainty of MVCT contouring compared with kVCT was demonstrated by DICE and volume variability indices (Wilcoxon signed rank test, p 0.05, in a multiple comparison Tukey test), center-of-mass distances (p = 0.3043, ANOVA test), DICE values (p = 0.1672, Wilcoxon signed rank test) and average and maximum symmetric distances (p = 0.2043, p = 0.8228 Wilcoxon signed rank tests). Results suggested that our contour propagation method could successfully substitute human contouring on MVCT images.
International Nuclear Information System (INIS)
Sebelin, E.
1997-01-01
Full-wave calculations based on trial functions are carried out for solving the lower hybrid current drive problem in tokamaks. A variational method is developed and provides an efficient system to describe in a global manner both the propagation and the absorption of the electromagnetic waves in plasmas. The calculation is fully carried out in the case of circular and concentric flux surfaces. The existence and uniqueness of the solution of the wave propagation equation is mathematically proved. The first realistic simulations are performed for the high aspect ratio tokamak TRIAM-1M. It is checked that the main features of the lower-hybrid wave dynamics are well described numerically. (A.C.)
Lightninig Induced Sferics Correlated with Whistler Propagation
Compston, A. J.; Said, R.; Linscott, I.; Inan, U. S.; Parrot, M.
2011-12-01
Lightning discharges generate broadband electromagnetic pulses, known as sferics, that efficiently propagate through the Earth-ionosphere waveguide. Some sferic energy can escape the Earth-ionosphere waveguide and propagate in a whistler mode, enabled by Earth's magnetic field, through the ionosphere. In this presentation, we correlate lightning discharge location and time data from the National Lightning Detection Network (NLDN) in the United States with burst mode electric field measurements from the DEMETER spacecraft to quantify and model whistler propagation through the ionosphere. Using the International Reference Ionosphere (IRI) model for electron density and the International Geomagnetic Reference Field (IGRF) model for magnetic field, we compare measured propagation with the Full Wave Method (FWM) finite element numerical code developed by N. G. Lehtinen and U. S. Inan. While a few studies have analyzed whistler propagation through the ionosphere using spacecraft measurements, spacecraft data have yet to be compared with the FWM as we have done here.
International Nuclear Information System (INIS)
Andreev, Pavel A.; Kuz’menkov, L.S.
2015-01-01
We consider quantum plasmas of electrons and motionless ions. We describe separate evolution of spin-up and spin-down electrons. We present corresponding set of quantum hydrodynamic equations. We assume that plasmas are placed in an uniform external magnetic field. We account different occupation of spin-up and spin-down quantum states in equilibrium degenerate plasmas. This effect is included via equations of state for pressure of each species of electrons. We study oblique propagation of longitudinal waves. We show that instead of two well-known waves (the Langmuir wave and the Trivelpiece–Gould wave), plasmas reveal four wave solutions. New solutions exist due to both the separate consideration of spin-up and spin-down electrons and different occupation of spin-up and spin-down quantum states in equilibrium state of degenerate plasmas
Electron beam directed energy device and methods of using same
Retsky, Michael W.
2007-10-16
A method and apparatus is disclosed for an electron beam directed energy device. The device consists of an electron gun with one or more electron beams. The device includes one or more accelerating plates with holes aligned for beam passage. The plates may be flat or preferably shaped to direct each electron beam to exit the electron gun at a predetermined orientation. In one preferred application, the device is located in outer space with individual beams that are directed to focus at a distant target to be used to impact and destroy missiles. The aimings of the separate beams are designed to overcome Coulomb repulsion. A method is also presented for directing the beams to a target considering the variable terrestrial magnetic field. In another preferred application, the electron beam is directed into the ground to produce a subsurface x-ray source to locate and/or destroy buried or otherwise hidden objects including explosive devices.
Methods of Analysis of Electronic Money in Banks
Directory of Open Access Journals (Sweden)
Melnychenko Oleksandr V.
2014-03-01
Full Text Available The article identifies methods of analysis of electronic money, formalises its instruments and offers an integral indicator, which should be calculated by issuing banks and those banks, which carry out operations with electronic money, issued by other banks. Calculation of the integral indicator would allow complex assessment of activity of the studied bank with electronic money and would allow comparison of parameters of different banks by the aggregate of indicators for the study of the electronic money market, its level of development, etc. The article presents methods which envisage economic analysis of electronic money in banks by the following directions: solvency and liquidity, efficiency of electronic money issue, business activity of the bank and social responsibility. Moreover, the proposed indicators by each of the directions are offered to be taken into account when building integral indicators, with the help of which banks are studied: business activity, profitability, solvency, liquidity and so on.
Zou, Peng
2017-05-10
Staggering grid is a very effective way to reduce the Nyquist errors and to suppress the non-causal ringing artefacts in the pseudo-spectral solution of first-order elastic wave equations. However, the straightforward use of a staggered-grid pseudo-spectral method is problematic for simulating wave propagation when the anisotropy level is greater than orthorhombic or when the anisotropic symmetries are not aligned with the computational grids. Inspired by the idea of rotated staggered-grid finite-difference method, we propose a modified pseudo-spectral method for wave propagation in arbitrary anisotropic media. Compared with an existing remedy of staggered-grid pseudo-spectral method based on stiffness matrix decomposition and a possible alternative using the Lebedev grids, the rotated staggered-grid-based pseudo-spectral method possesses the best balance between the mitigation of artefacts and efficiency. A 2D example on a transversely isotropic model with tilted symmetry axis verifies its effectiveness to suppress the ringing artefacts. Two 3D examples of increasing anisotropy levels demonstrate that the rotated staggered-grid-based pseudo-spectral method can successfully simulate complex wavefields in such anisotropic formations.
Study of short-pulse laser propagation in biological tissue by means of the boundary element method.
Ansari, Mohammad Ali; Massudi, Reza
2011-07-01
Propagation of short pulses of light through biological tissues can be studied by numerically solving the diffusion equation. The boundary integral method was used to convert the differential equation to integral form and the result was solved using the boundary element method. The effects of different optical parameters of the tissue, i.e. scattering, absorption coefficients and anisotropic factor, on temporal evolution of the diffusely reflected pulse were studied. The results were compared with those obtained using the finite difference time domain method and the boundary integral method was found to be more precise and faster than the last method. The method can be used to investigate reflected pulses in the study of cell morphology and tumours in different types of tissue.
Recent development in methods for electron optical computations
Czech Academy of Sciences Publication Activity Database
Lencová, Bohumila
2001-01-01
Roč. 93, č. 6 (2001), s. 434-435 ISSN 0248-4900 Institutional research plan: CEZ:AV0Z2065902 Keywords : electron optical computations * finite element method Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.829, year: 2001
Energy Technology Data Exchange (ETDEWEB)
Menouillard, T
2007-09-15
Computerized simulation is nowadays an integrating part of design and validation processes of mechanical structures. Simulation tools are more and more performing allowing a very acute description of the phenomena. Moreover, these tools are not limited to linear mechanics but are developed to describe more difficult behaviours as for instance structures damage which interests the safety domain. A dynamic or static load can thus lead to a damage, a crack and then a rupture of the structure. The fast dynamics allows to simulate 'fast' phenomena such as explosions, shocks and impacts on structure. The application domain is various. It concerns for instance the study of the lifetime and the accidents scenario of the nuclear reactor vessel. It is then very interesting, for fast dynamics codes, to be able to anticipate in a robust and stable way such phenomena: the assessment of damage in the structure and the simulation of crack propagation form an essential stake. The extended finite element method has the advantage to break away from mesh generation and from fields projection during the crack propagation. Effectively, crack is described kinematically by an appropriate strategy of enrichment of supplementary freedom degrees. Difficulties connecting the spatial discretization of this method with the temporal discretization of an explicit calculation scheme has then been revealed; these difficulties are the diagonal writing of the mass matrix and the associated stability time step. Here are presented two methods of mass matrix diagonalization based on the kinetic energy conservation, and studies of critical time steps for various enriched finite elements. The interest revealed here is that the time step is not more penalizing than those of the standard finite elements problem. Comparisons with numerical simulations on another code allow to validate the theoretical works. A crack propagation test in mixed mode has been exploited in order to verify the simulation
Energy Technology Data Exchange (ETDEWEB)
Darula, Stanislav; Kocifaj, Miroslav; Kittler, Richard [ICA, Slovak Academy of Sciences, Bratislava (Slovakia); Kundracik, Frantisek [Department of Experimental Physics, FMPI, Comenius University, Bratislava (Slovakia)
2010-12-15
To ensure comfort and healthy conditions in interior spaces the thermal, acoustics and daylight factors of the environment have to be considered in the building design. Due to effective energy performance in buildings the new technology and applications also in daylight engineering are sought such as tubular light guides. These allow the transport of natural light into the building core reducing energy consumption. A lot of installations with various geometrical and optical properties can be applied in real buildings. The simplest set of tubular light guide consists of a transparent cupola, direct tube with high reflected inner surface and a ceiling cover or diffuser redistributing light into the interior. Such vertical tubular guide is often used on flat roofs. When the roof construction is inclined a bend in the light guide system has to be installed. In this case the cupola is set on the sloped roof which collects sunlight and skylight from the seen part of the sky hemisphere as well as that reflected from the ground and opposite facades. In comparison with the vertical tube some additional light losses and distortions of the propagated light have to be expected in bended tubular light guides. Recently the theoretical model of light propagation was already published and its applications are presented in this study solving illuminance distributions on the ceiling cover interface and further illuminance distribution on the working plane in the interior. (author)
Directory of Open Access Journals (Sweden)
Jifei Zhao
2016-06-01
Full Text Available As an important electron source, Micro-Pulse electron Gun (MPG which is qualified for producing high average current, short pulse, low emittance electron bunches steadily holds promise to use as an electron source of Coherent Smith-Purcell Radiation (CSPR, Free Electron Laser (FEL. The stable output of S-band MPG has been achieved in many labs. To establish reliable foundation for the future application of it, the propagation of picosecond electron bunch produced by MPG should be studied in detail. In this article, the MPG which was working on the rising stage of total effective Secondary Electron Yield (SEY curve was introduced. The self-bunching mechanism was discussed in depth both in the multipacting amplifying state and the steady working state. The bunch length broadening induced by the longitudinal space-charge (SC effects was investigated by different theoretical models in different regions. The 2D PIC codes MAGIC and beam dynamic codes TraceWin simulations were also performed in the propagation. The result shows an excellent agreement between the simulation and the theoretical analysis for bunch length evolution.
Statistics of electron multiplication in multiplier phototube: iterative method
International Nuclear Information System (INIS)
Grau Malonda, A.; Ortiz Sanchez, J.F.
1985-01-01
An iterative method is applied to study the variation of dynode response in the multiplier phototube. Three different situations are considered that correspond to the following ways of electronic incidence on the first dynode: incidence of exactly one electron, incidence of exactly r electrons and incidence of an average anti-r electrons. The responses are given for a number of steps between 1 and 5, and for values of the multiplication factor of 2.1, 2.5, 3 and 5. We study also the variance, the skewness and the excess of jurtosis for different multiplication factors. (author)
Statistics of electron multiplication in a multiplier phototube; Iterative method
International Nuclear Information System (INIS)
Ortiz, J. F.; Grau, A.
1985-01-01
In the present paper an iterative method is applied to study the variation of dynode response in the multiplier phototube. Three different situation are considered that correspond to the following ways of electronic incidence on the first dynode: incidence of exactly one electron, incidence of exactly r electrons and incidence of an average r electrons. The responses are given for a number of steps between 1 and 5, and for values of the multiplication factor of 2.1, 2.5, 3 and 5. We study also the variance, the skewness and the excess of jurtosis for different multiplication factors. (Author) 11 refs
Shu, Hong; Mokhov, Sergiy; Zeldovich, Boris Ya; Bass, Michael
2009-01-01
A further extension of the iteration method for beam propagation calculation is presented that can be applied for volume Bragg gratings (VBGs) with extremely large grating strength. A reformulation of the beam propagation formulation is presented for analyzing the reflection of a laser beam by a deformed VBG. These methods will be shown to be very accurate and efficient. A VBG with generic z-dependent distortion has been analyzed using these methods.
Electron microscopy methods in studies of cultural heritage sites
Energy Technology Data Exchange (ETDEWEB)
Vasiliev, A. L., E-mail: a.vasiliev56@gmail.com; Kovalchuk, M. V.; Yatsishina, E. B. [National Research Centre “Kurchatov Institute” (Russian Federation)
2016-11-15
The history of the development and application of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray microanalysis (EDXMA) in studies of cultural heritage sites is considered. In fact, investigations based on these methods began when electron microscopes became a commercial product. Currently, these methods, being developed and improved, help solve many historical enigmas. To date, electron microscopy combined with microanalysis makes it possible to investigate any object, from parchment and wooden articles to pigments, tools, and objects of art. Studies by these methods have revealed that some articles were made by ancient masters using ancient “nanotechnologies”; hence, their comprehensive analysis calls for the latest achievements in the corresponding instrumental methods and sample preparation techniques.
Electron microscopy methods in studies of cultural heritage sites
International Nuclear Information System (INIS)
Vasiliev, A. L.; Kovalchuk, M. V.; Yatsishina, E. B.
2016-01-01
The history of the development and application of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray microanalysis (EDXMA) in studies of cultural heritage sites is considered. In fact, investigations based on these methods began when electron microscopes became a commercial product. Currently, these methods, being developed and improved, help solve many historical enigmas. To date, electron microscopy combined with microanalysis makes it possible to investigate any object, from parchment and wooden articles to pigments, tools, and objects of art. Studies by these methods have revealed that some articles were made by ancient masters using ancient “nanotechnologies”; hence, their comprehensive analysis calls for the latest achievements in the corresponding instrumental methods and sample preparation techniques.
Electron transfer with TD-Split, a linear response time-dependent method
International Nuclear Information System (INIS)
Bartell, Lizette A.; Reslan, Randa; Wall, Michael R.; Kennedy, Robert D.; Neuhauser, Daniel
2011-01-01
Graphical abstract: A simple method, time-dependent split (TD-Split) is developed for electron transfer through a TD evaluation of the lowest excitation energy from the ground state of the combined charged system. As an example, we study transfer between substituted fullerenes, primarily PCBM. Numerical linearization reduces the number of required iterations, and trends similar to experiment are found. Highlights: ► Electron transmission from charged-dimer transition-state excitation. ► Starting point: extended dimer charged (above-gap) homo, which is then excited. ► Excitation by real-time and linear response TD propagation. ► Analogous to two level system, but with full polarization included. ► TD-Split much larger than from static LUMO + 1–LUMO splitting for fullerene dimers. - Abstract: We present a simple method, time-dependent split (TD-Split) for A → B electron transfer by a TD evaluation of the lowest excitation energy from the ground state of the combined (AB) − system. As an example, we study transfer between substituted fullerenes, primarily PCBM. Electron transfer in such fullerene systems is important as it is often the bottleneck in organic solar cells. The TD-Split method is described in detail, including numerical linearization which reduces the number of required iterations, and comparison to other possible approaches. We also compare to other molecules such as C 60 Me 5 H, and find similar trends as experiment.
Method of determining the position of an irradiated electron beam
International Nuclear Information System (INIS)
Fukuda, Wataru.
1967-01-01
The present invention relates to the method of determining the position of a radiated electron beam, in particular, the method of detecting the position of a p-n junction by a novel method when irradiating the electron beam on to the semi-conductor wafer, controlling the position of the electron beam from said junction. When the electron beam is irradiated on to the semi-conductor wafer which possesses the p-n junction, the position of the p-n junction may be ascertained to determine the position of the irradiated electron beam by detecting the electromotive force resulting from said p-n junction with a metal disposed in the proximity of but without mechanical contact with said semi-conductor wafer. Furthermore, as far as a semi-conductor wafer having at least one p-n junction is concerned, the present invention allows said p-n junction to be used to determine the position of an irradiated electron beam. Thus, according to the present invention, the electromotive force of the electron beam resulting from the p-n junction may easily be detected by electrostatic coupling, enabling the position of the irradiated electron beam to be accurately determined. (Masui, R.)
Sirjoosingh, Andrew Rajendra
Nuclear quantum effects such as zero-point energy and hydrogen tunneling play an important role in a wide variety of chemical reactions. Moreover, non-Born-Oppenheimer effects are important in reactions such as proton-coupled electron transfer (PCET), which are integral to various electrocatalytic applications and bioenzymatic processes. The breakdown of the Born-Oppenheimer approximation between electronic and nuclear motions engenders the need for accurate characterization of the degree of nonadiabaticity. Furthermore, in regimes where the inclusion of these effects is vital, as it is for PCET systems, the development of non-Born-Oppenheimer quantum chemical methods is increasingly important. In this dissertation, we present diagnostics of electron-proton nonadiabaticity that can be obtained from standard electronic structure calculations and describe their application to representative systems, highlighting the mechanistic differences between two subclasses of PCET. In addition, we describe the development of new electronic structure methods within the nuclear-electronic orbital (NEO) framework, which is an orbital-based approach that inherently includes electron-proton nonadiabaticity by treating electrons and select protons quantum mechanically on equal footing. Previous studies using NEO involved applying mean-field-based approaches, which lacked sufficient electron-proton dynamical correlation, leading to overlocalized nuclear densities. Subsequent efforts focused on the development of explicitly correlated NEO approaches which, although accurate, were too computationally intractable to be practical for the study of PCET systems. In this dissertation, we describe two approaches to develop tractable NEO methods. Firstly, we describe the formulation of a multi-component density functional theory approach within the NEO framework, which involves the derivation of several electron-proton correlation functionals to accurately account for electron
Energy Technology Data Exchange (ETDEWEB)
Pisani, F
2000-02-15
In the fast igniter scheme, a recent approach proposed for the inertial confinement fusion, the idea is to dissociate the fuel ignition phase from its compression. The ignition phase would be then achieved by means of an external energy source: a fast electron beam generated by the interaction with an ultra-intense laser. The main goal of this work is to study the mechanisms of the hot electron energy transfer to the compressed fuel. We intent in particular to study the role of the electric and collisional effects involved in the hot electron propagation in a medium with properties similar to the compressed fuel. We carried out two experiments, one at the Vulcan laser facility (England) and the second one at the new LULI 100 TW laser (France). During the first experiment, we obtained the first results on the hot electron propagation in a dense and hot plasma. The innovating aspect of this work was in particular the use of the laser-shock technique to generate high pressures, allowing the strongly correlated and degenerated plasma to be created. The role of the electric and magnetic effects due to the space charge associated with the fast electron beam has been investigated in the second experiment. Here we studied the propagation in materials with different electrical characteristics: an insulator and a conductor. The analysis of the results showed that only by taking into account simultaneously the two propagation mechanisms (collisions and electric effects) a correct treatment of the energy deposition is possible. We also showed the importance of taking into account the induced modifications due to the electrons beam crossing the target, especially the induced heating. (author)
Holographic NDT methods for plastic pipe vibration and brittle crack propagation analysis
Markov, Vladimir B.; Boone, Pierre M.; Vanspeybroeck, Philippe
1995-11-01
Plastic pipes are frequently used for low pressure gas and water distribution. One of the main problems with their wide commercial applications is rapid crack propagation (RCP). This results in enormous losses of energy resources and environment pollution. Recent incidents show that it is of importance to find criteria to assess the safety conditions for large diameter piping before its installation. In this report some results of holographic non-destructive testing of plastic pipes are presented. Double-pulse holographic interferometry measurements of stress distribution at small scale steady state (S4) tests for 3 - 5 bar pressurized plastic pipes with (phi) 110 mm to 200 mm were performed. Also the mechanically induced vibration modes of non-pressurized (phi) 200 mm plastic pipe were visualized with the purpose to check stress distribution.
Directory of Open Access Journals (Sweden)
Axel Mauricio Herrera-Moreno
2013-04-01
Full Text Available The objective of this study was to evaluate methods of asexual propagation with stem cuttings in the aromatic plant species Lippia origanoides (accessions CA-90 and CA-93, Lippia alba (accession CA-300 and Tagetes zypaquirensis (accession CA-247 and determine the germination behavior of Tagetes caracasana (accession CA-10, in order to contribute to the establishment of these promising aromatics as potential new crops in Colombia. The factors evaluated were the substrate (fine coconut fiber (FCF; fine coconut fiber: coal slag 1:1 (FCFCS; fine coconut fiber: coal slag: river sand 1:1:1 (FCFCSRS and IBA hormone concentration (0, 2,000 and 4,000 mg L-1. Germination tests of seeds of the accession CA-10 were carried out in Petri dishes with 50 seeds per dish, with three replicates in controlled conditions and constant temperature (25°C, humidity (90% and total darkness. In general, the accessions CA-90, CA-93, CA-300 and CA-247 showed better rooting percentage, root length, number of roots and root dry weight in the fine coconut fiber substrate and a higher number of roots with an exogenous application of 2,000 mg L-1 IBA. L. alba and T. zypaquirensis responded better than L. origanoides to the treatments. The latter species showed a relatively poor performance and may require more complex and improved propagation methods to obtain more satisfactory results. T. caracasana seeds had a relatively short germination time (less than three weeks and relatively high germination under controlled laboratory and greenhouse conditions (70 and 60%, respectively; these percentages are high relative to wild species of the same genus, meaning this method of seed propagation is appropriate for this wild species
Hall, Thomas; Spindler, Gerhard; Becker, Peter; Grünewald, Karin; Pargmann, Carsten; Duschek, Frank
2017-11-01
Novel inherently fast methods basing upon fundamental Gaussian modes are presented to numerically simulate the propagation behavior of a low-quality laser beam, i.e., a beam characterized by a high quality factor M^2, in turbulent air. Actually, for a given initial diameter, beam wandering and spread at the target position is calculated. Test results are checked against respective simulations using higher-order mode beams having clearly defined quality factors and nearly perfect agreement is demonstrated. Experiments performed on the German Aerospace Center (DLR) laser test range at Lampoldshausen near Stuttgart satisfactorily accord with the predictions of the proposed simulation techniques.
Methods for recovering metals from electronic waste, and related systems
Energy Technology Data Exchange (ETDEWEB)
Lister, Tedd E; Parkman, Jacob A; Diaz Aldana, Luis A; Clark, Gemma; Dufek, Eric J; Keller, Philip
2017-10-03
A method of recovering metals from electronic waste comprises providing a powder comprising electronic waste in at least a first reactor and a second reactor and providing an electrolyte comprising at least ferric ions in an electrochemical cell in fluid communication with the first reactor and the second reactor. The method further includes contacting the powders within the first reactor and the second reactor with the electrolyte to dissolve at least one base metal from each reactor into the electrolyte and reduce at least some of the ferric ions to ferrous ions. The ferrous ions are oxidized at an anode of the electrochemical cell to regenerate the ferric ions. The powder within the second reactor comprises a higher weight percent of the at least one base metal than the powder in the first reactor. Additional methods of recovering metals from electronic waste are also described, as well as an apparatus of recovering metals from electronic waste.
Vocks, C.; Breitling, F.; Mann, G.
2011-01-01
During solar flares a large amount of electrons with energies greater than 20 keV is generated with a production rate of typically 1036 s-1. A part of them is able to propagate along open magnetic field lines through the corona into interplanetary space. During their travel they emit radio radiation which is observed as type III radio bursts in the frequency range from 100 MHz down to 10 kHz by the WAVES radio spectrometer aboard the spacecraft WIND, for instance. From the drift rates of thes...
Czech Academy of Sciences Publication Activity Database
Kvasnička, Pavel; Homola, Jiří
2014-01-01
Roč. 9, č. 4 (2014), s. 737-739 ISSN 1557-1955 R&D Projects: GA ČR GBP205/12/G118 Institutional support: RVO:67985882 Keywords : Microscopy * Diffraction gratings * Optical sensing and sensors Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.238, year: 2014
Electron paramagnetic resonance: a new method of quaternary dating
International Nuclear Information System (INIS)
Poupeau, G.; Rossi, A.; Universidade Federal Rural do Rio de Janeiro; Telles, M.; Danon, J.
1984-01-01
Significant progress has occurred in the last years in quaternary geochronology. One of this is the emergence of a new dating approach, the Electron Spin Resonance Method. The aim of this paper is to briefly review the method and discuss some aspects of the work at CBPF. (Author) [pt
Electron paramagnetic resonance: A new method of quaternary dating
International Nuclear Information System (INIS)
Poupeau, G.; Rossi, A.; Teles, M.M.; Danon, J.
1984-01-01
Significant progress has occurred in the last years in quaternary geochronology. One of this is the emergence of a new dating approach, the Electron Spin Resonance Method. The aim of this paper is to briefly review the method and discuss some aspects of the work at CBPF. (Author) [pt
Hall, Martin P. M.; Barclay, Leslie W.
The effects of the earth atmosphere on the radio-wave propagation (RWP) and their implications for telecommunication systems are discussed in reviews based on lectures presented at the Second IEE Vacation School on Radiowave Propagation, held at the University of Surrey in September 1986. A general overview of propagation phenomena is presented, and particular attention is given to the theory of EM wave propagation; radio system parameters; surface wave propagation; RWP in the ionosphere; VLF, LF, and MF applications and predictions; HF applications and predictions; clear-air aspects of the troposphere and their effects on RWP; and the nature of precipitation, clouds, and atmospheric gases and their effects on RWP. Also considered are terrestrial and earth-space propagation path predictions, the prediction of interference levels and coordination distances for frequencies above 1 GHz, propagation effects on VHF and UHF broadcasting, and propagation effects on mobile communication services.
Pereira, Daniel; Haiat, Guillaume; Fernandes, Julio; Belanger, Pierre
2017-04-01
Axial transmission techniques have been extensively studied for cortical bone quality assessment. However, the modeling of ultrasonic guided waves propagation in such a complex medium remains challenging. The aim of this paper is to develop a semi-analytical finite element method to simulate the propagation of guided waves in an irregular, multi-layer, and heterogeneous bone cross-section modeled with anisotropic and viscoelastic material properties. The accuracy of the simulations was verified against conventional time-domain three-dimensional finite element. The method was applied in the context of axial transmission in bone to investigate the feasibility of first arrival signal (FAS) to monitor degradation of intracortical properties at low frequency. Different physiopathological conditions for the intracortical region, varying from healthy to osteoporotic, were monitored through FAS velocity using a 10-cycle tone burst excitation centered at 32.5 kHz. The results show that the variation in FAS velocity is mainly associated with four of the eight modes supported by the waveguide, varying with velocity values between 550 and 700 m/s along the different scenarios. Furthermore, the FAS velocity is shown to be associated with the group velocity of the mode with the highest relative amplitude contribution at each studied scenario. However, because of the evolution of the mode with the highest contribution, the FAS velocity is shown to be limited to discriminate intracortical bone properties at low frequency.
Heat pulse propagation studies in TFTR
International Nuclear Information System (INIS)
Fredrickson, E.D.; Callen, J.D.; Colchin, R.J.
1986-02-01
The time scales for sawtooth repetition and heat pulse propagation are much longer (10's of msec) in the large tokamak TFTR than in previous, smaller tokamaks. This extended time scale coupled with more detailed diagnostics has led us to revisit the analysis of the heat pulse propagation as a method to determine the electron heat diffusivity, chi/sub e/, in the plasma. A combination of analytic and computer solutions of the electron heat diffusion equation are used to clarify previous work and develop new methods for determining chi/sub e/. Direct comparison of the predicted heat pulses with soft x-ray and ECE data indicates that the space-time evolution is diffusive. However, the chi/sub e/ determined from heat pulse propagation usually exceeds that determined from background plasma power balance considerations by a factor ranging from 2 to 10. Some hypotheses for resolving this discrepancy are discussed. 11 refs., 19 figs., 1 tab
Heat pulse propagation studies in TFTR
Energy Technology Data Exchange (ETDEWEB)
Fredrickson, E.D.; Callen, J.D.; Colchin, R.J.; Efthimion, P.C.; Hill, K.W.; Izzo, R.; Mikkelsen, D.R.; Monticello, D.A.; McGuire, K.; Bell, J.D.
1986-02-01
The time scales for sawtooth repetition and heat pulse propagation are much longer (10's of msec) in the large tokamak TFTR than in previous, smaller tokamaks. This extended time scale coupled with more detailed diagnostics has led us to revisit the analysis of the heat pulse propagation as a method to determine the electron heat diffusivity, chi/sub e/, in the plasma. A combination of analytic and computer solutions of the electron heat diffusion equation are used to clarify previous work and develop new methods for determining chi/sub e/. Direct comparison of the predicted heat pulses with soft x-ray and ECE data indicates that the space-time evolution is diffusive. However, the chi/sub e/ determined from heat pulse propagation usually exceeds that determined from background plasma power balance considerations by a factor ranging from 2 to 10. Some hypotheses for resolving this discrepancy are discussed. 11 refs., 19 figs., 1 tab.
Directory of Open Access Journals (Sweden)
Anton Bourdine
2015-01-01
Full Text Available This work presents fast and simple method for evaluation of polarization correction to scalar propagation constant of arbitrary order guided modes propagating over weakly guiding optical fibers. Proposed solution is based on earlier on developed modified Gaussian approximation extended for analysis of weakly guiding optical fibers with arbitrary refractive index profile in the core region bounded by single solid outer cladding. Some results are presented that illustrate the decreasing of computational error during the estimation of propagation constant when polarization corrections are taken into account. Analytical expressions for the first and second derivatives of polarization correction are derived and presented.
Propagator theory of atomic and molecular structure
International Nuclear Information System (INIS)
Oehrn, Y.
1976-01-01
It is not at all obvious which methods of use in quantum chemistry can be characterized as being without wavefunctions. There are, however, a number of methods that purpose to calculate atomic and molecular electronic structure and properties without the explicit use of many-electron wavefunctions. Fully realizing the arbitrariness of any classification of such methods as well as the absence of sharp boundaries between any choice of groups, the author separates the three kinds of approaches: (i) Local Density Energy Functional Methods, (ii) Density Matrix Methods, (iii) Propagator or Green's Function Methods. (Auth.)
System for cooling hybrid vehicle electronics, method for cooling hybrid vehicle electronics
Energy Technology Data Exchange (ETDEWEB)
France, David M.; Yu, Wenhua; Singh, Dileep; Zhao, Weihuan
2017-11-21
The invention provides a single radiator cooling system for use in hybrid electric vehicles, the system comprising a surface in thermal communication with electronics, and subcooled boiling fluid contacting the surface. The invention also provides a single radiator method for simultaneously cooling electronics and an internal combustion engine in a hybrid electric vehicle, the method comprising separating a coolant fluid into a first portion and a second portion; directing the first portion to the electronics and the second portion to the internal combustion engine for a time sufficient to maintain the temperature of the electronics at or below 175.degree. C.; combining the first and second portion to reestablish the coolant fluid; and treating the reestablished coolant fluid to the single radiator for a time sufficient to decrease the temperature of the reestablished coolant fluid to the temperature it had before separation.
Wang, Yu; Zhu, Jianxin
2012-05-15
This paper presents a novel process of extracting lead oxide nanoparticles from cathode-ray tube (CRT) funnel glass using self-propagating high-temperature synthesis (SHS) method. The impacts of added amount of funnel glass on the extraction ratio of lead, the lead extraction velocity and the micromorphology, as well as particle size of extracted nanoparticles were investigated. We found that self-propagating reaction in the presence of Mg and Fe(2)O(3) could separate lead preferentially and superfine lead oxide nanoparticles were obtained from a collecting chamber. The separation ratio was related closely to the amount of funnel glass added in the original mixture. At funnel glass addition of no more than 40wt.%, over 90wt.% of lead was recovered from funnel glass. High extraction yield reveals that the network structure of funnel glass was fractured due to the dramatic energy generated during the SHS melting process. The PbO nanoparticles collected show good dispersion and morphology with a mean grain size of 40-50nm. Copyright © 2012 Elsevier B.V. All rights reserved.
Nguyen, Vu-Hieu; Naili, Salah
2012-08-01
This paper deals with the modeling of guided waves propagation in in vivo cortical long bone, which is known to be anisotropic medium with functionally graded porosity. The bone is modeled as an anisotropic poroelastic material by using Biot's theory formulated in high frequency domain. A hybrid spectral/finite element formulation has been developed to find the time-domain solution of ultrasonic waves propagating in a poroelastic plate immersed in two fluid halfspaces. The numerical technique is based on a combined Laplace-Fourier transform, which allows to obtain a reduced dimension problem in the frequency-wavenumber domain. In the spectral domain, as radiation conditions representing infinite fluid halfspaces may be exactly introduced, only the heterogeneous solid layer needs to be analyzed by using finite element method. Several numerical tests are presented showing very good performance of the proposed procedure. A preliminary study on the first arrived signal velocities computed by using equivalent elastic and poroelastic models will be presented. Copyright © 2012 John Wiley & Sons, Ltd.
International Nuclear Information System (INIS)
Valeo, Ernest; Johnson, Jay R.; Kim, Eun-Hwa; Phillips, Cynthia
2012-01-01
A wide variety of plasma waves play an important role in the energization and loss of particles in the inner magnetosphere. Our ability to understand and model wave-particle interactions in this region requires improved knowledge of the spatial distribution and properties of these waves as well as improved understanding of how the waves depend on changes in solar wind forcing and/or geomagnetic activity. To this end, we have developed a two-dimensional, finite element code that solves the full wave equations in global magnetospheric geometry. The code describes three-dimensional wave structure including mode conversion when ULF, EMIC, and whistler waves are launched in a two-dimensional axisymmetric background plasma with general magnetic field topology. We illustrate the capabilities of the code by examining the role of plasmaspheric plumes on magnetosonic wave propagation; mode conversion at the ion-ion and Alfven resonances resulting from external, solar wind compressions; and wave structure and mode conversion of electromagnetic ion cyclotron waves launched in the equatorial magnetosphere, which propagate along the magnetic field lines toward the ionosphere. We also discuss advantages of the finite element method for resolving resonant structures, and how the model may be adapted to include nonlocal kinetic effects.
Energy Technology Data Exchange (ETDEWEB)
Ernest Valeo, Jay R. Johnson, Eun-Hwa and Cynthia Phillips
2012-03-13
A wide variety of plasma waves play an important role in the energization and loss of particles in the inner magnetosphere. Our ability to understand and model wave-particle interactions in this region requires improved knowledge of the spatial distribution and properties of these waves as well as improved understanding of how the waves depend on changes in solar wind forcing and/or geomagnetic activity. To this end, we have developed a two-dimensional, finite element code that solves the full wave equations in global magnetospheric geometry. The code describes three-dimensional wave structure including mode conversion when ULF, EMIC, and whistler waves are launched in a two-dimensional axisymmetric background plasma with general magnetic field topology. We illustrate the capabilities of the code by examining the role of plasmaspheric plumes on magnetosonic wave propagation; mode conversion at the ion-ion and Alfven resonances resulting from external, solar wind compressions; and wave structure and mode conversion of electromagnetic ion cyclotron waves launched in the equatorial magnetosphere, which propagate along the magnetic field lines toward the ionosphere. We also discuss advantages of the finite element method for resolving resonant structures, and how the model may be adapted to include nonlocal kinetic effects.
The finite product method in the theory of linear wave propagation
DEFF Research Database (Denmark)
Sorokin, Sergey; Chapman, John
2012-01-01
This paper presents a method of analysing the dispersion relation and field shape of any type of linear wave field for which the dispersion relation is transcendental. The method involves replacing each transcendental term in the dispersion relation by a finite-product polynomial. Details...... of the method are presented for several non-trivial examples, that of symmetric/anti-symmetric elastic waves in a layer and in a thin plate. In each case, the method gives a sequence of polynomial approximations to the dispersion relation of remarkable accuracy over a broad range of frequencies and wave numbers...
Propagation of Ion Acoustic Perturbations
DEFF Research Database (Denmark)
Pécseli, Hans
1975-01-01
Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered.......Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered....
Ledoux, L.A.F.; Berkhoff, Arthur P.; Thijssen, J.M.
The Conjugate Gradient Rayleigh method for the calculation of acoustic reflection and transmission at a rough interface between two media was experimentally verified. The method is based on a continuous version of the conjugate gradient technique and plane-wave expansions. We measured the beam
Local solution method for numerical solving of the wave propagation problem
Moiseenko, V. E.; Pilipenko, V. V.
2001-12-01
A new method for numerical solving of boundary problem for ordinary differential equations with slowly varying coefficients which is aimed at better representation of solutions in the regions of their rapid oscillations or exponential increase (decrease) is proposed. It is based on the approximation of the solution sought for in the form of a superposition of certain polynomial-exponential basic functions. The method is studied for the Helmholtz equation in comparison with the standard finite difference and finite element methods. The numerical tests have shown the convergence of the method proposed. In comparison with the standard methods the same accuracy is obtained on substantially coarser mesh. This advantage becomes more pronounced, if the solution varies very rapidly.
Density-functional method for nonequilibrium electron transport
DEFF Research Database (Denmark)
Brandbyge, Mads; Mozos, J.L.; Ordejon, P.
2002-01-01
We describe an ab initio method for calculating the electronic structure, electronic transport, and forces acting on the atoms, for atomic scale systems connected to semi-infinite electrodes and with an applied voltage bias. Our method is based on the density-functional theory (DFT) as implemented...... in the well tested SIESTA approach (which uses nonlocal norm-conserving pseudopotentials to describe the effect of the core electrons, and linear combination of finite-range numerical atomic orbitals to describe the valence states). We fully deal with the atomistic structure of the whole system, treating both...... the contact and the electrodes on the same footing. The effect of the finite bias (including self-consistency and the solution of the electrostatic problem) is taken into account using nonequilibrium Green's functions. We relate the nonequilibrium Green's function expressions to the more transparent scheme...
Quantum propagation and confinement in 1D systems using the transfer-matrix method
Pujol, Olivier; Carles, Robert; Pérez, José-Philippe
2014-05-01
The aim of this article is to provide some Matlab scripts to the teaching community in quantum physics. The scripts are based on the transfer-matrix formalism and offer a very efficient and versatile tool to solve problems of a physical object (electron, proton, neutron, etc) with one-dimensional (1D) stationary potential energy. Resonant tunnelling through a multiple-barrier or confinement in wells of various shapes is particularly analysed. The results are quantitatively discussed with semiconductor heterostructures, harmonic and anharmonic molecular vibrations, or neutrons in a gravity field. Scripts and other examples (hydrogen-like ions and transmission by a smooth variation of potential energy) are available freely at http://www-loa.univ-lille1.fr/˜pujol in three languages: English, French and Spanish.
New Combined Electron-Beam Methods of Wastewater Purification
International Nuclear Information System (INIS)
Pikaev, A.K.; Makarov, I.E.; Ponomarev, A.V.; Kartasheva, L.I.; Podzorova, E.A.; Chulkov, V.N.; Han, B.; Kim, D.K.
1999-01-01
The paper is a brief review of the results obtained with the participation of the authors from the study on combined electron-beam methods for purification of some wastewaters. The data on purification of wastewaters containing dyes or hydrogen peroxide and municipal wastewater in the aerosol flow are considered
14 CFR 1274.931 - Electronic funds transfer payment methods.
2010-01-01
... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Electronic funds transfer payment methods. 1274.931 Section 1274.931 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION... of the financial institution receiving payment. (2) The American Bankers Association 9-digit...
14 CFR 1260.69 - Electronic funds transfer payment methods.
2010-01-01
... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Electronic funds transfer payment methods. 1260.69 Section 1260.69 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GRANTS AND.... (2) The American Bankers Association 9-digit identifying number for wire transfers of the financing...
Melting and purification methods in electron beam furnaces. Pt. 1
International Nuclear Information System (INIS)
Stephan, H.
1975-01-01
After a general review on the market of electron beam furnaces, the melting methods and their variations are discussed in detail. The purification effects shown in a table allow a view on the main application. The losses of volatile alloy elements and the chances of compensation are specially discussed. (orig.) [de
Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek
2017-07-01
Standard computational methods used to take account of the Pauli Exclusion Principle into Monte Carlo (MC) simulations of electron transport in semiconductors may give unphysical results in low field regime, where obtained electron distribution function takes values exceeding unity. Modified algorithms were already proposed and allow to correctly account for electron scattering on phonons or impurities. Present paper extends this approach and proposes improved simulation scheme allowing including Pauli exclusion principle for electron-electron (e-e) scattering into MC simulations. Simulations with significantly reduced computational cost recreate correct values of the electron distribution function. Proposed algorithm is applied to study transport properties of degenerate electrons in graphene with e-e interactions. This required adapting the treatment of e-e scattering in the case of linear band dispersion relation. Hence, this part of the simulation algorithm is described in details.
Thick-Restart Lanczos Method for Electronic Structure Calculations
International Nuclear Information System (INIS)
Simon, Horst D.; Wang, L.-W.; Wu, Kesheng
1999-01-01
This paper describes two recent innovations related to the classic Lanczos method for eigenvalue problems, namely the thick-restart technique and dynamic restarting schemes. Combining these two new techniques we are able to implement an efficient eigenvalue problem solver. This paper will demonstrate its effectiveness on one particular class of problems for which this method is well suited: linear eigenvalue problems generated from non-self-consistent electronic structure calculations
El-Labany, S. K.; Sabry, R.; El-Taibany, W. F.; Elghmaz, E. A.
2010-04-01
Properties of small amplitude nonlinear ion-acoustic solitary waves in a warm magneto plasma with positive-negative ions and nonthermal electrons are investigated. For this purpose, the hydrodynamic equations for the positive-negative ions, nonthermal electron density distribution, and the Poisson equation are used to derive the corresponding nonlinear evolution equation; Zkharov-Kuznetsov (ZK) equation, in the small amplitude regime. The ZK equation is analyzed to examine the existence regions of the solitary pulses. It is found that compressive and rarefactive ion-acoustic solitary waves strongly depend on the mass and density ratios of the positive and negative ions as well as the nonthermal electron parameter. Also, it is found that there are two critical values for the density ratio of the negative-to-positive ions (υ), the ratio between unperturbed electron-to-positive ion density (μ), and the nonthermal electron parameter (β), which decide the existence of positive and negative ion-acoustic solitary waves. The present study is applied to examine the small amplitude nonlinear ion-acoustic solitary excitations for the (H+, O2-) and (H+, H-) plasmas, where they are found in the D- and F-regions of the Earth's ionosphere. This investigation should be helpful in understanding the salient features of the nonlinear ion-acoustic solitary waves in space and in laboratory plasmas where two distinct groups of ions and non-Boltzmann distributed electrons are present.
An Optical Streaking Method for Measuring Femtosecond Electron Bunches
International Nuclear Information System (INIS)
Ding, Yuantao
2011-01-01
The measurement of the ultra-short electron bunch length on the femtosecond time scale constitutes a very challenging problem. In the x-ray free electron laser facilities such as the Linac Coherent Light Source, generation of a sub-ten femtoseconds electron beam with 20pC charge is possible, but direct measurements are very difficult due to the resolution limit of the present diagnostics. We propose a new method here based on the measurement of the electron beam energy modulation induced from laser-electron interaction in a short wiggler. A typical optical streaking method requires a laser wavelength much longer than the electron bunch length. In this paper a laser with its wavelength shorter than the electron bunch length has been adopted, while the slope on the laser intensity envelope is used to distinguish the different periods. With this technique it is possible to reconstruct the bunch longitudinal profile from a single shot measurement. Generation of ultrashort x-ray pulses at femtoseconds (fs) scale is of great interest within synchrotron radiation and free electron laser (FEL) user community. One of the simple methods is to operate the FEL facility at low charge. At the Linac Coherent Light Source (LCLS), we have demonstrated the capability of generating ultrashort electron-beam (e-beam) with a duration of less than 10 fs fwhm using 20 pC charge. The x-ray pulses have been delivered to the x-ray users with a similar or even shorter pulse duration. However, The measurement of such short electron or x-ray pulse length at the fs time-scale constitutes a challenging problem. A standard method using an S-band radio-frequency (rf) transverse deflector has been established at LCLS, which works like a streak camera for electrons and is capable of resolving bunch lengths as short as 25 fs fwhm. With this device, the electrons are transversely deflected by the high-frequency time-variation of the deflecting fields. Increasing the deflecting voltage and rf frequency
Pernpointner, Markus; Visscher, Lucas; Trofimov, Alexander B
2018-02-05
A complete implementation of the polarization propagator based on the Dirac-Coulomb Hamiltonian is presented and applied to excitation spectra of various systems. Hereby the effect of spin-orbit coupling on excitation energies and transition moments is investigated in detail. The individual perturbational contributions to the transition moments could now be separately analyzed for the first time and show the relevance of one- and two-particle terms. In some systems different contributions to the transition moments partially cancel each other and do not allow for simple predictions. For the outer valence spectrum of the H 2 Os(CO) 4 complex a detailed final state analysis is performed explaining the sensitivity of the excitation spectrum to spin-orbit effects. Finally, technical issues of handling double group symmetry in the relativistic framework and methodological aspects of our parallel implementation are discussed.
Variational methods in electron-atom scattering theory
Nesbet, Robert K
1980-01-01
The investigation of scattering phenomena is a major theme of modern physics. A scattered particle provides a dynamical probe of the target system. The practical problem of interest here is the scattering of a low energy electron by an N-electron atom. It has been difficult in this area of study to achieve theoretical results that are even qualitatively correct, yet quantitative accuracy is often needed as an adjunct to experiment. The present book describes a quantitative theoretical method, or class of methods, that has been applied effectively to this problem. Quantum mechanical theory relevant to the scattering of an electron by an N-electron atom, which may gain or lose energy in the process, is summarized in Chapter 1. The variational theory itself is presented in Chapter 2, both as currently used and in forms that may facilitate future applications. The theory of multichannel resonance and threshold effects, which provide a rich structure to observed electron-atom scattering data, is presented in Cha...
DEFF Research Database (Denmark)
Santillan, Arturo Orozco; Pedersen, Christian Sejer; Lydolf, Morten
2007-01-01
An experimental implementation of a global sound equalization method in a rectangular room using active control is described in this paper. The main purpose of the work has been to provide experimental evidence that sound can be equalized in a continuous three-dimensional region, the listening zone......, which occupies a considerable part of the complete volume of the room. The equalization method, based on the simulation of a progressive plane wave, was implemented in a room with inner dimensions of 2.70 m x 2.74 m x 2.40 m. With this method,the sound was reproduced by a matrix of 4 x 5 loudspeakers...... filter for each transducer. The optimal arrangement of the loudspeakers and the maximum frequency that can be equalized is analyzed theoretically in this paper. The presented experimental results show that sound equalization was possible from 10 Hz to approximately 425 Hz in the listening zone. A flat...
Energy Technology Data Exchange (ETDEWEB)
Makita, M.; Nersisyan, G.; McKeever, K.; Dzelzainis, T.; White, S.; Kettle, B.; Dromey, B.; Doria, D.; Zepf, M.; Lewis, C. L. S.; Riley, D., E-mail: d.riley@qub.ac.uk [Centre for Plasma Physics, School of Mathematics and Physics, Queen' s University Belfast, University Road, Belfast BT7 1NN (United Kingdom); Robinson, A. P. L. [Central Laser Facility, Rutherford-Appleton Laboratory, Chilton Didcot, OX11 OQX (United Kingdom); Hansen, S. B. [Sandia National Laboratory, Albuquerque, New Mexico 87123 (United States)
2014-02-15
We have studied the propagation of fast electrons through laser irradiated Ti foils by monitoring the emission of hard X-rays and K-α radiation from bare foils and foils backed by a thick epoxy layer. Key observations include strong refluxing of electrons and divergence of the electron beam in the foil with evidence of magnetic field collimation. Our diagnostics have allowed us to estimate the fast electron temperature and fraction of laser energy converted to fast electrons. We have observed clear differences between the fast electron temperatures observed with bare and epoxy backed targets which may be due to the effects of refluxing.
Finite-Sample Bias Propagation in Autoregressive Estimation With the Yule–Walker Method
Broersen, P.M.T.
2009-01-01
The Yule-Walker (YW) method for autoregressive (AR) estimation uses lagged-product (LP) autocorrelation estimates to compute an AR parametric spectral model. The LP estimates only have a small triangular bias in the estimated autocorrelation function and are asymptotically unbiased. However, using
International Nuclear Information System (INIS)
Feit, M.D.; Fleck, J.A. Jr.
1989-01-01
We describe a spectral method for solving the paraxial wave equation in cylindrical geometry that is based on expansion of the exponential evolution operator in a Taylor series and use of fast Fourier transforms to evaluate derivatives. A fourth-order expansion gives excellent agreement with a two-transverse-dimensional split-operator calculation at a fraction of the cost in computation time per z step and at a considerable savings in storage
DEFF Research Database (Denmark)
Santillan, Arturo Orozco; Pedersen, Christian Sejer; Lydolf, Morten
2007-01-01
, which occupies a considerable part of the complete volume of the room. The equalization method, based on the simulation of a progressive plane wave, was implemented in a room with inner dimensions of 2.70 m x 2.74 m x 2.40 m. With this method,the sound was reproduced by a matrix of 4 x 5 loudspeakers...... in one of the walls. After traveling through the room, the sound wave was absorbed on the opposite wall, which had a similar arrangement of loudspeakers, by means of active control. A set of 40 digital FIR filters was used to modify the original input signal before it was fed to the loudspeakers, one......An experimental implementation of a global sound equalization method in a rectangular room using active control is described in this paper. The main purpose of the work has been to provide experimental evidence that sound can be equalized in a continuous three-dimensional region, the listening zone...
Botts, Jonathan; Savioja, Lauri
2015-04-01
For time-domain modeling based on the acoustic wave equation, spectral methods have recently demonstrated promise. This letter presents an extension of a spectral domain decomposition approach, previously used to solve the lossless linear wave equation, which accommodates frequency-dependent atmospheric attenuation and assignment of arbitrary dispersion relations. Frequency-dependence is straightforward to assign when time-stepping is done in the spectral domain, so combined losses from molecular relaxation, thermal conductivity, and viscosity can be approximated with little extra computation or storage. A mode update free from numerical dispersion is derived, and the model is confirmed with a numerical experiment.
Blok, C.; Kaarsemaker, R.C.
2013-01-01
Within the framework of the international KIWA quality label for rooting media representatives of plant propagators and the rockwool industry agreed to develop a method to characterize the influence of the rooting medium materials on the pH in cultivation. A method for the characterization of
Directory of Open Access Journals (Sweden)
Shouyan Jiang
2017-01-01
Full Text Available We model the fluid flow within the crack as one-dimensional flow and assume that the flow is laminar; the fluid is incompressible and accounts for the time-dependent rate of crack opening. Here, we discretise the flow equation by finite volume methods. The extended finite element methods are used for solving solid medium with crack under dynamic loads. Having constructed the approximation of dynamic extended finite element methods, the derivation of governing equation for dynamic extended finite element methods is presented. The implicit time algorithm is elaborated for the time descritisation of dominant equation. In addition, the interaction integral method is given for evaluating stress intensity factors. Then, the coupling model for modelling hydraulic fracture can be established by the extended finite element methods and the finite volume methods. We compare our present numerical results with our experimental results for verifying the proposed model. Finally, we investigate the water pressure distribution along crack surface and the effect of water pressure distribution on the fracture property.
Directory of Open Access Journals (Sweden)
Lin Luo
2017-01-01
Full Text Available The effect of a preexisting crack with different inclination angles and lengths on mechanical properties, fracture initiation, and propagation in a Brazilian disc was investigated in this paper. In the experiment, digital image correlation (DIC method was employed to record the deformation in the specimen. Different failure patterns, depending on inclination angles and lengths of the preexisting crack, were observed. The fracture initiation position deviates from the tips of the preexisting crack with the inclination angle increasing from 0° to 72° at an interval of 18° per increment. Secondary cracks are more likely to occur in the Brazilian disc with a more inclined and longer preexisting crack. A finite-discrete element combined method ELFEN was used in the numerical investigation to simulate the failure process. This investigation shows that there are good correlations between the experimental and numerical results. Digital image correlation is a good method to obtain the quantitive full-field strain distribution and to observe the strain evolution process in a jointed rock.
International Nuclear Information System (INIS)
McCoy, Michael L.; Moradi, Rasoul; Lankarani, Hamid M.
2011-01-01
This paper examines the effectiveness of analyzing impact events in mechanical systems for design purposes using simple or low ordered finite elements. Traditional impact dynamics analyses of mechanical systems namely stereomechanics, energy method, stress-wave propagation and contact mechanics approaches are limited to very simplified geometries and provide basic analyses in making predictions and understanding the dominant features of the impact in a mechanical system. In engineering practice, impacted systems present a complexity of geometry, stiffness, mass distributions, contact areas and impact angles that are impossible to analyze and design with the traditional impact dynamics methods. In real cases, the effective tool is the finite element (FE) method. The high-end FEA codes though may be not available for typical engineer/designer. This paper provides information on whether impact events of mechanical systems can be successfully modeled using simple or low-order finite elements. FEA models using simple elements are benchmarked against theoretical impact problems and published experimental impact results. As a case study, an FE model using simple plastic beam elements is further tested to predict stresses and deflections in an experimental structural impact
DEFF Research Database (Denmark)
Zhang, Changyi; Guo, Li; Deng, Ling
2010-01-01
during incubation of pMID-pcna3 and pMID-araS-pcna1 transformants under counter selection. Studying the propagation of mutant cells by semi-quantitative PCR analysis of the deleted target gene allele (Deltapcna1 or Deltapcna3) revealed that mutant cells lost propagativity, demonstrating that these pcna...
Development and application of advanced methods for electronic structure calculations
DEFF Research Database (Denmark)
Schmidt, Per Simmendefeldt
ground state energies, is used to calculate accurate adsorption energies for a wide range of reactions. The results are in good agreement with experimental values, where available. Additionally, a database consisting of 200 highly accurate adsorption energies is constructed to benchmark the accuracy......This thesis relates to improvements and applications of beyond-DFT methods for electronic structure calculations that are applied in computational material science. The improvements are of both technical and principal character. The well-known GW approximation is optimized for accurate calculations...... of electronic excitations in two-dimensional materials by exploiting exact limits of the screened Coulomb potential. This approach reduces the computational time by an order of magnitude, enabling large scale applications. The GW method is further improved by including so-called vertex corrections. This turns...
Nanobiotechnology in energy, environment and electronics methods and applications
Nicolini, Claudio
2015-01-01
Introduction: Present Challenges and Future Solutions via Nanotechnology for Electronics, Environment and Energy; Claudio NicoliniPart A: MethodsInfluence of Chromosome Translocation on Yeast Life Span: Implications for Long-Term Industrial Biofermentation; Jason Sims, Dmitri Nikitin, and Carlo V. BruschiPulsed Power Nanotechnologies for Disintegration and Breaking Up of Refractory Precious Metals Ores; Valentin A. Chanturiya and Igor Zh. BuninModeling of Software Sensors in Bioprocess; Luca Belmonte and Claudio NicoliniN
Nondestructive testing method for a new generation of electronics
Directory of Open Access Journals (Sweden)
Azin Anton
2018-01-01
Full Text Available The implementation of the Smart City system needs reliable and smoothly operating electronic equipment. The study is aimed at developing a nondestructive testing method for electronic equipment and its components. This method can be used to identify critical design defects of printed circuit boards (PCB and to predict their service life, taking into account the nature of probable operating loads. The study uses an acoustic emission method to identify and localize critical design defects of printed circuit boards. Geometric dimensions of detected critical defects can be determined by the X-ray tomography method. Based on the results of the study, a method combining acoustic emission and X-ray tomography was developed for nondestructive testing of printed circuit boards. The stress-strain state of solder joints containing detected defects was analyzed. This paper gives an example of using the developed method for estimating the degree of damage to joints between PCB components and predicting the service life of the entire PCB.
Directory of Open Access Journals (Sweden)
C. Möstl
2009-05-01
Full Text Available We analyze a magnetic signature associated with the leading edge of a bursty bulk flow observed by Cluster at −19 RE downtail on 22 August 2001. A distinct rotation of the magnetic field was seen by all four spacecraft. This event was previously examined by Slavin et al. (2003b using both linear force-free modeling as well as a curlometer technique. Extending this work, we apply here single- and multi-spacecraft Grad-Shafranov (GS reconstruction techniques to the Cluster observations and find good evidence that the structure encountered is indeed a magnetic flux rope and contains helical magnetic field lines. We find that the flux rope has a diameter of approximately 1 RE, an axial field of 26.4 nT, a velocity of ≈650 km/s, a total axial current of 0.16 MA and magnetic fluxes of order 105 Wb. The field line twist is estimated as half a turn per RE. The invariant axis is inclined at 40° to the ecliptic plane and 10° to the GSM equatorial plane. The flux rope has a force-free core and non-force-free boundaries. When we compare and contrast our results with those obtained from minimum variance, single-spacecraft force-free fitting and curlometer techniques, we find in general fair agreement, but also clear differences such as a higher inclination of the axis to the ecliptic. We further conclude that single-spacecraft methods have limitations which should be kept in mind when applied to THEMIS observations, and that non-force-free GS and curlometer techniques are to be preferred in their analysis. Some properties we derived for this earthward– moving structure are similar to those inferred by Lui et al. (2007, using a different approach, for a tailward-moving flux rope observed during the expansion phase of the same substorm.
Sun, Yangbo; Chen, Long; Huang, Bisheng; Chen, Keli
2017-07-01
As a mineral, the traditional Chinese medicine calamine has a similar shape to many other minerals. Investigations of commercially available calamine samples have shown that there are many fake and inferior calamine goods sold on the market. The conventional identification method for calamine is complicated, therefore as a result of the large scale of calamine samples, a rapid identification method is needed. To establish a qualitative model using near-infrared (NIR) spectroscopy for rapid identification of various calamine samples, large quantities of calamine samples including crude products, counterfeits and processed products were collected and correctly identified using the physicochemical and powder X-ray diffraction method. The NIR spectroscopy method was used to analyze these samples by combining the multi-reference correlation coefficient (MRCC) method and the error back propagation artificial neural network algorithm (BP-ANN), so as to realize the qualitative identification of calamine samples. The accuracy rate of the model based on NIR and MRCC methods was 85%; in addition, the model, which took comprehensive multiple factors into consideration, can be used to identify crude calamine products, its counterfeits and processed products. Furthermore, by in-putting the correlation coefficients of multiple references as the spectral feature data of samples into BP-ANN, a BP-ANN model of qualitative identification was established, of which the accuracy rate was increased to 95%. The MRCC method can be used as a NIR-based method in the process of BP-ANN modeling.
Li, Jian; Wang, Yachao; Wang, Feipeng; Liang, Suning; Lin, Xiang; Chen, Xiuping; Zhou, Jinghan
2017-11-01
Vegetable oils, mainly composed of triacylglycerol molecules, have been widely studied as new insulation materials in the recent years. In this work, we study the electronic properties of various triacylglycerol molecules with different degree of unsaturation by density functional theory (DFT). The ionization potential (IP), electron affinity (EA), and electron trap are estimated by theoretical analysis and experiments. The results show that the C atoms of cis Cdbnd C double bond make the primary contribution to the highest occupied molecular orbital (HOMO) of unsaturated triacylglycerol molecule; the IPs of fully unsaturated triacylglycerol molecules are almost confined to the narrow ranges from 7.30 to 7.45 eV in gas-phase and from 6.77 to 6.84 eV in liquid-phase correspond to LnLnLn and OOO molecules, respectively; the atoms of ester group and neighboring atoms make the primary contribution to the lowest unoccupied molecular orbital (LUMO) of both saturated and unsaturated triacylglycerol molecules; the EAs of triacylglycerol molecules are confined to the narrow ranges from -0.34 to -0.18 eV and the chemical trap is estimated to be 0-0.16 eV; the total trap is 0.32-0.36 eV. The IP distribution character and shallow trap feature maybe the main causes that vegetable oils demonstrate a low resistance against the fast streamers. The work can provide theoretical basis to molecular modification for performance improvement of vegetable insulating oils.
El-Labany, S. K.; Sabry, R.; El-Shamy, E. F.; Khedr, D. M.; Khedr
2013-10-01
Investigation of arbitrary amplitude nonlinear ion-acoustic solitary waves which accompany collisionless positive-negative ion plasmas with high-energy electrons (represented by kappa distribution) is presented. Arbitrary amplitude solitary waves are investigated by deriving an energy-integral equation involving a Sagdeev-like pseudopotential. The existence regions of solitary pulses are, defined precisely, modified by the superthermality of energetic electrons. Furthermore, numerical calculations reveal that both compressive and rarefactive pulses may exist for negative ion mass groups in Titan's atmosphere. The superthermality of energetic electrons are found to modify the existence domains of large amplitude ion-acoustic waves in Titan's atmosphere. The dependence of solitary excitation characteristics on the superthermal parameter, the negative ion concentration, the positive-to-negative ions mass ratio, and the Mach number have been investigated. The present study might be helpful to understand the excitation of fully nonlinear ion-acoustic solitary pulses that may appear in the interplanetary medium and/or in the astrophysical plasmas in general.
Directory of Open Access Journals (Sweden)
C. Möstl
2009-05-01
Full Text Available We analyze a magnetic signature associated with the leading edge of a bursty bulk flow observed by Cluster at −19 R_{E} downtail on 22 August 2001. A distinct rotation of the magnetic field was seen by all four spacecraft. This event was previously examined by Slavin et al. (2003b using both linear force-free modeling as well as a curlometer technique. Extending this work, we apply here single- and multi-spacecraft Grad-Shafranov (GS reconstruction techniques to the Cluster observations and find good evidence that the structure encountered is indeed a magnetic flux rope and contains helical magnetic field lines. We find that the flux rope has a diameter of approximately 1 R_{E}, an axial field of 26.4 nT, a velocity of ≈650 km/s, a total axial current of 0.16 MA and magnetic fluxes of order 10^{5} Wb. The field line twist is estimated as half a turn per R_{E}. The invariant axis is inclined at 40° to the ecliptic plane and 10° to the GSM equatorial plane. The flux rope has a force-free core and non-force-free boundaries. When we compare and contrast our results with those obtained from minimum variance, single-spacecraft force-free fitting and curlometer techniques, we find in general fair agreement, but also clear differences such as a higher inclination of the axis to the ecliptic. We further conclude that single-spacecraft methods have limitations which should be kept in mind when applied to THEMIS observations, and that non-force-free GS and curlometer techniques are to be preferred in their analysis. Some properties we derived for this earthward– moving structure are similar to those inferred by Lui et al. (2007, using a different approach, for a tailward-moving flux rope observed during the expansion phase of the same substorm.
Treyssède, Fabien; Gabard, Gwénaël; Ben Tahar, Mabrouk
2003-02-01
A nonstandard wave equation, established by Galbrun in 1931, is used to study sound propagation in nonuniform flows. Galbrun's equation describes exactly the same physical phenomenon as the linearized Euler's equations (LEE) but is derived from an Eulerian-Lagrangian description and written only in term of the Lagrangian perturbation of the displacement. This equation has interesting properties and may be a good alternative to the LEE: only acoustic displacement is involved (even in nonhomentropic cases), it provides exact expressions of acoustic intensity and energy, and boundary conditions are easily expressed because acoustic displacement whose normal component is continuous appears explicitly. In this paper, Galbrun's equation is solved using a finite element method in the axisymmetric case. With standard finite elements, the direct displacement-based variational formulation gives some corrupted results. Instead, a mixed finite element satisfying the inf-sup condition is proposed to avoid this problem. A first set of results is compared with semianalytical solutions for a straight duct containing a sheared flow (obtained from Pridmore-Brown's equation). A second set of results concerns a more complex duct geometry with a potential flow and is compared to results obtained from a multiple-scale method (which is an adaptation for the incompressible case of Rienstra's recent work).
Ma, Jianshe; Cai, Jinzhang; Lin, Guanyang; Chen, Huilin; Wang, Xianqin; Wang, Xianchuan; Hu, Lufeng
2014-05-15
Corynoxeine(CX), isolated from the extract of Uncaria rhynchophylla, is a useful and prospective compound in the prevention and treatment for vascular diseases. A simple and selective liquid chromatography mass spectrometry (LC-MS) method was developed to determine the concentration of CX in rat plasma. The chromatographic separation was achieved on a Zorbax SB-C18 (2.1 mm × 150 mm, 5 μm) column with acetonitrile-0.1% formic acid in water as mobile phase. Selective ion monitoring (SIM) mode was used for quantification using target ions m/z 383 for CX and m/z 237 for the carbamazepine (IS). After the LC-MS method was validated, it was applied to a back-propagation artificial neural network (BP-ANN) pharmacokinetic model study of CX in rats. The results showed that after intravenous administration of CX, it was mainly distributed in blood and eliminated quickly, t1/2 was less than 1h. The predicted concentrations generated by BP-ANN model had a high correlation coefficient (R>0.99) with experimental values. The developed BP-ANN pharmacokinetic model can be used to predict the concentration of CX in rats. Copyright © 2014 Elsevier B.V. All rights reserved.
Comparison of optimization methods for electronic-structure calculations
International Nuclear Information System (INIS)
Garner, J.; Das, S.G.; Min, B.I.; Woodward, C.; Benedek, R.
1989-01-01
The performance of several local-optimization methods for calculating electronic structure is compared. The fictitious first-order equation of motion proposed by Williams and Soler is integrated numerically by three procedures: simple finite-difference integration, approximate analytical integration (the Williams-Soler algorithm), and the Born perturbation series. These techniques are applied to a model problem for which exact solutions are known, the Mathieu equation. The Williams-Soler algorithm and the second Born approximation converge equally rapidly, but the former involves considerably less computational effort and gives a more accurate converged solution. Application of the method of conjugate gradients to the Mathieu equation is discussed
Monte Carlo methods in electron transport problems. Pt. 1
International Nuclear Information System (INIS)
Cleri, F.
1989-01-01
The condensed-history Monte Carlo method for charged particles transport is reviewed and discussed starting from a general form of the Boltzmann equation (Part I). The physics of the electronic interactions, together with some pedagogic example will be introduced in the part II. The lecture is directed to potential users of the method, for which it can be a useful introduction to the subject matter, and wants to establish the basis of the work on the computer code RECORD, which is at present in a developing stage
Method of electron emission control in RF guns
International Nuclear Information System (INIS)
Khodak, I.V.; Kushnir, V.A.
2001-01-01
The electron emission control method for a RF gun is considered.According to the main idea of the method,the additional resonance system is created in a cathode region where the RF field strength could be varied using the external pulse equipment. The additional resonance system is composed of a coaxial cavity coupled with a RF gun cylindrical cavity via an axial hole. Computed results of radiofrequency and electrodynamic performances of such a two-cavity system and results of the RF gun model pilot study are presented in. Results of particle dynamics simulation are described
Method of electron emission control in RF guns
Khodak, I V
2001-01-01
The electron emission control method for a RF gun is considered.According to the main idea of the method,the additional resonance system is created in a cathode region where the RF field strength could be varied using the external pulse equipment. The additional resonance system is composed of a coaxial cavity coupled with a RF gun cylindrical cavity via an axial hole. Computed results of radiofrequency and electrodynamic performances of such a two-cavity system and results of the RF gun model pilot study are presented in. Results of particle dynamics simulation are described.
Optimization method for electron beam melting and refining of metals
Donchev, Veliko; Vutova, Katia
2014-03-01
Pure metals and special alloys obtained by electron beam melting and refining (EBMR) in vacuum, using electron beams as a heating source, have a lot of applications in nuclear and airspace industries, electronics, medicine, etc. An analytical optimization problem for the EBMR process based on mathematical heat model is proposed. The used criterion is integral functional minimization of a partial derivative of the temperature in the metal sample. The investigated technological parameters are the electron beam power, beam radius, the metal casting velocity, etc. The optimization problem is discretized using a non-stationary heat model and corresponding adapted Pismen-Rekford numerical scheme, developed by us and multidimensional trapezional rule. Thus a discrete optimization problem is built where the criterion is a function of technological process parameters. The discrete optimization problem is heuristically solved by cluster optimization method. Corresponding software for the optimization task is developed. The proposed optimization scheme can be applied for quality improvement of the pure metals (Ta, Ti, Cu, etc.) produced by the modern and ecological-friendly EBMR process.
High-frequency emissions during the propagation of an electron beam in a high-density plasma
International Nuclear Information System (INIS)
Lalita and Tripathi, V.K.
1988-01-01
A relativistic annular electron beam passing through a high-density plasma excites Langmuir waves via Cerenkov interaction. The Langmuir waves are backscattered off ions via nonlinear ion Landau damping. At moderately high amplitudes these waves are parametrically up-converted by the beam into high-frequency electromagnetic radiation, as observed in some recent experiments. A nonlocal theory of this process is developed in a cylindrical geometry. It is seen that the growth rate of the Langmuir wave scales as one-third power of beam density. The growth rate of parametric instability scales as one-fourth power of beam density and the square root of beam thickness
Directory of Open Access Journals (Sweden)
E Ghasemikhah
2012-03-01
Full Text Available This study investigated the electronic properties of antiferromagnetic UBi2 metal by using ab initio calculations based on the density functional theory (DFT, employing the augmented plane waves plus local orbital method. We used the exact exchange for correlated electrons (EECE method to calculate the exchange-correlation energy under a variety of hybrid functionals. Electric field gradients (EFGs at the uranium site in UBi2 compound were calculated and compared with the experiment. The EFGs were predicted experimentally at the U site to be very small in this compound. The EFG calculated by the EECE functional are in agreement with the experiment. The densities of states (DOSs show that 5f U orbital is hybrided with the other orbitals. The plotted Fermi surfaces show that there are two kinds of charges on Fermi surface of this compound.
Simple method for generating adjustable trains of picosecond electron bunches
Directory of Open Access Journals (Sweden)
P. Muggli
2010-05-01
Full Text Available A simple, passive method for producing an adjustable train of picosecond electron bunches is demonstrated. The key component of this method is an electron beam mask consisting of an array of parallel wires that selectively spoils the beam emittance. This mask is positioned in a high magnetic dispersion, low beta-function region of the beam line. The incoming electron beam striking the mask has a time/energy correlation that corresponds to a time/position correlation at the mask location. The mask pattern is transformed into a time pattern or train of bunches when the dispersion is brought back to zero downstream of the mask. Results are presented of a proof-of-principle experiment demonstrating this novel technique that was performed at the Brookhaven National Laboratory Accelerator Test Facility. This technique allows for easy tailoring of the bunch train for a particular application, including varying the bunch width and spacing, and enabling the generation of a trailing witness bunch.
CSIR Research Space (South Africa)
Shatalov, M
2012-09-01
Full Text Available are transformed into systems of ordinary differential equations with initial conditions. This reduction is obtained by means of application of particular finite difference schemes to the spatial derivatives. Many of the wave propagation problems describing...
Electron swarm method as a tool to investigate multi-body electron attachment processes
Energy Technology Data Exchange (ETDEWEB)
Szamrej, I.; Forys, M.
1989-01-01
The electron swarm method has been used for the investigation of multi-body thermal electron attachment process. Ethylene, carbon dioxide and their mixtures were used as carrier gases. The rate constant for the reaction of thermal electrons with SF/sub 6/ has been measured and found to be (2.5 +- 0.2) x 10/sup -7/ cm/sup 3/center dotmol/sup -1/center dots/sup -1/. The mechanism and kinetics of thermal electron capture by N/sub 2/O was investigated in the mixtures with C/sub 2/H/sub 4/ and CO/sub 2/. A mechanism involving neutral van der Waals molecules (N/sub 2/Ocenter dotCO/sub 2/) has been proposed and the rate constants calculated to be 1.9 x 10/sup -10/ cm/sup 3/center dotmol/sup -1/center dots/sup -1/ for the formation of (N/sub 2/Ocenter dotCO/sub 2/) and 1.8 x 10/sup 30/ cm/sup 6/center dotmol/sup -2/center dots/sup -1/ for the three-body reaction with CO/sub 2/ as a stabilizing agent.
Method and device for efficiently updating data in electronic devices
Sánchez Espeso, Pablo Pedro; Díaz Suárez, Álvaro
2014-01-01
ABSTRACT: The invention relates to a method and a device for efficiently updating data in electronic devices, solving problems presented by existing techniques in a simple manner. The invention allows the device to be updated rapidly, with low energy consumption, and minimising the number of times the non-volatile memory unit (for example, flash) is erased, at a profitable cost. RESUMEN: Método y dispositivo para la actualización eficiente de datos en dispositivos electrónicos que resuelve...
Rapid method to estimate temperature changes in electronics elements
Directory of Open Access Journals (Sweden)
Oborskii G. A., Savel’eva O. S., Shikhireva Yu. V.
2014-06-01
Full Text Available Thermal behavior of electronic equipment is the determining factor for performing rapid assessment of the effectiveness of design and operation of the equipment. The assessment method proposed in this article consists in fixation of an infrared video stream from the surface of the device and converting it into a visible flow by means of a thermal imager, splitting it into component colors and their further processing using parabolic transformation. The result of the transformation is the number used as a rapid criterion for estimation of distribution stability of heat in the equipment.
Probe method of measuring the electron energy distribution in plasmas
International Nuclear Information System (INIS)
Amemiya, Hiroshi
1984-01-01
The function for the velocity distribution of electrons in plasma in a basic function associated with various phenomena. The probe method gives the distribution by a simple technique to insert a micro-electrode into plasma, and has good spatial resolution. It is specifically useful for weakly ionized, low temperature plasma. The purpose of this paper is to assist experimenters so that they can easily use this method for various phenomena by starting at its basic principle and explaining the scope of application and actual measuring techniques. The scope of application is considered by dividing it into the problems of sheath thickness, collision effect, the energy distribution of beam, the influence of probe end, probe surface phenomenon, magnetized plasma, the measurement of high energy tail, etc. For sheath thickness, it is accepted if the difference between sheath radius and probe radius is shorter than mean free path, and this is a measure for the application limit. The probe method is applicable as far as the beam density is far smaller than plasma density, and the symmetry of positive ion sheath is not disturbed. The surface area of a counter electrode should be 10 4 .Rc/lambda times or more of the probe surface area, where Rc is the radius of a counter electrode. The differentiation method of the probe characteristics includes A.C. method, high speed sweep measurement or digital method, and some applications are described. (Wakatsuki, Y.)
Effect of electron temperature on small-amplitude electron acoustic ...
Indian Academy of Sciences (India)
Sona Bansal
2018-03-14
Mar 14, 2018 ... Abstract. Effects of electron temperature on the propagation of electron acoustic solitary waves in plasma with stationary ions, cold and superthermal hot electrons is investigated in non-planar geometry employing reductive perturbation method. Modified Korteweg–de Vries equation is derived in the small ...
International Nuclear Information System (INIS)
Gomez, F.; Ondarza, R.
2003-01-01
The exact solution for the movement of a charged particle in the interaction of an electromagnetic pulse elliptically polarized spreading along a static and homogeneous magnetic field is obtained starting from the equation of force. The solution method allows to solve, in terms of the phase, the trajectory of an accelerated particle by a pulse of arbitrary width and modulated by an encircling in Gaussian form. The reported solutions in this work have diverse applications in the laser-plasma interaction physics. (Author)
Spectral-Product Methods for Electronic Structure Calculations (Preprint)
National Research Council Canada - National Science Library
Langhoff, P. W; Mills, J. E; Boatz, J. A
2006-01-01
.... The spectral-product approach to molecular electronic structure avoids the repeated evaluations of the one- and two-electron integrals required in construction of polyatomic Hamiltonian matrices...
Spectral-Product Methods for Electronic Structure Calculations (Postprint)
National Research Council Canada - National Science Library
Langhoff, P. W; Hinde, R. J; Mills, J. D; Boatz, J. A
2007-01-01
.... The spectral-product approach to molecular electronic structure avoids the repeated evaluations of the one- and two-electron integrals required in construction of polyatomic Hamiltonian matrices...
International Nuclear Information System (INIS)
Gutsev, G.L.; Klyagina, A.P.; AN SSSR, Moscow. Inst. Obshchej i Neorganicheskoj Khimii)
1982-01-01
Using the discrete variational Xα-method electronic structure of sulfur, selenium and tellurium hexafluorides is calculated. A connection of certain chemical properties with the calculated distribution of electron density is discussed. An explanation of the change of electron affinity in the series of the compounds is suggested
Selected Methods For Increases Reliability The Of Electronic Systems Security
Directory of Open Access Journals (Sweden)
Paś Jacek
2015-11-01
Full Text Available The article presents the issues related to the different methods to increase the reliability of electronic security systems (ESS for example, a fire alarm system (SSP. Reliability of the SSP in the descriptive sense is a property preservation capacity to implement the preset function (e.g. protection: fire airport, the port, logistics base, etc., at a certain time and under certain conditions, e.g. Environmental, despite the possible non-compliance by a specific subset of elements this system. Analyzing the available literature on the ESS-SSP is not available studies on methods to increase the reliability (several works similar topics but moving with respect to the burglary and robbery (Intrusion. Based on the analysis of the set of all paths in the system suitability of the SSP for the scenario mentioned elements fire events (device critical because of security.
Method of electroplating a conversion electron emitting source on implant
Srivastava, Suresh C [Setauket, NY; Gonzales, Gilbert R [New York, NY; Adzic, Radoslav [East Setauket, NY; Meinken, George E [Middle Island, NY
2012-02-14
Methods for preparing an implant coated with a conversion electron emitting source (CEES) are disclosed. The typical method includes cleaning the surface of the implant; placing the implant in an activating solution comprising hydrochloric acid to activate the surface; reducing the surface by H.sub.2 evolution in H.sub.2SO.sub.4 solution; and placing the implant in an electroplating solution that includes ions of the CEES, HCl, H.sub.2SO.sub.4, and resorcinol, gelatin, or a combination thereof. Alternatively, before tin plating, a seed layer is formed on the surface. The electroplated CEES coating can be further protected and stabilized by annealing in a heated oven, by passivation, or by being covered with a protective film. The invention also relates to a holding device for holding an implant, wherein the device selectively prevents electrodeposition on the portions of the implant contacting the device.
Electron microscopy of flatworms standard and cryo-preparation methods.
Salvenmoser, Willi; Egger, Bernhard; Achatz, Johannes G; Ladurner, Peter; Hess, Michael W
2010-01-01
Electron microscopy (EM) has long been indispensable for flatworm research, as most of these worms are microscopic in dimension and provide only a handful of characters recognizable by eye or light microscopy. Therefore, major progress in understanding the histology, systematics, and evolution of this animal group relied on methods capable of visualizing ultrastructure. The rise of molecular and cellular biology renewed interest in such ultrastructural research. In the light of recent developments, we offer a best-practice guide for users of transmission EM and provide a comparison of well-established chemical fixation protocols with cryo-processing methods (high-pressure freezing/freeze-substitution, HPF/FS). The organisms used in this study include the rhabditophorans Macrostomum lignano, Polycelis nigra and Dugesia gonocephala, as well as the acoel species Isodiametra pulchra. Copyright © 2010 Elsevier Inc. All rights reserved.
Evaluation on Electronic Securities Settlements Systems by AHP Methods
Fukaya, Kiyoyuki; Komoda, Norihisa
Accompanying the spread of Internet and the change of business models, electronic commerce expands buisness areas. Electronic finance commerce becomes popular and especially online security tradings becoome very popular in this area. This online securitiy tradings have some good points such as less mistakes than telephone calls. In order to expand this online security tradings, the transfer of the security paper is one the largest problems to be solved. Because it takes a few days to transfer the security paper from a seller to a buyer. So the dematerialization of security papers is one of the solutions. The demterilization needs the information systems for setteling security. Some countries such as France, German, United Kingdom and U.S.A. have been strating the dematerialization projects. The legacy assesments on these projects focus from the viewpoint of the legal schemes only and there is no assessment from system architectures. This paper focuses on the information system scheme and valuates these dematerlization projects by AHP methods from the viewpoints of “dematerializaion of security papers", “speed of transfer", “usefulness on the system" and “accumulation of risks". This is the first case of valuations on security settlements systems by AHP methods, especially four counties’ systems.
Mota, Bruno
2014-03-01
Most information in the central nervous system in general and the (simpler) spinal cord in particular, is transmitted along bundles of parallel axons. Each axon's transmission time increases linearly with length and decreases as a power law of caliber. Therefore, evolution must find a distribution of axonal numbers, lengths and calibers that balances the various tradeoffs between gains in propagation time, signal throughput and synchronicity, against volumetric and metabolic costs. Here I apply a variational method to calculate the distribution of axonal caliber in the spinal cord as a function of axonal length, that minimizes the average axonal signal propagation time, subject to the constraints of white matter total volume and the variance of propagation times, and allowing for arbitrary fiber priorities and end-points. The Lagrange multipliers obtained thereof can be naturally interpreted as 'exchange rates', e.g., how much evolution is willing to pay, in white matter added volume, per unit time decrease of propagation time. This is, to my knowledge, the first model that quantifies explicitly these evolutionary tradeoffs, and can obtain them empirically by measuring the distribution of axonal calibers. We are in the process of doing so using the isotropic fractionator method. I thank FAPERJ for financial support.
Wang, Xiao-Yen; Chang, Sin-Chung; Jorgenson, Philip C. E.
2000-01-01
The benchmark problems in Category 1 (Internal Propagation) of the third Computational Aeroacoustics (CAA) Work-shop sponsored by NASA Glenn Research Center are solved using the space-time conservation element and solution element (CE/SE) method. The first problem addresses the propagation of sound waves through a nearly choked transonic nozzle. The second one concerns shock-sound interaction in a supersonic nozzle. A quasi one-dimension CE/SE Euler solver for a nonuniform mesh is developed and employed to solve both problems. Numerical solutions are compared with the analytical solution for both problems. It is demonstrated that the CE/SE method is capable of solving aeroacoustic problems with/without shock waves in a simple way. Furthermore, the simple nonreflecting boundary condition used in the CE/SE method which is not based on the characteristic theory works very well.
Othmani, Cherif; Takali, Farid; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi
2016-09-01
The propagation of Rayleigh-Lamb waves in bi-layered structures is studied. For this purpose, an extension of the Legendre polynomial (LP) method is proposed to formulate the acoustic wave equation in the bi-layered structures induced by thin film Gallium Antimonide (GaSb) and with Aluminum Antimonide (AlSb) substrate in moderate thickness. Acoustic modes propagating along a bi-layer plate are shown to be quite different than classical Lamb modes, contrary to most of the multilayered structures. The validation of the LP method is illustrated by a comparison between the associated numerical results and those obtained using the ordinary differential equation (ODE) method. The convergency of the LP method is discussed through a numerical example. Moreover, the influences of thin film GaSb parameters on the characteristics Rayleigh-Lamb waves propagation has been studied in detail. Finally, the advantages of the Legendre polynomial (LP) method to analyze the multilayered structures are described. All the developments performed in this work were implemented in Matlab software.
International Nuclear Information System (INIS)
Shibata, Taiju; Ishihara, Masahiro
2003-01-01
Oxidation damage is one of the crucial factors to degrade mechanical properties of graphite components in the HTGRs. The oxidation increases the porosity of graphite and, hence, results in degradation. In order to evaluate the oxidation damage at neutron irradiated conditions, a new analytical method by ultrasonic wave propagation characteristics was developed. Irradiation effects, a dimensional change and a pinning of dislocations in crystals, on the propagation characteristics in graphite are taken into consideration in the method. It was shown that an equivalent velocity of the wave in graphite is increased by the irradiation, and that a signal height of a propagated waveform is increased by the irradiation, and it decreases with increasing porosity caused by the oxidation. The Young's modulus for an ideal graphite polycrystals without pore was evaluated by considering the wave velocity in them in order to evaluate the change of the apparent modulus at simultaneous irradiated and oxidized conditions as an application of the developed method. It was also shown that the oxidation-induced change of the modulus is appropriately evaluated by the method, suggesting that it is possible to evaluate the change for the irradiated conditions. It can be said from this study that the developed method is promising to evaluate the oxidation damage on graphite components in the HTGRs by nondestructive way. (author)
Energy Technology Data Exchange (ETDEWEB)
Othmani, Cherif, E-mail: othmanicheriffss@gmail.com; Takali, Farid; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi
2016-09-01
The propagation of Rayleigh–Lamb waves in bi-layered structures is studied. For this purpose, an extension of the Legendre polynomial (LP) method is proposed to formulate the acoustic wave equation in the bi-layered structures induced by thin film Gallium Antimonide (GaSb) and with Aluminum Antimonide (AlSb) substrate in moderate thickness. Acoustic modes propagating along a bi-layer plate are shown to be quite different than classical Lamb modes, contrary to most of the multilayered structures. The validation of the LP method is illustrated by a comparison between the associated numerical results and those obtained using the ordinary differential equation (ODE) method. The convergency of the LP method is discussed through a numerical example. Moreover, the influences of thin film GaSb parameters on the characteristics Rayleigh–Lamb waves propagation has been studied in detail. Finally, the advantages of the Legendre polynomial (LP) method to analyze the multilayered structures are described. All the developments performed in this work were implemented in Matlab software.
Jing, Yaqi; Meng, Qinghao; Qi, Peifeng; Zeng, Ming; Li, Wei; Ma, Shugen
2014-05-01
An electronic nose (e-nose) was designed to classify Chinese liquors of the same aroma style. A new method of feature reduction which combined feature selection with feature extraction was proposed. Feature selection method used 8 feature-selection algorithms based on information theory and reduced the dimension of the feature space to 41. Kernel entropy component analysis was introduced into the e-nose system as a feature extraction method and the dimension of feature space was reduced to 12. Classification of Chinese liquors was performed by using back propagation artificial neural network (BP-ANN), linear discrimination analysis (LDA), and a multi-linear classifier. The classification rate of the multi-linear classifier was 97.22%, which was higher than LDA and BP-ANN. Finally the classification of Chinese liquors according to their raw materials and geographical origins was performed using the proposed multi-linear classifier and classification rate was 98.75% and 100%, respectively.
International Nuclear Information System (INIS)
Jing, Yaqi; Meng, Qinghao; Qi, Peifeng; Zeng, Ming; Li, Wei; Ma, Shugen
2014-01-01
An electronic nose (e-nose) was designed to classify Chinese liquors of the same aroma style. A new method of feature reduction which combined feature selection with feature extraction was proposed. Feature selection method used 8 feature-selection algorithms based on information theory and reduced the dimension of the feature space to 41. Kernel entropy component analysis was introduced into the e-nose system as a feature extraction method and the dimension of feature space was reduced to 12. Classification of Chinese liquors was performed by using back propagation artificial neural network (BP-ANN), linear discrimination analysis (LDA), and a multi-linear classifier. The classification rate of the multi-linear classifier was 97.22%, which was higher than LDA and BP-ANN. Finally the classification of Chinese liquors according to their raw materials and geographical origins was performed using the proposed multi-linear classifier and classification rate was 98.75% and 100%, respectively
Directory of Open Access Journals (Sweden)
Guerfel, M.
2012-09-01
Full Text Available This paper reports for the first time a discrimination study based on the antioxidant compounds, oxidative stability and volatile compounds of virgin olive oil samples obtained from fruits of the main Tunisian olive cultivar (Chemlali using two methods of olive tree propagation (suckers and cuttings. There were significant differences between the oils from the two methods. Olive oil samples obtained from the fruits of trees from suckers had a higher content of oleic acid (63.8%, higher contents of chlorophyll and carotenoids (3.01 mg/ kg and 1.9 mg/kg respectively, a higher content of (E-2 hexenal (66.1% and a higher content in total phenols (890 mg/kg. Interestingly, more stable oil was obtained from the olives from suckers compared to the olives from cuttings. These results can be used to discriminate and to characterize the Chemlali olive oils from each origin of olive tree.
En este trabajo se presenta por primera vez un estudio de discriminación basado en compuestos antioxidantes, estabilidad oxidativa y compuestos volátiles de muestras de aceites de oliva virgen obtenidos de frutos de la principal variedad de aceitunas tunecinas (Chemlali a partir de dos métodos de propagación del olivo (chupones y estaquillas herbáceas. Se han encontrado diferencias significativas entre los aceites obtenidos por los dos métodos. Las muestras de aceites de oliva obtenidas de frutos de árboles de chupones tenían una mayor proporción de ácido oleico (63,8%, un mayor contenido de clorofila y de carotenoides (3,01 mg/kg y 1,9 mg/kg, respectivamente, un mayor contenido de (E-2 hexenal (66,1% y un mayor contenido en fenoles totales (890 mg/kg. Curiosamente, el aceite más estable se ha obtenido de las aceitunas de árboles de chupones, en comparación con las aceitunas de árboles de estaquillas herbáceas. Estos resultados pueden ser utilizados para discriminar y caracterizar los aceites de oliva Chamlali según el origen del olivo.
Abuzaid, N. (Nuha)
2016-01-01
Abstract Hartree-Fock theory, a computational method to solve electronic structure of molecules, is reviewed in this thesis. The emphasis is on spotlighting the physical reasoning behind the assumptions of the Hartree-Fock theory. Also, three post-Hartree-Fock electron correlation methods are introduced, configuration interaction, coupled cluster, and Møller-Plesset theory.
A SIMPLE METHOD FOR MEASURING THE ELECTRON-BEAM MAGNETIZATION
Energy Technology Data Exchange (ETDEWEB)
Halavanau, A. [Fermilab; Qiang, G. [Tsinghua U., Beijing, Dept. Eng. Phys.; Wisniewski, E. [Argonne; Ha, G. [POSTECH, Pohang; Power, J. [Argonne; Piot, P. [Fermilab
2016-10-18
There are a number of projects that require magnetized beams, such as electron cooling or aiding in “flat” beam transforms. Here we explore a simple technique to characterize the magnetization, observed through the angular momentum of magnetized beams. These beams are produced through photoemission. The generating drive laser first passes through microlens arrays (fly-eye light condensers) to form a transversely modulated pulse incident on the photocathode surface [1]. The resulting charge distribution is then accelerated from the photocathode. We explore the evolution of the pattern via the relative shearing of the beamlets, providing information about the angular momentum. This method is illustrated through numerical simulations and preliminary measurements carried out at the Argonne Wakefield Accelerator (AWA) facility are presented.
Manning, Robert M.; Vyhnalek, Brian E.
2015-01-01
The values of the key atmospheric propagation parameters Ct2, Cq2, and Ctq are highly dependent upon the vertical height within the atmosphere thus making it necessary to specify profiles of these values along the atmospheric propagation path. The remote sensing method suggested and described in this work makes use of a rapidly integrating microwave profiling radiometer to capture profiles of temperature and humidity through the atmosphere. The integration times of currently available profiling radiometers are such that they are approaching the temporal intervals over which one can possibly make meaningful assessments of these key atmospheric parameters. Since these parameters are fundamental to all propagation conditions, they can be used to obtain Cn2 profiles for any frequency, including those for an optical propagation path. In this case the important performance parameters of the prevailing isoplanatic angle and Greenwood frequency can be obtained. The integration times are such that Kolmogorov turbulence theory and the Taylor frozen-flow hypothesis must be transcended. Appropriate modifications to these classical approaches are derived from first principles and an expression for the structure functions are obtained. The theory is then applied to an experimental scenario and shows very good results.
Manning, Robert M.
2012-01-01
The method of moments is used to define and derive expressions for laser beam deflection and beam radius broadening for high-energy propagation through the Earth s atmosphere. These expressions are augmented with the integral invariants of the corresponding nonlinear parabolic equation that describes the electric field of high-energy laser beam to propagation to yield universal equations for the aforementioned quantities; the beam deflection is a linear function of the propagation distance whereas the beam broadening is a quadratic function of distance. The coefficients of these expressions are then derived from a thin screen approximation solution of the nonlinear parabolic equation to give corresponding analytical expressions for a target located outside the Earth s atmospheric layer. These equations, which are graphically presented for a host of propagation scenarios, as well as the thin screen model, are easily amenable to the phase expansions of the wave front for the specification and design of adaptive optics algorithms to correct for the inherent phase aberrations. This work finds application in, for example, the analysis of beamed energy propulsion for space-based vehicles.
Advanced cluster methods for correlated-electron systems
Energy Technology Data Exchange (ETDEWEB)
Fischer, Andre
2015-04-27
In this thesis, quantum cluster methods are used to calculate electronic properties of correlated-electron systems. A special focus lies in the determination of the ground state properties of a 3/4 filled triangular lattice within the one-band Hubbard model. At this filling, the electronic density of states exhibits a so-called van Hove singularity and the Fermi surface becomes perfectly nested, causing an instability towards a variety of spin-density-wave (SDW) and superconducting states. While chiral d+id-wave superconductivity has been proposed as the ground state in the weak coupling limit, the situation towards strong interactions is unclear. Additionally, quantum cluster methods are used here to investigate the interplay of Coulomb interactions and symmetry-breaking mechanisms within the nematic phase of iron-pnictide superconductors. The transition from a tetragonal to an orthorhombic phase is accompanied by a significant change in electronic properties, while long-range magnetic order is not established yet. The driving force of this transition may not only be phonons but also magnetic or orbital fluctuations. The signatures of these scenarios are studied with quantum cluster methods to identify the most important effects. Here, cluster perturbation theory (CPT) and its variational extention, the variational cluster approach (VCA) are used to treat the respective systems on a level beyond mean-field theory. Short-range correlations are incorporated numerically exactly by exact diagonalization (ED). In the VCA, long-range interactions are included by variational optimization of a fictitious symmetry-breaking field based on a self-energy functional approach. Due to limitations of ED, cluster sizes are limited to a small number of degrees of freedom. For the 3/4 filled triangular lattice, the VCA is performed for different cluster symmetries. A strong symmetry dependence and finite-size effects make a comparison of the results from different clusters difficult
A method to study electron heating during ICRH
International Nuclear Information System (INIS)
Eriksson, L.G.; Hellsten, T.
1989-01-01
Collisionless absorption of ICRF waves occurs either by ion cyclotron absorption or by electron Landau (ELD) and transit damping (TTMP). Both ion cyclotron absorption, and direct electron absorption results in electron heating. Electron heating by minority ions occurs after a high energy tail of the resonating ions has been formed i.e. typically after 0.2-1s in present JET experiments. Electron heating through ELD, and TTMP, takes place on the timescale given by electron-electron collisions which is typically of the order of ms. This difference in the timescales can be used to separate the two damping mechanisms. This can be done by measuring the time derivatives of the electron temperature after sawtooth crashes during ramp-up and ramp-down of the RF-power. (author) 4 refs., 4 figs
Automated methods for the summarization of electronic health records.
Pivovarov, Rimma; Elhadad, Noémie
2015-09-01
This review examines work on automated summarization of electronic health record (EHR) data and in particular, individual patient record summarization. We organize the published research and highlight methodological challenges in the area of EHR summarization implementation. The target audience for this review includes researchers, designers, and informaticians who are concerned about the problem of information overload in the clinical setting as well as both users and developers of clinical summarization systems. Automated summarization has been a long-studied subject in the fields of natural language processing and human-computer interaction, but the translation of summarization and visualization methods to the complexity of the clinical workflow is slow moving. We assess work in aggregating and visualizing patient information with a particular focus on methods for detecting and removing redundancy, describing temporality, determining salience, accounting for missing data, and taking advantage of encoded clinical knowledge. We identify and discuss open challenges critical to the implementation and use of robust EHR summarization systems. © The Author 2015. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved.
Ferrarese, Giorgio
2011-01-01
Lectures: A. Jeffrey: Lectures on nonlinear wave propagation.- Y. Choquet-Bruhat: Ondes asymptotiques.- G. Boillat: Urti.- Seminars: D. Graffi: Sulla teoria dell'ottica non-lineare.- G. Grioli: Sulla propagazione del calore nei mezzi continui.- T. Manacorda: Onde nei solidi con vincoli interni.- T. Ruggeri: "Entropy principle" and main field for a non linear covariant system.- B. Straughan: Singular surfaces in dipolar materials and possible consequences for continuum mechanics
Montesinos, E; Esteve, I; Guerrero, R
1983-01-01
Size frequency distributions of different phototrophic and heterotrophic microorganisms were determined by means of scanning and transmission electron microscopy and electronic particle sizing. Statistically significant differences existed among the three techniques used in this study. Cells processed for electron microscopy showed lower mean cellular volumes than those processed for electronic particle sizing, reflecting a shrinkage by factors ranging from 1.1 to 6.2 (mean, 2.3). Processing ...
Elward, Jennifer M; Thallinger, Barbara; Chakraborty, Arindam
2012-03-28
The electron-hole explicitly correlated Hartree-Fock method (eh-XCHF) is presented as a general strategy for investigation of electron-hole correlation and computation of electron-hole recombination probability. The eh-XCHF method is a variational method which uses explicitly correlated wavefunction that depends on the electron-hole inter-particle distances. It is shown that the explicitly correlated ansatz provides a systematic route to variationally minimize the total energy. The parabolic quantum dot is used as the benchmark system and the eh-XCHF method is used for computation of the ground state energy and electron-hole recombination probability. The results are compared to Hartree-Fock and explicitly correlated full configuration interaction (R12-FCI) calculations. The results indicate that an accurate description of the electron-hole wavefunction at short electron-hole inter-particle distances is crucial for qualitative description of the electron-hole recombination probability. The eh-XCHF method successfully addresses this issue and comparison of eh-XCHF calculations with R12-FCI shows good agreement. The quality of the mean field approximation for electron-hole system is also investigated by comparing HF and R12-FCI energies for electron-electron and electron-hole systems. It was found that performance of the mean field approximation is worse for the electron-hole system as compared to the corresponding electron-electron system.
Nagaso, Masaru; Komatitsch, Dimitri; Moysan, Joseph; Lhuillier, Christian
2018-01-01
ASTRID project, French sodium cooled nuclear reactor of 4th generation, is under development at the moment by Alternative Energies and Atomic Energy Commission (CEA). In this project, development of monitoring techniques for a nuclear reactor during operation are identified as a measure issue for enlarging the plant safety. Use of ultrasonic measurement techniques (e.g. thermometry, visualization of internal objects) are regarded as powerful inspection tools of sodium cooled fast reactors (SFR) including ASTRID due to opacity of liquid sodium. In side of a sodium cooling circuit, heterogeneity of medium occurs because of complex flow state especially in its operation and then the effects of this heterogeneity on an acoustic propagation is not negligible. Thus, it is necessary to carry out verification experiments for developments of component technologies, while such kind of experiments using liquid sodium may be relatively large-scale experiments. This is why numerical simulation methods are essential for preceding real experiments or filling up the limited number of experimental results. Though various numerical methods have been applied for a wave propagation in liquid sodium, we still do not have a method for verifying on three-dimensional heterogeneity. Moreover, in side of a reactor core being a complex acousto-elastic coupled region, it has also been difficult to simulate such problems with conventional methods. The objective of this study is to solve these 2 points by applying three-dimensional spectral element method. In this paper, our initial results on three-dimensional simulation study on heterogeneous medium (the first point) are shown. For heterogeneity of liquid sodium to be considered, four-dimensional temperature field (three spatial and one temporal dimension) calculated by computational fluid dynamics (CFD) with Large-Eddy Simulation was applied instead of using conventional method (i.e. Gaussian Random field). This three-dimensional numerical
A Reliability-Oriented Design Method for Power Electronic Converters
DEFF Research Database (Denmark)
Wang, Huai; Zhou, Dao; Blaabjerg, Frede
2013-01-01
Reliability is a crucial performance indicator of power electronic systems in terms of availability, mission accomplishment and life cycle cost. A paradigm shift in the research on reliability of power electronics is going on from simple handbook based calculations (e.g. models in MIL-HDBK-217F h...
International Nuclear Information System (INIS)
Hoffman, M J H; Claassens, C H
2006-01-01
A density matrix based fictitious electron dynamics method for calculating electronic structure has been implemented within a semi-empirical quantum chemistry environment. This method uses an equation of motion that implicitly ensures the idempotency constraint on the density matrix. Test calculations showed that this method has potential of being combined with simultaneous atomic dynamics, in analogy to the popular Car-Parrinello method. In addition, the sparsity of the density matrix and the sophisticated though flexible way of ensuring idempotency conservation while integrating the equation of motion creates the potential of developing a fast linear scaling method
Energy Technology Data Exchange (ETDEWEB)
Mouret, L
2002-11-01
The thesis concerns the development and implementation of numerical methods for solving the time-dependent Schroedinger equation. We first considered the case of electron-hydrogen scattering. The originality of our method is the use of a non-uniform radial grid defined by a Schwarz interpolation based on a Coulomb reference function. This grid allows many hydrogen bound states and associated matrix elements of various operators to be reproduced to machine accuracy. The wave function is propagated in time using a Split-Operator method. The efficiency of our method allows the wave function to be propagated out to large distances for all partial waves. We obtain excitation and ionization cross sections in excellent agreement with the best experimental and theoretical data. We subsequently adapted the method and the program package to study reactive atom-dihydrogen scattering. The wave packet is described using product Jacobi coordinates on a regular grid of radial coordinates combined with a basis of Legendre polynomials for the angular part (partial wave S). The wave function is analysed using a time-to-energy Fourier transform, which provides results over the energy range covered by the initial wave packet in one calculation. The method was first tested on the quasi-direct (F,H2) reaction and then applied to the indirect (C(1D),H2)reaction. The state-to-state reaction probabilities are in good agreement with those obtained by a time-independent approach. In particular, the strongly resonant structure of the (C(1D),H2) reaction probabilities is well reproduced. (author)
Energy Technology Data Exchange (ETDEWEB)
Suzuki, s.; Miyazaki, F. [Toyohashi University of Technology, Aichi (Japan); Nakane, K. [Nitto Denko Corp., Osaka (Japan)
1994-12-15
The measurement by an interference method at the tip of fast propagating cracks was investigated. To clarify the direction-dependent problem of dynamic cracks in a higher-order term, a high-precision stress field must be measured in every direction. In this method, the propagated interference fringes near the crack tip are shot at a speed of some hundreds of m/sec, and the coefficient of dynamic stress extension is obtained from the expression given when the number of fringes (`m`) in the interferences fringes is differentiated partially. The information below was obtained. The stress field in every direction can be analyzed by the interference method. However, the interference fringes in an area of absolute {theta} < 120{degree} are radially spread from the crack tip, so the precision of the interference fringes in the {gamma} direction deteriorates. In this area, the above partial differential is higher in precision when {alpha}m/{alpha}{theta} is used instead of {alpha}m/{alpha}{gamma}. The stress extension coefficient obtained by a caustic method can be verified if a stress field of {theta} = {plus_minus}72{degree} is analyzed by the interference method. By shooting in this optical system, the COD measurement, the K-value measurement of caustic light, and the stress field measurement by an interference method can be done simultaneously. 17 refs., 11 figs.
International Nuclear Information System (INIS)
Nakajima, Kenji
1977-01-01
In the gamma field for the whole plant irradiation of vegetatively propagated plants, artificial induction of mutations in rose, tea, mulberry and chrysanthemum has been studied since 1962. The studies include induction of wholly mutated shoots (sports), irradiation techniques for mutation induction, usage of cultivars in mutation breeding and re-treatment of induced mutations with gamma ray. The results so far attained are described as follows: effects of the cutting back treatment on the induction of sports; induction of radiation injuries and mutations by whole plant irradiation; and re-treatment of induced mutants with gamma ray. (Mori, K.)
Urrutxua, H.; Sanjurjo-Rivo, M.; Peláez, J.
2013-12-01
In year 2000 a house-made orbital propagator was developed by the SDGUPM (former Grupo de Dinámica de Tethers) based in a set of redundant variables including Euler parameters. This propagator was called DROMO. and it was mainly used in numerical simulations of electrodynamic tethers. It was presented for the first time in the international meeting V Jornadas de Trabajo en Mecánica Celeste, held in Albarracín, Spain, in 2002 (see reference 1). The special perturbation method associated with DROMO can be consulted in the paper.2 In year 1975, Andre Deprit in reference 3 proposes a propagation scheme very similar to the one in which DROMO is based, by using the ideal frame concept of Hansen. The different approaches used in references 3 and 2 gave rise to a small controversy. In this paper we carried out a different deduction of the DROMO propagator, underlining its close relation with the Hansen ideal frame concept, and also the similarities and the differences with the theory carried out by Deprit in 3. Simultaneously we introduce some improvements in the formulation that leads to a more synthetic propagator.
Sparrow, Victor W.; Pierce, Allan D.
1992-01-01
A theory which gives statistical predictions for how often sonic booms propagating through the earth's turbulent boundary layer will encounter caustics, given the spectral properties of the atmospheric turbulence, is outlined. The theory is simple but approximately accounts for the variation of ray tube areas along ray paths. This theory predicts that the variation of ray tube areas is determined by the product of two similar area factors, psi (x) and phi (x), each satisfying a generic harmonic oscillator equation. If an area factor increases the peak acoustic pressure decreases, and if the factor decreases the peak acoustic pressure increases. Additionally, if an area factor decreases to zero and becomes negative, the ray has propagated through a caustic, which contributes a phase change of 90 degrees to the wave. Thus, it is clear that the number of times that a sonic boom wave passes through a caustic should be related to the distorted boom waveform received on the ground. Examples are given based on a characterization of atmospheric turbulence due to the structure function of Tatarski as modified by Crow.
International Nuclear Information System (INIS)
Lahreche, A.; Beggah, Y.; Corkish, R.
2011-01-01
The effect of electron range on electron beam induced current (EBIC) is demonstrated and the problem of the choice of the optimal electron ranges to use with simple uniform and point generation function models is resolved by proposing a method to extract an electron range-energy relationship (ERER). The results show that the use of these extracted electron ranges remove the previous disagreement between the EBIC curves computed with simple forms of generation model and those based on a more realistic generation model. The impact of these extracted electron ranges on the extraction of diffusion length, surface recombination velocity and EBIC contrast of defects is discussed. It is also demonstrated that, for the case of uniform generation, the computed EBIC current is independent of the assumed shape of the generation volume. -- Highlights: → Effect of electron ranges on modeling electron beam induced current is shown. → A method to extract an electron range for simple form of generation is proposed. → For uniform generation the EBIC current is independent of the choice of it shape. → Uses of the extracted electron ranges remove some existing literature ambiguity.
Zitelli, J.
2011-04-01
The phase error, or the pollution effect in the finite element solution of wave propagation problems, is a well known phenomenon that must be confronted when solving problems in the high-frequency range. This paper presents a new method with no phase errors for one-dimensional (1D) time-harmonic wave propagation problems using new ideas that hold promise for the multidimensional case. The method is constructed within the framework of the discontinuous Petrov-Galerkin (DPG) method with optimal test functions. We have previously shown that such methods select solutions that are the best possible approximations in an energy norm dual to any selected test space norm. In this paper, we advance by asking what is the optimal test space norm that achieves error reduction in a given energy norm. This is answered in the specific case of the Helmholtz equation with L2-norm as the energy norm. We obtain uniform stability with respect to the wave number. We illustrate the method with a number of 1D numerical experiments, using discontinuous piecewise polynomial hp spaces for the trial space and its corresponding optimal test functions computed approximately and locally. A 1D theoretical stability analysis is also developed. © 2010 Elsevier Inc.
Whistler Wave Propagation Through the Ionosphere of Venus
Pérez-Invernón, F. J.; Lehtinen, N. G.; Gordillo-Vázquez, F. J.; Luque, A.
2017-11-01
We investigate the attenuation of whistler waves generated by hypotetical Venusian lightning occurring at the altitude of the cloud layer under different ionospheric conditions. We use the Stanford full-wave method for stratified media of Lehtinen and Inan (2008) to model wave propagation through the ionosphere of Venus. This method calculates the electromagnetic field created by an arbitrary source in a plane-stratified medium (i.e., uniform in the horizontal direction). We see that the existence of holes in electronic densities and the magnetic field configuration caused by solar wind play an important role in the propagation of electromagnetic waves through the Venusian ionosphere.
System and method for compressive scanning electron microscopy
Reed, Bryan W
2015-01-13
A scanning transmission electron microscopy (STEM) system is disclosed. The system may make use of an electron beam scanning system configured to generate a plurality of electron beam scans over substantially an entire sample, with each scan varying in electron-illumination intensity over a course of the scan. A signal acquisition system may be used for obtaining at least one of an image, a diffraction pattern, or a spectrum from the scans, the image, diffraction pattern, or spectrum representing only information from at least one of a select subplurality or linear combination of all pixel locations comprising the image. A dataset may be produced from the information. A subsystem may be used for mathematically analyzing the dataset to predict actual information that would have been produced by each pixel location of the image.
Managing electronic records methods, best practices, and technologies
Smallwood, Robert F
2013-01-01
The ultimate guide to electronic records management, featuring a collaboration of expert practitioners including over 400 cited references documenting today's global trends, standards, and best practices Nearly all business records created today are electronic, and are increasing in number at breathtaking rates, yet most organizations do not have the policies and technologies in place to effectively organize, search, protect, preserve, and produce these records. Authored by an internationally recognized expert on e-records in collaboration with leading subject matter experts worldwide
The finite difference method in electronic structure calculations
Energy Technology Data Exchange (ETDEWEB)
Fattebert, Jean -Luc [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-11-21
Since the development of quantum mechanics, we know the equations describing the behavior of atoms and electrons at the microscopic level. The Schroedinger equation is however too difficult to solve for more than a few particles because of the high dimensional space of the solution - 3N for N particles. So various simplified models have been developed. Furthermore, the first simplification usually introduced is the Born-Oppenhaimer approximation in which atomic nuclei are treated as classical particles surrounded by quantum electrons.
Kiss, Gellért Zsolt; Borbély, Sándor; Nagy, Ladislau
2017-12-01
We have presented here an efficient numerical approach for the ab initio numerical solution of the time-dependent Schrödinger Equation describing diatomic molecules, which interact with ultrafast laser pulses. During the construction of the model we have assumed a frozen nuclear configuration and a single active electron. In order to increase efficiency our system was described using prolate spheroidal coordinates, where the wave function was discretized using the finite-element discrete variable representation (FE-DVR) method. The discretized wave functions were efficiently propagated in time using the short-iterative Lanczos algorithm. As a first test we have studied here how the laser induced bound state dynamics in H2+ is influenced by the strength of the driving laser field.
International Nuclear Information System (INIS)
Berthiau, G.
1995-10-01
The circuit design problem consists in determining acceptable parameter values (resistors, capacitors, transistors geometries ...) which allow the circuit to meet various user given operational criteria (DC consumption, AC bandwidth, transient times ...). This task is equivalent to a multidimensional and/or multi objective optimization problem: n-variables functions have to be minimized in an hyper-rectangular domain ; equality constraints can be eventually specified. A similar problem consists in fitting component models. In this way, the optimization variables are the model parameters and one aims at minimizing a cost function built on the error between the model response and the data measured on the component. The chosen optimization method for this kind of problem is the simulated annealing method. This method, provided by the combinatorial optimization domain, has been adapted and compared with other global optimization methods for the continuous variables problems. An efficient strategy of variables discretization and a set of complementary stopping criteria have been proposed. The different parameters of the method have been adjusted with analytical functions of which minima are known, classically used in the literature. Our simulated annealing algorithm has been coupled with an open electrical simulator SPICE-PAC of which the modular structure allows the chaining of simulations required by the circuit optimization process. We proposed, for high-dimensional problems, a partitioning technique which ensures proportionality between CPU-time and variables number. To compare our method with others, we have adapted three other methods coming from combinatorial optimization domain - the threshold method, a genetic algorithm and the Tabu search method - The tests have been performed on the same set of test functions and the results allow a first comparison between these methods applied to continuous optimization variables. Finally, our simulated annealing program
Qiang, Bo; Brigham, John C.; McGough, Robert J.; Greenleaf, James F.; Urban, Matthew W.
2017-01-01
Shear wave elastography is a versatile technique that is being applied to many organs. However, in tissues that exhibit anisotropic material properties, special care must be taken to estimate shear wave propagation accurately and efficiently. A two-dimensional simulation method is implemented to simulate the shear wave propagation in the plane of symmetry in transversely isotropic viscoelastic media. The method uses a mapped Chebyshev pseudo-spectral method to calculate the spatial derivatives and an Adams-Bashforth-Moulton integrator with variable step sizes for time marching. The boundaries of the two-dimensional domain are surrounded by perfectly matched layers (PML) to approximate an infinite domain and minimize reflection errors. In an earlier work, we proposed a solution for estimating the apparent shear wave elasticity and viscosity of the spatial group velocity as a function of rotation angle through a low frequency approximation by a Taylor expansion. With the solver implemented in MATLAB, the simulated results in this paper match well with the theory. Compared to the finite element method (FEM) simulations we used before, the pseudo-spectral solver consumes less memory and is faster and achieves better accuracy. PMID:27221812
Islam, M J; Reza, A W; Kausar, A S M Z; Ramiah, H
2014-01-01
The advent of technology with the increasing use of wireless network has led to the development of Wireless Body Area Network (WBAN) to continuously monitor the change of physiological data in a cost efficient manner. As numerous researches on wave propagation characterization have been done in intrabody communication, this study has given emphasis on the wave propagation characterization between the control units (CUs) and wireless access point (AP) in a hospital scenario. Ray tracing is a tool to predict the rays to characterize the wave propagation. It takes huge simulation time, especially when multiple transmitters are involved to transmit physiological data in a realistic hospital environment. Therefore, this study has developed an accelerated ray tracing method based on the nearest neighbor cell and prior knowledge of intersection techniques. Beside this, Red-Black tree is used to store and provide a faster retrieval mechanism of objects in the hospital environment. To prove the superiority, detailed complexity analysis and calculations of reflection and transmission coefficients are also presented in this paper. The results show that the proposed method is about 1.51, 2.1, and 2.9 times faster than the Object Distribution Technique (ODT), Space Volumetric Partitioning (SVP), and Angular Z-Buffer (AZB) methods, respectively. To show the various effects on received power in 60 GHz frequency, few comparisons are made and it is found that on average -9.44 dBm, -8.23 dBm, and -9.27 dBm received power attenuations should be considered when human, AP, and CU move in a given hospital scenario.
NEW METHOD TO ATTACH WEARABLE ELECTRONICS TO CLOTHS
Directory of Open Access Journals (Sweden)
FERRI PASCUAL Josué
2015-05-01
Full Text Available The integration of electronic devices and sensors into textiles has many different potential applications. Textile fabrics, from clothing to upholstery and home textiles, are an integral part of daily life and the ability to combine electronics into textiles means that a huge range of valuable data can be collected and used by the wearer to monitor their health, performance and wellbeing, among other uses. One of the most pressing challenges is that of interconnecting electronic components via the textile fibres in a robust and reliable way. Another aspect to be studied is the ability for the electronics to be connected and disconnected when necessary; for example, when charging the batteries or washing the garment. It is this aspect that has been considered by this development to facilitate ease-of-use among the older people. In addition, the complete package must be comfortable enough not to restrict movement, and must be unobtrusive so as to avoid any embarrassment to the wearer. The present paper presents a new solution for the connection of electronic measuring and monitoring devices to textile sensors to monitor variables such as movement, temperature, heart rate and breathing.
New characterisation method of electrical and electronic equipment wastes (WEEE)
International Nuclear Information System (INIS)
Menad, N.; Guignot, S.; Houwelingen, J.A. van
2013-01-01
Highlights: ► A novel method of characterisation of components contained in WEEE has been developed. ► This technique was applied on several samples generated from different recycling plants. ► Handheld NIR and XRF were used to determine types of plastics and flame retardants. ► WEEE processing flow-sheet was suggested. - Abstract: Innovative separation and beneficiation techniques of various materials encountered in electrical and electronic equipment wastes (WEEE) is a major improvement for its recycling. Mechanical separation-oriented characterisation of WEEE was conducted in an attempt to evaluate the amenability of mechanical separation processes. Properties such as liberation degree of fractions (plastics, metals ferrous and non-ferrous), which are essential for mechanical separation, are analysed by means of a grain counting approach. Two different samples from different recycling industries were characterised in this work. The first sample is a heterogeneous material containing different types of plastics, metals (ferrous and non-ferrous), printed circuit board (PCB), rubber and wood. The second sample contains a mixture of mainly plastics. It is found for the first sample that all aluminium particles are free (100%) in all investigated size fractions. Between 92% and 95% of plastics are present as free particles; however, 67% in average of ferromagnetic particles are liberated. It can be observed that only 42% of ferromagnetic particles are free in the size fraction larger than 20 mm. Particle shapes were also quantified manually particle by particle. The results show that the particle shapes as a result of shredding, turn out to be heterogeneous, thereby complicating mechanical separation processes. In addition, the separability of various materials was ascertained by a sink–float analysis and eddy current separation. The second sample was separated by automatic sensor sorting in four different products: ABS, PC–ABS, PS and rest product. The
Energy Technology Data Exchange (ETDEWEB)
Borowik, Piotr, E-mail: pborow@poczta.onet.pl [Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warszawa (Poland); Thobel, Jean-Luc, E-mail: jean-luc.thobel@iemn.univ-lille1.fr [Institut d' Electronique, de Microélectronique et de Nanotechnologies, UMR CNRS 8520, Université Lille 1, Avenue Poincaré, CS 60069, 59652 Villeneuve d' Ascq Cédex (France); Adamowicz, Leszek, E-mail: adamo@if.pw.edu.pl [Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warszawa (Poland)
2017-07-15
Standard computational methods used to take account of the Pauli Exclusion Principle into Monte Carlo (MC) simulations of electron transport in semiconductors may give unphysical results in low field regime, where obtained electron distribution function takes values exceeding unity. Modified algorithms were already proposed and allow to correctly account for electron scattering on phonons or impurities. Present paper extends this approach and proposes improved simulation scheme allowing including Pauli exclusion principle for electron–electron (e–e) scattering into MC simulations. Simulations with significantly reduced computational cost recreate correct values of the electron distribution function. Proposed algorithm is applied to study transport properties of degenerate electrons in graphene with e–e interactions. This required adapting the treatment of e–e scattering in the case of linear band dispersion relation. Hence, this part of the simulation algorithm is described in details.
Hawkes, Peter W
2014-01-01
Advances in Imaging & Electron Physics merges two long-running serials-Advances in Electronics & Electron Physics and Advances in Optical & Electron Microscopy. The series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains. Contributions from leading authorities Informs and updates on all the latest developments in the field.
Propagation speed of gamma radiation in brass
International Nuclear Information System (INIS)
Cavalcante, Jose T.P.D.; Silva, Paulo R.J.; Saitovich, Henrique
2009-01-01
The propagation speed (PS) of visible light -represented by a short frequency range in the large frame of electromagnetic radiations (ER) frequencies- in air was measured during the last century, using a great deal of different methods, with high precision results being achieved. Presently, a well accepted value, with very small uncertainty, is c= 299,792.458 Km/s) (c reporting to the Latin word celeritas: 'speed swiftness'). When propagating in denser material media (MM), such value is always lower when compared to the air value, with the propagating MM density playing an important role. Until present, such studies focusing propagation speeds, refractive indexes, dispersions were specially related to visible light, or to ER in wavelengths ranges dose to it, and with a transparent MM. A first incursion in this subject dealing with γ-rays was performed using an electronic coincidence counting system, when the value of it's PS was measured in air, C γ(air) 298,300.15 Km/s; a method that went on with later electronic improvements. always in air. To perform such measurements the availability of a γ-radiation source in which two γ-rays are emitted simultaneously in opposite directions -as already used as well as applied in the present case- turns out to be essential to the feasibility of the experiment, as far as no reflection techniques could be used. Such a suitable source was the positron emitter 22 Na placed in a thin wall metal container in which the positrons are stopped and annihilated when reacting with the medium electrons, in such way originating -as it is very well established from momentum/energy conservation laws - two gamma-rays, energy 511 KeV each, both emitted simultaneously in opposite directions. In all the previous experiments were used photomultiplier detectors coupled to NaI(Tl) crystal scintillators, which have a good energy resolution but a deficient time resolution for such purposes. Presently, as an innovative improvement, were used BaF 2
Propagation speed of gamma radiation in brass
Energy Technology Data Exchange (ETDEWEB)
Cavalcante, Jose T.P.D.; Silva, Paulo R.J.; Saitovich, Henrique
2009-07-01
The propagation speed (PS) of visible light -represented by a short frequency range in the large frame of electromagnetic radiations (ER) frequencies- in air was measured during the last century, using a great deal of different methods, with high precision results being achieved. Presently, a well accepted value, with very small uncertainty, is c= 299,792.458 Km/s) (c reporting to the Latin word celeritas: 'speed swiftness'). When propagating in denser material media (MM), such value is always lower when compared to the air value, with the propagating MM density playing an important role. Until present, such studies focusing propagation speeds, refractive indexes, dispersions were specially related to visible light, or to ER in wavelengths ranges dose to it, and with a transparent MM. A first incursion in this subject dealing with {gamma}-rays was performed using an electronic coincidence counting system, when the value of it's PS was measured in air, C{sub {gamma}}{sub (air)}298,300.15 Km/s; a method that went on with later electronic improvements. always in air. To perform such measurements the availability of a {gamma}-radiation source in which two {gamma}-rays are emitted simultaneously in opposite directions -as already used as well as applied in the present case- turns out to be essential to the feasibility of the experiment, as far as no reflection techniques could be used. Such a suitable source was the positron emitter {sup 22}Na placed in a thin wall metal container in which the positrons are stopped and annihilated when reacting with the medium electrons, in such way originating -as it is very well established from momentum/energy conservation laws - two gamma-rays, energy 511 KeV each, both emitted simultaneously in opposite directions. In all the previous experiments were used photomultiplier detectors coupled to NaI(Tl) crystal scintillators, which have a good energy resolution but a deficient time resolution for such purposes
Electronically Nonadiabatic Dynamics via Semiclassical Initial Value Methods
Energy Technology Data Exchange (ETDEWEB)
Miller, William H.
2008-12-11
In the late 1970's Meyer and Miller (MM) [J. Chem. Phys. 70, 3214 (1979)] presented a classical Hamiltonian corresponding to a finite set of electronic states of a molecular system (i.e., the various potential energy surfaces and their couplings), so that classical trajectory simulations could be carried out treating the nuclear and electronic degrees of freedom (DOF) in an equivalent dynamical framework (i.e., by classical mechanics), thereby describing non-adiabatic dynamics in a more unified manner. Much later Stock and Thoss (ST) [Phys. Rev. Lett. 78, 578 (1997)] showed that the MM model is actually not a 'model', but rather a 'representation' of the nuclear-electronic system; i.e., were the MMST nuclear-electronic Hamiltonian taken as a Hamiltonian operator and used in the Schroedinger equation, the exact (quantum) nuclear-electronic dynamics would be obtained. In recent years various initial value representations (IVRs) of semiclassical (SC) theory have been used with the MMST Hamiltonian to describe electronically non-adiabatic processes. Of special interest is the fact that though the classical trajectories generated by the MMST Hamiltonian (and which are the 'input' for an SC-IVR treatment) are 'Ehrenfest trajectories', when they are used within the SC-IVR framework the nuclear motion emerges from regions of non-adiabaticity on one potential energy surface (PES) or another, and not on an average PES as in the traditional Ehrenfest model. Examples are presented to illustrate and (hopefully) illuminate this behavior.
Detection methods for cereal grains treated with low and high energy electrons
Cutrubinis, Mihalis; Delincée, Henry; Stahl, Mario; Röder, Olaf; Schaller, Hans Jürgen
2005-04-01
Cereal grains can be treated with low energy (<300keV) or high energy (1-10MeV) electrons for decontamination of phytopathogenic and spoilage organisms. In this preliminary study, wheat and barley samples were treated with low energy electrons of 145keV or high energy electrons of 10MeV. To identify the electron treatment, different detection methods have been investigated: (1) photostimulated luminescence (PSL), (2) thermoluminescence (TL), (3) electron spin resonance (ESR) and (4) DNA Comet Assay. These four methods are already standardised at a European level and are now adopted as general Codex methods for detection of irradiated foodstuffs. The results suggest that the most suitable detection methods for electron-treated grains are the PSL and TL methods. The results from the other two methods (ESR and Comet Assay) are not so promising because they seem only to be applicable in special cases.
An Efficient Method for Electron-Atom Scattering Using Ab-initio Calculations
Energy Technology Data Exchange (ETDEWEB)
Xu, Yuan; Yang, Yonggang; Xiao, Liantuan; Jia, Suotang [Shanxi University, Taiyuan (China)
2017-02-15
We present an efficient method based on ab-initio calculations to investigate electron-atom scatterings. Those calculations profit from methods implemented in standard quantum chemistry programs. The new approach is applied to electron-helium scattering. The results are compared with experimental and other theoretical references to demonstrate the efficiency of our method.
CLOPW; a mixed basis set full potential electronic structure method
Bekker, H.G.; Bekker, Hermie Gerhard
1997-01-01
This thesis is about the development of the full potental CLOPW package for electronic structure calculations. Chapter 1 provides the necessary background in the theory of solid state physics. It gives a short overview of the effective one particle model as commonly used in solid state physics. It
Ultraviolet and electron beams: energy efficient methods of curing
International Nuclear Information System (INIS)
O'Hara, K.
1982-01-01
The use of ultraviolet or electron beam radiation for the curing of surface coatings is described. Examples are taken from a number of industries, particular attention being paid to the paper varnishing and printed circuit industries. The components of the coatings used in these processes and toxicology and safety aspects are considered. (author)
Application of maximum entropy method for the study of electron ...
Indian Academy of Sciences (India)
demonstrate that the integrated powder data can be used for the analysis of electron density distribution using MEM and the bonding features can be understood in a better manner. However, the limitations lie in the quality of powder data sets used for the analysis. 2. Data treatment. The powder data of SrS, BaS and PuS ...
Energy Technology Data Exchange (ETDEWEB)
Ogata, R.; Liu, H. Q.; Ishiguro, M.; Ikeda, T. [Interdisciplinary Graduate School of Engineering Science, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Hanada, K.; Zushi, H.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A. [Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Nishino, N. [Department of Mechanical System Engineering, Graduate School of Engineering, Hiroshima University (Japan); Collaboration: QUEST Group
2011-09-15
A study of radial propagation and electric fields induced by charge separation in blob-like structures has been performed in a non-confined cylindrical electron cyclotron resonance heating plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak using a fast-speed camera and a Langmuir probe. The radial propagation of the blob-like structures is found to be driven by E x B drift. Moreover, these blob-like structures were found to have been accelerated, and the property of the measured radial velocities agrees with the previously proposed model [C. Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)]. Although the dependence of the radial velocity on the connection length of the magnetic field appeared to be different, a plausible explanation based on enhanced short-circuiting of the current path can be proposed.
New methods of determination of the total electron content in the transverse zone
International Nuclear Information System (INIS)
Keroub, I.H.
1976-01-01
New methods for the determination of T.E.C. in the transverse zone are developed in the present study. The methods are mainly based on a rigorous calculation of the propagation of electromagnetic waves in an anisotropic geophysical plasma. The methods are described according to the recorded information (satellitic frequencies, universal time) involved in their utilization. Finally, it is show how to apply these methods to any station situated at a geomagnetic latitude comparable with that of Haifa by way of a suitable treatment of the available information
Terauchi, M
2006-07-01
Electronic structures of boron-nitride (BN) nanotubes and a BN cone-structure material were studied by using a high energy-resolution electron energy-loss spectroscopy (EELS) microscope. A trial of the whole electronic structure study of hexagonal BN (h-BN), which consists of flat BN honeycomb layers, was conducted by a combination of EELS and X-ray emission spectroscopy (XES) based on transmission electron microscopy (TEM) (TEM-EELS/XES). The pi and pi+sigma plasmon energies of BN nanotubes (BNT) were smaller than those of h-BN. The pi+sigma energy was explained by the surface plasmon excitation. The spectrum of a two-wall BNT of 2.7 nm in diameter showed a new spectral onset at 4 eV. The valence electron excitation spectra obtained from the tip region of the BN cone with an apex angle of 20 degrees showed similar intensity distribution with those of BNTs. The B K-shell electron excitation spectra obtained from the bottom edge region of the BN cone showed additional peak intensity when compared with those of h-BN and BNT. The B K-shell electron excitation spectra and B K-emission spectra of h-BN were compared with a result of a LDA band calculation. It showed that high symmetry points in the band diagram appear as peak and/or shoulder structures in the EELS and XES spectra. Interband transitions appeared in the imaginary part of the dielectric function of h-BN experimentally obtained were assigned in the band diagram. The analysis also presented that the LDA calculation estimated the bandgap energy smaller than the real material by an amount of 2 eV. Those results of TEM-EELS/XES analysis presented that high energy-resolution spectroscopy methods combined with TEM is a promising method to analyze whole electronic structures of nanometer scale materials. Copyright (c) 2006 Wiley-Liss, Inc.
Energy Technology Data Exchange (ETDEWEB)
Guerch, Kévin, E-mail: kevin.guerch@onera.fr [ONERA, 2 Avenue Edouard Belin, 31055 Toulouse Cedex 4 (France); CIRIMAT – Institut Carnot (CNRS) Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 09 (France); Paulmier, Thierry [ONERA, 2 Avenue Edouard Belin, 31055 Toulouse Cedex 4 (France); Guillemet-Fritsch, Sophie; Lenormand, Pascal [CIRIMAT – Institut Carnot (CNRS) Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 09 (France)
2015-04-15
Dielectric materials used for spacecraft applications are often characterised under electron irradiation in order to study their physical and electrical mechanisms. For surface potential measurement, a small removable flat device based on the secondary electron spectrometer method has been developed and installed in the CEDRE irradiation test facility at ONERA (Toulouse, France). This technique was developed to get rid off specific issues inherent to the Kelvin Probe technique. This experimental device named REPA (Repulsive Electron Potential Analyser) allows in situ and real time assessment of the surface potential built up on dielectric materials under continuous electron irradiation. A calibration has been performed in order to validate this experimental setup. Furthermore, to optimise its efficiency, the physical behaviour of this device has been modelled and numerically simulated using Particle In Cell (PIC) model and a dedicated numerical code called SPIS (Spacecraft Plasma Interactions System). In a final step, electrical characterisations of a charged dielectric have been carried out under continuous electron irradiation with this new method. These results have been compared with measurements performed in same experimental conditions with conventional Kelvin Probe method. The experimental results have been discussed in this paper. To conclude, advantages of this experimental setup in regard of this application will be emphasised.
Electronic firing systems and methods for firing a device
Frickey, Steven J [Boise, ID; Svoboda, John M [Idaho Falls, ID
2012-04-24
An electronic firing system comprising a control system, a charging system, an electrical energy storage device, a shock tube firing circuit, a shock tube connector, a blasting cap firing circuit, and a blasting cap connector. The control system controls the charging system, which charges the electrical energy storage device. The control system also controls the shock tube firing circuit and the blasting cap firing circuit. When desired, the control system signals the shock tube firing circuit or blasting cap firing circuit to electrically connect the electrical energy storage device to the shock tube connector or the blasting cap connector respectively.
Computer simulation of electron beams
Energy Technology Data Exchange (ETDEWEB)
Sabchevski, S.P.; Mladenov, G.M. (Bylgarska Akademiya na Naukite, Sofia (Bulgaria). Inst. po Elektronika)
1994-04-14
Self-fields and forces as well as the local degree of space-charge neutralization in overcompensated electron beams are considered. The radial variation of the local degree of space-charge neutralization is analysed. A novel model which describes the equilibrium potential distribution in overcompensated beams is proposed and a method for computer simulation of the beam propagation is described. Results from numerical experiments which illustrate the propagation of finite emittance overneutralized beams are presented. (Author).
Chun, Sehun
2017-07-01
Applying the method of moving frames to Maxwell's equations yields two important advancements for scientific computing. The first is the use of upwind flux for anisotropic materials in Maxwell's equations, especially in the context of discontinuous Galerkin (DG) methods. Upwind flux has been available only to isotropic material, because of the difficulty of satisfying the Rankine-Hugoniot conditions in anisotropic media. The second is to solve numerically Maxwell's equations on curved surfaces without the metric tensor and composite meshes. For numerical validation, spectral convergences are displayed for both two-dimensional anisotropic media and isotropic spheres. In the first application, invisible two-dimensional metamaterial cloaks are simulated with a relatively coarse mesh by both the lossless Drude model and the piecewisely-parametered layered model. In the second application, extremely low frequency propagation on various surfaces such as spheres, irregular surfaces, and non-convex surfaces is demonstrated.
Mixed ionic-electronic conductor-based radiation detectors and methods of fabrication
Conway, Adam; Beck, Patrick R; Graff, Robert T; Nelson, Art; Nikolic, Rebecca J; Payne, Stephen A; Voss, Lars; Kim, Hadong
2015-04-07
A method of fabricating a mixed ionic-electronic conductor (e.g. TlBr)-based radiation detector having halide-treated surfaces and associated methods of fabrication, which controls polarization of the mixed ionic-electronic MIEC material to improve stability and operational lifetime.
2011-12-06
... manufacturing, exporting, and/or brokering defense articles or defense services. On February 24, 2011, the... International Traffic in Arms Regulations: Additional Method of Electronic Payment of Registration Fees AGENCY... method of electronic payment of registration fees, so as to provide a choice in and facilitate the...
Directory of Open Access Journals (Sweden)
С. М. Гонтаренко
2017-09-01
Full Text Available Purpose. To develop a method of propagation, stimulation of rhizomes growth in vitro culture for the genus Miscanthus representatives and their adaptation in the open field without the use of greenhouse complexes for acclimatization and completion of growing. Methods. Biotechnological procedures, mathematical and statistical analyses. Results. Prescription of nutrient medium was developed for explants inoculation, sprouts propagation, rhizomes growth stimulation in vitro. Such sterile explants as seeds, buds to be removed from rhizomes, parts of stems with bud were placed on modified media with mineral portion by Murashige and Skoog (MS that contained 0,5–1 dose of macroelements and one dose of microelements, vitamins (10 mg/l of thiaminum, 1,0 mg/l of pyridoxine, 1,0 mg/l of nicotinic acid and 1,0 mg/l of ascorbic acid supplemented with amino acids (250 mg/l of glutamic acid, 3 mg/l of tyrosine, 3 mg/l of arginine, 2 mg/l of hydroxyproline, plant growth regulators [0,5–1,0 mg/l of GA (gibberelline acid, 0,2 mg/l of 6-BAP (6-Benzylaminopurine, 0,1 mg/l of NAA (α-naphtylacetic acid] in different variations. After seed germination, buds emerging and sprouts formation 1–2 cm in height, for propagation purpose they were passivated on the medium of other composition that differed from previous one by the content and ratio of growth regulators, especially by a high concentration of cytokinins [6-BAP (0,4–0,5 mg/l, kinetin (0,5 mg/l, adenine (0,5 mg/k] in different variations in presence of GA (0,2 mg/l. In order to stimulate rhizomes growth, microclones were transferred on media with other composition and ratio growth regulators (6-BAP (0,2–0,3 mg/l + GA (0,5–1,0 mg/l or 6-BAP (0,2–0,3 mg/l + GA (0,5–1,0 mg/l + NAA (0,1 mg/l, in other words, with a high content of gibberellins. After the formation of rhizomes 10–15 cm in length, miscanthus plants were planted out in the open ground. Stimulation of
UWB radar multipath propagation effects
Czech Academy of Sciences Publication Activity Database
Čermák, D.; Schejbal, V.; NĚMEC, Z.; Bezoušek, P.; Fišer, Ondřej
2005-01-01
Roč. 11, - (2005), --- ISSN 1211-6610 R&D Projects: GA MPO FT-TA2/030 Institutional research plan: CEZ:AV0Z30420517 Keywords : UWB radar * multipath propagation Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering
Method for secure electronic voting system: face recognition based approach
Alim, M. Affan; Baig, Misbah M.; Mehboob, Shahzain; Naseem, Imran
2017-06-01
In this paper, we propose a framework for low cost secure electronic voting system based on face recognition. Essentially Local Binary Pattern (LBP) is used for face feature characterization in texture format followed by chi-square distribution is used for image classification. Two parallel systems are developed based on smart phone and web applications for face learning and verification modules. The proposed system has two tire security levels by using person ID followed by face verification. Essentially class specific threshold is associated for controlling the security level of face verification. Our system is evaluated three standard databases and one real home based database and achieve the satisfactory recognition accuracies. Consequently our propose system provides secure, hassle free voting system and less intrusive compare with other biometrics.
Dictionary-learning-based reconstruction method for electron tomography.
Liu, Baodong; Yu, Hengyong; Verbridge, Scott S; Sun, Lizhi; Wang, Ge
2014-01-01
Electron tomography usually suffers from so-called “missing wedge” artifacts caused by limited tilt angle range. An equally sloped tomography (EST) acquisition scheme (which should be called the linogram sampling scheme) was recently applied to achieve 2.4-angstrom resolution. On the other hand, a compressive sensing inspired reconstruction algorithm, known as adaptive dictionary based statistical iterative reconstruction (ADSIR), has been reported for X-ray computed tomography. In this paper, we evaluate the EST, ADSIR, and an ordered-subset simultaneous algebraic reconstruction technique (OS-SART), and compare the ES and equally angled (EA) data acquisition modes. Our results show that OS-SART is comparable to EST, and the ADSIR outperforms EST and OS-SART. Furthermore, the equally sloped projection data acquisition mode has no advantage over the conventional equally angled mode in this context.
Dictionary-Learning-Based Reconstruction Method for Electron Tomography
LIU, BAODONG; YU, HENGYONG; VERBRIDGE, SCOTT S.; SUN, LIZHI; WANG, GE
2014-01-01
Summary Electron tomography usually suffers from so-called “missing wedge” artifacts caused by limited tilt angle range. An equally sloped tomography (EST) acquisition scheme (which should be called the linogram sampling scheme) was recently applied to achieve 2.4-angstrom resolution. On the other hand, a compressive sensing inspired reconstruction algorithm, known as adaptive dictionary based statistical iterative reconstruction (ADSIR), has been reported for X-ray computed tomography. In this paper, we evaluate the EST, ADSIR, and an ordered-subset simultaneous algebraic reconstruction technique (OS-SART), and compare the ES and equally angled (EA) data acquisition modes. Our results show that OS-SART is comparable to EST, and the ADSIR outperforms EST and OS-SART. Furthermore, the equally sloped projection data acquisition mode has no advantage over the conventional equally angled mode in this context. PMID:25104167
Discrete variational methods and their application to electronic structures
International Nuclear Information System (INIS)
Ellis, D.E.
1987-01-01
Some general concepts concerning Discrete Variational methods are developed and applied to problems of determination of eletronic spectra, charge densities and bonding of free molecules, surface-chemisorbed species and bulk solids. (M.W.O.) [pt
Mulder, W.A.; Zhebel, E.; Minisini, S.
2013-01-01
We analyse the time-stepping stability for the 3-D acoustic wave equation, discretized on tetrahedral meshes. Two types of methods are considered: mass-lumped continuous finite elements and the symmetric interior-penalty discontinuous Galerkin method. Combining the spatial discretization with the
Wang, Xi; Chen, Shouhui; Zheng, Tianyong; Ning, Xiangchun; Dai, Yifei
2018-03-01
The filament yarns spreading techniques of electronic fiberglass fabric were developed in the past few years in order to meet the requirements of the development of electronic industry. Copper clad laminate (CCL) requires that the warp and weft yarns of the fabric could be spread out of apart and formed flat. The penetration performance of resin could be improved due to the filament yarns spreading techniques of electronic fiberglass fabric, the same as peeling strength of CCL and drilling performance of printed circuit board (PCB). This paper shows the filament yarns spreading techniques of electronic fiberglass fabric from several aspects, such as methods and functions, also with the assessment methods of their effects.
Unfolding method for first-principles LCAO electronic structure calculations
Lee, Chi-Cheng; Yamada-Takamura, Yukiko; Ozaki, Taisuke
2013-08-01
Unfolding the band structure of a supercell to a normal cell enables us to investigate how symmetry breakers such as surfaces and impurities perturb the band structure of the normal cell. We generalize the unfolding method, originally developed based on Wannier functions, to the linear combination of atomic orbitals (LCAO) method, and present a general formula to calculate the unfolded spectral weight. The LCAO basis set is ideal for the unfolding method because the basis functions allocated to each atomic species are invariant regardless of the existence of surface and impurity. The unfolded spectral weight is well defined by the property of the LCAO basis functions. In exchange for the property, the non-orthogonality of the LCAO basis functions has to be taken into account. We show how the non-orthogonality can be properly incorporated in the general formula. As an illustration of the method, we calculate the dispersive quantized spectral weight of a ZrB2 slab and show strong spectral broadening in the out-of-plane direction, demonstrating the usefulness of the unfolding method.
Unfolding method for first-principles LCAO electronic structure calculations
International Nuclear Information System (INIS)
Lee, Chi-Cheng; Yamada-Takamura, Yukiko; Ozaki, Taisuke
2013-01-01
Unfolding the band structure of a supercell to a normal cell enables us to investigate how symmetry breakers such as surfaces and impurities perturb the band structure of the normal cell. We generalize the unfolding method, originally developed based on Wannier functions, to the linear combination of atomic orbitals (LCAO) method, and present a general formula to calculate the unfolded spectral weight. The LCAO basis set is ideal for the unfolding method because the basis functions allocated to each atomic species are invariant regardless of the existence of surface and impurity. The unfolded spectral weight is well defined by the property of the LCAO basis functions. In exchange for the property, the non-orthogonality of the LCAO basis functions has to be taken into account. We show how the non-orthogonality can be properly incorporated in the general formula. As an illustration of the method, we calculate the dispersive quantized spectral weight of a ZrB 2 slab and show strong spectral broadening in the out-of-plane direction, demonstrating the usefulness of the unfolding method. (paper)
Unfolding method for first-principles LCAO electronic structure calculations.
Lee, Chi-Cheng; Yamada-Takamura, Yukiko; Ozaki, Taisuke
2013-08-28
Unfolding the band structure of a supercell to a normal cell enables us to investigate how symmetry breakers such as surfaces and impurities perturb the band structure of the normal cell. We generalize the unfolding method, originally developed based on Wannier functions, to the linear combination of atomic orbitals (LCAO) method, and present a general formula to calculate the unfolded spectral weight. The LCAO basis set is ideal for the unfolding method because the basis functions allocated to each atomic species are invariant regardless of the existence of surface and impurity. The unfolded spectral weight is well defined by the property of the LCAO basis functions. In exchange for the property, the non-orthogonality of the LCAO basis functions has to be taken into account. We show how the non-orthogonality can be properly incorporated in the general formula. As an illustration of the method, we calculate the dispersive quantized spectral weight of a ZrB2 slab and show strong spectral broadening in the out-of-plane direction, demonstrating the usefulness of the unfolding method.
Efficient electronic structure methods applied to metal nanoparticles
DEFF Research Database (Denmark)
Larsen, Ask Hjorth
of efficient approaches to density functional theory and the application of these methods to metal nanoparticles. We describe the formalism and implementation of localized atom-centered basis sets within the projector augmented wave method. Basis sets allow for a dramatic increase in performance compared...... and jumps in Fermi level near magic numbers can lead to alkali-like or halogen-like behaviour when main-group atoms adsorb onto gold clusters. A non-self-consistent NewnsAnderson model is used to more closely study the chemisorption of main-group atoms on magic-number Au clusters. The behaviour at magic...
Directory of Open Access Journals (Sweden)
Martin Říha
2007-01-01
Full Text Available The different type of own produce stimulators were tested at Berberis thunbergii L. 'Green Carpet', Berberis thunbergii 'Red Shift' and Berberis thunbergii 'Aureum'. We used the combination of growing inhibitors and quick-dip method, single quick-dip metod in solution of acetone and stimulant in form of gel. Groving inhibitors is including paclobutrazol and CCC in test. We used IBK, NAA, IAA and nicotin acid as auxins in quick-dip method. Medium was aceton solution.
Adaptive Electronic Quizzing Method for Introductory Electrical Circuit Course
Directory of Open Access Journals (Sweden)
Issa Batarseh
2009-08-01
Full Text Available The interactive technical electronic book, TechEBook, currently under development at the University of Central Florida, provides a useful tool for engineers and scientists through unique features compared to the most used traditional electrical circuit textbooks available in the market. TechEBook has comprised the two worlds of classical circuit books and an interactive operating platform such as laptops and desktops utilizing Java Virtual Machine operator. The TechEBook provides an interactive applets screen that holds many modules, in which each had a specific application in the self learning process. This paper describes one of the interactive techniques in the TechEBook known as, QuizMe, for evaluating the readers’ performance and the overall understanding for all subjects at any stage. The QuizMe will be displayed after each section in the TechEBook for the user to evaluate his/her understanding, which introduces the term me-learning, as a comprehensive full experience for self or individualized education. In this paper, a practical example of applying the QuizMe feature is discussed as part of a basic electrical engineering course currently given at the University of Central Florida.
Integrated Electronic Microscopy Method to Characterize BWR Crud Deposits
International Nuclear Information System (INIS)
Pop, Mike G.; Lockamon, Brian; Howe, James M.; Oleshko, Vladimir P.
2007-01-01
The primary objective of this paper is to present the best combination of analytical Electron Microscopy (EM) techniques suited for studying Boiling Water Reactor (BWR) fuel crud deposits in their 'as found' condition, for example un-adulterated portions of the deposits located in crevices at the surface of deposit. The secondary objective of the paper is to suggest a strategy to connect the analytical EM results with the Power Diffraction File (PDF-4) crystal database to ultimately explain crystal growth phenomena in crevices. The samples analyzed as part of this work were collected from steam generators in Nuclear Power Plants. These samples were selected as segregates for BWR deposits due to their similar structures and because they were freely releasable for study in the University labs. The samples were analyzed extensively through various EM techniques at magnifications up to 150,000 X. Subsequent evaluation of the analysis results demonstrated that the selected samples exhibited characteristics that were very close to second-burned fuel crud deposits from operating BWR plants. (authors)
DePrince, A. Eugene; Mazziotti, David A.
2010-01-01
The parametric variational two-electron reduced-density-matrix (2-RDM) method is applied to computing electronic correlation energies of medium-to-large molecular systems by exploiting the spatial locality of electron correlation within the framework of the cluster-in-molecule (CIM) approximation [S. Li et al., J. Comput. Chem. 23, 238 (2002); J. Chem. Phys. 125, 074109 (2006)]. The 2-RDMs of individual molecular fragments within a molecule are determined, and selected portions of these 2-RDMs are recombined to yield an accurate approximation to the correlation energy of the entire molecule. In addition to extending CIM to the parametric 2-RDM method, we (i) suggest a more systematic selection of atomic-orbital domains than that presented in previous CIM studies and (ii) generalize the CIM method for open-shell quantum systems. The resulting method is tested with a series of polyacetylene molecules, water clusters, and diazobenzene derivatives in minimal and nonminimal basis sets. Calculations show that the computational cost of the method scales linearly with system size. We also compute hydrogen-abstraction energies for a series of hydroxyurea derivatives. Abstraction of hydrogen from hydroxyurea is thought to be a key step in its treatment of sickle cell anemia; the design of hydroxyurea derivatives that oxidize more rapidly is one approach to devising more effective treatments.
International Nuclear Information System (INIS)
Rebuffi, L.
1987-10-01
The development and optimization of a microwave technique, concerning the high frequency (electronic cyclotron frequency) plasma heating is presented. The experiments are effectuated on the Fontenay-aux-Roses TFR tokamak, with 660 kw whole power, during 100 msec, produced at 60 GHz. Low power tests are performed on the different transmission line components (there are 3, formed by metallic circular waveguides). The work also includes: the development of a lens formed by thin metallic plans; the study of slotted surface mirror; the development of a system for the accurate measurement (5.10 -6 ) of the gyrotronic frequency; a theory, based on the equivalent circuits method, generalized to the rotational and polarization mirrors; the development of a numerical simulation code. A practical scheme, for the optimization of the parameters concerning the optical transmission line project, is given. The results of this work can be applied to the experiment involving power levels, frequencies and times of impulsion increasingly higher (respectively about MW, 100 GHz and 10s) than the reported ones. Moreover, they can also be used in any experiment in the microwave field [fr
Synthesis method for using in the design of an electron gun for gyrotion
International Nuclear Information System (INIS)
Silva, C.A.B.
1987-09-01
In this work a synthesis method is applied to the design of an electron gun for a 94GHz gyrotron. Using the synthesis method, it is found the shape of the electrodes compatible with the laminar flow which minimizes the action of space change on the electron velocity dispersion. A sistematic procedure is presented to fuid the parameters of the synthesis method which, in turn, are closely related to the characteristics of the aptoclechonic system. (author) [pt
First-principles method for electron-phonon coupling and electron mobility
DEFF Research Database (Denmark)
Gunst, Tue; Markussen, Troels; Stokbro, Kurt
2016-01-01
of the problem and, importantly, it keeps the anisotropy information stored in the coupling as well as the band structure. In addition, we perform calculations of the low-field mobility and its dependence on carrier density and temperature to obtain a better understanding of transport in graphene, silicene......, clamping, or similar). If the out-of-plane interaction is not actively reduced, the mobility of silicene will essentially be zero. For MoS2, we obtain several orders of magnitude lower mobilities compared to graphene in agreement with other recent theoretical results. The simulations illustrate......We present density functional theory calculations of the phonon-limited mobility in n-type monolayer graphene, silicene, and MoS2. The material properties, including the electron-phonon interaction, are calculated from first principles. We provide a detailed description of the normalized full...
Wave propagation in electromagnetic media
Davis, Julian L
1990-01-01
This is the second work of a set of two volumes on the phenomena of wave propagation in nonreacting and reacting media. The first, entitled Wave Propagation in Solids and Fluids (published by Springer-Verlag in 1988), deals with wave phenomena in nonreacting media (solids and fluids). This book is concerned with wave propagation in reacting media-specifically, in electro magnetic materials. Since these volumes were designed to be relatively self contained, we have taken the liberty of adapting some of the pertinent material, especially in the theory of hyperbolic partial differential equations (concerned with electromagnetic wave propagation), variational methods, and Hamilton-Jacobi theory, to the phenomena of electromagnetic waves. The purpose of this volume is similar to that of the first, except that here we are dealing with electromagnetic waves. We attempt to present a clear and systematic account of the mathematical methods of wave phenomena in electromagnetic materials that will be readily accessi...
International Nuclear Information System (INIS)
Noda, Shoji; Ohta, Yasunari; Yoshida, Hiroshi
1979-01-01
The reactions of electrons injected by field emission into solutions have been investigated. Free radicals generated by the dissociative electron attachment to chlorinated solutes in benzene solutions were detected by the spin trapping-ESR method, using pentamethylnitrosobenzene as a spin trapping agent. Nondissociative electron attachment to styrene caused by the field emission was also evidenced by detecting the α-methylbenzyl radical generated secondarily from the styrene radical anion. The electrons field-emitted into the solutions are captured almost quantitatively by the electron scavenging solutes. The field emission method has been found to be useful for generating authentically free radicals and for studying the anionic reaction induced by electrons without interference of countercations and of any reaction intermediates from solvent molecules. As an example of the chemical utilization of the field emission technique, the ESR parameters of the spin adducts of several hydrocarbon radicals have been collected by this technique. (author)
Energy Technology Data Exchange (ETDEWEB)
Geloni, Gianluca; Ilinski, Petr; Saldin, Evgeni; Schneidmiller, Evgeni; Yurkov, Mikhail
2009-05-15
We describe a novel technique to characterize ultrashort electron bunches in Xray Free-Electron Lasers. Namely, we propose to use coherent Optical Transition Radiation to measure three-dimensional (3D) electron density distributions. Our method relies on the combination of two known diagnostics setups, an Optical Replica Synthesizer (ORS) and an Optical Transition Radiation (OTR) imager. Electron bunches are modulated at optical wavelengths in the ORS setup.When these electron bunches pass through a metal foil target, coherent radiation pulses of tens MW power are generated. It is thereafter possible to exploit advantages of coherent imaging techniques, such as direct imaging, diffractive imaging, Fourier holography and their combinations. The proposed method opens up the possibility of real-time, wavelength-limited, single-shot 3D imaging of an ultrashort electron bunch. (orig.)
Application of Macro Response Monte Carlo method for electron spectrum simulation
International Nuclear Information System (INIS)
Perles, L.A.; Almeida, A. de
2007-01-01
During the past years several variance reduction techniques for Monte Carlo electron transport have been developed in order to reduce the electron computation time transport for absorbed dose distribution. We have implemented the Macro Response Monte Carlo (MRMC) method to evaluate the electron spectrum which can be used as a phase space input for others simulation programs. Such technique uses probability distributions for electron histories previously simulated in spheres (called kugels). These probabilities are used to sample the primary electron final state, as well as the creation secondary electrons and photons. We have compared the MRMC electron spectra simulated in homogeneous phantom against the Geant4 spectra. The results showed an agreement better than 6% in the spectra peak energies and that MRMC code is up to 12 time faster than Geant4 simulations
Calculating the SnS(010) surface electronic structure using the green function method
Jahangirli, Z. A.
2011-08-01
The electronic structure of the (010) surface in a layered SnS semiconductor terminating with Sn and S atomic planes is calculated by the Green function method. The electronic structure of a perfect crystal is calculated according to the linear combination of atomic orbitals (LCAO) using Slater s-, p-, and d-orbitals. Defect-induced changes in the density of states and the origin and orbital composition of electronic states in the band gap are discussed.
International Nuclear Information System (INIS)
Visbal, Jorge H. Wilches; Costa, Alessandro M.
2016-01-01
Percentage depth dose of electron beams represents an important item of data in radiation therapy treatment since it describes the dosimetric properties of these. Using an accurate transport theory, or the Monte Carlo method, has been shown obvious differences between the dose distribution of electron beams of a clinical accelerator in a water simulator object and the dose distribution of monoenergetic electrons of nominal energy of the clinical accelerator in water. In radiotherapy, the electron spectra should be considered to improve the accuracy of dose calculation since the shape of PDP curve depends of way how radiation particles deposit their energy in patient/phantom, that is, the spectrum. Exist three principal approaches to obtain electron energy spectra from central PDP: Monte Carlo Method, Direct Measurement and Inverse Reconstruction. In this work it will be presented the Simulated Annealing method as a practical, reliable and simple approach of inverse reconstruction as being an optimal alternative to other options. (author)
International Nuclear Information System (INIS)
Picard, R.R.
1989-01-01
Topics covered in this chapter include a discussion of exact results as related to nuclear materials management and accounting in nuclear facilities; propagation of error for a single measured value; propagation of error for several measured values; error propagation for materials balances; and an application of error propagation to an example of uranium hexafluoride conversion process
Bourlier, Christophe; Pinel, Nicolas; Kubické, Gildas
2013-09-01
In this article, the fields scattered by coated cylinders, a rough layer, and an object below a rough surface are computed by the efficient propagation-inside-layer-expansion (PILE) method combined with the physical optics (PO) approximation to accelerate the calculation of the local interactions on the non-illuminated scatterer, which is assumed to be perfectly conducting. The PILE method is based on the method of moments, and the impedance matrix of the two scatterers is then inverted by blocks from a Taylor series expansion of the inverse of the Schur complement. Its main interest is that it is rigorous, with a simple formulation and a straightforward physical interpretation. In addition, one of the advantages of PILE is to be able to hybridize methods (rigorous or asymptotic) valid for a single scatterer. Then, in high frequencies, the hybridization with PO allows us to significantly reduce the complexity in comparison to a direct lower-upper inversion of the impedance matrix of the two scatterers without loss in accuracy.
Energy Technology Data Exchange (ETDEWEB)
Sidler, Rolf, E-mail: rsidler@gmail.com [Center for Research of the Terrestrial Environment, University of Lausanne, CH-1015 Lausanne (Switzerland); Carcione, José M. [Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42c, 34010 Sgonico, Trieste (Italy); Holliger, Klaus [Center for Research of the Terrestrial Environment, University of Lausanne, CH-1015 Lausanne (Switzerland)
2013-02-15
We present a novel numerical approach for the comprehensive, flexible, and accurate simulation of poro-elastic wave propagation in 2D polar coordinates. An important application of this method and its extensions will be the modeling of complex seismic wave phenomena in fluid-filled boreholes, which represents a major, and as of yet largely unresolved, computational problem in exploration geophysics. In view of this, we consider a numerical mesh, which can be arbitrarily heterogeneous, consisting of two or more concentric rings representing the fluid in the center and the surrounding porous medium. The spatial discretization is based on a Chebyshev expansion in the radial direction and a Fourier expansion in the azimuthal direction and a Runge–Kutta integration scheme for the time evolution. A domain decomposition method is used to match the fluid–solid boundary conditions based on the method of characteristics. This multi-domain approach allows for significant reductions of the number of grid points in the azimuthal direction for the inner grid domain and thus for corresponding increases of the time step and enhancements of computational efficiency. The viability and accuracy of the proposed method has been rigorously tested and verified through comparisons with analytical solutions as well as with the results obtained with a corresponding, previously published, and independently benchmarked solution for 2D Cartesian coordinates. Finally, the proposed numerical solution also satisfies the reciprocity theorem, which indicates that the inherent singularity associated with the origin of the polar coordinate system is adequately handled.
FX-25 and FX-100 Propagation Experiments.
1982-07-01
TECHNICAL DETAILS 1. FX-100 Accelerator The FX-IO0 accelerator was a gas-insulated coaxial transmission line that was DC charged with a Van de Graaff ...physics of intense relativistic electron-beam propagation in low-density air is in pro- gress using beam generators at the Air Force Weapons Laboratory...experiments to investigate the physics of intense relativistic electron-beam propagation in low-density air is in progress using beam generators at the
Statistical Methods for Single-Particle Electron Cryomicroscopy
DEFF Research Database (Denmark)
Jensen, Katrine Hommelhoff
, several randomly oriented copies of the protein are available, each representing a certain viewing direction of the structure. This implies two main computational problems: (1) to determine the angular relationship between the individual projection images, i.e. determine the protein pose in each view...... from the noisy, randomly oriented projection images. Many statistical approaches to SPR have been proposed in the past. Typically, due to the computation time complexity, they rely on approximated maximum likelihood (ML) or maximum a posteriori (MAP) estimate of the structure. All methods presented...... statistical inversion to optimally cope with the high amount of noise, as well as to incorporate prior information to obtain more reliable estimates. For the first problem, we investigate the statistical recovery of the geometry between a set of projection images. In more detail, we show the equivalence...
Apparatus and methods for controlling electron microscope stages
Duden, Thomas
2015-08-11
Methods and apparatus for generating an image of a specimen with a microscope (e.g., TEM) are disclosed. In one aspect, the microscope may generally include a beam generator, a stage, a detector, and an image generator. A plurality of crystal parameters, which describe a plurality of properties of a crystal sample, are received. In a display associated with the microscope, an interactive control sphere based at least in part on the received crystal parameters and that is rotatable by a user to different sphere orientations is presented. The sphere includes a plurality of stage coordinates that correspond to a plurality of positions of the stage and a plurality of crystallographic pole coordinates that correspond to a plurality of polar orientations of the crystal sample. Movement of the sphere causes movement of the stage, wherein the stage coordinates move in conjunction with the crystallographic coordinates represented by pole positions so as to show a relationship between stage positions and the pole positions.
Radio wave propagation and parabolic equation modeling
Apaydin, Gokhan
2018-01-01
A thorough understanding of electromagnetic wave propagation is fundamental to the development of sophisticated communication and detection technologies. The powerful numerical methods described in this book represent a major step forward in our ability to accurately model electromagnetic wave propagation in order to establish and maintain reliable communication links, to detect targets in radar systems, and to maintain robust mobile phone and broadcasting networks. The first new book on guided wave propagation modeling and simulation to appear in nearly two decades, Radio Wave Propagation and Parabolic Equation Modeling addresses the fundamentals of electromagnetic wave propagation generally, with a specific focus on radio wave propagation through various media. The authors explore an array of new applications, and detail various v rtual electromagnetic tools for solving several frequent electromagnetic propagation problems. All of the methods described are presented within the context of real-world scenari...
Cupillard, Paul; Delavaud, Elise; Burgos, Gaël.; Festa, Geatano; Vilotte, Jean-Pierre; Capdeville, Yann; Montagner, Jean-Paul
2012-03-01
The spectral element method, which provides an accurate solution of the elastodynamic problem in heterogeneous media, is implemented in a code, called RegSEM, to compute seismic wave propagation at the regional scale. By regional scale we here mean distances ranging from about 1 km (local scale) to 90° (continental scale). The advantage of RegSEM resides in its ability to accurately take into account 3-D discontinuities such as the sediment-rock interface and the Moho. For this purpose, one version of the code handles local unstructured meshes and another version manages continental structured meshes. The wave equation can be solved in any velocity model, including anisotropy and intrinsic attenuation in the continental version. To validate the code, results from RegSEM are compared to analytical and semi-analytical solutions available in simple cases (e.g. explosion in PREM, plane wave in a hemispherical basin). In addition, realistic simulations of an earthquake in different tomographic models of Europe are performed. All these simulations show the great flexibility of the code and point out the large influence of the shallow layers on the propagation of seismic waves at the regional scale. RegSEM is written in Fortran 90 but it also contains a couple of C routines. It is an open-source software which runs on distributed memory architectures. It can give rise to interesting applications, such as testing regional tomographic models, developing tomography using either passive (i.e. noise correlations) or active (i.e. earthquakes) data, or improving our knowledge on effects linked with sedimentary basins.
A dynamic scanning method based on signal-statistics for scanning electron microscopy.
Timischl, F
2014-01-01
A novel dynamic scanning method for noise reduction in scanning electron microscopy and related applications is presented. The scanning method dynamically adjusts the scanning speed of the electron beam depending on the statistical behavior of the detector signal and gives SEM images with uniform and predefined standard deviation, independent of the signal value itself. In the case of partially saturated images, the proposed method decreases image acquisition time without sacrificing image quality. The effectiveness of the proposed method is shown and compared to the conventional scanning method and median filtering using numerical simulations. © 2013 Wiley Periodicals, Inc.
SU-F-T-71: A Practical Method for Evaluation of Electron Virtual Source Position
International Nuclear Information System (INIS)
Huang, Z; Jiang, W; Stuart, B; Leu, S; Feng, Y; Liu, T
2016-01-01
Purpose: Since electrons are easily scattered, the virtual source position for electrons is expected to locate below the x-ray target of Medical Linacs. However, the effective SSD method yields the electron virtual position above the x-ray target for some applicators for some energy in Siemens Linacs. In this study, we propose to use IC Profiler (Sun Nuclear) for evaluating the electron virtual source position for the standard electron applicators for various electron energies. Methods: The profile measurements for various nominal source-to-detector distances (SDDs) of 100–115 cm were carried out for electron beam energies of 6–18 MeV. Two methods were used: one was to use a 0.125 cc ion chamber (PTW, Type 31010) with buildup mounted in a PTW water tank without water filled; and the other was to use IC Profiler with a buildup to achieve charge particle equilibrium. The full width at half-maximum (FWHM) method was used to determine the field sizes for the measured profiles. Backprojecting (by a straight line) the distance between the 50% points on the beam profiles for the various SDDs, yielded the virtual source position for each applicator. Results: The profiles were obtained and the field sizes were determined by FWHM. The virtual source positions were determined through backprojection of profiles for applicators (5, 10, 15, 20, 25). For instance, they were 96.415 cm (IC Profiler) vs 95.844 cm (scanning ion chamber) for 9 MeV electrons with 10×10 cm applicator and 97.160 cm vs 97.161 cm for 12 MeV electrons with 10×10 cm applicator. The differences in the virtual source positions between IC profiler and scanning ion chamber were within 1.5%. Conclusion: IC Profiler provides a practical method for determining the electron virtual source position and its results are consistent with those obtained by profiles of scanning ion chamber with buildup.
The Measurement of Electron-Induced Erosion of Condensed Gases: Experimental Methods
DEFF Research Database (Denmark)
Schou, Jørgen; Sørensen, H.; Børgesen, P.
1984-01-01
Two experimental methods for measuring the erosion yield of condensed gases are described. One, the frequency-change method, utilizes a quartz-crystal microbalance operating at liquid-helium temperature. The other, the emissivity-change method is based on the strongly varying electron emission...... as a function of the condensed-gas film thickness. Satisfactory results have been obtained for both methods for solid Ne and D2 at electron energies up to 3 keV, and the mutual agreement is good as well. Accurate measurements are affected critically by the beam conditions, particularly if the erosion yield...... depends on the film thickness. The erosion yield has been measured for dominant electron sputtering of solid Ne ( ≈ 28 Ne-atoms/electron) as well as for beam-induced evaporation at 2 keV. In the latter case a clear lateral broadening of the erosion spot is observed....
Organizational-methodical provisions for the audit of operations with electronic money
Directory of Open Access Journals (Sweden)
Semenetz A.P.
2017-06-01
Full Text Available To obtain objective and unbiased information about the accuracy and completeness of electronic money transactions at the enterprise, it is necessary to conduct an audit. The results of the external audit of electronic money transactions help the company’s management personnel to assess the efficiency and rationality of using such a modern means of payment, such as electronic money, as well as verify the proper functioning of the internal control service. The work substantiates organizational and methodical provisions of the process of conducting an external audit of transactions with electronic money in terms of clarifying the organizational provisions for conducting an audit of transactions with electronic money, namely the definition of the purpose, task, subjects and objects of audit and sources of information. Accordingly, the purpose of the audit of operations with electronic money is to provide the auditor’s unbiased opinion on the reliability of the financial statements of the enterprise in terms of operations with electronic money. Within the scope of this dissertation, the object of external audit is operations with electronic money, since electronic money is a new and contemporary object of accounting, and therefore the development of scientifically grounded order of conducting external audit of the investigated object is necessary. The subject of an external audit of electronic money transactions is a set of business transactions in electronic money settlements, that is, transactions with their acquisition and repayment and the accuracy of displaying information about them in the financial statements. In the course of the study, the procedure for the implementation of external audit procedures during the stages of the process of electronic money audit at the enterprise was determined, which allowed to confirm the correctness of the accounting of a new and modern means of payment such as electronic money. These proposals are aimed
DEFF Research Database (Denmark)
Eriksen, Janus J.; Sauer, Stephan P. A.; Mikkelsen, Kurt Valentin
2012-01-01
picture leading to the PE-Random-Phase Approximation (PE-RPA) and bridge the expressions to a Second-Order Polarization Propagator Approximation (SOPPA) frame such that dynamic reaction field contributions are included at the RPA level in addition to the static response described at the SOPPA level...... but with HF induced dipole moments. We conduct calculations on para-nitro-aniline and para-nitro-phenolate using said model in addition to dynamic PE-RPA and PE-CAM-B3LYP. We compare the results to recently published PE-CCSD data and demonstrate how the cost effective SOPPA based model successfully recovers...... a great portion of the inherent PE-RPA error when the observable is the solvatochromic shift. We furthermore demonstrate that whenever the change in density resulting from the ground state-excited state electronic transition in the solute is not associated with a significant change in the electric field...
Directory of Open Access Journals (Sweden)
Yu Fan
2017-02-01
Full Text Available As a promising numerical tool of structural dynamics in mid- and high frequencies, the wave and finite element method (WFEM is receiving increasingly attention and applications. In this paper, an enhanced WFEM has been developed with a reduced model and a new eigenvalue scheme. The reduced model is applicable for structures with piezoelectric shunts or local dampers; the new eigenvalue scheme can mitigate the ill-conditioning when the wave basis is calculated. The enhanced WFEM is applied to a thin-wall structure with periodically distributed piezoelectric materials (PZT. Both free wave characteristics and forced response are analyzed and the influences of the suggested enhancements are presented. It is shown that if the control factors are properly chosen, these enhancements can improve the accuracy while accelerating the calculation. Resulting from the complexity of the application, these enhancements are not optional but imperative.
International Nuclear Information System (INIS)
Fernandez, L; Fernandez, G.E; Bertolino, G; Meyer, G
2001-01-01
The study of mechanical properties degradation of zirconium alloys due to hydrides assumes fundamental importance in the nuclear industry.During normal nuclear reactors operation, structural parts absorbed hydrogen generated from radiolysis of water, causing detrimental effects on mechanical properties.As a consequence, these materials are easily cracked in the presence of mechanical solicitation due to loss of ductility of the hydride-phase.The presence of cracks indicates fracture mechanic as the most suitable methodology in the study of mechanical properties degradation.In this work we used the crack tip opening displacement (CTOD) criteria to evaluate the detrimental effects on mechanical properties with the observation in SEM of crack propagation.The samples used were SEN (B) of Zry-4 and cathodic homogenous charged with hydrogen concentrations lower than 400 ppm
Efficient k⋅p method for the calculation of total energy and electronic density of states
Iannuzzi, Marcella; Parrinello, Michele
2001-01-01
An efficient method for calculating the electronic structure in large systems with a fully converged BZ sampling is presented. The method is based on a k.p-like approximation developed in the framework of the density functional perturbation theory. The reliability and efficiency of the method are demostrated in test calculations on Ar and Si supercells
A comparative study of different methods for calculating electronic transition rates
Kananenka, Alexei A.; Sun, Xiang; Schubert, Alexander; Dunietz, Barry D.; Geva, Eitan
2018-03-01
We present a comprehensive comparison of the following mixed quantum-classical methods for calculating electronic transition rates: (1) nonequilibrium Fermi's golden rule, (2) mixed quantum-classical Liouville method, (3) mean-field (Ehrenfest) mixed quantum-classical method, and (4) fewest switches surface-hopping method (in diabatic and adiabatic representations). The comparison is performed on the Garg-Onuchic-Ambegaokar benchmark charge-transfer model, over a broad range of temperatures and electronic coupling strengths, with different nonequilibrium initial states, in the normal and inverted regimes. Under weak to moderate electronic coupling, the nonequilibrium Fermi's golden rule rates are found to be in good agreement with the rates obtained via the mixed quantum-classical Liouville method that coincides with the fully quantum-mechanically exact results for the model system under study. Our results suggest that the nonequilibrium Fermi's golden rule can serve as an inexpensive yet accurate alternative to Ehrenfest and the fewest switches surface-hopping methods.
Shahid, A.; Zhou, Z.; Bhatti, M. M.; Tripathi, D.
2018-03-01
Nanofluid dynamics with magnetohydrodynamics has tremendously contributed in industrial applications recently since presence of nanoparticle in base fluids enhances the specific chemical and physical properties. Owing to the relevance of nanofluid dynamics, we analyze the nanofluid flow in the presence of gyrotactic microorganism and magnetohydrodynamics through a stretching/shrinking plate. The impacts of chemical reaction and thermal radiation on flow characteristics are also studied. To simplify the governing equations of microorganisms, velocity, concentration and temperature, the similarity transformations are employed. The couple governing equations are numerically solved using Successive Taylor Series Linearization Method (STSLM). The velocity profile, motile microorganism density profile, concentration profile, temperature profile as well as Nusselt number, skin friction coefficient, Sherwood number and density number of motile microorganisms are discussed using tables and graphs against all the sundry parameters. A numerical comparison is also given for Nusselt number, Sherwood number, skin friction, and density number of motile microorganisms with previously published results to validate the present model. The results show that Nusselt number, Sherwood number and density number diminish with increasing the magnetic field effects.
Faria, Luiz; Rosales, Rodolfo
2017-11-01
We introduce an alternative to the method of matched asymptotic expansions. In the ``traditional'' implementation, approximate solutions, valid in different (but overlapping) regions are matched by using ``intermediate'' variables. Here we propose to match at the level of the equations involved, via a ``uniform expansion'' whose equations enfold those of the approximations to be matched. This has the advantage that one does not need to explicitly solve the asymptotic equations to do the matching, which can be quite impossible for some problems. In addition, it allows matching to proceed in certain wave situations where the traditional approach fails because the time behaviors differ (e.g., one of the expansions does not include dissipation). On the other hand, this approach does not provide the fairly explicit approximations resulting from standard matching. In fact, this is not even its aim, which to produce the ``simplest'' set of equations that capture the behavior. Ruben Rosales work was partially supported by NSF Grants DMS-1614043 and DMS-1719637.
The application of the phase space time evolution method to electron shielding
Cordaro, M. C.; Zucker, M. S.
1972-01-01
A computer technique for treating the motion of charged and neutral particles and called the phase space time evolution method was developed. This technique employs the computer's bookkeeping capacity to keep track of the time development of a phase space distribution of particles. This method was applied to a study of the penetration of electrons. A 1 MeV beam of electrons normally incident on a semi-infinite slab of aluminum was used. Results of the calculation were compared with Monte Carlo calculations and experimental results. Time-dependent PSTE electron penetration results for the same problem are presented.
Weatherford, C. A.; Onda, K.; Temkin, A.
1985-01-01
The noniterative partial-differential-equation (PDE) approach to electron-molecule scattering of Onda and Temkin (1983) is modified to account for the effects of exchange explicitly. The exchange equation is reduced to a set of inhomogeneous equations containing no integral terms and solved noniteratively in a difference form; a method for propagating the solution to large values of r is described; the changes in the polarization potential of the original PDE method required by the inclusion of exact static exchange are indicated; and the results of computations for e-N2 scattering in the fixed-nuclei approximation are presented in tables and graphs and compared with previous calculations and experimental data. Better agreement is obtained using the modified PDE method.
Bruschi, Maurizio; Giuffreda, Maria Grazia; Lüthi, Hans Peter
2002-09-16
trans-Diethynylethene [(E)-hex-3-ene-1,5-diyne (1 a)], geminal-diethynylethene [3-ethynyl-but-3-ene-1-yne (1 b)], and tetraethynylethene [3,4-diethynyl-hex-3-ene-1,5-diyne (2)] are flexible molecular building blocks for pi-conjugated polymers with interesting electronic and photonic properties. The type of functionalization, the length of the polymer chain, and the choice of pi-conjugation pattern, play a crucial role in determining the properties of these compounds. To rationalize the impact of the different delocalization pathways in the various types of isomers (trans or geminal) on the molecular and electronic structure, a detailed theoretical investigation is presented. We develop a method based on the natural bond orbital (NBO) analysis of Weinhold, which allows one to correlate electron delocalization with molecular and electronic structure observables. The method reveals that the difference between trans (or through) and geminal (or cross) conjugation is not only due to the vertical pi conjugation, but also to the in-plane sigma hyperconjugation. The method is used to correlate the changes in molecular and electronic observables, such as the bond lengths or the absorption frequencies, with the electronic structure of the compounds under investigation. Moreover, this method allows us to predict how a certain substituent will affect the molecular structure and the electronic properties of a given backbone.
International Nuclear Information System (INIS)
Zunger, A.
1975-07-01
Semiempirical all-valence-electron LCAO methods, that were previously used to study the electronic structure of molecules are applied to three problems in solid state physics: the electronic band structure of covalent crystals, point defect problems in solids and lattice dynamical study of molecular crystals. Calculation methods for the electronic band structure of regular solids are introduced and problems regarding the computation of the density matrix in solids are discussed. Three models for treating the electronic eigenvalue problem in the solid, within the proposed calculation schemes, are discussed and the proposed models and calculation schemes are applied to the calculation of the electronic structure of several solids belonging to different crystal types. The calculation models also describe electronic properties of deep defects in covalent insulating crystals. The possible usefulness of the semieipirical LCAO methods in determining the first order intermolecular interaction potential in solids and an improved model for treating the lattice dynamics and related thermodynamical properties of molecular solids are presented. The improved lattice dynamical is used to compute phonon dispersion curves, phonon density of states, stable unit cell structure, lattice heat capacity and thermal crystal parameters, in α and γ-N 2 crystals, using the N 2 -N 2 intermolecular interaction potential that has been computed from the semiempirical LCAO methods. (B.G.)
Kandel, Yudhishthir; Denbeaux, Gregory
2016-08-01
We develop a novel iterative method to accurately measure electron beam shape (current density distribution) and monotonic material response as a function of position. A common method is to scan an electron beam across a knife edge along many angles to give an approximate measure of the beam profile, however such scans are not easy to obtain in all systems. The present work uses only an electron beam and multiple exposed regions of a thin film of photoresist to measure the complete beam profile for any beam shape, where the material response is characterized externally. This simplifies the setup of new experimental tools. We solve for self-consistent photoresist thickness loss response to dose and the electron beam profile simultaneously by optimizing a novel functional iteratively. We also show the successful implementation of the method in a real world data set corrupted by noise and other experimental variabilities.
Advances in imaging and electron physics
Mulvey, Tom
1995-01-01
Academic Press is pleased to announce the creation of Advances in Imaging and Electron Physics. This serial publication results from the merger of two long-running serials--Advances in Electronics and Electron Physics and Advances in Optical & Electron Microscopy. Advances in Imaging & Electron Physics will feature extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies,microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains.
Advances in imaging and electron physics
Hawkes, Peter W
1995-01-01
Academic Press is pleased to announce the creation of Advances in Imaging and Electron Physics. This serial publication results from the merger of two long running serials--Advances in Electronics and Electron Physics and Advances in Optical & Electron Microscopy. Advances in Imaging & Electron Physics will feature extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies,microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains. Continuation order customers for either of the original Advances will receiveVolume 90, the first combined volume.
Krylov subspace method for evaluating the self-energy matrices in electron transport calculations
DEFF Research Database (Denmark)
Sørensen, Hans Henrik Brandenborg; Hansen, Per Christian; Petersen, D. E.
2008-01-01
We present a Krylov subspace method for evaluating the self-energy matrices used in the Green's function formulation of electron transport in nanoscale devices. A procedure based on the Arnoldi method is employed to obtain solutions of the quadratic eigenvalue problem associated with the infinite...... calculations. Numerical tests within a density functional theory framework are provided to validate the accuracy and robustness of the proposed method, which in most cases is an order of magnitude faster than conventional methods....
A new method of testing space-based high-energy electron detectors with radioactive electron sources
International Nuclear Information System (INIS)
Zhang, S.Y.; Shen, G.H.; Sun, Y.; Zhou, D.Z.; Zhang, X.X.; Li, J.W.; Huang, C.; Zhang, X.G.; Dong, Y.J.; Zhang, W.J.; Zhang, B.Q.; Shi, C.Y.
2016-01-01
Space-based electron detectors are commonly tested using radioactive β-sources which emit a continuous spectrum without spectral lines. Therefore, the tests are often to be considered only qualitative. This paper introduces a method, which results in more than a qualitative test even when using a β-source. The basic idea is to use the simulated response function of the instrument to invert the measured spectrum and compare this inverted spectrum with a reference spectrum obtained from the same source. Here we have used Geant4 to simulate the instrument response function (IRF) and a 3.5 mm thick Li-drifted Si detector to obtain the reference 90 Sr/ 90 Yi source spectrum to test and verify the geometric factors of the Omni-Direction Particle Detector (ODPD) on the Tiangong-1 (TG-1) and Tiangong-2 (TG-2) spacecraft. The TG spacecraft are experimental space laboratories and prototypes of the Chinese space station. The excellent agreement between the measured and reference spectra demonstrates that this test method can be used to quantitatively assess the quality of the instrument. Due to its simplicity, the method is faster and therefore more efficient than traditional full calibrations using an electron accelerator.
Quantum chemistry the development of ab initio methods in molecular electronic structure theory
Schaefer III, Henry F
2004-01-01
This guide is guaranteed to prove of keen interest to the broad spectrum of experimental chemists who use electronic structure theory to assist in the interpretation of their laboratory findings. A list of 150 landmark papers in ab initio molecular electronic structure methods, it features the first page of each paper (which usually encompasses the abstract and introduction). Its primary focus is methodology, rather than the examination of particular chemical problems, and the selected papers either present new and important methods or illustrate the effectiveness of existing methods in predi
Methods of organization of SCORM-compliant teaching materials in electronic format
Directory of Open Access Journals (Sweden)
Jacek Marciniak
2012-06-01
Full Text Available This paper presents a method of organizing electronic teaching materials based on their role in the teaching process rather than their technical structure. Our method allows SCORM materials stored as e-learning courses („electronic books” to be subdivided and structured so that content can be used in multiple contexts. As a standard, SCORM defines rules for organizing content, but not how to divide and structure it. Our method uses UCTS nomenclature to divide content, define relationships between content entities, and aggregate those entities into courses. This allows content to be shared in different implementations of SCORM while guaranteeing that usability and consistency are maintained.
A modified method of calculating the lateral build-up ratio for small electron fields
International Nuclear Information System (INIS)
Tyner, E; McCavana, P; McClean, B
2006-01-01
This note outlines an improved method of calculating dose per monitor unit values for small electron fields using Khan's lateral build-up ratio (LBR). This modified method obtains the LBR directly from the ratio of measured, surface normalized, electron beam percentage depth dose curves. The LBR calculated using this modified method more accurately accounts for the change in lateral scatter with decreasing field size. The LBR is used along with Khan's dose per monitor unit formula to calculate dose per monitor unit values for a set of small fields. These calculated dose per monitor unit values are compared to measured values to within 3.5% for all circular fields and electron energies examined. The modified method was further tested using a small triangular field. A maximum difference of 4.8% was found. (note)
Modern map methods in particle beam physics
Berz, Martin
1999-01-01
Advances in Imaging & Electron Physics merges two long-running serials--Advances in Electronics & Electron Physics and Advances in Optical & Electron Microscopy. The series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains.
DEFF Research Database (Denmark)
Scharff, Annemette Bruselius; Jørgensen, Lise Bolt
2017-01-01
Transmission electron microscopy (TEM) was investigated to clarify the applicability of the method for assessing the condition of archaeological textiles from waterlogged environments. A description and evaluation of the TEM protocol is presented and the method was tested on new and artificially...
Methods of measurements on incidental X-radiation from electron tubes
International Nuclear Information System (INIS)
1977-01-01
The standard describes the method for detection of x-radiation and the method for the direct and indirect measurement of field pattern and exposure rate of random incidental radiation emanating from high voltage electron tubes. Required apparatus and calibration procedure for the exposure rate meter or film mount are described. (M.G.B.)
Topology optimization of wave-propagation problems
DEFF Research Database (Denmark)
Jensen, Jakob Søndergaard; Sigmund, Ole
2006-01-01
Topology optimization is demonstrated as a useful tool for systematic design of wave-propagation problems. We illustrate the applicability of the method for optical, acoustic and elastic devices and structures.......Topology optimization is demonstrated as a useful tool for systematic design of wave-propagation problems. We illustrate the applicability of the method for optical, acoustic and elastic devices and structures....
Mondal, Puskar; Korenaga, Jun
2018-03-01
The dispersion relation of the Rayleigh-Taylor instability, a gravitational instability associated with unstable density stratification, is of profound importance in various geophysical contexts. When more than two layers are involved, a semi-analytical technique based on the biharmonic formulation of Stokes flow has been extensively used to obtain such dispersion relation. However, this technique may become cumbersome when applied to lithospheric dynamics, where a number of layers are necessary to represent the continuous variation of viscosity over many orders of magnitude. Here, we present an alternative and more efficient method based on the propagator matrix formulation of Stokes flow. With this approach, the original instability problem is reduced to a compact eigenvalue equation whose size is solely determined by the number of primary density contrasts. We apply this new technique to the stability of the early crust, and combined with the Monte Carlo sensitivity analysis, we derive an empirical formula to compute the growth rate of the Rayleigh-Taylor instability for this particular geophysical setting. Our analysis indicates that the likelihood of crustal delamination hinges critically on the effective viscosity of eclogite.
Stochastic and epistemic uncertainty propagation in LCA
DEFF Research Database (Denmark)
Clavreul, Julie; Guyonnet, Dominique; Tonini, Davide
2013-01-01
When performing uncertainty propagation, most LCA practitioners choose to represent uncertainties by single probability distributions and to propagate them using stochastic methods. However, the selection of single probability distributions appears often arbitrary when faced with scarce information...... manner and apply it to LCA. A case study is used to show the uncertainty propagation performed with the proposed method and compare it to propagation performed using probability and possibility theories alone.Basic knowledge on the probability theory is first recalled, followed by a detailed description...
Nagy, Péter R.; Surján, Péter R.; Szabados, Ágnes
2014-01-01
Cross sections of inelastic light scattering accompanied by vibronic excitation in large conjugated carbon structures is assessed at the π-electron level. Intensities of Raman and vibrational Raman optical activity (VROA) spectra of fullerenes are computed, relying on a single electron per atom. When considering only first neighbor terms in the Hamiltonian (a tight-binding (TB) type or Hückel-model), Raman intensities are captured remarkably well, based on comparison with frequency-dependent linear response of the self-consistent field (SCF) method. Resorting to π-electron levels when computing spectral intensities brings a beneficial reduction in computational cost as compared to linear response SCF. At difference with total intensities, the first neighbor TB model is found inadequate for giving the left and right circularly polarized components of the scattered light, especially when the molecular surface is highly curved. To step beyond first neighbor approximation, an effective π-electron Hamiltonian, including interaction of all sites is derived from the all-electron Fockian, in the spirit of the Bloch-equation. Chiroptical cross-sections computed by this novel π-electron method improve upon first-neighbor TB considerably, with no increase in computational cost. Computed VROA spectra of chiral fullerenes, such as C76 and C28, are reported for the first time, both by conventional linear response SCF and effective π-electron models.
Method of synthesizing small-diameter carbon nanotubes with electron field emission properties
Liu, Jie (Inventor); Du, Chunsheng (Inventor); Qian, Cheng (Inventor); Gao, Bo (Inventor); Qiu, Qi (Inventor); Zhou, Otto Z. (Inventor)
2009-01-01
Carbon nanotube material having an outer diameter less than 10 nm and a number of walls less than ten are disclosed. Also disclosed are an electron field emission device including a substrate, an optionally layer of adhesion-promoting layer, and a layer of electron field emission material. The electron field emission material includes a carbon nanotube having a number of concentric graphene shells per tube of from two to ten, an outer diameter from 2 to 8 nm, and a nanotube length greater than 0.1 microns. One method to fabricate carbon nanotubes includes the steps of (a) producing a catalyst containing Fe and Mo supported on MgO powder, (b) using a mixture of hydrogen and carbon containing gas as precursors, and (c) heating the catalyst to a temperature above 950.degree. C. to produce a carbon nanotube. Another method of fabricating an electron field emission cathode includes the steps of (a) synthesizing electron field emission materials containing carbon nanotubes with a number of concentric graphene shells per tube from two to ten, an outer diameter of from 2 to 8 nm, and a length greater than 0.1 microns, (b) dispersing the electron field emission material in a suitable solvent, (c) depositing the electron field emission materials onto a substrate, and (d) annealing the substrate.
Energy Technology Data Exchange (ETDEWEB)
Glinec, Y
2006-09-15
This experimental study concerns the generation of electron beams with original properties. These electrons beams originate from the interaction of an ultra-intense and short laser pulse with a gas jet. Previously, these electron beams had a large divergence and a broad spectrum. A major improvement in this field was achieved when an electron beam with low divergence (10 mrad) and a peaked spectrum (170 MeV) was observed during this thesis, using a new single shot electron spectrometer. A parametric study of the interaction allowed to observe the evolution of the electron beam. Experiments have been carried out to deepen the characterization of the electron beam. The observation of transition radiation generated by the electrons at an interface shows that the electron beam interacts with the laser pulse during the acceleration. Radial oscillations of the electron beam around the laser axis, named betatron oscillations, were also observed on the electron spectra. Such a quasi-monoenergetic spectrum is essential for many applications. In order to justify the interest of this electron beam, several applications are presented: a sub-milli-metric gamma-ray radiography of dense objects, a dose profile of the electron beam comparable to present capabilities of photon sources for radiotherapy, a very short temporal profile useful for water radiolysis and the generation of a bright X-ray source with low divergence. (author)
A Fast Classification Method of Faults in Power Electronic Circuits Based on Support Vector Machines
Cui Jiang; Shi Ge; Gong Chunying
2017-01-01
Fault detection and location are important and front-end tasks in assuring the reliability of power electronic circuits. In essence, both tasks can be considered as the classification problem. This paper presents a fast fault classification method for power electronic circuits by using the support vector machine (SVM) as a classifier and the wavelet transform as a feature extraction technique. Using one-against-rest SVM and one-against-one SVM are two general approaches to fault classificatio...
International Nuclear Information System (INIS)
Kolkoori, Sanjeevareddy
2014-01-01
Austenitic welds and dissimilar welds are extensively used in primary circuit pipes and pressure vessels in nuclear power plants, chemical industries and fossil fuelled power plants because of their high fracture toughness, resistance to corrosion and creep at elevated temperatures. However, cracks may initiate in these weld materials during fabrication process or stress operations in service. Thus, it is very important to evaluate the structural integrity of these materials using highly reliable non-destructive testing (NDT) methods. Ultrasonic non-destructive inspection of austenitic welds and dissimilar weld components is complicated because of anisotropic columnar grain structure leading to beam splitting and beam deflection. Simulation tools play an important role in developing advanced reliable ultrasonic testing (UT) techniques and optimizing experimental parameters for inspection of austenitic welds and dissimilar weld components. The main aim of the thesis is to develop a 3D ray tracing model for quantitative evaluation of ultrasonic wave propagation in an inhomogeneous anisotropic austenitic weld material. Inhomogenity in the anisotropic weld material is represented by discretizing into several homogeneous layers. According to ray tracing model, ultrasonic ray paths are traced during its energy propagation through various discretized layers of the material and at each interface the problem of reflection and transmission is solved. The influence of anisotropy on ultrasonic reflection and transmission behaviour in an anisotropic austenitic weld material are quantitatively analyzed in three dimensions. The ultrasonic beam directivity in columnar grained austenitic steel material is determined three dimensionally using Lamb's reciprocity theorem. The developed ray tracing model evaluates the transducer excited ultrasonic fields accurately by taking into account the directivity of the transducer, divergence of the ray bundle, density of rays and phase
Energy Technology Data Exchange (ETDEWEB)
Kolkoori, Sanjeevareddy
2014-07-01
Austenitic welds and dissimilar welds are extensively used in primary circuit pipes and pressure vessels in nuclear power plants, chemical industries and fossil fuelled power plants because of their high fracture toughness, resistance to corrosion and creep at elevated temperatures. However, cracks may initiate in these weld materials during fabrication process or stress operations in service. Thus, it is very important to evaluate the structural integrity of these materials using highly reliable non-destructive testing (NDT) methods. Ultrasonic non-destructive inspection of austenitic welds and dissimilar weld components is complicated because of anisotropic columnar grain structure leading to beam splitting and beam deflection. Simulation tools play an important role in developing advanced reliable ultrasonic testing (UT) techniques and optimizing experimental parameters for inspection of austenitic welds and dissimilar weld components. The main aim of the thesis is to develop a 3D ray tracing model for quantitative evaluation of ultrasonic wave propagation in an inhomogeneous anisotropic austenitic weld material. Inhomogenity in the anisotropic weld material is represented by discretizing into several homogeneous layers. According to ray tracing model, ultrasonic ray paths are traced during its energy propagation through various discretized layers of the material and at each interface the problem of reflection and transmission is solved. The influence of anisotropy on ultrasonic reflection and transmission behaviour in an anisotropic austenitic weld material are quantitatively analyzed in three dimensions. The ultrasonic beam directivity in columnar grained austenitic steel material is determined three dimensionally using Lamb's reciprocity theorem. The developed ray tracing model evaluates the transducer excited ultrasonic fields accurately by taking into account the directivity of the transducer, divergence of the ray bundle, density of rays and phase
International Nuclear Information System (INIS)
Eberhart, J.-P.
1976-01-01
The following topics are discussed: theoretical aspects of radiation-matter interactions; production and measurement of radiations (X rays, electrons, neutrons); applications of radiation interactions to the study of crystalline materials. The following techniques are presented: X-ray and neutron diffraction, electron microscopy, electron diffraction, X-ray fluorescence analysis, electron probe microanalysis, surface analysis by electron emission spectrometry (ESCA and Auger electrons), scanning electron microscopy, secondary ion emission analysis [fr
Model of electronic energy relaxation in the test-particle Monte Carlo method
Energy Technology Data Exchange (ETDEWEB)
Roblin, P.; Rosengard, A. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. des Procedes d`Enrichissement; Nguyen, T.T. [Compagnie Internationale de Services en Informatique (CISI) - Centre d`Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)
1994-12-31
We previously presented a new test-particle Monte Carlo method (1) (which we call PTMC), an iterative method for solving the Boltzmann equation, and now improved and very well-suited to the collisional steady gas flows. Here, we apply a statistical method, described by Anderson (2), to treat electronic translational energy transfer by a collisional process, to atomic uranium vapor. For our study, only three levels of its multiple energy states are considered: 0,620 cm{sup -1} and an average level grouping upper levels. After presenting two-dimensional results, we apply this model to the evaporation of uranium by electron bombardment and show that the PTMC results, for given initial electronic temperatures, are in good agreement with experimental radial velocity measurements. (author). 12 refs., 1 fig.
Directory of Open Access Journals (Sweden)
Ivana Bilić
2011-02-01
Full Text Available Human resources represent one of the most important companies’ resources responsible in creation of companies’ competitive advantage. In search for the most valuable resources, companies use different methods. Lately, one of the growing methods is electronic recruiting, not only as a recruitment tool, but also as a mean of external communication. Additionally, in the process of corporate communication, companies nowadays use the electronic corporate communication as the easiest, the cheapest and the simplest form of business communication. The aim of this paper is to investigate relationship between three groups of different criteria; including main characteristics of performed electronic recruiting, corporate communication and selected financial performances. Selected companies were ranked separately by each group of criteria by usage of multicriteria decision making method PROMETHEE II. The main idea is to research whether companies which are the highest performers by certain group of criteria obtain the similar results regarding other group of criteria or performing results.
International Nuclear Information System (INIS)
Alloyeau, D.; Ricolleau, C.; Oikawa, T.; Langlois, C.; Le Bouar, Y.; Loiseau, A.
2009-01-01
Nanoparticles' morphology is a key parameter in the understanding of their thermodynamical, optical, magnetic and catalytic properties. In general, nanoparticles, observed in transmission electron microscopy (TEM), are viewed in projection so that the determination of their thickness (along the projection direction) with respect to their projected lateral size is highly questionable. To date, the widely used methods to measure nanoparticles thickness in a transmission electron microscope are to use cross-section images or focal series in high-resolution transmission electron microscopy imaging (HRTEM 'slicing'). In this paper, we compare the focal series method with the electron tomography method to show that both techniques yield similar particle thickness in a range of size from 1 to 5 nm, but the electron tomography method provides better statistics since more particles can be analyzed at one time. For this purpose, we have compared, on the same samples, the nanoparticles thickness measurements obtained from focal series with the ones determined from cross-section profiles of tomograms (tomogram slicing) perpendicular to the plane of the substrate supporting the nanoparticles. The methodology is finally applied to the comparison of CoPt nanoparticles annealed ex situ at two different temperatures to illustrate the accuracy of the techniques in detecting small particle thickness changes.
Energy Technology Data Exchange (ETDEWEB)
Alloyeau, D., E-mail: alloyeau.damien@gmail.com [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); Laboratoire d' Etude des Microstructures - ONERA/CNRS, UMR 104, B.P. 72, 92322 Chatillon (France); Ricolleau, C. [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); Oikawa, T. [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); JEOL (Europe) SAS, Espace Claude Monet, 1 Allee de Giverny, 78290 Croissy-sur-Seine (France); Langlois, C. [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); Le Bouar, Y.; Loiseau, A. [Laboratoire d' Etude des Microstructures - ONERA/CNRS, UMR 104, B.P. 72, 92322 Chatillon (France)
2009-06-15
Nanoparticles' morphology is a key parameter in the understanding of their thermodynamical, optical, magnetic and catalytic properties. In general, nanoparticles, observed in transmission electron microscopy (TEM), are viewed in projection so that the determination of their thickness (along the projection direction) with respect to their projected lateral size is highly questionable. To date, the widely used methods to measure nanoparticles thickness in a transmission electron microscope are to use cross-section images or focal series in high-resolution transmission electron microscopy imaging (HRTEM 'slicing'). In this paper, we compare the focal series method with the electron tomography method to show that both techniques yield similar particle thickness in a range of size from 1 to 5 nm, but the electron tomography method provides better statistics since more particles can be analyzed at one time. For this purpose, we have compared, on the same samples, the nanoparticles thickness measurements obtained from focal series with the ones determined from cross-section profiles of tomograms (tomogram slicing) perpendicular to the plane of the substrate supporting the nanoparticles. The methodology is finally applied to the comparison of CoPt nanoparticles annealed ex situ at two different temperatures to illustrate the accuracy of the techniques in detecting small particle thickness changes.
Fekete, Gábor; Fodor, Emese; Pesznyák, Csilla
2015-03-08
A novel method has been put forward for very large electron beam profile measurement. With this method, absorbed dose profiles can be measured at any depth in a solid phantom for total skin electron therapy. Electron beam dose profiles were collected with two different methods. Profile measurements were performed at 0.2 and 1.2 cm depths with a parallel plate and a thimble chamber, respectively. 108cm × 108 cm and 45 cm × 45 cm projected size electron beams were scanned by vertically moving phantom and detector at 300 cm source-to-surface distance with 90° and 270° gantry angles. The profiles collected this way were used as reference. Afterwards, the phantom was fixed on the central axis and the gantry was rotated with certain angular steps. After applying correction for the different source-to-detector distances and incidence of angle, the profiles measured in the two different setups were compared. Correction formalism has been developed. The agreement between the cross profiles taken at the depth of maximum dose with the 'classical' scanning and with the new moving gantry method was better than 0.5 % in the measuring range from zero to 71.9 cm. Inverse square and attenuation corrections had to be applied. The profiles measured with the parallel plate chamber agree better than 1%, except for the penumbra region, where the maximum difference is 1.5%. With the moving gantry method, very large electron field profiles can be measured at any depth in a solid phantom with high accuracy and reproducibility and with much less time per step. No special instrumentation is needed. The method can be used for commissioning of very large electron beams for computer-assisted treatment planning, for designing beam modifiers to improve dose uniformity, and for verification of computed dose profiles.
Systems and Methods for Fabricating Carbon Nanotube-Based Vacuum Electronic Devices
Manohara, Harish (Inventor); Toda, Risaku (Inventor); Del Castillo, Linda Y. (Inventor); Murthy, Rakesh (Inventor)
2015-01-01
Systems and methods in accordance with embodiments of the invention proficiently produce carbon nanotube-based vacuum electronic devices. In one embodiment a method of fabricating a carbon nanotube-based vacuum electronic device includes: growing carbon nanotubes onto a substrate to form a cathode; assembling a stack that includes the cathode, an anode, and a first layer that includes an alignment slot; disposing a microsphere partially into the alignment slot during the assembling of the stack such that the microsphere protrudes from the alignment slot and can thereby separate the first layer from an adjacent layer; and encasing the stack in a vacuum sealed container.
A rapid method of reprocessing for electronic microscopy of cut histological in paraffin
International Nuclear Information System (INIS)
Hernandez Chavarri, F.; Vargas Montero, M.; Rivera, P.; Carranza, A.
2000-01-01
A simple and rapid method is described for re-processing of light microscopy paraffin sections to observe they under transmission electron microscopy (TEM) and scanning electron microscopy (SEM) The paraffin-embedded tissue is sectioned and deparaffinized in toluene; then exposed to osmium vapor under microwave irradiation using a domestic microwave oven. The tissues were embedded in epoxy resin, polymerized and ultrathin sectioned. The method requires a relatively short time (about 30 minutes for TEM and 15 for SEM), and produces a reasonable quality of the ultrastructure for diagnostic purposes. (Author) [es
Modeling and Simulation of DC Power Electronics Systems Using Harmonic State Space (HSS) Method
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth
2015-01-01
based on the state-space averaging and generalized averaging, these also have limitations to show the same results as with the non-linear time domain simulations. This paper presents a modeling and simulation method for a large dc power electronic system by using Harmonic State Space (HSS) modeling....... Through this method, the required computation time and CPU memory for large dc power electronics systems can be reduced. Besides, the achieved results show the same results as with the non-linear time domain simulation, but with the faster simulation time which is beneficial in a large network....
International Nuclear Information System (INIS)
Fukuda, Yoshiyuki; Schrod, Nikolas; Schaffer, Miroslava; Feng, Li Rebekah; Baumeister, Wolfgang; Lucic, Vladan
2014-01-01
Correlative microscopy allows imaging of the same feature over multiple length scales, combining light microscopy with high resolution information provided by electron microscopy. We demonstrate two procedures for coordinate transformation based correlative microscopy of vitrified biological samples applicable to different imaging modes. The first procedure aims at navigating cryo-electron tomography to cellular regions identified by fluorescent labels. The second procedure, allowing navigation of focused ion beam milling to fluorescently labeled molecules, is based on the introduction of an intermediate scanning electron microscopy imaging step to overcome the large difference between cryo-light microscopy and focused ion beam imaging modes. These methods make it possible to image fluorescently labeled macromolecular complexes in their natural environments by cryo-electron tomography, while minimizing exposure to the electron beam during the search for features of interest. - Highlights: • Correlative light microscopy and focused ion beam milling of vitrified samples. • Coordinate transformation based cryo-correlative method. • Improved correlative light microscopy and cryo-electron tomography
Electron-molecule collision calculations using the R-matrix method
Energy Technology Data Exchange (ETDEWEB)
Tennyson, Jonathan, E-mail: j.tennyson@ucl.ac.u [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)
2010-06-15
The R-matrix method is an embedding procedure which is based on the division of space into an inner region where the physics is complicated and an outer region for which greatly simplified equations can be solved. The method developed out of nuclear physics, where the effects of the inner region were simply parametrized, into atomic and molecular physics, where the full problem can be formulated and hopefully solved ab initio. In atomic physics R-matrix based procedures are the method of choice for the ab initio calculation of electron collision parameters. There has been a number of R-matrix procedures developed to treat the low-energy electron-molecule collision problem or particular aspects of this problem. These methods have been extended to both positron physics and the R-matrix treatment of vibrational motion. The physical basis of the R-matrix method as well as its theoretical formulation are presented. Various electron scattering models within an R-matrix formulation including static exchange, static exchange plus polarization and close coupling are described with reference to various computational implementations of the method; these are compared to similar models used within other scattering methods. The need for a balanced treatment of the target and continuum wave functions is emphasised. Extensions of close-coupling based models into the intermediate energy regime using pseudo-states is discussed, as is the adaptation of R-matrix methods to problems involving photons. The numerical realisation of the R-matrix method is based on the adaptation of quantum chemistry codes in the inner region and asymptotic electron-atom scattering programs in the outer region. Use of bound state codes in scattering calculations raises issues involving continuum basis sets, appropriate orbitals, integral evaluation, orthogonalization, Hamiltonian construction and diagonalization which need to be addressed. The algorithms developed to resolve these issues are described as
Traveling interface modulations and anisotropic front propagation in ammonia oxidation over Rh(110)
Energy Technology Data Exchange (ETDEWEB)
Rafti, Matías [Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Fac. Cs. Exactas, Universidad Nacional de La Plata, 64 y Diag. 113 (1900), La Plata (Argentina); Institut für Physikalische Chemie und Elektrochemie, Leibniz-Universität Hannover, Callinstr. 3-3a, D-30167 Hannover (Germany); Borkenhagen, Benjamin; Lilienkamp, Gerhard [Institut für Energieforschung und Physikalische Technologien, Technische Universität Clausthal, Leibnizstr. 4, 38678 Clausthal-Zellerfeld (Germany); Lovis, Florian; Smolinsky, Tim; Imbihl, Ronald, E-mail: imbihl@pci.uni-hannvover.de [Institut für Physikalische Chemie und Elektrochemie, Leibniz-Universität Hannover, Callinstr. 3-3a, D-30167 Hannover (Germany)
2015-11-14
The bistable NH{sub 3} + O{sub 2} reaction over a Rh(110) surface was explored in the pressure range 10{sup −6}–10{sup −3} mbar and in the temperature range 300–900 K using photoemission electron microscopy and low energy electron microscopy as spatially resolving methods. We observed a history dependent anisotropy in front propagation, traveling interface modulations, transitions with secondary reaction fronts, and stationary island structures.