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1.
The difference field RCS (d-RCS) has been defined to analyze the scattering from the target above a rough surface. The electric
field integral equations (EFIEs) of the difference induced currentJ
sd on the rough surface, the induced electric currentJ
o and magnetic currentK
o on the dielectric target under a TE wave incidence are derived. A small portion of the rough surface towards the target along
the specular direction is taken to compute the scattering contributionE
s0 from the rough surface towards the target, which improves the computation speed. A numerical iterative approach is developed
to solve the EFIEs and bistatic d-RCS. The surface length for iterations is dependent on the scattering angle and discussed
for comparison with Johnson’s method. Using the Monte-Carlo method to generate the Pierson-Morkowitz (P-M) ocean-like rough
surface, bistatic d-RCS of the dielectric target, e.g. a cylinder or a square column, above the rough surface is numerically
simulated. The induced electric and magnetic currents on the dielectric target and the difference induced current on the rough
surface are numerically discussed. 相似文献
2.
D. Mannix P.C. de Camargo C. Giles A.J.A. de Oliveira F. Yokaichiya C. Vettier 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(1):19-25
We report on X-ray magnetic diffraction studies of the spin density wave antiferromagnetism formed in the conduction electron
band of chromium. Non-resonant X-ray magnetic scattering was used to directly determine that chromium has zero orbital magnetisation.
Furthermore, the azimuthal dependence of this scattering provides unique evidence that chromium forms a linearly polarised
wave. In the vicinity of the K absorption edge, resonant X-ray magnetic scattering was observed. A consistent model of the
magnetic scattering has been derived from the resonant and non-resonant magnetic amplitudes. The enhancement of the magnetic
intensity arises primarily from dipole transitions from the core 1s level to 4p states. Quadrupole transitions to the magnetic 3d states are essentially non-existent due to their sensitivity to (and the absence of) orbital moment. This effect is predicted
from atomic considerations of the 3d5 ( = 0) transition metal ions.
Received 22 September 2000 相似文献
3.
YE Hongxia & JIN Yaqiu Key Laboratory of Wave Scattering Remote Sensing Information 《中国科学G辑(英文版)》2005,48(6):723-738
1 Introduction Electromagnetic scattering from the target above or beneath a rough surface has at- tracted much interest during recent years, because of extensive applications to radar surveillance, target detection, ground radar probing, and so on[1―3]. In order to numeri- cally simulate scattering from composite model of the target and underlying rough sur- face, some fast numerical methods, such as general forward backward method and spec- trum acceleration algorithm (GFBM/SAA)[4,5], fin… 相似文献
4.
5.
Dragomir Tatchev 《哲学杂志》2013,93(12):1751-1772
The theory of small-angle scattering is reviewed with special attention paid to the anomalous scattering and multiphase systems. A general equation is derived that describes the scattering of a multiphase system as a sum of scattering functions of each of the phases, as if it scattered alone in a two-phase system, and interphase interference scattering functions. These scattering functions depend only on the spatial distribution of the phase boundaries, but not on the scattering density. Contrast variation techniques are most rewarding when the scattering density of only one phase can be varied. For anomalous small-angle X-ray scattering (ASAXS), this means the most favourable is the case in which resonant atoms are contained in one phase only. The general equation involves n(p ? 1) unknown partial atomic number density differences, where p is the number of phases and n the number of the different atom types in the sample. These partial atomic number density differences can be found if a suitable structure model is applied to calculate the phase scattering functions. Then, the phase compositions and densities can be calculated by solving a system of linear equations incorporating the atom number conservation law. The partial structure factors formalism is also reviewed. Corresponding equations for a system of n types of atoms and p phases are derived. The number of independent partial structure factors is p(p ? 1)/2 and depends on the number of phases, but not on the number of the types of the atoms in the sample, as in the case of wide-angle scattering. 相似文献
6.
7.
R. Itri J. Depeyrot F.A. Tourinho M.H. Sousa 《The European physical journal. E, Soft matter》2001,4(2):201-208
Small-angle X-ray scattering (SAXS) was performed on a series of Electric Double-Layered Magnetic Fluids (EDL-MF) composed
of ferrite type-- CoFe2O4, MnFe2O4, ZnFe2O4, NiFe2O4 and CuFe2O4--nanoparticles of different crystalline sizes ( D
XR ranging from 40 to 139?, as determined by X-ray diffraction). The information concerning the scattering objects was obtained
through the analysis of the distance distribution function p(r) and of the size distribution function D(R), both retrieved from SAXS data. The results show that EDL-MF, in the absence of an applied magnetic field, are composed
of small magnetic particle aggregates in solution. These agglomerates are elongated in one direction (chain-like) with the
longest dimension varying from 240 to 330?. The cross-section size is of the order of D
XR. The data also demonstrate that the maximum dimension of these aggregates is independent of the ferrite type. On the other
hand, the number of aggregated magnetic particles is nanoparticle-size-dependent. Accordingly, larger ferrite-type nanoparticles
as those with D
XR = 139? form aggregates composed of 2-3 magnetic particles, whereas smaller ones with D
XR
40? form agglomerates of about 6 magnetic particles in solution. As the nanoparticle size is reduced, it might increase the
particle surface defects. Such occurrence would affect the particle surface charge density, which could reduce the electrostatic
screening, favoring the agglomeration phenomenon.
Received 28 February 2000 and Received in final form 28 August 2000 相似文献
8.
Sunachand Patel 《Pramana》1985,25(6):685-694
Possible occurrence of scaling of differential cross-section for high energy hadronnucleus elastic scattering is demonstrated
takingp-4He scattering as an example and using three well-known scaling variables proposed earlier for hadron-hadron scattering. The
available data on differential cross-section ratio betweenE
lab=45 and 393 GeV are found to scale in all the three variables reasonably well and the positions of the dip and the secondary
maximum are found to follow the predicted patterns of behaviour as a function of energy. Extrapolating the fits to the available
slope-parameter data onto higher energies and using the scaling curves, the positions of the dip and the secondary maximum
and the differential cross-section ratio as a function of |t| are predicted for higher energies. 相似文献
9.
Anna V. Svanidze Sergey G. Lushnikov Vadim P. Romanov Seiji Kojima 《Journal of Raman spectroscopy : JRS》2012,43(10):1510-1514
We present results of Brillouin light scattering studies of lysozyme and guanidine hydrochloride solutions in the temperature range 290–350 K. The Brillouin spectra of 6 M guanidine hydrochloride have been found to contain an additional component in Rayleigh scattering that manifests itself as a broad quasi‐elastic scattering line centered at the unshifted frequency and described by a Lorentz function (i.e. a Debye relaxor with relaxation time τ1 ~ 25 ps at room temperature). The temperature dependence of τ1 is described by the Arrhenius law with activation energy Ea = 0.11 ± 0.01 eV and prefactor τ0= 0.33 ± 0.03 ps. The Brillouin spectra of lysozyme denatured by 6 M guanidine hydrochloride exhibit a more complicated structure of the additional contribution into Rayleigh scattering, which is fitted best of all by a sum of two Lorentzians centered at the unshifted frequency (with relaxation times τ1 ~ 19 ps and τ2 ~ 180 ps at 339 K). Possible origins of the quasi‐elastic scattering are discussed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
10.
Stimulated scattering off electron plasma mode is investigated analytically for the case when the pump wave is an intense
circularly polarised electromagnetic wave propagating parallel to a homogeneous dc magnetic field in an isotropic semiconductor-plasma.
The threshold electric field of the pump necessary for the stimulated Raman scattering and the growth rate of the parametrically
unstable mode have been obtained for two cases (i)B
0=0 and (ii) B0 ≠ 0. It is seen that the magnetic field does not significantly affect the threshold electric field as well as the growth
rate provided the cyclotron frequency is small compared to the frequency of the pump wave. The threshold conditions are also
found to be insensitive to the electron thermal velocity. 相似文献
11.
Ram K. Varma 《Pramana》2007,68(6):901-911
Quantum effects which have usually been associated with micro-scale phenomena can also arise on the macro-scale in situations
other than the well-known macro-quantum phenomena of superconductivity and superfluidity. Such situations have been shown
here to arise in processes involving inelastic scattering with bound or partially bound systems (not bound in all degrees
of freedom), and the macro-quantum behaviour is associated with the state of the total system in transition in the process
of scattering. Such a state is designated as a ‘transition-state’. It is pointed out that we have already observed such manifestations
for a particular system, the charged particles in a magnetic field where interference effects involving macro-scale matter
waves along the magnetic field have been reported [R K Varma et al, Phys. Rev.
E65, 026503 (2002)]
相似文献
12.
The recent neutron scattering data for spin-wave dispersion in HoMnO3 are well-described by an anisotropic Hubbard model on a triangular lattice with a planar (XY) spin anisotropy. Best fit indicates
that magnetic excitations in HoMnO3 correspond to the strong-coupling limit U/t >∼ 15, with planar exchange energy J = 4t
2
/U ≃ 2.5 meV and planar anisotropy ΔU ≃ 0.35 meV.
相似文献
13.
Extinction theorem was used to deduce the first order scattering cross-section including the double scattering effects for
the fluid-fluid rough surface. If the double scattering effects are neglected in the present method, the scattering cross-section
agrees with the result obtained by the perturbation method based on Rayleigh hypothesis. Calculations of scattering strength
were carried out, and comparisons with the first-order perturbation method based on Rayleigh hypothesis were also done. The
results show that double scattering effects are obvious with the increase of the root mean square of surface height and the
grazing angle when the valid condition k
1
h < 1 is satisfied.
Supported by the National Basic Research Program of China (Grant No. 2005CB422307) 相似文献
14.
J. -S. Real 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):463-468
The G0 experiment is dedicated to the determination of the strange quark contribution to the electric and magnetic nucleon
form factors for a large range of momentum transfers between 0.1 to 1(GeV/c)2 . This information is provided by the asymmetries of cross-sections measured with longitudinally polarized electrons in elastic
electron-proton scattering and quasi-elastic electron-deuteron scattering. A set of measurements at two different Q2 will allow the complete separation of the electric and magnetic weak, as well as axial nucleon form factors. This report
summarizes the physics case, gives details about the dedicated set-up used, and shows the results of the combination of the
strange quark contribution in the electric and magnetic form factors of the protons. The experiment was performed at the Jefferson Laboratory, during years 2003 and 2004, and will be completed after backward-angle measurements in 2006, 2007. 相似文献
15.
It is shown that magnetic surface mode frequencies in the amorphous ferromagnet Fe40Ni40B20 measured using Brillouin light scattering depend upon the incident laser light intensity: presumably due to local heating of the specimen due to the concentration of the light flux into a focal spot only a few microns in diameter. Surface mode frequencies extrapolated to zero light intensity are shown to be consistent with magnetic parameters measured using ferromagnetic resonance at 35.731 GHz to within ±0.5 GHz for specimens of amorphous Fe40Ni40B20. 0.5 GHz corresponds to a change of 0.17 kG in the saturation magnetization, 4πMs. 相似文献
16.
Spacer layer thickness fluctuation scattering in a modulation-doped AlxGa1-xAs/GaAs/AlxGa1-xAs quantum well 下载免费PDF全文
We theoretically study the influence of spacer layer thickness fluctuation(SLTF) on the mobility of a twodimensional electron gas(2DEG) in the modulation-doped Al x Ga 1 x As/GaAs/Al x Ga 1 x As quantum well.The dependence of the mobility limited by SLTF scattering on spacer layer thickness and donor density are obtained.The results show that SLTF scattering is an important scattering mechanism for the quantum well structure with a thick well layer. 相似文献
17.
Magda B. Fontes Sergey L. Bud'ko Mucio A. Continentino Elisa M. Baggio-Saitovitch 《Physica B: Condensed Matter》1999,270(3-4)
In this work we present a magnetoresistance study on the CeRu2Ge2 compound. We analyze the ρ(T) curves for several applied magnetic fields using the electron–magnon scattering model for a ferromagnetic spin arrangement. From this analysis, the field dependence of the energy gap of the magnon spectrum is obtained. The magnetoresistance ρ(H) at various temperatures arises from a normal metal contribution with an additional scattering mechanism due to electron–magnon interaction. 相似文献
18.
Using fits to the available data on the pion and deuteron electromagnetic form factors and the Chou-Yang model, the computed
values of differential cross-sections for high-energy pion-deuteron elastic scattering agree reasonably well with the available
experimental data. Whereas only a shoulder is expected to appear up to energies of several hundreds of GeV, a dip and a secondary
maximum are predicted to be conspicuous only forP
lab≫400 GeV/C. The position of the dip starts at a much lower value, |t
d| ≅ 0.5–0.6 GeV2, as compared to the corresponding position in thepp scattering. The positions of the first dip are plotted against total cross-section which can be verified by future high-energy
experiments. Limitations of the model predictions for ultrahigh energies are pointed out. 相似文献
19.
The effect of confinement from one, two or from all three directions on magnetic ordering has remained an active field of
research for almost 100 years. The role of dipolar interactions and anistropy are important to obtain, the otherwise forbidden,
ferromagnetic ordering at finite temperature for ions arranged in two-dimensional (2D) arrays (monlayers). We have demonstrated
that conventional low-temperature magnetometry and polarized neutron scattering measurements can be performed to study short-range
ferromagnetic ordering of in-plane spins in 2D systems using a multilayer stack of non-interacting monolayers of gadolinium
ions formed by Langmuir-Blodgett (LB) technique. The spontaneous magnetization could not be detected in the heterogeneous
magnetic phase observed here and the saturation value of the net magnetization was found to depend on the sample temperature
and applied magnetic field. The net magnetization rises exponentially with lowering temperature and then reaches saturation
following a T ln(βT) dependence. The T ln (βT) dependence of magnetization has been predicted from spinwave theory of 2D in-plane spin system with ferromagnetic interaction.
The experimental findings reported here could be explained by extending this theory to a temperature domain of βT<1. 相似文献
20.
Chord length distributions describe size, shape and spatial arrangement of geometrical objects (particles). The chord length
distribution is in principle proportional to the second derivative of the correlation function of small-angle scattering.
It is calculable from a relative measurement of the scattering intensity I(h). In structure research, the characterization of numerous particle systems can be achieved by comparing experimental chord
distributions with theoretical ones, provided the latter are available with sufficiently high precision for a lot of fundamental,
universal shapes. Both sides of this concept are exemplified: – the step from a relative measurement of the scattering intensity
of an isotropic two-phase sample to the chord length distribution (errors in and in , limited h-interval, corresponding to the region (1-2) nm < r in real space, must be observed); as well as the geometric matter of calculation of chord distributions as fingerprints for
basic geometric figures, including the non-convex case.
Received 15 March 1999 and Received in final form 26 April 2000 相似文献