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1.
We consider the radiation from oscillating electric and magnetic dipoles moving with constant velocity directed parallel or
antiparallel to the velocity of the surrounding medium. It is assumed that the medium in its rest frame is isotropic and has
no spatial dispersion. We obtain expressions for the spectral density of the radiated power. In the case of a nondispersive
medium, algebraic expressions for the total radiated power in the regime of “subluminal relative motion” are also obtained.
In particular, it is shown that the energy loss of a source is negative if it moves in the direction of the superluminal motion
of the medium and the source velocity is somewhat smaller than the medium velocity. It is noted that this phenomenon takes
place for a smaller difference between the velocities of the source and the medium compared with a similar phenomenon for
nonoscillating sources.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 4, pp. 316–328, May 2007. 相似文献
2.
E. V. Ponizovskaya A. M. Bratkovsky 《Applied Physics A: Materials Science & Processing》2009,95(4):1137-1142
Negative index materials (NIM) enable subwavelength resolution and are promising for applications in integrated optical systems,
since the mode volume is small. Most promising NIM systems essentially use noble metals (Ag, Au) with material losses much
lower than in other metals, but still rather hefty, like in metal–dielectric–metal “fishnets”. Therefore, we perform extensive
finite-difference time-domain modeling of NIM “fishnets” in combination with gain medium, InGaAsP multiple quantum wells in
the present work. The signal recovery is weak, which is related to weak overlap between the radiation field and the gain medium.
The signal modulation speed may be very large, in a picosecond range. 相似文献
3.
We consider the radiation from nonoscillating dipoles traveling with constant velocity directed parallel or antiparallel to
the velocity of a homogeneous transparent moving medium. It is assumed that the medium in its rest frame is isotropic and
has no spatial dispersion. We obtain expressions for the radiative energy losses and estimate the polarization energy losses
of electric and magnetic dipoles of different orientations. In particular, it is shown that the energy loss of a source is
negative if it moves in the direction of the medium motion and the source velocity is less than the medium velocity. Estimates
for the energy losses of dipoles in the cases of an electron beam and a flow of a weakly dispersive medium are given.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 6, pp. 502–512, June 2006. 相似文献
4.
The dispersion and excitation characteristics of the guided waves in a rod surrounded by an infinite solid medium (cladding)
are investigated. First, the bisection technique is employed to find all the roots of the dispersion function on the basis
of theoretical analysis and to obtain the complex phase and group velocity dispersion curves of the guided modes. Second,
according to their different dispersion characteristics, the guided modes are divided into two categories: normal modes and
Stoneley modes. And it is concluded that the normal modes merely exist in the “hard cladding” model in which the cladding’s
shear velocity is larger than the rod’s; while the Stoneley modes in cylindrical interface are highly dispersive and merely
exist in the model whose acoustical parameters satisfied the existence condition of the Stoneley waves. Third, the seldom
discussed issue, the excitation mechanisms of the guided waves, excited by three source models: symmetric point source, axial
and radial force sources, are simulated respectively. Attention is paid on the dominant mode which has better excitation sensitivity
and the suitable excitation frequency range. Moreover, the propagation characteristics of the Stoneley modes, ignored in previous
references, are analyzed and compared with those of the normal modes. 相似文献
5.
V. S. Zuev 《Optics and Spectroscopy》2010,109(5):760-762
This work presents an interpretation of experiments where laser action was observed in the so-called SPASER, a laser with
a nanoscale surface plasmon. The experimental implementation of SPASER was reported by M. A. Noginov et al. in the paper entitled
“Demonstration of SPASER-Based Nanolaser” and by Xiang Zhang et al. in the paper entitled “Plasmon Lasers at Deep Subwavelength
Scale”, both of which were published online in the advance online publication of Nature in August 2009. Nanoscale plasmonic modes experience huge losses; however, simultaneously, the probabilities of radiative
processes in atoms (molecules) leading to the emission of radiation into these modes increase 1000-fold compared to the probabilities
of radiation in free space. The similarity of the physical nature of the effects in SPASER with SERS is pointed out. 相似文献
6.
An event horizon for “relativistic” fermionic quasiparticles can be constructed in a thin film of superfluid 3He-A. The quasiparticles see an effective “gravitational” field which is induced by a topological soliton of the order parameter.
Within the soliton the “speed of light” crosses zero and changes sign. When the soliton moves, two planar event horizons (black
hole and white hole) appear, with a curvature singularity between them. Aside from the singularity, the effective spacetime
is incomplete at future and past boundaries, but the quasiparticles cannot escape there because the nonrelativistic corrections
become important as the blueshift grows, yielding “superluminal” trajectories. The question of Hawking radiation from the
moving soliton is discussed but not resolved.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 11, 833–838 (10 December 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
7.
B. N. Libenson 《Journal of Experimental and Theoretical Physics》2012,114(2):194-204
The Green’s function of the electric field of plasmons is determined in a semi-infinite medium with an abrupt plasma boundary
where nonequilibrium conduction electrons either undergo elastic reflection from the boundary or “stick” to it and give rise
to a stationary surface charge. The angular reflection of elastically scattered electrons can be either specular or diffuse.
The Green’s function is used to find the singleevent spectrum of energy loss by a fast electron moving parallel to the boundary.
The effect of electronboundary scattering parameters on the structure of bulk and surface plasmon resonances is analyzed.
The probability of transition radiation of bulk plasmon by an electron moving in vacuum is examined. A new type of surface
resonance is found under conditions of perfectly elastic scattering of conduction electrons from the plasma boundary, similar
in structure to a tangential surface plasmon. 相似文献
8.
9.
A new method for determination of satellite orbits by transfer 总被引:8,自引:8,他引:0
ZhiGang Li XuHai Yang GuoXiang Ai HuLi Si RongChuan Qiao ChuGang Feng 《中国科学G辑(英文版)》2009,52(3):384-392
The original idea of a new method for determination of satellite orbits by transfer is from Two-Way Satellite Time and Frequency
Transfer (TWSTFT). The original method is called “determination of satellite orbit by transfer”. The method is not only for
determination of satellite orbit but also for the time transfer with high accuracy and precision. The advantage is that the
accuracy and the precision for determination of satellite orbit are very high and the new method is favorable for various
applications. The combination of various signals disseminated and received forms various modes of satellite orbit determinations.
If receivers at stations receive the own station-disseminated signals via a satellite transponder, it forms an orbit determination
mode called “receiving the own station-disseminated signals mode”. If receivers at all stations receive the signals disseminated
from the master station via satellite transponders, it forms an orbit determination mode called “receiving the master station-disseminated
signals mode”. If all of receivers at stations receive all stations-disseminated signals via satellite transponders, it forms
an orbit determination mode called “receiving all stations-disseminated signals mode”. Also there are other combinations of
signals for satellite orbit determination. For different orbit determination modes with different signal combinations, their
rigorous formulae of processing are hereby presented in this paper. The accurate and the precise satellite orbit determination
for both of the modes, “receiving the own station-disseminated signals mode” and “receiving the master station-disseminated
signals mode” is attempted. It shows that the accuracy and precision for both of modes are nearly the same, the ranging accuracy
is better than 1 cm, and the observation residuals of satellite orbit determination are better than 9 cm in the observation
duration of 1 day.
Supported by the National Basic Research and Development Program of China (Grant No. 2007CB815503100453001) 相似文献
10.
O. G. Kudelin 《Thermophysics and Aeromechanics》2006,13(4):515-521
The two-dimensional boundary-value problem of the unsteady flow of an incompressible viscous gas moving behind the piston
in a “long” rectangular branch pipe is solved. An analytic solution is constructed for two velocity components with a refining
polynomial, which reduces to a system of nonlinear algebraic equations after the substitution into the governing system of
equations. By virtue of the solution uniqueness of the boundary-value problem under study, the only solution is found from
obtained values of the refining polynomial constants for each point of the branch pipe internal space for the velocity components
in analytic form. 相似文献
11.
The flow pattern around a thin strip horizontally towed at constant velocity in a continuously stratified liquid is visualized
by conventional “Vertical slit-Foucault’s knife”, “Maksoutov’s slit-thread” and “horizontal slit-regular grating” methods.
Using these sensitive high-resolution methods enables to reveal new kind of the streaky structure including a sequence of
thin sloping interfaces both on the strip surface and inside its wake. When velocity or distance from the strip increases,
the streaks may be turned into the sloping or nearly horizontal interfaces. Reconnections of outer edges of the streaks result
in appearance of a set of symmetrical “butterfly-like” vortices, which are perturbed by a shear flow inside the downstream
wake. Lift forces caused by a slope of the strip produce an asymmetry of the wake and lead to fast degeneration ofthe streaky
structures. 相似文献
12.
The probabilities of transitions between the Fock states of two electromagnetic field modes under the influence of coupling
between modes of finite duration are investigated. It is shown that the transition probability is a strongly oscillating function
of the mode numbers of the photons. Under conditions in which the coupling frequency exceeds the geometric mean of the mode
frequencies (strong coupling), large numbers of photons are excited in the mode with the lower frequency. The excitation of
a two-dimensional radiation field oscillator and the “red” asymmetry of the transition probabilities can be attributed to
instability of the classical two-dimensional oscillator with strong mode coupling.
Zh. éksp. Teor. Fiz. 112, 128–136 (July 1997) 相似文献
13.
E.G. Mishchenko M. Patra C.W.J. Beenakker 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):289-297
A theory is presented for the frequency dependence of the power spectrum of photon current fluctuations originating from a
disordered medium. Both the cases of an absorbing medium (“grey body”) and of an amplifying medium (“random laser”) are considered
in a waveguide geometry. The semiclassical approach (based on a Boltzmann-Langevin equation) is shown to be in complete agreement
with a fully quantum mechanical theory, provided that the effects of wave localization can be neglected. The width of the
peak in the power spectrum around zero frequency is much smaller than the inverse coherence time, characteristic for black-body
radiation. Simple expressions for the shape of this peak are obtained, in the absorbing case, for waveguide lengths large
compared to the absorption length, and, in the amplifying case, close to the laser threshold.
Received 8 August 2000 相似文献
14.
Yu. V. Petukhov 《Acoustical Physics》2011,57(3):401-410
Conditions that should be satisfied by the sound velocity profile of an oceanic waveguide for the dependence of the ray cycle
length on the ray phase velocity to contain smooth extrema are formulated. The extrema correspond to weakly divergent ray
beams forming “caustic” beams. It is found that diffraction effects cause a considerable smoothing of the sharp extrema that
occur in the dependence of the interference period of neighboring modes on their phase velocity. As a result, in addition
to the weakly divergent ray beams, weakly divergent diffraction beams and the corresponding “diffraction” caustics can be
formed. 相似文献
15.
A. Vukics H. Ritsch 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):585-599
We present a framework for efficiently performing Monte Carlo
wave-function simulations in cavity QED with moving particles. It
relies heavily on the object-oriented programming paradigm as realised
in C++, and is extensible and applicable for simulating open
interacting qua
ntum dynamics in general. The user is provided with a
number of “elements”, e.g. pumped moving particles, pumped lossy
cavity modes, and various interactions to compose complex interacting
systems, which contain several particles moving in electromagnetic
fields of various configurations, and perform wave-function
simulations on such systems. A number of tools are provided to
facilitate the implementation of new elements. 相似文献
16.
N. N. Rozanov 《Journal of Experimental and Theoretical Physics》2009,108(1):140-148
A theory of reflection and transmission of electromagnetic radiation by inhomogeneities of the parameters of a static transparent medium moving at the velocity of light is developed. Expressions are obtained for the Doppler frequency shift of radiation; it turns out that, under the condition of pronounced frequency dispersion, the frequency of incident radiation corresponds to two frequencies of reflected radiation (complementary waves). It is found that, as the velocity of an inhomogeneity tends to the phase velocity of radiation in the medium, the reflection and transmission coefficients of radiation by the inhomogeneity indefinitely increase. It is shown that the electromagnetic radiation frequency may increase severalfold, with a transformation coefficient of about unity, due to the Doppler shift by the inhomogeneities of a nonlinear medium that are induced by pulses (solitons) of intense counterpropagating radiation. 相似文献
17.
We investigate the process of gas trapping by a moving interference lattice formed by laser radiation of nonresonance frequency
(the optical gas trapping) with regard for intermolecular collisions. For the transitional regime (when the mean free path
of gas molecules λ is less than the lattice period) the energy and momentum transfer from a moving optical lattice to gas
is found to realize more intensively than in the case of a free molecular regime. The maximum values of the gas velocity and
heating are shown to be determined by the lattice velocity and weakly depend on the laser intensity.
The work was supported financially by the “Russian Science Support Foundation” and by the Russian Foundation for Basic Research
(Grants Nos. 06-08-00687 and 06-01-22000). 相似文献
18.
S. Fumeron P. Ben-Abdallah 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,97(2):195-208
The aim of this paper is to present several features of the couplings occurring between radiative transfer and the kinetics of a moving dielectric. After determining how the velocity field affects the apparent thermo-optical properties of matter, the energy transport problem is investigated in instationary regime and the general form of transient radiative transfer equation inside a moving medium is built. Then, the model is applied to the particular case of turbulent flows: a system of two equations for mean and fluctuating radiative energies is presented, and the resolution of this system is finally carried out. 相似文献
19.
This paper presents a heat transfer model to calculate the temperature field in moving glass rods heated by a CO2 laser. Conduction and radiation heat transfer in radial and axial directions are taken into account in the current model. The Rosseland diffusion approximation is incorporated to analyze the radiation heat transfer in the glass rod. A two-band model is used to simulate the spectral property of the glass. Results of the simulation show that glass rods of sufficiently large optical thickness should be treated as a semitransparent medium for radiative transfer, and it is reasonably accurate to assume it to be opaque to CO2 laser irradiation. It has been shown that the resulting temperature profile is strongly dependent on the laser parameters, i.e., the size of laser beam and the power of the laser. The diameter and speed of the moving glass rod are also important in determining the temperature field although the convective heat transfer coefficient between the glass rod and the environment has little effect. 相似文献