Instantaneous Formulation for Transitions Between Two Instantaneous Bound States and Its Gauge Invariance

We have precisely derived a ＂rigorous instantaneous formulation＂ for transitions between two bound states when the bound states are well-described by instantaneous Bethe-Salpeter （BS） equation （i.e. the kernel of the equation is instantaneous ＂occasionally＂）. The obtained rigorous instantaneous formulation, in fact, is expressed as an operator sandwiched by two ＂reduced BS wave functions＂ properly, while the reduced BS wave functions appearing in the formulation are the rigorous solutions of the instantaneous BS equation, and they may relate to Schroedinger wave functions straightforwardly. We also show that the rigorous instantaneous formulation is gauge-invariant with respect to the Uem（1） transformation precisely, if the concerned transitions are radiative. Some applications of the formulation are outlined.     

Interference effects in the coherent X-ray radiation of relativistic electrons in two- and three-layer targets

A dynamic theory of the coherent X-ray radiation of relativistic electrons in “amorphous medium–single-crystal” and “amorphous medium–free-space–single-crystal” targets is developed. Expressions for the spectral-angular distributions of diffracted transition radiation (DTR), parametric X-ray radiation, and a term describing their interference are obtained. The spectral-angular density of the DTR is represented as a sum of terms describing the diffracted transition radiation from various boundaries and a term describing the interference of these components. Interference effects in the spectral-angular and angular densities of radiation are studied.     

表面粗糙度对点扩散函数影响的研究

建立了粗糙波面点扩散函数。所建立的点扩散函数，包括“核”和“晕圈”两部份，前者随粗糙度的增加而减少，后者随粗糙度的增加而增加。     

Synthesis and characterization of CdS nanoparticle based multiwall carbon nanotube–maleic anhydride–1-octene nanocomposites

CdS nanoparticles were synthesized by sonication from cadmium chloride and thiourea using a multiwall carbon nanotube (MWCNT)–maleic anhydride (MA)–1-octene system as the matrix. The matrix was obtained by the “grafting from” approach from oxidized carbon nanotubes and maleic anhydride–1-octene. Multiwall carbon nanotubes used for reinforcing the matrix were synthesized by Catalytic Chemical Vapor Deposition using Fe–Co/Al₂O₃ as the catalyst. The obtained nanostructures were characterized by FTIR, XRD, Raman spectroscopy, TEM, SEM and UV–vis spectroscopy. The average CdS particle diameter was 7.9 nm as confirmed independently by TEM and XRD. UV–vis spectroscopy revealed that the obtained nanostructure is an appropriate base material for making optical devices. The novelty of this work is the use of the MWCNT–MA–1-octene matrix obtained via the “grafting from” approach for the synthesis of uniformly dispersed CdS nanocrystals by ultrasonic cavitation to obtain a polymer nanocomposite.     

Classical stochastic model of laser-stimulated surface processes and the selective nature of laser excitation via multiphonon couplings

The dynamical behavior of laser-stimulated surface processes (LSSP) is studied by the generalized Langevin equation via the memory effects of the damping kernel, the dephasing kernel and mode-mode interactions. The temperature-dependent averaged energy absorption rate (which characterizes the line shape) is calculated by solving the Laplace-Fourier transform of the velocity correlation function. The features of the response function and its overall line broadening are discussed in terms of Markovian processes. The nature of LSSP and laser-selective effects are discussed in terms of the multiphonon coupling strength and the related “internal resonant” condition. It is shown that laser-selective bond breaking is possible for a slow intramolecular vibrational relaxation rate which is governed by a high-order multiphonon process or a far off “internal resonance”.     

On the chiral magnetic effect in Weyl superfluid <Superscript>3</Superscript>He-A

In the theory of the chiral anomaly in relativistic quantum field theories (RQFTs), some results depend on a regularization scheme at ultraviolet. In the chiral superfluid ³He-A, which contains two Weyl points and also experiences the effects of chiral anomaly, the “trans-Planckian” physics is known and the results can be obtained without regularization. We discuss this on example of the chiral magnetic effect (CME), which has been observed in ³He-A in the 1990s [1]. There are two forms of the contribution of the CME to the Chern–Simons term in free energy, perturbative and non-perturbative. The perturbative term comes from the fermions living in the vicinity of the Weyl point, where the fermions are “relativistic” and obey the Weyl equation. The non-perturbative term originates from the deep vacuum, being determined by the separation of the two Weyl points in momentum space. Both terms are obtained using the Adler–Bell–Jackiw equation for chiral anomaly, and both agree with the results of the microscopic calculations in the “trans-Planckian” region. Existence of the two nonequivalent forms of the Chern–Simons term demonstrates that the results obtained within the RQFT depend on the specific properties of the underlying quantum vacuum and may reflect different physical phenomena in the same vacuum.     

基于支持向量机的玉米苗期田间杂草光谱识别

田间全面积均匀喷施除草剂不经济,还污染环境,精准喷施除草剂意义重大,其关键是正确识别杂草。用便携式野外光谱仪,在田间测量了玉米、马唐和稗草植株冠层在350～2 500 nm波长范围内的光谱数据,经过数据预处理,数据分析波长选为350～1 300和1 400～1 800 nm。数据处理采用支持向量机(SVM)模式识别方法。SVM具有可实现对小样本建模结构风险最小化、结果最优化、泛化能力强的优点。用线性、多项式、径向基和多层感知核函数对玉米和杂草建立二分类模型,结果表明,三阶多项式核函数SVM分类模型的正确识别率最高,达到80%以上,且支持向量比例较小。以二分类模型为基础,利用投票机制,建立了玉米、马唐和稗草的一对一多分类SVM模型,正确识别率达80%。田间光谱测量受光照、背景和仪器测量精度等条件的影响较大,但结果仍表明SVM结合光谱技术在田间杂草识别中应用潜力很大,此研究为田间杂草识别及传感器的建立提供了一种研究思路和应用基础。     

Raman scattering excited with 532 nm laser in bisphenol “AF” and its connection with bisphenol “A” and “S”

Bisphenol “AF,” a chemically similar replacement substitute for Bisphenol “A” which is a widespread environmental hormone, is studied by Raman spectroscopy (250–3500?cm^–1). Experimentally observed scattering peaks are illuminated by Density Functional Theory calculations. Principal component analysis is executed on the experimental Raman spectra of Bisphenol “AF” together with spectra of Bisphenol “A” and “S” reported earlier. Eight correlating molecular frequencies of Bisphenol “AF,” “A,” and “S” are found in contrast to 12 such frequencies of Bisphenol “A” and “S” only. The refined list of correlating frequencies manifests the existence of correlation in bisphenol family and clue toward their grouping, identification, detection, and screening together with mechanism responsible for toxicity.     

On the Energy of a “Two-Dimensional” Two-Electron Atom

With the use of the known solution of the Schrödinger equation for an electron in the nucleus field in the polar coordinates, the energy of a “two-dimensional” two-electron atom in the ground state, as well as its single ionization energy, has been calculated both in perturbation theory and with an almost century-old method of variation of the parameter Z in a trial wavefunction of the ground state. Since such two-dimensional atoms, e.g., helium atoms, can in principle be implemented in experiments by “freezing” of one degree of freedom in the phase of Bose–Einstein condensate, the conclusions made in this work can be tested. Fundamental features of the calculation of the energy of “one-dimensional” two-electron atoms and the formation of their Bose–Einstein condensate have also been discussed. The results obtained in this work coincide in a number of particular cases with the results obtained in a previous work, where some results were absent.     

To the theory of I–V characteristics of the superlattices

The influence of inelastic scattering on the I–V characteristics of “dirty” and “pure” superlattices (SL) in the quasielastic limit is studied. It is shown that the form of the I–V characteristics of “dirty” SL is determined solely by the frequency of elastic scattering in a wide range of parameters and that the electron-phonon interaction in “pure” SL leads to the formation of two regions with negative differential conductivity (NDC) on the I–V characteristics.     

Experimental investigation on the measurement deviations in recording brush discharges from insulating surfaces by Coulombmeters

The total charge on a charged sheet before and after a provoked brush discharge, their difference “C”, the induced charge “A” on different probes immediately before the discharge and their transferred charge “B” measured by commercially available Coulombmeters have been measured for probes from 2 mm to 25 mm in diameter including human thumb and shielded probe. The brush discharges were provoked on PTFE discs 10 cm–20 cm. The results obtained can be used for correct estimation of the incendivity of brush discharges between 10 nC and 90 nC.     

Photon-echo decay due to weak velocity-changing collisions

Using statistical arguments, we derive an exact expression (valid for any collision kernel) for the decay of a two-pulse photon echo in the limit in which the decay occurs as the result of “weak” (glancing) velocity-changing collisions.     

Influence of the inverse sheath on divertor plasma performance in tokamak edge plasma simulations

Recently, it was shown that strong electron thermionic emission from material walls could result in the formation of an “inverse sheath,” which prevents the flow of cold ions to the wall.^[1–3] Such regimes look very favourably from the point of view of plasma–material interactions at the edge of magnetic fusion devices, where the problem of the erosion of plasma-facing components under ion irradiation is one of the key issues for the development of future magnetic fusion reactors. However, it is not clear whether such regimes are compatible with edge plasma parameters and heat removal requirements in fusion reactors. To address the issue of practicality of the “inverse sheath” regime for edge tokamak plasma conditions, we perform a set of numerical simulations with 2D edge plasma transport code UEDGE^[4] for a DIII-D-like geometry and magnetic configuration. To describe both “standard” and “inverse sheath” conditions within the framework of the UEDGE code (which does not consider the sheath region per se), at the material surfaces, we apply effective boundary conditions that emulate both “standard” and “inverse sheath” regimes. We demonstrate that, for the same input parameters, spatial distributions of edge plasma parameters corresponding to detached divertor and “inverse sheath” regimes are similar, with only a few minor differences. We discuss the compatibility of “inverse sheath” regimes with core plasma parameters.     

Autoignition-controlled flame initiation and flame stabilization in a reacting jet in crossflow

This paper describes an analysis of the mechanisms of autoignition-controlled flame initiation and flame stabilization in a nonpremixed jet in crossflows, using simultaneous high-speed (10 kHz) tomographic particle image velocimetry, OH-PLIF and line-of-sight flame emissions. Measurements are conducted on a turbulent, transverse, reacting propane jet issued into a crossflow generated by combustion of natural gas at an equivalence ratio of 0.4 with the crossflow velocity of 10 m/s, the crossflow temperature of 1350 K and the jet momentum flux ratio of 41. While several prior studies have analyzed the lifted character of the flame in similar configurations, we show that several dynamic processes precede the leading edge of the lifted diffusion flame, including formation and evolution of “autoignition kernels”, “flame kernels” and “flame fragments”. “Autoignition kernels”, i.e., discrete compact reaction zones with the peak hydroxyl (OH) fluorescence intensity below that of the diffusion flame, initiate preferably at bulges along the jet periphery where the strain rates and the scalar dissipation rates are lower. The autoignition kernel grows in both size and the OH-fluorescence intensity as it convects downstream. An autoignition kernel transitions into a propagating flame kernel, which quickly gets distorted and elongated in the direction of the principal expansion strain rate to form a flame fragment. Neighboring flame fragments merge with each other and with the downstream diffusion flame via edge-flame propagation. Merging of upstream flame fragments with the downstream diffusion flame results in an upstream advancement of the diffusion-flame front. The diffusion flame front is intrinsically unsteady because of the rather random formation and evolution of autoignition kernels, flame kernels and flame fragments, presumably due to the stochastic velocity, the strain rate and mixture-fraction oscillations.     

The p-q model Boltzmann equation

The “p-q” model earlier introduced by the authors to describe persistent scattering under a scalar Boltzmann equation is here examined in detail. After deriving the scattering kernel and exhibiting its properties we obtain moment and similarity solutions and show how the model effectively parametrizes all intermediate conditions between the extremes of diffusion-like “small-scattering” and the strong-collisional limit of “diffuse-scattering” characteristic of earlier, more restrictive models. Both continuous and discrete-variable versions of the model are discussed and shown to be straightforwardly interrelated. Our derivations, carried out in natural energy-like variables, parallel those given recently by Ernst and Hendriks using transform methods.     

Generalized Langevin theory of multiphoton absorption dynamics of polyatomic molecules and the nature of laser-selective effects

The generalized Langevin equation (GLE) with memory effects describing the dynamical behavior of the multiphoton processes of polyatomic molecules is presented. The temperature-dependent absorption cross section is obtained by solving the Laplace-Fourier transform of the velocity autocorrelation function governed by the GLE. It is shown that the nature of the multiphoton absorption is characterized by the memory effects of the damping kernel, the dephasing rate and the intramolecular vibration relaxation rate. The laser-selective effects are discussed in terms of the multiquantum exchange processes and the related “internal resonant” condition.     

Noise-induced quasiperiodicity in a ring of unidirectionally-coupled nonidentical maps

Transitions from equilibrium to quasiperiodicity and from a two-cycle to a quasiperiodic regime are studied in a ring of unidirectionally-coupled nonidentical logistic maps. The former scenario is realized through a “soft” (Neimark–Sacker) bifurcation, while the latter through a “hard” (saddle-node) bifurcation. Special attention is paid on a noise-induced transition through “hard” bifurcation, where a phenomenon of structural stabilization of the quasiperiodic system near the bifurcation point is observed and analyzed in detail.     

The processes of thermal and “cold” ionization in caesium vapours

The processes of thermal and “cold” ionization for the calculation of the composition and conductivity of near-critical caesium vapours are considered. The degrees of thermal and “cold” ionization are calculated for the near-critical region, and the temperature and density regions with predominant role of the processes of “cold” ionization are indicated. The conductivity of caesium vapours is calculated as the sum of the conductivities of thermal electrons and jellium electrons. The obtained results agree with the experimental data on the gas branch of the binodal and the near-critical isotherms. These facts can serve as confirmation of the proposed hypothesis about the existence of the jellium in the gas–plasma region and its coexistence with thermally ionized electrons.     

Variations in the solar-cosmic-ray flux on the Earth’s orbit and their correlations with the soft X-ray solar activity during solar cycles 22 and 23

A method for collating time series of partially or fully simultaneous measurement into a unified weighted-averaged series particular on an interval enveloping all initial measurements was designed. This method is applied to GOES data obtained during the 22nd and 23rd solar-activity cycles to synthesize the daily-average series of the soft X-ray emission from the Sun at wavelengths 1–8 Å, the electron, proton, and α-particle fluxes in the energy ranges >2 MeV, >5MeV, and 4–10 MeV, respectively, and the magnitude of the total geomagnetic-field vector. The time structure of the above data series was studied by means of the spectral analysis. Correlations of the “flare” and “background” solar soft X-ray emissions with the above-mentioned particle fluxes and the geomagnetic field are studied.