Femtosecond filamentation induced fluorescence technique for atmospheric sensing

Recent progress in filament-induced atmospheric sensing is reviewed.Self-guided propagation of ultrashort laser pulses in air induces laser filamentation.All molecules in the path of a filament can be dissociated into highly excited fragments,resulting in emission of characteristic fluorescence spectra.The fluorescence spectra provide information about the various molecules in the filaments.By using a filament-induced"fingerprinting"fluorescence technique,molecules in the atmosphere can be identified.     

A decomposition study of moisture transport divergence for inter-decadal change in East Asia summer rainfall during 1958-2001

In this paper,we report on the results of an investigation into inter-decadal changes in moisture transport and divergence in East Asia for the two periods 1980-2001 and 1958-1979.The aim is to explore the mechanism of summer rainfall change in the region after abrupt changes.The relevant changes are calculated using ERA-40 daily reanalysis datasets.The results show that both stationary and transient eddy moisture transports to the Chinese mainland have declined since the abrupt change in atmospheric general circulation in the late 1970s,leading to more rainfall in South China and less in the North.The anomalous rainfall pattern coincides well with anomalous large-scale moisture divergence in the troposphere,of which stationary-wave or monsoon transport is dominant,in comparison with the contribution of the transient eddies.Furthermore,their divergences are found to be in opposite phases.In addition,meridional divergence is more important than its zonal counterpart,with an opposite phase in East Asia.Abnormal zonal moisture convergences appear in northwestern and northeastern parts of China,and are related to the excess rainfalls in these regions.An increase in transient eddy activity is one of the major mechanisms for excess rainfall in northern Xinjiang.Consequently,the anomalous rainfall pattern in East Asia results from a decline of the East Asian monsoon after the abrupt change,while the rainfall increase in northwestern China involves anomalies of both stationary waves and transient eddies on boreal westerly over the midand high latitudes.     

Chaos and quantum Fisher information in the quantum kicked top

Quantum Fisher information is related to the problem of parameter estimation.Recently,a criterion has been proposed for entanglement in multipartite systems based on quantum Fisher information.This paper studies the behaviours of quantum Fisher information in the quantum kicked top model,whose classical correspondence can be chaotic.It finds that,first,detected by quantum Fisher information,the quantum kicked top is entangled whether the system is in chaotic or in regular case.Secondly,the quantum Fisher information is larger in chaotic case than that in regular case,which means,the system is more sensitive in the chaotic case.     

Three-dimensional numerical investigations of the laser-beam interactions in an undulator

Laser-beam interaction in an undulator is commonly suggested in the development of free electron laser (FEL) schemes. In this paper, a three-dimensional algorithm is developed to assist in laser-beam interaction simulation in an undulator, which is built on the basis of the fundamentals of electrodynamics, i.e. the electron's behavior is determined by the magnetic field and the laser electric field in the time domain. On the basis of the algorithm, the detuning effect in a laser heater, the carrier envelope phase effect of a few-cycle laser in attosecond X-ray FEL schemes and output wavelength tuning in a high gain harmonic generation FEL are numerically discussed.     

Online ef fective backscattering estimation for ring laser gyro

Lock-in phenomenon in ring laser gyroscopes is directly related to effective backscattering,which includes both backscattering and nonuniform loss.Effective backscattering often differs in different states and can only be reflected in a working state via online estimation in the working state.Moreover,effective backscattering can result in the intensity modulation of beams in the opposite directions.The effective backscattering parameters can be obtained by measuring the weak modulations in the intensity signals under different rotation rates and by using the curve-fitting method.This letter demonstrates the online estimation of backscattering.     

Calculation of Decay μ → eγ in R ξ Gauge in a Model of Electroweak-Scale Right-Handed Neutrinos

The lepton flavor violating process μ - eγ has been previously studied in a model of electroweak-scale right-handed neutrinos. In that work the decay amplitude was computed in unitarity gauge, augmented by some technical considerations that correct the leading term thus obtained. This complication arises because the mixing matrices appearing in the weak charged currents are not unitary in the model. In this paper, we recalculate the amplitude in Re gauge. The cancellation of the ξ dependence in the final result serves as a useful check to both the obtained amplitude and the technical points made in the previous work.     

Competitive Exclusion Principle Revised by Noise

A fundamental tenet in theoretical ecology is the competitive exclusion principle. Two competitive species for a limited resource cannot coexist and thus one of the species will be driven to extinction. However, we show that noise can revise this principle in a resonance-like manner, which makes coherence resonance in the system. Our obtained results well enrich the findings in the interaction of populations in ecosystems, which may explain some filed observations in the real world.     

Low frequency Whistler waves excited in fast magnetic reconnection processes

Whistler waves generated in fast magnetic reconnection processes of collisionless high beta plasmas are reviewed in experiments and satellite observations, as well as in theory and simulation, and further studied in the two-fluid theory. It is found that low frequency whistler waves can be excited in tile ion inertial range of the reconnection region. The wave is found right-handed polarized with a quadrupolar out-of-plane magnetic perturbation, in accord with satellite observations in the geomagnetosphere.     

Structures of ^17F and ^17O, ^17Ne and ^17N in the Ground State and the First Excited State

The structures of two couples of mirror nuclei ^17F and ^17O, ^17Ne and ^17N in the ground state and in the first excited state are investigated using the relativistic mean-field approach. Two-proton halo in ^17Ne in the first excited state and in the ground state and two-neutron halo in ^17N in the first excited state are suggested.Meanwhile, one-proton halo in ^17F in the first excited state and one-neutron halo in ^17O in the first excited state are also suggested. The skin structure appears in ^17F and ^17N in the ground state.     

Flat limit of the de Sitter QFT in the rest frame vacuum

The problem of the flat limits of the scalar and spinor fields on the de Sitter expanding universe is considered in the traditional adiabatic vacuum and in the new rest frame vacuum we proposed recently,in which the frequencies are separated in the rest frames as in special relativity.It is shown that only in the rest frame vacuum can the Minkowskian flat limit be reached naturally fbr any momentum,whereas in the adiabatic vacuum,this limit remains undefined in rest frames in which the momentum vanishes.An important role is played by the phases of the fundamental solutions in the rest frame vacuum,which must be regularized to obtain the desired Minkowskian flat limits.This procedure fixes the phases of the scalar mode functions and Dirac spinors,resulting in their definitive expressions derived here.The physical consequenee is that,in the rest frame vacuum,the flat limits of the oneparticle operators are simply the corresponding operators of special relativity.     

Adaptive interference hyperspectral image compression with spectrum distortion control

As one of the next generation imaging spectrometers, interferential spectrometer has been paid much attention. With traditional spectrum compression methods, the hyperspectral images generated by interferential spectrometer can only be protected with better visual quality in spatial domain, but its optical applications in Fourier domain are often ignored. So the relation between the distortion in Fourier domain and the compression in spatial domain is analyzed in this letter. Based on this analysis, a novel coding scheme is proposed, which can compress data in spatial domain while reducing the distortion in Fourier domain. The bitstream of set partitioning in hierarchical trees （SPIHT） is truncated by adaptively lifting the rate-distortion slopes of zerotrees according to the priorities of optical path difference （OPD） based on rate-distortion optimization theory. Experimental results show that the proposed scheme can achieve better performance in Fourier domain while maintaining the image quality in spatial domain.     

Synchronization of Local Oscillations in a Spatial Rock-Scissors-Paper Game Model

We study a spatial rock-scissors-paper model in a square lattice and a quenched small-world network. The system exhibits a global oscillation in the quenched small-world network, but the oscillation disappears in the square lattice. We find that there is a local oscillation in the square lattice the same as in the quenched small-world 1 network. We define σ = 1/N ∑i（di-〈di〉^2 （where di is the density of a kind of species and （di） is the average value） as the variance of the oscillation amplitude in a certain local patch. It is found that σ decays in a power law with an increase of the local patch size R in the square lattice σ ∝ R^-σ, but it remains constant with an increase of the patch size in the quenched small-world network. We can speculate that in the square lattice, superposition between the local oscillations in different patches leads to global stabilization, while in the quenched small-world network, long-range interactions can synchronize the local oscillations, and their coherence results in the global oscillation.     

Recent progress on RF superconducting cavities

RF superconducting （SRF） cavities can work in continuous wave mode or long pulse mode. SRF technology has been developing rapidly since the end of the last century. RF superconducting technology is widely used in particle accelerators around the world. As the key elements, research on superconducting cavities is carried out worldwide. Besides Europe, the United States and Japan, many countries have already started SRF projects, such as Canada, India, Korea, etc. Great improvements on SRF technology have been made in China in recent years. Progress in SRF cavities is introduced in this paper.     

Mechanism and elimination of spectrum filtering in a high power mode-locked fibre laser witha free output coupler

The filtering mechanism of a free output coupler mode-locked laser based on large-mode-area photonic-crystal fibre is analysed. A filtering-soliton mode-locked laser with 495~fs pulse width and 21 nJ pulse energy is achieved. Another novel cavity configuration is established to eliminate the filtering effect. Pulses, each 457~fs in width and 16.5 nJ in energy, are obtained in a soliton-like regime. Pulses, each 387~fs in width and 15.8 nJ in energy, are also generated in a stretched pulse regime and could be dechirped to 119~fs externally to the cavity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Spin-1/2 relativistic particle in a magnetic field in NC phase space

This work provides an accurate study of the spin-l/2 relativistic particle in a magnetic field in NC phase space. By detailed calculation we find that the Dirac equation of the relativistic particle in a magnetic field in noncommutative space has similar behaviour to what happens in the Landau problem in commutative space even if an exact map does not exist. By solving the Dirac equation in NC phase space, we not only obtain the energy level of the spin-1/2 relativistic particle in a magnetic field in NC phase space but also explicitly offer some additional terms related to the momentum-momentum non-commutativity.     

Size effect in nuclear spin-lattice relaxation and atomic mobility for molten gallium particles

The spin-lattice relaxation rate of gallium isotopes in a melt was shown by NMR to increase considerably with a decrease in gallium particle size. The dominant relaxation mechanism of gallium embedded in an synthetic opal matrix changes from magnetic dipole to electrical quadrupole. The increase in the correlation time of atomic motion in gallium particles with a decrease in their size was estimated. For gallium in opal, the correlation time was found to increase by more than an order of magnitude. It was shown that a variation in atomic mobility becomes noticeable already in gallium particles about 5 μm in size. __________ Translated from Fizika Tverdogo Tela, Vol. 45, No. 12, 2003, pp. 2242–2246. Original Russian Text Copyright ? 2003 by Tien, Charnaya, Sedykh, Kumzerov.     

Surface defect gap solitons in two-dimensional optical lattices

We investigate the existence and stability of surface defect gap solitons at an interface between a defect in a two-dimensional optical lattice and a uniform saturable Kerr nonlinear medium. The surface defect embedded in the two-dimensional optical lattice gives rise to some unique properties. It is interestingly found that for the negative defect, stable surface defect gap solitons can exist both in the semi-infinite gap and in the first gap. The deeper the negative defect, the narrower the stable region in the semi-infinite gap will be. For a positive defect, the surface defect gap solitons exist only in the semi-infinite gap and the stable region localizes in a low power region.