1982／1983年季风准双周振荡的位相传播及地理特征

选取１９８２／１９８３年夏季（６～８月）欧洲中期预报中心８５０ｈＰａ、３００ｈＰａ两层纬向风场的网格点资料，采用复经验正交函数（ＣＥＯＦ）讨论了准双周振荡的位相传播及振荡的地理特征。结果表明：①２０°Ｎ以南对流层高层（３００ｈＰａ）１９８２年振荡显著区域是印度半岛至菲律宾东部一个西西北－东东南走向的带状区域４低层（８５０ｈＰａ）１９８２年５°～１５°Ｎ之间以及中国东南部及其沿海地区都是振荡的显著区域；而１９８３年３０°Ｎ以南振荡明显比１９８２年弱，只有中国东南沿海部分地区及孟加拉湾东南、马来西亚北部是振荡的显著区域。②对流层高层（３００ｈＰａ）１９８２年８５°～９０°Ｅ，３０°～４０°Ｎ的青藏高原是振荡的源区，其南传支波列可传到盂加拉湾北部的２０°Ｎ附近；而１９８３年青藏高原上８０°～９０°Ｅ，３５°～４０°Ｎ区域是振荡的汇区。

传播于理想液体内的非均匀平面波

利用声学非均匀平面波在两种各向同性的均匀介质分界面上的折射定律,论证和提出了在理想液体内产生非均匀平面波的方案,并用实验进行了验证。

Contrast enhancement of medical ultrasound imaging with reversal phase-inversion pulse technology

A new ultrasound contrast imaging technique was proposed for eliminating the harmonic components from the emission signal transmitted by the broadband ultrasonic system.Reversal phase-inversion pulse was used for the first time to separate the contrast harmonics from the harmonics in the emission signal to improve the detection of contrast micro-bubbles.Based on the nonlinear acoustic theory of finite-amplitude effects and the associated distortion of the propagating wave,the Bessel-Fubini series model was applied to describe the nonlinear propagation effects of the reversal phase-inversion pulse,and the Church's equation for zero-thickness encapsulation model was used to produce the scattering-pulse of the bubble.For harmonic imaging,the experiment was performed using a 64-element linear array,which was simulated by Field II.The results show that the harmonic components from the emission signal can be completely cancelled,and the harmonics generated by the nonlinear propagation of the wave through the tissue,can be reduced by 15-30 dB.Compared with the short pulse,the reversal phase-inversion pulse can improve the contrast and definition of the harmonic image significantly.

Effects of Phase Damping on Controlled Teleportation of a Qubit by a GHZ State

We investigate controlled teleportation ofa qubit via a GHZ state with the influence of phase damping in the Bloch sphere representation. We use the average trace distance to describe how close the output state is to the input state to be teleported. Our results show that the average trace distance is a function of decoherence rates and angles of the analyzer performed by the controller in the single-particle projective measurement. Moreover, for a fixed value of the decoherence rate, one can adjust the analyzer angle to achieve the optimal average trace distance.

Evanescent wave of extraordinary beam at uniaxial crystal surfaces

Under the circumstance of optical axis being in the incident plane,the evanescent wave of total reflection is studied when an extraordinary beam is incident from an isotropic medium upon a uniaxial crystal by using the general characteristics of uniaxial crystal and electromagnetic field.This paper presents the propagation directions of equiphase plane and the images of evanescent wave,and reveals that the equiamplitude plane and the equiphase plane are not in quadrature any more,and the phase difference between longitudinal wave and transversal wave does not equal π/2,either.But the reflectivity is still kept at 100.

Influence of relative phase on propagation effect in open V-type three-level system

In this paper we study the influence of the relative phase between .the probe and driving fields on propagation effect in an open Doppler broadening V-type three-level atomic system with spontaneously generated coherence （SGC） by using the calculation resuk of the density matrix motion equations and the propagation equations of the driving and probe fields. It is shown that the relative phase （Ф） has remarkable periodical influence on the propagation effect, and the period is 2π. By selecting appropriate value of Ф, we can get larger lasing without inversion （LW1） gain and longer propagation distance in which gain exists, and hence obtain higher probe field （i.e. LWI） intensity. When Ф=π/2, the largest LWI gain and probe field intensity can be got. In addition, the atomic exit rate （γ0） and ratio （S） of the atomic injection rates also have a considerable modulation role on the phase-dependent propagation effect. In certain value range of Y0 （S）, LWI gain and probe field intensity increase with γ0 （S） increasing. In the open system, LWI gain and probe field intensity much larger than those in the corresponding closed system can be obtained.

Numerical study on pulse trapping in birefringent photonic crystal fibers

Using an adaptive split-step Fourier method,the coupled nonlinear Schrdinger equations have been numerically solved in this paper.The nonlinear propagation of an ultrashort optical pulse in the birefringent photonic crystal fibers is investigated numerically.It is found that the phenomenon of pulse trapping occurs when the incident pulse is deviating from the principal axis of the fiber with some angle.Owing to the birefringence effect,the incident pulse can be regarded as two orthogonal polarized pulses.The phenomenon of pulse trapping occurs because of the cross phase modulation(XPM) between the two components.As a result,the bandwidth of the supercontinuum(SC) decreases compared with the case that the incident pulse is input along the principal axis.When the polarization direction of the incident pulse is parallel to the fast axis,the bandwidth of the supercontinuum is maximal.