The measurement of the phase constant of EH11 mode in the hollow dielectric waveguides

In this paper, we presented the results of experiments of propagation phase shift in the hollow dielectric waveguides of the radius a20 with farinfrared laser (wave length =0.337mm). The experimental results agree well with theoretical expecting values. The results also show that it is to exist a coupling length between TEM_oo mode and the funtamental hybrid waveguide EH₁₁ mode. The coupling length is obtained from our measurement.     

Cosmological models with constant deceleration parameter and bulk viscous mode

Recently Berman and Gomide have presented cosmological models with a constant deceleration parameter in general relativity without assuming a specific equation of state. It is shown that these models are equivalent to those with bulk viscosity. Some general remarks are made on the former models, including implications for violations of causality.     

Direct measurement of the pseudoscalar decay constant

The absolute branching fraction for the decay D⁺→μ⁺ν has been directly measured based on a data sample of about 33 pb⁻¹ collected around with the BES-II detector at the BEPC collider. A total of 5321±149±160 D⁻ mesons are reconstructed in nine hadronic decay modes. In the system recoiling against these singly tagged D⁻ mesons, 2.67±1.74 purely leptonic decay events of D⁺→μ⁺ν_μ are observed. Those yield the branching fraction of , and a corresponding value of the pseudoscalar decay constant .     

测量光栅常量的一种简便方法

介绍了用普通日光灯作光源测量光栅常量的简便方法。     

Elastic inconsistency of the force constant models for body centred tetragonal indium

The origin of the elastic inconsistency of a lattice dynamical model is analysed by resolving the atomic displacements of body centred tetragonal indium, along three mutually perpendicular directions. It is shown that the angular forces which include the three-body interactions as well as the mixed neighbour interactions, are mainly responsible for the elastic consistency of the CGW model, whereas the remaining models which neglect these interactions become elastically inconsistent as we go from cubic to tetragonal symmetry. Hence the former is unique and not equivalent to any of the latter, but a certain degree of equivalence exists among the force constants of the DAF, MAS, GTF and CGW models. The role played by two-body, three-body interactions and same neighbour, mixed neighbour interactions, the distortions introduced into the phonon dispersion curves of indium by the elastic inconsistency as well as the consequences of imposing the rotational invariance conditions on the force constants of a lattice dynamical model for non-cubic solids are discussed.     

Spectral-linewidth measurement with intracavity compensation for selective losses

We propose an intracavity method of determining the spectral linewidth based on the use of a special mode of operation of a laser with a magnetized atomic absorbing medium in an anisotropic cavity when the output radiation power of the laser does not depend on the optical density of the absorbing medium. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 283–285, May–June, 2000.     

测普朗克常量实验数据处理

提出了将实验数据进行分段曲线拟合,计算出曲线方程和交点的方法,并用LabVIEW8.6编写软件辅助数据处理,确定了截止电压U,经线性拟合可方便地得到精确的实验结果.     

改进恒Lyapunov指数谱混沌系统的同步方法与特性研究

改进恒Lyapunov指数谱混沌系统的特殊的分段线性结构及其全局线性调幅参数与倒相参数的存在性,赋予了其同步体系新的可实现性与可调节性.依据广义同步的原理,构造合适的驱动系统与响应系统,可以实现恒Lyapunov指数谱混沌系统的广义同步;改变响应系统的参数,可实现完全同步与广义投影同步;改进恒Lyapunov指数谱混沌系统的全局线性调幅参数能对驱动与响应系统的状态变量幅值实施同步升降控制,倒相参数能对某一特定状态变量实施同步倒相控制.这种同步体系无需专门的控制器,结构简单,易于实现.文章最后设计了同步体系的实现电路,实验仿真结果证明了混沌同步方法的可行性,也验证了恒指数谱混沌系统特殊参数对同步体系状态变量幅值与相位的调控作用.     

Improved measurement of the positive-muon lifetime and determination of the Fermi constant

The mean life of the positive muon has been measured to a precision of 11 ppm using a low-energy, pulsed muon beam stopped in a ferromagnetic target, which was surrounded by a scintillator detector array. The result, tau(micro)=2.197 013(24) micros, is in excellent agreement with the previous world average. The new world average tau(micro)=2.197 019(21) micros determines the Fermi constant G(F)=1.166 371(6)x10(-5) GeV-2 (5 ppm). Additionally, the precision measurement of the positive-muon lifetime is needed to determine the nucleon pseudoscalar coupling g(P).     

Stable single-mode operation of VCSELs with a mode selective aperture

We have developed single-mode vertical-cavity surface-emitting laser (VCSELs) with a mode selective aperture (MSA) in the DBR mirror that exhibits a high-order transverse-mode filtering effect. The VCSELs with an MSA were fabricated using standard intracavity-contacted VCSEL processes without any additional steps resulting from the simultaneous formation of the MSA and current aperture via a single-step oxidation. The VCSELs fabricated with a current aperture and MSA diameter of 5 and 7 μm, respectively, exhibited a stable single-mode operation with a side mode suppression ratio of over 35 dB and a divergence angle below 10° for the entire drive current range. PACS 42.55.Px; 85.35.Be     

New measurement of the electron magnetic moment and the fine structure constant

A measurement using a one-electron quantum cyclotron gives the electron magnetic moment in Bohr magnetons, g/2=1.001 159 652 180 73 (28) [0.28 ppt], with an uncertainty 2.7 and 15 times smaller than for previous measurements in 2006 and 1987. The electron is used as a magnetometer to allow line shape statistics to accumulate, and its spontaneous emission rate determines the correction for its interaction with a cylindrical trap cavity. The new measurement and QED theory determine the fine structure constant, with alpha{-1}=137.035 999 084 (51) [0.37 ppb], and an uncertainty 20 times smaller than for any independent determination of alpha.     

Elastic constant pressure derivatives and stability of the bcc phase of InTl alloys

Hydrostatic-pressure derivatives of the elastic stiffness constants have been measured ultrasonically in a bcc InTl alloy of composition near the eutectoid. The shear modulus $\text{1}\text{2}\text{(C}{}_{11}\text{?C}{}_{12}\text{)}$ is small, but does not soften under pressure: the eutectoid reaction is not directly associated with a mode softening shear instability. Anharmonic contributions to the excess vibrational entropy from the q 〈110〉, e 〈1$\text{1}$0〉 modes which stabilize the bcc structure are small compared with the harmonic contributions.     

Influence of the Earth's rotation on measurement of gravitational constant G with the time-of-swing method

In the measurement of the Newtonian gravitational constant G with the time-of-swing method,the influence of the Earth's rotation has been roughly estimated before,which is far beyond the current experimental precision.Here,we present a more complete theoretical modeling and assessment process.To figure out this effect,we use the relativistic Lagrangian expression to derive the motion equations of the torsion pendulum.With the correlation method and typical parameters,we estimate that the influence of the Earths rotation on G measurement is far less than 1 ppm,which may need to be considered in the future high-accuracy experiments of determining the gravitational constant G.     

基于少模光纤的全光纤熔融模式选择耦合器的设计及实验研究

提出了三种基于少模光纤的全光纤熔融模式选择耦合器. 根据模式匹配原理采用单模光纤与少模光纤熔融连接方式, 运用耦合模理论及光束传播法模拟分析了模式选择耦合器的结构参数对模式选择及耦合特性的影响, 实现了单模光纤中基模到少模光纤中不同阶模式的转换, 以满足不同的应用需求. 实验上以2× 2熔融光纤耦合器为例, 采用对称和非对称熔融拉锥方式, 分别实现了从基模到LP₁₁, LP₂₁模式的转换. 实验结果表明所得到的LP₁₁, LP₂₁模式在1530–1560 nm的波长带宽范围内均有较高的模式纯净度, 且模式耦合效率高于80%, 与理论模拟结果基本一致.     

Theory of the soft phonon mode and dielectric constant below the Peierls transition temperature

We discuss, within mean field theory, the behavior of the soft phonon mode and static dielectric constant below the Peierls transition temperature in a one-dimensional band conductor.     

High-order mode of polymeric waveguide selective excitation

Conditions for the selective excitation of multimode waveguide high-order modes by power trans-formation of fundamental modes of a tunnel connected waveguide are calculated. It is shown that the power conversion factor can reach 100% under phase-matching conditions, which can be satisfied by the selection of a second waveguide refractive index.     

激光散斑的亚像素位移法计算及比较

根据激光散斑相关测量中采用的插值法、梯度算法和牛顿一拉夫森迭代法3种亚像素位移算法的特点,逐一在亚像素尺度计算出磁流体干燥过程中的同一激光散斑图的偏均值和标准差变化曲线。基于得到的偏差均值和标准差讨论了3种算法处理激光散斑图的特点,比较了3种算法处理散斑图的计算精度、稳定性和计算用时。结果显示,在小变形的亚像素位移测量时,梯度算法的精度较高,且较为稳定,计算效率也较牛顿一拉夫森算法快约9倍。因此,在进行小变形亚像素位移测量时,采用梯度算法计算激光散斑是有效的。