Response characteristics of local vibrations in stay cables on an existing cable-stayed bridge

This paper examines local parametric vibrations in the stay cables of a cable-stayed bridge. The natural frequencies of the global modes are obtained by using a three-dimensional FE model. The global motions generated by (1) sinusoidal excitations using exciter, (2) a traffic loading, and (3) an earthquake are analyzed by using the modal analysis method or the direct integration method. The local vibration of stay cable is calculated by using a model in which inclined cable is subjected to time-varying displacement at one support during global motions. This paper describes the properties of the local vibrations in stay cables under these dynamic loadings by using an existing cable-stayed bridge.     

Location of acoustic emission sources generated by air flow

The location of continuous acoustic emission sources is a difficult problem of non-destructive testing. This article describes one-dimensional location of continuous acoustic emission sources by using an intelligent locator. The intelligent locator solves a location problem based on learning from examples. To verify whether continuous acoustic emission caused by leakage air flow can be located accurately by the intelligent locator, an experiment on a thin aluminum band was performed. Results show that it is possible to determine an accurate location by using a combination of a cross-correlation function with an appropriate bandpass filter. By using this combination, discrete and continuous acoustic emission sources can be located by using discrete acoustic emission sources for locator learning.     

Controllable optical multi-well trap and its optical lattices using compounded cosine patterns

This paper proposes a flexible scheme to form various optical multi-well traps for cold atoms or molecules by using a simple optical system composed of an compounded amplitude cosine-only grating and a single lens illuminated by a plane light wave or a Gaussian beam.Dynamic manipulation and evolution of multi-well trap can be easily implemented by controlling the modulation frequency of the cosine patterns.It also discusses how to expand this multi-well trap to two-dimensional lattices with single-or multi-well trap by using an orthogonally or non-orthogonally modulated grating,as well as using incoherent multi-beam illumination,and these results show that all the symmetric structures of two-dimensional Bravais lattices can be obtained facilely by using proposed scheme.     

An introduction to multi-GPU programming for physicists

We present and compare different approaches for using multiple Graphics Processing Units in the simulation of physical systems. As benchmarks we consider the time required to update a single spin of the 3D Heisenberg spin glass model, by using both the Over-relaxation and the Heat Bath algorithms, and the solution of a Poisson equation by using a finite-difference method. The results show that a suitable combination of techniques allows to hide almost completely the communication overhead by using the CPU as a communication coprocessor of the GPU. Large scale simulations on clusters of GPUs can be efficiently carried out by following the same approach for other applications where a clear cut exists between bulk and boundaries data.     

Dynamic recording of a digital hologram with single exposure by a wave-splitting phase-shifting method

The wave-splitting phase-shifting digital holography using a pixelated microretarder array is proposed. By using four intensity images recorded by the pixelated microretarder array, Stokes parameters of the incident wave can be calculated. The fully complex amplitude distribution of the object wave can be obtained by using Stokes parameters, if the polarization states of the object and reference waves are linear and orthogonal. Two sets of experimental results are provided to verify the feasibility of the proposed method. One is the result for a movie recording using a CW laser and the other is the result for instant recording using a single pulsed laser.     

Two-photon polymerisation of novel shapes using a conically diffracted femtosecond laser beam

Sub-micron ring, pillar and wall structures were written by two-photon polymerisation of a sol-gel resin using a femtosecond laser beam which was shaped using internal conical diffraction. The ring structure was written using a demagnified image of the ring-shaped beam which arises in conical diffraction of a narrow light beam. The pillar and wall structures were produced by imaging the Bessel beam formed by conical diffraction in combination with a converging lens.     

Magnetic properties of Ising metamagnet in both external longitudinal and transverse fields

The phase diagrams of a two-sublattice Ising metamagnet at finite temperature in a mixed longitudinal field and a transverse magnetic field are investigated by the use of an effective-field theory (EFT) with correlations. In addition to the second-order transition lines, the first-order transition lines are also presented in the phase diagrams, since the Gibbs free energy can be calculated numerically. The results show that there is no fourth-order critical line in the phase diagrams given by using EFT as found by using mean-field theory (MFT). The tricritical lines and their projection in the t−h_x plane obtained by using EFT are also quite different from those by using MFT. Only one type of phase diagram is obtained by using EFT while three kinds of phase diagrams are obtained by using MFT, which indicates that only the first kind of phase diagrams obtained by using MFT is reliable. Furthermore, it is shown that the region of first-order transitions increases as the transverse magnetic field h_x decreases.     

Acoustic radiation impedance of duct-nozzle system

A method is described to evaluate the radiation impedance spectra of a duct-nozzle system with and without mean flow by using measured reflection coefficient data. In this method the impedance at the junction of the duct and nozzle is first evaluated by using complex reflection coefficient data measured experimentally with an impulse technique. This impedance is then transferred to the nozzle exit by using a solution of the wave equation appropriate for the duct-nozzle system. The application of this method is described and results are presented to show the effect of nozzle geometry and the effect of mean flow on the radiation impedance of the duct-nozzle system. The results derived by using this method are compared with the similar results derived by using some approximate methods.     

高自由度体系微振动本征模式的求解方法

介绍两种求解高自由度体系微振动本征模式的方法．第一种方法：利用对称性经过物理分析寻找本征模式；第二种方法：利用对称性降低体系的自由度，然后用求解本征模式的一般方法解之．     

A second-order accurate finite volume method for the computation of electrical conditions inside a wire-plate electrostatic precipitator on unstructured meshes

In this paper, an unstructured cell-centered second-order accurate finite volume method is presented for the computation of electrical conditions inside wire-plate electrostatic precipitators. The potential equation was discretized using a second-order accurate scheme by invoking a new type of special line-structure. The space–charge density equation was discretized using a second-order upwind scheme, and solved using a new direct method. The local gradients are reconstructed by a weighted least-square reconstruction method. The method can deal with complex geometries by using unstructured meshes. Numerical experiments show that the predicted results agree well with the existing experimental data.     

基于多元素复合空心阴极灯的土壤有效养分测试

通过修改原子吸收分光光度计操作软件使其在利用单元素空心阴极灯进行测试的同时,可以直接装备多元素复合空心阴极灯进行相关测试.针对30个在北京取样的潮土样本,利用多元素复合空心阴极灯对其有效Cu,Fe,Zn,Mg,Ca含量进行了3次重复测试,同时与基于单元素空心阴极灯的测试进行了对比.结果表明,基于多元素复合空心阴极灯测试的土壤有效Cu,Fe,Zn,Ca含量与基于单元素空心阴极灯测试的呈显著线性相关关系,其R2均大于0.9,且线性回归方程的斜率接近于1;两种方法测试的土壤有效Mg含量之间的R2为0.86,其线性同归方程的斜率为o.85;对比数据之间经方差检验呈无显著性差异.因此,利用多元素复合空心阴极灯进行土壤养分测试不仅具有与单元素空心阴极灯相当的测试精度,还可节省40%～50%的测试时间从而提高测试效率.     

基于光子晶体光纤光脉冲压缩的理论研究

从理论上研究了单根光子晶体光纤的光脉冲压缩,利用较短的具有高非线性系数的光子晶体光纤可以实现较高质量的光脉冲压缩。针对单根光子晶体光纤压缩光脉冲的限制,提出了一种基于光子晶体光纤非线性环路镜中交叉相位调制效应的脉冲压缩方法。理论研究表明,这种脉冲压缩方式可以压缩自身功率较低的信号脉冲,相比于单根光子晶体光纤的方法,可以得到更高压缩质量的脉冲,通过合理选择控制光脉冲的参数,可以有效地抑制基座。     

Proposal of the nano-sensing device and system using a nano-waveguide transducer for distributed sensors

We propose a new concept of a distributed sensing system using a nano-waveguide and an array waveguide. The small change in physical quantity affects the change in device parameters such as refractive index or length, which is relatively absorbed and observed by the resonant wavelength. In principle, the dense wavelength separation is generated by using a soliton pulse propagating within a ring resonator system, whereas a resonant signal can be stored within the nano-waveguide, i.e. a transducer, which is formed by the sensing device. Induced change in the resonant signal at each wavelength occurs, and can be detected by using the optical spectrum analyzer. Such a proposed device is suitable to perform the measurements in the nano-scale regime such as force, stress and temperature. Moreover, the distributed or multiplexed sensing applications are also available using the nano-waveguide sensing device incorporating the array waveguide, which is discussed in details. Quantum measurement using the same system is also described.     

利用全反射原理测定水的折射率

介绍一种利用全反射原理测定水的折射率的方法。实验中利用He-Ne激光束在水底产生点光源,根据全反射原理对水底的暗影和水深进行测量,求出水的折射率。     

Deconvolution systems for coded aperture images of three-dimensional x-ray objects

A non-redundant distribution of ten point sources is used for coded aperture imaging. The coded image of a simple three-dimensional x-ray object is deconvoluted by means of three different decoding systems: by an optical projection system using spatially incoherent light, by an on-line optical set-up with information input using an electro-optic relay tube, and by a quasi-on-line electronic system using an electronic storage-tube. The three methods are compared with respect to signal-to-noise ratio, resolution, and convenience of handling.     

一种减小梯度线圈产生的涡流的方法

从原理上分析了减小梯度线圈的半径可以减小其在带抗涡流板磁体中引起的涡流.然后采用目标场方法设计了一组半径缩减的梯度线圈，并用Biot-Savart定理计算了这个梯度线圈的梯度线性区.最后通过磁共振成像实验证明了原理中分析得出的结论. 关键词： 梯度线圈 涡流 目标场 流函数     

Digital holographic imaging of aerosol particles in flight

This work describes the design and application of an apparatus to image aerosol particles using digital holography in a flow-through, contact-free manner. Particles in an aerosol stream are illuminated by a triggered, pulsed laser and the pattern produced by the interference of this light with that scattered by the particles is recorded by a digital camera. The recorded pattern constitutes a digital hologram from which an image of the particles is computationally reconstructed using a fast Fourier transform. This imaging is validated using a cluster of ragweed pollen particles. Examples involving mineral-dust aerosols demonstrate the technique's in situ imaging capability for complex-shaped particles over a size range of roughly 15-500 μm micrometers. The focusing-like character of the reconstruction process is demonstrated using a NaCl aerosol particle and is compared to a similar particle imaged with a conventional microscope.     

Non-Markoffian diffusion in a one-dimensional disordered lattice

Recent treatments of diffusion in a one-dimensional disordered lattice by Machta using a renormalization-group approach, and by Alexander and Orbach using an effective medium approach, lead to a frequency-dependent (or non-Markoffian) diffusion coefficient. Their results are confirmed by a direct calculation of the diffusion coefficient.Research supported by NSF Grant No. CHE 77-16308.     

Multiple access interference rejection in OCDMA using a two-photon absorption based semiconductor device

An experimental demonstration of a two-channel OCDMA system with detection performed using standard linear detection or a TPA-based nonlinear detector is presented. These results show an improvement in the extinction ratio of the decoded signal by ∼5 dB using TPA detection. A simulation model of the TPA detector used during the experiments was created and used in a four-channel OCDMA system simulation using both linear and nonlinear detection methods. The simulation results show that error-free performance is achievable for a 4-user system using the nonlinear TPA detector while the OCDMA system employing linear detection is severely limited by the effects of noise generated by adjacent optical channels (multiple access interference).