Microwave switching behaviors of Fe/Ag/Fe/Ag epitaxial films

In this study, Fe/Ag/Fe/Ag ferromagnetic structures were epitaxially grown on a GaAs(1 0 0) substrate. Using the Network Analyzer (Agilent 8510C), FMR (ferromagnetic resonant) signals were observed in samples as the in-plane magnetic field was applied to either hard- or easy-axes. Of interest was that our sample demonstrated a FMR-switching behavior in hard-axis but not in easy-axis. The detecting data showed that the switch magnetic field was much smaller than what has been stated previously in Fe/Cu/Fe systems by other laboratories. In addition to the frequency switch in FMR, we also observed a magnetic reversal behavior in its M–H curve. Data presented that both of the FMR and magnetic reverse took place in the same direction (hard-axis).     

Studies of picosecond spectro-temporal selection lasers using different dyes in microcavities with a two-stage-arrangement

Received: 18 April 1996/Revised version: 14 August 1996     

Technique for compensating excessive rigid body motion in nondestructive testing of large structures using shearography

A major limitation of speckle interferometry techniques including shearography is that the occurrence of rigid body motion produces a decorrelation of speckle patterns which destroys the fringe visibility. This paper demonstrates that digital shearography can tolerate much greater rigid body translation than a speckle size as predicted by the conventional speckle decorrelation theory. Excessive rigid body translation in digital shearography can be compensated by either translating the sensor/camera or digitally shifting one of the speckle patterns.     

C-band continuously tunable lasers using tunable fiber Bragg gratings

We report the development of a ring tunable fiber laser based on tunable fiber Bragg gratings (TFBG) integrated with an optical circulator. The TFBG is embedded inside a 3-piont bending device for wavelength tuning. The tunable laser operating in the C-band has power variation, tuning resolution, tuning range and laser line width of ±0.5 dB, 0.5 nm, 25.0 nm and less than 0.05 nm, respectively. As 40 mW of pump power is used, the ring tunable laser has a side mode suppression ratio of 60 dB and a power conversion efficiency of 25%. These specifications ensure the high-quality operation of a tunable laser.     

Thermally enhanced optical nonlinearity in nematic liquid crystal close to phase transition temperature

This study investigates the beam profile and the liquid crystal (LC) arrangement affected by an optical field on LC thin films at a temperature close to nematic-isotropic phase transition temperature (T_NI). A combined microscopic and conoscopic technique was used in experiments as a convenient way to analyze the optical nonlinearity that is associated with the molecular configuration of nematic liquid crystal (NLC). An optical field combined with thermal enhancement enhances molecular reorientation and causes additional molecular excitation along the axis of propagation of the beam. The reorientational nonlinearity yields an undulating structure with multi-foci; the length between each pair of foci increases with time, as described.     

BaFCl0.5Br0.5:Sm2+的荧光特性分析

本文是对无机光谱烧孔的典型材料BaFCl_0.5Br_0.5:Sm²⁺的发光动力学过程进行的探索。通过实验得到了⁵D₂、⁵D₁、⁵D₀→⁷F₀的荧光强度、荧光衰减曲线随温度的变化关系,对⁵D₂→4f5d带的热激活、⁵D_J间的无辐射弛豫,⁵D_J→⁷F₀的辐射跃迁等过程进行了分析。     

Polarized Laser Raman Spectra of the Crystal Cs3UO2F3

Abstract

Polarized Raman spectra of Cs₃UO₂F₅ in which the UO₂F₅ ^3? ion is in its statistical position have made it possible to assign definitely the Raman fundamental vibration modes as follows : v₁(A′¹) = 784, v₂(A′¹) = 423, v₈(E′²) = 325, v₈(E′²) = 219 and v₁₀(E″¹) = 259 cm^?1.     

Real-time monitoring of clamping force of a bolted joint by use of automatic digital image correlation

Bolts are widely used in industry for joining members together. The behavior and service life of bolted joints depend on several factors including bolt material, dimensions, surface finish, surface coating and thread tolerances. However, the uppermost factor affecting the reliability and durability is the correctness of the clamping force exerted by the bolt. Thus it is very important to monitor the bolt clamping force to ensure a proper preload during assembly process. Each of the available monitoring techniques including torque control, torque-angle control, strain gauged bolt and ultrasound suffers one or more limitations which affect the reliability of measurement. In this paper, we propose an alternative method for direct tension measurement, which utilizes a washer with a white light speckle pattern on its face as an optical force transducer. By measuring the strain of the washer using automatic digital image correlation, the clamping force can be determined. This method, which enables real-time monitoring of clamping force during fastening, has a potential of being used for mass measurement of clamping force in a production environment. Experiments conducted on bolted structures with washers of different sizes have demonstrated the reliability and usefulness of this new approach.     

A thermodynamic lattice theory on melting curve and eutectic point of binary alloys. Application to fcc and bcc structure

A thermodynamic lattice theory has been developed for determination of the melting curves and eutectic points of binary alloys. Analytical expressions for the melting curves of binary alloys composed of constituent elements with the same structure have been derived from expressions for the ratio of root mean square fluctuation in atomic positions on the equilibrium lattice positions and the nearest neighbor distance. This melting curve provides information on Lindemann’s melting temperatures of binary alloys with respect to any proportion of constituent elements, as well as on their eutectic points. The theory has been applied to fcc and bcc structure. Numerical results for some binary alloys provide a good correspondence between the calculated and experimental phase diagrams, where the calculated results for Cu_1−x Ni _x agree well with the measured ones, and those for the other alloys are found to be in a reasonable agreement with experiment.