In situ speckle observation of Tyrano/BMAS composites in shear strength measurements

Strain profiles of specimens during interlaminar shear strength tests, short beam and double-notched compression, were measured by a speckle interference method using Tyrano^TR-related fiber-reinforced BaO–MgO–Al₂O₃–SiO₂ glass matrix composites with different surface finished fibers. The speckle interference method could detect changes in shear strain during the tests before the initiation of crack(s). Crack initiation could be detected earlier/easier by the speckle interference method than by video monitoring in both tests. Surface finish affected the shear strain profiles in the specimens. Sliding at the interface seemed to be detected in the composites reinforced with Tyrano fiber having a carbon layer. The speckle interference method is useful for measuring strains over wide areas of the specimens.     

Toughness enhancement by polycarbosilane coating on SiC whiskers incorporated in Si3N4 matrix composite

Si₃N₄ matrix composite was fabricated by hot pressing with 20% SiC whiskers coated with polycarbosilane (PCS). The preceramic polymer on the whiskers was pyrolysed during sintering to form a carbon-rich layer at the whisker/matrix interface. Mechanical properties were measured, and compared to those of the composites with whiskers purified with HCl and HF. Elastic modulus and bending strength of the composite with PCS-coated whiskers were lower than those of the composites with other whiskers. Fracture toughness was measured by single-edge notched beam (SENB) and single-edge precracked beam (SEPB) methods. The toughness, including crack-growth resistance measured by the SEPB method, increased from 7.2 MPam^1/2 to 7.9 MPam^1/2 by PCS-coating on the whisker, while the toughness measured by the SENB method decreased from 6.5 MPam^1/2 to 5.7 MPam^1/2. The layer derived from PCS facilitated debonding at the whisker/matrix interface and activated the wake-toughening. Optical microscopic observation of the crack propagation near the interface confirmed enhancement of interfacial debonding by the PCS-coating.     

Airborne polarized lidar detection of scattering layers in the ocean

A polarized lidar technique based on measurements of waveforms of the two orthogonal-polarized components of the backscattered light pulse is proposed to retrieve vertical profiles of the seawater scattering coefficient. The physical rationale for the polarized technique is that depolarization of backscattered light originating from a linearly polarized laser beam is caused largely by multiple small-angle scattering from particulate matter in seawater. The magnitude of the small-angle scattering is determined by the scattering coefficient. Therefore information on the vertical distribution of the scattering coefficient can be derived potentially from measurements of the time-depth dependence of depolarization in the backscattered laser pulse. The polarized technique was verified by field measurements conducted in the Middle Atlantic Bight of the western North Atlantic Ocean that were supported by in situ measurements of the beam attenuation coefficient. The airborne polarized lidar measured the time-depth dependence of the backscattered laser pulse in two orthogonal-polarized components. Vertical profiles of the scattering coefficient retrieved from the time-depth depolarization of the backscattered laser pulse were compared with measured profiles of the beam attenuation coefficient. The comparison showed that retrieved profiles of the scattering coefficient clearly reproduce the main features of the measured profiles of the beam attenuation coefficient. Underwater scattering layers were detected at depths of 20-25 m in turbid coastal waters. The improvement in dynamic range afforded by the polarized lidar technique offers a strong potential benefit for airborne lidar bathymetric applications.     

Auger electron spectroscopy depth profiling studies on stationary and rotated samples of a new model metal/semiconductor multilayer structure

Multilayer structures for application in microelectronics are becoming increasingly complex. A sputter deposited multilayer structure composed of chromium, nickel and silicon layers with a total thickness of 310 nm on a smooth silicon substrate was characterized by transmission electron microscopy (TEM) and by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) depth profiling. AES depth profiles of the Ni/Cr/Si multilayers were obtained with Ar⁺ ion bombardment at various angles of incidence using stationary and rotated samples. In some cases a strong influence of semiconductor structure on the experimentally obtained metal-metal and metal-semiconductor interface widths was observed. Owing to ion beam induced Si(LVV) Auger electrons in the crater wall of the Ni/Cr/Si sample, a distortional influence on depth resolution during simultaneous AES analysis and ion sputtering was found. Silicide formation during sputtering at the silicon-metal interfaces was confirmed by XPS. The measured compositional depth profiles are explained with respect to the influence of polycrystalline metallic and amorphous semiconductor structures; the effects of ion beam induced topography, atomic mixing and silicide formation are discussed.     

Surface gradient integrated profiler for X-ray and EUV optics

A new ultraprecise profiler has been developed to measure, for example, asymmetric and aspheric profiles. The principle of our measuring method is that the normal vector at each point on the surface is determined by making the incident light beam on the mirror surface and the reflected beam at that point of coincident. The gradient at each point is calculated from the normal vector, and the surface profile is then obtained by integrating the gradients. The measuring instrument was designed in accordance with the above principle. In the design, four ultraprecise goniometers were applied to adjust the light axis for normal vector measurement. The angle-positioning resolution and accuracy of each goniometer are, respectively, 0.018 and 0.2 μrad. Thus, in the measuring instrument, the most important factor is the accuracy of the normal vectors measured by the goniometers. Therefore, the rotating angle-positioning errors were measured and calibrated. An elliptical profile mirror for nanometer hard-X-ray focusing was measured, and compared with the measured profile using a stitching interferometer. The absolute measurement accuracy of approximately 5 nm (peak-to-valley) was achieved. Then the measurements of 1000-mm-long flat, spherical and parabolic mirrors were demonstrated. The surface profiles of the mirrors were obtained by integrating the interpolated gradient.     

Technique for nonuniform poling of piezoelectric element and fabrication of Gaussian transducers

A new technique has been developed to polarize piezoelectric ceramic elements with a nonuniform electric field. Used as an ultrasonic transducer, the piezoelectric element will produce a corresponding nonuniform sound field. Ultrasonic transducers for generating specific field profiles can therefore be made by having a predetermined spatial pattern of polarization strength poled into the piezoelectric element. One of the desirable beam profiles is a Gaussian; it has the advantages of being free from near-field fluctuations and far-field sidelobes, and it is much easier to model than the usual piston transducers. This method was used to fabricate Gaussian beam transducers, and their measured field profiles compared well with the Gaussian beam model. Such transducers containing the built-in Gaussian amplitude profile can be electroded and mounted in the same manner as conventional piston transducers.     

Planar optical waveguides in Nd:BSO crystals fabricated by He and C ion implantation

Planar optical waveguides in Nd:BSO crystals were fabricated by the implantation of 500 keV He ions and 6.0 MeV C ions at two different substrate temperatures. The guiding modes were measured by the prism-coupling method with a He-Ne beam at 633 nm. The intensity calculation method (ICM) and reflectivity calculation method (RCM) were used for reconstructing refractive index profiles. The near-field intensity distribution of the waveguide, formed by He and C ions implanted after annealing at 300 °C, was measured by the end-face coupling setup. It was in reasonable agreement with the intensity of the waveguide mode simulated by the finite-difference beam propagation method (FD-BPM). The absorption spectra of the sample with He ions implanted at fluences of 3 × 10¹⁶ ions/cm² were measured using a spectrophotometer.     

Decorrelation characteristics of transverse blood flow along an intravascular array catheter

In recent years, a new method to measure transverse blood flow based on the decorrelation of radio frequency (RF) signals has been introduced. In this paper, we investigated the decorrelation characteristics of transverse blood flow measurement using an intravascular ultrasound (IVUS) array catheter by means of computer modeling. Blood was simulated as a collection of randomly located point scatterers. Moving this scattering medium transversally across the acoustical beam represented flow. First-order statistics were evaluated, and the signal-to-noise ratio from the signals was measured. The correlation coefficient method was used to present the results. The decorrelation patterns for RF and for RF-envelope signals were studied. The decorrelation patterns from the RF signals were in good agreement with those obtained from theoretical beam profiles. This agreement suggests that the decorrelation properties of an IVUS array catheter for measuring quantitative transverse blood flow can be assessed by measuring the ultrasound beam. A line of point scatterers, moved transversally across the acoustical beam (line spread function), can determine this decorrelation behaviour.     

The influence of nonlinear fields on miniature hydrophone calibration using the planar scanning technique

Miniature polyvinylidene fluoride (PVDF) hydrophones used in determining the power and intensity output of ultrasonic fields, including those radiated from diagnostic ultrasound equipment, were calibrated under a variety of field conditions using the planar scanning technique. A diagnostic B-scan piston-type transducer was used as a source, and the output intensity (spatial-peak pulse-average, or SPPA) was varied from 2 to 30 W/cm(2) while the total power was kept constant. The higher-intensity waveforms were significantly nonlinear in the focal region of the source. When the lateral beam profiles of the source (as measured by the hydrophone to be calibrated) were determined by positive-peak-detecting the ultrasonic pulse, the calibrated pressure sensitivity of the hydrophone systematically decreased as the field became progressively more nonlinear. When the beam profiles were measured using the pulse intensity integral, no systematic dependence of the calibration on field linearity was noted. These results imply that measured values of power and intensity of ultrasound diagnostic equipment may be dependent on the methodology utilized to map the lateral beam profiles of the transducer being measured, and the extent of nonlinear effects in the field under characterization.     

Fabrication and characterisation of aluminium clad aluminium–copper alloy cored rod

Abstract

The Ohno continuous casting process was successfully applied to cast cored rod with Al–Cu alloy as a core material and Al as a clad material. Good metallurgical bonding was observed at the core/clad interface. Ultrasonic characterisation and pulse–echo measurements were performed to assess the suitability of the material as an acoustic buffer rod. Acoustic velocity profiles across the rod diameter and acoustic anisotropy were measured using a 225 MHz line focus beam scanning acoustic microscope. Longitudinal wave measurements with excellent signal/noise ratios were obtained.

MST/3154     

碳纤维在电子束辐射过程中对树脂基复合材料界面性能的影响

采用XPS和Raman分析了电子束辐射对碳纤维表面性质的影响，研究了碳纤维与基体树脂之间的不充分接触对电子束固化复合材料层间剪切强度的影响，同时分析了碳纤维表面吸附的水分，碳纤维与基体树脂之间的空隙率和碳纤维表面在碳酸氢铵电解液中进行阳极氧化处理后对电子束固化复合材料界面性能的影响，分析了碳纤维表面在电子束辐射过程中与树脂基体的作用机理。     

LEED intensity measurements by an improved Faraday cup collector

A new collector for post diffraction acceleration LEED equipment is described. By changing the energy of the beam at normal incidence, the spots in the LEED pattern are moving in radial direction. The intensity of the scattered electrons is measured with a fixed electron collector on the whole length of a radial silt in the fluorescent screen scanned by a helix rotating around the axis of the electron gun. The method is capable of measuring intensity beam profiles and angular beam profiles by different modes of operation. The background is monitored simultaneously on the whole silt length allowing subsequent background control or subtraction and electronic processing of the signal. With the present set-up diffracted electron beam currents down to 10^?12 A can be detected. The measuring time for one point of an l(E) curve is limited by the rotary frequency of the helix and the time constants of the electronic equipment.     

Monte Carlo simulation of the photon beam characteristics from medical linear accelerators

The MCNPX code has been employed on a personal computer to calculate the dosimetric characteristics of the photon beams from the 6 MV Siemens MX2 and the 10 MV Varian Clinac 2100C linear accelerators. A model of the treatment head includes the major geometric structure within the beam path. The model was used to calculate the energy spectra of the photon beam, percentage depth dose and the dose profiles. The accuracy of the calculated results is examined by comparing them with the measured dose distributions for the two machines. The computed and measured depth dose curves agree to within 2% for all the depths beyond the build-up region for both treatment machines. The calculations agree to within 2% of the measured profiles within the 100-50% dose level. It has been found that the MCNPX code is an effective tool for simulating the clinical photon beam.     

Free vibration analysis of functionally graded beams with non-uniform cross-section using the differential transform method

Free vibrations of non-uniform cross-section and axially functionally graded Euler–Bernoulli beams with various boundary conditions were studied using the differential transform method. The method was applied to a variety of beam configurations that are either axially non-homogeneous or geometrically non-uniform along the beam length or both. The governing equation of an Euler–Bernoulli beam with variable coefficients was reduced to a set of simpler algebraic recurrent equations by means of the differential transformations. Then, transverse natural frequencies were determined by requiring the non-trivial solution of the eigenvalue problem stated for a transformed function of the transverse displacement with appropriately transformed its high derivatives and boundary conditions. To show the generality and effectiveness of this approach, natural frequencies of various beams with variable profiles of cross-section and functionally graded non-homogeneity were calculated and compared with analytical and numerical results available in the literature. The benefit of the differential transform method to solve eigenvalue problems for beams with arbitrary axial geometrical non-uniformities and axial material gradient profiles is clearly demonstrated.     

Measurement of the Diffusion Coefficient of Miscible Fluids Using Both Interferometry and Wiener's Method

Measurements of the diffusion coefficient of two miscible liquids are reported. The liquids are various combinations of pure silicone oils and those to which small amounts of solvents are added to control the difference in density between the fluids. The liquids were placed in a quartz cell such that the interface is initially horizontal. As the fluids diffuse, the profile of the index of refraction near the interface is time dependent and is related to the local concentration of the diffusing fluids. The concentration gradient profile was measured by a shearing interferometer incorporating a Wollaston prism, as well as Wiener's method. In the latter technique, a 45° light sheet was passed through the test cell, and the local deflection of the light beam was measured. The average diffusion coefficient was obtained by analysis of the measured concentration gradient profile, assuming that the diffusion process is one-dimensional and is characterized by a constant value of the diffusion coefficient.     

A New Method Combining Lagrangian Analysis with Hopkinson Pressure Bar Technique

Abstract: The Lagrangian analysis method is re‐analysed. It is shown that when a series of particle velocity profiles (or strain profiles) are measured to determine the dynamic stress–strain relation by the Lagrangian analysis, the crux is attributed to how to simultaneously measure both the stress and particle velocity wave profiles at a Lagrangian position by a combining stress–velocity gauge. The related experimental technique has not been satisfactorily solved yet. Thus, a new method combining the Lagrangian analysis with the Hopkinson pressure bar (HPB) technique is proposed. It is shown that the interface between the HPB and the specimen in fact provides such a combining gauge (called 1sv). Based on this technique, the so‐called ‘1sv + nv’ inverse analysis method is developed when particle velocity profiles are measured at n Lagrangian positions, and similarly the so‐called ‘1sv + nε’ inverse analysis method are developed when strain profiles are measured at n Lagrangian positions. The feasibility of the new method is evaluated by numerical simulations for a typical rate‐dependent viscoelastic material polymethyl methacrylate. The good agreement between the known ‘characteristics solutions’ and the present solutions confirms the validity of the proposed new method.     

Chemical characterization of plasma-polymerized hexamethyldisilazane by nuclear elastic recoil detection

Chemical composition profiles of plasma-polymerized hexamethyldisilazane thin films, deposited in microwave discharges, were measured by elastic recoil detection (ERD). The main fabrication variable during film deposition was the substrate temperature, which was varied from 25 to 650°C. Hydrogen, carbon and silicon concentrations and profiles to a depth of roughly 1 μm were measured by ERD. These concentrations were compared with results obtained by conventional chemical microanalysis, and agreement was found to be excellent. As in earlier work using other techniques, ERD confirmed the presence of a thin (approximately 50 nm) “oligomeric” layer at the free surface of the films. Erosive radiation damage caused by the probing ion beam on the carbon and hydrogen profiles was observed and investigated.     

基于界面单元的子结构协调技术

该文提出一种用于协调子结构的界面单元方法。基于广义变分原理,将两子域的刚度与界面单元刚度组装成耦合结构的整体刚度矩阵,求解新的平衡方程即可得到各个耦合子域的位移。界面单元的意义是对子域引入边界力,并建立边界上平衡关系和位移协调关系。该文利用悬臂梁单轴受拉案例验证了界面单元方法的精确性。为了使得界面单元能够应用到子结构混合试验中,引入静力凝聚与BFGS方法,这样只需通过提取边界上的力与位移即可实现多子域不共节点的边界协调问题。该文最终以悬臂梁案例验证了界面单元在解决非线性静、动力加载工况下的正确性。     

基于整体-局部弯曲模型的钢-混凝土组合梁界面滑移及其效应分析

提出了具有界面滑移的钢-混凝土组合梁截面弯矩由不考虑滑移的整体梁承担整体弯矩和自由滑移的叠合梁承担局部弯矩的整体-局部弯曲模型。基于Bernoulli梁理论和抗剪连接件线性剪力-滑移模型,建立了截面弯矩及剪力分配的计算方法,得到了整体-局部弯曲模型计算界面滑移及考虑界面滑移的截面应力和梁弯曲挠度的公式,并给出了集中荷载作用下简支组合梁的栓钉剪力及界面滑移计算公式。     

Correction of secondary ion mass spectrometry profiles for atom diffusion measurements

A simple method is proposed in order to correct experimental secondary ion mass spectrometry (SIMS) profiles. This method uses only one parameter which is experimentally accessible. It is tested in the case of As SIMS profiles in Si(001) acquired with three different primary ion beam energies: 1, 3, and 9 keV. This method is shown to give consistent corrections. The correction of SIMS profiles measured in a same sample with different analysis conditions leads to the same As distribution.