Scattering of plane acoustic waves by a transversely isotropic cylindrical shell—application to material characterization

Scattering of obliquely incident plane acoustic wave by an air-filled, transversely isotropic cylindrical shell immersed in water is investigated theoretically and experimentally. The normal mode expansion technique is employed for analyzing the scattering field, and then resonance modes of the shell appearing in modal scattering form functions are identified performing the resonance scattering analysis. Dispersion curves for Sholte-Stoneley, SH and Lamb waves are obtained and their characteristics are interpreted. Calculated backscattering and resonance spectra as well as dispersion curves are compared with those from ultrasonic experiments for two composite samples having the same nominal composition but fabricated under different conditions. Sensitive change of the dispersion curves is observed for both normal and oblique incidences, which demonstrates the feasibility of systematic inverse evaluation of damage or elastic constants of the composite shell using data from the acoustic scattering measurements.     

Progress in liquid crystalline dispersions: Cubosomes

Dispersed particles of bicontinuous cubic liquid crystalline phase, cubosomes, are self-assembled nanostructured particles that can be formed in aqueous lipid and surfactant systems. Contributions to cubosome research have come from the fields of biology, material science, medicine, and mathematics and much is known about their formation and properties. At the center of much of the discovery and innovation is the technique of cryo-transmission electron microscopy. Most of the research into cubosomes is motivated by potential applications in drug delivery and material synthesis although no commercialized product based on cubosomes is known. Recent advances in understanding and use of cubosomes are discussed in the context of some of the more promising application areas and the opportunities for microscopy techniques to make unique contributions to these areas.     

Anodic voltammetric behaviors of methotrexate at a glassy carbon electrode and its determination in spiked human urine

The anodic voltammetric behavior of methotrexate was studied at glassy carbon electrode in acetate buffer (pH = 3.6) solution using cyclic, square-wave voltammetric and chronocoulometric techniques. The oxidation of methotrexate is an irreversible diffusion-controlled process. The oxidation mechanism was proposed and discussed in this work. The dependence of the current on pH, the concentration and nature of buffer, and instrumental parameters were investigated to optimize the experimental conditions for the determination of methotrexate. It was found that in the range of 8.0 × 10⁻⁷–2.0 × 10⁻⁵ mol/L, the currents measured by square-wave voltammetry presented a good linear property as a function of the concentrations of methotrexate. In addition, validation parameters, such as reproducibility, sensitivity and recovery were evaluated as well. The proposed method was also successfully applied for the determination of methotrexate in diluted human urine with good satisfactory.     

Controllability properties of nonlinear behaviors

This paper proposes a topological framework for the analysis of the time shift on behaviors. It is shown that controllability is not a property of the time shift, while chain controllability is. This also leads to a global decomposition of behaviors.

     

On the use of nickel foil strain gages at varying temperatures

When a strain gage made of nickel foil attached on the surface of a specimen is subjected to repeated loads, the elastic stress is measured by observing slip-bands in the foil resulting from repeated strain. Calibration studies with rotating-bending tests at various temperatures between room temperature and 350°C are performed on round steel bars with nickel foil. The relation between the threshold stress for the first appearance of slip-bands and the number of stress cycles is examined at varying temperatures, which provides the calibration values of the nickel foil tested at varying temperatures. Assuming that the first appearance of slip-bands is based on the linear cumulative damage law, the calibration values at varying temperatures are calculated from those established by the calibration tests at several constant temperatures. It is found that the calculated calibration values agree well with the results obtained by the calibration tests at varying temperatures and that the calculation applying the linear cumulative damage law is a useful method to presume the calibration values at varying temperatures without performing the experiment.     

森林地表火火行为预测预报系统

本文从地表火蔓延的本质入手，建立了一整套求解地表火行为特征量的数学模型，并运用现代软件编制技术，成功地编制出预测预报地表火行为的计算机软件。该系统能预测复杂地形、气象条件和可燃物分布情形下，火蔓延过程中不同阶段的火行为状况。算例结果表明，系统在预测结果的合理性和准确性等方面优于美国的BEHAVE程序。     

Heterofullerenes: Structure and property predictions,possible uses and synthesis proposals

Summary Substituting carbon atoms of fullerenes by heteroatoms and vacancies will lead to new and yet unknown spherical-shaped molecules termed hereafter as heterofullerenes. The enormous structural diversity of these molecules is investigated and their structural, electronic and thermochemical properties are predicted using semiempirical computations. Computational results for complexes with ions lead to the hypothesis that these molecules behave like microscopic Faraday cages in which the electrons concentrate on the outer side of the sphere. It is predicted that some of these heterofullerenes are structurally and electronically similar to phthalocyanines and related molecules but offer many additional advantages. Potential uses such as adding heterofullerenes to fullerene materials, as superior starting materials for the fabrication of diamonds, as catalysts in hydrogenation reactions, as components of materials dominated until now by phthalocyanines, etc., are discussed. Simple synthetic routes to these compounds that are based on minor alternations of existing methods for fullerene production are proposed. On the basis of the thermochemical calculations, we believe that the most promising possibility consists of using metal cyanide/graphite composite target rods instead of pure graphite rods as in a conventional fullerene synthesis.     

On stress rate and plasticity constitutive equations referred to a body-fixed coordinate system

Investigators have viewed the stress rate in two different ways: the material (body-fixed) point of view and the Eulerian point of view. We discuss the Zaremba–Jaumann rate and Oldroyd’s rate from the material viewpoint and apply them to the material formulation of a theory of plasticity for materials undergoing anisotropic plastic deformation. Significant advantages of the material formulation are that the derivation of equations is straight forward, the distortion of yield surface can be easily accounted for, and the issue of self-consistent elastic equation does not arise.     

Dynamics of laser hole drilling with nanosecond periodically pulsed laser

Results are presented on the dynamics of the laser drilling process for a single hole using a periodically pulsed nanosecond laser with a repetition rate up to 60 kHz. The intensity dependence of drilling velocity was determined by measuring the delay time between the beginning of exposure and the moment when the hole opens. The hole collapse phenomenon was observed in our experiments. The competition process between material ejection and the flow of the liquid phase into the ejected area is supposed to be responsible for the hole collapse.     

Yield drag in a two-dimensional foam flow around a circular obstacle: Effect of liquid fraction

We study the two-dimensional flow of foams around a circular obstacle within a long channel. In experiments, we confine the foam between liquid and glass surfaces. In simulations, we use a deterministic software, the Surface Evolver, for bubble details and a stochastic one, the extended Potts model, for statistics. We adopt a coherent definition of liquid fraction for all studied systems. We vary it in both experiments and simulations, and determine the yield drag of the foam, that is, the force exerted on the obstacle by the foam flowing at very low velocity. We find that the yield drag is linear over a large range of the ratio of obstacle to bubble size, and is independent of the channel width over a large range. Decreasing the liquid fraction, however, strongly increases the yield drag; we discuss and interpret this dependence.