Chemical composition of volatile and fixed oils from of Salvia argentea L. (Lamiaceae) growing wild in Sicily

The chemical compositions of the essential oil and of the non-polar extracts (petroleum ether, dichloromethane) of the aerial parts (flowers, leaves and stems) of Salvia argentea L. were determined by GC-FID and gas chromatography–mass spectrometry analysis. 14-Hydroxy-α-humulene (40.1%) was recognised as the main constituents of the essential oil of S. argentea, together with 1,3,8-p-menthatriene (12.1%), globulol (7.4%) and β-sesquiphellandrene (5.8%). Tritriacontane (9.9% and 14.1%), heptacosane (8.4% and 10.5%), hentriacontane (8.3% and 10.9%), tetradecanal (8.4% and 10.2%) and methyldotriacontane (7.9% and 7.6%) were recognised as the main constituents of the extracts in petroleum ether and dichloromethane, respectively, whereas methyl linolenate (36.6% and 13.5%) and methyl myristoleate (10.5% and 18.5%) were recognised as the main constituents of the methylated extracts.     

基于四波混频效应实现弱光对强光信噪比优化的研究

我们理论上研究了基于热铷原子系综中的四波混频效应实现信噪比优化的系统。我们分析了非相敏放大器与相敏放大器中信号光信噪比的变化情况。在非相敏放大器中,信号光为相干态注入,闲置光为真空态注入,此时信号光在被放大的同时,信噪比降低,其噪声系数大于1。在相敏放大器中,信号光和闲置光均为相干态注入,此时在特定的条件下,信号光在被放大的同时信噪比得到提高,其噪声系数小于1。在注入光束间的相对相位=2 kπ(k为整数)时,信号光的有效增益最大且噪声系数最小。在这样的相对相位下,只要注入闲置光光强高于注入信号光光强的17.2%时,信号光就能够在被放大的同时信噪比得到提高。特别地,当注入闲置光光强同时低于注入信号光光强时,就实现了弱光对强光信噪比的优化作用。     

Representative Curves for Longitudinal Data via Regression Trees

Abstract

Simple superposition of individual curves, as arise in longitudinal studies, makes the detection of structure difficult due to clutter. This is especially true when the number of curves is large, but can even be exhibited in moderate sample settings when variability is high. Both Jones and Rice and Diggle, Liang, and Zeger proposed methods for identifying representative curves from a large collection that display the form and extent of variation of the curves. Here we propose the use of tree-structured regression, as adapted to longitudinal data, for this purpose. Properties of each method are described. A re-examination of atmospheric ozone data, analyzed by Jones and Rice, is also presented.     

ONSET CONDITION OF STRAIN LOCALIZATION IN MATRIX OF SATURATED POROUS MEDIA

Introduction Strainlocalizationofgeomaterialsisoneofmostpopularfailuretypesinnature,which canbeshowedaslandslidesandmudflowsinmountainousareasunderincessantorheavy raining,especiallythevegetationisseverelydamagedbywoodsharvest;pipingeffect,a typeoflocalfa…     

杆状弯曲行波型超声电机运动机理研究

为了深入研究杆状弯曲行波型超声电机的运动机理，本文分析了定子表面质点椭圆运动轨迹的形成，并将椭圆运动分解为产生驱动力的有效椭圆运动与使定、转子产生径向滑动的径向直线运动；然后基于有效椭圆运动变化情况，分析了在两相振幅不平衡和任意相位差情况下对转子运动平稳性的影响，为这类电机的设计和性能控制提供理论依据。     

Layered model of electrorheological fluid under flow

We present a theoretical model of the behavior of a concentrated electrorheological fluid (ERF) which explicitly takes into account the effects of conductivity. The increase in shear viscosity under an electric field is due to a layered structure between the electrodes, made up of the remnants of particle chains adhering to the electrodes by electrostatic image forces, and a freely flowing liquid layer where all the shear flow is concentrated. This layered model can explain the variation of electric current with shear rate, as well as the rheological response of a dynamic yield stress proportional to the square of the applied electric field.     

Saturated steam relative permeabilities of unconsolidated porous media

This paper presents a method and describes an experimental device for determining the steam-water relative permeabilites of unconsolidated porous media. The experimental conditions are as close as possible to those of geothermal reservoirs. The relative permeabilities have been obtained at 180 and 150?C. Their variations versus liquid saturation are quite classical. The air-water relative permeabilities have been measured also at room temperature. The values obtained under these three conditions are almost identical. However, the air-water relative permeability differs slightly from that of steam at 180 and 150?C. We think this discrepancy is acceptable in practice, as it is easier to determine the relative permeabilities for an air-water flow at room temperature than for a steam-water flow at high temperature and pressure.     

PVC/纳米Al2O3复合材料的力学性能研究

通过熔融共混方法制备了PVC/纳米Al2O3复合材料,研究了纳米粒子对PVC的增强、增韧效果。采用细观力学方法理论上求解了纳米复合材料的有效弹性模量,比较并分析了试验值和理论计算值的偏差。     

Hill condition and overall properties of composites

Summary We discuss the Hill principle's role and applications in modern micromechanics of industrial composite materials. Uniform boundary conditions, fundamental in micromechanics, are introduced as a class of Hill solutions. Mixed uniform conditions, basic for experimental testing, are analysed. Domains of application of the Hill principle are reviewed, like homogeneization of heterogeneous media, definition of effective properties and size effect in heterogeneous materials. Generalization of the Hill condition is realized for arbitrary materials, in particular for nonlinear inelastic composites with imperfect interfaces. Received 9 September 1997; accepted for publication 23 December 1997     

A study on an axial crush configuration response of thin-wall, steel box components: The quasi-static experiments

An experimental investigation was performed to study a specific axial crush configuration response of steel, square box components under quasi-static testing conditions. For a specific cross-sectional geometry/fabrication process, test specimens were obtained from commercially produced, welded tube lengths of ASTM A36 and ASTM A513 Type 1 plain low-carbon steels and AISI 316 and AISI 304 austenitic stainless steels. Removable grooved caps were used to constrain tube test specimen ends, and collapse initiators in the form of shallow machined grooves were used to control the initial transverse deformations of the test specimen sidewalls. The progressive plastic deformation for all of the test specimens was restricted to the prototype configuration response (fold formation process and the corresponding axial load-axial displacement curve shape) of the symmetric axial crush mode. Crush characteristics were evaluated and, for each material type, observed differences were less than 7% for maximum and minimum load magnitudes and less than 2% for energy absorption, displacement, and mean load quantities in both the initial phase and the secondary folding phase cycles. Overall, results of the study indicate that for a significant range of material strengths, a controlled and repeatable energy absorption process can be obtained for commercially produced steel box components undergoing symmetric axial crush response.