Fast Legendre spectral method for computing the perturbation of a gradient temperature field in an unbounded region due to the presence of two spheres

The temperature distribution around two spheres is considered when the main field has a constant gradient at infinity. Bispherical coordinates are used, together with a transformation of the dependent variable that leads to separation of variables. Then the solution can be sought in Legendre series with respect to one of the bispherical coordinates. An important element of the proposed work is the effective way to reduce an essentially 3D problem to a set of three 2D problems. The Legendre spectral method is shown to have an exponential convergence which is confirmed by the computations. The efficiency is so high that even for the hard cases of two closely situated spheres, an accuracy of 10^?10 is achieved with as few as 20 terms in the expansion. Solutions with both longitudinal and transverse gradients at infinity are obtained, and the contour lines of the temperature field are presented graphically. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010     

Natural bound in Kwiecinski's criterion for flatness

Kwiecinski has proved a geometric criterion for flatness: A morphism of germs of analytic spaces is not flat if and only if its fibre power has a vertical component, for some . We show how to bound using Hironaka's local flattener: If is not flat, then has a vertical component, where is the minimal number of generators of the ideal in of the flattener of .

     

一种多波长窄线宽环形掺铒光纤激光器

本文提出了一种利用多个光纤光栅串接来实现环形掺铒光纤多波长,窄线宽激光器的新颖方法,并在实验中验证了这一设计的合理性,得到了稳定的双波长输出。     

Hydrogen peroxide bleaching of cotton in ultrasonic energy

It is well known that, conventional hydrogen peroxide bleaching process is an important and a specific step for wet processors; however it has some problems such as long time, high energy consumption. On the other hand, using ultrasonic energy in bleaching is an alternative method for the conventional processes.

In this work, 100% cotton materials of different forms such as raw fibre, ring-spun yarns and knitted fabrics produced from these cottons, were treated with hydrogen peroxide in two different concentrations (5 mL/L and 10 mL/L), at three different temperatures (20 °C, 30 °C, 40 °C) and times (20 min, 30 min, 60 min). Whiteness Index of the samples were then measured spectrophotometrically and the overall results were compared.     

Steady light diffusion application to rheology: a new tool for the characterization of concentrated suspensions

We present new developments of steady light diffusion applied to rheology. Though many techniques allow the structural investigation of diluted or transparent media, very few give direct information on optically dense systems. The technique proposed here is based on the diffusion approximation and is thus valid for sheared, time-dependent flows.After recalling important theoretical results, we show the techniques ability to determine typical sizes and orientation of structures in shear flows for various concentrated suspensions (emulsions, and an industrial softener). In particular, it is able to demonstrate the effect of shear on the orientation of anisotropic objects. Moreover, the use of simple structural models incorporating the measured anisotropy allows good predictions of experimental rheological measurements. This new technique, applicable to a wide range of colloidal systems, is very helpful to characterize the shear induced structural organization of optically dense materials.This paper was presented at the first Annual European Rheology Conference (AERC) held in Guimarães, Portugal, September 11-13, 2003.     

XPM-induced intensity distortion due to dispersion in fibre Bragg grating filters

We investigate the conversion of cross-phase modulation (XPM) to intensity distortion due to dispersion in fibre Bragg grating (FBG) filters. We find that there can be significant XPM-induced intensity distortion, especially near the edges of the filter passband where the in-band dispersion is increasingly pronounced. Since FBG filter dispersion occurs above and beyond that in standard single-mode fibre, this enhances XPM-induced intensity distortion arising from dispersion and should be accounted for in system design.     

A structural model for the time-dependent recovery of mineral suspensions

A thixotropic recovery model has been developed that is based on consideration of the microstructural interactions that occur between particles within a suspension particle network. The model is based on Smoluchowski coagulation rate theory, utilizing second order kinetics to describe the thixotropic recovery behavior. The model is applied to Na-montmorillonite-based coal tailings suspensions and is also shown to be applicable to brown coal and bauxite residue suspensions. The model describes all the recovery data well, especially at intermediate to large recovery times. The recovery of the montmorillonite suspensions at short times was faster than predicted, indicating the existence of additional factors in early-time structure development. The discrepancy may have also been due to the highly anisotropic nature of the clay platelets. The recovery rate constant, K _r , increases with increasing solids concentration (for constant surface chemical conditions) as would be expected from the basis of the model. Received: 22 September 2000 Accepted: 16 March 2001     

Probing particle-particle interactions in flocculated oil-in-water emulsions using ultrasonic attenuation spectrometry

The flocculation of silicone oil-in-water emulsions ( φ = 0.1) containing quasi-monodisperse droplets was studied by ultrasound. The ultrasonic attenuation spectra of emulsions with different particle sizes (200-1600 nm) were measured between 0.5 and 10 MHz using an interferometer. Flocculation was induced by adding excess sodium dodecyl sulphate micelles to the emulsions to increase the attractive forces between the droplets. Droplet flocculation decreased the ultrasonic attenuation at low frequencies because of overlap of the thermal waves caused by the close proximity of the droplets within the flocs. A mean-field model which takes into account this effect was used to determine the droplet volume fraction within the flocs and thus to estimate the distance between the droplets. Received 17 July 2000     

高分子分散剂在陶瓷浓悬浮体制备中的应用

良好分散的陶瓷浓悬浮体是胶态成型实现的前提和关键。本文阐述了高分子分散剂的分散稳定作用及其在多种单相复相陶瓷浓悬浮体制备中的研究和应用,进而从高分子分散剂自身特性,陶瓷分散相和分散介质的物理化学性质以及陶瓷胶态成型工艺操作等方面,分析了各因素对高分子分散剂分散效果的影响,最后指出了能够优化陶瓷浓悬浮体性能的高分子分散剂的研究趋势。     

Bioactive Sol-Gel Coatings for Orthopaedic Prosthesis

Sol-gel materials have been proposed in last years for clinical applications. In this work, bioactive sol-gel coatings were prepared from suspensions of up to 25% wt. of bioactive glass (CaO·SiO₂·P₂O₅) particles in a hybrid sol obtained from TEOS and MTES. Thick dip-coatings showed in vitro bioactivity after a few days, but glass-particles dissolution promotes a slight reduction in the corrosion resistance. In order to overpass this problem, a two-stage sol-gel coating system that includes a first SiO₂ hybrid film, acting as barrier against corrosion, and an external bioactive layer from glass particle suspension is proposed. The obtained samples revealed significant improvement in their electrochemical behaviour, and showed in vitro bioactivity.