Weak coupling of a Reynolds model and a Stokes model for hydrodynamic lubrication

The Reynolds model is a reduced Stokes model, valid for narrow lubrication regions. In order to be able to handle locally non‐narrow regions such as pits or grooves, often displaying rapid geometrical variations, there is a need to be able to transit to the more accurate Stokes model. A fundamental problem is how to couple the two models in a numerical simulation, preferably allowing for different meshes in the different domains. In this paper, we present a weak coupling method for Reynolds and Stokes models for lubrication computations, including the possibility of cavitation in the different regions. The paper concludes with a numerical example. Copyright © 2010 John Wiley & Sons, Ltd.     

Utilization of inverse approach in the design of materials over nano‐ to macro‐scale

In the light of recent developments in computer technology, a promising and efficient way to design a material with a desired property would be to solve the inverse problem: use a physical property to predict structure. Here, we discuss the basic idea and mathematical foundation of the inverse approach, and proposed strategies for its utilization in the design of materials over nano‐ to macro‐scales. At the nano‐scale, analyzed strategies include scanning of a high‐dimensional space of chemical compounds for those compounds that have a targeted property, and identification of correlations in large databases of materials. However, unlike utilization of inverse approach at nano‐scale where full structural information ‐ atoms and their positions‐ is linked to targeted properties, at the meso‐ and macro‐scale, only partial structural information, manifested via structural motifs or representative volume elements, is available. We discuss the role of partial structural information in the inverse approach to the design of materials at those scales. Risks and limitations of the inverse approach are analyzed and dependence of the approach on factors such as structure parametrization, approximations in theoretical models, and feedback from structural characterization, is addressed.

     

The band gap and transmission characteristics investigation of local resonant quaternary phononic crystals with periodic coating

In this article, the investigation of the Lamb wave propagation in two-dimensional phononic crystals (PCs) composed of an array of periodic coating on a thin plate is presented. Compared with the traditional PCs usually consist of cylindrical scatters with uniform coatings in their exterior structure, the newly exterior coating structures with periodic alternant arrangement of two different materials are proposed. The band structures are calculated using finite element method. We discover that a complete band gap can be exhibited at low frequency. Furthermore, for a finite PCs plate, the computed transmission and resonance spectra shown an evident resonance nature which can be directly related to formation of the low-frequency gaps. The effects of different material parameters and arrangement mode of coating on the acoustic energy transmission and attenuation are also studied. Finally, the experimental transmission spectrum of the periodic coating PCs are also presented and compared with the numerical results. This study will provide useful support to the design of tuning band gaps and isolators in the low-frequency range.     

野生中草药木贼中微量元素的测定

目的测定中草药木贼中微量元素的含量。方法用湿法消化及于法灰化两种方法处理样品并进行了比较,用火焰原子吸收法测定了中草药木贼中7种微量元素的含量。结果测定结果湿法的RSD在0．5％～3．0％,干法的RSD在0．5％-7．5％之间。结论湿法处理金属离子损失小,测量精密度更好。木贼中微量元素的含量由高到低顺序为：Mg,Fe,Mn,Zn,Cu,Ph,Ni。     

Primary Studies on Variation in Position of Trifluoromethyl Groups in Several Aromatic Group‐14 Derivatives by 19F‐NMR Spectroscopy

Variation in the position of CF₃ groups in several aromatic Group‐14 compounds was studied by ¹⁹F‐NMR spectroscopy. In these compounds R_nECl_4?n (n=1 or 2; E=Si, Ge, or Sn; R=2,4,6‐(CF₃)₃C₆H₂ (=Ar), 2,6‐(CF₃)₂C₆H₃ (=Ar′), or 2,4‐(CF₃)₂C₆H₃ (=Ar″)), Ar, Ar′, and Ar″ are all bulky, strongly electron‐withdrawing ligands. The ¹⁹F‐NMR studies of the variation in position of the CF₃ substituents in these compounds as revealed by chemical shifts could be correlated with the electronegativities of the central elements E, and with intramolecular E–F interactions derived from single‐crystal X‐ray diffraction data. These interactions are considered to play an important role in the stabilization of these compounds.     

湖南辰溪特高有机硫煤的稀土元素特征及其成因

采用高分辨率电感耦合等离子质谱(HR-ICP-MS)技术测定辰溪晚二叠世高有机硫(7.75%)煤中的稀土元素(REEs)。辰溪煤中∑REE变化较大,从38.84 μg/g至305.85 μg/g,加权平均值为104.57 μg/g,高于世界煤均值,与中国煤相近。辰溪煤中有明显的Ce负异常(δCe=0.74~0.84)和Eu的负异常(δEu=0.55~0.69)。煤层剖面上稀土元素含量和分布模式的变化反映了成煤环境的波动,从底板到顶板陆源物质的影响减弱,而海水的影响增强。沉积环境的阶段性变化是导致剖面上下有机硫与黄铁矿硫比值相差悬殊的原因。辰溪煤中稀土元素与铁呈现了显著的正相关性(n=11,r=0.95),说明其物质来源和富集条件有一定相似性,即陆源物质和海水共同影响的结果。稀土元素的分布模式以及∑REE与灰分、Si、Al的相关性说明了其主要来源于陆源物质;辰溪煤中δCe与δEu在剖面上变化很小,说明海水对煤中的稀土元素存在重新改造的作用。     

Fast switching beam steering based on ferroelectric liquid crystal phase shutter and polarisation grating

We report on fast-switching and high-efficient optical beam steering based on a polymerisable liquid crystal polarisation grating (PG) in combination with ferroelectric liquid crystal (FLC) phase shutter. The PG was fabricated in a convenient single-step holographic exposure process using photo-sensitive azo-dye material as alignment layer for liquid crystal (LC) director. A binary electro-optical FLC was employed for circular polarisation selection, which enables the electro-tunable steering of the combined system. The efficiency of 95.7% with 82 μs switching time is obtained for 1064 nm laser. This work provides a versatile candidate for non-mechanical beam steering devices.     

Pine Needles (Pinus Sylvestris) as a Bioindicator of Sulphur and Heavy Metal Deposition in the Area Around a Pulp and Paper Mill Complex at Kemi,Northern Finland

Abstract

The determination of sulphur and heavy metals in plants is an integral part of many environmental studies. Pine needles (Pinus Sylvestris) have proved to be suitable air quality indicators for pollutants, especially for sulphur. This study was carried out in the vicinity of Kemi, a town situated on the Gulf of Bothnia in northern Finland. An industrial complex comprising two pulp and paper mills is located in the centre of the area. Scots pine (Pinus Sylvestris) needles were collected from 29 sampling sites. The samples were dried, homogenized and digested with nitric acid. The concentrations of the elements S, Fe, Zn, Ca, V, and Pb were determined by ICP-AES. According to our results pine needles (Pinus sylvestris) appear to be an ideal bioindicator and sampling material for identifying and assessing atmospheric sulphur pollution derived from pulp and paper mills and can complement the information provided by plant mapping studies around pulp and paper mills.     

Phase Systems and Post-Column Dithizone Reaction Detection for the Analysis of Organo-Mercurials by HPLC

Abstract

The suitability of HPLC (normal and reversed phase adsorption) with UV or post-column reaction detection for the analysis of organomercurials was investigated systematically. The separation of organomercurials is best carried out on a reversed phase system with a C-8 bonded phase material as the stationary phase and acetonitrile-aqueous sodium bromide mixtures as the mobile phase.

The precision and detection limit of the method and the efficiency of the extraction procedure were established. For the alkylmercury compounds the lowest limit of detection (80ppb) was obtained with the dithizone reaction detection and for the phenylmercury compounds with UV detection (60ppb). A chromatogram of a spiked fish (2ppmHg) and a river water sample (50ppbHg) is shown.