Composition and thermal stability of SiO2-based hybrid materials TEOS-MTEOS system

Hybrid materials with different amounts of organics permanently bound on the inorganic network obtained in the TEOS-MTEOS (tetraethoxysilan-methyltriethoxysilan) system are used for obtaining coatings with different optical and mechanical properties. To study the thermal stability of the mentioned materials, compositions with different molar ratios of the precursors were prepared. The influence of the solvent and water amounts on the gelation process was also investigated. The gels obtained were characterised by IR spectrometry and their decomposition temperatures were determined by DTA/TG. Thermal stability of the gels is rather influenced by their composition than the conditions of the gelation process. This revised version was published online in July 2006 with corrections to the Cover Date.     

Radiation dose contribution from coal-slags used as structural building material

A significant dose contribution on the population could be derived from coal slags used as isolation material. Extremely high natural activities are measured in the coal slag, derived from the region of the settlement Ajka, Hungary. In some buildings monitored, the elevated -doses were nearly 5–10 times higher than the world average ones. The annual average indoor radon concentrations from the slag exceeded 400 Bq/m³ and in some cases up to 1200 Bq/m³. Due to the elevated exposure and the radon concentrations in the dwellings the annual dose was estimated to 8–24 mSv/y more than 5–10 times of the world average one.     

CIRCULAR DICHROISM SPECTRA OF SYSTEM I PARTICLES FROM NORMAL CHLOROPLASTS AND CAROTENOID-DEFICIENT MUTANTS OF MAIZE

Abstract— Circular dichroism (CD) spectra were studied in System I particles prepared by digitonin fragmentation of chloroplasts of normal maize and carotenoid-deficient mutants. CD bands of pigment molecules were found to be higher in particles than in solutions. This phenomenon was most pronounced for the particles containing the carotenoid composition of normal chloroplast lamellae. The CD signal of chlorophylls bound to particles of carotenoid-deficient chloroplasts was closer to that found in solutions. This indicates that aggregation and/or binding of chlorophylls in carotenoid-deficient mutants may be less extensive than in normal chloroplasts.     

Study on curing reaction of 4-aminophenoxyphthalonitrile/bisphthalonitrile

<正>A series of phthalonitrile blending resins were prepared from 4-aminophenoxyphthalonitrile(APN) and 4,4'-bis(3,4- dicyanophenoxy)biphenyl(BPH) by directly powder-mixing and copolymerization.Differential scanning calorimeter(DSC) and dynamic rheology were used to study the curing reaction behaviors of APN/BPH blends,and the results indicated that the introduction of APN accelerated the curing rate of BPH,and the existence of BPH decreased the curing temperature of APN/BPH systems.The thermal stability of postcured APN/BPH resins was investigated by thermogravimetric analysis(TGA),and the TGA results indicated that the crosslinked polymers of APN/BPH systems possessed good thermal stability.     

Nuclear data for the cyclotron production of ~（117）Sb and ~（90）Nb

This presented study is to make comparison of cross sections to produce ¹¹⁷Sb and ⁹⁰Nb via different reactions with particle incident energy up to 70 MeV as a part of systematic studies on particle-induced activations on enriched Sn, Y₂O₃ and ZrO₂ targets, theoretical calculation of production yield, calculation of required thickness of target and suggestion of optimum reaction to produce Antimony-117 and Niobium-90.     

现代力学中的现代数学方法

本文简要介绍了力学与数学再次结合趋势的历史背景和现状。根据当代科学技术向力学提出的问题,简要综述了现代力学所涉及的现代数学领域和方法.     

Melamine-(H_2SO_4)_3 and PVP-(H_2SO_4)_n as solid acids:Synthesis and application in the first mono-and di-nitration of bisphenol A and other phenols

Melamine and poly vinylpyrrolidone（PVP） reacted with neat sulfuric acid readily to form two new organic solid acids namely melamine-（H₂SO₄）₃ and PVP-（H₂SO₄）_n.These solid acids were used for the first nitration of bisphenol A as well as other phenols in the presence of NH₄NO₃.Mono- and di-nitro bisphenol A have been characterized with IR and ¹H NMR techniques.     

A new reverse analysis to determine the constitutive response of plastically graded case hardened bearing steels

A new reverse analysis is presented that determines the plastic response of both nongraded and plastically graded materials (PGMs) without the need for traditional tension or compression tests. The method utilizes the concepts of expanding cavity model for strain hardening materials, Tabor’s rule of converting Vickers hardness to flow stress, representative plastic strain induced by indentation, and finite element modeling of the macro indentation process. A unique flow curve is determined when the experimentally measured increase in micro Vickers hardness matches that predicted by the proposed method within the plastic zone of a macro Vickers indent. The method is validated for a nongraded stainless steel first and then extended to determine the gradient in flow curves of plastically graded, case-hardened M50 NiL material, a widely used bearing steel. Such knowledge of the plastic response of the case hardened region will help optimize the design of case hardened bearings with longer rolling contact fatigue life and higher thrust load capabilities.     

THE INTERIOR LAYER SOLUTION TO NONLOCAL REACTION DIFFUSION EQUATIONS

An initial boundary value problem of semilinear nonlocal reaction diffusion equations is considered.Under some suitable conditions,using the asymptotic theory,the existence and asymptotic behavior of the interior layer solution to the initial boundary value problem are studied.