Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
Abstract This paper presets a new mathematical formulation chat provides a realistic and appropriate representation of foam behaviour in a porous medium. Foams are gaining increasing importance in the petroleum industry in a number of roles, notably as mobility control and/or blocking agents in enhanced oil recovery o…
A systematic study of the infrared photoluminescence from deep centres in polycrystalline CdSe layers is presented. The authors observe two emission bands at about 0.92 mu m and about 1.22 mu m. The evolution of the band shape and emission intensity quenching with temperature is analysed using a semiclassical model, a…
Hot pressed composites of Si3N4 containing 30% SiC whiskers have shown substantial improvements in strength and fracture toughness relative to monolithic silicon nitride. Injection molded samples made of this composite material distorted in a systematic manner during densification by hot isostatic pressing. Whisker or…
Thermal barrier coatings (TBC) have been used in jet engine combustors for over 15 years. However, it is only recently that they have been actively used in the harsh turbine environment on nozzle guide vane platforms. It is intended to use TBCs on vane airfoils, and on rotating turbine blades where the maximum payoff…
The observation of optical and electric first-order Freedericksz transitions in a homeotropically aligned nematic liquid crystal film induced by electric and optical fields, respectively, is reported. The experimental results are in good agreement with theoretical predictions.
We present the first precise characterization of the profile of the precursor films which progressively develop ahead of the macroscopic edge of a spreading liquid drop. Experiments are performed on a model system (nonvolatile high-molecular-weight polydimethylsiloxane on smooth silicon wafers), using an ellipsometer…
Abstract The effects of water‐soluble and monomer‐soluble impurities on the kinetics of emulsion polymerization of monomers following Case II kinetics (e.g., styrene) are investigated. Experimental studies reveal that impurities can have an appreciable effect on both polymer particle nucleation and growth. These effec…
Abstract The development of new methods of spinning cellulosic fibers requires a better understanding of their fibrillar structure in order to explain their special physical properties. By means of transmission electron microscopy (TEM), light microscopy (LM), small‐angle X‐ray scattering (SAXS), and wide‐angle X‐ray…
Abstract Various amounts of a styrene‐butadiene‐based triblock copolymer (SEBS) was used to compatibilize immiscible blends of high density polyethylene (HDPE) and an amorphous glassy phase consisting of either pure polystyrene (PS) or a miscible blend of PS and a polyether copolymer (PEC). PEC is structurally similar…
The Green's function method with the symmetry decoupling scheme has been used in the present paper to investigate the antiferroelectric phase transition in squaric acid (H2C4O4) crystal. It is shown that the phase transition is of first order. The transition temperature Tc and the order parameter Sc at transition poin…
Abstract In order to study the synthesis and properties of polysulfonamides containing thiophene links, 2,2‐bis(5‐chlorosulfonyl‐2‐thienyl)propane [BCTP], 2,2‐bis(5‐chlorosulfonyl‐2‐thienyl)butane [BCTB], 1,1‐bis(5‐chlorosulfonyl‐2‐thienyl)cyclohexane [BCTC], and 2,4‐dichlorosulfonyl thiophene [DCST] were prepared and…
The authors present an experimental and theoretical study of the interplay of the superconductivity (SC) and the charge density wave (CDW) formations in the quasi-one-dimensional conductor NbSe 3 . The application of high pressure or the doping of impurities results in the coexistence of the SC and CDW and then raises…
The epipelic diatoms from various water bodies from the south-western part of the Hornsund fiord area are presented. Altogether, 157 taxa (127 species together with their variants and forms) have been identified. The flora consists almost entirely of diatoms from the order Pennales which is represented predominantly B…
Some years ago Varotsos (1980) suggested a model for the calculation of the bulk modulus of mixed ionic crystals. It was shown initially that this model gives excellent results for the KCl-KBr mixed system. Giri and Mitra (1986) have recently indicated that it can be applied to the mixed systems CaF 2 -SrF 2 and GaP-G…
One of the intrinsic instabilities of permanent magnets is magnetic aftereffect. The magnetic field and temperature dependences of the magnetic aftereffect constant, S v , were measured for a Sm 2 Co 17 sintered magnet under the effective magnetic field, H eff , ranging from -230 to -700 kA/m and at a temperature rang…
New data concerning the refractive-index profiles in Ag/Na ion-exchanged waveguides are obtained using a parabolic-segment reconstruction method. The profiles can be described as second-order polynomials, but with a mean curvature b = 2·8 which is significantly greater than the originally suggested value 0·64. The pro…
Some of the spectroscopic properties of the promethium ion (Pm/sup 3+/) were investigated in order to assess its feasibility for laser action. The fluorescence spectra and decays from the /sup 5/F/sub 1.2/ manifolds were measured in 11 dielectric materials. The calculated peak emission cross sections are comparable to…
A logarithmic increase of resistance with decreasing temperature and a negative magnetoresistance have been observed on low stage acceptor graphite fiber intercalation compounds (GACs) at low temperature. These results may be explained within the framework of the recent theories of weak localization and electron-elect…
Abstract Electrical resistivities ϱ and lattice parameters of quasi‐two‐dimensional crystals of monoclinic η‐Mo 4 O 11 and orthorhombic γ‐Mo 4 O 11 are measured under hydrostatic pressure up to 1.2 GPa at room temperature. Both crystals have negative pressure coefficients of ϱ, which can be qualitatively explained by…
Les cristaux de scolecite sont constitues de secteurs de croissance {110}, {010} et {111} de symetrie triclinique alors que l'analyse par diffraction RX indique une symetrie monoclinique. Existence de deux types de maclages: l'un du a un arrangement asymetrique des ions calcium et des molecules d'eau, et l'autre du a…