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。
In this paper a theoretical investigation of convection currents in anisotropic porous media is performed. The porous layer is homogeneous and bounded by two infinite perfectly heat-conducting horizontal planes. The criterion for the onset of convection is derived. The supercritical steady two-dimensional motion, the…
Abstract This paper describes an experimental study of the centre of mass diffusion of linear hydrocarbon or deuterocarbon molecules, of the type (CH2)N or (CD2)N, through bulk polyethylene. N was varied between about 15 and 1500. The diffusion coefficient D was measured as a function of temperature, matrix morphology…
The movement of atoms during twinning is described as a simple relative movement and not by means of a shear parallel to the twin plane, even with added “shuffles”. It is shown that displacive waves similar to those which describe the β → ω transformation, can be associated with these atom movements.
Experimental evidence supports the hypothesis that the concentration and distribution of dissolved aluminum in ocean water are controlled by biological activity in the surface waters. The growth of the diatom Skeletonema costatum in artificial seawater media spiked with aluminum reduced the aluminum concentration to t…
We have made a high-resolution (0.12 eV) measurement of the electron energy-loss spectrum of the layered compound Ti${\mathrm{S}}_{2}$ for energy loss $E$ in the range 0.5-150 eV. After subtracting the contribution of plural scattering, we performed a Kramers-Kronig analysis to obtain the dielectric function. The refl…
In order to confirm the existence of an ordering transition in ice VI, an investigation of the thermal expansion was carried out at low temperatures 4.2° K–200° K and high pressure l0.54 kbar. (AIP)
The angular distribution of double scattering for aluminum and nickel have been studied using the relativistic Klein-Nishina cross section. The differences between the nonrelativistic Thomson cross section and the Klein-Nishina cross section are studied at different energies. The effects of using a momentum-dependent…
Laser action in dyes dissolved in liquid crystal matrices is described. Planar thin film structures, filled with rhodamine 6G dissolved in CBOA, M24, and K18 liquid crystals, have been studied. Lasing action has been obtained in the isotropic, nematic, and smectic mesophases. In liquid crystal mesophases, alignment of…
The detailed molecular interactions occurring during thermal degradation of PVC polymer formulations containing MoO3 additives are investigated using laser microprobe techniques coupled with mass analysis of the volatile pyrolysis products. Comparison with Sb2O3–PVC compounds indicate that the additive effects exhibit…
A fundamental study of bubble morphology development and apparent rheological properties in foam extrusion is reported. The influence of melt temperature, die length/diameter ratio, and blowing agent level on the morphology are considered. Measurements of the influence of blowing agent on viscosity, extrudate swell, a…
The long-wavelength vibrational modes of monoclinic GaTe have been investigated by Raman scattering and far-infrared absorption and reflection. The energies of 14 of the expected 18 Raman-active modes have been measured and their symmetries identified. Ten of the 15 predicted infrared-active modes have been found in t…
Experimental data on the dependence of the specific volume on temperature and pressure (PVT data) to 2000 kg/cm2 of isotactic polypropylene and isotactic poly(butene-1) are reported and discussed. The temperature range covered is 30–297°C for polypropylene and 30–246°C for poly(butene-1), thus encompassing the solid a…
We develop a classical theory for the intensity and the depolarization ratio of the light scattered (Raman or Rayleigh) by an absorbed molecule. It is assumed that the optical properties of the system can be described by the polarizability of the molecule and the dielectric constant of the two media. The presence of t…
Amorphous semiconducting films of the Si-B binary system have been prepared by rf plasma decomposition of silane-diborane gas mixtures. The infrared vibrational modes, optical absorption, conductivity, spin resonance, and hydrogen content of these films have been studied as a function of preparation conditions. These…
The fundamental vibration–rotation spectra of condensed DT and T2 were measured. The 24 separate spectral lines identified consist mainly of QQ, QR, QQ+So(0), and QQ+So(1) transitions. The last two appear as triad sets in D2–DT–T2 solutions because of double transitions between different isotopes. The QQ frequencies a…
Pressure–volume–temperature relationships of three low-density polyethylenes are reported in the temperature range of 30°–225°C and in the pressure range of 0–2000 kg/cm2. The same materials had previously been studied by the IUPAC Working Party on Structure and Properties of Commercial Polymers with regard to basic c…
The vibrational properties of six different polytypes of Pb${\mathrm{I}}_{2}$ crystals have been studied experimentally by means of Raman spectroscopy and x-ray diffraction. The crystals were prepared either by gel growth or by thermal annealing. The Raman spectra are used to determine features of the phonon dispersio…
The vibrational and electronic spectra for the sodium mono-, di-, and trianion salts of TCNQ prepared in vacuo by solvent-free vapor codeposition methods, have been measured. These data, combined with published vibrational assignments for neutral TCNQ and the monoanion salts of TCNQ, have permitted an empirical analys…
A new method is presented for a systematic calculation of the effective dielectric constant ${\ensuremath{\epsilon}}_{e}$ of a granular, two-component composite material with a precisely known microscopic geometry. The basic approach is to attempt to calculate the poles and residues of ${\ensuremath{\epsilon}}_{e}$ as…
Ordered collagen in native, intact rat tail tendon has been studied by means of optical second harmonic generation (SHG). The two independent hyperpolarizability tensor elements of the collagen molecule, β3 and β1, have been found to be of opposite sign and roughly equal in absolute magnitude. Evidence is presented fo…