DIFFUSION COEFFICIENTS OF CARBON DIOXIDE WITHIN TYPE 13X ZEOLITE PARTICLES

The self-diffusion processes of CO₂ in a single particle of commercial type 13X zeolite have been studied by a new sorption rate method using a constant volume, variable pressure system. Experiments were carried out at 303.2 and 343.2 K. An inverse analysis of experimental uptake curves based on a macropore and micropore series diffusion model was performed to determine effective diffusion coefficients for both macropore and micropore diffusion simultaneously. Knudsen diffusion occurs within the macropore and the micropore diffusion coefficients having values of the order 10^?15–10^?14 m²/s, which are slightly greater than the previously reported micropore diffusion coefficients of type 5A zeolite crystals.     

New gel-type polyolefin electrolyte film for rechargeable lithium batteries

A random poly(ethylene-co-acrylic acid) (PE-A) with an acrylic acid (AA) content of 5.0–20 mol% was functionalized by esterifying acrylic acid group with poly(ethylene glycol) monomethyl ether. Polyethylene oxide functional groups such as a pendant were introduced into the polyethylene backbone chain. The resulting polymer (PEGM-g-EAA) can be easily formed to a thin sheet and possesses the adhesion property such as gluing. Its thin film could absorb and hold a large quantity of the electrolyte solutions employed for the lithium batteries. The ionic conductivity of the PEGM-g-EAA gel electrolyte obtained with the starting PE-A with acrylic acid content of 9.0 mol% was a value of around 1.5 × 10⁻³ S cm⁻¹ at 20 °C. The ionic conductivity results obtained for the network type gel, which was entangled with the present PE-A-based polymer, were 1.1 × 10⁻³ S cm⁻¹ and 5.5 × 10⁻³ S cm⁻¹ at 0 °C and 80 °C, respectively. The characteristics of good thermostability, transparency and good adhesion to the electrodes have also been demonstrated. As an example, the test cell consisted of the proposed polyolefin gel electrolyte, a LiCoO₂ cathode and a lithium anode showed excellent charge/discharge characteristics.     

Phase Equilibria,Microstructure, and High-Temperature Strength of TiC-Added Mo-Si-B Alloys

TiC was added to Mo-Si-B alloys using a conventional Ar arc-melting technique, and the phase equilibria, microstructure evolution, and high-temperature strength at 1673 K (1400 °C) were investigated. The primary phase changed to Mo solid solution (Mo_ss), Mo₅SiB₂ (T₂), or TiC depending on the composition. Following the primary phase solidification, a Mo_ss + TiC, Mo_ss + T₂, or Mo_ss + T₂ + TiC + Mo₂C eutectic reaction took place as the secondary solidification step. In some alloys, Mo_ss + T₂ + TiC and Mo_ss + T₂ + Mo₂C eutectic reactions were present as higher-order solidification steps. After annealing at 2073 K (1800 °C) for 24 hours, Mo_ss, T₂, TiC, and Mo₂C coexisted stably with microstructural coarsening. The coarsening rate was much faster in an alloy with no TiC dispersion, suggesting that TiC has a strong pinning effect on the grain boundary and interface migration. Compression tests conducted at 1673 K (1400 °C) revealed strength properties of almost all the alloys that were better than those of the Mo-Hf-C alloy (MHC). Alloy densities were 9 g/cm³ or less, which is lighter than pure Mo and MHC (≥10 g/cm³) and competitive with Ni-base superalloys. TiC-added Mo-Si-B alloys are promising candidates for ultrahigh-temperature materials beyond Ni-base superalloys.     

Approximate conversion of a rational boundary gregory patch to a nonuniform B-spline surface

A rational boundary Gregory patch is characterized by the facts that anyn-sided loop can be smoothly interpolated and that it can be smoothly connected to an adjacent patch. Thus, it is well-suited to interpolate complicated wire frames in shape modeling. Although a rational boundary Gregory patch can be exactly converted to a rational Bézier patch to enable the exchange of data, problems of high degree and singularity tend to arise as a result of conversion. This paper presents an algorithm that can approximately convert a rational boundary Gregory patch to a bicubic nonuniform B-spline surface. The approximating surface hasC ¹ continuity between its inner patches.     

Spectroscopic study of polytoluidines in the UV-visible and IR regions

Electropolymerization of o-toluidine(o-methylaniline) and m-toluidine was carried out in acidic aqueous solution, and UV-visible and IR spectra of the resulting polymer films were obtained at various electric potentials and pHs. In Na₂SO₄ aqueous solution, poly(o-toluidine) gave considerably different UV-visible spectra from polyaniline, whereas, in HCl (pH ～ 0), the spectra of poly(o-toluidine) changed in the same way as polyaniline when the potential was varied. This spectral change depended also on counterion. This suggests that the intermediate state (radical cation) of poly(o-toluidine) is unstable in a neutral solution especially when a large counter ion exists, which is contrast to polyaniline. The dependency of the FT-IR spectra of poly(o-toluidine) on the potential and pH supported also the above result of UV-visible spectra. From both UV-visible and IR spectra under various conditions, it was found that o-toluidine and m-toluidine give the same polymer.     

Quantitation of 1,2-diacylglycerol in rat heart by latroscan TLC/FID

1,2-Diacylglycerol, which has been recognized as one of the intracellular second messengers, was measured quantitatively in the lipid extract from rat hearts using the thin layer chromatography and flame ionization detection (TLC/FID) method. Cholesterol acetate was added to the tissue as an internal standard, and the crude lipids from the tissue were purified with silicic acid column to eliminate phospholipids. Development of Chromarods was carried out using two solvent systems and a three-step development technique. The relationship of the peak area ratio detected by flame ionization detector to weight ratio was linear compared with cholesteryl acetate. The 1,2-diacylglycerol content in the rat heart in the unstimulated condition was 72.5±15.3 ng/mg wet wt (mean±SD).     

Creep strength of magnesium-based alloys

The high-temperature creep resistance of magnesium alloys was discussed, with special reference to Mg-Al and Mg-Y alloys. Mg-Al solid-solution alloys are superior to Al-Mg solid-solution alloys in terms of creep resistance. This is attributed to the high internal stress typical of an hcp structure having only two independent basal slip systems. Although magnesium has a smaller shear modulus than aluminum, the inherent creep resistance of Mg alloys is better than that of Al alloys. The creep resistance of Mg alloys is improved substantially by the addition of Y. Solid-solution hardening is the principal mechanism of the strengthening, but the details of the mechanism have not been elucidated yet. Forest dislocation hardening in concentrated alloys and dynamic precipitation in a Mg-2.4 pct Y alloy also contribute to the strengthening. An addition of a very small amount of Zn raises the dislocation density and significantly improves the creep resistance of Mg-Y alloys. This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following ASM committees: Materials Science Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee.     

Feature line extraction from unorganized noisy point clouds using truncated Fourier series

The detection of feature lines is important for representing and understanding geometric features of 3D models. In this paper, we introduce a new and robust method for extracting feature lines from unorganized point clouds. We use a one-dimensional truncated Fourier series for detecting feature points. Each point and its neighbors are approximated along the principal directions by using the truncated Fourier series, and the curvature of the point is computed from the approximated curves. The Fourier coefficients are computed by Fast Fourier Transform (FFT). We apply low-pass filtering to remove noise and to compute the curvature of the point robustly. For extracting feature points from the detected potential feature points, the potential feature points are thinned using a curvature weighted Laplacian-like smoothing method. The feature lines are constructed through growing extracted points and then projected onto the original point cloud. The efficiency and robustness of our approach is illustrated by several experimental results.