Higher order structures and toughening mechanisms for simultaneously polymerized polymethacrylate/polyurethane

Amorphous polymer/crystalline polymer blends can be prepared via the simultaneous polymerization of polymethacrylate/polyurethane combinations. The relationship between higher order structures and fracture mechanisms in these blends must be uncovered to elucidate the source of the increased fracture toughness of such materials. The present work involves the production of blended polymethacrylate/polyurethane and assess the internal structures of these specimens using optical and electron microscopy. These observations reveal the presence of both spherulites and elastomeric phases. The spherulites consisting of the polyurethane and are several micrometers in diameter whereas the phase-separated polyurethane elastomeric domains are approximately 100 nm in size. Multiple cracks, crack bridging and plastic deformation around the precrack tips of loaded specimens are evidently responsible for the increased toughness of these blends. The former two phenomena are attributed to the presence of spherulites while the plastic deformation of the methacrylate matrix is ascribed to cavitation of the polyurethane elastomeric phases in response to loading.     

A 400 K-transistor CMOS sea-of-gates array with continuous track allocation

A 0.8- mu m CMOS sea-of-gates (SOG) array with first-level wiring channels perpendicular to transistor rows and 40 0K transistors is integrated on a 6*7-mm/sup 2/ chip. Implementation of a 64-bit multiplier shows 60-percent gate utilization and density of 1410 G/mm/sup 2/. The wiring length of the multiplier is 70 percent of that in a conventional SOG.<>     

Transport properties of porous media from the microgeometry of a three-dimensional voronoi network

In this work a way of calculating effective transport coefficients from the microgeometry of a porous medium is presented. The model material consists of a random packing of uniform spheres, and by applying the Voronoi—Delaunay tessellation technique the void between the spheres is simulated as a network of cylindrical pores. The tessellation yields all the necessary information for the structural characterization, such as the pore diameter, pore angle and pore length distribution functions and the topological interconnection. The effective transport coefficients of ordinary diffusion, Knudsen flow and viscous flow are calculated numerically by mass balancing at each network node and over all nodes of the system. The results obtained agree very well with the experimental ones, especially for ordinary diffusion. For Knudsen and viscous flow, inaccuracies in the estimation of the pore overlapping volume cause a relative error between the numerical and experimental results of the order of 16%–33%.     

Rapid degradation of cucumber cotyledon lipoxygenase

The lipoxygenase activity from cucumber cotyledons grown with their embryonic axis was separated into two fractions having M(r)s of 90,000 and 96,000, respectively, by hydrophobic chromatography. However, from de-embryonated cucumber cotyledons, only one form of lipoxygenase having a M(r) of 90,000 was purified. The three lipoxygenases could not be distinguished from each other either immunologically or by their enzymatic properties. Furthermore, peptide maps of the 90,000 and 96,000-lipoxygenases were identical. In a crude homogenate of cucumber cotyledons, the 96,000-lipoxygenase was rapidly degraded to the 90,000-form. Thus, it was inferred that the 90,000-lipoxygenase was probably the 96,000-form which had lost a peptide fragment of 6,000. It is suggested that there is a specific proteolytic activity for the degradation of 96,000-lipoxygenase. Estimation of changes in the proteolytic activity during seedling growth suggests that the activity at least partly contributes to the rapid in vivo degradation of cucumber cotyledon lipoxygenase.     

Reaction between magnesium ammine complex compound and lithium hydride

The possibility of using ammonia as a hydrogen carrier is examined for the reaction between magnesium ammine complex MgCl₂(NH₃)₆ and lithium hydride LiH. Sample was milled at low temperature of −40 °C to avoid decomposition of MgCl₂(NH₃)₆ during the milling. The effects of milling time, milling speed (revolutions per minute), and catalysts on hydrogen storage properties were investigated by thermogravimetry, thermal desorption mass spectroscopy, and X-ray diffraction experiments. Experimental results indicated that a milled composite of Mg(NH₃)₆Cl₂ and catalyzed-LiH desorbed the ∼100% H₂ gas even at 125 °C in a closed system. The reverse reaction also proceeded by separately cooling MgCl₂ at lower temperature than 100 °C and heating LiNH₂ at 300 °C in the closed system.     

A video codec LSI for high-definition TV systems withone-transistor DRAM line memories

A video codec LSI for high-definition television (HDTV) systems has been developed. By using a time-compressed integration encoding technique, it converts a 20.0-MHz bandwidth luminance signal and two 5.0-MHz chrominance signals into a compressed image signal at 48.6-MHz sampling frequency. It is useful in many HDTV application systems, such as 400-Mb/s digital transmission system, a video disk player system, or an analog transmission system. Over 288000 elements, including a 52-kb one-transistor DRAM (dynamic random access memory) line memory specially developed for this LSI, were integrated on a 12.16×12.10-mm² chip. A standard cell layout method and a 1.2-μm CMOS logic LSI process were used     

Color gamut mapping based on a perceptual image difference measure

Gamut mapping is a color transformation technique to solve a problem caused by mismatch of gamuts among imaging devices. One plausible goal of gamut mapping is to find a reproduction that is perceptually closest to the corresponding original image when an exact color matching is not possible. Several measures to quantify the perceptual difference between images have been proposed and applied to the gamut mapping problem. However most of the measures, such as average color difference, are applied on a pixel‐wise basis and show poor correlation with human visual perception. This article describes a model of the perceptual image difference for a given pair of images, which takes the human's contrast sensitivity into account and applies the model to a gamut mapping for generating a reproduction with minimum perceptual image difference. The model has a multispatial‐frequency channel structure with tunable peak gains for each channel, which are determined by psychophysical experiments, so that the model output fits the observer's sensitivity to the image difference. A gamut‐mapped image with minimum perceptual image difference is obtained by an iterative minimization process. To evaluate the proposed method, subjective evaluation experiments are performed to construct ratio scales that measure perceptual image difference of gamut‐mapped reproductions generated by the proposed and pixel‐wise methods. Results show that the reproductions by the proposed method are perceived as perceptually closest to the original, and the model's estimate of perceptual difference correlates better with the experimentally measured perceived image difference than other pixel‐wise measures. © 1999 John Wiley & Sons, Inc. Col Res Appl, 24, 280–291, 1999     

Effects of polyglycerol esters of fatty acids and ethylene‐vinyl acetate co‐polymer on crystallization behavior of biodiesel

Biodiesel fuels (BDF) have many problems in the cold due to their crystallization properties. In particular, precipitation of large crystals of high‐melting fractions in BDF at low temperatures remarkably changes cold flow property of BDF and, thereby, it increases the values of cold filter plugging point. In this study, we evaluated polyglycerol esters of fatty acids (PGE) and ethylene‐vinyl acetate co‐polymer (EVA) as chemical additives to improve the cold flow property of palm oil‐based FAME (PFME). The results of solid fat content measurement indicate that the simultaneous addition of PGE and EVA showed synergistic effects on suppression of crystallization of PFME, however such effect was not observed when EVA was used alone. DSC thermograms indicated that the PGE additives not only decreased the crystallization temperature but also kinetically suppressed the crystal growth. Polarized light microscopy showed that the simultaneous addition of PGE and EVA led to the formation of considerably small and fine‐dispersed crystals of PFME. These results indicate that combined effects of PGE and EVA caused the formation of fine‐dispersed PFME crystals, which could improve the viscous properties of palm oil‐based BDF at relatively cold temperatures.