MLS‐based variable‐node elements compatible with quadratic interpolation. Part I: formulation and application for non‐matching meshes

Two‐dimensional variable‐node elements compatible with quadratic interpolation are developed using the moving least‐square (MLS) approximation. The mapping from the parental domain to the physical element domain is implicitly obtained from MLS approximation, with the shape functions and their derivatives calculated and saved only at the numerical integration points. It is shown that the present MLS‐based variable‐node elements meet the patch test if a sufficiently large number of integration points are employed for numerical integration. The cantilever problem with non‐matching meshes is chosen to check the feasibility of the present MLS‐based variable‐node elements, and the result is compared with that from the lower‐order case compatible with linear interpolation. Copyright © 2005 John Wiley & Sons, Ltd.     

Development of the PenTile Matrix™ color AMLCD subpixel architecture and rendering algorithms

Abstract— Color subpixel rendering is enhanced by co‐optimizing the color subpixel architecture and algorithms with respect to human vision. This has resulted in the PenTile? display technology, which provides double the information content per subpixel when compared to a conventional RGB Stripe display. Output performance results from mathematical modeling, software simulations, and prototype AMLCDs displays demonstrate significant quality improvements to both text and full‐color images in comparison to images from RGB Stripe displays that have the same number of subpixels and column drivers.     

The effect of temperature and extrusion speed on the consolidation of zirconium-based metallic glass powder using equal-channel angular extrusion

In this study, gas-atomized amorphous Zr_58.5Nb_2.8Cu_15.6Ni_12.8Al_10.3 (Vitreloy 106a) containing 1280 ppmw oxygen was consolidated by equal-channel angular extrusion (ECAE). The powder was vacuum encapsulated in copper cans and subjected to one extrusion pass in the temperature region above the glass transition temperature (T _g) and below the crystallization temperature (T _x). The effects of extrusion temperature and the extrusion rate on microstructure, thermal stability, hardness, and compressive strength are investigated. Compression fracture surfaces were examined to determine the deformation mechanisms. The consolidates in which the time-temperature-transformation (TTT) boundary was not crossed during processing exhibit differential scanning calorimetry (DSC) patterns similar to the initial powder, with a slight decrease in T _x. Compressive strengths of about 1.6 GPa are recorded in the consolidates processed at 30 °C and 40 °C below T _x, which is close to what is observed in cast counterparts. The fracture surfaces exhibit vein patterns covering up to 90 pct of the surface area in some samples, which are characteristic of glassy material fracture. The slight decrease in T _x after consolidation is attributed to thermal-history-dependent short-range order and formation of nanocrystalline islands. The present results show that ECAE is successful in consolidation of metallic glass powder. This processing avenue opens a new opportunity to fabricate bulk metallic glasses (BMGs) with dimensions that may be impossible to achieve by casting methods.     

Science and Technology of High Dielectric Constant Thin Films and Materials Integration for Application to High Frequency Devices

Thin films of Ba_1?x Sr _x Ti_1+y O_3+z (BST), were fabricated using both by RF-magnetron sputtering and MOCVD to demonstrate application to high frequency devices. Precise control of composition and microstructure is critical for the production of (Ba _x Sr_1?x )Ti_1+y O_3+z (BST) dielectric thin films with the large dependence of permittivity on electric field, low losses, and high electrical breakdown fields that are required for successful integration of BST into tunable high frequency devices. Here we review results on composition-microstructure-electrical property relationships of polycrystalline BST films produced by magnetron sputter deposition that are appropriate for microwave devices such as phase shifters. BST films with a multilayer structure were also developed with different Ti-elemental ratio in each layer to minimize losses and leakage current. Interfacial contamination from C and H species was studied and implications on electrical properties are highlighted. Finally, York's group at the University of California-Santa Barbara successfully integrated our BST films onto phase shifter arrays. The results show potential of BST films in such applications. Results from initial work on the integration of Cu-electrodes with BST films are also presented.     

Study on residual stress in viscoelastic thin film using curvature measurement method

Using LSM (laser scanning method), the radius of curvature due to thermal deformation in polyimide film coated on Si substrate is measured. Since the polyimide film shows viscoelastic behavior, i.e., the modulus and deformation of the film vary with time and temperature, we estimate the relaxation modulus and the residual stresses of the polyimide film by measuring the radius of curvature and subsequently by performing viscoelastic analysis. The residual stresses relax by an amount of 10% at 100°C and 20% at 150°C for two hours.     

Electron energy loss spectroscopy for analysis of inhaled ultrafine particles in rat lungs

Epidemiologic studies have associated cardiovascular morbidity and mortality with ambient particulate air pollution. Particles smaller than 100 nm in diameter (ultrafine particles) are present in the urban atmosphere in very high numbers yet at very low mass concentration. Organs beyond the lungs are considered as targets for inhaled ultrafine particles, whereby the route of particle translocation deeper into the lungs is unclear. Five rats were exposed to aerosols of ultrafine titanium dioxide particles of a count median diameter of 22 nm (geometric standard deviation, GSD 1.7) for 1 hour. The lungs were fixed by intravascular perfusion of fixatives immediately thereafter. TiO(2) particles in probes of the aerosol as well as in systematic tissue samples were analyzed with a LEO 912 transmission electron microscope equipped with an energy filter for elemental microanalysis. The characteristic energy loss spectra were obtained by fast spectrum acquisition. Aerosol particles as well as those in the lung tissue were unambiguously identified by electron energy loss spectroscopy. Particles were mainly found as small clusters with a rounded shape. Seven percent of the particles in the lung tissue had a needle-like shape. The size distribution of the cluster profiles in the tissue had a count median diameter of 29 nm (GSD 1.7), which indicates no severe clustering or reshaping of the originally inhaled particles. Electron energy loss spectroscopy and related analytical methods were found to be suitable to identify and localize ultrafine titanium dioxide particles within chemically fixed and resin-embedded lung tissue.     

Improvement in transdermal drug delivery performance by graphite oxide/temperature-responsive hydrogel composites with micro heater

Transdermal drug delivery system (TDDS) was prepared with temperature-responsive hydrogel. The graphite was oxidized and incorporated into hydrogel matrix to improve the thermal response of hydrogel. The micro heater was fabricated to control the temperature precisely by adopting a joule heating method. The drug in hydrogel was delivered through a hairless mouse skin by controlling temperature. The efficiency of drug delivery was improved obviously by incorporation of graphite oxide due to the excellent thermal conductivity and the increased interfacial affinity between graphite oxide and hydrogel matrix. The fabricated micro heater was effective in controlling the temperature over lower critical solution temperature of hydrogel precisely with a small voltage less than 1 V. The cell viability test on graphite oxide composite hydrogel showed enough safety for using as a transdermal drug delivery patch. The performance of TDDS could be improved noticeably based on temperature-responsive hydrogel, thermally conductive graphite oxide, and efficient micro heater.     

Pixel‐Structured Scintillator with Polymeric Microstructures for X‐Ray Image Sensors

We introduce a pixel‐structured scintillator realized on a flexible polymeric substrate and demonstrate its feasibility as an X‐ray converter when it is coupled to photosensitive elements. The sample was prepared by filling Gd₂O₂S:Tb scintillation material into a square‐pore‐shape cavity array fabricated with polyethylene. For comparison, a sample with the conventional continuous geometry was also prepared. Although the pixelated geometry showed X‐ray sensitivity of about 58% compared with the conventional geometry, the resolving power was improved by about 70% above a spatial frequency of 3 mm^?1. The spatial frequency at 10% of the modulation‐transfer function was about 6 mm^?1.