Image-based finite element mesh construction for material microstructures

One way of computing the macroscopic behavior of a material sample with complex microstructure is to construct a finite element model based on a micrograph of a representative slice of the material. The quality of the results produced with such a model obviously depends on the quality of the constructed mesh. In this article, we describe a set of routines that modify and improve the quality of a 2D mesh. Most of the routines are guided by an effective element “energy” functional, which takes into account the shape quality of the elements and the homogeneity of the elements as determined from an underlying segmented image. The interfaces and boundaries in the image arise naturally from the segmentation process. From these routines, we construct a close-to-automatic mesh generator that requires only a few inputs, such as the linear sizes of the largest and smallest features in the micrograph.     

Microstructural studies of PMMA impregnated mortars

Studies on cement concrete microstructures are carried out to explain experimentally observed phenomenon and for modeling of concrete at the macroscopic level. In this article, the preparation of polymer impregnated mortar (PIC) is carried out by partially or fully replacing the pores in the cement mortars (OPC) by PMMA. The effect of this polymer impregnation on density and morphology of the cement matrix is studied. The microstructural changes in the mortar, on exposure of these specimens to hydrochloric acid and sea water for 7 and 28 days, are also investigated in this article. The above studies indicated that the polymer addition decreased the voids in the mortar thereby preventing leaching of water soluble salts present in the OPC. It was observed that the polymer also prevented the external chemical media from permeating into the cement matrix and undergoing interactions with it. It is concluded that the durability and chemical resistance properties of the PIC are better compared with OPC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of pre rigor stretching on beef tenderness development

The objective of this study was to determine effects of pre rigor stretching on beef tenderness development. Beef loins (M. longissimus dorsi; n=24) were assigned to either stretching or non-stretching treatments and aged for 14days at -1.5°C. Sarcomere length, shear force, water-holding capacity and proteolysis were determined for the loins at 1, 7 and 14days of ageing. Stretching increased the length of the loins by 33% resulting in a trend of increasing sarcomere length (P=0.19). However, no significant differences for shear force values, purge, drip and cooking losses between treatments were found. Shear force values decreased with ageing times (P<0.05). Western blot assay found that stretching did not affect the extent of desmin degradation. The findings from the present study suggest that pre rigor stretching with the current increase in length will not contribute to tenderness improvement of the beef loins.     

Surface treatment effect of carbon fiber fabric counter electrode in dye sensitized solar cell

Dye sensitized solar cells (DSSC) with surface modified carbon fiber fabric (CF) counter electrodes were prepared and tested. Four different type of CF were used; carbon fiber (CF); carbon fiber etched with NaOH (ECF); carbon fiber with thermally deposited platinum (CFPt); and carbon fiber etched with NaOH followed by thermal deposition of platinum (ECFPt). For comparison, DSSC with thermally Pt deposited fluorine doped tin oxide (FTO/Pt) glass counter electrode was also prepared and tested. Scanning electron microscope (SEM) proved that surface morphology of the carbon fiber was roughened by the etching process and platinum deposition process. The I-V curves of each DSSC were measured under simulated light (1 Sun, AM 1.5) to get open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and efficiency (eta). Electrochemical impedance spectroscopy of each cell was measured also. It was found that higher efficiency is obtained in order of using ECFPt > CFPt > FTO/Pt > ECF > CF counter electrode.     

Halogen-free polyisobutylene by in situ methylation of living polyisobutylene using dimethylzinc

Summary Halogen-free polyisobutylene (PIB) was synthesized by in situ methylation of living PIB using dimethylzinc. Quantitative methylation of living PIB was achieved within 60 min using a ratio of [(CH₃)₂Zn]/[TiCl₄]₀= 1 without any side reactions. Under similar conditions, living PIB capped with 1,1-diphenylethylene (PIB-DPE⁺) yielded close to 1:1 mixture of methoxy- and methyl-functionality. By using the ratio of [(CH₃)₂Zn]/[TiCl₄]₀≥ 3, however, quantitative methylation of PIB-DPE⁺ could be achieved in 120 min without any side reactions as confirmed by spectroscopic and chromatographic analyses. Received: 1 February 2000/Revised version: 23 April 2000/Accepted: 23 April 2000     

Experimental studies on the instabilities of viscous fingering in a Hele-Shaw cell

When air is injected into silicone oil contained in a horizontal Hele-Shaw cell, a single air bubble forms and grows showing various interesting phenomena. In this study the effects of the bubble front velocity, air injection velocity at a nozzle, fluid properties and cell depth on the stability of the growing bubble were investigated experimentally. By using the modified capillary number involving the aspect ratio, we obtained the onset conditions of the unstable bubble. Also, the bubble width was analyzed both quantitatively and qualitatively. Before the bubble experiences splitting, the bubble front velocity is almost proportional to the air injection velocity. Therefore the latter velocity may be used in a practical sense.     

Preparation and evaluation of poly(2-hydroxyethyl aspartamide)-hexadecylamine-iron oxide for MR imaging of lymph nodes

The purpose of this study was to synthesize biocompatible poly(2-hydroxyethyl aspartamide)–C₁₆-iron oxide (PHEA-C₁₆-iron oxide) nanoparticles and to evaluate their efficacy as a contrast agent for magnetic resonance imaging of lymph nodes. The PHEA-C₁₆-iron oxide nanoparticles were synthesized by coprecipitation method. The core size of the PHEA-C₁₆-iron oxide nanoparticles was about 5 to 7 nm, and the overall size of the nanoparticles was around 20, 60, and 150 nm in aqueous solution. The size of the nanoparticles was controlled by the amount of C₁₆. The 3.0-T MRI signal intensity of a rabbit lymph node was effectively reduced after intravenous administration of PHEA-C₁₆-iron oxide with the size of 20 nm. The in vitro and in vivo toxicity tests revealed the high biocompatibility of PHEA-C₁₆-iron oxide nanoparticles. Therefore, PHEA-C₁₆-iron oxide nanoparticles with 20-nm size can be potentially useful as T2-weighted MR imaging contrast agents for the detection of lymph nodes.     

Effect of Pretreatment Conditions on the Catalytic Activity of Benzene Combustion Over SBA-15-Supported Copper Oxides

The effect of the pretreatment conditions on the catalytic combustion of benzene over copper oxides supported on SBA-15 was investigated. The catalytic activities of the reduced catalysts were higher than those of the unreduced catalysts, indicating that the metallic Cu is much more active than the copper oxides.     

Discrimination between natural and HPHT-treated type IIa diamonds using photoluminescence spectroscopy

We have performed low-temperature (8 K) photoluminescence (PL) measurements on 71 natural and 12 high-pressure-and-high-temperature (HPHT)-treated type IIa diamonds. The GR1, NV⁰, NV^?, H4, and H3 defect center PL signals are compared. Some distinct differences in the PL lineshape, intensity, and appearance of side-band PL signals are observed. Furthermore, we processed 6 of the natural diamond samples with the HPHT treatment to investigate the effect of the treatment on the PL spectrum. By systematically analyzing the differences in the PL spectra, we developed a scheme to discriminate natural and HPHT-treated diamonds with 99% validity.     

Effect of synthesis condition and annealing on the sensitivity and stability of gas sensors made of Zn-doped <Emphasis Type=Italic>γ</Emphasis>-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> particles

Gas sensors made of flame-synthesized Zn-doped γ-Fe₂O₃ nanoparticles were found to have high sensitivity and high aging resistance. Zinc-doped γ-Fe₂O₃ nanoparticles and microparticles were synthesized by flame spray pyrolysis (FSP). Gas sensors were fabricated with as-synthesized particles, and with particles that had been annealed. The sensors’ response to acetone vapor and H₂ was measured as fabricated, and measured again after the sensors were aged for three days. The sensors made from as-synthesized particles showed a gas sensing sensitivity 20 times higher than the literature value. However, sensors made of microparticles lost their sensing ability after three days of aging; sensors made of nanoparticles retained their gas sensing capability after aging. Sensors made of annealed particles did not have significant gas sensing capabilities. Analysis using the William and Hall method showed that the microstrains decreased significantly in both H₂/O₂ and H₂/Air flame synthesized particles after annealing. The results showed that sensors made of flame-synthesized particles have much higher sensitivity than sensors made of particles previously reported. Especially, sensors made of flame-synthesized nanoparticles are resistant towards aging. This aging resistance may be attributed to the particles’ ability to retain their microstrains.