Effect of constitutive models on the numerical simulation of viscoelastic flow at an entry region

The poor solutions of numerical simulations at a contraction has often been attributed to the numerical scheme used. However, the solution of a numerical simulation is also highly dependent on the constitutive equation. A study of various constitutive equations on the simulation of the 4:1 contraction flow is made in this paper, and their effects on the results analyzed. The constitutive models considered include the Upper Convected Maxwell model, the Oldroyd-B model, the White-Metzner model, the Phan-Thien-Tanner model and the Giesekus-Leonov model. It was found that although the Phan-Thien-Tanner model gave the best results, the solution at higher shear rates were still not satisfactory.     

Pressure death and tailing behavior of Listeria monocytogenes strains having different barotolerances

The objectives of this study were to investigate the variability among Listeria monocytogenes strains in response to high-pressure processing, identify the most resistant strain as a potential target of pressure processing, and compare the inactivation kinetics of pressure-resistant and pressure-sensitive strains under a wide range (350 to 800 MPa) of pressure treatments. The pressure resistance of Listeria innocua and nine strains of L. monocytogenes was compared at 400 or 500 MPa and 30 degrees C. Significant variability among strains was observed. The decrease in log CFU/ml during the pressure treatment was from 1.4 to 4.3 at 400 MPa and from 3.9 to >8 at 500 MPa. L. monocytogenes OSY-8578 exhibited the greatest pressure resistance, Scott A showed the greatest pressure sensitivity, and L. innocua had intermediate resistance. On the basis of these findings, L. monocytogenes OSY-8578 is a potential target strain for high-pressure processing efficacy studies. The death kinetics of L. monocytogenes Scott A and OSY-8578 were investigated at 350 and 800 MPa. Survivors at 350 MPa were enumerated by direct plating, and survivors at 800 MPa were enumerated by the most-probable-number technique. Both pressure-resistant and pressure-sensitive strains exhibited non-first-order death behavior, and excessive pressure treatment did not eliminate the tailing phenomenon.     

Ti-PS nanocomposites by plasma immersion ion implantation and deposition

We synthesize Ti-PS nanocomposites by plasma immersion ion implantation and deposition (PIII&D) technique. Ti nanoparticles at size of 5-15 nm are found in PS matrix. We propose the formation of Ti nanoparticles as a result of the combined effect of ion implantation and ion condensation in PIII&D process. X-ray photoelectron spectroscopy measurements reveal that Ti atoms have three different chemical states, metal, oxide and carbide. While surface Ti atoms are oxidized, embedded Ti atoms keep their metallic states by surrounding PS matrix. We characterize optical absorbance of Ti-PS nanocomposites by UV-VIS measurements. An adsorption peak due to the excitation of localized surface plasmon is found at wavelength 337.5 nm and the fractal nature of Ti-PS nanocomposites broaden absorption wavelength from UV to infrared. In addition, we use a protein assay to measure protein immobilization. It is found that the amount of protein immobilized on Ti-PS nanocomposites is almost twice than that on pristine PS. The enhancement mechanisms are attributed to the increased surface roughness as well as covalent linkages between protein molecules and functional groups on the surface of Ti-PS nanocomposites.     

Understanding the detrimental effect of nitrate presence on EBPR systems: effect of the plant configuration

The interaction between enhanced biological phosphorus removal (EPBR) and biological nitrogen removal may result in EBPR failure in full‐scale wastewater treatment plants (WWTPs). This work studies one of the common causes of this failure: the presence of nitrate in the anaerobic phase, which may act as an inhibitor for polyphosphate accumulating organisms (PAO) activity or may activate the competition between PAO and denitrifying bacteria for the carbon source. Several batch experiments were performed with different carbon sources (acetic acid, propionic acid and sucrose) at different nitrate concentrations using PAO‐enriched sludge from two different pilot plants: an anaerobic/aerobic sequential batch reactor (SBR) and an anaerobic/anoxic/aerobic (A²/O) continuous plant. The results imply that the operational conditions of the A²/O pilot plant selected a PAO population capable of i) coexisting with nitrate without an inhibitory effect and ii) outcompeting denitrifying bacteria for the carbon source, in contrast to the SBR pilot plant where nitrate had an inhibitory effect on EBPR. Copyright © 2012 Society of Chemical Industry     

Influence of thickness on nanomechanical behavior of Black Diamond™ low dielectric thin films for interconnect and packaging applications

In the present study, we have investigated the thickness dependence of mechanical properties of the Black Diamond? (SiOC:H, BD, Low-k) films, which are of great interest in current Cu/low-k Back End of the Line (BEOL) interconnect/packaging technologies. For this investigation the BD thin films of six different thicknesses 100, 300, 500, 700, 1,000 and 1,200 nm were deposited on the 8″ Si wafer by using plasma enhanced chemical vapor deposition (PECVD) technique. Nanoindentation and nanoscratch tests of the BD films were performed by using the Nano Indenter^® XP (MTS Corp. USA). In nanoindentation testing of the BD films, significant differences in the elastic modulus of the BD films were observed. In nanoscratch testing, it is found that the critical load (Lc) and scratch width increases as the thickness of the film increases. Cross-sectional analysis of residual nanoindentation impressions was carried out using atomic force microscopy (AFM) to study the deformation behavior. The nanoindentation and nanoscratch responses of the BD thin films of six different thicknesses are different and they are expected mainly due to the molecular reorganization in thin/ultra thin films.     

Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles

Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed.     

Anti‐inflammatory properties of high pressure‐assisted extracts of Grifola frondosa in lipopolysaccharide‐activated RAW 264.7 macrophages

The aim of this study was to determine the in vitro anti‐inflammatory properties of the shake extract (SE) and the high pressure‐assisted extract (PE) of the mycelia of Grifola frondosa in a lipopolysaccharide‐stimulated RAW 264.7 macrophage model. The content of total polysaccharides and β‐glucans of PE at 600 MPa (PE‐600) was 41.2 and 6.2 mg g^?1 dry weight, respectively, which were significantly higher than SE extracts. The results showed that treatment with 500 μg mL^?1 of PE by 600 MPa (PE‐600) did not reduce RAW 264.7 cell viability but did significantly inhibit the production of LPS‐induced NO, PGE₂ and intracellular ROS. The PE‐600 inhibited the activation of NF‐kB and then reduced the production of LPS‐induced TNF‐α, IL‐6 and IL‐1β in a dose‐dependent manner. Thus, the PE could be used as an alternative extraction method for improving the extraction efficacy of G. frondosa and serve as an alternative source of anti‐inflammatory agents.     

Heating rate dependent delamination of metal–polymer interfaces: experiments and modeling

Bimaterial interfaces in microelectronics packages are the most common regions of failure under thermo-mechanical excursions. In this work, we report experimentally observed role of heating rate on the delamination initiation and propagation across a metal-polymer interface in a microelectronic package. We observe that the rate of delamination propagation increases with increasing heating rate. When the heating rate increases, in addition to the higher amount of delamination growth per unit time, experimental results suggests that higher growth will also incur per unit temperature (loading). Correspondingly, the temperature at which complete delamination occur decreases. Using finite element modeling with cohesive interfaces, we provide a plausible explanation to this observed phenomenon. The analyses indicate that the mechanical behavior of the bimaterial interface is sensitive to both temperature and thermal rate.     

Support vector machines for urban growth modeling

This paper presents a novel method to model urban land use conversion using support vector machines (SVMs), a new generation of machine learning algorithms used in the classification and regression domains. This method derives the relationship between rural-urban land use change and various factors, such as population, distance to road and facilities, and surrounding land use. Our study showed that SVMs are an effective approach to estimating the land use conversion model, owing to their ability to model non-linear relationships, good generalization performance, and achievement of a global and unique optimum. The rural-urban land use conversions of New Castle County, Delaware between 1984–1992, 1992–1997, and 1997–2002 were used as a case study to demonstrate the applicability of SVMs to urban expansion modeling. The performance of SVMs was also compared with a commonly used binomial logistic regression (BLR) model, and the results, in terms of the overall modeling accuracy and McNamara’s test, consistently corroborated the better performance of SVMs.