Simulation of flow‐flexible body interactions with large deformation

A modified front‐tracking method was proposed for the simulation of fluid‐flexible body interactions with large deformations. A large deformable body was modeled by restructuring the body using a grid adaptation. Discontinuities in the viscosity at the fluid‐structure interface were incorporated by distributing the viscosity across the interface using an indicator function. A viscosity gradient field was created near the interface, and a smooth transition occurred between the structure and the fluid. The fluid motion was defined on the Eulerian domain and was solved using the fractional step method on a staggered Cartesian grid system. The solid motion was described by Lagrangian variables and was solved by the finite element method on an unstructured triangular mesh. The fluid motion and the structure motion were independently solved, and their interaction force was calculated using a feedback law. The interaction force was the restoring force of a stiff spring with damping, and spread from the Lagrangian coordinates to the Eulerian grid by a smoothed approximation of the Dirac delta function. In the numerical simulations, we validated the effect of the grid adaptation on the solid solver using a vibrating circular ring. The effects of the viscosity gradient field were verified by solving the deformation of a circular disk in a linear shear flow, including an elastic ring moving through a channel with constriction, deformation of a suspended catenary, and a swimming jellyfish. A comparison of the numerical results with the theoretical solutions was presented. Copyright © 2011 John Wiley & Sons, Ltd.     

Simulation of non-Newtonian ink transfer between two separating plates for gravure-offset printing

The inks used in gravure-offset printing are non-Newtonian fluids with higher viscosities and lower surface tensions compared to Newtonian fluids. This paper examines the transfer of a non-Newtonian ink between two parallel plates when the top plate is moved upward with a constant velocity while the bottom plate is held fixed. Numerical simulations were carried out using the Carreau model to explore the behavior of a non-Newtonian ink in gravure-offset printing. The volume of fluid (VOF) model was adopted to demonstrate the stretching and break-up behaviors of the ink. The results indicate that the ink transfer ratio is greatly influenced by the contact angle, especially the contact angle at the upper plate (α). For lower values of α, oscillatory or unstable behavior of the position of minimum thickness of the ink between the two parallel plates during the stretching period is observed. This oscillation gradually diminishes as the contact angle at the upper plate is increased. Moreover, the number of satellite droplets increases as the velocity of the upper plate is increased. The surface tension of the conductive ink shows a positive impact on the ink transfer ratio to the upper plate. Indeed, the velocity of the upper plate has a significant influence on the ink transfer in gravure-offset printing when the Capillary number (Ca) is greater than 1 and the surface tension dominates over the ink transfer process when Ca is less than 1.     

The effect of temporal separation of two Geiger mode avalanche photodiodes and variation of time bin widths on detection probabilities in LADAR system using two Geiger mode avalanche photodiodes

In this paper, the effect of temporal separation of two Geiger mode avalanche photodiodes and the variation of time bin widths on detection probabilities in LADAR system using two Geiger mode avalanche photodiodes (GmAPDs) was investigated. The system is implemented by using two GmAPDs with a beam splitter and applying comparative process to their ends. Then, the timing circuitry receives the electrical signals only if each GmAPD generates the electrical signals simultaneously. Although this system decreases the energy of a laser-return pulse scattered from the target, it is highly effective in reducing the false alarm probability because of the randomly distributed noise on the time domain. The temporal separation of two GmAPDs and the variation of the time bin widths result in the variation of detection probabilities. The experiments were performed to verify the effect of temporal separation of two GmAPDs and the variation of time bin widths on the detection probability in the LADAR system. As a result, the optimal temporal difference and the optimal time bin width were. Using these optimal values, a clear 3D image could be obtained by the simple acquisition of the raw time-of-flight data with high SNR.     

Probing actinide electronic structure through pu cluster calculations

Calculations of the electronic structure of clusters of plutonium have been performed, within the framework of the relativistic discrete‐variational method. These theoretical results and those calculated earlier for related systems have been compared to spectroscopic data produced in the experimental investigations of bulk systems, including photoelectron spectroscopy. Observation of the changes in the Pu electronic structure as a function of size provides powerful insight for aspects of bulk Pu electronic structure. © 2013 Wiley Periodicals, Inc.     

Synthesis of 7-Hydroxyspiropyran

The 7-acetoxyspiropyrans (4a and 4b) have been prepared by the reaction of Fischer's bases (3) with 2,4-diacetoxybenzaldehyde in refluxing ethanol in moderate yields. The acetyl group of 7-acetoxy-spiropyran 4a was easily removed to give a 7-hydroxyspiropyran 6 in high yield under the basic condition.     

Synthesis of 1,3-Diketones by Reaction of α-Haloketones with Acyl Cyanides Promoted by Samarium Diiodide

α-Haloketones reacted with acyl cyanides to form 1,3-diketones in the presence of samarium diiodide. The reaction was assumed to proceed via a mechanism involving samarium enolates formed in situ from α-haloketones.     

Covalent assembly of metal nanoparticles on cellulose fabric and its antimicrobial activity

We develop an antimicrobial active robust metal-cellulose nanohybrid by covalent assembly of metal nanoparticles on cellulose fabric using a simple impregnation of thiol-modified cellulose fabric in colloidal silver (Ag) or palladium (Pd) nanoparticle solutions. The combined results of high resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDXS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) reveal that the nanoparticles are highly loaded and dispersed in the thiol-modified cellulose fabric, and X-ray photoelectron spectroscopy (XPS) analysis reveals that the nanoparticles are immobilized in the fabric by a strong and stable covalent bond with thiol functional group. This robust covalent linkage between the nanoparticles and the fabric leads to a remarkable suppression of the release of metal nanoparticles from the fabric. In addition, the metal-cellulose nanohybrids show high antimicrobial activity in excess of 99.9 % growth inhibition of the microorganism. Thus, we anticipate that our metal-cellulose nanohybrid may not only protect cell damage caused by penetration and fixation of metal nanoparticles into the human body but also act as a sustainable biomedical textile.     

Grain rotations and distortions in the asymptotic variance of vacancy of the Boolean model

We consider the asymptotic variance of vacancy (AVV) in the high intensity small-grain Boolean model. Subjecting the grains to rotations or, more generally, linear distortions gives rise to a function which maps distortion distributions to the AVV of the corresponding Boolean model. We mainly study continuity properties of this function, where we use the L¹ Wasserstein metric on distortion distributions. An important role in the formulation and derivation of our results is played by notions of symmetry commonly used in multivariate analysis and stochastic simulation, such as conjugation-invariance and group models.