Nonlinear Dynamic Response of Cylindrical Roller Bearing–Rotor System with 9 Degree of Freedom Model Having a Combined Localized Defect at Inner–Outer Races of Bearing

This article presents a nonlinear dynamic model for a cylindrical roller bearing–rotor system with interaction forces between the inner race, outer race, and roller. Roller–race contacts are modeled predicting nonlinear stiffness (Hertz contact theory) and nonlinear damping for a rotor–cylindrical roller bearing system. Here a shaft–rotor bearing system is modeled with 9 degrees of freedom with one defect on the inner race and one defect on the outer race for a case of combined localized defects. In the mathematical formulation, contacts between rolling elements and inner and outer races are considered as nonlinear springs and nonlinear damping is taken into consideration. Contact force calculations with nonlinearity are solved using the Newton-Raphson method for n unknown nonlinear simultaneous equation. The Newmark-β implicit integration technique coupled with the Newton-Raphson method is used to solve the differential equations. The results are obtained in the form of a time domain plot, frequency domain plot, and phase plot/Poincare map. The validity of the proposed model is compared with experimental results. A bifurcation graph of speed versus peak amplitude predicts the behavior of the system.     

Adaptive enhancement of compressed SAR images

Synthetic aperture radar (SAR) imagery is an important global all-weather surveillance and mapping satellite imagery system. As space-borne systems have a limited storage capacity, it is imperative to heavily compress SAR images, possible with lossy compression schemes. As a result, SAR images need to be enhanced in earth stations. The work reported in this paper aims to address the issue of compression artefact removal of SAR images in an adaptive manner. The SAR images, compressed using the JPEG utility at significantly low bit rates, are enhanced by adaptively removing coding artefacts and speckle noise. As edges carry significant information in satellite imagery, a significant edge image is used for edge enhancement with selective removal of noisy edges. Further, an image sharpness metric is proposed in this work to serve as an objective no-reference metric for measuring the sharpness of SAR images.     

Vibrational properties of single-wall carbon nanotubes: a first-principles study

We present first-principles pseudopotential-based density functional theory (DFT) calculation of structures, full phonon dispersions and thermal properties of armchair single wall armchair carbon nanotubes (SWCNTs) in the isolated and bundle forms. Comparison between the properties of isolated and bundled nanotubes is used to estimate the intertube interaction. We determine correlation between vibrational modes of a graphene sheet and of the nanotube to understand how rolling of the sheet results in mixing between modes and changes in vibrational spectrum. The radial breathing mode hardens with increasing diameter (or decreasing curvature). We estimate thermal expansion coefficient of nanotubes within a quasiharmonic approximation and identify the modes that dominate thermal expansion of some of these SWCNTs both at low and high temperatures.     

A new glucose sensor based on encapsulated glucose oxidase within organically modified sol–gel glass

A non-mediated glucose biosensor is reported based on encapsulated glucose oxidase (GOD) within the composite sol–gel glass, which is prepared using optimum concentrations of 3-aminopropyltriethoxy silane, 2-(3, 4-epoxycyclohexyl)-ethyltrimethoxy silane, GOD dissolved in double distilled water and HCl. A white, smooth film of sol–gel glass with controlled thickness is also prepared at the surface of a Pt disk electrode without GOD to study the electrochemistry of ferrocene monocarboxylic acid at the surface of the modified electrode. The electrochemistry of ferrocene monocarboxylic acid at composite sol–gel glass electrode with varying thickness is reported. The GOD-immobilized film over the Pt disk surface shows a yellow colour. The new sol–gel glass in the absence and the presence of GOD is characterized by scanning electron microscopy (SEM). The enzyme-immobilized film of different thickness is made using varying concentrations of soluble sol–gel components applied to the well of the Pt disk electrode. The enzyme is cross-lined with the 3-aminopropyltriethoxysilane, one of the composite component of sol–gel glass using glyoxal at 4°C for 4 h. The response of non-mediated enzyme sensor is studied based on cyclic voltammetry and amperometric measurements. A typical amperometric response of the enzyme sensor having varying thickness of the modified sol–gel glass film is reported. The variation of the response time as a function of the film thickness is reported. The stability of cross-linked GOD to sol–gel glass is found to be more than a month without loss of enzymatic activity when the enzyme sensor is stored at 4°C.     

Motion Panoramas

In this paper we describe a method for analysing video sequences and for representing them as mosaics or panoramas. Previous work on video mosaicking essentially concentrated on static scenes. We generalize these approaches to the case of a rotating camera observing both static and moving objects where the static portions of the scene are not necessarily dominant, as it has been often hypothesized in the past. We start by describing a robust technique for accurately aligning a large number of video frames under unknown camera rotations and camera settings. The alignment technique combines a feature‐based method (initialization and refinement) with rough motion segmentation followed by a colour‐based direct method (final adjustment). This precise frame‐to‐frame alignment allows the dynamic building of a background representation as well as an efficient segmentation of each image such that moving regions of arbitrary shape and size are aligned with the static background. Thus a motion panorama visualizes both dynamic and static scene elements in a geometrically consistent way. Extensive experiments applied to archived videos of track‐and‐field events validate the approach. Copyright © 2004 John Wiley & Sons, Ltd.     

Perception of creaminess in foods

Food texture and mouthfeel play a crucial role in product and consumer acceptability. Creaminess, enjoyed by consumers, is a complex, multimodal sensory perception involving olfactory, gustatory and tactile cues. Oral viscosity and lubrication are the key underlying physical properties that define the mechanism of creaminess perception. Thickness, smoothness, mouth-coating, and dairy flavor can together play roles in the sensation of creaminess. The aim of this review is to present an understanding of the term” creaminess” along with different modalities involved in its perception, and to explore the oral physiological parameters and key physical properties that may be involved in the different oral modalities. An analysis of the previously examined links between food structure and composition and oral physiological parameters is presented. The review also presents a brief summary of previous models describing contributions of taste, aroma, and textural sensations. It emphasizes on the role of oral processing in testing proposed models with experimental evidence supporting those models and the future trends to enhance creaminess.     

Estimation of heat source model parameters for twin-wire submerged arc welding

Heat source models are mathematical expressions that represent the generation term in the fundamental heat transfer equation. Investigators have successfully demonstrated different heat source models for single-wire welding. The present investigation estimates the double ellipsoidal heat source model parameters for twin-wire application. The heat source model parameters have been estimated for varying set of welding conditions. It has been found that the heat source model parameters for twin-wire welding are different from the single-wire welding. Moreover, the heat source model parameters also depend upon process parameters. Effects of welding current, electrode polarity and wire diameter on the size of heat source model have been presented. Flux consumption is also found to play a significant role in deciding the heat source model parameters.     

Thickness dependent electronic structure of ultra-thin tetrahedral amorphous carbon (ta-C) films

Microstructural properties of ultrathin (1-10 nm) tetrahedral amorphous carbon (ta-C) films are investigated by Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, X-ray Photoelectron Spectroscopy, Raman spectroscopy and Atomic Force Microscopy (AFM). The CK-edge NEXAFS spectra of 1 nm ta-C films provided evidence of surface defects (C―H bonds) which rapidly diminish with increasing film thickness. A critical thickness for stabilization of largely sp³ matrix structure distorted by sp² sites is observed via the change of π*C═C peak behavior. Meanwhile, an increase in the film thickness promotes an enhancement in sp³ content, the film roughness remains nearly constant as probed by spectroscopic techniques and AFM, respectively. The effect of thickness on local bonding states of ultrathin ta-C films proves to be the limiting factor for their potential use in magnetic and optical storage devices.     

Characteristic of a multi-pass membrane separator for hydrogen separation through self-supported PdAg membranes

Dense PdAg membranes have shown immense potential to achieve high hydrogen purity required for proton exchange membrane (PEM) fuel cell. However, high hydrogen recovery and flux at lower transmembrane partial pressure is still a concern. In current study self-supported dense PdAg membranes were used to study the hydrogen recovery in a multi-pass membrane separator. Performance of a single and four collective membranes are tested in a single (without baffle) and multi-pass (with longitudinal baffles) membrane separator. Further, array of membrane configurations were tested experimentally by using longitudinal baffles and placing membranes at different locations. The hydrogen recovery for each configuration was measured experimentally. Experiments were performed using binary gas mixture 50H₂:50N₂ (v/v) at 3 bar pressure, 673 K temperature and gas-hourly space velocity (GHSV) 43 h^?1. The best assembly was further tested with typical methanol reformate gas composition by using simulated gas mixture of 50H₂:30N₂:18CO₂:2CO (v/v) at same operating condition. Numerical simulations were performed by using commercial software ANSYS 14.5 to understand the flow dynamics inside the separator with and without baffle. The results demonstrate that a multi-pass membrane separator enables to control hydrogen partial pressure radially along the length of reactor. This resulted in 33% enhancement in hydrogen recovery with multi-pass in comparison to single pass membrane separator.     

Complete liquification time test coupled with solvent fractionation technique to detect adulteration of foreign fats in ghee

Complete liquification time (CLT) test (min:s) exploits the physical property of milk fat as the time required by solid fat to melt completely at a defined temperature. It has been used to detect adulteration of groundnut oil and goat body fat when added singly and in combination with ghee. The Complete liquification time test for samples containing a combination of adulterants was carried out before and after solvent fractionation. The results revealed that adulterants added individually could be detected at higher levels (15%, w/w, groundnut oil in cow ghee; and 10%, w/w, goat body fat in buffalo ghee), while fractionation reduced the detection limit to lowest level (10%, w/w) used in this study.