Modelling of biaxial ratcheting behaviour of ultrahigh‐molecular‐weight polyethylene with viscoplasticity theory based on overstress for polymers

Biaxial ratcheting behaviour of ultrahigh‐molecular‐weight polyethylene (UHMWPE) has been modelled using the viscoplasticity theory based on overstress for polymers (VBOP) with the modified Chaboche kinematic hardening rule. Investigated loading condition is: axial strain‐controlled cyclic loading of thin‐walled tubular specimen in the presence of constant pressure. To improve the circumferential strain ratcheting response of UHMWPE, changes designed to account for kinematic hardening and tangent modulus effects are proposed. Numerical results are compared with previously obtained experimental data. It is shown that modified tangent modulus improves the model responses. The biaxial ratcheting behaviour of UHMWPE is modelled quantitatively with VBOP. © 2015 Society of Chemical Industry     

Ab-initio studies of pressure induced phase transitions in BaO

We use ab-initio Quantum Mechanics to study the zero temperature phase diagram of BaO. We calculate zero temperature Equations of State of different crystalline phases [B1 (NaCl), B8(NiAs), B2(CsCl), and distorted B2] using Density Functional Theory (DFT) with the generalized gradient approximation (GGA). We find the B1 structure to be the thermodynamically stable one at zero pressure; followed by three pressure induced phase transitions. We find that at P=11.3 GPa BaO transforms from B1 to B8; at P=21.5 GPa from B8 to distorted B2. The distorted B2 phase continuously approaches the B2 structure, the phase transformation occurs at P=62 GPa. We also study the band structure of BaO in its high pressure (B2) phase. For P=60.5 GPa, we find a band gap of 3.5 eV in agreement with experimetal value. We find metallization at P=230.6 GPa.     

Predicting the Displacement of Yoghurt by Water in a Pipe Using CFD

A numerical scheme based on the volume of fluid (VOF) method for predicting the displacement of one liquid by another has been verified versus electrical resistance tomography (ERT) and ultrasonic velocity profile (UVP) measurements for the displacement of yoghurt by water. The scheme using the VOF method predicts the skewed phase distribution as measured using ERT and the global structure of the velocity profile as measured using UVP. The phase distribution using the VOF method was compared with the results using the species transport model which allows for mixing between the phases. The species transport model was found to be less suitable for predicting the displacement of yoghurt by water since the turbulence model was unable to accurately predict the turbulent viscosity in the mixing zone between yoghurt and water, which resulted in a too high rate of mixing.     

Robust facial landmarking for registration

Finding landmark positions on facial images is an important step in face registration and normalization, for both 2D and 3D face recognition. In this paper, we inspect shortcomings of existing approaches in the literature and compare several methods for performing automatic landmarking on near-frontal faces in different scales. Two novel methods have been employed to analyze facial features in coarse and fine scales successively. The first method uses a mixture of factor analyzers to learn Gabor filter outputs on a coarse scale. The second method is a template matching of block-based Discrete Cosine Transform (DCT) features. In addition, a structural analysis subsystem is proposed that can determine false matches, and correct their positions.     

Characterisation and optical vapour sensing properties of PMMA thin films

The present article reports on the characterisation of spin coated thin films of poly (methyl methacrylate) (PMMA) for their use in organic vapour sensing application. Thin film properties of PMMA are studied by UV–visible spectroscopy, atomic force microscopy and surface plasmon resonance (SPR) technique. Results obtained show that homogeneous thin films with thickness in the range between 6 and 15 nm have been successfully prepared when films were spun at speeds between 1000?5000 rpm. Using SPR technique, the sensing properties of the spun films were studied on exposures to several halohydrocarbons including chloroform, dichloromethane and trichloroethylene. Data from measured kinetic response have been used to evaluate the sensitivity of the studied films to the various analyte molecules in terms of normalised response (%) per unit concentration (ppm). The highest PMMA film sensitivity of 0.067 normalised response per ppm was observed for chloroform vapour, for films spun at 1000 rpm. The high film's sensitivity to chloroform vapour was ascribed mainly to its solubility parameter and molar volume values. Effect of film thickness on the vapour sensing properties is also discussed.