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Batch Look Ahead Orthogonal Matching Pursuit
No full textCompressed sensing (CS) is a sampling paradigm that enables sampling signals at sub Nyquist rates by exploiting the sparse nature of signals. One of the main concerns in CS is the reconstruction of the signal after sampling. Many reconstruction algorithms have been proposed in the literature for the recovery of the sparse signals - Basis Pursuit, Orthogonal Matching Pursuit (OMP), Look Ahead Orthogonal Matching Pursuit (LAOMP) are some of the popular reconstruction algorithms. LAOMP, a modification of OMP, improves the reconstruction accuracy of OMP by employing a look ahead procedure. But LAOMP suffers from the drawback of being very expensive in terms of the computational time. In this paper we propose a modified version of the LAOMP algorithm called Batch-LAOMP which has a lesser computational complexity and also gives better performance in terms of reconstruction accuracy as seen from the results of the numerical experiments
Modeling mode-I fracture process in concrete at meso-scale: Computational aspects of lattice model and a comparison between results of two dimensional lattice simulation and acoustic emission measurements
No full textThis article reports a comparative study on the Acoustic Emission (AE) measurements and Two-Dimensional (2D) lattice simulation results related to mode-I fracture process in plain cement concrete Three Point Bend (TPB) specimen. Computational aspects and programming details of lattice modeling have been discussed. AE based b-values were compared with lattice modelling results. The meso-scale modeling of the heterogeneous Timoshenko Beam (TB) lattice and its Finite Element Analysis (FEA) was performed using programs developed by the authors in MATLAB and FORTRAN respectively. A tensile stress based fracture law was used to remove the beam elements reaching the threshold stress values. Since, the removal of an element from the lattice network can be considered similar to a `virtual' AE event, the number of failed elements in lattice network was compared with AE parameters recorded during the experiment. An attempt was also made to study the trend of the cumulative number of failed elements in lattice model with the trend of the b-value variation with load level. The trend of cumulative fractured beam elements observed from lattice simulation reflected the trend in AE recorded. By considering softening of cement matrix at element level, the simulation results seem to give better correlation with AE recorded
Deciphering the deformation mechanism in single point incremental forming: experimental and numerical investigation
No full textIn the present work, deformation mechanism in single-point incremental forming (SPIF) of drawing quality steel with a fully ferritic microstructure was studied. The effect of tool diameter and vertical step size on the micromechanisms of plastic deformation in SPIF was investigated by observing changes in microstructure and lattice rotation. It was observed that the fraction of grains with {111} normal direction (ND), which constitutes the gamma fiber in BCC materials, decreased with decrease in tool diameter and vertical step size. It is known that the state of deformation in SPIF is near to plane strain with the direction of major strain being always perpendicular to tool travel direction and negligible strain parallel to tool movement direction. Microstructural evidence for this observation and also for the presence of through thickness shear (TTS) components at smaller step size and tool diameter was observed. Viscoplastic self-consistent (VPSC) simulations revealed that the activity of {112} < 11<(1)over bar> > slip system decreased in comparison to {110} < 1<(1)over bar>1 > slip system in the presence of TTS which manifested as the deviation from {111} parallel to ND position at smaller step size and tool diameter
Microstructure, Texture and Mechanical Properties after Cold Working and Annealing in a Biomedical Ti-Nb-Ta Alloy
No full textbeta titanium alloys, comprising alloying elements such as Nb, Ta, Zr, are considered promising materials for use in orthopedic applications, as the lower elastic modulus of these alloys, reduces the chance of implant failure caused by stress shielding. The mechanical behavior of these alloys depend on the composition as well as the stability of the phases. In the present study, the effect of cold rolling and subsequent annealing on the microstructure, texture and mechanical behavior of a Ti-Nb-Ta-O alloy has been investigated. Structural characterization was done using x-ray diffraction (XRD) and optical microscopy. Mechanical properties were evaluated by estimation of hardness and elastic modulus. The results show that, (1) the alloy contains single-phase beta microstructure in both deformed as well as annealed condition with no evidence of deformation induced phase transformation, (2) the microstructures of cold worked alloy become increasingly inhomogeneous with dominance of shear bands at higher rolling strains, (3) high value of hardness to modulus ratio could be obtained in the present alloy due to stability of beta phase and interstitial strengthening
INFLUENCE OF NON-AXISYMMETRIC CONFINEMENT ON THE HYDRODYNAMIC STABILITY OF MULTI-NOZZLE SWIRL FLOWS
No full textInteraction between coherent flow oscillations and the pre-mixed flame sheet in combustors can result in coherent unsteadiness in the global heat release response. These coherent flow oscillations can either be self-excited (eg. the Precessing Vortex Core) or result from the hydrodynamic response of the flow field to acoustic forcing. Recent work has focused on understanding the various instability modes and fundamental mechanisms that control hydrodynamic instability in single nozzle swirl flows. However, the effect of multiple closely spaced nozzles as well as the non-axisymmetric nature of the confinement imposed by the combustor liner on swirl nozzle flows remains as yet unexplored. We study the influence of inter-nozzle spacing and non-axisymmetric confinement on the local temporal and spatiotemporal stability characteristics of multi-nozzle flows in this paper. The base flow model for the multi nozzle case is constructed by superposing contributions from a base flow model for each individual nozzle. The influence of the flame is captured by specifying a spatially varying base flow density field. The non-axisymmetric local stability problem is posed in terms of a parallel base flow with spatial variations in the two directions perpendicular to the streamwise direction. We investigate the case of a single nozzle and three nozzles arranged in a straight line within a rectangular combustor. The results show that geometric confinement imposed by the combustor walls has a quantitative impact on the eigenvalues of the hydrodynamic modes. Decreasing nozzle spacing for a given geometric confinement configuration makes the flow more unstable. The presence of an inner shear layer stabilized flame results in an overall stabilization of the flow instability. We also discuss qualitatively, the underlying voracity dynamics mechanisms that influence the characteristics of instability modes in triple nozzle flows
Lewis acid catalysis: regioselective hydroboration of alkynes and alkenes promoted by scandium triflate
No full textThe first commercially available scandium-catalysed selective hydroboration of alkynes and alkenes with HBpin (pin = OC-Me2CMe2O) in the presence of a catalytic amount of NaHBEt3 has been developed. This protocol can be applicable to a wide range of substrates including aromatic, aliphatic with cyclic and acyclic side chains, and heteroaryl systems with broad functional-group compatibility. Mechanistic studies revealed that the reaction occurs in a syn fashion via the sigma-bond metathesis between the alkenyl scandium species and HBpin
An ultra-stable redox-controlled self-assembling polypeptide nanotube for targeted imaging and therapy in cancer
No full textWe introduce a self-assembling polypeptide-based nanotube system having the ability to specifically target cancer cells. The nanotubes target the cancer cell surface through integrin engagement with the help of multiple RGD units present along their surface. While the nanotubes are non-toxic towards cells in general, they can be loaded with suitable drugs to be released in a sustained manner in cancer cells. In addition, the nanotubes can be utilized for cellular imaging using any covalently tagged fluorescent dye. They are stable over a wide range of temperature due to intermolecular disulphide bonds formed during the self-assembly process. At the same time, presence of disulphide bonds provides a redox molecular switch for their degradation. Taken together this system provides a unique avenue for multimodal formulation in cancer therapy
On the Size of Homogeneous and of Depth-Four Formulas with Low Individual Degree
No full textLet r >= 1 be an integer. Let us call a polynomial f (x(1), x(2),..., x(N)) is an element of Fx] a multi-r-ic polynomial if the degree of f with respect to any variable is at most r. (This generalizes the notion of multilinear polynomials.) We investigate the arithmetic circuits in which the output is syntactically forced to be a multi-r-ic polynomial and refer to these as multi-r-ic circuits. We prove lower bounds for several subclasses of such circuits, including the following. 1. An N-Omega((logN)) lower bound against homogeneous multi-r-ic formulas ( for an explicit multi-r-ic polynomial on N variables). 2. An (n/r(1.1))(Omega)((root d/r)) lower bound against depth-four multi-r-ic circuits computing the polynomial IMMn,d corresponding to the product of d matrices of size n x n each. 3. A 2(Omega)((root N)) lower bound against depth-four multi-r-ic circuits computing an explicit multi-r-ic polynomial on N variables
Multilayer planar inductor array based angular position sensor for cryogenic application
No full textThe design, development and testing of a cryogenically operated multilayer planar inductor array based eddy current angular position/rotation transducer is claimed. An array of 4 multi-layered coils is used to divide the 360 degrees into four sectors of 90 degrees each. Switching between each of the inductor is done by a cold electronics based multiplexer circuit coupled to an unbuffered inverter LC oscillator. The angular displacement is a function of frequency of cold electronic LC oscillator. The pickup coil forms the inductor of the oscillator which is operated down to 4.2 K and uses thermal cycled stable components. The change in frequency as a function of angular displacement was calibrated at cryogenic temperatures. The developed sensor was found to have good thermal stability, sensitivity and repeatability over the entire cryogenic range
COARSE TO FINE TRAINING FOR LOW-RESOLUTION HETEROGENEOUS FACE RECOGNITION
No full textRecently, near-infrared (NIR) images are being increasingly used for recognizing facial images across illumination variations and in low-light conditions. In surveillance scenarios, the captured NIR may have low-resolution which results in significant loss of discriminative information along with uncontrolled pose. In this work, we address the challenging task of matching these low-resolution (LR) uncontrolled NIR images with high-resolution (HR) controlled visible (VIS) images usually present in the database. Since the probe and gallery images differ significantly in terms of pose, resolution and spectral properties, we employ a two-stage approach. First, the images are transformed into a common space using metric learning such that the images of the same subject are pushed closer and those of different subjects are pushed apart. We then define an objective function which can simultaneously push both LR NIR and HR VIS samples towards the centroids of the HR VIS samples. We show that the approach is general and can be used for other data like RGB-D and also for matching across pose. Extensive experiments conducted on five datasets shows the effectiveness of our approach