50175 research outputs found
Sort by
Hydrophobic mediated growth of galvanic-nanobuds from germanium nanowires for a highly tunable SERS substrate
No full textPotential applications of SERS substrates lie in their ability to be of large area and reproducible with a high shelf life. Sensitivity, however, is a consequence of tunability of the substrate for the specific laser in use. These criteria are addressed using the reported SERS substrate with a galvanic-nanobud architecture through germanium nanowires. Dense germanium nanowires have been fabricated using a plasma enhanced chemical vapour deposition technique. Silver nanostructures were grown on the nanowires by hydrophobic interactions between the nanowire substrate and AgNO3 solution. A measurement method has been proposed to obtain the temporal information on nanobud formation, thereby optimizing the surface enhanced Raman scattered signal from such substrates in real-time for any wavelength. This eliminates the usage of computationally expensive numerical tools or additional characterization techniques to locate plasmon resonances of the substrates. The proposed optimization technique was further verified by cathodoluminescence measurements. Cathodoluminescence hotspot maps revealed the nature of the hotspots of the substrates optimized for 514 nm and 785 nm. Enhanced sensitivity and tunability of the substrates in the red spectral region present their plausible future application in biological domains
Preceding winter La Nina reduces Indian summer monsoon rainfall
No full textLeaving out the strong El Nino Southern Oscillation (ENSO) years, our understanding in the interannual variation of the Indian summer monsoon rainfall (ISMR) stands poor for the rest. This study quantifies the role of ENSO in the preceding winter on ISMR with a particular emphasis on ENSO-neutral summer and La Nina winter. Results show that, unlike the simultaneous ENSO-ISMR relationship, La Nina of previous winter reduces mean rainfall over the country by about 4% even during ENSO neutral summer. Moreover, when ENSO changes phase from La Nina in winter to El Nino in summer, ISMR is anomalously lower than during persisting El Nino years (-14.5% and -5.3%, respectively), increasing the probability of severe drought. This suppression effect of La Nina of the preceding winter on summer monsoon precipitation over India is mostly experienced in its western and southern parts. Principal component analysis of the zonal propagation of surface pressure anomalies from winter to summer along Northern Hemisphere subtropics decomposes interannual variations of seasonally persisting anomalies from zonal propagations. The dominant modes are associated with the seasonal transition of the ENSO phase, and are well correlated with date of onset and seasonal mean rainfall of monsoon over India. These results improve our understanding of the interannual variations of ISMR and could be used for diagnostics of general circulation models
Novel Vector Packing Heuristic for VM Placement based on the Divide-and-Conquer Paradigm
No full textVM Placement algorithms play a crucial role in determining data center utilisation and power consumption. The problem of VM Placement is to obtain an optimal packing of VMs on hosts such that the number of hosts required is minimum. The problem being NP-Hard, it becomes practically infeasible to get an optimal placement within the time constraints for making scheduling decisions. VM Placement can be modeled as a Multi-dimensional Vector Packing Problem(MDVPP). VPSolver, using arc-flow formulation with graph compression, gives an optimal solution for Bin-Packing and related problems. This paper proposes heuristics for large instances of MDVPP, based on the Divide-and-Conquer paradigm, using VPSolver. An extensive evaluation, with 3260 instances, comparing our heuristic with existing popular heuristics in 2D and 3D vector spaces is done which also includes VM Sizes obtained from utilisation traces of a private cloud. It is observed that for most large instances, our heuristic gives better solutions compared to existing methods sometimes at the cost of higher computation time taken. The proposed heuristic gives solutions where the number of bins required is reduced up to 7.34% and 8.15% for 2D and 3D vector spaces respectively
Studies on the biosorption of Pb(II) ions from aqueous solution using extracellular polymeric substances (EPS) of Pseudomonas aeruginosa
No full textThe extracellular polymeric substances (EPS) namely protein, polysaccharide, biosurfactant and deoxyribonucleic acid (DNA) in its purified forms isolated from Pseudomonas aeruginsa were independently investigated for their Pb(II) biosorption capacities and mechanisms. Two parameters namely concentration of EPS component and concentration of Pb(II) ions were optimized for maximum Pb(II) biosorption. The maximum amounts of Pb (II) uptake corresponded to 4.8 mg per mg of protein, 0.48 mg per mg of polysaccharide, 0.041 mg per mg of biosurfactant, 0.42 mg per mg of ssDNA (single-stranded DNA) and 0.30 mg per mg of dsDNA (double-stranded DNA). The biosorption isotherms of Pb(II) adhered to the Langmuir model, for the individual EPS components. The standard Gibbs free energy (Delta G degrees) values calculated using Langmuir constants showed that the biosorption of Pb(II) by the individual EPS component was spontaneous and attested to a chemisorption process. The FTIR studies revealed the functional groups responsible for Pb(II) binding and the EDAX studies confirmed the presence of lead on EPS after biosorption. The protein constituent showed the highest Pb(II) biosorption capacity among other components. The differences in the protein profile of P. aeruginosa in the presence and absence of Pb(II) ions using Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) could be attributed to the possible resistance mechanisms of P. aeruginosa cells
Testing Weyl gravity at galactic and extra-galactic scales
No full textWe examine the viability of Weyl conformal gravity as an alternative to the general theory of relativity. By using the extended rotation curve of the Milky Way and velocity dispersions of four globular clusters, we show that Weyl gravity predictions without resorting to dark matter comply with observations at the galactic scale. For the Milky Way, we demonstrate that the uncertainty in baryonic modeling results in a bracket of possible rotational velocities which well encompasses the diversity in rotation curve construction. Such diversity generally arises from differences in measurements of velocity anisotropy parameter, and the circular speed and Galactocentric distance of the Sun. Furthermore, we explore the ability of Weyl gravity to account for the inferred acceleration of Abell cluster 1689
Vibration isolation of buildings housed with sensitive equipment using open trenches - Case study and numerical simulations
No full textThe vibration isolation of buildings housed with sensitive equipment is always a challenging one due to the stringent vibration criteria imposed on them. The paper presents a case study on the vibration isolation scheme adopted for an important building of space research agency. The vibration levels in the building had to follow the vibration criterion which is in the form of a set of one - third octave band velocity spectra, expressed as vibration criterion curves. Various sources that can generate vibrations in the building were identified and assessed. The external sources and the internal sources of vibration were analyzed and the possible limits of vibrations were evaluated. The selection procedure of design frequency, which is the significant step in the design of vibration isolation trench under the passive isolation scheme, is explained. Numerical simulations were developed to evaluate the influence of trench parameters on the amplitude reduction of Rayleigh waves propagating across the trench. Based on the results from numerical simulations, the vibration isolation trench was designed to reduce the amplitudes of vibrations produced from external and internal sources
NON-LOCAL PATCH-BASED REGULARIZATION FOR IMAGE RESTORATION
No full textSeveral patch-based models have been proposed for image restoration in the literature. A common feature with these models is that patches are used for filtering or optimization, where the aggregation is often performed over a non-local (NL) neighborhood. We propose a NL patch-based regularizer, where patches are used (1) for computing weights between NL neighbors, and (2) for defining a TV-type norm in patch space. A general form of the latter construction was originally proposed by Peyre et al. and later studied by other authors. In most of these proposals, both the weights and the image are treated as variables, which makes the model non-convex. In particular, the corresponding numerical solvers cannot guarantee local optimality. On the other hand, our regularizer is convex. Along with an l(2) data fidelity term, we apply the regularizer for denoising, deblurring and super-resolution, and develop an efficient ADMM solver for computing the global minimum. An interesting finding is that, while our model is weaker than the non-convex counterparts, the minimizer of the former is generally closer to the ground truth than the reconstruction from the latter. Moreover, we demonstrate that our regularizer can outperform existing regularization techniques for deblurring and super-resolution
Search for heavy resonances decaying into a vector boson and a Higgs boson in final states with charged leptons, neutrinos and b quarks at root s=13 TeV
No full textA search for heavy resonances, decaying into the standard model vector bosons and the standard model Higgs boson, is presented. The final states considered contain a b quark-antiquark pair from the decay of the Higgs boson, along with electrons and muons and missing transverse momentum, due to undetected neutrinos, from the decay of the vector bosons. The mass spectra are used to search for a localized excess consistent with a resonant particle. The data sample corresponds to an integrated luminosity of 35.9 fb(-1) collected in 2016 by the CMS experiment at the CERN LHC from proton-proton collisions at a center-of-mass energy of 13 TeV. The data are found to be consistent with background expectations. Exclusion limits are set in the context of spin-0 two Higgs doublet models, some of which include the presence of dark matter. In the spin-1 heavy vector triplet framework, mass-degenerate W and Z resonances with dominant couplings to the standard model gauge bosons are excluded below a mass of 2.9 TeV at 95% confidence level
AdaDepth: Unsupervised Content Congruent Adaptation for Depth Estimation
No full textSupervised deep learning methods have shown promising results for the task of monocular depth estimation; but acquiring ground truth is costly, and prone to noise as well as inaccuracies. While synthetic datasets have been used to circumvent above problems, the resultant models do not generalize well to natural scenes due to the inherent domain shift. Recent adversarial approaches for domain adaption have performed well in mitigating the differences between the source and target domains. But these methods are mostly limited to a classification setup and do not scale well for fully-convolutional architectures. In this work, we propose AdaDepth -an unsupervised domain adaptation strategy for the pixel-wise regression task of monocular depth estimation. The proposed approach is devoid of above limitations through a) adversarial learning and b) explicit imposition of content consistency on the adapted target representation. Our unsupervised approach performs competitively with other established approaches on depth estimation tasks and achieves state-of-the-art results in a semisupervised setting
System Identification of a Small Scaled Helicopter using Simulated Annealing Algorithm
No full textDeveloping an autonomous helicopter requires designing of precise controllers, which can be a daunting task if system dynamics are not known accurately. Thus very accurate system dynamics should be available to design controllers. The main idea of this paper is to present Simulated Annealing (SA) algorithm as a tool in time domain parametric system identification of a RC helicopter (Align T-Rex 550L). In addition, Prediction Error Minimization (PEM) and Genetic Algorithm (GA) have been taken as reference identification algorithms for the purpose of comparison. The work includes collecting flight data and pre-processing of the recorded data, and time domain parametric identification of state space system for hovering condition. The rigid body dynamics of the helicopter is represented in the state space form that has 40 parameters. The accuracy of the identified system is verified by comparing estimated and actual responses, by Pearson Correlation Coefficient, also 90% confidence interval is calculated for each of the identified parameters. Results show a high level of correlation of the actual responses and estimated responses of the system identified using SA, because of its ability to jump out of local optima