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Influence of Nonaxisymmetric Confinement on the Hydrodynamic Stability of Multinozzle Swirl Flows
No full textInteraction between coherent flow oscillations and the premixed flame sheet in combustors can result in coherent unsteadiness in the global heat release response. These coherent flow oscillations can either be self-excited (e.g., 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 nonaxisymmetric nature of the confinement imposed by the combustor liner on swirl nozzle flows remains as yet unexplored. We study the influence of internozzle spacing and nonaxisymmetric confinement on the local temporal and spatiotemporal stability characteristics of multinozzle flows in this paper. The base flow model for the multinozzle 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 nonaxisymmetric 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 (ISL) stabilized flame results in an overall stabilization of the flow instability. We also discuss qualitatively, the underlying vorticity dynamics mechanisms that influence the characteristics of instability modes in triple nozzle flows
Thermoelectric properties of Pb and Na dual doped BiCuSeO
No full textBiCuSeO is a promising thermoelectric material not only because of its good thermoelectric properties, but also earth abundant constituents. In this report, Pb and Na have been simultaneously doped at the Bi site of BiCuSeO. Doping Pb is beneficial for the Seebeck coefficient whereas doping Na maintains the hole mobility. Both the dopants increase the carrier concentration and reduce the thermal conductivity by point-defect scattering. The samples with nominal composition Bi0.985-xNa0.015PbxCuSeO ( x=0.00, 0.04, 0.06 and 0.08) were prepared using two-step solid-state synthesis. The X-ray diffraction pattern reveals a small amount of Bi2O2.5 phase (<1 vol. %) which is responsible for adversely affecting the electrical conductivity of all the samples. Both the Seebeck coefficient and electrical resistivity decrease with increasing doping fraction due to increasing hole concentration. The highest power factor of 530 mu W/mK(2) was obtained for Bi0.905Na0.015Pb0.08CuSeO sample at 773 K because of moderate Seebeck coefficient and low electrical resistivity. A low lattice thermal conductivity of 0.37 W/m-K at 773 K was obtained in the Bi0.905Na0.015Pb0.08CuSeO. Due to this low lattice thermal conductivity combined with the high power factor, a zT of 0.63 was obtained for the Bi0.905Na0.015Pb0.08CuSeO sample at 773 K. (C) 2019 Author(s)
Machine vision benefits from human contextual expectations
No full textScene context is known to facilitate object recognition in both machines and humans, suggesting that the underlying representations may be similar. Alternatively, they may be qualitatively different since the training experience of machines and humans are strikingly different. Machines are typically trained on images containing objects and their context, whereas humans frequently experience scenes without objects (such as highways without cars). If these context representations are indeed different, machine vision algorithms will be improved on augmenting them with human context representations, provided these expectations can be measured and are systematic. Here, we developed a paradigm to measure human contextual expectations. We asked human subjects to indicate the scale, location and likelihood at which cars or people might occur in scenes without these objects. This yielded highly systematic expectations that we could then accurately predict using scene features. This allowed us to predict human expectations on novel scenes without requiring explicit measurements. Next we augmented decisions made by deep neural networks with these predicted human expectations and obtained substantial gains in accuracy for detecting cars and people (1-3%) as well as on detecting associated objects (3-20%). In contrast, augmenting deep network decisions with other conventional computer vision features yielded far smaller gains. Taken together, our results show that augmenting deep neural networks with human-derived contextual expectations improves their performance, suggesting that contextual representations are qualitatively different in humans and deep neural networks
New Bifunctional Metal-Organic Frameworks and Their Utilization in One-Pot Tandem Catalytic Reactions
No full textTwo new metal-organic framework (MOF) compounds were synthesized by a room temperature slow diffusion reaction. The compounds, Cd-3(C8H3SO7)(2)-(C10H8N4)(3)( C3H7NO)(2)] ( C3H7NO)(2)center dot(CH3OH)(4), I, and Cd-3(C8H3SO7)(2 )(C12H10N4)(3 )(C3H7NO)(2)] (C12H10N4)center dot(C3H7NO)(2), II, have comparable structures formed by Cd-sulfoisopthalate layers cross-linked by bipyridyl linkers forming three-dimensional structures. The compounds have both Lewis acidic (Cd metal centers) as well as basic (azine, free pyridine, and uncoordinated sulfo oxygens) sites, and they exhibited good catalytic activity for one-pot tandem deacetalization-Knoevenagel condensation reactions. The compounds exhibit catalytic activity both in the presence of a solvent as well as in solvent-free conditions. Compound I also exhibits good proton conductivity at room temperature
Hybrid scheme for factorisation: Factoring 551 using a 3-qubit NMR quantum adiabatic processor
No full textQuantum processors are potentially superior to their classical counterparts for many computational tasks including factorisation. Circuit methods as well as adiabatic methods have already been proposed and implemented for finding the factors of a given composite number. The main challenge in scaling it to larger numbers is the unavailability of large number of qubits. Here, we propose a hybrid scheme that involves both classical and quantum computation, based on the previous work of Peng et al, Phys. Rev. Lett. 101(22), 220405 (2008), which reduces the number of qubits required for factorisation. The classical part involves setting up and partially simplifying a set of bit-wise factoring equations and the quantum part involves solving these coupled equations using a quantum adiabatic process. We demonstrate the hybrid scheme by factoring 551 using a 3-qubit NMR quantum register
Revealing the role of microstructure architecture on strength and ductility of Ni microwires by in-situ synchrotron X-ray diffraction
No full textDeformation mechanisms of cold drawn and electropolished nickel microwires are studied by performing in-situ monotonous and cyclic tensile tests under synchrotron radiation. X-ray diffraction tests allow probing elastic strains in the different grain families and establishing a link with the deformation mechanisms taking place within the microwires. The measurements were carried out on several microwires with diameters ranging from as-drawn 100 mu m down to 40 mu m thinned down by electropolishing. The as-drawn wires exhibit a core-shell microstructure with <111> fiber texture dominant in core and heterogeneous dual fiber texture <111> and <100> in the shell. Reduction of specimen size by electropolishing results in a higher yield stress and tensile strength along with reduced ductility. In-situ XRD analysis revealed that these differences are linked to the global variation in microstructure induced by shell removal with electropolishing, which in turn affects the load sharing abilities of grain families. This study thus proposes a new way to increase ductility and retain strength in nickel microwires across different diameters by tuning the microstructure architecture
Efficient Computation of Entropy and Other Thermodynamic Properties for Two-Dimensional Systems Using Two-Phase Thermodynamic Model
No full textWe present a method based on the two-phase thermodynamic model (2PT) to calculate the entropy and free energy of various molecular systems in two dimensions (2D) using molecular dynamics (MD) simulations. The 2PT method has been used widely to calculate absolute entropy in a variety of molecular systems in three dimensions. When applying the idea to 2D systems, we found that the fluidicity that determines the decomposition of the vibrational density of states (DoS) into a solidlike and a gaslike component needs to be revised. The solid part is treated using quantum statistics, and the gas part is treated as a hard-disk fluid. We validate this method by computing thermodynamic properties of a two-dimensional Lennard-Jones fluid over a range of densities and temperatures and find excellent agreement with these quantities computed from the equation of state. More importantly, this method allows for the calculation of the entropy and free energy of 2D systems efficiently from a single MD trajectory of less than 50 ps; therefore, it can be a new, powerful way of assessing the thermodynamic properties in 2D problems
Reduction of imines catalysed by NHC substituted group 6 metal carbonyls
No full textThe catalytic activity of a series of metal carbonyls M(CO)(6)], and the corresponding NHC substituted M(CO)(5)(NHC)], (M = Cr, Mo, W) complexes was examined in the reduction of N-benzylideneaniline and acetophenone using silyl hydrides and isopropanol/KOH as reductants. The use of various additives and ultraviolet irradiation to promote the reduction of imines using silyl hydrides as reductants was explored. From a comparison of the reactivity of Mo(CO)(6)], Mo(CO)(5)(NHC)] and Mo(CO)(4)(bis NHC)] it was inferred that electron density on the metal centre plays a key role in the catalysis. Four of the best catalysts were then tested in the reduction of a variety of imines with different electronic and steric properties
Anticancer mechanism of troxerutin via targeting Nrf2 and NF-kappa B signalling pathways in hepatocarcinoma cell line
No full textTroxerutin (TX), a bioflavonoid widely present in various fruits and vegetables, has shown to exhibit numerous pharmacological properties including anti-neoplastic and anti-cancer activities. Nrf2 and NF-kappa B are the key transcription factors that regulate oxidative stress and inflammation, therefore we assessed whether TX modulate these pathways and its downstream proteins in HuH-7 hepatocarcinoma cells. TX induced apoptotic cellular and nuclear changes were examined by fluorescence staining techniques, agarose gel electrophoresis and flow cytometry. Oxidative stress was determined through biochemical analysis of antioxidant enzymes and lipid peroxidation profile. The protein expressions of NF-kappa B and Nrf2 pathway regulators, cell proliferation markers and apoptotic pathway mediators were evaluated by performing immunoblotting, immunocytochemistry and molecular docking. Our results revealed that TX inhibits the growth of HuH-7 cells in a concentration and time dependent manner. TX treated HuH-7 cells exhibited increased heme oxygenase (HO)-1 protein expression, augmented nuclear translocation of Nrf2, and reduced oxidative stress. Furthermore, TX suppressed the expression of IKK beta which subsequently inhibited the nuclear translocation of NF-kappa B (p65 subunit), and thus downregulated NF-kappa B mediated inflammatory responses, proliferation and cell survival. Collectively, our results indicate that TX exerts anti-cancer effect in HuH-7 hepatocarcinoma cells possibly through simultaneous regulation of the molecular signalling pathways, Nrf2 and NF-kappa B
Hydrogenation of CO2, carbonyl and imine substrates catalyzed by IrH3((PNP)-P-Ph-P-H)] complex
No full textA series of iridium and rhodium complexes M(COD)((PNP)-P-Ph-P-H)]Cl {M = Ir (1), Rh (2)}, MH2Cl((PNP)-P-Ph-P-H)] {M = Ir (3), Rh (4)} and IrH3((PNP)-P-Ph-P-H)] (6) supported by pincer ligand HeN(CH2CH2PPh2)(2) {(PNP)-P-Ph-P-H} have been synthesized and characterized. All complexes were isolated in good yields. The iridium trihydride complex IrH3((PNP)-P-Ph-P-H)] (6) was found to be an active catalyst for the hydrogenation of CO2 in 1 M aqueous KOH solution. It also acts as a catalyst for the base-free hydrogenation of carbonyl and imine substrates in MeOH. Under similar hydrogenation conditions, 2-cyclohexen-1-one undergoes solvent assisted tandem Michael addition-reduction mediated by bifunctional Lewis-acid-catalyst IrH3((PNP)-P-Ph-P-H)] in ROH (R = Me, Et) at room temperature. The complexes 1, 3, 4, and 6 were characterized by X-ray crystallography. Extensive hydrogen bonding interactions N-H center dot center dot center dot H-Ir (2.15 angstrom), N-H center dot center dot center dot center dot Cl (2.370 angstrom) were noted in the crystal structures of these complexes. (C) 2018 Elsevier B.V. All rights reserved