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A Twelve Concentric Multilevel Twenty-Four Sided Polygonal Voltage Space Vector Structure for Variable Speed Drives
No full textGenerating dense multilevel voltage space structure using polygons of higher sides is one of the novel and elegant method to suppress low-order harmonics and to obtain refined sinusoidal voltages using voltage source inverters for variable frequency drive application without passive filters. Apart from the advantages of conventional multilevel inverter topologies, schemes generating polygonal voltage space vector structure can equip full dc-bus utilization, low switching frequency strategies to eliminate low-order harmonics, and increased linear modulation range. In this paper, an induction motor drive scheme generating a highly dense multilevel 24-sided polygonal voltage space vector structure using a single dc source, which can eliminate harmonics till 23rd order from phase voltages, is presented. Cascaded power circuit topology with a flying capacitor inverter fed with a dc source and two low voltage floating capacitor fed H-bridge inverters is used. Detailed experimentally validated results, under scalar as well as indirect rotor field oriented control of induction motor are provided. Studies on voltage ripple and reactive energy in various floating capacitors, harmonic performance of output voltage for wide range of speed operation, are also included
BENCHOP - SLV: the BENCHmarking project in Option Pricing - Stochastic and Local Volatility problems
No full textIn the recent project BENCHOP - the BENCHmarking project in Option Pricing we found that Stochastic and Local Volatility problems were particularly challenging. Here we continue the effort by introducing a set of benchmark problems for this type of problems. Eight different methods targeted for the Stochastic Differential Equation (SDE) formulation and the Partial Differential Equation (PDE) formulation of the problem, as well as Fourier methods making use of the characteristic function, were implemented to solve these problems. Comparisons are made with respect to time to reach a certain error level in the computed solution for the different methods. The implemented Fourier method was superior to all others for the two problems where it was implemented. Generally, methods targeting the PDE formulation of the problem outperformed the methods for the SDE formulation. Among the methods for the PDE formulation the ADI method stood out as the best performing one
Temperature dependent growth of Cu2SnS3 thin films using ultrasonic spray pyrolysis for solar cell absorber layer and photocatalytic application
No full textTernary chalcogenide Cu2SnS3 (CTS) thin films are deposited on glass substrates using low cost ultrasonic spray pyrolysis (USP) technique by varying substrate temperatures 300 degrees C to 550 degrees C. Crystal structure of CTS thin film is found to change its phase from amorphous to tetragonal phase with increase in substrate temperature. Properties of as-deposited Cu2SnS3 thin films are studied using various characterization techniques. X-ray powder diffraction (XRD) studies confirm the formation of Cu2SnS3 tetragonal phase with orientation along (112) plane with increase in substrate temperature. Raman analysis revealed the formation of binary phase at 550 degrees C substrate temperature. Increase in substrate temperature resulted in stoichiometric nature of Cu2SnS3 films at 500 degrees C. The absorption coefficient of CTS films is found to be similar to 10(5) cm(-1) with band gap ranging from 1.35 eV to 1.48 eV. Electrical properties of CTS films exhibited p type conductivity with carrier concentration of the order of 10 21 cm(-3). The resistivity of the CTS films is found to vary from 1.5 x 10(-3) to 3.2 x 10(-3) Omega-cm. Photocatalytic effect of optimized Cu2SnS3 thin film under visible light (300 W) is examined with methylene blue (MB) dye and similar to 90% MB is degraded under 3 hours visible light irradiation. The above properties indicate that Cu2SnS3 is a potential candidate to be used for solar cell absorber layer and photocatalytic activity
Structure and Gating Dynamics of Na+/CI- Coupled Neurotransmitter Transporters
No full textNeurotransmitters released at the neural synapse through vesicle exocytosis are spatiotemporally controlled by the action of neurotransmitter transporters. Integral membrane proteins of the solute carrier 6 (SLC6) family are involved in the sodium and chloride coupled uptake of biogenic amine neurotransmitters including dopamine, serotonin, noradrenaline and inhibitory neurotransmitters including glycine and gamma-amino butyric acid. This ion-coupled symport works through a well-orchestrated gating of substrate through alternating-access, which is mediated through movements of helices that resemble a rocking-bundle. A large array of commercially prescribed drugs and psychostimulants selectively target neurotransmitter transporters thereby modulating their levels in the synaptic space. Drug-induced changes in the synaptic neurotransmitter levels can be used to treat depression or neuropathic pain whereas in some instances prolonged usage can lead to habituation. Earlier structural studies of bacterial neurotransmitter transporter homolog LeuT and recent structure elucidation of the Drosophila dopamine transporter (dDAT) and human serotonin transporter (hSERT) have yielded a wealth of information in understanding the transport and inhibition mechanism of neurotransmitter transporters. Computational studies based on the structures of dDAT and hSERT have shed light on the dynamics of varied components of these molecular gates in affecting the uphill transport of neurotransmitters. This review seeks to address structural dynamics of neurotransmitter transporters at the extracellular and intracellular gates and the effect of inhibitors on the ligand-binding pocket. We also delve into the effect of additional factors including lipids and cytosolic domains that influence the translocation of neurotransmitters across the membrane
On the influence of geometrical parameters on the spray characteristics of high shear injectors
No full textWe discuss the influence of geometrical parameters over the performance of high shear injector. High shear injector usually consists of a series of air swirlers (primary and secondary) with diverging flare at the exit and centrally mounted fuel nozzle. In this study, we have considered only parameters pertaining to air swirler i.e. geometrical swirl number (SNgea), flow split ratio (gamma), area ratio (Delta), flare angle (theta) and flow orientation of primary and secondary swirlers (co/counter rotation). The above parameters were categorized into two paradigms, first, SNgea, gamma, Delta are designated as internal geometrical parameters, which induces variations in the bulk Reynolds number at the exit. On the other hand, parameters like flare angle (theta), flow orientation doesn't yield any variations in bulk Reynolds number. Time resolved PIV (Particle Image Velocimetry; similar to 3500 frames/s) is employed to extract the topological structures of the flow field. The length scale (W/D-f), which embodies the radial extent of the recirculation zone is governed by near field swirl number (SN i o) and Reynolds number for cases with variations in SNgea, gamma, Delta. Contrarily, with variations in theta and flow orientation, (W/D-f) is found to be a function of near field swirl number f (SN10) only. The spatial distribution of the spray shows linear relationship with the W/D-f. Finally, the droplet size spectrum obtained from 3D PDI (Phase Doppler interferometer) also shows insensitivity with respect to the different test cases. This clearly indicates that in high shear atomizer configuration, spread of the spray can be altered without deterioration in uniformity and droplet size distribution
Influence of Cr on structural, spectroscopic and magnetic'' properties CoFe2O4 grown by the wet Chemical method
No full textThe Cr doped CoFe2O4 nano crystalline ceramics are synthesized using wet chemical method. The structural, morphological, functional, spectroscopic and magnetic properties of pure CoFe2O4 and Cr doped CoFe2O4 are characterized by XRD, FESEM, FTIR, Raman, Mossbauer spectroscopy and M-H hysteresis loop. The X-ray diffraction (XRD) patterns of undoped (x = 0) and doped (x not equal 0) samples reveal the formation of single phase cubic spinel structure. The lattice parameters and cation distribution between tetrahedral (A) and octahedral (B) sites of the samples (AB(2)O(4)) were obtained by Rietveld refinement of XRD patterns. The FESEM micrographs exhibit dense micro structure with small voids. The energy dispersive x-ray studies confirm the presence of Cr in CoFe2O4. The FTIR spectrum confirms that the peaks corresponding to the metal-oxygen bonds have shiftedtowards higher wavelength region. Raman spectrum exhibits broad peaks which confirm the existence of local disorder due to the inter-site cation migration between tetrahedral and octahedral sites. The Mossbauer spectroscopy reveals that the magnitude of magnetic hyperfine field of tetrahedral site (H-A) and octahedral site (H-B) decreases with increase in Cr doping in CoFe2O4 and that the decrease is more rapid in tetrahedral site (H-A) compared to that in octahedral site (H-B). And also confirm that the magnetic hyperfine fields (B-hf) are smaller relative to pure cobalt ferrite representing that super exchange interaction which is decreases as the Cr concentration increases. The magnetization studies reveal a decrease in the saturation magnetization (M-s) of CoFe2O4 with increase in Cr substitution. A similar and non-monotonic variation of coercivity (H-c) and magneto crystalline anisotropy (K) suggests that H-c is mainly determined by K
Sequential Random Distortion Testing of Non-Stationary Processes
No full textIn this work, we propose a non-parametric sequential hypothesis test based on random distortion testing (RDT). RDT addresses the problem of testing whether or not a random signal, Xi, observed in independent and identically distributed (i.i.d) additive noise deviates by more than a specified tolerance, tau, from a fixed model, xi(0). The test is non-parametric in the sense that the underlying signal distributions under each hypothesis are assumed to be unknown. The need to control the probabilities of false alarm (PFA) and missed detection (PMD), while reducing the number of samples required to make a decision, leads to a novel sequential algorithm, SeqRDT. We show that under mild assumptions on the signal, SeqRDT follows the properties desired by a sequential test. We introduce the concept of a buffer and derive bounds on PFA and PMD, from which we choose the buffer size. Simulations show that SeqRDT leads to faster decision-making on an average compared to its fixed-sample-size (FSS) counterpart, BlockRDT. These simulations also show that the proposed algorithm is robust to model mismatches compared to the sequential probability ratio test (SPRT)
Retention of strong intramolecular hydrogen bonds in high polarity solvents in binaphthalene-benzamide derivatives: extensive NMR studies
No full textAdvanced multidimensional NMR techniques have been employed to investigate the intramolecular hydrogen bonds (HBs) in a series of N,N `-(1,1 `-binaphthalene]-2,2 `-diyl)bis(benzamide) derivatives, with the site-specific substitution of different functional groups. The existence of intramolecular HBs and the elimination of any molecular aggregation and possible intermolecular HBs are ascertained by various experimental NMR techniques, including solvent polarity dependent modifications of HB strengths. In the fluorine substituted derivative, direct evidence for the engagement of organic fluorine in HB is obtained by the detection of heteronuclear through-space correlation and the coupling between two NMR active nuclei where the transmission of spin polarization is mediated through HBs ((1h)J(FH)). The extent of reduction in the strength of (1h)J(FH) on dilution with high polarity solvents directly provided the qualitative measure of HB strength. The HB, although becoming weakened, does not get nullified even in pure high polarity solvent, which is attributed to the structural constraints. The rate of exchange of a labile hydrogen atom with the deuterium of the solvent permitted the measurement of their half-lives, that are correlated to the relative strengths of HBs. The experimental NMR findings are further validated by XRD and DFT-based theoretical computations, such as, NCI and QTAIM
On Approximate Birkhoff-James Orthogonality and Normal Cones in a Normed Space
No full textWe study two notions of approximate Birkhoff-James orthogonality in a normed space, from a geometric point of view, and characterize them in terms of normal cones. We further explore the interconnection between normal cones and approximate Birkhoff-James orthogonality to obtain a complete characterization of normal cones in a two-dimensional smooth Banach space. We also obtain a uniqueness theorem for approximate Birkhoff-James orthogonality set in a normed space
Electrochemical insights into layered La2CuO4 perovskite: Active ionic copper for selective CO2 electroreduction at low overpotential
No full textLa2CuO4, a layered perovskites oxide was synthesized using solution combustion method at different calcination temperatures. XRD characterization and Rietveld refinement analysis confirms the pure phase of the synthesized material. The effect of calcination causes shrinking in the lattice parameters affirm the change in the oxygen stoichiometry. Four Probe (Van der Pauw's) and CP-AFM analysis were carried out to understand the influences of calcination temperature on electrical conductivity. Electrochemical investigations on La2CuO4 were performed at various negative potential ranges using cyclic voltammetry (CV) to identify the redox active centre. Thermodynamic calculations are further carried out to validate the electrochemical results in different mediums. Selective electrocatalytic conversion of CO2 to C-2-hydrocarbon (C2H4) with FE% of 40.3% which is 10 times higher than CH4 (FE% = 4.1%) emphasized the in-situ formation of Cu2O from the redox active centre present in La2CuO4. Hydrocarbons are generated at a very low overvoltage (-0.4 V RHE) in comparison to literature. XPS analysis indeed confirms the presence of Cu+ species i.e., in-situ generated Cu2O, on La2CuO4 after CV and CO2 electrocatalysis