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Secondary Breakup of Drops
No full textSecondary atomization of droplets generated from primary atomization is observed in high-speed flows. In natural scenarios, falling raindrops undergo aerodynamic breakup that modifies the resulting drop size distribution on the ground. In this article, we review some aspects of the drop breakup mechanisms, initial deformation, drag characteristics, and time scales of breakup. We also review some of the secondary atomization models, such as TAB and DDB, proposed in the literature. We discuss the role of new numerical algorithms for two-phase flow simulations in providing insights into the exact physical mechanisms involved during drop breakup
Hardy's inequality for the fractional powers of the Grushin operator
No full textWe prove Hardy's inequality for the fractional powers of the generalized subLaplacian and the fractional powers of the Grushin operator. We also find an integral representation and a ground state representation for the fractional powers of the generalized subLaplacian
Modification in the microstructural and electrochromic properties of spray-pyrolysed WO3 thin films upon Mo doping
No full textWO3 thin films were grown onto the glass and fluorine-doped tin oxide-coated glass substrates using chemical spray pyrolysis technique. X-ray diffraction analyses reveal that all the films possess orthorhombic phase of WO3. Morphologies of the films have been found to vary with Mo-doping concentrations. Three-dimensional atomic force micrographs reveal that the 5 at% Mo-doped film has the maximum image surface area and is optimal for improved electrochromic performance. Cyclic voltammetry studies show that the cathodic and anodic peak current densities have the highest values for the 5 at% Mo-doped WO3 film. Relative to the undoped film, the change from coloured to bleached state is faster for the 5 at% Mo-doped WO3 film. Considering the reversibility and the switching response from chronoamperometry and the coloration efficiency from cyclic voltammetry, it has been concluded that the 5 at% Mo-doped WO3 film has an optimal electrochromic response. GRAPHICS]
Mechanisms of Barrier Layer Formation and Erosion from In Situ Observations in the Bay of Bengal
No full textDuring the Bay of Bengal (BoB) Boundary Layer Experiment (BoBBLE) in the southern BoB, time series of microstructure measurements were obtained at 8 degrees N, 89 degrees E from 4 to 14 July 2016. These observations captured events of barrier layer (BL) erosion and reformation. Initially, a three-layer structure was observed: a fresh surface mixed layer (ML) of thickness 10-20 m; a BL below of 30-40-m thickness with similar temperature but higher salinity; and a high salinity core layer, associated with the Summer Monsoon Current. Each of these three layers was in relative motion to the others, leading to regions of high shear at the interfaces. However, the destabilizing influence of the shear regions was not enough to overcome the haline stratification, and the three-layer structure was preserved. A salinity budget using in situ observations suggested that during the BL erosion, differential advection brought high salinity surface waters (34.5 psu) with weak stratification to the time series location and replaced the three-layer structure with a deep ML (similar to 60 m). The resulting weakened stratification at the time series location then allowed atmospheric wind forcing to penetrate deeper. The turbulent kinetic energy dissipation rate and eddy diffusivity showed elevated values above 10(-7) W kg(-1) and 10(-4) m(2) s(-1), respectively, in the upper 60 m. Later, the surface salinity decreased again (33.8 psu) through differential horizontal advection, stratification became stronger and elevated mixing rates were confined to the upper 20 m, and the BL reformed. A 1D model experiment suggested that in the study region, differential advection of temperature-salinity characteristics is essential for the maintenance of BL and to the extent to which mixing penetrates the water column
Friction stir welding of ultra low carbon steel: microstructure, mechanical properties and electrochemical study
No full textIn the present investigation, the friction stir welding of ultra low carbon steel was carried out at different tool rotational speeds of 300 to 900 rpm in steps of 150 rpm for 30 mm/min traverse speed. The macro and microstructures were examined to identify the different areas of stir zone, thermomechanically affected zone and heat affected zone of the welded joints. Tensile strength of the welded joints was evaluated and maximum tensile strength of similar to 336 MPa was obtained at 450 rpm tool rotational speed. Microhardness was measured along the cross section of the welded joint. The maximum hardness was observed at stir zone when compared to thermomechanically affected zone and heat affected zone. The hardness values decreased with the increase in tool rotational speeds in the stir zone. Electrochemical study was investigated in 0.1 mol/L HCl solution using various electrochemical measurements such as open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization. The corrosion rate at stir zone decreased with the increase in tool rotational speed
The effect of strain on effective Duffing nonlinearity in the CVD-MoS2 resonator
No full textWe demonstrate all electrical measurements on NEMS devices fabricated using CVD grown monolayer MoS2. The as-grown monolayer film of MoS2 on top of the SiO2/Si wafer is processed to fabricate arrays and individual NEMS devices without the complex pick and transfer techniques associated with graphene. The electromechanical properties of the devices are on par with those fabricated using the exfoliation method. The frequency response of these devices is then used as a probe to estimate the linear thermal expansion coefficient of the material and evaluate the effect of strain on the effective Duffing nonlinearity in the devices
Consensus optimization for distributed registration
No full textWe consider the problem of jointly registering multiple point sets using rigid transforms. We propose a distributed algorithm based on consensus optimization for the least-squares formulation of this problem. In each iteration, the computation is distributed among the point sets and the results are averaged. For each point set, the dominant cost per iteration is the SVD of a square matrix of size d, where d is the ambient dimension. Existing methods for joint registration are either centralized or perform the optimization sequentially. The proposed algorithm is naturally more scalable than these methods. As an application, we integrate the proposed algorithm within a divide-and-conquer approach for sensor network localization. In particular, we are able to localize very large networks, which are beyond the scope of most existing localization methods. © 2018 IEEE
Leakage Current Patterns Observed in Polymeric Insulators Rotating Subjected to Wheel and Dip Test
No full textPresent paper discusses the behavior of leakage becomes unfit to electrical applications 2. current flowing through silicone rubber based polymeric insulators. These insulators are investigated experimentally using rotating wheel and dip test arrangement which is designed as per IEC/TR 62730. The test specimen used in the present study has creepage length of 725 mm and four of such specimens are employed on rotating wheel. These specimens rotate through contaminants and touches high voltages in a specific cycle that runs for 1000 hours. During the experimentation, leakage current is captured and recorded. This leakage current represents an interesting behavior which is reported in the present work. Further, to analyze the leakage current pattern, Fourier transform is employed to observe the changes in the specific frequency components. It is reported that the variation of power frequency component is exponentially decaying whereas the variation of third harmonics follows a double exponential pattern. The MATLAB curve fitting tool is used to determine the parameters that confines the changes. © 2018 IEEE
On Random Distortion Testing Based Sequential Non-Parametric Hypothesis Testing
No full textIn this work, we propose a new method for sequential binary hypothesis testing. The approach is non-parametric in the sense that it does not assume any knowledge of signal distributions under each hypothesis. The proposed framework is based on Random distortion testing (RDT) which addresses the problem of testing whether or not a random signal, deviates by more than a specified tolerance, τ, from a fixed value, ξ-0. We first state the problem setup and then discuss earlier approaches to solve the problem. We then propose a new sequential algorithm, T-SeqRDT, which is shown to control the probabilities of error while reducing the number of samples required to make a decision compared to the fixed-sample-size version of RDT. Finally, via simulations we compare T-SeqRDT to other algorithms and show its robustness compared to standard likelihood ratio based approaches. © 2018 IEEE
Disparate effects of PEG or albumin based surface modification on the uptake of nano- and micro-particles
No full textSurface modification of particulate systems is a commonly employed strategy to alter their interaction with proteins and cells. Past studies on nano-particles have shown that surface functionalization with polyethylene glycol (PEG) or proteins such as albumin increases circulation times by reducing their phagocytic uptake. However, studies on surface functionalized micro-particles have reported contradictory results. Here, we investigate the effects of surface functionalization using polystyrene particles with 4 different diameters ranging from 30 nm to 2.6 μm and coating them with either albumin or PEG. Our results show that with increasing particle size, surface functionalization has less to no effect on altering phagocytic uptake. The data also suggest that these differences are observed with a dense arrangement of molecules on the surface (dense brush conformation for PEG conjugation), appear to be independent of the serum proteins adsorbing on particle surfaces, and are independent of the endocytic uptake pathway. These results provide insight into the differences in the ability of surface modified nano- and micro-particles to avoid phagocytic uptake