Cut-and-connect of two antiparallel vortex tubes

Motivated by an early conjecture that vortex cut-and-connect plays a key role in mixing and production of turbulence, helicity and aerodynamic noise, the cross-linking of two antiparallel viscous vortex tubes via direct numerical simulation is studied. The Navier-Stokes equations are solved by a dealiased pseudo-spectral method with 64 cubed grid points in a periodic domain for initial Reynolds numbers Re up to 1000. The vortex tubes are given an initial sinusoidal perturbation to induce a collision and keep the two tubes pressed against each other as annihilation continues. Cross-sectional and wire plots of various properties depict three stages of evolution: (1) Inviscid induction causing vortex cores to first approach and form a contact zone with a dipole cross-section, and then to flatten and stretch; (2) Vorticity annihilation in the contact zone accompanied by bridging between the two vortices at both ends of the contact zone due to a collection of cross-linked vortex lines, now orthogonal to the initial vortex tubes. The direction of dipole advection in the contact zone reverses; and (3) Threading of the remnants of the original vortices in between the bridges as they pull apart. The crucial stage 2 is shown to be a simple consequence of vorticity annihilation in the contact zone, link-up of the un-annihilated parts of vortex lines, and stretching and advection by the vortex tube swirl of the cross-linked lines, which accumulate at stagnation points in front of the annihilating vortex dipole. It is claimed that bridging is the essence of any vorticity cross-linking and that annihilation is sustained by stretching of the dipole by the bridges. Vortex reconnection details are found to be insensitive to asymmetry. Modeling of the reconnection process is briefly examined. The 3D spatial details of scalar transport (at unity Schmidt number), enstrophy production, dissipation and helicity are also examined

An approach to Measure Transition Density of Binary Sequences for X-filling based Test Pattern Generator in Scan based Design

Switching activity and Transition density computation is an essential stage for dynamic power estimation and testing time reduction. The study of switching activity, transition densities and weighted switching activities of pseudo random binary sequences generated by Linear Feedback shift registers and Feed Forward shift registers plays a crucial role in design approaches of Built-In Self Test, cryptosystems, secure scan designs and other applications. This paper proposed an approach to find transition densities, which plays an important role in choosing of test pattern generator We have analyze conventional and proposed designs using our approache, This work also describes the testing time of benchmark circuits. The outcome of this paper is presented in the form of algorithm, theorems with proofs and analyses table which strongly support the same. The proposed algorithm reduces switching activity and testing time up to 51.56% and 84.61% respectively

Re-Scaling of Energy in the Stringy Charged Black Hole Solutions using Approximate Symmetries

This paper is devoted to study the energy problem in general relativity using approximate Lie symmetry methods for differential equations. We evaluate second-order approximate symmetries of the geodesic equations for the stringy charged black hole solutions. It is concluded that energy must be re-scaled by some factor in the second-order approximation.Comment: 18 pages, accepted for publication in Canadian J. Physic

Unconventional domain wall magnetoresistance of patterned Ni/Nb bilayer structures below superconducting transition temperature of Nb

Scattering of spin-up and spin-down electrons while passing through a ferromagnetic domain wall leads to an additional resistance for transport current, usually observed prominently in constricted magnetic structures. In this report, we use the resistance of the domain wall as a probe to find indirect signatures of the theoretically predicted spin-singlet supercurrent to spin-triplet supercurrent conversion effect of ferromagnetic domain walls. Here we examine the domain wall induced resistance in Ni stripe in a bilayer Ni/Nb geometry in the normal state and in the superconducting state of Nb. By making a 6um wide gap in the top Nb layer we routed the transport current through the Ni layer in the normal state and in the superconducting state of Nb. In the normal state of Nb, in-field transport measurements showed a clear domain wall magneto-resistance (DWMR) peak near the coercive field, where the domain wall density is expected to be maximum. Interestingly, however, below the superconducting transition temperature of Nb, the DWMR peak of the Ni layer showed a sharp drop in the field range where the number of domain walls becomes maximum. This observation may be a possible signature of magnetic domain wall induced spin-triplet correlations in the Ni layer due to the direct injection of spin-singlet Cooper pairs from Nb into the magnetic domain walls

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Perception and Opinion of Customers towards Automated Teller Machine Services with Special Reference to Kurdistan Region

Modern technology has changed human life by making it faster and easier. Technology innovation emerged as source of competitive strength and can achieve success through new innovation. ATM plays vital role in banking industry by providing all necessary banking facilities in easy and handy way to their customers at their doorstep. As Kurdistan is growing economy, therefore to assess perception and expectation of ATM customers, 315 respondents from different places of Kurdistan region were taken into consideration. This study is based on personal approach and observation. Structured questionnaire administered after taking opinion and modification by banking personal, customer discussion and review of literatures. For the convenience of respondents Likert measurement scales was used. To identify most service quality dimensions in connection with overall customer satisfaction; reliability test, descriptive analysis, correlation and coefficient and regression analysis test and ANOVA tests are done through SPSS 25.0. At the end it is concluded that most of factors are positively, significantly correlated with overall customer satisfaction. Based on personal discussion with customers and bank officials’ and literature reviews, recommendations are mentioned at the end

Numerical modelling of the impacts of sea level rise on seawater intrusion in unconfined coastal aquifers

Copyright © 2014 the University of Exeter.This study presents the application of a density-dependent finite element model to simulate the transient effects of sea level rise (SLR) on seawater intrusion (SWI) in a conceptual case of unconfined aquifer. The model considers both the unsaturated and saturated flow conditions. To model the natural process of SLR, a time-dependent boundary condition is used to define the hydrostatic head imposed by seawater at the coastal boundary where the effect of the gradual rise in the sea level with time is considered. The specified values of SLR are chosen, in the range of that predicted by IPCC (Intergovernmental Panel on Climate Change), for five different periods of time in the current century (from 2014 to 2100). The results indicate that a considerable advance in SWI can be expected in the coastal aquifers until the end of century. The rising of sea level is followed by the lifting of the groundwater table, especially near the shoreline, which gradually declines towards the inland boundary. The effects of spatial variations of the shoreline slope on SWI under SLR condition are also investigated. The results highlight that the flatter slopes of the shoreline intensify the landward process of seawater intrusion

The Coronal Structure of AB Doradus

We perform a numerical simulation of the corona of the young, rapidly rotating K0 dwarf AB Doradus using a global MHD model. The model is driven by a surface map of the radial magnetic field constructed using Zeeman-Doppler Imaging. We find that the global structure of the stellar corona is dominated by strong azimuthal tangling of the magnetic field due to the rapid rotation. The MHD solution enables us to calculate realistic Alfv\'en surfaces and we can therefore estimate the stellar mass loss rate and angular momentum loss rate without making undue theoretical simplifications. We consider three cases, parametrized by the base density of the corona, that span the range of possible solutions for the system. We find that overall, the mass and angular-momentum loss rates are higher than in the solar case; the mass loss rates are 10 to 500 times higher, and the angular momentum loss rate can be up to $3\times{10}^4$ higher than present day solar values. Our simulations show that this model can be use to constrain the wide parameter space of stellar systems. It also shows that an MHD approach can provide more information about the physical system over the commonly used potential field extrapolation.Comment: 13 pages, 7 figure