Branch-and-bound solves random binary IPs in poly(n)-time

Mathematical Programming - Branch-and-bound is the workhorse of all state-of-the-art mixed integer linear programming (MILP) solvers. These implementations of branch-and-bound typically use...     

Acoustic source localization

In this article different techniques for localizing acoustic sources are described and the advantages/disadvantages of these techniques are discussed. Some source localization techniques are restricted to isotropic structures while other methods can be applied to anisotropic structures as well. Some techniques require precise knowledge of the direction dependent velocity profiles in the anisotropic body while other techniques do not require that knowledge. Some methods require accurate values of the time of arrival of the acoustic waves at the receivers while other techniques can function without that information. Published papers introducing various techniques emphasize the advantages of the introduced techniques while ignoring and often not mentioning the limitations and weaknesses of the new techniques. What is lacking in the literature is a comprehensive review and comparison of the available techniques; this article attempts to do that. After reviewing various techniques the paper concludes which source localization technique should be most effective for what type of structure and what the current research needs are.     

Synthesis and photo physical properties of Au @ Ag (core @ shell) nanoparticles disperse in poly vinyl alcohol matrix

Synthesis of core @ shell (Au @ Ag) nanoparticle with varying silver composition has been carried out in aqueous poly vinyl alcohol (PVA) matrix. Core gold nanoparticle (~15 nm) has been synthesized through seed-mediated growth process. Synthesis of silver shell with increasing thickness (~1–5 nm) has been done by reducing Ag⁺ over the gold sol in the presence of mild reducing ascorbic acid. Characterization of Au @ Ag nanoparticles has been done by UV–Vis, High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) spectroscopic study. The blue shift of surface plasmon resonance (SPR) band with increasing mole fraction of silver has been interpreted due to dampening of core, i.e. Au SPR by Ag. The dependence of nonlinear optical response of spherical core @ shell nanoparticles has been investigated as a function of relative composition of each metal. Simulation of SPR extinction spectra based on quasi-static theory is done. A comparison of our experimental and the simulated extinction spectra using quasi-static theory of nanoshell suggests that our synthesized bimetallic particles have core @ shell structure rather than bimetallic alloy particles.     

Two-potential formula continued off-the-energy-shell

We derive an off-energy-shell generalization of the two-potential formula by using a coordinate-space approach and apply the formalism to construct algorithms for studying spatial behaviour of the fully off-shellT matrix. We also suggest some future applications of the proposed theory.     

A theoretical analysis of acoustic microscopy with converging acoustic beams

A theoretical analysis is carried out to synthesize acoustic material signatures (AMS) of solid plates immersed in water. The distinctive feature of this analysis is that it avoids three major simplifying assumptions of the presently available techniques, which are, paraxial approximation, assumption of perfect reflection and Gaussian summation of the incident field. Presently available techniques can avoid some but not all of these simplifying assumptions for computing the AMS. In this paper the analysis is carried out for lowfrequency acoustic waves generated by a cylindrical transducer without a lens rod. Reasons for these changes in the conventional acoustic microscope geometry is given. The AMS is synthesized for an aluminium plate in presence as well as in absence of water on its one side. As expected a significant difference is observed between the signatures generated under these two situations.     

Novel nonlinear wave equation: Regulated rogue waves and accelerated soliton solutions

A new exactly solvable ($1+1$)-dimensional complex nonlinear wave equation exhibiting rich analytic properties has been introduced. A rogue wave (RW), localized in space–time like Peregrine RW solution, though richer due to the presence of free parameters is discovered. This freedom allows to regulate amplitude and width of the RW as needed. The proposed equation allows also an intriguing topology changing accelerated dark soliton solution in spite of constant coefficients in the equation.     

Anomalous magnetic response of a quasi-periodic mesoscopic ring in presence of Rashba and Dresselhaus spin-orbit interactions

We investigate the properties of persistent charge current driven by magnetic flux in aquasi-periodic mesoscopic Fibonacci ring with Rashba and Dresselhaus spin-orbitinteractions. Within a tight-binding framework we work out individual state currentstogether with net current based on second-quantized approach. A significant enhancement ofcurrent is observed in presence of spin-orbit coupling and sometimes it becomes orders ofmagnitude higher compared to the spin-orbit interaction free Fibonacci ring. We alsoestablish a scaling relation of persistent current with ring size, associated with theFibonacci generation, from which one can directly estimate current for any arbitrary flux,even in presence of spin-orbit interaction, without doing numerical simulation. Thepresent analysis indeed gives a unique opportunity of determining persistent current andhas not been discussed so far.     

Formation of nanoscale aggregates of a coumarin derivative in Langmuir–Blodgett film

In the present communication, we report the formation of organized nanoscale aggregates of a coumarin derivative 7 Hydroxy-N-Octadecyl Coumarin-3-Carboxamide (7HNO3C) at the air–water interface and in Langmuir–Blodgett (LB) films in the presence and absence of stearic acid (SA). A pressure-area isotherm reveals that the 7HNO3C form stable monolayer at the air–water interface. However, the stability can be improved by mixing it with a fatty acid stearic acid (SA). The miscibility study shows that the nature of interaction is strongly dependent on the mixing ratio and surface pressure. At a mole fraction of 0.4 of 7HNO3C in SA, the attractive and repulsive interaction between these two molecules balance each other forming a stable film with nanoscale aggregates. UV-Vis absorption spectroscopic studies reveal the nature of the aggregates in LB films. Scanning electron microscopy gives compelling visual evidence of formation of nanoscale aggregates in the mixed LB films.     

Controlled Space Radiation concept for mesh-free semi-analytical technique to model wave fields in complex geometries

Numerical modelling of the ultrasonic wave propagation is important for Structural Heath Monitoring and System Prognosis problems. In order to develop intelligent and adaptive structures with embedded damage detector and classifier mechanisms, detailed understanding of scattered wave fields due to anomaly in the structure is inevitably required. A detailed understanding of the problem demands a good modelling of the wave propagation in the problem geometry in virtual form. Therefore, efficient analytical, semi-analytical or numerical modelling techniques are required. In recent years a semi-analytical mesh-free technique called Distributed Point Source Method (DPSM) is being used for modelling various ultrasonic, electrostatic and electromagnetic wave field problems. In the conventional DPSM approach point sources are placed along the transducer faces, problem boundaries and interfaces to model incident and scattered fields. Every point source emits energy in all directions uniformly. Source strengths of these 360° radiation sources are obtained by satisfying interface and boundary conditions of the problem. In conventional DPSM modelling approach it is assumed that the shadow zone does not require any special consideration. 360° Radiation point sources should be capable of properly modelling shadow zones because all boundary and interface conditions are satisfied. In this paper it is investigated how good this assumption is by introducing the ‘shadow zone’ concept at the point source level and comparing the results generated by the conventional DPSM and by this modified approach where the conventional 360° radiation point sources are replaced by the Controlled Space Radiation (CSR) sources.