In-Situ Analyzing the Influence of Thermoelectromagnetic Convection on the Nucleation Ahead of the Advancing Interface During Directional Solidification

Sn-3wt%Pb alloy was directionally solidified without and with a 0.08T transverse magnetic field(TMF),and real-time recorded by in-situ synchrotron X-ray imaging.Results indicate that TMF shortened the distance from the location of nucleation to the advancing interface,and accelerated the growth rate of the equiaxed crystal,which caused the columnar-to-equiaxed transition(CET)finally.The thermoelectromagnetic convection(TEMC)in front of the interface and around the crystal’s dendritic branch should respond to changes of the distance and the growth rate.     

Plates and edges

The backscattering from a rectangular plate at edge-on incidence is due essentially to the individual contributions from the front and trailing edges. The contribution of the front edge is analogous to that of a wire illuminated by a plane wave, but the rear edge excitation is almost wholly determined by current waves along the side edges of the plate.     

A moment method solution of a volume-surface integral equationusing isoparametric elements and point matching [TE scattering]

Three integral equations for TE (transverse electric) scattering by dielectric cylinders having large values of permittivity are examined. A moment-method solution of the volume-surface integral equation is developed employing isoparametric elements and point matching. The solution is shown to be accurate and stable than the traditional solutions using pulse basis, particularly in the case of scatterers having large refractive indices     

The minimization of the back scattering of a cylinder by central loading

A theoretical and experimental study of the minimization of the back scattering by a thin cylinder by central loading is presented. The induced current on a centrally loaded cylinder illuminated by a plane wave at normal incidence was determined theoretically and experimentally. The magnitude and phase of the induced current can be greatly changed by a central impedance. The optimum loading to achieve zero back scatter in the broadside direction from a thin cylinder shorter than two wavelengths and the optimum central impedance for the purpose of minimizing the broadside back scattering from a thin cylinder over a wide range of frequencies has been determined.     

Detailing Microstructural Evolution Roadmap in the Weld Metal of EH420 Shipbuilding Steel Subjected to Varied Reheating Inputs

Metallurgical and Materials Transactions A - Microstructural evolution roadmap in the weld metal of EH420 shipbuilding steel subjected to various reheating inputs has been investigated. As...     

Recovering missing slices of the discrete fourier transform using ghosts

The discrete Fourier transform (DFT) underpins the solution to many inverse problems commonly possessing missing or unmeasured frequency information. This incomplete coverage of the Fourier space always produces systematic artifacts called Ghosts. In this paper, a fast and exact method for deconvolving cyclic artifacts caused by missing slices of the DFT using redundant image regions is presented. The slices discussed here originate from the exact partitioning of the Discrete Fourier Transform (DFT) space, under the projective Discrete Radon Transform, called the discrete Fourier slice theorem. The method has a computational complexity of O(nlog(2)n) (for an n=N×N image) and is constructed from a new cyclic theory of Ghosts. This theory is also shown to unify several aspects of work done on Ghosts over the past three decades. This paper concludes with an application to fast, exact, non-iterative image reconstruction from a highly asymmetric set of rational angle projections that give rise to sets of sparse slices within the DFT.     

A comparative study of the OSRC approach in electromagneticscattering

A technique referred to as the on-surface radiation boundary condition (OSR) approach is applied to a variety of two-dimensional imperfectly conducting geometries. Specifically, analytical solutions and numerical data are presented for the scattering by elliptical and rectangular cylinders and restrictive strips. These are then compared with calculations using the traditional physical optics (PO) approximation and moment method (MM). Emphasis is on the accuracy afforded by using OSRC as opposed to the MM or PO formulations     

Coupling studies and shielding techniques for electromagnetic penetration through apertures on complex cavities and vehicular platforms

The multilevel fast multipole moment method is employed to compute the electromagnetic coupling and shielding of various aperture-coupled metallic enclosures. A phenomenological study of electromagnetic coupling, due to various slot shapes and sizes, with or without the presence of wire penetration is conducted. These slots are situated on over-moded cavities and two methods are proposed to mitigate slot coupling into the cavity's interior. As part of this work, we also investigate the coupling through similar slots and apertures within a complex platform such as an automobile. The proposed methods have shown to increase shielding by as much as 5-35 dB within the frequency range of interest.