EBG waveguides for contactless surface impedance measurements

A method for the estimation of sheet impedance of thin sample which does not require a direct contact with the sample under test is proposed. The surface impedance is calculated through an inversion procedure exploiting the scattering parameters obtained through a waveguide measurement setup. An inversion procedure based on the representation of the waveguide-air-waveguide section as a π junction is employed. In order to prevent the field leakage from the air gap created for hosting the thin sheet, an EBG surface is introduced on the flange of the waveguide. It is shown that the introduction of the EBG surface remarkably improves the estimation of the surface impedance of the thin sheet with respect to the case without EBG.

Mechanical Properties of Laser Treated Thin Sample of an Amorphous-Nanocrystalline Metallic Alloy Depending on the Initial Annealing Temperature

The ability to control the mechanical properties of metal alloys is an urgent task in materials science. For formation of certain operational properties, in most cases, it is enough to treat the working surface of the product by laser radiation. Classical processing methods are ineffective in relation to multicomponent amorphous-nanocrystalline metallic alloys. This is due to their limited use. Usually, this treatment leads to the loss of unique properties the amorphous-nanocrystalline material. Increasing crack resistance and microhardness is not an easy problem. The structure of an amorphous nanocrystalline material can be destroyed under the action of laser processing. Laser nanosecond treatment, as result of a complex effect on the surface, slightly affects the structure of material. The treated material is characterized by increased microhardness and crack resistance, while at the same time such changes may be controlled.

Constrained Magnetic Vector Inversion of Scanning Magnetic Microscopy Data for Modelling Magnetization of Multidomain Mineral Grains

<p>We are using 3D magnetic vector inversion (MVI) of scanning magnetic microscopy (SMM) data to investigate the fine‐scale magnetization of rock samples, and particularly of their remanence carriers, which can record geologically meaningful information. Previous investigations of magnetite grains suggest variable remanence intensities and directions coherent with multidomain behaviour. This research seeks to improve our understanding of the contribution of different microstructures on remanence acquisition.</p><p>SMM offers a spatial resolution down to tens of micrometers, allowing detailed investigation of discrete magnetic mineral grains, or magnetic textures and structures. However, all magnetic measurements are, at some scale, bulk measurements. Further analysis of the data is required to extract information about the magnetization within the samples: for this, we employ state-of-the-art MVI methods. The MVI problem suffers from a high degree of nonuniqueness. Additional constraints are required to obtain accurate, reliable and interpretable results. Such constraints are readily available for this application.</p><p>SMM instruments use magnetic shields or Helmholtz coils to allow collection of data in controlled magnetic fields, enabling the removal of induced magnetization effects. Measurements can be taken both above and below the sample. Individual magnetized mineral grains are easily outlined through optical and electron microscopy. The internal geometry of the oxide mineral phases and compositions can also be constrained. Physical property information constrains the range of magnetization intensity. As such, there is a tremendous amount of constraining information invaluable for reducing the nonuniqueness of the inverse problem. We use a highly flexible and functional inversion software package, MAGNUM, developed jointly at Mount Allison University and Memorial University of Newfoundland, that allows incorporation of all available constraints.</p><p>We take a multitiered approach for investigating specific magnetized grains. First, coarse regional inversions are performed to assess and remove any effects of other magnetized grains in the vicinity. The entire grain is then modelled with a homogeneous magnetization to obtain an approximate but representative bulk magnetization. The grain is then modelled as a collection of independent subdomains, each with a different homogeneous magnetization direction. Subsequently, more heterogeneous scenarios are considered by relaxing inversion constraints until the data can be fit to the desired degree.</p><p>Obtaining reliable information about the magnetic mineralogy of rock samples is vital for an understanding of the origin of rock bulk behaviour in both the laboratory and larger scale magnetic surveys. This work is among the first to simultaneously invert SMM data collected above and below a thin sample, which is critical for improving depth resolution on thicker samples. It is also the first time we have been able to incorporate all available constraints into inverse modelling to improve results.</p>

Влияние дискообразных непроводящих включений на электропроводность материала на постоянном токе

The influence of non-conductive disk-like inclusions (fractures) on the conductivity of a conducting medium in direct current is considered. To find the additional specific electrical resistance due to cracks, a self-consistent problem for the current density has been solved. In this case, a hydrodynamic analogy was used between the motion of an ideal incompressible fluid during potential flow around solids and electric current flowing around fractures. The functional dependences of the resulting relative additional specific electrical resistance of the material on the fracturing coefficient for thick and thin samples are found. A graphical visualization of these dependences shows that for a thick specimen, for all real values of the coefficient of fracturing, it is linear and is determined by the shape of the fractures. For a thin sample, the dependence of the relative additional the specific electrical resistance of the material on the fracturing coefficient is proportional to the thickness of the sample and is nonlinear. The obtained dependences of the additional electrical resistivity can be used, in particular, as a non-invasive method for determining the fracturing coefficient of rock samples conducting electric current.

GRAIN BOUNDARY MIGRATION IN THIN FILMS USING MONTE CARLO METHOD

This paper presents the evolution of a flat grain boundary in a thin sample, using a numerical algorithm based on the Monte Carlo method. The grain boundary is driven by an external force and the effect of the free surface is studied.The grain boundary migration on the free surface is spasmodic, which means that it has alternating periods of movement and stagnation. Stagnation periods are inversely proportional to the thickness of the sample. The results obtained computationally fitted acceptable with the theoretical results obtained by different authors.

Impact of Capital Structure on Financial Performance of Selected Multinational Companies in India

Hundreds of studies researching impact of capital structure on financial performance have been carried across the globe. A selected review of some of the latest ones reveal that most of them have been premised on a thin sample size. Ten such recent studies have minimum sample size of 10 organizations, minimum sample size of 237 organizations and a mean sample size of 56 organizations. The sample size choice has been largely ad-hoc not showing any relationship with the size of population. This research takes a scientific approach to study 400 multinational companies from India based on the population of around 5000 listed companies on the Bombay Stock Exchange. Due sectoral representation was given in the sample selected for the study. Here in this study the impact of capital structure on financial output of the selected companies was studied. Before the full-fledged study was carried, a pilot study was carried on the basis of 30 multinational companies. This article presents the conceptual foundations, literature review and findings from the pilot study

A Monte Carlo ray-tracing simulation of coherent X-ray diffractive imaging

Coherent diffractive imaging (CDI) experiments are adequately simulated assuming the thin sample approximation and using a Fresnel or Fraunhofer wavefront propagator to obtain the diffraction pattern. Although this method is used in wave-based or hybrid X-ray simulators, here the applicability and effectiveness of an alternative approach that is based solely on ray tracing of Huygens wavelets are investigated. It is shown that diffraction fringes of a grating-like source are accurately predicted and that diffraction patterns of a ptychography dataset from an experiment with realistic parameters can be sampled well enough to be retrieved by a standard phase-retrieval algorithm. Potentials and limits of this approach are highlighted. It is suggested that it could be applied to study imperfect or non-standard CDI configurations lacking a satisfactory theoretical formulation. The considerable computational effort required by this method is justified by the great flexibility provided for easy simulation of a large-parameter space.