Unique Measure for Geometrical Shape Object Detection-based on Area Matching

Object classifier often operates by making decisions based on the values of several shape properties measured from an image of the object. The paper introduces a unique definition of measure for 2-D geometrical object shape detection. Using this definition different object shapes can be identified on the basis of their degree of fitness parameter. Basically, we have fitted a 2-D polygon/curve on the object as a best fitted polygon/curve and computed the parameter degree of fitness which is the ratio of the matching area and non-matching area due to the fitted polygon/curve and the object both. The results show the effectiveness of the proposed measure.Defence Science Journal, 2012, 62(1), pp.58-66, DOI:http://dx.doi.org/10.14429/dsj.62.94

Scattering of elastic waves by periodic arrays of spherical bodies

We develop a formalism for the calculation of the frequency band structure of a phononic crystal consisting of non-overlapping elastic spheres, characterized by Lam\'e coefficients which may be complex and frequency dependent, arranged periodically in a host medium with different mass density and Lam\'e coefficients. We view the crystal as a sequence of planes of spheres, parallel to and having the two dimensional periodicity of a given crystallographic plane, and obtain the complex band structure of the infinite crystal associated with this plane. The method allows one to calculate, also, the transmission, reflection, and absorption coefficients for an elastic wave (longitudinal or transverse) incident, at any angle, on a slab of the crystal of finite thickness. We demonstrate the efficiency of the method by applying it to a specific example.Comment: 19 pages, 5 figures, Phys. Rev. B (in press

Magnetic glass in Shape Memory Alloy : Ni45Co5Mn38Sn12

The first order martensitic transition in the ferromagnetic shape memory alloy Ni45Co5Mn38Sn12 is also a magnetic transition and has a large field induced effect. While cooling in the presence of field this first order magnetic martensite transition is kinetically arrested. Depending on the cooling field, a fraction of the arrested ferromagnetic austenite phase persists down to the lowest temperature as a magnetic glassy state, similar to the one observed in various intermetallic alloys and in half doped manganites. A detailed investigation of this first order ferromagnetic austenite (FM-A) to low magnetization martensite (LM-M) state transition as a function of temperature and field has been carried out by magnetization measurements. Extensive cooling and heating in unequal field (CHUF) measurements and a novel field cooled protocol for isothermal MH measurements (FC-MH) are utilized to investigate the glass like arrested states and show a reverse martensite transition. Finally, we determine a field -temperature (HT) phase diagram of Ni45Co5Mn38Sn12 from various magnetization measurements which brings out the regions where thermodynamic and metastable states co-exist in the HT space clearly depicting this system as a 'Magnetic Glass'.Comment: Magnetic field tunes kinetic arrest and CHUF shows devitrification and melting of Magnetic glas

Lifshitz transition and van Hove singularity in a Topological Dirac Semimetal

A topological Dirac semimetal is a novel state of quantum matter which has recently attracted much attention as an apparent 3D version of graphene. In this paper, we report critically important results on the electronic structure of the 3D Dirac semimetal Na3Bi at a surface that reveals its nontrivial groundstate. Our studies, for the first time, reveal that the two 3D Dirac cones go through a topological change in the constant energy contour as a function of the binding energy, featuring a Lifshitz point, which is missing in a strict 3D analog of graphene (in other words Na3Bi is not a true 3D analog of graphene). Our results identify the first example of a band saddle point singularity in 3D Dirac materials. This is in contrast to its 2D analogs such as graphene and the helical Dirac surface states of a topological insulator. The observation of multiple Dirac nodes in Na3Bi connecting via a Lifshitz point along its crystalline rotational axis away from the Kramers point serves as a decisive signature for the symmetry-protected nature of the Dirac semimetal's topological groundstate.Comment: 5 pages, 4 Figures, Related papers on topological Fermi arcs and Weyl Semimetals (WSMs) are at http://physics.princeton.edu/zahidhasangroup/index.htm

Evidences of spatial (angular) filtering of sound beams by sonic crystals

We report experimental evidences of spatial (angular) filtering of sound beams propagating through sonic crystals. We show that at specific frequencies of the incident wave the paraxial plane wave compo- nents of the beam can be efficiently transmitted through the crystal, whereas the components propagat- ing at large angles are strongly reflected or deflected (filtered out) by the crystal. The modification of the angular field distribution results in formation of sound beams of relatively high spatial quality.The work was financieall supported by Spanish Ministry of since and Innovation and European Union FEDER through projects FIS2011-29731-C02-01 and -02, Generalitat Valenciana through the procect GV/2011/2055 and the UPV through PAID-05-12.Picó Vila, R.; Pérez Arjona, I.; Sánchez Morcillo, VJ.; Staliünas, K. (2013). Evidences of spatial (angular) filtering of sound beams by sonic crystals. Applied Acoustics. 74(7):945-948. https://doi.org/10.1016/j.apacoust.2013.01.003S94594874

Probing spin correlations using angle-resolved photoemission in a coupled metallic/Mott insulator system

Funding: European Research Council (Grant Nos. ERC-714193-QUESTDO and ERC-319286-QMAC), the Royal Society, the Leverhulme Trust (Grant Nos. RL-2016-006 and PLP-2015-144R); EPSRC for PhD studentship support through grant numbers EP/L015110/1 and EP/K503162/1. I.M. acknowledges PhD studentship support from the IMPRS for the Chemistry and Physics of Quantum MaterialsA nearly free electron metal and a Mott insulating state can be thought of as opposite ends of the spectrum of possibilities for the motion of electrons in a solid. Understanding their interaction lies at the heart of the correlated electron problem. In the magnetic oxide metal PdCrO2, nearly free and Mott-localized electrons exist in alternating layers, forming natural heterostructures. Using angle-resolved photoemission spectroscopy, quantitatively supported by a strong coupling analysis, we show that the coupling between these layers leads to an “intertwined” excitation that is a convolution of the charge spectrum of the metallic layer and the spin susceptibility of the Mott layer. Our findings establish PdCrO2 as a model system in which to probe Kondo lattice physics and also open new routes to use the a priori nonmagnetic probe of photoemission to gain insights into the spin susceptibility of correlated electron materials.Publisher PDFPeer reviewe

Colossal magnetoresistance in a nonsymmorphic antiferromagnetic insulator

Here we investigate antiferromagnetic Eu$_{5}$In$_{2}$Sb$_{6}$, a nonsymmorphic Zintl phase. Our electrical transport data show that Eu$_{5}$In$_{2}$Sb$_{6}$ is remarkably insulating and exhibits an exceptionally large negative magnetoresistance, which is consistent with the presence of magnetic polarons. From {\it ab initio} calculations, the paramagnetic state of Eu$_{5}$In$_{2}$Sb$_{6}$ is a topologically nontrivial semimetal within the generalized gradient approximation (GGA), whereas an insulating state with trivial topological indices is obtained using a modified Becke-Johnson potential. Notably, GGA+U calculations suggest that the antiferromagnetic phase of Eu$_{5}$In$_{2}$Sb$_{6}$ may host an axion insulating state. Our results provide important feedback for theories of topological classification and highlight the potential of realizing clean magnetic narrow-gap semiconductors in Zintl materials.Comment: Accepted in npj Quantum Materials. Author list and affiliations correcte

Strain-tuning of the magnetocaloric transition temperature in model FeRh films

The chemically ordered B2 phase of equiatomic FeRh is known to absorb or evolve a significant latent heat as it traverses its first-order phase transition in response to thermal, magnetic, and mechanical drivers. This attribute makes FeRh an ideal magnetocaloric material testbed for investigation of relationships between the crystalline lattice and the magnetic spins, which are especially experimentally accessible in thin films. In this work, epitaxial FeRh films of nominal 30 nm and 50 nm thicknesses with out-of-plane c-axis orientation were sputter-deposited at high temperature onto (0 0 1)-MgO or (0 0 0 1)-Al2O3 substrates and capped with Al, Au, Cr, or W after in situ annealing at 973 K to promote CsCl-type chemical order. In this manner a controlled strain state was invoked. Experimental results derived from laboratory and synchrotron x-ray diffraction combined with magnetometry indicate that the antiferromagnetic (AF)—ferromagnetic (FM) magnetostructural phase transformation in these films may be tuned over an ~50° range (373 K–425 K) through variation in the c/a ratio derived from lattice strain delivered by the substrate and the capping layers. These results supply fundamental information that might be used to engineer the magnetocaloric working material in new system designs by introducing targeted values of passive strain to the system