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Search results for: lattice algorithms
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Lattice filter based multivariate autoregressive spectral estimation with joint model order and estimation bandwidth adaptation
PublicationThe problem of parametric, autoregressive model based estimation of a time-varying spectral density function of a multivariate nonstationary process is considered. It is shown that estimation results can be considerably improved if identification of the autoregressive model is carried out using the two-sided doubly exponentially weighted lattice algorithm which combines results yielded by two one-sided lattice algorithms running...
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Identification of nonstationary processes using noncausal bidirectional lattice filtering
PublicationThe problem of off-line identification of a nonstationary autoregressive process with a time-varying order and a time-varying degree of nonstationarity is considered and solved using the parallel estimation approach. The proposed parallel estimation scheme is made up of several bidirectional (noncausal) exponentially weighted lattice algorithms with different estimation memory and order settings. It is shown that optimization of...
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Lattice filter based autoregressive spectrum estimation with joint model order and estimation bandwidth adaptation
PublicationThe problem of parametric, autoregressive model based estimation of a time-varying spectral density function of a nonstationary process is considered. It is shown that estimation results can be considerably improved if identification of the autoregressive model is carried out using the two-sided doubly exponentially weighted lattice algorithm which combines results yielded by two one-sided lattice algorithms running forward in...
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Lattice-commensurate skyrmion texture in a centrosymmetric breathing kagome magnet
PublicationSkyrmion lattices (SkL) in centrosymmetric materials typically have a magnetic period on the nanometer-scale, so that the coupling between magnetic superstructures and the underlying crystal lattice cannot be neglected. We reveal the commensurate locking of a SkL to the atomic lattice in Gd3Ru4Al12 via high-resolution resonant elastic x-ray scattering (REXS). Weak easy-plane magnetic anisotropy, demonstrated here by a combination...
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Eu2Mg3Bi4: Competing Magnetic Orders on a Buckled Honeycomb Lattice
PublicationThe honeycomb lattice and its derived variants provide information on modeling and designing quantum magnets. A novel magnetic material, Eu2Mg3Bi4, which stabilizes in a previously unknown buckled honeycomb lattice, was discovered by high-pressure and high-temperature methods. We report here on the synthesis exploration of pure single crystals, structural determination of the buckled honeycomb lattice of europium moments, and experimental observation...
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Kagome Lattice Promotes Chiral Spin Fluctuations
PublicationDynamical spin fluctuations in magnets can be endowed with a slight bent toward left- or right-handed chirality by Dzyaloshinskii-Moriya interactions. However, little is known about the crucial role of lattice geometry on these chiral spin fluctuations and on fluctuation-related transport anomalies driven by the quantum-mechanical (Berry) phase of conduction electrons. Via thermoelectric Nernst effect and electric Hall effect experiments,...
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Anti-plane surface waves in media with surface structure: Discrete vs. continuum model
PublicationWe present a comparison of the dispersion relations derived for anti-plane surface waves using the two distinct approaches of the surface elasticity vis-a-vis the lattice dynamics. We consider an elastic half-space with surface stresses described within the Gurtin–Murdoch model, and present a formulation of its discrete counterpart that is a square lattice half-plane with surface row of particles having mass and elastic bonds different...
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Enriched buckling for beam-lattice metamaterials
PublicationWe discuss two examples of beam-lattice metamaterials which show attractive mechanical properties concerning their enriched buckling. The first one considers pantographic beams and the nonlinear solution is traced out numerically on the base of a Hencky’s model and an algorithm based on Riks’ arc-length scheme. The second one concerns a beam-lattice with sliders and the nonlinear solution is discussed in analytic way and, finally,...
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LattE- first-principles lattice energy calculations
PublicationCrystal engineering is currently attracting much interest. Its aim is to create materials of predefined properties fulfilling the requirements imposed by the applications. There are several parameters describing crystal structures, but the most important one is probably the energy of a crystal lattice. It is the energy released by the system when crystalline solid is formed out of molecules or ions in gaseous phase. Approximate...
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On rotary inertia of microstuctured beams and variations thereof
PublicationWe discuss the classic rotary inertia notion and extend it for microstructured beams introducing new microinertia parameters as an additional dynamic response to microstructure changes. Slender structures made of beam- or platelet-lattice metamaterials may exhibit not only large translations and rotations but also general deformations of inner structure. Here we considered a few examples of beam-like structures and derive their...
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Planar Microwave Bragg Reflector Resonant Dielectric Sensor
PublicationIn this paper, a periodic structure is used to design a microwave Bragg reflector with the help of hexagonal lattice, which provides a 5 GHz wide stopband between the low-pass band with cut-off frequency 2.6 GHz and the bandpass response with start and stop frequency 7.8 GHz and 10.5 GHz, respectively. A defect in lattice allows passing a narrowband signal at 6 GHz which is found, from the dispersion relation, to be in the region...
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Wave transmission across surface interfaces in lattice structures
PublicationWithin the lattice dynamics formulation, we present an exact solution for anti-plane surface waves in a square lattice strip with a surface row of material particles of two types separated by a linear interface. The considered problem is a discrete analog of an elastic half-space with surface stresses modelled through the simplified Gurtin–Murdoch model, where we have an interfacial line separating areas with different surface...
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Ce site dilution effects in the antiferromagnetic heavy fermion CeIn3
PublicationLa-doped intermetallic single crystals of Ce1−xLaxIn3 were synthesized via an In self-flux method throughout the entire range (x = 0–1). The prototypical heavy-fermion compound CeIn3 shows an antiferromagnetic phase transition at 10.1 K and becomes superconducting near a critical pressure where TN is completely suppressed. As the La concentration increases, Ce moments are diluted, and the lattice constant increases linearly, satisfying Vegard’s...
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Hydrogen and chalcogen bonds in crystals of chalcogenadiazolecarboxylic acids – competition or cooperation?
PublicationThis article presents crystal structures of chalcogenadiazolecarboxylic acids bearing both a hydrogen and a chalcogen bond donor. The selected molecules varied in the size of the aromatic unit, the chalcogen atom and/or the position of the carboxyl group in the core structure. The most common synthons in their lattice are "R" _"2" ^"2" (8) self-complementary acid dimers or four-membered [Ch···N]2 rings. Supramolecular synthons...
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Dirac fermions and possible weak antilocalization in LaCuSb2
PublicationLayered heavy-metal square-lattice compounds have recently emerged as potential Dirac fermion materials due to bonding within those sublattices. We report quantum transport and spectroscopic data on the layered Sb square-lattice material LaCuSb2. Linearly dispersing band crossings, necessary to generate Dirac fermions, are experimentally observed in the electronic band structure observed using angle-resolved photoemission spectroscopy,...
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Reply to Comment on ‘Nanodiamond incorporated human liver mimicking phantoms: prospective calibration medium of magnetic resonance imaging’
PublicationDependence of the spin–lattice (T1) relaxation times on the nanodiamond concentration in human liver phantoms is discussed. Factors affecting stability and and reproducibility of these phantoms are presented. The need for comparative measurements on multiple MRI scanners for better understanding of potential variations in the obtained imaging data is emphasised.
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Quadratic stochastic operators on Banach lattices
PublicationWe study the convergence of iterates of quadratic stochastic operators that are mean monotonic. They are defined on the convex set of probability measures concentrated on a weakly compact order interval S = [0, f] of a fixed Banach lattice F. We study their regularity and identify the limits of trajectories either as the “infimum” or “supremum” of the support of initial distributions.
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An Analysis of Periodic Arrangements of Cylindrical Objects of Arbitrary Convex Cross Sections with the Use of Field Matching Method
PublicationA problem of electromagnetic wave scattering from multilayered frequency selective surfaces is presented. Each surface is composed of periodically arranged cylindrical posts of arbitrary convex cross-section. The method of analysis is based on the direct field matching technique for a single cell, and the transmission matrix method with the lattice sums technique for periodic arrangement of scatterers.
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Study of Aliphatic Polyurethanes by the Low-Field 1H NMR Relaxometry Method with the Inversion of the Integral Transformation
PublicationIn this paper, the distributions of the 1H nuclear magnetic resonance (NMR) spin–lattice and spin–spin relaxation times are used to characterize the mobility of different sections of macromolecules of aliphatic polyurethanes and the cross-linking density of polymer chains. The NMR relaxometry method with inversion of integral transformation is applied to study the effect of poly (ethylene glycol) and glycerol phosphate calcium...
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Crystal structure and physical properties of AePd1-xP1+x (Ae = Ca, Sr)
PublicationWe report the discovery of two new compounds AePd1-xP1+x (Ae = Ca, Sr) crystallized in different hexagonal structures. Single crystals of AePd1-xP1+x (Ae = Ca, Sr) are obtained using the Bi-flux method. Crystallographic analysis by both powder and single crystal X-ray diffraction shows that CaPd1-xP1+x crystallizes in a non-centrosymmetric hexagonal structure with the space group P-6m2 (No.187) and lattice parameters a = b = 4.0391(9)...
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A new open-source software developed for numerical simulations usingdiscrete modeling methods
PublicationThe purpose of this work is to present the development of an open-source software based on a discrete description of matter applied to study the behavior of geomaterials. This software uses Object Oriented Programming techniques, and its methodology design uses three different methods, which are the Discrete Element Method (DEM) [F. Donzé, S.A. Magnier, Formulation of a three-dimensional numerical model of brittle behavior, Geophys....
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Cyclic behaviour modelling of additively manufactured Ti-6Al-4V lattice structures
PublicationThe present work is concerned with the numerical modelling of the cyclic behaviour of Ti-6Al-4V lattice structures. In the study, diamond structures of titanium alloy produced by the additive laser powder bed fusion (LPBF) method with different degrees of relative density were used. Realistic geometric models of the studied mesostructures were generated using computed microtomography, taking into account the imperfections of the...
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Spin-glass behavior in a binary Pr 3 Ir intermetallic compound
PublicationPolycrystalline Pr3Ir was synthesized by arc melting. Its cementite-type crystal structure (Pnma) was confirmed by powder X-ray diffraction and estimated lattice parameters are in agreement with literature. Physical properties were measured by means of the ac and dc magnetic susceptibility, electrical resistivity and heat capacity. Our results indicate spin-glass behavior in Pr3Ir with a freezing temperature Tf = 6.58 K and activation...
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Structural and physical characterization of NpPt2In7
PublicationA new neptunium intermetallic compound, NpPt2In7, has been synthesized in polycrystalline form and characterized by several macroscopic techniques. A Rietveld analysis of its powder x-ray diffraction pattern shows that NpPt2In7 crystallizes in a tetragonal lattice with I4/mmm symmetry and lattice parameters a = 4.58471(3) Å, c = 21.5065(3) Å. Magnetic susceptibility, electrical resistivity, Hall effect, and heat capacity measurements indicate...
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Cooperativity of Halogen- and Chalcogen-Bonding Interactions in the Self-Assembly of 4‑Iodoethynyl- and 4,7-Bis(iodoethynyl)benzo-2,1,3-chalcogenadiazoles: Crystal Structures, Hirshfeld Surface Analyses, and Crystal Lattice Energy Calculations
PublicationSeveral new 4-iodoethynyl- and 4,7-bis- (iodoethynyl)benzo-2,1,3-chalcogenadiazoles were prepared, and a comprehensive analysis of the most prominent secondary bonding interactions responsible for the crystal self-assembly was performed using X-ray diffraction. The presence of both the iodoethynyl and chalcogenadiazole moieties allows an evaluation of the preference of these molecules to aggregate through either chalcogen- or halogen-bonding...
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Numerical investigation on dynamic response of a steel lattice tower under various seismic events
PublicationThe present paper presents the results of the numerical study designed to investigate the soil-structure flexibility effects on modal parameters (i.e. fundamental frequencies) and time-history analysis response (represented by the top relative displacements) of a 46.8 m high steel lattice tower subjected to a number of ground motions including also one mining tremor. In addition to the fixed-base condition, three different soil...
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Superconductivity in LiGa2Ir Heusler type compound with VEC = 16
PublicationPolycrystalline LiGa2Ir has been prepared by a solid state reaction method. A Rietveld refnement of powder x-ray difraction data confrms a previously reported Heusler-type crystal structure (space group Fm-3m, No. 225) with lattice parameter a= 6.0322(1) Å. The normal and superconducting state properties were studied by magnetic susceptibility, heat capacity, and electrical resistivity techniques. A bulk superconductivity with...
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Investigation of magnetic order in a new intermetallic compound Nd2PtGe3
PublicationIn the present study we report a successful synthesis of the new intermetallic compound Nd2PtGe3 by an arc-melting method. The powder X-ray diffraction analysis indicates that this compound crystallizes in an disordered variant of the AlB2-type structure (space group P6/mmm, no. 191) with lattice parameters a = 4.2455 Å and c = 4. 1933 Å. The compound exhibits a cluster-glass transition below Tf = 2.9 K, characterized through ac...
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Strong ellipticity conditions and infinitesimal stability within nonlinear strain gradient elasticity
PublicationWe discuss connections between the strong ellipticity condition and the infinitesimal instability within the nonlinear strain gradient elasticity. The strong ellipticity (SE) condition describes the property of equations of statics whereas the infinitesimal stability is introduced as the positive definiteness of the second variation of an energy functional. Here we establish few implications which simplify the further analysis...
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Application of a cellular automaton to simulations of granular flow in silos
PublicationA cellular automaton based on a gas model of hydrodynamics was used to calculate the kinematics of non-cohesive granular materials during confined flow in a mass flow and funnel flow model silo. In the model, collisions of particles were taken into account during granular flow. In addition, a simplified automaton was used wherein granular flow was assumed as an upward propagation of holes through a lattice composed of cells representing...
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Tuning the ferromagnetic phase in the CDW compound SmNiC2 via chemical alloying
PublicationWe report a study on tuning the charge density wave (CDW) ferromagnet SmNiC2 to a weakly coupled superconductor by substituting La for Sm. X-ray diffraction measurements show that the doped compounds obey Vegard’s law, where La (Lu) alloying expands (shrinks) the lattice due to its larger (smaller) atomic size than Sm. In the series Sm1−xLaxNiC2, CDW transition (TCDW =148K) for SmNiC2 is gradually suppressed, while the ferromagnetic...
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Curing epoxy with electrochemically synthesized Zn Fe3-O4 magnetic nanoparticles
PublicationCathodic electrodeposition (CED) was applied in synthesis of undoped and zinc (Zn) doped Fe3O4 nanoparticles. Changes in the lattice structure of nanoparticles were monitored using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) supported by dispersive X-ray spectrometry (EDS), and vibrating sample magnetometry (VSM). Detailed analyses explored the formation of ZnxFe3–xO4 nanoparticles with x ≈ 0.1,...
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Superconductivity in Bismuth Pyrochlore Lattice Compounds RbBi2 and CsBi2: The Role of Relativistic Effects
PublicationSuperconducting properties of two bismuthide intermetallic compounds, RbBi2 and CsBi2, were studied by means of experimental measurements and ab initio calculations. We show that in both compounds, the superconductivity emerges from the pyrochlore Bi lattice and its formation is heavily influenced by relativistic effects. Based on our analysis of the effect of spin–orbit coupling on the electron–phonon coupling, we suggest a possible...
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The homometallic warwickite V 2 OBO 3
PublicationThe synthesis, structure and elementary magnetic characterization of the homometallic warwickite V2OBO3 are reported. The material adopts the orthorhombic warwickite structure type at room temperature, space group Pnma (No. 62) with lattice parameters a = 9.2317(1) Å, b = 3.1172(1) Å, and c = 9.5313(1) Å. Temperature-dependent magnetic susceptibility, electrical resistivity, and specific heat measurements show anomalies near 35 K,...
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Chemical Pressure Tuning Magnetism from Pyrochlore to Triangular Lattices
PublicationGeometrically frustrated lattices combined with magnetism usually host quantum fluctuations that suppress magnetic orders and generate highly entangled ground states. Three-dimensionally (3D) frustrated magnets generally exist in the diamond and pyrochlore lattices, while two-dimensionally (2D) frustrated geometries contain Kagomé, triangular, and honeycomb lattices. In this work, we reported using chemical pressure to tune the magnetism...
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Structure and water uptake in BaLnCo2O6−δ (Ln =La, Pr, Nd, Sm, Gd, Tb and Dy)
PublicationThe structure of BaLnCo2O6-δ (Ln =La, Pr, Nd, Sm, Gd, Tb and Dy) was studied by the means of synchrotron radiation powder X-ray diffraction, neutron powder diffraction and Transmission Electron Microscopy (TEM), while water uptake properties were analysed with the use of thermogravimetry (TG) and water adsorption isotherms. The structure refinement revealed that the dominant phase in all compositions was orthorhombic with an ordering...
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Improving Thermal Insulation Properties for Prefabricated Wall Components Made of Lightweight Aggregate Concrete with Open Structure
PublicationPorous concrete is commonly used in civil engineering due to its good thermal insulation properties in comparison with normal concrete and high compression strength in comparison with other building materials. An extremely porous concrete, called ‘lightweight aggregate concrete with open structure’ (LAC), is used in some German plants to produce prefabricated wall components. They are used mainly in hall buildings, e.g. supermarkets....
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Electrical and structural properties of Nb-doped SrTiO3
PublicationNiobium-doped strontium titanate synthesized via conventional solid-state reaction has been studied. Influence of niobium content on the lattice parameters and electrical conductivity has been reported. Various reduction conditions have been investigated. For samples reduced in hydrogen at 1400°C, a transition from thermally activated to metallic behavior has been observed. Maximum electrical conductivity (ca. 55 Scm−1 at 650°C)...
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From flow to jamming: Lattice Gas Automaton simulations in granular materials
PublicationWe introduce the first extension of a Lattice Gas Automaton (LGA) model to accurately replicate observed emergent phenomena in granular materials with a special focus on previously unexplored jamming transitions by incorporating gravitational effects, energy dissipation in particle collisions, and wall friction. We successfully reproduce flow rate evolution, density wave formation, and jamming transition observed in experiments....
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Modelowanie kratownicy z kształtowników giętych na zimno z mimośrodami dodatnimi w węźle = Modelling of truss with cold-formed section and positive eccentricyty in the node.
PublicationThe topic of this research is establishing load-carrying capacity of compressed and tensed chords of trusses made of cold-formed open cross-sections. Occurrence of bending in the truss’ chord is the result of specific production technology assumed by the designer and producer of lattice girder’s systems. The aim of this research is to present methodology of conduct while creating numerical models that best depict the behaviour...
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Modeling of truss with cold-formed section and positive eccentricity in the node
PublicationThis work is dedicated to establishing the load carrying capacity of tensed and compressed truss’ nodes made of cold-formed open cross sections. The occurrence of bending in the truss’ nodes is the result of a specific production technology for system lattice girders assumed by the designer and the producer. The aim of this research is to present the methodology of conduct for creation of computational models that best depict the...
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Marcinkiewicz Averages of Smooth Orthogonal Projections on Sphere
PublicationWe construct a single smooth orthogonal projection with desired localization whose average under a group action yields the decomposition of the identity operator. For any full rank lattice \Gamma ⊂ R^d , a smooth projection is localized in a neighborhood of an arbitrary precompact fundamental domain R^d / \Gamma. We also show the existence of a highly localized smooth orthogonal projection, whose Marcinkiewicz average under the...
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Crystal growth and properties of a binary intermetallic ZrBi2 compound
PublicationSingle crystals of ZrBi2 were grown by a self-flux method. The material adopts TiAs2 structure type with lattice parameters: a = 10.233(4) Å, b = 15.581(2) Å, c = 3.994(5) Å. Crystals of ZrBi2 were studied by means of magnetic susceptiblity, specific heat and resistivity measurements. The compound reveals a metallic-like behavior (RRR = 30). The Sommerfeld coefficient equals γ = 1.59(16) mJ mol-1 K-2 and Debye temperature ΘD =...
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The electronic characterization of the cubic Laves-phase superconductor CaRh2
PublicationWe present the synthesis and experimental characterization of the electronic properties of the cubic Laves phase superconductor CaRh2. Its crystal structure was confirmed by powder X-ray diffraction and its ambient temperature lattice parameter (a = 7.5326(6) Å) is in good agreement with the literature. Magnetization, resistivity and heat-capacity measurements indicate that CaRh2 is a moderate-coupling type-II superconductor (λe-p = 0.89)...
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Crystal structures of (E)-3-(4-hydroxybenzylidene)chroman-4-one and (E)-3-(3-hydroxybenzylidene)-2-phenylchroman-4-one
PublicationThe synthesis and crystal structures of (E)-3-(4-hydroxybenzylidene)chroman-4-one, C16H12O3,I, and (E)-3-(3-hydroxybenzylidene)-2-phenylchroman-4-one,C22H16O3,II, are reported. These compounds are of interest with respect to biological activity. Both structures display intermolecular C—H---O and O—H---O hydrogen bonding, forming layers in the crystal lattice. The crystal structure of compound I is consolidated...
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Study of the Effect of Filling Thermoplastic Medical Polyurethane with PVA, PLA or Diatomite on the Relaxation Times Distributions of 1H NMR
PublicationIn this work, to characterize the mobility of diferent sections of the macromole‑ cules of polyurethane (PUR), polyvinyl alcohol (PVA), and polylactic acid (PLA), as well as the density of crosslinks of the polymer chains when using fllers, we used the distributions of spin–lattice and spin–spin relaxation times for the protons. It is shown that the rigidity of the thermoplastic polymers depends on the sizes of the granules of...
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A Nonlinear Model of a Mesh Shell
PublicationFor a certain class of elastic lattice shells experiencing finite deformations, a continual model using the equations of the so-called six-parameter shell theory has been proposed. Within this model, the kinematics of the shell is described using six kinematically independent scalar degrees of freedom — the field of displacements and turns, as in the case of the Cosserat continuum, which gives reason to call the model under consideration...
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9-(Trichloroacetylimino)acridine monohydrate
PublicationThe title compound, alternatively called N-acridin-9(10H)-ylidene-2,2,2-trichloroacetamide monohydrate, C15H9Cl3N2O·H2O, crystallizes in space group P21/c with Z = 4. The acridine moieties are arranged in layers, tilted at an angle of 15.20 (4)° relative to the ac plane, while adjacent molecules pack in a head-to-tail manner. Acridine and water molecules form columns along the b axis held in place by a network of hydrogen...
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Nonlinear strain gradient and micromorphic one-dimensional elastic continua: Comparison through strong ellipticity conditions
PublicationWe discuss the strong ellipticity (SE) conditions for strain gradient and micromorphic continua considering them as an enhancement of a simple nonlinearly elastic material called in the following primary material. Recently both models are widely used for description of material behavior of beam-lattice metamaterials which may possess various types of material instabilities. We analyze how a possible loss of SE results in the behavior...
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Superconductivity and ferromagnetism in Pd doped Y9Co7
PublicationThe ferromagnetic superconductor Y9Co7 was chemically doped to yield the solid solution Y9Co7-xPdx for 0 < x < 0.4. The lattice parameter a does not depend on x, whereas c increases with increasing Pd content up to x ¼ 0.2, the palladium solubility limit. The transition from ferromagnetism (TC ¼ 4.25 K) to superconductivity (Tsc ¼ 2.4 K) was observed only for the parent Y9Co7 compound. For the lowest tested Pd doping level (x ¼...