Elongations of magnetoactive elastomers (MAEs) under ascending-descending uniform magnetic fields were studied experimentally using a laboratory apparatus specifically designed to measure large ...extensional strains (up to 20%) in compliant MAEs. In the literature, such a phenomenon is usually denoted as giant magnetostriction. The synthesized cylindrical MAE samples were based on polydimethylsiloxane matrices filled with micrometer-sized particles of carbonyl iron. The impact of both the macroscopic shape factor of the samples and their magneto-mechanical characteristics were evaluated. For this purpose, the aspect ratio of the MAE cylindrical samples, the concentration of magnetic particles in MAEs and the effective shear modulus were systematically varied. It was shown that the magnetically induced elongation of MAE cylinders in the maximum magnetic field of about 400 kA/m, applied along the cylinder axis, grew with the increasing aspect ratio. The effect of the sample composition is discussed in terms of magnetic filler rearrangements in magnetic fields and the observed experimental tendencies are rationalized by simple theoretical estimates. The obtained results can be used for the design of new smart materials with magnetic-field-controlled deformation properties, e.g., for soft robotics.
Recently flames have emerged as a viable alternative method for the synthesis of carbon nanotubes and related nanostructures. The flame volume provides a carbon-rich chemically reactive environment ...capable of generating nanostructures during short residence times in a continuous single-step process. Various flame configurations, fuel types, and catalytic materials have been employed in an attempt to achieve controlled growth of multi-walled and single-walled carbon nanotubes as well as other carbon nanostructures such as nanofibers, carbon micro-trees, and whiskers. Premixed and non-premixed flames in co-flow and counterflow geometries were examined using low atmospheric and elevated pressures, various hydrocarbon fuels, oxygen enrichment, and dilution with inert gases were employed as well. Catalytic materials in the form of solid untreated supports, solid supports with pre-fabricated catalytic sites, and also in the form of aerosol have demonstrated high activity and selectivity in the growth of various nanostructures. The ability to synthesize and control carbon nanotube orientation, length, diameter, uniformity, purity, and internal morphology is essential for the fabrication of nanomechanical and electrical devices. An understanding of the growth mechanism and development of control methods such as the electric field, particle loading, and nanotemplates is critically important to address these issues. Today, flames are envisioned as the alternative technique for the synthesis of SWNTs in tons/year production scale leading to the development of related technologies such as purification and separation methods.
In the paper (Saveliev, in: AIP conference proceedings, vol 1333, p 134, 2011), the kinetic equation for two-particle distribution function was obtained by making use of exactly the same physical ...assumptions as Ludwig Boltzmann did. Instead of the collision integral, there are the linear scattering operator and the chaos projector in the right part of this equation. The Boltzmann equation follows from this two-particle equation without any additional assumptions after a simple integration. The article presents the method of generalized functions and considers the properties of the obtained exact solution for the two-particle kinetic equation for Maxwell's molecules, which is an intermediate asymptotics for problems of spatial homogeneous relaxation. After reducing the two-particle distribution function to a one-particle distribution function, the solution is reduced to the well-known Bobylev-Krook-Wu (BKW) mode.
•A new formalism of the n-body interatomic potentials is developed by explicitly accounting for 3-body interactions.•The interatomic potentials for V are constructed.•The formalism more accurately ...predicts properties of V in comparison with the available potentials.
An improved accuracy in the description of base characteristics of the bcc refractory metals, including melting point and heat of fusion, with the help of atomistic simulation methods, requires further development of reliable interatomic potentials, more precisely taking into account the angle part of interactions. A new approach for the description of interactions in atomistic systems based on known n-body expansion of the total energy has been developed. The embedded atom method (EAM) ansatz is derived from this expansion within a centrally symmetric approximation. With the developed approach, the total energy is regarded consisting of a pair potential part, 3-body interactions without model considerations and a term that describes all other n-body interactions like the embedded function of EAM. As an application, accurate many-body potentials for V have been constructed. The formation energies and volumes of self-interstitials and di-vacancies are calculated. The cohesive energy, elastic constants, phonon spectra, the vacancy formation and migration energies, surface energies, the transition to a rhombohedral phase with increasing pressure, the thermal expansion, the melting point and the heat of fusion have also been studied, and satisfactory agreement with available experimental data has been found.
An algorithm for solving problems of magnetic gas dynamics, which is adapted to the architecture of computing systems with extramassive parallelism, is discussed. The algorithm is based on a kinetic ...model that describes the dynamics of an ensemble of neutral and charged particles, as well as a magnetic field. As an illustration, the results of a 3D calculation of the dynamics of a conducting incompressible fluid (molten sodium) in a channel conjugated to a cavity are presented.
Processes in the dynamics of electrically conducting fluid flows in complex heat transfer systems are mathematically modeled in detail on high-performance parallel computing systems. The study is ...based on the kinetically consistent magnetogasdynamic approach adjusted to this class of problems. The kinetically consistent algorithm is well adapted to the architecture of high-performance computing systems with massive parallelism, so that complex heat transfer systems can be effectively studied with a high resolution. The approach, method, and algorithms are described, and numerical results are presented.
Choroid plexus, pineal gland, and habenula tend to accumulate physiologic calcifications (concrements) over a lifetime. However, until now the composition and causes of the intracranial ...calcifications remain unclear. The detailed analysis of concrements has been done by us using X-ray diffraction analysis (XRD), X-ray diffraction topography (XRDT), micro-CT, X-ray phase-contrast tomography (XPCT), as well as histology and immunohistochemistry (IHC). By combining physical (XRD) and biochemical (IHC) methods, we identified inorganic (hydroxyapatite) and organic (vimentin) components of the concrements. Via XPCT, XRDT, histological, and IHC methods, we assessed the structure of concrements within their appropriate tissue environment in both two and three dimensions. The study found that hydroxyapatite was a major component of all calcified depositions. It should be noted, however, that the concrements displayed distinctive characteristics corresponding to each specific structure of the brain. As a result, our study provides a basis for assessing the pathological and physiological changes that occur in brain structure containing calcifications.
A simplified quasi-gasdynamic system is considered. The possibility of using it for modeling on high-performance computer systems is discussed. Some numerical results are presented.
A kinetic model based on the use of a single-particle distribution function is used to describe dissipative magnetogasdynamic phenomena. Along with the original quasi-gasdynamic model, a simplified ...version that is more convenient for numerical implementation is considered and justified. Numerical results for a number of problems are presented.
A method of montmorillonite modification with polar oligourethane containing reactive amino groups has been developed. It is shown that functionalized montmorillonite is capable of adding aromatic ...and aliphatic diisocyanates, as well as sequential addition of aromatic diisocyanates and glycerol, which is essential for montmorillonite application as filler for polymer materials. According to wide-angle X-ray scattering, interlayer distance d
001
of montmorillonite in the obtained samples varies depending on nature of oligomer macromolecules in the interlayer space that is explained with different conformation and orientation of aromatic and aliphatic oligourethane fragments.
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