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Based on the analysis of the results of experimental studies of 12Х18Н10Т stainless steel specimens under a rigid (controlled deformation) process of deformation, which includes a sequence of ...monotonic and cyclic loading modes, some features and differences in isotropic and anisotropic hardening processes under monotonic and cyclic loading are revealed. To describe these features within the framework of the theory of plasticity in the space of the plastic strain tensor, a criterion for changing the direction of plastic deformation and a memory surface are introduced, which made it possible to separate the processes of monotonic and cyclic deformation. To describe the transient processes, evolutionary equations are formulated for the parameters of isotropic and anisotropic hardening. The calculated and experimental changes in the stress-strain states are compared for the process of monotonic and cyclic loading.
A variant of thermoviscoplasticity theory is proposed, by mathematical modeling of the viscoplastic behavior of a granulated nickel alloy under high-temperature conditions and based on flow theory ...with combined hardening. The variant of thermoviscoplasticity theory is generalized to nonisothermal loading and the dependence of the loading process on the strain rate. The results of experiments on uniaxial tension for cylindrical samples of a granulated nickel alloy at high temperatures and various strain rates are presented. The calculated viscoplastic strain diagrams are compared with experimental ones. Satisfactory agreement between the calculated and experimental results is observed, which indicates the adequacy of this variant thermoviscoplasticity theory and the method for identifying the material parameters.
In this paper, we consider the system of residual classes for data representation in communication channels. In this case, it is possible to perform parallel data processing without taking into ...account digit transfers. However, the most of communication channels are serial; therefore, we also consider the possibility of serial transmission of parallel data. We show that the use of the system of residual classes of Mersenne numbers as a base does not lead to decreasing the data transmission rate. We estimate the amount of information contained in the positions of the numbers of a positional code.
The paper considers the creep of a textile-reinforced thermoplastic composite with a glass filler under the action of a combined short-term cyclic and long-term static tensile loads at room ...temperature. The investigations were carried out on glass-fabric-reinforced polypropylene specimens, which were made by autoclave molding. The creep of the composite was experimentally investigated under a cyclic load at different amplitudes. The creep kernel has been calculated from experimental data according to the Boltzmann superposition principle. Other creep models of materials have been analyzed based on data from a review. The laws governing the short-term creep of polypropylene under the action of a static load have been determined. A behaviorial model of the composite under investigation under the considered conditions is proposed. Numerical calculations have been made with the aid of the proposed model using experimental results taken from other works, and a good agreement between them has been established. The peculiarities of the creep of textile-reinforced polypropylene under the considered conditions have been determined. The range of application of the model has been determined.
Nanostructured multicomponent (TiAlSiY)N coatings were fabricated by the cathodic-arc physical vapor deposition (CA-PVD). In this study, a bias potential applied to the substrate was − 200 and − ...500 V, and changes in structure and properties of coatings were investigated. Samples had a single-phase state with a face-centered cubic (FCC) lattice. Small crystallites of about 7.5 nm and texture with 110 axis were observed at − 500 V. However, lower bias potential resulted in the formation of crystallites of about 41.6 nm with 111 preferred orientation. Moreover, coatings were characterized by superhard state and demonstrated low wear, high abrasion and crack resistance. The testing of the polycrystalline cubic boron nitride (PCBN) cutting inserts covered with (TiAlSiY)N revealed an increase in the tool life coefficient during cutting by 1.66 times in comparison with the base tool material. Therefore, (TiAlSiY)N coating is a perspective material for application as a protective layer in cutting tools.
In addition to their use as colorants in food and cosmetics, various natural dyes possess photophysical properties that could enable their use as modular building blocks for preparing eco-friendly ...and non-toxic chromophores. Among the natural pigments, guaiazulene holds great potential due to its unique optical and electronic properties. Thus, in order to explore and understand the properties of guaiazulene-containing chromophores, a series of 4-styrylguaiazulenes 3a–l were prepared by condensation of the C-4 methyl group of naturally-occurring guaiazulene 1 with various aromatic carboxaldehydes 2a–l . Treatment of these analogs 3a–l with a strong acid protonates the electron-rich C-3 position and reveals a reversible halochromic behavior where the optical energy gap responds predictably to the electron-donor strength and the degree of π-conjugation. Additionally, acid-doping is accompanied by efficient fluorescence switch-on, where 3e (H + ) and 3g (H + ) exhibited considerably higher fluorescence quantum yields than the neutral precursor. These properties facilitated the design of a new non-erasable 3D fluorescence readout (permanent or write-once read-many, WORM) system, which is comprised of a switch-on fluorescent guaiazulene-containing chromophore 3e and a commercially available iodonium photo-acid generator (PAG) in thin polymethyl methacrylate (PMMA) films.
The structural and mechanical properties of NbN and Nb-Si-N films have been investigated both experimentally and theoretically, in their as-deposited and annealed states. The films were deposited ...using magnetron sputtering at substrate bias (UB) between 0 and −70V. While NbN films were found to crystallize in the cubic δ-NbN structure, Nb-Si-N films with Si content of 11–13at% consisted of a two-phases nanocomposite structure where δ-NbN nanocrystals were embedded in SiNx amorphous matrix. Films deposited at UB=0V were highly (001)-textured. Application of substrate bias potential led to a depletion of light atoms, and caused a grain size refinement concomitantly with the increase of (111) preferred orientations in both films. The maximum hardness was 28GPa and 32GPa for NbN and Nb-Si-N films, respectively. NbN and Nb-Si-N films deposited at UB=−70V exhibited compressive stress of −3 and −4GPa, respectively. After vacuum annealing, a decrease in the stress-free lattice parameter was observed for both films, and attributed to alteration of film composition. To obtain insights on interface properties and related mechanical and thermal stability of Nb-Si-N nanocomposite films, first principles molecular dynamics simulations of NbN/SiNx heterostructures with different structures (cubic and hexagonal) and atomic configurations were carried out. All the hexagonal heterostructures were found to be dynamically stable and weakly dependent on temperature. Calculation of the tensile strain-stress curves showed that the values of ideal tensile strength for the δ-NbN(111)- and ε-NbN(001)-based heterostructures with coherent interfaces and Si3N4–like Si2N3 interfaces were the highest with values in the range 36–65GPa, but lower than corresponding values of bulk NbN compound. This suggests that hardness enhancement is likely due to inhibition of dislocation glide at the grain boundary rather than interfacial strengthening due to Si-N chemical bonding.
Fluorescent contrast agents are important tools in cell biology and medical imaging due to their high sensitivity and relative availability. Diketopyrrolopyrrole (DPP) derivatives have been recently ...studied for applications in bioimaging, but certain drawbacks due to their inherent structure have stifled progress towards their widespread implementation. Aggregation caused quenching (ACQ) associated with π-π stacking in relatively rigid extended conjugation systems as well as hydrophobicity of previously reported DPPs make most unsuitable for biological imaging applications. Addressing these deficiencies, we report the synthesis and photophysical characterization of two new water-soluble diketopyrrolopyrole (DPP) probes that exhibit pronounced protein-induced fluorescence enhancement (PIFE) upon binding serum albumin protein. In vitro studies were also performed showing low cytotoxicity for the new DPP probes. Two-photon fluorescence microscopy (2PFM) images were obtained via excitation at 810 nm and emission in the NIR window of biological transparency, illustrating the potential of these compounds as nonlinear optical bioimaging probes.
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