•Co/Gd3Ga5O 12/Y3Fe5O12 heterostructures were grown by laser molecular beam epitaxy.•Selective YIG and Co magnetization curves were measured by MOKE and XMCD techniques.•Clear proximity effects were ...observed in heterostructures with 1 nm thick GGG spacer.•Ferromagnetic interaction between Co and YIG was explained by “orange peal” effect.
Interlayer magnetic coupling has been studied in the epitaxial system consisting of few nanometer thick magnetic layers of cobalt and yttrium iron garnet (YIG) separated by non-magnetic spacers of gadolinium gallium garnet (GGG). The samples were grown by laser molecular beam epitaxy on GGG(1 1 1) substrates. The layer morphology and crystal structure were characterized by atomic force microscopy, X-ray and electron diffraction techniques. MOKE and XMCD methods were applied for element selective study of the magnetization reversal in Co and YIG layers. For the Co/YIG/GGG heterostructures it has been found that magnetization loops of YIG and Co exhibit the same values of coercive field and are of the same shape indicating strong magnetic coupling between Co and YIG layers. In opposite, when YIG and Co are separated by a 1 nm thick GGG spacer layer, the coercive field of Co becomes very different from that of YIG. Moreover the center of YIG loop gets shifted in field whereas the sign and value of this shift depend on the current magnetic state of the Co layer. The magnetic interaction between Co and YIG can be interpreted in the terms of 2–3 Oe magnetic field induced in the YIG layer by the adjacent Co layer. This magnetic field is likely caused by the “orange peel” effect arising due to granular structure of Co layer.
Photocurable biocompatible hydrogels were fabricated from methacrylated gelatin and silk proteins (a recombinant analogue of spidroin from
Nephila clavipes
spider web and fibroin from the cocoons of ...the silkworm
Bombyx mori
). These polymers are widely applicable in tissue engineering due to their biocompatibility and biodegradability. Hydrogels were fabricated using two different methods that allowed to obtain either the macroscopic scaffolds or microstructures with a defined shape. Three-dimensional hydrogel samples were prepared via monomers solution photopolymerization for 10 min. As a result, the disk-shaped samples of hydrogels approximately 13 mm in diameter were fabricated. Their porous structure was confirmed by scanning electron microscopy. Microstructures were formed on coverslips using an Eclipse Ti-E microscope equipped with an A1 confocal module (Nikon, Japan) and 405 nm laser. This approach allows to control the topographic features of the obtained substrates, and it is viable for creating the micropattern surfaces to reveal for studying the interaction of cells with a substrate.
Tribotechnical polymer composites based on polytetrafluoroethylene with nanomodifiers of different compositions have been developed and their structure and properties have been studied.
The method for autonomous determination and estimation of soil parameters by robotic vehicles is described in the article. Basic requirements on the robotic chassis mathematical model allowing the ...estimation are listed. The main dependencies governing the interaction between the moving wheels/tracks and supporting ground are shown.
Based on the proposed loading model of a sliding bearing, the dependence of the load-bearing capacity of reinforced metal fluoroplastic sliding bearings on their geometric characteristics and force ...factors was studied using the finite element method. A calculation of stresses and deformations in the most pliable antifriction layer was carried out. It is shown that the distribution of stresses and deformations in the bearing is extremely uniform and depends on the thickness of the antifriction layer and the height of the bearing. Criteria for assessing the performance of sliding bearings under load were introduced and based on these criteria the results were compared with experimental data. The agreement between calculated and experimental data allows us to use the resulting methodology to determine the load-bearing capacity of slide bearings. The solutions make it possible to move from the experimental method of determining the load-bearing capacity of metal fluoroplastic sliding bearings to the calculated one and to design bearings with predetermined strength characteristics. This will help specialists designing bearing units improve the quality and speed of their development.
A model for calculation of the X-ray density of amorphous–crystalline polymers which for the first time takes into account the degree of ordering of the amorphous phase and the degree of deformation ...of the lattice cell was developed. Verification of the model by comparing calculated data with results of experimental X-ray studies was performed.
The authors propose a schematic structure of the intelligent system for the real time identification of the soil parameters during the movement of the tracked vehicle. The system is compared with the ...methods of the driving conditions prediction based on the analysis of databases, contactless telemetry, terrain scanning, etc. The possible advantages and disadvantages of these methods are specified. The descriptions of the system blocks are given, the purpose and interrelation between the components are considered in detail. Requirements of the blocks and separate components of the system are specified. The concept of integration of the system for identification of the soil parameters during the movement of the tracked vehicle into an autonomous motion control system is presented. The authors offer a method for the soil characterisation without the use of databases. The method is based on the solution of the direct and inverse problems of terramechanics for the tracked autonomous mobile complexes. The article contains typical performance examples fordifferent types of soils used for the development of the algorithms of the system foridentification of the soil parameters. Different identity criteria are proposed for checking the conformity of the soil performance models to its real performance. The article contains the analysis of the technical problems to be solved during development of a system for identification of the soil parameters.
Effectiveness of application of autonomous tracked vehicles depends on many factors. For the manned car, the driver decides how to choose the optimal speed. The speed of autonomous vehicles, ...especially over highly rough terrain, is significantly lower and is caused by the operation of an autonomous control system. In tracked chassis, one of the agility components is the turnability, which characterizes the control ability of the vehicle under the given conditions. Controllability and ride comfort define how the power-weight ratio influence the average vehicle speed. At the same time, the behavior of an autonomous vehicle during rotation depends not only on the power-weight ratio, but also on the dimensions of the tracks support surfaces; pressure on the ground; steering radius provided by steering drive; traction properties, as well as on road conditions (path curve, traction and steering resistance coefficients). The report presents the analysis of the dependence of tracks slipping on the speed of the tracked autonomous vehicle chassis. The parameters that determine the state of the chassis of an autonomous tracked vehicle are listed. The results of mathematical simulation of the tracked mobile robot movement for different types of soils and with different speeds are presented.
Acylation of tert‐butyl 3‐(methylamino)but‐2‐enoate with fluorinated acetic acid anhydrides occurred at the enamine carbon atom. The reaction of the resulting tert‐butyl ...3‐(methylamino)‐2‐(RFCO)but‐2‐enoates with alkyl hydrazines resulted in mixtures of isomeric pyrazoles that were easily separated by column chromatography. The target fluorinated pyrazole‐4‐carboxylic acids were obtained on a multigram scale.
Fluorinated pyrazolecarboxylic acids ― potential building blocks for agrochemical applications ― have been prepared on a multigram scale. The easy separation of the isomeric mixture of esters was the key feature of the synthesis.
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