A study of the influence of soft particle size and concentration on strength and strain properties of ceramic composites

In the paper a theoretical study of the influence of particle distribution of soft inclusions-agglomerates in a ceramic composite sample on its strength and deformation characteristics was carried out. A movable cellular automaton method was used to simulate a uniaxial compression test of two-dimensional rectangle composite samples. It was found that the average size of inclusions agglomerate-while maintaining the volume fraction of the particles of the soft phase has little effect on the strength and deformation properties of the simulated samples. The simulation results can help to understand the mechanical properties of such objects within any generalized model

Regiodivergent condensation of 5-alkoxycarbonyl-1H-pyrrol-2,3-diones with cyclic ketazinones en route to spirocyclic scaffolds

The condensation of 5-alkoxycarbonyl-1H-pyrrolediones with cyclic ketazinones was systematically investigated. It was discovered that the regioselectivity of this reaction can be easily swapped between two alternative directions affording derivatives of partially hydrogenated indole or benzofurane. The control of this regioselectivity is efficiently governed by steric effects at the hydrazone moiety of the ketazinone reagent

Experimental research on the thermal method of drilling by melting the well in ice mass with simultaneous controlled expansion of its diameter

During the seasonal work of the 64th Russian Antarctic Expedition in 2018-2019 at the “Vostok” drilling facility named after B.B.Kudryashov (“Vostok” station, Antarctic) specialists of Saint Petersburg Mining University conducted experimental investigations on the process of drilling by melting with simultaneous expansion of wells in the ice mass. A test bench and a full-scale model of a thermohydraulic reamer-drilling tool were developed, manufactured and tested for the research. The first bench tests of the full-scale model proved its efficiency and suitability for experimental drilling with simultaneous expansion of wells in ice mass; its operational capabilities were determined and the drawbacks that will be taken into account in future were found out. The article substantiates the choice of constructive elements for thermohydraulic reamer-drilling tool. It is determined that the technology of full diameter drilling with simultaneous expansion of the well in ice mass can be implemented by combining contact drilling by melting and convective expansion with creation of forced near-bottomhole annular circulation of the heated heat carrier. Dependencies of expansion rate on main technological parameters were determined: active heat power of heating elements in penetrator and circulation system, mechanical drilling rate, pump flow rate. According to the results of investigations, the experimental model of thermohydraulic reamer-drilling tool will be designed and manufactured for testing in conditions of well 5G

The integrated method to select drilling muds for abnormally high pressure formations

The article describes the method for choosing a drilling mud for drilling abnormally high pressure formations. A carefully selected drilling mud formulation would not only enhance an array of interrelated fluid properties, but also minimize the impact on the pay zones when the drill bit first penetrates the pay. To ensure a better assessment of drilling mud impact on the pay zone, it is reasonable to carry out the study focused on the analysis of technological parameters, involving filtration, acid and drilling mud tests, as well as formation damage analysis. This would enable evaluating the degree of mudding off, reservoirs acid fracturing effect and the risks of pipe sticking at significant depth. The article presents the results of the above-described study with regard to the currently used drilling mud and new experimental formulations developed at National Research Tomsk Polytechnic University (Drilling Mud and Cement Slurry Laboratory)

The Influence of LO Power Heating of the Tunnel Junction on the Performance of THz SIS Mixers

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Facile regiodivergent synthesis of spiro pyrrole-substituted pseudothiohydantoins and thiohydantoins via reaction of [e]-fused 1H-pyrrole-2,3-diones with thiourea

This work is licensed under a Creative Commons Attribution 4.0 International License.A highly divergent synthesis of regioisomeric thiohydantoins and pseudothiohydantoins spiro-fused to a pharmacologically valuable pyrrole-2-one fragment involving the reaction of [e]-fused 1H-pyrrole-2,3-diones with thioureas was developed. The obtained spiro pseudothiohydantoin derivatives were found to undergo a pseudothiohydantoin–thiohydantoin rearrangement. The reactions were shown to proceed under catalyst-free conditions in good yields, and the products were isolated without applying preparative chromatography methods

Design and Performance of a Sideband Separating SIS Mixer for 800-950 GHz

We present the design and results of characterization of a new sideband separating (2SB) mixer for 800-950GHz, based on superconductor-insulator-superconductor (SIS) junctions. This is the first waveguide 2SB SIS mixer demonstrated at such a high frequency. The design is following the classical quadrature hybrid architecture, meanwhile additional attention was put on the reduction of reflections in the RF structure in order to minimize the RF imbalance, to achieve a high image rejection ratio (IRR). The RF waveguide block was manufactured by micromilling and populated by single-ended SIS mixers developed earlier for upgrade of the CHAMP+ high-band array on the APEX telescope. These SIS mixers have double-sideband (DSB) noise temperatures from 210 to 400K. The assembled 2SB mixer yields a SSB noise temperature from 450 to 900K, with an IRR above 15dB in 95 of the band. Comparing the DSB and the SSB sensitivities, we find that the waveguide losses are as low as expected and do not exceed 0.6dB. The presented mixer is a prototype for use in a 2SB dual polarization receiver planned for deployment on the APEX telescope

Test Load Determination On Composite Standard Malaysian Rubber Constant Viscosity 60 For Earthquake Isolator

This paper describes the test load determination on composite Standard Malaysia Rubber constant viscosity 60 for earthquake isolators. The usage of natural rubber in the development of earthquake isolators for building application has led to the investigation on its mechanical properties such as hardness, elastic modulus and many more. In this study, the mechanical properties of Standard Malaysian Rubber with constant viscosity 60 with various percentage of carbon black were investigated. The main purpose of this study is to implement the usage of Standard Malaysian Rubber as the main substance in the development of earthquake isolators. The nano-indentation was carried out by using Berkovich tips at a constant load with various holding time and it recorded the highest hardness and elastic modulus values and possessed the lowest penetration depth. This test also revealed that the hardness and penetration depth were independent of the holding time. In contrast, the indentation elastic modulus was found to be highly affected by the holding time. By using the nano-indentation test, it can determined that the mechanical properties of Standard Malaysian Rubber, is more cost-effective, non-destructive, and requires small test piece as compared to the conventional technique

Analysis of Mechanical Safety of Stadiums for the World Cup 2018

It is obvious that contemporary design and construction of unique buildings and structures is unthinkable without mathematical (numerical) and computer modelling and advanced analysis ofload-bearing structures under various kinds ofloads and impacts. One of the most ambitious and important construction projects is the uniquelarge-span structures. These are, in particular, stadiums, sports palaces and water parks, shopping malls, pedestrian, road and railway bridges of various design solutions. The distinctive paper is devoted to theoretical foundations and results of mathematical (numerical) modeling of the state (in terms of the analysis of stress-strain state, strength and stability) of football stadiums built for the 2018 FIFA World Cup in Russia. Finite element method is used for approximation and high-precision numerical solution of corresponding boundary problems of structural mechanics. It is the most universal and powerful numerical method of mechanics. The paper, in particular, describes some features of development of finite element models and the main results of the analysis of the mechanical (structural) safety of three- dimensionallarge-span systems "soil foundation - reinforced concrete structures of foundations and stands - steel structures of the coating and facades" of these football stadiums with the basic and specialload combinations. In addition, the key procedures of scientific support during the corresponding expertise and assessments are outlined. Generally, socially significant and knowledge-intensive problem of providing mechanical (constructive) safety of unique combined objects of construction (three-dimensional systems "foundation - reinforced concrete structures of foundations and stands - steel structures of coating and facades") has been solved at a new level as a result of the performed complex of research works

Niobium Tunnel Junctions with Multi-Layered Electrodes

Abstract