Proposal to Increase the Level of Rural Business Activity after COVID-19

Our study uses a number of fundamental provisions of modern economics to ensure business excellence of enterprises, as well as used mathematical methods based on the use of integrated indicators in the direction of: leadership of scientific and technical cooperation, strategy of scientific and technical cooperation, people of knowledge, partnership and resources that matter, processes, products and services, research results, customer results, community and society vision. The study of key trends in the innovative development of domestic agribusiness is indicating the positive and negative aspects of proposal to increase the level of rural business activity. During the study it was found that this algorithm for assessing the level of business excellence, it is advisable to use it in order to identify the current state of the enterprise by the criteria of excellence, including evaluation of competitors. These exponential equations indicate that the algorithm of predictive calculation can be used in practice due to any changes in indicators.

Time-Domain Digital-to-Analog Converter for Spiking Neural Network Hardware

We propose a new digital-to-analog converter (DAC) for realizing a synapse circuit in mixed-signal spiking neural networks. We refer to this circuit as a “time-domain DAC (TDAC)”. It produces weights for converting a digital input code into voltage using one current waveform. Therefore, the TDAC is more compact than a conventional DAC consisting of many current sources and resistors. Moreover, a TDAC with leak resistance reproduces biologically plausible synaptic responses expressed as alpha functions or dual exponential equations. We also present numerical analysis results for a TDAC and circuit simulation results for a circuit designed using the TSMC 40 nm CMOS process.

Correlations between TDS and electrical conductivity for high-salinity formation brines characteristic of South Atlantic pre-salt basins

Total dissolved solids (TDS) is an important property in the characterization of natural waters for diversified applications, such as in geochemistry and the petroleum industry. Under appropriate circumstances, the determination of this parameter through correlations with the electrical conductivity (EC) of aqueous systems yields considerable advantages over the gravimetric method. However, the development of empirical equations correlating TDS and EC is still required due to the physical-chemical complexity of charge transport in multicomponent natural waters. Most existing correlations were built considering systems in the lower or medium salinity range. In this context, this research aims to provide experimental correlations between TDS and EC in a broad concentration range for high salinity formation brines characteristic of the pre-salt reservoirs. It contributes to filling a gap in the literature for geochemical systems of this nature. Moreover, correlations were also obtained for a concentrated desulphated seawater and an aqueous sodium chloride solution in the same salinity range. For all aqueous solutions, the polynomial fittings of degree greater than one fit the experimental data better compared to both linear and exponential equations. In addition, the solutions with higher concentration of divalent ions had lower EC than the solutions dominated by monovalent ions with the same ionic strength. This evidences the effect of ion pairing on the EC, particularly in solutions of high ionic strength. Therefore, the use of a general correlation to represent solutions with dramatic variations in chemical composition carries substantial error, particularly in the high salinity range. Thus, a specific correlation must be developed to represent brines with similar composition.

Triaxial Strength Criteria in Mohr Stress Space for Intact Rocks

Conventional triaxial strength criteria are important for the judgment of rock failure. Linear, parabolic, power, logarithmic, hyperbolic, and exponential equations were, respectively, established to fit the conventional triaxial compression test data for 19 types of rock specimens in the Mohr stress space. Then, a method for fitting the failure envelope to all common tangent points of each two adjacent Mohr’s circles (abbreviated as CTPAC) was proposed in the Mohr stress space. The regression accuracy of the linear equation is not as good as those of the nonlinear equations on the whole, and the regression uniaxial compression strength (σc)r, tensile strength (σt)r, cohesion cr, and internal frictional angle φr predicted by the regression linear failure envelopes with the method for fitting the CTPAC in the Mohr stress space are close to those predicted in the principal stress space. Therefore, the method for fitting CTPAC is feasible to determine the failure envelopes in the Mohr stress space. The logarithmic, hyperbolic, and exponential equations are recommended to obtain the failure envelope in the Mohr stress space when the data of tensile strength (σt)t are or are not included in regression owing to their higher R2, less positive x-intercepts, and more accurate regression cohesion cr. Furthermore, based on the shape and development trend of the nonlinear strength envelope, it is considered that when the normal stress is infinite, the total bearing capacity of rock tends to be a constant after gradual increase with decreasing rates. Thus, the hyperbolic equation and the exponential equation are more suitable to fit triaxial compression strength in a higher maximum confining pressure range because they have limit values. The conclusions can provide references for the selection of the triaxial strength criterion in practical geotechnical engineering.