К расчету поля конечного магнитного цилиндра с внутренним соосным цилиндрическим дефектом

Using the grid method, a numerical solution of the direct problem of magnetostatics for calculating the field of a finite cylinder with a constant magnetic permeability containing an internal inclusion in the form of a coaxial cylinder with a different magnetic permeability is carried out. The algorithm is created for an arbitrary external field. In order to assess the reliability and accuracy of the solution method, the results were tested using precisely solved problems. A comparison is also made with the results of the previously solved problem of a finite defect-free cylinder. The coordinate dependences of the components of the resulting field are constructed for different source data. The program adds to the library of magnetic control problems and can be used for high-quality verification with the results of model experiments, as well as for evaluating the geometric characteristics of an internal defect.

Rheological Properties of the Jojoba Biofuel

Jojoba oil biofuel is a potential alternative to diesel fuel with attractive properties, but its flow behavior under the operating conditions of a diesel engine still needs to be clarified. In this study, the rheological properties of the jojoba biofuel are presented in assessment with diesel fuel to experimentally evaluate both their flow behaviors at different operating temperatures. A Fann-type coaxial cylinder viscometer was employed. The shear stress of the tested biofuel rises considerably with the shear rate in a marginally nonlinear manner on a logarithmic scale. Rheograms indicate that the flow behavior decreases gradually and considerably in the temperature range of 30–90 °C. The viscosity of the jojoba oil biofuel declines considerably with the decreasing applied shear rate and temperature. Based on the experimental results, a suitable model is developed for predicting the viscosity characteristics of the tested biofuel during the heating and cooling cycles of a diesel engine.

Energy Consumption of Self-Compacting Concrete during Mixing and Its Impact on the Yield Stress Measured in the Ready-Mix Concrete Plant

To find the energy required during the mixing process of self-compacting concrete in a ready-mixed concrete plant and correlate the results with the yield stress of concrete. Power consumption required during the mixing of concrete is measured with a wattmeter connected to the mixing unit’s power supply. A coaxial cylinder viscometer is used to measure the yield stress of concrete. The clamp meter measures the power when the impeller rotates inside the coaxial cylinder viscometer, which is filled with concrete. When the impeller rotates in a coaxial cylinder filled with concrete, the power is measured by a clamp meter. Torque is obtained through the power relationship, which is an essential factor in determining the yield stress. The cost of a rheometer is so high that all construction industries, research institutions, and researchers cannot measure rheological parameters. Nowadays, all rheometers are automated; hence, the cost is very high. Tattersall’s approach of power requirement in mixing the concrete and calculating the yield stress reduces the complexity in determining the rheological parameter.

Effects of Sodium Hexametaphosphate Addition on the Dispersion and Hydration of Pure Calcium Aluminate Cement

The effects of sodium hexametaphosphate (SHMP) addition on the dispersion and hydration of calcium aluminate cement were investigated, and the relevant mechanisms discussed. The content of SHMP and the adsorption capacity of SHMP on the surface of cement particles were estimated using plasma adsorption spectroscopy and the residual concentration method. The rheological behavior of hydrate, ζ-potential value of cement particles, phase transformation and the microstructure of the samples were determined by coaxial cylinder rheometer, zeta probe, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that SHMP readily reacted with Ca2+, forming complexes [Ca2(PO3)6]2− ions which were subsequently adsorbed onto the surfaces of cement particles. When the content of SHMP was 0.05%, the adsorption ratio reached 99%. However, it decreased to 89% upon further increasing the addition of SHMP to 0.4%. The complexes [Ca2(PO3)6]2− adsorbed onto the surfaces of cement particles inhibited the concentration of Ca2+ and changed ζ-potential, resulting in enhanced electrostatic repulsive force between the cement particles and reduced viscosity of cement-water slurry. The experimental results indicate that the complexes [Ca2(PO3)6]2− covering the surfaces of cement particles led to a delayed hydration reaction, i.e., they extended the hydration time of the cement particles, and that the optimal addition of SHMP was found to be about 0.2%.