A Three-Component Mathematical Model of a Single-Axis Accelerometer for Measuring Pitch and Roll Angles

Measurement Techniques - We consider measurements of pitch and roll angles using compensation pendulum accelerometers with closed feedback. A three-component mathematical model of a single-axis...     

Analyzing the Conditions for the Electrolytic Formation of Ensembles from Metal Nanowires in the Pores of Track Membranes

Theoretical Foundations of Chemical Engineering - The effect of the electrolyte composition, mass-transfer conditions, pore diameter, interpore distance, and electric parameters on the formation of...     

Size and morphology-controlled synthesis of mesoporous hydroxyapatite nanocrystals by microwave-assisted hydrothermal method

We report the rapid microwave-assisted hydrothermal synthesis of mesoporous hydroxyapatite (HAp) nanocrystals with controlled size, morphology, and surface area using various organic modifiers as regulators. The products were analyzed for their crystalline nature, phase purity, morphology, particle size and pore size distribution. Results indicated that ascorbic acid, cetyltrimethyl ammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) play an important role to obtain needle like, rod like and fiber like mesoporous HAp nanocrystals with different specific surface area by controlling growth habit of HAp along c-axis. In addition, the prepared samples were B-type carbonated HAp similar to bone minerals. Therefore, the present approach can be a promising way to obtain precursor for making tissue engineering scaffolds, drug/protein delivery carriers and bone fillers with tunable characteristics.     

Thermodynamic Foundations of an Information-Based Systems Approach to Designing Complex Engineering Objects

Theoretical Foundations of Chemical Engineering - Thermodynamic foundations of an information-based systems approach to designing complex engineering objects with hierarchical structure using...     

Effect of frost-heave forces of soils on the bearing capacity of pyramidal piles

Conclusions 1. Foundations formed from short pyramidal piles can be used in soils slightly prone to heaving without any restructions placed on bearing capacity, and should never be used in soils highly prone to heaving. 2. The installation of foundations formed from short pyramidal piles 3–4 m long in soils moderately prone to heaving with a heaving modulus m ≤ 7 is possible in principle. In this case, however, the load on the pile should be limited to the value determined by computation as a function of the frost depth of the soil and the assigned length of the pile in conformity with the method outlined in the paper. 3. Since the results obtained and the conclusions drawn apply to piles only of three of the most widely used type sizes, and their investigation was limited only to three experimental sites, questions raised in the paper will require further study. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 6, pp. 8–11, November–December, 1989.     

Production of Powdered α-Fe2O3 with Multilevel Gradient Porosity

Russian Journal of Non-Ferrous Metals - This article discusses methods for producing a material with gradient multilevel porosity by sintering layer-by-layer distributed α-Fe2O3 nanopowders...     

Electrical resistivity of silicon nitride produced by various methods

It has been shown that the grain growth and amount of the glass phase influence the electrical resistivity of pressureless sintered and spark plasma sintered silicon nitride. Sintering additives strongly affect the impurity conductivity of pressureless sintered silicon nitride and slightly influence the intrinsic conductivity due to the longer sintering process as compared with the spark plasma sintering. It was demonstrated that Al₂O₃-Y₂O₃ lead to decrease in the electrical resistivity of SPSed silicon nitride due to increase in the band gap width as opposed to Al₂O₃-MgO. Effect of the sintering additive on the impurity conductivity is practically absent but there is a strong dependence of the sintering temperature for reported spark plasma sintered silicon nitride. However, intrinsic conductivity of SPSed silicon nitride is affected by both sintering temperature and sintering additive. It was also shown that electrical resistivity of produced ceramics is linearly depends on the content of β-Si₃N₄ and microhardness. Electrical resistivity of manufactured silicon nitride varied from 3.16·10⁹ to 1.73·10¹¹ Ω?m. It has been observed strong influence of the sintering additive and sintering temperature on the electrical properties of SPSed and pressureless sintered silicon nitride.