Probabilistic Assembly of a Ball Screw

Russian Engineering Research - The assembly of ball screws is considered theoretically and experimentally in the case where the screw and nut are combined with an optimal combination of systematic...     

The determination of the elastic properties of an anisotropic polycrystalline graphite using neutron diffraction and ultrasonic measurements

The elastic properties of an extruded graphite (GR-280) used in nuclear industry have been examined. The lattice preferred orientation was determined by time-of-flight neutron diffraction that revealed weak texture with a texture index of less than 1.2. The bulk elastic properties of polycrystalline graphite with such a texture have been calculated using various averaging methods and compared with the properties obtained from the measurements of the longitudinal sound velocities, performed using special equipment at different hydrostatic pressures up to 150 MPa. The static elastic modulus of the GR-280 graphite as well as the diffraction elastic modulus was measured in situ by high resolution neutron diffraction by observing the shift of the (0 0 2) Bragg reflection under uniaxial loads up to 20 MPa. The static elastic moduli of two pyrolytic graphites have also been measured for comparison. It was shown that the anisotropy of the elastic properties of reactor graphite GR-280 is due to the crystallographic texture formed during the extrusion process, but the internal pores and microcracks are not closed even at a pressure of 150 MPa and they greatly influence the exact values of the bulk elastic moduli of graphite.     

Key Aspects of the Digitization of Quality Control in Auto Assembly

Russian Engineering Research - A digital system for quality management in auto assembly is outlined. An approach is proposed for selecting the key operations requiring the introduction of a smart...     

Simple Models to Study Spectral Properties of Microbial and Animal Rhodopsins: Evaluation of the Electrostatic Effect of Charged and Polar Residues on the First Absorption Band Maxima

A typical feature of proteins from the rhodopsin family is the sensitivity of their absorption band maximum to protein amino acid composition. For this reason, studies of these proteins often require methodologies that determine spectral shift caused by amino acid substitutions. Generally, quantum mechanics/molecular mechanics models allow for the calculation of a substitution-induced spectral shift with high accuracy, but their application is not always easy and requires special knowledge. In the present study, we propose simple models that allow us to estimate the direct effect of a charged or polar residue substitution without extensive calculations using only rhodopsin three-dimensional structure and plots or tables that are provided in this article. The models are based on absorption maximum values calculated at the SORCI+Q level of theory for cis- and trans-forms of retinal protonated Schiff base in an external electrostatic field of charges and dipoles. Each value corresponds to a certain position of a charged or polar residue relative to the retinal chromophore. The proposed approach was evaluated against an example set consisting of twelve bovine rhodopsin and sodium pumping rhodopsin mutants. The limits of the applicability of the models are also discussed. The results of our study can be useful for the interpretation of experimental data and for the rational design of rhodopsins with required spectral properties.     

An approach for modeling the active transformation of microstructure of two‐phase Alloys in FEM simulation of technological chains in superplastic forming (SPF)

Optimization and broadening of the technological regimes of superplastic forming require more accurate accounting of the transformation of microstructure during all stages of the forming process. On the one hand, it is very important to predict the resultant microstructure in different parts of the formed structure as it determines the operation properties, and on the other hand, active transformation of microstructure can lead to either hardening (grain coarsening) or softening (grain refinement) of the material. These changes in the mechanical behavior of a material can be quite significant and need to be taken into account in the FEM simulation of superplastic forming processes to achieve the required accuracy. One approach for modeling the microstructural transformation in an FEM simulation for a two‐phase alloy is proposed herein. Constitutive model with internal variables is described. The questions of validity of macroscopic and microscopic equations are discussed. The approach for taking into account the transformation of metallographic texture is proposed.     

Emission characteristics of NaI(T1) crystals in intense pulsed photon fluxes

Power Physics Institute and Kurchatov Atomic Energy Institute. Translated from Atomnaya Énergiya, Vol. 71, No. 2, pp. 153–155, August, 1991.