INFLUENCE OF TANGENTIAL CUTTING FORCE ON A STRESS STATE OF GRINDING INSTRUMENT

Estimation of influence of tangential cutting force on a stress state of grinding instrument

Temperature field in the vacuum chamber of a ballistic gravimeter

A mathematical model for the temperature field of a ballistic gravimeter is developed based on a thermal conductivity boundary value problem to be solved by the finite element method. Genetic algorithms and the Nelder-Mead method are used to develop a way for synthesizing the parameters of electric heaters to reduce the temperature gradients inside the vacuum chamber of a ballistic gravimeter and to improve its technical parameters

Concept of an induction-dynamic catapult for a ballistic laser gravimeter

A design is proposed for an inductive-dynamic catapult in a ballistic laser gravimeter with a fixed inductor and an electrically conducting armature that moves together with the test object along a vertical axis. The catapult ensures improved accuracy of the gravimeter through direct conversion of electrical into kinetic energy. The electrical circuit of the catapult provides two successive current pulses to the inductor for launching and braking of the armature during the operating cycle

A ballistic laser gravimeter for a symmetrical measurement method with the inductive-dynamic catapult and auto-seismic vibration preventing

A ballistic laser gravimeter (BLG) with a symmetrical measurement method of the gravity acceleration (GA) is considered. Special treatment is given to the problem of eliminating the measurement error due throw of the catapult when it speeds up the test body (TB). It is possible to decrease the indicated errors thanks to the use of the induction and dynamic catapult. However, a short-term boost catapult generates vibrations of the basement (i.e. a pillar) and the mechanical elements of the gravimeter, what causes auto-seismic (i.e. recoil-related) component of the measurement error. To reduce them it is proposed to launch the TB with the help of a massive platform, installed on a light spring. It is shown, that the considered BLG can provide auto-seismic component of the measurement error of less than 1 μGal. With the reduction of the light spring constant the auto-seismic component of GA measurement uncertainty is reduced. The value of this measurement error can be reduced by the use of damping in the system of BG protection from auto-seismic fluctuations. A concept of BLG with induction-dynamic catapult for symmetric method of gravitational acceleration measuring is presented. The concept is based on using electromagnetic compensator of stiffness

A biomarker and isotope study of Paleoproterozoic ecosystems in the northern Australian McArthur Basin

Biomarkers represent an important source of information about ancient environments, especially in the Paleoproterozoic, where the body fossil record is comparatively scarce. The northern Australian McArthur Basin contains currently the oldest known indigenous biomarkers in the 1.64 Ga Barney Creek Formation (Fm). Based on published biomarker data, the oceans were almost exclusively inhabited by prokaryotic microorganisms, while eukaryotes with complex cell structure still played an insignificant role. However, newly recognized protosteroids in the Barney Creek Fm may record early stages in eukaryotic evolution. This thesis, which consists of four linked research topics, investigates biological community signatures and paleo-environments in a transect through the Barney Creek Fm succession and circumjacent units; explores preservation of organic matter associated with the Paleoproterozoic McArthur River zinc-lead ore deposit; and describes the influence of thermal maturity on compound-specific carbon and hydrogen isotopic composition of lipids in the Barney Creek Fm. Additionally, this research presents the discovery of trimethyl aryl isoprenoids from carbonaceous shales of the 1.73 Ga Wollogorang Fm in the McArthur Basin, revealing the activity of phototrophic bacteria and extending the biomarker record back in time by ~90 million years

Point- and contact-symmetry pseudogroups of dispersionless Nizhnik equation

Applying an original megaideal-based version of the algebraic method, we compute the point-symmetry pseudogroup of the dispersionless (potential symmetric) Nizhnik equation. This is the first example of this kind in the literature, where there is no need to use the direct method for completing the computation. The analogous studies are also carried out for the corresponding nonlinear Lax representation and the dispersionless counterpart of the symmetric Nizhnik system. We also first apply the megaideal-based version of the algebraic method to find the contact-symmetry (pseudo)group of a partial differential equation. It is shown that the contact-symmetry pseudogroup of the dispersionless Nizhnik equation coincides with the first prolongation of its point-symmetry pseudogroup. We check whether the subalgebras of the maximal Lie invariance algebra of the dispersionless Nizhnik equation that naturally arise in the course of the above computations define the diffeomorphisms stabilizing this algebra or its first prolongation. In addition, we construct all the third-order partial differential equations in three independent variables that admit the same Lie invariance algebra. We also find a set of geometric properties of the dispersionless Nizhnik equation that exhaustively defines it.Comment: 28 pages, minor correction

Effect of self-seismic oscillations of the foundation on the readout of a ballistic gravimeter with an induction-dynamic catapult

A mathematical model is developed for the vertical oscillations produced in the base–foundation system of a laser ballistic gravimeter with an induction-dynamic catapult and a symmetric configuration for measuring the acceleration of gravity. Analytic expressions are obtained for the force pulse acting on the foundation during acceleration of the test body that describe the oscillations in the mechanical system of the ballistic laser gravimeter. The effects of the measurement duration and the damping coefficient of the foundation on the results of measurements of the acceleration of gravity are studied