Abstract
In the present paper geometric locus of points (GLP) equidistant to a sphere and a plane is considered; the properties of the acquired surfaces are studied. Four possible cases of mutual ...location of a sphere and a plane are considered: the plane passing through the center of the sphere, the plane intersecting the sphere, the plane tangent to the sphere and the plane passing outside the sphere. GLP equidistant to a sphere and a plane constitutes two co-axial co-focused paraboloids of revolution. General properties of the acquired paraboloids were studied: the location of foci, vertices, axis and directing planes, distance between the sphere center and the vertices, the distance between the vertices. GLP for each case of mutual location of a plane and a sphere constitutes: in case one passes through the center of other, two co-axial co-focused oppositely directed paraboloids of revolution symmetrical with respect to the given plane; in case they intersect each other, two co-axial co-focused oppositely directed non-symmetrical paraboloids; in case they are tangent to each other, a paraboloid and a straight line passing through the tangency point; in case they have no common points, a pair of co-axial co-focused mutually directed paraboloids of revolution.
Abstract
The study focuses on the rheological behavior of a fluid based on a viscoelastic surfactant (Surfogel grade D, type 70-100, produced by JSC “Polyex”) in wide range of strain rates. This ...fluid is used for hydraulic fracturing technology as a proppant-carrying and proppant-retaining fluid in order to enhance oil recovery, including those with hard-to-recover oil and gas reserves. Quasi-static experiments to determine the values of the dynamic viscosity of the fluids under study were carried out using a falling ball viscometer (according to the Stokes method). The viscoelastic properties of fluids were studied using a Physica MCR501 rheometer with a cone-plane measuring system and an original rheometer with coaxial cylinders measuring system. The rheological properties of the fluid with the addition of proppant were studied using a Rheolab QS rheometer with a measuring system of the type of coaxial cylinders. The analysis of the rheological properties of fluids based on a viscoelastic surfactant has been carried out, and it has been established that fluids based on a viscoelastic surfactant has stable rheological properties over the entire range of strain rates, including fluid with proppant concentration up to 20%.
Microwave Radiometry (MWR) has the advantage that measurements of internal (i.e. deep) tissue temperature may be obtained non-invasively by measuring naturally emitted radiation in GHz range. The ...goal of the present study is to further the development of MWR for clinical application in assessment of patients with Low Back Pain (LBP). In particular, a protocol was developed in which MWR was used to measure internal temperature at the level of the spinous processes of the L1 to L5 vertebral bodies along median and left and right para-vertebral lines. The protocol was used to study 48 patients with clinically confirmed acute or sub-acute LBP and 27 Controls. Analysis revealed there to be a significant increase in deep tissue temperature with increasing pain severity as measured by using a Visual Analogue Scale (VAS) in patients with LBP (p < 0.05). In conclusion, MWR potentially allows for objective assessment of the magnitude of clinical symptoms in patients with LBP and shows promise for measuring pain severity.
The work is devoted to the development of a low-energy beam transport (LEBT) system for a high-current multicharged ion injector based on a superconducting ECR ion source. ECR ion sources are under ...development at the Joint Institute for Nuclear Research as part of a superheavy element research program. The LEBT includes a beam analysis system. The paper describes results of simulation of ion beam dynamics in the LEBT with the ideal field approximation for optic elements.
Abstract
The paper discusses the possibilities of constructing vectorized algorithms for solving problems of continuum mechanics, as well as the specialties of their software implementation in the ...MATLAB. These algorithms, on the one hand, widely use MATLAB functions designed to treat vectors and sparse matrixes, and on the other hand, are distinguished by high efficiency and counting speed.
The oxygen
K
-edge X-ray absorption spectra in EuBaCo
2
O
5.52 ± 0.02
and EuBaCo
2
O
5.24 ± 0.02
cobaltites are measured at temperatures of 300 and 440 K, which are below and above the ...metal–insulator transition temperature, respectively. According to these spectra, the substitution of Co
2+
ions for some Co
3+
ions with a decrease in the oxygen content in the chemical formula of a cobaltite and, hence, an increase in the relative fraction of CoO
5
pyramids with respect to the number of CoO
6
octahedra leads to an increase in the band gap by about 0.3 eV. The band structure of EuBaCo
2
O
5.5
is calculated using the method of linearized muffin-tin orbitals in the local density approximation taking into account the local Coulomb interaction. It is found that the low-spin state of Co
3+
ions occurs in CoO
6
octahedra in EuBaCo
2
O
5.5
, whereas the high-spin state of Co
3+
ions is typical of cobalt ions in pyramids.
The possibility of simplifying the mathematical model of aircraft motion, used to design an adaptive controller based on the principle of dynamic inversion, is considered. The effectiveness of a ...controller synthesized using such a simplified model is tested in standard piloting conditions and in the case of a pilot–aircraft system failure. To assess the accuracy of a tracking task for different variants of controller synthesis, flight simulator-based experiments were carried out.
An adaptive controller and a nonlinear rate limiter are presented in order to improve the flight safety of manually controlled reentry vehicles and supersonic transport (SST) aircraft. The adaptive ...controller is based on the principle of dynamic inversion. The calculation of the controller parameters corresponding to the aerodynamic coefficients of the vehicle was carried out by a proposed online identification procedure. The effectiveness of the adaptive controller was tested through a set of experiments performed using a ground-based simulator. The obtained results were used to estimate the probability of an accident due to pilot error for the basic Space Shuttle flight control system and for its improved version with the adaptive controller. It was found that using the adaptive controller causes high required rates of elevon deflection. Because of the actuator's rate limiting, this is a source of pilot-induced oscillations. To counteract these oscillations in the pilot-vehicle closed loop system, an adaptive nonlinear rate limiter is introduced. The effectiveness of using the adaptive prefilter for improving the flight safety and flying qualities of the Space Shuttle reentry vehicle and an SST was demonstrated in experiments involving a ground-based simulator.
•Real time dynamics identification ensures fast adaptive control.•Flight safety is considerably improved using adaptive flight control.•A well designed adaptive prefilter eliminates PIOs arising in case of low actuator rate limiting.•Adaptive flight control systems provide a considerable improvement of pilot-vehicle system performance.
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