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The possibility of replacing, blowing argon into flux paste, when welding joints with free formation, where it is technically impossible to use other techniques and methods of welding, providing stable formation with minimum geometric parameters of the back bead, is shown.

The surface of two dental implant systems, “Nobel Biocare” and “Alpha BiO”, and metal-containing nanoparticles, isolated from the tissues surrounding dental implants, has been investigated. The implant surface structure, the elemental and phase composition of particles, and their arrangement in the granulation tissue have been studied by X-ray tomography, transmission and scanning electron microscopy, z-contrast scanning transmission microscopy, electron diffraction, and energy-dispersive mapping, using microscopes Quanta 200-3D, FEI Тechnai Osiris at an accelerating voltage of 200 kV, and an X-ray microtomograph TOMAC. An analysis of the relief indicates that the emission of nanoparticles from the “Alpha BiO” implant surface to the adjacent tissues is more likely than from the “Nobel Biocare” implant surface. The particles of micrometer and submicrometer sizes of “Nobel Biocare” implants are found to consist mainly of titanium dioxide of both modifications, rutile and anatase, whereas in the case of “Alpha BiO” implants, along with titanium dioxide and titanium nitride, there are aluminum oxides in the particle composition. The elemental composition of nanoparticles is more diverse; it includes Fe, Ca, Na, Cl, S, Si, P, etc. It is revealed that microbial contamination does not always play the leading role in the suppression of previously obtained osteointegration.

The problem of the generation of cavitation self-oscillations in a liquid flow in a pipe with two resistances is considered. The first resistance is a cavitator, behind which there is an artificial ventilated cavity, where the mean pressure is greater than the atmospheric pressure, while the liquid and gas outflow into the atmosphere takes place through the second resistance. Investigations show that the self-oscillation frequencies are chiefly determined by the cavity properties and the conditions of the outflow into the atmosphere. The generation of different self-oscillation modes is directly associated with the number of waves formed along the cavity length. It is shown that the pressure pipeline properties and the cavity volume have an effect on the cavitation self-oscillation mode (up to four frequency modes can be observable at the same geometry and hydraulic flow parameters). The question arises of whether the self-oscillations can be used for generating pulsed jets at the outlet. It seems that it is the first mode regime that is most suitable for producing the pulsed jets, since in this case the pressure fluctuations in the cavity are maximum. Using the exponential Voitsekhovskii nozzle the regimes, in which an intermittent jet flow of the liquid is realized at the outlet, are experimentally obtained.

The study revealed that the application of flux paste to the back side of the welded joint during welding of low-alloyed steels provides control over the sizes of the root and its defect-free formation. It was found that the back bead height of the root welded with flux paste is 1.5 to 3 times less than that of the root welded with the same welding variables without flux paste.

Physical modeling of a ventilated cavity with a negative cavitation number has shown that at the same flow rate and head parameters different cavitation-induced self-oscillation patterns can be realized. The generation of these patterns depends on the feeding pipeline parameters. The high-speed videofilming shows that the physics of the process are the same in different frequency regimes, the wave propagation velocity in the jet flow is mainly determined by the cavitation number, and the difference between self-oscillation patterns is characterized by the number of the waves along the cavity length. A method of estimating the self-oscillation frequencies from the given flow geometry and the cavitation number is proposed.

Magnesium alloys are of great interest to the modern aircraft industry owing to rather high specific strength values. However, the problem of corrosion prevention is not still solved. Plasma electrolytic oxidation is the most promising protective technique for magnesium alloys. In this paper, improving the protective properties of plasma-sprayed electrolytic coating on ML5 casting magnesium alloy via optimization of the current regime is considered. The coatings formed at alternating pulses of the polarizing current are investigated by the electrochemical method. Formation of plasma-sprayed electrolytic coating on ML5 magnesium alloy is theoretically described.

An instrument for determining the nonlinear thermal properties of rocks under natural conditions is proposed. Software is developed for processing the temperature readings, obtained from the instrument sensors, using mainly the theory of the solution of inverse problems for a parabolic-type nonlinear equation. Practical examples of the determination of the nonlinear thermal properties of some materials are presented.

The conductivity tensor of a layered conductor with the Dirac-type energy spectrum of charge carriers placed in a quantizing magnetic field under the condition of normal skin-effect is investigated using the Method: of quantum kinetic equation. It is shown that under the cyclotron resonance conditions there appear high-temperature quantum oscillations of conductivity, which are weakly sensitive to thermal broadening of the Fermi level. We present the expressions for the classical and high-temperature contributions to the conductivity tensor which determine the conductivity in the range of not too low temperatures where the Shubnikov–de Haas oscillations are vanishing. The authors thank the CONCYTEC Fund and the National Council for Science and Technology of Peru for financial support.

A one-dimensional TVD correction scheme is described, which can be successfully applied not only in 1D calculations, but also in 2D - 3D modeling [1-2]. The advantage of the proposed scheme is the lack of solving matrix equations. The implementation of the scheme in conjunction with the large particle method was tested on the problems of arbitrary discontinuity breakup and strong point explosion. The modeling of acetylene combustion in a shock tube and its transition to detonation was performed depending on the conditions set on the surface of the tube, and the parameters of the problem.

The results of an experimental investigation of the self-oscillation regimes of liquid jet outflow into a plane channel with air injection in its dead end are presented. The effect of the volume of the cavity, or the air cushion, and its thickness (or channel width) on the flow is studied on a wide range of the gas injection rate and the liquid outflow velocity. The self-oscillation flow regimes are realized at a constant pressure of water in the supply tank and a constant mass flow rate of the air injected into the cushion. With increase in the air injection rate the self-oscillation regime realized at lower injection intensities is replaced by a higher-frequency regime. High-speed videofilming shows that the difference from the low-frequency regime consists in the absence of the direct interaction between the out flowing jet and the channel wall. It is found that in both low-frequency and high-frequency regimes the self-oscillation frequency and amplitude are independent of the cushion thickness but the moment of the regime changeover is determined by this parameter. It is established that there exists a threshold value of the cavity volume, behind which the low-frequency regime does not occur at any air injection rates.

The results of an experimental investigation of self-oscillatory jet outflow into a plane channel with air injection in its dead-ended part are presented. It is found that at fixed channel geometry and water supply system the main flow parameters depend on the air injection rate and the relative cavity volume. It is shown that with increase in the gas injection at a fixed cavity volume the self-oscillation intensity monotonically increases and the oscillations considerably change in nature, whereas the Strouhal number varies only slightly. At a fixed air injection coefficient the self-oscillation amplitude decreases with increase in the cavity volume and the self-oscillations stop at a certain threshold value. The flow pattern evolution with increase in the injection coefficient is studied in detail using high-speed filming. The developed surge flow pattern is described in detail.

The series of amorphous ferromagnetic glass-coated microwires of composition Co69Fe4Cr4Si12B11, manufactured by Taylor-Ulitovsky technique, was investigated. The series consisted of six types microwires fabricated under different technological conditions. The metallic nucleus and glass coating diameters of microwires ranged within 11-20 μm and 26-35 μm, respectively. Investigation of the magnetic propertiesof microwires was carried out using induction and the small-angle magnetization rotation techniques. The anisotropy field, the magnetostriction constant and the average value of the quenching stresses are estimated for all types of microwires. Based on the experimental data obtained, influence of technological parameters onthe microwire’s magnetic properties was investigated. Keywords: Amorphous ferromagnetic microwire, cobalt alloy, magnetic measurements, magnetostriction, internal stresses

The longitudinal electrical conductivity of a thin conducting film in the presence of electron and hole groups of charge carriers is calculated by the Kubo method under conditions such that the carrier motion is spatially quantized. It is shown that in the case of elastic scattering on impurities there are quantum high-temperature oscillations of the conductivity which are relatively insensitive to the temperature smearing of the Fermi level.

The processes of population of excited levels of a krypton atomic ion via electron-stimulated desorption are studied. The radiation yield per single exciting electron in the corresponding krypton spectral lines is measured by the optical time-of-flight mass spectrometric method. The efficiency of the processes studied is compared with that of electron-impact excitation of the same levels.

The hydrodynamics of a ventilated cavity with a negative cavitation number are studied experimentally. The pressure distributions in the closure region of the cavity, the “flow-pressure head” characteristics, and the cavitation number (or pressure coefficient) as a function of the gas-injection rate are measured. The two-phase flow pattern near the Taylor-unstable cavity boundary is investigated using spark photography and videophotography. The results are compared with the known theoretical and numerical data. It is shown that in the near-critical flow regime the basic mechanism of gas entrainment from the cavity is connected with the Rayleigh-Taylor instability. On this basis, the gas entrainment coefficient of the cavity is found to be proportional to the curvature of the cavity boundary and the square of the boundary length.

The population kinetics of the energy levels of atoms excited in a tube with an electron beam is studied. A method of separating the contributions made by direct electron impact and by secondary processes to the population of the levels considered is proposed.

The experimental investigation of the laws of friction at high relative speeds involves difficulties associated with ensuring that the experimental apparatus provides a sufficiently long slide path. In this paper an automated experimental apparatus is described. This makes it possible to study in a compact fashion the laws of fluid friction at speeds of approximately 150 m/sec under widely variable load and external pressure. The experimental relations for the friction moment coefficient for water in the laminar and turbulent regimes are compared with calculations made by the integral relations method of boundary layer theory. The results of series of experimental and theoretical studies of high-speed friction against ice in the developed fusion layer regime are presented. Questions of the effectiveness of using polymer additives to reduce friction at high speeds are considered. The experimental method described can be used to investigate friction problems involving pastes, emulsions, and other rheologically complex continuous media, in which under conditions of high velocity gradients (strain rates) qualitatively new effects are to be expected.

Investigation of time-of-flight spectra of excited krypton molecular ions observed under electron-beam bombardment of excitation tube electrodes is continued. Particular attention is focused on a study of the profile of the light signal produced in the dissociation of the molecular ions. An analysis of the light signal profile provides information on the processes involved in the formation and destruction of molecular ions. A model developed for these processes permitted calculation of the light signal profile. A comparison is made with experimental data on the spectral lines of krypton atoms and ions, whose excitation is caused by the destruction of the molecular ions.

The results of investigating hot-fluid cavitating flow in a pipe with a local contraction are presented for a broad temperature interval (water from cold to near-boiling) and various cavitation regimes — from the initial (bubble) to the supercavitation regime. Experimental relations for the amplitudes of the fluctuations and the fundamental frequencies are presented for a Venturi tube with various diffusers and for diaphragms of various dimensions. A flow model which takes into account the fluctuations of the vapor pressure in the cavity and, moreover liquid-cavity mass transfer effects is presented. It is shown that for a given flow geometry there is a limiting Jakob number below which the self-oscillating regime is impossible at any cavitation numbers.

Hot hole p-Ge masers and lasers operating in millimiter and far IR ranges (up to 100 μm) belong to a new group of tunable semiconductor generators discovered in the early ’80s(1). They are proposed to be used in solid state spectroscopy since their discovery. These generators may be preferable to other sources of the same frequency since it is possible to set the sourcer of radiation near by the sample and provide ultralow background radiation conditions in low temperature experiments.The performance of the tunable spectrometer with hote hole p-Ge emitter is demostrated by its application to studies of cyclotron resonance in strained multi-quantum-well (MQW) heterostructures (HS) Ge/Ge0.87Si0 13 and investigations of shallow impurities in these heterostructures.

1. The investigated titanium alloy, having high cyclic strength properties under steady loading, displays considerable scatter of fatigue testing results. 2. The distribution of the life logarithms can be approximated by a normal law only at high levels of stress, while the distribution of limited fatigue limits is well described by this law for a wide range of lives. 3. Prior loading below the fatigue limit increases somewhat the secondary fatigue limit, but the susceptibility of this titanium alloy to coaxing is not significant.

1. The apparatus described in this article makes it possible to obtain sufficiently accurate data on the strength of bimetal joints. 2. Electro-slag melting of grade M1 copper on steel St. 3 under correct conditions and with the aid of a suitable flux ensures the formation of faultless joints whose strength is approximately equal to that of annealed copper.

1. Values have been determined for shrinkage strains in multilayer glass fiber laminate plates type STKT-NA based on phenolformaldehyde binder type LBS-4 with dry and wet moulding methods, and reasons have been explained for their uneven distribution in each layer through the plate thickness. 2. With the wet method of plate moulding maximum values of shrinkage strains corresponding to the outer layer are greater by a factor of 1.5 than those with the dry moulding method, but the minimum strains corresponding to the middle layers are similar in value for both methods, and they may be assumed to be natural shrinkage strains for this material.

1. The use of a design In the form of a thin additional ring on the rim of a disk flywheel (type II) lowers the load-carrying capacity of the latter. 2. The use of a perforated disk (type IV) as a flywheel to reduce or equalize the stresses is inexpedient, since the stored kinetic energy is reduced more than the stresses. Theoretical determination of the actual stress-strain state of shaped disks made of anisotropic material requires the use of methods which consider the effect of axial anisotropy. 3. Henceforth in designing energy storage devices, a disk flywheel of type V should be considered to have promise.

This paper reports on an investigation of the spectral and polarizational characteristics of the luminescence of quartz glasses for the purpose of determining the nature of the elementary emitters accounting for absorption and luminescence and for the purpose of clarifying the structural details of the color centers developing in quartz glasses. The KI quartz glasses were studied with a natural concentration of germanium impurities of about 10/sup -3/ mass %; the work was also concerned with pure vitreous silica doped with germanium. The data indicate that the degree of polarization of identical luminescence bands is practically the same in the various samples and that the polarization patterns for the particular emission bands do not change in the three samples.

The purpose of the present study is to obtain a rather simple solution for this problem which is convenient for practical engineering computations, and to evaluate its discrepancy with the accurate solution, and also its correspondence with experimental data on the limiting bearing capacity for two flywheel models of various composite materials.

This paper attempts to optimize the geometric parameters of spoked flywheels made of composite materials from the point of view of maximum energy capacity. A cross section of the rim of the flywheel is shown, the area of which is expressed in a formula.