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We conducted a study on fatigue in flat samples of the VT3-1 titanium alloy using “soft” cyclic beam bending tests. For this purpose, we developed an innovative electromagnetic test bench. The test bench's electromechanical system induces mechanical vibrations at a frequency that matches the eigenfrequency of the sample, ensuring that the cyclic load frequency remains constant. The electromagnetic force bends the sample while the elastic force unbends it, producing a quasi-sinusoidal cyclic load. Through our investigation, we determined the impact of this cyclic loading on both cyclic strength and durability. Our findings indicate that the VT3-1 titanium alloy possesses high resistance to fatigue and an endurance limit. Furthermore, we observed a low variability of the experimental fatigue resistance in relation to the approximating fatigue curve, suggesting the alloy has high structural stability. This finding indicates that the VT3-1 titanium alloy possesses high structural stability. To assess eigenfrequency stability, we subjected the alloy samples to cyclic tests, interrupting them at a reference number of 50 million cycles to evaluate changes in eigenfrequencies and stability under loads close to the fatigue limit. The results showed that the titanium alloy has a high level of eigenfrequency stability. Interruptions in cyclic tests resulted in jump-like increases in eigenfrequencies, which was not observed in continuous tests. Nevertheless, the total eigenfrequency deviations from the initial value at the end of the tests were similar in both cases

This article presents experimental results of resistance against fracture upon static tension of cast aluminum matrix composites based on aluminum with various content of Al2O3 strengthening phase. The cast aluminum matrix composite materials were produced by the technology based on burnout of aluminum melt upon interaction with oxygen. Two batches of ingots with various content of solid phase were smelted for tests of static strength. The average particle size of strengthening phase of predominantly prismatic morphology was 60–80 μm, and their content varied from 15 to 25 %. The fracture surfaces obtained upon static uniaxial tension of the considered samples were studied on the samples destroyed at maximum stress. The fracture surfaces were analyzed using an optical microscope with expanded options due to improved long-focus system and digital processing of images based on unique procedure of 3D structure analysis. For indepth analysis of characteristic fracture region a scanning electron microscope was used equipped with energy and wavelength dispersive elemental analyzers. It was established in the studies that in the samples with lower content of dispersed phase, the fracture is characterized by mixed heterogeneous in terms of macrogeometry pattern. This can be interpreted as dry fibrous fracture with visible crystalline pimples and breakaways. With an increase in the solid phase, a mixed, sufficiently homogenous in terms of macrogeometry, fracture pattern of fanlike fibrous structure can be observed. Crystalline pimples were also detected of a different fracture surface area, as well as breakaways of other geometrical sizes. The features of changes in the relief of fracture surface and the fracture mechanisms of the obtained composites have been detected and described.

This article describes the methods used in the multidisciplinary study, preservation, and museumization of a wooden structure from a grave under the Early Iron Age kurgan 5 at Pazyryk in the Altai. The structure consisted of two chambers with additional elements on top. Its technological analysis was carried out during the excavations, and the structure was subjected to special treatment after extraction. At the side the mound, the outer cribwork was reconstructed; its details and technologies were evaluated. The stages in the field conservation of all artifacts are described. The museumization of the outer cribwork at the Anokhin National Museum of the Republic of Altai is outlined.

The paper presents the results of a study on the durability of cutting ceramics: a replaceable polyhedral plate developed at NSTU and cutting ceramics WOK-60 when processing hardened steel blanks made of 40X (45HRC) steel. As a result of the tests carried out, it was found that with the use of cutting modes developed at KNAU, the durability of SMP from cutting ceramics created at NSTU is more than 1.7 times higher than the performance of plates based on the WOK-60 material. At the same time, the roughness of the treated surface of the work piece was Ra = 0.35 ? 0.05 microns when using SMP from the developed ceramics Ra = 0.55 ? 0.05 microns when using WOK-60 plates. The stages of destruction of cutting ceramic plates are revealed, taking into account the hierarchy of structural scales.

We demonstrate theoretically cascaded fourth and second harmonics generation in a periodically oriented nonlinear crystal with a half-order of the periodical orientation. We consider a cascaded process in which four photons of the fundamental harmonic are initially converted into an intermediate photon of the fourth harmonic, which parametrically decays at the second stage into two photons of the second harmonic. We show that fractional phase matching can be achieved by using an asymmetric periodically poled grating. To describe the propagation and transformation of light inside a nonlinear crystal, the quantum spatial Heisenberg equations have been applied, using which the average numbers of photons of the fourth and second harmonics have been calculated as functions of the nonlinear crystal length.

Near- and far-fields of quantum-cascade lasers emitting in the spectral range near 8 μm have been studied. For all laser samples with a ridge width of 20 and 50 μm, lasing on the fundamental waveguide mode with a divergence of ~50° was observed for all laser samples with a ridge width of 20 and 50 μm along the “fast” axis. Along the “slow” axis, a multimode lasing and a competition between the fundamental and higher waveguide modes, which is manifested for lasers with a ridge width of 50 μm in an increase in the emission divergence from ~10° near the threshold to >50° when the lasing threshold is exceeded by a factor of 2–3. The divergence along the “slow” axis for lasers with ridge width of 22 μm remained invariable in the whole range of pumping currents and equaled ~50°. That there is a substantial contribution from the fundamental mode to the total emission intensity of quantum-cascade lasers, which is apparent from the far-field intensity distribution pattern, cannot be established exclusively on the basis of results obtained in near-field measurements.

Combination of phosphorus-free molecular beam epitaxy (MBE) with metal-organic chemical vapor deposition (MOCVD) enabled record-high power quantum-cascade lasers (QCLs) for 8µm spectral region with total output power of over 16W under pulsed pumping.

A method for generation of droplet quasi-Bessel beams using a conical lens with a rounded tip is demonstrated. The study of the longitudinal distribution of the intensity of the obtained quasi-Bessel beam showed that, due to the interference of two wavefronts that occurred as the generating beam passed through the rounded axicon, periodical intensity pulsations that looked like “drops” of light occurred in the resulting beam. These light beams can be used for micromanipulation of biological objects and in super-resolution microscopy. The application of an axicon with a rounded tip for generation of a droplet beam allows considerable simplification and miniaturization of the experimental setup, which paves the way for multiple practical applications.

—In this paper, we present studies of the characteristics of quantum-cascade lasers with a generation wavelength in the region of 8 μm at high temperatures of up to + 65°C. The characteristic temperatures of the temperature dependences of the threshold current and the differential efficiency are determined. Spectral studies showed the presence of two generation lines with a short wavelength of ~7800 nm and a long-wave wavelength of ~8100 nm. The observed competition between the short-wave and long-wave generation lines leads to a nonmonotonic character of the dependence of the radiation intensity on the pump current.

We demonstrate generation of "droplet" Bessel beams using semiconductor laser and an axicon with rounded tip. Interference of Bessel and Gaussian wave fronts leads to cancellation of side lobes of Bessel beam.

We theoretically demonstrate cascaded fourth and second harmonic generation in a periodically-poled nonlinear crystal with a fractional order of phase-matching period.

We derive the theory of the conical refraction for partially spatially coherent light using the Gaussian Schell-model. The effect of narrowing of the CR ring width due to reducing the coherence degree is predicted.

We demonstrate that the conical refraction of the input elegant Laguerre–Gaussian beams can be effectively described through generalized Bessel–Gaussian light beams. We performed numerical simulations and show good agreement between the exact solution and our proposed Bessel–Gaussian approximation model. Physical clarity of the proposed model has allowed us to explain the transition of the classical double-ring pattern of conical refraction in the Lloyd plane into a multi-ring one and predict new phenomenon such as the Raman spot shift and dependence of the conical refraction ring radius on the value of the orbital angular momentum.

Optimal allocation of computing systems resources is an important task in the context of constantly growing needs and limited financial capabilities of users. Cloud technologies help reduce the cost of information processing and storing while keeping in mind the requirements in security and reliability. The multi-agent systems usage allows to correctly transfer the decision-making functions for a specific case from the upper level of system control to the lower levels of executive processes. This approach allows increasing the control flexibility and improving the speed of decision-making.

The article describes a study into the large-scale effect and properties of surface layers of solids in case of the Al–Mg system (AMg2) aluminum alloy. It demonstrates the dependence of surface layer properties on the absolute sizes of bodies. The conclusions obtained can be extended to studying the influence of different shapes of solids on their surface and linear bulk properties. New technology development and technological advance constantly toughen metal consumption requirements of engineering devices thus making it rather difficult to avoid fatigue striations and cracks forming in critical parts. In certain cases they may form at the earliest stages of operation, i.e. parts run with cracks most of their life cycle. Therefore, comprehensive assessment of their performance and life requires reliable data on the evolution of cyclic strength and durability parameters, and maximum information on the process of damage accumulation at all stages of fatigue loading: stages of crack origin and development leading to structural failure. Therefore, the need to improve the methods of fatigue testing and failure pattern detection is one of the most relevant problems of technical advance. It is established that the difference in deformation at a surface leads to changes in work-hardenability that involves changes in surface damageability and strength performance of samples. An approach to the large-scale effect as a phenomenon is considered from the perspective of the difference in surface layer plastic deformation for samples of different absolute sizes.

Lasing of quantum cascade lasers is demonstrated at a radiation wavelength of 8100 nm at room temperature. Analysis of oscillograms of optical pulses is used to determine dependence of mean and peak radiation intensities on current. A delay of turn-on of quantum cascade lasers is experimentally estimated at a level of two times higher than the lasing threshold to be greater than theoretically estimated delay by several orders of magnitude.

The paper presents results of the processing parameter effect, i.e. the magnitude of cutting speed and cutting force component feed in turning of hardened steel grades 45, 40X, 50X, CVH hardness 45..50 HRC with the help of the tool equipped with cutting ceramics EQA-60. The laboratory bench has been used for experimental studies, including a screw-cutting lathe 1K625 and the measuring device STD.201-2. The presence of the cutting speed range providing the minimum magnitude of the cutting force components is established.

In this paper, we studied Bessel beams obtained using an axicon with a substantially rounded apex. A study of the interference of two wave fronts arising from the refraction of the generating beam on an imperfect axicon showed that rounding its apex results in periodic pulsations of intensity in the resultant quasi-Bessel beam resembling visually the “droplets” of light. The proposed mathematical model demonstrates excellent agreement with the experiment.

Results of an investigation of quantum cascade lasers of the 8-μm spectral range generating dual-frequency radiation at room temperature are presented. The dependences of radiation intensity for two lines of laser generation obtained as a result of investigation of the generation spectra revealed the presence of saturation and decay of the long-wavelength line of generation and linear growth of the intensity of the short-wavelength one. Based on analysis of the obtained data, a mechanism of the dual-frequency generation in the studied QCL samples is proposed Generation.

We report on conical refraction (CR) with low-coherence light sources, such as light-emitting diodes and decoherentized HeNe laser radiation, and demonstrate different CR patterns. In our experiments, a variation of the pinhole sizes from 25 to 100 µm and the distances to pinhole from 50 to 5 cm reduced spatial coherence of radiation that resulted in the disappearance of the dark Poggendorff's ring in the Lloyd's plane. This is attributed to the interference nature of the Lloyd's distribution and found to be in excellent agreement with the paraxial dual-cone model of conical refraction.

Currently, the task of predicting the accident rate of pipelines is relevant. To solve this problem, it is proposed to use the neural networks. Calculations using neural networks located in cloud services are not secure for the transmitted data. It is proposed to use a model of information security based on homomorphic encryption.

Vertical-cavity surface-emitting lasers with an active region based on submonolayer InGaAs quantum dots with an oxide-aperture diameter of ~1 μm have been studied. It is established that peaking of the output optical pulses to 50–100 ps can be achieved by pumping these lasers with 10–100 ns electric pulses at a repetition frequency of 10–100 kHz.

We study the propagation of Bessel beam, generated by an axicon with rounded tip, and find that such a defect may lead to the formation of the axially discontinuous central lobe with the structure similar to the ‘droplets’ of light.

We analyze, experimentally and theoretically, the pulsed generation in quantum well laser simultaneously operating from the ground (GS) and the excited (ES) states. We find that an exponential increase in the output power at the GS laser turn-on noticeably changes its timescale when the laser turns on at the ES wavelength, indicating extremely fast dynamical interaction between the lasing states.

We report on conical refraction (CR) experiments with low-coherent light sources such as light-emitting diodes (LEDs) that demonstrated different CR patterns. The change of a pinhole size from 25 to 100 μm reduced the spatial coherence of the LED radiation and resulted in the disappearance of the dark Poggendorf ring in the Lloyd's plane. This is attributed to the interference nature of the Lloyd's distribution and is found to be in excellent agreement with the paraxial dual-cone model of CR.

We report on a new experimental setup for the investigation of proton induced reactions on exotic nuclei in inverse kinematics. It was installed and successfully used in the scattering study of intermediate-energy protons ( ∼ 700 MeV / u ) on neutron-rich nuclei 6,8He produced with the FRagment Separator (FRS) at the GSI facility, Darmstadt. A new pure liquid-hydrogen target was successfully adapted allowing to obtain low-background data as compared to commonly used (CH2)n targets. Absolute differential cross-sections for elastic (p,6,8He) scattering were obtained at angles corresponding to 0.05 ⩽ | t | ⩽ 0.125 (GeV/c)2 of the four-momentum transfer squared (−t) leading to the first diffraction minimum and spanning more than two orders of magnitude. They complement an earlier measurement at smaller angles 0.0025 ⩽ | t | ⩽ 0.05 (GeV/c)2 performed at the same energy with an active target. Both data sets agree well in the overlap region t ≈ 0.05 (GeV/c)2 and enable a refined and comparative study of the radial distribution of the nuclear matter density.

This paper presents the results of experimental investigations of ( p , p n ) , ( p , p α ) and ( p , p 6 He) reactions with relativistic 6 He and 8 He beams impinging on a hydrogen target. Information on the structure of extremely neutron-rich nuclei was obtained by using the unique characteristic of quasi-free scattering processes and inverse kinematics. For the first time, momentum distributions of complex clusters inside 6 He and 8 He were measured. Spectroscopic factors for valence neutrons, α - and 6 He clusters were deduced from the experimental data. They demonstrate that the filling of the p 1 2 shell is the essential feature of the 8 He structure. It is shown that the 8 He cluster structure can be considered as a 6 He core plus two valence neutrons.

Semiexclusive measurements of the two-pion-production $p(\ensuremath{\alpha},{\ensuremath{\alpha}}^{'})p\ensuremath{\pi}\ensuremath{\pi}$ reaction have been carried out at an energy of ${E}_{\ensuremath{\alpha}}=4.2$ GeV at the Saturne-II (Saclay) accelerator with the SPES4-\ensuremath{\pi} installation. This reaction was investigated by simultaneous registration of the scattered \ensuremath{\alpha} particle and the secondary proton. The obtained results show that the two-pion production in inelastic \ensuremath{\alpha}-particle scattering on the proton at the energy of the experiment proceeds mainly through excitation in the target proton of the Roper resonance and its decay with emission of two pions in the isospin $I=0,S$-wave state.

The study of neutron-rich light nuclei near the drip line has attracted much attention as they exhibit a particular nuclear structure, namely an extended distribution of the valence neutrons surrounding a compact core. Recently the elastic proton scattering from 6,8He and 8,9,11Li at 700 MeV/u using an inverse kinematics was successfully measured at GSI [1,2]. A high-pressure hydrogen-filled ionization chamber was used as the target and a proton detector. The previous experiments were performed in the small range 0.002 ≤| t |≤ 0.05 (GeV/c)2 of the four-momentum transfer squared t and have yielded valuable information on the nuclear sizes and radial structure of nuclear matter density distributions with the aid of the Glauber multiple scattering theory. Recently, a novel experimental approach has been accomplished with the aim to deduce the differential p 6,8He cross sections in the t-range 0.05 ≤| t |≤ 0.25 (GeV/c)2 close to the expected first diffraction minimum.

Neutron-rich light nuclei near the neutron drip line have attracted much attention in recent years as they feature a particular nuclear structure, namely an extended distribution (so-called halo) of the valence neutrons surrounding a compact nuclear core. Elastic proton scattering is known as a suitable technique for exploring the nuclear matter distributions in the stable nuclei. It was successfully employed at GSI also for the radioactive nuclei 6,8He and 8,9,11Li [1–3]. The experimental technique of inverse kinematics was applied using radioactive beams with energies near 700 MeV/u. The elastic differential cross section for small-angle scattering (3° ≤ θCM ≤ 10°) was deduced from the data taken with the ionization chamber IKAR, as an active target, and a forward spectrometer. The method has been demonstrated to be very effective for obtaining valuable information on the nuclear matter distribution in the halo nuclei under investigation, such as 6He, 8He and 11Li. The previous measurements at small momentum transfer have been highly sensitive on the nuclear sizes and the radial distributions of the nuclear matter density. Recently, a novel experimental approach has been accomplished with the aim to deduce the differential p6,8He cross sections for larger angles (10≤ ± θCM ≤ 30°) that correspond to a higher momentum transfer which covers the region of the first diffraction minimum.

Absolute differential cross-sections for elastic p 6He and p 8He scattering were measured in inverse kinematics with secondary beams. In order to supplement data taken for small-angle scattering, differential cross-sections for higher momentum transfer were measured using liquid hydrogen target. Both data sets were analyzed together. They have permitted to deduce the radial shape of the nuclear matter distributions and the root-mean-square radii with the help of Glauber theory. In addition to a phenomenological analysis, used already in the previous work, a model-independent analysis with a help of a Sum-Of-Gaussians (SOG) method has been performed. The experimental p 6;8He elastic scattering cross-sections have also been compared with the predictions from various theoretical nuclear models.

We study nanosecond-scale dynamics and micrometer-scale lateral heating distribution in the quantum-cascade laser cavity under short-pulsed pumping. Detection of the material heating rate at 1s mK/ns is demonstrated.