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The article discusses one of the most widely used distribution laws for reliability analysis – Weibull distribution. It describes a wide range of processes for all stages of the life cycle of technical objects, including yield stress of steel distribution and failures in the reliability theory regarding the wide range of technical objects (e.g., metal cutting tools, bearings, compressors, and wheels). A significant number of works are devoted to evaluating distribution law parameters based on empirical data in search of the most precise one, ignoring the probabilistic character of the parameters themselves. Parameters may have a relatively wide confidence range, which can be considered the parameter estimation error compared to biases of parameters estimated by different methods. Moreover, many approaches should be used for certain selection volumes, including comprehensive calculating procedures. Instead, this paper suggested and statistically confirmed a universal simplified approach. It demands a minimal set of data and connects the shape and scale parameters of the Weibull distribution with the variation coefficient as one of the leading statistical characteristics. This approach does not demand variational sequence arrangement. Nevertheless, it is supposed to be quite efficient for the engineering practice of reliability analysis. The adequacy of the results was confirmed using generated selections analysis and experimental data on cutting tool reliability. Within the achieved results, it was also demonstrated that the variation coefficient reflects not only selection stability and variable volatility degree, which are its main aim, but the cause of failure as well.

Mid-IR lasing of a Tb3+-doped chalcogenide fiber has been demonstrated. Pumping was performed by a CW Er:ZBLAN laser, emitting at a wavelength of 2.795 µm. Fiber length optimization has made it possible to obtain output power up to 2 mW in the wavelength range of 5.2–5.3 µm at 1.8% slope efficiency and room temperature. [ABSTRACT FROM AUTHOR]

We report an investigation of a semiconductor disk laser (SDL) based on an InGaP/AlGaInP heterostructure emitting at a wavelength near 640 nm under in-well pumping by a pulsed rhodamine 6G dye laser with an emission wavelength of 601 nm. Use is made of structures with 25 quantum wells arranged in depth with a period of 193 nm. In a structure with a built-in Bragg mirror, a power of 3.5 W is reached at a wavelength of 642 nm with a slope efficiency of 7% with respect to the absorbed pump power. The achieved second harmonic power at a wavelength of 321 nm is approximately 30% of the maximum SDL power at the fundamental frequency. Under pumping above 250 W, the structure is destroyed due to strong adiabatic heating of the GaAs growth substrate. In a structure with a deposited broadband dielectric mirror, it is possible to reduce the adiabatic heating factor, implement double-pass pumping, and, accordingly, increase the supplied pump power. This makes it possible to obtain a pulse power of higher than 70 W at a wavelength of 645.5 nm with a slope efficiency of over 17%. [ABSTRACT FROM AUTHOR]

The ultrashort pulse laser based on a Cr2+:ZnSe monocrystal has been presented, utilizing carbon nanotubes as a saturable absorber. The saturable absorber consists of a sapphire substrate onto which nanotubes are deposited. Such a structure enables the realization of an element capable of simultaneously functioning as a saturable absorber and as a compensator for intracavity dispersion, as the substrate thickness can be chosen during fabrication, allowing for the adjustment of the introduced dispersion. Several laser resonator configurations are discussed, demonstrating the possibility of generating ultrashort laser pulses with durations down to 160 fs, a repetition rate of 135 MHz, an output power of 17 mW, and a central wavelength of 2.45 µm. [ABSTRACT FROM AUTHOR]

We report a study of a semiconductor disk laser (SDL) based on the AlxGa1 –xAs/AlyGa1 –yAs heterostructure, emitting at a wavelength near 780 nm, pumped by a pulsed dye laser with emission wavelengths of 601 and 656 nm. Use is made of a structure with a built-in Bragg mirror and 10 quantum wells (QWs) arranged in depth with a period equal to half the wavelength of laser radiation in the structure. Under pumping with λ = 601 nm, a power of 9.3 W is reached at a wavelength of 782 nm with a differential efficiency of 12%. Under pumping with λ = 656 nm, the differential efficiency remains almost unchanged, although the pump absorption in depth is more uniform. These results are compared with those obtained previously under pumping by lasers with wavelengths of 450 and 532 nm, as well as under electron-beam pumping. It is concluded that the distribution of nonequilibrium carriers over the QW is largely determined by their diffusion length, which is approximately 1 μm in this structure. [ABSTRACT FROM AUTHOR]

According to modern trends, the power grids with distributed generation will have an open system architecture. It means that active consumers, owners of distributed power units, including mobile units, must have free access to the grid, like when using internet, so it is necessary to have plug and play technologies. Thanks to them, the system will be able to identify the unit type and the unit parameters. Therefore, the main aim of research, described in the paper, was to develop and research a new method of electric parameters identification of synchronous generator. The main feature of the proposed method is that parameter identification is performed while the generator to the grid, so it fits in the technological process of operation of the machine and does not influence on the connection time of the machine. For the implementation of the method, it is not necessary to create dangerous operation modes for the machine or to have additional expensive equipment and it can be used for salient pole machines and round rotor machines. The parameter identification accuracy can be achieved by more accurate account of electromechanical transient process, and making of overdetermined system with many more numbers of equations. Parameter identification will be made with each generator connection to the grid. Comparing data obtained from each connection, the middle values can be find by numerical method, and thus, each subsequent identification will accurate the machine parameters.

The paper presents the studies of the Khuvsgul earthquake on January 11, 2021 at 21:32 UTC (January 12, 2021 at 05:32 local time), MW = 6.7, ML = 6.9, and the seismicity structure in the aftershock period for the Altai-Sayan mountain region and the Baikal rift zone, where the epicenter of this earthquake was located. Two faults are seismically activated, diverging from the southern end of the aftershock area at an acute angle: one in the northeast and one in the northwest direction, as well as transverse faults between them. According to the epicenter position and studies of the source area by other authors, the main event corresponds to the northeastern fault, and large aftershocks occurred at the junction of the northwestern fault with transverse faults feathering from the east. The main event was immediately followed by a series of large aftershocks, the strongest of which occurred on March 31, 2021 with ML = 6.2 and on May 3, 2021 with ML = 6.4. Spatial changes in the seismic regime of the aftershock region led to the predominant activity of its southern end. The junction area of the collisional structures of the Altai–Sayan folded zone and the rift structures of the Baikal depressions system is distinguished in seismicity as a block structure with increased seismicity near the block boundaries. First of all, these are the Tuva-Mongolian block and the eastern part of the Sayano-Tuva block. After the Khuvsgul earthquake of 2021, a block structure with the activation of the epicentral zones of the 1991 Busingol earthquake, the 2011–2012 Tuva earthquakes, and other structures seismically active until 2021 has increased seismic activity. It is proved that the 2014 Khuvsgul earthquake occurred under the basin of the same name and is associated with other faults than the 2021 earthquake and is not a direct precursor of the 2021–2022 activation. [ABSTRACT FROM AUTHOR]