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Using a tunable frequency stabilized CO₂ laser, the dependences of the unsaturated absorption coefficient in pure carbon dioxide on pressure were measured in the range 5-30 Torr, where line contours are described by the Voigt function. The absorption coefficients were measured at the center frequencies of R(8), R(22), R(34), P(22), and P(36) lines of the 10⁰0-00⁰1 transition in the temperature range 300-700 K. By means of the least squares method, the inverse problem is solved for the system of equations for absorption coefficients at different pressures in the temperature range under study. The self-broadening coefficient γ_CO2-CO2 and the probability of spontaneous emission A_ik are determined. A new formula is proposed for the dependence γ_CO2-CO2(T).

The filamentation conditions of a femtosecond laser pulse by its focusing in air are investigated experimentally and theoretically. A good agreement is observed between experimental and calculated data when neglecting the filament plasma. It is shown that at low numerical aperture (NA ≤ 2.15 x 10^-3), a Kerr nonlinearity plays a fundamental role in the formation, existence, and termination of a filament. At the initial stage, the Kerr effect leads to the beam self-focusing and emergence of the filament; at the final stage, to radiation defocusing and sharp decrease in its axial intensity due to the beam wave front distortions. In the case of aberration focusing, a spatial quasi-soliton is formed after a visible filament due to the balance between Kerr self-focusing and diffraction extending. The quasisoliton is a source of the directional white supercontinuum.

The recovery of steady-state lasing in a CuBr laser operating in the train mode is studied with the use of a computer-based control system. The control system provided the repetitively-pulsed, train, and waiting modes. The dependences of the recovery time on the pause duration and the strorage capacitor are derived. The specific recover times are determined; their dependences on the pause duration in the train mode are analyzed. A time delay between the start of pump pulses and appearance of lasing pulses is shown. The time where lasing is absent increases in the pause duration range from 0.2 to 10 ms; this time is set to about 15 ms if a pause is equal or longer than 10 ms.

Results of research of the CuBr laser operating characteristics working in the double-pulse excitation mode with a pulse repetition rate of 50 Hz are given. The possibilities of increasing the efficiency by optimizing the parameters of the excitation pulse and matching with the impedance of the plasma formed by a dissociating pulse are considered. Laser efficiency of 2.56% at an excitation pulse with average power of 16 mW and time delay between dissociation and excitation pulses of 150 ms is received. Specific energy of the dissociating pulse reached 22 mJ/cm³; and of the exciting, 0.4 mJ/cm³. Introduction of saturation inductance into the excitation circuit provides for the maximum efficiency of 2.7%.

The generalized observations over hypocenters of the strongest mining-induced events have shown that this type of deformation occurs as movement along the existing faults. From the experimental evidence, transition of a section of a fault to meta-stable state goes with the decrease of its dynamic shearing rigidity. The alteration of the mechanical properties starts long before macroscopic movement of the fault surfaces is recorded. This effect is detectable using instruments and can be used as a foundation for a new approach to monitoring of induced earthquakes.

The authors use mathematical model of structurally inhomogeneous rocks to describe the property of rocks to accumulate and release potential elastic energy. The finite element algorithm and bundled software are developed to solve plane boundary-value geomechanical problems. The article presents calculations of deformation of self-stress rock specimens. It is shown that the deformation curve depends both on the elastoplastic properties of the specimens and on their natural self-balanced stresses. Depending on sign, the stresses can either increase or decrease the limit load under which the specimens fail.

This paper presents one strain gradient model of zonal disintegration of rock mass near deep level tunnel. The governing equations and boundary conditions of the model are established. Numerical methods (quasi-Newton method and shooting method) are adopted to solve the obtained fourth-order equilibrium equations with higher order boundary conditions in terms of displacement. The stress field in elastic and plastic zones is obtained. The effects of model parameters on stresses distribution in surrounding the tunnel rock mass are examined. The necessary conditions for the formation of zonal disintegration are elucidated.

The authors propose methods and means to monitor deformation and subsidence of ore crown under mining of open-pit bottom reserves by room-and-pillar system with solidifying backfill in Mir Mine, Alrosa. The article describes layout and data of geomechanical monitoring. The mechanism of ore subsidence at the lower boundary of the safety pillar is determined.

The calculations of stress state and failure of rock mass in the vicinity of longwall in a coal bed with the high gas content in Polysaevskaya Mine, SUEK-Kuzbass, are described. The effect of the mining depth and coalbed gas pressure on the geomechanical situation in the longwall is illustrated. The authors discuss scenarios of directed crack formation in front of the longwall.

Roughness of the main crack surface is an assessment criterion for stress state of geomaterials for the quantitative connection has been found between the crack roughness and stress state of geomaterials. Roughness reduces with an increase in the maximum normal stresses in the zone of failure (the area of the maximum shear stresses). Based on this regularity, the method has been developed to assess stresses using the crack surface roughness in geomaterials.