ESTIMATED JUSTIFICATION OF TECHNICAL DECISION ON STRENGTHENING REINFORCED CONCRETE MACHINE HALL FLOOR

Introduction. In connection with the long-term operation of hydraulic structures (HPP), the installation of significant temporary loads, the presence of alternating effects on individual structural elements, it is possible to reduce the carrying capacity and strength of reinforced concrete structures. One of the most crucial elements is the reinforced concrete overlap of the machine hall, the work presents field and design studies, a proposal to strengthen the structures with external reinforcement. Materials and methods. The scientific and technical documentation was analyzed, instrumental studies and visual inspections of the state of the structures were carried out, and a 3D mathematical model was developed based on the finite element method. Multivariate non-linear computational studies of the actual stress-strain state of structures have been carried out. Results. Conducted visual and instrumental examination showed the presence of cracking on the lower edge of the reinforced concrete floor of the machine room. The simulation of the actual state of the structures has been carried out; according to the results of calculations, a schematic diagram of the gain of structures has been proposed. Conclusions. As a result of computational studies of stress-strain state, the occurrence of cracks on the lower edge of reinforced concrete floor of the machine hall was confirmed. When applying temporary technological loads to overlap, it is possible to achieve the yield strength of the reinforcement in certain zones. In order to ensure further safe operation of the structures, a conceptual amplification scheme based on the results of stress-strain state calculations has been proposed

Stress-controlled phonon-impurity resonant interactions in terahertz silicon lasers

Silicon terahertz lasers operate at frequencies between 1 THz and 7 THz under conditions of optical mid-infrared or far-infrared pumping and low lattice temperatures (‹30 K). The intracenter laser mechanism is based on optical transitions between excited states of group-V donors P, Sb, As and Bi, while Stokes stimulated light scattering is responsible for lasing in Si:Sb. In both cases population inversion is realized due to different rates of the phonon-assisted intracenter relaxation of captured electrons. The donor states, resonantly coupled by the interaction with intervalley phonons in the Si lattice, exhibit the shortest lifetimes that determines the specific laser schemes in n-Si. External stress applied to a Si crystal can release the resonant phonon-impurity coupling. By this it changes the laser operation transition and its efficiency