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

Magnetic Dirac semimetal state of (Mn,Ge)Bi2_2Te4_4

For quantum electronics, the possibility to finely tune the properties of magnetic topological insulators (TIs) is a key issue. We studied solid solutions between two isostructural Z$_2$ TIs, magnetic MnBi$_2$Te$_4$ and nonmagnetic GeBi$_2$Te$_4$, with Z$_2$ invariants of 1;000 and 1;001, respectively. For high-quality, large mixed crystals of Ge$_x$Mn$_{1-x}$Bi$_2$Te$_4$, we observed linear x-dependent magnetic properties, composition-independent pairwise exchange interactions along with an easy magnetization axis. The bulk band gap gradually decreases to zero for $x$ from 0 to 0.4, before reopening for $x>0.6$, evidencing topological phase transitions (TPTs) between topologically nontrivial phases and the semimetal state. The TPTs are driven purely by the variation of orbital contributions. By tracing the x-dependent $6p$ contribution to the states near the fundamental gap, the effective spin-orbit coupling variation is extracted. As $x$ varies, the maximum of this contribution switches from the valence to the conduction band, thereby driving two TPTs. The gapless state observed at $x=0.42$ closely resembles a Dirac semimetal above the Neel temperature and shows a magnetic gap below, which is clearly visible in raw photoemission data. The observed behavior of the Ge$_x$Mn$_{1-x}$Bi$_2$Te$_4$ system thereby demonstrates an ability to precisely control topological and magnetic properties of TIs

METHODOLOGY FOR STRENGTH ANALYSIS OF NORMAL CROSS-SECTIONS OF REINFORCED CONCRETE HYDRAULIC STRUCTURES STRENGTHENED WITH CARBON COMPOSITE MATERIALS

The way to strengthen concrete structures in civil engineering by adding external reinforcement using carbon fiber composites is widely spreading in recent years. A method for calculating the strength of reinforced concrete in hydro technical constructions with reinforcing by carbon fiber composite materials was invented with the aim to justify the solutions of strengthening concrete structures. It was taken into consideration that the characteristic features of mass reinforced concrete structure with sand operating loads which including backpressure of water in the cracks and in opened construction joints. It has evolved the relations for calculation of strength in normal cross section of bending reinforced concrete member of hydro technical constructions which strengthening with external reinforcement by carbon fiber

The results of the experimental studies of reinforced concrete structures of hydraulic structures with interconnect construction joints, reinforced by external reinforcement of carbon fiber

For the purposes of experimental validation of application of external reinforcement of carbon fiber to reinforce reinforced concrete structures of hydraulic structures the experimental models of typical structures of hydraulic structures with inter-block construction joints were tested. At the same time, beam-type models of concrete of class B15 with a reinforcement percentage of 0.39 % and concrete of class B25 with a reinforcement percentage of 0.83 % were tested for the effect of bending moment. The models of fragments of reinforced concrete structures of hydraulic structures of concrete class B15 with a reinforcement percentage of 0.445 % and concrete B25 with a reinforcement percentage of 0.7 % were tested for сentral extension. Reinforced concrete beam-type models were reinforced with external reinforcement of carbon tapes of the type FibArm 530/300. Models of hydraulic structures fragments were reinforced by external reinforcement from carbon tapes of the type FibArm Tape 530/300 and from carbon composite lamellae of the type FibArm Lamel 12/50. The reinforced concrete beam-type models were reinforced with carbon strips (longitudinal bands on the lower stretched face and transverse belts in the span and supporting zones). The models of fragments of reinforced concrete structures of hydraulic structures were reinforced with carbon strips and carbon composite slats directed along the action of longitudinal tensile force. The results of experimental studies showed a significant increase in the strength of reinforced concrete structures of hydraulic structures due to their reinforcement by external reinforcement of carbon fiber, and also revealed a special character of the crack formation due to the presence of inter-block construction joints. Subject of the research: the subject of the study: reinforced concrete structures of hydraulic structures (with interblock construction joints), reinforced with external reinforcement of carbon fiber. Materials and methods: reinforced concrete models were made from ordinary heavy-weight concrete of classes B15 and B25 and reinforcement of A500C class. The outer reinforcement was made of carbon tapes of the type FibArm Tape 530/300 and FibArm Lamel12 / 50. Experimental studies were carried out on the basis of physical modeling of characteristic reinforced concrete structures of hydraulic structures with interblock building joints. In this model, the beam type of concrete class B15 with a percentage of reinforcement of 0.39 % and of concrete class B25 with a percentage of reinforcement 0.83 % were tested for the action of bending moment. Models of fragments of reinforced concrete structures of hydraulic structures from concrete class B15 with a reinforcement percentage of 0.445 % and of concrete B25 with a reinforcement percentage of 0.7 % were tested for the effect of central stretching. Experimental models were equipped with control and measuring equipment for determining the values of deflections, deformations of concrete and reinforcement elements of models, crack opening width and interblock joints. Results: in the course of experimental studies, a significant increase in the strength of reinforced concrete structures of the hydraulic structures (in 1.47-2.34 times) was obtained under the action of the bending moment and the central extension due to their reinforcement by external reinforcement from the carbon fiber. Conclusions: based on the obtained experimental data on the significant increase in the strength of reinforced concrete structures of hydraulic structures (by 1.47-2.34 times) due to reinforcement by carbon composite tapes and carbon composite lamella, the substantiation of the use of external reinforcement from carbon bands and lamellas under the action of a bending moment and central extension. Also, a special type of cracking was observed, due to the presence of interblock joints, the study of which allows controlling the implementation of technical solutions for reinforcing, repairing, reconstructing reinforced concrete structures of hydraulic structures

TransArctic-2019 expedition ice thickness and snow height direct measurements at points of hydrological stations

Direct (contact) measurements of sea ice thickness, elevation and snow height performed at points of 59 hydrological (oceanographic) stations during the TransArctic-2019 expedition (28 March - 04 May 2019) are presented. Variables include time, geographical location (lat, lon) and measurements of minimum (imin, m) and maximum (imax, m) sea ice thickness, minimum (iemin, m) and maximum (iemax, m) sea ice elevation (above sea level), minimum (smi, m) and maximum (sma, m) snow height, hummock concentration (huct, in 1/10 of area coverage) and maximum hummocks height (humh, m). Data is presented in CSV, DBF and shapefile formats. TransArctic-2019 expedition was convened by the Arctic and Antarctic Research Institute (AARI) aboard AARI research vessel "Akademik Tryoshnikov" within the area of the Arctic Basin northward of the Franz-Josef Land archipelago. Points of the stations were the helicopter landing sites chosen on sufficiently level and thick ice along the sections at a distance of 10s-100s km from the drifting ship

Physical oceanography (CTD/Rosette) during the Akademik Tryoshnikov cruise Transarktika-2019 Leg 1 in 2019, Arctic Ocean

A standard Sea-Bird Electronics SBE911+ CTD system with a temperature and conductivity sensor was used to measure temperature, conductivity, and pressure at 180 stations during the Russian-international expedition Transarktika-2019 Leg 1 in the Barents Sea in March-May 2019 aboard the research vessel Akademik Tryoshnikov. We followed the manufacturer's recommendation to calculate salinity using Seabird processing software. The salinity is reported as Practical Salinity (PSU). Data were averaged at depth ranges of 1 m. Data are provided by the Antarctic and Arctic Research Institute (AARI) and reprocessed at the Helmholtz Centre for Polar and Marine Research, Alfred Wegener Institute. The Transarktika-2019 expedition was made possible by funding from the Russian Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet). The scientific research was also supported by RFBR grants No. 18-05-60048 and 18-05-60083

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

International audienceSpinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signal-to-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far