The article describes a method for producing semi-finished products from a copper alloy of the Cu–Ni–Cr–Si system for electrical purposes through the radial-shear rolling (RSR). From the Cu–Ni–Cr–Si ...alloy by hot deformation, rods with a diameter of 20 mm were obtained, which were then heat treated with quenching and aging. A detailed analysis of the microstructure and properties (mechanical and electrical) of the obtained samples was carried out after RSR and after heat treatment (HT). After RSR, material hardening occurs due to shear deformations forming a gradient structure with grain sizes varying from 8.22 μm to 15.95 μm between the surface and the center of the rod. The microstructure and mechanical property analysis showed that after heat treatment, the alloy is thermally hardened due to the precipitation of Ni2Si and Cr3Si particles uniformly distributed in the sample volume in the form of fine inclusions with an average size of 0.56–0.65 μm. After heat treatment, the alloy enhanced its mechanical properties (ultimate tensile strength (UTS) ~ 700–750 MPa, yield strength (YS) ~ 557–606 MPa, and elongation between 17 and 22%) and its electrical conductivity of 45.17% IACS from the 30.52% IACS of the RSR material. The improved mechanical properties of the heat-treated material are due to the different strength contributions mainly coming from dislocations and precipitates. The electrical conductivity improvement after the heat treatment is related to the dislocation density reduction and the increase in grain boundary misorientation due to the recrystallization phenomenon giving rise to a lower number of boundaries but with a twinning character. Thus, the RSR method offers a new industrial alternative for the production of semi-finished products from a Cu–Ni–Cr–Si alloy in the form of rods with diameters ranging from 10 to 55 mm.
•Radial shear rolling can produce copper rods of different diameters at an industrial scale.•The thermomechanical process using radial shear rolling gives rise to a heterogeneous material.•Aging treatment after radial shear rolling produces a remarkable combination of strength, ductility, and electrical conductivity.•Dislocations annihilation and grain boundaries misorientation change help to improve the material electrical conductivity.
Aim To study true prevalence of atrial fibrillation (AF) in a representative sample from the European part of the Russian Federation; to describe characteristics of patients with AF; and to ...provide the frequency of anticoagulant treatment.Material and methods Cross-sectional data of the EPOCH epidemiological study (2017) were used. Data were collected in 8 constituent entities of the Russian Federation; the sample size was 11 453 people. The sample included all respondents who had given their consent for participation and were older than 10 years. Statistical tests were performed in the R system for statistical data analysis.Results The prevalence of AF in the representative sample from the European part of the Russian Federation was 2.04 %. The AF prevalence increased with age and reached a maximum value of 9.6% in the age group of 80 to 89 years. The AF prevalence among females was 1.5 times higher than among men. With age standardization, the AF prevalence was 18.95 and 21.33 per 1,000 people for men and women, respectively. The AF prevalence increased in the presence of concurrent cardiovascular diseases (CVDs) or diabetes mellitus as well as with an increased number of comorbidities in the same person and reached 70.3 and 60.0 % in patients with 4 and 5 comorbidities, respectively. Patients with AF had a greater number of comorbidities and higher CHA2DS2VASc scores (5.0 vs. 2.0, p<0.001) compared to patients with CVDs without AF. Only 22.6 % of patients with CVD and AF took anticoagulants. Only 23.9% of patients with absolute indications for the anticoagulant treatment received anticoagulants.Conclusion The AF prevalence in the European part of the Russian Federation was 2.04 %; it increased with age and in patients with concurrent CVDs or diabetes mellitus. Most of AF patients (93.2 %) required a mandatory treatment with oral anticoagulants.
A physical model was proposed to describe the response of groundwater level in a coastal area to sea level variations. An impermeable interlayer is supposed to exist on the shore slope, simulating a ...layer of aufeis or frozen soil deepening into water and ending on the sloped bed at some depth under water. This interlayer hampers water exchange between the sea and the aquifer in the coastal zone. The results of this study were compared with those in similar studies with models containing no impermeable layer. New properties were revealed.
Based on the ADCIRC hydrodynamic finite element model, various seiche oscillation regimes in a narrow extended deep-water bay are investigated with a case study of Sevastopol Bay. Long waves ...penetrating into the bay through its inlet are considered perturbations. Calculations are made for perturbations with periods of 2.5, 2.9, and 6.2 min, belonging to the eigenmodes of the bay with different spatial structure: transverse; longitudinal-transverse, and longitudinal, respectively. The impact of these perturbations leads to generation of not only resonance modes with periods close to the perturbation period, but also an intense Helmholtz mode that occurs after the perturbation ceases and leads to a significant increase in the amplitude of level oscillations. In studies of seiches caused by perturbations in the form of monochromatic long waves coming from the open sea, it was not possible to confirm that the greatest potential hazard to the coastal zone of an elongated deep-water bay is represented by the so-called extreme modes with a transverse structure. A mode with a structure close to transverse was generated, but its maximum amplitude was 2.5 times less than that of longitudinal-transverse and longitudinal seiches. The largest amplification of the incident waves was noted for the longitudinal-transverse mode with a period of 2.9 min.
Study of the Process in the Energy Range GeV Achasov, M. N.; Barnyakov, A. Yu; Beloborodov, K. I. ...
Physics of atomic nuclei,
2023/12, Letnik:
86, Številka:
6
Journal Article
Recenzirano
The
cross section is measured in the center-of-mass energy range from 1.07 to 2.00 GeV in the decay channel
,
. The data set with an integrated luminosity of 242 pb
accumulated in the experiment with ...the SND detector at the VEPP-2000
collider is analyzed.
A linear approximation and a finite-element hydrodynamic model ADCIRC were used to study seiche oscillations in the system of Sevastopol bays caused by wave perturbations on the liquid boundary of ...the model domain. The calculations were carried out for perturbations with periods from 1 to 52 min with impact duration from 4 to 24 h. Resonance periods were found for the bays in the system. The effect of perturbations with a duration of >15 h with periods 1–15 min lead to the generation of intense high-frequency modes with periods 2.0–4.5 min, which become dominant over low-frequency modes (periods >10 min) in all Sevastopol bays, thus creating in them the conditions for harbor seiche formation. The bays interact with one another via energy exchange through their entries, resulting in the penetration of oscillations with periods of characteristics modes of each bay into adjacent bays. The Helmholtz mode of the Bay of Sevastopol (with a period of 48 min) manifests itself in all bays of the system.
A process for obtaining semifinished products in the form of pipes made of copper alloys for electrical purposes by means of screw rolling is proposed. The results of experimental piercing and ...rolling of tube samples made of Cu–0.75Cr alloy billets with a diameter of 45 mm are presented. The samples, 43.5 × 10.0 mm in size, obtained after piercing with the use of a two-roll screw rolling mill, have exact geometrical dimensions: the deviation of the outer diameter at the front end is less than 1%, that at the rear end is less 2.4%, the relative nonuniformity of pipe wall thickness at the front end amounts to 0.3–0.5%, and that at the rear ranges within 0.5–1.0%. The pierced pipe samples have been rolled by using a three-roll minimill for radial-shear rolling (RSR) with a different total reduction level; the samples have been obtained with an outer diameter of 30, 25, and 18 mm. The reduction process has been analyzed from the standpoint of stability and deformation of the mouth of pipe. In the case of a 30% relative reduction of the outer diameter, the rolling without a mandrel is accompanied by an increase in the wall thickness. The deviations of the inner diameter are within permissible limits. The experiments performed for obtaining samples based on the Cu–0.75Cr alloy by means of screw piercing and reduction using an RSR mill show that this technique could be implemented in industry. At the same time, in order to obtain a quality product, it is necessary to more exactly determine the deformation parameters (deformation level and reduction mode). Different variants for the heat treatment (HT) of the pipe samples and the effect of the HT mode exerted on the electrical conductivity and hardness are considered. After piercing, the samples exhibited a conductivity of 59.3% IACS. The maximum electrical conductivity of 76.7% IACS has been obtained for the samples after quenching from a temperature of 1020°C and aging at 450°C for 3 h. The results of this work show that it is fundamentally possible to obtain semifinished products based on copper alloys for electrical purposes by means of screw rolling.
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