One of the challenges of machining process is to improve the quality of machined surface by reducing the vibration of cutting tools. The research aims to suppress vibration using composite boring ...bars with an enhanced damping capacity. A new design of boring bars with different cross-sections is considered. Static and dynamic behavior of the proposed tools is investigated. A mathematical model for determining the eigenfrequency is proposed, and it is compared with computer simulation and experimental results. The validity of the proposed models is verified by conducting experimental machining tests in order to study the changes in vibro-acoustic signals depending on the cross-sections of the toolholder. The results show that the composite material significantly improves damping of boring bars, which leads to a reduction in the vibration compared to conventional boring bars.
The article presents a study of the currently functioning system of mathematical education in the Russian Federation. The importance of research areas related to mathematics for the Russian and world ...community has been substantiated. The analysis of the implementation of the modern Concept of Mathematical Education of the Russian Federation is carried out, achievements and problems are highlighted. The changes that have affected school and university mathematics education from the moment of approval of the Concept of Mathematical Education of the Russian Federation and up to the present, the positive and negative results of these changes are shown. On the basis of a survey conducted by the authors of representatives of the leading mathematical organizations of Russia for the changes necessary from their point of view that need to be introduced into the Concept of Mathematical Education, the most important and significant proposals for improving the quality of this sphere of education have been developed.
Statistical relations between the geomagnetic Dst index, cosmic ray variations, and solar wind characteristics are compared for Forbush decreases associated with: (i) coronal mass ejections from ...active regions (AR-CMEs) accompanied by solar flares, (ii) filament eruptions outside active regions, (iii) corotating interaction regions (CIRs) caused by high-speed streams from coronal holes, (iv) mixed events induced by two or more solar sources. Relationships of geomagnetic indices and parameters of cosmic rays and the solar wind are also compared between sporadic events with or without magnetic clouds (MCs) and between Solar Cycles (SCs) 23 and 24. The results reveal that interplanetary disturbances originated by AR-CMEs associated with an MC are most geoeffective and cause powerful geomagnetic storms, while CIRs create only moderate and weak storms. Sporadic and recurrent events differ in values of the Dst index and southward component of the magnetic field, as well as in the relationship between them. For sporadic events, geomagnetic activity is more affected by the presence or absence of an MC than by the type of solar source. Interplanetary disturbances associated with AR-CMEs are more effective in SC 23 while those associated with other types of solar sources have approximately the same geoeffectiveness in both SCs.
Forbush Effects and Geomagnetic Storms Belov, A. V.; Belova, E. A.; Shlyk, N. S. ...
Geomagnetism and Aeronomy,
06/2024, Letnik:
64, Številka:
3
Journal Article
Recenzirano
Forbush effects in galactic cosmic rays (according to the neutron monitor network data) and accompanying geomagnetic disturbances over a long period from 1957 to 2022 have been identified and ...studied. Statistical relationships between various parameters of cosmic ray flux variations and geomagnetic activity indices are analyzed. It has been established that the magnitude of Forbush effects depends nonlinearly on the class of geomagnetic storm. A moderate correlation (up to 0.67) was found between the extreme values of various geomagnetic activity indices (
Ap
,
Kp
,
Dst
) and cosmic ray characteristics. It is shown that the extreme values of cosmic ray and geomagnetic activity parameters are not always detected simultaneously: it depends on the sign of the
Bz
-component of the interplanetary magnetic field in a specific event.
Casting Aluminum Alloys Michael V Glazoff, Vadim S Zolotorevsky, Nikolai A Belov
2007, 2010, 2010-07-07
eBook
This monograph summarizes research conducted at Moscow Institute of Steel and Alloy during many decades in part together with Alcoa Inc. The research covered areas of the structure, properties, ...thermal resistance, corrosion and fatigue of aluminum alloys in industrial manufacturing. The book features:
Emphasis on interconnection among phase equilibria, thermodynamics and microstructure of alloys
Systematic overview of all phase diagrams with Al that are important for the development of casting aluminium alloys
Diagrams ("processing windows") of important technological properties such as castability, molten metal fluidity, tendency to hot pre-solidification cracking, porosity
Mathematical models for alloy mechanical properties facilitating the down-selection of best prospect candidates for new alloy development
New principles of design of eutectic casting aluminium alloys
Examples of successful novel casting alloy development, including alloys for high-strength applications, alloys with transition metals, and novel alloys utilizing aluminium scrap
At present, there are no studies on the analysis of the incidence of complications in patients with concomitant lesions of the coronary and internal carotid arteries (ICA) after combined operation of ...carotid endarterectomy (CE) and coronary artery bypass grafting (CABG) against the background of type 2 diabetes (T2D). However, there is no doubt that this condition can be a predictor of cardiovascular and wound complications during in-hospital and long-term postoperative periods.
Aim
. To study in-hospital and long-term outcomes of combined CABG+CE in patients with and without type 2 diabetes.
Material and methods
. This multicenter retrospective study for the period from January 2015 to December 2019 included 653 patients with concomitant atherosclerotic lesions of ICA and coronary arteries, who underwent combined CE+CABG. Depending on presence of type 2 diabetes, 2 groups were formed: group 1 (n=183) — patients with type 2 diabetes; group 2 (n=471) — patients without type 2 diabetes. The duration of postoperative follow-up was 37,8±14,9 months.
Results
. During hospitalization, significant differences in the incidence of death (group 1 =1,1%; group 2 =1,0%; p=0,97), myocardial infarction (MI) (group 1 =1,1%; group 2 =0,8%; p=0,76), bleeding events (group 1 =1,1%; group 2 =0,8%; p=0,76) were not detected. However, stroke (group 1 =3,8%; group 2 =0,4%; p=0,0008), sternal wound infection and mediastinitis (group 1 =3,3%; group 2 =0,2%; p=0,0006) were significantly more often developed in patients with type 2 diabetes.
In the long-term follow-up period, death (group 1 =6,6%; group 2 =1,1%; p<0,0001), MI (group 1 =4,9%; group 2 =0,8%; p=0,0008), stroke (group 1 =7,7%; group 2 =1,5%; p<0,0001), ICA restenosis (group 1 =8,8%; group 2 =1,6%; p<0,0001), repeated emergency myocardial revascularization (group 1 =7,2%; group 2 =1,5%; p=0,0002), repeated emergency cerebral revascularization (group 1 =8,8%; group 2 =1,6%; p<0,0001) were significantly more often recorded in patients with type 2 diabetes.
Kaplan-Meier curve analysis and its comparison using the log rank test revealed that the death, MI, and stroke were also significantly more often observed in patients with type 2 diabetes (p=0,0007, p=0,003, p<0,0001, respectively).
Conclusion
. Patients with type 2 diabetes who are referred for combined CE+CABG are at an increased risk of stroke, sternal wound infection and mediastinitis in the in-hospital postoperative period, as well as all adverse cardiovascular events in the long-term follow-up period.
The results of model numerical calculations are presented, showing the effect of the TRT vacuum vessel on the amplitudes and phases of the magnetic sensors signals, which are located on the inner and ...outer vacuum vessel surfaces. It is shown that the characteristic times of loop voltage sensors considerably depend on their position on the TRT vacuum vessel. Therefore, their accurate mutual matching is required, especially in the dynamic stage of the discharge, when high eddy currents are induced in the vacuum vessel. The results of numerical calculations for the case of periodic disturbances in the plasma column are presented. They showed that the vacuum vessel almost completely shields the signals of the magnetic sensors located on the outer surface of the vacuum vessel. Moreover, it affects not only the amplitudes of magnetic sensors signals, but also their phases. Numerical studies brought us to conclusion that it is of priority to install the magnetic sensors just on the inner surface of the TRT vacuum vessel.
In this work, the wear resistance and fracture characteristics of (Ti,Al)N-Cu, (Ti,Al)N-Ni, and (Ti,Al)N coatings deposited onto a carbide substrate by the filtered cathodic vacuum arc deposition ...method were investigated comparatively under various loading and friction conditions. The (Ti,Al)N-Cu and (Ti,Al)N-Ni metal-ceramic coatings showed an equiaxial structure with a ceramic phase grain size of about 15–20 nm. The coatings showed a hardness of about 50 GPa and maintained their fracture toughness (the relative work of plastic deformation was ~65%). The (Ti,Al)N ceramic coating showed a columnar structure having elements with a diameter of about 120 nm. This coating exhibited a hardness of about 27 GPa and was characterized by a significantly lower fracture toughness (the relative work of plastic deformation was ~45%).
The tribological properties of these coatings were examined at 20 and 500 °C. It was found that the metal-ceramic coatings showed significantly lower friction coefficient values (~0.56 and 0.61) than the ceramic coatings (~0.68 and 0.70).
The fracture pattern of the metal-ceramic coatings was obtained by simulating their abrasive wear during a scratch test. Complete abrasion of the coatings was not observed until 90 N. Under similar tests, the (Ti,Al) N coating showed adhesive destruction by the separation of large fragments from the substrate. Complete coating wear was observed at a load of ~70 N.
The erosion of the coatings during hydroabrasive treatment under multicycle impact loading was investigated. It was found that the nanostructured (Ti,Al) N-Cu and (Ti,Al)N-Ni coatings were 1.5 and 2 times less susceptible to wear than the (Ti,Al) N coating, respectively.
The wear characteristics of the coatings were analysed on the basis of their structures and physical and mechanical properties, including their H/E and H3/E2 parameters, which denote the resistance of a material to elastic and plastic deformation respectively.
•(Ti,Al,)N-Cu/Ni coatings with different Cu and Ni contents were deposited.•(Ti,Al,)N-Cu/Ni coatings are characterized by high resistance to abrasive wear.•(Ti,Al,)N-Cu/Ni durability was 3–4 fold as high as that of the (Ti,Al)N coating.•Cu/Ni-containing nitride coatings exhibit absence of complete wearing up to ~90 N.•(Ti,Al)N–Cu/Ni coatings perform as materials with high ductility and safety factor.
•Neural network application for event reconstruction can approach the best physically possible precision.•A neural network reconstruction algorithm gives a good estimation of expected ...performance.•Comparing two realistic detector models with neural network reconstruction allows to evaluate the potential benefits with an unbiased algorithm.•Larger thinner crystal plates provide the best overall resolution, smaller plates reduce the maximal possible error.
We use neural networks to evaluate and compare the spatial resolution of two different simulated monolithic PET detector elements. The effects of mixing events with single photoeffect interactions and multiple Compton scatterings are also studied.
Two PET detector models were used in this study. The first one consisted of a LYSO crystal plate with 19.25 × 19.25 × 12 mm3 dimensions and 256-channel photomultiplier with parameters modeled after a Hamamatsu S-13615-1050N-16 SiPM. The second model used a larger LYSO crystal (57.6 × 57.6 × 12 mm3) and a 64-channel Sensl ARRAYC-60035-64P-PCB photomultiplier.
A feed-forward neural network was used to reconstruct the point of 511 keV gamma interaction. The number of layers and the number of neurons per layer were varied.
The best resolution was achieved with the 57.6 × 57.6 mm2 detector model, with an average of 0.74 ± 0.01 mm for the XY plane and an average 1.01 ± 0.01 mm for the Z coordinate (depth of interaction).
Neural networks can be a powerful tool that can help to determine the optimal parameters for a design of an experimental device. This study demonstrates how neural networks can be used to evaluate the performance of two detector variants while not being dependent on specific signal and noise functions.
Changes in the global magnetic field of the Sun, the main parameter that modulates cosmic rays, lead to changes in the characteristics of solar activity and the heliospheric field. In this paper we ...consider the question of the response to a long-term weakening of the solar global magnetic field in the long-term modulation of cosmic rays of various energies in cycles with various directions of the polar magnetic field of the Sun. The 1991–2020 period, which includes two intervals with positive and negative directions of the solar global magnetic field, is analyzed. The study was performed based on continuous observations of cosmic rays by a network of neutron monitors, telescopes, and stratospheric balloons. The spectrum of variations for particles with an effective rigidity of
R
eff
= 5, 10, 20 GV was determined using our version of the global survey method. From 2018 to the present, a flat maximum of the cosmic ray flux is observed in the cycle 24/25 minimum, which confirms the drift theory of modulation for the positive direction of the global magnetic field on the Sun. During this period, low-energy variations (observed on spacecraft and in the stratosphere) exceed the value of variations in the base period (1987) by ~ 8% and is 0.8 of the maximal variation in the anomalous minimum of 23/24 in 2009. The maximal flux of particles of medium and high energies observed by neutron monitors and telescopes is by 1–2% lower than the 23/24 maximum. Their modeling contributes to the understanding of the process of modulation of cosmic rays by the electromagnetic fields of the heliosphere. In our proposed multiparameter model, the long-period modulation is described (with allowance for the delay) by a number of heliospheric characteristics.
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