The influence of ultra fine grained (UFG) and coarse grained (CG) microstructure of the titanium alloy Ti-6Al-4V on the strength of a diffusion bonded (DB) joint was studied using a laboratory DB ...fixture and a new shear test rig. The DB process was carried out at 725 °C and 825 °C during 2 and 4 h in a vacuum furnace. Coarsening of grain structure resulting from different DB cycles was quantified. The chain pores were observed at 725 °C for both microstructure conditions bonded during 2 h. The increase of bonding time up to 4 h leads to subsequent elimination of the pores. The UFG samples bonded at 725 °C showed a higher level of the shear strength than CG samples for both bonding times. The CG material demonstrated the highest shear strength after 4 h of DB bonding at 825 °C. The increase of the creep deformation of UFG samples when compared to the CG condition was observed as a result of DB at of 725 °C during 4 h.
In this paper we revisit the derivations of model equations describing long nonlinear longitudinal bulk strain waves in elastic rods within the scope of the Murnaghan model in order to derive a ...Boussinesq-type model, and extend these derivations to include axially symmetric loading on the lateral boundary surface, and longitudinal pre-stretch. We systematically derive two forced Boussinesq-type models from the full equations of motion and non-zero surface boundary conditions, utilising the presence of two small parameters characterising the smallness of the wave amplitude and the long wavelength compared to the radius of the waveguide. We compare the basic dynamical properties of both models (linear dispersion curves and solitary wave solutions). We also briefly describe the laboratory experiments on generation of bulk strain solitary waves in the Ioffe Institute, and suggest that this generation process can be modelled using the derived equations.
•Two forced Boussinesq-type equations are derived within the scope of Murnaghan model.•The models account for axially symmetric loading and longitudinal pre-stretch.•Basic dynamical properties of the models are discussed and compared.•The derived equations can be used for the modelling of soliton generation.
During the year, the territory of Ukraine is under the influence of various synoptic processes, which have a certain evolution in the surface conditions of the region and sometimes lead to the ...formation of unfavorable and dangerous weather conditions. The classification of synoptic processes makes it possible to create a set of daily synoptic situations taking into account the characteristics of a certain region, both for their use in weather forecasting and for studying the dynamics of regional synoptic processes under climate change. In this study, the modified version of Jenkinson and Collison method is used to classify synoptic processes on the territory of Ukraine, which is based on pressure data at the sea surface level and the geopotential heights at the level 500 hPa. The analysis of the obtained set of daily types of atmospheric circulation for the period 1948-2021 and the composite pressure fields built for each circulation type showed that all synoptic situations are clearly defined according to the classification and have seasonal features of frequency. During the year, advective processes of the western circulation group prevail, eastern advection is also often observed, and this type of circulation dominates in the spring months. The processes of the southern group are most relevant on the cold period of the year. Anticyclones occur more often over the region in winter and autumn, and cyclones are observed in summer and spring. The inclusion of 500 hPa level data in the classification makes it possible to take into account the three-dimensional structure of synoptic objects and distinguish such types of circulation as low cyclones and cold anticyclones, as well as troughs and cut-off lows at heights. It was found that low (thermal) cyclones and anticyclones make up a small proportionof synoptic situations, so the feasibility of their further inclusion in the typification for the territory of Ukraine is being discussed. The processes associated with the cut-off lows at the upper levels turned out to quite rare, but due to the possibility of the formation of dangerous weather conditions, this type of circulation is necessary in the classification of regional synoptic processes.
This study is focused on enhancement of the fatigue properties of Ultrafine Grain titanium (UFG Ti) processed by ECAP-Conform and subsequent drawing. By examining specific combinations of ...ECAP-Conform and drawing, we have shown that the size and shape of grains, dislocation substructure formation, and grain boundary state are among the main microstructural parameters that determine the strength and ductility in UFG Ti. The increase in fatigue resistance of UFG Ti to 610 MPa was attributed to the high values of strength and ductility (UTS = 1290 MPa with elongation = 13 %) This value is comparable with the fatigue resistance of the titanium alloy Ti–6Al–4V.
It was shown that introducing an ultrafine-grained (UFG) microstructure in pure metals as well as some alloys leads to strongly enhanced fatigue properties. The cyclic deformation behavior of UFG ...Ti-6Al-4V ELI (extra low interstitials) alloy is studied by both strain and stress controlled fatigue tests using plastic strain amplitudes between 3
×
10
−4 and 5
×
10
−3 and stress amplitudes ranging from 550 to 670
MPa. The UFG microstructures were obtained by equal channel angular pressing (ECAP) with different number of passes followed by a subsequent thermomechanical treatment (TMT). When compared to the conventional grain (CG) size counterpart, the UFG alloy exhibited a pronounced enhancement in the fatigue life in the S–N (Wöhler) diagram. It was also shown that additional UFG processing prior to TMT did not result in any further improvement of the fatigue resistance. Furthermore, microstructural investigations revealed a high cyclic stability of the UFG microstructure.
Parkinson’s disease (PD) is characterized by a long prodromal period, during which patients often have sleep disturbances. The histaminergic system and circadian rhythms play an important role in the ...regulation of the sleep–wake cycle. Changes in the functioning of these systems may be involved in the pathogenesis of early stages of PD and may be age-dependent. Here, we have analyzed changes in the expression of genes associated with the regulation of the sleep–wake cycle (Hnmt, Hrh1, Hrh3, Per1, Per2, and Chrm3) in the substantia nigra (SN) and striatum of normal male mice of different ages, as well as in young and adult male mice with an MPTP-induced model of the early symptomatic stage (ESS) of PD. Age-dependent expression analysis in normal mouse brain tissue revealed changes in Hrh3, Per1, Per2, and Chrm3 genes in adult mice relative to young mice. When gene expression was examined in mice with the MPTP-induced model of the ESS of PD, changes in the expression of all studied genes were found only in the SN of adult mice with the ESS model of PD. These data suggest that age is a significant factor influencing changes in the expression of genes associated with sleep–wake cycle regulation in the development of PD.
The problem of predicting the possible loads in a cellular network operation can be reduced to building a forecast on the possible number of calls directed to one gateway (PGW) within the given ...period of time. Having these data for all gateways in the network, it is possible to organize the optimal distribution of resources, prevent overloading of the gateways and, as a result, failures in the entire network operation. A statistical analysis of actual data collected by automated measuring systems on the nodes of a mobile network is carried out and the most suitable data for building forecasting models are identified. The results of the research on the possibility and effectiveness of the application of the mathematical models realized in constructing such a forecast by using machine learning methods such as linear regression,
k
-nearest neighbors (KNN), and random forest are presented. It is established that in order to solve the problem of building a short-term forecast on the number of requests that are to enter the server, it is not necessary to use complex models that require computing resources. Based on the calculated quality metrics, it is found that the most accurate forecast can be obtained by using a linear regression model.
The paper presents a novel algorithm based on digital holographic interferometry and being promising for evaluation of phase variations from highly noisy or modulated by speckle-structures digital ...holograms. The suggested algorithm simulates an interferogram in finite width fringes, by analogy with classical double exposure holographic interferometry. Thus obtained interferogram is then processed as a digital hologram. The advantages of the suggested approach are demonstrated in numerical experiments on calculations of differences in phase distributions of wave fronts modulated by speckle structure, as well as in a physical experiment on the analysis of laser-induced heating dynamics of an aqueous solution of a photosensitizer. It is shown that owing to the inherent capability of the approach to perform adjustable smoothing of compared wave fronts, the resulting difference undergoes noise filtering. This capability of adjustable smoothing may be used to minimize losses in spatial resolution. Since the method allows to vary an observation angle of compared wave fields, an opportunity to compensate misalignment of optical axes of these wave fronts arises. This feature can be required, for example, when using two different setups in comparative digital holography or for compensation of recording system displacements during a set of exposures in studies of dynamic processes.
We compared the immunogenicity of recombinant S. pneumoniae pneumolysin (rPly) when administered with and without Al(OH)3 adjuvant, and evaluated the protective properties of recombinant protein in ...the active defense experiment. It was shown that double immunization with rPly+Al(OH)3 increases the levels of IgG antibodies in comparison with the control (p<0.01), while triple immunization results in a more significant increase in IgG antibody levels (p<0.001). Double immunization with rPly without Al(OH)3 does not induce a significant increase in antibody levels in comparison with the control, while triple immunization results in a slight but significant increase in antibody levels (p<0.05). The active defense test proved the protective activity of rPly against S. pneumoniae serotype 3 at intranasal infection.We compared the immunogenicity of recombinant S. pneumoniae pneumolysin (rPly) when administered with and without Al(OH)3 adjuvant, and evaluated the protective properties of recombinant protein in the active defense experiment. It was shown that double immunization with rPly+Al(OH)3 increases the levels of IgG antibodies in comparison with the control (p<0.01), while triple immunization results in a more significant increase in IgG antibody levels (p<0.001). Double immunization with rPly without Al(OH)3 does not induce a significant increase in antibody levels in comparison with the control, while triple immunization results in a slight but significant increase in antibody levels (p<0.05). The active defense test proved the protective activity of rPly against S. pneumoniae serotype 3 at intranasal infection.
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