The overpressure and impulse of the compression phase behind perforated partitions (PPs) located across a conical shock tube (CST) during the propagation of a spherical shock wave in it are ...experimentally determined. In the experiments, partitions with a different permeability are used. The intensity of the shock wave incident on the partition is varied. The obtained degree of attenuation of the overpressure and impulse of the compression phase of the shock wave increases with a decrease in the permeability of the partition and an increase in the intensity of the wave, remaining practically constant along the length of the CST.
In this Letter, we study the destruction of a duralumin barrier when exposed to an aluminum jet (analogous to a fragment of industrial debris) at a velocity of 7–11 km/s in the presence of copper and ...aluminum metal shields. The effectiveness fraction of the shield protection, which is determined by the expansion of parts of the destroyed impactor between the shields, is distinguished. An increase in the efficiency of the shield protection due to the phase transitions of the interacting materials of the impactor and shield is determined.
The development and validation of a new experimental model that reflects the clinical characteristics of polymorbid pathology (including obesity, acute inflammation of the gastrointestinal tract, ...antibiotic-induced dysbiosis, and bone injury) with the general characteristics of systemic inflammatory response syndrome became the basis for testing of the efficiency of probiotics according to the age of experimental animals. The concentration of osteocalcin and matrix metalloproteinase-1 significantly increased in 7-month-old male Wistar stock rats under the influence of probiotics as compared to animals at the age of 9 months. A mixture of probiotic containing
Lactobacillus acidophilus
(LA-5) and
Bifidobacterium animalis
subsp
. lactis
(BB-12) strains at a concentration of 10
8
CFU per animal demonstrated its effectiveness in comparison with other used probiotics in relation to most of the studied parameters. Zinc-containing biomolecules (osteocalcin, bone fraction and total alkaline phosphatase, matrix metalloproteinase-1) are metabolic regulators modulated by probiotic strains.
The process of energy transfer to the emission centers is studied in ZnWO4 and ZnWO4:Mo single crystals in the temperature range 10–300K. A numerical simulation describing the process is presented; ...the temperature dependence of energy transfer efficiency to the intrinsic emission centers in ZnWO4 is shown to be defined by the modification of Onsager sphere radius. A competitive role of radiative relaxation channel related to the impurity of molybdenum is studied in ZnWO4:Mo. It is shown that below 60K the energy transfer to the MoO6 emission centers by free charge carriers terminates due to the self-trapping of holes at WO6 complexes.
•Mo impurity perturbs energy transfer to intrinsic emission centers at 300K.•Holes self-trapping at WO66− suppress emission of MoO6 centers at T<60K.•Modeling of the energy transfer process to intrinsic emission centers is presented.•Onsager sphere radius and thermalization length for ZnWO4 are calculated.
Screen protection of spacecraft from a high-speed elongated striker, which is equivalent to the most dangerous pieces of space debris, has been investigated. The kinetics of the penetration of an ...elongated striker into the barrier after passing through the screen protection has been analyzed. It has been shown that the efficiency of destabilization of an elongated high-speed striker on metal screens is determined by the partial evaporation of the striker and the screen interacting at speeds of 7–8 km/s.
Specific features of the flow during the detonation of high-explosive charge in a conical shock tube are revealed by analyzing the results of numerical simulation. It is established that the main ...difference between the flow in conical geometry and the spherical case is associated with a change in the flow parameters behind the shock wave due to interaction with the bounding surface (cone wall). Comparative analysis of the calculated results shows that the real performance factor of the conical shock tube can vary both over the length and cross-section of the tube.
The penetration of an aluminum jet into an aluminum alloy target with a speed of 8–11 km/s is investigated. An analysis of the kinetics and parameters of introduction, and the condition of the ...surface of the cavity after penetration suggests that the hydrodynamic nature of penetration is violated at speeds of more than 9 km/s because of fusion of interacting metals. The results of the study are intended to develop screen protection for spacecraft from the most dangerous fragments of space debris.
An analysis of the results of a three-dimensional numerical simulation of the flow in a conical shock tube (CST) with an angle of 38° revealed that the blast waves formed in such a tube have a ...pressure profile similar to spherical shock waves (SSWs) with a pronounced rarefaction phase following the compression phase. It is established that the main difference between the flow in conical geometry and the spherical case is related to the change in the flow parameters due to the interaction with the bounding surface(cone wall). The revealed inhomogeneity of the flow manifests itself in the form of pressure pulsations in the rarefaction phase in the absence of a secondary compression phase. It is concluded that a CST is an effective tool for reproducing dynamic loads under a spherical explosion.
The state of the cavity surface after the introduction of the copper jet into the metal barrier has been recorded and analyzed. A comparison of the cavity surface for jets providing only melting or ...melting with evaporation during unloading of shock-compressed copper was carried out. The final stages of pore development during solidification are fixed. The volume fraction of evaporation was estimated. The rapid unloading of the implementation areas and the emergence of pores in the volume before the destruction in the layer of the spreading jet result in an increase in the efficiency of the spacecraft screen protection during the evaporation of a fragment of artificial debris.
Optical and luminescent properties of anisotropic tungstate crystals Kolobanov, V.N.; Kamenskikh, I.A.; Mikhailin, V.V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2002, Letnik:
486, Številka:
1
Journal Article
Recenzirano
Features of the reflectivity spectra in the fundamental absorption region were analysed for a series of tungstates. The contribution of electronic states of cations to the formation of the bottom of ...the conduction band and the top of the valence band is demonstrated. Its relation with the dominant mechanism of the energy transfer to the emission centres and the nature of these centres is discussed.
PDF
