The results of a study of noise reduction in a subsonic turbulent jet using a lobed nozzle section are presented. Lobed nozzles with 6–12 lobes of different heights were considered. The experiments ...were carried out in two anechoic chambers: an anechoic chamber with aerodynamic noise sources at the Laboratory of Noise Generation Mechanisms and Modal Analysis of PNRPU and the AC-2 anechoic chamber with flow at TsAGI. The sound field of a subsonic jet flowing from a lobed nozzle was compared with the sound field of an equivalent round jet. The paper demonstrates ways to expand the frequency range in which jet noise is reduced using lobed nozzles. The thrust losses in lobed nozzles based on RANS calculation are estimated.
A method for producing a new generation of high-purity xenogenic biomatrixes suitable for implantation in a living organism is proposed. Special biocompatibility can be achieved by additional ...treatment with supercritical carbon dioxide and the introduction of dosed amounts of polylactides with molecular weight of 20 and 40 kDa in the porous space of the matrix. In vivo testing of the obtained materials showed their high biocompatibility with varying degrees of integration with surrounding tissues.
Abstract
Compensators of electrodynamic repulsion forces of closed electrical contacts are designed to increase the stability of the operation of switching electrical devices when short-circuit ...currents flow. The possibilities of increasing the efficiency of electrodynamic compensators (one-loop and two-loop) in their traditional design are very limited. The paper analyzes an electrodynamic compensator for high-current contacts, in which the free end of the inactive contact included in the design of the compensator with contact pads is bent 180 degrees towards the axis of rotation of the inactive contact. As a result of this, the shoulder, on which the electrodynamic force of repulsion of the contacts acts, decreases. In such a design, the moment of repulsion of the contacts will also be less and the fulfillment of the condition for its full compensation is facilitated. Formulas are given for calculating the additional electrodynamic force of the considered compensator and its contour coefficient. Calculations of the additional electrodynamic effort of the breaker compensator for a rated current of 630A with a short-time withstand current of 40kA have been performed. With the length of the bent part of the inactive contact equal to 25% of the total length of the current loop, the resulting electrodynamic force of the compensator increases by 4.69%. In this case, a 25% reduction in the torque that is repulsive to the contacts occurs.
Comparative tests are performed during repeated tension of structurally similar samples of fuselage panels with a SIAL-3-1R laminated aluminum–glass-reinforced plastic (GRP) shell and a shell made of ...aluminum alloy 1163 sheets, and their fatigue life until cracking and complete failure is determined. Instrumental methods of monitoring the integrity of the structure with the registration of cracks up to 5 mm long and monitoring their growth have been tested. Fractographic studies of the crack development of in the layered aluminum–GRP material are carried out. The advantages of using a metal–polymer layered material as the shell of aircraft fuselage panels in comparison with a traditional aluminum alloy are shown.
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It has been found that monasnicotinic acid (MNA) isolated from the fungus
Aspergillus cavernicola
VKM F-906 reduces the proliferation and migration of human prostate cancer cells LnCaP and inhibits ...the AKT–mTORC1 and FAK–Src signaling pathways. However, MNA also increases the level of HSP60 and the phosphorylation of c-Jun, factors that stimulate the vital activity of cancer cells. MNA-induced cellular responses appear only after 48 h, which indicates the involvement of either the products of MNA metabolism or tautomers arising during the MNA protonation due to the growth of cell cultures and utilization of the compound by human cells. These results suggest that MNA is a promising compound for the production of various derivatives that would inhibit oncogenic signaling pathways without stimulating the factors providing the survival of tumor cells.
Optical fiber (OF) with a relatively high level of the backward signal at a certain wavelength is developed and studied. An increase in the backward signal is reached due to the recording of multiple ...weak fiber Bragg gratings (FBGs) in the course of fiber pulling. A scheme that is simpler than the direct FBG recording through a phase mask is proposed and implemented. Fibers with FBG recorded with different ratios of the region with recorded gratings to the total length of OF are fabricated. An increase in the level of the backward signal relative to the level of the Rayleigh scattering by more than 30 dB is reached. Results of experimental study of the proposed OFs and examples of practical application are presented.
A new kinetic type of gel effect suppression in radical polymerization is described. Ring-opening polymerization of ketene acetals is characterized by auto-deceleration in the course of the reaction ...rather than the auto-acceleration, as well as increased reaction rate order with respect to the monomer. These features are caused by low reactivity of ketene acetals, as a result of which the addition of primary radicals to the monomer is the rate-limiting step in the initiation reaction. This should lead, firstly, to termination of the growth radicals at the primary radicals, and secondly, to the increased rate order with respect to the monomer concentration and, accordingly, to a decrease in the polymerization rate with its consumption.
Since June 2012 the ground-based microwave (MW) radiometer RPG-HATPRO (Radiometer Physics GmbH - Humidity and Temperature Profiler) G3 (generation 3) has been operating at the Faculty of Physics of ...St. Petersburg State University in constant mode with sampling interval of 1-2 s. The results of MW radiation brightness temperature measurements in 14 spectral channels of the RPG-HATPRO radiometer have been analysed for the time period December 2012 to November 2014. Within this time period, different data ensembles are compiled that have different duration and describe the variety of atmospheric situations at the observational site. Two different approaches are used for the assessment of the information characteristics of MW measurements. The first one is based on calculation of Shannon's information content that characterizes the number of atmospheric states distinguishable by measurements. We use the modification proposed by Kozlov - the 'information volume' approach. The second approach is based on calculation of the information quantity that characterizes the degree of correlation between measurements and atmospheric state parameter variations. The information quantities are calculated and analysed for the complete set of spectral channels and for two subsets that comprised seven so-called 'temperature' and seven so-called 'humidity' channels separately. Kozlov's 'information volume' approach is also applied to the problem of estimation of the optimal sampling interval of MW measurements. It is shown that for St. Petersburg University observation site that represents subarctic region with maritime climate: (1) the information volume of MW measurements for a cold and dry season is significantly less than for a warm and humid season due to lack of information from 'humidity channels'; (2) for stable atmospheric conditions the sampling interval of MW measurements should not be greater than 100-200 s; (3) the degree of correlation between MW measurements and atmospheric temperature and humidity does not considerably depend on season of observations.
The CBM ECAL Korolko, I E; Prokudin, M S; Zaitsev, Yu M
Journal of physics. Conference series,
01/2017, Volume:
798, Issue:
1
Journal Article
Peer reviewed
Open access
We present the design and performance of the Electromagnetic Calorimeter (ECAL) of the Compressed Baryonic Matter (CBM) Experiment at FAIR. The main purpose of the ECAL detector is the identification ...and the measurement of energy and position of photons and electrons, which are produced in high-energy heavy-ion collisions in the beam energy range from 4 to 40 AGeV. ECAL will measure spectra of photons and neutral mesons decaying in their photonic decay channels. Precise measurement of masses and widths of short-living mesons (η, η′, φ χc etc.) will shed light on the chiral symmetry restoration which is expected to occur in dense nuclear matter. Measurements of the π 0 and meson spectrum are important to study dependence of the particle yield on thermodynamical parameters of nuclear mater.
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