260 research outputs found
Peculiarities of educational environment at mining and metallurgical schools of the Urals
The relevancy of the issue under study stems from the contradiction between the need for a modern interpretation of the activities of mining and metallurgical schools, which had played a prominent role in the institutionalization of the vocational education environment as well as from moral “obsolescence” of research work results in this field. The goal of the article is the development of environmental indices of mining and metallurgical education of the Urals. The principal concept of research of this problem is the system approach, which allows considering the main peculiarities of the educational environment at mining and metallurgical schools of the Urals comprehensively. This article includes structurally significant characteristics of the educational environment at mining and metallurgical schools of the Urals. The contents of the article may be used for the purpose of modeling, designing and construction of an educational establishment (system) meeting the demands of the new communicational reality within the system of relations between education, industry, and social environment. © 2016 Chapaev, Erofeev and Dvořáková
Development of the recommendations on selection of glass-fiber reinforced polyurethanes for vehicle parts
© Research India Publications. Advanced polymer composites have essential features: high specific strength ratio, resistance to aggressive substances (water, fuel, oil, lubricants, weak alkalies and acids), wide operation temperature range (from -60 to +80 °C), sufficient durability (up to 10 years), high aesthetic qualities. The use of polymer composites for vehicle parts significantly reduces the curb weight of a vehicle, improves its dynamic behavior, increases its payload capacity, reduces its fuel consumption and emissions. The research was focused on the parts made of rigid glass-fiber reinforced polyurethane. The samples were made using the system based on polyol component А and isocyanate component B in a ratio of 1,75:1 (A:B). As a filler the glass fiber roving was used in the amount of 25 weight parts per 100 weight parts of the matrix component. The glass-fiber reinforced polyurethane parts were manufactured by spraying. The paper describes the comprehensive research of the glass-fiber reinforced polyurethane properties including the evaluation of thermal resistance, impact resilience, temperature resistance, Shore D hardness, acoustic absorption coefficient with the state-of-the-art test procedures and research equipment. The recommendations were developed to select glass-fiber reinforced polyurethanes for vehicle parts: for parts where the material is under high load during operation (temperature, impact resilience, etc.) it is recommended, whenever possible, to use the materials with larger thickness; for the parts where hardness is subject to special requirements – the materials with smaller thickness; during part production it is necessary to precisely carry out the operations of part manufacturing process to avoid any defects which are stress raisers and reduce the material strength
Study of effects of redispersable latex powders on hardening kinetics of cement-sand composites
Redispersable polymer powders act as boosters of the physical and mechanical properties in the cement-sand composite. For the studies the most typical redispersable polymer powders were used - Rhoximat PAV 22 and Rhoximat PAV 23 latex powders, by Rhodia. The analysis of the micrographs showed that the new formations of the cement rock had a pronounced needle-like form, and the cements with the additives were partially covered with the polymer film of the redispersable particles. The resulting polymer bridges and cords in the structure prevented growth of the cracks which were formed due to shrinkage and applied external force. Film-forming latex of redispersable powder can increase fracture energy of the cement-sand composite significantly. In view of this, of great significance is strength of the polymer itself. The higher strength polymer has, the greater force one should apply to fracture modified mixture. The basic components of Rhoximat PAV 22 and Rhoximat PAV 23 are vinyl acetate and vinyl versatate. Vinyl resins in the cement composites are known to develop a lattice which penetrates the structure formed by the cement gel, and, thus, act as an additional binder in the material
Production and investigation of properties of sulfide composite materials based on technogenic sulfur waste with titanium chloride as an activator
The modification with titanium chloride contributes to the increase in active sites of silica-containing compounds and opening of sulfur rings. As an activator, titanium chloride helps to make resistant and durable high-performance sulfur composite materials
Mechanosensitive calcium flashes promote sustained RhoA activation during tight junction remodeling
Epithelial cell–cell junctions remodel in response to mechanical stimuli to maintain barrier function. Previously, we found that local leaks in tight junctions (TJs) are rapidly repaired by local, transient RhoA activation, termed “Rho flares,” but how Rho flares are regulated is unknown. Here, we discovered that intracellular calcium flashes and junction elongation are early events in the Rho flare pathway. Both laser-induced and naturally occurring TJ breaks lead to local calcium flashes at the site of leaks. Additionally, junction elongation induced by optogenetics increases Rho flare frequency, suggesting that Rho flares are mechanically triggered. Depletion of intracellular calcium or inhibition of mechanosensitive calcium channels (MSCs) reduces the amplitude of calcium flashes and diminishes the sustained activation of Rho flares. MSC-dependent calcium influx is necessary to maintain global barrier function by regulating reinforcement of local TJ proteins via junction contraction. In all, we uncovered a novel role for MSC-dependent calcium flashes in TJ remodeling, allowing epithelial cells to repair local leaks induced by mechanical stimuli
Theoretical evaluation of rheological state of sand cement composite systems with polyoxyethylene additive using topological dynamics concept
© 2016 Trans Tech Publications, Switzerland.Presents the results of studies of contemporary materials in the field of rheological state. The topological mortar structure has been provided by theoretical evaluation of the rheological state of the cross-linked solutions and the experimental viscosity data of the sand cement mortar which has been modified by water-soluble additive – polyoxyethylene. The general model has been made for the structure of non-Newtonian liquideous systems including dilatant, pseudoplastic bodies with two main rheological active components in their structure – rigid and viscous phases. It is shown that in pseudoplastic systems, as the shear stress increases, the viscous phase grows because of the reduction of rigid phase content. In dilatant systems the converse situation has been observed. Furthermore, these phases are not clearly distinguishable, but to the contrary they are spatially interconnected in a complex way. The structure modeling has been made for non-Newtonian bodies using the Shklovskii-de Gennes model. The studies have found that the construction composite sand cement system is defined as the pseudoplastic body where cement and sand act as the rigid phase, water solution of polyoxyethylene – as the viscous phase. These findings can be used to prove the influence of polymer powder on the workability of dry mortar
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Buoyancy-Driven Coastal Currents off Oregon during Fall and Winter
During fall/winter off the Oregon coast, oceanographic surveys are relatively scarce because of rough
weather conditions. This challenge has been overcome by the use of autonomous underwater gliders deployed
along the Newport hydrographic line (NH-Line) nearly continuously since 2006. The discharge from the
coastal rivers between northern California and the NH-Line reach several thousands of cubic meters per
second, and the peaks are comparable to the discharge from the Columbia River. This freshwater input
creates cross-shelf density gradients that together with the wind forcing and the large-scale Davidson Current
results in strong northward velocities over the shelf. A persistent coastal current during fall/winter, which the
authors call the Oregon Coastal Current (OCC), has been revealed by the glider dataset. Based on a two-layer
model, the dominant forcing mechanism of the OCC is buoyancy, followed by the Davidson Current and then
the wind stress, accounting for 61% (±22.6%), 26% (±18.6%), and 13% (±11.7%) of the alongshore
transports, respectively. The OCC average velocities vary from 0.1 to over 0.5 m s⁻¹, and transports are on
average 0.08 (±0.07) Sverdrups (Sv; 1 Sv = 10⁶ m³ s⁻¹), with the maximum observed value of 0.49 Sv, comparable
to the summertime upwelling jet off the Oregon coast. The OCC is a surface-trapped coastal current,
and its geometry is highly affected by the wind stress, consistent with Ekman dynamics. The wind stress has an
overall small direct contribution to the alongshore transport; however, it plays a primary role in modifying the
OCC structure. The OCC is a persistent, key component of the fall/winter shelf dynamics and influences the
ocean biogeochemistry off the Oregon coast.Keywords: Fronts, Density currents, Coastal flows, Circulation/Dynamics, Baroclinic flows, Freshwater, Runoff, Atm/Ocean Structure/Phenomen
Building Heat-insulating Materials Based on the Products of the Transesterification of Polyethylene Terephthalate and Dibutyltin Dilaurate
In this paper, we offered a technological basis for production of heat-insulating polyurethane materials based on the aromatic polyester - the product of transesterification of polyethylene terephthalate and corrective additive - dibutyltin dilaurate. Also, we presented the formulation and properties of the developed polyurethanes
Measurement of the cross section with the CMD-3 detector at the VEPP-2000 collider
The process has been studied in the
center-of-mass energy range from 1500 to 2000\,MeV using a data sample of 23
pb collected with the CMD-3 detector at the VEPP-2000 collider.
Using about 24000 selected events, the cross
section has been measured with a systematic uncertainty decreasing from 11.7\%
at 1500-1600\,MeV to 6.1\% above 1800\,MeV. A preliminary study of
production dynamics has been performed
Study of the process in the c.m. energy range from threshold to 2 GeV with the CMD-3 detector
Using a data sample of 6.8 pb collected with the CMD-3 detector at the
VEPP-2000 collider we select about 2700 events of the process and measure its cross section at 12 energy ponts with about
6\% systematic uncertainty. From the angular distribution of produced nucleons
we obtain the ratio
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