Properties and Design Characteristics of the Fiber Concrete

AbstractUnder the contemporary conditions of permanent construction complication, the volume of reinforce-concrete structures that are in the process of exploitation of building function in the conditions of difficult loading is growing: they are exposed to the slanting bend, twisting and dynamic influences. These structures include foundations and ceilings of productive buildings installed with the use of vibrating equipment (flatting mills, press, metal-working machine-tools), beams for a faucet, highway coverage, bridge elements, air strips of the air fields, body elements of hydro energetic objects. The complex loaded structures shall meet the stringent requirements not only in terms of bending and compression resistance but also in terms of structural integrity maintenance (crack resistance). In case of the technological process change or formation of defects and damages, repair of these elements is not possible – they can be only replaced, and this will demand to stop the production, sort out a high-cube of reinforced-concrete structures and, consequently, lead to material expenses comparable with a new building construction. An increase of the exploitation term of the complex loaded reinforce-concrete structures is a topical and economically demanded research

Исследование работы стеклопластиковых крепежных элементов в стеновых конструкциях

The article is devoted to the study of pull-out tests of fiberglass plastic dowels installed in the walls made of lightweight concrete. The authors have undertaken experimental tests of anchors in use on the construction site and conducted analysis of test results.Работа посвящена исследованию характеристик сцепления композитных стеклопластиковых дюбелей с легким бетоном. Авторами проведены экспериментальные испытания анкеров в натурных условияx на строительной площадке и выполнен анализ результатов испытаний

HIV-care access among people with incarceration experience in St. Petersburg, Russia

Background: Little is known about the clinical care experiences of HIV-infected persons in St. Petersburg who have experience with incarceration. To address this question, we conducted a capture-recapture study to identify individuals who had been diagnosed with HIV infection while incarcerated and who subsequently presented for medical care in St. Petersburg, Russia following release from prison. Methods: We matched 292 HIV-positive prisoners tested by the prison system in 2010 to the medical records at the St. Petersburg AIDS Center in the following 4 years. Results: The data analysis shows that as many as half of HIV+ prisoners fail to seek treatment in the community upon release. Of those who had sought care post-release, only 36% were receiving HAART. Of the 109 individuals for whom tuberculosis testing was indicated post-release, 36.7% were found to be reactive. Conclusion: Despite the limitations of the data, this study is the first of its kind to review records documenting HIV care among prisoners in Russia post-incarceration. In addition to providing important descriptive information about this marginalized population, the findings from this study highlight areas where HIV control efforts could be improved in order to address the HIV epidemic in the Russian Federation

Внешняя среда как фактор выбора места проживания

Many people have certain problems with the choice of the place of living. The main idea of this article is to study the aspects of urban area environment which effect on this decision. The influence of these factors is analyzed on example of two cities: the big one and the small one.Многие люди имеют определенные проблемы при выборе места жительства. Основной идеей данной статьи является изучение аспектов городской окружающей среды, которые влияют на выбор места проживания людей. Влияние этих факторов анализируется на примере двух городов: один большой и один маленький по градостроительной классификации

Damage buildup in Si under bombardment with MeV heavy atomic and molecular ions

Accumulation of structural disorder in Si bombarded at −196 °C with 0.5 MeV ²⁰⁹Bi₁ and 1 MeV ²⁰⁹Bi₂ ions (the so-called molecular effect) is studied by Rutherford backscattering/channeling spectrometry. Results show that the damage buildup is sigmodal even for such heavy-ion bombardment at liquid nitrogen temperature. This strongly suggests that, for the implant conditions of this study, the buildup of lattice damage cannot be considered as an accumulation of completely disordered regions. Instead, damage-dose curves are well described by a cascade-overlap model modified to take into account a catastrophic collapse of incompletely disordered regions into an amorphous phase after damage reaches some critical level. Results also show that Bi₂ ions produce more lattice damage than Bi₁ ions implanted to the same dose. The ratio of lattice disorder produced by Bi₂ and Bi₁ ions is 1.7 near the surface, decreases with depth, and finally becomes close to unity in the bulk defect peak region. Parameters of collision cascades obtained using ballistic calculations are in good agreement with experimental data. The molecular effect is attributed to a spatial overlap of (relatively dense) collision subcascades, which gives rise to (i) nonlinear energy spike processes and/or (ii) an increase in the defect clustering efficiency with an effective increase in the density of ion-beam-generated defects.Research at StPSTU was supported in part by the Ministry for General and Professional Education of the Russian Federation

Effective ways to reduce leaching and formation of efflorescence on structures

Corrosion of the first kind (leaching) is the process of dissolution and removal to the surface of the structure of calcium hydroxide salts mainly under the action of a constant diffuse flow of water through a multi-level porous structure of the concrete composite. Technological methods to prevent the formation and reduction of efflorescence (leaching) when used in practice, improve durability of building structures and reduce operating costs. The paper explores the possibility of reduction or complete elimination of efflorescence on the surface of building structures due to the impact on calcium hydroxide in the composition of the Portland cement. © 2019 IOP Publishing Ltd. All rights reserved

Application of effective concrete composites to increase radiation protection of residential areas

The scientific article presents the analysis of studies of radiation safety of residential buildings in the city of Yekaterinburg, Sverdlovsk region and the results of the development of new building materials with protective properties. The review of available statistical data on the specified subject is carried out. It is revealed that the most simple and economically justified method of increasing the protection of the population from the radiation impact of man-made or natural environment is the construction of buildings with the use of innovative building materials or reconstruction of existing ones with the use of heavy concrete with effective radiation-protective aggregates. © Published under licence by IOP Publishing Ltd

Structural changes in metastable austenitic steel during equal channel angular pressing and subsequent cyclic deformation

The paper reports a substantial improvement of the static and cyclic strength of a Cr-Ni-Ti austenitic stainless steel nanostructured by equal channel angular pressing (ECAP). After ECAP at room temperature or 673 K, the mean grain size decreased from 14 µm to 430 nm or 940 nm, respectively; corresponding ultimate tensile strength increased from 610 MPa to 1230 MPa or 940 MPa, and the fatigue limit increased from 275 MPa to 375 MPa or 475 MP

Released momentum distribution of a Fermi gas in the BCS-BEC crossover

We develop a time-dependent mean-field theory to investigate the released momentum distribution and the released energy of an ultracold Fermi gas in the BCS-BEC crossover after the scattering length has been set to zero by a fast magnetic-field ramp. For a homogeneous gas we analyze the non-equilibrium dynamics of the system as a function of the interaction strength and of the ramp speed. For a trapped gas the theoretical predictions are compared with experimental results.Comment: 4 pages, 4 figure