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

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

Nucleation and twinning in tin droplet solidification on single crystal intermetallic compounds

βSn nucleation is a key step in the formation of microstructure in electronic solder joints. Here, the heterogeneous nucleation of βSn is studied in undercooled tin droplets spread on the facets of various intermetallic compounds (IMCs). Nucleation undercoolings are measured in solidifying droplets and are linked to orientation relationships (ORs) measured by electron backscatter diffraction (EBSD). Preferred ORs developed on all IMCs studied. For the more potent nucleants (αCoSn3, IrSn4, PtSn4, PdSn4) the ORs represent relatively simple atomic matches. ORs with lower potency nucleants (Cu6Sn5, Ag3Sn, Ni3Sn4) had more complex atomic matches that are explored based on matching of the closest packed atomic rows. βSn solidification twinning is shown to be more complex than has been reported previously: both nucleation on an IMC facet and cyclic twinning of that grain occurred in many droplets on Cu6Sn5, Ag3Sn, Ni3Sn4; in all twinned droplets the Sn twinning axis occurred along a direction on the IMC with the lowest linear atomic disregistry; and interrelated cyclic twins formed consisting of up to five rings of cyclic twins all related by shared Sn axes

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

The influence of primary Cu6Sn5 size on the shear impact properties of Sn-Cu/Cu BGA Joints

A method is presented to control the size of primary Cu6Sn5 in ball grid array (BGA) joints while keeping all other microstructural features near-constant, enabling a direct study of the size of primary Cu6Sn5 on impact properties. For Sn-2Cu/Cu BGA joints, it is shown that larger primary Cu6Sn5 particles have a clear negative effect on the shear impact properties. Macroscopic fracture occurred by a combination of the brittle fracture of embedded primary Cu6Sn5 rods and ductile fracture of the matrix βSn. Cleavage of the Cu6Sn5 rods occurred mostly along (0001) or perpendicular to (0001) with some crack deflection between the two. The deterioration of shear impact properties with increasing Cu6Sn5 size is attributed to (1) the larger microcracks introduced by the brittle fracture of larger embedded Cu6Sn5 crystals, and (2) the less numerous and more widely spaced rods when the Cu6Sn5 crystals are larger, which makes them poor strengtheners

Kinetics of grain refinemet in metallic materials during large strain deformation

The development of ultrafine grained microstructures in austenitic stainless steel and pure titanium subjected to large strain deformation was comparatively studied. The change in the volume fractions of newly developed ultrafine grains was used to quantify the progress in grain refinement during plastic deformatio

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