Analytical Possibilities of Rutherford Backscattering Spectrometry and Elastic Recoil Detection Analysis Methods

This paper presents the results of an experimental study of three samples containing various elements in the near-surface layers. The depth profiles of all the elements of different atomic masses from hydrogen to silver were investigated by Rutherford Backscattering Spectrometry (RBS) and Elastic Recoil Detection Analysis (ERDA). The experiments were performed by using the low-energy (about 2 MeV) 4He+ ion beams. The obtained results demonstrate the possibility of the RBS and ERDA methods in the investigation of depth profiles of any mass element with an atomic concentration of about 0.01 at.% and a depth resolution close to 10 nm

On Tamm's problem in the Vavilov-Cherenkov radiation theory

We analyse the well-known Tamm problem treating the charge motion on a finite space interval with the velocity exceeding light velocity in medium. By comparing Tamm's formulae with the exact ones we prove that former do not properly describe Cherenkov radiation terms. We also investigate Tamm's formula cos(theta)=1/(beta n) defining the position of maximum of the field strengths Fourier components for the infinite uniform motion of a charge. Numerical analysis of the Fourier components of field strengths shows that they have a pronounced maximum at cos(theta)=1/(beta n) only for the charge motion on the infinitely small interval. As the latter grows, many maxima appear. For the charge motion on an infinite interval there is infinite number of maxima of the same amplitude. The quantum analysis of Tamm's formula leads to the same results.Comment: 28 pages, 8 figures, to be published in J.Phys.D:Appl.Phy

Совершенствование методики расчёта параметров сортировочных горок

The paper presents a new approach to selection of design standards in design of hump yards, which are among the most important elements of railway stations. The height of gravity hump is a key parameter to ensure succesful and safe operations of separating railway cars at stations. Estimations of the gravity hump’s height are influenced mostly by the path length and the value of the main specific resistance to movement of the estimated free axles. Following currently changing structure of the processed car flow at stations, it is necessary to update the current methods. The objective of the study is to update the existing method of choosing of estimated free axle and estimated point while calculating the estimated height of marshalling gravity humps. Following the results of the study that used statistical and mathematical analysis the weight of the estimated free axle is proposed to be determined by the average value of the total car flow processed at the hump yard, and that calculations of estimated path length and estimated point should take into account the useful length and slopes of the sorting tracks. The application of the proposed changes in the methodology for determining the required height of gravity humps will help to increase the efficiency and safety of their operation. The methodology of the study, while its conclusions in the form of calculated values are intended for Russian railways, can be applied for conducting similar analysis at any railwayВ работе представлен новый подход к выбору расчётных нормативов при проектировании сортировочных горок, которые являются одним из важнейших элементов железнодорожных станций. Высота сортировочных горок является определяющим параметром в обеспечении успешной и безопасной работы по расформированию составов на станциях. Наибольшее влияние на расчётную высоту сортировочных горок оказывают длина пробега и величина основного удельного сопротивления движению расчётных бегунов. В связи с изменением в настоящее время структуры перерабатываемого вагонопотока на станциях требуется пересмотр существующих методик. Целью исследования является пересмотр существующей методики выбора расчётного бегуна и расчётной точки при определении расчётной высоты сортировочных горок. По результатам проведённого с использованием методов статистического и математического анализа исследования вес расчётного бегуна предлагается определять по средней величине всего вагонопотока, перерабатываемого на сортировочной горке, а расчётную длину пробега и расчётную точку принимать с учётом полезной длины и уклонов сортировочных путей. Применение предложенных изменений в методике определения потребной высоты сортировочных горок будет способствовать повышению эффективности и безопасности их работы. Методология исследования, при том, что непосредственно цифровые выводы предназначены для использования на российских железных дорогах, тем не менее может быть применена при проведении аналогичного анализа в условиях любых других железных дорог

Nuclear Reaction Network for Primordial Nucleosynthesis: a detailed analysis of rates, uncertainties and light nuclei yields

We analyze in details the standard Primordial Nucleosynthesis scenario. In particular we discuss the key theoretical issues which are involved in a detailed prediction of light nuclide abundances, as the weak reaction rates, neutrino decoupling and nuclear rate modeling. We also perform a new analysis of available data on the main nuclear processes entering the nucleosynthesis reaction network, with particular stress on their uncertainties as well as on their role in determining the corresponding uncertainties on light nuclide theoretical estimates. The current status of theoretical versus experimental results for 2H, 3He, 4He and 7Li is then discussed using the determination of the baryon density as obtained from Cosmic Microwave Background anisotropies.Comment: LaTeX, 83 pages, 30 .pdf figures. Some typos in the units of R-functions in appendix D and relative plots fixe

Cerenkov and sub-Cerenkov radiation from a charged particle beam

As a consequence of the relaxation of the phasing conditions between the moving charge and radiated wave for finite beam path lengths, the Cerenkov peak is broadened and the threshold energy is developed which is applicable to charged beams consisting of single point charge or charge bunch of finite size, as well as beams consisting of periodically repeated buncheshttp://archive.org/details/cerenkovsubceren00neigN

IMPROVEMENT OF BOARDWALK NAILED – SPAN BRIDGE STRUCTURES

The article is devoted to the implementation in practice of the construction of the new bridge boardwalk timber - nail span structures that meet the modern requirements of load capacity, reliability and durability. The authors propose and describe a new design of the span timber-beam-peg–nailed blocks with longitudinal-transverse orientation of the belt boards and carrying transverse reinforced concrete slab of the carriageway. The represented materials show the effectiveness of the proposed solutions

ON PERFECTION OF CONSTRUCTIVE AND TECHNOLOGICAL FORMS OF PLATE AND RIBBED TRANSFER STRUCTURES FROM GLUED TIMBER

Introduction. The paper presents the prefabricated whole-glued slab-ribbed superstructures, containing glued beams (fins) and a multi-layered wood-panel from horizontal cross-layers of blank boards, laid successively on glued beams and each other and interconnected by glue seams.Materials and methods. Because of the development of the constructive and technological forms of the considered superstructures, the authors propose the structure composed of plate and ribbed integrally transported prefabricated sections with the width of 3-3.5 m. The authors highlight that the combined action of the detached sections is provided through the nodes of combination on the adjacent ribs of  the sections without the complicated compression of all the elements of the superstructure including beams, plates, and diaphragms.Results. The analysis of the stress-deformed span by two methods indicates that both methods determine, with a sufficient degree of accuracy, the nature of the distribution of stresses and strains in sections of the structure. Moreover, the obtained values of the maximum deflections and stresses do not exceed the limit values established by the norms and the corresponding values in a similar construction of the structure with a solid timber slab.Conclusions. The paper shows that the proposed construction with the division of the whole-glued multiridged span structure into separate prefabricated, factory-made sections would significantly expand the usage of laminated wood in bridge construction