Aspects of structural degradation in old bridge steels by means of fatigue crack propagation

The paper presents conclusions drawn from studies related to old steel structures, especially those erected on the turn of the 19th century. The objects of interest of the authors were Wroclaw Pomorskie Bridges: the Central Pomorski Bridge and the North Pomorski Bridge (1885, 1930 respectively), as well as the Sand Bridge (1861). The material used for their construction was puddled steel or cast steel. In the course of long operation the steels (especially the puddled one) show susceptibility to degradation processes. In this paper the results of metallographic tests (light microscopy, SEM) and mechanical properties tests (hardness measurement, static tensile test) presenting the state of structural degradation have been presented. Also, the initial study results for the puddled steel coming from the Sand Bridge and concerning development of a fatigue crack have been presented. Basic quantities describing the kinetics of fatigue crack growth have been determined.Досліджено сталі мостів біля Вроцлава (Польща): дві пудлингові, експлуатовані з 1861 і 1885 рр., а також ливарну (1930 р.). Сталі, особливо пудлингові, чутливі до деградаційних процесів, що проявилось у зміні структури і механічних властивостей, найвідчутніше – у зниженні опору втомному росту тріщини.Исследованы стали мостов в районе Вроцлава (Польша): две пудлинговые, эксплуатируемые с 1861 и 1885 гг., а также литейную (1930 г.). Стали, особенно пудлинговые, чувствительны к деградационным процессам, что проявилось как в изменении структуры, так и механических свойств, наиболее значительно – в понижении сопротивления усталостному росту трещин

A new method for complexity determination by using fractals and its applications in material surface characteristics

In this article, a new method for complexity determination by using fractals in combination with an artificial intelligent approach is proposed and its application in laser hardening technology is detailed. In particular, nanoindentation tests were applied as a way to investigate the hardness properties of tool steel alloys with respect to both marginal and relevant changes in laser hardening parameters. Specifically, process duration and temperature were considered, together with nanoindentation, later related to surface characteristics by image analysis and Hurst exponent determination. Three different Machine Learning algorithms (Random Forest, Support Vector Machine and k-Nearest Neighbors) were used and predictions compared with measures in terms of mean, variability and linear correlation. Evidences confirmed the general applicability of this method, based on integrating fractals for microstructure analysis and machine learning for their deep understanding, in material science and process engineering

Kinetics of fatigue crack growth and crack paths in the old puddled steel after 100-years operating time

The goal of the authors’ investigations was determination of the fatigue crack growth in fragmentsof steel structures (of the puddled steel) and its cyclic behavior. Tested steel elements coming from the turn ofthe 19th and 20th were gained from still operating ancient steel construction (a main hall of Railway Station,bridges etc.). This work is a part of investigations devoted to the phenomenon of microstructural degradationand its potential influence on their strength properties. The analysis of the obtained results indicated that thoselong operating steels subject to microstructure degradation processes consisting mainly in precipitation ofcarbides and nitrides inside ferrite grains, precipitation of carbides at ferrite grain boundaries and degenerationof pearlite areas [1, 2]. It is worth noticing that resistance of the puddled steel to fatigue crack propagation inthe normalized state was higher. The authors proposed the new kinetic equation of fatigue crack growth rate insuch a steel. Thus the relationship between the kinetics of degradation processes and the fatigue crack growthrate also have been shown. It is also confirmed by the materials research of the viaduct from 1885, which hasnot shown any significant changes in microstructure. The non-classical kinetic fatigue fracture diagrams (KFFD)based on deformation (??) or energy (?W) approach was also considered. In conjunction with the results oflow- and high-cycle fatigue and gradual loss of ductility as a consequence (due to the microstructuraldegradation processes) - it seems to be a promising construction of the new kinetics fatigue fracture diagramswith the energy approach

Analytical two-center integrals over Slater geminal functions

We present analytical formulas for the calculation of the two-center two-electron integrals in the basis of Slater geminals and products of Slater orbitals. Our derivation starts with establishing a inhomogeneous fourth-order ordinary differential equation that is obeyed by the master integral, the simplest integral with inverse powers of all interparticle distances. To solve this equation it was necessary to introduce a new family of special functions which are defined through their series expansions around regular singular points of the differential equation. To increase the power of the interparticle distances under the sign of the integral we developed a family of open-ended recursion relations. A handful of special cases of the integrals is also analysed with some remarks on simplifications that occur. Additionally, we present some numerical examples of the master integral that validate the usefulness and correctness of the key equations derived in this paper. In particular, we compare our results with the calculations based on the series expansion of the exp(-\gamma r12) term in the master integral.Comment: 28 pages, 0 figures, 7 table

Directions of digital transformation of international trade in services in the context of the global crisis

International trade is an integral part of the economy of any country. In recent decades, the role of various services in the structure of international exchange has increased. Their range is expanding under the influence of the scientifc and technological revolution, which leads to signifcant changes in this area. At the same time, the regimes of international trade in services, as well as approaches to its national and multilateral regulation, are becoming more complex. All areas of activity, including cross-border service provision, are transforming in a rapidly changing world. In the context of the pandemic, the “digit” has become widespread, and the urgency of streamlining and further developing the international exchange of services has increased. Digitalisation, which has become one of the key features of the development of the world economy in the last decade, has accelerated the development of the service sector, but also contributed to the formation of new challenges for the development of trade in services. The digital transformation of international trade is shaping the new “digital realities” of the industry. Statistics from the ofcial regulators of international trade confrm these changes. The paper analyzes the dynamics of changes in international trade in services in the context of the global crisis and the impact of digitalization on it. The article shows how new patterns of international exchange of services are formed in the context of increased economic interdependence of countries

A novel and fast purification method for nucleoside transporters

Nucleoside transporters (NTs) play critical biological roles in humans, and to understand the molecular mechanism of nucleoside transport requires high-resolution structural information. However, the main bottleneck for structural analysis of NTs is the production of pure, stable, and high quality native protein for crystallization trials. Here we report a novel membrane protein expression and purification strategy, including construction of a high-yield membrane protein expression vector, and a new and fast purification protocol for NTs. The advantages of this strategy are the improved time efficiency, leading to high quality, active, stable membrane proteins, and the efficient use of reagents and consumables. Our strategy might serve as a useful point of reference for investigating NTs and other membrane proteins by clarifying the technical points of vector construction and improvements of membrane protein expression and purification. © 2016 Hao, Thomsen, Postis, Lesiuk, Sharples, Wang, Bartlam and Goldman.Peer reviewe

Symphony on strong field approximation

This paper has been prepared by the Symphony collaboration (University of Warsaw, Uniwersytet Jagiellonski, DESY/CNR and ICFO) on the occasion of the 25th anniversary of the 'simple man's models' which underlie most of the phenomena that occur when intense ultrashort laser pulses interact with matter. The phenomena in question include high-harmonic generation (HHG), above-threshold ionization (ATI), and non-sequential multielectron ionization (NSMI). 'Simple man's models' provide both an intuitive basis for understanding the numerical solutions of the time-dependent Schrodinger equation and the motivation for the powerful analytic approximations generally known as the strong field approximation (SFA). In this paper we first review the SFA in the form developed by us in the last 25 years. In this approach the SFA is a method to solve the TDSE, in which the non-perturbative interactions are described by including continuum-continuum interactions in a systematic perturbation-like theory. In this review we focus on recent applications of the SFA to HHG, ATI and NSMI from multi-electron atoms and from multi-atom molecules. The main novel part of the presented theory concerns generalizations of the SFA to: (i) time-dependent treatment of two-electron atoms, allowing for studies of an interplay between electron impact ionization and resonant excitation with subsequent ionization; (ii) time-dependent treatment in the single active electron approximation of 'large' molecules and targets which are themselves undergoing dynamics during the HHG or ATI processes. In particular, we formulate the general expressions for the case of arbitrary molecules, combining input from quantum chemistry and quantum dynamics. We formulate also theory of time-dependent separable molecular potentials to model analytically the dynamics of realistic electronic wave packets for molecules in strong laser fields. We dedicate this work to the memory of Bertrand Carre, who passed away in March 2018 at the age of 60

A matched-pair cluster design study protocol to evaluate implementation of the Canadian C-spine rule in hospital emergency departments: Phase III

BACKGROUND: Physicians in Canadian emergency departments (EDs) annually treat 185,000 alert and stable trauma victims who are at risk for cervical spine (C-spine) injury. However, only 0.9% of these patients have suffered a cervical spine fracture. Current use of radiography is not efficient. The Canadian C-Spine Rule is designed to allow physicians to be more selective and accurate in ordering C-spine radiography, and to rapidly clear the C-spine without the need for radiography in many patients. The goal of this phase III study is to evaluate the effectiveness of an active strategy to implement the Canadian C-Spine Rule into physician practice. Specific objectives are to: 1) determine clinical impact, 2) determine sustainability, 3) evaluate performance, and 4) conduct an economic evaluation. METHODS: We propose a matched-pair cluster design study that compares outcomes during three consecutive 12-months "before," "after," and "decay" periods at six pairs of "intervention" and "control" sites. These 12 hospital ED sites will be stratified as "teaching" or "community" hospitals, matched according to baseline C-spine radiography ordering rates, and then allocated within each pair to either intervention or control groups. During the "after" period at the intervention sites, simple and inexpensive strategies will be employed to actively implement the Canadian C-Spine Rule. The following outcomes will be assessed: 1) measures of clinical impact, 2) performance of the Canadian C-Spine Rule, and 3) economic measures. During the 12-month "decay" period, implementation strategies will continue, allowing us to evaluate the sustainability of the effect. We estimate a sample size of 4,800 patients in each period in order to have adequate power to evaluate the main outcomes. DISCUSSION: Phase I successfully derived the Canadian C-Spine Rule and phase II confirmed the accuracy and safety of the rule, hence, the potential for physicians to improve care. What remains unknown is the actual change in clinical behaviors that can be affected by implementation of the Canadian C-Spine Rule, and whether implementation can be achieved with simple and inexpensive measures. We believe that the Canadian C-Spine Rule has the potential to significantly reduce health care costs and improve the efficiency of patient flow in busy Canadian EDs