Study of the Vibratory Behavior of the Bridge under the Passage of Mobile Loads Convoys: Comparative Study between Uni-dimensional and Three-dimensional Modeling

In order to understand the dynamic behavior of bridges under the passage of convoys of moving vehicles, it was necessary to start with the example of a single moving force, however, this study was deemed insufficient because the bridge is under several vehicle forces simultaneously. As a result, this study focuses on the vibration of bridges subjected to convoys of several mobile loads. Based on the analysis of the equation of motion that manage this behavior for the case of a simply-supported unamortized thin beam, subjected to convoys of one, two, and three forces at constant speed. In order to verify the solution obtained for a convoy of n forces through the superposition of solutions of single force with a time offset, see the influence of the spacing ‘e’ between the forces of the convoy on the dynamic amplification factor and compare the results of the analytical study with those derived from the real model established by the software Csi Bridge

Global nonexistence of solutions for a system of nonlinear viscoelastic wave equations with degenerate damping and source terms

The global existence and nonexistence of solutions for a system of nonlinear wave equations with degenerate damping and source terms supplemented with initial and Dirichlet boundary conditions was shown by Rammaha and Sakuntasathien in a bounded domain Ω ⊂ Rⁿ, n = 1, 2, 3, in the case where the initial energy is negative. A global nonexistence result on the solution with positive initial energy for a system of viscoelastic wave equations with nonlinear damping and source terms was obtained by Messaoudi and Said-Houari. Our result extends these previous results. We prove that the solutions of a system of wave equations with viscoelastic term, degenerate damping, and strong nonlinear sources acting in both equations at the same time are globally nonexisting provided that the initial data are sufficiently large in a bounded domain Ω of Rⁿ, n ≥ 1, the initial energy is positive, and the strongly nonlinear functions f₁ and f₂ satisfy the appropriate conditions. The main tool of the proof is based on the methods used by Vitillaro and developed by Said-Houari.Глобальне існування та неіснування розв'язків системи нєлінійних хвильових рівнянь із виродженим затуханням та джерелами, доповненої початковими умовами та граничними умовами Діріхле, було встановлено Rammaha та Sakuntasathien у обмеженій області Ω ⊂ Rⁿ , n = 1, 2, 3, при від'ємній початковій енергії. Результат про глобальне неіснування розв'язку системи нелінійних в'язкоеластичних хвильових рівнянь із нелінійним затуханням та джерелами при додатній початковій енергії було отримано у роботі Messaoudi та Said-Houari. Наш результат узагальнює ці попередні результати. Доведено, що розв'язки системи хвильових рівнянь із в'язкоеластичним членом, виродженим затуханням та сильно нелінійними джерелами, що діють одночасно в обох рівняннях, глобально не існують, якщо початкові дані є достатньо великими в обмеженій області Ω в Rⁿ , n ≥ 1, початкова енергія є додатною, а сильно нелінійні функції f₁ та f₂ задовольняють відповідні умови. Доведення базується на методах, що були використані у роботі Vitillaro та розвинуті у роботі Said-Houari

Mupirocin-resistant Staphylococcus aureus in Africa: a systematic review and meta-analysis

Background Mupirocin is widely used for nasal decolonization of Staphylococcus aureus to prevent subsequent staphylococcal infection in patients and healthcare personnel. However, the prolonged and unrestricted use has led to the emergence of mupirocin-resistant (mupR) S. aureus. The aim of this systematic review was to investigate the prevalence, phenotypic and molecular characteristics, and geographic spread of mupR S. aureus in Africa. Methods We examined five electronic databases (EBSCOhost, Google Scholar, ISI Web of Science, MEDLINE, and Scopus) for relevant English articles on screening for mupR S. aureus from various samples in Africa. In addition, we performed random effects meta-analysis of proportions to determine the pooled prevalence of mupR S. aureus in Africa. The search was conducted until 3 August 2016. Results We identified 43 eligible studies of which 11 (26%) were obtained only through Google Scholar. Most of the eligible studies (28/43; 65%) were conducted in Nigeria (10/43; 23%), Egypt (7/43; 16%), South Africa (6/43; 14%) and Tunisia (5/43; 12%). Overall, screening for mupR S. aureus was described in only 12 of 54 (22%) African countries. The disk diffusion method was the widely used technique (67%; 29/43) for the detection of mupR S. aureus in Africa. The mupA-positive S. aureus isolates were identified in five studies conducted in Egypt (n = 2), South Africa (n = 2), and Nigeria (n = 1). Low-level resistance (LmupR) and high-level resistance (HmupR) were both reported in six human studies from South Africa (n = 3), Egypt (n = 2) and Libya (n = 1). Data on mupR-MRSA was available in 11 studies from five countries, including Egypt, Ghana, Libya, Nigeria and South Africa. The pooled prevalence (based on 11 human studies) of mupR S. aureus in Africa was 14% (95% CI =6.8 to 23.2%). The proportion of mupA-positive S. aureus in Africa ranged between 0.5 and 8%. Furthermore, the frequency of S. aureus isolates that exhibited LmupR, HmupR and mupR-MRSA in Africa were 4 and 47%, 0.5 and 38%, 5 and 50%, respectively. Conclusions The prevalence of mupR S. aureus in Africa (14%) is worrisome and there is a need for data on administration and use of mupirocin. The disk diffusion method which is widely utilized in Africa could be an important method for the screening and identification of mupR S. aureus. Moreover, we advocate for surveillance studies with appropriate guidelines for screening mupR S. aureus in Africa

Social readiness for Corona virus in Algeria: A monographic approach to Skikda

Since its emergence and spread, the current Corona virus (COF19) has become a hot and revered subject for study in various scientific fields, causing many researchers to learn about it and work on it for many purposes, either in pursuit of scientific knowledge, or in community participation.So this article comes down to a central problematic that works on the social readiness of the corona virus from a sociological perspective that sometimes touches other scientific disciplines, such as psychology and health, in the light of which we have worked together to achieve a key goal that revolves around knowledge of the dimensions and indicators in the field of this readiness.A questionnaire was distributed to a sample that consisted of 140 individuals in the city of Skikda.The results indicated-different dimensions of this readiness in terms of interacting with the spread of the virus, -increasing knowledge about it from multiple sources,- and taking preventive measures to confront it

Corrosion Inhibition of Alloy Al-Cu-Mg by Lanthanum Chloride in 0.5 M NaCl

Abstract: This work studies the corrosion behavior of Al-Cu-Mg alloy in 0.5M NaCl with rare earth salt inhibitor, lanthanum chloride (LaCl 3 ). LaCl 3 concentrations used are: 100, 200, 400, 800 and 1000 ppm. The study was carried out by potentiodynamic measurements, impedance electrochemical spectroscopy, cyclic voltametry and gravimetric method. The results obtained show that lanthanum acts as cathodic inhibitor by the reduction of the Tafel cathodic slopes. The inhibition mechanism can be explain by the hydroxide formation between the cations La(III) and ions OH -.This hydroxide precipitates forms a passive film on the alloy surface in the chlorinated medium. The inhibiting effectiveness reaches 89.09 % for 1000 ppm of LaCl 3

Corrosion Inhibition of Alloy Al-Cu-Mg by Lanthanum Chloride in 0.5 M NaCl

This work studies the corrosion behavior of Al-Cu-Mg alloy in 0.5M NaCl with rare earth salt inhibitor, lanthanum chloride (LaCl3). LaCl3 concentrations used are: 100, 200, 400, 800 and 1000 ppm. The study was carried out by potentiodynamic measurements, impedance electrochemical spectroscopy, cyclic voltametry and gravimetric method. The results obtained show that lanthanum acts as cathodic inhibitor by the reduction of the Tafel cathodic slopes. The inhibition mechanism can be explain by the hydroxide formation between the cations La(III) and ions OH- .This hydroxide precipitates forms a passive film on the alloy surface in the chlorinated medium. The inhibiting effectiveness reaches 89.09 % for 1000 ppm of LaCl3

Effect of Ions Y+3 Inhibitor on Mild Steel Corrosion in 0.5 N NaCl Under Hydrostatic and Hydrodynamic Regime

The corrosion inhibition of mild steel by Yttrium salt Y(NO3)3 6H2O at different concentrations in 0.5 N NaCl, has been carried out by potentiodynamic tests and electrochemical impedance spectroscopy (EIS).In ions Y+3 presence, the ions OH- formation at the interface (electrode / electrolyte ) by water and oxygen reduction ,precipitates oxide and hydroxyde composite in passive film. The current density decreases as a function of the inhibitor concentration; it varies from the value without inhibitor (i = 0.2139 m A /cm2) to the minimal value (i = 7.4.10-4m A/cm2) for 600 ppm concentration; the corresponding inhibitive efficiency reaches 99.65 %. On laminar hydrodynamic regime (w £ 3000 rpm), steel inhibition depends on rotation speed. It has been showed that passive film formation is all the more slowly than the rotation speed increases

Blow up of Coupled Nonlinear Klein-Gordon System with Distributed Delay, Strong Damping, and Source Terms

This present work deals with the blow up of the coupled Klein-Gordon system with strong damping, distributed delay, and source terms, under suitable conditions

Проблема износа термоэлектровязкоупругих материалов

In this paper, we consider a mathematical model of a contact problem in thermo-electro- viscoelasticity. The body is in contact with an obstacle. The contact is frictional and bilateral with a moving rigid foundation which results in the wear of the contacting surface. We establish a variational formulation for the model and we prove the existence of a unique weak solution to the problem. The proof is based on a classical existence and uniqueness result on parabolic inequalities, differential equations and fixed point arguments. We present a variational formulation of the problem, and we prove the existence and uniqueness of the weak solutionВ данной работе рассматривается математическая модель контактной задачи термоэлектровязкоупругости. Тело соприкасается с препятствием. Контакт фрикционный и двусторонний с подвижным жестким основанием, что приводит к износу контактирующей поверхности. Устанавливается вариационная формулировка модели и доказывается существование единственного слабого решения задачи. Доказательство основано на классическом факте существования и единственности параболических неравенств, дифференциальных уравнений и аргументов с фиксированной точкой. Приводится вариационная постановка задачи, доказывается существование и единственность слабого решени