Experimental Analysis of the Physical Degradation of Polymers – The Case of Polymethyl Methacrylate

Polymers are known to be sensitive to aging; their lifetime can be predicted through experimental tests. The present paper presents an experimental study on the long-term performance of polymethyl methacrylate (PMMA) exposed to solar and UV radiations, drinking water and sea water. The performance of this polymer was analyzed in terms of strain variation, strain at break in tension, and Young's modulus. The results obtained showed that the amount of absorbed water is independent of the nature of the solvent, and only the absorption kinetics may be regulated by the species contained in the medium. This seems to indicate that plastification of polymers is a reversible phenomenon. In addition, it was found that the tensile strength and elastic modulus drop with increasing immersion time. Compared with seawater, the absorption of drinking tap water, after 36 months, leads to a non-linear behavior of the polymethyl methacrylate. Exposition of  PMMA to UV radiation and global solar radiation, for the same duration of exposure, resulted in greater performance degradation when the polymer was exposed to UV radiation. In addition, the results obtained after a 19-month exposure period that the UV radiation changes the behavior of this material from viscoelastic to viscoplastic.  &nbsp

Mechanical Characterization of the Threshold Strain in Sand Liquefaction

DOBRY et al, YOUD have shown the existence of a shearing threshold strain in the vicinity of 10-4 which guides the occurrence of liquefaction. With tests on glass beads and sand from the Algiers bay, using a proper measuring system, we were able to arrive at a better resolution of this threshold and to the determination of its mechanical signification

Islam en 'Heimat' in SAID’s ‘Ich und der Islam’ en ‘Das Niemandsland ist unseres’

The article investigates two semi-autobiographic texts by the Iranian-German writer SAID, ‘Das Niemandsland ist unseres. West-östliche Betrachtungen’ and ‘Ich und der Islam’. The article focuses on the relationship between Heimat and islam against the background of SAID’s exile experience. The writer reflects upon the way language creates a safe space and functions as a new Heimat. SAID also defends islam as a spiritual religion, but rejects it in the form of a state ideology. In addition to that, he compares islam with the art of poetry and understand both as sources of religiosity

Role of Contemporary Sociology Theories in the Study of Mass Communication (Analytical Critical Perspective)

This Study was prepared to identify the contributions made by the theories of contemporary sociology in research and studies that highlight the mass communication, as these theories are considered the first laid theories upon which scientific research relied when the media was originated, how those theories contributed to the study of mass communication, and what are their abilities in dealing with it. Also, this Study aimed to identify the contemporary theories of sociology and to recognize the contributions made by the theories of contemporary sociology in research and studies that highlight the mass communication and the extent of the contributions of contemporary sociology in particular in the study of mass communication and the extent of the capabilities of these theories in dealing with the areas of mass communication in light of advanced media technology and the prompt response by the public to it? This Study used the analytical descriptive approach and reached a range of findings, including the variation in views, as the supporting studies indicated that there are great findings on its development in the specialization of its study at several levels, whether theoretical-related or methodological-related, and even in teaching disciplines in universities, but even at the level of practical application and its clear effects on the society. As for the opposing studies findings, the study of mass communication and its content has not yet reached and developed in a way that can become an independent and autonomous scientific school, as they perceive research and studies related to mass communication and its processes, to be premised on a group of specialists who follow the field of social and natural sciences togethe

The Fourier Singular Complement Method for the Poisson problem. Part II: axisymmetric domains

This paper is the second part of a threefold article, aimed at solving numerically the Poisson problem in three-dimensional prismatic or axisymmetric domains. In the first part of this series, the Fourier Singular Complement Method was introduced and analysed, in prismatic domains. In this second part, the FSCM is studied in axisymmetric domains with conical vertices, whereas, in the third part, implementation issues, numerical tests and comparisons with other methods are carried out. The method is based on a Fourier expansion in the direction parallel to the reentrant edges of the domain, and on an improved variant of the Singular Complement Method in the 2D section perpendicular to those edges. Neither refinements near the reentrant edges or vertices of the domain, nor cut-off functions are required in the computations to achieve an optimal convergence order in terms of the mesh size and the number of Fourier modes used

The Fourier Singular Complement Method for the Poisson problem. Part I: prismatic domains

This is the first part of a threefold article, aimed at solving numerically the Poisson problem in three-dimensional prismatic or axisymmetric domains. In this first part, the Fourier Singular Complement Method is introduced and analysed, in prismatic domains. In the second part, the FSCM is studied in axisymmetric domains with conical vertices, whereas, in the third part, implementation issues, numerical tests and comparisons with other methods are carried out. The method is based on a Fourier expansion in the direction parallel to the reentrant edges of the domain, and on an improved variant of the Singular Complement Method in the 2D section perpendicular to those edges. Neither refinements near the reentrant edges of the domain nor cut-off functions are required in the computations to achieve an optimal convergence order in terms of the mesh size and the number of Fourier modes used

La formación en alternancia en Francia: entre prácticas sociales y objeto de investigación

La formació en alternança (o dual) a França és una pràctica educativa antiga. Actualment, la trobem en diferents formacions i en diferents modalitats en l’ensenyament secundari i en l’educació superior. Tot i això, per a les ciències de l’educació és un objecte de recerca recent. Després de diferents experiències de pedagogs adscrits als moviments educatius populars o d’educació permanent, als anys vuitanta i noranta apareixen els primers treballs de sociòlegs i de didàctics sobre aquesta temàtica. Actualment, la preocupació dels investigadors en ciències de l’educació és avaluar els efectes de la formació en alternança sobre els processos de desenvolupament professional i de construcció identitària dels estudiants en formació inicial i dels treballadors en formació contínua. Per il·lustrar la nostra anàlisi, presentem diferents casos d’estudi en formació inicial a la universitat i en formació contínua superior.Co-op education (or sandwich courses) is a long-standing educational practice in France. Today it is present under various statuses and forms in secondary and higher education. In the education sciences, however, it became a subject of research much later on. After various narratives of militant teachers’ experiences of popular or life-long education educational movements, the first works by sociologists’ and educational specialists’ on this topic appeared in the 1980s and 1990s. At present, the concern of education science researchers is to estimate the effects of co-op education (or sandwich courses) on the processes of professional development and identity construction of post-graduate students or vocational trainees. To illustrate our reflection, we present different case studies in the initial phase of university education and in continuous higher education training.La formación en alternancia (o dual) en Francia es una práctica educativa antigua. En la actualidad se presenta en distintas formaciones, bajo diferentes formas en la educación secundaria y la educación superior. Para las ciencias de la educación, sin embargo, no se convierte en objeto de investigación hasta recientemente. Después de varias experiencias de pedagogos adscritos a los movimientos educativos populares en educación permanente, en los ochenta aparecen los primeros trabajos de sociólogos y didácticos sobre la temática. Hoy, la preocupación de los investigadores en ciencias de la educación es evaluar los efectos de la formación en alternancia sobre los procesos de desarrollo profesional y de construcción de la identidad profesional de los estudiantes durante su formación inicial y de los trabajadores en su formación continua. Para ilustrar nuestra reflexión, analizamos varios estudios de caso en la enseñanza universitaria inicial y en la formación continua superior