Search results for "WTO"
showing 10 items of 163 documents
Permeability and effective porosity of porous media
1997
The concept of permeability of porous media is discussed, and a modification of Kozeny’s permeability equation to include the effect of effective porosity is introduced. An analytical expression for the specific surface area of a system constructed of randomly placed identical obstacles with unrestricted overlap is derived, and a lattice-gas cellular automaton method is then used to simulate the dependence on porosity of permeability, tortuosity, and effective porosity for a flow of Newtonian uncompressible fluid in this two-dimensional porous substance. The simulated permeabilities can well be explained by the concept of effective porosity, and the exact form of the specific surface area. …
Deficiencias epistemológicas en la enseñanza habitual de los conceptos de campo y potencial eléctrico
1997
This article intends to analyse up to what extent the scarce learning produced when introducing the basic concepts on electrostatics is due to deficiencies and inadequacies in its routine teaching. So, on the one hand, we analyse what have been the principal epistemological leaps forward in the making of electricity as a science. On the other hand, we analyse Physics books and the teachers’ opinions.
Apparent universality of semiclassical gravity in the far field limit
2006
The universality of semiclassical gravity is investigated by considering the behavior of the quantities < ��^2 > and < {T^a}_b >, along with quantum corrections to the effective Newtonian potential in the far field limits of static spherically symmetric objects ranging from stars in the weak field Newtonian limit to black holes. For scalar fields it is shown that when differences occur they all result from the behavior of a single mode with zero frequency and angular momentum and are thus due to a combination of infrared and s-wave effects. An intriguing combination of similarities and differences between the extreme cases of a Schwarzschild black hole and a star in the weak fie…
Numerical study of the Kerr solution in rotating coordinates
2016
International audience; The Kerr solution in coordinates corotating with the horizon is studied as a testbed for a spacetime with a helical Killing vector in the Ernst picture. The solution is numerically constructed by solving the Ernst equation with a spectral method and a Newton iteration. We discuss convergence of the iteration for several initial iterates and different values of the Kerr parameters.
Application of 5E model for learning Mechanics through inquiry in secondary education
2018
En este trabajo se examina el proceso de resolución de una actividad de indagación sobre las leyes de Newton que consiste en diseñar un montaje con el cuál averiguar qué superficie es la más adecuada para arrastrar cajas de ropa en un almacén. Los participantes son 23 estudiantes de 4º de ESO. Para la toma de datos se recogen sus respuestas escritas relativas al diseño del dispositivo, a la toma de datos, interpretación de resultados y establecimiento de conclusiones. Para el análisis se examinan utilizando como herramienta el modelo de instrucción 5E. Los resultados principales apuntan a ciertas dificultades en los desempeños del alumnado relativos a la elaboración del montaje y a la expli…
EC Practice in the WTO: How Wide is the "Scope for Manouvre"?
2004
The EC’s implementation record in the WTO seems to reflect an attitude that, in accordance with the view traditionally maintained by the European Court of Justice from International Fruit to Portugal, finds its cornerstone in the principle of negotiations with a view to achieving mutually satisfactory solutions, even beyond the limits set by the DSU. Following these premises, the purpose of this paper is to analyse the impact that has been exercised on the EC’s contentious practice by interpretations of the WTO system given by the EC courts, in fine tuning with the stand taken by the EC’s political bodies. After having considered the legal and political reasons behind the case-law of the Co…
Answering Schrödinger's "What Is Life?"
2020
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A Study on Engineering Freshman Conceptual Understanding of Newtonian Mechanics
2021
Force concept inventory is a multiple-choice questionnaire commonly used to assess students’ conceptual understanding of Newtonian mechanics. We here show that a cluster analysis method can be used to study student answers to the force concept inventory to investigate their understanding of Newtonian mechanics and provide new insights into the use of the force concept inventory. We identi- fied groups of students characterized by similar correct answers as well as by non- correct answers to the questionnaire, whose analysis allowed us to highlight student misconceptions/non-normative conceptions. Such an analysis of student answers gave us insights into the relationships between the student…
Kinetic-Ising-model description of Newtonian dynamics: A one-dimensional example.
1993
We show that the Newtonian dynamics of a chain of particles with an anharmonic on-site potential and harmonic nearest-neighbor interactions can be described by a one-dimensional kinetic Ising model with most general Glauber transition rates, provided the temperature is low enough compared to the minimum barrier height. The transition rates are calculated by use of the transition-state theory. At higher temperatures, memory effects occur which invalidate this kinetic description. These memory effects are due to the appearance of dynamically correlated clusters of particles performing periodic oscillations over a certain time scale.
The influence of matrix rheology and vorticity on fabric development of populations of rigid objects during plane strain deformation
2002
Abstract The influence of vorticity and rheology of matrix material on the development of shape-preferred orientation (SPO) of populations of rigid objects was experimentally studied. Experiments in plane strain monoclinic flow were performed to model the fabric development of two populations of rectangular rigid objects with object aspect ratios (Rob) 2 and 3. The density of the rigid object populations was 14% of the total area. Objects were dispersed in a Newtonian and a non-Newtonian, power law matrix material with a power law exponent n of 1.2. The kinematic vorticity number (Wn) of the plane strain monoclinic flow was 1, 0.8 and 0.6 with finite simple shear strain of 4.6, 3.0 and 0.9,…