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Remarkable Properties (remarkable + property)
Selected AbstractsAbout Darcy's law in non-Galilean frameINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2004C. Geindreau Abstract This paper is aimed towards investigating the filtration law of an incompressible viscous Newtonian fluid through a rigid non-inertial porous medium (e.g. a porous medium placed in a centrifuge basket). The filtration law is obtained by upscaling the flow equations at the pore scale. The upscaling technique is the homogenization method of multiple scale expansions which rigorously gives the macroscopic behaviour and the effective properties without any prerequisite on the form of the macroscopic equations. The derived filtration law is similar to Darcy's law, but the tensor of permeability presents the following remarkable properties: it depends upon the angular velocity of the porous matrix, it verifies Hall,Onsager's relationship and it is a non-symmetric tensor. We thus deduce that, under rotation, an isotropic porous medium leads to a non-isotropic effective permeability. In this paper, we present the results of numerical simulations of the flow through rotating porous media. This allows us to highlight the deviations of the flow due to Coriolis effects at both the microscopic scale (i.e. the pore scale), and the macroscopic scale (i.e. the sample scale). The above results confirm that for an isotropic medium, phenomenological laws already proposed in the literature fails at reproducing three-dimensional Coriolis effects in all types of pores geometry. We show that Coriolis effects may lead to significant variations of the permeability measured during centrifuge tests when the inverse Ekman number Ek,1 is ,,(1). These variations are estimated to be less than 5% if Ek,1<0.2, which is the case of classical geotechnical centrifuge tests. We finally conclude by showing that available experimental data from tests carried out in centrifuges are not sufficient to determining the effective tensor of permeability of rotating porous media. Copyright © 2004 John Wiley & Sons, Ltd. [source] Addressing volumetric locking and instabilities by selective integration in smoothed finite elementsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 1 2009Nguyen-Xuan Hung Abstract This paper promotes the development of a novel family of finite elements with smoothed strains, offering remarkable properties. In the smoothed finite element method (FEM), elements are divided into subcells. The strain at a point is defined as a weighted average of the standard strain field over a representative domain. This yields superconvergent stresses, both in regular and singular settings, as well as increased accuracy, with slightly lower computational cost than the standard FEM. The one-subcell version that does not exhibit volumetric locking yields more accurate stresses but less accurate displacements and is equivalent to a quasi-equilibrium FEM. It is also subject to instabilities. In the limit where the number of subcells goes to infinity, the standard FEM is recovered, which yields more accurate displacements and less accurate stresses. The specific contribution of this paper is to show that expressing the volumetric part of the strain field using a one-subcell formulation is sufficient to get rid of volumetric locking and increase the displacement accuracy compared with the standard FEM when the single subcell version is used to express both the volumetric and deviatoric parts of the strain. Selective integration also alleviates instabilities associated with the single subcell element, which are due to rank deficiency. Numerical examples on various compressible and incompressible linear elastic test cases show that high accuracy is retained compared with the standard FEM without increasing computational cost. Copyright © 2008 John Wiley & Sons, Ltd. [source] Toughness of Spider Silk at High and Low Temperatures,ADVANCED MATERIALS, Issue 1 2005Y. Yang The toughness of the major ampullate silk of spiders is shown to increase at low temperatures, unlike synthetic fibers. This temperature dependence of the mechanical properties of spider silk, together with other remarkable properties, demonstrates the potential usefulness of such a super-fiber in harsh environments. The Figure shows a single fiber of Nephila edulis spider silk fractured in liquid nitrogen. [source] Stanislas Dehaene's Les neurones de la lectureMIND, BRAIN, AND EDUCATION, Issue 4 2008Antonio M. Battro ABSTRACT, Stanislas Dehaene has published a remarkable book on the neurons of reading. It is a comprehensive description of the main issues related to the "paradox of reading": how humans process linguistic information using the visual brain path while the brain has not evolved in the short period of time since the invention of writing. The article presents a powerful "neuronal recycling" hypothesis to explain the remarkable properties of our cultural neuroplasticity. Scientists and educators will find a trove of information and deep discussions regarding the universal challenge of teaching and learning to read. [source] Bioorganic studies on marine natural products,diverse chemical structures and bioactivitiesTHE CHEMICAL RECORD, Issue 5 2006Daisuke Uemura Abstract The discovery of new molecules contributes to the development of basic scientific concepts, leads to valuable drug-oriented compounds, and suggests possible new pharmacological reagents. Newly discovered substances can even be responsible for the creation of new scientific fields. Due to the radically different habitats of marine organisms, several notable examples of secondary metabolites from marine organisms have been isolated. Two of the most remarkable properties of these compounds are their structural and physiological diversities. These bioactive compounds are candidates for drugs or biological probes for physiological studies. Palytoxin is a polyol compound that shows extreme acute toxicity. Halichondrins are remarkable antitumor macrolides from sponge. Pinnatoxins, potent shellfish poisons, cause food poisoning. This paper describes bioorganic studies on such newly discovered wonders of nature. Several bioactive marine alkaloids and important substances involved in dynamic ecological systems are also described. © 2006 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 6: 235,248; 2006: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20087 [source] Semi-Solid Processing of Tailored Aluminium-Lithium Alloys for Automotive Applications,ADVANCED ENGINEERING MATERIALS, Issue 4 2007R. Sauermann Abstract This paper describes the development and evaluation of thixoformable Al-Li-Mg-based alloys performed at the collaborative research center SFB 289, RWTH Aachen. Scandium and zirconium were added to AlLi2.1Mg5.5 (A1420) with the aid of DoE (Design of Experiments), and precursor billets were manufactured by pressure induction melting (PIM). To evaluate the thixoformability of the synthesized alloys semi-solid processed connecting rods were manufactured by the rheo container process (RCP). Subsequent heat treatment raised the mechanical properties to maximum values of tensile strength, 430,MPa, yield strength of 250,MPa, and an elongation to fracture of 13,%. The RCP process was designed for the special requirements of highly reactive alloys. The paper presents the remarkable property and process benefits of the semi-solid processing of Al-Li alloys. [source] On the image of the limit q -Bernstein operatorMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 15 2009Sofiya Ostrovska Abstract The limit q -Bernstein operator Bq emerges naturally as an analogue to the Szász,Mirakyan operator related to the Euler distribution. Alternatively, Bq comes out as a limit for a sequence of q -Bernstein polynomials in the case 0 ACORN2: new developments of the ACORN conceptACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2009E. J. Dodson The density-modification procedures incorporated in ACORN, available in the CCP4 package, have proved to be very successful in solving and refining high-resolution crystal structures from very poor starting sets. These can be calculated from a correctly positioned initial fragment containing between 1 and 8% of the scattering power of the total structure. Improvements of ACORN, reported here and incorporated in the program ACORN2, have lowered the size of the fragment required and examples are given of structures solved with only 0.25% of the scattering power in the fragment, which may be a single atom. Applications of ACORN2 to structures with space group P1 have shown the remarkable property that when the starting point is a pair of equal atoms, or even a single atom placed at the origin, the refinement process breaks the centric nature of the initial phases and converges to phases corresponding to one of the two possible enantiomorphs. Examples are given of the application of ACORN2 to the solution and/or refinement of a number of known trial structures and to the refinement of structures when phases are available either from MAD or from a molecular-replacement model. [source]
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