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91.
One of the greatest challenges facing the cognitive sciences is to explain what it means to know a language, and how the knowledge of language is acquired. The dominant approach to this challenge within linguistics has been to seek an efficient characterization of the wealth of documented structural properties of language in terms of a compact generative grammar—ideally, the minimal necessary set of innate, universal, exception-less, highly abstract rules that jointly generate all and only the observed phenomena and are common to all human languages. We review developmental, behavioral, and computational evidence that seems to favor an alternative view of language, according to which linguistic structures are generated by a large, open set of constructions of varying degrees of abstraction and complexity, which embody both form and meaning and are acquired through socially situated experience in a given language community, by probabilistic learning algorithms that resemble those at work in other cognitive modalities. 相似文献
92.
K. Muthukkumaran P. Kuppusami R. Srinivasan K. Ramachandran E. Mohandas S. Selladurai 《Ionics》2007,13(1):47-50
Thermal properties of 15-mol% gadolinia doped ceria thin films (Ce0.85Gd0.15 O1.925) prepared by pulsed laser ablation on silicon substrates in the temperature range 473–973 K are presented. Thermal diffusivities
and thermal conductivities were evaluated using photoacoustic spectroscopy. The influence of grain size on thermal properties
of the films as a function of deposition temperature is studied. It is observed that the thermal diffusivity and the conductivity
of these films decreases up to 873 K and then increases with substrate temperatures. The thermal properties obtained in these
films are discussed on the basis of influence of grain size on phonon scattering. 相似文献
93.
Nishant N. Patel K. B. Joshi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):19-23
Using empirical pseudopotential method Γ-L crossover is found for
the Ga0.74Al0.26Sb. The conduction band minimum is observed to
switch at the (0.87, 0, 0) point for Ga0.51Al0.49Sb which shifts to
the X point for Ga0.21Al0.79Sb and remains at X leading finally to
indirect band gap in AlSb. Band structure calculations for a large number of
alloys are performed and bowing parameters bX and bL are proposed
for the EX and EL respectively. Our findings may serve as
directive to select the materials in a range of composition to examine the
bowing parameters and thereby effective mass experimentally for the
GaxAl1-xSb alloys. 相似文献
94.
S. Ansumali S. Arcidiacono S. S. Chikatamarla N. I. Prasianakis A. N. Gorban I. V. Karlin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(2):135-139
A general lattice Boltzmann method for simulation of
fluids with tailored transport coefficients is presented. It is
based on the recently introduced quasi-equilibrium kinetic models,
and a general lattice Boltzmann implementation is developed.
Lattice Boltzmann models for isothermal binary mixtures with a
given Schmidt number, and for a weakly compressible flow with a
given Prandtl number are derived and validated. 相似文献
95.
Resolution of computational aeroacoustics problems on unstructured grids with a higher-order finite volume scheme 总被引:1,自引:0,他引:1
X. Nogueira I. Colominas L. Cueto-Felgueroso F. Navarrina 《Journal of Computational and Applied Mathematics》2010,234(7):2089-2097
Computational fluid dynamics (CFD) has become increasingly used in the industry for the simulation of flows. Nevertheless, the complex configurations of real engineering problems make the application of very accurate methods that only work on structured grids difficult. From this point of view, the development of higher-order methods for unstructured grids is desirable. The finite volume method can be used with unstructured grids, but unfortunately it is difficult to achieve an order of accuracy higher than two, and the common approach is a simple extension of the one-dimensional case. The increase of the order of accuracy in finite volume methods on general unstructured grids has been limited due to the difficulty in the evaluation of field derivatives. This problem is overcome with the application of the Moving Least Squares (MLS) technique on a finite volume framework. In this work we present the application of this method (FV-MLS) to the solution of aeroacoustic problems. 相似文献
96.
Zhi Zeng Marina Hincapie Brian B. Haab Samir Hanash Sharon J. Pitteri Steven Kluck Jason M. Hogan Jacob Kennedy William S. Hancock 《Journal of chromatography. A》2010,1217(19):3307-3315
Protein glycosylation represents one of the major post-translational modifications and can have significant effects on protein function. Moreover, changes in the carbohydrate structure are increasingly being recognized as an important modification associated with cancer etiology. In this report, we describe the development of a proteomics approach to identify breast cancer related changes in either concentration and/or the carbohydrate structures of glycoprotein(s) present in blood samples. Diseased and healthy serum samples were processed by an optimized sample preparation protocol using multiple lectin affinity chromatography (M-LAC) that partitions serum proteins based on glycan characteristics. Subsequently, three separate procedures, 1D SDS-PAGE, isoelectric focusing and an antibody microarray, were applied to identify potential candidate markers for future study. The combination of these three platforms is illustrated in this report with the analysis of control and cancer glycoproteomic fractions. Firstly, a molecular weight based separation of glycoproteins by 1D SDS-PAGE was performed, followed by protein, glycoprotein staining, lectin blotting and LC–MS analysis. To refine or confirm the list of interesting glycoproteins, isoelectric focusing (targeting sialic acid changes) and an antibody microarray (used to detect neutral glycan shifts) were selected as the orthogonal methods. As a result, several glycoproteins including alpha-1B-glycoprotein, complement C3, alpha-1-antitrypsin and transferrin were identified as potential candidates for further study. 相似文献
97.
Hydraulic permeability is studied in porous media consisting of randomly distributed monodisperse spheres by means of computational fluid dynamics (CFD) simulations. The packing of spheres is generated by inserting a certain number of nonoverlapping spherical particles inside a cubic box at both low and high packing fractions using proper algorithms. Fluid flow simulations are performed within the interparticulate porous space by solving Navier-Stokes equations in a low-Reynolds laminar flow regime. The hydraulic permeability is calculated from the Darcy equation once the mean values of velocity and pressure gradient are calculated across the particle packing. The simulation results for the pressure drop across the packing are verified by the Ergun equation for the lower range of porosities (<0.75), and the Stokes equation for higher porosities (∼1). Using the results of simulations, the effects of porosity and particle diameters on the hydraulic permeability are investigated. Simulations precisely specified the range of applicability of empirical or semi-empirical correlations for hydraulic permeability, namely the Carman-Kozeny, Rumpf-Gupte, and Howells-Hinch formulas. The number of spheres in the model is gradually decreased from 2000 to 20 to discover the finite-size effect of pores on the hydraulic permeability of spherical packing, which has not been clearly addressed in the literature. In addition, the scale dependence of hydraulic permeability is studied via simulations of the packing of spheres shrunk to lower scales. The results of this work not only reveal the validity range of the aforementioned correlations, but also show the finite-size effect of pores and the scale-independence of direct CFD simulations for hydraulic permeability. 相似文献
98.
C. Vanneste 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(3):391-404
This paper presents an extension to electromagnetic fields of the wave automaton, which was introduced in recent years for
describing wave propagation in inhomogeneous media. Using elementary processes obeying a discrete Huygens' principle and satisfying
fundamental symmetries such as time reversal and reciprocity, this new wave automaton is capable of modeling Maxwell's equations
in 3+1 dimensions. It supplements the methods that were developed early for scalar and spinor fields.
Received 19 July 2001 相似文献
99.
Jesús A. De Loera Raymond Hemmecke Matthias Köppe Robert Weismantel 《Mathematical Programming》2008,115(2):273-290
We show the existence of a fully polynomial-time approximation scheme (FPTAS) for the problem of maximizing a non-negative
polynomial over mixed-integer sets in convex polytopes, when the number of variables is fixed. Moreover, using a weaker notion
of approximation, we show the existence of a fully polynomial-time approximation scheme for the problem of maximizing or minimizing
an arbitrary polynomial over mixed-integer sets in convex polytopes, when the number of variables is fixed.
A conference version of this article, containing a part of the results presented here, appeared in Proceedings of the 17th Annual ACM-SIAM Symposium on Discrete Algorithms, Miami, FL, January 22–24, 2006, pp. 743–748. The first author gratefully acknowledges support from NSF grant DMS-0608785, a 2003 UC-Davis Chancellor’s fellow award,
the Alexander von Humboldt foundation, and IMO Magdeburg. The remaining authors were supported by the European TMR network
ADONET 504438. 相似文献
100.
The second part of this paper deals with the systolic implementation of the computational kernel for factorial data analysis, defined in Part I, on special-purpose hardware. The framework of the study is that a sequence of different algorithms has to be performed on a unique hardware array. This fact has led us to the design of the programmable systolic array SARDA: this is a triangular array which consists of programmable nodes with local memory and programmable orthogonal connections. 相似文献