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31.
Avraham A. Melkman 《Journal of Approximation Theory》1996,84(3):265-273
We provide a different proof for Morken's result on necessary and sufficient conditions for a minor of the discrete B-spline collocation matrix to be positive and supply intuition for those conditions. 相似文献
32.
Decaprenylphosphoryl β-d-arabinofuranose (DPA) is a key arabinose donor in mycobacteria. In an effort to establish a practical synthetic scheme for DPA, the synthesis of nerylphosphoryl and farnesylphosphoryl β-d-arabinofuranoses has been developed. The products were obtained by coupling of a suitably protected β-d-arabinofuranosyl phosphate intermediate with activated forms of the C10 nerol and C15trans,trans-farnesol and subsequent deprotection. 相似文献
33.
Musical sound can be generated from numerical solutions obtained from simple physical models of wind-instruments. We call such synthesizers virtual instruments. Crude caricatures capture the global oscillation behaviour of original instruments, providing the musician with a means of expression comparable to that obtained when playing real instruments. Music is, however, produced by details of the flow which correspond to much smaller temporal and spatial scales than the control of the global oscillation. This suggests that one has to split the physical model into two distinct parts: a simple numerical oscillator followed by a complex sound production module, driven by the output of the first module. We illustrate the background of this idea by a discussion of the clarinet, the human voice, and the trombone.General invited lecture presented by A. Hirschberg at the 12th Italian Congress on Theoretical and Applied Mechanics AIMETA '95, Napoli, 3–6 October 1995. 相似文献
34.
Avraham A Melkman 《Journal of Mathematical Analysis and Applications》1977,61(3):739-751
Consider a spline s(x) of degree n with L knots of specified multiplicities R1, …, RL, which satisfies r sign consistent mixed boundary conditions in addition to s(n)(a) = 1. Such a spline has at most n + 1 ?r + ∑j = 1LRj zeros in (a, b) which fulfill an interlacing condition with the knots if s(x) ? = 0 everywhere. Conversely, given a set of n ?r + ∑j = 1LRj zeros then for any choice η1 < ··· < ηL of the knot locations which fulfills the interlacing condition with the zeros, the unique spline s(x) possessing these knots and zeros and satisfying the boundary conditions is such that s(n)(x) vanishes nowhere and changes sign at ηj if and only if Rj is odd. Moreover there exists a choice of the knot locations, not necessarily unique, which makes . In particular, this establishes the existence of monosplines and perfect splines with knots of given multiplicities, satisfying the mixed boundary conditions and possessing a prescribed maximal zero set. An application is given to double-precision quadrature formulas with mixed boundary terms and a certain polynomial extremal problem connected with it. 相似文献
35.
Lior C. Goldenberg Ian Hutcheon Norman Wardlaw Avraham J. Melloul 《Transport in Porous Media》1993,13(3):221-237
The rearrangement of matrix configuration due to the redistribution of clay particles was studied by introducing different suspensions into porous media. Clay (kaolinite) with low CEC (cation exchange capacity) and small flocs of high CEC clay (smectite) accumulated in regions of slow flow. In some experiments this was followed by rapid accumulation in regions of high velocity, impairing flow to a considerable degree. Clay with high CEC formed more voluminous structures which could bridge over a passage and impair the flow.In either case, whether small or large units of clay are involved, the final flow occurred mainly through open, preferred pathways. Such processes of redistribution and appearance of flow pathways may occur in subsurface porous media aquifers where forced gradients exist (e.g. in aquifers near the perforation of pumping wells and in places where large quantity of water are naturally or artificially recharged and in producing gas and oil fields). 相似文献
36.
Many analytical instruments (e.g., videofluorimeter and liquid chromatographs with spectrometric detectors) can produce two-dimensional data arrays. Rank-annihilation factor analysis enables chemical composition to be quantified from such an array. Solution by this method requires a search for a minimum value of an eigenvector which cannot be calculated even iteratively. The problem is presented here as a generalized eigenvalue problem and a direct solution is found by using singular value decomposition. 相似文献
37.
Alexandrowicz G Tashma T Feintuch A Grayevsky A Dormann E Kaplan N 《Physical review letters》2000,84(13):2973-2976
Novel implementation of the Fourier imaging technique on conduction electron spins in the one-dimensional organic conductors (FA)2PF6 (FA: fluoranthene) is reported. Two-dimensional spatial imaging of resolution 30 &mgr;m(2) is combined with the pulsed-gradient spin-echo technique, to derive maps revealing the local properties of the electron spin density and mobility. The maps generally show pronounced inhomogeneity of both density and mobility on the scale of approximately 30-300 &mgr;m. Highly mobile regions were identified to exist, and the mobility in these was quantitatively evaluated by a basic theoretical model of restricted diffusion. 相似文献
38.
39.
Avraham?AizenbudEmail author Dmitry?Gourevitch Siddhartha?Sahi 《Israel Journal of Mathematics》2015,206(1):39-88
The notion of derivatives for smooth representations of GL(n, ? p ) was defined in [BZ77]. In the archimedean case, an analog of the highest derivative was defined for irreducible unitary representations in [Sah89] and called the “adduced” representation. In [AGS] derivatives of all orders were defined for smooth admissible Fréchet representations (of moderate growth).A key ingredient of this definition is the functor of twisted coinvariants with respect to the nilradical of the mirabolic subgroup. In this paper we prove exactness of this functor and compute it on a certain class of representations. This implies exactness of the highest derivative functor, and allows to compute highest derivatives of all monomial representations.In [AGS] these results are applied to finish the computation of adduced representations for all irreducible unitary representations and to prove uniqueness of degenerate Whittaker models for unitary representations. 相似文献
40.
Uri Avraham 《Israel Journal of Mathematics》1981,39(1-2):167-176
We give some consistency results on the existence of uncountable free sets for nowhere-dense set mappings. For example, we
prove that it is relatively consistent with ZFC and Martin’s Axiom that any nowhere-dense set mapping defined on the reals
has an uncountable free set. 相似文献