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961.
The thermoreversible gelation of semi-diluted atactic polyacrylnitrile (PAN)/dimethylformamide (DMF)-solutions has been studied. The structural features of PAN/DMF-gels, formed by supercooling have been investigated by DSC-, x-ray- and swelling measurements. A new structural model has been introduced to describe the morphology of the junction zones of PAN/DMF-gels and to also explain the gelation behavior of PAN/DMF-solutions as the structural features of PAN/DMF-gels. The junction zones of a PAN/DMF-gel have been defined as ordered junction zones.A gelation enthalpy of about H=–6 kJ/mol supports the idea that an ordered junction zone is formed by intermolecularly neighboring stereoregular parts of atactic PAN chains due to a nucleation process in the solution. It can be defined as a strongly distributed fringed micelle. 相似文献
962.
Y. Zhang 《Journal of Optimization Theory and Applications》1993,77(2):323-341
This paper concerns solving an overdetermined linear systemA
T
x=b in the leastl
1-norm orl
-norm sense, whereA
m×n
,m<n. We show that the primal-dual interior point approach for linear programming can be applied, in an effective manner, to linear programming versions of thel
1 andl
-problems. The resulting algorithms are simple to implement and can attain quadratic or superlinear convergence rate. At each iteration, the algorithms must solve a linear system with anm×m positive-definite coefficient matrix of the formADA
T
, whereD is a positive diagonal matrix. The preliminary numerical results indicate that the proposed algorithms offer considerable promise.This research was supported in part by Grants NSF DMS-91-02761 and DOE DE-FG05-91-ER25100. 相似文献
963.
D. Y. Ye 《Journal of Optimization Theory and Applications》1993,76(2):287-304
LetA(·) be ann × n symmetric affine matrix-valued function of a parameteruR
m
, and let (u) be the greatest eigenvalue ofA(u). Recently, there has been interest in calculating (u), the subdifferential of atu, which is useful for both the construction of efficient algorithms for the minimization of (u) and the sensitivity analysis of (u), namely, the perturbation theory of (u). In this paper, more generally, we investigate the Legendre-Fenchel conjugate function of (·) and the -subdifferential (u) of atu. Then, we discuss relations between the set (u) and some perturbation bounds for (u).The author is deeply indebted to Professor J. B. Hiriart-Urruty who suggested this study and provided helpful advice and constant encouragement. The author also thanks the referees and the editors for their substantial help in the improvement of this paper. 相似文献
964.
A kinetic theory for the constitutive Theological relations of rapid granular shear flow of hard circular disks, characterized by a coefficient of restitutione and a surface roughness coefficient, is formulated. From a set of general constitutive equations for single-particle dynamical variables, the approximate expressions for the limit of small and large dimensionless dissipative parameterR
t
are obtained. HereR
t
is defined as the ratio /, where is the fluctuation of translational velocity from the mean flow velocity, is the diameter of a disk, and is the shear rate. At smallR
t
the theoretical predictions can be compared with exact computer simulation results of granular dynamics that are also reported. The agreement between theory and simulation is better than expected; the present theory is accurate up to high packing density in this region ofR
t
. 相似文献
965.
LetR be a ring with unit and invariant basis property. In [1], the authors define a functorK(_;R):TOP/LIP
c-LPEP by combining the open cone construction of [7] with a geometric module construction and show this functor is a homology theory. This paper shows that if attention is restricted to objects TOP/LIP
c with a homotopy colimit structure, then the functorK(_;R) is a Quinn homology theory, In particular, for each having a homotopy colimit structure,K(;R) is a homotopy colimit in the category of -spectra. Furthermore, the constituent spectra of this homotopy colimit are obtained naturally from the fibres of .Partially supported by the National Science Foundation under grant number DMS88-03148.Partially supported by the SNF (Denmark) under grant number 11-7792. 相似文献
966.
We study the Hopfield model of an autoassociative memory on a random graph onN vertices where the probability of two vertices being joined by a link isp(N). Assuming thatp(N) goes to zero more slowly thanO(1/N), we prove the following results: (1) If the number of stored patternsm(N) is small enough such thatm(N)/Np(N) 0, asN, then the free energy of this model converges, upon proper rescaling, to that of the standard Curie-Weiss model, for almost all choices of the random graph and the random patterns. (2) If in additionm(N) < ln N/ln 2, we prove that there exists, forT< 1, a Gibbs measure associated to each original pattern, whereas for higher temperatures the Gibbs measure is unique. The basic technical result in the proofs is a uniform bound on the difference between the Hamiltonian on a random graph and its mean value. 相似文献
967.
Topological properties of clusters are used to extract critical parameters. This method is tested for the bulk properties ofd=2 percolation and thed=2, 3 Ising model. For the latter we obtain an accurate value of the critical temperatureJ/k
B
T
c=0.221617(18). In the case of thed=3 Ising model with film geometry the critical value of the surface coupling at the special transitions is determined as J1c/J=1.5004(20) together with the critical exponents
1
m
=0.237(5) and=0.461(15). 相似文献
968.
969.
A. S. Said 《Journal of separation science》1979,2(2):63-67
The theory of composite chromatographic columns has been re-examined and general equations relating their efficiency to those of individual columns were derived. The derivations were based on elementary principles without reference to the principle of variance additivity. Derived also, were general equations for the efficiency of columns with continuously varying diameters, HETP and other properties from which formulae for special cases of practical interest were deduced. An example comparing the efficiencies of two columns, one conical and the other composite was given. The calculations show clearly that the conical column is superior in efficiency for the same total length and total retention volume. 相似文献
970.
K. A. Lyssenko D. V. Lyubetsky M. Yu. Antipin I. L. Odinets 《Russian Chemical Bulletin》2005,54(11):2484-2491
The nature of the intramolecular O—H...O bond was studied and its energy was estimated by X-ray diffraction analysis and quantum-chemical
calculations (B3LYP/6-311G**) of (diphenylphosphoryl)acylacetonitriles. The influence of the nature of the substituents at
the double bond in the H-bonded ring and the crystal packing effects on the hydrogen bond were investigated.
Dedicated to Corresponding Member of the Russian Academy of Sciences T. A. Mastryukova.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2406–2413, November, 2005. 相似文献