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931.
932.
1,3-Dienes and electron deficient alkenes are coupled in a one pot carbon-carbon bond formation reaction under mild conditions. 相似文献
933.
Jørgen Sand 《BIT Numerical Mathematics》1985,25(2):391-398
We construct a polyhedral norm in which the fixed-step backward differentiation formulas of order one to three are contractive when applied to any differential equation of the formy=(t)y, (t) 0 (i.e. A0-contractive). The result also holds for non-uniform step-sequences if combined with certain restrictions on the stepwise order-selection. 相似文献
934.
Jürgen Groh 《Mathematische Nachrichten》1985,122(1):157-165
A continuous strong Markov process X on the line generated by Feller's generalized second order differential operator DmD is considered. Supposed that the canonical scale p is locally the difference of two bounded convex functions, that the speed measure m contains a strictly positive absolutely continuous component, and that both boundaries of the state space R are inaccessible. Then the process X is characterized as a weak solution to a stochastic differential equation involving local time. 相似文献
935.
M. Gräff R. Scheidl H. Troger E. Weinmüller 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1985,36(6):803-821
Summary The post-buckling behavior of an elastic spherical shell is studied for large axisymmetric deformations. The complete post-buckling path is given for the experimentally confirmed single dimple solution in a load-deformation diagram, making use of the methods of local bifurcation theory, singular perturbation analysis and numerical analysis. From the specific form of the post-buckling path with its predominating unstable part follows the strong imperfection sensitivity of the shell structure.
Zusammenfassung Es wird das Nachbeulverhalten einer elastischen Kugelschale für große achsensymmetrische Deformationen untersucht. Der gesamte Nachbeulpfad wird für die experimentell bestätigte single dimple Lösung, die eine starke lokale Eindellung darstellt, angegeben, wobei Methoden der lokalen Verzweigungstheorie, der singulären Störungsrechnung und der numerischen Analysis verwendet wurden. Aus der besonderen Form des Nachbeulpfades mit seinem überwiegend instabilen Teil ist die starke Imperfektionsempfindlichkeit dieser Konstruktion deutlich erkennbar.相似文献
936.
Jürgen Weyer 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1985,36(4):499-507
We consider the nonlinear diffusion equationu
t
–a(x, u
x
x
)+b(x, u)=g(x, u) with initial boundary conditions
andu(t, 0)=u(t, 1)=0. Here,a, b, andg denote some real functions which are monotonically increasing with respect to the second variable. Then, the corresponding stationary problem has a positive solution if and only if(0,
*) or(0,
*]. The endpoint
* can be estimated by
, where
1
u denotes the first eigenvalue of the stationary problem linearized at the pointu. The minimal positive steady state solutions are stable with respect to the nonlinear parabolic equation.
Zusammenfassung Wir betrachten die nichtlineare Diffusionsgleichungu t –a(x, u x ) x +b(x, u)=g(x, u) mit Randbedingungen undu (t, 0)=u (t, 1)=0. Dabei sinda, b, undg monoton wachsende Funktionen bzgl. des zweiten Argumentes. Das zugehörige stationäre Problem hat genau dann eine positive Lösung, falls (0, *) oder(0, *]. Der Endpunkt * kann durch abgeschätzt werden, wobei 1 u den ersten Eigenwert des an der Stelleu linearisierten stationären Problems bezeichnet. Die minimale positive stationäre Lösung ist stabil bzgl. der obigen nichtlinearen parabolischen Gleichung.相似文献
937.
The attachment of single ions to putative adsorption sites in the tails of collagen fibers is investigated by means of molecular dynamics simulations and discussed with respect to the very early steps of apatite/collagen biomineral formation. Our studies clearly demonstrate an increased flexibility of the tails of the triple‐helical collagen protein. Apart from the termini of the backbone, several side chains were also observed to be freely accessible to ion attachment from aqueous solution. The teleopeptide was systematically scanned for suitable adsorption sites for calcium, phosphate and fluoride ions. Association of these ions was then explored from potential of mean force calculations. The resulting energy profiles reveal a variety of favorable protein‐ion bonds and hint at the suitability of the collagen tails to promote apatite aggregation. 相似文献
938.
Experimental observations of solitons in stimulated Raman scattering are reported. Soliton formation resulted from the introduction of a phase shift in the incident Stokes beam as predicted by theory. Pulse sharpening and retardation on propagation in the Raman medium have been observed along with amplitude diminution. The first two features were predicted and the third was not. Spontaneous soliton formation has been observed in the absense of any amplitude modulation or apparent phase shift in the optical fields, indicating that additional sets of initial conditions may result in soliton formation.Work performed under the auspices of the U.S. Department of Energy. 相似文献
939.
After reviewing problems which appear in the theory of teleparallelism (tetrad theory) based on a Lagrangian quadratic in the torsion, the possibility of adding higher-order terms is discussed. For a test Lagrangian,O(3)-symmetric vacuum solutions and spatially homogeneous and isotropic solutions are found. The latter contain nonsingular cosmological models. 相似文献
940.
Z. Füredi 《Graphs and Combinatorics》1985,1(1):51-56
Letn≥k≥1 be integers and letf(n, k) be the smallest integer for which the following holds: If ℱ is a family of subsets of ann-setX with |ℱ|<f(n,k) then for everyk-coloring ofX there existA
B ∈ ℱ,A∈B, A⊂B such thatB-A is monochromatic. Here it is proven that for a fixedk there exist constantsc
k
andd
k
such that
and
ask→∞. The proofs of both the lower and the upper bounds use probabilistic methods. 相似文献