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排序方式: 共有267条查询结果,搜索用时 325 毫秒
261.
Bingwen Liu 《Mathematische Nachrichten》2009,282(4):581-590
In this paper, we use the coincidence degree theory to establish new results on the existence and uniqueness of T ‐periodic solutions for a class of nonlinear n ‐th order differential equations with delays of the form x(n)(t) + f (x(n‐ 1)(t)) + g (t, x (t ‐ τ (t))) = p (t). 相似文献
262.
By the method of synthetic geometry, we define a seemingly new transformation of a three-dimensional projective space where
the corresponding points lie on the rays of the first order, nth class congruence C
n
1 and are conjugate with respect to a proper quadric Ψ. We prove that this transformation maps a straight line onto an n + 2 order space curve and a plane onto an n + 2 order surface which contains an n-ple (i.e. n-multiple) straight line. It is shown that in the Euclidean space the pedal surfaces of the congruences C
n
1 can be obtained by this transformation. The analytical approach enables new visualizations of the resulting curves and surfaces
with the program Mathematica. They are shown in four examples.
相似文献
263.
Chromatography: The separation technique of the 20th century 总被引:3,自引:0,他引:3
L. S. Ettre 《Chromatographia》2000,51(1-2):7-17
Summary M. S. Tswett contemplated the possibility of “chromatography” in 1899–1901 while carrying out his first research work on the
physico-chemical structure of plant chlorophylls, and he reported “on a new category of adsorption analysis” in 1903. The
evolution of chromatography followed the advances of this century: each decade brought new innovations based logically from
the previous one. By the end of the 20th Century chromatography has became the most widely used separation technique in chemistry
and biochemistry: thus, it is no exaggeration to call it the separation technique of the 20th Century. This paper investigates
the evolution of the various branches of chromatography.
An essential condition for all fruitful research is to have at one’s disposal a satisfactory technique. “Tout progrès scientific
est un progrès de méthode” as somebody once remarked. Unfortunately the methodology is frequently the weakest aspect of scientific
investigations. 相似文献
264.
pth Power Lagrangian Method for Integer Programming 总被引:1,自引:0,他引:1
When does there exist an optimal generating Lagrangian multiplier vector (that generates an optimal solution of an integer programming problem in a Lagrangian relaxation formulation), and in cases of nonexistence, can we produce the existence in some other equivalent representation space? Under what conditions does there exist an optimal primal-dual pair in integer programming? This paper considers both questions. A theoretical characterization of the perturbation function in integer programming yields a new insight on the existence of an optimal generating Lagrangian multiplier vector, the existence of an optimal primal-dual pair, and the duality gap. The proposed pth power Lagrangian method convexifies the perturbation function and guarantees the existence of an optimal generating Lagrangian multiplier vector. A condition for the existence of an optimal primal-dual pair is given for the Lagrangian relaxation method to be successful in identifying an optimal solution of the primal problem via the maximization of the Lagrangian dual. The existence of an optimal primal-dual pair is assured for cases with a single Lagrangian constraint, while adopting the pth power Lagrangian method. This paper then shows that an integer programming problem with multiple constraints can be always converted into an equivalent form with a single surrogate constraint. Therefore, success of a dual search is guaranteed for a general class of finite integer programming problems with a prominent feature of a one-dimensional dual search. 相似文献
265.
多模辐射场的广义非线性不等阶高阶压缩的一般理论 总被引:168,自引:61,他引:107
本文建立了多模辐射场的广义非线性不等阶高阶压缩的一般理论。首次提出了多模辐射场中各模压缩阶数不相等的Nj次方Y压缩、Nj次方H压缩以及Nj次方X压缩的一般性定义,并对Nj-Y最小测不准态、Nj-Y压缩最小测不准态、Nj-H最小测不准态、Nj-H压缩最小测不准态以及Nj-X最小测不准态和Nj-X压缩最小测不准态等进行了详细讨论。指出,Zhang等人在国际上提出的有关单模辐射场的振幅N次方压缩的定义、Mark Hilery在国际上提出的有关双模辐射场的“双模和压缩”与“双模差压缩”的定义以及由笔者新近提出的有关多模辐射场的N次方Y压缩、N次方H压缩和N次方X压缩等的定义,仅仅只是本文所提出的Nj次方Y压缩、Nj次方H压缩以及Nj次方X压缩等的一般性定义在各种不同条件下的特例. 相似文献
266.
267.