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121.
In this paper, we consider various problems concerning quasi-matchings and semi-matchings in bipartite graphs, which generalize the classical problem of determining a perfect matching in bipartite graphs. We prove a generalization of Hall’s marriage theorem, and present an algorithm that solves the problem of determining a lexicographically minimum -quasi-matching (that is a set of edges in a bipartite graph such that in one set of the bipartition every vertex has at least incident edges from , where is a so-called need mapping, while on the other side of the bipartition the distribution of degrees with respect to is lexicographically minimum). We obtain that finding a lexicographically minimum quasi-matching is equivalent to minimizing any strictly convex function on the degrees of the A-side of a quasi-matching and use this fact to prove a more general statement: the optima of any component-based strictly convex cost function on any subset of -sphere in are precisely the lexicographically minimal elements of this subset. We also present an application in designing optimal CDMA-based wireless sensor networks. 相似文献
122.
We consider Lie superautomorphisms of prime associative superalgebras. A definitive result is obtained for central simple
superalgebras: their Lie superautomorphisms are of standard forms, except when the dimension of the superalgebra in question
is 2 or 4. 相似文献
123.
Space inversion of spinors revisited: A possible explanation of chiral behavior in weak interactions
We investigate a model in which spinors are considered as being embedded within the Clifford algebra that operates on them. In Minkowski space M1,3, we have four independent 4-component spinors, each living in a different minimal left ideal of Cl(1,3). We show that under space inversion, a spinor of one left ideal transforms into a spinor of another left ideal. This brings novel insight to the role of chirality in weak interactions. We demonstrate the latter role by considering an action for a generalized spinor field ψαi that has not only a spinor index α but also an extra index i running over four ideals. The covariant derivative of ψαi contains the generalized spin connection, the extra components of which are interpreted as the SU(2) gauge fields of weak interactions and their generalization. We thus arrive at a system that is left–right symmetric due to the presence of a “parallel sector”, postulated a long time ago, that contains mirror particles coupled to mirror SU(2) gauge fields. 相似文献
124.
125.
Diversity‐Oriented Synthesis of Drug‐Like Macrocyclic Scaffolds Using an Orthogonal Organo‐ and Metal Catalysis Strategy
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Dr. André Grossmann Sean Bartlett Matej Janecek Dr. James T. Hodgkinson Prof. David R. Spring 《Angewandte Chemie (International ed. in English)》2014,53(48):13093-13097
Small‐molecule modulators of biological targets play a crucial role in biology and medicine. In this context, diversity‐oriented synthesis (DOS) provides strategies toward generating small molecules with a broad range of unique scaffolds, and hence three‐dimensionality, to target a broad area of biological space. In this study, an organocatalysis‐derived DOS library of macrocycles was synthesized by exploiting the pluripotency of aldehydes. The orthogonal combination of multiple diversity‐generating organocatalytic steps with alkene metathesis enabled the synthesis of 51 distinct macrocyclic structures bearing 48 unique scaffolds in only two to four steps without the need for protecting groups. Furthermore, merging organocatalysis and alkene metathesis in a one‐pot protocol facilitated the synthesis of drug‐like macrocycles with natural‐product‐like levels of shape diversity in a single step. 相似文献
126.
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129.
Matej Sitar Franc Kosel Miha Brojan 《Archive of Applied Mechanics (Ingenieur Archiv)》2014,84(2):263-275
The paper discusses a relatively simple method for determining large deflection states of arbitrarily curved planar elastica, which is modeled by a finite set of initially straight flexible segments. The basic equations are built using Euler–Bernoulli and large displacement theory. The problem is solved numerically using Runge–Kutta–Fehlberg integration method and Newton method for solving systems of nonlinear equations. This solution technique is tested on several numerical examples. From a comparison of the results obtained and those found in the literature, it can be concluded that the developed method is efficient and gives accurate results. The solution scheme displayed can serve as reference tool to test results obtained via more complex algorithms. 相似文献
130.
M. Stano N. Pinhão D. Loffhagen M. Kučera Z. Donkó Š. Matejčík 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(3):489-498
The electron drift velocity in argon with admixtures of up to 2% of nitrogen, hydrogen
or oxygen is measured in a pulsed Townsend system for reduced electric fields ranging from
0.1 Td to 2.5 Td. The results are compared with those obtained by Monte Carlo simulations
and from the solution of the electron Boltzmann equation using two different solution
techniques: a multiterm method based on Legendre polynomial expansion of the angular
dependence of the velocity distribution function and the
S
n
method applied to a density gradient
expansion representation of the distribution function. An almost perfect agreement between
the results of the three numerical methods and, in general, very good agreement between
the experimental and the calculated results is obtained. Measurements in Ar-O2
mixtures were limited by electron attachment to oxygen molecules, which contributes to the
measured drift velocity. As a result of this attachment contribution, the bulk drift
velocity becomes larger than the flux drift velocity if attachment is more probable for
electrons with energy below the mean value and smaller in the opposite case. Attachment
also contributes to the negative differential conductivity observed in Ar-O2
mixtures. 相似文献