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41.
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43.
There is only one gap in the isoperimetric spectrum 总被引:1,自引:0,他引:1
44.
Patrick B. Brady 《Tetrahedron letters》2009,50(9):975-20624
We report a method for catalytic phosphitylation utilizing phosphoramidites. Traditionally, this reaction is inefficient unless an excess of catalyst is present due to catalyst deactivation by an amine by-product. Isocyanate additives have been evaluated for scavenging the amine to facilitate catalyst turnover. A variety of alcohols and phosphoramidites were screened with 5 mol % catalyst. In the presence of additive, 83-97% conversion was achieved in contrast to 7-31% conversion without additive. 相似文献
45.
46.
Robert F. Brady Frederick E. Simon 《Journal of polymer science. Part A, Polymer chemistry》1987,25(1):231-239
New bicyclic and tricyclic compounds have been synthesized by the Lewis acid-catalyzed condensation of epoxides with cyclic acid anhydrides or cyclic bislactones. These materials take part in the anionic addition polymerization of amine-functional polyamides with diepoxides, and modify the shrinkage that is characteristic of the reaction. It is possible to control the extent of shrinkage by choosing an appropriate comonomer and by adjusting the concentration of this material in the reaction mixture. 相似文献
47.
We consider two-stage pure integer programs with discretely distributed stochastic right-hand sides. We present an equivalent
superadditive dual formulation that uses the value functions in both stages. We give two algorithms for finding the value
functions. To solve the reformulation after obtaining the value functions, we develop a global branch-and-bound approach and
a level-set approach to find an optimal tender. We show that our method can solve randomly generated instances whose extensive
forms are several orders of magnitude larger than the extensive forms of those instances found in the literature.
This work is supported by National Science Foundation grants DMI-0217190 and DMI-0355433. 相似文献
48.
Yuliy Baryshnikov Wil Brady Andrew Bressler Robin Pemantle 《Journal of statistical physics》2011,142(1):78-107
We analyze several families of two-dimensional quantum random walks. The feasible region (the region where probabilities do
not decay exponentially with time) grows linearly with time, as is the case with one-dimensional QRW. The limiting shape of
the feasible region is, however, quite different. The limit region turns out to be an algebraic set, which we characterize
as the rational image of a compact algebraic variety. We also compute the probability profile within the limit region, which
is essentially a negative power of the Gaussian curvature of the same algebraic variety. Our methods are based on analysis
of the space-time generating function, following the methods of Pemantle and Wilson (J. Comb. Theory, Ser. A 97(1):129–161,
2002). 相似文献
49.
Sparse asymptotic minimum variance based bearing estimation algorithm for a single vector hydrophone
For underwater target detection using a single vector hydrophone, sparse asymptotic minimum variance(SAMV) method is used to estimate the target bearing. The SAMV discretizes the entire scanning space and the target bearing is located at the position of the discrete direction. The SAMV algorithm utilizes the sparsity of the spatial signal to improve the estimation performance of the target bearing. Background noise level(BNL) of the bearing estimation of SAMV algorithm is lower than those of the conventional beam forming(CBF)method and minimum variance distortionless response(MVDR) method for different signal noise ratios(SNRs). When the SNR is higher than 0 d B, the direction-finding error of this algorithm is less than 2°. Moreover, the SAMV algorithm has a better dimensional orientation resolution capability. The experimental results show that the SAMV algorithm gives a bearing and time recording map with a lower BNL, which effectively verifies the effectiveness of SAMV algorithm in terms of underwater target detection. 相似文献
50.
分别采用全多孔型硅胶基键合强阴离子交换柱与氨丙基键合硅胶柱,在低波长 200 nm 处检测,分离测定了磷霉素 探讨了流动相条件,如p H 值、离子强度等对磷霉素保留及分离选择性的影响,优化分离条件,建立了一种测定磷霉素的高效液相色谱新方法方法简便、快速 相似文献