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排序方式: 共有8238条查询结果,搜索用时 31 毫秒
981.
V. A. Sadykov S. A. Beloshapkin E. A. Paukshtis G. M. Alikina I. Kochubei S. P. Degtyarev N. N. Bulgakov S. A. Veniaminov V. Netyaga R. V. Bunina A. N. Kharlanov E. V. Lunina V. V. Lunin V. A. Matyshak A. Ya. Rozovskii 《Reaction Kinetics and Catalysis Letters》1998,64(1):185-191
Transformation of surface nitrates under CH4 (CH4+O2) was found to ensure steady-state activity of Co-ZSM-5 in the selective catalytic reduction of nitrogen oxides by methane
(CH4-SCR). For Cu-ZSM-5, such species are mainly converted into NO. Relaxation of the coordination sphere due to oxygen and NO
adsorption, stability of C,N-containing intermediates and activation routes of hydrocarbons (methane, propane) were analyzed
as factors determining catalytic properties of Cu and Co cations. 相似文献
982.
Porous road surfaces reduce road traffic noise. A new method of noise reduction assessment is proposed. The noise generated by a few vehicles was measured two times: on an old surface with the dense asphalt and on a new surface with the porous asphalt. Subjective assessments of drive-by noise suggest that the sound exposure and the road surface coefficient can be used as the acoustical characteristics of a road surface. Their average values, with the average number of vehicles passing the receiver during a day or night, makes it possible to predict the equivalent continuous A-weighted sound pressure level for the new road surface. This is the main objective of this paper. 相似文献
983.
This paper characterizes the Castelnuovo-Mumford regularity by evaluating the initial ideal with respect to the reverse lexicographic order.
984.
Qi-ya Hu 《计算数学(英文版)》2002,(2)
1. IntroductionThe coupling of boundary elemellts and finite elements is of great imPortance for the nu-mercal treatment of boundary value problems posed on unbounded domains. It permits us tocombine the advanages of boundary elements for treating domains extended to infinity withthose of finite elemenis in treating the comP1icated bounded domains.The standard procedure of coupling the boundary elemeni and finite elemeni methods isdescribed as follows. First, the (unbounded) domain is divided… 相似文献
985.
There are several classes of interior point algorithms that solve linear programming problems in O(√nL) iterations. Among them, several potential reduction algorithms combine both theoretical (O(√nL) iterations) and practical efficiency as they allow the flexibility of line searches in the potential function, and thus
can lead to practical implementations. It is a significant open question whether interior point algorithms can lead to better
complexity bounds. In the present paper we give some negative answers to this question for the class of potential reduction
algorithms. We show that, even if we allow line searches in the potential function, and even for problems that have network
structure, the bound O(√nL) is tight for several potential reduction algorithms, i.e., there is a class of examples with network structure, in which
the algorithms need at least Θ(√nL) iterations to find an optimal solution.
The research of the author was partially supported by a Presidential Young Investigator Award DDM-9158118 with matching funds
from Draper Laboratory. 相似文献
986.
Ugo Azzena Giovanna DettoriMaria Vittoria Idini Luisa PisanoGrazia Sechi 《Tetrahedron》2003,59(40):7961-7966
Selective removal of the 4-methoxy group of 3,4,5-trimethoxystilbenes was performed under electron transfer conditions from Na metal in THF. Careful control of reaction conditions and quenching procedure allowed the synthesis of either (E)-3,5-dimethoxystilbenes or 3,5-dimethoxybibenzyls. 相似文献
987.
Hans Raj Tiwary 《Discrete and Computational Geometry》2008,40(3):469-479
For polytopes P
1,P
2⊂ℝ
d
, we consider the intersection P
1∩P
2, the convex hull of the union CH(P
1∪P
2), and the Minkowski sum P
1+P
2. For the Minkowski sum, we prove that enumerating the facets of P
1+P
2 is NP-hard if P
1 and P
2 are specified by facets, or if P
1 is specified by vertices and P
2 is a polyhedral cone specified by facets. For the intersection, we prove that computing the facets or the vertices of the
intersection of two polytopes is NP-hard if one of them is given by vertices and the other by facets. Also, computing the
vertices of the intersection of two polytopes given by vertices is shown to be NP-hard. Analogous results for computing the
convex hull of the union of two polytopes follow from polar duality. All of the hardness results are established by showing
that the appropriate decision version, for each of these problems, is NP-complete. 相似文献
988.
989.
ZHU Li-ping~ YANG Xiao-yan~ YU Zhou~ LIU Xiang-rong~ School of Finance Statist. East China Normal Univ. Shanghai China. Dept.of Statist. Zhejiang Univ.of Finance Economics Hangzhou China. 《高校应用数学学报(英文版)》2008,23(1):107-112
The single-index model with monotonic link function is investigated. Firstly, it is showed that the link function h(.) can be viewed by a graphic method. That is, the plot with the fitted response y on the horizontal axis and the observed y on the vertical axis can be used to visualize the link function. It is pointed out that this graphic approach is also applicable even when the link function is not monotonic. Note that many existing nonparametric smoothers can also be used to assess h(.). Therefore, the I-spline approximation of the link function via maximizing the covariance function with a penalty function is investigated in the present work. The consistency of the criterion is constructed. A small simulation is carried out to evidence the efficiency of the approach proposed in the paper. 相似文献
990.