共查询到20条相似文献,搜索用时 936 毫秒
1.
For a noncommutative Zariski ringR with associated graded ringG(R) of finite global dimension there is an injectionK
o(R) K
o
(G(R)). The result applies to certain rings of differential operators, in particular to the ring of germs of microlocal differential operators that also provides an example of a nonpositively filtered Zariski ring.Research fellow at UIA, supported by a grant from the Province of Antwerp.Supported by an NFWO grant. 相似文献
2.
Teresa Monteiro Fernandes 《Compositio Mathematica》2001,128(3):241-259
A new family of sheaves has been recently studied by M. Kashiwara and P. Schapira generalizing to constructible sheaves the notion of moderate and formal cohomology. We prove comparison theorems when we regard these sheaves as solutions of a D-module. These results are natural generalizations of those of Y. Laurent and the author. 相似文献
3.
In this note we reverse theusual process of constructing the Lie algebras of types G
2and F
4 as algebras of derivations of the splitoctonions or the exceptional Jordan algebra and instead beginwith their Dynkin diagrams and then construct the algebras togetherwith an action of the Lie algebras and associated Chevalley groups.This is shown to be a variation on a general construction ofall standard modules for simple Lie algebras and it is well suitedfor use in computational algebra systems. All the structure constantswhich occur are integral and hence the construction specialisesto all fields, without restriction on the characteristic, avoidingthe usual problems with characteristics 2 and 3. 相似文献
4.
We consider the Knizhnik–Zamolodchikov (KZ) and dynamical equations, both differential and difference, in the context of (gl
k
,gl
n
) duality. We show that the KZ and dynamical equations naturally exchange under the duality. 相似文献
5.
Alejandro Balbás José Garrido Silvia Mayoral 《Methodology and Computing in Applied Probability》2009,11(3):385-399
The current literature does not reach a consensus on which risk measures should be used in practice. Our objective is to give
at least a partial solution to this problem. We study properties that a risk measure must satisfy to avoid inadequate portfolio
selections. The properties that we propose for risk measures can help avoid the problems observed with popular measures, like
Value at Risk (VaR
α
) or Conditional VaR
α
(CVaR
α
). This leads to the definition of two new families: complete and adapted risk measures. Our focus is on risk measures generated by distortion functions. Two new properties are put forward for these:
completeness, ensuring that the distortion risk measure uses all the information of the loss distribution, and adaptability,
forcing the measure to use this information adequately.
This research was partially funded by
1,3
Welzia Management, SGIIC SA, RD Sistemas SA, Comunidad Autónoma de Madrid Grant s-0505/tic/000230, and MEyC Grant BEC2000-1388-C04-03 and by
2
the Natural Sciences and Engineering Research Council of Canada (NSERC) Grant 36860-06. 相似文献
6.
Lidia A. Zaozerskaya 《Journal of Mathematical Modelling and Algorithms》2006,5(2):201-213
We study a supply management problem with a linear cost function and its mixed integer program. A parametric family of such problems, possessing exponential L
k
-coverings, is constructed. Besides, the NP-hard expansion of the family, which has the same property, is formulated. 相似文献
7.
Input data modeling is a critical component of a successful simulation application. A perspective of the area is given with an emphasis on available probability distributions as models, estimation methods, model selection and discrimination, and goodness of fit. Three specific distribution classes (lambda,S
B
, TES processes) are discussed in some detail to illustrate characteristics that favor input models. Regarding estimation, we argue for maximum likelihood estimation over method of moments and other matching schemes due to intrinsic superior properties (presuming a specific model) and the capability of accommodating messy data types. We conclude with a list of specific research problems and areas warranting additional attention. 相似文献
8.
Charles Audet Pierre Hansen Alejandro Karam Chi To Ng Sylvain Perron 《Optimization Letters》2008,2(4):483-495
We consider the problem of separating two sets of points in an n-dimensional real space with a (hyper)plane that minimizes the sum of L
p
-norm distances to the plane of points lying on the wrong side of it. Despite recent progress, practical techniques for the
exact solution of cases other than the L
1 and L
∞-norm were unavailable. We propose and implement a new approach, based on non-convex quadratic programming, for the exact
solution of the L
2-norm case. We solve in reasonable computing times artificial problems of up to 20000 points (in 6 dimensions) and 13 dimensions
(with 2000 points). We also observe that, for difficult real-life instances from the UCI Repository, computation times are
substantially reduced by incorporating heuristic results in the exact solution process. Finally, we compare the classification
performance of the planes obtained for the L
1, L
2 and L
∞ formulations. It appears that, despite the fact that L
2 formulation is computationally more expensive, it does not give significantly better results than the L
1 and L
∞ formulations. 相似文献
9.
Feature selection for high-dimensional data 总被引:2,自引:0,他引:2
Augusto Destrero Sofia Mosci Christine De Mol Alessandro Verri Francesca Odone 《Computational Management Science》2009,6(1):25-40
This paper focuses on feature selection for problems dealing with high-dimensional data. We discuss the benefits of adopting
a regularized approach with L
1 or L
1–L
2 penalties in two different applications—microarray data analysis in computational biology and object detection in computer
vision. We describe general algorithmic aspects as well as architecture issues specific to the two domains. The very promising
results obtained show how the proposed approach can be useful in quite different fields of application. 相似文献
10.
J. Andrikonis 《Lithuanian Mathematical Journal》2009,49(2):123-139
We analyze the multimodal logic S4
n
with the central agent axiom. We present a Hilbert-type calculus, then derive a Gentzen-type calculus with cut, and prove
a cut-elimination theorem. The work shows that it is possible to construct a cut-free Gentzen-type calculus for this logic.
Moreover, it also provides analogous results for the multimodal logic K4
n
with the central agent axiom. 相似文献
11.
12.
Frances Y. Kuo Grzegorz W. Wasilkowski Henryk Wo
niakowski 《Journal of Approximation Theory》2008,152(2):135-160
We study the worst case setting for approximation of d variate functions from a general reproducing kernel Hilbert space with the error measured in the L∞ norm. We mainly consider algorithms that use n arbitrary continuous linear functionals. We look for algorithms with the minimal worst case errors and for their rates of convergence as n goes to infinity. Algorithms using n function values will be analyzed in a forthcoming paper.We show that the L∞ approximation problem in the worst case setting is related to the weighted L2 approximation problem in the average case setting with respect to a zero-mean Gaussian stochastic process whose covariance function is the same as the reproducing kernel of the Hilbert space. This relation enables us to find optimal algorithms and their rates of convergence for the weighted Korobov space with an arbitrary smoothness parameter α>1, and for the weighted Sobolev space whose reproducing kernel corresponds to the Wiener sheet measure. The optimal convergence rates are n-(α-1)/2 and n-1/2, respectively.We also study tractability of L∞ approximation for the absolute and normalized error criteria, i.e., how the minimal worst case errors depend on the number of variables, d, especially when d is arbitrarily large. We provide necessary and sufficient conditions on tractability of L∞ approximation in terms of tractability conditions of the weighted L2 approximation in the average case setting. In particular, tractability holds in weighted Korobov and Sobolev spaces only for weights tending sufficiently fast to zero and does not hold for the classical unweighted spaces. 相似文献
13.
S. P. Sidorov 《Journal of Approximation Theory》2002,118(2):188-201
In this paper, we will show that Lagrange interpolatory polynomials are optimal for solving some approximation theory problems concerning the finding of linear widths.In particular, we will show that
, where
n is a set of the linear operators with finite rank n+1 defined on
−1,1], and where
n+1 denotes the set of polynomials p=∑i=0n+1aixi of degreen+1 such that an+11. The infimum is achieved for Lagrange interpolatory polynomial for nodes
. 相似文献
Full-size image
14.
We define notion of a quaternionic and para-quaternionic CR structure on a (4n+3)-dimensional manifold M as a triple (ω1,ω2,ω3) of 1-forms such that the corresponding 2-forms satisfy some algebraic relations. We associate with such a structure an Einstein
metric on M and establish relations between quaternionic CR structures, contact pseudo-metric 3-structures and pseudo-Sasakian 3-structures.
Homogeneous examples of (para)-quaternionic CR manifolds are given and a reduction construction of non homogeneous (para)-quaternionic
CR manifolds is described. 相似文献
15.
N. I. M. Gould 《Journal of Optimization Theory and Applications》1988,56(1):89-126
We consider the following classes of nonlinear programming problems: the minimization of smooth functions subject to general constraints and simple bounds on the variables; the nonlinearl
1-problem; and the minimax problem. Numerically reliable methods for solving problems in each of these classes, based upon exploiting the structure of the problem in constructing simple differentiable penalty functions, are presented.This research was made possible by NSERC Grant No. A8442.The author would like to thank Mrs. J. Selwood of the Department of Combinatories and Optimization, University of Waterloo, Ontario, Canada for her excellent typesetting.This work was carried out in the Department of Combinatories and Optimization, University of Waterloo, Waterloo, Ontario, Canada. 相似文献
16.
A new predictor-corrector algorithm is proposed for solvingP
*(κ)-matrix linear complementarity problems. If the problem is solvable, then the algorithm converges from an arbitrary positive
starting point (x
0,s
0). The computational complexity of the algorithm depends on the quality of the starting point. If the starting point is feasible
or close to being feasible, it has
-iteration complexity, whereρ
0 is the ratio of the smallest and average coordinate ofX
0
s
0. With appropriate initialization, a modified version of the algorithm terminates in O((1+κ)2(n/ρ
0)L) steps either by finding a solution or by determining that the problem has no solution in a predetermined, arbitrarily large,
region. The algorithm is quadratically convergent for problems having a strictly complementary solution. We also propose an
extension of a recent algorithm of Mizuno toP
*(κ)-matrix linear complementarity problems such that it can start from arbitrary positive points and has superlinear convergence
without a strictly complementary condition.
The work of this author was supported in part by NSF, Grant DMS 9305760 and by an Oberman fellowship from the University of
Iowa Center for Advanced Studies. 相似文献
17.
Albert G. Buckley 《Mathematical Programming》1986,36(3):256-275
This work concerns the derivation of formulae for updating quasi-Newton matrices used in algorithms for computing approximate
minima of smooth unconstrained functions. The paper concentrates strictly on the techniques used to derive update formulae.
It demonstrates a technique in which problems of finding matrices in ℝ
n ×n
of minimum Frobenius norm are converted to equivalent problems, using vector representations in ℝ
n2
and ℝ
n(n+1)/2 of these matrices, and then solvingl
2-minimization problems. These problems are more directly dealt with, and indeed, the paper demonstrates how this technique
may be used to handle weighted sparse updates. 相似文献
18.
A process variability control chart 总被引:1,自引:0,他引:1
In this study a Shewhart type control chart namely the V
t
chart, is proposed for improved monitoring of the process variability of a quality characteristic of interest Y. The proposed control chart is based on the ratio type estimator of the variance using a single auxiliary variable X. It is assumed that (Y, X) follows a bivariate normal distribution. The design structure of the V
t
chart is developed for Phase-I quality control and its comparison is made with those of the S
2 chart (a well-known Shewhart control chart) and the V
r
chart (a Shewhart type control chart proposed by Riaz (Comput Stat, 2008a) used for the same purpose. It is observed that
the proposed V
t
chart outperforms the S
2 and V
r
charts, in terms of discriminatory power, for detecting moderate to large shifts in the process variability. It is observed
that the performance of the V
t
chart keeps improving with an increase in |ρ
yx
| , where ρ
yx
is the correlation between Y and X. 相似文献
19.
This paper generalizes two nonconforming rectangular elements of the Reissner-Mindlin plate to the quadrilateral mesh. The
first quadrilateral element uses the usual conforming bilinear element to approximate both components of the rotation, and
the modified nonconforming rotated Q
1 element enriched with the intersected term on each element to approximate the displacement, whereas the second one uses the
enriched modified nonconforming rotated Q
1 element to approximate both the rotation and the displacement. Both elements employ a more complicated shear force space
to overcome the shear force locking, which will be described in detail in the introduction. We prove that both methods converge
at optimal rates uniformly in the plate thickness t and the mesh distortion parameter in both the H
1-and the L
2-norms, and consequently they are locking free.
This work was supported by the National Natural Science Foundation of China (Grant No. 10601003) and National Excellent Doctoral
Dissertation of China (Grant No. 200718) 相似文献