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1.
Sharp bounds on expectations of lifetimes of coherent and mixed systems composed of elements with independent and either identically or non-identically distributed lifetimes are expressed in terms of expected lifetimes of components. Similar evaluations are concluded for the respective mean residual lifetimes. In the IID case, improved inequalities dependent on a concentration parameter connected to the Gini dispersion index are obtained. The results can be used to compare systems with component lifetimes ordered in the convex ordering. In the INID case, some refined bounds are derived in terms of the expected lifetimes of series systems of smaller sizes, and the expected lifetime of single unit for the equivalent systems with IID components. The latter can be further simplified in the case of weak Schur-concavity and Schur-convexity of the system generalized domination polynomial. 相似文献
2.
提出了一种新的尺度归一化方法,该方法不强调各变量在尺度上的归一,而是在原始数据的基础上,通过提高稳定性高且在不同类别样本中具有显著差异性的变量的权重,以增强与特征代谢物相关的信息.分别采用模拟数据和真实代谢组学数据对新归一化方法的性能进行评估,并与单位方差法(Unit variance)、变量稳定性(Variable ... 相似文献
3.
Recent work alludes to various 'controversies' associated with signature change in general relativity and claims to resolve them. As we have argued previously, these are in fact disagreements about the (often unstated) assumptions underlying various possible approaches. We demonstrate that the issue has not been resolved and the choice between approaches remains open. 相似文献
4.
5.
We describe rational knots with any of the possible combinations of the properties (a)chirality, (non-)positivity, (non-)fiberedness, and unknotting number one (or higher), and determine exactly their number for a given number of crossings in terms of their generating functions. We show in particular how Fibonacci numbers occur in the enumeration of fibered achiral and unknotting number one rational knots. Then we show how to enumerate rational knots of given crossing number depending on genus and/or signature. This allows to determine the asymptotical average value of these invariants among rational knots. We give also an application to the enumeration of lens spaces. 相似文献
6.
We introduce the notion of signature for relations in mapping class groups and show that the signature of a Lefschetz fibration over the 2-sphere is the sum of the signatures for basic relations contained in its monodromy. Combining explicit calculations of the signature cocycle with a technique of substituting positive relations, we give some new examples of non-holomorphic Lefschetz fibrations of genus and which violate slope bounds for non-hyperelliptic fibrations on algebraic surfaces of general type.
7.
It is well known that the signature operator on a manifold defines a K-homology class which is an orientation after inverting 2. Here we address the following puzzle: What is this class localized at 2, and what special properties does it have? Our answers include the following:
- •
- the K-homology class ΔM of the signature operator is a bordism invariant;
- •
- the reduction mod 8 of the K-homology class of the signature operator is an oriented homotopy invariant;
- •
- the reduction mod 16 of the K-homology class of the signature operator is not an oriented homotopy invariant.
8.
Weiping Zhang 《中国科学A辑(英文版)》1999,42(12):1279-1285
A mod 2 index theorem for the twisted Signature operator on 4
q
+ 1 dimensional manifolds is established. This result generalizes a result of Farber and Turaev, which was proved for the
case of orthogonal flat bundles, to arbitrary real vector bundles. It also provides an analytic interpretation of the sign
of the Poincare-Reidemeister scalar product defined by Farber and Turaev.
Project partially supported by the National Natural Science Foundation of China (Grant No. 19525102), the Fok Ying-Tung Foundation
and the Qiu Shi Foundation. 相似文献
9.
John G. Miller 《K-Theory》1998,13(4):363-402
Let A be a unital complex C* algebra, L*(A) the projective symmetric surgery groups, and K*(A) topological K theory. We define groups B*(A) of bordism classes of Fredholm complexes over A with Poincaré duality. These generalize the de Rham complex. It is shown that there are isomorphisms B*(A)K* (A) and B*(A) L*(A) given by abstract versions of the signature operator and symmetric signature. The remaining side of a triangle is formed by an isomorphism due to Mienko. 相似文献
10.
M. L. Balinski 《Mathematical Programming》1986,34(2):125-141
Where there is abundance of mystery and confusion in every direction, the truth seldom remains hidden for long. It's a matter of having plenty of angles to go at it from. Only the utterly simple crimes - the simplex crimes, you may say - have the trick of remaining baffling. - Sir John (from Michael Innes,The Open House (A Sir John Appleby Mystery), Penguin Books, 1974).A dual simplex method for the assignment problem leaves open to choice the activity (i,j) of rowi and columnj that is to be dropped in pivoting so long asx
ij
< 0. A choice (i,j) over columnsj having at least 3 basic activities that minimizesx
ij
is shown to converge in at most (
2
n-1
) pivots, and at most O(n
3) time, and it is argued that on average the number of pivots is at mostn logn.
Dedicated with affection to George B. Dantzig on the occasion of his seventieth birthday. 相似文献