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91.
92.
Green colored single crystals of a reduced sodium vanadium(III) monohydrogenphosphate, NaV(HPO4)2, were grown using a one-step mild hydrothermal method. The in situ reduction of V5+ to V3+ was performed using copper acetate as the reducing agent. The title compound crystalizes in the monoclinic space group Cc and exhibits a three-dimensional crystal structure that consists of distorted VO6 octahedra connected to PO3(OH) tetrahedra that are further connected via Na cations. The compound exhibits simple paramagnetic behavior at high temperatures and a discontinuity near 5 K is likely due to the onset of magnetic coupling. The compound was also characterized by TGA, IR and UV–vis spectroscopies. 相似文献
93.
Roee David Elazar Goldenberg Robert Krauthgamer 《Random Structures and Algorithms》2017,51(4):607-630
We study the problem of reconstructing a low‐rank matrix, where the input is an n × m matrix M over a field and the goal is to reconstruct a (near‐optimal) matrix that is low‐rank and close to M under some distance function Δ. Furthermore, the reconstruction must be local, i.e., provides access to any desired entry of by reading only a few entries of the input M (ideally, independent of the matrix dimensions n and m). Our formulation of this problem is inspired by the local reconstruction framework of Saks and Seshadhri (SICOMP, 2010). Our main result is a local reconstruction algorithm for the case where Δ is the normalized Hamming distance (between matrices). Given M that is ‐close to a matrix of rank (together with d and ), this algorithm computes with high probability a rank‐d matrix that is ‐close to M. This is a local algorithm that proceeds in two phases. The preprocessing phase reads only random entries of M, and stores a small data structure. The query phase deterministically outputs a desired entry by reading only the data structure and 2d additional entries of M. We also consider local reconstruction in an easier setting, where the algorithm can read an entire matrix column in a single operation. When Δ is the normalized Hamming distance between vectors, we derive an algorithm that runs in polynomial time by applying our main result for matrix reconstruction. For comparison, when Δ is the truncated Euclidean distance and , we analyze sampling algorithms by using statistical learning tools. A preliminary version of this paper appears appears in ECCC, see: http://eccc.hpi-web.de/report/2015/128/ © 2017 Wiley Periodicals, Inc. Random Struct. Alg., 51, 607–630, 2017 相似文献
94.
Sufficient dimension reduction (SDR) is a paradigm for reducing the dimension of the predictors without losing regression information. Most SDR methods require inverting the covariance matrix of the predictors. This hinders their use in the analysis of contemporary datasets where the number of predictors exceeds the available sample size and the predictors are highly correlated. To this end, by incorporating the seeded SDR idea and the sequential dimension-reduction framework, we propose a SDR method for high-dimensional data with correlated predictors. The performance of the proposed method is studied via extensive simulations. To demonstrate its use, an application to microarray gene expression data where the response is the production rate of riboflavin (vitamin B2) is presented. 相似文献
95.
Let A be a unital algebra and M be a unital A-bimodule. A linear map δ : A →M is said to be Jordan derivable at a nontrivial idempotent P ∈ A if δ(A) ? B + A ? δ(B) =δ(A ? B) for any A, B ∈ A with A ? B = P, here A ? B = AB + BA is the usual Jordan product. In this article, we show that if A = Alg N is a Hilbert space nest algebra and M = B(H), or A = M = B(X), then, a linear map δ : A → M is Jordan derivable at a nontrivial projection P ∈ N or an arbitrary but fixed nontrivial idempotent P ∈ B(X) if and only if it is a derivation. New equivalent characterization of derivations on these operator algebras was obtained. 相似文献
96.
杂交元本征应力模式和应力子空间的性质研究 总被引:3,自引:0,他引:3
详细讨论了有限元本征应力模式和应力子空间的性质,并着重讨论和进一步完善了与杂交应力有限元应力子空间有关的一些定理,为提出新方法提供了理论基础,主要包括:(1)证明了杂交元特征值不大于对应位移元的特征值;(2)证明了矩阵H非奇异的充分必要条件是假设应力模式线性无关;(3)证明了杂交元所对应位移元的本征应力模式形成的杂交元与该位移元相同;(4)证明了等价假设应力模式形成相同的杂交元;(5)证明了确定杂交元本征应力模式的充分必要条件是其范数平方等于所形成杂交元的变形模态特征值;(6)证明了杂交元假设应力模式与变形模态的能量一一对应的充分必要条件是假设应力模式彼此正交且与所对应位移元的本征应力模式除了一一对应者之外都正交。 相似文献
97.
一种大型结构特征值问题的并行解法 总被引:1,自引:1,他引:1
本文提出了一种求解大型结构固有频率与模态的并行解法。该方法在子空间迭代过程中,利用子结构刚度阵和质量阵并行进行凝聚,求得下一次的迭代基矢量,直到收敛。该算法在西安交通大学ELXS1-6400并行机上程序实现,计算结果表明能大幅度节省计算时间,同时也有效地节省了内存。 相似文献
98.
The controllability for switched linear system with time-delay in controls was first investigated. The whole work contains
three parts. This is the first part, including problem formulation and some preliminaries. Firstly, the mathematical model
of switched linear systems with time-delay in control functions was presented. Secondly, the concept of column space, cyclic
invariant subspace and generalized cyclic invariant subspace were introduced. And some basic properties, such as separation
lemma, were presented. Finally, a basic lemma was given to reveal the relation between the solution set of a centain integral
equations and the generalized cyclic invariant subspace. This lemma will play an important role in the determination of controllability.
All these definitions and lemmas are necessary research tools for controllability analysis.
Contributed by YE Qing-kai
Foundation items: the National Natural Science Foundation of China (69925307, 60274001); the National Key Basic Reasearch and Development
Program (2002CB312200); the Postdoctoral Program Foundation of China
Biography: XIE Guang-ming (1972∼), Doctor (E-mail: xiegming@mech.pku.edu.cn) 相似文献
99.
构造杂交应力单元的柔度矩阵H对角化方法 总被引:2,自引:1,他引:2
证明了杂交元柔度矩阵 H非奇异的充分必要条件是假设应力模式线性无关 ;以及等价应力模式形成相同的杂交元。在此基础上建立了假设应力模式的 Hilbert子空间 ,从而可以利用 Schmidt方法简单地得到等价的正交应力模式 ,实现了柔度矩阵 H对角化 ,使得杂交元形成过程中完全避免了繁杂的矩阵求逆运算 ,提高了杂交元分析的计算效率 ,特别在柔度矩阵不容易显式求逆的材料非线性分析中更具有实际意义 相似文献
100.
In this paper, continuity of the set-valued metric generalized inverse T∂ in approximatively compact Banach spaces is investigated by means of the methods of geometry of Banach spaces. Necessary and sufficient conditions for upper semicontinuity (continuity) for the set-valued metric generalized inverses T∂ are given. Moreover, authors also prove that if X is a nearly dentable space and H is a hyperplane of X, then H is approximatively compact iff PH(x) is compact for any x∈X. 相似文献