使用确定应力模型研究离心压气机叶片相互作用

离心压气机叶轮和扩压器叶片间空隙很小,在无叶区和半有叶区的流动非定常特性十分明显。特别是离心叶轮出口通常的射流／尾迹流动使得有叶扩压器进口在时间、空间两个尺度上都存在十分强烈的不均匀性。叶轮和扩压器叶片间的相互作用,历来都被认为是影响离心压气机效率和稳定工作范围的重要因素。本文引入确定应力模型和改进的计算域延伸方法,计算了Ｋｒａｉｎ离心压气机组的流场,着重分析了叶轮出口无叶区、半无叶区等叶片间相互作用最强烈的区域的复杂流动现象。     

管排数对翅片管蒸发器换热性能影响的仿真计算

通过对翅片管蒸发器建立集中参数模型,研究了管排数对变频空调蒸发器换热性能的影响。研究结果表明,管排数增加,总换热量的增加并不显著,但管排数每增加一排平均每排管的换热量减少18%左右;风机功率越大,达到最大换热量的管排数也越多。     

2k 3 型Hadamard 矩阵的一种构造方法

Hadamard 矩阵Hn 在很多领域中有相当的应用价值, 但Hn 的构造十分困难, 2k 型Hn 的构造已得到 解决, 非2k 型Hn 的存在性及存在时如何构造却未得到解决.本文提出了最佳偏移矩阵的概念, 得出了最 佳偏移矩阵与Hadamard 矩阵之间的关系, 在此基础上解决了2k3(k ≥2)型Hn 的构造问题.     

Invertibility of 2 × 2 operator matrices

Properties of right invertible row operators, i.e., of 1 × 2 surjective operator matrices are studied. This investigation is based on a specific space decomposition. Using this decomposition, we characterize the invertibility of a 2 × 2 operator matrix. As an application, the invertibility of Hamiltonian operator matrices is investigated.     

On the row merge tree for sparse LU factorization with partial pivoting

We consider the problem of structure prediction for sparse LU factorization with partial pivoting. In this context, it is well known that the column elimination tree plays an important role for matrices satisfying an irreducibility condition, called the strong Hall property. Our primary goal in this paper is to address the structure prediction problem for matrices satisfying a weaker assumption, which is the Hall property. For this we consider the row merge matrix, an upper bound that contains the nonzeros in L and U for all possible row permutations that can be performed during the numerical factorization with partial pivoting. We discuss the row merge tree, a structure that represents information obtained from the row merge matrix; that is, information on the dependencies among the columns in Gaussian elimination with partial pivoting and on structural upper bounds of the factors L and U. We present new theoretical results that show that the nonzero structure of the row merge matrix can be described in terms of branches and subtrees of the row merge tree. These results lead to an efficient algorithm for the computation of the row merge tree, that uses as input the structure of A, and has a time complexity almost linear in the number of nonzeros in A. We also investigate experimentally the usage of the row merge tree for structure prediction purposes on a set of matrices that satisfy only the Hall property. We analyze in particular the size of upper bounds of the structure of L and U, the reordering of the matrix based on a postorder traversal and its impact on the factorization runtime. We show experimentally that for some matrices, the row merge tree is a preferred alternative to the column elimination tree. AMS subject classification (2000)  65F50, 65F05, 68R10     

自聚焦排透镜参数分析及制作

自聚焦排透镜(SLR)是利用自聚焦透镜(SELFOC LENS)制作的一成象器件。本文就SLR的工作原理,及各参数对成象的影响进行了分析。并实际制作了几种不同规格的自聚焦排透镜为研制自聚焦排透镜提供了极好的基础。     

A new way to evaluate the Probability and Fresnel integrals

In this article, we show how Laplace Transform may be used to evaluate variety of nontrivial improper integrals, including Probability and Fresnel integrals. The algorithm we have developed here to evaluate Probability, Fresnel and other similar integrals seems to be new. This method transforms the evaluation of certain improper integrals into evaluation of improper integrals of the corresponding Laplace transform, which in many cases are much easier.     

Self-dual codes over F5 and s-extremal unimodular lattices

New s-extremal extremal unimodular lattices in dimensions 38, 40, 42 and 44 are constructed from self-dual codes over ${\mathbb{F}}_5$ by Construction A. In the process of constructing these codes, we obtain a self-dual $[44,22,14]$ code over ${\mathbb{F}}_5$. In addition, the code implies a $[43,22,13]$ code over ${\mathbb{F}}_5$. These codes have larger minimum weights than the previously known $[44,22]$ codes and $[43,22]$ codes, respectively.     

Study of modeling unsteady blade row interaction in a transonic compressor stage part 1: code development and deterministic correlation analysis

The average-passage equation system (APES) provides a rigorous mathematical framework for accounting for the unsteady blade row interaction through multistage compressors in steady state environment by introducing deterministic correlations (DC) that need to be modeled to close the equation system.The primary purpose of this study is to provide insight into the DC characteristics and the influence of DC on the time-averaged flow field of the APES.In Part 1 of this two-part paper,firstly a 3D viscous unsteady and time-averaging flow CFD solver is developed to investigate the APES technique.Then steady and unsteady simulations are conducted in a transonic compressor stage.The results from both simulations are compared to highlight the significance of the unsteady interactions.Furthermore,the distribution characteristics of DC are studied and the DC at the rotor/stator interface are compared with their spatial correlations (SC).Lastly,steady and time-averaging (employing APES with DC) simulations for the downstream stator alone are conducted employing DC derived from the unsteady results.The results from steady and time-averaging simulations are compared with the time-averaged unsteady results.The comparisons demonstrate that the simulation employing APES with DC can reproduce the time-averaged field and the 3D viscous time-averaging flow solver is validated.     

A PERTURBATION ANALYSIS FOR THE PROJECTION OF A STIFFLY SCALED MATRIX

In this paper we study the perturbation bound of the projection (WA )(WA ), where both the matrices A and W are given with W positive diagonal and severely stiff. When the perturbed matrix A=A δA satisfy several row rank preserving conditions, we derive a new perturbation bound of the projection.