基于LES方法两种接缝足球升阻力计算及飘球的力学分析

建立两种接缝形式足球的几何模型,通过LES方法计算足球模型的升阻力及相应流场情况．计算结果与相关文献对比,分析了计算误差的来源,并提出可行的处理方案．计算得到模型表面的接缝使得边界层分离点前移,分离区增大,从而阻力增大．计算结果同时表明,两种接缝对阻力的影响是相当的,对升力影响却不可忽视．计算得到升力的变化情况,并从涡脱落角度分析其特征．在此基础上,对“超自然现象”的飘球的力学机理进行了探讨．     

Boundary Harnack Principle for <Emphasis Type="Italic">p</Emphasis>-harmonic Functions in Smooth Euclidean Domains

We establish a scale-invariant version of the boundary Harnack principle for p-harmonic functions in Euclidean C ^1,1-domains and obtain estimates for the decay rates of positive p-harmonic functions vanishing on a segment of the boundary in terms of the distance to the boundary. We use these estimates to study the behavior of conformal Martin kernel functions and positive p-superharmonic functions near the boundary of the domain. H. A. was partially supported by Grant-in-Aid for (B) (2) (No. 15340046) Japan Society for the Promotion of Science. N. S. was partially supported by NSF grant DMS-0355027. X. Z. was partially supported by the Taft foundation.     

单位复超球上多复变解析函数的边值问题

讨论了二元复变解析函数在单位复超球区域上的某些边值问题,包括Dirichlet问题和Riemann-Hilbert问题,利用Cauchy公式、Plemelj公式以及级数展开的方法,我们对不同标数的情形,给出了所提问题可解的充分必要条件.     

Exact L 2 Small Balls of Gaussian Processes

We prove a comparison theorem extending Li(6) and develop a complex-analytic approach to treat L ² small ball probabilities of Gaussian processes. We demonstrate the techniques for the m-times integrated Brownian motions and in examples where one can not apply Li comparison theorem.     

C~n中单位球上的面积积分与BMO

设B是Cn中的单位球,S是Cn中的单位球面,Sα(f)是B上的面积积分.设f∈BMOA, 若存在正测度集E(?)S,使Sα(f)<∞在E上成立,则Sα(f)<∞在S上几乎处处成立,同时 Sα(f)∈ BMO(S)且存在常数C,使得||Sαf||*≤C||f||*.     

The -method, weak Lefschetz theorems, and the topology of Kähler manifolds

A new approach to Nori's weak Lefschetz theorem is described. The new approach, which involves the -method, avoids moving arguments and gives much stronger results. In particular, it is proved that if and are connected smooth projective varieties of positive dimension and is a holomorphic immersion with ample normal bundle, then the image of in is of finite index. This result is obtained as a consequence of a direct generalization of Nori's theorem. The second part concerns a new approach to the theorem of Burns which states that a quotient of the unit ball in () by a discrete group of automorphisms which has a strongly pseudoconvex boundary component has only finitely many ends. The following generalization is obtained. If a complete Hermitian manifold of dimension has a strongly pseudoconvex end and for some positive constant , then, away from , has finite volume.

     

Radial symmetry and regularity of solutions for poly-harmonic Dirichlet problems

Let B=B₁(0) be the unit ball in Rn and r=|x|. We study the poly-harmonic Dirichlet problem

     

On weighted spectral radius of unraveled balls and normalized Laplacian eigenvalues

For a graph G, the unraveled ball of radius r centered at a vertex v is the ball of radius r centered at v in the universal cover of G. We obtain a lower bound on the weighted spectral radius of unraveled balls of fixed radius in a graph with positive weights on edges, which is used to present an upper bound on the $s^{\text{th}}$ (where $s\ge 2$) smallest normalized Laplacian eigenvalue of irregular graphs under minor assumptions. Moreover, when $s=2$, the result may be regarded as an Alon–Boppana type bound for a class of irregular graphs.     

Comprehensive performance of a ball-milled La0.5Pr0.5Fe11.4Si1.6B0.2Hy/Al magnetocaloric composite

Due to the hydrogen embrittlement effect, La(Fe,Si)₁₃-based hydrides can only exist in powder form, which limits their practical application. In this work, ductile and thermally conductive Al metal was homogeneously mixed with La_0.5Pr_0.5Fe_11.4Si_1.6B_0.2 using the ball milling method. Then hydrogenation and compactness shaping of the magnetocaloric composites were performed in one step via a sintering process under high hydrogen pressure. As the Al content reached 9 wt.%, the La_0.5Pr_0.5Fe_11.4Si_1.6B_0.2H_y/Al composite showed the mechanical behavior of a ductile material with a yield strength of ~44 MPa and an ultimate strength of 269 MPa accompanied by a pronounced improvement in thermal conductivity. Due to the ease of formation of Fe-Al-Si phases and the several micron and submicron sizes of the composite particles caused by ball milling process, the magnetic entropy change of the composites was substantially reduced to ~1.2 J/kg· K-1.5 J/kg· K at 0 T-1.5 T.     

用单管落球法探讨蓖麻油粘度随温度的变化

从单管落球法出发,以测出蓖麻油粘度随温度变化的大量实验数据为基础,采用SPSS统计软件中线性回归与曲线拟合的方法,选择最佳统计模型,找到了两者之间的实验曲线及拟合方程.