Analysis of the convected Helmholtz equation with a uniform mean flow in a waveguide with complete radiation boundary conditions

In this paper, we propose complete radiation boundary conditions (CRBCs) for solutions of the convected Helmholtz equation with a uniform mean flow in a waveguide. We first study CRBCs for the Helmholtz equation in a waveguide. Noting that the convected Helmholtz equation is associated with the Helmholtz equation via the Prandtl–Glauert transformation, CRBCs for the convected Helmholtz equation is derived from CRBCs for the Helmholtz equation. We analyse well-posedness and convergence of approximate solutions satisfying CRBCs for the convected Helmholtz equation. In addition, simple numerical experiments will be presented to confirm the theoretical results.     

On the generalized Weyl problem for flat metrics in the hyperbolic 3-space

The paper deals with the study of complete embedded flat surfaces in H³${\mathbb{H}}^3$ with a finite number of isolated singularities. We give a detailed information about its topology, conformal type and metric properties. We show how to solve the generalized Weyl?s problem of realizing isometrically any complete flat metric with Euclidean singularities in H³${\mathbb{H}}^3$ which gives the existence of complete embedded flat surfaces with a finite arbitrary number of isolated singularities.     

ON SOLVABLE COMPLETE LIE SUPERALGEBRAS

The authors discuss the properties of solvable complete Lie superalgebra, proving that solvable Lie superalgebras of maximal rank are complete.     

Boundary interpolation in the ball

We solve a boundary interpolation problem in the reproducing kernel Hilbert space of functions analytic in the unit ball of with reproducing kernel 1/(1−∑₁^Nz_kw_k^*). We introduce the notion of Brune factor (or Blaschke–Potapov factor of the third kind) in this setting.     

氟添加方式对NiMo催化剂在浆态床上加氢脱硫性能的影响

以F为助剂,采用完全液相法制备了氟改性的NiMo/TiO₂-Al₂O₃浆状催化剂,考察了氟的添加方式对催化剂在浆态床上4, 6-二甲基二苯并噻吩(4, 6-DMDBT)加氢脱硫性能的影响.采用X射线衍射(XRD)谱、氢气程序升温还原(H₂-TPR)、N₂吸脱附实验(BET)、X射线光电子能谱(XPS)、高分辨率透射电镜(HRTEM)对催化剂进行了表征.结果表明,在不添加浓硝酸的情况下,在活性组分加入之前引入氟能显著提高催化剂的比表面积和孔径,促进反应过程中金属镍在催化剂表面的分散,更大程度地减弱催化剂中活性金属与载体间的相互作用,有效提高Mo的硫化度及MoS₂的堆积层数,从而生成了较多的II类Ni-Mo-S活性相,促进芳香环的加氢和C-S键的氢解,对4, 6-DMDBT有较高的加氢脱硫活性.     

一维光子晶体的有效折射率及色散特性

对有限长度一维光子晶体引入了复有效折射率的概念.它的实部描述了一维光子晶体的色散特性, 虚部反映了光在光子禁带被损耗衰减而消失的特征.从具体计算λ/4 波片堆组成的一维光子晶体的复有效折射率的结果可以看到,它的实部受到光子带结构的调制,在光子禁带及透射带中的一部分出现反常色散现象.在很大的频率范围内,有效折射率变得小于1.