一种通过梯形PPMgLN波导倍频实现带宽可调谐光源的理论研究

本文设计了一种梯形的周期极化掺镁铌酸锂(PPMgLN)波导,并通过在传播方向上引入温度梯度来拓宽其倍频(SHG)过程的泵浦光源可接收带宽。通过有限差分的光束传输法,计算波导的有效折射率,并进行波导尺寸的设计。结果表明,通过改变梯形波导不同位置的温度,使其形成一个温度梯度,可拓宽泵浦光源的波长可接收带宽。本文所设计的PPMgLN波导最大泵浦光源可接收带宽为C波段,即1 530~1 565 nm,该波导可倍频C波段,得到输出波段带宽为765~782.5 nm,温度调谐范围为30~150 ℃。     

求解矩阵方程AXB+CXD=F参数迭代法的最优参数分析

本文针对求矩阵方程AXB+CXD=F唯一解的参数迭代法，分析当矩阵A，B，C，D均是Hermite正（负）定矩阵时，迭代矩阵的特征值表达式，给出了最优参数的确定方法，并提出了相应的加速算法.     

On the structure and volume growth of submanifolds in Riemannian manifolds

The aim of this note is two-fold. First, we investigate the relations between the volume growth of a submanifold and its second fundamental form. In the second part, we discuss the relations between the index of some Schrödinger operators and the structure of a submanifold, and prove some one-end theorems.     

A Humidity-Induced Large Electronic Conductivity Change of 107 on a Metal-Organic Framework for Highly Sensitive Water Detection

The electronic conductivity (EC) of metal–organic frameworks (MOFs) is sensitive to strongly oxidizing guest molecules. Water is a relatively mild species, however, the effect of H₂O on the EC of MOFs is rarely reported. We explored the effect of H₂O on the EC in the MOFs (NH₂)₂-MIL-125 and its derivatives with experimental and theoretical investigations. Unexpectedly, a large EC increase of 10⁷ on H₂SO₄@(NH₂)₂-MIL-125 by H₂O was observed. Brønsted acid–base pairs formed with the −NH₂ groups, and H₂SO₄ played an important role in promoting the charge transfer from H₂O to the MOF. Based on H₂SO₄@(NH₂)₂-MIL-125, a high-performance chemiresistive humidity sensor was developed with the highest sensitivity, broadest detection range, and lowest limit of detection amongst all reported sensing materials to date. This work not only demonstrated that H₂O can remarkably influence the EC of MOFs, but it also revealed that post-modification of the structure of MOFs could enhance the influence of the guest molecule on their EC to design high-performance sensing materials.     

A Microporous Hydrogen-Bonded Organic Framework Based on Hydrogen-Bonding Tetramers for Efficient Xe/Kr Separation

Hydrogen-bonded organic frameworks (HOFs) have been emerging as a new type of very promising microporous materials for gas separation and purification, but few HOFs structures constructed through hydrogen-bonding tetramers have been explored in this field. Herein, we report the first microporous HOF (termed as HOF-FJU-46) afforded by hydrogen-bonding tetramers with 4-fold interpenetrated diamond networks, which shows excellent chemical and thermal stability. What's more, activated HOF-FJU-46 exhibits the highest xenon (Xe) uptake of 2.51 mmol g⁻¹ and xenon/krypton (Kr) selectivity of 19.9 at the ambient condition among the reported HOFs up to date. Dynamic breakthrough tests confirmed the excellent Xe/Kr separation of HOF-FJU-46a, showing high Kr productivity (110 mL g⁻¹) and Xe uptake (1.29 mmol g⁻¹), as well as good recyclability. The single crystal X-ray diffraction and the molecular simulations revealed that the abundant accessible aromatic and pyrazole rings in the pore channels of HOF-FJU-46a can provide the multiple strong C−H⋅⋅⋅Xe interactions with Xe atoms.     

椭圆PDE-约束优化问题的一个预条件子

针对由Galerkin有限元离散椭圆PDE-约束优化问题产生的具有特殊结构的3×3块线性鞍点系统,提出了一个预条件子并给出了预处理矩阵特征值及特征向量的具体表达形式.数值结果表明了该预条件子能够有效地加速Krylov子空间方法的收敛速率,同时也验证了理论结果.     

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In this paper, the asymptotic behavior of the weak solution (u_t)_{t\ge0} to the non-local Cauchy problems as stated in (1) is considered. Only using lower bounds of jumping kernel J(x,y) for large |x-y|, it is obtained that \|u_t\|_p\le c(t)\|u_0\|_q with any 1\le q相似文献   

Shared Values of Certain Nonlinear Differential Polynomials of Meromorphic Functions

In this paper,by using the idea of truncated counting functions of meromorphic functions,we deal with the problem of uniqueness of the meromorphic functions whose certain nonlinear differential polynomials share one finite nonzero value.