周期性多孔材料等效剪切模量与尺寸效应研究

提出了以圆筒扭转力学模型为基础, 预测周期性多孔材料等效剪切模量及其研究尺寸效 应的一种简单有效计算方法. 以方形孔和圆形孔两种典型多孔材料为例进行了数值计算求解; 同时, 建立了几何参数随体胞尺寸缩放因子$n$的解析关系, 证明了两种构型的周期性多孔材 料的等效剪切模量均随尺寸缩放因子$n$的增大而减小. 当$n \to \infty $时, 即体胞尺寸相对整体结构无限小时, 多孔材料的等效剪切模量趋近收敛于一个恒定值; 当体胞的材料体分比增大时, 多孔材料等效剪切模量也随之增大. 此外, 依据周 期性多孔材料的结构对称特性, 使用体胞子结构有限元计算模型进行等效剪切模量及其尺寸 效应的预测, 极大地提高了计算效率.     

Fabrication and characterization of Ce_(0.7)Zr_( 0.3)O_2 nanorods having high specific surface area and large oxygen storage capacity

Nanorod-like Ce 0.7 Zr 0.3 O 2 solid solutions were synthesized by a sodium dodecyl sulfate-assisted precipi- tation method. The samples were characterized by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and specific surface area measurement. Typical Ce 0.7 Zr 0.3 O 2 nanorods were 40 nm in average diameter and 450 nm in length, with specific surface area and oxygen storage capacity of 194 m 2 /g and 374 mol/g, respectiv...     

Robust partially mode‐dependent H∞ filtering for discrete‐time nonhomogeneous Markovian jump neural networks with additive gain perturbations

This paper studies the robust partially mode‐dependent H_∞ filtering for nonhomogeneous Markovian jump neural networks with additive gain perturbations. The discrete time‐varying jump transition probability matrix is considered to be a polytope set. A partially mode‐dependent filter with additive gain perturbations is constructed to increase the robustness of the filter, which is subjects to H_∞ performance index. Based on the Lyapunov function approach, sufficient conditions are established such that the filtering error system is robustly stochastically stable. The efficiency of the new technique is illustrated by an illustrative example and a biological network example.     

Spreading and vanishing in a diffusive intraguild predation model with intraspecific competition and free boundary

This paper is concerned with the spreading and vanishing phenomena in a diffusive intraguild (IG) predation model with intraspecific competition and free boundary in one dimensional space. The main objective is to obtain the asymptotic behavior of spread of an invasive or new IG prey species via a free boundary. In two cases, we prove a spreading‐vanishing dichotomy for this model, specifically, the IG prey species either successfully spreads to infinity as t→∞ at the front and survives in the new environment or spreads within a bounded area and dies out in the long run. The long time behavior of (R,N,P) and criteria for spreading and vanishing are also obtained. And then, we estimate the asymptotic spreading speed of the free boundary when spreading happens. Besides, two numerical examples are given to illustrate the impacts of initial occupying area and expanding capability on the free boundary.     

Isomorphism in Wavelets

Journal of Fourier Analysis and Applications - Two scaling functions $$\varphi _A$$ and $$\varphi _B$$ for Parseval frame wavelets are algebraically isomorphic, $$\varphi _A \simeq \varphi _B$$, if...     

Dynamics of a Predator-prey Model with Delay and Fear Effect

Recent manipulations on vertebrates showed that the fear of preda- tors, caused by prey after they perceived predation risk, could reduce the prey''s reproduction greatly. And it''s known that predator-prey systems with fear ef- fect exhibit very rich dynamics. On the other hand, incorporating the time delay into predator-prey models could also induce instability and oscillations via Hopf bifurcation. In this paper, we are interested in studying the com- bined effects of the fear effect and time delay on the dynamics of the classic Lotka-Volterra predator-prey model. It''s shown that the time delay can cause the stable equilibrium to become unstable, while the fear effect has a stabi- lizing effect on the equilibrium. In particular, the model loses stability when the delay varies and then regains its stability when the fear effect is stronger. At last, by using the normal form theory and center manifold argument, we derive explicit formulas which determine the stability and direction of periodic solutions bifurcating from Hopf bifurcation. Numerical simulations are carried to explain the mathematical conclusions.     

Rapid transfer alignment of laser SINS using quaternion based angular measurement

A novel rapid transfer alignment algorithm for laser strapdown inertial navigation system (SINS) is studied. Transfer alignment have typically relied on velocity measurements from the master SINS as the source of alignment information, but lever arm error must be compensated accurately while velocity information is utilized, all most every quaternion based error model is nonlinear, so nonlinear filtering algorithms are need, suffering from computational complex and large error. Aim at these problems, a novel improved rapid transfer alignment algorithm formulation is presented, applying quaternion to built the process and measurement models, the improvement employs a special manipulation of the measurement equation results in a linear pseudo-measurement equation, thus the classical linear Kalman filter is employed to estimate the state, need not lever arm error compensation, results in the reduce of computational burden. Observability analysis of this new transfer alignment algorithm has been done based on the piece-wise constant system (PWCS) method, results show that the presented algorithm can accomplish the initial alignment task perfectly. A transfer alignment simulation system is also developed for the evaluation and analysis of the presented algorithm, simulation results are confirmed with the theoretical conclusion, which can achieve the transfer alignment accuracy about 1 mrad within 10 s.     

楔形盒染料掺杂胆甾相液晶激光器研究

设计制作了楔形盒掺杂激光染料PM580的胆甾相液晶器件, 研究了激光辐射行为. 在楔形液晶盒中出现了一系列与楔棱平行的向错线和不同规则形状的晶畴, 胆甾相液晶形成了平面态排列. 采用固体Nd:YAG倍频532 nm 波长激光作为抽运光, 获得调谐精度约1 nm, 调谐范围约17 nm的一维波长可调谐激光器. 楔形盒中, 液晶扭曲力与取向膜表面锚定力相互平衡的过程中胆甾相液晶螺距伸张, 光子禁带位置移动, 从而调谐光子禁带边沿出射激光波长. 关键词： 胆甾相液晶 楔形盒 激光辐射     

Semi-Synthesis and In Vitro Anti-Cancer Evaluation of Magnolol Derivatives

Magnolol (MAG), a biphenolic neolignan, has various biological activities including antitumor effects. In this study, 15 MAG derivatives were semi-synthesized and evaluated for their in vitro anticancer activities. From these derivatives, compound 6a exhibited the best cytotoxic activity against four human cancer cell lines, with IC₅₀ values ranging from 20.43 to 28.27 μM. Wound-healing and transwell assays showed that compound 6a significantly inhibited the migration and invasion of MDA-MB-231 cells. In addition, Western blotting experiments, performed using various concentrations of 6a, demonstrated that it downregulates the expression of HIF-1α, MMP-2, and MMP-9 in a concentration-dependent manner. Overall, these results suggest that substituting a benzyl group having F atoms substituted at the C2 position on MAG is a viable strategy for the structural optimization of MAG derivatives as anticancer agents.