Orientation-dependent Hydrodynamic Instabilities from Chemo-Marangoni Cells to Large Scale Interfacial Deformations

The interplay between chemistry and interfacial-tension-driven hydrodynamic instabilities has been studied experimentally. The system on hand consists of two immiscible liquids separated along an initially plane interface at which an interfacial reaction takes place to produce in situ a surfactant. It is identified that the dynamics of the system depends on the orientation of the Hele-Shaw cell with respect to the vector of gravity. If the nele-Shaw cell is placed vertically, Marangoni cells with vigorous convection develop in both phases along a nearly planar interface. However, if the Hele-Shaw cell is tilted off the gravity, the instabilities in the system are characterized by the large scale interracial deformation with a spatio-temporal periodicity together with the chemo-Marangoni convection. The focus is on the exploration of the transition from the cellular mode to the large scale interfacial deformation.

Numerical research on stability control of roofs of water-rich roadway

In order to study the strength-weakening law of roofs of water-rich roadway, this study used FLAC software, and simulated and analyzed the failure characteristics of the surrounding rock of water-rich roadway under the condition of different cross sections and support parameters, finally obtained the stress distribution of the principle stress of the roadway as well as the displacement variation of its surrounding rock. Results indicate that the roof stability of roadway with semicircular cross section is better than the roadway with inclined rectangular cross section under water-rich condition. Besides, the surrounding rock deformation of roadway under the action of water shows a pronounced increase compared to the roadway without the action of water due to the fact that water will obviously weaken the surrounding rock of roadway, especially its roof. It is very beneficial to control roof stability of water-rich roadway and guarantee the roadway stability during its service life by improving the pretension of bolt and cable as well as decreasing inter-row spacing of the bolt.

Synthesis of texture-excellent mesoporous alumina using PEG1000 as structure-directing agent

By varying concentration of PEG1000 as a structure-directing agent,mesoporous alumina with excellent textural properties was synthesized.The prepared mesoporous alumina displays high thermal stability,as shown by its textural properties at different calcination temperatures of 600-850 °C.Characterization by SEM and TEM revealed that the added PEG surfactant induced the formation of petal-like alumina.XRD results clarified that all samples were amorphous and their peaks were around the peaks of γ-alumina.N_2 adsorption-desorption analysis showed that the prepared mesoporous alumina,if with PEG1000 in hydrolysis of aluminum isopropoxide,had excellent textural properties with large specific surface area,high pore volume and suitable pore size.The petal-like structure existing in the alumina samples improved their textural parameters,and the role and influential mechanism of PEG1000 were analyzed.

Tunnel face stability and ground settlement in pressurized shield tunnelling

An analysis of the stability of large-diameter circular tunnels and ground settlement during tunnelling by a pressurized shield was presented. An innovative three-dimensional translational multi-block failure mechanism was proposed to determine the face support pressure of large-shield tunnelling. Compared with the currently available mechanisms, the proposed mechanism has two unique features:(1) the supporting pressure applied to the tunnel face is assumed to have a non-uniform rather than uniform distribution, and(2) the method takes into account the entire circular excavation face instead of merely an inscribed ellipse. Based on the discrete element method, a numerical simulation of the Shanghai Yangtze River Tunnel was carried out using the Particle Flow Code in two dimensions. The immediate ground movement during excavation, as well as the behaviour of the excavation face, the shield movement, and the excavated area, was considered before modelling the excavation process.

Stress-Induced Phase Transformation in Incompressible Materials and Stability of Multi-Phase Deformation

The stress-induced phase transformation in incompressible materials and the interfacial stability of multi-phase deformation were studied. The existence of multi-phase deformation was determined through exploring whether the material would lose the strong ellipticity at some deformation gradient. Then, according to the stability criterion which is based on a quasi-static approach, the stability of the multi-phase deformation in incompressible materials was investigated by studying the growth/decay behaviour of the interface in the undeformed configuration when it is perturbed. At last, the way to define multi-phase deformation in incompressible materials was concluded and testified by a corresponding numerical example.

Study on Preparation and Properties of Enamel Material

Reference to the domestic and foreign relevant technical data, the paper design and manufacture enamel materials with a temperature resistant shock resistance and acid resistance excellent chemical stability, research on microscopic morphology of the enamel surface by scanning electron microscope, the experiment results showed： mill addition certain amount of zirconium silicate crystal in enamel material, enable enamel material to form composite materials of amorphous material and zirconium silicate crystals, it can effectively improve its temperature shock property; it is necessary to improve the enamel material temperature resistance shock property, but also maintain its excellent acid resistance, there is a optimal weight range mill addition into zirconium silicate crystal.

空间光学大型镜面若干关键力学问题综述

回顾了国内外空间光学大型镜面相关领域的发展现状和趋势.结合已经开展的工作,讨论了在极端约束条件下,先进空间光机结构所要解决的材料选择、结构优化和超轻量化设计、表面应力调控和预应力加工技术等问题;指出了超大口径镜面减重、超轻量化镜面面形稳定性、离轴非球面宽动态范围精密面形调节等须进一步研究的方向.

新型中小口径反射镜消热刚性支撑结构设计

为解决传统柔性支撑中小口径空间反射镜组件热稳定性与结构刚度间的矛盾,提出了一种新型刚性支撑结构,并为某高分辨率空间相机研制了通光口径Φ214 mm的高精度次镜组件。采用“镜体-锥套-支撑筒-刚性基板”组合,通过延长、优化热应力在组件内部的传递路径实现了消热目的。刚性支撑次镜组件重2.6 kg、4℃均匀温升工况下面形变化均方根(RMS)仿真值为2.573 nm,装调重力工况下镜体倾角和位移分别为2.028″、0.566μm,与传统柔性支撑方案相比具有突出的优势。实测次镜的面形精度RMS为0.0181λ(λ=632.8 nm),在16℃及24℃时次镜面形变化量不超过0.0025λ;组件基频达到502.1 Hz,在快速高低温循环及大量级振动后次镜面形基本维持不变;装配容差测试中,次镜在0.02 mm不平度的作用下仅发生微弱变形。刚性支撑结构可以显著提升中小口径反射镜工作性能,在遥感器光机结构研制领域内具有广阔的应用前景。

Hyperbolicity of elliptic Lagrangian orbits in the planar three body problem

The linear stability of Lagrangian elliptic equilateral triangle homographic solutions in the classical planar three body problem depends on the mass parameter β = 27（m1m2 ＋ m2m3 ＋ m3m1）/（m1 ＋ m2 ＋ m3）2∈ [0,9] and the eccentricity e ∈ [0,1）.In this paper we use Maslov-type index to study the stability of these solutions and prove that the elliptic Lagrangian solutions is hyperbolic for β ＆gt; 8 with any eccentricity.