均匀准方形α-Fe_2O_3颗粒的制备

用改进的凝胶溶胶法在 １００ ℃时陈化高浓度的 Ｆｅ（ Ｏ Ｈ）３ 凝胶制备窄粒度分布的准方形 α Ｆｅ２ Ｏ３ 颗粒， 并探讨成核过程及 α Ｆｅ２ Ｏ３ 的形成机制． 结果表明， 以 Ｆｅ Ｃｌ３ 溶液添加到 Ｎａ Ｏ Ｈ 溶液中的反向添加法， 在碱性条件下制备 Ｆｅ（ Ｏ Ｈ）３ 凝胶， 可提高 α Ｆｅ２ Ｏ３ 的成核率。

硅酸盐对Ferrihydrite相转化为α-Fe2O3微粒形貌的调控作用

以Ferrihydrite(又称水合氧化铁hydrous iron oxide)为反应前驱物,Fe(II)为催化剂,在微量Na2SiO3存在下,控制pH=6～9范围内合成出了亚微米级纺锤形和准立方形α-Fe2O3微粒.研究了初始pH,Na2SiO3浓度,Ferrihydrite老化方式对相转化时间和产物形貌的影响,利用XRD,SEM等手段对产物进行了表征.结果表明,Na2SiO3对Ferriihydrite催化相转化有一定的抑制作用,是影响其相转化过程及产物形貌的关键.在弱碱性条件下,[Si]/[Fe3+]为0.01时可直接获得纺锤形(轴比≥2)或准立方形(300～400nm)α-Fe2O3粒子,并对形成机理进行了初步讨论.

在Auto CAD2.6版中使用24针打印机的方法

Auto CAD2.6版应用相当广泛,它是个必使用数字协处理器也能运行的最高版本.其绘图功能大.绘图质量高,不失为一个适应性强、经济实用的版本.由于它对硬件质量要求不高,使其成为在教学上用得较多的一种软件.然而,该版本提供的针式打印机均为九件打印机驱动程序,没有提供24针打印机驱动程序.

Sensor array calibration for uniform rectangular array in presence of mutual coupling and sensor gain-and-phase errors

The sensor array calibration methods tailored to uniform rectangular array(URA)in the presence of mutual coupling and sensor gain-and-phase errors were addressed.First,the mutual coupling model of the URA was studied,and then a set of steering vectors corresponding to distinct locations were numerically computed with the help of several time-disjoint auxiliary sources with known directions.Then,the optimization modeling with respect to the array error matrix(defined by the product of mutual coupling matrix and sensor gain-and-phase errors matrix)was constructed.Two preferable algorithms(called algorithm I and algorithm II)were developed to minimize the cost function.In algorithm I,the array error matrix was regarded as a whole parameter to be estimated,and the exact solution was available.Compared to some existing algorithms with the similar computation framework,algorithm I can make full use of the potentially linear characteristics of URA's error matrix,thus,the calibration precision was obviously enhanced.In algorithm II,the array error matrix was decomposed into two matrix parameters to be optimized.Compared to algorithm I,it can further decrease the number of unknowns and,thereby,yield better estimation accuracy.However,algorithm II was incapable of producing the closed-form solution and the iteration operation was unavoidable.Simulation results validate the excellent performances of the two novel algorithms compared to some existing calibration algorithms.

Calibrated explosive triangle for determining capacity of explosion of gas mixtures

Determination of the capacity for explosion of gas mixtures in a sealed area is very important for mining engineers.If this capacity is high,it would be very dangerous for rescue workers to proceed with their rescue operations.A number of methods have been developed to determine the capacity for explosion of gas mixtures in sealed areas.One of the more popular methods is the Coward explosive triangle,published by Coward.He presented a fast and easy way to determine the capacity for explosion of gas mixtures,which has proved to be a very useful tool for mining engineers and members of rescue teams.However,due to few drawbacks in this method;potential errors would be introduced when it is applied.In a brief introduction we first describe the Coward method and then,we propose and discuss new calibrated explosive triangles.We demonstrate the method in two case studies where we compare our results with those of the old model.The results indicate that the calibrated method have improved accuracy and reliability.Therefore,assessments can be made more accurately.

一种用于LSPR传感器的准正方型银纳米颗粒阵列制备

首先控制聚苯乙烯纳米球(PS球)乳液在基片上的干燥温度,采用自组装方法,使用单一粒径的PS球制备出单层的PS球亚稳态正方排列结构模板。然后,在模板上通过磁控溅射法沉积一层银膜。利用纳米球光刻技术,去掉PS球模板得到二维正方点阵排列的准正方形银纳米颗粒阵列结构。

Simulation of hydraulic fracture utilizing numerical manifold method

A 2nd order numerical manifold method(NMM) based method is developed to simulate the hydraulic fractures propagating process in rock or concrete. The proposed method uses a weak coupling technique to analyze the fluid phase and solid phase. To study the seepage behavior of the fluid phase, all the fractures in solid are identified by a block cutting algorithm and form a flow network. Then the hydraulic heads at crack ends are solved. To study the deformation and destruction of solid phase, the 2-order NMM and sub-region boundary element method are combined to solve the stress-strain field. Crack growth is controlled by the well-accepted criterion, including the tension criterion or Mohr-Coulomb criterion for the initialization of cracks and the maximum circumferential stress theory for crack propagation. Once the crack growth occurs, the seepage and deformation analysis will be resolved in the next simulation step. Such weak coupling analysis will continue until the structure becomes stable or is destructed. Five examples are used to verify the new method. The results demonstrate that the method can solve the SIFs at crack tip and fluid flow in crack network precisely, and the method is effective in simulating the hydraulic facture problem. Besides, the NMM shows great convenience and is of high accuracy in simulating the crack growth problem.

Study on intelligent control technology for forming steel pipe of pipeline with JCO process

Based on plastic bending engineering theory and machine vision technology, the intelligent control technology for forming steel pipe with JCO process is presented in this paper. By ‘twice pre-bending method’ in the first forming step, the springback law can be obtained. With the springback law and the target angle, the exact punch displacement which determines the formed angle in each bending step is predicted. In the succedent forming steps, the bending process is carried out with the exact punch displacement by real-time revising the springback law. And the angle error in each forming step is calculated by comparing the actual formed angle with the target angle. By conducting compensation for the last angle error in the next forming step, each precise bending process step is realized. A system of intelligent control technology for forming the steel pipe was developed. A calibration method is proposed to calculate the exterior parameters of the CCD camera, in which the equilateral triangle is em-ployed as the calibrating board and only one image needs to be captured. A mathematical model, which converts the angle in the image into the actual formed angle, is derived. The experimental results showed that the ellipticity of the formed pipes was less than 1.5% and the high-quality pipes can be manufactured without the worker's operating experience by employing the in-telligent control technology.

Beyond the Friedmann-Lema tre-Robertson-Walker Big Bang Singularity

Einstein＇s equation,in its standard form,breaks down at the Big Bang singularity.A new version,equivalent to Einstein＇s whenever the latter is defined,but applicable in wider situations,is proposed.The new equation remains smooth at the Big Bang singularity of the Friedmann-Lemaatre-Robertson-Walker model.It is a tensor equation defined in terms of the Ricci part of the Riemann curvature.It is obtained by taking the Kulkarni-Nomizu product between Einstein＇s equation and the metric tensor.

Almost Global Strong Solutions to Quasilinear Dissipative Evolution Equations

The author proves a global existence result for strong solutions to the quasilinear dissipative hyperbolic equation (1.1) below, corresponding to initial values and source terms of arbitrary size, provided that the hyperbolicity parameter ε is sufficiently small. This implies a corresponding global existence result for the reduced quasilinear parabolic equation (1.4) below.

不朽的恋歌─—泰姬·玛哈尔陵

不朽的恋歌─—泰姬·玛哈尔陵竞昕我修筑的城市，被大自然摧毁了；我主张的哲理，受到后世的鄙夷；我建立起的王国，早已被人忘记。剩下来的唯有由于你的美丽产生出来的微妙的爱情和被你的爱情复活了的美的产物。─—纪伯伦《废墟间》在巴勒贝克那著名古迹太阳城（现黎巴...

Simulation of Unsteady State Performance of a Secondary Air System by the 1D-3D-Structure Coupled Method

This paper describes the calculation method for unsteady state conditions in the secondary air systems in gas turbines. The 1D-3D-Structure coupled method was applied. A 1D code was used to model the standard components that have typical geometric characteristics. Their flow and heat transfer were described by empirical correlations based on experimental data or CFD calculations. A 3D code was used to model the non-standard components that cannot be described by typical geometric languages, while a finite element analysis was carried out to compute the structural deformation and heat conduction at certain important positions. These codes were coupled through their interfaces. Thus, the changes in heat transfer and structure and their interactions caused by exterior disturbances can be reflected. The results of the coupling method in an unsteady state showed an apparent deviation from the existing data, while the results in the steady state were highly consistent with the existing data. The difference in the results in the unsteady state was caused primarily by structural deformation that cannot be predicted by the 1D method. Thus, in order to obtain the unsteady state performance of a secondary air system more accurately and efficiently, the 1D-3D-Structure coupled method should be used.