应用均匀设计方法提高筒形件的成形质量

均匀设计是试验设计方法的一种。采用有限元技术和均匀设计方法对筒形件在拉深成形过程中的摩擦系数、压边力、凹模口圆角半径等工艺参数进行优化设计。优化后的仿真结果在提高成形裕度和抑制厚度的变化方面取得很好的效果。该方法还可以明显减少模拟计算次数，提高优化效率，改善板料冲压成形的仿真计算精度。     

Synthesis of 100 μm uniform porous spheres by SPG emulsification with subsequent swelling of the droplets

100 μm porous p(styrene-co-divinylbenzene) (PS-DVB) microspheres were synthesized by employing a particular membrane emulsification technique, and subsequent swelling of the seed droplets. DVB dissolving a water-insoluble substance, hexadecane (HD), and an initiator was permeated through a SPG (Shirasu porous glass) membrane, and the uniform (seed) droplets were released to a stabilizer solution acting as the continuous phase. The average droplet size was around 30 μm, and this emulsion was mixed with a secondary emulsion of much smaller size consisting of more hydrophilic components, a mixture of styrene, middle chain alcohol (C6 to C8), dichlorobenzene, and isoamyl acetate, which promotes the degradative diffusion process of the components. After all the droplets in the secondary emulsion virtually disappeared, the seed droplets were swollen to a maximum 110 μm. Polymerization was carried out at 348 K under a nitrogen atmosphere. Uniform porous spheres of 100 μm with the coefficient of variation less than 10% were obtained. Specific surface area was 350 m²/g. Careful controlling of the specific gravity of swollen droplets and the choice of solvents balancing between the good solvency for the polymer and polarity (solubility in water) proved vital in order that the polymerization may proceed without an extensive phase separation in the early stage, which eventually induces breakup of the droplets. The three component system, isoamyl acetate-hexanol-o-dichlorobenzene, provided an adequate cosolvent for these purposes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 931–942, 1997     

活性自转向稠化酸解堵技术在克拉玛依油田的应用

报道了将活性自转向稠化酸用于高温高压裂缝－孔隙型油藏油吉酸化解堵技术,概括介绍了活性自转向稠化酸的基本组成和性能指标,作用原理,解堵工艺,详细介绍了用活性自转向稠化酸对新疆克拉玛依油田石田作业区油井酸化解堵的应用效果。     

Plasma behavior in a non‐equilibrium disk MHD generator with a spatially non‐uniform seed fraction

The influence of azimuthal non‐uniformity of the seed fraction on plasma structure and performance in a non‐equilibrium disk MHD generator is investigated with a two dimensional r–θ numerical simulation. It is found that a locally high seed fraction causes mainly non‐uniformity of gas‐dynamical properties, whereas a locally low seed fraction develops a non‐uniform plasma. Both locally high and low seed fractions reduce generator performance considerably. These results suggest a spatially uniform seed fraction should be required for high power generation. ©1999 Scripta Technica, Electr Eng Jpn, 126(4): 48–54, 1999     

基于两方程湍流模型的均匀流中湍流动能衰减规律研究

通过理论推导和数值模拟,从湍流模型封闭系数的确定过程、输运方程扩散项的影响因素、入口边界条件和网格尺度等方面分析标准k-ε模型、标准k-ω模型和SST k-ω湍流模型在计算均匀来流时湍流动能的衰减规律及其本质物理区别;通过数值模拟分析中性大气条件下湍流动能的衰减规律.结果表明,在均匀流中,采用标准k-ε湍流模型,入口湍...     

A least-squares approach for uniform strain triangular and tetrahedral finite elements

A least-squares approach is presented for implementing uniform strain triangular and tetrahedral finite elements. The basis for the method is a weighted least-squares formulation in which a linear displacement field is fit to an element's nodal displacements. By including a greater number of nodes on the element boundary than is required to define the linear displacement field, it is possible to eliminate volumetric locking common to fully integrated lower-order elements. Such results can also be obtained using selective or reduced integration schemes, but the present approach is fundamentally different from those. The method is computationally efficient and can be used to distribute surface loads on an element edge or face in a continuously varying manner between vertex, mid-edge and mid-face nodes. Example problems in two- and three-dimensional linear elasticity are presented. Element types considered in the examples include a six-node triangle, eight-node tetrahedron, and ten-node tetrahedron. © 1998 John Wiley & Sons, Ltd.     

External stabilizability of nonlinear systems with some applications

The aim of this paper is to discuss the existence of suitable feedback laws which provide stability (in a technical sense to be specified) with respect to inputs and initial conditions of the state response of a nonlinear system. © 1998 John Wiley & Sons, Ltd.     

Characterizations of J-lossless time-varying systems via the chain scattering approach

In this paper, via the chain scattering formalism, we derive the inequality condition for a bounded I/O operator which is associated with a finite-dimensional linear time-varying system to be lossless or J-lossless. The characterizations for J-losslessness apply to a J-lossless time-varying system which is either exponentially stable, anti-stable or one with a uniform stable/anti-stable decomposition of its state space. Uniform time-varying realizations are considered as they are required for the proof of the necessity of the state space characterizations. The results provide an extension to the state space characterizations of linear time-invariant J-lossless systems which belong to RL _∞. The characterizations for (J,J′)-lossless LTV systems are also derived. © 1998 John Wiley & Sons, Ltd.     

基于假设检验匹配约束的点云配准算法研究

针对点云配准中效率低、误差大、抗噪性弱等问题,提出了一种改进的基于t检验的迭代最近点(T-ICP)算法。在初始配准阶段,采用统计分析对源点云和目标点云中的离群点进行标记并提取非离群点,然后采用主成分分析法(PCA)计算非离群源点云和非离群目标点云之间的变换矩阵,并将变换矩阵应用于源点云。在精配准阶段,以迭代最近点(ICP)算法作为基本框架,通过对候选点对的邻域距离分布进行t检验来剔除错误点对,并采用均匀分布策略来搜索点对,保证点云的完整形态配准。实验结果表明,相较于迭代最近点算法以及近两年一些改进的配准算法,该算法在效率和精度上分别提高了10%~50%和4%~40%,并具有较好的鲁棒性。