上瓦开周向槽椭圆轴承动态特性分析

本文推导了计及惯性的Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程的简化形式，分析了考虑开槽区流体周向惯性的上瓦开周向槽椭圆轴承的动态特性。     

Gasification of charcoal using supercritical CO2 at high pressures

A novel one-shell high temperature and high pressure semi-continuous reactor has been developed for the study of the Boudouard reaction at temperatures up to 820 °C and pressures up to 32.5 MPa. Semicontinuous gasification of charcoal using supercritical CO₂ has been achieved at conversions up to 90.8% (w/w) at LSHV between 20 and 30 h⁻¹ after 5–9 h. A gasification model is proposed and validated. Effective rates of gasification (1.32 ± 0.12) × 10⁻⁶ to (6.10 ± 2.03) × 10⁻⁵ s⁻¹ were obtained. The results indicated that this method is technically feasible for the on-line production of high pressures streams of CO/CO₂ in the lab for carrying out further chemistries, avoiding the use of CO high pressure bottles.     

HEAT TRANSFER BETWEEN ROUGH SURFACES IN CONTACT OVER A HIGHLY ELLIPTICAL CONTOUR AREA: COMPARISON OF EXPERIMENTAL AND NUMERICAL RESULTS

This paper describes experimental and numerical studies of heat transfer between surfaces in contact over a highly elliptical area in a gas or in vacuum. Measurements of the steady-state thermal resistance of a high aspect ratio contact formed between cylindrical steel surfaces with widely different radii of curvature (76 cm vs 0.95 cm) are reported for two levels of surface roughness (0.05 μm and 1.0 μm rms) and compared to 3-D numerical results obtained with the multigrid method. Theoretical results obtained by evaluating the contact conductance acting over each surface element within the contour area with a method developed previously for rough but nominally flat surfaces are shown to be in excellent agreement with the rough surface experimental data.     

Region-Based Hierarchical Image Matching

This paper presents an approach to region-based hierarchical image matching, where, given two images, the goal is to identify the largest part in image 1 and its match in image 2 having the maximum similarity measure defined in terms of geometric and photometric properties of regions (e.g., area, boundary shape, and color), as well as region topology (e.g., recursive embedding of regions). To this end, each image is represented by a tree of recursively embedded regions, obtained by a multiscale segmentation algorithm. This allows us to pose image matching as the tree matching problem. To overcome imaging noise, one-to-one, many-to-one, and many-to-many node correspondences are allowed. The trees are first augmented with new nodes generated by merging adjacent sibling nodes, which produces directed acyclic graphs (DAGs). Then, transitive closures of the DAGs are constructed, and the tree matching problem reformulated as finding a bijection between the two transitive closures on DAGs, while preserving the connectivity and ancestor-descendant relationships of the original trees. The proposed approach is validated on real images showing similar objects, captured under different types of noise, including differences in lighting conditions, scales, or viewpoints, amidst limited occlusion and clutter.     

椭圆工件机器视觉尺寸检测系统设计与实现

本文介绍了椭圆工件机器视觉检测系统的构成和软件功能模块,重点阐述了统计聚类和Hough变换相结合检测椭圆像素尺寸的新算法。在降低Hough变换参数维度的情况下,利用椭圆自身特征减少无效数据统计存储量。     

椭圆参考轨道指定区域最优交会研究

研究了椭圆参考轨道指定区域最优交会问题。为了实现在指定区域完成最优交会,采用以参考轨道真近点角为自变量的线性化时变Tschauner-Hempel交会动力学模型,按照设定的真近点角交会域和最优二次性能指标设计最优交会控制,加权矩阵随真近点角变化。为方便指定区域最优控制问题求解,采用区段混合能法递推求解时变黎卡提矩阵微分方程和状态轨线。对远距、近距异面交会和共面交会三种情况设定不同的交会域进行了仿真研究,结果表明方法能保证在设定的真近点角域内完成交会,交会控制能耗小,精度高。     

Stress intensity factors of an inclined elliptical crack near a bimaterial interface

In this paper the stress intensity factors are discussed for an inclined elliptical crack near a bimaterial interface. The solution utilizes the body force method and requires Green’s functions for perfectly bonded semi-infinite bodies. The formulation leads to a system of hypersingular integral equation whose unknowns are three modes of crack opening displacements. In the numerical calculation, unknown body force densities are approximated by using fundamental density functions and polynomials. The results show that the present method yields smooth variations of stress intensity factors along the crack front accurately. Distributions of stress intensity factors are presented in tables and figures with varying the shape of crack, distance from the interface, and elastic modulus ratio. It is found that the inclined crack can be evaluated by the models of vertical and parallel cracks within the error of 24% even for the cracks very close to the interface.     

椭圆截面工件车削加工

通过对工件椭圆截面的分析,提出了一种新型的椭圆截面车削加工的方法,在比较了目前的椭圆插补算法的基础上,设计了一种采用极坐标的、适合于车削系统使用的新型的椭圆插补算法。     

椭球封头圆柱形爆炸容器振动特性研究

对椭球封头圆柱形爆炸容器在中心点爆炸状态下的 19次有效炮实验给予了介绍并对实验结果的壳体振动特性进行了分析。理论和实验分析表明 ,在封闭容器内爆炸冲击载荷具有明显的脉冲激励特征 ;容器壳体的振动频谱主要受前 10阶固有频率的影响 ;随着冲击载荷的增加 ,其壳体的主振频率将趋于相应壳体的呼吸频率 ,其应变增长具有减少的趋势 ;联接螺栓的振动模态主要受相应圆柱壳体和封头轴向振动模态的影响 ,并出现了在时域上其振动模态在圆柱壳振动模态和封头轴向振动模态间跳变的现象。     

Numerical analysis of slender elliptical concrete filled columns under axial compression

This paper presents a non-linear finite element model (FEM) used to predict the behaviour of slender concrete filled steel tubular (CFST) columns with elliptical hollow sections subjected to axial compression. The accuracy of the FEM was validated by comparing the numerical prediction against experimental observation of eighteen elliptical CFST columns which carefully chosen to represent typical sectional sizes and member slenderness. The adaptability to apply the current design rules provided in Eurocode 4 for circular and rectangular CFST columns to elliptical CFST columns were discussed. A parametric study is carried out with various section sizes, lengths and concrete strength in order to cover a wider range of member cross-sections and slenderness which is currently used in practices to examine the important structural behaviour and design parameters, such as column imperfection, non-dimension slenderness and buckling reduction factor, etc. It is concluded that the design rules given in Eurocode 4 for circular and rectangular CFST columns may be adopted to calculate the axial buckling load of elliptical CFST columns although using the imperfection of length/300 specified in the Eurocode 4 might be over-conservative for elliptical CFST columns with lower non-dimensional slenderness.