用计算法处理相贯圆柱的展开问题

本文推导出了两圆柱体相贯线通用计算公式,说明了相贯线的展开方法,并给出了用计算机绘制其表面展开图的程序框图。     

相贯线划规

划线工划相贯线时,通常先在硬纸板上划上相贯线展开图,然后再描到圆柱体上进行下料,比较麻烦也不精确。我设计的划规可直接在圆柱体上划     

用VBA开发AutoCAD精确绘制相贯件表面展开图系统

通过对相贯两圆柱体数学模型的研究,建立了展开曲线方程。用VBA编制了通用的计算机程序,将展开图在AutoCAD上绘制,实现了两个任意大小、任意相对位置圆柱体相贯展开图的参数化CAD。该方法具有快速、准确、修改方便的特点,具有很强的工程实用性。     

实现圆柱相贯轨迹的空间凸轮 CAD

介绍了空间圆柱体相贯线的方程,利用反转法建立了圆柱凸轮曲面的计算方法,提出了根据许用压力角选择平均圆柱半径的方法。     

AUTOLISP编程实现正交开孔圆管展开图快速绘制

正本文以AUTOLISP编程实现了正交圆孔中心位置确定、两母线投影定宽的展开和正交圆孔相贯线的展开。在该程序生成相贯线展开图时,将图样中圆孔细分为80份,并生成展开图中点的对应位置,应用了"SPLINE"命令进行绘制,该内容直接针对于现场加工,有着重要的实际应用价值。三种图形直接在AUTOCAD中生成,从而减少了软件对接过程的繁琐,提高了工作效率和作图质量。     

截交线和相贯线的绘制要点--求特殊点

介绍了截交线和相贯线的绘制要点：圆锥体被截时椭圆长短轴端点的投影分别是椭圆对称中心两个端点的投影;回转体相贯线上一些隐藏的特殊点要判断准确;同一种回转体的直径发生变化时,相贯线也随之发生改变。     

探测器组盲区CAD分析与重叠角计算公式

本文目的是计算探测器的盲区。文中提出了一种圆锥体与球体相贯求官区的方法;用CAD技术给出了直观图和精确的数据。最后,推导了方位视场重叠角的计算公式,并验证之。     

曲面相贯线上的圆角过渡实用算法

圆柱体相贯线上的圆角表示法是CAD和计算机辅助设计中众所周知的难题。所有的CAD/CAM软件中都没有这一功能。本文借助"滚球法",以二次圆弧曲线的NURBS生成原理为基础,利用NURBS方法可精确表示圆及圆弧的特点,给出了构造圆柱体相贯线上圆角过渡曲面的实用算法,同时给出了过渡曲面的NURBS表示。     

斜圆锥体交线的展开计算

斜圆锥体交线的展开图形状较复杂且不易确定,用常规的方法更难找到较好的解决方法。而且类似替代的方法就避开了常规方法中遇到的问题,并能计算和准确的确定。文中对这种方法进行了详细的分析,提出的处理方法为斜圆锥体交线展开和类似问题的解决找到了一种很好的思路。     

斜圆锥体交线的展开计算

斜圆锥体交线的展开图形状较复杂且不易确定 ,用常规的方法更难找到较好的解决方法。而用类似替代的方法就避开了常规方法中遇到的问题 ,并能计算和准确的确定。文中对这种方法进行了详细的分析 ,提出的处理方法为斜圆锥体交线展开和类似问题的解决找到了一种很好的思路。     

偏斜交圆柱圆锥表面展开图计算机绘制数模原理

分析了轴线偏斜交的圆柱与圆锥相对位置关系,建立了偏斜交圆柱、圆锥表面展开图及相贯曲线绘制的数学模型,并编制了通用计算机绘图程序,给出计算机绘制的展开图样例。     

Aerodynamic load maps of bluff bodies: Measurement and diagnostics

Bluff bodies may assume arbitrary attitudes in a flow, causing aerodynamic loads that are sensitive to attitude. The Continuous rotation technique obtains 6-component loads on bluff bodies with 1-degree azimuth resolution about selected axes at a rate of 1 revolution per minute. The load coefficient variation is Fourier transformed and the resulting complex series is truncated in order to obtain rapidly computable, analytical formulae. The method is applied to bluff body shapes including cylinders, a cuboid, a flat plate and a porous box. A cylinder whose length is equal to its diameter, is used to show that rate effects, hysteresis, vortex shedding and other unsteady aerodynamic phenomena are negligible below 10 revolutions per minute. Approaches to generalize the aerodynamic loads on yawed finite cylinders of various aspect ratio are studied. The reasons for differences in aerodynamic load behavior between 2 cylinder models, are analyzed. To complement experiments, the ROTCFD unsteady Navier Stokes code is used to perform diagnostic computations. Methods to generalize the predictions are explored. Maps of the leading coefficients of the Fourier series of each load component over the aspect ratios space, are interpolated. The interpolation varies sharply for aspect ratios between 0.5 to 1. The variation is more gradual beyond aspect ratio 2. By aspect ratio 4, a ‘high aspect ratio’ limit appears to be reached.     

摄影测量的动态测量应用

摄影测量技术是通过空间交会的原理计算出空间点的三维坐标.借助于高精度的照相机和快速图像处理器,摄影测量可以实现对多点的实时测量监控,从而计算出被测物的姿态、位置、形状以及它们的变化.通过数学建模,分析了摄影测量的动态测量原理,包括仪器部件坐标系的建立,活动部件坐标系的动态跟踪.并以比利时KRYPTON产品为例,介绍了典型摄影测量系统的应用技术,以及它们在航天航空汽车制造等领域中的应用实例.     

国内底部单缸液压圆锥破碎机的差距及发展趋势

介绍了底部单缸液压圆锥破碎机的特点,并从材料、设计等方面分析了国产底部单缸液压圆锥破碎机存在的问题,指出随着投入的增加、技术的进步,底部单缸液压圆锥破碎机将有广阔的应用前景。     

从投影图重建二次曲面

首次定义了二次曲面截交线——位于三维空间的二次曲线的坐标概念,建立了截交线与其投影曲线坐标之间的约束关系,给出了从二次曲面正投影的轮廓线及截交线的投影重建二次曲面和截平面的计算公式,据此建立了从轮廓线和截交线投影重建二次曲面体的方法。     

多类型管切割数控轨迹建模与仿真

本研究是面向一种相贯线切割机数控系统开展的。该机床能对圃管、方管和圆锥管等管材进行空间加工，以使工件能精确的组合连接。为新的多轴空间加工数控系统产品的进一步开发提供理论基础和实践平台。     

Photoreceptor cells in the Xenopus retina

This review summarizes our present state of knowledge about spectrally different photoreceptor cell types in the Xenopus retina. The classification of the photoreceptors was based on morphology, combined with immunolabelling with various anti-visual pigment antibodies and other molecular probes on semithin sections and retinal wholemounts. The majority of photoreceptors is represented by rods. Altogether 97-98% of the total rod population consists of the principal ("red") rods that are selectively labeled by N-terminal specific anti-bovine rhodopsin monoclonal antibodies (mAbs) and are maximally sensitive to green light. The other, rare, blue-sensitive rod type ("green rod") is thinner, not stained by these antibodies but binds C-terminal specific anti-rhodopsin mAbs. The major representatives of the cones are red-sensitive and consist of a morphologically heterogeneous group comprising both (principal and accessory) members of double cones, as well as large single cones. Outer segments in this group are selectively labeled by mAb COS-1, specific to the L/M group of cone visual pigments. Another, relatively rare cone type is similar in size, but slightly smaller than the large single cone and is not labeled by mAb COS-1. This cone type is assumed to have a blue-sensitive cone visual pigment. The third, least abundant, and immunocytochemically distinct cone type is a small single (miniature) cone, which binds mAb OS-2 relatively strongly, and anti-rhodopsin mAbs 4B4 and 1D4 weakly. By exclusion, this small single cone may be identical with the UV-sensitive cone. Further studies are needed, however, to identify the color sensitivity of the latter two cone types.     

不同微细造型几何形貌对润滑性能影响的数值模拟

建立了圆柱形、球冠形、锥形、六角形截面、三角形截面、正方形截面等表面微细造型几何形貌的数学模型,结合微细形貌润滑理论模型,采用多重网格法,分析了这些不同几何形貌对两滑动表面摩擦润滑性能的影响。分析结果表明:球冠造型形成油压的区域要明显大于圆柱和圆锥造型形成的油压区域;在相同表面占有率和微细造型深度下,正三角形造型有效油膜压力的区域较大,在相对滑动的表面中形成的间隙大,摩擦因数小。     

High- and low-frequency noise in Cs and in liquid metal ion sources

Fundamental Physics space missions set rigid thrust noise limits for liquid metal ion thrusters used as actuators on drag-free platforms aboard the spacecraft. We have measured current-, voltage- and thrust noise of Cs and In LMIS, foreseen as prime candidates in these missions. In the high-frequency range, quasiperiodic oscillations around ∼10⁵ Hz can be observed for both types of emitters with frequency depending on emission current. In the low-frequency range (1–10⁻³ Hz), which is particularly important for drag-free control, different types of noise events are observed, which in some instances show definite signs of deterministic chaos (period doubling, self-similarity). High-frequency current oscillations are generally ascribed to electro-hydrodynamic oscillations of the TAYLOR cone and the jet at its apex, with concomitant emission of charged nanodroplets. Comparison of theory and experiment shows unsatisfactory agreement in predicted vs. measured current oscillation frequencies and large disagreement in droplet emission frequencies. No theory is presently available for describing low-frequency noise events. In terms of a linearized Mair theory it is, however, shown that these noise events can be efficiently described by spontaneous variations in electrical emitter impedance. In spite of this impedance noise, the mission requirements for thrust noise (<0.1 μN/Hz^1/2) can be met by a thrust-stabilized In emitter.     

组合式圆锥面自定心装配心轴

在装配或装配焊接领域,对组合式圆柱面装配心轴的应用局限性进行了研究,设计出了组合式圆锥面自定心装配心轴。利用该装配心轴圆台的圆形横截面与各圆形横截面的圆心同轴的原理,解决了现有组合式圆柱面装配心轴无自定心功能,且专用性很强和通用性很差的问题,从而取代了现有的组合式圆柱面装配心轴。数控机床镗孔时,该装配心轴能快速确定孔的中心,从而取代了百分表。该装配心轴不仅节省库存空间,而且1根组合式圆锥面自定心装配心轴可代替若干根组合式圆柱面装配心轴,有利于降低装配心轴的制造成本,减少装配心轴的数量,也有利于标准化管理和库房管理。