Comments on the shortcomings of predicting the precision of Cavalieri volume estimates based upon assumed measurement functions

It is well known that the estimation of an object's volume by means of serial cross-sections, the so-called Cavalieri method, yields an unbiased estimate. But by itself it provides no means by which to estimate how precise this estimate is unless the shape of the volume is fully known beforehand. This knowledge can only be partially determined from the serial section information that is collected. Methods have been developed that claim to surmount this difficulty by using the serial section data to create a mathematical model of the volume's shape properties. The model then is used to estimate (predict) the precision of the volume estimate (its CE) from the single set of data available. Unfortunately, the theory underlying the model is flawed and so the model itself amounts to no more than an unsubstantiated guess about the shape of the volume. Therefore, the precision of the volume estimates that one obtains from the method is only as good as the model and this cannot be ascertained from the single set of acquired data. In this letter I explain the inadequacies of the modelling method. I suggest that it be used only with caution, if at all. Instead I suggest two alternative ways to predict the CE, one that is based upon a rule-of-thumb approach to the object's shape, and another that is based upon spectral analysis of the measurement function and that is easy to implement with available computer software.     

梯形断面水力计算的一种新方法

本文从梯形水力最优断面的基本思路出发，通过理论分析找到了梯形断面水力计算的一种新方法——即通过特征参数进行梯形断面的水力计算。     

压裂泵往复密封性能及机理研究

根据流体动压润滑理论，对压裂泵柱塞密封摩擦副的润滑机理进行了理论分析。在排出和吸入行程，柱塞密封摩擦副均能满足流体动压润滑的条件，即在柱塞与密封界面上能形成并保持一定厚度的油膜润滑密封，从而达到减小摩擦提高寿命的目的；建立了摩擦界面油膜厚度和泄漏量的计算公式。利用有限元法理论，对密封圈的压力沿轴向的分布规律、泄漏量与压力变化关系进行了模拟计算。对往复密封圈沿轴向压力分布、泄漏量随压力变化进行了测试；试验结果表明，建立的计算模型具有较高的计算精度，揭示了压裂泵的密封机理。     

浅析作业成本法在企业中的有效实施

本文通过对作业成本法及其应用情况的总结和归纳,就企业如何有效实施作业成本法进行了粗浅的探讨。     

浅谈水泥基渗透结晶型防水材料标准及性能指标

针对GB18445-2001《水泥基渗透结晶型防水材料》标准在使用过程中发现的一些问题，对标准中的部分性能指标的确定及试验方法提出修改意见。     

In the theory of blast waves

The behavior of the blast wave from an exploding spherical volume is investigated mathematically over the entire range of blast-wave propagation. The computational method uses analytical results for a similar problem for a point explosion with counter pressure and the theory of an asymptotically equivalent point explosion. The asymptotic solution of the gas-dynamic equations away from the explosion site is matched to the initial conditions of blast-wave formation due to the disintegration of the detonation shock upon its arrival at the boundary of the exploding volume. The spatial distribution of the blast-front pressure is found for combustible gaseous systems and solid explosives. The theoretical results obtained agree quantitatively with available experimental measurements. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 93–99, July–August, 2006.     

ZnO压敏陶瓷最佳掺杂含量的理论计算

从对电子薄膜材料研究中得到的最佳掺杂含量定量理论推广到ZnO陶瓷材料。该理论建立了电子薄膜材料的某一物理性能与晶体结构、制备方法和掺杂剂含量之间的联系，给出了一个能够拟合实验曲线的具有确定物理意义的抛物线方程。该方程的极值点确定了最佳掺杂含量与晶体结构和制备方法之间的定量关系，进而得到了一个掺杂最佳含量的表达式。系统地分析了ZnO压敏陶瓷的掺杂改性的实验结果，应用此表达式定量计算了ZnO压敏陶瓷的最佳掺杂含量，定量计算的结果与实验数据相符合。该理论也适用于其他薄膜材料最佳掺杂含量的理论计算。     

Material state remapping in computational solid mechanics

A computational procedure for remapping material state information from one finite element mesh to another is described. The procedure is useful in connection with evolving meshes for inelastic problems, as for example occur in the context of fracture simulation and adaptive mesh refinement. The proposed method is based on weak enforcement of equality between corresponding fields on the two meshes, where piecewise‐constant fields on both meshes are generalized from the quadrature‐point values. The essential algorithmic problem is that of calculating the volume partition of an arbitrary convex region with respect to a covering set of disjoint convex regions. Instead of geometrically resolving the associated intersections, the problem is herein approximated by a constrained optimization problem, which may be readily and efficiently solved computationally. This formulation is a main contribution of the paper. Computational examples are given that illustrate the effectiveness of the proposed procedure. Copyright © 2002 John Wiley & Sons, Ltd.     

玻璃两面重叠手印拍摄机理

根据斯涅尔定律和菲涅尔公式阐述清水衬底法消除玻璃下界面手印或玻纹的影像，以及用偏振光，紫外线拍摄玻面痕迹的方法和机理。     

弹药包装冲击强度试验方法的改进研究

介绍一种新的弹药包装冲击强度试验方法，应用该试验方法可以防止冲击强度试验时出现与期望值相反的现象。