Geometric Hermite interpolation for space curves

This paper considers the geometric Hermite interpolation for spacial curves by parametric quartic Bézier curve. In additon to position and tangent direction, the curvature vector is prescribed at each knot. We prove that under appropriate assumptions the interpolant exists locally with one degree of freedom. Moreover, we prove the interpolant is 6th order accurate.     

Uncertainty measures for rough formulae in rough logic: An axiomatic approach

Rough set theory, initiated by Pawlak, is a mathematical tool in dealing with inexact and incomplete information. Various types of uncertainty measure such as accuracy measure, roughness measure, etc, which aim to quantify the imprecision of a rough set caused by its boundary region, have been extensively studied in the existing literatures. However, a few of these uncertainty measures are explored from the viewpoint of formal rough set theory, which, however, help to develop a kind of graded reasoning model in the framework of rough logic. To solve such a problem, a framework of uncertainty measure for formulae in rough logic is presented in this paper. Unlike the existing literatures, we adopt an axiomatic approach to study the uncertainty measure in rough logic, concretely, we define the notion of rough truth degree by some axioms, such a notion is demonstrated to be adequate for measuring the extent to which any formula is roughly true. Then based on this fundamental notion, the notions of rough accuracy degree, roughness degree for any formula, and rough inclusion degree, rough similarity degree between any two formulae are also proposed. In addition, their properties are investigated in detail. These obtained results will be used to develop an approximate reasoning model in the framework of rough logic from the axiomatic viewpoint.     

Evaluation of acoustic beacon characteristics for navigation tasks

The goal of the present study was to investigate the human factors issues related to acoustic beacons used for auditory navigation. Specific issues addressed were: (1) the effect of various beacon characteristics on human accuracy in turning toward the direction of the acoustic beacon; (2) the difference between real and virtual environments on human accuracy in turning toward the acoustic beacon; and (3) the perceived sound quality of various acoustic beacons. Three experiments were conducted in which acoustic beacons were presented in a background of 80 dBA pink noise. Results of the localization tasks revealed that (a) presentation mode (continuous versus pulsed beacon sound) did not affect the overall localization accuracy or number of front-back confusion errors; and (b) the type of acoustic beacon affected the size of localization error. Results of the sound quality assessment indicated that listeners had definite preferences regarding the type of sound being used as a beacon, with (a) non-speech beacons preferred over speech beacons, (b) a beacon repetition rate of 1.1 rps preferred over either the 0.7 or 2.5 rps rates, and (c) a continuous operation of a beacon preferred over a pulsed operation. Finally, sound quality ratings and localization errors were highly negatively correlated. This finding demonstrates the usefulness and practical values of sound quality judgements for audio display design and evaluation.     

ERPN32-200离心泵机械密封失效原因分析

通过对ERPN32-200离心泵机械密封失效原因的分析,发现机械密封的实际密封效果不仅与机械密封自身的性能有关,而且与相关零部件的加工尺寸的精度等级以及维修时的装配质量有着重要的关系,同时针对不同的问题提出了相应的措施,延长了机械密封的使用寿命。     

基于星体标定的光电跟踪系统测角精度评定

测角精度是光电跟踪系统中一项最重要的技术指标，通常是以校准塔和方位标为基准进行单项误差标定再综合，其过程繁锁、周期长。介绍一种基于星体标定的精度评价方法，建立了系统误差模型，分析了该方法的标定精度。以光电经纬仪为评价目标，研究了精度评定系统组成结构、试验条件、试验和数据处理方法。试验结果表明该方法具有标定过程简单、快速，标定精度高等优点，其标定误差小于3”。     

A multi-dimensional solver for the steady Euler equations

In this paper a numerical algorithm for the solution of the multi-dimensional steady Euler equations in conservative and non-conservative form is presented. Most existing standard and multi-dimensional schemes use flux balances with assumed constant distribution of variables along each cell edge, which interfaces two grid cells. This assumption is believed to be one of the main reasons for the limited advantage gained from multi-dimensional high order discretisations compared to standard one-dimensional ones. The present algorithm is based on the optimisation of polynomials describing the distribution of flow variables in grid cells, where only polynomials that satisfy the Euler equations in the entire grid cell can be selected. The global solution is achieved if all polynomials and by that the flow variables are continuous along edges interfacing neighbouring grid cells. A discrete approximation of a given spatial order is converged if the deviation between polynomial distributions of adjacent grid cells along the interfacing edge of the cells is minimal. Results from the present scheme between first and fifth order spatial accuracy are compared to standard first and second order Roe computations for simple test cases demonstrating the gain in accuracy for a number of sub- and supersonic flow problems.     

0.1级高精度电容式电压互感器的开发

电力系统中新技术的应用促进了CVT向0.1级高精度方向的发展.如何保证准确级的准确性和稳定性是0.1级CVT设计中关键的问题.本文分析了附加误差对总误差的影响程度,并讨论了中间电压对输出容量及其他性能的影响关系,提出了关键问题的解决措施.     

温度变化对CVT准确度的影响

温度对CVT准确度的影响,以往基本是通过理论计算。本文通过试验,发现理论计算值与试验值的差别。初步试验表明,温度对CVT误差的影响较小。     

Index for quality control in anthropometric surveys

In an anthropometric measurement process, there are many factors which are error sources even if the observers are highly trained. Systematic or bias errors are possible and they are not clearly noticeable. In this work we propose two simple and adimensional indices to use in the quality control of anthropometric surveys.

Such indices are applicable only to a few anthropometric variables but the results found by this control can be an indication of the quality of the complete measurement process. The indices are defined as

and ses index is the same when the measures are obtained in sitting position. The observer must take those measurements again when the index values are higher than a selected threshold value before approving or rejecting the measure.

Relevance to industry

Anthropometric data are used in a wide variety of consumer products and in processes of industrial design. Wrong precision of data could cause problems in the industrial products. Those indices are useful to improve the accuracy and quality control of data.     

应用GPS授时时角拍星法标校测角精度

在用拍星法标校高精度测角设备过程中,针对通常采用天文授时存在的授时难、理论值误差大等问题,提出了应用 GPS 授时时角拍星法进行拍星标校。授时精度的提高和新时角算法的运用,大大提高了拍星标校的理论值精度,标校精度可达 5″以内,并在高精度测角设备上得以应用。