CATC — A Computer Aided Tolerance Control system

Computer utilization in manufacturing systems is increasing at a rapid rate. Developments thus far have been disjointed. Much work needs to be done in the area of integrating computer aided design and computer aided manufacturing (CAD/CAM). Tolerance control is an important component in the integration of CAD and CAM. Selection of design tolerances affects the build-ability of a product. The selection of manufacturing processes and sequence of processes affects process tolerance stacking. Unexamined process tolerance stacking leads to scrap and rework. A computer aided tolerance control (CATC) system is presented in this paper. This system is based on the tolerance chart technique. The CATC system is interactive and uses computer graphics for information display. The system can be used for computer aided process planning (CAPP) and for CAD/CAM integration.     

THE LIMITATION OF MUTUAL IMPEDANCE PRECISION TO THE SIDELOBE LEVEL OF ARRAY ANTENNA

Accurate mutual coupling correction is necessary for an array antenna to reach ultra-low sidelobe level.If the mutual impedance or mutual coupling coefficient matrix of an array isperfectly known,theoretically,one can compensate the effects of mutual coupling completelyand realize the desired low sidelobe level.However,the mutual impedance matrix obtainedwhether by calculation or by measurement has limited precision,which limits the effectiveness ofcompensation.This paper deals with the requirements on the precision of mutual impedance forcompensation in ultra-low sidelobe array antennas.The relationship between mutual impedanceerrors and the amplitude and phase errors of an array is derived,by which the relationship betweenthe mutual impedance errors and the sidelobe level is obtained.     

不同叶龄鸭跖草对咪唑乙烟酸的耐药性差异及生理基础研究

应用盆栽的方法,比较了不同叶龄鸭跖草对咪唑乙烟酸的耐药性。结果表明,随着叶龄的增大,施药后鸭跖草叶中丙二醛（MDA）含量变化量下降,而叶绿素含量、光合速率及气孔导度恢复越快。由于3叶期开始鸭跖草耐药性迅速增强,因此,3叶以前是鸭跖草施药的最佳时期。     

计算机辅助公差设计(CATD)中粗糙集理论及应用

对粗糙集理论和计算机辅助公差设计的一般流程进行了简单描述,粗糙集理论在基于制造成本的计算机辅助公差设计中的应用。利用粗糙集理论在同时满足支持度和可信度的基础上对规则进行筛选约简,从而提高了计算机辅助公差设计决策的准确性和合理性。     

Effect of Ni<Superscript>2+</Superscript>, V<Superscript>4+</Superscript> and Mo<Superscript>6+</Superscript> concentration on iron oxidation by <Emphasis Type="Italic">Acidithiobacillus ferrooxidans</Emphasis>

The ferrous oxidation ability of Acidithiobacillus ferrooxidans was studied in the presence of Ni²⁺, V⁴⁺ and Mo⁶⁺ in 9 K media in order to implement the culture in the bioleaching of spent catalyst. The rate of iron oxidation decreased with increasing concentration of metal ions, but the rate of inhibition was metal-ion dependent. The tolerance limit was critical at a concentration of 25 g/L Ni²⁺, 5 g/L V⁴⁺ and 0.03 g/L Mo⁶⁺. The growth rate of microorganisms was negligible at concentrations of 6 g/L V⁴⁺ and 0.04 g/L Mo⁶⁺. Levels and degree of toxicity of these ions have been quantified in terms of a toxicity index (TI). The toxicity order of metal ions was found to be Mo⁶⁺>V⁴⁺>Ni²⁺. The significance and relevance of multi-metal ion tolerance in Acidithiobacillus ferrooxidans has been highlighted with respect to bioleaching of spent refinery catalyst.     

连杆小头侧面定位基准加工的定位问题

详细地分析了D114柴油机连杆小头侧面两定位基准加工的定位问题,并针对现有的问题提出了新的解决方法:设计了一套夹具。此夹具经工艺试验,完全可以解决连杆定位基准加工的精度问题。     

伪准确计算的高故障容忍度冗余电路实现

本文提出了伪准确计算的概念。集成电路规模的扩大和制造工艺中不断增加的缺陷给大规模集成电路的测试和验证带来巨大的压力。针对故障容忍度（Fault Tolerance,FT）的研究是缓解测试和验证压力的有效方向。传统的错误容忍度的研究和相关的电路设计主要通过冗余的可替换电路实现无错误电路（有时只针对特定目标程序）。本文通过重新定义“准确”,提出了伪准确定义的概念,并通过创新的冗余电路结构实现。示例电路为冗余伪准确反相器。本文通过伪准确反相器与三模冗余（triple-modular redundancy TMR）和双备用（two spares）等FT技术的比较,给出伪准确计算的实现原理、误差积累分析。示例电路的仿真和分析表明伪准确计算在缩减测试成本和提高系统可靠性方面有潜在的价值。     

A model-based approach to form tolerance evaluation using non-uniform rational B-splines

Tolerance evaluation is critical to quality assurance in modern manufacturing. In contrast to traditional measurement which relies on specific hard gauges, coordinate measuring machines provide more flexibility for dimensional measurement and tolerance evaluations. To fully automate CMM inspection and tolerance evaluation, CAD/CMM integration is an important key. Although the subject of CAD-directed inspection has been widely researched, CAD model-based tolerance evaluation has received less attention. This paper presents a CAD model-based approach for evaluating general form tolerances using non-uniform rational B-splines. Unlike classical methods which construct substitute geometric features from the measurement data, this method evaluates form tolerances by comparing the measurement data with a nominal CAD model. Non-uniform rational B-spline (NURBS) is used to represent general form features since NURBS offers a common format for modeling different form features. With this unified database, a general best-fit algorithm is developed that can be applied to the evaluation of various form tolerances. Computer simulations have been performed on different form features to study the robustness and efficiency of the algorithm. Application to the profile analysis of turbo charger housing and turbine blade die segments are also presented.