Study on plastic deformation in cone-type rotary piercing process using model piercing mill for modeling clay

Pierce rolling is the rolling performed first in the production of seamless pipes. In both barrel-type rotary piercing and cone-type rotary piercing, the material is subjected to shearing deformation due to rotary forging. Only a few experimental studies on cone-type rotary piercing have been conducted to obtain the strain components. This paper describes the plastic deformation in the cone-type rotary piercing process using a model piercing mill with modeling clay. First, the model piercing mill is designed and fabricated, and then the effects of the cross-angle and feed angle on the strain components are clarified. It was found that, when the cross-angle is approximately 20°, the longitudinal section of the specimen before rolling becomes the longitudinal section of the specimen after rolling, irrelevant of the feed angle.     

A Monitoring and Diagnostic Approach for Stochastic Textured Surfaces

We develop a supervised-learning-based approach for monitoring and diagnosing texture-related defects in manufactured products characterized by stochastic textured surfaces that satisfy the locality and stationarity properties of Markov random fields. Examples of stochastic textured surface data include images of woven textiles; image or surface metrology data for machined, cast, or formed metal parts; microscopy images of material microstructure samples; etc. To characterize the complex spatial statistical dependencies of in-control samples of the stochastic textured surface, we use rather generic supervised learning methods, which provide an implicit characterization of the joint distribution of the surface texture. We propose two spatial moving statistics, which are computed from residual errors of the fitted supervised learning model, for monitoring and diagnosing local aberrations in the general spatial statistical behavior of newly manufactured stochastic textured surface samples in a statistical process control context. We illustrate the approach using images of textile fabric samples and simulated two-dimensional stochastic processes, for which the algorithm successfully detects local defects of various natures. Supplemental discussions, results, data and computer codes are available online.     

人工神经网络在皮尔斯电子枪设计中的应用

基于人工神经网络（ANN）的皮尔斯电子枪初值设计方法,不但能有机地结合迭代综合法与非迭代综合法的优点,还能把前人体现在实验数据中的设计经验通过训练样本融入到其中,从而设计出很接近实验值的新电子枪。在有较多电子枪实验数据的情况下,ANN法的优点尤为显著,经20多支电子枪的检测结果表明：ANN法的设计值比综合法的计算值更接近实验结果。     

A Note on Diagnosing Multivariate Conditional Heteroscedasticity Models

In this paper we consider several tests for model misspecification after a multivariate conditional heteroscedasticity model has been fitted. We examine the performance of the recent test due to Ling and Li ( J. Time Ser. Anal. 18 (1997), 447–64), the Box–Pierce test and the residual-based F test using Monte Carlo methods. We find that there are situations in which the Ling–Li test has very weak power. The residual-based diagnostics demonstrate significant under-rejection under the null. In contrast, the Box–Pierce test based on the cross-products of the standardized residuals often provides a useful diagnostic that has reliable empirical size as well as good power against the alternatives considered.     

用于时钟芯片的Pierce晶体振荡器设计

分析了Pierce晶体振荡器的起振条件以及传统结构的局限性.基于CSMC 0.5 μmCMOS工艺设计实现了一种应用于时钟芯片的32.768 kHz的Pierce晶体振荡器电路.采用自动增益控制(AGC)结构,提高了频率稳定性,降低了功耗;使用单位增益放大器稳定静态工作点,有效地减小了版图的面积.通过Spectre对电路进行仿真,结果显示,电源电压在1.5～5.5 V电路输出频率都有较好的精度,最大的频率误差为0.085%,阿伦方差为2×10-8/s,在3 V电源电压下,静态平均电流仅300 nA,版图面积为300 μm×150 μm,满足时钟芯片低功耗、高稳定性、较宽的电源适用范围和节约版图面积的要求.     

符号诠释项下产品仿生形态设计方法

目的 探索以诠释项为理论基础的产品仿生设计思路,并将其转化为产品造型仿生设计方法。方法 以仿生设计层次为基础,以皮尔斯符号三性论为切入点,阐述生物、产品在形态符号解释和功能符号解释方面的内容。建立生物对象符号解释和产品对象符号解释间的联系,并以此映射关系为基础,提出产品形态仿生设计的方法。结果 通过符号解释之间的联系,以实践的方式建立鲸鱼与2种不同产品间的联系,分别推导出2款具备典型生物特征且产品类别指示明显的设计方案。结论 仿生产品设计结果作为符号,被指向其生物对象和产品对象,以诠释项为基础建立的产品仿生设计层次关系,将提高生物特征和产品特征融入设计结果中的效率,同时也可以使用户以更准确的方式接收并理解产品所表现出的设计意义。