Traveling-wave piezoelectric linear motor Part I: the stator design.

A new type of piezoelectric linear motor incorporating a traveling wave has been developed. The linear motor is comprised of a stator and a carriage. The stator design, which consists of a meander-line structure and gear teeth mounted on the meander-line structure, is the focus of this article. The meander-line structure is constructed with bimorph actuators arranged in a line. These actuators are driven by two phased sets of alternating current (ac) in order to generate a traveling wave. The traveling wave is transferred to the gear teeth, by which the carriage is driven. Modeling of the stator is derived by use of a strain energy method. The performance of various materials is evaluated by analytical and experimental methods. The analytical and the experimental results are quite approximate. Modal analysis is investigated using ANSYS. Appropriate modes associated with ultrasonic levels of resonant frequency are selected to obtain desired motion and to enhance the output performance. Surface speed for various applied input voltage are studied and indicate a nearly linear relationship. The stator in combination with the carriage makes up the linear motor.     

一种实验炼钢渣的穆斯堡尔谱研究

一种实验炼钢渣不同炉次样品的室温透射穆斯堡尔谱由两组裂距较大的四极分裂双峰和一组裂距较小的双峰组成，它们分别相应于具有不同微观环境的Ｆｅ＾２＋和Ｆｅ＾３＋。参照文献中已知ＦｅｘＯ的穆斯堡尔谱数据，可确定该渣中的主要含铁相为ＦｅｘＯ。Ｘ射线衍射相分析给出相同的结果。按亚谱的面积比计算出Ｆｅ＾２＋和Ｆｅ＾３＋的相对含量分别为８５％和１５％左右。进一步选取与样品晶体结构相联系的原子簇模型。用ＭＳ－Ｘａ方     

The As-prepared surfaces of C-axis-oriented Nd1Ba2Cu3Oy thin films characterized using scanning probe microscopes

Recently, superconducting Nd₁Ba₂Cu₃O_y (Ndl23) thin films with high superconducting transition temperature (T _c) have been successfully fabricated at our institute employing the standard laser ablation method. In this paper, we report the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) system operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode. Contour plots of the spirals show that the step heights of the spirals are not always the integer or half-integer number of thec-axis parameter of the structure. This implies that the surface natural termination layer of the films may not be unique. This result is supported byI-V STS measurements. The surface morphology of the Nd123 thin films is compared with that of thec-axis-oriented Y₁Ba₂Cu₃S_y thin films. Surface atomic images of the as-prepared Nd123 thin films are obtained employing both STM and AFM. STS measurements show that most of the surfaces are semiconductive. The results of STS measurements together with the fact that we are able to see the surface atomic images using scanning probe microscopes suggest that exposure to air does not cause serious degradation to the as-prepared surfaces of Nd123 thin films.     

Hierarchical production control for a flow shop with dynamic setup changes and random machine breakdowns

In this paper, we study a manufacturing system consisting of two machines separated by two intermediate buffers, and capable of producing two different products. Each product requires a constant processing time on each of the machines. Each machine requires a constant non-negligible setup change time from one product to the other. The demand rate for each product is considered to be piecewise constant. Each machine undergoes failure and repair. The time-to-failure and time-to-repair are exponentially distributed random variables. The setup change and processing operations are resumable. We model our system as a continuous time, continuous flow process. An optimal control problem is formulated for the system to minimize the total expected discounted cost over an infinite horizon. To determine the optimal control policy structure, a discrete version of the problem is solved numerically using a dynamic programming formulation with a piecewise linear penalty function. A real-time control algorithm is then developed with the objective of maintaining low work-in-process inventory and keeping the production close to the demand. The algorithm uses a hierarchical control structure to generate the loading times for each product on each machine in real time and to respond to random disruptions in the system. The system is simulated using this algorithm to study its performance. The performance of the algorithm is also compared to alternative policies.     

Adaptive predictive control algorithm based on Laguerre Functional Model

Laguerre Functional Model has many advantages such as good approximation capability for the variances of system time‐delay, order and other structural parameters, low computational complexity, and the facility of online parameter identification, etc., so this model is suitable for complex industrial process control. A series of successful applications have been gained in linear and non‐linear predictive control fields by the control algorithm based on Laguerre Functional Model, however, former researchers have not systemically brought forward the theoretical analyses of the stability, robustness, and steady‐state performance of this algorithm, which are the keys to guarantee the feasibility of the control algorithm fundamentally. Aimed at this problem, we introduce the principles of the Incremental Mode Linear Laguerre Predictive Control (IMLLPC) algorithm, and then systemically propose the theoretical analyses and proofs of the stability and robustness of the algorithm, in addition, we also put forward the steady‐state performance analysis. At last, the control performances of this algorithm on two different physical industrial plants are presented in detail, and a number of experimental results validate the feasibility and superiority of IMLLPC algorithm. Copyright © 2005 John Wiley & Sons, Ltd.     

High-cycle fatigue characterization of titanium 5Al-2.5Sn alloy

High-cycle fatigue behaviour of titanium 5Al-2.5Sn alloy at room temperature has been studied. S-N curve characterization is performed at different stress ratios ranging from 0 to 0.9 on a subsized fatigue specimen. Both two-stress and three-stress level tests are conducted at different stress ratios to study the cumulative fatigue damage. Life prediction techniques of linear damage rule, double linear damage rule and damage curve approaches are applied, and results are compared with the experimental data. The agreement between prediction and experiment is found to be excellent.     

红外测温技术在离心复合铸造轧辊生产上的应用

本文分析了离心复合铸造轧辊生产过程中离心机停机温度和时间对轧辊质量的影响 ,提出了用先进的红外测温技术来预报停机温度和时间 ,以实现微机监控适时停机 ,保证轧辊内外层熔合良好 ;同时指出了红外测温技术在离心复合铸造轧辊生产上的应用前景     

塑料包装应用及技术进展

塑料在包装领域有着广泛的应用，其中聚酯（PET）性能优良，应用领域不断扩大。介绍了塑料包装不断通现的新技术，以及塑料包装环保问题的几点思路。     

Synthesis,characterization, and thermal properties of phosphorus‐containing,wholly aromatic thermotropic copolyesters

A series of phosphorus‐containing, wholly aromatic thermotropic copolyesters from acetylated 2‐(6‐oxide‐6H‐dibenz〈c,e〉〈1,2〉oxa phosphorin‐6‐yl)‐1,4‐dihydroxy phenylene, p‐acetoxybenzoic acid, terephthalic acid, and isophthalic acid were prepared by melting polycondensation. The structure and basic properties of the polymers, such as the glass‐transition temperature (T_g), melting temperature (T_m), thermal stability, crystallinity, and liquid crystallinity, were investigated with Fourier transform infrared, elemental analysis, differential scanning calorimetry (DSC), thermogravimetric analysis, wide‐angle X‐ray diffraction, and hot‐stage polarizing optical microscopy. The copolyesters had relatively high T_g values ranging from 183 to 192°C. The T_m values obtained from DSC curves for samples P‐20 and P‐25 were 290 and 287°C, respectively (where the number in the sample name indicates the molar fraction of the phosphorus‐containing monomer in the reactants). The initial flow temperatures of other samples observed with hot‐stage polarizing microscopy were 271–290°C. The 5% degradation temperatures in nitrogen ranged from 431 to 462°C, and the char yields at 640°C were 41–52%. All the copolyesters, except P‐40, were thermotropic and nematic. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1278–1284, 2002