纤维对薄层砂浆早期塑性收缩的影响

提出了一种利用视频显微镜技术来测量薄层砂浆早期塑性收缩的新方法,研究了纤维种类、聚丙烯纤维掺量及长度、纤维几何形态对薄层砂浆早期塑性收缩的影响。结果表明随着聚丙烯纤维掺量的增加,砂浆的塑性收缩值有所减小,说明聚丙烯纤维的掺入可以有效地抑制砂浆的塑性收缩;3mm、12mm长的聚丙烯纤维较6mm、9mm长的聚丙烯纤维对砂浆塑性收缩的抑制作用大;在抑制砂浆收缩性能上圆形截面纤维优于Y形截面纤维;掺聚丙烯纤维试样的塑性收缩较掺玄武岩纤维试样小,但两者的差距不大。     

A Torso-Imaging System to Quantify the Deformity Associated With Scoliosis

This paper describes a low-cost imaging system that is used to quantify the torso deformity that is associated with scoliosis. The system consists of image-capture and image-analysis components. The image-capture component obtains full-torso scans using a rotating positioning platform and one or two surface digitizers. The image-analysis component assesses torso shape. Results of system calibration and error analysis (accuracy of reproduction based on tests on a calibration box, a plaster cast, and a human subject) show that the system can be used to quantify the deformity associated with scoliosis.     

基于支持向量机的小样本响应曲面法研究

当影响因素和响应输出的关系较为复杂时,应用传统响应曲面法(RSM)、非参数响应曲面法(NPRSM)和人工神经网络(ANN)难以拟合真实的响应曲面,不仅需要大的样本量,而且泛化风险大,不易达到全局最优.将RSM归结为可有限制地主动获取样本的小样本机器学习问题,提出了一种基于支持向量机(SVM)的RSM.以大间隔网格取样,利用SVM拟合过程,对拟合方程寻优确定极值大致区域,再逐步缩小间隔求精.算例研究表明,该方法的拟合与泛化性能优于NPRSM和基于ANN的RSM,能在小样本条件下建立全局性数值模型,寻优可以得到多个极值.     

关于设计程序的一种策略

从产品是功能的载体角度来讨论产品设计的一种新的核心策略,以期对设计程序的改革有所启发和引导。     

Thermal-Diffusivity Measurements of Mexican Citrus Essential Oils Using Photoacoustic Methodology in the Transmission Configuration

Photoacoustic methodology in the transmission configuration (PMTC) was used to study the thermophysical properties and their relation with the composition in Mexican citrus essential oils providing the viability of using photothermal techniques for quality control and for authentication of oils and their adulteration. Linear relations for the amplitude (on a semi-log scale) and phase, as functions of the sample’s thickness, for the PMTC was obtained through a theoretical model fit to the experimental data for thermal-diffusivity measurements in Mexican orange, pink grapefruit, mandarin, lime type A, centrifuged essential oils, and Mexican distilled lime essential oil. Gas chromatography for distilled lime essential oil and centrifuged lime essential oil type A is reported to complement the study. Experimental results showed close thermal-diffusivity values between Mexican citrus essential oils obtained by centrifugation, but a significant difference of this physical property for distilled lime oil and the corresponding value obtained by centrifugation, which is due to their different chemical compositions involved with the extraction processes.     

A Simple Aqueous Solution Based Chemical Methodology for Preparation of Mesoporous Alumina: Efficient Adsorbent for Defluoridation of Water

In this paper, we report a simple aqueous solution based chemical method for preparation of mesoporous γ-Al₂O₃ which can be used for removal of fluoride ions from water. The synthesized Al₂O₃ and commercial Al₂O₃(Grade AD101-F, ACE Manufacturing and Marketing, Baroda, India) were characterized by using powder x-ray diffractometer, N₂ adsorption–desorption surface area and pore size analyzer, and high resolution transmission electron microscope. Synthesized Al₂O₃ contains a wormhole-like mesoporous structure with 358.7 m² g^?1 Brunauer–Emmett–Teller (BET) surface area and 0.8 cm³ g^?1 pore volume. Batch adsorption studies were performed to determine the fluoride adsorption capacity of Al₂O₃. The effect of different parameters such as contact time, initial fluoride concentration, pH, and adsorbent dose was studied to understand the fluoride adsorption behavior of the synthesized Al₂O₃ under various conditions. The kinetics results showed that the fluoride adsorption on synthesized Al₂O₃ followed pseudo-second-order kinetics. Adsorption equilibrium data fitted well to the Freundlich equation and indicated multilayer adsorption of fluoride on the surface of Al₂O₃. Synthesized Al₂O₃ demonstrated significantly improved fluoride adsorption capacity and faster kinetics than commercial Al₂O_3.     

非晶TiO2-Cr薄膜对罗丹明B的光催化降解研究

采用磁控溅射法,在室温下制备了Cr掺杂非晶TiO2光催化薄膜.以降解罗丹明B为实例,探讨了pH值、外加氧化剂、反复使用次数对光催化降解率的影响.研究表明,非晶TiO2-Cr薄膜具有良好的光催化活性,pH值和外加氧化剂对光催化降解率影响很大,在研究范围内,pH值为4.0,H2O2浓度为3.0 ml/L使罗丹明B的光催化降解率最大.随着反复使用次数的增加,活性逐渐降低.这是由于光催化剂的基本能带结构的改变和对副反应产物的吸附引起的.     

基于热成像的薄片材料热扩散率快速无损检测

针对传统热扩散率测量方法对热激励、边界和试样尺寸有严格要求等苛刻条件,提出一种适用于薄片材料的热扩散率测量新方法。该方法采用热成像技术采集受激光激励引起的材料表面温度场变化数据,将其通过曲线拟合对导热微分方程中的微分项进行估测,求取微分方程解析解转化为对代数方程求解以确定热扩散率值,因而无需严格控制边界条件、初始条件和热激励。通过仿真分析验证了理论模型的合理性,并对H62黄铜和304不锈钢材料进行了实测,对比文献参考值表明测量偏差均在6.0%以内,测量重复性为4.3%,可满足快速无损的测量要求。     

A Tolerance Design Method for Electronic Circuits Based on Performance Degradation

Due to the effects of manufacturing tolerances and environmental conditions, component parameters vary and degrade with time. This may cause performance measures of electronic circuits to deviate from design specifications. Therefore, a tolerance design method based on performance degradation is proposed for electronic circuits, so as to improve the robustness of output characteristics. First, sensitive components causing output fluctuation are determined via orthogonal experiment and PSpice simulation. Then, degradation path models are established to describe the degradation process of sensitive components. The predicted values worked out by the degradation path models are substituted into the simulation model for Monte Carlo analysis. Besides, output characteristics and performance reliability are evaluated according to Monte Carlo simulation. Finally, optimum allocation is carried out for component tolerances as per minimum life cycle cost. The proposed method is illustrated by a case study of light‐emitting diode (LED) driver. Copyright © 2013 John Wiley & Sons, Ltd.     

基于改进的判定表的故障树建模方法

针对过程控制系统故障树建模问题提出了一种以步进方式求结构函数的判定表法。采取以事件为条件桩、0和1为条件项的二态判定表的方式,列举各事件所有可能的状态组合,根据每种情况下部件的相互作用演绎输出事件,然后对具有相同输出事件的事件序列求并集以排除重复事件和不相关事件,得到约简的结构函数。通过对硝酸冷却系统建模的验证,用这种方法建树的结果与原文的结果是一致的。     

A Method for Performance Degradation Modeling Based upon the Accelerated Experiment

Performance degradation modeling plays an important role in prognostics and health management of mechanical system. Influenced by the complex structure of the hydraulic pump and the limited experiment standards, it is hard to establish an appropriate performance degradation model. To fulfill current requirements, a method for establishing the performance degradation model based on accelerated experiment is proposed. In order to describe the general trend of the degradation, the double-stress exponential model is firstly established as the theoretical degradation model. On this basement, combined with the characteristics of the experiment, the accelerating coefficient is settled; meanwhile, the procedures for assuring the model parameters are presented. Furthermore, based on the accelerated experiment of the hydraulic pump under various stresses, the performance degradation model is finally established. Result of the experimental analysis indicates that the proposed method is applicable and the presented model is effective to measure the performance degradation of pump.     

CVD金刚石薄膜的介电性能研究

对直流电弧等离子体ＣＶＤ制备的金刚石薄膜的介电性能进行了研究,结果表明,金刚石薄膜的介电性能主要取决于样品的多昌性质以及表面和晶界处的非金刚石相和杂质成分。     

A New Method to Extract Noise Parameters Based on a Frequency- and Time-Domain Analysis of Noise Power Measurements

A new on-wafer noise parameter measurement method at a 2.8-18-GHz frequency band is presented. This measurement method is based on both temporal and spectral analysis of noise power measurements. We present the method and the experimental results on an active two-port. It requires less equipment than the classic noise parameter measurement method. It gives direct results for 801 points in the 2.8-18-GHz frequency band.     

基于粗糙集理论的模糊神经网络及其在化纤生产过程中的应用

提出一种基于粗糙集理论的模糊神经网络系统,首先运用粗糙集理论来发现大量样本数据中的概略化的规则,然后根据这些规则来设计神经网络的结构模型,并利用神经网络技术对模型进行训练。化纤工业中抽丝冷却侧吹风过程的模拟仿真实验,证明了该方法的有效性和可行性。