基于FPGA的伺服驱动高精度位置反馈研究

伺服驱动向CNC反馈进给轴的位置量时,转换存在量化误差,如果处理不当.持续多个周期转换就存在积累误差.文中提出一种以CNC脉冲当量之半为量尺的方法,以减法代替除法求得反馈脉冲量和误差,保证每一个周期的误差小于一个脉冲当量.同时在每一次计算电机编码器测得的位置量时加入上次误差的方向和大小,从而保证了积累误差小于一个脉冲当量,实现了伺服驱动向CNC的高精度位置反馈.     

Diode laser sensor for measurements of CO, CO(2), and CH(4) in combustion flows

A diode laser sensor has been applied to monitor CO, CO(2), and CH(4) in combustion gases with absorption spectroscopy and fast extraction-sampling techniques. Survey spectra of the CO 3nu band (R branch) and the 2nu(1) + 2nu(2)(0) + nu(3) CO(2) band (R branch) near 6350 cm(-1) and H(2)O lines from the nu(1) + 2nu(2) and 2nu(2) + nu(3) bands in the spectral region from 6345 to 6660 cm(-1) were recorded and compared with calculated spectra (from the HITRAN 96 database) to select optimum transitions for species detection. Species concentrations above a laminar, premixed, methane-air flame were determined from measured absorption in a fast-flow multipass absorption cell containing probe-sampled combustion gases; good agreement was found with calculated chemical equilibrium values.     

Pseudophase information from the complex analytic signal of speckle fields and its applications. Part II: statistical properties of the analytic signal of a white-light speckle pattern applied to the microdisplacement measurement

To provide a theoretical background for the superiority of the signal-domain phase-only correlation (SDPOC) technique proposed here for microdisplacement measurement, we study the first- and the second-order statistical properties of the complex amplitude of an analytic signal of a white-light speckle pattern, under the assumption of a Gaussian random process, and give a formula for the autocorrelation function of the pseudophase associated with the complex analytic signal. Based on these results, we show mathematically that SDPOC has a performance advantage over conventional intensity-based correlation techniques.     

纳米铜胶体的合成及表征

以NaBH4为还原剂,表面活性剂CTAB为稳定分散剂,通过化学反应从硫酸铜溶液制备了纳米铜胶体,并研究了稳定分散剂浓度对纳米铜胶体颗粒的氧化、大小及团聚状态的影响.结果表明:当稳定分散剂浓度足够高时,所得纳米铜胶体颗粒大小均匀、分散性好,且能有效地防止颗粒的氧化及团聚.     

Changes in neuropsychological functioning over 10 years following adolescent substance abuse treatment.

Previously, Anderson, Ramo, Cummins, and Brown (2010) described six distinct patterns of alcohol and other drug (AOD) use during the decade following adolescents' treatment for alcohol and other substance use disorders (A/SUD). This time period represents a phase of significant neurodevelopment, and the influence of substance use on the brain is a concern. In the present study, we examined patterns of neuropsychological function over these 10 years in relation to the AOD trajectories identified for youth as they transition into their twenties. Participants were part of a longitudinal research project following adolescents with and without A/SUD who received neuropsychological examinations at baseline and up to 7 times thereafter spanning 10 years (N = 213; 46% female at baseline). Neuropsychological trajectories were significantly related to substance involvement patterns over time on measures of verbal learning and memory (ps = .011 to p = .0002), and verbal attention/working memory (p = .020), with heavier use patterns generally followed by poorer cognition. Heavy use of alcohol alone was independently associated with poorer verbal memory over time. Furthermore, substance withdrawal symptoms during each follow-up time point were related to poorer verbal learning and memory scores (ps     

实验室排风柜面风速测试方法的对比研究及实验验证

面风速是排风柜性能的重要指标,本文对各国排风柜面风速测试标准进行总结和分析,比较了在测试条件、测试仪器、测试方法、结果的分析等方面的差异.通过构建的实验台对排风柜进行面风速的实测,根据多台不同厂家不同型号的排风柜面风速的实测结果,研究分析面风速分布特点,指出了实际测试中操作面上需重点关注的区域.     

高性能覆铜板用交联性聚苯醚树脂

简要介绍了高性能覆铜板对基材的性能要求及聚苯醚树脂作为覆铜板基材的优缺点,详细地阐述了各种交联性聚苯醚树脂的基本特性和制备方法。在保持聚苯醚树脂原有优良电气性能的基础上,通过引入各种可交联性基团,很好地解决了在覆铜板应用中聚苯醚树脂耐溶剂性和耐热性差的问题。     

马尾藻岩藻黄素的提取条件优化及抗氧化、抗炎作用

以马尾藻为原料,探讨岩藻黄素的提取工艺,并对纯化后的岩藻黄素进行体外抗氧化和抗炎作用研究。结果表明,马尾藻岩藻黄素提取液在4 ℃避光保存25 d 很稳定;通过单因素试验和正交试验确定最佳提取条件：以新鲜冷冻马尾藻为原料,提取溶剂为90%乙醇∶丙酮=3∶1（体积比）,料液比为1∶15（g/mL）,提取温度为50 ℃、100 r/min振荡提取6 h 后再超声辅助提取15 min,在此条件下岩藻黄素提取率为0.816 mg/g 海藻湿重。抗氧化试验结果显示,马尾藻岩藻黄素的氧化自由基吸收能力（oxygen radical absorbance capacity,ORAC）值为1 761 μmol TE/g,对DPPH 自由基和羟自由基的清除率IC50 分别为0.102 mg/mL 和0.146 mg/mL。细胞实验结果表明,100 μg/mL 以下的马尾藻岩藻黄素对小鼠小胶质瘤细胞（BV-2）无明显毒性;与脂多糖（lipopolysaccharide,LPS）诱导的模型组相比,60 μg/mL 的马尾藻岩藻黄素显著降低细胞上清中一氧化氮（nitric oxide,NO）和白细胞介素-6（interleukin-6,IL-6）含量。综上所述,马尾藻中岩藻黄素的提取率与很多因素密切相关,并具有显著的抗氧化和抗炎作用。     

基于GL Studio的雷达显示器仿真

探讨应用GL Studio辅助开发仿真雷达显示器.首先直接时所要显示的图形符号及数字静态建模,然后对其中需要动态变化的部分调用API函数进行实时驱动,最终实现常规、偏心雷达平面位置显示器(PPI)的仿真.该雷达显示器仿真明显减少了直接从底层开发所需的工作量,仿真界面清晰,目标运动实时性好.