Automatic Headspace Sampling for Determination of Ethylene Dibromide Residues in Cereals

Abstract

The possibility was investigated to apply a commercially available automatic head-space sampler in trace analysis of ethylene dibromide (EDB, 1,2-dibromoethane), in cereals.

Samples of rice and wheat flour were thermostatted in closed vials at 70[ddot]C for 30min. The top gas was then automatically introduced into a gas chromatograph equipped with an electron capture detector. Quantitation was performed using external standards (untreated samples spiked with solutions of EDB in N,N′-dimethylacetamide).

The relative standard deviation of the method was 3.4% for rice and 4.5% for wheat flour, at a residue level of 0.008 mg/kg. The detection limit was 0.001 mg/kg (the official EC residue tolerance is 0.01 mg/kg).

Preliminary experiments with other fumigants were carried out as well.

The headspace technique in question has the following advantages over other methods for determining EDB residues in cereals: 1. No sample pre-treatment like extraction, steam distillation, purge and trap etc.; 2. Automated sample handling; 3. “Clean” chromatograms.     

A 10-MHz SOI-Based Face Shear Square Micromechanical Resonator

A 10-MHz face shear (FS) square micromechanical resonator based on silicon-on-insulator (SOI) technology is presented in this paper. In order to examine the improvement of quality factor as well as motional resistance Rx in this structure, the center-stem anchor is employed in this study. The benefit of anchoring the square in the center, which is the nodal point, is that the energy losses through the anchor can be minimized. Hence, a quality factor value of 2.0 million and the motional resistance of 8.2 kΩ can be obtained with an FS mode resonator via finite element (FE) simulation. The results show the significance of the FS mode in this design, not only in its structure but also in its square-extensional mode and Lame-mode. Additionally, an SOI-based fabrication process is proposed to support the design.     

基于JC-5600ATE的单/双电源运算放大器测试方法

集成运算放大器具有成本低、功能多等优点,可广泛用于自动控制系统、测量仪表等其他电子设备中。近年来集成运放的指标在不断提高,性能也在不断提升,伴随着运算放大器的发展,对用来考核运算放大器指标的测试技术也提出了相应的要求,对测试系统(Automatic Testing Equipment,以下简称ATE)的性能要求也相应变高。阐述了单、双电源集成运算放大器在JC-5600ATE上的测试方法,并分析了两者的测试差异。     

基于信捷PLC对细石混凝土泵电气系统的设计

为了推进细石混凝土泵的国产化,在保证产品性能的前提下,降低其电气系统的生产成本,采用以国产信捷PLC(Programmable Logic Controller)为主的控制元件对细石混凝土泵电气系统进行了设计。在保证细石混凝土泵使用稳定性的同时,降低了其电气系统的制造成本,提高了适用性。所设计电气系统经菏泽永安机械制造有限公司检验使用,实际应用情况良好。     

基于集成运放的太阳能控制器

现有光伏系统的控制器普遍选用微控制器为核心,为使之与电子技术课程教学案例开发相结合,提出采用集成运放替代微控制器的智能太阳能控制器方案,并以直流12V/10A小功率应用为研究实例。实验结果表明该控制器方案可行,且电路简单、成本低廉,适用于实验教学与课程设计。     

考虑运动受限的履带式移动机器人轨迹跟踪控制

针对履带式移动机器人的轨迹跟踪控制问题进行研究,首先,建立了履带式移动机器人的运动学模型和跟踪误差模型；其次,设计了转速有限时间控制和线速度滑模控制的轨迹跟踪控制律,并给出了考虑运动受限作用下的控制律修正表达式；最后,基于MATLAB对所提控制律进行仿真,对比分析了不考虑运动受限情况下跟踪控制效果;结果表明,设计的跟踪控制律能够实现履带式移动机器人对圆轨迹的有效跟踪,且考虑运动受限作用的控制律更加符合实际;文章研究分析了运动受限作用对于移动机器人轨迹跟踪控制的影响,分析结果对其他移动机器人的运动控制研究具有参考价值。     

地方视频会议会商系统的建设与应用

建设多媒体业务的视频会议系统,综合语音、图像、数据等信息,通过网络介质进行远距离高速传输,可增强在不同区域交流的亲切感和临场感,提供一种简便而有效的工作手段,充分发挥视频会议实时高效的特点,将显著提高决策和工作效率,尤其能为政府在防灾减灾的指挥决策方面起到积极快速反应的作用。     

现代检测技术在数控机床中的应用

介绍现代检测技术及检测装置在数控机床中的应用,详细分析位置检测装置在数控机床中的重要作用,归纳总结检测元件发生故障的原因,以达到经验共享的目的。     

基于PLC的三维调整机同步控制系统设计与实现

针对三维调整机难以实现多台同步工作，设计了基于PLC的同步控制方案。在同步控制系统方案中，采用西门子PLC通过工业无线以太网进行同步控制，由各维度油缸的位移传感器来保证同步控制的精确性。经实验，证实了此系统的精度满足设计要求，实现了同步控制的效果。