PLC在膜分离制氮机温度控制系统中的应用

为了提高膜分离制氮机中进气的相对温度,稳定氮气的质量,消除温度因素对膜组的不良影响,设计了以可编程序控制器(PLC)为核心、采用比例积分微分(PID)算法的膜分离制氮机温度控制系统,并详细介绍了PLC的硬件组成、软件结构及与人机界面设计。通过仿真为实验提供了参考的调节参数,实验表明,该方案可以取得满意的准确度,同时可以通过人机界面修正温度控制的相应参数,提高温度控制的精度。     

含温度补偿的便携式土壤水分测定仪研制

针对现有土壤水分测定仪的不足,研制了一种新型的便携式土壤水分测定仪。传感器快速测量出土壤温、湿度数据,GPS自动获取时间、经纬度信息,数据既可临时保存在仪器的存储芯片中,又可通过GPRS/GSM将数据及时发送到后台数据库和手机用户。通过温度补偿和野外验证实验得出,温度补偿项为Δy=0.0002 t3-0.011 t2+0.444 1 t-6.423 2,仪器所有功能运行正常,测量绝对误差为-3.64%~3.82%,平均绝对误差为2.24%,精度较高,适合在地方农技和水利部门推广应用,有助于农业水利信息化水平的提高。     

低密度泡沫玻璃的研究与应用

低密度泡沫玻璃是利用碎玻璃制造的一种气孔率大于90%的隔热保温材料,它具有强度高、导热系数小、吸水率低、不吸湿、耐腐蚀等特性,在潮湿环境下抗冻性能好,是一种优良的低温、超低温隔热保温材料。该产品用途广泛,所用的原材料简单易得,但生产工艺过程比较复杂,生产过程控制精度要求较高,容易产生各种缺陷而影响产品的质量。本文对低密度泡沫玻璃的生产工艺过程进行详细的分析研究,提出相应的措施,确保产品的低密度和高成品率,提高产品的性能,扩大产品的使用范围。     

超声波传感器在沙子料位检测中的应用

为提高混凝土的质量,配比很重要,其中沙子精确计量是关键因素之一。提出并设计了超声波系统测量沙子料位;为保证测量精度,采取自动增益控制电路和温度补偿。经实验证明:该方法简单、可行,为沙子质量的检测提供了一种新的参考方法。     

基于集成温度传感器的硅微陀螺仪数字化温度补偿研究

提出了一种基于集成温度传感器的硅微陀螺仪数字化温度补偿方法。首先,介绍了集成温度传感器的硅微陀螺仪基本结构原理,分析了硅微陀螺仪动力学方程以及温度变化对硅微陀螺仪谐振频率、品质因数、标度因数和零偏的影响。然后,设计了基于FPGA的硅微陀螺仪数字化补偿电路。最后,经过温度特性实验得到标度因数和零偏随温度变化曲线,建立了温度补偿模型,提出分段温度补偿方法。经过温度补偿后,标度因数和零偏的温度系数分别由316.66×10-6/℃和366.22°/(h·℃)减小为69.67×10-6/℃和115.25°/(h·℃),证明了补偿方法的正确性和可行性。     

近十年常温干法精脱硫专利技术发展动态

收集了近十年来国内的常温干法精脱硫专利，并分类列举出各种脱硫剂的物化性质和几种常温精脱硫工艺，重点阐述了该技术的优缺点及其未来发展方向。     

基于模糊PID算法的空调机组温度控制

针对中央空调系统空调机组温度控制的非线性、滞后性及时变性等特点,设计了基于模糊PID算法的空调机组温度控制系统,实现了空调机组温度的实时在线控制.该系统选用MCGS组态软件实现系统运行状态的监控,使用西门子S7-1200 PLC进行现场设备控制.运行结果表明模糊PID控制器设计合理,有效改善了空调过程的调节品质,提高了空调机组的温度控制质量.     

A型地铁空调系统及客室内流场数值分析

为给目前国内A型地铁车辆的舒适度设计提供理论参考,针对地铁车辆静压风道结构特点,基于k-ε两方程湍流模型和SIMPLE算法,建立包含空调送风风道和客室的三维计算模型.对计算模型的空气流动和传热状况进行CFD数值计算.计算过程综合考虑车体壁面传热和人体散热等多种传热.分析计算结果得到客室内温度场和速度场的分布规律,并对空调通风设计方案进行量化评估.计算结果表明:客室内人体头部区域温度场分布均匀,平均温度为26.6℃,最大温差为6℃;车厢内有较理想的气流组织形式,速度分布范围为0.50~0.79 m/s,而且客室端部和中部区域人体头部周围速度较大.将计算结果与欧洲EN 14750-1标准进行对比分析,认为乘客的舒适性较好.     

High temperature polymerization of propylene catalyzed by MgCl2‐supported Ziegler–Natta catalyst with various cocatalysts

Four cocatalysts, referred to as ethylaluminoxanes, were synthesized by the reaction between triethylaluminium (AIEt₃) and water under various molar ratios of H₂O/Al at ?78°C. Aluminoxanes were used as cocatalysts for a MgCl₂‐supported Ziegler–Natta catalyst for propylene polymerization at temperatures ranging from 70 to 100°C. When the polymerization was activated by AlEt₃, the activity as well as the molecular weight and isotacticity of the resulting polymer gradually dropped as the temperature varied from 70 to 100°C. When ethylaluminoxane was employed as the cocatalyst, good activity and high molecular weight and isotacticity were obtained at 100°C. Furthermore, when the cocatalyst varied from AlEt₃ to ethylaluminoxane, the atactic fraction and polymer fraction with moderate isotacticity decreased and the high isotactic fraction slightly increased, which indicated that the variation of the cocatalyst significantly affects the isospecificity of active sites. It was suggested that the reactivity of the Al‐Et group and the size of the cocatalyst were correlated to the performance of the Ziegler–Natta catalyst at different temperatures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1978–1982, 2006     

Effect of Twin-Plane Reentrant Edge on the Coarsening Behavior of Barium Titanate Grains

When BaTiO₃ ceramics were sintered at relatively low temperatures (≤1250°C), the grains with reentrant edges caused by a (111) double twin grew exclusively. As a result, a microstructure with a bimodal grain-size distribution composed of platelike large grains and fine matrix grains was obtained. In contrast, at the usual sintering temperature between 1250° and 1350°C, grains containing a (111) double twin did not exhibit any growth advantage. In this case, a coarse and uniform microstructure was obtained. When this coarse-grained specimen was further heat-treated at 1365°C, the grains possessing a double twin were observed to grow exclusively again. The results were explained in terms of a coarsening process controlled by two-dimensional nucleation.