Derivation of a control oriented low order model of the dynamics of an infrared oven for the continuous drying of a thin sheet of material

A model consisting of three partial non-linear differential equations for describing the humidity and temperature of a thin sheet of material and of the temperature of the air flow as a function of time and position in an infrared dryer was reduced to a model more adaptable to direct digital control. To begin with the original model was discretized along the length of the dryer and then linearized. Models of orders ranging from 12 to 72 were analyzed for controllability and observability. Using Moore's method, the models thus obtained were further reduced to a controllable state space model of order 5 that produced satisfactory results and for which stability was preserved. Simulated open loop responses of the reduced model to discrete perturbations in emitter electrical power, inlet humidity and velocity of the web, produced satisfactory dynamic and steady-state responses when compared to responses of the original model subjected to similar perturbations. The steady-state responses showed absolute errors for humidity and temperature of the web less than 1.3% [g water/100 g] and 2.2°C, respectively.     

基于晶闸管的直流可控避雷器关键技术

电网换相换流器(LCC)与模块化多电平换流器(MMC)级联系统具备诸多独特优势,但其低压端模块化多电平换流器(MMC)由多个电压源换流器(VSC)换流器并联组成,当发生交流侧故障时会引起低压端直流母线过电压。为抑制MMC过电压问题,提出在直流母线侧安装直流可控避雷器。对交流侧故障时MMC过电压机理进行了理论分析,提出了直流可控避雷器拓扑结构。在深入分析直流可控避雷器不同运行方式的基础上,给出了直流可控避雷器的直流混合可控开关所需的极限电流耐受能力。为实现开关触发的快速性,提出在直流混合可控开关中采用串联晶闸管阀组方案。通过晶闸管Cauer计算模型仿真研究了极限电流下晶闸管阀组瞬态结温,验证了设计方案的合理性。基于某规划直流工程进行直流可控避雷器设计,并给出了主设备布置方案。基于PSCAD/EMTDC平台搭建了系统的仿真模型,验证了所提出的直流可控避雷器拓扑抑制系统MMC过电压的有效性。     

Fe/TiO_2纳米复合物的制备、表征及其性能

采用溶胶-凝胶结合氢气还原方法,制备了Fe与TiO2两相共存的纳米复合物。透射电子显微镜(TEM)图片显示,纳米复合物的颗粒大小为100~300nm,且具有明显的核/壳结构。X射线衍射结果表明,纳米复合物中存在a-Fe与金红石型TiO2结构,未发现其他杂相。振动样品磁强计(VSM)的测量结果表明,样品具有较高的比饱和磁化强度。研究表明,通过控制前驱物的用量,能有效改变样品的磁性。热重分析(TGA)结果表明,样品具备很好的抗氧化性。复合介电谱和磁谱表明,在测量的微波频率范围内,样品的介电损耗大于磁损耗。     

ZnO一维纳米结构在金属基底上的原位生长和表征

以Cu—Zn合金片为基底并提供Zn源,在含氧气氛中通过调控反应温度和氧偏压,采用热氧化法直接在Cu-Zn合金片上大面积可控地合成了多种形貌的ZnO一雏纳米材料薄膜（包括纳米带、纳米片、纳米梳和纳米线等）,采用多种分析方法对产物的形貌、结构进行了详细的表征,并对其相应的生长模型进行了讨论。结果表明,反应温度和氧偏压对ZnO纳米结构的生长至关重要,随着反应温度升高或氧含量的减少,气相Zn／O物种的偏压比增加,ZnO纳米结构尺寸变小。     

生物冶金ORP与关键工艺参数关联规则的挖掘

针对生物冶金提金率难以提高这一难题,通过深入分析生物冶金工艺,依据工艺现场实测数据库、新型数据分析方法和数据挖掘方法,得到氧化还原电位(ORP)与工艺过程可控因素间的可描述数学关系,为可控工艺参数的优化控制提供指导依据,进而提高生物冶金提金率。     

Controllable optimized designs of an ideal reactive distillation system using genetic algorithm

The steady state economic optimization to obtain the most economical controllable design of a double feed ideal reactive distillation (RD) column is demonstrated using real coded genetic algorithm. The novelty of the work is in the development of a simple procedure based on steady state criteria for controllability. The optimization is performed for four scenarios corresponding to a sequential increase in the number of design variables. Results show that limiting the optimization search space to only those designs that satisfy the controllability criteria leads to optimized designs that are only slightly (<2%) more expensive than the most economical design without controllability considerations. The former designs however exhibit much better controllability in terms of effectively handling a large through-put change using two-point temperature inferential control and avoiding a steady state transition under open loop operation. Results also show that the location of the fresh feeds is a dominant design variable with designs that do not constrain the feed tray location to be immediately above and below the reactive zone being substantially more economical.     

Preparation of ultrafine silver powders with controllable size and morphology

The ultrafine silver powders were prepared by liquid reduction method using Arabic gum as dispersant. The effects of different dispersants, pH values, and temperature on the morphology and particle size of silver powders were investigated. It is found that Arabic gum can better adsorb on silver particles via chemical adsorption, and it shows the best dispersive effect among all the selected dispersants. The particle size of silver powders can be finely tuned from 0.34 to 4.09 μm by adjusting pH values, while the morphology of silver powders can be tuned by changing the temperature. The silver powders with high tap density higher than 4.0 g/cm³ were successfully prepared in a wide temperature range of 21.8–70 °C. Especially, the tap density is higher than 5.0 g/cm³ when the temperature is optimized to be 50 °C. The facile process and high silver concentration of this method make it a promising way to prepare high quality silver powders for electronic paste.     

以溴酸根插层锌铝水滑石为载体构建新溴源体系

以溴酸根插层锌铝水滑石(Zn/Al-Br O3–-LDHs)为载体,与Br-等还原剂构建形成新型溴源体系。为实现溴源体系在实际应用中的有效控溴,对Zn/Al-Br O3–-LDHs中Br O3–的释放行为进行了研究,并考察了温度、交换离子类型、p H值等因素对Br O3–释放行为的影响。结果表明:升高温度会加快Br O3–的释放,交换离子的交换性越强,Br O3–释放得越快,在p H值为9.0的磷酸盐缓冲溶液中的释放速率要比在p H值为4.0的磷酸盐缓冲溶液中快。采用4种动力学模型对水滑石中Br O3–的释放过程进行动力学拟合,结果表明:LDHs-Br O3–中Br O3–的释放行为符合Bhaskar方程,属粒内扩散控制过程。用LDHs-Br O3–/Br–构建的溴源体系合成了3,5-二溴-2-氨基苯甲酸甲酯,收率为94.7%,纯度为99.8%。     

两自由度可控装载机构动力学分析与研究

针对一种新型装载机工作装置进行了动力学分析和实验研究。分析了各构件的受力,并利用达朗贝尔原理建立了可控装载机构动态静力学模型,求解了各铰点约束反力及主动杆的驱动力矩,并在此基础上进行了主动杆输入功率预估。建立可控装载机构虚拟样机模型,利用ADAMS对其进行了动态静力仿真,得到了两主动杆驱动转矩及功率曲线。在已采购电机和减速机的基础上,根据动力学仿真结果搭建了该可控装载机构电传动系统及相关可控机构式装载机样机,并进行了200 kg、300 kg土块,以及400 kg铁块的场地举升实验。上述研究及实验结果为可控机构式装载机的进一步设计研发提供理论基础及参考。     

基于数字PID和89C52单片机的温度控制系统

针对在工业生产过程中经常需要高稳定度的恒温环境,传统模拟式仪表结合简单的PID控制较难达到目标的情况．提出了基于数字PID控制算法和89C52单片机的温度控制系统。该系统通过温度传感器DS1820对温度进行采样和转换．然后执行数字PID控制,输出控制量来调节可控硅触发端的通断,从而实现对温度的控制。水温可以在一定范围内由人工设定,并能在环境温度降低时实现自动调整。结果表明：通过将数字PID算法和89C52单片机结合使用,使整个控制系统的温度控制精度提高了10％,输出温度的误差小于2％,不仅满足了对温度控制的要求,而且还可应用到对其它变量的控制过程当中。