一种基于变结构的预测控制算法及其应用研究

将变结构控制方法引入预测控制中，提出了一种基于变结构的预测控制算法。与传统的预测控制方法相比，该算法具有设计简单、易于实现的优点。将其应用于火电机组过热汽温控制进行仿真研究，结果表明所提出的预测控制算法具有优良的控制性能和很好的鲁棒性。     

Particle packings minimizing density gradients of coarse-grained compacts

The influence of particle size distributions on the density, density gradient and strength of uniaxially two-sided die-pressed cylinders was investigated. To design the particle size distributions with a maximum grain size of 3 mm, a continuous gap-grading model was applied. The bulk densities were measured before and after firing (1600 °C) and the cold crushing strength after firing. Some fired samples were axially and radially cut to analyze the density distribution and gradients. Densities and strength correlated and were highest for increasing amounts of the finest fraction (0–0.02 mm) up to 45 wt%. The density gradients were lowest for high amounts of fines leading to an improved pressure transmission and densest packing. Additionally, the gradients were low for high amounts of coarse grains leading to a pressure transmission through a formed coarse grain skeleton. Summarized, densest compacts with lowest density gradients were achieved for particle packings with a reduced amount of medium sized grains.     

Influence of solvents on the photoinduced birefringence in chitosan films incorporating azo dyes

The photoinduced birefringence arising from trans–cis–trans isomerization has been studied in chitosan cast films doped with the azo dye Ponceau‐S. The chitosan/Ponceau‐S films are highly resistant to several solvents, which allowed the study of their optical storage features after immersion in various solvents. We demonstrate that the induced birefringence and its dynamics are influenced by the solvent. From experiments using such different solvents as water, dimethylsulfoxide, ethylene glycol, methanol and chloroform, it was found that the induced birefringence and the writing rate increase linearly with the dielectric constant of the solvent. At high dielectric constant, photoinduced molecular reorientation is facilitated, leading both to a larger birefringence and faster dynamics. Copyright © 2007 Society of Chemical Industry     

Improved spinel-containing refractory castables for slagging gasifiers

In gasifiers the reaction of a carbon feedstock with oxygen and water takes place to produce synthetic gas. The decrease of the operation temperature at the refractory lining by an innovative gasification technology permits the development of new chrome oxide free materials fulfilling economical as well as ecological aspects. Considering this aspect, spinel-containing refractory castables with increasing spinel content have been investigated according to their thermomechanical properties, phase formation as well as their resistance against corrosion attack by molten coal slag under gasification-similar conditions. In order to determine the influence of spinel and cement in the alumina-spinel castables, increasing spinel amounts and cement types has been added to alumina. In particular, MA-spinel cement has been applied. It has been shown, that the addition of MA-spinel cement to spinel-rich alumina improves the corrosion resistance against molten slag remarkably.     

Effects of different calcium salts on properties of milk related to heat stability

Insoluble calcium salts were added to milk to increase total calcium by 30 mM, without changing properties influencing heat stability, such as pH and ionic calcium. There were no major signs of instability associated with coagulation, sediment formation or fouling when subjected to ultra high temperature (UHT) and in‐container sterilisation. The buffering capacity was also unaltered. On the other hand, addition of soluble calcium salts reduced pH, increased ionic calcium and caused coagulation to occur. Calcium chloride showed the largest destabilising effect, followed by calcium lactate and calcium gluconate. Milk became unstable to UHT processing at lower calcium additions compared to in‐container sterilisation.     

安森美半导体16W xDSL调制解调器AC-DC适配器参考设计

文章介绍了安森美半导体用于xDSL调制解调器AC—DC适配器的一种经过完备构建及测试的Green Point^TM解决方案。     

Rheological Characterization of Slurries for the Preparation of Alumina Foams via Replica Technique

Five commercially available thickeners were used to prepare thickened alumina slurries for foam production using the replica technique. The solid content and the type of thickener significantly affected the rheological properties, whereby an increase in the solid content caused both the viscosity and the thixotropy to increase. For the evaluation of the consistency index and of the level of shear‐thinning behavior, the power law fluid model (Ostwald de Waele) was used. The rheological properties play a key role during the coating process in the replica technique. However, relatively little information is available on the effect of slurry rheology on the properties of reticulated foam ceramics. In this study, the influence of viscosity, thixotropy, and the level of shear‐thinning behavior on the coating behavior is evaluated. The results indicate a strong influence of the viscosity and the level of shear‐thinning behavior on coating behavior.     

Porous materials for alkali contaminated environments

This study presents the synthesis of alkali aluminosilicates based on the stoichiometry of KAlSiO₄ by a hydrothermal treatment followed by a sintering step. The aim was to create formed porous samples which could be a potential material in high temperature applications with alkali corrosive conditions. The material composition was adjusted using analysis of variance (ANOVA) to reach resistance to alkali corrosion of the synthesized material. A casting process was established replacing a part of the raw materials by pre-sintered material to produce porous samples. The final samples were characterized with regard to bulk density, refractoriness under load, cold crushing strength and thermal conductivity. The results showed similar properties compared to conventional materials.