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排序方式: 共有10000条查询结果,搜索用时 359 毫秒
981.
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研究具有外界正弦扰动作用下MIMO系统的最优跟踪控制问题.根据扰动特点,假设拉格朗日算子化简求解系统两点边值问题,通过求解Riccati方程和矩阵方程分别在有限时域和无限时域得到系统前馈反馈最优跟踪控制律.证明了最优跟踪控制律的存在唯一性条件,并给出了最优跟踪控制律的实现算法.构造降维参考输入观测器解决了控制律中前馈项物理不可实现问题.仿真结果表明了该方法的有效性. 相似文献
985.
掺粉煤灰的橡塑复合材料研究和开发 总被引:2,自引:0,他引:2
概述了粉煤灰再利用的必要性及掺有粉煤灰的橡塑复合材料的应用研究和开发概况,介绍了国内橡塑粉煤灰复合材料的研究及开发进展,综述了橡塑粉煤灰复合材料的应用。 相似文献
986.
A unique blowing-assisted electro-spinning process has been demonstrated recently to fabricate hyaluronic acid (HA) nanofibers. In this article, effects of various experimental parameters, such as air-blowing rate, HA concentration, feeding rate of HA solution, applied electric field, and type of collector on the performance of blowing-assisted electro-spinning of HA solution were investigated. With the assistance of air-blowing, the solution-feeding rate could be increased to 40 μl/min/spinneret and the applied electric field could be decreased to 2.5 kV/cm. The optimum conditions for consistent fabrication of HA (with a molecular weight of ∼3.5 million) nanofibers involved the use of an air-blowing rate of around 70 ft3/h and a concentration range between 2.5 and 2.7% (w/v) in aqueous solution. Two benign methods to fabricate water-resistant HA nanofibrous membranes without the use of reactive chemical agents were demonstrated: (a) the exposure of HA membranes in hydrochloric acid (HCl) vapor, followed by a freezing treatment at −20 °C for 20-40 days; and (b) the immersion of HA membranes in an acidic mixture of ethanol/HCl/H2O at 4 °C for 1-2 days. Although both methods could produce hydrophilic, substantially water-resistant HA nanofibrous membranes (the treated membranes could keep their shape intact in neutral water at 25 °C for about 1 week), the immersion method (6) was shown to be more versatile and effective. IR spectroscopy was used to investigate this ‘cross-linking’ mechanism in the solid HA membrane. Viscosity studies of acidic HA solutions under varying freezing conditions were also carried out. It was found that when the freezing time exceeded 8 h, the HA solution became gel-like and exhibited a large increase in the hydrogen-bond concentration. Thus, the resistance to water solubility could be due to the high density of hydrogen bonds in the solid HA membranes that were treated by the ‘freezing’ approach. 相似文献
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Summary Three PEO-PSt-PEO triblock polymers and their parent ho-nopolystyrene have been studied by means of light scattering technique
in chloroform, toluene and ethyl acetate. It has been found that the weight average molecular weights calculated by using
the equation Mapp-
were unbelievable negative values; and the largest deviation appeared for the sample with PEO mole content of about 50%.
Data of PSt-PEO-PSt triblock polymers in literature have been quoted and discussed. 相似文献