Sontag型构造性预测控制算法的性能分析

Sontag型构造性预测控制策略是为了降低约束非线性预测控制的在线计算量和分离闭环系统稳定性与性能指标而提出的一种有效算法。在算法名义稳定的条件下,运用逆最优控制理论,分析约束连续时间非线性系统Sontag型预测控制器的逆最优性和鲁棒性问题,得到控制器具有鲁棒性的充分条件,为更好地理解该控制算法和算法的实施提供了理论依据。最后,应用仿真实例验证了本文结论的有效性。     

逆合成孔径雷达系统建模与仿真

逆合成孔径雷达(ISAR)可以获得运动目标的高分辨图像,具有广阔的应用前景,然而ISAR研究面临着缺乏实验平台和数据支撑的困难。首先,介绍了ISAR成像原理;然后,按照ISAR成像流程,将仿真系统划分为引导信息、回波信号、信号处理、二维成像、宽带识别等模块,建立了各个模块所包含的数学模型与仿真模型;最后,设计了ISAR数学仿真系统的系统功能和模块交互结构,给出了系统实现。应用表明,该系统具有灵活的内部结构和较为通用的交互接口,有利于不同算法的内嵌,可以为ISAR技术研究提供仿真平台和仿真数据支撑。     

Degradation induced by nanostructural evolution of polylactide/clay nanocomposites in the isothermal cold crystallization process

BACKGROUND: The aim of the work presented was to study the nanostructural evolution of clay tactoids during the isothermal cold crystallization of polylactide/clay nanocomposites (PLACNs). An interesting degradation behavior of the polylactide (PLA) matrix, however, was observed simultaneously with nanostructural evolution. The possible mechanisms of degradation and structural evolution are discussed. RESULTS: The evolution of the nanostructure and the degradation were studied online or offline using parallel plate rheometry, X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy, gel permeation chromatography and thermogravimetric analysis. The results showed that the intercalation level of the clay tactoids further increased during cold crystallization, leading to simultaneous degradation of the PLA matrix, which was further confirmed by the marked change of small‐ and large‐amplitude oscillatory shear flow behavior of the PLACNs before and after cold crystallization. CONCLUSION: The increase of the intercalation level of the tactoids is due to the diffuse in movement of the PLA chain segments during cold crystallization. In this case, chain‐end scission occurs more easily, especially for those PLA chains around the loose edge and defect site of the tactoids during crystallization, which results in a simultaneous degradation of the PLA matrix. Hence, both the linear and nonlinear dynamic viscoelastic properties show a remarkable change after cold crystallization. Copyright © 2009 Society of Chemical Industry     

Study on the surface roughness of ceramic shells and castings in the ceramic shell casting process based on expandable pattern

A method to form a thin smooth film of wax on the surface of the foam pattern was proposed by introducing the molten wax in this work. Organic smoothing coatings for the foam pattern were also prepared and their effects on the surface roughness of the foam patterns, shells and castings were investigated. Effects of the facecoat slurry used to fabricate ceramic shells on the surface roughness of the shells and castings were studied. The analysis of results indicates that the surface smoothing coatings and the wax smoothing film both greatly decreased the surface roughness of ceramic shells and castings from 3.2-6.3 μm to 0.8-2.5 μm (Ra), and the surface roughness of shells and castings would be improved if the facecoat slurry is prepared with finer filler materials.     

Ce改性SBA-15分子筛催化合成棕榈酸甲酯

用浸渍法对SBA-15分子筛进行Ce改性,制备了Ce(SO4)2/SBA-15催化剂,采用X射线衍射、红外光谱、N2吸附-脱附、热重-差热分析方法对试样进行了表征。表征结果显示,Ce已进入SBA-15分子筛中,制得的Ce(SO4)2/SBA-15催化剂保持高度有序的介孔二维六角结构。用Hammett指示剂法测得Ce(SO4)2/SBA-15催化剂的表面酸强度为0.99~1.80,酸量为0.2344mmol/g。采用Ce(SO4)2/SBA-15催化剂催化甲醇和棕榈酸酯化合成棕榈酸甲酯,优化的合成条件为:n(棕榈酸)∶n(甲醇)=1∶15,催化剂用量为棕榈酸质量的5.0%,反应时间8h。在此条件下,酯化率大于92%。     

高强快干稳定淀粉粘合剂的研制

介绍一种高强快干稳定淀粉粘合剂的制备方法，并对其配方和工艺进行了讨论，通过比较，其经济和技术指均优于同类产品。     

叶坊水轮泵电站技改扩容的实践与体会

福建建瓯市叶坊水轮泵电站，利用闲置的水轮泵机坑进行技术改造，采用异步电机发电，扩大电力装机330kW，投资省、工期短、效益好，配置合理、有效利用了水资源，促进了农村水利水电产业结构的调整和经济发展。     

现代空战指挥系统与攻击系统研究分析

针对现在空战中指挥系统与攻击系统的数据融合存在的不足，给出了经过改进后的现代空战指挥系统及攻击系统流程图及原理；介绍了攻击系统中的火控解算原理并进行了分析和优化计算，为完善现代空战指挥及攻击系统理论提供了一定依据；同时对战术决策及逻辑攻击有一定的指导作用。     

化学发光法测定液体烃类中氮含量方法的研究

本文阐述了化学发光法测定液体烃类中氮含量方法的基本原理，考察了方法的精密度，准确度以及测量线性范围，并与微库仑测氮法做了比较。化学发光法具有操作简单，分析快速，选择性好，抗干扰能力强等许多优点。可直接测定液体类中含量为０．１－５０００ｍｇ／Ｌ的氮，单次亲品分析周期３－５ｍｉｎ，各项分析指标达到ＡＳＴＭ分析方法要求。     

导弹与运载火箭制导系统回顾与发展方向设想

对导弹与运载火箭制导系统历史与发展过程进行了回顾，分析了目前科学技术的发展对制导系统的要求。在此基础上结合新一代武器研制背景和大运载及空间技术的研制需求，研究提出了目前及今后制导系统研究重点与发展方向。