An integrated approach to hypersonic entry attitude control

This paper presents an integrated approach based on dynamic inversion(DI)and active disturbance rejection control(ADRC)to the entry attitude control of a generic hypersonic vehicle(GHV).DI is frstly used to cancel the nonlinearities of the GHV entry model to construct a basic attitude controller.To enhance the control performance and system robustness to inevitable disturbances,ADRC techniques,including the arranged transient process(ATP),nonlinear feedback(NF),and most importantly the extended state observer(ESO),are integrated with the basic DI controller.As one primary task,the stability and estimation error of the second-order nonlinear ESO are analyzed from a brand new perspective:the nonlinear ESO is treated as a specifc form of forced Li′enard system.Abundant qualitative properties of the Li′enard system are utilized to yield comprehensive theorems on nonlinear ESO solution behaviors,such as the boundedness,convergence,and existence of periodic solutions.Phase portraits of ESO estimation error dynamics are given to validate our analysis.At last,three groups of simulations,including comparative simulations with modeling errors,Monte Carlo runs with parametric uncertainties,and a six degrees-of-freedom reference entry trajectory tracking are executed,which demonstrate the superiority of the proposed integrated controller over the basic DI controller.     

Novel Method To Optimize the Structure of Reticulated Porous Ceramics

A novel method has been developed for the fabrication of silicon nitride reticulated porous ceramics (RPCs) with regulated structure, using polyurethane sponge as the template. This technique includes two centrifuging steps. In the first stage, the polyurethane sponges are coated with thin slurry through high-speed centrifuging. After the slurry on sponges dried, a high-strength green body without filled cells is obtained. In the second stage, because of improved adhesion between the body and the slurry after the first coating, the body with uniformly thick strut is produced by recoating the as-prepared green body with thixotropic slurry and centrifuging again. The loading content of slurry and the pore diameter of the RPCs body greatly depend on the slurry viscosity in the process of recoating. The strut diameter and pore diameter of the RPCs are effectively optimized by modulating the slurry viscosity.     

古马隆树脂型聚氨酯防水涂料

介绍一种以古马隆树脂改性的新型双组分聚氨酯防水涂料，并对其原材料的选择、配方、生产工艺等方面进行了研究。     

面向内部威胁的最优安全策略算法研究

内部攻击行为具有很强的伪装性,这使得检测结果具有不确定性.攻击图模型经常用于描述攻击行为的多个攻击步骤之间的因果关系,但在计算最优安全策略时,很少考虑到当前观测事件所具有的不确定性,也没有从概率的角度刻画安全防护策略实施后对攻击成功概率带来的影响.在前人的概率攻击图模型研究基础上,首次提出了一种面向内部威胁的安全防护策略概率攻击图(measures probablitity attack graph,MPAG)模型,在该模型中较为完备地讨论了内部攻击的3类不确定性,并引入安全防护措施节点及其对攻击成功的概率影响.在该模型基础上,最优安全防护策略计算被证明是一个NP难问题,一种贪心算法被提出解决该问题,该算法能在多项式时间内动态计算近似最优安全防护策略集合.最后给出一个真实的内部威胁网络环境的概率攻击图实例,说明该模型及相应的贪心算法能根据当前观测事件及其置信概率,计算满足一定代价限制条件的近似最优安全防护策略集合.     

相容剂对聚丙烯／滑石粉增容作用研究

作者采用熔融接技方法制备PP-g-AA和PP-g-MAH,并比较了这两种相容剂对PP/滑石粉体系的增容效果。着重研究了引发剂含量、单体含量对PP-g-AA增容作用的影响以及PP-g-AA用量对PP/滑石粉体系力学强度的影响。     

共沉淀法制备纳米氧化镁的研究

以氯化镁与碳酸钠为原料,采用共沉淀法,研究了反应溶液的pH值、反应物浓度、反应温度、反应时间和煅烧温度对制备纳米氧化镁粉体的影响,通过透射电镜(TEM)、X射线衍射(XRD)、热重分析(TG)对样品的性能进行测试,获得纳米氧化镁平均粒径约12 nm,且分布较均匀.     

一种基于对等网络的云资源定位算法

提出用分布式哈希表(DHT)为每台云服务器产生一个唯一的节点编号,该编号作为网络拓扑结构、检索信息存储和信息查询共同的标志符,从而形成一个适合分布式计算的结构化P2P覆盖网.设计了新的拓扑和路由协议来解决云资源的常数跳定位问题.仿真实验表明,经典的P2P算法平均查找跳数与网络规模成正相关,无法依据云计算的实际需要人为地控制查找跳数;该算法的平均查找跳数与网络规模无关,随着网络规模的增大而趋向于设定值,可以解决云资源的常数跳定位问题.     

高职院校无线网络的规划与设计

高职院校一般规模比较小,WLAN就比较适合这个范围使用,通过无线网络可以很好的弥补目前有线网络的不足,使教职工和学生可以随时随地的进行网上办公和学习。通过需求分析,找到网络架设的重点;通过无线网络的安全性分析,使学校在购买相关设备的时候可以有所参考;通过无线网络的管理,使大家深刻认识到网络管理的重要性。     

水/有机溶剂两相体系微生物催化不对称还原制备(S)-4-氯-3-羟基丁酸乙酯

研究了水/有机溶剂两相体系中,出芽短梗霉SW0202细胞催化4-氯乙酰乙酸乙酯(COBE)不对称还原制备(S)-4-氯-3-羟基丁酸乙酯(CHBE)的过程.有机溶剂的选择表明邻苯二甲酸二丁酯为该反应最适有机溶剂,与单一水相体系相比,水/邻苯二甲酸二丁酯两相体系能明显改善反应效率.通过系统考察一些因素如相体积比、振摇速度、反应温度和pH等对反应速度、摩尔转化率和产物光学纯度的影响发现,这些因素对还原反应的初速度和摩尔转化率有较明显的影响,而对产物的光学纯度影响不明显.优化后的条件为:水与有机溶剂的相体积比1∶1,振摇速度180 r·min-1,温度30℃,pH 7.0.在该优化反应条件下,水/有机溶剂两相体系中出芽短梗霉SW0202细胞催化COBE生成(S)-CHBE不对称还原反应的最大摩尔转化率和产物的光学纯度分别达到了94.8%和97.9%e.e.,在用Na2CO3溶液控制水相pH 7.0条件下,有机相中的产物浓度积累达58.2 g·L-1.     

Charge/discharge characteristics of sulfur composite cathode materials in rechargeable lithium batteries

The charge and discharge characteristics of lithium batteries with sulfur composite cathodes have been investigated. The sulfur composites showed novel electrochemical characteristics. The analysis of the differential capacity indicated that the discharge process showed two voltage plateaus of 2.10 V and 1.88 V, and the charge process also presented two voltage plateaus of 2.22 V and 2.36 V. The overcharge test showed that the composite cannot be charged over 4.0 V, the voltage always stopped at about 3.9 V during charging, indicating that the composite presented the intrinsic safety for the overcharge of lithium batteries. The overcharge can cause serious safety problem for the conventional Li-ion batteries. The overcharge test also showed that the batteries with sulfur composite were destroyed when the upper cut-off voltage was over 3.6 V. However, the composite presented good reversible capacity after it was deep discharged even to 0 V. It showed stable cycleability and high cycling capacity of 1000 mAh g⁻¹ when cycling between 0.1 V and 3.0 V, indicative of the different characteristic from the conventional oxide cathode materials. The prototype polymer battery with the composite cathode material presented the energy density of 246 Wh kg⁻¹ and 401 Wh L⁻¹.