模糊PID控制光电跟踪系统的抗干扰性分析

机载光电跟踪系统是一个复杂的非线性系统,影响其性能品质的因素很多。笔者建立的数学模型是略去很多非线性因素建立的线性模型,是没有外界干扰下的模型,和实际系统有一定的区别。为说明模糊自适应PID控制对不确定性系统有较强的鲁棒性,引入模型参数摄动方法,即增加外界干扰时进行仿真研究。最终得到了系统稳定的结论,为模糊自适应PID控制器的设计提供了理论依据。     

热极化光纤中线性电光系数对调制频率的响应

热极化方法可在熔石英熊猫保偏光纤器件中产生线性电光效应,由此可制成热极化光纤器件.为获得热极化光纤器件的调制频率响应特性,进行了热极化保偏光纤的调制频率响应实验研究,并探讨了其机理.实验表明,已制成的热极化熊猫光纤,在其上所加调制频率小于1 kHz的范围内,会使极化产生的线性电光系数产生声频共振.当调制频率大于2 kHz后,电光效应基本不受调制频率的影响.机理分析表明,热极化使非晶态的熔石英光纤中形成了类晶体结构.极化光纤中产生的反压电效应会导致器件的线性电光系数产生声频共振.     

机载光电探测跟踪系统总体精度分析方法研究

机载光电探测跟踪系统是一种光、机、电高度综合的复杂系统,光、机、电三种误差相互耦合传递,对系统性能影响的机理比较复杂。本文在分析了影响系统精度的因素和经典的误差合成原理之后,给出了简化了的机载光电探测跟踪系统的精度计算方法。     

光电经纬仪中激光测距发射系统设计

论述了在光电经纬仪上应用激光测距装置的重要性,即可实现单台经纬仪确定目标位置.介绍了激光测距的原理及测距方程,针对光电经纬仪中激光测距系统的结构特点,对测距分系统发射系统进行了设计,实现了各种复杂条件下的激光测距.     

基于激光测距的机载光电成像系统目标定位

针对小型机载光电平台无法准确获取视轴指向问题,设计了一种基于激光测距的目标定位算法。利用机载光电侦察平台锁定跟踪目标的特性,对同一目标多次测量,采用激光测距装置获取目标与载机间的距离信息。根据WGS-84定义的地球椭球模型建立系统的测量方程。考虑到测量方程的非线性,利用扩展卡尔曼滤波对目标位置进行估计。该定位方法精度只受到GPS接收机定位精度和激光测距机测量精度的影响,目标定位误差与机载光电侦察设备视轴指向测量无关。采用蒙特卡洛法仿真分析载机位置测量误差及激光测距系统位置误差对目标定位的影响,结果显示该算法定位精度较高。采用飞行试验数据验证了该目标定位算法的有效性,在飞行高度8 000 m时,目标定位精度优于8 m。相比于传统定位算法,该方法可将定位精度明显提高。同时此定位方法易于部署,可操作性强,具有较大的应用价值。     

Specific surface modification of liposomes for gut targeting of food bioactive agents

Liposomes have become a research hotspot in recent years as food delivery systems with attractive properties, including the bilayer structure assembled like the cell membrane, reducing the side-effect and improving environmental stability of cargos, controlling release, extending duration of functional ingredients, and high biodegradable and biocompatible abilities in the body. However, the conventional liposomes lack stability during storage and are weak in targeted absorption in the gastrointestinal track. At present, surface modification has been approved to be an effective platform to shield these barricades and help liposomes deliver the agents safely and effectively to the ideal site. In this review, the gastrointestinal stability of conventional liposomes, cargo release models from liposomes, and the biological fate of the core materials after release were emphasized. Then, the strategies in both physical and chemical perspectives to improve the stability and utilization of liposomes in the gastrointestinal tract, and the emerging approaches for improving gut targeting by specifically modified liposomes and the intestinal receptors relative to liposomes/cargos absorption were highlighted. Last but not the least, the safety, challenges, and opportunities for the improvement of liposomal bioavailability were also discussed to inspire new applications of liposomes as oral carriers.     

A geospatial framework to support integrated biogeochemical modelling in the United Kingdom

Anthropogenic impacts on the aquatic environment, especially in the context of nutrients, provide a major challenge for water resource management. The heterogeneous nature of policy relevant management units (e.g. catchments), in terms of environmental controls on nutrient source and transport, leads to the need for holistic management. However, current strategies are limited by current understanding and knowledge that is transferable between spatial scales and landscape typologies. This study presents a spatially-explicit framework to support the modelling of nutrients from land to water, encompassing environmental and spatial complexities. The framework recognises nine homogeneous landscape units, distinct in terms of sensitivity of nutrient losses to waterbodies. The functionality of the framework is demonstrated by supporting an exemplar nutrient model, applied within the Environmental Virtual Observatory pilot (EVOp) cloud cyber-infrastructure. We demonstrate scope for the use of the framework as a management decision support tool and for further development of integrated biogeochemical modelling.     

Pharmacokinetics and efficiency of brain targeting of ginsenosides Rg1 and Rb1 given as Nao-Qing microemulsion

Nao-Qing solution has been shown to be clinically effective in the treatment of acute ischemic stroke (AIS). The purpose of this study was to improve the pharmacokinetics and brain uptake of Nao-Qing, administered as an oil-in-water microemulsion. Sprague–Dawley (SD) rats were given Nao-Qing microemulsion by intranasal or intragastric routes. Samples of blood, brain, heart, liver, lung and kidney were collected at pre-determined time intervals, and the contents of ginsenosides Rg1 and Rb1 (active ingredients of the Nao-Qing microemulsion) were analyzed by high-performance liquid chromatography (HPLC). The results showed that contents of ginsenosides Rg1 and Rb1 in Nao-Qing microemulsion was 8475.13?±?54.61?μg/ml and 6633.42?±?527.27?μg/ml, respectively, and that the particle size, pH and viscosity of the microemulsion were 19.9?±?5.07?nm, 6.1 and 3.056?×?10^?3?Pas, respectively. Absorption of ginsenoside Rg1 was higher than that of ginsenoside Rb1, which was barely detectable after intragastric administration; furthermore, the concentration of ginsenoside Rg1 in blood and other tissues at each time point was lower for intragastric than for intranasal administration. Compared with intragastric administration, intranasal administration resulted in a shorter t_max (0.08 versus 1?h), a higher C_max (16.65 versus 11.29?μg/ml), and a higher area under the concentration–time curve (AUC) (592.91 versus 101.70?μg?h/ml) in the brain. The relative rates of uptake (R_e) and the ratio of peak concentration (C_e) in the brain were 126.31% and 147.48% for ginsenoside Rg1, respectively. These data illustrate that intranasal administration can promote the absorption of drugs in Nao-Qing microemulsion and achieve fast effect.