A multilevel sampled‐data approach for resilient navigation and control of autonomous systems

Autonomous systems are rapidly becoming an integrated part of the modern life. Safe and secure navigation and control of these systems present significant challenges in the presence of uncertainties, physical failures, and cyber attacks. In this paper, we formulate a navigation and control problem for autonomous systems using a multilevel control structure, in which the high‐level reference commands are limited by a saturation function, whereas the low‐level controller tracks the reference by compensating for disturbances and uncertainties. For this purpose, we consider a class of nested, uncertain, multiple‐input–multiple‐output systems subject to reference command saturation, possibly with nonminimum phase zeros. A multirate output‐feedback adaptive controller is developed as the low‐level controller. The sampled‐data (SD) design of this controller facilitates the direct implementation on digital computers, where the input/output signals are available at discrete time instances with different sampling rates. In addition, stealthy zero‐dynamics attacks become detectable by considering a multirate SD formulation. Robust stability and performance of the overall closed‐loop system with command saturation and multirate adaptive control are analyzed. Simulation scenarios for navigation and control of a fixed‐wing drone under failures/attacks are provided to validate the theoretical findings.     

基于船载卫星通信三轴天线的跟踪搜索技术

针对船载卫星通信三轴天线跟踪系统,介绍了船载三轴天线的系统组成,提出了一种基于捷联惯导的船载三轴天线跟踪搜索技术。天线以目标地理角为中心,通过坐标转换将目标地理角转换为天线的目标甲板角,调整AEC三轴使其及时准确地跟随目标甲板角。目前,该方法已经成功应用于多种船载三轴天线。实践表明,该方法能够快速准确地搜索到目标卫星,并实现对目标卫星的稳定跟踪。     

CBK searching (chemistry-biology-keyword): Performing cross-discipline collaborative searches

A debate over whether a search is a chemistry or a biology search is becoming increasingly more frequent within search teams. The line between non-text chemistry and biology searching has become blurred in recent years. The appearance of “non-natural” amino acids and modified peptides, for example, has given rise to the questions: Is it a structure? Is it a sequence? Could it be both? It may not be a question of one or the other, but perhaps working with a colleague to bring the best possible answer to the client. Several examples clarify the line and present guidance when beginning a search. Consider the size of the molecule, how many amino acids are present and what the client needs in order to best cover all bases and create a more comprehensive search report.     

嵌套式复合型材构件制造技术及其专用机床

嵌套式冷轧复合型材构件制造技术包括平整、加强筋成型、第一辊压模具组成型、冲孔、主截面成型、第二辊压模具组的横截面成型、嵌套合抱、第一构件与第二构件嵌套抱合后成为复合型材构件与第三辊压模具组紧贴等工序组成,在冲孔工序之前先完成加强筋成型工序,保证冲孔加工后的孔距尺寸精度,显著提高产品质量;上述所有工序都是设置在同一条生产线上的专用机床连续自动完成,实现了嵌套式冷轧复合型材构件的自动化生产,节约工时,降低产品成本。     

用PCR技术检测水中隐孢子虫

介绍了一种检测水中隐孢子虫的巢式PCR方法：根据Cryptosporidium parvum 18s rRNA基因序列选用了两对引物，特异性扩增了该基因可变区中1056bp和435bp目标片段。加标试验表明，该方法的检测限为10个卵囊。     

新疆西南部金、铜成矿构造环境及找矿前景

用板块构造观点，对新疆区域构造格局及成矿构造环境提出了新的认识。把南疆划分出塔里木北被动陆缘、塔里木西阿克赛，钦巴什－库尔良裂谷、公格尔－桑株塔格地块、塔里木南活动陆缘、冈底斯板块和喀喇昆仑缝合带。论证了各构造单元的构造演化及成矿构造环境，指出裂谷带及缝合带是找寻金、铜的重要成矿构造环境。     

建筑节能并行设计方法探讨

在分析建筑节能设计信息模型的基础上,介绍了建筑节能并行设计微循环模型,分析了其设计过程的分解与修正,提出适用于建筑节能并行设计的回溯搜索策略,最终使设计效率得到提高。     

限幅特性在鱼雷控制系统设计中的应用

限幅特性技术在鱼雷控制系统设计和工程实现中已被广泛应用,本文以继电控制的鱼雷深度纵倾系统为例,分析了限幅器的限幅特性作用机理和系统工作原理,在对系统数学描述的基础上,进行了限幅参数优化仿真计算与分析。结果表明,限幅特性不但可以方便地实现控制状态的自动转换,而且可以发挥系统最大能力,使得鱼雷寻深弹道到达最优,满足鱼雷深浅水的使用要求,该结论对工程设计具有指导意义。     

基于IAPF与多层Morphin搜索树的移动机器人路径规划

针对传统人工势场法(artificial potential field,APF)的易出现振荡、死区、局部极小值等缺陷。提出一种结合机器人位置、速度、加速度及障碍物位置等信息的改进人工势场法(improved artificial potential field,IAPF)。利用Morphin算法计算效率高、易结合全局路径规划算法的优点,提出一种多层Morphin搜索树算法。首先,利用改进人工势场法完成路径的全局规划,在此基础上在障碍物附近用多层Morphin搜索树算法进行路径规划。利用MATLAB仿真测试表明,所提出的改进人工势场法与多层Morphin搜索树的混合算法,在移动机器人自主路径规划中,能有效缩短路径长度,提高到达目标点的效率,高效完成路径规划。     

Valuing the environment in developing countries: modelling the impact of distrust in public authorities' ability to deliver public services on the citizens' willingness to pay for improved environmental quality

In this paper, we employ the choice experiment method to estimate citizens' valuation of an intervention that proposes to improve the quality of the wastewater deposited in the Ganges River, India. We interviewed 150 randomly selected citizens of Chandernagore, along the banks of the Ganges River, to elicit their willingness to pay (WTP) for this intervention, measured in terms of higher municipality taxes. The findings reveal that almost all of the citizens value wastewater quality, though majority protested the intervention, and stated that they donot trust the authorities for effective management of funds. These protest responses were controlled for with the nested logit model. The results reveal that the citizens are willing to pay significant amounts for improved wastewater quality. Municipalities could rely to some extent on their citizens' WTP higher taxes but municipalities' performance, trustworthiness, accountability, as well as the citizens' perceptions of these, should be improved.