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.     

Fault detection and identification for a class of continuous piecewise affine systems with unknown subsystems and partitions

This paper establishes a novel online fault detection and identification strategy for a class of continuous piecewise affine (PWA) systems, namely, bimodal and trimodal PWA systems. The main contributions with respect to the state‐of‐the‐art are the recursive nature of the proposed scheme and the consideration of parametric uncertainties in both partitions and in subsystems parameters. In order to handle this situation, we recast the continuous PWA into its max‐form representation and we exploit the recursive Newton‐Gauss algorithm on a suitable cost function to derive the adaptive laws to estimate online the unknown subsystem parameters, the partitions, and the loss in control authority for the PWA model. The effectiveness of the proposed methodology is verified via simulations applied to the benchmark example of a wheeled mobile robot.     

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。     

Evaluation of duct opening protection in two-hour fire walls and partitions

There is a continuing debate among fire protection specialists on the value and role of fire dampers in preventing fire spread via HVAC duct systems. It has been recognized that fire dampers are not required under all circumstances. For example, NFPA 90A,Standard for the Installation of Air Conditioning and Ventilation Systems, does not require the installation of fire dampers in ducts penetrating one-hour fire-rated walls and partitions. Additionally, there are circumstances where the closure of dampers may affect critical environmental air systems. In these situations, the value of fire dampers must be determined in terms of an overall risk assessment. It has been suggested that the role of fire dampers be considered in terms of the total building fire protection system, but a quantitative approach for such an assessment has been previously unavailable. In particular, there has been no data related to the performance of a duct system when subjected to a standard two-hour fire exposure. Gewain et al. have described an equivalency approach and full-scale fire test data for the protection of duct openings in two-hour fire-resistant walls and partitions. The objective of this paper is to review and summarize the equivalency rationale and test data and describe engineering methods available to apply an equivalency approach more generally. The approach was developed for situations where horizontal steel ventilation ducts penetrate fire-rated walls and partitions. The approach does not address smoke dampers or ducts containing combustible materials.     

大尺度高低跨柱面屋盖的风压系数分区研究

针对大尺度高低跨柱面屋盖体系风压分布变化梯度较大、跨间相互干扰以及此类屋盖风压分区无相关规范可查阅等问题,在得到各种风向下最不利极值风压的基础上,采用K-means聚类的风压系数快速分区方法将高低跨柱面屋盖表面划分为多个区域,并计算了各区域的分区风压系数。同时,在高低跨柱面屋盖风压系数分区研究过程中,对K-means方法的k值取值范围和最佳k值确定方法进行针对性改进。结果表明,高低跨柱面屋盖的边缘属于风敏感部位,而中间部分风压变化较小,因而在进行大尺度平屋盖抗风设计时,采用聚类方法进行风压分区更为合理。     

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.     

嵌套连接冷弯斜卷边Z形连续檩条的受弯性能试验研究

本文对嵌套连接的冷弯斜卷边Z形连续檩条的受弯性能进行了试验研究。试验分两部分,一是搭接段极限承载力试验,以确定常用范围内搭接负弯矩段的极限承载力;二是两跨连续檩条试验,目的是确定搭接段截面的抗弯刚度。试验分上下翼缘均有自攻钉和仅上翼缘有自攻钉两种情况。对于承载力试验,搭接长度的范围为截面高度的3～5.625倍。通过对5种不同搭接长度和方式共30个试件的破坏性试验发现,破坏都是由受压下翼缘的屈曲引起,且破坏主要发生在搭接开始处。当中间支座处弯矩是搭接开始处弯矩的两倍时破坏出现在中间支座处,此时单个截面的承载力仍然与破坏发生在搭接开始处的情况接近。在试验所用试件的搭接长度范围内,搭接长度对承载能力的影响不大;但搭接段檩条下翼缘是否有自攻钉对搭接段承载能力有约5%的影响。对两跨连续梁,分搭接长度为跨度的10%和20%的两种情况,上下翼缘均有自攻螺钉和仅上翼缘有自攻螺钉两种构造,共进行了11个试验,试验结果表明,搭接长度较长时搭接     

Locality‐Conscious Nested‐Loops Parallelization

To speed up data‐intensive programs, two complementary techniques, namely nested loops parallelization and data locality optimization, should be considered. Effective parallelization techniques distribute the computation and necessary data across different processors, whereas data locality places data on the same processor. Therefore, locality and parallelization may demand different loop transformations. As such, an integrated approach that combines these two can generate much better results than each individual approach. This paper proposes a unified approach that integrates these two techniques to obtain an appropriate loop transformation. Applying this transformation results in coarse grain parallelism through exploiting the largest possible groups of outer permutable loops in addition to data locality through dependence satisfaction at inner loops. These groups can be further tiled to improve data locality through exploiting data reuse in multiple dimensions.     

Integrated optimisation on flow-shop production with cutting stock

This paper addresses the integrated scheduling optimisation on flow-shop production with one-dimensional cutting stock in make-to-order environments. The upstream cutting-stock process provides the items for the downstream production, while the flow-shop production can be executed only when the required items are released. The efficient schedules on cutting plan and the production sequence should be determined in a coordinated manner to improve the overall efficiency. This study aims to find an integrated schedule to minimise the makespan of the entire manufacturing process. We develop a hybrid algorithm by integrating a local search method and some efficient strategies under the nested partitions framework. Numerical experiments show that the proposed approach is capable of achieving high-quality solutions within a reasonable time.