Exponential-Alpha Safety Criteria of a Class of Dynamic Systems With Barrier Functions

A classic kind of researches about the operational safety criterion for dynamic systems with barrier function can be roughly summarized as functional relationship,denoted by⊕,between the barrier function and its first derivative for time t,where⊕can be“=”,“<”,or“>”,etc.This article draws on the form of the stable condition expression for finite time stability to formulate a novel kind of relaxed safety judgement criteria called exponential-alpha safety criteria.Moreover,we initially explore to use the control barrier function under exponential-alpha safety criteria to achieve the control for the dynamic system operational safety.In addition,derived from the actual process systems,we propose multi-hypersphere methods which are used to construct barrier functions and improved them for three types of special spatial relationships between the safe state set and the unsafe state set,where both of them can be spatially divided into multiple subsets.And the effectiveness of the proposed safety criteria are demonstrated by simulation examples.

Safety Performance of a Precast Concrete Barrier: Numerical Study

The numerical simulation for a new type of precast concrete barrier for viaducts is carried out systematically.To obtain an accurate representation of the damage state of the concrete barrier under the impact of a vehicle,a stochastic damage-plasticity model of the concrete is adopted in the finite element model.Meanwhile,a simplified mathematical model of the impact between vehicles and the concrete barrier was established and the input energy was converted to the impact load to facilitate the investigation of the safety performance of the concrete barriers.On this basis,a refined finite element(FE)model of a precast concrete barrier was developed.The impact locations,impact load,boundary constraints,and reinforcement types were used as variables and the dynamic response of the precast concrete barrier was systematically analyzed under 36 working conditions.The simulated results indicated that the damage state of the concrete barrier and the stress of the reinforcing bars were accurately and quantitatively reflected.According to the computed results,some suggestions were put forward for selecting the appropriate reinforcement type of the precast concrete barrier and the connection between the superstructure and foundation.

Constrained Moving Path Following Control for UAV With Robust Control Barrier Function

This paper studies the moving path following(MPF)problem for fixed-wing unmanned aerial vehicle(UAV)under output constraints and wind disturbances.The vehicle is required to converge to a reference path moving with respect to the inertial frame,while the path following error is not expected to violate the predefined boundaries.Differently from existing moving path following guidance laws,the proposed method removes complex geometric transformation by formulating the moving path following problem into a second-order time-varying control problem.A nominal moving path following guidance law is designed with disturbances and their derivatives estimated by high-order disturbance observers.To guarantee that the path following error will not exceed the prescribed bounds,a robust control barrier function is developed and incorporated into controller design with quadratic program based framework.The proposed method does not require the initial position of the UAV to be within predefined boundaries.And the safety margin concept makes error-constraint be respected even if in a noisy environment.The proposed guidance law is validated through numerical simulations of shipboard landing and hardware-in-theloop(HIL)experiments.

模拟新建桥梁安全屏障高冲击等级的碰撞测试

针对汽车碰撞桥梁护栏事故频发,人员伤亡较大的情况,进行了新建桥梁安全屏障碰撞的研究。研究模拟新建桥梁的安全屏障在高冲击等级碰撞测试中的效果,分析碰撞中影响车体变形以及碰撞点、碰撞角度、碰撞速度等安全性因素。试验结果表明,在碰撞测试中桥梁护栏的变形程度与吸收的能量呈正比例。新建桥梁需要重视安全屏障的材料、结构设计的合理性,以提高安全屏障吸能水平。

采样控制下的Markov跳变系统稳定性与安全性分析

研究针对连续Markov跳变系统的稳定性和安全性问题通过状态采样控制器保证了其稳定性和安全性。首先,与通常只考虑Markov系统的稳定性不同的是,系统的安全性问题也被考虑了。其次,系统的安全性通过引入控制障碍函数的方法得到解决。因此,系统分析及计算变得极其复杂。最后,通过设计采样控制器保证了系统的稳定性和安全性,并提供了一个有效的数值例子验证了提出方法的有效性。

筑牢北方重要生态安全屏障之认知六人谈

为了治理北方生态环境,我国改革开放之初实施了“三北”防护林工程,实施的手段主要是植树造林,用以防沙固沙,业已取得重大成果。北方生态环境明显好转,沙漠治理工作取得显著成效。生态人类学立足“三北”生态环境的特殊性,从生态治理与区域可持续发展的视角,指出该工程下一步应重视草与树的比例,确保固沙植物水资源分配达到平衡状态。同时,要利用当地形成的地方性知识,在保护生态环境的同时,带动当地经济的增长,筑牢北方重要生态安全屏障的同时,实现当地乡村振兴的目标。

iRoot BP Plus根尖屏障术对年轻恒牙根尖炎患者的治疗效果及安全性分析

目的探讨iRoot BP Plus根尖屏障术对年轻恒牙根尖炎患者的治疗效果及安全性。方法选取2020年1月至2021年10月新钢中心医院收治的72例年轻恒牙根尖炎患儿作为研究对象,按照随机数字表法分为对照组与研究组,每组36例。对照组采用Vitapex根尖诱导成形术治疗,研究组采用iRoot BP Plus根尖屏障术治疗,两组均观察至术后3个月。比较两组临床疗效及局部肿痛程度[视觉模拟评分法(VAS)]、龈沟液内细胞生长因子水平[碱性成纤维细胞生长因子(bFGF)、血管内皮细胞生长因子(VEGF)]、牙根生长发育状况、并发症发生率。结果研究组治疗总有效率为94.44%,高于对照组的77.78%,差异有统计学意义(P<0.05);术后1个月,两组局部肿痛VAS评分低于术前,且研究组低于对照组,差异有统计学意义(P<0.05);术后3个月,两组龈沟液内bFGF、VEGF均高于术前,且研究组高于对照组,差异有统计学意义(P<0.05);术后3个月,两组患牙冠根比及患牙根管壁厚度均高于术前,且研究组高于对照组,差异有统计学意义(P<0.05);研究组术后3个月并发症发生率为5.56%,低于对照组的25.00%,差异有统计学意义(P<0.05)。结论iRoot BP Plus根尖屏障术治疗年轻恒牙根尖炎患者疗效确切,能减轻肿痛等症状,调节龈沟液相关细胞生长因子表达,促进牙根生长发育,且安全性高,值得临床推广应用。

Safety assessment methodology for a German high-level waste repository in clay formations

In the ANSICHT project that was jointly carried out by DBE TECHNOLOGY Gmb H,BGR,and GRS g Gmb H,two generic geological site models were used to develop a first draft of a methodology to demonstrate the safety of a high-level waste(HLW) repository in argillaceous formations in Germany,taking into account the regulatory requirements.The main results of the project are characterised by the developed repository concepts adapted to the geological conditions.The specific quantifications of the integrity criteria and their exemplary application with calculational proofs were used to demonstrate the integrity of the host rocks.The development of site-specific FEP(features,events,and processes) cataloges provided a complete system description for evaluation of the repository evolution.The developed work flow of the demonstration concept illustrated the complete sequence of the safety proof in a transparent way.It shows that various steps have to be performed,possibly iteratively,to provide a successful safety proof.The results form a useful tool in the pending search for a HLW repository site,especially when providing a basis for comparing safety analyses of different sites in Germany.

Integrated risk management: a Petrobras application in offshore well construction safety to minimize critical emergency disconnections

In order to avoid mistakes and to save a great deal of time in analysis, an innovative methodology was developed that can analyze the well operations and rig characteristics involved to define the best emergency disconnect sequence （EDS） available. A solution was developed based on the characteristics of the rigs and blowout preventers （BOPs）, and six variables were considered that directly affect the choice of EDS. All possible combinations of 64 scenarios were analyzed, and the priority of choice of the EDS was defined empirically. This paper presents an approach to EDS risk management and examples of exposure time （time without riser safety margin and shear capability） for the same well, which can be lowered from 13% to 0.1%. The impact of this reduction is related to the ability of the BOP to cut some of the heavy casings, in addition to improved availability of EDS modes. This implementation opened up many possibilities for the performance of risk exposure analysis, enabling comparison of several BOP configurations of contracted rigs and selection of the best options. This innovative approach allowed a better management of the rig schedules, prioritizing safety aspects and making it possible to allocate the fleet in a systematic way.

Development of a battery-operated floating-electrode dielectric barrier discharge plasma device and its characteristics

In this work,a portable floating-electrode dielectric barrier discharge(FE-DBD)device is designed with a rechargeable battery as the power supply.The characteristics of the FE-DBD with a metal electrode and human hand are studied and compared.The human contact safety is verified by calculating the current through the human body based on the equivalent circuit model.Escherichia coli inactivation experiments confirm the efficacy of the FE-DBD device in the envisaged applications.

一种基于控制围栏函数的安全约束优化求解方法

为提高MPC-CBF算法框架解空间的可行域范围,提出了一种可优化的离散控制围栏函数,将控制围栏函数衰减系数作为一可变参数进行优化,从而动态调整CBF约束范围,实现安全性与可行性的综合优化处理。实验结果表明:该改进算法可有效提升MPC-CBF算法框架解空间的可行域范围,并可在保证安全约束得到有效满足的前提下,生成多样化的运动行为。

非线性系统的安全分析与控制:障碍函数方法

近年来,非线性系统的安全分析与控制已成为控制领域中的热门研究方向,而障碍函数则是该方向的一种重要工具.基于障碍函数的安全分析与控制方法具有计算效率高、鲁棒性强等优点.本文首先从多个角度介绍了基于障碍函数的非线性系统安全性分析的理论成果,并进一步综述了障碍函数方法在非线性系统安全控制中的最新进展.最后,简要地介绍了当前基于障碍函数的安全分析与控制理论中一系列尚未解决的问题,并指出了未来可能发展的一些研究方向.

永久性弃置井封堵效果的试验评价

随着油气资源的持续开发,无商业开采价值的油气弃置井日益增多,弃置井的封堵效果是其永久保持井筒完整性的关键。为此,基于永久性弃置井特点及封堵技术规范和要求,提出了一种永久性弃置井封堵屏障单元的封堵效果测试及评价方法,自主研发了评价套管内水泥塞和套管外水泥环封堵有效性及可行性的测试系统,并模拟我国西北典型井井下工况开展了弃置井管内水泥塞和管外水泥环的密封性能测试和界面力学性能测试,获取了水泥塞、水泥环的突破压力、击穿压力及其与套管之间界面力学参数,分析了水泥塞/水泥环长度对其密封性能的影响规律,并拟合得到了水泥塞/水泥环长度与封堵压力的函数关系,对比了水泥塞与水泥环的密封性能及界面力学性能,明确了水泥塞/水泥环密封性能与界面力学性能之间的相关性,发现了水泥塞与水泥环封堵屏障的薄弱区。研究成果可为永久性弃置井封堵水泥浆体系及施工参数的“量身定制”提供依据。

基于停车视距约束的高速公路弯道声屏障设置可行性研究

为探究高速公路弯道声屏障设置的可行性,基于横净距探究视距最差情况下弯道声屏障对停车视距的影响。通过HintCAD构建高速公路不同曲线类型、设计速度、车道数、圆曲线半径组合而成的曲线平面图模型,生成每种组合下平面图的视距包络图,共获得180组不同组合情况下的平曲线最大横净距。引入回归分析方法得到高速公路弯道路段满足不同停车视距约束的最大横净距与圆曲线半径之间的关系模型。根据关系模型和高速公路曲线路段实际横净距,计算出曲线路段加入声屏障后满足停车视距约束的最小圆曲线半径阈值,可用于判断曲线路段设置声屏障的可行性。

基于改进DS-贝叶斯网络的滩海管道风险评价

为量化滩海油气管道泄漏风险,提出一种结合改进证据理论和贝叶斯网络的风险评价模型。通过构建滩海管道泄漏风险指标体系、安全屏障模型,确定贝叶斯网络拓扑结构。引入改进证据理论融合专家打分意见,确定节点先验概率与条件概率,由贝叶斯网络正反推断出滩海管道的泄漏风险与风险因子敏感性。模型可准确计算管道泄漏风险值且降低意见均衡化与评价的主观性。为验证模型的适用性,计算了某滩海管道泄漏风险值,结果显示该海域管段的泄漏风险值为0.001 52。

复杂多孔结构对丙烷爆炸的影响

为了揭示复杂多孔障碍物对丙烷/空气爆炸动力学参数的影响,采用小尺寸爆炸管道,运用高速摄像技术和数据采集手段,分析不同试验条件下火焰穿越复杂多孔障碍物前后的形态及管内压力变化。结果表明:受复杂多孔障碍物的影响,爆炸火焰穿过障碍物时,会触发Richtmyer Meshkov不稳定性,火焰失稳,形态复杂;随着障碍物阻塞率的增加,爆炸火焰到达障碍物所在位置的时间减小;复杂多孔障碍物对爆炸火焰有明显的激励作用,火焰传播速度随障碍物阻塞率的增加而增加;在所有试验中,火焰传播速度均在0.4~0.5 m的管段攀升至最大;障碍物阻塞率增加,管道出口端的最大爆炸压力增加,达到最大爆炸压力所需的时间增加,爆燃指数随障碍物上圆孔的间距增加而增加。

我国高速铁路声屏障气动效应研究与探索

针对高速铁路声屏障的安全可靠性,从气动效应角度阐述其研究现状、研究成果及存在的挑战,并基于我国高速铁路声屏障应用场景,探讨列车脉动力的主要影响因素和声屏障结构的振动特性,结合技术标准中与气动效应相关的要求和规定,提出完善标准体系的相关建议,并对未来的重点研究方向进行展望。结果表明:列车脉动力受列车运行速度、列车车型及声屏障设置位置等因素的共同影响,列车脉动力与运行速度的平方基本服从线性关系;声屏障气动效应还与车头流线型、车体截面形状等列车气动性能参数相关,相同速度条件下不同车型的脉动力差异可达45%;在列车脉动力作用下,声屏障钢立柱以横向振动为主,呈现典型受弯构件的特征,而单元板以整体往复横向运动为主,振幅受安装状态的影响显著,声屏障动力性能评估重点为结构的低频振动;未来可结合声屏障结构振动特征和服役性能变化情况,深化声屏障气动荷载产生机理和动力分析方法的研究,探索声屏障服役性能演变机理和规律,完善声屏障结构安全性能检测评估体系,发展快速高效检测技术。

风屏障破坏所致风载突变对桥梁列车行车安全影响研究

为研究桥上风屏障局部破坏对桥梁列车行车安全性的影响,以某四塔公铁两用斜拉桥为背景,进行列车动力响应和行车安全性影响参数分析。推导列车通过风屏障破坏段时车辆和桥梁的风荷载,并通过桥梁和列车节段模型风洞试验,测得计算所需气动力系数;在此基础上建立风-车-轨-桥耦合振动模型,研究了风屏障破坏段长度、平均风速和列车车速对列车动力响应及行车安全的影响。结果表明:突风效应会导致列车横向位移达到最大值,遮风效应会使列车横向加速度达到最大值;随风屏障破坏段长度、平均风速和列车车速的增加,列车动力响应随之增加;风屏障破坏会增加列车的轮重减载率和脱轨系数,并且高风速下各节车辆在风屏障破坏段的脱轨系数差异较大;仅在风速不大于10 m/s时,列车可以180 km/h的车速安全通过风屏障破坏段。

安全的混成系统神经网络控制器生成与验证

控制器生成是混成系统控制中的重要问题.生成具有安全保证的控制器,关系着混成系统在安全攸关领域的使用.提出了一种为混成系统生成具有安全保证的神经网络控制器的方法.神经网络控制器的安全性由与其同时生成的障碍证书保证.为了生成安全的神经网络控制器,首先确定控制器的网络结构,并基于混成系统构造训练数据集;然后,根据保证控制器安全的障碍证书条件编码神经网络训练时的损失函数.当训练完成后,学习到的神经网络控制器对于训练数据集中的数据是安全的,但对于整个混成系统可能并不安全.为了检验学习到的控制器在整个系统上的安全性,将其安全验证问题转化为一组混合整数规划问题,并使用数值优化器求解,以得到形式化保证的结果.工作实现了安全神经网络控制器生成工具SafeNC,并评估了它在8个基准系统上的性能.实验结果表明:SafeNC可以生成包含6个隐藏层的具有1804个神经元的安全神经网络控制器;同时,与现有方法相比,SafeNC可为更复杂的系统生成安全的神经网络控制器,更有效且更具扩展性.

深远海恶劣海洋环境下溢油回收作业的风险评估方法

为了更科学合理地对深远海恶劣海洋环境下溢油作业进行综合风险评估,建立了一种多层耦合关系视角下的安全屏障绩效评估模型,基于各类安全屏障的特点,分别采用适宜的绩效评估方法,计算各类屏障的绩效水平,精细展现各类风险因素对系统整体安全状态的影响程度,量化深远海恶劣海洋环境下溢油回收作业的安全风险等级。结果显示,深远海恶劣海洋环境下溢油回收作业整体风险处于较高等级。从屏障层次细化角度来看,人员管理屏障与环境屏障风险等级处于较高风险,设备屏障风险处于中等风险。同时,针对各层屏障中定量挖掘出的较高风险因素,提出针对性的安全管控措施,也为其他类型的深远海救助作业风险评估提供有益借鉴。