Multi-circular formation control with reinforced transient profiles for nonholonomic vehicles:A path-following framework

This article investigates a multi-circular path-following formation control with reinforced transient profiles for nonholonomic vehicles connected by a digraph.A multi-circular formation controller endowed with the feature of spatial-temporal decoupling is devised for a group of vehicles guided by a virtual leader evolving along an implicit path,which allows for a circumnavigation on multiple circles with an anticipant angular spacing.In addition,notice that it typically imposes a stringent time constraint on time-sensitive enclosing scenarios,hence an improved prescribed performance control(IPPC)using novel tighter behavior boundaries is presented to enhance transient capabilities with an ensured appointed-time convergence free from any overshoots.The significant merits are that coordinated circumnavigation along different circles can be realized via executing geometric and dynamic assignments independently with modified transient profiles.Furthermore,all variables existing in the entire system are analyzed to be convergent.Simulation and experimental results are provided to validate the utility of suggested solution.

A Novel Prescribed-Performance Path-Following Problem for Non-Holonomic Vehicles

The issue of achieving prescribed-performance path following in robotics is addressed in this paper,where the aim is to ensure that a desired path within a specified region is accu-rately converged to by the controlled vehicle.In this context,a novel form of the prescribed performance guiding vector field is introduced,accompanied by a prescribed-time sliding mode con-trol approach.Furthermore,the interdependence among the pre-scribed parameters is discussed.To validate the effectiveness of the proposed method,numerical simulations are presented to demonstrate the efficacy of the approach.

Environmental Impact Assessment Follow-Up of Seismic Survey Offshore Activities in Brazil

Follow-up of environmental impacts is an integral part of the Environmental Impact Assessment (EIA) process, closely related to the effectiveness of the instrument. EIA follow-up has been receiving a lot of interest from scientists and practitioners, though it is recognized as one of the weakest points of EIA systems globally. Also, EIA follow-up is influenced by the context, mainly in terms of the types of projects or activities and their related impacts on the environment. Therefore, the present paper is focused on the investigation of the follow-up stage applied to the activity of seismic survey coupled with offshore oil & gas exploitation in Brazil. Research was based on a qualitative approach that included document analysis and semi-structured interviews with analysts involved in EIA processes, and sought to generate evidence of effectiveness of the EIA follow-up as conducted by the Federal Environment Agency (Ibama) in order to situate the practice of follow-up in the broader context of international best practice principles. Based on the findings, it was concluded that, due to the peculiarities of offshore seismic survey, it is necessary to promote adaptations in the procedures for monitoring impacts in order to ensure proper alignment with the principles and conceptual foundations that guide EIA practice. Specifically, the timing of the execution of the activity imposes challenges for its integration into the “conventional” cycle that has guided the monitoring of the impacts in the EIA of projects.

Parent-Reported Reasons for Loss-to-Follow Up in Patients Hospitalized at the Neonatology Unit at Laquintinie

Introduction: Despite the known benefits of newborn follow-up clinics, attendance has historically been difficult. Infants with reported follow-up difficulty have a greater incidence of severe sensorimotor and cognitive deficits and poorer access to early intervention programs. Our objective was to determine the parent-reported reasons for loss-to-follow up in patients hospitalised at the neonatology unit of Laquintinie Hospital. Methodology: We carried out a cross-sectional study through phone interviews with parents/caregivers of patients hospitalised at Laquintinie over a 2-year period from 1st January 2021 to 31st December 2022. A non-standardised structured interview guide was used for data collection. Loss-to-follow up referred to absence to at least one visit as recorded in the neonatal follow-up chart. All necessary administrative and ethical considerations were duly respected. Results: Most neonates were born through vaginal delivery (n = 313, 69.45%). The neonates were admitted at a median gestational age of 33 weeks (Q1-Q3;32 - 35) and the median duration of hospitalisation was 12 days (Q1 - Q3;8 - 18). A total of 23 neonates had died at the time of interview giving a mortality rate of 5.1%. The three most reported reasons for loss-to-follow-up was lack of money (n = 310, 68.13%), assumption that follow-up had ended (n = 37, 8.13%), and newborn that died (n = 23, 5.1%). Conclusion: This study highlights the significant impact of financial constraints and absence of a robust follow-up system on poor uptake of neonatal follow-up post-discharge in resource limited settings like Cameroon. Our results serve as advocacy for national health insurance especially in neonates.

缺乏位置信息的视觉移动机器人leader-following编队控制

针对视觉移动机器人编队在缺乏位置信息情况下的控制问题,提出一种基于视觉的leader-following编队反馈控制方法。该方法利用leader标志物特征点在follower摄像机像平面上的坐标信息设计了观测器,对leader与follower间的相对位置进行估计,基于相对位置估计量与它们速度的关系,设计出leader-following编队反馈控制器,通过Lyapunov理论证明了闭环系统的稳定性。仿真结果表明,该控制方法能有效解决缺乏位置信息情况下视觉移动机器人编队的控制问题。

FEA-Based Fatigue Life Assessment of Cycloidal Displacement Cam and Flat-Faced Follower Mechanism

Cam-followers provide reliable and controlled motions in various mechanical systems. Due to the highly fluctuating load between the cam and follower in operation, the cam-follower may be subjected to a high risk of contact fatigue failure. This paper assesses the fatigue life of a cycloidal displacement cam and a flat-faced follower under the defined loads and constraints. Computer-aided design (CAD) model of the cam-follower is developed in CATIA software and imported to ANSYS software for finite element analysis (FEA) of fatigue life. MATLAB programming is developed for determining the appropriate spring constant and pre-load force to always keep the cam and follower in contact. The fatigue life of the cam-follower has been estimated under the specified operating conditions. The analysis method can be applied to investigate the fatigue life of cams with other profiles, including the modified trapezoidal functions, polynomial functions, etc.

GRACE与GRACE Follow-On重力卫星数据揭示出的黄河流域2002-2020年干旱特征

研究黄河流域干旱时空变化特征,对认知黄河流域水资源演化规律具有重要意义。本文充分利用GRACE(gravity recovery and climate experiment)与GRACE-FO(GRACE Follow-On)重力卫星在大尺度范围下监测水文信息变化中的优势,基于2002年4月至2020年7月GRACE和GRACE-FO RL06 Mascon数据,计算了黄河流域陆地水储量异常(terrestrial water storage anomaly,TWSA)及对应的水储量亏损赤字(water storage deficit index,WSDI),据此分析了黄河流域上游、中下游干旱事件及其严重性、干旱持续时间、平均与最大水储量赤字等干旱特征,并与其他4种常用干旱指数,标准降水蒸散发指数(standardized precipitation evaporation index,SPEI)、自矫正帕尔默干旱指数(self correct-Palmer drought severity index,sc-PDSI)、标准化降水指数(standardized precipitation index,SPI)和标准化径流指数(standardized runoff index,SRI)识别结果进行了对比分析。研究结果表明:在WSDI识别出的黄河流域上游、中下游分别发生的5期干旱事件及其对应的干旱等级中,存在其他传统干旱指数未识别现象;在黄河流域以往干旱事件识别中,WSDI也展现出了较其他4种传统干旱指数显著的识别优势。相比传统干旱指标多仅依赖于稀疏地表水文监测信息,基于重力卫星监测数据的WSDI干旱指标可在大尺度范围下有效识别出流域干旱特征。

Leader-following多自主体系统时变编队跟踪控制

考虑时变时延,研究了高阶leader-following多自主体系统的分布式时变编队跟踪控制问题.针对连续高阶多自主体系统,设计了基于观测器的时变编队跟踪控制协议,通过状态变换,将系统的时变编队跟踪控制问题,转变为误差系统的稳定性问题.然后利用图论及李雅普诺夫稳定定理,研究了系统实现时变编队跟踪控制的充分条件,并且指出时变编队参考函数与时变时延无关.最后,数据仿真结果证明了所设计的协议能使follower自主体实现时变编队,并且跟踪leader自主体的轨迹.

Finite-Time Sideslip Differentiator-Based LOS Guidance for Robust Path Following of Snake Robots

This paper presents a finite-time sideslip differentiator-based line-of-sight(LOS)guidance method for robust path following of snake robots.Firstly,finite-time stable sideslip differentiator and adaptive LOS guidance method are proposed to counteract sideslip drift caused by cross-track velocity.The proposed differentiator can accurately observe the cross-track error and sideslip angle for snake robots to avoid errors caused by calculating sideslip angle approximately.In our method,the designed piecewise auxiliary function guarantees the finite-time stability of position errors.Secondly,for the case of external disturbances and state constraints,a Barrier Lyapunov functionbased backstepping adaptive path following controller is presented to improve the robot’s robustness.The uniform ultimate boundedness of the closed-loop system is proved by analyzing stability.Additionally,a gait frequency adjustment-based virtual velocity control input is derived to achieve the exponential convergence of the tangential velocity.At last,the availability and superiority of this work are shown through simulation and experiment results.

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.

LSTM-DPPO based deep reinforcement learning controller for path following optimization of unmanned surface vehicle

To solve the path following control problem for unmanned surface vehicles(USVs),a control method based on deep reinforcement learning(DRL)with long short-term memory(LSTM)networks is proposed.A distributed proximal policy opti-mization(DPPO)algorithm,which is a modified actor-critic-based type of reinforcement learning algorithm,is adapted to improve the controller performance in repeated trials.The LSTM network structure is introduced to solve the strong temporal cor-relation USV control problem.In addition,a specially designed path dataset,including straight and curved paths,is established to simulate various sailing scenarios so that the reinforcement learning controller can obtain as much handling experience as possible.Extensive numerical simulation results demonstrate that the proposed method has better control performance under missions involving complex maneuvers than trained with limited scenarios and can potentially be applied in practice.

Investigating the characteristic delay time in the leader–follower behavior in children single-file movement

The single-file movement experiment offered a convenient way to investigate the one-dimensional leader–follower behavior of pedestrians. This study investigated the time delays of children pedestrians in the leader–follower behavior by introducing a time-dependent delayed speed correlation. A total of 118 German students from the fifth grade(aged11–12 years old) and the 11th grade(aged 17–18 years old) participated the single-file experiment. The characteristic delay time for each pedestrian was identified by optimising the time-dependent delayed speed correlation. The influences of the curvature of the experimental scenario, density, age, and gender on the delay time were statistically examined. The results suggested that to a large extent, the revealed characteristic delay time was a density-dependent variable, and none of the curvatures, the age and gender of the individual, and the age and gender of the leader had a significant influence on it. The findings from this study are variable resources to understand the leader–follower behavior among children pedestrians and to build related simulation models.

Knowledge,perceptions,and practice towards adverse events following immunization surveillance among vaccination workers in Zhejiang province,China

Objective:To access the level of knowledge,perceptions,and practice towards adverse events following immunization(AEFI)surveillance among vaccination workers in Zhejiang province,China.Methods:This was a cross-sectional survey involving 768 vaccination workers.Data were collected using self-administered questionnaires and analyzed by using SAS 9.3 software.Knowledge,perceptions,and practice on AEFI surveillance were summarized using frequency tables.The mean±SD value was used as the cut-off for defining good(values≥mean)and poor(values<mean)knowledge,perceptions or practice.Binary logistic regression analysis was used to determine sociodemographic variables associated with knowledge,perceptions,and practice towards AEFI.Results:The proportions of good knowledge,perceptions and practice on AEFI surveillance were 78.13%,57.81%and 66.15%,respectively.Having a higher education background,longer years of experience,previous training on AEFI and≥30 years of age were factors associated with good knowledge,perceptions and practice on AEFI surveillance among vaccination workers.Conclusions:Over half of the respondents had good knowledge,perceptions and practice on AEFI surveillance work.Interventions on improving the vaccination workers’knowledge,perceptions and practice on AEFI surveillance should be considered in order to develop a more effective surveillance system.

Trade credit financing for supply chain coordination under financial challenges:a multi‑leader–follower game approach

This study is designed to solve supply chain inefficiencies caused by some members’financial problems,such as capital shortages and financing restrictions in a stochastic environment.To this end,we have established a supply chain finance framework by designing two novel coordinating contracts based on trade credit financing for different problem settings.These contracts are modeled in the form of multi-leader Stackelberg games that address horizontal and vertical competition in a supply chain consisting of multiple suppliers and a financially constrained manufacturer.However,previous studies in the trade credit literature have addressed only simple vertical competition,that is,seller-buyer competition.To solve the proposed models,two algorithms were developed by combining population-based metaheuristics,the Nash-domination concept,and the Nikaido-Isoda function.The results demonstrate that the proposed supply chain finance framework can eliminate supply chain inefficiencies and make a large profit for suppliers,as well as the financially constrained manufacturer.Furthermore,the results of the contracts’analysis showed that if the manufacturer is required to settle its payments to suppliers before the end of the period,the trade credit contract cannot coordinate the supply chain because of a lack of incentive for suppliers.However,if the manufacturer is allowed to extend its payments to the end of the period,the proposed trade credit financing contract can coordinate the supply chain.Finally,the sensitivity analysis results indicate that the worse the financial status of the manufacturer,the more bargaining power suppliers have in determining the contract parameters for more profit.

Precious Scrolls of Chinese Devout Women Buddhist Followers:A Case Study of Wilt Idema’s Pitfalls of Piety for Married Women

Deeply-rooted in China’s popular culture,precious scrolls(Baojuan)are the golden material to display popular religious belief of the mass.Based on the rare texts sorted and annotated by Shang Lixin,Dutch Sinologist Wilt L.Idema continues his journey of translating precious scrolls.Focused on the theme of devoted women Buddhist followers in Ming dynasty,he explores the ethical choices of married women in facing the betrayal of servants or concubines.His translations not only add important reading material to Western readers in the field of Chinese popular literature,but also set standard for the coming translators in rendering Chinese ballads.

综合心理行为护理对后续精神分裂症患者负性情绪和认知功能的影响

目的:探讨综合心理行为护理对精神分裂症后续情绪行为反应和功能情况的影响。方法:选择2022年10月1日~2023年11月30日收治的248例精神分裂症患者,根据随机数字表法分为对照组和研究组各124例,两组均按照医嘱服用药物治疗,对照组采用常规护理,研究组采用综合心理行为护理;比较两组护理前后认知功能[采用MATRICS共识认知成套测验(MCCB)]、负性情绪[采用焦虑自评量表(SAS)、抑郁自评量表(SDS)],患者对护理的满意度。结果:护理后,研究组MCCB中语言流畅性、连线、数字序列、空间广度、语言记忆、持续操作管理、情绪管理维度均高于护理前(P<0.01,P<0.05),对照组语言流畅性、连线、数字序列、空间广度、持续操作管理、情绪管理维度评分均高于护理前(P<0.01,P<0.05),研究组语言流畅性、连线、数字序列、空间广度、语言记忆、视觉记忆、持续操作管理、情绪管理维度评分均高于对照组(P<0.01,P<0.05);护理后,两组SDS、SAS评分均低于护理前(P<0.01),且研究组低于对照组(P<0.01);研究组患者对护理的满意度高于对照组(P<0.01)。结论:综合心理行为护理对后续神经分裂症患者负性情绪、认知功能均具有改善作用,提高患者对护理的满意度。

良性阵发性位置性眩晕患者七年大数据回顾分析

目的良性阵发性位置性眩晕(BPPV)是最常见的外周性前庭疾病,但目前我国尚缺乏对BPPV大样本数据的回顾性分析,本研究旨在为BPPV患者家庭疾病预警和防范提供相应的理论依据。方法回顾性选取2014年6月—2021年6月中国人民解放军总医院眩晕诊疗中心数据库中眩晕患者45807例的临床资料,其中符合BPPV诊断患者5883例,根据其类型分类,统计患者年龄、性别、就诊时间、首诊BPPV类型、复诊BPPV类型等信息。使用Python 3.7进行数据可视化。结果BPPV患者中,女性3909例,男性1974例,50~59岁人群BPPV患者最多,且各BPPV类型中,女性患者比例均高于男性患者。所有眩晕患者位置性试验(+)阳性率为12.8%。不同类型BPPV比例中后管BPPV比例为64.5%,水平管BPPV比例为30.9%。有1092例BPPV复诊记录,首次诊断BPPV至复诊阴性有411例,234例患者BPPV类型在2~6次的就诊过程中有改变,BPPV类型转换比较常见的是左右耳PC-BPPV之间变化(71例)。结论本研究大数据显示,BPPV患者主要分布在50岁左右人群,女性患者约为男性的2倍。LC-BPPV患者比例远高于前期研究数据,约占所有BPPV患者的30.9%。在长期随访中,除大部分患者的BPPV类型没有发生变化外,主要的耳石变化存在后管侧别之间、后管与水平管之间进行转换的趋势。

《广州管圆线虫病诊断标准》(WS/T 321—2010)在福建省和云南省实施情况的跟踪评价

目的了解《广州管圆线虫病诊断标准》(WS/T 321—2010)(简称《标准》)的实施情况,为《标准》的推广和进一步修订、完善提供科学依据。方法通过分层抽样的方式抽取福建省和云南省的省、市、县和乡镇4级的疾病预防控制机构(简称疾控机构)和医疗机构的专业技术人员作为调查对象,采用调查对象自填问卷的方式开展《标准》实施情况调查。结果共调查工作人员308人,回收有效问卷308份。《标准》知晓率为71.10%(219/308),不同特征调查对象中,≥50岁(81.40%,35/43)、市级单位(79.76%,67/84)、疾控机构(88.24%,105/119)、从事寄生虫病防治工作(85.71%,114/133)、高级职称(82.86%,58/70)、本科文化程度(77.09%,138/179)、公共卫生专业(86.21%,75/87)等人群的《标准》知晓率较高,且随着年龄增加和职称升高,《标准》知晓率呈上升趋势(χ^(2)_(趋势)=8.272、8.258,P均<0.01);知晓途径主要是业务培训(65.30%,143/219)和自主查阅(60.73%,133/219)。在《标准》的使用情况方面,知晓《标准》的调查对象中,有75.34%(165/219)会在工作中使用,15.98%(35/219)会经常使用。不同宣贯方式中,宣传资料的普及率最高(58.77%,181/308);75.32%(232/308)的调查对象认为专题讲座的宣贯效果好。能正确且完整掌握诊断原则、感染方式、临床表现、实验室检查方法和诊断类型等知识的调查对象人数分别为292人(占94.81%)、102人(占33.12%)、130人(占42.21%)、117人(占37.99%)和152人(占49.35%)。绝大多数调查对象(占89.61%,276/308)认为标准的可操作性好或较好。宣贯力度对标准实施的影响最大(占80.84%,249/308)。91.88%(283/308)的调查对象认为现行标准不需要修订。结论《标准》仍适用于当前阶段的诊断需求,应继续加大对专业人员的宣贯力度,提高其认知和应用水平。

老年人体育锻炼与人际交往能力的交叉滞后分析

目的:探讨老年人体育锻炼与人际交往能力的相互作用关系。方法:采用体育锻炼量表与人际交往能力量表,以江西省、贵州省、湖南省及重庆市4所老年大学859名学生为研究对象进行为期6个月的两次追踪调查。结果:①重复测量方差分析结果显示,前后测体育锻炼之间差异不显著,前后测人际交往能力之间差异不显著。②相关分析结果显示,体育锻炼与人际交往能力之间的同时性相关和继时性相关均显著(T1:r=0.47,P<0.001;T2:r=0.17,P<0.001)。③交叉滞后回归分析结果显示,在控制前测人际交往能力后,前测体育锻炼对后测人际交往能力存在显著正向预测作用(β=0.21,P<0.001);在控制前测体育锻炼后,前测人际交往能力对后测体育锻炼存在显著正向预测作用(β=0.19,P<0.001)。结论:老年人体育锻炼与人际交往能力均具有一定的稳定性,体育锻炼与人际交往能力之间存在纵向因果关系,可进行双向正向预测。

跟网型变换器的小扰动同步稳定机理分析与致稳控制

弱电网下,跟网型变换器易出现因阻尼不足导致的小扰动同步失稳问题。为此,该文借鉴复转矩分析理论,计及复杂控制耦合,建立跟网型变换器的复转矩模型。量化多环控制耦合、线路阻抗、控制参数等因素对系统阻尼转矩的影响,从阻尼的角度揭示跟网型变换器的小扰动同步失稳机理。根据理论分析,提出一种基于相位补偿的锁相环阻尼重塑控制策略,通过补偿多环控制耦合引入的负阻尼,增强变换器的小扰动同步稳定性。最后,开展相应的仿真与实验,验证理论分析的正确性与改进控制策略的有效性。