ROS2 Real-time Performance Optimization and Evaluation

Real-time interaction with uncertain and dynamic environments is essential for robotic systems to achieve functions such as visual perception,force interaction,spatial obstacle avoidance,and motion planning.To ensure the reliability and determinism of system execution,a flexible real-time control system architecture and interaction algorithm are required.The ROS framework was designed to improve the reusability of robotic software development by providing a distributed structure,hardware abstraction,message-passing mechanism,and application prototypes.Rich ecosystems for robotic development have been built around ROS1 and ROS2 architectures based on the Linux system.However,because of the fairness scheduling principle of the default Linux system design and the complexity of the kernel,the system does not have real-time computing.To achieve a balance between real-time and non-real-time computing,this paper uses the transmission mechanism of ROS2,combines it with the scheduling mechanism of the Linux operating system,and uses Preempt_RT to enhance the real-time computing of ROS1 and ROS2.The real-time performance evaluation of ROS1 and ROS2 is conducted from multiple perspectives,including throughput,transmission mode,QoS service quality,frequency,number of subscription nodes and EtherCAT master.This paper makes two significant contributions:firstly,it employs Preempt_RT to optimize the native ROS2 system,effectively enhancing the real-time performance of native ROS2 message transmission;secondly,it conducts a comprehensive evaluation of the real-time performance of both native and optimized ROS2 systems.This comparison elucidates the benefits of the optimized ROS2 architecture regarding real-time performance,with results vividly demonstrated through illustrative figures.

A Survey on the Evaluation Literacy of College English Teachers Under the Online Teaching Mode

Under the online teaching model,the evaluation literacy of college English teachers has become one of the critical factors affecting students’learning effects[1].This study uses a self-compiled questionnaire to investigate the current status of evaluation literacy of college English teachers under the online teaching model from four aspects:evaluation awareness,evaluation knowledge,evaluation ability,and evaluation ethics.The results show that college English teachers’overall evaluation literacy level is relatively high,but there are areas for improvement.Based on the survey results,suggestions are put forward to improve teachers’evaluation literacy,such as changing teaching concepts and increasing self-reflection;strengthening training and learning to enhance professional development awareness;conducting cooperative research and emphasizing team strengths.

Restoring force correction based on online discrete tangent stiffness estimation method for real-time hybrid simulation

In real-time hybrid simulation（RTHS）, it is difficult if not impossible to completely erase the error in restoring force due to actuator response delay using existing displacement-based compensation methods. This paper proposes a new force correction method based on online discrete tangent stiffness estimation（online DTSE） to provide accurate online estimation of the instantaneous stiffness of the physical substructure. Following the discrete curve parameter recognition theory, the online DTSE method estimates the instantaneous stiffness mainly through adaptively building a fuzzy segment with the latest measurements, constructing several strict bounding lines of the segment and calculating the slope of the strict bounding lines, which significantly improves the calculation efficiency and accuracy for the instantaneous stiffness estimation. The results of both computational simulation and real-time hybrid simulation show that：（1） the online DTSE method has high calculation efficiency, of which the relatively short computation time will not interrupt RTHS; and（2） the online DTSE method provides better estimation for the instantaneous stiffness, compared with other existing estimation methods. Due to the quick and accurate estimation of instantaneous stiffness, the online DTSE method therefore provides a promising technique to correct restoring forces in RTHS.

Direct immune-SCIR public-opinion propagation model based on real-time online users

Current public-opinion propagation research usually focused on closed network topologies without considering the fluctuation of the number of network users or the impact of social factors on propagation. Thus, it remains difficult to accurately describe the public-opinion propagation rules of social networks. In order to study the rules of public opinion spread on dynamic social networks, by analyzing the activity of social-network users and the regulatory role of relevant departments in the spread of public opinion, concepts of additional user and offline rates are introduced, and the direct immune-susceptible, contacted, infected, and refractory (DI-SCIR) public-opinion propagation model based on real-time online users is established. The interventional force of relevant departments, credibility of real information, and time of intervention are considered, and a public-opinion propagation control strategy based on direct immunity is proposed. The equilibrium point and the basic reproduction number of the model are theoretically analyzed to obtain boundary conditions for public-opinion propagation. Simulation results show that the new model can accurately reflect the propagation rules of public opinion. When the basic reproduction number is less than 1, public opinion will eventually disappear in the network. Social factors can significantly influence the time and scope of public opinion spread on social networks. By controlling social factors, relevant departments can analyze the rules of public opinion spread on social networks to suppress the propagate of negative public opinion and provide a powerful tool to ensure security and stability of society.

Comparison of delay compensation methods for real-time hybrid simulation using frequency-domain evaluation index

The delay compensation method plays an essential role in maintaining the stability and achieving accurate real-time hybrid simulation results. The effectiveness of various compensation methods in different test scenarios, however, needs to be quantitatively evaluated. In this study, four compensation methods （i.e., the polynomial extrapolation, the linear acceleration extrapolation, the inverse compensation and the adaptive inverse compensation） are selected and compared experimentally using a frequency evaluation index （FEI） method. The effectiveness of the FEI method is first verified through comparison with the discrete transfer fimction approach for compensation methods assuming constant delay. Incomparable advantage is further demonstrated for the FEI method when applied to adaptive compensation methods, where the discrete transfer function approach is difficult to implement. Both numerical simulation and laboratory tests with predefined displacements are conducted using sinusoidal signals and random signals as inputs. Findings from numerical simulation and experimental results demonstrate that the FEI method is an efficient and effective approach to compare the performance of different compensation methods, especially for those requiring adaptation of compensation parameters.

A Study of Appling Online Writing Website to English Writing Teaching: A Structured Critical Review and Evaluation of OWL Online Writing Lab

This report is to evaluate an online writing website. The name of the online resource is the Purdue Online Writing Lab (http://owl.english.purdue.edu/owl/). This website at Purdue University offers writing resources and instructional materials for both teachers and students for in-class or out-of-class teaching and learning of writing. Its interactive, integrative, and pragmatic approach to the teaching and learning of writing on the Internet deserves our attention.

Online Delay-Evaluation Control for Networked Control Systems

This paper presented an evaluation approach of time delays for networked control systems (NCS). An improved scheme based on optimal LQG control was designed to achieve desired performance despite the uncertain delays in the system. The experimental results illustrate the effectiveness of the proposed control design and satisfactory performance of the closed loop system.

Online Delay-Evaluation Approach in Networked Control Systems

This paper presents an online evaluation approach of time delays for networked control systems (NCS), which characterizes the time delays without any synchronized clock in the network and any assumptions of time delays. With this approach, an optimal control scheme based on the approach is designed to achieve the desired performance despite the uncertain delays in the system. The experimental results based on CANbus illustrate the effectiveness of the proposed control design and satisfactory performance of the closed-loop system.

Should Online Essays Be Used in Academic Evaluations?

China＇s current academic evaluation system sees publications in core journals as a basic index to measure the academic qualification and quality of an academic institute,

A lateral-immobilization zebrafish microfluidic chip-based system for in vivo real-time evaluation of antithrombotic agents

Thrombosis remains a major global health concern mainly characterized by high rates of morbidity and mortality.Animal models serve as an indispensable tool to understand the underlying pathogenesis of thrombosis and assess the efficacy of novel antithrombotic drugs.Currently,zebrafish has emerged as a valuable model organism for thrombosis research.However,the traditional method of studying zebrafish thrombosis requires a laborious and time-consuming procedure,including anesthesia and manual immobilization of zebrafish.In this study,based on hydrodynamic force,a lateral-immobilization zebrafish microfluidic chip(LIZMC)was designed to evaluate the cardiovascular system of multiple larvae within a single microscope field of view.Specifically,coupling with microscope imaging,real-time monitoring of the peripheral blood circulation in the tail of phenylhydrazine(PHZ)-induced zebrafish thrombosis was enabled.Furthermore,the reliability of LIZMC for in vivo evaluation of antithrombotic agents in zebrafish was verified using aspirin.Collectively,this novel LIZMC-based system can be used for in vivo zebrafish thrombosis studies and rapid screening of antithrombotic agents.

以Online Judge为突破口的程序设计课程全过程学业评价改革实践

针对传统学业评价模式的弊病,本文以我校高级语言程序设计课程为例,介绍了以Online Judge(程序在线评测)平台为突破口,实现全过程学业评价的改革,提升学生培养质量。

Implementation and Evaluation of Infertility Reflection in Early Pregnancy after the Use of Assisted Reproductive Technology: A Feasibility Study

Background: This study aims to evaluate the infertility reflection in early pregnancy after assistive reproductive therapy (ART), including 1) process evaluation (the use and evaluation of infertility reflection) and 2) outcome evaluation (satisfaction of care needs, anticipatory anxiety towards the loss of a pregnancy or fetus, cognition of infertility experience, and depression and anxiety). Methods: This program evaluation study used a one-group pre-post-test design. The participants were 50 primiparas who had undergone ART at two fertility treatment facilities in a metropolitan area in Japan. For the infertility reflection, they conducted an online reflection. Data were collected three times: at the 5th week of pregnancy (Time 1), the 8th week of pregnancy as the final consultation at the clinic (Time 2), and the 16th week of pregnancy as the final point of early pregnancy (Time 3). Results: The data from 40 participants were analyzed. More than 80% of the users of the online reflection positively evaluated the appropriateness and usefulness of the methods and contents. Organized thoughts and feelings by reflection were shown as the reasons for the usefulness. The evaluation of the online reflection showed a relatively strong correlation with the Care Need Satisfaction Scale (CNSS) for both Time 2 and Time 3, but the online reflection did not show a significant correlation with the other outcome variables. There were no significant differences in outcome variables between users and non-users of online reflection between Time 2 and Time 3. Conclusions: Attempts at the reflection in early pregnancy require modified methods that do not have a negative impact and lead to the fulfillment of needs.

A comparative analysis of major Chinese and English online question-answering communities

This paper compares 12 representative Chinese and English online questionanswering communities(Q&A communities) based on their basic functions, interactive modes, and customized services. An empirical experiment from a comparative perspective was also conducted on them by using 12 questions representing for four types of questions,which are assigned evenly to three different subject fields so as to examine the task performance of these 12 selected online Q&A communities. Our goal was to evaluate those online Q&A communities in terms of their quality and efficiency for answering questions posed to them. It was hoped that our empirical research would yield greater understanding and insights to the working intricacy of these online Q&A communities and hence their possible further improvement.

Mechanism and application of an online intelligent evaluation model for energy consumption of a reheating furnace

An online model was proposed to identify the reasons behind changes in the energy consumption of the reheating furnace of a steel processing plant.The heat conversion of the furnace was analyzed and integrated with the fuel consumption of the furnace to obtain a model of the energy consumption.Combined with the mechanism analysis,the basic parameters affecting energy consumption were determined,and four key influencing factors were obtained:furnace output,furnace charging temperature,furnace tapping temperature,and steel type.The specific calculation method of the contribution of each influencing factor was derived to define the conditions of the baseline energy consumption,while the online data were used to calculate the energy value and the actual performance value of the baseline energy consumption.The contribution of each influencing factor was determined through normalization.The cloud platform was used for database reconstruction and programming to realize the online intelligent evaluation of the energy consumption of the reheating furnace.Finally,a case study of the evaluation of the practical energy consumption of a steel rolling furnace in a steel plant was presented.The intelligent evaluation results were quantified and displayed online,and the performance of the system in reducing production line energy consumption was demonstrated.

在线异步联邦学习的客户优化选择与激励

联邦学习能够在保护用户隐私的前提下,使不同的客户端合作共同训练同一模型,如何激励高质量的客户端参与联邦学习是关键。在线联邦学习环境中,由于参与训练的客户端随机到达和离开,每轮参与报价的客户端动态变化,对客户端的在线质量评估与选择是一个难题。针对这一挑战提出了在线联邦学习激励算法,以优化在线客户端的选择和预算分配,提高预算约束下在线环境联邦学习的性能。该算法将预算按阶段划分并根据历史样本信息计算最优的质量密度阈值,其主要思想是对客户端模型质量进行动态评估,在此基础上采用质量阈值准入机制,同时对参与训练的客户端数量进行限制。从理论上证明了激励算法满足激励相容性、预算可行性和个体理性。实验结果表明,提出的在线激励算法在不同比例搭便车客户端的情况下都能有良好的性能,在预算充足且有搭便车和有误标标签的客户端情况下比已有方法在EMNIST-B和CIFAR-10两个数据集上分别提高约4%和10%。

平台型医学课程在线教学学习效果评价指标与评价标准研究

当前,中国高等教育正积极推动高质量发展,提升高等教育在线课程教学质量是我国高等教育实现“变道超车”的重要战略步骤。就医学课程而言,深入研究平台型医学课程在线教学学习效果评价指标与评价标准是进行学习效果评价的重要前提,是提升平台型医学课程在线教学质量的重要基础。根据“以学生发展为中心”的教育理念,以学习效果评价有利于促进学生与教师发展为宗旨,以医学本科生培养目标、毕业要求、课程目标为具体内容,提出平台型医学课程在线教学学习效果评价指标与评价标准,为平台型医学课程在线教学学习效果评价奠定基础,为促进学生自主学习、教学持续改进提供支撑。

大规模线上教学质量保障体系构建与实证分析

随着信息技术对教育教学方式的影响,长期或短期的大规模线上教学已成为突发应急状态下开展教育教学活动的关键手段,在丰富教学模式的同时也对教学质量提出了新挑战。基于评价优化思想,从教学活动内涵特征出发,提出了“实时数据追踪、短期反馈改进、长期评价优化”的大规模线上教学质量保障体系,并依据教学质量监控数据元素设计,针对Q高校大规模线上教学活动中教学资源、课堂主体、教学方式方法、教学效果等数据进行了实证分析,提出的质量保障体系构建和实施途径对大规模线上教学持续改进十分有效。

面向多目标优化主动运维的电能表远程在线评价系统设计

针对传统电能表远程在线评价系统中存在的系统建造成本耗费较大、评价结构过于繁琐等问题,从评价系统的构建和评价算法两方面开展研究。在评价系统的设计方面,加入反馈,使得该评价系统不仅可以整合各项评价指标进行规律化的采集,还可以对评价指标进行实时反馈,提高了评价的效率和评价信息传输的效率。在评价算法方面,基于解耦评价算法对电能表的运行状态和采集数据进行评价,对数据信息进行归纳处理,并根据大量的数据样本进行条理化分析评价。通过仿真实验可知,硬件反馈线路的数据传输效率高达98.6%,具有很好的传输能力。

干部考核标准化线上评议系统的研究和应用

本研究旨在探讨计算机和网络技术在政务部门的标准化应用情景研究,通过设计、研发、应用干部考核标准化线上评议系统,并在疫情特殊环境下得到应用,实现既符合疫情人群不聚集的要求,又加快推进线上考核评议工作标准化的进程,本文对其研究与应用进行了讨论和分析。这些结果对于深入理解政务业务标准化具有重要意义。