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.

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.

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.

Real-time lane departure warning system based on principal component analysis of grayscale distribution and risk evaluation model

A technology for unintended lane departure warning was proposed. As crucial information, lane boundaries were detected based on principal component analysis of grayscale distribution in search bars of given number and then each search bar was tracked using Kalman filter between frames. The lane detection performance was evaluated and demonstrated in ways of receiver operating characteristic, dice similarity coefficient and real-time performance. For lane departure detection, a lane departure risk evaluation model based on lasting time and frequency was effectively executed on the ARM-based platform. Experimental results indicate that the algorithm generates satisfactory lane detection results under different traffic and lighting conditions, and the proposed warning mechanism sends effective warning signals, avoiding most false warning.

A Non-Contact Original-State Online Real-Time Monitoring Method for Complex Liquids in Industrial Processes

Failures are very common during the online real-time monitoring of large quantities of complex liquids in industrial processes, and can result in excessive resource consumption and pollution. In this study, we introduce a monitoring method capable of non-contact original-state online real-time monitoring for strongly coated, high-salinity, and multi-component liquids. The principle of the method is to establish the relationship among the concentration of the target substance in the liquid （C）, the color space coor- dinates of the target substance at different concentrations （L＊, a＊, b＊）, and the maximum absorption wave- length （λmax）; subsequently, the optimum wavelength λT of the liquid is determined by a high-precision scanning-type monitoring system that is used to detect the instantaneous concentration of the target substance in the flowing liquid. Unlike traditional monitoring methods and existing online monitoring methods, the proposed method does not require any pretreatment of the samples （i.e., filtration, dilution, oxidation/reduction, addition of chromogenic agent, constant volume, etc.）, and it is capable of original- state online real-time monitoring. This method is employed at a large electrolytic manganese plant to monitor the Fe3. concentration in the colloidal process of the plant＇s aging liquid （where the concentra- tions of Fe3＋, Mn2＋, and （NH4）2SO4 are 0.5-18 mg.L 1, 35-39 g.L 1, and 90-110 g.L 1, respectively）. The relative error of this monitoring method compared with an off-line laboratory monitoring is less than 2%.

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.

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 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。

Legitimation of Business Model Innovation from the Perspective of Evaluator Categorization:A Case Study of the Emergence of Online Car-Hailing

Business model innovation faces multiple tests of legitimacy.Most extant research in this area has been conducted from institutional and strategic perspectives while paying insufficient attention to the perspective of evaluators.Based on the institutionalization of China's online car-hailing industry from 2012 to 2018,this paper analyzes the legitimacy judgment of the stakeholders from the perspective of evaluator categorization and explores the legitimation mechanism of business model innovation.It finds that evaluators judge the legitimacy of business models based on category cognition.Therefore,to achieve the bridging,spillover,and accumulation effects of legitimacy,the legitimation strategy of online car-hailing platforms should dynamically adapt to different evaluators,judgment models,and categorization standards.Ultimately,as quantitative changes lead to qualitative changes,the legitimation of innovative business models is achieved in this way.In this process,stakeholders categorize and evaluate online car-hailing based on prototypes and value goals,and establish a two-way interactive mechanism,which is from behavior guided by cognition to cognition given feedback by behavior.This paper combines the legitimacy judgment with category theory to explain how individual cognition drives the emergence of new categories and identifies a series of legitimacy strategies based on categorization,thus providing theoretical support and practical inspiration for exploring the legitimation of business model innovation.

Social Influence Analysis： Models, Methods, and Evaluation

Social influence analysis （SIA） is a vast research field that has attracted research interest in many areas. In this paper, we present a survey of representative and state-of-the-art work in models, methods, and eval- uation aspects related to SIA. We divide SIA models into two types： microscopic and macroscopic models. Microscopic models consider human interactions and the structure of the influence process, whereas macroscopic models consider the same transmission probability and identical influential power for all users. We analyze social influence methods including influence maximization, influence minimization, flow of influence, and individual influence. In social influence evaluation, influence evaluation metrics are introduced and social influence evaluation models are then analyzed. The objectives of this paper are to provide a comprehensive analysis, aid in understanding social behaviors, provide a theoretical basis for influencing public opinion, and unveil future research directions and potential applications.

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.

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。

医学课程在线教学学习效果评价体系研究

面对大数据时代的新要求以及不断变化的新型冠状病毒肺炎疫情挑战,线上教学成为高等教育中备受瞩目的新形式。依托教学平台进行在线教学,能够使优质教育资源共享,为学生带来全新的教学感受,以及个性化体验;同时,平台提供的学生学习行为与学习成绩数据更利于教师精准施教。因此,医学课程在线教学亦需要在多方面进行改进与优化,研究基于教学平台的医学课程在线教学学习效果评价体系将为进一步建设医学一流课程、一流专业提供有力支撑,具有重要的理论意义与实践价值。