Active video games in fully immersive virtual reality elicit moderate-to-vigorous physical activity and improve cognitive performance in sedentary college students

Background:Active video games are a new method for increasing physical activity(PA).Fully immersive virtual reality(VR)is a hardware device on which an active video game can run.Active(video games in)VR(AVR),might increase immersion,game engagement,and moderate-to-vigorous PA(MVPA),thereby yielding greater exercise-related benefits,e.g.,cognitive performance.Methods:We examined the induction of MVPA via an AVR and a sedentary VR(SVR)as well as the effects of VR play on cognitive performance,which was monitored using 2 different methods.Each of 29 sedentary college students attended three 20-min laboratory sessions(AVR,SVR,or control)in a randomized order;during the control session,they sat quietly doing nothing.A fully immersive headset was used for the 2 video game sessions.We monitored and computed participants’PA using hip-wom accelerometers(wGT3 x-bt;ActiGraph,Pensacola,FL,USA)and a heart rate band(Polar H7;Polar,Kempele,Finland).After each session,the participants completed a mnemonic similarity test(MST)to measure recognition memory.They also filled out a motion sickness questionnaire and an abbreviated game experience questionnaire.Results:The AVR session induced a significantly greater heart rate and more time spent in MVPA than did either of the other 2 sessions regardless of the PA monitoring method.AVR elicited greater game experience questionnaire-assessed sensory and imaginative immersion,challenge,and positive affect than did SVR.The mnemonic similarity test recognition score was marginally higher post-AVR session than it was post-SVR session.Conclusion:AVR elicited MVPA without a significant increase in motion sickness and induced a better game experience and better borderline cognitive performance than did SVR.

Active Power Allocation of Virtual Synchronous Generator Using Particle Swarm Optimization Approach

In recent years, the penetration of renewable energy sources (RES) is increasing due to energy and environmental issues, causing several problems in the power system. These problems are usually more apparent in microgrids. One of the problems that could arise is frequency stability issue due to lack of inertia in microgrids. Lack of inertia in such system can lead to system instability when a large disturbance occurs in the system. To solve this issue, providing inertia support to the microgrids by a virtual synchronous generator (VSG) utilizing energy storage system is a promising method. In applying VSG, one important aspect is regarding the set value of the active power output from the VSG. The amount of allocated active power during normal operation should be determined carefully so that the frequency of microgrids could be restored to the allowable limits, as close as possible to the nominal value. In this paper, active power allocation of VSG using particle swarm optimization (PSO) is presented. The results show that by using VSG supported by active power allocation determined by the method, frequency stability and dynamic stability of the system could be improved.

Control method for semi-active suspension based on virtual prototype

The simple dynamic model is often adopted to deal with control questions in research on semi-active suspension. The model has more theoretic meanings than authentic ones because of difference between practical and physical models. The virtual prototype has remarkable advantages in its application simulation processes. It is not only faster and more veracious, but also of better visualization of the simulation results.

关于Active Worlds在教育领域中的应用

虚拟世界能够充分挖掘计算机和通讯技术的技术潜能,将用户获取信息的空间由二维拓展到三维,能够提供高沉浸性、高交互性的虚拟学习环境。文章对国外发展成熟的虚拟世界Active Worlds的特点、功能及技术等方面进行了介绍,并分析了国外运用Active Worlds进行教学的案例,总结出利用Active Worlds开展教学的四种形式:游戏型、建模型、场景型、混合型,得出ActiveWorlds应用于教学的启示,以期为我国在教育中使用虚拟世界提供可操作化的教学步骤。

Novel Control Strategy for Multi-Level Active Power Filter without Phase-Locked-Loop

Active power filter (APF) using novel virtual line-flux-linkage oriented control strategy can not only realizes no phase-locked-loop (PLL) control, but also achieves a good inhibitory effect to interfere. However, there are some problems in the conventional method, such as the error of amplitude, the shift of phase angle and the non-determinacy of initial oriented angle. In this paper, two one-order low-pass filters are adopted instead of the pure integrator in the virtual line-flux-linkage observer, which can steady the phase and amplitude. Furthermore, an original scheme of harmonics detection under the rotating coordinate is advanced based on the simplified space vector pulse width modulation (SVPWM) strategy. Meanwhile, by using the new SVPWM algorithm, the voltage space vector diagram of the three-level inverter can be simplified and applied into that of two-level inverter, and this makes the control for Neutral Point potential easier.

An fNIRS-Based Study on Prefrontal Cortex Activity during a Virtual Shopping Test with Different Task Difficulties in Brain-Damaged Patients

We developed a Virtual Shopping Test with three different task levels for assessment of daily cognitive function using virtual reality technology. The objective of present study was to investigate the difference on task performance, brain activation and subjective assessment in relation to the difficulty levels of the tasks. Subjects were asked to buy specific 2 items in Task 1, 4 items in Task 2, and 6 items in Task 3 at a virtual mall. The tasks and questionnaires were conducted on 10 convalescent brain-damaged patients and 6 healthy young adults. Hemodynamic changes in the prefrontal cortex (PFC) during activation due to the tasks were examined using functional near-infrared spectroscopy. As the result, the mean total time was significantly longer for the patients than for healthy subjects. PFC showed a greater response for related Task 2 than Task 1 in shopping and moving phase in patient group. The patients evaluated Tasks 1 and 2 are more difficult and bring more psychological load than healthy adults subjectively. That is, although the healthy adults did not show large difference in their task performances as well as PFC responses, they can evaluate the differences between three task levels, subjectively, while which could not be for the patients means that patients could not distinguish the difference of the tasks, subjectively. The results suggest that 4-item shopping task might be enough difficulty level that causes brain activation for the brain-damaged patients.

Using Virtual Reality to Promote Physical Activity

The purpose of this research is to develop an immersive virtual fitness center as an intervention to promote physical activity and examine its impacts on users’ exercise plans and exercise behaviors. The virtual reality (VR)-based intervention includes three main features: enabling the users to control their avatar, personalizing the avatar to look the same as the user, and visualizing the positive consequences of exercising. We conducted an experiment to randomly assign participants to two treatment groups: experiencing either the self or another person losing weight because of exercising in the virtual environment. The findings demonstrated that the self-avatar group exercised more in the voluntary section than the other-avatar group. However, participants in the self-avatar condition perceived a lower level of sense of presence compared to participants in the other-avatar condition. Compared to people in the control condition who watched and followed the exercise from a workout video, those who exercised in the virtual fitness center, regardless of whether the avatar was based on the self’s image or another person’s image, planned to spend more time on exercising in the following week. Theoretical and practical implications for using VR technology to promote health-related behavioral change, and why personalization decreases perceived sense of presence in the virtual environment are discussed.

孤岛微电网多虚拟同步发电机频率无差协调控制策略

传统虚拟同步发电机的频率控制为有差控制,且虚拟惯量的引入使得虚拟同步发电机呈现二阶振荡特性,导致孤岛微电网多虚拟同步发电机并联系统在受到负荷扰动时面临频率偏移和有功超调的问题。针对此,提出了一种多虚拟同步发电机频率无差协调控制方法。该方法包含了兼具有功精确分配的频率无差调节控制和阻尼改进控制两部分,通过利用母线频率全局一致的“通信”效果,以分散式的形式协调系统内各台虚拟同步发电机,可主动消除微电网频率稳态偏差且实现各台虚拟同步发电机按照容量承担负荷有功功率,并抑制系统的有功超调。最后,通过仿真和实验验证了所提控制方法的有效性。

储能虚拟惯量主动支撑与调频状态转移控制

释放储能装置的频率支撑潜力,将是提升风、光高占比系统并网稳定性的关键。该文首先对比分析常规发电机组的固有惯量、风电机组的虚拟惯量及储能的惯性支撑特性。其次,根据系统中的储能容量配置,约束量化储能的虚拟惯量,为系统惯量需求提供评估依据,以保障频率安全。在此基础上,利用储能独特的功率支撑特性,提出恒频控制与调频状态转移控制结合的储能并网频率主动支撑控制策略,突破虚拟惯量及一次调频的传统控制模式。最后,搭建风电高渗透电网仿真系统,验证储能装置在所提控制策略下能够显著提升系统的频率稳定性,改善其对电网的主动支撑性能。

基于电路等效的并网逆变器失稳分析与稳定控制

以并网逆变器为功率接口的新能源发电系统在弱电网条件下易发生振荡失稳问题。该文将并网逆变器的控制回路可视化为电路元件组成的虚拟阻抗,基于该电路模型分析了弱电网条件下电流内环与锁相环交互作用导致并网逆变器振荡失稳的机理,在此基础上,提出了基于有源阻尼的稳定控制设计方法,并对不同有源阻尼控制的电路特性以及稳定性提升能力进行了对比分析。研究结果表明,针对锁相环引入负电阻造成的振荡失稳问题,阻抗-高通滤波器型有源阻尼控制策略具有更优的稳定性提升能力。最后通过PSCAD/EMTDC仿真和远宽StarSim控制器硬件在环实验对比了不同有源阻尼控制策略的振荡抑制效果,并验证了阻抗-高通滤波器型有源阻尼控制的动态性能。结果表明,所设计的稳定控制能够在200 ms内有效抑制系统振荡,并且可实现在短路比为1的极弱电网条件下稳定运行。

基于角频率暂态前馈的VSG控制策略

针对虚拟同步发电机(VSG)并网时,输出功率的稳态性能与动态性能之间存在耦合,无法同时满足抑制有功振荡和电网一次调频的需求,提出基于角频率暂态前馈的控制策略,通过补偿输出功率,减小Δω,进而减小振荡过程。该控制策略可以有效抑制有功振荡,并且实现了稳态性能与动态性能间的解耦,不会影响一次调频特性,同时提高了响应速度。首先建立VSG有功闭环小信号模型,分析了输出功率稳态性能与动态性能之间的矛盾,并根据同步发电机功角特性分析了有功振荡机理;在此基础上提出了基于角频率暂态前馈的控制策略,利用闭环零极点与Bode图分析了所提控制策略对系统的影响;最后通过仿真和RT-LAB半实物平台验证了所提控制策略的可行性与优越性。

基于自适应虚拟电阻的低压微电网有功均分下垂控制策略

由于低压微电网中各分布式电源的线路阻抗不匹配,传统的下垂控制策略难以按照下垂系数合理分配有功功率。为此,提出一种无需通信的自适应虚拟电阻下垂控制方法。通过将微电网中每个分布式发电机(DG)单元输出的有功功率和电压传送给自适应虚拟电阻控制器中,在保证电压和频率稳定控制的前提下实现功率按逆变器容量比例进行精确分配。论文对改进方法的微电网逆变器进行小信号稳定性分析,以优化控制器有关控制参数。仿真和实验结果验证了所提控制方法的有效性。

基于超前滞后环节附加前馈阻尼的VSG控制策略

虚拟同步发电机(virtual synchronous generator,VSG)在引入同步机二阶转子运动方程,增大电力系统等效惯量的同时,也引入了同步发电机的振荡特性,有功低频振荡等动态稳定性问题也随之而来。引入调速侧电力系统稳定器(governor power system stabilizer,GPSS)能有效抑制VSG的功率低频振荡,但其在超调量及调节时间方面的控制效果仍有待提高。通过建立VSG的小信号模型从极点配置角度分析其稳定性,揭示基于GPSS的VSG控制策略在功率动态响应上存在较高超调和较长调节时间的原因。基于此,参考GPSS控制思想,提出了一种基于超前滞后环节附加前馈阻尼补偿的虚拟同步发电机控制策略。并从理论上分析验证了所提控制策略在不影响系统稳态特性的前提下,能够提供调整自由度更高的正阻尼,在有效地抑制功率超调的同时提高了系统的调节速度,从而更好地抑制了有功功率的低频振荡。最后通过MATLAB/Simulink进行对比仿真,仿真结果与理论分析结果一致,证明了所提控制策略的正确性和有效性。

虚拟现实技术在医院ICU患者早期活动中的应用研究进展

早期活动对于重症监护病房(Intensive Care Unit,ICU)患者康复至关重要,虚拟现实技术作为一种新兴的治疗手段,逐渐应用于ICU患者的早期活动中,为ICU患者的早期活动提供了新的选择。文章旨在综述虚拟现实技术在ICU患者早期活动中的应用研究进展,并重点关注其在护理方面的应用,阐述现存的问题及发展前景,旨在为医护人员充分利用虚拟现实技术对ICU患者进行早期活动训练提供新的视角和参考。

基于自抗扰的直驱风电机组强迫振荡抑制研究

风剪切和塔影效应会导致直驱式风电机组产生强迫功率振荡,影响系统的安全稳定运行。因此,提出了一种基于自抗扰控制的虚拟惯量控制方法,该方法通过扩张状态观测器观测估计系统扰动量,同时利用跟踪微分器调整系统频率的参考值,优化风电机组控制功率。仿真结果表明,相比传统的虚拟惯量控制,所提方法具有更好的抗干扰性,能更有效地对扰动进行观测估计并补偿,达到抑制直驱式风电并网系统强迫振荡的目的。

基于有功分数阶微分校正的储能VSG并网有功响应策略

为了解决在有功功率指令、电网频率2种扰动情况下储能虚拟同步机(VSG)并网有功难以兼顾良好的动态特性和稳态性能的问题,提出了一种基于有功分数阶微分校正的VSG(AFDC-VSG)并网有功响应优化控制策略。分别建立典型VSG、AFDC-VSG这2种控制策略的并网有功闭环小信号模型,并给出相应的参数设计过程。利用MATLAB/Simulink仿真软件对比分析不同控制策略在2种扰动下储能VSG的并网有功响应特性,并建立储能VSG并网系统的实验平台。仿真和实验结果共同验证了所提AFDC-VSG策略在优化储能VSG并网有功响应性能方面的有效性与优越性。

人格化构建逻辑下的虚拟偶像设计研究

目的虚拟偶像作为重要的未来传播媒介,本文探究其人格化设计路径及构建逻辑。方法以媒介理论视角介入偶像崇拜演进过程,分析虚拟偶像崇拜的本质,以人格心理学中的需求层次论及情感化设计为框架进行理论拓展,对虚拟偶像人格要素展开剖析及模型构建。采用案例分析法,以市场中30位虚拟偶像为例,从偶像文化实践的动态过程切入对人格要素各维度的对比归纳,由此总结其人格化构建逻辑。结果提出了基于“形象人格-感知人格-精神人格”的虚拟偶像人格化构成模型,并从造型设计、展演叙事和文化衍生三个层级开展其设计规律的探索。结论虚拟偶像人格化实际是对“虚拟介质如何保持自我主体性”的关切,其设计需要考量文化、技术与情感的三方关系,不断塑造利于价值认同的偶像角色以期更好地发挥榜样精神。在构建良好偶像文化生态的同时,也为这一面向未来的虚拟文化创意产品提供设计参照与启示。

虚拟现实技术在脑性瘫痪儿童青少年身体活动和健康中的应用:系统综述的系统综述

目的系统综述虚拟现实(VR)技术在脑瘫儿童青少年身体活动和健康领域的应用模式和健康效益的系统综述的相关研究证据。方法检索Pub Med、Embase、CINAHL、SPORTDiscus、Google Scholar、Psyc INFO和中国知网,收集并筛选2020年1月至2024年3月公开发表的VR技术在脑瘫儿童青少年身体活动和健康中应用的系统综述,根据PRISMA指南,报告VR技术应用于脑瘫儿童青少年身体活动与健康领域的技术模式和效益的相关证据。结果最终纳入8篇英文文献,来自中国、沙特阿拉伯、印度尼西亚和巴西4个国家,涉及5692例脑瘫儿童青少年,研究类型均为系统综述,主要来源于临床医学、治疗和临床风险管理、游戏和游戏化、身体移动治疗等领域期刊。研究对象年龄为4~18岁,健康状况为脑瘫,主要涉及痉挛性偏瘫和痉挛性双瘫。涉及的VR技术包括沉浸式环境模拟,交互式动感游戏化,虚拟训练和指导,基于人工智能的活动数据追踪与分析、动作捕捉和反馈、生物反馈集成和可穿戴技术应用,以及增强现实集成5种典型的技术应用模式。每次干预15~90 min,每周1~15次,干预强度为中等~剧烈,持续1~24周。VR技术在脑瘫儿童青少年身体活动领域的应用,提升了脑瘫儿童青少年参与身体活动的兴趣,增强了交互式活动的感受,通过与可穿戴技术、生物反馈技术和数据追踪技术的结合,能够实时监测、追踪、分析和反馈活动状况,改善身体功能和活动功能。结论沉浸式环境模拟、交互式动感游戏化等VR技术,可以提升脑瘫儿童青少年参与身体活动的兴趣和身体活动参与水平,改善身体素质和活动,促进行为健康,提高整体健康水平和生活质量。

提高储能VSG并网有功响应性能的暂态阻尼策略

储能虚拟同步发电机(VSG)的并网有功在有功指令与电网频率2种扰动下存在动态超调与稳态偏差。提出有功微分反馈补偿(ADFBC)和有功微分前馈补偿(ADFFC)2种暂态阻尼策略,并在分别建立典型VSG、ADFBC和ADFFC 3种策略并网有功闭环小信号模型的基础上,给出了相应的参数设计方法。仿真和实验对比结果均验证了所提ADFBC和ADFFC暂态阻尼策略可有效提高储能VSG并网有功响应,在2种扰动下其并网有功既无动态超调又无稳态偏差。

气体介质绝缘强度的化学键组合理论

寻找能够替代SF6的新型绝缘气体介质非常具有挑战性,采用构效关系模型进行虚拟筛选是发现目标替代气体的有效手段.受计算资源限制,亟需发展准确快速计算气体绝缘强度的理论方法.本文建立了基于化学键理论的气体绝缘强度计算方法,根据分子的价键结构确定化学键类型和数目,优化各化学键的特征绝缘强度,累加获得任意气体的绝缘强度.与63种气体的实验结果相比,理论值与实验值的相关系数和均方根误差分别为0.970和0.16,能够满足高通量虚拟筛选的计算需求.揭示了气体绝缘强度与化学键的内在关联,提出了若干具有应用潜力的新型绝缘气体分子结构.