Modulation of Void Motion Behavior in a Magnetized Dusty Plasma

Based on fluid equations, we show a time-dependent self-consistent nonlinear model for void formation in magnetized dusty plasmas. The cylindrical configuration is applied to better illustrate the effects of the static magnetic field, considering the azimuthal motion of the dusts. Tile nonlinear evolution of the dust void and the rotation of the dust particles are then investigated numerically. The results show that, similar to the unmagnetized one-dimensional model, the radial ion dragplays a crucial role in the evolution of the void. Moreover, the dust rotation is driven by the azimuthal ion drag force exerting on the dust. As the azimuthal component of ion velocity increases linearly with the strength of the magnetic field, tile azimuthal component of dust velocity increases synchronously. Moreover, the angular velocity gradients of the dust rotation show a sheared dust flow around the void.

Identification of traffic object's motion behavior based on track

To extract the track parameters of a traffic object in traffic video and identify its motion behavior,a new method is proposed based on CamShift(Continuously Adaptive Mean Shift)and HMM(Hidden Markov Model).First,an object entering the video scene is located and tracked by the CamShift based algorithm,then its track parameters are obtained.Next,the track parameters are processed to form the observation sequence of HMM,and the motion behavior modeling and probability evaluation are implemented based on HMM.At last,the behavior identification and behavior statistics of the tracked traffic object in video are achieved.Experiments show that this method can be used to sort and recognize the motion behavior of the traffic object by its corresponding behavior track,and to do some statistics or corresponding process schemes.

Motion behavior of non-metallic particles under high frequency magnetic field

Non-metallic particles, especially alumina, are the main inclusions in aluminum and its alloys. Numerical simulation and the corresponding experiments were carried out to study the motion behavior of alumina particles in commercial pure aluminum under high frequency magnetic field. At the meantime, multi-pipe experiment was also done to discuss the prospect of continuous elimination of non-metallic particles under high frequency magnetic field. It is shown that: 1) results of numerical simulation are in good agreement with the experimental results, which certificates the rationality of the simulation model; 2) when the intensity of high frequency magnetic field is 0.06 T, the 30 μm alumina particles in melt inner could migrate to the edge and be removed within 2 s; 3) multi-pipe elimination of alumina particles under high frequency magnetic field is also effective and has a good prospect in industrial application.

Experimental and numerical investigation of the roll motion behavior of a floating liquefied natural gas system

The present paper does an experimental and numerical investigation of the hydrodynamic interaction and the response of a single point turret-moored Floating Liquefied Natural Gas(FLNG) system,which is a new type of floating LNG(Liquid Natural Gas) platform that consists of a ship-type FPSO hull equipped with LNG storage tanks and liquefaction plants.In particular,this study focuses on the investigation of the roll response of FLNG hull in free-decay motions,white noise waves and also in irregular waves.Model tests of the FLNG system in 60%H filling condition excited by both white noise waves and irregular waves combined with steady wind and current have been carried out.Response Amplitude Operators(RAOs) and time histories of the responses are obtained for sway,roll and yaw motions.Obvious Low Frequency(LF) components of the roll motions are observed,which may be out of expectation.To facilitate the physical understanding of this phenomenon,we filter the roll motions at the period of 30 s into two parts:the Wave Frequency(WF) motions and the Low Frequency(LF) motions respectively.The results indicate that the LF motions are closely related to the sway and yaw motions.Possible reasons for the presence of the LF motions of roll have been discussed in detail,through the comparison with the sway and yaw motions.As for the numerical part,the simulation of the modeled case is conducted with the help of the software SESAM.A good agreement between experiments and calculations is reported within the scope of trends.However,the numerical simulations should be further improved for the prediction of the FLNG system in the heading sea.

The Marking Technology in Motion Capture for the Complex Locomotor Behavior of Flexible Small Animals(Gekko gecko)

Animals have evolved a variety of behavior patterns to adapt to the environment. Motion-capture technology is utilized to quantify and characterize locomotor behaviors to reveal the mechanisms of animal motion. In the capture of flexible, small animals with complex locomotor behaviors, the markers interfere with each other easily, and the motion forms(bending, twisting) of the moving parts are obviously different;thus, it is a great challenge to realize accurate quantitative characterization of complex locomotor behaviors. The correlation between the marker properties, including the size and space length, and the precision of the system are revealed in this paper, and the effects of diverse marker shapes on the capturing accuracy of the captured objects in different motion forms were tested. Results showed that the precision of system is significantly improved when the ratio of the space length to the diameter of the markers is larger than four;for the capture of the spatial twisting motion of the flexible object, the hexagon markers had the lowest spatial lost-marker rate relative to the circle, triangle, and square. Customized markers were used to capture the locomotor behavior of the gecko-inspired robot(rigid connection) and the gecko(flexible connection). The results showed that this marking technology can achieve high accuracy of motion capture for geckos(the average deviation was approximately 0.32 mm, and the average deviation’s variation rate was approximately 0.96%). In this paper, the marking technology for the motion capture of flexible, small animals with complex motion is proposed;it can effectively improve the system precision as well as the capture accuracy, and realize the quantitative characterization of the complex motion of flexible, small objects. It provides a reliable technical means to deeply study the evolution of the motion function of small animals and advance systematic research of motion-capture technology.

浮选气泡尺寸对粗颗粒-气泡涡旋湍流脱附机制的影响

气泡是浮选过程中不可或缺的重要角色,其尺寸对颗粒-气泡间相互作用有着显著影响,然而气泡尺寸对粗颗粒-气泡涡旋湍流脱附机制的影响尚未清晰。为此,采用自制的颗粒-气泡受限湍流脱附测试平台探索了涡旋湍流中不同气泡尺寸的气絮体上颗粒的脱附行为,并运用Image-ProPlus图像处理软件对颗粒脱附过程的动力学参数进行了测量分析。结果表明:在确保气泡浮力的前提下,减小气泡尺寸能够显著提升粗颗粒-气泡的矿化气絮体在涡旋湍流中的稳定性;涡旋湍流中气絮体上颗粒的脱附主要表现为流体剪切、气泡振荡和颗粒离心三种脱附形式,方腔内涡旋结构的改变对气絮体上颗粒的脱附方式至关重要;区别于传统离心脱附理论,涡旋湍流驱使下颗粒并非单独在气泡表面做高速离心运动,而是与气泡一起做离心运动,且小气泡与颗粒在方腔内共同旋转时,位于气泡外缘的颗粒与气泡运动速度接近,相应气絮体稳定性高,颗粒不易发生离心脱附,而大气泡形成的气絮体中,气泡外缘的颗粒与气泡运动速度差异明显增大,颗粒相对于气泡旋转更快,从而使得颗粒所受离心力显著增强,增加了离心脱附的可能性。研究结果有望对涡旋湍流场中粗颗粒的脱附机制提供一个基本认识。

基于深度学习的高超声速飞行器运动行为识别

高超声速飞行器具有机动大、速度高、航程远、威胁强等特点,已成为各大国重点发展的武器装备,识别其运动行为能为防御和拦截提供有力的技术支持。本文对有禁飞区等复杂约束条件下的高超声速飞行器运动行为识别问题开展研究:首先通过分析高超声速飞行器的运动特点,建立能够充分描述其行为模式的参数化运动方程;然后基于优化思想求解有禁飞区等复杂约束条件下的航迹规划问题,构建其数据集;最后基于深度学习方法设计高超声速飞行器运动行为识别算法。试验结果表明:所设计的识别算法能够实现对高超声速飞行器运动行为的识别,且具有一定的泛化能力,可为后续防御决策提供一定的参考。

现实情境羽毛球运动员接发球预判的视觉行为特征研究

旨在测试不同水平羽毛球运动员现场接发球的预判表现与视觉行为差异,研究现实情境下羽毛球运动员接发球预判的视觉行为特征。24名被试分为专家组和新手组参与测试,通过高速摄像机录制分析被试接发球预判的准确率和反应时,利用便携式眼动仪追踪记录被试视觉行为信息。结果发现,两组被试接发球启动时间和接发效果统计学差异极为显著(P<0.01);准备阶段,两组被试在球与场外区域注视时间的统计学差异极为显著(P<0.01);执行阶段,两组被试在头、肩、场外注视时间的统计学差异极为显著(P<0.01);飞行阶段,新手后场与专家后场、新手前场与专家前场统计学差异显著(P<0.05)。结论:在接发球预判过程中,羽毛球专家的启动时间短,接发效果较好,而新手组启动时间长且接发效果差。羽毛球专家的注视轨迹较为集中,无关注视较少,具有高效的视觉搜索模式,而新手组注视轨迹较为分散,无关注视较多,视觉搜索效率低。研究结果可以直接应用于羽毛球运动实践,为羽毛球运动员接发球预判技能、视觉注意技能训练提供理论基础与实践指导。

基于运动特征提取和2D卷积的鱼类摄食行为识别研究

为了促进渔业装备智能化,近年来基于视频流的鱼类摄食行为识别研究受到了广泛关注。针对基于视频流的传统识别方法模型过于复杂,难以在边缘计算设备部署的问题,提出了一种轻量级的2D卷积运动特征提取网络Motion-EfficientNetV2,该网络以视频流为输入,能够有效识别鱼类摄食行为。提出的模型以EfficientNetV2为主干网络,基于TEA和ECANet构建了运动特征提取模块Motion,并将该模块嵌入到EfficientNetV2的每个Fused-MBConv模块中,使改进后的EfficientNetV2具有运动特征提取能力。同时使用ECANet对EfficientNetV2网络中的MBConv进行改进,增强其通道特征提取能力。在此基础上利用空洞卷积扩大感受野,提高大范围特征提取能力。试验结果表明,Motion-EfficientNetV2的参数量和浮点运算量分别为9.3×106和1.31×1010,优于EfficientNetV2。在TSN-ResNet50、TSN-EfficientNetV2、C3D以及R3D模型上进行对比试验,本文模型在降低参数量和浮点运算量的同时,使识别准确率提高到93.97%。该研究对于渔业装备智能化升级和科学养殖具有推动作用。

基于改进蜣螂算法的并联机器人轨迹优化

提出了基于改进的蜣螂优化算法的并联机器人时间最优轨迹优化方法。对Delta并联机器人进行运动学逆解分析,基于NURBS曲线对并联机器人轨迹进行规划,使用改进的蜣螂优化算法对并联机器人轨迹进行优化,设置关键路径点并通过并联机器人运动学逆解模型求出各路径点对应的关节角度。模拟实验结果表明,与蜣螂优化算法相比,改进的蜣螂优化算法能够提升并联机器人的运动效率,缩短并联机器人的运动时间。

基于BCW的健康教育联合分级运动应用于青少年支气管哮喘病人的效果

目的:探究基于行为改变理论(behavior change wheel, BCW)的健康教育联合分级运动应用于青少年支气管哮喘病人的效果。方法:选取2021年5月—2022年5月于医院就诊的105例青少年支气管哮喘病人,按照随机数字表法分为对照组(52例)和观察组(53例)。对照组予以分级运动干预,研究组在对照组基础上实施基于BCW的健康教育。观察两组病人哮喘改善情况、干预前后的疾病认知情况和生活质量情况。结果:连续干预6个月后,观察组病人哮喘改善优良率为90.57%,明显高于对照组的71.15%(P<0.05);哮喘疾病知识问卷中的用药知识、诱发因素、疾病本质及自我管理维度评分均明显高于对照组(P<0.001);成人哮喘生命质量量表中的心理状态、哮喘症状、活动受限维度评分也明显高于对照组(P<0.001)。结论:基于BCW的健康教育联合分级运动应用于青少年支气管哮喘病人的效果显著,可明显改善病人的哮喘症状,提升病人对疾病相关知识的认知情况,改善病人生活质量。

Effects of gully terrain on stress field distribution and ground pressure behavior in shallow seam mining

This study proposes a novel approach to study stress field distribution and overlying ground pressure behavior in shallow seam mining in gully terrain.This approach combines numerical simulations and field tests based on the conditions of gully terrain in the Chuancao Gedan Mine.The effects of gully terrain on the in situ stress field of coal beds can be identified by the ratio of self-weight stress to vertical stress(η) at the location corresponding to the maximum vertical stress.Based on the function η =j(h),the effect of gully terrain on the stress field of overlying strata of the entire field can be characterized as a significantly affected area,moderately affected area,or non-affected area.Working face 6106 in the Chuancao Gedan Mine had a coal bed Jepth <80 m and was located in what was identified as a significantly affected area.Hence,mining may cause sliding of the gully slope and increased loading(including significant dynamic loading) on the roof strata.Field tests suggest that significant dynamic pressures were observed at the body and foot of the gully slope,and that dynamic loadings were observed upslope of the working face expansion,provided that the expanding direction of the working face is parallel to the gully.

水流作用下裂隙内沉积颗粒起动临界流速研究

为了优化阻塞裂隙的水力冲刷工艺参数,采用物理试验和理论分析相结合的方法,建立了水流作用下颗粒起动有效作用流速数学模型,研究了水流作用下裂隙内不同形状颗粒的起动方式和颗粒起动临界流速随颗粒粒径、流体密度和裂隙高度的变化特性。结果表明:近圆颗粒和椭球颗粒主要以滚动方式起动,扁平颗粒以滑动方式起动;颗粒起动临界流速随颗粒粒径的增大呈现对数增大的变化规律,随流体密度的增大呈减小的变化规律;进一步地,由于颗粒起动有效作用流速与裂隙高度的增大呈负相关的变化规律,因此颗粒起动临界流速随裂隙高度的增大而增大。为提升阻塞裂隙的水力冲刷效果,应采用的方法是增加流体介质的密度,促使裂隙内更多的沉积颗粒发生起动。此外,当水力冲刷工艺运用至裂隙发育的地带时,应该适当提高水力冲刷工艺的注水量,提高堵塞裂隙的水力冲刷工艺效果。

基于自适应高斯模型和运动能量的异常行为识别

为有效识别监控视频中的群体异常行为,提出一种基于自适应高斯模型和运动能量的异常行为识别方法。将自适应帧间差分法融入混合高斯模型中,对运动目标进行提取,计算行为发生个体的动态能量,利用行为发生各方的位置关系计算出交互能量,最终计算出异常行为事件的整体能量总值,从而实现群体异常行为的有效识别。实验结果表明,该文算法对人群异常行为具有较好的识别效果,算法实时性较好,具有一定的应用推广价值。

基于低分辨率红外阵列传感器的头部运动检测

在驾驶和在线课堂这类持续时间较长的行为中,人们容易出现分心而导致事故发生或上课效率差。为检测这类分心行为,提出了一种基于低分辨率红外阵列传感器的头部运动检测方法,它在实现行为监测的同时也保护了个人隐私。首先,基于图像处理方法提取了人体的显著区域;然后设计了一种三维图像融合算法来提取时空域的变化信息;最后,设计了一个改进的残差网络来实现头部运动分类。面向驾驶和在线课堂应用场景设计了10种头部运动。实验结果表明,在50 cm到100 cm的检测范围内,平均识别率为96.76%,处理速度为9帧/s,优于现有算法。将该系统应用于车内实测,也达到了93.7%的准确率。

自动驾驶安全挑战:行为决策与运动规划

在自动驾驶技术发展中,安全性一直作为首要因素被业界重视.行为决策与运动规划系统作为该技术的关键环节,对智慧属性具有更高要求,需要不断地随着环境变化做出当前的最优策略与行为,确保车辆行驶过程中的安全.文中分别对行为决策和运动规划系统进行深层次阐述,首先,介绍行为决策中基于规则的决策算法、基于监督学习的决策算法、基于强化学习的决策算法的算法理论及其在实车中的应用.然后,介绍运动规划中基于采样的规划算法、基于图搜索的规划算法、基于数值优化的规划算法和基于交互性的规划算法,并对算法的设计展开讨论,从安全角度分析行为决策和运动规划,对比各类方法的优缺点.最后,展望自动驾驶领域未来的安全研究方向及挑战.

基于图像的地铁车站施工人员不安全行为识别研究

为了解决人工监测不能实时看护和及时管理地铁车站施工人员的不安全行为等问题,构建了基于KNN,MLP和LSTM模型的不安全行为识别神经网络模型。首先,通过行为理论研究和现场调查分析,对地铁车站施工不安全行为进行了分类;其次,通过实验构建人体数据集,基于人体骨骼关节点提取不安全行为特征,并进行模型训练;最后,基于MobileNet V1的SSD目标检测算法对施工人员进行定位和追踪,结合射线法判断目标是否跨越不安全区域并发出警报,搭建神经网络模型对施工人员的不安全行为进行识别,并获得计算识别率。结果表明:传统机器学习算法KNN总体准确率为93.45%,优化后的MLP和LSTM两种神经网络模型总体准确率分别达到93.94%和93.68%,相对KNN算法分别提高了0.49%和0.23%。因此所提模型能有效识别施工人员不安全行为,可为地铁施工安全智能识别技术应用提供参考。

顾及外连通性的PIR传感器网络行为轨迹重构方法

热释电红外(Passive Infrared,PIR)传感器人体行为研究目前主要集中于特征建模与识别,对轨迹重构的研究相对较少且易忽略传感器布设环境的影响,导致重构结果不确定性较大。为提高重构轨迹的完备性,该文将传感器与环境的连通性作为PIR传感器网络轨迹重构中的约束条件,从空间相邻、时间连续、传感器外连通三方面对轨迹重构过程进行优化。以PIR传感器系统模拟场景中对象随机移动为例,对传感器的响应数据进行轨迹重构,得到对象的连续行为轨迹,结果与场景模拟轨迹基本一致,验证了该文方法的有效性。

机—电联合作用下尖端电极中金属微粒的运动行为与局部放电特性

GIS内自由金属微粒的运动、集聚行为导致金属微粒在电力设备内部分布广泛,使得绝缘子表面的闪络电压降低,对设备的绝缘状态造成潜在性的威胁。本文搭建自由金属微粒机—电联合试验平台,研究机—电共同作用下尖端电极中金属微粒的放电特性与运动特性,总结出工频电压和机械振动对于金属微粒起跳及运动行为的影响规律。试验结果表明尖端电极下,球形微粒与线性微粒均保持在底电极上沿弧面进行小幅滚动,增加工频电压幅值会使得微粒沿弧面晃动的上下界高度提升,增加机械振动幅值会使得微粒出现一定的起跳动作,且运动的随机性增加;放电产生的PRPD谱图整体保持尖端放电的典型特征,飞行谱图整体保持三角脉冲群的典型特征,但仅存在单一的三角峰,并从受力分析与空间电荷的角度对运动行为与放电特性进行解释。文中的研究为实际工程应用多缺陷中金属微粒的检测提供了一种有效的方法。

中药复方精油抗晕动病疗效评价

目的:观察雾化吸入中药复方精油对小鼠晕动症的预防作用。方法:预先分别给予小鼠雾化吸入高、低剂量浓度(0.1 mL/只、0.03 mL/只)15 min中药复方精油、腹腔注射东莨菪碱(1 mg/kg)后制备晕动症动物模型,立即观察小鼠旷地行为实验、自发活动实验和晕动病症状,晕反应指数评价各实验组抗晕动病效果,比较中药复方精油及东莨菪碱对小鼠晕动病的预防治疗作用。结果:旷地行为实验发现,东莨菪碱组和雾化吸入中药复方精油的小鼠腹部离地时间、尾巴离地时间明显少于空白组(P<0.01);东莨菪碱组和中药复方精油均能明显增加小鼠自发活动次数(P<0.01);东莨菪碱组和中药复方精油组均能明显降低小鼠晕反应指数总分(P<0.01)。结论:通过雾化吸入中药复方精油和腹腔注射东莨菪碱对小鼠晕动病均有不同程度的预防和缓解作用,为防晕精油产品开发和有效地应用于临床提供科学依据。