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在验证机械能守恒定律实验中,针对小球经过光电门时瞬时速度的测量不准确的问题,提出了两点改进的方法:考虑到光束的有效宽度,建议将瞬时速度公式进行修正;另外调节光束垂直照在小球的悬线上.这两种改进方法能够使验证机械能守恒定律实验更加准确. 相似文献
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向心力大小演示实验是高中物理教学中一个很重要的演示实验.在人教版物理教材中,采用圆锥摆粗略验证向心力表达式,该实验是利用铁架台、小球、细线、秒表、天平、刻度尺等器材完成的.实验时,小球在水平面内做匀速圆周运动,用刻度尺测量出小球做圆周运动的半径r和小球距悬点的竖直高度h,利用天平、秒表分别测量出小球的质量m和运动n圈的时间t,得出指向圆心的合力为 相似文献
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为解决落球法测量液体黏度实验中小球速度v的测不准等问题,制作了高速显示的LED秒表,用数码相机记录小球通过高度h上下两端时标尺上的位置h_1和h_2以及当时LED秒表的示数t_1和t_2,进而计算小球速度v.实验测定了小球在甘油中的终极速度和刚进入甘油时的下落情况.结果表明:该方法不仅测量小球速度v的重复性较好,而且还能用于判定小球是否进入匀速状态. 相似文献
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光电吊舱在稳像和目标跟踪过程中存在摩擦力矩、不平衡力矩等干扰力矩,从而影响速度环响应精度;另一方面,吊舱视频跟踪器图像传输和处理造成的延迟也会造成跟踪滞后,因此必须进行延时补偿。提出基于预测跟踪的滑模变结构控制方法,采用微分预测跟踪器实现对视频跟踪器的延迟补偿,采用预测跟踪器估计出的目标运动角速率构成自适应补偿参数,以调整滑模变结构控制量,改进的滑模控制算法在补偿干扰力矩的同时抑制了抖振现象。仿真及实验结果表明:改进的控制方法能够有效补偿干扰力矩和跟踪器延迟造成的误差,相对于传统PID控制,其跟踪误差减小为原来的1/3,并且该算法已经在相关系统上得到应用。 相似文献
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IntroductionIn-scanner head motion is a common cause of reduced image quality in neuroimaging, and causes systematic brain-wide changes in cortical thickness and volumetric estimates derived from structural MRI scans. There are few widely available methods for measuring head motion during structural MRI. Here, we train a deep learning predictive model to estimate changes in head pose using video obtained from an in-scanner eye tracker during an EPI-BOLD acquisition with participants undertaking deliberate in-scanner head movements. The predictive model was used to estimate head pose changes during structural MRI scans, and correlated with cortical thickness and subcortical volume estimates.Methods21 healthy controls (age 32 ± 13 years, 11 female) were studied. Participants carried out a series of stereotyped prompted in-scanner head motions during acquisition of an EPI-BOLD sequence with simultaneous recording of eye tracker video. Motion-affected and motion-free whole brain T1-weighted MRI were also obtained. Image coregistration was used to estimate changes in head pose over the duration of the EPI-BOLD scan, and used to train a predictive model to estimate head pose changes from the video data. Model performance was quantified by assessing the coefficient of determination (R2). We evaluated the utility of our technique by assessing the relationship between video-based head pose changes during structural MRI and (i) vertex-wise cortical thickness and (ii) subcortical volume estimates.ResultsVideo-based head pose estimates were significantly correlated with ground truth head pose changes estimated from EPI-BOLD imaging in a hold-out dataset. We observed a general brain-wide overall reduction in cortical thickness with increased head motion, with some isolated regions showing increased cortical thickness estimates with increased motion. Subcortical volumes were generally reduced in motion affected scans.ConclusionsWe trained a predictive model to estimate changes in head pose during structural MRI scans using in-scanner eye tracker video. The method is independent of individual image acquisition parameters and does not require markers to be to be fixed to the patient, suggesting it may be well suited to clinical imaging and research environments. Head pose changes estimated using our approach can be used as covariates for morphometric image analyses to improve the neurobiological validity of structural imaging studies of brain development and disease. 相似文献
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光电跟踪仪低对比度目标捕获能力检验方法研究 总被引:1,自引:0,他引:1
提出了一种光电跟踪仪低对比度目标捕获能力检验方法。该方法采用可调对比度无穷远目标源作为检验装置,为被检光电跟踪仪提供对比度可准确度量的光学基准目标,用于检验光电跟踪仪的针对低对比度目标的捕获能力。介绍了检验装置的原理、组成和目标对比度标定方法,对检验结果进行了分析。该检验方法综合了光学系统性能、光电接收器性能、图像处理电路和软件及信噪比等各项指标对目标对比度的影响,全面真实地反映了电视跟踪仪的跟踪性能。 相似文献
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以人在球体上走动引起球体向前滚动为例,利用牛顿定律说明人-球系统中内力、外力与运动之间的关系.尽管阻碍球体滚动的地面摩擦是人-球系统向前运动的必要条件,且作为外力与系统动量变化率相等,但从运动的因果关系考察,人与球体之间的竖直作用力才是系统运动的真正动力. 相似文献
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Hong Han Zehui Jiang Rui Zhang Jing Lyu 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(12):1-7
We investigate the dynamics of a plastic ball on a vibrated platform in air by introducing air damping effect into the completely inelastic bouncing ball model. The air damping gives rise to larger saddle-node bifurcation points and a chaos confirmed by the largest Lyapunov exponent of a one-dimensional discrete mapping. The calculated bifurcation point distribution shows that the periodic motion of the ball is suppressed and a chaos emerges earlier for an increasing air damping. When the reset mechanism and the linear stability which cause periodic motion of the ball both collapse, the investigated system is fully chaotic. 相似文献
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对球从粗糙斜面滚下后在铅垂圆形轨道上的运动进行了全面、系统的分析,给出了由纯滚动状态转换为又滚又滑状态的条件,推出了确定球离开圆形轨道位置的方程,纠正了某些文献中的错误结果。 相似文献
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分析了小球在斜槽内横向作非简谐阻尼振动同时又在其纵向作匀加速直线运动的轨迹的理论公式.让粘满碳粉的小球在铺有坐标纸的斜槽内运动,记录真实运动轨迹,从实验图像中可以看出振幅越来越小、波长越来越长,这与理论分析相符. 相似文献
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