Dynamic properties of neurons in cortical area MT in alert and anaesthetized macaque monkeys.

In order to see the world with high spatial acuity, an animal must sample the visual image with many detectors that restrict their analyses to extremely small regions of space. The visual cortex must then integrate the information from these localized receptive fields to obtain a more global picture of the surrounding environment. We studied this process in single neurons within the middle temporal visual area (MT) of macaques using stimuli that produced conflicting local and global information about stimulus motion. Neuronal responses in alert animals initially reflected predominantly the ambiguous local motion features, but gradually converged to an unambiguous global representation. When the same animals were anaesthetized, the integration of local motion signals was markedly impaired even though neuronal responses remained vigorous and directional tuning characteristics were intact. Our results suggest that anaesthesia preferentially affects the visual processing responsible for integrating local signals into a global visual representation.     

Rapid motion aftereffect seen within uniform flickering test fields

Prolonged viewing of a moving pattern selectively elevates the threshold for a pattern moving in the same direction and induces the classical motion aftereffect (MAE). The aftereffect is seen as a slow drift in the opposite direction, which is visible even with the eyes shut or while viewing a uniform field. However, as we report here, a strikingly different aftereffect is seen when the test field is uniform and sinusoidally flickered: the field is filled with rapid motion in the direction opposite the adapting motion. This flicker MAE has distinct properties: the adapting grating must be of low spatial frequency; the effect is promoted by high contrast and high temporal frequencies of both adapting and test stimuli; and the aftereffect does not transfer interocularly. In all these respects the flicker MAE differs from the traditional MAE. Motion detectors have been identified in human vision by the threshold detectability and discriminability of moving patterns and by selective adaptation. The flicker MAE selectively taps a class of transient motion mechanisms that are selective for rapid motion and low spatial frequency. Uniform flicker is an effective stimulus for these mechanisms. It thus appears that the human visual system contains at least two distinct classes of mechanisms for sensing motion.     

足球高踢技术动作下肢环节链的生物力学特征分析

目的:探讨大学足球校队足球运动员与一般健身者在执行足球高踢动作时,整个动作下肢各肢段及关节活动范围,为足球教学人员及教练员的课堂教学提供参考.方法:采用Qualisys运动图像拍摄及解析系统(瑞典)获取足球高踢动作摆动腿各肢段运动学参数.拍摄频率100帧/s,数字摄像机将撷取到反光球反射的模拟讯号,透过视讯与模拟讯号处理器,将模拟讯号转换成数字信号,进而获得相应运动学参数.结果:(1)在相近的时相阶段,足球运动员大腿肢段后摆最大角度、小腿肢段后摆最大角度、足肢段后摆最大角度均显著大于一般健身者;(2)高踢过程中,足球运动员膝关节总活动范围与一般健身者并无差异,前者踝关节活动度范围显著大于一般健身者;(3)足球运动员与一般健身者执行高踢动作的总时间、足踢最大高度、下肢各肢段达到最大后摆时间、最大角度峰值、最大后摆角速度及最大前摆角速度等参数发生的时间与一般健身者无差异.结论:与一般健身者相比,足球运动员是通过增加下肢肢段的后摆角度,从而获得较快的肢段速度.     

Miniature eye movements enhance fine spatial detail

Our eyes are constantly in motion. Even during visual fixation, small eye movements continually jitter the location of gaze. It is known that visual percepts tend to fade when retinal image motion is eliminated in the laboratory. However, it has long been debated whether, during natural viewing, fixational eye movements have functions in addition to preventing the visual scene from fading. In this study, we analysed the influence in humans of fixational eye movements on the discrimination of gratings masked by noise that has a power spectrum similar to that of natural images. Using a new method of retinal image stabilization, we selectively eliminated the motion of the retinal image that normally occurs during the intersaccadic intervals of visual fixation. Here we show that fixational eye movements improve discrimination of high spatial frequency stimuli, but not of low spatial frequency stimuli. This improvement originates from the temporal modulations introduced by fixational eye movements in the visual input to the retina, which emphasize the high spatial frequency harmonics of the stimulus. In a natural visual world dominated by low spatial frequencies, fixational eye movements appear to constitute an effective sampling strategy by which the visual system enhances the processing of spatial detail.     

存储转发方式的RPR环中分组传输延时分析

基于排队论,对存储转发方式的弹性分组环中分组传输延时进行了分析．讨论了高、低优先级业务的分组在弹性分组环中的延时,以及不同优先级的业务分组传输延时与环节点数目之间的关系．     

Robust Stabilization of Delayed Systems with Rank-1 Type Uncertainties

This paper deals with the problem of robust stabilizationfor the systems with rank-1 type uncertainties and mul-tiple state delay.Firstly,a new delay-dependent crite-ria is presented for unforced normal delayed system to bestable.Based on the obtained criteria,a new LMI ap-proach is developed for robust stabilization of a class ofuncertain delay systems via linear memoryless state feed-back control law.The results depend on the size of thedelays and are given in terms of linear matrix inequali-ties.And so no tuning procedure for scalars and/or ma-trices is required and the results are less conservativethan those of delay-independent.Finally,an illustra-tive example is presented.     

V2V三维宽带信道建模与统计特性分析

针对5G车对车(vehicle to vehicle, V2V)无线通信系统,基于几何随机建模方法,提出一种改进的三维宽带多输入多输出(multiple-input and multiple-outpit, MIMO)信道模型。引入多共焦半椭球体模型用于研究不同传播延迟下的V2V信道统计特性,结合时变的路径长度、信号角度和莱斯因子表征V2V信道的非平稳特性。推导了空-时相关函数、多普勒功率谱密度等关键信道统计特性的数学表达式。分析了城市和高速场景下信道相关特性的差别,并研究了车流密度、运动方向、天线角度、传播延迟等因素对信道统计特性的影响。结果表明,城市场景下的时间相关性和空间相关性明显低于高速场景;不同传播延迟下的V2V信道统计特性有明显差异;信道相关性同天线阵列角度、收发车运动方向和时间变化密切相关。模型仿真结果为车载通信提供了一些有价值的结论,可以作为未来V2V通信系统设计、优化和评估的有效指导。仿真结果与实测数据较好地吻合,证明模型能正确表征V2V无线信道的相关特性。     

Sound velocities of majorite garnet and the composition of the mantle transition region

The composition of the mantle transition region, characterized by anomalous seismic-wave velocity and density changes at depths of approximately 400 to 700 km, has remained controversial. Some have proposed that the mantle transition region has an olivine-rich 'pyrolite' composition, whereas others have inferred that it is characterized by pyroxene- and garnet-rich compositions ('piclogite'), because the sound velocities in pyrolite estimated from laboratory data are substantially higher than those seismologically observed. Although the velocities of the olivine polymorphs at these pressures (wadsleyite and ringwoodite) have been well documented, those of majorite (another significant high-pressure phase in the mantle transition region) with realistic mantle compositions have never been measured. Here we use combined in situ X-ray and ultrasonic measurements under the pressure and temperature conditions of the mantle transition region to show that majorite in a pyrolite composition has sound velocities substantially lower than those of earlier estimates, owing to strong nonlinear decreases at high temperature, particularly for shear-wave velocity. We found that pyrolite yields seismic velocities more consistent with typical seismological models than those of piclogite in the upper to middle parts of the region, except for the potentially larger velocity jumps in pyrolite relative to those observed at a depth of 410 km. In contrast, both of these compositions lead to significantly low shear-wave velocities in the lower part of the region, suggesting possible subadiabatic temperatures or the existence of a layer of harzburgite-rich material supplied by the subducted slabs stagnant at these depths.     

交叉口快速公交车道共享策略及延误时间研究

为了缓解因交叉口公交优先策略引起的社会车辆延误加剧,在设置有快速公交(bus rapid transit,BRT)专用道的交叉口提出一种借道系统.社会车辆在一定条件下可以借用BRT道通过交叉口,通过动态控制BRT车道的使用权限,可以显著提高BRT道利用率;然后在借道系统的基础上,根据BRT车到达时间的不同,利用三角形法对社会车辆进行延误分析;最后利用Lingo求解软件进行算例分析.对比启用借道系统前后的社会车辆延误,结果表明启用借道系统后交叉口社会车辆延误平均值明显小于启用前;BRT车辆在一定时间内到达交叉口,借道系统效果最好,社会车辆延误率最低;随着社会车辆到达率的增加,借道系统共享优化率升高,优化幅度变大.借道系统并没有影响BRT优先,交叉口整体延误率降低.     

Estimation of Incident-Induced Congestion on Signalized Arteries Using Traffic Sensor Data

This paper describes how to derive quantitative information about the effect of traffic incidents on urban traffic flow from the raw measurements detected by sectional loop sensors. The two critical parameters of the travel delay and queue length, which reflect the temporal and spatial properties of incident-induced congestion, cannot be directly determined from commonly used loop sensors. The modified queuing diagram is used here to quantify incident-induced queues and travel delays on signalized arteries using sensor data from the targeted and upstream links. The method is tested using data generated by the VISSIM simulation model, with results indicating its efficiency and accuracy with an average relative travel delay error of 18.67% for all samples which falls to 8.07% for high volume and very high volume conditions.     

Motion Tracking with Fast Adaptive Background Subtraction

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A neural representation of depth from motion parallax in macaque visual cortex

Perception of depth is a fundamental challenge for the visual system, particularly for observers moving through their environment. The brain makes use of multiple visual cues to reconstruct the three-dimensional structure of a scene. One potent cue, motion parallax, frequently arises during translation of the observer because the images of objects at different distances move across the retina with different velocities. Human psychophysical studies have demonstrated that motion parallax can be a powerful depth cue, and motion parallax seems to be heavily exploited by animal species that lack highly developed binocular vision. However, little is known about the neural mechanisms that underlie this capacity. Here we show, by using a virtual-reality system to translate macaque monkeys (Macaca mulatta) while they viewed motion parallax displays that simulated objects at different depths, that many neurons in the middle temporal area (area MT) signal the sign of depth (near versus far) from motion parallax in the absence of other depth cues. To achieve this, neurons must combine visual motion with extra-retinal (non-visual) signals related to the animal's movement. Our findings suggest a new neural substrate for depth perception and demonstrate a robust interaction of visual and non-visual cues in area MT. Combined with previous studies that implicate area MT in depth perception based on binocular disparities, our results suggest that area MT contains a more general representation of three-dimensional space that makes use of multiple cues.     

Perceptual consequences of centre-surround antagonism in visual motion processing

Centre-surround receptive field organization is a ubiquitous property in mammalian visual systems, presumably tailored for extracting image features that are differentially distributed over space. In visual motion, this is evident as antagonistic interactions between centre and surround regions of the receptive fields of many direction-selective neurons in visual cortex. In a series of psychophysical experiments we make the counterintuitive observation that increasing the size of a high-contrast moving pattern renders its direction of motion more difficult to perceive and reduces its effectiveness as an adaptation stimulus. We propose that this is a perceptual correlate of centre-surround antagonism, possibly within a population of neurons in the middle temporal visual area. The spatial antagonism of motion signals observed at high contrast gives way to spatial summation as contrast decreases. Evidently, integration of motion signals over space depends crucially on the visibility of those signals, thereby allowing the visual system to register motion information efficiently and adaptively.     

基于时间轴小波变换的运动对象分割算法研究

对时间轴一维小波变换的视频运动对象分割算法进行了研究。将视频序列进行时间轴一维小波变换,利用变换后的高频帧信息提取出初步的运动掩模图像;进行数学形态学后处理,以消除各种噪声的影响和对象的不连通性,得到理想的运动掩模图像。实验结果表明该方法分割效果较好,分割出的运动对象可直接应用于基于对象的视频编码,且算法耗时较少。     

基于残差神经网络的高强度运动超分辨率图像重构

针对实际拍摄的亚像素信息较少的低分辨率运动图像,重构图像通常较为模糊,甚至不能分辨。为此,提出一种新的基于残差神经网络的高强度运动超分辨率图像重构方法。令沿运动方向的亮度保持恒定,通过光流场匹配实现高强度运动图像的运动估计;根据运动估计结果和超分辨率重构的基本思想,将BP神经网络看作残差神经网络的基础建立残差神经网络,对残差神经网络进行训练,参照训练样本将经插值法放大若干倍的待重构高强度运动图像作为输入,将高分辨率图像和输入图像间的残差作为输出,把输入和输出累加获取超分辨率图像,实现若干放大倍数高强度运动超分辨率图像的重构。实验结果表明,所提方法运动估计准确,重构图像清晰、质量佳。     

An analysis of the polar motion series from VLBI observations

From the reduction of 2893 globally distributed astrometric and geodetic VLBI sessions from August 1979 to the end of 1998, coordinates of 722 radio sources at J2000.0, coordinates and velocities of 128 stations at J1997.0 and about 20 years Earth Orientation Parameters were estimated. From the analysis of the resultant polar motion series, the following are demonstrated: (ⅰ) During the VLBI data span the Markowitz wobble is not exhibited. (ⅱ) The amplitudes of both annual and Chandler wobble show temporal variations, with the former being more obvious than the latter. (ⅲ) Wavelet analysis shows that all the signals in the polar motion series are characterized by temporal variation in amplitudes. If we take any signal as strictly periodic, it is impossible to remove it completely from the polar motion series by least-squares fit because the hypothesis of a constant amplitude conflicts with VLBI measurements. (ⅳ) By applying a filter, the secular polar motion was found to be (2.74±0.01) mas/a towards (83.9±0.3) °W longitude, which is smaller in rate and more westward in direction compared with those determined from optical observations or the combination of optical and space geodetic observations.     

基于时间轴小波变换的运动对象分割算法研究

对时间轴一维小波变换的视频运动对象分割算法进行了研究。将视频序列进行时间轴一维小波变换，利用变换后的高频帧信息提取出初步的运动掩模图像；进行数学形态学后处理，以消除各种噪声的影响和对象的不连通性，得到理想的运动掩模图像。实验结果表明该方法分割效果较好，分割出的运动对象可直接应用于基于对象的视频编码，且算法耗时较少。     

混合编程技术在电子稳像中的应用

为提高电子稳像系统中重要环节－－运动估计的计算速度,结合Intel公司Pentium处理器新增的MMX指令,采用混合编程技术,在使用Visual C 进行程序设计和开发的过程中,用嵌入MMX汇编语言实现计算量密集的运动估计,极大地提高了运动估计的计算速度,通过混合编程技术的运用有效地满足了电子稳像系统中运动估计部分对计算速度的要求。     

基于CameraLink高清图像跟踪器设计

针对以前标清摄像机PAL视频分辨率低,容易受干扰,传输延迟,导致图像跟踪器跟踪效果不理想。选用高清摄像机作为图像跟踪器图像输入源,基于高清摄像机CameraLink接口,设计了一款高清图像跟踪器。该图像跟踪器采用全数字接口,处理高清视频,数据处理量大,抗干扰强,提高了跟踪性能。     

机器结构声发射的表征:自由速度和导纳的测量

本文对机器结构声发射的表征作了实验研究.所推荐的源描述符要求对机器与支撑结构的接触点的自由速度作测量,同时对机器的源导纳作测量或估算.本文对平动和转动的速度测量作了讨论,对力和力矩导纳的测量也作了描述.对一个机器家族——为建筑物服务的离心风扇,在三个自由度、多支撑点上的源描述符进行了评价.数据的表示作了简化.从而使得同类型的机器和一个机器中不同振动分量间可以作比较.在所研究的机器中,似乎在低频区垂直力分量引起的发射占主要.然而力矩的贡献却随着频率的增加,其相对重要性也增加,可能在高频区会占据主要地位.