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1.
A method for parametric identification of an object motion model represented in terms of generalized polynomials is proposed. The method is based on a stationary direction finder that, in addition to its own angular measurements, obtains data about the slant range to the observed object.  相似文献   

2.
Exact solutions for some oscillating motions of Oldroyd-B fluids, between two infinite coaxial circular cylinders, are established by means of the Laplace transform. These solutions, presented as sum of the steady-state and transient solutions describe the motion of the fluid at small and large times and reduce to the similar solutions for Maxwell, second grade and Newtonian fluids as limiting cases. After some time, when the transients disappear, the starting solutions tend to the steady-state solutions which are periodic in time and independent of the initial conditions. The required time to obtain the steady-state for the cosine and the sine oscillations of the boundary is determined by graphical illustrations. This time decreases if the frequency of the velocity of the boundary increases.  相似文献   

3.
This paper presents a direction detection and tracking object color update algorithm used to track moving objects that change colors. Different from traditional color-based tracking methods, which use an initial color distribution in order to track objects as long as the object carries the full or partial initial color, this method introduces a color update method used to quickly find the new object color in a new location if the object changes its color partially or completely; the updated color is then used to locate the object. In our algorithm, an initial color pattern is used to track an object using the color. During the tracking, an object’s new location is at first estimated and then used to detect any color change. If the color has changed, a new color pattern is updated based on the changes in the previous color distribution, and then the new color pattern is used to calculate the current location of the object. This algorithm utilizes the property that the movement of an object can be estimated either by using the object’s shadow or by background subtraction. The implementation of our algorithm results in an effective real-time object tracking. The validity of the approach is illustrated by the presentation of experiment results obtained using the methods described in this paper.  相似文献   

4.
《Ergonomics》2012,55(5):609-616
This study investigated the effect of object curvature, normal force and material on skin friction coefficient. Twelve subjects slid their middle fingertip pad against a test object with small (11 mm), medium (18, 21 mm) or large (flat object) radii of curvature, while maintaining a normal force of 1, 10 or 20 N. Tested materials were aluminium and four rubber hoses. The average friction coefficient was 0.6 for aluminium and 0.9 for the rubber hoses. As normal force increased from 1 to 20 N, the average friction coefficient decreased 46%. Friction coefficient did not vary significantly with object curvature. The citation of friction coefficient data requires careful attention to normal force levels with which they are measured, but not so much to object curvature between 11 mm and infinity. This study provides skin friction coefficient data that are needed for design of objects that are manipulated with the hands. The investigation of the effect of object curvature on skin friction coefficient has important implications to ergonomics practices as many objects handled in everyday activities have curved surfaces.  相似文献   

5.
A mobile mechanism capable of moving along a rough plane inclined surface using the motion of internal masses according to the harmonic law is considered. Oscillations of internal masses have equal frequencies and different phases. It is shown that using this principle of motion the mechanism can move upward along an inclined plane. Maximization conditions of the established motion velocity are given.  相似文献   

6.
We have shown previously that it is possible to accurately reconstruct periodic motions in 3D from a single camera view, using periodicity as a physical constraint from which to perform geometric inference. In this paper we explore the suitability of the reconstruction techniques for real human motion. We examine the degree of periodicity of human gait empirically, and develop algorithmic tools to address some of the challenges arising from this type of motion, including reconstructing motions that deviate from pure periodicity, properly handling the trajectories of multiple points on an articulated body, and proposing a distance function for measuring the difference between two reconstructions. Importantly, we illustrate the usefulness of these techniques by applying them to the tasks of view-invariant activity classification, clinical gait analysis and person identification.  相似文献   

7.
利用拉氏算子鉴别运动模糊方向   总被引:7,自引:0,他引:7  
提出一种新的鉴别运动模糊图像的运动模糊方向的方法,它利用拉氏算子对运动模糊图像进行无方向性的二阶微分,并求微分图像的自相关,发现自相关图像中数值较大的点(鉴别点)能够有效标示出运动模糊方向。选取适当数目的候选鉴别点,并利用聚类方法剔除其中的奇异点,得到鉴别点;过零频尖峰(自相关图像的中心点)画一条直线,计算各个鉴别点到该直线的距离,求距离和;改变直线方向,当距离和最小时,直线的方向即为运动模糊方向。数据实验表明,这一新的运动模糊方向鉴别方法,具有抗噪声能力强、适用范围广、计算量小、鉴别精度高、稳定性好的优点.  相似文献   

8.
This article describes a novel technique for detecting a human and his or her body direction using the histograms of oriented gradients (HOG) feature. The HOG feature is a well-known feature for judging a human, but normally it contains a background feature, which has a negative influence on the judgment. This article proposes the employment of the HOG feature based on a human model. The feature is also employed for detecting the direction of a human body. Experimental results show the effectiveness of the proposed technique compared with conventional ones.  相似文献   

9.
In this paper, we show how a statistical model of facial shape can be embedded within a shape-from-shading algorithm. We describe how facial shape can be captured using a statistical model of variations in surface normal direction. To construct this model, we make use of the azimuthal equidistant projection to map the distribution of surface normals from the polar representation on a unit sphere to Cartesian points on a local tangent plane. The distribution of surface normal directions is captured using the covariance matrix for the projected point positions. The eigenvectors of the covariance matrix define the modes of shape-variation in the fields of transformed surface normals. We show how this model can be trained using surface normal data acquired from range images and how to fit the model to intensity images of faces using constraints on the surface normal direction provided by Lambert's law. We demonstrate that the combination of a global statistical constraint and local irradiance constraint yields an efficient and accurate approach to facial shape recovery and is capable of recovering fine local surface details. We assess the accuracy of the technique on a variety of images with ground truth and real-world images  相似文献   

10.
We construct a class of non-Markov discrete-time stationary random processes with countably many states for which the entropy of the one-dimensional distribution is infinite, while the conditional entropy of the “present” given the “past” is finite and coincides with the metric entropy of a shift transformation in the sample space. Previously, such situation was observed in the case of Markov processes only.  相似文献   

11.
This paper examines spurious Granger causality between a trend stationary process with structural breaks and a stochastic trend process. Monte Carlo simulations show that whether or not there are deterministic variables in the testing models, the sample size and the parameter values of the data generation process can affect the empirical frequencies of spurious Granger causality relations in different degrees. The analysis also points out that an alternative rank-based causality test method can avoid the risk of spurious causality to some extent by adopting an intercept and deterministic trend term in the testing regressions.  相似文献   

12.
The recently proposed reduced convex hull support vector regression (RH-SVR) treats support vector regression (SVR) as a classification problem in the dual feature space by introducing an epsilon-tube. In this paper, an efficient and robust adaptive normal direction support vector regression (AND-SVR) is developed by combining the geometric algorithm for support vector machine (SVM) classification. AND-SVR finds a better shift direction for training samples based on the normal direction of output function in the feature space compared with RH-SVR. Numerical examples on several artificial and UCI benchmark datasets with comparisons show that the proposed AND-SVR derives good generalization performance  相似文献   

13.
The instability of the Marangoni toroidal flows in microchannels is of interest in various areas such as microfluidics and heat transfer. Using pure liquid as working fluid in this study, the phenomena of Marangoni symmetry-to-asymmetry transition which does not arise from the buoyancy was observed. The experiments used a vertical cylindrical channel and the meniscus was formed at the bottom outlet to minimize the buoyant influences. Two microscopes were used to have top view and side view of the meniscus simultaneously. The Marangoni flow field on the meniscus was obtained by means of tracing particles. It was observed that the Marangoni flow on a concave meniscus was always nearly symmetrical, while that on a convex meniscus was out of symmetry with only one single vortex occupying the whole channel. The experimental results were highly consistent to the simulation results of authors’ previous 3D numerical model (Pan and Wang in Microfluid Nanofluid 9:657, 2010). Theoretical analysis together with newly developed numerical models is employed to dig into the mechanisms. The inward (from the meniscus edge to the center) Marangoni flow is found not as stable as the outward one. Based on the heat transfer analysis, a concave meniscus always has a colder edge thus the flow is outward and stable; while a convex enough meniscus could have an inward flow thus not stable and tends to lose the symmetry. The amplification mechanism of the inward Marangoni flow is comprehensively explained. Two conditions are required for the inward flow to lose the symmetry, i.e., the bulk liquid must be warmer than the meniscus, and the Marangoni number must be above a certain small value.  相似文献   

14.
介绍了煤炭大数据的来源及特征,分析了当前煤炭大数据应用现状;阐述了煤炭大数据平台化发展对于煤炭大数据应用的意义,分析了煤炭大数据平台建设过程中在数据共享、数据质量、安全性、专业人才等方面存在的问题,提出建设煤炭大数据平台应进行顶层设计、完善煤炭数据标准体系、培养专业人才、合理设计平台框架。  相似文献   

15.
The indeterminacy of conic motion is analyzed in terms of Lie group theory. It is shown that an image motion of a conic is associated with a group ofinvisible motions that do not cause a visible change of the conic. All such groups are isomorphic to the group associated with a special conic called thestandard circle, for which the group of invisible motions is the (three-dimensional)Lorentz group. Similar results are obtained forinvisible optical flows. Finally, our analysis is extended toconic stereo: the 3-D position and orientation of a conic in the scene are computed from two projections. This algorithm also works with one camera if a circular pattern is projected from a light source.  相似文献   

16.
The development of control algorithms, including optimal control ones, in the collision avoidance problem for a system of two pendulums with a controllable common base is considered. Two problems are solved. The first one searches for the law of variation of the bounded control force that makes the system move from its initial state of rest to the given final state of rest during a finite time and ensures the pendulums do not collide in the process of oscillatory motions. The second problem searches for the performance-optimal law of variation of acceleration of the base and the bounded force that generates the acceleration. The algorithms for constructing the sought controls that use Kalman controllability conditions and Pontryagin’s maximum principle method are presented. The dynamics of the system involved is simulated for the constructed control laws. The numerical results of both problems are compared to find that implementation of the developed performance-optimal control algorithm can help significantly decrease the releasing time of the pendulums while preventing a possible collision.  相似文献   

17.
In this article, equations of motion of a manipulator, whose mechanism has a tray installed with a passive revolute joint, are derived after consideration of the characteristics of the driving source. Considering the relative motion between the tray and the object, the trajectories of the velocity for saving energy are calculated by iterative dynamic programming. Also, the dynamic characteristics of manipulator control based on the trajectory for saving energy are analyzed theoretically and investigated experimentally.  相似文献   

18.

The charged particle motion for certain configurations of oscillating magnetic fields can be simulated by a Volterra integro-differential equation of the second order with time-periodic coefficients. This paper investigates a simple and accurate scheme for computationally solving these types of integro-differential equations. To start the method, we first reduce the integro-differential equations to equivalent Volterra integral equations of the second kind. Subsequently, the solution of the mentioned Volterra integral equations is estimated by the collocation method based on the local multiquadrics formulated on scattered points. We also expand the proposed method to solve fractional integro-differential equations including non-integer order derivatives. Since the offered method does not need any mesh generations on the solution domain, it can be recognized as a meshless method. To demonstrate the reliability and efficiency of the new technique, several illustrative examples are given. Moreover, the numerical results confirm that the method developed in the current paper in comparison with the method based on the globally supported multiquadrics has much lesser volume computing.

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19.
20.
In this paper, we propose a crowd motion partitioning approach based on local-translational motion approximation in a scattered motion field. To represent crowd motion in an accurate and parsimonious way, we compute optical flow at the salient locations instead of at all the pixel locations. We then transform the problem of crowd motion partitioning into a problem of scattered motion field segmentation. Based on our assumption that local crowd motion can be approximated by a translational motion field, we develop a local-translation domain segmentation (LTDS) model in which the evolution of domain boundaries is derived from the Gateaux derivative of an objective functional and further extend LTDS to the case of scattered motion field. The experiment results on a set of synthetic vector fields and a set of videos depicting real-world crowd scenes indicate that the proposed approach is effective in identifying the homogeneous crowd motion components under different scenarios.  相似文献   

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