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SIFT based algorithm for point feature tracking
Adrian BURLACU,Cosmin COPOT,Corneliu LAZAR
Annals of Dunarea de Jos , 2007,
Abstract: In this paper a tracking algorithm for SIFT features in image sequences is developed. For each point feature extracted using SIFT algorithm a descriptor is computed using information from its neighborhood. Using an algorithm based on minimizing the distance between two descriptors tracking point features throughout image sequences is engaged. Experimental results, obtained from image sequences that capture scaling of different geometrical type object, reveal the performances of the tracking algorithm.
A tracking algorithm based on SIFT

重庆邮电大学学报(自然科学版) , 2011,
Abstract: To resolve moving objects sheltering, a new object tracking algorithm is presented. The first three frames are used to establish the background model. Then, contiguous-frame subtracting and background subtracting are used to separate the moving objects automatically. SIFT feature is computed for each moving object. When sheltering is detected, SIFT features are used to match the sheltered region with the single moving object. The location of single moving objects in the sheltered region is located by the coordinate of the feature points. Then, RANSAC is used to optimize the SIFT features matching. Experiments show that our algorithm can track the sheltered objects accurately. It can effectively resolve moving objects sheltering and track moving objects continuously and stably.
Evaluation of the optical conductivity tensor in terms of contour integrations  [PDF]
Laszlo Szunyogh,Peter Weinberger
Physics , 2000, DOI: 10.1088/0953-8984/11/50/333
Abstract: For the case of finite life-time broadening the standard Kubo-formula for the optical conductivity tensor is rederived in terms of Green's functions by using contour integrations, whereby finite temperatures are accounted for by using the Fermi-Dirac distribution function. For zero life-time broadening, the present formalism is related to expressions well-known in the literature. Numerical aspects of how to calculate the corresponding contour integrals are also outlined.
Contour Tracking of Targets with Large Aspect Change  [cached]
Behzad Jamasbi,Seyed Ahmad Motamedi,Alireza Behrad
Journal of Multimedia , 2007, DOI: 10.4304/jmm.2.6.7-14
Abstract: In this paper we present a novel method for tracking contour of a moving rigid object in natural video sequences from a mobile camera. While a mobile camera is keeping track of a moving target, any change in relative orientation or position of the target and camera may cause a change in the view of target captured by the camera. This is called the target aspect change and known as a challenge in tracking. Especially, a large aspect change may reveal some previously hidden parts of the target, and this is the case we have handled in our algorithm. In proposed contour tracking method the motion model of the target is estimated using corner matching and LMedS statistical method. This model is used together with an active contour (snake) to track the target efficiently. The snake we propose is capable of swelling locally, so that it can swell and include newly appeared parts of the target in case of a large aspect change. Detecting target newly appeared parts, is based on the fact that a part of target should move consistently with other parts and inconsistently with the background. When a new part is detected the nearby part of the snake is stimulated to swell. In this way the snake will include any new part of the target revealed by a large aspect change. Several experiments have been conducted to show the promise of proposed algorithm.
Target Contour Recovering for Tracking People in Complex Environments
Jianhua Zhang,Sheng Liu,Y. F. Li,Jianwei Zhang
Computational and Mathematical Methods in Medicine , 2012, DOI: 10.1155/2012/506908
Abstract: Recovering people contours from partial occlusion is a challenging problem in a visual tracking system. Partial occlusions would bring about unreasonable contour changes of the target object. In this paper, a novel method is presented to detect partial occlusion on people contours and recover occluded portions. Unlike other occlusion detection methods, the proposed method is only based on contours, which makes itself more flexible to be extended for further applications. Experiments with synthetic images demonstrate the accuracy of the method for detecting partial occlusions, and experiments on real-world video sequence are also carried out to prove that the method is also good enough to be used to recover target contours.
Robust Tract Skeleton Extraction of Cingulum Based on Active Contour Model from Diffusion Tensor MR Imaging  [PDF]
Wu Li, Xiaoping Hu
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056113
Abstract: Cingulum is widely studied in healthy and psychiatric subjects. For cingulum analysis from diffusion tensor MR imaging, tractography and tract of interest method have been adopted for tract-based analysis. Because tractography performs fiber tracking according to local diffusion measures, they can be sensitive to noise and tracking errors can be accumulated along the fiber. For more accurate localization of cingulum, we attempt to define it by skeleton extraction using the tensors' information throughout the tract of cingulum simultaneously, which is quite different from the idea of tractography. In this study, we introduce an approach to extract the skeleton of cingulum using active contour model, which allows us to optimize the location of cingulum in a global sense based on the diffusion measurements along the entire tract and contour regularity. Validation of this method on synthetic and experimental data proved that our approach is able to reduce the influence of noise and partial volume effect, and extract the skeleton of cingulum robustly and reliably. Our proposed method provides an approach to localize cingulum robustly, which is a very important feature for tract-based analysis and can be of important practical utility.
Estimation of Infants' Cry Fundamental Frequency using a Modified SIFT algorithm  [PDF]
Dror Lederman
Computer Science , 2010,
Abstract: This paper addresses the problem of infants' cry fundamental frequency estimation. The fundamental frequency is estimated using a modified simple inverse filtering tracking (SIFT) algorithm. The performance of the modified SIFT is studied using a real database of infants' cry. It is shown that the algorithm is capable of overcoming the problem of under-estimation and over-estimation of the cry fundamental frequency, with an estimation accuracy of 6.15% and 3.75%, for hyperphonated and phonated cry segments, respectively. Some typical examples of the fundamental frequency contour in typical cases of pathological and healthy cry signals are presented and discussed.
Flux Tensor Constrained Geodesic Active Contours with Sensor Fusion for Persistent Object Tracking  [cached]
Filiz Bunyak,Kannappan Palaniappan,Sumit Kumar Nath,Gunasekaran Seetharaman
Journal of Multimedia , 2007, DOI: 10.4304/jmm.2.4.20-33
Abstract: This paper makes new contributions in motion detection, object segmentation and trajectory estimation to create a successful object tracking system. A new efficient motion detection algorithm referred to as the flux tensor is used to detect moving objects in infrared video without requiring background modeling or contour extraction. The flux tensor-based motion detector when applied to infrared video is more accurate than thresholding ”hot-spots”, and is insensitive to shadows as well as illumination changes in the visible channel. In real world monitoring tasks fusing scene information from multiple sensors and sources is a useful core mechanism to deal with complex scenes, lighting conditions and environmental variables. The object segmentation algorithm uses level set-based geodesic active contour evolution that incorporates the fusion of visible color and infrared edge informations in a novel manner. Touching or overlapping objects are further refined during the segmentation process using an appropriate shapebased model. Multiple object tracking using correspondence graphs is extended to handle groups of objects and occlusion events by Kalman filter-based cluster trajectory analysis and watershed segmentation. The proposed object tracking algorithm was successfully tested on several difficult outdoor multispectral videos from stationary sensors and is not confounded by shadows or illumination variations.
Affine invariability of contour structure tensor

QU Ying,YANG Dan,ZHANG Xiao-hong b,
曲 颖
,杨 丹,张小洪b

计算机应用研究 , 2012,
Abstract: This paper proved the affine invariability of contour structure tensor by studying the algebraic properties of its determinant: the extreme points described by the determinant of the contour structure tensor under the affine transform remain no change.It only influenced the response of each point on the contour by scale transform and independent of translation and rotation transform.Finally, experiment results verify the high stability of the algorithm based on contour structure tensor by comparing its repeatability with some classical contour corner detection algorithms.
Testing scalar-tensor theories and PPN parameters in Earth orbit  [PDF]
Andreas Sch?rer,Raymond Angélil,Ruxandra Bondarescu,Philippe Jetzer,Andrew Lundgren
Physics , 2014, DOI: 10.1103/PhysRevD.90.123005
Abstract: We compute the PPN parameters $\gamma$ and $\beta$ for general scalar-tensor theories in the Einstein frame, which we compare to the existing PPN formulation in the Jordan frame for alternative theories of gravity. This computation is important for scalar-tensor theories that are expressed in the Einstein frame, such as chameleon and symmetron theories, which can incorporate hiding mechanisms that predict environment-dependent PPN parameters. We introduce a general formalism for scalar-tensor theories and constrain it using the limit on $\gamma$ given by the Cassini experiment. In particular we discuss massive Brans-Dicke scalar fields for extended sources. Next, using a recently proposed Earth satellite experiment, in which atomic clocks are used for spacecraft tracking, we compute the observable perturbations in the redshift induced by PPN parameters deviating from their general relativistic values. Our estimates suggest that $|\gamma - 1| \sim |\beta -1| \sim 10^{-6}$ may be detectable by a satellite that carries a clock with fractional frequency uncertainty $\Delta f/f \sim 10^{-16}$ in an eccentric orbit around the Earth. Such space experiments are within reach of existing atomic clock technology. We discuss further the requirements necessary for such a mission to detect deviations from Einstein relativity.
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