摘要 :
In the past several decades, many lateral track buckling studies have been conducted in an effort to determine an allowable safe temperature increase for preventing the occurrence of buckling. The present analysis builds on some o...
展开
In the past several decades, many lateral track buckling studies have been conducted in an effort to determine an allowable safe temperature increase for preventing the occurrence of buckling. The present analysis builds on some of these studies, but uses recently derived frame-type equations that more accurately represent the response of the rail-tie structure in the lateral plane, The presented analysis takes into account the effects of the torsional stiffness of the rail fasteners, the lateral bending stiffness of the cross-ties, and the track gauge to model more accurately the lateral response of the track panel to temperature increases. It determines effective ways to raise the allowable safe temperature increase, whether by increasing the axial and lateral resistances or by increasing the rotational stiffness of the fasteners. Also, the effect of lateral tie-stiffness on the safe temperature increase is examined.
收起
摘要 :
Measurements of alpha-recoil-track densities in mica as a basis for geological dating depend on an etch model relating the number of tracks per unit volume (N-RT) to the counted number of etched tracks per unit area (rho(RT)). The...
展开
Measurements of alpha-recoil-track densities in mica as a basis for geological dating depend on an etch model relating the number of tracks per unit volume (N-RT) to the counted number of etched tracks per unit area (rho(RT)). The model of Gogen and Wagner (2000) implies that.RT increases linearly with etch time (t(E)), so that NRT can be calculated from the slopes or intercepts of step-etch functions rho(RT)(tE). This model rests on the assumption that the etch rate of the mica surface (nu(V)) and the horizontal etch pit growth rate (nu(H)) are both constant, in contradiction with experimental results and computer simulations of mineral dissolution. We present results of four different experiments aimed at relating etch pit densities to volumetric track densities. Step-etch data are vulnerable to observation-related artefacts at increasing tE and lack the resolution to confirm or refute the supposed linear increase of rho(RT.) with tE. The intercepts of regression lines fitted to step-etch data are imprecise and perhaps inaccurate. Intercept estimates based on mirror-image counts and (etch)-anneal-etch experiments indicate that nu(V) increases during the initial etching stages. The (etch)-anneal-etch results show that no pre-etch is in fact required, implying that surface tracks are more resistant to annealing than tracks in the bulk of the mineral. Track-size measurements confirm that nu(H) is also not constant but decreases with increasing etch-pit size. The results show that no recoil-track etch pit in phlogopite etched in 40% HF grows larger than ca. 7 mu m and that the track-size distribution becomes quasi-invariant at >6 min etching. This signifies that there exist accessible etching conditions at which the etch-pit size distribution becomes a fixed, distorted reflection of the size distribution of latent recoil tracks. It is not improbable that track addition and loss also cancel each other out in this equilibrium state, in which case both the etch-pit size distributions and densitie rho(RT) become independent of etch time. (C) 2015 Elsevier B.V. All rights reserved.
收起
摘要 :
Track-to-track association (T2TA) aims at unifying batch numbers of tracks, reducing redundancy, and clarifying the situation. It is the precondition and foundation of track fusion, situation awareness, and traffic control. Existi...
展开
Track-to-track association (T2TA) aims at unifying batch numbers of tracks, reducing redundancy, and clarifying the situation. It is the precondition and foundation of track fusion, situation awareness, and traffic control. Existing methods based on statistical reasoning or fuzzy math bring some problems that are difficult to solve simultaneously, such as unreasonable assumptions, unsuitable models, uncertain thresholds, and long association times. In the light of the above problems, in this paper, we proposed a T2TA method via Track Fusion and Track Segmentation (TF-TS). The track fusion module fuses and extracts track features from several tracks to reduce the dependency on prior assumptions, motion models, and thresholds. The track segmentation mapping module transforms track tensors into association matrices directly to improve association efficiency. With four kinds of constraints, the association matrices inferred by TF-TS are close to the real one. TF-TS can reduce the dependence on the assumptions, motion models, and thresholds. It can also reduce the traversal calculation of tracks and increase the association efficiency. The global AIS tracks are used to train and test our model, and association results demonstrate that the proposed method can associate tracks in complex scenarios. Moreover, the efficiency is improved and the demand for the real-time association is satisfied.
收起
摘要 :
Purpose: A study of real-time adaptive radiotherapy systems was performed to test the hypothesis that, across delivery systems and institutions, the dosimetric accuracy is improved with adaptive treatments over non-adaptive radiot...
展开
Purpose: A study of real-time adaptive radiotherapy systems was performed to test the hypothesis that, across delivery systems and institutions, the dosimetric accuracy is improved with adaptive treatments over non-adaptive radiotherapy in the presence of patient-measured tumor motion.
收起
摘要 :
Purpose. The purpose of study is to identify the features of the railway track work deformation by establishing the boundaries of the track sustainability depending on the design and condition of systems of the upper and lower tra...
展开
Purpose. The purpose of study is to identify the features of the railway track work deformation by establishing the boundaries of the track sustainability depending on the design and condition of systems of the upper and lower track structure, plan of a line for the possibility of forming a regulatory framework for reliability and functional safety of railway track in Ukraine. Methodology. The complete method of S. P. Pershyn of determination the critical values of compressive strength was used for the achievement of the purpose. Findings. The author found that the ratio of the minimum values of compressive force under the certain bending deformation can be used as evaluation conditions of the track deformation resistance and basis for formation the base of reliability and functional safety of the Ukrainian railway track. Originality. The theoretical position for the consideration the deformation stability of the upper and lower track structure were proposed. It will allow studying the process of deformation work of the system, which changes its state during a particular operating time. Thus, it allows determining the parameters of the functional reliability of the train as a part of security pass of the rolling stock on the track, accounting its technical condition. Practical value. Usually for the safe passage of rolling stock the parameters of the oscillations of the ?vehicle – track? are determined. These parameters are normalized with the instructions on design and maintenance of the railway track. Changes in the regulatory framework of rail transport in recent years provide the observance of its functional safety that are not included in the existing regulations of the railway track. Therefore it is necessary the issue of effect impact assessment of the rolling stock on the track to consider as a dynamic process, limit states criteria of which are determined on the basis of existing norms, correlated with the reliability states, and to develop criteria for security throughout the life cycle on their basis. At considering the dynamic process of track oscillation and rolling stock must take into account the deformation resistance of the track. This issue was addressed only in terms of changes in temperature deformations. This study provides a basis at which it is possible to take into account the stiffness of deformation for the ability of regulatory framework formation for reliability and functional safety of railway track in Ukraine.
收起
摘要 :
The existence of motion blur can inevitably influence the performance of visual object tracking. However, in contrast to the rapid development of visual trackers, the quantitative effects of increasing levels of motion blur on the...
展开
The existence of motion blur can inevitably influence the performance of visual object tracking. However, in contrast to the rapid development of visual trackers, the quantitative effects of increasing levels of motion blur on the performance of visual trackers still remain unstudied. Meanwhile, although image-deblurring can produce visually sharp videos for pleasant visual perception, it is also unknown whether visual object tracking can benefit from image deblurring or not. In this paper, we present a Blurred Video Tracking (BVT) benchmark to address these two problems, which contains a large variety of videos with different levels of motion blurs, as well as ground-truth tracking results. To explore the effects of blur and deblurring to visual object tracking, we extensively evaluate 25 trackers on the proposed BVT benchmark and obtain several new interesting findings. Specifically, we find that light motion blur may improve the accuracy of many trackers, but heavy blur usually hurts the tracking performance. We also observe that image deblurring is helpful to improve tracking accuracy on heavily-blurred videos but hurts the performance of lightly-blurred videos. According to these observations, we then propose a new general GAN-based scheme to improve a tracker’s robustness to motion blur. In this scheme, a fine-tuned discriminator can effectively serve as an adaptive blur assessor to enable selective frames deblurring during the tracking process. We use this scheme to successfully improve the accuracy of 6 state-of-the-art trackers on motion-blurred videos.
收起
摘要 :
Despite significant advances in particle imaging technologies over the past two decades, few advances have been made in particle tracking, i.e., linking individual particle positions across time series data. The state-ofthe- art t...
展开
Despite significant advances in particle imaging technologies over the past two decades, few advances have been made in particle tracking, i.e., linking individual particle positions across time series data. The state-ofthe- art tracking algorithm is highly effective for systems in which the particles behave mostly independently. However, these algorithms become inaccurate when particle motion is highly correlated, such as in dense or strongly interacting systems. Accurate particle tracking is essential in the study of the physics of dense colloids, such as the study of dislocation formation, nucleation, and shear transformations. Here, we present a method for particle tracking that incorporates information about the correlated motion of the particles. We demonstrate significant improvement over the state-of-the-art tracking algorithm in simulated data on highly correlated systems.
收起
摘要 :
In both military and civilian surveillance systems such as Air Traffic Control (ATC) systems, tracking targets in clutter using radar involves dealing with a number of challenges, all related to real time decision and data fusion ...
展开
In both military and civilian surveillance systems such as Air Traffic Control (ATC) systems, tracking targets in clutter using radar involves dealing with a number of challenges, all related to real time decision and data fusion theories. A major challenge is to detect the real targets through the received measurements in real time and to activate the tracking process.
收起
摘要 :
This paper studies the effect of railway track design parameters on the expected long-term degradation of track geometry. The study assumes a geometrically perfect and straight track along with spatial invariability, except for th...
展开
This paper studies the effect of railway track design parameters on the expected long-term degradation of track geometry. The study assumes a geometrically perfect and straight track along with spatial invariability, except for the presence of discrete sleepers. A frequency-domain two-layer model is used of a discretely supported rail coupled with a moving unsprung mass. The susceptibility of the track to degradation is objectively quantified by calculating the mechanical energy dissipated in the substructure under a moving train axle for variations of different track parameters. Results show that, apart from the operational train speed, the ballast/substructure stiffness is the most significant parameter influencing energy dissipation. Generally, the degradation increases with the train speed and with softer substructures. However, stiff subgrades appear more sensitive to particular train velocities, in a regime which is mostly relevant for conventional trains (100-200 km/h) and less for high-speed operation, where a stiff subgrade is always favorable and can reduce the sensitivity to degradation substantially, with roughly a factor up to 7. Also railpad stiffness, sleeper distance and rail cross-sectional properties are found to have considerable effect, with higher expected degradation rates for increasing railpad stiffness, increasing sleeper distance and decreasing rail profile bending stiffness. Unsprung vehicle mass and sleeper mass have no significant influence, however, only against the background of the assumption of an idealized (invariant and straight) track. Apart from dissipated mechanical energy, the suitability of the dynamic track stiffness is explored as an engineering parameter to assess the sensitivity to degradation. It is found that this quantity is inappropriate to assess the design of an idealized track. (c) 2018 Elsevier Ltd. All rights reserved.
收起
摘要 :
Purpose. The tasks of modeling the interaction of track and rolling stock are basic ones for most areas of mo-dern scientific research of railway transport. The compilation of the model by the principle of Lagrange d'Alembert has ...
展开
Purpose. The tasks of modeling the interaction of track and rolling stock are basic ones for most areas of mo-dern scientific research of railway transport. The compilation of the model by the principle of Lagrange d'Alembert has found a very wide application for solving the problems of rolling stock dynamics. Representation of the railway track in the model of crew movement can be implemented in several ways, which, among other things, will differ in detail. The purpose of this work is to create a methodology for representing the railway track in mathematical mo-dels of interaction with rolling stock and obtaining practical results for different characteristics and design of the track and the level of maximum speed. Methodology. The problem consists of determining such characteristics of the path as the reduced mass, the stiffness coefficient, and the dissipation coefficient. As a tool for solving this problem it was used the model of the stress-strain behavior of the railway track based on the joint use of the elastic wave propagation equations to describe the geometry of the outline of the part of the system space that is involved in the interaction at a given time and the equations of dynamic equilibrium of its deformation. This makes it possible to take into account the dynamics of the deflection of the under-rail base, which is especially important for the conditions of passenger traffic, which can be carried out at high speed. Findings. Theoretically justified stiffness and dissipation coefficients of the railway track for calculating the dynamics of rolling stock in modern models based on systems of equations in accordance with the Lagrange d'Alembert principle are obtained. The established va-lues, in contrast to those given in other sources, have a reasonable dependence on the design of the path and the speed of movement. Originality. The approaches of railroad track representation in models of rolling stock described by systems of equations by the Lagrange-d'Alembert principle are expanded. A method for determining the characteristics of the railway track for such models is developed based on the results of variant calculations of the dynamic deflection of the rail from the passage of the wheel. Practical value. The values of the stiffness and dissipation coefficients of the railway track are obtained depending on the design and speed of motion for practical use in appropriate models of interaction between track and rolling stock.
收起
原文获取