The Experts below are selected from a list of 86352 Experts worldwide ranked by ideXlab platform
Ken Kamrin - One of the best experts on this subject based on the ideXlab platform.
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power law scaling in granular rheology across flow geometries
2020Co-Authors: Ken KamrinAbstract:Based on discrete element method simulations, we propose a new form of the constitutive equation for granular flows independent of packing fraction. Rescaling the stress ratio μ by a power of dimensionless temperature Θ makes the data from a wide set of flow geometries collapse to a master curve depending only on the inertial number I. The basic power-law structure appears robust to varying particle properties (e.g., Surface Friction) in both 2D and 3D systems. We show how this rheology fits and extends frameworks such as kinetic theory and the nonlocal granular fluidity model.
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Effect of particle Surface Friction on nonlocal constitutive behavior of flowing granular media
2014Co-Authors: Ken Kamrin, Georg KovalAbstract:A recently proposed nonlocal rheology for dense granular flow, based on the concept of nonlocal granular fluidity, has demonstrated predictive capabilities in multiple geometries. This work is concerned with determining how the parameters of this continuum model arise from the properties of the grains themselves. We perform a controlled study investigating how the Surface Friction of the grains influences the continuum parameters, with a focus on how the nonlocal amplitude, the model’s one new parameter, is affected. This is achieved comparing two-dimensional discrete-element simulations of flowing disks to numerical solutions of the model in planar shear and several annular shear geometries. A multi-step calibration scheme for the continuum parameter extraction is developed and implemented. Results indicate the nonlocal amplitude varies less than an order of magnitude over a wide range of Surface Frictions, with a slight tendency to increase as Surface Friction decreases, particularly in a regime of small Surface Friction. Our data also show that the stress and flow-rate variables deviate little from a local relationship as Surface Friction vanishes, which corroborates certain existing experimental findings.
Yinhai Wang - One of the best experts on this subject based on the ideXlab platform.
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Road Surface Friction prediction using long short-term memory neural network based on historical data
2020Co-Authors: Chenglong Liu, Xianming Shi, Zhiyong Cui, Yinhai WangAbstract:Road Surface Friction significantly impacts traffic safety and mobility. A precise road Surface Friction prediction model can help to alleviate the influence of inclement road conditions on traffic...
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Time-aware gated recurrent unit networks for forecasting road Surface Friction using historical data with missing values
2020Co-Authors: Zhiyong Cui, Shuo Wang, Yinhai WangAbstract:An accurate road Surface Friction forecasting algorithm can allow travelers and managers to schedule trips and maintenance activities based on the road weather condition to enhance traffic safety and efficiency in advance. Previously, scholars developed multiple forecasting models to predict road Surface conditions using historical data. However, historical dataset used for model training may have missing values caused by multiple issues, e.g. the data collected by on-vehicle sensors may be influenced when vehicles cannot travel due to high economic and labor cost or weather-related issues. The missing values in the road Surface condition dataset can damage the effectiveness and accuracy of the existing prediction methods. This study proposed a road Surface Friction forecasting algorithm by employing a time-aware Gated Recurrent Unit (GRU-D) networks that integrate a decay mechanism as extra gates of the GRU to handle the missing values and forecast the road Surface Friction in future periods simultaneously. The evaluation results present that the proposed GRU-D networks outperform all selected baseline algorithms. The impacts of missing rate on predictive accuracy, learning efficiency, and learned decay rates are investigated as well. The findings can help improve the forecasting accuracy and efficiency of road Surface Friction prediction using historical data with missing values, therefore mitigating the negative impact of wet or icy road conditions on traffic safety and efficiency.
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time aware gated recurrent unit networks for road Surface Friction prediction using historical data
2019Co-Authors: Zhiyong Cui, Shuo Wang, Yinhai WangAbstract:An accurate road Surface Friction prediction algorithm can enable intelligent transportation systems to share timely road Surface condition to the public for increasing the safety of the road users. Previously, scholars developed multiple prediction models for forecasting road Surface conditions using historical data. However, road Surface condition data cannot be perfectly collected at every timestamp, e.g. the data collected by on-vehicle sensors may be influenced when vehicles cannot travel due to economic cost issue or weather issues. Such resulted missing values in the collected data can damage the effectiveness and accuracy of the existing prediction methods since they are assumed to have the input data with a fixed temporal resolution. This study proposed a road Surface Friction prediction model employing a Gated Recurrent Unit network-based decay mechanism (GRU-D) to handle the missing values. The evaluation results present that the proposed GRU-D networks outperform all baseline models. The impact of missing rate on predictive accuracy, learning efficiency and learned decay rate are analyzed as well. The findings can help improve the prediction accuracy and efficiency of forecasting road Surface Friction using historical data sets with missing values, therefore mitigating the impact of wet or icy road conditions on traffic safety.
A A M Holtslag - One of the best experts on this subject based on the ideXlab platform.
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evaluation and model impacts of alternative boundary layer height formulations
1996Co-Authors: D H P Vogelezang, A A M HoltslagAbstract:We study bulk formulations for the boundary-layer height which are currently in use for atmospheric modelling. The formulations are based on various forms of the Richardson number, and these are evaluated with Cabauw field data in stable conditions. Results for both a large-eddy simulation model and anE-e turbulence closure model for neutral boundary layers are also utilised. An updated formulation is introduced, which combines the effects of shear in the outer region of the boundary layer with Surface Friction. The updated formulation has a better performance for neutral boundary layers with upper level stratification. The findings are illustrated with a single-column model for a case with relatively high winds over the tropical ocean including shallow cumulus convection, and for a case with fair weather over land. We also show that for stable conditions, the updated formulation performs better than estimates on the basis of Surface Friction alone.
Susan L Tighe - One of the best experts on this subject based on the ideXlab platform.
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pavement Surface Friction and noise integration into the pavement management system
2010Co-Authors: Alauddin Ahammedm M A Ahammed, Susan L TigheAbstract:Pavement Surface Friction is an essential attribute of highway safety. The desired Surface Friction should also accommodate the seasonal and long-term variations. The available Surface Friction dep...
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early life long term and seasonal variations in skid resistance in flexible and rigid pavements
2009Co-Authors: Mohammad Alauddin Ahammed, Susan L TigheAbstract:Skidding contributes to up to 35% of wet weather accidents. Increased temperature and Surface wear and polishing may affect the available Friction and further increase skid-related accidents. Several studies have attempted to examine and quantify these variations mostly with inadequate or inappropriate conclusions. The Surface Friction of both portland cement concrete (PCC) and asphalt concrete (AC) pavements was measured monthly to determine the influencing factors and quantify the seasonal fluctuation. Skid number (SN) and pertinent data of the Long-Term Pavement Performance program were obtained for both PCC and AC pavements, incorporating all geographic and climatic regions of the United States and Canada, to determine the contributing factors and quantify the long-term and early-life variations of Surface Friction. Surface Friction was shown to fluctuate as a result of ambient or pavement temperature fluctuation at 0.35 British pendulum number per 1°C change in temperature. The effect of prior weathe...
Jorge A Prozzi - One of the best experts on this subject based on the ideXlab platform.
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incorporating Surface microtexture in the prediction of skid resistance of flexible pavements
2014Co-Authors: Pedro A Serigos, Andre De Fortier Smit, Jorge A ProzziAbstract:Monitoring and managing the skid resistance of the highway network is necessary for controlling and reducing the number of road accidents. High-speed measurements of Surface texture can be used as a surrogate parameter for controlling a pavement's Surface Friction on the highway network. The two components of Surface texture that affect skid resistance are the macrotexture and the microtexture. However, the technologies commonly used for measuring pavement texture at highway speeds account only for the macrotexture. This study explored ways to characterize the microtexture of pavement Surfaces with the main objective of quantifying the effect of accounting for both components of the texture on the prediction of skid resistance, as measured by a British pendulum tester. Various methods for characterizing the microtexture were compared to determine which one better predicted Surface Friction. The study used field measurements of Surface texture and Friction performed on various in-service flexible pavements...
