The Experts below are selected from a list of 29865 Experts worldwide ranked by ideXlab platform
Yongfu Li - One of the best experts on this subject based on the ideXlab platform.
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a car following model considering the effect of electronic throttle Opening Angle under connected environment
Nonlinear Dynamics, 2016Co-Authors: Yongfu Li, Li Zhang, Srinivas Peeta, Xiaozheng He, Taixiong Zheng, Yinguo LiAbstract:This study proposes a new car-following model considering the effect of electronic throttle Opening Angle to capture the characteristics of connected autonomous vehicular traffic flow. The proposed model incorporates the Opening Angle of electronic throttle into the full velocity difference (FVD) model by assuming that the information of electronic throttle dynamics is shared by vehicles through vehicle-to-vehicle communications. The stability condition of the proposed car-following model is obtained using the perturbation method. Numerical experiments are constructed on three scenarios, start, stop, and evolution processes, to analyze the vehicular traffic flow characteristics of the proposed model. The results of numerical experiments illustrate that the proposed car-following model has a larger stable region compared with FVD model. Also, it demonstrates that the proposed car-following model can better present the characteristics of connected and autonomous vehicular flow in terms of the smoothness and stability with respect to the space headway, position, velocity, and acceleration/deceleration profiles.
Yinguo Li - One of the best experts on this subject based on the ideXlab platform.
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a car following model considering the effect of electronic throttle Opening Angle under connected environment
Nonlinear Dynamics, 2016Co-Authors: Yongfu Li, Li Zhang, Srinivas Peeta, Xiaozheng He, Taixiong Zheng, Yinguo LiAbstract:This study proposes a new car-following model considering the effect of electronic throttle Opening Angle to capture the characteristics of connected autonomous vehicular traffic flow. The proposed model incorporates the Opening Angle of electronic throttle into the full velocity difference (FVD) model by assuming that the information of electronic throttle dynamics is shared by vehicles through vehicle-to-vehicle communications. The stability condition of the proposed car-following model is obtained using the perturbation method. Numerical experiments are constructed on three scenarios, start, stop, and evolution processes, to analyze the vehicular traffic flow characteristics of the proposed model. The results of numerical experiments illustrate that the proposed car-following model has a larger stable region compared with FVD model. Also, it demonstrates that the proposed car-following model can better present the characteristics of connected and autonomous vehicular flow in terms of the smoothness and stability with respect to the space headway, position, velocity, and acceleration/deceleration profiles.
Ghassan S. Kassab - One of the best experts on this subject based on the ideXlab platform.
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Increase in Opening Angle in hypertension off-loads the intimal stress: a simulation study.
Journal of biomechanical engineering, 2009Co-Authors: Chong Wang, Ghassan S. KassabAbstract:The stress distribution in the vessel wall has important bearing on vascular function including intima, media, and adventitia. The residual strain in the vessel wall has been thought to largely normalize the transmural stress distribution with slightly higher values at the intima. In hypertension, the compensatory increase in Opening Angle is thought to maintain a uniform stress distribution. We have recently shown that the circumferential stress at adventitia may exceed that at intima at physiological loading due to large Opening Angle (OA) in normal porcine coronary arteries. The objective of this study was to show that increases in Opening Angle subsequent hypertension can further shift the stress from the intima to the adventitia. The change in stress distribution during acute hypertension was calculated using available data on the changes in vessel geometry, material property, and internal pressure during hypertension. It was found that the increase in OA following acute hypertension off-loads the stress from intima to adventitia, therefore, relieving some of the stress increase in the intimal layer induced by the sudden pressure increase. This has important implications for hypertension where it may shift the excessive stress from the inner layer to the outer layer. This may be a protective mechanism for the intima layer in hypertension.
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A generalized Maxwell model for creep behavior of artery Opening Angle.
Journal of biomechanical engineering, 2008Co-Authors: Wei Zhang, Xiaomei Guo, Ghassan S. KassabAbstract:An artery ring springs open into a sector after a radial cut. The Opening Angle characterizes the residual strain in the unloaded state, which is fundamental in understanding stress and strain in the vessel wall. A recent study revealed that the Opening Angle decreases with time if the artery is cut from the loaded state, while it increases if the cut is made from the no-load state due to viscoelasticity. In both cases, the Opening Angle approaches the same value in 3 h. This implies that the characteristic relaxation time is about 10,000 s. Here, the creep function of a generalized Maxwell model (a spring in series with six Voigt bodies) is used to predict the temporal change of Opening Angle in multiple time scales. It is demonstrated that the theoretical model captures the salient features of the experimental results. The proposed creep function may be extended to study the viscoelastic response of blood vessels under various loading conditions.
Chunglee Kim - One of the best experts on this subject based on the ideXlab platform.
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pulsar binary birthrates with spin Opening Angle correlations
The Astrophysical Journal, 2010Co-Authors: R Oshaughnessy, Chunglee KimAbstract:One ingredient in an empirical birthrate estimate for pulsar binaries is the fraction of sky subtended by the pulsar beam: the pulsar beaming fraction. This fraction depends on both the pulsar's Opening Angle and the misalignment Angle between its spin and magnetic axes. The current estimates for pulsar binary birthrates are based on an average value of beaming fractions for only two pulsars, i.e., PSRs B1913+16 and B1534+12. In this paper, we revisit the observed pulsar binaries to examine the sensitivity of birthrate predictions to different assumptions regarding Opening Angle and alignment. Based on empirical estimates for the relative likelihood of different beam half-Opening Angles and misalignment Angles between the pulsar rotation and magnetic axes, we calculate an effective beaming correction factor, f b,eff, whose reciprocal is equivalent to the average fraction of all randomly selected pulsars that point toward us. For those pulsars without any direct beam geometry constraints, we find that f b,eff is likely to be smaller than 6, a canonically adopted value when calculating birthrates of Galactic pulsar binaries. We calculate f b,eff for PSRs J0737–3039A and J1141–6545, applying the currently available constraints for their beam geometry. As in previous estimates of the posterior probability density function P() for pulsar binary birthrates , PSRs J0737–3039A and J1141–6545 still significantly contribute to, if not dominate, the Galactic birthrate of tight pulsar-neutron star (NS) and pulsar-white dwarf (WD) binaries, respectively. Our median posterior present-day birthrate predictions for tight PSR-NS binaries, wide PSR-NS binaries, and tight PSR-WD binaries given a preferred pulsar population model and beaming geometry are 89 Myr–1, 0.5 Myr–1, and 34 Myr–1, respectively. For long-lived PSR-NS binaries, these estimates include a weak (×1.6) correction for slowly decaying star formation in the galactic disk. For pulsars with spin period between 10 ms and 100 ms, where few measurements of misalignment and Opening Angle provide a sound basis for extrapolation, we marginalized our posterior birthrate distribution P() over a range of plausible beaming correction factors. We explore several alternative beaming geometry distributions, demonstrating that our predictions are robust except in (untestable) scenarios with many highly aligned recycled pulsars. Finally, in addition to exploring alternative beam geometries, we also briefly summarize how uncertainties in each pulsar binary's lifetime and in the pulsar luminosity distribution can be propagated into P(.
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Pulsar Binary Birthrates with Spin-Opening Angle Correlations
The Astrophysical Journal, 2010Co-Authors: Richard O'shaughnessy, Chunglee KimAbstract:Empirical birthrate estimates for pulsar binaries depend on the fraction of sky subtended by the pulsar beam: the pulsar beaming fraction. This fraction depends on both the pulsar's Opening Angle and the misalignment Angle between its spin and magnetic axes. Previous estimates use the average value for only two pulsars, i.e. PSRs B1913+16 and B1534+12. We explore how birthrate predictions depend on assumptions about Opening Angle and alignment, using empirically-motivated distributions to define an effective beaming correction factor, f_{b,eff}. For most known pulsars, we expect f_{b,eff} to be less than 6. We also calculate f_{b,eff} for PSRs J0737-3039A and J1141-6545, applying the currently available constraints for their beam geometry. Our median posterior birthrate predictions for tight PSR-NS binaries, wide PSR-NS binaries, and tight PSR-WD binaries are 89/Myr, 0.84/Myr, and 34/Myr, respectively. For pulsars with spin period between 10 ms and 100 ms, we marginalized our posterior birthrate distribution P(R) over a range of plausible beaming correction factors. Our predictions are robust, changing little between several alternative misalignment Angle distribution models. [ABRIDGED]
Daniel Hopton - One of the best experts on this subject based on the ideXlab platform.
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a new connection between the jet Opening Angle and the large scale morphology of extragalactic radio sources
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: Martin Krause, Paul Alexander, Julia M Riley, Daniel HoptonAbstract:In the case of an initially conical jet, we study the relation between jet collimation by the external pressure and large-scale morphology. We first consider the important length-scales in the problem, and then carry out axisymmetric hydrodynamic simulations that include, for certain parameters, all these length-scales. We find three important scales related to the collimation region: (i) where the sideways ram pressure equals the external pressure, (ii) where the jet density equals the ambient density and (iii) where the forward ram pressure falls below the ambient pressure. These scales are set by the external Mach number and Opening Angle of the jet. We demonstrate that the relative magnitudes of these scales determine the collimation, Mach number, density and morphology of the large-scale jet. Based on the analysis of the shock structure, we reproduce successfully the morphology of Fanaroff–Riley (FR) class I and II radio sources. Within the framework of the model, an FR I radio source must have a large intrinsic Opening Angle. Entrainment of ambient gas might also be important. We also show that all FR I sources with radio lobes or similar features must have had an earlier FR II phase.
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a new connection between the Opening Angle and the large scale morphology of extragalactic radio sources
arXiv: Cosmology and Nongalactic Astrophysics, 2012Co-Authors: Martin Krause, Paul Alexander, Julia M Riley, Daniel HoptonAbstract:In the case of an initially conical jet, we study the relation between jet collimation by the external pressure and large-scale morphology. We first consider the important length-scales in the problem, and then carry out axisymmetric hydrodynamic simulations that include, for certain parameters, all these length-scales. We find three important scales related to the collimation region: (i) where the sideways ram-pressure equals the external pressure, (ii) where the jet density equals the ambient density, and (iii) where the forward ram-pressure falls below the ambient pressure. These scales are set by the external Mach-number and Opening Angle of the jet. We demonstrate that the relative magnitudes of these scales determine the collimation, Mach-number, density and morphology of the large scale jet. Based on analysis of the shock structure, we reproduce successfully the morphology of Fanaroff-Riley (FR) class I and II radio sources. Within the framework of the model, an FR I radio source must have a large intrinsic Opening Angle. Entrainment of ambient gas might also be important. We also show that all FR I sources with radio lobes or similar features must have had an earlier FR II phase.
