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Deceleration

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Serge P. Hoogendoorn – One of the best experts on this subject based on the ideXlab platform.

  • Continuous traffic flow modeling of driver support systems in multiclass traffic with intervehicle communication and drivers in the loop
    IEEE Transactions on Intelligent Transportation Systems, 2009
    Co-Authors: Serge P. Hoogendoorn
    Abstract:

    This paper presents a continuous traffic-flow model for the explorative analysis of advanced driver-assistance systems (ADASs). Such systems use technology (sensors and intervehicle communication) to support the task of the driver, who retains full control over the vehicle. Based on a review of different traffic-flow modeling approaches and their suitability for exploring traffic-flow patterns in the presence of ADASs, kinetic traffic-flow models are selected because of their good representation on both the aggregate level (congestion dynamics) and the level of the individual vehicle (vehicular interactions either directly or through intervehicle communication). The human-kinetic modeling approach is presented. It is a multiclass variant of kinetic traffic-flow models that is strongly based on individual driver behavior, i.e., on fully continuous acceleration/Deceleration behavior and explicit modeling of the activation level of the driver. The strength of this modeling approach is illustrated by application to a driver-assistance system that uses intervehicle communication. It warns drivers when approaching sharp Decelerations in a queue tail. The explorative analysis shows that the system results in safer and smoother transition from free-flowing to congested traffic. It also avoids compression of the queue tail, thus preventing the emergence of stop-and-go congestion patterns.

Jon Hore – One of the best experts on this subject based on the ideXlab platform.

  • Kinematics of Arm Joint Rotations in Cerebellar and Unskilled Subjects Associated with the Inability to Throw Fast
    The Cerebellum, 2008
    Co-Authors: Dagmar Timmann, Sherry Watts, Jon Hore
    Abstract:

    Cerebellar subjects and unskilled throwers cannot produce fast arm movements when throwing. We investigated the arm movement kinematics associated with this lack of skill. Cerebellar subjects and matched controls, and skilled throwers throwing with their skilled (dominant) and unskilled (nondominant) arms, were instructed to make slow, medium, and fast 3-D overarm throws from a sitting position. Only the fast throws were analyzed in detail. Joint motions were computed from angular positions of arm segments recorded with search coils. When throwing, both the cerebellar group and the unskilled-arm group had slower arm movements, and slower elbow extension and wrist flexion velocities than their reference groups. They also had similar magnitudes of many kinematic parameters, e.g., both cerebellar and unskilled groups had similar elbow extension and wrist flexion velocities. Compared to their reference groups, both the cerebellar and unskilled-arm groups also had a smaller elbow extension acceleration, a smaller shoulder adduction Deceleration, and the absence of a large elbow extension Deceleration before ball release. Similar decreases in joint velocities and in joint accelerations and Decelerations in the cerebellar and unskilled groups are consistent with the idea that the absence of the skill of throwing fast in both groups is associated with an inability to exploit interaction torques.

S. Watts – One of the best experts on this subject based on the ideXlab platform.

  • Braking of elbow extension in fast overarm throws made by skilled and unskilled subjects
    Experimental Brain Research, 2005
    Co-Authors: J. Hore, D. B. Debicki, S. Watts
    Abstract:

    A previous computer simulation study of overarm throws in 2D showed that reversal of elbow torque by antagonist muscle action late in the throw led to increased wrist flexion velocity and to increased ball speeds. We tested the hypothesis that the skill of making fast overarm throws in 3D involves Deceleration (braking) of elbow extension before ball release, and that this is an active mechanism. Skilled and unskilled throwers were instructed to throw baseballs at a fast speed. Arm segment angular positions in 3D at 1,000 Hz were recorded with the search-coil technique (which records angular motions). In skilled throws, but not in unskilled throws, there was a period (mean 17 ms) of rapid elbow extension Deceleration before ball release. However, there was relatively little biceps EMG activity associated with the very large magnitude of elbow Deceleration. This finding and other work suggests that elbow extension Deceleration results in part from interaction torques associated with late-occurring shoulder rotations, and only in part from elbow flexor contraction. During the period when elbow extension was decelerating, the forearm in space was undergoing angular acceleration (because of internal rotation at the shoulder) which would be expected to produce a torque at the wrist in the extensor (not flexor) direction. The results show that elbow extension Deceleration occurs before ball release in fast (skilled) 3D throws, and that it does not produce forearm angular Deceleration. Whether it produces forearm translational Deceleration, which could increase wrist flexion velocity, remains to be determined.

Roberto Sassi – One of the best experts on this subject based on the ideXlab platform.

  • acceleration and Deceleration capacity of fetal heart rate in an in vivo sheep model
    PLOS ONE, 2014
    Co-Authors: Massimo W Rivolta, Tamara Stampalija, D Casati, Bryan S Richardson, Michael G Ross, Martin G Frasch, Axel Bauer, E Ferrazzi, Roberto Sassi
    Abstract:

    Background: Fetal hearheart rate (FHR) variability is an indirect index of fetal autonomic nervous system (ANS) integrity. FHR variability analysis in labor fails to detect early hypoxia and acidemia. Phase-rectified signal averaging (PRSA) is a new method of complex biological signals analysis that is more resistant to non-stationarities, signal loss and artifacts. It quantifies the average cardiac acceleration and Deceleration (AC/DC) capacity. Objective: The aims of the study were: (1) to investigate AC/DC in ovine fetuses exposed to acute hypoxic-acidemic insult; (2) to explore the relation between AC/DC and acid-base balance; and (3) to evaluate the influence of FHR Decelerations and specific PRSA parameters on AC/DC computation. Methods: Repetitive umbilical cord occlusions (UCOs) were applied in 9 pregnant near-term sheep to obtain three phases of MILD, MODERATE, and SEVERE hypoxic-acidemic insult. Acid-base balance was sampled and fetal ECGs continuously recorded. AC/DC were calculated: (1) for a spectrum of T values (T= 1 divided by 50 beats; the parameter limits the range of oscillations detected by PRSA); (2) on entire series of fetal RR intervals or on “stable” series that excluded FHR Decelerations caused by UCOs. Results: AC and DC progressively increased with UCOs phases (MILD vs. MODERATE and MODERATE vs. SEVERE, p < 0.05 for DC T = 2-5, and AC T = 1-3). The time evolution of AC/DC correlated to acid-base balance (0.4 < vertical bar rho vertical bar < 0.9, p < 0.05) with the highest D r D for 2 <= T <= 7. PRSA was not independent from FHR Decelerations caused by UCOs. Conclusions: This is the first in-vivo evaluation of PRSA on FHR analysis. In the presence of acute hypoxic-acidemia we found increasing values of AC/DC suggesting an activation of ANS. This correlation was strongest on time scale dominated by parasympathetic modulations. We identified the best performing T parameters (3 <= T <= 5),and found that AC/DC computation is not independent from FHR Decelerations. These findings establish the basis for future clinical studies.

Kingsley E. Haynes – One of the best experts on this subject based on the ideXlab platform.