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Different Velocities (different + velocity)
Selected AbstractsOn linear-parameter-varying (LPV) slip-controller design for two-wheeled vehiclesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 12 2009Matteo Corno Abstract This paper describes the application of linear-parameter-varying (LPV) control design techniques to the problem of slip control for two-wheeled vehicles. A nonlinear multi-body motorcycle simulator is employed to derive a control-oriented dynamic model. It is shown that, in order to devise a robust controller with good performance, it is necessary to take into account the dependence of the model on the velocity and on the wheel slip. This dependence is modeled via an LPV system constructed from Jacobian linearizations at different velocities and slip values. The control problem is formulated as a model-matching control problem within the LPV framework; a specific modification of the LPV control synthesis algorithm is proposed to alleviate controller interpolation problems. Linear and nonlinear simulations indicate that the synthesized controller achieves the required robustness and performance. Copyright © 2008 John Wiley & Sons, Ltd. [source] Hydrodynamic investigation of USP dissolution test apparatus IIJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2007Ge Bai Abstract The USP Apparatus II is the device commonly used to conduct dissolution testing in the pharmaceutical industry. Despite its widespread use, dissolution testing remains susceptible to significant error and test failures, and limited information is available on the hydrodynamics of this apparatus. In this work, laser-Doppler velocimetry (LDV) and computational fluid dynamics (CFD) were used, respectively, to experimentally map and computationally predict the velocity distribution inside a standard USP Apparatus II under the typical operating conditions mandated by the dissolution test procedure. The flow in the apparatus is strongly dominated by the tangential component of the velocity. Secondary flows consist of an upper and lower recirculation loop in the vertical plane, above and below the impeller, respectively. A low recirculation zone was observed in the lower part of the hemispherical vessel bottom where the tablet dissolution process takes place. The radial and axial velocities in the region just below the impeller were found to be very small. This is the most critical region of the apparatus since the dissolving tablet will likely be at this location during the dissolution test. The velocities in this region change significantly over short distances along the vessel bottom. This implies that small variations in the location of the tablet on the vessel bottom caused by the randomness of the tablet descent through the liquid are likely to result in significantly different velocities and velocity gradients near the tablet. This is likely to introduce variability in the test. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 2327,2349, 2007 [source] Noninvasive assessment of energy expenditure in childrenAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2006Isabelle Sarton-Miller This study establishes an affordable, simple, and noninvasive method to assess energy expenditure (EE) in children, an underrepresented group. The method is based on regression modeling, where prediction of oxygen consumption (VO2), a proxy of EE, was deduced from heart rate (HR) and several variables that adjusted for interindividual variability. Limb activities (arms vs. legs) and posture (sitting vs. standing) were represented in the regression as dichotomous covariates. The order of activities and intensities was randomized. Seventy-four children (aged 7,10 years), raised at sea-level (Seattle, WA), comprised the sample. Anthropometric measures were taken, and VO2 and HR were measured for activities using the arms in sitting and standing positions (mixing and punching), as well as walking at different velocities on a treadmill. Repeated measures and least square regression estimation were used. HR, body mass, number of hours of physical activity per week (HPA), an interaction term between sitting and standing resting HR, and the two dichotomous variables, sex and limbs, were significant covariates; posture was not. Several equations were developed for various field uses. The equations were built from sea-level data, but ultimately this method could serve as a baseline for developing a similar approach in other populations, where noninvasive estimation of EE is imperative in order to gain a better understanding of children's energetic issues. Am. J. Hum. Biol. 18:600,609, 2006. © 2006 Wiley-Liss, Inc. [source] Gait disturbances in patients with schizophrenia and adaptation to treadmill walkingPSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 3 2005ALBERT PUTZHAMMER md Abstract, This study evaluated the gait patterns of schizophrenic patients at free gait and at three fixed velocities on a treadmill. The effects of illness and antipsychotic treatment on gait parameters and on adaptation to treadmill walking were compared. Gait parameters of 14 drug-naïve schizophrenic patients, 14 patients treated with conventional antipsychotics, 14 patients treated with olanzapine, as well as 14 matched controls were assessed on a walkway and on a treadmill at three different velocities (very slow, intermediately slow, and comfortable) using an ultrasonic movement analysis system. At free gait, all patients showed a significantly decreased gait velocity, predominantly due to a shorter stride length, when compared to the controls, with the most striking difference observed between the patients treated with conventional neuroleptics and the controls (anova, P , 0.001). Cadence (steps per second) did not differ between the investigated groups. When gait was evaluated on the treadmill, differences in stride length and cadence were significant only at the very slow treadmill velocity (anova, P , 0.05). In all patient groups, mean stride length was decreased and cadence compensationally increased. Significant differences between the patient groups were no longer detectable. With increasing treadmill velocities, gait parameters of all patient groups normalized. The results show that, like in patients with Parkinson's Disease, impaired gait parameters can also be normalized in schizophrenic patients by external stimulation via treadmill walking. [source] Mechanical and neural stretch responses of the human soleus muscle at different walking speedsTHE JOURNAL OF PHYSIOLOGY, Issue 13 2009Neil J. Cronin During human walking, a sudden trip may elicit a Ia afferent fibre mediated short latency stretch reflex. The aim of this study was to investigate soleus (SOL) muscle mechanical behaviour in response to dorsiflexion perturbations, and to relate this behaviour to short latency stretch reflex responses. Twelve healthy subjects walked on a treadmill with the left leg attached to an actuator capable of rapidly dorsiflexing the ankle joint. Ultrasound was used to measure fascicle lengths in SOL during walking, and surface electromyography (EMG) was used to record muscle activation. Dorsiflexion perturbations of 6 deg were applied during mid-stance at walking speeds of 3, 4 and 5 km h,1. At each walking speed, perturbations were delivered at three different velocities (slow: ,170 deg s,1, mid: ,230 deg s,1, fast: ,280 deg s,1). At 5 km h,1, fascicle stretch amplitude was 34,40% smaller and fascicle stretch velocity 22,28% slower than at 3 km h,1 in response to a constant amplitude perturbation, whilst stretch reflex amplitudes were unchanged. Changes in fascicle stretch parameters can be attributed to an increase in muscle stiffness at faster walking speeds. As stretch velocity is a potent stimulus to muscle spindles, a decrease in the velocity of fascicle stretch at faster walking speeds would be expected to decrease spindle afferent feedback and thus stretch reflex amplitudes, which did not occur. It is therefore postulated that other mechanisms, such as altered fusimotor drive, reduced pre-synaptic inhibition and/or increased descending excitatory input, acted to maintain motoneurone output as walking speed increased, preventing a decrease in short latency reflex amplitudes. [source] Mathematical analysis of vortex sheetsCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 8 2006Sijue Wu We consider the motion of the interface separating two domains of the same fluid that moves with different velocities along the tangential direction of the interface. The evolution of the interface (the vortex sheet) is governed by the Birkhoff-Rott (BR) equations. We consider the question of the weakest possible assumptions such that the Birkhoff-Rott equation makes sense. This leads us to introduce chord-arc curves to this problem. We present three results. The first can be stated as the following: Assume that the Birkhoff-Rott equation has a solution in a weak sense and that the vortex strength is bounded away from 0 and ,. Moreover, assume that the solution gives rise to a vortex sheet curve that is chord-arc. Then the curve is automatically smooth, in fact analytic, for fixed time. The second and third results demonstrate that the Birkhoff-Rott equation can be solved if and only if only half the initial data is given. © 2005 Wiley Periodicals, Inc. [source] Effect of gamma-ray irradiation on the physicochemical properties of flour and starch granule structure for wheatINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2009Jun Wang Summary Effect of gamma irradiation on the physicochemical properties of flour and starch granule structure of wheat was compared to non-irradiated wheat. The moisture content of wet gluten and titratable acidity of wheat flour were significantly affected by gamma irradiation. This treatment also destroyed the starch granules of wheat grain and their breakage augmented as the dose of gamma irradiation increased, apparently resulting in the increase of small starch granules. Probably, these results were due to the disruption of large molecule, such as proteins, lipids and starch. The irradiated wheat flour for RVA pasting properties (flour viscosity) was also evaluated. Besides the difference in RVA profile, starch pasting curves showed a considerable decrease for six main parameters as gamma irradiation dose at different velocity increased. [source] | |||||||||||||