The Experts below are selected from a list of 11937 Experts worldwide ranked by ideXlab platform
V. Sankaranarayanan - One of the best experts on this subject based on the ideXlab platform.
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State‐constrained stabilization of Beam‐Balance systems
International Journal of Robust and Nonlinear Control, 2008Co-Authors: Arun D. Mahindrakar, V. SankaranarayananAbstract:We present nonlinear control techniques to stabilize a Beam-Balance system with state constraints. We consider two different actuator configurations: the first one is actuated by a cart moving on the Beam, while in the second case, the actuation is by a single electromagnet. In the first case, the constrained stabilization problem is solved via an output feedback controller designed using feedback linearization, Luenberger-like observer and linear matrix inequality based optimization. In the second case, a Lyapunov-based controller is proposed that takes care of both the input and state constraints. Copyright © 2007 John Wiley & Sons, Ltd.
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state constrained stabilization of Beam Balance systems
International Journal of Robust and Nonlinear Control, 2008Co-Authors: Arun D. Mahindrakar, V. SankaranarayananAbstract:We present nonlinear control techniques to stabilize a Beam-Balance system with state constraints. We consider two different actuator configurations: the first one is actuated by a cart moving on the Beam, while in the second case, the actuation is by a single electromagnet. In the first case, the constrained stabilization problem is solved via an output feedback controller designed using feedback linearization, Luenberger-like observer and linear matrix inequality based optimization. In the second case, a Lyapunov-based controller is proposed that takes care of both the input and state constraints. Copyright © 2007 John Wiley & Sons, Ltd.
Walter Kündig - One of the best experts on this subject based on the ideXlab platform.
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measurement of newton s gravitational constant
Physical Review D, 2006Co-Authors: St. Schlamminger, E. Holzschuh, R.e. Pixley, Frithjof Nolting, Jürgen Schurr, Walter Kündig, Ulrich StraumannAbstract:A precision measurement of the gravitational constant $G$ has been made using a Beam Balance. Special attention has been given to determining the calibration, the effect of a possible nonlinearity of the Balance and the zero-point variation of the Balance. The equipment, the measurements, and the analysis are described in detail. The value obtained for $G$ is $6.674\text{ }252(109)(54)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\text{ }\text{ }{\mathrm{m}}^{3}\text{ }{\mathrm{kg}}^{\ensuremath{-}1}\text{ }{\mathrm{s}}^{\ensuremath{-}2}$. The relative statistical and systematic uncertainties of this result are $16.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $8.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, respectively.
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determination of the gravitational constant with a Beam Balance
Physical Review Letters, 2002Co-Authors: St. Schlamminger, E. Holzschuh, Walter KündigAbstract:The Newtonian gravitational constant $G$ was determined by means of a novel Beam-Balance experiment with an accuracy comparable to that of the most precise torsion-Balance experiments. The gravitational force of two stainless steel tanks filled with 13 521 kg mercury on 1.1 kg test masses was measured using a commercial mass comparator. A careful analysis of the data and the experimental error yields $G=6.674\text{ }07(22)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\text{ }{\mathrm{m}}^{3}\text{ }{\mathrm{k}\mathrm{g}}^{\ensuremath{-}1}\text{ }{\mathrm{s}}^{\ensuremath{-}2}$. This value is in excellent agreement with most values previously obtained with different methods.
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A Beam Balance experiment to determine the gravitational constant
Conference Digest Conference on Precision Electromagnetic Measurements, 2002Co-Authors: St. Schlamminger, E. Holzschuh, Walter KündigAbstract:The goal of our experiment is a precision measurement of the gravitational constant G by means of a Beam Balance. The gravitational forces of two large and movable field masses act on test masses and change their weights. First measurements have been successfully completed with a relative uncertainty of 230 ppm. Since then various upgrades and improvements have been implemented.
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Determination of the gravitational constant using a Beam Balance
Conference on Precision Electromagnetic Measurements. Conference Digest. CPEM 2000 (Cat. No.00CH37031), 2000Co-Authors: St. Schlamminger, E. Holzschuh, Walter KündigAbstract:We describe an experiment to measure the Newtonian gravitational constant G. The gravitational forces of large field masses on test masses are measured using a Beam Balance. A preliminary result with a relative uncertainty of 220/spl times/10/sup -6/ has been published recently. In the meantime various modifications of the experiment have been made.
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A value for G from Beam-Balance experiments
Measurement Science and Technology, 1999Co-Authors: Frithjof Nolting, St. Schlamminger, Jürgen Schurr, Walter KündigAbstract:A high-precision measurement of the Newtonian gravitational constant G by means of a Beam Balance is being carried out at the University of Zurich. We have made test measurements in which the gravitational force of 103 kg of water was used and G was determined with a relative standard uncertainty of 220 × 10-6. Currently, measurements with 13.5 × 103 kg of mercury are in progress. These measurements are not completed yet, but a preliminary result is presented.
Larry W Jenkins - One of the best experts on this subject based on the ideXlab platform.
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the rotarod test an evaluation of its effectiveness in assessing motor deficits following traumatic brain injury
Journal of Neurotrauma, 1994Co-Authors: Robert J Hamm, Brian R Pike, Dianne M Odell, Bruce G Lyeth, Larry W JenkinsAbstract:ABSTRACT The purpose of the present experiment was to examine the effectiveness of a modified rotarod test in detecting motor deficits following mild and moderate central fluid percussion brain injury. In addition, this investigation compared the performance of the rotarod task with two other commonly used measures of motor function after brain injury (Beam-Balance and Beam-walking latencies). Rats were either injured with a mild (n = 14) or moderate (n = 8) level of fluid percussion injury or were surgically prepared but not injured (n = 8). All rats were assessed on all tasks for 5 days following their respective treatments. Results revealed that both the mild and moderate injury levels produced significant deficits in the ability of the animals to perform the rotarod task. Performance on the Beam-Balance and Beam-walking tasks were not significantly impaired at the mild injury level. It was only at the moderate injury level that the Beam-Balance and Beam-walking tasks detected deficits in motor perform...
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The effect of age on motor and cognitive deficits after traumatic brain injury in rats.
Neurosurgery, 1992Co-Authors: Robert J Hamm, Bruce G Lyeth, Larry W Jenkins, Daphne M. White-gbadebo, Ronald L. HayesAbstract:Abstract Age is one of the most important predictors of outcome after human traumatic brain injury. This study used fluid percussion brain injury to investigate the effects of aging on outcome after brain injury in rats. Three-month-old (n = 8) and 20-month-old (n = 11) rats were injured at a low level (1.7-1.8 atm) of fluid percussion brain injury or received a sham injury (n = 6 for both age groups). Body weight and motor function (Beam Balance and Beam walking) were assessed before injury and for the first 5 days after injury. Cognitive outcome was assessed with the Morris water maze on Days 11 to 15 after injury. Injury did not produce significant weight loss in either age group. At the low level of brain injury used in this study, the 3-month-old rats did not demonstrate any significant motor deficits on the Beam-Balance or Beam-walking tasks. However, the 20-month-old rats displayed significant Beam-Balance deficits on each of the 5 postinjury test days and significant Beam-walking deficits for the first 3 postinjury days. Although Morris water maze performance was impaired in both age groups, the magnitude of impairment was greater in the aged animals. These data demonstrate that traumatic brain injury in the aged animal is marked by increased motor and cognitive deficits, in the absence of pronounced compromise of the animal's general health.(ABSTRACT TRUNCATED AT 250 WORDS)
Arun D. Mahindrakar - One of the best experts on this subject based on the ideXlab platform.
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State‐constrained stabilization of Beam‐Balance systems
International Journal of Robust and Nonlinear Control, 2008Co-Authors: Arun D. Mahindrakar, V. SankaranarayananAbstract:We present nonlinear control techniques to stabilize a Beam-Balance system with state constraints. We consider two different actuator configurations: the first one is actuated by a cart moving on the Beam, while in the second case, the actuation is by a single electromagnet. In the first case, the constrained stabilization problem is solved via an output feedback controller designed using feedback linearization, Luenberger-like observer and linear matrix inequality based optimization. In the second case, a Lyapunov-based controller is proposed that takes care of both the input and state constraints. Copyright © 2007 John Wiley & Sons, Ltd.
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state constrained stabilization of Beam Balance systems
International Journal of Robust and Nonlinear Control, 2008Co-Authors: Arun D. Mahindrakar, V. SankaranarayananAbstract:We present nonlinear control techniques to stabilize a Beam-Balance system with state constraints. We consider two different actuator configurations: the first one is actuated by a cart moving on the Beam, while in the second case, the actuation is by a single electromagnet. In the first case, the constrained stabilization problem is solved via an output feedback controller designed using feedback linearization, Luenberger-like observer and linear matrix inequality based optimization. In the second case, a Lyapunov-based controller is proposed that takes care of both the input and state constraints. Copyright © 2007 John Wiley & Sons, Ltd.
Stefan Zausinger - One of the best experts on this subject based on the ideXlab platform.
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neurological impairment in rats after subarachnoid hemorrhage a comparison of functional tests
Journal of the Neurological Sciences, 2008Co-Authors: Serge C Thal, K Mesmer, Robert Schmidelsaesser, Stefan ZausingerAbstract:Abstract Functional outcome has become a key parameter for the determination of the efficacy of therapeutic interventions. Unfortunately, functional tests are not established for filament perforation induced subarachnoid hemorrhage (SAH). Therefore, we evaluated generally applied functional tasks for their potential to discriminate between various degrees of neuronal damage. Rats were subjected to SAH by an endovascular filament and were randomly assigned to controls treated with 0.9% NaCl, moderately neuroprotective therapy with 7.5% NaCl, and highly effective neuroprotection by 7.5% NaCl + 6% dextran 70 (HSD). Functional deficit was quantified daily using Beam Balance task, prehensile traction task, rotarod, a 6-point motor function score and a general neurological 100-point score. Only the HSD group exhibited significantly more surviving neurons at postoperative day 7. Despite significant variations in histomorphometry, Beam Balance, prehensile traction and rotarod failed to distinguish between groups. On the other hand, the 100-point neuroscore showed improved neurological recovery on postoperative day 1 for HSD. The 100-point neuroscore failed to discriminate between treatment arms at later time points and therefore seems to reflect predominantly early neurological dysfunction. In conclusion, the results of pure motor tasks after experimental SAH in rats should be carefully interpreted. The integration of a test regimen to examine long term cognitive deficits after rat SAH might be valuable to gain additional information about the functional consequences of morphological damage.
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neurological impairment in rats after transient middle cerebral artery occlusion a comparative study under various treatment paradigms
Brain Research, 2000Co-Authors: Stefan Zausinger, Edwin Hungerhuber, A Baethmann, Hannsjurgen Reulen, Robert SchmidelsaesserAbstract:Abstract The assessment of the functional outcome — in addition to the conventional endpoints as histomorphometry of the ischemic brain damage — for the evaluation of cerebroprotective therapies is increasingly recommended, although there is little consensus on appropriate procedures. We evaluated a battery of sensorimotor tasks in rats after transient middle cerebral artery occlusion (MCAO) to select those with the highest potential to discriminate between various degrees of neuronal damage. A total of 40 Sprague–Dawley rats were subjected to 90 min of MCAO and assigned to one of four treatment arms: (1) sham-operated controls, (2) vehicle-treated controls, (3) moderately effective neuroprotection by 2×100 mg/kg α-phenyl-N-tert-butyl nitrone (PBN), (4) highly effective neuroprotection by mild hypothermia (33°C). Functional deficits were daily quantified using the Beam Balance task (1.5 cm, 2.5 cm diameter rectangular and 2.5 cm diameter cylindrical Beam), the prehensile traction task, the rotarod, and a six-point neuro-score. Infarction of cerebral cortex and basal ganglia was assessed one week after ischemia. Treatment with PBN significantly reduced cortical infarction (−31%), while treatment with hypothermia resulted in a significantly smaller infarct volume of cortex (−94%) and basal ganglia (−27%). Beam Balance, prehensile traction and rotarod failed to demonstrate any difference in motor performance. The six-point neuro-score showed a significant correlation with cortical infarction from day 2 and with total infarct volume from day 3. The smaller the reduction of infarct volume, the later the corresponding difference in neuro-score became apparent. Functional outcome after MCAO in rats can be assessed by a relatively simple measurement of neurological deficit. The slope of functional recovery is closely related with the degree of the morphological, particularly cortical damage. If expected treatment effects are small, an observation period of at least 3 days should be planned for the study design. The functional impairment from focal brain ischemia and its subsequent recovery could provide valuable information for future studies evaluating the neuroprotective potential of novel agents and procedures.