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Page 403 of 977 Results 4021 - 4030 of 9762

Irene Tamagnone, Maura Casadio, Vittorio Sanguineti
QUANTIFYING PERFORMANCE AND VARIABILITY IN REWARD-BASED MOTOR SKILL LEARNING

This study investigates motor skill learning in a specific situation in which the only information provided on performance consists of a reward signal. Subjects performed a point-to-point movement. After the end of the movement we displayed a score based on the distance from a hidden via-point - the maximum score corresponds to the via-point belonging to the trajectory path. The score was the sole information available on task performance and subjects got no additional clues of how to make it high. The task is highly redundant, as infinite trajectories are compatible with the maximum score. We specifically looked at how subjects explore the task space and how they exploit task redundancy to maximize their performance. We also compared the experimental data with the solution predicted by an optimal feedback control model. The main findings were that (i) movement outcomes are largely determined by the subject-specific history of exploration; (ii) during learning, path variability gradually decreased; (iii) for the majority of subjects the point of minimum variability gradually gets closer to the point at minimum distance from the hidden via-point; and (iv) overall, subjects don’t converge to the ‘optimal control’ solution.

Takashi Sakamoto, Toshiyuki Kondo
THE ROLE OF MOTOR INTENTION DURING PASSIVE MOTOR LEARNING

In robotic rehabilitation context, it has been believed that having an active motor intention is a crucial factor. However, the effectiveness of passive motor learning with/without motor intention has not been clearly understood. To clarify this question, we investigate whether passive arm movements by a robotic manipulandum affect the motor learning of an arm-reaching task under an unfamiliar visuomotor rotation. Experimental results suggest that passive motor experiences have positive effect on the motor learning, even though it is signi?cantly smaller than active motor learning. Moreover, we found that there was no signi?cant difference whether subjects had motor intention or not during passive motor experiences.

Tetsuro Funato, Koji Hashizume, Shinya Aoi, Nozomi Tomita, Kazuo Tsuchiya
EXPERIMENTAL VALIDATION OF NONLINEAR PID CONTROL MODEL FOR HUMAN SWAY DURING STANDING

Human standing motion shows long-term perturbation. The present research considers this perturbation is a limit-cycle solution of nonlinear PID control including nonlinear proportional control and integral control, and shows the existence of such controls in human experiment.

Shinya Aoi‚ Tetsuro Funato‚ Nozomi Tomita‚ Kazuo Tsuchiya
NEUROMUSCULOSKELETAL MODEL OF HUMAN RUNNING BASED ON MUSCLE SYNERGY

In the present study, we developed a neuromusculoskeletal model for human running and performed computer simulation of the running gait. We constructed the musculoskeletal part of the model based on biomechanical findings and constructed the nervous system model based on physiological findings of central pattern generators and muscle synergy. We investigated functional roles of the nervous system to produce the running gait and examined the dynamic characteristics during the running gait.

Se Jin Park, Murali Subramaniyam, Moon Kug Moon, Dong Gyun Kim
VISUAL FATIGUE ASSESSMENT OF WATCHING 3D TELEVISION BY ELECTROENCEPHALOGRAM AND SUBJECTIVE EVALUATION

Watching 3D on TV bombards the eyes and brain with a succession of flashing images that appear for a fraction of a second. This technology puts potential health risks such as visual fatigue, motion sickness, lingering depth perception problems, disorientation and decreased postural stability, especially children and teenagers may be more susceptible to health issues associated with viewing in 3D. This study performed the visual fatigue assessment of watching 3D on TV in teenagers (age: 18.81 ± 0.53 years) by electroencephalogram (EEG) for brain waves and subjective evaluation. A total of 27 subjects including male and female were considered. The Biopac system’s Acqknowledge program was used as a physiological workstation. The significant (p < 0.05) increase in the beta frequency was observed after watching 3D visuals. This result supported by the subjective evaluation; which shows that the amount of 3D visual fatigue was greater than that of 2D.

Vahit Ciftci, Basak Akselli Yilmazkaya, Hakan Kaykisizli
BLOCKAGE EFFECT OF MECHANICAL ANEMOMETERS

Investigation of the blockage effects of the mechanical anemometers that are located at the end of the wind tunnel during the calibration process is one of the important research projects in the flow metrology.
The presence of anemometer and its support structure that are placed at the end of the wind tunnel causes a reduction in the cross sectional area of the flow and hence a variation in the velocity distribution. It is evident that the flow rate and so the flow velocities are changed by a factor “k”, strongly depending on the frontal area of the anemometer with its support structure and the changing velocities.
In this study, two different sizes of vane anemometers with propeller diameters 20 and 70 mm were used as test anemometers which were located in the center of the tunnel end. The reference static-pitot tube anemometer was placed in the center, 60 cm away from the measuring end of the tunnel. Five different velocities, between 2 m/s and 19 m/s, were used for measurement.
For two different propeller diameter sizes of vane anemometers and their support structures, blockage areas were measured carefully. Then using continuity equation, correlations between reference anemometer velocities and test anemometer velocities were found for two different sizes of anemometers and actual error equations were drawn. Thus, a calibration procedure was prepared.
The measured velocities, using the 70 mm propeller size vane anemometer, were 3 to 9 percent higher than the reference velocities.
In addition, before the test (without blockage) and during the test, variation in the reference anemometer velocities were found constant as 2 percent, except low velocities, for the 70 mm propeller size vane anemometer.

W. Rawes, M. L. Sanderson
ULTRASONIC AMPLITUDE AND TIME MEASUREMENTS IN GAS IDENTIFICATION

This paper describes work which has been undertaken to identify individual gases and gas mixtures employing techniques which are based solely on ultrasonic means. The method employs broad-band capacitive ultrasonic transducers to measure the transmission of ultrasound over a wide range of frequencies across the gas or gas mixture under investigation. The results can be used to infer the composition of the gas and thus estimate such properties such as the density or calorific value of the gas or gas mixtures. The relevance of this work is mainly in its use in the gas distribution and transmission system where increasingly ultrasonic flow measurements are being employed and where an additional ultrasonic measurement would convert the volumetric flowmeter into an energy meter.

P. Schley, R. Kleinrahm, M. Jaeschke, R. Janssen-van Rosmalen, J. A. Schouten
FEASIBILITY STUDY OF A CORRELATIVE ENERGY MEASUREMENT SYSTEM FOR NATURAL GASES

The paper presents a new correlative energy measurement method developed under a joint project of Ruhrgas AG, Germany, and Nederlandse Gasunie N. V., the Netherlands. The paper mainly refers to the results obtained from a previous feasibility study proposing a method using as input parameters dielectric permittivity, speed of sound and CO2 mole fraction. On the basis of these input parameters, superior calorific value and natural gas composition can be determined. Total uncertainty envisaged for superior calorific value is 0.2 %. Initial laboratory tests confirm that the uncertainty envisaged can be obtained or is even better. The method is to be tested in the field soon.

Ronald A. Berg, Jan G. Drenthen
A FLAMELESS CALORIMETER

This paper describes the design and operation of a new reference calorimeter based on a flameless combustion technique.
Within this technique, a mixture of (reference) gas and air is passed over a noble metal element that is electrically heated to a constant temperature. The gas is oxidized as it encounters the temperature of the noble metal element and rises above auto-ignition temperature within a small combustion cavity. The precise value of the electrical energy, required to heat the element, is stored.
The same procedure is again carried out with the (unknown sample) gas and the same air supply. The ratio of the value of the electrical energy now required to heat the element and the reference electrical energy, is inversely proportional to the ratio of the calorific values of the two gases.
The new instrument meets the ASTM 4891 standard and is designed to be integrated into a complete energy measurement system with an expected uncertainty in heating value of better than 0.25% and a repeatability better than 0.15%. The first test results of the instrument measuring low calorific- and high calorific gases are shown.

Eliphas Wagner Simões, Rogério Furlan, Dong Ho Choi
MICROFLUIDIC DEVICES FOR GAS FLOW CONTROL

This paper is focused on the study of microfluidic devices implemented in silicon. Microactuators with no moving parts, microfluidic amplifiers, were integrated with microchannels. The operation of the obtained devices was analyzed in terms of gas flow control and division. Considering flow control, the devices presented proportional and symmetrical behavior with high proportional flow gains (output flow/control flow), similar to fluidic amplifiers with supply hydraulic diameters higher than hundreds of microns. For operation with flow division, a transition to a linear behavior between the supply flow and supply pressure is observed and the devices presented symmetrical output characteristics. Also, in this case, at moderate supply pressures, the results of numerical simulation indicate the possibility of internal choked flow, at the output of the supply nozzle, and supersonic regime in the interaction region.

Page 403 of 977 Results 4021 - 4030 of 9762