Rise time

About: Rise time is a research topic. Over the lifetime, 4748 publications have been published within this topic receiving 47512 citations.

Comparison of signal-to-noise ratio of myoelectric filters for prosthesis control.

Abstract: A comparison of signal-to-noise ratios and rise times was performed on several myoelectric filters used for muscle-force estimation and prosthesis control. Linear, averaging, and adaptive filters were compared using single as well as multiple electrode pairs (spatial filtering). The filters were matched for having the same rise time (0-95%) and the signal-to-noise ratios were measured off-line using the same myoelectric signal recording. The linear filter was a low-pass filter with a time constant of 80 ms. The averaging filter had an averaging time of 250 ms. The adaptive filter was the same as is used in the Utah Artificial Arm. The adaptive filter varied its time constant according to the rate of change of the signal mean. If the rate was high, the time constant was set low. If the rate was low, the time constant was set high. Spatial filtering is where the myoelectric signals from four cutaneous sites over the same muscle were summed, that is, spatially filtered, and the resultant signal was smoothed by the linear, averaging, or adaptive filter. Significant improvement in the signal-to-noise ratio has been shown over conventional linear or averaging filters when using spatial and adaptive filtering, both when used separately and when used together.

Subnanosecond time response of large-area superconducting stripline detectors for keV molecular ions

Abstract: A large-area (200×200 μm2) superconducting stripline detector based on a parallel configuration of superconducting Nb nanowires is presented. We show that the parallel configuration provides a smart way to control the physical nonequilibrium state induced by the molecular impacts, which allows realizing large sensitive area and subnanosecond response at the same time. The experiments were carried out with molecular ions radiation in a keV energy range. The observed rise time was below 400 ps and the relaxation time was 500 ps, the best in this class of superconducting molecular detectors.

Pulsed Ultrasonic Transit Time Flowmeter

Abstract: The difference in effective velocity of sound pulses propagated alternately upstream and downstream through moving blood is a measure of the blood velocity. A blood flowmeter based on this principle has been developed and employed in routine experiments over a period of four years. The travel time of sound pulses passing diagonally through the blood vessel is measured by gating a ramp voltage generator during the transit of each sound pulse from the transmitter crystal to the receiver crystal. The peak voltage attained by the ramp is stored and compared with the peak voltage attained by the subsequent ramp when the direction of propagation is reversed. The cycle is repeated 400 times each second so that a 400 cps carrier is formed. The amplitude of the carrier is proportional to the magnitude of the flow, and the phase of the carrier indicates direction of flow. The total PP noise and long-term drift is less than 7(10)-11sec difference in transit time over a four-hour measurement period, under optimal conditions. Here a demodulator limited the rise time of the instrument to 20 msec. Each upstream-downstream measurement requires only 240 ?sec of the total available 2500 ?sec, so that a time sharing technique may be used to operate many flowmeters simultaneously without mutual interference. The transducers are light (about 5 grams) and economical to construct.

Influence of Polarity and Rise Time of Pulse Voltage Waveforms on Diesel Particulate Matter Removal Using an Uneven Dielectric Barrier Discharge Reactor

Abstract: The influence of polarity and rise time of the pulse voltage on the removal of particulate matter (PM) emitted from a diesel engine was investigated using a dielectric barrier discharge reactor. Four kinds of pulse voltage waveforms (positive, negative, positive–negative and negative–positive) were used. It was found that the energy efficiency for PM removal is just a function of energy injection and that there are no obvious influences on PM removal and energy efficiency within the voltage waveforms except the negative pulse voltage of a peak voltage below 8 kV. A comparison of PM removals using various kinds of pulse voltage waveforms and different types of plasma reactors is given.

Transient Analysis of Single and Coupled Lines with Capacitively-Loaded Junctions

Abstract: Transient processes are studied for a single line or a pair of coupled lines consisting of line sections with different characteristic admittances and with capacitances loaded at the junctions of line sections. Equations for the Laplace transform of the reflection and transmission coefficients of single and coupled lines are derived for the general case. When the capacitances are loaded at regular intervals, the corresponding expressions of the transient response waveforms at different terminal ports of these lines for both a step and a ramp input are developed. Based on the theoretical analysis, we illustrate the transient responses to ramp signals on some simplified computer signal lines, such as parallel-plate lines with transverse ridges, and parallel striplines with perpendicular crossing strips sandwiched between common upper and lower ground planes. The numerical results suggest that signals with a rise time of t/sub r/<50 ps will cause too much distortion, and should not be used when the length of the line is longer than 2 cm.