Rise time

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

Subjective loudness of N-wave sonic booms.

Abstract: A loudspeaker‐driven simulation booth with extended rise‐time capability (down to 0.22 ms) has been used for subjective loudness tests of N‐wave sonic booms. The test series compared signatures over a range of 0.22–10 ms in rise time, 100–250 ms in duration and 0.5–2.5 psf (24–120 Pa) in peak overpressure. In one sequence, the tradeoff between rise time and overpressure was measured for equal loudness; in another, the tradeoff between duration and overpressure. For equal loudness 10‐ms rise time required 8‐dB higher overpressure than for 1‐ms rise time. Duration had little effect in the range 100–200 ms, but at 250 ms noticeably enhanced the loudness. These results confirm those measured by Shepherd and Sutherland made at 1‐ms rise time and above (except for the anomalous enhancement at 250‐ms duration), and extend the measurements down to 0.22 ms. There is also good agreement with theoretical predictions (Johnson–Robinson, Zepler–Harel methods) except for the 10‐ms rise time and 250‐ms duration cases.

Double-stage gate drive circuit for parallel connected IGBT modules

Abstract: Solid state modulators are increasingly being used in pulsed power applications. In these applications IGBT modules must often be connected in parallel due to their limited power capacity. In a previous paper, we introduced a control method for balancing the currents in the IGBTs. In this paper, we investigate techniques to minimize the modules' rise and fall times, which can positively impact the modulator's output pulse parameters, which in turn must meet the application's specifications. Further, a reduction in rise and fall times lowers switching losses and thus increases the modulator's efficiency. To reduce the voltage rise time of the pulse without increasing the maximal over-voltage of the parallel IGBTs we have investigated a double-stage gate driver with protection circuits to avoid over-voltages and over-currents. Additionally voltage edge detection has been implemented to improve current balancing. Our measurement results reveal the dependency of the rise-time and turnoff losses on the design parameters of the gate drive. We show that our design achieves a 62% reduction in the turn-off rise time, and a 32% reduction in the turn-off losses.

Temperature and end‐plate currents in rat diaphragm.

Abstract: 1. Spontaneous miniature end-plate currents (m.e.p.c.s.) were recorded in rat diaphragm at 7, 22 and 37 degrees C at -80 mV. The onset rate, measured as 20-80% rise time, was sensitive to temperature with activation energy 14 kcal mol-1 deg-1, and was not sensitive to membrane voltage between -60 and -130 mV. 2. The rise time recorded by external electrodes was 144 microseconds at 37 degrees C (6) and was similar to that found by internal electrodes. 3. The fall time was temperature-sensitive with activation 18 kcal, and was prolonged when the end-plate was hyperpolarized. 4. With acetylcholine (10 microM) the current increased to a peak and then fell within 30 s to a value which declined slowly. From fluctuation analysis the channel open time of 237 microseconds (7) at 37 degrees C was estimated. External recording gave comparable values (4). Comparison of the initial estimates with those obtained after 3-6 min of continued application showed no consistent change. The channel conductance was 26 pS at 37 degrees C. 5. The time constant of m.e.p.c. decay was consistently longer than the channel open time obtained from noise analysis. 6. With carbachol (40 microM) the current increased to a peak and then declined to a steady value. Fluctuation analysis by internal and external recording gave an increase of 5% in root mean square current with channel open time of 83 microseconds (6) at 37 degrees C, and channel conductance 17 pS.

Analysis of laser induced acoustic pulse probing of charge distributions in dielectrics

Abstract: Some features of the laser induced acoustic pulse method for the determination of electric field or charge distributions in dielectrics are analysed. Three aspects of this method are described. 1) The electric field can be derived by a numerical method whose resolution depends essentially on the rise time of the pressure wave. Measurements are described which support this analysis. 2) The mechanisms of generation of the pressure wave are studied; a method is described which allows the production of hundreds of pulses without noticeable alteration, with a good energy conversion efficiency. 3) The influence of the elastic properties of the material on the attenuation and dispersion of the wave is considered. Measurements performed on Polyfluoroethylenepropylene (FEP) samples show that one has to take these parameters into account if the rise time of the pressure is much shorter than the transit time.

Seismic source influence in pulse attenuation studies

Abstract: Analysis of pulse rise time data produced from repetitive piezoelectric and magnetostrictive seismic sources shows that the change in rise time as a function of distance is source dependent. Thus a linear rise time law of the form τ = τ0 + CT/Q, with C source independent, cannot be used to assess the attenuation of rock in situ. In fact, application of such a law to the data results in a significant overestimate in the value of Q. A numerical example is also presented to show that in terms of filter theory a linear rise time law is ill founded. An alternative, source independent method of assessing the attenuation is employed for both constant-Q and non-constant-Q models, and it is found that either model may be made to give a reasonable fit to the data. However, it is shown that if a non-constant-Q mechanism is operating, then there is probably less than a 5% change in Q over the frequency range 0.80–70.OkHz.