20,382 research outputs found

    Transistor biased amplifier minimizes diode discriminator threshold attenuation

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    Transistor biased amplifier has a biased diode discriminator driven by a high impedance /several megohms/ current source, rather than a voltage source with several hundred ohms output impedance. This high impedance input arrangement makes the incremental impedance of the threshold diode negligible relative to the input impedance

    Current-switching technique for analog pulse circuits

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    Circuit technique uses a signal diode as a series current-pass element. Technique is applied to the design of a biased amplifier circuit and a nanosecond-pulse stretcher circuit

    Pulse stretcher has improved dynamic range and linearity

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    Current-switching pulse stretcher overcomes the diode nonlinearity and capacitive feedthrough of voltage switching diode-capacitor stretchers and lengthens nanosecond pulses so that their amplitude may be determined and extends the dynamic range of the pulse stretcher. The rise time of the output pulse in response to a step function is approximately 5 nanoseconds

    The Effect of Spatial Curvature on the Classical and Quantum Strings

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    We study the effects of the spatial curvature on the classical and quantum string dynamics. We find the general solution of the circular string motion in static Robertson-Walker spacetimes with closed or open sections. This is given closely and completely in terms of elliptic functions. The physical properties, string length, energy and pressure are computed and analyzed. We find the {\it back-reaction} effect of these strings on the spacetime: the self-consistent solution to the Einstein equations is a spatially closed (K>0)(K>0) spacetime with a selected value of the curvature index KK (the scale f* is normalized to unity). No self-consistent solutions with K0K\leq 0 exist. We semi-classically quantize the circular strings and find the mass mm in each case. For K>0,K>0, the very massive strings, oscillating on the full hypersphere, have m2Kn2    (nN0)m^2\sim K n^2\;\;(n\in N_0) {\it independent} of α\alpha' and the level spacing {\it grows} with n,n, while the strings oscillating on one hemisphere (without crossing the equator) have m2αnm^2\alpha'\sim n and a {\it finite} number of states N1/(Kα).N\sim 1/(K\alpha'). For K<0,K<0, there are infinitely many string states with masses mlogmn,m\log m\sim n, that is, the level spacing grows {\it slower} than n.n. The stationary string solutions as well as the generic string fluctuations around the center of mass are also found and analyzed in closed form.Comment: 30 pages Latex + three tables and five figures (not included

    Tunnel diode circuit used as nanosecond-range time marker

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    Simple tunnel diode time marker circuit determines the time at which an event occurs in a scintillation crystal. It is capable of triggering at voltages as low as the noise level of a 10-stage PM tube

    Pulse-height defect due to electron interaction in dead layers of Ge/Li/ gamma-ray detectors

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    Study shows the pulse-height degradation of gamma ray spectra in germanium/lithium detectors to be due to electron interaction in the dead layers that exist in all semiconductor detectors. A pulse shape discrimination technique identifies and eliminates these defective pulses

    Observations of thunder with the Arecibo VHF radar

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    An experiment was carried out at the Arecibo Observatory in Puerto Rico in August 1985 to study Doppler velocities in a thunderstorm environment with a beam pointed 2.5 degrees off-vertical. Researchers detected two types of echoes associated with lightning. The first was associated with scattering from the lightning channel itself and had characteristics similar to those observed previously with meteorological radars. The second appeared to be due to scattering from the turbulence organized by phase fronts of an acoustic wave generated by lightning. The observations were consistent with a wave traveling at a velocity near the speed of sound and having a vertical phase velocity component of 40 m/s
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