Showing papers on "Pulse duration published in 1978"

Resistive hose instability of a beam with the Bennett profile

Abstract: The resistive hose instability of a self‐pinched relativistic beam is examined with emphasis placed on the important case of the Bennett current profile JB(r) ∝ (1+r2/a2)−2. Previously known results applicable to a general profile are recovered and extended in several directions. An essential new feature in this study is the use of distributed particle mass to model orbital phase‐mixing effects produced by the anharmonic pinch field. Resonant growth is considerably reduced, and the instability when viewed in the beam reference frame is shown to be convective rather than absolute. The peak amplitude of a disturbance wave packet moves from the point of its inception in the beam pulse toward the pulse tail. The disturbance subsequently damps if the pulse length is finite; thus, propagation over distances that are long compared with the particle betatron wavelength is possible. The predicted growth rate and group velocity of the mode are shown to be in fair agreement with the results of numerical simulation.

Remote control system capable of transmitting the information with the aid of an infra red beam using PPM or an ultrasonic beam using PDM

Abstract: A remote control system for TV receiver control. The system uses infra-red transmission to trasmit an infra-red data pulse on each edge of a pulse duration signal comprising a coded pattern of binary 0 and 1 bits which are formed by pulses of respective different lengths. The original pulse duration signal can be reconstituted at a receiver by a bistable element which is responsive to the infra-red data pulses. Since the regenerated modulating waveform could be in anti-phase with the original modulating waveform, the sequence of data pulses is transmitted twice and an additional data pulse is transmitted between successive transmissions, so that one or the other of the two regenerated modulating waveforms must be in phase with the original modulating waveform.

The acoustic characteristics of the skull

Abstract: Many investigators have stated that the difficulties of imaging with acoustical energy through the skull result from the marked attenuation of the energy by the skull. In the literature measurements of total attenuation have been confused with those for absorption. Measurements made by us show that absorption by compact bone varies between 2–3 dB cm −1 MHz −1 and, in the low megaHertz region appears to be directly proportional to frequency. It has also between shown that the convoluted inner surface of the ivory bone of the inner table of the skull may degrade the collimation and directionality of the beam by refraction. Cancellous bone, such as is present in the dipole of the skull, greatly attenuates the energy. It is postulated that this largely results from scattering. It is also postulated that the energy propagates through cancellous bone as two components, one in the soft tissues and the other partly in the bony spicules. Observations suggest that attenuation due to scattering much more markedly affects the latter of these components and scatters more greatly the higher frequencies in a pulse of broad bandwidth. The energy in each component has varying propagation paths so that the later cycles in the pulse of each component are subject to increasing interference as a result of the variations in propagation times. The two components moreover may have different propagation times so that interference may occur between the pulses of each component as well. All of these phenomena degrade the collimation, coherence, directionality, beam width, pulse length, frequency and other properties of the ultrasonic energy upon which imaging through the skull depends. The interference effects described above are least for the first cycle in the pulse which usually is not the cycle of highest amplitude. Since, in the free field, most of the energy is concentrated around the beam axis, most of the energy in the field which is deflected from its normal propagation path is deflected away from the beam axis. Thus the directionality of the beam is least degraded in the beam axis. The effects of the skull in degrading the properties of the ultrasonic pulse would therefore be lessened if the amplitude of the first cycle of the pulse and the directionality of its energy could be used for imaging.

Self-stimulation in the rat: Quantitative characteristics of the reward pathway.

Abstract: Quantitative characteristics of the neural pathway that carries the reinforcing signal in electrical self-stimulation of the brain were established by finding which combinations of stimulation parameters give the same performance in a runway. The reward for each run was a train of evenly spaced monophasic cathodal pulses from a monopolar electrode. With train duration and pulse frequency held constant, the required current was a hyperbolic function of pulse duration, with chronaxie c approximately 1.5 msec. With pulse duration held constant, the required strength of the train (the charge delivered per second) was a hyperbolic function of train duration, with chronaxie C approximately 500 msec. To a first approximation, the values of c and C were independent of the choice either of train duration and pulse frequency or of pulse duration, respectively. Hence, the current intensity required by any choice of train duration, pulse frequency, and pulse duration dependent on only two basic parameters, c and C, and one quantity, Qi, the required impulse charge. These may reflect, respectively, current integration by directly excited neurons; temporal integration of neural activity by synaptic processes in a neural network; and the peak of the impulse response of the network, assuming that the network has linear dynamics and that the reward depends on the peak of the output of the network.

Adaptive properties of olfactory receptors analysed with odour pulses of varying durations.

Abstract: 1. The adaptive properties of salamander of olfactory receptors have been analysed in extracellular unit recordings. Stimulation has been by step pulses of odour of varying durations for 1--10 sec. 2. The most common response was a prolonged impulse discharge that continued throughout the duration of the pulse and terminated abruptly within 1 sec of the end of the pulse. The interval for termination was relatively independent of the pulse duration. Pulses were frequently followed by a period of impulse inactivity lasting 1--3 sec, usually independent of previous pulse duration. 3. The impulse discharges were typically slowly adapting. Initially, during the first 1--2 sec, the frequency rose to 5--10 impulses/sec, at threshold concentration. In some cases, the initial level was maintained throughout the pulse, with little or no adaptation. More commonly, there was a distinct initial phasic peak, followed by decay to a lower level of 4--8 impulses/sec, which was maintained during the pulse. It was concluded that most olfactory receptors are slowly adapting, with variable phasic responsiveness dependent on odour concentration and other factors. 4. Reductions in impulse activity, compared with background, during a pulse were rarely seen. Methods for increasing the level of background activity and the use of very long duration pulses were necessary in order to bring out this type of response. Uniformly reduced activity throughout a pulse was seen clearly in only one case. A pattern consisting of a waning and then recovery of impulse frequency during a pulse was also observed in rare cases. 5. The results have shown that olfactory receptor discharges characteristically have a relatively precise relation to step pulses of odour of varying duration. The properties of the response have implications for the steps involved in the overall processes of activation and inactivation of receptor mechanisms at the olfactory mucosa.

A relatively short cylindrical broadband antenna with tapered resistive loading for picosecond pulse measurements

Abstract: A relatively short cylindrical antenna with continuously tapered resistive loading has been studied for the purpose of picosecond pulse measurements. The antenna considered is a nonconducting cylinder with continuously deposited varying-conductivity resistive loading. The current distributions on the antenna were numerically calculated using the method of moments. Using these current distributions, other quantities such as input admittance, near-field and farfield radiation patterns, and radiation efficiency, were also numerically calculated and compared with the results using the Wu-King's approximate current distribution. Agreement is relatively good except at high frequencies kh > \pi/2 where the method of moments appears to give better results. To verify the theoretical results, several resistively loaded antennas were fabricated, and their picosecond pulse receiving characteristics were analyzed for the frequency range between 5 kHz and 5 GHz. The experimental results indicate excellent linear amplitude and phase response over the frequency range. This provides the unique capability of this antenna to measure fast time-varying electromagnetic fields with minimal pulse-shape distortion due to nonlinear amplitude or phase characteristics.

A transversely rf‐excited CO2 waveguide laser

Abstract: An electrodeless CO2 waveguide laser with transverse rf pumping is described. In the rf cw mode, the laser emits up to 0.6 W at 100 Torr. In the rf pulse mode, atmospheric operation has been achieved with pulse duration of 20 μs and peak power of a few watts at a repetition rate of 300 Hz.

Pulse Interval and Width Modulation for Video Transmission

Abstract: This paper proposes new pulse analog modulation system; Pulse Interval and Width Modulation suitable for light emitting diodes. In this system pulses have information on both their width and interval between them. Pulse Interval and Width Modulation is characterized by the following compared with Pulse Interval Modulation. First: Pulse repetition frequency is reduced by one half. Second: Duty ratio is 50 % on the average. Third: More power is needed while carrier to noise ratio could be improved instead. The paper shows how it works and comparison with another pulse analog modulation such as Pulse Frequency Modulation or Pulse Interval Modulation. The paper also shows an experiment of twin channel transmission employing two light emitting diodes, two optical fiber transmission lines and two PIN photodiodes as an example of application of Pulse Interval and Width Modulation.

Active‐passive mode‐locked oscillators at 1.054 μm

Abstract: We report on the characteristics of active‐passive mode‐locked phosphate‐glass oscillators. These highly reliable oscillators operate at 1.054 μm and are characterized by the absence of satellite pulses for pulse durations tp≳80 psec. They have very high peak‐to‐background contrast of 107 to 108. Transform‐limited pulse widths between 80 and 600 psec are reliably generated using a pair of intracavity etalons. The reproducibility of the pulse durations is better than ±10%, that of the pulse‐train maximum about ±10 to 20%. Single‐pulse selection with ±5% amplitude fluctuation has been achieved with threshold‐pulse selectors. For pulses shorter than 50 psec, satellite pulses are occasionally observed. A theoretical explanation for this observation is given.

Generation and measurement of subpicosecond electron beam pulses.

Abstract: The generation and measurement of subpicosecond electron beam pulses by the transverse‐longitudinal combination gate system is described. The temporal property of the pulse gate is analyzed with the help of the longitudinal emittance diagram. Close agreement has been obtained between the calculated pulse width and the observed one which was measured by the Lissajous’s figure method. A beam pulse of 0.2 ps (FWHM) was produced.

Electrical synchronizing circuits

Abstract: There is disclosed an electrical circuit arrangement for phase-synchronizing a first pulse train with a second pulse train, in which the algebraic phase difference between each pulse of one pulse train and the next pulse of the other pulse train is measured for each of a predetermined number of pulses of one of the pulse trains. The algebraic average phase difference is then determined over the said predetermined number of pulses, and the absolute phase of the pulses of the first pulse train is then adjusted in correspondence with the average phase difference so as to bring the two pulse trains closer into phase equality.

Submicrosecond time resolution observations of PSR0950 + 08

Abstract: PULSARS were discovered by Hewish et al.1 using an instrument with higher time resolution than was conventionally used in radioastronomy. From the short time duration pulses they detected they placed an upper limit of 4.8 × 103 km on the size of the objects, assuming that a radiating region producing a pulse of duration t cannot be larger than ct, the distance light can travel during the pulse. Other observers2–5 have since reduced this size limit with improved time resolution, with the objective of determining the size of the fundamental radiating elements. We report here our observations of isolated unresolved 0.8 µs micropulses, which, if the conventional assumption is made, result from emitting volumes less than 250 m in extent. We also show that even with our high time resolution the observations are consistent with Rickett's amplitude modulated noise model6 for pulsar emission, where all of the observed intensity fluctuations can be represented as the modulation of a more fundamental gaussian noise process.

Electric massage apparatus and method

Abstract: An apparatus for and a method of treatment of animals, including humans, with a pulsating electrical potential that is applied across electrodes placed on the animals. In a first embodiment the pulsating electrical potential has a first characteristic, including pulse repetition rate, pulse amplitude, and pulse polarity, for a first period of time and then a second characteristic, again including pulse repetition rate, pulse amplitude and pulse polarity, for a second period of time. In a second embodiment, the electrodes and their placement on the animal are controlled so that the electrical potential has a voltage-to-current ratio within an optimum range.

Electronic pain control with scanned output parameters

Abstract: A first oscillator dictates the pulse duration and frequency of stimulating signals; the oscillator output wave form is coupled to an output amplifier stage, and thence to the patient. A scanning oscillator provides a substantially linear ramp voltage, which in turn controls pulse duration, pulse frequency, and pulse intensity modulators. In turn, these modulators appropriately establish conditions within the first oscillator and the output stage whereby the output parameters are scanned through respective predetermined ranges, thereby periodically achieving optimum stimulating conditions.

Experiments on second‐sound shock waves in superfluid helium

Abstract: The waveform and velocity of second‐sound waves in superfluid helium have been studied experimentally using superconducting, thin‐film probes. The second‐sound waves were generated with electrical pulses through a resistive film. Variations in pulse power, pulse duration, and bath temperature were examined. As predicted theoretically, the formation of a shock was observed at the leading or trailing edge of the waves depending on bath temperature. Breakdown of the theoretical model was observed for large pulse powers. Accurate data for the acoustic second‐sound speed were derived from the measurements of shock‐wave velocities and are compared with previous results.

Digital apparatus for correcting a time-base error in a television video signal

Abstract: A digital time base corrector for correcting a time-base error in a television video signal, the video signal including a horizontal synchronizing signal and a color burst signal. The start of a write-in clock pulse oscillator is determined by a one-cycle portion of the color burst signal which has been extracted from the video signal in a prefixed phase relationship with the horizontal synchronizing signal. Oscillation frequency control at the write-in clock pulse oscillator is performed in response to the phase deviation of the write-in clock pulse from the extracted one-cycle burst signal portion. Phase-locking of the write-in clock pulse oscillator is performed in response to the phase difference, from the extracted one-cycle burst portion, of a selected one of first and second pulses, the first pulse occurring at the rate of the subcarrier signal and the second pulse occurring at the rate of the horizontal synchronizing pulse. Both pulses are obtained from the write-in clock pulse. The present invention adapts the time-base corrector to allow broader phase fluctuations of the write-in clock pulse with respect to the color burst and the horizontal synchronizing signal of the incoming video signal.

Pulse electrodepositing method

Abstract: Electrodeposition is carried out using an electric current which is applied in the form of pulses between a workpiece and an electrode in an electrolyte from which metal is to be deposited upon the workpiece. The pulses have a pulse duration not greater than 100 microseconds and the pulse duration is preferably between 1-50 microseconds while the off time or interval between adjacent pulses is more than twice as long as the on time of the pulses.

Radio motor control system

Abstract: A radio control system having a radio-controlled model toy on which a d-c power supply, a receiver and two electric motors are mounted, and a transmitter for maneuvering the radio-controlled model toy, and characterized in that the transmitter is constructed so that a control pulse signal having a pulse level representing signal "1" and a pulse level representing signal "0" is transmitted and the duration of the signal "1" pulses is increased or decreased, and that the receiver is constructed so that driving current is supplied to a motor during the signal "1" pulse duration and to another motor during the signal "0" pulse duration.

On the effects of different laser energy sources upon the iris of the pigmented and the albino rabbit.

Abstract: The irides of pigmented and albino rabbits have been irradiated by a) a CW argon laser beam (exposure duration up to 1 s), b) a 1 ms pulses Nd:YAG laser and c) a 30 ns pulses Q-switched ruby laser The immediate and long-term pathologies were analysed by scanning and transmission electron microscopy over a period of 13 months At both the gross and ultrastructural levels, damage configuration may differ considerably, depending on the three modes of irradiation For each source there are both thermal and mechanical damage components and the significance of mechanical effects increases with decreasing pulse duration for a constant pulse energy In the argon experiments, tissue destruction is predominantly a consequence of heat, resulting from conduction and convection The subsequent regeneration of tissue after such heat-induced trauma is fast The effects of the Nd:YAG laser, at the irradiance levels used in the present study, are again predominantly of a thermal nature and are caused by heating and local evaporation The pigmented and the nonpigmented iris epithelium are destroyed and widespread decay of the stroma occurs over some months Such damage never results in full repair The most prominent feature of Q-switched ruby laser irradiations is their independence of the iris pigment content In contrast, at the energy levels studied, the argon laser is entirely ineffective, whilst the effect of the Nd:YAG laser is much reduced in the absence of pigment The consequences of these findings for the clinical applications of such lasers are discussed

Technique for tracking amplitude fades for multi-amplitude signalling

Abstract: Amplitude variations in a multi-amplitude transmission system are tracked by monitoring amplitude variations over a substantial data time span through the use of a technique in which the percentage of time that a maximum-valued reference amplitude is exceeded is made equal to the percentage of time that a minimum-valued amplitude is not obtained. For this purpose, received data samples are multiplied by an adjustable gain constant to obtain an amplitude product. The amplitude product is then compared with reference values corresponding to the maximum and minimum amplitudes. If the amplitude product exceeds the maximum amplitude reference, the gain constant is decreased, and if the amplitude product is smaller than the minimum amplitude reference, the gain constant is increased. To implement this technique on a percentage basis, a storage device, such as an up/down counter, is loaded with a prescribed number corresponding to the percentage range over which the gain adjustment is measured and the contents of the counter are controllably incremented or decremented depending upon received gain products. Modification of the gain constant can be in accordance with a fixed value or one which is a function of the difference between the amplitude product and the maximum or minimum reference values.

Engine fuel injection control apparatus with simultaneous pulse width and frequency adjustment

Abstract: In a fuel injected vehicle engine having pulse generating apparatus for controlling the activation of a fuel injector for the duration of fuel injection pulses according to the fuel requirements of the engine, apparatus responsive to the normal duration of the pulses is effective, when the normal pulses are shorter than a predetermined minimum desired pulse duration, to increase simultaneously both the intervals between the pulses and the durations of the pulses by a common factor N from the normal interval and durations, to increase fuel flow accuracy at low fuel supply rates.