A seismic investigation of the Witwatersrand earth tremors*

1946 ◽  
Vol 36 (2) ◽  
pp. 49-80
Author(s):  
P. G. Gane ◽  
A. L. Hales ◽  
H. A. Oliver
Keyword(s):  
Timing Accuracy ◽  
Time Signals ◽  
Seismic Investigation ◽  
Mechanical Seismographs

Abstract The results are presented of an investigation of the foci of Witwatersrand earth tremors by means of 5 small mechanical seismographs. Timing accuracy of about 0.05 sec. was obtained by the use of synchronous electric clocks at each station, the time marks from which were correlated daily by means of radio time signals. The instruments are described, and an account of the locating procedure is given. The average velocities for the area were found to be Vp = 5.40 ± .07 km/sec., Vs = 3.19 ± .03 km/sec. The energy in a large tremor was estimated to be of the order of 1018 ergs.

Movement time as a determiner of timing accuracy.

1969 ◽  
Vol 79 (1, Pt.1) ◽  
pp. 43-47 ◽  
Author(s):  
Richard A. Schmidt
Keyword(s):  
Movement Time ◽  
Timing Accuracy

scholarly journals The VIT Transform Approach to Discrete-Time Signals and Linear Time-Varying Systems

Eng ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 99-125
Author(s):  
Edward W. Kamen
Keyword(s):  
Discrete Time ◽  
Initial Conditions ◽  
Linear Time ◽  
Order Term ◽  
Initial Time ◽  
Time Varying ◽  
Varying Coefficients ◽  
Time Signals ◽  
Time Varying Systems ◽  
Time Varying Coefficients

A transform approach based on a variable initial time (VIT) formulation is developed for discrete-time signals and linear time-varying discrete-time systems or digital filters. The VIT transform is a formal power series in z−1, which converts functions given by linear time-varying difference equations into left polynomial fractions with variable coefficients, and with initial conditions incorporated into the framework. It is shown that the transform satisfies a number of properties that are analogous to those of the ordinary z-transform, and that it is possible to do scaling of z−i by time functions, which results in left-fraction forms for the transform of a large class of functions including sinusoids with general time-varying amplitudes and frequencies. Using the extended right Euclidean algorithm in a skew polynomial ring with time-varying coefficients, it is shown that a sum of left polynomial fractions can be written as a single fraction, which results in linear time-varying recursions for the inverse transform of the combined fraction. The extraction of a first-order term from a given polynomial fraction is carried out in terms of the evaluation of zi at time functions. In the application to linear time-varying systems, it is proved that the VIT transform of the system output is equal to the product of the VIT transform of the input and the VIT transform of the unit-pulse response function. For systems given by a time-varying moving average or an autoregressive model, the transform framework is used to determine the steady-state output response resulting from various signal inputs such as the step and cosine functions.

scholarly journals Car2Car Communication Using a Modulated Backscatter and Automotive FMCW Radar

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3656
Author(s):  
Antonio Lazaro ◽  
Marc Lazaro ◽  
Ramon Villarino ◽  
David Girbau ◽  
Pedro de Paco
Keyword(s):  
Power Supply ◽  
Communication Systems ◽  
Microwave Frequency ◽  
Proof Of Concept ◽  
Driver Assistance ◽  
Switching Rate ◽  
Fmcw Radar ◽  
Time Signals ◽  
Video Sensors ◽  
24 Ghz

This work proposes the use of a modulated tag for direct communication between two vehicles using as a carrier the wave emitted by an FMCW radar installed in the vehicle for advanced driver assistance. The system allows for real-time signals detection and classification, such as stop signal, turn signals and emergency lights, adding redundancy to computer video sensors and without incorporating additional communication systems. A proof-of-concept tag has been designed at the microwave frequency of 24 GHz, consisting of an amplifier connected between receiving and transmitting antennas. The modulation is performed by switching the power supply of the amplifier. The tag is installed on the rear of the car and it answers when it is illuminated by the radar by modulating the backscattered field. The information is encoded in the modulation switching rate used. Simulated and experimental results are given showing the feasibility of the proposed solution.

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