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Results 81 - 90 of 92
2/1/1982 - Contract reportsAn evaluation was made of one of several improved underground communication systems sponsored by the U.S. Bureau of Mines. The system was installed in a typical metal-nonmetal, room-and-pillar mine and utilized ultrahigh frequency repeaters connected to...
A Feasibility Study for the Detection of Weak Electromagnetic Signal/ Bursts With Hard-Limited Arrays11/1/1981 - Contract reportsA prototype detector using electromagnetic signals for finding trapped miners has previously been built and tested. The signals are generated from transmitters carried on the miner's belt and powered by his head lamp battery and the receiver is a human ...
A survey of electromagnetic noise reports was performed and a summary of the results are given.
7/1/1980 - Contract reportsThis report assesses the expected detectability, on the surface above mines, of electromagnetic signals produced in the 630- to 3,030-hz frequency band by a rescue transmitter activated by miners trapped underground. The implications of the results and ...
1/1/1976 - Reports of InvestigationsCoalbeds exhibit a directional permeability, with the maximum permeability oriented parallel to the face cleat. Thus, the most efficient pattern of vertical degasification holes for a coalbed is dependent upon cleat orientation. Analysis of surface joi...
Two different techniques were used to make measurements of the absolute value of electromagnetic noise in an operating coal mine, Itmann No. 3 Mine, located near Mullens, West Virginia. The electromagnetic environment created by 250-volt dc and 550- and...
Measurements of the absolute value of electromagnetic noise and attenuation along a hoist rope were made in an operating Hard-Rock Mine, Lucky Friday Mine, located near Wallace, Idaho. The specific measured results are given in a number of spectral plot...
The time and amplitude statistics necessary to adequately describe electromagnetic (EM) noise in mines are illustrated through computer soft- ware techniques. They are 1) Allan Variance Analyses (AVA), 2) Interpulse Spacing Distributions (ISD), 3) Pulse...
Two different techniques were used to make measurements of the absolute value of electromagnetic noise in and above an operating coal mine, McElroy Mine, located near Moundsville, West Virginia. The electromagnetic environment created by 300-volt dc and...
Two different techniques were used to make measurements of the absolute value of electromagnetic noise in an operating coal mine, Robena No. 4, located near Waynesburg, Pennsylvania. One technique measures noise over the entire electromagnetic spectrum ...