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1995 Midnite Mine Radiation Survey

Description: Abstract: During the week of September 4, 1995, personnel from the U.S. Bureau of Mines conducted a Ra-226 survey at the Midnite Mine. One hundred thirty measurements were made on a rectangular grid with 150-m spacings. Concurrently, Shepherd Miller, Inc., took gross gamma readings in gR/h at the same grid points. In addition, the USBM collected 17 soil samples to be analyzed for radium, thorium, and potassium. The results of this survey are summarized in this report.
Date: 1996
Creator: Stroud, William P. & Droullard, Robert F.

3DTOM, Three-Dimensional Geophysical Tomography

Description: Abstract: 3DTOM is a DOS-compatible computer program developed by the Mines U.S. Bureau of for three-dimensional tomographic imaging of the subsurface at mine sites. The program uses the simultaneous iterative reconstruction technique (SIRT) to invert travel- time data and produce maps of wave velocity, or to invert amplitude data and generate maps of wave attenuation coefficients. Either seismic (compressional and/or shear) or electromagnetic (e.g., radio or radar) wave data may be used. Ray tracing in 3DTOM uses several different methods, including ray bending, network theory, and a combination of these. User-defined constraints are important in reducing the mathematical nonuniqueness of inversions based on limited data. 3DTOM permits the use of hard constraints, or soft constraints based on fuzzy logic, to allow for uncertainty in the constraints. Reliable subsurface images are useful in many different mine-related problems, including void detection, fracture detection, fluid monitoring, and qualitative stress evaluation.
Date: 1996
Creator: Jackson, M. J. & Tweeton, Daryl R.

An Adaptive System for Process Control

Description: Abstract: Researchers at the U.S. Bureau of Mines (USBM) have developed adaptive process control systems in which genetic algorithms (GA's) are used to augment fuzzy logic controllers (FLC's). GA's are search algorithms that rapidly locate near-optimum solutions to a wide spectrum of problems by loosely modeling the search procedures of natural genetics. FLC's are rule-based systems that efficiently manipulate a problem environment by modeling the "rule-of-thumb" strategy used in human decisionmaking. Together, GA's and FLC's include all of the capabilities necessary to produce powerful, efficient, and robust adaptive control systems. To perform efficiently, such control systems require a cont element to manipulate the problem environment, an analysis element to recognize changes in the problem environment, and an adaptive element to adjust to the changes in the problem environment. The control system also employs a computer simulation of the problem environment. Details of an overall adaptive control system are discussed. A specific laboratory acid-base pH system is used to demonstrate the ideas presented; all results are from the physical laboratory system and not from a computer simulation.
Date: 1995
Creator: Karr, Charles L.; Gentry, E. J. & Stanley, D. A.

Adhesion of Diamond Films on Tungsten

Description: The U.S. Bureau of Mines has investigated the chemical vapor deposition of diamond films on tungsten substrates. The effects of deposition parameters on the adhesion of the films was determined. The films were produced using a hot filament chemical vapor deposition system. Parameters investigated were substrate temperature and methane concentration in the feed gas. Film quality, morphology, and composition were characterized by scanning electron microscopy and Raman spectroscopy. Adhesion testing was performed using an indentation technique, and the results were quantified by relating adhesion to interface fracture toughness. Diamond films with well-faceted crystalline morphology with grain size greater than 1 pm had poor adhesion properties regardless of substrate temperature or methane concentration. Diamond films with smooth morphologies consisting of rounded clusters of small (<0.2 pm) diamond crystallites and amorphous carbon phases displayed much higher adhesion, although the conditions that led to the growth of these films are not understood.
Date: 1995
Creator: Maggs, K. J.; Walkiewicz, J. W. & Clark, A. E.

Application of Field Measurements and Computer Modeling to Evaluate Deep Mine Shaft Stability in Northern Idaho

Description: Abstract: Researchers at the U.S. Bureau of Mines have developed personal-computer-based data acquisition, instrumentation, and mine visualization and modeling techniques to evaluate a mine accessway in a deep hard-rock mine in northern Idaho. These techniques were applied to a mine shaft in a large silver mine that has been in operation for many years. A very deep, rectangular, timber-supported shaft extending to depths exceeding 2.3 km (7,500 ft) had been deforming continuously as a result of nearby mining, resulting in operational problems. Preliminary visual observations and rock and support monitoring confirmed that severe diagonal distortion was occurring. Extensive field measurements and data analysis confirmed initial observations, provided insights into the cause of deformation, and defined a general approach to structural modeling. Computer analysis of the problem was initiated by developing a three-dimensional model of the terrain. This represented a volume of rock approximately 80 km3 (40 x 1010 ft) and an area on the surface surrounding the mine 9 km2 (3 square miles). Based on this model, a three-dimensional, finiteelement analysis was conducted to establish boundary conditions for sequentially more detailed two- and three-dimensional submodels of the shaft area. Results from the computer study are being used to develop new approaches to mine design and to provide design guidelines for deep mine accessways subject to severe rock-mass loading conditions.
Date: 1996
Creator: Beus, Michael J.; Orr, T. J. & Whyatt, J. K.

Bending Fatigue Tests on Flattened Strand Wire Rope at High Working Loads

Description: Abstract: The U.S. Bureau of Mines established a wire rope research laboratory to examine the factors that affect the safety and the useful life of wire rope. In the most recent work, two 32-mm 6x27H flattened strand ropes were degraded on a bending fatigue machine. The two tests were run at constant loads of 285 and 347 kN or safety factors of 2.5 and 2. Nondestructive and tensile strength tests were performed on samples of the ropes to determine the relationship between rope deterioration and rope breaking strength. Neither the area loss nor the number of broken wires measured from nondestructive tests could be used as clear indicators of the loss of strength. However, it was found from the tensile tests for both rope specimens that the strength loss was associated with the reduction of breaking strain. This suggests that measuring the strain of many short sections of a rope in the elastic region may locate the high stress sections and thus determine the condition of the rope.
Date: 1995
Creator: Wang, Richard C. & Shapiro, David E.

Beneficiation of Iron-Copper Ores from Kasaan Peninsula, Prince of Wales Island, Alaska

Description: Report issued by the Bureau of Mines over studies conducted on the beneficiation of iron-copper ores. As stated in the summary, "this report summarizes the results of laboratory testing of copper-bearing magnetite ore from the Poorman, Rush and Brown, and Copper Center deposits, Kasaan Peninsula, Prince of Wales Island, southeastern Alaska" (p. 1). This report includes tables, maps, and illustrations.
Date: February 1957
Creator: Wells, R. R.; Erspamer, E. G. & Sterling, F. T.