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By Thomas O. Glover

Cameroon continued to enjoy sustained economic growth that began with its independence in 1960. Growth in the gross domestic product (GDP) averaged 2.8% per year during the 1960's and the first half of the 1970's. Starting in 1976 and for the succeeding 10 years, the GDP accelerated rapidly owing to the coming on-stream of Cameroon's small but domestically significant offshore oil industry. In 1985, the GDP grew by 7.8%, but in 1986, it was only up 5.5%. The country's sustained economic growth in dollar terms of gross national product (GNP) per capita reached $1,075 in 1986. The ranking in GNP per capita by the International Monetary Fund put Cameroon in the middle-income category for developing countries. The sustained economic growth rate up to 1986 was due to the injection of income from oil into the economy, but crude oil price reductions in 1986 brought a slowdown. In 1986, crude oil production grew to 200,000 barrels per day, an increase of 8.2% from that of 1985. Most of the oil came from the Société Nationale Elf Aquitaine (SNEA) wells in the multifield Rio del Rey complex. Additional output came from the Moudi Field operated by Compagnie Française des Pétroles S.A. Proven oil reserves in Cameroon were 540 million barrels. At 1986 production rates, and in the absence of further discoveries, Cameroon will have exhausted its recoverable oil reserves by the year 1995. Owing to worldwide crude price reductions, the country's oil income fell 60% between 1985 and 1986, from $1.82 billion2 to $0.72 billion. Cameroon's refinery operator commenced operating the Sonara refinery in 1981 at Point Limboh. Sonara's capacity of 43,000 barrels per day was small by most standards. In 1986, natural gas reserves, estimated at 100 billion cubic meters, were not produced commercially because there were no domestic users. Proposals for a multibillion-dollar liquefied natural gas plant at Kribi had been submitted; however, work on the plant had not commenced.

Jan 1, 1988

To provide a faster means to open and close permissible electrical enclosures. Approach: An inspection and repair port with a multiple start thread which provides a permissible joint has been developed and tested. How It Works: The inspection port screw thread has a large pitch, which allows the port cover to be rotated from fully closed 10 fully open, in less than one revolution. See Figure 1. When the cover is screwed back in. it be-gins engagement within one eighth turn because the screw design has eight separate threads. To prevent Its unauthorized opening, the port cover has a bolt guarded by ears which accept a padlock. The threads are designed to tolerate a reasonable amount of grit without binding, although wipe-off cleanness is necessary during reassembly. Enclosures of two different sizes each fitted with the quick-access port, were

Jan 1, 1976

By Harry Dobroski

Communications with moving tracked vehicles in a rail haulage mine pose a difficult problem. These communications take place from dispatcher to vehicles or from vehicle to vehicle via the trolley line, which is a very poor communications line. As a result, deadspots and high-signal areas can occur anywhere along the line, or signal can decrease simply as a function of distance. An analysis is made of the trolley line as a communications line, and methods of improving its characteristics are discussed. Data from inmine experiments are presented, showing actual improvements in communications. Recent Bureau developments in new hardware are also discussed. These include an adaptive speaker control for existing carrier phones and a new generation of improved carrier phones.

The coal reserve base is defined for coalbeds having sufficient thickness for underground mining within a depth range compatible with economic recovery. The reserve data are compiled by the Federal Bureau of Mines by updating and reevaluating previous estimates of the U.S. Geological Survey, State geological surveys, and others. Through the application of computer techniques, the tonnages are compiled by State, county, coalbed, and rank. Coal reserve base is allotted to sulfur categories by a statistical apportionment of data from available Bureau of Mines reports and records. The coal reserve base in those States east of the Mississippi River, minable by underground methods, is estimated to be 169 billion tons in coalbeds greater than 28 inches in thickness to a maximum depth of 1,000 feet. Excluding those coals in reliability categories other than measured and indicated, the underground reserve base includes 162 billion tons of bituminous coal and 7 billion tons of anthracite. Of the total, 27 billion tons contains 1.0 percent or less sulfur. Most of this low-sulfur coal is in the southern Appalachian area. Approximately 16 percent of the underground reserve base is without available analyses. Included in this report is a glossary of terms applicable to a classification system for coal resources and reserves. The purpose of this system is to provide a common yardstick for determining coal resources and reserves.

Jan 1, 1974

Provide long-term measurement of mine sidewall closure in backfilled stapes subject to flooding. Approach A water resistant extensometer is made by enclosing a rod-actuated transducer in a telescoping tube which is enclosed within an oil-filled outer housing. How It Works To assemble a water resistant extensometer, a cylinder -shaped transducer and two support rings are pushed into the small-diameter section of the telescoping tube where the transducer is held in place by friction. The outside of the small-diameter section of the telescoping tube is then greased and slid into the slightly larger-diameter section. See drawing. The cylinder-shaped transducer contains a potentiometer whose actuating arm is attached to a stainless steel extension rod that passes through one end of the telescoping tube. A similar rod is attached to the opposite end of the transducer body, and extends through the other end of the telescoping tube. A coil spring inside the large diameter end of the telescoping tube extends the tube

Jan 1, 1978

By N. C. Dunham

"The Bureau of Mines exploratory work on the Bear Lodge, Wyo., fluorite property wider the strategic minerals Program was completed in November 1944. Exploration consisted of surface trenching, shaft sinking, and drifting at shallow depth. Doak C. Cox of the Federal Geological Survey visited the area during the latter part of 1944 and napped the Bear Lodge property.The Bear Lodge property is situated in the Black Hilts National Forest in eastern Crook County, Wyo., 6 miles north of the community of Sundance (fig. 1). Sundance is 29 miles northwest of Upton, Wyo., a station on the Chicago, Burlington, & Quincy Railroad and 43 miles southwest of a siding on the Chicago & Northwestern Railroad, 3 miles south of Belle Fourche, S. Dak. U. S. Highway 14 passes through Sundance in an east-west direction. Sundance may be reached from the south over U. S. Highway 85 and Wyoming State Highway 585.The Bear Lodge property i a situated in the Boer Lodge Mountains in secs. 15, 22, and 23, T. 52 N., R. 63W., 6th P.M.The topography in the vicinity of the fluorite deposits consists essentially of rounded hills which slope gently to the valley floors. Near the north end of the Property the terrain steepens locally, and the canyon walls are Precipitous along the courses of several streams. There is an adequate supply of water and native timber for mining purposes. The average elevation near the deposits is 5,700 feet.The climate of the region is relatively moderate. The summers are usually warm, with frequent rainstorms. Temperatures often fall below zero during the winter months. Snowfalls are moderate to heavy.Fluorite occurrences in the Bear Lodge area have been known since 1914; however, fluorite was not discovered on the Bear Lodge property until 1943, when prospectors working on a nearby manganese deposit found fluorite mineralization in the limestone. No production has been recorded from the property."

Apr 1, 1946

By P. L. Loyselle, B. D. Comilsen, D. H. Carlson, J. H. Johnson

"In-mine airborne particulate samples have been successfully collected and the relative amounts of diesel and coal determined using the Laser Raman Quantitative Analysis (LRQA) method. This method allows analysis of filters which have been collected by a method similar to that used to determine the airborne respirable dust concentration in us underground coal mines. Samples were taken near the feeder-breaker, on haulage vehicles, and in the returns. Sampling methodologies were developed for coal-only and diesel-only particulate reference samples with sufficient filter loading for the LRQA method. A statistical analysis of reproducibility has been carried out. Samples have been collected simultaneously at two locations using the LRQA and the size-selective sampling methods. Good agreement between the two methods has been found.INTRODUCTIONThe goal of this research has been to develop the Laser Raman Quantitative Analysis (LRQA) method to measure the composition of respirable particulate, i.e. the fractions of coal and of diesel particulate, in the mine ambient air. In earlier Bureau of Mines sponsored research, we successfully demonstrated that the LRQA method could be used to measure the fraction of Diesel Particulate Matter (DPM) in coal/diesel particulate mixtures which were prepared in the laboratory.(I) 'The immediate objective was to test and refine this LRQA method on samples collected in a diesel underground coal mine.Specific objectives required to meet this goal include:I) Develop in-mine sample collection methods which will insure sufficient particulate loading on filters for LRQA. ,2) Develop methodology for in-mine collection of reference samples (""coal-only"" and ""diesel-only"" filters) which arc required for quantitative LRQA. 3) Analyze precision and accuracy of the LRQA method. 4) Compare composition measurements with another analytical method, i.e. the University of Minnesota/Bureau of Mines size selective sampling Micro-Orifice Uniform Deposit Impactor (MOUDI) method.An advantage of the LRQA method is that it allows analysis of filters which have been collected by a method similar to that used to determine the respirable dust concentration in US underground coal mines. No new sampling instruments and techniques are required. Transfer of sample from collection substrate to analysis substrate is not necessary. Furthermore, other analyses can be made on the same sample since the technique is nondestructive."

Jan 1, 1988

By John C. Edwards, Gene F. Friel

A series of liquid fuel fire experiments evaluated the comparative responses of five types of commercially available smoke detectors and a diffusion-mode carbon monoxide (CO) detector under normal and reduced airflow conditions based upon the alarm times of the detectors. These experiments were conducted in the Safety Research Coal Mine at the U.S. Bureau of Mines Pittsburgh Research Center. Two of the smoke detectors had manufacturer set alarms. For the other three smoke detectors, an alarm point was defined in terms of their background analog signal and the detector's electrical output noise under ambient conditions. A correlation was developed of the travel time of 5 ppm CO between pairs of CO detectors with the travel time calculated from entry and crosscut volumes and measured airflow. Based upon the relative performance of smoke detectors in this limited study, smoke detectors can be as effective as CO detectors for mine fire detection once identifiable alarm values are defined. Implementation of smoke detectors as part of an atmospheric mine monitoring system will improve mine safety.

Jan 1, 1996

By Douglas F. Scott

In 1981 the U.S. Bureau of Mines and U.S. Geological Survey conducted a mineral survey of the Pyramid RARE II area (No. 5023) covering 23,500 acres (9,500 ha) of E1 Dorado National Forest and 7,900 acres (3,200 ha) of the Lake Tahoe Basin Management Unit (fig. 1). The Bureau of Mines investigation did not reveal mineral deposits in the area. Samples taken from silicified and limonite-stained metasedimentary rocks and aplite dikes were void of precious or base metals or uranium. Placer samples from stream gravels contained no gold values. Molybdenite occurs in quartz stringers within quartz monzonite near Grass Lake, adjacent to the area; no extension; were found in the area.

Jan 1, 1982

By John R. Benham

In 1979 and 1980, the U.S. Bureau of Mines and U.S. Geological Survey conducted a mineral survey of the 20,500 acre Black Butte RARE II area (No. 5102) in the Los Padres National Forest (fig. 1). The work by the Bureau of Mines indicates that the potential tor mineral resources in the area is low. Samples of outcrops and stream channels contained no economic minerals. A mercury deposit near a granodiorite-sedimentary rock contact occurs 2 mi northeast of the study area, but similar deposits have not been discovered within the area. Geothermal potential exists near Tassajara Hot Springs, but no thermal springs occur in the area; nor have oil, gas, or coal resources been found.

Jan 1, 1982

In 2004, data obtained from the Mine Safety and Health Administration (MSHA) indicated a total of 891 underground (6.2%) and 13,587 surface (93.8%) mining operations.

Sep 1, 2007

By Arthur M. Hartstein

The Bureau of Mines, through contract with Ultrasystems, Inc., obtained data on the oxidative degradative behavior of a number of materials used in coal mines. Tests were performed using a stagnation burner arrangement. Materials examined included those used in typical coal mining operations such as (1) polyvinyl chloride-containing materials. (2) neoprene compositions, (3) rigid foams (urethanes/isocyanates), (4) miscellaneous materials (including jute, fiber glass, and polyethylene), (5) coal, (6) fluids (phosphate esters, organic esters, oil-water emulsions), and (7) composites. The composite comprised a mixture of a phosphate ester fluid with (1) coal, (2) a representative polyvinyl chloride sample, or (3) a neoprene-type composition. A number of decomposition products are identified that could represent a potential health hazard to miners including HC1, CO, SO2 and H2S, if they were generated to exceed toxic levels.

Jan 1, 1974

By Annie G. Smelley

As a part of research conducted in its mission to effect pollution abatement, the Bureau of Mines, U.S. Department of the Interior, is developing a dewatering technique that allows for disposal of clay wastes, for reuse of water now lost with clays, and for reclamation of mined land. The technique utilizes a high-molecular-weight nonionic polyethylene oxide polymer (PEO) that has the ability to flocculate and dewater materials containing clay wastes. In laboratory experiments, coal-clay waste, potash-clay brine slurry, phosphatic clay waste, uranium tailings, and talc tailings were successfully consolidated. Coal-clay was te was consolidated from 3-. 6 to 57 percent; potash-clay brine slurry was consolidated from 3.8 to 35 percent; phosphatic clay waste from 15.6 to 49 percent; uranium tailings from 15.4 to 67 percent; tailings from talc production from 9.7 to 53 percent; and an acidic Ti02 slurr slurry from 1.68 to 30 percent.

Jan 1, 1980

By Barry W. Klein

The U.S. economy was considerably stronger in 1976 than in 1974 or 1975. Real gross national product (GNP) rose sharply in the first quarter of 1976 and then increased at a more moderate rate for the remainder of the year. The unemployment rate fell until June and then increased for moat of the remainder of the year, finishing at the same rate as it had started the year. The inflation rate continued to decline in 1976. Reasons for the relatively low rate (compared with those of 1974 and 1975) included small increases in food prices and only moderate increases in energy prices. Total U.S. output measured in terms of GNP increased 11.6% in 1976. Real GNP in 1972 constant dollars rose 6.2%. Inflation as measured by the implicit price deflator increased 5.1%. In real terms, gross private domestic investment for residential structures rose 22.7% in 1976 after declining 14.7%a in 1975; State and local Government expenditures increased 1.4% in 1976; and personal consumption expenditures for services rose 4.5%. The Federal Reserve Board (FRB) index of industrial production increased 10.2%.

Jan 1, 1978

By C. F. McCarroll

[Laboratory research and, control in the u?odnction an; utilization of petroleum and its product s have eqLmde& greatly during the past decade, rind much of the routine control and experimental equipment noirr requires the con-stant daily use of liquid nercury. In spite of this greater use, very little consideration has becn given to the hazard that might be occasioned by the toxic vapors of mercury unavoicl.a~l.p spilled or otherwise exposed to the atmosphere during the normcl 2rgced1u.e of ln30r~tor;~r operations. A sfmple visual exami~stion gf' sone of the laborztories reveals the prescnce of a considerable quantity of mercury in the craclcs of floors, on work tebles, ad on and mo7md eql~ipmeilt st.ads. Usually this yercurj ie contaminated with oily and dirt BO th~t it remint; in R finely divided state and a srnarl amount presents a relativell- lag? surface for evaporation. Since mercury shows meas~rable vo!-atility st a tempero.turc as lor^ 2s 8.5O F., mercury vapor will bo present in the atnosphere of anjr laboratory wbr.e mercury is exposed. promiscuously]

Jan 1, 1939

By Sean Gallagher

Background. There is currently little information regarding factors associated with specific modes of motion segment failure using a fatigue failure model. Methods. Thirty-six human lumbar motion segments were fatigue tested using spinal compressive and shear loads that simulated lifting a 9 kg weight in three torso flexion angles (0°, 22.5°, and 45°). Twenty-five segments failed via fatigue prior to the 10,000 cycle maximum. These specimens were visually inspected and dissected so that the mode(s) of failure could be determined. Failure modes included endplate fractures (classified into nine varieties), vertebral body fractures, and/or zygapophysial joint disruption. Logistic regression analyses were performed to determine whether certain morphometric variables, amount of motion segment flexion, disk degeneration scores, and/or loading characteristics were associated with the occurrence of specific failure modes. Findings. Results indicated that stellate endplate fractures were associated with increased posterior shear forces (P < 0.05) and less degenerated discs (P < 0.01). Fractures running laterally across the endplate were associated with motion segments having larger volumes (P < 0.01). Endplate depression was more common in smaller specimens (P < 0.01), as well as those experiencing increased posterior shear force (P < 0.05). Zygapophysial joint damage was more likely to occur in a neutral posture (P < 0.01). Interpretation. These results suggest that prediction of failure modes (e.g., specific endplate fracture patterns) may be possible (at least for older specimens) given knowledge of the spinal loads along with certain characteristics of the lumbar spine. Published by Elsevier Ltd. Keywords: Lumbar spine; Endplate fractures; Zygapophysial joints; Morphometry; Disk degeneration; Motion segments; Aging

Jan 1, 2006

By H. R. Shell, Robert C. Johnson, Wilbur H. Warwick

Alpha silicon nitride fibers , Si3N4 , were successfully grown in graphite crucibles by a new method utilizing silicates and silicon ( S in equations below) as sources of silicon and using carbon , aluminum , and silicon as reducing agents (R in equations below ) . The basic reaction mechanism is believed to be generally as follows : 1,300 - 1,500 ° C S + R + N₂ SiO + RO + N₂ › 3Si0 + R + 2N₂ _1,300 - 1,500° C 3RO + Si¸N • ( 1 ) ( 2 ) A build - up of coatings on the solid raw- material particles hindered the evolution of silicon or silicon monoxide vapor and thereby slowed down further formation of silicon nitride fibers . Free oxygen in the crucible caused the formation of amorphous silicon dioxide ( SiO2 ) fibers . This problem was solved by passing , entering , and exiting gases through layers of lump graphite inside the reaction vessel . The silicon nitride fibers grew best around 1,400 ° C. Nitrogen flow rates from 4 to 6 liters per minute were adequate . The fiber widths were generally only a few microns whereas their lengths sometimes reached one - quarter inch or more . Chemical and X- ray analyses indicated that bulk fiber samples were usually 80 to 90 percent Si3N4 . The fibers had good oxidation resistance to about 1,260 ° C. Thermal shock resistance was excellent . Electrical resistance was determined .

Jan 1, 1964

By Tom Tallone

In the majority of metal and nonmetal mining operations, narrow vein deposits are being mined with slusher hoists. Thin; method of mucking is costly, due in part to its inherent labor intense operation and to its inability to muck 100 pct of the deposits. Mechanized equipment would greatly improve the material handling in narrow vein mining and would dramatically reduce the operational cost. The Compact Loader/Trammer, known as the "mini-mucker" has been developed to increase productivity of the load/haul/dump portion of the typical narrow vein mining cycle. This is Volume II of the final report and concerns the operation and maintenance of the mini-mucker. Volume I covers a general and design review of the activities on the subject contract and are available under separate cover.

Jan 1, 1985

By Anthony T. Xannacchione, Luis E. Vallejo

At present, there is little knowledge concerning the shear strength of clays containing floating rock particles with concentrations from 0 to 30%. In practice, the effect of rock particles is typically disregarded in shear strength analysis The two primary reasons for this are: 1) a lack of agreement concerning the influence of rock particles on material strength, and 2) the expense and difficulty of testing day-rack mixtures with existing laboratory procedures. These factors have impeded the development of successful slope remediation design techniques far colluviums derived from resistant sedimentary rocks or spoil produced from surface mining. This study reviewed 3 1 technical papers which contain analysis of shear strengths for clay and sands with varying mixtures of rock particles. These technical papers, published over the last 40 years, are comprised of field case studies, laboratory evaluations, and theoretical analysis. Evaluation of this body of knowledge ha shown that the shear strength gradually increases with increasing percentages of floating particles in unsaturated clays.

By Arthur J. Hudson, Lawrence W. Scott

The performance of RETIMET metal foam as a flame arrester on explosion-proof enclosures was investigated by the U.S. Bureau of Mines both in laboratory tests and at the U.S. Mine Safety and Health Administration&apos;s (MSHA&apos;s) Approval and Certification Center, Triadelphia, WV. The objective of this research was to develop a permissible pressure vent for use on lightweight, vented, explosion- proof enclosures. In laboratory tests, four grades of RETIMET, a stainless steel foam material, were evaluated: (1) 45 NC-7, (2) 45 NC-13, (3) 80 NC-7, and (4) 80 NC-13. Explosive gas mixtures were prepared by a dynamic flow system. Ignition was by a low-voltage arc. Each grade of RETIMET metal foam successfully arrested the flame front in all methane-air tests. To evaluate RETIMET metal foam on large, commercial size enclosures, a multicompartmented enclosure was designed and tested in MSHA&apos;s explosion gallery in Triadelphia, WV. Extensive explosion testing revealed that a minimum vent-area-to-enclosure-volume ratio of 11.33 in2/ft3 is required to keep internal pressure rises below 3 psig. The RETIMET metal foam functioned satisfactorily in all tests as evidenced by the absence of external ignitions.

Jan 1, 1992