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By Ralf Vergeiner

The most famous landmark of the city of Graz (Austria) is the clock tower on the castle hill. An underground chamber was built as a multifunctional structure beneath this landmark. The required structure was designed as cavern. The overburden to the clock tower in the north side of the cavern was only 30 m. To allow access from the city to the chamber and the clock tower, a vertical shaft was built near the cavern. Rock excavation was by drill and blast method. The pilot shaft was made by the raise-boring method. Because the location of the building site was in the center of Graz, special care was taken to minimize deformations and vibrations so as to protect surrounding buildings.

Jan 1, 2001

By V. T. Vacariu, P. D. Georgescu, N. Tomus

To assess the potential for radioactive pollution unique to the environmental conditions of the Bacau phosphogypsum waste dump, surface samples were taken, drillings were performed on the entire waste dump's height, and the Ra226 distribution on the height and surface considered to contain a medium content of the radium of 0.57 Bq/gr was studied. Thus, the waste dump's radioactive potential was estimated at 30-40 Ci in equivalent Ra226. Also analyzed was the granulometric composition of the phosphogypsum and the distribution of Ra226 on granulometric orders, which indicated that the radium was concentrated in the very fine fractions. Parameters were set up for the classification by hydrocycloning to obtain a fine class (less than 41 microns) having a radium content of more than 0.9 Bq/gr and a coarse class having less than 0.37 Bq/gr. A chemical process was devised for removal of the radium from the phosphogypsum with the possibility for recovering the contained sulfur.

Jan 1, 1999

By Ronald J. Thomas

Prior to 1974, bauxite-producing countries were poorly informed about important aspects of the bauxite/alumina/aluminium industry. This placed them at a disadvantage in negotiations over the development of the industry with interested parties. Since the formation of IBA, its member governments have acquired a fuller awareness of the structure and operation of the industry. The role of IBA is to enlarge the relevant information base of member governments, to act as a forum for the exchange of information on the industry and to form a focal point for multilateral discussions on problems in the industry with corporate interests and with governments of consuming countries.

Jan 1, 1984

By Bernard J. Reddy

This paper describes in detail the economic forces affecting cobalt supply, demand, and prices. The major factors that will determine the growth or decline in the use of cobalt in each of its applications are discussed. The flows of cobalt from mine to refinery are described on a company-by-company basis. The paper concludes with a discussion of how the characteristics of the supply and demand sides of market interact to determine cobalt prices.

Jan 1, 1986

By G. A. Campbell

Mining companies have been very interested in the presence of a number of small but high-grade ore bodies of base metals in northern Wisconsin and the west/central section of the Upper Peninsula (UP) of Michigan. The region is rural with outdoor recreation/tourism and lumbering being the key industries. The economy of the region is based on the use of its natural resources, and mining is not a new activity to the region, especially the UP. The western UP was historically a key mining district for copper and iron, and today the central UP has a significant iron-mining district. However, all efforts to develop the base metal ore bodies have been met with a storm of controversy involving the local community, regional activists, Native Americans, and the state government, and only one mine has gone into operation. There is concern by some stakeholders about the sustainability of mining in communities that depend on the environment for tourism, recreation, and other commercial activities. There have been four attempts to get the necessary approvals to mine in this region: the successful Flambeau Mine effort (Wisconsin), the failed Crandon project (Wisconsin) and Lynne project (Wisconsin) efforts, and the continuing effort to get the Eagle Project (UP of Michigan) approved. The cases are presented to illustrate the project situation, the history of the permitting effort, and the opposing parties and their concerns. The case of the Eagle Project is looked at in detail by using the method of discourse communities and discourse analysis. Results of the analysis provide insight into the communication efforts to address community concerns about sustainability and what more can be done to improve this dialogue.

Jan 1, 2008

By J. W. Leonard

Since the interpolation of exploratory data 1 can be no better than sampling procedures, a series of field experiments were conducted in an effort to determine whether hand-cut channel or core washability determinations best represent continuous miner produced run of mine coal. By obtaining a core drilled to within a few feet of channels taken from an underground face and then overmining both locations; core, channels and run-of-mine coal allocations were obtained from a common sample and all allocations were subjected to identical washability determinations. In order to compare results, basic rules2,3 previously anticipated and later published by the writer were employed. The first rule states that "For any full seam washability determination, the sulfur versus ash function for increasing cumulative specific gravity float coal fractions is linear". The second rule states that "For any full seam washability determination, the recovery versus ash function for increasing cumulative specific gravity float coal fractions is logarithmic".

Jan 1, 1988

By Theodore M. Gurr, James J. Bartels

Phosphate produced fertilizers provide the phosphorous nutrients required by plant life to sustain significant growth, thus improving the production of food for the world's population. Phosphorous replenishment of soil currently can be obtained efficiently by no other means than by direct application of phosphate fertilizer to the soil. Phosphate products are also utilized in animal feeds, detergent, and various industrial processes. Thirty-three countries are presently mining phosphate rock for the production of fertilizers, and its process byproducts. The major phosphate rock producers are the United States, the former Soviet Union, Morocco, and China [(Table 1)]. Phosphate rock is generally defined as a rock material that contains phosphate minerals which are sufficient for commercial usage. Phosphate minerals are found in sedimentary igneous and metamorphic rocks. Economic resources of phosphates are primarily developed from sedimentary rock sources. The apatite mineral family comprises the majority of phosphate constituents from both sedimentary and igneous rocks. Igneous phosphate rocks are generally composed of fluroapatite whereas sedimentary rocks are generally composed of carbonate fluroapatite, or chlorapatite. Phosphate rock is mined by a multitude of processes, including surface and underground mining. The mined rock requires mechanical and chemical processing to liberate the phosphate for utilization as fertilizer. Approximately 85% of the world's phosphate production uses sulfuric acid, with the remaining processes utilizing nitric and phosphoric acids. Ammonia is also introduced in the manufacture of liquid fertilizer, ammonium phosphate and ammonium polyphosphate. GEOLOGY Mineralogy and Chemical Properties Phosphate most commonly is derived from the mineral apatite, which is chemically described as CA5(F,Cl,OH)(PO4)3. Apatite is also broken up into the composite apatite minerals which are fluroapatite Ca5F(PO4)3, chlorapatite Ca5Cl (PO4)3 and hydroxyl-apatite Ca5(OH)(PO4)3. Carbonate CO3 can substitute for PO, forming carbonate apatite, called francolite. The guano phosphate (bird excrement) mineralogy commonly occurs as brushite CaHP04.2H20, monetite CaHPO4, whitlockite Ca3(PO4), and dahlite Ca10(PO4)6(OH)2. Apatite minerals form from igneous sources where they are developed deep in the earth's crust; and the cooling processes are slow, producing long, hexagonal prismatic to tabular crystals. The termination of the crystal can be basal plans or pyramids. In some instances, the crystals are bipyramids. Faster cooling, or sedimentary derived apatites are more commonly cryptocrystalline. Collophane is a name given to cryptocrystalline apatite found in phosphate rock in fossil form. Apatite minerals are relatively soft and are used to describe the 5 hardness on the Mohs scale. Cleavage is poor and develops along the C(0001). The color of apatite minerals varies from colorless, to violet, and blue, but are predominantly green or brown; luster is vitreous to subresinous. Collophane's physical appearance is often opaline, dense, with colloform structure and sometimes concretionary, nodular or pulverulent. Phosphate Bearing Materials Origins Phosphate deposits of igneous and metamorphic origins have been well defined. Sedimentary origins have been defined, but with a greater degree of uncertainty. Research in the 1980s proved out some of these processes through studies of real time deposition in Chile, Peru, and Australia. Igneous intrusive alkali rock and associated contact metamorphic rocks, provide approximately 20% of the world's phosphate. Fluorine containing apatite minerals are the most common materials containing phosphorous. Fluorapatite occurs in most igneous rocks. Fluorapatite and fluorine hydroxylapatite, together with carbonate varieties of these, are important members of the group. Where an essentially pure chlorapatite, carbonate apatite, and hydroxylapatite are rare and restricted in occurrence, the fluorine containing types occur in most all igneous rocks as early formed accessory mineral, usually in microscopic crystals, and may occur as extremely large bodies as magmatic segregations from alkalic igneous rocks. Apatite is also found crystallized in pegmatitic faces of both acidic and basic types of igneous rocks. More specifically, apatite is associated with magnetite deposits, in hydrothermal veins, especially those formed at relatively high temperatures, and in veins of the Alpine type. Apatite is common in both regionally and contact metamorphosed rocks, especially in the crystalline limestones where it is associated with sphene, zircon, pyroxine amphibole, spinel vesuvianite, phlogopite, talc, chloride schists, and as a contact metamorphic mineral.

Jan 1, 1994

By Francis S. Kendorski

INTRODUCTION Caving offers the lowest cost per ton of any large-scale mining method, but its successful application demands an ore body that conforms to several rigid requirements. The deposit must be of wide areal extent, massive and not spotty in ore values, and insensitive to ore dilution. It must also be a rock mass that breaks up readily. There are only three active caving operations in the US-Climax, Henderson, and San Manuel-but caving methods have recently taken on new importance as deeper lower grade mineral occurrences and ore bodies are found. These deposits are too deep for surface min¬ing methods, and too low grade to support any type of underground mining except a bulk method such as caving. Announced discoveries or indications that may be amenable to caving include: Climax's Mt. Emmons molybdenum discovery in Colorado; Molycorp's Goat Hill molybdenum prospect in New Mexico; the Phelps Dodge molybdenum deposit in Beaver County, UT; Arizona copper occurrences such as Asarco's Sacaton, Hanna's Casa Grande, Noranda's Lakeshore, and Ken¬necott's Safford; Anaconda's suspected deep copper de¬posit in Butte, MT; Anaconda's Carr Fork, UT, deposit; and perhaps others. CAVABILITY'S ROLE IN FEASIBILITY STUDIES Caving is a system of underground mining which removes support from underneath an ore body. As a result, the rock mass fractures, fails, and flows vertically downward by gravity to be collected in previously ex¬cavated funnels. Types of ore that have been mined by caving include molybdenum, copper, iron, nickel, as¬bestos, and diamonds (Julin and Tobie, 1973). It is primarily a large-scale method, with production rates of more than 45 300 t/d (50,000 stpd) having been achieved. However, the initial capital investment before return is very high, often in the hundreds of millions of dollars. The cavability of an ore body or mineral occurrence is a critical item in the feasibility study of a proposed mine, not only from the point of overall minability, but from the point of impact on other costs such as blasting, loading, hauling, crushing, and grade recovered. Aside from the often-asked question of, "Will it or will it not cave?" the real questions are, "Can we afford to make it cave, carry the rock away, and extract the mineral?" The last is not a topic of this chapter, but the first two are. The cavability of an ore deposit or mineral occur¬rence is based on many things, but clearly, if a large enough area is undermined, any rock mass will cave. The result could be a violent collapse as occurred at Urad, CO (Kendrick, 1970), or perhaps the rock mass will cave beyond the ore boundary. Another unfavor¬able result could be ore blocks that are too large for the equipment and orepasses to handle without considerable secondary blasting. Weak rock with numerous fractures may produce a very fine ore when it caves, resulting in dilution and ground control problems. DETERMINING STRUCTURAL DOMAINS It has long been recognized that the geologic nature of an ore body is important to cavability (King, 1946). Such items as weak rock material, intensity of fractur¬ing, and severity of faulting all contribute to the success of a caving operation, and information regarding these is required as a minimum for the cavability determination. In practice, the rock mass-defined as the blocks of intact rock together with the intervening fractures, joints, faults, bedding planes, and other discontinuities-that contains the ore body, as well as the surrounding and overlying rock, must be examined in a systematic and detailed fashion. Surficial geology maps must be pre¬pared, exploration holes drilled, and core logged for en¬gineering information. The fracturing of the rock mass must be studied to ascertain the three-dimensional dis¬tribution of fractures and their characteristics, and faults must be located and described. The strength and other mechanical properties of the rock material, the fracture surfaces, and the fault filling materials must be tested and reported for later use by designers and planners. With this basic information and an understanding of the geologic setting, the rock mass can be divided into one or more structural domains which tend to behave similarly in response to engineering activities (Robertson and Piteau, 1970). One must keep in mind that the determination of the structural domains goes beyond the geologic units present. Several lithologic units may be lumped together, while a single lithologic unit can be divided into multiple domains. Major faults often form their own domain, and the direction of engineering ac¬tivity-for example, cave advance to the north rather than the south-may alter rock mass behavior, resulting in different domains. As an example of the detailed rock fracture map¬ping required for such studies, the structural domain determinations at the Climax mine (Kendorski, 1973) are shown in Fig. 1. The circles are Schmidt equal area projections of the three-dimensional attitudes of frac¬tures (Ramsay, 1967) mapped in detail at various rock exposures. The attitude of fractures is important to the cavability determination since it dictates the directional behavior of the rock mass as it fails, and determines the effectiveness of arching, keying, and rock block inter¬locking. Low-angle fractures must be present to allow movement of the rock in the vertical direction during undermining (Mahtab and Dixon, 1976); if low-angle planes of weakness are absent, the rock mass may arch with a keystone effect, rather than moving vertically downward.

Jan 1, 1982

By D. A. Norrgran, J. A. Marin

Introduction The recent development of rare earth permanent magnets has revolutionized the field of magnetic separation. The advent of rare earth permanent magnets in the 1980s provided a magnetic product that was an order of magnitude stronger than that conventional ferrite magnets. This allowed for the design of high-intensity magnetic circuits that operated energy free and that surpassed electromagnets in the strength and effectiveness. New applications and design concepts that focused on the mineral and metal processing industries have evolved. This technology led to the development of various magnetic separators specifically designed for mineral processing applications. Applications that were not previously considered are now being used in primary mineral upgrading, recycling and secondary recovery. Historical perspective Lodestone was the first naturally occurring permanent magnetic material known. Lodstone was most likely used to upgrade iron ore by early civilizations. By the 1600s, the early magnet technology had advanced to quench-hardened iron-carbon alloys. The practical significance of magnetic separation was formally recognized in 1792 when an English patent was issued for separating iron ore by magnetic attraction. By today's standards, carbon steel is a very poor magnet material. It is easily demagnetized and has a very low energy product of much less than I MGOe (Million-Gauss-Oerstads). This was state-of-the-art technology for almost 300 years until chromium was added to magnet feedstock, which resulted in a three-fold increase in the energy product. The well documented addition of cobalt to permanent magnets in 1917 initiated the 30-year era of "Alnico" magnets that at the time provided a superior magnetic energy product. Since then, the science of magnetism has advanced rapidly and is now considered a highly developed branch of physics and material science. Permanent magnets have had an extremely long history. Figure 1 presents a chronology of permanent magnets that illustrates the increase in energy product. Amazing developments in material science have taken place in the last two decades. The gradual advancement of permanent magnet technology was shattered in 1967 with the initial development of samarium-cobalt (rare earth) magnets. Since that time, the advent of neodymium-boron-iron magnets provided such an increase in energy product that new design concepts were considered. New avenues of study were introduced by the complexities in the material science and physics involved in describing these new permanent magnets. Furthermore, applications for permanent magnets that were previously not considered were now viable. Rare earth elements Rare earth elements have claimed the attention of scientists for the past century. These elements were originally termed "rare" because they were thought to be quite scarce. Since then, however, geological studies have shown them to be relatively abundant. The discovery and identification of rare earth elements is complicated by the inherent difficulties in separating them from each other. The rare earth elements comprise the fifteen transition elements of Group IIIB, Period 6, of the periodic table. These elements extend from lanthanum to lutetium and are commonly called the lanthanide series. Samarium and neodymium are the two most common elements used in the commercial manufacture of rare earth permanent magnets. Commercial grade rare earth magnets There are only a few common types of rare earth magnets that are considered in the circuit design for magnetic separators. Early rare earth magnets of commercial significance (introduced in 1970) consisted of the first generation of sintered SmCo5. The energy product of these magnets ranged up to 23 MGOe, which provided the initial impetus to the field of high-energy permanent magnets. Although these magnets did not produce the extremely high magnetic field strengths of current rare earth magnets, they were relatively temperature stable. Containing 66% Co, they are the most expensive of the basic commercial rare earth permanent magnets. Their use is limited today because they are being replaced by second and third generation rare earth permanent magnets.

Jan 1, 1995

By P. Tsakiris

The increasing social interest for the environmental issues, forces the authorities to enact more rigorous regulations. The mining industry is one of the sectors that concentrate vigorous remonstrance. It is an absolutely justified reaction, as a result of the numerous contaminated and polluted sites that have been inherited by previous operations and they remain unremedied. The lack of a consolidated global legislation, transfers the burden of decisions to the national level. This paper consists of two parts. At the first part, it discusses the critical role of the state to form an effective environmental policy, feasible for the context of the national economy. Afterwards it analyses two of the main points, which must be considered by the regulator for the excavation activity, the abandoned sites and the duration of the mining investment. The aims are to defuse, in the short-term, the public pressure, protecting the economic growth and, at the same time, to form a basic structure for the development of the corporate social responsibility. The second part presents an alternative financial instrument for the Greek regulatory framework, conformed to the characteristics of the Greek Economy, and analyses the expected benefits both for the business and the social welfare.

Jan 1, 2002

By E. A. Metz

Silicon dioxide, silica, is the most common oxide in the earth' s crust. The health effects of silicon dioxide dust have been known since Biblical times. Agricola's book, published in the mid 1500's on occupational medicine, described a lung disease that afflicted miners. He observed a disease in miners that caused shortness of breath, coughing and wasting. Add fever, chest pains and fatigue and we have the current symptom complex of silicosis. As we approached the 21stcentury, the Labor Department began an aggressive campaign to combat silicosis-a preventable disease. Unfortunately, many publications do not clearly differentiate the polymorphs of silica known to mineralogists. Crystalline silica, i.e., alpha quartz, tridymite and cristobalite need to be considered differently from the amorphous forms of silica. Freshly fractured surfaces of the silica and host specific responses will be examined. Recent research focuses on the biologic interactions of free radicals generated by mineral particles. This results in cell injury and DNA damage, in turn leading to fibrogenesis and possibly carcinogenesis. In addition to particle-cell interactions, emphasis is given to lung defense mechanisms.

Jan 1, 1998

By Earl Cook

Introduction Men like physical power because it gives control over nature and over other men. Physical power comes in two common forms: explosive and non-explosive. In both forms, the most powerful devices yet invented make use of nuclear energy: on the one hand, the hydrogen or fusion bomb, and, on the other hand, a nuclear power plant. For some nations, nuclear power offers a measure of independence not otherwise available in a time of diminishing and unevenly allocated fossil fuels. Consequently, it has great attraction. Unfortunately, the application of nuclear energy (especially fission energy) to either explosive or electrical power entails a singular risk, that of injury from ionizing radiation, both natural and induced; this risk is found in all stages of the nuclear-fuel cycle, from mining of fissionable materials to the disposal of wastes produced in the "burning" of nuclear fuels. The health costs of nuclear power were not fully assessed in the early stages of the development of nuclear technology and some of them were not properly guarded against, either in the USA, which led the world into the nuclear age, or in Canada, which followed an independent path. What I shall do in this paper is to sketch the history of nuclear regulation in our two countries, to point out what I consider similarities and differences, and to suggest that regulatory history, as perceived by a concerned public, has a great deal to do with what is possible today and probable tomorrow, in other words, with public acceptance or rejection of the nuclear option. The U.S. situation As we sow, so shall we reap. In the USA, further expansion of the nuclearpower industry has been almost stymied by government actions that reflect mounting public concern. There is no national storage facility for spent reactor fuel and it has been decided not to reprocess it; consequently, existing power plants are about to choke on their own wastes. Since the Three Mile Island accident, no new nuclear plants have received operating licenses, although several are ready to start up. The uncertainty of future government action has caused the abandonment of plans for a number of new nuclear plants. In addition, many research projects related to medicine and agriculture, which produce low-level radioactive wastes, are about to be shut down for lack of licensed disposal facilities. Some would maintain that this situation has come about because of the low benefit-to-cost

Jan 1, 1980

By S. J. Cohen

Changes in our energy, national security, and commerce needs have necessitated identification of new sources of minerals, such as rare earths, lithium, copper, silver, aluminum, titanium, and the minerals on the U.S. Geological Survey’s (USGS) list of critical minerals (USGS, 2022). With the need to domestically produce these minerals, more mining will be required within the U.S. Some of these critical minerals deposit with naturally occurring radioactive materials (NORM), therefore, mining these minerals may concentrate NORM to the point that some states may require licensing and radiation protection programs. NORM is not regulated by the Federal government; it is regulated by the individual states. Consequently, overall national state of NORM regulation is chaotic with each individual state either choosing to regulate or not regulate NORM, and, if a state chooses to regulate NORM, then that state develops its own unique regulations. Further complicating the regulatory environment, states utilize a wide variety of strategies for regulating NORM, which sometimes results in inappropriate regulations, inconsistencies with specific radionuclides that are regulated, and inconsistencies with specific NORM types that are regulated. This paper will review the nature of NORM regulations, identify regulatory traps, and provide general guidance for identifying NORM and potentially avoiding regulatory jeopardy. Because of the chaotic nature of NORM regulations nationally, seeking guidance from qualified professionals with relevant expertise is recommended. Also, contacting the appropriate regulatory agency to gain a complete understanding of the NORM regulatory environment is useful for maintaining compliance.

Feb 1, 2023

By George G. Reed

Approximately 200 samples of iron ores and other iron- bearing materials have been tested for amenability to treatment by the R-N process in bench scale laboratory work. Twelve large lots, ranging in size from 900 net tons to 18,500 net tons, but generally 3,000 to 4,000 tons each, have been processed in the R-N demonstration plant. The ores tested in the demonstration plant ranged from 27 to 70 percent iron content and gave excellent results. (1) The demonstration plant has a nominal daily capacity of 50 tons of high quality iron briquettes and has now operated for over five years. A continuing program of process improvement is carried on between demonstration on potential licenses ores. An important development is the complete elimination of any secondary products which, in the past (2,3,4,5), resulted from treatment of certain low-grade ores.

Jan 1, 1960

By Robert N. Pratt

The rapid acceleration and sweeping consequences of what we have all come to characterize as "the ecology movement" has marked a period of serious trial and challenge for the mining industry. It has blossomed into a major factor in our daily business and added a significant new dimension to the problems we must meet and overcome as businessmen. It has become an important new consideration at a time when we must continue to cope with our traditional problems such as rising costs, competition at home and abroad, and the always vital necessity to continually develop new and better technology to produce more minerals more efficiently and more economically. The body of law embracing environmental quality control grows each day, becomes more complex and offers more contradictions. And there is little relief in sight. The requirement to comply with sound environmental regulations -- or challenge unrealistic legislation -- has placed a major burden on the private sector. The economic significance of enacted and proposed environmental regulation is pressing management in the mining industry to some hard decisions -- basic day-to-day business decisions and decisions which acknowledge the undoubted long-term effects of the new laws.

Jan 1, 1973

By J. E. Oberholtzer, M. G. Fernald

INTRODUCTION Approximately six years ago the U.S. Bureau of Mines (USBM) developed a data acquisition system (DAS) specifically designed for measuring radon levels and other environmental parameters during studies of means to control radiation hazards in underground uranium mines. The DAS system records data in machine readable form using a paper tape punch, which represented the state-of-the-art at that time for a moderate cost output device. However, the use of paper tape as a recording medium for field studies is somewhat unwieldy. Reducing the raw data required either that the tape be shipped to a computer center equipped with a high-speed paper tape reader or that the tape be transmitted at low speed over the telephone lines to a remote computer. Transmitting, at ten characters per second, the data from a 10-channel DAS taking Four readings per hour would require about 30 minutes For each 24-hour day's data. Telephone lines from remote mine sites are often of marginal quality and data errors can be introduced during transmission. Paper tape punches are also prone to occasional punching errors. Both problems make it necessary to carefully check for and correct data errors, a process which is possible because each DAS produces an independent printed data record, but the error checking and correction process can be quite laborious. Aware of recent advances in microcomputer technology which have brought the price of a personal computer down to about the cost of a paper tape punch 5-10 years ago, the Bureau decided to explore the feasibility of using a low-cost personal computer in the field to process DAS data in real time. On behalf of the Bureau, Arthur D. Little, Inc., developed a simple interface circuit which permits an Apple II computer to accept data from one or two DAS units as it is being transmitted to the paper tape punches. Computer software converts each measurement to appropriate engineering units, e.g., radon concentration, Working Levels, air velocity, temperature, or barometric pressure. The computer also calculates 1-hour and 8-hour running averages of all converted data and prints those results as soon as they are obtained on a line printer located at the test site for immediate inspection. After development, the system was used continuously and successfully for a 5-month period at a Utah uranium mine. DAS DESIGN AND MODIFICATION Each of the two USBM data acquisition systems used in this work consists of two separate modules. A multiplexer module located below ground near the measurement transducers acquires signals from each of nine tranducers. Six input channels were devoted to measurements of radon or Working Level. The outputs of those transducers, photomultiplier tubes or G-M tubes, respectively, are digital pulse trains which are accepted directly by the mutliplexer. Three channels were used for environmental parameters--air velocity, temperature, and/or barometric pressure. Each of the environmental tranducers is fitted with dedicated linearizing and voltage-to-frequency conversion circuitry so that the outputs to the multiplexer are also pulse trains having frequencies of one tenth of the value of the measured parameter expressed in the appropriate engineering units. A 100-Hz reference signal was input into the tenth channel for use in monitoring system integrity and performance. All ten pulse trains are then timeseries multiplexed into a signal line for transmission to the above-ground data acquisition module. Above ground, the composite signal is de-multiplexed into ten separate lines, each of which is connected to a digital counter which converts the pulse train to a numerical value. The acquisition of each set of readings is initiated by an adjustable "scan cycle comparator" timer. The acquisition process proceeds in three phases. First, radon and Working Level channels are counted for an extended period of time, typically 5-10 minutes depending on activity, because of the low pulse rates involved. Then the other four channels are counted for ten seconds, and finally, all ten readings, along with the Julian day and time of day are output serially onto paper tape and printed on a strip printer. When the scan cycle comparator reaches its preset time (15-minute cycle times were used in this work), it resets itself, initiates another readout cycle, and begins timing again. The only modification made to the data acquisition systems used in this work was to disconnect the scan cycle comparator in one unit, which became the "slave" and bring in the scan cycle comparator signal from the other unit, the "master", to initiate data acquisition cycles in the slave. Synchronizing the two data acquisitions in this fashion and using two slightly different radon counting times insured that the two systems never attempted to output data to the Apple II at the same time. THE APPLE II COMPUTER The Apple II computer used in this work was equipped with 48 KBytes of semiconductor random access memory (RAM), two floppy diskette drives, a Centronics Model 730 impact matrix printer and a modulator for driving an ordinary color television as a video display device. A single California Computer Systems Model 7720A dual 8-bit bidirectional parallel input/output (I/O) card was installed in the Apple to accept the digital data from both data acquisition systems. This card is

Jan 1, 1981

By Jaroslav Vicek, Alois Adamus

In the Czech Republic nitrogen was first used for the fight against the mine fire in 1949 (Hajek,1969). In the years 1949¬1996 the consumption of nitrogen in the Ostrava-Karvina Coal Basin /OKB/ reached more than 220 mil. m-3. The main source of nitrogen in the OKB is a central pipeline now. Gas nitrogen is used for the prevention of spontaneous combustion in gobs of longwall faces. The nitrogen infusion technology (Froger,1985), often called "franca technology", has been applied in the Czech coal mines since 1982. The aspects of the nitrogen infusion technol¬ogy can be theoretically solved by the calculation of mixing two gas streams in the filtration space. Longwall faces are parts of the ventilation network of the coal mine. The intake airflow of the longwall face is divided into the airflow passing through the face and a part of air losses passing through the gob. Air leakages through the gob and nitrogen in¬jected into the gob mix there. There is the main problem to solve air leakages in the gob. Usually, the principles of the gob aerody¬namics were used by many authors (Glusberg,1988;Voracek, 1994; Sulkowski,1993; Michailov, 1995; Dziurzynski, 1995; Kolarczyk, 1995; Saghafi, 1995; Sedlaty, 1993) that are applied to our case as well.

Jan 1, 1997

By William G. Holroyd

In January 1992, the Office of the US Trade Representative announced that the People's Republic of China had agreed to protect US intellectual property, including computer software, sound recordings, agrichemicals and pharmaceuticals. Under the agreement, China will make significant improvements in its patent, copyright and trade-secret laws. Ambassador Carla A. Hills, the US trade representative, said "this agreement should create significant opportunities for US firms interested in marketing high valued-added products to China." Principal beneficiaries will include the agrichemical and computer industries, as well as pharmaceutical, entertainment. The agreement will safeguard these industries' intellectual property, stimulating new exports to China and helping to generate additional growth in the US. Refractory grade bauxite was included in the mineral category of the $1.5 billion of Chinese products on which the US government threatened to impose an immediate 100% trade tariff. Refractory bauxite is available from Guyana and Brazil at higher cost and in different grades. However, refractory brick manufacturers would have had little choice but to pass on the costs to their consumers. Although the United States and China are separated by political ideology and internal governing structures, this agreement recognizes the importance of a $19 billion trading relationship. Consequently, the renewal of China's most favored-nation trading status in the US congress in -June 1992 was all but assured. Many US companies doing business in China and Hong Kong have been quietly increasing their investments since 1989. These companies can now concentrate on developing sales to the domestic Chinese market. This market is expected to surpass 1.2 billion people in 1995 and approach 1.3 billion by the end of the century.

Jan 1, 1993

By Argenis Gamboa

The Arab community is formed by around twenty countries in Africa and Asia, linked basically by a common language-Arabic - and the same religion, the muslim. They jointly occupy around 12 million square kilometers with a total population of around 140 million people. Nevertheless, these nations differ widely in their geographic area and population. Thus, while Egypt has a territory of over a million square kilometers and a population of nearly 40 million people, Kuwait, Qatar and Bahrain have, among the three of them, less than 30, 000 square kilometers and a million inhabitants. The per capita income also vary greatly, depending on whether they are oil producing countries or not. Generally speaking, it can be said that these countries economies have been based on oil or agriculture and that in these last years, they have been making serious efforts to increase their degree of industrialization and have greatly improved their infrastructure. This trend has resulted in the development of the iron and steel industry, which is still in a stage of primary development.

Jan 1, 1979

By L. Gertsch, R. Gertsch

Mechanical mining is steadily gaining in usage in the mining industry. A variety of machines are now being used, including tunnel boring machines, roadheaders, continuous miners, surface miners and augers. These machines have advantages compared to drill-and-blast mining methods, including increased safety, lower cost, uniform muck size and accurately sized openings. A century of experience with mechanical methods has paid dividends to the coal industry. Current trends guarantee eventual development of true general-purpose hard-rock mechanical mining machines. When several significant challenges have been met, mechanical miners will become integrated mining systems and will determine the design of mines.

Jan 1, 2002