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New Zealand's Land and Income Tax Act 1954 contains unique incentives for companies engaged in mining certain specified minerals or petroleum. Sections 152 and 153 provide for the taxable income of such companies to be based not on profits made but on dividends paid to shareholders. A significant saving in tax results, particularly where profits are not distributed: but the Act attempts to ensure that undistributed profits are used for further mineral exploration and development. To encourage investment in the mining industry, persons taking up shares in a company mining for the specified minerals or petroleum are entitled to a one-third deduction in respect of monies paid on the shares and used by the company for its purposes; and company shareholders may make loans to the company and write-off such loans for tax purposes to an amount of up to half their taxable income. Maximum utilisation of the tax incentives calls for careful consideration as to whether a mining or petroleum company should be financed by way of loan capital or share capital.

Jan 1, 1971

By David G. Adam

Introduction Syncrude Canada Ltd. is the operating company for a consortium of industry and government participants that produce synthetic crude oil from their leases in the Athabasca Oil Sands. Production from the $2.3 billion (1978) integrated mining, extraction, and bitumen upgrading and utility complex started in September 1978. Production is currently about 6.4 Mm3/a (40 million bbl per year) of high quality synthetic crude oil. This is done by upgrading the extracted bitumen from the oil sands mined. Plans are to increase the production to 8 Mm3/a (50 million bbl pier year) by 1989. At that time, the mining operation will be required to deliver 100 Mt/a (110 million stpy) of oil sand (ore) to the extraction plants, and handle quantities of waste ranging from 50 to 75 Mt/a (55 to 83 million stpy). The Syncrude plant is located at Mildred Lake, 40 km (25 miles) north of Fort McMurray and 480 km (300 miles) north of Edmonton, Alberta. Climate, particularly winter, is therefore a major factor affecting the design and operation of all the Syncrude production facilities. Bitumen production, consisting of overburden removal, oil/sand mining, bitumen extraction, and tailings disposal, account for about half the total SCO production costs. Considerable research and development, therefore, continues to be applied to improve both material handling and bitumen recovery methods. Potential applications for feeder breakers were identified in the material handling aspects of both overburden and oil sand mining to reduce cost and to attain planned production increments. Overburden removal Overburden materials on the leases comprise thin Pleistocene sands, gravel and fill, and sands, silts and clays of the thicker Clearwater Formation with the silt to clay components predominating. The latter contains multiple leases of hard siltstone with unconfined compressive strengths up to 148 MPa and thicknesses up 0.1 to 0.9 m (1 to 3ft). Characteristics of the overburden as well as the climatic environment and scale of operation present unique problems for the efficient removal of the material. In a bucketwheel/conveyor system, the weak silty clay formations require relatively flat working slopes for safe operation, while the siltstone lenses and frozen overburden require blasting or selective removal by other equipment. These factors, combined with the normal bucketwheel/conveyor design parameters, lead to high capital investment and relatively inefficient use of that capital. Hydraulic mining alternatives, including dredging, are constrained by severe clay settling problems in the waste disposal

Jan 6, 1986

By Yang Jian-guang, Deng Zi-xiang, Zhang Xu-liang, Li Jun-yuan

"Hyperaccumulator biomass harvested after heavy-metal phytoremediation must be considered as hazardous waste that should be contained or treated appropriately before disposal or reuse. As a potential method to detoxify the biomass and to convert this material to a suitable bio-energy resource, the hydrothermal upgrading process was applied to remove heavy metals and upgrading crude bio-oil from Pteris vittata stems and leaves harvest. Parameters such as material granularity, temperature, Liquid/Solid (L/S, ml/g), pressure, duration and catalysts were examined for their effect on the removal efficiency of heavy metals and upgrading efficiency of crude bio-oil. Maximum heavy metal removal efficiency of>99% and crude bio-oil upgrading efficiency of 83% were attained with an 200 mesh (75 µm) granularity, LIS 40:1and23 MPa at 380°C in the presence ofO.l mol L-1 K2C03 for 30 min. GC-MS analysis results show that the resulting bio-oil mainly consists of benzene 11 %, ketone 42%, alcohols 14%, alkene 15% and ester 11 %, etc., and the relative molecular weight distribution lies in 94-282, carbon number distribution lies in 6-18, calorific value is 32MJkg-1.IntroductionPhytoremediation of soil or water with hyperaccumulator has been extensively explored in recent years [1-4]. Living plants can clean up soils or waterways. This approach exploits the ability of various plant species to thrive in high metal environments where large amounts of toxic elements are accumulated, such as heavy metals, and is particularly appropriate when slow remediation of relatively low metal concentrations is acceptable. Advantages compared with existing remediation methods include the minimal site destruction and destabilization, low environmental impact, and favourable aesthetics; advantages compared with biosorption include continuous in situ regeneration of the biomass, and the ability of living plant cells to supplement passive sorption of metals with metabolic mechanisms of metal uptake and detoxification [5-8]."

Jan 1, 2014

Since 2008 rapid advances have been made in technologies for the sensing and sorting of ores, particularly copper, and copper-related ores. Advances include significant increases in the sensitivity and throughput, specifically in the area of bulk sorting. Such advances were not possible without contemporaneous advances in the understanding of copper orebodies, in particular the understanding and quantification of the heterogeneity required within an orebody to support an effective sort, regardless of the technology deployed to do this. This paper covers fundamental knowledge in the characterization of orebodies and their ores for sorting; relationships between measures of heterogeneity and sorting response; the design of bulk sorting systems that can exploit this heterogeneity to add value to copper operations; and, a quantification of the value that can be generated from bulk sorting at a case study mine. INTRODUCTION Society currently puts increasing pressure on industries to move towards cleaner and more efficient means of production, and the mining industry is no exception. Mining additionally faces other factors increasing the pressure to be more efficient: high-grade and easily accessible reserves have become largely depleted, therefore the mined grade at operations across most commodities, including and in particular copper, is decreasing. Additionally, the grade of new discoveries in the sector continues to decrease (Schodde, 2011). Factor in the high capital cost of processing facilities and the low levels of efficiency of current grinding circuits, and the situation for such mines becomes dire. Sorting, by maximizing the amount of ore extracted while simultaneously reducing the waste content in ore delivered to downstream processes (whether simply transport and crushing, or more sophisticated circuits such as grinding and flotation or leaching) has long been of interest to mining operations and projects struggling with low margins (Bamber, 2012). However, until recently sorting technologies that are both cost effective and effective at such high throughputs have not been commercially available.

Jan 1, 2019

By George W. Maynard Maynard

IN this paper I desire to embody the results of some personal observations of the working of the Siemens direct process as I witnessed it for a part of three days at the works of the Siemens-Anderson Company, in Pittsburgh. This preliminary investigation was to have been followed up by one extending over a considerable period of time, and would have embraced analytical and physical tests. Circumstances over which I had no control, resulting in the temporary suspension of work, have postponed the presentation of a complete paper. If the opportunity is afforded me, I purpose doing this at a future meeting of the Institute. To those interested in the development of the process, reference is made to the papers of Dr. Siemens in the Journal of the Iron and Steel Institute for the years 1873 and 1877, and to the paper of our late lamented brother, Holley, in the 8th volume of the Transactions of our own Institute. Dr. Siemens, in the introduction to his paper "On the Manufacture of Iron and Steel by Direct Process," read before the Iron and Steel Institute in September, 1877, says: " In mixing comparatively rich iron ore in powder with about 25 per cent. of its weight of pounded coal, and in exposing this mixture for some hours to the heat of a common stove or of a smith's fire, metallic iron is formed, which, on being heated to the welding-point on the same smith's hearth, may be forged into a horseshoe of excellent quality. The admixture with the ore of some fluxing materials, such as lime or clay, will, in most cases, be of advantage to rid the iron of adherent slag." This is the keynote of the Siemens direct process. Dr. Siemens says further: "If we regard the production of wrought iron from an abstract point of view, we perceive that we have to accomplish two things, viz., the deoxidation of the ore, and the fusion of the earthy matter .mixed with it; and if we calculate the amount of carbon necessary to accomplish this end, we shall find that in using, say, hematite ore, consisting of peroxide of iron with from 10 to 15 per cent. of silica, we shall require barely 40 per cent. of carbonaceous matter per ton of iron contained in the' ore to effect its reduction, and also the fusion of the slag."

Jan 1, 1882

By Ryron O. Pickard

"The Berkeley safety station of the U. S. Bureau of Mines was recently informed that a geologist was killed through entering an abandoned 90-foot exploratory shaft without making a preliminary test of the shaft atmosphere. He was one of a geological party which was investigating coal lands in California. The only light that he carried into the shaft was an electric flash light. After he had descended a short distance, one of his associates on the surface heard him exclaim, ""This place is full of gas, I am coming up"", He had no more than finished the remark when he was seen to lose his grip on the ladder and fall down the shaft. He was apparently weakened from impure air in the shaft, and could no longer suppers himself on the ladder. When his body was recovered, it was found that his neck had been broken by the fall.This is the ;second recent accident that has been called to the writer's attention where a life has been lost in abandoned exploratory workings; the other fatality being in Minnesota where a mining engineer was overcome while sampling a shallow pit in iron-ore formations. This engineer was on the bottom of the shallow pit and died before help could reach him. It was generally supposed that each of these deaths were due to poisonous gases, but the writer believes, after reviewing the information available, that death in both instances may have been directly caused by deficiency in oxygen.Frequently in the daily press there are items relative to lives being lost through cleaning out old wells, and as a general rule such accidents are also caused by impure atmospheres.In every abandoned shaft or pit, or in fact, any old working where the air has been stagnant for a considerable time, there is always danger of oxygen deficiency, as the oxygen which originally comprised one-fifth of the atmosphere may be appreciably replaced by gases that do not support life, usually by carbon dioxide (black damp) or methane (fire damp). Much valuable information on the subject of mine atmospheres, mine gases, and the effect of oxygen deficiency onthe human system is contained in Miners' Circular 14, ""Gases Found in Coal Mines"" by G.F. Burrell and F. M. Seibert; Technical Paper 122, ""Effects of Oxygen Deficincy on Small Animals and Men"", by G. A. Burrell and G. G. Oberfell; and ''Chit of Properties of Mine Gees"" by G. A. Burrell. These publications of the Bureau of Mines should be rent by all who are interested in the subject of this paper."

Nov 1, 1921

By Patrick D. McLaughlin

Crater blasting techniques have had relatively little application in the surface mining industry. This is not surprising, considering the geometry required to efficiently use cratering. The more widely known blasting operations that employ some form of cratering are listed below.

Jan 1, 1992

By R. M. Campoy

Mexico's mineral wealth has long been recognised and indeed has played a historically significant role on a world scale. The dynamics of the Mexican mineral industry have experienced a dramatic transformation especially over the last two decades. This transformation has mainly been instigated by the high growth rates and industrialisation of the Mexican economy since the 1960's. This paper focuses on the base metals sector of the industry which represents one of the major contributors to this transformation. The objective is to present a brief base metals review and to discuss some recent occurrences which pertain to this sector of the industry. This is followed by a discussion of mining's relevance in the current economic situation in Mexico. With this overview as background, the investment climate, primarily from a domestic investor's perspective and secondly in terms of foreign investment, is discussed. Finally, some recent government initiatives, including tax and accounting changes, are outlined. Any one of the sections of this paper can easily be developed into an extensive and indepth analysis; however, the intention of this paper is to provide the reader with a broad overview of the topics discussed.

Jan 1, 1985

By Luis Vassallo

El presente trabajo señala los beneficios que pueden obtenerse de la adopción inteligente de una estrategia de colaboración electrónica que responda a las necesidades de este segmento y que proporcione soluciones de verdadero valor agregado. Así, el modelo monolítico que prevaleció por muchos años, donde cada empresa era propietaria de las licencias mineras, operadora, mantenedora, contratista, vendedora, embarcadora y financiera, está desapareciendo. En la cadena de valor del proceso minero intervienen más empresas, contribuyendo valores agregados específicos y especializando funciones. Este cambio demanda mayores flexibilidades de los sistemas de información que deben ser totalmente abiertos, y permitir el intercambio instantáneo de información que facilite reaccionar oportunamente a las diferentes variables de la operación. Por ello, la colaboración electrónica permite a la minería adaptarse a un mundo que está cambiando.

Aug 25, 2002

By M. S. Kabibwa, E. K. C. Chanda

In planning for the future, Nkana Division deepened the Mindola sub-vertical shaft which was commissioned in 1994 in order to access the 30 Mt of ore between 1274 and 1570 m levels. The Nkana Synclinorium which is estimated to contain 250 Mt of ore is being accessed from the vicinity of Central Shaft. These areas are being planned with the intention of maximizing the use of computers in geological modelling and mine design so as to overcome the inadequacies of manual planning techniques. As a result, there is an increased demand for quality output from the computerized mine planning system the division has been developing over the last few years. A new workstation comprising the Hewlett Packard HP 71 51100 MHz and a CRX graphics monitor was acquired in 1995 together with the LYNX (version 3.09 and version 4.0) Mine Modelling System. Currently the workstation is being used for geological modelling and mine design for the Zerofold at Central Shaft and the Mindola mining at depth project. AutoCAD and Mine Works Planner have been added to the sys- tem configuration. Mine Works Planner is likely to replace Lo- tus123 for mine scheduling tasks. Computer applications in the area of mine planning at Nkana has led to considerable time savings and improved efficiency in areas formerly performed manually and has allowed speedy processing of data that would otherwise have proved too time consuming. Nevertheless, a lot of work still needs to be done in the areas of geostatistics, stope design and financial modelling of mining options. For the foreseeable future computer based planning will operate parallel to manual methods until such a time as sufficient personnel are proficient in the use of computer systems. This paper describes the program of computerization at Nkana Division, reviews current applications and the benefits and experience gained and discusses the promise of current and future developments.

Jan 1, 1996

By J. J. Pye, J. B. Drew

The surface-diffusion coefficients of Ni63 diffusing on low-index planes of nickel single crystals have been measured over the temperature range from 400° to 1000°C using a precision autoradio-gvaphic technique. The activation energy for sur -face diffusion appears to he the same on the {111}, {110), and (100) planes and amounts to -0.60 ev. This is in good agreement with the value (-0.62 ev) reported for (111) planes obtained by mass-transport techniques. In an earlier paper, the authors have reported self surface-diffusion coefficients on silver.' In that work, a deviation of the diffusion coefficients from linearity in the Arrhenius plot was observed at high temperatures. This effect was attributed to a loss of tracer atoms into the bulk by volume diffusion. The purpose of the present work was to extend the technique developed to the nickel surface-diffusion system up to the point where volume diffusion would come into play. The nickel system especially lends itself to this technique due to the high efficiency of the isotope in darkening the film and the large absorption of the weak radiation (0.063 mev /3- particle of the trapped tracer atoms. The diffusion coefficients and ictivation energy for different orientations on nickel can also be compared with a report published by Blakely and Mykura 2 where a mass-transfer technique was used. This paper reports the self surface diffusion of nickel on the low-index planes over a wide temperature range using a precision autoradiographic technique. EXPERIMENTAL PROCEDURE The experiment is similar to that described in the earlier publication consisting of a radioactive needle as a source resting on a flat, smooth, chemically polished surface annealed in a dynamic dry-hydrogen atmosphere. The needle is held snugly on the surface by a holder fabricated from commercially pure nickel. The point source is made by grinding down a small-diameter nickel rod until a tip of approximately 0.1 mm radius is formed. It is then etched and the needle tip plated with the radioactive isotope Ni63. Nickel single crystals were used whose main impurities were spectrographically determined as Co 0.05, Fe 0.007, C 0.005, and S 0.003 pct. The surfaces, oriented to within 1/2 deg of the low-index planes, were carefully mechanically polished and etched in a 50-30-10-10 hot solution of acetic, nitric, sulfuric, and phosphoric acids giving a smooth polished surface. The crystals were then washed in distilled water and alcohol. Annealing temperatures ranged from 400° to 1000°C with a furnace arrangement in which the crystals could be brought up to temperature in times short compared to diffusing times. The temperature was maintained constant to ±10°C. In the temperature range investigated, the ratio of the surface-diffusion coefficient to the volume-diffusion coefficient (Ds/Du) was 105 or more and the mean bulk-penetration values, calculated from literature values of volume-diffusion coefficients,3 were on the order of 10-5 cm. After the diffusion anneal, the sintered needle is removed, and both the radius of the needle point and spot left on the crystal face are measured. The crystal is then placed on photographic film. Diffusion profiles are obtained by scanning the film with a recording microdensitometer which has a slit width of 10µ. DISCUSSION AND RESULTS The experimental conditions are such that the source strength and needle radius are essentially constant and the time is adjusted such that the mean bulk penetration is small. An exactly analogous heat-flow problem has been considered by Carslaw and Jaeger4 and the solution can be written in integral form as:

Jan 1, 1964

Jan 1, 1940

By R. V. Ramani

In 1970, of the 603 million tons of coal produced in the United States, 339 million tons, or 56%, were produced by under- ground mines. While the ratio of underground to surface production has been decreasing in the last few years, it is anticipated that a 60:40 ratio of underground to surface-mined coal will remain for some time. Underground coal operators are continuing to invest in new mines and are interested in increasing the efficiency of all their operations. One area for improvement is in mine planning and design, particularly in the area of selection of equipment for operation. Because of the availability of a wide variety of equipment, a fair degree of selectivity can be exercised in the choice of equipment for a particular job. However, such a choice must be made on the basis of technological facts and forecasts related to the mining operation. If the mining conditions can be reasonably predicted, along with a mining plan, it should be possible to insure the selection of the right equipment for the particular application. In order to increase the efficiency of underground coal operations, it is necessary to understand not only the operating system in detail, but the inter-relationships between system components and the operating environment. With such an understanding comes the application of simulation and other operations research techniques to plan and operate mining systems. Computer simulation studies have been successfully adapted to underground coal mining, and applications by Prelaz et al. (1965), and Manula and Sanford (1969) are some that are being used by the mining companies. However, a need still exists for better understanding of certain intra-system and system-environment interactions in order that computer simulation programs may be provided with better input data for more effective application. This paper deals with one aspect of the coal-winning system in need of better definition, namely, studying the performance of continuous miners.

Jan 1, 1973

By P. T. Bissert, L. Yan, M. D. Klein

"Federal regulations require that refuge alternatives (RAs) are located within 305-m (1000-ft) of the working face and spaced at one-hour travel distances in the outby area in underground coal mines in the event that miners cannot escape during a disaster. The Mine Safety and Health Administration mandates that RAs provide safe shelter and livable conditions for a minimum of 96 hours while maintaining the apparent temperature (AT) below 35°C (95°F). The National Institute for Occupational Safety and Health used a validated thermal simulation model to examine the mechanisms of heat loss from the RA to the ambient mine and the effect of mine strata composition on the final internal dry bulb temperature (DBT) for mobile tent-type RAs. The results of these studies show that most of the heat loss from the RA to the ambient mine is due to radiation (51%) and conduction (31%). Three mine width/height configurations and three mine strata compositions were examined. The final DBT inside the RA after 96 hours varied less than 1°C (1.8°F) for the three mine width/height configurations and less than 2°C (3.6°F) for the three mine strata compositions. INTRODUCTION Following a mine disaster, workers will try to escape the mine. If their escape is futile, they can take shelter in a refuge alternative (RA). In 2008, the Mine Safety and Health Administration (MSHA) mandated RAs in mines to ensure that a safe and livable shelter is provided for a minimum of 96 hours, and that the apparent temperature (AT) does not exceed 35°C (95°F) inside the RA [1]. An ongoing concern with RAs is the potential to exceed this limit. The temperature rise inside an RA is due to the metabolic heat released by the occupants as well as heat released by the carbon dioxide scrubbing system. The National Institute for Occupational Safety and Health (NIOSH) tested a 10-person tent-type training unit RA in its Safety Research Coal Mine (SRCM) to investigate heat buildup in RAs. The 10-person capacity for the tested RA is based on 1.4 m2 (15 ft2) of floor space per miner. NIOSH-developed simulated miners, which are heat input devices that generate both sensible and latent heat, were used to represent the metabolic heat generation of an average miner (117 W) for testing in the SRCM. It was found that the number of occupants in an RA may need to be reduced based on the ambient mine temperature, which varies from mine to mine [2]. To further research temperature rise inside an RA, ThermoAnalytics, Inc. (TAI) was contracted by NIOSH to perform thermal simulations of the tested 10-person mobile tent-type RA. TAI developed a thermal model of the SRCM using RadTherm software, which incorporates a human thermal model (HTM) to represent the equivalent metabolic heat loss of a miner within the RA’s enclosed environment. The thermal model was previously validated by comparing simulation results with test results [3]. During a mine disaster in which miners would have to take shelter in an RA, mine ventilation may not be available. As such, mine ventilation was off for both the testing in the SRCM as well as in the simulations. This paper discusses the heat loss mechanisms and the effects of mine strata composition and mine width and height associated with a ten-person tent-type RA."

Jan 1, 2016

For the first time in its history the Institute will hold a meeting in the State of Arizona. A few years ago Arizona stood third in the copper-producing districts of the United States. Since that time, with the development of porphyry mines, the output has gone up with great rapidity until it not only is the leading district, but its output at the present tune is at the rate of nearly double the Montana output; which now stands second in the list. In connection with this development, most interesting departures have been made in methods of mining, concentration and smelting. Principles of mining and metallurgy of the greatest interest will be covered by papers which will appear in the Bulletin and be presented at Technical Sessions, while ample opportunity 'will ,be- afforded for those who go to the meeting to see all the points of interest to them. In addition, members will be well rewarded by the marvelous natural features to be seen on the trip, including the petrified forests, the cliff dwellings on the Apache Trail and the Grand Canyon of Arizona. It is planned to start the special train from New York, but members and guests may join the special at other points en route as indicated by the following schedule: ITINERARY Thursday; September 14th, Lv New York Grand Central Terminal 5.30 p.m. Dinner in dining car, a la carte

Jan 9, 1916

By G. Zhu

Bulk and differential laboratory flotation tests have been carried out using a synthetic mixture of chalcopyrite and molybdenum ore. In addition to boiling and roasting, six different depressants are tested so that the best conditions of separation can be identified. These reagents include sodium cyanide with and without zinc sulfate, potassium ferrocyanide, sodium hydrosulfide, arsenic Noke's reagent, and sodium sulfide. The data indicate that most of these reagents are effective chalcopyrite depressants. However, sodium hydrosul fide can be used preferably if economic, operational, and environmental factors are taken into consideration.

Jan 1, 1983

By David L. Holt

The contribution of grain boundary shear to total elongation, CS/E&apos;, has been measured in an Al-Zn eu-tectoid alloy that was quenched from above the invariant temperature, then annealed at 250° C to a grain size of&apos; 1.8 p. At 250°C, ks/E&apos; is low at both high and low strain rates, but reaches a maximum, estimated as 60 pct at an intermediate rate of 5 X 10 per rnin. Rate sensitivity, as measured by the index m = a log a/a log E&apos;, follows the same trend, and furthermore the maximum values of m and -cur at approximately the same strain rate. This result, combined with the metallographic observation that boundary migration enhances boundary shearing, is interpreted as supporting a previous suggestion that the high rate sensitivity characterizing super-plasticity is the result of combined boundary shearing and migration. It is suggested that the latter event relieves stress concentrations at triple points, and smoothes boundaries so that stress is governed largely by a viscous boundary shear. GrAIN boundary shear has been considered in relation to superplasticity in several recent papers.&apos; The problem has been to explain the high strain rate sensitivity of flow stress, and the variation of rate sensitivity with strain rate (E&apos;) and grain size (L). The requirements for superplasticity, small L and high T, suggest the reasonableness of an approach to high rate sensitivity involving grain boundary shear. Further support came from experiments on the A1-Cu eutectic alloy,&apos; where it was found that strain rate sensitivity of cast material annealed to produce an equiaxed, micron-size grain is always low; taking as an index of rate sensitivity m = a log a/a log <, m < 0.3. However, m in hot-worked alloy of comparable grain size can be as high as 0.7. In the cast and annealed material, each phase is a single crystal, the only boundaries are interphase boundaries, and it is, consequently, geometrically impossible for boundary shear to contribute to deformation in any major way. Other observations (for hot-worked material) were a-L at constant (low) strain rates and indications that the rate of recrystallization was enhanced as strain rate increased. As a result of this work, it was proposed that high rate sensitivity arises from a deformation mode of boundary shear associated with boundary migration. Migration serves to relieve stress concentrations at triple points, and smoothes boundaries so that they assume properties of fluid films. On the other hand, the low rate sensitivity observed at high and low strain rates reflects deformation of bulk material. Measurement of the variation of grain boundary shear with strain rate and m have not yet been made. Such measurements are important, especially in view of a proposal, differing in detail from the above, that high m arises merely from a transition between a grain boundary shear mode of deformation at low rates to a transgranular mode at high rates.2&apos;4 In the present work, the contribution of boundary shear to total deformation is measured and in addition metallographic observations are made on surfaces of deformed specimens to look at the interaction between boundary shear and migration. The Al-Zn eutectoid alloy was chosen for its homogeneous, fine-grained structure, which is obtained readily without hot-working. It has also been the subject of a previous phenom-enologically directed study. EXPERIMENTAL Material. Compression specimens, cross section 4 by + in., length \ in., were machined from a sand-cast ingot of composition 77.5 wt pct Zn, 22.5 wt pct Al. (The melt was prepared from 99.9 pct Zn and 99.99 pct Al.) After homogenization at 375°C for 50 hr, the specimens were quenched in brine and removed before the heat evolution that accompanies de -composition of the high-temperature phase.5&apos;6 The resulting microstructure, see Fig. l(a), was too fine for grain boundary sliding to be easily studied; coarser structures were obtained by annealing for various times at 2 50°C. Annealing was terminated by a brine quench. Final average intercept lengths between all grain boundaries (both interphase and those lying in a phase), L, were: 0.5 p [annealed for 15 min, Fig. (a)], 0.8, 1.1, and 1.8 p [Fig. l(b)l. Testing Procedure. An Instron machine was used for most of the compressive deformation. Tests were of two types: those in which crosshead velocity was changed in steps to measure m as a function of strain rate15 and tests at constant velocity to a fixed (engineering) strain of -0.2 (20 pct). Stress reached a steady-state value (a) which was plotted, on a logarithmic scale, against log strain rate (E&apos;). An alternate and equivalent evaluation of m was to take the slope of the log o vs log 6 curve. Time at temperature before testing was 15 min. Strain rates covered by the Instron (4 x lo-&apos; to 4 x 10&apos; per min) were insufficient; at a higher rate of 5 x lo2 per min a gas-operated testing machine was used, the gas driving a piston to compress the specimen at a controlled velocity.&apos; To obtain points on the log a vs log E&apos; curve at low rates, specimens were compressed by a dead weight. strain rate was an average value computed by dividing strain at the end of test by loading time. In some tests strain was measured at fractions of the loading time; creep rate was found to be reasonably constant.

Jan 1, 1969

By Robin J. Hickson

The Grasberg copper-gold deposit was discovered in the spring of 1988, one year before the planned closure of Freeport Indonesia&apos;s original Ertsberg openpit copper mine. In spite of Grasberg&apos;s remote location, 600 m (1968 ft) above the Ertsberg, atop a hitherto inaccessible mountain, Freeport-McMoRan brought its latest open-pit mine into production in the last week of 1989, less than two years after discovery. Freeport Indonesia&apos;s (FI) copper-gold mining operations are located in Irian Jaya, the easternmost province of Indonesia on the western side of the island of New Guinea. Fl&apos;s six ore deposits are all located within a 10- x 10-km&apos; (3.9- x 3.9-sq mile) Contract of Work area. They are all between the elevations of 2900 and 4300 m (9515 and 14,100 ft) above sea level, some 96 km (60 miles) from the island&apos;s southern coast. A 118-km (74-mile) access route connects FT&apos;s port site of Amamapare on the Arafura Sea to the project area. The first section is an 18-km (11-mile) barge waterway. The final 100-km (63mile) is a two-lane gravel highway. The highway terminates 9 km (5.5 miles) beyond the FI townsite at the project&apos;s central mill, some 2850 m (9250 ft) above sea level. The mining areas are separated from the mill by a 780-m (2560-ft) sheer cliff face. The world&apos;s longest free span tramway system, with a total length of more than 1.6 km (1 mile), is the only means of access for men and materials between the mill and the surface mines. Weight restrictions for the tramway for equipment considered for the project are 15.4 t (17 st). The minimum clear width dimension of two tunnels along the portsite access road is 5.6 m (18.4 ft).

Jan 1, 1991

By Joseph J. Wallace

1. The investigation shows that nine coal beds have been mined in Harlan County, of which the Harlan and Upper Elkhorn No, 3 are the most important from the standpoint of present production. Of less importance are the Hindman, Flag, Haddix, Wax, Fire Clay, Armburgy, and Upper Elkhorn No. 2. The Harlan, Upper Elkhorn No. 3, and Upper Elkhorn No. 2 beds contain the largest remaining known reserves. 2. Known measured and indicated reserves in all beds, based on a minimum thickness of 14 inches and 1,800 tons per acre-foot of coal in place, are estimated at 2,138 million short tons as of January I, 1932. Of this total, 1,956 million short tons is in beds 28 inches and more thick. Areas in each bed were omitted from the estimate because available data relative to the bed characteristics are too meager for making an estimate that conforms with the definitions of measured and indicated coal adopted for this study, Should future drilling or development prove reserves in these areas, such reserves should be added to the total estimated reserves.

Jan 1, 1954

By E. V. Manlapig, M. C. Harris

"The complexity of the flotation process has made the identification of an appropriate model structure, for use in the prediction of flotation circuit performance, far from obvious. Work performed under the auspices of the AMIRA P9 flotation program has indicated that the metallurgical performance achieved from a flotation cell arises from the interaction of two essentially independent property classes, namely the cell operating conditions and the properties of the cell feed stream. These observations have led to the development of a model structure that associates a constant set of flotation parameters to the streams of the circuit, which are transformed into a flotation response depending on the operating conditions within the flotation cell.A variety of alternative model structures exist within the literature which do not make this distinction between cell and stream flotation properties, and many of these models are in widespread use for flotation optimisation and design studies, both in industry and academia.In this paper, data collected from an industrial flotation circuit is used to derive the parameters associated with two different types of flotation models. Simulations performed using these models demonstrate the need to differentiate between cell and feed properties. A model that does not differentiate between these two properties fails to successfully predict the metallurgical performance of a flotation circuit after a disturbance."

Jan 1, 2003