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By L. A. Puchkov

Problems of how to use artificial intelligence (AI) methods and expert systems (ES) to control complex industrial projects have lately become significant in practical terms. Mining ventilation systems undoubtedly belong to complex multi dimensional objects of control with stochastic nonstationary and nonlinear processes. Formal models based on automated ventilation control, do require awkward algorithmic solutions, moreover, a number of tasks become the operator's headache, and the quality of their solution depends on his experience and intuition. These tasks include: - identifying pre-accidental situations and determining their causes; - making well-grounded decisions with regard to changing ventilation regimes, forecast of mining operations taken account of; - controlling ventilation systems in emergency situations, e.g. when in accident, etc. It is in this context that we have for a number of years been investigating how to practically use AI methods for operative control in dynamic aero-and-gas mining processes, one of our research directions being devoted to working out a consulting programme for the ventilation system operator. Our researching and modeling problem was identification of aero-and-gas situation in different parts of ventilation network and its interpretation in order to determine possible causes for gas regime changing and unexpected consequences. We would single out the following stages in this task: I. Operative information procession coming to the data base from the sensors and analysis of hypothetical versions (using the associative rules base) with regard to factors which have caused significant parameter fluctuations (e.g. C%(t), H(t), Q(t) etc.)., 2. Selection of hypotheses in the knowledge base and forming conclusions in accordance with reliability scale. 3. Clarifying the obtained conclusions in dialogue with the operator. 4. Correcting the associative rules base.

Jan 1, 1992

By Roderic A. Ellman

The new Woodrow Wilson Bridge (WWB) will replace the existing bridge over the Potomac River to connect Alexandria, Virginia to Prince Georges County, Maryland. The new WWB will extend approximately 1.1 miles across the river, with a 367-ft long bascule span in the main river channel where the water depth is about 36 ft. The subsurface soil profile consists of up to 50 ft of a soft organic silty clay layer that is very vulnerable to scour, underlain by a deep deposit of hard sandy clay. Foundation construction in the Potomac River required the use of cofferdams to allow structural concrete work to be performed in the dry. This paper will the present the types of cofferdams used to construct the foundations for the WWB replacement project. The bridge is primarily comprised of fixed spans in relatively shallow water and a bascule span over a navigation channel in relatively deep water. Foundation construction included the installation of 48" to 72" open end steel pipe piles and cast-in-place concrete pile caps. To achieve the desired bridge appearance, pile caps were required to extend below the water surface and below the existing river bottom in shallow water locations. Conventional steel sheet pile cofferdams with tremie concrete seal were used to construct fixed span, shallow water piers. Selection of deep water bascule span foundation cofferdams was governed by several factors including contraction scour, environmental considerations and cost. Potomac River cofferdams, i.e., relatively shallow depth cofferdams that are supported by the foundation piling were selected. This cofferdam system provided a shallow profile which minimized contraction scour and the amount of filling in the river. Design issues include load selection and cofferdam stability in very soft alluvial soils. Construction issues include erection sequence, tremie concrete mix design and placement procedures.

Jan 1, 2005

By R. W. Pugh, S. L. Ma

"High carbon rods are typically used as the grinding media in rod mills. Usually an AISI I 090 grade of steel is used which provides the high hardness needed for abrasion resistance and sufficient toughness to prevent rod breakage.Work to improve performance in the past has mainly concentrated on increasing the hardness for improved abrasion resistance. This has been accomplished by adding alloys to the steel which uniformly increase the hardness across the rod section.However uniformly increasing the hardness of the rod produces a more brittle product and at high hardness l1evels can lead to rod breakage problems. Heat treatment processes can be used to selectively increase the surface hardness to high levels while maintaining the core at lower hardness levels to give a product that wears slower without breakage. AltaSteel has developed and mill tested a higher hardness heat treated grinding rodThis paper describes the development of a simple model to predict performance improvement with different hardness profiles and the AltaSteel heat-treated grinding rod process. Mill characteristics of the Endako operation are summarized and predicted performance improvements based on hardmess are compared to the approximate 25% achieved in trials running since July, 1991 at this mill. Early results of other mill trials are also presented.INTRODUCTIONAltaSteel, in Edmonton is a major supplier of grinding media. We have a strong desire to continually increase the quality and performance of our products and thereby improve the efficiency of our customers' processes. In the area of grinding rods, we wanted to produce a product with a significant improvement in wear rate. Second to energy, rod consumption usually represents the next highest cost in processing. This paper presents our development of a heattreated grinding rod that has reduced consumption by about 25% in trials to date."

Jan 1, 1993

By Gerald R. Dickens

Massive sulfide ores and Fe-Mn oxyhydroxide precipitates represent two extremes of a spatial continuum of hydrothermal deposition along oceanic ridges. Elemental variations across this continuum are of interest to economic geologists as a prospective geochemical exploration tool. Theoretical considerations suggest that certain physical and chemical parameters can be used to model compositional variations within the far-field (i.e., Fe-Mn oxyhydroxide) component as a function of distance from ridge axis; however, testing and verification of such models generally has been precluded because the few available distal hydrothermal sediment sequences have been sampled at low resolution and/or are highly diluted with biogenic components (e.g., siliceous and calcareous tests). Recent ocean drilling (ODP Leg 145; Sites 885/886) in the North Pacific successfully recovered an extensive record of "biogenic-free" distal hydrothermal precipitates from an area approximately 60 km south of the Chinook Trough at longitude 168.1 °W. Geophysical and geomorphological evidence suggests the Chinook Trough is the southern lithospheric scar marking initiation of late Cretaceous north-south rifting, implying that recovered hydrothermal materials record distal hydrothermal precipitation from the now-subducted Kula-Pacific spreading ridge. The Chinook Trough hydrothermal sequence is a continuous 15 my record of "biogenic-free" hydrothermal Fe-Mn oxyhydroxide precipitation mixed with eolian clays. It was deposited during the late Cretaceous, early Paleocene (80-65 Ma) as the perpendicular distance from ridge axis increased from 75 to 600 km. A high-resolution geochemical analysis of this hydrothermal sequence reveals distinct trends for the up-core (equivalent to increasing distance from ridge) distribution patterns of Fe, Sc, As, and rare earth elements (REE). Iron concentrations exhibit an S-shape distribution pattern with respect to increasing

Jan 1, 1994

By W. G. McBride

The mining industry has already become highly technical in all its branches and this has brought about specialization in mining engineering. Increasing demand for mineral products, exhaustion of high-grade or easily worked deposits, and narrowing of the fields for exploration and development, are forcing mines to greater depth and to working material of lower grade and more complex composition. The Robinson Deep at its Turf shaft has reached a depth of 7,640 feet and expects to go to 8,500 feet; Miami Copper, under normal market conditions, profitably mines ore running only 16 pounds of copper to the ton; Alaska Juneau is making a profit on ore running about $1.15 per ton in gold; and many mines are handling ores of an extremely complex nature. In each case, the success of these operations has depended upon the application of sound scientific principles and good business methods to the problems involved. It may be safely assumed that mining at great depth and the exploitation of low-grade, or complex, ores will become more and more important as time goes on, and this means that greater and greater demands will be made upon the technical skill and business ability of the mining engineer. To meet this condition, the more or less haphazard methods of training the young engineer that have prevailed in the past will have to be replaced by a careful and well-ordered system of engineer-training. Upon the industry and the older mining engineer falls the duty of providing means to assist the deserving student to prepare himself properly to meet the increased demands that are falling upon his profession. Consideration of the training of the mining engineer involves a decision as to what constitutes his field of usefulness. Technical control of methods and processes obviously falls upon the engineer, but there are still many who doubt his usefulness in the executive field, particularly in positions involving close contact with the men and work. Many engineers have failed as shift-boss or foreman, but this has been generally due to fault in the management in using men who were temperamentally unfit to lead others or who lacked the necessary preliminary training.

Jan 1, 1932

Since the Rio Declaration on Environment and Development in 1992 in Rio de Janeiro and the publication of the agenda 21, the concept of Sustainable Development has become one of the major issues for governmental politics, societal developments and entrepreneurial policies. Current projects that deal with Sustainable Development in the mineral raw materials sector mainly focus on large-scale mining operations - especially for open pit mining - or on artisanal small scale mining. Artisanal small scale mining is in this connexion characterised as non-mechanized and mostly illegal mining activities. The number of workers is mostly far below 20. However, until now there exist no assessments or analyses with respect to the actual or potential contribution of industrial small scale mining to sustainable development. Industrial small scale mining refers to high technology or highly mechanized/automated extraction of small, high-grade deposits that due to their small size ? in combination with geological, depth and other constraints ? are not economically exploitable with large-scale mining operations. The Institute of Mining Engineering I and the Institute for Processing of Mineral Raw Materials at the RWTH Aachen University in Germany is currently conducting a research project financed by the German Research Foundation in order to investigate this issue. In the course of this project the sustainability of industrial small scale mining will be assessed. Therefore sustainability indicators, an assessment system and recommendations as well as options for actions and policies will be developed, in order to evaluate current industrial small scale mining activities as well as the potential for future developments in industrial small scale mining, both from a technological as well as from the point of view of sustainability, considering economical, social and environmental chances and risks.

Jan 1, 2007

By G. S. Walker, W. van Bronswijk

The accurate determination of free cyanide and metal cyanide complexes is of increasing interest to Carbon-in-Pulp (CIP) gold extraction operations as cyanide consumption is an important economic factor in the processing of complex ores. Characteristically complex ores are high cyanide consumers and these ores usually contain a range of sulfide minerals e.g. covellite (CuS), digenite (Cu1,S), chalcocite (Cu, S), Pyrrhotite (Feci-x)S), marcasite (FeS2), arsenic and antimony sulfides and zinc sulfide. These minerals can consume significant quantities of cyanide, e.g. various copper(!) cyanide complexes such as CuCN, Cu(CN)2·, Cu(CN)/ and Cu(CN)/ can form, depending on the cyanide to copper ratio in solution. Measurement of free and complexed cyanide is thus a prerequisite for efficient cyanide dosage control. Free cyanide can be determined potentiometrically or amperometrically but the methods are prone to error and are laborious [1]. Metal cyanide complexes can be determined by reverse phase HPLC, however, the species ofa single cation (e.g. Cu(CN)i-, Cu(CN);2 and Cu(CN)/) elute as one species [2]. Additionally the high amount of suspended matter in CIP leach solutions tends to introduce errors. Raman spectroscopy has the potential to be used as an in­line or on-line method of analysis. Free cyanide and the cyanides of gold, silver, copper and iron have been studied in aqueous alkaline solutions with a view to developing such a method. Spectra were obtained with a Bruker RFSl00 FT-Raman spectrometer using a 1064 nm laser delivering 800 mW of power at the sample. Depending on the solution, 250, 1000 or 4000 scans at 4 cm-1 resolution were accumulated. The cyanide stretches observed were relatively narrow (10 15 cm-1 full width at half height) and well resolved (Figure 1 ).

Jan 1, 1995

By E. J. Rogans, W. N. Cartner

Carbon technology has largely superseded filtration plants as the more acceptable gold recovery technology. This has, over the last two decades, provided a tremendous driving force for the development of new equipment. One of the main focus areas of this technological development is the development of effi­cient interstage screening systems. Several variations of exter­nal and internal screens are available, with the more recent shift away from air cleaned units to mechanically swept units. This paper discusses the development of one such mechanically swept interstage screen and how the development led to the suc­cessful implementation of a carousel type of CIP operation. The first generation Pump-cell emerged as a consequence of the success achieved with the mechanically swept NKM screen, The idea was to modify the screen to incorporate the functions of pumping, screening and agitation in a single drive unit, the screen generating sufficient lift for interstage slurry flow so that all contactors would be at the same level. This sys­tem was further incorporated as a high intensity modular CIP contactor, i.e. low slurry residence times combined with high carbon concentrations. A discussion on the kinetic gold adsorp­tion theory and its manipulation in the design of the pump-cell concept is discussed in a paper published in a previous Randol Conference< 1), Testwork carried out at Vaal Reefs proved the concept of the Pump-cell on a pilot plant scale<2), which resulted in the building in 1990 of the first large Pump-cell plant at West Witwatersrand Gold Mine designed to treat 340m3 of pulp per hour and , even though the plant operated successfully with respect to gold recovery performance, a few problems were experienced with the basic engineering design(3),

Jan 1, 1996

By Junho Lee, Lin Huang, Alejandro Martinez, Charles Aubeny

Offshore wind farms are one of the principal sources of renewable energy worldwide due to their large potential for energy generation and remote locations. In the U.S., a number of offshore wind farms have been operating for several years on the East Coast, while two potential locations have been approved on the West Coast. While the shallower waters in the Atlantic Ocean allow for building wind turbines with fixed foundations like monopiles, the substantial water depths of the Pacific Ocean, which can exceed 1,000 m (3,280 ft), require the use of floating turbines with mooring systems. In fact, 65% of the U.S. offshore wind resources are located in deep water regions where water depth is greater than 60 m (197 ft). Since foundation systems typically account for 15-20% of the total construction cost of floating offshore wind turbines, optimizing the design can have a large impact on their cost competitiveness with respect to other sources like onshore wind and solar. A strategy that has received signifi­cant attention recently is to share anchors between floating wind turbines. This differs from the conventional configuration consisting of three nonshared anchors per turbine. The benefits of the shared anchor configur­ation are significant. For example, if every anchor in a wind farm is shared by three turbines, this reduces the number of required anchors by a factor of three. The capacity of offshore anchors depends on a number of factors including the loading inclination angle, embedment depth, soil properties and loading history. Of these, the former depends on the water depth, distance between turbines and mooring line configuration (i.e., taut versus catenary). This article focuses on assessing the effect of the loading angle on the monotonic capacity of ring anchors in sand.

Sep 1, 2024

By D. S. Greig

There was a decline in the Italian oil production in 1933 and also in the footage drilled. A total of about 194,500 bbl. of crude oil was produced in the Emilia district of northern Italy from the same fields in production as in 1932. New drilling to the extent of 80,700 ft. failed to find new production to compensate for the decline in old wells, and no new fields were discovered in spite of an active exploration campaign by the government-owned company A.G.I.P., which has just completed the first year of a five-year exploration program. This company drilled a total of about 33,000 ft. The majority of its tests were drilled in the Po Valley upon locations selected by geophysical methods. This company is changing over to the rotary system for all future wells. It produced about 16,600 bbl. of oil from wells near Salsomaggiore and in the Po Valley. The Petroli d&apos;Italia, which operates the old fields of Montechino, Valleja and Gratera south of Piacenza, has been doing normal development drilling in the endeavor to extend its present fields. Also it was drilling two exploration wells in the Torino district. It drilled a total of about 13,930 ft. and produced approximately 12,645 bbl. of very high-grade oil (specific gravity about 0.765). The Societa Petrolifera Italiana was occupied chiefly in exploratory drilling in the endeavor to extend its producing fields at Salsomaggiore and at Vallezza, south of Parma. It was also drilling one exploration well at Rile dell7Olio near Voghera on the line Milan-Genoa. It drilled a total of 33,849 ft. and obtained a production from its two fields of 165,273 bbl. It also produced 123,220 gal. of casinghead gasoline from Vallezza field absorption plant.

Jan 1, 1934

By Alice Barreto Bevitori, Frederico Muylaert Margem, Noan Tonini SImonassi, Caroline Oliveyra, Sergio Neves Monteiro, Isabela Leão Amaral da Silva

"The mechanical behavior and the fracture characteristics of composites with DGEB/TETA epoxy matrix reinforced with up to 30% in volume of continuous and aligned ramie fibers were evaluated by tensile tests. Specimens with selected thin fibers aligned along the tensile axis were room temperature tested to rupture. The fracture surface was analyzed by scanning electron microscopy. The results showed significant increase in both the ultimate tensile strength and the elastic modulus. The fracture analysis indicated the possible mechanism for the fiber/matrix interaction, which could be responsible for the composite performance.IntroductionSince the middle of last century, polymer composites have substitute many conventional monolithic materials in applications ranging from aerospace to sport [l]. The main advantages of these composites are the low density and flexible properties specially using fiber as reinforcement to suit the mechanical performance requirements [2]. These are usually high strength and stiffuess requirements that could be reached with synthetic fibers such as gloss, carbon and aramid fibers. Its most commonly used example is ""fiberglass"", i.e., a thermoset polymer matrix composite reinforced with glass fiber. Indeed, ""fiberglass"" has a specific strength of the order of 500 MPa.cm3/g, which is the double of the strongest steels like the maraging. This motivated, at earlier times, ""fiberglass"" to replace many conventional materials including wood and natural fiber composites. Today, ""fiberglass"" has a wide range of uses from aerospace systems and appliances to sport and leisure components. However, its fabrication as well as those of any synthetic fiber such as carbon and aramid composites, requires a relatively large amount of energy. Presently, a growing concern exists regarding the consequences to the environmental by gases like C02 associated with both the energy consumption and the processing of synthetic fibers and their composites. These gases are well known responsible for global warming [3]."

Jan 1, 2013

By Albert Williams

A large proportion of the work performed in wet-crushing silver mills is devoted to the handling and re-handling of pulp between the battery and the pans. There seems to be no generally applicable substitute for the settling-tanks, and in the present system of constructing mills the tanks involve an amount of labor which may be regarded as disproportionate and unnecessary, in view of the automatic improvements which have been introduced in other directions. This diffculty has been met, however, by Boss&apos;s continuous process, in which the pulp flows directly from the mortars to the first of a series of constantly working overflow-pans. This method has been adopted at the Noonday mill, Bodie, California; the Harshaw, Arizona; the Sierra Grande, New Mexico ; and the Prietas, Sonora. The continuous process, while giving excellent results with special ores, and under peculiar local conditions (such as a deficiency in water supply), is not, I believe, claimed to be available for all raw-amalgamating mills, notwithstanding its well-merited popularity for certain work. Some trouble has been experienced from the tendency to concentration in the pans, though this can be avoided by skilful manipulation. It has also the disadvantage inherent in combinations of distinct operations ; it requires a very nice adjustment of the water supply to obtain full battery efficiency without running the pans too thin, though the latter defect is partially compensated for by the gradual thickening of the pulp as it proceeds through the series of pans. The objection is similar to that which holds in a parallel duplex process, that of combining roasting and smelting in a single furnace, where each operation is injuriously affected by the necessity of fitting it in with another and entirely different one.

Jan 1, 1883

By Christopher Smith

The critical nature of detonator function in blast design and its effects upon performance and safety of a blasting operation are well documented. Numerous laboratory and field studies have shown dynamic shock waves, generated by the detonating explosives in a shot, to be detrimental to the performance of the explosive columns in the adjacent boreholes. Laboratory tests conducted in Japan have explored the possible effects of dynamic precompression upon cartridges of emulsion explosives, which had been sensitized with different hotspot void producing methods. These tests uncovered significant differences in the magnitude of the dynamic shock wave pressures measured inside the different emulsion explosive cartridges, and demonstrated these pressure differences by crushing detonator shells inserted inside the emulsion cartridge. Basically, the results of these tests clearly showed the magnitude of the compressive force applied to the detonator inside the primed explosive cartridge to be a function of the mechanism that had been used to sensitize the emulsion (i.e., glass microspheres, plastic spheres, chemical gassing). The current study was designed to further explore the actual detonator failure mechanism in these dynamic precompression tests using live detonators inside the emulsion cartridge as opposed to empty detonator shells. The testing involved inserting commercial delay detonators inside emulsion charges, which had been sensitized with common hotspot void producing agents, and subjecting the primed explosive cartridge to the dynamic pressure wave generated by an underwater donor explosive charge. The effects of variations in the emulsion’s sensitization method upon the damage inflicted to the detonator were studied. Depending upon the degree of detonator damage, detonator crushing can lead to varying degrees of detonator malfunctions, ranging from sympathetic initiation of the detonator, to a reduction in delay time accuracy, to reduced detonator output, to complete detonator failure. Each of these malfunctions can have serious detrimental effects upon the performance and safety of a blasting operation.

Jan 1, 2006

By W. P. Blake

One of the most remarkable iron-ore districts of the world is found in Southern Utah, in Iron County, about 270 miles south of Salt Lake City, and 10 miles west of Cedar City. This region has long been known in a general way; but, being at present somewhat difficult of access, it has been rarely visited by &apos;any of our members. Professor Newberry has published somewhere a short description. Last year, by the invitation of J. R. Walker, Esq., of Salt Lake City, one of our associate members, I formed one of a party, including Professor G. W. Maynard and W. S. Keyes, to visit and inspect the region. A special car was placed at our disposal by the courtesy of Hon. John Sharp, Superintendent of the Utah Central Railway. From the present southern terminus of the road at Milford, a drive of 55 miles took us to Cedar City, about 10 miles east of the iron region. The ores outcrop in a low range of hills or mountains, and stand out in such bold relief from the general surface, and are so massive and jet black, that they may be seen for miles before they are reached. These outcrops extend in long lines over the hills, and mark very . clearly the course of the beds, conforming generally to the inclosing stratified formations, probably of Palaeozoic age. These rocks are somewhat obscure, but there are large outcrops of limestone without much alteration. This, in places, appears to be the adjoining rock, at others the wall-rocks are porphyry, and at others apparently a quartzite and a fine-grained felsite. The beds of iron-ore are from 10 to 100 feet and more in thick ness, and some of the outcrops extend unbroken continuously for 1000 feet and more. It consists chiefly of magnetite and hematite,

Jan 1, 1886

Completion of a project requires two separate money-focused activities, namely economic evaluation of the cash flows underlying the project (before financing) and if the economics look promising, how it can be financed. Economic evaluation might be best led by a person with a technical-operating background, whereas financing might be best led by an accountant. Both should be presented in simple language with easy to understand models. Economic evaluation has a sad and bad history because it evolved from the fringes of accounting. Anyone can become a self-appointed practitioner. Some still take pride in mathematical complexity without realising that they distance themselves from the decision-makers and alienate other team members. Today there is no evaluation modelling consistency across the mining industry and this reflects poorly on our discipline. It is not tolerated amongst our peers in engineering and accounting. In 2009 æbest practiceÆ economic evaluation modelling is well defined. It is:easy to follow;tailored to its purpose;transparent;discipline, rigour and consistency;recording of all source data; and hencequick to audit. Mantra: If you cannot readily understand my model you do not have a problem, I do! The task of the economic model is to make the range of business cases underlying the decision easy to understand. Intellectual power is used to simplify the decision to its key issues and risks and to present the full range of possible business outcomes in readily understood terms. Project team members, management and the board must be able to make their decisions with æeyes wide openÆ. A steering committee should be established to develop a set of standards and practices that could be adopted for economic modelling within the industry. The industry needs to purge itself of the undisciplined economic evaluation modelling that now characterises the discipline.

Jan 1, 2009

By I. E. Puddington

The property of surface tension in liquids is said to have been known to Leonardo de Vinci in about 1500. Approximately&apos;300 years later Thomas Young and others provided the ground rules relating surface tension to the wetting of solids and to the pressure drop across curved surfaces. In retrospect it seems remarkable that more than 100 additonal years were required for substantial technological use to be made of the-information. Thus super critical and freeze drying to avoid shrinkage of finely divided solids have only seen industrial use since the 1930&apos;s and doubtless additional possible applications will be equally slow in finding concurrence of conditions to make them attractive economically. The use of a second liquid phase that preferentially wets ,a suspended solid as a flocculant for that solid was pointed out in 1943 (1). Combining this phenomenon with mechanical energy to alter the morphology of the flocs or with surface chemistry to utilize it in the selective flocculation in mixed solids required more than an additional decade. A major stimulant in advancing surface energy based technology &apos;of suspensions was the report by D. I. Stock in 1952 (2) that mechanical agitation of a dry suspension of barium sulphate in benzene produced dense microspheres of the solid with highly desirable sedimentation characteristics. Investigation of this observation revealed that it resulted from small quantities of water in the system and mechanistically the phenomenon was identical with that reported in 1943.withthe addition of mechanical packing (3). Here then was a base from which to separate more efficiently suspended solids, to make small spheres from powders, to separate selected components from mixtures of finely divided solids or to break emulsions. Each of these possible branches of technology has been slow in developing on other than an experimental scale although considerable

Jan 1, 1979

By David A. Thomas, John F. Peck

Sam Leber (General Electric Refractory Metals Laboratory)—I think that the authors should differentiate between the curved grains obtained by swaging and the crumpled grains produced by drawing. This can be seen most easily in the transverse sections of Fig. 2d, and is also apparent in Fig. 2c. This difference in structure indicates that the mode of deformation shou1d affect the texture, since the cylindrical texture should be maintained or even increased by the curved grains developed by swaging. Drawing, on the other hand, crumples the grains. This should convert the cylindrical texture into a normal fiber texture. This has been substantiated by a comparison of tungsten wires fabricated by similar drawing and swaging schedules. Although cylindrical textures have been detected in drawn iron wires, they were weak in comparison to tungsten wires which included swaging as part of the fabrication process. It should also be noted that large curved surfaces developed by swaging are concentric with the surface. The postulated (100) surface of these crystals would be confirmed by a (100) cylindrical texture, as was observed in tungsten. The preservalion of the (100) cylindrical texture by swaging would maintain the <100> direction in the radial position required for easy flow. This might provide a partial explanation for the decreased rate of work hardening observed in the swaged wire. J. F. Peck and D. A. Thomas (authors&apos; reply) — The authors appreciate Dr. Leber&apos;s comments on the differences in textures, microstructures, and properties of swaged and drawn wires. The evidence of the prominence and persistence of the cylindrical texture in swaged bee wires seems quite consistent with our microstructural observations and interpretations. We are presently engaged in further work to correlate the development of texture and micro-structure in drawn bee metals.

Jan 1, 1962

By D. F. Watson, G. M. Philip

The article cited above reflects the difficulty that is often encountered in interpreting different aspects of kriging. Baafi et al. write: "Due to negative kriging weights, negative block grades may be obtained in some extreme situations, which makes no practical sense." Their solution to this particular problem is to constrain the kriged estimates to data values that have positive weights, i.e., reduce the subset size contributing to the estimation. As Journel (1986, p. 133) has already observed, "Negative weights are no evil." Indeed, they are an ineluctable result of the Lagrangian multipliers in the system of simultaneous equations. The fact that data distant from the estimation point may be given negative weights simply means that the influence of such distant values must be negated because their influence is contradictory to closer values (as illustrated by Baafi et al. in their Figs. 3 and 4). Of course negative kriging weights applied to distant grade values will not in themselves induce negative grade at some central interpolation point. Negative grade values, rather, seem to be a particular artifact of automatic methods of estimation involving accumulations (Philip and Watson, 1985a, 1985b, 1987b). The elimination of negative weights, suggested by Baafi et al., is likely to exacerbate a quite different problem of kriging and piecewise spline interpolation discussed elsewhere (Philip and Watson, 1987a). In interpolating large data sets of scattered observations, changing local subsets or neighborhoods must be selected automatically. Because of the mathematical formulation of kriging and spline interpolation, discontinuities then occur between closely-spaced estimation points as the subset used in the estimation changes. If this subset is reduced in number and size, the discontinuities will be amplified and more common.

Jan 1, 1988

MR. DICKINSON: There is an increase of dust in machine loading, especially with the McKinlay loading and cutting machine which was extremely dusty. MR. FORRESTER: Declared more dust must be expected because when loading by machinery, the coal is shot harder in order to make it easier for the machine to pick it up. He believes however, that there was less hazard because of the closer supervision possible by reason of the concentration of operation. MR. McAULIFFE: Machine loading more dusty than hand loading. D. HARRINGTON: The hazard is greatly increased by modern methods of loading. Not only do the methods increase the quantity of dust, but they also increase the rapidity of mining and the increased quantity of coal broken down causes large quantities of gas to be released. The number of motors on loading machines and conveyors add to the hazard. No more dangerous places can be found for such motors than at the working face where there is excessive quantities of pure coal dust and where there is more gas than along any other point. Regarding Mr. Herres remarks that the machine loading was safer on account of the concentration and possibility of close supervision, Mr. Harrington said he believed concentration likely to prove a source of danger rather than its preventive. At Dolomite, Alabama, a number of men had assembled, and as a result what was a relatively small explosion killed a large number of men. Concentration is not without its dangers to mine operations. MR. McAULIFFE: These arguments do not appeal to me. Few places are better sprinkled than the working places in a machine loading mine. There is. more effective supervision, and there can be more ventilation. I believe machine loading will increase safety by that very concentration that Mr. Harrington deplores.

Jan 1, 1925

By C. M. Acuna

Scarcity of high grade copper low impurity content ores is a reality and processing of low grade dirty concentrates is a need. In spite of this fact, innovative strategies have to be looked at to comply with day to day more stringent environmental regulations. From this perspective the production of matte grades over 70% in copper presents several merits, but it must be contrasted with the fractional distribution of impurities reporting to the condensed phases. Converting of white metal high in arsenic content results in moderate fraction of arsenic to gas, but high deportment to blister. Therefore, production of anode copper, as required by the electrolytic refinery, may result in several operational difficulties. Furthermore, by recycling the flue dust and slag produced in the smelting-fire refining cycle, the arsenic content in the feed to smelting increases and so does in the resulting anode copper. The Teniente Converter, as a smelting unity, has probed suitable for production of high matte grade near white metal composition but regarding distribution behaviour of impurities there is lack of reliable data, specially when processing concentrates over 1% in arsenic content. In the new scenario, i.e. low grade copper high arsenic content concentrates, to fully asses the merits of this technology the effect of matte grade, secondary materials recycling and arsenic in feed upon the distribution coefficient of arsenic between slag and matte, mainly, must be evaluated both from a theoretical approach and by use of industrial data. Based on available data correlations of distribution coefficient, matte grade and matte/slag ratios with arsenic in feed and copper content in slag are worked out. Based on these results suggestions as to matte grades facilitating to deal more efficiently with the handling of smelting byproducts are proposed.

Jan 1, 2006