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By R. M. Rose, K. A. Jones

Resistive measurements ulere made on superconducting niobium single crystals in transverse magnetic fields. Crystals were grouln in both high and ulfrahigh vacua, doped with stnall quantities of oxygen, and annealed in ultrahigh vacua at temperatures from 900' to 1350°C. Maxima in the fluxoid pinr~ir~g force were observedfor the [100] and [210] directions. The increase of the critical current density with dissoved oxygen was seen to saturate at relatively low concentration. This behavior, and the variation of J, and residual resistivity (as a function of oxygen content and annealing) of both clean and dirty gassy) crystals, is seen as a consequence of the formation of clusters with (210)~b habit planes and (200)ffo common boundaries. These suboxide clusters are apparenlly stable at high temperatures and very low oxygen concentrations. It is generally known that dissolved oxygen at concentrations well below the solubility limit sharply increases the critical current density of superconducting niobium.' Such a result would not be expected if Nb-0 solutions were random, not even as the result of segregation on the scale usually encountered in solid solutions. According to the Kim-Anderson theory of flux creep,' the critical transport current density is determined by the pinning force Fp associated with some feature of the microstructure. As the Lorentz force. a or (J X R), of the transport current in the magnetic field approaches Fp, flux creep and then flux flow occur. The pinning force is expected to be quite small if the heterogeneity involved is significantly smaller than tte range of coherency which for niobium is circa 250~.~ Although the strain field of an individual oxygen atom in the niobium lattice is relatively large, it does not seem plausible that individual atoms could be so effective as to account for the data. Also, ~ramer~ found that straining and strain aging specimens containing small amounts of oxygen on occasion decreased the residual resistivity. A possible explanation for the above behavior may be found in the work of van Ooijen and van der Goot,= who found that annealing changed J, for niobium foils containing oxygen, and they attributed the changes to ordering of the oxygen atoms. This phenomenon has been observed by other investigators using X-ray and PROCEDURE Cylindrical 4-in.-diam niobium single crystals with axial orientations [ill], [110], [112], and [oo~] were grown from pure niobium, see Table I for analysis, in an ion-pumped ultrahigh-vacuum system using the electron beam floating zone technique. Total pressure during growth was lo-'9 torr: the oxygen partial pressure was less than lo-" torr, as determined by a mass spectrometer. These crystals will be referred to as the "clean" crystals. Similar crystals were also grown in another system at a pressure of 5 X 10"6 torr. These crystals will be referred to as the "dirty" crystals. Specimens 14 in. long were cut from the as-grown crystals and one end was polished down to no. 600 carbide paper smoothness. A back-reflection Laue photograph was then taken in order to fix the crystallo-graphic directions transverse to the crystal. The critical current density J,, the current density necessary to produce a voltage drop of 1.0 pv between voltage leads placed a in. apart, was determined as a function of the magnitude and direction of the transverse magnetic field and of the oxygen concentration. The technique and experimental arrangement was essentially similar to that of Tedmon et al.' In the remainder of this paper, the azjmuthal angle $ for the field H is referenced to the [ I101 direction in all four crystals, and oxygen was added in small equal increments by anodization and annealing.7 The resistivity ratio, RR, of the resistance at room ternperature to that at 4.2"K (H =7.00 kG) was determined as well.

Jan 1, 1970

By J. G. Richardson, K. H. Coats

During the initial growth of a gas bubble in an aquifer storage reservoir the injected gas tends to override the water. The resulting low displacement efficiency and high rate of gas travel down-structure make it difficult to maintain water-free production. This paper illustrates the use of two-dimensional, two-phase calculations to simulate this gas-water displacement. Calculations were performed for a stratified aquifer and for several homogeneous sands differing in permeability, porosity and thickness. Results are discussed and compared with performance predictions obtained from the simpler Buckley-Leuerett and Dietz formulas. This comparison indicates the necessity for the two-dimensional calculations in realistically simulating the gravity override of the water by injected gas. INTRODUCTION In recent years natural gas has been stored near markets in aquifers where insufficient storage capacity is available in depleted fields. Operators of these aquifer storage reservoirs have encountered technical problems relating to the gas-water displacement accompanying initial growth of the gas bubble. Injected gas tends to override the water, with a resultant low displacement efficiency and high rate of gas travel down-structure toward spill points. Low displacement efficiency makes if difficult to sustain water-free gas production. Sometimes the fingering of gas down-structure may be so pronounced that the injection rate must be severely curtailed, which excessively lengthens the time required for bubble growth. This paper is concerned with estimating — for given aquifer characteristics and fluid properties — the displacement efficiency, rate of gas movement down-structure and rate of gravity drainage of water behind the gas front. Several published articles relate to simulative capability necessary to handle this problem. The Dietz formula1 and Buckley-Leverett2 method have some applicability to the problem; Woods and comer3 reported one-dimensional, radial calculations which accounted for the two-phase flow of gas and water. Most recent research directed toward understanding aquifer behavior in relation to gas storage has concentrated on single-phase flow in aquifer.4 Douglas, Peaceman and Rachford5 presented a method for calculating multidimensional two-phase flow in reservoirs; their method has been applied in work reported by Nielsen and Tek,6 Blair and peaceman7 and Goddin.8 Refs. 5 and 7 show comparisons between experimental data and calculations similar to those employed here. One purpose of this paper is to illustrate the use of two-dimensional, two-phase flow calculations in simulating the difficult problem of water displacement by gas in a vertical cross-section. The pronounced fluid density and viscosity differences combine with the disparity in horizontal and vertical dimensions of the cross-section to pose one of the more difficult problems in reservoir simulation. The calculations described account for capillary and gravity forces, relative permeability and reservoir heterogeneity. An example reservoir is described and calculated results are presented for a variety of injection rates and values of permeability, reservoir thickness and dip angle. A second purpose is to compare the two-dimensional calculations with results obtained from the Buckley-Leverett and Dietz formulas. For this reason most calculations were performed for a simplified example reservoir to which the latter techniques might reasonably be applied. However, the computer program employed applies equally well to cases involving arbitrary spatial variations of permeability, porosity, reservoir thickness and dip angle.

On the following pages are abstracts of papers published by the Institute during the year 1931 as Technical Publications, Preprints, and in bound volumes. For abstracts of papers that appear in bound volumes in 1931 but that were published as Technical Publications in 1930, see the Transactions, 1930. Papers that appear in the volume in which this list is printed are not abstracted here. Many of the Technical Publications have been reprinted in bound volumes. Information regarding this disposition, and number of pages in each paper, may be found in the list beginning on page 616. The abstracts are grouped as follows: Page Page Metal Mining....................... 578 ing and Metallography of Non-Milling and Concentration........... 578 ferrous Alloys)................586 IronandSteel...................... 580 Coal Division.. ................ 592 Petroleum and Gas.............. 598 Mctallurgy......................... 585 .............. 613 Institute of Metals Division (Found- Geophysical Prospecting......... 613 Metal Mining Use of Models for the Study of Mining Problems. By Philip B. Bucky. (Tech. Pub. No. 425, 12,000 words.)—This paper describes a research project undertaken to provide a means of studying the behavior of weighty structures such as mines, dams, foundations, etc., with models of the same material in the laboratory. The paper shows that in general it can be done. The underlying theory is explained, the apparatus which was developed and built to do this is described, and the results of laboratory experiments with sandstone mine structures are given. There is discussion of the accuracy of results with the present equipment, the model size necessary, and of the size and type of equipment necessary for the obtaining of results of practical value in the field. Milling and Concentration Ball Mill Studies, I. By A. W. Fahrenwald and Harold E. Lee. (Tech. Pub. No. 375. 25,000 words.)—This paper presents the results of an extensive experimental study of some of the numerous elements entering into ball mill grinding. All apparatus used was equipped with ball bearings. Every experiment was accompanied by a power measurement accurate to 0.005 hp. Quartz was used. Each element studied, such as ball load, was varied systematically. Power curves were obtained for the mill for three general sets of conditions; namely, (1) balls only (2) balls and quartz and (3) balls, quartz and water. For each general condition, power curves were obtained for various mill speeds, ball loads and ball sizes. For conditions 2 and 3, feed sizc and weight and pulp dilution also were studied as variables. The mill output, in grams of finished product per unit of time, was obtained for each test. In a general way, output (mill capacity) paralleled the power data and this attached

Jan 1, 1931

By Charles C. Russell, Glenn C. South

A primary factor in the selection of coals for making coke at high temperatures is the amount of pressure the coal will exert upon the oven walls when carbonized in modem by-product ovens.l-3 This factor has become increasingly important in recent years because of demands for increased throughput and higher coke yields. As a result of the increasing necessity for assessing coals in regard to their carbonization pressures, more and more research work is being directed toward developing labora-tory-scale tests for predicting carbonization pressures and for showing how blends of coking coals may be modified to eliminate pressures liable to damage coke-oven walls. The specific reasons have never been defined as to why some blends of coking coals develop dangerous carbonization pressures and others do not, therefore specific procedures to eliminate dangerous pressures could not be prescribed. It is true that the major processes occurring during carbonization have been described by many writers,4 and there is a general agreement on the ideas of the changes that occur as coal is transformed into coke. However, there is little evidence relating the processes occurring during carbonization to the pressure developed and the available evidence is very incomplete and often contradictory. This deficiency arises in part from the fact that the fundamental causes of pressure development have not been defined, at least from experimental data, and in turn this is the result of the lack of satisfactory testing equipment for studying the problem. Operating experience has shown several ways of reducing or eliminating dangerous pressures,5 but probably none of these ways is applicable to all blends of coking coals, and such empirical methods often lead to production of inferior coke. They are trial-and-error methods, not designed to remedy specific causes of pressure development. The number of laboratory-scale testing devices designed to estimate the carbonization pressures that result when coals are carbonized in commercial ovens is probably well over a hundred.6 Few of these instruments have remained in use for any length of time, either because the predictions were not sufficiently accurate or, more often, because too many exceptions were found. Often testing devices are operated without any attempt at duplication of conditions in commercial ovens and erroneous and contradictory results are frequently obtained. Therefore, it has seemed desirable to study the properties of coal itself and to determine any relationships between the properties of the coal and the carbonization pressures developed. Relationship between Properties of Coal and Carbonization Pressure Attempts to determine relationships between various properties of coal and carbonization pressures, for the most parti have been indirect because no satisfactory and reliable laboratory testing device has

Jan 1, 1944

By Glenn C. South, Charles C. Russell

A primary factor in the selection of coals for making coke at high temperatures is the amount of pressure the coal will exert upon the oven walls when carbonized in modem by-product ovens.l-3 This factor has become increasingly important in recent years because of demands for increased throughput and higher coke yields. As a result of the increasing necessity for assessing coals in regard to their carbonization pressures, more and more research work is being directed toward developing labora-tory-scale tests for predicting carbonization pressures and for showing how blends of coking coals may be modified to eliminate pressures liable to damage coke-oven walls. The specific reasons have never been defined as to why some blends of coking coals develop dangerous carbonization pressures and others do not, therefore specific procedures to eliminate dangerous pressures could not be prescribed. It is true that the major processes occurring during carbonization have been described by many writers,4 and there is a general agreement on the ideas of the changes that occur as coal is transformed into coke. However, there is little evidence relating the processes occurring during carbonization to the pressure developed and the available evidence is very incomplete and often contradictory. This deficiency arises in part from the fact that the fundamental causes of pressure development have not been defined, at least from experimental data, and in turn this is the result of the lack of satisfactory testing equipment for studying the problem. Operating experience has shown several ways of reducing or eliminating dangerous pressures,5 but probably none of these ways is applicable to all blends of coking coals, and such empirical methods often lead to production of inferior coke. They are trial-and-error methods, not designed to remedy specific causes of pressure development. The number of laboratory-scale testing devices designed to estimate the carbonization pressures that result when coals are carbonized in commercial ovens is probably well over a hundred.6 Few of these instruments have remained in use for any length of time, either because the predictions were not sufficiently accurate or, more often, because too many exceptions were found. Often testing devices are operated without any attempt at duplication of conditions in commercial ovens and erroneous and contradictory results are frequently obtained. Therefore, it has seemed desirable to study the properties of coal itself and to determine any relationships between the properties of the coal and the carbonization pressures developed. Relationship between Properties of Coal and Carbonization Pressure Attempts to determine relationships between various properties of coal and carbonization pressures, for the most parti have been indirect because no satisfactory and reliable laboratory testing device has

Jan 1, 1944

By George D. Graffin.

The first use of graphite is lost in the mists of time. It was used by primitive man to make drawings on the walls of caves and by the Egyptians to decorate pottery. As early as 1400 A.D. graphite crucibles were being made in the Haffnerzell district of Bavaria. Through the Middle Ages graphite was confused with other minerals, especially galena and molybdenite. Two common names that are still used for the mineral are "Plumbago," meaning leadlike, and "Black Lead." The latter name implied that graphite is either composed of lead or at least contains a large percentage of it. Gessner is credited with having recognized it as a separate mineral in 1565, but its composition was not determined until 1779, when Scheele demonstrated that graphite oxidized to carbon dioxide, thus proving its carbon constitution. In 1789, Werner named it "graphite" from the Greek word "graphein," meaning to write. The United States has long relied on foreign countries for its graphite supplies. This reliance has been due more to the lack of suitable domestic graphites than to any particular preference for buying minerals overseas. Ceylon (now Sri Lanka) graphites were imported as early as 1820, and Madagascar graphites have been imported since the properties on that island were opened up about a hundred years later. Mexico has long supplied the United States with most of its requirements for amorphous graphite. Physical Properties and Classification Graphite is found in laminated, flaky aggregates disseminated in schistose rocks. It also occurs in veins and exhibits a foliated or fibrous structure. Graphite is a black lustrous mineral that crystallizes in the hexagonal system, with rhombohedral symmetry. The crystals have tabular form and are six-sided; the faces are commonly striated. The flakes have perfect basal cleavage and are opaque. When well crystallized, the flakes have a black metallic luster while the amorphous material is black and earthy, with a microcrystalline compactness. The flakes feel greasy. Graphite is an excellent conductor of heat and electricity. It melts at approximately 3550°C at a triple point under 1250 psi. It sublimes between 3300-3500°C at 14.7 psi. At 3726°C a second triple point occurs at approximately 100,000 atmospheres. Thermal oxidation in the presence of oxygen begins at 300°C and the rate increases with temperature. The three forms of carbon (charcoal, graphite, and diamond) are distinguished by chemical and physical tests. The specific gravity of charcoal is 1.3 to 1.9, of graphite 2.266 g/ cm3 (crystal density), and of diamond 3.5. Graphite has a hardness of 1 to 2 (Mohs' scale). Natural graphite can be divided into three classes: disseminated flake, crystalline vein (fibrous or columnar), and amorphous. Flake graphite is a lamellar form found in metamorphic rocks, such as marble, gneiss, and schist. Each flake is separate, having crystallized as such in the rock. Crystalline vein graphite is found in the form of well defined veins or as pocket accumulations along the intrusive contacts of pegmatites with limestones. The graphite of such deposits is of two types, foliated and columnar. The important Sri Lanka (Ceylon) deposits are vein type. Amorphous graphite is commonly found as minute microcrystalline particles more or less uniformly distributed in feebly metamorphic rocks, such as slates and shales, or in beds consisting practically entirely of graphite. The latter usually are metamorphosed coal seams and carry as much as 80-85% graphitic carbon, while the former, being altered carbonaceous sediments, commonly range from 25 to 60%

Jan 1, 1983

By John H. Walthall, Raymond L. Copson, Travis P. Hignett

In October 1942, the War Production Board requested the Tennessee Valley Authority to undertake investigations to determine the feasibility of producing alumina suitable for reduction in aluminum cells, from clays and other domestic materials, by a lime-sintering, soda-ash leaching process. The work was undertaken by the chemical engineering staff of the Authority under the general direction of the War Metallurgy Committee of the National Academy of Sciences. The investigation included small-scale tests to determine the most suitable conditions for the process, and construction and operation of a pilot plant to obtain data for evaluation of the process and for design of a plant. The results of this investigation are described in the present paper. Sources of Alumina Alumina for the commercial production of aluminum is obtained from bauxite by the Bayer process. The tremendous demand for aluminum for wartime uses is causing rapid exhaustion of the high-grade bauxite deposits in the United States. On the other hand, there is an abundance of aluminous materials such as clay and lower grades of bauxite, which are not suitable for treatment by the Bayer process because of their high silica content. The Tennessee Valley Authority has conducted research and pilot-plant work for more than 5 years on methods for the production of alumina from clay and low-grade bauxite. Particular attention has been given to the high-grade white kaolin found in Carroll County, Tennessee. Exploratory drilling has demonstrated that at least 4 1/2 million tons of kaolin containing in excess of 34 per cent AlzOI is available in this area by strip-mining methods. It has been estimated that hundreds of millions of tons of clay of similar quality occur in the Tennessee Valley region. The Process The process is illustrated in the flowsheet (Fig. I), and consists essentially of the following steps: I. Heating a mixture of clay and limestone to form a sinter containing calcium aluminate and dicalcium silicate. z. Leaching this sinter with a dilute sodium carbonate solution, to form a sodium aluminate solution and a calcium carbonate, calcium silicate residue, which is discarded. 3. Treating the sodium aluminate solution with carbon dioxide to precipitate aluminum trihydrate and regenerate the sodium carbonate solution, which is recycled. 4. Heating the aluminum trihydrate to produce alumina. The process was considered promising because of the abundance and cheapness of the two raw materials, clay and limestone; and because, as compared with an acid process, smaller amounts of critical

Jan 1, 1944

By A. J. McEvily, R. C. Boettner, C. Laird

The processes leading to fatigue failure in the low-cycle range were studied to obtain an understanding of the basis of Coffin's law. Particular attention was paid to the manner of mack nucleation and to the determination of the portion of the total lifetime spent in crack propagation. It was observed that cracks are nucleated at surface notches meated during reversed plastic deformation, Principally at grain boundaries, and that crack growth occupies greater than 75 pct of the fatigue life. When inclusions are present, they are often the primary sites of crack initiation. From consideration of the incremental distances advanced by a crack in each cycle and of the lifetimes of different materials, it appears that the universality of Coffin's law arises from the similarity of crack-tip strain for a given applied strain amplitude, irrespecti7:e of material. STUDIES of low-cycle fatigue have been particularly rewarding in that a simple correlation between fatigue lifetime and plastic-strain range has been shown to exist. This empirical relationship takes the forml,2 Nner=C [1] where N is the number of cycles to failure, Er is the plastic-strain range defined as the total plastic strain per cycle (the sum of the tensile plastic strain plus the compressive plastic strain), n, the exponent, is a constant independent of the material to a first-order approximation and often has a value of about 0.5, and C is a constant which for a number of ductile and metallurgically stable materials is approximately 0.65 for fully reversed strain.3 This relationship has been shown to be valid for a wide variety of metals and alloys and is often referred to as Coffin's law. However, it is yet not clear why so many different metals and alloys exhibit the same over-all behavior in the low-cycle range. Less is known about the mechanisms of fatigue failure in the low-cycle range than in the high-cycle range, but it is expected that the processes would have much in common. For example, an important characteristic common to both high-and low-cycle ranges is that fatigue crack propagation can occupy a considerable portion of the total lifetime. This has been shown by Laird and smith4 by a count of the number of ripples present on the fracture surface of copper specimens, each ripple corresponding to one cycle of load. On the other hand, some marked differences have been noted. For example, in copper,5 nickel, and aluminum4 there is a greater tendency for grain boundary cracking to occur as the strain amplitude is increased. The purpose of the present work was to study further the processes leading to fatigue failure in the low-cycle range and to obtain an understanding of the basis for the validity of Coffin's law. Particular attention has been paid to the manner of crack initiation and to the determination of the portion of total lifetime spent in crack propagation. MATERIALS A number of metals and alloys were tested, although more attention was focused on a particular few, once general trends had become apparent. Alloys were selected so as to investigate the effects of crystal structure, number of phases, stacking-fault energy, and impurity content. The materials in this grouping were: high-purity copper OFHC copper 1100 aluminum (commercially pure) 70-30 brass (Cu-30 wt pct Zn)

Jan 1, 1965

By Harrison R. Cooper

The key to concentrator automation is practical means for obtaining continuous assay data from concentrator streams. The technique most successfully used is x-ray fluorescence analysis. The practical reality of on-stream x-ray analysis has been achieved through effort over the past twenty years, marked by an occasional breakthrough, but more typically a step-by-step development to which many individuals and organizations have contributed. The net result of this progress is the present capability to install on-stream x-ray analyzer systems on a turn-key basis. It is now possible to provide all components of an x-ray analysis system as a completely engineered unit which can be put into immediate use, minimizing needs for specialized application knowledge to benefit from continuous assaying in process control. The economic factors which influence the choice of system and limitations of the x-ray fluorescence technique for slurry analysis are reviewed.

Jan 1, 1976

By W. J. Reagan

THE problem of increasing output and decreasing percentage of rejections is a vital one in the manufacture of steel of any kind. The making of basic open-hearth steel for use in rolled steel wheels, tires for locomotive and car wheels, and forgings of various kinds, is a highly specialized industry. The increase in weight of railway rolling stock of all kinds, and the high speed that the public demands of transportation facilities, make it imperative that steel for use in this class of material shall be of the highest quality obtainable. During the past few years it has been the writer's good fortune to have opportunity-to study the defects in basic open-hearth steel, and also the results obtained by various changes in open-hearth practice, on such defects. The opportunity for study and the details available are rarely found in the manufacture of steel of any kind. It seems reasonable to assume that many of the results determined here can be applied to the production of steel of other types with a decided improvement in quality, a decrease in the percentage of rejections and an increase in output. All of the material described is basic open-hearth steel with the following range of analysis: carbon, 0.50 to 0.85 per cent.; phosphorus and sulfur, 0.04 coax.; silicon, 0.15 to 0.35; manganese, 0.50 to 0.75. All of this material is bottom-cast, therefore tapping and pouring temperatures are higher than in top-cast production. Ingots used in this type of work are of standard length with varying diameters. The ingot is known as duodecagonal, or twelve-sided. The standard body length is 88 in. and the hot top length, 14 in. Fig. 1 shows a typical ingot of this type. The diameter varies from 13 to 30 in. Ingots for special forgings, which cannot be made in molds of standard size, are made in molds of various sizes and designs. These ingots are sliced cold, into blocks of various lengths, depending upon the weight of the forging to be made. Fig. 2 shows the ingot-after coming from the slicing lathe. Just sufficient metal remains between blocks to hold the ingot in one piece while it is being removed from the lathe; then steel wedges are inserted between the blocks and the blocks are broken apart. This affords abundant opportunity for inspection, as the interior of the

Jan 1, 1930

[NUMERICAL CODE TO MAPS (Region Listed in Roman Numerals after Each Petroleum Section) 1 Alaska 2 Arizona 3 Black Hills 4 Boston 5 Carlsbad Potash 6 Central Appalachia 7 Chicago 8 Cleveland 9 Colorado 10 Columbia 11 Connecticut 12 Delta (VIII) 13 Detroit 14 East Texas (VI) 15 El Paso 16 Gulf Coast (VII) 17 Kansas (IX) 18 Lehigh Volley 19 Mid-Continent (IX) 20 Minnesota 21 Montana 22 Nevada 23 New York]

Jan 1, 1961

By R. E. Old

THROUGH the use of pressure and production records, formation properties and bottom-hole sample data, the performance of an oil reservoir may be studied analytically to define and evaluate the natural forces acting on and within the reservoir. Use is made of material-balance methods and the equations for natural water encroachment to estimate reserves. Methods for calculation of pressures are given. A study of the Jones sand, Schuler field, Arkansas, has been made and is given here to illustrate the value of the methods discussed.

Jan 1, 1942

By W. H. Yarroll

This paper presents a general discussion of the utility of the statistical technique known as multiple correlation, and gives three specific examples of its application. The first demonstrates the most simple form, or straight-line, multiple correlation. The other two demonstrate multiple correlation analysis in best-fitting third-degree parabolas. With the increasing availability of digital computers, the method becomes entirely feasible where heretofore its use was impractical. The advantages of the method are discussed, and curves are presented which were developed by computerizing the regression equations developed in the examples. The method described in this paper is for use with complex systems, and the examples given are complex metallurgical systems. This subject falls under the general classification of cybernetics, which is defined' as "the science of control and communication, in the animal and the machine." Machine, in this case, can include chemical and physical processes which take place within machines and processing equipment of all kinds. The classical approach to scientific investigation has been the construction of simple models and the changing of variables one at a time. This method is wholly inadequate for obtaining useful information from the complex systems of modern technology including many of our flotation and hydrometallurgical processes. Cybernetics offers the method by which complex systems which have been implemented as an art in the past can now be analyzed with all the discipline of a science. Mathematical techniques for achieving multiple correlation analysis have decided advantages over some of the other statistical methods.2-4 Multiple correlation does not require a series of experiments that have been rigidly planned as do many of the other statistical methods. For this reason, it can be used effectively for interpretation of information from op- erating plants, where planned experiments are impractical, as well as for laboratory experiments. First-degree multiple correlation has been used for many years, and was useful, but limited to linear or nearly linear relationships. The technique described in this paper provides a method for analyzing systems which may be non-linear. This particular technique is multiple correlation analysis in best-fitting third-degree parabolas. It is quite possible that lack of reference to the technique has been due to the overwhelming mass of computations it requires even for relatively simple problems. With the advent of computers, however, its use has become entirely feasible. For the benefit of those who may not be familiar with the subject, it might be well to pause at this point to discuss multiple correlation analysis — what it is and what it achieves. To go back to the old familiar fitting of a set of points with a best-fitting straight line by the least squares procedure, it is conceded that this a good method where there is only one independent variable influencing the dependent variable under consideration, and providing that the relationship is linear. In most fields of investigation, however, there are usually a number of factors exerting important influence, and they frequently bear relationships with the dependent variable other than straight line. Under these conditions, it is easy to see how misleading a simple correlation study might be. Multiple correlation can be used for any number of variables. Within the experience of the writer, this technique has been used to establish regression equations for determination of carbon rate, burden permeability, and production rate on iron blast furnaces, production rate on open hearth steel furnaces, life of molds for steel ingots, rolled steel tensile strength and various defects in rolled products, the performance of ore dressing equipment, and optimization of extractive metallurgical process variables. The discovery of mathematical correlation does not prove, per se, true cause-and-effect relationship, but simply establishes a hypothesis. If the regression equation can be used to make successful predictions of what will happen with future arrays of independent variables, then one can feel reasonably assured that true cause-and-effect relationships have been discovered.

Jan 1, 1968

By R. J. Piros, Brusenback, D. A. Dahlstrom

DEWATERING fine coal has been a serious problem to many operators who desired to wet-wash finer sizes and maintain high recovery. Centrifugal driers have become popular for this purpose for sizes between 3/8 in. and 14 mesh. Below 14 mesh the perforated screen centrifuges lose a large per- cent in the effluent solid bowl types that do retain -14 mesh coal, produce excessive degradation, tend to retain the highest ash fraction in any size fraction, and are subject to abrasion, which results in higher maintenance. In 1949 Truax-Traer Coal Co. planned a cyclone installation at their Ceredo preparation plant to recover coal down to 150 mesh with approximately a 14-mesh top size. Since available centrifugal equipment was not considered satisfactory, an investigation of rotary vacuum filters was begun in cooperation with the Peterson Filters and Engineering Co. to determine the suitability of the Peterson Top Feed Reservoir (TFR) filter. This investigation, which is described below, has resulted in a highly satisfactory installation of two 6x10-in. Peterson TFR filters that have been in operation over a year. After some preliminary laboratory batch vacuum filter tests, a pilot plant double-drum Peterson TFR filter was installed at Ceredo to prove the feasibility of vacuum filtration and determine optimum conditions. The full scale units were then installed on the basis of the pilot plant results. This was followed by an extensive research program on vacuum filtration in the laboratory at Northwestern University to investigate basic design and operating variables and their influence on final moisture con- tent of the filter cake. A method of scale-up from laboratory batch tests to the full-size unit was also proposed and proved. Because of the importance of dewatering fine coal today, it was felt that the results of the three steps should be made available for the use of others facing this problem. The work at Northwestern is given in a theoretical section following the discussion of the pilot plant and full- scale operation. Fig. 1 is a flow diagram of the cyclone and filter installation. The feed is drawn from below the

Jan 1, 1952

By Ford R. Bryan, Edward F. Runge

BECAUSE of the need for ductile heat resistant alloys of non-strategic composition, there has been metallurgical development of Fe-A1 alloys possessing improved ductility and hot strength, together with high oxidation resistance. Iron and alu- minum form solid solutions up to approximately 35 pct Al. Alloys in the 8 to 12 pct A1 range are characterized by excellent oxidation resistance, high electrical resistivity' and, when appropriately alloyed, have creep rupture strength equivalent to that of the austenitic stainless steels.' At higher aluminum levels, the magnetic properties are of considerable interest. Nachman and Buehler" have recently reported on the desirable magnetic characteristics of the 16 pct alloy.

Jan 1, 1957

By Hans Lundberg

IN ORDER to comprehend the help and information that may be expected from electrical prospecting, it is necessary to have at least a general knowledge of the methods and principles involved in preparing and interpreting results obtained in the field. Electrical prospecting is rather complicated, both in theory and practice, and in order to make a brief description clear to the practical mining man it has been necessary to idealize and generalize the problems, at the risk of having such simplification criticized by the theoretical man. This simplification must not be misinterpreted as showing a lack of theoretical knowledge. FIG. 1.-FLOW OF CURRENT IN AND AROUND A CONDUCTING BODY. For its operation, electrical prospecting mainly, depends on the fact that most metallic ores conduct an electric current much more readily than barren rocks. If an electric current flows through a block of ground within which a body of chalcopyrite is enclosed in country rock of. schist, the current will find less resistance to its passage through the chalcopyrite than through the schist, even though the passage through the latter be much shorter. This is because the longer path through the chalcopyrite offers less resistance, owing to the superior electrical conductivity of the chalcopyrite (Fig. 1).

Jan 1, 1928

By H. M. Day

THE constitution of the system silver-mercury has attracted the attention of many investigators during the last two decades, but since their results are for the most part in poor agreement, there is little need for a review of their individual contributions. It remained for the very careful thermal and microscopic investigation of Murphy1 in 1931 to give the constitutional diagram in its present and unquestioned form, which is shown in Fig. 1. He devised methods for taking cooling curves on alloys under high pressures and for the microscopic observation of alloys which contained liquid mercury as a structural constituent at ordinary temperatures. The compositions of the intermediate phases were con-firmed and supplemented through X-ray analyses by Preston and Stenbeck.3 According to Murphy, at 276° C. silver is able to dissolve 44 to 45 weight per cent of mercury, which may increase at lower tempera-tures to about 50 per cent. Preston concluded that the saturation boundary occurred at 46 ± 2 per cent at 100° C. From the values reported in the literature, these are the only ones that may be accepted as lying even in the right region.

Jan 1, 1938

THE. extraordinary volume of work done in this period, and the multiplicity of subject matter, make a year-by-year historical account undesirable, if the account is not to be an assembly of unrelated fragments. We shall, instead, undertake to narrate the development in this period of each of the branches of the subject separately, hoping that their interrelations will be self-evident. There is a certain arbitrariness in the selection of subject matter in the following sections. The development of important engineering alloys-for example, high-speed steel-is disregarded, for it is the primary purpose of this account to relate the advances in ideas, the growth of the science of metals; other historical accounts relate these parallel advances. Nor are advances in techniques stressed, though occasionally the most important are noted; nor is the progress described in allied fields such as welding, cutting, etc.; for though these developments have very frequently made possible the advances herein related, they are far too numerous to recount in anything short of a ponderous volume. There is a more serious arbitrariness, however; it is not an easy matter to draw the boundaries of physical metallurgy, and some contiguous subjects have been omitted that perhaps should have been included, such as, for example, corrosion, gases in metals, the magnetic behavior of metals and alloys, and certain other fields in the physics of metals. REACTIONS IN ALLOYS--DIFFUSION Many of the reactions occurring in alloys proceed by the operation of the process of diffusion in the solid state: the annealing of mixed powders to form alloys, the homogenization of castings or forgings, the freezing of alloys, the treatment of clad metals, the loss

Jan 1, 1948

By Stephen Krickovic

THERE is today no proven continuous mining machine that can be used under all the varying conditions found in most bituminous coal mines. During the last five years, however, both the machines and methods of using them have been improved. Coal operators can now exercise a fair degree of selectivity, except those who must struggle with thick and hard partings and operate in seams less than 40 in. thick. It must be realized, then, that more than one type of continuous miner may be used advantageously in the same coal mine. Although this appears to violate the standardization generally sought after, the gain can more than offset added maintenance and, to a lesser degree, operating problems. It is equally important to realize that most coal mines will require one or more conventional loader setups in the plan of total mechanization. Seam variations, adverse physical conditions, and special designs of main headings for haulage and ventilation, to name only three reasons, may render 100 pct use of continuous miners uneconomical. Of course, this situation may change. In one mine, prior to 1954, machines that ripped coal from the face achieved only average results, as compared to the impressive performance of boring-type units in another coal mine. A boring-type unit was therefore selected for the first mine in the belief that the chance of success would be greater if it were used in a combined cutting and wedging operation, cutting a full face in its forward movement. The miner was located in a part of the mine where a special projection could be readily developed, a solid area scheduled for mining according to the overall progress plan. All openings surrounding the particular area were carefully investigated for the presence of sulfur balls. Fig. 1 (opposite) shows the representative seam section, containing the several pyritic bands 1/4 to 1/2 in. thick; a characteristic Pittsburgh seam parting averaging 5 to 6 in. of slate, coal, and slate; and the occasional py-rite lenses 2 to 3 in. thick. Under normal conventional mining methods, the top 10 or 12 in. and the bottom 4 in. are left in place to offer roof protection

Jan 1, 1958

By Dr. O’Neil Thomas J., Donald W. Gentry

Pure gold was hidden in the quartz, they said, 'Twas proved by dreams and signs, and rods divining, By chemic tests, and spirits of the dead, In fact by everything-except by mining. " from R.E. White, "The Mining Town," Alta California, August 18,1873 Textbooks in mining engineering have traditionally covered ore reserve estimation and mine valuation in a single volume. Indeed, Examination and Valuation of Mineral Property by R. D. Parks (1957), having been the standard of the profession for over 20 years, is a classic example. However, the state of knowledge in these two fields has grown tremendously. Most mining engineering curricula now cover these topics in separate courses, and in practice, these tasks are usually performed by different individuals. Thus, this trend now suggests the need for separate, specialized publications rather than a single volume for both topics. Because of the separate development of the science of ore reserve estimation, it is important to state at the beginning what this chapter does not cover. It does not address in detail the design of sampling programs, sampling methods, or the processing of samples or sample data compilation. There are a number of suitable references available on these topics, including Peters (1978), Gy (1979), as well as the previously cited book by Parks. Furthermore, this chapter does not cover in any substantial detail either the traditional methods for using sample data to calculate ore reserves or the more recently developed geostatistical methods. The traditional methods are thoroughly covered by Popoff (1966) and more concisely by Barnes (1980). Among the more useful references for statistical applications in ore reserve estimation are Barnes (1980), David (1977), and Clark (1979). A thoughtful review of the entire science and art of ore reserve estimation is provided by King, McMahon, and Bujtor (1982). In spite of the fact that expansion of knowledge now calls for separate books on ore reserve estimation and financial evaluation, neither publication can ignore the important interrelationships between the two fields. In regard to this text, the unique and crucial role of ore reserves can not be omitted entirely; however, the field is now simply too extensive to treat here in any comprehensive manner.

Jan 1, 1984