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By R. B. Mears, E. H. Dix, R. H. Brown

In the Institute of Metals Division Lecture of 1940, E. H. Dix, J~.(I)~ discussed the acceleration of the rate of corrosion by high constant stresses. Experimental data obtained on this subject at the Aluminum Research Laboratories and a theory compatible with these facts were included in that lecture. The present paper contains data and ideas subsequently developed at the Aluminum Research Laboratories. Dix pointed out that in order for acceleration of corrosion by constant stress to occur: (1) There must exist in the alloy a susceptibility to selective corrosion along more or less continuous paths, as for in- stance at grain boundaries, and (2) There must exist a condition of high stress acting in a direction tending to pull the metal apart along these continuous paths. Acceleration of corrosion rate by stress is not confined to any one alloy system. Table I lists some of the metals and alloys and some of the corroding environments in which acceleration of corrosion by stress was sufficient to cause cracking (stress- corrosion cracking). It will be noted that the variety of alloys in which stress-corrosion cracking has occurred is rather large. Also, it will be observed that

Jan 1, 1945

By C. A. Hartnagel, D. H. Newland

Most of the petroleum produced in New York State is obtained by flooding; that is, water drive. No important oil fields have been developed during the past 30 years, nor does there seem much hope that the productive oil areas will be substantially enlarged in the future. There is some prospect that additional supplies may be obtained by deeper drilling, but deep tests for gas to the Oriskany sandstone in some of the oil-producing areas have been without results so far as any discoveries of oil are concerned. Although the flooding method had been made legal in 1919, and some floods had been in operation previous to 1921, that year marks the beginning of a rapid increase in oil production by the new method. The flush production of oil in New York was in 1882, shortly after the discovery of the Richburg pool in Allegany County. The oil production in that year amounted to 6,685,000 bbl. The 1937 production of 5,478,000 bbl. was the largest since the flush production of 55 years ago. The effectiveness of water-flooding for increasing oil production from the old New York fields is shown in Table 1. Table 1.—Production of Oil in New York since 1921 Year Barrels Year Barrela 1921 988,000 1929 3,377,000 1922 1,000,000 1930 3,647,000 1923 1,250,000 1931 3,363,000 1924 1,440,000 1932 3,508,000 1925 1,695,000 1933 3,181,000 1926 2,242,000 1934 3,804,000 1927 2,603,000 1935 4,236,000 1928 3,377,000 1936 4,633,000 1937 5,478,000 The area of the New York oil fields is about 60,000 acres. It has been estimated that not over one-fourth of the area is being flooded. Very little of flooded territory has ceased to produce. Some leases flooded by the early, less scientific methods are being again subjected to the water

Jan 1, 1938

By Bezalel C. Haimson

We have developed a new wireline hydrofracturing technique for in situ stress measurement which eliminates the need for drill rig and drill rod and renders the tripping of the straddle or impression packers continuous, fast, and inexpensive. Wireline conductors facilitate the use of downhole pressure transducers. We have confirmed the suitability of the new technique by testing it in a deep hole near the Monticello Reservoir, South Carolina. Our measurements indicate two local stress fields, one of them apparently linked to the impoundment-related induced seismicity.

Jan 1, 1984

By J. L. Zakin, G. K. Patterson, J. M. Rodriguez

Correlation has been obtained between drag-reducing characteristics for turbulent flow in a pipe and measurable properties of several polymer solutions. Several concentrations of high molecular weight polymethyl methacrylate in toluene, high molecular weight polyisobutylene in both toluene and cyclohexane, medium molecular weight polyisobutylene in cyclohexane and benzene and low molecular weight polystyrene in toluene were studied. Data obtained in these nonpolar solvents and literature data for more polar solvents were successfully correlated as the ratio of measured friction factor to purely viscous friction factor vs the modified Deborah number vrl/D0.2 where 71 is the first-mode relaxation time of the solution estimated by the Zimm theory. A shift factor which is a function of intrinsic viscosity 1/(4[?] - 1) allowed all the data obtained with nonpolar solvents to be correlated as a single function. For these systems, most of the data fit a single curve to within + 5 percent of the average friction factor ratio. The shift factor did not give a unique function of the data for the more polar systems. INTRODUCTION The phenomenon of drag reduction in polymer solutions was first studied by Toms1 in dilute solutions of polymethyl methacrylate in mono-chlorobenzene. The drag ratio for flow through circular tubes has been defined2 as the ratio of the pressure. drop of the solution to the pressure drop of the solvent at the same flow rate. The drag ratio is less than 1.0 for a drag-reducing fluid. Practical use of drag reduction is being made in fracturing operations in the petroleum industry.3 A more fundamental quantity is the friction factor ratio, defined as the ratio of the observed pressure drop to that predicted for a solution of the same viscosity characteristics and density at equal flow rates using the Dodge-Metzner friction factor equation4 Viscous solutions with drag ratios greater than 1.0 can have friction factor ratios less than 1.0. For practical applications, it is drag reduction which is of interest. However, for correlation the fundamental ratio is the friction factor ratio. In recent years, drag reduction has been studied extensively. Recent studies have shown that reasonable predictions of the incipience of drag reduction in polymer solutions can be made from the properties of the solutions and the flow Variables.5 However, it has not been possible to predict accurately the amount of drag reduction to be expected for a given polymer solution without any drag-reducing turbulent flow data on the same solution.6 For flow through circular tubes it is well established that there is a concentration effect and a diameter effect on drag reduction. Toms1 observed that drag reduction increases with an increase in the concentration of the solution up to an optimum concentration beyond which, due to the increased viscosity of the solutions, the drag ratio increased with an increase in concentration. Hershey 7 observed that for dilute Newtonian polymer solutions in nonpolar hydrocarbon solvents, a normal transition region may be obtained followed by a departure from the von Karman equation (on a friction factor-generalized Reynolds number chart). The point of departure is a function of diameter: the smaller tubes depart at the lower Reynolds numbers. Concentrated solutions may show no abrupt transition region, but merely an

By G. R. M. Del Giudice, A. F. Taggart, Othon A. Ziehl

In a previous paper1 in which one of the authors collaborated, it was postulated that All dissolved reagents which, in flotation pulps, either by action on the to-be-floated or on the not-to-be-floated particles affect their floatability, junction by reason of chemical reactions of well recognized types between the reagent and the particle affected. This generalization, apparently, like many pioneer structures, had for certain observers a flimsy appearance, and these, judging its stability rather by the number than by the character of its foundation posts, have attempted variously to overthrow it, either by the frontal attack of general denial, or by the flanking movement involved in assuming that those cases in which the facts were unknown or unproved were, therefore, discordant. But as time has passed and further evidence on the question has accumulated, it has become apparent that the results of verifiable experiments add stone by stone to the substructure of the hypothesis, and that the super-tructure has lost nothing in weathering. The present paper constitutes an examination of the opposing positions in the light of the more recent evidence developed. It will clarify the discussion if, at this point, we state more fully the implications of the disputed hypothesis. In the first place, it is explicitly limited to reagents that are dissolved in the water of the flotation pulp. Next, it refers only to such of these dissolved reagents as act on the solid particles in the pulp to affect their floatability. This includes the collectors, activators, and certain depressors and gangue-control reagrnts, but not the pure frothers, and not, necessarily, conditioners whose function seems to be merely that of pH control, although in certain cases it has been demonstrated that such control has the effect of regulating the primary reaction of the collector, depressor, or the like. Finally, there is no limitation as to the nature of the chemical reaction postulated.

Jan 1, 1935

By John V. Beall

AMONG electrical manufacturers, interest in the outlook for copper supplies has not diminished despite signs of a healthier market following price decontrol. Reason: Electrical utility industry output is expected to grow at an average annual rate of 6 pct for the next 15 years. A more graphic description of the growth ahead is given in the Eighth Quarterly Report of the Director of Defense Mobilization as follows: "Power generating capability, which amounted to 63 million kw at the time of Korea, now stands at more than 81 million. The established goal for installed capability at the end of 1955 is 116 million kw. Orders already on the books of power equipment manufacturers, if fulfilled on schedule, will bring installed capability to over 123 million kw by the end of 1956-and more orders for equipment are yet to come." These statistics portend an impressive requirement for copper, not only for power plants and distribution lines themselves but for the multitude of industry and domestic end-uses.

Jan 4, 1953

By Robert F. Winkle

A detailed breakdown of mining costs, available to management on monthly and year-to-date bases, is mandatory for a controlled and efficient mining operation. A simple lump sum reporting of costs may indicate a profit or loss differential, but it does not allow an effective search for areas of possible cost reduction. Moreover, functional reporting is necessary on a timely basis so as to note trends of increasing costs In specific areas, which in turn allow possible preventive action by management. Definitive cost information helps to eliminate the tendency to overlook areas where cost Improvements can be made. A good cost control system points out salient operational weaknesses by: ( 1 ) allowing comparison of functional costs with similar costs of other mines and (2) pinpointing sudden increases over unit empirical costs within the organization. In general, the cost accounting structure is relatively uniform within large open pit mines, but surprisingly some systems will overlook the need for detailed breakout in comparatively high cost areas. In some other systems, unrelated costs will be lumped together, preventing careful analysis of cost accrual.

Jan 1, 1979

FIRE tubes are commonly made in order to frighten horses or to harm enemy soldiers, but although fire issues from them, they do not cause much damage because they cannot be used at a distance. If you wish to use them, you are not able to approach close to the enemy, for if there is anyone who is afraid, he does not let you approach nor does he come near you until he sees that they have finished burning. Thus, in short, the assault with this is one that is seen beforehand, and for which there is always time to decide on some action in defense. It is indeed true that they are beautiful things to see and when the name tubes of fire is heard it terrifies those who do not have a defense ready. When four, six, or indeed ten or twelve of these are put in the hands of as many courageous and united men, they are surely good in forcing passage on a guarded bridge, or in entering or holding a gate, road, or other narrow place. They serve also for setting fire to dwellings or the enemy's supplies,

Jan 1, 1942

By K. H. Coats

This paper describes an approximate technique for handling the problem of percolation of evolved gas upwards through the oil column in computer simulation of natural depletion. This technique has been incorporated into a general model for simulating three-phase flow in one, two or three dimensions. The mathematical model for perfonning these calculations is described in detail in a separate article. 1 While vertical gas percolation occurs during natural depletion in a reservoir of any configuration, it is especially pronounced in the pinnacle reel or bioherm. The reel may have an areal extent less than one section with a thickness of up to 800 It. The upward percolation of evolved gas often limits the time step in calculations as little as one day. Using this small time step, computer expense for a single 30- to 40-year simulation on even a one-dimensional basis has exceeded 92,000. The method described here for handling the percolation allows time steps of 60 days or more (depending on reservoir size and production rate), resulting in a considerable reduction in computing expense. The method also allows calculations in which secondary gas caps build up in tight zones of the oil column below the main gas cap. The validity of the method is indicated in connection with an example pinnacle reef field. Calculated results using a 2-day time step (where the method in question is not needed and not invoked) are compared with results using the method and a 60-day time step. The comparison shows good agreement. Results from one- and two-dimensional simulations of the reef are presented along with the corresponding computing times on the CDC 6600 computer. A three-dimensional simulation was also performed and the required computing time is given. INTRODUCTION A general analysis for simulating three-dimensional, three-phase flow in reservoirs has been developed. 1 In applying this model to reservoirs undergoing natural depletion, a time-step restriction was encountered due to the flow of evolved gas upwards through the oil column and toward the gas cap. A remedy for this problem has been incorporated in the analysis and is described here. The time-step restriction is encountered only in calculations which include flow in the vertical or near vertical direction. The restriction occurs to some extent in reservoirs of any geometrical configuration, but it is especially pronounced in the pinnacle reef or bioherm where the ratio of thickness to areal extent is unusually large. This paper describes the problem, a method of handling it, incorporation of the method in the three-dimensional, three-phase model, and, finally, a test of the method's validity in an application to an example pinnacle reef reservoir. THE PROBLEM During the early stages of reservoir depletion, pressure falls below bubble point in progressively lower regions of the oil column. Continuing production results in evolution of dissoived gas throughout the oil column. This gas then percolates upwards toward the top of the reservoir. If the gas encounters a sufficiently low permeability zone in its travel upward, then it can accumulate and form a secondary gas cap. If no zones are encountered which are tight enough to hold gas against the gravity forces, then the gas travels on until it reaches the top of the sand or the main gas cap. Numerical simulation of multiphase flow in reservoirs is generally performed with time steps such that the flow of a fluid into or out of a block in one time step is a fraction (considerably less than one) of the total amount of that fluid present in the block. Use of a time step where the time step's

Jan 1, 1969

By T. E. Brower

SHORTLY after our previous paper on this subject was printed,1 we located a source of uncertainty in the results arising from the unexpected fact that hydrogen slowly reduces silica at 1100° C. in presence of iron, even when the iron nowhere touches the silica, although in absence of iron it does not do so. This difficulty has been completely obviated by the use of a small high-frequency furnace, which enables us to heat the specimen for analysis without raising the temperature of the silica vessel to a point at which any appreciable reduction of the silica glass occurs. We now describe this modification of procedure, and present some typical results obtained with it. For any given specimen of steel, the results are entirely definite and. reproducible, but their precise significance is still open to some question, as indeed is true of all methods of oxygen determination so far developed. Further elucidation of this question is to be expected from the cooperative comparison of the several methods now under way under the auspices of the Bureau of Standards at the instance of the Iron and Steel Division of the A.I.M.E.

Jan 1, 1934

By H. L. Lovell, L. H. E. Weyher

Cyclones have been used successfully in the mineral industries to solve solid-liquid as well as solid-solid separation problems in the processing of fine particles. Substantial information is available about the operation of cyclones as thickeners, classifiers, and concentrators using a dense medium. However, very little is known about the operation of the cyclone as a fine coal concentrator not using dense medium. This application of the cyclone, namely to wash fine coal in water, requires that classification phenomena be minimized in order to arrive at an effective separation of the high density ash and sulfur-bearing mineral particles from the low density coal particles over a wide particle size range. The authors have investigated the role of feed pressure, orifice diameters, and vortex-finder length in the cyclone washing of fine coal (--1/4 in.) in water. The results of this investigation show that cyclone washing of fine coal in water is an effective unit operation particularly capable of reducing the inorganic pyritic sulfur content. The combination of hydrocyclones with complimentary equipment such as Sieve bends, shaking tables, and flotation units appears to be especially promising and may ultimately yield fine coal processing systems that could approximate the high recovery efficiencies of today's coarse coal cleaning circuits. In the future, fine coal beneficiation can be expected to receive even greater research emphasis as a result of increasing sulfur restrictions on all major coal markets. In a previous paper, work, conducted at the Pennsylvania State University, on the hydrocyclone washing of fine coal was discussed.' The initial evaluation based on that wo-rk demonstrated the feasibility of hydrocyclones as fine-coal cleaning devices, and in that previous paper selected test data were presented that showed in principle how product yield and assay respond to variations of the major cyclone operating variables. The present paper reports in greater detail on the findings and presents a comprehensive evaluation of the data as follows: (1) Hydrocyclone throughput rates were related to feed pressure and other variables by regression equations. These equations are compared with other capacity-vs.-pressure drop expressions taken from the literature on classification cyclones. (2) The flow ratio was found to be the most important variable for the separation of the solids. Control of this ratio through various cyclone operating parameters is discussed. (3) The data on the product yield as well as the ash and sulfur assays from the tests were evaluated by means of correlation and multiple regression analyses. Because size-classification phenomena cannot be suppressed completely in hydrocyclone washers, product yield and assay data are regressed against cyclone operating variables separately for different size classes. These equations then reveal how the interactions of the cyclone operating variables vary in terms of the separation for different size classes. (4) Density partitions from additional tests were analyzed by supplementing product-size analyses with sink-float analyses of the separated product size classes. The evaluation of these data show how classification phenomena affect separation by density. The results demonstrate in particular the feasibility of the hydrocyclone washer for removing pyritic sulfur from fine coal. In addition to these specific findings, the investigation points up the value, in general, of using hydrocyclone washers in combination with unit operations such as screening, table concentration, and flotation. In order to make optimum use of the hydrocyclone washers and work out the most effective combination of unit operations, it is important to have careful flowsheet analyses corresponding to the given feed and product requirements. Analyses of this kind are now possible by means of computer simulation of flowsheets and other operation research tools. INTRODUCTION Before proceeding with the detailed treatment and evaluation of our results, it will be useful to review the fundamental aspects of cyclone separators and also restate the experimental procedures and data handling employed in these studies. Review of Cyclone Fundamentals: AS shown in Fig. 1, the basic components of cyclones commonly used

Jan 1, 1970

By R. I. Jaffee, F. C. Holden, H. R. Ogden

Alpha solutes increase the strengths of Ti-Mn alloys through solid-solution strengthening. The substitutional a addition, aluminum, decreases, and the interstitial solutes, carbon and nitrogen, increase the rate of nucleation and growth of a from ß. The best combinations of properties of a-ß alloys are obtained when there is a sufficient quantity of a phase in the structure to dissolve the a solutes. OF the many different titanium-base alloy systems, the predominant alloy type is the a-ß alloy. The properties of the a-ß alloys are dependent on solid-solution strengthening and heat-treatment effects involving the a-ß ratio and transformation reactions. Another variable which influences the mechanical properties of a-ß alloys is the a-stabilizer content of the alloy. An a solute may be present as an intentional addition, such as aluminum, or as an impurity element, such as carbon, oxygen, or nitrogen. It is known that these a stabilizers, when added to titanium, form single-phase alloys which are not heat treatable but which obtain their strength from solid-solution strengthening. Thus, it would be expected that a additions to a-ß alloys would increase the strength of the alloys by solid-solution strengthening of the a phase. In addition, they would affect the transformation kinetics of the ß-to-a reactions and other processes based on the instability of the ß phase. The effects of heat treatment and structure on the mechanical properties of Ti-Mn alloys have been shown in a previous paper.6 This system offers a good base to demonstrate the effects of typical a solutes on the properties of a-ß alloys. The three a solutes described in this work are aluminum, representative of a substitutional a solute, nitrogen, representative of an interstitial a solute, and carbon, representative of an interstitial compound-forming element. The effects of heat treatment and microstructure on the properties of a alloys containing these three elements are described in concurrent publications. Some of these data are used for base-line points in several of the curves used for illustration herein. Experimental Procedures Iodide titanium was used as the base for all of the alloys studied in this work. The alloys were prepared as ½ lb ingots by double arc melting in an argon atmosphere. The ingots were forged to ¾ in. rounds, vacuum annealed for 6 hr at 900°C at a pressure of 10 ' to 10-5 mm of Hg to remove hydrogen, and hot swaged to 1/4 in. diam rod. After me- chanical descaling, test specimens were prepared for heat treatment. The alloys used in this study together with the fabrication temperatures are given in Table I. Heat treatments were done in argon. For the most part, the specimens were sealed in Vyeor capsules under a partial pressure of argon. Quenching was accomplished by breaking the capsule under water. Other cooling methods used included oil quench, argon cool (simulated air cool in an argon atmosphere), and furnace cool. The times for the various heat-treating temperatures are given in Table 11. The tests performed on the alloys consisted of tensile tests on ? in. diam specimens, hardness tests, and microimpact tests. Specimen sizes have been adequately described in a previous publication.' The micrographs presented in this paper were taken from specimens cut from the shoulders of broken tensile specimens. Final polishing was done with Linde B on a slow-speed wheel, and the specimens were etched with a 1½ HF — 3½ HNO, solution. Ti-N-Mn Alloys The transformation diagram and microstructures of the Ti-0.1 pct N-Mn alloys used in this investigation are given in Fig. 1. The effect of small nitrogen additions on the binary Ti-Mn diagram is to raise the ß-transus temperature with little effect on the a solubility of manganese. Also, as has been noted previously,' high manganese-content alloys containing nitrogen, when quenched from temperatures high in the ß field, contain a subgrain boundary phase which appears to be nitrogen-rich a. Marten-site is formed when alloys containing less than about

Jan 1, 1956

By D. L. Feucht, R. L. Longini

The semiconductor heterojunction is considered in terms of simple models which may lead to an understanding of move complex heterojunctions. Metallurgical and electrical properties of hetero-junctions aye discussed including the interface structure, energy -band diagram, and carrier transbovt across the interface. It is found that in a heterojunction all mechanisms such as injection, tunneling, and junction recombination found in simple junctions play modified voles. INTERFACES between materials (grain boundaries, the electrical junction between two differently doped materials in a single crystal, the oxide-metal interface, or metal-metal junctions) are of considerable importance in many situations. These various interfaces all have one very fundamental thing in common. Quantum mechanically speaking, the wave functions of the electrons in one material may penetrate the other material but, in general, only to the extent of angstroms. From an electrical point of view the conduction mechanism changes as a current passes through such junctions. In some cases the change is tremendous, in others almost negligible. The interface, then, is the locus of a change of conduction mechanisms. Some of these, particularly in semiconductors, are well-understood. The ordinary p-n junction in a single crystal can be the locus of an injection mechanism or a tunneling process, depending on conditions. The mechanisms are probably best understood in semiconductors because of the possible simplified view of particlelike conduction. The bands are either nearly filled or nearly empty and band overlap is seldom involved. The same fundamentals are probably important in other situations too but they are very difficult to look at naively. Although the simple look at the semiconductor case only gives us a relatively rough picture which must then be refined, the other systems, which involve a more complex situation, immediately are in many ways too difficult. There are too many initial choices of complex systems and therefore it is not possible to be even reasonably certain of any one model. Because of the relative simplicity of semiconductors, their good and controllable structure, and because of the ability to make many measurements on them not normally available to either metals or insulators! they are probably the best understood materials. It is therefore desirable to use them as a tool to further the understanding of interfaces in general. Semiconductor-heterojunction concepts were first proposed by kroemer1 in 1957. This was followed several years later by reports on the fabrication and experimental characteristics of heterojunction structures by Anderson2 and Diedrich and jotten.3 I) THE HETEROJUNCTION STRUCTURE To get down to hardware, when we refer to a semiconductor heterojunction we imply that there exists an intimate contact between different semiconductor materials. We could put two pieces of material together, complete with oxide layers, we could remove the oxides, or we could even melt the interface and hopefully get wetting and a good "bond" on solidifying. In fact we could by some means grow a crystal of one material using the other as a seed. Essentially we are interested only in the last two because they are the simplest to look at analytically. The degree of perfection of fit varies greatly and is reflected somewhat in the arc welder's joint strength. The lattice match of the two materials, their orientation, and so forth. is obviously necessary for a good bond but so is the continuity of any polar bonds which are involved such as in the III-V semiconductors. The mechanical misfit between two similar lattices can be described in terms of edge dislocations. The edge-type dislocations must be very close together for the usual misfit and there must be dislocations for each of several different Burger's vectors in order to produce a lattice match. The .'dangling bonds'' resulting will be involved in producing interface charge. Order of magnitude estimates of the charge density extrapolated from low densities of dislocations in homogeneous materials give 5 x 1013 cm-2 Ge-Si and 1 X 1012 cm-2 Ge-GaAs electronic charges. Edge dislocations also act as very active recombination centers between holes and electrons. One lattice "matching" difficulty usually exists even if two structures have essentially the same lattice constants as they will have different coefficients of therma1 expansion. Thus, on cooling from the usually high temperature of fabrication to room temperature, dislocations are produced, a good fit not existing at both temperatures. In brittle materials this shrinkage may even result in cracking. For the Ge-Si interface the mismatch is about 2 x 10 -6 per degree whereas it is less than 10"7 per degree between germanium and GaAs. The exact effect of the misfit is dependent on the thickness of the materials involved. For a very

Jan 1, 1965

By Graham Swan, Ove Alm

In-situ fracture toughness experiments have been performed with a scanning electron-microscope. The rock, Stripa granite, was loaded both in tension and three-point bending using the same size notched plates. Observations, which included crack extension measurements as a function of load, are presented in the form of R-curves. The data does not sup- port the proposition that R-curves can be regarded as independent of specimen configuration for this granite. Typically crack extension was seen to begin at loads of 70-80 % failure load. Tensile specimens showed considerably greater sub-critical crack growth than the bend specimens. Evaluation of the approximate fracture toughness Km for both specimen types produced as expected erroneously low estimates Of KIC, being worst in the case of the tensile specimen. Some crack extension data for Stripa granite using the indirect methods of compliance calibration, fluorescent dye penetrant and acoustic emission are compared. In a material such as Stripa granite it is considered that no single method is without its limitations.

Jan 1, 1982

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

"Who is the man who views the mines and promptly turns them down? Who is the one that thinks this is the short cut to renown? Who is it gives the bum advice to the innocent financier? The knowledge-feigning, theory- straining mining engineer." -Anonymous INTRODUCTION Taxes levied against mining properties and operations are a critical cost in the economic evaluation of mining investments. Indeed, taxes represent a substantial cost of doing business in the minerals industry and often have a significant impact on corporate investment decisions. A good example was the postponement of mineral development in the state of Wisconsin, primarily because of what was perceived to be excessive taxes imposed by that state. In many respects mining investments are no different from other industrial investments. Astute taxing authorities should recognize that geologic endowment is a necessary but clearly not a sufficient condition for mineral investments. The fact that a mineral deposit exists does not necessarily mean that it will ultimately be developed-a point that many taxing authorities fail to recognize. While it is true that ore deposits are not mobile in the sense that they cannot be physically moved to a district having more favorable taxes, corporate investment capital certainly is mobile and flows to ventures which maximize wealth to the firm. In short, higher taxes reduce project yields and tend to drive investment capital elsewhere. The appropriate type and level of taxation imposed upon the mining industry continues to be a very controversial and emotion-charged topic. Mining activities have been taxed at various levels over the years due to widely differing taxation philosophies. Location has also influenced taxation policies, as evidenced by the diversity of tax laws and assessment procedures applied to mineral deposits by the various states. Indeed, mineral taxation varies from state to state, from county to county, and from one mineral commodity to another. Whether or not a given tax is appropriate for a specific mineral deposit, or even an industry, is a difficult problem to assess. First, the type or kind of tax which should be imposed must be considered. Second, it is most important to define a fair and unambiguous base against which to levy the tax. Finally, one must consider the tax rate to be applied to this base. It is the combination of these two components

Jan 1, 1984

By Donald O. Rausch, Adolph Soderberg

4.1-1. Introduction. Open pit mine planning must be correlated to all phases of a mining operation. The factors that must be considered in planning an open pit mine are numerous and must reflect the characteristics and surrounding conditions of a particular orebody. Therefore, only an outline of the subject can be presented here to aid the planning engineer in pointing out procedures that are generally applicable to pit design. The presentation is directed toward the planning of an open pit copper mine, but the procedures discussed should apply in most cases to any type of metallic or nonmetallic orebody. In planning an open pit mine the pertinent elements that must be included are: assays, geology, tonnage and areal extent of ore reserves, topography, mining equipment, economic factors of operating costs, capital expenditures, profit, types of ore, pit limits, cut-off grade, stripping ratio, rate of production, pit slopes, bench heights, road grades, ore metallurgical characteristics, hydrological conditions, property lines, and marketing considerations. 4.1-2. Sampling. Sampling must be adequate to classify the various materials to be removed from an open pit mine. Drillhole assays are plotted on sections and plan maps with ore and waste blocked out by selected bench intervals. These maps are prepared to depict the geological and other conditions existing on each mine level. The confidence factor to be applied to sampling and the resultant assays values must be given careful consideration. In uniformly disseminated de- posits, the confidence factor will approach unity. For widely fluctuating values, the average assay values should be discounted somewhat, the degree depending upon such factors as drillhole spacing. Such samples, at best, represent a very few pounds for hundreds to thousands of tons of ore

Jan 1, 1968

By D. G. Westlake

The electrical resistance of a series of V-H alloys (0 to 3.5 at. pct H) has been measured over the temperature range G° to 360°. Interstitial impurities made contributions to the residual resistivity, but not the ideal resistivity. The contribution of hydrogen in solid solution is expressed by Ap = 1.12 microhm-cm per at. pct H; but the contribution of precipitated hydride was negligible. A portion of the so1vu.s for the V-H phase diagram is presented. The solubility limit is given by In N (at. pct H) = (5.828 i 0.009) - (2933 i 44)/RT. Comparison of critical temperatures joy hydride precipitation and published critical temperatures for hydrogen embrittlement suggests the two are related. ThiS study was initiated as part of an investigation of the mechanism by which small concentrations of hydrogen embrittle the hydride-forming metals at low temperatures. It has already been shown that, in the case of hcp zirconium, a reduction in ductility accompanies the strengthening resulting from precipitation of a finely dispersed hydride phase.''' Our attempts to detect a similar precipitation of a second phase at low temperatures in V-H alloys by transmission electron microscopy have been thwarted because we have been unable to prepare thin foils that are representative of the bulk material with respect to hydrogen concentrati~n.~'~ The present investigation establishes the solvus of the V-H system at subambient temperatures. Subsequently, we hope to be able to determine whether the embrittlement temperature is related to the critical temperature for precipitation of the hydride in a given V-H alloy. veleckis5 has proposed a partial phase diagram for the V-H system based on extrapolations of the pressure-composition relations he measured at higher temperatures. Kofstad and wallace' conducted a similar study of single-phase alloys but did not attempt to establish the phase diagram. Zanowick and wallace' and ~aeland' have studied a portion of the phase diagram by X-ray diffraction, but they investigated no alloys in the hydrogen concentration range 0 to 3 at. pct, the range of interest to us. EXPERIMENTAL PROCEDURE The vanadium was obtained from the Bureau of Mines, Boulder City, Nev., in the form of electrolytic crystals. The analyses supplied with them listed 230 ppm by weight metallic impurities, 20 ppm C, 100 ppm N, and 290 ppm 0. The crystals were electron-beam-melted into an ingot that was rolled to 0.64 mm. Strips, 60 mm long and 4.2 mm wide, were cut from the sheet, and both rolled surfaces were ground on wet 600-grit Sic paper to produce specimens 0.4 mm thick. They were wrapped in molybdenum foil, vacuum-encapsulated in quartz, and annealed 4 hr at 1273°K. The specimens were annealed in a dynamic vacuum of 2X lo-' Torr for 30 min at 1073°K for dehydrogenation, and charged with the desired quantity of hydrogen by allowing reaction with hydrogen gas at 1073°K for 2 hr and cooling at 100°K per hr. Purified hydrogen was obtained by thermal decomposition of UH3. Sixteen specimens were studied: two contained no hydrogen and the others had hydrogen concentrations between 0.5 and 3.5 at. pct (hydrogen analyses were done by vacuum extraction at 1073°K). Electrical resistances were measured by the four-terminal-resistor method on an apparatus similar to the one described by Horak.~ The specimen holder was designed so that both current and potential leads made spring-loaded mechanical contact with the specimen. The potential leads were 30 mm apart, and the current leads were 55 mm apart. The current was 0.10000 amp. We used the following baths for the indicated temperature ranges: liquid nitrogen, 77°K; Freon 12, 120" to 230°K; Freon 11, 230" to 290°K; and ethanol, 290" to 340°K. Temperatures lower than 77°K were achieved by allowing the specimen to warm up after removal from liquid helium. Temperatures above 77°K were measured by a calibrated copper-constantan thermocouple (soldered to the specimen holder) and below 77°K by a calibrated carbon resistor. The temperature of the bath changed less than 0.l0K between duplicate measurements of the resistance. RESULTS AND DISCUSSION Typical plots of resistivity p vs temperature T are shown in Fig. 1. In the interest of clarity, only five curves are presented and the data points have been

Jan 1, 1968

By E. L. Bruce

GOLD occurs ill many mineral deposits in the rocks of the Canadian Shield. It is present in the ores of many base metals and a considerable quantity is recovered as a by-product from the production of copper at Noranda, of nickel and copper at Sudbury and of copper and zinc at Flinflon. But the greater part of the gold production of Canada is from deposits in which gold is the only metal of value. No gold is obtained from placer deposits within the borders of the Canadian Shield. A brief review of the geological relations of some of the gold deposits of the Canadian Shield will be presented in an attempt to explain certain associations. Only those which are being worked for their gold content will be considered and descriptions will be confined to representative types of deposits, chiefly those of major importance; a few others, differing in certain features from those of the older and larger mines, will be included in order to illustrate the general conditions in which gold occurs in these ancient rocks. Brief summaries will be given of the geological relations of the Beattie and Siscoe mines of northern Quebec, of the mines of the Porcupine and Kirkland Lake areas of northeastern Ontario and of the Howey, Central Patricia and Little Long Lac mines of northwestern Ontario. Genetic relations to igneous rocks of granitic composition, outcropping in the vicinity, have been assumed for many of these deposits. Undoubtedly the ore minerals have been derived from igneous sources and, for some occurrences, there is evidence suggestive of genetic relationship between the ore bodies and neighbouring intrusive rocks. During the past few years, however, many investigators have expressed doubt of the genetic relationship of certain ore bodies to igneous masses near which they occur. As will be seen from references in the following descriptions the importance of the structural conditions in localizing deposition has been realized. This is pointed out for Canadian pre-Cambrian gold deposits by E. T. Dougherty, who also refers to the

Jan 1, 1937

By M. L. Pearce

A comparison of the isotope-dilution, vacuum-fusion, and chemical methods of analysis for nitrogen in Si-Fe is made with particular emphasis on the effect of sample history. The superiority of the isotope-dilution method from the point of view of 1 HE analytical techniques used to determine nitrogen in Si-Fe have been subjected to close scrutiny in recent years primarily because of the marked influence of the element on the properties of the alloy. These investigations have led to a diversity of opin- both precision and accuracy is demonstrated. The solubility of nitrogen in 3.06 pct Si-Fe is investigated and the effect of silicon content on the activity coefficient of nitrogen is derived. ion regarding the reliability of the vacuum-fusion and chemical methods of nitrogen analysis when applied to si- Fe.'-' A majority of workers appear to favor the vacuum-fusion method over chemical methods particularly in those cases where part of the nitrogen may exist as silicon nitride or the total nitrogen content is very low. Contrary views have been expressed, however,' and it has been demonstrated that for some Si-Fe alloys both methods yield results which are significantly lower than those

Jan 1, 1963

By Toshimi Yamane

The internal friction of cold-worked titanium iso-thermally annealed at temperature below the recrystallization temperature was measured. The internal friction was calculated from the half width of a resonance curve of the specimen which was vibrated transversally by the electromagnetic method. The experimental results were as follows: 1) The specimens annealed for a long time at temperature below the re crystallization temperature after cold working have the strain-amplitude dependent internal friction. 2) The internal friction increased by the cold working was decreased during the isothermal annealing. The reason of decrease of the internal friction is considered to be caused by the annihi-lation of lattice defects. 3) There is a linear relation between logQt-1/Q0-1 and (1/T)2/3 below the recrys-tallization temperature, where Q0-1 is the internal friction standing 24 hr at the room temperature after cold rolling, Qt-1 is the internal friction annealed at T°K for t min. 4) The hardness of the cold-worked titanium does not change by the annealing at 300°C for a long time but decreases by annealing at 400ºand 460°C. METALS, when cold worked, show sharp changes in physical and mechanical properties' The internal friction of cold-worked metals increases sharply and has a maximum value1,2 connected with working de- grees. The increased internal friction of cold-worked metals is recovered by annealing. This phenomenon is the well known effect called Köster effect. The recovery of the internal friction occurs earlier than the changes in tensile properties, hardness, or X-ray diffraction, and is very sensitive to the structure of a metal. The mechanism of the recovery at a temperature lower than the recrystallization temperature is being considered variously by many investigators: there are such views as the annihilation of dislocations by smith,' the rearrangement of dislocations mentioned by Nowick,4 and interaction of dislocation with point defects.5 Smith and Nowick also considered the interaction but it is so difficult for them to explain the rearrangement mechanism systematically, it being not considered a special model; therefore, we do not explain it quantitatively. Experiments measuring the recovery of the internal friction of cold-worked metals were performed by Gordon and Nowick6 on NaCl, and by Smith on copper. In addition, there are many studies, particularly those of measurements on copper by other investigators. There are comparatively many investigations on aluminum and iron which are the cubic system,'-' but only a few on metals of the hexagonal system.10 In view of this, I investigated cph titanium at room temperature and measured the internal friction after annealing isothermally at temperature lower than the recrystallization temperature. SAMPLES AND EXPERIMENTAL METHOD samples for the experiment were cut from a 6-mm titanium plate. The long direction of samples was

Jan 1, 1963