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By Lijun Xu, Jan M. Mutmansky

"Mutmansky, J.M. and· Lijun Xu, 1989. Some observations on particulates collected in underground coal mines using diesel and non-diesel equipment. Min. Sci. Technol., 9: 207-218.The results obtained when sampling twenty underground coal mine sections, each in a different mine, are outlined. The sampling effort was oriented toward a detailed characterization of coal mine dusts and thus eight-stage Anderson Model 298 impactors were used as the primary collection instrument. This instrument allowed a fairly detailed size distribution for each of the particulates sampled. Because four of the mines used diesel outby equipment and/or diesel shuttle cars at the face, it is possible to make some comparisons of the particulate distributions in diesel versus non-diesel mines.One of the more interesting results is the pattern that exists in mines lising diesels only for outby utility haulage. Particulates in these mines seem to be consistently heavy in the fine size ranges, perhaps being of significant concern to the industry. While no definite conclusions can be drawn from the limited data, a more detailed study of particulates may provide a better picture of particulate loadings.IntroductionThe subject of particulate emiss1ons from underground diesel equipment is currently a very important topic as health concerns and regulation of diesel particulate emissions have created new environmental problems for mine operators. The amount of particulate matter originating from diesels has not been extensively measured and problems of differentiating coal and mineral dust from diesel particulates make existing data questionable.However, it is necessary to make an assessment of the problem in order to solve it. It is known that particulates from diesel engines are solid aerosols formed in the combustion process. Technically, this places the particles in the category of fumes. It is also known from tests where no mineral dust could be a factor in the measurements that about 90% of diesel particles are less than 1 µm in aerodynamic diameter [3]. To measure the diesel component of a coal/diesel particulate to measure, Johnson et al. [2] have developed procedures for utilizing laser Raman spectroscopy. The determination of diesel content in a coal/diesel mixture is difficult due to the chemical similarity of the two organic materials. However, laser Raman spectroscopy, which is often used for identification of organic materials, has potential if the Raman spectra for the two materials are different and unique. The study concluded that an accuracy of ±~% could be achieved for mixtures containing up to 55% diesel particulate. The method is relatively complex and would need further development for routine application."

Jan 1, 1990

By Mishra BK, Agrawala S

The traditional method of scale-up uses the population-balance model. In particular, the selection function values for a material are determined in a laboratory mill and a variety of correlations are used to scale these values to plant scale mills. For example, the factor D2-5L (D-mill diameter, L-mill length) appears in many power correlations. The number of collisions is proportional to the number of balls (aD2L), the frequency of mill rotation ((x 1/4D-) and effectiveness of impact ((XD), which gives rise to the 'D2.5L' expression. However, what is lacking in this expression is that it does not throw light on the intensities of collisions. In other words, the collision intensities in both laboratory and plant scale mills are implied to be identical. This fact has been very limiting. Alternatively, the collision frequencies and intensity of impacts can be computed with the discrete element code. This code computes the motion and collision of each individual ball in the ball charge. Therefore the number of collisions and the fraction of collisions in the energy range Et, E2.òòE. (collision energy density) are calculated for a given mill size and operating conditions. Then, using the breakage function determined in drop-weight experiments, the evolution of size distribution is computed for a lab mill. The collision frequency and energy density for larger mill sizes are shown. The fundamental theory outlined for the calculation of size distribution is equally applicable for the large mill, which is the basis for scale-up.

Jan 1, 1993

By J. W. Harshbarger, E. L. Montgomery

The region of metallic ore deposits in northern Chile, southern Peru, western Bolivia, and northwestern Argentina occurs in arid zones at altitudes as high as 6 km (19,700 ft). Because surface water supplies are meager, new mines require unexploited sources of water. Prolific ground water aquifers occur in salar basins in this region of the Andean Highlands. Exploration water wells have been constructed and aquifer characteristics have been tested in eight salar basins. Results indicate ground water quality is good. Aquifer transmissivity and storage computed from results of pumping tests indicate maximum capacities of more than 170 L/sec (2700 gpm) for individual production water wells. Results of investigations conducted by the authors demonstrate that ground water reservoirs in the Andean Highlands comprise a source of large quantities of water for the mineral industry.

Jan 1, 1986

By M. R. Louthan, C. L. Angerman

In polycrystalline Zircaloy-2 the orientation of zirconium hydride precipitates is influenced by an applied stress during hydride precipitation; hydride platelets are oriented nearly parallel to a compres-sive stress and perpendicular to a tensile tress. 1,2 A similar effect has been observed in the Ti-H system, where precipitation of the low-density hydride platelets occurred on habit planes made energetically favorable by the application of stress. 3 Recently, stress activation of hydride habit planes in zirconium and Zircaloy-4 was also demonstrated. The hydrides precipitated on {101l), {112l} and (2131) planes in both zirconium and Zircaloy-4; however, no platelets were found near the prism-plane positions in the Zircaloy-4 samples. Investigations at the Savannah River Laboratory, using polycrystalline Zirc_aloy-2 samples, have confirmed the (101l) and (1121) habit planes but also showed that the prism planes were active hydride habit planes. Using single-surface stereographic analysis and back-reflection Laue techniques, most of the previously reported habit planes for a zirconium were observed.4"1 and one additional plane, the (1013) plane, was noted, Table I. All the habit planes observed had the form (101l) or { 112l) indicating that these planes are the habit planes for hydride precipitation in poly-crystalline Zircaloy-2. The specimens used in these studies were cut from large-grained weld areas of seam-welded tubing and were hydrided in either a static steam autoclave at 400°C and 1500 psig or in a modified Sieverts apparatus at 400°C.

Jan 1, 1967

By Frederic P. Dewey

By the old method of determining platinum in ores and bullion, the silver-alloy first obtained in the regular course of assay is parted in strong sulphuric acid and the residual metal weighed. This is re-alloyed with silver by a second cupellation and parted in nitric acid, the residual metal being again weighed. Any difference shown between the two weighings is assumed to be, and is called, platinum. Sometimes it is SO, and if any considerable amount of platinum be present, there will be a decided difference between the two weighings; but a slight difference is no real evidence whatever of the presence of platinum. On the other hand, the second weight may equal or possibly exceed the first, even when traces of platinum are present. Again, other members of the platinum group may go into solution in nitric acid more or less. If present, these would be called platinum and escape detection. The method does not provide any direct tests whatever as to the presence or absence of platinum. It is often indecisive, and sometimes gives erroneous results. It is, therefore, quite unsatisfactory. Being called upon many times to determine platinum in a wide variety of materials, particularly when present in very small amounts, I have realized the disadvantages and defects of this old method. In an article on the solubility of gold in nitric acid,' I have briefly outlined a method of gathering a little gold out of a solution containing much silver, which furnishes the basis of

Jan 1, 1913

By J. H. Brophy, A. I. Prill

The authors have previously investigated the solid-state activated sintering of tungsten powder with various Ni-Cu additions.' Log shrinkage vs log time plots showed changes in slope from 4 to x at intermediate times during the sintering process. This was attributed to a change in the rate-controlling mass-transport process from solution of tungsten into the tungsten-alloy interface to diffusion of tungsten in this interface. It was postulated that the melting of the activating layer should not affect this transport process. However, the superposition of rearrangement due to the presence of a liquid phase complicates the data analysis. It is the purpose of this note to apply the analysis of Prill, Hayden, and rohy' to account for "rearrangement shrinkage'? in liquid-phase sintering of the W-Ni-Cu system. This results in "solution-precipitation stage" shrinkage plots which were comparable to those obtained in solid-phase activated sintering of the same system. If one assumes total shrinkage to be the sum of rearrangement and solution precipitation, the effects can be isolated easily.2 This results in the general equation:

Jan 1, 1967

By C. H. B. Leitch, T. N. MacAuley, R. L. Linnen, A. E. Williams-Jones

"The Trout Lake stockwork molybdenum deposit is temporally and spatially related to the emplacement of a late Cretaceous granodiorite-tonalite stock in southeastern British Columbia and contains an estimated 49 million tonnes grading O.I9% MoS2- No metal zonation patterns are apparent, with the exception of peripheral tungsten skarn, and exploration was guided largely by geological interpretation. It is typical of the granodiorite, or fluorine-poor type of molybdenum deposit. Molybdenite is contained within a quartz-feldspar vein stockwork and coeval dissemination in igneous (and less commonly metasedimentary) hosts. In general, molybdenite is strongly associated with alkali feldspars, but in detail it is intimately associated with incipient muscovite replacement of albite and K-feldspar; veins that lack feldspars are also typically barren of molybdenite. These textures suggest that fe/dspathic alteration (and precipitation in veins) was an important precursor to mineralization, and the occurrence of similar textures elsewhere (e.g. Henderson) suggest that early feldspathic alteration is important to the genesis of molybdenum deposits in general. Molybdenite deposition at Trout Lake was preceded by contact metamorphism, skarn and potassic alteration, and was overprinted by muscovite-ankerite (phyllic) alteration. Only moderate temperature changes are recorded by the metamorphic and alteration mineral assemblages (350°C to 450°C}; however, with time, fluids became increasingly more acidic and enriched in C02- In light of the intimate molybdenitemuscovite intergrowths, the decrease of pH probably exerted a major control on mineralization.IntroductionGranite-hosted molybdenum deposits can be classified in terms of the composition of the related intrusion, e.g., the granodiorite and granite types of Mutschler et a!. (1981), or the calc-alkaline, alkali-calcic, and alkalic types of Westra and Keith (1981). They have also been classified on the basis of their fluorine contents (Theodore and Menzie, 1984) with the fluorine-rich and -poor varieties roughly corresponding to granite- and granodiorite-type deposits, respectively. For economic reasons, most exploration and research has concentrated on the high-grade/large tonnage granite-type of deposit, exemplified by Climax. F1uorine-poor, granodiorite-type deposits are, however, the most common type in Canada and have been mined in the past (e.g., Endako). In this paper, the authors summarize the research that has been carried out on the fluorinepoor Trout Lake deposit (Boyle and Leitch, 1983; Linnen, 1985; Linnen and Williams-Jones, 1987; 1990) and use what has been learned to develop guidelines for the future exploration of fluorinepoor, granodiorite-type molybdenum deposits."

Jan 1, 1995

By Tozawa K, Nishimura T, Sasaki K

Liquidus surfaces in a part of the systems ZnO-PbO-Si02 and ZnO-"FeO"-SiO 2 were constructed by the quenching method. The ex- periments were carried out in air in the system ZnO-PbO-Si02. In the part investigated the primary phases were three ternary compounds (PbO.ZnOòSiO2, 2PbOòZnO.2SiO2 and barysilite), three lead silicates, Zn2SiO4 and SiO2. Iso- therms on the liquidus surface of each primary phase field were determined from 750 to 1300¦C. In the system ZnO-"FeO"-SiO 2 the experiments were carried out in an atmosphere of purified nitrogen. In the part investigated the primary phases were Fe2SiO4, Zn2SiO4 and Si02. Iso- therms on the liquidus surface of each primary phase field from 1150 to 1300¦C and the ternary eutectic (1130¦C, 15.9% ZnO, 48.2% "FeO" and 35.9% Si02) were determined.

Jan 1, 1980

Traditional in situ fan flow test methods under accepted standards require determinations to be made of both static pressures and total pressures during testing. This is to determine the resultant velocity pressures, which are vital in the accurate determination of the final fan airflow. These crucial velocity pressure (Vp) determinations are normally determined using simple manometric instrumentation such as an electronic manometer or an inclined liquid filled manometer. There is relatively little noise or fluctuation in the static pressure determinations and they can be quite easily and accurately recorded. There is almost always considerable fluctuation in the velocity pressure determinations though due to the highly turbulent and irregular velocity profile normally found in such in situ installations. This velocity turbulence means that the recording of such data is subject to random human error as the observer tries to average such fluctuations mentally during the observation period. Worse than this, and in the extreme, the recording of such velocity pressure data could actually easily be misreported if, for some reason, persons chose to do so.The author has devised a field method using highly accurate quartz crystal logging barometers to objectively record these velocity pressures. The method eliminates the ability to either mistakenly or intentionally misreport these crucial velocity pressures and is carried out in parallel with the recognised methodology, so result comparisons can be drawn. As such, a far greater level of confidence can be achieved in the final flow performance results than using the traditional more subjective method. Further to this it is difficult and almost impossible to refute the results using this ancillary substantiation method.The accurate determination of fan flows due to the impost of the carbon tax has taken on much more significance given the financial impacts in Australia at this time. The methodology detailed herein can be applied equally for both fan flow compliance testing and the verification of mine airflow data for greenhouse gas emission evaluations.The paper utilises the results of one 24-point pitot traverse to demonstrate the various findings. These include the very wide range of velocity pressures, which were logged at most of the measuring stations. It also illustrates how the method is utilised and compares the results derived from both this method and the more subjective traditional method along with the benefits of logging the velocity pressure results during the testing process.CITATION:Rowland, J A, 2013. Removing some subjectivity from traditional BS 848 and ISO 5802 in situ fan flow tests, in Proceedings The Australian Mine Ventilation Conference , pp 155-162 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By M. L. Samuels

In a recent paper the authors1 discussed the reactions to tempering of hypereutectoid steels quenched from 1000' C., as revealed by studies on changes in hardness, electrical resistivity, coercive force and metallo-graphic charaeteristics. The data, which related specifically to tempering temperatures of 550°, 650" and 710" C., for varying periods up to 125 hr., permitted the following important conclusions: 1. The rate of softening of the steels at the temperatures examined differed markedly although the steels were of "similar" general chemical composition. 2. The temperature of maximum softening spread over a range from about 650" C, to the eutectoid inversion. 3. The divergence in behavior was ascribed, at least in part, to a profound difference in tendency to graphitization on annealing at sub-eutectoid temperatures. 4. The mode of spheroidization of the cementite, as revealed by metallographic studies, also varied considerably in the different steels. The purpose of the present investigation is to pursue further the study of the difference in behavior of the steels on tempering over a wider range of temperature. To this end the following features have received particular attention: 1. Comparison of temperatures of maximum softening of the various steels when the quenched samples were tempered for 5 hi. and for 75 hr. followed by furnace cooling and by quenching in water. 2. Deterrnirlation of the effect of quenching temperature, prior to tempering, on the rate of softening. Quenching temperatures of 1000" and 850" C. were used in the investigations. 3. Examination of the microstructures obtained with the various heat-treatments employed.

Jan 1, 1938

By N. J. Grant, A. W. Mullendore, Y. Ishida

Creep tests were performed at 500°F on polished specimens of A1-3 pct Cu at stresses of 2000, 4000, and 6000 psi. The effects of the size and distnbution of the second phase were studied in connection with the mechanisms of deformation, especially grain boundary sliding. Although the amount of grain boundary sliding varied considerably for the different heat treatments, yestriction of grain boundary sliding is not due primarily to precipitate on the grain boundary. NUMEROUS prior investigations of grain boundary sliding, notably those of McLean, 1 Rachinger, 2 Rhines, Bond, and Kissel, 3 and Brunner and Grant,4 have established the importance of this phenomenon in the deformation of pure aluminum and its solid-solution alloys at elevated temperatures. An extension of this kind of study to the case of a simple two-phase structure is an important step towards understanding the deformation behavior of more complex alloys. A two-phase A1-3 pct Cu alloy was selected for this study. The creep behavior of alloys in this system has been studied by Sully and Hardy,5 by Underwood, Marsh, and Manning,' and by Pelloux, Chaudhuri, and Grant.7 In these studies, the prior heat treatments were such that some precipitation took place during the tests in most cases. Pelloux, Chaudhuri, and Grant7 studied the creep of A1-2 and 3 pct Cu alloys in the overaged condition. Their results indicated that the structure most effective in promoting high-temperature strength consisted of a fine, closely spaced grain precipitate and large, widely spaced particles on the grain boundary. The present work consists of quantitative meas- urements of grain boundary sliding during creep of an A1-3 pct CU alloy with four different precipitate distributions. The aims were to quantitatively define the role of the second phase on grain boundary sliding, and to obtain information regarding the mechanism of grain boundary sliding. MATERIALS AND PROCEDURE A high-purity A1-3 pct Cu alloy, kindly supplied by Alcoa, was used in this investigation. The composition of the alloy in weight percent was as shown in Table I. This composition is such that A12Cu exists as a second phase at temperatures below 850°F. A homogeneous grain size of 0.6 to 0.8 mm was obtained by annealing the machined test bars for 5 min at 1000°F, furnace cooling to 930°F, and homogenizing for 5 hr. Following the recrystalli-zation and homogenizing anneal, four different heat treatments shown in Fig. 1 were utilized. The F7 and F5 treatments utilize a furnace cool to the aging temperature while Q7 and Q5 have a water quench from the homogenization temperature before aging. Figs. 2 to 5, and Table 11, show the size and shape of precipitate dispersions obtained with the above heat treatments. The heat treatments produce variations in the dispersion both in the grains and along the grain boundaries. Precipitate particles along the grain boundaries are rounded and large (about 1.5 p diameter) in the F5 and F7 structures (Figs. 3 and 5). The grain boundary precipitate was somewhat smaller (0.9 p diameter) in the Q7 structure and no grain boundary precipitate was detected in the Q5 structure using light microscopy. The pre-

Jan 1, 1964

By M. L. Samuels

In a recent paper the authors1 discussed the reactions to tempering of hypereutectoid steels quenched from 1000' C., as revealed by studies on changes in hardness, electrical resistivity, coercive force and metallo-graphic charaeteristics. The data, which related specifically to tempering temperatures of 550°, 650" and 710" C., for varying periods up to 125 hr., permitted the following important conclusions: 1. The rate of softening of the steels at the temperatures examined differed markedly although the steels were of "similar" general chemical composition. 2. The temperature of maximum softening spread over a range from about 650" C, to the eutectoid inversion. 3. The divergence in behavior was ascribed, at least in part, to a profound difference in tendency to graphitization on annealing at sub-eutectoid temperatures. 4. The mode of spheroidization of the cementite, as revealed by metallographic studies, also varied considerably in the different steels. The purpose of the present investigation is to pursue further the study of the difference in behavior of the steels on tempering over a wider range of temperature. To this end the following features have received particular attention: 1. Comparison of temperatures of maximum softening of the various steels when the quenched samples were tempered for 5 hi. and for 75 hr. followed by furnace cooling and by quenching in water. 2. Deterrnirlation of the effect of quenching temperature, prior to tempering, on the rate of softening. Quenching temperatures of 1000" and 850" C. were used in the investigations. 3. Examination of the microstructures obtained with the various heat-treatments employed.

Jan 1, 1938

By R C. Schodde

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Over the last decade (2005–2014), a total of 439 significant deposits of gold and base metals were found in the world. Twenty (or 4.6 per cent) of these deposits were in the Pacific/South-East Asia (Pacific/SE Asia) region. In terms of contained metal, the region accounted for 1.6 per cent of gold and 13.8 per cent of copper found in the world. With regard to nickel and zinc/lead, the region’s contributions were insignificant.Over the same period, the Pacific/SE Asia region accounted for 6.6 per cent and 12.6 per cent of all gold and copper exploration expenditures in the world respectively. After adjusting for by-product credits, unreported discoveries and likely growth in resource, the unit discovery cost for the region was US$199/oz (compared to a world average of US$50/oz). For comparison, the unit discovery costs for the previous decade were US$55/oz and US$25/oz respectively. The region’s unit discovery cost for copper was US$0.036/lb (versus a world average of US$0.040). For comparison, the unit discovery costs for the previous decade were US$0.026/lb and US$0.008/lb Cu respectively.The region’s mediocre discovery performance doesn’t reflect its distribution of known mineralisation. Some countries within the region have a very good endowment per square kilometre.It is noted that the intensity of exploration (and resulting success) would be boosted if governments provided a more mining- and investment-friendly business environment and generated better precompetitive geological data sets (to identify new exploration targets and boost the country’s perceived mineral prospectivity). A multivariable regression analysis of a decade of data from the Fraser Institute’s mining company surveys found that a ten point increase in the Policy Perception Index or a 0.1 point increase in the Mineral Potential Index could boost (in the short term) exploration expenditures by 1.9 per cent and 2.7 per cent respectively. The resulting economic benefits of an expanded mining sector would be significant. The same story applies elsewhere in the world.CITATION:Schodde, R C, 2015. Discovery performance for gold and base metals in the Pacific/South-East Asia – 2005–2014, in Proceedings PACRIM 2015 Congress, pp 25–34 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Dave N. K., T. P. Lim

"A fast, reliable and accurate method for radium-226 determination in environmental water samples has been devised, using an alpha spectroscopic technique. The correlation between barium-133 and radium-226 in the barium-radium sulphate precipitation mechanism was studied and in the limited experimental recovery range, the coefficient of correlation was r = 0.986. A self-absorption study for various barium carrier concentrations was also undertaken to obtain the least broadening of alpha energy line widths. An optimum value of 0.3 mg barium carrier was obtained for chemical recovery in the range of 85%.IntroductionWith the increase in uranium mining activities, the migration and spread of radioactivity via various environmental pathways is of great concern. Because of its inherent biological hazard and relatively long half-life, (approximately 1620 years), raidum-226 is frequently monitored as a measure of radioactive contamination of the environment. It is, therefore, necessary to modify existing methods for rapid determination of radium-226 in environmental samples for quick corrective measures in the event of seepage, dam leakage or discharge violations."

Jan 1, 1981

By H. W. R. Wardlaw

This paper shows how the cost of the drilling operation per 100-ft drilled can be related directly to bit weight, rotary speed and hydraulic horsepower variations. This enables optimum drilling conditions to be determined in a rapid and concise manner. The paper also shows how data for such calculations cun be obtained quickly and accurately by the "drill-off" method suggested by Lubinski. Examples are given to illustrate the principles and methods used. INTRODUCTION The problem of drilling oil wells at lowest cost and hazard needs little introduction, since it has been with us virtually from the earliest days of our industry. With better understanding of the effect of the various factors of bit weight, rotary speed and hydraulic jet action, however, the problem has recently taken on a more scientific aspect, and engineers or groups of engineers have been assigned to study many of the facets of this problem not immediately apparent to the general observer. Moreover, the availability of better equipment and materials has enabled certain practices to be adopted which were hitherto impractical or uneconomic. This has paved the way for further efforts to reduce footage costs, and so on. The improvements to be made in drilling technology and cost reduction are by no means exhausted, and we still frequently hear of new records being set and new materials and equipment becoming available. Some of the analytical methods used by the author to assist in promoting faster and more economic methods of drilling, particularly in Venezuela, form the basis for this descriptive study. STATEMENT OF THEORY AND DEFINITIONS In a highly competitive industry, it is no longer permissible to regard penetration rate as the sole criterion for drilling efficiency. Every new technique, however spectacular, must nowadays be viewed in the cold light of whether it will eventually lead to lower cost per foot drilled. In the exposition which follows, therefore, actual drilling rates will play only a secondary role, and attention will be focused on the more important aspect of cost per foot drilled. Changes in drilling factors such as weight and rotary speed will be studied in the light of how they directly affect the cost of operations. The advantage of this method is twofold—(1) cost increments are indicated directly; and (2) the relationships are, surprisingly enough, simpler than those relating to drilling rates. To achieve these advantages, it is necessary to introduce a new unit of measurement which, although unfamiliar, is readily understood. The unit in question will be referred to as the "actual drilling cost factor" and will be designated by the symbol h. The unit is defined as the number of rotating hours taken to penetrate 100 ft of formation. The unit can be obtained immediately from the actual drilling rate (r) in feet per hour; thus, This latter transformation is so easily effected that it may be convenient to use h as an international symbol for drilling cost, and to delay conversion to dollars, bolivars, pounds, etc, per foot until actually required (e.g., for fiscal reasons, etc.). In actual operations, h was found to vary in a relatively simple manner with increases in bit weight. The variation in h with rotary speed was found to be somewhat more complex. However, this also could be enormously simplified by introducing a further factor known as L or relative bit life. The factor L is also defined very simply by dividing 1,000 by the rotary speed (N) in revolutions per minute.

By F. D. Rosi, C. A. Dube, B. H. Alexander

WHEN a deformed polpcrystalline metal is heated to a sufficiently high temperature, a recrystallized structure develops which consists of small, essentially stress-free grains. This transformation is referred to as primary recrystallization. Under certain conditions, on prolonged annealing of the specimens, a type of grain coarsening occurs in which a small number of grains commence to grow at various points by devouring the neighboring finegrained primary structure, which, in itself, exhibits a marked stability toward normal grain growth. This grain coarsening process has been referred to by Burgers' as "secondary recrystallization" or "exaggerated grain growth." Although much work has been done on recrystallization and growth processes, present knowledge of the factors which determine the occurrence and growth of secondary grains is inadequate for the advancement of a theory which accounts for the observed characteristics of this recrystallization phenomenon. In this respect, it would be important to make measurements of the velocity of growth of these large secondary grains. The early work of Feitnecht2 on aluminum showed that the size of secondary grains increased with temperature and time, suggesting that such measurements would be possible. More recently, Burgers1 found that the growth velocity of these grains in aluminum was constant over a large time interval, as is generally found for the growth velocity of primary grains in a uniformly deformed test piece.3-5 It is reasonable to expect that the determination of the activation energy of the secondary growth process might lead to a better understanding of the underlying atomic mechanism. This investigation, therefore, is one of a series primarily designed to measure the growth velocity of secondary grains at various temperatures for silver, copper, and aluminum. It is hoped that these studies along with those of orientation relationships, will establish a sound basis for theorizing as to the origin and nature of the secondary transformation. Experimental Procedure The metal used in the present investigation was high-purity silver (999.9 fine), which was supplied in the form of cold-rolled plates 0.250 in. thick. These plates were annealed at 500°C for 1 hr and then straight-rolled to a thickness of 0.04 in. in three reductions of approximately 45 pct, followed in each case by an anneal at 450°C for 1/2 hr. The 0.04 in. sheets were given a final reduction of approximately 50 pct, which resulted in a thickness of 0.02 in., thereby insuring two-dimensional crystal growth. Individual specimens of this material about 1x3 cm were used for all heat treatments, unless otherwise noted. The annealing was carried out under an atmosphere of argon in an Inconel tube furnace whose temperature was controlled to within -+2°C. Metallographic examination of the secondary transformation was accomplished by mechanically polishing the specimens on one side to approximately one half their thickness through 2/0 metallographic emery paper, and then electrolytically polishing in a solution of potassium ferrocyanide and sodium cyanide. With a current density of approximately 20 amp per sq dm, the time required to obtain a satisfactory surface varied from 3 to 5 min. Standard potassium bichromate was used to etch the electrolytically polished surfaces. A heavy etch with this solution produced a sharp contrast between the secondary grains and the fine-grained primary structure, darkening the latter while leaving the large secondary grains bright. All area measurements of the secondary crystals were made with a planimeter on enlarged tracings of the grains.

Jan 1, 1953

By NATHANIEI HERZ

(Cleveland Meeting, October, 1912.) THE formula very frequently used for computing the economical size of pipe to transmit compressed air is that of D'Arcy, as follows: d5(p1-p2)/w1l D-c w11 Where, D = the volume of compressed air delivered in cubic feet per minute,-at the final pressure. c = an experimental coefficient determined for the various sizes of pipe. d = the diameter of the pipe in inches. 1 = the length of the pipe in feet. P1 = the initial gauge-pressure in pounds per square inch. p2= the final gauge-pressure in pounds per square inch. W1 = the density of the air, or the weight in pounds per cubic foot at the initial pressure, p,. The most common case is that in which the given quantities are: the quantity of air required, the length of the pipe, and the initial pressure. The method of solution is to assume a pressure-loss and to compute the remaining factor, c/d5, thus giving the size of pipe corresponding to the assumed loss of pressure. It is always desirable to try two or more pressure-drops, in order to find the combination that is most satisfactory, since often a small change in the size of pipe will reduce or increase the loss of pressure several pounds. An alternative method is to assume a size of pipe and calculate the corresponding pressure-drop. Each method involves a series of tedious calculations to arrive at the most economical solution, and also requires the use of tables giving the constant, c, the actual diameters corresponding to the nominal pipe-sizes, the density of the air, w1, and often, for convenience, a table giving the

Dec 1, 1912

By Georgene Renner, William R. Yernberg, William Gleason

American Commercial (ACI) offers a selection of ground control solutions. Beginning with steel liner plates installed in the Gratiot Avenue sewer system in Detroit, MI 1920, ACI is one of the leading designers and manufacturers of underground steel supports in North America. ACI is also a leader in fire-proofing underground structures with its Promat Fire Protection Boards. The sandwich panels have been used in many new and retrofit tunnel and underground construction projects worldwide. Ease of installation and replacement, cost effectiveness and superior performance have made this product line the premier choice of owners and designers for structural protection, fire-life safety requirements and architectural finish needs.

Jan 1, 2007

By Regina N. Tempel, Laurie S. Balistrieri, Lisa L. Stillings, Lisa A. Shevenell, Maggy F. Lengke

Dexter pit lake, within the townsite of Tuscarora, Nevada, has been in existence since 1990 and provides a natural laboratory for the study of cycles of trace elements associated with ore deposits (e.g. As, Cu, Pb, and Se). Our goal in this study is to develop and calibrate methods of geochemical modeling that may be applied to estimating the concentrations and fluxes of trace elements in pit lake systems. Our initial modeling work considers limnology, hydrology, wall rock mineralogy and geochemistry, benthic fluxes, and colloid composition. Results from our work may be useful in evaluating water quality in the arid West.

Jan 1, 2000

By Thomas H. Clagett

ThE Pocahontas coal field comprises the area in Tazewell County, Va. and Mcrcer and McDowell counties, W. Va., in which Nos. 3 and 4, Pocahontas seams of bituminous coal are mined. It is a mountainous region with ridges rising 300 to 1000 ft. (91 to 305 111.) above the very narrow valleys and, except for some poorly kept farms along the tops of the ridges and the area occupied by the mining and coking plants and villages, is wooded throughout. First shipments were made from Pocahontas in 1883. There are now about 100 mines, 95 per cent. of which are drift mines. At the end of 1920, approximately 298,000,000 gross tons of coal had been produced and 35,000 acres of coal mined. No. 3 seam is from 4 to 10 ft. (1.2 to 3 m.) thick, but the change is gradual and the thickness fairly uniform in any particular locality. It has a streak of bone, about 2 in. (5 cm.) thick, to which the coal adheres on both sides. In parts of the field this bone is replaced by hard slate, usually from 2 to 4 in. thick. The seam has a slate or fireclay bottom and a draw-slate top. No. 4 seam is from 65 to 80 ft. (19.8 to 24 m.) above No. 3 seam, and of minable section only in the western part of the field. It is from 3 to 8 ft. thick and has two streaks of bone, cach from 1 to 2 in. thick. It has a fireclay or slate bottom and is overlaid by from 4 to 24 in. of a laminated coal and slate, locally termed "black rash," which is separated from the coal seam by about 3 in. of slate. This "black rash" averages about 2.5 per cent. ash, but contains some clean coal. The coal in both seams is quite soft. Cleavage sufficieiltly well defined to exert an influence on the mining is rare. Overlying strata arc slates, shales, and sandstones, the sandstones predominating, extending from 30 to 1000 ft. above No. 3 seam. The strata directly above the draw slate of No. 3 seam, or "black rash" of No. 4 seam, and up to the first sandstone are usually slates or shales, about 10 ft. thick over the.

Jan 1, 1923