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By G. R. Hopkins

"Summary An apparent decline in fuel efficiency at refineries, which first became came evident in 1930 and continued through 1933, was checked in 1933 when the average amount of heat needed to refine a barrel of crude oil amounted to 660,000 B.t.u. This compares with an average requirement of 692,000 B.t.u. In 1932 and with a low of 639,000 B.t.u. in 1929. (See fig. 1.) The improvement in fuel economy in 1933 probably was closely related to the increase of 5 per cent in crude runs to stills. As much of the fuel burned at refineries is utilized for purposes other than under crude-oil stills and in relatively stable amounts, it is evident that a material increase in crude runs will usually reflected in a decrease in average fuel requirements. Another factor which has influences fuel economy at refineries in the past is the trend in cracking, a refining process requiring more than the average expenditure of heat. In 1933 production of gasoline by cracking increased slightly, but no appreciable rise in heat requirements resulted as an equivalent amount of fuel was saved in improved technique, particularly in the field of heat exchange.Since the beginning of the refining industry, the transition in fuels has been from solid to liquid to gaseous; in other words, the leadership was first held by coal, then passed to oil, and is now held by gas. In 1933, 54.7 percent of the total heat units generated came from gas, 39.0 percent from oil (including acid sludge), and 6.3 percent from coal and coke. The principal change in the relative importance of the various refinery fuels in recent years has been the rapid growth in consumption of refinery or still gas at the expense of all the other common fuels. Still gas owes its ascendency to its cheapness and availability, and probably it would have become the primary refinery fuel years ago if recovery methods had been perfected. The relative importance of coal showed a small increase in 1933, the first gain recorded since these surveys were inaugurated in 1925. The increase in use of coal was undoubtedly due to increased operations at plants using it,"

Feb 1, 1935

By Richard I. Petritz

A brief review of today's processing of integvated circuits is given. The major trends in the development of advanced integvated electronics are identified as 1) the broadening of the integvated circuit concept to a large class of circuit function, 2) the processing of more complex circuits within relatively small chips of silicon, and 3) the processing of very large electronic functions on complete slices of silicon. This latter trend, called array technology, is then developed in detail. Emphasis is given to defining the key tech-nological problems. Current progress being made is illustrated. THIS paper will endeavor to identify the major trends in advanced integrated electronics technology. One of these, array technology, will be developed in some detail. The array technology discussion will identify the key problem areas. Since it is the scope of the entire meeting' to present specific progress in the science and technology of integrated electronics, we shall indicate general directions being explored rather than discuss comprehensively solutions to the problems. In order to set the stage for the discussion of future trends in integrated-electronics technology, let us briefly compare the processes by which circuits are fabricated through discrete-device technology with that of integrated circuits technology. The reader is referred to the December 1964 issue of Proceedings of IEEE2 for a comprehensive review of integrated electronics. The article3 by Jay Lathrop is an excellent discussion of integrated-circuits technology. A discussion of the history of semiconductor technology is contained in Ref. 4. A) Current Status of Integrated Electronics. Fig. 1 (top) shows the process by which circuits are constructed from discrete devices. Key points are: 1) Slices containing large numbers of transistors or diodes are processed separately. 2) The slices are scribed into small chips (on the order of 15 mils on a side is about as small as can be conveniently handled) each chip containing one transistor. 3) Each device is specified separately—circuit -function specs are derived largely from device specs. 4) Circuits are formed by connecting together the discrete devices. 5) The number of circuit connections required is approximately equal to the number of devices. 6) There are potentially many more discrete devices per inch2 of semiconductor—only our lack of ability to handle them in discrete form prevents us from going to several orders of magnitude higher density iin Fig. 1, 400,000 transistors are discussed at 1.5 mils on a side). The bottom part of Fig. 1 illustrates the integrated circuit process. Key points are: 1) On the same slice of silicon, transistors, diodes, and resistors are processed grouped to do a complete circuit function. 2) While still in slice form, the components are interconnected into circuit functions by an evaporation process, eliminating the need for separate interconnection steps later. Dramatic improvements in cost and reliability are realized. With a simple flash of metalization thousands of interconnections are reliably made. 3) The slices are scribed into chips which contain complete circuit functions. 4) The circuit functions are specified-not each component in the circuit. This important point was missed by some of the early opponents to integrated circuitry. They argued that, with device yields at x pct, integrated circuit yields would be pct, where n is the required number of devices to make a circuit. This argument leads to extremely low yields for integrated circuits. The fallacy of the argument is that in integrated circuits each device is not specified separately. Furthermore, since a device is forever integrated into a specific circuit function, it need meet only the requirements for that particular function. Discrete devices, on the other hand, are tightly specified so that they can be applied to a variety of circuit functions. 5) Extremely high packing densities are achievable because one need only make the basic devices as large as the circuit demands. Their size is not dictated by handling requirements. A current example

Jan 1, 1967

By H. S. George

A method of illumination that enhances the value of microscopic study of opaque materials, as in metallography. By simulating natural lighting, structures. That possess relief are given a natural appearance. An example is included of the revelation of a hitherto invisible microconstituent. Erroneous interpretation is avoided. For example, etching figures in ferrite, heretofore considered to be pits, are revealed as pyramids, standing in bas-relief. Suggestions on technique are given, for, while the method is obvious, practice and attention to detail are requisite. ON one occasion when it seemed desirable to reveal under the microscope not only the metallic structure of an alloy, but certain small non-metallic inclusions, that are ordinarily obliterated by etching, it was discovered that, by partly eclipsing the illuminating pencil of light rays, the residual light was thrown on the object from one side and the structure was brought out in relief. At the same time, the non-metallic inclusions were retained in clear view. In this first demonstration of lighting obliquely through the objective a card was thrust part way into the light beam between the arc iris, and the light filter; the shadow of the card on the filter served to locate its position. Next several stiff-paper disks of various diameters were mounted on flexible wires some plasticine on the other end of the wires made it easy to adjust and maintain a disk at any desired position in the light beam. To facilitate manipulation, an assortment of disks, was mounted on a wheel, as shown in Fig. 1. The purpose of partly eclipsing the light beam was discussed in an earlier paper.1 There it was pointed out that the usual methods of illuminating opaque objects for microscopic examination lend an, un-natural appearance to, the view, while the new method, which has been termed conical illumination, revels the true relationship of constituents by simulating natural lighting.

Jan 3, 1924

By Mohamed A. Younis, Robert J. F. Goodfellow

This paper investigates the design approaches taken and the philosophy employed during the construction of the Metropolitan Airport Commission (MAC) storm tunnels, part of the Phase 4 Segment of the MAC Trunk Storm Sewer Project at Minneapolis St.-Paul International Airport, located in Minneapolis, Minnesota. URS Corporation was retained to provide a design and Construction Management (CM)services for the MAC Trunk Storm Sewer Project. A case history of the design and construction challenges of the project is presented. The MAC storm tunnels consisted of the construction of twin 10-foot inside diameter (I.D.) tunnels within 7 feet of an existing 72-inch I.D. storm pipe at the base of a 70-foot high highway embankment. The analysis required during the design stage of the project is discussed. This analysis and our design approach provided a defensible framework and justification to make design decisions on relevant issues including: allowable spacing of new and existing structures; preferred order of construction; expected ground deformation behavior; response of lining types to adjacent construction; and effects of proposed changes to design at the submittal stage and during construction.

Jan 1, 2003

By W. R. Bean

Probably few, if any, of the many serious problems confronting malleable foundries have been more difficult of solution than the question as to why malleable that is ductile, black in fracture, and normal in all respects before galvanizing should, by that process, be rendered brittle, brilliantly crystalline or "white" in fracture, and of low resistance to shock. So far as we are aware, the technical literature contains no data or discussions on this subject, except two referencesl,2 of a general character. It is apparently a question that every one concerned, producer and consumer alike, has been willing to evade as far as possible. Various theories as to the cause of the deterioration have been given but such checking of these theories as we have done indicates that there was no sound basis for most of them. This work on the galvanizing of malleable was first undertaken in 1916, and has continued until the present time. We now feel that for all practical purposes we have reached a solution and are glad to be able to offer it in a form that can be readily applied to production processes. It is impossible to give here a detailed account of the early work done on this problem. A great number of tests were instituted and an enor-

Jan 1, 1923

By B. H. Eccleston

The Bureau of Mines, in cooperation with the American Petroleum Institute, studied the effect of fuel volatility and front-end fuel composition on the amount and photochemical reactivity of automobile exhaust and fuel-system evaporative emissions. The study involved six gasolines--the base fuel, three fuels of varied volatility, and two fuels differing from the base and from each other in front-end olefin content. Data were obtained from 16 vehicles operated on a chassis dynamometer using a speed-load-time cycle that approximated a typical urban trip. Tests were made at ambient temperatures of 20°; 45°, 70°, and 95° F, using a climate-controlled dynamometer room. The amount of hydrocarbon emission and its probable photochemical effect, a potential contribution to pollution, is expressed as weight (reactivity equivalent) of a moderately reactive material, ethylene. Emissions of oxides of nitrogen, car-bon monoxide, and aldehydes were also observed. Results showed that reduction of volatility from currently typical levels serves to reduce both the amount and the reactivity equivalent of evaporative losses with a slight penalty by way of higher exhaust emissions. Alternatively, reducing the amount of light (low boiling) olefin in the fuel had no effect on the amount of hydrocarbon pollutant but did significantly reduce the reactivity equivalent of the emissions. Neither volatility change nor chemical changes to the fuel significantly affected the nonhydrocarbon emissions.

Jan 1, 1970

By E. H. Jr. Dix

IN selecting the subject, "Acceleration of the Rate of Corrosion by High Constant Stresses," for the 1940 Institute of Metals Division Lec-ture, I have been influenced by its highly theoretical and speculative nature as well as by the great practical importance of the correct inter-pretation and appraisal of the engineering significance of the phenomenon. I lay no claim to originality in talking on this topic, since it has been the subject of discussion for over a quarter of a century. However, as our technical thinking advances, old phenomena take on new and more significant aspects. In our studies at the Aluminum Research Labora-tories, we have encountered many perplexing and seemingly contradictory results and have been fascinated by the problem of dovetailing all of the many pieces of information to make a complete picture. I hope that in the brief period of this lecture I may share with you some of the enjoy-ment we have had in attempting to meet this challenge to metallur-gical science. The emphasis generally has been placed on the spontaneous failure by cracking of a metal under the combined action of high stress and corrosion, hence the present-day use of the terms "stress corrosion" or "stress corrosion cracking." The older term "season cracking," applied more specifically to copper-base alloys, includes, by inference, the element of time. For the purpose of the discussion today I will use "stress corro-sion" to cover broadly the effect of stress in accelerating the rate of corrosion of metals. To stay within the limits of allotted time the dis-cussion will cover the effect of high static stresses rather than repeated or dynamic stresses, which would take us into the related field of corro-sion-fatigue. The subject is particularly appropriate for an Institute of Metals Division Lecture because much the same phenomenon has been observed in almost all metal systems. Thus, in addition to the season cracking of brass may also be mentioned the "caustic embrittlement" of steel boiler

Jan 1, 1940

By Earl L. Phillips

The Bureau of Mines conducted laboratory tests on samples of pozzolanic-cement concrete to develop a low-strength backfill. Results show that support costs can be lowered by replacing a portion of the portland cement in mine backfill with pozzolan (fly ash) and lime. Unconfined compression tests on various ratios of fly ash to cement in 84 samples produced compressive-strength curves that can be used to estimate the best backfill mix for any mine.

Jan 1, 1981

By B. Stuckert, P. Sheehan, J. Balfour, B. (Manas) Das, D. Fawcett

"With the growth of large scale surface mining operations, waste disposal and stability of waste dumps pose a challenging problem to engineers. Vibrations due to blasting operations proximal to these dumps further complicates dump design. Many dumps which are statically stable may become unstable due to the effects of blasting vibrations.A joint project between CANMET and Smoky River Coal Ltd. has been initiated to study the dynamic stability of waste dumps. The study involves development of an analytical algorithm combined with field monitoring to assess dump performance.Another objective of the study is to provide baseline data for a vibration attentuation relationships for sedimentary rock (coal) environments: most studies to date are for base metal mines. The effect of dump thickness on vibration response is also addressed.The key objective of the study is to present a methodology for assessing the dynamic stability of waste dumps. Implicit in this methodology are a number of assumptions concerning vibration attenuation in sedimentary rock environments, and response of the dump material to induced vibration. Where possible, these assumptions have been compared with monitoring data as a check on their validity."

Jan 1, 1989

By F. M. Morris

A large reserve of thick coal in southwest Virginia was developed by Clinch-field Coal Co. in 1957-1958 to produce a nominal rate of 1500 tph raw coal. Operation features coal cleaning in transit. Refuse removed averages 35 pct. Evolution of plant from initial conception to completion is discussed, selection of means applied is explained, and performance to date us design expectation is described. The long-range plan calls for ultimate handling capacity of 40,000 tpd raw coal with anticipated clean coal capacity of 26,000 tpd on a three-shift basis. From a materials handling viewpoint, the Moss No. 3 operation is principally of interest as an ensemble. Generally speaking, it uses time-tested equipment and ideas but some of these are employed on a scale that may be new in the industry. At present about 20,000 tpd of raw coal are being handled. This is expected to increase to 40,000 tpd as soon as business conditions justify it. The purpose of this paper is to discuss the evolution of the plant as to materials handling practices, to describe briefly the equipment and methods used, and to comment on performance in certain areas. The subject divides itself naturally into four phases: 1) operations at the mines, 2) transportation from mines to plant, 3) raw coal handling into the plant, and 4) transportation of refuse away from the plant. OPERATIONS AT THE MINES The coal reserves for Moss 3 are in southwest Virginia where Dickenson, Russell, and Buchanan Counties come together. This area contains about 15 square miles and over 100,000,000 tons of coal. Here the No. 4 (Tiller) and No. 5 (Jawbone) seams of the Norton Formation lie so closely together that for practical purposes, they constitute one seam of coal. This seam, which is called the Thick Tiller, varies from 10 to 18 ft in thickness and underlies Sandy Ridge, a mountain cresting between 2400 and 3300 ft above sea-level. At 18-ft seam height (which is considered to be the maximum practical mining height) the parting between seams will be about 3 1/2 ft thick and each bench of coal will be about 7 ft thick. Depending on the amount of impurities in the seams Drover. total reject in this height coal may approximate 50 pet by wt. It will average about 35 pet for the property as a whole. The first move in developing this resource was made in 1953 when contour maps of several square miles around Duty, Va., including all the known outcrop, were made by photogrammetry. At this time, it was felt the prospective operation would be served by the Clinchfield Railroad and a photogrammetric route survey was made by this railroad from Haysi to Duty. Study of the resulting maps indicated only one site—adversely owned—which might accommodate the size washing plant to be erected. Water resources of a dependable nature seemed nonexistent. In 1954 bulk washability tests were made on the Tiller Bench at the Moss No. 1 preparation plant. The tests indicated this portion of the seam, mined separately, would wash to 4 pet ash with good recovery. Also in 1954, development of Moss No. 2, south of Sandy Ridge, was begun. This mine is in the Tiller Seam where it is about 100 ft below the Jawbone Seam. The reasons for developing a mine in the normal Tiller Seam before tackling the Thick Tiller seemed compelling: Railroad service could be established quickly, communications were better (though not good!), more was known of the seam (it had been mined in the years 1911 to 19241, and there was no essential property to be acquired. After some legal skirmishing, the Norfolk & Western Railroad was granted the right to serve the new mine. Three decades earlier the old mine had been served by the Clinchfield Railroad. The event which triggered active development of Moss 3 was the Appalachian Power Co.'s decision in 1956 to build a 450,000-kva power plant on Clinch River at Carbo. This solved the problem of marketing the steam coal which inevitably must be a product of a mine in the Thick Tiller. Management promptly decided to build the preparation plant at Carbo where an excellent site was owned; where railroad service existed; where telephone service could be obtained; and where roads, bridges, and water supply were tolerable.

Jan 1, 1961

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 Hsun Hu, B. B. Ruth

The rates of migration of high-angle boundaries in zone-refined aluminum crystals rolled 20 to 70 pct in the (110)[i12/ orientation were studied. Following a recovery anneal at an appropriate temperature to stabilize the polygonized structure, boundary migration rates of artificially nucleated grains were measwed isothermally at several temperatures. Results indicate that the rate of boundary migration depends strongly on the amount of deformation and on the cell size of the polygonized matrix, and is related to the driving free energy by a power function. The degree of anisotropy in growth 0.f the re crystallized grains nn&apos;th preferred mientation is independent of deformation; the migration rates of the fast-moving and the slow-moping boundary segments of a gowing grain differ by as much as one order of magnitude. The actir\ation energy fm a grain boundary migration, although nearly the same for both the fast-moving and the slow-moving boundaries for a given deformalion, decreases from 45 to 30 kcal per mole with an increase in deformation from 20 to 70 pct reduction. Re crstallization by the growth of the artificially nucleated grains results in preferred orientation. The Percentuge of&apos; grains favorably oriented for growth increases with increasing deformation. None of these grains corresponds to the ideal Kronberg-Wilson orientation relationship. The observed growth aniso-tropy is discussed in terms of boundary structure. The boundary velocity as a function of the cell inter -facial area, or the driving free energy, is discussed in the light of current theories of boundary migration. It is well established that recrystallization with re-orientation occurs by the migration of high-angle boundaries of strain-free grains. The driving force for this process is provided by the free energy stored in the metal during deformation. A quantitative study of the effect of varying driving force on grain boundary migration in deformed metals has not been possible heretofore, primarily because of: 1) concurrent recovery steadily decreasing the available driving free energy for boundary migration, &apos;-3 and 2) in-homogeneity of strain in the deformed metal.4 Aust and Rutter3 studied grain boundary migration in striated single crystals of zone-refined lead. Although the driving free energy in such crystals remains unaltered during annealing, this method does not provide a range of driving free energies over which measurements of grain boundary migration can be made. In the present investigation, the rates of migration of high-angle boundaries in deformed aluminum zone- refined single crystals were studied at various temperatures, after deformation ranging from 20 to 70 pct reduction by rolling at -78°C in the (ll0)[i12] orientation. The boundary migration rates along different crystallographic directions were determined under steady-state conditions, i.e., in the absence of competing recovery processes or impingement of recrystallized grains growing into the deformed single crystal matrix. Simultaneous recovery was eliminated by suitable anneals prior to the boundary migration measurements. The recrystallized grains, which grew a ni so tropically into the homogeneously polygonized matrix, developed flat boundary segments during early stages of growth. These boundary segments subsequently migrated along a direction approximately normal to the boundary plane into the matrix rystal. Increasing deformation over the range employed was estimated to increase the driving free energy for boundary migration by about five times. The kinetics of the boundary migration process, examined under these conditions, indicate that the boundary velocity is greatly affected by a small change of the driving free energy in the matrix crystals. These results were examined in the light of the current theories of grain boundary migration. EXPERIMENTAL PROCEDURES Single crystal strips (9 by 1 by 0.125 in.) of zone-refined aluminum, were seed-grown by the Bridgman method in a high-purity graphite mold (<lo ppm ash) at 1 in. per hr. Precautions were taken to minimize contamination of the metal during crystal preparation and subsequent handling. Spectrographic analysis of the metallic impurities in the grown crystals is Qven in Table I. The crystals were rolled in the (110)[112] orientation at -78°C to various reductions in thickness, ranging from 20 to 70 pct, in 10 pct increments. The desired reduction was achieved by many rolling passes, each being no more than 0.002 in. To minimize surface friction, the crystal was rolled between two thin layers of teflon. For those crystals rolled more than 40 pct, it was necessary to remove the disturbed surface layers by electropolishing at -5" to -10°C at an intermediate stage of rolling. The edges of deformed crystals were removed by a jeweler&apos;s saw while submerged in alcohol at -78° C to obtain samples of about ? by i in. The distorted metal at the cut edges and the surface layers were then removed by electropolishing, with removal of a minimum of 0.004 in. from each surface. The thickness of the crystals prior to rolling was chosen so that the final thickness was 0.025 in. for all samples. These deformed single crystals were each prean-nealed for 1 hr at an appropriate temperature in the range of 130" to 280°C, depending upon the amount of deformation. The purpose of this preannealing was to

Jan 1, 1970

By V. Galla

In the present paper, two large diameter columns 2 m tall and 1.3 m diameter filled with crushed (finer) and run off mine (coarser) heap leach materials respectively were used to perform unsaturated flow studies. Instruments measuring moisture content and matric suction were placed in the columns at different depths as water was applied at calibrated flow rates from the top of the columns. The outflows from the columns were recorded using tipping bucket rain gauge placed at the bottom of the columns. Unsaturated hydraulic parameters were also obtained for the heap leach materials, scalped (passing 4.75 mm sieve size) and whole (passing 37.5 mm sieve size) sample. The measurements obtained from the columns were later compared with unsaturated flow modeling results. The comparison indicated sensitivity towards the sample size selection for unsaturated hydraulic parameters, and initial conditions considered in the model.

Jan 1, 2009

By Richard H. Bube

Photoelectronic radiation detectors may be conveniently classified as homogeneous intrinsic, homogeneom extrinsic, or junction type. Highly photosensitive homogeneous intrinsic photodetectors may be prepared from a number of different II-VI, III-V, or IV materials. Such materials require the presence of specific imperfections that can act as sensitizing centers to provide long majority carrier lifetime. Homogeneous extrinsic photodetectors are of interest primarity for infrared detection, and consist principully of germaniuim and silicon with suitable inpurities. A vaviety of junction photodetectors exist, with silicon us the most common material for them all. The following extrema in performance are found: 1) highest photoconductivity gain in homogeneous intrinsic photodetectors; 2) smallest response time (highest frequency response) in p-i-n junctions; 3) largest gain-bandwidth product in avalanche diodes. ALTHOUGH the total number of materials exhibiting photoconductivity effects is very large, only a relatively few of these have appropriate properties for a practical photoelectronic radiation detector. In fact if one surveys the commercial detectors currently available, one finds that the field is dominated by some ten or fewer materials. These are summarized in Table 1 in terms of the other important variable in detector fabrication, the structure of the material, i.e., whether the material is used as a single crystal or in polycrystalline form, and whether the material is used as a homogeneous detector or whether the detector depends upon the existence of a junction or barrier in the material. The principal wavelength range for each type of material is also shown, together with an indication of the utilization of intrinsic or extrinsic excitation. For the purposes of the present comparison of various detectors, it will be convenient to discuss two main topics: homogeneous photodetectors and junction photodetectors. The performance of a photoelectronic radiation detector is measured in terms of two parameters: the photoconductivity gain, and the response time of the detector. A convenient figure-of-merit is given by the ratio of gain to response time, often called the gain-bandwidth product. The photoconductivity gain is a device parameter since it varies in many cases with the applied voltage and the detector geometry, and should be distinguished from the actual photosensitivity of the material involved. This photosensitivity can be conveniently given as the product of free carrier lifetime and mobility in the material. The photoconductivity gain is defined as the number of charge carriers which pass between the electrodes per second for each photon absorbed per second, where G is the photoconductivity gain, is the pho-tocurrent in amperes, e is the electronic charge in coulombs, and F is the total number of electron-hole pairs created in the photo conductor per second by the absorption of light. The gain may also be expressed as the ratio of the lifetime of a free carrier to the transit time for that carrier, i.e., the time required for the carrier to move between the electrodes. For a material in which one-carrier conductivity dominates, where T is the lifetime of a free carrier, ttr is the transit time for this carrier, p is the carrier mobil-ity, V is the applied voltage, and L is the electrode spacing. From Eq. [2] it follows that the photoconductivity gain is proportional to the photosensitivity of the material (tP), the proportionality constant being The photosensitivity of a material, and hence the photoconductivity gain of a device utilizing the material, depends on the lifetime of the free carriers as a critical parameter. In a homogeneous material this lifetime is determined by the nature of imperfections in the material, and in an inhomogeneous material the lifetime is determined by the specific junction structure. The speed of response, the other basic photodetec-tor parameter, is determined by factors quite similar to those important for photoconductivity gain. Imperfections are of primary importance in homogeneous materials, and the structure of the junction is a determining factor in junction devices. For infrared detectors it has become common to define another quantity designed to indicate directly how effective the detector is in distinguishing between a small photoconductivity signal and random noise due to the detector and its environment. The detectivity D* is given by

Jan 1, 1968

By Sabine Noelte, Mikko Petteri Rantamäki, Christopher Robben, Anssi Takala, Karl-Erik Rånman

"Sensor-based ore sorting is on its way to establish as a standard option for physical separation. The increasing number of installations in coal, iron ore, industrial minerals and hard-rock metal mining segments underlines the technological and financial potential that is beginning to be untapped. The Ma’aden Phosphate installation with 1.650 t/h sensor-based ore sorter feed sets a new benchmark for the possible capacity of stationary installations. Besides stationary installations, including multiple sorters parallel in different size ranges and multiple stages, containerised semi-mobile plants are applied. These offer two advantages, first being the reduction of transport costs when applied close to the mining face. The second is that semi-mobile systems enable processing of tens of thousands of tonnes of ore in a piloting phase with an approximate duration of 0.5 to six months, verifying the results laboratory mini-bulk tests on 5–10 tonnes of sample. This is especially important for low-grade metal ores because of the inherent Fundamental Sampling Error, as well as the Grouping and Segregation Error. The paper elaborates the results achieved within the I2MINE project, treating polymetallic ore at the Boliden Concentrator in Sweden.INTRODUCTIONSensor-based ore sorting (SBS) is becoming a standard option for physical separation, applied in all segments of mineral production. The Umm Wu’al project sets the bar for stationary SBS installations with 1,650 t/h feed (TOMRA, 2015). TOMRA Sorting Solutions has finalised an agreement in cooperation with Outotec to supply Outotec-branded sorting solutions for the mining and metallurgical industry (TOMRA, 2014). Especially for low-grade hard rock metal ores, an interdisciplinary approach is necessary applying experts for all aspects of mineral production. Due to the impact on the whole process stream, it is important on the end user side to have high level managerial support and involve all disciplines to ensure that all stake holders are involved in the analysis."

Jan 1, 2016

By F. C. Langenberg

It is the purpose of this paper to present a limited amount of experimental data obtained on the Charpy impact machine. Several concrete examples will be given showing the relation existing between the results obtained upon the Charpy impact machine and the behavior of the parts tested when in service. Although it is pointed out by G. Charpy and A. Cornu-Thenard1 that it is first necessary to determine a satisfactory working process before studying the correlation between the results of these tests and the behavior of the parts tested in service, this ideal course cannot be strictly adhered to. If a certain part repeatedly fails in service and the available tests give no indication of its cause, advantage must be taken of any possible means that will solve the problem; therefore, even though the reliability of the results obtained by the Charpy impact machine have been questioned by many, it was necessary to use this instrument without giving careful consideration to its possible sources of error. It would seem that the conclusions arrived at by Charpy -and Cornu-Thenard justify the assumption that the precision obtained by this machine is comparable to that obtained by the other more common forms of testing. The second general conclusion arrived at by them, namely, that the impact test upon notching does not offer any direct correlation to the ordinary tests, is also borne out by many hundred determinations made in the laboratories at Watertown Arsenal. This statement, however, should be qualified as follows: Other ordinary tests include the static tensile test from bars taken in a longitudinal direction and the Brinell hardness. The author agrees that no law is yet known for the computation of the energy absorbed in the rupture of bars of the same material but of different dimensions. Although Charpy and Cofnu-Thenard do not refer in their valuable article to the use of the Charpy machine in industrial practice, it should be stated that this instrument has been in constant use in the laboratory at Watertown Arsenal for several years, and is now employed for both routine and experimental testing.

Jan 1, 1920

By Robert H. Richards

The extent to which sizing by sieves should be carried, as a preliminary to the separation, by jigging, of minerals of different specific gravities, has been a matter of controversy for many years. The subject has been investigated by several authorities, yet the ground does not seem to have been completely covered, nor are the questions involved entirely settled. For my present purpose I shall refer to but three investigators—Rittinger, Munroe, and Hoppe. In seeking additional light, I have gone over part of the old ground which has been considered satisfactorily settled; and since these preliminary tests have thrown light on some points, they have been included in this paper. In the investigations here described, I have confined myself, for several reasons, wholly to small sizes—grains of 0.1 inch in diameter and less. Rittinger&apos;s work was mainly done upon larger sizes, and there is much need among millmen of information concerning the smaller sizes. Moreover, these sizes brought the investigation within the means at my disposal. The laws that have been claimed as the laws of jigging by the several authorities are: 1. The law of equal-settling particles. 2. The lam of interstitial currents. 3. The law of acceleration. 4. The law of suction. The first of these has been considered by investigators, generally, to be the most important of all, and the larger part of the work of jigging is thought to be governed by it. But that it does not cover the whole of jigging is clear to all; and to account for the increased efficiency which we may call the extra jigging-catch, the other three laws have been advanced. The investigation described in this paper was undertaken to determine, as far as possible, to what extent each of the four laws con-

Jan 1, 1895

By J. E. Burke, Y. G. Shiau

SEVERAL attempts have been made to account for the fact that grains in a fully recrystallized metal will coarsen on annealing Two fundamentally different hypotheses have been advanced; with several variations of each. One school considers that the cause of grain growth is the surface energy of the grain boundary The theory of Jeffries1 that grain size and grain size contrast control growth is an example The second school considers the primary cause to be a difference in the lattice energy on either side of the grain boundary The more perfect grains are considered to grow at the expense of their less perfect neighbors, with a decrease in free energy, and a consequent increase in the stability of the system. Burgers2 presents the case for the strain or lattice imperfection theory of grain growth quite completely The latter theory is attractive, since there is no doubt that differences in lattice energy or lattice perfection can cause grain boundary migration A recrystallization nucleus grows for this reason as was beautifully demonstrated by van Arkel and Ploos van Amstel3 Although it is generally stated that grain growth does not precede recrystallization, several workers4,5 have shown that small strains may induce a single crystal in an aggregate to grow, or at least may cause some&apos; grain boundary migration The origin and nature of the imperfections that are considered to be responsible for normal grain growth have never been clearly described, but it is generally agreed that they are a consequence of the difficulty of atomic reorientation in the solid state, and that they do not seriously differ from the type of imperfection that-can be introduced by mechanical deformation An object of the present work was to determine whether the introduction of mechanical deformation would cause grain growth in a specimen which would not otherwise show it under the conditions used It was also planned to determine the effect of such deformation the rate of growth in a specimen which would show - growth in the unstrained condition Recently Maddigan and Blank6 have indicated that slightly strained specimens of alpha brass can undergo considerable growth prior to recrystallization if annealed at low temperatures French7 has reported that at deformations less than 17 pct it is very difficult to detect the beginning of recrystallization in the same material. It was therefore planned to broaden this work to include a complete study of the microscopic behavior of alpha brass under conditions of temperature, time, grain size and deformation such that recrystallization would not occur or would occur to only a small extent EXPERIMENTAL PROCEDURE The brass was prepared by melting cathode copper and commercially pure zinc

Jan 1, 1947

By N. A. Gokcen

The construction and operation of a simple and accurate vacuum-fusion apparatus are described in detail. Absolute accuracy of the oxygen analysis has been determined by the reduction of oxides weighed to 20.01 mg. The Bureau of Standards steel samples have been analyzed repeatedly, and their inadequacy for the acceptable range of oxygen is presented. The limits of interference of manganese, aluminum, and titanium, and the effects of tin and water-cooling of the furnace tube have been investigated in detail. ANALYSIS by the vacuum-fusion method consists of melting a sample in a degassed graphite crucible under high vacuum and extracting oxygen as carbon monoxide, and nitrogen and hydrogen as gaseous elements. The resulting gas mixture is analyzed for its constituents, from which oxygen, nitrogen, and frequently hydrogen may be determined within 1/2 hr or less. The history and summary of methods1-4 and extensive reviews of literature&apos;.&apos; for the determination of gases in metals have been published in detail. The foundation of the modern vacuum-fusion method of analysis was laid by Jordan and Eckman,11 and Oberhoffer and his associates.1, 10 Diergarten,11, 12 Meyer,13 Thanheiser et al.,14, 15 Ericson and Benedicks,16 Ziegler,17, 18 Sloman,16-23 Thompson et al.,24 and later many others contributed to the improvement, accuracy, and limitations of the method. In some investigations, however, the limitations of the procedure and the errors involved in the analysis require further critical examination and evaluation. In many apparatuses, lunnecessarily complicated and cumbersome features and elaborate precautionary measures do not have conclusive advantages. The purpose of this invest:igation was, therefore, a) to construct a very simple and accurate apparatus, b) to determine the absolute accuracy of results, c) to establish the limits of interference of manganese. aluminum, and titanium, d) to reexamine critically the reduction and recovery of oxygen from oxide powders of various sizes, and e) to evaluate critically the eight steels of the Bureau of Standards."&apos; Apparatus The apparatus used in this investigation is shown in Fig. 1. It has been used for over three years, during which several modifications were made. A brief description of the apparatus is as follows. The transparent silica or Vycor tube, E, is joined to the Pyrex head, B, by mean of a face to face ground joint sealed with mercury. A similarly sealed ball and socket joint would also have been satisfactory. A standard tapered ground joint, successfully used by some investigators, was tried, but in the absence of grease or vacuum cement it was very difficult to disassemble the joint. The graphite crucible, G, 15/16 or l 1/8 in. OD, 2 1/2 or 3 in. high, 1/10 in. wall, shown enlarged in Fig. 3a, is made from the rods containing less than 0.08 pet ash. Two baffles, overlapping sufficiently to prevent spattering, are inserted in two opposite slots cut on a band saw. Two small holes in the baffles permit the temperature measurement of the melt. A second type of crucible, Fig. 2, G, shown enlarged in Fig. 3b, is also satisfactory, though not as convenient as the crucible shown in Fig. 3a. Somewhat similar but more elaborate crucibles with baffles were first tried by Ericson and Benedicks,&apos;" but were abandoned in favor of a crucible with a stopper and a peripheral graphite powder filter. Various versions of their crucible with a stopper have later been used by other analysts, 10-27, 27-30 The crucible is packed directly in E, Figs. 1 and 2, with —35 + 48 graphite powder for shielding and insulation. A minimum layer of 7 mm of powder is necessary for keeping E cool and minimizing the blank. The first use of graphite powder was made by Sloman,10-23 Who found that —200 mesh was the most satisfactory. The author tried various size powders from +20 to —100 mesh and found that a) particles of 28 mesh or larger were not sufficiently insulating and were heated by the induction current, b) the powder finer than 60 mesh packed too much and did not readily permit the escape of gases even when the crucible was heated very slowly; hence, the powder was occasionally blown out of the side in the crucible and in the mercury pump. The optimum size powder is, therefore, 35 to 48 mesh size or 0.4 mm in average diameter. The furnace is designed to eliminate excessive amounts of

Jan 1, 1959

By Lars G. Olavson

A prototype roof bolt which can be remotely placed by pumping has been developed by the Bureau of Mines. It is known as the "Pumpable Bolt". With the objective of field testing the effectiveness of the pumpable Bolt roof support system a mining machine was developed capable of installing Pumpable Bolts in the normal production cycle of a typical underground coal mine. The machine was built and the pumpable Bolt concept tested and evaluated as a total system in shop and mine tests. The machine was operated in the mining cycle of two mines and pumpable Bolts were installed at both mine sites.

Jan 1, 1976