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By John F. McElhiney, Hosseim Kazemi

This chapter is a review of fluid flow and mass trans- port in fractured rocks. The topics include: single-phase and multiple-phase flow theory, formation productivity or injectivity improvement by artificial fracturing, and mass transport associated with fracture acidizing. Possible extension and application of such ideas to in situ mining in fractured rocks are presented.

Jan 1, 1974

By A-A. Bogno, Ch. -A. Gandin, A. Maitre, H. Henein

Most metallic materials are produced from their liquid state. In order to control the properties of industrial products, it is very important to understand their solidification path and the resulting microstructures which can be significantly affected by melt undercooling. High undercooling results in rapid solidification and a refined microstructure with minimal microsegregation. This paper reports on the analysis of rapidly solidified Al-Cu droplets obtained by a single fluid atomization process, Impulse Atomization. A quantitative analysis by Rietveld refinement method of the Neutrons Diffraction data was carried out to determine the fraction of the intermetallic Al2Cu. Knowing the fraction of Al2Cu, the eutectic fractions and corresponding dendritic and eutectic undercoolings were estimated using the metastable extensions of solidus and liquidus lines of the Al-Cu system calculated by Thermo-Calc. In addition to this work, a model of microsegregation coupled with ThermoCalc software via TQ (application programming interface of ThermoCalc) and the Wang-Beckerman model for dendritic growth velocities has been developed for binary alloys. This has led to the development of a phenomenological relationship between primary phase undercooling and initial growth velocity. A comparison of estimated primary undercoolings using a coarsening model with the adiabatic undercoolings for each alloy composition has confirmed that solidification occurs under adiabatic conditions during recalescence.

Jan 1, 2014

By R. Pérez, James A. Finch, F. Tavera, Cesar O. Gomez

"Gas holdup is a variable which affects the operation of flotation columns. On one hand, gas holdup is a function of bubble size (a function of sparger type, frother characteristics and concentration, and air flowrate), tailings flowrate, solids content, and mixing patterns in the collection zone. On the other, gas holdup defines flotation kinetics and carrying capacity. Therefore, gas holdup is a useful variable to control and diagnose the operation of a flotation column, but the lack of a reliable sensor for on-line gas holdup monitoring has prevented its use in industry.This work describes the principle and the practical difficulties associated with the development of a gas holdup sensor based on the measurement of the electrical conductivity of dispersions. Two different approaches have been devised. These approaches will be described and test results presented of prototypes in laboratory and industrial columns.Background.Several years ago, a research program was initiated at McGill to use electrical conductivity as the basis for developing sensors for process measurements in mineral processing. Electrical conductivity is an intensive property which is a function of the concentration of the different phases present in a dispersion. The initial focus was on the detection of the interface between two dispersions with different characteristics (i.e., that between the collection and froth zones in flotation columns or that between clear water and sedimented solids in thickeners). The technique works in this case by searching for the location at which a sudden change in specific conductivity occurs, as a consequence of different gas holdup or solids content, and absolute values of the specific conductivity of the dispersions involved are not necessary1,2."

Jan 1, 1995

By Gerry Houlahan

The east span of the 3.5 km long SF-Oakland Bay Bridge is supported by different types of foundations along its span. Starting from the west, its first 460 m section comprising twin concrete box-girders is supported by sands and rock on Yerba Buena Island. A 620 m long steel suspension span then bridges a 25 m deep channel that is formed in sediments overlying rock. Twin concrete box girder structures, each 2.4 km long, complete the stretch over the remainder of San Francisco Bay to the engineered earth fill landing at its east end. For most of its length, the Skyway bridges water 3 to 10 m deep over soft surficial Young Bay Mud. The foundation types include spread footings with hold-downs, steel and concrete piles that are set in drilled rock sockets up to 3 m in diameter and 2.5 m diameter steel tubular piles driven to penetrations of up to 100 m. The design and construction-related considerations are presented. The different foundation types, influences of the site geology and earthquake demands on the substructures are discussed. The seismic motions of the bridge superstructures and substructures, as well as the depth-varying soil motions, influenced the foundation design. Together with performance-based design criteria, including post-earthquake footing displacement limits, these seismic demands influenced various aspects of the foundation design, including the use of battered and vertical piles.

Jan 1, 2013

By John E. Tilton

The ability of companies and countries to mine copper and other mineral commodities competitively and in the process to generate new wealth depends on their mineral endowment. Chile, for example, produces and exports copper because it is well endowed with high-quality, low-cost deposits. This production creates wealth that benefits mining companies and their stockholders, the government, local communities, as well as copper consumers around the world. The widespread perception that mineral endowment must largely determine competitiveness, or what economists call comparative advantage, must be true at any particularly moment. Countries with abundant reserves must be competitive. This follows from the definition of reserves — the quantity of a mineral commodity found in discovered deposits that are profitable to exploit under current conditions. As a result, it is a tautology and not particularly interesting. The important question is what causes reserves to change over time, producing in the process new wealth and shifts in competitiveness?

Jan 1, 2003

By D. A. Gulley, L. J. MacDonnell, William A. Vogely

INTRODUCTION Environmental impacts are most commonly associated with air and water pollution. Not- withstanding this fact, to many people the primary disruption caused by mineral extraction is the change in the character of the locale. That is, the environmental impact of mining includes, but is not limited to, the generation of residuals. The dramatic transformation of wilderness or rural land often creates strong reactions to mineral development. Thus, the basic issues of land use management are a useful addition to environmental discussion. In this section, we take up a discussion of federal, state, and local land use management regimes, along with a brief introduction to the potential role of economic analysis. Elsewhere in this volume, land management issues are discussed from other orientations, and the interested reader may wish to look there as well. Locatable Minerals on Federal Lands Legislation and Administration: Access to hard-rock minerals on the public lands is governed by the General Mining Law of 1872. This law declares that "valuable mineral deposits in land belonging to the United States . . . are hereby declared to be free and open to exploration and purchase . . . ." In order to initiate rights, prospectors are required to physically stake claims of specified sizes and shapes following basic procedures set by federal law which may be supplemented by the individual states. Rights to these claims are protected at the exploration stage so long as actual possession is maintained and diligent exploration activity is underway. If a valuable mineral deposit is discovered on the claim, the claimholder earns the exclusive right of possession as against private parties so long as the claim is properly maintained. To maintain this exclusive right the claimholder must per- form $100 worth of labor or improvements, known as assessment work, on each claim every year and make related annual filings with the U. S. Department of the Interior. If the existence of a valuable mineral deposit can be demonstrated, and other legal requirements are met, the claimholder may receive a patent giving full title to the claimed land, including the surface in most cases. The purchase price is either $2.50 or $5 .OO per acre. The Mining Law has remained largely un- changed by legislative amendment during its now more than 100-vear existence. However, while the law itself has not changed, its interpretation and administration have changed considerably. Written at a time of rapid western expansion of the U.S. following the Civil War, the intent of the law was to promote mineral development by inviting unrestricted prospecting and by selling the lands containing mineral deposits at a minimal charge. As federal land policy shifted from one of rapid disposal into private ownership to one of retention and management for a number of uses, mineral patenting requirements have been administered more strictly. The most critical issue concerns what must be demonstrated to establish the existence of a valuable mineral deposit. The so-called "prudent man" standard was established in the case of Castle v. Womble (19 L.D. 455 (1894)):

Jan 1, 1985

By J. T. Shimmin

THE past twenty-five years has been a period of unparalleled improvement in all lines of mining and metallurgical equipment, but probably none has undergone greater refinement and development than the vacuum filter. Beginning a quarter of a century ago, there has been steady advancement in the art of vacu-um filtration until today its use has become virtually standard practice for dewatering throughout the entire metallurgical industry as well as in important parts of the chemical and industrial processing fields. The credit for the first successful application of vacuum filtration 'at the Consolidated Mercury mines in Utah in 1902 undoubtedly belongs to George Moore. There, it is said, his filter reduced the loss of gold in the slime and sand from $1.25 to 40c. per ton. Successful applications were subsequently made by Mr. Moore at the Liberty Bell mines, Telluride, Colo., the Lundberg, Dorr &Wilson mill at Terry, S. D., and elsewhere. E. L. Oliver is generally credited with, having done the most to work out the necessary continuity of op-eration exemplified in the well-known continuous vacu-um filter which bears his name. Others made improve-ments also, but in my opinion all the new ideas advanced in recent years are modifications of the fundamental principles originated by the two pioneers, Moore and Oliver. Considerable interest has been shown recently in the new type of continuous internal-type vacuum filter which is associated with my own name1. In response to frequent inquiries regarding it and the steps which led up to its invention, I am giving herewith a brief account of the early history of this development and some of the more important installations which have been made during the last year or so. A. M. Nicholas (now deceased), an Australian engi-neer, conceived the idea, several years ago, of manu-facturing a continuous vacuum filter with the filter medium applied upon the inside of the drum, as con-trasted with existing drum filters in which the medium is applied externally. Nicholas recognized that a ma-chine of this type would be simpler than one with a tank and would overcome some of the difficulties en-countered with tank filters on certain classes of pulps, and he appreciated the value of having filtration take place in the same direction as the gravitational settle-ment of the solid particles in the pulp, the pulp being retained within the drum instead of being held against the outside surface. The ease of starting up after a shut down was likewise realized by Nicholas. It was tried in the United States, but was not entirely success-ful primarily due to mechanical defects.

Jan 5, 1928

By T. Dunn

FMC Corporation has achieved a significant cost reduction through a new proprietary solution mining and processing technology at its Green River, Wyoming Soda Ash Facility. In the first phase, completed in October 1995, trona ore is dissolved, recovered and processed with the new technology, and then fed into an existing refining plant, replacing dry mined and calcined trona ore. The second phase, completed in April 1996, produced a fmal high purity product and increased capacity by 635,000 t/a (700,000 tpy). Both phases were completed under budget and well ahead of schedule.

Jan 1, 1998

By Murali Thirukkonda, Rahul Shah, Srinivas Tangrila, Shankar Rachakonda, Jan Kajuch, Arthur Gurson

"High-temperature superconductors have potential for a variety of applications such as power generators, superconducting magnets for mine sweepers or ship propulsion motors, and magnetic levitation transportation systems. Interest in the use of superconducting wires and tapes increased dramatically after the discovery of high-critical-temperature (high-Tc) oxide superconducting compounds, which offer operating temperatures above that of liquid nitrogen. Several techniques have been proposed to produce commercially viable high-Tc oxide based superconducting wires. One of the promising methods involves multi-pass powder-in-tube (PIT) wire drawing followed by rolling and heat treatment. This work focuses on the development of a numerical model to simulate the PIT drawing process for fabrication of long lengths of silver sheathed Bi-2212 superconducting wires. The finite element based model was used to predict densification of the oxide powder, wire drawing forces, and silver sheath thickness during drawing. A cap-type pressure dependent constitutive equation was implemented in the model to simulate the powder behavior. The model incorporated experimentally obtained material data for the silver and powder. Results indicate that powder densification is increased by decreasing the initial silver thickness and increasing the silver strength. Data from wire drawing experiments were used to verify model predictions. IntroductionSuperconducting wires and tapes can be used to carry large dc currents with no measurable loss due to resistivity. When used in superconducting magnets for power generators, motors, levitation devices, magnetic detectors, or energy storage devices, they could potentially result in significantly reduced energy losses. In the past, most prototypes were tested in liquid helium at 4.2K [1]. However, the necessity to provide liquid-helium cooling systems proved to be a serious limitation in commercialization. In 1986 high-critical-temperature (high-Tc) oxide superconductors were discovered [2], which could allow for higher operating temperatures above liquid nitrogen (77 K). Since then, both academia and industry have concentrated their efforts on the development of high-Tc oxide superconducting wires, tapes and coils. As yet, large scale fabrication of long lengths of these wires with the required current carrying capacity and mechanical properties remains an enormous challenge."

Jan 1, 1994

By Álvaro Lúcio

This paper outlines the DPC process as na economic and environment friendly option for the use of cultivated forest as a source of raw material for metallurgical charcoal.The DPC process was specially developed to bring logistic, environmental, technical, economic and global energy efficiency when compared to termal1 the existing biomass carbonization process. The DPC process utilizes the volatile materials (condensable and non condensable) as a source of the energy required by the carbonization process guarantying its complete combustion. As result the DPC process avoids the burning of termal1 the loaded wood, obtaining a higher charcoal to biomass yield, and avoids the emission to the atmosphere of polluting gases. Gases emitted by the carbonizing wood have na energy termal1e enough to dry the wood soon after its harvesting. By avoiding the storage in the field during na average of 150 days, the resulting economy is quite significant. As a termal1e1 the higher charcoal to biomass yield na termal1e1e economy is obtained through the reduction of the cultivated forest term. This paper emphasizes the economic advantages of the DPC process.

Aug 16, 2017

By R. G. Vardiman, M. R. Achter

Observations of dislocation structure in niobium are presented using two techniques. Triangular pits developed by electroetching are confined to orientations in the stereographic triangle between the (111) pole and planes of the (1ll) zone and require the presence of carbon. Some unusual electroetching phenomena at other orientations are noted. A chemical etch of dislocations decorated by the addition of carbon to 50 ppm reveals the complete dislocation line structure in a surface layer up to 30 p deep, with a resolution of less than 1 p. This effect is independent of surface orientation. The structure of subboundary nets may be resolved for misorientations up to about 1'. Dislocation structures found in strain anneal grown crystals, such as helices, prismatic loops, and high-density areas, are observed. The measurement of dislocation density is discussed and values obtained in different ways are compared. IN the course of some work on the response of refractory metals to thermal-mechanical treatments, it was desired to examine the defect structure of relatively low dislocation density crystals of niobium in bulk form. Surface and bulk methods for the observation of dislocations have been reviewed by ~melinckx,' and include etch pitting, decoration, and various X-ray techniques. The dislocation line structure has been developed by decoration in a few metals, although observations were limited to certain orientations, or by the coarseness and nonselectivity of the precipitate. The most commonly used technique is etch pitting. In niobium, etch pits have been developed chemically'0," in material of high impurity content and electrolyti-cally'' in relatively pure material. In this paper, etch pits developed electrolytically, and the dislocation line structure of a surface layer developed by decoration and chemical etching, are examined, and observations are presented from both techniques. EXPERIMENTAL METHODS Our starting material was electron-beam-melted niobium, swaged to 4 or -in.-diam rod. Chemical analysis is given in Table I. Single crystals were grown by a strain anneal technique using 1 to 2.5 pct of strain and growth temperatures of 1700" to 2300"~.'~ Some crystals grown by zone melting were also examined. The desired surface orientation was exposed either by spark machining or by sectioning with a cut-off wheel and prepared for etching by electro-polishing.

Jan 1, 1969

By J. A. Cole

The mill project at Lone Tree was commissioned in October, 1993, followed by the commissioning of the autoclave pressure oxidation circuit in February, 1994. Discussion of the first year of milling operations at Lone Tree is presented. The mill is currently operating above the design rate of 2,267 mt/d (2,500 st/d). Both phases of the start-up were essentially trouble free. The few problems that were encountered and the respective solutions are addressed.

Jan 1, 1995

By W. A. Eardley

FIFTEEN years ago the world's deepest oil well penetrated the earth about 7300 ft. That depth has now been more than doubled. Why has such deep drilling become necessary and how has it become possible? Three factors have had an important bearing: (1) Depletion of shallow zones, making it necessary to search for deeper producing measures. (2) The perfection of prospecting methods, which have been success- fully used to locate favorable buried structures, many at great depth. (3) Improvement in the quality of steels used for drilling.

Jan 1, 1940

By Sean Hunter

Artificial Intelligence has a long history but is currently coming strongly into focus with new advancements. This leads to questions many people are asking: what exactly is AI, how can it be used effectively in mining operations, and what foundation is required to make AI implementations successful? In mining, many AI applications exist, from drill pattern optimization to predictive maintenance. However, many implementations struggle due to data integration challenges. Mining operations generate large amounts of data from many sources, such as fleet management systems, drill sensors, process control systems, and laboratory results. Unfortunately, this data often exists in silos where it’s difficult to get it out, making AI applications unable to leverage it. Worse still, tools that use AI don’t always provide their data back to the system, creating even further data silos. All these problems make it hard to take advantage of the data at the mine, slowing down and reducing the effectiveness of AI. This paper presents a comprehensive approach to organizing mining data using an AI-ready knowledge graph system. We will first explore the evolution of AI in mining, from early expert systems to modern machine learning applications. Then, we will detail how a knowledge graph can integrate business context, operational data, and AI models into a cohesive system that enables more effective AI implementations across mining operations. The proposed method has been developed considering both the unique data challenges faced by the mining industry, while also considering best practices learned from the AI field at large. By following this approach, it’s possible to better utilize existing data, getting higher quality and more complete results faster, and in a way that’s reusable and composable.

Feb 1, 2025

By Marc C. Bétournay

A number of successful proof-of-concept projects have been carried out to replace conventional power application, such as diesel and rechargeable batteries, in underground mine vehicles. This has led to the development of the world?s first fuelcell production vehicle, a mine locomotive. A mine loader project has also started and several other projects are planned. These projects are providing the mining industry with the required information to make this technology shift possible. The application of fuelcell power will yield several important benefits such as the elimination of underground diesel emissions, significant reduction in the primary extraction?s sector greenhouse gas emissions and support for a more productive scenario. This article reviews these successes, discusses ongoing and potential projects and presents the technology application benefits that could be possible for mining operations.

May 1, 2003

The Burra Burra Mine is situated in complexly folded Torrensian dolomites and limestones forming the faulted axial region of a major anticline. The orebody mined was largely of secondary origin and confined between two faults, Kingston's on the west and Tinline's on the east. The orebody occurred at the junction between cherty dolomites and a clastic limestone with a large mass of marble breccia along its western margin. Secondary ore consisted of carbonates and oxides in the breccia and the ore bed and detrital copper minerals deposited as part of a clastic breccia in sinkholes and solution cavities in the dolomites and ore beds.Primary sulphides occur disseminated in the marble breccia and in stratiform habit in the ore bed. Kingston's so-called "lode" may be mineralized marble breccia.The marble breccia appears to be of diapiric or sedimentary origin and there is evidence to support a sedimentary origin for some of the copper sulphides. No igneous rocks have been discovered within 20 miles of the mine and any hydrothermal activities were probably at comparatively low temperature. The possibility of extensive stratiform and disseminated copper sulphide mineralization in the marble breccia and ore bed requires testing by further drilling and geophysical surveys.INTRODUCTIONThe re-interpretation of Burra Burra geology and ore formation discussed in this paper resulted from a comprehensive investigation of the mine and its surrounding district begun in December 1961 and in progress at the time of writing. (February 1963). The decision to investigate Burra Burra was taken after a thorough examination of records and reports of all non-ferrous metal deposits throughout South Australia and was given impetus by a report by Thomson (1963) suggesting a sedimentary origin for the copper mineralization. Although the author does not concur fully with Thomson's interpretation there is no doubt that sedimentary processes have played an important part in the formation of the Burra Burra copper deposit, nor is there any doubt that igneous activity played no part.

Jan 1, 1963

By D. E. Wolfson, D. A. Reynolds, F. W. Smith

IN 1948 the U. S. Bureau of Mines began a three-phase program to evaluate the extent and quality of U. S. coking coal: 1) a factual appraisal of known recoverable reserves in beds of mineable thickness, 2) a study of preparation characteristics, and 3) a study of carbonization properties. A previous paper presented the methods used in assessing reserves.' Although this investigation is only partly completed, data on coking properties of the Pittsburgh district coals are now available. The results are presented in this article. When coals are selected for manufacture of metallurgical coke more factors must be considered than for any other major use, as no basic industry requires coal of such high quality and uniformity. This is particularly true in the Pittsburgh district, where blast furnace practice is based on use of cokes from high quality coals. Although it is true that inferior coals are carbonized in other industrial areas, both here and abroad, the Pittsburgh coals are the best economically obtainable in the required tonnages, even though they are not the most desirable for metallurgical use. In the general evaluation of suitability of coals for coke making, particular attention is given to: 1) reserve, 2) ash and sulfur content, 3) inherent properties of forming strong, well fused coke, 4) expanding characteristics, and 5) blending properties. Items 1 and 2 are covered in detail in the first two phases of the survey, and coking behavior is considered in items 3 through 5. Problems is Coal Evaluation: Although not all coal beds of immediate or potential use to the coking industry in the Pittsburgh area have been tested for their coking properties, enough tests have been made to permit certain generalized statements. Virtually all the coals that will be used in this district are from the Appalachian region, and except for high oxygen coals from outcrops or stripping operations, they are coking coals. Hence the evaluation problem is not so much that of distinguishing between coking and noncoking coals as attempting to measure quantitatively differences in the coking and expanding properties of the better coking coals. Quantitative differentiation between good coking coals, is complex, since differences in their coking abilities are frequently of about the same magnitude as the precision of the test. Small-scale tests are generally unsuitable for measuring these slight differences, and there has been gradual acceptance of pilot-scale tests. Test Methods Employed: All the data reported here were obtained in two units known as the Bureau of Mines-American Gas Association (BM-AGA) carbonization apparatus and the sole-heated expansion oven. The BM-AGA unit, which consists essentially of a cylindrical steel retort about 18 in. diam and 26 in. high, carbonizes enough coal (180 lb) to allow evaluation of the coke by standard methods of the American Society for Testing Materials. The BM-AGA carbonization procedure and methods of testing the gas, liquid, and solid products have been described.' Expanding characteristics of the coals were determined in the sole-heated expansion oven," wherein the coal charge, heated from the bottom only, is carbonized under a constant applied force and the linear expansion or contraction is measured. Although results in this oven have never been quantitatively correlated with the expansion behavior of coals in conventional slot ovens, they are useful in assessing expansion behavior. In this report discussion will be confined to results obtained from these pilot-scale units, although the following data are available for most coals: proximate and ultimate analyses, free swelling index, agglutinating value, and plasticity. Sources of Coals Tested: In selection of coals for coke manufacture, economic considerations are as important as quality, and each coke plant balances these two factors to meet requirements of the most satisfactory coke at lowest price. Although these economic factors may in some instances outbalance small differences in coke quality, they are usually specific to each coke plant and cannot be given in any general statement. Recognizing that coal and plant operating costs are beyond the scope of the survey, the USBM evaluates the coking quality of various coals without regard to their competitive economic status. For the purpose of this article, coals of interest to the Pittsburgh district are arbitrarily defined as

Jan 1, 1958

By John J. McKetta. Jr., Louis B. Lesem, George H. Fancher

The proration of oil produced in the field frequently is based partially or entirely upon the gas-oil ratio of wells. The measurement of the gas-oil ratio is one of the more important field tests in regulatory and pro-ration work, and the test always should be conducted according to standardized methods and procedure. Obviously, the gas-oil ratio and the volume of gas produced by a well depend upon many factors but should be independent of the method of measurement and of the devices used to measure gas and oil. Consequently, the volume of gas accompanying a barrel of oil produced by a well may be measured by any reliable and accurate device or instrument. Frequently either a critical flow prover or an orifice well tester is used for this purpose, and for a particular well the same rate of flow of gas should be obtained regardless of whether a critical flow prover or an orifice well tester is employed in the test. In Texas, when using either instrument, either Capacity Table 1 or 5' is employed in making the necessary computations. If the tables are used, a discrepancy always is found whenever the two instruments are compared by extrapolation to the same conditions of flow. Clearly, Tables 1 and 5 must be at fault in some respects. The orifice well tester and the Bureau of Mines type of critical flow prover are essentially the same instrument; both devices utilize a square-edged orifice 1/8 in. in di-ameter as the primary element, and both freely discharge gas to the atmosphere. Tables for the orifice well tester' have been published in the ranges of 0 to 15 in, of water and 0 to 40 in. of mercury (Hg) differential in pressure. Coefficients for the critical flow prover have been published for differentials in pressure greater than 75 psia. An extrapolation of either differs from the other set of data as much as 18 per cent at some points. No immediately obvious reasons for the discrepancy was found, and data available from the literature were insufficient to effect reconciliation. Consequently, a series of experiments was performed to check the available data and to determine discharge coefficients for the two devices in an overlapping range of differential pressure. The correlating equation used in preparation of tables such as Tables 1 and 5' is the so-called hydraulic equation, Q = C1 vh .....(1) The tables cover orifice sizes from 1/8 through 1 1/4 in. A second set of tables, for use with greater differentials in pressure, apply only to the 3/4, 1, and 1 1/4-in. orifice plates over a pressure range of 0 to 40 in. of Hg. The correlating equation used in preparation of the tables is Q = C2 vH(29.32 + 0.3H)/G . (2) Each of these equations is valid only for the range to which it has been applied, and neither equation is valid for extrapolation. Theoretical equations for flow through an orifice are based upon assumptions of fractionless flow and an emergent jet the size of the orifice. A multiplier, C,, called the discharge coefficient, is inserted into the theoretical expression to compensate for both frictional losses and the contraction of the jet experienced in the plane of the orifice. Buckingham3 shows that C, should vary with the ratio of upstream to downstream pressure for flow of a compressible fluid at any average linear velocity through the orifice less than the velocity of sound. Work published by the National Advisory Committee for Aeronautics4 indicates that the variation continues into the so-called critical flow region until the vena contracta coincides with the plane of the orifice. The NACA work, however, does not indicate a leveling off of the coefficient. The work of the Bureau of Mines5 for the critical flow prover was based on differential pressures greater than 75 psi and indicates that the discharge coefficient, Cd, is constant in this region at a value of about 0.86.

Jan 1, 1958

By Carlos Maurício F. Vieira, Lázaro A. Pizatto, Marcus Paulo Cardoso, Sergio Neves Monteiro, Joao Victor C. Nunes, Gustavo S. R. Matheus, Frederico M. Margem

The interest in composites with natural fibers is due, among other factors, to the growing worldwide concern with the preservation of environment and renewable raw materials. The natural fibers have many particular properties that make them an attractive alternative to traditional synthetic fibers. The advantages of using these fibers are: low cost, renewability, biodegradability, low toxicity, abundance and specific strength. The searching for new suitable, economically viable and technologically advanced materials justifies the accomplishment of this work that aims at comparing the mechanical behavior of polyester matrix composites with epoxy matrix composites reinforced with hemp fibers Izod impact tested. The specimens with dimensions: 10 63 12.7 mm, made in different volume fractions of fiber: 0–30 vol%. The samples were tested at PANTEC pendulum model XC-50 located at LAMAV/UENF. With this research was possible to analyse the mechanical properties of these two new materials.

Mar 1, 2018

By J G Reid

In the period since 1989 the Yabulu Nickel Refinery of Queensland Nickel has undergone a transformation both in terms of the nickel laterite ore feed and the refined nickel product. These two changes were mutually supporting, as will be shown in the following paper. It had been realised since the early-1980s that the Greenvale orebody would be exhausted by 1992. Consequently planning had been in progress throughout the 1980s for the importation of overseas ore as a replacement for the Greenvale ore. The existence of extensive lateritic ore deposits in New Caledonia and Indonesia made these locations the natural focus of attention. With the three Japanese ferronickel smelters sourcing their nickel garnierite ore feed from these locations it was relatively easy for the miners to supply the overlying limonite ore to Yabulu. This limonite ore was previously discarded as waste. The Yabulu refinery now receives about 85 per cent of its ore from these two overseas sources. The transition from Greenvale ore to imported ore occurred gradually between 1989 and 1993. It was during the ore importation planning stage of the mid 1980s that Queensland Nickel commenced the technical investigation which led to the ammoniacal solvent extraction (ASX) plant installation and the product change from nickel oxide to nickel metal.

Jan 1, 1994