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By Maria Anita de Paula Negreti

Neste trabalho, foram obtidos compósitos poliméricos de Óxido de Grafite (GO) incorporado em Poli(metaclilato de metila) (PMMA). A obtenção do Óxido de Grafite foi realizada pelo método de Hummers modificado. Em seguida foi ainda adicionada uma etapa secundária de tratamento térmico à 1000ºC no GO obtido a fim de expandir as lamelas de grafite e remover os grupos funcionais aderidos durante o ataque ácido do grafite. As cargas obtidas foram caracterizadas com o auxílio das técnicas de Difração de Raios-X (DRX), constatando a expansão das folhas após o tratamento térmico. O estudo comparativo dos compósitos de matriz polimérica com 3 % de concentração de GO antes e após o tratamento térmico foi realizado com o objetivo de entender a contribuição nas propriedades reológicas do polímero com a adição da carga de GO. Os resultados reológicos apresentaram um aumento da viscosidade complexa tanto no ensaio de Varredura de Tempo, quanto no Cisalhamento Oscilatório de Pequenas Amplitudes (COPA).

Aug 16, 2017

By Ying Gu

Automated mineralogy methods and tools, such as the Mineral Liberation Analyzer (MLA) and the QEMSCAN, are now widely used for ore characterization, process design and optimization. Several case studies published recently demonstrate that large gains can be obtained through grinding and flotation optimization guided by automated mineralogy data. However, since automated mineralogy can only provide the information pointing to where the process gains can be made, it does not directly impact the production gain. Thus, a question is often asked: how to value the contribution of automated mineralogy to process improvement of a particular plant. This appears to be a difficult question. On close examination however, it is found that this is essentially a question of the value of information and it is reasonably well documented in various other industries. Hubbard (2010), in chapter 7 ?Measuring the Value of Information?, dealt with exactly this type of problem. The value of information is the reduced risk of an investment and opportunity loss. The methods Hubbard developed can be applied to estimate the value of automated mineralogy, as well as metallurgical test work, which also produces information that reduces the risk of investment. This paper first introduces Hubbard?s theory on the value of information and how to measure it. It then applies his methods to estimate the value of automated mineralogy, using Anglo Platinum?s fine grinding project as an example. In this case, the value of automated mineralogy includes the reduction in investment risk worth US$ 62.5million, in project rejection worth US$197 million and in opportunity loss worth US$320 million. In the end, a general model is developed to allow the simulation of the value of automated mineralogy in different mining operations constrained by different parameters.

Sep 1, 2012

By Leonardo Rosas Sánchez, Darío Ángel Bulla

"The two track road sector between Cisneros-Loboguerrero (having a length of 14 km and 11 short unidirectional tunnels) is a new highway still on construction located along the existing Highway Buga – Buenaventura (Colombia). Due to the steep topography, difficult geological/geotechnical conditions, the traditional portal construction approach was impossible to be implemented in eleven (11) of the twenty two (22) portals. In this specific project, the skewed portal approach was developed as the optimal and more effective solution. The construction time and costs of portals were reduced in 21 months and 75%, respectively. At the same time, the natural equilibrium of the slopes was maintained, thus, facilitating adequate safety factors along the useful life of the project. This document pretends to show a detailed design experience (and the construction of the entry portal of tunnel 11 (left)). INTRODUCTION The Cisneros-Loboguerrero project is a 14 km length dual lane highway, connecting productive zones with the Pacific Ocean along the current Bogota-Buenaventura highway as shown in Figure 1. The project is located at the northern side of the Dagua River Valley. The preliminary design suggested constructing portals under challenging topographical conditions, i.e., slope cuts having heights between 50 to 100 m (some having slopes > 100%) requiring complex developments and having very high risks.The entry portal of tunnel 11 (left) was the first portal successfully built by implementing the skewed portal approach. Later, this approach was used as a model for the construction of the other ten (10) portal having similar topographic and geotechnical conditions. The development of this new alternative provided a considerable reduction on the construction time of portals, thus relieving a critical path in this project."

Jan 1, 2016

By J Walshe, G Duclaux, L A. Fisher, R Hough, J S. Cleverley, M F. Gazley

Characterisation of hydrothermal gold systems across multiple scales is increasingly important for our understanding of ore deposit genesis and for targeting new mineralisation. Published work on multiscale mineral system exploration focuses either on applying a single technique across scales or on incorporating a series of techniques across a limited scale range. Typically, these studiesÆ spatial scales vary from crustal to deposit-scale and have successfully linked the distribution and shape of major orebodies to fault systems or varying lithostratigraphy. But, is this scale small enough to answer fundamental questions about the relative timing, processes interactions and mechanisms involved in the formation of ore deposits? We illustrate the potential of a deposit to microscale study, using the Plutonic Gold Mine in Western Australia as an example, to better understand hydrothermal gold systems. Using an integrated approach combining lithological and alteration logs, various geochemical data set, meso- to microscale structural and textural observations and spatial data assimilation, we have revisited the fundamental processes involved in the formation of this significant gold deposit.CITATION:Duclaux, G, Hough, R, Gazley, M F, Fisher, L A, Walshe, J and Cleverley, J S, 2013. A multiscale approach to hydrothermal gold systems - unravelling mineralisation processes at the Plutonic Gold Mine, in Proceedings World Gold 2013 , pp 95-98 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By James W. Mitchell

On December 2, 1942, a scientific team lead by Nobel Prize winner Enrico Fermi first initiated and controlled a self-sustaining nuclear chain reaction. This historic event occurring beneath the stands of the University of Chicago football stadium instantly created an entirely new and tremendously broad area of technology. Indeed, the event probably changed the course of world history and considering the curret energy shortage, it probably came none too soon. Following many technological breakthroughs in the ensuing years, this event led to the first full scale nuclear fueled electric generating plant. In December, 1957, the Shippingport Nuclear Power Plant became operational and the United States had entered the era of the nuclear fueled electric generating station. Today, only fifteen years later, there are some thirty-five operating nuclear power plants in the United States with another 56 under construction and 116 on order. Still, we are only scratching the surface of this tremendous energy source. In 1970, less than one-percent of the total electric generating capacity in the United States was nuclear fueled. By 1985, it is projected that 45% of our generating capacity will result from nuclear power plants. These projections are based upoa statistics of six months to a year ago and considering the current energy shortage and recent attempts by the United States Atomic Energy Commission (USAEC) to speed the licensing process and encourage standardized plants, the contribution of nuclear power to our total generating capacity may be even greater. In summary, it is obvious that nuclear power is now, and will continue, playing an important role in our future. Those factions of government, industry and the professional community charged with fully developing this tremendous energy source must deal with it rationally, logically and expediently. The various environmental considerations in nuclear plant siting play an important role in the overall plan.

Jan 1, 1974

By E. L. Piper

Natural graphite has been known for many centuries, having first been reported as a distinct mineral form by Gessner in 1565. At that time, graphite was used extensively as pencil "lead" because of the ease with which it marks paper. It is a black, unctuous material found as flakes, lumps, or needles in scattered locations throughout the world. The less crystalline, or "amorphous", natural graphites are thought to have been formed from coal under conditions of high temperature and pressure. The more crystalline varieties, such as those mined in Ceylon, probably were precipitated from molten solutions or were pyrolyzed from gaseous carbon compounds. Recognition of the good thermal and electrical conductivity of graphite, together with its highly refractory nature, led to an increasing number of appli¬cations for this material. Clay and pitch bonded natural graphite has been used in crucibles, refractories, foundry facings, and other high-temperature appli¬cations. These forms constitute the most important current uses for natural graphite in the United States. Other products containing natural graphite include batteries, lubricants, pencils, brake linings, etc.

Jan 1, 1973

By Luis Ángel De Montreuil

El oro nativo es un elemento inerte de condiciones primarias que en muchos depósitos se encuentra en las zonas de oxidación. Sin embargo, el destino del oro durante los procesos de oxidación es controlado principalmente por la naturaleza y tamaño de las partículas de oro en los depósitos primarios. En ese sentido, el presente texto describe este proceso de oxidación y el posterior enriquecimiento secundario de los yacimientos de oro. Para ello, se realiza una estratigrafía de las zonas de óxidos y sulfuros supergénicos de los yacimientos auríferos a través de muestreos sistemáticos, mineragrafía, petrografía y ensayos químicos. Dicho proceso permite establecer una mejor planificación del tratamiento metalúrgico y releva la presencia de ricos horizontes auríferos en un yacimiento, en cuyo caso el tratamiento metalúrgico puede ser selectivo.

Jan 1, 1985

By W. Z. Choi

A model describing size reduction and mineral liberation during grinding has been extended to include multiple classes of composite particles. The majority of the model parameters have been directly determined using computerized image processing equipment to analyze the products from batch grinding tests. A coarse-grained sphalerite ore from Tennessee, representing a nearly ideal binary mixture of sphalerite and dolomite, has been used to experimentally validate the model for the case of dry, batch grinding. In all cases, excellent agreement has been observed between the model predictions and the experimental results.

Jan 1, 1986

By Glenn C. Reed

This report is one of a series describing investigations within the Missouri River Basin in Montana made by mining engineers of the Bureau of Mines Minerals Division, Region II. The primary purpose of these investigations is to provide information to agencies of the Department of the Interior and and others concerned with the planning of Federal power developments in the basin. The report contains such factual data as have been authorized for public distribution. The field investigations in Broadwater County were made during the late fall of 1948 and the summer of 1949. Virtually all known metallic mineral deposits and some nonmetallic mineral deposits within the county were investigated. However, some long inactive mines and prospects on which little or no information is of record may have been omitted inadvertently. Many of the mines and prospects have been inactive for extended periods. Most of the underground workings now are inaccessible. Because of such conditions, impressions gained by the inspection of surface features have been supplemented necessarily, where possible, by information obtained from Federal and State publications.

Jan 1, 1951

By Juan L. Luque Lanza

Durante las fases de minado como la exploración, desarrollo, preparación y explotación de una zona mineralizada, surgió la necesidad de clasificar geomecánicamente el terreno a través del uso los conceptos básicos de la mecánica de rocas y la integración de dicha disciplina al planeamiento del minado de una mina subterránea. Por ello, el presente texto describe el proceso de esta metodología que consiste en la clasificación del terreno según los grupos de similar comportamiento y la elaboración de planos geomecánicos, con la finalidad de encontrar la relación existente entre el tiempo límite y el espacio activo para una excavación subterránea, diseño y cámaras pilares en la mina subterránea de Yauricocha.

Aug 26, 1988

By William J. Miles

From a historical perspective, bentonite is the common rock term for various uses and applications. Its name originates from water-based muds near Fort Benton used for lubrication of wagon wheels during the 19th century migration to western territories (which are presently part of the United States) when the pioneers ran out of axle grease. From a clay mineralogy perspective, bentonite is composed primarily of montmorillonite, an expandable magnesium aluminum silicate clay mineral. When magnesium occupies an octahedral structural site that usually contains an aluminum atom, a negative charge is created. In order to neutralize negative charges, cations are drawn to the interlayer surfaces between clay mineral sheet structures. Modem applications for bentonite depend on the sodium or calcium cation populations and other characteristics of the clay mineral. When sodium is the dominant cation, the material is called sodium bentonite, also known as swelling bentonite, western bentonite or Wyoming bentonite. When calcium or magnesium is the dominant cation, the material is called calcium bentonite, also known as non-swelling bentonite w southern bentonite.

Jan 1, 2012

By Constantin D. Pitis

?Demand-side measure" means a rate, measure, action or program undertaken to conserve energy or promote energy efficiency?? (BCUC, 1996) In actual economical environment, business sustainability requires high-efficiency technological processes. That is why the efficiency concept has to be present at all levels of industrial activities. Nowadays, some purchasing decisions are still driven predominately by the purchase price, in spite of the evidence that such price represents up to 5 % to 7 % of the total costs of ownership with full consequences of energy efficiency and the impact on total ownership costs. The paper presents essentials of converter types and basics of the Global Efficiency (GEff) Concept that has been promoted over the last few years in South African industries (Pitis et al., 2006/7). GEff concept is proven as a useful tool used on price-efficiency decisions. Theoretical and technical aspects of this concept were substantiated with case studies. First part presented in this paper will describe how GEff concept was used on price ? efficiency decisions when single input or direct converters and systems (considered as low value equipments) have been replaced. Besides the impact of energy savings and new innovative developments, the paper suggests general other benefits of: ? Technical and economical performance improvements and competitiveness of mining corporations to international standards; ? Defusing incipient energy crisis in the sector; ? Improving environmental conditions; ? Creating new job opportunities in mining sector. Proposed concept in this paper could be further developed as models of improving companies? corporate energy policies.

May 1, 2010

By Nicolas Moscoso, Gerald Verbeek, Marcel Bielefeld, Rob van Dorp

Upon recently, most offshore foundations were based on a number of driven piles that were installed with an impact hammer. With the increase in offshore windfarms two major developments have occurred: the shift from jackets to monopiles, leading to increase of the diameter of the foundation piles, and a shift from impact hammers to vibro hammers. As the use of vibratory hammers is becoming more and more common practice, the need for accurate vibro-driving simulation software has increased, which requires that the soil modelling is enhanced to address soil fatigue during pile driving and to predict reliably the soil behavior and resistance during pile driving. In addition pile driving monitoring, which is routine for piles driven with an impact hammer, needs to become common practice. This paper addresses advances in soil modelling that allows more accurate pile driving simulation as well as the application of Vibro Driving Analysis (VDA) or Monitoring (VDM) to validate the simulation results. This is illustrated by a case study of the test pile for the Delft Offshore Turbine project, a 28 m long monopile with a diameter of 4 m that was driven 15 m into dense sand layers using a vibro hammer. After some 6 months the pile was extracted, and pile driving simulations and VDA were done both for the installation and extraction phase. 1. INTRODUCTION At the end of 2017, the total worldwide offshore wind power capacity was 18.8 GW [1]. The vast majority of offshore wind farms are currently in Northern Europe, which together account for over two thirds of the total offshore wind power installed worldwide, followed by East Asia, while developments in North America are still in very early stages.

Jan 1, 2019

By R. V. Ramani, R. Bhaskar

"The control of respirable dust in mines has been given paramount importance due to the health and safety implications associated with fine dust. The understanding of the temporal and spatial behavior of dust has been recognized as essential for increasing the efficiencies of the existing control techniques and for developing new control strategies. Mining-related studies in this area are, in general, limited. They are also mostly experimental. Some mathematical and computer analyses have been attempted. In this paper, first a review of the mathematical studies performed in the last three decades in this area is presented. Second, a mathematical model for analyzing dust flow in mines is proposed. The model takes into account a number of factors affecting dust transport. It incorporates varying dust generation source strengths and dispersion, deposition, and coagulation of dust in mine airways. Finally, application areas for the model are discussed. A computer program based on the mathematical model has been developed. The program will output the dust concentration in the mine atmosphere as a function of time and distance from the source. The amount of dust deposited on the sides, roof, and floor of the airway is also determined.IntroductionAn airborne dust cloud is a complex system containing particles of varied size, density, shape and state of aggregation. The behavior of the particles is dependent on a number of complex physical mechanisms, often opposing in nature. The net interaction results in the ambient concentration. This size dependent behavior of particles contrasts with that of gases, an area quite widely studied.The term aerosol is used to describe clouds of microscopic and submicroscopic particles in air such as chemical smoke or particulate matter released from smoke stacks. An aerosol system can be regarded as an arbitrary element of volume filled with gas and suspended particles of possible highly variable physiochemical nature. The parameters that are used to describe an aerosol system include concentration, mass average velocity and particle mass and radius. In characterizing such systems, several assumptions are made. Among these is the assumption that particles are smooth, inert and rigid spheres. Again, for example, when the particles are in transport, the possibility of collision exists. As a result of the collision, the particles may coalesce to form larger particles. The probability of sticking is considered a known quantity (lady, 1970). In this paper, the application of the principles used in aerosol systems is explored for the study of the transport and deposition of fine coal dust in underground mines."

Jun 1, 1988

By Kazuyuki Kikuta

MMAJ, a govemmental organization in Japan, has carried out a 4 year project for the development of the decontamination and metals recovering technology for the fly ashes from municipal waste incineration. Heavy metals (zinc, lead and copper) are recovered as raw materials for the non-ferrous metals production, without formation of any waste materials to be disposed. More than 500 thousands tonnes a year of fly ashes generation from the municipal waste incineration has been one of the main social issues in Japan, because most of them need to be disposed to the registered areas after decontamination, and occupy 5% of the municipal wastes disposed. The segregation, flotation and chemical process are applied to the treatment of the primary fly ash from municipal waste incineration, and MF (Mitsui-type blast furnace) Process after the chlorine removal to the secondary fly ash. The main results of experiments are -About 90% of heavy metals, zinc, lead and copper, can be recovered from the primary and the secondary fly ashes to the products for the non-ferrous metals production. -Both of the leaching residue from the primary fly ash treatment and the slag from the secondary fly ash treatment can be used as a raw material for the cement production, meaning that the decontamination technology for the ashes without the landfill has been established. -Dioxins in the primary ash can be decomposed satisfactorily, and the dioxins content in the segregation furnace gas is less than O.lng-TEQ/Nm3 without any gas cleaning system

Jan 1, 2003

By M. A. Bergougnou, I. Inculet, K. I. Burgess

This paper describes the electrostatic methods of separating various minerals, reviews the principles of fluidization and outlines the technique of electrostatic sorting in fluidized beds. The application of the method to the benefication of coal is emphasized.

Jan 1, 1970

Gus C. Henning, New York City: In taking up the discussion of these specifications it is necessary that I give definitions of what I understand under the term " Specifications." There may be three kinds, viz.: (1) Specifications in general; (2) Standard Specifications; (3) Standard International Specifications. 1. A Specification is a document used in commerce which should clearly define the qualities of material to be supplied by the producer, the tests which shall be applied for their determination, and the methods which shall be applied for the purpose of determining that the entire product shall possess such qualities, properties and finish as are desired. The terms used in such document must be applied in accordance with their strict technical definitions as used by those most conversant with them, and the language should be of such accuracy that there can be but a single interpretation of each and every clause. A specification is a part of a contract, and should be legally perfect and accurate. Inaccuracy of definition and dic-

Jan 1, 1903

By Adrien Antenen, Didier Villette

CITRON has developed a new process for the recycling of hydroxide sludge, household batteries, catalysts, automobile shredding residues, grinding sludge and other metal containing organic and inorganic waste. A pilot plant with a capacity of 1,000 tons per year has started operations in April 1998. In August 1999, an industrial plant became operational with an initial treatment capacity of 23,000 tons.

Jan 1, 2000

By Compiled by Staff

"The Bureau of Mines was established in the public interest to conduct inquiries and scientific and technologic investigations concerning mining and the preparation, treatment, and utilization of mineral substances; to promote health and safety in the mineral industries; to conserve material resources and prevent their waste; to further economic development; to increase efficiency in the mining, metallurgical, quarrying, and other mineral industries; and to inquire into the economic conditions affecting those industries. The organic act of the Bureau, as amended by Congress and· approved February 25, 1913, made it the province, and duty of the Bureau of Mines to ""disseminate· information concerning these subjects in such manner as will best carry out the purposes of this Act.""In accordance with this directive, the Bureau reports the findings of its research and investigations in its own series of publications and also in articles that appear in scientific, technical, and trade journals; in proceedings of conventions and seminars; in reference books; and in other non Bureau publications. The number of these reports, the wide range of subjects they cover, and the variety of mediums in which they appear make the kind of list and index presented in this special publication both necessary and valuable. This issue of the Bureau of Mines List of Publications and Articles describes reports and articles published during the period January 1, 1990, to December 31,1991. It, supplements the 50-year list of Bureau publications issued from July 1, 1910, to January 1, 1960;1 the 50-year list of articles by Bureau authors published outside the Bureau from July 1, 1910, to January 1, 1960;2 and the 5-year lists of publications and articles from January 1, 1960, to December 31, 1964,3from January 1, 1965, to December 31, 1969,4 from January 1, 1970, to December 31, 1974,5 from January 1, 1975, to December 31,1979,6 from January 1, 1980, to December 31, 1984,7 and from January 1, 1985, to December 31, 1989.8"

Jan 1, 1992

By Frank A. Stephens

The process of converting iron ore (principally Fe,03 or Fe30,) into iron carbide (Fe,C) to be used as feedstock for steel-making yields complex mixtures of several Fe-containing compounds as a function of processing conditions. In addition to the above compounds (hematite, magnetite and cementite), the mixtures typically contain wustite (FeO) and metallic iron(Fe). Mossbauer spectroscopy has been developed into aquantitative analytical method for monitoring the degree of conversion to carbide from samples periodically extracted from a fluidized bed reactor type of pilot plant. Calibration of absolute quantities of the above five compounds is based on standards prepared from known mixtures of the high purity individual phases. The PC-based spectrometer allows fitting of the well-known spectral components of each of the five phases, the resulting spectral areas then being compared with the calibration curves via PC software to yield the weight fraction of each. Emphasis has been placed on standardizing and simplifying the analysis procedure for routine use in an industrial environment.

Jan 1, 1993