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By Miyuki Morioka, Michael J. Griffin

Discomfort, annoyance, or interference with activities due to exposure to vibration is only expected if the vibration exceeds the threshold for the perception of vibration. When there is more than one vibration input to the body (e.g. at the hands, seat and feet), the sensation is first experienced at the location with greatest sensitivity. Knowledge of differences in the thresholds of perception for vibration at the hand, seat, and feet should assist the identification of sources of discomfort caused by vibration. Perception thresholds for vibration have been determined in several studies, but only a few studies have investigated perception thresholds in the horizontal direction for hand-transmitted vibration 1, 6 or whole-body vibration 4-5, and there has been little consideration of perception thresholds for the foot resting on a vibrating surface. This study determines absolute thresholds for the perception of sinusoidal lateral vibration, examining the effect of vibration frequency (8 to 315 Hz for the hand and foot; 2 to 315 Hz for the seat) and the effect of input location (the hand, the seat and the foot). Methods Three groups of twelve males aged between 20 and 29 years participated in the experiment. Subjects in each group attended an experiment to determine perception thresholds for lateral vibration via either a rigid handlebar (30 mm diameter) at the left hand (left hand), or a rigid contoured seat (250 mm x 150 mm), or a footrest at the left foot (30.5 mm x 10.5 mm with 10-degree inclination). For the non-exposed hand (right hand) or foot (right foot), a stationary handle and footrest with the same dimensions as the vibrating handle and footrest were provided so that the same body posture was adopted among the three groups of subjects. An up-down (staircase) algorithm was employed to determine thresholds in conjunction with a three-down one-up rule. A single test stimulus (2.0 seconds) was presented with a cue light illuminated during this period. The task of the subjects was to indicate whether they perceived the vibration stimulus or not. The threshold was calculated from the mean of the last two peaks and the last two troughs, omitting the first two reversals. Results The median absolute thresholds of the 12 subjects determined at each frequency for the hand, seat and foot are shown in Figure 1. A frequency dependence of the threshold contours within the investigated frequency range is evident, with similar shape to the threshold contours

Jan 6, 2006

By Bob Rappolt

Discussion Points Part 1: Global Mining Industry/Related Issues ? Historical Metal Price Trends. ? Historical LME Metal Stockpiles. ? China?s Demand for Metal. ? World Population Growth, Demands and Development. Discussion Points (cont?d) Part 2: Canadian Mining Industry ? Where are we? And where are we going? ? What progress have we made in the past 20 years regarding: ? Safety -Employee Levels ? Labour -Relative Compensation ? Productivity - Technological Advance ? Where do we stand regarding mineral production? ? What does the future hold for us?

Apr 1, 2005

By J. J. Stacey

Large mining companies generally follow the distributed ownership corporate model, with a board of directors responsible for decisions that affect both shareholder value and stakeholders of the company. The board is simultaneously responsible for setting the culture and values of the corporation, which drive performance and priorities. Companies listed on the Johannesburg Securities Exchange (JSE) commit to sustainable development in various ways, either by virtue of implementing the King Code of Governance 2009 (King III) and/or through their own public reporting on social and environmental matters. Many mining companies make public statements regarding their support for environmental stewardship, ethical behaviour, and fair treatment of communities. It is a local, regional, and indeed, global phenomenon that companies fail to deliver on these statements. Research was carried out through the Institute of Directors of Southern Africa in 2007, and followed up in 2012, regarding directors? understanding of sustainable development issues, the relative priorities, what is needed for ?radical change? to effect sustainable development, and what enables or constrains the latter. Pertinent findings of both surveys are presented in this paper, and it is suggested that ?on-the-ground? performance may be indicative of the nature of leadership and decisions in the topmost ranks of the company. The results indicated that environmental concerns fall consistently below social issues. Financial capital ranked most important, and while environmental issues are recognized as being of strategic concern for the long-term, they ranked as being the lowest importance of all ?Five Capitals? (Financial, Manufactured, Social, Human, and Natural). Social capital ranked second lowest, with black economic empowerment being the only high-priority social issue. There is also evidence that certain companies within the mining sector fail to recognize their absolute dependence on natural resources. Much is made in academic and popular literature of the need for a new type of leadership for the radical shift to sustainable development: at company level this implies therefore a new type of director. The research found that only 14 per cent of directors felt that board decisions are consistent with their personal values; while intentions are strong to behave ethically and serve sustainable development, actions to give effect to these intentions lag significantly. Respondents indicated that the top impediments to courageous leadership for sustainable development related to personal issues of maintaining the image of being a director, fear of appearing weak, fear of being a lone voice, and bowing to board-colleague peer pressure.

Jan 1, 2014

The present Pacific Ocean arose from rapid sea-floor spreading that commenced in the late Mesozoic, and continues to the present day. It started within what is here called the Medusa complex of seaways, basins and troughs with spreading ridges and volcanic arcs, that girdled the earth, including the Palaeotethys and Neotethys of Eurasia between Gondwanaland and Laurasia. Detailed mapping and analysis of palaeofaunas and volcanic arcs indicate that several seaways, rather than one or two, extended throughout Tethys, and into areas now occupied by the Pacific Ocean. The Medusa complex developed under a long sustained wrench regime, right lateral at least from New Zealand to Eur.ope, and saw the origin, maturation and closure of elongate and oval basins under erratic sea-floor spreading, in which no Eulerian pole of rotation remained fixed for long. The name Medusa stems from the analogy of snake-like writhing hair to the constantly shifting development of basins and orogens within the complex. The Indian Ocean split and opened up Gondwanaland concomitant with the later development and deformation of the Tethyan segment- of Medusa, whereas, to the east, the Pacific Ocean opened within Medusa itself, and dispersed Medusa around the rim of the Pacific through sea-floor spreading and strike-slip faulting.

Jan 1, 1987

By Harry L. Siebert, Thomas Gelormino

Rock excavation in urban areas occurs with maximum public exposure and, with the aid of explosives, is one of the challenges facing this industry today. Such excavation is also a hidden factor in areas of new growth, revitalization or upgrading existing facilities in or near urban areas.

Jan 1, 1985

By Swades Kumar Chaulya, Vikash Kumar, Sushma Kumari, Naresh Kumar, Girendra Mohan Prasad, Monika Choudhary

During harsh weather conditions, the presence of fog, dust in the environment degrades the image’s quality, which affects the visibility of drivers of heavy earth-moving machinery in opencast mines. Due to low visibility, mining operations cannot be carried out as drivers are easily prone to accidents. This paper proposes a technique that includes developing a vision enhancement system called perceptive driving assistant system for increasing visibility of real-time video of the road in front of the vehicle for operators of heavy earth-moving machinery at opencast mines during harsh weather conditions to overcome the problem. The system consists of high-quality Internet Protocol cameras and thermal cameras for real-time image processing and other well-defined devices, which is quite capable of enhancing the visibility of the image, outlining edges of the road, and detecting obstacles present on the path of operators for smooth driving and reducing threat of accidents. A high-speed graphical processing unit has been used for quality-performance parallel computing, which is well suited for real-time operations to empower fast real-time operations. The calculated frame per second (fps) of image enhancement, object detection, and edge detection is 17.91, 15.91, and 25.09 fps, respectively. The actual frame rate is 26.07 fps, and after applying the algorithm, the final frame rate is 19.65 fps. The calculated accuracy of the object detection model is 81.23%. Field trials indicate that the developed system has performed adequately during foggy weather.

Sep 21, 2022

By Swades Kumar Chaulya, Vikash Kumar, Sushma Kumari, Naresh Kumar, Girendra Mohan Prasad, Monika Choudhary

Opencast mines are vulnerable to inclement weather conditions as it disrupts the day-to-day activities at these mines. To address the problem, a perceptive driving assistant system (PDAS) has been developed to increase the visibility of real-time video of the road in front of the vehicle for operators of heavy earth-moving machinery (HEMM) at opencast mines in harsh weather conditions.

Apr 1, 2023

By Robert Bissonette, Samir Sbai

Machine Situational Awareness (MSA) requires the ability to efficiently evaluate the probability of interaction of objects within the environment, without creating false alarms or ignoring materializing hazards. To do this, an MSA system needs to assign context to observed object activity and integrate as much information about object identity, kinematics, behavior, and current state as possible. This paper describes how known object characteristics, attributes, and activities (drilling, dumping, driving, etc.) can refine interaction probabilities and help identify rogue actors that introduce anomalous risks to the health and safety of miners. Path projections need to incorporate velocity and direction as a function of time while accounting for terrain, safety response, environmental factors, current assigned activity, etc. This paper also describes the methodology for properly prioritizing responses to place the highest value on human safety.

Feb 1, 2024

By D. G. Cerigo, D. M. Bryce, P. H. Jennings

This paper summarizes the results of an experimental and economic study undertaken to evaluate the feasibility of treating an oxidized orebody of about 10 million tons, grading about 0.75 per cent copper, by agitation leaching and by percolation leaching.

Jan 1, 1968

Up to 80 per cent of the copper in a bornite ore can be quickly leached with percolating acidified ferric sulphate solutions. The upper limit for rapid copper extraction is set by the conversion of bornite to slowly dissolving chalcopyrite. The dissolution occurs in two stages: a rapid linear initial stage, followed by a slow, non-linear stage. The initial step is largely controlled by the rate of oxidant supply (Fe2(S04)3); temperature is not an important variable during the initial reaction. The second leaching stage is controlled by chemical and physical factors and is temperature dependent. The initial copper leaching rates are insensitive to both the concentration of the ferrous sulphate reaction product, and the sulphuric acid concentration.

Jan 1, 1973

By E. H. Phillips, A. F. Keenan

6.2-1. Historical Development. Hammering on hand-held drill steel was the earliest type of percussion drilling. It was not until 1838 that Singer developed a steam-operated drilling machine that lifted a drilling bar and let it drop by gravity. J. J. Couch of Philadelphia patented the first percussion drill in 1849. His machine was a steam drill which literally hurled the drill bar at the rock and retracted it by means of a ratcheted wheel. Later J. W. Fowle added automatic rotation of the steel. In 1871, Simon Ingersoll patented a rock drill mounted on a tripod which permitted drilling holes at any angle, vertical to horizontal. Up to the turn of the century, percussion drills in use were piston-type drills. The drill steel was solid and attached to an extension of the drill piston. Hole cleaning was accomplished by the pumping action of the steel in the hole. Down-holes were drilled wet and cleaned with a blow pipe while up-holes were drilled dry, allowing the cuttings to drop out by gravity. The forerunner of our present hammer drill was the free-piston drill which was first patented in 1884, by Sargent. Because solid drill steel was used, it did not successfully clean down holes. J. G. Leyner solved the problem of applying the hammer drill principle to down-hole and horizontal-hole work in 1897. The key was to pass com- pressed air and water through hollow drill steel to clean the hole. Leyner's work on valves and rotation mechanisms increased the blows per minute of hammer drills from 300 or 400 up to 1800 and more blows per minute and made possible the first lightweight drilling machines. The development of automatic feeds followed. 6.2-2. Percussion Drills. TYPES OF DRILLS. There are two types of percussion drills in use today; the piston drill and the hammer drill. In the

Jan 1, 1968

By Giorgio Höfer-Öllinger, Peter Pointner, Manfred Stadlober

"SUMMARY Investigations from tunnel face are part of risk mitigation measures during the excavation works. With the tunnel equipment, percussion drillings of up to 30-40m can be achieved. Core drillings are state of art method for investigation exceeding 50m. At Koralm base tunnel, up to 270m deep percussion drillings were performed with drilling rigs and accompanied by an intensive investigation program. These investigations consisted of monitoring during the drilling, field tests (with packer, using the preventer, borehole imaging) and in laboratory. Percussion drillings are cheaper and save time of interruption of the excavation progress. INTRODUCTION As part of a proper risk management, horizontal advance drillings during excavation of underground works can be seen as state of art and meet wide acceptance. Core drillings, deep and shallow percussion drillings can be differed. The selection of the type of drilling, meanwhile, causes intensive discussions. On the one hand, only a core drilling allows a direct investigation of the rock mass expected during later excavation works. On the other hand core drillings are expensive in both cost and time – if there is no excavation progress during the investigation measures – in construction time. Percussion drillings can be performed as rapid investigation measure with the excavation equipment (“Jumbo”) allowing two dimensional image of the ground around the cross section. There is some limitation concerning a reasonable depth of approximately 30m and a borehole diameter of 76mm. The applications of preventer, packer or borehole imaging are hardly applicable. By use of a drilling rig depths of percussion drillings of several hundred meters can be achieved relative easily and there is less limitation of the borehole diameter. Installation of a preventer is possible, as well as packer tests and borehole measurements (imaging, gyroscope, borehole geophysics). The gap of information between core and percussion drilling cannot be closed completely, but it can be reduced substantially and sufficiently by combination of an intensive program of measurements and analysis accompanying the investigation works."

Jan 1, 2016

The tungsten carbide insert bit has probably advanced blasthole drilling more than any other single improvement. Tungsten carbide inserts have longer life, maintain sharper edges, and penetrate faster than hardened steel edge bits. Before the tungsten carbide hit appeared, all-steel bits were used. Even with the new bits, blasthole drilling costs vary with the type of equipment used and its condition; the hole's length and diameter; the rock's texture, hardness, and nature; the operator efficiency. To help reduce drilling costs, the operator should be familiar with the use and care of drill bits. This article provides information about tungsten carbide rock bits used for percussion drilling. Consideration of tungsten carbide rock bits includes looking at bit materials [ ] as well as bit operation and maintenance. Two basic tungsten carbide rock hits are the button bit and the four-wing carbide insert bit. Three common hit-to-drill-steel connections are the bottom drive, tapered drive, and shoulder drive. Bottom drive bits arc typically used for singlepass or longhole drilling, with all percussion drills from handheld sinkers to heavy track drills. Tapered socket bits are available with shallow or deep carhide inserts, for the lowest cost depending on the rock type being drilled. Shoulder drive bits are available in all-steel or carbide insert design.

Jan 12, 1981

By Henry H. Roos

NTRODUCTION In the mining industry, a "drill jumbo" is a drilling unit equipped with one or more rock drills and mounted on a mechanical conveyance. Jumbos range from single¬drill ring drills mounted on simple steel skids to sophisti¬cated multiple-drill units mounted on diesel engine powered carriers and equipped with automatic controls and sound-abatement cabs. Individual types of jumbos usually are designed for specific tasks such as fan drilling in sublevel caving operations. Some units, such as development jumbos, can be utilized for several functions in addition to their normal applications, e.g., for production drilling in room-and-pillar operations, stoping in cut-and-fill mining, etc. Mine operators can purchase individual components from manufacturers, assembling these components into a jumbo suitable for specific conditions. However, this requires that mine personnel have good engineering and mechanical abilities. Although manufacturers of jumbos maintain facilities for designing machines to meet con¬ditions created by new mining methods and unusual ap¬plications, the cost of the engineering and experimental work for new types of jumbos should be evaluated in terms of both costs and benefits; it may be advantageous to plan the mining operation so that existing and proven units can be utilized. GENERAL SELECTION CRITERIA Since the operating conditions vary in underground mines, the design of a jumbo must be selected to cope with the individual characteristics of the mine. The necessary considerations include access space into the working areas, grades expected to be encountered, radii of the curves, ambient temperatures, the characteristics of the rock, the acidity or alkalinity (pH rating) of the mine water, etc. Access to Mine Workings The mine workings must be accessible to the selected jumbo. Frequently, a jumbo must be disassembled at least partially to pass through the mine shafts. There¬fore, a bolted construction allowing disassembly into pieces of suitable size and weight is desirable in most applications. Type of Undercarriage Generally, a crawler-type undercarriage should not be used in trackless mines having acidic mine water. The acidic water causes an electrolytic action between the individual crawler parts and causes rapid corrosion and early failures. Propulsion A two-wheel drive on a pneumatic-tired jumbo is marginal for grades exceeding 12%. A four-wheel drive unit with good weight distribution is capable of operat¬ing on grades of up to 35%. At least 30% of the gross vehicle weight (GVW) should be carried on the steering axle; otherwise, the steering tires may not have sufficient traction on loose road surfaces and may "plow" instead of steer. To assure stable operation in mines with steep grades, the height of the center of gravity of the jumbo should be considered. It should not make the unit prone to rolling over on the steep grades that may be encoun¬tered. Turning Ability In confined working areas, a skid-steering or crawler unit has the best maneuverability. An articulated carrier is preferable when base-rotated parallel booms are being utilized. A rigid-frame jumbo with automotive steering is compact and economical, having lower maintenance requirements than the other two types. However, the turning radius of a rigid-frame unit is wider than either the skid-steering or articulated units, and this wider turning radius may be detrimental in mines with narrow drifts. JUMBO COMPONENTS Rail Undercarriages A mine with a rail-transportation system generally utilizes drill jumbos that are mounted on rail-type under¬carriages. With a light load and good weight distribu¬tion, this carrier may consist of a simple two-axle four-wheel platform onto which the boom-mounting brackets are attached. As the depth of the round and the penetration rates increase, the weight of the equip¬ment installed on the chassis also increases. The greatest problem with a heavy overhung load is balancing the carrier; a three-boom unit may require a substantial amount of counterweighting to maintain an acceptable 70% to 30% axle-load balance. Although lengthening the wheelbase helps balance the unit, a long wheelbase increases the turning radius, often creating problems on curves and sometimes requiring a swivel truck-type chassis. A good rule of thumb for a simple four-wheel undercarriage is to maintain a wheelbase length to track gage-width ratio that does not exceed 2.5 to 1.0. For a larger ratio, a swivel truck should be utilized. Swing-out outriggers or roof jacks help keep a jumbo in place during the drilling cycle. Usually, a rail-mounted jumbo is not self-propelled. Instead, it is maneuvered into place by a locomotive. Occasionally, several headings are being advanced in close proximity, and a self-propelled jumbo is con¬venient. In electrified mines, such a jumbo utilizes conventional battery-powered traction gear; in dieselized mines, hydrostatic drive components offer good flexi¬bility. The tractive power requirements of a typical rail jumbo may be calculated from the formula: HP = [(RR + GR) X Sl/[33,000 X Em X Eh]

Jan 1, 1982

By Pat McLaughlin

Environmental constraints are pushing many operators to change from large rotary blastholes to the smaller diameter holes drilled with down-hole or top-hammer rigs. Productivity improvements over the years with these two drilling techniques has taken some of the bite out of the transition, while improved fragmentation and more uniform muck due to the tighter patterns can help offset increased explosives costs.

Jan 1, 1995

Beall: Mr. Donovan, would you tell me something about your early life, leading up to your going into I he mining industry? Donovan: I was born in St. Charles, Minn., on November 18, 1879. At that time my father was a school teacher, but he later entered the Congregational ministry. He was pastor in several small Minnesota towns, so we moved about quite a bit.

Jan 8, 1966

By José Artur Albano de Guimarães

A temperatura de carregamento do ferro-gusa no convertedor é de suma importância para o acerto do balanço térmico do convertedor. Dessa maneira, o presente trabalho teve como objetivo a proposição de uma equação de modelamento da perda térmica na panela de ferro-gusa da thyssenkrupp CSA com o intuito de prever, com melhor acurácia, a temperatura de carregamento no convertedor. Os resultados encontrados pelo modelo foram comparados com os valores reais de perda térmica na panela e concluiu-se que a equação desenvolvida se mostrou bastante assertiva e abrangente. Foram consideradas novas variáveis nesta abordagem que, até então, não eram utilizadas pelo modelo de perda térmica nas panelas de ferro-gusa da CSA.

Oct 30, 2017

By Izabela Diniz Duarte

Perdas térmicas decorrem do armazenamento do aço líquido em panelas. O controle da temperatura do aço líquido é condição essencial para se obter um produto final de alto nível de qualidade. Este trabalho buscou avaliar a transferência de calor a partir do aço para o refratário da panela e para a camada de escória, utilizando um modelo numérico (Computational Fluid Dynamics). As perdas de calor dão origem a correntes de convecção dentro do banho e a consequência típica desse fenômeno é a estratificação térmica. Foi avaliada a influência de parâmetros tais como espessura da camada de escória, tipo de revestimento refratário e a temperatura de encharque. As perdas térmicas para o refratário lateral e do fundo da panela se mostraram maiores que as perdas térmicas para a camada de escória. Nas condições estudadas a espessura de camada de escória não apresenta influência significativa sobre as perdas, ao contrário do tipo de refratário e temperatura de encharque.

Aug 16, 2017

There is no simple answer to the question, "What is the meaning of life?" The expressions of life are so multiple that life has different meanings for different spheres of thought, such as art, science, or philosophy; and it conveys a different significance to different persons, according to their individual development and interests. Life is complex from a philosophical point of view. The meaning of life is superficially positive and unmistakable only when approached from a mechanistic view- point; namely, that of biology or biochemistry, since these deal with the physicochemical basis of life processes. However, such a purely mechanistic or biochemical approach to the significance of life and the interpretation of man's behavior on the basis of purely physical laws is certain to run into trouble. Similarly, a concentration of effort upon materialistic advances in world progress is extremely dangerous. The possible consequences of splitting the atom, development of guided missiles, and possible bacterial warfare are timely examples. Man becomes more self-reliant as he extends his scientific and technologic discoveries and learns how to shape natural conditions to his own desires. When man will be able to travel to other planets in atomically propelled space ships and destroy whole worlds by pushing a button, a possibility which now seems to be within the realm of the predictable future, he will need the strong-

Jan 1, 1950

By Pollyana de Aragão Trigueiro

A distribuição de soluto durante a solidificação rápida de uma liga Ag-15%massaCu, foi obtida numericamente. No presente trabalho, utilizamos um modelo de difusão de entalpia e concentração médias, proposto anteriormente, para a solidificação de uma gota de liga binária (atomização). Nossos resultados mostram que a refusão da estrutura pode gerar um perfil de microssegregação em ligas solidificadas rapidamente bastante diferente dos que resultam da solidificação perto do equilíbrio.

Aug 7, 2018