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By Mario Samamé Boggio

El presente texto revisa el desarrollo de la ciencia, la tecnología y la ingeniería desde la Antigüedad hasta la actualidad y su interacción en las sociedades respectivas.

Nov 1, 1978

By J. C. Bayles

Jan 1, 1885

By H. E. McKinstry

LIKE nearly everything else, mining geology has been reconverting. Many geologists had been in military and other government service. Many more, with mining companies, had been working primarily toward increasing production from known reserves. All of these are turning now toward their normal peacetime endeavor-the search for new ore; for most mining companies, finding themselves with accumulated deficits in development work, are more than ready to go ahead with their postwar plans made a year or more ago but still stalled at the close of 1945 for lack of man power. These plans include not merely development in the old home camp but also wide exploration for new prospects both domestic and foreign. Most of the large concerns have geologists and engineers in the field in the United States, despite the outlook for higher mining costs here, and at least half a dozen strong American companies are already investigating opportunities abroad, notwithstanding past unhappy experiences in certain Latin-American nations which have welcomed capital but later found means of preventing investors from reaping the reward of their enterprise. A few of these new foreign expeditions are following well-planned programs, but too many, in their haste to get any sort of footing, are proceeding without well-considered policy. with the result that their geologists can do little more than desultory scouting.

Jan 1, 1946

By Zsuzsanna Zborovszky

[Certain chapters of the tentative document entitled, "Test Requirements for instruments & Apparatus to be Considered for MESA Intrinsically Safe Certification" are evaluated and supporting data are presented on certain key issues with the purpose of helping the regulatory agency in improving the above document. The subjects discussed in detail are: hot wire ignition with W and BeCu wires; the most sensitive methane-air :and propane air ratio; the ignition limits for inductive-resistive circuits in 8.3°; methane-air mixtures in the 24-OV, 100 mH-2 [ ]H range, the resistive ignition limit as a special case when L ? 0; the capacitive-resistive ignition limit representing a four ,dimensional problem is analyzed and discussed in general and the variation of the ignition limit using Vo and/or r2 as a parameter are determined experimentally. The ignition limit is also determined for the [r1 ,~ r2] = 0 case ("capacitor alone") and for the most dangerous capacitive resistive circuit combination. The ignition limits are below the limits proposed in the document. A survey of the different factors influencing the ignition is made as to their suitability to provide a constant safety factor. It is shown that a constant safety factor cannot be achieved. The best method for applying a safety factor appears to be the increase of initial pressure or use of other gas mixture. The revision of the safety factor concept and ignition limit curves is recommended.]

Jan 1, 1980

By Steve Colbum

LTl’s MapStar LPS (laser positioning system) utilize both tripod mounted and hand held reflectorless distance meters. These are eye safe, easy-to-use, and specifically designed to endure the harsh environment characteristic to the mining, quarry and explosives industries. Survey data collected by the systems is digitally stored in a ruggedized data collector and then processed with a specialized, interactive software program, which can be run on any standard PC. Win Prof, the Windows-based analytical software package is used to reduce the data for generating bench face profiles, surfaces, volumes, estimating true burdens and mining ratio calculations. In addition, the software has many other built-in routines to calculate powder factors, toe shear, to map structural contacts and to predict the flyrock potential based on the Burden to Energy ratios. An extensive, built-in library of explosive’s data facilitates these calculations. It will also conform automatically to user-specified minimum and/or maximum burden in relation to the explosive energy, hole diameter and bench geometry - for both vertical and inclined holes. Numerical data can be represented in 2D or 3D to emphasize the hole-burden-face relationships.In this workshop, the MapStar LPS instruments and Win Prof analytical software will be thoroughly demonstrated. Demonstrations include equipment configuration, typical field setups and several effective survey procedures, including processing of some sample data.

Jan 1, 2000

By S. H. Miller

Biodegradable hydraulic fluids can save tens or hundreds of thousands of dollars in fines and clean up costs in the event of a hydraulic fluid leak or spill. When properly selected, applied, maintained and monitored, a biodegradable fluid will have a long useful life and will protect equipment as well as or better than conventional petroleum based hydraulic fluids.

Jan 1, 2000

By Piotr Litwa

The paper focuses on actions aiming at improvement of work safety in mines, particularly in those extracting hard coal, taking into account the characteristics of natural hazards in Polish underground mining and the reasons of mining disasters connected with those hazards. It refers to conclusions addressed to scientific and research centres, drawn during last decade by Commissions appointed by the President of the State Mining Authority in order to investigate reasons and circumstances of incidents, which till now, could not have been accomplished because of financial reasons. Furthermore, the paper presents basic assumptions of the Strategic Research Project Improvement of work safety in mines, announced by the National Centre for Research and Development at State Mining Authority?s President request.

Aug 1, 2013

By Harry H. Power

WORK of the Committee on Education of the Petroleum Division has been under way for approximately-one year. Although some progress has been made, further activities of the Committee are necessary in order to discuss mutual problems more thoroughly by a unified group interested primarily in this field of specialization.

Jan 1, 1944

By Vinod K. Sikka, René Cooper

"Cohoes, New York 12047 Intermetallics are an attractive class of advanced materials. The aluminide intermetallics offer advantages including: (1) lower density, (2) oxidation resistance, (3) carburization resistance, and (4) interesting mechanical properties because of their ordered crystal structure. Even though the attractive properties of the aluminides and other intermetallics have been known for nearly four decades, their practical applications have not been developed for two reasons: (1) the poor ductility (in some cases, both ambient and high temperatures) and (2) the lack of processability into meaningful components. Recent advances such as ductilization of Ni3Al by small additions of boron and the knowledge that environmental effects are the major cause of poor ductility in Fe3Al and FeAl systems have brought the intelmetallics into the forefront of research and their commercial applications. This paper has described a method for melting Ni3AI-based alloys that successfully utilize the exotherrn for the formation of NiAl from the elemental materials. The reaction-synthesis method has also been utilized for the production of NiAI and NiAI-based alloy powders from the elemental powders. The reaction-synthesized powders of NiAI and NiAI-based alloys were consolidated by hot extrusion and evaluated for tensile properties over a temperature range from room temperature to 1050ºC. The powder-processing conditions have been found to have more influence on the ductile-to-brittle transition temperature of NiAI than the powder-production method.IntroductionIntermetallics are an attractive class of advanced materials [1-11]. The alum in ide interrnetallics offer advantages including: (1) lower density, (2) oxidation resistance, (3) carburization resistance, and (4) interesting mechanical properties because of their ordered crystal structure. Even though the attractive properties of the aluminides and other interrnetallics have been known for nearly four decades, their practical applications have not been developed for two reasons: (I) the poor ductility (in some cases, both ambient and high temperatures) and (2) the lack of processability into meaningful components. Recent advances such as ductilization of Ni3Al by small additions of boron and the knowledge that environmental effects are the major cause of poor ductility in Fe3Al and FeAl systems have brought the intermetallics into the forefront of research and their commercial applications. The paper will briefly review the processing techniques being pursued for the commercial applications of Ni3Al-based intermetallics. The major emphasis of the paper will deal with synthesis of Ni3Al and NiAI intelmetallics."

Jan 1, 1994

By R. G. Diale, H. R. Chauke, T. M. Ledwaba, P. E. Ngoepe

FeCo alloys play an important role in soft magnetic materials with a wide range of technological applications due to their high saturation magnetization and Curie temperature. However, these alloys have low ductility at room temperature. The ductility can be improved by the ternary addition of elements such as V. A density functional theory supercell approach was used to generate B2 Fe50Co50-xVx (0 ≤ x ≤ 50) structures and the properties were evaluated at different atomic percentage compositions to determine the ductility at room temperature. The structures were fully optimized to obtain better equilibrium ground-state properties such as lattice parameters and thermodynamic properties for both binary and ternary systems. The stability of Fe50Co50- xVx was evaluated from the heats of formation, elastic properties, and phonon dispersion curves. Furthermore, magnetic strength was evaluated from magnetic moments. It was found that all structures are thermodynamically stable due to the negative heats of formation. The calculated Pugh’s ratio and Poisson’s ratio confirm that alloying with V effectively improved the ductility. It was also found that Fe50Co50-xVx showed a positive shear modulus for the entire concentration range investigated, in agreement with phonon dispersion curves. The ternary addition of V to the FeCo system resulted in reduced magnetic strength due to a decrease in magnetic moments. These findings reveal that B2 FeCo-V alloys can be used as components and actuators for the automotive industry.

Jun 10, 2024

By J. Jankovic

Numerous advantages have been recognized for solid oxide fuel cells (SOFCs) operating at temperatures of 500-700°C. However, there are several issues related to low temperature SOFCs, such as high electrolyte resistance and high electrode polarization. One of the routes to enhance the electrode performance, particularly for the cathode, is to use new materials with optimized microstructure. In this work, the plasma-spraying technique, recognized to have several advantages over presently used deposition techniques, was used to deposit cathode materials onto ceramic and stainless steel substrates to obtain highly porous structures. Cathode materials with composition of Lao 6Sr0.4Co02Fe0 8O3 (LSCF) were employed in the powder form. The LSCF was prepared from powder precursors with different pore formers and binder levels, or from already produced, single-phase LSCF. The (La0.8Sr0.2)0.98MnO3 (LSM) cathode material was also processed for comparison purposes. The deposition process was developed to obtain coatings with good bond strength, porosity, film thickness and residual stresses. The phase and microstructure of deposited materials were characterized using XRD and SEM.

Jan 1, 2005

By R. A. Harris

In this study Pt-Al thin films were prepared via electron beam physical vapour deposition (EB-PVD) with an atomic concentration ratio of Pt25:Al75. These films were heat treated at temperatures ranging from 150°C to 650°C for annealing times from 4 to 60 minutes. The resulting microstructure of these thin films were obtained via secondary electron imaging used in conjunction with depth profiling with the aid of scanning auger microscopy (PHI 700).Elemental maps of the micrographs were obtained. Simulations, based on a chemical potential Monte Carlo method1, were run for various interaction parameters. From these simulations theoretical depth-profiles and proposed microstructures were obtained. These were compared to the experimentally measured depth profiles and elemental maps. Keywords Monte Carlo, chemical potential, depth profile, Pt-Al thin films.

Jan 1, 2011

By Hannu Johto

Boliden Harjavalta has operated a flash smelter for nickel sulphide concentrates in Finland since late 1959. The original nickel flash smelting process was modified in 1995 to a novel nickel matte smelting (DON) with semi-low iron where the batchwise operated converting became obsolete. Since that, the process has been applied to multiple chemically variable nickel sulphide concentrates with high environmental performance. In this paper, the status of the current smelter operations is described together with the recent modernizations of the nickel flash smelting furnace and the slag cleaning furnaces.

By R. L. Lincoln

The effects of adding from 1 to 50 atomic percent (a/o) to vanadium were investigated by the Bureau of Mines. Properties studied included as-cast and annealed hardness, microstructure, fabricability at room temperature and elevated temperature, tensile strength, electrical resistivity, and oxidation resistance at 625° and 800° 2. Additions of small amounts of hafnium resulted in lessened as-cast hardness, decreased electrical resistivity, impaired roll- ability, increased oxidation resistance, and greater tensile strength. Larger amount of hafnium caused greater as-cast hardness, increased electrical resistivity, further impaired rollability, continued increase in oxidation resistance, and lessened tensile strength. INTRODUCTION The purpose of this study was to determine the effect of hafnium additions on the properties of vanadium and to learn if this binary alloy had any special or unusual properties. This investigation is a part of a larger research project in which new and expanded uses of vanadium are being sought. Domes tic vanadium is found frequently in combination with uranium, and because of the demand for uranium as a nuclear fuel, there now exists a surplus of vanadium-bearing minerals and vanadium pentoxide as a byproduct of uranium production. Primary principles of conservation demand that greater use be made of this readily available surplus; finding suitable metals to alloy with vanadium to enhance its properties is one way to increase its utilization. This report is the result of an investigation of the effects on the properties of vanadium when hafnium is added in amounts from 1 to 50 a/o.

Jan 1, 1962

By Helen E. Edwards

The Bureau of Mines is engaged in a systematic evaluation of the thermodynamic properties of combustion gases. These studies are designed to provide basic thermodynamic information of high accuracy facilitating the theoretical study of flame and combustion phenomena. This report is the third of a series3/ presenting results of the study for particular fuel-oxidant systems. The equilibrium composition of the products of combustion and the adiabatic flame temperatures of specified oxyacetylene systems have been computed.

Jan 1, 1953

By R. W. Fountain, J. Chipman

THE solubility of nitrogen in iron and steel has been of considerable interest due to the role of nitrogen in strain-aging and in quench-aging. It is generally considered that quench-aging is the result of precipitation of carbide and nitride particles from supersaturated solid solution, while strain-aging results from the segregation of carbon and nitrogen atoms to dislocations.1-9 The rate of strain-aging is controlled primarily by the amount of carbon and nitrogen in solution and the temperature. In experiments on strain-aging of pure iron with only carbon or nitrogen as impurities, Fast" has shown that even after 40 hr at 50°C carbon did not give any strain-aging while

Jan 1, 1959

By M. Redfearn

"DUST COLLECTION EQUIPMENT LIST Primary Dust CollectorModular Mikro-Pulsaire - Model 2G1-96TR Capacity: 20,000 c.f.m.Bags: Total of 288; 8' x 4 1/2"" diameterMaterial: Dacron HCE feltAir to cloth ratio: 7.55/1Bags are changed every 6-9 months. Sent to A & L Services for cleaning at a cost of less than 1/3 the price of a new bag. No new bags have been required since start-up 4 years ago.Blow hack: 35 c.f.m. at 100 p.s.i.Fan: Joy Manufacturing, Model 3300, Type 4S, Backward inclined fan.Impeller: 33"" diameter36"" diameter Inlet33"" diameter Outlet at 3200 f.p.m. velocity1945Motor:,60 H.P., 1780 r.p.m.Capacity: 23,400 c.f.m.Design:,20,000 c.f.m.,•Actual:,17,500-19,000 c.f.m. depending on bag condition.Dust Slurry Agitator: Port-a-flo Model 050-350Major Maintenance:The fan was sped up from 1830 to 1945 r.p.m. and balanced at the higher speed. Several months later the impeller destructed beyond repair. A new shaft and impeller was installed, casings straightened, and bearings reused. Unit is currently running at 1945 r.p.m. No definite cause for the impeller failure has been found, although it might be attributed to improper balancing."

Jan 1, 1976

By Carl Lee

OXYGEN-FREE high-conductivity copper (OFHC brand) that is now being commercially offered for the first time represents a notable achievement in electro-metallurgy and is the outcome of endeavors that have extended over a long period. Its manufacture is novel in that electrolytically refined copper is melted in electric furnaces and cast into vertical water-cooled molds. The ingots show the "pipe" characteristic of sound gas-free metal and microscopic examination even at high magnification reveals no cuprous oxide in the copper. Owing to the patent situation, the United States Metals Refining Co., the producers, cannot at this time divulge the details of manufacture, but the operations are under precise control so that the castings are of great uniformity and the copper contains no residual deoxidant. Figs. 1 and 2 show photographs of cross-sections of a wirebar and a billet, both vertically cast.

Jan 1, 1933

By Carl Lee

WITH the modern trend toward motor drive in coal mines, more careful forethought should be given to future layouts than has usually been done in the past. Both top and bottom equipment of future new mines is likely to differ radically from those of a decade ago. No one is able to predict very far ahead, but provisions can be made to allow for uncertainty. One thing stands out: the mine of the future will be laid out for long life compared to that of the small mine of the past, where an inexpensive top plant, simple equipment, a small timbered shaft, small cars, light rail, hand loading and mule haulage all contributed to a short economical life.

Jan 1, 1933

By Alexander Coucoulas

FABRICATION of thin-film circuits deposited on glass substrates requires the formation of permanent electrical contacts. Since thin films are in the order of a few thousand angstroms thick and are deposited on nonconductive surfaces such as glass, new methods of lead attachment are being pursued in the microelectronics industry. Ultrasonic welding is being considered in thin-film technology since joining can be accomplished between a wide variety of dissimilar materials.l,' Ultrasonic welding is accomplished by a transducer-coupling-tip system which converts high-frequency electrical energy into mechanical vibrations and delivers it into the weld region. During the process the tip oscillates in a direction parallel to the surface of the weldments, inducing shear stresses in the work pieces which are clamped between the tip and anvil. Though the basic bonding mechanism is not clearly understood, it has been described as closely akin to friction welding. In the course of an investigation concerned with ultrasonic we!ding of aluminum wires to tantalum thin films (1400A) deposited on glass, low weld strengths were related to glass failure. Upon investigating this condition, an improved method of bonding was developed where the aluminum was held at a temperature where a minimum amount of strain hardening occurred during the introduction of ultrasonic energy. Experimental Procedure. Aluminum wires (0.015 in,) were bonded to tantalum thin films with an optimized set of welding parameters (power, time, clamping force) employing a commercial 100-w 60-kc ultrasonic welder. Forty-five degree shear-peel tests, where the lead is pulled at a 45-deg angle with respect to the substrate at 0.2 in. per min, produced a large variation from zero to the strength of the wire, Table I. Inspection of the weld region generally revealed: glass cracking before and after testing; the removal of glass nuggets from the substrate by the lead during testing, Table I; thin-film penetration. In an effort to improve the shear-peel strength, the aluminum between the tip and substrate was heated above ambient temperature through an argon gas media prior to and during welding with the same parameters employed above. With the addition of heat: wire deformation was increased; shear-peel tests all failed at the weld-wire junction, leaving the bonded portion undisturbed; no evidence of glass cracking or film penetration prior to or after testing was observed. In order to prevent failure at the weld-wire junction due to excessive wire deformation, 0.035-in. aluminum wires were welded to tantalum thin films with an optimized set of welding and heating parameters. As

Jan 1, 1967