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By Vern Pfannenstiel

Jan 1, 2005

By E. T. Peters, L. E. Tanner

In the course of a study concerned with the rnechanical behavior of the intermetallic compound CO3V, both structural observations and anomalous electrical-resistivity behavior indicated the presence of a new high-temperature phase in an alloy with the stoichiometric composition, Co-22.4 wt pet V. The evidence, which is given below, suggests that the new phase is situated between the low-temperature ordered hexagonal phase, k,1, 2and the high-temperature disordered fee solid solution, a,3 within a small range of temperature in the vicinity of 1070°C. Structural studies included X-ray diffraction analysis* and electron-transmission microscopy examination* of stoichiometric composition speci- mens homogenized for 1 hr at 1200oC and either air-cooled or water-quenched. The air-cooled specimens yielded X-ray diffraction evidence of the k phase, while electron microscopy revealed a microstructure of both heavily and moderately faulted regions as shown in Fig. 1. The high density of stacking faults (or fine twins) in region A is reminiscent of hexagonal cobalt following its allotropic transformation.4 Selected-area diffraction from this region revealed distinct superlattice reflections of the ordered hexagonal phase, as well as continuous rel-streaks which were normal to the fault planes in the micrograph. The latter is indicative of extremely small spacings between the faults.' Regions such as ß were found to be only partially transformed to the k phase. Attempts to study the antiphase domain structure by either bright- or dark-field techniques were unsuccessful in these initial studies. This was due to the low intensity of the superlattice reflections arising from the closeness of the cobalt and vanadium scattering factors. Quenching Co3V from above Tc appears to suppress the formation of the k phase. Both X-ray and electron-diffraction results indicated that the disordered phase, a, was partially ordered during severe cooling and that the structure of the ordered phase was of the L12 (Cu3Au) type,6 designated here as a'. As in the case of the hexagonal phase, examination of the domain structure was unsuccessful; however, significant information concerning the morphology of this condition was revealed by the appearance of dislocation arrays. In particular, it

Jan 1, 1965

By AIME

Rapid exhaustion of iron ore in Minnesota's Mesabi range has led the Jones & Laughlin Steel Corp. to develop the world's largest open quarry mine for magnetite iron ore, at Star Lake, N. Y. Already contributing more than one eighth of the total iron ore used by the Corporation, the expanding Benson mines are destined to become Jones & Laughlin's important source of ore within the next ten years. In 1947 over 650,000 long tons of high-grade ore was produced. Output this year is expected to reach 800,000 long tons and studies are under way to increase production further. The future of the Benson mines is assured as present indications show large reserves of ore. The property, briefly described in M & M for November 1943, then under

Jan 1, 1948

By Andre Cezar Zingano

"The empirical approach for pillar design assumes that geological conditions should be perfect, such as horizontal seams, and that pillar strength and behavior will only depend on the coal seam strength and the vertical pressure caused by the overburden thickness on the coal seam; this vertical pressure is based on the tributary area. Empirical methods do not consider the effect of the interface between the roof and pillar or the floor and pillar.The effect of the interface shear strength on final coal pillar strength has been studied since the 1960s. However, few case studies have been generated from that, especially in shallow underground coal mining (less than 100 meters). This case study involves a mining section at the 101 coal mine in the Santa Catarina state of Brazil, which is experiencing pillar rib spalling and yielding because of a 1-to 2-cm-thick clay layer at the area of contact between the coal seam and immediate roof. The depth of the coal seam is 60 m on average and 2.3 m in height. This particular section also has 12-14% (7-8°) of seam inclination. The pillar size varies from l lxll to 13xl2m; thus, the safety factor (SF) based on the ARMPS approach is more than 1.5. The objective of this paper is to determine the cause of the pillar yielding and study the effect of the clay layer at the interface between the roof and pillar, including the inclination of the coal seam. This study conducted empirical and numerical models (2D and 3D) to understand the effect of the thin clay layer. The conclusion is that the clay layer affected the strength of the interface between roof and pillar, causing rib spalling and reducing the pillar strength.INTRODUCTIONPillar stability and deformation depends on the coal seam strength and vertical pressure caused by the overburden thickness on the coal seam, and this vertical pressure is based on the tributary area. The effect of the interface shear strength on the final coal pillar strength has been studied since the 1960s. However, few case studies have been generated from that, especially in shallow underground coal mining (less than 100 m). This interface could be represented by a thin clay layer or an abrupt contact between the coal seam and a rigid sandstone layer of the immediate roof. These two interface conditions are found in the coal mines of Brazil, and the effect of the interface shear strength could increase when the seam's inclination is higher."

Jan 1, 2016

By Carl H. Hobbs

The beach at the resort city of Virginia Beach, Virginia has been and increasingly will be dependent upon artificial nourishment for maintenance and for hurricane protection. Both existing base-level maintenance operations and planned substantial enhancement programs out strip the capabilities of traditional terrestrial resources to provide the required quantities of sand. Our research program, an amalgam of projects from several funding sources, has located and defined suitable quantities of beach quality sand for use on the city's beaches. The work also has furthered our understanding of the region's Quaternary history. Initially, reconnaissance level, high-resolution, sub-bottom profiles and surficial grab samples taken on the basis of sub- marine geomorphology identified two geographically and geologically separate areas worthy of further exploration. Further profiling supplemented with some cores further defined the potential sand reserves. The Sandbridge Shoal site is a large and discrete Holocene sandbody atop late Pleistocene strata. The sands in region offshore of the commercial area known as the Resort Strip appear to be recent fill within fluvial(?) channels cut into the older subsurface. Each of these resources is within roughly 5 km of major sites targeted for beach nourishment and/or hurricane protection and contains sand with appropriate geotechnical properties. Ongoing work will better define the dimensions and limits of the sand bodies and provide data to enable determinations to be made concerning exploitation. Ultimately decisions concerning the overall beach enhancement-hurricane protection projects will involve economic, environmental, technical, and social considerations.

Jan 1, 1995

By Armando M. Lago

Secular and cyclical patterns of postwar sources and uses of funds of the mineral sector are analyzed. A simultaneous equation behavior model of sources and uses of funds is developed for both mining firms and integrated producers, and these models were put through the task of predicting the financial and expenditure be-havior of mineral corporations in response to mergers and changes in investment tax credits and depletion allowances. Finally, the quantitative analysis methodology is applied to the analysis of optimum capital structure of mining corporations. The postwar changes that have occurred in the expenditure and financial behavior of mineral corporations are reviewed, particularly the relative importance of factors that affect the industry's supply and demand for funds. This quantitative statistical investigation of factors affecting sources and uses of funds of mineral corporations is achieved through the formulation of a simultaneous equation model of sources and uses of funds. After a description of the study sample, the postwar cyclical and secular financial behavior of mineral corporations is analyzed in detail. An econometric model of mineral corporate financial behavior is formulated. This model is then estimated and reviewed. Policy issues regarding depletion allowances, investment tax credits, and industrial organization of the mineral sector are discussed. Finally, the optimum financial structure of mining firms is discussed and the effect of corporate financial structure on the mining corporations' average cost of capital is analyzed.

Jan 1, 1971

By Z. Hyder

Simulation and modeling is powerful tool to analyze real time data and can be used to analyze different scenarios using appropriate software that may reduce need of infield data collection process and can predict reasonably accurate results. In this paper the real time data of a mine is used to simulate and model the stresses on the pillars and evaluate the pillar strength and safety factor. The material properties assigned to the model are obtained by testing the representative samples taken from the selected locations of the mine. The mine under investigation has 50 ft wide pillars and 50 ft wide rooms under an average overburden of 650 feet. The effect of reduced pillar dimensions and increased roof span on overall stability of mine and extraction ratio is analyzed using LaModel [1] software. The predicted results of the reducing pillar size are analyzed to compares the current mining practices with the optimized room and pillar size to get better extraction ratio without comprising the safety.

Jan 1, 2011

By John W. Burd

A system is described for the simultaneous deposition of epitaxial layers on as many as eight substrates. A high degree of uniformity of both physical and electrical characteristics is achieved in the films. Variation of film thicknesses is consistently less than ±10pct within a wafer and from wafer to wafer within a run with the variation typically on the order of 55 pct. Composition variation of GaAs1-x PX layers within a wafer and from wafer to wafer within a run is consistently less than 51 pct. Electrical evaluation of the films by several techniques indicates excellent doping uniformity within a wafer and from wafer to wafer within a run. Mobilities for lightly doped GaAs films at 300°K are consistently >6000 cm2 v-1 sec-1 and mobilities > 7000 cm2 v- 1 sec-1 are regularly attainable. Techniques for the preparation of material with carrier concentrations from 1 x 1015cm-3 to 1 x 1019 cm-3 n-type and 5 x 1016 to 5 x 1018 cm-3 p-type are discussed. METHODS for the preparation of 111-V compounds by vapor phase reactions have been extensively reported in the literature.1-6 Almost all of the apparatus described for these various methods are suitable for processing one or at the most a very limited number of wafers simultaneously. With the recent rapid advances in the use of vapor grown GaAs for microwave oscillators and GaAs1-xPx as visible light emitters the requirements for these materials are steadily increasing. In order to satisfy these requirements it is necessary to move from a laboratory scale apparatus to one which is capable of processing a large number of wafers simultaneously. Desirable features would be a high degree of uniformity among the wafers and good reproducibility from run to run. The apparatus to be described fulfills these requirements very well. DISCUSSION The various methods reported in the literature can be classified under three headings: 1) closed tube, 2) open tube, and 3) the close-spaced method. Of these three the open-tube method is the most amenable for scale-up to a manufacturing process. It is the most versatile and the various operating conditions can be more precisely controlled than with the other two methods. A number of chemical reactions may be used to achieve vapor-phase growth of 111-V compounds. Sev-era1 of the more generally used reactions are shown in Fig. 1. All of these reactions have the following points in common: 1) generation of a volatile group III(Ga) species by the reaction of the transport agent (halide or HC1) with either Ga or GaAs, 2) introduction of the Group V(As and/or PI component, 3) a method of adding dopant, if desired, and 4) a region in which deposition from the vapor will occur and form as a single crystal epitaxial film on the substrates. The laboratory scale reactors permit the hot re-actant gases to flow into the relatively cooler deposition zone and pass successively over the several substrates which are arrayed along the long axis of the tube parallel to the gas flow. With this arrangement the composition of the reactant stream is continually changing as solid material is deposited on each successive substrate. As a result of this changing gas composition the reaction driving force also changes from substrate to substrate and the degree of uniformity of layer thickness, doping level, and so forth, is poor. This effect can be partially overcome by imposing a controlled temperature gradient along the deposition region to compensate for change in gas composition. However, even when this is done variations in layer thickness on the order of 30 to 40 pct are common and as high as 50 pct are frequently experienced between adjacent wafers in the tube. To expand this arrangement to a large number of wafers would only increase the nonuniformity from the first to last wafer in the line. From the above discussion the two undesirable features of changing gas composition and temperature gradient become evident. A reactor system which eliminates or minimizes these undesirable features is one in which the apparatus is mounted vertically as shown schematically in Fig. 2. The vertical mounting permits the disposition of a number of substrates on a suitable support so that all wafers are at the same vertical height in the furnace and hence at essentially the same temperature. By using only a single row of wafers the reactant gas mixture passes over only one substrate in its path through the reactor. Thus the two undesirable features of changing gas composition and temperature gradient are minimized. An additional design feature which further minimizes temperature variations is rotation of the substrate holder. Rotation serves to integrate any radial temperature gradient existing around the resistance heated furnace. A photograph of a reactor assembly at the completion of a run is shown in Fig. 3. MATERIAL PREPARATION Apparatus. Although any of the several chemical systems shown in Fig. 1 are adaptable for use in this apparatus the one generally used is System 2, the hydride synthesis system. This system has been de-

Jan 1, 1970

By Wu Jie Mei, Li Yao Liang, Franz-Werner Gerressen, Arthur Bi

Diaphragm walls (D-walls) are known as underground structural elements commonly used for retention systems and permanent foundation elements. In addition, they are also quite often used as deep groundwater barriers, called Cut-Off-Walls (COW). Shanghai ranks third among the most densely populated metropolises in the world. In 1990, only eight million people lived there. Today, Shanghai has about25 million inhabitants. The increasing demand to accommodate the infrastructure of growing megacities like Shanghai pushes the required depth for subway, sewage and foundation projects to the limit. Future projects will demand excavation depths of more than 100 m (328 ft) on a regular basis. Already carried out reference projects will be described and a general outlook for upcoming projects will be given. The paper also explains the installation process in general focusing on the use of trench cutter technology. INTRODUCTION D- walls are known as underground structural elements, commonly used as retention systems for excavation pits and shafts as well as permanent foundation walls or elements. It is anticipated that, with the increasing trend of utilizing more and more underground space to accommodate environmental considerations and urban/suburban development, there will be an increasing requirement for diaphragm wall usage in even more difficult conditions and with increasing depth. The trench cutter is the most important tool for performing this work. The hydraulic grab, a well-known and valuable excavation tool for d-walls reaches its limits in terms of depth and when cutting rock. Therefore the trench cutter technology will be in the focus of this paper. The trench cutter itself is a reverse circulation excavation tool. It consists of a heavy steel frame with two drive gears attached to its bottom end, which rotates in opposite direction around the horizontal axis. Cutter wheels are mounted onto the drive gears. As they rotate, the soil beneath the cutter wheels is continuously broken up, removed, mixed with the bentonite slurry in the trench and moved towards the opening of the suction box of the pump? A centrifugal pump located right above the cutter wheels conveys the slurry via a hose system up to a desanding plant. There the slurry loaded with soil and rock particles is cleaned and returned into the trench.

Jan 1, 2018

By Qun Wang, Elena A. Alonso, Janusz S. Laskowski

Primary normal long-chain amines are insoluble in saturated brine. Their colloidal solubility (dispersion) in concentrated electrolyte solutions is strongly affected by the presence of surfactants (frothers). This paper shows that a better usage of alcohol type surfactants, which are commonly used in potash ore flotation as frothers, can significantly improve the flotation of both coarse and fine sylvite particles. A new process of potash ore flotation is developed, which includes premixing an effective frother with an aqueous solution of amine or emulsion of extender oil containing amine. With such a combination of flotation reagents, KC1 particles up to 5 mm in size float very well in the short flotation column, and particles up to 2 mm float in a mechanical cell; when used to treat fine fraction-containing sample, this method may as well provide an improved concentrate grade.

Jan 1, 1995

By Kubik K

Recent significant advances in the Global Positioning System (GPS) have contributed to making real-time kinematic/dynamic process for decimetre to centimetre-level positioning more reliable and ready for the production-use. As a result of research and development efforts in this area, a robust real-time kinematic (RTK) GPS positioning prototype system has been established at QUT for both scientific and engineering purposes. This system is finding applications in a wide range of automobile robots or automatic guidance vehicle systems. This paper first summarises the theoretical basis necessary for centimetre real-time kinematic positioning, then gives a brief description for the real-time dynamic GPS system developed at QUT. The paper summarises the results of a designed vehicle tracking test. The results demonstrated that the differences between RTK filtering solutions and OTF solutions are in the order of magnitude of about 20 centimetres and the accuracy of OTF solutions are in the levels of two centimetres. This confirms that the RTK system delivers three-dimensional position with decimetre-to-centimetre accuracy. This particular RTK processing system is robust and reliable, although the system is referred to as a prototype and will be further developed.

Jan 1, 1997

By E. L. Garton

Analyses of samples of crude oil from fields in West Texas have been published from time to time in Bureau of Mines reports.3/ Analyses of 100 samples of crude oil from West Texas) collected during 1946 to 1952) are presented in this report. The production of crude oil from the fields in this portion of Texas totaled 381,129,000 barrels4/ during 1951 - an amount greater than that of any previous year. Total cumulative production of this area through 1951 was 2,792,692,000 barrels.5/ Table 1 gives monthly production figures for 1951 and yearly totals for the preceding 10 years (1942-1951) [ ]

Jan 1, 1953

By I. N. Zavarine

The observations presented in this paper were recorded during a study of the spheroidizing process. Spheroidization of cementite in steel is either brought about to develop a set of desirable mechanical properties or is an incidental result of mechanical and heat-treating manipulations. Physical properties of steel are materially influenced by the state of the cementite. Conversion of cementite from the lamellar to the spheroidal state is usually accompanied by a decrease of hardness and of strength and by an increase in ductility. The spheroidized structure is usually considered as an ultimate step in the process of the softening of steel. The unorthodox hardening of a 3.5 per cent Ni steel (SAE No. 2330) after a heat-treatment that previously proved entirely suitable for a complete spheroidization of cementite in carbon steels led to the observations that constitute the subject of the present paper. Experimental Procedure The steels used for the experiments described were bought on the market. All were in the form of 3/4-in. round bars. Their chemical compositions are given in Table 1. The spheroidization of cementite in steels can be obtained in several ways. The method used in the present work is, perhaps, the least known. It consists of cyclic heating and cooling of steel, the temperature being

Jan 1, 1939

By I. N. Zavarine

The observations presented in this paper were recorded during a study of the spheroidizing process. Spheroidization of cementite in steel is either brought about to develop a set of desirable mechanical properties or is an incidental result of mechanical and heat-treating manipulations. Physical properties of steel are materially influenced by the state of the cementite. Conversion of cementite from the lamellar to the spheroidal state is usually accompanied by a decrease of hardness and of strength and by an increase in ductility. The spheroidized structure is usually considered as an ultimate step in the process of the softening of steel. The unorthodox hardening of a 3.5 per cent Ni steel (SAE No. 2330) after a heat-treatment that previously proved entirely suitable for a complete spheroidization of cementite in carbon steels led to the observations that constitute the subject of the present paper. Experimental Procedure The steels used for the experiments described were bought on the market. All were in the form of 3/4-in. round bars. Their chemical compositions are given in Table 1. The spheroidization of cementite in steels can be obtained in several ways. The method used in the present work is, perhaps, the least known. It consists of cyclic heating and cooling of steel, the temperature being

Jan 1, 1939

By Kenneth Seaver

Discussion of the paper of KENNETH SEAVER presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 105, September, 1915, pp. 1913 .to 1927. J. W. RICHARDS, South Bethlehem, Pa.-This paper concerns a very large industry, and an important detail in that industry. Within sight of where I live in Bethlehem, Pa., are coke works in which $2,500,000 was lost by the use of improper bricks in the coke ovens. This was the fundamental reason of the failure of the plant. The old ovens have all been torn out and replaced by new ovens built of proper bricks. This may emphasize the commercial importance of this subject. When speaking about coke-oven brick, the first thing that comes to my mind is how important it would he if it were possible to. get a brick of better heat conductivity. The heat for coking coal has to go through the thickness of the brick. The silica brick used has low heat conductivity as compared with some other refractories; magnesite brick probably has four times its heat conductivity. The coke oven needs bricks of high heat conductivity. Any process which would increase the heat conductivity of silica brick would undoubtedly shorten the coking process.

Jan 12, 1915

By E. J. Magri, D. M. Hawkins

This paper deals with an experimental programme carried out with a gold analyser in the period June to September 1979 at Loraine Gold Mines. The results were found to be reproducible, with no overall or conditional bias when the measurements were compared with those obtained from chip samples. The standard error of estimation of a 3 m reef exposure, which was the sampling interval, can be reduced by a factor of 2,5 if the complete stretch is scanned, rather than the taking of one chip sample in its centre. Complete statistical and computational procedures were developed for the fitting of the normal-Iognormal model to observed analyser data and for the determination of the most likely gold grade for a particular analyser measurement. (This corection procedure is necessary since a significant number of negative analyser measurements can be observed.) Panel averages of uncorrected scans showed a small conditional bias relative to those of corrected scans. However, uncorrected panel averages can be used for on-the-spot decisions regarding whole panels. For standard calculations of ore reserves, use should be made of corrected scans. Under reasonable assumptions, the use of the detector in the selective mining of low-grade narrow reefs such as the Basal Reef at Loraine Gold Mines, when compared with the conventional chip-sampling method, can result in a saving of as high as R40 million in present-money terms over the life of a project. The difference could be even larger in a highly variable reef like the B Reef at Loraine Gold Mines.

Jan 1, 1987

By Descour Jozef, Suguru Shirasagi, Takuji Yamamoto, Koji Murakami

For TBM tunneling no visual inspection of excavated ground is possible. This may hinder the high-speed excavation, particularly in complex ground conditions. The TBM Excavation Control System was developed for better prediction of geological conditions ahead of the tunnel face during excavation. The seismic reflector tracing produces volumetric images of anomalies in the ground in “near-real time.” These images are verified using logging data from pilot boring and TBM driving data, to improve reliability and precision of ground mapping. Also good correlation was obtained between the rock strength index computed from TBM data, and one derived from volumetric seismic images.

Jan 1, 2007

By H. B. Salisbury

The Bureau of Mines conducted research to determine if low-grade California chromite ores could be beneficiated to produce products suitable for commercial use. This research is part of a Bureau goal to provide technology capable of using low-grade domestic ores to meet emergency demands of the Nation for metals and minerals and in particular those minerals, such as chromite, which are considered critical. Two ores from California were ground and treated using gravity concentration and magnetic separation techniques. An are from Auburn in central California, assaying 2.5 pct Cr203, was treated by tabling and magnetic separation to yield a nonmagnetic product containing 44.7 pct Cr203 at a recovery of 36.4 pct. Core drilling samples from the Seiad Creek area of northern California, assaying about 6 pct Cr203, were upgraded by tabling to yield a concentrate containing nearly 50 pct Cr203 with a recovery of 50 pct. Both products are suitable for metallurgical and/or chemical use.

Jan 1, 1981

By B. J. Pieters

The paper describes the difficulties experienced with inferior coking coals as Iscor began using larger blast furnaces for the production of liquid iron. Research conducted at Iscor from 1977 to 1979 showed that benefits could be gained from the use of partially briqueted charges, and it was decided to install briqueting plants at the Vanderbijlpark and Newcastle Works. Details are given of the later plant, which was supplied by a consortium consisting of Voest Alpine, Didier Engineering, and Sumitomo Metal Industries. Sumitomo also supplied information on the optimization of coke quality along the lines of their Sumicoal System. The results have been a marked improvement in coke quality, much better blast-furnace operation, and increased productivity.

Jan 1, 1991

By AIME AIME

THE accompanying photograph: submitted by C. L. Bransford, assistant district manager of the Republic Steel Corp., in Birmingham. Ala., shows the remains of the old Tannehill blast furnaces, one of the first furnace plants in the South. They were built by Moses Stroup and operated during the Civil War period, when cannon balls were cast there. The record day's run of this furnace plant was said to be 30 tons of iron. The furnaces were fed by a water-wheel-operated bellows and used charcoal, a product of the neighboring forest. They were first owned and operated by the Pioneer Mining & Manufacturing Co., that later became the Republic Iron & Steel Cu., and subsequently the Republic Steel Corp. in that district.

Jan 1, 1936