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By Raymond D. Potts

"Minntac is a taconite mining, concentrating and pelletizing operation located near the town of Mountain Iron, Minnesota, U.S.A. It is totally owned and operated by USX Corporation and represents its largest source of domestic iron units. Minntac began producing fluxed pellets in 1988 and has produced both acid and fluxed pellets since then. This paper compares the acid and fluxed pellets produced at Minntac. It reviews modifications that have been made to the plant flowsheet and discusses areas recognized for improvement since the beginning of fluxed pellet production. It also comments briefly on the performance of Minntac fluxed pellets in USX blast furnaces and the future of fluxed pellets at Minntac.IntroductionMinntac was built in three steps with each step designed to produce 6 million long tons of acid pellets per year. The actual production has varied though. Figure I shows the production by year at Mirmtac. Step I began production in 1967, Step 2 in 1972 and Step 3 in 1978. Mirmtac produced 16.5 million tons in 1979 but only 3.5 million tons in 1982 when the facility was shut down for six months because of the lack of demand for pellets. Since the initial start up, Mirmtac has produced over 200 million long tons of pellets. Until 1987, all the pellets produced were ""acid"" pellets. In 1987, equipment to produce ""fluxed"" pellets was installed and tested. In 1988, full scale production of fluxed pellets began."

Jan 1, 1991

By O Tiili, A Dixon

Many minerals processing plants need to have greater efficiency in current times and optimise their process performance in order to maintain high profitability. This is even more so in the current economic climate. In the case of large flotation cells, such as TankCell«-300 with over 300 m3 active capacity, ensuring consistent operation and optimal flotation conditions is particularly critical, given the high impact on overall process and throughput of such cells. As there are fewer cells to control and monitor, there is also a lower initial capital cost for instrumentation - the requirements, however, are higher. Despite such compelling reasons, instrumentation and basic control in flotation cells has not changed much in recent years. The standard is still to use traditional feedback (PI algorithm) controls for slurry level and flotation air. A new advanced instrumentation and control package for large flotation cells has recently been developed by Outotec and has been installed at Macraes.In addition to the standard basic instrumentation and control, the new system at Macraes consists of a froth image analysis system, a froth velocity control, and a level control system which utilises adaptive feedforward compensation. There are three TankCell«-300 cells in operation at Macraes since November 2007 and the new control system was commissioned in December 2007.The paper will include comparative data from pre- and postsystem installation and discusses benefits including optimised recovery, improved performance, as well as ease of operation.

Jan 1, 2009

By Thomas M. Barczak

Longwall operators are again pushing the envelope in terms of life expectancy for longwall shields. State-of-the-art shields are now expected to last more than 60,000 loading cycles, twice the life expectancy compared with those of a decade ago. A review of trends in shield design shows that shields continue to increase in both size and capacity. Some state-of-the-art shields now weigh over 30 tons and provide up to 1,200 tons of support capacity. Although life expectancy has increased and modern shields are structurally more reliable, premature failures do still occur. This paper provides an engineering and operational assessment of shield design and provides key points to observe in what causes premature shield failures. Design practices to improve structural margins of safety that will prevent premature failures from occurring are also examined. A survey of recent shield failures is provided, as well as trends in shield design and how they might impact the performance and longevity of a shield. Hydraulic failures are more common than structural failures. Although hydraulic failures occur on all aging longwall shields, they often go undetected for long periods, resulting in degraded support capacity that can lead to serious ground control problems. The fundamentals of shield hydraulics are described in order to evaluate hydraulic failures that plague all shields at some point in their service life, and practical methods to detect hydraulic failures are examined. The paper concludes with recommendations for inspecting damaged shields and safety precautions regarding their continued use.

Jan 10, 2000

By H. Al-Kazzaz

The 2-mm butt joints of ZE41A-T5 sand castings were laser welded using 1.6 mm EZ33A-T5 filler wire and a continuous wave Nd:YAG system at a power of 4 kW, surface defocusing and various welding speeds, Compared with the base metal, the fusion zone showed significant grain refinement due to high cooling rate, No grain coarsening was observed in the heat affected zone (HAZ). The porosity area percentage and total solidification crack length in the fusion zone (FZ) were reduced as the welding speed increased from 4 to 7 m/min, Fusion zone area, total penetration depth, and weld width decreased with increased welding speed, The hardness in the FZ was similar to or higher than the base metal after a natural aging of about one year, but there was a drop in the hardness of the HAZ, The HAZ width decreased with increasing the welding speed, Tensile test showed that a joint efficiency of approximately 75 ? 90 % was obtained.

Jan 1, 2005

By J. R. Koehler

Yield pillar-based gate road designs oftentimes fail to provide mine operators with adequate ground control because of the unknowing misemployment of "critically" sized pillars. A "critical" pillar is one that is too large to either yield nonviolently or yield before the roof and floor sustain permanent damage, but is too small to support full abutment loads. To demonstrate the critical pillar concept, a field study of a tapering gate road was conducted by the U.S. Bureau of Mines at the Sunnyside Coal Mines, Sunnyside, UT. Extreme pillar stresses and associated coal bumps characterize the response to first panel mining of a 16.8-m wide critical design. Significantly lower pillar stresses, early yielding of the pillar and adjacent panel rib, and an absence of coal bumps suggest that a narrower 12.2-m-wide design more closely approaches proper yield pillar dimensions. Probehole drilling of several 1 O.6-m-wide pillars revealed low stress levels and substantial pillar and panel rib yielding prior to abutment onset, indicating a properly functioning yield pillar design.

Jan 1, 1995

By René Winand

A new process was studied at large laboratory scale at Université Libre de Bruxelles, under contract with Metallurgie Hoboken-Overpelt. A two cathodes (1m long ; 0.2 m high) channel cell was used at 2000 A/m2, with an electrolyte flow rate up to 1.8 m/sec. The main results may be summarized as follows : cathodes are electro¬refined grade in analysis ; metallographic structure and surface roughness are kept under control up to 1.3 cm (one side deposits) ; silver in cathode is controlled by CI and Br ions in solution ; organics must be used at very low concentrations (in the range of 0.1 mg/1, with a consumption of about 0.01 mg/lh).

Jan 1, 1987

By A. D. Hughes

A relatively small area in Malaya, about 200 miles long by 40 miles wide, is the most important source of tin in the world. Some tin is recovered in other parts of the peninsula. Of the tin mined, 98 pct is recovered from alluvial deposits. From 1935 to 1941 the average annual world production of tin was 190,000 tons. The average annual production from Malaya during the same period was 62,000 tons or about one third of the total. Other producing countries, in order of importance, were the Netherlands East Indies 34,000 tons, Bolivia 30,000, Belgian Congo, Nigeria, Siam, Burma, China, and a few others with smaller amounts. The serious shortage of tin during the war period was due to the fact that the Japanese were occupying Malaya, Netherlands East Indies, Siam, Burma, and China which, together, formerly were producing 65 pct of the world supply.

Jan 1, 1949

By R. Winand, P. Harlet

he cathodes produced are of electrorefined grade; metallographic structure and surface roughness are controlled to a depth of 1.3 cm (single-side deposits); silver levels in the cathode are regulated by the presence in solution of Cl- and Br- ions; organics must be used at very low concentrations (around 0.1 mg/l with a consumption of about 0.01 mg/l/hr). The required concentrations of additives were established according to a well-defined strategy based on the consumption of organics at the cathode by a mass transfer limited-process.

Jan 4, 1992

By H. W. Sheffer

Technical and economic aspects of community refuse disposal systems and their effects on the environment are identified and described. Seven landfills and two incineration systems, located throughout the United States, are reviewed.

Jan 1, 1971

By S Lakemond, L I. Ku, J Vaughan

Conventional processing of poly-metallic gold containing flotation concentrates are challenging for a number of reasons. One reason is that substantial copper and zinc in the cyanide leach solution compete with gold and silver for carbon adsorption sites. In this study, metal-cyanide adsorption kinetics and equilibrium are measured on three samples of coconut derived activated carbon and one sample of synthetic carbon. Loading selectivity was confirmed to be in the order gold>silver>copper>zinc for all carbon samples. The synthetic carbon tested showed promising results in terms of loading kinetics and capacity for precious metals.CITATION:Lakemond, S, Ku, L I and Vaughan, J, 2013. Effect of carbon type on adsorption of Cu, Zn, Ag and Au from mixed cyanide solution, in Proceedings World Gold 2013 , pp 411-418 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By Daniel G. DiCanio

This report describes a computer-based model for estimating the tangible costs of injuries and deaths from work-related accidents in underground coal mines. The study undertook to identify and quantify the elements of accident costs, including field visits to coal mines, insurance carriers, and public agencies. The mathematical models developed for each tangible element of accident cost are presented in Volume I of the report. A listing of the computer programs which comprise the model and instructions for using the programs are presented in Volume II. Statistical distributions of mining family characteristics, data on 95 miners killed in underground accidents, and other basic data used to develop the model are presented in Volume III. Application of the model to a data base of 9,286 accidents which occured in underground bituminous coal mines during 1974 yielded a total of $56,900,000 in tangible costs to industry, mining families, and public agencies. Loss of income to the families of miners injured or killed in these accidents accounted for 47 percent of the total.

Jan 1, 1976

By Henrique Hipolito, Caio Alves

Waelz process is a method applied in the zinc oxide production and is one of the largest sources of carbon emissions within the zinc industry. The solid carbon used for heating and for reduction reactions is provided mainly by the coke fed with the EAFD in the Waelz kiln. Both chemical composition and physical properties of the coke are important to transportation and to the process. Decarbonizing the Waelz process by replacing the traditional fuel source using alternative biogenic fuel, for example, offers a potential solution to reduce the carbon footprint, which is aligned with the ESG perspective.

Sep 29, 2023

By C. R. Watts

The feasibility of producing composites containing nickel or molybdenum fibers in a beryllium matrix was inrestigated. The composties studied were jabricaled by powder mallurgical techniques. The 1-mil-diarr nickel fibers reacled completely below 900°C, converling the fibers .from nickel to Ni5Be2,. As the /LO/-pressing temperalure as raised above 1110oC, tlie nickel diffused outward from the beryllide fibers. The solid solubility of nickel in beryllium was clboul 20 wt pet at the 1100°C pressing temperature a1 the zone-fiber interface. The 1.5-mil-diam molybdenum fibers slzolred no evidence of reaction and little evidence of diffitsion after pressing at 900°C. Between 1000° and 1050°C pressing conditions, the fibers began lo react , producing 1ayers of MoBe2 and MoBe12, respectively surrounding the molybdenurn core. The struture remained the same at 1100°C with no evidenre of solid solubility of the molybdenum in the berylium or vice versa. In recent years a considerable amount of attention has been devoted to the determination of methods for improving the mechanical properties of materials through the use of fiber or whisker reinforcement. Previous work with metal matrix composites indicates that the study of the chemical compatibility of the fiber and matrix is an area requiring greater understanding. The metal-metal or ceramic-metal interface is frequently subject to chemical reactions that may result in the formation of hard brittle intermetal-lic compounds and/or low melting point eutectic compositions. The reaction products may reduce both the low-temperature and elevated-temperature strength of the composite by weakening the fiber-matrix bond, producing premature failure at the interface. It is well-known that most metal-metal systems and many metal-ceramic systems of interest for structural composites are thermodynamically unstable,'-" particularly at elevated temperatures. If, however, the rate of reaction under the conditions of fabrication is sufficiently low. composites can be fabricated that can be used efficiently for indefinite periods at low temperatures and for short periods at elevated temperatures. This paper presents the results of a series of tests to determine the compatibility of nickel and molybdenum fibers with beryllium at various hot-pressing temperatures. Nickel was selected as a candidate fiber material primarily because the relatively ductile fibers might be useful as crack arresters in applications such as ballistic impact where crack growth can result in catastrophic failure. The high density and the reactivity of nickel were primary factors detracting from its selection as a possible reinforcement. Molybdenum with a modulus of elasticity of 52 Xlo6 psi is one of the few metallic materials having a modulus higher than beryllium (42 X lo6). Its high modulus, coupled with its refractory characteristics, made molybdenum an attractive candidate for a relatively stable fiber reinforcement for beryllium. Its density, being higher than that of nickel and over five times that of beryllium: detracted from its other characteristics. EXPERIMENTAL PROCEDURE The specimens were prepared from beryllium powder with a dispersed phase of fibers by powder metallurgical techniques. P-20 grade powder, Table I, from Berylco was used as the matrix material. Short lengths of 0.001-in.-nominal-diam nickel fibers supplied by the Sigmund Cohn Corp. and 0.0015-in.-nominal-diam molvbdenum fibers obtained from the General Electric Co. were used as the dispersed phase. The composite constituents were combined under an argon atmosphere by mechanically mixing the powders and fibers. The compositions used were nominally 1 vol pct fibers. After mixing. the composites were hot-pressed into a-in.-diam pellets under an argon atmosphere at 900°, 1000". 1050". and 1100°C at a pressure of 6000 psi with no hold time at these temperatures so that a comparison could be made between the resultant microstructure and hot-pressing temperature. The billet was heated at a rate on the order of 30°C per min to the desired temperature and then cooled at a somewhat slower rate. The microstructure obtained should be considered as characteristic of the integrated time-temperature history of the sample, as well as the maximum temperature attained. Upon removal from the hot-pressing dies. the specimens were cut. mounted. and polished by standard procedures. No etchant was used in specimen preparation. Photomicrographs, electron microprobe scans, and electron back-scatter pictures were made. X-ray dif-fractometer patterns were made of several of the specimens. but only the lines for beryllium could be resolved. Specimens for optical and electron microprobe examination were selected partially for the roundness of the cross section. A round cross section was taken to indicate that the body of the fiber was approximately normal to the surface and that therefore effects due to fiber material immediately below the surface could be neglected. RESULTS AND DISCUSSION The microprobe scans indicated that nickel reacted as low as 900°C, converting the entire fiber cross section to NisBe21. Fig. l(a). There was no evidence of further reaction from the optical or the back-scatter pictures, Figs. 2(n) and 3(a).

Jan 1, 1970

By E. C. Keeley

THE property of Buffalo Ankerite Gold Mines, Limited, is in Delora township, Porcupine area, Ontario. The southwestern part of the property is ground formerly owned by Marbuan Gold Mines, Limited, which was acquired by Buffalo Ankerite in January, 1936. Until 1938, the Ankerite (or North) mine and the Marbuan (or South) mine continued as separate operations, each developed through a surface shaft and winze to the 1050 level and each having its own mill. This meant high hoisting costs, which, in 1936 and 1937, amounted to 36 cents per ton. In 1938, the underground workings of the two mines were connected on the 1050 level, and ore from both mines was hoisted at the main, or No. 2, shaft of the North mine, location of which is shown in Figure l. This shaft was discontinued at a depth of 1150 feet because, owing to the soft nature of the talc (serpentine) rock in which it was sunk, it had to be concreted throughout, and also because of its great distance--1,100 feet and 1,400 feet, respectively-from the North and South orebodies.

Jan 1, 1945

By F. W. Horton

This paper covers the salient features of the occurrence and mining of sheet mica in the United States and the preparation of mica for market; presents the results of a study of the physical properties of domestic and foreign micas, which the author hopes may he of interest to every mica user, as it definitely answers many questions as to the suitability of various minas for particular purposes; and discusses mica-trade conditions and the future outlook for the domestic mica industry. ACKNOWLEDGMENTS The author takes pleasure in acknowledging his indebtedness to J. R. Thoenen, of the United Stator Bureau of Mines, under whose guidance the work reported herein was performed, and to Frank L. Hess, also of the Bureau, for information on the geological and mineralogical characteristics of mica-bearing pegmatites.

Jan 1, 1935

By Sebastian Avalos, Julian M. Ortiz, Willy Kracht

Semi-autogenous grinding mills play a critical role in the processing stage of many mining operations. They are also one of the most intensive energy consumers of the entire process. Current forecasting techniques of energy consumption base their inferences on feeding ore mineralogical features, SAG dimensions, and operational variables. Experts recognize their capabilities to provide adequate guidelines but also their lack of accuracy when real-time forecasting is desired. As an alternative, we propose the use of real-time operational variables (feed tonnage, bearing pressure, and spindle speed) to forecast the upcoming energy consumption via machine learning and deep learning techniques. Several predictive methods were studied: polynomial regression, k-nearest neighbor, support vector machine, multilayer perceptron, long short-term memory, and gated recurrent units. A step-by-step workflow on how to deal with real datasets, and how to find optimum models and final model selection is presented. In particular, recurrent neural networks achieved the best forecasting metrics in the energy consumption prediction task. The workflow has the potential of being extended to any other temporal and multivariate mineral processing datasets.

Jun 16, 2020

By B. K. Parekh, Z. Chen

INTRODUCTION The need for cleaning and recovery of fine (minus 28 mesh or 0.5 mm) coal fraction has increased in recent years. This results from realizing a substantial recovery of ultraclean coal from the waste stream improving overall Btu (heat) recovery, providing extra revenue for the coal industry. Also the potential of using the clean coal so obtained for making coal-water mixture which could replace oil. An additional benefit of recovery clean coal from the waste stream is reducing environmental concern of burning uncleaned coal and in waste disposal. Deashing of coal by physical beneficiation processes is limited by the degree to which ash components are liberated from coal. Conventional processes have been inefficient in terms of Btu recovery, for ultrafine coal. Chemical cleaning methods, which involves leaching of ash material from coal, have provided ultraclean coal at high Btu recoveries, are more costly than the physical cleaning methods. An advanced physical separation technique that appears to address the need discussed above is selective flocculation. This technique which has been successfully utilized in iron ore beneficiation offers the potential of processing fine and ultrafine coal to produce a clean fuel. OBJECTIVES The main objective of the present study is to investigate applicability of selective flocculation technique for recovery of clean coal product from the waste coal slurry supplied by the Peabody Coal co., from their three different coal preparation plants. It is also the objective of the program to conduct preliminary economic study of the selective flocculation process.

Jan 1, 2002

"Since the publication of a literature review on this topic (McIvor and Finch. 1986), the author has been involved in more than thirty rod milling efficiency tests at seven different milling operations. There have also been several interesting additional articles on rod milling found in the literature. This update describes the most important findings from investigations carried out since the previous review, as well as developments in the techniques used to evaluate the grinding efficiency of rod mills.Rod Mill Power DrawA series of power draw versus charge level measurements were taken on the rod mills at Leg Mines Selbaie and Kidd Creek Mines Limited (McIvor. 1989). These revealed a significant (about 10070) loss in power draw with the installation of new liners, a common observation among rod mill operators. This loss in power draw depends on the liner design, particularly the average thickness and lifting face profile of the new liner. The theoretical power usage of both mills was approximately 5070 lower than that given by the Allis-Chalmers power draw formula (Rowland. 1982).The shape of the power draw versus charge level curve suggested an opportunity for reducing media consumption. By increasing mill speed, power draw could be maintained with a smaller mill load, most significantly for mills operating with high charge levels. Analysis of data from 62 installations confirmed this (McIvor, 1989). On average, a 10 percentage point increase in critical speed results in a 15070 in specific media consumption (Le. kg of steel consumed per kWh of energy consumed). Table 1 lists a number of relatively high speed rod milling installations. No negative effects on the drive train, liner life, or the tendency for rods to tangle have been reported. A reduced lifting angle of the new liner leading face (e.g. 45 versus 90 degrees from the mill perimeter) is recommended for higher speed rod mills (Leclerq, 1990)."

Jan 1, 1995

By George W. King

The yield strength of a dispersion-hardened W-3.8 vol pct Tho,alloy, in both the recovered and recrys-tallized condition, was investigated and cornpared with that ofrecrystallized pure tungsten over the temperature range of 325" to 2400°C. It is deduced that the Orowan mechanism is obeyed in the recrystallized alloy. In the recovered alloy, a further enhancement of the yield strength results from the retained substructure which is stable up to temperatures in excess of 2700°C. Temperature and strain rate cycling tests were also performed, and the apparent activation energy for the deformation process was derived. This activation energy, - 3 ev, for the recovered and also the recrystallized alloy was about the same as that for re crystallized pure tungsten. However, the activation volume of the recovered alloy, -10-2 cu cm, was about an order of magnitude lower than that of the recrystallized alloy or pure tungsten. This fact accounts for an enhancement oj- the temperature dependence of the yield stress of the recovered alloy. A dislocation velocity exponent of about 4 to 13 was deduced frorn the strain rate cycling tests , which is in good agreement with values reported for tungsten single crystals. VARIOUS theories have been developed to explain the enhanced yield strength of a metal containing a dispersed second phase of small hard particles. These theories are thoroughly reviewed by Kelly and Nicholson.' The theoretical models can be separated into two types. The first type assumes direct interactions between moving dislocations and dispersoids. One of the most widely investigated models for this mechanism is the bowing out of dislocations between the dis-persoids and their subsequent pinching off in order to bypass the obstacles. This is the well-known Orowan mechanism.' The second type is an indirect effect of the dispersion because of its ability to stabilize to high temperatures the substructure introduced by cold working. In this instance, the increment in the yield strength is expected to be inversely proportional to the square root of the subgrain diameter. In the present work, a quantitative study was made of the strengthening effect caused by a thoria dispersion in a recrystallized W-3.8 vol pct Thoz alloy over the temperature range 325" to 2400°C. The results are compared with the increment predicted for the Orowan mechanism based on the calculations by ~shb~.~ In addition, the alloy was tested in the recovered state so that any additional strengthening resulting from the substructure produced during fabrication could be measured. The respective contributions can be separated in this manner, provided that the particle size distribution of the dispersion remains the same in both the work-hardened and the recrystallized state. Particle size distribution measurements showed that this condition was met in the present work. I) EXPERIMENTAL PROCEDURES A) Material Production and Fabrication. The alloy investigated is essentially the same as that reported much earlier by ~effries,~ who also found the strength of tungsten to be improved by the thoria dispersion. The procedure for producing the alloy consisted of mechanically blending a thorium nitrate solution in proper concentration with tungsten oxide (WO3) powder, followed by hydrogen reduction to metal powder. After reduction, the dispersed second phase is present as thoria (Thoz). The pure tungsten powder used for comparison was produced in the same manner except that the thoria doping step was omitted. The powders were consolidated by cold pressing and self-resistance sintering in hydrogen. The resulting ingot had a cross section about 0.6 sq in. and a density about 93 pct of theoretical. The ingot was swaged to 0.174-in.-diam rod at temperatures varying from 1650°C initially to -1200°C near final rod sizes. Two intermediate recrystallization anneals were employed during fabrication. Analysis of the swaged rods is reported in Table I. B) Electron Microscopy Techniques. Carbon extraction rrPxcas prepared by a technique reported by ~00' were used to quantitatively evaluate the thoria particle size and distribution. Electron nlicrographs of extraction replicas were taken at 20,000 times but were then enlarged two to three times in printing. The areas photographed were randomly selected. A Zeiss Particle Size Analyzer (Model TGZ3) was used to count and measure the sizes of all particles present on the print. About three thousand particles were counted in determining a distribution curve. Electron transmission microscopy was used to determine the effect of annealing on the substructures of the materials. Thin foils were produced by a two-stage thinning process. The rods were first ground on emery paper to ribbons about 10 mils thick and then a jet of 5 pct KOH was used to electrolytically reduce a portion of the cross section of the ribbon. Final perforation was achieved by immersing the specimen in a 5 pct KOH solution and electrolytically polishing at a current density of about 0.3 amp cm-'. The foils were examined with a Hitachi HU-11A electron microscope. C) Tensile Testing. Tensile testing was performed in an Instron Testing Machine equipped with a radiation-type vacuum furnace which operates at about 1O"S torr at temperatures as high as 2400 °C. The same furnace was used for annealing the tensile specimens.

Jan 1, 1970

By Arthur E. Bruszak, Marcel Vanpée

In many practical combustion systems ignition may occur through contact with hot burned gases . Such a process plays a vital role in flame stabilization on bluff bodies . It is also of importance in the ignition of firedamp by the hot spent gases of explosives used in mines . Also , in the communication of flames through narrow channels , a problem of practical importance in flameproofing electrical equipment , the propagation of the flame is essentially a reignition process in which hot burned gases are the agent of ignition . In the actual ignition problem a great variety of conditions may be visualized . Ignition may occur where pockets of hot gases are surrounded by cold explosive mixtures or where pockets of cold mixture may be surrounded by hot gases . Alternately , a flowing stream of combustible mixture may be initially in contact with another stream of hot combustion products , or a jet of hot gases may flow into a cold quiescent mixture ; the jet may be laminar or turbulent , continuous or discontinuous . The hot gas may also consist of the oxidant ( air for instance ) and the cold combustible pure fuel . This study by the Bureau of Mines is concerned only with ignition produced by a continuous jet of gas ( hot ) flowing into a practically quiescent cold mix- The investigation of ignition by bursts of hot gases or by turbulent jets is outside the scope of this report , and work performed on this phase of the problem has been published elsewhere

Jan 1, 1963