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By A. Blake Caldwell

The continental margins and ocean basins represent by far the largest unexplored frontier for discovery and development of mineral values. In April 1971, Deepsea Ventures, Inc., at a press conference in its Gloucester Point, Va. headquarters, announced what may become the first commercial deepsea venture--15,000 ft below the ocean surface. During the presentation, Deepsea's president, John E. Flipse, announced that studies made by company personnel had proven the feasibility of mining, transporting, and milling L million tpy of manganese nodules taken from the ocean floor, and that, based on current conditions and prevailing construction costs, a venture of this magnitude would cost about $200 million split evenly between mining and processing facilities. A subsidiary of Tenneco, Deepsea has tentatively reserved 1976 as the year in which it plans to mine, process and market the nodules.

Jan 1, 1971

By Laurance Reid

HIGH compression ratios, resulting from high injection pressures and relatively low recovery process pressures, constitute a major problem, which has confronted those engaged in gas recycling for condensate production since the beginning of that practice. Despite the numerous process developments and improvements, no entirely satisfactory solution for this prob-lem has been presented to date. Often, where the residue gas from the recovery process must be recompressed for subsurface injection, there is a substantial difference between the required injection pressure and the plant-operating pressure required to produce maximum recovery of condensate. These limitations result in high compression ratios, which, in turn, neces-sitate excessive compressor investment and operating cost. As an alternative, the operating pressure may be increased in order to lessen the compressor requirements but such a saving often is purchased at the expense of decreased condensate recovery, caused by operation at the higher pressure. Regardless of the choice, the net result is a diminished return on the capital invested in the project. The goal of future development in this field must be the complete recovery of all valuable hydrocarbon components in the reservoir fluid at pressures that, regarded as compressor suction pressure, will require minimum compressor horsepower to inject the residue gas into the formation. A com-pression ratio of 1.5 has been established as an optimum for modern compressor equipment." Therefore, in order to con-form to this optimum condition, a 3000-lb. injection pressure would require that the condensate recovery process be operated at 2000 lb. per sq. inch.

Jan 1, 1940

By R. F. Mehl, B. Lustman

THE formation of intermediate phase layers in cementation processes has been subjected to extensive qualitative investigation though to relatively little quantitative study; this work has recently been fully summarized by F. N. Rhines.1 It is necessary here only to enumerate the general conclusions drawn concerning the kinetic laws governing the growth of intermediate layers and to state what is known concerning the structural changes accompanying the generation of phase layers. I. When the intermediate phase is protective in type-i.e., when its density is less than that of the base metal, so that a continuous coating is formed and maintained the isothermal growth of the phase follows a simple parabolic equation: X2 = kt [I] where X is the thickness of the alloy layer, k the reaction rate constant, and t the time. The applicability of this equation to diffusion processes is tested by plotting the square of the thickness versus time, or by plotting the thickness versus the square root of time; the resultant achievement of a straight line in such. a plot has been con¬sidered sufficient proof of the validity of this equation. Exceptions have been found where liquid phases are involved in the reaction, where the diffusion layer is cracked,2 and where thin semimetallic oxide and sulphide coatings are formed on metals.3 In the first two cases the thickness increases linearly with time, and in the latter it is a logarithmic function of time. 2. The rate of thickening varies with temperature according to the Arrhenius equation k = Ae-Q/RT [2] where k is the parabolic rate constant of Eq. I, or some other rate-descriptive function, A is the action constant, e the base of natural logarithms, Q the heat of activation, R the gas constant, and T absolute temperature. This equation has been found to be generally valid except when transformations occur during reaction in either the base metal or in the reaction layer; in such instances Eq. 2 is still applicable with different values for the constants A and Q above and below the transformation temperature. 3. All phases that are stable at the temperature at which diffusion occurs will appear in the interdiffusion of two components. In some cases certain of the phases may be too thin to be observed and identified easily. Nonequilibrium phases have never been noted in thick reaction layers; i.e., layers of a thickness that may be discerned microscopically. The relative, thickness of each phase in a diffusion layer is proportional to the concentration gradient and to the rate of diffusion in that phase .4 The reaction layers tend to have a

Jan 1, 1942

By T. Sterry Hunt

I HAVE in a previous communication called the attention of the Institute to the geognostical relations of the crystalline iron ores belonging to the Eozoic rocks of North America, at which time I noticed (1) those associated with the gneisses of the Laurentian series, (2) those of the crystalline schists of the Huronian, as seen in Northern Michigan and in many localities along the Appalachians ; (3) those of Southeastern Missouri associated with petrosilex porphyries and schistose rocks, and presumed to be nearly of the same age with those of the Huronian schists; and (4) the highly titaniferous ores of the Norian or Labradorian series from Essex County, N. Y., and from various parts of Canada. It may here be remarked that, although the presence of titanium is most marked in the Norian ores, this objectionable element is sometimes found in the schistose ores of the Huronian, and to a lesser extent in certain Laurentian magnetites. The ores of each of these geological divisions have their individual peculiarities, which serve to distinguish them to such a degree that the magnetites and specular ores of the Laurentian are as dissimilar to those of the Huronian as are the crystalline silicated rocks of the two series. As it happens that these mineralogical dissimilarities correspond to differences in composition and in adaptability to different processes of manufacture, which, in the present condition of the iron industry, are objects of special consideration to metallurgists, it will be seen that these geognostical distinctions become of great practical importance. During the past year I was desired by the Geological Commissioners of Pennsylvania to devote a few weeks to certain geological studies in the eastern part of the State, in the course of which I was enabled to make, with regard to its crystalline iron ores, some observations to which I desire to call the attention of the Institute. I may mention, in passing, that the great South Mountain belt, from the Schuylkill to the Delaware, is composed of Laurentian rocks, in which are found the characteristic ores of the series like those of the Highlands of New Jersey and New York, and of the Adiron-

Jan 1, 1876

Meeting of Sept. 25, 1914.-The Committees to have charge of the arrangements for the Annual Meeting in New York, Feb. 15 to 18, 1914, were appointed. It was voted that the Secretary of the Institute take up with the Chairmen of the Local Sections the question of arranging for the transportation to the meetings of the Institute of the members of the respective sections. The Board of Directors unanimously voted to extend to each and all of the members of the Local Committees of the Salt Lake Meeting its hearty thanks for their efforts which resulted in the very successful meeting. The President was authorized to sign the letter to the President of the United States in regard to the appointment of some representative of the mineral industry upon the Federal Trade Commission. An appropriation of $250 was granted to the Southern California Local Section. The By-Laws of the Utah Local Section were approved. Upon recommendation of the Committee on Membership, 133 members, 7 associates and 13 juniors were elected to membership. BRADLEY STOUGHTON, Secretary.

Jan 11, 1914

By Jan H. Hommen

TRENDS IN MINE FINANCE Reviewing historical trends may help in dealing with future funding strategies. The first trend is the increase in the use of debt to fund corporate America. Surprisingly, when comparing that with other corporates in the global marketplace, the U.S. does not look too poorly. Japanese, in particular, but also German companies, are much more leveraged than their U.S. counterparts. Note that in Japan and Germany the government and the consumer have shown substantial restraints when it comes to credit. Not so in the U.S. where the savings rate (4%) is much lower than that in Japan (20%) and in Germany (14%). As a result, the cost of leverage is substantially lower in Japan and in Germany than in the U.S. Lower debt costs in these countries allows one to obtain more of it for the same price. The close relationships between financial institutions, corporations and governments in Japan and Germany also make the risk of leverage more bearable and understandable. Also note that interest rate volatility in these countries is more subdued. The investor base in common stock is also changing. Private pension funds have been net sellers of equities during the last few years while public pension funds have been net buyers. Individuals are basically out of the market. It is estimated that over $330 billion of equity was retired in the U.S. through 1986-1988. The reasons are well known: restructurings, buy-backs, takeovers, mergers, and buy-outs. This de-equitization is likely to continue as the cost of equity capital is higher than the cost of debt capital, even on a before-tax basis. Because there has been no market for equity since October 19, 1987, junk bonds have replaced equity capital in the corporate finance structure. The non-investor-grade borrower has access to the public markets through high-yielding debt securities that often look like senior equity. Deregulation has also provided 24-hour markets; securitization can now liquify assets that before were rusting on balance sheets; information processing and communication tools give facts that are instantaneously available, creating the need for products to cover risk and exposures unknown before the start of the information and technology explosion. Thus we now have swaps, options, futures, options on futures, caps, as well as program trading, portfolio insurance, index funds, etc. Globalization will be unstoppable. Today's environment demands it. Corporations are now global competitors, even though they may have never shipped a product off-shore. Boundaries are disappearing and impediments have been removed. Stocks can be issued in a global offering with distribution in all major financial centers of the world. The high leverage of Japanese companies has made common stocks very scarce, which with the high savings rate, makes equity capital inexpensive in Japan. If markets were perfect everyone would issue stock in Tokyo and buy it back in New York. This would certainly stop the bleeding on the balance of payments. With the deficit balance of payments in America, it is no surprise that the cost of money is expensive here. The risk-return relationship on U.S. equity is not favorable enough to appeal to Japanese equity investors. The Tokyo-market, helped by a stronger yen, surpassed New York as the most important equity market in the world. The question is, will the Tokyo market hold up when Japanese domestic consumption increases at the expense of savings? In the U.S. debt markets, the plain vanilla debenture is making a comeback after a period of absence. Commercial paper has replaced short term bank borrowings for working capital funding by larger corporations. The banks have made an interesting comeback with loan sale programs that will continue to attract borrowers. There will be a continuing

Jan 1, 1990

By A. B. Calhoun

These mines, which belong to the Burma Corporation, Ltd., formerly a London company now incorporated in Rangoon, Burma, are situated in the semi-independent state of Tawng-Peng, one of the small divisions comprising the northern Shan states and erroneously known as part of Upper Burma. Bawdwin is approximately 23' 6' N. latitude and 97" 20' E. longitude, 450 miles north of Rangoon, 169 miles northcast of Mandalay and 50 miles south and west of the Province of Yunnan, China (see Fig. 1). Although the mines were worked by the Chinese during the Ming Dynasty, 1412 A. D., the most extensive operations took place between 1796 and 1851, when the mines contributed largely to the silver market of China. During the reign of Tung Chik, 1868 A. D., they were abandoned partly because of the Mohammedan rebellion in Yunnan, which made life and property insecure, but largely because of the difficulty of operating the mines on account of water and poor ventilation. Since that time practically nothing was done, although the Burmese kings are said to have made several sporadic attempts to work the mines, until 1891 when Europeans were attracted by the great slag dumps (assaying about 40 per cent. lead) which the Chinese had left after extracting the silver. After a railroad and smelter had been built and 200,000 to 300,000 tons of slag smelted for lead, exploration work was started and old workings cleaned out in order to locate the remnants of the orebody that it was supposed the Chinese had left. After two years of most discouraging work, the remains of a large orebody was discovered by the Dead Chinaman Tunnel or what is the 171-ft., or No. 2 level adit. From then on the development was rapid and today the Chinaman is considered one of

Jan 1, 1923

By A. B. Calhoun

These mines, which belong to the Burma Corporation, Ltd., formerly a London company now incorporated in Rangoon, Burma, are situated in the semi-independent state of Tawng-Peng, one of the small divisions comprising the northern Shan states and erroneously known as part of Upper Burma. Bawdwin is approximately 23' 6' N. latitude and 97" 20' E. longitude, 450 miles north of Rangoon, 169 miles northcast of Mandalay and 50 miles south and west of the Province of Yunnan, China (see Fig. 1). Although the mines were worked by the Chinese during the Ming Dynasty, 1412 A. D., the most extensive operations took place between 1796 and 1851, when the mines contributed largely to the silver market of China. During the reign of Tung Chik, 1868 A. D., they were abandoned partly because of the Mohammedan rebellion in Yunnan, which made life and property insecure, but largely because of the difficulty of operating the mines on account of water and poor ventilation. Since that time practically nothing was done, although the Burmese kings are said to have made several sporadic attempts to work the mines, until 1891 when Europeans were attracted by the great slag dumps (assaying about 40 per cent. lead) which the Chinese had left after extracting the silver. After a railroad and smelter had been built and 200,000 to 300,000 tons of slag smelted for lead, exploration work was started and old workings cleaned out in order to locate the remnants of the orebody that it was supposed the Chinese had left. After two years of most discouraging work, the remains of a large orebody was discovered by the Dead Chinaman Tunnel or what is the 171-ft., or No. 2 level adit. From then on the development was rapid and today the Chinaman is considered one of

Jan 1, 1923

The War Department is appealing to skilled workmen and scientifically or technically trained men to enlist in any one of a large number of engineering troops needed for immediate action in France. Any registrant under the selective service law, who has not actually been called to service, may be immediately inducted into an engineer organization at his own request. Application for induction should be made to the Chief of Engineers, giving a complete statement of the applicant's qualifications. Any man who is physically qualified, between the ages of 18 and 21, or between 31 and 40, may voluntarily enlist for an engineer organization, provided he proves to the recruiting officer that he is experienced or skilled in any engineering trade, or is a handy main who is' especially suited for engineering work. There are about 600 recruiting stations in the United States, and an officer at any one of these will enlist a candidate for an engineer organization if he is suitable. Enlistment is in the grade of private. Subsequent promotion to the rank of non-commissioned officer is secured by merit. It is intended to fill many of the vacancies which will occur from time to time among the commissioned officers by selection from the ranks. A few of the special services, of most interest to mining and metallurgical workmen, urgently needed by the army, are as follows: Crane Operating and Maintenance Regiments; Depot Detachments; Electrical and Mechanical Regiments; General Construction Battalions; Mining Regiments; Quarry Regiments; Battalions for the construction, maintenance, and operation of railways; Road Building Battalions; Sapper Regiments; Supply and Shop Battalions; Surveying, Ranging and Map Reproduction Regiments; Water Supply Companies; and many others. All of these organizations will be assigned to such duties as competent

Jan 4, 1918

By A. N. Holden, J. H. Hollomon

Inhomogeneous yielding during the early stages of plastic flow has been observed in many metals and has long been a subject of controversy. Low carbon steel, when strained at room temperature, exhibits a distinct yield point at which the metal ceases to behave elastically and begins to flow plastically without further increase in stress,† often with an actual decrease in stress from that existing at the yield point. One manifestation of this behavior is the familiar Lüders lines. The extent of the yield point elongation (the plastic strain which results without raising the stress above that at the initial yield point) may be several percent. Several explanations of this type of yielding in steels have appeared in the literature:1-3}; 1. The segregation of carbides or other constituents at the grain boundaries of ferrite forms cell-like blocks which break down at a higher stress than that at which the ferrite alone will flow. 2. The precipitation of various constituents within the ferrite itself in some way blocks initial flow until a higher stress is reached, after which a great deal of flow occurs without further increase in stress. 3. The restraining influence of neighboring, less favorably oriented grains in a polycrystal results in a storing up of energy, which on yielding is sufficient to cause the continued propagation of slip bands on the multiplicity of slip systems available in adjacent iron crystals without increase in stress. 4. Local segregation of carbon atoms increases the stress required for the initial propagation of dislocations. The stress required for further deformation is lower.3 Such an explanation would require the presence of upper and lower yield points in single crystals. Low and Gensamer2 have shown that heterogeneous yielding can be eliminated by removal of carbon and nitrogen from polycrystalline steels by wet-hydrogen treatment. They also demonstrated that the re-introduction of minute amounts of carbon or nitrogen caused a return of the yield point. Observations of the initial flow of single crystals containing small amounts of carbon and nitrogen- should provide a clue to the explanation of inhomogeneous yielding. Previous tests of iron crystals4-6 can not be considered conclusive because it is uncertain whether the carbon and nitrogen were satisfactorily removed by the decarburization technique employed. The purpose of the experiments described herein was to determine whether single iron crystals containing either carbon or nitrogen would exhibit in-homogeneous yielding. Experimental Procedures THE PREPARATION OF SINGLE CRYSTALS All crvstals were formed in the following way. Aluminum killed sheet material 80 mils thick was machined into specimens of the outer contour shown in Fig 1. These mildly tapered specimens were decarburized at 730°C for 16 hr in hydrogen that had been bubbled rapidly through water maintained at 70°. The resultant grain size after decarburizing was approximately ASTM 5. Several stress-strain curves were made of the decarburized niate-

Jan 1, 1950

By S. F. Emmons

Geological Sketch.-The rhyolite area near Silver Cliff includes what may be called the Silver Cliff plateau, with Round mountain and the intervening valley. The plateau is about 2 miles long and 1 mile wide. From its northern part rise the White hills, which have no special topographic importance, as their highest point is only 400 ft. above the northern edge of the rhyolite mass. Round mountain, on the other hand, is a quite sharply pointed conical hill, so steep-sided as to constitute an important topographic feature, although its elevation above the plains around it is barely 700 ft. The summit of Round mountain is dense banded rhyolite, with steep, irregular clip; the southern end is breccia containing fragments of the banded rock. There are slight exposures of glassy forms of rhyolite on the lower slopes. On the east, the Archaean rocks extend half-way up the side of the mountain, and the contact between them and the rhyolite is vertical, or dips steeply to the west. This mountain is supposed to be at the vent from which the rhyolite of the plateau was poured out. The Silver Cliff plateau occupies the site of a former basin, in which at one time there was probably a lake. At the time of the rhyolitic outburst of the Rosita hills there was a local eruption of the same character in this region, commencing with showers of volcanic ash and of rock-fragments, which filled the lake and built tip about it hills which have since been removed in great measure by erosion. At present the southern half of the plateau is capped by solid lava to a depth in places of 150 ft. The cliff of blackened rhyolite on the southern edge, where the main discovery of ore was made, is from 30 to 50 ft.

Jan 1, 1913

By AIME AIME

REVIVAL of mining in Yavapai County, Arizona, was the topic of a meeting held at Prescott, on Aug. 24 and 25, sponsored by the Mining Committee of the Yavapai County Chamber of Commerce, with the active cooperation of the Arizona Industrial Congress, the Arizona Section of the A. r. M. E., and the Arizona chapter of the American Mining Congress. Three hundred prospectors, small operators, and mining men from all parts of the State were in attendance. All sorts of mining problems were included in the discussion and all the research facilities of the large companies were offered to aid the prospectors and small operators. The meeting was considered one of the most successful held in the Southwest.

Jan 1, 1929

By J. W. Stewart

THE aim of this paper is to point out the various ways in which design is taught in standard four-year mining engineering curricula in American colleges and universities; to discuss the reasons apparently justifying the great diversity of procedure that exists along this line; and to indicate possible solutions to the difficulties now attending the teaching of design. A study was made of typical four-year mining engineering curricula in 15 colleges and universities of the United States (Table I). Great diversity in content of the various design courses, if taught as described, became apparent immediately. It appeared that it might be both interesting and instructive if the cause for this colorful variety could be found. Was the cause local mining conditions, departmental individuality, or actual necessity? Study of the school catalogues revealed that the various design courses could be classified into two fairly distinct types; namely, (I) those dealing with mine equipment or structures, and (2) those dealing with underground layout of mine workings. It seemed reasonable to label the first type of course "mining design" and the second type "mine design." Some such distinction must have been in the minds of mining educators, for we find both names (i.e., mine design and mining design) used to designate the design courses included in the various mining curricula. Unhappily, the name and the apparent content of such courses do not, in all instances, conform to the classification made here, although in most instances such conformation does obtain (Table I). It is possible that in the exceptional case the method of teaching a design course, and consequently the content of it, may have been changed at some time without change in the name of the course. Apparently only 3 of the 15 schools made an effort to cover both types of design in their curricula (Table I). Two other schools did not list or describe any course of study that could with certainty be taken as a design course. Of the remain¬ing to schools, 9 gave a mining-design type of course and one gave a strictly mine-design type. Obviously, the preponderance of design courses afforded are of the mining-design type. Why? To answer this question, it is necessary to make a study of the prerequisites for the two types of design courses taught. In all schools the design courses were taught in the senior year; in eight, design was taught throughout both semesters; in two, it was taught during the first semester only; and in three it was taught during the second semester only. Consequently, excepting the last three cases noted, it is obvious that all prerequisites for a design course should be completed by the end of the junior year. PREREQUISITES What are the probable prerequisites for the different kinds of design courses as they appear to be taught? Let us take first the case of the mine-design type of course, having to do with layout of underground workings. Here it would seem that logical

Jan 1, 1941

By B. L. Averbach

THE rolling process may be considered as a case of a nonhomogeneous plastic flow. In such a heterogeneous deformation there is no direct general solution, and the plastic deformation varies from point to point as a function of the coordinates. It is practicable to determine these plastic strains only at the conclusion of the rolling process, and the local strains can be studied by observing the deformations produced in a suitably placed grid system. Strains at the surface of a bar after rolling have been reported by MacGregor and Coffin,' but the strain distributions within the bar have not been previously observed. Siebel² has investigated the plastic deformations resulting from wire-drawing by splitting the wire along its axis, milling a grid coordinate system on the inner plane surfaces, and binding the .wire together so that it would pull through a die as a single unit. This method was possible because of the rotational symmetry of the die. In the rolling process, however, such a system was not readily applicable. This paper describes another method of including a grid system, and reports some preliminary data on the plastic rolling strains within a square bar. Experimental Procedure 2.1 mm wide (144 network squares per sq in.) was punched from a thin lead sheet with a steel die and supported in a brass mold by thin copper wires. Pure tin was then poured around the grid to form a solid bar, with the network securely imbedded at. a given position. This bar was then machined to a square 15.2 mm (0.60 in.) wide, and then radiographed. The lead grid was quite adherent and sufficiently ductile to follow the deformation of the bar faithfully. The network lines also remained sharp enough to maintain a high radiographic contrast, and the tin bar, with the grid included, could withstand considerable deformation at room temperature without splitting at the interface. In order to fill the mold, it was necessary to cast the tin at 260-280°C and during pouring the lead grid was supported at short intervals to prevent warping. Some shrinkage cavities were encountered, but only bars which were free of shrinkage in the network region were used. This method is similar to the one employed by Steinberg" in an investigation of the strain distribution in a tensile specimen. Before rolling, the machined bars were radiographed in two directions to obtain accurate initial dimensions of each square and to observe whether the grid was straight and correctly positioned. The rolling was performed in a small hand mill with 2 in. diam rolls at room temperature, and a 20 pct reduction based on the original height was employed. The rolls were clean and no lubricant was used. Halfway through the bar, at the center of the network, the rolls were reversed and the bar extracted. These bars were then radiographed again

Jan 1, 1951

By D. R. THOMAS

GENERALLY speaking, the production of other metals in Mexico fluctuates with that of silver. The first commercial discovery of mineral was in Taxco, Guerrero, in 1552. Five years later, the patio process was introduced at Pachuca, by Bartolome de Medina. In 1884, the main line of the Mexican Central R. R. was completed and a few years later, the National railway. In 1907, the patio process, after 350 years of successful operation, was replaced by cyanidation. Soon after the completion of the railroads, smelters were built at various points and provided means of treating ores that could not be treated by any of the processes existing at that time, such as patio, lixiviation, or pan amalgamation. As a result, a number of mines were developed along the railroads and even far \ out in the mountains. In order to facilitate the shipment of this ore to the smelters, purchasing agencies were established, which for a time were very profitable; most of these agencies are now permanently closed.

Jan 1, 1921

By B. A. Rogers

IN addition to the usual methods of manufacturing steel, a number of special processes have been the subject of considerable experimentation-and use in manufacturing practice. A number of these methods have been of a type in which a rapid refining action has been secured through the intimate mixture of fluid slag with fluid metal. The persistence with which more rapid methods are sought is indicated by the current interest in the Aston' method for producing wrought iron and in the Perrin2 process for dephosphorizing and deoxidizing steel. In the Perrin process, in particular, the mixing action is extremely vigorous and the reactions proceed with surprising speed.

Jan 1, 1936

By J. W. Stewart

THE aim of this paper is to point out the various ways in which design is taught in standard four-year mining engineering curricula in American colleges and universities; to discuss the reasons apparently justifying the great diversity of procedure that exists along this line; and to indicate possible solutions to the difficulties now attending the teaching of design. A study was made of typical four-year mining engineering curricula in 15 colleges and universities of the United States (Table I). Great diversity in content of the various design courses, if taught as described, became apparent immediately. It appeared that it might be both interesting and instructive if the cause for this colorful variety could be found. Was the cause local mining conditions, departmental individuality, or actual necessity? Study of the school catalogues revealed that the various design courses could be classified into two fairly distinct types; namely, (I) those dealing with mine equipment or structures, and (2) those dealing with underground layout of mine workings. It seemed reasonable to label the first type of course "mining design" and the second type "mine design." Some such distinction must have been in the minds of mining educators, for we find both names (i.e., mine design and mining design) used to designate the design courses included in the various mining curricula. Unhappily, the name and the apparent content of such courses do not, in all instances, conform to the classification made here, although in most instances such conformation does obtain (Table I), It is possible that in the exceptional case the method of teaching a design course, and consequently the content of it, may have been changed at some time without change in the name of the course. Apparently only 3 of the I5 schools made an effort to cover both types of design in their curricula (Table I). Two other schools did not list or describe any course of study that could with certainty be taken as a design course. Of the remaining 10 schools, 9 gave a mining-design type of course and one gave a strictly mine-design type. Obviously, the preponderance of design courses afforded are of the mining-design type. Why? To answer this question, it is necessary to make a study of the prerequisites for the two types of design courses taught. In all schools the design courses were taught in the senior year; in eight, design was taught throughout both semesters; in two, it was taught during the first semester only; and in three it was taught during the second semester only. Consequently, excepting the last three cases noted, it is obvious that all prerequisites for a design course should be completed by the end of the junior year. PREREQUISITES What are the probable prerequisites for the different kinds of design courses as they appear to be taught? Let us take first the case of the mine-design type of course, having to do with layout of underground workings. Here it would seem that logical

Jan 1, 1941

Recently the Colorado Engineering Council was formed "to coördinate the work of various technical, scientific, and engineering organizations, promote the welfare and professional standing of their members, and foster a more general recognition of the engineer in civic matters." The membership consists of local associations of members of the national engineering societies and other local engineering, scientific, or technical associations.

Jan 8, 1919

By T. L. Chu, G. A. Gruber

Silica films hare been rleposited 011 silicon substmtes at 400° to 600°C by a chemical-transport technique using hydrogen fluoride as the transport agent ill a closed system. This transport takes place from a source materia1 1071: temperature to substrates at higher temperatures, as indicated by the thermochemistry of the transport reaction. The experimental variables of- the transport process, such as the substrate temperature, the pressure pi the transport agent, and so forth, have been studied. The rate -determining step of the transport process appears to he the ),ale of chemical reaction in the source region. The transported films are similar to thermally grown silica films in physical proper-ties with the exception of 'some what higher dissolrrtion rates. SILICA films deposited on suitable substrates serve many purposes in electronic devices. They are used for the fabrication of tunneling devices, the surface passivation of devices, and the shielding of devices from nuclear radiation: and as selective masks against the diffusion of specific impurities into semiconductors. Doped silica films can also be used as sources for the diffusion of impurities into semiconductors. Several oxidation and deposition techniques for the preparation of silica films have been developed to meet the requirements of these applications. The therma1 oxidation of silicon by oxygen or steam at temperatures above 900 C is commonly used in silicon technology. The deposition techniques are perhaps more advantageous since they usually require lower temperatures and are not limited to silicon substrates. Silica films have been deposited on silicon and other substrates by reactive sputtering and chemical reactions. The sputtering of silicon in an oxygen atmosphere is capable of depositing good-quality silica films on silicon' and gallium arenide. Many chemical reactions are known to yield silica at room temperature or higher. These reactions may involve intermediate steps. However, the final step yielding silica should take place predominately on the substrate surface in order to produce adherent films. When silica is formed in the gas phase by volume reactions, no adherent deposit can be obtained. Generally, the experimental conditions of a reaction can be varied so that the surface reaction predominates over the volume reaction. The chemical reactions which have been used successfully for the deposition of silica films are briefly as follows. The pyrolysis of alkoxysilanes in an inert atmosphere or under reduced pressure has been employed to deposit silica films on germanium3 and silicon4 at 650" to 750°C in a flow system. The deposition of silica films from alkoxysilanes has also been achieved at nearly room temperature by a low-pressure plasma. Device quality silica films have been deposited on germanium and gallium arsenide by the deposition of an amorphous thin silicon film followed by oxidation at 600" to 700" . Silica films for high-temperature capacitors have been produced by the hydrolysis of silicon tetrabromide at 950°C in argon and hydrogen atmospheres.7 We have developed a chemical-transport technique for the deposition of silica films on semiconductor substrates at relatively low temperatures. The thermochemistry of the transport reaction, the experimental variables of the transport process, and the properties of the transported silica films are described in this paper. THERMOCHEMICAL CONSDERATIONS The transport of solid substances by chemical reactions in the presence of a temperature gradient has been used for the preparation of films and crystals of many electronic materials. In this technique, a gaseous reagent is chosen so that it reacts reversibly with the solid substance under consideration to form volatile products. Since the equilibrium constants of most reactions are temperature-dependent, the transport of these products to regions of suitable temperature in the reaction system would cause the reverse reaction to take place. depositing the original solid. When the equilibrium is shifted toward the formation of the solid as the temperature is decreased, the solid is transported from a high-temperature zone to a lower-temperature region, and vice versa. This chemical-transport technique can be carried out in a closed or gas-flow system. In a closed system, chemical equilibrium is presumably established in the different temperature regions of the system, and the transport agent regenerated in the deposition region repeats the transport process in a cyclic manner. The local chemical equilibrium may not be approached in a flow system: however, this system offers a greater degree of flexibility. Silica reacts reversibly with hydrogen fluoride and this reaction was chosen for the transport process. The over-all reaction between silica and hydrogen fluoride may be written as: SiO2(s) + 4HF(g-) = SiF4Ur) + 2H2O(^)

Jan 1, 1965

By Anna H. Connard

SUMMARY The discussion focusses on developments in the debt/equity swap market since the Marte project was negotiated in early 1988. It emphasises carrying forward the recent market trends to anticipate the breadth and scope of debt/equity conversions for mine development in the 1990s. Secondary market prices of LDC paper, conversion values and political influences in the host countries and the use of near debt and commodity-based instruments as components of mine financing in debt/equity deals will be placed in the perspective of recent trends and expectations for the future. THE MARTE PROJECT The Marte mine is a gold porphyry deposit in Chile's high Atacama, for which financing was put together at the beginning of 1988. The Marte project was financed by a combination of common equity and loans. It was unusual that the equity infusions were made under different programs. Some of the international equity was infused with fresh funds via DL 600. Other common foreign equity was provided through the conversion of Chilean bank debt under Chapter XIX. On the loan side,. export credits for the import component of machinery and equipment were sought. Local bank financing was negotiated for the remainder of ' the project's anticipated cost. The debt conversion market in Chile was at its apex in terms of interest, activity and government support when the mine financing was arranged. The price of Chilean paper in the secondary market hovered about 62 to 66 cents per U.S. dollar of face value. Meanwhile, the Chilean government was negotiating conversion redemptions significantly closer to full face value. The government differentiated between debt paper exchanged for corporate investors who had sourced that paper in the secondary market, and debt paper held by bank investors who would incur a transaction loss in the conversion. The use of a combined DL 600lChapter XIX equity financing created different yield calculation bases for the various investors. Chapter XIX prevents remittance of profits before year 5 and capital repatriation before year 11. Investors choosing this vehicle have either for a corporate policy in the target project not to declare dividends until repatriation is allowed, or they have to seek uses for the peso liquidity that would be generated through dividend declarations in the early years. However, DL 600 investors face no such waiting period on dividends, nor do they have restrictions imposed on cashing out of the investment before the 11th year. Therefore, any equity structure with components of both investment mechanisms will have inherent differences in cost basis and future income flows for the various participants. This equity imbalance is defensible if the investment motivations of the parties are analyzed: a mining investor using fresh funds looks for a hurdle return on equity calculated at conservative commodity prices, with as much flexibility to reap upside benefits as possible; a mining investor choosing to invest through a debt conversion mechanism will realize a modest short term gain on the conversion, reducing his effective cost basis, but sacrificing some return because of the waiting period on repatriation of dividends. INVESTMENT OBJECTIVES A bank investor exchanging his own paper for an equity participation in a mining project realizes a conversion loss on the transaction. He seeks a risk adjusted acceptable hurdle rate of return to recoup that loss over time. Motivation for the bank investor to take that loss may be derived partly from a strategy to diversify its existing portfolio by internal policy and externally regulated guidelines. The bank will compare yields on its loan portfolio to that country with anticipated dividend flows discounted back at a risk adjusted rate. It will analyze the project with return objectives of yield enhancement over time and with

Jan 1, 1990