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By John Rusnak

The Coal Mine Roof Rating (CMRR) is a practical rock mass classification system for use in design of mine openings. Data can be obtained for this purpose from exploration drill cores if simple geotechnical logging and rock mechanics testing is conducted. The CMRR is an excellent method to quantify rock characteristics for engineering purposes. It bridges the gap between geologic description and engineering design. The CMRR was utilized in the design of a 10,000 fl. long coal belt conveyor tunnel connecting an Eastern Associated Coal Corp. mine and preparation plant in Boone County, West Virginia. Data gathering and analysis techniques are discussed involving the calculation of the CMRR and its application in the design of the tunnel, which was driven through a thin coal bed zone. The preliminary findings have correlated well with actual roof and mining conditions encountered during driving the tunnel and it is concluded the CMRR is an effective method to utilize geologic data from exploration core holes for engineering analysis and design.

Jan 1, 1998

By Rebecca Hope, Derick Moolman, Frikkie Malan

"Despite the lip service that has been paid to pro-active plant maintenance processes over recent years, a significant portion of maintenance in industry is still reactive. The business driving force to prevent expensive production opportunity costs arising from “break-down maintenance” is obvious. Various benefits can be derived from successfully deploying remote equipment diagnosis technology and associated business processes.From an end-client’s viewpoint these include the ability to predict and take actions to prevent equipment breakdowns, increasing the lifetime of equipment by responding to appropriate operating instructions and therefore improving the return on capital expenditure. Better planning and scheduling of maintenance priorities and resources with performance measures like an Equipment Health Index are also possible. The knowledge that a qualified supplier engineer is constantly in touch with the operating conditions of their equipment, albeit remotely, is more than a comfort, and can be translated into quantifiable cost savings and improved supplier service levels."

Jan 1, 2003

Enhancement of Energy Efficiency in Fine Grinding of Copper Sulfide Minerals Using a Pilot-Scale Stirred Media Mill - IsaMill The mineral liberation size of run of mine ores has dramatically reduced over recent years. As a result, the demand for fine grinding which is the most energy-intensive form of grinding has markedly increased in the minerals industry. Furthermore, the fine grinding costs increase exponentially with decreasing product particle size. As a result of the increased energy requirement for fine grinding, it is desirable to optimise fine grinding processes such as stirred media milling (ie IsaMill) to enhance energy efficiency, throughput and the product fineness. In the present study, the influence of slurry rheology, grinding media type and grinding media-to-feed size ratio on energy efficiency in a pilot-scale IsaMill was investigated under certain industrially relevant pulp processing conditions. It was shown that a critical rheological state existed, below which the energy required to achieve an 80 per cent passing (ie P80) 20 ¦m product size was unaffected by shear rheology (ie apparent viscosity and shear yield stress) whilst above which the grinding energy required increased dramatically with increasing shear rheology. Colorado River sand (3.35 mm) showed higher energy efficiency than MT1 ceramic media (2.5 mm) for a target P80 of 20 ¦m in the solids concentration range of 38 to 55 per cent by weight, but the former experienced more than four times the wear rate of the later. The high wear rate of the Colorado River sand may be due to its much lower hardness. For feeds with an 80 per cent passing (ie F80) 70 to 110 ¦m, 2.0 or 2.5 mm MT1 media appeared to be more energy efficient than 3.5 mm MT1 media whilst a media-to-feed size ratio of 41 to 53 is applicable for ~50 ¦m (ie F80) feeds for efficient grinding.

Sep 13, 2010

By R. Boom, J. Halder, B. Snoeijer, B. Deo, A. Overbosch

Operational data of BOF and the slag samples for different starting conditions of phosphorus(0.06–0.26 per cent P) and silicon content (0.3–1.2 per cent Si) of hot metal have been analysed. The contribution of parameters that are well known to affect phosphorus distribution at tap, like basicity, temperature, FeO content of slag, slag mass etc., is investigated through the models of ionic theory of slag, optical basicity, regular solution approach and molecular theory of slag. The best overall results are obtained by the model based on molecular theory of slag in which several operational parameters are also incorporated. The investigations of different slag samples, based on optical, SEM, EPMA and X-ray studies, reveal the effect of MgO and Al2O3on slag morphology and phosphorus distribution in different phases. It is important to consider phosphorus distribution ratio in the solid and liquid part of slag. The solid part of slag, which is mostly dicalciumsilicate, can contain up to 5 per cent phosphorus. The phosphorus content of the liquid part of slag may depend upon the phosphorus content of hot metal or phosphorus load of slag. It is found that incorporation of effect of dicalciumsilicate in the model improves the accuracy of prediction. For better process control, the addition of iron ore towards the end of blow must be avoided while treating high phosphorus hot metal or during the production of ultra low phosphorus steels. Keywords: steelmaking, BOF, phosphorus distribution, slag morphology, MgO, Al2O3,dicalciumsilicate, process control, models

Jan 1, 2004

By A. L. Foote

This is the final report of work accomplished during 1973-75 under U. S. Bureau of Mines Contract No. H0242015, "System for Handling Underground Mine Supplies and Materials." The purpose of the contract was to develop a mechanical device which could safely perform handling tasks that are normally done manually in underground bituminous coal mines. The report discusses studies leading to construct-ion of a battery-operated, three-wheel vehicle with a six-degree-of-freedom manipulator. Supportive design studies included collection and analysis of production, manual functions, and injury data on the underground bituminous coal mining industry. Transfer tasks in section storage and working places were the prime candidates for mechanical handling. Functional specifications were developed for two handling devices (one to handle existing unit loads and one to handle repackaged unit loads) and for a vehicle to mount the handling device. Design concepts for nine different handling devices were developed and a cost/benefit evaluation made for each. Detail design, capital and operating costs, and method improvement savings data were developed for two battery-operated vehicles and for two different manipulators. The three-wheel vehicle with anthropomorphic manipulator was chosen for development.

Jan 1, 1978

A comprehensive review of ore pass records, from ten Quebec underground mines, indicated some of the limitations of available design tools to predict the occurrence of ore pass interlocking hang-ups in metal mines. The Distinct Element Method was used to perform a series of numerical experiments in order to investigate the influence of ore pass geometry, rock fragments shape and size distribution on material flow in an ore pass. Guidelines have been developed to help limit the occurrence of interlocking hang-ups in an ore pass. The proposed guidelines were evaluated with respect to field observations. Ein kompletter Bericht der Erzrollezeichnungen, von 10 Quebec unterirdischen Gruben, hat einige der Beschränkungen der vorhandenen Designwerkzeuge angezeigt, um das Auftreten Erzrolle der blockierenhang-ups in den Metallgruben genau vorauszusagen. Eine Reihe numerische Experimente mit der eindeutigen Element-Methode, wurden aufgenommen, um den Einfluss von Erzrollegeometrie, Partikelform nachzuforschen und Felsenkorngrößenverteilungen auf Materialfluss in ein Erz überschreiten. Dieses hat zu die Entwicklung der Richtlinien geführt deren Implementierung das Auftreten der blockierenhang-ups in eine Erzrolle begrenzen sollte. Die vorgeschlagenen Richtlinien wurden in Bezug auf Labor- und Feldbeobachtungen ausgewertet. Une revue de la performance actuelle des cheminées à minerai dans 10 mines souterraines du Québec a indiqué les limites des outils de conception servant à dimensionner les cheminées pour minimiser le nombre d’accrochages par enchevêtrement rocheux. Des séries de modélisations numériques, utilisant la méthode des éléments distincts, ont été réalisées afin d’évaluer l’influence de la géométrie des cheminées, de la forme des fragments rocheux et de la distribution granulométrique sur l’écoulement du matériel dans les cheminées. Cet exercice a permis de développer des lignes directrices pour le dimensionnement des cheminées afin de limiter l’occurrence d’accrochage par enchevêtrement rocheux. Les lignes directrices proposées ont été évaluées en fonction des observations effectuées sur le terrain.

Jan 1, 2003

By Larry A. Haas

Carbonyl sulfide (COS) was decomposed to sulfur and CO in a silent electrical discharge. A threshold of about 4 kv at 60 Hz was required to dissociate the gas in a laboratory ozonizer at 790 torr with electrode gaps between 1 and 5.5 mm. Above the threshold value, the reaction rate increased with increasing voltage with helium or nitrogen diluent. With the latter diluent, higher voltages had to be applied to obtain the same yield in the 4-to 12-kv range. The COS decomposition rate increased with COS concentration, but a saturation value was reached at about 10 pct COS. The reaction rate decreased at low linear gas velocities as obtained at lower gas flows, larger electrode gaps, or larger reactor volumes. Increasing gas temperature also decreased the decomposition rate. The presence of solid adsorbents such as quartz wool, bauxite, or charcoal had no significant effect on the reaction rate. The addition of S02 did not affect the COS decomposition rate, but small amounts of water decreased the reaction rate. Over 50 pct of the COS was decomposed at room temperature and atmospheric pressure in a l7-kv ozonizer using a gas containing 0.9 pct COS in helium flowing at a rate of 0.3 liter/min. The average current was less than 5 ma. This method has possible application in eliminating the toxic air pollutant, COS, which is generated in petroleum refineries and in processes involving reactions between sulfurous and carbonaceous materials. Carbon monoxide that is formed can be further oxidized to CO2 after the collection of elemental sulfur.

Jan 1, 1972

By R H. Sibson

The gold province of Otago occupies an area of upwarped basement, the Otago Schist, comprising predominantly quartzofeldspathic and volcanogenic metasediments. This assemblage is the product of collisional tectonic deformation and associated metamorphism, mainly to lower greenschist facies, during the Rangitata Orogeny (200-100 Ma). Historically this region has produced 240 tonnes of gold, 4% (10 t.) of which was from the mining of Cretaceous goldquartz mineralised vein systems. Auriferous vein systems in the Otago Schist are mainly hosted within NW trending normal fault-fracture arrays, however NW trending reverse fault-hosted vein systems also occur. We propose that the Late Cretaceous-mid Tertiary Otago Schist structure represents a regional anticlinorium containing flexural folds of at least two wavelengths. The anticlinorium structure has been quantified by determining variations in angular discordance between schistosity and the Otago Peneplain, a Late Cretaceous-mid Tertiary erosion surface covering most of the Otago district. A structural model for the evolution of the post-collisional anticlinorium requires the cooling surficial zone (carapace) of a retrograding metamorphic belt to behave as an elastic lid. Erosion of topographic load on the carapace drove isostatic uplift, which was greatest in the tectonically thickened core of the orogen. In this way differential uplift produced flexural deformation in the elastic carapace, expressed as a large scale arching of the orogenic belt. Flexure created tangential longitudinal strains in the outer-arc, leading to extension and the formation of mineralised normal faults. These structures are separated by a neutral surface from shortening and associated mineralised reverse faults in the inner-arc. Our structural model predicts that the distribution of auriferous lodes should be localised about zones of maximum flexural curvature, where the tangential longitudinal strains are highest. As a result, NW-SE hinge regions separating schistosity dip domains in the Otago gold province may have new found significance as potential exploration targets.

Jan 1, 1995

By Robert S. Sanford, Harold C. Pierce

"At one time the Alaskan Eskimo lived in many small settlements scattered along the Arctic coast. These settlements extended as far south as Bristol Bay and several miles inland on the large rivers. When the white man established trading posts, schools, hospitals, and missions, these people gradually congregated around them in a few large villages. The natural fuel supply near many of the large villages along the Arctic coast became exhausted as a result of the abnormally large influx of people from small outlying settlements.The population of Barrow, Alaska, according to the 1940 census, is 363 persons, but since that time it has increased considerably, and later estimates place the present population between 400 and 500 persons. With the exception of 25 white persons, the entire population is comprised of Eskimos.The government maintains a school, hospital, radio station, and weather station at Barrow. In addition to the government, installations, there is a church, a privately owned trading post, and cooperative store owned by the Eskimos.For many years the Barrow Eskimos depended on driftwood and petroleum residue from Cape Simpson for their fuel supply. This fuel provided not only warmth for the Eskimo during the long cold winters but also heat for melting ice, the only source of 'water during .the winter. In recent years the sources of petroleum residue and driftwood have not been adequate to meet the demands for fuel During the winter of 1942-43 and again in 1943-44, Barrow experienced an acute shortage of fuel.The fuel problem at Barrow was brought to the attention of Governor Ernest E. Gruening, who was instrumental in getting a Bureau of Mines engineer4/ to investigate reported coal occurrences in the vicinity. Coal deposits along the Meade River and at Peard Bay were examined during the spring and fall of 1943. The Alaska Native Service shipped in mining equipment in September 1943 and commenced stripping an open-pit mine on the Meade River in June 1944. In conjunction with this work, an engineer5/ of the Bureau explored by churn drilling to determine the tonnage of- coal in the vicinity of the mine. In addition to this work, the Bureau of mines examined coal deposits in Peard Bay area and along the Kuk River south of Wainwright."

Nov 1, 1924

Extraction and Characterisation of Extracellular Polymeric Substances from the Mineral Surface During Bioleaching of Chalcopyrite Concentrate A mixed culture of moderately thermophilic microorganisms was used to bioleach chalcopyrite concentrate in a stirred tank reactor. The results show that up to 84.7 per cent of copper extraction could be achieved in 24 days at a pulp density of 6 per cent. The leaching rate of chalcopyrite concentrate tended to increase with an increase of dissolved total iron concentration. Furthermore, the extracellular polymeric substance (EPS) on the surface of the chalcopyrite concentrate was extracted and analysed. EPS was extracted at the first, third, eighth, 16th and 24th day during bioleaching, which mainly consisted of proteins, lipids, sugars and ferric irons. After the eighth day the total amount of EPS remained relatively constant. However, the amount of ferric iron in the EPS decreased in a large scale. The ore residue analysis indicates that the decrease of ferric iron was mainly due to the formation of jarosite on the mineral surface.

Sep 13, 2010

By B. Gazea, A. Kontopoulos, A. Kourtis, K. Adam

Static tests give a measure of the balance between acid-producing and acid-neutralising mineral components in a material, while kinetic tests determine acid generation and neutralisation over a long period. Drill-core samples from the amphibolite and gneiss host rocks of the Stratoni lead-zinc sulphide deposit in Greece and mine/mill waste samples from Stratoni and Olympias were examined by the standard acid base accounting, BCR and net acid production tests. Mineralogical data on the materials and resulting residues were used to illustrate the differences between the methods and establish their ranges of applicability. BCR seems to simulate most closely the conditions prevailing during generation of acid mine drainage but is time-consuming and requires elaborate equipment. Acid base accounting is suggested for standard screening; net acid production might be used in the field or for solids with less than 10% S

Jun 19, 1905

By Peter Klaver

Deep tunnels have been used for decades for the temporary storage of large volumes of urban runoff, both storm water and combined sewer overflow (CSO). Tunnels are attractive because they reduce surface disruption and do double duty as storage and conveyance systems, collecting overflows from multiple locations and transporting them for treatment to various facilities. Like any hydraulic system, however, there are dynamic effects that must be fully understood during the design phase so that the final constructed product does not have unintended negative consequences. Preliminary sizing of storage tunnels is typically based on the total volume required. For example, if studies have determined that a volume of 56.8 ML (15 million gal) will provide the intended level of control, then that figure can be used, along with a preliminary idea of the desired tunnel length, to compute the required diameter. Of course, filling a long tube with water from various points along the way is not at all the same as pouring water into a bucket, and these dynamic effects require additional attention from design engineers. The rapid filling of storage tunnels can lead to the formation of bores, which are essentially moving walls of water. An open channel bore can build in height until it reaches the crown of the tunnel, at which point it becomes a pipe-filling bore. Figure 1 depicts both kinds of bores moving upwards in a rapidly filling tunnel. Bores can strike the ends of tun-nels with tremendous force, driving water and entrained air upwards into dropshafts and creating strong pressure surges in portions of the tunnel that are already filled. If the hydraulic surges are high enough to reach grade, they can cause overflows and/or damage structures at the surface. Trapped air pockets can occur through several phenomena, including the reflection of bores off dropshaft structures and the occurrence of ?premature pressurization.? The latter refers to the situation where the inflow to a tunnel is increasing more rapidly than the tunnel can convey it, such that the pipe becomes surcharged at an upstream point while points downstream are still flowing as an open channel. These air pockets are a great nuisance as they migrate toward points in the tunnel where they can rise to the surface, which are often shafts that are already filled with water (Fig. 2). The ?geyersing? that results can be hazardous and costly.

Jan 3, 2010

By Jonathan E. Ludlow

A field test was conducted to demonstrate and quantify the relationship between deep cutting and the creation of airborne respirable dust for longwall mining With a double-ended ranging drum shearer. The testing program was carried out on the 3 North longwall of North American Coal Company's Quarto No. y mine in Claringten, Ohio. Continuous recordings of the dust levels were made at both the midface and tail ate areas. Data were collected during 27 shifts during which time 81 complete mining, cycles took place. Both drum speed and the number of picks per line were varied systematically during the testing program to alter the depth of cut while the production rate was held constant by maintaining a constant haulage speed. The test results indicated that at the midface position, airborne respirable dust was strongly dependent upon the depth of cut as influenced by both the drum speed and number of picks. Drum speed had a much stronger effect than number of picks over the experimental range, since a halving of drum speed reduced dust levels by approximately 60 percent while removal of every other vane pick resulted in only a 2.1 percent reduction at constant production. At the tailgate position, however, neither effect was strongly apparent. A tendency for the slower drum speeds to he associated with reduced power consumption and higher haulage speeds (and therefore production rates) was also noted. It is recommended that longwall operators oper¬ate at the lowest available drum speed wherever possible.

Jan 1, 1981

By Dale S. Preece

The blast-induced movement and final location of geologic layers that may cause environmental problems can be predicted using discrete element methods. This prediction capability can be used by mine operators to locate the material in the muck pile during excavation which would allow encapsulation to prevent groundwater infiltration.

Jan 1, 1994

By R. Webster

"Daniel Krige’s influence on soil science, and on soil survey in particular, has been profound. From the 1920s onwards soil surveyors made their maps by classifying the soils and drawing boundaries between the classes they recognized. By the 1960s many influential pedologists were convinced that if one knew to which class of soil a site belonged then one would be able to predict the soil’s properties there. At the same time, engineers began to realize that prediction from such maps was essentially a statistical matter and to apply classical sampling theory. Such methods, though sound, proved inefficient because they failed to take account of the spatial dependence within the classes.Matters changed dramatically in the 1970s when soil scientists learned of the work of Daniel Krige and Georges Matheron’s theory of regionalized variables. Statistical pedologists (pedometricians) first linked R.A. Fisher’s analysis of variance to regionalized variables via spatial hierarchical designs to estimate spatial components of variance. They then applied the mainstream geostatistical methods of spatial analysis and kriging to map plant nutrients, trace elements, pollutants, salt, and agricultural pests in soil, which has led to advances in modern precision agriculture. They were among the first Earth scientists to use nonlinear statistical estimation for modelling variograms and to make the programmed algorithms publicly available. More recently, pedometricians have turned to likelihood methods, specifically residual maximum likelihood (REML), to combine fixed effects, such as trend and external variables, with spatially correlated variables in linear mixed models for spatial prediction. They have also explored non stationary variances with wavelets and by spectral tempering, although it is not clear how the results should be used for prediction. This paper illustrates the most significant advances, with results from research projects."

Jan 1, 2015

By Naoki Hosoya, Setsuo Maeda

This paper addresses establishment of an experimental system for measuring biodynamic response (BR) of hand-arm system at the NIIH in Japan. BR measurement system at the NIIH is nearly equivalent to NIOSH installed system. The feasibility of the system is examined through the apparent mass (AM) measurement of the empty handle and a set of calibration masses. Apparatus The grip force was measured by using the handle shown in Fig. 1. The handle has two force sensors (KISTLER, 9212) and one accelerometer (PCB, 356A12). A low-pass filter with 5 Hz cut-off frequency was used to the grip force from measured force signal. Figure 2 shows BR measurement system in this study. The push or pull force at the handle was measured by using the force plate (KISTLER, 9286AA). The grip force and the push / pull force were displayed on a monitor. The shaker (IMV, VE-100S) is used to vibrate the hand-arm system along the forearm axis (Zh direction) (ISO 10068, 1998; ISO 5349-1, 2001). In most situations force actions for operating tools are expressed by grip, push, pull and combined these actions. These actions can be simulated in the test system. AM was obtained by performing H1 estimator in the PULSETM system (B&K, 3109) and it is denoted at the one-third octave band center frequencies. [ ] Methods In order to investigate the reliability of the system, AM measurement of the handle was performed. It is assumed that the handle is rigid in the upper limit of adoptive frequency range in this study. This assumption is validated in AM measurement of the empty handle. A pseudo-random vibration in the frequency range of 10 to 1,250 Hz was used and its amplitude is 1.0 (m/s2)2/Hz with a flat power spectral density (PSD) in the experiment. Measured AM includes the mass effect of the measuring cap in a subject experiment. Compensated apparent mass AMc(?) is obtained by Eq. (1) 1-2.

Jan 6, 2006

By Paul A. Roy

The North Shore Connector Project for the Port Authority of Allegheny County constructs twin Tunnel Boring Machine (TBM) tunnels through cohesive soils and rock beneath the Allegheny River and a narrow city street in Pittsburgh, PA. The tunnel alignment includes an historic building on shallow foundations, modern buildings on deep foundations, and an office building constructed directly over the alignment during the design of the tunnel sections. This paper provides an overview and update of the general site conditions, TBM tunnel design, and support of excavation for the TBM launching pit. Deformation limits, ground improvement, monitoring and mitigation plans are also discussed.

Jan 1, 2008

Decision-making regarding plant-scale reagent dosage regimes and air rates is a topic of ongoing investigation and high importance. The current work explains some techniques that have proven useful in deciding on plant-scale flotation operating regimes. Specific focus has been placed on the reagents: frother and depressant, as well as some discussion around the control of air rate and froth depth. Air rate has been selected based on its effects on the froth phase. Froth velocity and froth height above the cell lip are the two variables measured and used to select the operating air rate. Pulp level is then adjusted to increase or decrease mass pull. A technique has been developed using the Anglo Platinum Bubble Sizer on an industrial flotation cell to determine the relationship between bubble size and frother concentration. This technique has been extended to measure the equivalent frother concentration or frothabilities of various streams on a rougher bank. A mass balance for frother was performed successfully, and this provided a better understanding of the way frother moved in the rougher bank. With this knowledge, more informed decisions can be made about frother addition required in subsequent flotation stages. For depressant, a new protocol for deciding on dosage rate has been developed. The depressant dosage should be based on the amount of fresh feed material reporting to a bank. Currently 400 g per ton of fresh feed has been assumed a reasonable starting point, with promising results. Improved froth stability and grades were observed. There is scope for more accurately defining the optimal dosage rate. Importantly, the combined effect of changing the chemistry and the hydrodynamics together has been demonstrated. A significant upward shift in the grade-recovery relationship for a cleaner bank was observed.

Jan 1, 2013

By L. Chen, G. A. Brooks, S. A. Nightingale

The dissolution of alumina and magnesia has been investigated using laser scanning confocal microscopy (alumina) and a rotating finger apparatus (magnesia) to assess the effects of temperature, composition and forced convection on the rate of dissolution in CaO-SiO2-Al2O3based slags. The two techniques have differing strengths and limitations, and provide complementary methods for studying dissolution. Alumina dissolution was studied for temperatures from 1477 to 1577°C. Based upon the data, the rate controlling mechanism was thought to be mass transfer control in the slag. The diffusion coefficients for the alumina particles are estimated to be in the range 10-11to 10-10m2.s. MgO degradation for sample rotation speeds of 50 to 800 rpm at 1500 and 1530°C was studied for both congruent and incongruent dissolution. The results show that the rate of dissolution for this is primarily controlled by a diffusion mass transfer mechanism for congruent dissolution except at the highest rotation speed. For incongruent dissolution, the mechanism is much more complex, with the morphology and distribution of the spinel reaction product having a significant effect. At high speeds and prolonged times, mechanical forces played a major role in the degradation process. Keywords; kinetics, corrosion, refractories, dissolution rate, inclusions, mass transfer, slags, steelmaking

Jan 1, 2004

By George K. Burke

Underpinning of a structure has been traditionally expensive, time consuming, and, in many cases, caused as much settlement to the existing structure as it was trying to prevent. As underpinning is normally one of the initial tasks and on the critical path on a construction project, there is immense pressure on the subcontractor to speed up his operation so the new structure can proceed; this can cause an adversarial relationship to develop between the owner, engineers, general contractor and subcontractor. Since its introduction to the North American market in the late 1980's, Jet Grouting has not solved all these problems, but where utilized, has shown economical benefits, a faster and safer installation, and a minimal movement of the structures being underpinned. A history of the development of jet grouting is presented; a comparison of this technique versus other grouting methods, a description of the jet grouting system with emphasis on the triple rod systems; case histories of jet grouting used for underpinning and conclusions and references are included to follow the program's themes of: - Recognizing Solutions to Today's Problems - Defining Tomorrows Challenges - Putting America on a Solid Foundation

Jan 1, 1991