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By James C. Barker

Recent investigations of a 55-km long trend of intrusive complexes on southern Prince of Wales Island have identified significant resources of Nb, Y, REE. U, Zr, and a host of potential by-product metals. The northwesterly trend comprises multi-phased sodic alkaline and peralkaline diorite, monzonite, syenite, and riebeckite granite. There are at least three significant deposit types recognized, two of which, 1) pegmatite dikes/vein-dikes that zone laterally from the intrusions and 2) concentrically zoned pegmatites, contain most of the lithophile metals. A third, epigenetic replacement-type mineralization, contains much of the U resource. Other deposit types with minor or unknown resource potential include diatremes, carbonatite, and placers. This report summarizes the deposit evaluations, characterizes the mineralization, and estimates the resources. To date a total of 40.7 million tons of mineralized material is estimated as indicated or inferred. Most of the Y203 plus REO is at a grade exceeding 0.5% and half of the Nb20S exceeds 0.125%. Tonnage estimates would likely be substantially lncreased with additional exploration. Mineralogy is generally fine-grained and complex, and consists of more than a dozen principal REE-Y-Nb-U-Th-Zr phases, the sum of which may compose up to half of the rock. Approximately half of the REE-Y content comprises the heavy yttrium subgroup which is uncommon compared to deposits elsewhere. Although the Alaskan deposits are likely subeconomic at today's metal prices and consumption levels. recent technological advances suggest future demand may increase.

Jan 1, 1988

By T. R. A. Davey

A simple model for metal solution behaviour may be derived, on the basis of dilute solution solubilities (where? log concentration of solute varies linearly with reciprocal temperature) and not-so-dilute region solubilities (where the log of the alpha-function at saturation frequently varies linearly with reciprocal temperature) and assuming activity to vary according to the quadratic formalism in between. Matte binary systems usually exhibit regular .solution behaviour when the constituent species are chosen appropriately. In many recent papers, metal solubilities in .slags are expressed as the sum of several different and supposedly independant molecular species (e.g. oxides, sulfides, chlorides), Such a view is untenable because of the now proven ionic nature of slags. Some possible reasons for the great effect of sulfur on copper solubilities in slags are discussed.

Jan 1, 1985

By M. Jortikka

The smelting process of the old reverberatory furnace including its capacity has been improved over the years in different ways eg. with oxy-fuel burners, parallel reactors with the reverb or with various modifications of the reverb furnace itself. The future reverb modifications with old concepts are difficult or impossible as the increased copper losses in slag call for separate slag treatment and particularly the process modifications do not solve the environmental issues but instead mean unavoidable high capital and operating costs in gas cleaning and sulphur recovery. During the last decades improvement in process performance and increase in capacity of copper flash smelters has been achieved easily by substituting the pre-heated process air by highly oxygen enriched air. The flash furnaces of today, however, are inherently designed to operate with high oxygen enrichment. Further process improvement with a view to production costs and capacity increase as well as to the more stringent environmental requirements is possible with even higher oxygen enrichment. This, apart from the advantages it generates, requires improvements in and careful design of the feed system, concentrate burner, furnace cooling and the off-gas line as well as adaption of the flash converting instead of the conventional Peirce-Smith converters. A logical answer even for the revamping of the reverb smelters in the future is the total replacement of the reverb furnaces with flash smelting together with flash converting. This paper discusses the possibilities for future process improvements of the existing flash smelters taking into account the process concepts, equipment modifications and capital aspects not forgetting the environmental issues. The revamping of the PASAR smelter in Philippines is introduced as an example of a recent success story.

Jan 1, 1994

By N. Voennann

Stillwater Mining Company operates an electric furnace at its smelter in Columbus, Montana to treat a Ni-Cu-platinum group metal concentrate along with secondary PGM bearing materials. Hatch Associates has designed several improvements to this furnace, which was originally built by others. Implementation of these relatively low cost improvements has resulted in substantial increases in furnace availability and capacity, along with reduced unit costs. ? The improvements included: ? Installation of water-cooled copper cooling elements to stabilize refractory wear and increase furnace life.- ? Improved furnace 'bindings, to enhance the furnace's structural integrity by improving the contact between the refractory and cooling elements, and by promoting tight brick joints resistant to matte or slag leaks. ? Adjustment of the electrode regulator to allow higher furnace power levels. ? Installation of an automated air-slide (aeration conveyor) feed system to evenly distribute the furnace feed in an insulating layer on the bath surface. This "black-top" practice reduces unit energy costs and makes available additional smelting capacity.- ? Electrode seals to reduce ingress of air that absorbs heat before exiting the furnace in the off-gas stream. The saved energy can be used to smelt additional concentrate. This paper describes the above furnace modifications, and the benefits derived from their implementation.

Jan 1, 1998

By Derek J. Fray

Electric arc furnace dusts, especially those containing zinc ferrite, are notoriously difficult to process to give valuable products and non-toxic residues. The ideal process would remove and recover the toxic non-ferrous metals as pure metals, of commercial value, and non-toxic residue which can be used as a raw material in the steel industry. From an examination of the thermodynamics of the oxides and chlorides of the various elements in the dust, it is apparent that the chlorides of the toxic non-ferrous elements are more stable than the oxides while the reverse applies to the ferrous elements. This offers the opportunity for a complete separation of the zinc, lead and cadmium from the iron oxide. Results are presented for the chlorination of electric arc furnace dusts under oxidising conditions and the subsequent treatment of the chlorides to recover the pure metals and chlorine which can be recycled back to the reactor.

Jan 1, 1994

By Richard D. Hagni

The United States is dependent upon foreign sources for more than 93% of its bauxite and alumina supply. Domestic production of bauxite, which comes from Alabama, Georgia and Arkansas, is limited to those bauxite ores containing less than about l ½ % iron. Bauxites with higher iron contents are generally not utilized because they cause problems in bauxite calcining and especially because they produce undesirable brick discoloration and cracking. In order to improve beneficiation and expand the utilization of high-iron or ferruginous bauxites, a mineralogical and textural study has been conducted on selected samples from the Eufaula, Alabama, bauxite district. Reflected light microscopic, petrographic, and X-ray techniques have shown that a variety of iron minerals are present, including hematite, goethite, lepidocrosite, siderite, pyrite, marcasite, and ilmenite. Although the iron minerals may be locally concentrated into concretions and pisolites, most occur as very fine grains that are disseminated and show a variety of intergrowths. Mineralogical and textural observations indicate that the fine-grained iron mineral grains may be amenable to high gradient magnetic separation.

Jan 1, 1981

By E. James Quinn

Solvent extraction technology using EHEHPA (2-ethylhexyl phosphonic acid, 2-ethyhexyl mono ester) is the norm for industrial separations of rare earth elements. This process has some shortcomings, including a large number of stages compared to most SX processes and high acid requirement for stripping of the heavy rare earths. In this work, we examine a number of alternative mixed solvent extraction systems: (i) Mixtures of organophosphonic and phosphinic acids such as EHEHPA/Cyanex 272 or Cyanex 572; (ii) Ionic liquid mixtures of EHEHPA with quaternary ammonium chloride (Aliquat 336); and (iii) Mixtures of carboxylic acids for yttrium/lanthanide separations. We discuss and compare the efficacy of these systems with reference to the Nd/Sm separation, which is of industrial significance. Based on the extraction chemistry and the use of modelling tools to define the counter-current solvent extraction circuit, we present a techno-economic analysis of a separation plant and discuss the impact of various solvent systems on the capital expenditure (CAPEX) and operating costs (OPEX).

By Gaballah Djona M.

Spent hydrorefining catalysts contain about 5 % of CoO and/or NiO, 12 % of MoO3 and up to 10 % of V205. They are generally supported by alumina and contain up to 25 percent of C, S and hydrocarbons. Such materials are potentially hazardous to the soil and to water resources. Selective chlorination of raw unroasted samples with Cl2 + air gas mixture had been investigated. At temperatures lower than 600 °C, it was possible to recover more than 90 % of nickel and cobalt chlorides, about 99 % of the molybdenum and up to 75 % of vanadium chlorinated compounds. CoCl2 and Ni/Cl2 were extracted from the chlorination residues by their dissolution with acidified water. Molybdenum and vanadium chlorinated compounds were recovered by selective condensation from the vapor phase. The chlorination of Al2O3 could be limited to less than 6 %. The scale up of this treatment was successful and a flow-sheet is proposed.

Jan 1, 1995

By Donald P. Ziegler, James F. Klausner, Srinivas S. Garimella

"By 2015, nearly half the world's population will live in ""water stressed"" areas. Production of fresh water utilizing waste heat from industrial processes has been identified globally as a research priority.About 15% of the electricity required to produce aluminum is lost as waste heat in the off-gas. However, the low temperature (low grade) of the heat limits reuse. The off-gases contain 50-150 ppm SO2 ; tightening regulations coupled with increasing coke sulfur levels are motivating SO2 control, for which seawater scrubbing is attractive for smelters with suitable access.We describe a process that produces fresh water, utilizing the waste heat while scrubbing SO2 . It uses direct contact between seawater and off-gas to humidify the off-gas. The vapor is subsequently condensed. In smelter trials, a unit treating a slip stream produced high quality water in the anticipated quantity, attaining over 95% SO2 scrubbing. Future work involves scaling the process to be economically attractive.BackgroundPopulation growth, coupled with industrialization and urbanization, are increasing demand for water. Water scarcity already affects every continent. Around 1.2 billion people, or almost one-fifth of the world's population, live in areas of water scarcity, and 500 million people are approaching this situation. By 2025, 1.8 billion people will be living in countries or regions with absolute water scarcity, and two-thirds of the world's population could be living under water stressed conditions (< 1,700 m3 per person annually) [1]. An assessment by the U.S. General Accounting Office revealed that under normal conditions, by 2013, water managers in 36 states in the USA anticipate water shortages, and that the number might grow to 46 states under drought conditions [2].The obvious choice to alleviate water scarcity is the 97% of available water in the oceans, which is saline and requires desalination for use in biological, agricultural and industrial applications. Technologies developed for desalination include Thermal Distillation, Reverse Osmosis (RO), Electro-Dialysis, and Vacuum Freezing. Distillation and RO are the most commercially prominent. Thermal distillation technologies include Multiple Effect Distillation (MED) and Multi-Stage Flashing (MSF). The report commissioned by the World Bank [3] is one of the many excellent references on desalination technologies. According to the International Desalination Association working paper [4], there were more than 17,348 industrial scale desalination plants installed or contracted by 2004. The total production from these plants is on the order of 8.3 billion imperial gallons per day. RO provides 47.2% of the total capacity. The leading thermal process, MSF, provides 36.5% of the total capacity. Although MSF and RO technologies currently provide the most cost effective means for desalination, their drawback is that they are very energy intensive, and whether or not they remain cost effective strongly depends on energy prices and energy supply."

Jan 1, 2012

By J. T. I. Poijärvi

Outokumpu Harjavalta Metals Oy operates copper and nickel smelters, three sulphuric acid plants and nickel refinery at Harjavalta and copper refinery and precious metal plant at Pori. The by-products of these plants are presented in this paper. The by-products of the smelters include products from slag cleaning of flash smelting furnaces and converters, flue dusts and smelter off-gases. Weak acid and sludges from cleaning of smelter off-gases and acids are the by-products of the acid plants. The by-products out of the copper refinery are crystallized metal sulphates and sludges from electrolyte purification, on which a co-production process of the copper tankhouse is based. The main by-products of the precious metals plant are products from anode slime treatment and platinum metal group concentrates in the recovery of precious metals. Sludges from nickel matte leaching and precipitates from solution purification are the by-products of the nickel refinery. The formation, treatment and processing as well as the research work done for the utilization instead of dumping of the by-products in the production of copper and nickel will also be discussed in this paper.

Jan 1, 1995

By S. K. Wu, Ray Y. Lin, Sunil Annaji

Infrared joining of TiAI using aluminum foils as the filler material was investigated at temperatures between 1050 °C and 1350 °C in a flowing argon environment for times varying between 15 and 60 seconds. Using aluminum foils, the attempt was to form the Al3Ti phase in the joint as a result of reaction between Al and TiAI at temperatures above the melting point of Al. It has been found based on X-ray diffraction and TEM analysis that, Al3Ti, indeed is the product of infrared joining of TiAI using Al as the joining alloy. Al3 Ti was detected even in the joint processed at 1050 °C for only 15 seconds. Since the aluminum foil used in this study contains 27 at% Si, the t 2 phase in the Ti-Al-Si ternary system is believed to have also formed at the joint/base TiAI interface. Cross sectional studies on the joined specimens have shown different degrees of reaction depending on the temperature and time of joining. Micro hardness evaluations across the joint show that the hardness near the center of the joint is typically smaller than that near the joint edge next to the base material. However, as the joining temperature and time increase, the increment of the hardness at the center of the joint is faster than that around the periphery of the joint.

Jan 1, 1996

By Kazuyuki Kikuta

MMAJ, a govemmental organization in Japan, has carried out a 4 year project for the development of the decontamination and metals recovering technology for the fly ashes from municipal waste incineration. Heavy metals (zinc, lead and copper) are recovered as raw materials for the non-ferrous metals production, without formation of any waste materials to be disposed. More than 500 thousands tonnes a year of fly ashes generation from the municipal waste incineration has been one of the main social issues in Japan, because most of them need to be disposed to the registered areas after decontamination, and occupy 5% of the municipal wastes disposed. The segregation, flotation and chemical process are applied to the treatment of the primary fly ash from municipal waste incineration, and MF (Mitsui-type blast furnace) Process after the chlorine removal to the secondary fly ash. The main results of experiments are -About 90% of heavy metals, zinc, lead and copper, can be recovered from the primary and the secondary fly ashes to the products for the non-ferrous metals production. -Both of the leaching residue from the primary fly ash treatment and the slag from the secondary fly ash treatment can be used as a raw material for the cement production, meaning that the decontamination technology for the ashes without the landfill has been established. -Dioxins in the primary ash can be decomposed satisfactorily, and the dioxins content in the segregation furnace gas is less than O.lng-TEQ/Nm3 without any gas cleaning system

Jan 1, 2003

By A. E. Torma

In recent years the copper industry has gained considerable economic stability. An essential part of this industrial wealth is attributable to the successful application of bio-mediated heap and dump leaching techniques in the recovery of copper from low-grade resources. This study evaluated the leachability of a chalcopyrite conlentrate using naturally occurring mixed culture of predominantly Thiobacillusferrooxidans and Thiobacillus thiooxidans. For the effects-of pulp density, the overall reaction rate constant (k) and the order of reaction (n) have been determined to be 1.93 h-1 and 1.36, respectively. Cyclic voltammetric measurements revealed that intermediate reactions are involved in the chalcopyrite oxidation. Using the Price approach, it was shown that the dissolution of chalcopyrite is solid state diffusion controlled.

Jan 1, 1992

By Upali Siriwardane, Tushar V. Kudale, Naidu V. Seetala

"Cellulose acetate (CA) membranes with 25% triethyl citrate (TEC) as plasticizer were prepared with varying thickness for CO2 gas separation from water-gas-shift (WGS) reaction products. The AFM analysis of the CA membrane showed that the uniform coating had fewer and smaller pores as the film thickness increased, and corroborated by gas permeability studies. The CO2 permeability has decreased faster than CO permeability with the CA/TEC membrane thickness, and findings support that the CA membrane could be used to entrap CO2. Several CA/TEC membranes were also staked to increase the separation efficiency. Positron Annihilation Lifetime Spectroscopy (PALS) was used to estimate the nano-porosity (pore size and concentration) changes of CA/TEC films. PALS results show a decrease in pore size with increasing CA-TEC concentration in acetone, while the pore concentration increases. The PALS results are correlated with the CO2/CO permeability variations as the CA-TEC concentration change.IntroductionHydrogen is one of the main energy sources available for the future advancement of clean fuel technologies especially for fuel cells. Generation of hydrogen and CO2 from Water Gas Shift (WGS) reaction mixtures of CO and H2O is of interest to many researchers since it allows a large scale production of hydrogen [1, 2]. Once hydrogen is produced using the WGS reaction, the output products contain mixture of CO, CO2, H2, and water vapor. Metallic membranes have been used as hydrogen separation membranes [3-6]. As H2 is separated from the mixture using the metal membranes, we need to separate CO2, and find ways of sequestration of CO2 to avoid environmental problems by greenhouse gasses. Polymeric Membranes have been used for CO2 separation [7]. Plasticizer can control the micro-structural properties such as pore size and concentration of polymer membranes [8], which influence the size/molecular weight dependent diffusion rates of the gas molecules. We have used cellulose acetate with triethyl citrate as plasticizer to separate CO2 from the WGS reaction products. Positron annihilation lifetime spectroscopy (PALS) is very sensitive and able to identify different kinds of defects and their agglomerates such as vacancies, vacancy loops, and voids [9, 10]. PALS has been successful in determining the free volume in polymers that influence the properties of the polymers [11, 12]. Microscopic properties of the free volume obtained from PALS have been correlated to macroscopic properties [13, 14]. We used PALS to study the nanoporosity (pore size and concentration) and fractional free volume changes of CA/TEC films, and used to understand the variations observed in the CO2/CO permeability as the CA-TEC concentration in the membranes change."

Jan 1, 2014

By J. D. Budai, D. H. Lowndes, D. P. Norton, D. K. Christen, B. C. Chakoumakos, J. R. Thompson, B. C. Sales

"Artificially-layered structures, consisting of (Sr,Ba,Ca)CuO2 layers in the tetragonal, ""infinite layer"" crystal structure, have been grown by pulsed-laser deposition. Superlattice chemical modulation is observed for structures with SrCuO2 and (Sr,Ca)CuO2 layers as thin as a single unit cell (~3.4 Å). In addition, novel thin film superconductors were formed by using the constraint of epitaxy to stabilize SrCuO2/BaCuO2 superlattices in the infinite layer structure. Using this approach, two new structural families, Ba2Srn-1CUn+l O2n+2+ d) and Ba4Srn-1CUn+3O2n+6+ d, have been synthesized which superconduct at temperatures as high as 70 K. These results represent not only the synthesis of new structural families of superconductors, but also demonstrate that pulsed-laser deposition and epitaxial stabilization can be effectively used to engineer artificially-layered thin-film materials.Advances in the understanding of epitaxial thin-film growth of the cuprates have heightened interest in creating artificially layered superconductors.(1-3) The layered structure of the copper oxide superconductors opens the possibility of forming novel materials by carefully controlling the epitaxial growth of sub-units of the crystal structures. Thin-film growth methods offer unique opportunities for the atomic engineering of new high-temperature superconducting (HTSc) materials through the ability to form artificially layered crystal structures.(4,S) Moreover, the surfaces of single-crystal substrates provide an ""atomic template"" that can be used to stabilize epitaxial films in metastable crystal structures.An important development in forming new HTSc compounds by artificially-layered epitaxy has been the epitaxial growth of (Sr,Ca)CuO2 films in the so-called infinite layer structure.(6-17) This material, which can be considered the parent compound of all of the copper oxide superconductors, has a relatively simple, layered structure consisting of CUO2 planes separated by planes of alkaline earth elements.(18) Bulk synthesis of (Sr,Ca)CuO2 with the tetragonal, infinite layer structure generally requires the use of high pressure and high temperature bulk processing techniques.(19-24) However, recent experiments show that this metastable compound can be epitaxially stabilized at less than atmospheric pressure, resulting in the growth of tetragonal (Sr,Ca)CuO2 single crystal thin films of the infinite layer defect perovskite structure by pulsed-laser deposition (PLD) over a wide range of growth conditions.(6-17)"

Jan 1, 1994

By Don Ibana

Supported by the Minerals Council of Australia (MCA) through the Minerals Tertiary Education Council (MTEC), three Australian universities–Curtin University, Murdoch University and the University of Queensland–have formed the Metallurgical Education Partnership (MEP) to jointly develop and deliver an engineering design capstone unit–Metallurgical Process and Plant Design–in their respective undergraduate programs in extractive metallurgy, in order to enhance the students’ educational experience. A unique feature of the program is the close interaction of the students in all three universities and a significant involvement of industry professionals. Now in its sixth year, it is clear that this unit is achieving its objectives

Jan 1, 2014

Although anion exchange resins are widely used for gold recovery in Russia and the former CIS, accounting for almost 50 percent of gold recovery in that part of the world, the technology has not been adopted in the West, apart from one small operation in South Africa. This situation is likely to change as the gold industry heads into the twenty first century. With gold prices having declined steadily through the 1990&apos;s, mining companies are under great pressure to reduce costs and improve gold recovery. Most studies on the use of resins for gold recovery from cyanide solution or pulp have shown that this technology has the ability to achieve both these goals. Resins can also be used to recover and recycle free and complexed cyanide in gold plant tailings, which has the potential to significantly lower operating costs, and latest developments in this area of technology are discussed. Finally, recent studies on thiosulphate leaching of gold have&apos;shown that this process is very well suited to the treatment of carbonaceous, preg-robbing ores from the Carlin trend (Nevada, USA), and elsewhere in the world, because the gold thiosulphate complex does not load on to carbon. Whilst this obviously benefits the leaching process, it means CIP and CIL are ineffective in this situation, and the use of ion-exchange resins for gold recovery from thiosulphate leach solution are discussed.

Jan 1, 1998

By Taufiq Hidayat

Accurate description of complex phase equilibria provide the foundations for the improvement of non-ferrous pyrometallurgical smelting and recycling processes. Recent advances in microanalysis and experimental techniques enable accurate phase equilibria characterisation. Quantitative microanalytical techniques including Electron Probe X-ray Microanalysis and Laser Ablation ICP-MS enable the concentrations of major and minor elements present in different phases in samples to be accurately measured providing data that cannot be obtained using bulk chemical analysis techniques. High-temperature equilibration experiments coupled with the subsequent analysis of elementary reactions at micro- and macro-scales ensure the attainment of equilibrium conditions, and therefore, ensure true phase equilibria information is obtained. Examples of the application of the improved methodology on the investigation of phase equilibria of low-order and complex, multi-component gas/slag/matte/metal/solids Cu2O–PbO–ZnO–Al2O3–CaO–MgO– FeO–Fe2O3–SiO2–S systems and the distribution of minor element are provided. The experimental study is closely integrated with thermodynamic database development for the above system. Example of implementation of the research outcomes into industrial operations is demonstrated.

By Thomas Gliick, Jianming Lu, David Dreisinger

"The recovery of manganese from the Boleo project of Baja Mining is via an acid oxidation and acid reduction process in seawater. Manganese as manganese dioxide is leached into solution as manganese sulphate with the addition of sulphur dioxide gas as a reductant and then precipitated as a manganese carbonate. The use of the manganese carbonate intermediate to produce electrolytic manganese metal (EMM) has been extensively studied. The manganese carbonate can be used in place of natural (MnC03) or reduced ores (MnO) of manganese as a feed to the EMM plant. Manganese carbonate can be dissolved in spent electrolyte from manganese plating, followed by purification using ammonium sulphide precipitation of minor elements and then electrowinning in a selenium free process. The results of small cell testing of manganese electrowinning are reported.IntroductionThe Boleo Project of Baja Mining is a greenfields development currently under construction approximately 5 km north of the town of Santa Rosalia, Baja California Sur, Mexico. The Boleo property is held by the Mexican company, Minera y Metalurgica del Boleo S.A. de C. V. (MMB). MMB is owned 70% by Baja Mining Corp. and 30% by a consortium of Korean companies consisting of KORES - Korea Resources Corporation, LS Nikko Copper, Hyundai Hysco, SK Networks and lljin Copper.The Boleo deposit has Measured and Indicated resources of264.7 million tonnes grading 1.50% copper equivalent (CuEq) & Inferred resources of 159.9 million tonnes grading 1.15% CuEq. The calculation of copper equivalent is based on a combination of metal prices and predicted metallurgical recoveries (Table I). The metallurgical recoveries have been confined by extensive bench and pilot plant testing. Proven and probable reserves are available at Boleo to provide for more than a 30 year mine life. Initially, 25 years of mine life and 23 years of process plant operation have been scheduled in the February 2010 Technical Report Update (www.sedar.com)"

Jan 1, 2012

By I. M. Ritchie

Cyanide owes its great success as a lixivant for gold to the great strength of the Au-CN bond. A replacement for cyanide must similarly be a strong complexant for gold (I) or gold (III). The various alternatives are briefly considered and it is concluded that only thiosulfate has a reasonable chance of replacing cyanide as a relatively non-toxic lixivant at the present time. However, there are considerable technical problems to be overcome before thiosulfate can be considered to be a realistic alternative to cyanide. Firstly, the leaching of gold using aerated ammoniacal thiosulfate with copper as a catalyst is a complex process which needs to be understood and controlled carefully in order to achieve maximum recoveries with minimum reagent losses. Secondly, there needs to be an option similar to the CIP process for recovering and concentrating the dissolved gold thiosulfate complex from pulps produced in the processing of low grade gold ores. The prospects for overcoming these technical&apos; challenges are evaluated and discussed.

Jan 1, 1998