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By Jeff Hiedeman, Clint Sestrich, Christopher Hyle

Westslope Cutthroat trout have declined in distribution and abundance across their range and currently occupy about 59% of their historic habitat. Due to hybridization with non-native species such as rainbow trout, genetically pure populations persist in only 10% of that range. A westslope cutthroat trout population with relatively high genetic purity (97%) and conservation importance persists in less than two linear stream miles in the headwaters of the South Fork Madison River in southwest Montana. The relative purity of this population has been maintained through the presence of a downstream intermittent reach. However, spring flows fill the intermittent reach, creating a connection between occupied westslope cutthroat trout habitat in the headwaters and the habitat of competing trout species downstream.

Jan 1, 2011

By Akira Usui

The details in small-scale variability of the geological occurrence and chemical composition of ferromanganese crusts are not yet well understood, although the northwestern Pacific seamounts are believed to be among the most promising areas for rare metal resources. Our belief is that geological observations and geochemical analyses are still insufficient for economic evaluation or for discussion of depositional processes and environments. Our team, composed of geologists, mineralogists, geochemists, physical engineers, and microbiologists has attempted to utilize an ROV for in-situ measurement and for sampling of undisturbed and uncontaminated ferromanganese crusts at three typical seamounts in the NW Pacific near the Japanese Exclusive Economic Zone. The first ROV geological survey of ferromanganese crusts was successfully completed, and the ROV proved to be the most powerful, efficient and elegant method to date. The collected samples (more than total 1 ton of crusts, at more than 100 sites along a total of approximately 10 km of survey lines) were most suitable to analyze water-depth dependency and secular variation of their composition. The intact surfaces of crusts, collected without the usual abrasion caused by dredging, were also valuable for microbial study of Mn oxidizing bacteria. The ROV sampling devices, however, can be improved with further sophisticated drills or rock saw blades in the future.

Jan 1, 2011

By Qing-hua Tian, Li-then Cheng, Xue-yi Guo

In order to recycle valuable metals from silver separated residue, a novel method using alkaline smelting at low temperature was proposed. The main factors affecting the main metal recovery such as the smelting temperature, smelting time, liquid-to-solid ratio and alkali addition were investigated comprehensively. The behavior of the main metal elements, such as Pb, Sn, Sb and Bi in silver separated residue was also discussed. The results indicated that amphoteric metals such as Pb and Sn can be smelted into the melt, while other metal elements, such as Sb and Bi were left in the residue.

Jan 1, 2011

By D. Brandt

The Dos Pobres Mine is a copper oxide heap-leach operation located near Safford, AZ. Mine production is 163 kt/d (180,000 stpd) with a stripping ratio of 2:1. During the startup phase of the mine, the required fragmentation size was easy to achieve as the ore was highly weathered and fractured near the surface. As the mine depth increased, the proper fragmentation size became harder to achieve due to less weathering and different rock types. Because copper recovery increases as crusher product size decreases, achieving the appropriate product size at the crusher is the operating priority. The engineering department began a project to improve fragmentation through blasting and thus increase throughput in the crushing system. It soon became clear that input from other departments was going to be required to make this a safe and economical project. Therefore, the crush and convey and ore control departments worked together to evaluate all available data on blast patterns and explosive loads and tracked performance and results. Using image analysis, drill energy index and databases, improved fragmentation size has been achieved and results have been verified while controlling costs.

Jan 1, 2011

By F. Baldini, M. S. Borges

"The proposed method emphasizes the optimization of waste management with regard to the exploitation of raw materials incorporated in the remains of industry, as well as the economics of natural resources as an environmental impact assessment. This system [tool] allows: (a) the conversion of an environmental liability into an asset by finding a line of appropriate research for each type of waste and the development of new materials applicable to other industries, (b) the performance of internal control of the waste generated (production, storage, final destination) as well as legal conformity.Objectives:1.1 General objective:To design a collaborative system for socio-environmental management of industrial waste.1.2 Specific objective:Develop evidence of concepts;Evaluate the deployment of the inventory of waste in an industry;Enable the conversion of an environmental liability into an asset by finding a line of research appropriate to the waste: a case study;Evaluate the environmental legislation in the legal mechanisms that influence company decisions.IntroductionThe global economy is undergoing major changes, among these changes; it should be highlighted those related to technological progress and environmental quality.While the industrialized countries and higher levels of economic growth dominate modem technology, developing countries are identified by a different growth pattern, using the annual growth rate of Gross Domestic Product per capita [3, 18].Growth is when the GDP grows, in percent, over the previous year. Development, on the other hand, is when the countries change their technologies and improve their internal structure. Thus, the growth considers the accumulation of wealth, while the development is concerned with the distribution of wealth, improvement of the quality oflife and environmental quality [3, 18].As the UNESCO report shows (1999), the biggest problem is between consumption and development, what is produced and the end that is given to the product. Therefore, product and by-product have equal importance in the quantity produced [29].On one hand there is a positive relationship between indicators of economic growth and technological progress, however, on the other hand, these transformations are a paradox, confirmed by the dramatic use of environmental resources and the lack of technologies for recycling of industrial scrap."

Jan 1, 2011

By D. W. Alexander

Researchers from the Office of Mine Safety and Health Research (OMSHR) of the National Institute for Occupational Safety and Health (NIOSH) completed field trials during coal mine rescue contests using simulated gas detectors in place of placards. The gas monitor simulator (GMS) devices replaced static, paper placards to deliver gas concentration data. Eleven teams were observed during the field contest, which was approved by the Mine Safety and Health Administration (MSHA). GMS devices were given to three team members, the captain, and both gasmen. Observation of teams revealed that team members changed behavior by acknowledging and sharing information more often while using the GMS. As a result of this research, it has been demonstrated that under the existing contest format, the newly developed GMS device may be used with no adverse impact on team contest performance. Furthermore, when GMS technology advantages are used, contest realism is improved. In the future, competency assessment may be incorporated.

Jan 1, 2011

By Jay L. Hodkinson

Replacement of an aging twin span river crossing in Vermont required a temporary bridge to accommodate traffic during construction. Soils beneath the temporary approach embankment consisted of very soft organic clayey silt underlain by interbedded, loose alluvial fine sand and silt/clayey silt. Reinforcement was required for the southern temporary approach embankment to limit settlement and to increase global stability factors of safety. A ground improvement design was developed using Rammed Aggregate Pier® reinforcement and was included in the contract documents as an FHWA Category II Experimental Feature. Instrumentation intended to document the performance of the supported embankment was installed. Piers were then constructed and monitoring commenced as embankment and bridge construction occurred. Weekly instrumentation data reports indicated continuing excess pore water pressure, settlement, and lateral deformation of the subgrade soils as the embankment and temporary bridge abutment was constructed. In response to the unanticipated monitoring results, further investigation indicated that significant deviations from the conditions and basis upon which the ground support design was developed were made during construction. This paper discusses these deviations and their specific impacts to embankment support performance, how these deviations occurred, the role that the ground support system played in maintaining global stability, measures taken to limit further detrimental impacts to the embankment, and provides recommendations for contract document preparation and construction oversight to prevent similar situations from occurring on future projects.

Jan 1, 2011

By D. Lansburg

Electronic detonators are increasingly being used in today’s blasting in quarries, seismic, surface and underground mines. Electronic detonators offer several distinctive features over electric and non-el (shock tube) detonators including better timing accuracy resulting in excellent fragmentation and vibration control, field programmability and digital safety means. Because of the prerequisite electrical communications between the electronic detonators and the blasting machine, the layout or hook-up of these detonators can play an important role in obtaining the communication fidelity.

Jan 1, 2011

By W. S. Steinberg

In 1963, the full-scale engineering study for the development of an iron, steel, and vanadium plant was initiated. This was the birth of Evraz Highveld and its process flow as it is known today. Highveld started out as a steelworks that produced steel and vanadium-bearing slag from a titaniferous magnetite iron ore mined from its own mine site near Steelpoort. The process utilized co-current rotary kilns for prereduction, and submerged-arc furnaces for the production of pig iron with approximately 1.15% vanadium. Because of various technical challenges that the submerged-arc furnaces experienced over the years, a decision was taken in 2004 to convert the furnaces to open slag bath (OSB) operation, in order to enable the maximum production of iron and vanadium while improving the control over operational parameters. The conversion proved to be highly successful and, since 2005, three furnaces have been converted to OSB operation. The fourth furnace will be converted in the first half of 2011. The conversion to OSB furnaces not only yields higher vanadium recovery to the metal at the iron plant, but also improves the overall throughput of the steel plant. This is the result of the higher carbon content of the liquid iron from the OSB furnaces, eliminating the need for anthracite addition to the shaking ladle process. This reduces the blowing time by approximately 60%. The conversion of the furnaces to OSB configuration is seen as an enabling technology change and a prerequisite to the implementation of other plant improvements that are envisaged. The long-term vision of EHSV is to convert five furnaces to OSB mode, and permanently decommission the two remaining submerged-arc furnaces. This will allow EHSV to maintain current steel and vanadium production but at a significantly improved overall efficiency.

Jan 1, 2011

By Z. Mullard

The introduction of social media platforms has ushered in a new era of interaction and information exchange, which impact business-to-society relationships. Mining companies are closely watching these platforms, as the industry takes a cautious approach to control flows of information. This paper explores the risks, challenges and opportunities of using social media, based on a qualitative mixed methods investigation with stakeholders from the Canadian mining industry. Generational and language barriers, misunderstanding and limited motivation from regulators make implementing social media platforms challenging and risky at an organizational level. The benefits of social media include being able to mobilize communities and share information in real time. Despite the challenges, the study found that 62% of mining stakeholders are incorporating social media tools, mostly in an ad hoc manner. Flexible strategies for transparent communication and public engagement are creating new opportunities for information exchange.

Jan 1, 2011

By David C. Kraft

Helical piles and ground anchors were used to meet critical design and constructability requirements for an urban forest Canopy Walk at the Atlanta Botanical Garden, Atlanta, GA. The 12-foot wide pedestrian walkway path was to be nestled among the treetops of a forest, extending to 600 ft. in length, and soaring 40 ft. high above the forest floor. Of particular concern during construction was that the foundation system for the temporary steel shoring system had to be non-invasive to the subsoil, could not damage the forest floor, trees, root systems, or foliage, and upon completion of the concrete walkway pour, could be removed, again without disturbing the subsoil. Accubrace, Inc. designed and installed all the helical foundation types, as well as provided steel braces, typically used in Tilt-Up building construction, for the walkway project. The braces, some extending to 43 ft. in length, were used to provide lateral support against wind loads for the walkway form. In addition, the braces acted as secondary support for lateral loads during the placement of wet concrete along the 600 ft. length of the walkway. Helical foundation products installed included vertical compression piles, ground anchors for tension rods, and ground anchors for the braces. The installation of the piles and anchors was particularly challenging since the forest floor elevation varied as much as 50 ft. due to the presence of a ravine. Information is provided on the subsoil conditions, required loads, design, installation, and acceptance criteria for each helical product type installed for the project. The results of vertical and lateral load tests on the helical piles in the pre-construction phase, conducted in conformance to project specifications are presented. Photographs to illustrate the nature and complexity of the project are included. The concrete pour for the walkway was successfully completed on December 12, 2009, and the walkway was opened for visitors in May, 2010.

Jan 1, 2011

By H. J. McQueen

Before 1950, hot working was simply deforming above the recrystallization point and gave a soft product compared to cold working. From 1960 onwards, improved testing in compression and torsion (stress, strain rate, temperature, quenching) provided valid specimens for microstructural analysis by polarized optical and transmission electron microscopy (TEM). Indeed, TEM was essential to uncovering the hot working mechanisms because it could distinguish between cold and hot substructures (dynamic recovery) in either initial or new grains (dynamic recrystallization). Over the years, teams at Concordia, McGill and UBC obtained NSERC support for students and equipment. CANMET built up a hot forming group having capabilities from high-rate cam-plastometer compression to rolling of experimental alloy billets; this was combined with latest metallographic instruments for fundamental research. Al alloys of every class (2000, 3000, 5000, 7000, 8000) were studied to understand the effects of solutes, precipitates, dispersoids and composites. The complex flow patterns in extrusion were clarified and modeled by finite element methods. Physical simulations of rolling schedules (up to 20 passes and reductions of 98%) by torsion provided evidence of microstructure development during both the passes and the softening intervals, thus clarifying development of texture in different alloys. The results frequently appeared in proceedings of Light Metals symposia and Canadian Metallurgical Quarterly

Jan 1, 2011

By L. Bergkvist

"History can provide many answers with regard to what today’s mining industry looks like and how we got to where we are today. It has always been self-evident that safety has to be given the highest priority and, throughout history, many mine workers have been injured, become ill and have even sacrificed their lives due to the way in which attempts have been made to extract the ore, often due to ignorance of the dangers being faced. In more recent stages of history we have seen certain dangers being compensated by means of higher wages and bonus systems in order to have the work carried out: one example of this is when the rock heating method was employed and the men who first went underground to put out the fires that were burning, were paid extra. The working conditions, to which these people were exposed, with smoke-filled closed spaces, shortened their life expectancy considerably and today we can ask ourselves whether it is really possible to value these efforts just by higher wages. In all mines worldwide the working environment has been improved and many mining companies have a zero vision where work-related injuries and accidents are concerned. Despite this, incidents of varying severity still occur and a continuous improvement process and ongoing training is necessary in order to constantly minimise risks and improve the working environment. Atlas Copco takes this into account in all its development and we not only review our own production units but also the needs of our customers, with regard to the machinery that is produced in order to cater for customers’ safety and production objectives. Underground mining probably started at the beginning of the 11th century when people with modest tools tried to extract ores that were present in the bedrock. Methodology has developed enormously over the years with a strong focus on increased efficiency and higher production. In different parts of the world the development is driven forwards at different rates depending on which controlling factors are regarded as necessary. Political decisions, profit goals and productivity have partly controlled the development, but the greatest factor where improvement is concerned still remains with increased understanding of the totality. During more than 1000 years since underground mining has been conducted, all individuals at all levels have constantly improved their expertise and the human element has been of great importance with regard to the development that has been made, even though technology often occupies a leading role when we describe the improvements made."

Jan 1, 2011

By Jan E. Nesset, James A. Finch, Frank Rosenblum, Rebecca Payant

"Under certain conditions of moisture and oxygen, sulphides can spontaneously heat, a phenomenon known as self-heating. In this paper, we test a hypothesis that galvanic interaction between some sulphides can promote self-heating. Galvanic interaction is controlled by restpotential difference between minerals and their surface area of contact (particle size). In order to decrease rest-potential, four sulphides were tested: pyrite, chalcopyrite, sphalerite and galena. Two series of samples consisting of mixtures of two sulphides, each representing a mass fraction of 50 %, were run in standard self-heating tests. The first series comprised five mixtures, two with low rest-potential difference (pyrite-chalcopyrite and chalcopyrite-sphalerite) and three with high rest-potential difference (pyrite-galena, chalcopyrite-galena and pyrite-sphalerite). The second series was performed on a pyrite-sphalerite mixture at four particle sizes (80 % passing 850 µm, 300 µm, 75 µm and 38 µm). The first series showed that the individual sulphides and the mixtures of low rest-potential difference did not self-heat but the mixtures of high rest-potential difference did self-heat. The second series showed that self-heating increased inversely with particle size (increased specific surface area) and revealed that it was the fineness of the pyrite (high rest-potential sulphide) that governed the self-heating effect, indicating the rate-limiting step is the reduction reaction on pyrite (cathodic mineral). The increase in self-heating with high rest-potential difference and increasing particle fineness supports the hypothesis that galvanic interaction contributes to sulphide self-heating. A possible mechanism based on the hydrogen sulphide hypothesis is proposed where the reduction reaction at the cathodic mineral surface is ferric to ferrous. The understanding gained will be of interest to those involved in storage, shipping and disposal of sulphide minerals.INTRODUCTIONSulphide mineral ores are the major source of most base metals such as copper, zinc, nickel and lead. Once the ore is extracted, the sulphide minerals are liberated by size reduction (crushing and grinding), concentrated by flotation, and the concentrates sent for further processing to extract the metal (smelting and refining). At the various stages from mining to concentrate shipment and tailings storage, the sulphides are exposed to a variety of environments, which under certain conditions of air (oxygen), humidity and temperature can cause them to heat. Since no external heat source is involved, this pyrophoric process is known as spontaneous heating or, more commonly, self-heating. The self-heating of sulphides is associated with oxidation reactions under moist conditions. If the heat generated is greater than the heat dissipated, the sulphides will self-heat and the material temperature will rise. This can make working conditions potentially dangerous as oxygen is consumed from the surrounding air and significant quantities of sulphur dioxide (SO2) can be released (Ninteman, 1978)."

Jan 1, 2011

By F. Carew

Accurate knowledge of what mass and grade is to hand and where it is stored is key to mine efficiencies and overall profitability. In order to make the right decisions and align production with stockpile capacity, feed and contract demand, a clear and accurate view from production through blending and processing is required. The use of a mine production management solution can provide you with a high degree of confidence in and visibility into validated data as well as auditable and traceable material movements, activities and surveys. A robust calculation engine enables mass and grade changes to propagate to material movements and stockpiles to ensure you are getting the most accurate view at all times. Tracked changes in material balances can be readily incorporated in revised production schedules to close the loop. The availability of accurate, timely information, coupled with predictive trend indicators, is a significant advance in narrowing the gap between claimed and planned production that is common to many mines, regardless of commodity. This paper provides an overview of a Mine Production Management System (MPMS) and explains how the system helps address the challenges listed above.

Jan 1, 2011

By Boyd Davis, Vladimiros Papangelakis, Joshua LaMarre, Jan de Bakker

"HCl leaching using molten salt hydrates has the potential to improve the extraction of nickel from laterite ores. However, as in other HCl leaching applications, recovery of HCl is key to process economics. Spray pyrohydrolysis, which is used in current chloride-based flowsheets, is associated with a high energy cost. The authors have developed a proposed laterite leach circuit using an alternative HCl recovery route. The leach circuit envisions a leach by concentrated (33%) HCl in an MgCl2 molten salt hydrate (MSH) or brine medium, followed by Ni/Co recovery and iron precipitation. Magnesium and chloride are precipitated from solution as magnesium hydroxychloride; this hydroxychloride is thermally decomposed to produce HCl gas. The proposed flowsheet employs a chloride leach circuit with simpler equipment and lower energy cost than in the conventional practice of pyrohydrolysis. Laboratory work investigated key aspects of the flowsheet, including precipitation of magnesium hydroxychlorides and their composition; magnesium hydroxychloride thermal decomposition; and iron control.Introduction As sulphide nickel ores become harder to mine and more complex to process, laterite ores will increase in importance. Laterite ore deposits can be divided into two main mineralogies. Limonite ores consist mostly of hydrated iron oxide, FeOOH, with 1-3% nickel substituting for the iron. Saprolite ores consist of iron-magnesium silicates, (Fe, Mg)2Si04, again with some nickel substituting for the metal ions. Limonite ores can be treated using the HP AL (High Pressure Acid Leach) process, in which the ore is reacted with sulphuric acid at high temperature in an autoclave. HP AL, however, cannot in general be used to treat saprolite ores because the magnesium enters solution and consumes sulphuric acid, which results in excessive spending on lixiviant. It is therefore desirable to find a hydrometallurgical process specifically for saprolite ores that can provide better results than the treatment options currently available."

Jan 1, 2011

Lonmin, earlier than any other primary platinum producer, had to deal with the concentrating and smelting of UG2-rich ores and concentrates respectively. Smelting was performed at a fairly modest scale compared to the company's industry peers in the platinum group metals (PGMs) industry, and was focused on smelting concentrates obtained through low mass pulls while still maintaining high recoveries at its concentrators. Lonmin gradually smelted larger quantities of UG2 concentrates. Initially two 2.3 MW Infurnco furnaces were commissioned in 1982, followed by three 5 MW circular 3-electrode Pyromet furnaces in 1991. Deep electrode immersions and moderately high hearth power densities were used in all the designs. Lonmin decided to continue with circular furnace technology when it planned its new high-intensity No. 1 Furnace. Neither Lonmin nor the technology supplier and EPCM company foresaw the challenges that scale-up would bring when applied to the smelting of UG2-rich concentrate blends. Superimposed on the high chromite content, was the low base-metal loading, mineralogical difficulties, and fine particle size that resulted from milling of all concentrates (especially UG2 and recycle materials within the smelter). Through a process of fundamental diagnoses of furnace run-outs and wear patterns observed during repairs, the main challenges operating this high-intensity furnace were identified as sulphur vapour corrosion of the copper coolers, uneven and unpredicted movements of refractory bricks with associated copper cooler lift and matte tapblock movement, the formation of three-phase 'mushy' zones, high refractory and taphole wear rates, uncertainty in matte level and associated insufficient matte buffer height, and high furnace operating temperatures. These factors seldom worked in isolation and will be explored in more detail in the paper. The variability in furnace feed characteristics led Lonmin to redesign Furnace No. 1, to invest in backup furnace capacity, and to invest in improved monitoring and control. These improvements consisted of online and high-frequency off-line monitoring of feed chemistry and mineralogy, online pressure monitoring of water-cooled circuits, an alternative matte liquid level measurement in the furnace, and electrode immersion estimation. Improvements were also made at the converters by installing and utilizing optical spectral analysis of the converter flame to characterize converter behaviour and achieve the desired iron end-point for white matte. This paper also briefly discusses the current and future expansion plans, as well as ancillary operations at the smelter such as flue-gas handling and materials handling.

Jan 1, 2011

By B. Zeifert, C. Martínez-Morales, A. Romero-Serrano, A. Pineda-Rivera, H. Martínez-Gutiérrez, G. Diaz-Sandi

In this work, the effects of CaO/SiO2 ratio and the FeSO4 and FeS2 contents on the stability of the mineralogical species in chromium-based slags were studied. The chemical stability was evaluated by leaching with an acid solution. The main Cr-compounds in slags with FeSO4 and CaO/SiO2=1 were FeCr2O4 and Ca3Cr2Si3O12, while Cr3S4 predominated in slags with FeS2. The slags with CaO/SiO2=2 mainly contained CaCr2O4. The highest Cr concentration levels in the leaching liquors corresponded to slags with CaO/SiO2= 2, and the lowest Cr concentration corresponded to slags with high FeSO4 or FeS2, owing to the stable binding of chromium in the compounds FeCr2O4, Cr3S4 and FeS•Cr2O3.

Jan 1, 2011

By B. Oraee

Accurate estimation of equipment costs is a key factor in feasibility study and evaluation of design alternatives of mining projects. In this paper, capital and operation costs of backhoe loaders are estimated using multiple linear regression (MLR), based on principle component analysis (PCA). These cost functions are consisted of five independent variables; bucket size, digging depth, dump height, weight and horse power. The MLR is conducted in two steps. At the first correlation between independent variables is omitted using PCA technique. Thereafter, MLR functions are established using selected significant PCs and total cost functions are constituted as functions of initial variables. At the end, accuracy of functions are evaluated using mean absolute error rate method.

Jan 1, 2011

By Hongbo Zhu, Jinhui Peng, Linqing Dai

"To optimize the process variables for making direct reduced iron (DRI) by microwave heating, the reduction temperature, reduction time and the ratio of coal to material were studied with the central composite design (CCD) and their interactions on the Metallization rate were also investigated. The predictive polynomial quadratic equations model was analyzed by ANOVA. Optimal conditions of making DRI can be concluded as follows: 28 min at 1139?, the ratio of coal to material is 20.95%. Under these conditions, the metallization rate is up to 97.06%.1. IntroductionThere are some technical problems in making direct reduced iron (DRI) or sponge iron using iron ore concentrates containing coal and lime. In reduction of the iron ore concentrates containing coal with microwave heating, the strength of pellets needn’t to be considered. It reduces the costs and improve quality of materials, but also eliminates the need for pellet preparation process, simplifying the process and achieving a cleaner production.Microwave energy is a clean energy, and has characteristic of selective heating. The speed of heating is also fast. It researched by Chen Jin that when the mole mass of C: O is 0.627 and the microwave power is 15KW, it only spends 15min from 15? to 1021.6? with 1 kg iron ore containing coal with microwave heating [1]. There are many factors affecting metallization rate. In order to find a suitable condition for reduction process, it is necessary to design a series of suitable experiments.Response surface methodology (RSM) is one of the relevant multivariate techniques which can deal with multivariant experimental design strategy, statistical modeling and process optimization [2–5]. It is used to examine the relationship between one or more response variables and a set of quantitative experimental variables or factors. This method is often employed after the identification of the vital controllable factors to find the factor settings that optimize the response. Designs of this type are usually chosen when a curvature in the response surface is suspected. The process optimization of the microwave reduced iron ore was seldom reported in literature. Hence the present work intends to assess the effects of variables such as reduction time, reduction temperature and the ratio of coal to identify the optimum conditions using a central composite design (CCD). The characteristic of product was assessed using scanning electron microscope (SEM)."

Jan 1, 2011