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By C. O. Swanson

THE purpose of this paper is to discuss the use of the dip needle in the field of mining geology. The subject matter is new only to the extent that it reflects the writer' s added experience in recent years. The treatment is brief, and those interested in a more extended analysis are referred to the articles listed at the end of the paper. In the discovery and tracing of mineral deposits, the clip needle, like most other geophysical instruments, can be used in two ways. One method may be termed direct; the other, indirect. The direct method is that of finding or following certain ore-bodies by virtue of their magnetic properties. Explicitly, or by inference, it is the method which many mining men and practising geophysicists have in mind when they consider whether or not a certain property should be studied by geophysical means. In the ideal case, this method demands little or no knowledge of geological conditions. The indirect method uses the clip needle as an aid to purely geological studies in working out the structure of a mineralized area. Although not as simple as the direct method, it enjoys a much wider field of usefulness. The writer's experience in the past fifteen years, which is believed to be typical, is that the indirect method finds application four or five times as often as the direct method. The indirect method is of particular value because it furnishes information concerning the relationship between geological structure and ore occurrence. Most mining engineers will agree that structural control is an important factor in the localization of ore deposits, and therefore that the subject under consideration is of some interest in mining geology. Specifically, then, the present purpose is to outline the principles and practice of using the clip needle in working? out geological structure.

Jan 1, 1941

By D. F. Malan

"This document highlights some of the topical problems associated with the design and support of deep tabular excavations in hard rock. The displacement discontinuity boundary element method has been used for at least five decades to analyse stress and displacement distributions around narrow width excavations with complex plan outlines. The assumption is made in most cases that the rock mass surrounding the excavation is perfectly elastic. Although this approach works well to minimise stress concentrations in practice, it has limitations as important parameters, such as the effect of mining rate, cannot be investigated. Recently, a limit equilibrium model has been studied as a means to enhance standard layout design exercises by including an interactive on-reef damage model. This approach can include explicit energy release dissipation computations. A second problem faced by engineers in the mining industry is the evaluation of pillar and remnant stress. The paper highlights two aspects namely the effect of element size in displacement discontinuity modeling on pillar stress and the difficulty to estimate the effect of total closure on the regeneration of stress in old mining areas. Regarding the support of the tabular excavations, current efforts are focussed on providing improved aerial coverage using hangingwall bolting and temporary nets. An unresolved issue is the installation of permanent mesh in low stoping width areas. INTRODUCTIONSince 1886, more than 50 000 tons of gold has been mined in the Witwatersrand Basin of South Africa (Hartnady, 2009). The nearby platinum mines also saw significant growth in recent years and more than 80% of the world’s platinum group metal reserves are contained in the Bushveld Complex of South Africa (Nell, 2004). Apart from the economic aspects, the mines served as an outstanding rock engineering “laboratory” for many decades owing to the deep, tabular nature of the excavations. The period from 1960 to 1980 was especially lucrative in terms of research and world-renowned researchers investigated the support and rockburst problems (e.g. see Cook et al., 1966; Salamon, 1968; Bienawski, 1973; Wagner, 1984). Many of the rock-related problems nevertheless persist up to the present day and this paper explores some of these problems and recent progress. The production of gold declined substantially in recent years (Hartnady, 2009) and well-directed rock engineering research can play a meaningful role to slow this trend. The objective of the document is to highlight critical areas requiring additional research and not to discuss the topics in detail. The reader is referred to the many references for additional information. The paper only focuses on three areas namely numerical modelling, pillar stress estimation and aerial support. Although these are diverse topics, it is included in one paper to illustrate the many unsolved and practical problems associated with deep tabular excavations."

Jan 1, 2015

By F. Chiesa

The permanent mould process, which is a favoured process for producing premium quality aluminium casting, is rarely used to produce magnesium alloy parts. This may be attributed different factors such as: the reservation with which the automotive industry considers using magnesium in structural castings; also the relative hot shortness of most magnesium alloys when compared to aluminium A356/357 is another factor. A third reason stems from the fact that the "heat content" of magnesium is much less than that of aluminium, resulting in the difficulty, for a relatively slow process such as permanent mould (versus pressure die casting), to reach a mould dynamic equilibrium temperature sufficiently high to avoid premature freezing and misruns. The present work will address this problem by carrying out controlled cycling of a laboratory mould, poured with aluminium and magnesium alloys. The influence of insulation of the mould and artificial electric heating on the run-in mould temperature will be determined experimentally. A thermal model will be sought for these thermal devices that will allow to predict the thermal behaviour of moulds of different geometry before a single casting is poured. The model will be tested on an industrial casting in a workshop environment.

Jan 1, 2006

By J. H. Brown

"THE need for continuing education has been recognized only in fairly recent years as a major concern of the engineering profession. Formerly, it was acknowledged that engineers were required, at least informally, to follow the professional literature and to give some attention to new technical and technological developments. However, those relaxed days, when progress could be followed in a casual or incidental evening of reading, have disappeared in these days of mushrooming information. The engineer is now in the position of the man trying to control the flow from a fire hydrant with a child's pail. Our problem is that of developing an effective flow system -be it trough, hose, pipe or a bigger pail.The first step in achieving an effective means for continuing the education process is to realize that the need for the system is really an outgrowth of an increasingly sophisticated society. It is merely one more symptom of that society; others would• include the facts that new engineering graduates are more highly trained than those of several years ago, that graduate schools are now the norm and that even some fairly recent technologies are becoming outdated. There-fore, let us examine the education-al systems from which the bulk of the increasing sophistication has grown."

Jan 1, 1966

By T. L. Sadlier-Brown, Andrew E. Nevin

"Common properties of commercial geothermal steam reservoirs are a magmatic heat source, the presence of water in vapour and liquid phases, and a surrounding seal of low permeability. The latter may be due to a combination of hydrologic load, argillic alteration and mineral precipitates. The temperature and pressure of vapour and liquid co-existing in equilibrium at maximum enthalpy may approximate 451°F and 450 psi. Steam reservoirs do not necessarily vent steam, but fluid which breaches and mixes with meteoric waters may emerge as hot springs. A systematic exploration program in Western Canada would involve a sequence of four stages utilizing geological, geochemical and geophysical techniques. The geochemical parameters of hot spring waters, such as silica, lithium and potassium content, give some indication of the basic reservoir temperature. The geology of Quaternary volcanics, including reservoir rocks, structure and rock alteration, is of prime importance. The costs of preliminary indirect methods are no more than those of oil and gas exploration; however, high temperatures compound drilling problems and costs. Exploration expenditures of twenty million dollars or so might be needed for a significant discovery. British Columbia and the Yukon Territory contain abundant Cenozoic volcanic rocks and over 50 thermal spring complexes (some with as many as 20 springs in one complex). Six regions are tentatively picked for exploration. Four regions coincide geographically with post-1980 electric power facilities and loads, and with possible alternatives such as potential dam sites. The Lillooet River region, Terrace region and Western Vancouver Island region have inferred potential for the existence of a plus-500-Mw geothermal reservoir. The Kootenay region may or may not have such potential. The Stikine River region has strong evidence of geothermal endowment, but the anticipated power market of the middle future might be only 30-50 Mw. The Whitehorse, Y.T., and Atlin, B.C., region has a belt of thermal springs and Recent cinder cones. The anticipated middle-future needs are real enough, but in absolute terms they are small, say 20-30 Mw. Legislation and policy on geothermal resource rights are lacking in British Columbia and the Yukon Territory at this time. As well as making policy, governmental organizations will play a significant role in geothermal development as buyers of steam or electricity. The role of industry is visualized as assuming the high-cost and high-risk exploration effort, provided the nature of this effort is understood by government."

Jan 1, 1973

By Peter Dunn

London Mining Plc. is developing an iron ore project in Sierra Leone. The Marampa mine is a brownfield development effort, having been operated by others since the 1930?s until low iron ore prices forced closure. Peak production of the prior operations was approximately 2.5 Mt/a in the 1960?s. Following civil war In Sierra Leone, London Mining obtained the mining license in 2006 and commenced activity to redevelop the Marampa mining and processing operations. There are two ore deposits of interest for development as well as a resource comprised of tailings from previous operations. Phase 1 will be the mining of the tailings resource with a 1.8 Mt/a plant producing 66 per cent Fe sinter feed, expandable to 3.6 Mtpa. The first phase is currently under construction with start-up expected in the third quarter of 2011. Phase 2 will include development of the two ore deposits. These deposits are weathered secondary ore and the main primary ore resource. Phase 2 is currently under prefeasibility study and targets a final 16 Mt/a concentrate production in 2016. Outotec partnered with London Mining on testing efforts to develop the magnetic separation flowsheet using SLon VPHGMS machines to process the Marampa material. This paper explains the flowsheet development process for the weathered and primary ores commencing with sample characterization and detailed parametric investigations to evaluate SLon performance. The final flowsheet configuration is explained, including expected circuit recoveries and concentrate quality, clearly demonstrating the performance of the SLon VPHGMS circuit in iron ore tailings treatment applications.

May 1, 2011

Overview n Why we audited the IRS n How we did it n What we discovered n What we learned n Where we are going next The unbroken chain of safety The Internal Responsibility System (IRS) The network of roles and relationships in a workplace, through which everyone works with mutual commitment to reduce or eliminate hazards.

May 1, 2003

By A. Robles-Vega

Personnel of Mexicana de Cobre, a subsidiary of Southern Copper located in Nacozari, Sonora Mexico have been working in the past few years on the development of a process to treat and manage, in an environmentally accepted practice, the residues and effluents generated during the process. To date, this team has been reviewing existing technologies and also has explored new alternatives. At the end of this phase, a novel, efficient and complete process has been configured which will be able to treat some solid and liquid streams such as Teniente converter dust, Peirce Smith converter dust, a Sb-rich precious metals slag, copper refinery electrolyte bleed, acid plant blowdown and an acid bleed of the precious metals plant. The process will consist of a leaching stage, followed by a very selective copper precipitation using novel technology which has been named as back reactions. After copper precipitation, impurities (As, Sb and Bi) will be precipitated mainly as arsenic trisulfide (As2S3) using H2S(g) which will be generated by means of a new process developed in our company. At the end of the process, small volumes of arsenic trisulfide will be vitrified and then disposed as a stable residue.

Jan 1, 2007

By Norman O. Lotter, André R. Laplante

"The pursuit of concentrator surveying for purposes of metal accounting or process optimization has not yet connected with the well-published realm of geostatistics. The reality of lognormality in time has seldom been discussed. One publication by Krige, 1962, examined such effects for a gold concentrator in South Africa, towards an information system that would provide feedback to the mining and surveying teams on grade control of ore mined.During present studies which are designing and testing a new survey model, called statistical benchmark surveying, it was found that the distributions of feed, concentrate and tailings bear significant residual signs of the parent lognormality in space. The multiple hosting of paymetals in different mineral species complicates the understanding of these distributions. These features have to be recognized and treated in order to perform appropriate quality control on the diagnostic sampling performed in the pursuit of statistical benchmark surveying.It is shown in this paper that the above two features can actually be used to advantage in the diagnosis of continuous periods of operations data ahead of such surveying, including the estimation of recoverable paymetals in flotation tailings from a graphical method.INTRODUCTIONAssessment of Concentrator PerformanceMilling and flotation, sometimes accompanied by gravity separation, are well-established unit processes, which have traditionally been used to treat ore that has been mined. This is because these processes liberate, then separate, the valuable minerals, which contain paymetals, from host gangue. This is often done by a combination of crushing and grinding processes, or autogenous grinding, to liberate the paymetal minerals, followed by gravity separation and/or flotation, to separate these valuable minerals into a concentrate, or several concentrates. These concentrate(s) have a lower bulk than the parent ore from which they are derived. Further, they contain a high percentage of the valuable minerals. Accordingly, they are more economically treated in subsequent beneficiation processes than the ore from which they were produced."

Jan 1, 2005

By C. W. Drake, J. H. Walsh

"The Canadian Carbonization Re-search Association was formed during 1965, with seven founding members representing four integrated steel companies, two coal companies and one high-temperature tar processing company. The purpose of this paper is to review the circumstances which led to the formation of this new research association and to discuss its general objectives. Also discussed will be the organization of the Association, the nature of its relationship with the Department of Energy, Mines and Resources in the early stages, and some of the technical programs which have now been initiated."

Jan 1, 1967

By D. A. Livingstone

"INTRODUCTORY REMARKS BY PANEL CHAIRMAN - D. A. LIVINGSTONEThe mining industry has progressed significantly from the dusty mines and mills of decades past to the modern processing complexes of today, and improved technology has made great strides in eliminating debilitating lung discuss. More recently, the public's environmental awareness is also working to enforce more stringent regulations and controls in tl1e matter of dust in working places.There are numerous excellent texts and handbooks outlining the principles of collection of dust produced in the various unit operations entailed in the crushing, screening and the transport of ore. However, it is painfully obvious that dust emanating from belt return idlers and scrapers, take-up pulleys, skirting, larger and deeper chutes, clean-up operations, etc., which I choose to refer to as fugitive dust, presents some seemingly unmanageable difficulties, or at least difficulties inordinately costly to correct. Possibly static electricity is adding to the difficulties. In my view, these problems are magnified in many of our B. C. operations where ore from open pit mines in cold climates is frequently crushed in unheated buildings, thereby precluding the simple and obvious use of water sprays for dust suppression.It is hoped that the presentations and discussion which follow will emphasize some of these unusual problerr.s and suggest corrective measures, either tried or planned."

Jan 1, 1976

By J. L. Huisman

Bio(hydro)metallurgy is the latest development in the ongoing search for efficient and economic metal winning processes. In addition to bioleaching, other biotechnology-based applications are becoming more and more accepted. In this paper the THIOMET process for general effluent treatment is described. With this process, it is possible to produce sulfide on-site and on-demand and to use the sulfide to precipitate metals, even selectively when required. The process is ideally suited as a treatment to remove metals after, for example, an acid regeneration process. Another process is proposed that deals with stainless steel pickling bleeds. Such effluents typically contain nitrate, iron, nickel, chromium(VI) and other species. This one process handles these compounds, as well as other metals.

Jan 1, 2006

By N. Saracoglu, J. P. Golightly, R. H. Wallis, J. J. Brummer

"The McClean uranium deposits are located 11 km west northwest of the Rabbit Lake Mine. Their average grade is 1.8 % U3O8 , and they contain 6. 350 tonnes of uranium oxide in seven pods of variable grade and mineral assemblage. They are hosted by both basal Athabasca Group and the regolith developed on the underlying crystalline basement. The major mineral facies are: sulphide, arsenide, 'bleached', and hematite, with the important uranium minerals being coffinite, uraninite and pitchblende. Abundances of carbon and sulphur isotopes are consistent with their derivation from pyritic graphite in basement gneisses. Isotopes of oxygen and hydrogen suggest equilibration at temperatures of about 200°C. Ar39/ Ar40 age determination of illite associated with ore suggest mineralization began about 1300 m.y. ago and that significant alteration had ceased by about 1170 m.y. ago though Pb/ U data suggest the deposits continued to evolve into the Mesozoic.IntroductionThe McClean deposits lie on the eastern side of the Athabasca Basin of northern Saskatchewan where they are part of a cluster of uranium deposits lying west of Wollaston Lake (Fig. 1). The general stratigraphy is schematically portrayed in Figure 2 which emphasizes that mineralization is hosted by both the Athabasca Group and the underlying regolith and also that the deposits are preserved at depth and have not suffered from preand post-Pleistocene weathering and erosion. This circumstance, combined with their simple shape and the presence of seven separate zones of mineralization (pods) allows a description, based on over 450 fully cored drill holes, to be made of the wide variation in chemistry, grade, alteration patterns and position relative to the sub-Athabasca Group unconformity. Ar39 / Ar40 age determinations have been made of illites associated with regolith, Athabasca Group and mineralization and studies are in progress on C, S, 0 and H isotopes of mineralized material and host rocks. Only some of these data have been published; Brummer et al., (1981); Golightly et al., (1982); Bray et al., (1982); and Saracoglu et al., (1983). The only other published data on McClean geology are by Tremblay (1982, 1983)."

Jan 1, 1986

By W. Gordon Muir

This paper deals with the exploration, development and current operations of the salt mine at Goderich, Ontario operated by the Sifto Salt Division of Domtar Chemical Limited. The rock salt is obtained from a bed 1,760 feet below the surface, 75 feet thick, extending under Lake Huron. Annual production is in excess of one million tons. Large mobile equipment is used. Details of this equipment, as well as the shaft layout, which permits the equipment to be lowered underground with a minimum of trouble are outlined. Mining, crushing and screening procedures' are rev1ewed. Reference is also made to productivity salt distribution and uses.

Jan 1, 1967

By J. Duby

"A description is given of a series of tests performed to determine the comparative effects which dynamic and static straining, in compression, have on the physical strength properties of mild steel and an aluminum alloy. The dynamic deformation was imposed during the passage of single stress pulses of about 100 micro-second duration. These pulses were recorded with strain gauges mounted near both ends of the specimen. The resulting records were analysed using a simple wave theory; there from the dynamic stress-strain curves for the respective metals were deter-mined and were then compared with the static stress-strain relation. The respective hardnesses of the metals after deformation are evaluates by means of static stress-strain curves in compression. The micro-structures of the metals before and after deformation are also shown. It is observed that dynamic de-formation considerably modifies the rate of strain hardening. This modified hardening appears to be persistent. The observed differences in physical strength properties and micro-structures are discussed in the light of the accepted dislocation theory for metals."

Jan 1, 1960

By Philip J. Guerney, S. O’ Leary, André R. Laplante

"Concentration of dense mineral phases (s.g. greater than 7) for characterisation of individual particles and mineral grains by electron microscopy is a well established technique for the detection and characterisation of valuable mineral phases. This presentation describes the type of data that can be generated when both the concentration and characterisation steps are carried to higher levels than typical. The concentration step is the gravity recoverable gold (GRG) protocol that has been used for over 100 ore samples. This protocol yields three concentrates that represent three progressive degrees of grinding and liberation. Three ore samples were subjected to the GRG protocol and three size classes of each concentrate were characterised using the mineral liberation analyser (MLA), an automated, EDX-based tool. This presentation briefly presents GRG and MLA technology, and then focuses on the results obtained: photos, images and databank, the latter used to evaluate the extent of particle liberation and particle shape.INTRODUCTIONThe practice of gravity concentration prior to characterization of mineral samples using electron beam microscopy is solidly established. Typically, a dense liquid such as tetrabromoethane (density: 2.97 g/cm3) is used to reject the light phase, typically carbonates and silicates. The heavy phase, mostly sulphides, oxides and precious metals, is then mounted in a polymer matrix and examined using beam microscopy.Both the pre-concentration and the sample preparation/examination steps have seen significant advances over the past ten years, but are not without problems. A major issue of preconcentration is that most dense liquids used are toxic, tetrabromoethane being a prime example. More recently, a dense liquid with little or no toxicity (sodium polytungstate, distributed by Sometu Inc.) has become commercially available, but its use is limited to relatively low s.g. splits around 3 g/cm3. Dense liquids are viscous, and their use is limited to particles coarser than 37 µm, although centrifuge separation can probably lower this limit to around 10 µm. Magnetogravimetric separators can achieve much higher specific density cuts, but upgrading below 100 µm or in the presence of magnetic minerals remains a problem. The use of centrifuge separators such as the 3-in Knelson Concentrator (KC MD3) or the Falcon 4-in SB (SB4) is particularly attractive since these units can easily process large masses (by laboratory standards) and achieve a cut density well above those of dense liquids."

Jan 1, 2003

By Sakellariou M., Ferentinou M.

Determination of the nonlinear behavior of multivariate dynamic systems often presents a challenging and demanding task. Therefore, complex geomechanics systems are an ideal area for the application of intelligent methods. Often the physical problem is controlled by nonlinear equations, conveying to the use of neural networks. Hudson, (1992a), aiming at efficient engineering modelling and design, introduced and developed Rock Engineering Systems (RES) approach, through the implementation of generic interaction matrix GIM. This approach has been used for a wide variety of rock engineering and other problems, resulting in many case studies available, which illustrate the application of RES to rock engineering problems. Considering the spectrum of the coding methods for the Generic Interaction Matrix, we suggest an objective coding approach. Among the five proposed coding GIM methods, the coding method according to the slope of Pi and Pj relation is relatively accurate, but it might be difficult or impossible to establish or estimate the exact relation of Pi vs Pj for most of the variables involved within a rock engineering system. Self organising maps, are a special type of unsupervised artificial neural networks, which can learn from complex, multidimensional data, and transform them to visually decipherable clusters. The proposed, coding of the GIM, is performed through the combined use of scatter plots produced through, (SOM), and the coding according Pi vs Pj slope. Naghadehi et al., (2013) constructed a database of worldwide experience, in open-pit mine slope stability, the selection of the principal factors was based on Hudson (1992a) who proposed an ‘atlas’ of factors affecting the stability of rock slopes. Slope classification was performed according to status of stability. The rating of the GIM matrix was completed, coupling scatter matrix produced by SOM training, and Pi vs Pj slope plot. Results refer to the identification of clusters, according to status of stability within the original multivariate data set, and the rating of the principal factors according to the dominance and interaction intensity within the open pit mines RES.

Jan 1, 2015

By C. I. Godwin

"The relative-value (R-value), discrimination-factor (D-factor), and vector-ratio (V-ratio) method (RDVM) provides a geological knowledge-based statistical and geological-genetic interpretation scheme for geochemical data that enhances discovery in geochemical exploration. The practical advantage of RDVM is that it synthesizes geochemical features geologically related to ore-deposit discovery in three steps: reclassifying element concentrations using log-probability plots into R-values; calculating geologically defined D-factors from R-values; and determining V-ratios. D-factors are the sum of R-values, divided by the number of R-values summed. Based on the analyses selected, D-factors mimic rock or mineral deposit signatures. V-ratios refine interpretations of rock type and vector to orebody locations.RÉSUMÉ La méthode de la valeur relative (valeur R), du facteur de discrimination (facteur D) et du rapport de vecteurs (rapport V) (RDVM), fournit un schéma d’interprétation des données géochimiques basé sur les statistiques et les connaissances géologiques et la génétique géologique; ce schéma contribue aux découvertes en exploration géochimique. L’avantage pratique de la RDVM est qu’elle fait la synthèse des caractéristiques géochimiques reliées géologiquement à des découvertes de gisements de minerais en trois étapes : une reclassification des concentrations des éléments au moyen de courbes de probabilité logarithmique en valeurs R; un calcul des facteurs D définis géologiquement à partir des valeurs R et la détermination des rapports V. Les facteurs D sont la somme des valeurs R divisés par le nombre de valeurs R additionnées. Selon les analyses choisies, les facteurs D imitent les signatures de la roche ou des gisements minéraux. Les rapports V peaufinent les interprétations des types de roches et dirigent vers des emplacements de gisements."

Jan 1, 2016

By Dart Wantland

"AbstractThe scope of geophysics in civil engineering and the nature of exploration geophysics are briefly discussed. Engineering problems amenable to geophysical attack are illustrated by specific examples. The various methods available, accuracy of results, and costs are treated. The possibilities of new uses of geophysical techniques are pointed out.IntroductionTHE SCOPE of geophysics in engineering is different than in oil or mining exploration. In civil engineering, geophysics solves specific problems; as for example, what is the depth to bed-rock along the axis of a proposed dam? The area to be surveyed is of limited extent, and the subsurface information .sought is relatively near the surface. The engineering geophysicist is not called upon to investigate geological basins or extensive mineralized areas or to probe for data to thousands of feet in depth. The geophysical tools employed in the three fields are, however, quite similar; the differences are mainly in the objectives.The Natural Geophysical ExplorationThe terms geophysics and geophysical exploration have been used heretofore and will .be employed in what follows. The question is, therefore, What is geophysical exploration?Geophysical exploration is a line of field work where measurements are made at the ground surface with special instruments to get geological subsurface information. Briefly stated, geophysics is a form of exploration that supplements geological work. It is a blend of physics and geology since physical measurements are made •at the surface of the ground that can be interpreted in terms of subsurface conditions."

Jan 1, 1953

In most instances, the preferred mining methods in steeply dipping narrow vein deposits are selective methods such as cut and fill or shrinkage. The main advantage of these methods lies in the higher degree of control over dilution that can be achieved. However, where ore body geometry lends itself to it, high yield bulk methods can also be attractive. Higher productivity (and the associated lower costs) and lower worker exposure are some of the significant advantages that have made such methods so popular. The Lapa gold mine located in North-Western Quebec uses the long hole mining method (with cemented rock fill) very successfully despite challenging ground conditions. This paper focuses on the experience of the mine with regards to drilling and blasting practices. Firstly, the reasons that prompted the selection of this mining method at Lapa are examined. Secondly, the challenges that the difficult ground conditions found at Lapa pose to drilling and blasting are discussed. Finally, the results of trials of different drilling and blasting strategies that were performed at the mine are presented with particular emphasis on the lessons learned.

Aug 1, 2013