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By M Akbarpour, M Osanloo

In mining industries, materials handling costs represent a significant component of the operational cost. A variety of methods have been applied in surface mine equipment selection in order to select the suitable loading system with the lowest loading operation cost. These are queuing theory, bunching theory, linear programming and genetic algorithm. Among them, genetic algorithm is a simple method and applied for preliminary selection of the loading system. In this study, gathering information from anomaly No 2 of Gol-e-Gohar iron mine of Iran, loading system (number and its capacity) has been optimised by genetic algorithm. The study results showed that two shovels 8.25 m3 are required for the removal of 60 million tonnes of overburden. After removal overburden, these two shovels contribute to the extraction of 42 million tonnes of ore with a stripping ratio of 1:1.

Jan 1, 2007

A mining operation can be identified as demonstrating prudent management when a number of vital characteristics are evident.All risks and opportunities that are critical to the on-going success of the operation have been identified and are being effectively managed. All significant tasks and events are plan driven. All levels of management visibly support the policies of the operation through their attitude, behaviour and actions as well as words. Supporting evidence for required activity and the outcomes is readily available. Improvement mechanisms are working to advance the key business processes. Everyone is working towards satisfying the needs of the stakeholders of the operation. When these characteristics are integrated with the satisfaction of all legislative requirements, all industry codes and optionally all relevant international management system standards then an operation is fulfilling all the requirements of a Due Diligence Process. The majority of mining operations do not show all of these characteristics and therefore unnecessarily suffer from missed profit opportunity and constant cost pressure, less than acceptable safety and health and environmental performance and consequent poor relations with employees, unions and regulators. In these operations the characteristics to be observed are quite different.Serious incidents are occurring with no sign of a rate decrease. The operation lurches from one panic ituation to another. Management are absent in their leadership, but very active in developing rules and enforcement methodologies. The operation has no history. Re-inventing the wheel with employees who come and go at an alarming rate seems to be forever occurring. All efforts are directed at controlling the business outputs with a strong emphasis on blame. Everyone is trying to look busy to avoid the ever-present cost reduction threats. To change to more prudent management utilising a Due Diligence Process is not theoretically difficult. However it does take clear direction, focussed efforts, supporting actions with appropriate tools and perhaps most importantly an internal desire and drive to become such an operation. A Due Diligence Process is about doing the important things that have to be done, providing the understanding of why they are important, demonstrating proof of activity and effectiveness, and leading the way through effective management.

Jan 1, 1998

By B T. Qin, C Zhu, Y W. Jia, Y Lu, F L. Li, Q L. Shi

Air leakage through rock fractures in coal mining is a major cause of coal spontaneous combustion. In order to overcome the deficiency of the existing fire control technology and prevent coal spontaneous combustion by isolating coal from oxygen, the article proposes a novel technology of inorganic solidified foam (ISF) with high expansion to fill fractures effectively. ISF consists of fly ash, cement, setting accelerator, redispersible polymer powder, water and aqueous foam. For preparing homogeneous and stable ISF, a preparation system with a pore type foam generator, a mixer device installed with a hollow shaft and helical blades, air compressor, slush pump and monitoring instruments was developed, and the working principles of key devices were elucidated. Based on a series of experiments on the different ratios of each component material and technological parameters of the preparation system, ISF with a foam expansion ratio of 8~10 and dry density of 250–400 kg/m3 was prepared. The relationship between elastic compressive strength, modulus of elasticity and density was summarised. Based on the injection experiment for fracture of loose coal pile with high temperature, the characteristics of sealing air leakage, compressive strength, thermal insulation, flow and cooling of ISF in the fresh state were investigated, indicating that ISF can effectively cut off the air leakage and cover the coal sample to reduce the temperature in the earlier stage, and ISF can remain stable and not crack. The ISF was applied to Luwa coalmine to seal small coal pillar pressure fractures and loose coal fractures in goaf. After press-casting the ISF in Luwa coalmine, the pressure-difference of inner-outer increased, meaning the effect of external conditions on the pressure-difference decreased, showing that it could plug the air leakage effectively.CITATION:Qin, B T, Shi, Q L, Lu, Y, Zhu, C, Li, F L and Jia, Y W, 2015. The novel technology of inorganic solidified foam with high expansion for preventing coal spontaneous combustion, in Proceedings The Australian Mine Ventilation Conference, pp 121–126 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

An international raw material partnership, a $164 million 900,000 long ton per year aluxAna plant; an ideal location at Gladstone, Queensland, Australia - this is Queensland Alumina Limited, on stream in 1967 expanded 50 per cent by the end of 1968. Queensland Alumina Limited is the world¦s most modern alumina refining operation which is owned by an international consortium of four companies; Kaiser Aluminum & Chemical Corporation of the United States with 52 per cent; Alcan Aluminium of Canada with 20 per cent; Pechiney of France with 20 per cent; Conzinc Rio Tinto of Australia, 8 per cent. Q.A.L. operates as a co-operative -- the partners do not draw profits from the venture. Instead, each member of the consortium draws alumina in proportion to his share of the ownership. The method of disposal of this alumina is for the partner to decide.

Jan 1, 1969

By Dunstan N, Valentine C

Gas power was first used on the Sons of Gwalia mine in January 1911, when a twin-cylinder Crossley engine of 167 hp was installed to belt-drive a 112 kw 550-volt ac generator. This engine was connected with a No 8 Crossley up-draught suction gas producer, using mulga charcoal as fuel.A second Crossley engine, of 400 hp direct-coupled to a 550-volt ac generator, was installed in 1912, and operated by a down-draught wood producer.This was followed by a large Kynoch twin tandem four-cylinder engine, rated at 660 hp, sea level, with a rope drive to the crushing and treatment sections of the plant.These engines operated until January 1921, when the plant and power house were destroyed by fire. After the fire, both Kynoch and second Crossley engines were salvaged and reconditioned and they continued to give useful service for some years.

Jan 1, 1932

By Daoust G, Dubois JF

The optimal sequence of decisions on rates of production and cutoff grades is obtained by a dynamic programming model. The main parameters are : 1. the size of the deposit, average grades and grade distributions, 2. the operating costs of mining and concentration, 3. the investments in mine and mill, 4. the smelter charge, 5. the price(s) of the metal, 6. the recovery and the grade of the concentrate, 7. the rate of interest, 8. the taxation formulae, 9. the upper limit to rate and the rate interval and 10. the upper and lower limits to cutoff and the cutoff interval. An amount of ore can be mined at various rates while applying various cutoff grades. It is assumed that a decision to mine at a certain rate during a period conducts to a certain state regardless of the cutoff grade. This assumption which is valid for several

Jan 1, 1977

By Ellyett C. D

This paper is an appraisal of the application of optical-mechanical-scanners operating in the non-photographic infrared wavelengths (3-5 and 8-14 micrometres) to mineral exploration in Australia. Pundamental principles of the operation of airborne scanners and their data output, thermal infrared (IR) imagery, are summarized. It is contended that thermal IR imagery often depicts the distribution of electromagnetic radiation emitted from earth surface materials better than aerial photographic techniques because optical-mechanical-scanners sample wavebands which straddle the wavelength peak of earth surface emission. To illustrate the geological features which such scanners can depict, reference is made to thermal IR imagery of a number of areas in Australia where the technique has been applied for exploration purposes. The images demonstrate that this technique can detect structural features like faults and folds, stratigraphic data by distinguishing different rock types and delineating their

Jan 1, 1973

By Mowat BA, Leach TM

The Morobe Goldfield in Papua New Guinea has produced in excess of 120 tonnes of gold from predominantly alluvial sources. Hardrock gold has been mined historically at Wau (23t) and Edie Creek (40 and geological resources have been established at Hidden Valley (780, Kerimenge (360 and Hamata (30t). Numerous prospects have also been identified within the goldfield. Primary gold mineralisation is related to intrusion of dacitic to andesitic Edie Porphyry (2.4 to 3.8 Ma), often with associated diatremes, which have intruded along major regional structures. A full spectrum of deposit styles from proximal (mesothermal) to distal (epithermal) to the porphyry source is recognised. The transition between the proximal and distal styles is recognised both between deposits and within an individual deposit. The deposit styles should be termed porphyry related gold mineralisation rather than given the generic epithermal and mesothermal labels.

Jan 1, 1995

By A R. A Gomes

The Metropolitan Rapid Transit Authority (MRTA) Initial System Project (ISP) - Underground Structures North, UGN, is the northern section of the blue line, which is the first stage of an underground mass transport rail system of 77 km to be implemented in the central area of Bangkok, Thailand. The UGN section (Huai Kwang - Bang Sue) consists of approximately 8 km of twin single track bored tunnels, nine underground stations and some short cut and cover tunnel sections. The paper focuses on the main issues involved in the structural design of the precast concrete lining, which is the definitive structural support of the bored tunnels. It includes an overview of the site and geotechnical conditions, specific properties of precast concrete linings, ground-structure modelling, approach for the assessment of load conditions and respective sectional forces and particulars of the detailing of the reinforcement and the segment testing program.

Jan 1, 1999

Declining from surface provides access, haulageway, ventilation and provision for ser- vices for stoping and development. Three boom jumbos and 3.8 m3 capacity diesel loaders are used in decline development, the majority of which is driven at a gradient of 1 in 9. Primary ventilation is drawn from the mine through raisebored airways and high pressure contra rotating fans provide secondary ventil- ation. To meet schedules a special decline crew was formed on similar lines to a mining con- tractor. The basis of payment for the mining party was changed and the net effect was to accelerate development. Ground conditions demand constant support and this is achieved with chemical anchor rock bolts, multistrand grouted bolts and shotcrete. Major local shear zones are encountered and when they are to be driven through, a combina- tion of the above methods, involving a spiling technique, is used.

Jan 1, 1977

Much has been written about leadership over the years. It is probably one of the most written about but least understood and defined concepts in business. Leadership and management are often confused and blurred, and inspirational words such as mentor, coach, motivator and the like, are often interspersed when describing a leader. There are a few things we do know about leadership:The only thing common to all leaders is that they are different.Leadership is not the sole domain of business; it applies to every aspect of human endeavour. We are all required to lead at times, and we all have it in our ability to lead. There is no set of predetermined competencies, which a leader must possess to be effective. Hence there is no course in the world that can teach you to become a leader. There is no such thing as the perfect leader. Leadership is a verb, not a title; you actually have to do it to be judged a leader. All leaders no matter how you define the term, must leave a legacy. Thus in the busy world we all live in, what are the lessons in leadership that we can all learn from, that will assist us all in our pursuit of leadership. The purpose of today is to put forward a framework for leadership that I have been researching and working on for many years. It is not the definitive framework, merely a framework. Out of today you will take your own collective thoughts, learnings, observations, experiences, education and training, and collective wisdom, and apply it to yourself.

Jan 1, 2004

By P Marianelli, J Theiler, B Beamish, A Spillman

The presence of reactive pyrite in waste rock contributes to the hazard of spontaneous combustion in emplacement facilities as it acts as an initiator of self-heating at low ambient temperatures. Organic carbon also present in the waste rocks acts as a fuel at elevated temperatures above 120°C and can lead to thermal runaway resulting in eventual ignition. A new laboratory test method (adiabatic incubation testing) is now available that can identify the presence of reactive pyrite and quantify the self-heating behaviour of the waste rock. McArthur River Mine has a waste rock profile that contains pyritic shale units, which have created spontaneous combustion events in the past. A systematic sampling and testing program is underway to characterise the spontaneous combustion hazard likelihood of the McArthur River Mine waste rocks to provide a sound database for future mine planning of the waste removal and emplacement. This paper presents some initial outcomes of this program and shows the leading practice in spontaneous combustion hazard assessment and management that has been adopted at McArthur River.CITATION:Beamish, B, Marianelli, P, Theiler, J and Spillman, A, 2018. Spontaneous combustion hazard assessment of McArthur River Mine waste rock, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 422–426 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By P Albert, S Crispin, J Hertrijana

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Martabe gold mine is Indonesia’s largest precious metals-only producer and is also one of few significant hard rock mine developments in the past 15 years. Martabe is located on the west coast of the island of Sumatra in the North Sumatra province. The mine commenced operation in mid-2012, producing over 280 koz of gold and 1.5 Moz of silver in its first full year of production.Martabe consists of a cluster of six currently identified high-sulfidation epithermal deposits. The deposits lie in a north–south corridor with an approximately 8 km strike length and 1.5 km width. The total Measured, Indicated and Inferred Mineral Resource Estimate of the deposits is currently 8.2 Moz of gold and over 75 Moz of silver.The exploration program at Martabe has added more than 2 Moz of gold and 15 Moz of silver to the Mineral Resource estimates (Measured, Indicated and Inferred categories) since G-Resources acquired the project in 2009. This has been achieved at an average cost of US$17 in exploration expenditure per ounce of resource added, which includes helicopter-supported drilling programs in rugged forest terrain.The factors that led to this exploration success at Martabe include: in the first instance and most importantly, recognition of the geological potential of the mineralised system continually updating and improving ‘orebody knowledge’ and applying new ideas to the exploration program ongoing engagement and consultation by world professionals with geological expertise in similar systems ongoing executive management support for the program the high quality of work completed by previous owners a strong focus on quality control, staff development and operational safety, with the JORC Code (in particular Table 1 of the Code) as the underlying basis for quality control continual and positive engagement with government, community and other external stakeholders.This paper will discuss in detail the first of these two factors. It is important for the modern exploration team to recognise that mineral potential on its own is not sufficient for exploration success, so this paper will touch on the other factors as secondary but crucial considerations.CITATION:Crispin, S, Hertrijana, J and Albert, P, 2015. Exploration success at the Martabe gold mine, Indonesia, in Proceedings PACRIM 2015 Congress, pp 567–572 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By F Faraj, M Pal, M Haest, M Bradshaw, H Lang, K Hume

MineSense Technologies Ltd. is revolutionising grade control at mining operations by installing ShovelSense® sensors on buckets that measure the grade of every load before it is dumped in the truck. This allows the mine to exploit grade variations at a resolution that was not available before, reducing the amount of ore loss to the waste stream and removing waste from material destined for processing. These changes dramatically improve the profitability and sustainability of mining operations. ShovelSense relies on X-ray fluorescence analysis of the rocks as they flow in the bucket and is integrated with fleet management to direct the trucks to the right destination. Lab simulations of ShovelSense measurements on porphyry copper ores show correlations between predictions and lab measurements at 0.98 r-squared with a coefficient of variation of 10 per cent. Visualisation of copper grade predictions in three dimensions shows a reasonable match with the dig plan, but with local changes in the ore-waste contact due to more accurate contact identification, related to blast movement and other mining factors. Correct delineation of these contacts ensures ore trucks are not sent to the waste dump and waste trucks are diverted from the crusher, creating enormous value for the operation and the environment.

Mar 22, 2022

By S Khadhraoui, T Yusuf, C Kirmse, E Hecker, R Degel, A Akouch, N Borowski, M Reuter

For an optimal design and control of metallurgical processes, a deep understanding of the thermodynamics of the governing reactions is required. Modelling the thermochemical behaviour of those reactions is complex, as it involves multi-component and multi-phase systems. For this purpose, thermodynamic computing systems such as FactSage™ (Bale et al, 2016), which combine Gibbs energy minimisation routines with large databases of optimised thermodynamic data of solutions and compounds, have been used within the SMS group GmbH. Recently, the successful integration of those thermodynamic computing systems into the digital platforms of SMS has been achieved through ChemApp, which made running complex thermochemical calculations in Python-integrated development environments possible. ChemApp is a programmer’s package for thermochemistry and incorporates the Gibbs energy minimiser of FactSage™ as reported by Petersen and Hack (2007) as well as by Zietsman and Petersen (2018). The digital platforms link the fundamental and the industrial aspects together and can be applied as a process advisor, or for the evaluation of the environmental footprint and the economic implications of different process routes, as discussed by Reuter (2023). Two examples illustrating the progress of the developments in this regard will be introduced: 1. The Tilting Refining Furnace (TRF) for copper scrap recycling and refining to anode copper (the BlueControlApp). 2. Dephosphorisation control for the oxygen steelmaking process (Basic Oxygen Furnace (BOF)).

Jun 19, 2024

By M I. Pownceby, A Torpy, C Johnson, N C. Wilson

To extract uranium from low-grade, calcrete-hosted uranium (CHU) ore is challenging owing to the presence of carbonate and swelling clay gangue minerals that require an alkaline lixiviant to be used. Western Australia possesses ~75 000 U3O8 t in CHU resources. Improvements to alkaline leach extraction practices would improve the economic potential of these deposits.A column leach study of CHU ore was run for 105 days using an alkaline carbonate-bicarbonate lixiviant. The uranium content of the liquor plateaued after 75 days at ~275 mg U/L; the calculated maximum solution capacity was 800 mg U/L. Spiked peaks and troughs were seen in the data set beyond the 60th day, where concentrations ranged from 220 - 290 mg U/L, indicating possible cyclic uptake and loss of uranium from the solution.Pristine and leached ore samples were geochemically analysed and mineralogically characterised at high resolution using a field emission gun-electron probe micro-analyser (FEG-EPMA). Results showed that leached ore samples from the top of the column contained less carnotite than pristine ore. In contrast, leached ore samples from the column base contained regions with more carnotite than pristine ore, indicating precipitation. Three carnotite grain micro-structures were identified in the leached ore; fan-spherulite, granular and core-shell cubes, with evidence for multiple growth phases.Evidence of carnotite precipitation was seen at the edge of and in pore spaces within montmorillonite and dolomite grains. The point of zero charge of both minerals is lower than the pH of the lixiviant (pH 10.8), thus the mineral surfaces are negatively charged and would not attract UO2(CO3)34- ions out of solution. Similarly, the decrease in the uranium content of the lixiviant is not attributed to super-saturation, as this was unlikely to have been achieved. Work is ongoing to understand the reason for carnotite precipitation and the fluctuations in the lixiviant uranium concentration that are seen.CITATION:Johnson, C, Pownceby, M I, Wilson, N C and Torpy, A, 2013. Microscale characterisation of pristine and processed ore - implications for leaching calcrete-hosted uranium ore, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013 , pp 303-316 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 29, 2013

By A J. Clough

There has been an unprecedented rise in the fatality rate in the Australian mining industry over the last few years. The factors behind this rise are not clear; however, it is noted that the increase in fatalities has occurred during a fall in commodity prices.This paper examines prevention methods and systems to deal with hazards that have the potential to result in either single or multiple fatalities. Managing the risks associated with mine ventilation is used to illustrate the principals behind the approach.The paper also touches on the broad science of human error and proposes a multifaceted approach to controlling and preventing fatal risks.A summary of the steps involved in developing an effective principal hazard management plan is provided.CITATION:Clough, A J, 2015. Ensuring an effective principal hazard management plan, in Proceedings The Australian Mine Ventilation Conference, pp 3–8 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By G Stephenson, G MacDonald, A Yeomans, S Sinclair, V Knott

Rio Tinto has actively committed to progressive reclamation, concurrent with commercial operations, at its Diavik Diamond Mine. The most significant piece of progressive reclamation undertaken at Diavik to date has been the construction of an engineered thermal rock cover for the mine’s largest waste rock storage area. This 80-metre-tall and 2000-metre-long area is known as the Waste Rock Storage Area – North Country Rock Pile (WRSA-NCRP) and contains the operationally segregated potentially acid-generating waste rock mined over the last 20 years. As part of the mine plan, an opportunity was recognised where a limited 1.5 per cent of the WRSANCRP surface area was required for storage of the balance of life-of-mine generated waste rock and a decision was made to advance the closure design almost a decade ahead of final closure. With over 12 860 000 tonnes of material placed and 57 443 dozer hours logged since cover construction, progressive reclamation on the WRSA-NCRP is scheduled to be complete in mid-2023, three years before planned cessation of commercial operations in 2026. The progressive closure of the WRSA-NCRP demonstrates Rio Tinto’s commitment to not only closure, but modern best practices with integrated mine closure. Over the past seven years, Diavik has overcome multiple implementation hurdles for this project including the psychology of operational standby, the financial mechanisms required to support closure, working within the constraints of a mine plan and the associated operational organisational structures. This paper outlines the lessons learned to provide an example of successful integrated mine planning for closure. The North Country Rock Pile project had three major learnings which resulted in an effective organisational structure that allowed for the execution of an integrated planning model for progressive closure. The initial hurdle the project faced was adapting the psychology of an operational open pit mining team. The team was an experienced mining group who came in with the perspective to target the shortest haul possible resulting in the initial perception that the longer haul of material to the NCRP was an un-necessary task impacting operational performance metrics. After the installation of an improved dispatch tracking system and performance metrics, it was possible to demonstrate that the mine was shovel constrained. This showcased the short haul was generating an increase in queue time not production. With updated performance metrics, the team was aligned to target a decrease standby through haulage to the NCRP. These performance metrics had to be reinforced by financial mechanisms. The operations team was able to offset costs by charging time to the capital project set-up for the closure of the NCRP. This allowed the operations team to receive credit for time that would have otherwise likely been standby. As well, the progressive closure project was able to receive the benefit of not having to incur costs for the drill, blast and load as that was done as part of the operation. This was a significant benefit to the project and one of the primary drivers for the early approvals of the work as the project costs were limited to the incremental haulage distance and placement of the material. Life of Mine Conference 2023 | Brisbane, Australia | 2–4 August 2023 114 While the combined operational and progressive closure approach provided financial advantages, it did result in the project being constrained by the operational activities. A traditional capital project is managed through a linear execution plan where the deliverables within a project are within the realm of control of the project execution team. However, the NCRP project had to be continuously adapted to the outcomes of the pit operations. This included geotechnical constraints, ore delivery, and other operational delays. To adapt, the planning module had to be dynamic but not reactive to allow for adjustments on a shift-by-shift basis. Based on this requirement the Diavik Closure Projects structure adopted a mine planning format. The team executed a similar planning timeline and reporting structure as the mine operations team, allowing planning to be integrated into the operational planning structures on a daily, weekly, monthly and quarterly basis. This resulted in the Projects team as a core pillar of the mine planning team. The process of continuous improvement spanned six years and has resulted in the project being ahead of schedule and under budget for the project’s scheduled progressive closure completion date of June 2023. The North Country Rock Pile project supports the argument that bulk earthworks progressive closure projects should be integrated into the operational mine plan. If the project is aligned the mine plan it allows for dynamic adjustments which capitalise on evolving opportunities inevitable in an operating mine. These cultural and organisational alignments should be supported by appropriate performance metrics and financial mechanisms to ensure united priorities. The result of this alignment provides long-term financial savings for the business as well as delivery of closure objectives.

Aug 2, 2023

By S B. Martin, M P. Simpson, J L. Mauk

The Martha deposit in Waihi, New Zealand, is a giant adularia-sericite epithermal gold-silver deposit that formed 6.0 to 6.1 Ma, and has produced over 6.4 Moz gold and 39.9 Moz. Fluid inclusion analyses were undertaken on a limited number of vein samples from Martha. The results from this eight week student project are preliminary but agree with previous studies. There is little variation between primary and secondary inclusions and between different vein types, except that homogenisation temperatures of the inclusions in sphalerite grains are on average 20¦ to 30¦C higher than the average quartz vein values. Overall the temperatures of homogenisation ranged from 182¦ to 258¦C and final ice melting temperatures ranged from 0.0¦ to 2.8¦C. Unusual black inclusions were also found associated only with the ginguro bands. Some of these appear to be solid sulphide inclusions but others are not so clear.

Jan 1, 2007

Long-range side-scan sonar and conventional geophysical data for the Peru Trench region (8`S-15¦S latitude) have been analysed. The data show that the Peru Trench is a site of sediment subduction where bending-induced normal fault-ing of the Nazca plate plays a key role. The sediments are continually removed from the trench axis region by their inclusion in normal fault-defined void spaces, such as grabens. In the process of subduction, the sediments are often offscraped, folded arid kneaded temporarily at the base of the shoreward trench slope. The subduction complex comprising such sediments is narrower than 20 km and its volume remains more or less constant due to regular removal of its contents along with the down-going plate. Addi-tionally, morphology of the subducting Nazca plate is responsible for subduction erosion of the South American plate, where the horst blocks cause tectonic erosion by abrasion and the grabens provide a mechanism for removal of the eroded material.

Jan 1, 1990