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By D Craw, D Wilson, D Chappell

Gold is extracted by cyanidation of a sulphide-rich concentrate at Macraes mine, and after cyanidation, the concentrate is discharged to tailings impoundments. The concentrate tailings were discharged to a dedicated concentrate impoundment from 1989 to 1993, afterwhich they were blended with the flotation tailings. Since mid-1998, concentrate tailings have been redirected to the dedicated concentrate impoundment. The concentrate tailings contain up to 1 ppm gold, and will be reprocessed in the future. However, it is a regulatory requirement that a contingency plan be in place to rehabilitate the concentrate tailings should the mine operation cease for any reason. Initial predictions suggested that the sulphide-rich tailings would oxidise and acidify, creating a potential long term environmental problem. Investigations of the state of the tailings after 4 years show that these predictions were overly conservative. Only minor oxidation has occurred in the upper 2 metres of the tailings where the pH has locally dropped from 10 (discharge condition) to between 7 and 8. Below 2 metres, the tailings are essentially unchanged from their deposition state. The low rate of change in the tailings is due to their very low permeability which in turn is a consequence of the fine grain size (ca. 15 ¦m). Dewatering is extremely slow, and incursion of oxygenated water is negligible. Calculations suggest that water movement over 30 m will take at least 100 years and possibly 1000 years. The contingency plan is to capitalise on the very low permeability and keep the tailings from drying with a semipermeable cap. A layer of limestone will be added to the top of the tailings, beneath the cap, to enhance alkalinity of any percolating water. If acidification does occur, contrary to expectations, any acid produced will be neutralised by underlying calcite-bearing schist, schist in the concentrate impoundment wall, and the flotation tailings immediately downstream. In addition, dilution by alkaline ground and surface waters would further ameliorate any acidic discharge.

Jan 1, 1998

Jan 1, 1965

By S. Ganguly

Slag samples taken from adjacent to the furnace wall of a submerged arc ferromanganese smelting furnace have been found to contain high concentrations of K2O. To characterize the phase equilibria relevant to these slags experimental studies have been carried out to determine pseudo-ternary sections of the form ?MnO?-CaO-(SiO2+Al2O3) with a fixed Al2O3/SiO2 weight ratio of 0.65 and 6.0 wt% K2O for temperatures in the range 1523-1673 K. In the pseudo-ternary section investigated the primary phase fields are found to be mullite, 3Al2O3?2SiO2; corundum, Al2O3; spinel, MnO?Al2O3; manganosite solid solution, (Mn,Ca)O; dicalcium silicate,2CaO?SiO2; gehlenite 2CaO?Al2O3?SiO2; anorthite CaO?Al2O3?2SiO2; kalsilite KAlSiO4 and leuciteKAlSi2O6. It was found that the presence of K2O in the slag decreases liquidus temperature in the anorthite and gehlenite primary phase fields. The manganosite primary phase field is expanded in the direction of increased (Al2O3+SiO2) and the liquidus temperatures in the manganosite primary phase field are increased significantly with the presence of K2O in the slag.

Jan 1, 2007

By Stephen Tadolini

The annulus thickness, for bolts anchored with resin, effects the systems final performance. Recent developments in the manufacturing process of these support systems, coupled with improved resin characteristics, have resulted in design changes to minimize hole drilling requirements and reduce resin usage. The amount of resin to properly anchor a 7/8-SRD (Special Rolled Dimensions) bolt in a 25.4 mm (1-in) diameter hole has been reduced to about one-third of the resin required to anchor a No. 7 rebar bolt (22 mm (7/8-in) diameter) traditionally installed in a 35 mm (1-3/8-in) diameter borehole. More importantly, laboratory and field tests, indicate that higher bond strengths and anchorage capacities can be realized with reduced annulus systems. These factors have a direct bearing on reinforcement efficiency and subsequent roof support performance.

Jan 1, 1998

By J Dwyer, M Hill

Downer’s mining division has made an operational and financial commitment to developing engineered solutions that mitigate the risks associated with operator proximity to uncontrolled development drill boom movements, and unguarded rotating drill steels.With the potential for serious injury or fatality, these identified risks are categorised as critical. Previous attempts by the industry to engineer them out have produced limited success, with numerous incidents still occurring year on year. Ultimately, the industry (as a whole) remains reliant on procedural prevention for operator safety.Downer understood the success of such an initiative would largely depend on the effective collaboration between operational experience, technology experts and automation. With so many variables requiring consideration; such as physical operator movement, machine boom movements, variable machine positions, and underground environmental impacts – challenging traditional technologies was necessary to deliver an optimal solution.For that reason, discrete detection (similar to laser curtains or beams) was considered not fit for purpose. The use of situational mapping, using rotating lasers, however, provided the optimal solution. The lasers collect data that is then processed using a custom software application.The software application is specifically programmed for tracking and classifying objects within detection zones, using advanced algorithms and filtering. Recognition and removal of non-positive disturbances are possible without losing personnel detection capability. The detection of relevant classified objects (humans) is determined by analysis of object size, age, movement, and speed etc. When the relevant object is detected, an alarm and inhibit function is applied preventing drilling functions.Any breach of the safety zone (forward of the front jacks) will automatically disable the hydraulic boom function. This can only be reset in the cabin once the person or persons have returned past the front jacks of the development drill into the safety zone.Downer, in collaboration with partner YUMARR Automation, has successfully developed this reliable boom isolation system, and is called JumboGuard. The system has now been commissioned and installed across all Downer Mining development drill fleets, operating in Australia.CITATION:Hill, M and Dwyer, J, 2017. JumboGuard – automatic boom isolation system, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 287–294 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By Richard H. Bares

This report describes the purpose and application of seventeen statistical and mathematical procedures used in a series of studies made in the project ?A Systems Approach to the Reclamation of Strip-Mined Areas in North Dakota". The objective is to help readers better understand the utility of these procedures.

Jan 1, 1982

By R. W. Watson

A belt-wearable self-contained self-rescuer (SCSR) manufactured by the CSE Corp. and designated the "SR-1OO" was evaluated for safety in the underground mine environment by the U.S. Bureau of Mines. The evaluation consisted of laboratory tests on the chemicals contained in the unit and field trials to simulate the mine environment. This report summarizes the test results and compares the results with those from earlier tests with chemical and compressed oxygen self-rescuers. It was concluded that the new SCSR did not pose any different or more severe hazards than the earlier units. In view of the mine-proven safety record of the SCSR's now in service, no reason could be found to disallow use of the belt-wearable unit.

Jan 1, 1991

1. Book review Technology of metal powders- recent developments, edited by L. H. Yaverbaum. New Jersey, Noyes Data Corporation, 1980. 400 pp. (Reviewer: B. K. Loveday) 2. New books The use of microprocessors, by M. Aumiaux. New York, Wiley, 1980. 176 pp. $25,50. Aluminium smelter technology, a pure and applied approach, by K. Grojtheim and B. J. Welch. Diisseldorf, Aluminium-Verlag GmbH (P.O. Box 1207, D-4000, Federal Republic of Germany). 146 pp. DM48. Coal-bridge to the future. New York, Harper & Row, 1980. $35. System modeling and response.. theoretical and experimental approaches, by O. Doebelin. New York, Wiley, 1980. 576 pp. $26. Environmental and climatic impact of coal utilization, edited by J. J. Singh and A. Deepak. New York, Academic Press, 1980. 646 pp. $39,50. Proceedings of the Third European Conference on Mixing, York, England, April 1979, edited by H. S. Stephens and C. A. Stapleton. BHRA Fluid Engineering (Cranfield, Bedford Mk43 OAJ, U.K.), 1980. 2 volumes. 500 pp. $50. Lignite technology, edited by P. Nowacki. New Jersey, Noyes Data Corporation, 1980. 228 pp. $42. The application of rock mechanics to cut-and jill mining. London, Institution of Mining and Metallurgy, 1980. Papers presented at the Fifth International Symposium on Jet Cutting Technology, Hanover, Federal Republic of Germany, June 1980, edited by H. S. Stephens and B. Jawis. BHRA Fluid Engineering (Cranfield, Bedford Mk 43 OAJ, U.K.), 1980. 438 pp. £38. World coal resources.. methods of assessment and results, by G. Fettweis. Amsterdam, Elsevier, 1979. 425 pp. $80,50. Geophysical and geochemical techniques for exploration of hydrocarbons and minerals, edited by M. Sittig. New Jersey, Noyes Data Corporation, 1980. 300 pp. $40. Financial Times mining international year book 1980. Longman Group Ltd (Periodicals and Directories Division, Longman House, Burnt Mill, Harlow, Essex CM20 2JE, England). £24 surface, £34 airmail. National Symposium on the Availability of Strategic Minerals, edited by M. J. Jones. London, Institution of Mining and Metallurgy, 1980. 109 pp. 3. NIM reports Report No. 1941 The recovery of chromite and platinum from the UG-2 Upper Chromitite Layer .of the Bushveld Complex at the Pandora Mine (first published 10th Mar., 1978). Report No. .2012 A mineralogical investigation of borehole cores from the Trompsburg Complex (first published 6th Apr., 1979). Report No. 2038 The leaching of sphalerite in acidic ferric sulphate media in the absence of elemental oxygen. Report No. 2052 An investigation of the impurities in native gold by neutron-activation analysis. Report No. 2056 The mineralogy and geochemistry of the copper, lead, and zinc sulphides of the Otavi Mountainland. Report No. 2058 A n elementary introduction to image analysis - a new field of interest at the National Institute for Metallurgy. Report No. 2059 Distributed computer control of industrial processes. Report No. 2060 The analysis, by atomic-absorption spectrophotometry, of activated charcoal.

Jan 1, 1980

By A. D. Thomas, V. N. Rampton, S. Paradis, C. F. Gleeson

"A shallow till sampling program was completed on a 1 km grid over the St . George Batholith in southern New Brunswick. The ""B"" soil horizon was analyzed for Cu, Pb, Zn, Ag, Co, Mo, U and Sb and the heavy minerals from the ""C"" soil horizon were analyzed for W, Sn and A u. The results delineated four of five recorded W occurrences, three of four recorded Mo occurrences, all recorded Cu occurrences and one recorded Au occurrence. The results indicate that shallow till sampling in conjunction with bedrock and Quaternary mapping can inexpensively define exploration targets in terrain similar to that underlain by the St. George Batholith.A similar program was carried out in eastern Ontario involving the analysis of four separates from the till, the ""8"" soil horizon, the -50 mesh fraction, the -250 mesh and the heavy mineral fraction of the ""C"" soil horizon and humus. Also sampling was carried out near known gold occurrences at closer spacings. Regionally, anomalous results from all sample media clearly defined a large auriferous shear zone and associated splays. Over one known showing all media clearly defined the showing and a secondary zone. On the regional scale the heavy mineral fraction gave the best anomaly definition and contrast, but the -250 mesh fraction was found to be the most cost effective for defining exploration targets. For detailed surveys, humus was found to be cost-effective."

Jan 1, 1986

By S Henderson

The Thames gold-silver deposits are part of the Hauraki goldfield, situated within the Miocene to Pliocene calc-alkaline Coromandel Volcanic Zone (CVZ). The Waitangi vein system is one of the mineralised ore shoots in the Thames district. The Thames gold deposits are characterised by shallow level epithermal vein mineralisation with phyllic to advanced argillic alteration assemblages and abundant sulphide minerals including pyrite, arsenopyrite, chalcopyrite, galena and sphalerite. Gold occurs as electrum in association with sulphide minerals. Microprobe analyses.of sphalerite grains from the Waitangi deposit mostly range from 0.8 to 1.5 mole % FeS, although one sample contains 9.5 mole % FeS. Arsenopyrite from Waitangi yields a range from 33.1 to 34.6 atomic As (%). There is no discernible correlation between the FeS content of sphalerite and gold grade in the Waitangi deposit suggesting that gold deposition is probably not controlled by changes in temperature and activity of sulphur aS2 that control the FeS content of sphalerite. The possible causes for gold deposition are thought to be boiling, mixing and changes in pH. Sulphur isotope analyses of mixed sphalerite-galena and sphalerite-galena-ehalcopyrite samples yield a narrow range of d34SCDT values (-1.0 to 0.9 ë;n=5), whereas late spongy pyrite gives unusually light sulphur isotope values (-16.7 to -27.9 ë; n=4). The sulphur isotopic values of base metal sulphides from Waitangi suggest that the sulphur was derived from a magmatic source. However, the source of light sulphur in the late pyrite grains is not known. Preliminary fluid inclusion+studies indicate homogenisation temperatures between 173¦ and 284¦C and salinities of 0.23.0 NaCI equiv. wt % (uncorrected for C02). Vein quartz at Waitangi yields d18OSMOW values from 6.8 to 12.7 ë (n=23). The calculated oxygen isotopic composition of ore fluids is between -2.1 to 3.8 ë at 250¦C and -0.1-5.8 ë at 300¦C. Oxygen isotope analyses have revealed significant variations in d18O values with elevation and gold grades. Zones of gold enrichment coincide with a zone of variable oxygen isotope values at the top of the vein system, where boiling and/or fluid mixing most likely occurred. Oxygen isotope values varying with gold grades within the Waitangi conduits suggest that d18O values may be useful in targeting bonanza grade gold mineralisation in epithermal vein systems.

Jan 1, 1993

By S. Asokan, D. Rathod, Ch. V. G. K. Murty

Tata Steel, a steel arm of Tata Group, is Asia's first and India's largest integrated private sector steel company. Tata Steel’s turnover in fiscal 2004-05 was nearly US$ 3.25 billion. As part of its vision to grow in related industries, Tata Steel is poised to enter the Titania businesses in the Indian state of Tamil Nadu. The Titania project will involve mining, separation of ilmenite & other co-minerals, beneficiation of ilmenite to synthetic Rutile and further maximum value addition to Titanium metal. This paper outlines the journey from the concept to current findings of the Bankable Feasibility Study in developing Sattankulam Heavy Mineral Sands Deposits in the State of Tamil Nadu, India by Tata Steel.

Jan 1, 2005

By Michael J. Kelly

IAMGOLD?s Westwood project is the site for the largest, by volume, bored vent raise in North America. When completed, it will be the fifth largest bored worldwide in a single pass. This paper will review the highest capacity raise drill system ever built (Redbore 100); as well as the technical difficulties in a single pass boring a 2,773 ft x 20 ft to 22 ft diameter raise. The difficult ground conditions and associated problems will be reviewed, as well as the solutions to overcome them. Use of the RVDS drilling tool to achieve .04% accuracy (14.5?) and the Geotube® water filtration system will also be covered.

Oct 1, 2010

By Anna Paula Littig Berger

A remoção do fosfóro através do processo de desfosforação do ferro-gusa tem sido cada vez mais relevante, devido a influência que exerce de forma prejudicial as propriedades do aço e devido a extensão do cenário de escassez de minérios com menor teores de fosfóro. Este trabalho tem como objetivo a avaliação termodinâmica computacional de misturas a base de dolomita e finos de minério utilizadas no processo de desfosforação realizado em panela para o refino do ferro-gusa. Foi utilizado o software Factsage para avaliação termodinâmica, tendo este se mostrado eficaz na determinação da concentração de fósforo de equilíbrio no metal, fases presentes e temperatura de fusão das misturas. Verificou-se uma tendência de maiores valores de eficiência para o processo de desfosforação quando aumenta-se a razão de massa de desfosforante e massa de gusa.

Aug 17, 2017

By R. Thorpe, M. Dosbaba, A. Kopriva, A. Niiranen, J. Ruokanen

"Automated Mineralogy (AM) is an important diagnostic tool in flotation plants as it adds ore and particle mineralogical properties to traditional mass and chemical data. AM is used in project development, for future ore studies and for diagnosing concentrator operations. With the exception of operations who own central laboratory or on-site systems, the use of AM is often limited to the analysis of a comparatively small set of samples. Metrix Plant Technologies has partnered with TESCAN to integrate TIMA AM technology into the implementation of Performance Assessment Campaigns (PAC). Routine daily composite samples from the mill are analysed mineralogically on a size-by-size basis over several weeks. All the relevant metallurgical, process control and mineralogical data is combined into a single large database for mass balancing and interactive examination. This paper describes the implementation and results of a PAC at the Agnico Eagle Kittilä gold mine in Finland. Although challenging, the addition of mineralogical data as dependent variables in multivariate analysis leads to a much deeper understanding of the root cause effect of events driving the flotation performance. INTRODUCTION TO STUDY The Kittilä mine, owned by Agnico Eagle, is Europe’s largest primary gold mine, with annual production of approximately 180,000 Oz. The operation is located in Lapland in northern Finland, and is currently expected to operate until 2035. The location of the operation is shown in Figure 1. Historically, the mine was an open pit, although in recent years ore is sourced solely from underground operations. The processing plant features crushing and grinding, followed by carbon flotation and sulphide flotation. Carbon concentrate is a waste stream, and sulphide concentrate reports to pressure oxidation (autoclave) and CIL circuits for gold extraction. The final flowsheet is shown in Figure 2. Following commissioning in late 2008, the operation achieved commercial production on May 1st 2009. Gold recovery in flotation gradually increased to a 92-96% range at a throughput of ~3500-4000 tonnes per day. In late 2014, the operation commissioned a plant expansion to ~5000 tonnes per day. Following a commissioning period, the operation stabilised with recoveries in a 90-94% range, which over any given period was determined to be ~2% lower with statistical significance. The trends from start-up of gold recovery in flotation and throughput are shown as follows in Figure 3. In early 2016, Agnico Eagle Kittilä mine, along with Agnico Eagle Technical Services (AETS) partnered with Metrix Plant Technologies and TESCAN, to perform a Performance Assessment Campaign (PAC) at Kittilä, involving automated mineralogy on five key streams at Kittilä on 40 days selected from a 50 day period between February 15th and April 4th 2016, when plant operations were stable. In addition to the mineralogical data, metallurgical and operational data were pooled into a single, powerful database to explore opportunities for the operation to improve recovery in a sustained manner, ideally to the levels pre-expansion."

Jan 1, 2017

By Gray Mullins

This paper presents experimental results from a study to assess the interface bond between a cast-in-place concrete seal slab and prestressed concrete piles in cofferdams. Three different seal slab placement conditions - fresh water, salt water and bentonite slurry - were evaluated and the results compared against controls where no fluid had to be displaced by the concrete. Normal pile surfaces were investigated. Additionally, the situation of ?soil caked? piles was also investigated. Both model and full-scale tests were conducted. In the model tests, twenty eight 15 cm square prestressed sections were used with the embedment depth varied between d-2d, where d is the width of the pile. In the full-scale tests, 16 specimens were tested. The prestressed piles were 36 cm square with the embedment varied between 0.5d-2d. Four of the sixteen piles were cast with embedded gages located at the top, middle and bottom of the interface region. The results showed that loads were transferred to the piles over an effective area, not the entire embedded depth. Significant bond stresses developed even for the worst placement condition. Recommendations are made for revising current values in specifications.

Jan 1, 2013

By R Ratlou

Increased contamination due to sand in spiral feed has had a negative effect on the efficiency of spiral concentrators at Navigation Plant. The no. 1 seam at Kromdraai opencast, which was previously mined by underground bord and pillar methods, is now susceptible to spontaneous combustion because of air ingress into the old workings which are exposed in the opencast high wall. This posed a risk in the loss of reserves to burnt coal. As solutions, buffer blasting of the preceding cut to collapse bords and soft overburden dressing of un-collapsed bords were implemented to prevent air entering the workings. The latter remedy resulted in increased contamination due to addition of sand in Run of Mine. After evaluating alternatives, a low capital option was selected. The 110t/hr Teetered Bed Separator (TBS) has been installed, primarily to desand and upgrade the feed to the spiral concentrators. The unit indicated an upgrade with a yield increase of 0.4% during test work and is currently showing an overall plant yield increase of 0.97%.

Jan 1, 2006

By A. M. R. Neiva

The WNW-ESE-trending hydrothermal veins cut alternating mica schists and quartzites of mainly Ordovician age and, to the west, a Hercynian muscovite-biotite granite. They have been prospected and developed to a depth of 300 m and reserves of 20 t Au estimated. The paragenetic sequence and chemical compositions of the ore minerals are generally similar to those at Jales to the south. Gold, electrum and aurian silver form inclusions in arsenopyrite, pyrite, galena, sphalerite, pyrrhotite and quartz and also occur in veinlets that cut these minerals. Silver has been found in gold, electrum, aurian silver, tetrahedrite, freibergite and the Ag-Pb-Sb sulphide owyheeite. Early arsenopyrite crystallised at an estimated 480 degrees C and the more common, later arsenopyrite in which Au and Ag are generally included at 430-300 degrees C. Sphalerite crystallised at 307-100 degrees C. Monoclinic pyrrhotite may have been formed by the inversion of hexagonal pyrrhotite at 248 degrees C

Jun 16, 1905

To provide a faster means to open and close permissible electrical enclosures. Approach: An inspection and repair port with a multiple start thread which provides a permissible joint has been developed and tested. How It Works: The inspection port screw thread has a large pitch, which allows the port cover to be rotated from fully closed 10 fully open, in less than one revolution. See Figure 1. When the cover is screwed back in. it be-gins engagement within one eighth turn because the screw design has eight separate threads. To prevent Its unauthorized opening, the port cover has a bolt guarded by ears which accept a padlock. The threads are designed to tolerate a reasonable amount of grit without binding, although wipe-off cleanness is necessary during reassembly. Enclosures of two different sizes each fitted with the quick-access port, were

Jan 1, 1976

By J. W. Klokow, K. L. Riemer, R. I. L. Ferreira

As a result of the increased depth of mining in the South African gold mining industry mining induced seismicity is a severe problem. One of the strategies within the industry to contain the problem is to incorporate a system of regularly spaced stabilising pillars into mine layouts. At the Driefontein Gold Mine a system of closely spaced dip pillars is used to contain seismic energy emissions. Comparisons of seismic data for several mining clusters initially indicated a possible measure of success in the containment and occurrence of larger events. A detailed analysis of data over a 5-year period since the start of mining however, has revealed a delayed seismic response to the increasing strike spans. Significant changes marked by an increase in certain seismic variables have been observed at mining spans of between 100 to 120 meters and could be of significance to pillar spacing in the design of deep level mining layouts. La sismicité occasionnée par l’exploitation minière est un problème grave dans les mines profondes de l’industrie minière aurifère en Afrique du Sud. Une des stratégies utilisées dans l’industrie a été de maîtriser le problème en incorporant un système de piliers de stabilisation régulièrement espacés dans la disposition des mines. A la Driefontein Gold Mine, un système de piliers de pendage proches les uns des autres est utilisé pour contenir les émissions d’énergie sismique. Au début, des comparaisons de donnés sismiques pour plusieurs groupes d’extraction ont indiqué un succès possible dans la limitation et l’occurrence d’évènements sismiques. Cependant, une analyse détaillée des données sur une période de 5 années a révélé un délai entre la progression de l’extraction et une réponse sismique accrue. Des changements considérables dans les variables sismiques ont été observés dans des intervalles d’extraction entre 100 et 120 mètres, ce qui pourrait être significatif pour l’espacement des piliers dans la conception de la disposition des mines de fond. Resultierend aus den zunehmenden Tiefen des Bergbaus in der südafrikanischer Goldbergbauindustrie stellt sich die vom Bergbau hervorgerufene Seismizität als bedrohliches Problem dar. Es war eine der Strategien innerhalb der Industrie, das Problem dadurch einzudämmen, daß regelmäßig plazierte Stabilisierungspfeiler in den Bergbaulayouts inkorporiert wurden. In der Driefontein Gold Mine wird ein System von knapp aneinandergesetzten im Abfallbereich befindliche Pfeiler benutzt, um seismische Energieemissionen einzudämmen. Vergleiche der seismischen Daten für mehrere Bergbaugruppen zeigten anfangs ein mögliches Maß von Erfolg in der Eindämmung und im Auftreten von größeren Fällen an. Eine ausführliche Analyse von Daten über einen 5jährigen Zeitraum hat jedoch ergeben, daß eine Verzögerung zwischen der Progression des Bergbaus und einer erhöhten seismischen Reaktion besteht. Bedeutende Änderungen in den seismischen Variablen wurden an Bergbauspannen von 100 bis 120 Metern beobachtet und könnten für Abstandsbemessung von Pfeilern im Design des Tiefbergbaulayouts von Bedeutung sein.

Jan 1, 2003

By H G. Bosmare, G Bedser, C V. B Cunningham

Peak Quany has achieved substantial improvements to its bottom lie by giving close attention to blasting practice, and in pr@icnlar by introducing electronic delay detonators for routine production blasting. The precision and flexibility provided by these units has enabled the quarry to gain control over fmes and curtail oversize without increasing explosive usage. In addition, the extent of nuisance from blasting vibrations has been reduced.

Jan 1, 1998