969 resultados para Zinc mines and mining


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Mode of access: Internet.

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Mode of access: Internet.

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Vols. -1952 issued as a supplement to division's Mineral information service; as division's Special publication.

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Mode of access: Internet.

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The Jameson Cell is a high intensity flotation device, which utilises induced air from the atmosphere. It was developed jointly by Mount Isa Mines and Professor Graeme Jameson of the University of Newcastle in the 1980s. It is proven to generate fine bubbles, in the order of 300 to 500 µm, in a high intensity, high shear and compact zone contained in the downcomer. This aerated mixture exits the downcomer into the pulp zone, which is the quiescent mineral and gangue separation zone. A number of Australian base metal flotation circuits feature a reverse flotation stage at the head of the circuit. Testwork and plant operating data has shown that the use of a Jameson Cell in the prefloat cleaner application has further improved prefloat gangue recovery and selectivity. Operation of a Jameson Cell in a carbonaceous/pyrite prefloat cleaner duty at the Mt Isa copper concentrator increased copper recovery and reduced pyrite in the copper concentrate. Testwork at Zinifex Century Zinc Mine showed a decrease in zinc losses by the utilisation of Jameson Cell prefloat cleaner. Appraisal of a Jameson Cell in a scalping role within the Mt Isa Copper Concentrator indicated significant benefits could be achieved.

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According to Solitander C. P., the extraction of lake ore from Eastern Finland lakes considerably rose in the 1870 - 1880 period in relation with the increasing demand from the ironworks being operated in the region. In St. Petersburg, Nicholas Putiloff, a business tycoon and State Minister owned the Haapakosken, Huutokosken and Oravin ironworks which were using 99% of lake ore for their supply. During this period the biggest production came from lake Sysmäjärvi in the Joroinen county with 3676 tonnes at an average concentration of 35.94% Fe, 4.55% Mn, 0.26% P and 0.04% S. The Värtsilä ironworks used the lake ore coming from 49 lakes, the biggest production coming from lake Loitimojärvi with 14535 tonnes of ore with a medium at concentration of 30.8% Fe. Möhkö ironworks took advantage of the 59 lakes, the largest of which was from lake Koitere with 4301 tonnes at 41.3% Fe. The Karttula ironworks were also significant in the consumption of ferromanganese lake ore.

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Aim: To assess the effect of adding zinc oxide nanoparticles to dental adhesives on their anti-microbial and bond strength properties. Methods: 45 human premolars were cut at the cement enamel junction (CEJ) and the crowns were sliced into buccal and lingual halves. The specimens were classified into three groups, etched with 37% phosphoric acid for 15 s and rinsed for 30 s. Single Bond, Single Bond+5% zinc oxide and Single Bond+10% zinc oxide were used in the first, second and third groups. A cylinder of Z250 composite was bonded and cured for 40 s. For anti-bacterial testing, 10 samples of each group were assessed by direct contact test; 10 μL of bacterial suspension was transferred into tubes containing adhesives and incubated for one hour; 300 μL of brain heart infusion (BHI) broth was added to each tube and after 12 h, 50 μL of bacteria and broth were spread on blood agar plates and incubated for 24 h. Results: The colony count decreased significantly in the second and third groups compared to the first. Conclusions: Incorporation of zinc oxide nanoparticles into dental adhesives increases their anti-microbial properties without affecting their bond strength.

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Les métaheuristiques sont très utilisées dans le domaine de l'optimisation discrète. Elles permettent d’obtenir une solution de bonne qualité en un temps raisonnable, pour des problèmes qui sont de grande taille, complexes, et difficiles à résoudre. Souvent, les métaheuristiques ont beaucoup de paramètres que l’utilisateur doit ajuster manuellement pour un problème donné. L'objectif d'une métaheuristique adaptative est de permettre l'ajustement automatique de certains paramètres par la méthode, en se basant sur l’instance à résoudre. La métaheuristique adaptative, en utilisant les connaissances préalables dans la compréhension du problème, des notions de l'apprentissage machine et des domaines associés, crée une méthode plus générale et automatique pour résoudre des problèmes. L’optimisation globale des complexes miniers vise à établir les mouvements des matériaux dans les mines et les flux de traitement afin de maximiser la valeur économique du système. Souvent, en raison du grand nombre de variables entières dans le modèle, de la présence de contraintes complexes et de contraintes non-linéaires, il devient prohibitif de résoudre ces modèles en utilisant les optimiseurs disponibles dans l’industrie. Par conséquent, les métaheuristiques sont souvent utilisées pour l’optimisation de complexes miniers. Ce mémoire améliore un procédé de recuit simulé développé par Goodfellow & Dimitrakopoulos (2016) pour l’optimisation stochastique des complexes miniers stochastiques. La méthode développée par les auteurs nécessite beaucoup de paramètres pour fonctionner. Un de ceux-ci est de savoir comment la méthode de recuit simulé cherche dans le voisinage local de solutions. Ce mémoire implémente une méthode adaptative de recherche dans le voisinage pour améliorer la qualité d'une solution. Les résultats numériques montrent une augmentation jusqu'à 10% de la valeur de la fonction économique.

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Placer miners in Alaska’s interior were part of the last great gold rush in North America. As word of gold in the Fairbanks Mining District traveled down the Yukon River, a wave of miners from the Klondike placer fields in Dawson, along with a assortment of speculators and inexperienced green horns from the Lower 48 converged on the confluence of the Tanana and Chena rivers hoping to strike it rich. The steamers coming from Dawson were integral; they carried miners with experience working the frozen subarctic placer deposits of the Klondike. These miners encountered new environmental challenges that required the development of new technologies and mining methods to efficiently harvest gold. These methods and machines were brought into Fairbanks and further perfected to account for the local conditions. This thesis describes the local mining technologies and methods employed in the Fairbanks district and the landscape patterns created during the placer mining boom years of 1903-1909, decline years of 1910-1923 and recovery of 1923-1930.

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Les métaheuristiques sont très utilisées dans le domaine de l'optimisation discrète. Elles permettent d’obtenir une solution de bonne qualité en un temps raisonnable, pour des problèmes qui sont de grande taille, complexes, et difficiles à résoudre. Souvent, les métaheuristiques ont beaucoup de paramètres que l’utilisateur doit ajuster manuellement pour un problème donné. L'objectif d'une métaheuristique adaptative est de permettre l'ajustement automatique de certains paramètres par la méthode, en se basant sur l’instance à résoudre. La métaheuristique adaptative, en utilisant les connaissances préalables dans la compréhension du problème, des notions de l'apprentissage machine et des domaines associés, crée une méthode plus générale et automatique pour résoudre des problèmes. L’optimisation globale des complexes miniers vise à établir les mouvements des matériaux dans les mines et les flux de traitement afin de maximiser la valeur économique du système. Souvent, en raison du grand nombre de variables entières dans le modèle, de la présence de contraintes complexes et de contraintes non-linéaires, il devient prohibitif de résoudre ces modèles en utilisant les optimiseurs disponibles dans l’industrie. Par conséquent, les métaheuristiques sont souvent utilisées pour l’optimisation de complexes miniers. Ce mémoire améliore un procédé de recuit simulé développé par Goodfellow & Dimitrakopoulos (2016) pour l’optimisation stochastique des complexes miniers stochastiques. La méthode développée par les auteurs nécessite beaucoup de paramètres pour fonctionner. Un de ceux-ci est de savoir comment la méthode de recuit simulé cherche dans le voisinage local de solutions. Ce mémoire implémente une méthode adaptative de recherche dans le voisinage pour améliorer la qualité d'une solution. Les résultats numériques montrent une augmentation jusqu'à 10% de la valeur de la fonction économique.

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Anecdotal evidence from the infrastructure and building sectors highlights issues of drugs and alcohol and its association with safety risk on construction sites. Operating machinery and mobile equipment, proximity to live traffic together with congested sites, electrical equipment and operating at heights conspire to accentuate the potential adverse impact of drugs and alcohol in the workplace. While most Australian jurisdictions have identified this as a critical safety issue, information is limited regarding the prevalence of alcohol and other drugs in the workplace and there is limited evidential guidance regarding how to effectively and efficiently address such an issue. No known study has scientifically evaluated the relationship between the use of drugs and alcohol and safety impacts in construction, and there has been only limited adoption of nationally coordinated strategies, supported by employers and employees to render it socially unacceptable to arrive at a construction workplace with impaired judgement from drugs and alcohol. A nationally consistent collaborative approach across the construction workforce - involving employers and employees; clients; unions; contractors and sub-contractors is required to engender a cultural change in the construction workforce – in a similar manner to the on-going initiative in securing a cultural change to drink-driving in our society where peer intervention and support is encouraged. This study has four key objectives. Firstly, using the standard World Health Organisation AUDIT, a national qualitative and quantitative assessment of the use of drugs and alcohol will be carried out. This will build upon similar studies carried out in the Australian energy and mining sectors. Secondly, the development of an appropriate industry policy will adopt a non-punitive and rehabilitative approach developed in consultation with employers and employees across the infrastructure and building sectors, with the aim it be adopted nationally for adoption at the construction workplace. Thirdly, an industry-specific cultural change management program will be developed through a nationally collaborative approach to reducing the risk of impaired performance on construction sites and increasing workers’ commitment to drugs and alcohol safety. Finally, an implementation plan will be developed from data gathered from both managers and construction employees. Such an approach stands to benefit not only occupational health and safety, through a greater understanding of the safety impacts of alcohol and other drugs at work, but also alcohol and drug use as a wider community health issue. This paper will provide an overview of the background and significance of the study as well as outlining the proposed methodology that will be used to evaluate the safety impacts of alcohol and other drugs in the construction industry.

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This paper presents an approach to providing better safety for adolescents playing online games. We highlight an emerging paedophile presence in online games and offer a general framework for the design of monitoring and alerting tools. Our method is to monitor and detect relationships forming with a child in online games, and alert if the relationship indicates an offline meeting with the child has been arranged or has the potential to occur. A prototype implementation with demonstrative components of the framework has been created and is introduced. The prototype demonstration and evaluation uses a teen rated online relationship-building environment for its case study, specifically the predominant Massive Multiplayer Online Game (MMO) World of Warcraft.