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Distribuição espacial e plano de amostragem para a cigarrinha-das-raízes, Mahanarva fimbriolata (Stal., 1854), em cana-de-açúcar.; Spatial pattern and sampling plan for sugarcane root froghopper , Mahanarva fimbriolata (Stål., 1854).

Stingel, Erich
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/07/2005 PT
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36.52%
O objetivo deste trabalho foi avaliar a distribuição espacial de adultos e ninfas da cigarrinha-das-raízes da cana-de-açúcar, Mahanarva fimbriolata (Stål., 1854) (Hemiptera: Cercopidae), a eficiência do sistema de amostragem atualmente empregado em escala comercial, a possibilidade de estimar a população de ninfas por meio da contagem de espumas e, a partir desses resultados, estabelecer um plano de amostragem confiável, prático e de baixo custo para utilização em programas de manejo integrado desta praga. A determinação da distribuição espacial foi feita em Ourinhos e Guariba-SP, demarcando-se três parcelas de 1,1 ha, em talhão colhido mecanicamente sem a queima da palha e com histórico de ataque da cigarrinha-dasraízes. As avaliações foram feitas em três épocas diferentes, contando-se o número de adultos e ninfas na base das touceiras, em 50% da área da parcela. Os adultos e ninfas de M. fimbriolata distribuem-se de forma agregada ou contagiosa na cultura da cana-de-açúcar e este padrão de distribuição não se altera ao longo das gerações, nem é influenciado pelo nível de infestação ou variedade cultivada. Utilizando-se os dados obtidos nestes experimentos calculou-se, para cada local e época de amostragem...

Avaliação de diferentes cronogramas de coletas de amostras biológicas em estudos de bioequivalência e análise da influência de teor de fármaco sobre os resultados destes estudos; Evaluation of the effects on different doses and sampling schedules on the assessment of bioequivalence

Kano, Eunice Kazue
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/03/2008 PT
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36.48%
Os estudos de bioequivalência são realizados em humanos, por meio da administração dos medicamentos em estudo pela mesma via extravascular, sob condições experimentais padronizadas, seguida pela determinação das concentrações plasmáticas do fármaco em função do tempo. Nestes estudos considera-se que curvas estatisticamente semelhantes de decaimento sanguíneo de fármacos produzem o mesmo resultado em termos de eficácia e segurança. A partir das curvas de concentração em função do tempo obtidas, determinam-se os parâmetros farmacocinéticos Cmax, tmax e ASC. A bioequivalência entre dois produtos é estabelecida por meio do IC 90%, que deve estar entre 80 a 125% para os parâmetros farmacocinéticos Cmax e ASC. O cronograma de coleta de amostras biológicas é um dos aspectos mais críticos no planejamento de estudos de bioequivalência, pois este afeta diretamente a determinação dos parâmetros farmacocinéticos utilizados na avaliação da bioequivalência. Outro aspecto importante relacionado a este tipo de estudo é a diferença de teor entre os produtos a serem submetidos ao estudo de bioequivalência, que segundo a legislação brasileira vigente, deve ser menor ou igual a 5%. Neste trabalho foram avaliados diferentes cronogramas de coleta de amostras sangue...

Métodos de amostragem de solos para a determinação de carbono em três ambientes; Soil sampling methodologies for carbon stock determination in three environments

Medina Sotomayor, Jaime Felipe
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/05/2009 PT
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36.5%
Paralelamente à aceitação dos reservatórios de carbono florestais para mitigar o impacto do dióxido de carbono emitido à atmosfera, gera-se uma demanda de técnicas que permitam mensurar e monitorar o carbono das florestas nos projetos de desenvolvimento limpo. Os erros que provém da amostragem, são muito maiores que os associados ao processo de análise de amostras, assim, é importante desenvolver planos de amostragem adequados que permitam alcançar a precisão desejada e sem viés na informação. Desta maneira, o objetivo do estudo foi conhecer o comportamento do estoque de carbono nos solos, na fazenda Três Lagoas, localizada no Município de Angatuba, São Paulo, Brasil, área com diferente cobertura e uso de solo: Eucalipto, Pastagem e Floresta Nativa, e conhecer como o sistema de amostragem influencia as estimativas assim como o esforço amostral necessário para a determinação do estoque de carbono. Coletaram-se 406 unidades amostrais distribuídas nas profundidades 0-10 cm e 10-20 cm e por meio da estatística clássica determinou-se que o estoque de carbono é de 39,6 MgC.ha-1. O menor esforço amostral necessário foi determinado na amostragem sistemática estratificada, com uma distância de amostragem na grade de 979 m. A geoestatística foi uma ferramenta que permitiu conhecer o alcance prático da variável (650 m). Pelo valor da diferença do critério de Akaike...

Tamanho, forma de parcelas e suficiência amostral para avaliação e monitoramento do componente vegetal de ecossistemas em restauração com cinco anos de idade no estado de São Paulo; Size, shape of plots and sampling sufficiency for assessment and monitoring of the 5 aged plant component of ecosystem restoration in the state of São Paulo

Fragoso, Ariadina Callegari Ferrari
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/12/2014 PT
Relevância na Pesquisa
36.51%
A avaliação e o monitoramento são etapas fundamentais para testar teorias e metodologias usadas na restauração ecológica, além de indicar ações corretivas que podem ser aplicadas para garantir o sucesso dos projetos. No entanto, para que estas atividades sejam realmente efetivas e proporcionem resultados seguros é necessário o uso de ferramentas estatísticas em seu planejamento e aplicação para que os dados obtidos sejam precisos e seguros. O objetivo deste estudo é testar o tamanho, a forma de parcelas e a suficiência amostral para avaliar e monitorar áreas em processo de restauração no Bioma Mata Atlântica com idade aproximada de cinco anos. Foram amostradas três áreas que inseridas na Floresta Estacional Semidecidual com cerca de cinco anos submetidas ao plantio total de mudas e inseridas em paisagens fragmentadas. Para amostragem foram alocadas sistematicamente 10 parcelas em SOS (Itu) e ARA (Batatais) e 7 parcelas em A_Q (Batatais) com dimensões de 12x20 m2. Os indivíduos amostrados receberam uma placa numerada, e foram registradas as medidas de CAP de todos os ramos se ao menos um deles tiver CAP >= 10 cm. Para caracterização dos locais a regeneração natural foi amostrada em parcelas de 2x2 m2 incluindo indivíduos com altura maior ou igual a 0...

Sampling density and proportion for the characterization of the variability of Oxisol attributes on different materials

Siqueira, D. S.; Marques, J.; Pereira, G. T.; Barbosa, R. S.; Teixeira, D. B.; Peluco, R. G.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 172-182
ENG
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 11/06053-3; Establishing a soil sampling plan is one of the most important stages for providing the detailed information required for sustainable land management. This study aims to investigate the most appropriate sampling density and proportion for the characterization of Oxisol attributes on different materials, using the magnetic susceptibility (MS). The studied area is located in Sao Paulo State, Brazil, in Guatapard Town and its size is 380 ha. To evaluate the subsampling effect in the variability description, 60 samples were collected from part of the area (150 ha) in the density of one point per 2.5 ha, using both simple sampling and subsamples with three points. Different sampling densities were obtained (3; 4; 5; 6; 7; 8; and one point per 9 ha) by the exclusion of points. The evaluated attributes were: clay content; base saturation and MS at 0.00-0.25 and 0.25-0.50 m depths. There were no differences among spatial variability maps generated from either simple or subsamples. This information might precede a change in the sampling system for the agricultural industry. The minimal sampling density required so that there is no loss in the spatial variability representativeness was one point per 7 ha. MS may be used to upgrade clay content estimates in the sampling proportion of three points of MS for per clay point (one point per 2.5 ha for MS: one point per 7 ha). (C) 2014 Elsevier B.V. All rights reserved.

Probability sampling design in ethnobotanical surveys of medicinal plants

Espinosa,Mariano Martinez; Bieski,Isanete G. C.; Martins,Domingos Tabajara de Oliveira
Fonte: Sociedade Brasileira de Farmacognosia Publicador: Sociedade Brasileira de Farmacognosia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 EN
Relevância na Pesquisa
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Non-probability sampling design can be used in ethnobotanical surveys of medicinal plants. However, this method does not allow statistical inferences to be made from the data generated. The aim of this paper is to present a probability sampling design that is applicable in ethnobotanical studies of medicinal plants. The sampling design employed in the research titled "Ethnobotanical knowledge of medicinal plants used by traditional communities of Nossa Senhora Aparecida do Chumbo district (NSACD), Poconé, Mato Grosso, Brazil" was used as a case study. Probability sampling methods (simple random and stratified sampling) were used in this study. In order to determine the sample size, the following data were considered: population size (N) of 1179 families; confidence coefficient, 95%; sample error (d), 0.05; and a proportion (p), 0.5. The application of this sampling method resulted in a sample size (n) of at least 290 families in the district. The present study concludes that probability sampling methods necessarily have to be employed in ethnobotanical studies of medicinal plants, particularly where statistical inferences have to be made using data obtained. This can be achieved by applying different existing probability sampling methods...

ESTIMATING PRECISION OF SYSTEMATIC SAMPLING IN FOREST INVENTORIES

Mello,José Marcio de; Scolforo,Henrique Ferraço; Raimundo,Marcel Régis; Scolforo,José Roberto Soares; Oliveira,Antônio Donizette de; Filho,Antônio Carlos Ferraz
Fonte: Editora da Universidade Federal de Lavras Publicador: Editora da Universidade Federal de Lavras
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
Relevância na Pesquisa
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The sampling technique commonly used in forest inventories is the systematic sampling. This study aimed to evaluate the estimator of the variance of the mean proposed by Cochran for a systematic sampling technique in forests with high and low percentages of the sampled area. The study areas comprised native vegetation in Minas Gerais. To assess the efficiency of the estimators in situations involving high sampling rates (determined as the percentage of the area sampled), a fragment where a census was conducted was used. The remaining fragments comprised situations involving low sampling rates, and for these fragments, inventory accuracy was determined using the Cochran estimator. As a result it was observed, in the fragment where the census was conducted, that the structure of the correlation coefficient proposed by Cochran remained approximately constant for the area, and to the extent that sampling rate reduced, the impact of the Cochran estimator on the inventory accuracy decreased. For the fragments with a low sampling rate, it could be inferred that the sampling rate was a key factor for the correlation proposed by Cochran to have an impact on the forest inventory accuracy. The use of this estimator is indicated for fragments with a sampling rate greater than 10% of the area.

Comparison of Sweep Net., D-Vac., and Absolute Sampling., and Diel Variation of Sweep Net Sampling Estimates in Lentils for Pea Aphid (Homoptera: Aphididae)., Nabids (Hemiptera: Nabidae)., Lady Beetles (Coleoptera: Coccinellidae)., and Lacewings (Neuroptera: Chrysopidae)

Schotzko, D. J.; O’Keeffe, L. E.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica Formato: text/html
EN
Relevância na Pesquisa
36.53%
Relative accuracy of sweep net sampling was compared with D-vac (D-vac, Riverside, Calif.) and absolute sampling methods for determining population densities of pea aphid, Acyrthosiphon pisum (Harris), Nabi. s spp., Hippodamia spp., and Chrysopa spp. in lentils (Lens culinaris Medikus). Relative effects of the a biotic environment, predators, and time of sampling on population estimates also were determined during 2 yr. Original counts, area, and volume adjustments were used to evaluate accuracy of the sampling method. Volume adjustment was most accurate and was used in all subsequent evaluations. Sweep net estimates of pea aphid, Nabis spp., and Hippodamia spp. densities were similar to those obtained with absolute and D-vac sampling methods, although sweep net sampling consistently gave lower population estimates than those found for absolute sampling. In these experiments, the sweep net did not adequately sample the Chrysopa spp. in lentils. The time of sampling was significant when sampling for pea aphid; however, it was not as important for sampling of the three insect predators. Each year, sweep net samples were taken randomly at two locations in two fields every hour for 72 consecutive hours. The a biotic factors studied were light intensity...

Binomial Sequential Sampling Plans for Adult Female Twospotted Spider Mites (Acari: Tetranychidae) on Hops

Wright, Lawrence C.; Cone, Wyatt W.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica Formato: text/html
EN
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Binomial sequential sampling plans, based on Wald’s sequential probability ratio test, were developed for adult female twospotted spider mites, Tetranychus urticae Koch, on main stem hop leaves at the 2 m elevation for early season sampling and at the 2 + 4 m heights combined for mid- to late season sampling. The 2 + 4 m sampling plan was tested by sampling data sets, which were generated by the Monte Carlo method. Increasing the tally threshold improved the operating characteristic curves and sampling plan robustness and caused the average sample number and percent of maximum sample termination curves to be more peaked around the critical density. Increasing the tally threshold generally reduced the magnitude of sequential sampling errors. Sequential decision errors made at means above the critical density were more serious than errors made below it. When the maximum of 100 samples was taken, the data set mean was generally above the critical density. Therefore, when 100 samples have been taken and no decision has been reached, the sampler should be aware that the field mean is near, and likely greater than, the critical density. The sampling plans were based on a nominal threshold of 5 adult female spider mites per leaf. The plans could be modified using data in this article to develop sampling plans based on an economic threshold when one is determined.

Binomial and Numerical Sampling for Estimating Density of Baris coerulescens (Coleoptera: Curculionidae) on Oilseed Rape

Badenhausser, Isabelle; Lerin, Jacques
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica Formato: text/html
EN
Relevância na Pesquisa
36.54%
Baris coerulescens Scopoli is a pest attacking the tap root of oilseed rape and other cruciferae. Sampling plans based on 6 yr of surveys were devised to estimate the mean number of immatures per plant. When the required precision (SE/¯x) is around 0.10, sampling must be based on insect counts in the roots, and sequential sampling based on a variance-mean model provides a reasonable tool. When using the proportion of plants infested with at least 1 insect, a binomial sampling plan can be used to estimate the mean density with a level of precision ≥0.40. A better precision can be reached (≥0.25) and a smaller sample size is required, when using the proportion of plants infested with at least 2 insects. Sampling characteristics of the binomial sampling plan developed with the proportion of plants with at least 2 insects and precision 0.30 showed that it can be used for intermediate means from 2 to 6 insects per plant. In these conditions, means are well estimated and the sampling time is reduced when compared with sampling based on insect counts. Minimizing sampling time led to developing a sampling strategy with precision 0.30, consisting of using binomial sampling when the proportion of infested plants with at least 2 insects is in the range 0.50–0.80 and in using numerical sequential sampling in other cases. Simulations of these sampling plans were carried out on 16 bootstrap samples that cover a wide range of means from 0 to 10 insects per plant.

Counting Ants (Hymenoptera: Formicidae): Biodiversity Sampling and Statistical Analysis for Myrmecologists

Ellison, Aaron M.; Gotelli, Nicholas J.; Dunn, Robert R.; Sanders, Nathan J.
Fonte: Austrian Society of Entomofaunistics Publicador: Austrian Society of Entomofaunistics
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.53%
Biodiversity sampling is labor intensive and is especially challenging for myrmecologists, because the sampling units (individual workers) do not correspond in a simple way to the natural units of diversity (individual nests). Because it is usually not possible to reach a sampling asymptote for ants, comparisons of species richness among collections have to be carefully standardized for the number of individuals and number of samples examined. Asymptotic estimators allow for extrapolation to an estimated asymptote of species richness, and rarefaction curves permit meaningful comparisons of samples by interpolating data to a standardized number of sampling units. Winkler sacks of leaf litter and specialized traps for arboreal ants often yield distinctive sets of species in tropical and subtropical latitudes. These microhabitats are best treated as distinctive assemblages that can be compared with stratified sampling. Within other habitat types, different baiting and sampling methods yield similar, but not identical sets of species, and many authors have advocated using a diversity of methods to gain the greatest coverage of species. However, many of the distinctive species that are sampled by a particular method are rare, and are just as likely to have been found with other sampling methods. The estimated similarity in composition of ants sampled by different methods in the same habitat is probably more similar than has been appreciated. Recent published comparisons of sampling efficiency have shown that hand-collecting accumulates species more efficiently than the more commonly used pitfall traps or baits. However...

Diversity and distribution of groundwater fauna in a calcrete aquifer: does sampling method influence the story?

Allford, A.; Cooper, S.; Humphreys, W.; Austin, A.
Fonte: C S I R O Publishing Publicador: C S I R O Publishing
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
36.5%
There has been an increase in the number of studies examining the spatial and temporal patterns in species richness, community structure and population dynamics of groundwater organisms. These studies have raised the issue of uncertainty about the comparability of different sampling methods, and questions of whether sampling bias may exist. Recently, a diverse subterranean fauna was discovered in calcrete (carbonate) aquifers of the Yilgarn Region of central Western Australia. Little is known about the community structure and population dynamics in these aquifers. One important issue is whether current sampling methods adequately sample the species richness and abundance of the fauna to allow for comparative studies. Here we investigate the effectiveness of three sampling methods: haul net sampling, pumping with a 12-V impeller pump, and a discrete interval sampler. The methods were trialled over 16 months with >250 samples taken from 55 uncased bore holes. No significant taxonomic bias was detected across the sampling methods. However, sampling using a haul net was found to be the most efficient method for capturing the available taxa per unit time when sampling bores are less than 10 m deep, with pumping being the least efficient. These results are discussed in relation to the problems of studying stygofauna in Western Australian calcrete aquifers...

Field sampling of cork value before extraction in Portuguese "montados"

Almeida, Alice M.; Tomé, Margarida
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2010 ENG
Relevância na Pesquisa
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The assessment of cork quality and the estimation of cork value are very important to forest landowners, for management purposes and for cork commercialisation. The Forest Producers Associations have been using a sampling scheme with the objective of estimating cork value (price per unit of weight, usually kg) before extraction, based on the sampling of individual trees along a zigzag transect that covers the entire stand. The sampling error is usually too high, but, from a practical standpoint, it is difficult to increase the sampling intensity if it would imply an increase in sampling costs. The aim of this work was to propose, from data collected in six stands representative of the cork oak stands in Portugal, an alternative sampling methodology with a more efficient precision/ cost ratio. Precision and costs of alternative sampling designs based on clusters of different sizes, complemented with analysis of the intracluster correlation coefficient, were studied in order to propose the most adequate sampling strategy. Single-stage cluster sampling with clusters of 5–7 trees guarantees a reasonable sampling error (10–15%) and can be conducted without a large increase in cost

Factors attributing to the failure of endometrial sampling in women with postmenopausal bleeding

Visser, N.; Breijer, M.; Herman, M.; Bekkers, R.; Veersema, S.; Opmeer, B.; Mol, B.; Timmermans, A.; Pijnenborg, J.
Fonte: Munksgaard International Publishers Publicador: Munksgaard International Publishers
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
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Objective: To determine which doctor- and patient-related factors affect failure of outpatient endometrial sampling in women with postmenopausal bleeding, and to develop a multivariable prediction model to select women with a high probability of failed sampling. Design: Prospective multicenter cohort study. Setting: Three teaching hospitals in the Netherlands. Population: Women presenting with postmenopausal bleeding with an indication for endometrial sampling. Methods: Multivariable logistic regression was performed to evaluate the impact of doctor's training level and patient's characteristics on failure of sampling. Main outcome measures: Failure of endometrial sampling, classified as technical failure or insufficient tissue for diagnosis. Results: In 74 (20.8%) of the 356 included women, sampling technically failed, and in 84 (29.8%) the amount of tissue was insufficient for diagnosis. Nulliparity [odds ratio (OR) 3.8, 95% confidence interval (CI) 1.8–7.9] and advanced age (OR 1.03 per year, 95% CI 1.00–1.06) were associated with technical failure. Advanced age was associated with insufficient sampling (OR 1.04 per year, 95% CI 1.01–1.07), and endometrial thickness >12 mm decreased the chance of insufficient sampling (OR 0.3...

Sampling systems matched to input processes and image classes

Bopardikar, Ajit
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
36.57%
This dissertation investigates sampling and reconstruction of wide sense stationary (WSS) random processes from their sample "random variables". In this context, two types of sampling systems are studied, namely, interpolation and approximation sampling systems. We aim to determine the properties of the filters in these systems that minimize the mean squared error between the input process and the process reconstructed from its samples. More specifically, for the interpolation sampling system we seek and obtain a closed form expression for an interpolation filter that is optimal in this sense. Likewise, for the approximation sampling system we derive a closed form expression for an optimal reconstruction filter given the statistics of the input process and the antialiasing filter. Using these expressions we show that Meyer-type scaling functions and wavelets arise naturally in the context of subsampled bandlimited processes. We also derive closed form expressions for the mean squared error incurred by both the sampling systems. Using the expression for mean squared error we show that for an approximation sampling system, minimum mean squared error is obtained when the antialiasing filter and the reconstruction filter are spectral factors of an ideal brickwall-type filter. Similar results are derived for the discrete-time equivalents of these sampling systems. Finally...

Nonuniform sequential sampling for signal analysis

Hall, Peter; Yin, Jiying
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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New electronic technologies for signal analysis raise the possibility of sampling very rapidly, with a time-varying density, and determining empirically both the sampling rate and the window width as the signal evolves in time. These opportunities also point to the possibility of sequentially sampling in a time-varying way in more traditional problems. Motivated by these ideas, we establish a sampling formula, valid in cases where both sampling rate and window width may be varied. The formula states that, in terms of the ways in which these quantities should alter with time, optimal performance is achieved when the window width is inversely proportional to squared sampling rate, and sampling rate is directly proportional to squared bias.

An overview of sampling best practice in African mining

Spangenberg,I.C.; Minnitt,R.C.A.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
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The status of sampling practices in the gold mining industry in Africa was determined as an initial step in a process to standardize sampling practices in the mining industry. Twenty-one gold mines, twenty metallurgical plants, and thirteen laboratories were rated for the potential influence of the relevant sampling errors on each component of the particular sampling system. The findings of the study on the status of equipment, standards, procedures, and management principles were presented in a dissertation (Spangenberg, 20121) and are now used by AngloGold Ashanti's mines in the quest for correct sampling practices. The information is also used to compile a guideline on leading practice procedures for sampling methods in gold mining. This article is an overview of sampling best practice found in African mining

Mechanical sampling - a manufacturer's perspective

Steinhaus,R.C.; Minnitt,R.C.A.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
Relevância na Pesquisa
36.53%
With the advent of the First World Conference on Sampling and Blending (WCSB1) in Denmark in 2003 and the subsequent biannual meetings, together with other sampling conferences held on a regular basis, the central tenets of sound sampling practice and theory are spreading throughout the minerals industry. End-users and project houses, or groups who execute the projects, are all now better-informed about the principles of 'correct' sampling and preparation. To support this, many large mining companies now have their own in-house champion who will advise and ensure that the supply of sampling equipment is correct in terms of design and application, which further contributes to improved metallurgical accounting. The presence of a sampling champion also ensures that consistent and acceptable standards in regard to sampling practice are maintained throughout the group. This has, in turn, placed a greater degree of responsibility on the shoulders of sampling equipment suppliers, in terms of their equipment designs and product offerings, as well as applications knowledge for effective installation of equipment on client plants. This paper attempts to highlight the significant challenges that sampling equipment manufacturers often face with regard to complying with the newly understood requirements of best practice and sampling equipment design. Manufacturers invariably face issues with end-users or project houses...

Pitfalls in Vezin sampling for finely crushed materials by

Kruger,C.; van Tonder,E.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
Relevância na Pesquisa
36.52%
Anglo American Platinum has adopted a strategy of best practice principles (BPP) for sampling, mass measurement, analysis, and metal accounting for more than a decade now. When new plants are designed, the most suitable sampling equipment and sampling protocols are implemented and material flows and plant layouts are designed around sampling strategies. A few years ago, a crushing plant for a high-grade matte stream was commissioned. The design called for the high-grade material to be crushed to 95% passing 2 mm, and the design allowed for a single-cutter primary Vezin sampler taking increments from a gravity flowing stream at regular intervals while filling a tanker for pneumatic offload at the base metal refinery. This was a single point of sampling and analysis that would measure the wanted output from the smelting complex and the input to the refineries. In addition, the design incorporated the functionality to collect increments in an 'interleaved' fashion from the Vezin sampler for internal precision checks. The metal accounting strategy for Anglo Platinum involves the ongoing measurement of all inputs, outputs, and stock levels for all operations for platinum group metal (PGM) and base metal (BM) content. Included are yearly stocktakes...

Sampling in the South African minerals industry

Minnitt,R.C.A.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
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36.55%
Although not fully accepted in South Africa, the Theory of Sampling originally proposed by Pierre Gy is fast becoming the cornerstone of sampling practice throughout the world. The growing acceptance of Gy's Theory of Sampling in South Africa can be attributed to a number of factors, chief amongst them being the development of a tradable mineral asset market, the promulgation of the Mineral and Petroleum Resources Development Act (MPRDA), the growing number of commercial and academic courses that are offered on sampling, and the regulation of the industry through internationally acceptable guidelines and rules for reporting and trading in mineral assets. The size of the South African minerals industry and the dependence of our economy on mineral production have also meant that correct sampling is of key importance to mineral trade. ISO standards have been the principal guides for producers of mineral bulk commodities who produce to customers' specifications, whereas Gy's insights have been most readily accepted by precious and base metals producers whose product is sold into metal markets. Understanding of small-scale variability is essential in the precious and base-metal industries, but detailed studies of the effects of heterogeneity have not been as productive in the bulk commodities. Sampling practices at different stages of mineral development from exploration...