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Balls mill work index determination guide.
No full textA etapa de cominuição é uma das principais fontes de gasto energético em uma planta de processamento mineral e tem como objetivo a redução do minério em tamanho suficiente para viabilizar os processos subsequentes de beneficiamento mineral. O cosumo energético operacional desta etapa podem ser estimados em laboratório, a partir de uma amostra, por procedimentos padronizados. O índice de trabalho (WI) é um dos métodos usados para que haja uma previsão de gasto de energia e seja possível o “scale up” do cicuito de moagem. Este trabalho tem como objetivo descrever a metodologia para determinação do índice de trabalho pelo ensaio de moinho de bolas através da teoria de Bond, incluindo os ajustes que ocoreram ao longo dos anos, tendo em vista a disseminação e aplicação dessa metodologia de análise de processos de moagem em escala industrial. Este estudo foi dividido em duas etapas: uma teórica com a revisão bibliográfica do método de bancada para determinação do BWI pela teoria de Bond e uma etapa prática com a execução do ensaio em moinho de bolas no Laboratório de Processamento Mineral da Universidade Federal de Ouro Preto (UFOP), utilizando o software VKA WI para os cálculos.The comminution stage is one of the main sources of energy consumption in the mineral processing plant and its objective is to reduce the ore to a sufficient size to enable the subsequent beneficiation processes. The operational costs of this step can be measured in laboratory by scientific formulas using a sample. The work index (WI) is a method used to forecast the energy consumption in the ore comminution and make it possible to scale up. This work aims to present the methodology for determining the work index by the ball-mill test through Bond's theory in view of the dissemination of this analysis methodology for industrial processes. This study has a theoretical stage with a bibliographic review on the method of applying the BWI determination by Bond's theory and a practical stage with the execution of the ball-mill test in the Mineral Processing Laboratory at Federal University of Ouro Preto (UFOP), using VKA WI software
Effect of intercritical austenitizing temperature on the kinetics of martensitic transformation and microstructural evolution in a API-OCTG grade K55 steel.
No full textAços API-5CT grau K55 são especificados para tubos de revestimento de poços de exploração de óleo e gás. Eles
podem ser fabricados por laminação sem costura, seguida de têmpera e revenimento (processo clássico). No entanto, diversos
segmentos industriais têm apontado a utilização de microestruturas bifásicas (ferrita-martensita) como uma alternativa para
melhorar a relação resistência mecânica-tenacidade de diversos produtos. Considerando a possibilidade de obtenção de um
tubo bifásico por meio da aplicação de têmpera após austenitização intercrítica, este estudo pioneiro investigou o efeito da
temperatura de austenitização intercrítica sobre as frações de fases e a cinética de transformação martensítica de um aço
API-5CT grau K55. Concluiu-se que, para este aço, a faixa de temperatura de austenitização intercrítica está compreendida
entre 750 °C e 820 °C. Verificou-se um aumento significativo nas temperaturas Ms
e Mf
, assim como da fração de martensita
com a elevação da temperatura de austenitização. Em relação à cinética de transformação martensítica, concluiu-se que o
efeito autocatalítico no início da transformação é mais atuante quanto maior a temperatura de austenitização. Modelos de
previsibilidade que descrevem a evolução das temperaturas Ms
e Mf
, assim como da cinética de transformação martensítica,
em função da condição de austenitização, foram aplicados com sucesso.API-5CT grade K55 steels are specified for oil and gas exploration (casing pipes) and they can be manufactured as
quenched and tempered seamless pipes (classic process). However, several industrial segments have pointed out that the
use of biphasic microstructures (ferrite-martensite) is a great alternative to improve the mechanical strength-toughness
ratio of several products. Considering the possibility of obtaining a biphasic pipe applying quenching heat treatments
after intercritical austenitizing, this pioneering study investigated the effect of the intercritical austenitizing temperature
on the phase fractions and the martensitic transformation kinetics in an API-5CT grade K55 steel. It was concluded that,
for this steel, the intercritical austenitizing temperature range is between 750 °C and 820 °C. There were significant
increases in Ms
and Mf
temperatures, as well as a rise in the martensite fraction with increasing austenitizing temperature.
Regarding the kinetics of martensitic transformation, it was concluded that the autocatalytic effect at the beginning of the
transformation is more active the higher the austenitizing temperature. Predictability models that describe the evolution
of Ms
and Mf
temperatures, as well as the kinetics of martensitic transformation, as an austenitizing condition function
were successfully applied
Validity of the GLIM criteria for the diagnosis of malnutrition in patients with colorectal cancer : a multicenter study on the diagnostic performance of different indicators of reduced muscle mass and disease severity.
No full textObjectives: To assess the concurrent and predictive validity of different combinations of Global Leadership Initiative on Malnutrition (GLIM) criteria in patients with colorectal cancer considering different indicators of reduced muscle mass (MM) and the effects of the disease. Methods: A secondary analysis with patients with colorectal cancer. The reduced MM was assessed by arm muscle area, arm muscle circumference, calf circumference, fat-free mass index, skeletal muscle index (SMI) and skeletal muscle. Cancer diagnosis or disease staging (TNM) was considered for the etiologic criterion referred to as the effect of the disease. The other phenotypic and etiologic criteria were also evaluated, and we analyzed 13 GLIM combinations. Concurrent validity between GLIM criteria and Patient-Generated Subjective Global Assessment was evaluated. Logistic and Cox regression were used in the predictive validation. Results: For concurrent validity (n = 208), most GLIM combinations (n = 6; 54.5%) presented a moderate agreement with Patient-Generated Subjective Global Assessment and none showed satisfactory sensitivity and specificity (>80%). Reduced MM evaluated by SMI and SMI were present in the GLIM combinations associated with postoperative complications (odds ratio, ≥2.0), independent of other phenotypic and etiologic criteria. The combinations with reduced MM considering any method and fixed phenotypic criteria and TNM were associated with mortality (hazard ratio, ≥2.0). Conclusions: Satisfactory concurrent validity was not verified. The GLIM diagnosis of malnutrition was associated with postoperative complications and mortality
Petrocronology of metapelitic rocks : a review of key concepts.
No full textRochas metapelíticas são importantes marcadores petrocronólogicos, não apenas pelas variadas e sensíveis paragêneses minerais e presença de fases datáveis, mas também por sua ampla e contínua distribuição ao longo de terrenos, permitindo, assim, estudos integrados e detalhados do metamorfismo e eventos em diferentes regiões. O presente trabalho visou sintetizar aspectos relevantes à caracterização petrológica e geocronológica de metapelitos para regimes de pressão média. Considerando o sistema químico KFMASH (K2 O, FeO, MgO, Al2 O3, SiO2, H2 O), minerais como clorita, muscovita, cloritoide, biotita, estaurolita, granada, cordierita, andaluzita, cianita, sillimanita e feldspato potássico são típicos da paragênese de metapelitos para baixas ou médias pressões, desde que haja disponibilidade química e condições P-T para sua formação. De forma geral, tem-se como distintivas, com o aumento das condições P-T e o aparecimento dos respectivos minerais-índice, as zonas metamórficas da clorita, biotita, granada, estaurolita, cianita, sillimanita e sillimanita + ortoclásio. Para a determinação petrogenética e das condições do metamorfismo desses litotipos, estudos macro- e microestruturais, associados com análises de química mineral e de rocha total, propiciam a aplicação de métodos termobarométricos diversos, desde os convencionais, passando pelos otimizados e diagramas isoquímicos de fases e chegando nos termômetros monoelementares, cada qual com suas especificidades e aplicações. De modo a promover um estudo petrocronológico dos litotipos, fases minerais como zircão, granada, monazita e rutilo, em seus respectivos sistemas isotópicos, possibilitam atribuir idades a esses eventos metamórficos e, com a integração e interpretação dos dados obtidos, construir a trajetória P-T-t-d de formação dessas rochas e dos eventos/estágios dos processos envolvidos. Uma abordagem sistemática, de acordo com as particularidades da rocha, deve ser empregada, garantindo, assim, a acurácia dos resultados obtidos.Metapelitic rocks are key petrochronological markers, not only for their varied and sensitive mineral paragenesis and presence of datable phases but also due to their broad and continuous distribution along terrains, thus supporting integrated and detailed studies of the metamorphism and events that took place in different regions. Therefore, the present work aimed to synthesize relevant aspects to the petrological and geochronological characterization of metapelites for medium pressure regimes. Considering the KFMASH (K2 O, FeO, MgO, Al2 O3, SiO2, H2 O) system, minerals such as chlorite, muscovite, chloritoid, biotite, staurolite, garnet, cordierite, andalusite, kyanite, sillimanite, and potassium feldspar are distinctive of these rocks paragenesis in low to medium pressure regimes, as long as there is chemical availability and sufficient P-T conditions for their formation. With the increase in P-T conditions and the appearance of the respective index-minerals, the indicative metamorphic zones are as follow: chlorite, biotite, garnet, staurolite, kyanite, sillimanite, and sillimanite + orthoclase. For the petrogenetic and metamorphic conditions of characterization of such lithotypes, macro- and microstructural studies, associated with mineral chemistry and bulk-rock rock analysis, favor the application of different thermobaro- metric methods, from conventional ones through optimized and isochemical phase-diagrams, to single-element thermometers, each one with its particularities and application possibilities. To promote a petrochronological study, mineral phases such as zircon, garnet, monazite, and rutile, using their respective isotopic systems, allow assigning ages to these metamorphic events and, with the integration and interpretation of the data obtained, constraining the P-T-t-d trajectory of rocks formation. A systematic approach must be employed, in accordance with the particularities of the studied rock, hence guaranteeing the accuracy of the results obtained
Les entrepreneurs publics et les risques pour l’innovation dans le secteur public.
No full textEste artigo analisa os riscos às inovações no setor público conducentes à implementação de ideias alternativas ou ao retorno às velhas práticas. Aplicam-se técnicas quantitativas e qualitativas para analisar os riscos à gênese e à difusão das Redes de Cooperação para a Prevenção e Combate à Corrupção (RCPCC) no Brasil. Verificou-se a presença de cinco riscos: crises políticas, circulação de elites, presença de “passageiros não pagantes”, barreiras hierárquicas e pautas restritas a interesses específicos. O artigo impacta a agenda de pesquisa sobre inovação no setor público ao apontar a necessidade de investigações futuras sobre o trabalho cotidiano de agentes comprometidos com a inovação.This article analyzes the risks to public sector innovations leading to the implementation of alternative ideas or a return to old practices. Quantitative-qualitative techniques are applied to analyze the risks to the genesis and the dissemination of Cooperation Networks for the Prevention and Combat of Corruption in Brazil. The presence of five risks was verified: political crises, circulation of elites, presence of “non-paying passengers”, hierarchical barriers and guidelines restricted to specific interests. The article impacts the research agenda on innovation in the public sector by pointing out the need for future investigations into the daily work of agents committed to innovation
Design sonoro e dimensão acústica da cena na peça Estopim.
No full textO artigo tem como foco o projeto de design sonoro para a peça Estopim, do grupo Teatro
do Tumulto, formado por alunos e professores do curso de teatro da UFOP (Ouro
Preto/MG) e que pesquisa as relações entre tecnologia e política na cena teatral. Tendo
como referência o conceito de dimensão acústica da cena, descreve as etapas de
criação sonora e os elementos musicais do espetáculo, elaborados como forma de
integração dos planos presenciais e audiovisuais mobilizados na encenação. Aborda
tanto as referências teóricas que balizaram a proposta sonora quanto os aspectos
práticos de sua execução
A data-centric approach for Portuguese speech recognition : language model and its implications.
No full textRecent advances in Automatic Speech Recognition
have made it possible to achieve a quality never seen before
in the literature, both for languages with abundant data, such
as English, which has a large number of studies, and for
the Portuguese language, which has a more limited amount
of resources and studies. The most recent advances address
speech recognition problems with Transformers based models,
which have the capability to perform the speech recognition
task directly from the raw signal, without the need for manual
feature extraction. Some studies have already shown that it is
possible to further improve the quality of the transcription of
these models using language models within the decoding stage,
however, the real impact of such language models is still not
clear, especially for the Brazilian Portuguese scenario. Also, it is
known that the quality of the data used for training the models
is of paramount importance, however, there are few works in the
literature addressing this issue. This work explores the impact of
language models applied to Portuguese speech recognition both
in terms of data quality and computational performance, with
a data-centric approach. We propose an approach to measure
similarity between datasets and, thus, assist in decision-making
during training. The approach indicates paths for the advancement
of the state-of-the-art aiming at Portuguese speech recognition,
showing that it is possible to reduce the size of the language
model by 80% and still achieve error rates around 7.17%
for the Common Voice dataset. The source code is available at
https://github.com/joaoalvarenga/language-model-evaluation
ILS-based algorithms for the profit maximizing uncapacitated hub network design problem with multiple allocation.
No full textThis study addresses a hub network design problem to maximize net profit. This problem considers an
incomplete hub network with multiple allocation that does not impose capacity constraints, does not allow
direct connections between non-hub nodes, and accepts the demand to be partially met, being satisfied only
when profitable. To tackle this problem, which is NP-hard, we propose two heuristic algorithms based on the
Iterated Local Search (ILS) metaheuristic, a standard ILS algorithm, and an Enhanced ILS algorithm, which
increases the perturbation level only after a few unsuccessful attempts at improvement. Both algorithms use
Random Variable Neighborhood Descent in the local search. Computational experiments were performed using
benchmark instances for hub location problems, and statistical analyzes of the algorithms were presented.
Numerical results confirm that both algorithms yield good-quality solutions with an acceptable runtime. In
particular, the proposed algorithms obtain the optimal solution for most instances with up to 150 nodes,
which have known optimal solutions. Furthermore, the proposed algorithms were able to handle instances
with up to 500 nodes