This paper presents an optimization methodology for the geometric configuration of a room–and–pillar mining project,considering safety and operational restrictions while maximizing ore recovery.An underground mangan...This paper presents an optimization methodology for the geometric configuration of a room–and–pillar mining project,considering safety and operational restrictions while maximizing ore recovery.An underground manganese mine was chosen as a case study to investigate the capabilities of the presented methodology.A software package(OPTIMINE)was implemented to address the computational demand in an automated manner.Three–dimensional finite difference analyses were performed in FLAC3D and used as implicit functions to consider safety in terms of the factor of safety and room convergence.The obtained results showed that recovery could be increased from 44%to more than 80%in a safe manner.展开更多
The literature has shown the efficiency of exercise in the control of type 2 diabetes(T2D), being suggested as one of the best kinds of non-pharmacological treatments for its population. Thus, the scientific productio...The literature has shown the efficiency of exercise in the control of type 2 diabetes(T2D), being suggested as one of the best kinds of non-pharmacological treatments for its population. Thus, the scientific production related to this phenomenon has growing exponentially. However, despite its advances, still there is a lack of studies that have carried out a review on the acute effects of physical exercise on metabolic and hemodynamic markers and possible control mechanisms of these indicators in individuals with T2 D, not to mention that in a related way, these themes have been very little studied today. Therefore, the aim of this study was to organize and analyze the current scientific production about the acute effects of physical exercise on metabolic and hemodynamic markers and possible control mechanisms of these indicators in T2 D individuals. For such, a research with the following keywords was performed:-exercise; diabetes and post-exercise hypotension; diabetes and excess post-exercise oxygen consumption; diabetes and acute effects in PUBMED, SCIELO and HIGHWIRE databases. From the analyzed studies, it is possible to conclude that, a single exercise session can promote an increase in the bioavailability of nitric oxide and elicit decreases in postexercise blood pressure. Furthermore, the metabolic stress from physical exercise can increase the oxidation of carbohydrate during the exercise and keep it, in high levels, the post exercise consumption of O2, this phenomenon increases the rate of fat oxidation during recovery periods after exercise, improves glucose tolerance and insulin sensitivity and reduces glycemia between 2-72 h, which seems to be dependent on the exercise intensity and duration of the effort.展开更多
The disposal of mining tailings has increasingly focused on the use of dry stacks.These structures offer more security since they use filtered and compacted material.Because of the construction method and the heights ...The disposal of mining tailings has increasingly focused on the use of dry stacks.These structures offer more security since they use filtered and compacted material.Because of the construction method and the heights achieved,the material that compounds the structure can be subjected to different stress paths along the failure plane.The theoretical framework considered in the design of these structures generally is the critical state soil mechanics(CSSM).However,the data in the literature concerning the uniqueness of critical state line(CSL)is still controversial as the soil is subjected to different stress paths.With respect to tailings,this question is even more restricted.This paper studies two tailings with different gradings due to the beneficial processes over extension and compression paths.A series of drained and undrained triaxial tests was conducted over a range of initial densities and stress levels.In the q-p'plane,different critical stress ratio(M)values were obtained for compression and extension stress paths.However,the critical state friction angle is very similar with a slightly higher critical state friction angle for extension tests.Curved stress path dependent CSLs were obtained in the n-lnp0 plane with the extension tests below the CSL defined in compression.Regarding the fines content,the studied tailings presented very similar M and critical state friction angle values.However,the fines content af-fects the volumetric behavior of the studied tailings and the CSLs on the n-lnp0 plane shift downwards with the increasing fines content for compression and extension tests.In relation to dilatancy analysis,the fines content did not present an evident influence on the dilatancy of the materials.However,different values of mean stress ratio N were obtained between compression and extension tests and can corroborate the existence of non-unique CSLs for these materials.展开更多
The disposal of filtered tailings in high dry stacks can induce particle breakage,changing the material's behaviour during the structure's lifetime.The grading changes influence material properties at the crit...The disposal of filtered tailings in high dry stacks can induce particle breakage,changing the material's behaviour during the structure's lifetime.The grading changes influence material properties at the critical state,and this is not mature for intermediate artificial soils(tailings)in a broad range of confining pressures.In this paper,it aims to describe the behaviour of iron ore tailings in a spectrum of confining pressures broader than the reported in previous studies.A series of consolidated drained(CD)triaxial tests was carried out with confining pressures ranging from 0.075 MPa to 120 MPa.These results show that the amount of breakage plays an essential role in the response of iron ore tailings.The existence of curved critical state line(CSL)in both specific volume(ν)-logarithm of mean effective stress(p′)and deviatoric stress(q)-mean effective stress(p′)planes,and different responses in the deviatoric stress-axial strain-volumetric strain curves were verified.An inverse S-shaped equation was proposed to represent the silty-sandy tailings'behaviour up to high pressures onν-lnp′plane.The proposed equation provides a basis for enhancing constitutive models and considers the evolution of the grading up to severe loading conditions.The adjustment considered three regions with different responses associated with particle breakage at different pressure levels.展开更多
Mining activity in Brazil has significantly contributed to the country development.However,this contribution is not always fully noticed by society.This study aims to bring more evidence to this mining activity contri...Mining activity in Brazil has significantly contributed to the country development.However,this contribution is not always fully noticed by society.This study aims to bring more evidence to this mining activity contribution,based on highly regarded development indicators,such as the HDI(Human Development Index),created by the UNDP(United Nations Development Programme).The HD1 was traditionally designed as an instrument to evaluate the degree of countries development and was subsequently deployed to states and municipalities(IDHM(Municipal Human Development Index)for Brazilian municipalities).In addition to lDHM released by the UNDP,FIRJAN(Federation of the Industries of the State of Rio de Janeiro)developed its own IFDM(FIR JAN Municipal Development Index).The statistical analysis shows that the average of the municipalities with mining activities has superior development indices than those with non-mining activities,especially in the two major mining states:Minas Gerais and Parfi.展开更多
The EFVM （Vitoria Minas Railroad） is one of the main railways in Brazil. It transports freight trains of ore, 220 wagons each. These wagons have 2 boogies of 2 axles each and 32 metric tons on metre gauge. Elastic s...The EFVM （Vitoria Minas Railroad） is one of the main railways in Brazil. It transports freight trains of ore, 220 wagons each. These wagons have 2 boogies of 2 axles each and 32 metric tons on metre gauge. Elastic strains were measured on a special part of this railway due to these trains. The main load to evaluate stresses and strains was a G 16 Locomotive, a C-C kind from Vale, a Brazilian Company. The measurements were obtained by dynamic deflectometer installed on a main line of this railway, near Ipatinga, a city from Minas Gerais, one of Brazil states. This track was equipped to obtain stresses under an equal repeated static load A simulation of the stresses was made under critical strain by Ferrovia 1.0 software. It was also made an evaluation of unequal results from neighbor sleepers taking in comparison two equipped parts of this railway, one with compacted ballast and no compaction to the other. The results were strain limited, avoiding breakage or damage to the studied rails. This work analyses these measurements focusing on the improvement of track quality.展开更多
Antibiotic resistance represents a widespread problem in milk production.The identification of compounds for a topically applied ointment used in mastitis therapy remains elusive.Compounds from the genus Hymenaea can ...Antibiotic resistance represents a widespread problem in milk production.The identification of compounds for a topically applied ointment used in mastitis therapy remains elusive.Compounds from the genus Hymenaea can be administered in cases of multi-drugresistant Staphylococcus aureus infection for ruminant species,but the protective properties are not well known.Wi this research the aim is verify the protective effects of H.martiana against S.aureus infection in bovine mammary epithelial cell line(MAC-T)and to obtain an antioxidant profile evaluation in vitro.The MAC-T cells were challenged with S.aureus after being exposed to the extract of the H.martiana in the protective assay.For the verification of the viability of the MAC-T cells,the MTT assay was performed,and was used dilutions of the plant extract,starting at 2.5%.The extract of H.martiana was evaluated for antioxidant aspect in different dilutions by FRAP,ORAC and DPPH.A variety of flavonoids(quercetin,luteolin,etc.)have been identified as the main components by using mass spectrometry,reinforcing our in vitro findings that flavonoids,especially quercetin,have a medicinal profile capable of killing mastitis-causing bacteria.An excellent antioxidant pattern was observed in the 2.5%solution;however,membrane integrity in MAC-T cells was compromised.Those findings suggest low dilutions of H.martiana extract has a desirable protective effect from S.aureus pathogenesis.Our in vitro studies can be gleaned upon for further in vivo studies.展开更多
The objective of this study is to present a tailings recovery project in a dam located in northern Brazil;the tailings in this dam have high concentrations of iron. The sustainable recovery of mineral resources can be...The objective of this study is to present a tailings recovery project in a dam located in northern Brazil;the tailings in this dam have high concentrations of iron. The sustainable recovery of mineral resources can be achieved using the dredging method. The methodology used was based on two drilling projects conducted in 2001 and 2010;these projects contained samples with information on the chemical composition and particle size fractions. The dredging system was designed to operate with four cutter suction dredgers. For operation, factors such as productivity, pumping distance and material flow were considered. The material contained in the dam was estimated using the natural neighborhood interpolation method;this resulted in approximately 192 million tons of tailings, with an average iron content of 63.37%. Based on these data, a 13-year mining plan was prepared, with the potential to maximize the use of the tailings and reduce the environmental impacts, thus contributing to a circular economy.展开更多
To extract ore from open pit mines,the associated waste material must also be removed.In most mining operations,the amount of waste rock is greater than the amount of ore.Waste from the pits is usually disposed of in ...To extract ore from open pit mines,the associated waste material must also be removed.In most mining operations,the amount of waste rock is greater than the amount of ore.Waste from the pits is usually disposed of in piles,which results in environmental impacts,such as alterations in the natural landscape,possible contamination of soil and water,and the generation of dust and particulates.One way to reduce these environmental impacts and achieve a circular economy(CE)is to use waste rock to construct the pavement layers of mine roads.Another possibility would be to move only the amount of waste necessary to release the ore of interest;in addition to reducing costs,this approach would reduce the volume of waste disposed of in piles.In this study,to reduce the movement of this compact waste,a change in the planned slope is proposed,and the compact waste and surplus material in a long-term mining plan are evaluated.The new optimized geometries,which meet the requirements for road pavement material and remain stable,as indicated by 2D geotechnical finite element modeling,were incorporated into the mining plan of Pit A,an iron mining complex in northern Brazil.The new mining plan was further subjected to economic analysis,which revealed the variations in the tonnage of ore and waste rock(mostly fresh mafic),as well as the change in the net present value(NPV),compared with the original mining plan.The results indicated that the change in geometry led to a reduction of 4.42 Mt in fresh mafic movement.This reduction directly impacted the NPV of the mine plan,with an increase of US$6.88 million.展开更多
The mechanics of unsaturated soils is a relatively recent and evolving field of study.This paper introduces an innovative machine learning-based approach for developing constitutive models to describe the soil-water r...The mechanics of unsaturated soils is a relatively recent and evolving field of study.This paper introduces an innovative machine learning-based approach for developing constitutive models to describe the soil-water retention curve,hydraulic conductivity,and shear strength of unsaturated soils.These models were built using comprehensive soil characterization data and triaxial test re-sults,incorporating parameters such as gravel,sand,silt,and clay content,plas-ticity index,porosity,and permeability.Equations were implemented using al-gorithms developed in the Mathematica®programming environment.The re-sults demonstrate that the proposed models are both physically consistent and experimentally validated,exhibiting high precision and practical applicability.While this approach significantly optimizes the development of constitutive models,it does not replace the need for conventional testing,instead serving as a robust complementary tool.The proposed methodology offers an efficient and reliable solution for generalizing constitutive models across various un-saturated soil types,advancing knowledge and applications in the field.展开更多
A geostatistical study was conducted with the objective of developing a better understanding of the sediments deposited in the tailings dam of an iron mine located in Brazil.The samples,derived from two drilling campa...A geostatistical study was conducted with the objective of developing a better understanding of the sediments deposited in the tailings dam of an iron mine located in Brazil.The samples,derived from two drilling campaigns conducted in 2001 and 2010,were statistically evaluated and validated for the construction of both a 3D geological model and an estimated model.The geological body modeling process was performed using an implicit method,which was based on the interpretation and adjustments of vertical sections and considered the positions of the samples and the grades of the chemical components of interest.In addition,the primitive topography was also considered to determine the base and limits of the deposit,as well as the current topography.The ordinary kriging(OK)method was chosen to estimate the grades of the chemical components and the retained/passing percentages of the particle size fractions described in the samples.The kriging model was validated through two analyses:mean comparison and drift analyses.The total tonnage of the estimated model was 287.14 Mt,with an average Fe grade of 63.89%.展开更多
The importance of identifying the caliber in advance is in knowing the exact quantity of mangos,by weight,that a determined crop season(complete periods of the mango cycle from growth up to fruit harvest)will provide....The importance of identifying the caliber in advance is in knowing the exact quantity of mangos,by weight,that a determined crop season(complete periods of the mango cycle from growth up to fruit harvest)will provide.This study uses Random Forest method to predict the percentage distribution of the calibers of four mango varieties from Brazil’s largest exporter and producer.Our proposed approach was conducted in the following steps:data collection;data preprocessing;predictive model building;and model evaluation.The data correspond to three crop seasons,namely those of 2019,2020,and 2021.Each data line corresponds to a plot with the percentage of a determined caliber at the end of a crop season.The number of rows in the dataset is 5503,with 37.33%,31.47%,22.76%,and 8.44%corresponding to the Keitt,Tommy Atkins,Kent,and Palmer varieties,respectively.The variables are Productivity,(N)Nitrogen,Number of plants(units),Plants/hectare,Month of floral induction,(Zn)Zinc,(S)Sulfur,(B)Boron,Caliber,and Percentage of caliber.The Python programming language was used to preprocess the data,do exploratory analysis,develop the algorithms of the Random Forest Regressor,and compile the lines of the code in Visual Studio Code.Python libraries were used during the study,such as pandas for data handling and Scipy for removing outliers to avoid any biases in the data.The YellowBrick library was used for the feature selection process.Four regression models were created using Random Forest(RF),one for each variety of fruit that composes the dataset.The algorithms showed satisfactory results for Kent,Keitt,Tommy Atkins,and Palmer mangoes,with the following R^(2)of the models:87.29%,74.37%,87.69%,and 62.75%,respectively.During the Feature Selection step,nitrogen(N)was perceived to be highly important in all the models,highlighting the representative nature of this element in fruit formation.From the models created,it is possible to predict the percentage distribution of the calibers of mangos from each growing area 6 months in advance,using data that characterize each area and information on the presence of leaf nutrients as input.展开更多
The required treatment and monitoring of contaminants in wastewater reinforces the development of low-cost adsorbents/chemosensors,introducing advantages relative to the detection/removal of toxic metals and dyes.Here...The required treatment and monitoring of contaminants in wastewater reinforces the development of low-cost adsorbents/chemosensors,introducing advantages relative to the detection/removal of toxic metals and dyes.Herein,it is reported a two-step process of fabrication of fluorescent carbon dots via the hydrothermal treatment of amino acids for the following encapsulation in electrospun fibers.The prominent anionic behavior of electrospun fibers of Eudragit L100 was explored for adsorption of cationic dyes(methylene blue and crystal violet)-with the prevailing electrostatic interaction of parts being favored by the formation of monolayers on the surface of adsorbents.On the other hand,the controlled release of carbon dots(CDs)from fibers to the reactor can be explored for a second application:the nitrogen ligands from released glycine-based carbon dots can be explored to indicate the presence of metal ions in aqueous solution.Our experiment resulted in a quenching in the fluorescence of the CDs in order of 90%in the emission of particles in the response of the presence of Fe^(3+) ions,characterizing a promising perspective for this experimental system.展开更多
The São Francisco River Basin,located in eastern Brazil,has undergone a significant amount of anthropogenic changes in the last several decades,such as agricultural expansion,irrigation activities,mining,and the ...The São Francisco River Basin,located in eastern Brazil,has undergone a significant amount of anthropogenic changes in the last several decades,such as agricultural expansion,irrigation activities,mining,and the construction of large dams.Together,these changes have altered the historic sediment budget and have led to an aggradation of sediments in the navigation channel,impacting the ability to efficiently ship agricultural commodities to regional ports.In an effort to aid decision makers in future waterway navigation planning,an international partnership between the Brazilian government agency CODEVASF and the US Army Corps of Engineers(USACE)was created.Through this partnership a SWAT model of the 630000 km2 São Francisco River basin was developed to better understand both the historic and current sediment budget within the navigation channel.The SWAT model of the São Francisco River Basin was calibrated for hydrology and sediment loads.Monthly discharges were calibrated at 17 Agência Nacional deÁguas(ANA)gages,with Nash-Sutcliffe efficiency(NSE)values ranging from 0.42 to 0.75 for an eleven year simulation.Sediment loads were calibrated to an ANA sediment gage located in the Middle São Francisco River Navigation Channel,with a PBIAS(Percent Bias)of 11.6.Based on model results,the aggradation rate of sediment in the São Francisco River and major tributaries has increased by approximately 20 Mt since Pre-European settlement of the basin(from approximately 7 Mt/a to 27 Mt/a).This increase has contributed to an impaired navigation channel due to shoaling of sandy sediments in the navigation channel.展开更多
Aims Soil plays an important role in the formation and heterogene-ity of habitats and thus can cause changes in vegetation struc-ture and plant diversity.The differentiation between Cerrado/savanna and forest is well ...Aims Soil plays an important role in the formation and heterogene-ity of habitats and thus can cause changes in vegetation struc-ture and plant diversity.The differentiation between Cerrado/savanna and forest is well known,but the relationship between soil and habitats from savannic or forest formations still needs to be better understood,particularly in tropical ecotonal areas.We studied the association between attributes of plant com-munities,namely structure and diversity,and physicochemical characteristics of soils in the Caatinga domain at the transition to Cerrado in Brazil.Methods Chemical and physical analyses of soils were performed in samples of 38 plots from savannic formations and 30 plots from forest forma-tions.Vegetation was characterized floristically and structurally in all plots,five habitats being assessed in each plant formation.Soil features and vegetation parameters were highly distinct among the different habitats.Important Findingsin general,forest habitats were more nutrient rich than savannic formation.Furthermore,soil variables showed effects both on vegetation structure and on its species diversity,more pronouncedly in the savannic formations.Habitats were structurally distinct,and diversity differed between savannic and forest communities;however,a higher differentiation occurred when the savannic formation habitats were compared among them.Although plant diversity did not differ among forest formation habitats,soil attributes showed a close relationship with edaphic factors and can contribute for similar vegetation.The soil-vegetation relationship in highly diverse ecotonal landscapes is important from the conservation biology point of view and aid in the execution of proactive plans for the maintenance of biodiversity.Thus,we noticed that diversity and soil behaves distinctly between savannic and forest communities.展开更多
Background:Coronavirus disease 2019(COVID-19)was confirmed in Brazil in February 2020.Since then,the disease has spread throughout the country,reaching the poorest areas.This study analyzes the relationship between CO...Background:Coronavirus disease 2019(COVID-19)was confirmed in Brazil in February 2020.Since then,the disease has spread throughout the country,reaching the poorest areas.This study analyzes the relationship between COVID-19 and the population's living conditions.We aimed to identifysocial determinants related to the incidence,mortality,and case fatality rate of COVID-19 in Brazil,in 2020.Methods:This is an ecological study evaluating the relationship between COVID-19 incidence,mortality,and case fatality rates and 49 social indicators of human development and social vulnerability.For the analysis,bivariate spatial correlation and multivariate and spatial regression models(spatial lag model and spatial error models)were used,considering a 95%confidence interval and a significance level of 5%.Results:A total of 44.8%of municipalities registered confirmed cases of COVID-19 and 14.7%had deaths.We observed that 56.2%of municipalities with confirmed cases had very low human development(COVID-19 incidence rate:59.00/100000;mortality rate:36.75/1000000),and 52.8%had very high vulnerability(COVID-19 incidence rate:41.68/100000;mortality rate:27.46/1000000).The regression model showed 17 indicators associated with transmission of COVID-19 in Brazil.Conclusions:Although COVID-19 first arrived in the most developed and least vulnerable municipalities in Brazil,it has already reached locations that are farther from large urban centers,whose populations are exposed to a context of intense social vulnerability.Based on these findings,it is necessary to adopt measures that take local social aspects into account in order to contain the pandemic.展开更多
Aims Understanding the factors that control biodiversity distributions at different spatial scales has been a key challenge for conservation efforts.That biodiversity,reflected in differences in species compositions a...Aims Understanding the factors that control biodiversity distributions at different spatial scales has been a key challenge for conservation efforts.That biodiversity,reflected in differences in species compositions among sites(beta diversity),can be derived from species replacement(turnover)and is driven by multiple factors.Here,we sought to tackle this issue through two questions related to threatened Brazilian seasonally dry forests:(i)what is the contribution of species turnover to beta diversity?and(ii)which factors drive variations in species compositions among forest patches?Methods We sampled tree species and environmental variables(soils and climate)in 17 dry forest patches spaced almost 300 km apart.We used the beta diversity partitioning framework to determine the contribution of turnover.We used redundancy analysis,with properly controlled spatial structure,to assess the contributions of the environmental and spatial factors to the variations of the species composition.Important Findings Beta diversity among the patches was mainly represented by the turnover component(98.2%),with Simpson dissimilarity superior to other regions of the country(means of 0.89 and 0.71 in multiple site and pairwise measures,respectively).The environmental factors measured explained more than space,representing 30.3%of the variation of the species composition,of which 28.1%was nonspatially structured.We suggest that 300 km represents a threshold at which edaphic and climatic predictors have similar effects in determining community turnover(14.9%and 12.6%,respectively,without spatial structure).Thus,conservation strategies should be considered across landscapes to effectively protect tropical forest diversity,as even considering the different climatic aspects covered by the scale,landscaped edaphic varieties are important drivers of species turnover.展开更多
文摘This paper presents an optimization methodology for the geometric configuration of a room–and–pillar mining project,considering safety and operational restrictions while maximizing ore recovery.An underground manganese mine was chosen as a case study to investigate the capabilities of the presented methodology.A software package(OPTIMINE)was implemented to address the computational demand in an automated manner.Three–dimensional finite difference analyses were performed in FLAC3D and used as implicit functions to consider safety in terms of the factor of safety and room convergence.The obtained results showed that recovery could be increased from 44%to more than 80%in a safe manner.
基金Supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq)and Coordenaāo de Aperfeioamento de Pessoal de Nível Superior(CAPES)
文摘The literature has shown the efficiency of exercise in the control of type 2 diabetes(T2D), being suggested as one of the best kinds of non-pharmacological treatments for its population. Thus, the scientific production related to this phenomenon has growing exponentially. However, despite its advances, still there is a lack of studies that have carried out a review on the acute effects of physical exercise on metabolic and hemodynamic markers and possible control mechanisms of these indicators in individuals with T2 D, not to mention that in a related way, these themes have been very little studied today. Therefore, the aim of this study was to organize and analyze the current scientific production about the acute effects of physical exercise on metabolic and hemodynamic markers and possible control mechanisms of these indicators in T2 D individuals. For such, a research with the following keywords was performed:-exercise; diabetes and post-exercise hypotension; diabetes and excess post-exercise oxygen consumption; diabetes and acute effects in PUBMED, SCIELO and HIGHWIRE databases. From the analyzed studies, it is possible to conclude that, a single exercise session can promote an increase in the bioavailability of nitric oxide and elicit decreases in postexercise blood pressure. Furthermore, the metabolic stress from physical exercise can increase the oxidation of carbohydrate during the exercise and keep it, in high levels, the post exercise consumption of O2, this phenomenon increases the rate of fat oxidation during recovery periods after exercise, improves glucose tolerance and insulin sensitivity and reduces glycemia between 2-72 h, which seems to be dependent on the exercise intensity and duration of the effort.
基金wish to express their appreciation to Vale S.A.and Brazilian Research Council(CNPq)for the support to the research group.
文摘The disposal of mining tailings has increasingly focused on the use of dry stacks.These structures offer more security since they use filtered and compacted material.Because of the construction method and the heights achieved,the material that compounds the structure can be subjected to different stress paths along the failure plane.The theoretical framework considered in the design of these structures generally is the critical state soil mechanics(CSSM).However,the data in the literature concerning the uniqueness of critical state line(CSL)is still controversial as the soil is subjected to different stress paths.With respect to tailings,this question is even more restricted.This paper studies two tailings with different gradings due to the beneficial processes over extension and compression paths.A series of drained and undrained triaxial tests was conducted over a range of initial densities and stress levels.In the q-p'plane,different critical stress ratio(M)values were obtained for compression and extension stress paths.However,the critical state friction angle is very similar with a slightly higher critical state friction angle for extension tests.Curved stress path dependent CSLs were obtained in the n-lnp0 plane with the extension tests below the CSL defined in compression.Regarding the fines content,the studied tailings presented very similar M and critical state friction angle values.However,the fines content af-fects the volumetric behavior of the studied tailings and the CSLs on the n-lnp0 plane shift downwards with the increasing fines content for compression and extension tests.In relation to dilatancy analysis,the fines content did not present an evident influence on the dilatancy of the materials.However,different values of mean stress ratio N were obtained between compression and extension tests and can corroborate the existence of non-unique CSLs for these materials.
文摘The disposal of filtered tailings in high dry stacks can induce particle breakage,changing the material's behaviour during the structure's lifetime.The grading changes influence material properties at the critical state,and this is not mature for intermediate artificial soils(tailings)in a broad range of confining pressures.In this paper,it aims to describe the behaviour of iron ore tailings in a spectrum of confining pressures broader than the reported in previous studies.A series of consolidated drained(CD)triaxial tests was carried out with confining pressures ranging from 0.075 MPa to 120 MPa.These results show that the amount of breakage plays an essential role in the response of iron ore tailings.The existence of curved critical state line(CSL)in both specific volume(ν)-logarithm of mean effective stress(p′)and deviatoric stress(q)-mean effective stress(p′)planes,and different responses in the deviatoric stress-axial strain-volumetric strain curves were verified.An inverse S-shaped equation was proposed to represent the silty-sandy tailings'behaviour up to high pressures onν-lnp′plane.The proposed equation provides a basis for enhancing constitutive models and considers the evolution of the grading up to severe loading conditions.The adjustment considered three regions with different responses associated with particle breakage at different pressure levels.
文摘Mining activity in Brazil has significantly contributed to the country development.However,this contribution is not always fully noticed by society.This study aims to bring more evidence to this mining activity contribution,based on highly regarded development indicators,such as the HDI(Human Development Index),created by the UNDP(United Nations Development Programme).The HD1 was traditionally designed as an instrument to evaluate the degree of countries development and was subsequently deployed to states and municipalities(IDHM(Municipal Human Development Index)for Brazilian municipalities).In addition to lDHM released by the UNDP,FIRJAN(Federation of the Industries of the State of Rio de Janeiro)developed its own IFDM(FIR JAN Municipal Development Index).The statistical analysis shows that the average of the municipalities with mining activities has superior development indices than those with non-mining activities,especially in the two major mining states:Minas Gerais and Parfi.
文摘The EFVM （Vitoria Minas Railroad） is one of the main railways in Brazil. It transports freight trains of ore, 220 wagons each. These wagons have 2 boogies of 2 axles each and 32 metric tons on metre gauge. Elastic strains were measured on a special part of this railway due to these trains. The main load to evaluate stresses and strains was a G 16 Locomotive, a C-C kind from Vale, a Brazilian Company. The measurements were obtained by dynamic deflectometer installed on a main line of this railway, near Ipatinga, a city from Minas Gerais, one of Brazil states. This track was equipped to obtain stresses under an equal repeated static load A simulation of the stresses was made under critical strain by Ferrovia 1.0 software. It was also made an evaluation of unequal results from neighbor sleepers taking in comparison two equipped parts of this railway, one with compacted ballast and no compaction to the other. The results were strain limited, avoiding breakage or damage to the studied rails. This work analyses these measurements focusing on the improvement of track quality.
基金The student was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil(CAPES)with the doctoral scholarship(2017)The student has the support of the scholarship grant number 2017/22041-1,Sao Paulo Research Foundation(FAPESP)+1 种基金The plant analysis is supported by the Facepe Pronem(APQ-0741106/2014)We want to thank Dr.Magna Coroa Lima(UNIVIÇOSA/MG)for providing the bacteria from cases of caprine mastitis used in our study and Dr.Aberlado Silva Júnior(UFV/MG)for the opportunity to use the facilities.
文摘Antibiotic resistance represents a widespread problem in milk production.The identification of compounds for a topically applied ointment used in mastitis therapy remains elusive.Compounds from the genus Hymenaea can be administered in cases of multi-drugresistant Staphylococcus aureus infection for ruminant species,but the protective properties are not well known.Wi this research the aim is verify the protective effects of H.martiana against S.aureus infection in bovine mammary epithelial cell line(MAC-T)and to obtain an antioxidant profile evaluation in vitro.The MAC-T cells were challenged with S.aureus after being exposed to the extract of the H.martiana in the protective assay.For the verification of the viability of the MAC-T cells,the MTT assay was performed,and was used dilutions of the plant extract,starting at 2.5%.The extract of H.martiana was evaluated for antioxidant aspect in different dilutions by FRAP,ORAC and DPPH.A variety of flavonoids(quercetin,luteolin,etc.)have been identified as the main components by using mass spectrometry,reinforcing our in vitro findings that flavonoids,especially quercetin,have a medicinal profile capable of killing mastitis-causing bacteria.An excellent antioxidant pattern was observed in the 2.5%solution;however,membrane integrity in MAC-T cells was compromised.Those findings suggest low dilutions of H.martiana extract has a desirable protective effect from S.aureus pathogenesis.Our in vitro studies can be gleaned upon for further in vivo studies.
文摘The objective of this study is to present a tailings recovery project in a dam located in northern Brazil;the tailings in this dam have high concentrations of iron. The sustainable recovery of mineral resources can be achieved using the dredging method. The methodology used was based on two drilling projects conducted in 2001 and 2010;these projects contained samples with information on the chemical composition and particle size fractions. The dredging system was designed to operate with four cutter suction dredgers. For operation, factors such as productivity, pumping distance and material flow were considered. The material contained in the dam was estimated using the natural neighborhood interpolation method;this resulted in approximately 192 million tons of tailings, with an average iron content of 63.37%. Based on these data, a 13-year mining plan was prepared, with the potential to maximize the use of the tailings and reduce the environmental impacts, thus contributing to a circular economy.
文摘To extract ore from open pit mines,the associated waste material must also be removed.In most mining operations,the amount of waste rock is greater than the amount of ore.Waste from the pits is usually disposed of in piles,which results in environmental impacts,such as alterations in the natural landscape,possible contamination of soil and water,and the generation of dust and particulates.One way to reduce these environmental impacts and achieve a circular economy(CE)is to use waste rock to construct the pavement layers of mine roads.Another possibility would be to move only the amount of waste necessary to release the ore of interest;in addition to reducing costs,this approach would reduce the volume of waste disposed of in piles.In this study,to reduce the movement of this compact waste,a change in the planned slope is proposed,and the compact waste and surplus material in a long-term mining plan are evaluated.The new optimized geometries,which meet the requirements for road pavement material and remain stable,as indicated by 2D geotechnical finite element modeling,were incorporated into the mining plan of Pit A,an iron mining complex in northern Brazil.The new mining plan was further subjected to economic analysis,which revealed the variations in the tonnage of ore and waste rock(mostly fresh mafic),as well as the change in the net present value(NPV),compared with the original mining plan.The results indicated that the change in geometry led to a reduction of 4.42 Mt in fresh mafic movement.This reduction directly impacted the NPV of the mine plan,with an increase of US$6.88 million.
文摘The mechanics of unsaturated soils is a relatively recent and evolving field of study.This paper introduces an innovative machine learning-based approach for developing constitutive models to describe the soil-water retention curve,hydraulic conductivity,and shear strength of unsaturated soils.These models were built using comprehensive soil characterization data and triaxial test re-sults,incorporating parameters such as gravel,sand,silt,and clay content,plas-ticity index,porosity,and permeability.Equations were implemented using al-gorithms developed in the Mathematica®programming environment.The re-sults demonstrate that the proposed models are both physically consistent and experimentally validated,exhibiting high precision and practical applicability.While this approach significantly optimizes the development of constitutive models,it does not replace the need for conventional testing,instead serving as a robust complementary tool.The proposed methodology offers an efficient and reliable solution for generalizing constitutive models across various un-saturated soil types,advancing knowledge and applications in the field.
文摘A geostatistical study was conducted with the objective of developing a better understanding of the sediments deposited in the tailings dam of an iron mine located in Brazil.The samples,derived from two drilling campaigns conducted in 2001 and 2010,were statistically evaluated and validated for the construction of both a 3D geological model and an estimated model.The geological body modeling process was performed using an implicit method,which was based on the interpretation and adjustments of vertical sections and considered the positions of the samples and the grades of the chemical components of interest.In addition,the primitive topography was also considered to determine the base and limits of the deposit,as well as the current topography.The ordinary kriging(OK)method was chosen to estimate the grades of the chemical components and the retained/passing percentages of the particle size fractions described in the samples.The kriging model was validated through two analyses:mean comparison and drift analyses.The total tonnage of the estimated model was 287.14 Mt,with an average Fe grade of 63.89%.
文摘The importance of identifying the caliber in advance is in knowing the exact quantity of mangos,by weight,that a determined crop season(complete periods of the mango cycle from growth up to fruit harvest)will provide.This study uses Random Forest method to predict the percentage distribution of the calibers of four mango varieties from Brazil’s largest exporter and producer.Our proposed approach was conducted in the following steps:data collection;data preprocessing;predictive model building;and model evaluation.The data correspond to three crop seasons,namely those of 2019,2020,and 2021.Each data line corresponds to a plot with the percentage of a determined caliber at the end of a crop season.The number of rows in the dataset is 5503,with 37.33%,31.47%,22.76%,and 8.44%corresponding to the Keitt,Tommy Atkins,Kent,and Palmer varieties,respectively.The variables are Productivity,(N)Nitrogen,Number of plants(units),Plants/hectare,Month of floral induction,(Zn)Zinc,(S)Sulfur,(B)Boron,Caliber,and Percentage of caliber.The Python programming language was used to preprocess the data,do exploratory analysis,develop the algorithms of the Random Forest Regressor,and compile the lines of the code in Visual Studio Code.Python libraries were used during the study,such as pandas for data handling and Scipy for removing outliers to avoid any biases in the data.The YellowBrick library was used for the feature selection process.Four regression models were created using Random Forest(RF),one for each variety of fruit that composes the dataset.The algorithms showed satisfactory results for Kent,Keitt,Tommy Atkins,and Palmer mangoes,with the following R^(2)of the models:87.29%,74.37%,87.69%,and 62.75%,respectively.During the Feature Selection step,nitrogen(N)was perceived to be highly important in all the models,highlighting the representative nature of this element in fruit formation.From the models created,it is possible to predict the percentage distribution of the calibers of mangos from each growing area 6 months in advance,using data that characterize each area and information on the presence of leaf nutrients as input.
基金supported by the Brazilian agencies’FINEP,CAPES,FAPESB,FACEPE,and CNPq.Y.X.acknowledges FAPERJ(Grant numbers E-26/010.000978/2019 and E-26/010.001550/2019).
文摘The required treatment and monitoring of contaminants in wastewater reinforces the development of low-cost adsorbents/chemosensors,introducing advantages relative to the detection/removal of toxic metals and dyes.Herein,it is reported a two-step process of fabrication of fluorescent carbon dots via the hydrothermal treatment of amino acids for the following encapsulation in electrospun fibers.The prominent anionic behavior of electrospun fibers of Eudragit L100 was explored for adsorption of cationic dyes(methylene blue and crystal violet)-with the prevailing electrostatic interaction of parts being favored by the formation of monolayers on the surface of adsorbents.On the other hand,the controlled release of carbon dots(CDs)from fibers to the reactor can be explored for a second application:the nitrogen ligands from released glycine-based carbon dots can be explored to indicate the presence of metal ions in aqueous solution.Our experiment resulted in a quenching in the fluorescence of the CDs in order of 90%in the emission of particles in the response of the presence of Fe^(3+) ions,characterizing a promising perspective for this experimental system.
文摘The São Francisco River Basin,located in eastern Brazil,has undergone a significant amount of anthropogenic changes in the last several decades,such as agricultural expansion,irrigation activities,mining,and the construction of large dams.Together,these changes have altered the historic sediment budget and have led to an aggradation of sediments in the navigation channel,impacting the ability to efficiently ship agricultural commodities to regional ports.In an effort to aid decision makers in future waterway navigation planning,an international partnership between the Brazilian government agency CODEVASF and the US Army Corps of Engineers(USACE)was created.Through this partnership a SWAT model of the 630000 km2 São Francisco River basin was developed to better understand both the historic and current sediment budget within the navigation channel.The SWAT model of the São Francisco River Basin was calibrated for hydrology and sediment loads.Monthly discharges were calibrated at 17 Agência Nacional deÁguas(ANA)gages,with Nash-Sutcliffe efficiency(NSE)values ranging from 0.42 to 0.75 for an eleven year simulation.Sediment loads were calibrated to an ANA sediment gage located in the Middle São Francisco River Navigation Channel,with a PBIAS(Percent Bias)of 11.6.Based on model results,the aggradation rate of sediment in the São Francisco River and major tributaries has increased by approximately 20 Mt since Pre-European settlement of the basin(from approximately 7 Mt/a to 27 Mt/a).This increase has contributed to an impaired navigation channel due to shoaling of sandy sediments in the navigation channel.
基金Fundação de AmparoàPesquisa do Estado de Minas Gerais(FAPEMIG)Secretaria de Estado de Ciência,Tecnologia e Ensino Superior(SECTES-MG)(FAPEMIG-SECTES-MG agreement 12.070/09).
文摘Aims Soil plays an important role in the formation and heterogene-ity of habitats and thus can cause changes in vegetation struc-ture and plant diversity.The differentiation between Cerrado/savanna and forest is well known,but the relationship between soil and habitats from savannic or forest formations still needs to be better understood,particularly in tropical ecotonal areas.We studied the association between attributes of plant com-munities,namely structure and diversity,and physicochemical characteristics of soils in the Caatinga domain at the transition to Cerrado in Brazil.Methods Chemical and physical analyses of soils were performed in samples of 38 plots from savannic formations and 30 plots from forest forma-tions.Vegetation was characterized floristically and structurally in all plots,five habitats being assessed in each plant formation.Soil features and vegetation parameters were highly distinct among the different habitats.Important Findingsin general,forest habitats were more nutrient rich than savannic formation.Furthermore,soil variables showed effects both on vegetation structure and on its species diversity,more pronouncedly in the savannic formations.Habitats were structurally distinct,and diversity differed between savannic and forest communities;however,a higher differentiation occurred when the savannic formation habitats were compared among them.Although plant diversity did not differ among forest formation habitats,soil attributes showed a close relationship with edaphic factors and can contribute for similar vegetation.The soil-vegetation relationship in highly diverse ecotonal landscapes is important from the conservation biology point of view and aid in the execution of proactive plans for the maintenance of biodiversity.Thus,we noticed that diversity and soil behaves distinctly between savannic and forest communities.
文摘Background:Coronavirus disease 2019(COVID-19)was confirmed in Brazil in February 2020.Since then,the disease has spread throughout the country,reaching the poorest areas.This study analyzes the relationship between COVID-19 and the population's living conditions.We aimed to identifysocial determinants related to the incidence,mortality,and case fatality rate of COVID-19 in Brazil,in 2020.Methods:This is an ecological study evaluating the relationship between COVID-19 incidence,mortality,and case fatality rates and 49 social indicators of human development and social vulnerability.For the analysis,bivariate spatial correlation and multivariate and spatial regression models(spatial lag model and spatial error models)were used,considering a 95%confidence interval and a significance level of 5%.Results:A total of 44.8%of municipalities registered confirmed cases of COVID-19 and 14.7%had deaths.We observed that 56.2%of municipalities with confirmed cases had very low human development(COVID-19 incidence rate:59.00/100000;mortality rate:36.75/1000000),and 52.8%had very high vulnerability(COVID-19 incidence rate:41.68/100000;mortality rate:27.46/1000000).The regression model showed 17 indicators associated with transmission of COVID-19 in Brazil.Conclusions:Although COVID-19 first arrived in the most developed and least vulnerable municipalities in Brazil,it has already reached locations that are farther from large urban centers,whose populations are exposed to a context of intense social vulnerability.Based on these findings,it is necessary to adopt measures that take local social aspects into account in order to contain the pandemic.
基金This work was supported by the Fundação de Amparo à Pesquisa do Estado de Minas Gerais(FAPEMIG)[12.070/2009].
文摘Aims Understanding the factors that control biodiversity distributions at different spatial scales has been a key challenge for conservation efforts.That biodiversity,reflected in differences in species compositions among sites(beta diversity),can be derived from species replacement(turnover)and is driven by multiple factors.Here,we sought to tackle this issue through two questions related to threatened Brazilian seasonally dry forests:(i)what is the contribution of species turnover to beta diversity?and(ii)which factors drive variations in species compositions among forest patches?Methods We sampled tree species and environmental variables(soils and climate)in 17 dry forest patches spaced almost 300 km apart.We used the beta diversity partitioning framework to determine the contribution of turnover.We used redundancy analysis,with properly controlled spatial structure,to assess the contributions of the environmental and spatial factors to the variations of the species composition.Important Findings Beta diversity among the patches was mainly represented by the turnover component(98.2%),with Simpson dissimilarity superior to other regions of the country(means of 0.89 and 0.71 in multiple site and pairwise measures,respectively).The environmental factors measured explained more than space,representing 30.3%of the variation of the species composition,of which 28.1%was nonspatially structured.We suggest that 300 km represents a threshold at which edaphic and climatic predictors have similar effects in determining community turnover(14.9%and 12.6%,respectively,without spatial structure).Thus,conservation strategies should be considered across landscapes to effectively protect tropical forest diversity,as even considering the different climatic aspects covered by the scale,landscaped edaphic varieties are important drivers of species turnover.
