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Wax deposition mechanisms and the effect of emulsions and carbon dioxide injection on wax deposition: Critical review

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Petroleum 2020年第3期6卷 215-225页

作者： A.M.Sousa H.A.Matos L.Guerreiro cerena Department of Chemical Engineering Instituto Superior Técnico Universidade de Lisboa Partex Oil and Gas

Wax deposition inside the tubing walls endures being a critical operational challenge faced by the petroleum industry. The build-up of wax deposits may lead to the increase of pumping power, as well as the decrease of flow rate or, even, to the total blockage, with production losses and high operational costs. The current paper is a critical review of the main deposition mechanisms involved in wax deposition. Most of wax deposition models regard molecular diffusion as the dominant wax deposition mechanism. However, there are other deposition mechanisms which can also play a role. As most oil fields produce water along with crude oil, the deposition process for oil-water emulsions has also been investigated. Furthermore, carbon dioxide injection effects upon wax appearance temperature along its current applications onto wells have been reviewed. Having a total awareness of the wax deposition mechanisms background is the key factor to prevent the wax precipitation and control the deposition of solid wax crystals.

关键词： Wax deposition mechanism Molecular diffusion Brownian diffusion Shear dispersion Shear removal Thermal diffusion Emulsions Carbon dioxide

Engineering complex systems applied to risk management in the mining industry

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International Journal of Mining Science and Technology 2017年第4期27卷 611-616页

作者： Domingues Maria S.Q. Baptista Adelina L.F. Diogo Miguel Tato cerena - Centre for Natural Resources and the Environment Faculty of Engineering University of Porto Porto 4200-465 Portugal CLEGI-Centre Lusiada of Research and Development in Engineering and Industrial Management University Lusiada-North Vila Nova de Famalicao 4760-108 Portugal

Related to complexity, there is a wide diversity of concepts, ranging from ‘‘systemic" to ‘‘complex", implying a need for a unified terminology. Per different authors, the main drivers of complexity can be found in human behaviour and uncertainty. This complexity, structural or dynamic can be organizational, technological, or nested in their relationship. ISO international standard 31000:2009 definition of risk management ‘‘coordinated activities to direct and control an organization with regard to risk", when applied to economic sectors, industry, services, project, or activity, it requires the use of models or theories as guidelines. Therefore, as its basic elements comprehend human behaviour and/or uncertainty, risk management to be effective and adapted as much as possible to reality, must be operational within complex systems, as already demonstrated in different R&D environments. Risk management faces demanding challenges when approaching specific and endogenous needs, such as the mining sector. This paper presents a multivariable function analysis methodology approach based on complex system modelling and through real data corresponding to a risk management tool in the mining sector.

关键词： Risk Risk management Complex systems Mining Decision making

Kinetic approach to the study of froth flotation applied to a lepidolite ore

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International Journal of Minerals,Metallurgy and Materials 2016年第7期23卷 731-742页

作者： Nathália Vieceli Fernando O.Durao Carlos Guimaraes Carlos A.Nogueira Manuel F.C.Pereira Fernanda Margarido Center for Innovation Technology and Policy Research-IN+Instituto Superior T6cnicoUniversity of Lisbon1049-001 LisboaPortugal cerena-Centro de Recursos Naturais e Ambiente DECivilInstituto Superior TecnicoUniversity of Lisbon1049-001 LisboaPortugal LNEG-Laboratorio Nacional de Energia e Geologia I.P.Campus do Lumiar1649-038 LisboaPortugal

The number of published studies related to the optimization of lithium extraction from low-grade ores has increased as the demand for lithium has grown. However, no study related to the kinetics of the concentration stage of lithium-containing minerals by froth flotation has yet been reported. To establish a factorial design of batch flotation experiments, we conducted a set of kinetic tests to determine the most selective alternative collector, define a range of pulp p H values, and estimate a near-optimum flotation time. Both collectors（Aeromine 3000 C and Armeen 12D） provided the required flotation selectivity, although this selectivity was lost in the case of pulp p H values outside the range between 2 and 4. Cumulative mineral recovery curves were used to adjust a classical kinetic model that was modified with a non-negative parameter representing a delay time. The computation of the near-optimum flotation time as the maximizer of a separation efficiency（SE） function must be performed with caution. We instead propose to define the near-optimum flotation time as the time interval required to achieve 95%–99% of the maximum value of the SE function.

关键词： lepidolite lithium ore treatment froth flotation kinetic analysis

Portuguese Society of Intensive Care Score for Predicting SARS-CoV-2 Infection Applied to Inpatients with Pneumonia: A Reliable Tool?

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Open Journal of Respiratory Diseases 2021年第2期11卷 49-60页

作者： Ana Alfaiate David Noivo Vera Clérigo Vera Durão Fernando Durão Margarida Castanho Susana Sousa Lígia Fernandes Paula Duarte COVID-19 Service Pulmonology Department Setúbal Hospital Center Setúbal Portugal DECivil/cerena Técnico Lisboa Lisboa Portugal

Objectives: Early identification of patients with the novel coronavirus induced-disease 2019 (COVID-19) and pneumonia is currently challenging. Few data are available on validated scores predictive of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection. The Portuguese Society of Intensive Care (PSIC) proposed a risk score whose main goals were to predict a higher probability of COVID-19 and optimize hospital resources, adjusting patients’ intervention. This study aimed to validate the PSIC risk score applied to inpatients with pneumonia. Methods: A retrospective analysis of 207 patients with pneumonia admitted to a suspected/confirmed SARS-CoV-2 infection specialized ward (20/03 to 20/05/2020) was performed. Score variables were analyzed to determine the significance of the independent predictive variables on the probability of a positive SARS-CoV-2 rRT-PCR test. The binary logistic regression modeling approach was selected. The best cut-off value was obtained with the Receiver Operating Characteristic (ROC) curve together with the evaluation of the discriminatory power through the Area Under the Curve (AUC). Results: The validation cohort included 145 patients. Typical chest computed-tomography features (OR, 12.16;95%

关键词： SARS-CoV-2 Infection COVID-19 Pneumonia Risk Score

Optimization of an innovative approach involving mechanical activation and acid digestion for the extraction of lithium from lepidolite

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International Journal of Minerals,Metallurgy and Materials 2018年第1期25卷 11-19页

作者： Nathalia Vieceli Carlos A.Nogueira Manuel F.C.Pereira Fernando O.Durao Carlos Guimaraes Fernanda Margarido Center for Innovation Technology and Po icy Research-IN+Instituto Superior T6cnicoUniversity of Lisbon1049-001 LisboaPortugal LNEG-Laborat6rio Nacional de Energia e Geologia I.P.Campus do Lumiar1649-038 LisboaPortugal cerena-Centro de Recursos Naturais e Ambiente DECivilInstituto Superior T6cnicoUniversity of Lisbon1049-001 LisboaPortugal

The recovery of lithium from hard rock minerals has received increased attention given the high demand for this element. There- fore, this study optimized an innovative process, which does not require a high-temperature calcination step, for lithium extraction from le- pidolite. Mechanical activation and acid digestion were suggested as crucial process parameters, and experimental design and re- sponse-surface methodology were applied to model and optimize the proposed lithium extraction process. The promoting effect of amorphi- zation and the formation of lithium sulfate hydrate on lithium extraction yield were assessed. Several factor combinations led to extraction yields that exceeded 90%, indicating that the proposed process is an effective approach for lithium recovery.

关键词： lepidolite lithium mechanical activation acid digestion optimization extraction

Quantitative estimation of bubble volume fraction of submarine seep plumes by modeling seismic oceanography data

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Journal of Oceanology and Limnology 2023年第2期41卷 673-686页

作者： Tonggang HAN Jiangxin CHEN Leonardo AZEVEDO Bingshou HE Huaning XU Rui YANG Key Lab of Submarine Geosciences and Prospecting Techniques Ministry of EducationOcean University of ChinaQingdao 266100China Key Laboratory of Gas Hydrate Ministry of Natural ResourcesQingdao Institute of Marine GeologyQingdao 266071China Laboratory for Marine Mineral Resources Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China cerena DECivilInstituto Superior TécnicoUniversidade de LisboaAv.Rovisco PaisLisbon 1049-001Portugal

Submarine seep plumes are a natural phenomenon in which different types of gases migrate through deep or shallow subsurface sediments and leak into seawater in pressure *** detected using acoustic data,the leaked gases frequently exhibit a flame-like *** numerically modelled the relationship between the seismic response characteristic and bubble volume fraction to establish the bubble volume fraction in the submarine seep *** show that our models are able to invert and predict the bubble volume fraction from field seismic oceanography data,by which synthetic seismic sections in different dominant frequencies could be numerically simulated,seismic attribute sections(e.g.,instantaneous amplitude,instantaneous frequency,and instantaneous phase)extracted,and the correlation between the seismic attributes and bubble volume fraction be quantitatively determined with functional *** instantaneous amplitude is positively correlated with bubble volume fraction,while the instantaneous frequency and bubble volume fraction are negatively *** addition,information entropy is introduced as a proxy to quantify the relationship between the instantaneous phase and bubble volume *** the bubble volume fraction increases,the information entropy of the instantaneous phase increases rapidly at the beginning,followed by a slight upward trend,and finally ***,under optimal noise conditions,the bubble volume fraction of submarine seep plumes can be inverted and predicted based on seismic response characteristics in terms of seismic attributes.

关键词： seismic oceanography submarine seep plumes bubble volume fraction seismic response characteristics seismic attribute analysis quantitative analysis

Characteristic strength and acoustic emission properties of weakly cemented sandstone at different depths under uniaxial compression

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International Journal of Coal Science & Technology 2021年第6期8卷 1288-1301页

作者： Bin Liu Yixin Zhao Cun Zhang Jinlong Zhou Yutao Li Zhuang Sun Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources China University of Mining and Technology(Beijing)Beijing 100083China School of Energy and Mining Engineering China University of Mining and Technology(Beijing)Beijing 100083China cerena Pavilhao de MinasInstituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais1049-001 LisbonPortugal School of Mechanics and Civil Engineering China University of Mining and Technology(Beijing)Beijing 100083China

As coal mining is extended from shallow to deep areas along the western coalfield,it is of great significance to study weakly cemented sandstone at different depths for underground mining *** from depths of 101.5,203.2,317.3,406.9,509.9 and 589.8 m at the Buertai Coal Mine were *** characteristic strength,acoustic emission(AE),and energy evolution of sandstone during uniaxial compression tests were *** results show that the intermediate frequency(125-275 kHz)of shallow rock mainly occurs in the postpeak stage,while deep rock occurs in the prepeak *** initiation strength and damage strength of the sandstone at different depths range from 0.23 to 0.50 and 0.63 to 0.84 of peak strength(σ_(c)),respectively,decrease exponentially and are a power function with *** precursor strength ranges from 0.88σ_(c)to 0.99σ_(c),increases with depth before reaching a depth of 300 m,and tends to stabilize after 300 *** ratio of the initiation strength to the damage strength(k)ranges from 0.25 to 0.62 and decreases exponentially with *** failure modes of sandstone at different depths are tension-dominated mixed tensile-shear *** failure mainly occurs at the unstable crack propagation *** count of the shear failure bands before the peak strength increases gradually,and increases first and then decreases after the peak strength with burial *** cumulative input energy,released elastic energy and dissipated energy increase with *** elastic release rate ranges from 0.46×10^(-3)to 198.57×10^(-3)J/(cm^(3)s)and increases exponentially with depth.

关键词： Burial depth Weakly cemented sandstone Acoustic emission(AE) Characteristic strength Energy evolution Failure mode

Distinct BSRs and their implications for natural gas hydrate formation and distribution at the submarine Makran accretionary zone

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Journal of Oceanology and Limnology 2021年第5期39卷 1871-1886页

作者： Bin LIU Waseem Haider SYED Jiangxin CHEN Xiguang DENG Li YANG Leonardo AZEVEDO Minliang DUAN Tingting WU Jinfeng MA Keliang LI Key Laboratory of Marine Mineral Resources Ministry of Natural ResourcesGuangzhou Marine Geological SurveyGuangzhou 510760China National Institute of Oceanography Karachi 75600Pakistan Key Laboratory of Gas Hydrate Ministry of Natural ResourcesQingdao Institute of Marine GeologyQingdao 266071China Laboratory for Marine Mineral Resources Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China cerena/Instituto Superior Técnico Lisbon UniversityLisbon 1049-001Portugal Key Lab of Submarine Geosciences and Prospecting Techniques MOE andCollege of Marine GeosciencesOcean University of ChinaQingdao 266100China

To investigate the nature of gas hydrates in the Makran area,new high-resolution geophysical data were acquired between *** data collected comprise multibeam and two-dimensional multi-channel seismic reflection *** multibeam bathymetry data show East-North-East(ENE)ridges,piggy-back basins,canyon and channel systems,and the morphology of the abyssal *** and discontinuous bottom simulating reflectors(BSRs)occur in the piggy-back basins on most of the seismic profiles *** BSRs cut the dipping layers with strong amplitude and reversed *** BSRs indicate a transition along a dipping high-permeable sand layers from gas-rich segment to the gas hydrate-bearing segment and sugge st alternating sediments of fine and relatively coarse grain *** BSRs are highly dynamic and attributed to slumps occurring in the study *** BSRs induced by slumps are located both at deep and shallow depths,responding to the temperature or pressure *** the first time,BSRs are observed in the abyssal plain of the Makran area,being associated with anticline structures,which do not show large spatial continuity and are strongly conditioned by structural conditions such as anticlines and fluid migration pathways,including deep fault,gas chimney,and high-permeable sedimentary *** results may help to assess the gas hydrate potential within the piggy-back basins and to determine the most promising target ***,results about the abyssal plain BSR may help to locate hydrocarbon reservoirs in the deep ocean.

关键词： gas hydrate-bearing sand-prone sediments double bottom simulating reflector(BSR) multiple BSR canyon channel system abyssal plain

Experimental and numerical characterization of 3D‑printed scaffolds under monotonic compression with the aid of micro‑CT volume reconstruction

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Bio-Design and Manufacturing 2021年第2期4卷 222-242页

作者： R.Baptista M.F.C.Pereira A.Maurício D.Rechena V.Infante M.Guedes CDP2T Departamento de Engenharia MecanicaEscola Superior de Tecnologia de SetúbalInstituto Politécnico de Setúbal2910‑761 SetúbalPortugal cerena DECivilInstituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais11049‑001 LisbonPortugal IDMEC Instituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais11049‑001 LisbonPortugal IPFN Instituto Superior TécnicoUniversidade de Lisboa1049‑001 LisbonPortugal CeFEMA Instituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais11049‑001 LisbonPortugal

Even when damaged by injury or disease bone tissue has the remarkable ability to *** this process is limited by large size bone defects,tissue engineering is responsible for restoring,maintaining or improving tissue *** are support structures,designed to be implanted in the damaged site,supporting mechanical loads and protecting the regenerating bone *** this paper,3D-printed PLA scaffolds with three different porosity values and two different geometries were experimentally and numerically ***-CT analysis showed that fused filament fabrication can be used to produce scaffolds with the desired porosity and 100%of interconnected *** monotonical compression,scaffolds apparent compressive modulus increased from 89 to 918 MPa,while yield stress increased from 2.9 to 27.5 MPa as porosity decreased from 70 to 30%.Open porosity decreased up to 8%on aligned scaffolds and 14%on staggered scaffolds,after compression,while scaffold’s surface-to-volume ratio highest reduction(7.48 to 4.55 mm−1)was obtained with aligned low porosity ***-CT volume reconstruction allowed for scaffold simplified numerical models to be built and *** agreement was found when predicting scaffold’s apparent compressive ***,it can be concluded that 3D printing is a viable scaffold manufacturing technique for trabecular bone replacement.

关键词： Scaffold Pore design Mechanical behavior Micro-CT analysis Finite element method