555 research outputs found

    Rapid postglacial rebound amplifies global sea level rise following West Antarctic Ice Sheet collapse

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    Earth_Model_Data is a zipped folder containing the Earth model data for both the standard model (V3D_SD and V3D_RH). A readme file is in this folder. FPRINT_CODE is a zipped folder containing the fingerprint code. A readme file for the code is also in this folder. WAmask_512.gz is a mask for West/East Antarctica, used for masking out changes in East Antarctica. All other files are sea-level outputs for each of the runs on a degree 512 Gauss-Legendre grid (uniform longitudes but unevenly spaced latitudes, as described in the readme for FPRINT_CODE). Files are named SLt_??? and numbered from 0 (elastic response) to 105 (10 ky). They have a 1D layout, with the first line being the time tag in years followed by 512*1024 row entries. A time array is included (tt_v10.dat). More details are in README.tx

    Mitigation of environmental hazards of sulfide mineral flotation with an insight into froth stability and flotation performance

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    Today\u27s major challenges facing the flotation of sulfide minerals involve constant variability in the ore composition; environmental concerns; water scarcity and inefficient plant performance. The present work addresses these challenges faced by the flotation process of complex sulfide ore of Mississippi Valley type with an insight into the froth stability and the flotation performance. The first project in this study was aimed at finding the optimum conditions for the bulk flotation of galena (PbS) and chalcopyrite (CuFeS₂) through Response Surface Methodology (RSM). In the second project, an attempt was made to replace toxic sodium cyanide (NaCN) with the biodegradable chitosan polymer as pyrite depressant. To achieve an optimum flotation performance and froth stability, the third project utilized two types of nanoparticles; silica (SiO₂) and alumina (Al₂O₃) as process aids. The fourth project investigated the impact of water chemistry on the process outcomes in an attempt to replace fresh water with sea water. In the last project, five artificial intelligence (AI) and machine learning (ML) models were employed to model the flotation performance of the ore which will allow the building of intelligent systems that can be used to predict the process outcomes of polymetallic sulfides. It was concluded that chitosan can be successfully used as a biodegradable depressant. Alumina nanoparticles successfully enhanced both froth stability and flotation performance while silica nanoparticles did not. Seawater had a negative effect on both the froth stability and the grade of lead (Pb) and copper (Cu) but it improved the recoveries of both Pb and Cu minerals. Hybrid Neural Fuzzy Interference System (HyFIS) ML model showed the best accuracy to be adopted for automated sulfide ore flotation process in the future --Abstract, page iii

    The shallow shelf approximation as a "sliding law" in a thermomechanically coupled ice sheet model

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    The shallow shelf approximation is a better ``sliding law'' for ice sheet modeling than those sliding laws in which basal velocity is a function of driving stress. The shallow shelf approximation as formulated by \emph{Schoof} [2006a] is well-suited to this use. Our new thermomechanically coupled sliding scheme is based on a plasticity assumption about the strength of the saturated till underlying the ice sheet in which the till yield stress is given by a Mohr-Coulomb formula using a modeled pore water pressure. Using this scheme, our prognostic whole ice sheet model has convincing ice streams. Driving stress is balanced in part by membrane stresses, the model is computable at high spatial resolution in parallel, it is stable with respect to parameter changes, and it produces surface velocities seen in actual ice streams.Comment: 12 pages of text; 4 tables; 27 figures; submitted to JGR Earth Surfac

    Refining Greenland geothermal heat flux through stable isotope analysis

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    Geothermal heat flux is an important control on the dynamics of glaciers and ice sheets. In Greenland however, only few direct observations of geothermal heat flux exist. The exact spatial distribution and magnitude of heat flux in Greenland is therefore largely unknown. Many studies have attempted to constrain heat flux in Greenland indirectly by modelling it based on other observable variables, such as the seismic and magnetic structure of the Greenland lithosphere, or through techniques that extrapolate the existing measurements onto models of the Greenland lithology. Various estimates of Greenand heat flux have been produced this way, however many do not agree well with each other and show large inter- estimate variability both in terms of magnitude and spatial distribution of estimated heat flux values. Stable isotope composition of basal meltwater has previously not been considered in efforts to constrain Greenland geothermal heat flux. The ice layers in the Greenland ice sheet show large differences in δ18O values resulting from changes in climate throughout their deposi- tional history. If different ice layers are in contact with the bed, then spatial differences in geothermal heat flux will affect the local meltrates these layers experience at the ice sheet base and hence modulate the amount of meltwater each layer contributes into the subglacial drainaige system. If the δ18O values of the melting ice layers are sufficiently different, the isotopic composition of the mixed meltwater that flows through the subglacial hydrological system will be different for different spatial distributions of geothermal heat flux. By simulating the basal meltwater production in Greenland based on different published estimates of Greenland geothermal heat flux, I show in this thesis that different heat fluxes result in differences in the age distribution of the basal ice. In particular, the presence and extent of Eemian ice in central northern Greenland shows substantial differences for different heat flux estimates. As Eemian ice, being interglacial ice, shows higher δ18O val- ues than ice from the last glacial period, the modelled differences in Eemian extent result in detectable differences in the isotopic composition of the basal meltwater in North-east Greenland on the order of few permille. Stable isotope composition of basal meltwater might thus have the potential to contribute to the discussion about a heat flux hotspot in central northern Greenland.Master's Thesis in Earth ScienceGEOV399MAMN-GEO

    Hydrodynamic Characterization of Physicochemical Process in Stirred Tanks and Agglomeration Reactors

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    A short review of the state of the art in experimental and computational fluid dynamics (CFD) characterization of micro-hydrodynamics and physicochemical processes in stirred tanks and agglomeration reactors is presented. Results of experimental and computational studies focusing on classical mixing tanks as well as other innovative reactors with various industrial applications are briefly reviewed. The hydrodynamic characterization techniques as well as the influence of the fluid dynamics on the efficiency of the physicochemical processes have been highlighted including some of the limitations of the reported modeling approach and solution strategy. Finally, the need for specialized CFD codes tailored to the specific needs of fluid-particle reactor design and optimization is advocated to advance research in this field

    Development and Validation of a Knee-Thigh-Hip LSDYNA Model of a 50th Percentile Male.

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    With the introduction of air bags, occupant safety in frontal car crashes has been improved for upper regions of the body, such as the head and thorax. These improvements, however, have not helped improve the safety for the lower extremities, increasing their percentage of injuries in car crashes. Though lower extremity injuries are usually not life threatening, they can have long lasting physical and psychosocial consequences. An LSDYNA finite element model of the knee-thigh-hip (KTH) of a 50th percentile adult male was developed for exploring the mechanics of injuries to the KTH during frontal crash crashes. The model includes a detailed geometry of the bones, the mass of the soft tissue, and a discrete element representation of the ligaments and muscles of the KTH. The bones were validated using physical tests obtained from the National Highway Traffic and Safety Administration\u27s (NHTSA) test database. The geometry, the material properties and the failure mechanisms of bone materials were verified. A validation was also performed against a whole-body cadaver test to verify contributions of passive muscle and ligament forces. Failure mechanisms in the tests and simulations were compared to ensure that the model provides a useful tool for exploring fractures and dislocations in the KTH resulting from frontal vehicle crashes. The validated model was then used to investigate injury mechanisms during a frontal car crash at different occupant positions. The role of muscle forces on these fracture mechanisms was explored and simulations of frontal impacts were then reproduced with the KTH complex at different angles of thigh flexion, adduction and abduction. Results show that the failure mechanism of the lower limb can significantly depend on the occupant position prior to impact. Failure mechanisms in the simulations were compared to results found in literature to ensure the model provides a useful tool for predicting fractures in the lower limb resulting from out-of-position frontal vehicle crashes. The FE model replicate injury criteria developed for ligament failure and suggested lowering the actual used axial femur force threshold for KTH injures both in neutral and out-of-position KTH axial impacts

    INVESTIGATION OF MICRO BUBBLE FOR THE REMOVAL OF SUSPENDED PARTICLE AND ENHANCEMENT OF DISSOLVED OXYGEN IN POLLUTED WATER

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    Filtration and precipitation are generally used in wastewater treatment to separate pollutants. However, they are not cost effective and have problems of filter waste and time consumption. The smaller particles are left even after a filtration process, depending upon the porosity of the filter. This research proposes a new approach of using compressed air to lift up micro suspended particles in polluted water. The novelty of the approach is in its sustainability, cost effectiveness and faster solution to micro pollutant separation. Air is forced through a submerged micro diffuser to produce micro bubbles, which flow upward and entrain suspended particles to separate them from water. The study was carried experimentally and a lab test rig was designed and implemented. Bubble size plays an important role in moving suspended particles upwards due to the buoyancy force, which in turn depends upon the vertical component of bubble velocity. Generally, the larger bubbles tend to change shape due to high buoyancy force. The bubble velocity is characterized by the Froude number and Reynolds number. The strategies to control the bubble size in monodispersed (single size) and polydispersed (multi size) cases are presented in this research. To simulate the real wastewater physiochemical characteristics (surface tension, density, viscosity, etc), Glycerin is added to distilled water in various volume fractions of 0.1% to 0.5%. The relationship between air pressure, vertical and horizontal velocities, as well as bubble size is studied. These parameters (bubble diameter, vertical velocity) lead to high effectiveness of suspended particles separation, and are validated by measuring the low concentration of pollutant (PPM), corresponding to the turbidity level. The amount of suspended particles in relation to turbidity has been studied and it is found that the turbidity level of 6.9 NTU decreases to 3.66 NTU, using 1-10 micron porous sintered glass as a submerged diffuser and at 12 10-3 m3/min air flow. In most biological wastewater treatment systems, a submerged diffuser is used to provide oxygen and mixing to degrade the organic matter. In this study, the effectiveness of micro diffusers in the degradation of organic matter was investigated. The nitrification performance using both micro and macro diffusers was evaluated by measuring ammonium-nitrogen (NH4-N) and nitrate-nitrogen (NO3-N). The experimental values were compared with the theoretical values derived from the kinetic calculations. Two batch experiments were conducted for the estimation of the kinetic parameters for the degradation and the nitrification of organic matter at 1 hour, 3 hours, 6 hours, and 24 hours until 48 hours, in steps of 3 hours for each batch of experiments. From the measurement results, the degradation kinetic COD parameter (kCOD) of the micro diffuser was found to be 1.46 times higher than the macro diffuser. Therefore the degradation kinetics of soluble COD parameter (ksCOD) of the micro diffuser was found to be 1.5 times higher than macro diffuser. The difference between micro and millimeter diffusers in removed COD was approximately 6%. , and in removed sCOD was approximately 16%. The main data parameters in Nitrification of wastewater were ammonium and nitrate. The measurement results of ammonium and nitrate using micro diffuser was achieved at 3% higher than macro diffuser

    Control-Oriented Modeling and Experimental Validation of a Deoiling Hydrocyclone System

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    As the treated water from offshore oil and gas production is discharged to the surrounding sea, there is an incentive to improve the performance of the offshore produced water treatment, to reduce the environmental pollutants to the sea. Regulations determine both the maximum allowed oil concentration and the total annual quantity. It is reasonable to assume that when better separation equipment or methods are developed, the regulation will become more strict, and force other producers to follow the trend towards zero harmful discharge. This paper develops and validates a hydrocyclone model to be used as a test-bed for improved control designs. The modeling methodology uses a combination of first-principles to define model structure and data-driven parameter identification. To evaluate and validate the separation performance, real-time fluorescence-based oil-in-water (OiW) concentration monitors, with dual redundancy, are installed and used on sidestreams of a modified pilot plant. The installed monitors measure the inlet and outlet OiW concentration of the tested hydrocyclone. The proposed control-oriented hydrocyclone model proved to be a reasonable candidate for predicting the hydrocyclone separation performance

    Current Challenges and Advancements on the Management of Water Retreatment in Different Production Operations of Shale Reservoirs

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    Publisher's Note : MDPI Stays neutral with regard to jurisdictional claims in published maps and institutional affiliationsNowadays, water savings on industrial plants have become a significant concern for various plants and sections. It is vitally essential to propose applicable and efficient techniques to retreat produced water from onshore and offshore production units. This paper aimed to implement the PFF (Photo Fenton Flotation) method to optimize the water treatment procedure, as it is a twostage separation technique. The measurements were recorded for the HF (hydraulic fracturing) and CEOR (chemically enhanced oil recovery) methods separately to compare the results appropriately. To assure the efficiency of this method, we first recorded the measurements for five sequential days. As a result, the total volume of 2372.5 MM m3/year of water can be saved in the HF process during the PFF treatment procedure, and only 20% of this required fresh water should be provided from other resources. On the other hand, the total volume of 7482.5 MM m3/year of water can be saved in CEOR processes during the PFF treatment procedure, and only 38% of this required fresh water should be provided from other resources. Therefore, the total water volume of 9855 MM m3 can be saved each year, indicating the efficiency of this method in supplying and saving the water volume during the production operations from oilfield unit

    Computational analysis of single rising bubbles influenced by soluble surfactant

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    This paper presents novel insights about the influence of soluble surfactants on bubble flows obtained by Direct Numerical Simulation (DNS). Surfactants are amphiphilic compounds which accumulate at fluid interfaces and significantly modify the respective interfacial properties, influencing also the overall dynamics of the flow. With the aid of DNS local quantities like the surfactant distribution on the bubble surface can be accessed for a better understanding of the physical phenomena occurring close to the interface. The core part of the physical model consists in the description of the surfactant transport in the bulk and on the deformable interface. The solution procedure is based on an Arbitrary Lagrangian-Eulerian (ALE) Interface-Tracking method. The existing methodology was enhanced to describe a wider range of physical phenomena. A subgrid-scale (SGS) model is employed in the cases where a fully resolved DNS for the species transport is not feasible due to high mesh resolution requirements and, therefore, high computational costs. After an exhaustive validation of the latest numerical developments, the DNS of single rising bubbles in contaminated solutions is compared to experimental results. The full velocity transients of the rising bubbles, especially the contaminated ones, are correctly reproduced by the DNS. The simulation results are then studied to gain a better understanding of the local bubble dynamics under the effect of soluble surfactant. One of the main insights is that the quasi-steady state of the rise velocity is reached without ad- and desorption being necessarily in local equilibrium
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