81 research outputs found
Moist Rayleigh-Benard Convection
No full textWe report the observations from turbulent thermal Rayleigh-Benard convection experiment with a two-phase liquid-vapor binary mixture. Evaporation/condensation processes in a turbulent convection are accompanied by the formation of cloud like structures above the liquid-vapor interface. We also found that a liquid film condensation on the underside of the top plate results in regular hexagonal patterns of falling droplets
Design and fabrication of a twin disc tribometer and a study of wear and friction of hardened 1060 steel under combined rolling and sliding
No full textIn this research work, wear of steel was studied under different loading and sliding conditions. A twin-disc tribometer was designed and built for studying wear of steels under combined rolling and sliding contact. The samples were made from 1060 steel in the form of circular discs and heat treatment was performed to attain hardness of ~330 HV. Thirteen sets of experimental conditions were made from six different normal loads and three different slip speeds. Experiments were split into eight intervals and run for a constant sliding distance of 1500 m. Wear track width was measured through image processing using which wear volume was estimated. Archard’s wear law was applied for the estimation of wear rates. The results demonstrate that experiments with lower slip speed has higher wear rates when compared to the experiments with higher slip speed. This indicates that for a constant sliding distance, slower the sliding under a rolling and sliding contact, higher the wear rate would be.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2020-08-01The student, Prabhakaran Balasubramanian, accepted the attached license on 2018-07-18 at 12:02.The student, Prabhakaran Balasubramanian, submitted this Thesis for approval on 2018-07-18 at 12:17.This Thesis was approved for publication on 2018-07-19 at 08:35.DSpace SAF Submission Ingestion Package generated from Vireo submission #12913 on 2018-09-27 at 11:19:23Made available in DSpace on 2018-09-27T16:34:22Z (GMT). No. of bitstreams: 2
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Previous issue date: 2018-07-19Embargo set by: Seth Robbins for item 107822
Lift date: 2020-09-27T16:34:29Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 107822 on 2020-09-28T09:15:19Z
Naturally fractured reservoir characterization: Advanced workflows for discrete fracture network modeling
No full textNatural fractures in subsurface rocks are a source of heterogeneity that impacts flow and transport behaviour. The presence of fracture discontinuities needs to be modelled explicitly due to observed deviations from the continuum assumption of porous media. The departures are due to both individual properties (such as aperture, infill, and roughness) and global network properties (such as topological summary and length distribution). Understanding flow patterns due to effects of rock fractures networks is essential formany applications such as exploiting hydrocarbons, geothermal heat extraction, subsurface nuclear waste storage, and water aquifer development. Assessing the impact of fractures in modelling studies requires fracture network data which is difficult to sample from seismic data (due to image resolution issues) and borehole data (owing to sparse sampling). Outcrop analogue data provide a means to sample networkswhile honouring both spatial position and topological relationships.Applied Geolog
Pore Pressure Effects on Net Fracture Pressure and Hydraulic Fracture Containment
No full textIn hydraulic fracture modelling, fracture geometry along with the net pressure distribution in the fracture are the parameters the values of which are sought to be predicted away from the wellbore. In current industry standard fracture modelling packages, fracture dimensions are obtained from equilibrium height growth simulation models that are based on linear elasticity equations. Due to simplifying assumptions made in these pseudo 3D lumped models, there is considerable discrepancy between the model predicted fracture geometry and the ground truth as revealed from tiltmeter and microseismic fracture mapping techniques. Not only is the geometry different, but the observed fracturing net pressure is also higher. From numerous mapped field cases it has been established that the fractures are more contained than what is modeled.The lumped models that are commonly used for real time pressure matching and diagnostics have the advantages of faster computation and can also be trained to adhere to mapped microseismic results using field specific coefficients. Coupled simulation models that use discretized grids are computationally intensive but can give more accurate results since they incorporate more of the relevant physics that affects fracture propagation. The use of effective stress as the propagation criteria rather than the stress intensity factor approach from Linear Elastic Fracture Mechanics introduces the pore pressure effect into the simulation. The pore pressure effect on effective stress and its relationship with fracture net pressure has been qualitatively observed from both field and experimental observations. The pore pressure effect is thus surmised to be an important factor that affects fracture growth and this study seeks to investigate that hypothesis. An analysis of more than 400 datafrac injections performed in clastic reservoirs and spanning a wide range of geological ages and depositional environments were studied to establish a relationship between observed net pressure and the effective stress in the reservoir. Synthetic geomechanical cases that represent underpressured, hydrostatic and overpressured reservoirs were built using the range of fracture design parameters from the database. An additional high effective stress case was built to appraise the upper limits of effective stress as observed from the treatments. A planar explicitly coupled 3D fracture simulator (Frac3D) based on an effective stress criterion and which uses cohesive element nodes near fracture tip was used to simulate fracture growth for the synthetic cases. The numerical results obtained from this FEM – FDM coupled simulator established that the pore pressure effect is indeed a significant parameter. The fracture dimensions were seen to be more radial with depletion and longer when overpressured. The net pressure increased with depletion and fracture width was highest in this case. The high pressure high effective stress case resulted in higher net pressure than the depleted case and this was indicative of the dominance of a high closure stress over the pore pressure effect. In direct comparisons with the lumped model the Frac3D simulator predicts higher net pressures and more contained fractures whereas the lumped model tended to understimate net pressure and overestimate fracture dimensions. Based on comparison of the Frac3D results and the field fracture treatment analysis, this thesis establishes a empirical correlation between fracture net pressure and effective stress for datafrac injections. The comparison between the synthetic simulations and the Frac3D simulations presents conclusive evidence that lumped models based on linear elasticity are inadequate in representing the pore pressure effect. The obtained correlation may be applied as a pressure matching parameter for datafrac injections prior to using other parameters in the general fracture diagnostics workflow. The pore pressure effect also serves as an explanation for fracture containment in the absence of vertical stress contrast.Civil Engineering and GeosciencesGeoscience & EngineeringPetroleum Engineerin
Cardiovascular, respiratory, and related disorders: key messages from Disease Control Priorities, 3rd edition.
No full textCardiovascular, respiratory, and related disorders (CVRDs) are the leading causes of adult death worldwide, and substantial inequalities in care of patients with CVRDs exist between countries of high income and countries of low and middle income. Based on current trends, the UN Sustainable Development Goal to reduce premature mortality due to CVRDs by a third by 2030 will be challenging for many countries of low and middle income. We did systematic literature reviews of effectiveness and cost-effectiveness to identify priority interventions. We summarise the key findings and present a costed essential package of interventions to reduce risk of and manage CVRDs. On a population level, we recommend tobacco taxation, bans on trans fats, and compulsory reduction of salt in manufactured food products. We suggest primary health services be strengthened through the establishment of locally endorsed guidelines and ensured availability of essential medications. The policy interventions and health service delivery package we suggest could serve as the cornerstone for the management of CVRDs, and afford substantial financial risk protection for vulnerable households. We estimate that full implementation of the essential package would cost an additional US24 in the average lower-middle-income country. The essential package we describe could be a starting place for low-income and middle-income countries developing universal health coverage packages. Interventions could be rolled out as disease burden demands and budgets allow. Our outlined interventions provide a pathway for countries attempting to convert the UN Sustainable Development Goal commitments into tangible action
The MPS-Based Fracture Network Simulation Method: Application to Subsurface Domain
No full textNatural fractures conduct fluids in subsurface reservoirs. Quick and realistic predictions of the fracture network organization and its fluid flow efficiency from limited amount of data is critical to optimize resources productivity. We recently developed a method based on multiple point statistics (MPS) technique to produce geologically-constrained fracture network simulations. The method allows to account for the intrinsic non-stationarity of these networks by considering a multivariate input data instead of averaged distribution of fracture parameters. In addition, the method considers probability maps reflecting the influence of fracture drivers in the network variability. Consequently, the simulated fracture networks derived from the innovative MPS approach are geologically better constrained than in classical discrete fracture network modelling approaches. This paper proposes to apply this method in subsurface conditions where available data are sparsely distributed. We developed a workflow where data are gathered from wellbore and from additional sources (outcrops). These data are used to extrapolate a network around the borehole as training images and themselves are extrapolated at the reservoir scale following a geological probability map.This work also presents innovations on the way how training images and probability maps that may integrate more geology constrain than relying almost entirely on available data.Accepted Author ManuscriptApplied Geolog
Investigating spatial heterogeneity within fracture networks using hierarchical clustering and graph distance metrics
No full textRock fractures organize as networks, exhibiting natural variation in their spatial arrangements. Therefore, identifying, quantifying, and comparing variations in spatial arrangements within network geometries are of interest when explicit fracture representations or discrete fracture network models are chosen to capture the influence of fractures on bulk rock behaviour. Treating fracture networks as spatial graphs, we introduce a novel approach to quantify spatial variation. The method combines graph similarity measures with hierarchical clustering and is applied to investigate the spatial variation within large-scale 2-D fracture networks digitized from the well-known Lilstock limestone pavements, Bristol Channel, UK. We consider three large, fractured regions, comprising nearly 300 000 fractures spread over 14 200 m2 from the Lilstock pavements. Using a moving-window sampling approach, we first subsample the large networks into subgraphs. Four graph similarity measures – fingerprint distance, D-measure, Network Laplacian spectral descriptor (NetLSD), and portrait divergence – that encapsulate topological relationships and geometry of fracture networks are then used to compute pair-wise subgraph distances serving as input for the statistical hierarchical clustering technique. In the form of hierarchical dendrograms and derived spatial variation maps, the results indicate spatial autocorrelation with localized spatial clusters that gradually vary over distances of tens of metres with visually discernable and quantifiable boundaries. Fractures within the identified clusters exhibit differences in fracture orientations and topology. The comparison of graph similarity-derived clusters with fracture persistence measures indicates an intra-network spatial variation that is not immediately obvious from the ubiquitous fracture intensity and density maps. The proposed method provides a quantitative way to identify spatial variations in fracture networks, guiding stochastic and geostatistical approaches to fracture network modelling.Applied Geolog
Joule heating effects on electroosmotic entry flow
No full textElectroosmotic flow is the transport method of choice in microfluidic devices over traditional pressure-driven flow. To date however studies on electroosmotic flow have been almost entirely limited to inside microchannels. This work presents the first experimental study of Joule heating effects on electroosmotic fluid entry from the inlet reservoir (i.e. the well that supplies fluids and samples) to the microchannel in a polymer-based microfluidic chip. Electrothermal fluid circulations are observed at the reservoir-microchannel junction which grow in size and strength with the increasing alternating current to direct current voltage ratio. Moreover a 2D depth-averaged numerical model is developed to understand the effects of Joule heating on fluid temperature and flow fields in electrokinetic microfluidic chips. This model overcomes the problems encountered in previous unrealistic 2D and costly 3D models and is able to predict the observed electroosmotic entry flow patterns with a good agreement
Correction: The Effect of Rural-to-Urban Migration on Obesity and Diabetes in India: A Cross-Sectional Study
No full text[This corrects the article on p. e1000268 in vol. 7.].
The Academic Editor's name and institution were erroneously omitted from the metadata of the PDF and HTML versions of this article. The Academic Editor providing expert input on this paper was Peter Byass, Umeå Centre for Global Health Research, Department of Public Health and Clinical Medicine, Umeå University, Sweden. For more information about the role of the Academic Editor in PLoS Medicine's editorial process, see our Author Guidelines: http://www.plosmedicine.org/static/guidelines.action#overview
Mitochondria and Endoplasmic Reticulum Dysfunction in Parkinson’s Disease
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
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