253 research outputs found
Spinodal decomposition in the inverse cascade of two-dimensional, binary-fluid turbulence
No full textWe study spinodal decomposition in the inverse-cascade regime of two dimensional turbulence in symmetric, binary fluid mixtures. We show that turbulence leads to break up of domains whose size, in the inverse cascade regime, is proportional to the Hinze scale. Even more strikingly, we show that the inverse cascade of energy is blocked by the formation of domains
Particles and Fields in Superfluids: Insights from the Two-dimensional Gross-Pitaevskii Equation
No full textWe study the dynamics of active particles in two-dimensional superfluids at temperature , for a variety of initial configurations, by carrying out extensive direct-numerical-simulations of the two-dimensional, Galerkin-truncated Gross-Pitaevskii equation. Our study elucidates the interplay of particles and fields, in both simple and turbulent flows. We show that particle collisions can be inelastic, if the repulsive interactions between particles is weak, and elastic otherwise. We show that assemblies of many particles and vortices yield turbulent spatiotemporal evolutions
Multifractal Droplet Dynamics in Two-Dimensional, binary-fluid turbulence
No full textWe present the most extensive direct numerical simulations, attempted so far, of statistically steady, homogeneous, isotropic turbulence in two-dimensional, binary-fluid mixtures with air-drag-induced friction. We model this mixture by using the Cahn-Hilliard-Navier-Stokes equations and choose parameters, e.g., the surface tension, such that we have a droplet of the minority phase moving inside a turbulent background of the majority phase. Our study reveals that a single droplet, whose mean radius lies in the inertial range of scales, (a) enhances the the forward-cascade part of the energy spectrum of two-dimensional turbulence and (b) stretches the tails of the PDF of the Okubo-Weiss parameter . We show that the dynamics of the droplet is affected significantly by the turbulence in the fluid. In particular, the PDFs of the components of the acceleration shows wide, non-Guassian tails. We characterize the time dependence of the deformation of the droplet and show that it exhibits multifractality
Real-space Manifestations of Bottlenecks in Turbulence Spectra
No full textAn energy-spectrum bottleneck, a bump in the turbulence spectrum between the inertial and dissipation ranges, is shown to occur in the non-turbulent, one-dimensional, hyperviscous Burgers equation and found to be the Fourier-space signature of oscillations in the real-space velocity, which are explained by boundary-layer-expansion techniques. Pseudospectral simulations are used to show that such oscillations occur in velocity correlation functions in one- and three-dimensional hyperviscous hydrodynamical equations that display genuine turbulence
Universal Statistical Properties of Inertial-particle Trajectories in Three-dimensional, Homogeneous, Isotropic, Fluid Turbulence
No full textWe obtain new universal statistical properties of heavy-particle trajectories in three-dimensional, statistically steady, homogeneous, and isotropic turbulent flows by direct numerical simulations. We show that the probability distribution functions (PDFs) P(Φ), of the angle Φ between the Eulerian velocity u and the particle velocity v, at a point and time, scales as P(Φ) ∼Φ−, with a new universal exponent ≃ 4
Mutual-Friction Coefficients in Two-Dimensional Superfluids: From the Gross-Pitaevskii equation to the Hall-Vinen-Bekharevich-Khalatnikov Two-fluid Model
No full textWe start from the two-dimensional Gross-Pitaevskii equation (GPE) and develop algorithms for the ab-initio determination of the temperature (T) dependence of the mutual-friction coefficients, α and α, and the normal-fluid density Pn, which appear as parameters in the Hall-Vinen-Bekharevich-Khalatnikov (HVBK) two-fluid model for a superfluid. In the second part of our study, we elucidate the statistical properties of two-dimensional, homogeneous, isotropic superfluid turbulence in the simplified HVBK model, with values for the mutual-friction coefficients that are comparable to those we obtain from the first part of our study
How does trade impact agricultural productivity?
No full textThe student, Akshay Pandit, submitted this Thesis for approval on 2020-07-22 at 15:29.This Thesis was approved for publication on 2020-07-23 at 10:50.DSpace SAF Submission Ingestion Package generated from Vireo submission #15729 on 2020-10-02 at 15:34:07Made available in DSpace on 2020-10-07T22:44:48Z (GMT). No. of bitstreams: 2
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Previous issue date: 2020-07-23"Agricultural production has faced increased demands over the last half century from an expanding economy and population. We live in a globalized world, in which agriculture is deeply intertwined in international markets and trade. In this paper, we address the overarching research question: ""What is the impact of trade on agricultural productivity?''. To this end, we present a comprehensive statistical and econometric analysis on the relationship between international trade and agricultural production. We use national-scale data on crop yield, area harvested, production, and trade for the last half century (1961-2016) from the Food and Agricultural Organization of the United Nations. We introduce novel weighting and decomposition analyses to explore the relationship between trade and crop productivity. To determine the causal impact of trade on agriculture we implement instrumental variable (IV) econometric methods. We find that trade has led to an increase in global agricultural productivity over time (e.g. through increased productivity, the intensive margin). Global productivity gains have accrued primarily through the participation of more countries in global trade (e.g. expanding the area of contribution, the extensive margin). Additionally, we find that trade has enabled global crop consumption to increase. These findings indicate that trade openness leads to greater productivity in agriculture in general. This work highlights that trade can help to achieve productivity gains in agriculture and potentially help the world to address remaining yield gaps."Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-08-01The student, Akshay Pandit, accepted the attached license on 2020-07-22 at 15:28.Embargo set by: Seth Robbins for item 116267
Lift date: 2022-10-07T22:44:53Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Onl
Utility of Supine Spirometry in Children with Neuromuscular Disorders
No full textBackground Children with neuromuscular disorders (NMD) have progressive loss of muscle strength and function which can lead to respiratory failure. Postural change in spirometry has been previously used in adult patients to detect diaphragmatic dysfunction, sleep disordered breathing and early respiratory failure. Postural spirometry changes in children with NMD have been advocated in guidelines for the assessment of NMD but not extensively studied. Aim To explore the relationship between postural changes in forced vital capacity [FVC] and polysomnography (PSG) in the assessment of early sleep disordered breathing in children with NMD. Method In this prospective cross sectional study, children with NMD from neurogenetic and respiratory clinics performed spirometry in sitting (si) and supine (su) position. Control group consisting of age and gender matched healthy children also underwent lung function testing. PSG was performed within 6 months of spirometry. Spirometry was acceptable according to ATS standards and PSGs scored according to AASM guidelines. Results Of 40 children with NMD who performed spirometry, 30 were able to perform acceptable supine spirometry. Underlying diagnoses were heterogeneous, with majority having Duchenne Muscular dystrophy (n=17). Mean age was 12.3 years (range 8 to 17yrs,SD ±3) with 21 males and 9 females. Mean FEV1sit and FVCsit were 78% (SD ±22) and 75%(SD±20.4) respectively. SpO2 mean 96% [92 to 98%] and SpO2 nadir was 87% (84 to 96%). Mean% ΔFVC (sit – sup) in these children was 9% (range +6 to -28%,SD±11). When compared with control group, there was a significant difference in supine spirometry between the two groups (p<0.001). PSG data was available on 30 children with NMD. Mean total AHI 6.9/hr (0.3 to 29,±5.9), obstructive AHI 5.2/hr (0.2 to 10), REM AHI 14.3/hr (0.1 to 34.7). On comparing supine spirometry with Total AHI, there was a moderate correlation with with presence of sleep disordered breathing (r=0.62, p=0.001) in those breathing spontaneously. Children established on non-invasive ventilation (NIV) showed a poor correlation with supine spirometry. In order to demonstrate the relationship of supine spirometry with evidence of hypoventilation, correlation was performed between change in postural spirometry and rise in CO2 from non-Rem to REM sleep. The mean (SD) rise was 6mmHg (±1.9) with a range of 4 mmHg to 11 mmHg. Coefficient of correlation was 0.04 (p=0.8) and therefore was not significant. When the NMD group was split between those spontaneously breathing and those established on NIV, there was a poor correlation between supine spirometry and rise in CO2 in both the groups spontaneously breathing (r=0.02,p=0.9) NIV (r=0.13,p=0.74) Conclusion In this cohort study, children with NMD with mild restrictive lung disease have postural changes in spirometry which are significantly greater than healthy controls. The changes in supine spirometry however do not correlate with nocturnal hypoventilation on polysomnography in patients with mild neuromuscular diseas
India's National Water Policy: 'feel good' document, nothing more
No full text10.1080/07900627.2019.1576509International Journal of Water Resources Development35061015-102
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