233 research outputs found
The Effect of Modifications of Activated Carbon Materials on the Capacitive Performance: Surface, Microstructure, and Wettability
No full textIn this review, the efforts done by different research groups to enhance the performance of the electric double-layer capacitors (EDLCs), regarding the effect of the modification of activated carbon structures on the electrochemical properties, are summarized. Activated carbon materials with various porous textures, surface chemistry, and microstructure have been synthesized using several different techniques by different researchers. Micro-, meso-, and macroporous textures can be obtained through the activation/carbonization process using various activating agents. The surface chemistry of activated carbon materials can be modified via: (i) the carbonization of heteroatom-enriched compounds, (ii) post-treatment of carbon materials with reactive heteroatom sources, and (iii) activated carbon combined both with metal oxide materials dan conducting polymers to obtain composites. Intending to improve the EDLCs performance, the introduction of heteroatoms into an activated carbon matrix and composited activated carbon with either metal oxide materials or conducting polymers introduced a pseudo-capacitance effect, which is an additional contribution to the dominant double-layer capacitance. Such tricks offer high capacitance due to the presence of both electrical double layer charge storage mechanism and faradic charge transfer. The surface modification by attaching suitable heteroatoms such as phosphorus species increases the cell operating voltage, thereby improving the cell performance. To establish a detailed understanding of how one can modify the activated carbon structure regarding its porous textures, the surface chemistry, the wettability, and microstructure enable to enhance the performance of the EDLCs is discussed here in detail. This review discusses the basic key parameters which are considered to evaluate the performance of EDLCs such as cell capacitance, operating voltage, equivalent series resistance, power density, and energy density, and how these are affected by the modification of the activated carbon framework
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
Development of an enzyme free glucose sensor based on copper oxide-graphene composite by using green reducing agent ascorbic acid
No full textReal-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
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