State Diffusion Research Articles

The Cheng-Minkowycz problem for quadratic convective and radiative heat transfer in a nanofluid saturated porous medium: A revised model

The characteristics of heat transport in a porous medium saturated by a nanoliquid subject to non-linear variations of density-temperature relation and a novel quadratic thermal radiation are studied. For the first time, the well-known Cheng-Minkowycz problem was revisited by nonlinear convection and radiation. The governing equations, based on Darcy's law and Buongiorno's model, are simplified using boundary layer theory, which is further solved by the finite element method. The parameterization of the problem is used to describe the characteristics of the Boussinesq quadratic approximation, Brownian diffusion, quadratic radiation, thermophoretic diffusion, and no-mass flux conditions on the rheological and heat transport features. Our results demonstrate that the rate of heat transport (Nusselt number) is reduced due to thermophoretic diffusion, and the rate of reduction increases with increasing Lewis number values. The Nusselt number is improved due to increasing the values of the Brownian motion parameter at the rate of 0.00616835 and 0.00113362 for the cases of linear thermal radiation and quadratic thermal radiation, respectively. The improvement/reduction rate of the Nusselt number is higher for the case of quadratic thermal convection than for linear thermal convection. Furthermore, the heat transfer rate is achieved for the convection parameter, temperature ratio, and radiation parameter.

Nanoimprinted arrays of glassy carbon nanoelectrodes for improved electrochemistry of enzymatic redox-mediators

In the present study, the preparation and electrochemical application of perfectly ordered arrays of glassy carbon nanoelectrodes (GC-NEAs) is presented. After careful morphological characterization, we examined the voltammetric behaviour on GC-NEAs of some redox mediators commonly used in enzymatic electrochemical biosensors. GC-NEAs were fabricated by using nanoimprint lithography to generate ordered arrays of nanoholes, with average radius of 145 nm, onto a polycarbonate thin film deposited on a glassy carbon plate. The redox mediators examined were (ferrocenylmethyl)trimethylammonium (FA+) as typical redox mediator for oxidase enzymes and Azure A and B as examples of mediators used for reductase enzymes. The voltammetric signals recorded indicate that the here prepared GC-NEAs operate under total overlap diffusion conditions, with an accessible potential window significantly wider than the one typical of arrays of gold nanoelectrodes. Interestingly, the electrochemical behaviour of the GC-NEAs perfectly fits with what expected on the basis of the geometrical features of the array demonstrating the role of these parameters in ruling the contribution of capacitive and faradic currents of the array which reflect in improved detection capabilities.

Simulated Trapping of Solar Energetic Protons for the 8–10 March 2012 Geomagnetic Storm: Impact on Inner Zone Protons as Measured by Van Allen Probes

AbstractSolar energetic protons (SEPs) have been shown to contribute significantly to the inner zone trapped proton population for energies <100 MeV and L > 1.3 (Selesnick et al., 2007, https://doi.org/10.1029/2006sw000275). The Relativistic Electron Proton Telescope (REPT) on the Van Allen Probes launched 30 August 2012 observed a double‐peaked (in L) inner zone population throughout the 7‐year lifetime of the mission. It has been proposed that a strong SEP event accompanied by a CME‐shock in early March 2012 provided the SEP source for the higher L trapped proton population, which then diffused radially inward to be observed by REPT at L ∼ 2. Here, we follow trajectories of SEP protons launched isotropically from a sphere at 7 Re in 15 s cadence fields from an Lyon‐Fedder‐Mobarry coupled to Rice Convection Model global magnetohydrodynamic (MHD) simulation driven by measured upstream solar wind parameters. The timescale of the interplanetary shock arrival is captured, launching a magnetosonic impulse propagating azimuthally along the dawn and dusk flanks inside the magnetosphere, shown previously to produce SEP trapping. The MHD‐test particle simulation uses Geostationary Operational Environmental Satellite (GOES) proton energy spectra to weight the initial radial profile required for the radial diffusion calculation over the following 2 years. GOES proton measurements also provide a dynamic outer boundary condition for radial diffusion. A direct comparison with REPT measurements 20 months following the trapping event in March 2012 supports this novel combination of short‐term and long‐term evolution of the newly trapped protons.

Laves Phase Precipitation Behavior in HiperFer (High Performance Ferritic) Steel with and without Boron Alloying

High-chromium ferritic stainless HiperFer steels were developed for high-temperature applications in power conversion equipment. The presented research describes the precipitation behavior of the Laves phase after the thermomechanical treatment of Fe-17Cr-0.6Nb-2.4W HiperFer alloys with and without the addition of 55 ppm boron. The boron-alloyed variant was produced with the aim of enhancing grain boundary strengthening and consequently increasing creep resistance. The focus is set on the effect of boron on the thermomechanically induced precipitation of (Fe,Cr,Si)2(Nb,W) Laves phase at grain boundaries. The addition of boron modifies the diffusion conditions in the area of grain boundaries. Consequently, the formation of Laves phase is promoted and the particle growth and coarsening process are suppressed. The impact of boron addition was validated by performing creep and thermomechanical fatigue testing in the standard processing state of HiperFer steel. In the B-alloyed variant, increased creep ductility through the modification of the particle-free zone widths at high-angle grain boundaries was encountered. Nevertheless, an optimized thermomechanical treatment is necessary to fully utilize the increased ductility effect for the creep strength optimization of the B-alloyed grade.

Performance analysis of a concentrated direct absorption solar collector (DASC) with nanofluids using computational fluid dynamics and discrete ordinates radiation modelling (CFD-DORM)

This study utilises computational modelling to investigate the application of thermal nanofluids in direct absorption solar collectors (DASC), including the effect of optical and thermal properties on the prediction of thermal energy production. A single-phase, computational fluid dynamics (CFD) model has been used to understand the hydrothermal behaviour of nanofluids operated at high temperature. A non-gray discrete ordinate radiation model (DORM) was coupled to the CFD to capture the dependence of optical parameters on the bulk temperature variation. In order to increase the robustness of the numerical modelling approach, the extinction coefficient of the solar participating media, including the reflective and transmissive behaviour of the semitransparent wall, were taken into consideration. Results show that the exergy efficiency is lower when using fully diffusive conditions at the semitransparent wall as opposed to fully specular conditions. Overall, exergy efficiency decreases with the Nusselt number, Nu, (until Nu=10∼12), although it increases with non-dimensional irradiation. When modelling with temperature-dependent as opposed to temperature-independent properties of the working fluid, the Carnot efficiency was found to vary by 0.67% to 3.30%. Additionally, a correlation between the hydraulic entrance length and Reynolds number, Re, (in the range Re<1,000) has been established and this can be applied for the further hydrothermal analysis. This study serves as a basis for future numerical modelling of any volumetric solar receiver that takes into account the various key system performance indicators of the solar participating media.

Fast Identification of Micro-Health Parameters for Retired Batteries Based on a Simplified P2D Model by Using Padé Approximation

Better performance consistency of regrouped batteries retired from electric vehicles can guarantee the residual value maximized, which greatly improves the second-use application economy of retired batteries. This paper develops a fast identification approach for micro-health parameters characterizing negative electrode material and electrolyte in LiFePO4 batteries on the basis of a simplified pseudo two-dimensional model by using Padé approximation is developed. First, as the basis for accurately identifying micro-health parameters, the liquid-phase and solid-phase diffusion processes of pseudo two-dimensional model are simplified based on Padé approximation, especially according to enhanced boundary conditions of liquid-phase diffusion. Second, the reduced pseudo two-dimensional model with the lumped parameter is proposed, the target parameters characterizing negative electrode material (εn, Ds,n) and electrolyte (De, Ce) are grouped with other unknown but fixed parameters, which ensures that no matter whether the target parameters can be achieved, the corresponding varying traces is able to be effectively and independently monitored by lumped parameters. Third, the fast identification method for target micro-health parameters is developed based on the sensitivity of target parameters to constant-current charging voltage, which shortens the parameter identification time in comparison to that obtained by other approaches. Finally, the identification accuracy of the lumped micro-health parameters is verified under 1 C constant-current charging condition.

Comparison of Standardized Methods for Determining the Diffusion Coefficient of Chloride in Concrete with Thermodynamic Model of Migration

This research paper is the result of observations made during tests according to various standards carried out on behalf of industry. The article presents diffusion coefficient values calculated according to the thermodynamic migration model for twenty different concrete mixes and some selected mixes of the codified approaches known as ASTM 1202, NT BUILD 443, NT BUILD 492, ASTM 1556. The method used here, according to the thermodynamic model of migration, allows determination of the value of the diffusion coefficient after short studies of the migration of chloride ions into concrete and was described in earlier works by one of the authors. Unfortunately, when using standard methods, the values of diffusion coefficients differ significantly from each other. In each concrete, diffusion tests were carried out in the conditions of long-term natural diffusion to verify the values determined by standard methods and according to the thermodynamic model of migration. The analysis conducted for this research paper reveals that the chloride permeability test method according to the standard ASTM C1202-97 has an almost 2.8-fold greater dispersion of the obtained results compared to the thermodynamic model of migration. It was observed that the standard NT BUILD 492 has a 3.8-fold dispersion of results compared to the method with the thermodynamic model of migration. The most time-consuming method is the standard method NT BUILD 443. The largest 3.5-fold dispersion of values concerning the reference value are observed in that method. Moreover, a method based on a thermodynamic migration model seems to be the best option of all analyzed methods. It is a quite quick, but laborious, method that should be tested for a larger number of concrete mixes. A great advantage of this method is that it is promising for a wide range of concrete mixtures, both plain concrete and concrete with various additives and admixtures, as well as high-performance concrete.

Elimination, permanence, and exclusion in a competition model under Allee effects

&lt;abstract&gt;&lt;p&gt;In this paper, we study a system of nonlinear partial differential equations that models the population dynamics of two competitive species both under Allee effects. The consideration of the model includes Logistic growth with Allee effects, Lotka-Volterra competition, diffusion, initial density and boundary conditions on the habitat. In the reaction-diffusion system, we employ the method of upper and lower solutions to address questions on self-elimination or persistence, as well as permanence or competitive exclusion. Specific conditions on biological parameters are explicitly given for extinction, coexistence and competitive exclusion of the species under various boundary conditions. Numerical simulations for the model are demonstrated to illustrate our results from mathematical analysis.&lt;/p&gt;&lt;/abstract&gt;

Observation of peritectic couple growth for a hyper-peritectic alloy under microgravity conditions

Under specific conditions, peritectic alloys can form microstructures that behave similar to regular eutectic alloys, with two solid phases growing in a coupled manner directly from the melt. This so-called peritectic couple growth (PCG) is significantly affected by convection. Thus, Bridgman-type experiments were performed onboard the International Space Station using the transparent peritectic alloy, tris(hydroxymethyl)aminomethane–neopentyl glycol (TRIS–NPG). Under these purely diffusive conditions, the formation of PCG, its development over time, and its dependence on the applied process conditions were studied. In this paper, we provide novel insights into the appearance of PCG and the challenges associated with corresponding experiments.

Inhalation health risk assessment of incineration and landfill in the Bohai Rim, China

An inhalation health risks assessment of 96 waste to energy (WtE) plants and 178 landfills in the Bohai Rim, located in northeast China, has been conducted. Based on the latest emission inventories in 2020, WRF/CALPUFF was used to simulate the diffusion of pollutants. Population-weighted hazard index (HI) and carcinogenic risk (CR) of incineration and landfill for each pollutant and each target organ impacted were calculated. The health risks of incineration and landfill were correlated with per capita municipal solid waste (MSW) disposal quantity, emission factors, pollutant toxic effects and local migration and diffusion conditions. The HI of incineration and landfill in the Bohai Rim were 4.07 × 10−3 and 4.79 × 10−3, respectively, which was lower than the acceptable level (HI < 1), while the CR of incineration and landfill were 4.72 × 10−7 and 2.58 × 10−7, respectively, which was also lower than the acceptable level (CR < 1 × 10−6). The non-carcinogenic risks of incineration mainly targeted respiratory system and development system, while the non-carcinogenic risks of landfill mainly targeted nervous system and respiratory system. The carcinogenic risks of incineration mainly targeted respiratory system and digestive system, while the carcinogenic risks of landfill mainly targeted hepatic system and respiratory system.With the trend that incineration phase in, while landfill phase out, the number of patients for 15 target organ diseases caused by the disposal of unit mass MSW would decrease in the Bohai Rim, ranging from 1.8 × 10−8 – 1.8 × 10−2 (pop/t)，especially in developed provinces, such as Beijing and Tianjin. However, the number of patients for 4 target organ diseases caused by the disposal of unit mass MSW would increase, ranging from 1.18 × 10−6 - 5.28 × 10−3 (pop/t). Based on pollutants' pathogenic mechanisms, this study innovatively accessed and compared incineration and landfill's health risks of target organs, and provide technical and policy suggestions based on the changing trend of MSW disposal methods in the future.

Analysis and Petrov–Galerkin numerical approximation for variable coefficient two-sided fractional diffusion, advection, reaction equations

In this paper we investigate the variable coefficient two-sided fractional diffusion, advection, reaction equations on a bounded interval. It is known that the fractional diffusion operator may lose coercivity due to the variable coefficient, which makes both the mathematical and numerical analysis challenging. To resolve this issue, we design appropriate test and trial functions to prove the inf-sup condition of the variable coefficient fractional diffusion, advection, reaction operators in suitable function spaces. Based on this property, we prove the well-posedness and regularity of the solutions, as well as analyze the Petrov–Galerkin approximation scheme for the proposed model. Numerical experiments are presented to substantiate the theoretical findings and to compare the behaviors of different models.

Glucose absorption drives cystogenesis in a human organoid-on-chip model of polycystic kidney disease

In polycystic kidney disease (PKD), fluid-filled cysts arise from tubules in kidneys and other organs. Human kidney organoids can reconstitute PKD cystogenesis in a genetically specific way, but the mechanisms underlying cystogenesis remain elusive. Here we show that subjecting organoids to fluid shear stress in a PKD-on-a-chip microphysiological system promotes cyst expansion via an absorptive rather than a secretory pathway. A diffusive static condition partially substitutes for fluid flow, implicating volume and solute concentration as key mediators of this effect. Surprisingly, cyst-lining epithelia in organoids polarize outwards towards the media, arguing against a secretory mechanism. Rather, cyst formation is driven by glucose transport into lumens of outwards-facing epithelia, which can be blocked pharmacologically. In PKD mice, glucose is imported through cysts into the renal interstitium, which detaches from tubules to license expansion. Thus, absorption can mediate PKD cyst growth in human organoids, with implications for disease mechanism and potential for therapy development.

Supersaturation as a Galenic Concept for Improving the Cutaneous Bioavailability of Drugs in Topical Therapy.

The essential force that allows an epicutaneously applied drug to penetrate the skin is mediated by diffusion. The physicochemical properties of the skin tissue at the site of application and the concentration gradient of the dissolved drug between the vehicle and the stratum corneum are decisive here. One way to specifically improve these diffusion conditions is to use supersaturation. This uses the physical principle of the difference between the solubility curve and precipitation curve (Ostwald-Miers range). During the conversion of the application vehicle into the segregation vehicle, supersaturation of the dissolved drug substance in a solvent is achieved by evaporation, e.g., of a solubilizer. In principle, the change in solubility can also be achieved by heating and then cooling a solution. This principle has already been realized in a formulation of a fixed combination of calcipotriol and betamethasone dipropionate, two lipophilic drugs susceptible to hydrolysis, and is available on the market as a spray foam.

A chemotaxis‐Stokes system with nonhomogeneous boundary condition: Global large‐datum solution and asymptotic behavior

AbstractIn this paper, we study the global solvability and stabilization to a chemotaxis‐Stokes model with porous medium diffusion and mixed nonhomogeneous boundary value conditions in three‐dimensional space. When m is slightly bigger than 1, we can get a solution with strong regularity, but when m is close to 1, the regularity of the solution becomes weak. Specifically, our results are divided into two cases: (i) and (ii) . For case (i), we obtain a global bounded weak existence with good regularity for any initial datum, and for decay incoming oxygen, we also prove that the bounded solution will converge to a constant steady state. But for case (ii), it is hard to obtain the boundedness of solutions, and a global “very” weak solution is obtained.

Breakup regime of flashing jet under thermal nonequilibrium and mechanical forces and its relationship with jet characteristics during depressurized releases of superheated liquid

Accidental superheated liquid emissions into the atmosphere yield two-phase releases. The resulting flashing jet, driven by thermal nonequilibrium and mechanical forces, breaks up into massive droplets, fostering beneficial conditions for fire, explosion, and toxic diffusion. In this work, a 20 L tank was built to examine two-phase flow behaviors during depressurized releases of superheated liquids via a high-speed camera and phase Doppler anemometry. Different breakup regimes of flashing jet and dimensionless groups that effectively represent thermodynamic (RpJa) and mechanical (WevOh) driving effects were determined. Based on the interaction between the two effects, quantitative criteria to distinguish different regimes were developed. The accompanying jet characteristics, including jet angle (θ), area fraction (fA), droplet diameter (dSMD), and droplet velocity (ud), and their relationship with jet breakup were revealed. Results show that non-flashing (NFB), partially flashing (PFB), and fully flashing (FFB) breakups coincide with RpJa(WevOh)1/7 < 41, 41 ≤RpJa(WevOh)1/7 < 223, and 223 ≤RpJa(WevOh)1/7, respectively. For small-sized nozzles (d≤3 mm), θ2 and fA2 increase within 41 ≤RpJa(WevOh)1/7 < 558 and then keep stable. The difference for large-sized nozzles resides in 223 ≤RpJa(WevOh)1/7 < 558 (early FFB regime), where θ2 and fA2 decrease slightly due to the enhanced droplet evaporation. In 41 ≤RpJa(WevOh)1/7, dSMD2 decreases and ud2 increases, but at an extremely low rate within 558 ≤RpJa(WevOh)1/7.

Cellulose degradation products and high ionic strength enhance the retardation of strontium in hydrated cement paste

The present concept for the disposal of some low- and all intermediate-level radioactive waste in the United Kingdom involves grouting with cement in steel drums and placement in a geological facility. The vaults would then be backfilled with low strength, high porosity cement-based materials designed to promote a pervasive, alkaline environment in which many of the radioactive species present are sparingly soluble. This work investigates the interaction of strontium with such a backfill under both diffusive and advective conditions given the potential significance of the fission product 90Sr. An important characteristic of the United Kingdom waste inventory is the abundance of organic compounds, including cellulosic materials; consequently, the experiments were repeated with products of alkaline cellulose degradation. Additional experiments were performed at high ionic strength simulating anticipated changes in the salinity of the groundwater. The effective diffusivity (De) of strontium in the absence of the organic compounds ranged between 5.5 × 10−11 and 8.5 × 10−11 m2 s−1, with a distribution coefficient (Rd) of between 2.8 × 10−3 and 3.1 × 10−3 m3 kg−1. The presence of organic compounds and/or an increase of ionic strength enhanced the retardation of strontium. The results indicate that the retention of strontium by hydrated cement paste occurs via a reversible ion exchange mechanism rather than mineralisation and is promoted by decalcification of the calcium silicate hydrate phases.

Controlling Threshold and Resistive Switch Functionalities in Ag‐Incorporated Organometallic Halide Perovskites for Memristive Crossbar Array

AbstractHalide perovskites (HPs) can be the effective functional materials for the sneak‐path current issue in the memristive crossbar array. Herein, an efficient strategy is proposed to integrate the HPs‐based bidirectional threshold and bipolar resistive switches (TS and RS). The resistance change characteristics from volatile threshold to nonvolatile resistive switching are modulated by controlling Ag doping concentration in the MAPbI3. HPs provide the diffusive condition and the quantity of Ag regulates the radius of its network. A low amount of Ag contributes to weak network with a short lifetime. However, when the amount of Ag increases, the conductive filament becomes more robust, showing a long lifetime. A MAPbI3:Ag TS with a low Ag content is developed, showing a steep switching slope (1 mV per decade), fast switching speed (&lt; 80 ns), and low off‐current (10 nA). And, a MAPbI3:Ag RS with a high Ag content is developed, showing multilevel storage capability and long retention time (1400 s). Finally, these TS and RS coupled into the 1S‐1R integrated component, resulting the development of the maximum crossbar array size to 1.4 × 1012. This study offers an efficient methodology for tailoring the resistance change characteristics and a promising strategy for practical HPs‐based memristive crossbar application.

GLAD Based Advanced Nanostructures for Diversified Biosensing Applications: Recent Progress.

Glancing angle deposition (GLAD) is a technique for the fabrication of sculpted micro- and nanostructures under the conditions of oblique vapor flux incident and limited adatom diffusion. GLAD-based nanostructures are emerging platforms with broad sensing applications due to their high sensitivity, enhanced optical and catalytic properties, periodicity, and controlled morphology. GLAD-fabricated nanochips and substrates for chemical and biosensing applications are replacing conventionally used nanomaterials due to their broad scope, ease of fabrication, controlled growth parameters, and hence, sensing abilities. This review focuses on recent advances in the diverse nanostructures fabricated via GLAD and their applications in the biomedical field. The effects of morphology and deposition conditions on GLAD structures, their biosensing capability, and the use of these nanostructures for various biosensing applications such as surface plasmon resonance (SPR), fluorescence, surface-enhanced Raman spectroscopy (SERS), and colorimetric- and wettability-based bio-detection will be discussed in detail. GLAD has also found diverse applications in the case of molecular imaging techniques such as fluorescence, super-resolution, and photoacoustic imaging. In addition, some in vivo applications, such as drug delivery, have been discussed. Furthermore, we will also provide an overview of the status of GLAD technology as well as future challenges associated with GLAD-based nanostructures in the mentioned areas.

Investigating Southeast Asian biomass burning by the WRF-CMAQ two-way coupled model: Emission and direct aerosol radiative effects

Southeast Asia (SEA) is one of the world's major sources of biomass burning (BB). In this study, the recently released Weather Research and Forecasting-Community Multiscale Air Quality (WRF-CMAQ) two-way coupled model was used with the Global Fire Emissions Database Version 4, to investigate the effect of BB emissions on the meteorology and air quality over SEA in March and April 2015. The results show that the model performance was improved by considering BB emissions. When BB pollutants reach the free troposphere, they can be transported by westerly and southwesterly winds to downstream regions. The contributions of BB were up to 48.4 and 35.5 ppbv to surface O3 concentrations and 251.0 and 104.4 μg/m3 to surface PM2.5 concentrations in March and April, respectively. The BB emission caused aerosol direct radiative effect (DRE) on the monthly mean clear-sky downward shortwave flux at the ground surface to decrease by −65.4 and −33.6 W/m2 in March and April, respectively. The surface temperature decreased over the land (by a maximum of −0.24 °C in March) and increased over the sea, while the temperature at higher levels tended to increase (to a maximum of 0.12 °C in March). The BB aerosol DRE caused the planetary boundary layer height (PBLH) to decrease by a maximum of −91.2 m in March. Surface O3 concentrations decreased generally owing to variations in the shortwave flux and temperature. Moreover, the decreased PBLH worsened the diffusion condition within the PBL but also caused larger amounts of BB emissions to penetrate the free atmosphere. This led to a decrease in surface PM2.5 concentrations in southern Indochina and an increase in Myanmar. These findings highlight the key effects of BB emissions on local and downwind meteorology and air quality over SEA and demonstrate the practical applications of the WRF-CMAQ coupled model.

Unique CO2-modified VO2(B) nanosheets for lithium batteries with high electrochemical performance

Heteroatom doping has always been a common modification method for lithium-ion batteries (LIBs) cathodes. The addition of guest heteroatoms to the material can adjust the microstructure of the host material, and enlarge the lattice spacing or form the vacancy defect of oxygen, which can effectively improve the Electrochemical performance of materials. Herein, CO2-modified VO2(B) nanorods were synthesized via a simple one-step hydrothermal method. Thanks to the extended layer spacing in VO2(B) that results from CO2 small molecules, the synthesized CO2-VO2 electrode exhibits a high initial capacity of 251.1 mA g−1 at 100 mA g−1, and a capacity retention of 81.8 % after 80 cycles. It is worth noting that the CO2-VO2 electrode also has a high rate capacity (170.0 mAh g−1 at 1 A g−1), and the capacity recovery rate can reach 84.5 % even under the condition of variable current. Further studies showed that the role of CO2 small molecules as a pillar in the interlayer of VO2(B) and a weak electrostatic attraction between OCO2 and Li+ existed, resulting in a robust crystal structure and convenient Li-ion diffusion conditions during the (de)intercalation of lithium ions in VO2(B). This study opens the way for further exploration of the application of small molecule doping in the field of lithium-ion batteries.