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It has been generally accepted and often mentioned in the text books that gradient in chemical potential of a species is the fundamental driving force for its diffusion. However, a general derivation of the interrelation between the diffusion flux of a component and chemical potential gradients in a non-ideal solution is lacking. Although there have been various studies in the literature reporting such interrelations for a binary system, they all assume constant molar volume. In a non-ideal system though molar volume changes with composition. Hence, in the present work, kinetic theory is used to derive a relation between diffusion flux and the chemical potential gradients for a multicomponent system with composition dependent molar volume. It is shown that the velocity of the marker as measured in a diffusion couple experiment should consist of the drift velocity (⁠ U N ⁠) due to change in molar volume accompanied by diffusion as well as the Kirkendall velocity caused by vacancy equilibration process. For the assumption of volume change occurring only in the direction of diffusion, the Kirkendall velocity is same as the marker velocity measured in a diffusion couple. However, if the lattice is allowed to relax in all directions, the contribution of U N to the marker velocity can be significant. This is shown to be as high as 20% for Cu in a Cu-Ni diffusion couple. [ABSTRACT FROM AUTHOR]

Introduction: The production of fluxes for hardfacing by submerged arc welding is based on the consumption of natural minerals. However, there are slags that contain the oxide systems required for a flux. Hardfacing makes it possible to reincorporate worn parts into service. Objective: To evaluate, by means of the Circular Economy approach, the obtaining of fluxes from slags for hardfacing by submerged arc welding. Materials and Methods: A conceptual scheme is proposed, with a Circular Economy approach, to obtain fluxes for hardfacing, using slag and conceiving hardfacing for the restitution to service of worn parts or to manufacture parts with greater durability. Two variants are proposed: The production of ferroalloys, using slags as matrix for a flux, and the obtaining of fluxes, using slags discarded from other productions. Results and Discussion: Different cases are addressed: 1. Obtaining ferrochromium-manganese, conceiving the use of slags as a matrix of a hardfacing flux; 2. Obtaining a hardfacing flux, using slags from submerged arc welding; 3. Obtaining a hardfacing flux, using slag from steel production. The fluxes obtained make hardfacing possible, for the rehabilitation of worn parts or for the manufacture of more wear-resistant parts. Conclusions: The conceptual scheme is validated, by a Circular Economy approach, in obtaining fluxes for hardfacing with the use of slag, making possible the restoration to service of worn parts or to manufacture new, higher-quality parts. [ABSTRACT FROM AUTHOR]

This study reports on the accumulation rates and 210Pb fluxes in Spitsbergen, Svalbard archipelago, wetlands. Six peat cores were collected in the Hornsund region, SW Spitsbergen (77°N) in 2007. The ages of peat layers were obtained with the Constant Flux/Constant Sedimentation and Constant Rate of Supply models based on the 210Pbdating technique. The obtained 210Pb flux values ranged from 28 to 50 Bq m-2 y-1, which was consistent with the level of 222Rn emanation estimated for northern latitudes. The values of vertical and mass accumulation rates were slightly lower than reference data for peatlands of 50°-70°N. Furthermore, the vertical variations of peat accumulation rates exhibited the highest values in the upper part of the examined cores. The increasing tendency may be due in part to low compaction and low decomposition in the youngest peat layers. The analysis of the peat accumulation rate as a function of organic matter content and bulk density revealed positive and negative correlations, respectively, rather strong in both cases. The air temperature and precipitation gradients in the last few decades may have affected peat growth rates, which should be thoroughly investigated in future projects. Undoubtedly, the reported findings have provided a valuable addition to the relatively sparse dataset on recent peat deposits in Spitsbergen. [ABSTRACT FROM AUTHOR]

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Buoyant shear layers encountered in many engineering and environmental applications have been studied by researchers for decades. Often, these flows have high Reynolds and Richardson numbers, which leads to significant/intractable space-time resolution requirements for direct numerical simulation (DNS) or large eddy simulation (LES). On the other hand, many of the important physical mechanisms, such as stress anisotropy, wake stabilization, and regime transition, inherently render eddy viscosity-based Reynolds-averaged Navier-Stokes (RANS) modeling inappropriate. Accordingly, we pursue second-moment closure (SMC), i.e., full Reynolds stress/flux/variance modeling, for moderate Reynolds number nonstratified, and stratified shear layers for which DNS is possible. A range of submodel complexity is pursued for the diffusion of stresses, density fluxes and variance, pressure strain and scrambling, and dissipation. These submodels are evaluated in terms of how well they are represented by DNS in comparison to the exact Reynolds-averaged terms, and how well they impact the accuracy of full RANS closure. For the nonstratified case, SMC model predicts the shear layer growth rate and Reynolds shear stress profiles accurately. Stress anisotropy and budgets are captured only qualitatively. Comparing DNS of exact and modeled terms, inconsistencies in model performance and assumptions are observed, including inaccurate prediction of individual statistics, non-negligible pressure diffusion, and dissipation anisotropy. For the stratified case, shear layer and gradient Richardson number growth rates, and stress, flux and variance decay rates, are captured with less accuracy than corresponding flow parameters in the nonstratified case. These studies lead to several recommendations for model improvement. [ABSTRACT FROM AUTHOR]

Single crystals of Na2Mn3(P2O7)2 compound have been first obtained during the examination of interaction in the Na2O-P2O5-Mn2O3-NaF (10 wt.%.) system in the fluxes with Na2O:P2O5 molar ratios ranging from 0.52 to 0.76 (saturated with manganese(III) oxide 25.0-32.0 wt.%) at the temperatures of 960-880°C. Optimum conditions for the synthesis and growing of single crystals of Na2Mn3(P2O7)2 compound have been determined. Complete X-ray diffraction analysis of the synthesized phosphate Na2Mn3(P2O7)2 has been performed. According to its structure, the double phosphate Na2Mn3(P2O7)2 belongs to the triclinic crystal system, spatial grid P1; lattice parameters are as follows: a=5.359 Å, b=6.563 Å, c=16.299 Å, α=81.29°, β=82.70°, γ=72.44°, V=538.23 ų, Z=4, Ccalc= 3.447 g cm-3. Structural features of synthesized phosphate have been determined. The structure is composed of continuous chain of distorted octahedra [MnO6] spacing along the direction ob. Diphosphate groups of tetrahedra [PO4] divide the chains [MnO6] and also run along ob direction. Pairwise linked pentagonal bipyramids of sodium divide the «units» of polyhedral of manganese and phosphorus, filling the channels along oy axis. The crystalline structure of Na2Mn3(P2O7)2 includes three nonequivalent, according to their crystallography, octahedra of manganese with slightly distorted form. The compound has been studied using X-ray diffraction and X-ray phase analyses, differential thermal analysis, IR spectroscopy and complete chemical analysis. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dynamic behaviors of molten pools during active laser welding of thick 304 stainless steel plates are monitored in real time by utilizing a high-speed camera system. The effects of various active fluxes on the dynamic variations of molten pools are analyzed, and the results are compared with the uncoated specimens. The research reveals that all the molten pools present periodic variations. Among them, the specimen coated with NaF active flux exhibits the shortest cycle of molten pool change, with a single cycle duration of approximately 0.5 s. The specimen coated with TiO2 active flux exhibits the longest cycle of molten pool change, and the single cycle duration is around 1.1 s. Moreover, the molten pools also show varying widths. The maximum molten pool width is found with the specimen coated with CeO2 active flux, whose value is 3.277 mm. Meanwhile, the minimum molten pool width is found with the specimen coated with NaF active flux, whose value is 1.799 mm. In addition, the coating of active fluxes also produces certain effects on molten pool stability. The specimen coated with NaF active flux presents intense emission of metal vapor during welding, drastic oscillation of the molten pool, and severe spattering of metal particles. Contrastively, the molten pool of the specimen coated with Cr2O3 active flux is rather stable. In conclusion, by selecting an appropriate active flux, the cycle of molten pool variation can be prolonged, the pool stability can be enhanced, and the occurrence of spattering and other defects can be suppressed. [ABSTRACT FROM AUTHOR]

Mountain belts modulate denudation flux and hydrologic processes and are thus fundamental to nutrient cycling on Earth’s surface. We used europium anomalies in detrital zircons to track mountain-building processes over Earth’s history. We show that the average thickness of active continental crust varied on billion-year time scales, with the thickest crust formed in the Archean and Phanerozoic. By contrast, the Proterozoic witnessed continuously decreasing crustal thickness, leaving the continents devoid of high mountains until the end of the eon. We link this gradually diminished orogenesis to the long-lived Nuna-Rodinia supercontinent, which altered the mantle thermal structure and weakened the continental lithosphere. This prolonged orogenic quiescence may have resulted in a persistent famine in the oceans and stalled life’s evolution in Earth’s middle age. [ABSTRACT FROM AUTHOR]

We investigate the relationship between the global distribution of deep slab dips (at 250‐ to 300‐km depth) and pressure and circulation in the upper mantle. Using an analytic method to compute dynamic pressure in a 3‐D global upper mantle domain, and a force balance between slab dip, slab buoyancy, and pressure, we model dips for all major subduction zones. Overall, our models suggest that global‐scale mantle flow, as dictated by the shapes and velocities of Earth's plates and slabs, plays a fundamental role in creating the global pattern of slab dips. The dip trends of the South American and western Pacific subduction zones are controlled, in our models, by spatial variations in the dynamic pressure associated with flow. Our best fitting models produce global root mean square dip misfits of less than 10° for asthenospheric viscosities of 2.5–4.0 × 1020 Pas. This result is only obtained with a large flux of asthenosphere from upper to lower mantle at subduction boundaries, occurring on the overriding plate side of slabs, without which dips are significantly steeper than observed. This effect cannot be resolved by processes that affect only certain subduction systems and requires flux of asthenosphere into the lower mantle at subduction systems globally (or an alternative mechanism that produces more negative pressures on the overriding plate side of slabs). Upper mantle pressure fields that fit global slab dips yield negative dynamic pressure on the upper plate side of slabs, positive pressure on the subducting plate side, and an east‐to‐west pressure increase beneath the Pacific Plate. Key Points: By linking dip to mantle pressure via a force balance, we investigate global mantle flow as constrained by the Earth's slab dip distributionModels produce pressure fields consistent with Earth dips when material is down fluxed into the lower mantle on the upper plate side of slabsSlab dips provide a constraint on dynamic pressure patterns in the upper mantle [ABSTRACT FROM AUTHOR]

Carbon fluxes at the land‐atmosphere interface are strongly influenced by weather and climate conditions. Yet what is usually known as "climate extremes" does not always translate into very high or low carbon fluxes or so‐called "carbon extremes." To reveal the patterns of how climate extremes influence terrestrial carbon fluxes, we analyzed the interannual variations in ecosystem carbon fluxes simulated by the Terrestrial Biosphere Models (TBMs) in the Inter‐Sectoral Impact Model Intercomparison Project. At the global level, TBMs simulated reduced ecosystem net primary productivity (NPP; 18.5 ± 9.3 g C m−2 yr−1), but enhanced heterotrophic respiration (Rh; 7 ± 4.6 g C m−2 yr−1) during extremely hot events. TBMs also simulated reduced NPP (60.9 ± 24.4 g C m−2 yr−1) and reduced Rh (16.5 ± 11.4 g C m−2 yr−1) during extreme dry events. Influences of precipitation extremes on terrestrial carbon uptake were larger in the arid/semiarid zones than other regions. During hot extremes, ecosystems in the low latitudes experienced a larger reduction in carbon uptake. However, a large fraction of carbon extremes did not occur in concert with either temperature or precipitation extremes. Rather these carbon extremes are likely to be caused by the interactive effects of the concurrent temperature and precipitation anomalies. The interactive effects showed considerable spatial variations with the largest effects on NPP in South America and Africa. Additionally, TBMs simulated a stronger sensitivity of ecosystem productivity to precipitation than satellite estimates. This study provides new insights into the complex ecosystem responses to climate extremes, especially the emergent properties of carbon dynamics resulting from compound climate extremes. Plain Language Summary: Terrestrial ecosystems sequestrate a large amount of carbon dioxide from the atmosphere, which helps to mitigate climate warming. Climate extremes, such as droughts and heatwaves, play a significant role in determining the capacity of land ecosystems in carbon uptake. In the past decades, terrestrial biosphere models have been widely used to investigate the magnitude and variations of carbon fluxes between land and the atmosphere. In this study, we attempted to understand how model‐simulated carbon fluxes respond to climate anomalies and extremes at the global level and across regions. Analysis of model simulations showed significant spatial variations in the sensitivity of carbon fluxes to climate variations. Interestingly, concurrences of abnormal temperature and precipitation could have stronger impacts on carbon fluxes than individual temperature or precipitation extreme event. This study is important for better understanding climate extreme impacts on ecosystem dynamics and the global carbon cycle. Key Points: Impacts of temperature or precipitation extremes on carbon fluxes could be amplified due to their interactive effectsHot extremes lead to a larger carbon loss in tropics while ecosystems in the arid and semi‐arid zones show the largest sensitivity to precipitationModels simulated larger sensitivity of ecosystem productivity to precipitation than satellite product, particularly in tropics [ABSTRACT FROM AUTHOR]

The information about the current-carrying ability of a type-II superconductor can be obtained by studying the flux relaxation and vortex penetration phenomena in the superconductor. In early studies, the infinite series models of the flux relaxation and vortex penetration phenomena were constructed at a vanishing current density and vanishing internal field, respectively. However, this is not the only possibility. Here, it is shown that one can reconstruct the theoretical models at the critical points. The new polynomial model of the flux relaxation (vortex penetration) phenomenon was constructed by expanding the vortex activation energy as an infinite series of the current density (internal field) about the critical current density (equilibrium internal field). The unification of the polynomial models was proposed. The inverse model of the flux relaxation (vortex penetration) phenomenon was also constructed by expanding the vortex activation energy as an infinite series of the inverse current density (inverse internal field) about the critical current density (equilibrium internal field). [ABSTRACT FROM AUTHOR]

A unified model of grain-boundary segregation kinetics is established, which can simulate the equilibrium and non-equilibrium grain-boundary segregation kinetics during isothermal ageing. The results of model fittings/predictions are in a good consistence with those of the experiments. Values of several important parameters, such as vacancy formation energy, vacancy migration energy, and complex migration energy derived by model fittings, show a reasonably good agreement with those in the references. Relationship between the equilibrium and non-equilibrium grain-boundary segregation mechanisms is discussed in detail. The segregation peak/depletion trough observed in the non-equilibrium segregation kinetics may be ascribed to the vacancy flux. The equilibrium segregation kinetics is considered as a special case in non-equilibrium segregation kinetics with the zero vacancy flux. Both the equilibrium and non-equilibrium segregation kinetics are believed to be dominated by vacancy-solute complex flux. The proposed unified model can be a significant progress in grain-boundary segregation theory, with applications in guiding the design of materials. [ABSTRACT FROM AUTHOR]

Vortex penetration and flux relaxation phenomena carry information about the pinning ability, and consequently current-carrying ability, of a type-II superconductor. However, the theoretical descriptions of these phenomena are currently limited to the cases with special initial conditions. A generalization to the recently developed infinite series models is presented here. It is shown that one can convert a vortex penetration process with a nonzero initial internal field into a process with a zero initial internal field by introducing some time parameters. Similarly, one can also convert a flux relaxation process starting with an arbitrary internal field into a process starting with a melting internal field by introducing a virtual time interval. Therefore, one can predict the melting internal field (or critical current density) from a flux relaxation process starting with a lower internal field. Finally, I show that the vortex penetration process in an ideal superconductor is strongly time dependent because of the surface barrier and internal field repulsive force. But the flux relaxation process does not occur in the ideal superconductor. [ABSTRACT FROM AUTHOR]

The possibility to discriminate between the relative importance of the fluxes of energy and matter in plasma-surface interaction is demonstrated by the energy flux measurements in low-temperature plasmas ignited by the radio frequency discharge (power and pressure ranges 50-250 W and 8-11.5 Pa) in Ar, Ar+H2, and Ar+H2+CH4 gas mixtures typically used in nanoscale synthesis and processing of silicon- and carbon-based nanostructures. It is shown that by varying the gas composition and pressure, the discharge power, and the surface bias one can effectively control the surface temperature and the matter supply rates. The experimental findings are explained in terms of the plasma-specific reactions in the plasma bulk and on the surface. [ABSTRACT FROM AUTHOR]

The reactive flux between folded and unfolded states of a two-state protein, whose coarse-grained dynamics is described by a master equation, is expressed in terms of the commitment or splitting probabilities of the microstates in the bottleneck region. This allows one to determine how much each transition through a dividing surface contributes to the reactive flux. By repeating the analysis for a series of dividing surfaces or, alternatively, by partitioning the reactive flux into contributions of unidirectional pathways that connect reactants and products, insight can be gained into the mechanism of protein folding. Our results for the flux in a network with complex connectivity, obtained using the discrete counterpart of Kramers’ theory of activated rate processes, show that the number of reactive transitions is typically much smaller than the total number of transitions that cross a dividing surface at equilibrium. [ABSTRACT FROM AUTHOR]

The steady-state flux through a singly occupied membrane channel is found for both discrete and continuum models of the solute dynamics in the channel. The former describes the dynamics as nearest-neighbor jumps between N sites, while the latter assumes that the molecule diffuses in a one-dimensional potential of mean force. For both models it is shown that the flux is the same as that for a simple two-site model with appropriately chosen rate constants, which contain all the relevant information about the more detailed dynamics. An interesting consequence of single occupancy is that the flux has a maximum as a function of the channel-solute interaction. If this interaction is too attractive, the molecule will never leave the channel, thus blocking it for the passage of other molecules. If it is too repulsive, the solute molecule will never enter the channel. Thus the flux vanishes in the two limits and, hence, has a maximum somewhere in-between. In the framework of the diffusion model, we find the optimal intrachannel potential of mean force that maximizes the flux using the calculus of variations. For a symmetric channel this potential is flat and occupies the entire channel. In the general case of an asymmetric channel, the optimal potential is obtained by tilting the optimal flat potential for the corresponding symmetric channel around the channel center, so that the solute is driven towards the reservoir with the lower solute concentration by a constant force. This implies that the flux is higher when the solute binding near the channel exit is stronger than that near the entrance. [ABSTRACT FROM AUTHOR]

We present a method for computing stationary distributions for activated processes in equilibrium and nonequilibrium systems using forward flux sampling. In this method, the stationary distributions are obtained directly from the rate constant calculations for the forward and backward reactions; there is no need to perform separate calculations for the stationary distribution and the rate constant. We apply the method to the nonequilibrium rare event problem proposed by Maier and Stein, to nucleation in a 2-dimensional Ising system, and to the flipping of a genetic switch. [ABSTRACT FROM AUTHOR]

This paper explores stochastic models for the study of ion transport in biological cells. It considers one-dimensional models with time-varying concentrations at the boundaries. The average concentration and flux in the channel are obtained as kernel representations, where the kernel functions have a probabilistic interpretation which contributes to a better understanding of the models. In particular, the kernel representation is given for the flux at a boundary point, providing a correct version of a representation found in the literature. This requires special attention because one of the kernel functions exhibits a singularity. This kernel representation is feasible due to the linearity of the system that arises from the assumed independence between ions. [ABSTRACT FROM AUTHOR]

A density functional theory of diffusion is developed for lattice fluids with molecular flux as a functional of the density distribution. The formalism coincides exactly with the generalized Ono–Kondo density functional theory when there is no gradient of chemical potential, i.e., at equilibrium. Away from equilibrium, it gives Fick’s first law in the absence of a potential energy gradient, and it departs from Fickian behavior consistently with the Maxwell–Stefan formulation. The theory is applied to model a nanopore, predicting nonequilibrium phase transitions and the role of surface diffusion in the transport of capillary condensate. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Structural and compositional analyses of a MnSi layer have been performed to elucidate the growth mechanism. The MnSi layer was grown by reactive deposition epitaxy in the presence of an Sb flux. The existence of Sb was found at the MnSi/Si interface and on the surface of MnSi layer by secondary ion mass spectrometry. In addition, x-ray photoelectron spectroscopy measurement shows that MnSb is formed on the surface of the grown MnSi layer. On the atomic scale, scanning transmission electron microscopy observations reveal the existence of an Sb–Mn–Sb structure at the interface between the MnSi layer and the Si substrate. The formation of the MnSb plays an important role for the improvement of crystalline quality of the silicide layer, acting both as a surfactant and as a compliant substrate for stress relief. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Recycling of aluminium, particularly aluminium beverage cans is important due to several economic and environmental reasons. Aluminium beverage cans are by far the most recycled consumer beverage packages globally, by units, weight and percentage recycled. It amounts to more than twice the recycling rate and recycled content percentages for beverage packages of other materials. Recycling of aluminium requires only 5-10% of the energy for primary aluminium production. In this paper, the melting of cans wastes in microwave furnace as well as the treatment of noxious emissions in a microwave thermal filter has been preliminary investigated. Melting temperature, composition of the melting - protection fluxes as well as waste/flux ratio on the metal recovery efficiency have been investigated. During the cans waste melting, due to the burning of paint and lacquer coatings, environmental toxic compounds such as: volatile organic compounds (VOCs) (acetone, benzene, ethylbenzene, styrene, toluene, etc.) have been detected in the effluent gases. The treatment was carried out by passing the gases through a microwave susceptor granular material filter (SiC balls), placed in a microwave transparent tube. It was observed that the temperature of the filter has a major influence on the neutralization of the toxic compounds, the content in the gases being reduced below the legal limits. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Henan University of Science & Technology, Natural Science is the property of Editorial Office of Journal of Henan University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • Methodology to determine flux and temperature distributions for stationary MBE. • GaAsBi growth regimes determined in high resolution with respect to the As/Ga ratio. • Strong variation of Bi incorporation and structural properties. • Material optimization by fine-tuning the As/Ga ratio. Abstract The control of Bi incorporation and material properties in III-V-Bi alloys has proved challenging due to their high sensitivity to the epitaxial growth parameters. Here, we present a methodology for determining the variation in the Ga, As, and Bi fluxes and the temperature across a stationary substrate in molecular beam epitaxy. By correlating the flux distributions with material properties, we identify distinct regimes for epitaxy of GaAsBi. In particular, we devise a detailed image of the interplay between Bi incorporation and structural properties of a bulk GaAs 0.96 Bi 0.04 layer grown on GaAs(1 0 0) with respect to the As/Ga ratio. The influence of As/Ga is analyzed with high resolution over the important stoichiometric range (i.e. As/Ga = 0.6–1.6). Growth outside the near-stoichiometric As/Ga regime leads to decreased Bi incorporation, decreased structural quality and the formation of Ga, Ga/Bi or Bi droplets. On the other hand, growth at As/Ga = 1.00–1.17 leads to maximized material quality. For this regime, the surface roughness is further optimized by fine-tuning the As/Ga ratio to suppress surface mounding to a value of 0.5 nm. The results reveal the extreme sensitivity of GaAsBi growth to small variations in the As/Ga ratio, and demonstrate the applicability of stationary growth in studying these effects. [ABSTRACT FROM AUTHOR]

The reconstruction of the angular and spatial intensity distribution from radiative flux maps measured in high flux solar simulators (HFSS) or optical concentrators is an ill-posed inverse problem requiring special solution strategies. We aimed at providing a solution strategy for the determination of intensity distributions of arbitrarily complicated concentrating facilities. The approach consists of the inverse reconstruction of the intensities from multiple radiative flux maps recorded at various positions around the focal plane. The approach was validated by three test cases including uniform spatial, Gaussian spatial, and uniform angular distributions for which we successfully predicted the intensity for a square-shaped target with edge length of 0.5 m and for a displacement range spanning ±1.5 m at a resolution of 3.2 × 106 elements, yielding relative errors between 19.8-26.4% and 15.7-25.6% when using Tikhonov regularization and the conjugate gradient least square (CGLS) method, respectively. The latter method showed superior performance and was used at a resolution of 2.35 × 107 elements to analyze EPFL's HFSS comprising 18 lamps. The inverse solution for a single lamp retrieved from experimentally measured and simulated radiative flux maps showed peak intensities of 13.7 MW/m²/sr and 16.0 MW/m²/sr, respectively, with a relative error of 81.1%. The inverse reconstruction of the entire simulator by superimposing the single lamp intensities retrieved from simulated flux maps resulted in a maximum intensity of 18.8 MW/m2/sr with a relative error of 80%. The inverse method proved to provide reasonable intensity predictions with limited resolution of details imposed by the high gradients in the radiative flux maps. [ABSTRACT FROM AUTHOR]

The detailed characterization of the thermal boundary layer under periodic fluctuations is vital to improve the performance of cooled turbine airfoils, as well as to assess noise thermal and structural fatigue. In the present contribution, we performed detailed unsteady Reynolds-averaged Navier-Stokes (URANS) simulations to investigate wall heat flux response to periodic flow velocity fluctuations over a flat plate. We also investigated the boundary layer response to sudden flow acceleration including periodic flow perturbations, caused by inlet total pressure variations. During a flow acceleration phase, the boundary layer is first stretched, resulting in an increase of the wall shear stress. Later on, due to the viscous diffusion, the low momentum flow adjusts to the new free stream conditions. The behavior of the boundary layer at low frequency is similar to the response to an individual deceleration followed by one acceleration. However, at higher frequencies, the mean flow topology is completely altered. One would expect that higher acceleration rates would cause a further stretching of the boundary layer that should cause even greater wall shear stresses and heat fluxes. However, we observed the opposite; the amplitude of the skin friction coefficient is abated, while the peak level is a full order of magnitude smaller than at low frequency. [ABSTRACT FROM AUTHOR]

Highlights • The performance of hollow and flat-sheet polyurethane (PU) membranes synthesized with different additives and solvent were evaluated with oil-in- water emulsion. • The steady-state permeate flux and the rejection of oil in percentage (%) at two different modes was determined. • Change in morphological properties of the membrane are found to have a significant effect on the permeate flow rate and oil removal. • Generation of cavitation and Brownian motion by the ultrasonic were the dominant mechanisms responsible for ultrafiltration. Abstract Ultrafiltration has been proven to be very effective in the treatment of oil-in-water emulsions, since no chemical additives are required. However, ultrafiltration has its limitations, the main limits are concentration polarization resulting to permeate flux decline with time. Adsorption, accumulation of oil and particles on the membrane surface which causes fouling of the membrane. Studies have shown that the ultrasonic is effective in cleaning of fouled membrane and enhancing membrane filtration performance. But the effectiveness also, depends on the selection of appropriate membrane material, membrane geometry, ultrasonic module design, operational and processing condition. In this study, a hollow and flat-sheet polyurethane (PU) membranes synthesized with different additives and solvent were used and their performance evaluated with oil-in-water emulsion. The steady-state permeate flux and the rejection of oil in percentage (%) at two different modes were determined. A dry/wet spinning technique was used to fabricate the flat-sheet and hollow fibre membrane (HFMs) using Polyethersulfone (PES) polymer base, Polyvinylpyrrolidone (PVP) additive and N, N-Dimethylacetamide (DMAc) solvent. Ultrasonic assisted cross-flow ultrafiltration module was built to avoid loss of ultrasonic to the surrounding. The polyurethane (PU) was synthesized by polymerization and sulphonation to have an anionic group (–OH; –COOH; and –SO 3 H) on the membrane surface. Changes in morphological properties of the membrane had a significant effect on the permeate flow rate and oil removal. Generation of cavitation and Brownian motion by the ultrasonic were the dominant mechanisms responsible for ultrafiltration by cracking the cake layers and reducing concentration polarization at the membrane surface. The percentage of oil after ultrafiltration process with ultrasonic is about 90% compared to 49% without ultrasonic. Ultrasonic is effective in enhancing the membrane permeate flux and controlling membrane fouling. [ABSTRACT FROM AUTHOR]

Abstract The flux reconstruction (FR) method has gained popularity within the research community. The approach has been demonstrated to recover high-order methods such as the discontinuous Galerkin (DG) method. Stability analyses have been conducted for a linear advection problem leading to the energy stable flux reconstruction (ESFR) methods also named Vincent–Castonguay–Jameson–Huynh (VCJH) methods. ESFR schemes can be viewed as DG schemes with modally filtered correction fields. Using this class of methods, the linear advection diffusion problem has been shown to be stable using the local discontinuous Galerkin scheme (LDG) to compute the viscous numerical flux. This stability proof has been extended for linear triangular and tetrahedra elements. Although the LDG scheme is commonly used, it requires, on particular meshes, a wide stencil, which raises the computational cost. As a consequence, many prefer the compact interior penalty (IP) or the Bassi and Rebay II (BR2) numerical fluxes. This article, for the first time, derives, for both schemes, a condition on the penalty term to ensure the stability for the linear diffusion equation. The derivations are based on Gauss Legendre flux points and on periodic boundary conditions. Moreover the article proposes that for both the IP and BR2 numerical fluxes, the stability of the ESFR scheme is independent of the auxiliary correction field. A von Neumann analysis is conducted to study the maximal time step of various ESFR methods. Highlights • Theoretical proof of stability condition for the diffusion equation for the ESFR methods. • Independency of the auxiliary correction field when employing the ESFR methods with compact numerical fluxes. • Von Neumann analysis to demonstrate the maximal time step for various ESFR schemes. [ABSTRACT FROM AUTHOR]

Abstract This paper details synthesis methods that were used to fabricate phase-pure Nd 3 BSi 2 O 10 using a LiCl-flux method. In this study, a variety of conditions were evaluated to find the optimal processing parameters for maximizing the Nd 3 BSi 2 O 10 yield including the mass ratio of LiCl to target mass of Nd 3 BSi 2 O 10 (i.e., 1:3, 1:2, 1:1, 2:1, and 6:1) as well as the soak temperature (i.e., 700, 800, or 900 °C) at the 1:1 ratio. It was found that the optimal ratio of LiCl:Nd 3 BSi 2 O 10 was 1:1 and the optimal heat-treatment temperature was 900 °C (of those temperatures evaluated). Product made from the 1:1 material synthesized at 900 °C was recovered and fired at temperatures of 925–1350 °C. After 4-h firings at temperatures of 925–1100 °C, the Nd 3 BSi 2 O 10 phase purity was found to be 100% with powder X-ray diffraction, but started to decompose at the longer firing times at 1100 °C and higher temperatures (1350 °C) at the 4-h dwell time. Thus, the lowest firing temperature for achieving a phase-pure pellet was 925 °C under the conditions studied here. The phase-pure sample was found to contain 28 vol% open porosity determined by Archimedes' method. The durability of the Nd 3 BSi 2 O 10 product was examined in flow-through conditions at 90 °C with contacting solution between pH 90ºC 4.1 and 10.1. The release rate of Nd from the material had a maximum at pH 90ºC 4.1 calculated to be 4.93 g m−2 d−1 and a minimum release rate of Nd at pH 90ºC 7.7 of <1.34 × 10−5 g m−2 d−1. These release rates are roughly three orders of magnitude lower than what is normally measured from typical glass waste forms at pHs of 7–9. [ABSTRACT FROM AUTHOR]

Abstract The temporal shoreline position is a key indicator of coastal development and provides information on beach dynamics. Previous studies have indicated that there is a strong relationship between riverine sediment fluxes and beach volume. As such, worldwide hydroelectric projects and the associated damming infrastructure have decreased suspended sediment loads, and consequently increasing coastal erosion and deterioration of wetlands. The study was conducted along the coastline of the San Pedro River and the Santiago River on the Pacific coast of Mexico. Both rivers discharge into the ocean separated by 12 km of coastline, however the San Pedro River does not present dams through its watershed. Contrary, six dams had been constructed along the Santiago River since 1976. Results indicated that after 45 years, the San Pedro River coastline presented minimum variability and a total of 379 ha of accretion. Contrary, the Santiago River coastline showed major erosion trends with a total of 669 ha of beach and wetland losses. Our study highlights the feasibility of combining historical remote sensing data and GIS analysis in order to assess coastal variability trends when field-based surveys are not available. Highlights • Hydroelectric projects have decreased suspended sediment loads to coastlines. • We examined coastline changes along two contrasting rivers separated by 12 km. • Series of remote sensing data covering 45 years were analyzed. • We report considerable accretion along the river with no constructed dams. • We report major coastal ecosystems losses along the river with six dams. [ABSTRACT FROM AUTHOR]

Floods are dominant controls on export of solutes from catchments. In contrast, low‐flow periods such as droughts are potentially dominant control points for biogeochemical processing, enhancing spatiotemporal variation in solute concentrations, stream metabolism, and nutrient uptake. Using complementary time series (i.e., an Eulerian reference frame) and longitudinal profiling (i.e., a Lagrangian reference frame), we investigated hydrologic controls on temporal and spatial variation in solute flux and metabolism in the Lower Santa Fe River (FL, USA), where highly colored surface water mixes with exceptionally clear groundwater from springs. Gage measurements suggest groundwater inputs ranged from <1% (during extreme floods) to 86% (during extreme drought) of total discharge (Q). Mass transport of most solutes was dominated by high‐Q periods. Most solute C‐Q relationships exhibited statistically significant slope breakpoints near the transition between surface and groundwater dominance. In particular, parameters controlling water column light attenuation were chemostatic above median Q but markedly reduced at low Q. As a result, river metabolism and assimilatory nitrate (NO3−) uptake were consistently suppressed at high Q and enhanced at low Q, with greater variability in response to drivers other than water column light transmittance. Spatial variation in solute concentrations was also enhanced at low Q, induced by discrete groundwater inflow and biogeochemical processing along the reach. Contrasting reference frames yielded corroborative evidence for transport dominance at high Q, which damps spatiotemporal heterogeneity. In contrast, low‐Q periods enable localized mixing controls on solute concentrations and high rates of metabolism and nutrient processing that increase spatiotemporal variability. Plain Language Summary: Floods transport a large mass of dissolved and suspended material. A large fraction of total export occurs during these few events. However, floods reduce water clarity limiting photosynthesis and attenuate other coupled biological transformations of transported material. Rivers are far more reactive at low flow, such as during droughts. Key Points: Floods are dominant controls on solute mass transportLow Q enhances spatiotemporal variation in concentrations and rates of biogeochemical processingSupporting inferences can be made using complementary reference frames [ABSTRACT FROM AUTHOR]

TIG welding process has high levels of stability and permits more refined control than the majority of other arc welding processes. The principal disadvantages of TIG lie in the limited thickness of material which can be welded in a single pass. Activated Flux Tungsten Inert Gas (A-TIG) welding can increase the joint penetration and weld depth/width ratio, thereby reducing angular distortion of the weldment. In this review paper, A-TIG welding properties of nonferrous metals are examined. How the flux increases the penetration depth is explained and then the effects of the chemical composition and thickness of the flux are described in detail. [ABSTRACT FROM AUTHOR]

Abstract A comparative study was done on the synthesis of oxide free ZrB 2 -xZrC (x = 20 and 30 wt%) through MASHS and MASPS process in the Mg/ZrO 2 /B 2 O 3 /C system. The effect of Mg, B 2 O 3 on the efficiency of synthesis process was examined. In MASHS route, the addition of excessive amounts of Mg and B 2 O 3 did not cause complete reduction of ZrO 2 even if primary mixture was activated by mechanical alloying before SHS process. It was also found that mere addition of Mg was not efficacious in synthesis of pure composites in MASPS. However, when extra B 2 O 3 was added to the primary mixture, peaks of ZrO 2 were not detected in the synthesized powders when MASPS was applied. The reaction mechanism was also studied. [ABSTRACT FROM AUTHOR]

Highlights • The influence of membrane oscillation on pore (slot) blocking has been investigate. • Membrane pore blocking was found to be a linear function of the applied shear rate. • Higher deformation of oil drops were noticed at a lower interfacial tension. • Lower number of drops in the permeate was found at a higher interfacial tension. • The divergence between experimental data and the model was due the slots, deforming drops and applied shear. Abstract Deformable oil drops of two interfacial tensions (namely, 4 and 30 mN m−1) were filtered through a slotted-pore membrane (with pore dimensions of 4 × 400 μm) at four vibrational shear rates (namely, 0, 1200, 3200 and 8000 s−1) and two permeate fluxes (namely, 200 and 1000 l m−2 h−1). The membrane material was made of nickel. The membrane surface was modified with Poly tetra fluoroethylene (PTFE)F for better performance in-terms of higher flux rate rejection. The oil with the lower interfacial tension was more deformable, because the increase in TMP was less due to the passage of even larger drops to the slot opening, also the permeate quality was lower as a result of the higher concentration of the oil in the permeate. The impact of interfacial tension was more significant under the following conditions; first at lower shear rates, the particle back-transport effects become more dominant than the deformability effects at higher shear rates, and secondly at the higher permeate flux, the higher permeate drag enhances the deformability effects. Discrepancies were observed between experimental results and model predictions based on circular membrane pores and non-deformable foulants. In the future, it is expected that a better agreement of the experimental results and the analytical model could be obtained if the model is modified for the slotted pore membrane. [ABSTRACT FROM AUTHOR]

Abstract We have developed a method for measuring fluxes of PCBs from natural waters using air and water passive samplers deployed simultaneously in the Indiana Harbor and Ship Canal (IHSC). Net volatilization of ƩPCBs was determined for 2017, and ranged from 1.4 to 2.8 μg m−2 d−1, with a median of 2.0 μg m−2 d−1. We confirm earlier findings that the IHSC experiences constant release of gas-phase PCBs. Gas-phase and freely-dissolved water ƩPCB samples median were 4.0 ng m−3 and 14 ng L−1, both exhibiting increasing concentrations over the year of study, and with a strong positive correlation between them (R2 = 0.93 for ƩPCBs). The relative concentrations of individual PCB congeners were very similar between air and water samples, and resemble Aroclor 1248, a mixture previously reported to contaminate the IHSC sediments. Monthly variability of the volatilization fluxes was primarily driven by the freely-dissolved water concentration changes (R2 = 0.87). Although different sampling methods were performed to estimate air-water fluxes between the month of August of 2006 and 2017, ƩPCB net fluxes have decreased by more than 60%, suggesting that either dredging at IHSC from 2012 to 2017 or reduction of upstream sources have decreased the freely-dissolved water concentrations of PCBs, thus reducing the air-water net volatilization in IHSC. Finally, we have shown that this passive sampling approach represents a simple and cost-effective method to assess the air-water exchange of PCBs, increase analytical sensitivity, enable measurements over time, and reduce uncertainties related to unexpected episodic events. Graphical abstract Image 1 Highlights • Passive samplers used to measure gas-phase and freely-dissolved PCB concentrations. • Increase in gas-phase and freely-dissolved concentrations were observed over 2017. • PCB net volatilization was estimating during the entire study. • Reduction of ∼60% in net volatilization was found between August 2006 and 2017. PCB net volatilization was estimated for 2017 from the waters of the Indiana Harbor and Ship Canal, IN, using passive samplers. [ABSTRACT FROM AUTHOR]

The suppression of titanium oxide reduction enables both successful separation of iron from slag and smooth production operations for the smelting of vanadium titanomagnetite. This study investigates the distribution behavior of titanium between the hot metal and enriched titanium slag during the electric furnace smelting of vanadium titanomagnetite metallized pellets. Activity calculations indicate that the TiO2 activity decreases with increasing amounts of CaO and MgO, whereas the TiO2 activity increases with smelting temperature. Additionally, high temperature experiments demonstrate that the titanium distribution ratio between the molten iron and titanium slag decreases with increasing CaO content in the slag. With the presence of high CaO content, increasing MgO content does not have a significant influence on the titanium distribution ratio. The titanium distribution ratio decreases with an increase in slag optical basicity but increases with an increment of the smelting temperature. [ABSTRACT FROM AUTHOR]

The behavior of silicon during smelting of vanadium titanomagnetite metallized pellets in an electric furnace has been investigated thermodynamically and experimentally. Thermodynamic calculations indicated that the activities of free oxygen ion and silicate increase with increasing CaO and MgO content in the titanium slag, whereas silica activity decreases as CaO and MgO increase. High-temperature experiments demonstrated that the Si content in the molten iron and distribution ratio of silicon between metal and slag decreased with suitable additions of CaO and MgO, but increased with smelting temperature. The Si content in the iron positively correlated with the Ti content in the iron but showed no obvious relationship with the V content in the iron. The Si and Ti contents increased with increasing smelting temperature. The Si content should be controlled below about 0.2 wt.% for effective and comprehensive smelting of vanadium titanomagnetite. [ABSTRACT FROM AUTHOR]

Solar energetic particles are one of the main sources of particle radiation seen in space. In the first part of September 2017 the most active solar period of cycle 24 produced four large X‐class flares and a series of (interplanetary) coronal mass ejections, which gave rise to radiation storms seen over all energies and at the ground by neutron monitors. This paper presents comprehensive cross comparisons of in situ radiation detector data from near‐Earth satellites to give an appraisal on the state of present data processing for monitors of such particles. Many of these data sets have been the target of previous cross calibrations, and this event with a hard spectrum provides the opportunity to validate these results. As a result of the excellent agreement found between these data sets and the use of neutron monitor data, this paper also presents an analytical expression for fluence spectrum for the event. Derived ionizing dose values have been computed to show that although there is a significant high‐energy component, the event was not particularly concerning as regards dose effects in spacecraft electronics. Several sets of spacecraft data illustrating single event effects are presented showing a more significant impact in this regard. Such a hard event can penetrate thick shielding; human dose quantities measured inside the International Space Station and derived through modeling for aircraft altitudes are also presented. Lastly, simulation results of coronal mass ejection propagation through the heliosphere are presented along with data from Mars‐orbiting spacecraft in addition to data from the Mars surface. Key Points: Corrected particle flux measurements taken by different instruments on-board different platforms at Earth and Mars show good agreement/correlationDose calculations based on a full spectral fit to fluence indicate this was one of the 20 largest particle events of the past 45 years but still almost an order of magnitude below the largest eventsIn situ single event observations show significant increases due to the enhancements and calculations show moderate enhancements for humans at aircraft altitudes [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A facile approach was proposed for preparing positively charged NF membranes. • In this approach, PEI dissolved in the coagulation bath makes in situ chemical crosslinking with PAI. • Selectivity of the membrane for magnesium salt separation is higher than commercial membranes. • The crosslinked membrane showed excellent chemical stability when stored in HCl solution at pH 3. Abstract Polyamide-imides (PAI) are attractive materials for membrane formation due to their high chemical and thermal stability. In this study, we report a facile approach for preparing positively charged nanofiltration (NF) membranes using a one-step process. Polyethylenimine (PEI) was dissolved in a coagulation bath and formed in-situ ionic crosslinking with PAI during phase inversion. The membranes were characterized by attenuated total reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM), contact angle and zeta potential measurements. The most positively charged membrane was obtained when the pH of the coagulation bath was adjusted to 10. This membrane showed a significant decrease in contact angle and surface roughness and increase in the pure water permeability (PWP) compared to the plain PAI membrane. The salt rejection performance of the crosslinked PAI membrane was measured using MgCl 2 , CaCl 2 , NaCl and Na 2 SO 4 salts. The rejection of Mg2+ and Ca2+ ions was found to be 95.6% and 90.2%, respectively. The crosslinked membrane showed excellent chemical stability when stored in HCl solution at pH 3 up to 7 days. Antifouling behaviour of the optimized membrane was tested using bovine serum albumin (BSA) and flux recovery ratio of the membrane was found to be 92.2% at the end of 3 h filtration. The results suggest that the positively charged PAI membranes crosslinked with PEI may have a potential in recovering valuable cationic metals from acid mine wastewater. [ABSTRACT FROM AUTHOR]

The effect of MgO on crystallization and heat transfer of fluoride-free mold fluxes was studied using single/double-hot thermocouple technique (SHTT/DHTT) and infrared emitter technique (IET), respectively. SHTT experiments demonstrated that the increase of MgO concentration promoted the crystallization tendency of mold fluxes. XRD analysis showed that the dominant phases changed from CaSiO3 to CaSiO3/Ca2MgSi2O7/Ca11Si4B2O22, and to Ca2MgSi2O7 as the MgO content was increased. The heat flux across mold flux disks was reduced from 671 to 615 kW/m2 in IET experiments when MgO concentration was increased from 0.9 to 4.9 mass pct. [ABSTRACT FROM AUTHOR]