Dependence Of Flux Research Articles

Transport and emergent stratification in the equilibrated Eady model: the vortex-gas scaling regime

We numerically and theoretically investigate the Boussinesq Eady model, where a rapidly rotating density-stratified layer of fluid is subject to a meridional temperature gradient in thermal wind balance with a uniform vertically sheared zonal flow. Through a suite of numerical simulations, we show that the transport properties of the resulting turbulent flow are governed by quasigeostrophic (QG) dynamics in the rapidly rotating strongly stratified regime. The ‘vortex gas’ scaling predictions put forward in the context of the two-layer QG model carry over to this fully three-dimensional system: the functional dependence of the meridional flux on the control parameters is the same, the two adjustable parameters entering the theory taking slightly different values. In line with the QG prediction, the meridional heat flux is depth-independent. The vertical heat flux is such that turbulence transports buoyancy along isopycnals, except in narrow layers near the top and bottom boundaries, the thickness of which decreases as the diffusivities go to zero. The emergent (re)stratification is set by a simple balance between the vertical heat flux and diffusion along the vertical direction. Overall, this study demonstrates how the vortex-gas scaling theory can be adapted to quantitatively predict the magnitude and vertical structure of the meridional and vertical heat fluxes, and of the emergent stratification, without additional fitting parameters.

Spatial variability of denitrification enzyme activity and actual denitrification emissions on Missouri claypan soils

AbstractDenitrification in agricultural soils is responsible for the majority of anthropogenic N2O production. The objective of this research was to assess denitrification potential and the spatial dependence of soil N2O flux from claypan soils in the Central Claypan Region of Missouri. Surface soil samples (0–10 cm) were collected on a 90‐m grid from two claypan fields, one conventionally managed in a corn (Zea maysL.)–soybean [Glycine max(L.) Merr.] rotation with tillage and without cover crops (Field 1), and the other managed as a corn–soybean–wheat (Triticum aestivumL.) rotation with no‐till and cover crops (Field 3). The denitrification enzyme activity (DEA) protocol was used to measure denitrification potential and actual soil denitrification rates of N2O and N2were measured with the N‐free atmospheric recirculation method (N‐FARM). In both fields, DEA fluxes were highest in the toeslope, with a rate of 1.4 kg N ha–1d–1in Field 1, and 1.8 kg N ha–1d–1in Field 3. Actual denitrification was dominated by N2(>85%) rather than N2O emissions, and it was considerably lower than DEA. Actual N2, N2O, and total denitrification (N2+ N2O) fluxes were not different between fields; however, only total denitrification flux showed an effect of landscape position similar to that of DEA in both fields. Although the high smectitic clay content of upland soils provides environmental conditions suitable for denitrification, these results indicate that the accumulation of soil C in the toeslope position controlled DEA and actual denitrification rates.

Effect of heavy inert ion strikes on cell density-dependent profile variation and distortion during the etching process for high-aspect ratio features

Vertical scaling technique faces a physical limitation in 3D NAND device fabrication, even assuming superior etching technology. Another promising scaling technique to increase the storage density is lateral scaling, which increases the number of holes between slit and slit from four to nine and above. However, unpredictable small critical dimension, feature-to-feature variation, and distortion occur. To elucidate the profile deteriorations induced by the lateral scaling, we analyzed the effect of the angular etching yield dependency of the incident ion fluxes into a given feature using the multiscale technology computer-aided design methodology. As one of the inherent features of the gas, incident angle θmax in which the sputtering yield achieves its maximum value is a crucial factor for analyzing and modeling etching profiles. Moreover, the impact of the heavy inert ion strikes on the unpreferred etching profiles was investigated. In this study, the synergy of lower energy ions, larger fluxes, and larger θmax of heavy inert ions decrease the feature-to-feature variation, reducing hard mask distortion without the etch rate reduction.

Spectral calibration of photon-counting detectors at high photon flux.

Calibration of photon-counting detectors (PCDs) is necessary for quantitatively accurate spectral computed tomography (CT), but the calibration process can be complicated by nonlinear flux-dependent physical factors such as pulsepile-up. This work develops a method for spectral sensitivity calibration of a PCD-based spectral CT system that incorporates nonlinear flux dependence and can thus be employed at high photonflux. A calibration model for the spectral response and polynomial flux dependence is proposed, which incorporates prior x-ray source spectrum and PCD models and that has a small set of parameters for adjusting to the spectral CT system of interest. The model parameters are determined by fitting transmission data from a known object of known composition: a step-wedge phantom composed of different thicknesses of aluminum, a bone equivalent, and polymethyl methacrylate (PMMA), a soft-tissue equivalent. This fitting employs Tikhonov regularization, and the regularization strength and the polynomial order for the intensity modeling are determined by bias and variance analysis. The spectral calibration and nonlinear intensity correction is validated on transmission measurements through a third material, Teflon, at different x-ray photon fluxlevels. The nonlinear intensity dependence is determined to be accurately accounted for with a third-order polynomial. The calibrated spectral CT model accurately predicts Teflon transmission to within 1% for flux levels up to 50% of the detectormaximum. The proposed PCD calibration method enables accurate physical modeling necessary for quantitative imaging in spectral CT. Furthermore, the model applies to high flux settings so that acquisition times will not be limited by restricting the spectral CT system to low fluxlevels.

Determining the maximum operating temperature of permanent magnets via in-situ measurement of the magnetic flux

The temperature stability of a magnet is crucial for applications. Traditionally, the designers determine the maximum operating temperature (Tom) of a permanent magnet by either the linearity of the B(H) curve or the irreversible flux loss. However, the reliability and efficiency of the traditional methods are challenging. Here, a new method of “in-situ measurement of the magnetic flux at elevated temperature” is introduced. By studying the temperature-dependence of magnetic flux for the Nd-Fe-B magnet, we find that the magnetic flux declines linearly as the temperature increases. Upon approaching a specific temperature, there occurs a rapid and nonlinear decline of magnetic flux.This temperature can be defined as Tom. Furthermore, the magnetic flux dependence on time at elevated temperature is also investigated, wherein the logarithmic relaxation is observed. The decay rate of magnetic flux could be related to the exposure temperature. If the decay rate of maximum magnetic flux loss is acceptable below a given temperature, we can also define the temperature as Tom.

Two-stream interaction problem and its application to mass transport

Classical boundary layer theory is effectively extended to study two-stream interaction problems. In particular, by proper scaling we invent a universal curve which relates the second-derivative initial condition of the normalized stream function to the first-derivative free-stream condition. This relationship is independent of any fluid property, and the Blasius flow profiles in respective streams are connected by matching at the interface. Accurate approximations to the universal curve are constructed by piecewise third-order polynomials. This technique finds an excellent application to mass transport problem of solvents from one immiscible fluid to another, namely, extraction of fluid as an interfacial problem. Analytical formula is obtained to show explicit dependence of mass flux on the nonlinear Blasius profiles, partition coefficient, Schmidt numbers, ratio of mass transfer coefficients, ratio of kinematic viscosities as well as the contact length of the two immiscible fluids. In other words, given these physical parameters, we directly obtain the mass flux simply by numerical quadrature of integrals involving the Blasius profiles.

Catchment response to intense rainfall: Evaluating modelling hypotheses

AbstractFloods resulting from high‐intensity rainfall events are known to be difficult to simulate. The catchment response to such events is very heterogeneous due to complex combinations of hydrological processes at fine temporal and spatial scales. The goal of this study is to find a way to inform the structure of a hydrological model on the variability in catchment response to rainfall events. To that end, rainfall intensity was used as a proxy for the activation of fast heterogeneous runoff processes. We developed three hypotheses that increase the versatility of a hydrological model by modifying the volume and temporal distribution of effective rainfall when high‐intensity rainfall events occur. These modifications were implemented within the GR5H lumped rainfall–runoff model. The different model versions were run on 229 French catchments where 10 652 flood events were selected. Model performance was assessed considering five groups of catchments, and model performance was also evaluated based on three event characteristics. Results showed that introducing a dynamic dependency of fluxes to rainfall intensities at the hourly time step helps to improve the simulation of floods, especially on Mediterranean catchment areas. Generic values of the additional parameters are proposed to limit the increase in calibration complexity.

Analytical Discrete-Ordinates Solutions for Improved 1D Models of Particle Transport in Ducts with Wall Migration

Analytical discrete-ordinates (ADO) solutions are developed for two improved one-dimensional (1D) models of particle transport in ducts that include wall migration. One of the studied models is based on an approximation of the transverse and azimuthal dependencies of the angular flux in terms of two basis functions, while the other uses three. Particle migration in the wall is modeled by an exponential displacement kernel. Numerical results for duct reflection and transmission probabilities are reported for various test cases, including some cases of thermal-neutron transport through iron, concrete, and graphite ducts that have been defined and studied by other authors. A comparison is performed with a set of published results comprising realistic results obtained with the Monte Carlo code MCNP and results from a numerical implementation of the discrete-ordinates method for the model based on three basis functions. To resolve some issues raised during the comparison process, a numerical discrete-ordinates solution of the problem has also been implemented in the course of this work.

Study on divertor heat flux under n = 3 and n = 4 resonant magnetic perturbations using infrared thermography diagnostic in EAST

Resonant magnetic perturbations (RMPs) with high toroidal mode number n are considered for controlling edge-localized modes (ELMs) and divertor heat flux in future ITER H-mode operations. In this paper, characteristics of divertor heat flux under high-n RMPs (n = 3 and 4) in H-mode plasma are investigated using newly upgraded infrared thermography diagnostic in EAST. Additional splitting strike point (SSP) accompanying with ELM suppression is observed under both RMPs with n = 3 and n = 4, the SSP in heat flux profile agrees qualitatively with the modeled magnetic footprint. Although RMPs suppress ELMs, they increase the stationary heat flux during ELM suppression. The dependence of heat flux on during ELM suppression is preliminarily investigated, and further splitting in the original strike point is observed at during ELM suppression. In terms of ELM pulses, the presence of RMPs shows little influence on transient heat flux distribution.

A new quasilinear saturation rule for tokamak turbulence with application to the isotope scaling of transport

A new quasilinear saturation model SAT3 has been developed for the purpose of calculating radial turbulent fluxes in the core of tokamak plasmas. The new model is shown to be able to better recreate the isotope mass dependence of nonlinear gyrokinetic fluxes compared to contemporary quasilinear models, including SAT2 (Staebler et al 2021 Nucl. Fusion 61 116007), while performing at least as well in other key equilibrium parameters. By first quantifying the isotope scaling of gyrokinetic flux spectra, it is shown that the deviation from the gyroBohm scaling of fluxes originates primarily in the magnitude of the saturated potentials. Using this result SAT3 was formulated using observations made from gyrokinetic data, including a novel and robust relation between the 1D potential spectrum and the radial spectral widths. This serves to define the underlying functional forms of SAT3 before then connecting to the linear dynamics, including a difference in saturation level between ITG- and TEM-dominated turbulence, with the resulting free parameters having been fit to a database of high-resolution nonlinear CGYRO simulations. Additional features outside of the database are included, including E × B shear and multi-ion plasma capability. The methodology used in the development of SAT3 represents an algorithm which can be used in the improvement and generation of future saturation models.

On temperature and flux dependence of isotropic silicon etching in inductively coupled SF[formula omitted] plasma

Silicon etching in fluorine-containing plasma has numerous applications due to its high etch rate and smooth profile surface in both anisotropic and isotropic modes. The fluorine source gas significantly affects etching characteristics. Sulfur hexafluoride (SF6) plasma has an order of magnitude higher etch rate in comparison to other fluorine sources and it is mainly used in deep etching processes, such as cryogenic etching. Meanwhile, fundamental reactions underlying this process are still an active research subject. There is only minimal data on the surface reaction probability and most of the existing data is limited to a single plasma condition and sample temperature. In this work, a series of isotropic etching experiments under varying fluorine densities and sample temperatures are performed. In parallel, plasma diagnostics techniques, such as Langmuir probe, optical emission spectrometry, and actinometry, are employed and key plasma parameters deduced. Etching profiles are analyzed, and etch rate and reaction probability values for each etch condition are calculated. The fluorine flux dependence of reaction probability is explained with a kinetic model and model parameters are obtained via curve fitting. No significant temperature dependence of silicon etching parameters is observed.

On the total energy conservation of the Alcubierre spacetime

In this article, we consider the Alcubierre spacetime, such a spacetime describes a “bubble” that propagates with arbitrary global velocity. This setting allows movement at a speed greater than that of light.There are some known problems with this metric, e.g., the source's negative energy and the violation of the source's energy conservation when the bubble accelerates.We address these two issues within the realm of the Teleparallel Equivalent of General Relativity (TEGR). The energy conservation problem can be solved when considering the energy of the gravitational field itself. The total energy of the spacetime, gravitational plus source, is conserved even in accelerated motion.We explicitly show the dependence of energy and gravitational energy flux on the frame of reference, one adapted to a static observer and the other to a free-falling one in the same coordinate system.Addressing the problem of energy negativity of the source, we find that a static observer measures positive energy of the source, while an Eulerian observer measures a negative one. Thus, we surmise that negative energy may be a reference problem.

Electro-osmosis Aided Thin-Film Evaporation from a Micropillar Wick Structure.

The heat-dissipating capacity of a surface having micropillar wick structures, which resembles the evaporator section of a vapor chamber, is mainly limited by the liquid flow rate through the porous structure (permeability) and the capillary pressure gradient. The efficacy of a regular vapor chamber is determined from two parameters, namely, the dry-out heat flux and temperature of the evaporator surface. These two parameters possess a counter relation to each other. The work described herein introduces and evaluates the performance of a novel idea of electro-osmosis-aided thin-film evaporation from a micropillar array structure. This study is conducted using a discretized approach that is validated against the thin-film evaporation model and additionally the electro-osmotic flow model with pre-existing pressure gradient conditions. The unique feature of this approach is that it results in an increment in the magnitude of dry-out heat flux without significantly changing the surface temperature, wherein the increase in permeability is due to the addition of electro-osmotic flow. This comprehensive model considers various geometries, zeta potentials, and extremal electric fields and establishes the beneficial effects of the application of an external electric field. The results are used to predict the sensitivity and the dependence of the dry-out heat flux and the evaporator surface temperature on these parameters. For a host of electro-osmotic parameters considered herein, a maximum increment of up to 320% in the dry-out heat flux is observed for an external electric field of 105 V/m. The study, therefore, conclusively demonstrates the beneficial impact of electro-osmosis in enhancing the dry-out heat flux without any significant Joule heating.

Temperature and Heat Flux Dependence of Interfacial Thermal Resistance for Water Between Platinum, Palladium, Lead and Nickel Nanochannel Walls

Temperature and Heat Flux Dependence of Interfacial Thermal Resistance for Water Between Platinum, Palladium, Lead and Nickel Nanochannel Walls

Methodology For Calculating Automotive Oil Radiator

The paper highlights the relevance of the problem of determining the amount of heat supplied by an internal combustion engine to a liquid cooling system when creating typical series of unified heat exchangers for tractor and combine engines (power units). A properly designed cooling system further guarantees the maintenance of the optimal thermal mode for the engine operation. A methodology for calculating the coolant characteristics of the cooling system was proposed in order to prevent possible problems related to increased parts wear, early loss of oil lubricating properties, the engine (individual units) and rubbing parts overheating, a decrease in engine power and a deterioration in the quality of the fuel-air mixture entering the cylinders.Research purpose To develop a methodology for calculating the amount of heat to be dissipated by the oil radiators of a liquid cooling system (lubrication system) being exposed to various load and engine speed modes.Materials and methods It was proposed to determine the amount of heat to be dissipated by the liquid-oil heat exchanger of the engine lube oil cooling system.Results and discussion The calculation method for oil radiators presents the calculation of the heat obtained by oil during the operation of 37-110 kilowatts automotive engines. The heat-dissipating ability of the oil surface is determined. A parameter taking into account the oil radiator heat flow is identified. The graphs of the oil surface and heat flux dependence on the engine power are presented.Conclusions The method for calculating the temperature and dynamic characteristics of the automotive engine cooling system has been developed. It makes it possible to carry out research on the radiator thermal and technical characteristics in various operating modes of machines and coolants of systems, various heat exchanger structural materials (metal, polymer), with an error of 1.5-8.0 percent.

A Nonlinear Control of Linear Slider Considering Position Dependence of Interlinkage Flux

Linear sliders are linear actuators using linear motors. It is used in many applications, such as factory lines and linear motor cars. In recent years, the demand for smaller semiconductor devices has been increasing due to the proliferation of smartphones. High-precision positioning of linear motors is needed because manufacturing semiconductor devices uses the stage with linear motors. However, linear motors have nonlinearity due to the position dependence of interlinkage flux. It affects precise positioning. In this study, the nonlinear characteristics due to the position dependence of the flux are expressed as a mathematical model by using a distributed constant magnetic circuit. A method compensating it using an operator-based feedback controller with the obtained mathematical model is proposed. The effectiveness of the proposed method is confirmed by simulating and experimenting with the reference following disturbance elimination.

The Effect of Grain Size on Porewater Radiolysis

AbstractThe radiolysis of porewaters by uranium, thorium, and potassium in mineral grains is a recognized source of molecular hydrogen in rock‐hosted and sediment‐hosted fluids. This radiolytic hydrogen is of geomicrobiological interest as a potential energy source (electron donor) for microbial metabolism, especially in energy‐limited settings such as the marine deep biosphere or the subsurface of Mars. Previous efforts to predict the production of radiolytic hydrogen from columns of rock and sediment have tended to rely upon analytic models that cannot account for the attenuation of mineral radiation by grains larger than ∼30 µm. To address this, we have developed a Monte Carlo method to simulate the physics of mineral radiation and evaluate the production of H2 as a function of mineral grain size and radioisotope composition. The results confirm that grain size is a major control on radiolytic H2 yield. For example, using the standard geological classification of grain sizes, we find that clay can produce up to an order of magnitude more H2 per unit time than sand. The magnitude of this effect is illustrated using compositional data from real geological units in order to demonstrate the dependence of radiolytic hydrogen flux on natural radionuclide concentration and bulk porosity.

Solar Flux Influence on the In‐Situ Plasma Density at Topside Ionosphere Measured by Swarm Satellites

AbstractIn this study, we perform the first comprehensive comparison of ion density (Ni) in the topside ionosphere measured by the Langmuir probe (LP) and faceplate (FP) of the thermal ion imager on board Swarm satellites. Our results show a systematic difference between the LP and FP derived Ni values, and the systematic difference shows prominent dependences on solar flux, local time, and season. Although both Ni datasets show generally good linear regression with electron density (Ne) measurements from the incoherent scatter radar (ISR) located at Jicamarca, the Ni derived from LP shows an additional dependence on the solar flux, while such a dependence cannot be seen in the FP‐derived Ni. We suggest that the solar flux dependence of LP‐derived Ni is related to the ion compositions change at Swarm altitude, which has not been properly accounted for in the LP processing algorithm. More light ions (e.g., H+), diffusing down from the plasmasphere to the Swarm altitude, seem to cause the overestimation of Ni from LP during low solar activity. A linear relation between the Swarm LP‐derived Ni and ISR Ne is derived, and such a function is recommended to be implemented into further updates of the Swarm LP plasma density data.

Statistical Survey of Arase Satellite Data Sets in Conjunction With the Finnish Riometer Network

AbstractDuring disturbed geomagnetic conditions, the energetic particles in the inner magnetosphere are known to undergo precipitation loss due to interaction with various plasma waves. This study, investigates the energetic particle precipitation events statistically using coordinate observations from the ground riometer network and the inner‐magnetospheric satellite mission, Arase. We have compared cosmic noise absorption (CNA) data obtained from the Finnish ground riometer network located in the auroral/sub‐auroral latitudes with the comprehensive data set of omnidirectional electron/proton flux and plasma waves in ELF/VLF frequency range from the Arase satellite during the overpass intervals. The study period includes one and a half years of data between March 2017 and September 2018 covering Arase conjunctions with the riometer stations from all magnetic local time sectors. The relation between the plasma flux/waves observed at the satellite with the riometer absorptions are investigated statistically for CNA (absorption >0.5 dB) and non‐CNA (absorption <0.5 dB) cases separately. During CNA events, Arase observed elevated electron flux in the medium energy range (2–100 keV), and plasma wave activity in the whistler‐mode frequency range (0.5–3 kHz) of the spectra. Our study provides an estimate of the statistical dependence of the electron flux and plasma wave observations at Arase with the ground reality of actual precipitation.

Solar Flux Dependence of Post‐Sunset Enhancement in Vertical Total Electron Content Over the Crest Region of Equatorial Ionization Anomaly

AbstractBased on 10 years' of vertical total electron content (VTEC) data in solar cycle 24 from Ahmedabad (23.0°N, 72.6°E, dip angle 35.2°), a station under the crest region of equatorial ionization anomaly (EIA), it is shown that both the integrated residual and total post‐sunset enhancements in VTEC are conspicuous during Equinox and December solstice when solar flux level exceeds 110 solar flux unit (sfu) with the exception of the year 2012–2013. The post‐sunset enhancements are absent in June solstice at this local time even if the solar flux level exceeds 110 sfu. The integrated residual and total VTEC enhancements during post‐sunset hours are found to be linearly correlated with the solar flux level in Equinox and December solstice. It is noted that a parabolic fit works better for the integrated total VTEC enhancement during December solstice suggesting a possible saturation of VTEC enhancements at high solar flux levels. Based on these observations and Thermosphere Ionosphere Electrodynamics‐General circulation model (TIE‐GCM) outputs, it is argued that the pre‐reversal enhancement (PRE) in the equatorial F region zonal electric field works in tandem with latitudinal gradient in the F region plasma density to determine the degree of VTEC enhancement over the EIA crest region during post‐sunset hours. These results highlight the solar flux dependence of the post‐sunset enhancement of VTEC over the crest region and show that sudden stratospheric warming events in 2012–2013 suppressed these enhancements in December solstice even if solar flux levels exceeded 110 sfu.