Mixing Law Research Articles

Using hydro-chemograph analyses to reveal runoff generation processes in a Mediterranean catchment

The paper deals with the hydro-chemical analysis performed in order to reveal processes, sources, paths and timing of the runoff generation in an experimental catchment representative of the hilly, terrigenous and forested watershed in the Mediterranean humid eco-region of southern Italy. The analysis is based on the data recorded at the outlet of the catchment during 2013–2014. A mixing law procedure was applied on discharge (Q) and electrical conductivity (EC) data, by using the Q–EC end members previously collected at selected groundwater, sub-surficial and surficial stations. In this way, we found four bound curves delimiting fields in a Q–EC plot, each with hydro-chemograph value ranges. At annual time scale, the analysis revealed a seasonal behaviour of the hydrological response, different for the wet period, when the aquifer is recharging, and the dry periods, when the aquifer is discharging, despite frequent summer rain showers. At event time scale, the catchment seems to show the behaviour of a typical hydro-geomorphic threshold system. We interpreted this behaviour as due to a progressive addition of water from distinctive components (i.e. deep aquifer, riparian corridor, hillslope and hollow), each with originally different mechanisms of runoff production (i.e. groundwater, groundwater ridging, saturation excess, infiltration excess and soil pipe exfiltration) and response time. During the event, the contributing areas enlarge upward the riparian corridors and the zero-order basins, where the aforementioned components become superposed and the mechanisms interact more and more. We hypothesize that the threshold values between different states of the system are defined by the intersections of the boundary curves on the Q–EC plot. Different patterns in the Q–EC hysteretic cycles are prevalently related to the pre-event soil saturation and groundwater contributions to stormflow and recharge mechanisms. Copyright © 2016 John Wiley & Sons, Ltd.

Parametric study of the explosivity of graphite-metals mixtures

The explosivity of dust clouds is greatly influenced by several parameters which depend on the operating conditions, such as the initial turbulence, temperature or ignition energy, but obviously also on the materials composition. In the peculiar case of a mixture of two combustible powders, the physical and chemical properties of both dusts have an impact on the cloud flammability and on its explosivity. Nevertheless, no satisfactory ‘mixing laws’ predicting the mixture behavior are currently available and the composition variable to be considered for such models greatly depend on the safety parameters which have to be determined: from volume ratios for some thermal exchanges and ignition phenomena, to surface proportions for some heterogeneous reactions and molar contents for chemical reactions. This study is mainly focused on graphite/magnesium mixtures as they are encountered during the decommissioning activities of UNGG reactors (Natural Uranium Graphite Gas). Due to the different nature and reactivity of both powders, these mixtures offer a wide range of interests. Firstly, the rate-limiting steps for the combustion of graphite are distinct from those of metals (oxygen diffusion or metal vaporization). Secondly, the flame can be thickened by the presence of radiation during metal combustion, whereas this phenomenon is negligible for pure graphite. Finally, the turbulence of the initial dust cloud is modified by the addition of a second powder. In order to assess the explosivity of graphite/magnesium clouds, a parametric study of the effects of storage humidity, particle size distribution, ignition energy, and initial turbulence has been carried out. In particular, it was clearly demonstrated that the turbulence significantly influences the explosion severity by speeding up the rate of heat release on the one hand and the oxygen diffusion through the boundary layer surrounding particles on the other hand. Moreover, it modifies the mean particle size and the spatial dust distribution in the test vessel, impacting the uniformity of the dust cloud. Thus, the present work demonstrates that the procedures developed for standard tests are not sufficient to assess the dust explosivity in industrial conditions and that an extensive parametric study is relevant to figure out the explosive behavior of solid/solid mixtures subjected to variations of operating conditions.

Theoretical derivation of a Brie‐like fluid mixing law

ABSTRACTPrediction of the velocity of acoustic waves in partially saturated rocks is very important in geophysical applications. The need to accurately predict acoustic velocities has resulted in a widespread popularity of Brie's effective fluid mixing law. This empirical model together with Gassmann's formula are used routinely in fluid substitution problems in petroleum geophysics and seismic monitoring of carbon capture and storage. Most attempts to justify Brie's model have been focused on interpretation in terms of patchy saturation models and attaching meaning to the Brie parameter in terms of the patch size. In this paper, using a microstructural description of the rock and a parameter relating to capillary pressure, we calculate an effective fluid modulus that is very similar to Brie's law. The fluid mixing law we propose is independent of frequency and has a solid theoretical foundation. This proposed law produces analytically harmonic and arithmetic averaging at the endpoints. Our results indicate that Brie‐like behaviour may not necessarily be related to frequency‐ and patch‐size‐ dependent phenomena.

Evaluation of the Effect of Clay Nanoparticles on Mechanical Properties of Recycled Polyethylene

Over recent years, industrial applications of polymer/nanoclay nanocomposites have increased, because of their improved properties such as HDT, gas barrier ability, dimensional stability, mechanical properties, optical transparency, and flame retardation. In this work, we studied the mechanical properties of organically modified nanoclay (montmorillonite) dispersions in recycled film blowing extrusion grade polyethylene (rPE) matrix at different nanoclay contents. Results showed that the mechanical properties of the composites depend strongly on the nature and concentrations of nanoclay. The experimental values of the composites were compared to those obtained by using mixing laws. We showed that the mechanical properties correctly accounted for the experimental results at low concentrations of nanoclay particle. At concentrations higher than a few percentages, these laws fail to interpret the experimental results and all experimental results must take into account some parameters such as the particle size, their distribution, and the formation of agglomerates. The Experimental results of recycled polyethylene showed chain entanglement and decreased chain mobility, leading to an increase of brittleness and decreasing plastic behavior.

Development of a Semi-Analytical Algorithm for the Retrieval of Suspended Particulate Matter from Remote Sensing over Clear to Very Turbid Waters

Remote sensing of suspended particulate matter, SPM, from space has long been used to assess its spatio-temporal variability in various coastal areas. The associated algorithms were generally site specific or developed over a relatively narrow range of concentration, which make them inappropriate for global applications (or at least over broad SPM range). In the frame of the GlobCoast project, a large in situ data set of SPM and remote sensing reflectance, Rrs(λ), has been built gathering together measurements from various coastal areas around Europe, French Guiana, North Canada, Vietnam, and China. This data set covers various contrasting coastal environments diversely affected by different biogeochemical and physical processes such as sediment resuspension, phytoplankton bloom events, and rivers discharges (Amazon, Mekong, Yellow river, MacKenzie, etc.). The SPM concentration spans about four orders of magnitude, from 0.15 to 2626 g·m−3. Different empirical and semi-analytical approaches developed to assess SPM from Rrs(λ) were tested over this in situ data set. As none of them provides satisfactory results over the whole SPM range, a generic semi-analytical approach has been developed. This algorithm is based on two standard semi-analytical equations calibrated for low-to-medium and highly turbid waters, respectively. A mixing law has also been developed for intermediate environments. Sources of uncertainties in SPM retrieval such as the bio-optical variability, atmospheric correction errors, and spectral bandwidth have been evaluated. The coefficients involved in these different algorithms have been calculated for ocean color (SeaWiFS, MODIS-A/T, MERIS/OLCI, VIIRS) and high spatial resolution (LandSat8-OLI, and Sentinel2-MSI) sensors. The performance of the proposed algorithm varies only slightly from one sensor to another demonstrating the great potential applicability of the proposed approach over global and contrasting coastal waters.

Finite-size effects in a model for plasticity of amorphous composites.

We discuss the plastic behavior of an amorphous matrix reinforced by hard particles. A mesoscopic depinning-like model accounting for Eshelby elastic interactions is implemented. Only the effect of a plastic disorder is considered. Numerical results show a complex size dependence of the effective flow stress of the amorphous composite. In particular, the departure from the mixing law shows opposite trends associated to the competing effects of the matrix and the reinforcing particles, respectively. The reinforcing mechanisms and their effects on localization are discussed. Plastic strain is shown to gradually concentrate on the weakest band of the system. This correlation of the plastic behavior with the material structure is used to design a simple analytical model. The latter nicely captures reinforcement size effects in (logN/N)(1/2), where N is the linear size of the system, observed numerically. Predictions of the effective flow stress accounting for further logarithmic corrections show a very good agreement with numerical results.

Measurements on the Effects of Moisture on the Complex Permittivity of High Temperature Ash

An analysis of the effect moisture has on the effective relative complex permittivity of ash particles created within fires has been presented within this paper. The inclusion of moisture within this hydroscopic material has a significant effect on the effective complex permittivity and, hence, its scattering ability. The investigations developed a mixing law model for describing moisture ingress in a 1000 $ ^{\circ}{\hbox{C}}$ burnt eucalypt ash sample. Using the measured trend found in the eucalypt samples, the effective complex permittivity with respect to the inclusion of moisture has been modeled with an empirical modification to the tri-phase unified mixing law.

The influence of small amounts of linear polycaprolactone chains on the crystallization of cyclic analogue molecules

C-PCL/L-PCL blends show a synergistic decrease in their isothermal crystallization rates as compared to the expectation of a simple mixing law due to the threading effect of the linear on the cyclic chains.

Inversion-based interpretation of logging-while-drilling gamma-ray spectroscopy measurements

Neutron-induced spectroscopy measurements are commonly used to quantify in situ elemental compositions of rocks from the processing of measured gamma-ray energy spectra. However, geometric effects on the measured spectroscopy logs, such as thin beds, dipping beds, and deviated well trajectories, can cause shoulder-bed averaging that compromises the assessment of the true layer elemental composition. We have developed an inversion-based interpretation method to evaluate layer elemental compositions from spectroscopy measurements acquired with a commercial 14-MeV pulsed-neutron logging-while-drilling spectroscopy tool. The algorithm is based on a new spectroscopy fast-forward simulation technique, and it estimates layer-by-layer elemental relative yields, weight concentrations, and their uncertainties. Calculations are performed with inelastic and capture gamma-ray spectroscopy measurements that arose from high- and low-energy neutron interactions, respectively. This strategy provides two sets of data that independently validate estimated elemental compositions and can ascertain chemical elements present in only one measurement mode. In laminated formations in which layer thicknesses are appreciably below the vertical resolution of the tool, it is impossible to quantify layer properties with inversion methods. We have therefore developed an additional interpretation method based on a spectroscopy mixing law to estimate elemental compositions within individual laminae. The new inversion-based interpretation methods were successfully verified with two challenging synthetic cases and implemented in two field cases with varying lithology and well trajectories. Our results found that the developed methods reduced shoulder-bed averaging effects on the measured spectroscopy logs by as much as a 0.4 yield fraction and a 0.17 weight fraction. Estimated elemental compositions with reduced shoulder-bed averaging effects improved the calculations in subsequent spectroscopy-based petrophysical interpretation.

A hydrological approach to estimating daily glacier ablation

Reduced meltwater discharge owing to glacier retreat can have severe impacts on downstream water users. To assess these impacts, it is essential to differentiate between water from glacier melt and other sources. We propose a method for doing this on a daily time scale by applying a mixing law to electrical conductivity and proglacial discharge measurements. Daily ablation is then estimated by applying a recession law to the glacier melt component. Testing this method on summer hydrology and meteorology measurements from the Baounet Glacier (France) taken over six consecutive years (2008–2013) allowed us to reconstruct daily ablation during the ablation period. Mean ablation rates ranged from 20 to 30 mm·day−1. Air temperature measurements showed that periods of low ablation during the summer were linked to cooler days and snowfall periods. Comparisons for three consecutive summers showed that the ablation rates obtained by summing calculated daily ablation were statistically similar to the rates recorded by ablation stakes.

New Analytical Method To Calculate Matrix- and Fluid-Corrected Total Porosity in Organic Shale

Summary Estimation of total porosity from neutron and density porosity logs in organic shale (source rock) is challenging because these logs are substantially affected by fluid and matrix-composition effects. Conventional interpretation of neutron and density porosity logs often includes corrections for shale concentration in which the main objective is to improve the calculation of nonshale porosity in hydrocarbon-bearing zones. These corrections are not desirable in unconventional rock formations because shale pores can be hydrocarbon-saturated. Neutron and density porosity readings across shale zones are sometimes averaged by use of the root-mean-square (RMS) method. We introduce a new and simple analytical expression for total porosity that effectively separates both matrix and fluid effects on neutron and density porosity logs. The expression stems from a new nonlinear mixing law for neutron migration length that is coupled with the linear-density mixing law to calculate total porosity and fluid density. The method is applied in two sequential steps: First, separate corrections for only matrix effects are implemented to enhance the neutron-density crossover for qualitative interpretation of fluid type; second, the coupled equation is used to estimate fluid density and actual porosity devoid of matrix and fluid effects. Calculated porosity and fluid density can be used further to calculate water saturation from density logs. One remarkable feature of this method is the ease with which it can be applied to obtain accurate and reliable results. Application of the method only requires knowledge of single-component nuclear properties and mineral volumetric concentrations. One can obtain nuclear properties from a set of charts for multiple fluid types and minerals provided in this paper, whereas one can calculate mineral concentrations on the basis of available triple combo logs or gamma ray spectroscopy logs. Two synthetic and four field examples (two conventional and two shale-gas reservoirs) are used to test the method. First, we describe an application in a conventional siliciclastic sedimentary sequence in which only shale concentration calculated from gamma ray logs is required to improve the estimation of porosity in shaly sections. Second, we document several applications in which gamma ray spectroscopy logs are used together with a reliable hypothesis for clay type to define mineral properties. Results compare well with nuclear-magnetic-resonance (NMR) and core measurements, whereas the new method outperforms the conventional RMS procedure, especially in the cases of gas-bearing, low-porosity organic shale. The new analytical method can be readily implemented on an Excel spreadsheet and requires minimal adjustments for its operation.

Significantly enhanced high-frequency permeability for composites with amorphous-membrane-fillers prepared using an infiltration method

Amorphous-membrane-filler composites have been fabricated using an infiltration method. The composites are able to significantly increase the permeability by 200%, as compared to general amorphous flake composites. SEM and magnetic measurement show that the amorphous flakes in membrane are in-plane arrangement. A model, which considers the effect of flake arrangement on demagnetizing factor Nd and permeability, is proposed. The effect of the arrangement of flakes is equivalent to an effective Nd, which is equal to 1/3 and zero for random and complete in-plane arrangements, respectively. Due to in-plane arrangement of amorphous flakes, the decreased Nd leads to significantly enhanced permeability for the amorphous-membrane-filler composites, based on the Maxwell–Garret mixing law.

Mineral–vegetal co-milling: An effective process to improve lignocellulosic biomass fine milling and to increase interweaving between mixed particles

Fine-milling is a crucial objective for lignocellulosic biomass valorization. Co-milling appears to be a promising technique to improve its efficiency. However, the mechanisms occurring while co-milling remain poorly understood. In this study, an experimental work was performed to produce co-milled powders from both lignocellulosic (wheat, straw or pine sawdust) and mineral materials (limestone, quartzite or tile) with very contrasted physicochemical properties. The main consequences of co-milling were studied for both materials. A two-component mixing law for the prediction of the blend properties was proposed (particle sizes and true densities) to highlight the gain of this single processing step compared to separate milling and mixing. The predicted values were compared with experimental data for co-milled powders at 7 biomass contents from 0% to 100%. In all cases, co-milling leads to a reduction in particle size of lignocellulosic materials and create strong interweaving with mineral particles.

Probing the Debye Dielectric Relaxation in Supercooled Methanol

The explanation of the dielectric dynamics in methanol would offer knowledge of the Debye relaxation in supercooled monoalcohols. However, due to the fast crystallization, it is hard to attain the dynamics of pure methanol in the deeply supercooled region. In this paper we studied the dynamics of methanol - 2-ethyl-1-hexanol mixtures with methanol concentration up to 80 mol% using dielectric and calorimetric measurements. Two main relaxations are detected in the dielectric spectra of the mixtures, and the slower one generally reproduces the Debye relaxation features reported in earlier studies of other monoalcohols. The validity of the ideal mixing law is verified for the relaxation time of the slower dynamics in the mixtures. The results suggest that the Debye relaxation is present in the dielectric spectra of methanol. The temperature dependence of the Debye relaxation time is constructed for the supercooled methanol.

Review advice on mixing law and media to manage university crises

Bad things can happen at universities. When they do, the university's legal interests are not the only things at stake. Issues of liability and damages often pale in comparison to the university's reputational interests. A university viewed by the public as dangerous, uncaring, untrustworthy or irresponsible is likely to face difficulties in attracting students, faculty and financial support. A strong reputation built over decades can be tarnished overnight.

Rheology of two-phase systems: A microphysical and observational approach

Ductile shear zones commonly contain distinctive bands of high strain rock characterized by intimately mixed fine-grained two-phase or polyphase material. These ultramylonite bands are weaker than the surrounding material, and may play a critical role in strain localization. How such zones develop, how the phases become evenly dispersed, the bulk rheology, and the controls on grain size, are all unclear. The following generic scenario may resolve some of these questions.1) Dislocation creep and dynamic recrystallization cause grain-size reduction: commonly, the recrystallized grain sizes of the two phases differ.2) Grain size reduction causes a switch to grain-boundary diffusion creep, which requires grain-boundary sliding. Diffusion allows one phase to fill spaces that open between grains of the other: this will happen most rapidly in the finer-grained phase. The grain size of the resulting mixture is therefore controlled by that of the finer-grained phase. This leads to mixing and dispersion of the two phases, producing a fine-grained, evenly dispersed two-phase aggregate.3) The bulk rheology will be controlled by grain-boundary diffusion creep of the two phases, with the grain size controlled by the finer-grained phase.Bulk flow laws can be developed for quartz-feldspar and olivine-orthopyroxene ultramylonites based on these concepts, using appropriate mixing laws.

Development of Dynamic Light Controller for Variable CCT White LED Light Source

ABSTRACTIn this article, a simple dynamic light controller (DLC) is proposed, designed, and fabricated for practical realization of variable correlated color temperature (CCT) but constant light output white light emitting diode (WLED) light source. This WLED light source consists of alternate strings of warm white (WW) and cool white (CW) LEDs. Light control logic of developed DLC is based on Grassman’s color mixing law and hence the range of CCT variation of the test light source lies within the CCT values of the WW and the CW LEDs. A pulse width modulation (PWM) technique is applied to implement the light control logic and embedded in a PIC microcontroller to control the light outputs of two WLED arrays through enhanced PWM mode with dual PWM output. The developed controller is connected with the test light source and controllable by infrared (IR) remote within a distance of 4 m. Thus, the developed DLC is an integrated module consisting of an IR receiver, IR decoder, control signal (PWM) generator, amplifier, and switching device. Performance of the developed DLC is experimentally validated for a set of desired CCT points (2840–5750 K) and constant illuminance (300 lx) measured at a fixed distance. Measured CCT values show maximum deviation of 160 and 194 K for warm white and cool white regions, respectively, compared to desired CCT points. On the other hand, the deviation of measured illuminance values lies within to with respect to set illuminance value of 300 lx. Variations of measured CCT lie within the acceptable range. Experimental results establish the satisfactory performance of the developed DLC.

Subchannel analysis with turbulent mixing rate of supercritical pressure fluid

The subchannel analysis with turbulent mixing rate law of supercritical pressure fluid (SPF) is carried out for supercritical-pressurized light water cooled and moderated reactor (Super LWR). It is different from the turbulent mixing rate law of pressurized water reactor (PWR), which is widely adopted in Super LWR subchannel analysis study, the density difference between adjacent subchannels is taken into account for turbulent mixing rate law of SPF. MCSTs are evaluated on three kinds of fuel assemblies with different pin power distribution patterns, gap spacings and mass flow rates. Compared with that calculated by employing turbulent mixing rate law of PWR, the increase in MCST is smaller even when peaking factor is large and gap spacing is uneven. The sensitivities of MCST on non-uniformity of the subchannel area and power peaking are reduced.

Total sulfate vs. sulfuric acid monomer concenterations in nucleation studies

Abstract. Sulfuric acid is known to be a key component for atmospheric nucleation. Precise determination of sulfuric-acid concentration is a crucial factor for prediction of nucleation rates and subsequent growth. In our study, we have noticed a substantial discrepancy between sulfuric-acid monomer concentrations and total-sulfate concentrations measured from the same source of sulfuric-acid vapor. The discrepancy of about 1–2 orders of magnitude was found with similar particle-formation rates. To investigate this discrepancy, and its effect on nucleation, a method of thermally controlled saturator filled with pure sulfuric acid (97% wt.) for production of sulfuric-acid vapor is applied and rigorously tested. The saturator provided an independent vapor-production method, compared to our previous method of the furnace (Brus et al., 2010, 2011), to find out if the discrepancy is caused by the production method itself. The saturator was used in a H2SO4–H2O nucleation experiment, using a laminar flow tube to check reproducibility of the nucleation results with the saturator method, compared to the furnace. Two independent methods of mass spectrometry and online ion chromatography were used for detecting sulfuric-acid or sulfate concentrations. Measured sulfuric-acid or total-sulfate concentrations are compared to theoretical predictions calculated using vapor pressure and a mixing law. The calculated prediction of sulfuric-acid concentrations agrees very well with the measured values when total sulfate is considered. Sulfuric-acid monomer concentration was found to be about 2 orders of magnitude lower than theoretical predictions, but with a temperature dependency similar to the predictions and the results obtained with the ion-chromatograph method. Formation rates are reproducible when compared to our previous results with both sulfuric-acid or total-sulfate detection and sulfuric-acid production methods separately, removing any doubts that the vapor-production method would cause the discrepancy. Possible reasons for the discrepancy are discussed and some suggestions include that the missing sulfuric acid is in clusters, formed with contaminants found in most laboratory experiments. One-to-two-order-of-magnitude higher sulfuric-acid concentrations (measured as total sulfate in this study) would contribute to a higher fraction of particle growth rate than assumed from the measurements by mass spectrometers (i.e. sulfuric-acid monomer). However, the observed growth rates by sulfate-containing vapor in this study does not directly imply a similar situation in the field, where sources of sulfate are much more diverse.

A study on an online measurement method to determine the oil discharge ratio by utilizing Coriolis mass flow meter in a calorimeter

In this paper, an online measurement method of oil discharge ratio (ODR) is experimentally investigated based on a compressor calorimeter with the Coriolis mass flowmeter (CMF). In this method, the oil concentration is determined by a linear mixing law of the specific volume model using the density of the refrigerant, oil and refrigerant-oil mixture obtained by CMF. During the testing, the light absorption method is also conducted simultaneously for the comparison. The results indicate that the presented CMF based density method has an average relative deviation of 4.28%. The accuracy of the CMF based density method is superior to the light absorption method, which has the relative deviation of −8∼23% compared with the standard sampling method. The presented CMF-based method can be expected to be used for future ODR measurement due to its non-sampling, online, and accurate features.