Simple Deposition Model Research Articles

Element Formation in Radiation-hydrodynamics Simulations of Kilonovae

Understanding the details of r-process nucleosynthesis in binary neutron star merger (BNSM) ejecta is key to interpreting kilonova observations and identifying the role of BNSMs in the origin of heavy elements. We present a self-consistent, two-dimensional, ray-by-ray radiation-hydrodynamic evolution of BNSM ejecta with an online nuclear network (NN) up to a timescale of days. For the first time, an initial numerical relativity ejecta profile composed of the dynamical component and spiral-wave and disk winds is evolved including detailed r-process reactions and nuclear heating effects. A simple model for the jet energy deposition is also included. Our simulation highlights that the common approach of relating in postprocessing the final nucleosynthesis yields to the initial thermodynamic profile of the ejecta can lead to inaccurate predictions. Moreover, we find that neglecting the details of the radiation-hydrodynamic evolution of the ejecta in nuclear calculations can introduce deviations of up to 1 order of magnitude in the final abundances of several elements, including very light and second r-process peak elements. The presence of a jet affects element production only in the innermost part of the polar ejecta, and it does not alter the global nucleosynthesis results. Overall, our analysis shows that employing an online NN improves the reliability of nucleosynthesis and kilonova light-curve predictions.

A Simple Deposition Model for Debris Flow Simulation Considering the Erosion–Entrainment–Deposition Process

This study aimed to determine the depositional effect and improve the identification of debris flow risk zones. To accomplish this goal, we developed a two-dimensional debris flow model (Deb2D) based on a hyperbolic conservation form of the mass and the momentum balance equation with consideration of the erosion–entrainment effect as well as the depositional effect. In this model, we implemented a widely-used rheological equation—the Voellmy equation—and a quadtree adaptive grid-based shallow-water equation. This model was applied to two study sites to assess the depositional effect. The impact area, volume of soil loss, maximum velocity, inundated depth, and erosion depth resulting from the debris-flow modeling were compared with the field data. The simulation results with/without deposition were evaluated using the receiver operating characteristic method. The implementation results of the erosion–entrainment model with deposition showed superior accuracy when estimating the damage range and flow time.

Random deposition with spatially correlated noise (RD-SCN) model: Multi-affine analysis

Abstract We study the random deposition model with long-range spatially correlated noise. In this model the particles deposit in a power-law distance of each other as Δ i , j = i n t [ u − 1 2 ρ ] , where u is chosen randomly over the range (0,1) and ρ is the correlation strength. The results show that the enhancement of ρ exponent is accompanied by the appearance of irregularities and jumps in the height fluctuations. In spite of scaling exponents dependent to correlation strength in other linear and non-linear growth equations, enhancement of the correlation strength, does not change the growth exponent β = 1 / 2 . As the short-range correlations in growth equations result in roughness saturation, the results show that the long-range correlations in this growth model does not saturate the interface width for any system size. The fractal analysis of the height fluctuations performed via the multi-fractal detrended fluctuation analysis (MF-DFA) revealed that the synthetic rough surfaces with ρ = 0 are mono-fractal with the Hurst exponent H = 0.5 . It verifies the un-correlated fluctuations in the simple random deposition model. For the correlation strengths in the range [0,1], the Hurst exponent increases in the range [ 1 2 , 1 ) with a mono-fractal behavior. In the critical exponent of ρ c , multi-affinity is occurred. For ρ > ρ c = 1 the mono-fractal feature of the height fluctuations tends to the multi-affine one and the strength of multi-affinity increases by enhancement of ρ exponent. The results show that the observed multi-affinity is because of deviation from the normal distribution and appearance of correlations among small and large fluctuations.

Effects of the Growth Kinetics on Solute Diffusion in Porous Films

For the development of porous materials with improved transport properties, a key missing ingredient is to determine the relations between growth kinetics, structure, and transport parameters. Here, we address these relations by studying solute diffusion through three-dimensional porous films produced by simple deposition models with controlled thickness and porosity. We simulate growing films with competitive aggregation rules that incorporate lateral aggregation (relative rate proportional to $p$), which leads to pore formation, and surface relaxation ($1-p$) that favors compaction. By connecting a solute source at the basis and a drain at the top outer surface of the films, we extract the effective diffusion coefficients from steady-state simulations. We find that for a given film thickness, the larger the $p$, the larger the effective porosity and diffusivity, but the smaller the tortuosity. Keeping constant growth conditions (i.e., same $p$), the increase of thickness always leads to an increase of effective porosity, but a nontrivial behavior in the diffusivity occurs: for $p\leq 0.7$, the diffusion coefficient is larger in thicker films; this is accompanied by a decrease of the tortuosity with the thickness, thus indicating that growth continuously improves pore structure for diffusion. Microscopically, such a result is associated with narrower distributions of local solute currents at higher points of films. Particularly for $p\geq 0.9$, in which film porosity is $\sim 0.65-0.7$, the tortuosity is between $1.3$ and $2$, increases with the thickness, and has maximal changes near $25\%$. Pairs of values of porosity and tortuosity that we obtain here, for the thickest films, agree with those experimentally measured in some porous electrodes. Noteworthy, the increase of film thickness is generally favorable for diffusion in their pores, and exceptions have small losses in tortuosity.

Source areas, connectivity, and delivery rate of sediments in mountainous-forested hillslopes: A probabilistic approach

In mountainous-forested landscape, quantifying the materials produced at hillslope scale that effectively reach the channel network with a given probability is currently challenging, due to the uncertainties in modelling the frequency-magnitude distribution of failures and in determining the sediment connectivity between unstable areas and channel network.The purpose of this study is to develop a modular approach to assess the sediment source areas and the probability of mobilization from hillslope, and to estimate the probability of sediment input to the streams proposing a new connectivity index.The first goal was faced adopting a 3D probabilistic slope stability method that includes the spatially distributed characteristics of forest coverage. The second aim was tackled by comparing sediment travel distance and the minimum-topographic distance to reach the nearest stream. A simple deposition model was applied to estimate the percentage of the sediment entering into the stream network.The methodology was tested on three headwater catchments in northern Italian Alps. The outputs were landslide susceptibility maps, which showed robust performances when compared to the available landslide inventories (AUC > 0.726), and maps of the probability that sediment reaches the channel network. In this way, it was possible to identify which areas are the most susceptible to landsliding, how many sediment materials can be mobilised with a given probability, and which is the degree of sediment connectivity with the channel system. Results obtained for the tested catchments, compared with data available from the literature, showed that the proposed methodology is of general validity, especially for those territories characterized by rainfall-triggered landslides and forest coverage.This study, then, provides a robust framework to improve debris-flow risk management and to implement watershed management strategies, such as planning forestry operations or positioning retention structures addressed to increase slope stability and to reduce sediment delivery.

Learning universality and scaling from simple deposition models

We use deposition models of kinetic roughening of a growing surface to introduce the concepts of universality and scaling and to analyze the qualitative and quantitative role of different parameters. In particular, we focus on two classes of models where the deposition is accompanied by a local relaxation process within a distance δ. The models are in the Edwards-Wilkinson universality class, but the role of δ is nontrivial.

Albedo matters: Understanding runaway albedo variations on Pluto

The data returned from NASA’s New Horizons reconnaissance of the Pluto system show striking albedo variations from polar to equatorial latitudes as well as sharp longitudinal boundaries. Pluto has a high obliquity (currently 119°) that varies by 23° over a period of less than 3 million years. This variation, combined with its regressing longitude of perihelion (360° over 3.7 million years), creates epochs of “Super Seasons” where one pole is pointed at the Sun at perihelion, thereby experiencing a short, relatively warm summer followed by its longest possible period of winter darkness. In contrast, the other pole experiences a much longer, less intense summer and a short winter season. We use a simple volatile sublimation and deposition model to explore the relationship between albedo variations, latitude, and volatile sublimation and deposition for the current epoch as well as historical epochs during which Pluto experienced these “Super Seasons.” Our investigation quantitatively shows that Pluto’s geometry creates the potential for runaway albedo and volatile variations, particularly in the equatorial region, which can sustain stark longitudinal contrasts like the ones we see between Tombaugh Regio and the informally named Cthulhu Regio.

A Simple Physics-Based Model for Particle Rebound and Deposition in Turbomachinery

A new model is proposed for predicting particle rebound and deposition in environments relevant to gas turbine engines. The model includes the following physical phenomena: elastic deformation, plastic deformation, adhesion, and shear removal. It also incorporates material property sensitivity to temperature and tangential-normal rebound velocity cross-dependencies observed in experiments. The model is well-suited for incorporation in computational fluid dynamics (CFD) simulations of complex gas turbine flows due to its algebraic (explicit) formulation. Model predictions are compared to coefficient of restitution data available in the open literature as well as deposition results from two different high-temperature turbine deposition facilities. While the model comparisons with experiments are in many cases promising, several key aspects of particle deposition remain elusive. The simple phenomenological nature of the model allows for parametric dependencies to be evaluated in a straightforward manner. It is hoped that this feature of the model will aid in identifying and resolving the remaining stubborn holdouts that prevent a universal model for particle deposition.

Deposition Measurements From the Full-Scale Radiological Dispersal Device Field Trials.

In 2012, Defence Research and Development Canada led a series of experiments, titled the Full-Scale Radiological Dispersal Device Field Trials, in which short-lived radioactive material was explosively dispersed and the resulting plume and deposition were characterized through a variety of methods. Presented here are the results of a number of measurements that were taken to characterize the radioactive ground deposition. These included in situ gamma measurements, deposition filter samples, and witness plate measurements that were taken in situ with handheld beta survey meters. The results from the different measurement techniques are compared to each other and to a simple deposition model. Results showed that approximately 3% of the original source activity was deposited in the immediate vicinity of ground zero, and an additional 15-30% of the original activity was deposited within 450 m of ground zero. Implications of these results for emergency response are discussed.

Use of the Distance Transform for Integration of Local Measurements: Principle and Application in Chemical Engineering.

We propose an original methodology to integrate local measurement for nontrivial object shape. The method employs the distance transform of the object and least-square fitting of numerically computed weighting functions extracted from it. The method is exemplified in the field of chemical engineering by calculating the global metal concentration in catalyst grains from uneven metal distribution profiles. Applying the methodology on synthetic profiles with the help of a very simple deposition model allows us to evaluate the accuracy of the method. For high symmetry objects such as an infinite cylinder, relative errors on global concentration are lower than 1% for well-resolved profiles. For a less symmetrical object, a tetralobe, the best estimator gives a relative error below 5% at the cost of increased measurement time. Applicability on a real case is demonstrated on an aged hydrodemetallation catalyst. Sampling of catalyst grains at the inlet and outlet of the reactor allowed conclusions concerning different reactivity for the trapped metals.

The eigenpairs of a Sylvester–Kac type matrix associated with a simple model for one-dimensional deposition and evaporation

A straightforward model for deposition and evaporation on discrete cells of a finite array of any dimension leads to a matrix equation involving a Sylvester–Kac type matrix. The eigenvalues and eigenvectors of the general matrix are determined for an arbitrary number of cells. A variety of models to which this solution may be applied are discussed.

On sediment extent and runup of tsunami waves

Tsunami sediments play an important role in tsunami hazard assessments. Recent tsunami events and their associated tsunami deposits have produced a wealth of sediment data. Surveys of recent tsunami events observed that maximum inland tsunami inundation exceeds the maximum inland extent of sand deposition. A driving question of tsunami sedimentology is whether the difference between maximum tsunami inundation and inland extent of sand can be employed as a measure of inundation for past events for which only the extent of the sand is known. Attempts to infer the causative flow characteristics from these sediments often suffer from uncertainties in the data and from restrictive assumptions made in inversion models. The latter demonstrates that the interaction between the tsunami flow and the movable bed is not fully understood. In our contribution, we employ numerical simulations of tsunami propagation and inundation with MOST and a simple model for deposition. In our simulations, we vary the onshore slope, the initial amplitude, which can be interpreted as offshore wave amplitude, and the grain size. While the initial amplitude and onshore slope influence the difference between maximum inundation and sand extent, the grain size has little effect. The link between the onshore slope, initial amplitude and the difference between the maximum tsunami inundation and inland sediment extent can be employed as a first-order quantitative tool to estimate tsunami flow characteristics and maximum inundation from tsunami deposits. We anticipate these results will improve tsunami hazard assessments and narrow the gap between field observations and numerical simulations.

Lichen and soil as indicators of an atmospheric mercury contamination in the vicinity of a chlor-alkali plant (Grenoble, France)

Atmospheric mercury (Hg) deposition around a mercury cell chlor-alkali plant located near Grenoble, south-east France, was assessed using Hg concentrations in lichens and soils. Hg content in the epiphytic Xanthoria parietina lichen ranged from ∼0.07 to ∼2.51 μg g −1, and concentrations decreased with increasing distance to the plant, with a contamination radius of ∼2 km. Soil Hg concentration profiles were consistent with an atmospheric origin, with higher concentrations in the upper part of the profiles. Concentration of Hg in lichens and top soils (0–10 cm depth) as a function of the distance to the chlor-alkali plant exhibited highly similar variations. Using a simple first-order deposition model, mean Hg fallouts for the whole history of chlor-alkali plant are estimated to ∼36 g Hg day −1 in this area, compatible with values reported for reactive gaseous mercury (RGM) emissions of similar industrial plants. Using literature data on RGM to total Hg emission ratio, we estimate that the plant emitted ∼650 kg Hg year −1. Two kilometres away from the plant, Hg content in top soils falls to values of (0.13 ± 0.07) μg g −1 Hg, which is the local anthropogenic geochemical background level, but higher than unperturbed geochemical background found at the bottom of soil profiles (below 40 cm depth) estimated to (0.04 ± 0.01) μg g −1 Hg. The present study evidences that lichens are a pertinent proxy for soil Hg contamination around chlor-alkali plants. They are attractive biomonitoring tools since sampling and preparations protocols for lichens are less time consuming than those used for soils.

Particle Deposition onto Charge-Heterogeneous Substrates

The deposition of model colloidal particles onto striped charge-heterogeneous surfaces was studied to determine the influence of surface chemical heterogeneity on the deposit morphology. The charge heterogeneity was created employing self-assembled monolayers of carboxyl- and amine-terminated alkanethiols using a soft lithographic technique. Polystyrene sulfate microspheres and fluorescent polystyrene nanoparticles were sequentially deposited onto the patterned substrate under no flow (quiescent) condition. The deposited structures and the micropatterns were imaged using a combination of phase contrast and fluorescence microscopy. The experimental particle deposition behavior was compared to predictions based on random sequential adsorption (RSA) employing a Monte Carlo technique. Comparison of radial distribution obtained from experimental data was made with the theoretical results and found to be in good agreement despite the use of a simple binary probabilistic model in the simulations. The primary conclusion from the study is that particles tend to preferentially deposit at the edges of the favorable stripes. However, the extent of this bias can be controlled by the proximity of consecutive favorable stripes (or width of the intervening unfavorable stripes) as well as the particle size relative to the stripe width. Second, a simple binary probability distribution-based Monte Carlo RSA deposition model adequately predicts the deposit structure, particularly the periodicity of the underlying patterns on the substrate. These observations suggest that the patterns could be encrypted by the deposited particles, which can subsequently be decoded, given the proper "key" or information that is based on analyzing the deposit morphology.

Polyurethane unimorph bender microfabricated with Pressure Assisted Microsyringe (PAM) for biomedical applications

This paper describes a new microfabrication technique for bender-type electromechanical actuators made of an elastomeric electroactive polymer. The technique is based on a computer-controlled deposition of the active material with a microsyringe. The paper describes the developed microfabrication system and proposes a simple deposition model. The realization of solid-state unimorph bender actuators made of polyurethane as electrolyte and a mixture of carbon black and polyurethane as electrodes is presented. Prototype actuators fabricated both with the new technique were driven with electrical field of 100 V/μm and showed bending angles higher than 30°. In this way, we have demonstrated that it is possible to fabricate polyurethane based microactuators using a polyurethane/carbon black composite such as device.

A point source analytical model of inverse pulsed laser deposition

A simple analytical model for inverse pulsed laser deposition is proposed. In the model the motion of the evaporated material is assumed to emerge as from a point source located above the surface of evaporation at some distance. The obtained thickness profiles of inverse deposited films agree well with those calculated by the test particle Monte Carlo method. The proposed approach has been applied for analysis of experimental data on inverse pulsed laser deposition of graphite in nitrogen atmosphere with nanosecond pulses of laser fluences between 1 and 7 J/cm2. The model describes well the thickness profiles and pressure dependence of film growth rate for inverse deposition.

The Kinetics of Sulphate Deposition in Seeded and Unseeded Tests

Summary In a previous paper (Boak et al. 2005), we addressed the issue: What level of sulphate reduction is required to eliminate the need for scale inhibitor squeezing? In this earlier work, we developed the idea of a simple kinetic scheme for sulphate deposition on the basis of a "safe envelope" concept within which the system could operate. Central to the safe envelope approach is the choice of rate constant for barite deposition and this can be estimated experimentally under various conditions appropriate to the specific field application. Experimental results on kinetic barite deposition in low sulphate brine mixtures were presented previously (Boak et al. 2005). However, these previous results were carried out for unseeded solutions (i.e., no solid barite or sand particles were added to the scaling solutions). The following questions were raised If barite particles were present, would this mean that the solution supersaturation (Sp) would reduce to 1 very rapidly thus over-ruling any kinetic deposition effects? Does the presence of sand particles have the same effect as barite particles? In the case of both barite or sand particles does the size of the particles (i.e. the surface area per unit mass) have any effect on the barite deposition rate? In addition, a very simple kinetic model for bulk deposition of barite was used for which the long time behavior was that barite is deposited until the limiting ion was totally consumed. However, it is known that barite has some solubility at higher levels of sodium chloride and the kinetic model should limit to this value. This may be an important consideration especially in lower sulphate (or lower barium) brines. Experimental results are presented in this paper which both address and answer the above questions, and extend the analysis with an improved kinetic model for barite deposition. Even in the presence of seed materials (barite and sand of various surface areas), clear rate effects can be observed and rate constants can be derived. As expected, barite seed material of higher surface area induces faster depletion of the scaling ions to a supersaturation ratio of 1 than barite of lower surface area. However, allowing for the effect of surface area, the barite seed material shows a clearly enhanced potential to induce scale formation than the sand. In addition, the safe envelope model is extended by considering a more accurate analytical kinetic model which limits correctly to the equilibrium solubility of barite at long times.

Particle deposition in the pulmonary region of the human lung: Multiple breath aerosol transport and deposition

Comprehensive knowledge of aerosol deposition in the lung during multiple breathing cycles is essential to understanding the long term adverse effects of environmental particulate pollution as well as various therapeutic strategies for aerosolized drug delivery. In this work, a simple semi-empirical model for whole lung aerosol bolus dispersion and deposition developed in an accompanying study [Park, S.S. and Wexler, A.S., 2007. Particle deposition in the pulmonary region of the human lung: A semi-empirical model of single breath transport and deposition. Journal of Aerosol Science 38(2), 228–245] was used to estimate regional particulate dosimetry during multiple breaths. To further validate the transport and deposition model of Park and Wexler [2007. Particle deposition in the pulmonary region of the human lung: A semi-empirical model of single breath transport and deposition. Journal of Aerosol Science 38(2), 228–245], the washin and washout experiments of Davies and coworkers were simulated; predictions compared well to observations. Typical models of pulmonary particle deposition simulated transport to these distal airways by a flow-through approximation where particle-laden air is assumed to flow into the airways and out the alveoli, but resting tidal volumes do not transport particles to the distal pulmonary airways in a single breath. By simulating tidal transport and deposition over a series of breath, we find that the concentration of retained particles as a function of lung depth increases with each tidal cycle and these particles penetrate deeper with succeeding breaths. The retained particle concentration increases more slowly with each breath, so that after the 8th breath, the concentration distribution within the lung attains a steady state. Comparison with observed data and previous model predictions is made in terms of total and generational deposition fractions at steady state. After accounting for the retained fractions, the total predicted deposition fraction was similar to the experimental data while other previous model predictions underestimated it. Predicted deposition fraction per generation showed similar patterns to other model simulations yet higher deposition fractions in the more proximal pulmonary regions. This is a result of the enhanced alveolar deposition in the first half of the acinar generations due to alveoli expansion and contraction.

Realization of conducting polymer actuators using a controlled volume microsyringesystem

This paper presents a new microfabrication technique for bender-type electromechanicalactuators made of conducting polymers. The technique is based on a computer-controlleddeposition of the active material with a microsyringe. The paper describes thedeveloped microfabrication system and proposes a simple deposition model usedfor an accurate control of the thickness of deposited layers. The realization ofsolid-state bimorph bender actuators made of polyaniline and a solid polymerelectrolyte is presented. Prototype actuators fabricated with the new techniqueand stimulated in air with square wave potential differences ranging between−0.5 and+1 V showed bendingangles higher than ± 60°.

A simple model for gravitational deposition of non-diffusing particles in oscillatory laminar pipe flow and its application to small airways

Gravitational deposition of non-diffusing particles from oscillatory laminar flows in a horizontal pipe is studied. Developing a simple mathematical model, we demonstrate that when the time for gravitational sedimentation ( T d) becomes appreciable relative to the time for flow oscillation ( T), the gravitational deposition may no longer be approximated by the classical solution based on steady flow (J. Aerosol Sci. 3 (1972) 351). The analysis shows that an error caused by this approximation increases with the ratio of T d/ T (for instance, the errors in the estimation of deposition site are 1.5%, 5.9%, and 128% for T d/ T=0.05, 0.1, and 0.5, respectively); the application of the commonly used steady flow-based solutions to dominantly oscillatory flows, such as tidal breathing in lung airways, may therefore significantly underestimate local deposition density. We conclude that the oscillatory nature of tidal airflow must be taken into account when one calculates gravitational deposition of micrometer size particles in small airways of the human lung.