Deposition Model Research Articles

An improved model for predicting hydrate formation and deposition in horizontal annular flow

The formation and deposition of hydrates in pipelines form flow barriers, which affect the safety of offshore oil and gas transportation. In this study, an improved model of hydrate formation and deposition is established by considering the non-uniform distribution of liquid film and droplets resulting from gravity, which is a non-negligible factor in the accurate prediction of hydrate deposition in horizontal annular flow. The uneven distributions of the hydrate deposit thickness along the radial and axial directions in a horizontal annular flow were calculated using the proposed model. Three different deposition characteristics of hydrates along the radial direction were found: concave W-type, convex W-type, and Ω-type. Meanwhile, the radial hydrate deposit thickness gradually increased as the gas flow rate increased. With an increase in the liquid flow rate, a greater axial distance between the pipe section and inlet results in a clearer increase in the radial hydrate deposit thickness. In addition, a peak value of the hydrate deposit thickness occurs at a certain position in the axial direction. This study provides a theoretical basis for the prediction and prevention of hydrate blockages during offshore gas transportation.

Construction and testing of a model for predicting droplet deposition based on Gaussian process regression

To realize precision spraying, predicting the pesticide application dose based on the structural characteristics of the plant canopy is a crucial step. However, most of the current precision spraying techniques are based on canopy characteristics with no consideration given to the effect of canopy characteristics on droplet particle population. As a result, the droplet deposition value is far from being ideal. Herein, we explored the effects of canopy density and spraying volume on the distribution of droplet deposition in simulated citrus tree canopies and constructed a prediction model for droplet deposition. In this research, the three-dimensional (3D) reconstruction of fruit tree canopy was obtained using binocular camera and a new method was proposed to describe simulated citrus tree canopy density using three-dimensional point cloud. The optimal description of the interrelationship between 3D point cloud and fruit tree canopy density was determined by comparing the determination coefficients, Akaike information criterion and relative errors of the four fitting functions. Through our experiments, a droplet deposition prediction model based on Gaussian process regression was established by changing the duty cycle of the solenoid valve to adjust the spray volume, with simulated citrus trees as the target and water sensitive paper as the sampling method for collecting droplet deposition data. The experimental results show that the distribution of droplet deposition in the upper and lower layers of the canopy varies, but within the same layer droplets can produce relatively uniform deposition in similar canopy density areas with correlation coefficients greater than 0.6. When the canopy density reached 4.35 m2/m3, the amount of droplet deposition was anomalous. The prediction model, after training, has good ability of predicting droplet deposition with R2 higher than 0.79. At the same time, it was found in the research that differences occurred between the prediction accuracy of the droplet deposition prediction model in the upper canopy layer and that in the lower canopy layers, in which the R2 of the prediction model in the lower layer could reach 0.82, while in the upper layer it was 0.79. It is expected that our research on droplet deposition prediction can provide a new research perspective for precision spraying technology in plant protection operations.

First quantitative constraints on chlorine 36 dry deposition velocities on grassland: Comparing measurements and modelling results

Once released into the atmosphere, radionuclide dry deposition represents a major transfer process. It can be accurately characterized by its deposition velocity. However, this parameter is poorly constrained for most radionuclides, including chlorine 36. Chlorine 36 is a radionuclide of cosmogenic and anthropogenic origin. It may be discharged into the environment as gases and/or particles during the decommissioning of nuclear plants and the recycling of nuclear fuels. In this study, chlorine 36 deposition velocities are, for the first time, experimentally determined on grass downwind from the Orano La-Hague plant. The atmospheric chlorine 36 measurements were on average 50 nBq.m−3 for the gaseous fraction and 19 nBq.m3 for the particulate fraction. To measure the chlorine 36 transferred from the atmosphere to the grass, a method was devised for extracting the chlorides contained in solid matrices. With this method, chlorides were extracted with a mean efficiency of 83%. Chlorine 36 concentrations in the grass were on average 4 μBq.g−1, suggesting fast uptake of atmospheric chlorine 36. The yielded 36Cl dry deposition velocities varied with the season and were between 1 × 10−3 and 6 × 10−3 m s−1. The chlorine 36 depositions were modelled by adapting the existing deposition models and based on meteorological and micro-meteorological data. The dry deposition velocities calculated by the model showed less than one order of magnitude of difference with those determined experimentally. The deposition fluxes calculated by the model showed that the atmospheric depositions were predominantly gaseous chlorine 36 (>97%). However, on remote sites, the particulate fraction could be larger and have a greater influence on dry deposition. As chlorine 36 is a highly soluble and bioavailable element, these results will enable a better study of its behaviour in the environment and a more accurate evaluation of its dosimetric impact.

Evaluation of the relative deviation for coagulation and gravitational sedimentation model from experimental results of submicron aerosol in water vapor environments

This paper evaluates the relative bias of submicron aerosol coagulation and gravity deposition experiments and model prediction results under water vapor conditions, and discusses the model prediction bias results at high steam fraction. When submicron aerosols are at room temperature and lower vapor molar ratios, the model predictions and experimental results are in good agreement. When the molar fraction of steam is high, the prediction results of the model are poor. Through analyzing thermal data and conducting gas superheating experiments, it was found that under saturated steam conditions in the experimental vessel, the number of suspended small droplets also increases with the increase of steam molar fraction. The presence of these droplets alters the coagulation and sedimentation results of submicron aerosols. Based on experimental data, this paper adds correction coefficients of coalescence and sedimentation to the original model, making it suitable for predicting submicron aerosol coagulation and sedimentation under high steam molar fraction.

Proteomic Analysis of Two Different Methods to Induce Skin Melanin Deposition Models in Guinea Pigs.

In this study, we analyzed the differential expression and key signaling pathways of proteins in the skin of guinea pigs with melanin deposition caused by two different modeling methods by utilizing proteomics techniques. Guinea pig skin melanin deposition models were: (1) induced by ultraviolet (UV) irradiation alone (U group), (2) induced by UV combined with progesterone injection (P group), and guinea pigs treated without any treatment were used as blank group (B group). H&E staining and Masson staining were used to observe the extent of skin damage and melanin deposition in guinea pigs. The differentially expressed proteins (DEPs) in the skin tissues of melanin-deposited guinea pigs were screened by proteomic techniques, the functions of DEPs were analyzed, and a protein-protein interaction network (PPI) was constructed. There was a significant difference in grayscale between the U and P groups of guinea pig skin before and after modeling (P < 0.01). H&E and Masson staining showed that the U and P groups both exhibited incomplete keratinization of the stratum corneum, increased proliferation of epidermal cells with large nuclei and disordered arrangement, neovascularization of the dermis, and increased the number of melanin particles in the epidermis of the U and P groups of guinea pigs compared with the B group. Proteomics analysis showed that there were 171 DEPs between the U and P groups. These DEPs focused on biological processes such as fibrillar collagen trimer, extracellular matrix containing collagen proteins, metalloproteinase activity, and peroxidase activity. The melanin pigmentation model induced solely by UV radiation negatively regulates biological processes such as extracellular matrix and collagen synthesis, while inducing significant skin photoaging. The combination of progesterone injections and UV radiation-induced melanin pigmentation model can cause abnormal protein expression in fatty acid and phospholipid metabolism, possibly being closer to the environment of melasma formation.

Effects of tumour heterogeneous properties on modelling the transport of radiative particles.

Dose calculation plays a critical role in radiotherapy (RT) treatment planning, and there is a growing need to develop accurate dose deposition models that incorporate heterogeneous tumour properties. Deterministic models have demonstrated their capability in this regard, making them the focus of recent treatment planning studies as they serve as a basis for simplified models in RT treatment planning. In this study, we present a simplified deterministic model for photon transport based on the Boltzmann transport equation (BTE) as a proof-of-concept to illustrate the impact of heterogeneous tumour properties on RT treatment planning. We employ the finite element method (FEM) to simulate the photon flux and dose deposition in real cases of diffuse intrinsic pontine glioma (DIPG) and neuroblastoma (NB) tumours. Importantly, in light of the availability of pipelines capable of extracting tumour properties from magnetic resonance imaging (MRI) data, we highlight the significance of such data. Specifically, we utilise cellularity data extracted from DIPG and NB MRI images to demonstrate the importance of heterogeneity in dose calculation. Our model simplifies the process of simulating a RT treatment system and can serve as a useful starting point for further research. To simulate a full RT treatment system, one would need a comprehensive model that couples the transport of electrons and photons.

Calibration of redox thresholds in black shale: Insight from a stratified Mississippian basin with warm saline bottom waters

Depositional models for black shale formation rely on a detailed understanding of redox conditions and how they relate to basin development. Here, we calibrate multiple redox proxies (Fe speciation, U and Mo systematics, and pyrite framboid distributions) in the Bowland Shale, a major hydrocarbon unit in the Mississippian basin of northern England, and develop a depositional model for black shale deposition in basins adjacent to extensive carbonate platforms. The transition from deep ramp carbonates to basinal mudrocks initially occurred under oxic conditions before anoxic conditions began to expand from basin-center locations. By the end of Bowland Shale deposition, ∼10 m.y. later, black shale deposition extended from the basin, where platform-edge carbonates were deposited, into shallow-water settings. By this stage, euxinic conditions were widespread throughout the Bowland Shale. The prolonged persistence of euxinia during younger Bowland Shale deposition, and the sharp transition to fully oxygenated facies at the basin margin, suggest there was a well-developed water-column pycnocline. Black shale development in silled basins is traditionally interpreted to form beneath a halocline with a positive water balance caused by freshwater run-off (estuarine circulation). This model is not considered appropriate in this case. Bowland Shale deposition was terminated by the onset of turbidite deposition supplied by a major deltaic system; but for most of its history, the basin was surrounded by carbonate platforms that are unlikely to have experienced brackish conditions. The encroachment of the clastic system saw the rapid improvement of basinal oxygenation in the uppermost Bowland Shale, and even minor turbidite sandstones within the black shales coincided with a weakening in the intensity of euxinia, which suggests that fresher, sediment-laden waters flushed out and oxygenated the basin. We therefore suggest a warm saline bottom-water model for black shale deposition, with basinal waters generated on the adjacent carbonate platforms due to evaporation. Such a scenario is likely more broadly applicable to basinal black shales that developed adjacent to shallow-water carbonate successions.

Modelling Outer Ash Deposition Rates in Second Generation Atmospheric Pressure Oxy-Fuel Combustion Systems

ABSTRACT The particle size distribution (PSD) measurements of coarse fly-ash particles (diameter, dp >10 µm) near the depositing surface are often not available, creating challenges in formulating mechanistic models for ash deposition. This void may be partially alleviated if measurements of deposition rate and PSD of the ash deposits are available. This is demonstrated using well-resolved Computational Fluid Dynamic simulations in conjunction with a particle viscosity and particle kinetic energy based capture criterion to model the outer ash deposition processes for three different fuels (two types of coal and Rice Husk) during their combustion in AIR and O2/CO2 (70/30 vol %, OXY70; 50/50 vol %, OXY50) oxidizer compositions. First, deposition rate predictions for monodisperse fly-ash particles (10 µm < dp < 150 µm) encompassing the aforementioned scenarios were carried out. The PSD of the fly-ash particles were then inferred by mass-weighted averaging the monodisperse fly-ash diameters to match the measured deposition rates as well as the deposit ash PSD. While the methodology proved to be promising in the coal-firing scenarios, the deposit ash PSD predictions for Rice Husk were smaller than their corresponding measurements and may be attributed to irregular particle sizes or necessary modifications to surface capture characteristics.

Chemical surface tuning of zinc metal anode toward stable, dendrite-less aqueous zinc-ion batteries

The commercialization of Zn batteries is confronted with urgent challenges in the metal anode, such as dendrite formation, capacity loss, and cracking or dissolution. Here, surface interfacial engineering of the Zn anode is introduced for achieving safety and dendritic-free cycling for high-performance aqueous Zn batteries through a simple but highly effective chemical etching-substitution method. The chemical modification induces a rough peak-valley surface with a thin fluorine-rich interfacial layer on the Zn anode surface, which regulates the growth orientation via guiding uniform Zn plating/stripping, significantly enhances accessibility to aqueous electrolytes and improves wettability by reducing surface energy. As a result, such a synergetic surface effect enables uniform Zn plating/stripping with low polarization of 29 mV at a current density of 0.5 mA cm−2 with stable cyclic performance up to 1000 h. Further, a full cell composed of a fluorine-substituted Zn anode coupled with a β-MnO2 or Ba-V6O13 cathode demonstrates improved capacity retention to 1000 cycles compared to the pristine-Zn cells. The proposed valley deposition model provides the practical direction of surface-modified interfacial chemistries for improving the electrochemical properties of multivalent metal anodes via surface tuning.

Porosity and conductivity in ballistic deposition with power-law distributed noise

The ballistic deposition model of rod-like particles with power-law distributed noise is studied by the Monte Carlo simulation. In this modified model instead of particles with fixed unit sizes, vertical rods whose length follows the power-law distribution [Formula: see text] are deposited, where [Formula: see text] denotes the power-law strength exponent. This deposition leads to porous rock structures with varying porosity and conductivity. The time evolution of the surface roughness and the porosity of the resulting structures are studied. The conductivity of the structures is calculated using the parallel resistors in the percolation model using a random walk algorithm. Finally, we discuss the relation between porosity, conductivity and the strength exponent of the power-law noise. The results show that the surface roughness increases as a pseudo-step function versus deposition time for [Formula: see text], which leads to an observable reduction in porosity and conductivity. By increasing the [Formula: see text] exponent, the growth exponent of [Formula: see text] for the Gaussian model appears. The conductivity increases as [Formula: see text] versus porosity, [Formula: see text], and remains constant for [Formula: see text] which the value of [Formula: see text] has been identified for BD.

The estimation of water erosion with RUSLE and deposition model: A case study of the Bin El-Ouidane dam catchment area (High Atlas, Morocco)

The estimation of water erosion with RUSLE and deposition model: A case study of the Bin El-Ouidane dam catchment area (High Atlas, Morocco)

Numerical analysis of catalyst particle deposition characteristics in a flue gas turbine with an improved particle motion and deposition model

To more accurately understand and predict the deposition behavior of catalyst particles in the flue gas turbine cascade, test and numerical combined study is performed in this paper. Based on the systematic analysis of the deposition process and physical mechanism of the catalyst particles, the traditional DRW model, critical velocity particle deposition model and removal model were corrected with the user defined function custom function and validated with the actual deposition morphology. On this basis, the effects of the particle Stokes number and flue gas parameters on the particle deposition characteristics of the flue gas turbine cascade were detailed investigated. The results show that the revised DRW model, critical velocity and removal model can more accurately predict the deposition location and deposition rate of particles in the turbine cascade. With the increase in the Stokes number of particles, the average particle impact rate on the blade surface gradually increased, while the average deposition rate showed a trend of first increasing and then decreasing. The average deposition rate of particles in the rotor blade surface is roughly twice as high as that in the stator surface. With the increase of the flue gas expansion ratio, the deposition rate of particles less than 3 μm gradually increases, while the deposition rate of particles greater than 3 μm tends to decrease. In addition, the change in the flue gas expansion ratio has no obvious effect on the particle deposition distribution in different size ranges.

Study on aerosol thermophoretic force and thermophoresis deposition model in reactor building

During nuclear reactor severe accident, the input of external passive containment cooling system will result in significant aerosol thermophoresis deposition in reactor building, which plays important factor affecting the safety assessment of nuclear reactor. Ratio of aerosol particles radius and gas molecule mean free path (Kn number) in reactor building is not greater than 2, corresponding to the near-continuous medium zone and transition zone. Firstly the typical thermophoretic force equations for these zones are evaluated. Combined with key influencing factors analysis, the correction factor connected to Kn number is introduced to address the deviation in the prediction for the transition zone of the current equations. The modified thermophoretic force equation obviously improves the underestimation of the original equation and is then used to obtain the thermophoresis deposition coefficient. According to experimental validation, the obtained coefficient is more accurate than the model that is widely employed in analysis codes in predicting the thermophoresis deposition of aerosol particles. Finally, fluid continuity, momentum, energy and particle continuity equations are established with deduced thermophoresis deposition coefficient and solved numerically. The thermophoresis deposition model considering natural convection (CT model) is established by theoretical derivation and fitting with the numerical solutions. By introducing the effects of natural convection on temperature distribution and aerosol concentration distribution the CT model could accurately describe the aerosol thermophoresis deposition behavior under natural convection conditions for Kn number is not greater than 2, which can be applied to aerosol thermophoresis deposition prediction in reactor building.

Pollen grading prediction scale for patients with Artemisia pollen allergy in China: A 3-day moving predictive model.

Artemisia pollen is the most prevalent outdoor aeroallergen causing respiratory allergies in Beijing, China. Pollen allergen concentrations have a direct impact on the quality of life of those suffering from allergies. Artemisia pollen deposition grading predictions can provide early warning for the protection and treatment of patients as well as provide a scientific basis for allergen specific clinical immunotherapy. To develop a model of Artemisia pollen grading to predict development in patients with pollen allergy. Artemisia pollen data from four pollen monitoring stations in Beijing as well as the number of Artemisia pollen allergen serum specific immunoglobulin E positive cases in Beijing Tongren Hospital from 2014 to 2016 were used to develop a statistical model of pollen deposition and provide optimised threshold values. A logarithmic correlation existed between the number of patients with Artemisia pollen allergy and Artemisia pollen deposition, and the average pollen deposition for three consecutive days was most correlated with the number of allergic patients. Based on the threshold of the number of patients and the characteristics of Artemisia pollen, a five-stage pollen deposition grading model was developed to predict the degree of pollen allergy. Graded prediction of pollen deposition may help pollen allergic populations benefit from preventive interventions before onset.

The deposition kinetics of barium sulphate scale: model development

The deposition kinetics of barium sulphate scale: model development

Modelling particle deposition onto surfaces in historic buildings

A comprehensive model of indoor particle deposition onto surfaces of historic interiors was developed. The model takes into account the most important deposition processes observed in historic buildings: Brownian and turbulent diffusion, gravitational settling, turbophoresis, and thermophoresis. The developed model is expressed as a function of important parameters characterizing historic interiors: the friction velocity - capturing the effect of the indoor airflow intensity, the difference between the temperature of the air and the surface, and surface roughness. In particular, a new form of the thermophoretic term was proposed to account for an important mechanism of surface soiling driven by frequent large temperature differences between indoor air and surfaces in historic buildings. The form adopted allowed the temperature gradients to be calculated down to low distances from the surfaces and showed insignificant dependence of the temperature gradient on the diameter of particles, which yielded a meaningful physical description of the process. The predictions of the developed model agreed with the outcome of the previous models, in turn correctly interpreting the experimental data. The model was used in simulating the total deposition velocity in a small-size church taken as an example of a historic building, heated in the cold period. The model adequately predicted the deposition processes and proved to be able to map magnitudes of deposition velocities for specific surface orientations. The crucial effect of the surface roughness on the deposition paths was documented.

Zeolite associated with silicification in a volcano-sedimentary context, southern Brazil

In the Paraná Basin context, a volcano-sedimentary interaction is noticeable and some remarkable zeolite aggregates appear in the sediments deposited inside volcanic cavities (mega vesicles). Silicification is likewise associated with sediments. Consequently, analysis such as petrography, X-ray diffraction, Scanning Electron Microscopy, and mainly electronic microprobe confirmed the clinoptilolite. This type of zeolite, under the given conditions, is attributed to low temperatures and appears in a feature known as geodes with sediments. Clinoptilolite is formed from the alteration of the volcanic host rock. This alteration develops by dissolution, remobilization, and precipitation and can form silicification and zeolitization. The study of this association contributes to the understanding of post-magmatic processes, sedimentary processes, dissolution of the volcanic host rock, remobilization of silica, and then precipitation of silica and zeolite as cementation in the sediments. Since this feature is in the context of volcanic alteration rocks and intense fracturing, the framework suggests a permeable and porous system that contributed to processes like infiltration, transportation, silicification, and zeolitization as cementation. Furthermore, a formation and deposition model for the geodes with sediments feature is also suggested for this context.

Global nitrogen and sulfur deposition mapping using a measurement–model fusion approach

Abstract. Global reactive nitrogen (N) deposition has more than tripled since 1860 and is expected to remain high due to food production and fossil fuel consumption. Global sulfur emissions have been decreasing worldwide over the last 30 years, but many regions are still experiencing unhealthily high levels of deposition. We update the 2010 global deposition budget for reactive nitrogen and sulfur components with new regional wet deposition measurements from Asia, improving the ensemble results of 11 global chemistry transport models from the second phase of the United Nations Economic Commission for Europe's Task Force on Hemispheric Transport of Air Pollution (HTAP II). The observationally adjusted global N deposition budget is 114.5 Tg N, representing a minor increase of 1 % from the model-only derived values, and the adjusted global sulfur deposition budget is 88.9 Tg S, representing a 6.5 % increase from the modeled values, using an interpolation distance of 2.5∘. Regionally, deposition adjustments can be up to ∼ 73 % for nitrogen and 112 % for sulfur. Our study demonstrates that a global measurement–model fusion approach can improve N and S deposition model estimates at a regional scale, with sufficient availability of observations; however, in large parts of the world, alternative approaches need to be explored. The analysis presented here represents a step forward toward the World Meteorological Organization's goal of global fusion products for accurately mapping harmful air pollution deposition.

A particle deposition model considering particle size distribution based on the Eulerian approach

The problem of ash deposition on heat exchange surfaces is one of the main causes hindering the safe and efficient operation of conventional boilers. Hence, looking into the particle deposition characteristics on heat transfer surfaces as well as the formation process and the deposition mechanism is essential. In this study, a particle deposition model considering the particle size distribution based on the Eulerian approach is presented to predict the dynamic deposition process of multi-sized particles on the surfaces of heat exchange tubes. The model harnesses the advantages of the Eulerian approach and takes into account the particle size distribution as well as the interaction between them. By coupling computational fluid dynamics (CFD) analysis with the population balance model, and the embedding user-defined function code with the deposition model, the deposition characteristics of the multi-sized particles are predicted. It is established that the simulation findings of this model, as opposed to models for average-sized particles, are in greater accord with the experimental data by comparing the model predictions against published experimental results, with the average relative deviations are reduced by 9.28%, 8.11%, and 7.14%, respectively. The weighted average of the latter three dimensionless deposition velocities of multi-sized particles are all greater than those of average-sized particles. Moreover, the net deposition mass of multi-sized particles is 9.34% higher than that of average-sized particles.

Microdrilling Studies PLA/Bronze Composite Samples Printed Using Fused Deposition Model

Fused deposition models (FDMs) are the latest trends for constructing complicated and instinctive 3D printing. Polylactic acid (PLA) is the most widely used raw material in extrusion-based three-dimensional (3D) printing in many areas since it is biodegradable and environmentally friendly; however, its utilization is limited due to some of its disadvantages such as mechanical weakness and water solubility rate. To increase the mechanical properties of the FDM, nano bronze particles have been added as advanced research. Printing the hole less than a millimetre is complicated, and there is a limited report available in FDM. In this paper, polylactic acid (PLA) with a 14% bronze composite filament is made by hot extruding under the desired FDM conditions. The samples are built with 100% infilled density with 45° orientation to a sample size of 50 × 50 × 10 mm. To examine the printing state and the effect of microdrilling on the printed specimen, two different specimens are printed with and without holes. An industrial drill with specified feed, speed, and cutting width is used to perform the test. The size of the drilled hole is checked by scanning electron microscopy. The quality of the drilled hole and the wear of the tool is investigated and reported. According to the observation, it is noted that the secondary machining operation becomes unavoidable to have a hole of less than a millimetre. Machining, cutting speed, and feed speed influence the delamination zone and the circumference of the hole.