Diffusion Rules Research Articles

The diffusion of dust in a fully-mechanized mining face with a mining height of 7 m and the application of wet dust-collecting nets

In order to gain a more in-depth knowledge of the diffusion and pollution rules of dust from multiple sources in a fully-mechanized mining face with a mining height of 7 m, and design some effective dust-suppression measures. This study focuses on the No. 22305 fully-mechanized mining face in the Bulianta Mine, and employs CFD-Fluent software for conducting numerical simulations on the dust concentration's distribution in the respiratory zone on the footway. According to the results of the numerical simulations: due to an air leakage around the air-intake corner, the airflows in the goaf moved in a spiral pattern; they then moved stably in the goaf because of an air leakage between the hydraulic supports parallel to the coal cutter; the dust produced in the coal cutting and support movement processes were superposed on the leeward side of the coal cutter, and a dust belt, with a length of approximately 36 m and a concentration of over 2850 mg/m3, was formed; at 0–120 m on the leeward side of the coal cutter, the dust concentration at the respiratory height exceeded 1700 mg/m3 and exhibited no significant settlement along the way; and dust concentrations at the mining height range of 0–1.55 m and 5.55 m–6.80 m were higher than those at a mining height range of 1.55–5.55 m. Accordingly, a novel dust removal system, comprising wet roller-shutter, dust-collecting nets in the coal mining area and full cross-section, wet dust-collecting nets in the return airway, was designed. The field measurement results show that the overall dust-removal efficiency of this system was 69.6%.

Numerical simulations on airflow-dust diffusion rules with the use of coal cutter dust removal fans and related engineering applications in a fully-mechanized coal mining face

In order to achieve effective dust suppression during coal cutting process in a fully-mechanized coal mining face by using coal cutter dust removal fans, this study first conducted numerical simulations on the airflow-dustmigration rules. Then, by combining simulation results with experimental measurements and field tests, a novel hydraulic axial-flow dust coal cutter removal fan was developed. Simulation results demonstrated that, during the coal cutting process, high-concentration dust clusters exceeding 1000 mg/m3 were produced 0–20 m away from the coal cutter on the leeward side, which then spread to the operating space along the footway. After using dust removal fans, the concentration of the dust clusters on the leeward side of the coal cutter was reduced to below 500 mg/m3. The dust removal fans were then applied to the 3up705 fully-mechanized coal mining face at seven-five Coal Mine for field measurements. According to the measured results, the use of these dust removal fans can effectively reduce the dust concentration in the operating region around the coal cutter, and the dust removal rates of total dust and respirable dust reached up to 66.5% and 61.8%, respectively. Therefore, the dust removal fans performed well in terms of dust suppression in fully-mechanized coal mining faces.

Stability control of air pollutant diffusion in Weakly Decaying Delayed States

At present, the air pollution problem in our country is prominent and the air pollution is getting more and more serious. Air pollution poses a great threat to the life and health of everyone and the development of the whole society and economy. In order to effectively carry out the air pollution control, we need to accurately grasp the air pollutants in the air diffusion and migration rules, the use of aerodynamic model of weak attenuation of air pollutant particles diffusion model was studied, the Gaussian Diffusion Model The basic structure, the method of parameter determination and the secondary development of GIS were studied deeply. The mathematical model of air pollutant diffusion was constructed by the close coupling method. Furthermore, the aerodynamic analysis of air pollutant particles diffusion under weak decay conditions is given, and the decay control of air pollutants under steady meteorological conditions that are unfavourable to diffusion is pointed out. After visualizing the diffusion results, it can directly and accurately grasp the influence range of pollutants, provide strong support for the research and governance of atmospheric pollution, and at the same time, provide a scientific basis for emergency treatment of sudden atmospheric pollution incidents.

Micro-scale pollution mechanism of dust diffusion in a blasting driving face based on CFD-DEM coupled model.

In order to investigate the diffuse pollution mechanisms of high-concentration dusts in the blasting driving face, the airflow-dust coupled model was constructed based on CFD-DEM coupled model; the diffusion rules of the dusts with different diameters at microscopic scale were analyzed in combination with the field measured results. The simulation results demonstrate that single-exhaust ventilation exhibited more favorable dust suppression performance than single-forced ventilation. Under single-exhaust ventilation condition, the motion trajectories of the dusts with the diameter smaller than 20μm were close to the airflow streamline and these dusts were mainly distributed near the footway walls; by contrast, under single-forced ventilation condition, the motion trajectories of the dust particles with a diameter range of 20~40μm were close to the airflow streamlines, and a large number of dusts with the diameter smaller than 20μm accumulated in the regions 5m and 17~25m away from the head-on section. Moreover, under the single-exhaust ventilation, the relationship between dust diameter D and negative-pressured-induced dust emission ratio P can be expressed as P = - 25.03ln(D) + 110.39, and the dust emission ratio was up to 74.36% for 7-μm dusts, and the path-dependent settling behaviors of the dusts mainly occurred around the head-on section; under single-forced ventilation condition, the z value of the dusts with the diameter over 20μm decreased and the dusts with a diameter smaller than 7μm are particularly harmful to human health, but their settling ratios were below 22.36%. Graphical abstract The airflow-dust CFD-DEM coupling model was established. The numerical simulation results were verified. The migration laws of airflow field were obtained in a blasting driving face. The diffusion laws of dusts were obtained after blasting.

The effects of the installation position of a multi-radial swirling air-curtain generator on dust diffusion and pollution rules in a fully-mechanized excavation face: A case study

A great number of dusts are produced in the fully-mechanized excavation face during coal-cutting process. In order to block the dusts within the unmanned operating zone in front of the roadheader driver, this study combined FLUENT numerical simulation and field measurement for examining the dust's diffusion and pollution rules when both multi-radial swirling air-curtain generator and wet dust removal fan were used in the fully-mechanized excavation face; moreover, dust suppression performances when the generator was 5–50 m away from the head-on section (i.e., Lg) in the excavation face were investigated in depth. According to numerical simulation results, when Lg was 5–20 m, the diffusion distance of high-concentration dusts (with a concentration over 10 mg/m3) first increased and then decreased as the generator moved further away from the head-on section; when Lg was 14.8 m, dust pollution and diffusion were most serious; When Lg was 30.3–38.4 m, dust was diffused to the back of the roadheader driver, i.e., dust's diffusion and pollution cannot be effectively blocked in head-on region; When Lg was 20–30.3 m and Lg was 38.4 m, the generated dusts in coal cutting were significantly blocked within the range 5.88 m away from the head-on section, thereby exhibiting favorable dust-suppression performances; in particular, when Lg was 25 m, optimal dust-suppression performance can be obtained. Finally, the accuracy of the present numerical simulation results was validated by field measurement results.

Simulation experiments on the controllability of dust diffusion by means of multi-radial vortex airflow

In order to control the diffusion of dusts towards the working area in an excavation face, a novel multi-radial vortex wind generator was designed and developed in this study. Using a self-designed simulation system, the multi-radial vortex airflow migration and dust diffusion rules were experimentally investigated. As to the airflow migration, it was easier to form the dust suppression air curtains with uniform airflow distribution at a longer distance away from the head-on section (Lvortex), under smaller forced-to-exhaust ratio (Y), forced air flow rate (Qforced) and axial-to-radial-ratio (Z), with the airflow pointing to the head-on section. As to the control of dust diffusion, the dust concentration decreased gradually with the increase of Lsection. As the distance away from the head-on section increased, the control capacity of dust diffusion firstly weakened and then strengthened. The smaller values of forced-to-exhaust ratio and axial-to-radial ratio and the larger forced air flow rate would be beneficial to the control of dust diffusion. When the ventilation parameters were reasonably set, the airflow distribution of the dust suppression air curtain, the airflow direction and the hindrance on dust diffusion tended to be stable. Additionally, the optimal ventilation parameters were determined in this study, i.e., Lvortex = 20 m, Y = 5:4, Qforced = 200 m3/min and Z = 1:9. Under the optimal condition, the average removal ratios of total dusts and respirable dusts were as high as 96.02% and 95.51%, respectively.

Constitutive model for methane desorption and diffusion based on pore structure differences between soft and hard coal

This paper aims to improve the accuracy and applicability of gas diffusion mathematical models from coal particles. Firstly, a new constitutive model for gas diffusion from coal particles with tri-disperse pore structure is constructed by considering the difference in characteristics between soft coal and hard coal. The analytical solution is then derived, that is, the quantitative relationship between gas diffusion rate (Qt/Q∞) and diffusion time (t). The pore structure parameters of soft coal and hard coal from Juji coal mine are determined. Gas diffusion rules are numerically calculated and investigated by physical simulation methods. Lastly, the applicability of this model is verified. The results show that the homogeneous model only applies to the gas diffusion process of hard coal during the initial 10min. The calculation results from this model and the physical experimental results of soft coal and hard coal are nearly identical during the initial 30min.

基于Fluent模拟区域水体热污染预测研究

本文建立了一个用于预测评估电厂温排水对受纳水体水温分布影响情况的数学模型,通过对国内某电厂在河流夏季和冬季两种不利的水文条件下，就电厂运行正常工况和非正常工况两种情况下，对温排水进入水体后的水流运动及温度扩散规律进行了研究。研究发现：总体上，温排水的温升影响区域主要体现在排水口下游250 m以内，在河道中主要沿河道纵向扩散，在250 m后温升效应显著下降，温升影响范围明显变小，温度几乎与河流环境一致；而对不同季节的水文条件下，在温升明显区域影响范围内，夏季的温升影响比冬季温升影响要强，且其横向分布范围变大；就不同工况而言，温升范围影响变化不明显，但对温升范围影响变化而言，非正常工况下的温升影响效果相对较大。最后，通过模拟预测的结果与实测的实际结果对比，验证结果比较理想，说明本模型可以应用于相似的工程和研究，预测结果可以为电厂设计和环境评价提供科学依据。 This paper set up a mathematical model by power plant cooling water used for predicting water temper-ature distribution effect of receiving waters; based on a domestic power plant in the river in summer and winter which are unfavorable hydrological conditions, under the power plant running normal condition and abnormal conditions in both cases, the water movement and diffusion rules of cooling water after entering water temperature were studied. Research found that: overall, the cooling water influence area of the temperature rise is mainly manifested in the downstream port within 250 m, mainly along the river longitudinal dispersion in the river. After 250 m, the temperature rise effect significantly reduces; temperature influence range significantly decreases, and the cooling water temperature is almost con-sistent with the river environment. Under the hydrological conditions of different seasons, in the obvious temperature rise effect region, the influence of the temperature rise of summer is more obvious than winter, and the transverse distribution range of summer is larger. In terms of different working conditions, the temperature rise effect change is not obvious, but for the influence on the temperature range change, the temperature rise effect of the abnormal condition is bigger. Finally, through the actual simulation of the predicted and the measured results, the verification results are more ideal, demonstrating that this model can be applied to similar engineering and research, and prediction results can provide the scientific basis for power plant design and environment evaluation.

Parameter analysis and identification of the multiple-advanced manufacturing mode diffusion model

To better understand the development of advanced manufacturing modes in the competitive diffusion, this article analyzes and identifies the parameters of the multiple-advanced manufacturing modes diffusion model. First, considering the diffusion characteristics, the competitive multiple-advanced manufacturing modes diffusion model is described. Second, various parameters of the diffusion model are analyzed to reveal their influence on the diffusion process. Third, a parameter identification model and a further parameter identification algorithm based on an improved genetic algorithm are proposed. Finally, based on a practical application of the diffusion model, the parameter identification model is constructed, and optimized parameters are obtained for the multiple-advanced manufacturing mode diffusion model. And the resulting model output is compared and contrasted with real data. The proposed model and algorithm provide a new approach to the identification of parameters in the diffusion model, which allows us to better understand the diffusion rules, help enterprises to predict the diffusion status of advanced manufacturing modes, and provide a decision-making basis for enterprises and governments.

Controlling the coal dust at transshipment point: A study of the foam-sol foaming device

In order to effectively control the dust at the transshipment point with foam-sol, this paper attempted to study the characteristics of dust diffusion at transshipment point and the foam-sol foaming device with diffusion outlet was also designed in this paper. To study the diffusion rules of coal dust, fluent discrete phase model was utilized in the numerical simulation, as the coal dust was thrown down at a horizontal velocity of 2.5m/s. A foam-sol foaming device was designed, through which foaming agent could be automatically sucked into the Venturi by the negative pressure. The automatic controller was also equipped, which could transform the energy of the compressed air into the constant pressure difference so that the gelling agent could be qualitatively added into the gel container. The diffusion outlet that could spray out foam-sol in a continuous, conical and 3D manner was also designed. Moreover, this paper also carried out the contrast experiments on dust removal efficiency among water, aqueous foam and foam-sol. The results clearly show that the symmetrical whirlpools appeared below the inlet where the largest whirlpool diameter was 0.52m, and the horizontal distance from swirl range to the inlet was approximately 0.69m. By using the self-designed foaming device, the foaming was multiplied by 30 times and the volume ratio with water and foaming agent reached 95%:5%. In this context, the gas pressure was controlled at 0.3MPa, with gas flow at 15m3/h and water flow at 0.5m3/h, with water pressure controlled between 0.34 and 0.36MPa. The foam-sol has the highest dust removal efficiency than other agents.

REDOR constraints on the peptidoglycan lattice architecture of Staphylococcus aureus and its FemA mutant

The peptidoglycan of Gram-positive bacteria consists of glycan chains with attached short peptide stems cross-linked to one another by glycyl bridges. The bridge of Staphylococcus aureus has five glycyl units and that of its FemA mutant has one. These long- and short-bridge cross-links create totally different cell-wall architectures. S. aureus and its FemA mutant grown in the presence of an alanine-racemase inhibitor were labeled with d-[1-13C]alanine, l-[3-13C]alanine, [2-13C]glycine, and l-[5-19F]lysine to characterize some details of the peptidoglycan tertiary structure. Rotational-echo double-resonance (REDOR) NMR of isolated cell walls was used to measure internuclear distances between 13C-labeled alanines and 19F-labeled lysine incorporated in the peptidoglycan. The alanyl 13C labels in the parent strain were preselected for C{F} and C{P} REDOR measurement by their proximity to the glycine label using 13C13C spin diffusion. The observed 13C13C and 13C31P distances are consistent with a tightly packed architecture containing only parallel stems in a repeating structural motif within the peptidoglycan. Dante selection of d-alanine and l-alanine frequencies followed by 13C13C spin diffusion rules out scrambling of carbon labels. Cell walls of FemA were also labeled by a combination of d-[1-13C]alanine and l-[15N]alanine. Proximity of chains was measured by C{N} and N{C} REDOR distances and asymptotic plateaus, and both were consistent with a mixed-geometry model. Binding of an 19F-labeled eremomycin analog in the FemA cell wall matches that of binding to the parent-strain cell wall and reveals the proximity of parallel stems in the alternating parallel–perpendicular mixed-geometry model for the FemA peptidoglycan lattice. This article is part of a Special Issue entitled: NMR Spectroscopy for Atomistic Views of Biomembranes and Cell Surfaces. Guest Editors: Lynette Cegelski and David P. Weliky.

Random walk on lattices: graph-theoretic approach to simulating long-range diffusion-attachment growth models.

Interest in thin-film fabrication for industrial applications have driven both theoretical and computational aspects of modeling its growth. One of the earliest attempts toward understanding the morphological structure of a film's surface is through a class of solid-on-solid limited-mobility growth models such as the Family, Wolf-Villain, or Das Sarma-Tamborenea models, which have produced fascinating surface roughening behaviors. These models, however, restrict the motion of an incidence atom to be within the neighborhood of its landing site, which renders them inept for simulating long-distance surface diffusion such as that observed in thin-film growth using a molecular-beam epitaxy technique. Naive extension of these models by repeatedly applying the local diffusion rules for each hop to simulate large diffusion length can be computationally very costly when certain statistical aspects are demanded. We present a graph-theoretic approach to simulating a long-range diffusion-attachment growth model. Using the Markovian assumption and given a local diffusion bias, we derive the transition probabilities for a random walker to traverse from one lattice site to the others after a large, possibly infinite, number of steps. Only computation with linear-time complexity is required for the surface morphology calculation without other probabilistic measures. The formalism is applied, as illustrations, to simulate surface growth on a two-dimensional flat substrate and around a screw dislocation under the modified Wolf-Villain diffusion rule. A rectangular spiral ridge is observed in the latter case with a smooth front feature similar to that obtained from simulations using the well-known multiple registration technique. An algorithm for computing the inverse of a class of substochastic matrices is derived as a corollary.

Diffusion Behavior and Analysis of the Green Manufacturing Mode Under the Influence of Government

This paper deals with the competition diffusion model of the green manufacturing mode, as well as parameter analysis and identification of the model. The aim is to better reveal the diffusion rules of the green manufacturing and provide a new quantitative way to diffusion study on advanced manufacturing modes. First, considering the diffusion characteristics of the green manufacturing mode, the competition diffusion model of the green manufacturing mode is established. Second, the model is analyzed, and qualitative results are presented. Government influence parameter is analyzed to reveal its influence on the diffusion process. Third, based on a practical application of the diffusion model, a parameter identification model is proposed. A parameter identification algorithm based on genetic algorithm (GA) is proposed to obtain optimized parameters for the diffusion model. The resulting model output is compared and contrasted with real data. Finally, the application of the model is explained. The proposed model and algorithm disclose the diffusion rules of the advanced manufacturing modes, and provide a new approach to the identification of parameters in the diffusion model. This helps to understand the diffusion status of advanced manufacturing modes and provides a decision-making basis for enterprises and governments.

Distributed Adaptive Networks: A Graphical Evolutionary Game-Theoretic View

Distributed adaptive filtering has been considered as an effective approach for data processing and estimation over distributed networks. Most existing distributed adaptive filtering algorithms focus on designing different information diffusion rules, regardless of the nature evolutionary characteristic of a distributed network. In this paper, we study the adaptive network from the game theoretic perspective and formulate the distributed adaptive filtering problem as a graphical evolutionary game. With the proposed formulation, the nodes in the network are regarded as players and the local combiner of estimation information from different neighbors is regarded as different strategies selection. We show that this graphical evolutionary game framework is very general and can unify the existing adaptive network algorithms. Based on this framework, as examples, we further propose two error-aware adaptive filtering algorithms. Moreover, we use graphical evolutionary game theory to analyze the information diffusion process over the adaptive networks and evolutionarily stable strategy of the system. Finally, simulation results are shown to verify the effectiveness of our analysis and proposed methods.

Synchronous equilibrium model for the diffusion of mutually exclusive particles in a heterogeneous lattice of adsorption sites

Through straight synchronization and proper manipulation of a sequential Monte Carlo glass-forming rule introduced by Fröbose and Jäckle [J. Stat. Phys. 42, 551 (1986)], we constructed a synchronous, non-glass-forming rule for diffusion of mutually exclusive particles in a lattice of adsorption sites. The rule satisfies detailed balance in the presence of both homogeneous and heterogeneous adsorption energies. Our model differs from the usual lattice-gas cellular automata diffusion rules in that the mutual exclusion holds on the lattice sites rather than on the channels which connect neighboring sites, and from the mass-conserving cellular automata rules in the use of a no-partitioning scheme. The first aim of this work is to show that, although some prescriptions in the synchronous rule are introduced just to allow that both detailed balance and mutual exclusion can coexist with synchronicity, the diffusion process produced by the rule is not anomalous so that the rule can be regarded as a diffusion model. We then compare the diffusion isotherms of several test systems with the ones obtained by means of sequential Monte Carlo simulations of Arrhenius jumps of particles on a lattice. Finally, we apply the rule to the case of a (100) fcc model surface and estimate the amount of time correlation in the migration process, and show that the synchronous rule produces higher correlations and slightly lower diffusivity than the sequential Monte Carlo counterpart.

Research on competition diffusion of the multiple-advanced manufacturing mode in a cluster environment

This paper deals with competition diffusion of multiple-advanced manufacturing modes in a cluster environment, to reveal the competition diffusion rules of the advanced manufacturing mode. First, the influencing factors on advanced manufacturing mode diffusion in a cluster environment are analysed. Second, the diffusion properties and the diffusion mechanism are analysed, and the competition diffusion model of multiple-modes is established. Third, the model is analysed and the qualitative results are presented. Finally, the application of the diffusion model is exemplified and simulated (by matlab 7.1), producing results that are consistent with qualitative analysis that also verifies the correctness of the model. In addition, the influence of the cluster environment is discussed. The diffusion model helps enterprises understand the diffusion rules of the advanced manufacturing modes and provides a decision-making basis for enterprises and government.

Simulation of Structural Features of Atmospheric Boundary Layer of Chengdu Urban Agglomeration

In the present paper, features of the atmospheric boundary layer of Chengdu urban agglomeration were identified and transfer, diffusion and conversion rules of atmospheric pollutants in the boundary layer were analyzed by using the mesoscale meteorological model, WRF(Weather Research & Forecasting)to simulate the temporal and spatial distribution and features of the flow field, temperature field, humidity field, and atmospheric mixed layer height of Chengdu urban agglomeration. As a result, basic data were provided for developing the plan for the coordinated development of the urban agglomeration economy and environment. The simulation show that, in Sichuan Basin, south wind and east wind prevail on the near-ground surface and 850 hPa isobaric surface while west wind and southwest wind prevail on the 700 hPa isobaric surface. Under the influence of the mountains around the basin, the flow field on the near-ground surface forms circulation in the south of the basin. The atmosphere strongly exchanges in the vertical direction below 1500 m and the exchange becomes weaker upwards. The ground temperature field distribution is low in northwest and high in southeast. The urban heat island effect is obvious, and especially the “big heat island” occurs in the urban agglomeration. In winter, temperature inversion frequently happens. In terms of ground humidity field, in winter and spring, it is low in northwest and high in southeast, which is opposite in summer; in autumn, humidity is low in west and high in east. Regarding the mixed layer height of the study area, it reaches the minimum value in winter and the maximum value in summer; the daily mixed layer height reaches the maximum value between 14:00 and 15:00 and reaches the minimum value in the small hours.

MODELING OF THIN FILM GROWTH ON A TILTED MISCUT SUBSTRATE: STATISTICAL PROPERTIES AND THE OPTIMUM GROWTH CONDITIONS

Most studies of thin film growth simulations are performed on flat substrates. However, in reality, a substrate is usually miscut leading to a vicinal surface with a small tilt. The goal of this work is to study effects of an initial configuration of a miscut substrate on the grown film. The Das Sarma–Tamborenea model with modified diffusion rules is used for the simulations. The modification is done to allow variation in the surface diffusion length and mobility of adatoms. The results show that the optimum conditions that lead to step-flow growth are long diffusion length and small step height.

Spatial Coordination of Pervasive Services through Chemical-Inspired Tuple Spaces

To support and engineer the spatial coordination of distributed pervasive services, we propose a chemical-inspired model, which extends tuple spaces with the ability of evolving tuples mimicking chemical systems, that is, in terms of reaction and diffusion rules that apply to tuples modulo semantic match. The suitability of this model is studied by considering a self-adaptive display infrastructure providing people nearby with several visualization services (advertisements, news, personal and social content). The key result of this article is that general-purpose chemical reactions inspired by population dynamics can be used in pervasive applications to enact spatial computing patterns of competition and gradient-based interaction.

Chinese Calligraphy Brush Stroke Interactive Model with Ink Diffusion Style

This paper presents an interactive method of using ink diffusion, and gradually approaching simulation brush character with style of Chinese painting and calligraphy. Try to use materials based on the Chinese ink painting: ink and rice paper, according to their characteristics to build the diffusion rules to simulate text ink. Although the initial can show the phenomenon of ink rendering, they can only show diffusion of the ink with black lines, Can not rendering a complete ink diffusion behavior, it is difficult to form a sense of artistic calligraphy. It proposes Interactive model to amend the power of the brush pen and puts forward a binding behavior of ink broken down. The results show that based on the pratice physical meaning, considering the interaction of the two materials(ink and rice paper), appropriate to improve the mathematical equation model to render the calligraphy image more in line with Chinese ink painting style.