Agglomerate Model Research Articles

Reactive liquid-liquid test system ZnSO4/D2EHPA: Equilibrium, thermochemical, structural, and spectroscopic insights from experiments and density functional theory

The reactive liquid-liquid test system of the European Federation of Chemical Engineering (EFCE) ZnSO4/D2EHPA has been the subject of studies for decades. Although much information is known at a process engineering level, some is yet to be established from a fundamental chemical point of view. This is the case of the molecular structure of the zinc organocomplex formed at high loading conditions, which is still experimentally unproven due to the chemical similarities involved, as previous studies propose the formation of ZnR2 (breakage model) or (ZnR2)2 (agglomeration model) species. To gain further insight into such a classical hydrometallurgical system, two strategies were applied in this work using reported experimental measurements ranging from low to high loading conditions: equilibrium data fitting and computational chemistry by means of DFT calculations. Both analyses have pointed out that (ZnR2)2 is more favorable to be formed than ZnR2 species. The conclusions were supported by the revisited spectral, thermochemical, and equilibrium stoichiometry information. The bond and angle strain in the metal center seem to be among the main reasons behind the results. Moreover, the formation of D2EHPA dimers instead of monomers is crucial in order to guarantee reaction spontaneity.

A method for humidifying fine particles of coking coal: Agglomeration characteristics and dust dynamics analysis

The chemical agglomeration technology can effectively remove fine particles during coking coal loading and unloading. Aiming at the traditional agglomerator has the high price and secondary pollution problems, the new method of viscosifying fine particles was established. The fine particles were contacted with the soap solution through the cyclone circumfluence to increase viscosifying and agglomerate. The regulation and control of uniform humidification of whole particles were studied, and the relations among humidification, agglomeration, dust suppression and agglomeration conditions of fine particles were discussed. By establishing the agglomeration model and mechanical model, the influence of agglomeration on the force and velocity distribution of particles was analyzed based on CFD. The results showed that the soap solution has a strong effect on agglomeration of particle size less than 0.5 mm. The adsorption and flocculation of the polymer chain in the soap can promote the agglomeration of the fine particles. In the area of vortex formed by swirling air, with the mass addition ratio of soap powder increases from 5% to 15%, the coating efficiency of fine particles increases from 82% to 96%. The agglomeration results show that the average concentration of the fine particles decreases by nearly 20% finally.

CFD simulation of agglomeration and coalescence in spray dryer

Particle size distribution is of utmost importance in spray dryers. Controlling the degree of agglomeration and coalescence is vital for manufacturing products that conform to the requirements. To predict the particle size accurately, this study presents a CFD model of particle agglomeration and droplet coalescence in a counter-current spray dryer. The stochastic agglomeration model was modified to incorporate more realistic droplet-droplet, droplet-particle and particle-particle interactions. Binary droplet collisions in the atomization zone of a spray dryer can result in either coalescence or separation. The boundaries between collision regimes were experimentally determined, and existing binary collision models were validated for water and milk concentrate to include the effect of viscous forces on collision outcomes. A high-speed camera was used to record the kinematic and physical properties of the droplets to identify various collision regimes. A suitable model was then incorporated in CFD simulations of spray drying. Using existing experimental data from a counter-current spray dryer with strong agglomeration, it is shown that the model can accurately predict product particle properties under different process conditions.

Nonlinear vibration and instability of a randomly distributed CNT-reinforced composite plate subjected to localized in-plane parametric excitation

This study presents a semi-analytical formulation for the nonlinear vibration and dynamic instability of a randomly distributed carbon nanotube-reinforced composite (RD-CNTRC) plate. Three cases of localized in-plane periodic loadings are studied. The analytical stress fields within the RD-CNTRC plate for all the in-plane stress components (σij, (i, j = x, y)) are developed by solving the in-plane elastic problem using Airy's stress approach. The effective mechanical properties of the RD-CNTRC plate are evaluated by the Eshelby-Mori-Tanaka technique. The plate is modeled based on higher-order shear deformation theory (HSDT) in conjunction with the von-Kármán nonlinearity. Using Hamilton's principle, the governing partial differential equations (PDEs) are derived, whose approximate solution is sought, referring to the Galerkin method. The resulting nonlinear ODEs are solved using the Incremental Harmonic Balance (IHB) Method to compute the nonlinear vibration response of the RD-CNTRC plate. Further dropping the nonlinear terms, these ODEs are solved by Bolotin's method to trace the instability region. The proposed semi-analytical method is an effective strategy for studying the influence of different parameters such as agglomeration models, CNT mass fraction, pre-loading, and boundary conditions on the nonlinear vibration and dynamic instability characteristics of the RD-CNTRC plates. The reduced computational effort allows the design phase to be supported in selecting parameters when designing RD-CNTRC plates with stability and vibration requirements.

Does Industrial Agglomeration or Foreign Direct Investment Matter for Environment Pollution of Public Health? Evidence From China.

This article focuses on the interaction between China's industrial agglomeration, foreign direct investment (FDI) and environmental pollution of public health in the past 15 years. By conducting theoretical and empirical research, we try to reveal the relationship and mechanism between the economic growth and public health from the perspective of environmental pollution. By constructing an embedded theoretical model of industrial agglomeration and FDI, this article combines other environmental pollution influencing factors, expounds the impact mechanism of industrial agglomeration on environmental pollution. Based on the provincial-level panel data of China on environmental pollution and industrial agglomeration, the empirical test is carried out through the threshold panel regression model. According to the results, industrial agglomeration can significantly rectify the regional environmental pollution, thereby benefiting public health. FDI has a phased impact on the relationship between industrial agglomeration and environmental pollution. Specifically, when the level of FDI is low, the positive improvement effect of industrial agglomeration on environmental pollution is relatively strong. This is mainly because industrial agglomeration can promote economic growth, technological progress, and enhance environmental awareness. When the level of FDI exceeds the first threshold and continues to rise, the positive improvement effect of industrial agglomeration is maximized. Before the level of FDI exceeds the second threshold, this effect gradually weakens. The population concentration and excessive expansion of city scale brought about by industrial agglomeration will lead to the increase of regional resource and energy consumption, thus aggravating environmental pollution. The policy implication is that while the government and enterprises are vigorously increasing the level of foreign investment, they must pay equal attention to economic growth and public health, and the level of industrial agglomeration should match the level of foreign investment so as to give full play to the positive improvement effect of industrial agglomeration on environmental pollution, and realize the coordinated development of the regional economy, environment and population health.

Optimization of Transports in a Proton-Exchange Membrane Fuel Cell Cathode Catalyst Layer at High Current Densities: A Coupled Modeling/Imaging Approach

The heterogeneous nature of the cathode catalyst layer has been a major obstacle toward the comprehension of the mechanisms hindering the PEMFC performance at high current densities. To deconvolute these, an approach coupling multiscale modeling and multiscale electron microscopy characterization—allowing to move from the local to the cathode catalyst layer scale—is adopted. Here, an agglomerate scale model is developed and coupled with a MEA-scale model. Different structures are analyzed and the effects of certain structural parameters (Pt particle size, agglomerate structure and Nafion layer thickness) on the electrode performance are quantified and discussed. Reducing the Pt particle size is found to improve performance in most cases, though the improvement margin is highly dependent on the structure, and to a certain extent, on the particle spatial distribution. It is found that thickening the Nafion film is detrimental for performance only when the porosity is not sufficiently large. Performance gains upon structure rearrangement into an ideal-type structure (Nafion and pore tortuosities minimized to unity) are also quantified. These analyses have unvealed the main mechanism limiting performance when shifting to moderate/high current densities and allowed quantifying and ranking the physical phenomena hampering performance by order of importance.

Modelling Particle Agglomeration on through Elastic Valves under Flow

This work proposes a model of particle agglomeration in elastic valves replicating the geometry and the fluid dynamics of a venous valve. The fluid dynamics is simulated with Smooth Particle Hydrodynamics, the elastic leaflets of the valve with the Lattice Spring Model, while agglomeration is modelled with a 4-2 Lennard-Jones potential. All the models are combined together within a single Discrete Multiphysics framework. The results show that particle agglomeration occurs near the leaflets, supporting the hypothesis, proposed in previous experimental work, that clot formation in deep venous thrombosis is driven by the fluid dynamics in the valve.

A Monodisperse Population Balance Model for Nanoparticle Agglomeration in the Transition Regime.

Nanoparticle agglomeration in the transition regime (e.g. at high pressures or low temperatures) is commonly simulated by population balance models for volume-equivalent spheres or agglomerates with a constant fractal-like structure. However, neglecting the fractal-like morphology of agglomerates or their evolving structure during coagulation results in an underestimation or overestimation of the mean mobility diameter, , by up to 93 or 49%, repectively. Here, a monodisperse population balance model (MPBM) is interfaced with robust relations derived by mesoscale discrete element modeling (DEM) that account for the realistic agglomerate structure and size distribution during coagulation in the transition regime. For example, the DEM-derived collision frequency, , for polydisperse agglomerates is 82 ± 35% larger than that of monodisperse ones and in excellent agreement with measurements of flame-made TiO2 nanoparticles. Therefore, the number density, , mean, and volume-equivalent diameter, , estimated here by coupling the MPBM with this and power laws for the evolving agglomerate morphology are on par with those obtained by DEM during the coagulation of monodisperse and polydisperse primary particles at pressures between 1 and 5 bar. Most importantly, the MPBM-derived , , and are in excellent agreement with the data for soot coagulation during low temperature sampling. As a result, the computationally affordable MPBM derived here accounting for the realistic nanoparticle agglomerate structure can be readily interfaced with computational fluid dynamics in order to accurately simulate nanoparticle agglomeration at high pressures or low temperatures that are present in engines or during sampling and atmospheric aging.

Enterprise heterogeneity, agglomeration model, and urban exports: Evidence from Chinese cities and micro enterprises

Heterogeneous enterprise agglomeration is an important perspective in understanding urban exports and reshaping the new advantages of urban openness. This paper considers data from China’s industrial enterprises and municipality-level panel data from 192 cities to systematically examine enterprises’ heterogeneity, agglomeration patterns, and urban exports. The results reveal that: (1) the heterogeneity in enterprise productivity exhibits a significant promotional effect on urban exports in China’s central and northeastern regions, but not on its western regions; (2) specialized agglomeration positively affects exports in the central and western regions and in small and medium-sized cities, while diversified agglomeration significantly and positively impacts the eastern and northeastern regions and small and large cities; and (3) thresholds exist in determining the effects of agglomeration and sequencing on urban exports and their sequence by considering heterogeneity in enterprises’ productivity. This work provides important policy implications for the development of export trade in cities and countries by suggesting a focus on rational planning and adjustments to regional industrial policies, improvements to talent flow mechanisms, and construction of social infrastructures. HIGHLIGHTS Heterogeneous enterprise agglomeration can shape exports from city-based businesses A new simultaneous model determines how to increase urban exports Heterogeneity can have various impacts in different Chinese regions and cities Increasing productivity and exports requires strategic planning for optimization

Effect of Impeller and Gas Stirring on Agglomeration Behavior of Polydisperse Fine Particles in Liquid

Agglomeration, coalescence and flotation of non-metallic inclusions in steel melt are effective for obtaining “clean steel.” In this study, the agglomeration and breakup behaviors of particles with a primary particle size distribution (hereinafter, polydisperse particles) in a liquid under impeller and gas stirring were compared by numerical calculations and model experiments. The particle-size-grouping (PSG) method in the numerical agglomeration model of particles was combined with a breakup term of agglomeration due to bubble bursting at the free surface. Polydisperse and monodisperse polymethylmethacrylate (PMMA) particles were used in the agglomeration experiments. The agglomeration rate of the polydisperse particles under impeller stirring was increased by an increasing energy input rate, whereas the agglomeration rate under gas stirring decreased under this condition due to the larger contribution of the breakup of agglomerated particles during bubble bursting in gas stirring. At the same energy input rate, agglomeration of polydisperse particles was larger under impeller stirring than under gas stirring. The agglomeration rate of polydisperse particles was larger than that of monodisperse particles under both impeller and gas stirring at the same energy input rate. The computational temporal changes in the total number of particles were in good agreement with the experimental results. This means that the difference in the agglomeration behaviors observed in impeller and gas stirring can be explained by the turbulent coagulation and subsequent agglomerated particle breakup in gas stirring. The computational temporal change in the number of each group approximately agreed with the experimental change in both impeller and gas stirring.

Location of Airbnb and hotels: the spatial distribution and relationships

Ubicación de los hoteles y preferencias: distribución espacial y relacionesPropósitoEl propósito de este estudio es comparar la distribución espacial de Airbnb y los hoteles en Londres y examinar la relación entre los factores demográficos, socioeconómicos y ambientales y la oferta de estos dos tipos de oferta de alojamiento.Diseño/metodología/enfoqueLa información local de los anuncios de Airbnb en Londres se recopiló a través de Insideairbnb.com. Los datos recopilados se examinaron mediante análisis de autocorrelación geoespacial y modelos econométricos espaciales.ResultadosLos resultados indican que Airbnb predomina en las zonas aledañas a los atractivos turísticos populares y las zonas periféricas de la ciudad, mientras que en la zona centro Airbnb y los hoteles se encuentran en estado de convivencia. El modelo monocéntrico y el modelo de aglomeración podrían extenderse al contexto de la acomodación entre pares. La ubicación de Airbnb y los hoteles tradicionales se basa en diferentes factores.OriginalidadEste estudio amplía los modelos teóricos de ubicación de hoteles en el contexto de Airbnb y arroja luz sobre la distinción entre estos dos modelos comerciales en términos de factores de ubicación.Limitaciones de la investigaciónEl estudio se basa en datos secundarios debido a la disponibilidad de datos. Y se basa en el caso de Londres, por lo que los hallazgos pueden no reflejar la situación de las ciudades pequeñas y los destinos rurales.Implicaciones practicesLos hallazgos sugieren que las autoridades locales deberían prestar más atención a la seguridad laboral de las empresas profesionales y restringir los alquileres a corto plazo alrededor de las atracciones turísticas.

Innovation agglomeration and urban hierarchy: evidence from Chinese cities

ABSTRACT Innovation agglomeration leads to changes in the hierarchical structure of innovation, driving regional economic development. We establish a general equilibrium framework for urban innovation, that is to say, the process of production in a city can be divided into the knowledge production sector and final goods production sector. By this we explain the positive matching relationship between innovation agglomeration and a city’s position in the urban hierarchy (herein called urban tier). Then we empirically analyse 286 prefecture level Chinese cities to evaluate the impact of urban tier on innovation agglomeration using a two-way fixed effect model. To reveal the nonlinear relationship between urban hierarchy and innovation agglomeration, panel quantile and threshold regression models were also used. The main results show that: (1) The spatial structure of innovation in Chinese cities is consistent with the urban tier, and the urban tier plays a significant role in promoting innovation agglomeration. (2) Heterogeneous spatial structures of innovation among urban tiers are reflected in the higher agglomeration of innovation resources in high-tier cities, and the impact of city scale on innovation agglomeration is nonlinear. When the city scale reaches a certain threshold value, its impact on innovation agglomeration is significantly strengthened.

Multiscale modeling of proton exchange membrane fuel cells by coupling pore-scale models of the catalyst layers and cell-scale models

ABSTRACT Numerical models that accurately describe the nano/microscale transport phenomena in the proton exchange membrane fuel cells (PEMFC) are highly required. In this study, a multiscale PEMFC model is developed by coupling a pore-scale model for the catalyst layer (CL) and a cell-scale model. In the pore-scale model, oxygen transport and electrochemical reaction under different platinum loadings within porous agglomerates are simulated. The pore-scale model, as a sub-grid model, is then coupled into a two-phase and non-isothermal cell-scale model. The multiscale model developed successfully predicts the impact of Platinum loading on the limiting current density, while the traditional one with the classical agglomerate model fails to. Detail distributions of important variables including concentration, current density, and saturation are discussed. Furthermore, using the multiscale model, ionomer content is optimized to improve the cell performance as well as reduce the performance loss when Pt loading is reduced. It is demonstrated that multiscale model incorporating nano/microscopic transport phenomena is promising to more accurately reveal the coupling mechanisms of multiple reactive transport processes in PEMFCs.

The effect of agglomeration and slightly weakened CNT–matrix interface on free vibration response of cylindrical nanocomposites

Estimation of the effective homogenized properties is an essential step in the application of carbon nanotube (CNT)-reinforced composites. The difference between the experimental results and continuum-based homogenization schemes has motivated this work to present a modified Mori–Tanaka homogenization approach for CNT-reinforced nanocomposites. The agglomeration of CNT fibres in the matrix phase and slight weakening of the CNT–matrix interface are considered, which are incorporated in the effective homogenized properties of the nanocomposites using a two-parameter agglomeration model and interface spring-layer model, respectively. The nanotube fibres in the well-dispersed form are considered as cylindrical inclusions in the isotropic polymeric matrix. The bundled structure of CNTs is first modelled as cylindrical inclusions in the matrix and later as cumulative spherical inclusions in the hybrid matrix. Further, the effective material properties of nanocomposites are used to study the free vibration response of cylindrical panels reinforced with CNT fibres. Efficient higher-order shear and normal deformation theory is adopted, and fundamental natural frequencies are evaluated for a different set of agglomeration and interface weakening parameters using an analytical approach. The results show a significant reduction in the material stiffness as well as the natural frequency with increasing degree of agglomeration. At the same time, a slightly weakened interface is found less severe for stiffness reduction. An analysis of straight aligned CNTs highlighted their larger vulnerability to agglomeration than randomly distributed CNTs in the matrix.

ФРАКТАЛЫ В ИННОВАЦИОННОЙ КЛАСТЕРНОЙ МОДЕЛИ ПРОСТРАНСТВЕННОГО РАЗВИТИЯ ГОРОДСКИХ АГЛОМЕРАЦИЙ

The article proposes a model of cluster innovative development of urban agglomerations in the form of open closed rings using fractals. The existing dissipative properties of the space of urban agglomerations, such as openness, nonlinearity, instability, nonequilibrium, require transformations to preserve their structures. Fractals, possessing the property of self-similarity, allow organizing the territorial space of urban agglomerations based on the ability to build a territorial system from any part of its object (invariance). Since innovative elements are the basis for the development of urban agglomerations, it seems expedient to create an innovative cluster model in the geometric form of closed open rings, taking into account the already existing fractals, which are a local aggregate and interconnection, integrated into the system of urban agglomeration and carrying out innovative and technological activities based on technology parks or business incubators as elements of research and production infrastructure. When forming innovative clusters, it is necessary to take into account the location of functioning (existing) fractals when choosing places for the placement of innovative elements - the functional planning organization of an urban agglomeration. The classic version of the innovative cluster model of urban agglomeration may include the following belt-sectoral functional zones located from the center to the periphery: post-industrial, industrial, recreational, new. As a result, in the sectoral zones, depending on the functions performed, certain innovation clusters are formed. The proposed methodological approach includes qualitative indicators that must be taken into account when forming innovative clusters - innovative and technological activities of enterprises, professional personnel, financial instruments, investment field, transport and logistics infrastructure, research centers, a single information space, regional and local authorities. self-government. The formation and development of urban agglomerations on the basis of an innovative cluster model in the form of closed open rings using fractals makes it possible to achieve a synergistic effect due to nonlinear relationships and functional interconnection between business entities (cluster relationships), the capacity of a single market and the use of various resources, the formation of innovation centers and transport -logistic complexes, incl. in peripheral territories.

Polluting firms' location choices and pollution havens in an R&D-based growth model for an international emissions trading market

We investigate the effect of grandfathered permit allocation and abatement productivity for carbon emissions on growth rate, firms' location choices, foreign direct investment, and total pollution in an agglomeration model with innovation. We consider grandfathered permit allocation as potential rent. We find a distribution effect wherein increasing (decreasing) permit price raises (reduces) firms' rent, thereby stimulating (inhibiting) RD and the growth rate. Decreasing the permit level (improving abatement productivity) prompts firms to locate from the South (North) to the North (South) in the long run via this effect. Thus, our results imply that improving abatement productivity leads to support of the pollution haven hypothesis.

An Assessment of Thick Nanocomposite Plates’ Behavior under the Influence of Carbon Nanotubes Agglomeration

The influence assessment of carbon nanotubes (CNTs) agglomeration on CNT-reinforced composite (CNTRC) thick plates’ behavior is the main aim of the present work. CNTs are known to agglomerate into clusters even for relatively low volume fractions, which imposes the need to characterize the effects this may introduce in structures behavior, also knowing that recent works have concluded that neglecting agglomeration phenomenon may lead to an overestimation of the mechanical properties of nanocomposites. Hence, it matters to understand how the arising of these clusters may affect the static and free vibrational behaviors of low side-to-thickness nanocomposite plates. To this purpose, the nanocomposite plate properties’ estimation is performed by using the two-parameter model of agglomeration based on the Eshelby–Mori–Tanaka approach, while for behavioral analyses one considers a Higher-order Shear Deformation Theory (HSDT) based on the displacement field of Kant, implemented through the finite element method. The analyses developed consider a set of parametric studies involving the assessment of the influence of side-to-side ratios, side-to-thickness ratios, boundary conditions, and CNTs’ distributions along the thickness. The results obtained allow concluding that the transverse deflections and fundamental frequencies of these structures are significantly influenced by the CNTs’ agglomeration.

Development and validation of an agglomeration model for CFD simulations of aerosol dispersion in the frame of Fukushima fuel debris retrieval

ABSTRACT This article is devoted to demonstrate the feasibility of laser cutting technique for the fuel debris retrieval into the Fukushima Daiichi damaged reactors. IRSN is involved in a project led by ONET Technologies, in collaboration with CEA, to evaluate the risk occurred by the dispersion of aerosols emitted by the dismantling operations [4].During the laser cutting operations of fuel debris in air condition, particles will be produced, inducing a potential risk of dispersion into the environment. Hence, evaluating the fate of these particles after their emission is one of the safety key issues for these dismantling operations. In this objective, IRSN performed CFD simulations of dispersion of particles representative of inactive fuel debris simulants (1)(2)(3)(4).The first numerical results (5) showed a quite good agreement but some improvements were needed to take into account complex particle size distributions (PSD). Consequently, this article proposes an alternative method to better initialize the agglomeration calculation, in order to take account for different kinds of particle size distribution in the CFD simulations and to better evaluate the fate of aerosols produced by the debris cutting in the damaged reactors of Fukushima-Daiichi pedestal.

Fracture, aggregation and segregation in dry, granular flows

Particle fracture, the formation of small particles as the result of the breakage of large ones, and aggregation, the formation of large particles as the result of the combination of small ones, have important implications in industry (e.g. food processing, pharmaceutical production) and geophysics (e.g., snow avalanches and rock debris flows). Also, the presence of particles of different size that result from fracture and aggregation can induce segregation, resulting in the migration of large and small particles to different regions of the flow. Here, we formulate simple models for fracture and agglomeration and analyze the evolution of measures of the relative concentration of two sizes of spheres due the combined effects of fracture, aggregation, and segregation in dense, dry, granular flows. Particle breakage and combination is influenced by the frequency of collisions, by the local number density of the spheres, and by the particle kinetic energy. Segregation is predicted using a kinetic theory proposed by Larcher & Jenkins [2].

The development model of homestay tourism agglomeration in Yangtze River Delta from the L-R-D perspective

The development model of homestay tourism agglomeration in Yangtze River Delta from the L-R-D perspective