Agglomerate Model Research Articles

Assessing the impact of regional coordinated development on a low-carbon future: Evidence from the Beijing-Tianjin-Hebei Coordinated Development Strategy

The Beijing-Tianjin-Hebei Coordinated Development Strategy (BTHCDS) is an important way for China to explore the construction of an ecological civilization. Whether it can effectively reduce carbon emission (CE) not only affects the quality of the strategy’s implementation but also has important implications for optimizing the low-carbon development model of the urban agglomeration and advancing the “dual carbon” process of China. Based on the panel data between of 30 provinces between 2004 and 2019, this study employed the synthetic control method (SCM) to construct a counterfactual path and assess the impact of BTHCDS on CE reduction at both the whole regional and provincial levels. The results show that the BTHCDS has a positive leading role in shaping the region’s low-carbon future and can drive the overall CE reduction in the Beijing-Tianjin-Hebei region at an annual rate of 9.38%. Despite short-term fluctuations in implementation, the CE reduction effect of BTHCDS has shown a steady trend of expanding overall. The CE reduction effects of BTHCDS exhibit heterogeneity across individual provinces, but there is no “pollution haven.” This study enriches research on the effect of regional coordinated integration development on CE reduction and provides an important policy reference for low-carbon development in other urban agglomerations.

An aluminum agglomeration model based on realistic pocket distribution via microcomputed tomography

An aluminum agglomeration model based on realistic pocket distribution via microcomputed tomography

Influence of operating conditions on heat and mass transfer in PEMFCs with platinum loading random distributions

The catalyst loading random distribution has a divergent effect on heat transfer and electrical property inside fuel cells than the catalyst loading homogeneous distribution, but the effects of different stoichiometric ratios and average platinum loadings on electrical property, heat as well as species transfer in the fuel cell considering catalyst content random setting are still unclear. Hence, the impacts of stoichiometric ratios and average platinum loadings on the electrical property of fuel cell considering catalyst content random distribution are explored in this paper by using a steady state, two-dimensional, two-phase, non-isothermal fuel cell model coupled the catalyst layer agglomerate model considering the multi-scale problem of catalyst layer. Results indicate that stoichiometric ratio and average platinum loading do not influence the effect direction of catalyst content distributed randomly on the output power. However, with the stoichiometric ratio rising, the impact degree of catalyst content distributed randomly on the output power first enhances and then diminishes. When the stoichiometric ratio is 1.3, the power density of uniform random distribution changes the most, decreasing by 3.91 %. As the average platinum loading rises, the impact degree of catalyst content distributed randomly on the output power gradually decreases. The power density of uniform random distribution decreases by 4.93 % when the catalyst content is 0.2 mg/cm2. Furthermore, the variation trends of temperature distribution, product and reactant content with stoichiometric ratio and average platinum loading under the platinum loading random distribution condition are consistent with that under the platinum loading homogeneous distribution condition. However, as the stoichiometric ratio rises, the reaction rate distribution becomes more uniform for normal random and homogeneous distributions, but the reaction rate distribution becomes uneven under uniform random distribution.

Numerical study of proton exchange membrane water electrolyzer performance based on catalyst layer agglomerate model

In this work, a two-dimensional two-phase model of proton exchange membrane water electrolyzer (PEMWE) is developed, in which the catalyst layer (CL) is represented using agglomerate model. The effects of CL composition, porous transport layer (PTL) material properties and operating conditions on PEMWE performance are investigated. The results indicate that small size of catalyst agglomerate around 0.25 μm would benefit PEMWE performance. Appropriate increase of catalyst loading, porosity and ionomer volume fraction in the CL improves PEMWE performance, but their further increment leads to high mass transfer resistance, limiting the improvement of electrolyzer performance. The porosity and ionomer volume fraction of the catalyst layer are suggested to be lower than 0.5 and 0.6, respectively. The catalyst loading should be lower than 1.5 mg cm−2 when the CL porosity is higher than 0.3. The PTLs with high permeability, porosity and low contact angle is beneficial for the gas–liquid two-phase flow and avoiding the overheat and water shortage in the electrolyzer. Increasing the inlet velocity accelerates the bubble removal process, but might results in significant temperature drop, degrading the PEMWE performance. The most suitable temperature of inlet liquid is around 353.15 K. The results provide important guidance for the optimization design of high-performance PEMWE.

Effect of tapered porous ribs on the performance of Proton exchange membrane fuel cells

The conventional trench ridge structure suffers from the difficulty of removing liquid water and poor gas transport performance. The water removal and gas transport performance inside the flow field are enhanced by introducing a tapered porous rib flow field (TPRFF). In order to investigate the performance of TPRFF, a complex three-dimensional, multiphase, non-isothermal agglomeration model was developed using numerical techniques. The numerical results show that the TPRFF exhibits significant improvements in oxygen concentration distribution, oxygen distribution uniformity and water removal compared to a conventional parallel flow field (CPFF). In addition, the dissolved water content remained almost constant while the liquid water saturation was lower. The study also investigated the effect of different cathode exit heights on the performance of the fuel cell using TPRFF. The results showed that the net power density increased by 14.0 %, 11.9 %, 8.7 %, and 1.5 % for outlet heights of 1.3 mm, 1.0 mm, 0.7 mm, and 0.4 mm, respectively, while it decreased by 27 % for an outlet height of 0.1 mm. Finally, the effect of different stoichiometric ratios on cell performance was also investigated in the novel flow field.

Evaluating the Governance Ability of Urban Public Health Using EM-AHP-TOPSIS Method: A Case Study in China.

Evaluating the governance capacity of urban public health is the key to improving the level of urban public health. We aimed to evaluate the governance ability of urban public health. An index system of governance ability of urban public health was established. The governance ability of urban public health was evaluated, and major constraints against the ability improvement were analyzed through the EM (Entropy Method)-AHP (Analytic Hierarchy Process)-TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) model and data of urban agglomeration in Yangtze River Delta, China in 2023. Shanghai, Nanjing, Hangzhou, Suzhou, and Ningbo rank top 5 in terms of governance ability of public health, and they are in the first echelon. Hefei, Yancheng, Wuxi, Taizhou and Shaoxing rank 6-10, and they are in the second echelon. The remaining 17 cities are in the third echelon. Major sources of governance ability of urban public health and major factors that decrease governance ability are Medical Facility (A12), Health Improvement (A33), Medical Staff (A13), Government Ability (A11), and Health Loss (A34). For urban agglomeration in Yangtze River Delta, China, public health foundations, environmental exposure risks, public health performance, and public health emergencies all can influence the governance ability of public health. Accurate evaluation of the governance ability of urban public health can provide guidance and policy propositions to improve the governance system of public health and improve the emergency coordination ability of the government.

Design, analysis and development of a proton exchange membrane in fuel cell

This research presents the design and fabrication of a Proton Exchange Membrane fuel cell (PEMFC) utilising open pore cellular metal foam as the material for the flow plate. Efficient housing designs are suggested for both the hydrogen and oxygen sides, achieved by implementing. The study identifies the flow regime via the open pore cellular metal foam flow plate using Computational Fluid Dynamic (CFD) modelling and analysis techniques. Energy, environmental and economic analyzes (4E) and multi-objective optimization of a PEM fuel cell equipped with coolant channels Energy analysis of a proton exchange membrane fuel cell (PEMFC) with an open-ended anode using agglomerate model: A CFD study A transient heat and mass transfer CFD simulation for proton exchange membrane fuel cells (PEMFC) with a dead-ended anode channel. This research can provide appropriate references and recommendations for future Proton Exchange Membrane Fuel Cell (PEMFC) flow channel designs. The performance improvements of flow channel designs become significant at elevated current density, and with the output voltage increasing to 25.8 %. The estimated performance power of the fuel cell was 6 W, meaning that it was unlikely that the 10 W target would be achieved. In reality, the designs proved to have an excellent open circuit voltage of over 0.9 V, however, the maximum current achieved was below the target, and thus limiting the power to only about 2.1 Watts. The purpose of this paper is to give a general theoretical guidance for current and future relevant R&D activities aiming at high-performance, durable, and low-cost fuel cells as well as a thorough overview of the issues, advancements, and perspectives of the flow-field designs for bipolar plates in PEMFC.

Late Pebble Accretion of Comet 81P/Wild 2 Nucleus: Evidence from a Plagioclase-bearing Chondrule Fragment, Pyxie

Comet 81P/Wild 2 is a ∼4.5 km-sized primordial object that almost has not been modified by internal heating by 26Al decay. Its nucleus could have been formed by hierarchical agglomeration or gravitational collapse of pebble swarms concentrated by streaming instability. To shed light on the cometesimal formation mechanism from laboratory sample analysis, we reexamined the 26Al–26Mg isotope systematics of the plagioclase-bearing fragment, Pyxie (from Wild 2 track 81), with significantly improved analytical precision. The revised upper limit of the initial (26Al/27Al)0 of Pyxie is ≤1.5 × 10−6, 2 times smaller than those estimated from other Wild 2 fragments. Assuming homogenous distribution of 26Al in the early solar system, the minimum crystallization age of Pyxie is estimated to be >3.6 Ma after calcium–aluminum-rich inclusions. Additional petrologic examination demonstrated that it is a chondrule fragment formed in disk environments enriched in moderately volatile elements comparable to the Si-rich rim of CR chondrules before accreting by comet Wild 2. The late accretion of the Wild 2 nucleus with most silicates likely from a common source are not favored by the hierarchical agglomeration model that considers early and continuous accretion. Instead, the results are more in line with comet formation by gentle gravitational collapse of pebbles when the 26Al abundance is extremely low (26Al/27Al ≤ 1.5 × 10−6) before gas dispersal.

Attraction Agglomeration and Destination Agglomeration: The Case of Chinese National Scenic Areas

We examine the effect of attraction and destination agglomerations on tourism revenues and tourist flows. Using data from 184 national scenic areas in China for the 2012 to 2017 period as the case study for our two-level agglomeration model, we find that the attraction agglomeration yields cooperative competition at the micro level of tourist districts. This co-existence of compatible and competitive effects determines not only individual national scenic areas’ tourism revenues and tourist flows but also the attractiveness of tourist districts where these national scenic areas are located. At the macro level of tourism destinations, we find that the destination agglomeration only yields a competitive effect, adversely affecting the tourism revenues and tourist flows of individual national scenic areas inside these tourism destinations. Our results suggest that policymakers must consider cooperative competition when managing existing tourist attractions and planning for future ones.

Numerical Simulation of Effects of Catalyst Layer Parameters on Heat Transfer in Proton Exchange Membrane Fuel Cells

A non-isothermal, two-dimensional, two-phase fuel cell agglomerate model is used, and studies are done on how platinum loading and catalyst layer thickness affect heat transfer in fuel cells. Results indicate that as the cathode platinum content and catalyst layer (CL) thickness rise, the electrical property is improved. The maximum power density corresponding to the platinum loading of 0.40 mg/cm2 increases by 8.92% compared with 0.20 mg/cm2, and the maximum power density corresponding to the CL thickness of 17.5 µm increases by 4.63% compared with 10.0 µm. Temperature variation trends in CLs from entry to exit and inside the cell along the thickness direction do not change. Furthermore, with the CL thickness as well as platinum content increasing, the temperature increment inside cathode gas diffusion layer as well as CL is more obvious, and temperature distribution uniformity within the cell deteriorates. The impact of platinum loading on the temperature in the cell is more obvious than that of CL thickness. In the selection about platinum content and thickness of CL, temperature distribution uniformity and electrical property should be weighed.

Research progress and prospects on agglomeration models and simulation methods of aluminum particles in aluminum‐based composite propellants

Research progress and prospects on agglomeration models and simulation methods of aluminum particles in aluminum‐based composite propellants

The Impact of New-Type Urbanization Policy on Urban Green Total Factor Productivity: New Evidence from China

China’s new-type urbanization has been instrumental in fostering high-quality economic and social progress. This research explores the impact and underlying mechanisms of the new-type urbanization policy on urban green total factor productivity (GTFP) by analyzing a sample of 165 Chinese prefecture-level cities from 2009 to 2020. Utilizing the difference-in-differences (DID) approach, the study uncovers several key findings: (1) compared to non-pilot areas, the new-type urbanization policy significantly boosts urban GTFP by 43.5%, supporting a shift towards more sustainable and eco-friendly urban growth; (2) the analysis of impact mechanisms indicates that these policies enhance urban GTFP through technological innovation and environmental regulation; and (3) the urban agglomeration model test reveals that being part of an urban agglomeration amplifies the effects of the new-type urbanization policy on GTFP. These results underscore the significance of these policies in driving sustainable and high-quality urban development in China, offering valuable insights for policymakers to formulate and implement effective urbanization strategies.

Проблемы и перспективы развития межбюджетных отношений в городских агломерациях России

The development of urban agglomerations is an urgent direction of the state policy of the Russian Federation in the field of territorial development. The purpose of this article is to identify current problems in the sphere of budgetary interaction within urban agglomerations and to develop approaches to building an optimal system of inter-budget relations in different agglomeration models. Among them we can distinguish the traditional model (in which the core is an urban district, the satellite zone — municipalities located in the same subject of the Russian Federation), the interregional model (municipalities forming an agglomeration are located in several subjects of the Russian Federation) and the model of agglomeration formed around a city of federal significance. The result of the study is a set of proposals for building interrelated measures in the field of inter-budget relations aimed at creating conditions to stimulate agglomeration processes. The proposals include recommendations for certain amendments and additions to the current budgetary legislation in order to adapt the instruments of inter-budget regulation to the needs of territorial development.

Using a three-dimensional computational fluid dynamics model and an agglomerate model to investigate the effect of varying agglomerate parameters and output voltages on proton exchange membrane fuel cell performance

Modeling of proton exchange membrane (PEM) fuel cells is attracting more attention as fuel cell technology continues to develop. In this study, we considered a hybrid model that combines an agglomerate model based on the agglomeration of catalyst particles and the coverage-dependent kinetic equation of platinum oxide for ORR, and another 3D numerical model of a PEM fuel cell based on computational fluid dynamics (CFD). The obtained results from our developed models were validated with experimental results from literature. In fact, we investigated the effects of changing the agglomerate radius (Ragg), the ionomer volume fraction within the agglomerate (Yi,agg), the effective agglomerate surface area (Ai,agg), the distribution of the gases and the temperature on the cell performances.The results revealed that the cell performances are strongly influenced by changing Ragg and Yi,agg for medium and high current densities: The activation loss increases with increasing Ragg and decreasing Yi,agg. Also, Ai,agg increases with decreasing Ragg and increasing Yi,agg. In addition, the PEM fuel cell's power output is significantly enhanced when Ragg is decreased and Yi,agg is increased, the optimal power being obtained for values of Ragg=100nm and Yi,agg = 0.6. The numerical results also showed that decreasing the output voltage from 0.95V to 0.35V can accelerate the electrochemical reaction process.

Premature agglomeration?: Two phases of development with spatial sorting

AbstractClusters in the developing world do, to a large extent, attract low‐educated individuals, and these clusters are in some cases, characterized by urbanization without industrialization. This contrasts starkly to clusters in advanced economies that attract high‐skilled individuals and entrepreneurs. In this paper, we develop a model of agglomeration and spatial sorting that is consistent with these two types of different agglomeration processes in developed and developing countries. We show that a poor country that has an agglomeration with low skilled individuals, may get stuck in this equilibrium, but that free mobility of human capital from the outset nevertheless is superior from the perspective of total social welfare.

Land as a binding constraint to cluster-based development in Ethiopia: To cluster or not to cluster?

As one of the agglomeration models targeting cluster-based rural development, cluster farming has been promoted in Ethiopia and it is already reported to have significant welfare implications, but participation rates are not as high as expected. This study examines the role of land as a constraint to the development of cluster-based development in Ethiopia both using extensive and intensive measures of cluster farming. The study further disaggregates farm households based on their farm size to better understand potential heterogeneities in the relationship between farm size and cluster farming. The paper also documents other household socio-economic and network characteristics that may matter in cluster farming. We use a large-scale farm household data from 3,969 households coupled with some expert insights on cluster farming in Ethiopia. Households in the study areas grow major staples such as maize, wheat, teff, malt barley, and sesame in four main regions of Ethiopia. We employ a double hurdle model to examine both the decision to participate and the extent to which households participate in cluster farming. By extent of participation, we refer to the amount of land and share of land farm households contribute to cluster farming. For robustness purposes, we also estimate the Tobit and Linear Probability Models. We show a positive association between farm size and cluster farming both at the extensive and intensive margins. This relationship turns negative for large amounts of land. This shows that cluster farming increases with farm size up to a threshold beyond which it declines. We also find suggestive evidence that participation rates are lower for small-scale farms, but also declines for large-scale farms. In addition, we show that access to information and network characteristics also matter in enabling cluster farming. The findings of this study are relevant in the framework of plans to upscale the cluster-based development initiative in Ethiopia. Attention to landholding issues is key and may be an important area where policy action can be geared to boost cluster farming. Moreover, our results inform potential targeting plans that aim to increase the participation of small-scale farmers who are usually the intended targets of such programs.

A water pollution haven hypothesis in a dynamic agglomeration model for fisheries resource management

A water pollution haven hypothesis in a dynamic agglomeration model for fisheries resource management

Research on the mechanism and policies of polycentric agglomeration for promoting the upgrading of China's position in the global production value chain

Recently, with the increasing trend of anti-globalization, China's manufacturing industry has encountered instability in the supply of upstream products in international trade, a challenge that has given rise to an urgent demand for ways to improve China's position in the global production chain. In response to this challenge, the 14th Five-Year Plan puts forward the strategic goal of building multi-level, multi-node, networked city clusters and trade powerhouses, which provides new development opportunities for China to strengthen its position in the global production chain through the model of polycentric agglomeration. In order to gain a deeper understanding of the impact of polycentric agglomeration on the position of enterprises in the global production chain, this project will use the instrumental variable estimation method to conduct an empirical study. This method can help us accurately identify the causal relationship between polycentric agglomeration and global production chain position and assess the differential impact of different agglomeration patterns on firms' production chain position. Through this study, we expect to reveal how polycentric agglomeration can enhance firms' global production chain positions through mechanisms such as optimizing resource allocation, promoting technological innovation, and strengthening industrial chain synergies. In addition, we plan to explore the impact of polycentric agglomeration on the evolution of firms' roles in global value chains and on international trade competitiveness. The objective of this study is to provide targeted recommendations for policymakers and enterprises to help them achieve high-quality development of China's manufacturing industry by optimizing the structure of polycentric agglomeration in the context of global production chain restructuring. Through this comprehensive study, we expect to provide scientific decision support and action guidelines for China's sustainable upgrading and competitiveness enhancement in global production chains.

Method for predicting the size of Ni1/3Mn1/3Co1/3(OH)2 particles precipitated in a stirred-tank semi-batch crystallizer using CFD and particle agglomeration models

NixMnyCoz(OH)2 is widely used as a precursor for the cathode active material LiNixMnyCozO2 in lithium ion batteries, and the precursor size, which determines the size of the active cathode material, affects the characteristics of lithium-ion batteries. This paper proposes a method for predicting the particle size of Ni1/3Mn1/3Co1/3(OH)2 precipitated by semi-batch reaction crystallization. The distribution of supersaturated components formed in the reactor varies with the reactor scale, feed conditions of the raw material solution, and agitation conditions. Therefore, the method presented in this paper considers the effects of these conditions on particle growth. First, to identify the turbulent dispersion and concentration distribution of the supersaturated components formed in the reaction crystallizer, a computational fluid dynamics (CFD) model was constructed consisting of the governing equations of hydrodynamics and the mass balance equations of the supersaturated components considering the production by neutralization and consumption by precipitation. Next, a model of agglomeration was constructed that focused on the balance of the binding and breaking up energies for the particle pairs. The binding energy was quantified based on the bridging between particle pairs by surface deposition. The breaking up-energy was quantified based on the hydrodynamic forces when the agglomerate passes through the impeller. These models were fitted using experimental results for the final average size of the Ni1/3Mn1/3Co1/3(OH)2 secondary aggregate, which was precipitated in a small-scale stirred-tank type semi-batch reaction crystallizer. The models predicted the experimental results of the final average size in a large-scale crystallizer, with the feeding conditions of the raw material solution and stirring conditions as experimental parameters, within ±20%. The models may be used to analyze semi-batch reaction crystallization systems of NixMnyCoz(OH)2 of any composition by adjusting the model parameters according to the procedure developed in this study.

Monte Carlo modeling of particle agglomeration during polymer pyrolysis in bubbling fluidized bed

During the bubbling fluidized bed polymer pyrolysis process, the agglomeration of inert materials frequently leads to defluidization. To simulate this phenomenon, a novel time-driven Monte Carlo model is presented, which comprises two main stages: the layering period and the agglomeration period. The simulation results are then compared with experimental data from literature. From a qualitative analysis perspective, the simulation results effectively replicate the trends in defluidization times under various operating conditions. In terms of quantitative analysis, the predicted defluidization times exhibit a good consistency with the measured values (R2=0.804). Furthermore, information extracted from the simulation, which is hard to obtain experimentally, is applied for further discussion. It allows to explore the composition of bed materials at the defluidization moment under different operating conditions. Additionally, a comparison of particle size distributions at same operational time under various operating conditions is performed. In general, the developed model provides a robust foundation for extending its application to other polymer pyrolysis processes as well as co-pyrolysis processes.