Agglomeration Characteristics Research Articles

Coupling Coordination Relationship between Cultural Landscape Conservation and Socio-Economic System in Ethnic Villages of Southeast Guizhou

Amidst the transition from agriculture to tourism, ethnic villages are facing issues of “misalignment” and “disequilibrium” between economic growth and cultural heritage conservation. Previous research has often isolated the effects of cultural heritage conservation or socio-economic development, neglecting their reciprocal influences within the coupling coordination. This study addresses this gap by assessing 43 villages in Leishan County, quantifying the preservation status of the cultural landscape (PSCL) and socio-economic level (SEL) using a comprehensive evaluation model and revealing the coupling coordination relationship between PSCL and SEL in each village with the coupling coordination degree (CCD) model. Spatial autocorrelation and the geographical detector model reveal the spatial agglomeration characteristics and influential factors of the CCD. The results highlight three findings. (1) The majority of villages (93%) are in a moderate imbalance stage or a serious imbalance stage, underscoring an urgent need for targeted policies. (2) Spatial autocorrelation analysis exposes significant clustering, with the northwest corner exhibiting the most pronounced high-value aggregation, which contrasts with the southern region’s low-value clustering. A ‘low–high’ clustering pattern is observed in the northern region, while the southwestern corner presents a ‘high–low’ distribution. (3) Key determinants affecting the CCD include the tourism revenue, tourist volume, resident participation in tourism, village hollowing level, and number of historical buildings. The interactions between driving factors show non-linear and two-factor enhancement effects. This study concludes with policy recommendations advocating for context-specific strategies to enhance the CCD, emphasizing the importance of aligning cultural preservation with economic progress in ethnic villages.

Spatiotemporal Distribution and Regional Imbalance of China’s Digital Economy

The digital economy is an important driving force for promoting national economic growth and achieving high-quality economic transformation, and is a key force in achieving the sustainable development goals (SDGs). This paper measures the digital economy development level of 30 provinces in China from 2013 to 2021 utilizing the entropy of weighting approach, and in order to further reveal its intrinsic laws and differences, it uses three-dimensional kernel density analysis, the Dagum Gini coefficient, spatial autocorrelation analysis, and cold hot spot analysis to explore the spatial and temporal evolution characteristics of the digital economy and its regional imbalance. The empirical results show that ① China’s digital economy has been steadily increasing, spatially showing the characteristics of gradual decrease from east to west and from coast to inland, with obvious spatial agglomeration characteristics and an increasing trend. ② There are obvious regional imbalances in the digital economy, with the southeast coastal region leading significantly. ③ The overall regional differences are large but reduced, mainly from intra-regional differences, the and inter-regional contribution is low. The research in this paper provides data support for revealing the spatial and temporal evolution characteristics of digital economic development and provides new path support for the balanced development of China’s regional digital economy.

Spatiotemporal Characterization of the Three-Dimensional Morphology of Urban Buildings Based on Moran’s I

The three-dimensional morphological analysis of urban buildings constitutes a pivotal component of urban planning and sustainable development. Nevertheless, the majority of current research is two-dimensional in nature, which constrains the comprehensive understanding of urban spatial–temporal evolution. The existing body of three-dimensional studies frequently fails to consider the temporal dimension of architectural change and lacks a detailed examination of micro areas such as communities and streets. In order to accurately identify the patterns of spatial–temporal evolution in urban architectural morphology, this study focuses on the Yau Tsim Mong District in Hong Kong, utilizing three-dimensional data. By innovatively integrating temporal factors, constructing a spatial–temporal weight matrix, and applying the spatial–temporal Moran’s I, this study conducts an in-depth quantitative analysis of Coverage, Staggeredness, and Duty Cycle at the community scale, neighborhood scale, and urban scale. From 2014 to 2023, the global spatial–temporal Moran’s I of key urban morphology indicators in Yau Tsim Mong District has exhibited a marked increase, underscoring the close interrelationship and significant optimization between urban morphology and overall development. The findings illustrate that urban architecture is undergoing a process of agglomeration and high homogeneity, with strategic shifts emphasizing efficient spatial utilization and refined design. The analysis at the neighborhood scale is of particular importance, as its independent and complete spatial structure effectively captures local dynamics, revealing high-value agglomeration and low-value dispersion characteristics. This suggests that buildings in the Yau Tsim Mong District are being constructed in a more compact manner at the neighborhood level, which reflects the precision and efficiency of urban planning and the rationality of spatial planning. These significant findings provide valuable references for the development planning and governance of sustainable cities. They enhance urban governance capabilities and promote the optimization of urban development strategies, ensuring steady progress on the path of efficiency, harmony, and sustainability.

Priority Intervention Evaluation of Community Regeneration in Megacities Based on the Business Improvement District (BID) Model: A Case Study of Tianjin, China

This study aims to start from the macroscale of the megacity, explore a top-down operational technical path from the identification of community regeneration units as the evaluation objects to the BID priority intervention evaluation, and then propose differentiated community regeneration strategies based on the BID model. In the post-epidemic era, it is necessary for global megacities to take new measures in urban regeneration to respond to worldwide changes and challenges. As an innovative tool to promote central city revitalization, the BID model has played an important role in community transformation. In the context of the continuous decentralization of population and industry in China’s megacities, it is urgent to explore the technical path to apply the BID model to local community regeneration. Given the shortcomings of existing studies in the method to identify the scope of BID implementation and evaluate intervention priorities, this study takes Tianjin, a megacity in China, as an example and uses DBSCAN (density-based spatial clustering of applications with noise) and service area analysis to define the community regeneration units with commercial agglomeration characteristics as the objects. Then, the BID priority intervention evaluation system is constructed from the two measurement aspects of the intervention potential and the necessity of community regeneration to classify the BID intervention priorities of community regeneration units. The main conclusions are as follows: 1. When the DBSCAN analysis parameters take the minimum number of elements as 30 and the search distance as 120 m, the result is most suitable for identifying community units with commercial agglomeration of the study area; 2. Population vitality, especially working and residential population density, is the key factor affecting BID intervention potential, while road network density is an important indicator for determining the necessity of community regeneration; 3. Community regeneration units with high BID priority levels need to develop differentiated regeneration strategies combining their BID intervention potential, regeneration necessity characteristics, and location attributes. These conclusions can provide references for the governments of megacities to screen and establish BIDs.

Temporal and Spatial Distribution Characteristics of Inbound Tourism Flow in Guangxi, China

The D-Q model was used to analyze the temporal and spatial distribution characteristics of inbound tourism flow in Guangxi by collecting index data from 2011 to 2019. The results showed that the temporal and spatial distribution of inbound tourism flow presented obvious single-core agglomeration characteristics. The polarization was serious, and the phenomenon of "poverty trap" became more and more obvious. The regional imbalance was prominent. The quantity and quality coordination of inbound tourism flow was poor. The spatial dislocation phenomenon appeared. The overall distribution pattern of inbound tourism flow might remain stable, and the number of cities maintaining a stable state presented a relatively large proportion. Finally, some countermeasures were put forward to promote the development of inbound tourism in Guangxi.

Spatial and Temporal Dynamics of Homestays on Chongming Island: A Systemic Analysis in the Context of World-Class Eco-Island Development

As the development of world-class eco-islands progresses, the homestay sector on Chongming Island has burgeoned, emerging as a pivotal catalyst for rural tourism and economic prosperity. This study, leveraging Chongming Island as a case study, systematically analyzes the spatiotemporal distribution of homestays across island-wide, township, and village scales, employing methodologies such as the spatiotemporal evolutionary tree model. It delves into the intricate systemic framework underpinning homestay development, elucidating the dynamics of interaction mechanisms. Furthermore, it examines the evolving roles of diverse stakeholders throughout various developmental phases, grounded in stakeholder theory. The study reveals that (1) Chongming’s homestays on the island, townships, and village scales show very obvious agglomeration characteristics, mainly concentrated in the A-level scenic spots and in and out of the island traffic junction. (2) The growth of homestays in Chongming shows an increasing trend year by year, with the growth rate slowing down after 2020, and can be divided into four main phases, which are closely related to the construction phase of the eco-island. (3) The evolution of Chongming Island’s homestay is a multifaceted natural–human system intricately shaped by a confluence of five interdependent subsystems: natural ecology, social culture, multiple stakeholders, geographical location, and transport infrastructure. At different stages of development, under the synergistic effect of multiple stakeholders, the homestays on Chongming Island eventually formed a governance structure led by the government and co-managed by the development company, external entrepreneurs, and local villagers. These insights not only augment the scholarly discourse on stakeholder dynamics within the homestay industry but also offer pragmatic enlightenment for strategic planning and the advancement of holistic urban–rural integration in Chongming and the broader Shanghai region.

Evolution and zoning of the "production-living- ecological" spatial pattern in the coastal urban agglomeration of Guangdong, Fujian and Zhejiang

Clarifying the spatial differentiation patterns and evolutionary characteristics of urban territories is the basis and prerequisite for enhancing regional spatial governance capacity and realizing sustainable urban development patterns. In order to make up for the inadequacy of the existing coastal urban agglomerations of Guangdong, Fujian and Zhejiang in the exploration of regional evolutionary characteristics and zoning. Based on the theory of production-life-ecology space, the land use data from 2010 to 2020 are used to analyze the land space pattern and evolution characteristics of urban agglomeration by applying the methods of transfer matrix, kernel density analysis, and comparative advantage index. The results show that: (1) the ecological space continued to decrease and the area of production space and ecological space continued to increase. (2) The high-value areas of production space show multinuclear diffusion, the high-value areas of ecological space are mainly distributed in a faceted manner, and the living space are distributed in a band along the coastline. (3) The entire urban agglomeration was categorized into six types of land function zones based on the comparative advantage indices of the three spaces at the county scale.

Wetting and aggregation mechanisms of coal molecules via XTG and SDBS based on molecular simulation

To study the interaction process of sodium dodecyl benzene sulfonate (SDBS) and xanthan gum (XTG) molecules in a composite dust suppressant and its influence mechanisms on the wettability and agglomeration characteristics of bituminous coal dust, Material Studio software was used to establish water–XTG binary system models, water–SDBS–XTG ternary system models, and water–SDBS–XTG–coal quaternary system models. Then, molecular dynamics simulations were performed through angular distribution, relative concentration distribution, mean squared displacement (MSD), and interaction energy to study the interaction mechanism between SDBS and XTG and the change in wettability of coal dust. Results showed that the configuration in the binary system changed after stabilization, and SDBS transformed from a disordered state into a directional arrangement with the head group oriented toward the liquid phase and the tail group oriented toward the gas phase. In the ternary system, the head group of SDBS interacted with the XTG molecules, and the XTG wound into a helical structure, reducing the viscosity of the solution. With an increase in the number of SDBS molecules, the angle of the head group of SDBS and the tail chain of SDBS increased to 113.95°. The number of H bonds in the system increased from 1676 to 1697. In the quaternary system, the rate of change of the diffusion coefficient continuously increases. The absolute value of the interaction energy increased from 5920.48 kJ/mol to 9295.35 kJ/mol. The higher the concentration of SDBS, the better the adsorption effect, and the more stable the molecular configuration. The number of H bonds and the distribution area of the overlapping region between water and coal gradually increased, indicating that the larger the area where water molecules could penetrate into the coal molecules, the better the wetting effect on coal. This study reveals the intermolecular interaction process and the mechanisms of coal dust wetting and agglomeration in a composite dust suppressant. It provides theoretical support for the application of this composite dust suppressant.

Land Green Utilization Efficiency and Its Driving Mechanisms in the Zhengzhou Metropolitan Area

Improving land green use efficiency is of great significance for promoting high-quality economic development and promoting the modernization of harmonious coexistence between humans and nature. In this study, the super-efficiency SBM model with non-expected output was used to measure the level of land green use efficiency at county scale in the Zhengzhou metropolitan area from 2005 to 2020. Based on this, the spatio-temporal evolution and spatial agglomeration characteristics were analyzed. Finally, the driving mechanisms were revealed by using the geographical detector model. The results were as follows: (1) From 2005 to 2020, the land green use efficiency of the Zhengzhou metropolitan area fluctuated from 0.5329 to 0.5164, with an average annual decline rate of 0.21%, exhibiting three stages: decline, rise, then another slight decline. At the city level, Luohe City had the highest land green use efficiency, while Zhengzhou City had the lowest. (2) The land green use efficiency of the Zhengzhou metropolitan area showed a significant spatial positive correlation, Moran’s I index increased from 0.1472 to 0.2991, and the spatial agglomeration effect was continuously enhanced. On the local scale, high-high (H-H) aggregation and low-low (L-L) aggregation were dominant, high-high (H-H) aggregation areas were mainly distributed in the southwest and southeast of the Zhengzhou metropolitan area, and low-low (L-L) aggregation areas were mainly distributed in the central and western parts of the Zhengzhou metropolitan area. (3) There is heterogeneity in the degree of influence of different driving factors on land green use efficiency in the Zhengzhou metropolitan area, which is ranked as topographic relief (X7) > forest coverage rate (X8) > social consumption (X6) > industrial structure (X3) > urbanization rate (X2) > economic development (X1) > industrial added value scale (X5) > financial expenditure (X4). q values were 0.1856, 0.1119, 0.1082, 0.0741, 0.0673, 0.0589, 0.0492 and 0.0430, respectively. The interaction of two factors can enhance the explanatory power of land green use efficiency in the Zhengzhou metropolitan area. Except for the interaction of topographic relief and forest coverage rate, the other factors all show double factor enhancement. The explanatory power of the interaction between topographic relief and urbanization rate is the strongest, at 0.3513. In the future, policy regulation should be carried out from the perspectives of the interaction of social and economic conditions such as improving forest coverage rate, improving consumption power, optimizing industrial structure and improving land green use mechanisms to promote the improvement of land green use efficiency.

Spatiotemporal Response of Ecosystem Service Value to Land Use Change in the Lanzhou-Xining Urban Agglomeration over the Past 20 Years

With rapid urbanization and human activities exacerbating threats to the degradation of various ecosystem services in modern urban agglomerations, the exploration of the state of ecological security at the scale of urban agglomerations is of great significance. This study considered the Lanzhou-Xining Urban Agglomeration as the research area, based on the land use data in 2000, 2005, 2010, 2015, and 2020. At the same time, the landscape ecological risk index was introduced. The land use change characteristics of the Lanzhou-Xining Urban Agglomeration were analyzed by using the land use transfer matrix, the value per unit area equivalent factor method, and the bivariate spatial autocorrelation analysis method to elucidate the impacts of the changes in the ecological risk index induced by the land use transition on the value of ecosystem services. This study analyzed the land use change characteristics of the Lanzhou-Xining Urban Agglomeration and elucidated the impacts of changes in the ecological risk index on the value of ecosystem services caused by land use transformation. The results showed that:① During the period from 2000 to 2020, the land use types of the Lanzhou-Xining Urban Agglomeration were mainly dominated by grassland, cropland, and forest land. The construction land area had expanded significantly mainly from cropland and grassland, and the six land use types had strong cross-transformation. The total area of land use change was 6 646.05 km2. ② In terms of spatial changes, the spatial pattern of ecosystem service value in the Lanzhou-Xining Urban Agglomeration had not undergone obvious transformation. However, the regional variability was significant, generally showing the distribution characteristics of high in the northwest and low in the southeast. ③From the perspective of temporal change, the value of ecosystem services in the Lanzhou-Xining Urban Agglomeration showed an upward trend, with the total flow of value increasing from 186.459 billion yuan to 192.156 billion yuan, with a total value-added of 5.697 billion yuan. ④ There was a rising trend in the overall ecological risk index of the Lanzhou-Xining Urban Agglomeration over the past 20 years. Low ecological risk areas and lower ecological risk areas dominated the ecological risk areas. There was a significant positive correlation between the value of ecosystem services and the ecological risk index. This study aimed to reveal the understanding of the impacts of land-use practices on ecosystem service values and ecological risks, to provide important references for regional ecological risk management and land-use policy formulation, and thus to promote the high-quality development of the ecological environment in the Yellow River Basin.

Agglomeration Characteristics and Influencing Factors of Urban Innovation Spaces Based on the Distribution Data of High-Tech Enterprises in Harbin

In the knowledge economy, innovation is playing an increasingly important role in urban sustainable development. Thus, how to strengthen the construction of innovation spaces has become a significant issue. Based on data from high-tech enterprises in the central urban area of Harbin, this study analyzes the distribution, agglomeration characteristics, and influencing factors of urban innovation spaces. The influencing factor index system was constructed based on four aspects: innovation support, service facilities, the social environment, and the natural environment. After analyzing these influencing factors through comparing the results obtained with an ordinary least squares (OLS) model and a geographical weighted regression (GWR) model, the GWR model was determined to have a better fitting effect and was thus used for further analysis. The findings are as follows: (1) Five closely related clusters of innovation spaces are identified. Innovation space has a significant agglomerating distribution pattern. (2) Overall, factors supporting innovation and transportation station factors have a positive effect on the agglomeration of innovation spaces, while natural environment factors have a negative effect on small innovation areas. (3) By region, the aggregation of innovation spaces in downtown areas is slightly negatively affected by service facilities, whereas those in the Harbin New District are mainly supported by policies and those in the Pingfang District are positively affected by the quantity of the labor force. Finally, based on the research results, some suggestions are put forward to promote the development of urban innovation spaces. This paper has certain guiding significance for optimizing and improving the construction and development of urban innovation spaces.

The Spatial and Temporal Distribution, Flow Network and its Characteristics of Population in Henan Province

Based on the WorldPop center population data set and the dynamic monitoring data of China 's floating population, this paper analyzes the spatial and temporal changes of regional population and the characteristics of flow network and its influencing factors with the help of ArcGIS spatial analysis and mapping function and geographic detector model. It shows that: The regional difference of population spatial distribution in Henan Province is obvious and extremely uneven, and the population agglomeration speed of Zhengzhou metropolitan zone is obviously accelerated. The regional differentiation of population change in Henan Province is serious, and the population attraction of Zhengzhou is increasing, The population of Undertake industrial transfer zone such as Shangqiu and Zhoukou continued contraction. The population growth area and the population contraction area are more concentrated in space, showing the characteristics of spatial agglomeration. In addition, economic factors are still the main driving factors of population change in Henan Province. The influence of service industry on population change is increasing, and the explanatory power of traditional agriculture, forestry, animal husbandry and fishery and manufacturing industry on population change is decreasing. The integrated development of secondary and tertiary industries will further affect the future population distribution pattern of each region.

Structural Evolution and Its Determinants of Domestic Value-Added Network of Digital Service Exports Based on Temporal Exponential Random Graph Model

ABSTRACT Digital service trade has become an important engine of world economic growth, and its competitive landscape is also evolving. We construct domestic value-added networks of digital service exports (DVAN-DSEs) from 1995 to 2018 based on the world input-output table, and explores their structural evolution and determinants using Temporal Exponential Random Graph Model. We find that (a) the DVAN-DSEs present the features of agglomeration, heterogeneity, reciprocity and unevenness. (b) The United States and European countries are the core in DVAN-DSEs. (c) Preference attachment, structural embeddedness, delayed reciprocity, stability, variability, Matthew effect in GDP, population and Internet coverage, geographical proximity, cultural similarities, and regional trade agreements play important roles in the evolution of DVAN-DSEs. (d) Structural embeddedness and geographic proximity only facilitate new relationship construction, while other factors influence both relationship establishment and maintenance. Countries should build network facilities, expand trading partners and promote trade agreement negotiations to facilitate the development of digital service trade.

Carbon emission reduction enabled by informatization construction: an analysis of spatial effects based on China's experience.

The "dual-carbon" objective presents a huge challenge for China and the world, with profound implications for the advancement of China's eco-friendly economy. Additionally, informatization development has a significant impact on the level of carbon emissions in both local and neighbouring regions. Therefore, we employ panel data from 30 provinces in China spanning the years 2012 to 2021, and use the Kernel density estimate and Moran's index to explore informatization level and carbon emissions space agglomeration characteristics. We elucidate the nonlinear relationship and heterogeneity between informatization improvement and carbon emissions based on the spatial Durbin model. The primary findings are as follows. Firstly, we discover a distinct spatial clustering phenomenon which the informatization level is high in coastal areas and low in inland areas, whereas carbon emissions are low in the south and high in the north. Secondly, the effect of the informatization level on carbon emissions is shown as a U-shaped and non-linear correlation, signifying inhibitory and subsequently promoting phases. Thirdly, we reveal the negative influence on carbon emissions caused by spatial lag terms of the informatization level, and find that a higher local informatization level will have an inhibitory effect on carbon emissions in neighbouring areas. Finally, there is a spatial heterogeneity in the impact of the informatization level on carbon emissions, which presents the U-shaped relation between informatization level and carbon emissions varies across the North-South subregion and the three major economic subregion of China.

Multiscale structure analysis of a pH-responsive gelatin/hydroxypropyl methylcellulose phthalate blend using small-angle scattering

HypothesisHydroxypropyl methylcellulose phthalate (HPMCP) is an enteric polymer that has been employed in drug delivery systems to delay the release of the encapsulated active pharmaceutical ingredients through its pH-responsive solubility change. This has been recently demonstrated as an effective means for delaying the drug release from gelatin/HPMCP hydrogels at gastric pH values. However, structural characteristics of HPMCP agglomeration in gelatin/HPMCP hydrogels is not well understood thus limiting further tailoring of their material properties. ExperimentsWe investigated the multiscale structure of a gelatin/HPMCP hydrogel (1:1 by weight) between pH 2 and 6 at 37 °C, i.e. above the upper critical solution transition temperature of gelatin, using small-angle X-ray scattering and contrast-variation small-angle neutron scattering to understand the pH-responsive structure of HPMCP and the cross-correlation between gelatin and HPMCP. FindingsAgglomeration of HPMCP between pH 2 and 4 was evidenced by the formation of mass fractal structures, with a fractal dimension ranging from 1.5 to 2.7, comprising primary particles with a radius of gyration ranging from 70 to 140 Å. Blending with gelatin influenced the fractal structure of HPMCP and the primary particle size. Gelatin and HPMCP exhibited negative cross-correlation in all probed length scales and pH values, which was attributed to volume-exclusion interaction in a double-network-like solution architecture.

Exploring Ecological Management Plans for Typical Systems in Arid Areas from the Perspective of Ecosystem Service Value Evolution

Ecological management zoning plays a significant role in optimizing resource utilization, improving ecosystem service function, and promoting coordinated regional development. Taking Hexi Corridor as a representative region of the Mountain–Oasis–Desert composite system in arid regions of Asia, this study analyzed the spatial and temporal evolution of ecosystem service values and explored the influencing mechanism based on the optimal parameters-based geographical detector model. We have comprehensively divided ecological management zones and proposed corresponding control strategies. The results show that (1) the Hexi Corridor is characterized by regional differentiation, which is composed of three systems: The southern mountain system, central oasis system, and northern desert system. The mountain system is mainly composed of forestland and grassland, the oasis system is mainly composed of cropland, and the desert system is mainly composed of unused land. The conversion of land use mainly involves the conversion of unused land to cropland and grassland, while grassland is mainly converted to cropland. (2) The ecosystem service value of the Hexi Corridor increased significantly and demonstrated agglomeration characteristics in space. The highest value areas are mainly distributed in the southern mountain, with higher value and medium areas mainly distributed in the central oasis, and the lowest value areas are mainly located in the northern desert. (3) Socio-economic factors greatly influence the spatial differentiation of ecosystem service values in the Hexi Corridor, with natural environmental factors having less impact. Additionally, the internal interaction of natural environmental factors is the most significant. (4) The Hexi Corridor is divided into three ecological management zones: Ecological function protection zone, ecological and agricultural coordinated development zone, and ecological and urbanization coordinated development zone. This research has important reference value for global ecological management in arid regions.

Study on the impact of APAM residue on the settlement characteristics of coal slurry agglomerates

ABSTRACT Residual dosage has a significant impact on the settling characteristics of coal slurry flocs and the sedimentation efficiency of coal slurry. This study conducted sedimentation stirring experiments to measure the supernatant grayscale, floc size, settling velocity, and residual anionic polyacrylamide (APAM) under varying energy inputs. The investigation focused on the correlation between different levels of APAM residual and the settling characteristics of coal slurry flocs. The results show that having APAM residuals in the first three stages helps with sedimentation. This leads to lower residual levels, higher grayscale in the supernatant, bigger floc sizes, and better settling velocities. However, in the fourth stage, as APAM residual levels increased once more, the supernatant grayscale decreased linearly, floc breakup became severe, and settling velocities neared stagnation. In the second stage, a correlation was noticed between higher APAM residual levels and better settling properties of coal slurry flocs. By studying residual dosage and energy input, guidance on how to optimize the sedimentation efficiency of the thickener and reduce dosage can be provided.

Investigation of aluminum particle ignition dynamics in various propellant environments

The ignition delay of aluminum particles can be profoundly influenced by the agglomeration and combustion characteristics of solid propellants. In this experimental study, the ignition of individual aluminum particles in nitrate ester plasticized polyether (NEPE) and hydroxyl‑terminated polybutadiene (HTPB) propellant atmospheres was examined using laser ignition tests and high-speed photography. Focus was directed at the effects of the atmospheric composition, pressure, and aluminum particle size (500, 800 and 1000 µm). It was observed that the non-homogeneous reaction heat generation and convective heat exchange rates during particle ignition could be increased by increasing the CO2 content or ambient temperature, resulting in a shorter ignition delay time. This explains why aluminum particles tended to burn more efficiently in nitrate ester plasticized polyether than in hydroxyl‑terminated polybutadiene. In addition, it was found that the ignition delay time decreased with increasing pressure and was inversely proportional to the particle size squared. An ignition model for aluminum particle ignition in a multi-component atmosphere was developed and validated to describe the temperature change and energy transfer during ignition. The calculated ignition delay times were found to be within 5% of the experimental values. The model also showed that increasing the ambient temperature was more effective than increasing the CO2 content at enhancing ignition, and that CO2 was more effective than O2, which was itself more effective than H2O. Overall, this study provides useful insight into the ignition characteristics of aluminum particles in different propellant environments. The results could be used to develop more effective propellant formulations, optimize combustion processes, and improve safety in the handling and use of aluminum-based propellants.

Spatio–Temporal Dynamic Characteristics and Driving Mechanisms of Urban Compactness in Central China

As a result of rapid urbanization in China, the spatial restructuring of towns and cities has significantly impacted urban compactness. The study of the spatio–temporal characteristics and driving mechanisms of urban compactness in central China is a strategic imperative and conducive to promoting regional sustainable development that is based on easing the contradiction between land resource supply and demand and reducing energy consumption. Therefore, this study focused on 80 prefecture-level cities in central China, utilizing barycenter model and GTWR model, among others, to analyze the spatio–temporal evolution pattern of urban compactness from 2006 to 2020 and its driving factors, with the aim of uncovering the intrinsic mechanisms behind enhancing urban compactness in the area. The results show the follows: (1) The urban compactness in central China has generally shown an upward trend, with a pronounced spatial clustering around provincial capital cities and the spatial changes in compactness predominantly concentrated in the north–south direction. (2) Various factors have influenced urban compactness, where government intervention and population aggregation present as bi-directional driving factors, while the effective use of land resources and high-quality industrial development, among others, present as positive driving factors. The spatio–temporal heterogeneity and agglomeration features of each driving factor are significant. (3) Further analysis indicates that the effective use of land resources is the primary factor in enhancing urban compactness, followed by technology. Therefore, we should adhere to the concept of compact cities and gradually promote the compactness of cities in central China based on the impact of the driving factors.

Effects of land utilization transformation on ecosystem services in urban agglomeration on the northern slope of the Tianshan Mountains, China

Land utilization transformation (LUT) is a key factor affecting ecosystem services (ESs). The urban agglomeration on the Northern Slope of the Tianshan Mountains (UATM) is located in a typical arid region with extremely fragile ecological environment. However, the impact of LUT on the spatial pattern of ESs in the region over the past 20 years is not clear. This study aimed to explore LUT characteristics of the urban agglomeration on the UATM using a land transfer matrix, information entropy, land utilization intensity, and land utilization dynamic degree. Various ESs indexes were quantitatively measured using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model, and the effect of LUT on ESs was revealed through a geographic detector and spatial auto-correlation analyses. The results of this study led to the following conclusions: First, between 2000 and 2020, the primary land utilization types in UATM were arable land, grassland, and bare land, with significant cross-transformations occurring among these types. Meanwhile, LUT showed marked differences among different regions. LUT changed rapidly and significantly in the central region; in contrast, slower and slight changes were observed in the northern and southern regions. Second, during the research period, habitat maintenance, water yield and carbon sequestration decreased, and the soil retention function increased. The accelerated urban development in the second decade led to more rapid changes in ESs. Finally, both the structure and intensity of land utilization showed the strongest explanatory capability for changes in ESs. Different dimensions of LUT showed significant interactions with ESs. Therefore, it is advisable to guide LUT scientifically, promote vegetation restoration projects, alleviate the impacts of human activities and climate change on ESs, and enhance the ecological safety and environmental sustainability of UATM and even arid regions in Central Asia.