Dynamic Evolution Characteristics Research Articles

Multilayer networks for measuring interconnectedness among global stock markets through the lens of trading volume-price relationship

Using daily data spanning from 5 January 2004 to 22 November 2022, we quantify the spillover effects between 42 global stock markets. Specifically, combining causal structure learning and Elastic-Net-VAR methods, we innovatively construct multilayer causal networks based on volume-price relationship. Then, we analyze the network characteristics of multilayer spillover networks from system and market levels. Our findings indicate that there is heterogeneity in risk spillovers of price and volume networks, highlighting how trading volume spillover network play an important role in the risk contagion. Furthermore, multilayer interconnected networks confirm the risk spillovers between volume and price, and it exhibits significant differences compared to single-layer network. In addition, at system-level, each network layer shows unique network structures and dynamic evolution characteristics. At market-level, global stock markets play different roles in emitting or receiving shocks through various transmission channels. Our study emphasizes the importance of intra- and inter-layer risk propagation in multilayer networks based on volume and price, and has significant implications for developing investment strategies and global portfolio risk management.

Spatial Analysis and Prediction of Ecological Welfare Performance: Evidence from 284 Prefecture-level Cities in China

The general debate of the 78th session of the United Nations reaffirmed the importance of the Sustainable Urban and Community Development Goal (SDG 11), however, the pervasive accounting gaps still lead to significant challenges in the monitoring and evaluation of SDG 11 indicators. This paper focuses on ecological welfare performance accounting, aiming to assess the weaknesses and internal gaps of regional SDG 11 at the aggregate level, so as to promote eco-city planning and management, improve the well-being potential of urban residents, and reduce the adverse impact on the ecological environment. Taking China as a developing country as a case, the two-stage DEA model is used to measure the ecological welfare performance of 284 cities in China from 2007 to 2022, and the spatiotemporal pattern of efficiency at each stage of the ecological welfare transformation process is described, a modified gravitational model is constructed to transform the "attribute data" of ecological welfare performance into "relationship data", and the characteristics of network structure are described with the help of social network analysis, and the formation mechanism of the spatial correlation network of ecological welfare performance is revealed and its dynamic evolution characteristics are revealed through the spatial Markov chain.

Ethnic diversity and divergent perceptions of climate change: a case study in Southwest China

Understanding divergent perceptions of ethnic groups to climate change in mountainous regions home to multi-ethnic cultures and the factors influencing these perceptions is crucial for policymakers to predict the trending impacts of climate change and make long-term decisions. Based on the case of Southwest China, 1216 households were interviewed by questionnaire surveys to gain insight into the perceptions of local people on the dynamic evolution characteristics of climate events in the uplands of Yunnan, China, which is an area home to rich ethnic diversity, and also to determine the factors that influence these perceptions. Results indicated that climate events have now become important events for farmers’ livelihoods, ranking only after family diseases and livestock diseases. Drought, long-term drought, and erratic rainfall are the three kinds of climatic events with the most significant increase in frequency and severity in mountainous areas. Farmers’ perceptions on whether drought, long-term drought, and erratic rainfall occurred 10 years ago as well as changes in frequency and severity are significantly influenced by characteristics of respondents, ethnic culture, geographical environment of farmer residences, farmland characteristics, and sources of livelihood. Ultimately, taking ethnic differences into consideration for long-term planning will be an important part of the local response to climate change in the future.

River valley urban network and morphology: A study on the urban morphology evolution of Lanzhou.

The present study investigates the dynamic evolution characteristics of urban spatial morphology by analyzing real road network data from 2000, 2010, and 2020, along with nighttime lighting data employing spatial analysis methods and spatial syntax models. Accordingly, two separate dimensions of urban morphology: internal and external, are covered. First, the integration and synergy of interior morphology features are analyzed using spatial syntactic modeling. Subsequently, the spatial compactness, fractal dimension, and level of center of gravity shift of the city are assessed by combining the nighttime lighting data with the earlier dataset. This analysis facilitated the deep exploration of the spatiotemporal evolution of the city's external morphology. Building upon this foundation, the interaction between the "internal and external" domains was analyzed further. The main findings of the study reveal a synchronous pattern of urban expansion throughout the evolution of urban spatial morphology. Furthermore, the urban form was observed to undergo a progressive transformation, transitioning from a "single core" morphology to a "primary and secondary double core" morphology. Over time, this development progressed and evolved into a "belt-like multi-core" structure. Additionally, the coupling characteristics further validate the relationship between the structure of the road network and the urban morphology in river valley-type cities. In particular, accessibility of dense and horizontally distributed transportation network was found to significantly influence the spatial development of these cities. As observed, the findings provides valuable insights into understanding the characteristics of internal and external associations regarding urban spatial patterns.

Experimental investigation on liquid length of direct-injection ammonia spray under engine-like conditions

The utilization of ammonia fuel in internal combustion engines holds significant promise in achieving carbon neutrality objectives. High-pressure direct injection technology offers precise control over fuel quantity and mixture formation. However, it is crucial to control the impingement of the liquid phase to minimize emissions, especially in the case of ammonia. In this study, we employ the diffused back illumination imaging technique to investigate the dynamic evolution characteristics of the liquid phase in evaporating ammonia sprays, via a comparison with diesel fuel. Parameters, including injection pressure, fuel temperature, nozzle diameter, ambient pressure, and ambient temperature are examined and assessed under engine-like conditions. Our findings highlight the distinct dynamic evolution behavior of diesel spray, which is characterized by periodic detachments of large droplet clusters and cyclic variations in liquid penetration. This contrasts with the smoother evolution of ammonia spray. Notably, during the quasi-steady state, the liquid penetration in ammonia spray exhibits a significant increasing trend due to the large latent heat of evaporation. Finally, a predictive 1D model is proposed with consideration of multiple influencing factors. The findings offer valuable insights into comprehending and modeling the evaporating ammonia spray, thereby contributing to enhanced efficiency and cleaner combustion processes within ammonia engines.

Research on the Interaction Mechanism of Multi-Fracture Propagation in Hydraulic Fracturing

During the hydraulic-fracturing process, stress interference occurs among multiple wells and fractures, potentially affecting the trajectory of hydraulic fracture propagation. Previous studies have largely overlooked the influence of proppant support stresses on the trajectories of fracture propagation. This paper establishes a mathematical model, grounded in the boundary element method, designed to compute the propagation of multiple fractures, considering both proppant support on the fracture surface and dynamic perturbations within the local stress field. The findings of this research reveal that the stress field induced by hydraulic fracturing exhibits dynamic evolution characteristics, necessitating a comprehensive study of the fracture initiation and extension across the entire fracturing time domain. The effect of the residual fracture width under proppant action on the in situ stress field cannot be ignored. During simultaneous fracturing, hydraulic fractures are inclined to propagate in the direction of the maximum horizontal principal stress, particularly as the in situ differential stress escalates. Staggered fracturing between wells has been proven to be more effective than head-to-head fracturing. Simply increasing the well spacing cannot solve the problem of inter-well fracture interference. In zipper fracturing, adjusting the fracturing sequence can inhibit the fracture intersections between wells, thereby controlling the trajectory of fracture propagation. The aforementioned research has considerable significance in guiding the control of fracture morphology during hydraulic-fracturing processes.

Research on the three-dimensional spatio-temporal dynamic evolution and kinematic characteristics of loess landslides induced by strong earthquakes

Research on the three-dimensional spatio-temporal dynamic evolution and kinematic characteristics of loess landslides induced by strong earthquakes

Examining organizational collaboration and resource flows of disaster response system based on a time-dynamic perspective

Increasing the efficiency of organizational collaboration and resource flows is key to improving the emergency response performance. Given that previous studies did not consider the interactions and dynamic characteristics of emergency response organizations and resources, this study divided the emergency response into four stages and analyzed the relationship between organizational collaboration and resource flows by combining the network attributes of emergency response goals at each stage. The 2022 Luding earthquake was selected as a case study, and a multisource mixed data method was used to identify 381 organizations and 2496 organizational relationships. Using the social network analysis, the dynamic evolution characteristics of the emergency response networks (ERNs) and organization-resource two-mode networks were analyzed. The results showed that the ERNs generally exhibited the following trends: a more compact structure, balanced distribution, evolution from decentralization to centralization, and homogenous organizational collaboration. A correlation existed between changes in the organizational status and ERN attributes, with government organizations always at the core and non-profit organizations gradually rising. The evolution of the resources was closely related to the network attributes and organizational relationships. We identified the strengths of China's current emergency management system, such as enhanced performance, improved information infrastructure, and emphasis on the engagement of the military and social organizations. We recommend the following for future practice: enhancing the information technology system, establishing a mechanism for the participation of social forces, and strengthening the management of emergency stockpiles. These will help improve the disaster emergency management performance and reduce casualties and losses.

Characterization of pore structures after ASP flooding for post-EOR

With the global assistance of oil fields entering the stage of improving oil recovery, diversified composite flooding technology has become one of the key research targets. This article takes composite flooding to improve oil recovery as the research object, explores the differential mechanism of crude oil displacement efficiency under water flooding and composite flooding conditions, and elucidates the dynamic evolution characteristics of pore structure before and after composite flooding. Results show that: (a) The permeability and porosity of Daqing oilfield cores have a good correlation. The porosity of cores after water driving and ternary composite driving mainly ranged from 23.6 % to 27.4 % and 22.8 %–26.8 %. The water-driving permeability mainly ranged from 168 × 10−3 μm2 to 2162 × 10−3 μm2. Ternary composite driving permeability mainly ranges from 302 × 10−3 μm2 to 2307 × 10−3 μm2. (b) Compared with water driving, quartz and clay minerals are corroded by alkali during ternary composite driving. (c) Under the condition of similar permeability, the average pore size of the core after ternary composite driving is smaller than the average pore size after water driving.

Dynamic energy evolution and fragmentation characteristics of damaged rock under impact compression loading

Dynamic energy evolution and fragmentation characteristics of damaged rock under impact compression loading

Study on Dynamic Evolution and Erosion Characteristics of Cavitation Clouds in Submerged Cavitating Water Jets

The dynamic evolution behavior of submerged water jet cavitation clouds was studied by combining experiments and simulation. The formation, development, shedding, and collapsing process of a void cloud was analyzed by high-speed camera technology, and the influence of jet pressure was studied. Cavitation water jet erosion experiments were carried out on AL6061 specimens with standard cylindrical nozzles, and the correlation between cavitation cloud evolution and material erosion was studied by surface analysis. The results showed that the evolution of a cavitation cloud has obvious periodicity, that one period is about 0.8 ms, and its action region can be divided according to the attenuation rate of the jet velocity of the nozzle axis. The attenuation rate of the jet velocity at the nozzle axis in the central jet action zone is less than or equal to 82.5%, in the mixed action zone greater than 82.5% and less than 96%, and in the cavitation action zone greater than or equal to 96%. The erosion damage characteristics in different regions of the mixed action zone are significantly different.

A Large-Scale Three-Dimensional Apparatus to Study Failure Mechanisms of Rockfalls in Underground Engineering Contexts.

Rockfalls are an important factor affecting underground engineering safety. However, there has been limited progress in understanding and predicting these disasters in the past few years. Therefore, a large-scale three-dimensional experimental simulation apparatus to study failure mechanisms of rockfalls occurring during underground engineering was developed. This apparatus, measuring 4 m × 4 m × 3.3 m in size, can achieve vertical and horizontal symmetric loading. It not only simulates the structure and stress environment of a rock mass but also simulates the stepwise excavation processes involved in underground engineering. A complete simulation experiment of rockfalls in an underground engineering context was performed using this apparatus. Dynamic evolution characteristics of block displacement, temperature, natural vibration frequency, and acoustic emissions occurring during rockfalls were studied during the simulation. These data indicate there are several indicators that could be used to predict rockfalls in underground engineering contexts, leading to better prevention and control.

Study on the methodology of emergency decision-making for water transfer project contingencies: A case-based reasoning and regret theory approach.

To tackle the global water imbalance problem, a multitude of inter-basin water transfer projects have been built worldwide in recent decades. Nevertheless, given the complexity and safety challenges associated with project operation, effective emergency decision-making is crucial for addressing unforeseen incidents. Hence, this research has developed a two-stage emergency decision-making framework to tackle the uncertainty in the development trends of emergencies in inter-basin water transfer projects. (1) The first stage mainly utilizes case-based reasoning techniques to extract historical case information and disposal plans for inter-basin water transfer projects. Subsequently, a holistic similarity model is built by employing structural similarity and local attribute similarity algorithms to identify highly similar historical cases. (2) The second stage involves the optimization and adjustment of decision-making plans based on the dynamic evolution characteristics of emergencies. It utilizes the theory of decision-makers regret psychology and combines it with practical case studies to verify the scientific rationality of the method. This enables it to achieve effective multidimensional expression and rapid matching of scenarios, satisfying the decision-making requirements of "scenario response". Finally, this study compares the results obtained from this method with those computed using the traditional TOPSIS method and fuzzy comprehensive evaluation method, further validating its feasibility and effectiveness. In practice, this method can provide effective support for decision-makers work.

Spatial-temporal evolution and trend prediction of ecological civilization construction efficiency from the perspective of audit

The performance evaluation of ecological civilization construction is an important content of ecological civilization audit. The super-efficiency slacks-based measure model measured inter-provincial ecological civilization construction efficiency based on the panel data of Chinese provinces and cities during 2000–2020. Based on the time series and spatial correlation analyses, the traditional and spatial Markov probability transfer matrixes were constructed to explore the spatial and temporal dynamic evolution characteristics of China’s ecological civilization construction efficiency and predict its long-term trend. The study revealed that China’s ecological civilization construction efficiency has a “bimodal” distribution with a stable increase in fluctuation. The gap between the peak heights is small; however, the overall ecological civilization construction efficiency is low. We also revealed that from the long-term evolution trend forecast, most provinces and cities gradually shift to higher levels of ecological civilization construction efficiency and gradually evolve into having a gradual increase pattern in the geographical context of low ecological civilization construction efficiency, resulting in the long-term evolution of the stable state performance. In the geographic context of low ecological civilization construction efficiency, the long-term evolution of the stable state is a partial “single-peaked” distribution. Finally, we analyzed the directions for improvement in this study and suggested that inter-regional ecological civilization construction policy connections and the fortification of inter-regional ecological civilization construction cooperation and exchange can effectively improve China’s ecological civilization construction efficiency, narrow the gap between provinces and cities, and promote the construction of ecological civilization.

Spatial differences, dynamic evolution and influencing factors of China's construction industry carbon emission efficiency

Improving the construction industry carbon emission efficiency (CICEE) is crucial for achieving sustainable development. To promote low-carbon development in the construction industry, it is essential to measure carbon emission efficiency (CEE) and analyze spatial differences, dynamic evolution, and influencing factors. This study measures CICEE in 30 provinces in China from 2005 to 2019 and evaluates CEE using the minimum distance to a strong efficient frontier (MinDS) model with undesirable outputs. Subsequently, the Dagum Gini coefficient and its decomposition, as well as spatial autocorrelation analysis, are used to explore the sources of spatial differences and the spatial clustering pattern of CEE. The dynamic trend of CEE is analyzed through kernel density estimation, traditional and spatial Markov chains. Finally, geographical detectors are used to detect the explanatory factors and their interactions on spatial differences in CEE. The results of this study show that the CICEE presents an increasing and then decreasing trend, with the highest CEE in the eastern region, followed by the central and northeastern regions, and the lowest in the western region. Additionally, the eastern region exhibits the highest intra-regional differences and the highest inter-regional differences with the western region. Meanwhile, CEE shows a positive spatial correlation, with high-high (H-H) clustering in the eastern region and low-low (L-L) clustering in the western and northeastern regions. Polarization has been evident throughout the entire country and its four regions in recent years. It is challenging to achieve the CEE transfer through rapid advancement, and the efficiency of neighboring provinces will influence the potential transfer of the local province. Finally, factors such as enterprise scale, economic development level, degree of openness to the outside world, innovation level, industrial structure, and energy consumption structure all affect the spatial differences in CEE, with the interaction effect being higher than the single factor. This study presents a novel computational model to measure CICEE, analyzes the structural factors contributing to the spatial differences in CICEE, and provides theoretical support for the synergistic improvement of CEE across different regions. Combining with spatial autocorrelation analysis, the spatial distribution characteristics of CICEE are analyzed from the static level. This study provides a comprehensive examination of the evolution trend of CICEE, focusing on its dynamic evolution characteristics and the long-term transfer dimension. Additionally, geographical detector technology is introduced for the first time to analyze the influencing factors of spatial differences in CICEE. providing scientific evidence for the sustainable and coordinated development of different regions in China's construction industry. Furthermore, this study also contributes to the development of varied strategies for improving CICEE in China.

Regional disparities, dynamic evolution, and spatial spillover effects of urban-rural carbon emission inequality in China

ObjectiveThis study recalculates the carbon emissions of urban and rural residents in China, analyzing the dynamic evolution trends of urban and rural carbon emissions. It explores the spatial spillover effects centered around the inequality in carbon emissions between urban and rural areas.MethodsThe study calculates the carbon emissions of urban and rural residents in each province based on the IPCC method. Non-parametric kernel density estimation is employed to depict the dynamic evolution characteristics of national, urban, and rural carbon emissions. The Theil Index is used to measure the disparities in urban and rural carbon emissions in major strategic regions, further applying the Theil Index to evaluate the inequality of urban and rural carbon emissions across provinces. This helps identify the driving factors affecting the inequality of urban and rural carbon emissions and their spatio-temporal effects.FindingCarbon emissions from urban and rural residents in China present a divergent development pattern. Urban emissions have increased, with inter-provincial disparities widening; rural emissions tend to stabilize, with slight growth in inter-provincial gaps. The overall inequality of carbon emissions in various regions of China experiences a three-phase journey of rise, decline, and stabilization. Urban inequality first increases then decreases, while rural inequality gradually lessens, showing clear regional and urban-rural differences. Market and government factors significantly impact the inequality of urban and rural carbon emissions. The development of the digital economy aids in reducing inequality and generates significant spatial spillover effects. The relationship between economic development level and carbon emission inequality is U-shaped. Industrial structure optimization can reduce urban-rural inequality, but its spatial spillover effect is not significant. Government intervention has limited effects, while environmental regulations may increase inequality. Opening up to the outside world helps reduce inequality, and the impact of population density is complex.

What factors contribute to the formation of interorganizational collaboration networks: A longitudinal study in response to COVID‐19 emergency

AbstractIn the realm of addressing large‐scale emergencies, interorganizational collaboration emerges as a crucial strategy for effectively mitigating crises. However, the existence of institutional and procedural disparities poses significant challenges in establishing collaborative networks among diverse organizations. Moreover, the determinants influencing cooperative formations exhibit heterogeneity across distinct network structures. This research employs proximity theory and the Exponential Random Graph Model (ERGM) to comprehensively examine the dynamic evolution of interorganizational collaboration networks. Our primary objective is to investigate the effects of institutional proximity, organizational proximity, geographical proximity and social proximity on the formation of interorganizational collaboration networks. Textual data was meticulously collected from the Wisers database and official websites. The findings underscore the pivotal roles of institutional and organizational proximity in fostering interorganizational collaboration networks, while the impact of geographical proximity is relatively insignificant. Additionally, we delve into the driving factors that influence the formation of diverse structural networks. Social proximity emerges as a significant catalyst for horizontal collaborative networks but impedes the establishment of vertical collaborative relationships. Furthermore, we partition the entire emergency response process into six stages to explore the dynamic evolution characteristics of these networks. The results reveal an overall decentralized structure with a tendency toward clustering in the collaborative network. These findings hold substantial significance as they elucidate the influential factors driving the formation of diverse collaborative networks in a dynamic context. Therefore, this research bears implications for policymakers and practitioners aiming to enhance their emergency response capabilities with optimal efficiency.

Study on mechanism of unsteady gas-liquid two-phase flow in liquid-ring vacuum pump

To investigate the gas-liquid two-phase flow mechanism in liquid-ring vacuum pump, the large-eddy simulation coupled with volume-of-fluid method (LES-VOF) was used to numerically simulate the unsteady gas-liquid flow characteristics in pump. The structure of gas-liquid flow within pump and its dynamic evolution characteristics were studied, and the hydraulic excitation characteristics induced by gas-liquid flow were analyzed. The result shows that the channel vortex inside the impeller on the pump suction side gradually flows out of the flow passage with the rotation of the impeller, and continuously mixes with the wake vortex at the outlet of the impeller and the separation vortex at the inner wall of the casing. The evolution and development of vortex structures with different intensities and scales near the inner wall of the suction side casing have a relatively large contribution to pressure fluctuation. The wake vortex at the impeller outlet of the exhaust side gradually enters the flow passage and dissipates gradually with time. There is an obvious high-intensity backflow vortex in the exhaust section due to the pressure difference between the flow channels near the leading edge of the exhaust port, which leads to obvious rotor-stator interaction in the exhaust section.

Understanding drought propagation through coupling spatiotemporal features using vine copulas: A compound drought perspective

Accurately evaluating drought impact on agriculture poses a challenge to regional food security, particularly in compound drought (i.e., meteorological and agricultural drought co-occurring) scenarios. This study presents a novel approach utilizing Vine copula for coupling spatiotemporal features to evaluate drought propagation. Three-dimensional clustering method was employed to identify meteorological and agricultural drought events, which excelled in capturing dynamic evolution characteristics (duration, area, severity, etc.) as well as integrating them into comprehensive meteorological drought intensity (IMD) and agricultural drought intensity (IAD). Through spatiotemporal matching, compound drought events were extracted from the meteorological-agricultural drought event pairs. From compound drought perspective, compound duration (CD) and compound area (CA) were devised to characterize drought propagation potential across time and space. Finally, the Vine copula method was employed to model the interdependence between four key coupling features, namely IMD, IAD, CD, and CA, and evaluate the probability of triggering agricultural drought with different intensity levels. Results showed that CD and CA can respectively characterize the temporal and spatial accumulation scale of drought propagation. At a certain IMD level, CD significantly influences the propagation probability (i.e., “stratification” phenomenon), while CA increases the probability proportionally. Probability evaluation lacking spatiotemporal information may underestimate the likelihood of drought propagation characterized by “low-IMD” but “long-CD” or “large-CA”. The four-dimensional Vine copula structure can effectively couple dependence relationships of compound drought characteristics, and exhibits reliable robustness. This research provides stakeholders accurate probabilistic evaluation under compound drought scenarios, offering new insight into drought propagation.

Fault mechanism and dynamic two-phase flow behavior of liquid slugging in reciprocating compressors

Liquid slugging is a fatal fault for large process compressors, leading to transient overpressure, the deformation and fracture of vital pressure-bearing parts, and even gas leakage or explosion. In the study reported here, to reveal the mechanism of overpressure formation, numerical simulations were conducted by means of the volume-of-fluid method to explore the dynamic evolution characteristics of the two-phase flow pattern. Then, high-speed photography was applied to capture the dynamic changes of the liquid boundary in the modified cylinder from different views, thus realizing the validation of the numerical model. This study reveals the significant influence of increased rotational speed on fluid flow patterns, impeding liquid discharge and exacerbating overpressure events. Additionally, changes in pressure waveform and a distinctive waveform feature were identified as effective diagnostic indicators for detecting fluid slugging. Next, a nondestructive pressure monitoring reconstruction method based on measuring bolt strain was proposed. The strain-based pressure showed good agreement with the simulated results, thereby validating its effectiveness and feasibility as an early warning indicator for liquid slugging. This study offers new perspectives on the failure mechanism of liquid slugging in reciprocating compressors by delving into the behavior of two-phase flow, with the potential to enhance the theoretical foundation of compressor condition monitoring and fault diagnosis.