Dynamic Evolution Process Research Articles

Research on the Evolutionary Law of Fracture Formation in Loose Seams Under High-Intensity Mining with Shallow Depth

The western mining regions of China, known for shallow-buried and high-intensity mining activities, face significant ecological threats due to damage to loose strata and the surface. The evolution of fissures within the loose layer is a critical issue for surface ecological environment protection in coal mining areas. The study employed field measurements, mechanical experiments, numerical simulations, and theoretical analysis, using the ‘triaxial consolidation without drainage’ experiment to assess the physical and mechanical properties of various strata in the loose layer. Additionally, the PFC2D numerical simulation software was employed to construct a numerical model that elucidates the damage mechanisms and reveals the evolution of loose layer fissures and the development of ground cracks. The research findings indicate that during shallow-buried high-intensity mining loose layer fissures undergo a dynamic evolution process characterized by “vertical extension-continuous penetration-lateral expansion”. As the working face advances, these fissures eventually propagate to the surface, forming ground cracks. The strong force chains within the overlying rock (or soil) layers develop in the form of an “inverted catenary arch”. As the arch foot and the middle of the arch overlap, fissures propagate along these strong force chains to the surface, resulting in ground cracks. The study elucidates the surface damage patterns in shallow-buried, high-intensity mining, offering theoretical insights for harmonizing coal mining safety with ecological conservation in fragile regions.

Study on corrosion behavior and first-principle analysis of M50 steel in lubricating oil contaminated by salt water

The corrosive wear of M50 steel in lubricating oil contaminated with saline is a form of wear that often occurs within the main shaft bearings of aviation engines carried by aircraft working at sea. In the present paper, the corrosion behavior of M50 steel in lubricating oil contaminated with saline was studied. The open-circuit potential, polarization curve and impedance spectrum were analyzed by rotating electrochemical corrosion wear test. A three-layer interface microscopic molecular model was established with Materials Studio to simulate the dynamic corrosion evolution process of M50 steel self-matching pairs and the adsorption energy was calculated. The results show that the corrosion type is pitting corrosion. With the increase of saline concentration, the corrosion area becomes wider and shallower, and the size of the pitting core gradually decreases. The weight loss of M50 steel increases over time, but the trend slows down, which is also shown in the MS simulation results. Electrochemical tests show that the tribocorrosion of M50 steel is related to load, speed. As the load increases, the corrosion rate decreases. And, as the speed increases, the corrosion rate increases. This has practical significance for extending the understanding of tribocorrosion of M50 steel in marine atmospheric environments.

Modeling fiber alignment in 3D printed ultra-high-performance concrete based on stereology theory

This paper introduces a theoretical model for forecasting fiber orientation in 3D-printed ultra-high-performance concrete (3DP-UHPC). Initially, the dynamic evolution process of fiber alignment in 3DP-UHPC was characterized using X-ray computed tomography (X-CT) and image analysis. The results indicated that fiber alignment during extrusion process was primarily constrained by the rigid boundary of nozzle. Leveraging stereology theory, the regularity of fiber alignment affected by boundary effects was elucidated. Following layer deposition, the flattening effect resulting from the nozzle's extrusion force and gravity of upper layers influenced fiber alignment along printing direction. To quantify this impact, a flattening correction coefficient was introduced to modify fiber orientation coefficient in an ideal state. Finally, considering the overlapping effect of boundary and flattening on fiber orientation in 3DP-UHPC, a theoretical model was developed to predict fiber orientation. The model demonstrated robust adaptability, providing valuable insights into the design of 3DP-UHPC with improved fiber reinforcement efficiency.

Gradient structured Al alloy with a synergistic improvement of strength-ductility obtained by friction stir processing

One Al 6061 with gradient microstructure is prepared by friction stir processing (FSP). Microscopic characterization indicates that the regulation of grain size gradient could be achieved by adjusting the process parameters of FSP. The mechanical property test indicates that one gradient Al 6061 combines an ultimate tensile strength of 266 MPa with a uniform elongation of 27 %, and the other comes 258 MPa with 29 %, which provides an excellent combination of strength and ductility. Moreover, the molecular dynamics (MD) method is employed to reconstruct and simulate the mechanical behavior of the gradient region and the dynamic evolution of the microstructure. When the stacking faults (SFs) with antisymbolic Burgers vector meet and detwinning occurs, grain refinement will induce localized strengthening. When the Shockley partials occur cross-slip, numerous sessile dislocations obstruct the dislocation motion more facilitate strain hardening. Meanwhile, a unique interaction mechanism between shear bands (SBs) and intergranular cracks in Al 6061 is discovered in plastic deformation. The coarse net-like SBs in the small-grain region are highly susceptible to catastrophic fracture of the material, and the large cracks formed within the severely band-like SBs in the large-grain region weaken the strength substantially. However, the formation of sessile dislocations in the gradient region effectively mitigates strain localization and inhibits the nucleation of large cracks. The results interpret the dynamic evolution process of gradient microstructure prepared by FSP and the mechanism of strengthening and toughening and provide process and theoretical references for the research and development of new engineering materials.

Structural properties and mechanical behavior of three-dimensional cylindrical particle-like systems under in situ loading

To investigate the mechanical behavior of granular systems and their impact on density uniformity during compression, a three-dimensional micro-CT in situ loading experiment was conducted on a cylindrical granular system. The granular system was subjected to tomographic scanning and reconstruction, and the variation patterns of structural parameters such as volume fraction, porosity, and intrinsic density during the in situ loading process were analyzed. Internal pores within the granular system were extracted to obtain changes in pore area at each layer, allowing for an analysis of the evolving patterns of layered pore areas across different regions of the granular system during loading. This characterization elucidated the dynamic evolution process of compaction within the granular system. A contact network model for the granular system was established using particle contact area as a representation of inter-particle contact forces, revealing inherent connections between particle contact networks and macroscopic mechanical behaviors within the granular system.

Multi-Component Lithiophilic Alloy Film Modified Cu Current Collector for Long-Life Lithium Metal Batteries by a Novel FCVA Co-Deposition System.

Surface modification of Cu current collectors (CCs) is proven to be an effective method for protecting lithium metal anodes. However, few studies have focused on the quality and efficiency of modification layers. Herein, a novel home-made filtered cathode vacuum arc (FCVA) co-deposition system with high modification efficiency, good repeatability and environmental friendliness is proposed to realize the wide range regulation of film composition, structure and performance. Through this system, ZnMgTiAl quaternary alloy films, which have good affinity with Li are successfully constructed on Cu CCs, and the fully enhanced electrochemical performances are achieved. Symmetrical cells constructed with modified CCs maintained a fairly low voltage hysteresis of only 13mV after 2100h at a current density of 1mA cm-2. In addition, the capacity retention rate is as high as 75.0% after 100 cycles in the full cells. The influence of alloy films on the dynamic evolution process of constructing stable artificial solid electrolyte interphase (SEI) layer is revealed by in situ infrared (IR) spectroscopy. This work provides a promising route for designing various feasible modification films for LMBs, and it displays better industrial application prospects than the traditional chemical methods owing to the remarkable controllability and scale-up capacity.

Vulnerability simulation and evaluation of urban metro operation system: A hybrid structural equation model with system dynamics approach

To effectively identify the influence factors of urban metro operation system (UMOS) vulnerability and research the dynamic evolution process of system vulnerability, ensuring the long-term safety of UMOS, a hybrid method integrating structural equation model (SEM) and system dynamic (SD) is proposed to evaluate the UMOS vulnerability. The vulnerability evaluation indexes system of UMOS is established by questionnaire design, which includes four dimensions of personnel, equipment, management and environment. The effectiveness of the method is verified by taking Wuhan metro system in China as an example. The results indicate that (1) The influence of personnel, equipment, management and environment factors on UMOS is 30.2 %, 27.6 %, 21.6 % and 20.6 %, respectively. (2) The passenger flow level and emergency rescue system level have the greatest influence on the vulnerability of UMOS via sensitivity analysis. (3) Extreme weather conditions have the greatest impact on the environment sub-system vulnerability, which in turn affects the UMOS. Hence, the proposed method herein can simulate the long-term vulnerability of the entire UMOS and formulate corresponding improvement measures, thereby achieving sustainable transportation development.

Numerical Simulation Study on Evolution Process of Carrying-Soil Effect of Rectangular Pipe Jacking

The carrying-soil effect is an important factor affecting the success or failure of rectangular pipe jacking construction. Because it is difficult to explore the dynamic evolution process of the carrying-soil effect in the field test, this paper relies on the pipe jacking project of a comprehensive pipe gallery in Suzhou City, and uses ABAQUS 2021 finite element software to simulate the jacking process of rectangular pipe jacking. Based on the theory of plastic mechanics of rock and soil and the related research and application status, the equivalent plastic strain index is introduced as the basis for judging the failure boundary of soil in the numerical simulation results, and the boundary between the carrying-soil area and the surrounding soil is determined, that is, the shear fracture surface. According to the principle of plastic potential energy, the development direction of the fracture surface is consistent with the direction of plastic flow, so as to predict the development direction of the boundary of the carrying-soil area. According to the change in the equivalent plastic strain cloud map with the jacking mileage, the evolution process of the carrying-soil effect is clarified, and the dynamic evolution law of the carrying-soil area is revealed, which is of great significance for predicting the disturbance of the surrounding soil during the construction of rectangular pipe jacking and accurately evaluating the environmental effect of the construction.

Reconstructing tumor clonal heterogeneity and evolutionary relationships based on tumor DNA sequencing data.

The heterogeneity of tumor clones drives the selection and evolution of distinct tumor cell populations, resulting in an intricate and dynamic tumor evolution process. While tumor bulk DNA sequencing helps elucidate intratumor heterogeneity, challenges such as the misidentification of mutation multiplicity due to copy number variations and uncertainties in the reconstruction process hinder the accurate inference of tumor evolution. In this study, we introduce a novel approach, REconstructing Tumor Clonal Heterogeneity and Evolutionary Relationships (RETCHER), which characterizes more realistic cancer cell fractions by accurately identifying mutation multiplicity while considering uncertainty during the reconstruction process and the credibility and reasonableness of subclone clustering. This method comprehensively and accurately infers multiple forms of tumor clonal heterogeneity and phylogenetic relationships. RETCHER outperforms existing methods on simulated data and infers clearer subclone structures and evolutionary relationships in real multisample sequencing data from five tumor types. By precisely analysing the complex clonal heterogeneity within tumors, RETCHER provides a new approach to tumor evolution research and offers scientific evidence for developing precise and personalized treatment strategies. This approach is expected to play a significant role in tumor evolution research, clinical diagnosis, and treatment. RETCHER is available for free at https://github.com/zlsys3/RETCHER.

A multi-scale deep residual network-based guided wave imaging evaluation method for fatigue crack quantification

Abstract As a promising structural health monitoring (SHM) technology, guided wave (GW) imaging is gaining increasing attention for crack monitoring of aircraft structures. However, actual fatigue crack propagation is a complex dynamically evolving process affected by various variabilities. It is still challenging to accurately track and quantify the dynamic fatigue crack propagation with GW imaging methods. Therefore, in order to achieve more accurate fatigue crack quantification, this paper proposes a multi-scale deep residual network-based GW imaging evaluation method. A convolutional neural network (CNN) is utilized to evaluate the entire pixel distribution of GW imaging maps to fuse damage-related information from multiple GW monitoring paths. By designing multi-scale convolutional kernels and deep residual learning, a robust quantitative image feature extraction is ensured with the dynamic evolution process of fatigue crack growth and the performance degradation is avoided as the CNN goes deeper, thereby improving the quantification accuracy. The method is validated on a fatigue test of landing gear beams, which are important load-carrying aircraft structural components. The results demonstrate that the proposed method can extract multi-scale crack length-related features and accurately track fatigue crack propagations. For batch specimens, the maximum quantification error is reduced from the original 6.1mm to 1.6mm, marking a significant improvement.

Optimal acquisition time estimation method for CSEM with high-order pseudo-random signal

High-order pseudo-random signal is gradually being applied in controlled-source electromagnetic (CSEM) exploration. In contrast to the conventional single-frequency sweep mode, the high-order pseudo-random signal enables simultaneous transmission of multiple frequencies. However, estimating a fixed acquisition time based on observed noise levels often results in poor adaptability for high-order pseudo-random signal, which only require reception of one set of waveform. In this study, we presented an estimation method for acquisition time for CSEM with high-order pseudo-random signal using an improved logistic function. The improved logistic function was proposed to introduce a time-decay factor into the governing equation for the first time. By considering the transformation rule of noise statistical characteristics with time, the specific parameters of the function have been determined to better describe the dynamic evolution process of the signal quality. The effective frequencies were extracted at various acquisition times based on the noise evaluation number, and the resulting quantity of effective frequencies was used as the fitting target. Guidance for the fieldwork was determined based on the average time of the saturation period, in accordance with the properties of the function. The reliability of the improved logistic function was validated through a transmission current data simulation. The proposed method was demonstrated through the measured data from both strong and weak interference areas.

An in-situ three-dimensional study of the dynamic and mechanism during spark plasma sintering of aluminum alloys

An in-situ plasma spark sintering (SPS) apparatus, coupled with laboratory X-ray microscopy, was utilized to three-dimensionally investigate the dynamic evolution process of 7055 aluminum alloy during SPS process. The influences of sintering temperatures and particle morphology on the sintering kinetics were discussed in detail. It was observed that elevating the sintering temperatures enhanced both the rate of densification and the final compactness of the alloy. Furthermore, three-dimensional quantitative analysis of pore evolution indicated that greater discrepancies in powder size between neighboring particles facilitated pore elimination during sintering by increasing available interstitial spaces. Mechanistic analysis rationalized these observations by attributing the enhanced sintering kinetics to the greater particle size disparity, which resulted in higher necking curvature and accelerated densification. The present study therefore provides a comprehensive three-dimensional in-situ quantitative analysis on the dynamic SPS process, and is expected to advance the current comprehension of sintering mechanisms at the micron scale.

Modelling the Blast Cracking Processes of Rock Masses Using a Total Lagrange Meshless Method

The dynamic damage of surrounding rock masses has a great impact on the tunnel stability during the drilling and blasting construction processes. However, traditional FEM has some difficulties in simulating the blast damage processes of rock masses during mesh re-divisions. In our work, the smoothing kernel function in traditional SPH method has been improved, and the momentum equation considering the blasting load is derived, which realizes the modeling of the dynamic damage evolution processes under the SPH framework. Firstly, two typical examples are numerically simulated: 1) Upper slow and lower steep “Y” shaped fissure and 2) Upper short and lower long “Y” shaped fissure. The simulation results are compared with previous experimental results to verify the correctness of the SPH method. Then, the progressive blast damage processes are simulated, and the effects of different stress wave loading modes, different pre-existing fissure distances, different fissure dip angles as well as different ground stress levels on the blast cracking morphologies are investigated. Results show that: The blast cracks first appear around the blast hole, then the radial cracks propagate to the model boundary; The radial crack length increases with the increase of peak blast stress wave; The length of the horizontal radial crack decreases and the length of the vertical radial crack increases with the increase of the horizontal ground stress; The existence of pre-existing fissure prevents the further extension of the blasting cracks, and the increase of the fissure dip angle leads to the crack propagation at the fissure tips; The increase of fissure distance leads to the larger crack propagation in the around the fissure; The damage count increases with the increase of peak blast stress wave; The increase of the ratio of horizontal stress to vertical stress decreases the damage count; The damage counts increase with the increase of fissure dip angles; The damage degree of the model increases with the increase of the fissure distance.

The theoretical study of high-order dissipation soliton molecules evolution in a passively mode-locked fiber laser

High-order solitons represent a special form of soliton. Due to the complexity of their spatial structure and dynamic evolution, they have important applications in communication systems such as wavelength division multiplexing and secure communication. However, compared to traditional solitons, research on the spectral evolution of high-order solitons is still insufficient. In this paper, through precise control of laser parameters, the dynamic evolution process from stable dissipative single soliton to complex dissipative 8-order soliton molecules in passively mode-locked fiber lasers was successfully simulated. This demonstrates the complexity of solitons interaction and reveals the regularity of soliton molecules order with variations in four parameters: the small signal gain coefficient, nonlinear coefficient, gain bandwidth and the polarization controller angle. Through deep analysis of the order of soliton molecules, pulse shape and spectral shape of dissipative soliton molecules, we showcase the potential of fine-tuning laser parameters to achieve high-order dissipative soliton molecules. This work provides important references for the optimization design and expanded applications of lasers, further driving the development of high-performance, high-efficiency fiber laser technology.

Measurement and Spatial-Temporal Evolution of Industrial Carbon Emission Efficiency in Western China

As it is an important industrial base in China, it is of great significance to improve the industrial carbon emission efficiency in the western region to promote the low-carbon sustainable development of the region. This paper selects the input–output panel data of 11 provinces in western China from 2010 to 2021, and adopts the three-stage DEA model to measure the industrial carbon emission efficiency in western China under a non-traditional geographic division at the overall and regional levels and analyze its influencing factors. The Dagum Gini coefficient, its decomposition method, and the kernel density estimation method are used to analyze the regional differences and dynamic evolution process of industrial carbon emission efficiency in the western region. The results of the study show that (1) after removing environmental and random factors, the industrial carbon emission efficiency in western China has been improved, but there are inter-regional differences, characterized by “the third region > the second region > the first region”; (2) the levels of green development, shared development, innovative development, and coordinated development have a positive impact on the improvement of industrial carbon emission efficiency in western China, while the level of industrialization has a relatively smaller influence, and economic development, government support, open development level, and energy consumption structure have not yet played a significant role; (3) the spatial differences in the efficiency of industrial carbon emissions in western China have generally increased during the sample period, with inter-regional differences being the main source; and (4) the industrial carbon emission efficiency in western China is characterized by overall improvements in time and space but with stage differences and multi-polarization of regional differences. This study has a certain reference value for improving industrial carbon emission efficiency in western China.

Avalanche dynamics in nonconservative water droplet

The self-organized criticality (SOC) exhibits excellent performance in describing the dynamic features of multi-body systems in nature. It is usually considered that conservative law is a necessary condition for the existence of SOC. However, mass or energy dissipation typically exists in the process from self-organization to a critical state in natural systems such as earthquakes and air pollution, namely, non-conservation. At present, few physical experiments have systematically explored the SOC behavior in a non-conservative system, compared to numerical simulations. This study is the first to design a non-conservative sandpile experiment using water droplets. Based on this experiment, the dynamic evolution process of avalanches in a non-conservative system has been analyzed. The results show that the avalanche size of water droplets follows a power-law distribution, as the water mass decays with time. This phenomenon obeys the rules of scale-free distribution, which is consistent with SOC behavior. Moreover, the waiting time of water droplets avalanche follows a stretched exponential distribution. These results suggest that SOC behavior still exists in non-conservative multi-body systems, which is affected by the decay coefficient. We then explore the mechanism by which the decay coefficient affects the transition of the system to a critical state in the non-conservative sandpile model (NBTW). We find that only when the decay coefficient is small do the inequality measures, Gini coefficient g and Kolkata index k, exhibit nearly universal values, similar to the mechanism of the system transitioning to a critical state in the traditional BTW model. When the decay coefficient is large, the NBTW model shows scaling-limited effects and the scaling exponent of avalanche size increases with the decay coefficient. Furthermore, we use the NBTW model to study how the decay coefficient influences the scaling exponent of avalanche size. We find that the NBTW model can effectively explain the variability of scaling exponents observed in different SOC systems and establish a quantitative relationship between the mass decay coefficient and the avalanche size scaling exponent. This study provides new insight into SOC behavior in non-conservative systems in nature.

Deciphering Subduction Polarity During Ancient Arc‐Continent Collisions

AbstractThe closure of an ancient ocean basin via oceanic arc‐continent collision has two subduction styles with opposite polarities, which may proceed via subduction polarity reversal (SPR) or a subduction zone jump (SZJ). Interpreting the geometry or kinematic evolution of ancient collisional zones, especially the original subduction polarity, can be challenging. Here we used 2D thermo‐mechanical modeling to investigate the dynamic evolution process of SPR versus SZJ. Our modeling predicts different structural, topographic, magmatic, and basin histories for SPR and SZJ, which can be compared against, and help interpret, the geologic record past sites of oceanic closure during collisional orogens. Our results match geologic observations of past collisions in Kamchatka, eastern Russia, and the Banda Arc, eastern Indonesia, and thus our results can help effectively decode the evolutionary history of past arc‐continent collisions.

Assessing the Sustainable Development Level of the Tourism Eco-Security System in the Chengdu-Chongqing Urban Agglomeration: A Comprehensive Analysis of Dynamic Evolution Characteristics and Driving Factors

Based on the DPSIR framework, this study constructed an evaluation index system to assess the sustainable development levels of the tourism eco-security system (TESS-SDL) present in the Chengdu-–Chongqing urban agglomeration and synthesized multi-dimensional analysis methods to explore its spatiotemporal evolution characteristics and driving factors to provide an important theoretical and practical basis for promoting the sustainable development of the regional tourism eco-security system. The results showed the following: (1) From 2011 to 2021, the regional TESS-SDL was generally at a medium level and showed a trend of steady growth. Although the gap between cities was widening year by year, the speed of the TESS-SDL exceeded the speed of the widening gap, promoting the coordinated development of the regional TESS-SDL. (2) The spatial spillover effect of the regional TESS-SDL was obvious; however, the siphoning effects of Chongqing and Chengdu were strong, and the demonstration effect was insufficient. (3) The dynamic evolution process of the TESS-SDL shows a strong self-locking effect. The risk of downward development (lower sustainability) is greater than the potential for upward development (higher sustainability) and is significantly influenced by neighboring cities. (4) In terms for assessing the driving factors, open-door and green-development policies show positive facilitating effects, while the positive influencing capacities of information technology, economic development, and tourism are moving toward having negative effects; the influencing effect of technological innovation has transitioned from positive to negative.

Tripartite Evolutionary Game Analysis of Product Quality Supervision in Live-Streaming E-Commerce

With the rapid development of information technology, live-streaming e-commerce has risen rapidly as a new business model. However, product quality problems that exist in the development of live-streaming e-commerce continue to emerge. The influence of strategic interactions between social media influencers, live-streaming e-commerce platforms, and consumers on product quality deserves to be studied. Therefore, this paper constructs a tripartite game model of “social media influencers–the live-streaming e-commerce platform–consumers” and analyzes the dynamic evolution process of the strategy selection among subjects and influencing factors by using evolutionary game theory. This study shows that products with high functional value are more likely to stimulate consumer rights protection behavior, prompting social media influencers to shift from lax to strict quality control. But when the emotional value is high, consumers are more inclined to give up on defending their rights, which leads to the maintenance of lax quality control, and the platform supervision will be weakened accordingly. Moreover, less quality differences motivate social media influencers to choose lax quality control. An increase in quality differences will promote a shift from an equilibrium strategy to strict quality control. However, if the penalty of the platforms is not strong enough, this strategic shift will not happen. In addition, a high percentage of platform commissions can encourage influencers to implement strict quality control, while platforms can maintain weak supervision. This study’s findings provide valuable guidance for understanding and managing product quality issues in live-streaming e-commerce. In the future, the government will be considered a new player in the game in studying the impact of its policies on product quality in live-streaming e-commerce.

Multi-perspective feedback-attention coupling model for continuous-time dynamic graphs

Abstract Representation learning over graph networks has recently gained popularity, with many models showing promising results. However, several challenges remain: (1) most methods are designed for static or discrete-time dynamic graphs; (2) existing continuous-time dynamic graph algorithms focus on a single evolving perspective; and (3) many continuous-time dynamic graph approaches necessitate numerous temporal neighbors to capture long-term dependencies. In response, this paper introduces a Multi-Perspective Feedback-Attention Coupling (MPFA) model. MPFA incorporates information from both evolving and original perspectives to effectively learn the complex dynamics of dynamic graph evolution processes. The evolving perspective considers the current state of historical interaction events of nodes and uses a temporal attention module to aggregate current state information. This perspective also makes it possible to capture long-term dependencies of nodes using a small number of temporal neighbors. Meanwhile, the original perspective utilizes a feedback attention module with growth characteristic coefficients to aggregate the original state information of node interactions. Experimental results on one dataset organized by ourselves and seven public datasets validate the effectiveness and competitiveness of our proposed model.