Dynamic Formation Mechanism Research Articles

Dynamic formation of gradient structure by microparticle impact — A crystal plasticity material point method study

Metallic materials with unique microstructure can achieve desirable strength-ductility synergy. However, effectively fabricating and precisely controlling microstructure distribution in metals remain challenging. Microparticle impact, the key process of cold spray technique, can lead to a gradient structure in the particle, which may also serve as a promising additive manufacturing technology. To investigate the dynamic formation mechanism of heterogeneous microstructure and its significant influencing factors, the crystal plasticity material point method (CPMPM) is developed, especially for microstructure formation under a high strain rate and large deformation. Our work provides a quantitative analysis of evolution of structural gradient during impact. It is found that decreasing grain size can afford a larger structural gradient and there is negligible influence on the compression ratio of particles. It suggests that microstructure distribution can be tailored by optimizing the impact process without influencing vertical deformation of particles.

Dynamic mechanism and structural property analysis of microfluidic-obtained pea protein fiber

Although protein-based fibers have been developed, the preparation of inexpensive, safe and environmentally friendly plant protein fibers is still a hot topic. Herein, we constructed the microfluidic chip to produce protein fiber using pea protein and a small amount of cellulose nanofibers. The results demonstrated that compared to pea protein alone, the pea protein-based fiber produced through microfluidic spinning exhibited a smooth and dense surface structure, good thermal stability, higher Zeta potential and antioxidant activity, and lower surface hydrophobicity and sensitization. Furthermore, we comprehensively revealed the dynamic formation mechanism of pea protein-based fiber. During the fiber preparation process, hydrodynamics led the protein and cellulose nanofibers to align gradually along the flow direction, enhancing their molecular orientation. Additionally, strong hydrodynamic shear force altered the protein structure, transitioning its spatial structure from random coil and α-helix to β-sheet, and promoting a binding of protein to cellulose nanofibers. This research may offer theoretical guidance for the application of pea protein-based fiber in the preparation of hypoallergenic protein-based fibers and the construction of foodborne delivery materials.

Two pulsed activities of the Emeishan large igneous province in southwestern China inferred from dolomite U-Pb geochronology and significance

Abstract The Emeishan large igneous province (ELIP) was a major geological event that took place around the Middle–Late Permian boundary. The major episode of the ELIP is generally considered to have occurred at 260–259 Ma, although an increasing number of geological data have suggested that multiple episodes of magmatic activity might have occurred. Here we report a study of a Lower Permian dolomite whose formation was influenced by the ELIP in the Sichuan Basin of southwestern China. Results show two new pulsed activities at 273.2 ± 9.7 Ma to 269.1 ± 12.0 Ma (ELIP-I) and 263.2 ± 10.3 Ma to 258.7 ± 8.1 Ma (ELIP-II). The two stages of the ELIP magmatism and thermal activity controlled the regional tectonic, sedimentary, and diagenetic evolution and exerted a profound influence on the oil and gas reservoirs, source rocks, and lithofacies paleogeography. This study is the first to interpret the timing of the ELIP from analysis of hydrothermal dolomite and provides new clues and data for improving our understanding of the dynamic formation mechanism and Earth system of the ELIP.

Damage features and dynamic formation mechanism of the Tangjiashan landslide triggered by the Wenchuan earthquake with a composite hypocenter

The Wenchuan earthquake triggered many landslides, which caused many casualties and led to considerable property losses. Due to the compositionality of the hypocenter mechanism of the Wenchuan earthquake, research on the effects of a composite hypocenter on the dynamic responses of landslides is urgently necessary. Using geological field investigations, a block discrete element method simulation, and related theoretical analysis, the dynamic formation mechanism and main controlling mechanical factors of the Tangjiashan landslide were revealed. The results demonstrated the following. Firstly, the dynamic responses of the slope involved progressive deformation, critical failure, disintegration, fragmentation, collision, climb, return, and accumulation. Secondly, when the earthquake lasted for approximately 23 s, the critical failure occurred, and the sliding mass near the shoulder reached a vertical acceleration of approximately 2.8 g at this time. Thirdly, the second and third subhypocenters contributed to the progressive deformation and critical failure, and vertical seismic forces were dominant contributions to these responses. Fourthly, the disintegration, fragmentation, collision, climb, return, and accumulation were mainly controlled by the self-gravity and local topography and were slightly influenced by subhypocenters. Based on these conclusions, the study of the dynamic formation mechanism of this type of landslide has increased the level of understanding.

Pore-Scale Oil-Water Flow Behaviors in Different Development Adjustment Schemes for Enhancing Oil Recovery in Waterflooding

Development mode adjustment is an important measure to further enhance oil recovery after primary waterflooding. Investigating the oil-water flow behaviors in the pores is significant to deepening the understanding of the macrobehavior of waterflooding and the designation of the reservoir development plan. Previous studies mainly focused on the change in recovery factor and macroflow characteristics, while less attention was paid to the causes of the change in recovery factor and the difference in macrocharacteristics. In this paper, the numerical simulation technology by coupling the Navier-Stokes equation with the method of volume of fluid is employed to investigate the dynamic formation mechanism of the remaining oil at pore-scale in the primary waterflooding, and then the pore-scale oil-water two-phase behaviors under three waterflooding development adjustment schemes: changing flooding direction, turning extraction well to injection well, and increasing injection rate are studied. The research shows that when the viscous resistance of the water-bearing channel is less than the sum of the capillary barrier and drainage capillary resistance (the resistance in the displacement of wetting phase displacement using the nonwetting phase), the remaining oil is formed. Water➔oil➔water➔oil displacement mode is formed in the process of changing flow direction, which makes the force of the phase interface tend to balance, reduces the capillary effect in waterflooding, and improves oil recovery. In the process of developing the scheme of turning extraction into an injection well, through multipoint injection, it advances from the central water-bearing area to the oil-bearing area on both sides in multiple paths, forming a larger spatial spread range than that in the change of flooding direction. Under the influence of the capillary barrier effect and drainage capillary resistance, when the injection rate is increased, the remaining oil can restart to move only when the flowing rate exceeds a certain value. The small viscous resistance in the water-bearing channel and the lateral resistance from the capillary barrier limiting the lateral sweep of water are the primary reasons for the insignificant improvement of oil recovery under the condition of a low liquid injection rate. The findings of this study can help for better understanding of pore-scale flow mechanism behaviors and their influences on the macroscopic development features in the waterflooding process.

Molecular-level insights into the heterogeneous variations and dynamic formation mechanism of leached dissolved organic matter during the photoaging of polystyrene microplastics

Microplastics (MPs) and their derivatives have received worldwide attention owing to their adverse effects on ecosystems. However, molecular diversity and dynamic formation of dissolved organic matter (DOM) during the photoaging of MPs remain unclear. Herein, we explored a molecular‒level formation mechanism for polystyrene MP (MPPS)‒derived DOM (PSDOM) during the photoaging of MPs to explain the evolution, heterogeneity, and sequential response of molecules to irradiation. Two‒dimensional correlation spectroscopy was applied to correlate the variations of PSDOM molecules detected by Fourier transform–ion cyclotron resonance mass spectrometry with those of MPPS functional groups detected by Fourier transform infrared spectroscopy. Irradiation‒induced PSDOM contained the most highly unsaturated structures with oxygen, but showed fewer aromatic structures than natural aquatic DOM. Photochemical transformations occurred between saturated‒reduced and oxidized molecules during PSDOM leaching, with the low‒oxidized and high‒oxidized molecules undergoing considerable changes in the normal carbon oxidation state and molecular number, respectively. The primary sequential response of PSDOM molecules to increasing irradiation time [low‒oxidized/high‒weight (450<m/z<800) → high‒oxidized → saturated/low‒weight molecules (m/z<450)] corresponded to the response of MPPS functional groups (aromatic C‒H → carbonyl → aromatic ring, CH2 bend → C‒H groups), demonstrating well synergistic relationships between them. These novel findings will contribute to the understanding of underappreciated behaviors or risks of MPDOM in aquatic ecosystems.

Synergistic Effect of Sr‐O Divacancy and Exposing Facets in SrTiO 3 Micro/Nano Particle: Accelerating Exciton Formation and Splitting, Highly Efficient Co 2+ Photooxidation (Small 44/2022)

Co2+ Photooxidation Multiple crystal surface exposure gives SrTiO3 micro/nano crystal better photocatalytic performance. In addition to the exposed crystal surface, the vacancy is vitally important. In article number 2202659, Li-zhu Wu, Dongping Duan, and co-workers investigate the dynamic formation mechanism of atomic vacancies of SrTiO3 crystal deeply, and more importantly, the Sr-O di-vacancies play an important role in the transition of exciton and free carriers. The photocatalytic reaction of Co2+ is used as the probe reaction, and the unique SrTiO3 possesses a high photooxidation efficiency of Co2+ resulting from more free carriers.

(Invited) Towards First-Principles Prediction of Early SEI Formation

Despite decades of work, there is still considerable uncertainty regarding the major components of the solid-electrolyte interface (SEI) and its dynamic formation mechanism as a function of electrolyte and anode composition. Here we present a new data-driven first-principles framework using a combination of high-throughput calculations, reaction networks, machine learning and microkinetic modeling. Our automated methodology is based on a systematic generation of relevant species using a general fragmentation/recombination procedure which provides the basis for a vast thermodynamic reaction landscape, calculated with density functional theory. We explore this landscape using stochastic methods and shortest pathfinding algorithms, which yield the most likely reaction pathways which are then refined with transition state calculations and kinetic information. The results of the framework show promise in being able to automatically recover previous insights on single reaction pathways, as well as successfully predicting the early dynamics and competitive nature of the SEI formation. As examples, we present formation mechanisms of LEMC as compared to LEDC and recover the Peled-like separation of the SEI into inorganic and organic domains resulting from rich reactive competition. By conducting accelerated simulations at elevated temperature, we track SEI evolution, confirming the postulated reduction of lithium ethylene monocarbonate to dilithium ethylene monocarbonate and hydrogen gas. These findings furnish fundamental insights into the dynamics of SEI formation and demonstrate a path forward toward a predictive understanding of electrochemical passivation.

A Data-Driven Packaging Efficiency Optimization Method for a Low Carbon System in Agri-Products Cold Chain

The of monitoring the Internet of Things (IoT) in the cold chain allows process data, including packaging data, to be more easily accessible. Proper optimization modelling is the core driving force towards the green and low-carbon operation of cold chain logistics, laying the necessary foundation for the development of a data-driven modelling system. Since efficient packaging is necessary for loss control in the cold chain, its final efficiency during circulation is important for realizing continuous loss prevention and efficient supply. Thus, it is urgent to determine how to utilize these continuously acquired data and how to formulate a more accurate packaging efficiency control methodology in the agri-products cold chain. Through continuous monitoring, we examined the feasibility of this topic by focusing on the concept of data-driven evaluation modelling and the dynamic formation mechanism of comprehensive packaging efficiency in cold chain logistics. The packaging efficiency in the table grape cold chain was used as an example to evaluate the comprehensive efficiency evaluation index system and data-driven evaluation framework proposed in this paper. Our results indicate that the established methodology can adapt to the continuity of comprehensive packaging efficiency, also reflecting the comprehensive efficiency evaluation of the packaging for different times and distances. Through the evaluation of our results, the differences and the dynamic processes between different final packaging efficiencies at different moments are effectively displayed. Thus, the continuous improvement of a low-carbon system in cold chain logistics could be realized.

Atomic-scale silicidation of low resistivity Ni-Si system through in-situ TEM investigation

Nickel silicide has many advantages, such as low resistivity and low formation temperature; therefore, it has been widely used in the fields of solar cells, transistors and complementary metal-oxidesemiconductor (CMOS) devices. To obtain high-quality nickel-silicide thin film, solid-state reaction is a convenient and efficient fabrication method. For better understanding of the dynamic formation mechanism, we used in-situ transmission electron microscopy (TEM) to record the diffusion behavior during the heating process. In this work, three-steps annealing process to synthesize different nickel silicides corresponding to the various formation temperatures were investigated systematically. At 250 °C, the product of the first-step annealing was inverted-triangle Ni2Si, embedded in the Si substrate. Then, well-distributed NiSi thin film was synthesized, having the lowest resistivity among Ni-Si system at 400 °C. Finally, NiSi2, a Si-rich product, would form during the third-step annealing at 600 °C. NiSi2 product and Si substrate have small lattice mismatch; thus, the epitaxial relationship would be observed. We provide the evidence of diffusion behaviors and structural identification of Ni-Si system. Furthermore, these results are beneficial for the formation of specific nickel silicides, which is expected to optimize the fabrication of microelectronics.

Cooperative Catalysis by Multiple Active Centers in Nonoxidative Conversion of Methane

A breakthrough in direct, nonoxidative conversion of methane was accomplished on a silica-confined single-atom iron catalyst (Fe©SiO2) in 2014. However, the formation mechanism of the identified active center (FeSiC2©SiO2) remains mysterious and the catalytic reaction mechanism is still under debate. Here, we report a dynamic formation mechanism of FeSiC2©SiO2 starting from FeO3©SiO2 by combining density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. It is found that FeSiC2©SiO2 is formed under the reaction atmosphere of methane, which undergoes two periods: the removal of oxygen and the insertion of carbon species. The removal of oxygen by generating CO/CO2 is the dominant way, and the insertion of carbon species can be facilely achieved once oxygen is removed. Importantly, during the formation of FeSiC2©SiO2, six other active centers, FeSiO2©SiO2, FeCO2©SiO2, FeSiCO©SiO2, FeC2O©SiO2, FeSi(CH2)2©SiO2 and FeSi(CH)2©SiO2, are revealed, which deliver different and cooperative catalytic behaviors on methane conversion and thus demonstrate a combined gas-phase and surface reaction mechanism.

Simulation and Filed Test on Dynamic Formation Mechanism of the Rotary Percussion Drilling Tool

Rotary percussion drilling tool can effectively improve the drilling speed in the hard formation. However, due to the impact of drilling fluid, the erosion of the dynamic and static valve disc is serious, which can reduce the impact effect. In this paper, the flow field characteristics and erosion characteristics of the dynamic forming mechanism are analyzed by numerical simulation and test, while the dynamic and static valve disc of dynamic formation mechanism is improved, which is verified by field test. The results show that the pressure from the entrance to the surrounding walls is higher and higher. The maximum velocity of drilling fluid is distributed near the edge of the outlet. The study will provides theoretical and technical guidance for increasing tool life and rate of penetration in hard formations.

Dynamics of Online Collective Attention as Hawkes Self-exciting Process

AbstractUnderstanding the dynamic formation mechanism of online collective attention has been attracted diversified interests such as Internet memes, viral videos, or social media platforms and Web-based businesses, and has practical application in the area of marketing and advertising, propagation of information. Bulletin Board System, or BBS can be regarded as an ecosystem of digital resources connected and shaped by collective successive behaviors of users. Clicks and replies of the posts quantify the degree of collective attention. For example, the collective clicking behavior of users on BBS gives rise to the up and down of focus on posts, and transporting attention between topics, the ratio between clicks and replies measure the heat degree of a post. We analyzed the dynamics of collective attention millions of users on an interactive Tianya Zatan BBS. By analyzing the dynamics of clicks we uncovered a non-trivial Hawkes process self-exciting regularity concerning the impact of novelty exponential decay mechanism. Here, it able to explain the empirical data of BBS remarkably well, such as popular topics are observed in time frequently cluster, asymptotic normality of clicks. Our findings indicate that collective attention among large populations decays with a exponential decaying law, suggest the existence of a natural time scale over novelty fades. Importantly, we show that self-exciting point processes can be used for the purpose of collective attention modeling.

Dynamic formation mechanism of water droplet and induced surface discharges on silicone rubber composites

Wettability has become one of the most important factors influencing power equipment insulation system in coastal power grid, which can seriously threaten the safety of power grid. This paper aimed at numerical simulation and experimental investigation on dynamic formation mechanism of water droplet and induced surface discharges on silicone rubber composites under different AC voltages, considering the factors of surface tension and droplet volume. Obtained results reveal that the spreading coefficient increases with increasing the electric field intensity from 1 to 5 kV/cm and with increasing the droplet volume from 10 to 50 µL. The spreading coefficient shows a decreasing tendency when the surface tension increases from 29.3 to 61.0 mN/m. Moreover, the maximum of surface electric field shows an increasing tendency under the condition of increasing both the droplet volume and the surface tension. On the basis of the physical model of droplet deformation, the electric field force and the surface tension play a significant role in the process of droplet deformation. Meanwhile, the experimental results are consistent with the simulation analysis, reflecting that the droplet deformation and the induced surface discharges mainly depend on two parameters: the droplet volume and the magnitude of applied voltage.

Mechanism of Dynamic Formation of Ultrafine Ferrite Grains during High Temperature Processing in Steel

The grain refinement mechanism of ferrite dynamically transformed (DT) from austenite is investigated in a 10Ni–0.1C steel. For decades, it has been debated whether dynamic recrystallization (DRX) contributes to the grain refinement of DT ferrite. Here, the authors show that the role of DRX has been previously underestimated in grain refinement of ferrite and intrinsically it is the DRX that leads to ultra grain refinement of DT ferrite. The DT ferrite shows an unconventional grain growth behavior, that is, grain coarsening at an early stage of transformation with subsequent grain refinement by DRX, which strongly depends on the strain rate. The high strain concentration on fine ferrite grains within the austenite + ferrite structure produced by DT mainly contributes to the occurrence of DRX to form ultrafine‐grained ferrite structures.

Apatite fission track geochronology of the Southern Hunan province across the Shi-Hang Belt: insights into the Cenozoic dynamic topography of South China

ABSTRACTThe Shi-Hang Belt is a Mesozoic tectonic zone and has always been regarded as the boundary between the Yangtze and Cathaysia blocks. It occupies a key tectonic location and attracts considerable attention due to its dynamic formation mechanism. However, its Cenozoic dynamic process is poorly constrained. The Cenozoic activation of the Shi-Hang Belt, as well as its cooling and exhumation, aids in dating the onset time of the formation of the mountain ranges and reveals the deformation process of the South China Block. To uncover the history of its Cenozoic cooling and denudation, apatite fission-track (AFT) thermochronology was applied to batholiths and strata spread across the Shi-Hang Belt in the Hunan Province. Twenty-three samples are dated with ages ranging from 23.6 ± 1.5 to 45.8 ± 3.0 Ma. Except for two older ages (42.1 ± 2.6 and 45.8 ± 3.0 Ma), the other ages range from 23 to 36 Ma with less variation on both sides of the Chenzhou–Linwu fault. The thermochronological modelling of 15 measured samples demonstrates that rocks rapidly passed through the AFT partial annealing zone to the near surface at different onset times from 36 to 23 Ma. The regional AFT cooling pattern is unrelated to the internal structures of the Shi-Hang Belt characterized by a Mesozoic fold-thrust feature. We attribute the Cenozoic exhumation of the Shi-Hang Belt to the dynamic topography of the South China Block, which is related to mantle downwellings and upwellings due to several episodes of quick subduction of the Pacific Plate underneath Eurasia during the Late Cretaceous–early Cenozoic and the Oligocene–early Miocene. The far-field effect of the India–Tibet collision may have contributed to the exhumation of the Shi-Hang Belt.

Research on Dynamic Mechanism of Green Coal Mine Construction

The green coal mines is the only way to change the extensive development mode of the coal mines.After analysis of dynamic formation mechanism of the green coal mine construction,this paper thinks the impetus of the green coal mine construction includes external impetus and internal impetus,where external impetus includes government support,environmental protection pressure,the degree of regional capital market maturity and technology innovation system of coal industry and internal impetus includes the drive of responsibility and interest,the ensuring strength of organization and culture,the enterprises technology innovation system and the sustainable development ability.This paper proposes a dynamic factors interaction model of green coal mine construction and some suggestions to construct green coal mines.

Important influencing factors analysis of airport sustainable development capacity: The case of China

Purpose: This paper seeks to define and build the formation mechanism for airport sustainable development capacity. Design/methodology/approach: Structure Equation and System Dynamic Model are used to research the formation mechanism of airport sustainable development capacity. Findings: The most influencing factors are: airport own investment, Gross Domestic Product and power consumption of unit income. Originality/value: Firstly, a new concept to evaluate the dynamic work on sustainable development is proposed, which is defined as airport sustainable development capacity. Secondly, the formation mechanism of airport sustainable development capacity is studied through Structure Equation Model and System Dynamics model. It fills in the gap of existing research whose main focus is static evaluation of airport sustainable development capacity and influencing factors identification rather than dynamic formation mechanism.

The Late Pleistocene activity of the eastern part of east Kunlun fault zone and its tectonic significance

The nearly EW-trending East Kunlun fault zone is the north boundary of the Bayan Har block. The activity characteristics and the position of the eastern end of its eastward extension are of great significance to probing into the dynamic mechanism of formation of the east edge of the Tibetan Plateau, and also lay the foundation for seismic risk assessment of the fault zone. The following results are obtained by analysis based on satellite image interpretation of landforms, surface rupture survey, terrace scarp deformation survey, and terrace dating data on the eastern part of the East Kunlun fault zone: (1) the Luocha segment is a Holocene active fault, where a reverse L-shape paleoearthquake surface rupture zone of about 50 km long is located; (2) the Luocha segment is characterized by left-lateral slip movement under the compression-shear condition since the later period of the Late Pleistocene, with a rate of 7.68–9.37 mm/a and a vertical slip rate of 0.7–0.9 mm/a, which are basically in accord with the activity rate of segments on its west side. The results indicate that it is a part of eastward extension of the East Kunlun fault zone; (3) the high-speed linear horizontal slip of the nearly EW-trending East Kunlun fault zone is blocked by the South China block at east, and transforms into the vertical movement of the nearly SN-NNE trending Minjiang fault zone and the Longmenshan fault zone, and the uplift of Longmenshan and Minjiang. The area where transform of the two tectonic systems occurred confines the position of the east end; (4) Luocha segment and Maqu segment constitute the “Maqu seismic gap”, so, seismic risk at Maqu segment is higher than that at Luocha segment, which should attract more attention.

Dynamic formation mechanism of airport competitiveness: The case of China

With the rapid development of Chinese economy, the demand of air transportation has increased enormously and airports are facing intensive competition, so the issue of how to enhance airport competitiveness has attracted serious concern of the public. The formation mechanism of airport competitiveness is very complex and the research is insufficient on this topic. In this paper, index system of airport competitiveness is built from four aspects: Regional Development, Production Factors, Demand Conditions and Support Industry. Dynamic formation mechanism of airport competitiveness is studied through Structure Equation Model as well as System Dynamic with the historical data of 25 Chinese airports from 2006 to 2010. Then the influencing mechanism of some important influencing factors is analyzed with the help of Vensim software, which verifies the rationality of the model. The results show that airport investment and city R&D inputs are the two most important influencing factors of airport competitiveness, which could provide guidance for decision makers on airport competitiveness cultivation.