Macroscopic Perspective Research Articles

Spatio-temporal dynamic change mechanism analysis of traffic conflict risk based on trajectory data

Analyzing risk dynamic change mechanism under spatio-temporal effects can provide a better understanding of traffic risk, which helps reinforce the safety improvement. Traditionally, spatio-temporal studies based on crash data were mostly conducted to explore crash risk evolution mechanism from a macroscopic perspective. Dynamic change mechanism of short-term risk within a small-scale area deserves exploration, which cannot be captured in macroscopic crash-based studies. It is practical to analyze traffic conflict risk as a surrogate safety measure, which can preferably overcome the limitations of crash-based studies. This study aims to explore the spatio-temporal dynamic change mechanism of conflict risk based on trajectory data. Both conflict frequency and severity are integrated and assessed by applying fuzzy logic theory to develop the whole risk indicator. Trajectories on U.S. Highway101 from NGSIM dataset are utilized and aggregated. A two-step framework is proposed to analyze the risk dynamic change mechanism. The spatial Markov model is firstly applied to explore the transition probability of risk level, and then the panel regression approach is employed to quantify the relationship between spatio-temporal risk and traffic characteristics. Modeling results show that (1) the dynamic change trend of safety states differs under different spatial lag conditions, and it can be well depicted by the spatial Markov model; (2) dynamic spatial panel data modeling method performs better than the model that only considers temporal or spatial dependency. The novel proposed framework promotes a systematic exploration of conflict risk from a mesoscopic perspective, which contributes to assess the real-time road safety more comprehensively.

Numerical Simulation of a Simplified Reaction Model for the Growth of Graphene via Chemical Vapor Deposition in Vertical Rotating Disk Reactor

The process of graphene growth by CVD involves a series of complex gas-phase surface chemical reactions, which generally go through three processes, including gas phase decomposition, surface chemical reaction, and gas phase diffusion. The complexity of the CVD process for growing graphene is that it involves not only chemical reactions but also mass, momentum, and energy transfer. To solve these problems, the method of numerical simulation combined with the reactor structure optimization model provides a good tool for industrial production and theoretical research to explore the influencing factors of the CVD growth of graphene. The objective of this study was to establish a simplified reaction model for the growth of graphene by chemical vapor deposition(CVD) in a vertical rotating disk reactor (VRD). From a macroscopic modeling perspective, computational fluid dynamics (CFD) was used to investigate the conditions for the growth of graphene by chemical vapor deposition in a high-speed rotating vertical disk reactor on a copper substrate surface at atmospheric pressure (101,325 Pa). The effects of gas temperature, air inlet velocity, base rotation speed, and material ratio on the surface deposition rate of graphene in a VRD reactor were studied, and the technological conditions for the preparation of graphene via the CVD method in a VRD reactor based on a special structure were explored. Compared with existing models, the numerical results showed the following: the ideal growth conditions of graphene prepared using a CVD method in a VRD reactor involve a growth temperature of 1310 K, an intake speed of 470 mL/min, a base speed of 300 rpm, and an H2 flow rate of 75 sccm; thus, more uniform graphene with a better surface density and higher quality can be obtained. The effect of the carbon surface deposition rate on the growth behavior of graphene was studied using molecular dynamics (MD) from a microscopic perspective. The simulation showed that the graphene surface deposition rate could control the nucleation density of graphene. The combination of macro- and microsimulation methods was used to provide a theoretical reference for the production of graphene.

리걸테크의 도입과 형사전자소송의 가능성 및 한계

When The Act on the Use of Electronic Document in Criminal Justice Procedures is fully implemented in 2024, it is expected that full-fledged electronic litigation will be possible in criminal procedures. The scope of application of The Act on the Use of Electronic Document in Criminal Justice Procedures is limited to criminal justice affairs, but in the long run, it will expand to the macroscopic perspective of digitalization and intelligent informatization of overall criminal justice services. However, even if the law or system is established, there may be various expected problems in the process of operation. To this end, in this paper, first of all, the obstacles to the activation of Legal Tech, which is the environmental basis of electronic criminal proceedings, were examined. After confirming the specific aspects of the litigation, we examined the points where the electronic criminal proceedings can function or expand in the trial process In this paper, first of all, the fundamental cause of the lack of discussion on Legal Tech, which can be the environmental basis of electronic criminal proceedings, was identified. While accepting legal tech, such as intelligent information technology, the author raised issues such as our still conservative legal system and practices, information accessibility of personal information, and intellectual property rights infringement. Next, as a supplementary point for the success of electronic criminal proceedings, a plan to resolve the reluctance of those involved in the case in electronic criminal proceedings and a plan to prevent abuse of accumulated data were presented. Next, in the introduction process by stage of litigation, it was ordered to improve the system considering the difference in digital literacy in the process of submitting litigation documents, the issue of equality in the process of distributing electronic documents, and legislative overhaul for exceptions to the provision of service. On the other hand, the implementation of the Criminal Procedure Electronic Documents Act provides significant implications for e-discovery. In the disclosure of evidence, the practice of written caution will be overcome, and various problems raised in the academic world in relation to the refusal of the investigation agency to disclose evidence will be resolved. It will be possible to examine the adequacy of the reason for refusal by the investigative agency, and in particular, it will be possible to secure the binding force of the court's order to disclose evidence and prepare a separate regulation so that the investigative agency cannot refuse the order to disclose evidence. In addition, in this paper, we also looked at the possibility of using intelligent information technology in determining the verifiable power or reliability of electronic remote statements and statements that can be used in courts.

Microscopic, mesoscopic, and macroscopic structural correlations between the international energy “investment–trade” networks based on network motifs

In recent years, international energy investment and energy trade activities have developed rapidly. Because energy has commodity and financial product attributes, there is often a correlation between international energy trade and investment. This correlation has regional specificity due to the uneven geographical distribution of energy production and consumption. The existing literature mainly studies the correlation between the international energy “investment–trade” systems from a macroscopic or microscopic perspective. However, the relationship between them among countries from a mesoscopic perspective has not been fully demonstrated. With the development of economic globalization, we need to pay attention to whether the energy trade model of countries can reflect their preference for choosing investment partners and whether the energy investment model can reflect energy trade cooperation. In this paper, by taking the frontier approach of network motifs, we analyzed the correlation between international energy trade and investment from more than 200 economies worldwide from the macroscopic perspective, microscopic perspective, and local structure from a mesoscopic perspective. Meanwhile, we compared the results of the study in 2018 with those in 2022 to obtain the impact of international events on the international energy “investment–trade” networks. We found that 1) the structures of energy trade and investment networks are similar from a macroscopic perspective, which is the basis for exploring the correlation between energy trade and investment. 2) Bilateral cooperation and transaction transmission are important local structures of energy trade and energy investment activities. 3) The formation of an equal and close local structure among economies in energy trade is more likely to be preferred for investment cooperation, and forming a representative local structure with statistical significance among economies in energy investment is more likely to obtain energy trade cooperation. This work innovatively adopts motifs to study the correlation between energy investment and trade, which can help energy investors predict the direction of investment and provide guidance to governments in formulating energy trade policies.

Comprehensive understanding of tetracycline hydrochloride adsorption mechanism onto biochar-based gel pellets based on the combination of characterization-based and approximate site energy distribution methods

The application of sludge-based biochar and its derivatives to remove antibiotics from aquatic media has long been recognized as an environmentally-friendly approach since it delivers the scenario of waste treatment by wastes. Despite the existence of various proposed adsorption mechanisms, a comprehensive analysis that combines macroscopic and microscopic perspectives remains insufficient. Herein, surface modification (Fe3O4) and spherization (chitosan) were employed to improve the adsorption capacity of sludge-based biochar toward tetracycline hydrochloride (TC). The as-prepared gel pellets (FeB-11) exhibited high adsorption capacity toward TC in aqueous with maximum uptake of 206.98 mg⋅g−1 under 298K. The combination of characterization-based and approximate site energy distribution (ASED) methods concluded that surface complexation played the primary role in enhancing the adsorption capacity of FeB-11 for TC, while space filling, hydrogen bonding, π-π interaction, electrostatic interaction and ion exchange also contributed to the adsorption process. The introduction of chitosan and Fe3O4 weakened physisorption but strengthened chemisorption, and Fe3O4 was proposed as the primary promoter for TC adsorption due to the better affinity between TC molecules and FeB-11 which Fe3O4 brought. Concentrated and high distribution frequency of adsorption sites with high adsorptive energy were the primary surface property responsible for the remarkable TC adsorption capacity exhibited by FeB-11 in the macroscopic perspective. These findings underscored the importance of combining macroscopic and microscopic perspectives to understand the prioritization among various adsorption mechanisms, other than solely proposing various mechanisms, which was useful to help design efficient adsorbents.

Experimental and numerical study on the mechanical behaviors and crack propagation of sandstone containing two parallel fissures

For the rocky slope with potential sliding hazard, there are a larger number of flaws such as fractures and joints, which greatly affect the stability and safety of the slope. Thus, it is important and relevant to the behavior of fractured rock from a macroscopic and mesoscopic perspective by experiments and numerical simulation. In this paper, the mechanical properties and crack evolution behavior of grey sandstone containing two parallel fissures under the uniaxial compression tests were evaluated by experimental and bond-based Peridynamics (BB-PD) simulation. The results show that with the increase of fissure dip angle, the peak strength, elastic modulus and Poisson's ratio of pre-cracked sandstone samples under uniaxial compression condition gradually increase. At the same time, the total energy, dissipated energy and elastic peak energy of fractured sandstone also increase with the increase of fissure dip angle. In order to validate the experimental findings, a set of calibration parameters were used to model the intact samples using BB-PD. The numerical simulation reproduced the stress–strain curves, mechanical parameters and failure modes of double-fractured sandstone. Based on the results of indoor experiments and numerical simulations, it is concluded that the failure mode of double-fractured sandstone has three types under uniaxial compression: tensile failure, shear failure and conjugate shear failure. As the fissure dip angle increases, the main control factor for failure of sample gradually changes from rock bridge failure to secondary crack coalescence, and the stress distribution of fractured sandstone gradually changes from high stress concentration in the rock bridge zone to uniform stress distribution as a whole.

Investment obstacles of main countries situated along the 21st century Maritime Silk Road – a perspective of risk assessment

ABSTRACT The 21st Century Maritime Silk Road (MSR) is a development strategy initiated by the Chinese Government to respond to the changing global landscape. As this initiative progresses, growing number of enterprises are exploring investment opportunities overseas. Consequently, it has become increasingly important to address the investment obstacles faced by these enterprises. This paper assesses the investment environment of 22 countries along the MSR from three perspectives: the macroscopic perspective of country risk, the intermediate perspective of market environment risk, and the microscopic perspective of enterprise operational risk. Such a risk assessment is crucial in facilitating Chinese enterprises that seek to expand overseas. The research findings indicate that the investment risks in countries along the MSR are substantia, and enterprises should be cautious when investing. Drawing on the analysis, this paper presents macroscopic and microscopic control measures that both governments and enterprises can implement to alleviate investment barriers.

Effect of horizontal stress on fractal characteristics of rockburst fragments in coal mining

With the continuous increase in underground engineering depth, the risk of coal–rock dynamic disasters, such as rockburst, is becoming increasingly serious and complex threatening the safety of coal resources. To study the effect of horizontal stress on fractal characteristics of rockburst fragments in coal mining, this paper uses a digital drilling instrument to perform rockburst proneness tests on andesite and granite specimens with different horizontal stresses. Fractal theory is used to calculate the fractal dimension of the rockburst fragments for several combinations of parameters. The residual elastic energy index is combined with the fractal dimension of rockburst fragments to assess the propensity of rockbursts from macroscopic and microscopic perspectives. The experimental results show that the positive correlation between the fractal dimension and the AEF obtained under the two methods. The fractal dimensions of andesite and granite are 1.507–1.80 and 1.734–1.979, respectively. According to the rockburst proneness criterion, it is predicted that andesite and granite are all strong rockbursts under confining pressures of 20 MPa, 30 MPa and 50 MPa. Therefore, it is of some theoretical relevance to investigate the rockburst mechanism in terms of both the AEFand fractal dimensions of fragments under different unloading conditions.

A Trans-Scale Study on the Influence of Water Content and Particle Size on Matric Suction

Exploring the water retention properties of unsaturated soil from the perspective of a liquid bridge has been a popular issue in recent years. This study first measures the soil–water characteristic curves (SWCCs) of granular specimens to determine the influence of particle size on matric suction from a macroscopic perspective. Then, the internal mechanism of the influence of particle size and volumetric water content on matric suction is analyzed from the mesoscopic perspective by using the Young–Laplace (Y–L) equation to calculate matric suction between two equal spheres. The macroscopic and mesoscopic experiments both show that matric suction decreases with an increase in particle radius. Moreover, identifying the internal mechanism of SWCC from the liquid bridge perspective is only applicable when the influence of gravity can be disregarded or is in the transitional stage. The influence of volumetric water content and sphere radius on matric suction is mostly caused by the variation in the outer radius of the liquid bridge ( r 1 ) and the neck radius of the liquid bridge ( r 2 ). With an increase in volumetric water content and sphere diameter, the increasing rate of r 1 is much higher than r 2 , and the macroscopical matric suction gradually decreases.

On the relationship between the mechanical strength and mineral microstructure of biotite granite under temperature influence

Many studies are currently focusing on the mechanical properties of granite from macroscopic and microscopic perspectives, but only several studies on the influence of rock mineral composition on the mechanical properties using a combined macro-micro assessment. The biotite granite in the Gaoligong Mountains was selected as the research object, and the variation strength characteristics at 20–130°C were obtained through uniaxial compression experiments. The rock’s uniaxial compressive strength and elastic modulus reached peak values at 40°C. The main mineral components of the rock determined by X-ray powder diffraction were quartz, biotite, albite, and potash feldspar. With Material Studio software, molecular dynamics simulations were carried out on the crystal models of quartz, biotite, albite, and potash feldspar at 20–130°C, and relevant mechanical parameters were calculated. The macroscopic and microscopic experimental data were compared and analyzed. The results show that: 1) due to the thermal expansion of minerals in the rock, the original cracks between particles are partially closed, and the sample strength is the largest at 40°C; 2) temperature mostly affects quartz and biotite phases, and the rock strength increases first and then decreases with the temperature increase. The mechanical properties of albite and potash feldspar are less affected by temperature; 3) macroscopic and microscopic experimental results show that the rock strength reaches the peak value in a certain temperature range. The obtained critical temperature is different because the rock sample also contains a small amount of argillaceous rock, siliceous rock, phyllite, and some siliceous and calcareous cement beside the main mineral composition; 4) The structural changes of quartz and biotite are affected by temperature. The bond length of the quartz crystal decreases while that of the biotite crystal first increases and then decreases with the temperature. The mechanism of the temperature influence on the increase of the rock strength is different for these two crystal phases, and it requires further exploration.

Experimental study on the shear creep characteristics of joints under wetting-drying cycles

To better understand the shear creep characteristics of joints under wetting-drying cycles, multi-stage shear creep experiments are firstly conducted on the joints subjected to different wetting-drying cycles. Then, the shear creep damage characteristics of joints are investigated from the microscopic and macroscopic perspectives through wave velocity tests, scanning electron microscope observations, and failure morphologies. The investigation demonstrates that the increasing wetting-drying cycles lead to a porous and disintegrated microstructure of joints, which further results in increases in the shear deformation and steady-creep rate, and decreases in the failure strength and long-term strength. With increasing wetting-drying cycles, the wear rate of joints decreases and the damaged region of joints becomes smaller and invisible. Furthermore, a classification of the shear creep process of joints containing four stages is firstly proposed based on the test results. It is found that the presence of asperities on the rough joints is the physical basis of the existence of strengthening and cutting stages of the shear creep process. Finally, based on the experimental results, a new fractional-order damage creep model of joints considering wetting-drying cycles is proposed.

Wafer-Scale Graphene Growth on Si/SiO2 Substrates via Metal-Free Chemical Vapor Deposition

The direct growth of graphene on an insulator plays a crucial role in various applications, such as optoelectronic devices, supercapacitors, sensors, and so on. However, how to synthesize large area, homogeneous monolayer graphene with high quality remains a primary challenge. How to evaluate the flake size of directly grown graphene from a macroscopic perspective is yet to be explored. Herein, a full monolayer wafer-scale graphene film covering a silicon/silicon oxide substrate was realized via atmospheric pressure chemical vapor deposition under an optimized temperature, growth time, and methane flow rate. Both the Raman mapping and AFM characterization confirm that a homogeneous monolayer graphene was obtained (I2D/IG = 4.89, FWHM2D = 19.08). The transfer-free graphene exhibited a Hall mobility of 1864.6 cm2·V–1·S–1. Moreover, an empirical formula has been developed by applying the Monte Carlo method with the measured results to reflect the dependence of the resistivity of the graphene film on its flake size distributions as ρ=ρ01−k(1d2)0.4835. This work is highly compatible with present semiconductor device processing techniques and is expected to be highly desirable for Si-based graphene applications.

Study on the Contribution of Land Use and Climate Change to Available Water Resources in Basins Based on Vector Autoregression (VAR) Model

Under the influence of global climate change and urbanization processes, the number of available water resources (AWRs) in basins has become significantly more uncertain, which has restricted the sustainable development of basins. Therefore, it is important for us to understand the relationship between land use (LU) patterns and climate change on AWRs in a basin for sustainable development. To this end, the vector autoregressive (VAR) method was adopted to construct a quantitative model for AWRs in the basin in this study. Taking the Yiluo River Basin (YRB) as an example, the dynamic relationship between the five elements of agricultural land (AD), woodland (WD), grassland (GD), construction land (CD), and annual precipitation (PREP) and AWRs in the basin was studied. The results show the following: (1) The constructed VAR model was stable, indicating that the use of the proposed VAR model to characterize the degree of the effect of LU pattern and PREP on AWRs in the YRB was reasonable and effective. (2) AWRs in the YRB showed a downward trend, and their responses to the change in LU and PREP were delayed. The changes in the AWRs in the YRB tended to occur the year after changes to the LU pattern and PREP occurred. (3) In the long run, the degree of the contribution of each influencing factor to changes to AWRs was 23.76% (AD), 6.09% (PREP), 4.56% (CD), 4.40% (WD), and 4.34% (GD), which meant that the impact of the LU pattern was more than 90%. This study provides new ideas for similar research, water resource allocation, and LU planning in other river basins from a macroscopic perspective.

Farmland abandonment in the mountainous areas from an ecological restoration perspective: A case study of Chongqing, China

Farmland abandonment reflects the decline of rural areas, resulting in a series of vicious chain reactions, hindering the promotion of the comprehensive rural revitalization strategy. From the perspective of ecological restoration, this paper integrated multi-source data such as Landsat, GF-1, and Google Earth images and household survey data, aiming to reveal the spatiotemporal pattern, attribution, and mechanism of farmland abandonment in typical mountainous areas over the past 20 years by employing spatial analysis and mathematical models and to promote comprehensive management of abandoned farmland. The results are as follows. (1) The scope of abandoned farmland in Chongqing has been expanding, with the abandoned area growing from 142,385.8 hm2 to 345,778.4 hm2 from 2000 to 2020, with the initially abandoned farmland mostly concentrated in the northeastern areas, such as Chengkou, with an abandonment rate of 21.8%, and thereafter, spreading in all directions; In the end, abandoned farmland was concentrated in northeastern and southeastern Chongqing, such as Wuxi and Youyang, with abandonment rates of approximately 25.1% and 20%, respectively. (2) The attribution of farmland abandonment mainly includes wild boar damage, labour shortage, and natural conditions, among which wild boar proliferation has become an important factor under the background of ecological restoration. (3) Ecological restoration has produced a counter-servicing effect of the ecosystem on human beings, forming a vicious circle in the mountainous countryside where ecological restoration continues to aggravate farmland abandonment. The contribution of this study is to investigate the pattern of farmland abandonment from both macroscopic and microscopic perspectives. At the same time, this paper explores the intrinsic mechanism between ecological restoration and farmland abandonment and proposes scientific countermeasures to break the vicious cycle of ecological restoration that continues to exacerbate farmland abandonment in mountainous areas.

Effects of casein phosphopeptides on thermal stability and sensory quality of whey protein emulsions containing calcium beta-hydroxy-beta-methylbutyrate

This study aimed to elucidate the effect of casein phosphopeptides (CPP) on the thermal stability and sensory quality of whey protein emulsions containing calcium beta-hydroxy-beta-methylbutyrate (WPEs-HMB-Ca). The interaction mechanism among CPP, HMBCa, and WP in the emulsions before and after autoclaving (121 °C, 15 min) was systematically investigated from macroscopic external and microscopic molecular perspectives. It was found that WPEs-HMB-Ca treated by autoclaving resulted in an increase in droplet size (d4,3 = 24.09 μm) due to aggregation/flocculation of proteins, along with a stronger odor with higher viscosity, compared to those without autoclaving. When CPP:HMB-Ca = 1:25 (w/w) in the emulsion, the droplets exhibited a more uniform and consistent state in the emulsion. In addition, CPP was able to inhibit the formation of complex spatial network structures of proteins during autoclaving by binding with Ca2+, thus improving the thermal stability and storage stability of WPEs-HMB-Ca. This work might provide theoretical guidance for developing functional milk drinks with good thermal stability and flavor.

Genocide or Vicissitude: A Study on the Effects of Language Education Policies Shift for Uyghur in Xinjiang, China

Language education has profound implications for multiple dimensions of society. Zooming into one of the most populous ethnic minority groups within the Xinjiang Uyghur Autonomous Region, this study examines the reciprocal effects of language education policy on the social role of Uyghurs based on several crucial policy documents. Influenced by multiple factors, including political, societal, cultural, and historical aspects, education on the Uyghur language for the Uyghur people has mainly been weakened. Instead, Mandarin studies became mandatory as part of the minority education system. This study was conducted with methodologies of onsite ethnographic study and interviews to approach the question from a qualitative perspective. Following the macroscopic perspectives, findings reveal that the policies positively impacted Uyghurs economically but raised difficulties for them in inheriting their ethnic cultures. At the same time, implications are discussed following the microscopic perspectives. Finally, concentrating on an individuals self-construal and social identity establishment, it argues the high possibility of the young generation of Uyghur falling under a self-identification crisis when not mastering their mother tongue, the Uyghur language.

Effect of thermal barrier coatings and integrated cooling on the conjugate heat transfer and thermal stress distribution of nickel-based superalloy turbine vanes

Based on the comprehensive design of the thermal barrier coatings (TBCs) and advanced integrated cooling systems for the Ni-based superalloy turbine vanes. This study employs a multidisciplinary method to research the aerothermal performance and elastic thermal stress of the first stage Ni-based superalloy (DS GTD 111) turbine guide vane cooled by an integrated cooling system and TBC thickness of 0.5 mm. The results show that the highest temperature and average temperature on the substrate under TBC decreased by 126 K and 110 K, respectively. For the vanes without and with TBC, the thermal stresses are concentrated on the midchord region of the suction side, the upper edge of film holes outflow, and junction regions between the vane root, tip, and endwalls, which bear high-temperature gradient and high temperature. However, TBC reduces stress value by 50%∼95% in thermal stress concentration regions of the substrate, which significantly reduces the slip systems activated regions on the substrate. In addition, the activation of the dominant slip system (DSS) is a further optimization objective for cooling turbine vanes. This study provides macroscopic and microscopic perspectives for improving integrated cooling structures of actual vanes in the design process by comprehensively considering aerothermal and thermomechanical performance.

Definition of a Dietary Pattern Expressing the Intake of Vegetables and Fruits and Its Association with Intestinal Microbiota

Daily dietary habits directly or indirectly influence the intestinal microbiota, and the resulting changes in its composition and metabolic activity alter the health conditions of the host. Although many studies have analyzed the association between individual nutrients/food items and intestinal microbiota, the assessment of the diet and intestinal microbiota from a macroscopic perspective has not yet been performed in Japan. Therefore, we focused on vegetables and fruits and aimed to identify dietary patterns of high intake of these foods and to examine their relationship with the intestinal microbiota. This cross-sectional study included 1019 healthy individuals aged ≥20 years in a rural area in northern Japan. Six dietary patterns were detected by factor analysis using the brief-type self-administered diet history questionnaire (BDHQ) data to identify the “vege pattern”, which was the dietary pattern rich in vegetables and fruits. Permutational multivariate analysis of variance revealed changes in β-diversity according to dietary patterns. In multivariable-adjusted models, the adherence to the vege pattern was positively correlated with α-diversity. This is the first study to reveal a correlation between intestinal microbiota and dietary habits rich in vegetables and fruits in a rural area of Japan.

Assessing climatic impact on transition from Neanderthal to anatomically modern human population on Iberian Peninsula: a macroscopic perspective

The Iberian Peninsula is of particular interest for the research on the Neanderthal (NEA) to anatomically modern human (AMH) population transition. The AMHs arrived in Iberia last from Eastern Europe and thus any possible contacts between the two populations occurred here later than elsewhere. The transition process took place in the earlier part of the Marine Isotope Stage 3 (∼60–27 cal ka BP) as repeated and profound climate changes challenged the population stability. To investigate how climate change and population interactions influenced the transition, we combine climate data with archaeological-site data to reconstruct the Human Existence Potential, a measure of the probability of human existence, for both the NEA and AMH populations in the Greenland Interstadial 11–10 (GI11-10) and Stadial 10–9/Heinrich event 4 (GS10-9/HE4) times. It is found that during GS10-9/HE4, large parts of the peninsula became unsuitable for NEA human existence and the NEA settlement areas contracted to isolated coastal hot spots. As a consequence, the NEA networks became highly unstable, triggering the final collapse of the population. The AMHs arrived in Iberia in GI10 but were confined to patches in the northern most strip of the peninsula. They were soon facing the much colder climate of GS10-9/HE4, which prevented their further expansion or even caused a contraction of their settlement areas. Thus, due to the constellation of climate change and the dispersal of the two populations into different regions of the peninsula, it is unlikely that the NEAs and AMHs coexisted in extensive areas and the AMHs had a significant influence on the demography of the NEAs.

Flexible electrospun FeCo/carbon hybrid nanofiber films as binder-free anodes for enhanced lithium storage performance

The design of electrodes with excellent mechanical elasticity is the significant to developing flexible electronic devices with mechanical endurance and outstanding lithium storage properties. Herein, the flexible FeCo/carbon hybrid nanofiber membranes (named as FeCo@CNFM) were successfully prepared via electrospinning and subsequent carbonization process. From the macroscopic perspective, the FeCo@CNFM can bend at a large angle without any destruction, and be directly used as working electrode of lithium ions batteries (LIBs) without any expensive additives, demonstrating its extraordinary mechanical flexibility. From the microscopic perspective, the homogeneously dispersed fine FeCo nanoparticles and the three-dimensional (3D) interconnected transport network constructed of carbon nanofibers significantly shorten the lithium-ion transfer distance, eliminate the volume fluctuation during lithiation/delithiation process, enhance the utilization rate of active materials, and promote the electrical conductivity of the composite electrode, thus leading to remarkably improved electrochemical properties. As a consequence, the optimized FeCo@CNFM manifests a superior discharge capacity of 584.9 mA h g−1 at 100 mA g−1 after 100 cycles with long cycling stability and good rate capability of 227.1 mA h g−1 even at a large current rate of 2 A g−1, making it a promising flexible self-supporting anode for LIBs.