Space-time Evolution Research Articles

Spatiotemporal Evolution Characteristics in Ecosystem Service Values Based on Land Use/Cover Change in the Tarim River Basin, China

This paper explores the watershed land use and ecosystem services value (ESV) space-time evolution characteristics in the Tarim River Basin in China’s arid northwest. The study applies spatial correlation analysis using Landsat TM remote sensing images for 1990, 2000, 2010, and 2018. The land use data are extracted and the ESV coefficients are adjusted accordingly. The results show as follows: (1) From 1990 to 2018, land use in the Tarim River Basin changed significantly. Construction land, cultivated land, and water exhibited an increasing trend, while grassland, forest land, and water indicated a decreasing trend. Construction land increased the most, while water decreased the most. (2) Overall, ESV in the Tarim Basin charted a downward trend, from 872.884 billion RMB in 1990 to 767.165 billion RMB in 2018. From 2015 to 2018, the Basin’s ESV suffered the largest declines, with grassland ESV accounting for over 39% of the loss and adjustment services accounting for over 62%. (3) During the study period, the spatial distribution of ESV in the study area showed spatial distribution characterized that was either high in all directions or low in the middle, with significant positive spatial autocorrelation. The spatial distribution of ESV dynamic changes showed that ESV value-added regions were distributed in the southeast portion of the study area, while the ESV loss regions were distributed in the western and northern portions of the study area.

Memory-dependent derivative versus fractional derivative (II): Remodelling diffusion process

The memory-dependent derivative (MDD) is a new substitution for the fractional derivative (FD). It reflects the memory effect in a more distinct way. As an application, the representative heat diffusion process is remodeled with it. In fact, due to the existence of heat-conduction paradox, the time-space evolution mechanisms of this process are challenges to the modelers. The paradox cann’t be ascribed to the classical Fourier law, and the results show that the newly-constructed temporal MDD model is more reasonable than the Maxwell-Cattaneo, the temporal FD, the spatial FD and the common ones. Moreover, different mediums may accord with different memory times and weighted functions. This freedom of choice reflects the flexibility of MDD in modelling. It can be borrowed for exploring other diffusion problems.

Space-time analysis of ovarian cancer mortality rates by age groups in spanish provinces (1989\u20132015)

BackgroundOvarian cancer is a silent and largely asymptomatic cancer, leading to late diagnosis and worse prognosis. The late-stage detection and low survival rates, makes the study of the space-time evolution of ovarian cancer particularly relevant. In addition, research of this cancer in small areas (like provinces or counties) is still scarce.MethodsThe study presented here covers all ovarian cancer deaths for women over 50 years of age in the provinces of Spain during the period 1989-2015. Spatio-temporal models have been fitted to smooth ovarian cancer mortality rates in age groups [50,60), [60,70), [70,80), and [80,+), borrowing information from spatial and temporal neighbours. Model fitting and inference has been carried out using the Integrated Nested Laplace Approximation (INLA) technique.ResultsLarge differences in ovarian cancer mortality among the age groups have been found, with higher mortality rates in the older age groups. Striking differences are observed between northern and southern Spain. The global temporal trends (by age group) reveal that the evolution of ovarian cancer over the whole of Spain has remained nearly constant since the early 2000s.ConclusionDifferences in ovarian cancer mortality exist among the Spanish provinces, years, and age groups. As the exact causes of ovarian cancer remain unknown, spatio-temporal analyses by age groups are essential to discover inequalities in ovarian cancer mortality. Women over 60 years of age should be the focus of follow-up studies as the mortality rates remain constant since 2002. High-mortality provinces should also be monitored to look for specific risk factors.

Spin networks and the big bang singularity avoidance in the AdS/CFT correspondence

We propose a new version of the $AdS/CFT$ correspondence, where polymer structures similar to Loop Quantum Cosmology spin networks can be induced on an isotropic and homogeneous flat Randall-Sundrum II brane, corresponding to the holographic duals of closed string states living in the bulk. Such polymer structures drive a discrete evolution of the braneworld spacetime that leads to the regularization of the Big Bang singularity. The present results show that the $AdS/CFT$ conjecture can be a possible bridge between String theory and Loop Quantum Gravity.

Research on Urban and Rural Coordination Development and Its Driving Force Based on the Space-time Evolvement Taking Guangdong Province as an Example

Based on the background of the change in the urban–rural relationship in Guangdong Province, this paper constructs an analysis framework of urban and rural coordination development. Using the data of 19 administrative units above prefecture level in Guangdong Province, this paper studies the space–time evolution of urban and rural coordination development during 2000–2015 through Principal Component Analysis (PCA) and Exploratory Spatial Data Analysis (ESDA) and explores the influencing factors and driving forces behind it. It is found that there is club convergence in the urban and rural coordination development in Guangdong Province. This kind of convergence is reflected in the findings that the east bank of the Pearl River estuary is the best area for the urban and rural coordination development where Guangzhou, Dongguan, Shenzhen is the core and the level of urban and rural coordination development in the east, west and north of Guangdong Province is relatively low, which also reflects a geographical polarization feature. Based on the analysis of the factors that promote the urban and rural coordination development in the main years of 2000–2015, it can be concluded that location, economic development and urbanization level are the most important driving forces, followed by industrial structure. This research can be used as a decision-making reference for urban and rural coordination development and new countryside construction in China in the New Era.

Microjet formation from the grooved surface of aluminum under shock waves with different pulse durations

The shock-induced microjet phenomenon has attracted much attention due to its importance in shock compression science and technology. The existing researches have shown that shockwave profile has a significant effect on the microjet formation. This work investigates the influence of shock pulse duration on the microjet systematically based on smoothed particle hydrodynamics simulations and theoretical analysis. In fact, when the pulse duration of shock wave is more than 7.31 times the time of shock front passing through groove, the microjet mass and its time-space evolution will be consistent with the case under supported shock. It is shown that there is a critical value for the shock pulse duration (about 4.21 times the time of shock front passing through groove), below which the effect of shock pulse duration is distinct. With decreasing the shock pulse duration, the mass from spike to bubble experiences a rapid increase due to the increase of the velocity gradient behind the free surface, while the mass from spike to the theoretical free surface experiences a gradual reduction because the shock energy reduces. As a result, the spike becomes very thinner and the bubble amplitude is lengthened. The damage will be localized around the groove region. Besides, with the interaction between the release stage of incident waves and the release waves from the groove, the cavities and different low-density fragments are observed.

Photon production and elliptic flow from a momentum-anisotropic quark-gluon plasma

The emission of real photons from a momentum-anisotropic quark-gluon plasma (QGP) is affected by both the collective flow of the radiating medium and the modification of local rest frame emission rate due to the anisotropic momentum distribution of partonic degrees of freedom. In this paper, we first calculate the photon production rate from an ellipsoidally momentum-anisotropic QGP including hard contributions from Compton scattering and quark pair annihilation and soft contribution calculated using the hard thermal loop (HTL) approximation. We introduce a parametrization of the nonequilibrium rate in order to facilitate its further application in yield and flow calculations. We convolve the anisotropic photon rate with the space-time evolution of QGP provided by 3+1d anisotropic hydrodynamics (aHydro) to obtain the yield and the elliptic flow coefficient $v_2$ of photons from QGP generated at Pb-Pb collisions at LHC at 2.76 TeV and Au-Au collisions at RHIC at 200 GeV. We investigate the effects of various parameters on the results. In particular we analyze the sensitivity of results to initial momentum anisotropy.

The stratigraphic evolution of a submarine channel: linking seafloor dynamics to depositional products

ABSTRACT We investigate the relationship between the cross-sectional geomorphic expression of a submarine channel as observed on the seafloor and the stratigraphic product of long-lived erosion, bypass, and sediment deposition. Specifically, by reconstructing the time–space evolution of an individual channel fill (i.e., channel element) exposed in outcrop, we establish a genetic link between thick-bedded channel-element-axis sandstone to thinly interbedded channel-element-margin deposits. Although the bounding surface between axis sandstone and margin thin beds is sharply defined, it is composed of a series of geomorphic surface segments of various ages; as such, the composite stratigraphic surface (∼ 17 m relief) was formed from numerous incision events that repeatedly sculpted the conduit. By demonstrating the origin of the stratigraphic surface, we conclude that geomorphic surfaces with 2–7 m of erosional relief were largely responsible for the observed intra-channel-element architecture (and ultimately, the composite 17-m-thick element). The widely documented channel element axis-to-margin architecture is a product of submarine-channel thalweg dynamics, primarily recording interactions between the seafloor and the basal high-concentration layers of channelized turbidity currents.

Electromagnetic Scattering by Artificial Plasma Clouds in the Ionosphere

Vaporized samarium (Sm) has been released in the ionosphere for artificially creating plasma clouds, which may be tailored as radio wave reflectors for over-the-horizon communications. The model of samarium releases needs to be further refined for filling the gap between experimental observations and theoretical simulations. A sophisticated simulation model, so far to date, for samarium release in the ionosphere has been developed, and the redundancy reaction, inversion, and the photochemical reactions are all taken into account. The model results are consistent with experimental observations. Due to the geomagnetic field and neutral wind, the shape of artificial plasma clouds significantly changes. The error of the spherically symmetric reflection model is large. According to the density distribution of plasma clouds, the geometric theory of diffraction (GTD) is introduced here to deal with the electromagnetic scattering. The GTD-based scattering model has been established and used to study the time–space evolution of the ground-received power patterns in this article.

Spatio-temporal Analysis of the Relationship between Regional Resources and Environment and Economic Development Based on Computer Technology

This paper uses computer entropy calculation method to take the Yangtze River Economic Belt as the research object, combined with the theory of resource and environmental carrying capacity, sustainable development, and coupled systems, selects 11 provinces and cities in the Yangtze River Economic Belt as the research object, and establishes a time-space evolution cycle. Coupling model of capital and resources environment. The research results show that during the five-year period, the carrying capacity of regional environmental resources has shown that the eastern and western parts are better and the central part is weaker. Over time, the carrying capacity has gradually improved. In terms of sustainable development, the eastern coordination ability is strong, and the central and western areas are weak. In terms of time, resources, environment and economy are developing in a more coordinated direction. In view of the above, the paper puts forward corresponding development suggestions, hoping to enhance the development potential of the Yangtze River Economic Belt.

Mechanobiology predicts raft formations triggered by ligand-receptor activity across the cell membrane

Clustering of ligand-binding receptors of different types on thickened isles of the cell membrane, namely lipid rafts, is an experimentally observed phenomenon. Although its influence on cell’s response is deeply investigated, the role of the coupling between mechanical processes and multiphysics involving the active receptors and the surrounding lipid membrane during ligand-binding has not yet been understood. Specifically, the focus of this work is on G-protein-coupled receptors (GPCRs), the widest group of transmembrane proteins in animals, which regulate specific cell processes through chemical signalling pathways involving a synergistic balance between the cyclic Adenosine Monophosphate (cAMP) produced by active GPCRs in the intracellular environment and its efflux, mediated by the Multidrug Resistance Proteins (MRPs) transporters. This paper develops a multiphysics approach based on the interplay among energetics, multiscale geometrical changes and mass balance of species, i.e. active GPCRs and MRPs, including diffusion and kinetics of binding and unbinding. Because the obtained energy depends upon both the kinematics and the changes of species densities, balance of mass and of linear momentum are coupled and govern the space-time evolution of the cell membrane. The mechanobiology involving remodelling and change of lipid ordering of the cell membrane allows to predict dynamics of transporters and active receptors –in full agreement with experimentally observed cAMP levels– and how the latter trigger rafts formation and cluster on such sites. Within the current scientific debate on Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) and on the basis of the ascertained fact that lipid rafts often serve as an entry port for viruses, it is felt that approaches accounting for strong coupling among mechanobiological aspects could even turn helpful in better understanding membrane-mediated phenomena such as COVID-19 virus-cell interaction.

Spatiotemporal trends and influence factors of global diabetes prevalence in recent years.

Diabetes is one of the most widespread global epidemics and has become the main component of the global disease burden. Based on data regarding the prevalence of diabetes in 203 countries and territories from 2013 to 2017, we employed the Bayesian space-time model to investigate the spatiotemporal trends in the global diabetes prevalence. The factors influencing the diabetes prevalence were assessed by the Bayesian LASSO regression model. We identified 77 (37.9%) hotspots with a higher diabetes prevalence than the global average, 10 (0.4%) warm spots with global average level and 116 (57.1%) cold spots with lower level than global average. Of the 203 countries and territories, 68 (33.5%), including 31 hotspots, 5 warm spots and 32 cold spots, exhibited an increasing trend. Of these, 60 experienced an annual increase of more than 0.25%, and 8 showed an increasing trend. Three populous countries, namely China, the USA and Mexico, exhibited a high prevalence and an increasing trend simultaneously. Three socioeconomic factors, body mass index (BMI), urbanization rate (UR) and gross domestic product per capita (GDP-PC), and PM2.5 pollution were found to significantly influence the prevalence of diabetes. BMI was the strongest factor; for every 1% increase in BMI, the prevalence of diabetes increased by 2.371% (95% confidence interval (95% CI): 0.957%, 3.890%) in 2013 and by 3.045% (95% CI: 1.803%, 4.397%) in 2015 and 2017. PM2.5 pollution could be a risk factor, and its influencing magnitude gradually increased as well. With an annual PM2.5 concentrations increase of 1.0% in a country, the prevalence of diabetes increased by 0.196% (95% CI: 0.020%, 0.356%). The UR, on the other hand, was found to be inversely associated with the prevalence of diabetes; with each UR increase of 1%, the prevalence of diabetes decreased by 0.006% (95% CI: 0.001%, 0.011%).

Study on the Failure Mechanism for Coal Roadway Stability in Jointed Rock Mass Due to the Excavation Unloading Effect

Aiming at the large deformation instability problem caused by the excavation unloading of a coal roadway in deep-buried slowly inclined jointed rock mass, the geomechanical parameters and deformation failure characteristics of an engineering geomechanical model were investigated. The in-situ stress state of the model was measured with the stress relief method. The geological and mechanical properties of roadway surrounding rock were described. The surrounding rock structure was revealed with the electron microscopy scanning method, micro-fractures and randomly distributed joints highly developed in roadway surrounding rock. Field investigation and monitoring indicated the cross-section of roadway surrounding rock shrank continuously and the deformation distribution was obviously asymmetric. Shotcrete spalling and cable broken failures frequently occurred in the middle and ride side of roof and right rib. Based on the geomechanical conditions of the coal roadway, a discrete element numerical model of coal roadway in gently inclined jointed rock mass was established. The parameters of rock mass in the numerical model were calibrated. The model ran in unsupported condition to restore the evolution process of stress, crack propagation and deformation in roadway surrounding rock due to gradual deviatoric stress release caused by excavation. On this basis, the space-time evolution characteristics and law of stress, crack propagation and deformation were obtained and then the asymmetric large fragmentation and dilatation deformation failure mechanism of roadway surrounding rock in deep-buried slowly inclined jointed rock mass was revealed. The failure reasons of the support structure were analyzed, and the relevant support principles were proposed. The research results can provide scientific references for the stability control of roadways excavated in jointed rock mass.

Migration characteristics of CO under forced ventilation after excavation roadway blasting: A case study in a plateau mine

Multiple toxic gases, such as carbon monoxide (CO), are generated after excavation roadway blasting of plateau mines. To eliminate environmental pollution in a timely manner and avoid potential occupational hazards to miners, a three-dimensional unsteady roadway model was established based on field data of the Pulang copper mine in Yunnan province, China. Computational Fluid Dynamics (CFD) method was used to explore the space-time evolution characteristics of CO under different working conditions, and the grey correlation analysis was applied to study the correlation values of the influencing factors on the CO dispersion coefficient in the roadway. The results demonstrate that in the early stage of the roadway with forced ventilation, the mass concentration of CO in the vortex area near the working area was obviously higher than elsewhere, and in the later stage of ventilation, the mass concentration of CO at the bottom of the roadway was higher than that at the top. The most significant changes of the CO appeared within 500 s before ventilation. The mass-weighted average concentration of CO in the cross-section of the roadway presented a Gaussian-like distribution with respect to the ventilation time. The first stage represented a period of rapid growth, and the second stage exhibited a period of variable speed decline. The ventilation time when the mass concentration of CO in the roadway reached the upper limit of occupational exposure was generally between 700 s and 900 s, and the safe re-entry time was greater than 15 min. The grey correlation analysis revealed that the major influencing factors of CO migration in the roadway of the plateau mine, were, in a descending sequence, as follows: the distance between ventiduct mouth and working face, ventilation volume, and altitude, and the corresponding correlation coefficients were 0.9931, 0.7792, and 0.4366, respectively. The altitude was inversely proportional to the CO dispersion coefficient, and the distance between ventiduct mouth and working face was directly proportional to the ventilation coefficient corresponding to the CO dispersion coefficient. This research can provide guidance on optimising the ventilation design of roadways in plateau mines, thus ensuring the occupational health of cleaners.

Exact solutions of space-time local fractal nonlinear evolution equations: A generalized conformable derivative approach

In this work, a generalized type of conformable local fractal derivative (GCFD) is employed to investigate some nonlinear evolution equations. A modern technique for solving the nonlinear evolution equations is introduced. This technique based on the GCFD, the first integral method, and the functional variable method. As applied examples, new exact solutions of the space-time local fractal Schrödinger-Hirota equation and the space-time local fractal modified KdV-Zakharov-Kuznetsov equation are established. The results acquired confirm that the proposed GCFD is to describe the rigorous structure of complex physical phenomena without heredity and nonlocality. The obtained solutions are compared with some past results from literature. Moreover, some of these solutions are physically interpreted and graphically sketched.

Measurement and space-time evolution of health level under constraint of environmental pollution, China: 2002-2016.

China's massive energy consumption and low energy efficiency have caused severe environmental pollution and posed great threat to the national health level. The general occurrence of health complications caused by cumulative environmental pollution in China is on the rise. This paper attempts to shed light on the evolutionary trajectory of health level in China under the constraint of environmental pollution. Firstly, on the basis of environmental pressure and environmental elasticity, an evaluation system of environmental pollution is constructed, and China's environmental pollution level is obtained with combination evaluation method. An evaluation system for measuring health level is proposed based on three dimensions of health, namely health foundation, health behavior and environment, and health protection. To avoid possible bias caused by neglecting environmental pollution in estimating health level and emphasize the health depletion by environmental pollution, this paper adopts pollution levels to correct health levels. Finally, an analysis is made concerning the temporal and spatial evolution characteristics of health level on the basis on the Theil index and spatial distribution map. The results reveal three facts: (1) Environmental pollution level in China is lowering with improvement in environmental quality; (2) The overall health level in China is rising, but the local health level is deteriorating; and (3) The spatial distribution of the health level is characterized by unbalance. From the perspective of difference, intra-regional difference is greater than inter-regional difference. The health level difference between the provinces in the same region is the main contribution to the overall difference. In terms of spatial distribution, the lower health level is mainly concentrated in the north, while the higher health level is found in the southern provinces and parts of the western provinces.

Numerical relativity in spherical coordinates: A new dynamical spacetime and general relativistic MHD evolution framework for the Einstein Toolkit

We present SphericalNR, a new framework for the publicly available Einstein Toolkit that numerically solves the Einstein field equations coupled to the equations of general relativistic magnetohydrodynamics (GRMHD) in a 3+1 split of spacetime in spherical coordinates without symmetry assumptions. The spacetime evolution is performed using reference-metric versions of either the Baumgarte-Shapiro-Shibata-Nakamura equations or the fully covariant and conformal Z4 system with constraint damping. We have developed a reference-metric version of the Valencia formulation of GRMHD with a vector potential method, guaranteeing the absence of magnetic monopoles during the evolution. In our framework, every dynamical field (both spacetime and matter) is evolved using its components in an orthonormal basis with respect to the spherical reference-metric. Furthermore, all geometric information about the spherical coordinate system is encoded in source terms appearing in the evolution equations. This allows for the straightforward extension of Cartesian high-resolution shock-capturing finite volume codes to use spherical coordinates with our framework. To this end, we have adapted GRHydro, a Cartesian finite volume GRMHD code already available in the Einstein Toolkit, to use spherical coordinates. We present the full evolution equations of the framework, as well as details of its implementation in the Einstein Toolkit. We validate SphericalNR by demonstrating it passes a variety of challenging code tests in static and dynamical spacetimes.

Photonic Transmittance in Metallic and Left Handed Superlattices

We study the transmission of electromagnetic waves through layered structures of metallic and left-handed media. Resonant band structures of transmission coefficients are obtained as functions of the incidence angle, the geometric parameters, and the number of unit cells of the superlattices. The theory of finite periodic systems that we use is free of assumptions, the finiteness of the periodic system being an essential condition. We rederive the correct recurrence relation of the Chebyshev polynomials that carry the physical information of the coherent coupling of plasmon modes and interface plasmons and surface plasmons, responsible for the photonic bands and the resonant structure of the surface plasmon polaritons. Unlike the dispersion relations of infinite periodic systems, which at best predict the bandwidths, we show that the dispersion relation of this theory predicts not only the bands, but also the resonant plasmons’ frequencies, above and below the plasma frequency. We show that, besides the strong influence of the incidence angle and the characteristic low transmission of a single conductor slab for frequencies ω below the plasma frequency ω p , the coherent coupling of the bulk plasmon modes and the interface surface plasmon polaritons lead to oscillating transmission coefficients and, depending on the parity of the number of unit cells n of the superlattice, the transmission coefficient vanishes or amplifies as the conductor width increases. Similarly, the well-established transmission coefficient of a single left-handed slab, which exhibits optical antimatter effects, becomes highly resonant with superluminal effects in superlattices. We determine the space-time evolution of a wave packet through the λ / 4 photonic superlattice whose bandwidth becomes negligible, and the transmission coefficient becomes a sequence of isolated and equidistant peaks with negative phase times. We show that the space-time evolution of a Gaussian wave packet, with the centroid at any of these peaks, agrees with the theoretical predictions, and no violation of the causality principle occurs.

Peculiar behavior of the instability in systems with weak electron beam-plasma coupling

A study is developed, which allows investigating weakly coupled electron beam-plasma systems in general form regardless on geometry and specific parameters. In this case the instability acquires completely new aspects. In contrast to the well-known case of strong coupling, the role of the beam natural oscillations becomes decisive. The instability is due to the growth of the beam wave of negative energy. The study shows that the space-time evolution of an initial perturbation in weakly coupled beam-plasma systems is described by partial differential equation of second order. The equation is solved. Obtained expression for the fields’ space-time distribution gives most complete information on the instability: growth rates, velocities of unstable perturbations, influence of the dissipation on the instability, its character, (absolute/convective), etc. Most of the information is unavailable by conventional methods. In particular, the results clearly show that with an increase in the level of dissipation in the plasma, the instability transforms into a new, previously unknown type of dissipative streaming instability (DSI). Its growth rate depends on dissipation more critically than the growth rate of the single known DSI.

Thermodynamics of hot strong-interaction matter from ultrarelativistic nuclear collisions

Collisions between heavy atomic nuclei at ultra-relativistic energies are carried out at particle colliders to produce the quark-gluon plasma, a state of matter where quarks and gluons are not confined into hadrons, and colour degrees of freedom are liberated. This state is thought to be produced as a transient phenomenon before it fragments into thousands of particles that reach the particle detectors. Despite two decades of investigations, one of the big open questions is to obtain an experimental determination of the temperature reached in a heavy-ion collision, and a simultaneous determination of another thermodynamic quantity, such as the entropy density, that would give access to the number of degrees of freedom. Here we obtain the first such determination, utilizing state-of-the-art hydrodynamic simulations. We define an effective temperature, averaged over the space-time evolution of the medium. Then, using experimental data, we determine this temperature, the corresponding entropy density and speed of sound in the matter created in lead-lead collisions at the Large Hadron Collider. Our results agree with first-principles calculations from lattice quantum chromodynamics and confirm that a deconfined phase of matter is indeed produced.