Space-time Evolution Research Articles

Characterization and experimental verification of the rotating synthetic aperture optical imaging system

The rotating synthetic aperture (RSA) optical imaging system employs a rectangular primary mirror for detection. During the imaging process, the primary mirror rotates around the center to achieve the aperture equivalent to the long side of the rectangle at different rotation angles. As a result, the system’s point spread function changes over time, causing periodic time-varying characteristics in the acquired images’ resolution. Moreover, due to the rectangular primary mirror, the images obtained by the RSA system are spatially asymmetric, with a lower resolution in the short side’s direction than in the long side’s direction. Hence, image processing techniques are necessary to enhance the image quality. To provide reference for the study of image quality improvement methods, we first characterize the imaging quality degradation mechanism of the RSA system and the time–space evolution law of the imaging process. We then establish an imaging experiment platform to simulate the dynamic imaging process of the RSA system. We quantify the RSA system’s impact on image degradation using objective indexes. Subsequently, by comparing the imaging experiment results with theoretical analysis, we verify the spatially asymmetric and temporally periodic imaging characteristics of the RSA system. Lastly, we introduce image super-resolution experiments to assess the limitations of directly applying generic deep learning-based single image super-resolution methods to the images captured by the RSA system, thereby revealing the challenges involved in improving image quality for the RSA system.

A bilateral preconditioning for an L2-type all-at-once system from time-space non-local evolution equations with a weakly singular kernel

A bilateral preconditioning for an L2-type all-at-once system from time-space non-local evolution equations with a weakly singular kernel

Numerical investigation on the rotor-turbulence interaction noise

Noise from a turbomachinery component, such as compressors and turbines, is an important issue to be resolved in aerospace and ocean engineering applications. The rotor of a turbomachinery assembly usually could operate downstream to other flow structures (fuselages, stators, control surfaces, etc.) that produce either large-scale or small-scale turbulence structures, which are highly complex and are being distorted while they are ingested into the rotor, which generate the rotor-turbulence interaction noise. The presented work conducted numerical simulation research on a ten-bladed rotor ingesting different turbulence structures. The large eddy simulation (LES) and Ffowcs-Williams and Hawkings (FW-H) methods were used to predict the flow-induced noise from the rotor. The results show that the time-space evolution of the upstream turbulent structure when it passes towards the rotor. In addition, the differences in the turbulence ingestion noise at different inflow speeds and rotational speeds were studied. Furthermore, the sound generation mechanism of turbulent ingestion noise was explored using a newly proposed near-field sound source analysis method. In summary, this study can help to improve the understanding of the physical mechanisms of unsteady forces and noise generated by a rotor when it interacts with ingesting turbulent flows.

Impact of vorticity and viscosity on the hydrodynamic evolution of hot QCD medium

The strongly interacting transient state of quark-gluon plasma (QGP) medium created in ultra-relativistic collisions survives for a duration of a few fm/c. The spacetime evolution of QGP crucially depends on the equation of state (EoS), vorticity, viscosity, and external magnetic field. In the present study, we obtain the lifetime of a vortical QGP fluid within the ambit of relativistic second-order viscous hydrodynamics. We observe that the coupling of vorticity and viscosity significantly increases the lifetime of vortical QGP. The inclusion of a static magnetic field, vorticity, and viscosity makes the evolution slower. However, the static magnetic field slightly decreases the QGP lifetime by accelerating the evolution process for a non-rotating medium. We also report the rate of change of vorticity in the QGP, which will be helpful in studying the behavior of the medium in detail.

Interaction of the Cosmic Dark Fluid with Dynamic Aether: Parametric Mechanism of Axion Generation in the Early Universe

We consider an isotropic homogeneous cosmological model with five interacting elements: first, the dynamic aether presented by a unit timelike vector field; second, the pseudoscalar field describing an axionic component of the dark matter; third, the cosmic dark energy, described by a rheologic fluid; fourth, the non-axionic dark matter coupled to the dark energy; and fifth, the gravity field. We show that the early evolution of the Universe described by this model can include two specific epochs: the first one can be characterized as a super-inflation epoch; the second epoch is associated with an oscillatory regime. The dynamic aether carries out a regulatory mission; the rheologic dark fluid provides the specific features of the spacetime evolution. The oscillations of the scale factor and of the Hubble function are shown to switch on the parametric (Floquet-type) mechanism of the axion number growth.

Spacetime evolution of lepton number densities and wave-packet-like effects for neutrino flavor and chiral oscillations in quantum field theory

Spacetime evolution of lepton number densities and wave-packet-like effects for neutrino flavor and chiral oscillations in quantum field theory

The space-time evolution and driving mechanism of coordinated development of modern logistics industry and tourism industry

Modern logistics and tourism are part of the tertiary industry, and their "food, accommodation, travel, travel, shopping, entertainment" six elements are increasingly integrated. Mutual promotion, comprehensiveness, and circulation for the coordinated development of the two provide a huge space and possibilities. This study uses the entropy weight comprehensive evaluation method and provincial 21-year Panel data to measure and evaluate the coordinated development level of the modern logistics and tourism industry in 31 Chinese provinces (districts and cities). ArcGIS 10.5 studies cold and hot regions in the coordinated growth of contemporary logistics and tourism across the research period. The study's findings revealed that: ①Modern logistics and tourism coordination has decreased in the east, west, and east directions, and changes in eastern provinces (districts and cities) over the research period were not significant or consistent. Most provinces (districts and cities) in the central area have low coupling coordination, and the upward tendency is clear, notably in Hubei, Anhui, and Henan provinces; most western provinces, except Sichuan Province, have imbalanced decline. ② Low-coupling coordinated provinces decreased while moderate-coupled provinces increased during the research period. Hot spots concentrated and expanded, whereas cold spot regions diminished. ③Each province's seven driving forces affect modern logistics and tourism. This research will help regions coordinate tourism and logistics.

Fenton: A Systematic Review of Its Application in Wastewater Treatment

The use of new technologies for the removal of pollutants from wastewater has become globally necessary due to the complexity and facilities defined by conventional treatments. Advanced oxidative processes, specifically the Fenton process, have become widely applied given their low cost and ease of use. Therefore, this study aimed to evaluate the progression of the scientific publications on the implementation of Fenton process, investigating their space–time evolution. Additionally, useful solutions, trends, and gaps in the applications for the removal of pollutants with this methodology were identified, and also different remediation strategies and the design of new treatments for wastewaters were identified within this scientometric analysis. Bibliometric research was conducted in two scientific databases, Web of Science and Scopus, from 2011 to 2022, and we identified 932 and 1263 studies with the word “Fenton,” respectively. When these publications are associated with the treatment of alternative effluents, an increase in publications from 2011 (r = 0.95, p < 0.001) and 2013 (r = 0.93, p < 0.001) was observed when analyzing both databases, indicating the relevance of the theme. Among these studies, several of them were conducted on the bench scale (89.8% and 98.3%, Web of Science and Scopus, respectively) and in aqueous matrix (97.8% and 98.4%, Web of Science and Scopus, respectively), with being China the main country with publications associated with these words (28.33% and 41.9%), while Brazil is related to 3.65% and 2.29% of the total studies in Web of Science and Scopus, respectively. In addition, this review provides a guideline for new applications for different species in the matrices and describes the evolution of technological solutions to meet Sustainable Development Goal 6: clean water and sanitation.

Spatial-epidemiological analysis of population aging in counties in Jiangsu Province, 1990-2020

Objective: To analyze the space-time evolution trend of population aging at the county level in Jiangsu Province from 1990 to 2020. Methods: Taking each county of Jiangsu Province as the research object, we selected data from the fourth to the seventh national population censuses. We used the aging coefficient and age concentration rate as static and dynamic indicators to measure the degree of population aging, respectively. We also used spatial correlation analysis to study the spatial and temporal patterns and evolution characteristics of aging in counties in Jiangsu Province. Results: The degree of aging in each county of Jiangsu Province has been deepening, and the degree of aging gradually evolves from high in southern Jiangsu and low in northern Jiangsu to high in central Jiangsu and low in southern and northern Jiangsu and shows obvious spatial aggregation. From 1990 to 2020, the population aging in Jiangsu Province has accelerated, among which the aging from 2010-2020 is the fastest. The aging progress appeares the fastest in 2010-2020. Conclusion: From 1990 to 2020, population aging in Jiangsu Province has been deepening, with the fastest progress in the last decade and an obvious spatial aggregation.

Thermodynamic quantities and phase transitions of five-dimensional de Sitter hairy spacetime* *Supported by the National Natural Science Foundation of China (12075143)

In this study, we take the mass, electric charge, hair parameter, and cosmological constant of five-dimensional de Sitter hairy spacetime as the state parameters of the thermodynamic system, and when these state parameters satisfy the first law of thermodynamics, the equivalent thermodynamic quantities of spacetime and the Smarr relation of five-dimensional de Sitter hairy spacetime are obtained. Then, we study the thermodynamic characteristics of the spacetime described by these equivalent thermodynamic quantities and find that de Sitter hairy spacetime has a phase transition and critical phenomena similar to those of van de Waals systems or charged AdS black holes. It is shown that the phase transition point of de Sitter hairy spacetime is determined by the ratio of two event horizon positions and the cosmic event horizon position. We discuss the influence of the hair parameter and electric charge on the critical point. We also find that the isochoric heat capacity of the spacetime is not zero, which is consistent with the ordinary thermodynamic system but differs from the isochoric heat capacity of AdS black holes, which is zero. Using the Ehrenfest equations, we prove that the critical phase transition is a second order equilibrium phase transition. Research on the thermodynamic properties of five-dimensional de Sitter hairy spacetime lays a foundation for finding a universal de Sitter spacetime thermodynamic system and studying its thermodynamic properties. Our universe is an asymptotically dS spacetime, and the thermodynamic characteristics of de Sitter hairy spacetime will help us understand the evolution of spacetime and provide a theoretical basis to explore the physical mechanism of the accelerated expansion of the universe.

Collective dynamics of polarized spin-half fermions in relativistic heavy-ion collisions

Standard relativistic hydrodynamics has been successful in describing the properties of the strongly interacting matter produced in the heavy-ion collision experiments. Recently, there has been a significant theoretical advancement in this field to explain spin polarization of hadrons emitted in these processes. Although current models have successfully explained some of the experimental data based on the coupling between spin polarization and vorticity of the medium, they still lack a clear understanding of the differential measurements. This is commonly interpreted as an indication that the spin needs to be treated as an independent degree of freedom whose dynamics is not entirely bound to flow circulation. In particular, if the spin is a macroscopic property of the system, in equilibrium its dynamics should follow hydrodynamic laws. Here, we develop a framework of relativistic hydrodynamics which includes spin degrees of freedom from the quantum kinetic theory for Dirac fermions and use it for modeling the dynamics of matter. Following experimental observations, we assume that the polarization effects are small and derive conservation laws for the net baryon current, the energy–momentum tensor and the spin tensor based on the de Groot–van Leeuwen–van Weert definitions of these currents. We present various properties of the spin polarization tensor and its components, analyze the propagation properties of the spin polarization components, and derive the spin-wave velocity for arbitrary statistics. We find that only the transverse spin components propagate, analogously to the electromagnetic waves. Finally, using our framework, we study the space–time evolution of the spin polarization for the systems respecting certain space–time symmetries and calculate the mean spin polarization per particle, which can be compared to the experimental data. We find that, for some observables, our spin polarization results agree qualitatively with the experimental findings and other model calculations.

Evaluation of urban flood resilience and its Space-Time Evolution: A case study of Zhejiang Province, China

Urban floods have become increasingly frequent in recent years, highlighting the need for resilience evaluation and the identification of strategies to improve urban flood resilience. In this study, a system of resilience evaluation indicators is proposed to quantitatively evaluate the level of urban flood resilience. The entropy method used to calculate the resilience index and the space–timepermutationscanmethod used to analyze the space–time aggregation characteristics of urban resilience levels are combined to establish a methodology for evaluating urban flood resilience. An evaluation indicator system for urban flood resilience is proposed, encompassing aspects of natural, economy, society, and infrastructure. This system attuned to the local needs of urban flood resilience evaluation, tests the applicability of the Guide for Safety Resilient City Evaluation (GB/T 40947–2021) in this study. Moreover, it incorporates key common indicators extracted from prior studies on urban flood resilience evaluation. Zhejiang Province, a flood-prone area in China, is selected as the study area, and the proposed evaluation indicator system is used to evaluate the urban flood resilience levels in Zhejiang and their space–time trends from 2011 to 2020. The results show that resilience levels have improved in the natural, economic, and infrastructure aspects, while the resilience levels of social aspect remain high. From 2011 to 2014, two distinct aggregation patterns emerged, delineated as inland-type and coastal-type aggregation areas. An analysis of both patterns was conducted, considering an array of influencing indicators, such as green coverage rate in built-up areas, population age structure index, gross domestic product, density of resident population in built-up areas, and per capita disposable income. The period from 2014 to 2020, however, did not reveal any significant aggregation characteristics. This study provides a reference for establishing an urban flood resilience evaluation indicator system and an in-depth understanding of urban flood resilience, and targeted recommendations to bolster urban flood resilience in the study area.

Editorial: Patterns and trends of time–space evolution of volcanism, from local to global

Editorial: Patterns and trends of time–space evolution of volcanism, from local to global

"In Search of an Integrated Corona Knowledge Ecosystem for Actionable Health Policy – A Mind Mapping Voyage and an Exploratory Decomposition in Spatial Pandemetrics"

"This paper seeks to map out the knowledge re quirements and infrastructure needed for a com prehensive and quantitative analysis of the societal and geographical dimensions of effective policies regarding COVID-19 (‘coronametrics’ or ‘pandemet rics’). After a sketch of limitations and challenges in corona research, a multi-layer mind map is designed in order to systematically scan the cognitive needs in the corona domain and to address both health policy and socioeconomic-medical information requirements in a geographic context, with a par ticular view to the use of actionable dashboards. A systematic decomposition of the corona knowledge system is pursued to acquire a coherent insight into gaps in corona knowledge, with particular emphasis on policy and research relevance. It turns out that the study of causality patterns in the complex space time evolution of COVID-19 is the Achilles’ heel in the analysis of pandemetrics and calls for new effective and preventive research"

Key Modes of Ignition and Maintenance of Corona Discharge in Air

Theoretical and experimental studies of various modes of corona discharge operation in atmospheric pressure air are presented in this short review. The original results of modeling negative corona discharges are presented, taking into account the non-stationary plasma-chemical kinetics of charged particles in air plasma. The space–time evolution of the discharge in needle-to-plane geometry is investigated and analyzed. Several stages of discharge development are revealed from the moment of initiation of a low-negative current corona to the quasi-stationary mode of a glow discharge. Experimental data of the authors are presented. Modern technology and diagnostic equipment with a wide variation of the main parameters (the shape and polarity of the applied voltage, the type of gap, etc.) was used. The measurement of the optical characteristics of the plasma glow was carried out with high spatial resolution. Corona discharge current pulse profiles in the air at atmospheric pressure have been recorded with subnanosecond time resolution. With a positive polarity of the pin electrode and high voltage, a transition from a spherical streamer initiating a corona discharge to a cylindrical streamer is shown. The author’s results are rigorously evaluated through a critical comparison with findings from other research groups.

Corrosion morphology prediction of civil infrastructure using a physics-constrained machine learning method

Corrosion morphology prediction for civil infrastructure using physics-based simulation is computationally challenging due to the coupled multi-physics simulations involved in long-term corrosion prognostics. Machine learning (ML)-based surrogate modeling provides a promising way of overcoming this challenge. This paper presents a physics-constrained ML method for surrogate modeling of a high-fidelity multi-physics pitting corrosion simulation, which is solved using a phase-field method. The proposed surrogate model consists of a convolutional variational autoencoder to reduce the dimension of pitting corrosion shape images and a Bayesian multi-layer perceptron network (also known as the Bayesian Latent Space Time Evolution Network) to model the evolution of the corrosion pit morphology over time. To account for the fact that corrosion damage without repair is an irreversible process, a physics constraint is added to the surrogate model to ensure that the corrosion rate is strictly negative. The proposed physics-constrained surrogate modeling method is compared with a purely data-driven surrogate modeling method which integrates a convolutional neural network autoencoder with a Gaussian process regression (GPR) model-based nonlinear autoregressive exogenous model. The results show that the proposed physics-constrained surrogate model is significantly more accurate than the purely data-driven GPR-based surrogate model.

Space–time observation of the dynamics of soliton collisions in a recirculating optical fiber loop

We present experiments performed in a recirculating fiber loop in which we realize the single-shot observation of the space and time interaction of two and three bright solitons. The space–time evolutions observed in experiments provide clear evidence of a nearly-integrable nonlinear wave dynamics that can be easily interpreted within the framework of the inverse scattering transform (IST) method. In particular collisions between solitons are found to be almost perfectly elastic in the sense that they occur without velocity change and with only a position (time) shift quantitatively well described by numerical simulations of the integrable nonlinear Schrödinger equation. Additionally our experiments provide the evidence that the position (time) shifts arising from the interaction among three solitons are determined by elementary pairwise interactions, as it is well known in the IST theory.

Impact of string interactions on the space–time evolution of hadronic vertices

We investigate the space–time picture of string evolution and hadron production in a fully string-based model for high energy collisions involving heavy-ions. We find that although the density of strings is quite large at the time of hadronization in a central heavy-ion collision, the initial overlap between them right after the collisions is not necessarily large. We also find that when including string-string interactions using the so-called shoving model, the density of strings is decreased which should dampen the rapid increase in string tension in the rope hadronization with multiplicity that we found in a previous paper.

Thermodynamics of phase transition in Reissner–Nordström–de Sitter spacetime

The Reissner-Nordstrm̈-de Sitter (RN-dS) spacetime can be considered as a thermodynamic system. Its thermodynamic properties are discussed that the RN-dS spacetime has phase transitions and critical phenomena similar to that of the Van de Waals system or the charged AdS black hole. The continuous phase transition point of RN-dS spacetime depends on the position ratio of the black hole horizon and the cosmological horizon. We discuss the critical phenomenon of the continuous phase transition of RN-dS spacetime according to Landau theory of continuous phase transition, that the critical exponent of spacetime is same as that of the Van de Waals system or the charged AdS black hole, which have universal physical meaning. We find that the order parameters are similar to those introduced in ferromagnetic systems. Our universe is an asymptotically dS spacetime, thermodynamic characteristics of RN-dS spacetime can help us understand the evolution of spacetime and provide a theoretical basis to explore the physical mechanism of accelerated expansion of the universe.

Timing control of impulse self balancing latch opening of expansion wave gun

Aiming at the problem of accurate latch opening control of expansion wave gun automatic gun, the mathematical model of accurate latch opening time is established, the travel curve of projectile and expansion wave, the velocity curve of projectile and expansion wave are studied, and the occurrence time of expansion wave and the time close to projectile are simulated and analyzed; The time-space evolution relationship between expansion wave velocity and local sound velocity, projectile velocity and gas velocity is simulated; The average pressure time curve and chamber resultant force curve of the two launch modes are compared and analyzed. After the projectile moves for 2.7ms, the chamber pressure and chamber resultant force of expansion wave launch are significantly reduced; The dynamic model of inertial latch opening is established; The changes of projectile initial velocity and recoil force under different latch opening times are studied. The test shows that the recoil force and recoil distance are greatly reduced when the projectile initial velocity decreases very weakly, which shows that the simulation calculation of latch opening time is accurate.