Spatiotemporal Convergence Research Articles

A Benchmark for Neutron Kinetics Methods in Hexagonal Geometry

A new benchmark solution has been developed to aid in the development of neutron kinetics solvers for hexagonal geometries, such as those in water-water energetic reactors. This benchmark problem is based on the two-dimensional, two-group, International Atomic Energy Agency–Hex steady-state benchmark problem. Two transient problems are presented: a ramp and a step transient. To create a benchmark-quality solution to this transient problem, a basic neutron kinetics model was added to the computer program LUPINE (Liquid metal–cooled fast reactor Utility for Physics Informed Nuclear Engineering). LUPINE solves neutron kinetics equations in general unstructured mesh. First, the LUPINE kinetics solvers are verified using the TWIGL benchmark problems. Then the methods in LUPINE are used to perform a spatiotemporal convergence analysis to ensure that the solutions are sufficiently converged. Finally, Richardson extrapolation is performed to obtain the reference solutions for these new kinetics benchmark problems.

On the importance of fundamental computational fluid dynamics toward a robust and reliable model of left atrial flows.

Computational fluid dynamics (CFD) studies of left atrial flows have reached a sophisticated level, for example, revealing plausible relationships between hemodynamics and stresses with atrial fibrillation. However, little focus has been on fundamental fluid modeling of LA flows. The purpose of this study was to investigate the spatiotemporal convergence, along with the differences between high- (HR) versus normal-resolution/accuracy (NR) solution strategies, respectively. Rigid wall CFD simulations were conducted on 12 patient-specific left atrial geometries obtained from computed tomography scans, utilizing a second-order accurate and space/time-centered solver. The convergence studies showed an average variability of around 30% and 55% for time averaged wall shear stress (WSS), oscillatory shear index (OSI), relative residence time (RRT), and endothelial cell activation potential (ECAP), even between intermediate spatial and temporal resolutions, in the left atrium (LA) and left atrial appendage (LAA), respectively. The comparison between HR and NR simulations showed good correlation in the LA for WSS, RRT, and ECAP ( ), but not for OSI ( ). However, there were poor correlations in the LAA especially for OSI, RRT, and ECAP ( .55, .63, and .61, respectively), except for WSS ( ). The errors are comparable to differences previously reported with disease correlations. To robustly predict atrial hemodynamics and stresses, numerical resolutions of 10 M elements (i.e., .5 mm) and 10 k time-steps per cycle seem necessary (i.e., one order of magnitude higher than normally used in both space and time). In conclusion, attention to fundamental numerical aspects is essential toward establishing a plausible, robust, and reliable model of LA flows.

Impact of industry-university-research collaboration and convergence on economic development: Evidence from chengdu-chongqing economic circle in China

Collaboration among industry, universities, and research is crucial for building an innovative nation. Although industry-university-research collaborative innovation (IURCI) and time-space convergence can drive innovation, increase productivity, and spur economic development, their effects on the regional economy have not been thoroughly examined in existing literature. Therefore, this study investigates the impact of industry-university-research collaborative innovation (IURCI) and time-space convergence on economic development in China. Specifically, we focus on local-level cities in the Chengdu-Chongqing Economic Circle (CCEC) and construct an evaluation index system and time-space convergence model to measure the effects of IURCI and time-space convergence on economic development from 2007 to 2021. Our findings indicate that the efficacy of IURCI on economic development in China follows an inverted U-shaped curve, meaning that the marginal impact of IURC may decrease as more creative funds are deployed. Furthermore, the positive marginal effect of inventive talent input may decrease when it surpasses a certain value in an open innovation environment. The spatiotemporal convergence of collaborative innovation and development levels of IURCI in the CCEC shows significant differences. Regionally, the development level of IURCI in different regions exhibits significant differences in state and speed of convergence. In the southern Sichuan urban agglomeration, the collaborative innovation level of industry, education, and research follows an evolutionary process from convergence to divergence and then to convergence. Policymakers should pay close attention to the spatial effect of high-level development of regional IURCI and promote regions with higher development to drive regions with relatively weak development levels.

Spatiotemporal differentiation and convergence characteristics of green economic efficiency in China: from the perspective of pollution and carbon emission reduction.

Accurate quantification of pollution and carbon emission reduction policies, as well as analysis of green economic efficiency (GEE), are of great significance to accelerating green economic development in China and contributing to pollution prevention and carbon peaking. Using data from 2006 to 2022, this study incorporates pollution and carbon emission reduction policies into the evaluation system, and uses a model with slacks-based measures and a directional distance function (SBM-DDF) to calculate the GEE of 30 provinces. The Dagum Gini coefficient, kernel density estimation, and spatiotemporal convergence analysis are used to analyze the spatiotemporal differentiation and convergence characteristics of GEE. The findings show that the strengths of the pollution and carbon emission reduction policies are increasing but vary greatly among the provinces. China's overall GEE has a time trend with the characteristics of "decline-fluctuation-stable." The Dagum Gini coefficient reveals the relative differences between the major regions. Both the intra-regional and inter-regional differences tend to widen over time and the latter explains most of the sources of the overall differences. Kernel density estimation shows that the absolute differences between the provinces are generally widening, whereas the absolute differences between the provinces in the central and western regions are smaller than those in the eastern region. No obvious σ convergence characteristics exist in the country overall and the three major regions, but β convergence characteristics are present in each region. The factors affecting changes in the GEE of each region are not the same. The study suggests that the China should further improve the implementation of pollution and carbon emission reduction policies, pay attention to the regional differences and convergence issues of GEE, and promote the coordinated development of green economy in different regions. This study innovatively quantifies the policies related to pollution and carbon emission reduction, providing empirical evidence for understanding the performance of pollution and carbon emission reduction policies in various regions. Furthermore, this study incorporates policies as inputs into the GEE evaluation system, reveals the spatiotemporal differentiation of GEE, thereby providing reference for green economic transformation and sustainable development.

Regional differences and spatio-temporal convergence of environmental regulation efficiency in the Yellow River Basin, China

Regional differences and spatio-temporal convergence of environmental regulation efficiency in the Yellow River Basin, China

Agricultural production efficiency estimation and spatiotemporal convergence characteristic analysis in the Yangtze River Economic Belt: A semi‐parametric metafrontier approach

AbstractThe sustainable development goals regard improving agricultural production efficiency (APE) as the main method to solve food security problems. Based on the geographical cognition, combined with the functional positioning, we used meta semi‐parametric linear programming and spatial convergence models to analyze the spatiotemporal convergence characteristics of APE in the Yangtze River Economic Belt from 2000 to 2020. The results show that (1) under the framework of metafrontier analysis, the APE increases while maintaining an olive‐shaped stable structure of “sharp at both ends and wide in the middle”; (2) the efficiencies in agricultural production areas and the middle reaches has obviously declined compared with that of non‐agricultural production areas; and (3) non‐spatial factors and spatial factors jointly drive the convergence. The research results can provide references for clarifying the evolution law of regional agriculture and formulating differentiation macro policies.

Matricials methods applied to the solution of the Ginzburg-Landau equations

In this contribution we propose two numerical methods for the solution of the system of two non-linear coupled differential Ginzburg-Landau equations. These proposals are based firstly on taking a matrix view considering the quasi-linear coupled system, as a second option, considering the computational molecule with its respective restriction of the values and eigen-vectors of the matrix. We clearly and concisely obtained the eigenvalues that lead us to an optimal spatio-temporal convergence solution of said system of equations. We compare the numerical convergence times obtained by these three methods with the known time found by applying the link variable method.

Rethinking the Contribution of Land Element to Urban Economic Growth: Evidence from 30 Provinces in China

In China, disputes regarding the benefits and drawbacks of land finance have been heated, but the role of land in urban economic growth has received insufficient attention, particularly on a macro scale. This research used the Cobb–Douglas production function model to investigate the role of land in urban economic growth. Then, we conducted an empirical test using panel data from 30 provinces from 2000 to 2019, with the goal of revealing the role of land in urban growth and spatio-temporal inequalities in China. Furthermore, to find the spatial steady-state level of land contributions, σ convergence, absolute β convergence, and condition β convergence tests were applied. The results show that: (1) China’s urban economic development was influenced by the combined element of land, capital, and labor; (2) the contribution of land to China’s urban economy experienced a turning point during the “12th Five-Year Plan”; (3) the spatio-temporal convergence of the contribution of land showed convergence in the east but nonconvergence in the central and western regions; and (4) β convergence demonstrated convergence in eastern, central, and western China. Given the complex and turbulent international political and economic context, the Chinese government should think about how to foster continuous energy by supporting land-supply policies that are adapted to local needs.

Positron-emitting radiotracers spatially resolve unexpected biogeochemical relationships linked with methane oxidation in Arctic soils.

Arctic soils are marked by cryoturbic features, which impact soil-atmosphere methane (CH4 ) dynamics vital to global climate regulation. Cryoturbic diapirism alters C/N chemistry within frost boils by introducing soluble organic carbon and nutrients, potentially influencing microbial CH4 oxidation. CH4 oxidation in soils, however, requires a spatio-temporal convergence of ecological factors to occur. Spatial delineation of microbial activity with respect to these key microbial and biogeochemical factors at relevant scales is experimentally challenging in inherently complex and heterogeneous natural soil matrices. This work aims to overcome this barrier by spatially linking microbial CH4 oxidation with C/N chemistry and metagenomic characteristics. This is achieved by using positron-emitting radiotracers to visualize millimeter-scale active CH4 uptake areas in Arctic soils with and without diapirism. X-ray absorption spectroscopic speciation of active and inactive areas shows CH4 uptake spatially associates with greater proportions of inorganic N in diapiric frost boils. Metagenomic analyses reveal Ralstonia pickettii associates with CH4 uptake across soils along with pertinent CH4 and inorganic N metabolism associated genes. This study highlights the critical relationship between CH4 and N cycles in Arctic soils, with potential implications for better understanding future climate. Furthermore, our experimental framework presents a novel, widely applicable strategy for unraveling ecological relationships underlying greenhouse gas dynamics under global change.

Verification of MOOSE/Bison's Heat Conduction Solver Using Combined Spatiotemporal Convergence Analysis

Abstract Bison is a computational physics code that uses the finite element method to model the thermo-mechanical response of nuclear fuel. Since Bison is used to inform high-consequence decisions, it is important that its computational results are reliable and predictive. One important step in assessing the reliability and predictive capabilities of a simulation tool is the verification process, which quantifies numerical errors in a discrete solution relative to the exact solution of the mathematical model. One step in the verification process—called code verification—ensures that the implemented numerical algorithm is a faithful representation of the underlying mathematical model, including partial differential or integral equations, initial and boundary conditions, and auxiliary relationships. In this paper, the code verification process is applied to spatiotemporal heat conduction problems in Bison. Simultaneous refinement of the discretization in space and time is employed to reveal any potential mistakes in the numerical algorithms for the interactions between the spatial and temporal components of the solution. For each verification problem, the correct spatial and temporal order of accuracy is demonstrated for both first- and second-order accurate finite elements and a variety of time-integration schemes. These results provide strong evidence that the Bison numerical algorithm for solving spatiotemporal problems reliably represents the underlying mathematical model in MOOSE. The selected test problems can also be used in other simulation tools that numerically solve for conduction or diffusion.

Geological setting and genesis of the Kurmansky gabbro-trondhjemite massif (Middle Urals)

This paper reports the results of petrogeochemical studies of the Kurmansky gabbro-trondhjemite massif (eastern slope of the Middle Urals), lying in the western part of the large Reftinsky allochthonous block within the accretion East Uralian megazone. The relevance of this study is determined by the uncertainty in geodynamic setting and formation conditions of the rock massif and its role in the evolution of the Ural Mobile belt. We specified the countours of the massif. It is shown that the rocks were resulted from spatiotemporal convergence of partial melting in the mantle and lower crust at the island-arc stage of the Ural Mobile belt evolution. Partial melting of mantle peridotite, under the influence of an aqueous fluid rising from the subduction zone, initiated the occurrence of basite melts. The separation of the melt and its subsequent evolution to the compositions of gabbrodiorite and diorite took place at Ptot=10 kbar. Trondhjemites were formed as a result of partial melting of amphibolites at Ptot≥8 kbar, PH2O=0.1–0.2 kbars. The crystallization of trondhjemites in the crust was accompanied by the wollastonite skarns on contact with carbonate rock and xenoliths culminated at mesoabyssal level, Ptot=PH2O=1 kbar. The comparison between the composition of Kurmansky gabbro-trondhjemite massif and the island-arc- and collision-related magmatic suites in the region allowed us to assume that the Kurmansky massif belongs to the independent Early Devonian (?) gabbro-trondhjemite complex of island arc origin. The rock metamorphism conditions were evaluated, with the transformations supposedly related to the accretion of early island arc complexes at the Murzinsky-Aduysky microcontinent, which took place in the Devonian.

Ecological situation and changes in food demand in the EU member states and selected OECD countries: Spatio-temporal analysis

The ongoing process of globalization significantly affects the level of socio-economic development of countries and the progressing economic convergence. Along with the economic development of countries, changes in the level and structure of household consumption occur as a result of getting richer. The aim of the study is to analyze the unification of demand for food in households of the EU Member States and selected OECD countries in 1995–2019, with particular emphasis on spatial relationships. The study also addresses the issue of the relationship between changes in the level and structure of consumption of households with their ecological situation. This relationship is very important due to the assumptions about the idea of sustainable consumption. In the study of the equalization of the level of expenditure on food, the approach of β-absolute convergence and β-conditional convergence were applied. In the second approach, spatio-temporal convergence models were also estimated, taking into account the similarity of food expenditure, conditioned by the geographical location of territorial units. Moreover, the similarity of the ecological situation between analyzed countries was determined, which is the basis for the creation of an additional connection matrix, used in the estimation of spatio-temporal convergence models. The spatio-temporal analysis was based on spatial autoregressive model (SAR) and spatial error model (SE). This study confirms that in the analyzed countries in period of 1995–2019, there was an equalization of the level and share of household expenditure on food, related to the unification of consumption possibilities, determined by the convergence of disposable income.

Transportation Development, Spatiotemporal Convergence, and Urban Land Use: Study of the Opening of High-Speed Rails in the Yangtze River Delta, China

Abstract The rapid development of high-speed rail (HSR) has accelerated urbanization of the Yangtze River Delta (YRD). However, the impacts of HSR opening, opening time of HSR, and heterogeneity ef...

Second-order schemes for axisymmetric Navier–Stokes–Brinkman and transport equations modelling water filters

Soil-based water filtering devices can be described by models of viscous flow in porous media coupled with an advection–diffusion–reaction system modelling the transport of distinct contaminant species within water, and being susceptible to adsorption in the medium that represents soil. Such models are analysed mathematically, and suitable numerical methods for their approximate solution are designed. The governing equations are the Navier–Stokes–Brinkman equations for the flow of the fluid through a porous medium coupled with a convection-diffusion equation for the transport of the contaminants plus a system of ordinary differential equations accounting for the degradation of the adsorption properties of each contaminant. These equations are written in meridional axisymmetric form and the corresponding weak formulation adopts a mixed-primal structure. A second-order, (axisymmetric) divergence-conforming discretisation of this problem is introduced and the solvability, stability, and spatio-temporal convergence of the numerical method are analysed. Some numerical examples illustrate the main features of the problem and the properties of the numerical scheme.

A class of analytic solutions for verification and convergence analysis of linear and nonlinear fluid-structure interaction algorithms

Fluid-structure interaction (FSI) problems are pervasive in the computational engineering community. The need to address challenging FSI problems has led to the development of a broad range of numerical methods addressing a variety of application-specific demands. While a range of numerical and experimental benchmarks are present in the literature, few solutions are available that enable both verification and spatiotemporal convergence analysis. In this paper, we introduce a class of analytic solutions to FSI problems involving shear in channels and pipes. Comprised of 16 separate analytic solutions, our approach is permuted to enable progressive verification and analysis of FSI methods and implementations, in two and three dimensions, for static and transient scenarios as well as for linear and hyperelastic solid materials. Results are shown for a range of analytic models exhibiting progressively complex behavior. The utility of these solutions for analysis of convergence behavior is further demonstrated using a previously published monolithic FSI technique. The resulting class of analytic solutions addresses a core challenge in the development of novel FSI algorithms and implementations, providing a progressive testbed for verification and detailed convergence analysis.

Patterns of Police, Fire, and Ambulance Calls-for-Service: Scanning the Spatio-Temporal Intersection of Emergency Service Problems

Abstract Independent analysis of police, fire, and ambulance calls for service demonstrates common patterns in emergency service activity. Targeted, place-focused interventions have been demonstrated to prevent future problems for emergency services. This research builds on these findings to examine the spatial and temporal intersection of police, fire, and ambulance incidents to explore the potential utility of enhanced collaboration between emergency-first responders. Using police and fire data from Surrey, BC, Canada, from 2011 to 2013, spatial and temporal patterns of police-, fire-, and ambulance-related incidents were examined. Initial analyses demonstrate that 36% of the City’s area experienced 72% of incidents responded to over this 3-year study period. Focusing on this high-volume area, the spatial and temporal intersection of these incident types was explored. Spatially, lattices of varying cell sizes (250 m, 500 m, and 1,000 m) were placed over the study area. Temporally, incident volume was examined across the entire 3-year study period, and at yearly and monthly intervals. Incidents were placed within these spatial and temporal frameworks and visual inspection was utilized to assess the convergence of service demand. Regardless of the cell grid size, police, fire, and ambulance incidents were spatially and temporally concentrated, with the top 10% of cells accounting for approximately 50% of all incidents across all services. Furthermore, there was considerable spatio-temporal convergence in cells which account for the top decile of call volume for all incident types. A 2 × 2 typology is proposed to classify locations (in this case grid cells) based on (1) the frequency at which they generate high demand for services (sporadic versus persistent), and (2) the combination of agencies required to respond to high demand problems (single versus convergent). The spatial and temporal convergence of emergency service problems observed in this study suggests that an interagency approach to problem identification will enhance problem analysis processes. Working in conjunction with established problem-focused intervention strategies (such as problem-oriented policing), the volume-service typology provides a framework that can contribute to the development of appropriate problem-responses. This, we hope, will support emerging efforts to increase the extent to which emergency-first responder agencies collaborate to maximize efficiency and effectiveness, and reduce harm.

Spatiotemporal Convergence of Crime and Vehicle Crash Hotspots: Additional Consideration for Policing Places

Policing strategies that seek to simultaneously combat crime and vehicle crashes operate under the assumption that these two problems have a corollary relationship—an assumption that has received scant empirical attention and is the focus of the present study. Geocoded vehicle crash, violent crime, and property crime totals across were aggregated to Indianapolis census blocks over a 36-month period (2011-2013). Time series negative binomial regression and local indicators of spatial autocorrelation analyses were conducted. Results indicate that both violent and property crime are significantly related to vehicle crash counts, both overall and during the temporal confines of patrol tours. Relationship strength was modest. Spatiotemporal analysis of crime and crash data can identify places for police intervention and improved scholarly evaluation.

Historical amphibian declines and extinctions in Brazil linked to chytridiomycosis.

The recent increase in emerging fungal diseases is causing unprecedented threats to biodiversity. The origin of spread of the frog-killing fungus Batrachochytrium dendrobatidis (Bd) is a matter of continued debate. To date, the historical amphibian declines in Brazil could not be attributed to chytridiomycosis; the high diversity of hosts coupled with the presence of several Bd lineages predating the reported declines raised the hypothesis that a hypervirulent Bd genotype spread from Brazil to other continents causing the recent global amphibian crisis. We tested for a spatio-temporal overlap between Bd and areas of historical amphibian population declines and extinctions in Brazil. A spatio-temporal convergence between Bd and declines would support the hypothesis that Brazilian amphibians were not adapted to Bd prior to the reported declines, thus weakening the hypothesis that Brazil was the global origin of Bd emergence. Alternatively, a lack of spatio-temporal association between Bd and frog declines would indicate an evolution of host resistance in Brazilian frogs predating Bd's global emergence, further supporting Brazil as the potential origin of the Bd panzootic. Here, we Bd-screened over 30 000 museum-preserved tadpoles collected in Brazil between 1930 and 2015 and overlaid spatio-temporal Bd data with areas of historical amphibian declines. We detected an increase in the proportion of Bd-infected tadpoles during the peak of amphibian declines (1979-1987). We also found that clusters of Bd-positive samples spatio-temporally overlapped with most records of amphibian declines in Brazil's Atlantic Forest. Our findings indicate that Brazil is post epizootic for chytridiomycosis and provide another piece to the puzzle to explain the origin of Bd globally.

Development Plan of Facility Importance, Risk, and Damage Estimation Inventory Construction for Assisting Disaster Response Decision-Making

The safety of SOC facilities is constantly under threat by the globally increasing abnormal climate. Responding to disasters requires prompt decision-making such as suggesting evacuation paths. For doing so, spatio-temporal information with convergence of disaster information and SOC facility information must be utilized. Such information is being collected separately by the government or related organizations, but not collectively. The collective control of the separately collected disaster information and the generation of SOC facility safety and damage information are required for prompt disaster response. Also, as disaster information requires spatio-temporal convergence in its nature, the construction of an inventory that integrates related information and assists disaster response decision-making is required. A plan to construct a facility importance, risk, and damage estimation inventory for assisting prompt disaster response decision-making is suggested in this study. Through this study, the disaster and SOC facility-related data, which are being managed separately, can be collected and standardized. The integrated information required for the estimation of facility importance, risk, and damage can be provided. The suggested system is expected to be used as a decision-making tool for proactive disaster response.

Responses of non-eye movement central vestibular neurons to sinusoidal horizontal translation in compensated macaques after unilateral labyrinthectomy

After vestibular labyrinth injury, behavioral deficits partially recover through the process of vestibular compensation. The present study was performed to improve our understanding of the physiology of the macaque vestibular system in the compensated state (>7 wk) after unilateral labyrinthectomy (UL). Three groups of vestibular nucleus neurons were included: pre-UL control neurons, neurons ipsilateral to the lesion, and neurons contralateral to the lesion. The firing responses of neurons sensitive to linear acceleration in the horizontal plane were recorded during sinusoidal horizontal translation directed along six different orientations (30° apart) at 0.5 Hz and 0.2 g peak acceleration (196 cm/s(2)). This data defined the vector of best response for each neuron in the horizontal plane, along which sensitivity, symmetry, detection threshold, and variability of firing were determined. Additionally, the responses of the same cells to translation over a series of frequencies (0.25-5.0 Hz) either in the interaural or naso-occipital orientation were obtained to define the frequency response characteristics in each group. We found a decrease in sensitivity, increase in threshold, and alteration in orientation of best responses in the vestibular nuclei after UL. Additionally, the phase relationship of the best neural response to translational stimulation changed with UL. The symmetry of individual neuron responses in the excitatory and inhibitory directions was unchanged by UL. Bilateral central utricular neurons still demonstrated two-dimension tuning after UL, consistent with spatio-temporal convergence from a single vestibular end-organ. These neuronal data correlate with known behavioral deficits after unilateral vestibular compromise.