Flow Intensity Research Articles

Major patterns in the introgression history of Heliconius butterflies

Gene flow between species, although usually deleterious, is an important evolutionary process that can facilitate adaptation and lead to species diversification. It also makes estimation of species relationships difficult. Here, we use the full-likelihood multispecies coalescent (MSC) approach to estimate species phylogeny and major introgression events in Heliconius butterflies from whole-genome sequence data. We obtain a robust estimate of species branching order among major clades in the genus, including the ‘melpomene-silvaniform’ group, which shows extensive historical and ongoing gene flow. We obtain chromosome-level estimates of key parameters in the species phylogeny, including species divergence times, present-day and ancestral population sizes, as well as the direction, timing, and intensity of gene flow. Our analysis leads to a phylogeny with introgression events that differ from those obtained in previous studies. We find that Heliconius aoede most likely represents the earliest-branching lineage of the genus and that ‘silvaniform’ species are paraphyletic within the melpomene-silvaniform group. Our phylogeny provides new, parsimonious histories for the origins of key traits in Heliconius, including pollen feeding and an inversion involved in wing pattern mimicry. Our results demonstrate the power and feasibility of the full-likelihood MSC approach for estimating species phylogeny and key population parameters despite extensive gene flow. The methods used here should be useful for analysis of other difficult species groups with high rates of introgression.

Major patterns in the introgression history of Heliconius butterflies.

Gene flow between species, although usually deleterious, is an important evolutionary process that can facilitate adaptation and lead to species diversification. It also makes estimation of species relationships difficult. Here, we use the full-likelihood multispecies coalescent (MSC) approach to estimate species phylogeny and major introgression events in Heliconius butterflies from whole-genome sequence data. We obtain a robust estimate of species branching order among major clades in the genus, including the 'melpomene-silvaniform' group, which shows extensive historical and ongoing gene flow. We obtain chromosome-level estimates of key parameters in the species phylogeny, including species divergence times, present-day and ancestral population sizes, as well as the direction, timing, and intensity of gene flow. Our analysis leads to a phylogeny with introgression events that differ from those obtained in previous studies. We find that Heliconius aoede most likely represents the earliest-branching lineage of the genus and that 'silvaniform' species are paraphyletic within the melpomene-silvaniform group. Our phylogeny provides new, parsimonious histories for the origins of key traits in Heliconius, including pollen feeding and an inversion involved in wing pattern mimicry. Our results demonstrate the power and feasibility of the full-likelihood MSC approach for estimating species phylogeny and key population parameters despite extensive gene flow. The methods used here should be useful for analysis of other difficult species groups with high rates of introgression.

Analysis of the influence of swirling flow on the boiling heat transfer characteristics of two-phase flow

The Eulerian-Eulerian (EE) simulation approach + GENeralized TwO Phase (GENTOP) concept and two-fluid three-flow field with droplet were used to simulate the heat and mass transfer. Analysis encompassed the examination of steam and liquid phase distributions, as well as flow pattern transitions. Heat transfer enhancements were quantified using a comprehensive heat transfer factor. The disturbance intensity of the secondary flow was characterized by the absolute vortex flux. Results revealed a correlation between the intensity of the secondary flow and axial length, indicative of progressive fluid disturbance enhancement. Additionally, the maximal motion of the steam phase vortex was observed both near the wall and channel center. The EE+GENTOP concept exhibited superior capability in reproducing multi-scale flow including small-scale dispersed bubbles and large-scale continuous steam (coalescence and break-up). For investigations into the entrainment and deposition of liquid droplets in annular flow, the selection of a two-fluid three-flow field with the droplet model is recommended.

Rayleigh-Benard Convection Inside Square Cavities Filled with Thermodependent Non-Newtonian Fluids and Subjected to External Magnetic Field

The aim of this study is to numerically evaluate the Rayleigh-Benard natural convection magnetohydrodynamic (MHD) of a non-Newtonian fluid along a square cavity whose viscosity depends on the temperature. The rheological behavior of the fluids under consideration is represented using the Ostwald-De-Weale power law. Subsequently, the dominant equations are transformed into a non-dimensional form and computed using the finite volume method (FVM). The literature was used to validate the model, and excellent agreement was achieved by varying the fluid characteristics with Prandtl numbers , Hartmann numbers, , Rayleigh numbers, , the behavior index, n, and inclination angle, . The numerical results are discussed in terms of velocity, mean Nusselt number , maximum current function , streamlines, and isotherms. The study finds that the onset of convection is delayed with increasing values of n and Ha. Additionally, it revealed that the flow intensity and heat transfer decrease as the Hartmann number rises for both Newtonian and non-Newtonian fluids. At very high Ha values, the heat transfer is mainly assured by the conduction regime. Moreover, the temperature-dependent viscosity in MHD results in the disappearance of the Centro symmetry of the central cell and the migration of the center towards the active wall.

ОСНОВНІ ПРОБЛЕМИ ІНЖЕНЕРНО-ПЛАНУВАЛЬНИХ РІШЕНЬ ТРАНСПОРТНИХ РОЗВ’ЯЗОК ТИПУ «РОЗІРВАНЕ КІЛЬЦЕ» ТА ШЛЯХИ ЇХ УСУНЕННЯ

Introduction. Interchange designs that provide specific benefits to road users will always be of interest. It is extremely interesting a type of interchange in the same level named in literary sources as a «hamburger roundabout» or «throughabout». Usually, two separate lanes run through the extended roundabout, crossing each other inside the interchange. Such intersections can be regulated by both road signs and traffic lights, depending on their size and the intensity of incoming traffic flows. Problem Statement. The analysis of the designs of the intersection at one level by the type of throughabout is insufficiently presented both in the normative documentation for the design of highways and in modern scientific periodicals. However, this type of intersection refers to alternative junctions used in road construction practice in European countries. Thus, an urgent task is to evaluate the operational efficiency indicators and surrogate traffic safety indicators of the throughabout, which can later serve as a basis for making decisions about the need to construct this type of intersection. Purpose – to identify the main problems of the interchange by the type of throughabout based on the analysis of traffic efficiency and safety indicators, carried out by the method of traffic microsimulation.

A fusion model of temporal graph attention network and machine learning for inferring commuting flow from human activity intensity dynamics

Accurately estimating commuting flow is essential for optimizing urban planning and traffic design. The latest graph neural network (GNN) model with the encoder-decoder-predictor components has several limitations. First, it ignores the temporal dependency of node features for node embedding. Second, different estimation methods used in the decoder and predictor make it difficult to distinguish the contribution of node embedding or estimation method to flow estimation. Third, finer-grained socio-economic features of nodes are difficult to obtain due to low data availability. To address these problems, this study proposes a fusion model of temporal graph attention network and machine learning (TGAT-ML) to infer commuting flow from dynamic human activity intensity distribution. The model first constructs a commuting network with temporal human activity intensity as node features. A temporal graph attention network is then developed to capture the spatiotemporal dependency. The learned node embedding is generated by using a machine learning method in the decoder. Finally, based on learned node embedding and machine learning method used in the decoder, the commuting flow intensity is estimated. Results from an empirical study using the Baidu heat map data of Guangzhou city indicate that the proposed fusion model TGAT-ML outperforms all other baseline models. This study proves that the model performance can be significantly enhanced by determining the edge existence through commuting time-based approach, integrating temporal convolution with graph convolution, and unifying flow estimation method in both decoder and predictor. This work enables commuting flow estimation from dynamic human activity intensity and broadens existing flow generation research in terms of data and methodology.

An experimental study on horizontal well waterflooding in the Cretaceous porous carbonate reservoir of Oman

Porous carbonate reservoirs, prevalent in the Middle East, are lithologically dominated by bioclastic limestones, exhibiting high porosity, low permeability, intricate pore structure, and strong heterogeneity. Waterflooding through horizontal wells is commonly used for exploiting these reservoirs. However, challenges persist, such as significant uncertainty and complex operational procedures regarding adjustment effects during the exploitation. The USH reservoir of the Cretaceous D oilfield, Oman exemplifies typical porous carbonate reservoirs. It initially underwent depletion drive using vertical wells, followed by horizontal well waterflooding in the late stage. Currently, the oilfield is confronted with substantial developmental challenges, involving the understanding of residual oil distribution, effective water cut control, and sustaining oil production since it has entered the late development stage. Employing a microscopic visualization displacement system equipped with electrodes, this study elucidated the waterflooding mechanisms and residual oil distribution in the late-stage development of the USH reservoir. The results reveal that the reservoir's vertical stacking patterns act as the main factor affecting the horizontal well waterflooding efficacy. Distinct water flow channels emerge under varying reservoir stacking patterns, with post-waterflooding residual oil predominantly distributed at the reservoir's top and bottom. The oil recovery can be enhanced by adjusting the waterflooding's flow line and intensity. The findings of this study will provide theoretical insights of waterflooding mechanisms and injection-production adjustments for exploiting other porous carbonate reservoirs in the Middle East through horizontal wells.

Effect of non-uniform heat rise/fall and porosity on MHD Williamson hybrid nanofluid flow over incessantly moving thin needle

In this work, a novel enhanced model of the thermophysical characteristics of hybrid nanofluid is introduced. An innovative kind of fluid called hybrid nanofluid has been engineered to increase the heat transfer rate of heat and performance of thermal system. A growing trend in scientific and industrial applications pushed researchers to establish mathematical models for non-Newtonian fluids. A parametric study on theheat transfer and fluid flow of a Williamson hybrid nanofluid based on AA7075-AA7072/Methanol overincessantly moving thin needle under the porosity, Lorentz force, and non-uniform heat rise/fallis performed. Due to similarity variables, the partial differential equations governing the studied configuration undergo appropriate transformation to be converted into ordinary differential equations. The rigorous built-in numerical solver in bvp4c MATLAB has been employed to determine the numerical solutions of the established non-linear ordinary differential equations. It is worthy to note that velocity declines for both AA7075/Methanol nanofluid and AA7075- AA7072/Methanol hybrid nanofluid, but highervelocitymagnitudes occur for theAA7075/Methanol whilethe Williamson fluid parameters increased. It is alsoconcluded that as the porosity parameter isincreased, the flow intensity decreases gradually. It is worthy to note that for both non-uniform heat-rise and fall parameters, the temperature of the fluid gets stronger. Mounting valuesof needle thickness parameter leads to reduction in fluid speed and temperature. It is noticedthat as volume fractions of both types of nanoparticles are augmented then fluidvelocity and temperature amplify rapidly. A Comparison of current and published results is performed to ensure the validity of the established numerical model.

Effects of antiplatelet therapy on menstrual blood loss in reproductive-aged women: a systematic review

BackgroundThe effects of antiplatelet therapy on menstrual bleeding have not been well characterized. ObjectivesTo systematically review the effects of antiplatelet therapy on menstrual bleeding. MethodsA literature search was performed for studies of reproductive-aged women who received antiplatelet therapy. Characteristics of menstrual bleeding both before and after initiation of antiplatelet therapy and from comparison groups were collected. Two reviewers independently assessed the risk of bias in individual studies. ResultsThirteen studies with a total of 611 women who received antiplatelet therapy were included. Types of antiplatelet drugs used were aspirin (n = 8), aspirin and/or clopidogrel (n = 2), prasugrel (n = 1), and not specified (n = 2). Risk of bias was assessed at moderate (n = 1), serious (n = 8), critical (n = 2), and no information (n = 2). Three studies reported changes in menstrual blood loss volume. One of these showed no increase during antiplatelet therapy; the other 2 studies suggested that aspirin may increase menstrual blood loss volume. In 3 studies that assessed the duration of menstrual bleeding, up to 13% of women reported an increased duration of menstruation. In 5 studies that reported the intensity of menstrual flow, 13% to 38% of women experienced an increase in the intensity of flow. Five studies reported the prevalence of heavy menstrual bleeding in women who received antiplatelet therapy, with estimates ranging from 7% to 38%. ConclusionThere is lack of high-quality data on the effects of antiplatelet therapy on menstrual bleeding. Aspirin may increase menstrual blood loss, at least in a minority of women, whereas the effects of P2Y12 inhibitors are unknown.

X-ray Imaging of Two-Phase Flow Regimes in a Liquid Metal Swirling Downward Flow With Side Wall Gas Injection

The formation and behavior of gas bubbles is experimentally investigated in a liquid metal downward pipe flow, a configuration that largely corresponds to the situation in a submerged entry nozzle (SEN) in the continuous casting process in steel making. The experimental mockup is operated at room temperature using the ternary alloy GaInSn as model fluid. Argon gas is injected through an orifice located in the SEN wall. The gas distribution in the pipe is visualized by means of the X-ray radiography. The set-up is completed by an electromagnetic stirrer, which is used to create a swirling flow in the tube. Depending on the volume flow rates of the gas and the liquid metal, as well as the intensity of the swirl flow generated by the stirrer, 4 flow regimes are observed: (1) the formation of an almost stationary gas pocket in the region below the injection point without any electromagnetic stirring, (2) a twisted void zone along the side wall, (3) a straight void zone in the center of the pipe, and (4) a bubble chain in the core of the pipe flow. The experiments reveal that the wetting conditions at the inner SEN wall have a decisive influence on the resulting flow regime.

The AMPK-Sirtuin 1-YAP axis is regulated by fluid flow intensity and controls autophagy flux in kidney epithelial cells

Shear stress generated by urinary fluid flow is an important regulator of renal function. Its dysregulation is observed in various chronic and acute kidney diseases. Previously, we demonstrated that primary cilium-dependent autophagy allows kidney epithelial cells to adapt their metabolism in response to fluid flow. Here, we show that nuclear YAP/TAZ negatively regulates autophagy flux in kidney epithelial cells subjected to fluid flow. This crosstalk is supported by a primary cilium-dependent activation of AMPK and SIRT1, independently of the Hippo pathway. We confirm the relevance of the YAP/TAZ-autophagy molecular dialog in vivo using a zebrafish model of kidney development and a unilateral ureteral obstruction mouse model. In addition, an in vitro assay simulating pathological accelerated flow observed at early stages of chronic kidney disease (CKD) activates YAP, leading to a primary cilium-dependent inhibition of autophagic flux. We confirm this YAP/autophagy relationship in renal biopsies from patients suffering from diabetic kidney disease (DKD), the leading cause of CKD. Our findings demonstrate the importance of YAP/TAZ and autophagy in the translation of fluid flow into cellular and physiological responses. Dysregulation of this pathway is associated with the early onset of CKD.

Groundwater dynamics in intertidal zones of beach aquifers during salt-fingering flow

At aquifer-sea interfaces, submarine groundwater discharge (SGD) and related chemical loads are closely related to groundwater environment in the intertidal zone of coastal aquifers. Although unstable salinity distribution in the intertidal zone associated with salt-fingering flow has been known as a natural phenomenon for some coastal aquifers, a quantitative understanding of groundwater dynamics in the intertidal zone during salt-fingering flow is still lacking. This study investigated the movement features of salt fingers and the response laws of freshwater discharge zone (FDZ) in the intertidal zone, considering the fixed and seasonal inland conditions. The results revealed that during salt-fingering flow, the finger was repeatedly generated and detached from the intertidal zone. Horizontally, the finger moved toward the sea, and the finger speed first increased at the development stage, then remained unchanged at the separation stage, and finally decreased at the mergence stage. The movement speed of salt fingers was closely related to ambient freshwater flow in the FDZ. In the vertical direction, the finger first permeated downward with a decreasing speed, and then the upward discharge of fresh groundwater in the FDZ region with an increased flow velocity pushed the finger upwards with an increasing speed. In contrast to the results in a stable intertidal regime, the width of FDZ at the aquifer-sea interface fluctuated over time, and the variation trends possessed a well agreement with the flux of fresh groundwater discharge. This suggested that the width of FDZ at the aquifer-sea interface can be used as an indicator of fresh groundwater discharge, even in an unstable regime, to provide a basis for field monitoring. The intensity of salt-fingering flow varied over time under the condition of seasonal freshwater inflow. The mean duration of salt fingers decreased slightly with the increase of seasonal freshwater periods due to a decrease in the interface perturbation for the intertidal environment. These findings lay the foundation for gaining a better understanding of the potential implications of salt-fingering flow on SGD and related solute transports.

Evaluation of collar efficiency to prevent scouring around cylindrical bridge piers under live bed condition

The present study was carried out to experimentally investigate the effect of single and double collar on development of local scouring around cylindrical bridge piers under live-bed condition. The single collar with diameter of 3 times the pier diameter placed on the streambed level and double collars one on the streambed level and one on a lower elevation were used. Tests were conducted with different flow intensities equal to 1.4, 2.0, 2.4, 2.8 and 4.0 where flow intensity is defined as the ratio of bed shear velocity to shear velocity of bed material at threshold of motion. One experiment was also carried out with flow intensity of 4.7 at which dunes were washed out and transition flow regime prevailed. The duration of the experiments was long enough to assure complete dune formations and multiple traverses of dunes through the pier location. Results showed that the scour depth fluctuated between a maximum and a minimum value due to the bed features migration. A graph was developed to show the efficiency of single and double collars at different positions and under different flow intensities. With two collars in place, the mean and maximum scour depths at the highest flow intensity, reduced by about 53% and 35% respectively. Efficiency of collar was better in lower flow intensities. Finally, based on the present results, a design table is presented for the elevation of the lower collar based on the flow intensity.

Clarification of the Regional Methodology for Calculating Potential Soil Flushing from Meltwater for the Northern Forest-Steppe of Central Siberia

Abstract—The need to verify, modernize and refine existing models for calculating potential soil flushing from the effects of meltwater is due to the small number of studies of this type of erosion in the forest-steppe zone of Central Siberia and, as a consequence, the inability to reliably determine how accurate the calculation methods are in their current form under these conditions. For the agricultural zone of the Krasnoyarsk Territory, a regional model has been developed for calculating potential soil flushing based on a Universal equation and the Instructions’ formula. This paper presents the results of its verification, performed using the results of the author’s field measurements of soil flushing from meltwater by measuring removal cones on agricultural lands of the northern forest-steppe of Central Siberia (Krasnoyarsk forest-steppe). A refined version of the Regional Methodology is proposed, adapted to local hydrometeorological conditions and representing the formula of this model with an added correction factor \(K,\) taking into account the influence of the previous autumn moistening of soils and the intensity of water flow to the soil surface during snowmelt. Refinement and adaptation of the methodology allowed to increase the accuracy of the results of its application by an average of three times compared to the original type of the model, the average error decreased from 0.3 to 0.11. The refined version of the Regional methodology was tested in the course of the author’s research of snow-fall soil erosion in the Krasnoyarsk forest-steppe.

Correlation and agreement between infrared thermography and a thermometer for equine body temperature measurements.

Body temperature is a vital sign that determines physical status. Infrared thermography (IRT) is more frequently used for assessing horses' temperature because of its ease of use and less contact with the horses, making it a safer measurement method. However, the accuracy of IRT remains unclear; therefore, this study aimed to assess the potential use of IRT as an alternative method for measuring horse body temperature. Temperatures were measured in 14 horses. A digital thermometer was used to collect rectal temperature (RT), whereas a thermographic camera was used for IRT at three different positions to obtain the center of body temperature (CBT), head temperature (HT), and eye temperature (ET). The protocol was performed over 30 days, repeated thrice daily: morning (6:00-8:00), afternoon (14:00-15:00), and evening (17:00-19:00). Environmental factors, including humidity, ambient temperature, wind flow, and light intensity, were recorded indirectly according to the time of day and cooling device use. Mean RT, CBT, HT, and ET were 37.33°C, 34.08°C, 35.02°C, and 35.14°C, respectively. Center of body temperature was lower than RT by an average of 3.24°C (95% confidence interval [CI], 5.4°C-1.09°C). HT was lower than RT by an average of 2.3°C (95% CI, 4.33-0.28). The eye position showed the least difference between RT and infrared temperature, with an average of 2°C (95% CI, 0.7-3.92). However, there was no significant correlation between RT and infrared temperature at any position. Spray and vaporizer use significantly affected IRT and time of day (p = 0.05). Although IRT has advantages in terms of non-invasiveness and reduced stress on horses, its accuracy and reliability may be compromised by environmental variables, which interfere with infrared measurement. Future research should specifically focus on investigating environmental factors.

Experimental Study of the Effect of Geometric Dimensions of Rectangular Piano Key Overflow Crest on the Flow Intensity Coefficient

Experimental Study of the Effect of Geometric Dimensions of Rectangular Piano Key Overflow Crest on the Flow Intensity Coefficient

Flow structure analysis of nanofluid impingement on modified target surface under different design parameters

The flow structures of jet impingement dominate heat and mass transfer process, even the whole thermal performance. In this study, we have inspected the flow structures and mechanism of nanofluid jet impingement onto a dimpled target surface with different design parameters. Investigations are performed for the relative depth of dimple ([Formula: see text]), the jet-to-plate spacing ([Formula: see text]), nanoparticle volume concentration ([Formula: see text]), and Reynolds number (Re) ranging to explore the mechanism of flow structure variations. Results indicate that these parameters have a significant effect on the flow structure of nanofluid jet impingement near the dimpled target surface. The flow begins to separate after passing the edge of the dimple along with the curvature of a dimple. [Formula: see text] will affect the form and location of flow separation and reattachment, and [Formula: see text] will affect the intensity of separation flow. The length of the flow separation bubble varies in different [Formula: see text] cases. When [Formula: see text] increases, the impinging energy and the velocity near the dimple edge decreases. The different Re has little effect on the length of the flow separation bubble and the tendency of the pressure coefficient (Cp). These results can provide further mechanism inspiration for the design of the flow structure of nanofluid jet impingement.

Spatiotemporal flow force model of source/sink human mobilities within city

Human mobility is of importance in supporting smart cities, urban planning and constructions of resilient environments. Previous studies on dominant mobility models (i.e., gravity and radiation models) rarely describe the refined spatiotemporal process of human mobility flow forces especially within city. To address this gap, this paper proposes a spatiotemporal flow force model (FFM) of sink/source human mobilities within city, which is derived from Navier-Stokes equation in the field of fluid mechanics. The FFM model outperforms the gravity and radiation models in modeling the refined spatiotemporal flow force process of source/sink human mobilities, in the aspect of intensity and direction of mobility flow force. Comparison results show that the gravity and radiation models in the source mobility scenario can give a rough force estimation about the total outflow from source mobility areas while without the capability of explaining the specific directions of mobility flow from source mobility areas. Pearson correlation coefficient between the intensity results of the two models and those of FFM range from 0.65 to 0.90 and direction differences between the results of the two models and FFM respectively show no clear regularity. In the sink mobility scenario, the direction of mobility flows can be estimated well by the gravity and radiation models while the intensity of mobility flow between small-scale areas within cities is susceptible to inaccuracies. Pearson correlation coefficient ranges from 0.13 to 0.59 and direction differences follow a stepped distribution from high to low within the range of 0° to 180°. In addition, the potential field of human mobility flow force provides a powerful tool for visually analyzing mobility flows within cities. This proposed model enriches human mobility models and is generalizable in supporting smart cities, urban planning, and constructions of resilient environments in terms of the refined spatiotemporal process of mobility flow force.

Exploring the Impact of Flow Experience on College Students' Sense of Acquisition in Ideological and Political Theory Courses

In the context of China, higher education institutions, including colleges and universities, bear the significant responsibility of cultivating proficient contributors and future representatives aligned with the socialist agenda. This is achieved through the provision of ideological and political theory courses. However, students face challenges in achieving desired educational outcomes in these courses. Therefore, it is necessary to investigate the process of knowledge acquisition in ideological and political theory courses as experienced by students. This study employs a qualitative case study methodology, based on flow theory, conducted in a selected college located in Shijiazhuang, Hebei Province, China. The research aims to gather relevant insights by examining data collected from 15 participants through individual semi-structured interviews. Subsequently, the qualitative data is meticulously analyzed using MAXQDA 2020 software. The findings of this study reveal that the factors influencing college students' perception of ideological and political theory courses encompass both internal factors, such as learning behavior and learning holistic quality, as well as external factors, including teaching behavior and teaching holistic quality. Drawing on the model developed in this study to elucidate the impact on college students' sense of acquisition in ideological and political theory courses, it is posited that flow experience constitutes the core factor influencing college students' sense of acquisition, whereby the intensity of flow experienced by college students in ideological and political courses directly affects the extent of their sense of acquisition. This research expands the scholarly exploration of instructional and pedagogical advancements specific to ideological and political theory courses within Chinese tertiary education institutions. Moreover, understanding the influential factors shaping the knowledge acquisition and comprehension process among college students in these courses has the potential to contribute to innovative educational approaches and strategies.

A social-ecological network approach to quantify the supply-demand-flow of grain ecosystem service

The supply-demand flow of food is crucial for accurately assessing ecosystem services and human well-being. However, quantifying the direction and intensity of dynamic ecosystem service (ES) flows is challenge. This study establishes a social-ecological network (SEN) framework to quantify the supply-demand flow of grain ES, which involves analyzing spatiotemporal patterns of supply and demand to distinguish between social and ecological aspects, identifying supply and demand nodes to define administrative boundaries, building a social-ecological network between supply and demand nodes, and measuring the intensity and direction of the supply-demand flow of grain ES. Taking the Pearl River Basin of China as an example, the supply-demand flow of grain ES was analyzed across three different scales during 2000–2019. The results indicated that there are significant spatial differences and mismatches in the supply-demand-flow of grain ES. The grain supply ranges from 29.18 Mt to 32.42 Mt, while grain demand ranges from 19.51 Mt to 25.28 Mt, respectively. The evolution of grain SEN reveals that most flow exhibits local characteristics, six prefecture-level city demand nodes were expected, and five prefecture-level city supply nodes with the highest flow intensity contributed a total flow intensity of 8.06–10.10 Mt. The supply nodes increased from 74.5% to 82.5% and demand nodes decreased from 25.5% to 17.5% during 2000–2019. The SEN approach can be effectively and visually used to quantify the supply-demand-flow of grain ES, support ecosystem management, and promote decision-making on food resource allocation.