Dominant Flow Direction Research Articles

Information flow dynamics between cryptocurrency returns and electricity consumption: A comparative analysis of Bitcoin and Ethereum

Understanding energy consumption associated with cryptocurrency mining gained increasing attention, with the literature focusing mainly on Bitcoin. This study uses data from the two energy consumption indices, to estimate static and dynamic transfer entropies. The results provide a nuanced understanding of the bidirectional relationships and their implications. The dominant direction of information flow for Bitcoin is from electricity consumption to returns, while for Ethereum, it is from returns to electricity consumption, suggesting that Ethereum's returns significantly impact electricity consumption patterns. Results highlight the need for policies that integrate energy forecasting and environmental sustainability considerations and has significant implications for policymaking.

Unsteady electroosmotic flow of Carreau–Newtonian fluids through a cylindrical tube

The present study aims to investigate the fully developed electroosmotic flow of Carreau–Newtonian fluids within a circular tube, considering two different boundary conditions of zeta potential. The unsteady behavior of Carreau–Newtonian fluids, is attributed to the pulsatile pressure-driven flow. Studying two distinct formulations, slip and no-slip zeta potentials, illustrates the relative movement of fluid particles and the charged surface. The proposed study’s framework is divided into two regions: a central region containing a non-Newtonian Carreau fluid exhibiting both shear-thinning and thickening behavior, and a peripheral region containing a Newtonian fluid with the effect of an electrical double layer at the solid wall of the cylindrical tube. The Poisson–Boltzmann equation under the assumption of Debye–Hückel approximation governs the potential distribution due to the electric double layer, facilitating the examination of electroosmotic flow through tube. Obtaining analytical solutions for the momentum equations in both regions becomes challenging due to the inclusion of pulsatile pressure-driven flow and a non-Newtonian Carreau fluid. Asymptotic series expansions are employed, utilizing small parameters such as the Weissenberg number (We≪1) and a pulsatile Reynolds number (α≪1), to derive velocity expressions for both regions. Wall shear stress fluctuations, as indicated by time-averaged wall shear stress and oscillatory shear index are assessed to gauge the temporal variation of wall shear stress from the dominant blood flow direction. By utilizing potential and hydrodynamic variables, an asymptotic formulation for the streaming potential is developed to ascertain the asymptotic expression of electrokinetic energy conversion efficiency and scrutinize the impacts of pertinent physical parameters on it. The proposed study prominently shows that the Debye–Hückel parameter, Weissenberg number, pulsatile Reynolds number, and time-dependent pressure gradient significantly influence the fluid velocity, flow rate, and flow resistance. The notable determination of the present study is that the velocity amplitude and electrokinetic energy conversion efficiency are enlarged in the slip-dependent case relative to the no-slip zeta potential. It is noteworthy that as inertial forces become more prominent compared to viscous forces, both time-average wall shear stress and oscillatory shear index experience a slight decrease, although the reduction in oscillatory shear index is minimal owing to the absence of obstruction within the tube wall. The NDSolve numerical scheme in Mathematica software is employed to calculate numerical solutions for the governing equations, which are subsequently verified against results obtained through asymptotic analysis. The findings of this study are expected to deepen our understanding of unsteady electroosmotic flows of Carreau fluid and contribute to the design and development of advanced microfluidic devices with enhanced performance for various applications.

Boundary effect and heat vortices of hydrodynamic heat conduction in graphene

A SIMPLE like algorithm is proposed for numerically solving the Guyer-Krumhansl equations. Results show that thermal conductivity of suspended graphene depends on the heat flux boundary conditions. If the strength of the point source is fixed, only when the strength of the point sink exceeds a critical value can the heat vortices occur in the heat flux vector field. We also find that heat vortices only appear when the side length perpendicular to the dominant heat flow direction exceeds a critical value. Furthermore, the no-slip boundary condition is beneficial for the generation of heat vortices, while the specular phonon-boundary interactions can disrupt the heat vortices. These findings will contribute to experiments on heat vortex in the heat flux field of suspended graphene. Finally, it is found that the heat can flow from some cold regions to hot regions for the hydrodynamic heat conduction in suspended single-layer graphene.

Comparing numerical modelling, traditional machine learning and theory-guided machine learning in inverse modeling of groundwater dynamics: A first study case application

This study proposes to test the hypothesis that theory-guided machine learning model can be effectively applied to model the behavior of a real aquifer. For this purpose, a theory-guided multilayer perceptron model (TgMLP) for real aquifers was developed to simulate groundwater flow dynamics. A comparison of the performance of the TgMLP with that of a numerical model (NumMod) and a traditional multilayer perceptron model (MLP) was performed. The ability of these three models to capture the spatiotemporal dynamics of groundwater was evaluated, the degree of PDE violation of the TgMLP model was also assessed, and the applicability of these three models in a real-world setting was discussed. The Saint-Honoré unconfined aquifer (Quebec, Canada), which has been extensively monitored over the last few years, was used as an experimental laboratory for this study. Historical groundwater levels, recharge, precipitation, mean temperature and streamflow data were used to calibrate/train/validate and test the models. The results show that the performance of the TgMLP far exceeds that of the numerical and traditional MLP models, that the MLP model is a good interpolator but is unable to extrapolate, and that only the numerical and TgMLP models are able to capture the spatiotemporal dynamics of groundwater flow and represent the dominant flow direction in the aquifer. It was found that the TgMLP model better approximates the solution of the PDE at 70% of the locations. These results support the hypothesis that TgMLP is effective in modeling the spatiotemporal dynamics of groundwater in a real aquifer even if improvements are needed. Although the TgMLP model is capable of representing groundwater flow dynamics to some degree, its implementation requires much higher computational costs than a numerical model; however, these can be reduced with the use of a GPU to speed up the calculations.

High-precision laser powder bed fusion of 18Ni300 maraging steel and its SiC reinforcement composite materials

Thanks to the need for refinement in the mold field, high-precision laser powder bed fusion (HP-LPBF) has become a critical technique for manufacturing new high-precision molds. The influence of HP-LPBF process parameters for densification of 18Ni300 maraging steel (MS18Ni300), as well as the related optical micrograph (OM), microstructure, phase composition, and mechanical properties of optimal relative density specimens, were comprehensively examined in this study. The sequence of HP-LPBF process parameters on the relative density of the specimens was investigated using the orthogonal experimental method. With a relative density of 99.18 ± 0.11 % and a surface roughness of 3.59 ± 0.32 μm, the optimal process parameters was attained. The influence of adding SiC on the specimens' OM, microstructure, phase composition, and mechanical properties were compared and studied. The results show that the building direction (BD) is the dominant heat flow direction in HP-LPBF by EBSD analysis and that the rotating 67° scanning strategy can effectively improve the isotropy of the mechanical properties of HP-LPBF parts. The MS18Ni300 specimen has a particularly thin cellular microstructures with a diameter of 6.11 μm. In addition, the dominant phase composition of the MS18Ni300 specimen was martensite (α). The microstructure of SiC (volume fraction of 1 %)/MS18Ni300 (M1) composites was significantly refined, and changes in the microstructure were primarily due to SiC's physical properties. The addition of SiC particles leads to a weakening of the preferred crystallographic orientation of the grains. The average grain size was 3.21 μm. No new phases were produced, but the mechanical properties were improved. The ultimate tensile strength and hardness of M1 were 1.33 GPa and 390.2 HV, respectively. The strengthening mechanism of SiC was discussed.

A multi-criteria approach of assessing groundwater potential, recharge and flow in the transboundary Tuli Karoo Basin

Abstract Quantitative estimates of amount of groundwater resources are required in the transboundary Tuli Karoo Basin to better manage and promote sustainable conjunctive use of the aquifer. Unfortunately, such important data and information are lacking. The aim of this study was to map groundwater potential zones and model groundwater recharge as well as groundwater flow in the Tuli Karoo Basin (12,164 km2) using geospatial techniques. To delineate groundwater potential zones, nine thematic maps of groundwater conditioning factors were computed and weighted using Saaty's Analytical Hierarchy Process (AHP). To validate the groundwater potential map, a Kruskal–Wallis test was performed. Groundwater recharge and groundwater flow direction were estimated in a coupled Geographic Information System (GIS) and modelling environment using the soil–water–balance model (SWB) and British Geological Survey (BGS) groundwater tool, respectively. Results for groundwater potential mapping showed that the area is dominated by high ground water potential which covers about 57.8% (6,915.1 km2) of the basin. The Kruskal–Wallis test showed that the median values of the borehole yields vary significantly between the different groundwater potential zone classes (P-value <0.0001). Estimated groundwater recharge using SWB model showed that the maximum annual potential recharge for the Tuli Karoo Basin was 13.2 mm/year for the 10-year period from 2010 to 2020. Results from the BGS tool for groundwater flow show that the dominant groundwater flow direction is southeast. The results showed that there is no link between groundwater flow direction and surface water flow direction. This study is relevant in water development policy, water-related development aid, community planning and technical decision making for hydrogeologists, catchment managers, water planners and non-specialists alike.

An Approach to Include Hydrogeologic Barriers With Unknown Geometric Properties in Groundwater Model Inversions

AbstractHydrogeological barriers can significantly impact groundwater model predictions. They are, however, often excluded from, or misrepresented in, groundwater models if their presence is unknown or their properties are poorly constrained. Here we show that sharp barriers can be included in groundwater model inversion, even where their presence is uncertain. We describe an approach utilizing "phantom structures"—randomly located, linear groups of model cells assigned a unique hydraulic conductivity value—to improve identifiability of barriers. Algorithmic parameter estimation using model‐independent parameter estimation code (PEST) is implemented to determine model structures that best match the hydraulic head and groundwater age observation data from a hypothetical aquifer. Our results show that for a series of case studies, this method was successful in inferring the appropriate location and properties of hydrogeological barriers, when that barrier was not aligned with the dominant flow direction. We compare these results to model inversion using traditional pilot points. The phantom structures approach shows promise in identifying hydrogeological structures and in reproducing groundwater flow across a model domain. Our results demonstrate that the geometric properties of geological structures can remain flexible in a model inversion. This is a step toward reducing conceptual model uncertainty where the presence and properties of hydrogeologic barriers are undefined.

Quantifying the impacts of groundwater abstraction on Ganges river water infiltration into shallow aquifers under the rapidly developing city of Patna, India

Study regionPatna is located on the southern bank of the River Ganges in Bihar, India. Rapid population growth over the past few decades has driven an increase in groundwater abstraction from aquifers under the city. Study focusThis study exeplores the pumping-induced water exchange between the River Ganges and groundwater under transient conditions between 2009 and 2015, using a numerical simulation. The deterministic water exchange model within an uncertainty quantification was used to reveal the controlling factors affecting river water infiltration. New hydrological insights for the regionModelling reveals that under baseline (eno pumping) conditions, the dominant (~ 91% of the year) flow direction is from the aquifer to the river, which reverses (~ 9% of the year) when the river stage is high. When a municipal pumping well is implemented, river water infiltration into the aquifer increases to 68% of the year. The groundwater pumping rate is found to be the most important factor affecting the river water infiltration, whilst the groundwater table level is most sensitive to the well distance from the river, followed by pumping rate. Optimizing the location, depth and pumping rate of new wells in the area could mitigate fluvial contamination of the aquifer and help maintain groundwater levels.

Virtual Water Flow Pattern in the Yellow River Basin, China: An Analysis Based on a Multiregional Input-Output Model.

Research on the Yellow River Basin’s virtual water is not only beneficial for rational water resource regulation and allocation, but it is also a crucial means of relieving the pressures of a shortage of water resources. The water stress index and pull coefficient have been introduced to calculate the implied virtual water from intraregional and interregional trade in the Yellow River Basin on the basis of a multi-regional input–output model; a systematic study of virtual water flow has been conducted. The analysis illustrated that: (1) Agriculture is the leading sector in terms of virtual water input and output among all provinces in the Yellow River Basin, which explains the high usage. Therefore, it is important to note that the agricultural sector needs to improve its water efficiency. In addition to agriculture, virtual water is mainly exported through supply companies in the upper reaches; the middle reaches mainly output services and the transportation industry, and the lower reaches mainly output to the manufacturing industry. Significant differences exist in the pull coefficients of the same sectors in different provinces (regions). The average pull coefficients of the manufacturing, mining, and construction industries are large, so it is necessary to formulate stricter water use policies. (2) The whole basin is in a state of virtual net water input, that is, throughout the region. The Henan, Shandong, Shanxi, Shaanxi, and Qinghai Provinces, which are relatively short of water, import virtual water to relieve local water pressures. However, in the Gansu Province and the Ningxia Autonomous Region, where water resources are not abundant, continuous virtual water output will exacerbate the local resource shortage. (3) The Yellow River Basin’s virtual water resources have obvious geographical distribution characteristics. The cross-provincial trade volume in the downstream area is high; the virtual water trade volume in the upstream area is low, as it is in the midstream and downstream areas; the trade relationship is insufficient. The Henan and Shandong Provinces are located in the dominant flow direction of Yellow River Basin’s virtual water, while Gansu and Inner Mongolia are at the major water sources. Trade exchanges between the midstream and downstream and the upstream should be strengthened. Therefore, the utilization of water resources should be planned nationwide to reduce water pressures, and policymakers should improve the performance of agricultural water use within the Yellow River Basin and change the main trade industries according to the resource advantages and water resources situation of each of them.

Interaction Between High-Rise Building, Wind and Pollution in District Twenty-Two of Tehran Municipality, Iran

<p>The large cities are facing with a phenomenon called high-rise buildings which is due to the increasing of the population and also developing the cities. One of the negative impacts of high-rise buildings is the change in urban wind flow. Air pollutions is a major problem in the cities and the wind play an important role in the dispersion of air pollutions. The most probable wind direction for Tehran is west and hence district twenty-two of Tehran municipality which is located in northwest of Tehran (Capital of Iran) is in the dominant direction of wind flow. This paper presents a numerical method to investigate the interaction between the wind flow, pollution and high-rise buildings in district twenty-two of Tehran municipality. The effect of these phenomenon on the other regions is considered as well. Computational fluid dynamics (CFD) by ANSYS Fluent software has been used in order to simulate the problem. The results of this study indicate the existing buildings and their layout had no effect on wind velocity and trapping the pollution and do not cause an increasing of the local concentration of pollutants. So the geometry and layout of buildings allow the flows and environmental pollutants to pass.</p>

Hydrodynamic and microbiological characterisation of free ground water in the city of Bafoussam, (West Cameroon)

Abstract The work presented here aims to carry out a physical characterisation of soils to understand their hydrodynamic behaviour and estimate the susceptibility of each group of soils to microbiological pollution. The field work associated with the laboratory work consisted of monitoring the hydrodynamic behaviour of previously identified and selected well waters, measuring the permeabilities of the soil samples and analysing the bacteriological parameters of the sampled well waters. At the end of this work, the piezometric data show a dominant SE-NW and ENE-OSW flow direction. The water levels vary significantly between the wet and dry seasons. The granulometric analysis of the soils reveals CU>3 showing a spread out granulometry with very low permeabilities of the order of 1.58×10−7 m/s and moderately high permeabilities of the order of 1.86×10−5 m/s. The microbiological data show pollution of human origin with a high bacterial load in the rainy season represented by a maximum of 240 CFU of Escherichia coli exceeding the WHO standards for drinking water. The majority of the polluted samples come from soils developed on granites and basalts, which are the most susceptible to pollution, making the groundwater vulnerable.

Ontogeny of a subtidal point bar in the microtidal Venice Lagoon (Italy) revealed by three‐dimensional architectural analyses

AbstractSedimentological and architectural features of meandering subtidal channels are relatively unexplored, and their deposits are commonly investigated based on facies models set up for intertidal meandering channels. The Venice Lagoon (northern Adriatic Sea, Italy) is affected by a micro‐tidal regime and hosts a dense network of active and buried tidal channels. It represents an excellent natural laboratory to improve the current knowledge on subtidal meander morphodynamics and related deposits. In this study, the integration of high‐resolution geophysical images and core data allows reconstruction of the architectural three‐dimensional model of a meandering subtidal palaeochannel, which is buried below a modern subtidal flat. The study palaeochannel was 35 m wide and 3 m deep, and formed three adjacent meander bends and related point bars. A detailed three‐dimensional architectural reconstruction was carried out for deposits associated with one of these meander bends, that was crossed by a minor, low‐sinuosity channel with two minor bank‐attached bars. This reconstruction highlights that the study point bar has a horseshoe shape, which arose from the onset of bar accretion from an already‐sinuous channel. Reconstructed growth stages of the studied bends show that point‐bar accretion can follow different styles of planform transformation, also experiencing simultaneously landward (or seaward) deposition according to the dominant flow direction (i.e. local tidal asymmetry). The analyses show that planform transformations occurred in parallel with elevation changes of the related channel thalweg, which shaped pools with geometry varying with the radius of curvature of the bend. The present study highlights the relevance of high‐resolution three‐dimensional reconstructions to link palaeomorphodynamic processes with related sedimentary products.

Spatial self-organization of marine agglutinated microbial carbonate build-ups: Insights from stratigraphic forward modelling using Stromatobyte3D

Microbialites span a substantial fraction of Earth history, and have important meanings for understanding long-term history of life and environment. Key controls on microbialite morphology and distribution include substrate topography, hydrodynamic conditions, water depth, salinity, light intensity, and sedimentation rates. This leads to potentially complex combinations of control by internal spatial feedbacks and also external factors. This complexity is explored here using Stromatobyte3D, a new numerical stratigraphic forward model that calculates microbialite accumulation due to in-situ precipitation, sediment trapping and binding, and sedimentation from suspension, controlled by evolving topography and water flow due to waves, tides or other currents. Results show that with increasingly strong spatial interactions of microbialite growth with water and suspended sediment, particularly the influence of hydrodynamics on in-situ microbialite growth and suspended sediment deposition patterns, three distinct microbialite morphologies are produced, from isolated columns, through elongated mounds, to ridges elongated in the dominant flow direction. Quantitative analysis demonstrates a dominant antecedent substrate topographic control on microbialite nucleation and growth in the absence of water flow, declining as hydrodynamic processes and strong spatial interactions are introduced causing mounds to accrete and coalesce laterally in the flow direction. Formation of coherent morphological patterns, produced by spatial interactions between topography, hydrodynamics, microbialite growth, and sedimentation from suspension, and independent of initial condition, is evidence of spatial self-organization. Modelled morphologies are strikingly similar to observations from modern marine agglutinated microbialite strata, suggesting modelled processes and their behaviours are realistic, and can therefore be useful to assist field interpretations of observed microbialite morphologies where similar processes were operating together.

Network and geometric characterization of three-dimensional fluid transport between two layers.

We consider transport in a fluid flow of arbitrary complexity but with a dominant flow direction. One of the situations in which this occurs is when describing by an effective flow the dynamics of sufficiently small particles immersed in a turbulent fluid and vertically sinking because of their weight. We develop a formalism characterizing the dynamics of particles released from one layer of fluid and arriving in a second one after traveling along the dominant direction. The main ingredient in our study is the definition of a two-layer map that describes the Lagrangian transport between both layers. We combine geometric approaches and probabilistic network descriptions to analyze the two-layer map. From the geometric point of view, we express the properties of lines, surfaces, and densities transported by the flow in terms of singular values related to Lyapunov exponents, and define a specific quantifier, the finite depth Lyapunov exponent. Within the network approach, degrees and an entropy are considered to characterize transport. We also provide relationships between both methodologies. The formalism is illustrated with numerical results for a modification of the ABC flow, a model commonly studied to characterize three-dimensional chaotic advection.

Model-based estimation of plastic debris accumulation in Banten Bay, Indonesia, using particle tracking - Flow model hydrodynamics approach

Coastal pollution caused by marine debris in Banten Bay is increasing and threatening the environmental and ecological sustainability of the bay's coastal area. This study aims to simulate the particle tracking of floating plastic debris within Banten Bay and to estimate the coastal debris accumulation for the period 2018 to 2028 based on numerical spatial modeling. To determine the dominant direction of plastic debris flow, we recorded floating plastic waste at four locations (Bojonegara port, Karangantu Estuary, Cibanten Estuary, and the Sunda Straits) by releasing wooden drifters. The numerical model was developed using a Particle Tracking module based on the Langevin equation. In comparison to data provided by the drifter survey, the particle tracking showed a similar distribution trace that tended to move westward during the northeast monsoon and eastward during the southwest monsoon. During the northeast monsoon, marine debris intake peaked, ranging from 2.25 kg to 5.75 kg. We estimated that over the ten years modeled plastic debris accumulation would increase by approximately 11%, to a maximum rate of 9.42 kg/day. Of particular concern, it is modeled that 41% of Banten Bay will be covered by plastic debris in 2028 if effective mitigations are not immediately applied. We recommend conducting a coastal cleanup operation every ten days so that coastal debris deposits can be well-controlled.

Assessment of declining groundwater levels due to excessive pumping in the Dhaka District of Bangladesh

Hydrogeologically, the aquifers of the Dhaka district are located in the B, H and J zones of a total of 15 BWDB-UNDP (1982) groundwater development zones and were considered to have a high groundwater potential. Unplanned and excess groundwater extraction is causing a decline of groundwater potentiometric heads in the area. Groundwater level data from nineteen (19) years of the two aquifers of the Dhaka district have been analyzed to observe how the patterns of water level changes vary throughout the area. The Mann–Kendal (M–K) test with Theil-slope Sen's slope exhibits three categories of groundwater level changes. In densely populated city areas, the trend is extremely negative, with steep declines and annual changing rates that range from − 1.5 m/year to − 2.11 m/year; − 1.01 m/year to − 1.09 m/year in newly urbanized areas; and that range from 0.01 m/year to − 0.36 m/year in the rural areas. The pattern of changing decline trends was observed through six (6) year interval contour maps from 2000 to 2018, and three groundwater zones have been described in the district on the basis of water level changes. This assessment indicated that the dominant groundwater flow direction in the area is in an easterly direction towards urban areas, and that significant groundwater declines are occurring even on the peripheries of the city area. Probable causes of groundwater depletion and approaches to mitigate this issue have been discussed on the basis of geological and hydrogeological studies and investigations in the area.

Effective fractures and their contribution to the reservoirs in deep tight sandstones in the Kuqa Depression, Tarim Basin, China

The Mesozoic Cretaceous reservoirs with a burial depth of more than 4500 m (14,764 ft) in the Kuqa Depression of the Tarim Basin are rich in natural gas resources, categorized under the typical deep tight sandstone reservoirs. Based on the analysis of cores, borehole image logs, thin sections, and laboratory testing, this study comprehensively evaluated the effective fractures in deep tight sandstone reservoirs and illuminated the contribution of effective fractures to the properties of these reservoirs. Tectonic fractures are an important component in these reservoirs. More than 70% of these fractures are not filled by any minerals, and their apertures vary greatly, measured from a few to hundreds of microns. The influencing factors of the effective fractures in these reservoirs include tectonism, diagenesis, and in-situ stresses. The fractures that are formed at earlier tectonic movements are more susceptible to be filled with minerals. The diagenetic facies of strong cementation exhibit a higher abundance of mineral-filled fractures, while dissolution can cause fracture apertures to become larger and makes them more effective. The unfilled fractures, which are parallel to the maximum horizontal stress component, show larger apertures and therefore are more effective. Laboratory tests indicate that effective fractures contribute less to the reservoir storage space, with an average porosity contribution rate of 3.95%. However, the permeability of samples with microscopic effective fractures was found 1-2 orders of magnitude higher than those without such fractures, since these fractures are main pathways that can connect scattered pores to improve the effectiveness of storage space. Moreover, the macroscopic effective fractures with a smaller angle from the maximum horizontal stress component decide the dominant reservoir fluid flow direction. Consequently, effective fractures exhibit a leading contribution to the reservoir permeability.

Ravenstein Revisited: The Analysis of Migration, Then and Now

In 1876, 1885 and 1889, Ernst Ravenstein, an Anglo-German geographer, published papers on internal and international migration in Britain, Europe and North America. He generalized his findings as “laws of migration”, which have informed subsequent migration research. This paper aims to compare Ravenstein’s approach to investigating migration with how researchers have studied the phenomenon more recently. Ravenstein used lifetime migrant tables for counties from the 1871 and 1881 censuses of the British Isles. Data on lifetime migrants are still routinely collected but, because of the indeterminate time interval, they are rarely used to study internal migration. Today, internal migration measures from alternative sources are used to measure internal migration: fixed interval migrant data from censuses and surveys, continuous records of migrations from registers, and “big data” from telecommunications and internet companies.
 Ravenstein described and mapped county-level lifetime migration patterns, using the concepts of “absorption” and “dispersion”, using migration rates and net balances. Recently, researchers have used lifetime migrant stocks from consecutive censuses to estimate country to country flows for the world. In the last decade, an Australian-led team has built an international database of internal migration flow data and summary measures. Methods were developed to investigate the modifiable areal unit problem (MAUP), in order to design summary internal migration measures comparable across countries. Indicators of internal migration were produced for countries covering 80 percent of the world’s population.
 Ravenstein observed that most migrants moved only short distances, anticipating the development of “gravity” models of migration. Recent studies calibrated the relationship between migration and distance, using gravity models. For mid-19th century Britain, Ravenstein found the dominant direction of internal migration to be towards the “centres of commerce and industry”. Urbanization is still the dominant flow direction in most countries, though, late in the process, suburbanization, counter-urbanization and re-urbanization can occur. Ravenstein focussed on place-specific migration, whereas today researchers describe migration flows using area typologies, seeking spatial generality. Ravenstein said little about migrant attributes except that women migrated more than men. In recent decades, the behaviour of migrants by age, sex, education, ethnicity, social class and partnership status have been studied intensively, using microdata from censuses and surveys.
 Knowledge about processes influencing internal and international migration has rarely been built into demographic projections. Scenarios that link migration with sub-national or national inequalities and with climate or environmental change are influencing the design of policies to reduce inequalities or slow global warming.
 * This article belongs to a special issue on “Internal Migration as a Driver of Regional Population Change in Europe: Updating Ravenstein”.

Corticomuscular interactions during different movement periods in a multi-joint compound movement

While much is known about motor control during simple movements, corticomuscular communication profiles during compound movement control remain largely unexplored. Here, we aimed at examining frequency band related interactions between brain and muscles during different movement periods of a bipedal squat (BpS) task utilizing regression corticomuscular coherence (rCMC), as well as partial directed coherence (PDC) analyses. Participants performed 40 squats, divided into three successive movement periods (Eccentric (ECC), Isometric (ISO) and Concentric (CON)) in a standardized manner. EEG was recorded from 32 channels specifically-tailored to cover bilateral sensorimotor areas while bilateral EMG was recorded from four main muscles of BpS. We found both significant CMC and PDC (in beta and gamma bands) during BpS execution, where CMC was significantly elevated during ECC and CON when compared to ISO. Further, the dominant direction of information flow (DIF) was most prominent in EEG-EMG direction for CON and EMG-EEG direction for ECC. Collectively, we provide novel evidence that motor control during BpS is potentially achieved through central motor commands driven by a combination of directed inputs spanning across multiple frequency bands. These results serve as an important step toward a better understanding of brain-muscle relationships during multi joint compound movements.

Emporal and Spatial Variability of Rainfall in Modelling of Stormwater Outflows

Abstract The article presents issues related to modeling of the rainfall-runoff phenomenon. As factors influencing the simulation results, the velocity and direction of precipitation relative to the drainage basin were indicated. The possibility of underestimating the cross-sections of rainwater channels as a result of overlapping rain wave directions and the dominant flow direction in the rainwater channel network was pointed out. The research results to date indicate a reduction in the symptoms of this phenomenon as the complexity of the channel network increases. The final verification was based on the actual catchment. Calculations were made using the Epa SWMM 5.1.013 software. The results are presented in a graphic form to illustrate the variability of stormwater outflow.