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Hydraulic turbine test stands represent an important link in the efficient utilization of the energy potential of water flows. The realization of these turbines begins with an approximate design, based on the differential equations of motion of ideal fluids, and continues with successive stages of performance testing in the laboratory, on small-scale models. Using different similarity criteria based on geometric, kinematic and dynamic similarities, the conclusions drawn from the operation of the model will also be valid for the real machine. The purpose of the paper is to present some points of view on the realization of three types of stands for small hydraulic turbines, of which two are patented and one is a patent application. These stands simulate real operating conditions on permanent flowing water with velocities, flows and falls for small hydraulic turbines that can be installed on the water line, in locations that do not use dams or other expensive water storage facilities. The main author of the patent documentation makes a synthesis of the constructive-functional characteristics of the respective stands through this article. [ABSTRACT FROM AUTHOR]

In this study, we attempt to experimentally investigate the flow turbulence structure in a partly vegetated channel. To achieve the objective of this study, we conducted extensive measurements of flow velocities within and outside the vegetated area, where the flow is fully developed. The experiments were conducted in a very large channel at the Coastal Engineering Laboratory of the Department of Civil, Environmental, Building Engineering and Chemistry at the Polytechnic University of Bari, Italy. The instantaneous three flow velocity components were accurately measured using a 3D-Acoustic Doppler Velocimeter (ADV)-Vectrino system at high frequency. Flow behaviors through the vegetated area, at the interface, and in the unobstructed area were analyzed via time-averaged velocities, turbulence intensity, correlation properties, spectral analysis, and vortex identification. Experimental results showed the development of three distinct characteristic flow zones: (i) a vegetated area of low streamwise velocity, high turbulence intensities, dominant inward interactions, and more intense power spectrum, (ii) a shear layer zone of increasing streamwise velocity, more enhanced transverse flow motion, exponential decrease in turbulence intensities, and frequent ejection and/or outward interaction events, and (iii) a free-stream zone of higher and almost constant streamwise velocity, lower turbulence intensities, frequent sweep and/or inward interaction events, and less intense streamwise power spectrum. The results brought further insights into the flow behaviors in these characteristic flow zones. The extensive and detailed measured data can provide a basis for improving and calibrating numerical simulations of partly vegetated channels. [ABSTRACT FROM AUTHOR]

We develop a deterministic predator–prey compartmental model to investigate the impact of their velocities on their interactions. Prey hides in a refuge area and comes out of this area when predation pressure declines. To avoid predation, prey can limit their velocity. For antipredator behaviour, we examined that prey mortality increases when either predator or prey velocity increases while raising antipredator behaviour increases prey density. We proved that predator free equilibrium is globally asymptotically stable and co-existing equilibrium will be globally stable under certain conditions. We find that transcritical bifurcations occur at predator-free equilibrium at the certain value of the death rate of the predator. [ABSTRACT FROM AUTHOR]

We develop a deterministic predator–prey compartmental model to investigate the impact of their velocities on their interactions. Prey hides in a refuge area and comes out of this area when predation pressure declines. To avoid predation, prey can limit their velocity. For antipredator behaviour, we examined that prey mortality increases when either predator or prey velocity increases while raising antipredator behaviour increases prey density. We proved that predator free equilibrium is globally asymptotically stable and co-existing equilibrium will be globally stable under certain conditions. We find that transcritical bifurcations occur at predator-free equilibrium at the certain value of the death rate of the predator.

Using satellite imagery, this study investigates the spectral reflectance characteristics of crops at the OHMK farm in Eastern Kazakhstan, focusing on wheat and barley. The analysis reveals significant differences in spectral re- flectance, particularly in the visible and near-infrared regions, and tracks change over time during different growth stages. Employing principal component analysis (PCA), strong correlations are observed between specific spectral bands and principal components, providing insights into crop variability. Derived equations enable the estimation of principal component values based on spectral information. These findings have implications for crop monitoring, management, and precision agriculture, offering potential yield optimization and resource allocation improvements. The study highlights the potential use of spectral reflectance analysis for crop health assessment and yield prediction, with implications for agricultural decision-making and enhanced productivity. Further research is needed to expand the application of this approach to other crops and conditions. [ABSTRACT FROM AUTHOR]

This study aims to investigate the potential of GNSS data in earthquake zoning and risk assessment in a seismically active region. The study area is located in Uzbekistan, where the interaction of several tectonic plates results in frequent earthquakes. The study focused on two periods from October to October of the next year, respectively, for 2018 and 2019, 2019 and 2020 to analyze GNSS velocities and earthquake zoning maps to identify areas at high risk of seismic activity. The study also utilized GIS and spline interpolation to create continuous surface maps of risk zones based on earthquake hazard data. The results showed that the entire study area is at high seismic risk, with a tendency for rotational movement in the zone of intersection of tectonic plates. Velocities range from 1.56-20.3 mm/yr and 1.64-14 mm/yr for the two periods. Moreover, the analysis of vertical earth surface displacements indicates a tendency towards soil subsidence in the western part and uplift in the northeastern part of the study area. The study concludes that GNSS analysis can provide valuable insights into seismic hazard assessment and improve our understanding of the tectonic processes leading to earthquakes. [ABSTRACT FROM AUTHOR]

The connection between the heat transfer and characteristic flow velocities of planetary core-style convection remains poorly understood. To address this, we present novel laboratory models of rotating Rayleigh–Bénard convection in which heat and momentum transfer are simultaneously measured. Using water (Prandtl number, P r ≃ 6 ) and cylindrical containers of diameter-to-height aspect ratios of Γ ≃ 3 , 1.5 , 0.75 , the non-dimensional rotation period (Ekman number, E) is varied between 10 − 7 ≲ E ≲ 3 × 10 − 5 and the non-dimensional convective forcing (Rayleigh number, R a ) ranges from 10 7 ≲ R a ≲ 10 12 . Our heat transfer data agree with those of previous studies and are largely controlled by boundary layer dynamics. We utilize laser Doppler velocimetry (LDV) to obtain experimental point measurements of bulk axial velocities, resulting in estimates of the non-dimensional momentum transfer (Reynolds number, R e ) with values between 4 × 10 2 ≲ R e ≲ 5 × 10 4 . Behavioral transitions in the velocity data do not exist where transitions in heat transfer behaviors occur, indicating that bulk dynamics are not controlled by the boundary layers of the system. Instead, the LDV data agree well with the diffusion-free Coriolis–Inertia–Archimedian (CIA) scaling over the range of R a explored. Furthermore, the CIA scaling approximately co-scales with the Viscous–Archimedian–Coriolis (VAC) scaling over the parameter space studied. We explain this observation by demonstrating that the VAC and CIA relations will co-scale when the local Reynolds number in the fluid bulk is of order unity. We conclude that in our experiments and similar laboratory and numerical investigations with E ≳ 10 − 7 , R a ≲ 10 12 , P r ≃ 7 , heat transfer is controlled by boundary layer physics while quasi-geostrophically turbulent dynamics relevant to core flows robustly exist in the fluid bulk. [ABSTRACT FROM AUTHOR]

Mexico is surrounded by a highly dynamic tectonic environment, where the area of greatest influence is in the west, since it is where large earthquakes occur and tectonic blocks are generated due to the subduction of two oceanic plates in the North American plate. In the present study, the horizontal velocities of 15 GNSS stations of continuous operation are calculated, over a period of 11 years, which are located within the Jalisco Block, Mexico with the objective of analyzing the current dynamics of this tectonic block, which is mainly influenced by the oblique subduction of the Rivera plate.

Abstract Background Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) allows sophisticated quantification of left atrial (LA) blood flow, and could yield novel biomarkers of propensity for intra-cardiac thrombus formation and embolic stroke. As reproducibility is critically important to diagnostic performance, we systematically investigated technical and temporal variation of LA 4D flow in atrial fibrillation (AF) and sinus rhythm (SR). Methods Eighty-six subjects (SR, n = 64; AF, n = 22) with wide-ranging stroke risk (CHA2DS2VASc 0–6) underwent LA 4D flow assessment of peak and mean velocity, vorticity, vortex volume, and stasis. Eighty-five (99%) underwent a second acquisition within the same session, and 74 (86%) also returned at 30 (27–35) days for an interval scan. We assessed variability attributable to manual contouring (intra- and inter-observer), and subject repositioning and reacquisition of data, both within the same session (same-day scan–rescan), and over time (interval scan). Within-subject coefficients of variation (CV) and bootstrapped 95% CIs were calculated and compared. Results Same-day scan–rescan CVs were 6% for peak velocity, 5% for mean velocity, 7% for vorticity, 9% for vortex volume, and 10% for stasis, and were similar between SR and AF subjects (all p > 0.05). Interval-scan variability was similar to same-day scan–rescan variability for peak velocity, vorticity, and vortex volume (all p > 0.05), and higher for stasis and mean velocity (interval scan CVs of 14% and 8%, respectively, both p 0.05). SR subjects showed significantly greater interval-scan variability than AF patients for mean velocity, vortex volume, and stasis (all p 0.05). Conclusions LA peak velocity and vorticity are the most reproducible and temporally stable novel LA 4D flow biomarkers, and are robust to changes in heart rate, blood pressure, and differences in heart rhythm.

The aim of this study was to create a 3D crustal deformation model for Estonia, based on dense Global Navigation Satellite System (GNSS) data (geodetic points with velocities) and validate the existing models of horizontal and vertical crustal deformations with velocities from Estonian GNSS measurements. The observations performed for at least eight years at Estonian GNSS permanent stations and during the GNSS campaign measurements of 1997, 2008 and 2017 on the Estonian 1st-order geodetic reference network were used as input data. Coordinates of the geodetic points were calculated in the ITRF2008 reference frame using the Precise Point Positioning method. Horizontal and vertical velocities (in the North, East and Up directions) were calculated for a total of 22 GNSS points. Models for horizontal and vertical velocities were calculated using the removeâcomputeârestore method. The model of glacial isostatic adjustment (GIA) of the Nordic Geodetic Commission NKG2016GIA was used as a reference model. Residual velocities of GNSS points showed a good fit with respect to the reference model. The residual velocities were analysed by geostatistical methods and the prediction surfaces of the residual velocities were modelled. After adding the surface of the residual velocities back to the reference model NKG2016GIA, the modelled surface EST2020VEL was obtained. The obtained model was compared with the up-to-date intraplate deformation model NKG_RF17VEL. It was found that recent Fennoscandian intraplate deformation models NKG2016LU and NKG_RF17VEL fitted well with the Estonian GNSS data. However, both models are systematically shifted with respect to the Estonian GNSS data. For applications in Estonia, it is better to use the fitted model EST2020VEL. The uncertainty of the model is estimated to be lower than ±0.5 mm/a.

The connection between the heat transfer and characteristic flow velocities of planetary core-style convection remains poorly understood. To address this, we present novel laboratory models of rotating Rayleigh–Bénard convection in which heat and momentum transfer are simultaneously measured. Using water (Prandtl number, Pr≃6) and cylindrical containers of diameter-to-height aspect ratios of Γ≃3,1.5,0.75, the non-dimensional rotation period (Ekman number, E) is varied between 10−7≲E≲3×10−5 and the non-dimensional convective forcing (Rayleigh number, Ra) ranges from 107≲Ra≲1012. Our heat transfer data agree with those of previous studies and are largely controlled by boundary layer dynamics. We utilize laser Doppler velocimetry (LDV) to obtain experimental point measurements of bulk axial velocities, resulting in estimates of the non-dimensional momentum transfer (Reynolds number, Re) with values between 4×102≲Re≲5×104. Behavioral transitions in the velocity data do not exist where transitions in heat transfer behaviors occur, indicating that bulk dynamics are not controlled by the boundary layers of the system. Instead, the LDV data agree well with the diffusion-free Coriolis–Inertia–Archimedian (CIA) scaling over the range of Ra explored. Furthermore, the CIA scaling approximately co-scales with the Viscous–Archimedian–Coriolis (VAC) scaling over the parameter space studied. We explain this observation by demonstrating that the VAC and CIA relations will co-scale when the local Reynolds number in the fluid bulk is of order unity. We conclude that in our experiments and similar laboratory and numerical investigations with E≳10−7, Ra≲1012, Pr≃7, heat transfer is controlled by boundary layer physics while quasi-geostrophically turbulent dynamics relevant to core flows robustly exist in the fluid bulk.

Fractures in Earth's critical zone influence groundwater flow and storage and promote chemical weathering. Fractured materials are difficult to characterize on large spatial scales because they contain fractures that span a range of sizes, have complex spatial distributions, and are often inaccessible. Therefore, geophysical characterizations of the critical zone depend on the scale of measurements and on the response of the medium to impulses at that scale. Using P-wave velocities collected at two scales, we show that seismic velocities in the fractured bedrock layer of the critical zone are scale-dependent. The smaller-scale velocities, derived from sonic logs with a dominant wavelength of ~0.3 m, show substantial vertical and lateral heterogeneity in the fractured rock, with sonic velocities varying by 2,000 m/s over short lateral distances (~20 m), indicating strong spatial variations in fracture density. In contrast, the larger-scale velocities, derived from seismic refraction surveys with a dominant wavelength of ~50 m, are notably slower than the sonic velocities (a difference of ~3,000 m/s) and lack lateral heterogeneity. We show that this discrepancy is a consequence of contrasting measurement scales between the two methods; in other words, the contrast is not an artifact but rather information—the signature of a fractured medium (weathered/fractured bedrock) when probed at vastly different scales. We explore the sample volumes of each measurement and show that surface refraction velocities provide reliable estimates of critical zone thickness but are relatively insensitive to lateral changes in fracture density at scales of a few tens of meters. At depth, converging refraction and sonic velocities likely indicate the top of unweathered bedrock, indicative of material with similar fracture density across scales.

Global Navigation Satellite Systems (GNSS) are used for different purposes in geodesy, like engineering geodesy, land management, real estate cadastre, land surveying, etc. However, high-precision GNSS measurements are used primarly for determination of reference networks, and for investigation of geodynamical phenomena as tectonic plates movements, which is the focus of this paper. An active GNSS network of Bosnia and Herzegovina (BIHPOS) was used for calculation of coordinates and velocities of networks' stations. Data from 23 stations were processed using scientific software GAMIT/GLOBK (version 10.7), developed on MIT (Massachusetts Institute of Technology). A sub-centimeter accuracy of coordinates is achieved and accuracy of calculated velocities is better than 1 mm/year. Station velocities interpretate geodynamics of Bosnia and Herzegovina. Six IGS stations were used, as reference datum stations. Reference stations analysis results are in good match with EUREF Permanent GNSS Network velocities, while BIHPOS stations velocities (at 13 stations in Bosnia and Herzegovina) show very similar trend to the velocities obtained from regional geodynamic campaigns (CERGOP).

Seismic tomography is used to infer compositional variations and environmental conditions in active subduction zones. In some regions, low P‐wave (Vp) and S‐wave (Vs) velocities and high Vp/Vs are documented near and along the plate boundary, and are interpreted to reflect high pore fluid pressures in metasedimentary rocks. However, there are limited experimental data with which to constrain the in‐situ wave speeds of metasedimentary rocks, particularly under elevated pore pressure. To determine whether the velocities of metasedimentary rocks are consistent with low wave speeds and high Vp/Vs, we measured the ultrasonic velocities of the Orocopia schist, a greenschist facies metapelite, in the laboratory. Velocities were measured under dry and saturated conditions, at effective pressures between 1 and 136 MPa, parallel and normal to foliation, and at room temperature. We find that, under fluid‐saturated conditions, the velocities of the Orocopia schist and Vp/Vs are consistent with anomalous values in subduction zones (Vp<6.5 km/s, Vs<3.2 km/s, and Vp/Vs>2) at effective pressures less than 10 MPa and normal to foliation. We used differential effective medium models and microscopy to quantify the contributions of mineralogy, mineral fabric, porosity, and pore shape to Vp, Vs, and their anisotropies. We find that, although mineralogy and mineral anisotropy impart some control on the wave velocities, aligned, small aspect ratio pores (0.005–0.03) are required to explain the measured velocities and high Vp/Vs. The low Vp and Vs and high Vp/Vs in subduction zones can be explained by phyllosilicate‐rich metapelitic rocks under near‐lithostatic pore pressure. Plain Language Summary: The speed at which waves travel through the Earth is controlled by the minerals that form the rocks, the amount and shape of the voids between the minerals, and the water that fills the voids. The speed of these waves can be mapped in the subsurface with a tool named seismic tomography. Tomography is commonly used to image subduction zones, where one tectonic plate is pushed under the other and where the largest earthquakes on Earth happen. Scientists observe a distinct signature in the seismic waves traveling through these fluid‐filled rocks that have been used to understand whether fluid‐filled voids affect earthquakes. This study aims to determine how the minerals and the shape of these void spaces influence the wave speeds. We measured the wave speeds of a rock type found at 30–40 km in subduction zones and in the laboratory and used numerical simulations to understand the results. We find that the combination of intermediate to high amounts of sheet silicate minerals and pressurized fluids can explain the distinctive seismic signature observed from tomography. Key Points: In a water‐saturated greenschist facies metapelite, foliation normal Vp/Vs is greater than 2 at effective stresses below 10 MPaLow wave speeds and high Vp/Vs are controlled by aligned, small aspect ratio pores, as well as aligned phyllosilicatesThe alignment of compliant pores is the primary control on wave velocity anisotropy and mineral alignment imparts a secondary control [ABSTRACT FROM AUTHOR]

In this paper, we study the (3+1)-dimensional variable-coefficient Kudryashov–Sinelshchikov (vc-KS) equation, which characterizes the evolution of nonautonomous nonlinear waves in bubbly liquids. The nonautonomous lump solutions of the vc-KS equation are produced via the Hirota bilinear technique. The characteristics of trajectory and velocity of this wave are analyzed with variable dispersion coefficients. Based on the positive quadratic function assumption, we further discuss two types of interactions between the soliton and lump under the periodic and exponential modulations. Then, we give the breathing lump waves showing the periodic oscillation behavior. Finally, we obtain the second-order nonautonomous lump solution, which also shows periodic interactions if we select trigonometric functions as the dispersion coefficients. [ABSTRACT FROM AUTHOR]

The aim of this study was to create a 3D crustal deformation model for Estonia, based on dense Global Navigation Satellite System (GNSS) data (geodetic points with velocities) and validate the existing models of horizontal and vertical crustal deformations with velocities from Estonian GNSS measurements. The observations performed for at least eight years at Estonian GNSS permanent stations and during the GNSS campaign measurements of 1997, 2008 and 2017 on the Estonian 1st-order geodetic reference network were used as input data. Coordinates of the geodetic points were calculated in the ITRF2008 reference frame using the Precise Point Positioning method. Horizontal and vertical velocities (in the North, East and Up directions) were calculated for a total of 22 GNSS points. Models for horizontal and vertical velocities were calculated using the remove-compute-restore method. The model of glacial isostatic adjustment (GIA) of the Nordic Geodetic Commission NKG2016GIA was used as a reference model. Residual velocities of GNSS points showed a good fit with respect to the reference model. The residual velocities were analysed by geostatistical methods and the prediction surfaces of the residual velocities were modelled. After adding the surface of the residual velocities back to the reference model NKG2016GIA, the modelled surface EST2020VEL was obtained. The obtained model was compared with the up-to-date intraplate deformation model NKG_RF17VEL. It was found that recent Fennoscandian intraplate deformation models NKG2016LU and NKG_RF17VEL fitted well with the Estonian GNSS data. However, both models are systematically shifted with respect to the Estonian GNSS data. For applications in Estonia, it is better to use the fitted model EST2020VEL. The uncertainty of the model is estimated to be lower than ±0.5 mm/a. [ABSTRACT FROM AUTHOR]

Experiments were conducted in a straight channel that widens from a single channel to a compound channel based on a real navigation channel with a similar shape in a mountainous region of China. Flow entered the single channel and then the compound channel with vegetated floodplains. The channel widened at the interface between the single and compound channels, resulting in different flow depths between the single and compound channels. An equation was proposed to estimate the percentage that the flow depth decreased from the single channel to the compound channel. Vegetation increased the floodplain resistance, causing more water to flow in the main channel and yielding a greater mean velocity in the main channel relative to the nonvegetated case. The velocity reached a maximum and gradually decreased until reaching a constant in the compound channel. Sediment motion (bedload vs. deposition) was determined by the local bed shear and the critical bed shear. Sediment was deposited in the compound channel at the position where the local bed shear was smaller than the critical bed shear. When the floodplains were vegetated, the increase in the main channel velocity enhanced the local bed shear, which surpassed the critical bed shear; thus, deposited sediment was reinitiated and moved downstream, and no deposition was observed. [ABSTRACT FROM AUTHOR]

Background: Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) allows sophisticated quantification of left atrial (LA) blood flow, and could yield novel biomarkers of propensity for intra-cardiac thrombus formation and embolic stroke. As reproducibility is critically important to diagnostic performance, we systematically investigated technical and temporal variation of LA 4D flow in atrial fibrillation (AF) and sinus rhythm (SR). Methods: Eighty-six subjects (SR, n = 64; AF, n = 22) with wide-ranging stroke risk (CHA2DS2VASc 0–6) underwent LA 4D flow assessment of peak and mean velocity, vorticity, vortex volume, and stasis. Eighty-five (99%) underwent a second acquisition within the same session, and 74 (86%) also returned at 30 (27–35) days for an interval scan. We assessed variability attributable to manual contouring (intra- and inter-observer), and subject repositioning and reacquisition of data, both within the same session (same-day scan–rescan), and over time (interval scan). Within-subject coefficients of variation (CV) and bootstrapped 95% CIs were calculated and compared. Results: Same-day scan–rescan CVs were 6% for peak velocity, 5% for mean velocity, 7% for vorticity, 9% for vortex volume, and 10% for stasis, and were similar between SR and AF subjects (all p > 0.05). Interval-scan variability was similar to same-day scan–rescan variability for peak velocity, vorticity, and vortex volume (all p > 0.05), and higher for stasis and mean velocity (interval scan CVs of 14% and 8%, respectively, both p < 0.05). Longitudinal changes in heart rate and blood pressure at the interval scan in the same subjects were associated with significantly higher variability for LA stasis (p = 0.024), but not for the remaining flow parameters (all p > 0.05). SR subjects showed significantly greater interval-scan variability than AF patients for mean velocity, vortex volume, and stasis (all p < 0.05), but not peak velocity or vorticity (both p > 0.05). Conclusions: LA peak velocity and vorticity are the most reproducible and temporally stable novel LA 4D flow biomarkers, and are robust to changes in heart rate, blood pressure, and differences in heart rhythm. [ABSTRACT FROM AUTHOR]

Dispersion of planktonic propagules connects shoreline populations of many marine species, and considerable effort has been directed at understanding this process. However, gaps in knowledge persist. In particular, relatively little information has been available regarding transport over the innermost portions of the continental shelf and its impacts on larval distributions and population connectivity. I quantified velocity in nearshore waters at 5 sites along the California coast and investigated characteristics relevant for dispersing larvae. Mean depth-averaged velocities increased with distance from shore at all sites. This repeated and consistent “coastal boundary layer” (CBL) pattern exhibits a logarithmic profile that resembles that associated with the “law of the wall” of smaller-scale turbulent boundary layers, despite differences in spatial dimension and governing physics. A tentative scaling of dominant terms in an alongshore momentum balance suggests nontrivial levels of lateral stress, but small cross-shore gradients in this quantity. Such a trend of near-constant lateral stress, when combined with simple representations of horizontal mixing (i.e., eddy viscosity) that increase approximately linearly with distance from shore, provides a possible explanation for the observed logarithmic velocity pattern. I incorporated these gradients in alongshore velocity and mixing into a 2-dimensional Lagrangian particle-tracking model to explore effects of the CBL on dispersal and self-retention for a variety of sites and life histories. Incorporating a CBL decreased mean dispersal distances up to 56% and was more profound for shorter pelagic larval durations (PLD) and gentler bathymetric slopes associated with broader CBLs. Most notable is that the presence of a CBL increased self- retention by as much as three orders of magnitude, which indicates that ignoring the reduced velocities in the CBL may overestimate population connectivity. These model results were echoed by measurements of planktonic communities within the field. I measured cross-shore distributions of crustacean larvae within the CBL in northern California (between 250 and 1100 m from shore) and found high larval abundances within the CBL, peaking inshore of the 30 m isobath (1 km from shore). However, abundances decreased substantially in the inner portion of the CBL, and there were distinct larval communities between the nearshore and the rest of the CBL. These patterns persisted across sample dates, suggesting that the spatial structure of nearshore larval communities is robust to changes in physical conditions. High larval abundance within the CBL coupled with the potential of the CBL to reduce alongshore larval transport suggests that larvae may exhibit behaviors that interact with recirculating flow features to elevate local retention. Because of these consequences, CBLs should be considered in future models of coastal transport, as they appear to have large effects on population dynamics of marine species.

Global Navigation Satellite Systems (GNSS) are used for different purposes in geodesy, like engineering geodesy, land management, real estate cadastre, land surveying, etc. However, high-precision GNSS measurements are used primarly for determination of reference networks, and for investigation of geodynamical phenomena as tectonic plates movements, which is the focus of this paper. An active GNSS network of Bosnia and Herzegovina (BIHPOS) was used for calculation of coordinates and velocities of networks' stations. Data from 23 stations were processed using scientific software GAMIT/GLOBK (version 10.7), developed on MIT (Massachusetts Institute of Technology). A sub-centimeter accuracy of coordinates is achieved and accuracy of calculated velocities is better than 1 mm/year. Station velocities interpretate geodynamics of Bosnia and Herzegovina. Six IGS stations were used, as reference datum stations. Reference stations analysis results are in good match with EUREF Permanent GNSS Network velocities, while BIHPOS stations velocities (at 13 stations in Bosnia and Herzegovina) show very similar trend to the velocities obtained from regional geodynamic campaigns (CERGOP). [ABSTRACT FROM AUTHOR]

Detection of aircrafts in satellite images is a challenging problem when the background is strongly reflective clouds with varying transparency. We develop a fast and effective detection algorithm that can find almost all aircrafts above and between clouds in Sentinel-2 multispectral images. It exploits the time delay of a few seconds between the recorded multispectral images such that a moving aircraft is observed at different positions due to parallax effects. The aircraft speed, heading and altitude are also calculated accurately. Analysing images over the English Channel during fall 2020, we obtain a detection accuracy of 80%, where the most of the remaining were covered by clouds. We also analyse images in the 1.38 μm water absorption band, where only 61% of the aircrafts are detected.

Abstract This paper reports the results of a series of laboratory experiments on forming synthetic methane and tetrahydrofuran (THF) hydrates in sand samples and measuring their acoustic properties, i.e. P- and S-wave velocities. Experimental data were used for validating different effective acoustic velocity models connecting P- and S-wave velocities to the hydrate saturation. The envelope-cementing effective model gives the best fit for the methane gas-hydrate formation using the "excess-gas" method. These results may represent the case of onshore hydrate deposits formed from gas accumulations, e.g. Messoyakha Field in Siberia. The load-bearing effective model gives the best fit for THF hydrate formation that avoids gas phase in the system. These results should be typical to the most widespread hydrate deposits forms in marine sediments from the dissolved methane. We compare our experimental data with a compilation of similar published results to confirm their reliability and support our conclusions. Calibrated effective models can be further used for developing seismic-exploration methods for characterizing as well as confirming the origination history of natural gas-hydrate accumulations of different type. Highlights • Effective acoustic velocity models differ for different natural gas-hydrate deposits. • Load-bearing effective model fits data for THF synthetic hydrates. • Envelope-cementing model fits data for "excess-gas" methane-hydrate formation. • Envelope-cementing effective model corresponds to gas hydrates in Messoyakha Field. [ABSTRACT FROM AUTHOR]

The measurements of the EUREF (IAG Regional Reference Frame Sub-Commission for Europe) densification in Estonia were conducted in the summer of 1997. The network has since been remeasured twice (in 2008 and 2017), including also available national GNSS reference stations. In the present study all three campaigns have been recomputed and the results are expressed in the latest International Terrestrial Reference Frame ITRF2014 (ITRF, 2019). As a result, the coordinates of the Ist order geodetic points were specified. The RMS errors of the individual coordinate components with respect to the average of the three campaigns were 1.9 mm, 2.9 mm and 2.8 mm for north, east and up components, respectively. Also, the velocity estimates for the points were estimated and compared to corresponding regional velocity models. The discrepancies (in terms of standard deviation) with land uplift model NKG2005LU were in average 0.2 mm/year only. The resulting horizontal velocities however are subject to further research. [ABSTRACT FROM AUTHOR]

Vibrations caused by some industrial sources (forges, presses etc.) are transmitted to the ground, generating different surface waves, with significant effects on building foundations, as well as some effects on buildings and their occupants. The structural dynamic response to this type of vibration also depends on the phenomenon of structure-soil interaction and the phenomenon of attenuation/amplification of vibrations. The principle of the applied method consists in determining the actual values of the characteristic parameters from the recorded vibrations in-situ /in building, in order to verify the fulfilment of the velocity criteria which are correlated with certain degrees of damage. In view of the means of controlling vibrations (at source, by transmission and in remote buildings) with physical or on human perception effects, the made assessments will determine whether the prevailing frequency produced by industrial equipment, within the monitored activities, is finds itself in the area of adjacent buildings' frequencies, with possible effects on the comfort of the inhabitants. The article aims to present comparatively the results obtained from the some instrumented sites. [ABSTRACT FROM AUTHOR]

In the modern geodesy the role of the permanent station is growing constantly. The proper treatment of the time series from such station lead to the determination of the reliable velocities. In this paper we focused on some pre-analysis as well as analysis issues, which have to be performed upon the time series of the North, East and Up components and showed the best, in our opinion, methods of determination of periodicities (by means of Singular Spectrum Analysis) and spatio-temporal correlations (Principal Component Analysis), that still exist in the time series despite modelling. Finally, the velocities of the selected European permanent stations with the associated errors determined following power-law assumption in the stochastic part is presented.

Dispersal, establishment, and spread of aquatic invasive species such as the zebra mussel (Dreissena polymorpha) can be influenced by riverine velocities and volumetric flows in invaded lake-stream ecosystems. Zebra mussels, which have a planktonic larval form (veliger), disperse rapidly downstream from a source population. Concentrations, dispersal, and body conditions of zebra mussel veligers were studied under different volumetric flow, or discharge, conditions in a coupled lake-stream ecosystem in northern Texas, USA. Veliger densities in lotic environments were strongly related to population dynamics in upstream lentic source populations. A strong exponential decrease in veliger density was observed through a 28-km downstream study reach. Increased water releases from the source reservoir increased veliger flux and dispersal potential, concomitantly increasing veliger flux and decreasing transit time. However, passage through release gates in the dam and increased turbulence in the river during high-discharge events could negatively affect body condition of veligers, and veliger body condition generally decreased from the source population to the farthest downstream site and was lower for veligers during periods of high discharge. Thus increased discharge appears to reduce the proportion of viable veligers because of increased turbulence-induced mortality. Colonization of distant downstream reservoirs can occur if discharge and propagule pressure are sufficient or if interim habitats are suitable for establishment of in-stream populations. [ABSTRACT FROM AUTHOR]

Experimental studies have been made of the permissible regimes of processing ultrahigh molecular weight polyethylene GUR 2122 with molecular mass of 4.5 million g/moles in a laboratory extruder with an auger diameter 32 mm and a ratio L/D = 20 at temperatures of 155-165oC. On the basis of rotational viscometry, the rheological properties of the melt are described. A mathematical model and a numerical method for calculating the motion of ultrahigh molecular weight polyethylene melt in the auger and in the moulding rigging are proposed. The velocity and stress fields have been determined. [ABSTRACT FROM AUTHOR]

The swash zone is the part of the beaches that are consecutively dry and wet due to the rise and fall of the sea by waves and tides. This zone is particularly important in beach systems, as here erosion and accretion of the coastline and coastal inundation occur; therefore, understanding of the dynamics in this zone allows the prediction and mitigation of potential impacts on beaches, dunes and coastal structures under different climate scenarios. In situ measurements of variables such as pressure, velocity and sediment concentrations on the swash were carried out for the first time at two beaches in the Colombian Caribbean: Costa Verde beach, (Ciénaga) and Hollywood beach (Cartagena). The data were used to compare the velocity and sediments transport patterns in the swash zone due to the beach slope on this zone and to the influence of different wave frequencies (IG or SS). In addition, a first approximation to link small spatio-temporal scales (swash cycles) with larger spatio-temporal processes (erosion-accretion) was carried out. [ABSTRACT FROM AUTHOR]

Besides the methodology of triangulation and geodetic networks nowadays, the permanent stations of satellite receivers exist, giving extra asset to geodetic daily practice. Permanent stations perform observations incessantly for the visible satellites. However, the coordinates of these stations are often changing over time due to geophysical and tectonic processes. Consequently, these changes are perceived to modern observations. So, along with the coordinates of geodetic points in a given epoch, their changes over time (e.g. the velocities of their movements) are also considered. Furthermore, any change to the reference system definition or/and to the network’s geometry can significantly impact the estimated coordinates and velocities. This paper investigates the reference datum definition problem (or datum problem, or zero order design problem) in a such network over time, which is later generalized for the study of the deformation control-networks. Emphasis is given to techniques of time-dependent 2D transformation models, with numerical tests on a simulation network. [ABSTRACT FROM AUTHOR]

Based on typical characteristics and teaching features of exploration technology and engineering specialty, a comprehensive experiment of rock physics was designed to investigate the effects of pressure, temperature and fluid on velocities of the rock. The rock that was placed in a reactor with loading axial pressure and confining pressure and heated by the heating ring was used to measure P-and S-wave velocities under high temperature and high pressure. The results indicated that P-and S-wave velocities of the rock increase with pressure increase and decrease with temperature increase, and P-wave velocity of water saturated rock is higher than that of gas saturated rock while S-wave velocity of water saturated rock is less than that of gas saturated rock. This exploratory research will help students to understand theoretical knowledge of the textbooks, and cultivate their practical abilities and innovation abilities. [ABSTRACT FROM AUTHOR]