Predominant Direction Research Articles

Wind variability over a large lake with complex topography: Lake of the Woods

Lake of the Woods spans two geological regions: the Precambrian Shield and the Glacial Lake Agassiz Lakebed. The lake watershed’s complex topography influences wind speeds and directions. We study wind variability over Lake of the Woods using reanalysis data and wind observations at seven sites. A wind variability index is proposed as a measure of lake-wide spread in wind direction. Our results show that the directional variability depends on wind speeds, with higher variability at lower speeds. The wind variability also changes throughout the year; it is more pronounced in spring (Apr-Jun) and fall (Sep-Oct) and less pronounced during winter (Dec-Jan). Observed wind directions are 60% more variable than reanalysis wind, indicating a need for higher-resolution reanalysis to resolve local wind effects due to topographic changes. Based on the statistical hierarchical clustering method, our analysis shows that geographically variable wind can be grouped into three regions to represent the predominant wind directions accurately. Clustering results also suggest spatial coverage gaps in the existing meteorological observation network. We reassess the existing network and propose a new meteorological observation site in the southeast basin near Morson, Ontario. Our study is of significance for water quality management because the wind is the key driver of water circulation, transport, and mixing in the lake, and accurate wind measurements are necessary to better constrain the underpinning physical, biological, and biochemical processes in mechanistic ecological models.

Integration of satellite gravimetry, multispectral imagery and digital elevation model for investigating crustal deformation in the Niger Delta Basin

Remotely acquired gravity data from satellite gravimetry is integrated into the study to investigate crustal deformation in the Niger Delta Basin. The Niger Delta Basin is a well-documented example of a passive margin delta that has gravitationally deformed. The gravity-driven deformation has not been fully understood, and new trends may be emerging. In this study, we assess and delineate structural deformation and sediment accumulation of the Agbada and Akata stratigraphic sequences within the basin's prograding clastic wedge. This was done through the integration of data from the Gravity Recovery and Climate Experiment (GRACE) mission, Landsat 8 satellite imagery, and the Advanced Land Observation Satellite (ALOS) World 3D-30 m (AW3D) DEM. The methodology workflow incorporated gravity modelling from GRACE data, lineament extraction from Landsat imagery, and drainage network analysis from the AW3D DEM. The Niger Delta Basin as seen on the gravity models depicts large-scale block faults with a well-defined graben structural topography. This eventually shows that the basin is dominated by growth faulting with differential subsidence. The predominant directions of the mapped lineaments are in the N-S and W-E directions. With over 18,500 lineaments, the W-E direction is marginally the dominant direction of the two predominant directions. Many linear structures such as shear zones and fractures which have different orientations and directions characterise the study area. Also present are the minor N-S fractures which are attributed to brittle deformation and sets of NE-SW and NW-SE trends, produced by transcurrent movements as the structural framework of the Nigerian basement complex are dominated by the NE-SW lineaments. However, the complexity in the structural geometry and thrusting sequences in the Niger Delta shows the patterns of growth structure and imbricate thrusting. The structural pattern also exhibits outward radial gravity spreading of dip-orientated, extensional structures that include delta slope radial grabens and tear faults. Radial spreading has likely increased the segmentation of Niger Delta regional depo-belts in the N-S direction. It is observed that most of the structural deformations in the basin are syn-formational, evolving at the same time as sediment deposition.

MODELING OF THE WELD PRIMARY MACROSTRUCTURE FORMATION AT LASER WELDING

In modern shipbuilding, those enterprises and shipyards that introduce innovative and highly efficient technologies gain an advantage in the competitive struggle. The experience of the largest European shipyards, such as Meyer Werft and Blohm und Voss in Germany, Kvaerner Massa Yard in Finland, Fincantieri in Italy, shows the great potential of laser equipment in creating breakthrough technologies in shipbuilding. The leading role among the developed technologies is played by the technologies of laser and laser-arc welding. Compared to arc welding, laser and laser-arc welding increase the welding speed by 2-3 times, and a decrease in butt gaps leads to a decrease in the need for welding consumables. The approaches to creating a model for predicting the metal structure and mechanical properties of a welded joint in laser welding are discussed in the paper. This will make it possible to establish welding modes at the preproduction stage and obtain the properties of welded joints specified by the designer. This model is based on mathematical calculations of the thermal regime of welding and the process of crystallization of welds. A mathematical model of laser welding is used, taking into account the presence of a vapor-gas channel, which allows laser radiation to penetrate the entire thickness of the weld, which ensures the formation of a deep, narrow weld. The results of the calculation make it possible to determine the shape of the penetration pool and the position of the main temperature lines in the heat-affected zone. For beam welding methods, it is proposed to approximate the surface of the melt pool (crystallization front) by a cubic spline. Its main advantage is that the entire shape of the surface is modeled most accurately and completely, which allows you to build the surfaces of all areas of the bath without excluding any parts. On the basis of such a spline, the predominant direction of crystallite growth, their growth rate in the direction of welding are determined, and the integral characteristics of the emerging primary macrostructure of the weld metal are found. Based on the criteria characterizing the process of crystallization, a prediction of the macrostructure of the weld metal is given.

Longshore sediment transport rate from the field measured wave and sediment characteristics along the coast of Karaikal, India

ABSTRACT The change in the shoreline greatly influences the coastal developments such as maritime trade, fishing activities, coastal transport, and tourism. Due to the requirements of vast developments along the coast near major habitat zones, such as the Karaikal coast along the east coast of India, it is essential to understand the longshore sediment transport (LST) movement to plan for any coastal systems to protrude. A detailed LST estimate has been made with the predicted wave climate using the wind-wave model, WAM. The wave characteristics are compared with the field measurements off the coast considered herein. The LST rates computed using five different sediment transport formulae and the method of integrating the distribution of sediment transport rates within the surf zone have been computed to understand the variations of the estimate in each method. Although the predominant direction of sediment movement is towards the north, there is a seasonal variability of LST based on the prevailing monsoon wind direction. Monitoring and analysis of the LST are important as it is required in designing coastal structures.

Do Seabirds Control Wind Drift during Their Migration across the Strait of Gibraltar? A Study Using Remote Tracking by Radar

This study presents data on the directional flying behaviour of the five most abundant seabird species migrating across the Strait of Gibraltar in relation to the wind, as observed from the north coast, based on radar tracking, and identified to species level by visual observations. A total of 318 seabird trajectories were analysed, illustrating the expected east–west or west–east movements in spring and autumn. We hypothesised that the seabirds that cross the Strait channel during their migrations would behave differently with respect to compensation for wind direction, depending on their flight styles, the migratory period, and the prevailing winds. In this regard, our results showed that flapping birds (Razorbill, Puffin, Northern Gannet, and Balearic shearwater) compensated for wind drift independently of the season and the predominant wind direction. This agrees with the theory that suggests that under moderate winds and whenever visual contact with the coastline is present (as in the case of our study), migrants should compensate for wind drift to avoid being drifted towards the coast, off their main direction of flight. However, Cory’s shearwater, an active gliding seabird with long, slender wings, showed an adaptive directional response to wind, allowing it to be drifted in spring when westerly tailwinds were prevalent, but compensated for wind in autumn, when both easterly and westerly winds were similarly frequent. This adaptive flight behaviour allows it to take advantage of the prevailing tailwinds in spring, gaining ground speed and saving energy during its passage through the Strait, while in autumn, more frequent headwind conditions and a more directional migration to the south may favour compensating for wind drift. Our results support the usefulness of bird radar as a remote tool for describing the pattern of animal movements in the marine environment, as well as their behavioural response to atmospheric conditions. These studies are particularly relevant in the current framework of climate change.

Nearshore submerged wave farm optimisation: A multi-objective approach

To be commercially viable, wave energy converters (WECs) will need to be deployed in arrays or “wave farms” to generate significant amounts of energy and to have the costs of these farms minimised. However, when designing a wave farm, there are a number of trade-offs to be made between competing objectives; for example, between the power production potential and installation costs, with the optimal design for one objective not necessarily favourable for the other. In this study, we developed a multi-objective optimisation methodology to allow rigorous evaluation of the trade-offs amongst multiple objectives. We demonstrate the methodology for four objectives: (1) maximising power production, (2) minimising the foundation loads, (3) minimising the number of foundations and (4) minimising the total export cable length required. However, the method is flexible and can be used for optimising a range of other parameters. A case study examining multi-objective optimisation of a wave farm using the developed probability-based evolutionary strategy was conducted for a proposed development site in Albany, Western Australia. The wave farms were composed of 5, 10 and 20 fully submerged cylindrical point-absorber type WECs similar to Carnegie Clean Energy's CETO-6 device. Simulations show that the optimal layouts preferring maximum power formed a single line perpendicular to the predominant wave direction; the optimal layouts preferring minimum cable length and a minimum number of foundations form multiple lines; whereas the optimal layouts preferring minimum foundation loads formed multiple lines in line with the predominant wave direction. By applying a cost model and non-dominated sorting, the methodology allowed us to quantify the trade-offs between power production and cost.

Seismic microzoning of the Delhi metropolitan area, India— I: Seismicity modeling

AbstractSeismic activity parameters ( and values in a Gutenbdataer–Richter relationship, maximum magnitude , and predominant focal depths ) have been estimated for a grid of square cells of size 0.1° in latitudes and longitudes covering a large region bound by 24°−33°N and 72°−82°E to define input seismicity for microzoning of the Delhi metropolitan area. For this purpose, seven area types of seismic sources are first identified from a detailed seismotectonic evaluation of the region. Two of these sources form part of the Northwestern Himalaya and the remaining five encompass the intraplate area including and surrounding the National Capital Region. The seismic activity parameters are then estimated for each source zone by compiling a comprehensive catalog of 4483 past earthquakes with magnitudes of 2.0 or more covering the 1720–2020 period. All the grid cells in each source are initially assigned the same values of parameters , , and as those for the source zone; whereas parameter has been redefined for each grid cell using the cumulative occurrence rate of earthquakes above the minimum magnitude of completeness for the source zone. To account for possible uncertainties in past earthquake locations, values of the activity parameters thus assigned to all the grid cells in the region are spatially smoothed using an elliptical Gaussian kernel with a major axis along the predominant strike direction for the source zone of each grid cell. The grid cells across the source zone boundaries are also included in the smoothing process to normalize the effects of any subjectivity introduced in defining the source zone boundaries. Our estimations of seismic activity parameters thus obtained can be considered in the development of a robust and physically realistic seismicity model for practical engineering applications, which was made possible by our use of a sufficiently long duration of the earthquake catalog along with complete reporting of data up to magnitudes very close to the expected maximum magnitude in each source zone. We have also estimated the seismic activity parameters for the Hindu Kush subduction zone, which is then idealized by a point source.

Hydrocarbon pollution in the waters and sediments of the Kerch Strait

The results of studying the content and composition of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons in the suspended particulate matter of surface waters and in the surface layer of bottom sediments in 2019–2021 in the Kerch Strait in comparison with earlier studies in other areas of the Black Sea (Theodosia Gulf, Tuapse area, Coastal waters of the Crimean Peninsula, Big Sochi, Central part of the Sea) are presented. Despite the high concentrations of aliphatic hydrocarbons (especially in the waters of the strait itself: 28–254 on average 87 μg/L. The highest content of aliphatic hydrocarbons was confined to the cross-section through the Kerch Strait. Accumulation of aliphatic hydrocarbons, as well as the suspended particulate matter, occurs in the western part of the Strait, which is associated with the predominant wind direction and coastal orography. The composition of alkanes did not correspond to the smooth distribution of homologues characteristic of oil. Their distribution was bimodal in most samples, which may indicate a mixed genesis of alkanes. Among the low-molecular-weight alkanes either even numbered autochthonous alkanes n-C16, C18, C22, arising during the microbial transformation of aliphatic hydrocarbons, or n-C17, indicating the inclusion of phyto- and zooplankton alkanes, prevailed. Despite the different sources of hydrocarbons input, the distribution of the total concentrations of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons basically coincided. Polycyclic aromatic hydrocarbons composition was dominated by fluoranthene and pyrene, which are formed in high-temperature combustion processes Low values of the Σnaphthalenes/Phen ratio (0.05–0.11) may indicate an insignificant inclusion of petroleum polyarenes.In contrast to suspension of surface waters, the highest content of hydrocarbons in the surface sediments was found not in the strait, but at stations in areas with aleurite-pelitic sediments, which is due to the pattern of currents in these areas and the higher sorption capacity of finely dispersed sediments. The average Corg content in July 2020, was 1.8 times lower (0.34%) than in September 2019 (0.63%), and aliphatic hydrocarbons, on the contrary, was 2.2 times higher (47 μg/g) than in April 2019 (21 μg/g). In surface sediments the maximum concentration of aliphatic hydrocarbons was established in July 2020 (233 μg/g), and the highest average content in July 2021 (58 μg/g). This area is also associated with higher concentrations of aliphatic hydrocarbons in the composition of Corg –≥1%. The composition of alkanes in surface sediments differed from their composition in suspension. The ratio of low-to-high molecular weight homologues (L/H = 0.08–0.54) was lower and the odd-to-even ratio (CPI = 1.19–4.58) was higher than in particulate matter. Due to the coarse composition of sediments, the content of polycyclic aromatic hydrocarbons in their surface layer was lower (0–631 ng/g) compared to other areas of the Black Sea. In their composition, along with fluoranthene and pyrene, methylated naphthalene homologues also belonged to the dominant compounds. Correlation analysis of individual polyarenes, as well as factor analysis, indicates their mixed genesis oil + pyrogenic, with the preference of the latter in most samples. The entry of pollutants into the marine environment increases the hydrocarbons content in water and bottom sediments, creating a modern hydrocarbon background.

A graph-theory based directed network feature for thermal anisotropy

The effective thermal conductivity of a granular material varies with the predominant heat transfers direction. The anisotropic effective thermal conductivity is known to be dominated by the microstructure in a dry material. However, no microstructural parameters that are well related to thermal anisotropy have been proposed. After analysing the heat transfer mechanisms at the particle scale, this work constructs new directed weighted thermal networks for both lattice and randomly distributed sphere packings, by considering particles as nodes and local heat transfer paths with thermal resistance as directed edges. With the implementation of graph theory to the directed weighted thermal networks, the shortest preferential heat transfer paths between nodes paired at opposite faces of a sample across the driving temperature gradient direction are identified. Based on the shortest heat transfer paths, a new sample-scale feature named “directed network thermal resistance” is computed for each sample. This new parameter accounts for particle connectivity, interparticle contact orientation and contact quality simultaneously. After computing the effective thermal conductivity of each sample in different directions using a weighted thermal network model, it is found that directed network thermal resistance is inversely proportional to anisotropic effective thermal conductivity.

Central Commands to the Elbow and Shoulder Muscles During Circular Planar Movements of Hand With Simultaneous Generation of Tangential Forces.

This study examines some of the non-linear effects of signal transduction in the human motor system, with particular emphasis on muscle hysteresis. The movement tests were analyzed in a group of eight subjects, which were asked to develop tangential force using visual biofeedback while performing slow, externally imposed, circular movements of right hand holding a moving handle operated by a computerized mechatronic system. The positional changes in the averaged EMGs of the elbow and shoulder muscles were compared for all combinations of direction of movement and generated force. Additionally, for one of the subjects, there was carried out MRI identification and 3D printing of the bones of the forelimb, shoulder, scapula and collarbone, which made it possible to reconstruct for him the length and force traces of all the muscles under study. The averaged EMG traces in muscles of both joints show their close correspondence to the related force traces, however, the co-activation patterns of activity in agonists and antagonists were also often encountered. The EMG waves related to the respective force waves were strongly dependent on the predominant direction of the muscle length changes within the correspondent force wave locations: the EMG intensities were higher for the shortening muscle movements (concentric contractions) and lower during muscle lengthening (eccentric contractions). The data obtained allows to suggest that for two-joint movements of the forelimbs, it is sufficient to consider the force and activation synergies (patterns of simultaneous activity in different muscles), ignoring at the first stage the effects associated with kinematic synergy. On the other hand, the data obtained indicate that the movement kinematics has a strong modulating effect on the activation synergy, dividing it into concentric and eccentric subtypes, in accordance with the known non-linear features of the muscle dynamics. It has been shown that the concentric and eccentric differences in the responses of the shoulder muscles are more clearly distinguishable than those in the elbow muscles. The shoulder muscles also have a more pronounced symmetry of the averaged EMG responses with respect to the ascending and descending phases of force waves, while demonstrating a lower degree of antagonist cocontraction. The data obtained suggest that the central commands in two-joint movements are determined mainly by the interdependence of force and activation synergies including both intra- and inter-joint components, while kinematic synergy can be interpreted as a potent modulator of activation synergy.

First Assessment of Mercury (Hg) Concentrations in Skin and Carapace of Flatback Turtles (Natator depressus) (Garman) From Western Australia

Mercury pollution in the surface ocean has more than doubled over the past century. Within oceanic food webs, sea turtles have life history characteristics that make them especially vulnerable to mercury (Hg) accumulation. In this study we investigated Hg concentrations in the skin and carapace of nesting flatback turtles (Natator depressus) from two rookeries in Western Australia. A total of 50 skin samples and 52 carapace samples were collected from nesting turtles at Thevenard Island, and 23 skin and 28 carapace samples from nesting turtles at Eighty Mile Beach. We tested the influence of turtle size on Hg concentrations, hypothesising that larger and likely older adult turtles would exhibit higher concentrations due to more prolonged exposure to Hg. We compared the rookeries, hypothesising that the turtles from the southern rookery (Thevenard Island) were more likely to forage and reside in the Pilbara region closer to industrial mining activity and loading ports (potential exposure to higher environmental Hg concentrations) with turtles from the northern rookery (Eighty Mile Beach) more likely to reside and feed in the remote Kimberley. Turtles from the Eighty Mile Beach rookery had significantly higher skin Hg concentrations (x̄ = 19.4 ± 4.8 ng/g) than turtles from Thevenard Island (x̄ = 15.2 ± 5.8 ng/g). There was no significant difference in carapace Hg concentrations in turtles between Eighty Mile Beach (x̄ = 48.4 ± 21.8 ng/g) and Thevenard Island (x̄ = 41.3 ± 16.5 ng/g). Turtle size did not explain Hg concentrations in skin samples from Eighty Mile Beach and Thevenard Island, but turtle size explained 43.1% of Hg concentrations in the carapace of turtles from Eighty Mile Beach and 44.2% from Thevenard Island. Mercury concentrations in the flatback turtles sampled in this study are relatively low compared to other sea turtles worldwide, likely a result of the generally low concentrations of Hg in the Australian environment. Although we predicted that mining activities would influence flatback turtle Hg bioaccumulations, our data did not support this effect. This may be a result of foraging ground overlap between the two rookeries, or the predominant wind direction carrying atmospheric Hg inland rather than seaward. This is the first Hg study in skin and carapace of flatback turtles and represents a baseline to compare Hg contamination in Australia’s surrounding oceans.

Aerobiological Pollen Deposition and Transport of Fraxinus excelsior L. at a Small Spatial Scale

The ongoing fragmentation of ash populations due to ash dieback requires an effective gene flow between individuals; thus, investigations on ash pollen transport are essential. In this study, comprehensive aerobiological field experiments at two seed plantations in Baden-Württemberg were conducted in 2019 and 2020 in order to study the influence of phenology and meteorology (especially wind) on pollen transport using self-constructed gravimetric pollen traps located 1.5 and 5 m a.g.l. Our main objectives were to investigate the local scale dispersion of ash pollen and to evaluate the recommended distance (i.e., 400 m) from seed plantations to other ash trees according to the German Forest Reproduction Act. Our results showed a link between pollen transport and meteorology, the onset of phenological development, and the topography of the plantation. The plantation at Schorndorf was characterized by a slope and associated cold air flows, suggesting that this could be a factor contributing to higher pollen levels at the downslope traps. In addition, in many cases, the cardinal direction associated with the highest pollen impaction was also identical with the predominant wind direction. Analyzing pollen data for single traps in detail, we found that the highest total pollen catch (31%) was measured outside the plantations in 2019, a year with very low flower development. In contrast, most pollen (33%) was caught within the plantation in 2020, which presented a much stronger pollen year than 2019 (with a factor of 11 regarding total sums). This indicates, in the lower pollen year, a potential higher contribution of trees from outside the plantation, and thus it can be recommended that seed harvesting of ash trees in the plantations should preferentially take place in full mast years. Interestingly, the total pollen deposition in Emmendingen at 5 m height showed little difference compared to the traps at 1.5 m height, but there was a large temporal difference pointing to vertical variations in pollen availability. In general, we found that ash pollen was transported for a larger distance than 400 m, but the amount of pollen decreased substantially with increasing distance. At a distance of 200 m, there was already approx. 50% less pollen captured from the air. However, even at a distance of 500 m, more than 10% of the pollen was still captured. In order to ensure cross-pollination of healthy ash trees, the distance of ash individuals or stands should not be too large, and there should be no spatial separation (e.g., by conifer stands).

Post-Nourishment Changes of an Artificial Gravel Pocket Beach Using UAV Imagery

Monitoring and analysis of changes in the volume and area of nourished beaches is crucial to inform any beach renourishment programme. The aim of this study is to utilise UAV surveys and SfM photogrammetry to assess the beach nourishment performance of an artificial gravel beach exposed to a range of external forcing, including storms. The paper presents results from nineteen UAV surveys conducted between January 2020 and January 2021 at Ploče, an artificial beach in Rijeka (Croatia). The beach was nourished twice and eleven storm events, ranging from weak to strong, were recorded during this period. The Agisoft Metashape software was used to obtain point clouds and digital elevation models (DEMs) from UAV images; Matlab and CloudCompare were used for further analysis of the DEMs. The accuracy and precision of the DEMs was assessed and uncertainty levels of ±5 cm were applied to all derived DEMs. The study provides new insights into the response of the emerged part of the beach to storms. Predictably, the largest changes were recorded after the first storm following beach nourishment. The longshore variability in the beach response to storms was identified from full 3D point clouds. Most of the lost sediment was from the east side of the beach, while the rest of the beach aligned with the predominant wave direction through cross-shore and longshore processes. Offshore/onshore sediment exchange between the lower and upper beach face on the western side manifested itself in beach profile steepening and berm formations. Overall, changes in beach volume and area were small, indicating that this artificial beach is relatively stable. The embayed layout following the natural coastal configuration appears to be effective in retaining nourished sediment on the beach. This work highlights the need to consider pocket embayed beaches in three dimensions, as traditional transect studies can overlook the three-dimensional behaviour. This study also highlighted the wider potential of UAVs and SfM for studies of high-resolution elevation changes on natural and artificial beaches, as well as for coastal monitoring of beach nourishment.

NATURALLY VENTILATED CLASSROOMS: CO2 AND COVID PROTECTION

ABSTRACT: Natural ventilation has become one of the most effective and sustainable strategies to address COVID-19 in confined spaces. Air intake through windows and other openings improves the Indoor Air Quality (IAQ) of a classroom, decreases the likelihood of respiratory disease transmission with an adequate social distance of about 1.5 m and is affordable in terms of energy consumption. In this study, a comparison of CO2 concentration, wind speed, number of people, type of ventilation and window surfaces of a school in a Mediterranean climate is carried out for 4 different cases of opening. For this purpose, CO2 levels were measured in different classrooms with different window openings (33%, 67%, 81%, 81%). (33%, 67%, 81% and 100% respectively). In addition, three types of ventilation (cross ventilation, partial cross ventilation and multidirectional ventilation) were analyzed in a time period between February and March 2021. The results show an interaction between CO2 levels and the type of ventilation. Thus, the fact that the window surface is a critical factor in reducing CO2 concentrations was determined, considering that the distance between students was approximately 1.5 m. Therefore, the orientation of buildings towards the predominant wind direction and the Window to Floor Ratio (WFR) should be reconsidered in new constructions. Keywords: natural ventilation, indoor air quality, carbon dioxide (CO2) concentration, school, WFR.

MeePaSoL: A MATLAB-based GUI software tool for shoreline management

Headland-bay beaches (HBBs) are ubiquitous on Earth and many coastal scientists and engineers have attempted to define their planform since the 1940s, by employing laboratory tests, analytical tools, numerical models, and empirical equations. One of the latest attempts in numerical modeling is the development of a MATLAB-based GUI software called “MeePaSoL” to facilitate the application of the empirical parabolic model for HBBs. This visualization package can be applied to determine the predominant wave direction to the shoreline planform of a HBB in static equilibrium, and to minimize the uncertainty in locating downdrift control point while using other software. The background concepts (e.g., parabolic model, equilibrium beach and wave orthogonality hypothesis) are introduced, and the operation procedure with stepwise guides for applying MeePaSoL are given to assist the users. The reliability of MeePaSoL is validated by comparing the wave direction given by this package with that by the wave energy flux approach derived from field data. Examples of engineering applications are then demonstrated, covering local to regional wave direction, the effect of jetty/breakwater length and direction, harbor siltation in a macro-tidal environment, and devising engineering works for shoreline management in Korea. Sensitivity and uncertainty are also discussed.

Combined enhancement of thermal and chemical performance of closed thermochemical energy storage system by optimized tree-like heat exchanger structures

The full exploitation of thermochemical energy storage potential is still hampered by several technical limitations, such as the poor heat and mass transfer in the reactive beds. This paper addresses the need of enhancement of heat and mass transfer in solid-gas reactive beds by proposing, investigating and optimizing the use of branched fins made of high conducting material. Two reactor configurations in closed-system operation are examined, and the optimal fin designs are derived by means of surrogate models based on high-fidelity finite elements predictions. The results indicate the use of optimized branched fins to increase the amount of discharged energy up to +9.1% compared to literature benchmarks. However, in the instance of reactive beds where transfer of heat and mass mainly occur along the same predominant direction, fins bifurcations might also hamper the transfer of reactants, leading to diminished thermal performance particularly during the latest stages of the energy discharge process. As a consequence, the optimal number of bifurcations is smaller for reactors that require to operate for longer discharge time. Conversely, such trend is not present in the instance of reactive beds where transfer heat and mass mainly occur along district and mutually orthogonal directions. In this case the typical heat transfer maximization design guidelines can be adopted, indicating a negligible influence of mass transfer on the optimal fins architecture.

Harnessing elastic anisotropy to achieve low-modulus refractory high-entropy alloys for biomedical applications

A high-priority target in the design of new metallic materials for load-bearing implant applications is the reduction of Young’s modulus approximating that of cortical bone in the predominant loading direction. Here, we explore how directionally preferential bulk elastic properties of implant materials are achieved by harnessing elastic anisotropy. Specifically focusing on recently proposed biocompatible refractory high-entropy alloys (RHEAs) in the body-centered cubic structure, we conduct systematic density-functional theory calculations to investigate the single-crystal elastic properties of 21 Ti-containing RHEAs. Our results provide evidence that the valence electron count has a dominant influence on elastic anisotropy and crystal directions of low Young’s modulus and high torsion modulus in the RHEAs. By means of modeling the orientation distribution function for crystallographic texture, we examine the effect of non-random texture on the anisotropic poly-crystalline Young’s modulus and torsion modulus with varying texture sharpness. We adopt fiber textures that can result from rolling and distinct texture orientations that can form during rapid directional solidification. We discuss the potential for lowering Young’s modulus in the RHEAs by using single crystals or textured aggregates. Furthermore, we prepare four of the theoretically considered alloys by arc-melting and report their lattice parameters, quasi-isotropic Young’s moduli, and Wickers hardnesses.

Wave-induced sediment and rhodolith mobility on a narrow insular shelf dominated by wave variability (Fernando de Noronha Archipelago, Brazil)

This study combines numerical modeling and empirical equations to define spatial fields of wave-induced sediment and rhodolith mobility in a narrow insular shelf that is subject to a seasonal wave regime: the Fernando de Noronha insular shelf. From analyses of the annual, summer and winter wave climates, we noticed an intense directional variability in swell waves coming predominantly from opposing directions between the studied seasons (northern swell in summer and southern swell in winter), reflecting higher wave energy on the north coast during summer and lower energy during winter. The longitudinal transport at the northern coast, which is predominantly oriented to the southwest, is also higher in the summer months and lower in the rest of the year. To describe the spatial variation in wave-induced mobility under summer and winter wave conditions, we consider empirical sediment movement equations, based on mean grain size and density values. Carbonate bioclastic sediments, which are predominant in the Fernando de Noronha shelf, are remobilized by waves throughout the entire shelf. However, in the nearshore zone, this movement occurs intensely for all sizes. The depth and shelf side affected by wave-induced mobility vary according to the wave climate variability that determines the direction and type of wave prevailing in the regime. When swell waves come from the north (summer scenarios), mobility is greater mainly on the northern shelf; however, when trade wind waves come from the southeast and swell waves come from the south (winter scenarios), greater movement is produced on the south face. Wave-induced sediment mobility occurs at depths of up to 60 m, near the shelf break, indicating the importance of the shelf morphology. The movement of rhodoliths, which presents a lower density and larger diameter than the sediments, eventually occurs under extreme wave conditions up to depths of approximately 30 m in areas that vary seasonally around the island according to the predominant wave direction. These characteristics are favorable to rhodolith development. With our results, we hope to better understand the wave action on the bottoms of high-energy island shelves by identifying the sediment movement patterns attributed to wave climate variability and morphological characteristics of the shelf.

Morphology of Traveling Wave Disturbances Recorded in Eastern Siberia in 630 nm Atomic Oxygen Emission

Our paper presents the results of investigating wave structures detected in 630 nm atomic oxygen emission intensity (airglow height is ~180–300 km). The study employs data from a wide-angle optical system installed at the Geophysical Observatory of the ISTP SB RAS (51°48′ N, 103°04′ E). It describes the algorithm to identify wave disturbances and determine their main parameters in the optical system images. The results obtained due to automatic processing of 2014–2021 data archives are presented. The most probable values of the wave disturbances propagation velocity are about 80 m/s. The horizontal wavelengths and periods are in the range of ~30–400 km and 60–120 min, respectively. The predominant direction of disturbances propagation is to the southwest. The received data of optical and radio observations are compared. We found both similarities and differences in the wavelike structures direction, which are to be investigated in the future.

Propagation Direction Analyses of Medium‐Scale Traveling Ionospheric Disturbances Observed Over North America With GPS‐TEC Perturbation Maps by Three‐Dimensional Spectral Analysis Method

AbstractWe applied a novel three‐dimensional spectral analysis method to GPS‐TEC perturbation (GPS‐TECP) maps to study the propagation direction of daytime and nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) over North America. By this method, we can automatically calculate the phase velocity spectrum and directionality of MSTIDs. We focused on the periods of high MSTIDs occurrence, namely, June–July 2006 and November–December 2006, to study nighttime and daytime MSTIDs. We divided North America into the west (100°–130°W, 25°–55°N) and east (70°–100°W, 25°–55°N) parts. Our results show that both daytime and nighttime MSTID propagations exhibit strong longitudinal variations as a function of local time and day‐to‐day variations. The power peaks of daytime MSTIDs are from 10:00–16:00 LT in the west part and 10:00–14:00 LT in the east part. The predominant propagation directions of daytime MSTIDs are southward (southeastward) in the west (east). The daytime local time variations demonstrate that the MSTIDs display directional change in the west part; however, a similar directional change is not very pronounced in the east part. The local time variations of nighttime MSTIDs shows the power peaks from 22:00–02:00 LT in the west and 20:00–00:00 LT in the east. We found that the predominant propagation direction in the west part is westward with a wider azimuthal band (∼210°–300°) than the east part (∼210°–240°). By comparing nighttime propagation directions between the western and eastern parts, we reached the conclusion that the magnetic declination angle affects the propagation direction.