Strong Variations Research Articles

SEISMIC MITIGATION EFFECT FOR LARGE-SPACE UNDERGROUND STRUCTURES CONSIDERING SPATIALLY VARYING SOIL PROPERTIES

The seismic response of the large-space underground structure (LSUS) is significantly influenced by the physical properties of the surrounding soil media, while the soil owns a strong spatial variability. This study proposes a seismic response analysis process of the soil-LSUS interaction system is proposed, which can consider the characteristic of the spatially distributed soil properties. The proposed process begins with establishing the spatially random field model of the soil properties using the improved latent space method. Then, the model is calibrated based on the real data and Bayesian approach, and the realization of the random field is accomplished. Further, the soil-LSUS interaction finite element (FE) model is established, which incorporating the soil physical properties generated from the random field. Finally, the nonlinear time-history analysis of the soil-LSUS interaction FE model is conducted. As an illustration of the proposed process, a typical LSUS located in Guangzhou is selected as an example, and the seismic mitigation measure which the lead-filled steel tube damper (LFSTD) is installed between the intermediate column and the top beam is adopted for the LSUS. The influence of the spatial variability of soil properties on the seismic mitigation effect of the LSUS is investigated. Results indicate that the spatial variability of the soil properties can cause a minor influence on the force and deformation of the intermediate column and the energy dissipation ratio between the LFSTD and structure, while it can bring a significant influence on the maximum deformation and force and the shape of the hysteresis loop of the LFSTD.

Local controls on magma fertility in the Mio-Pliocene metallogenic belt of central Chile: Exploration implications

Understanding what produces and how to detect fertile magmas, capable of forming large, economic porphyry-type deposits, is not only a major scientific quest, but it is also relevant economically, as it could lead to better exploration models and higher success rates in mineral exploration. In this work, we use new and previous geochemical and geochronological data from the Mio-Pliocene metallogenic belt of Central Chile to assess the existing tools to detect fertile magmas, study their spatiotemporal variations at different scales and discuss the geological and exploration implications of our findings.Our results suggest that the geochemical ratios currently used to detect fertile magmas are effective, as there is a good correlation between fertile signatures and the presence of known porphyry Cu deposits and prospects, with few false positives, which might be explained by the exhumation and erosion of most of the metal-rich part of the hydrothermal systems.Regarding the genesis of fertile magmas, the spatiotemporal variations we document here are not satisfactorily explained by the processes commonly brought forward to produce this type of intrusions, such as crustal thickening and subduction of sediments, crustal fragments or oceanic fracture zones. These processes operate at regional- or continental-scales in entire arc segments, while magma fertility shows strong contrasts in several coeval intrusions separated only by a few kilometers or tens of kilometers, emplaced within the same arc segment, under the same tectonic regime, crustal thickness and subduction parameters. This implies that there is a strong local control on the production of fertile magmas.Our results support the notion that the most important variable affecting the generation of fertile magmas in subduction margins, is magma residence time at different crustal levels. This variable has a strong local control, as it will depend not only on the overall crustal thickness or the regional tectonic regime, but also on the local orientation of structural pathways controlling magma ascent through the crust, relative to the predominant stress tensor. If magma pathways are oriented at higher angles relative to the maximum stress, magma residence times will be longer, allowing the fractionation of abundant hornblende (giving the residual magma its characteristic fertile or “adakite-like” signature) and the accumulation of magmatic sulfides which can be remobilized by later magmatic pulses; becoming progressively more oxidized due to intra-crustal processes; and concentrating large amounts of incompatible volatiles and metals in the residual melts. This can explain the strong variability observed in magma fertility in nearby coeval intrusions, and also in cross-cutting intrusions separated by very short time periods, which might have followed different ascent pathways.Our results also suggest that the Teno-Maule segment, in the southernmost part of the Mio-Pliocene metallogenic belt, shows striking differences in magma fertility patterns compared with the rest of the belt. There, fertile magmas are scarce and, contrary to the northern part of the belt, there is no evidence of an enhanced magma fertility during the late Miocene – early Pliocene.

Dynamics of quasi-steady ponded infiltration under contrasting plant cover and management strategies

The runoff infiltration partitioning has direct consequences on preservation of water resources in rural territories, both in agricultural plots and uncultivated areas (e.g. ditches, channels, grass strips), and requires a better understanding of the variability of soil infiltration capacity by disentangling the complex links between soil, vegetation and management. The general objective of the study was to investigate the temporal variation in quasi-steady ponded infiltration rates of a fluvisol soil under bare and different cover crop type (a Malvaceae with a tap-root system and a Poaceae with a fibrous root system) and management conditions (burning, mowing, and chemical weeding) that are commonly found in the Mediterranean vineyards. A modified double-ring infiltration method was used to repeat measurement of the quasi-steady ponded infiltration, fcp, on the same location over time. Placed on a 64 m2 plot area with minimal distances between individual measurements of 30 cm, the setup allowed evaluation of variability among measurements that were conducted within the plot. The results showed a significantly lower fcp for bare soil than covered soil, and a two-fold higher fcp for soil covered by Malvaceae than Poaceae. A seasonal effect in fcp was observed, with the highest fcp in summer and the lowest in winter. The study revealed a strong spatial variability in fcp along a transect of a few tens of centimeter, and showed no significant effect of management strategies compared to the vegetated control. The results revealed the importance of considering both plant traits and season rather than vegetation management strategies to explain quasi-steady ponded infiltration rates.

Topology of anisotropic glasses from persistent homology analysis

Glasses are typically isotropic, but permanent or transient anisotropy can be induced by tensile strain. We use persistent homology (PH) analysis to explore the topological effects of such anisotropy in SiO2Na2O glass ensembles with variable alkali concentration as a function of frozen-in anisotropic strain. Statistical information was extracted on ring (H1) and cavity (H2) features, whereby anisotropic stretching was found to induce strong variations in the ring topology of the –O-Si-O- backbone, but only minor changes in the overall cavity statistics or in the Na distribution (the Na distribution was found to be governed by H2 persistence). Tensile fracture led to total recovery of network topology relative to the pristine (isotropic) glass. In revealing such reactions, PH and persistence similarity analysis may help to differentiate purely entropic orientation and irreversible structural alterations leading to glass anisotropy.

Spatial and temporal variability of environmental proxies from the top 120 m of two ice cores in Dronning Maud Land (East Antarctica)

Abstract. The Antarctic ice sheet's future contribution to sea level rise is difficult to predict, mostly because of the uncertainty and variability of the surface mass balance (SMB). Ice cores are used to locally (kilometer scale) reconstruct SMB with a very good temporal resolution (up to sub-annual), especially in coastal areas where accumulation rates are high. The number of ice core records has been increasing in recent years, revealing an important spatial variability and different trends of SMB, highlighting the crucial need for greater spatial and temporal representativeness. We present records of density, water stable isotopes (δ18O, δD, and deuterium excess), major ions concentrations (Na+, K+, Mg2+, Ca2+, MSA, Cl−, SO42-, and NO3-), and continuous electrical conductivity measurement (ECM), as well as age models and resulting surface mass balance from the top 120 m of two ice cores (FK17 and TIR18) drilled on two adjacent ice rises located in coastal Dronning Maud Land and dating back to the end of the 18th century. Both environmental proxies and SMB show contrasting behaviors, suggesting strong spatial and temporal variability at the regional scale. In terms of precipitation proxies, both ice cores show a long-term decrease in deuterium excess (d-excess) and a long-term increase in δ18O, although less pronounced. In terms of chemical proxies, the non-sea-salt sulfate (nssSO42-) concentrations of FK17 are twice those of TIR18 and display an increasing trend on the long-term, whereas there is only a small increase after 1950 in TIR18. The SO42-/Na+ ratios show a similar contrast between FK17 and TIR18 and are consistently higher than the seawater ratio, indicating a dominant impact of the nssSO42- on the SO42- signature. The mean long-term SMB is similar for FK17 and TIR18 (0.57 ± 0.05 and 0.56 ± 0.05 mi.e.yr-1, respectively), but the annual records are very different: since the 1950s, TIR18 shows a continuous decrease while FK17 has shown an increasing trend until 1995 followed by a recent decrease. The datasets presented here offer numerous development possibilities for the interpretation of the different paleo-profiles and for addressing the mechanisms behind the spatial and temporal variability observed at the regional scale (tens of kilometers) in East Antarctica. The “Mass2Ant IceCores” datasets are available on Zenodo (https://doi.org/10.5281/zenodo.7848435; Wauthy et al., 2023).

Multi-Timescale Characteristics of Southwestern Australia Nearshore Surface Current and Its Response to ENSO Revealed by High-Frequency Radar

The surface currents in coastal areas are closely related to the ecological environment and human activities, and are influenced by both local and remote factors of different timescales, resulting in complex genesis and multi-timescale characteristics. In this research, 9-year-long, hourly high-frequency radar (HFR) surface current observations are utilized together with satellite remote sensing reanalysis products and mooring data, and based on the Empirical Orthogonal Function (EOF) and correlation analysis, we revealed the multi-timescale characteristics of the surface currents in Fremantle Sea (32°S), Southwestern Australia, and explored the corresponding driving factors as well as the impact of El Niño-Southern Oscillation (ENSO) on the nearshore currents. Results show that the currents on the slope are dominated by the southward Leeuwin Current (LC), and the currents within the shelf are dominated by winds, which are subject to obvious diurnal and seasonal variations. The strong bathymetry variation there, from a wide shelf in the north to a narrow shelf in this study region, also plays an important role, resulting in the frequent occurrence of nearshore eddies. In addition, the near-zonal winds south of 30°S in winter contribute to the interannual variability of the Leeuwin Current at Fremantle, especially in 2011, when the onshore shelf circulation is particularly strong because of the climatic factors, together with the wind-driven offshore circulation, which results in significant and long-lasting eddies. The southward Leeuwin Current along Southwestern Australia shows a strong response to interannual climatic variability. During La Niña years, the equatorial thermal anomalies generate the westward anomalies in winds and equatorial currents, which in turn strengthen the Leeuwin Current and trigger the cross-shelf current as well as downwelling within the shelf at Fremantle, whereas during El Niño years, the climate anomalies and the response of coastal currents are opposite. This paper provides insights into the multi-timescale nature of coastal surface currents and the relative importance of different driving mechanisms. It also demonstrates the potential of HFR to reveal the response of nearshore currents to climate anomalies when combined with other multivariate data. Meanwhile, the methodology adopted in this research is applicable to other coastal regions with long-term available HFR observations.

Vertical distribution of Candidatus Methylomirabilis and Methanoperedens in agricultural soils.

Candidatus Methylomirabilis-related bacteria conduct anaerobic oxidation of methane (AOM) coupling with NO2- reduction, and Candidatus Methanoperedens-related archaea perform AOM coupling with reduction of diverse electron acceptors, including NO3-, Fe (III), Mn (IV) and SO42-. Application of nitrogen fertilization favors the growth of these methanotrophs in agricultural fields. Here, we explored the vertical variations in community structure and abundance of the two groups of methanotrophs in a nitrogen-rich vegetable field via using illumina MiSeq sequencing and quantitative PCR. The retrieved Methylomirabilis-related sequences had 91.12%-97.32% identity to the genomes of known Methylomirabilis species, and Methanoperedens-related sequences showed 85.49%-97.48% identity to the genomes of known Methanoperedens species which are capable of conducting AOM coupling with reduction of NO3- or Fe (III). The Methanoperedens-related archaeal diversity was significantly higher than Methylomirabilis-related bacteria, with totally 74 and 16 operational taxonomic units, respectively. In contrast, no significant difference in abundance between the bacteria (9.19 × 103-3.83 × 105 copies g-1 dry soil) and the archaea (1.55 × 104-3.24 × 105 copies g-1 dry soil) was observed. Furthermore, the abundance of both groups of methanotrophs exhibited a strong vertical variation, which peaked at 30-40 and 20-30cm layers, respectively. Soil water content and pH were the key factors influencing Methylomirabilis-related bacterial diversity and abundance, respectively. For the Methanoperedens-related archaea, both soil pH and ammonium content contributed significantly to the changes of these archaeal diversity and abundance. Overall, we provide the first insights into the vertical distribution and regulation of Methylomirabilis-related bacteria and Methanoperedens-related archaea in vegetable soils. KEY POINTS: • The archaeal diversity was significantly higher than bacterial. • There was no significant difference in the abundance between bacteria and archaea. • The abundance of bacteria and archaea peaked at 30-40 and 20-30cm, respectively.

Quantifying Spatial Heterogeneities of Surface Heat Budget and Methane Emissions over West-Siberian Peatland: Highlights from the Mukhrino 2022 Campaign

The study presents the first results from the multi-platform observational campaign carried out at the Mukhrino peatland in June 2022. The focus of the study is the quantification of spatial contrasts of the surface heat budget terms and methane emissions across the peatland, which arise due to the presence of microlandscape heterogeneities. It is found that surface temperature contrasts across the peatland exceeded 10 °C for clear-sky conditions both during day and night. Diurnal variation of surface temperature was strongest over ridges and drier hollows and was smallest over the waterlogged hollows and shallow lakes. This resulted in strong spatial variations of sensible heat flux (H) and Bowen ratio, while the latent heat varied much less. During the clear-sky days, H over ryam exceeded the one over the waterlogged hollow by more than a factor of two. The Bowen ratio amounted to about unity over ryam, which is similar to values over forests. Methane emissions estimated using the static-chamber method also strongly varied between various microlandscapes, being largest at a hollow within a ridge-hollow complex and smallest at a ridge. A strong nocturnal increase in methane mixing ratio was observed and was used in the framework of the atmospheric boundary layer budget method to estimate nocturnal methane emissions, which were found to be in the same order of magnitude as daytime emissions. Finally, the directions for further research are outlined, including the verification of flux-aggregation techniques, parameterizations of surface roughness and turbulent exchange, and land-surface model evaluation and development.

A 30-year (1992-2021) time-series of Kd(PAR) at the North Sea - Baltic Sea transitional zone - trends in light attenuation and Chlorophyll a

Light attenuation is of fundamental importance for photosynthesis in marine and freshwater environments and quantified as Kd(PAR). A 30-year (1992–2021) long time-series of Kd(PAR) (n = 945) from Aarhus Bay, at the North Sea - Baltic Sea transition obtained with 1–5 measurements per month is analyzed. The time-series showed a weak but not statistically significant positive trend with an average Kd(PAR) of 0.30 ± 0.08 m−1. Monthly based time-series of Kd(PAR) showed, in comparison, significant differences with average maximum values in March of 0.38 ± 0.09 m−1 compared to a minimum in June of 0.26 ± 0.03 m−1. There were statistically significant positive Kd(PAR) trends in April and December and a negative trend in October. Accordingly, the depth limit of eelgrass and macroalgae decreased from 8 to 5 m in April. The strong variability in Kd(PAR) in February and March related to the phytoplankton spring bloom in Aarhus Bay both in timing and strength, given the strong and significant correlation between Chl a and Kd(PAR). Partitioning showed that non-Chl a attenuation related to CDOM and suspended matter increased from 0.20 m−1 to 0.29 m−1 between 1992 and 2007 but was constant from then on. The Chl a specific attenuation coefficient varied around an average of 0.019 ± 0.008 m2 (mg Chl a)−1 and showed only small variations over time. The frequency of CTD casts and light measurements decreased between 1992 (n = 52 per year) and 2022 (n = 15 per year) but no parallel trends in average Kd(PAR) were observed. No significant trend (1992–2021) in annual average Chl a concentrations in Aarhus Bay was detected. The importance of high-resolution measurements in time are emphasized and at least monthly to track the strong seasonal variation.

Challenges in quantifying the responses of Black-legged Kittiwakes Rissa tridactyla to habitat variables and local stressors due to individual variation

ABSTRACT Capsule Strong individual variation was observed in the responses of Black-legged Kittiwakes Rissa tridactyla to environmental covariates related to foraging behaviour and habitat selection, and in the overlap with nearby offshore windfarms (OWFs). Aims To determine whether environmental covariates consistently drive Kittiwake foraging behaviour and how this may influence overlap with local potential stressors at the population and individual levels. Methods We used two complimentary methods (Hidden Markov Models and Step Selection Functions) to classify the at-sea behaviour of Kittiwakes and identify environmental covariates associated with foraging at a colony in northeast Scotland during the 2021 breeding season. We also calculated the overlap, by behaviour, of individuals with several operational and proposed OWFs within the vicinity. Results We found no evidence for habitat selection at the population level, with uncertainty in which conditions were linked to foraging, due to considerable variation in the responses of individuals to local environmental conditions. This was attributed to unmeasured intrinsic variation among individuals and high competition among conspecifics and other seabird species. We also observed variation among individuals in the extent of overlap with a local stressor, OWFs, by behaviour. Conclusion Individuals within a population that do not respond consistently to environmental conditions will likely vary in their vulnerability to local stressors, in this case to OWFs. This could lead to unforeseen population-level consequences if not accounted for. Therefore, it is important to identify and understand variation among individuals to better establish population-level consequences of different foraging areas and overlap with stressors to reduce uncertainty in current impact assessments.

X-Ray Polarized View of the Accretion Geometry in the X-Ray Binary Circinus X-1

Cir X-1 is a neutron star X-ray binary characterized by strong variations in flux during its eccentric ∼16.6 day orbit. There are also strong variations in the spectral state, and it has historically shown both atoll and Z state properties. We observed the source with the Imaging X-ray Polarimetry Explorer during two orbital segments, 6 days apart, for a total of 263 ks. We find an X-ray polarization degree in these segments of 1.6% ± 0.3% and 1.4% ± 0.3% at polarization angles of 37° ± 5° and −12° ± 7°, respectively. Thus, we observed a rotation of the polarization angle by 49° ± 8° along the orbit. Because variations of accretion flow, and then of the hardness ratio, are expected during the orbit, we also studied the polarization binned in hardness ratio and found the polarization angle differing by 67° ± 11° between the lowest and highest values of the hardness ratio. We discuss possible interpretations of this result that could indicate a possible misalignment between the symmetry axes of the accretion disk and the Comptonizing region caused by the misalignment of the neutron star’s angular momentum with respect to the orbital one.

Image Matching by Bare Homography.

This paper presents Slime, a novel non-deep image matching framework which models the scene as rough local overlapping planes. This intermediate representation sits in-between the local affine approximation of the keypoint patches and the global matching based on both spatial and similarity constraints, providing a progressive pruning of the correspondences, as planes are easier to handle with respect to general scenes. Slime decomposes the images into overlapping regions at different scales and computes loose planar homographies. Planes are mutually extended by compatible matches and the images are split into fixed tiles, with only the best homographies retained for each pair of tiles. Stable matches are identified according to the consensus of the admissible stereo configurations provided by pairwise homographies. Within tiles, the rough planes are then merged according to their overlap in terms of matches and further consistent correspondences are extracted. The whole process only involves homography constraints. As a result, both the coverage and the stability of correct matches over the scene are amplified, together with the ability to spot matches in challenging scenes, allowing traditional hybrid matching pipelines to make up lost ground against recent end-to-end deep matching methods. In addition, the paper gives a thorough comparative analysis of recent state-of-the-art in image matching represented by end-to-end deep networks and hybrid pipelines. The evaluation considers both planar and non-planar scenes, taking into account critical and challenging scenarios including abrupt temporal image changes and strong variations in relative image rotations. According to this analysis, although the impressive progress done in this field, there is still a wide room for improvements to be investigated in future research.

Molecular and mineral responses of corals grown under artificial Calcite Sea conditions.

The formation of skeletal structures composed of different calcium carbonate polymorphs (e.g. aragonite and calcite) appears to be both biologically and environmentally regulated. Among environmental factors influencing aragonite and calcite precipitation, changes in seawater conditions-primarily in the molar ratio of magnesium and calcium during so-called 'Calcite' (mMg:mCa below 2) or 'Aragonite' seas (mMg:mCa above 2)-have had profound impacts on the distribution and performance of marine calcifiers throughout Earth's history. Nonetheless, the fossil record shows that some species appear to have counteracted such changes and kept their skeleton polymorph unaltered. Here, the aragonitic octocoral Heliopora coerulea and the aragonitic scleractinian Montipora digitata were exposed to Calcite Sea-like mMg:mCa with various levels of magnesium and calcium concentration, and changes in both the mineralogy (i.e. CaCO3 polymorph) and gene expression were monitored. Both species maintained aragonite deposition at lower mMg:mCa ratios, while concurrent calcite presence was only detected in M. digitata. Despite a strong variability between independent experimental replicates for both species, the expression for a set of putative calcification-related genes, including known components of the M. digitata skeleton organic matrix (SkOM), was found to consistently change at lower mMg:mCa. These results support the previously proposed involvements of the SkOM in counteracting decreases in seawater mMg:mCa. Although no consistent expression changes in calcium and magnesium transporters were observed, down-regulation calcium channels in H. coerulea in one experimental replicate and at an mMg:mCa of 2.5, pointing to a possible active calcium uptake regulation by the corals under altered mMg:mCa.

When constructional choice is a matter of context: sembrare-constructions across a continuum of text genres

SEEM-verbs constructions, such as those with Italian sembrare ‘seem’, have been widely studied, with much of the research investigating the alternation between impersonal constructions with finite complementation, and personal (“raising”) constructions governing an infinitival clause. However, most of the studies on the matter seem to disregard the role of the extra-linguistic context of production in the choice between said alternants, even though in various languages there seems to be a strong variability between written and spoken situations (Davies 1997a, b; Cornillie 2007; Pisciotta 2023). The aim of this study is thus to evaluate the relevance of extra-linguistic context (operationalized as text genre), as opposed to linguistic factors, in the choice between mi sembra che ‘it seems to me that’, sembra che ‘it seems that’ and sembrare+infinitive in Italian. We do so by integrating a Construction Grammar perspective with studies on register variation and on orality and scripturality, adopting a point of view that decomposes written and spoken language in a continuum of text genres (Voghera 2017). A multifactorial analysis is carried out on 405 total occurrences of (mi) sembra che and sembrare+infinitive constructions, extracted from written and spoken Italian corpora, by fitting a Conditional Inference Tree. The results show that, at least for mi sembra che and sembrare+infinitive, the heaviest role in determining the choice of the constructions is played by the degree of dialogicity and planning of text genres, which are split by the model in three groups: conversational speech, an intermediate group consisting of fiction prose and monological speech, and non-fiction prose. Furthermore, data reveal that a continuum-based perspective on text genres allows us to interpret and to draw generalizations on the behaviour of sembrare-constructions. These results encourage us to take into account and to encode text genres in the description of constructions, even “traditional” and less idiosyncratic ones.

Erosivity index based on climatological norms from 1991 to 2020 for the state of Rio Grande do Sul

Erosivity index based on climatological norms from 1991 to 2020 for the state of Rio Grande do Sul

Investigating the Relationship between Debt Burden Servicing and Infrastructural Development in Nigeria.

This study evaluates debt burden and servicing as it relates to infrastructural development in Nigeria for the period 1992-2021. The study embraced annual time-series data and employed the Fully Modified Ordinary Least Squares (FMOLS) estimation techniques to examine the relationship between the variables. The findings revealed that there exist a positive and significant relationship between domestic debt and infrastructural development; as well as external debt and infrastructural development. The implication of the findings is that increases in domestic and external debt of the federal government leads to an increase in Infrastructural development. More so, a significant and strong relationship was established between infrastructural development, domestic debt, external debt and exchange rate, while all the dependent variables were found to be responsible for 81% variation in the state of infrastructural development in Nigeria. The study, therefore, concluded that domestic and external debt remains strong and active variables driving infrastructural development in Nigeria. It suggested that Public debt should be used for the purpose for which it was borrowed for and such, debts should be used on the basic infrastructural development that will help to improve on the business environment and economic output making for ease of repayment

Sudden Commencements and Geomagnetically Induced Currents in New Zealand: Correlations and Dependance

AbstractChanges in the Earth's geomagnetic field induce geoelectric fields in the solid Earth. These electric fields drive Geomagnetically Induced Currents (GICs) in grounded, conducting infrastructure. These GICs can damage or degrade equipment if they are sufficiently intense—understanding and forecasting them is of critical importance. One of the key magnetospheric phenomena are Sudden Commencements (SCs). To examine the potential impact of SCs we evaluate the correlation between the measured maximum GICs and rate of change of the magnetic field (H′) in 75 power grid transformers across New Zealand between 2001 and 2020. The maximum observed H′ and GIC correlate well, with correlation coefficients (r2) around 0.7. We investigate the gradient of the relationship between H′ and GIC, finding a hot spot close to Dunedin: where a given H′ will drive the largest relative current (0.5 A nT−1 min). We observe strong intralocation variability, with the gradients varying by a factor of two or more at adjacent transformers. We find that GICs are (on average) greater if they are related to: (a) Storm Sudden Commencements (SSCs; 27% larger than Sudden Impulses, SIs); (b) SCs while New Zealand is on the dayside of the Earth (27% larger than the nightside); and (c) SCs with a predominantly East‐West magnetic field change (14% larger than North‐South equivalents). These results are attributed to the geology of New Zealand and the geometry of the power network. We extrapolate to find that transformers near Dunedin would see 2000 A or more during a theoretical extreme SC (H′ = 4000 nT min−1).

Environmental Conditions in Estuaries of the Southeast United States: Long-Term Trends and Seasonal Drivers

Due to their location at the intersection of marine and freshwater ecosystems, estuaries are subject to the impacts of global change from both the ocean and land. Recent evidence has demonstrated numerous changes to environmental conditions within estuarine ecosystems, from increasing temperatures to changes in primary production, among others. We utilized long-term, high-temporal-resolution data on water temperature, salinity, dissolved oxygen, and chlorophyll-a concentrations in 3 National Estuarine Research Reserves in the southeast United States to characterize trends and seasonal drivers of estuarine water quality. We document spatiotemporal variability in long-term trends and seasonal patterns, with ubiquitous increases in water temperature over our study period (1995–2022) mainly driven by changes during winter months (December to February), concurrent with slight reductions in dissolved oxygen through time. We also document strong spatiotemporal variability in trends in salinity and chlorophyll-a concentration both across and within estuaries. Understanding the changes in biophysical conditions in estuarine ecosystems is critical to ensure our ability to predict the ecosystem functions and services estuaries can provide as climate conditions continue to change.

Behaviour of ultra-short radio waves refraction in the lower atmospheric layer of the coastal zone of the Bolshye Yeravninsky Lakes

The propagation of ultra-short waves is influenced by weather conditions. Meteorological inhomogeneities in the atmosphere cause refraction of the ultra-short wave beam. Measurements of meteorological parameters at h1 = 2 and h2 = 10 m have been carried out using an atmospheric-soil measuring complex installed in the coastal zone of Big Eravninsky Lakes at the Forest-Steppe permafrostecological station “Eravninsky” in Buryatia. There is a strong daily variability of the refractive gradient, and the refractive gradient values scatter ranges from –0.820 to +0.307 N-units In the lower ten-meter layer of the troposphere. It is discovered that in summer, meteorological conditions favorable for the superrefraction appearance are observed in this area.

An optimized particle swarm optimization algorithm for turbine torque and generator load parameter identification

Hydraulic turbine control system is a complex system with strong nonlinearity and multiple variables. Therefore, in order to better control the turbine system, it is necessary to obtain the parameters of key components. Aiming at the limitation of the traditional particle swarm optimization algorithm in global search ability, mutation operator and dynamic inertia weight coefficient are introduced to enhance the search ability of the algorithm. In addition, in order to further improve the global search performance of the algorithm, this paper combines the optimized particle swarm optimization algorithm with genetic algorithm to form a hybrid parameter identification algorithm. The hybrid algorithm not only uses the fast convergence of particle swarm optimization (PSO), but also uses the global search advantage of genetic algorithm (GA) to realize efficient and accurate identification of turbine torque and load parameters. Through MATLAB2021a/Simulink simulation experiments, the application effect of the algorithm in the identification of turbine torque and generator load parameters is verified. The simulation results show that the optimized particle swarm optimization algorithm has significant advantages in the accuracy and robustness of parameter identification, and the identified parameters have a high degree of fitting with the actual measured torque and speed. This study not only provides a new optimization strategy for the parameter identification of turbine regulation system, but also provides an effective intelligent algorithm solution for the parameter identification of nonlinear system.