Strong Fluctuations Research Articles

Environmental factors as drivers of the spatial distribution of the copepods Eurytemora affinis affinis and Eurytemora velox in the Scheldt tributaries

The main tributaries of the Scheldt estuary offer an interesting setting to study the response of organisms to various environmental conditions. The Bovenscheldt and the Dender are closed to tidal entrance by locks, and are hence essentially fresh water systems with low turbulence. The Durme and the Rupel, with its two sub-tributaries (the Beneden-Nete and the Dijle), receive estuarine water at each tide and as such, present a fresh-brackish water gradient according to the geographic location of their confluence with the estuary and the tidal phase. This paper aims (1) to determine the spatial-temporal distribution of two calanoid copepod species: Eurytemora affinis affinis (Poppe, 1880) and E. velox (Lilljeborg, 1853) in these tributaries and (2) the environmental conditions favoring each species development. Species distribution and abundance data, collected in the four tributaries between 2018 and 2021 are analyzed by Generalized Linear Mixed Models (GLMM) and the results are interpreted in the context of ecosystem functioning. A spatial structuring between E. affinis affinis and E. velox was revealed. Whilst E. affinis affinis develops best in the tidal tributaries such as the Durme and Rupel, E. velox is more typical of the non-tidal ones: the Bovenscheldt and the Dender. The tidal tributaries have high Particulate Organic Matter (POM) concentrations due to tidal turbulence, and hence generally lower oxygen concentrations than the non-tidal ones (<10–11 mg L−1). Factors favoring E. affinis affinis development in the tidal tributaries are higher chlorinity, pH and diatom abundance than in the non-tidal ones. In the non-tidal tributaries, with lower POM concentrations, phytoplankton activity more strongly influences the overall oxygen balance, with oxygen concentrations often rising above 10–11 mg L−1 and sometimes showing high variability. The results suggest that E. affinis affinis might suffer from hyperoxia-induced oxidative stress under these high oxygen conditions and advocate the necessity to include this aspect in further research. E. velox, which is most abundant in those tributaries, seems to be more tolerant to hyperoxia and strong fluctuations in O2 concentrations than E. affinis affinis.

Elasticity of bilayer lipid membranes from their density correlation function

ABSTRACT We study the density correlation function (DCF) of DPPC lipid bilayers. We compare Molecular Dynamics (MD) results with theoretical predictions obtained with a mesoscopic description, in terms of the lipid membrane elasticity. One key objective of our work is the quantification of the lipid membrane elasticity directly from the DCF, both for the membrane undulations and local membrane thickness. Our method does not require the definition of instantaneous surfaces or internal variables defining lipid orientations. Building on our previous work, here we focus on the intralayer correlations, i.e. the DCF of lipids residing on the same monolayer, by tracking only the position of the phosphorus atoms in a lipid head group. We demonstrate the relevance of the intralayer two-dimensional (2D) correlations to the total DCF. We further show that all-atom (AA) and coarse grained (CG) lipid forcefields, feature distintively different DCFs. The CG forcefield predicts results in good agreement with the mesoscopic predictions, for the entire wavevector range; the AA forcefield (CHARMM36) predict strong peristaltic fluctuations at long wavevectors q ≳ 0.8 nm − 1 , which are absent in the CG lipid model (MARTINI).

Anomalous properties in normal and superconducting states of Sc2Ir4-xSix due to flat band effect driven by spin-orbit coupling

Correlation effect may be induced by the flat band(s) near the Fermi energy, as demonstrated in twisted graphene, Kagome materials, and heavy Fermion materials. Unconventional superconductivity may arise from this correlation effect and show deviation from the phonon-mediated pairing as well as the Landau Fermi liquid in the normal state. Here, we report the anomalous properties in normal and superconducting states in the Laves phase superconductor Sc2Ir4-xSix with a kagome lattice and silicon doping. By doping silicon to the iridium sites, a phase diagram with nonmonotonic and two-dome-like doping dependence of the superconducting transition temperature Tc was observed. The samples in the region of the second dome, including Sc2Ir3.5Si0.5 with the optimal Tc, exhibit non-Fermi liquid behavior at low temperatures after superconductivity is suppressed, as evidenced by the divergence of the specific heat coefficient and the semiconducting-like resistivity, together with a strong superconducting fluctuation in the optimally doped samples. Combined with first-principles calculations, we attribute the anomalous properties in normal and superconducting states to the correlation effect, which is intimately induced by the flat band effect when considering the strong spin-orbit coupling.

Ground state of the staggered Heisenberg-Γ honeycomb model in a magnetic field

We study the ground state properties of the S=1/2 staggered Heisenberg-\GammaΓ honeycomb model under a magnetic field based on analytical and numerical methods. Our calculations show that the conventional zigzag and stripy phases are favored because of the staggered Heisenberg interaction away from the pure \GammaΓ limit. In our classical analysis, we find that the field induces a series of competing magnetic phases with relatively large unit cells in the region sandwiched between the two magnetic phases with long-range ordering. In the quantum treatment, these large magnetic unit cells are destabilized by strong quantum fluctuations that result in the stabilization of a gapless quantum spin liquid behavior. In a honeycomb \GammaΓ magnet, we disclose an intermediate-field gapless quantum spin liquid phase driven by a tilted field away from the out-of-plane direction only for a narrow region between the low-field zigzag and high-field fully polarized phases.

Coastal Eukaryotic Plankton Diversity of the Southern Adriatic as Revealed by Metabarcoding

Plankton studies serve as a basis for marine ecosystem research, but knowledge of marine plankton is still incomplete due to its extreme taxonomic and functional complexity. The application of metabarcoding is very valuable for the characterisation of the plankton community. The plankton community of the Southern Adriatic is subject to strong environmental fluctuations and changes, which underlines the need for frequent, reliable and comprehensive characterisation of the plankton. The aim of this study was to determine the taxonomic composition and seasonal distribution of eukaryotic plankton in the Southern Adriatic. Plankton samples were collected monthly for one year at the coastal station of the Southern Adriatic and metabarcoding was used for taxonomic identification. The results showed a high taxonomic diversity and dynamic seasonal distribution patterns for both the protist and metazoan plankton communities. Metabarcoding revealed both the core, year-round plankton community and previously unrecorded plankton organisms in the Southern Adriatic. The results provide for the first time a comprehensive overview of the plankton community in this area by metabarcoding. The identified seasonal patterns of plankton genera and species in the Southern Adriatic will contribute to the understanding of plankton interactions and future changes in community diversity characterisation.

Short-term industrial load forecasting based on error correction and hybrid ensemble learning

Accurate industrial load forecasting is a prerequisite for ensuring the smooth operation of the power system. Due to the strong fluctuation and complex characteristics of industrial loads, it is difficult to accurately predict short-term power demand. To address this issue, this paper proposes a deep learning prediction model based on hybrid ensemble and error correction. The proposed model is divided into two phases: in the first phase, deep power features are extracted from multivariate data through a hybrid ensemble strategy consisting of Random Subspace, Boosting, Ensemble Pruning, and Multi-Objective Molecular Dynamics Theory Optimization Algorithm (MMDTOA). First, the strategy splits high-dimensional industrial data into multiple sub-datasets. Subsequently, for the features of each sub-dataset, the proposed MMDTOA is applied to perturb the parameters of GRU to generate base learning machines that balance accuracy and diversity. Finally, these base learning machines are integrated by kernel ridge regression stacking. Among them, the two-stage selection strategy and co-evolutionary strategy are embedded into the MMDTOA to enhance the optimization searching effect; in the second stage, a combined error correction strategy is proposed by utilizing the residual information in the prediction results. By combining the dynamic Gaussian error correction function and GRU error correction model, the prediction accuracy of the ensemble model is further improved; Experimental results on real Korean datasets show that the proposed method achieves a minimum value of 3.684% and 7.266% in NMAE and NRMSE, which outperforms eight comparative models, such as SVM, ELM, and CNN, with higher accuracy and robustness.

Strong Local Polarization Fluctuations Enabled High Electrostatic Energy Storage in Pb-Free Relaxors.

Electrostatic energy-storage ceramic capacitors are essential components of modern electrified power systems. However, improving their energy-storage density while maintaining high efficiency to facilitate cutting-edge miniaturized and integrated applications remains an ongoing challenge. Herein, we report a record-high energy-storage density of 20.3 J cm-3 together with a high efficiency of 89.3% achieved by constructing a relaxor ferroelectric state with strongly enhanced local polarization fluctuations. This is realized by incorporating highly polarizable, heterovalent, and large-sized Zn and Nb ions into a Bi0.5Na0.5TiO3-BaTiO3 ferroelectric matrix with very strong tetragonal distortion. Element-specific local structure analysis revealed that the foreign ions strengthen the magnitude of the unit-cell polarization vectors while simultaneously reducing their orientation anisotropy and forming strong fluctuations in both magnitude and orientation within 1-3 nm polar clusters. This leads to a particularly high polarization variation (ΔP) of 72 μC cm-2, low hysteresis, and a high effective polarization coefficient at a high breakdown strength of 80 kV mm-1. This work has surpassed the current energy density limit of 20 J cm-3 in bulk Pb-free ceramics and has demonstrated that controlling the local structure via the chemical composition design can open up new possibilities for exploring relaxors with high energy-storage performance.

Nonlinear phenomena in charge transport properties of a hole-doped organic spin-liquid compound

The nonlinear electric conductivity of κ-(BEDT-TTF)4Hg2.89Br8, which is known as a hole-doped spin liquid, has been observed by single crystal transport measurements using dc and ac excitations. This compound is known as a charge transfer complex with strong magnetic fluctuations accompanied by electron mass enhancement at ambient pressure. We discuss the nonlinear dc conductivity drastically emerging below 100 K. We also performed ac impedance measurements of this compound and compared the results with those of a typical dimer-Mott compound of deuterated κ-(d8-BEDT-TTF)2Cu[N(CN)2]Br, located just near the Mott boundary. The analyses of the Nyquist plots of κ-(d8-BEDT-TTF)2Cu[N(CN)2]Br and κ-(BEDT-TTF)4Hg2.89Br8 reveal qualitatively different features. The former shows a behavior pertinent to the inhomogeneous distribution of domains due to a mixing of metal and insulating phases, taking into account the influence of the proximity effect, while the doped spin liquid has a distinct semicircle-type frequency dependence in its Nyquist plot in the whole temperature range studied. We conclude that the nonlinear conductivity is intrinsically peculiar to the doped dimer Mott system, where the charge degrees of freedom dominate the itinerancy. We attribute the anomalous features, such as non-Fermi liquid behavior, heat capacity enhancement, and strong antiferromagnetic fluctuations in κ-(BEDT-TTF)4Hg2.89Br8, to a kind of charge confinement effect retained in the hole-doped spin-liquid state.

An Adaptive Tracking Method for Moving Target in Fluctuating Reverberation Environment

In environments with a low signal-to-reverberation ratio (SRR) characterized by fluctuations in clutter number and distribution, particle filter-based tracking methods may experience significant fluctuations in the posterior probability of existence. This can lead to interruptions or even loss of the target trajectory. To address this issue, an adaptive PF-based tracking method (APF) with joint reverberation suppression is proposed. This method establishes the state space model under the Bayesian framework and implements it through particle filtering. To keep the weak target echoes, all the non-zero entries contained in the sparse matrix processed by the low-rank and sparsity decomposition (LRSD) are treated as the measurements. The prominent feature of this approach is introducing an adaptive measurement likelihood ratio (AMLR) into the posterior update step, which solves the problem of unstable tracking due to the strong fluctuation in the number of point measurements per frame. The proposed method is verified by four shallow water experimental datasets obtained by an active sonar with a uniform horizontal linear array. The results demonstrate that the tracking frame success ratio of the proposed method improved by over 14% compared with the conventional PF tracking method.

Field control of symmetry-broken and quantum disordered phases in frustrated moiré bilayers with population imbalance

We determine the ground states and excitation spectra of the paradigmatic four-flavor Heisenberg model with nearest- and next-nearest-neighbor exchange couplings on the triangular lattice in a field controlling the population imbalance of flavor pairs. Such a system arises in the strongly correlated limit of moiré bilayers of transition metal dichalcogenides in an electric displacement field or in-plane magnetic field, and can be simulated via ultracold alkaline-earth atoms. We argue that the field tunes between effective SU(4) and SU(2) symmetries in the balanced and fully polarized limits and employ a combination of mean-field calculations, flavor-wave theory, and exact diagonalization to analyze the intermediate, imbalanced regime. We find different symmetry-broken phases with simultaneous spin and excitonic order depending on the field and next-nearest-neighbor coupling. Furthermore, we demonstrate that there is a strongly fluctuating regime without long-range order that connects candidate spin liquids of the SU(2) and SU(4) limit. The strong fluctuations are facilitated by an extensive classical degeneracy of the model, and we argue that they are also responsible for a strong polarizability at 1/3 polarization that survives from the mean-field level to the exact spectrum. Published by the American Physical Society 2024

Participatory Geomonitoring for Future Mining—Resilience Management in the Cavern Storage Epe (Germany)

Integrated geo- and environmental monitoring in mining represents a high-dimensional challenge (location, altitude/depth, time and sensors). This is challenging for experts but poses great problems for a multitude of participants and stakeholders in building up a complete process understanding. The Epe research cooperation aims to elucidate the ground movement at the Epe cavern storage facility with a public participation process. The research cooperation was founded by the city of Gronau, the citizens’ initiative cavern field Epe, the company EFTAS, Münster, and the Research Center of Post-Mining at the Technische Hochschule Georg Agricola, Bochum. This research cooperation is the first in Germany to involve direct collaboration between science and the public. In the cavern field, which has been in operation since the 1970s, brine is extracted, and at the same time natural gas, crude oil and helium, as well as hydrogen in the future, are stored in the subsurface. The technical focus of this work was the development of a high-resolution spatiotemporal analysis of ground movements. The area is monitored annually by the mining company’s mine surveyor. The complexity of the monitoring issue lies in the fact that the western part is a bog area and a former bog area. Furthermore, the soils in the eastern part are very humus-rich and show strong fluctuations in the groundwater and therefore complex hydraulic conditions. At the same time, there are few fixed scatterers or prominent points in the area that allow high-resolution spatiotemporal monitoring using simple radar interferometry methods. Therefore, the SBAS method (Small Baseline Subset), which is based on an aerial method, was used to analyze the radar interferometric datasets. Using an SBAS analysis, it was possible to evaluate a time series of 760 scenes over the period from 2015 to 2023. The results were integrated with the mine survey maps on the ground movement and other open geodata on the surface, the soil layers and the overburden. The results show complex forms of ground movement. The main influence is that of mining. Nevertheless, the influence of organic soils with drying out due to drought years and uplift in wet years is great. Thus, in dry years, ground subsidence accelerates, and in wet years, ground subsidence not only slows down but in some cases also causes uplift. This complexity of ground movements and the necessary understanding of the processes involved has been communicated to the interested public at several public information events as part of the research cooperation. In this way, an understanding of the mining process was built up, and transparency was created in the subsurface use, also as a part of the energy transition. In technical terms, the research cooperation also provides a workflow for developing the annual mine survey maps into an integrated geo- and environmental monitoring system with the development of a transparent participatory geomonitoring process to provide resilience management to a mining location.

Analysis of Water Conservation Priority Locations in Upper Sub Watershed

Water is useful for supplying household, industrial, and agricultural needs. The availability of water supports food security and decent life. The process of sustaining water resources requires conservation, which is in line with sustainable development goals. The Keyang sub watershed is one of the catchment areas of the Upstream Madiun River, located in East Java. The development of agriculture land in Keyang sub watershed increases the number of disasters. The Central Statistics Office of Ponorogo Regency recorded 24 floods, 11 drought disasters, and 42 landslides in Keyang sub watershed during 2020. Floods and drought disasters in the same location show strong fluctuations in water resources, so Keyang sub watershed requires water conservation actions. The aim of this study is to analyze priority locations for water conservation. Indicateurs de Ruissellement Intense Pluvial (IRIP) is a method for determining water conservation priority locations. IRIP divides surface runoff vulnerability area into three types: generation area, transfer area, and accumulation area. Each area requires different adaptations to conservation techniques. The result shows that Keyang sub watershed has 4.96% strong potential surface runoff generation area. This priority area is suitable for wetland development, agroforestry, and sustainable agriculture. Then, Keyang sub watershed has 0.03% strong potential area of surface runoff transfer, this area is compatible with prevention of erosion and landslides. Keyang sub watershed has 0.63% very strong potential and 18.42% strong potential for surface runoff accumulation area. Accumulation area appropriate for developing flood mitigation strategies.

Spatiotemporal variability at seasonal and interannual scales of terrestrial water variation over Tibetan Plateau from geodetic observations

ABSTRACT In the context of ongoing global climate warming, researchers have observed an intricate relationship between the variability of Terrestrial Water Storage (TWS) on the Tibetan Plateau (TP) and climate anomalies. In this study, we utilize a combination of Global Navigation Satellite System (GNSS), Gravity Recovery and Climate Experiment (GRACE), and precipitation data to investigate the response of TWS on the TP to extreme climate changes, with a focus on seasonal and interannual variations. Our findings reveal that the first Common Mode Component (1st CMC) extracted from GNSS coordinate time series exhibits strong interannual fluctuations. Additionally, both GNSS and GRACE-inferred TWS demonstrate noticeable anomalous changes during the 2015/2016 period. The estimated periods of the 1st CMC of GNSS and GRACE-inferred TWS are approximately 5 and 7 years, respectively. Both reach a minimum during the extreme climate event in 2015/2016. Furthermore, we investigate the spatial variation of summer precipitation before and after the extreme drought event on the TP. It reveals that the inflection point of TWS occurs approximately 1 year prior to the drought event, suggesting a consistent spatial propagation process between precipitation and TWS. This indicates that the changes of TWS during this drought event were primarily influenced by precipitation. Finally, we evaluate the response of 12 sub-basins on the TP to the drought event that occurred in 2015/2016. The regions experiencing significant abnormal fluctuations in TWS are mainly located in inner and northeastern plateau. These regions show rapid upward changes in the TWS and demonstrate a strong spatial consistency with summer precipitation.

Analysis of UAV data communication stability method in extreme environment

In order to get in touch with the affected area smoothly after the disaster, this paper uses drones as air base stations. Their high mobility and sensitivity make them apt for such critical roles. However, during extreme weather conditions, these unmanned aerial vehicles (UAVs) encounter various challenges that can impair their stability and, consequently, their ability to serve as reliable air base stations. As a result, signal transmission can be interrupted or severely limited. Among the common factors affecting UAV stability are strong winds, temperature fluctuations, heavy rainfall, and electromagnetic interference. These factors can cause the UAVs to deviate from their intended flight paths, drop in altitude, or even lose connection with the ground control. As a consequence, the reliability of communication, so critical in emergency situations, gets compromised. To address the problem of degraded UAV stability, several solutions have been proposed and implemented. One approach involves enhancing the drone's onboard stabilization systems, incorporating advanced algorithms that allow it to autonomously adjust to environmental changes. Another strategy is the deployment of a network of drones, ensuring redundancy. If one drone faces difficulties, another can take over, maintaining the communication link. Furthermore, advances in materials science have led to the development of UAVs with more robust structures, capable of withstanding the rigors of adverse weather conditions. Lastly, the use of ground-based boosters or repeaters can amplify signals, ensuring that even if a UAV's transmission is weak, the communication remains uninterrupted.

Noncentrosymmetric Triangular Magnet CaMnTeO6: Strong Quantum Fluctuations and Role of s0 versus s2 Electronic States in Competing Exchange Interactions.

Noncentrosymmetric triangular magnets offer a unique platform for realizing strong quantum fluctuations. However, designing these quantum materials remains an open challenge attributable to a knowledge gap in the tunability of competing exchange interactions at the atomic level. Here, a new noncentrosymmetric triangular S=3/2 magnet CaMnTeO6 is created based on careful chemical and physical considerations. The model material displays competing magnetic interactions and features nonlinear optical responses with the capability of generating coherent photons. The incommensurate magnetic ground state of CaMnTeO6 with an unusually large spin rotation angle of 127°(1) indicates that the anisotropic interlayer exchange is strong and competing with the isotropic interlayer Heisenberg interaction. The moment of 1.39(1)µB, extracted from low-temperature heat capacity and neutron diffraction measurements, is only 46% of the expected value of the static moment 3µB. This reduction indicates the presence of strong quantum fluctuations in the half-integer spin S=3/2 CaMnTeO6 magnet, which is rare. By comparing the spin-polarized band structure, chemical bonding, and physical properties of AMnTeO6 (A=Ca, Sr, Pb), how quantum-chemical interpretation can illuminate insights into the fundamentals of magnetic exchange interactions, providing a powerful tool for modulating spin dynamics with atomically precise control is demonstrated.

Vertical distribution characteristics of the typhoon gust factor based on a 356-m high meteorological gradient tower

The characteristics of typhoon gust factors (GF) are important for the design of high-rise buildings in coastal areas. Most research on GF are based on observational data near the ground. This has made it difficult to meet the increasing demand for high-rise building designs in recent years. Thus, improving the knowledge of the vertical distribution of GF inside the typhoon is necessary and helpful for the design of high-rises and the prevention of gust disasters. In this study, the data from a 365-m high meteorological tower were used to explore the vertical distribution features of the gust factor within the atmospheric boundary layer (ABL) of typhoons in coastal region. The results indicate that: (1) The statistical probability distribution of GF during the typhoon exhibits a non-Gaussian distribution at all observational heights of the tower. While the generalized extreme value distribution (GEV) can well describe the properties of the probability distribution of GF at different heights. (2) The GF have a weak relationship with the average wind speed. However, GF have a strong relationship with turbulence intensity and increases linearly with the turbulence intensity. Notably, the results from the previous empirical model of the GF do not fully match the parameterised results during typhoons in this study. (3) In the typhoon boundary layer, the bulk wind shear plays a significant role in generating turbulent eddies with scales comparable to the observation height, especially at lower layer. Besides, the strong turbulent fluctuations at near-ground layers may be a result of the coupling of several elements. The turbulent momentum flux transported downward from the upper layers has a significant impact on the peak gust, and the downward transported energy may further enhance the turbulent motion in lower layers, which may lead to a higher gust factor near the surface.

Dynamic response characteristics of solid oxide cell stacks for seawater/CO2 co-electrolysis under strong fluctuation electricity

This work focused on the intermittent characteristics of renewable energy and studied the dynamic response characteristics of seawater/CO2 co-electrolysis on solid oxide cell stacks to produce syngas under strong fluctuation electricity conditions. The results showed that when using a strong fluctuating current density of 58.2–658.1 mA/cm2 to simulate wind turbines, the power variation of the solid oxide cell stack was almost in line with the simulated wind turbine power variation curve. The theoretical conversion rate of solid oxide cell stack electrolysis products is linearly related to the current density. The measured H2O+CO2 conversion rate is similar to the theoretical value, and the current variation hardly changes the H2/CO ratio in the exhaust gas. Therefore, solid oxide electrolysis cell stacks have strong adaptability to fluctuating electricity.

Evolution of individual variation in a competitive trait: a theoretical analysis.

When competitive traits are costly, negative frequency dependence can maintain genetic variance. Most theoretical studies examining this problem assume binary polymorphisms, yet most trait variation in wild populations is continuous. We propose that continuous trait variation can result from continuous variation in resource quality and that, specifically, the shape of the resource distribution determines trait maintenance. We used an individual-based model to test which conditions favour the stable maintenance of variation and which cause temporal fluctuations in trait values. This approach, inspired by contrasting outcomes of previous studies regarding variance and fluctuations in trait values, clearly showed a decisive role played by the shape of resource distributions. Under extreme conditions, e.g., the absence of resource variation or with very scarce resources for weak competitors, traits evolved to a single non-competitive or highly competitive strategy, respectively. Most other distributions led to strong temporal fluctuations on trait values or the maintenance of stable, standing variation. Our results thus explain the contradicting outcomes of previous theoretical studies and, at the same time, provide hypotheses to explain the maintenance of genetic variation and individual differences. We suggest ways to empirically test the proposed effects of resource variation on trait maintenance.

Unconventional anomalous Hall effect in Zintl thermoelectric Eu[formula omitted]ZnSb[formula omitted

The outstanding performance of thermoelectric materials is intimately related to complicated electronic band structures that may comprise topological linear dispersion bands. In this work, the exotic magnetism and magneto-transport properties of thermoelectric Eu2ZnSb2 single crystal are investigated. Temperature- and field-dependent magnetization reveal an antiferromagnetic (AFM) ground state and highly localized magnetic moments of Eu2+ ions. The longitudinal resistivity [ρxx(T)] and magnetoresistivity (MR) unveil the coexistence of underlying ferromagnetic (FM) and AFM fluctuations. Furthermore, an unconventional anomalous Hall effect (UAHE) for both above and below the AFM phase transition temperature (TN) is observed, which is suggested to be caused by the vacancy-induced Weyl bands and strong magnetic fluctuations. Our work is benefit for understanding the exotic band structures and thermoelectric properties in Eu2ZnSb2.

Improving short-term offshore wind speed forecast accuracy using a VMD-PE-FCGRU hybrid model

The integration of large-scale offshore wind power into the power grid presents significant challenges for grid operation and dispatch due to the variability and intermittency of offshore wind energy. However, non-stationarities and noise in wind speed time series pose challenges. This study proposes a VMD-PE-FCGRU methodology to address this challenge of predicting offshore wind speeds. Firstly, the Variational Mode Decomposition (VMD) algorithm decomposes the original wind speed signal, considering the strong fluctuations and high noise inherent to offshore wind energy. A corresponding performance evaluation index is established to assess the effectiveness of this deconstruction process. To further enhance the model's (GRU) ability to capture time series information, a Position Encoding layer (PE) has been added, and the network is deepened through a Fully Connected Neural Network (FCNN). This allows multi-dimensional time series features to be input into the Gated Recurrent Unit (GRU) network for forecast. The accuracy of the proposed method is then verified using measured historical data from the wind tower of an offshore wind farm in Guangdong. Experimental results demonstrate that the proposed method can accurately forecast short-term wind speeds for offshore wind farms, with a Mean Absolute Error (MAE) of 0.199 and a Mean Absolute Percentage Error (MAPE) of only 2.45%. Moreover, the qualified rate (r) reaches 100%, providing an accurate reference for real-time power grid dispatching and can inform decision-making for the integration of offshore wind power into the grid.