bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel maximum correntropy adaptive extended Kalman filter for vehicle state estimation under non-Gaussian noise
Authors: Qi Dengliang , Feng Jingan , Wan Wenkang , Song Bao
Published: November 2022

For vehicle state estimation, conventional Kalman filters work well under Gaussian assumptions. Still, they are likely to degrade dramatically in the practical non-Gaussian situation (especially the noise is heavy-tailed), showing poor accuracy and robustness. This article presents an estimation technique based on the maximum correntropy criterion (MCC) combined with an adaptive extended Kalman filter (AEKF), and an extended Kalman filter (EKF) based on the MCC has also been studied. A lateral-longitudinal coupled vehicle model is developed, while an observer containing the state vectors such as yaw rate, sideslip angle, vehicle velocity and tire cornering stiffness is designed using easily available in-vehicle sensors and low-cost GPS. After analyzing the algorithmic complexity, the proposed algorithm is validated by sine steering input and double lane change driving scenarios. Finally, it is found that MCC combined with AEKF/EKF has stronger robustness and better estimation accuracy than AEKF/EKF in dealing with non-Gaussian noise for vehicle state estimation.
Pixel Centroid Characterization with Laser Speckle and Application to the Nancy Grace Roman Space Telescope Detector Arrays
Authors: Hirata Christopher M. , Merchant Christopher
Published: November 2022

The Nancy Grace Roman Space Telescope will use its wide-field instrument to carry out a suite of sky surveys in the near-infrared. Several of the science objectives of these surveys, such as the measurement of the growth of cosmic structure using weak gravitational lensing, require exquisite control of instrument-related distortions of the images of astronomical objects. Roman will fly new large-format (4 × 4 k) Teledyne H4RG-10 infrared detector arrays. This paper investigates whether the pixel centroids are located on a regular grid by projecting laser speckle patterns through a double slit aperture onto a non-flight detector array. We develop a method to reconstruct the pixel centroid offsets from the stochastic speckle pattern. Due to the orientation of the test setup, only x-offsets are measured here. We test the method both on simulations, and by injecting artificial offsets into the real images. We use cross-correlations of the reconstructions from different speckle realizations to determine how much of the variance in the pixel offset maps is signal (fixed to the detector) and how much is noise. After performing this reconstruction on 64 × 64 pixel patches, and fitting out the best-fit linear mapping from pixel index to position, we find that there are residual centroid offsets in the x (column) direction from a regular grid of 0.0107 pixels rms (excluding shifts of an entire row relative to another, which our speckle patterns cannot constrain). This decreases to 0.0097 pix rms if we consider residuals from a quadratic rather than linear mapping. These rms offsets include both the physical pixel offsets, as well as any apparent offsets due to crosstalk and remaining systematic errors in the reconstruction. We comment on the advantages and disadvantages of speckle scene measurements as a tool for characterizing the pixel-level behavior in astronomical detectors.
Multiqudit quantum hashing and its implementation based on orbital angular momentum encoding
Authors: Akat’ev D O , Vasiliev A V , Shafeev N M , Ablayev F M , Kalachev A A
Published: November 2022

A new version of quantum hashing technique is developed wherein a quantum hash is constructed as a sequence of single-photon high-dimensional states (qudits). A proof-of-principle implementation of the high-dimensional quantum hashing protocol using orbital-angular momentum encoding of single photons is implemented. It is shown that the number of qudits decreases with increase of their dimension for an optimal ratio between collision probability and decoding probability of the hash. Thus, increasing dimension of information carriers makes quantum hashing with single photons more efficient.
Microwave absorption and bandwidth study of Y2Co17 rare earth soft magnetic alloy with easy-plane anisotropy
Authors: Ma Yun-Guo , Qiao Liang , Zheng Zu-Ying , Hao Hong-Bo , Wang Hao , Sun Zhe , Tu Cheng-Fa , Wang Tao , Yang Zheng , Li Fa-Shen
Published: November 2022

The easy-plane anisotropy of the Y2Co17 rare earth soft magnetic alloy has high saturation magnetization and operating frequency, and good impedance matching. Therefore, it is expected to become a kind of high-performance microwave absorbing material. In this paper, Y2Co17 alloy was prepared by a reduction-diffusion method, and its micropowder was prepared as polyurethane (PU) based composite absorbing materials (Y2Co17/PU composites). The microwave properties of composites with different volume fractions were calculated. The composites showed outstanding absorption characteristics in the range of 20–30 vol%, and the minimum reflection loss (RL) was less than −50 dB. When the volume fraction was 25%, the effective absorption bandwidth could cover the X-band at a thickness of 1.5 mm, and the Ku-band at a thickness of 1.08 mm. The absorption mechanism was analyzed by the interface reflection model. The RL absorption peak bandwidth mechanism was discussed by using the amplitude relation and calculating the effective absorption bandwidth at different thicknesses. The effective absorption bandwidth values were in good agreement with the theoretical expectation.
Lossless embedding: A visually meaningful image encryption algorithm based on hyperchaos and compressive sensing
Authors: Wang Xing-Yuan , Wang Xiao-Li , Teng Lin , Jiang Dong-Hua , Xian Yongjin
Published: November 2022

A novel visually meaningful image encryption algorithm is proposed based on a hyperchaotic system and compressive sensing (CS), which aims to improve the visual security of steganographic image and decrypted quality. First, a dynamic spiral block scrambling is designed to encrypt the sparse matrix generated by performing discrete wavelet transform (DWT) on the plain image. Then, the encrypted image is compressed and quantified to obtain the noise-like cipher image. Then the cipher image is embedded into the alpha channel of the carrier image in portable network graphics (PNG) format to generate the visually meaningful steganographic image. In our scheme, the hyperchaotic Lorenz system controlled by the hash value of plain image is utilized to construct the scrambling matrix, the measurement matrix and the embedding matrix to achieve higher security. In addition, compared with other existing encryption algorithms, the proposed PNG-based embedding method can blindly extract the cipher image, thus effectively reducing the transmission cost and storage space. Finally, the experimental results indicate that the proposed encryption algorithm has very high visual security.
Fabrication of honeycomb AuTe monolayer with Dirac nodal line fermions
Authors: Wang Qin , Zhang Jie , Huang Jierui , Shi Jinan , Zhang Shuai , Guo Hui , Huang Li , Ding Hong , Zhou Wu , Zhang Yan-Fang , Lin Xiao , Du Shixuan , Gao Hong-Jun
Published: November 2022

Two-dimensional honeycomb lattices show great potential in the realization of Dirac nodal line fermions (DNLFs). Here, we successfully synthesized a gold telluride (AuTe) monolayer by direct tellurizing an Au(111) substrate. Low energy electron diffraction measurements reveal that it is (2×2) AuTe layer stacked onto (3×3) Au(111) substrate. Moreover, scanning tunneling microscopy images show that the AuTe layer has a honeycomb structure. Scanning transmission electron microscopy reveals that it is a single-atom layer. In addition, first-principles calculations demonstrate that the honeycomb AuTe monolayer exhibits Dirac nodal line features protected by mirror symmetry, which is validated by angle-resolved photoemission spectra. Our results establish that monolayer AuTe can be a good candidate to investigate 2D DNLFs and provides opportunities to realize high-speed low-dissipation devices.
Electron-impact ionization of W9+ and W10+
Authors: Bao Runjia , Wei Junkui , Chen Lei , Li Bowen , Chen Ximeng
Published: November 2022

Electron-impact single-ionization (EISI) cross sections for W
q+ (q = 9, 10) ions have been calculated by using the level-to-level distorted-wave (LLDW) method with emphasis on the contribution of metastable states to the total ionization cross sections. Contributions from direct-ionization (DI) and excitation-autoionization (EA) processes are taken into account. The calculated cross sections include the contributions from both the ground configuration and the long-lived metastable states with lifetimes exceeding 10−6 s. Calculated cross sections are in good agreement with experimental measurements when the influence of metastable states on the total ionization cross section are well considered.
Development of a Geographically Distributed Real-Time Test Facility
Authors: Avras A , Jennet K , Syed M H , Smailes M
Published: November 2022

Europe’s electric power network is entering a period of extreme flux as we move to an era where it is dominated by non-linear, asynchronous generation such as wind power plants. The rapid rise of new technologies in this space has led to increasingly complex interactions within the power network that are difficult to cover through traditional test regimes. Existing facilities are not fully equipped to address these new system orientated challenges and while investing in new sites and facilities is one way forward, this is likely to be prohibitively expensive and runs the risk of only being applicable to niche applications. This work presents the first stage in an alternative approach which seeks to address these challenges through the pooling of existing resources. In this concept, geographically distributed test facilities are combined virtually to create new capabilities and perform complex system level validations. This can be done through a Geographically Distributed – Power Hardware in the Loop (GD-PHIL) setup. To achieve this, each site requires a PHIL setup allowing the Device Under Test (DUT) to interact in real time with a simulation. This work will present the outcome of the first step towards the development of such a network, developing and demonstrating the stable communications interfaces necessary to link geographically distributed real time simulators from two different manufacturers.
Multiscale Simulation of Offshore Wind Variability During Frontal Passage: Brief Implication on Turbines’ Wakes and Load
Authors: Bakhoday-Paskyabi Mostafa , Krutova Maria , Bui Hai , Ning Xu
Published: November 2022

Enhancing the performance of offshore wind park power production requires, to a large extent, a better understanding of the interactions of wind farms and individual wind turbines with the atmospheric boundary layer over a wide range of spatiotemporal scales. In this study, we use a multiscale atmospheric model chain coupled offline with the aeroelastic Fatigue, Aerodynamics, Structures, and Turbulence (FAST) code. The multiscale model contains two different components in which the nested mesoscale Weather and Research Forecast (WRF) model is coupled offline with the Parallelized Large-eddy Simulation Model (PALM). Such a multiscale framework enables to study in detail the turbine behaviour under various atmospheric forcing conditions, particularly during transient atmospheric events.
Stochastic modeling of geometric imperfections for buckling analysis of suction buckets
Authors: Böhm M , Schaumann P
Published: November 2022

Recently, suction buckets have become a very prominent foundation for bottom fixed and floating offshore wind turbines. They are embedded with an installation force that stems from water evacuation inside the bucket. This internal negative pressure leads to a high risk of structural buckling. The buckling strength is significantly reduced by geometric imperfections. In previous work, equivalent geometric imperfection forms were introduced and the lower bound was evaluated. However, it has not yet been possible to identify a generally appropriate imperfection form. A probabilistic design approach based on realistic imperfections was not yet considered for suction buckets. Therefore, in this work, a stochastic modeling approach is introduced, which bases on measured data. The imperfection is decomposed to the half-wave cosine Fourier representation. Realizations of the imperfection pattern are generated by filtering white noise with the amplitude spectrum. They are then applied as out of plane deviations on a geometrically and materially nonlinear finite element model and evaluated. The resulting buckling pressure distribution can then be evaluated for different reliability levels. By considering more realistic imperfections and a plastic soil model, the buckling pressure increases by up to a factor of two compared to the conservative stress-based buckling approach.
Observation and Large Eddy Simulation of Coastal Winds at Anholt Offshore Wind Farm
Authors: Chanprasert W. , Sharma R. N. , Cater J. E. , Norris S. E.
Published: November 2022

LiDAR and wave buoy data from the Anholt offshore wind farm have been analysed to determine the seasonal variability of the coastal winds. The wind shear exponent and turbulence intensity were used to classify the atmospheric stability. The occurrence of a Low- Level Jet (LLJ) event in the offshore environment was also studied. Three different periods that represent near-neutral, unstable, and stable atmospheric stratification were chosen for comparison with Large Eddy Simulation (LES) results. The LiDAR data showed that the atmosphere can be typically classified as unstably stratified in summer, while near-neutral stratification was frequently observed in winter. These resulted in higher mean wind speeds, wind velocity shear and directional shear in winter with lower turbulence intensity (TI). The occurrence of LLJ was found to be highest at a wind speed of 6 m/s at 86 m height, and the most frequent maximum velocity in the LLJ was observed between approximately 126 m and 186 m. For the wave data analysis, sea surface roughness was calculated using the wave steepness method, and it was found to be generally less than 0.4 mm, while the wind and wave misalignment was frequently less than 30°. The LES results matched the LiDAR profiles well for all atmospheric conditions, even though LES slightly underestimated the Turbulent Kinetic Energy (TKE) and directional shear for near-neutral conditions.
Development of a Methodology for a WT Gearbox Robustness Test
Authors: Gnauert Jonas , Krause Alexander , Jacobs Georg , Bosse Dennis
Published: November 2022

The paper presents a novel test method to address non-calculative failure modes in wind turbine gearboxes through a metrological robustness evaluation. The method is exemplarily shown for the evaluation of the failure mode “fretting corrosion” which is caused by ring creep at roller bearings. The method was also verified for the failure modes smearing and rehardening. Through the proposed gearbox robustness test, it is for the first time possible to test gearboxes against relevant failure modes and to establish a baseline to compare the robustness of gearboxes with each other. This allows identifying design elements that increase the gearbox robustness and boosters a further increase in availability and reliability of wind turbines.
GA based algorithms for offshore wind farm collector cable optimization
Authors: Ho Wei-Chung
Published: November 2022

In the capital-intensive offshore wind farm industry, the collector cable optimization problem arises primarily due to electric infrastructure expense contributing high rate of initial investment cost. In this study, a multistage solution was developed for optimal locations, the number of offshore substations (OSSs), and inter-array cable routing determination. In the first, a novel GA method picks up the initial OSSs number and location from the candidate site list, then capacities minimum span tree (CMST) is applied to identify valid cable routings. Finally, optimal OSSs location, quantity, and cable paths are obtained through an iterative process. The results of a library real wind farms case are introduced in paper proves the feasibility of the proposed method and showed this study can apply on real practice for optimal decision in OWF cable design.
Optimisation of power cable ampacity in offshore wind farm applications
Authors: Høyer-Hansen M , Hellesø S M , Solheim K T , Mehammer E B , Eberg E , Pedersen P A
Published: November 2022

Inter-array power cables are used to connect wind turbines to the collector and export cable. In the transition from turbine tower to sea, the cable is installed in a J-tube, which has an unfavourable thermal environment and can thus be the thermal bottleneck of the cable installation. To optimize cable installation and reduce CAPEX, improved transient ampacity calculations can be used to determine the dynamic rating. In this work FEM have been applied to calculate the ampacity of a three-core HV cable situated in a J-tube. It was found that by including the trajectory of solar influx, the maximum temperature increased above the admittable cable core temperature compared to the steady-state case. High cable loads will always coincide with wind and thus increased convective heat transfer. By increasing the heat transfer coefficient to a value corresponding to wind speed of 20 m/s at high power production and thus large current, it was found the highest core cable temperature decreased by 18 °C compared to the steady-state case. These more accurate ampacity calculations can be exploited by either increasing the admissible current in the cable by 17% or decreasing the cable cross section.
Flexibility Analysis of O&G Platform Power System with Wind Energy Integration
Authors: Khan Khalid Salman , Sousa Mateus L. , Santos Guilherme B. , Monaro Renato M. , Salles Mauricio B.C.
Published: November 2022

Many researchers and operators are assessing the impact of wind energy integration into the gas turbines based conventional power system due to the intermittent and variable nature. The flexibility characteristics of the gas turbines are vital to guarantee adequate performance at different levels of wind energy penetration to meet the demand of the O&G platform. This study aims to verify the impact of increasing flexibility of the offshore O&G platform’s power system. Therefore, the conventional O&G platform power system is modelled and compared with the post-flexibilization or state-of-the-art power system at different dynamic restrictions of the Open-Cycle Gas Turbines (OCGT) like ramp rates, minimum loading, uptime and downtime, and start-up/shut-down costs. Subsequently, the conventional and state-of-the-art power system model are then simulated at different levels of wind energy penetration, to analyze the system response of the O&G platform, as the intermittent wind energy can generate critical power system instability and imbalance. The proposed model has 4 OCGTs of 33.3MW (locally installed at the O&G platform) and 4 offshore floating wind turbines of 15MW that is satisfying 2 different load profiles of O&G platform (68MW and 34MW average load). The simulation results highlighted that the state-of-the-art power system accommodated higher shares of wind energy as compared to the conventional power system due to the flexible constraints. Also, the flexible power system achieved higher levels of fuel saving, when simulated for 100 hours. The same case study was considered for 25 years and the hours of fuel saving at 5% was 1733 hours and 20% of wind penetration resulted in 1857 hours of fuel saving. The study was performed in the modified Python for Power System Analysis (PyPSA), a python based free simulation toolbox for optimizing the power dispatch.
Towards a particle-flow framework for uncertainty quantification, with applications in wind plant system dynamics and control
Authors: Merz Karl O.
Published: November 2022

The method of particle flow, originally developed for solving Bayes’ formula, is extended to provide a general transformation between two probability distributions. It is shown that this can enable the use of a chaos expansion for uncertain or stochastic dynamic systems. The approach is demonstrated on a simple example. The method is potentially relevant for the real-time control of wind plants. For example, it could be used to obtain a probabilistic estimate of the wind field inside a wind farm using a combination of measurements from the turbines and modelling. Time lags and wake effects make this problem non-Gaussian, which the particle-flow method is well-suited to handle. It remains to be seen, however, whether there is a compelling reason to use a chaos expansion for stochastic dynamic analysis. Functions implementing the methods have been programmed in the Julia language.
Design of Stand-Alone O&G Water Injection System Fed by Wind Generation with Battery Support
Authors: Otremba L , Santos I V M dos , Khan K S , Monaro R M , Salles M B C
Published: November 2022

The promising area of offshore wind power has encouraged wind generation to supply Oil & Gas (O&G) facilities. A potential arrangement comprises a Water Injection System (WIS), as a method for oil recovery in reservoirs, connected to a wind turbine and a Battery Energy Storage System (BESS). However, the wind intermittency poses a challenge for an isolated wind-powered system operation. Therefore, this paper considers a design of a stand-alone system comprised of: a WIS, wind turbine, and BESS based on DC-link interconnection; and proposes a methodology to operate this system aiming to reduce the number of WIS stops. The methodology is based on two perspectives: an energetic analysis in which an energy analytical tool is developed to size the BESS; and a dynamic evaluation performed considering a DC-link voltage-based control to assist the load operation by reducing the WIS stops. The results have shown an adequate performance of the WIS even during moments of lower-wind power generation to the proposed methodology.
Numerical simulations of a 15MW wind turbine on a concrete TLP with rigid pipe tendons
Authors: Pierella Fabio , Avila Oscar Sainz , Sanz Clara Garcia , Ashraf Abid , Aitor Navarro Alonso , Kim Taeseong
Published: November 2022

In this work, we analyze the stability of a concrete TLP platform with a square hull, designed for a 15 MW wind turbine. We verify the natural frequencies in the different degrees of freedom (DOFs) and two ultimate state design load cases (DLC) via two independent models, one in HAWC2+WAMIT from DTU and one in Orcaflex+AQWA from Bluenewables (BN). The decay tests show that the platform eigenfrequencies are outside of the main wave excitation range, and that the models predict the same natural periods within ±5%, with a maximum deviation 20% for the roll period (2.4 s vs. 2.23 s). In the ultimate load states (DLC 1.6 and 6.1), the platform motions are mainly driven by the wind and wave forcing. A small resonance is observed for the pitch motion, driven by the aerodynamic loads, and for the surge, driven by the difference-frequency components of the second-order wave excitation force. The tendons tension reaches a maximum of Nmax
= 30 MN for DLC 6.1 (HS
= 10.9 m, Tp
= 14.0 s, Vref
= 42.3ms−1). In both DLC 6.1 and DLC 1.6 the tendons are far from the compression limit, with a safety margin of ≈ 8 MN for the analyzed test cases.
Unmoored: a free-floating wind turbine invention and autonomous open-ocean wind farm concept
Authors: Raisanen Jack H , Sundman Stig , Raisanen Troy
Published: November 2022

This paper contributes to emerging deep offshore wind literature by presenting the design for a novel free-floating offshore wind turbine for deep water use. The wind turbine uses one large underwater propeller to maintain its position and move as needed, while two small propellers turn the unit. This allows access to areas of high energy production potential in the open ocean out of reach to contemporary floating wind turbines, which are anchored to the seabed. An autonomous ocean-based wind farm concept is also presented. Together, the semi-autonomous wind turbines form a floating wind farm in the open ocean. A separate unit uses electricity from the wind turbines to produce climate-neutral fuels such as hydrogen (H2) and ammonia (NH3) for transport and eventual use.
Development of an analytical uncertainty model for ship-based lidar measurements
Authors: Rubio H , Gottschall J
Published: November 2022

Ship-based lidar systems are a cost-efficient alternative for retrieving highly-reliable offshore wind data. However, the non-stationary nature of ship-mounted lidars hinders the comparison against reference datasets and, therefore, a straightforward characterization of the uncertainty levels associated with these sorts of measurements. For this reason, in this paper we have set up and report an analytical model for estimating the uncertainties of ship-based lidar measurements. The model follows the standard uncertainty propagation method considering the relevant parameters for assessing the wind speed from pulsed Doppler-lidar observations, such as the half cone opening angle, the radial velocity estimation, or the lidar beams’ orientations. Additionally, the derivation of the presented uncertainty model contemplates the technology-specific variables and considerations like the ship linear velocity or tilting, as well as the implementation of a motion correction algorithm.
Review of LIDAR-assisted Control for Offshore Wind Turbine Applications
Authors: Russell A. J. , Collu M. , McDonald A. , Thies P. R. , Mortimer A. , Quayle A. R.
Published: November 2022

Nacelle-mounted, forward-facing Light Detection and Ranging (LIDAR) technology is able to provide knowledge of the incoming wind so that wind turbines can prepare in advance, through feedforward control. LIDAR can aid in improving wind turbine performance across the full operating range, assisting with torque control in below rated wind speeds, pitch control in above rated wind speeds and yaw control for correctly aligning the turbine rotor with the incoming wind direction. The motivations are for decreasing structural loads, resulting in reduced maintenance and extended lifetimes of turbines and their components, and increasing power capture, both of which can lead to reductions in the levelised cost of energy. This paper provides a review of control strategies that have been employed for LIDAR-assisted turbine control. This paper reviews the computational and practical studies that have been performed for both bottom-fixed and floating turbines and the journey that the field has undertaken since its conceptualisation. Detail is provided of the key differences between fixed and floating offshore turbine dynamics. The paper concludes with guidance for future work within the field, with a focus on floating turbines, as the extent of the literature is scarce when compared to bottom-fixed. Suggestions are offered for how the future studies can better account for the current and future industry landscape. Opportunities for testing of LIDAR-assisted floating turbine control in the field, its benefits for floating substructure design, and the steps needed to be taken to ensure its increased utilisation on industrial projects are also discussed.
Wind and soil model influences on the uncertainty in fatigue of monopile supported wind turbines
Authors: Sørum SH , Bachynski-Polić EE , Amdahl J
Published: November 2022

Several alternative engineering models are available for the use in analysis of offshore wind turbines. However, it is not always clear which of the models will yield the most accurate or sufficiently conservative results. This paper investigates the effect of using two alternative soil-structure interaction models and two wind coherence models. The focus is on assessing how these modelling choices influence the predicted long-term fatigue damage in the support structure. The two soil models are a macro-element model and a p-y-curve model with Rayleigh damping. This gives differences in both the damping and stiffness properties of the turbine model. The differences between the two soil models tend to decrease as the turbine size increases. The wind coherence models considered are the Kaimal spectrum with exponential coherence and the Mann uniform shear turbulence model. The Kaimal model predicts the highest response at low frequencies, while the Mann model gives the highest response predictions at higher frequencies. Which turbulence model predicts the highest long-term fatigue damage is then determined by the natural frequencies, rotor and blade passing frequencies of the different turbines.
Joint optimization of preventive and condition-based maintenance for offshore wind farms
Authors: Toftaker Håkon , Bødal Espen Flo , Sperstad Iver Bakken
Published: November 2022

High costs of maintenance and lost production during downtime are a challenge to the offshore wind industry, and there is a great potential to improve cost efficiency by improved maintenance and control strategies utilizing condition monitoring information. As wind farms get older, there is also an increased need to find ways of extending the lifetime of wind turbines allowing continued operation. This may be obtained by de-rating strategies, meaning adjustments of the power production to reduce the fatigue loads on the turbines. This subsequently means wind farm operators are faced with a trade-off between maximizing power production while limiting the degradation of the turbines. To investigate the best trade-off, this paper presents an optimization framework that considers component condition and planned power production to find the best times to perform predetermined preventive and condition-based maintenance on an offshore wind farm. To solve the scheduling problem, it is formulated as a constrained integer linear program, maximizing the net income for the planning horizon. The proposed method considers logistic restrictions, wind and electricity price forecasts, control strategies, component condition and probability of failure. Moreover, the method uses a short time horizon (days) to utilise weather forecasts and a long time horizon (weeks) to better capture the impact of deteriorating condition. The model is presented in a general framework for accounting for component condition in offshore wind farm operation and maintenance. It is illustrated for a specific potential application, considering condition monitoring of main bearings and corrosion of structural elements as examples.
Method to identify insufficient sub-models in MBS models of wind turbine drivetrains
Authors: Züch Vitali , Jacobs Georg , Loriemi Amin , Jakobs Timm , Nievelstein Lucas
Published: November 2022

A significant factor for success of energy production based on renewables is the expanded use of wind energy. For this reason, the wind energy will remain a central element of renewable power generation. As a result of the increased demand on wind energy, a trend towards higher power and torque densities of wind turbine drivetrains can be observed in the current and future development of wind turbines. These trend results in a more compact design of wind turbine drivetrains. Thus, drivetrains become more complex and have stronger interactions between the individual components and therefore the future design of wind turbines will rely more and more on sophisticated simulation models of whole assemblies. Consequently, a general and objective method is needed to quantify the quality of these models and their sub-models. This paper will introduce a modelling quality parameter (MQP) which allows the objective quantification of model quality by comparison between measurement and simulation data. The MQP highlights insufficient sub-models and their need for further improvements.
A perspective on plant robotics: from bioinspiration to hybrid systems
Authors: Meder Fabian , Baytekin Bilge , Del Dottore Emanuela , Meroz Yasmine , Tauber Falk , Walker Ian , Mazzolai Barbara
Published: November 2022

As miscellaneous as the Plant Kingdom is, correspondingly diverse are the opportunities for taking inspiration from plants for innovations in science and engineering. Especially in robotics, properties like growth, adaptation to environments, ingenious materials, sustainability, and energy-effectiveness of plants provide an extremely rich source of inspiration to develop new technologies—and many of them are still in the beginning of being discovered. In the last decade, researchers have begun to reproduce complex plant functions leading to functionality that goes far beyond conventional robotics and this includes sustainability, resource saving, and eco-friendliness. This perspective drawn by specialists in different related disciplines provides a snapshot from the last decade of research in the field and draws conclusions on the current challenges, unanswered questions on plant functions, plant-inspired robots, bioinspired materials, and plant-hybrid systems looking ahead to the future of these research fields.
Ambient fine particulate matter and ozone pollution in China: synergy in anthropogenic emissions and atmospheric processes
Authors: Jiang Yueqi , Wang Shuxiao , Xing Jia , Zhao Bin , Li Shengyue , Chang Xing , Zhang Shuping , Dong Zhaoxin
Published: November 2022

Since 2013, China has taken a series of actions to relieve serious PM2.5 pollution. As a result, the annual PM2.5 concentration decreased by more than 50% from 2013 to 2021. However, ozone pollution has become more pronounced, especially in the North China Plain. Here, we review the impacts of anthropogenic emissions, meteorology, and atmospheric processes on ambient PM2.5 loading and components and O3 pollution in China. The reported influence of interannual meteorological changes on PM2.5 and O3 pollution during 2013–2019 ranged from 10%–20% and 20%–40%, respectively. During the same period, the anthropogenic emissions of NO
x
, SO2, primary PM2.5, NMVOC and NH3 are estimated to decrease by 38%, 51%, 35%, 11% and 17%, respectively. Such emission reduction is the main cause for the decrease in PM2.5 concentration across China. However, the imbalanced reductions in various precursors also result in the variation in nitrate gas-particle partitioning and hence an increase in the nitrate fraction in PM2.5. The increase of ozone concentration and the enhancement of atmospheric oxidation capacity can also have substantial impact on the secondary components of PM2.5, which partly explained the growth of organic aerosols during haze events and the COVID-19 shutdown period. The uneven reduction in NO
x
and NMVOC is suggested to be the most important reason for the rapid O3 increase after 2013. In addition, the decrease in PM2.5 may also have affected O3 formation via radiation effects and heterogeneous reactions. Moreover, climate change is expected to influence both anthropogenic emissions and atmospheric processes. However, the extent and pathways of the PM2.5-O3 interplay and how it will be impacted by the changing emission and atmospheric conditions making the synergetic control of PM2.5 and O3 difficult. Further research on the interaction of PM2.5 and O3 is needed to provide basis for a scientifically-grounded and effective co-control strategy.
Sustainability of fresh groundwater resources in fifteen major deltas around the world
Authors: van Engelen J , Essink G H P Oude , Bierkens M F P
Published: November 2022

Population growth, urbanization and intensification of irrigated agriculture in the world’s deltas boost the demand for fresh water, with extensive groundwater extraction as a result. This, in turn, leads to salt water intrusion and upconing, which poses a threat to freshwater and food security. Managing fresh groundwater resources in deltas requires accurate knowledge about the current status and behaviour of their fresh groundwater resources. However, this knowledge is scarcely present, especially for groundwater at larger depths. Here, we use three-dimensional variable-density groundwater model simulations over the last 125 ka to estimate the volume of fresh groundwater resources for 15 major deltas around the world. We estimate current volumes of onshore fresh groundwater resources for individual deltas to vary between 1010 m3 and 1012 m3. Offshore, the estimated volumes of fresh groundwater are generally smaller, though with a considerably higher variability. In 9 out of 15 simulated deltas, fresh groundwater volumes developed over thousands of years. Based on current groundwater extraction and recharge rates, we estimate the time until in-situ fresh groundwater resources are completely exhausted, partly leading to groundwater level decline and mostly replacement with river water or saline groundwater. This straightforward analysis shows that 4 out of 15 deltas risk complete exhaustion of fresh groundwater resources within 300 m depth in 200 years. These deltas also suffer from saline surface water which means their groundwater resources will progressively salinize. With a fourfold increase in extraction rates, seven deltas risk a complete exhaustion within 200 years. Of these seven deltas, six suffer from saline surface water. We stress that the groundwater of these six vulnerable deltas should be carefully managed, to avoid non-renewable groundwater use. The progressive exhaustion of fresh groundwater resources in these deltas will hamper their ability to withstand periods of water scarcity.
Mixed-phase regime cloud thinning could help restore sea ice
Authors: Villanueva D , Possner A , Neubauer D , Gasparini B , Lohmann U , Tesche M
Published: November 2022

Cloud geoengineering approaches aim to mitigate global warming by seeding aerosols into clouds to change their radiative properties and ocurrence frequency. Ice-nucleating particles (INPs) can enhance droplet freezing in clouds, reducing their water content. Until now, the potential of these particles has been mainly studied for weather modification and cirrus cloud thinning. Here, using a cloud-resolving model and a climate model we show that INPs could decrease the heat-trapping effect of mixed-phase regime clouds over the polar oceans during winter, slowing down sea-ice melting and partially offsetting the ice-albedo feedback. We refer to this concept as mixed-phase regime cloud thinning (MCT). We estimate that MCT could offset about 25% of the expected increase in polar sea-surface temperature due to the doubling of CO2. This is accompanied by an annual increase in sea-ice surface area of 8% around the Arctic, and 14% around Antarctica.
On a family of coupled diffusions that can never change their initial order
Authors: Mengütürk Levent Ali , Mengütürk Murat Cahit
Published: November 2022

We introduce a real-valued family of interacting diffusions where their paths can meet but cannot cross each other in a way that would alter their initial order. Any given interacting pair is a solution to coupled stochastic differential equations with time-dependent coefficients satisfying certain regularity conditions with respect to each other. These coefficients explicitly determine whether these processes bounce away from each other or stick to one another if/when their paths collide. When all interacting diffusions in the system follow a martingale behaviour, and if all these paths ultimately come into collision, we show that the system reaches a random steady-state with zero fluctuation thereafter. We prove that in a special case when certain paths abide to a deterministic trend, the system reduces down to the topology of captive diffusions. We also show that square-root diffusions form a subclass of the proposed family of processes. Applications include order-driven interacting particle systems in physics, adhesive microbial dynamics in biology and risk-bounded quadratic optimization solutions in control theory.
Experimental investigation of dynamic stall flow control using a microsecond-pulsed plasma actuator
Authors: XU Zeyang , WU Bin , GAO Chao , WANG Na , JIA Tianhao
Published: November 2022

To alleviate the performance deterioration caused by dynamic stall of a wind turbine airfoil, the flow control by a microsecond-pulsed dielectric barrier discharge (MP-DBD) actuator on the dynamic stall of a periodically pitching NACA0012 airfoil was investigated experimentally. Unsteady pressure measurements with high temporal accuracy were employed in this study, and the unsteady characteristics of the boundary layer were investigated by wavelet packet analysis and the moving root mean square method based on the acquired pressure. The experimental Mach number was 0.2, and the chord-based Reynolds number was 870 000. The dimensionless actuation frequencies F
+ were chosen to be 0.5, 1, 2, and 3, respectively. For the light dynamic regime, the MP-DBD plasma actuator plays the role of suppressing flow separation from the trial edge and accelerating the flow reattachment due to the high-momentum freestream flow being entrained into the boundary layer. Meanwhile, actuation effects were promoted with the increasing dimensionless actuation frequency F
+. The control effects of the deep dynamic stall were to delay the onset and reduce the strength of the dynamic stall vortex due to the accumulating vorticity near the leading edge being removed by the induced coherent vortex structures. The laminar fluctuation and Kelvin–Helmholtz (K–H) instabilities of transition and relaminarization were also mitigated by the MP-DBD actuation, and the alleviated K-H rolls led to the delay of the transition onset and earlier laminar reattachment, which improved the hysteresis effect of the dynamic stall. For the controlled cases of F
+ = 2, and F
+ = 3, the laminar fluctuation was replaced by relatively low frequency band disturbances corresponding to the harmonic responses of the MP-DBD actuation frequency.
Ultrathin HfO2/Al2O3 bilayer based reliable 1T1R RRAM electronic synapses with low power consumption for neuromorphic computing
Authors: Wang Qiang , Wang Yankun , Luo Ren , Wang Jianjian , Ji Lanlong , Jiang Zhuangde , Wenger Christian , Song Zhitang , Song Sannian , Ren Wei , Bi Jinshun , Niu Gang
Published: November 2022

Neuromorphic computing requires highly reliable and low power consumption electronic synapses. Complementary-metal-oxide-semiconductor (CMOS) compatible HfO2 based memristors are a strong candidate despite of challenges like non-optimized material engineering and device structures. We report here CMOS integrated 1-transistor-1-resistor (1T1R) electronic synapses with ultrathin HfO2/Al2O3 bilayer stacks (<5.5 nm) with high-performances. The layer thicknesses were optimized using statistically extensive electrical studies and the optimized HfO2(3 nm)/ Al2O3(1.5 nm) sample shows the high reliability of 600 DC cycles, the low Set voltage of ∼0.15 V and the low operation current of ∼6 µA. Electron transport mechanisms under cycling operation of single-layer HfO2 and bilayer HfO2/Al2O3 samples were compared, and it turned out that the inserted thin Al2O3 layer results in stable ionic conduction. Compared to the single layer HfO2 stack with almost the same thickness, the superiorities of HfO2/Al2O3 1T1R resistive random access memory (RRAM) devices in electronic synapse were thoroughly clarified, such as better DC analog switching and continuous conductance distribution in a larger regulated range (0–700 µS). Using the proposed bilayer HfO2/Al2O3 devices, a recognition accuracy of 95.6% of MNIST dataset was achieved. These results highlight the promising role of the ultrathin HfO2/Al2O3 bilayer RRAM devices in the application of high-performance neuromorphic computing.
Some products in fusion systems and localities
Authors: Henke Ellen
Published: November 2022

The theory of saturated fusion systems resembles in many parts the theory of finite groups. However, some concepts from finite group theory are difficult to translate to fusion systems. For example, products of normal subsystems with other subsystems are only defined in special cases. In this paper the theory of localities is used to prove the following result: Suppose

F

\mathcal {F}

is a saturated fusion system over a

p
p

-group

S
S

. If

E

\mathcal {E}

is a normal subsystem of

F

\mathcal {F}

over

T
≤
S

T\leq S

, and

D

\mathcal {D}

is a subnormal subsystem of

N

F

(
T
)

N_\mathcal {F}(T)

over

R
≤
S

R\leq S

, then there is a subnormal subsystem

E

D

\mathcal {E}\mathcal {D}

of

F

\mathcal {F}

over

T
R

TR

, which plays the role of a product of

E

\mathcal {E}

and

D

\mathcal {D}

in

F

\mathcal {F}

. If

D

\mathcal {D}

is normal in

N

F

(
T
)

N_\mathcal {F}(T)

, then

E

D

\mathcal {E}\mathcal {D}

is normal in

F

\mathcal {F}

. It is shown along the way that the subsystem

E

D

\mathcal {E}\mathcal {D}

is closely related to a naturally arising product in certain localities attached to

F

\mathcal {F}

.
The sharp Hardy–Moser–Trudinger inequality in dimension 𝑛
Authors: Nguyen Van Hoang
Published: November 2022

Wang and Ye [Adv. Math. 230 (2012), pp. 294–320] prove a Hardy–Moser–Trudinger inequality in dimension two which improves both the classical Moser–Trudinger inequality and the classical Hardy inequality in the unit disc. In this paper, we generalize their result both to the higher dimensional unit ball and to the singular weighted cases as well. More precisely, we prove that
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="sup Underscript StartLayout 1st Row u element-of upper W 0 Superscript 1 comma n Baseline left-parenthesis double-struck upper B Superscript n Baseline right-parenthesis comma 2nd Row integral Underscript double-struck upper B Superscript n Baseline Endscripts StartAbsoluteValue nabla u EndAbsoluteValue Superscript n Baseline d x minus left-parenthesis StartFraction 2 left-parenthesis n minus 1 right-parenthesis Over n EndFraction right-parenthesis Superscript n Baseline integral Underscript double-struck upper B Superscript n Baseline Endscripts StartFraction StartAbsoluteValue u EndAbsoluteValue Superscript n Baseline Over left-parenthesis 1 minus StartAbsoluteValue x EndAbsoluteValue squared right-parenthesis Superscript n Baseline EndFraction d x less-than-or-equal-to 1 EndLayout Endscripts integral Underscript double-struck upper B Superscript n Baseline Endscripts e Superscript left-parenthesis 1 minus StartFraction beta Over n EndFraction right-parenthesis alpha Super Subscript n Superscript StartAbsoluteValue u EndAbsoluteValue Super Superscript StartFraction n Over n minus 1 EndFraction Baseline StartAbsoluteValue x EndAbsoluteValue Superscript negative beta Baseline d x less-than-or-equal-to upper C">

sup

u
∈

W
0

1
,
n

(

B

n

)
,

∫

B

n

|

∇
u

|

n

d
x
−

(

2
(
n
−
1
)

n

)

n

∫

B

n

|

u

|

n

(
1
−

|

x

|

2

)
n

d
x
≤
1

∫

B

n

e

(
1
−

β
n

)

α
n

|

u

|

n

n
−
1

|

x

|

−
β

d
x
≤
C

\sup _{\substack {u\in W^{1,n}_0(\mathbb {B}^n),\\ \int _{\mathbb {B}^n} |\nabla u|^n dx -\left (\frac {2(n-1)}n\right )^n \int _{\mathbb {B}^n} \frac {|u|^n}{(1-|x|^2)^n} dx \leq 1}}\int _{\mathbb {B}^n} e^{(1-\frac \beta n)\alpha _n |u|^{\frac n{n-1}}} |x|^{-\beta } dx \leq C

\]
for any

β
∈
[
0
,
n
)

\beta \in [0,n)

,

n
≥
3

n\geq 3

where

α
n

=
n

ω

n
−
1

1

n
−
1

\alpha _n = n \omega _{n-1}^{\frac 1{n-1}}

and

ω

n
−
1

\omega _{n-1}

is the surface area of the

n
−
1

n-1

dimensional unit sphere. The proof of Wang and Ye is based on the blow-up analysis method which seems not work in the higher dimensions. In this paper, we propose a new approach based on the method of transplantation of Green’s functions to prove our inequality. As a consequence, we obtain a singular Moser–Trudinger inequality in the hyperbolic spaces which confirms affirmatively a conjecture by Mancini, Sandeep and Tintarev [Adv. Nonlinear Anal., 2 (2013), pp. 309–324].