bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gate tunable terahertz cyclotron emission from two-dimensional Dirac fermions
Authors: Benhamou-Bui B. , Consejo C. , Krishtopenko S. S. , Szola M. , Maussang K. , Ruffenach S. , Chauveau E. , Benlemqwanssa S. , Bray C. , Baudry X. , Ballet P. , Morozov S. V. , Gavrilenko V. I. , Mikhailov N. N. , Dvoretskii S. A. , Jouault B. , Torres J. , Teppe F. 
Published: November 2023

Two-dimensional Dirac fermions in HgTe quantum wells close to the topological phase transition can generate significant cyclotron emission that is magnetic field tunable in the terahertz frequency range. Due to their relativistic-like dynamics, their cyclotron mass is strongly dependent on their electron concentration in the quantum well, providing a second tunability lever and paving the way for a gate-tunable, permanent-magnet Landau laser. In this work, we demonstrate the proof-of-concept of such a back-gate tunable THz cyclotron emitter at a fixed magnetic field. The emission frequency detected at 1.5 T is centered at 2.2 THz and can already be electrically tuned over 250 GHz. With an optimized gate and a realistic permanent magnet of 1.0 T, we estimate that the cyclotron emission could be continuously and rapidly tunable by the gate bias between 1 and 3 THz, that is to say on the less covered part of the THz gap.
Geodesics motion of test particles around Schwarzschild-Klinkhamer wormhole with topological defects and gravitational lensing
Authors: Ahmed Faizuddin 
Published: November 2023

AbstractThis study investigates the geodesic motion of test particles, both massless and massive, within a Schwarzschild-Klinkhamer (SK) wormhole space-time. We specifically consider the influence of cosmic strings on the system and analyze the effective potential, and observing that the presence of a cosmic string parameter alters it for null and time-like geodesics. Moreover, we calculate the deflection angle for null geodesics, and demonstrate that the cosmic string modifies this angle and induces a shift in the results. Additionally, we extend our investigation in this SK-wormhole space-time but with a global monopole. We explore the geodesic motion of test particles in this scenario and find that the effective potential is affected by the global monopole. Similarly, we determine the deflection angle for null geodesics and show that the global monopole parameter introduces modifications to this angle. Lastly, we present several known solutions for space-times involving cosmic strings and global monopoles within the framework of this SK-wormhole.
A clarification on prevailing misconceptions in unimodular gravity
Authors: Bengochea Gabriel R. , León Gabriel , Perez Alejandro , Sudarsky Daniel 
Published: November 2023

Abstract
The traditional presentation of Unimodular Gravity (UG) consists on indicating that it is an alternative theory of gravity that restricts the generic diffeomorphism invariance of General Relativity. In particular, as often encountered in the literature, unlike General Relativity, Unimodular Gravity is invariant solely under volume-preserving diffeomorphisms. That characterization of UG has led to some confusion and incorrect statements in various treatments on the subject. For instance, sometimes it is claimed (mistakenly) that only spacetime metrics such that |det gμν
| = 1 can be considered as valid solutions of the theory. Additionally, that same (incorrect) statement is often invoked to argue that some particular gauges (e.g. the Newtonian or synchronous gauge) are not allowed when dealing with cosmological perturbation theory in UG. The present article is devoted to clarify those and other misconceptions regarding the notion of diffeomorphism invariance, in general, and its usage in the context of UG, in particular.
Small corrections to 1989 NIST constant-volume gas thermometry data
Authors: Harvey Allan H 
Published: November 2023

Abstract
Constant-volume gas thermometry data published in 1989 for the difference between the thermodynamic temperature and the International Practical Temperature Scale of 1968 are corrected in two ways. A refined estimate of the thermal expansivity of the material of the gas bulb, published in 1990, increases the thermodynamic temperature by amounts on the order of 1 mK–3 mK. Better knowledge of the nonideality of helium gas reduces the uncertainty of the nonideality correction to near zero and decreases the thermodynamic temperature by amounts on the order of 0.1 mK–0.5 mK. The net effect is a small increase in the thermodynamic temperature derived from the 1989 experiments. The magnitude of this increase is approximately 2 mK at 505 K, increasing to 3 mK at temperatures near 700 K, and then diminishing to near 0.5 mK at the highest temperature of the measurements (933 K). These corrections are smaller than the uncertainty of the experiments, but may be of significance for future recommendations for the relationship between the thermodynamic temperature and the consensus scale in this temperature range.
Collision avoidance of autonomous ships in inland waterways – A survey and open research problems
Authors: Tran Hoang Anh , Johansen Tor Arne , Negenborn Rudy R. 
Published: November 2023

Abstract
Promoting autonomous surface ships in inland waterways traffic (IWT) is a potential solution towards reducing road traffic and transport emission footprints. Over the last decade, there has been a growing research on autonomous ships for open waters. However, applying this research to the IWT domain is not straightforward. The IWT, due to its confined waterways, poses a different challenge than the open sea case. Due to the confined waterways, inland ships face several hydrodynamic phenomena that they rarely encountered in the open sea, such as shallow water, banks, or ship-to-ship effects. Furthermore, the higher traffic density in inland waterways also requires a different solution for sensing and control systems.
This paper offers an overview of the current developments on autonomous collision avoidance for inland waterway ships that covering different problems of safety navigation for ship in IWT. A short analysis is presented to highlight the strengths and weaknesses of each approach. We also discuss the current research gaps and what could be improved to enable the operation of inland autonomous ships.
Use Case Remote Pilotage – Technology Overview
Authors: Grundmann Robert , Ujkani Arbresh , Weisheit Jonathan , Seppänen Jedi , Salokorpi Mirva , Burmeister Hans-Christoph 
Published: November 2023

Abstract
Starting from a short study on pilotage transfers in terms of safety and sustainability as a motivation, this paper will draft trust requirements from pilots and navigators to remote based systems, before the capabilities of Extended Reality (XR) for these requirements are highlighted. This is followed by outlining the technical approach used within Sea4Value Fairway (S4VF) project and Remote Pilotage – Operational, innovative and Manageable Alternatives for Navigation routines (RePO MAN). The technical implementation within the context of the the use case method is explained and a consolidation of these use cases within the framework of RePO MAN and the possibility of adaptation in further field tests up to implementation is considered. Finally, limitations and deficits of remote pilot concepts will be outlined using the example of RePO MAN merged with the results of the S4VF project.
Real-time 360 degrees view for the operator of milliAmpere 2
Authors: Paasche Mathias Thoresen , Helgesen Øystein Kaarstad , Brekke Edmund Førland 
Published: November 2023

Abstract
In the evolving domain of autonomous marine operations, accurate perception and representation of the surrounding environment are crucial for safe and effective execution. This paper addresses this issue by developing and testing a near real-time 360-degree bird’s eye view system for the situations where the ferry, milliAmpere 2, has to be manually controlled by a local operator onboard. The goal was to aid the operator during the critical phase of docking, by displaying the surrounding area of the ferry from a bird’s eye view. The bird’s eye view was made by using inverse perspective mapping on the undistorted images from the 8 cameras onboard. The system was implemented in Python, and aimed to reach a run-time of less than 200ms. This goal was reached during the initial phase of the work. However, during live testing, only near real-time performance was achieved. Despite some shortcomings, the operators found the system to be a “useful additional assistance” during the docking process.
Generating Structured Set of Encounters for Verifying Automated Collision and Grounding Avoidance Systems
Authors: Pedersen Tom Arne , Vasanthan Chanjei , Karolius Kristian , Engelhardtsen Øystein , Houweling Koen Pieter , Jørgensen Are 
Published: November 2023

Abstract
It is a clear consensus in the maritime industry that ships, both conventional and with automated Collision and Grounding Avoidance (CAGA) systems, shall be navigated following the Convention on the International Regulations for Preventing Collisions at Sea (COLREG), ensuring a level playing field and a common understanding of the responsibilities between conventional and autonomous ships, allowing safe co-existence in the waterways. Simulation-based testing is expected to play an important role to explore and document safety and the ability to adhere to the COLREG, as it allows for rigorous testing of performance and failure handling before the software is installed on the ship. Many terms in COLREG used to specify acceptable behavior are qualitative, such as “ample time” and “apparent maneuver” and need to be viewed in light of a specific situation to be applied in practice. As the COLREG includes a large set of obligations specific to different types of situations, a significant number of ship encounters spread out across the different aspects of the regulations will be necessary to enable any judgments about the overall ability to adhere to these rules. The work presented in this paper provides a method and software toolbox for generating ship encounters to allow a systematic assessment of the vessel’s ability to act according to COLREG using simulation-based testing, and it is made freely available to vendors, students, or any other actors involved in the development or assurance of algorithms for automated collision and grounding avoidance systems.
Increased tower eigenfrequencies on floating foundations and their implications for large two- and three-bladed turbines
Authors: Anstock Fabian , Kessler Alois , Schorbach Vera 
Published: November 2023

Abstract
If the tower of a bottom-fixed turbine is put on a floating foundation, such as a spar, semi-submersible, or barge, its eigenfrequency increases. In the investigated case, the tower eigenfrequency rose to about twice its previous value. For bottom-fixed applications, the comparatively high blade-passing frequency of a three-blade turbine (3P) leaves a great bandwidth to design a light and soft tower with a low-enough eigenfrequency. On one of those floaters, however, the eigenfrequency of the same tower might neither be high nor low enough to avoid eigenfrequency excitation by 3P around rated speed. Due to the lower blade passing frequency of a two-bladed wind turbine (2P), the same tower eigenfrequency is high enough by default, enabling considerable material savings or at least eliminating the severe eigenfrequency excitation issue of its bottom-fixed version. Additionally, cost benefits in the whole life-cycle of two-bladed turbines remain. 20MW two- and three-bladed turbines were analyzed numerically on an upscaled version of the UMaine VolturnUS-S semi-submersible, confirming the reasoning.
The performance of two control strategies for floating wind turbines: lidar-assisted feedforward and multi-variable feedback
Authors: Guo Feng , Schlipf David , Lemmer Frank , Raach Steffen , Özinan Umut , Adam Raphaël , Choisnet Thomas 
Published: November 2023

Abstract
In this paper, we analyze the performances of two control strategies and their combination on a floating turbine through OpenFAST simulations. The floating wind turbine is modeled based on the demonstrative FLOATGEN, which consists of a 2MW wind turbine mounted on the Damping Pool platform designed by BW Ideol. The lidar-assisted control utilizes lidar wind preview to achieve blade pitch feedforward control. The multi-variable feedback additionally uses the platform pitch rate to determine blade pitch. By simulations with the above-rated wind and irregular wave conditions, both control strategies and their combination has the potential to reduce turbine vibrations. Especially, combining lidar-assisted control and multi-variable feedback control brings the most significant reduction in the standard deviations of rotor speed (>36%), low-speed shaft torque (>30%), and blade root moment (>15%).
New model for structural optimisation of airborne wind energy systems with rotary transmission
Authors: Wacker Jannis , McWilliam Michael , Muskulus Michael , Gaunaa Mac 
Published: November 2023

Abstract
Rotary Airborne Wind Energy Systems (RAWES) are networks of wings that act as flying wind turbines. The power extracted from the wind can be transmitted to ground-based generators through open tensegrity structures. In recent years, there have been different approaches to the topology of the Tensile Rotary Power Transmission (TRPT) and prototype designs are often driven by trial-and-error. This paper proposes a steady-state model with numerical optimisation to accelerate the development and prototyping of AWES by supporting the evaluation of new design concepts.
The coupled steady state model uses aerodynamics and structural dynamics to analyse the AWES performance. A novelty is, that the model includes both cross-wind pressure drag and axial friction drag acting on the tethers and frames in the tensegrity structure. Validation of the model has been achieved using data from field measurements of two prototypes.
In conclusion, using the proposed optimisation, RAWES with TRPT can be designed to maximise power density, coefficients of performance or power harvesting factor. While RAWES will not be able to outperform conventional wind turbines, they have the potential advantages in niche applications due to reduced costs and simplified logistics resulting from reduced material usage.
Numerical modelling of a hydro-pneumatic energy storage system for smoothing power fluctuations from offshore wind
Authors: Borg A , Sant T , Buhagiar D , Cutajar C , Farrugia R N 
Published: November 2023

Abstract
Energy storage systems are imperative in tackling the regulation of electricity supply and demand mismatch to avoid curtailment of wind energy. Co-locating energy storage in the same operating region as the offshore wind farms allows for an unobtrusive environment while also steering away from rising land prices. The presented work involves an offshore Hydro-Pneumatic Energy Storage (HPES) system made up of a subsea accumulator pre-charged with compressed air. The Energy Conversion Unit (ECU) of the system consists of a megawatt-scale hydraulic pump and a turbine. This paper discusses a novel numerical model developed in Python™ for simulating the operation of the ECU pump and turbine of the offshore HPES system by using a simple moving average, based on a time window of wind data, whilst also introducing a one-step-ahead forecasting model. The results of the research are split into two parts; Firstly, the analysis and validation of the Seasonal Auto Regressive Integrated Moving Average (SARIMA) forecasting model is performed. Secondly, results on the pump and turbine performance based on the smoothened power are shown. The research found that despite the centrifugal pump limitations due to variable head operation, a smoothened power output is efficiently (> 90 %) attained in retaining the intermittent power generated.
Optimising the operation of wind powered electrolysers
Authors: Ferguson J L B , Kervyn M , Nambiar A 
Published: November 2023

Abstract
Integrated wind power – hydrogen systems may make a useful contribution to achieving climate targets. Both centralised wind powered electrolysers and multi-MW decentralised solutions are likely to see multiple electrolyser units/systems deployed together. Since the efficiency of electrolysers is a function of their load factor, there is a possibility of optimising operation of the individual units in order to maximise the overall plant efficiency. Here we outline optimal strategies for electrolysis facilities with two, three and four independent units, and find that using these optimised strategies can increase annual wind powered hydrogen production by 2.3 - 3.8%, depending on the specific set up. By quantifying the increase in hydrogen production through using optimised control strategies, this research can help industry to identify the best overall control scheme for electrolyser plants composed of multiple units.
Design and control of all-DC offshore wind power plant with MMC-based DC/DC high-power converters
Authors: Follo Alessandra , Saborío-Romano Oscar , Tedeschi Elisabetta , Cutululis Nicolaos A. 
Published: November 2023

Abstract
This paper presents the modelling of an all-direct-current (all-DC) offshore wind power plant (OWPP) which employs DC/DC high-power converters based on modular multilevel converter (MMC) technology. A coordinated control strategy for such OWPP, designed to maximise the power output and maintain the DC voltages close to the nominal values, is also proposed. With the proposed strategy, wind turbines (WTs) are controlled to provide maximum power output according to a local maximum power point tracking (MPPT) reference signal together with a centralised curtailment signal. The response of the designed 600 MW all-DC OWPP is tested by means of dynamic simulations in MATLAB/Simulink.
Dynamic moisture diffusion in transformer winding insulation
Authors: Linhjell Dag , Mehammer Eirill Bachmann 
Published: November 2023

Abstract
Wind power production is intermittent due to varying wind conditions. This leads to frequent temperature changes in the wind farm transformers, which in turn affects the lifetime of the transformer winding insulation. To extend the lifetime through prediction of effects from dynamic loading, new models for degradation of insulation systems are needed. This article is laying the foundations of a model for dynamic moisture migration in the winding insulation of wind farm transformers. Relevant equations and approximations are presented and an experimental setup for laboratory testing of transformer insulation ageing related moisture migration under dynamic loading is described. The demonstration experiment clearly shows moisture migration through paper layers in a simple physical winding insulation model. As the ageing of cellulose is very moisture-dependent, the migration should clearly be included in models of ageing under dynamic load.
Maritime logistics optimisation for predictive maintenance at offshore wind farms
Authors: Halvorsen-Weare Elin Espeland , Nonås Lars Magne 
Published: November 2023

Abstract
For offshore wind farms, a move from a preventive and corrective maintenance regime to a predictive maintenance regime requires new methods for modelling approaches for maritime logistics planning. This paper presents an overview of the maritime logistics planning problem for a predictive maintenance regime and introduces the current state-of-the-art for operational research in the field of operation and maintenance at offshore wind farms. Findings are that a combination of the vessel resource scheduling problem for operation and maintenance at offshore wind farms with predictive analysis and digital twins is a promising future research step. A framework for a decision support tool is presented that will help bridge the gap, both with respect to the academic path, and the gap between academic research and industry.
Design Optimization of Floating Offshore Wind Turbine Substructure Using Frequency Domain Modelling and Genetic Algorithm
Authors: Benifla Victor , Adam Frank 
Published: November 2023

Abstract
Floating offshore wind turbines are becoming increasingly popular as a promising technology for producing cleaner energy. However, in order to be competitive with fixed offshore wind projects or even onshore wind projects, the costs associated with floating offshore wind turbines must be significantly reduced. To tackle this challenge, this paper presents a comprehensive framework for optimizing the design of floating offshore wind turbine substructures and their components. The innovative open-source frequency-domain dynamic model RAFT is used to take into account the aerodynamic, hydrodynamic and mooring forces that impact the stability and dynamics of the floating system. The numerical model is coupled with an efficient genetic algorithm to minimize the structural mass of the floating platform while maintaining its stability and dynamic performance. The geometrical parametrization of the substructure, the implementation of the numerical model, and the overall optimization process are all thoroughly detailed in this paper, along with preliminary results that demonstrate the potential cost reductions that can be achieved through this framework.
A Reinforcement Learning framework for Wake Steering of Wind Turbines
Authors: Lye Kjetil Olsen , Tabib Mandar V , Johannessen Kjetil André 
Published: November 2023

Abstract
Ideally, optimum power for a single turbine is obtained when the wind-turbine is aligned with the wind direction. However in multi-turbine wind-farm set-up, wake effects lead to decreased power production from downstream turbine [1, 2, 3, 4, 5]. Hence, a control strategy based on wake steering involves misalignment of upstream turbines with the wind direction causing their wakes to deflect away from downstream wind turbines needs to be investigated. A great deal of work has been put into dynamically controlling the orientation of the individual wind turbines to maximize the power output of the farm [6, 7, 8, 9]. In the wake-steering based control, the misaligned wind turbines produce less power, while the performance of downstream turbines gets enhanced which increases overall net power gain for the wind power plant. Traditionally, the benefits of wake steering have been demonstrated assuming fixed wind directions (e.g., using high-fidelity modeling). Amongst the most recent techniques, particularly promising is the use of Reinforcement learning (RL), which is a branch of machine learning where models are trained to make decisions based on observations of their environment. It is a flexible framework for devising strategies for solving optimal control problems in a broad range of applications across the sciences. Early attempts at using Reinforcement learning for wake steering have been carried out [7, 8, 9], and show promising results. In practice, however, wake-steering controllers must operate in dynamic wind environments in which the wind conditions are estimated from imperfect measurements. Hence, a reinforcement learning framework is developed in this work for dynamic wind conditions. The results show that the framework is promising, and we compare the deep reinforcement learning approach against a considerably more expensive traditional optimization approach which serves as a good baseline. Future work could include looking at more realistic wake models, steering in the presence of noisy observations, and incorporating weather predictions.