bluuebunny/crossref_metadata_2025 huggingface dataset:
“Venezuela hawaii, chelsea!”
Authors: Nassenstein Nico
Published: May 2024

This contribution focuses on Langila, a language practice or “speech style” that emerged in the first decade after
the millenium in the Congolese capital of Kinshasa, characterized by lexical creativity and specific phonological manipulative
strategies. I analyze Langila speakers’ use of global place names, fashionable brands, and names of institutions, and to some
extent specific (manipulated) personal names as pseudo-onomastic references from an anthropological-linguistic perspective,
understanding “games with names” (Storch 2019) as a cultural practice that contributes
to the novelty factor in specific ways of speaking in the Congolese capital of Kinshasa and in social media. It is crucial for the
discussion of “labelling” and “branding” practices in contexts of cultural importance in African languages to consider why and how
speakers use, manipulate, and recontextualize semiotic links to names of artefacts, places, and people – and how this changes the
onomastic value of these named, unnamed, and renamed concepts in ludic interaction. The paper thus circles around two main
research questions: How are “labels” (anthroponyms, toponyms) semantically and in terms of their referential and indexical use
changed to creative lifestyle emblems and become part of the everyday lexicon? How are contexts of cultural importance named and
(re)labelled by a speaker, drawing from “manipulated” repertoires that involve (partially homophonic) anthroponymic or toponymic
references actually intended to mislead or to confuse the hearer? This contribution investigates the role of onomastic references
that are used to denote and label central concepts in Langila.
Exchangeable leaders of collectively migrating glioma abuse N-cadherin trafficking
Authors: Kawauchi Takeshi , Ito Shiho
Published: May 2024

Collectively migrating cells consist of leaders and followers with different features. In this issue, Kim et al. (https://doi.org/10.1083/jcb.202401057) characterize the leader and follower cells in collective glioma migration and uncover important roles of YAP1/TAZ-mediated regulation of N-cadherin in the leader cells.
Signature of electrothermal transport in 18 nm vertical junctionless gate-all-around nanowire field effect transistors
Authors: Rezgui Houssem , Wang Yifan , Mukherjee Chhandak , Deng Marina , Maneux Cristell
Published: May 2024

Addressing temperature hot-spots resulting from self-heating effects (SHE) poses a significant challenge in the design of emerging nanoscale transistors, such as vertical junctionless nanowire field-effect transistors (VNWFETs), due to reduced thermal conductivity. Consequently, electrothermal modeling becomes crucial for a comprehensive understanding of the underlying physical mechanisms governing carrier degradation and thermal conduction in these nanoscale devices. In this study, we present an enhanced drift-diffusion model coupled with nonlocal Guyer–Krumhansl equations to accurately capture carrier-phonon interactions and explore the electrothermal characteristics of gate-all-around (GAA) VNWFETs. Pulsed current–voltage (I–V) measurements are employed to investigate the performance of a state-of-the-art 18 nm VNWFET technology. Furthermore, we report on the influences of both trapping and SHE under high-bias conditions for varying pulse widths. Our findings reveal that optimization of mobility degradation mechanisms allows for improved control over the physical behavior of carrier transport in these emerging technologies. Through careful consideration of these factors, it becomes possible to enhance the overall performance of GAA VNWFETs, particularly in mitigating temperature hot-spots and addressing challenges associated with SHEs.
Understanding the depolarization phenomena in (1−x) Na0.5Bi0.5TiO3. (x) Ba0.85Ca0.15Ti0.90Zr0.10O3 solid solutions using in-situ temperature dependent Raman spectroscopy
Authors: Samantaray Koyal Suman , Maneesha P , Bhaumik Indranil , Sen Somaditya
Published: May 2024

A decrease in depolarization temperature (T
d) from 456 K to 352 K was observed with an increase in BCZT substitution in the NBT for the (1−x) Na0.5Bi0.5TiO3. (x) Ba0.85Ca0.15Ti0.90Zr0.10O3 solid solutions. A transition towards a higher ergodic state was elucidated with an increase in BCZT content that helped to reduce the free energy barrier, hence lesser thermal energy was required to depolarize the modified systems. Furthermore, a decrease in remnant polarization and coercive field, coupled with an increase in energy storage (W
stored) and efficiency (η%) with higher BCZT content. In-situ temperature-dependent Raman spectra provide additional insights, highlighting the faster changes in phonon shifts and lifetimes corresponding to the A–O, B–O, and BO6 vibrations around the depolarization temperature (T
d). The observed phase transformation to a P4bm phase at temperatures significantly higher than T
d is substantiated by Raman shift and phonon lifetime variations in the modes associated with the A–O and B–O vibrations. The transitions can be understood as: at T ∼ T
d the polar nano regions (PNRs) start to appear due to weakening of bonds, T > T
d all the long-range ferroelectric domains transform to PNRs converting the material to a fully ergodic state, and at much higher temperatures (T ≫ T
d) the R3c PNRs vanish and P4bm PNRs appear.
BerryEasy: a GPU enabled python package for diagnosis of nth-order and spin-resolved topology in the presence of fields and effects
Authors: Tyner Alexander C
Published: May 2024

Multiple software packages currently exist for the computation of bulk topological invariants in both idealized tight-binding models and realistic Wannier tight-binding models derived from density functional theory. Currently, only one package is capable of computing nested Wilson loops and spin-resolved Wilson loops. These state-of-the-art techniques are vital for accurate analysis of band topology. In this paper we introduce BerryEasy, a python package harnessing the speed of graphical processing units to allow for efficient topological analysis of supercells in the presence of disorder and impurities. Moreover, the BerryEasy package has built-in functionality to accommodate use of realistic many-band tight-binding models derived from first-principles.
Quantitative predictive theories through integrating quantum, statistical, equilibrium, and nonequilibrium thermodynamics
Authors: Liu Zi-Kui
Published: May 2024

Today’s thermodynamics is largely based on the combined law for equilibrium systems and statistical mechanics derived by Gibbs in 1873 and 1901, respectively, while irreversible thermodynamics for nonequilibrium systems resides essentially on the Onsager Theorem as a separate branch of thermodynamics developed in 1930s. Between them, quantum mechanics was invented and quantitatively solved in terms of density functional theory (DFT) in 1960s. These three scientific domains operate based on different principles and are very much separated from each other. In analogy to the parable of the blind men and the elephant articulated by Perdew, they individually represent different portions of a complex system and thus are incomplete by themselves alone, resulting in the lack of quantitative agreement between their predictions and experimental observations. Over the last two decades, the author’s group has developed a multiscale entropy approach (recently termed as zentropy theory) that integrates DFT-based quantum mechanics and Gibbs statistical mechanics and is capable of accurately predicting entropy and free energy of complex systems. Furthermore, in combination with the combined law for nonequilibrium systems presented by Hillert, the author developed the theory of cross phenomena beyond the phenomenological Onsager Theorem. The zentropy theory and theory of cross phenomena jointly provide quantitative predictive theories for systems from electronic to any observable scales as reviewed in the present work.
Comparison of shielding effects of over-glasses-type and regular eyewear in terms of occupational eye dose reduction
Authors: Shindo Ryota , Ohno Saya , Yamamoto Keisuke , Konta Satoe , Inaba Yohei , Suzuki Masatoshi , Zuguchi Masayuki , Chida Koichi
Published: May 2024

Given the new recommendations for occupational eye lens doses, various lead glasses have been used to reduce irradiation of interventional radiologists. However, the protection afforded by lead glasses over prescription glasses (thus over-glasses-type eyewear) has not been considered in detail. We used a phantom to compare the protective effects of such eyewear and regular eyewear of 0.07 mm lead-equivalent thickness. The shielding rates behind the eyewear and on the surface of the left eye of an anthropomorphic phantom were calculated. The left eye of the phantom was irradiated at various angles and the shielding effects were evaluated. We measured the radiation dose to the left side of the phantom using RPLDs attached to the left eye and to the surface/back of the left eyewear. Over-glasses-type eyewear afforded good protection against x-rays from the left and below; the average shielding rates on the surface of the left eye ranged from 0.70–0.72. In clinical settings, scattered radiation is incident on physicians’ eyes from the left and below, and through any gap in lead glasses. Over-glasses-type eyewear afforded better protection than regular eyewear of the same lead-equivalent thickness at the irradiation angles of concern in clinical settings. Although clinical evaluation is needed, we suggest over-glasses-type Pb eyewear even for physicians who do not wear prescription glasses.
Blade fouling fault detection based on shaft orbit generative adversarial network
Authors: Huang Xin , Ma Jun , Shao Huajin , Chen Wenwu , Qu Dingrong , Pan Long , Zhang Weiya
Published: May 2024

To address the challenges of accuracy and interpretability in mechanical fault detection models, this study proposes a shaft orbit generative adversarial network (SOGAN) and applies it to detect blade fouling faults. Variational autoencoder (VAE) is used as the foundational network architecture for extracting high-dimensional latent features from the shaft orbit images. Concurrently, the invariant moments of the shaft orbit images are extracted and embedded in a bypass within the generator, thereby enhancing the accuracy of fault detection. Two sets of real-world blade fouling fault data are collected and meticulously analyzed. The proposed SOGAN model demonstrates significant performance improvements, with average increases of 18.91%, 10.20%, and 26.79% in accuracy compared to the autoencoder, VAE, and GANomaly algorithms, respectively. The F1 scores for both the groups exceed 0.98. The data generated by the proposed SOGAN model exhibit a trend-wise correspondence with the finite element modeling data. In addition, the use of gradient information for the localization and visual analysis of anomalies dynamically tracks the spatial evolution of the rotor shaft orbit throughout its lifecycle. The data generation capability and interpretability of the proposed model can effectively support digital twin modeling and health management of rotating machinery.
DGVINS: tightly coupled differential GNSS/visual/inertial for robust positioning based on optimization approach
Authors: Li Xiaowan , Cheng Fang , Li Yuanqi , Shen Pengli , Hu Yuhang , Lu Xiaochun
Published: May 2024

Due to the fragility of single-sensor positioning technology in complex scenarios, especially in complex urban areas, multi-sensor positioning technology is becoming increasingly popular. To further improve the robustness of the positioning system by fully utilizing the information from various sensors, this article proposes a differential-GNSS-visual-inertial navigation system (DGVINS) that tightly fuses differential global navigation satellite system (GNSS), vision and inertial information to provide accurate, robust and seamless position information for intelligent navigation applications. DGVINS effectively utilizes all sensor measurements within the factor graph optimization framework. When using the carrier phase of GNSS, single-epoch ambiguity optimization is employed to prevent cycle slip detection and adapted to complex environments. We conducted experiments on public datasets with various features and compared the performance of simple differential-GNSS (DGNSS), DGNSS + Inertial, and the state-of-the-art GNSS-visual-inertial navigation systems. We also compared the performance of different combinations of GNSS differential factors in various environments. Due to the superiority of differential GNSS and its appropriate integration with visual and inertial measurements, the experimental results demonstrate that DGVINS exhibits significant improvements in accuracy, stability, and continuity in both GNSS-challenged and vision-challenged environments.
Enhancing motor impedance measurements: broadening the spectrum from low to high frequencies
Authors: Jie Huamin , See Kye Yak , Chang Yongqi , Gao Richard Xian-Ke , Fan Fei , Zhao Zhenyu
Published: May 2024

Three-phase induction motors serve as critical parts in various industrial applications, lauded for their high energy efficiency and notable power density. Obtaining their broadband impedance information is paramount for analyzing conducted emissions, evaluating overvoltage ringing, and assessing motor health status. Nonetheless, conventional methods for motor impedance measurements typically rely on Kelvin clip leads or extension cables, which are effective only in a relatively low-frequency region (i.e. below 1 MHz). This paper presents an improved approach to extend the measurable spectrum from low to high frequencies, up to 120 MHz. The proposed method develops a series of fixture adapters to enable seamless interconnection between the terminals of an induction motor and the coaxial ports of an impedance analyzer. The parasitics introduced by these adapters are identified using boundary-element analysis, and their impacts are minimized based on the de-embedding concept. Experimental results affirm the accuracy and effectiveness of the proposed method for four types of motor impedances (i.e. single-phase, phase-to-ground, common-mode, and differential-mode) across a broad frequency range from 100 Hz to 120 MHz. Moreover, the inaccuracy of motor impedance measurements at high frequencies (i.e. above 1 MHz) using conventional methods, including Kelvin clip leads and extension cables, is also demonstrated.
Reply to comment on ‘Modeling for predicting survival fraction of cells after ultra-high dose rate irradiation’
Authors: Shiraishi Yuta , Matsuya Yusuke , Fukunaga Hisanori
Published: May 2024

Liew and Mairani commented on our paper ‘Modeling for predicting survival fraction of cells after ultra-high dose rate irradiation’ (Shiraishi et al 2024a Phys. Med. Biol.
69 015017), which proposed a biophysical model to predict the dose–response curve of surviving cell fractions after ultra-high dose rate irradiation following conventional dose rate irradiation by considering DNA damage yields. They suggested the need to consider oxygen concentration in our prediction model and possible issues related to the data selection process used for the benchmarking test in our paper. In this reply, we discuss the limitations of both the present model and the available experimental data for determining the model’s parameters. We also demonstrate that our proposed model can reproduce the experimental survival data even when using only the experimental DNA damage data measured reliably under normoxic conditions.
Incorporating large larmor radius effects in the full wave code TORIC
Authors: Brambilla Marco , Bilato Roberto
Published: May 2024

In this note we describe how Large Larmor Radius corrections can be incorporate in TORIC and other codes which solve the Finite Larmor Radius wave equations in toroidal axisymmetric geometry.
Characterization of a filamentary discharge ignited in a gliding arc plasmatron operated in nitrogen flow
Authors: Böddeker Simon , Gröger Sven , Bibinov Nikita , Awakowicz Peter
Published: May 2024

A gliding arc plasmatron (GAP) is a promising warm plasma source for the use in gas conversion applications but lacks an understanding of the plasma dynamics. In this paper, the gliding arc plasma conditions of a GAP operated with nitrogen flow (10 slm) are characterized using optical emission spectroscopy (OES) and numerical simulation. A simultaneously two-wavelength OES method and Abel inversion of the measured images with a spatial resolution of 19.6 μm are applied. The collisional radiative model used in this study includes Coulomb collisions of electrons. An iterative method of plasma parameter determination is applied. The determined values of the electric field up to 49 Td and electron density up to 2.5∙1015 cm−3 fit well to the plasma parameters received with different diagnostics methods in comparable plasma sources. Additionally, the electric current, which is calculated using the determined reduced electric field and electron density, is compared with the measured one.
Superjunction IGBT with split carrier storage layer
Authors: Yoon Tae Young , Shin Dongho , Kim Hyunwoo , Kim Jang Hyun
Published: May 2024

The insulated gate bipolar transistor (IGBT) is crucial in high-voltage applications due to its characteristics, like breakdown voltage (BV) and on-state voltage V
CE(sat). However, its slower turn-off time, attributed to hole mobility, restricts its frequency range. Techniques such as the carrier storage layer (CSL) and super-junction (SJ) structures aim to optimize BV and V
CE(sat) through hole density and field distribution. Combining CSL and SJ offers advantages, yet challenges remain regarding E-field concentration. In this work, the split CSL concept introduces a solution by optimizing BV and E
off through effective field distribution and hole extraction acceleration respectively while maintaining V
CE(sat). Split CSL, which is divided into a high doping layer (HDL) and a low doping layer (LDL), reduces the burden on the gate oxide by distributing the E-field evenly when in the off-state due to the difference in doping concentration. During the turn-off, the hole current is concentrated on the LDL, which has relatively low resistance, thereby accelerating hole extraction. Simulation-based results showcase improvements in the proposed structure’s properties. Further optimization of HDL and LDL concentrations enhances the structure’s performance. It is clear that the split CSL structure presents the potential for advancing IGBT capabilities. The application of the split CSL structure resulted in significant improvements: the turn-off time was reduced by 32.4% and the BV increased by 32.5 V compared to conventional CSL-SJ structures. These enhancements highlight the effectiveness of the split CSL design in optimizing the IGBT’s performance attribute.
Tunable rebound of millimeter-sized rigid balls by magnetic actuation of elastomer-based surface microstructures
Authors: Kriegl Raphael , Jezeršek Matija , Kravanja Gaia , Hribar Luka , M Mukhi Soham , Kokot Gašper , Drevenšek-Olenik Irena , Shamonin Mikhail
Published: May 2024

A novel method for controlling the rebound behavior of small balls made of Al2O3 with a radius of 2.381 mm is presented. It uses different types of micro-structured surfaces of soft magnetoactive elastomers. These surfaces were fabricated via laser micromachining and include fully ablated surfaces as well as micrometer-sized lamellas with a fixed width of 90 µm, height of 250 µm and three different gap sizes (15, 60 and 105 µm). The lamellas can change their orientation from edge-on to face-on configuration according to the direction of the external magnetic field from a permanent magnet. The orientation of the external magnetic field significantly influences the rebound behavior of the balls, from a coefficient of restitution e of

≈

0.5

to < 0.1. The highest relative change in the coefficient of restitution between zero field and face-on configuration of

≈

80
%

is observed for lamellas with a gap of 60 µm. Other characteristics of the ball rebound such as the penetration depth into an Magnetoactive elastomer and the maximum deceleration are investigated as well. The proposed method does not require a constant power supply due to the use of permanent magnets. It may find novel applications in the field of impact engineering.
RBFNN-based UWB 4 × 4 MIMO antenna design with compact size, high isolation, and improved diversity performance for millimeter-wave 5G applications
Authors: Sellak Lahcen , Khabba Asma , Chabaa Samira , Ibnyaich Saida , Yong Vincent Kai Loung , Baddou Atmane , Zeroual Abdelouhab
Published: May 2024

The millimeter-wave spectrum has emerged as a compelling solution to address the pressing need for high-data-rate capabilities in the development of 5G technology systems. Spanning between 20 GHz and 40 GHz, this spectrum encompasses several prominent frequency bands crucial for advancing 5G applications. In light of this, our study presents a thorough investigation into the design and performance of a compact cross-shaped slot broadband antenna, complemented by a 4 × 4 Multiple-Input Multiple-Output (MIMO) configuration tailored for 5G operations at 28 GHz. The primary objective of this study is to develop an antenna system capable of achieving an extended bandwidth ranging from 20 GHz to 40 GHz, effectively covering the crucial frequency bands essential for 5G millimeter-wave (mmWave) operations. To accomplish this, the optimization of antenna performance is meticulously carried out using the Radial Basis Function Neural Networks (RBFNN) model. The RBFNN model serves as a robust tool for establishing the intricate relationship between antenna dimensions, resonant frequency, and bandwidth. Subsequently, the developed RBFNN model is employed to predict optimal antenna dimensions, ensuring resonance at 28 GHz and meeting specified bandwidth targets. The single antenna is designed with a rectangular patch and a cross-shaped slot and is constructed on the low loss Rogers RT Duroid 5880 substrate. This design reaches an outstanding bandwidth of 19.5 GHz, and exhibits excellent radiation characteristics, with a high radiation efficiency of up to 99% and a corresponding gain of 5.75 dB. The antenna’s design and performance are rigorously designed using HFSS software, which is then compared to the results acquired using CST software. In addition, the proposed MIMO configuration offers excellent performance in terms of key features such as small size (16×16.2 mm2), very wide bandwidth of 20 GHz, good gain of 6.75 high isolation exceeding 35 dB, and significant improvements in diversity performance measures such as Envelope Correlation Coefficient (ECC), Diversity Gain (DG), Channel Capacity Loss (CCL), Total Active Reflection Coefficient (TARC), and Mean Effective Gain (MEG). The potential of the proposed MIMO configuration for high-speed applications is particularly remarkable. Practical verification of the MIMO configuration is carefully carried out by fabrication and measurement. Experimental results strongly confirm the effectiveness of the proposed antenna design, establishing it as a competitive challenger for 5G technology.
Rapidly chemical preparation of Mn doped ZnO nanostructures for photocatalysis efficiency based on UV light system and mechanism insights
Authors: Fatolahi Leila , Janani Baadal Jushi
Published: May 2024

Through a facile chemical precipitation process, pure zinc oxide (ZnO) and various ratio of Mn-doped zinc oxide (Zn1-xMnxO) nanostructured materials were synthesized. The degradation of an azo dye acid orange 2 (AO-2) solution under UV light was investigated using the synthesized materials as photocatalysts. XRD, FTIR, DLS, FESEM, EDS, PL, BET, magnetic, TGA and UV–vis techniques were used to elucidate the structural, functional, particle, elemental, morphological, and optical aspects of the catalysts. The XRD and FESEM analysis showed the hexagonal ZnO structure and spherical shape of the ZnO nano-photocatalyst, respectively. The crystal sizes of Zn1-xMnxO are 27.40–38.31 nm. The optical band gap energy of Zn1-xMnxO are 2.53–3.10 eV. Under UV irradiation for 60 min, MZ-25 NPs demonstrated better degradation (100.0%) of AO-2 dye. The effect of various factors such as catalyst quantity, and pH of the dye solution on the rate removal was investigated. After 60 min of UV light irradiation, dye removal was obtained under ideal conditions (with catalyst loading of 3 mgL−1, and pH 4). The rate constant values of MZ-25 sample are determined to be 0.0219 min−1. The scavenging test reveals that ∙O2
− and ∙OH are responsible for the photo-degradation of AO-2 dye.
Multiple optomechanically induced transparency generated slow light in an array of optomechanical system
Authors: Xie Bao-Hao , Chen Hua-Jun
Published: May 2024

We present an array of optomechanical systems which consist of an optical cavity and three nanomechanical resonators. Introducing Jaynes-Cumming (J-C) coupling in the nearest neighbor resonator allows for the formation of optomechanical systems with arrays of N nanomechanical resonators. Using a strong pump field and a weak probe field to drive the optical cavity simultaneously, we investigated the coherent optical response and the probe transmission spectrum manifested as multiple optomechanically induced transparency. We illustrate the impact of probe-cavity detuning, J-C coupling strength, and the number of nanomechanical resonators on the transparent window. In particular, we analyze nanomechanical resonators and find that increasing their number results in multiple transparent windows and slow light at different frequencies. We also find that the slow light effect can be enhanced by increasing the number of nanomechanical resonators with odd numbers at resonance. These findings imply that the arrays of optomechanical system can be used for multichannel optical communications and multichannel quantum information processing.
Radiation-induced defects in the InGaN/GaN superlattice structure
Authors: Li Ye , Jiang Shangting , He Hongyu , Wang Xinlin
Published: May 2024

With the molecular dynamics method, this paper investigates radiation-induced defects in the In0.16Ga0.84N/GaN superlattice structure (SLS) and the In0.04Ga0.96N/GaN SLS. In the temporal evolution of cascades, most of vacancies recombine with interstitials. The Monte Carlo simulations about the proportions of PKAs induced by 3 MeV protons were also considered in this work for calculating the weighted averages of surviving defects. For the In0.16Ga0.84N/GaN SLS irradiated by protons, around 82.6 percent of surviving vacancies are Ga vacancies while around 88.9 percent of surviving interstitials are Ga interstitials. For the In0.04Ga0.96N/GaN SLS irradiated by protons, around 87.3 percent of surviving vacancies are Ga vacancies while around 88.6 percent of surviving interstitials are Ga interstitials. N vacancies, N interstitials, and In vacancies also exist in irradiated InGaN/GaN SLS. Details about different types of defects are presented in this paper, which helps explain the microscopic mechanism of irradiated InGaN/GaN SLS. Since different types of defects have different influences on electronic and optical properties, simulations about the proportions of various defects in irradiated InGaN/GaN SLS help experimentalists find the effective factors of radiation-related changes in electronic and optical properties.
Effective action approach for preheating
Authors: Xu Bin , Xue Wei
Published: May 2024

We present a semiclassical non-perturbative approach for calculating the preheating
process at the end of inflation. Our method involves integrating out the decayed particles within
the path integral framework and subsequently determining world-line instanton solutions in the
effective action. This enables us to obtain the effective action of the inflaton, with its
imaginary part linked to the phenomenon of particle creation driven by coherent inflaton field
oscillations. Additionally, we utilize the Bogoliubov transformation to investigate the evolution
of particle density within the medium after multiple inflaton oscillations. We apply our approach
to various final state particles, including scalar fields, tachyonic fields, and gauge fields.
The non-perturbative approach provides analytical results for preheating that are in accord with
previous methods.
Electromagnetically induced gratings created by extremely short non-overlapping pulses of light in a three-level resonant medium
Authors: Arkhipov Rostislav
Published: May 2024

In a fixed spectral range, single- and half-cycle electromagnetic pulses have the shortest duration. Half-cycle pulses are promising tools for ultrafast control of quantum systems. Previously, the possibility of using a sequence of single- and half-cycle attosecond pulses to generate and ultrafast control light-induced population difference gratings has been demonstrated. However, such studies have been carried out using different approximations, such as the sudden perturbation theory and the two-level model for the resonant medium. In this paper, based on the numerical solution of constitutive equations for elements of the density matrix and wave equation it is shown that it is possible to generate and control population gratings in a three-level medium without using the approximation of sudden perturbations used in previous studies. It is shown that taking into account the additional level of the medium does not lead to a violation of the effect of generating such gratings. This extends the applicability of previous results.
An efficient frequency-domain based methodology for the preliminary design of FOWT substructures
Authors: Reig M A , Mendikoa I , Petuya V
Published: May 2024

An efficient frequency domain numerical tool for the preliminary design of the Floating Offshore Wind (FOW) substructures is developed, and validated against one of the leading state-of-the-art time domain based numerical tools: OpenFAST. It has been proven that the present tool enables to reach to similar conclusions as the state-of-the-art tools with a substantial reduction of the computational effort. This is achieved through two novel methods that obtain the hydrodynamic loads acting on the floating substructures. One estimates the linear hydrodynamic coefficients, and the other predicts the second-order wave loads. When combined with a simplified frequency domain response model, a quick assessment of the dynamics of numerous platform designs can be performed, accelerating the floater preliminary design process. The proposed method has been validated by carrying out a comparative analysis on a semi-submersible platform design space, characterised by the column diameter, the separation between the columns and the platform draft. The response motions have been compared against OpenFAST. Furthermore, the high efficiency of the proposed frequency domain tool makes it suitable to perform several sensitivity analyses that will allow for a better understanding of the dynamics and fine tune the foundations design accordingly from the early stages of design.
Experimental Development and Field Validation of Rock Anchors for Sustainable Onshore Foundations
Authors: Suchorzewski Jan , Flansbjer Mathias , Chaudhari Ojas , Williams Portal Natalie
Published: May 2024

The development of an innovative rock anchor prototype manufactured using high strength steel sheets produced locally in Sweden is the core of the PROWIND concept. Steel sheets provide a design freedom to easily manufacture complex geometries, which can be advantageous to enhance the shear force transmission in the bond-length segment of the anchor. The underlying challenge of this concept has been to design a solution which meets the design requirements of today and future technological advancements, all while keeping conventional installation practices in mind. The project followed a 4-step development process: (1) concept analysis and modelling, (2) small-scale prototypes testing and (3) large scale lab-validation and lastly (4) field validation. The performance of the developed rock anchor prototype and grouting material was experimentally quantified on both small and large-scale test specimens and also validated in full scale in the field concerning installation process, proof-loading and maintaining the prestress over time. The PROWIND anchors with the end feature with ribbed design have 4-5 times higher load bearing capacity. The experience from the anchor installation proved that the developed grout and anchors are faster and easier to install. The field test in two different geological conditions has proven that the news design is reducing the required anchorage length to just 1 meter. The restressing of anchors is fully possible with the proposed lock-off solution with a nut. All of those contribute to lower costs of installations and possibly longer service-life.
Scalable SCADA-Based Calibration for Analytical Wake Models Across an Offshore Cluster
Authors: Binsbergen Diederik van , Daems Pieter-Jan , Verstraeten Timothy , Nejad Amir , Helsen Jan
Published: May 2024

A multi-level hyperparameter optimization framework is performed to calibrate analytical wake models in the context of multiple wind farms within the Belgian-Dutch offshore cluster. The calibration, applied on the TurbOPark model with Gaussian wake profile, is performed on different scales. Initially, calibration focused solely on internal wake effects, followed by a calibration for individual wind farms, considering both internal and external wake effects, and finally performing the calibration using SCADA data from multiple wind farms within the concession zone, with and without accounting for blockage. It was observed that calibrating wakes for freeflow wind directions using internal wakes only results in tuning parameters similar to the calibration involving both intra-and-inter farm wake effects. Minor variations are noted between wind farms, with dependencies on wind speed and wind direction across all cases. When the tuning parameter is calibrated using SCADA data from multiple wind farms, a significant reduction in the tuning parameter was observed, compared to calibration that focuses on one wind farm per calibration. Analyzing the model residual error for wind coming from the north-west reveals that the calibrated wake model effectively accounts for cluster wake effects. Furthermore, a consistent and substantial presence of heterogeneous inflow perpendicular to the wind direction originating from the south-west is observed, which is not captured by the modeling framework, which assumes homogeneous inflow. The observed trend of inflow heterogeneity suggests that the discrepancy cannot be attributed solely to blockage effects.
Enhancing standard CFD based practices for site assessment through polynomial surrogates for estimating uncertainty in wind speed
Authors: Lakdawala Zahra , Kassem Hassan , Schulte Jonas
Published: May 2024

One of the challenges in digitizing the wind energy sector is to have reliable, accurate and efficient data assessment and prediction tools. We believe that accurate surrogates are key towards improving efficiency and reliability for informed decision making. For a quantitative understanding of wind and energy in complex terrains, a detailed site assessment is done, most often using mesoscale and/or microscale computational fluid dynamics (CFD) based approach. Typically, one would require multiple scenarios/case for a CFD simulator to incorporate the influence of a parameter on variability of wind speed and energy production. These simulations are computationally expensive, and the industry is constantly on a look out for more efficient methods. Towards this end, we propose using a polynomial surrogate based on Polynomial Chaos Expansion (PCE) for uncertainty quantification that requires only a few CFD simulations to assess the variability of wind speed with respect to variability in an input parameter. The variability estimates from PCE were first validated against the standard Monte Carlo method on simple benchmarks and then tested for complex terrains. In this work, we present results that help us understand how canopy foliage, particularly its height, impacts the variability in wind speed in complex terrains. Since the polynomial surrogate relies only on a limited set of input variations (forest height) to estimate the variability distributions for wind speed locally (for specified points of interests), it has proven to be a low-cost and accurate method for estimating uncertainty. In this paper, we discuss the results for wind speed variability for five sites with varying complexity using the polynomial surrogate model. Furthermore, the singular value decomposition (SVD) entropy value is used to quantify terrain complexity for the sites considered. We show how the variability in wind speed can potentially be correlated to terrain complexity. This is our first attempt in providing an empirically (including multiple sites) derived relationship that can be used as a basis for fast and reliable variability estimator for wind resource planners.
Linking the microstructure with strain-life curves for improved utilization of the lightweight potential of thick-walled nodular cast iron
Authors: Pittel C , Niewiadomski J , Bleicher C
Published: May 2024

The assessment of the fatigue life of critical, highly stressed component areas is an important aspect in the design of thick-walled components for wind turbines made of nodular cast iron. With the demand for resource efficiency through lightweight design combined with a certain capability to withstand extreme loads and special events, this issue is becoming increasingly important. However, there are still gaps in the description of local strain-based material behaviour. For the design and local strain-based fatigue assessment of large cast components, possibilities to determine the fatigue life as accurately as possible must be provided by standards and guidelines. The paper aims to provide a wide range of material and fatigue data from one common source for general design interests. During research projects at Fraunhofer LBF, material properties for the PRAM-based fatigue life assessment and the elastic-plastic material behaviour have been derived from 9 nodular cast iron grades with 44 microstructural variations. To describe the influence of the technological size effect on cyclic stress-strain and PRAM-N curves the quasi-static parameters (tensile strength and elongation at break) and the microstructure (nodularity and graphite particle density) are considered. In addition, suggestions for scatter bands in the strain-based design approach are given to the designers of thick-walled GJS components.
The compatibility of nitrided W18Cr4V steel in a sodium environment
Authors: Fu Xiaogang , Liang Na , Zhang Wei , Tao Liu , Qin Bo , Ruan Zhangshun , Long Bin
Published: May 2024

The guideway friction pairs are the key components of the loading elevator and unloading elevator in the refueling system for sodium cooled fast reactor. With the excellent hardness and wear resistance in air, nitrided W18Cr4V steel is a candidate material for the guideway friction pairs. In order to evaluate the applicability in the high-temperature sodium, it is important to conduct the compatibility tests of nitrided W18Cr4V steel for different exposure time. The results show that the nitrogen content of nitrided W18Cr4V steel decreased obviously after 1000 h, 2000 h and 3000 h sodium compatibility tests at 540 °C and the nitrided strengthening effect of W18Cr4V steel gradually decreased with the test duration increasing.
Advancements in perovskite solar cell efficiency through blade coating techniques and post-treatment optimization
Authors: Qiang Ziyue , Wu Yao , Wang Caixia , Gao Xiang , Li Jihong , Sun Shuang , Dong Ningbo , Jiang Jun , Zhao Xiaoxia
Published: May 2024

Addition of lead chloride (PbCl2) improves the crystallization kinetics of perovskites by suppressing the formation of δ-phase during large-area perovskite film fabrication. However, this addition results in formation and accumulation of lead iodide (PbI2) platelet atop the film, which adversely affects carrier transport. To eliminate the negative effect of PbI2 accumulation and simultaneously obtain a dense, mirror-like perovskite film, a post-treatment method involving blade coating formamidinium iodide (FAI) under air atmosphere is used. Instead of being washed away, as reported in literatures using spin coating process, PbI2 platelets are converted into cesium lead halide perovskites (CsPbX3) through reaction with Cs and halide present in the original perovskite Cs0.22FA0.78Pb(I0.85Br0.15)3. An efficiency enhancement of (>10%) is achieved by FAI treatment, which does not require fast solvent removal or nitrogen (N2) atmospheres, indicating that FAI blade coating is an effective and straightforward method for the post-treatment of excess PbI2.
Forgetfulness of turbulent energy cascade associated with different mechanisms
Authors: Araki Ryo , Vela-Martín Alberto , Lozano-Durán Adrián
Published: May 2024

The small scales of high Reynolds number turbulence exhibit the statistical universality by forgetting about the large scales during the energy cascade. In this study, we revisit this schematic description with an information-theoretic point of view. Our objective is to understand the importance of different cascade mechanisms in this process. To this end, we compute the “information flux”, the information-theoretic measure of causality formulated by one of the authors, of the decomposed inter-scale energy transfer. For the kinetics, the ratio of the inertial-range inter-scale energy transfer between the strain self-amplification (SSA) and the vortex stretching (VS) mechanisms is 5 : 3. However, for the information-flux, the VS contribution is roughly twice as large as the SSA. We also find several deviations between the kinetics and the informatics, highlighting the nontrivial nature of information distributed among different scales and mechanics in turbulence. This result infers that the SSA is a less efficient mechanism than the VS in terms of information transfer, and contributes to losing the large-scale information.
Predictability of decay events in transitional wall-bounded flows
Authors: Morón Daniel , Vela-Martín Alberto , Avila Marc
Published: May 2024

Extreme events in turbulent flows are in general linked with sudden changes in the dynamics of the system. Despite the increasing interest in modelling these events, their predictability remains largely unexplored. Here we focus on the case of sudden turbulence/chaos decay in pipe flow and in a reduced-order model of shear flows (Moehlis, Faisst and Eckhardt, 2004). We study the predictability of decay events with massive ensembles of simulations. For this purpose we introduce a new pseudo-spectral GPU code to perform fast simulations of turbulent pipe flow and describe a methodology to characterize predictability of decay events using the results of the ensembles of simulations. We report the decrease of predictability as one goes back in time with respect to a decay event, and show that this decrease does not need to be monotonic.
The role of nonlinear interactions in the onset of drag increase in flow over riblets
Authors: Viggiano B , Camobreco C J , Wong J , Luhar M , García-Mayoral R , Chung D , Gayme D
Published: May 2024

Characterizing the mechanisms that contribute to the onset of drag increase over micro-grooves (riblets) as the spacing increases is critical to design strategies for riblet-based drag reduction. This study decomposes the roughness function to investigate different mechanisms associated with the breakdown of drag reduction as riblet spacing is increased. We obtain the roughness function through direct numerical simulations (DNS) in a minimal channel and restricted nonlinear (RNL) models. Both the traditional RNL decomposition and an augmented RNL (ARNL) model that includes additional nonlinear interactions are employed as computationally tractable, reduced order representations of the flow field. RNL and ARNL results are compared to those of DNS in minimal channels to investigate the role of the different scale-dependent nonlinear interactions contributing to the roughness function. A comparison of the co-spectra arising from the minimal channel DNS with that from RNL and ARNL simulations indicates that general trends are captured by both reduced order models. However, the additional nonlinearity introduced in the ARNL model produces closer correspondence in the observed structural features of the DNS results. In particular, the ARNL better captures the signatures of the dispersive flow and the texture-coherent fluctuations. There is also a noticeable improvement observed in the profiles of the added stress contributions obtained with the ARNL model versus the RNL model.
Periodic bursting cycles on the edge to square duct turbulence
Authors: Scherer Markus , Uhlmann Markus , Kawahara Genta
Published: May 2024

The long-time behaviour of trajectories embedded in the edge manifold between the laminar and turbulent basins of attraction is investigated in order to identify simple invariant solutions to the Navier-Stokes equations in straight ducts with square cross-section. With the aid of the iterative bisection procedure of Toh and Itano (J. Fluid Mech., vol. 481, 2003, pp. 67-76), we detect three travelling waves that represent attracting ‘edge states’ within the separatrix and saddles w.r.t. the full state space. All three travelling waves are presumably connected to solutions known in the community. In other situations, the edge states to which trajectories are attracted seem to be invariant periodic cycles that feature a rich dynamics: Along each cycle, the flow oscillates periodically between two flow states, in each of which streamwise vorticity is predominantly residing near one set of parallel walls, while the vortical activity associated to the other pair of opposing walls is markedly reduced. This ‘switching’ dynamics is accompanied by intermittent bursting-like high-dissipation excursions. While we cannot rigorously prove that the identified periodic cycle is a periodic orbit rather than a finite-precision approximation to a heteroclinic cycle, sound arguments for the former supposition are given. Interestingly, the different phases of the periodic cycle qualitatively resemble a similar ‘switching’ behaviour observed in (chaotic) marginal turbulence, which suggests that the found periodic cycles could help understanding the characteristic dynamics of duct turbulence at low Reynolds numbers.
Prediction of turbulent energy based on low-rank resolvent modes and machine learning
Authors: Fan Yitong , Chen Bo , Li Weipeng
Published: May 2024

A modelling framework based on the resolvent analysis and machine learning is proposed to predict the turbulent energy in incompressible channel flows. In the framework, the optimal resolvent response modes are selected as the basis functions modelling the low-rank behaviour of high-dimensional nonlinear turbulent flow-fields, and the corresponding weight functions are determined by data-driven neural networks. Turbulent-energy distribution in space and scales, at the friction Reynolds number 1000, is predicted and compared to the data of direct numerical simulation. Close agreement is observed, suggesting the feasibility and reliability of the proposed framework for turbulence prediction.
Matrix numerical method for probability densities of stochastic delay differential equations
Authors: Antary Nils , Holubec Viktor
Published: May 2024

Stochastic processes with time delay are invaluable for modeling in science and engineering when finite signal transmission and processing speeds can not be neglected. However, they can seldom be treated with sufficient precision analytically if the corresponding stochastic delay differential equations (SDDEs) are nonlinear. This work presents a numerical algorithm for calculating the probability densities of processes described by nonlinear SDDEs. The algorithm is based on Markovian embedding and solves the problem by basic matrix operations. We validate it for a broad class of parameters using exactly solvable linear SDDEs and a cubic SDDE. Besides, we show how to apply the algorithm to calculate transition rates and first passage times for a Brownian particle diffusing in a time-delayed cusp potential.