bluuebunny/crossref_metadata_2025 huggingface dataset:
The Alarming Situation of Highly Pathogenic Avian Influenza Viruses in 2019–2023
Authors: Zhang Zhiwei , Lei Zhao
Published: June 2024

Avian influenza viruses (AIVs) have the potential to cause severe illness in wild birds, domestic poultry, and humans. The ongoing circulation of highly pathogenic avian influenza viruses (HPAIVs) has presented significant challenges to global poultry industry and public health in recent years. This study aimed to elucidate the circulation of HPAIVs during 2019 to 2023. Specifically, we assess the alarming global spread and continuous evolution of HPAIVs. Moreover, we discuss their transmission and prevention strategies to provide valuable references for future prevention and control measures against AIVs.
Disinformation on the COVID-19 pandemic and the Russia-Ukraine War: Two sides of the same coin?
Authors: Sánchez del Vas Rocío , Tuñón Navarro Jorge
Published: June 2024

Recently, Europe has been embroiled in serious disinformation crises. In 2020, the WHO declared the term “infodemic” due to the massive increase in hoaxes about the COVID-19 pandemic. In 2022, Russia’s invasion of Ukraine was dubbed the first digital world war. In this context, this research aims to establish similarities and differences between disinformation disseminated in Europe related to the pandemic during 2020–2021 and the war between Russia and Ukraine throughout 2022–2023. The methodology is based on triangulation, combining quantitative content analysis of fact-checking publications (N = 812) from eight fact-checkers representing four European countries (Spain, Germany, the United Kingdom, and Poland) and qualitative interviews with specialized agents (N = 8). Regarding the main findings, the frequency and nature of verified hoaxes during critical events, such as the COVID-19 pandemic and the Ukraine conflict, are closely intertwined with peaks in current events. Initially, both crises saw a surge in hoax verifications, but this trend gradually declined, particularly in the case of the Ukraine conflict. Hoaxes related to the pandemic were primarily disseminated in written form, whereas the complexities of the Russian-Ukraine war hindered widespread hoax dissemination in an audiovisual way. The typology of hoaxes correlated with their format, with fabricated content predominant in pandemic hoaxes and out-of-context images prevalent in those related to the conflict. Social media, notably Facebook and X (Twitter), emerged as the primary platforms for hoax dissemination, overshadowing traditional media channels. In both events, disinformation aimed to provoke emotional responses and polarize audiences, emphasizing the role of social networks in amplifying disinformation during crises.
Theoretical design of molecular diode based on thiol- and amino- terminated molecules
Authors: Yue Xiaolong , Zou Min , Di Xianfei , Wang Ziqin , Hu Wei
Published: June 2024

Utilizing density functional theory (DFT) and non-equilibrium Green’s function, we systematically studied the electrical transport and rectification properties of thiol- and amino-terminated molecules embedded in graphene nanoribbons. We firstly found the thiol-terminated molecules show better electron transport properties compared to the amino-terminated, which can be attributed to the strong electronwithdrawing ability and favorable coupling effects. Secondly, the symmetrical molecules show almost symmetrical current-voltage (I-V) curves and exhibit negligible rectification effects. On the other hand, the asymmetrical molecules exhibit asymmetrical I-V curves and better rectification performance. The rectification effect is closely related to molecular asymmetry degrees. For example, the rectification ratio of asymmetric N6 ((E)-Nl-(3-aminopropyl)-but-2-ene-1,4-diamine) molecule is much smaller than the N4 (5-phenylthiazole-2,4-diamine) and N5 (2,6-diaminohexane-1,1,5-triol) molecules. Furthermore, we found the rectification ratio of the asymmetrical amino-terminated molecules can reach 400, while the biggest rectification ratio of the thiol-terminated molecule can only reach 45. These findings offer crucial insights for future graphene molecular electronic device design.
Topological spectral bands with frieze groups
Authors: Lux Fabian R. , Stoiber Tom , Wang Shaoyun , Huang Guoliang , Prodan Emil
Published: June 2024

Frieze groups are discrete subgroups of the full group of isometries of a flat strip. We investigate here the dynamics of specific architected materials generated by acting with a frieze group on a collection of self-coupling seed resonators. We demonstrate that, under unrestricted reconfigurations of the internal structures of the seed resonators, the dynamical matrices of the materials generate the full self-adjoint sector of the stabilized group C*-algebra of the frieze group. As a consequence, in applications where the positions, orientations and internal structures of the seed resonators are adiabatically modified, the spectral bands of the dynamical matrices carry a complete set of topological invariants that are fully accounted by the K-theory of the mentioned algebra. By resolving the generators of the K-theory, we produce the model dynamical matrices that carry the elementary topological charges, which we implement with systems of plate resonators to showcase several applications in spectral engineering. The paper is written in an expository style.
Chemically reactive and aging macromolecular mixtures. I. Phase diagrams, spinodals, and gelation
Authors: Zhang Ruoyao , Mao Sheng , Haataja Mikko P.
Published: June 2024

Multicomponent macromolecular mixtures often form higher-order structures, which may display non-ideal mixing and aging behaviors. In this work, we first propose a minimal model of a quaternary system that takes into account the formation of a complex via a chemical reaction involving two macromolecular species; the complex may then phase separate from the buffer and undergo a further transition into a gel-like state. We subsequently investigate how physical parameters such as molecular size, stoichiometric coefficients, equilibrium constants, and interaction parameters affect the phase behavior of the mixture and its propensity to undergo aging via gelation. In addition, we analyze the thermodynamic stability of the system and identify the spinodal regions and their overlap with gelation boundaries. The approach developed in this work can be readily generalized to study systems with an arbitrary number of components. More broadly, it provides a physically based starting point for the investigation of the kinetics of the coupled complex formation, phase separation, and gelation processes in spatially extended systems.
Nanoparticle migration on the microchannel wall surface in low-Reynolds-number nanofluids
Authors: Ko Seongjun , Lee Junho , Yu Jiwon , Banerjee Debjyoti , Kang Seok-Won
Published: June 2024

In this study, nanoparticle deposition probabilities were numerically estimated for aqueous TiO2–water nanofluid flows (containing a colloidal suspension of TiO2 nanoparticles with a nominal diameter of 50 nm) in a microchannel under constant heat flux boundary conditions. To determine the effect of different thermo-hydraulic conditions on the nanoparticle migration near the wall surface at very low Reynolds numbers (i.e., ∼5), a user-defined function code for nanoscale interactions between molecules was considered in addition to the Euler–Lagrange model based on conventional computational fluid dynamics and heat transfer methods. The simulation results were compared with experimental observations to assess the accuracy of the numerical model. Furthermore, the effects of various parameters, such as the flow rate, wall temperature, and particle concentration, on the deposition probability of nanofluids were studied. The dominant factors enhancing the deposition probability were as follows: nanoparticle fraction (1.64) > flow rate (1.30) > heat flux (1.0).
Investigation on activation characterization, secondary electron yield, and surface resistance of novel quinary alloy Ti–Zr–V–Hf–Cu non-evaporable getters
Authors: Yigit Kaan , Wang Jie , Si Qingyu , Du Xin , Sun Qiuyu , Zhang Yinqiao , Li Zhifeng , Wang Sheng
Published: June 2024

The performance of next-generation particle accelerators has been adversely affected by the occurrence of electron multipacting and vacuum instabilities. Particularly, minimization of secondary electron emission (SEE) and reduction of surface resistance are two critical issues to prevent some of the phenomena such as beam instability, reduction of beam lifetime, and residual gas ionization, all of which occur as a result of these adverse effects in next-generation particle accelerators. For the first time, novel quinary alloy Ti–Zr–V–Hf–Cu non-evaporable getter (NEG) films were prepared on stainless steel substrates by using the direct current magnetron sputtering technique to reduce surface resistance and SEE yield with an efficient pumping performance. Based on the experimental findings, the surface resistance of the quinary Ti–Zr–V–Hf–Cu NEG films was established to be 6.6 × 10−7 Ω m for sample no. 1, 6.4 × 10−7 Ω m for sample no. 2, and 6.2 × 10−7 Ω m for sample no. 3. The δmax measurements recorded for Ti–Zr–V–Hf–Cu NEG films are 1.33 for sample no. 1, 1.34 for sample no. 2, and 1.35 for sample no. 3. Upon heating the Ti–Zr–V–Hf–Cu NEG film to 150 °C, the XPS spectra results indicated that there are significant changes in the chemical states of its constituent metals, Ti, Zr, V, Hf, and Cu, and these chemical state changes continued with heating at 180 °C. This implies that upon heating at 150 °C, the Ti–Zr–V–Hf–Cu NEG film becomes activated, showing that novel quinary NEG films can be effectively employed as getter pumps for generating ultra-high vacuum conditions.
Aqueous solution chemistryin silicoand the role of data-driven approaches
Authors: Banerjee Debarshi , Azizi Khatereh , Egan Colin K. , Donkor Edward Danquah , Malosso Cesare , Pino Solana Di , Mirón Gonzalo Díaz , Stella Martina , Sormani Giulia , Hozana Germaine Neza , Monti Marta , Morzan Uriel N. , Rodriguez Alex , Cassone Giuseppe , Jelic Asja , Scherlis Damian , Hassanali Ali
Published: June 2024

The use of computer simulations to study the properties of aqueous systems is, today more than ever, an active area of research. In this context, during the last decade there has been a tremendous growth in the use of data-driven approaches to develop more accurate potentials for water as well as to characterize its complexity in chemical and biological contexts. We highlight the progress, giving a historical context, on the path to the development of many-body and reactive potentials to model aqueous chemistry, including the role of machine learning strategies. We focus specifically on conceptual and methodological challenges along the way in performing simulations that seek to tackle problems in modeling the chemistry of aqueous solutions. In conclusion, we summarize our perspectives on the use and integration of advanced data-science techniques to provide chemical insights into physical chemistry and how this will influence computer simulations of aqueous systems in the future.
Conditions for an emergent gauge field in planar artificial spin ices with the dumbbell model approach
Authors: Nascimento F. S. , de Oliveira L. B. , Duarte D. G. , de Araujo C. I. L. , Moura-Melo W. A. , Pereira A. R.
Published: June 2024

Magnetic structure factor (MSF), calculated from ground state configuration previously obtained by Monte Carlo simulation in different rectangular artificial spin ices, is employed to investigate ground state degeneracy. Our analysis considers the importance of nanoislands size to the ratio between rectangle sides in the lattice parameters via a dumbbell model. Pinch points in MSF along with residual entropy, determined for a number of different rectangular lattices with disconnected nanoislands, point out the conditions for the emergency of a gauge field, through which magnetic monopoles interact effectively.
Insights into the structure and dynamics of K+ ions at the muscovite–water interface from machine learning potential simulations
Authors: Raman Abhinav S. , Selloni Annabella
Published: June 2024

The surfaces of many minerals are covered by naturally occurring cations that become partially hydrated and can be replaced by hydronium or other cations when the surface is exposed to water or an aqueous solution. These ion exchange processes are relevant to various chemical and transport phenomena, yet elucidating their microscopic details is challenging for both experiments and simulations. In this work, we make a first step in this direction by investigating the behavior of the native K+ ions at the interface between neat water and the muscovite mica (001) surface with ab-initio-based machine learning molecular dynamics and enhanced sampling simulations. Our results show that the desorption of the surface K+ ions in pure ion-free water has a significant free energy barrier irrespective of their local surface arrangement. In contrast, facile K+ diffusion between mica’s ditrigonal cavities characterized by different Al/Si orderings is observed. This behavior suggests that the K+ ions may favor a dynamic disordered surface arrangement rather than complete desorption when exposed to deionized water.
Expressions of epistemic stance in computer-mediated L2 speaking assessment
Authors: Gablasova Dana , Harding Luke , Brezina Vaclav , Dunlea Jamie
Published: June 2024

Learner and L2 user corpora are increasingly valued in language testing and assessment as they can inform test
design, revision, and validation. This paper illustrates the benefits of using an L2 corpus to explore patterns of epistemic
stance marking in computer-mediated speaking tests with no live human interlocutor. Drawing on the British
Council-Lancaster Aptis Corpus – comprising over 630,000 words of L2 speech – we explored the frequency of epistemic
stance markers (adverbial, adjectival and verbal) across proficiency levels and speaking task types. The analysis revealed that
epistemic stance was prevalent in test-taker discourse and that frequency was influenced by L2 proficiency and task type. The
findings demonstrate that computer-mediated speaking tests can elicit expressions of epistemic stance in a comparable way to tests
which involve human-human interaction. Implications are drawn for examiner training, test preparation, and an enriched
understanding of the elements of pragmatic competence that can be elicited in computer-mediated speaking assessment.
Proficiency-rated learner corpora
Authors: Forti Luciana
Published: June 2024

In this position paper, I argue that proficiency-rated learner corpora should gain a more prominent role in
data-driven learning (DDL). With specific reference to DDL, proficiency-rated learner corpora can provide typical, atypical and
erroneous target language data at different levels of proficiency, which can be meaningfully used in the design of learning
activities. This makes them pivotal in expanding the scope of DDL to include mid- and lower-level proficiency learners more
extensively. Although the field of learner corpus research has been promoting learner corpus use in DDL for a long time, only a
small fraction of DDL studies make use of a learner corpus. As a contribution to overcome this hiatus, I will demonstrate how
using a specific proficiency-rated learner corpus (i.e., the CELI corpus; Spina et al., 2022, 2023) can enrich the design of DDL activities, making
them more adaptable to a wider range of learner needs.
Effect of annealing temperature on the structural, optical, morphological, and photocatalytic properties of TiO2 thin films prepared by sol-gel spin-coating and electron beam physical vapor deposition
Authors: Dong Xiaoshuo , Mamat Mamatrishat , Baikeli Yiliyasi
Published: June 2024

TiO2 thin films were prepared by sol-gel spin-coating (SGSC) and electron beam-physical vapor deposition (EB-PVD) methods and annealed at different temperatures (Ta
). X-ray diffraction spectroscopy (XRD) results show that the TiO2 films prepared by the SGSC method transformed from the anatase single phase to the coexistence of anatase and rutile with the increase of Ta
. However, TiO2 films prepared by the EB-PVD method existed only in the anatase phase, and the crystalline strength was enhanced with the increase of Ta
. Meanwhile, particles of TiO2 targets annealed at different Ta
showed a rutile phase for TiO2 target particles in the EB-PVD method. The results indicate that the EB-PVD method hinders the nucleation growth and phase transformation of TiO2 films. Scanning electron microscopy and atomic force microscopy also show that the grain size and R
ms of TiO2 thin films prepared by the SGSC method increased with the increase of Ta
, and the grain size becomes inhomogeneous when the rutile phase is formed. Ultraviolet–visible results show that the forbidden bandwidth and light absorption capacity increase with increasing Ta
. For the EB-PVD method, the grain size and surface roughness gradually increased when the Ta
of the films was less than 800 °C, while annealing at 800 °C changed the direction of growth and nucleation, and also produced surface cracks; XRD verified the hypothesis that the EB-PVD method hinders the nucleation growth as well as the phase transition of the films. Weak differences in the optical absorption properties and bandgap values of the films also indicate that the EB-PVD method hinders the phase transformation of TiO2 films. Finally, the results of degradation of methylene blue (MB) under simulated visible light showed that the films prepared by the SGSC method gradually improved the photocatalytic performance with the enhancement of the crystalline strength of the anatase phase. The TiO2 films prepared by the EB-PVD method improved the photocatalytic performance with the increase of the active area.
WITHDRAWN: Degradation of phenol in ground and distilled waters by nanosecond discharge plasma in air
Authors: Beloplotov Dmitry Viktorovich , Petrenko Tatiana , Sosnin Eduard A , Kudryashov Sergey , Sorokin Dmitry A , Zhang Cheng
Published: June 2024

Withdrawal

This article has been withdrawn by IOP Publishing following the discovery that several authors are affiliated with an institution (Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences) that is subject to sanctions by the US government. To ensure compliance with sanctions regulations, this article has been withdrawn from IOPscience.
Why the pyrochlore-like antiferromagnet NaCu3F7 is magnetically non-frustrated
Authors: Lévêque Julien , Rebolini Elisa , Lepetit Marie-Bernadette , Saúl Andrés
Published: June 2024

We present a theoretical study of the magnetic properties for the pyrochlore-like NaCu3F7 compound, which surprisingly experience little or no frustration. The magnetic effective exchange interactions were calculated using ab-initio methods explicitly treating the electronic correlation. A model Hamiltonian (quantum Heisenberg Hamiltonian, and for comparison a spin 1/2 Ising Hamiltonian) was built from these interactions and used to determine the zero temperature magnetic order versus magnetic field. The magnetic order at zero magnetic field is non frustrated and associated with the propagation vector

q
→

=
(
0
,
0
,
0
)

. The magnetization versus magnetic field reveals the existence of a 1/3 plateau that could be observed in high-pulsed magnetic field experiments. Analyzing the magnetic interactions, we highlight the importance of the magnetic ion nature, and the lattice distortion, in the non-frustrated nature of the NaCu3F7 magnetic structure, despite its triangular/Kagome subnetworks. We believe that this non-frustrated behavior could also take place in other triangular copper-based systems.
High-temperature magnetic anomaly via suppression of antisite disorder through synthesis route modification in a Kitaev candidate Cu2IrO3
Authors: Haraguchi Yuya , Nishio-Hamane Daisuke , Matsuo Akira , Kindo Koichi , Katori Hiroko Aruga
Published: June 2024

By incorporating inert KCl into the Na2IrO3 + 2CuCl → Cu2IrO3 + 2NaCl topochemical reaction, we significantly reduced the synthesis temperature of Cu2IrO3 from the 350 °C reported in previous studies to 170 °C. This adjustment decreased the Cu/Ir antisite disorder concentration in Cu2IrO3 from ∼19% to ∼5%. Furthermore, magnetic susceptibility measurements of the present Cu2IrO3 sample revealed a weak ferromagnetic-like anomaly with hysteresis at a magnetic transition temperature of ∼70 K. Our research indicates that the spin-disordered ground state reported in chemically disordered Cu2IrO3 is an extrinsic phenomenon, rather than an intrinsic one, underscoring the pivotal role of synthetic chemistry in understanding the application of Kitaev model to realistic materials.
Fermi level pinning in metal oxides: influence on photocatalysis and photoelectrochemistry
Authors: Mamedov D , Karazhanov S Zh , Alonso-Vante N
Published: June 2024

Photocatalysis and photoelectrochemical (PEC) reactions are complex processes involving both the physical properties and surface chemistry of the semiconductor photocatalyst. Their interplay applies specific limitations on the performance of different materials in light-driven reactions, often despite their optimal band structure and optical absorption. One of the ways to properly characterize the photocatalytic and PEC properties of semiconductors remains the measurement of the photopotential, which characterizes a driving force of photoinduced processes in the material. In this work, we give a general scope on the photopotential in PEC reactions that finds its origin in semiconductor physics. It is shown that the photopotential does not always play an interchangeable role with the photocurrent in comparative analysis of the photocatalytic performance of different materials. Furthermore, a correlation between the photopotential and the kinetics of methylene blue dye photocatalysis is shown for anatase-TiO2, CeO2 and WO3 as photocatalysts. Fermi level pinning (FLP) in the bandgap of CeO2 is observed limiting the photoactivity of the compound, which is attributed to the high defectivity of CeO2. A short review is given on the possible origins of FLP in metal oxides and ways to overcome it. It is pointed out that the shift of the Fermi level after illumination of CeO2 can trigger the chemical instability of the material accompanied by the FLP process.
Effect of thermal fluctuations on the nontrivial topology of the d + id superconducting phase
Authors: Groshev A G , Arzhnikov A K
Published: June 2024

The behavior of the topological index (TI), characterizing the properties of superconducting phases of quasi-two-dimensional systems with nontrivial topology, is investigated depending on the temperature and system parameters. For this purpose, a method of calculating the TI, based on a self-consistent functional-integral theory, is proposed. The chiral d + id superconducting phase of a quasi-two-dimensional model with effective attraction between the electrons located at the nearest sites of a triangular lattice is considered. It is shown that the structure of the energy dependence of the self-energy function, which occurs when taking into account thermal fluctuations, does not lead to a change in the topological properties of the system. It is found that taking into account thermal fluctuations with an increase in the effective attraction between electrons expands the temperature range in which the value of the TI is close to the integer

C
1

≃
−
2

.
Topological behavior of spectral singularities in topological Weyl semimetals
Authors: Sarisaman Mustafa , Tasdemir Sevval , Rostamzadeh Saber
Published: June 2024

In this study, we examine the topological character of spectral singularities by using transverse magnetic (TM) mode configuration in a Topological Weyl Semimetal (TWSM). TM mode configuration restrains the effect of Kerr/Faraday rotations and therefore does not allow an extra degree of freedom to occur. We find out that surface currents arise due to topological terms on the surface of TWSM slab where no Fermi arcs are localized. We also investigate the contribution of the Θ-term, which is the origin of axions in topological materials, and especially theb-term, to the topological properties. As a result of our study, we clearly reveal the topological character ofb-term for the first time and we demonstrate the Weyl degeneracy situation in an obvious manner. Our system produces circular currents in the plane of propagation, maintaining a cyclotron shape motion. The presence ofb-term causes the induced current to be topologically protected. Our findings verify that topological properties of TWSM containing two opposite chirality Weyl fermions are robust against external influences. With the findings of our study, the appropriate conditions for the construction of a topological laser and the values that the system parameters can take have been demonstrated.
A hybrid effective medium description for nanoporous gold films and thickness-mediated control of optical absorption
Authors: Singh Jaspreet , Gupta Nitish Kumar , Sarkar Subhendu
Published: June 2024

With the increasing demand for sensing platforms operating across UV, visible, and near-infrared wavelengths, nanoporous gold has emerged as an ideal substrate for rapid, quantitative detection of analytes with excellent specificity and high sensitivity. This study investigates thickness-mediated compositional changes and their impact on scattering characteristics of thin nanoporous gold films fabricated using selective chemical etching. Specifically, we observe thickness-induced morphological and structural changes across different fabricated samples from 25 to 100 nm in thickness. Upon their optical characterization across UV–VIS-NIR spectral regime, we notice that the constitutional differences among samples manifest distinctively & deterministically in their total optical scattering response. In order to gain insights into these observed scattering responses and to fathom the subtle connections between structural properties of NPG films and their optical response, a hybrid theoretical model comprising Maxwell-Garnett & Bruggeman effective medium approximations has been adopted. Our approach not only allows to appropriately account for the inhomogeneous nature of these films, but also corroborates well with the atomic force microscopy characterizations of the fabricated samples. Furthermore, tracing such a theoretical model is important as it helps in systematically ascertaining additional loss terms emerging in the complex dielectric function of films due to their nanoscale porosity & roughness, permitting a good reproduction of measured optical spectra. We believe, our approach will not only facilitate accurate regulation of losses in NPG thin films but will also aid in deriving customized optical performance from them, thereby advancing their potential applications in sensing and beyond.
Method for fabricating a mesh ripple filter for charged-particle therapy
Authors: Tanaka Sodai , Inaniwa Taku
Published: June 2024

Objective. A simple, low-cost ripple filter consisting of multiple mesh sheets (mRiFi) was previously developed to reproducibly widen the Bragg peak of heavy-ion beams. To fabricate the mRiFi, the mRiFi parameters such as the wire material, wire diameter, wire spacing, and number of mesh sheets had to be determined. However, it was unclear how these parameters contribute to shifting and widening of the Bragg peak as well as to lateral spreading of the beam passing through the mRiFi. The purposes of this study were to clarify the contributions and to propose a recipe for fabricating a mRiFi with the desired performance values. Approach. We established an analytical calculation method to estimate shifting and widening of the Bragg peak and lateral spreading of heavy-ion beams passing through the mRiFi for given mRiFi parameter values. We also performed Monte Carlo simulations to validate the analytical calculation method. The recipe for fabricating the mRiFi with desired performances was established based on the analytical calculation method. Using the recipe, we fabricated the mRiFi for multi-ion therapy and evaluated its performance through demonstration experiments with helium-, carbon-, oxygen-, and neon-ion beams. Main results. The difference between the results of the Monte Carlo simulation and the analytical calculation was less than 0.4 mm for the peak shift, 0.15 mm for the peak width, and less than 0.11 mm for the lateral beam size which validated the analytical calculation method. The experimentally observed shift and width of the Bragg peak were consistent with the analytical calculations. Significance. We proposed a method to determine mRiFi parameters for fabricating a mRiFi with a desired performance, i.e. adequate widening of the Bragg peak with an acceptable peak shift and lateral beam spread. The proposed method allows anyone to fabricate a simple and low-cost mRiFi satisfying desired specifications.
Integrating muscle fiber orientation from visible human data into radiotherapy target volumes
Authors: Buti Gregory , Ajdari Ali , Chen Yen-Lin , Bridge Christopher P , Sharp Gregory C , Bortfeld Thomas
Published: June 2024

Objective. A major challenge in treatment of tumors near skeletal muscle is defining the target volume for suspected tumor invasion into the muscle. This study develops a framework that generates radiation target volumes with muscle fiber orientation directly integrated into their definition. The framework is applied to nineteen sacral tumor patients with suspected infiltration into surrounding muscles. Approach. To compensate for the poor soft-tissue contrast of CT images, muscle fiber orientation is derived from cryo-images of two cadavers from the human visible project (VHP). The approach consists of (a) detecting image gradients in the cadaver images representative of muscle fibers, (b) mapping this information onto the patient image, and (c) embedding the muscle fiber orientation into an expansion method to generate patient-specific clinical target volumes (CTV). The validation tested the consistency of image gradient orientation across VHP subjects for the piriformis, gluteus maximus, paraspinal, gluteus medius, and gluteus minimus muscles. The model robustness was analyzed by comparing CTVs generated using different VHP subjects. The difference in shape between the new CTVs and standard CTV was analyzed for clinical impact. Main results. Good agreement was found between the image gradient orientation across VHP subjects, as the voxel-wise median cosine similarity was at least 0.86 (for the gluteus minimus) and up to 0.98 for the piriformis. The volume and surface similarity between the CTVs generating from different VHP subjects was on average at least 0.95 and 5.13 mm for the Dice Similarity Coefficient and the Hausdorff 95% Percentile Index, showing excellent robustness. Finally, compared to the standard CTV with different margins in muscle and non-muscle tissue, the new CTV margins are reduced in muscle tissue depending on the chosen clinical margins. Significance. This study implements a method to integrate muscle fiber orientation into the target volume without the need for additional imaging.
A transient site balance model for atomic layer etching
Authors: Vella Joseph R , Hao Qinzhen , Elgarhy Mahmoud A I , Donnelly Vincent M , Graves David B
Published: June 2024

We present a transient site balance model of plasma-assisted atomic layer etching of silicon (Si) with alternating exposure to chlorine gas (Cl2) and argon ions (Ar+). Molecular dynamics (MD) simulation results are used to provide parameters for the model. The model couples the dynamics of a top monolayer surface region (‘top layer’) and a perfectly mixed subsurface region (‘mixed layer’). The differential equations describing the rates of change of the Cl coverage in the two layers are transient mass balances. Model predictions include Cl coverages and rates of etching of various species from the surface as a function of Cl2 or Ar+ fluence. The simplified phenomenological model reproduces the MD simulation results well over a range of conditions. Comparing model predictions directly to experimental optical emission spectroscopy data, as reported in a previous paper (Vella et al 2023 J. Vac. Sci. Technol. A 41, 062602), provides further evidence of the accuracy of the model.
A rotary self-sensing magnetorheological damper based on triboelectric nanogenerator
Authors: Zhao Shiyu , Hu Rongchang , Han Guanghui , Deng Huaxia , Ma Mengchao , Zhong Xiang , Gong Xinglong
Published: June 2024

A rotary self-sensing magnetorheological (MR) damper(RSMRD) based on a triboelectric nanogenerator is proposed in this study, which can provide variable torque and state self-sensing without a power supply. Compared with traditional self-sensing devices, the sensing part of RSMRD has the advantages of small size, no external power supply, and good low-frequency response. The feasibility of the angular velocity self-sensing (AVS) function is verified through theoretical derivation and experimental verification. The experimental results demonstrate a linear relationship between the output voltage generated by the AVS component and the rotational speed of the rotating shaft. Additionally, the torque characteristics of the rotary self-sensing MR damper are tested, revealing a torque generation of approximately 9.26 N

⋅

m at a current of 1.6 A. Furthermore, a fuzzy control algorithm for vehicle braking is proposed, based on the model parameters of RSMRD. The simulink software is used to establish a dynamic model of 1/4 car braking, with an initial braking speed of 15 m s−1. The results indicate that the vehicle comes to a complete stop after 1.64 s, with a braking distance of 10.93 m. Throughout the braking process, the vehicle slip rate remains close to the optimal slip rate of 0.2.
Dynamic soil-structure interaction of a continuous railway bridge
Authors: Tehrani Seyed Amin Hosseini , Andersson Andreas , Zangeneh Abbas , Battini Jean-Marc
Published: June 2024

This paper presents an efficient 2D beam model of a continuous single-track concrete slab bridge considering the effect of surrounding soil conditions at the location of the retaining walls. A 3D model is used to investigate the backfill soil’s added flexibility for different soil properties. It is shown that for the first bending mode, the additional dynamic stiffness of the backfill soil can be modeled using equivalent vertical and rotational springs. Various experimental tests have been performed on the studied railway bridge, including forced vibration tests and train passage loadings. Good agreement is found between the 2D model and the experimental data. It is shown that removing the soil causes both a shift in the structure’s natural frequencies (and their corresponding resonant speed) and a substantial increase in acceleration amplitude. This may give the impression that the bridge is not suitable for highspeed train passage. It is also shown that the bridge’s response to train passage is mainly governed by the first bending mode.
Higher-order moment stability of large wind turbine blades under stochastic perturbations
Authors: Caracoglia Luca
Published: June 2024

The current trend in offshore wind energy is to design and install systems with larger swept areas that yield unprecedented efficiency. Long and slender blades are needed to achieve this objective. As a result of aerodynamic and structural tailoring, slender blades are particularly susceptible to various dynamic instability phenomena during standard operations. One of these phenomena is the bending-torsion flutter that may lead either to structural failure or system breakdown. The research author has been examining blade flutter under the influence of stochastic perturbations, which include both flow turbulence and aeroelastic load variability.

A reduced-order Markov model has been used to describe the effects of the various random perturbations. Mean-square stability has been recently explored; results suggest that perturbations may negatively impact the flutter angular speed and increase the risk of failure.

In this study the model is employed to investigate moment stability beyond mean squares, observing that dynamic instability involves nonlinear propagation of the perturbations and may exhibit amplitude dependency. Third-order instability is investigated and compared against previous numerical results. The NREL 5MW reference wind turbine blade is used as a benchmark example.
A robust estimation of the response of floating wind turbines through piecewise linearization
Authors: Meng J , Mostert W , Chatzis M N
Published: June 2024

Floating wind turbines (FWT) enable access to substantial wind resources in deep waters. They are hence anticipated to contribute significantly to the carbon-neutral target. Popular simulation tools for this relatively new offshore technology adopt the linear potential flow theory borrowed from the offshore oil and gas industry to evaluate the hydrodynamic forces, which are calculated around the equilibrium position of the platform. However, the compliance of the floating platform can potentially lead to large motions under combined wind and wave actions. To address this issue, the present work proposes a new piecewise linearization approach that can capture the nonlinearity by re-linearizing the wave-platform interaction system at instantaneous platform positions (operating points). A state-basis transformation algorithm is developed to ensure that the consistent physical basis is used across all operating points when calculating the fluid radiation force using the state-space representation. This new approach is implemented in a FWT Simulink model, and an open-source boundary element method code, Nemoh, is used to calculate the hydrodynamic force for the linearized wave-platform system at each operating point. Free vibration tests of a 5-MW ITIBarge FWT are examined to demonstrate the effectiveness of the piecewise linearization approach. The results obtained by this new approach are compared to the common practice of linearizing around the equilibrium, and the new approach is found to be able to conduct a fast and robust evaluation of the nonlinear hydrodynamics for FWTs.
A Multiaxial Test Framework for the Evaluation of Human Gait-Induced Loads on Lateral Harmonic Surfaces
Authors: Castillo Bryan , Thomson Peter , Marulanda Johannio
Published: June 2024

The introduction of increasingly resistant and light-weight materials in the construction industry, coupled with the hypothesis of a global regeneration of urban structures with higher technical and aesthetic requirements, has resulted in civil structures such as bleachers, stairs, slabs, and foot-bridge being vulnerable to excessive vibrations due to dynamic loads, especially human-induced loads. These loads present adaptive phenomena due to structural vibrations generated by the coupling effects of Human-Structure Interaction (HSI). Two main aspects are considered in the effects of HSI: the change in dynamic properties of the structure due to the additional presence of non-stationary mass, and the degree of coupling between people in transit, as well as between them and the structure. Therefore, this paper focuses on the study of the last aspect considered through the development of a Dynamic Platform, the Human-Structure Interaction Multiaxial Test Framework (HSI-MTF), to acquire three-dimensional loads induced by human gait under the effects of lateral harmonic motions. An experimental campaign was conducted with a test subject to evaluate gait loads under lateral sinusoidal movements and on rigid surface. The lateral loads, and frequency content induced by the human gait during the HSI-MTF lateral surface displacement protocols were analyzed.
Engineering methodology to assess the seismic out-of-plane response of two-way spanning unreinforced masonry walls with multiple openings
Authors: Toshniwal S , Sluijs J , Meijers S J H , Sharma S , Messali F
Published: June 2024

Unreinforced masonry buildings show high vulnerability to seismic loading, especially in the out-of-plane direction. Two-way spanning walls are characterized by effective restraints at at least one lateral side of the wall. Their seismic performance under out-of-plane loading has been studied in the literature for walls without openings or with one opening, but it lacks understanding in case of multiple openings. This study presents an engineering approach to calculate the out-of-plane capacity of two-way spanning walls with two openings. Five wall configurations were analysed via non-linear pushover analyses, and crack-pattern evolution tracked. A methodology was proposed which involves dividing the wall into panels whose performance is assessed separately. The division is based on the crack propagation observed in the numerical simulations. Two panels are defined as the wall portions comprised between a side support and an opening which are classified and analysed as three-sided supported walls. Another component corresponds to the wall portion between the two openings and is analysed as a one-way spanning wall. The assessment of the individual panels is based on formulations provided in the Dutch guidelines NPR-9998:2020 which show that the one-way spanning wall panel is the governing one, which is further proved by the analytical calculations.
Analysis and Optimization of a Hybrid Testing Methodology Using a Small-Scale Set-up
Authors: van Vugt G. , Henriques J. , Vandoren B. , Degée H.
Published: June 2024

Hybrid testing provides an efficient and less costly way to explore the response of structural systems to realistic dynamic or seismic loading. However, the required equipment to execute hybrid tests are high-cost tools. To get insight in the hybrid testing methodology, a small-scale set-up has been developed in this project.

An Arduino UNO controls the system that imposes the displacement to a linear actuator. Connecting the small-scale set-up, i.e., the Arduino UNO, to MATLAB allows imposing a time history to the physical substructure. A load cell measures the restoring force which will be communicated to MATLAB by the Arduino UNO. Numerical integration based on the Gravouil-Combescure scheme with Classic Lagrange Multipliers (CLM) determines the displacement for the next time step.

This paper describes hot spots of the methodology and the results of a demonstrative experimental test. The experiment consists of a 4 degree of freedom (DOF) numerical model combined with a 1 DOF physical specimen. The installed linear actuator only has one gearing option, which leads to a possible overshooting loop.

Interesting conclusions can be drawn from the analysis of the small-scale set-up in view of its future upscaling and implementation of the hybrid test method at laboratory scale. Firstly, the linear actuator requires a non-negligible amount of time to reach the imposed displacement which imposes boundary conditions in the MATLAB directives. Secondly, a velocity-controlled actuator is essential in the exploitation of hybrid testing. Thirdly, the displacement tolerance influences the stability of the system. If one increases the displacement tolerance, the risk of an overshooting loop decreases. However, the accuracy might be influenced. Good balance must therefore be found between stability and accuracy.
Physics-based and data-driven modeling of the parameter-varying vibration dynamics of a simplified gantry manipulator
Authors: Mikkelsen Jens Kristian , Avendaño-Valencia Luis David , Schlette Christian
Published: June 2024

The work of this conference paper considers a simplified cartesian manipulator of a gantry robot set up as a pinned-pinned Euler-Bernoulli beam with the purpose of analysing the structural dynamics when subjected to a moving load/cart and a surface roughness. A physics-based beam-cart model is created utilising principles of physical domain substructuring methods to create coupled system matrices for modal analysis purposes. Here, the frozen modal properties as well as frequency response functions are calculated and used in a time simulation of the induced vertical vibrations when the cart traverses the beam. The simulated time signal of the physics-based model is extracted and used for further data-driven system identification. Here, the Linear Parameter-Varying Auto Regressive model is used with a Maximum Likelihood estimator as well as a Bayesian non-linear regression estimator to calculate the frozen power spectral density and natural frequencies. Furthermore, the two estimators are compared where they demonstrate similar predictive performance whereas the Bayesian estimator yields lower standard deviation of the calculated parameters.
Non-linear dynamic analysis of Collapsed grandstand
Authors: Xu T , Meijers W , Meijers SJH , Verlinde R
Published: June 2024

On the 17th of October 2021 a grandstand of the Goffert stadium partially collapsed while a crowd was jumping on it. It was concluded that the main reason of the collapse was that the load of a jumping crowd exceeded the design load of 4 kN/m2, as specified in the NEN 6702. The load also exceeds the current design load of 5 kN/m2 NEN-EN 1991-1-1. A geometrically and physically non-linear finite element (FEM) model was used to obtain the backbone curve of the response of the grandstand. The push-down analysis was force-controlled to allow the grandstand to rotate and deform freely, so that the failure mechanism could develop freely. The jumping load was modelled with a Fourier series based on the contact ratio, the coordination, and the weight of the crowd. These three parameters were estimated with video footage of the collapse. The mass of the people was roughly 3.5 kN/m2. An equivalent SDOF system was set up based on analytical formulae and the backbone curve. With this model the non-linear dynamic behaviour of the grandstand was assessed. Failure was found with the estimated jumping load after roughly the same number of jumps as was seen on video.
Design and experimental verification of an extended KDamper - based vibration absorber
Authors: Mantakas A , Chondrogiannis K A , Kalderon M , Kapasakalis K , Chatzi E , Sapountzakis E J , Antoniadis I A
Published: June 2024

Recently, researchers have proposed an innovative negative stiffness-based vibration control concept, namely the KDamper absorber. The envisaged mechanism comprises a combination of appropriate stiffness, damping and mass elements, including a negative stiffness element. Previous studies have formulated the mathematical framework of the system, as well as design and optimization algorithms. These take into consideration the application of interest and geometrical and manufacturing limitations, regarding the vibration control components, including the realization of the negative stiffness mechanics. The KDamper has been numerically and analytically implemented as a vibration control concept for seismic protection of bridges, buildings as well as wind turbines and noise mitigation panels, while results indicated its beneficial effect towards vibration attenuation. For the first time, an experimental set-up of the proposed mechanism is designed by adopting an optimization procedure and tested under horizontal harmonic and seismic shaking. Results highlight the vibration control properties of the proposed system and validate previous numerical and analytical studies. The experimental device serves as a proof of concept of the KDamper absorber and showcases its advantages as well as application limitations that should be considered in future research.