bluuebunny/crossref_metadata_2025 huggingface dataset:
Is HealthPathways viewed as a useful and trustworthy source of information by health professionals?
Authors: Tretheway Rebecca , Visser Victoria , Mollard Sarah
Published: April 2024

Objective HealthPathways is a web-based platform designed for use during a consultation to offer health professionals locally agreed information to support clinical and referral decision making. This study aimed to investigate whether access to specific HealthPathways pages in the North Coast New South Wales (NSW) region increased during specific critical events. High pageviews is used as a proxy for platform usefulness, and/or trust as a source of up-to-date information. Methods Data were extracted from Google Analytics from December 2015 to December 2021. Descriptive statistics were generated for the total number of pageviews for all pages by month and year (2015–2021); for the top 15 most viewed pages in 2019, February–March 2020 inclusive (early COVID-19 pandemic period), 10–24 March 2021 (North Coast NSW region local disaster declaration period) and 26 June–11 October 2021 (NSW COVID-19 lockdown period); and for monthly pageviews for the Influenza Immunisation pathway (2016–2021). Results Access to specific pages in HealthPathways increased alongside the occurrence of critical events affecting the region. Spikes in access to specific pages were seen during COVID-19 lockdown periods, during natural disasters, as well as during the annual influenza season. Conclusions HealthPathways is viewed as a useful and trusted source of information for health professionals in the North Coast NSW region. HealthPathways provides an opportunity for timely dissemination of information during critical events, including natural disasters and emergencies.
Associations between receiving non-consensual image and video sexts and average sleep duration among adolescents and young adults
Authors: Ganson Kyle T. , O’Connor Carolyn , Nagata Jason M. , Testa Alexander , Jackson Dylan B. , Pang Nelson , Mishna Faye
Published: April 2024

Background Sexting is the sending and receiving of nude or partially nude images or videos. Despite it being a part of contemporary relationships, it can have adverse effects. This is particularly the case when receiving non-consensual sexts. To date, there remains a gap in the literature on whether receiving non-consensual sexts is associated with poor sleep. Therefore, the aim of this study was to determine the association between receiving non-consensual sexts and average sleep duration. Methods Data from Wave 2 (2022) of the Canadian Study of Adolescent Health Behaviours (N = 906) were analysed. Multinomial logistic regression analyses were used to determine the association between receiving non-consensual sexts (both image and video) in the past 12 months and average sleep duration (≤5 h, 6 h, 7 h, 8 h, and ≥9 h) in the past 2 weeks. Analyses were stratified by gender. Results Girls and women who received non-consensual image and video sexts, compared to those who did not, were more likely to report ≤5 h of average sleep in the past 2 weeks, relative to 8 h of average sleep. There were no significant findings among boys and men. Conclusion Findings underscore that receiving non-consensual image and video sexts may negatively impact sleep among girls and women, which may be contextualised by trauma responses experienced because of gender-based sexual violence. Healthcare and mental health professionals should be made aware of this association to provide effective care to girls and women.
Reflecting on Indonesia’s young academy movement
Authors: Rakhmani Inaya , Yusuf Arief Anshory , Saleh Hasnawati , Sakhiyya Zulfa , Pertiwi Kanti , Nasir Sudirman , Wiratraman Herlambang P. , Juliandi Berry , Nugroho Yanuar , Jompa Jamaluddin
Published: April 2024

In the past three decades, there has been a rise in young academy movements in the Global North and South. Such movements, in at least Germany and the Netherlands, have been shown to be quite effective in connecting scientific work with society. Likewise, these movements share a common goal of developing interdisciplinary collaboration among young scientists, which contributes to the growth of a nation’s—but also global—scientific endeavors. This paper focuses on the young academy movement in the fourth-largest country hosting the biggest Muslim population in the world, which is also the third-most populous democracy: Indonesia. We observe that there has been rising awareness among the young generation of scientists in Indonesia of the need to advocate for the use of sciences in responding to upcoming and current multidimensional crises. Science advocacy can be seen in their peer-based identification of Indonesia’s future challenges, encompassing the fundamental areas for scientific inquiry, discovery, and intervention. We focus on the Indonesian Young Academy of Sciences (ALMI) and its network of young scientists. We describe ALMI’s science communication practice, specifically SAINS45 and Science for Indonesia’s Biodiversity, and how they have been useful for policymakers, media, and school engagements. The article closes with a reflection on future directions for the young academy movement in Indonesia and beyond.
Lecanemab blocks the effects of the Aβ/fibrinogen complex on blood clots and synapse toxicity in organotypic culture
Authors: Singh Pradeep Kumar , Simões-Pires Elisa Nicoloso , Chen Zu-Lin , Torrente Daniel , Calvano Marissa , Sharma Anurag , Strickland Sidney , Norris Erin H.
Published: April 2024

Proteinaceous brain inclusions, neuroinflammation, and vascular dysfunction are common pathologies in Alzheimer’s disease (AD). Vascular deficits include a compromised blood–brain barrier, which can lead to extravasation of blood proteins like fibrinogen into the brain. Fibrinogen’s interaction with the amyloid-beta (Aβ) peptide is known to worsen thrombotic and cerebrovascular pathways in AD. Lecanemab, an FDA-approved antibody therapy for AD, clears Aβ plaque from the brain and slows cognitive decline. Here, we show that lecanemab blocks fibrinogen’s binding to Aβ protofibrils, preventing Aβ/fibrinogen-mediated delayed fibrinolysis and clot abnormalities in vitro and in human plasma. Additionally, we show that lecanemab dissociates the Aβ/fibrinogen complex and prevents fibrinogen from exacerbating Aβ-induced synaptotoxicity in mouse organotypic hippocampal cultures. These findings reveal a possible protective mechanism by which lecanemab may slow disease progression in AD.
Toward vanishing droplet friction on repellent surfaces
Authors: Backholm Matilda , Kärki Tytti , Nurmi Heikki A. , Vuckovac Maja , Turkki Valtteri , Lepikko Sakari , Jokinen Ville , Quéré David , Timonen Jaakko V. I. , Ras Robin H. A.
Published: April 2024

Superhydrophobic surfaces are often seen as frictionless materials, on which water is highly mobile. Understanding the nature of friction for such water-repellent systems is central to further minimize resistance to motion and energy loss in applications. For slowly moving drops, contact-line friction has been generally considered dominant on slippery superhydrophobic surfaces. Here, we show that this general rule applies only at very low speed. Using a micropipette force sensor in an oscillating mode, we measure the friction of water drops approaching or even equaling zero contact-line friction. We evidence that dissipation then mainly stems from the viscous shearing of the air film (plastron) trapped under the liquid. Because this force is velocity dependent, it can become a serious drag on surfaces that look highly slippery from quasi-static tests. The plastron thickness is found to be the key parameter that enables the control of this special friction, which is useful information for designing the next generation of ultraslippery water-repellent coatings.
Bioenergetics of iron snow fueling life on Europa
Authors: Sahai Nita , LaRowe Doug , Senko John M.
Published: April 2024

The main sources of redox gradients supporting high-productivity life in the Europan and other icy ocean world oceans were proposed to be photolytically derived oxidants, such as reactive oxygen species (ROS) from the icy shell, and reductants (Fe(II), S(-II), CH
4
, H
2
) from bottom waters reacting with a (ultra)mafic seafloor. Important roadblocks to maintaining life, however, are that the degree of ocean mixing to combine redox species is unknown, and ROS damage biomolecules. Here, we envisage a unique solution using an acid mine drainage (AMD)-filled pit lakes analog system for the Europan ocean, which previous models predicted to be acidic. We hypothesize that surface-generated ROS oxidize dissolved Fe(II) resulting in Fe(III) (hydr)oxide precipitates, that settle to the seafloor as “iron snow.” The iron snow provides a respiratory substrate for anaerobic microorganisms (“breathing iron”), and limits harmful ROS exposure since they are now neutralized at the ice-water interface. Based on this scenario, we calculated Gibbs energies and maximal biomass productivities of various anaerobic metabolisms for a range of pH, temperatures, and H
2
fluxes. Productivity by iron reducers was greater for most environmental conditions considered, whereas sulfate reducers and methanogens were more favored at high pH. Participation of Fe in the metabolic redox processes is largely neglected in most models of Europan biogeochemistry. Our model overcomes important conceptual roadblocks to life in icy ocean worlds and broadens the potential metabolic diversity, thus increasing total primary productivity, the diversity and volume of habitable environmental niches and, ultimately, the probability of biosignature detection.
Iron silicate perovskite and postperovskite in the deep lower mantle
Authors: Yang Ziqiang , Song Zijun , Wu Zhongqing , Mao Ho-kwang , Zhang Li
Published: April 2024

Ferromagnesian silicates are the dominant constituents of the Earth’s mantle, which comprise more than 80% of our planet by volume. To interpret the low shear-velocity anomalies in the lower mantle, we need to construct a reliable transformation diagram of ferromagnesian silicates over a wide pressure–temperature (
P-T
) range. While MgSiO
3
in the perovskite structure has been extensively studied due to its dominance on Earth, phase transformations of iron silicates under the lower mantle conditions remain unresolved. In this study, we have obtained an iron silicate phase in the perovskite (Pv) structure using synthetic fayalite (Fe
2
SiO
4
) as the starting material under
P-T
conditions of the lower mantle. Chemical analyses revealed an unexpectedly high Fe/Si ratio of 1.72(3) for the Pv phase in coexistence with metallic iron particles, indicating incorporation of about 25 mol% Fe
2
O
3
in the Pv phase with an approximate chemical formula (Fe
2+
0.75
Fe
3+
0.25
)(Fe
3+
0.25
Si
0.75
)O
3
. We further obtained an iron silicate phase in the postperovskite (PPv) structure above 95 GPa. The calculated curves of compressional (
V
P
) and shear velocity (
V
S
) of iron silicate Pv and PPv as a function of pressure are nearly parallel to those of MgSiO
3
, respectively. To the best of our knowledge, the iron silicate Pv and PPv are the densest phases among all the reported silicates stable at
P-T
conditions of the lower mantle. The high ferric iron content in the silicate phase and the spin-crossover of ferric iron at the Si-site above ~55 GPa should be taken into account in order to interpret the seismic observations. Our results would provide crucial information for constraining the geophysical and geochemical models of the lower mantle.
A realist interpretation of unitarity in quantum gravity
Authors: Sen Indrajit , Alexander Stephon , Dressel Justin
Published: April 2024

Unitarity is a difficult concept to implement in canonical quantum gravity because of state non-normalisability and the problem of time. We take a realist approach based on pilot-wave theory to address this issue in the Ashtekar formulation of the Wheeler–DeWitt equation. We use the postulate of a definite configuration in the theory to define a global time for the gravitational-fermionic system recently discussed in Alexander et al (2022 Phys. Rev. D 106 106012), by parameterising a variation of a Weyl-spinor that depends on the Kodama state. The total Hamiltonian constraint yields a time-dependent Schrodinger equation, without semi-classical approximations, which we use to derive a local continuity equation over the configuration space. We implement the reality conditions at the level of the guidance equation, and obtain a real spin-connection, extrinsic curvature and triad along the system trajectory. We obtain quantum corrections to deSitter spacetime from the guidance equation. The non-normalisable Kodama state is naturally factored out of the full quantum state in the conserved current density, opening the possibility for quantum-mechanical unitarity. We also give a pilot-wave generalisation of the notion of unitarity applicable to non-normalisable states, and show the existence of equilibrium density for our system. Lastly, we find unitary states in mini-superspace by finding an approximate solution to the Hamiltonian constraint.
Comments on ‘Why not energy conservation?’ (2016 Eur. J. Phys.
37 015801)
Authors: Baumgarten C
Published: April 2024

We report about some obvious and severe flaws in Shawn Carlson’s paper titled ‘Why not energy conservation’, published in the (2016, Eur. J. Phys.
37, 015801).
The eye caustic of a ball lens
Authors: Quick Thomas , Grebe-Ellis Johannes
Published: April 2024

Lens phenomena, such as caustics, image distortions, and the formation of multiple images, are commonly observed in various refracting geometries, including raindrops, drinking glasses, and transparent vases. In this study, we investigate the ball lens as a representative example to showcase the capabilities of Berry’s eye caustic as an optical tool. Unlike the conventional paraxial approximation, the eye caustic enables a comprehensive understanding of image transformations throughout the entire optical space. Through experimental exploration, we establish the relationship between the eye caustic and traditional light caustics. Furthermore, we provide mathematical expressions to describe both the caustic and the image transformations that occur when viewing objects through the ball lens. This approach could be of interest for optics education, as it addresses two fundamental challenges in image formation: overcoming the limitations of the paraxial approximation and recognizing the essential role of the observer in comprehending lens phenomena.
Elementary examples of renormalization from mechanics and integral calculus
Authors: Denny Mark
Published: April 2024

Two classical mechanical systems—block-and-tackle machines and nonlinear oscillators—exhibit renormalization of numerical parameters. A simple one-dimensional integral illustrates several other facets of renormalization (regularization, renormalization group, resummation). These examples provide insight for students and non-specialists into the workings of a subtle, complicated and historically misunderstood subject.
Local near-field scattering data enables unique reconstruction of rough electric potentials
Authors: Cañizares Manuel
Published: April 2024

The focus of this paper is the study of the inverse point-source scattering problem, specifically in relation to a certain class of electric potentials. Our research provides a novel uniqueness result for the inverse problem with local data, obtained from the near field pattern. Our work improves the work of Caro and Garcia, who investigated both the direct problem and the inverse problem with global near field data for critically singular and

δ

-shell potentials. The primary contribution of our research is the introduction of a Runge approximation result for the near field data on the scattering problem which, in combination with an interior regularity argument, enables us to establish a uniqueness result for the inverse problem with local data. Additionaly, we manage to consider a slightly wider class of potentials.
Advancements in bifunctional catalysts for unitized regenerative fuel cells: exploring polaronic conduction and heterostructure designs
Authors: Sharma Uma , Jha Pardeep K , Jha Priyanka A , Singh Prabhakar
Published: April 2024

This study investigates the development and performance evaluation of a bifunctional catalyst tailored for unitized regenerative fuel cells (URFCs), capable of facilitating both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in fuel cell and electrolyzer modes. The primary challenge addressed is the creation of electrocatalysts exhibiting high activity and corrosion resistance for oxygen reduction and water oxidation at the oxygen electrode. A novel catalyst structure based on La0.5Sr0.5Fe0.5Ti0.5O3(LSFT), i.e. LSFT/ZnO/LSFT with a thickness of

∼

2
 
μ

m, is explored within an environmentally friendly medium. This catalyst demonstrates superior performance characteristics, including reduced overpotential in HER and enhanced stability during oxygen/hydrogen evolution processes in neutral medium. This study identifies the formation of interfacial polarons and polaronic charge modulation resulting from the incorporation of ZnO in LSFT, leading to multifunctional OER/HER behavior. Notably, the proposed interfacial small polaron mechanism offers valuable insights into complex interfacial phenomena and holds promise for applications in diverse heterostructures involving layered 2D materials and transition metal oxides. Moreover, the robust LSFT/ZnO/LSFT catalyst exhibits exceptional stability, maintaining for 168 h of oxygen evolution at a constant potential of approximately 1.66 V for a current density of 1 A cm−2 in a neutral medium. These findings mark a significant advancement in URFC technology and present promising avenues for clean energy storage solutions.
Optimal speckle size and signal processing for displacement measurements using a 4f optical setup
Authors: Spaett A , Zagar B G
Published: April 2024

Fully developed laser speckle patterns are, due to their high contrast and statistical nature, well suited to measure strain and displacement via an appropriately designed measurement system. Laser speckle patterns are formed when a sufficiently coherent light source, such as a HeNe-laser, illuminates an optically rough surface. Therefore, methods based on laser speckle patterns can be applied to any surface scatterer with a minimum mean surface roughness of about a quarter of the laser’s wavelength. This includes also materials such as thin natural and technical fibres as well as foils, for which the presented measurement system, including the digital signal processing, was designed. In order to achieve the best possible resolution of a speckle-based measurement system, combined with a sufficiently small measurement uncertainty, all available design parameters must be optimised. One of these parameters is the speckle size, which is dependant on the properties of the imaging optics. In this paper a subjective laser speckle-based measurement system based on a so-called 4f-optical setup is presented. This setup allows the speckle size to be controlled in both axial and lateral dimensions separately, which is achieved with the help of an aperture in the Fourier plane of the optics. It is shown that the optimal speckle size for the presented measurement system, not only depends on the physical setup, but also on the signal processing applied. The signal processing routine estimates displacements of the speckle pattern, leading to an estimate for the strain. Additionally, it is demonstrated that the optimal speckle size can be lower than the commonly reported optimum between two and five pixel pitches, necessary to circumvent aliasing in the image data. While this is shown for a measurement setup using 4f-optics, the results are of general importance to speckle-based strain or displacement measurement systems and should thus be taken into account.
The RUL prediction based on improved Wiener degradation model for wet friction components
Authors: Wu Jianpeng , Li Pengpeng , Wang Liyong , Huang Xiaozan , Yang Jian , Du Molin
Published: April 2024

The wet clutch is a critical component of the comprehensive transmission system, and its reliability determines the stability of heavy equipment operation. As the core component of the wet clutch, the life of the wet friction components directly affects the reliability of the wet clutch. To accurately predict the wet friction components remaining useful life (RUL), an improved Wiener degradation model is established. Compared to traditional models, it sets drift parameters as random parameters to consider the randomness of degradation process. The life and degradation data of wet friction components are obtained through accelerated life test, and the composite degradation indicator is constructed by screening and fusing degradation data. Innovatively, we fuse life and degradation data to reduce early errors in RUL prediction of wet friction components. The result shows that the RUL prediction average absolute error of the improved Wiener degradation model is 0.31 h in the accelerated life range of 80 h–110 h, which verifies the accuracy of the model.
A hybrid approach to soft sensor development for distillation-in-series plant under input data low variability
Authors: Mozharovskii Igor , Shevlyagina Svetlana
Published: April 2024

This paper presents a hybrid approach for integrating fundamental process knowledge with measurement data to soft sensor (SS) development with improved estimation capability. Measurement data from sensors are collected and used as inputs for a first-principles model to emulate the data close to restrictions of the operating regulations, thus addressing a low variability problem of the inputs. Next, variables from measurement data and results of the first-principles modeling are combined to extend the training dataset for SSs, which become of a hybrid type in nature. To improve an estimation capability, a cascade-forward neural network and algorithm for alternating conditional expectation for nonparametric SS development was used. It was shown that the estimation capabilities of the developed SS can be improved by extending the training dataset with first-principles model data approximating the upper and lower limits of the process regime, the size of which in total does not exceed 21% of industrial data alone. As a result, the designed hybrid SS demonstrates a better efficacy in predicting quality index of the targeted distillation product with significantly reduced mean absolute error.
A dislocation density-based crystal plasticity constitutive model: comparison of VPSC effective medium predictions with ρ-CP finite element predictions
Authors: Patra Anirban , Tomé Carlos N
Published: April 2024

This work presents a dislocation density-based crystal plasticity constitutive model for glide kinetics, strengthening and dislocation density evolution, implemented in the effective medium-based visco-plastic self consistent (VPSC) framework and the spatially resolved, ρ-CP crystal plasticity finite element framework. Additionally, a distribution of intragranular stresses is introduced in the VPSC framework, instead of the conventionally used mean value of grain stress for effective medium calculations. The ρ-CP model is first calibrated to predict the mechanical response of a bcc ferritic steel with an initial rolled texture. The same set of constitutive model parameters are then used in VPSC to predict the aggregate stress–strain response and total dislocation densities. For these VPSC simulations, the interaction parameter governing the interaction between the grain and the effective medium in the Eshelby inclusion formalism, and a scalar parameter representative of the distribution of intragranular stresses within a grain, are used to calibrate the VPSC predictions in order to match the predictions of the ρ-CP model. A parametric study is performed to understand the effect of these two parameters on the VPSC predictions. Further, simulations are also performed for a random untextured polycrystal to identify the corresponding VPSC simulation parameters for predicting a similar response as the ρ-CP model. The novelty of the work is in the same set of constitutive models and associated parameters have been implemented in VPSC and ρ-CP to predict similar aggregate stress–strain response and total dislocation densities. This finite element-calibrated effective medium crystal plasticity approach reduces the computational time by at least two orders of magnitude and represents an advance towards the development of multiscale crystal plasticity modeling tools.
Exploring the evolution mechanisms of indentation and scratching on diamond structural transformation based on molecular dynamics
Authors: Tong Hua , Yang Yue , Liu Yunhai , Wang Xiaowen , Luo Yiyao , Zhang Hu , Mao Dongbi
Published: April 2024

Diamond, possessing high hardness and chemical stability, finds wide-ranging applications across various industries. However, during the friction process, a graphitization phenomenon may occur, which changes the mechanical properties of the diamond. In this study, molecular dynamics simulation was performed using SiC ball to investigate the influence of indentation depth and temperature on the graphitization transition of the diamond surface. The results showed that the dominant factor affecting the sp2 hybridization ratio during the indentation process was stress, while the temperature was the dominant factor during sliding. The results of this study can be used to understand the friction and wear behavior of diamonds and SiC ball and provide theoretical references for the industrial application of diamonds.
A mathematical analysis of the adiabatic Dyson equation from time-dependent density functional theory
Authors: Corso Thiago Carvalho
Published: April 2024

In this article, we analyse the Dyson equation for the density–density response function (DDRF) that plays a central role in linear response time-dependent density functional theory (LR-TDDFT). First, we present a functional analytic setting that allows for a unified treatment of the Dyson equation with general adiabatic approximations for discrete (finite and infinite) and continuum systems. In this setting, we derive a representation formula for the solution of the Dyson equation in terms of an operator version of the Casida matrix. While the Casida matrix is well-known in the physics literature, its general formulation as an (unbounded) operator in the N-body wavefunction space appears to be new. Moreover, we derive several consequences of the solution formula obtained here; in particular, we discuss the stability of the solution and characterise the maximal meromorphic extension of its Fourier transform. We then show that for adiabatic approximations satisfying a suitable compactness condition, the maximal domains of meromorphic continuation of the initial DDRF and the solution of the Dyson equation are the same. The results derived here apply to widely used adiabatic approximations such as (but not limited to) the random phase approximation and the adiabatic local density approximation. In particular, these results show that neither of these approximations can shift the ionisation threshold of the Kohn–Sham system.
Development of a smart artificial muscle using optical fibres
Authors: Tian Weihang , Wakimoto Shuichi , Yamaguchi Daisuke , Kanda Takefumi
Published: April 2024

A McKibben artificial muscle is a fluid-driven soft actuator comprising sleeve fibres and rubber tube. However, as typical bulky and rigid displacement sensors are unsuitable as sensor elements in soft actuators, displacement sensing is challenging for the McKibben artificial muscle. Therefore, we propose an optical fibre-based smart artificial muscle (OSAM) to estimate self-displacement from the bending loss of the optical fibre used as the sleeve fibre. The optical fibre can be effortlessly integrated into the OSAM sleeve using a braiding machine, which is generally used for manufacturing strings, easing the mass production process. The radius of curvature of the optical fibre changed when the OSAM was driven. The displacement of the artificial muscle was estimated based on the sensor output. To demonstrate the usefulness of OSAM, displacement feedback control experiments were conducted using the optical fibre sensor integrated into OSAM. From the results, OSAM’s displacement showed a good response to the target displacement. Therefore, the developed artificial muscle can facilitate displacement feedback control without requiring external sensors, which in turn can improve the performance of rehabilitation and wearable devices.
A locally resonant metamaterial beam with tunable electromagnetic stiffness based on the electromechanical analogy network
Authors: Deng Shiqi , He Yanyong , Wu Yudong , Ding Weiping
Published: April 2024

Locally resonant acoustic metamaterials offer distinctive advantages in controlling low-frequency elastic waves. However, passive structures often face limitations due to narrow bandgaps and fixed working band once they are fabricated. This paper introduces a novel metamaterial beam with tunable bandgaps. This achievement is made possible by employing one electromagnet and three permanent magnets to create an electromagnetic spring. The initial stiffness, provided by the spiral beam, collaborates with the electromagnetic components to establish a local resonant unite cell featuring tunable composite stiffness. Subsequently, an analogy network is formulated for the metamaterial beam based on electromechanical analogy theory. This network not only elucidates the generation mechanism and regulatory principles of bandgaps but also serves as a paradigm for the proactive design of the metamaterial beam with external control sources, particularly under finite period conditions. Finally, theoretical analysis and experimental results collectively demonstrate the flexibility of the proposed metamaterial beam in effectively suppressing low-frequency elastic waves across a wide frequency range.
Actuation strategy characterizations of a vibro-impact crawling robot driven by dielectric elastomer actuators
Authors: Cao Chongjing , Wu Chuang , Li Xiaozheng , Gao Xing
Published: April 2024

Vibro-impact crawling robots driven by the emerging dielectric elastomer actuators (DEAs) feature the advantages of reduced system complexity and bidirectional locomotion capability. However, due to the lack of systematic dynamic models and in-depth investigations, the fundamental locomotion principles of the robots are still unclear and therefore their applications in real-world scenarios remain hindered. In this paper, a comprehensive dynamic model of this robot is developed by considering the complex interactions between the electro-mechanical coupling, impact mechanism, and multiple nonlinear friction characteristics. By incorporating extensive modeling and experimental studies, we explain the fundamental principles that lead to the bidirectional locomotion of the robot. The actuation strategies for both forward and backward locomotion are characterized in-depth, which include the actuation frequencies, relative phases, and waveforms. Three typical contact surface cases (i.e. rigid & dry, rigid & viscous, compliant & viscous) are considered in this paper, where we report the changes in the optimal actuation strategies for bidirectional locomotion with the contact surfaces and reveal the influences of key factors of friction coefficient, viscosity, and material compliance. The key findings reported in this work can build foundations for developing a highly robust and efficient DEA-driven vibro-impact crawling robot for broad applications.
A semi-analytical simulation method for bi-directional functionally graded cantilever beams under arbitrary static loads
Authors: Zhang Long , Liao Wenlin , Fan Juntao , Feng Song
Published: April 2024

This paper presents a novel semi-analytical simulation approach for analysing the behaviour of bi-directional functionally graded cantilever beams subjected to arbitrary static loads, such as concentrated moments, concentrated forces, distributed force and their combinations applied at any location along the beam. The fundamental equations governing the cantilever beam’s response are derived, on the basis of which the proposed semi-analytical method is implemented using MATLAB programming language. The simulation results include field variables as well as stress contours, providing a compressive understanding of the beam’s behaviour. To validate the accuracy and reliability of the proposed method, a convergence study is conducted in comparison with the graded finite element method (GFEM) and analytical solutions. In the end, the developed method is applied to simulate the bending behaviour of bi-directional functionally graded cantilever beams under various loads individually and their combinations. The stress contours and deflection curves obtained from the simulation are compared with the solutions obtained using GFEM, revealing that the developed method possesses excellent capability in accurately simulating the bending behaviour of cantilever beams.
Low-energy avionic piezoelectric deicing system
Authors: Jomaa Modar , Lévy Pierre-Etienne , Vasic Dejan , Costa François , Ali Marwan
Published: April 2024

Piezoelectric actuators are widely used in several applications and are becoming increasingly attractive in aircraft and industrial contexts, mainly when efficiency and economical energy conversion are required. One of these applications is the avionic piezoelectric deicing system. Piezoelectric actuators are considered as a potential solution for developing a low-energy ice protection system for aircraft. This type of system applies vibration to the structure by activating its own resonant frequencies to generate sufficient stress to break the ice and cause it to delaminate from the substrate. The deicing mechanism depends strongly on the chosen excitation mode, whether it is flexural (bending) mode, extension (stretching) mode, or a combination in between, hence affecting the efficiency and effectiveness of the deicing process. In this contribution, a proof of concept of a deicing system utilizing lightweight piezoelectric actuators with minimal power requirement is proposed. Deicing was demonstrated with a power input density of 0.074 W cm−2 and a surface ratio of 0.07 piezoelectric actuators per cm2. First, a numerical method for positioning piezoelectric actuators and choosing the proper resonance mode was validated to assist in the system’s design. Then, the numerical method was used to implement piezoelectric deicing on a more representative structure of an aircraft wing or nacelle. Finally, a converter topology adapted for deicing application was proposed.
Consequence of anisotropy on flocking: the discretized Vicsek model
Authors: Karmakar Mintu , Chatterjee Swarnajit , Paul Raja , Rieger Heiko
Published: April 2024

We numerically study a discretized Vicsek model (DVM) with particles orienting in q possible orientations in two dimensions. The study investigates the significance of anisotropic orientation and microscopic interaction on macroscopic behavior. The DVM is an off-lattice flocking model like the active clock model (ACM; Chatterjee et al 2022 Europhys. Lett.
138 41001) but the dynamical rules of particle alignment and movement are inspired by the prototypical Vicsek model (VM). The DVM shows qualitatively similar properties as the ACM for intermediate noise strength where a transition from macrophase to microphase separation of the coexistence region is observed as q is increased. But for small q and noise strength, the liquid phase appearing in the ACM at low temperatures is replaced in the DVM by a configuration of multiple clusters with different polarizations, which does not exhibit any long-range order. We find that the dynamical rules have a profound influence on the overarching features of the flocking phase. We further identify the metastability of the ordered liquid phase subjected to a perturbation.
Measurement of infrared magic wavelength for an all-optical trapping of 40Ca+ ion clock
Authors: Huang Yao , Wang Miao , Chen Zheng , Li Chengbin , Zhang Huaqing , Zhang Baolin , Tang Liyan , Shi Tingyun , Guan Hua , Gao Ke-Lin
Published: April 2024

For the first time, we experimentally determine the infrared magic wavelength for the 40Ca+

4
s

2

S

1

/

2

→
3
d

2

D

5

/

2

electric quadrupole transition by observation of the light shift canceling in 40Ca+ optical clock. A ‘magic’ magnetic field direction is chosen to make the magic wavelength insensitive to both the linear polarization purity and the polarization direction of the laser. The determined magic wavelength for this transition is 1056.37(9) nm, which is not only in good agreement with theoretical predictions (‘Dirac–Fock plus core polarization’ method) but also more precise by a factor of about 300. Using this measured magic wavelength, we also derive the differential static polarizability to be −44.32(32) a.u., which will be an important input for the evaluation of the blackbody radiation shift at room temperatures. Our work paves a way for all-optical-trapping of 40Ca+ optical clock.
Long-wave infrared laser irradiation damage effect on GaAs/AlGaAs quantum well infrared photodetector
Authors: Sun Jiaxin , Qian Chuanpeng , Liu Xiaolin , Xu Zuodong , Zhang Yan , Li Xiangyang , Lu Wei , Zhang Jianmin , Ye Xisheng
Published: April 2024

The damage effect and mechanism of laser irradiation on long-wave focal plane array (FPA) GaAs/AlGaAs quantum well infrared photodetector (QWIP) were preliminarily explored by using numerical simulation and experiment methods. Piecewise functions were employed to simulate the complex boundary structure of the QWIP, enabling the numerical simulation investigation of mono-pulse, nano-second, long-wave infrared laser irradiation damage effect on the QWIP. The highest QWIP temperature, the highest surface temperature and the maximum circumferential thermal stress were analyzed in relation to laser energy density. The pulse average energy density thresholds of thermal decomposition damage, melting damage and thermal stress-induced damage were theoretically obtained. Preliminary experiments were then conducted by using a mono-pulse, nano-second, 7.2 μm all-solid-state long-wave infrared laser. The experimental results revealed a point-shape damage in QWIP response measurement after the irradiation by a laser pulse of average energy density 1.30 J cm−2, due to the decomposition of GaAs. At a higher average energy density 5.42 J cm−2, both melting and stress-induced damages appeared, with the damage morphology predominantly influenced by stress-induced damage, resulting in the occurrence of blind pixels or the losing of pixels. Furthermore, at laser pulse average energy density 12.48 J cm−2, line-shape damage of the QWIP was observed.
Terahertz generation of Airy beam with polarization conversion in a reflective vanadium dioxide metasurface
Authors: Zhou Zhesheng , Zhang Runxuan , Chen Zijun , Nie Ruixing , Pan Zimo , Song Zhengyong
Published: April 2024

Airy beam possesses a wide range of applications owing to its special properties of non-diffraction, self-accelerating, and self-healing. However, conventional Airy beam generators are not conducive to their miniaturization or integration. In this paper, a technique for generating Airy beam is introduced with polarization conversion within the frequency range of 0.9–1.2 THz based on a reflective vanadium dioxide (VO2) metasurface. Our design is composed of VO2 elliptical patch, SiO2 spacer, and gold substrate. When the metallic VO2 is involved, the proposed metasurface can efficiently generate cross-polarized Airy beam since amplitude and phase distributions of reflected wave are modulated simultaneously by rotating tilt angle of each VO2 patch. Conversely, when the insulating VO2 is involved, the metasurface does not generate Airy beam. In addition, we demonstrate broadband effect and autofocusing phenomenon of the metasurface. The proposed Airy beam generator may be of great interest for beam shaping, biomedical imaging, and laser fabrication.
Stable stripe and vortex solitons in two-dimensional spin-orbit coupled Bose–Einstein condensates
Authors: Guo Yuan , Idrees Muhammad , Lin Ji , Li Hui-jun
Published: April 2024

We present a flexible manipulation and control of solitons via Bose–Einstein condensates. In the presence of Rashba spin–orbit coupling and repulsive interactions within a harmonic potential, our investigation reveals the numerical local solutions within the system. By manipulating the strength of repulsive interactions and adjusting spin–orbit coupling while maintaining a zero-frequency rotation, diverse soliton structures emerge within the system. These include plane-wave solitons, two distinct types of stripe solitons, and odd petal solitons with both single and double layers. The stability of these solitons is intricately dependent on the varying strength of spin–orbit coupling. Specifically, stripe solitons can maintain a stable existence within regions characterized by enhanced spin–orbit coupling while petal solitons are unable to sustain a stable existence under similar conditions. When rotational frequency is introduced to the system, solitons undergo a transition from stripe solitons to a vortex array characterized by a sustained rotation. The rotational directions of clockwise and counterclockwise are non-equivalent owing to spin–orbit coupling. As a result, the properties of vortex solitons exhibit significant variation and are capable of maintaining a stable existence in the presence of repulsive interactions.
Destabilization of geodesic acoustic-like mode in the presence of poloidally inhomogeneous heat sources in tokamak plasmas
Authors: Lee Young-Hoon , Lee Jungpyo
Published: April 2024

The effects of poloidally inhomogeneous heat sources are investigated through a gyrokinetic formula in collisionless toroidal plasmas. A gyrokinetic dispersion relation is newly derived under the assumption that equilibrium parallel heat flows are generated to remove the injected poloidally nonuniform heat source. The dispersion relation is numerically solved, considering both inboard and outboard heat source injections. In the case of the inboard source injection, both Stringer spin-up and geodesic acoustic mode (GAM) are excited. Conversely, outboard injection leads to the emergence of a heat source-driven GAM (referred to as Q-GAM), featuring a frequency around half that of the standard GAM. Various physical quantities of the Q-GAM, such as mode frequency and source threshold, are analyzed through parametric scans. The Q-GAM exhibits similarities with the energetic-particle-driven GAM (EGAM), particularly in its frequency range, and both belong to one of the strong Landau damped poles. Despite having distinct driving mechanisms and structural differences in parallel velocity and poloidal coordinates, the response function of the perturbed parallel pressure to the potential, mainly contributing to the destabilization of each mode around half of the GAM frequency, is derived to have a similar form for both the Q-GAM and EGAM cases.
Size effect on vibration properties of axially moving nanoplates under different boundary conditions
Authors: Jing Wang , Yanglan Yu
Published: April 2024

The nonlocal strain gradient theory is employed to investigate the transverse free vibration characteristics of two-dimensional nano-plates with axial velocities. A generalized Hamiltonian principle has been used to establish the vibration governing equations for the system as well as the corresponding boundary conditions. By applying complex modal analysis to three boundary conditions, the plate’s natural frequency is determined, including four-end simply supported, four-end clamped, and opposite-edge simply supported and clamped, and comparing the effect of the size parameters on the natural frequency in relation to the boundary conditions; based on different theories, the effects of changing boundary conditions on natural frequencies are systematically compared. In the numerical study, it is demonstrated that the size effect significantly influences only the self-oscillation frequency at the nanoscale, whereas the nonlocal parameter as well as the material characteristic parameter have “softening” and “hardening” effects on the equivalent stiffness of the nanoplates, respectively, which are directly related to their natural frequencies. Compared to simple supports, clamped boundary conditions are more significantly affected by size parameters. In addition, higher order frequencies exhibit greater sensitivity and are susceptible to changes in boundary conditions and size parameters.
ScxAl1-xN piezoelectric film grown at room temperature
Authors: Liu Jingyan , Ma Liang , Ma Yaming , Yang Shuqiang , Chen Yuxin , Zeng Seng , Shang Zhengguo , He Xianming , Wang Hongli
Published: April 2024

In order to overcome the shortcomings of AlN piezoelectric thin films such as low piezoelectric coefficient and low electromechanical coupling coefficientrealize, ScxAl1−xN thin films with CMOS process compatibility were prepared by pulsed DC reactive magnetron sputtering. High performance ScxAl1−xN piezoelectric thin films were prepared at room temperature by optimizing process parameters including power, gas flow ratio, substrate temperature, seed layers and so on. The phase separation phenomenon was investigated through XRD, TEM, and XPS. We found that the phase separation is related to the appearance of rocksalt ScN and led to the degeneration of film properties. The existence of ScN phase is a key factor affecting the performance of ScxAl1−xN. The results show that the piezoelectric constant d33 of ScAlN film achieved 27.5 pC/N and the full width at half maximum (FWHM) of the rocking curve is 1.9° in room temperature when the content of Sc reaches 35%.
A novel sensible smart mask using micro thermal-electric energy conversion elements
Authors: Zhang Yun , Ren Xiaoming , Gou Yanjie , Shen Qingke
Published: April 2024

With the improvement of people’s living standards, more and more people begin to pay attention to their own health status. The mode of monitoring human physiological indicators is gradually shifting to a family-based and miniaturized development model that focuses on prevention. Respiratory rate is an important parameter that reflects the health status of the human body. It is an important diagnostic basis for doctors in clinical prevention and diagnosis of related diseases. Therefore, it is necessary to develop a portable monitoring instrument that can dynamically monitor the human respiratory frequency index in real time. Since most of the existing wearable respiratory frequency detection devices have some disadvantages such as low accuracy, high cost and difficulty in promotion, this paper proposes a new type of smart mask based on thermoelectric effect to monitor human respiratory frequency in real time. The respirator system has the advantages of small size, light weight and suitable for face. Compared with other heavy breathing devices, it has obvious advantages. The Seebeck effect of thermoelectric energy conversion element (TECE) can be used to reflect the respiratory frequency of human body under different respiratory conditions. Experiments show that the sensor has high accuracy and can accurately reflect even small changes in respiratory frequency.
Advancing simulation efficiency for MEMS electrostatic actuators
Authors: Wang Lei , Liu Haiyun , Liu Xing
Published: April 2024

This paper presents an overview of the research progress on Multiphysics simulation of MEMS electrostatic actuators. MEMS electrostatic actuators have shown significant development potential in applications such as ADWSS and VOA. However, the increasing size and complexity of these devices have posed challenges to traditional Multiphysics simulation methods, leading to lengthy computational times that hinder the overall device development process. In order to enhance simulation efficiency and meet the demands of device development, the use of simplified single physics field models have been explored. The results have demonstrated that the simplified single physics filed simulation model yields comparable results to traditional Multiphysics simulations with an error tolerance of within 10%, while reducing simulation time by 80-90%.