bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical and experimental analysis of the cavitation and flow characteristics in liquid nitrogen submersible pump
Authors: Wei Aibo , Wang Weibo , Hu Yun , Feng Shujuan , Qiu Limin , Zhang Xiaobin
Published: April 2024

In this paper, the cavitation and flow characteristics of the unsteady liquid nitrogen (LN2) cavitating flow in a submersible pump are investigated through both experimental and numerical approaches. The performance curve of the LN2 submersible pump is obtained via experimental measurement. Numerical simulations are performed using a modified shear stress transport k–ω turbulence model, incorporating corrections for rotation and thermal effects as per the Schnerr–Sauer cavitation model. The numerical framework is verified by comparing the cavitation morphology features with previously reported visual data of the LN2 inducer and aligning pump performance data with those obtained from experimental tests of the LN2 submersible pump. The results indicate that cavitation at the designed flow rate predominantly manifests as tip clearance vortex cavitation in the inducer. Increased flow rates exacerbate cavitation, potentially obstructing the flow passage of the impeller. The vortex identification method and the vorticity transport equation are employed to identify the vortex structures and analyze the interaction between cavitation and vortices in the unsteady LN2 cavitating flow. The vortex structures primarily concentrate at the outlet of the impeller flow passage, largely attributed to the vortex dilation term and baroclinic torque. The influence of thermal effects on the cavitation flow of submersible pumps is analyzed. An entropy production analysis model, comprehensively involving various contributing factors, is proposed and utilized to accurately predict the entropy production rate within the pump. This study not only offers an effective numerical approach but also provides valuable insight into the cavitation flow characteristics of the LN2 submersible pump.
Thermal optimization of shock-induced separation in a natural laminar airfoil operating at off-design conditions
Authors: Sengupta Aditi , Shandilya Narottam
Published: April 2024

A series of implicit large eddy simulations have been conducted to implement thermal control on the transonic shock-boundary layer interactions (SBLIs) over a natural laminar flow airfoil, operating beyond the drag divergence Mach number. The study focuses on the SHM1 airfoil, where the baseline flow exhibits shock-induced separation under specific conditions: free stream Mach number M∞=0.78, angle of attack α=0.38°, and Reynolds number Re=8×106. A time-periodic surface heat flux is introduced, strategically located near the shock structures of the unaltered flow, and the impact of heating vs cooling is investigated through instantaneous Schlieren visualizations and vorticity dynamics, and time-averaged load distributions and boundary layer parameters. Time-averaged Mach contours are utilized to measure the shock strength and extent, revealing that thermal control effectively mitigates the detrimental impact of transonic SBLI on the airfoil's performance. Cooling control emerges as the more effective method, and a case featuring multiple cooling controls near the shock structures demonstrates superior efficacy in controlling shock waves and suppressing shock-induced separation. This optimized configuration results in an improved aerodynamic efficiency of 12.65% compared to the baseline flow.
Vortex–airfoil interaction noise control using virtual serrations and surface morphing generated by leading-edge blowing
Authors: Zhang Yaowen , Yan Xicai , Li Yong
Published: April 2024

Suppression of vortex–airfoil interaction noise from a rod-airfoil model by virtual serrations and surface morphing formed by the leading-edge (LE) blowing was investigated experimentally in an anechoic wind tunnel. The control efficiency of the virtual serrations and surface morphing was evaluated and analyzed by setting different air flow rates (Q), deflection angles (α), and orifice number (M). Noise measurements by far-field microphones show that both can effectively reduce the peak tonal noise generated by the vortex–airfoil interaction, with the control efficiency increasing with the increment of flow rate Q. As for the LE serration, the noise reduction increases with the virtual serration amplitude ratio Av (=Ub/U∞, Ub: blowing velocity; U∞: wind speed), but decreases slightly with the deflection angle α. A reduction of 12–14 dB is obtained when Av = 3.7 and α = 0° or 10°, and there exists a critical amplitude of Av = 1.5, under which no noise reduction is achieved. Compared to the serration at the same flow condition, the virtual surface morphing has much lower control efficiency, with a maximum noise reduction of 3–5 dB. The flow visualization by the particle image velocimetry technique reveals that both build buffer zones in the front of the airfoil LE, preventing the vortices from directly impinging upon the solid LE, thus reducing the intensity of vortex–airfoil interaction. In particular, the virtual serration breaks up the large-scale vortex structure into small-scale vortices, manifesting its high noise control efficiency.
Photoluminescence from CdGa and HgGa acceptors in GaN
Authors: Reshchikov M. A. , Andrieiev O. , Vorobiov M. , Demchenko D. O. , McEwen B. , Shahedipour-Sandvik F.
Published: April 2024

Photoluminescence from GaN implanted with Cd or Hg ions was studied and compared with first-principles calculations. In Cd-implanted GaN, the blue band (BLCd) with a maximum at 2.7 eV is attributed to the CdGa acceptor with an ionization energy of 0.55 eV. In Hg-implanted GaN, the green band (GLHg) with a maximum at 2.44 eV is attributed to the HgGa acceptor with an ionization energy of 0.77 eV. The shapes of the BLCd and GLHg bands are asymmetric, with a similar Franck–Condon shift of about 0.28 eV. The electron- and hole-capture coefficients for the CdGa and HgGa acceptors are found. The experimentally found parameters agree reasonably well with first-principles calculations using HSE hybrid functional satisfying the generalized Koopmans' theorem.
Internal tsunami waves in a stratified ocean induced by explosive volcano eruption: A parametric source
Authors: Talipova Tatiana , Pelinovsky Efim , Didenkulova Ekaterina
Published: April 2024

This article discusses the problem of generating internal waves during explosive eruptions of underwater volcanoes. The importance and novelty of such studies are associated with the emerging data on the observation of internal waves during a volcanic eruption in the Tonga Archipelago in 2022 reported in Zhang and Li [“Oceanic internal waves generated by the Tongan volcano eruption,” Acta Oceanol. Sin. 41(8), 1–4 (2022)]. Using Le Méhaute's parametric model originally suggested to calculate surface waves, internal waves in the ocean with a constant buoyancy frequency are calculated. Internal waves are trains of different modes, the parameters of which were found for different ratios between the radius of the equivalent source and the depth of the basin. Even at relatively small distances from the source (tens of km), wave amplitudes changeover time periods consisting of several days, which confirms the possibility of delineating the tsunami source by internal waves.
Functional specialization of hippocampal somatostatin-expressing interneurons
Authors: Chamberland Simon , Grant Gariel , Machold Robert , Nebet Erica R. , Tian Guoling , Stich Joshua , Hanani Monica , Kullander Klas , Tsien Richard W.
Published: April 2024

Hippocampal somatostatin-expressing (
Sst
) GABAergic interneurons (INs) exhibit considerable anatomical and functional heterogeneity. Recent single-cell transcriptome analyses have provided a comprehensive
Sst
-IN subpopulations census, a plausible molecular ground truth of neuronal identity whose links to specific functionality remain incomplete. Here, we designed an approach to identify and access subpopulations of
Sst
-INs based on transcriptomic features. Four mouse models based on single or combinatorial Cre- and Flp- expression differentiated functionally distinct subpopulations of CA1 hippocampal
Sst-
INs that largely tiled the morpho-functional parameter space of the
Sst
-INs superfamily. Notably, the
Sst;;Tac1
intersection revealed a population of bistratified INs that preferentially synapsed onto fast-spiking interneurons (FS-INs) and were sufficient to interrupt their firing. In contrast, the
Ndnf;;Nkx2-1
intersection identified a population of oriens lacunosum-moleculare INs that predominantly targeted CA1 pyramidal neurons, avoiding FS-INs. Overall, our results provide a framework to translate neuronal transcriptomic identity into discrete functional subtypes that capture the diverse specializations of hippocampal
Sst
-INs.
Transient social–ecological dynamics reveal signals of decoupling in a highly disturbed Anthropocene landscape
Authors: Lin Qi , Zhang Ke , Giguet-Covex Charline , Arnaud Fabien , McGowan Suzanne , Gielly Ludovic , Capo Eric , Huang Shixin , Ficetola Gentile Francesco , Shen Ji , Dearing John A. , Meadows Michael E.
Published: April 2024

Understanding the transient dynamics of interlinked social–ecological systems (SES) is imperative for assessing sustainability in the Anthropocene. However, how to identify critical transitions in real-world SES remains a formidable challenge. In this study, we present an evolutionary framework to characterize these dynamics over an extended historical timeline. Our approach leverages multidecadal rates of change in socioeconomic data, paleoenvironmental, and cutting-edge sedimentary ancient DNA records from China’s Yangtze River Delta, one of the most densely populated and intensively modified landscapes on Earth. Our analysis reveals two significant social–ecological transitions characterized by contrasting interactions and feedback spanning several centuries. Initially, the regional SES exhibited a loosely connected and ecologically sustainable regime. Nevertheless, starting in the 1950s, an increasingly interconnected regime emerged, ultimately resulting in the crossing of tipping points and an unprecedented acceleration in soil erosion, water eutrophication, and ecosystem degradation. Remarkably, the second transition occurring around the 2000s, featured a notable decoupling of socioeconomic development from ecoenvironmental degradation. This decoupling phenomenon signifies a more desirable reconfiguration of the regional SES, furnishing essential insights not only for the Yangtze River Basin but also for regions worldwide grappling with similar sustainability challenges. Our extensive multidecadal empirical investigation underscores the value of coevolutionary approaches in understanding and addressing social–ecological system dynamics.
PurA is the main target of aurodox, a type III secretion system inhibitor
Authors: Watanabe Yoshihiro , Haneda Takeshi , Kimishima Aoi , Kuwae Asaomi , Suga Takuya , Suzuki Takahiro , Iwabuchi Yoshiharu , Honsho Masako , Honma Sota , Iwatsuki Masato , Matsui Hidehito , Hanaki Hideaki , Kanoh Naoki , Abe Akio , Asami Yukihiro , Ōmura Satoshi
Published: April 2024

Anti-microbial resistance (AMR) is one of the greatest threats to global health. The continual battle between the emergence of AMR and the development of drugs will be extremely difficult to stop as long as traditional anti-biotic approaches are taken. In order to overcome this impasse, we here focused on the type III secretion system (T3SS), which is highly conserved in many Gram-negative pathogenic bacteria. The T3SS is known to be indispensable in establishing disease processes but not essential for pathogen survival. Therefore, T3SS inhibitors may be innovative anti-infective agents that could dramatically reduce the evolutionary selective pressure on strains resistant to treatment. Based on this concept, we previously identified a polyketide natural product, aurodox (AD), as a specific T3SS inhibitor using our original screening system. However, despite its promise as a unique anti-infective drug of AD, the molecular target of AD has remained unclear. In this paper, using an innovative chemistry and genetic biology-based approach, we show that AD binds to adenylosuccinate synthase (PurA), which suppresses the production of the secreted proteins from T3SS, resulting in the expression of bacterial virulence both in vitro and in vivo experiments. Our findings illuminate the potential of PurA as a target of anti-infective drugs and vaccination and could open a avenue for application of PurA in the regulation of T3SS.
Attacking epistemic personhood on Twitter/X
Authors: Padilla Cruz Manuel
Published: April 2024

This paper reports on an examination of the actions that Spanish epistemic agents perform in order to question,
challenge, undermine and/or destroy the epistemic personhood of an informer on Twitter, recently been renamed ‘X’. Relying on a
corpus of reactions to information about sanitary measures released during the COVID-19 pandemic by an allegedly reliable and
trustworthy information source, namely the Spanish Ministry of Health, the analysis looks into the said actions and how these are
arranged in larger digital discourse sequences. While contributing to extant research on conflict talk in Spanish on social
networks, the paper also aims to raise vulnerable epistemic agents’ awareness of the varied forms and dynamics of threats to
epistemic personhood as a way of empowering them to identify and counteract such threats.
Hole-Doped Nonvolatile and Electrically Controllable Magnetism in van der Waals Ferroelectric Heterostructures
Authors: Jiang 姜 Xinxin 新新 , Wang 王 Zhikuan 智宽 , Li 李 Chong 冲 , Sun 孙 Xuelian 雪莲 , Yang 杨 Lei 磊 , Li 李 Dongmei 冬梅 , Cui 崔 Bin 彬 , Liu 刘 Desheng 德胜
Published: April 2024

Electrical control of magnetism in van der Waals semiconductors is a promising step towards development of two-dimensional spintronic devices with ultralow power consumption for processing and storing information. Here, we propose a design for two-dimensional van der Waals heterostructures (vdWHs) that can host ferroelectricity and ferromagnetism simultaneously under hole doping. By contacting an InSe monolayer and forming an InSe/In2Se3 vdWH, the switchable built-in electric field from the reversible out-of-plane polarization enables robust control of the band alignment. Furthermore, switching between the two ferroelectric states (P
↑ and P
↓) of hole-doped In2Se3 with an external electric field can interchange the ON and OFF states of the nonvolatile magnetism. More interestingly, doping concentration and strain can effectively tune the magnetic moment and polarization energy. Therefore, this provides a platform for realizing multiferroics in ferroelectric heterostructures, showing great potential for use in nonvolatile memories and ferroelectric field-effect transistors.
Neural network time-series classifiers for gravitational-wave searches in single-detector periods
Authors: Trovato A , Chassande-Mottin E , Bejger M , Flamary R , Courty N
Published: April 2024

The search for gravitational-wave (GW) signals is limited by non-Gaussian transient noises that mimic astrophysical signals. Temporal coincidence between two or more detectors is used to mitigate contamination by these instrumental glitches. However, when a single detector is in operation, coincidence is impossible, and other strategies have to be used. We explore the possibility of using neural network classifiers and present the results obtained with three types of architectures: convolutional neural network, temporal convolutional network, and inception time. The last two architectures are specifically designed to process time-series data. The classifiers are trained on a month of data from the LIGO Livingston detector during the first observing run (O1) to identify data segments that include the signature of a binary black hole merger. Their performances are assessed and compared. We then apply trained classifiers to the remaining three months of O1 data, focusing specifically on single-detector times. The most promising candidate from our search is 4 January 2016 12:24:17 UTC. Although we are not able to constrain the significance of this event to the level conventionally followed in GW searches, we show that the signal is compatible with the merger of two black holes with masses

m
1

=

50.7

−
8.9

+
10.4

M

⊙

and

m
2

=

24.4

−
9.3

+
20.2

M

⊙

at the luminosity distance of

d

L

=

564

−
338

+
812

Mpc

.
Simulating electromagnetic cascades with Lorentz invariance violation
Authors: Saveliev Andrey , Alves Batista Rafael
Published: April 2024

Lorentz invariance violation (LIV) is a phenomenon featuring in various quantum gravity models whereby Lorentz symmetry is broken at high energies, potentially impacting the behaviour of particles and their interactions. Here we investigate the phenomenology of LIV within the context of gamma-ray–induced electromagnetic cascades. We conduct detailed numerical simulations to explore the expected manifestations of LIV on gamma-ray fluxes, taking into account relevant effects such as pair production and inverse Compton scattering. Additionally, we consider processes forbidden in the standard model, namely vacuum Cherenkov emission and photon decay. Our analysis reveals that these modifications result in distinct characteristics within the measured particle fluxes at Earth, which have the potential to be observed in high-energy gamma-ray observations.
Gravitational wave peeps from EMRIs and their implication for LISA signal confusion noise
Authors: Oliver Daniel J , Johnson Aaron D , Berrier Joel , Glampedakis Kostas , Kennefick Daniel
Published: April 2024

Scattering events around the center of massive galaxies will occasionally toss a stellar-mass compact object into an orbit around the massive black hole (MBH) at the center, beginning an extreme mass ratio inspiral (EMRI). The early stages of such a highly eccentric orbit are not likely to produce detectable gravitational waves (GWs), as the source will only be in a suitable frequency band briefly when it is close to periapsis during each long-period orbit. This repeated burst of emission, firmly in the millihertz band, is the GW peep. While a single peep is not likely to be detectable, if we consider an ensemble of such subthreshold sources, spread across the Universe, together they may produce an unresolvable background noise that could obscure sources otherwise detectable by the Laser Interferometer Space Antenna. Previous studies of the extreme mass ratio signal confusion background focused either on parabolic orbits near the MBH or events closer to merger. We seek to improve this characterization by implementing numerical kludge waveforms that can calculate highly eccentric orbits with relativistic effects. Our focus is on orbits at the point of capture that are farther away from the MBH. Here we present the waveforms and spectra of peeps generated from recent calculations of EMRIs/extreme mass ratio bursts capture parameters and discuss how these can be used to estimate the signal confusion noise generated by such events. We demonstrate the effects of changing the orbital parameters on the resulting spectra as well as showing direct comparisons to parabolic orbits and why the GW ‘peep’ needs to be studied further. The results of this study will be expanded upon in a further paper that aims to provide an update on the EMRI signal confusion noise problem.
Semi-analytical calculation of the force between two magnets with rhombus-shaped cross-sections
Authors: Li Tianjian , Ding Chenyang , Yang Xiaofeng
Published: April 2024

Analytical calculations of interaction forces between permanent magnets are essential for the fast and accurate modeling of magnetic springs and bearings. Whereas extensive research has been conducted on interaction forces between cuboidal magnets, there is a lack of research on force calculations between other prismatic magnets in existing literature. This paper newly develops a semi-analytical method for force calculation between two magnets with rhombus-shaped cross-sections. The method is based on interaction force between two rectangular magnetically charged surfaces which are inclined toward each other. Under a Cartesian coordinate system, two components of the force between inclined rectangular magnetically charged surfaces are presented with fully analytical expressions, whereas the other component is expressed with one numerical integral. By applying these expressions repeatedly, the force between two magnets with rhombus-shaped cross-sections is derived. Moreover, a test rig is constructed to validate this semi-analytical method. Furthermore, the method can be extended to force calculations between prismatic magnets with arbitrary-shaped cross-sections, which allows a simple and fast modeling of many magnetic applications.
Nanosecond repetitively pulsed plasmas with MHz bursts for CO2 dissociation
Authors: Post Antoine , Budde Maik , Vervloedt S C L , Engeln Richard , Huiskamp Tom
Published: April 2024

A novel pulsed power source capable of nanosecond pulses with burst frequencies up to 1 MHz is employed to create atmospheric pressure pulsed plasma in pure CO2 gas. The short bursts contain up to four nanosecond pulses. The CO2 conversion and corresponding energy efficiency are measured ex-situ with Fourier-transform infrared absorption spectroscopy. Trends in the absorption line profile of in-situ quantum cascade laser infrared absorption spectroscopy indicate an elevated vibrational temperature of CO2 with an increasing number of pulses per burst. The key result of this paper is that the dissociation energy efficiency is higher when operating the plasma in burst mode. Furthermore, a larger number of pulses in a burst is associated with a further increase of the dissociation efficiency. The highest efficiency measured is

(
17.7
±
0.3
)

% for single pulses spaced 2 ms apart, and

(
20.0
±
0.3
)

% for bursts of three pulses, with an in-burst frequency of 1 MHz and bursts spaced 4 ms apart.
Perpendicular magnetic properties and field-free current-induced switching in W/CoFeB/MgO trilayers with a compensating oblique W underlayer
Authors: Li G S , Zhu Z Z , Wang Z , Ke J T , Wang P J , Bi L Z , Hu C Q , Zhang Y , Cai J W
Published: April 2024

Zero-field magnetization switching (ZFS) driven by current-induced spin–orbit torque (SOT) holds significant importance in spintronic applications. The introduction of a lateral asymmetric structure (LAS) through oblique deposition proves to be an effective strategy for breaking inversion symmetry, thereby enabling SOT-driven ZFS. However, the coexistence of wedge thickness structure and slanted columnar microstructure in the obliquely deposited films poses challenges in distinguishing their respective effects. In this study, we conducted a comparative investigation of the perpendicular magnetic properties and current-induced switching in W/Co40Fe40B20/MgO films by oblique sputtering of the W underlayer at a fixed tilting angle and at two opposite tilting angles with its wedge thickness compensated. We have found that the perpendicular magnetic properties of the Co40Fe40B20 layer are significantly altered at large tilting angles, irrespective of whether the W wedge thickness is compensated. Notably, at a tilting angle of 50°, ZFS is realized for both the conventional oblique sample and the compensating oblique sample, with the switching polarity contingent on the final tilting direction of the W layer. We have identified a gradient in perpendicular magnetic anisotropy in these samples, attributed to the laterally varying roughness associated with the slanted columnar microstructure of the W underlayer. This study underscores the dominant role of microscopic LAS in obliquely deposited films in breaking SOT symmetry. Our research sheds light on the impact of the slanted columnar microstructure on the magnetic and magneto-transport properties of films, offering valuable insights for advancing spintronic device research.
A metasurface for suppressing mode conversion and achieving directional reflection of shear horizontal wave
Authors: Fu Mingtao , Zhu Qingfeng , Miao Hongchen
Published: April 2024

The lowest-order shear horizontal (SH0) guided wave in a plate is crucial for nondestructive testing and structural health monitoring due to its nondispersive nature. However, mode conversion at the interface for the SH0 wave complicates the received information and increases the difficulty of signal analysis. In this work, an elastic metasurface is proposed to suppress mode conversion at the interface and to reflect the SH0 wave directionally. The metasurface comprises a series of rectangular elements with a specific phase gradient covering the 2π phase range. The effectiveness of the proposed metasurface is confirmed through finite element simulations and experimental validation. The results indicate that the metasurface can significantly reduce the amplitude of the reflected lowest-order symmetric Lamb wave when compared to the reflection without the metasurface, while simultaneously allowing the reflected SH0 wave to propagate at the designed angle. Furthermore, the metasurface maintains its functionality for SH0 wave with incident angles varying from 0° to 25°. This study provides a viable approach for suppressing mode conversion and modulating the reflection behavior of SH0 wave, which is expected to find applications in nondestructive testing and structural health monitoring.
Spray-lithography of hybrid graphene-perovskite paper-based photodetectors for sustainable electronics
Authors: Malik Sunaan , Zhao Yining , He Yutong , Zhao Xinyu , Li Hongyu , Yi Wentian , Occhipinti Luigi G , Wang Mingqing , Akhavan Shahab
Published: April 2024

Paper is an ideal substrate for the development of flexible and environmentally sustainable ubiquitous electronic systems. When combined with nanomaterial-based devices, it can be harnessed for various Internet-of-Things applications, ranging from wearable electronics to smart packaging. However, paper remains a challenging substrate for electronics due to its rough and porous nature. In addition, the absence of established fabrication methods is impeding its utilization in wearable applications. Unlike other paper-based electronics with added layers, in this study, we present a scalable spray-lithography on a commercial paper substrate. We present a non-vacuum spray-lithography of chemical vapor deposition (CVD) single-layer graphene (SLG), carbon nanotubes (CNTs) and perovskite quantum dots (QDs) on a paper substrate. This approach combines the advantages of two large-area techniques: CVD and spray-coating. The first technique allows for the growth of SLG, while the second enables the spray coating of a mask to pattern CVD SLG, electrodes (CNTs), and photoactive (QDs) layers. We harness the advantages of perovskite QDs in photodetection, leveraging their strong absorption coefficients. Integrating them with the graphene enhances the photoconductive gain mechanism, leading to high external responsivity. The presented device shows high external responsivity of ∼520 A W−1 at 405 nm at <1 V bias due to the photoconductive gain mechanism. The prepared paper-based photodetectors (PDs) achieve an external responsivity of 520 A W−1 under 405 nm illumination at <1 V operating voltage. To the best of our knowledge, our devices have the highest external responsivity among paper-based PDs. By fabricating arrays of PDs on a paper substrate in the air, this work highlights the potential of this scalable approach for enabling ubiquitous electronics on paper.
A Christmas story about quantum teleportation
Authors: Fitzgerald Barry W , Emonts Patrick , Tura Jordi
Published: April 2024

Quantum teleportation is a concept that fascinates and confuses many people, in particular, given that it combines quantum physics and the concept of teleportation. With quantum teleportation likely to play a key role in several communication technologies and the quantum internet in the future, it is imperative to create learning tools and approaches that can accurately and effectively communicate the concept. Recent research has indicated the importance of teachers enthusing students about the topic of quantum physics. Therefore, educators at both high school and early university level need to find engaging and perhaps unorthodox ways of teaching complex, yet interesting topics such as quantum teleportation. In this paper, we present a paradigm to teach the concept of quantum teleportation using the Christmas gift-bringer Santa Claus. Using the example of Santa Claus, we use an unusual context to explore the key aspects of quantum teleportation, and all without being overly abstract. In addition, we outline a worksheet designed for use in the classroom setting which is based on common naive conceptions from quantum physics. This worksheet will be evaluated as a classroom resource to teach quantum teleportation in a subsequent study.
A thermodynamic analysis of alternative cooling options for beverages
Authors: Costa Danielle C , Mata Angélica S , Nascimento Fábio S , Silva Saulo L L
Published: April 2024

The so-called artificial ices are easily found on the market nowadays. They are commercialized with the promise of freezing drinks in general. The advantage over traditional ice is that they do not dilute drinks during the cooling process. These artificial ices come in a variety of forms, including plastic, gel, stone, and metal. In this study, we investigate theoretically and experimentally the effectiveness of these objects in comparison to traditional water ice (ordinary ice). Our findings suggest that artificial ice produced without water provides a less significant cooling effect when compared to those made with water and traditional water ice. Additionally, we observed that the material used to coat the ice has a significant impact on the cooling process and can be selected based on its specific application. We also suggest an experimental parameter that can be used to verify the effectiveness of these objects. Finally, our results are supported by thermodynamic laws.
Study of an adiabatic and free rotation of a block around a fixed axis using videoanalysis
Authors: Falcari Derick , da Rocha Carlos Antônio , Manarelli Flávio Henrique , Bertuola Alberto Carlos
Published: April 2024

This work is a proposal for a basic physics class in which the statics and dynamics of a rigid body are approached simultaneously using a single experimental apparatus. A mechanical system was used to study the rotation of a rigid prismatic block around one of its edges. In the first part of this study (statics), the block is subjected to the action of a variable external force, the intensity of which decreases as the inclination of the block increases. The external force produces a slow rotation (adiabatic rotation) until it is in an unstable equilibrium configuration. The experiment allows data to be collected on the external force as a function of the block’s angle to the support surface. The graph of the theoretical force relative to the angle of the block with the surface is presented together with the experimental points. From the analytical expression of the force, the work is obtained and compared with the work of the weight force. In the graphical representation of work as a function of angle, a symmetry is identified in the curve drawings. In the second part (dynamics), the block is moved to rotate freely. The falling time is calculated considering two types of independent initial conditions. The first condition is a perturbation in angular velocity and the other in the initial angle. The graphs of the falling times as a function of the predicted perturbations are presented and the concordance between the experimental data and the respective theoretical curves can be checked. All equations obtained from the physical modelling are verified experimentally, through laboratory testing, image analysis and videoanalysis. The experimen-tal techniques and results are presented in detail throughout this paper. The practices described in this work are in harmony with active learning in physics teaching.
Sliding down an inclined plane: a new method for measuring gravitational acceleration and kinetic friction in upper-secondary school
Authors: Johansson Andreas , Kilde Löfgren Sebastian , Enger Jonas
Published: April 2024

An essential goal of teaching experimental physics is to engage students in exploring the validity of models and refining them. To comprehend, test, and revise scientific models, students need well-designed learning activities that enable them to practice the necessary skills. In this paper, we critically review the prevalent assumption in contemporary literature that the coefficient of kinetic friction can be treated as a constant for a certain surface pair. Further, we introduce a novel approach for calculating gravitational acceleration by measuring accelerations on inclined planes. The study indicates that kinetic friction changes with different inclinations of the plane and cannot be assumed to be constant even with typical classroom laboratory equipment. Measuring the gravitational acceleration (g) via inclined planes can result in significant deviations if varying kinetic friction is not considered. This paper proposes a lab activity to investigate the validity of a naïve friction model, by measuring the well-defined gravitational acceleration (g) with controlled precision, in an upper secondary classroom setting.
Work done by static friction on a bouncing ball
Authors: Cross Rod
Published: April 2024

It is commonly assumed that static friction does no work. However, if a ball is incident obliquely without spin on a horizontal surface, then the ball bounces with topspin. Work is therefore done by the friction force at the bottom of the ball to increase the rotational kinetic energy of the ball, even if the force is due to static friction.
Ultra-fast in vivo directional dark-field x-ray imaging for visualising magnetic control of particles for airway gene delivery
Authors: Smith Ronan , Morgan Kaye , McCarron Alexandra , Cmielewski Patricia , Reyne Nicole , Parsons David , Donnelley Martin
Published: April 2024

Objective. Magnetic nanoparticles can be used as a targeted delivery vehicle for genetic therapies. Understanding how they can be manipulated within the complex environment of live airways is key to their application to cystic fibrosis and other respiratory diseases. Approach. Dark-field x-ray imaging provides sensitivity to scattering information, and allows the presence of structures smaller than the detector pixel size to be detected. In this study, ultra-fast directional dark-field synchrotron x-ray imaging was utlilised to understand how magnetic nanoparticles move within a live, anaesthetised, rat airway under the influence of static and moving magnetic fields. Main results. Magnetic nanoparticles emerging from an indwelling tracheal cannula were detectable during delivery, with dark-field imaging increasing the signal-to-noise ratio of this event by 3.5 times compared to the x-ray transmission signal. Particle movement as well as particle retention was evident. Dynamic magnetic fields could manipulate the magnetic particles in situ. Significance. This is the first evidence of the effectiveness of in vivo dark-field imaging operating at these spatial and temporal resolutions, used to detect magnetic nanoparticles. These findings provide the basis for further development toward the effective use of magnetic nanoparticles, and advance their potential as an effective delivery vehicle for genetic agents in the airways of live organisms.
ReconU-Net: a direct PET image reconstruction using U-Net architecture with back projection-induced skip connection
Authors: Hashimoto Fumio , Ote Kibo
Published: April 2024

Objective. This study aims to introduce a novel back projection-induced U-Net-shaped architecture, called ReconU-Net, based on the original U-Net architecture for deep learning-based direct positron emission tomography (PET) image reconstruction. Additionally, our objective is to visualize the behavior of direct PET image reconstruction by comparing the proposed ReconU-Net architecture with the original U-Net architecture and existing DeepPET encoder–decoder architecture without skip connections. Approach. The proposed ReconU-Net architecture uniquely integrates the physical model of the back projection operation into the skip connection. This distinctive feature facilitates the effective transfer of intrinsic spatial information from the input sinogram to the reconstructed image via an embedded physical model. The proposed ReconU-Net was trained using Monte Carlo simulation data from the Brainweb phantom and tested on both simulated and real Hoffman brain phantom data. Main results. The proposed ReconU-Net method provided better reconstructed image in terms of the peak signal-to-noise ratio and contrast recovery coefficient than the original U-Net and DeepPET methods. Further analysis shows that the proposed ReconU-Net architecture has the ability to transfer features of multiple resolutions, especially non-abstract high-resolution information, through skip connections. Unlike the U-Net and DeepPET methods, the proposed ReconU-Net successfully reconstructed the real Hoffman brain phantom, despite limited training on simulated data. Significance. The proposed ReconU-Net can improve the fidelity of direct PET image reconstruction, even with small training datasets, by leveraging the synergistic relationship between data-driven modeling and the physics model of the imaging process.
X-ray source motion blur modeling and deblurring with generative diffusion for digital breast tomosynthesis
Authors: Gao Mingjie , Fessler Jeffrey A , Chan Heang-Ping
Published: April 2024

Objective. Digital breast tomosynthesis (DBT) has significantly improved the diagnosis of breast cancer due to its high sensitivity and specificity in detecting breast lesions compared to two-dimensional mammography. However, one of the primary challenges in DBT is the image blur resulting from x-ray source motion, particularly in DBT systems with a source in continuous-motion mode. This motion-induced blur can degrade the spatial resolution of DBT images, potentially affecting the visibility of subtle lesions such as microcalcifications. Approach. We addressed this issue by deriving an analytical in-plane source blur kernel for DBT images based on imaging geometry and proposing a post-processing image deblurring method with a generative diffusion model as an image prior. Main results. We showed that the source blur could be approximated by a shift-invariant kernel over the DBT slice at a given height above the detector, and we validated the accuracy of our blur kernel modeling through simulation. We also demonstrated the ability of the diffusion model to generate realistic DBT images. The proposed deblurring method successfully enhanced spatial resolution when applied to DBT images reconstructed with detector blur and correlated noise modeling. Significance. Our study demonstrated the advantages of modeling the imaging system components such as source motion blur for improving DBT image quality.
Finite element simulation and experimental investigation of in-situ laser-assisted diamond turning of monocrystalline silicon
Authors: Hu Wangjie , Zhao Xuesen , Sun Tao , Zhang Junjie
Published: April 2024

While the effectiveness of in-situ laser-assisted diamond turning (In-LAT) for promoting the ductile machinability of monocrystalline silicon has been demonstrated, the underlying cutting mechanisms remain inadequately understood. In this study, we investigate the fundamental mechanisms involved in the In-LAT of monocrystalline silicon by finite element (FE) simulations and experiments. Specifically, a FE model of In-LAT of monocrystalline silicon is developed, which incorporates a Drucker–Prager constitutive model to address the brittle fracture of the material, as well as temperature-dependent materials properties to address the thermal softening effect. Furthermore, experiments of In-LAT of monocrystalline silicon are conducted with the self-developed In-LAT device, including tapering cutting and end face cutting. Simulation results demonstrate that In-LAT significantly increases the critical depth of cut for the brittle-to-ductile transition of monocrystalline silicon in tapering cutting mode by 72.2% compared to conventional cutting, accompanied with significantly reduced cutting forces, continuous chip profile and reduced surface brittle damage. The promotion of ductile machinability of monocrystalline silicon under In-LAT is attributed to the reduction and dispersion of stress in the cutting zone, which is in contrast to the significant stress concentration at the rake face and cutting edge in conventional cutting. And simulation results also provide an optimal temperature field of 900 K for the In-LAT of monocrystalline silicon, above which the excessive plastic flow accompanied by thermal accumulation results into deteriorated surface roughness. These findings provide valuable insights for understanding the cutting mechanisms of In-LAT and the parameter optimization for In-LAT application.
The effect of TiSi2 healing improver in self-healing ability of ceramics
Authors: Tamagawa Yuki , Okayasu Kazuto , Nakao Wataru
Published: April 2024

A method to enhance the temperature range in which continuous self-healing fiber-reinforced ceramics (shFRCs) can self-heal is proposed to obtain a new high-temperature structural material. The effect of TiSi2 oxidation on self-healing was investigated using SiC, a typical self-healing agent, and TiSi2, which oxidizes at a lower temperature than SiC. Mixtures of SiC and TiSi2 powders were prepared by wet-mixing, and changes in their high-temperature oxidation behavior were investigated using thermogravimetry/differential thermal analysis. The oxidation of TiSi2 at 1000 °C enhanced the oxidation rate of SiC by 2–3 times. A shFRC consisting of an Al2O3 matrix, an interface layer of SiC and TiSi2, and Al2O3 fiber bundles was fabricated by slurrying and filament-winding. The strength recovery of the shFRC following three-point bending was investigated, and results indicated that the prepared material recovered 50 times faster than conventional shFRCs at 1000 °C. The self-healing improver described in this study can promote the oxidation of self-healing agents via its reaction heat. Thus, this improver may be applied as a practical component of self-healing materials.
Modeling and experimental evaluation of the stepping characteristic on a walking-type piezoelectric actuator
Authors: Yun Hao , Yuan Lusheng , Wei Shaoliang , Aoyagi Manabu
Published: April 2024

Aiming at the suppression of backward motion, a walking-type piezoelectric actuator was developed in this paper. Two walking modes of ellipse-shaped walking and rhombus-shaped walking were discussed. The dynamic models in the x and y direction were established to simulate the stepping characteristics of two walking modes. The simulated results depicted that the actuator was able to achieve stepping displacement free of backward motion. A prototype was fabricated, and a series of experiments were conducted. The experiments indicated that, under two walking modes, there was a backward displacement in each operating cycle due to assembly errors. To suppress backward motion, a solution to compensate for the assembly errors by varying the bias voltage difference between two stators was proposed. After correcting the assembly errors, the backward displacements were almost eliminated and reduced by 71.4% from 0.28 to 0.08 μm and 68.1% from 0.22 to 0.07 μm, respectively under the ellipse-shaped walking mode and rhombus-shaped walking mode, which proved the effectiveness of the proposed actuator.
Evaluation of strain-sensitive behavior in elastomeric conductive nanocomposites containing carbon nanotubes-a finite element-percolation model approach
Authors: Haghgoo Mojtaba , Alidoust Alireza , Ansari Reza , Hassanzadeh-Aghdam Mohammad Kazem
Published: April 2024

A finite element (FE)-percolation model approach is developed to predict the strain-sensitive response of the three-dimensional (3D) representative volume element (RVE) of carbon nanotube (CNT)-elastomeric nanocomposite. In the simulation model, CNTs are modeled as solid, impenetrable cylinders inside a cubic insulating matrix. FE simulation is performed to evaluate the structural response of the RVE under applied strain. The FE model updates the locations of the CNTs in the deformed RVE. The paths are found using a suitable 3D resistance network associated with different percolation paths involved in the critical distance criterion. The percolation model utilizes the paths found to identify the electrical circuit for predicting tunneling conductivity. The simulating algorithm is used to study the influence of tunneling barrier height, nanotube volume fraction, and geometrical aspects. The lowest critical distance criterion is achieved for higher volume fractions and the most heightened sensitivity is obtained for lower CNT aspect ratios.
Next-to-leading-order relativistic and QCD corrections to prompt
pair photoproduction at future
colliders*
Authors: He 何 Zhi-Guo 志国 , Jin 金 Xiao-Bo 小博 , Kniehl Bernd A. , Li 李 Rong 荣
Published: April 2024

Within the framework of nonrelativistic-QCD factorization, we calculate both the next-to-leading-order relativistic and QCD corrections to prompt

pair production, with feed-down from

mesons, via photon-photon collisions at future

colliders, including the Future Circular Lepton Collider (FCC-ee), the Circular Electron Positron Collider (CEPC), and the Compact Linear Collider (CLIC). We present total cross sections and distributions in single

transverse momentum and rapidity, as well as in

pair invariant mass. The relativistic and QCD corrections both turn out to be large and negative. However, the production rates are large enough for useful experimental studies.
p-adic Brownian motion is a scaling limit
Authors: Weisbart David
Published: April 2024

A p-adic Brownian motion is a continuous time stochastic process in a p-adic state space that has a Vladimirov operator as its infinitesimal generator. The current work shows that any such process is the scaling limit of a discrete time random walk on a discrete group. Earlier work required the exponent of the Vladimirov operator to be in

(
1
,
∞
)

, and the convergence was the weak convergence of probability measures on the Skorohod space of paths on a compact time interval. The current approach simplifies the earlier approach, allows for any positive exponent, eliminates the restriction to compact time intervals, and establishes some moment estimates for the discrete time processes that are of independent interest.
The overlap of generalized coherent states of any rank one simple Lie algebra and its classical limit
Authors: Pranzini Nicola
Published: April 2024

We provide a formula for computing the overlap between two generalized coherent states of any rank one simple Lie algebra. Then, we apply our formula to spin coherent states (i.e.

su

(
2
)

algebra), pseudo-spin coherent states (i.e.

su

(
1
,
1
)

algebra), and the

sl

(
2
,

R

)

subalgebras of Virasoro. In all these examples, we show the emergence of a semi-classical behavior from the set of coherent states and verify that it always happens when some parameter, depending on the algebra and its representation, becomes large.