bluuebunny/crossref_metadata_2025 huggingface dataset:
A two-way coupled fluid–structure interaction method for predicting the slamming loads and structural responses on a stiffened wedge
Authors: Xiao Jiawei , Liu Cong , Han Bingbing , Wan Decheng , Wang Jianhua
Published: July 2024

Ships navigating through rough seas are subjected to slamming loads from waves, which can lead to structural damage and maritime accidents. The wedge model is commonly employed to investigate slamming loads and structural responses. While a stiffened wedge closely resembles a real ship hull plate, incorporating it into fluid–structure interaction simulations presents challenges. This paper proposes a two-way coupled fluid–structure interaction method to examine slamming loads and structural responses of a free fall non-prismatic stiffened steel wedge. Hydrodynamic loads are determined through Reynolds-averaged Navier–Stokes computations using OpenFOAM, while structural responses are predicted using the finite element analysis (FEA) software Calculix. To achieve two-way coupling between computational fluid dynamics and FEA simulations, a coupling library for partitioned multi-physics simulations, preCICE, is introduced. The computed impact pressure and stress align well with available experimental data. Various free fall heights are investigated in the numerical simulations. The results indicate that elastic deformation mitigates impact pressure, while the presence of transverse ribs enhances the rigidity of the flexible plate. The duration of pressure and the peak slamming pressure exhibit an inverse correlation. Greater free fall heights result in shorter pressure duration times, and smaller free fall heights may reduce rise time. Three-dimensional effects cause pressure to decrease along the midpoint of the plate toward both sides. Additionally, structural stress in the central area exceeds that in the areas on both sides at the same height. In conclusion, the proposed two-way coupled model proves suitable for accurately and efficiently computing hydroelastic slamming on flexible wedges.
Large-scale semi-organized rolls in a sheared convective turbulence: Mean-field simulations
Authors: Asulin A. , Tkachenko E. , Kleeorin N. , Levy A. , Rogachevskii I.
Published: July 2024

Based on a mean-field theory of a non-rotating turbulent convection [T. Elperin et al., Phys. Rev. E 66, 066305, (2002)], we perform mean-field simulations (MFS) of sheared convection that takes into account an effect of modification of the turbulent heat flux by the non-uniform large-scale motions. This effect is caused by the production of additional essentially anisotropic velocity fluctuations generated by tangling of the mean-velocity gradients by small-scale turbulent motions due to the influence of the inertial forces during the lifetime of turbulent eddies. These anisotropic velocity fluctuations contribute to the turbulent heat flux. As the result of this effect, there is an excitation of large-scale convective-shear instability, which causes the formation of large-scale semi-organized structures in the form of rolls. The lifetimes and spatial scales of these structures are much larger compared to the turbulent scales. By means of MFS performed for stress-free and no-slip vertical boundary conditions, we determine the spatial and temporal characteristics of these structures. Our study demonstrates that the modification of the turbulent heat flux by non-uniform flows leads to a strong reduction of the critical effective Rayleigh number (based on the eddy viscosity and turbulent temperature diffusivity) required for the formation of the large-scale rolls. During the nonlinear stage of the convective-shear instability, there is a transition from a two-layer vertical structure with two rolls in the vertical direction before the system reaches steady-state to a one-layer vertical structure with one roll after the system reaches steady state. This effect is observed for all effective Rayleigh numbers. We find that inside the convective rolls, the spatial distribution of the mean potential temperature includes regions with a positive vertical gradient of the potential temperature caused by the mean heat flux of the convective rolls. This study might be useful for understanding the origin of large-scale rolls observed in atmospheric convective boundary layers, as well as in numerical simulations and laboratory experiments.
Time-series-analysis-based detection of critical transitions in real-world non-autonomous systems
Authors: Lehnertz Klaus
Published: July 2024

Real-world non-autonomous systems are open, out-of-equilibrium systems that evolve in and are driven by temporally varying environments. Such systems can show multiple timescale and transient dynamics together with transitions to very different and, at times, even disastrous dynamical regimes. Since such critical transitions disrupt the systems’ intended or desired functionality, it is crucial to understand the underlying mechanisms, to identify precursors of such transitions, and to reliably detect them in time series of suitable system observables to enable forecasts. This review critically assesses the various steps of investigation involved in time-series-analysis-based detection of critical transitions in real-world non-autonomous systems: from the data recording to evaluating the reliability of offline and online detections. It will highlight pros and cons to stimulate further developments, which would be necessary to advance understanding and forecasting nonlinear behavior such as critical transitions in complex systems.
Wind characteristics around a skyway bridge of high-rise buildings
Authors: Chen Wan-Yi , Su Yu-Li , Juan Yu-Hsuan
Published: July 2024

To respond the expansion of urban centers, the proliferation of high-rise buildings demands a better understanding of the aerodynamic phenomena around skyway bridges connecting these structures. This analysis, utilizing the advanced computational fluid dynamics verified by wind tunnel test data, investigates the wind characteristics around such bridges, crucial for structural stability, pedestrian comfort, and aerodynamic efficiency. This study focuses on the interactions between a 2 × 2 building array with a building height-to-street width ratio of 30 and a skyway bridge, investigating those factors such as bridge influence, building structures, building height, and bridge position. Using the three-dimensional steady Reynolds-averaged Navier–Stokes equations along with the Reynolds stress model for turbulence closure, the results show that the presence of skyway bridge significantly modifies local wind patterns. Wind speed and turbulence intensity are impacted differently based on the bridge's upstream or downstream settings. Downstream bridges tend to reduce wind speeds due to the sheltering effects, while upstream placement of bridge can enhance wind flow, affecting both the structural design and pedestrian comfort. Additionally, building height variations adjacent to the bridge influence wind velocity and pressure profiles, with taller buildings intensifying wind speeds at lower levels because of the channeling effects. These insights are pivotal for optimizing the skyway bridge designs to improve airflow distribution, enhance environmental sustainability, and ease wind-caused disturbances, offering a guideline for future architectural and urban planning in high-rise districts.
A scale-similarity based workflow for self-supervised reconstruction of small-scales in turbulence using deep learning
Authors: Dash Priyabrat , Aditya Konduri
Published: July 2024

Deep learning has been extensively utilized for modeling and analysis of fluid turbulence. One such application is the use of super-resolution (SR) algorithms to reconstruct small-scale structures from their large-scale counterparts for turbulent flows. To date, all SR algorithms have been supervised or require unpaired reference data at a high resolution for training. This renders the model inapplicable to practical fluid flow scenarios, in which the generation of a high-resolution ground truth by resolving all scales down to the Kolmogorov scale becomes prohibitive. Hence, it is imperative to develop physics-guided models that exploit the multiscale nature of turbulence. Considering SR as a state-estimation problem, we present a self-supervised workflow based on deep neural networks to reconstruct small-scale structures that are relevant to homogeneous isotropic turbulence. In addition to visual similarity, we assessed the quality of the obtained reconstruction using spectra, structure functions, and probability density functions of the gradients of velocity and a passive scalar. From the analysis, we infer that the outputs of the workflow are in statistical agreement with the ground truth, for which the training pipeline is agnostic. Insights into learnability, interpretability, and generality of the trained networks have been provided as well. The results of this study can be leveraged to devise techniques for the reconstruction of small-scale structures using large-eddy simulation data.
Quantum rates in dissipative systems with spatially varying friction
Authors: Bridge Oliver , Lazzaroni Paolo , Martinazzo Rocco , Rossi Mariana , Althorpe Stuart C. , Litman Yair
Published: July 2024

We investigate whether making the friction spatially dependent on the reaction coordinate introduces quantum effects into the thermal reaction rates for dissipative reactions. Quantum rates are calculated using the numerically exact multi-configuration time-dependent Hartree method, as well as the approximate ring-polymer molecular dynamics (RPMD), ring-polymer instanton methods, and classical molecular dynamics. By conducting simulations across a wide range of temperatures and friction strengths, we can identify the various regimes that govern the reactive dynamics. At high temperatures, in addition to the spatial-diffusion and energy-diffusion regimes predicted by Kramer’s rate theory, a (coherent) tunneling-dominated regime is identified at low friction. At low temperatures, incoherent tunneling dominates most of Kramer’s curve, except at very low friction, when coherent tunneling becomes dominant. Unlike in classical mechanics, the bath’s influence changes the equilibrium time-independent properties of the system, leading to a complex interplay between spatially dependent friction and nuclear quantum effects even at high temperatures. More specifically, a realistic friction profile can lead to an increase (or decrease) of the quantum (classical) rates with friction within the spatial-diffusion regime, showing that classical and quantum rates display qualitatively different behaviors. Except at very low frictions, we find that RPMD captures most of the quantum effects in the thermal reaction rates.
Exploring the generation and annihilation of three-dimensional nulls through MHD simulations in initially chaotic magnetic field devoid of nulls
Authors: Maurya Yogesh Kumar , Bhattacharyya Ramit , Pontin David I. , Kumar Sanjay
Published: July 2024

Three-dimensional (3D) magnetic nulls are abundant in the solar atmosphere, as has been firmly established through contemporary observations. They are established to be important magnetic structures in, for example, jets and circular ribbon flares. Although simulations and extrapolations support this, the mechanisms behind 3D null generation remain an open question. Recent magnetohydrodynamic simulations demonstrated magnetic reconnections to be responsible for both generating and annihilating 3D nulls. However, these simulations began with initial magnetic fields already supporting preexisting nulls, raising the question of whether magnetic reconnection can create nulls in fields initially devoid of them. Previously, this question was briefly explored in a simulation with an initial chaotic magnetic field. However, the study failed to precisely identify locations, topological degrees, and natures (spiral or radial) of nulls, and it approximated magnetic reconnection without tracking the magnetic field lines in time. In this paper, these findings are revisited in light of recent advancements and tools used to locate and trace nulls, along with the tracing of field lines, through which the concept of generation/annihilation of 3D nulls from chaotic fields is established in a precise manner.
Accelerating QM/MM simulations of electrochemical interfaces through machine learning of electronic charge densities
Authors: Grisafi Andrea , Salanne Mathieu
Published: July 2024

A crucial aspect in the simulation of electrochemical interfaces consists in treating the distribution of electronic charge of electrode materials that are put in contact with an electrolyte solution. Recently, it has been shown how a machine-learning method that specifically targets the electronic charge density, also known as SALTED, can be used to predict the long-range response of metal electrodes in model electrochemical cells. In this work, we provide a full integration of SALTED with MetalWalls, a program for performing classical simulations of electrochemical systems. We do so by deriving a spherical harmonics extension of the Ewald summation method, which allows us to efficiently compute the electric field originated by the predicted electrode charge distribution. We show how to use this method to drive the molecular dynamics of an aqueous electrolyte solution under the quantum electric field of a gold electrode, which is matched to the accuracy of density-functional theory. Notably, we find that the resulting atomic forces present a small error of the order of 1 meV/Å, demonstrating the great effectiveness of adopting an electron-density path in predicting the electrostatics of the system. Upon running the data-driven dynamics over about 3 ns, we observe qualitative differences in the interfacial distribution of the electrolyte with respect to the results of a classical simulation. By greatly accelerating quantum-mechanics/molecular-mechanics approaches applied to electrochemical systems, our method opens the door to nanosecond timescales in the accurate atomistic description of the electrical double layer.
Experimental study on the influence of water depth and bed slope variations on dam-break flood wave propagation
Authors: Zhou Xidong , Su Lijun , Yuan Hao , Mao Yunfei , Sun Qian
Published: July 2024

Damage to dam structures frequently results in catastrophic consequences. Consequently, understanding of the characteristics of the movement of dam-break flow along the sloping wet bed can assist in the issuance of timely flood warnings and risk mitigation. In this study, a series of large-scale flume experiments was conducted with the objective of investigating the effects of upstream and downstream water depth and bed slope on the propagation of dam-break waves. The water level is measured and processed to calculate the wavefront velocity. Results show that the wave propagation behavior can be classified as bore and undular waves through the global Froude numbers (Frx) and local Froude numbers (Frl). When Frx < 1.225 or Frl < 1.475, the dam-break wave propagates as the undular wave. In the undular wave state, the wavefront velocity (U) decreases with increasing water depth ratio α. Additionally, the U with Frx shows a similar trend, where the experimental value surpasses the analytical solution. The dimensionless maximum wave height (ΔHmax) increases with Frx and then decreases. The deviation from the analytical solution ranges between 67.22% and 127.38%. When Frx > 1.225 or Frl > 1.475, the dam-break wave propagates as the bore wave. In the bore wave state, the U increases slightly with the water depth ratio α, while the change rule of U with Frx is similar to it. The dimensionless maximum wave height (ΔHmax) remains relatively constant as Frx increases, showing a high degree of consistency with the analytical solution. The presence of bed slope results in increased wavefront velocity and wave heights, while an increase in α results in the emergence of more pronounced undular wave phenomena. Furthermore, the experimental results are compared with existing analytical solutions, and the validity of the analytical solutions and their limitations are discussed.
Study on the response of the winding direction of multi-layer CORC cable to its electromagnetic characteristics
Authors: Jia Rongli , Zhou Wenhai , Liang Rui , Su Bingxu , Hu Zongwu
Published: July 2024

A Conductor on Round Core (CORC) cable wound with a high-temperature superconductor is an important cable concept for high-current density applications. It is widely used in large power systems because of its advantages of good flexibility and high engineering current density. However, the complex design structure of CORC cable makes it very difficult to understand its electromagnetic properties (such as AC loss). In particular, the different winding directions of each layer in multi-layer cable have a great influence on its electromagnetic characteristics. In this paper, the H-method is used to solve the electromagnetism and mechanics equations. The influence of the winding direction of CORC cable on its electromagnetic field distribution characteristics, AC loss, and mechanical variation under the action of external magnetic field is investigated. The AC loss study of single-layer cable reveals that when the applied magnetic field is increased from 0.01 to 0.02 and 0.03 T, the AC loss peak of the cable increases by 107 and 103 orders of magnitude, respectively, indicating that the effect of low applied magnetic field on the AC loss of the cable is more significant. For multi-layer cables, cables with opposite winding directions have a greater depth of current density penetration than cables with the same winding direction. In addition, the mechanical variations of multi-layer cables with different winding orientations are explored. The results show that the Mises stress in the cable with the same winding direction is about 32% higher than that of the cable with the opposite winding direction, which indicates that the method of winding the cable in the opposite direction between adjacent layers of tape can avoid excessive mechanical stress.
Interfacial conditioning in physics informed neural networks
Authors: Biswas Saykat Kumar , Anand N. K.
Published: July 2024

Physics informed neural networks (PINNs) have effectively demonstrated the ability to approximate the solutions of a system of partial differential equations (PDEs) by embedding the governing equations and auxiliary conditions directly into the loss function using automatic differentiation. Despite demonstrating potential across diverse applications, PINNs have encountered challenges in accurately predicting solutions for time-dependent problems. In response, this study presents a novel methodology aimed at enhancing the predictive capability of PINNs for time-dependent scenarios. Our approach involves dividing the temporal domain into multiple subdomains and employing an adaptive weighting strategy at the initial condition and at the interfaces between these subdomains. By employing such interfacial conditioning in physics informed neural networks (IcPINN), we have solved several unsteady PDEs (e.g., Allen–Cahn equation, advection equation, Korteweg–De Vries equation, Cahn–Hilliard equation, and Navier–Stokes equations) and conducted a comparative analysis with numerical results. The results have demonstrated that IcPINN was successful in obtaining highly accurate results in each case without the need for using any labeled data.
Transcranial thermoacoustic imaging based on the fast back-projection algorithm with nonuniform speed of sound layering
Authors: Yang Zeqi , Zhu Xiaozhang , Zhao Zhiqin , Huang Lin
Published: July 2024

Thermoacoustic imaging (TAI) has the potential for detecting hemorrhagic stroke. However, in transcranial TAI, the speed of sound (SoS) between the skull and brain tissue varies significantly. Therefore, if the image reconstruction assumes a uniform SoS, accurately locating the hemorrhagic lesion becomes challenging. In this Letter, we propose a fast inhomogeneous layer back-projection (BP) method based on the basic boundary line with a statistical approach to reconstruct TA images for noninvasive and non-ionizing hemorrhage detection. To validate our proposed method, we conducted numerical simulations using real human skull data and two phantom transcranial TAI experiments. In the numerical simulation, the proposed method improves the structural similarity index measure from 0.034 879 for BP with uniform SoS to 0.624 44. The phantom experimental results demonstrate that the proposed method renders the targets in the reconstructed image more consistent with the real targets. In the case of considering a three-layer SoS distribution, the time reversal method requires 1 min and 37.391 s to reconstruct a 201 × 201 pixels TA image. Meanwhile, the proposed method accomplishes the same-sized TA image reconstruction in only 2.113 397 s. The simulation and experimental results indicate that the proposed method enhances TAI's ability for accurate and fast identification of cerebral hemorrhage.
Structure-based investigation of a DNA aptamer targeting PTK7 reveals an intricate 3D fold guiding functional optimization
Authors: He Axin , Wan Liqi , Zhang Yuchao , Yan Zhenzhen , Guo Pei , Han Da , Tan Weihong
Published: July 2024

DNA aptamers have emerged as novel molecular tools in disease theranostics owing to their high binding affinity and specificity for protein targets, which rely on their ability to fold into distinctive three-dimensional (3D) structures. However, delicate atomic interactions that shape the 3D structures are often ignored when designing and modeling aptamers, leading to inefficient functional optimization. Challenges persist in determining high-resolution aptamer–protein complex structures. Moreover, the experimentally determined 3D structures of DNA molecules with exquisite functions remain scarce. These factors impede our comprehension and optimization of some important DNA aptamers. Here, we performed a streamlined solution NMR-based structural investigation on the 41-nt sgc8c, a prominent DNA aptamer used to target membrane protein tyrosine kinase 7, for cancer theranostics. We show that sgc8c prefolds into an intricate three-way junction (3WJ) structure stabilized by long-range tertiary interactions and extensive base–base stackings. Delineated by NMR chemical shift perturbations, site-directed mutagenesis, and 3D structural information, we identified essential nucleotides constituting the key functional elements of sgc8c that are centralized at the core of 3WJ. Leveraging the well-established structure–function relationship, we efficiently engineered two sgc8c variants by modifying the apical loop and introducing

L

-DNA base pairs to simultaneously enhance thermostability, biostability, and binding affinity for both protein and cell targets, a feat not previously attained despite extensive efforts. This work showcases a simplified NMR-based approach to comprehend and optimize sgc8c without acquiring the complex structure, and offers principles for the sophisticated structure–function organization of DNA molecules.
Overlapping role of synaptophysin and synaptogyrin family proteins in determining the small size of synaptic vesicles
Authors: Park Daehun , Fujise Kenshiro , Wu Yumei , Luján Rafael , Del Olmo-Cabrera Sergio , Wesseling John F. , De Camilli Pietro
Published: July 2024

Members of the synaptophysin and synaptogyrin family are vesicle proteins with four transmembrane domains. In spite of their abundance in synaptic vesicle (SV) membranes, their role remains elusive and only mild defects at the cellular and organismal level are observed in mice lacking one or more family members. Here, we show that coexpression with synapsin in fibroblasts of each of the four brain-enriched members of this family—synaptophysin, synaptoporin, synaptogyrin 1, and synaptogyrin 3—is sufficient to generate clusters of small vesicles in the same size range of SVs. Moreover, mice lacking all these four proteins have larger SVs. We conclude that synaptophysin and synaptogyrin family proteins play an overlapping function in the biogenesis of SVs and in determining their small size.
Force, inertia and motion from Aristotle to nowadays didactics
Authors: Bocci Franco
Published: July 2024

This study delves into the historical development of the core principles of dynamics, namely the interplay between forces and motion. We explore the intricate and nonlinear transition from the Aristotelian framework, which held sway for eighteen centuries, to the Newtonian paradigm. We posit that the complexity of this transition largely stems from what we perceive as an inadequate understanding of force. Our focus lies particularly on the seminal contributions of Galileo and the subsequent remarkable advancements made by Newton. However, we also note that, somewhat surprisingly, the transition does not conclude with Newton himself. What is commonly known as Newtonian dynamics in modern textbooks diverges significantly from the original theory outlined in the Principia, and we endeavour to elucidate these disparities. In the concluding sections, we scrutinise the implications of these concepts for contemporary teaching methodologies. Specifically, we delve into various interpretations of the Principle of Inertia, the Second Law, and their interrelationship, pinpointing what we perceive as weak points in current didactic approaches and proffering some suggestions for effectively imparting these concepts.
The three-dimensional harmonic oscillator and solid harmonics in Bargmann space
Authors: Sunko D K , Ciosłowski J
Published: July 2024

The three-dimensional harmonic oscillator is solved in Bargmann space. The treatment is pedagogically more transparent than the standard ones, at the price of introducing the Bargmann transform in the context of the one-dimensional oscillator. The standard solid harmonics are similarly derived with minimal technical effort, amounting to a complete self-contained exposition suitable for introductory courses in quantum mechanics or mathematical methods of physics. It provides an early exposure to wavelets, with important contemporary applications in signal analysis and quantum optics.
Highly efficient meta-lens integrated holographic surface antenna
Authors: Hao Yazheng , Yang Rui , Li Chunhui , Wang Yan
Published: July 2024

We demonstrate the generation of highly directive circularly polarized beams by proposing a meta-lens to calibrate the near fields over the holographic surface. Such a design possesses the merits of ultra-low profile as a lens system on the basis of phase compensation of a specific radiating aperture rather than the conventional consideration of the lens focus, and the ratio between the overall height of the antenna architecture and diameter of radiating aperture is only 0.09. Especially, the proposed meta-lens integrated holographic surface also offers a satisfactory solution to improve the overall efficiency of holographic antennas, and the experimental results verify the proposed design with 27.6 dBic measured gain and 40.4

%

aperture efficiency at 15 GHz. We expect the proposed strategy of integrating phase compensation lens closely over the holographic surface, pave the way for highly efficient meta-radiators with ultra-low profile.
Strain-dependence of Te interstitial diffusion in CdTe
Authors: Hamadna Sameer , Amar Jacques G
Published: July 2024

While the dominant defects which control non-radiative recombination and long-range interstitial diffusion in CdTe correspond to Cd vacancies and Te anti-sites, the short-range diffusion of Te and Se interstitials between these defects is also of interest, since they both play a role in defect passivation. In addition, since CdTe thin films are typically polycrystalline and may also involve interfaces with materials with different lattice constants, the effects of strain are also of interest. Here we present the results of molecular dynamics (MD) simulations of Te interstitial diffusion in zincblende CdTe for values of the triaxial strain ranging from −2% (compressive) strain to +2.8% (tensile) strain. By carrying out MD simulations of Te interstitial diffusion over a range of temperatures, and then carrying out Arrhenius fits, we have determined the effective activation barrier

E

a

and prefactor D
0 for each value of the global strain. We find that both

E

a

and D
0 exhibit non-monotonic behavior, increasing with both compressive and tensile strain. We also present an analysis of the key diffusion pathways for 3 different values of the strain which explains the non-monotonic strain dependence obtained in our simulations. Our results also indicate that in each case, the diffusion of interstitial Te involves a variety of concerted events with a wide range of activation barriers.
Optical response of Higgs mode in superconductors at clean limit: formulation through Eilenberger equation and Ginzburg–Landau Lagrangian
Authors: Yang F , Wu M W
Published: July 2024

Both macroscopic Ginzburg–Landau Lagrangian and microscopic gauge-invariant kinetic equation suggest a finite Higgs-mode generation in the second-order optical response of superconductors at clean limit, whereas the previous derivations through the path-integral approach and Eilenberger equation within the Matsubara formalism failed to give such generation. The crucial treatment leading to this controversy lies at an artificial scheme that whether the external optical frequency is taken as continuous variable or bosonic Matsubara frequency to handle the gap dynamics within the Matsubara formalism. To resolve this issue, we derive the effective action of the superconducting gap near Tc
in the presence of the vector potential through the path-integral approach, to fill in the long missing gap of the microscopic derivation of the Ginzburg–Landau Lagrangian in superconductors. It is shown that only by taking optical frequency as continuous variable within the Matsubara formalism, can one achieve the fundamental Ginzburg–Landau Lagrangian, and in particular, the finite Ginzburg–Landau kinetic term leads to a finite Higgs-mode generation at clean limit. To further eliminate the confusion of the Matsubara frequency through a separate framework, we apply the Eilenberger equation within the Keldysh formalism, which is irrelevant to the Matsubara space. By calculating the gap dynamics in the second-order response, it is analytically proved that the involved optical frequency is a continuous variable rather than bosonic Matsubara frequency, causing a finite Higgs-mode generation at clean limit.
An online comprehensive health monitoring system for automotive auxiliary converter
Authors: Wu Chenhao , Xia Qian , Cui Zhexin , Su Yongqing , Yue Jiguang , Lyu Feng
Published: July 2024

As an essential part of the electronic system in electric vehicles, the automotive auxiliary converter (AAC) connects the batteries and burdens the auxiliary power supply. This paper mainly proposes an online comprehensive health monitoring system for AAC. Firstly, based on the control diagram of the LLC resonant converter, three critical components are emerging, including capacitor, optocoupler, and semiconductor. These components can partly reflect the operation condition of the output loop, feedback loop, and control link, respectively. Then the characteristics parameters of these three components, equivalent series resistance of the capacitor, current transfer ratio of the optocoupler, and on-resistance of the semiconductor jointly construct the three-dimensional health monitoring vector. Finally, the online monitoring accuracy is verified and the proposed system can thus effectively promote the operation and maintenance of AAC. Furthermore, the online health monitoring system enables a flexible expansion, which can be further customized into different kinds of power converters, showing high applicability and practicality.
Measurement of air-water counter-current flow rates in vertical annulus using multiple differential pressure signals and machine learning
Authors: Cao Feng , Dang Ruirong , Dang Bo , Zheng Huifeng , Ji Anzhao , Chen Zhanjun
Published: July 2024

Gas–liquid counter-current flow in vertical annulus is involved in several industrial fields such as petroleum engineering. For example, in coalbed methane wells with liquid pump drainage, obtaining the real-time flow rate of gas–liquid two-phase in the annulus is crucial for the development management of coalbed methane wells. However, due to complex flow conditions, this demand is difficult to achieve through traditional flow metering means. Therefore, this paper proposes a flow prediction method based on multi-group differential pressure signals and machine learning technology. Air-water two-phase flow experiments were carried out on a vertical annulus pipeline with inner and outer diameters of 75 mm/125 mm and adjustable eccentricity. The probability density function and power spectrum density of 3 groups of differential pressure signals collected at different height intervals in the annulus were used as model inputs. A gas–liquid two-phase flow prediction model was constructed based on the artificial neural network model, and the model hyper-parameters were optimized using Bayesian optimization. The results show that on the 440-group test dataset under the combined conditions of air superficial velocity of 0.06–5.04 m s−1, water superficial velocity of 0.03–0.25 m s−1, and pipeline eccentricity of 0, 0.25, 0.5, 0.75, 1, etc. This model can achieve average prediction errors of 9.12% and 29.34% for gas and water flow rates respectively. This method can be applied to the non-throttling, non-invasive measurement of phase flow rate under the condition of annulus air-liquid counter-current flow.
The direction vector assisted INS/spectral redshift integrated navigation system for spacecraft
Authors: Peng Xu , Li Yan , Hu Gaoge , Gao Guangle
Published: July 2024

A reliable and autonomous navigation system is crucial for achieving high survivability of spacecraft. As a novel autonomous navigation system, an inertial/spectral redshift (INS/SRS) integrated navigation system can correct the navigation errors of INS through redshift and direction vector information from celestial bodies. However, since SRS needs to obtain position measurements by integrating the velocity information of the spacecraft, the position error from INS/SRS diverges. Therefore, this paper investigates a direction vector-assisted INS/SRS integrated navigation system for spacecraft. It examines the relationship among the position of the spacecraft, redshift, and direction vectors from celestial bodies. Then, a direction vector-assisted SRS is proposed, which can solve the position information of spacecraft directly by using redshift and direction vector information. Finally, the direction vector-assisted SRS is combined with INS to form the direction vector-assisted INS/SRS integrated navigation system. Simulations and comprehensive analysis demonstrate that the proposed integrated navigation system has better performance than the conventional INS/SRS integrated navigation system.
Dynamic characteristic analysis and key parameter optimization of throttling orifice type air damping air spring
Authors: Chen Junjie , Huang Ziqi , Kang Sheng , Yang Qin , Yuan Xianju , Huang Peng , Gan Yu Feng
Published: July 2024

The unique hysteretic characteristic of rubber bellows and the nonlinear flow of internal airflow in the system results in the significant nonlinear dynamic characteristic of throttling orifice type air damping air springs (OADASs). To solve the problem of mathematical representation of dynamic characteristic and key parameters optimization of throttling OADAS, this paper comprehensively considers the hysteretic characteristic of rubber bellows under variable pressure, the nonlinear dynamic characteristic model and linear model of throttling OADAS are established based on the concepts of gas thermodynamics and fluid mechanics. The static and dynamic characteristic tests of the throttling OADAS are conducted, to verify the accuracy and effectiveness of the proposed model, and to reveal the influence laws of excitation amplitude, excitation frequency, and throttling orifice diameter on the quantitative characterization indexes. Finally, a complete throttling orifice diameter optimization method is proposed based on the eight-degree-of-freedom model of the entire vehicle. Optimization results illustrate that the RMS values of the vertical acceleration of the body and the vertical acceleration of the driver are decreased by 19.02% and 38.44%, respectively. Overall, the outcomes of this paper can provide the design idea and theoretical basis for air damping matching and active suspension control.
Influence of cutoff radius and tip atomic structure on energy barriers encountered during AFM tip sliding on 2D monolayers
Authors: Lim Jaehun , Moon Donghyeon , Kim Sunghyun , Kim Suenne
Published: July 2024

In computational studies using the Lennard–Jones (LJ) potential, the widely adopted 2.5 σ cutoff radius effectively truncates pairwise interactions across diverse systems (Santra et al 2008 J. Chem. Phys.
129 234704, Chen and Gao 2021 Friction
9 502–12, Bolintineanu et al 2014 Part. Mech.
1 321–56, Takahiro and Kazuhiro 2010 J. Phys.: Conf. Ser.
215 012123, Zhou et al 2016 Fuel
180 718–26, Toxvaerd and Dyre 2011 J. Chem. Phys.
134 081102, Toxvaerd and Dyre 2011 J. Chem. Phys.
134 081102). Here, we assess its adequacy in determining energy barriers encountered by a Si monoatomic tip sliding on various two-dimensional (2D) monolayers, which is crucial for understanding nanoscale friction. Our findings emphasize the necessity of a cutoff radius of at least 3.5 σ to achieve energy barrier values exceeding 95% accuracy across all studied 2D monolayers. Specifically, 3.5 σ corresponds to 12.70 Å in graphene, 12.99 Å in MoS2 and 13.25 Å in MoSe2. The barrier values calculated using this cutoff support previous experiments comparing friction between different orientations of graphene and between graphene and MoS2 (Almeida et al 2016 Sci. Rep.
6 31569, Zhang et al 2014 Sci. China
57 663–7). Furthermore, we demonstrate the applicability of the 3.5 σ cutoff for graphene on an Au substrate and bilayer graphene. Additionally, we investigate how the atomic configuration of the tip influences the energy barrier, finding a nearly threefold increase in the barrier along the zigzag direction of graphene when using a Si(001) tip composed of seven Si atoms compared to a monoatomic Si tip.
Non-invasive pulse arrival time is associated with cardiac index in pediatric heart transplant patients with normal ejection fraction
Authors: Kwon Soon Bin , Weinerman Bennett , Nametz Daniel , Megjhani Murad , Lee Isaac , Habib Anthony , Barry Oliver , Park Soojin
Published: July 2024

Objective. Cardiac Index (CI) is a key physiologic parameter to ensure end organ perfusion in the pediatric intensive care unit (PICU). Determination of CI requires invasive cardiac measurements and is not routinely done at the PICU bedside. To date, there is no gold standard non-invasive means to determine CI. This study aims to use a novel non-invasive methodology, based on routine continuous physiologic data, called Pulse Arrival Time (PAT) as a surrogate for CI in patients with normal Ejection Fraction (EF). Approach. Electrocardiogram (ECG) and photoplethysmogram (PPG) signals were collected from beside monitors at a sampling frequency of 250 samples per second. Continuous PAT, derived from the ECG and PPG waveforms was averaged per patient. Pearson’s correlation coefficient was calculated between PAT and CI, PAT and heart rate (HR), and PAT and EF. Main Results. Twenty patients underwent right heart cardiac catheterization. The mean age of patients was 11.7 ± 5.4 years old, ranging from 11 months old to 19 years old, the median age was 13.4 years old. HR in this cohort was 93.8 ± 17.0 beats per minute. The average EF was 54.4 ± 9.6%. The average CI was 3.51 ± 0.72 l min−1 m−2, with ranging from 2.6 to 4.77 l min−1 m−2. The average PAT was 0.31 ± 0.12 s. Pearson correlation analysis showed a positive correlation between PAT and CI (0.57, p < 0.01). Pearson correlation between HR and CI, and correlation between EF and CI was 0.22 (p = 0.35) and 0.03 (p = 0.23) respectively. The correlation between PAT, when indexed by HR (i.e. PAT × HR), and CI minimally improved to 0.58 (p < 0.01). Significance. This pilot study demonstrates that PAT may serve as a valuable surrogate marker for CI at the bedside, as a non-invasive and continuous modality in the PICU. The use of PAT in clinical practice remains to be thoroughly investigated.
Longitudinal-twist wave converter based on chiral metamaterials
Authors: Lemkalli Brahim , Kadic Muamer , El Badri Youssef , Guenneau Sébastien , Mir Abdellah , Achaoui Younes
Published: July 2024

Advances in material architectures have enabled endowing materials with exotic attributes not commonly available in the conventional realm of mechanical engineering. Twisting, a mechanism whereby metamaterials are used to transform static axial load into twist motion, is of particular interest to this study. Herein, computations based on the finite element method, corroborated by a theoretical approach derived from applying Lagrange’s equations to a monoatomic spring-mass system, are employed to explore the longitudinal-twist (L-T) conversion exhibited by a chiral tetragonal-beam metamaterial. Firstly, we perform an eigenvalue analysis taking into account the polarization states to highlight the contribution of the longitudinal mode in the L-T conversion. We contrast the twisting behavior of the chiral cell with that of other homogeneous medium, octagonal-tube, and non-chiral cells. Moreover, we demonstrate the influence of the cell’s chirality on the L-T conversion using both time-domain and frequency-domain studies. The findings indicate that at least a portion of the longitudinally propagating wave is transformed into twist throughout a broad frequency range and even quasi-totally converted at distinct frequencies.
Rhodian Epigraphic Culture and Society
Authors: Zachhuber Juliane
Published: July 2024

This chapter considers the aftermath of the Rhodian synoecism and the historical developments of the new social and political creation of Rhodes throughout the Hellenistic period. It does this first by focusing on historiographical accounts (in particular by non-Rhodian observers), sketching the well-known image of the successful maritime commercial centre, a melting pot in the south-eastern Aegean, governed by a democracy, but with a powerful aristocracy. The chapter then shifts to consider the ample evidence of epigraphy, and to what extent the picture provided by Rhodian epigraphic culture maps onto that projected by historians. An analysis of Rhodian epigraphy illuminates striking local divergences and the importance of sanctuaries as spaces for epigraphic display, as well as offering a clear picture of how Rhodians presented and saw themselves and their society.
Gods of the Rhodian State: Helios and Athena
Authors: Zachhuber Juliane
Published: July 2024

Rhodian religion was dominated by two gods: Helios and Athena. This chapter digs into the religious significance and cultic presence of both deities. Helios was chosen as the new patron deity of the unified Rhodian state, giving him an unusually prominent poliad position in the late classical Greek world. Much about his cult remains uncertain, including the precise location of his sanctuary, and how he was worshipped. This section suggests seeing the famous Colossus primarily as a religious offering, and further explores the similarities between Helios and other gods, including Apollo and Poseidon, as well as his long-lasting perception as a Rhodian god. Athena has a much longer cultic presence on Rhodes, and provides us with a much greater body of evidence. Her local cults are compared in terms of their sites and their worshippers, and commonalities and idiosyncrasies are drawn out.
Measurement of inward leakage of full-face masks in EN and ISO standards: comparison of gas and aerosol test agents
Authors: Santandrea Audrey , Marchal Mathieu , Chazelet Sandrine , Marsteau Stéphanie
Published: July 2024

In Europe, respiratory protective devices must be certified before they can be marketed. Among the parameters of interest, inward leakage (IL) characterizes the tightness between the face seal and the face, to verify that the device is well-designed. European standard EN 13274-1 (2001) and International Organization for Standardization (ISO) standard ISO 16900-1 (2019) specify that IL should be measured using sodium chloride (NaCl) aerosol or sulfur hexafluoride (SF6) gas. For reusable masks made of nonporous materials, both test agents are considered equally acceptable. However, the few studies that have compared IL values measured with various aerosols and gases have come to divergent conclusions. This work then aimed to measure IL with the test agents recommended by the standards to determine whether they are really equivalent. Since krypton (Kr) is an interesting candidate for replacing SF6 in standard tests, IL was assessed with SF6 and Kr simultaneously, and with NaCl aerosol using various calculation methods.

Tests were carried out on 5 models of full-face masks donned on a headform connected to a breathing machine simulating 3 sinusoidal breathing rates of various intensities. The respirator fit on the headform was evaluated using a controlled negative pressure method to determine a manikin fit factor. Four scenarios were then tested to represent very poor, bad, good, and excellent fit. Gas concentration was measured using a mass spectrometer, and IL was calculated for SF6 and Kr. A combination of 3 devices allowed the determination of the number-based concentration of particles with diameters between 20 nm and 2 µm, and IL was calculated for each of the 33 channels, as well as using a cumulative number concentration. In addition, to comply with standards, a conversion was carried out to calculate IL using a cumulative mass concentration.

The results of this work evidenced that the IL values measured with NaCl were systematically lower than those determined with gases. IL was also shown to vary with particle size, with a maximum value exceeding that calculated with cumulative concentrations (in number or mass). As part of the revision of the standards, protocols for measuring inward leakage should be redefined. On the one hand, acceptability thresholds should be re-evaluated according to the nature of the test agent (gas or aerosol), as it is clear that the 2 options do not give the same results for a given configuration. On the other hand, the aerosol leakage measurement protocol needs to be reworked to enable the measurement of a well-defined, robust, and reproducible inward leakage value.
The Epistemic Goals of the Humanities
Authors: Grimm Stephen R
Published: July 2024

The sciences aim to get at the truth about the nature of the world. Do the humanities have a similar goal—namely, to get at the truth about things like novels, paintings, and historical events? I consider a few different ways in which the humanities aim at the truth about their objects, in the process giving rise to epistemic goods such as knowledge and understanding. Two works in the humanities are used as test cases: the historian Tyler Stovall’sParis Noir (1996) and the musicologist Susan McClary’s article, ‘The Blasphemy of Talking Politics During Bach Year’ (1987).