bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular dynamics study on the effect of cementite structure on the mechanical properties of pearlite
Authors: Zhang Haichao , Chen Yinli , Sun Yanhui 
Published: June 2024

Abstract
The effect of cementite structure on the mechanical properties of pearlite were investigated using molecular dynamics simulations. Three types of cementite structures were considered: single crystal, nanocrystalline, and a mixture of nanocrystalline and amorphous structures. The study found that regardless of the cementite structure, the ferrite phase in the pearlite exhibited plastic deformation first due to the activation of its internal {112} 〈111〉 slip system during tensile loading, resulting in macroscopic yielding of the pearlite. However, the difficulty of plastic deformation in the ferrite phase varied with different cementite structures. Compared to the other two types of cementite structures, the ferrite phase in the pearlite containing single crystal cementite exhibited the most difficult plastic deformation, leading to the highest peak stress. As the strain increased, the plastic deformation in the ferrite transferred through the ferrite-cementite interface to the cementite. After the plastic deformation transferred to the cementite, the different cementite structures exhibited distinct mechanical responses: the single crystal cementite structure experienced cleavage fracture, the nanocrystalline cementite structure underwent plastic deformation induced by grain boundary slip, while the nanocrystalline-amorphous mixture cementite structure showed shear deformation in the amorphous cementite and plastic deformation induced by grain boundary slip in the nanocrystalline cementite. Due to the influence of cementite mechanical response mechanism, the flow stress of the pearlite was minimal when the cementite in the pearlite were in single crystal structure. The study also revealed that when the cementite was in nanocrystalline structure, the flow stress of pearlite decreases with the grain size decreasing from 4.25 nm to 2.68 nm. When the cementite is a mixture of nanocrystalline and amorphous structure, the flow stress of pearlite decreases as the thickness of amorphous layer increases from 1 nm to 2 nm.
Design and analysis of Minkowski fractal shaped metasurface absorber with broadband and polarization-insensitive characteristics using a tunable graphene layer for terahertz applications
Authors: Rekha Vutukuri Sarvani Duti , Prasad Nagandla , Madhav B T P , Alathbah Moath 
Published: June 2024

Abstract
The proposed research article’s main goal is to demonstrate a terahertz (THz) broadband absorber for high-speed wireless communication applications. The proposed structure is a compact one and possesses three layers. The ground layer acts as a metal reflector, lossy silicon acts as a dielectric material and finally a graphene layer in the shape of a minkowski fractal acts as a radiating patch for the proposed design. We have chosen a thickness of 5 μm for the lossy silicon which has a dielectric constant of 11.90. The bottom layer of the proposed design contains a good conductive material like gold with a conductivity of 4.561 e+007 s m−1 with a thickness of 0.2 μm. The thickness of a monolayer graphene is one nanometer, and the overall unit cell size of the proposed structure is 12 × 12 μm2. Because of its symmetrical nature, the proposed absorber offers a broad response to both TM and TE modes irrespective of any polarization angle. The proposed absorber can operate in the terahertz frequency range and has achieved two broad frequency bands from 3.34–3.98 THz and 4.6–5.30 THz, with an absorption percentage greater than 90. We can observe peak absorption frequencies at 3.60 THz and 5.04 THz, which exhibit an absorption percentage close to unity. Additionally, we validated the proposed broadband absorber using an equivalent circuit approach and verified it using the ADS tool.
Hydrodynamics of (1+1) dimensional fluid in the presence of gravitational anomaly from first order thermodynamics
Authors: Seenivasan Abhinove Nagarajan , Chakrabarti Sayan , Majhi Bibhas Ranjan 
Published: June 2024

Abstract
Considering (1+1)-dimensional fluid in presence of gravitational trace anomaly, as an effective description of higher-dimensional fluid, the hydrodynamics is discussed through a first order thermodynamic description. Contrary to the existing approaches which are second order in nature, the fluid velocity is identified through the auxiliary field required to describe the Polyakov action for the effective description of relevant energy-momentum tensor. The thermodynamic and fluid quantities, on a static black hole spacetime, are calculated both near the horizon as well as at the asymptotic infinity. The Unruh vacuum appears to be suitable one for the present analysis, in contrast to Israel-Hartle-Hawking vacuum which is consistent with second order description. As in anomaly cancellation approach to find the Hawking flux the Unruh vacuum is consistent with the required conditions, in reverse way we interpret this fluid description as an alternative approach to find these required conditions to calculate the same in anomaly cancellation approach.
Constraints on Bianchi-I type universe with SH0ES anchored Pantheon+ SNIa data
Authors: Verma Anshul , Patel Sanjeet K. , Aluri Pavan K. , Panda Sukanta , Mota David F. 
Published: June 2024

Abstract
We study the Bianchi-I cosmological model motivated by signals of statistical isotropy violation seen in cosmic microwave background (CMB) observations and others. To that end, we consider various kinds of anisotropic matter that source anisotropy in our model, specifically Cosmic strings, Magnetic fields, Domain walls and Lorentz violation generated magnetic fields. These anisotropic matter sources, taking one at a time, are studied for their co-evolution with standard model (isotropic) sources viz., dust-like (dark/normal) matter, and dark energy modelled as cosmological constant. We constrain the Hubble parameter, density fractions of anisotropic matter, cold dark matter (CDM), and dark energy (Λ) in a Bianchi-I universe with planar symmetry i.e., which has a global ellipsoidal geometry, and try to find signatures of a cosmic preferred axis if any.
The latest compilation of Type Ia Supernova (SNIa) data from Pantheon+SH0ES collaboration is used in our analysis to obtain constraints on cosmological parameters and any preferred axis for our universe.
In our analysis, we found mild evidence for a cosmic preferred axis. It is interesting to note that this preferred axis lies broadly in the vicinity of other prominent cosmic anisotropy axes reported in the literature from diverse data sets.
Also we find some evidence for non-zero (negative) cosmic shear and eccentricity that characterize different expansion rates in different directions and deviation from an isotropic scale factor respectively.
The energy density fractions of two of the sources considered are found to be non-zero at a
2σ confidence level.
To be more conclusive, we require more SNIa host galaxy data for tighter constraints on distance and absolute magnitude calibration which are expected to be available from the future JWST observations and others.
Fate of oscillating homogeneous ℤ2-symmetric scalar condensates in the early Universe
Authors: Ai Wen-Yuan , Wang Zi-Liang 
Published: June 2024

Abstract
Dark matter, if represented by a ℤ2-symmetric scalar field, can manifest as
both particles and condensates. In this paper, we study the evolution of an oscillating
homogeneous condensate of a ℤ2-symmetric scalar field in a thermal plasma in an FLRW
universe. We focus on the perturbative regime where the oscillation amplitude is sufficiently
small so that parametric resonance is inefficient. This perturbative regime necessarily comprises
the late stage of the condensate decay and determines its fate. The coupled coarse-grained
equations of motion for the condensate, radiation, and spacetime are derived from first principles
using nonequilibrium quantum field theory. We obtain analytical expressions for the relevant
microscopic quantities that enter the equations of motion and solve the latter numerically. We
find that there is always a nonvanishing relic abundance for a condensate with a ℤ2
symmetry that is not spontaneously broken. This is because its decay rate decreases faster than
the Hubble parameter at late times due to either the amplitude dependence or the temperature
dependence in the condensate decay rate. Consequently, accounting for the condensate contribution
to the overall dark matter relic density is essential for ℤ2 scalar singlet
dark matter.
Data-driven modelling of visual receptive fields: comparison between the generalized quadratic model and the nonlinear input model
Authors: Almasi Ali , Sun Shi H , Jung Young Jun , Ibbotson Michael , Meffin Hamish 
Published: June 2024

Abstract

Objective: Neurons in primary visual cortex (V1) display a range of sensitivity in their response to translations of their preferred visual features within their receptive field: from high specificity to a precise position through to complete invariance. This visual feature selectivity and invariance is frequently modeled by applying a selection of linear spatial filters to the input image, that define the feature selectivity, followed by a nonlinear function that combines the filter outputs, that defines the invariance, to predict the neural response. We compare two such classes of model, that are both popular and parsimonious, the generalized quadratic model (GQM) and the nonlinear input model (NIM). These two classes of model differ primarily in that the NIM can accommodate a greater diversity in the form of nonlinearity that is applied to the outputs of the filters. Approach: We compare the two model types by applying them to data from multielectrode recordings from cat primary visual cortex in response to spatially white Gaussian noise After fitting both classes of model to a database of 342 single units (SUs), we analyze the qualitative and quantitative differences in the visual feature processing performed by the two models and their ability to predict neural response. Main results: We find that the NIM predicts response rates on a held-out data at least as well as the GQM for 95% of SUs. Superior performance occurs predominantly for those units with above average spike rates and is largely due to the NIMs ability to capture aspects of the model’s nonlinear function cannot be captured with the GQM rather than differences in the visual features being processed by the two different models. Significance: These results can help guide model choice for data-driven receptive field modelling.
Analysis of taVNS effects on autonomic and central nervous systems in healthy young adults based on HRV, EEG parameters
Authors: Kang Donghun , Choi Youngseok , Lee Jongshill , Park Eunkyoung , Kim In Young 
Published: June 2024

Abstract

Objective. Transcutaneous auricular vagus nerve stimulation (taVNS), a non-invasive method of stimulating the vagus nerve, simultaneously affects the autonomic nervous system (ANS) and central nervous system (CNS) through efferent and afferent pathways. The purpose of this study is to analyze the effect of taVNS on the ANS and CNS through heart rate variability (HRV) and electroencephalography (EEG) parameters of identified responders. Approach. Two sets of data were collected from each of 10 healthy adult male subjects in their 20 s, and five HRV parameters from the time domain (RMSSD, pNN50, pNN30, pNN20, ppNNx) and two EEG parameters (power of alpha band, power of delta band) were extracted. Main results. Based on pNN50, responders to taVNS were identified; among them, pNN50 (p = 0.0041) and ppNNx (p = 0.0037) showed significant differences before and after taVNS. At the same time, for alpha power and delta power of EEG, significant difference (p < 0.05) was observed in most channels after taVNS compared to before stimulation. Significance. This study demonstrated the validity of identifying responders using pNN50 and the influence of taVNS on both the ANS and CNS. We conclude that taVNS can be used to treat a variety of diseases and as a tool to help control the ANS and CNS.
Numerical simulation of train-induced aerodynamic pressure on railway noise barriers
Authors: Liu Dongyun , Wang Chao , Gonzalez-Libreros Jaime , Enoksson Ola , Hojsten Tommy , Tu Yongming , Elfgren Lennart , Sas Gabriel 
Published: June 2024

Abstract
Noise barriers built parallel to the railway to reduce noise pollution, will be subjected to strong aerodynamic pressure from high-speed trains and have significant dynamic responses under such pressure. Based on computational fluid dynamics (CFD), the numerical simulation of train-induce aerodynamic pressure on noise barriers was performed. Time-varying pressure and its distribution along height direction of noise barriers were analysed, and the effect of different factors on results, i.e., the distance from noise barriers to track centre and height of noise barrier, were discussed. Results show that the geometric changes in train head and tail cause the obvious transient pressure pulse, and the pressure magnitude from head is higher than that from tail. With the measuring height increases, the pressure gradually decreases, which can be well characterized by height coefficient equation from Germany DB code. The pressure magnitude increases non-linearly with the distance to track centre decreases. Importantly, height of noise barrier is also an important factor affecting pressure magnitude on noise barriers and with the height of noise barrier increases, the pressure magnitude gradually increases but tends to be stable at higher height. Exponential equation can well characterize such effect of height of noise barrier on train-induced aerodynamic pressure.
Methods for reducing the output scatter of results for determining realistic damping factors of railway bridges
Authors: Stollwitzer A , Bettinelli L , Fink J 
Published: June 2024

Abstract
A realistic and economical computational assessment of the dynamic behaviour of railway bridges requires input parameters that correspond to reality. In this context, the computationally applied damping factor has a decisive influence on the results. However, the standard prescribes damping factors regarded as highly conservative, which makes in-situ measurements on structures often necessary to classify a bridge categorized as critical in prior as non-critical. Regarding in-situ tests, a measurement-based determination of the damping factor is inevitably accompanied by a scattering of the results due to the measurement method used and results from the individual scope of action of the person evaluating the test. This contribution presents methods and analysis tools for determining the damping factor in the frequency and time domain, intending to reduce the scatter of results and limit the scope of action of the evaluating person. Based on a single-degree-of-freedom system, more advanced procedures and methods are presented and explained using an exemplary steel railway bridge. The basic idea is to use the least square method to adjust the recorded amplitude-frequency response (frequency domain) or the decay process (time domain) based on in-situ measurements by a mathematically defined curve.
Detection and assessment of rail discontinuities using a multibody vehicle-track model
Authors: Vishwakarma Abhilash , Dasgupta Anirvan , Racherla Vikranth 
Published: June 2024

Abstract
In this work, a method is proposed to detect and assess discontinuous/fractured rail by analyzing the axle-box acceleration. The method uses a combination of unsupervised-machine learning algorithm and time-frequency analysis to detect the defect. In the previous work, fishplate rail joints modeling and impact loading induced by the track discontinuities was analyzed [1, 2]. Most of the past work has been reported on fishplate joints, and not much work is found related to the broken welded rail joint. Hence, a study is performed to detect the rail discontinuities using axle-box acceleration. A multibody vehicle-track model is used to generate the acceleration data. The multibody vehicle-track model is developed in SIMPACK. The vehicle model consists of a coach, two bogies, and four axles. Linear spring and damper system is used to model the primary and secondary suspension of the vehicle. The equivalent stiffness of the track along the length of the track is calculated and imported into the SIMPACK model. A finite element-based Euler-Bernoulli beam model is used to calculate the equivalent vertical stiffness of the rail and its support. Sleepers/rail fasteners stiffness is modeled using equispaced springs that support the overhanging portion of the rail. These equispaced springs have stiffness equal to the combined stiffness of the railpad, sleeper, and ballast. Track vertical irregularity of levels five is modeled. These track irregularities are generated from the power spectral density function obtained by the Federal Railway Administration (FRA) of America. Results are obtained for different vehicle speeds, axle loads, and overhanging lengths. To detect the defect, the axle-box acceleration is processed in two stages. In the first stage, a clustering algorithm is applied to locate the rail joint. Statistical features are calculated for the axle-box acceleration. Feature selection is done by the principal component analysis (PCA). The clustering algorithm works very well in locating the rail joints for fractured rail from the rest of the track irrespective of vehicle speed, axle-load, and different overhanging portions of rail. After locating the rail joint, in the second stage, continuous wavelet transform method is applied to the data to measure the level of the defect. The continuous wavelet transform efficiently classifies the severity of the defect in terms of the frequency content in the response.
A framework recommendation for updating running safety design criteria of non-ballasted railway bridges using statistical investigations
Authors: Allahvirdizadeh R , Andersson A , Karoumi R 
Published: June 2024

Abstract
As far as the authors are aware, the threshold for vertical acceleration of the bridge deck was chosen based on the assumption that the induced dynamic loads would overcome gravity at higher accelerations, resulting in loss of contact between wheels and rail; however, the previous studies do not support this hypothesis. Considering these inconsistencies, a better understanding of the simplified design criteria is essential before conducting further studies such as the calibration of partial safety factors. Therefore, this study considers a set of representative design scenarios to statistically compare wheel-rail contact loss with other criteria that can be derived from moving load models, such as vertical accelerations and bridge deck deflections. Based on the analyzes performed, deflection seems to be a better criterion than acceleration to control the running safety limit-state; although the results presented do not necessarily show a very strong correlation between these two criteria. Therefore, the k-means clustering approach is used together with 5% lower quantiles of the collected data to propose potential new thresholds. It should be noted that due to the limited number of analyzes, the approach presented in this study can be considered as a possible framework for further updates of the current design method rather than drawing general conclusions.
Finite element model updating for the dynamic response of continuous deck railway viaducts leading to efficient digital twins
Authors: Tarque Nicola , Goicolea José María , Cuevas Rocío G. , Martínez José Luis 
Published: June 2024

Abstract
Bridges and viaducts are key infrastructure elements within high speed railway lines, for which dynamic actions due to traffic are one of the main actions for design of new structures or evaluation of existing ones. This paper describes techniques based on experimental measurements and numerical finite element models leading to efficient digital twins, to be used for predictive maintenance, within the framework of an innovative prototype for a continuous predictive maintenance system installed in the La Marota 381 m long viaduct, in the high-speed line between Córdoba and Málaga in Spain. This system includes both model-based methods as well as data-based methods for maintenance decisions. Here we focus on the work for model-based acceleration performance, comparing in real time measurements from accelerometer sensors and predictions from a digital twin. The digital twin is an autonomous structural modal analysis software derived from a finite element model previously calibrated with Operational Modal Analysis experimental data. Results obtained from 3 representative high-speed trains are shown and compared in terms of root-mean-square (RMS) and moving window RMS of accelerations between the measured and numerical predictions. These allow to establish criteria and thresholds for predictive maintenance alerts.
Field measurement data set of wind turbine tower for enhanced calculation of vortex-induced vibration
Authors: Kurniawati Ika , Lupi Francesca , Seidel Marc , Höffer Rüdiger , Niemann Hans-Jürgen 
Published: June 2024

Abstract
From July 2021, a full-scale measurement campaign is carried out on two wind turbine towers with smooth surfaces (k/D ≈ 1.0·10-6). Tower response (through accelerations) and wind pressure on the surface are measured. Throughout the one-year monitoring period, there were challenges in transferring full-scale data into a ready-to-use VIV data set. For example, the spatially varying wind conditions despite the small distance between the met masts and the towers. This work aims to provide a ready-to-use full-scale data set for the development of VIV prediction models. A data selection approach based on three simultaneous measurements of wind conditions and maximum moving standard deviation of oscillations s proposed. In addition, the load parameters obtained from the wind pressure measurements in the field and from wind tunnel tests are considered. An enhanced calculation is carried out by defining local aerodynamic damping for sectional heights of the tower. A comparison of the data set with the calculated response is presented to assess the calculation method and to give ideas on sensitive input parameters considering the full-scale condition.
Torsional aero-elastic oscillations of an elastically mounted circular cylinder
Authors: Demchenko Yaroslav , Vedeneev Vasily , Zubkov Alexander 
Published: June 2024

Abstract
The object of this study is a system consisting of a rigid thin-walled cylinder of finite span, mounted on an elastic cantilever beam transversely to the direction of the subsonic air flow in a wind tunnel. The purpose is to identify and analyze the mechanisms of various types of aero-elastic resonant excitation of the system for the use in energy harvesting designs based on vortex-induced vibrations. The results of an experimental study are presented. In contrast to similar works with a similar configuration of the model that performs transverse translational oscillations, we discovered previously unexplored VIVs type in which the cylinder rotates around the cantilever support.