bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multivariate signal-to-noise ratio as a metric for characterizing spectral computed tomography
Authors: Rajagopal Jayasai R , Farhadi Faraz , Saboury Babak , Sahbaee Pooyan , Negussie Ayele H , Pritchard William F , Jones Elizabeth C , Samei Ehsan 
Published: June 2024

Abstract

Objective. With the introduction of spectral CT techniques into the clinic, the imaging capacities of CT were expanded to multiple energy levels. Due to a variety of factors, the acquired signal in spectral CT datasets is shared between these images. Conventional image quality metrics assume independence between images which is not preserved within spectral CT datasets, limiting their utility for characterizing energy selective images. The purpose of this work was to develop a metrology to characterize energy selective images by incorporating the shared information between images within a spectral CT dataset. Approach. The signal-to-noise ratio (SNR) was extended into a multivariate space where each image within a spectral CT dataset was treated as a separate information channel. The general definition was applied to the specific case of contrast to define a multivariate contrast-to-noise ratio (CNR). The matrix contained two types of terms: a conventional CNR term which characterized image quality within each image in the spectral CT dataset and covariance weighted CNR (Covar-CNR) which characterized the contrast in each image relative to the covariance between images. Experimental data from an investigational photon-counting CT scanner was used to demonstrate the insight of this metrology. A cylindrical water phantom containing vials of iodine and gadolinium (2, 4, and 8 mg ml−1) was imaged under conditions of variable tube current, tube voltage, and energy threshold. Two image series (threshold and bin images) containing two images each were defined based upon the contribution of photons to reconstructed images. Analysis of variance (ANOVA) was calculated between CNR terms and image acquisition variables. A multivariate regression was then fitted to experimental data. Main Results. Image type had a major difference on how Covar-CNR values were distributed. Bin images had a slightly higher mean and wider standard deviation (Covar-CNRlo: 3.38 ±17.25, Covar-CNRhi: 5.77 ± 30.64) compared to threshold images (Covar-CNRlo: 2.08 ±1.89, Covar-CNRhi: 3.45 ± 2.49) across all conditions. ANOVA found that each acquisition variable had a significant relationship with both Covar-CNR terms. The multivariate regression model suggested that material concentration had the largest impact on all CNR terms. Signficance. In this work, we described a theoretical framework to extend the SNR to a multivariate form that is able to characterize images independently and also provide insight regarding the relationship between images. Experimental data was used to demonstrate the insight that this metrology provides about image formation factors in spectral CT.
Increased performance of A-DA’D-A type acceptor based organic solar cell using a thermally coevaporated cathode-modifying blend layer
Authors: Li Longdi , Li Jiatong , Qiu Mengyu , Jia Boyu , Qin Dashan , Zhan Xiaowei 
Published: June 2024

Abstract
The blend thin films of bathocuproine and fullerene (BCP:C60) have been thermally coevaporated to modify the active layer/cathode interfaces in organic solar cells. The BCP forms a much smaller-barrier contact with cathode than the C60. Because the surface zone of active layer is polymer donor-rich and small-molecular acceptor-deficient, C60 molecules make insufficiently large contact area with electron acceptor, leading to inefficient electron extraction. However, BCP molecules penetrate the surface of active layer, due to the smaller molecular size of BCP than that of C60, and likely form sufficiently large contact area with electron acceptor thereby to enable efficient electron extraction. Compared to conventional 10 nm BCP, 10 nm BCP:C60 (1:1 in mass ratio) enables higher efficiency based on the active layer using A-DA’D-A type acceptor, mostly because C60 constituent dissociates some excitons photogenerated in the polymer donor of surface zone and thereby increases short-circuit current density. The current research provides novel insights into the development of cathode-modifying layers for organic solar cells.
Optoelectronic, thermoelectric and 3D-Elastic properties of lead-free inorganic perovskites CsInZrX6 (I, Cl and Br) for optoelectronic and thermoelectric applications
Authors: Harbi A , Pingak Redi Kristian , Moutaabbid M 
Published: June 2024

Abstract
Halide perovskite materials have recently gained worldwide attention since they offer a new cost-effective way to generate renewable and green energy. In the current work, the structural, electrical, elastic, optical and thermoelectric properties of new perovskites CsInZrX6 (I, Cl and Br) were explored by density-functional theory (DFT). The results indicated that the computed lattice parameters agree really well with the current experimental and theoretical results. Moreover, the band structure profile strongly suggests that the compounds exhibit a semiconducting nature with a direct band gap. The analysis of their optical properties reveals that the perovskites possess a low reflectivity (below 23%) and a high optical absorption coefficient (106 cm−1). This is also supported by the evaluation of their calculated elastic constants and their related parameters in cubic structure which show that these compounds are brittle, mechanically stable and possess covalent bonds. On the other hand, in addition to exhibiting outstanding optoelectronic and mechanical characteristics, CsInZrCl6 also possesses dynamical stability, making it a promising candidate for application in various optoelectronic devices except for solar cells due to its relatively large bandgap. Furthermore, the BoltzTraP software was used to compute the materials’ thermoelectric properties, with the computed values of the figure of merit (ZT) for CsInZrBr6, CsInZrCl6 and CsInZrI6 being 0.76, 0.73 and 0.725, respectively. This is also a strong indication that these materials are potential for thermoelectric applications.
Electronic and optical characteristics of CaLiX3 (X = Cl, Br, I) perovskite compounds using the Tran–Blaha modified Becke–Johnson potential
Authors: Allaf Hatem , Allali Djamel , Radjai Missoum , Bouhemadou Abdelmadjid , Saad Essaoud Saber , Bedjaoui Abdelhak , Bin-Omran Saad , Khenata Rabah , Al-Douri Yarub , Chaba Mouna Sarah 
Published: June 2024

Abstract
We present the results of a comprehensive investigation using the full-potential linearized augmented plane wave approach to analyze the structural characteristics, electronic structures, and optical spectra of the perovskite compounds CaLiX3 (X = Cl, Br, or I). Various functionals were employed to simulate the exchange–correlation interactions. The calculated equilibrium structural parameters, obtained using the generalized gradient approximation, are consistent with the existing findings in the literature. The computed electronic structures reveal that the Tran–Blaha modified Becke–Johnson potential significantly enhances the bandgap. For all CaLiX3 compounds studied, we predicted an indirect bandgap. Additionally, we observed a gradual decrease in the bandgap as the atomic size of the X element increases. The electronic states constituting the various energy bands were evaluated by computing the partial and total densities of states. In addition, we computed a variety of optical spectra, including the complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity, and electron energy loss function. The results demonstrate that a decrease in the bandgap leads to an increase in the zero-frequency limit of the dielectric function

ε

(
0
)

.

The origins of the peaks and structures in the optical spectra were identified.
Paraxial propagation characteristics of a controllable anomalous hollow vortex beam in free space
Authors: Qiu Yuzhong , Liu Zhirong 
Published: June 2024

Abstract
Propagation of a recently proposed controllable anomalous hollow vortex (CAHV) beam is investigated. Based on the integral formula of generalized Huygens–Fresnel diffraction, analytical expression for the CAHV beam through a paraxial ABCD optical system is derived. The factors that affect the intensity pattern are determined by the beam’s controllable parameters a, c
x, c
y, and the topological charge m. Results show that the Gaussian distribution features are controlled by parameter a, and the horizontal and vertical stretching deformations of the beam are adjusted by parameters c
x and c
y, respectively. For a controllable anomalous hollow (CAH) beam, when propagating in free space, it could initially maintain anomalous hollow property and the size of the spot increases with the increase of the propagation distance. Due to the CAHV beam carries the optical vortex, a dark hollow channel appears in the center of the beam during propagation, and the channel structure changes with the increase of topological charge. Additionally, the Poynting vector of CAHV beam proves the direction of energy flow corresponding to the intensity distribution. Results obtained in this paper could have potential applications in particle trapping and optical control.
Upper bound on thermal gravitational wave backgrounds from hidden sectors
Authors: Drewes Marco , Georis Yannis , Klaric Juraj , Klose Philipp 
Published: June 2024

Abstract
Hot viscous plasmas unavoidably emit a gravitational wave background, similar to electromagnetic black body radiation.
We study the contribution from hidden particles to the diffuse background emitted by the primordial plasma in the early universe.
While this contribution can easily dominate over that from Standard Model particles, we find that both are capped by a generic upper bound that makes them difficult to detect with interferometers in the foreseeable future.
We illustrate our results for axion-like particles and heavy neutral leptons.
Finally, our results suggest that previous works overestimated the gravitational wave background from particle decays out of thermal equilibrium.
Gamma-rays and neutrinos from giant molecular cloud populations in the galactic plane
Authors: Roy Abhijit , Joshi Jagdish C. , Cardillo Martina , Sarmah Prantik , Sarkar Ritabrata , Chakraborty Sovan 
Published: June 2024

Abstract
The recent IceCube detection of significant neutrino flux from the inner Galactic plane has provided us valuable insights on the spectrum of cosmic rays in our Galaxy. This flux can be produced either by a population of Galactic point sources or by diffused emission from cosmic ray interactions with the interstellar medium or by a mixture of both. In this work, we compute diffused gamma-ray and neutrino fluxes produced by a population of giant molecular clouds (GMCs) in our Galaxy, assuming different parametrizations of the Galactic diffused cosmic ray distribution. In particular, we take into account two main cases: (I) constant cosmic ray luminosity in our Galaxy, and (II) space-dependent cosmic ray luminosity, based on the supernovae distribution in our Galaxy. For Case-I, we found that the neutrino flux from GMCs is a factor of ∼ 10 below compared to π
0 and KRA
γ
best-fitted models of IceCube observations at 105 GeV. Instead, for Case-II the model can explain up to ∼ 90 % of the neutrino flux at that energy. Moreover, for this last scenario IceCube detector could be able to detect neutrino events from the Galactic centre regions. We then calculated gamma-ray and neutrino fluxes from individual GMCs and noticed that several current and future Cherenkov telescopes and neutrino observatories have the right sensitivities to study these objects. In particular, very neutrino-bright region such as Aquila Rift is favourable for detection by the IceCube-Gen2 observatory.
From lab to life: assessing the impact of real-world interactions on the operation of rapid serial visual presentation-based brain-computer interfaces
Authors: Ahsan Awais Muhammad , Ward Tomas , Redmond Peter , Healy Graham 
Published: June 2024

Abstract

Objective. Brain-computer interfaces (BCI) have been extensively researched in controlled lab settings where the P300 event-related potential (ERP), elicited in the rapid serial visual presentation (RSVP) paradigm, has shown promising potential. However, deploying BCIs outside of laboratory settings is challenging due to the presence of contaminating artifacts that often occur as a result of activities such as talking, head movements, and body movements. These artifacts can severely contaminate the measured EEG signals and consequently impede detection of the P300 ERP. Our goal is to assess the impact of these real-world noise factors on the performance of a RSVP-BCI, specifically focusing on single-trial P300 detection. Approach. In this study, we examine the impact of movement activity on the performance of a P300-based RSVP-BCI application designed to allow users to search images at high speed. Using machine learning, we assessed P300 detection performance using both EEG data captured in optimal recording conditions (e.g. where participants were instructed to refrain from moving) and a variety of conditions where the participant intentionally produced movements to contaminate the EEG recording. Main results. The results, presented as area under the receiver operating characteristic curve (ROC-AUC) scores, provide insight into the significant impact of noise on single-trial P300 detection. Notably, there is a reduction in classifier detection accuracy when intentionally contaminated RSVP trials are used for training and testing, when compared to using non-intentionally contaminated RSVP trials. Significance. Our findings underscore the necessity of addressing and mitigating noise in EEG recordings to facilitate the use of BCIs in real-world settings, thus extending the reach of EEG technology beyond the confines of the laboratory.
Damage Identification of Railway Bridge trough temporal Autoregressive modelling under Train Loads
Authors: Anastasia S. , García-Macías E. , Ubertini F. , Gattulli V. , Poveda P. , Torres B. , Ivorra S. 
Published: June 2024

Abstract
The damage identification of railway bridges poses a formidable challenge given the large variability in the environmental/operational conditions that such structures are subjected to along their lifespan. Within a research project devoted to the continuous monitoring of a real in-operation bridge, the Mascarat Viaduct in Alicante (Spain), this paper investigates the potential use of strain sensors and autoregressive (AR) modelling to extract highly sensitive damage features. The viaduct, built in the beginning of the 20th century, belongs to the TRAM line 9 in the province of Alicante (Spain). The viaduct is instrumented with a dense network of strain sensors and accelerometers for monitoring the structural response under train passages. As an initial exploratory investigation, and with the aim of developing a physics-based digital twin of the viaduct, this work presents an introductory numerical assessment of the potential use of strain measurements and AR models for fast damage identification. To this aim, a finite element model (FEM) of the viaduct has been developed to simulate the dynamic response of the viaduct under moving train loads. On this basis, a two-class damage classifier (damaged or non-damaged) is developed by exploiting time series of continuously identified AR parameters. The presented results and discussion evidence the usefulness of the proposed methodology, offering an unsupervised damage detection approach with minimum computational efforts.
Vibration serviceability of footbridges in crowded conditions: crowd dynamics simulations vs guidelines’ predictions
Authors: Tubino F , Venuti F 
Published: June 2024

Abstract
Vibration serviceability assessment in crowded conditions requires a reliable human-induced loading model taking into account pedestrian interaction. Current guidelines provide simplified procedures to determine the maximum dynamic response based on very simplified loading models. The main objective of this paper is to assess the reliability of current guidelines for vibration serviceability assessment of footbridges. With this aim, an extensive campaign of numerical simulations of bidirectional pedestrian traffic is carried out through an agent-based model, considering variable pedestrian densities and deck widths. The results of numerical simulations are first compared against the experiments available in the literature in terms of fundamental diagram of the mean walking speed as a function of pedestrian density. Then, starting from numerical simulations, the dynamic response of a class of footbridges is estimated numerically and compared with guidelines’ predictions in order to assess their reliability.
Crowd-induced loading on footbridges: reliability of an Equivalent Spectral Model
Authors: Tubino F , Van Nimmen K 
Published: June 2024

Abstract
Vibration serviceability assessment of footbridges requires a reliable probabilistic model for multi-pedestrian loading and a suitable approach to take into account human-structure interaction. In the present paper, the human-induced dynamic response of footbridges is analysed using a mode superimposition approach. The power spectral density functions of the modal loads are defined according to an equivalent spectral model, and suitable equivalent dynamic properties of each mode are estimated for the human-structure coupled system. The validation against the Eeklo Footbridge benchmark dataset confirms the reliability of the proposed approach.
Experimental study of active human-structure interaction during running on footbridges
Authors: Lottefier Jasper , Broeck Peter Van den , Vanwanseele Benedicte , Nimmen Katrien Van 
Published: June 2024

Abstract
Slender footbridges are predominantly sensitive to human-induced vibrations. While the previous two decades have focussed on pedestrian-induced vibrations, topical research questions are investigating the impact of running actions. The currently available load model for vibration serviceability assessments only applies to a single runner on a rigid surface. The present work investigates whether low-frequency vertical vibrations of the supporting surface affect the running motion, known as active human-structure interaction. To facilitate characterisation, an extensive measurement campaign was organised. First, a treadmill was placed on a rigid surface as reference and secondly on a vibrating footbridge, excited by a mechanical shaker. The measurement setup enables the simultaneous registration of the contact forces, body motion, running motion metrics on a step-by-step basis and the structural response. The results indicate that human-structure interaction phenomena do occur while running on a vertical vibrating surface. The main effects include changes of the peak contact force, determined by the relative phase between the body motion and the footbridge’s motion. Moreover, when running (near) resonance, two stable running regimes can occur. The first resembles a non-resonant runner (constantly alternating between in- and out-of-phase) while the second resembles resonant running by keeping a fairly constant phase with the structure.
Lightweight footbridges subjected to streams of pedestrians: tests and discussion of a crowd-structure interaction model
Authors: Gallegos-Calderón Christian , Naranjo-Pérez Javier , Jiménez-Alonso Javier F. , Díaz Iván M. 
Published: June 2024

Abstract
Human-induced vibrations in slender lightweight footbridges have been extensively investigated in the last 30 years. In existing guidelines, the dynamic response of a footbridge can be assessed considering the pedestrians as external non-interacting loads acting on the structure. For a more realistic load model, individuals defined as single Degree of Freedom (DOF) dynamic systems moving along the structure have been employed by researchers and practitioners. Hence, Human-Structure Interaction (HSI) is considered in the dynamic analysis. Adopting this approach to calculate the vibration levels on a footbridge may lead to a costly computational problem when dealing with a crowd due to the large number of DOFs associated to the pedestrians. Recently, a frequency-domain procedure based on a coupled crowd-structure system has been proposed by the authors to overcome the aforementioned issue. To further validate the proposal, the analytical results should be contrasted with experimental measurements. In this sense, this paper presents the dynamic response of two footbridges under the action of streams of walking pedestrians. A laboratory fibre reinforced polymer structure is firstly analysed, and an in-service cable-stayed steel footbridge is secondly studied. The vibration serviceability of both pedestrian structures is assessed considering 0.20 and 0.50 pedestrians/m2. For each bridge, the experimental results are compared with predictions computed through the application of load models from existing guidelines. In addition, the frequency-domain proposal is employed to calculate the steady-state structural response while accounting for HSI. Since dynamic parameters of the human body must be defined for the second approach, different values available in literature are employed. Results demonstrate the overestimation of the response when provisions stated in current design documents are used. Also, the benefits of the novel procedure to consider Crowd-Structure Interaction on lightweight footbridges are highlighted.
Modal analysis of a footbridge under pedestrian traffic and additional shaker loading
Authors: Purpura Laura , Güner Hüseyin , Hoffait Sébastien , Dënoel Vincent 
Published: June 2024

Abstract
This paper investigates the possibility of identifying the modal properties of footbridges while they are subjected to pedestrian traffic using the CSI algorithm. The analysis is based on vibration data collected from a footbridge under different pedestrian densities. The results show that the CSI algorithm provides consistent modal properties, but the identified damping ratio seems to be significantly influenced by pedestrians. This is likely due to the human-structure interaction. Identified apparent damping ratios appear plausible, but of course not representative of the bare structure. Overall, while the CSI algorithm helps alleviate the limitations of the authors’ previous approache to modal identification with a custom shaker, the practical usefulness of identifying modal properties of footbridges under pedestrian traffic is therefore limited.
On the Dynamic Assessment of a Cable-Stayed Footbridge: The Iron Bridge
Authors: Colmenares Daniel , Ruhani Shaho , Karoumi Raid 
Published: June 2024

Abstract
Human-induced loads may produce resonance when the forcing frequency coincides with the natural frequency of the system. In this work, the dynamic assessment of a pedestrian cable-stayed bridge in Uppsala, Sweden is presented. The dynamic properties of the system have been identified and a loading scenario is evaluated. A comparison between the theoretical and measured acceleration of the bridge is made using a detailed finite element model. Different modelling aspects are considered and evaluated by studying their influence on the natural frequencies of the system such as the tie rods system, railings, and boundary conditions. Moreover, a parametric analysis of the elastic modulus of the cast iron material with respect to the boundary conditions of the system is presented to quantify the uncertainties of the system. Special focus is given to the resonant response of the first natural frequency of the bridge potentially compromising the serviceability limit state of the structure. Furthermore, the scenario of a single pedestrian jogging on the spot is evaluated and a hypothetical standing crowd is considered to illustrate the benefits of taking into account the human-structure interaction effect. A considerable reduction of the dynamic response of the system is found, highlighting the importance of the human-structure-interaction effect.