bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimizing anti-perturbation capability in single-shot wide-field multimode fiber imaging systems
Authors: Feng Zefeng , Yue Zengqi , Zhou Wei , Xu Baoteng , Liu Jialin , Hong Yanhua , Xiong Daxi , Yang Xibin
Published: March 2024

In recent years, multimode fiber (MMF) has emerged as a focal point in ultrathin endoscopy owing to its high-capacity information transmission. Nevertheless, the technology's susceptibility to external perturbances limits its practical applications. In this study, we employ a single MMF as both the illumination unit and imaging probe and utilize this single-shot wide-field MMF imaging system to investigate the impact of LED and laser sources on anti-perturbation capabilities. Experimental results demonstrate that, in the absence of deformations in the MMF, both LED and laser-based systems achieve an average structural similarity (SSIM) index of around 0.8 for the reconstructed image, utilizing advanced deep learning techniques, with the laser-based system performing slightly better. However, under unknown MMF configurations post-deformation, the SSIM remains robust at 0.67 for the LED-based system, while the laser-based system drops the average SSIM to 0.45. The results reveal that LED has anti-perturbation capability in single-shot wide-field MMF imaging systems. These findings indicate significant potential for future anti-perturbation studies in endoscopy employing MMF imaging.
Surface hydrodynamic characteristic analysis of underwater robots applied to perception of lateral lines
Authors: Li Ao , Guo Shuxiang
Published: March 2024

Inspired by the hydrodynamic perception abilities based on lateral lines on fish surfaces, the artificial lateral lines (ALLs) based on pressure and flow sensors were proposed by the researchers. As the ALLs are widely used in underwater robots, the mechanisms of lateral line perception are urgently needed to be studied. Based on the lattice Boltzmann method, immersion boundary method, and large eddy simulation, a three-dimensional numerical model of underwater robot motion is established and verified. The distribution and variation of velocity and surface pressure on robots with different shapes under different flow fields are studied in detail. It is found that the robots with the upstream surface curvature aspect ratio of 1:1 are more suitable for placing ALLs. Then, similarly, the hydrodynamic perception abilities of robots with different sizes are further investigated. It was observed that the smaller the robot size, the better the perception ability. In addition, sensing devices are more suitable for placement on the upstream surface of the robots. These conclusions can also explain the physiological characteristics of cavefish with well-developed lateral lines in nature. Finally, based on the above analysis, to guide the shape design and sensor layout of the robots, an evaluation index for the perception ability of the robot is proposed. The reliability of the evaluation index is verified by using a machine learning method based on polynomial regression to predict the flow field. The R-square of machine learning can reach 0.99 at the upstream surface of the robot.
Hydraulic performance improvement of a two-way pumping station through bell mouth shape design
Authors: Zheng Yunhao , Li Yanjun , Zhu Xingye , Yuan Shouqi , Zhang Huiyan , Wang Hongliang
Published: March 2024

A two-way pumping station is a specialized device that facilitates bidirectional water pumping and drainage. The pressure pulsation characteristics of two-way pumping stations have emerged as a prominent research focus in the field of hydraulic engineering. In this work, with the aim of systematically proposing optimization measures to ensure operational stability, a transient numerical simulation is conducted to elucidate the influence mechanism of the suspension height of the bell mouth (SHb) on the internal flow field and pressure pulsation of a two-way pumping station. High-precision experiments are performed to compare time-frequency domain characteristics under different SHb using a continuous wavelet transform (CWT). The findings indicate that an appropriate reduction in SHb effectively reduces unstable flow and pressure pulsation within the inlet conduit, consequently reducing the pressure pulsation of the impeller. With a reduction in SHb, the influx of low-velocity backflow into the bell mouth is prevented and the generation and propagation of suction vortices are suppressed. However, the reduction amplifies the flow impact between the mainstream flow and the bell mouth wall. The spatial distribution of the pressure pulsation is also examined, and it is found that a reduction in SHb increases the pressure pulsation intensity on the side facing the incoming flow and on the rear side, while the mainstream area tends to exhibit stability. In terms of time-frequency domain characteristics, a reasonable reduction in SHb leads to improved circumferential uniformity of the impeller inflow and the effective suppression of low-frequency disturbances.
“Return to equilibrium” anisotropy model for non-equilibrium Reynolds stress closures
Authors: Brereton G. J.
Published: March 2024

A long-standing question in the Reynolds-averaged modeling of turbulent flow is how to predict accurately flows with temporal or spatial unsteadiness. In this paper, we present a “return to equilibrium” approach to modeling the unsteady Reynolds stress anisotropy bij in terms of differential transport equations, the solutions to which are constrained by algebraic closures for bij in flows at equilibrium and by the corresponding rapid-distortion-theory solutions for flows far from equilibrium. When coupled with scale equations for the turbulent kinetic energy and the dissipation rate, these anisotropy evolution equations comprise a complete closure scheme for which no additional model coefficients are required. Evaluations of this closure scheme, in which two different existing equilibrium algebraic models for bij were employed, were carried out for homogeneous turbulence in flows with a step imposition of shear, with continuously oscillatory shear at different frequencies and with a prescribed time-dependent plane-strain rate. Good agreement was achieved between model predictions and experimental/simulation target data in all test cases, with either Girimaji's bij model or a structure-based bij model used as the equilibrium algebraic closure.
Enhancing the lubrication performance of the oil films in piston/cylinder pairs by textures
Authors: Wei Xiaofeng , Zhou Weixuan , Yao Xin , Haidak Gaston , Wang Dongyun , Li Shenghu
Published: March 2024

The long-term wear of the piston/cylinder pair is the main failure reason for axial piston pumps. In this paper, the dynamics of textured films to enhance the lubrication performance of piston/cylinder pairs is investigated systematically. The oil film is divided into three regions: the head region, the texture region, and the tail region. The Reynolds equation is used to predict the dynamics, which includes the carrying capacity and the friction. Influences of the texture geometries and the working conditions are presented in sequence. The results show that the texture enhances the lubrication performance by the collective effect. A shorter head length and a larger area ratio always benefit the lubrication performance, while increasing the texture region length does not always lead to positive effects, and the cell length is found to have negligible influences. The texture effect is found to be enhanced with larger shearing velocities and to be restrained with higher inlet pressures. It is also shown that the texture is effective for small inclination angles. Furthermore, a one-dimensional model is performed to unravel the mathematical mechanism, and an explicit expression is given for the texture region length.
Low-noise cryogenic microwave amplifier characterization with a calibrated noise source
Authors: Malnou M. , Larson T. F. Q. , Teufel J. D. , Lecocq F. , Aumentado J.
Published: March 2024

Parametric amplifiers have become a workhorse in superconducting quantum computing; however, research and development of these devices has been hampered by inconsistent and, sometimes, misleading noise performance characterization methodologies. The concepts behind noise characterization are deceptively simple, and there are many places where one can make mistakes, either in measurement or in interpretation and analysis. In this article, we cover the basics of noise performance characterization and the special problems it presents in parametric amplifiers with limited power handling capability. We illustrate the issues with three specific examples: a high-electron mobility transistor amplifier, a Josephson traveling-wave parametric amplifier, and a Josephson parametric amplifier. We emphasize the use of a 50-Ω shot noise tunnel junction (SNTJ) as a broadband noise source, demonstrating its utility for cryogenic amplifier amplifications. These practical examples highlight the role of loss as well as the additional parametric amplifier “idler” input mode.
Probing elemental diffusion and radiation tolerance of perovskite solar cells via non-destructive Rutherford backscattering spectrometry
Authors: Parashar Mritunjaya , Sharma Mohin , Saini Darshpreet Kaur , Byers Todd A. , Luther Joseph M. , Sellers Ian R. , Kirmani Ahmad R. , Rout Bibhudutta
Published: March 2024

Mixed organic–inorganic halide perovskite-based solar cells have attracted interest in recent years due to their potential for both terrestrial and space applications. Analysis of interfaces is critical to predicting device behavior and optimizing device architectures. Most advanced tools to study buried interfaces are destructive in nature and can induce further degradation. Ion beam techniques, such as Rutherford backscattering spectrometry (RBS), is a useful non-destructive method to probe an elemental depth profile of multilayered perovskite solar cells (PSCs) as well as to study the inter-diffusion of various elemental species across interfaces. Additionally, PSCs are becoming viable candidates for space photovoltaic applications, and it is critical to investigate their radiation-induced degradation. RBS can be simultaneously utilized to analyze the radiation effects induced by He+ beam on the device, given their presence in space orbits. In the present work, a 2 MeV He+ beam was used to probe the evidence of elemental diffusion across PSC interfaces with architecture glass/ITO/SnO2/Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3/spiro-OMeTAD/MoO3/Au. During the analysis, the device active area was exposed to an irradiation equivalent of up to 1.62 × 1015 He+/cm2, and yet, no measurable evidence (with a depth resolution ∼1 nm) of beam-induced ion migration was observed, implying high radiation tolerance of PSCs. On the other hand, aged PSCs exhibited indications of the movement of diverse elemental species, such as Au, Pb, In, Sn, Br, and I, in the active area of the device, which was quantified with the help of RBS.
On the influence of spanwise deformation on lift coefficient and trailing vortices properties at low Reynolds number
Authors: Solis P. , Garrido-Martin M. , Duran E. , Gutierrez-Castillo P. , del Pino C.
Published: March 2024

We conducted experiments using a single non-deformed and two spanwise deformed wing models for a constant chord-based Reynolds number, Re=20×103. We carried out all experiments to consider several angles of attack α lower than the stall value. The lift forces between non-deformed and spanwise deformed wings present differences depending on the angle of attack. A first finding of the experimental study is that, for smaller values of the angle of attack, e.g., α = 4°, the non-deformed wing case has higher lift values than the highest spanwise deformed wing. However, for larger values of the angle of attack, such as α = 8°, we found a higher lift for the spanwise deformed case. Additionally, velocity fields of the trailing vortex have been taken by two-dimensional particle image velocimetry, finding that both theoretical models by Batchelor [J. Fluid Mech. 20, 645 (1964)] and by Moore and Saffman [Proc. R. Soc. Lond. Ser. A 333, 491 (1973)] can be fitted to experimental measurements obtained from non-deformed and spanwise deformed wing models, the latter model giving the best results for all angles of attack. Finally, we computed the circulation of the trailing vortex using two different methods with the same result and observing that this estimated circulation level directly correlates with the measurement of the lift force.
Assessing the reinforced molecular/mechanical behaviors of GOs@Mo-MOFs films deposited via electrophoresis onto microdevices: Experimental and theoretical perspectives
Authors: Cao Zhiyong , Gong Chuang , Xue Qiannan , Wang Hairen , Qu June , Jin Junsong , Sun Lushi , Wang Xinyun
Published: March 2024

One of the primary hurdles in microdevice fabrication lies in ascertaining the most impactful tactics for adapting metal surfaces. Through a one-pot tackle and distinct mechanochemical reactions evoked by 15 min aqueous wet sand-milling (SM-15), we successfully grafted Mo-based metal–organic frameworks (Mo-MOFs) onto graphene oxides (GOs). Following this, a convenient and readily scalable methodology of electrophoretic deposition was implemented to create controllable thickness of SM-15 GOs@Mo-MOFs lubricating films, achieving considerable enhancements of 143% and 91% in hardness and Young’s modulus, respectively, when compared to those of SM-15 Mo-MOFs. The successful synthesis of SM-15 GOs@Mo-MOFs was corroborated using strategies such as x-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. Analyses using the micro-tribotester indicated that the new film exhibited a lowest friction coefficient of roughly 0.5 when imposed with a load of 5 N and sliding speed of 8 mm/s. In addition, the optical profiler nano-indentation in situ scanning probe microscope revealed that SM-15 GOs@Mo-MOFs films had smaller and shallower scratches and grooves compared to SM-15 Mo-MOFs ones. The calculated results of key descriptors (EHOMO, ELUMO, ΔE, etc.) in density functional theory quantitatively disclosed the interaction mechanisms between GOs@Mo-MOFs molecules and microdevices. We first scrutinized the innate properties of molecule adsorption energy and frictional mechanical behaviors using synergetic cross-scale simulations, such as Monte Carlo and finite element methods. The expectation was that this process would motivate a valuable technique for shielding in the thriving micromanufacturing.
Effect of surface ablation on aerodynamic heating over a blunt cone in hypersonic airflow
Authors: Han Leibao , Han Yufeng
Published: March 2024

The hypersonic airflow around a blunt cone coupled with carbonaceous surface ablation is numerically simulated to analyze the impacts of ablation on aerodynamic heating. Ablative reactions, including oxidation, nitridation, and sublimation, are found to affect aerodynamic heating mainly through the surface thermal effect (STE) and the gas-phase chemistry thermal effect (GCTE). Specifically, the sublimation reactions produce significant STE and GCTE. The STE of the sublimation reactions is not always endothermic. Downstream along the cone surface, the condensation of gas-phase C atoms on the wall leads to heat release. The GCTE is exothermic and increases the boundary layer temperature. The oxidation reaction generates weak GCTE but powerful STE, which is exothermic overall. On the contrary, nitridation reaction only leads to appreciable GCTE, characterized by releasing heat. The STE of nitridation is quite small and can be neglected. Oxidation and nitridation reactions often dominate the downstream region of the cone. In addition, in the head region where the ablation reactions are intense, ablation processes could generate considerable diffusive heat flux, increasing the total incident heat flux. Simultaneously, mass ejection can carry away much heat from the surface.
Experimental investigation on interaction between extreme waves and a submerged barrier
Authors: Kong Liang , Li Xiaochen , Lu Hongchao , Ren Kang , Gao Ying , Liu Kun
Published: March 2024

We present experimental results of a group of focused waves propagating over a submerged barrier positioned in various locations on the bottom of a flume. The study investigates the effect of the relative distance between the fixed focusing position and different barrier installation positions on the characteristics of the wave group. The surface elevation and skewness are observed to approach a crest just on top of the barrier's rear. It can be also suggested that the presence of the barrier may affect the evolution of the wave group for approximately two times of the barrier length, as indicated by the frequency component distribution. In the time domain, a small tail with mildly higher energy is generally observed when the gauge is fixed at the front surface of the barrier. It suggests that long waves at lower frequencies propagate at higher speeds, while short waves at higher frequencies are intercepted due to the barrier.
Identifying gap-closings in open non-Hermitian systems by biorthogonal polarization
Authors: Mandal Ipsita
Published: March 2024

We investigate gap-closings in one- and two-dimensional tight-binding models with two bands, containing non-Hermitian hopping terms, and open boundary conditions (OBCs) imposed along one direction. We compare the bulk OBC spectra with the periodic boundary condition (PBC) spectra, pointing out that they do not coincide, which is an intrinsic characteristic of non-Hermitian systems. The non-Hermiticity, thus, results in the failure of the familiar notions of bulk-boundary correspondence found for Hermitian systems. This necessitates the search for topological invariants which can characterize gap-closings in open non-Hermitian systems correctly and unambiguously. We elucidate the behavior of two possible candidates applicable for one-dimensional slices—(1) the sum of winding numbers for the two bands defined on a generalized Brillouin zone and (2) the biorthogonal polarization (BP). While the former shows jumps/discontinuities for some of the non-Hermitian systems studied here, at points when an edge mode enters the bulk states and becomes delocalized, it does not maintain quantized values in a given topological phase. On the contrary, BP shows jumps at phase transitions, and the quantized value of one or zero, which corresponds to whether an actual edge mode exists or whether that mode is delocalized and absorbed within the bulk (not being an edge mode anymore).
Motion characteristics of a modularized floating solar farm in waves
Authors: Wei Yujia , Zou Detai , Zhang Deqing , Zhang Chao , Ou Binjian , Riyadi Soegeng , Utama I. K. A. P. , Hetharia Wolter , Wood Tim , Huang Luofeng
Published: March 2024

Modularized floating solar farms exhibit the potential to replace conventional steel-frame ones, effectively remedying hydroelastic issues of a very large floating structure through discrete modules with mechanical connections. However, the response of the discrete modules under cyclic wave loading has not been fully understood. This paper assesses the motion characteristics and expansibility of modularized floaters in waves, based on computational results from fluid–structural interaction simulations. A crucial factor, denoted as the ratio of frame length to wavelength R=Ls/λ, is determined to predict the motions of a large floating solar system in head waves. Results indicate that the motion characteristics is predictable based on the R value. The empirical relationship between the R value and the motion of every unit in an array is analyzed. In particular, the results calculated from using the multiple-rigid-bodies method are also compared with those from using the single-large-hydroelastic-body method, and it was found that these two results are similar when R > 1. This similarity allows for predicting the multi-hinged bodies' behavior in waves through a simplified hydroelastic approach. Overall, this study reports insights that are useful for the design and optimization of modularized solar farms and can help address cyclic loading and motion concerns for long-term durability.
Exact and explicit analytical solution for the Sakiadis boundary layer
Authors: Barlow N. S. , Reinberger W. C. , Weinstein S. J.
Published: March 2024

It has recently been established [Naghshineh et al. IMA J. of Appl. Math., 88, 1 (2023)] that a convergent series solution may be obtained for the Sakiadis boundary layer problem once key parameters are determined iteratively using the series itself. Here, we provide exact and explicit analytical expressions for these parameters, including that associated with wall shear, thus completing the exact analytical solution. The resulting solution to the Sakiadis problem is summarized here for direct use.
Probing active nematics with in situ microfabricated elastic inclusions
Authors: Vélez-Cerón Ignasi , Guillamat Pau , Sagués Francesc , Ignés-Mullol Jordi
Published: March 2024

In this work, we report a direct measurement of the forces exerted by a tubulin/kinesin active nematic gel as well as its complete rheological characterization, including the quantification of its shear viscosity,
η
, and its activity parameter,
α
. For this, we develop a method that allows us to rapidly photo-polymerize compliant elastic inclusions in the continuously remodeling active system. Moreover, we quantitatively settle long-standing theoretical predictions, such as a postulated relationship encoding the intrinsic time scale of the active nematic in terms of
η
and
α
. In parallel, we infer a value for the nematic elasticity constant,
K
, by combining our measurements with the theorized scaling of the active length scale. On top of the microrheology capabilities, we demonstrate strategies for defect encapsulation, quantification of defect mechanics, and defect interactions, enabled by the versatility of the microfabrication strategy that allows to combine elastic motifs of different shapes and stiffnesses that are fabricated in situ.
Experimenting with audio description
Authors: Rojo López Ana María , Ramos Caro Marina
Published: March 2024

After years in the shadows of translation, research on audio description (AD) is now gaining momentum thanks to its contribution to a more accessible and inclusive world. This paper claims that experimental AD studies have a rightful place in cognitive translation and interpreting studies (CTIS) and discusses some of its limitations and prospects. The first section introduces the relevance and interest of choosing accessibility as a general field of study and AD as a modality of accessible translation. The second section takes a snapshot of existing experimental AD studies and summarizes their main results. Then, useful tips are provided to help confront relevant challenges. The final section discusses the potential of AD research for advancing our knowledge of sensory, multimodal, and cognitive processing and for transferring research results to society.
Toronto’s Respite Program for Families of Children with Complex Needs
Authors: Fei Ailin , Day Jonathon , Ewing Annie
Published: March 2024

Destination Toronto (DT), Toronto’s Destination Marketing Organization (DMO), aims to bring visitors and conference attendees to Toronto. DMOs have an extensive network in the visitor economy that they can activate to address social issues in their communities. The well-being of caregivers to children with complex special needs is often overlooked despite the important role they play. The visitor economy can contribute some relief to this group by providing a pleasant break from day-to-day responsibilities of care. DT uses its network of tourism-related businesses to give back to the community through the Relax, Recharge, Renew (RRR) Program, offering a weekend trip to parents and caregivers of children with special needs. This case study displays the importance of having social intrapreneurs who drive change to provide resident-tailored tourism experiences and underscores the significance of local partnerships. Additionally, realistic considerations for replicability at other destinations are discussed. The case study highlights the potential to expand collaboration in the hospitality and tourism sector, providing enriching experiences to underserved residents.

Information

© The Authors 2024
Understanding Trauma Symptoms Experienced by Young Men under Youth Justice Supervision in an Australian Jurisdiction
Authors: Hamilton Hannah N. , Malvaso Catia G. , Day Andrew , Delfabbro Paul H. , Hackett Louisa
Published: March 2024

Exposure to adversity or maltreatment is known to correlate with high-risk behaviors that can increase the risk of contact with the criminal justice system; however, few studies have focused on the role of trauma symptoms and other behaviors that may develop in response to exposure to adverse life events. We also know far less about the role of these experiences in young men compared to young women who have been in contact with the youth justice system. In this study, we examine the associations between different patterns of trauma symptomatology and adverse childhood experienced (ACEs), substance use, behavioral difficulties, and re-offending in a sample of 141 young men under the supervision of a Youth Justice (YJ) agency in Australia. Trauma symptoms were reported by over ninety percent of participants, with Latent Class Analysis used to identify four subgroups of young men based on their clustering of trauma symptomatology: internalizing, externalizing, high, and low trauma symptoms groups. The characteristics of young men across these groups were, however, remarkably similar. Over four-fifths scored in the clinical range for substance use and externalizing behavior problems, while recidivism was reported in over three-quarters of young men across all groups. These findings have implications for the development of trauma-informed responses by specialist adolescent mental health services as well as for adult forensic services that seek to understand the developmental origins of psychopathology and offending behavior. There appears to be a strong rationale for more compassionate and trauma-informed justice system practices.
Anti-de Sitter momentum space in 3D and 4D quantum gravity
Authors: Amelino-Camelia Giovanni , Lobo Iarley P , Palmisano Giovanni
Published: March 2024

There has been strong interest in the possibility that in the quantum-gravity realm momentum space might be curved, mainly focusing, especially for what concerns phenomenological implications, on the case of a de Sitter momentum space. We here take as starting point the known fact that quantum gravity coupled to matter in

2
+
1

spacetime dimensions gives rise to an effective picture characterized by a momentum space with anti-de Sitter geometry, and we point out some key properties of

2
+
1

-dimensional anti-de Sitter momentum space. We observe that it is impossible to implement all of these properties in theories with a

3
+
1

-dimensional anti-de Sitter momentum space, and we then investigate, with the aim of providing guidance to the relevant phenomenology focusing on possible modified laws of conservation of momenta, the implications of giving up, in the

3
+
1

-dimensional case, some of the properties of the

2
+
1

-dimensional case.
Exploring magnetic interactions between magnets and a magnetizable alloy
Authors: Machado Natália Alves , Cruz Frederico A O , Hahn Marcelo , Carvalho Paulo Simeão
Published: March 2024

Traditional problems in mechanics usually involve forces that generate motions described by analytical solutions, easily obtained from differential equations. However, when magnetic forces are involved, problems can be very complex to describe analytically. In this paper, we describe the problematic situation of magnets that attract a coin of a magnetizable alloy. The experiment was filmed with a camera at a high rate frame. A Coulomb-type model inversely proportional to the square of the distance between the magnets and the coin was tested to fit the experimental results, without much success. The problem was then solved analytically, assuming that the force exerted on the coin varies exponentially with the distance between them. The experimental data were compared with those predicted by the theoretical model. The results confirm that the theoretical model is the most adequate to describe the kind of interaction involved, showing that this interaction is very different from that usually found in problems with gravitational, electrical or elastic forces. This work opens up future perspectives for investigations with attractive and repulsive forces between magnets.
Teaching about non-deterministic physics: an almost forgotten fundamental contribution of Marie Curie
Authors: Margaritondo G
Published: March 2024

The first historical steps of radioactivity research offer an excellent opportunity to teach a key concept of modern physics: non-deterministic phenomena. However, this opportunity is often wasted because of historical misconceptions and of the irrational fear of radioactive effects. We propose here a lecturing strategy - primarily for undergraduate students - based on interesting historical facts. In particular, on a key conceptual contribution by Marie Curie, an attractive figure for the young women and men of today. Paradoxically, this milestone is almost unknown, whereas it should contribute to her immortal fame -- perhaps as much as the discovery of radium.
Thermal conductivity of crystalline Ge2Sb2Te5: lattice contribution and size effects in the cubic phase quantified by approach-to-equilibrium molecular dynamics
Authors: Bel-Hadj Ibrahim , Guerboub Mohammed , Lambrecht Achille , Ori Guido , Massobrio Carlo , Martin Evelyne ,   ADynMat consortium
Published: March 2024

Approach-to-equilibrium molecular dynamics simulations are carried out for the cubic phase of crystalline Ge2Sb2Te5, using interatomic forces derived from a machine learning interatomic potential (MLIP) trained with ab initio calculations. The use of this MLIP potential significantly reduces the computational burden, allowing for the study of systems over 70 nm in length. Above 20 nm, the thermal conductivity of the lattice plateaus at

0.37
±
0.01

 W K−1 m−1 in agreement with measurements reported in the literature. However, below 20 nm, size effects lead to a reduction in thermal conductivity which is systematically calculated.
Pion valence quark distribution at physical pion mass of N

f
= 2 + 1 + 1 lattice QCD
Authors: Holligan Jack , Lin Huey-Wen
Published: March 2024

We present a state-of-the-art calculation of the unpolarized pion valence-quark distribution in the framework of large-momentum effective theory (LaMET) with improved handling of systematic errors as well as two-loop perturbative matching. We use lattice ensembles generated by the MILC collaboration at lattice spacing a ≈ 0.09 fm, lattice volume 643 × 96, N

f
= 2 + 1 + 1 flavors of highly-improved staggered quarks and a physical pion mass. The LaMET matrix elements are calculated with pions boosted to momentum P

z
≈ 1.72 GeV with high-statistics of O(106) measurements. We study the pion PDF in both hybrid-ratio and hybrid-regularization-independent momentum subtraction (hybrid-RI/MOM) schemes and also compare the systematic errors with and without the addition of leading-renormalon resummation (LRR) and renormalization-group resummation (RGR) in both the renormalization and lightcone matching. The final lightcone PDF results are presented in the modified minimal-subtraction scheme at renormalization scale μ = 2.0 GeV. We show that the x-dependent PDFs are compatible between the hybrid-ratio and hybrid-RI/MOM renormalization with the same improvements. We also show that systematics are greatly reduced by the simultaneous inclusion of RGR and LRR and that these methods are necessary if improved precision is to be reached with higher-order terms in renormalization and matching.
3D imaging and temporal evolution recognition of concrete internal defects based on GPR
Authors: Wang Zhengfang , Li Bo , Lei Ming , Xu Jing , Wang Wenying , Yu Shaohuai , Yu Fei , Jiang Haonan , Li Zhenpeng , Jiang Yuchen , Wang Jing , Sui Qingmei
Published: March 2024

Periodic inspections and recognition of temporal evolution for concrete internal defects are important for the long-term operation of civil engineering infrastructures. This study proposes a method integrating convolutional neural network (CNN) with maximum intensity projection (MIP) for 3D imaging and temporal evolution recognition of concrete internal defects. The proposed method utilizes MIP to process multiple ground penetrating radar (GPR) B-scans and generates 2D projected GPR B-scans containing spatial information. SegNet coupled with the Lovász softmax loss function is introduced to reconstruct 2D defects from projected GPR B-scans. Subsequently, 3D imaging result is reconstructed from 2D imaging results by 3D reconstruction module. Finally, the defect change extraction module realizes recognition of defect changes based on 3D imaging results at different time. The superiority of proposed method is validated based on both synthetic and real GPR data, which presents better recognition results and less time consumption than existing 3D CNN-based method.
Crack identification method for magnetic particle inspection of bearing rings based on improved Yolov5
Authors: Yang Yun , Zuo Jinzhao , Li Long , Wang Xianghai , Yin Zijian , Ding Xingyun
Published: March 2024

The fluorescent magnetic particle inspection technique is often used for surface crack detection of bearing rings due to its advantages of simple operation and high sensitivity. With the development of computer vision technology, more and more visual algorithms are used in magnetic particle inspection for defect detection. However, most of these current algorithm models have low detection accuracy and poor efficiency, making it difficult to meet the precision requirements of production testing and affecting the overall pace of production processes. To address this problem, this paper proposes an improved algorithm model based on Yolov5. Firstly, MobileNetV3-small is utilized to construct the backbone feature extraction network, reducing the network’s parameter count and enhancing its detection speed. In addition, Bidirectional Feature Pyramid Network is implemented to facilitate swift and efficient multi-scale feature fusion, while the C3 module in the neck is replaced with C2f to enhance detection precision. Finally, Focal-Loss EIoU is adopted as the loss function to improve the model’s accuracy in positioning the crack borders. Experimental results demonstrate that the precision of this model in detecting surface cracks in bearing rings achieves an impressive 95.1%, while the recall reaches 90.4%. The mAP stands at 0.946. When compared to the original Yolov5s network, this model showcases a reduction in network parameters by 32.1% and a significant increase in frames per second by 40.0%. These improvements effectively fulfill the production process’s demands for crack detection tasks, providing a balance between accuracy and efficiency.
Synergistic coupling of thermomechanical loading and irradiation damage in Zircaloy-4
Authors: Long Daniel J , Liu Yang , Hardie Chris , Dunne Fionn P E
Published: March 2024

This work addresses in-situ synergistic irradiation and thermomechanical loading of nuclear reactor components by linking new mechanistic understanding with crystal plasticity finite element modelling to describe the formation and thermal and mechanical annihilation of dislocation loops. A model of pressurised reactor cladding is constructed to extract realistic boundary conditions for crystal plasticity microstructural sub-modelling. Thermomechanical loads are applied to the sub-model to investigate (i) the unirradiated state, (ii) synergistic coupling of irradiation damage and thermal annihilation of dislocation loops, (iii) synergistic coupling of irradiation damage without thermal annihilation of dislocation loops, and (iv) a post-irradiated state. Results demonstrate that the synergistic coupling of irradiation damage and thermomechanical loads leads to the early onset of plasticity, which is exacerbated by the thermal annihilation of dislocations, while the post-irradiated case remains predominantly elastic due to substantial irradiation hardening. It is shown that full synergistic coupling leads to localisation of quantities linked with crack nucleation including geometrically necessary dislocations and stress.
Simple quantitative examples illustrating how the centrifugal and Coriolis forces ‘rescue’ Newton’s second law in rotating frames
Authors: Ng Chiu-King
Published: March 2024

This paper is prepared for those who have already learned the physics of circular motions and the centripetal force and are curious about the centrifugal and Coriolis forces. Instead of deriving them or exploring the theory, we aim to bring forward several quantitative examples to illustrate what conceptually they are, along with evidencing the notion that ‘Newton’s second law in rotating reference frames holds only when the centrifugal and Coriolis forces are in action’. All our examples involve mostly circular motions, and, most importantly, our approach to dealing with the frame transformation is without using the equations and purely on a qualitative argument basis.
High performance Boson sampling simulation via data-flow engines
Authors: Morse Gregory , Rybotycki Tomasz , Kaposi Ágoston , Kolarovszki Zoltán , Stojčić Uroš , Kozsik Tamás , Mencer Oskar , Oszmaniec Michał , Zimborás Zoltán , Rakyta Péter
Published: March 2024

Boson sampling (BS) is viewed to be an accessible quantum computing paradigm to demonstrate computational advantage compared to classical computers. In this context, the evolution of permanent calculation algorithms attracts a significant attention as the simulation of BS experiments involves the evaluation of vast number of permanents. For this reason, we generalize the Balasubramanian–Bax–Franklin–Glynn permanent formula, aiming to efficiently integrate it into the BS strategy of Clifford and Clifford (2020 Faster classical boson sampling). A reduction in simulation complexity originating from multiplicities in photon occupation was achieved through the incorporation of a n-ary Gray code ordering of the addends during the permanent evaluation. Implementing the devised algorithm on FPGA-based data-flow engines, we leverage the resulting tool to accelerate boson sampling simulations for up to 40 photons. Drawing samples from a 60-mode interferometer, the achieved rate averages around 80 s per sample, employing 4 FPGA chips. The developed design facilitates the simulation of both ideal and lossy boson sampling experiments.
Work statistics at first-passage times
Authors: Mamede Iago N , Singh Prashant , Pal Arnab , Fiore Carlos E , Proesmans Karel
Published: March 2024

We investigate the work fluctuations in an overdamped non-equilibrium process that is stopped at a stochastic time. The latter is characterised by a first passage event that marks the completion of the non-equilibrium process. In particular, we consider a particle diffusing in one dimension in the presence of a time-dependent potential

U
(
x
,
t
)
=
k

|

x
−
v
t

|

n

/

n

, where k > 0 is the stiffness and n > 0 is the order of the potential. Moreover, the particle is confined between two absorbing walls, located at

L

±

(
t
)

, that move with a constant velocity v and are initially located at

L

±

(
0
)
=
±
L

. As soon as the particle reaches any of the boundaries, the process is said to be completed and here, we compute the work done W by the particle in the modulated trap upto this random time. Employing the Feynman–Kac path integral approach, we find that the typical values of the work scale with L with a crucial dependence on the order n. While for n > 1, we show that

⟨
W
⟩
∼

L

1
−
n

 
exp

k

L

n

/

n

−
v
L

/

D

for large L, we get an algebraic scaling of the form

⟨
W
⟩
∼

L
n

for the n < 1 case. The marginal case of n = 1 is exactly solvable and our analysis unravels three distinct scaling behaviours: (i)

⟨
W
⟩
∼
L

for v > k, (ii)

⟨
W
⟩
∼

L
2

for v = k and (iii)

⟨
W
⟩
∼
exp

−
(
v
−
k
)
L

for v < k. For all cases, we also obtain the probability distribution associated with the typical values of W. Finally, we observe an interesting set of relations between the relative fluctuations of the work done and the first-passage time for different n—which we argue physically. Our results are well supported by the numerical simulations.
Structural maturation of myofilaments in engineered 3D cardiac microtissues characterized using small angle x-ray scattering
Authors: van Dover Geoffrey , Javor Josh , Ewoldt Jourdan K , Zhernenkov Mikhail , Wąsik Patryk , Freychet Guillaume , Lee Josh , Brown Dana , Chen Christopher S , Bishop David J
Published: March 2024

Understanding the structural and functional development of human-induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs) is essential to engineering cardiac tissue that enables pharmaceutical testing, modeling diseases, and designing therapies. Here we use a method not commonly applied to biological materials, small angle x-ray scattering, to characterize the structural development of hiPSC-CMs within three-dimensional engineered tissues during their preliminary stages of maturation. An x-ray scattering experimental method enables the reliable characterization of the cardiomyocyte myofilament spacing with maturation time. The myofilament lattice spacing monotonically decreases as the tissue matures from its initial post-seeding state over the span of 10 days. Visualization of the spacing at a grid of positions in the tissue provides an approach to characterizing the maturation and organization of cardiomyocyte myofilaments and has the potential to help elucidate mechanisms of pathophysiology, and disease progression, thereby stimulating new biological hypotheses in stem cell engineering.
Quantum yield in induced-junction silicon photodiodes at wavelengths around 400 nm
Authors: Werner Lutz , Linke Ulrike , Müller Ingmar , Kubarsepp Toomas , Sildoja Meelis-Mait , Tran Trinh , Gran Jarle
Published: March 2024

The quantum yield in silicon has previously been assumed to be of significance only in the ultraviolet spectral range. Due to the low internal losses of induced-junction silicon photodiodes and their predictability it is possible for the first time to make more accurate estimation of the quantum yield. We report on measurement of quantum yield in induced-junction silicon photodiodes. The results show that the quantum yield can be larger than unity even at wavelengths around 450 nm. A model of the quantum yield has been fitted to the experimental data and can be implemented in the spectral responsivity models to maintain high accuracy predictability to around 160 ppm down to 360 nm.
Explainable machine learning predictions of perceptual sensitivity for retinal prostheses
Authors: Pogoncheff Galen , Hu Zuying , Rokem Ariel , Beyeler Michael
Published: March 2024

Objective. Retinal prostheses evoke visual precepts by electrically stimulating functioning cells in the retina. Despite high variance in perceptual thresholds across subjects, among electrodes within a subject, and over time, retinal prosthesis users must undergo ‘system fitting’, a process performed to calibrate stimulation parameters according to the subject’s perceptual thresholds. Although previous work has identified electrode-retina distance and impedance as key factors affecting thresholds, an accurate predictive model is still lacking. Approach. To address these challenges, we (1) fitted machine learning models to a large longitudinal dataset with the goal of predicting individual electrode thresholds and deactivation as a function of stimulus, electrode, and clinical parameters (‘predictors’) and (2) leveraged explainable artificial intelligence (XAI) to reveal which of these predictors were most important. Main results. Our models accounted for up to 76% of the perceptual threshold response variance and enabled predictions of whether an electrode was deactivated in a given trial with F1 and area under the ROC curve scores of up to 0.732 and 0.911, respectively. Our models identified novel predictors of perceptual sensitivity, including subject age, time since blindness onset, and electrode-fovea distance. Significance. Our results demonstrate that routinely collected clinical measures and a single session of system fitting might be sufficient to inform an XAI-based threshold prediction strategy, which has the potential to transform clinical practice in predicting visual outcomes.
Unveiling the role of tropical Pacific on the emergence of ice-free Arctic projections
Authors: Jahfer Sharif , Ha Kyung-Ja , Chung Eui-Seok , Franzke Christian L E , Sharma Sahil
Published: March 2024

The observed sea ice concentration (SIC) over the Arctic has receded substantially in recent decades, and future model projections predict a seasonally ice-free Arctic in the second half of this century. Nevertheless, the impact of the Pacific on Arctic sea ice projections has yet to receive much attention. Observations show that summertime Arctic SIC growth events are related to the weakening of the Aleutian low and cooling events over the equatorial Pacific, and vice versa. We demonstrate that under various Coupled Model Intercomparison Project Phase 6 projections, the models in which the impact of El Niño-driven SIC loss is significantly higher than the La Niña-related SIC growth tend to turn seasonally ice-free by about 10–20 years ahead of the ensemble mean under high-emission future scenarios. We show how the non-linear impact of the El Niño Southern Oscillation (ENSO) on Arctic SIC resulted in a faster decline of summertime sea ice. The ENSO-related SIC changes in the multi-model ensemble mean of Arctic SIC are considerably lower than the internal variability and anthropogenic-driven changes. However, the asymmetric interannual ENSO effects over several decades and the resultant changes in surface heat fluxes over the Arctic lead to significant differences in the timing of sea ice extinction. Our results suggest that climate models must capture the realistic tropical Pacific–Arctic teleconnection to better predict the long-term evolution of the Arctic climate.
Enhanced sensitivity and tunability of thermomechanical resonance near the buckling bifurcation
Authors: Liu Hanqing , Baglioni Gabriele , Boix-Constant Carla , van der Zant Herre S J , Steeneken Peter G , Verbiest Gerard J
Published: March 2024

The high susceptibility of ultrathin two-dimensional (2D) material resonators to force and temperature makes them ideal systems for sensing applications and exploring thermomechanical coupling. Although the dynamics of these systems at high stress has been thoroughly investigated, their behavior near the buckling transition has received less attention. Here, we demonstrate that the force sensitivity and frequency tunability of 2D material resonators are significantly enhanced near the buckling bifurcation. This bifurcation is triggered by compressive displacement that we induce via thermal expansion of the devices, while measuring their dynamics via an optomechanical technique. We understand the frequency tuning of the devices through a mechanical buckling model, which allows to extract the central deflection and boundary compressive displacement of the membrane. Surprisingly, we obtain a remarkable enhancement of up to 14× the vibration amplitude attributed to a very low stiffness of the membrane at the buckling transition, as well as a high frequency tunability by temperature of more than 4.02

%

K−1. The presented results provide insights into the effects of buckling on the dynamics of free-standing 2D materials and thereby open up opportunities for the realization of 2D resonant sensors with buckling-enhanced sensitivity.