bluuebunny/crossref_metadata_2025 huggingface dataset:
Reflection and transmission phenomenon of ultrasonic waves in a layered structure of functionally graded porous piezoelectric material
Authors: Vashishth Anil K , Bareja Umang
Published: November 2024

In this paper, the reflection and transmission characteristics of ultrasonic waves in a structure composed of a fluid half-space lying over functionally graded porous piezoelectric (FGPP) layers resting on the FGPP base are studied. Functionally graded porous piezoelectric materials (FGPPMs) provide a potential way to optimize performance in a variety of applications, including ultrasonics. They stand out for their customized electromechanical features and progressive property fluctuations. The material parameters of FGPPMs are assumed to change along the thickness direction. The transfer matrix is determined for the FGPP layers. The amplitude and energy ratios have been determined analytically. Numerical computation has been done to assess the effect of the angle of incidence, porosity, frequency, and gradation on reflected and transmitted energy ratios. In addition, the influence of selecting materials such as

BaTiO

3

,

PZT
−
5
H

, and

PZT
−
7
H

for the FGPP layers on the energy ratio curves is also demonstrated. The graphical analysis has examined the impact of the number of FGPP layers positioned above the half-space. The variation of the acoustic impedance for various porosities is also plotted. The graph indicates that the porosity in the structure may be changed to regulate the acoustic impedance. This will assist in reducing the energy loss at the ceramic medium interface and useful in underwater sonar detectors and medical ultrasonic imaging equipment, as well as non-destructive evaluation applications.
Analysis and comparison of three energy harvesting circuits for impact-type piezoelectric energy harvester
Authors: Yang Liu , Wei Tingcun , Chen Nan , Wang Yizhen , Shi Xue
Published: November 2024

The impacted-type piezoelectric energy harvesters (IPEHs) are widely used to harvest the energy of low-frequency impact forces from raindrops, human motion, machines, and other environmental sources. Owing to the typically low impact frequency, the output voltage between the two excitations undergoes damping. The attenuation coefficient λ, which reflects the damping rate, directly affects the performance of the energy harvesting circuit. This study analyzes and compares the variations of three energy harvesting circuits: full-bridge rectifier (FBR), parallel synchronized switch harvesting on inductor (P-SSHI), and synchronous electrical charge extraction (SECE) circuits under varying λ. First, the ideal energies of the three energy harvesting circuits during one impact event are summarized according to their maximum output power per half-cycle related to λ. Derivations of the IPEH with self-powered FBR, P-SSHI, and SECE circuits are provided, including the energy consumption and start-up voltage. Furthermore, these self-powered circuits connected with an IPEH are simulated. The optimal load resistance and capacitance of these circuits are analyzed relative to the variation of λ. The optimal load resistance of the SECE circuit varies significantly as λ increases, whereas the optimal loads of other circuits remain relatively constant. The output energies of the three self-powered circuits are analyzed as the force intensity and λ vary. The P-SSHI circuit yields the highest energy when appropriate components are selected. Under large λ or weak external forces, the output energy of the FBR circuit surpasses that of the SECE circuit. Finally, the three self-powered circuits are implemented in the IPEH. The experimental results show that the self-powered P-SSHI circuit generates the highest energy, with the figure of merit gradually increasing with the external force, which is consistent with the theoretical analysis. The guidance provided in this study is a reference for designing IPEH circuits.
Non-equilibrium thermodynamics in f(R, T) gravity and dark energy
Authors: Akbarpour Sudabeh , Sefiedgar Akram S , Rashidi Narges
Published: November 2024

Modifying general relativity may be a suitable approach to solve the dark energy problem. Among the various theories of modified gravity, we consider the f(R, T) gravity, in which R is the Ricci scalar and T is the trace of the energy-momentum tensor. As an intriguing property, the conservation equation does not hold in f(R, T) gravity. It means that the divergence of the energy-momentum tensor does not vanish. Using the formalism of irreversible thermodynamics of open systems in the presence of matter creation or matter annihilation, one can explore the physical interpretation of non-conservative energy-momentum tensor. Comparing the non-conservative energy-momentum tensor in f(R, T) gravity with the one in an irreversible open system, one may conclude that there may be a flow of energy from the gravitational sector to the matter sector, which may result in matter creation. In this paper, we study the f(R, T) gravity in the presence of the ordinary matter and the scalar field from the viewpoint of the irreversible thermodynamics of open systems to explore the possibility of matter creation. The matter creation rate, the creation pressure, the entropy production rate and the temperature evolution can be obtained. This possible matter creation in f(R, T) gravity can be considered as a component of energy which may play the role of dark energy in the recent accelerated expanding phase of the Universe.
The study of the impact of Bi2O3 on the x-ray shielding efficacy of the new barium-magnesium-boro-tellurite ceramic system
Authors: Kheswa B V
Published: November 2024

This computational study delves into the influence of Bi2O3 concentration on the x-ray shielding capabilities of (x)Bi2O3 + (55-x)B2O3 + 15TeO2 + 10MgO + 20BaO, with x ranging from 0 to 40 mol%. The investigation revealed that higher Bi2O3 content leads to increased linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), and effective atomic number (Zeff). Conversely, the half-value thickness (HVT), tenth-value thickness (TVT), and mean-free path (MFP) decrease as Bi2O3 concentration rises. Furthermore, the study noted a linear increase in LAC with Bi2O3 mol% at 16%, 3%, and 12% per mol% in the 15-30 keV, 40-80 keV, and 100-300 keV energy ranges, respectively. Thus, the (x)Bi2O3 + (55-x)B2O3 + 15TeO2 + 10MgO + 20BaO glass configuration demonstrates the promising potential for x-ray shielding, particularly effective for energies below 40 keV and above 80 keV, with efficacy increasing with higher Bi2O3 concentrations.
Generation of Terahertz radiation from a soliton cavity in a laser-plasma system
Authors: Verma Deepa , Sengupta Sudip , Sen Abhijit , Tiwari Sanat
Published: November 2024

Using particle-in-cell simulations, we demonstrate a novel mechanism for the generation of terahertz radiation in a laser-plasma system. The radiation originates from current oscillations trapped in a stable soliton cavity created by the laser in the under-dense plasma region. These oscillations behave like a current dipole antenna. The characteristics of the antenna can be controlled by tuning the laser-plasma parameters to achieve the desired output frequency. We discuss the optimum conditions for the physical realization of this mechanism and its potential practical applications.
Studies on the effect of SiC nanopowder concentration and discharge energy on surface roughness and recast layer in micro ED milling of Inconel 718 alloy
Authors: Boominathan Elumalai , Krishnan Giridharan , Gurijala Chakravarthi , VM Jothiprakash
Published: November 2024

Micro-EDM is one of the most viable processes for micromachining hard and conductive materials. However, the slow machining rate, high tool wear rate, and poor surface quality caused by the inherent nature of the material removal mechanism continue to pose significant challenges. This study explores the impact of silicon carbide (SiC) nanopowder (25 nm–35 nm) blended dielectric on micro-electro discharge milling of Inconel 718 alloy. The experiments were conducted using a multipurpose micromachining center equipped with a rotating spindle and Resistor Capacitor type micro-EDM module. Micro-channels were machined using various concentrations of SiC nanopowder (0 to 0.4 g l−1) in the dielectric fluid, under different discharge energy levels ranging from 7.2 μJ to 720 μJ. The process was controlled by a specialized dielectric circuit that used ultrasonic agitators and mechanical stirrers to ensure uniform nanopowder distribution during machining. The surface roughness, crater diameter and recast layer thickness were analysed. The results showed that adding SiC nanopowder reduced surface roughness up to 19.15% across all discharge energy ranges. This reduction was due to the nanopowder lowering the dielectric breakdown voltage, increasing the inter-electrode gap, and distributing energy more evenly, which resulted in smaller and more uniformly distributed craters. Surface roughness decreased further as the nanopowder concentration increased. Additionally, the study found that the inclusion of SiC powder reduced the thickness of the recast layer up to 55.3% at all energy levels by reducing the energy per spark and enhancing the removal of molten material. High-Resolution Scanning Electron Microscope (HRSEM) and Energy Dispersive x-ray Spectroscopy (EDS) analyses revealed that material migration onto the machined surface was minimized, and surface defects such as microcracks and voids were less prevalent at lower energy levels. Overall, SiC nanopowder improved the surface quality and reduced the white layer thickness in micro-EDM milling of Inconel 718.
Chaotic dynamics of a carbon nanotube oscillator with symmetry-breaking
Authors: Wang Zhen , Yang Yantao , Parastesh Fatemeh , Cao Shuping , Wang Jinni
Published: November 2024

Carbon nanotubes (CNTs) are pivotal components in nanoelectromechanical applications. Investgaing the dynamics of CNTs helps in expanding our understanding of their mechanical properties in nanoengineering endeavors. This study delves into the chaotic characteristic of single-walled carbon nanotube (SWCNT) systems involving phase-shifting external excitation and cubic nonlinear damping. Employing compactification theory, we investigate the system’s dynamics at infinity, unveiling its global structure. Analytic solutions for homoclinic/heteroclinic orbits are derived, and utilizing the Melnikov method, we establish criteria for chaos onset in this periodically excited, perturbed SWCNT system. Through bifurcation diagrams, Lyapunov exponent spectra, Poincaré sections, and homoclinic bifurcation surfaces, we empirically confirm the occurrence of chaos, substantiating our theoretical analyses with simulation results.
Organic-inorganic hybrid dye-sensitized solar cells with bismuth ferrite sandwiched between rhodamine-6G and helical ZnO-dense nano-chains
Authors: Bera Amalendu , Sardar R H , Chattopadhyay Sourav
Published: November 2024

Organic–inorganic hybrid dye-sensitized solar cells (DSSC) were grown on a conducting glass substrate employing multiple layers of bismuth-ferrite (BFO) sandwiched between Zinc oxide helical nanochain and Rhodamine- 6 G dye. The zinc oxide layer has been used as a n-type semiconductor window layer. To increase the carrier concentration ZnO has been doped with aluminium. The bismuth ferrite layer served as an electron-blocking layer, while rhodamine 6 g acted as a dye synthesizer. When the window layer is pure ZnO and the BFO layer is properly optimized, solar cell efficiency increases from 0.7% to 1.3%. Aluminum doping in ZnO, combined with an identical BFO layer, increases efficiency from 1.37% to a maximum of 2.1% without employing any kind of electrolyte. Doping the Zn site with Al enhances the efficiency of such a DSSC structure by 1.53 times. BFO limits charge recombination, which leads to enhanced efficiency as an outcome. A parametric analysis was carried out to determine the optimal BFO thickness for increased solar cell efficiency. The main advantages of this optimal DSSC structure are that it is economical, efficient, and does not require any liquid electrolyte. The stability was higher because there was no use of liquid electrolytes.
Two linearized difference schemes on graded meshes for the time-space fractional nonlinear diffusion-wave equation with an initial singularity
Authors: Gahalla Mohmed Elmahdi Emadidin , Yi Yang , Huang Jianfei
Published: November 2024

In this article, two linearized difference schemes are considered to solve a class of time-space fractional nonlinear diffusion-wave equations with weak singularity near the initial time based on its equivalent integro-differential equation. The Crank-Nicolson method combined with the trapezoidal product integration rule with graded meshes is implemented to approximate the Riemann-Liouville integral. The fractional central difference formula and a novel compact difference method are used to construct fully discrete difference schemes. Using the energy method, the stability and convergence of the proposed schemes are demonstrated in terms of the L
2 norm with the accuracy of

O

N

−
min
{
r
σ
,
2
}

+

M

−
2

and

O

N

−
min
{
r
σ
,
2
}

+

M

−
4

, respectively. The theoretical analysis is complemented by numerical results.
Non-monotonically changes in double Schottky barrier of MnCO3–doped ZnO varistors during DC aging
Authors: Lan Peixiang , Zhao Xia , Yue Yinghu , Wang Xin , Zhang Boyu , Lyu Xuebin , Guo Zixin
Published: November 2024

ZnO varistors play a crucial role as core component in metal oxide arresters due to their excellent nonlinear current density-electrical field (J–E) characteristics. After long-term operation under DC stress (DC aging), the J–E curves of ZnO varistors invented in the last decade cross with the original curve. Unexpectedly, the ‘crossover’ phenomenon cannot be explained by the vastly-accepted ion migration mechanism by which the barrier height monotonically declines after DC aging. In the present study, aging and recovery experiments were carried out on MnCO3-doped ZnO varistors. The symmetry of J–E characteristics in the same direction as and the opposite direction to the DC stress was compared, parameters of double Schottky barrier were analyzed, and evolution of point defects was deduced using dielectric spectra. It was found that, in addition to ion migrations, there are electrons ionized by zinc interstitials filling the interface states in the early stage of aging. Because these processes are dominant in different stages, the barrier height changes non-monotonically. MnCO3 can suppress the formation of zinc interstitials, so it simultaneously inhibits ion migrations and filling of the interface states by electrons. When 0.38 mol% MnCO3 is doped, J–E characteristics and the Schottky barrier of ZnO varistors show the smallest deviations during aging and recovery. The findings are helpful in updating criteria for the long-term stability of ZnO varistors and suggest that modifications to their formulae targeting the suppression of the filling the interface states by electrons are also expected to bolster the stability.
Experimental investigation of toe laser intensity effects on capsule compression in indirect-drive inertial confinement fusion
Authors: Yang Weiming , Duan Xiaoxi , Li Yulong , Zhang Yuxue , Jing Longfei , Guan Zanyang , Zhang Chen , Liu Hao , Zhang Huan , Dong Yunsong , Li Zhichao , Yang Dong , Wang Zhebin , Yang Jiamin
Published: November 2024

In indirect-drive inertial confinement fusion (ICF) research, the meticulous design and optimization of laser parameters are crucial for achieving high-gain ignition. The intensity of the toe laser, used for ablating the hohlraum sealing membrane, is a subtle but equally critical parameter. This study introduces a novel experimental approach using the Velocity Interferometer System for Any Reflector (VISAR) to assess the impact of toe laser intensity on the compression of fusion capsules. By tracking the reflectivity of tracer layers and shock velocities in liquid deuterium, the adverse effects of insufficient toe laser intensity on capsule compression have been unveiled for the first time. From a comparison with hydrodynamic simulations, we show that below a critical threshold of 0.23 × 1014 W cm−2, the adiabat, a measure of the fuel’s compression efficiency, increases markedly with the toe laser intensity decreases, whereas it remains stable within the range of (0.23 ∼ 7) × 1014 W cm−2. Our findings provide critical insights on toe laser parameter design, enhancing our understanding of the role of toe laser intensity in ICF experiments. This research not only refines the parameters for laser operation but also underscores the importance of precision in achieving the desired implosion efficiency, contributing to the development of nuclear fusion as a clean energy source.
Unified mesoscale picture of nonlinear generation of zonal flows in toroidal geometry
Authors: Wang Zihao , Wang Shaojie
Published: November 2024

Recent experimental findings on limit-cycle-oscillations indicate that the nonlinear driving of the turbulent poloidal Reynolds stress to zonal flows (ZFs) is not a significant factor in the toroidal geometry, sparking fundamental controversial issues within the fusion community. By using the global nonlinear gyrokinetic simulations, we propose a unified mesoscale picture of nonlinear driving of ZFs in the ion-temperature-gradient turbulence. ZFs are nonlinearly driven by the turbulent energy flux and the turbulent poloidal Reynolds stress. The turbulent energy flux is not shielded by the toroidal geometry effect in nonlinearly driving ZFs. The turbulent poloidal Reynolds stress is not shielded on the time scale shorter than the ion bounce period; however, on the time scale longer than the ion bounce period, the turbulent poloidal Reynolds stress is indeed shielded by the toroidal geometry effect.
Multi-messenger astronomy in the new physics modality with GPS constellation
Authors: Sen Arko P. , Pfeffer Kalia , Ries Paul , Blewitt Geoff , Derevianko Andrei
Published: November 2024

We explore a novel, exotic physics, modality in multi-messenger astronomy. We are interested in exotic fields emitted by the mergers and their direct detection with a network of atomic clocks. We specifically focus on the rubidium clocks onboard satellites of the Global Positioning System. Bursts of exotic fields may be produced during the coalescence of black hole singularities, releasing quantum gravity messengers. To be detectable such fields must be ultralight and ultra-relativistic and we refer to them as exotic low-mass fields (ELFs). Since such fields possess non-zero mass, the ELF bursts lag behind the gravitational waves emitted by the very same merger. Then the gravitational wave observatories provide a detection trigger for the atomic clock networks searching for the feeble ELF signals. ELFs would imprint an anti-chirp transient across the sensor network. ELFs can be detectable by atomic clocks if they cause variations in fundamental constants. We report our progress in the development of techniques to search for ELF bursts with clocks onboard GPS satellites. We focus on the binary neutron star merger GW170817 of August 17, 2017. We find an intriguing excess in the clock noise post LIGO gravitational wave trigger. Potentially the excess noise could be explained away by the increased solar electron flux post LIGO trigger.
A definition of the SI second based on several optical transitions
Authors: Lodewyck Jérôme
Published: November 2024

A new definition of the SI second based on optical transitions is expected to be adopted within the next 10 years. Several options for this redefinition are currently under consideration. Among them, a definition based on several transitions would take advantage of the variety of high performance optical frequency standards. In this paper, we review practical aspects such a definition entails, and propose a detailed analysis of its strengths and weaknesses.
Towards practical quantum secure time transfer
Authors: Villaseñor E. , Shimizu K. , Chandrasekara R. , Lau W. Y. S. , Gensemer S.
Published: November 2024

Accurate clock synchronization and time transfer are vital for positioning, navigation, and timing systems, however, current systems are susceptible to attacks, such as spoofing. Quantum secure time transfer (QSTT) can address this threat by providing a method to validate the authenticity of the time signals used. In this work, we analyze the feasibility of free-space QSTT between two mobile transceivers. Using various techniques, we model the free-space channel to estimate the maximum ranges achievable while guaranteeing a defined level of security. The results indicate that QSTT is feasible for daytime operations up to a distance of 14 km, while nighttime operations can be achieved up to 30 km. This study can be used to design the next pathfinder experiments towards the development of practical QSTT.
REFIMEVE frequency and time network and applications
Authors: Cantin E , Lopez O , Chardonnet C , Amy-Klein A , Rabault M , Coget G , Rosenbusch P , Ménoret V , Quintin N , Tønnes M , Pointard B , Mazouth-Laurol M , Alvarez-Martinez H , Lim C B , Tuckey P , Abgrall M , Le Targat R , Pottie P-E
Published: November 2024

We present the development and current status of the REFIMEVE national research infrastructure, which disseminates time and frequency reference signals generated at LNE-SYRTE to research labs all over France. Using mainly the optical fiber backbone of RENATER, the French National Research and Education Network, REFIMEVE currently provides an optical frequency reference to around 15 labs, and to connection points to Germany, the UK, Italy and Switzerland. The robustness of the various types of equipment specifically developed for the transfer of ultrastable frequencies and the efficient supervision system have enabled us to demonstrate uptimes of over 90%. We show the latest development we have carried out to extend the network to CERN in Switzerland, with a branching link showing residual frequency fluctuations of 3×10−15 for 1 s measurement time, and a few 10−19 at long term. We discuss the issue of data processing for long periods of time and how to mitigate the effects of missing data to achieve reliable link uncertainty estimates. Thanks to these performances, the REFIMEVE network has been used for the precise comparison of primary and optical clocks in Europe, and the REFIMEVE optical signal is currently being exploited in France by user laboratories for photonics, laser stabilisation or control and atomic and molecular high-resolution spectroscopy.
Validating a lutetium frequency reference.
Authors: Arnold K J , Bustabad S , Qi Zhao , Qichen Qin , Zhang Zhiqiang , Zhao Zhang , Barrett M D
Published: November 2024

We review our progress in developing a frequency reference with singly ionized lutetium and give estimates of the levels of inaccuracy we expect to achieve in the near future with both the 1
S
0 ↔ 3
D
1 and 1
S
0 ↔ 3
D
2 transitions. Based on established experimental results, we show that inaccuracies at the low 10−19 level are readily achievable for the 1
S
0 ↔ 3
D
1 transition, and the frequency ratio between the two transitions is limited almost entirely by the BBR shift. We argue that the frequency ratio measured within the one apparatus provides a well-defined metric to compare and establish the performance of remotely located systems. For the measurement of an in situ frequency ratio, relativistic shifts drop out and both transitions experience the same electromagnetic environment. Consequently, the uncertainty budget for the ratio is practically identical to the uncertainty budgets for the individual transitions. If the ratios for two or more systems disagree we can be certain at least one of the clock assessments is incorrect. If they agree, subsequent comparisons on one transition would only differ by relativistic effects. Since motional effects are easily assessed and typically small for a heavy ion, only the differential gravitational red-shift will significantly contribute and this can be confirmed by comparison on the second transition.
A thermal-noise-limited fiber frequency reference with

0.1
Hz
/

Hz

stability
Authors: Zhang Ya , Bandutunga Chathura P. , McRae Terry G. , Gray Malcolm A. , Chow Jong H.
Published: November 2024

We develop an all-passive, fiber frequency reference with a state-of-the-art short-term stability of

0.1
Hz
/

Hz

. We explore the impact of intrinsic fiber thermal noise and show it limits the system in the 1 Hz Fourier frequency band.
Quantum measurement limits to clock precision
Authors: Milburn G J , Kewming M
Published: November 2024

The role of projection noise, an example of quantum measurement noise, in clock design has been well understood for some time. It is based on a particular measurement protocol — Ramsey interferometry. In this paper we discuss more general quantum measurement schemes to estimate the period/frequency of a clock system based on continuous readout of a driven quantum system. The measurement needs to be chosen so as to provide a precise counting signal. We give an example based on a superconducting circuit clock.
Analysis of Stamping Forming and Springback of Arc-shaped Corrugated Diaphragm
Authors: Wang Yu , Zhang Chunguang , Li Shangqing , An Lei , Wu Ye
Published: November 2024

The arc-shaped corrugated diaphragm is the packaging component of pressure sensors, and the quality of diaphragms directly affects the performance of pressure sensors. Diaphragms are usually produced by blanking process. Common production defects include the severe warping and the insufficient forming height. In order to reduce production defects, this paper uses the flat punch and the corrugated punch as research objects to clarify the effect of production process and punch structure on diaphragm production quality. The results show that the production process causes the diaphragm to have a convex warping tendency, which is opposite to the warping tendency caused by corrugation. Moving the corrugation away from the center of the diaphragm and increasing the corrugation spacing can improve the diaphragm quality, while the effect of the corrugation height can be ignored.
Implementation of A Generalized Spring Element for Fastener Simulation of Complex Mechanical Structures In SABRE Software
Authors: Zhang Chang-Xing , Chang Liang , Guo Yu-Chao , Wang Li-Kai
Published: November 2024

When bolts, rivets, and other fasteners in complex engineering machinery structures are modeled using spring elements, internal constraints may arise if the two connected nodes are not coincident, leading to computational errors. To facilitate the modeling of fasteners and extend the application scope of spring elements, this paper constructs a generalized spring element, whose stiffness is calculated using the Huth formula, and deformation is determined by the difference between the two endpoint displacements rigidly transformed to the internal reference point. Based on the characteristics of this element, an explicit expression for the stiffness matrix of the generalized spring element is derived. Accordingly, the implementation of this element has been integrated into the autonomous structural analysis software SABRE. Verification through typical engineering examples shows that the proposed generalized spring element can accurately simulate the load-bearing behavior of fasteners in structures, with analysis errors less than 3% when compared to NASTRAN software.
An online learning-based method for predicting milling energy consumption under tool wear
Authors: Li Mingyao , Zhu Shuo , Jiang Zhigang , Yan Wei , Zhang Hua , Liu Yunhan
Published: November 2024

Accurate prediction of milling energy consumption under tool wear can provide a realistic basis for timely adjustment of process solution and tool replacement. However, complex machining characteristics lead to dynamic changes in tool wear and process parameters, resulting in increased uncertainty in energy consumption deviation, which in turn affects the accuracy of energy consumption prediction. Therefore, this paper proposes an energy consumption prediction method for milling based on BI-SSA-OSELM online learning, considering tool wear. Firstly, the mechanism of tool wear on energy consumption is analyzed from the point of view of material removal power to identify the key factors affecting machining energy consumption. Based on this, cutting and tool geometry parameters are used as model inputs, and the online sequential extreme learning machine (OSELM) algorithm is applied to build the energy consumption model. The model’s hyperparameters are optimized using the sparrow search algorithm (SSA). A drift detection algorithm based on Bernstein’s inequality (BI) is then introduced to guide SSA-OSELM in online learning, to save time for online learning. Results show that the proposed method’s mean absolute error (MAE) is less than 3%, validating the model’s effectiveness and superiority.
Observation of Subsurface Cracks on Flat PEEK Race-Alumina Ball Bearing in Water under 1700 N at 1000 rpm
Authors: Machino Sasuga , Kajiwara Shuhei , Matsubayashi Soji , Kida Katsuyuki
Published: November 2024

Polymers have features of low friction coefficient, chemically resistant, corrosive resistant, and non-conductive. Hence, many tribology productions of polymers such as bearings, gears, and rollers are developed. However, the mechanism of failure such as rolling contact fatigue has not been explained clearly. In recent studies, the observation of subsurface crack growth was important for understanding the failure mechanisms of the polymer ball bearings in water lubrication. In this research, we conducted overall cross-sectional observations to investigate the growth behaviour of subsurface cracks. The cross-sectional areas of the failure were observed. Moreover, we focused on the crack length, depth, angle and direction of propagation of the subsurface cracks. We concluded that as the distance of crack location from the centre of the contact track increased, the depth and length of the subsurface cracks increased. Most of the subsurface cracks propagated from the inner and outer areas toward the centre of the contact track.
LES of flow dynamics downstream of bluff bodies with inclined upper surfaces
Authors: Caban L , Wawrzak A , Tyliszczak A , Thévenin D
Published: November 2024

This study focuses on the flow dynamics downstream of cylindrical bluff bodies with flat, concave, and convex surfaces, where a fuel jet is injected at the bluff body center and the oxidiser flows through a duct surrounding the bluff body. The flow is assumed to be non-reactive and the main attention is put to the mixing process. The research is carried out using the Large Eddy Simulation (LES) method, employing two computational codes: ANSYS Fluent and an in-house high-order code SAILOR. We analyze the extent to which the inclination of the upper bluff body surface modifies the flow behavior in its immediate vicinity and how it affects the size and position of a recirculation zone formed downstream.
Development of triple-helical recombinant collagen-silver hybrid nanofibers for anti-methicillin-resistant Staphylococcus aureus (MRSA) applications
Authors: Fu Caihong , Ma Jianrui , Liu Guangyu , Fan Yirui , Wei Nannan , Xiao Jianxi
Published: November 2024

The escalating threat of healthcare-associated infections highlights the urgent need for biocompatible antibacterial materials that effectively combat drug-resistant pathogens. In this study, we present a novel fabrication method for triple-helical recombinant collagen (THRC)-silver hybrid nanofibers, specifically designed for anti-methicillin-resistant staphylococcus aureus (MRSA) applications. Utilizing a silver-mediated crosslinking strategy, we harness a low-power 38 W lamp to enable silver ions (Ag+) to mediate crosslinking across various proteins. Mechanistic insights reveal the pivotal role of nine amino acids in facilitating this reaction. The THRC maintains its native structure, forming well-ordered nanofibers, while other globular proteins form a distinctive network-like structure. THRC also serves as a reducing and dispersing agent, facilitating the in situ synthesis of highly dispersed silver nanoparticles (AgNPs) (∼7 nm in diameter) within the nanofibers. Systematic investigation of the reaction conditions between THRC and Ag+ demonstrates the versatility of this novel approach for nanofiber fabrication. The incorporation of AgNPs imparts exceptional antibacterial activity to the THRC/AgNPs nanofibers, exhibiting a minimum inhibitory concentration of 19.2 mg l−1 and a minimum bactericidal concentration of 153.6 mg l−1 against MRSA. This innovative approach holds significant potential for developing antibacterial protein-based biomaterials for infection management in wound healing and other biomedical applications.
Effects of drought on optimum temperature of carbon fluxes in temperate grasslands
Authors: Su Tiancheng , Wang Yanbing , You Cuihai , Han Xingguo , Chen Shiping
Published: November 2024

Ecosystem carbon flux components, including ecosystem gross primary productivity (GPP), ecosystem respiration (ER), and net ecosystem productivity (NEP), are the most direct indicators of ecosystem production capacity, carbon sequestration, and climate regulation strength. Nevertheless, little is known about how water availability affects the temperature responses of carbon flux components in water-limited ecosystems. Based on a long-term eddy observation dataset of temperate grasslands in northern China, we analyzed the effects of drought on the optimum temperature of carbon flux components (

T

opt

flux

) in temperate grassland ecosystems and clarified the relative contributions of vegetation and climate factors to

T

opt

flux

. We found that the optimum temperatures of carbon flux components were widespread across different grassland types, with a significant lower optimum temperature of NEP (

T

opt

NEP

, 17.32 ± 3.21 °C) than that of GPP (

T

opt

GPP

, 18.67 ± 2.53 °C) and ER (

T

opt

ER

, 19.30 ± 1.94 °C). Drought significantly reduced

T

opt

NEP

, but had no significant effects on

T

opt

GPP

and

T

opt

ER

. Obvious shifts of occurrence date of

T

opt

flux

were also observed in the years with different precipitation regimes. That is,

T

opt

GPP

and

T

opt

NEP

occurred significantly earlier than seasonal maximum temperature (

T

max

) in the dry years, while

T

opt

flux

significantly lagged behind the occurrence of

T

max

in the wet years. Water availability and vegetation factors co-regulated the spatiotemporal variations of

T

opt

flux

. In the dry years, precipitation and soil water content predominated the changes in

T

opt

GPP

and

T

opt

ER

, whereas vegetation structure (leaf area index) and physiological characteristics played a more important role in the wet years. Our study not only provided the first evidence for the widespread existence of

T

opt

flux

of different carbon fluxes, but also addressed the remarkable impacts of drought on

T

opt

flux

and their occurrence date in the water-limited grasslands. Therefore, incorporating the unimodality of these observed temperature responses of ecosystem carbon fluxes into land carbon models is necessary for improving the accuracy of carbon sequestration predictions.
Lack of evidence for alternative stable states in Northern Hemisphere forests during the past 8 ka
Authors: Schild Laura , Hébert Raphaël , Herzschuh Ulrike , Laepple Thomas
Published: November 2024

With increased pressure from anthropogenic climate change, boreal forests are suspected to be approaching tipping points which could cause large-scale changes in tree cover and affect global climatic feedback. However, evidence for this proposed tipping is sparse and relies heavily on observations on short time scales from remote sensing data and space-for-time substitutions. Here we make use of an extensive pollen data set including 239 records of large lakes to investigate the existence of alternative stable forest cover states in the boreal forest and its adjacent biomes during the last 8000 years. By using a multimodality measure on time series of reconstructed tree cover we find very little multimodality in pollen data. To test whether this lack of multimodality is caused by limitations in the paleo data set we perform surrogate experiments. Surrogate data with alternative stable states based on the paleo vegetation–climate relationship were generated and significant multimodality was found more often than for the pollen-based tree cover (24.7% and 5.3% respectively). The response of tree cover to climate may, therefore, be more gradual and not as abrupt as would be expected from remote sensing analyses on stability. The apparent alternative stability hypothesized in the analyses of climate–vegetation relationships could be due to the strong spatial heterogeneity of environmental factors and vegetation responses as an artifact of space-for-time substitutions. Even though current and upcoming shifts in the boreal forest are indisputable and a reason for strong concern, these changes could happen gradually without going through large-scale tipping between alternative stable states. To aid adaptation and conservation measures, more knowledge is needed about boreal forest drivers and their spatial heterogeneity.
Explaining decision structures and data value for neural networks in crop yield prediction
Authors: von Bloh Malte , Seiler Benjamin , van der Smagt Patrick , Asseng Senthold
Published: November 2024

Neural networks are powerful machine learning models, but their reliability and trust are often criticized due to the unclear nature of their internal learned relationships. We explored neural network learning behavior in wheat yield prediction using game theory-based methods (SHapley Additive exPlanations, Shapley-like, cohort Owen), examined data impact on model performance and show optimization approaches. By identifying and removing harmful data samples, we demonstrated a significant improvement in prediction accuracy. We show that neural networks can learn decision patterns that often align with agronomic causal relationships. Building on these insights we propose a novel approach using an autoencoder to detect statistical implausible decisions, allowing us to flag and correct potential ‘misjudgements’, resulting in an 11% reduction in global model error. The proposed explainability methods can optimize the neural network training process through improved data acquisition and revising the internal learning process. This enhancement presents neural networks as trustworthy simulation agents for agricultural research, capable of supporting new scientific discoveries and assisting in real-world applications.
Dual-band circular dichroism in chiral metamaterial absorber based on vanadium dioxide
Authors: Zhenglan Zhou , Junwen Zhu
Published: November 2024

Chiral metamaterial absorbers are instrumental in a wide array of applications, encompassing multifaceted optoelectronic devices, information-encrypting metamaterials, and thermal-controlled imaging and detection systems. In this study, we showcase a Ꞩ-shaped chiral metamaterial integrated with a vanadium dioxide substrate, which enables dynamic tuning of terahertz (THz) dual-band circular dichroism (CD). This absorber boasts spin-selective absorption, stemming from the selective excitation of the plasmon polaron mode on its horizontal microrod. Notably, right-handed circularly polarized light (CPL) experiences near-perfect absorption at resonance, whereas left-handed circular polarization is absorbed to a much lesser degree, yielding pronounced CD. This exceptional chiral selectivity facilitates dual-band CD effects, with peak values reaching 0.814 and 0.784. Furthermore, by manipulating the conductivity of vanadium dioxide, we can dynamically adjust both the CD and absorption peaks of the chiral metamaterial. The maximum modulation depth of the CD response can attain values as high as 0.807 and 0.776. Our work presents a novel design strategy for the active control and modulation of CPL, thereby expanding the horizons of metamaterial absorber applications within the THz spectrum.
The channel capacity of the free space communication link based on Bessel-like beams
Authors: Litvin Igor A , Munar-Vallespir Pere , Nötzel Janis
Published: November 2024

This study investigates the information channel capacity of free-space communication links based on Bessel-like beams (BLBs) and compares it to that of conventional Gaussian beams (GBs). We examine optical communication links employing amplitude coding for beams with BLB spatial field distribution and orbital angular momentum (OAM)-based coding for single-photon optical communication. Our study explores both unperturbed and perturbed propagation scenarios, considering random phase fluctuations caused by atmospheric turbulence and amplitude attenuation due to absorbing obstacles. Our results show that BLBs provide higher channel capacity than GBs at short distances (within a few kilometers of propagation distance), but GBs outperform BLBs at longer distances. In turbulent environments, BLBs experience more significant capacity degradation than GBs, though they maintain higher capacity in OAM-based single-photon links for distances under 1–2 km.
Proposal for superconducting photodiode
Authors: Parafilo A V , Sun M , Sonowal K , Kovalev V M , Savenko I G
Published: November 2024

We propose a concept of a superconducting (SC) photodiode—a device that transforms the energy and ‘spin’ of an external electromagnetic (EM) field into the rectified steady-state supercurrent and develop a microscopic theory describing its properties. For this, we consider a two-dimensional thin film cooled down below the temperature of SC transition with the injected dc supercurrent and exposed to an external EM field with a frequency smaller than the SC gap. As a result, we predict the emergence of a photoexcited quasiparticle current, and, as a consequence, oppositely oriented stationary flow of Cooper pairs. The strength and direction of this photoinduced supercurrent depend on (i) such material properties as the effective impurity scattering time and the nonequilibrium quasiparticles’ energy relaxation time and (ii) such EM field properties as its frequency and polarization.
Effect of welding layers and interlayer temperature on welding residual stress and deformation of Q345/316L dissimilar steel
Authors: Zhu Yongyou , Zheng Jianneng , Li Houbin , Liu Yuping , Huang Bensheng , Li Tianning , Tang Peng
Published: November 2024

Dissimilar steel welding is widely used in machinery, chemical industry, electric power and other fields. Due to the different welding materials, the distribution of residual stress and deformation of welded joints is complex. In order to study the influencing factors and variation rules of residual stress and deformation distribution of dissimilar steel joints, considering the nonlinear physical and mechanical properties of welding materials and the latent heat of phase change during welding, based on the SYSWELD platform, taking Q345 carbon steel and 316L stainless steel as the research objects, the double ellipsoid heat source model was used to study the effects of welding layers and interlayer temperature on the residual stress and deformation of joints. The results show that the increase of the number of welding layers is beneficial to expand the distribution of residual stress, and has no obvious effect on the residual stress of the weld, but it will reduce the residual stress of the base metal near the weld. However, the increase of the number of layers will also aggravate the deformation of the weld. Therefore, it is necessary to consider the design of the number of welding layers considering the thickness of the component. At the same time, the study also found that the interlayer temperature has a certain influence on the residual stress and deformation of the joint. The increase of the interlayer temperature will reduce the welding angle deformation, and has little effect on the transverse shrinkage and the residual stress of the joint. Therefore, a lower interlayer temperature should be selected for multi-layer and multi-pass welding of dissimilar steel to ensure the quality of the welded joint.
Performance characteristics of self-compacting concrete containing lateritic fine aggregate as a partial replacement to natural river sand
Authors: Bhat P Kiran , C Rajasekaran , Das B B
Published: November 2024

This study identifies the use of processed lateritic fine aggregate (LFA) as a sustainable material for the replacement of natural fine aggregate (NFA) in self-compacting concrete (SCC). Cubes were cast with LFA replacements from 10% to 80% with an interval of 10% for checking the compressive strength development at 28 and 90 days. The findings demonstrate that the replacement of 30% NFA with LFA leads to the optimum performance, resulting in compressive strengths of 45.5 MPa and 53 MPa after 28 and 90 days of curing. Similar trends are also noted with the specimens cast for splitting tensile and flexural strengths as per IS 516: 2021. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Thermogravimetric analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) were performed to understand the surface morphology, material characterization, and composition differences between the control mix (C30F) and optimized lateritic SCC (C30F30L). SEM and EDX analysis demonstrated the contribution of the introduced fly ash particles to the strengthening of concrete. TGA with DTA has shown the more complicated denser structure of the C30F mix, and FTIR has confirmed the presence and formation of the C–S–H gel. Si–O–Si asymmetric stretching band has extra peaks, and with FTIR, O–C–O asymmetrical bending and stretching wave band have a lower intensity than the C30F mix due to the partial replacement of LFA. In addition, it is also observed from the durability studies that C30F30L showed an increase in pore volume and capillary pore network compared to C30F mix.
Carbon based materials in conducting tissue engineering
Authors: Sancar Elif , Oktay Büşra , Ahlatcıoğlu Özerol Esma
Published: November 2024

Conducting materials based on carbon have been widely investigated in conducting tissue engineering applications due to their outstanding physical, chemical, thermal, and electric properties in recent years. Carbon based conductive materials can generate or respond to electrical signals, allowing them to provide controlled electrical stimulation to cells or tissues. Conductive tissue engineering (CTE) holds great promise for a wide range of applications, including nerve regeneration, cardiac tissue engineering, muscle tissue engineering and neural interfaces. In this review, recent progress in conducting tissue engineering applications by using these carbon-based materials in conducting tissue engineering including nerve tissue engineering, cardiac tissue engineering, muscle tissue engineering application were given in detail.
Biocompatibility of Bi2Se3 regarding primary mixed retinal cells
Authors: Nguyen Diep , Forster Valérie , Potey Anaïs , Alviset Agathe , Picaud Serge , Politano Antonio
Published: November 2024

Bismuth chalcogenides have a groundbreaking impact on materials science because of their potential applications in spintronics and optoelectronics, especially for their properties as topological insulators. Investigation of the biocompatibility of the electrode material at the tissue/electrode interface is essential to assess the use of topological insulators in bioelectronics. Here, we addressed the biocompatibility of Bi2Se3 by demonstrating that porcine primary mixed retinal cells can survive on its surface with or without poly-D-lysine/laminin coating. Neuronal and glial cell survival were demonstrated using cell culture and imaging techniques. These results highlight the promising potential of Bi2Se3 for integration into bioelectronic devices, particularly for the development of neural interfaces and other biomedical applications.