bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced inertia friction welding of aluminum alloy and high-strength steel using CrCoNi interlayer: Microstructural and mechanical characterization
Authors: Jiang Qiming , Wu Wei , Yang Hongrui , Li Kunhang , Zhang Guangchuan , Huang Hong
Published: September 2024

The significant disparities in physical and chemical properties between aluminum alloy and high-strength steel pose substantial challenges for conventional friction joining techniques. To address this issue, this study proposes a novel approach utilizing inertial friction welding with an interlayer to join these dissimilar materials. A CrCoNi medium entropy alloy sheet was selected as the interlayer due to its intermediate melting point, thermal conductivity, strength, and surface hardness between 6061-T6 aluminum alloy and 42CrMo steel, as well as its high element mixing entropy. These properties were deemed crucial for balancing interface heat generation and regulation the formation of intermetallic compounds. The experimental procedure involved embedding the CrCoNi sheet into the end face of the 6061-T6 aluminum alloy, followed by the application of IFW to join the aluminum alloy with 42CrMo high-strength steel. This investigation focuses on examining the effects of three distinct friction speeds (3800, 4000, and 4200 rpm) on the microstructural characteristics and mechanical properties of the regulating joints with the CrCoNi interlayer. Results demonstrate that the CrCoNi enhances the temperature at the steel-side interface through friction with 42CrMo steel and 6061-T6 aluminum, combined with adjustments in the friction sequence and duration, promoting plastic deformation. The axial transfer of heat creates a temperature gradient at the joint, enabling low-temperature welding on the aluminum side and forming a mechanical interlocking structure at the interface. The diffusion of Cr, Co, and Ni elements regulates the type and thickness of interfacial intermetallic compounds, ultimately enhancing the joint's strength. The thickness of the intermetallic compounds AlNi3, FeAl3, AlCo, and Fe2Al5 formed at the interface is less than 2 µm. A phase transformation occurred at the 42CrMo high-strength steel interface, leading to the formation of numerous needle-like martensites, which increased the Vickers hardness in the welding seam to 763.9 HV. The joint's tensile strength initially increased and then decreased with increasing friction speed, reaching a maximum of 168.7 MPa at 4000 rpm, which is more than 60% of the aluminum alloy base material's tensile strength.
Versatile hybrid optical waveguides in amorphous silicon carbide with enhanced functionality and performance
Authors: Khoshmehr Mohammad Talebi , Dashtabi Mahdi Mozdoor , Nikbakht Hamed , Rodriguez Bruno Lopez , Sharma Naresh , Zadeh Iman Esmaeil , van Someren Bob , Akca B. Imran
Published: September 2024

In most optical waveguides employed within photonic integrated circuits, light confinement is achieved by etching the high-index layer. However, these waveguides often lack versatility in optimizing optical properties, such as mode size, shape, dispersion, and polarization. Moreover, they frequently suffer from high coupling losses and their propagation losses are significantly influenced by the quality of the etching process, especially for materials with high mechanical rigidity. Here, we present a hybrid optical waveguide concept that effectively addresses these limitations by combining a strip of easily processible low-index material (SU8) with a high-index hard-to-etch guiding layer (amorphous silicon carbide, SiC). Our approach not only eliminates the need for SiC etching but also offers flexibility in waveguide design to accommodate advanced functionalities. One of the key advancements of this hybrid configuration is its ability to suppress the transverse magnetic mode by 62 dB at 1550 nm, effectively functioning as a transverse electric pass waveguide. This simplifies the measurements by eliminating the need for polarization controllers and polarizers. Furthermore, through tailored waveguides, we achieve 2.5 times higher coupling efficiency compared to untapered hybrid SiC waveguides. We also demonstrate that thermal baking of the polymer layer reduces the scattering losses from 1.57 to 1.3 dB/cm. In essence, our hybrid approach offers a versatile way of realizing low-loss SiC-based integrated optical components with advanced features, such as excellent polarization suppression, flexible mode shapes, and dispersion control, compared to etched counterparts.
Exotic compounds of monovalent calcium synthesized at high pressure
Authors: Kong Jun , Shi Kaiyuan , Oganov Artem R. , Zhang Jiaqing , Su Lei , Dong Xiao
Published: September 2024

It is well known that atoms of the same element in different valence states show very different chemical behaviors. Calcium is a typical divalent metal, sharing or losing both of its valence electrons when forming compounds. Attempts have been made to synthesize compounds of monovalent calcium ions for decades, but with very little success (e.g., in clusters). Pressure can result in substantial changes in the properties of atoms and chemical bonding, creating an extensive variety of unique materials with special valence states. In this study, using the ab initio evolutionary algorithm USPEX, we search for stable calcium–chlorine (Ca–Cl) system compounds at pressures up to 100 GPa. Besides the expected compound CaCl2, we predict three new compounds with monovalent Ca to be stable at high pressures, namely, CaCl, Ca5Cl6, and Ca3Cl4. According to our calculations, CaCl is stable at pressures above 18 GPa and is predicted to undergo a transition from nonmagnetic Fm-3m-CaCl to ferromagnetic Pm-3m-CaCl at 40 GPa. Ca5Cl6 and Ca3Cl4 are stable at pressures above 37 and 73 GPa, with space groups P-1 and R-3, respectively. Following these predictions, we successfully synthesized Pm-3m-CaCl in laser-heated diamond anvil cell experiments. The emergence of the unusual valence state at high pressures reveals exciting opportunities for creating entirely new materials in sufficiently large quantities for a variety of potential applications.
Improvement of voltage-controlled magnetic anisotropy effect by inserting an ultrathin metal capping layer
Authors: Nozaki Takayuki , Ichinose Tomohiro , Yamamoto Tatsuya , Yakushiji Kay , Yuasa Shinji
Published: September 2024

We report systematic investigations of the effect of ultrathin capping layer insertion on the magnetic, magnetotransport, and voltage-controlled magnetic anisotropy (VCMA) properties in magnetic tunnel junctions (MTJs) with top free layer structure. Various kinds of ultrathin capping materials (Ir, Mo, TaB, Mg, Cr, Ti, and Ta) were introduced into the top free layer structure, which is comprised of MgO/CoFeB/X/MgO, where X is the inserted capping material. On insertion of an ultrathin Ir capping layer thinner than 0.3 nm, both the perpendicular magnetic anisotropy and the VCMA efficiency were improved by approximately a factor of two compared to the case without inserting an ultrathin metal capping layer. Mo insertion was also seen to be effective in improving the annealing tolerance. The developed structure can provide a novel approach for the development of high-performance voltage-driven MTJs, which can be applied, for example, for voltage-controlled magnetoresistive random access memory.
Predicting orientation in extruded wood polymer composites
Authors: Pashazadeh Sajjad , Suresh Arvindh Seshadri , Ghai Viney , Moberg Tobias , Brolin Anders , Kádár Roland
Published: September 2024

A general procedure for combining material functions and numerical modeling to predict the orientation of highly filled wood polymer composites (WPCs) in a single screw extrusion and validation thereof is elaborated in this study. Capillary rheometry was used to determine the shear viscosity and wall slip functions as well as the melt density of the biocomposites. The numerical model consisted of a model film die where the melt flow was simulated using a finite element method in the generalized Newtonian constitute equation framework. Fiber orientation was modeled using the Folgar–Tucker approach and included fiber–fiber interaction during the process. Reference extrusion tests were performed on a single screw extruder on the biocomposites. The extrusion setup included two melt pressure transducers that were used to determine the die inlet initial conditions (end of the extruder/die inlet) and provide feedback on the wall slip boundary conditions (pressure discharge along the die). Overall, the pressure error between experiments and simulations was less than 6.5% for all screw speeds investigated in 20 wt. % WPCs. Extrudates were produced, and the wood fiber orientation was estimated based on scanning electron microscopy micrographs and image analysis and compared with the simulations of fiber orientation. We show that the general procedure outlined can be calibrated to predict the overall orientation distribution of wood fiber biocomposites during single screw extrusion.
Macrospin study on magnetization reversal in synthetic antiferromagnetically coupled composite of perpendicularly magnetized nanomagnets
Authors: Yamaji Toshiki , Imamura Hiroshi
Published: September 2024

Magnetization reversal in a synthetic antiferromagnetically coupled composite of perpendicularly magnetized nanomagnets is theoretically explored based on the macrospin model. The analytical expressions of magnetization reversal are derived. The analytical results are confirmed by the results of the Landau–Lifshitz–Gilbert simulation. Furthermore, we find that a critical antiferromagnetic coupling constant exists at which the dynamics of magnetization reversal changes, and we obtain its analytical expression. This report provides a fundamental analysis insight into antiferromagnetic spintronic phenomena suitable for applications in ultra-high speed devices and nonvolatile memory technologies, for example, state-of-the-art voltage-controlled magnetoresistive random access memory.
A comprehensive investigation and optimization of superheat degree on performance of supersonic nozzle by considering non-equilibrium condensation and entropy generation analysis
Authors: Xia Rujie , Li Delu , Faghih Aliabadi Mohammad Ali
Published: September 2024

Non-equilibrium condensation (NQC) induced heat transfer in the supersonic nozzle (SSN) results in entropy production and alters the flow structure. The analysis of entropy production offers valuable insights for enhancing the design of industrial equipment by pinpointing the origins of energy losses. The interplay between frictional entropy, thermal entropy, and NQC is a fascinating but relatively unexplored subject in the field. This study aims to examine the impact of the superheat degree on NQC, frictional entropy, and thermal entropy. The goal is to enhance our understanding of the interconnectedness among these three parameters and their relationship. The findings revealed that within the SSN, the generation of frictional entropy surpasses that of thermal entropy generation. Upon analyzing the variations in entropy production with an increase in the degree of superheat, a general trend of ascending–descending can be observed for thermal, frictional, and total entropy productions. Furthermore, as the degree of superheat increases, both the droplet diameter and liquid mass fraction within the nozzle decrease. Optimization techniques were employed to determine the optimal degree of superheat for the given scenario. After the optimization process, the range of 70–90 was identified as the optimal degree of superheat. At a superheat degree of 70, the parameters of production entropy, input flow rate, condensation loss, and energy kinetics undergo changes of 19.3%, 9.8%, 99.9%, and 14.3%, respectively.
Ni3S2 particle–embedded nanotubes as a high-performance electrocatalyst for overall water splitting
Authors: Zhu Pengcheng , Ye Li , Li Xiaolei , Wang Tianxing , Zhong Yao , Zhuang Lin
Published: September 2024

Hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs) are crucial for renewable energy production. Developing stable, cost-effective, and highly catalytic HER and OER electrocatalysts is paramount. In this study, a combination of hydrothermal synthesis and annealing was used to fabricate nickel sulfide (Ni3S2) particle–embedded nanotubes supported on nickel (Ni) foam (Ni3S2 PN/NF). The Ni3S2 PN/NF structures featured a highly branched morphology with a large specific surface area, surpassing that of conventional Ni metal nanotubes. This design increased the number of reactive sites and enhanced the charge-transfer process. The Ni foam substrate expanded the contact area of Ni3S2, thereby improving conductivity and facilitating the adsorption/desorption of intermediates on the Ni3S2 surface. Density functional theory calculations showed that the electronic structure of Ni3S2 provides excellent conductivity. Moreover, the multi-branched structure and inherent conductivity of the NiS nanomaterials enhanced the Ni3S2 PN/NF performance in 1M KOH, with overpotentials of 87 and 210 mV with iR compensation at 10 mA cm−2 for the HER and OER, respectively. The synthesized Ni3S2 PN/NF also exhibited robust durability for 20 h. These results demonstrate that Ni3S2 PN/NF is an excellent catalyst for both HER and OER.
Effects of residual oxygen on superconducting niobium films
Authors: Manzo-Perez Miguel , Jamalzadeh Moeid , Huang Zhujun , Tong Xiao , Kisslinger Kim , Nykypanchuk Dmytro , Shahrjerdi Davood
Published: September 2024

The integration of niobium (Nb) into emerging superconducting circuits can enhance their performance and function. However, growth of high purity Nb can be challenging due to its high reactivity with oxygen. Here, we examine the role of residual oxygen inside the growth chamber in transforming the structural, chemical, and superconducting properties of Nb films. We demonstrate that an increase in unintentional oxygen impurities lowers the superconducting critical temperature of Nb. This evolution coincides with the reduction of Nb crystal domains, which are separated by highly disordered oxygen-rich regions. Moreover, chemical analysis reveals the formation of niobium monoxide within the film during growth. These findings provide a comprehensive picture of how residual oxygen in the growth chamber can affect the properties of the Nb films. This study contributes to the materials science and engineering knowledge of superconducting Nb growth.
Experimental study on flow/noise of a circular cylinder with concentric/eccentric microperforated ring fairings
Authors: Lu Tao , Li Yong
Published: September 2024

The effects of microperforated ring fairings on the flow and noise of a circular cylinder were investigated experimentally at Reynolds number based on the cylinder diameter (D) ranging between 1.3 and 2.6 × 104. The fairings were installed either concentrically or eccentrically, and the parameters investigated are the perforation rate σ (11.8%–34.6%), the clearance ratio δ/D (0.1–0.3), and the deflection angle θ (0°–180°). The noise was measured using far-field microphones, and flow characteristics were tested by the particle image velocimetry (PIV) and a dynamic balance. The acoustic results showed that the aerodynamic noise of the cylinder generally decreases with the increase in the perforation rate σ and the clearance δ. The maximum noise reduction at the fundamental vortex shedding frequency can reach 25 dB when arranged concentrically at δ/D = 0.3 and σ = 34.6%. Under the same perforation and clearance, the eccentric arrangement at θ = 60°–120° significantly improves the noise control performance. Flow visualization by PIV test demonstrated that the perforated fairing effectively controls the unsteady flow downstream of the cylinder and attenuates the large-scale vortex shedding, resulting in the noise reduction. The force measurement results showed that unsteady lift coefficient is significantly reduced, but the mean drag coefficient of the cylinder together with the fairings is generally higher than the bare cylinder. Nevertheless, the increment in drag coefficient can be lessened by eccentrically arrangement of fairings at deflection angle between θ = 60°–120°.
Hollow ion atomic structure and X-ray emission in dense hot plasmas
Authors: Rosmej Frank B. , Fontes Christopher J.
Published: September 2024

Hollow ion X-ray emission is of great interest in high-energy-density research, since negligible opacity allows studies from the interior of very dense objects. In this paper, ionization potential depressions of the isoelectronic sequences for single and double K-shell vacancies are obtained from a pure ab initio multiconfiguration Hartree–Fock simulation including exact exchange terms and finite temperature dense plasma effects. It is demonstrated that the simultaneous representation of these ab initio data in the form of a map of hollow ion X-ray transition energies enables identification of important steps in the matter evolution and ionization dynamics. Mapping along the isoelectronic sequence as a function of the pumping energy of a X-ray free electron laser also enables visualization of the impact of ionization potential depression on the pathways of hollow ion formation.
MoS2 bipolar junction photo-transistor (BJPT) with high gain and millisecond speed
Authors: Yang Yujue , Zhang Yongchao , Liu Zihao , Long Yin , Li Ziyu , Yao Chunyang , Zhang Xin , Dong Huafeng
Published: September 2024

Semiconducting two-dimensional (2D) MoS2 has emerged as a promising material for logic transistors and photodetectors, benefiting from its considerable mobility and strong light–mater interaction, along with the low cost and large area growth. However, the reported MoS2 based photodiode and photoconductor suffer from either absence of gain or slow dynamic response, limiting their practical application with high sensitivity. Herein, the lateral bipolar junction photo-transistors (BJPT) with both PNP and NPN architectures are fabricated by partial chemical doping, which combine the advantages of both photodiode and photoconductor by producing a high photo-gain of ∼103 electrons per photon adsorption due to the carrier amplification and remaining a well dynamic response with speed less than 10 ms. In this device, we achieve a high responsivity of 2 × 103 A/W and high sensitivity with specific D* up to 7.2 × 1011 Jones at 635 nm in the amplification region. This work demonstrates a BJPT device scheme that can combine both high gain and fast temporal response in a single device, promoting the wide applications of 2D ultra-thin photodetectors.
MoSe2 nanoflakes for zinc ion storage
Authors: Jiang Renzhi , Cai Yuncheng
Published: September 2024

Zinc-ion batteries (ZIBs) have become a highly desirable energy storage technology due to their significant advantages, such as low cost and high safety; however, the limitation of cathode materials has become a major factor restricting the development of ZIBs. Here, molybdenum diselenide (MoSe2) nanoflakes were investigated for the first time as a novel cathode for ZIBs. The unique two-dimensional (2D) layered structure of MoSe2 provides convenient channels and multiple active sites for zinc (Zn) ion diffusion. MoSe2 showed a specific capacity of 30.1 mA h/g at 0.1 A/g as well as almost no capacity decay at 1.0 A/g after 1500 cycles. Further, the Zn–MoSe2 coin cell successfully excited a light-emitting diode, showing good application prospects. Moreover, there was almost no aging of the battery after cycling, thus indicating satisfactory application potential. This work broadens the application of 2D materials in ZIBs.
Dual-purpose wave farm with nonlinear stiffness mechanism for energy extraction and wave attenuation
Authors: Jin Huaqing , Zhang Haicheng , Zheng Siming , Lu Ye , Xu Daolin , Greaves Deborah
Published: September 2024

This study proposes a novel model of a dual-purpose nonlinear wave farm, wherein multiple wave energy converters (WECs) equipped with nonlinear stiffness mechanism (NSM) are deployed for energy production and wave attenuation. A hybrid semi-analytical approach integrating the eigenfunction expansion matching method (EEMM) with the multi-harmonic balance method (MHBM) is developed to address the nonlinear wave-structure interactions among an array of WECs. Each device is modeled as a truncated cylinder, and the effects of the nonlinear interaction on power absorption and wave evolution from the array are studied. The analytical results are validated through published experimental results and computational fluid dynamics (CFD) results. A multi-parameter analysis is conducted to explore the impact of various factors including power takeoff (PTO) damping, NSM configuration, wave direction, and layout geometry on both wave power absorption and wave evolution. The results demonstrate that the nonlinear wave farm exhibits improved power-capture efficiency and enhanced wave attenuation compared to the linear wave farm, attributed to the phase control mechanism of NSM. This work may provide profound guidelines for large-scale wave energy exploitation and coast protection.
First- and second-order unconditionally stable and decoupled schemes for the closed-loop geothermal system based on the coupled multiphysics model
Authors: Wang Xinhui , Li Xiaoli
Published: September 2024

In this paper, we construct first- and second-order implicit–explicit schemes for the closed-loop geothermal system, which includes the heat transfer between the porous media flow with Darcy equation in the geothermal reservoir and the free flow with Navier–Stokes equation in the pipe. The constructed fully discrete schemes are based on the exponential auxiliary variable method in time, which we have proposed in Li et al. [“New SAV-pressure correction methods for the Navier-Stokes equations: Stability and error analysis,” Math. Comput. 91, 141–167 (2022)] and the finite element method in space. These schemes are linear and uniquely solvable, decoupling not only the two flow regions but also the temperature field, and only require solving a sequence of linear differential equations with constant coefficients at each time step. In addition, we rigorously prove that the constructed first- and second-order schemes are unconditionally stable without any time step and stability parameter restrictions. Finally, some numerical simulations, including convergence tests, the benchmark problem for thermal convection in a square cavity, and the heat transfer in simplified closed-loop geothermal systems, are demonstrated to present the reliability and efficiency of the constructed schemes.
Numerical investigation on Al2O3 droplet spreading and its prediction model exploration based on Harris Hawks optimization-generalized regression neural network in stereolithography
Authors: Wu Weiwei , Fu Jiangyuan , Gu Minheng , Ding Shuang , Zhang Yanjun , Wei Xinlong
Published: September 2024

The laying process is crucial in using stereolithography (SL) for molding Al2O3 parts. However, most studies focus on the laying process of macroscopic slurry; there needs to be more focus on microscopic exploration. Studying from a microscopic perspective can help us understand the influence of its parameters on droplet spreading and infer the macroscopic changes of the slurry based on the changes in droplet spreading to understand why parameters cause macroscopic changes in the slurry. A pseudopotential model based on Sisko's non-Newtonian behavior in lattice Boltzmann method is proposed to study the spreading process of droplets and validated using wetting characteristics. The previous layers of the platform and the printed solid are investigated to understand the effect of laying velocity on the spreading diameter, the thickness, and the both-sided contact angles. The results indicate that a higher laying velocity leads to a larger spreading diameter, a smaller spreading thickness, and a smaller left contact angle. However, it also increases the contact angle difference between the two sides, leading to uneven slurry. The droplet spreads more unevenly when the previous laying surface is the printed solid. At the same velocity, the droplet spreads with a smaller diameter, thicker thickness, and larger contact angle on the printed solid surface. Therefore, a higher laying velocity in the SL laying process is not recommended, especially when the front layer is a printed solid. Although a higher laying velocity will increase the laying area and reduce laying time, it will cause protrusions at the front edge, and inconsistent laying thickness of the same layer will affect the following photosensitive curing process. The Harris Hawks optimization-generalized regression neural network algorithm is proposed and compared with other common artificial intelligence algorithms to predict the spreading parameters. The comparison shows that the proposed algorithm provides a more stable and accurate prediction of spreading parameters.
Lagrangian coherent structures around a bridge pier with scour hole
Authors: Kalidindi Murali Krishnamraju , Khosa Rakesh
Published: September 2024

Accurate prediction of scour depth is essential for the safety of the bridge. The downflow upstream of the pier plays a significant role in scour hole formation. The present study used Lagrangian coherent structures (LCSs) to derive an expression to estimate the force exerted by the downflow on the sediment bed. The LCSs extracted a trapping region upstream of the pier, which trapped the fluid, which was then converted into downflow. The expressions derived in this Letter can be used to improve the efficiency of scour depth prediction equations.
Unconventional two-dimensional quantum oscillations in three-dimensional thick SrRuO3 films
Authors: Matsuki Yuta , Nishihaya Shinichi , Kriener Markus , Oshima Ren , Miwa Fumiya , Uchida Masaki
Published: September 2024

SrRuO3 is a prototypical transition metal oxide that hosts rich physical properties, including itinerant ferromagnetism, high conductivity, and intrinsic Hall effect originating in the Weyl points. Recently, high-quality SrRuO3 films with residual resistivity ratios of more than 50 have been reported to exhibit quantum oscillations at low temperatures in spite of their strong electron correlation. While the origin of the oscillations has been discussed in relation to Weyl orbits based on the Weyl semimetal band structure, so far experimentally reported results are consistent neither with each other nor with theoretically expected behavior, leaving the origin of the oscillations in SrRuO3 films still elusive. In this report, we have carefully evaluated the quantum oscillations observed in three-dimensional thick SrRuO3 films with a high residual resistivity ratio of RRR = 82. We reveal the coexistence of two oscillation components both derived from two-dimensional electronic states and with slightly different masses, suggesting the involvement of surface Fermi arc states formed between different Weyl point pairs.
Enhanced e–e interaction in suspended 2DEG evidenced by transverse magnetic focusing
Authors: Egorov Dmitry A. , Pokhabov Dmitriy A. , Zhdanov Evgeny Yu. , Shevyrin Andrey A. , Bakarov Askhat K. , Pogosov Arthur G.
Published: September 2024

The features of electron–electron (e–e) interaction in a two-dimensional electron gas (2DEG) in GaAs/AlGaAs heterostructures, including the case of structures detached from the substrate in which this interaction is enhanced, are experimentally studied using transverse magnetic focusing over a wide temperature range. The measurements reveal pronounced resonant ballistic magnetoresistance peaks that are suppressed with increasing temperature and satisfy the condition of magnetic focusing. This suppression is caused by e–e scattering, which gets stronger with increasing temperature. Analysis of the temperature suppression of ballistic peaks allowed us to determine the temperature dependence of the e–e scattering length as well as the effective dielectric constants, which are 12 and 8 in the non-suspended and suspended cases, respectively. The significant decrease in effective dielectric constant in the suspended sample clearly indicates the enhancement of e–e interaction as a result of suspension.
The role of the water contact layer on hydration and transport at solid/liquid interfaces
Authors: Gäding J. , Della Balda V. , Lan J. , Konrad J. , Iannuzzi M. , Meißner R. H. , Tocci G.
Published: September 2024

Understanding the structure in the nanoscopic region of water that is in direct contact with solid surfaces, so-called contact layer, is key to quantifying macroscopic properties that are of interest to e.g. catalysis, ice nucleation, nanofluidics, gas adsorption, and sensing. We explore the structure of the water contact layer on various technologically relevant solid surfaces, namely graphene, MoS2, Au(111), Au(100), Pt(111), and Pt(100), which have been previously hampered by time and length scale limitations of ab initio approaches or force field inaccuracies, by means of molecular dynamics simulations based on ab initio machine learning potentials built using an active learning scheme. Our results reveal that the in-plane intermolecular correlations of the water contact layer vary greatly among different systems: Whereas the contact layer on graphene and on Au(111) is predominantly homogeneous and isotropic, it is inhomogeneous and anisotropic on MoS2, on Au(100), and on the Pt surfaces, where it additionally forms two distinct sublayers. We apply hydrodynamics and the theory of the hydrophobic effect, to relate the energy corrugation and the characteristic length-scales of the contact layer with wetting, slippage, the hydration of small hydrophobic solutes and diffusio-osmotic transport. Thus, this work provides a microscopic picture of the water contact layer and links it to macroscopic properties of liquid/solid interfaces that are measured experimentally and that are relevant to wetting, hydrophobic solvation, nanofluidics, and osmotic transport.
A new player in the biogenesis of lysosome-related organelles
Authors: Shi Anbing
Published: September 2024

How are Rab GTPases regulated during lysosome-related organelle (LRO) biogenesis? Li et al. (https://doi.org/10.1083/jcb.202402016) identify LYSMD proteins as crucial activators of Rab32-family GTPases in LRO development, shedding light on the previously ambiguous mechanisms governing Rab functionality in this process.
Inertia in relativistic mechanics
Authors: Germano Massimo
Published: September 2024

A general and explicit expression for inertia of a body of mass m in special relativity is given, valid for all the cases, as a function of mass, velocity modulus and angle between applied force and velocity vectors. An expression containing the total energy E in the determination of inertia is also obtained. This could be useful to clarify to students the actual role of mass and energy in the definition of the concept of inertia, connecting the two different contexts of Newtonian and relativistic mechanics.
Feynman's puzzle and the twins: applying the equivalence principle and the red shift
Authors: Derbes David
Published: September 2024

Two puzzles, one not well known and one notorious, are answered exactly and in an elementary fashion with the help of the gravitational red shift and the equivalence principle. The first is Feynman’s question: What motion maximizes the time recorded by a clock moving vertically, if it leaves the Earth and returns at a fixed terrestrial time? The second is the supposed inconsistency in the ages of two twins reunited after one has made a round trip at relativistic speed to a distant star.
Addendum: Multichannel quantum defect theory of strontium bound Rydberg states (2014 J. Phys. B: At. Mol. Opt. Phys. 47 155001)
Authors: Vaillant C L , Jones M P A , Potvliege R M
Published: September 2024

Newly calculated multichannel quantum defect theory parameters and channel fractions are presented for the singlet and triplet S, P and D series and singlet F series of strontium. These results correct those reported in Vaillant et al (2014 J. Phys. B: At. Mol. Opt. Phys.
47 155001).
Exploring the influence of plasma temperature on the evolution of boron molecular species in laser-induced plasma
Authors: Mohan Anandhu , Banerjee Anannya , Sarkar Arnab
Published: September 2024

The impact of plasma temperature on the formation and evolution of distinct and unique molecular species recorded as molecular signatures from laser induced plasma (LIP) was examined in this study. A definitive correlation between plasma temperature and the formation of molecular species has been established through a comprehensive temporal analysis of BO and BO2 molecular bands. The utilization of the signal-to-envelope ratio diagrams allowed for pinpointing the optimal temperature range for molecule emission. Notably, the molecule BO exhibited an ideal temperature range of 10,000–11,000 K for the proper formation of molecular emission bands, while BO2 preferred temperatures between 8,000–9,000 K. These optimal temperature ranges remained consistent regardless of the laser irradiation wavelength or ambient gas conditions of Ar, air or He studied in this work. These key findings highlight the significant influence of plasma temperature in shaping the molecular species observed in LIP.
Curing deformation compensation in bonding assembly for high-precision linear displacement encoder sensors
Authors: Yang Hongfan , Wang Jiayi , Xia Huanxiong , Liu Jianhua , Ao Xiaohui , Liu Xin , Li Da , Wang Yuhe
Published: September 2024

Linear displacement encoder sensors extensively appear in high-precision instruments, in which the core scale is usually bonded with the scale base by adhesives. However, the curing shrinkage of the adhesives often causes a warping deformation of the moving ruler, which in turn leads to a decrease in measurement accuracy. To improve the accuracy of the bonding assembly, this paper proposes a novel deformation compensation method. A force control fixture is first designed, and a tensile force is applied to tense the scale base. The scale is then bonded to the scale base, and the tensile force is maintained until the adhesive is cured. The optimal tensile force is determined to minimize the warping deformation by combining a finite-element simulation and an artificial fish swarm algorithm. The optimal result is verified experimentally, where the warping deformation is measured using a homemade three-dimensional digital image correlation system. The experimental results demonstrate that the warping deformation of the moving ruler is reduced by 89.2% using the proposed method.
Dual-channel feature extraction hybrid attention network for detecting infrared small targets
Authors: Nie Suzhen , Cao Jie , Miao Jiaqi , Hou Haiyuan , Hao Qun , Zhuang Xuye
Published: September 2024

For military early warning, forest fire prevention, and maritime search and rescue, infrared small target detection is critical. However, because of the low contrast and inconspicuous features of infrared small targets, rendering most existing methods ineffective in restoring target edge details or misidentifying the background as a target. This paper proposes a dual-channel feature extraction network (DCFE-Net) with hybrid attention, which enables the network to suppress the background and enhance the target by designing dual-channel feature extraction and multi-layer feature fusion. Specifically, the dual-channel mainly consists of a convolutional attention fusion module, which adaptively integrates feature map correlations by introducing a hybrid attention module to capture global information while enhancing the feature representation of small targets, and a feature compression extraction module, which utilizes depth-separable convolutional combinations to carry out fine-grained target feature extraction while reducing the loss of details. In addition, the multilevel feature enhancement module ensures that the network can capture targets at different scales through skip connection operations, while avoiding small targets from being overwhelmed by deep features, making them simultaneously semantically informative and detailed. Therefore, the network can fuse multilevel features for effective information extraction. According to the experimental results, DCFE-Net performs best in false alarm rate and detection probability.
Assessment of the relational strength between triggers detected in physiological signals and the occurrence of atrial fibrillation episodes
Authors: Pluščiauskaitė Vilma , Sološenko Andrius , Jančiulevičiūtė Karolina , Marozas Vaidotas , Sörnmo Leif , Petrėnas Andrius
Published: September 2024

Objective. Despite the growing interest in understanding the role of triggers of paroxysmal atrial fibrillation (AF), solutions beyond questionnaires to identify a broader range of triggers remain lacking. This study aims to investigate the relation between triggers detected in wearable-based physiological signals and the occurrence of AF episodes. Approach. Week-long physiological signals were collected during everyday activities from 35 patients with paroxysmal AF, employing an ECG patch attached to the chest and a photoplethysmogram (PPG)-based wrist-worn device. The signals acquired by the patch were used for detecting potential triggers due to physical exertion, psychophysiological stress, lying on the left side, and sleep disturbances. To assess the relation between detected triggers and the occurrence of AF episodes, a measure of relational strength is employed accounting for pre- and post-trigger AF burden. The usefulness of ECG- and PPG-based AF detectors in determining AF burden and assessing the relational strength is also analyzed. Main results. Physical exertion emerged as the trigger associated with the largest increase in relational strength for the largest number of patients (p < 0.01). On the other hand, no significant difference was observed for psychophysiological stress and sleep disorders. The relational strength of the detected AF exhibits a moderate correlation with the relational strength of annotated AF, with r = 0.66 for ECG-based AF detection and r = 0.62 for PPG-based AF detection. Conclusions. The findings indicate a patient-specific increase in relational strength for all four types of trigger. Significance. The proposed approach has the potential to facilitate the implementation of longitudinal studies and can serve as a less biased alternative to questionnaire-based AF trigger detection.
Materials & design approaches for enhanced performance of mechanically compliant thermoelectric generators (TEGs): a review
Authors: Daraghma H S , Ferry D B , Rao S G , Hawwa M A , Gondal M A , Rojas J P
Published: September 2024

In the pursuit of sustainable solutions to the ever-increasing demand for renewable energy, mechanically compliant thermoelectric generators (TEGs) have garnered significant attention owing to the promise they present for application in generating power from waste heat in mechanically challenging scenarios. This review paper examines the ongoing advancements in the efficiency and applicability of TEGs through novel material engineering and design innovations. It delves into the improvement of their thermoelectric (TE) properties via micro- and nanostructural modifications and explores architectural advancements aimed at enhancing functionality and power output. Notably, the integration of TEGs into flexible, stretchable, and wearable electronics has been a significant development, expanding their applications in various domains such as healthcare monitoring, remote sensing, and consumer electronics. The review emphasizes the critical interplay between electronic, thermal, and mechanical aspects in optimizing TEGs performance. By providing an in-depth exploration of these multifaceted interactions and highlighting the significant advancements in materials and design, this review aims to underscore the importance of TEGs in a cleaner and more efficient era of energy generation, with a particular focus on their emerging applications across diverse fields.
Nonlinear vibration of a loaded string in energy harvesting
Authors: Liu Tao , Zhao Chaoyang , Yang Yaowen , Yuan Weifeng
Published: September 2024

Designing wideband energy harvesters using beam structures typically involves complexities, particularly in low-frequency and low-energy environments where the limitations of beam structures become more evident. To address these challenges, this study proposed a strategy for energy harvesting using a loaded-string system and established a theoretical model to investigate its performance. A parametric study was conducted for the string system, examining the effects of initial tension, mass location, material stiffness and excitation amplitude. The accuracy of the proposed model was verified through experimental validation. Both theoretical and experimental analyses observed a frequency shifting phenomenon, demonstrating the wideband characteristics of the system. Furthermore, the proposed string structure allows for convenient parameter adjustments, enabling the tuning of its natural frequency and operating bandwidth to meet more stringent practical requirements. The string system provides a new direction for designing energy harvesters to harness low-frequency energy from the ambient environment.
Thirring universe model
Authors: Yılmaz Nazmi , Akıllı Mahmut , Akdeniz K G
Published: September 2024

In recent years, there has been a significant amount of research focused on Thirring instantons. This study aims to employ the Thirring quantum model as a theoretical Universe model to gain a more profound understanding of the beginning of the Universe. For this, we propose to analyze the entropy of the quantum states of zero energy Thirring instanton solutions and the transition to other quantum states. Our findings by also using Lyapunov exponents and the cyclic attractors as comparative nonlinear methods show that there is no entropy corresponding to instanton solutions with zero energy and that the sudden increase in entropy indicates the formation of the Universe. We evaluate the implications of this study in terms of the standard Universe model. Thus we anticipate that these results have the potential to contribute significantly to our understanding of the origin of the Universe and highlight the role of chaos and complexity in its evolution.
Effect of Dy3+ ions on physical, structural and thermal properties of ZnNaPbB glasses
Authors: Manjeet  , Anu  , Deopa Nisha , Kumar Anand , Chahal Rishi Pal
Published: September 2024

In this report, inspired by the excellent spectroscopic characteristics of dysprosium (Dy3+) ions doped borate glasses, a series with the composition (70-x)B2O3-10ZnO-10PbO-10Na2CO3-xDy2O3 (here ‘x’ have the values as 0.1, 0.5, 1.0, 1.5 and 2.0 in mol % ) was made using the melt quenching process and named as ZnNaPbBDy0.1 to ZnNaPbBDy2.0. Here we study the physical, structural and thermal properties of Dy3+ ions doped Zinc Sodium Lead Borate (ZnNaPbB) glasses through different characterization techniques like Fourier transform infrared (FT-IR), Raman spectroscopy, Differential scanning calorimetry (DSC) and decay spectroscopy. Several physical parameters were evaluated to assess the effect of Dy3+ inclusion. FT-IR and Raman spectra confirm the presence of BO3 and BO4 structural units. The data recorded by DSC spectra have been used to predict the glass transition temperature (Tg). The nature of decay spectra was estimated which diverges from exponential to non-exponential at higher concentrations. The decay spectral data is used to calculate the experimental lifetimes for all the glass samples. The Inoakutti Hirayama (I-H) model and Dexter’s plot are used to confirm the type of interaction between the donor and acceptor Dy3+- Dy3+ ions is dipole–dipole in nature that is responsible for the emission intensity quenching with concentration. All the above results might be advantageous for variety of applications in photonic devices.
Design and analysis of circular sheet junctionless double gate vertical nanotube (CSJL-DG-VNT) FET for DC/Analog/RF applications: device to circuit implementation
Authors: Bhukya Sunitha , Nistala Bheema Rao
Published: September 2024

This paper investigates the influence of geometrical variations on the performance characteristics of a novel circular sheet junctionless double gate vertical nanotube (CSJL-DG-VNT) FET through 3D numerical simulations at sub-5nm technology node. Initially, the proposed device is compared with NWFET and NSFET, and shown favourable performance. The ION/IOFF current ratio is improved to 51.9% when gate length (Lg) is sweeping from 8 nm to 12 nm. The decrease in L

g
leads to enhanced analog/RF metrics such as gm, gm/Id, and fT. It was observed that opting for the shortest L

g
may be advantageous for certain parameters, albeit at the expense of others, depending on the specific application requirements. Further, while maintaining a constant L

g
, variations in the thickness tNT from 5 to 10 nm were carried out to evaluate the analog/RF performance for device optimization. It was observed that lower tNT (5 nm) values yielded improved IOFF current around ∼ 2 order and DIBL is 32.77% when compared with higher tNT (10 nm) due to ameliorated channel control from both inner and out gate of VNT. Subsequently, at an optimal L

g
and t

NT
the temperature (T) varied from 250 K to 450 K to analyze the device characteristics, indicating that a lower T should be favoured. Furthermore, the device is used for designing a common-source (CS) amplifier with tNT variations and noticed that at 5 nm of t

NT
outperforms highest gain (AV) ∼ 6.8 V/V when compared to 7 nm and 10 nm.
Static, cylindrically symmetric spacetime in the coincident f(Q) gravity
Authors: Kirezli Pınar , Özceylan Nilhan
Published: September 2024

In this paper we consider a static, cylindrically symmetric spacetime with coincident f(Q) gravity. Since the field equation of this spacetime in symmetric teleparallel gravity is suitable for choosing the function of f(Q) in the form of power series and exponential forms which are in coherent with cosmological observations, anisotropic perfect fluid solutions of these forms are discussed for this spacetime. Energy densities, directional pressures and energy conditions are plotted and analysed for a few different metric potentials. Although corresponding cosmic strings violate all energy conditions in both f(Q) functions, the corresponding Levi-Civita solution violates all energy conditions in the power law function of f(Q), but for exponential f(Q) gravity they are satisfied in small regions.
Λ

6

He

(1−, 2−) spin doublet in a Λ + n + α cluster model
Authors: Meoto E F , Lekala M L , Ojukwu E C
Published: September 2024

The spin singlet and spin triplet states of the helium-6-lambda hypernucleus are studied in configuration space as a three-body problem, using the hyperspherical method. This hypernucleus is treated as a Λ + n + α cluster model. Since the α particle core has a spin of 0, this is an ideal hypernucleus from which to understand spin dependence in hyperon-nucleon potentials. In this paper, the hyperon-nucleon potential considered is the GLM-YN0 Λ-n potential, which is a simulation of the NSC97f potential obtained through inverse scattering theory. Due to violations of the cluster structure, two-body potentials underbind the helium-6-lambda hypernucleus. This issue is addressed by including a three-body force to complement these two-body forces. A three-body force, whose strength is spin dependent, is used to guide predictions of the spin triplet state of helium-6-lambda which is not yet known experimentally.