bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating the effects of ultrasonic assistance on TIG welding of AA7075 alloys: a machine learning-based optimization study using RSM-PSO
Authors: A Dhilip , Nampoothiri Jayakrishnan
Published: November 2024

This study explores the impact of ultrasonic assistance on TIG welding of AA7075 alloys, leveraging a machine learning-based optimization approach combining Response Surface Methodology (RSM) and Particle Swarm Optimization (PSO). A central composite design matrix was developed to investigate the effects of process parameters on microhardness and weld defects. A predictive model was constructed, utilizing process parameters as inputs and microhardness as the output. PSO optimization was then applied, followed by experimental validation. The model demonstrated high accuracy, with R-squared values of 0.9808 and 0.9862 for conventional and ultrasonic-assisted TIG welding. Confirmation tests showed an error margin of less than 1%. The optimal process parameters under ultrasonic vibration were identified as welding current (50.38 A), gas flow rate (12.42 l min−1), and filler material (ER5356). The predicted microhardness (153.16 HV) closely matched the actual value (150.71 HV), with an error of 1.6%. Tensile and fractography analyses further validated the optimized welding parameters. This research showcases the potential of integrating ultrasonic vibration with RSM-PSO optimization to enhance weld quality and mechanical properties of AA7075 alloy joints, offering valuable insights for industrial applications.
TRMD: a transformer-based reverse design model for quad-band metasurface absorbers
Authors: Ma Jindong , Ma Zihang , Li Muyang , Li Yujie , Tan Benying , Ding Shuxue
Published: November 2024

Metasurfaces have the ability to manipulate electromagnetic waves, which allows for the creation of functions such as perfect absorbers. The goal of a perfect absorber is to achieve high absorption peaks within a specific frequency band. This paper introduces an improved metasurface absorber structure that can achieve efficient absorption in four different frequency bands within the range of 2-9 GHz. In the field of metasurface design, deep learning methods have been recently applied due to their powerful data processing capabilities. However, these methods have primarily used fully connected neural networks and Long Short-Term Memory (LSTM). Despite their capabilities, fully connected networks and LSTM struggle to capture the global information in absorption spectrum data, leading to less accurate predictions. In this study, it was observed that the Transformer model can effectively capture global information using Multi-Head Self-Attention (MHSA) and is not affected by the length of the data. Based on this observation, this paper presents a lightweight model consisting solely of an encoder, achieving a Mean Squared Error (MSE) that is one-twentieth of the State-of-the-Art (SOTA). This model predicts metasurface structure based on target absorption spectra, enabling users to rapidly obtain metasurface absorber structures directly from input absorption spectra. The model consists of two parts: embedding and encoder. The embedding processes input absorption spectra data and adds positional encoding, while the encoder extracts spectral data features. MHSA effectively captures contextual information of absorption spectra, emphasizing key feature information. The final model achieved a MSE convergence of 2 × 10−4 and a coefficient of determination (R
2)value of 0.998, successfully optimizing the design of multi-band metasurface absorbers. Moreover, the predicted results from the model exhibit an absorption spectrum that is highly consistent with the target spectrum.
Investigation of structural, magnetic, and dielectric properties of BaFe12O19/Pr1−xSrxCoyMn1−yO3 composites; an emerging aspirant for high frequency applications
Authors: Younus Sidra , Murtaza G , Alhummiany Haya , Hassan M , Al-Anazy Murefah Mana , Mahmood Q , Yousef El Sayed , Alshomrany Ali S
Published: November 2024

In this work, barium hexaferrite/perovskite BaFe12O19/Pr1-xSrxCoyMn1-yO3 composite ferrites were synthesized using single step sol–gel auto-combustion method. The lattice parameters and stabilized structural phases were studied using x-ray diffraction (XRD). The average crystallite size was found in the range of 51.6 nm–71.7 nm. Field Emission Scanning Electron Microscopy (FE-SEM) micrographs showed agglomerated particles having hexagonal as well as platelets like spherical shapes. Magnetic measurements done using vibrating sample magnetometer revealed that composite S3 (BaFe12O19/Pr0.75Sr0.25Co0.25Mn0.75O3) exhibits low saturation magnetization (35.3 emu g−1), and coercivity (775 Oe). Dielectric analysis revealed that, at 1 MHz frequency, the tangent loss (1.3) and dielectric loss (22.5) are highest for the composite S3 (BaFe12O19/Pr0.75Sr0.25Co0.25Mn0.75O3), whereas largest dielectric constant (20.7) was exhibited by S4 (BaFe12O19/Pr0.5Sr0.5Co0.5Mn0.5O3). Similarly, composite S2 (BaFe12O19/PrMnO3) (having the highest quality factor of 4.05) exhibited the largest resistivity (18885.8 Ω-cm), while composite S3 (BaFe12O19/Pr0.75Sr0.25Co0.25Mn0.75O3) showed highest AC conductivity (0.00125 (Ω-cm)−1). The investigated composites are found excellent choice for designing devices for applications involving high-frequency interference and electromagnetic shielding due to their unique magnetic and dielectric properties.
Teleparallel geometry with spherical symmetry: the diagonal and proper frames
Authors: van den Hoogen R.J. , Forance H.
Published: November 2024

We present the proper co-frame and its corresponding (diagonal) co-frame/spin connection pair for spherically symmetric geometries which can be used as an initial ansatz in any theory of teleparallel gravity. The Lorentz transformation facilitating the move from one co-frame to the other is also presented in factored form. The factored form also illustrates the nature of the two degrees of freedom found in the spin connection. The choice of coordinates in restricting the number of arbitrary functions is also presented. Beginning with a thorough presentation of teleparallel gravity using the metric affine gauge theory approach and concentrating on f(T) teleparallel gravity, we express the field equations in the diagonal co-frame. We argue that the choice of diagonal co-frame may be more advantageous over the proper co-frame choice. Finally, assuming one additional symmetry, we restrict ourselves to the Kantowski-Sachs teleparallel geometries, and determine some solutions.
Efficient hybrid technique for generating sub-grid haloes in reionization simulations
Authors: Barsode Ankur , Choudhury Tirthankar Roy
Published: November 2024

Simulating the distribution of cosmological neutral hydrogen (HI) during the epoch of
reionization requires a high dynamic range and is hence computationally expensive. The size of the
simulation is dictated by the largest scales one aims to probe, while the resolution is determined
by the smallest dark matter haloes capable of hosting the first stars. We present a hybrid
approach where the density and tidal fields of a large-volume, low-resolution simulation are
combined with small haloes from a small-volume, high-resolution box. By merging these two boxes of
relatively lower dynamic range, we achieve an effective high-dynamic range simulation using only
13% of the computational resources required for a full high-dynamic range simulation. Our method
accurately reproduces the one- and two-point statistics of the halo field, its cross-correlation
with the dark matter density field, and the two-point statistics of the HI field computed using a
semi-numerical code, all within 10% accuracy at large scales and across different redshifts. Our
technique, combined with semi-numerical models of reionization, provides a resource-efficient tool
for modeling the HI distribution at high redshifts.
Observation of Weibel magnetic fields in laser-produced interpenetrating flows
Authors: Shi 施 Chuanqi 川奇 , Yuan 袁 Dawei 大伟 , Sun 孙 Wei 伟 , Zhang 张 Yapeng 雅芃 , Qiu 邱 Zhijie 志杰 , Wei 魏 Huigang 会冈 , Zhang 张 Zhe 喆 , Yuan 远 Xiaohui 晓辉 , Zhao 赵 Gang 刚
Published: November 2024

Weibel instability is a promising candidate mechanism for collisionless shock formation in astrophysical systems. Capturing the underlying physics of Weibel instability will help us to understand the astrophysical shock formation, magnetic field generation and amplification, particle acceleration, and so on. Laboratory astrophysics, provides a new way to study these microphysics in controlled conditions. At Shenguang-II laser facility, the interpenetrating plasma flows are generated by eight laser beams irradiating a pair of opposing foils to mimic the supernova explosion and the ejecta sweeping up the surrounding medium. Evolution of collisionless interpenetrating plasma flows is observed using optical diagnostics. Filamentary structures appear in the interaction region and the associated magnetic strength is measured about 40 T. Theoretical analysis and simulations indicate that these characteristics are induced by nonlinear Weibel instability.
Constrain the Jerk Parameters with DESI 2024 Data
Authors: Wu Jia-Wei , Hong Kun-Yuan
Published: November 2024

The deceleration coefficient q and the jerk coefficient j obtained by the Taylor expansion of the scale factor a(t) play an important role in the study of cosmology. The current value of these coefficients for a cosmological model reflects the transition time between the phases dominated by dark energy and matter and can be used to determine if and how much the universe is decelerating. Thus, these coefficient values offer a way of constraining a particular cosmology model. Research based on this scenario was completed by Orlando Luongo and Marco Muccino. However, some approaches in this method should be tested prudently because some conditions such as

dd

L

dz

>
0

and

dH

dz

>
0

may not be guaranteed. In this study, we used the MAPAge model to reconstruct the jerk parameters (q
0 and j
0) with DESI 2024 data. Using the MAPAge model ensures particular physical circumstances are satisfied in the approach of determining the jerk parameters. Compared to the previous method, which used the Taylor expansion series q
0, j
0, and s
0 as model-independent parameters, we obtained more physical and slightly different results for the jerk parameters. Our results suggest that the DESI 2024 BAO data set favours different jerk parameters compared to the jerk parameters in the standard ΛCDM model.
A Method to Assess the Applicability and Accuracy of the Modified Gaussian Model (MGM) on the Rock Samples’ Spectral Interpretation
Authors: Gao Fang , Liu Bin , Zhou Qin , Li Chun-Lai
Published: November 2024

The Chang’e-4 mission obtained spectral data of multiple rock targets on the lunar surface. The Modified Gaussian Model (MGM) is usually applied to the spectral interpretation of powder samples, its applicability and accuracy on the rock targets remain to be further evaluated. The rock slice of lunar meteorite NWA 4734 is used to conduct comprehensive analysis of the petrography, mineralogy and laboratory spectroscopy, which will provide important ground truth for the MGM interpretation of lunar in situ spectra of rock samples. First, a scanning electron microscope (SEM), Energy Dispersive Spectrometer (EDS), and Electron Probe Micro-Analyzer (EPMA) analysis results indicate that: (1) almost all plagioclase in NWA 4734 have been converted to maskelynites, which indicate that the meteorite has undergone severe impact metamorphism; (2) the chemical composition of pyroxene and olivine is significantly heterogeneous, showing a distribution characteristic of magnesium-rich core and iron-rich rim, further indicating that NWA 4734 has undergone multiple crystallization and differentiation. Second, this article focuses on the rock slice of NWA 4734's greyscale image of the Back Scattering Electron (BSE), and obtains the proportion of High-Calcium Pyroxene (HCP) in the total pyroxenes of this sample by calculating the area percentage using the pixel counting method. The result shows that the proportion of HCP is 72% ± 5.4%, which can be used as a ground truth to evaluate the interpretation applicability and accuracy of MGM. A field spectrometer (ASD) is used to measure the visible and near-infrared reflectance spectra (450–2500 nm) of the rock slice from NWA 4734 in the same area as the BSE image obtained by SEM, and MGM is used to deconvolve the ASD spectra, and the average proportion of HCP is estimated to be 71% ± 10.1%. The results between the MGM and the pixel counting are comparable within the error range, which demonstrates the applicability of MGM on interpretation of the rock samples on the lunar surface.
Impurity transport driven by kinetic ballooning mode in the strong gradient pedestal of tokamak plasmas
Authors: Huang Shanni , Guo Weixin , Wang Lu
Published: November 2024

The impurity transport driven by kinetic ballooning mode (KBM) is theoretically studied in the DIII-D H-mode strong gradient pedestal plasmas. From the electromagnetic gyrokinetic equation, including the correction of the strong radial electric field, the dispersion relationship of KBM instability with non-trace impurity is firstly derived. Then, the turbulent impurity flux and ion heat flux, as well as the associated transport coefficients, are further calculated. Through the parametric dependence analysis of analytical results, it is found that dilution effects of light fully ionized impurities can reduce the drive of KBM by affecting the kinetic pressure gradient parameter

α

and diamagnetic effects, thus leading to a decrease in both the absolute value of the real frequency

|

ω
r
′

|

and the growth rate

γ

k

′

of KBM instability. Stronger dilution effects by increasing the impurity charge number

Z

or steepening the impurity density profile correspond to stronger effects. Moreover, the removal efficiency of light fully ionized impurities, quantified by the ratio between the impurity diffusivity and effective ion heat conductivity

D

z

χ

i

eff

≈

1
−

b

z

+

4

ω

Dz

/

ω
r
′

3

(

1
+

1

/

η

i

)

/

2

, increases with an increase of

Z

mainly due to the smaller impurity finite Larmor radius (FLR) effects reflected by

b

z

∝

1

/

Z

. Besides, the increase of the impurity density gradient can significantly enhance

D

z

/

χ

i

eff

, and this is because stronger impurity dilution effects make a larger magnetic drift term

|

ω

Dz

|

/

|

ω
r
′

|

(

ω

Dz

is the magnitude of impurity magnetic drift frequency) and

η

i

(the ratio of ion density gradient scale length to ion temperature gradient scale length). For heavy metal impurities with a concentration of

10

−
4

, the peaking factor (PF) is positive, which means that its density profile is inwardly peaked, and the PF decreases with the enhancement of impurity FLR effects. These results may provide some theoretical reference on understanding the physical mechanism of impurity transport in the pedestal of H-mode plasmas.
Ultralow phase noise optoelectronic oscillator
Authors: Yan Dongliang , Ge Jun , Liu Dan
Published: November 2024

The optoelectronic oscillator(OEO)’s main technological advantage over the traditional microwave oscillator is its ultra-low phase noise property. In this article, we have been using a high-power low-RIN laser, a long fiber loop, and an ultra-low noise optical connection to generate an OEO with a phase noise of -162.5dBc/Hz@10kHz at a frequency of 10 GHz to investigate the optoelectronic oscillator’s single-loop structure. More significant factors on OEO have been explored in this work, including residual phase noise of the optoelectronic link, linear operating state of the optical link, optical power input to the photodetector, and photodetector bias voltage.
Next-Generation Chip Scale Atomic Clocks
Authors: Kitching John , Hummon Matt , McGehee William , Wang Ying-Ju , Schima Susan
Published: November 2024

We describe three independent research directions focussed on the development of next-generation chip-scale atomic clocks, which combine small size, low power consumption and manufacturability with high frequency stability. The use of optical transitions in microfabricated vapor cells improves both short- and long-term frequency stability to near 10−13 at the cost of the added complexity of a chip-scale optical frequency comb. Chip-scale atomic beam microwave clocks have been successfully demonstrated and offer the potential for microsecond-level timing accuracy over one week. And finally, Sr vapor cells have been developed with lifetimes exceeding 250 hours and residual gas pressures below 1 Torr.
Contributions of the optical lattice clock NICT-Sr1 to TAI calibration and UTC(NICT) steering
Authors: Hachisu H , Nemitz N , Tønnes M , Ito H , Ohtsubo N , Miyauchi Y , Morikawa M , Matsubara K , Gotoh T , Ido T
Published: November 2024

Our efforts with the optical lattice clock NICT-Sr1 are now focused on contribution to both the international and the local timescale. Since 2018, NICT-Sr1 has been recognized as a secondary frequency standard and frequently contributed to BIPM’s monthly calibration of the rate of the international atomic time TAI. This fulfils one of the criteria that the Consultative Committee for Time and Frequency has set for the redefinition of the SI second. Another, ancillary condition is addressed by NICT-Sr1’s contributions to the generation of Japan Standard Time, which began in 2021 and enabled a reduction of the deviation from the international timescale to typically 4 ns over more than two years.
Robust design and performance of NPL Cs fountain clocks
Authors: Szymaniec K , Hendricks R J , Whale J , Wilson A , Walby S , Knapp M , Foot C J
Published: November 2024

We report on developments in the atomic fountain systems being built and operated at NPL. An improved generation of Cs fountains has been developed, with units being constructed for use by both NPL and commercial customers. These systems combine world-class stability and accuracy with increased reliability and can run for long periods of time without maintenance. Here we describe how the NPL fountains work, and present performance data for the latest systems. We describe some of the applications of these fountains, both in time scale implementation and fundamental science. We also present an overview of a miniature atomic fountain that is being developed, which will help make fountain technology accessible to a wider range of sectors.
Incorporation of hydrogen masers into a free ensemble timescale aimed for optically steered UTC(k)
Authors: Ido T , Ito H , Hachisu H , Nemitz N , Ohtsubo N , Miyauchi Y , Morikawa M , Tønnes M , Matsubara K
Published: November 2024

The combination of a single hydrogen maser and an intermittently operated optical clock can generate a highly accurate timescale, but it is difficult to address a sudden deterioration of the hydrogen maser. This issue can be resolved by the use of an ensemble. By estimating the frequency drift of multiple individual hydrogen masers, it is possible to incorporate them as the main contributors to an ensemble time scale that benefits from their long-term stability. Such a timescale is in operation at UTC(NICT) since August 2023. To determine the required adjustments for frequency offset and drift of the free-running timescale, we refer to a separate timescale generated from a hydrogen maser steered according to intermittent operation of an optical clock. In combination, this realizes a robust and accurate timescale.
Progress on the optically detected magnetic-state-selected cesium beam clock
Authors: Li Yuanhao , Chen Sifei , Liu Chen , Fan Lifeng , Li Chaojie , Wang Yanhui
Published: November 2024

The optically detected magnetic-state-selected cesium beam clock is a new type of compact cesium clock developed by Peking University. The principle and performance of our clock are introduced in the article as well as our recent researches on beam optics, signal-to-noise ratio, spectrum linewidth and light shift.
Progress in the miniature trapped ion optical clock development with 16 cc sealed trap tube
Authors: Hoang Thai M. , Zhang Wei , Le Thanh , Mulholland Sean , Langlois Mehdi , Park Yuna , Matsko Andrey B. , Prestage John , Yu Nan
Published: November 2024

Optical clocks have well surpassed the frequency stability performance of microwave clocks. They have been mainly limited to tabletop setups and large rack-mount systems. Miniaturizing optical clocks will make the new technology and capability more ubiquitously applied to applications from navigation to fundamental science. Here we aim to develop a miniature space optical clock (mSOC) with the size of a compact microwave clock and capable of achieving a short-term stability of 10−14
τ
−1/2 and noise floor of 10−16. In this paper, we will describe the mSOC concept, discuss the experimental setup, and present recent results. We have demonstrated trapping single ions and characterized the ion lifetime in a 16-cc trap tube. The trap tube is completely sealed off without any active pump. We also constructed a clock laser referenced to a small ultra-low expansion reference cavity at a low 10−14 level and observed the clock transition.
A compact cold atom cavity clock
Authors: Bregazzi A. , Batori E. , Lewis B. , Affolderbach C. , Mileti G. , Griffin P. , Riis E.
Published: November 2024

A sample of laser cooled atoms are created inside an additively manufactured loop-gap microwave cavity using a grating magneto-optic trap requiring only a single laser cooling beam. Using a Ramsey excitation scheme with free evolution times of up to 20 ms and based on the 87Rb ground-state clock transition, we demonstrate a short-term stability of 1.5×10−11
τ
−1/2, averaging down to 2×10−12 after 100 s. The short-term stability limit is found to be dominated by the signal to noise ratio of the Ramsey fringes while for longer timescales the limitation is magnetic field noise due to the experiment being magnetically unshielded. Potential improvements to the setup and its operation point to a viable route forward for a miniaturised atomic microwave clock.
The development and future of the Faraday laser
Authors: Wang Zhiyang , Shi Hangbo , Liu Zijie , Miao Jianxiang , Shi Tiantian , Chen Jingbiao
Published: November 2024

Faraday lasers, distinguished by their utilization of the Faraday anomalous dispersion optical filter (FADOF), employ atomic transitions for mode selection. This sets them apart from other semiconductor diode lasers, which commonly employ gratings, interference filters, and etalons for frequency selection and initiating laser oscillation. A notable advantage of Faraday lasers is their resistance to noises in driving current and the temperature of the laser diodes. Additionally, the using of FADOF enables the output frequency of the laser to align with atomic transition lines immediately when powering the lasers with driving current above the threshold. This paper presents the advancements in Faraday laser system technology spearheaded by our group, outlining a forward-looking research agenda aimed at continually enhancing the performance of Faraday lasers. This endeavor seeks to establish these lasers as frontrunners in the next generation of laser used in precision spectroscopy, with specific applications in atomic physics, quantum metrology, and quantum precision measurement technology.
Trapping of triply charged thorium-229 for a nuclear clock
Authors: Yamaguchi A , Shigekawa Y , Haba H , Wada M , Katori H
Published: November 2024

We developed an ion trap system for triply charged thorium-229 (229Th3+). We used uranium-233 as the ion source, which supplied 229Th3+ ions in the nuclear ground state and low-lying isomeric state (229mTh3+) at 8.3 eV. Our ion trap system allows the laser spectroscopy of 229mTh3+ toward the nuclear clock.
Superradiant active optical atomic clocks: motivations and current challenges
Authors: Matusko Martina , Delehaye Marion
Published: November 2024

Current state-of-the-art frequency standards are passive optical atomic clocks where the frequency of an optical resonator is stabilized to a narrow atomic transition. Passive clocks have achieved unprecedented stabilities of 6.6 × 10−19 over one hour of averaging time [1]. However, they face intrinsic limitations, particularly due to thermal and mechanical fluctuations of the local oscillator. To surpass the limitations of the passive clocks and go beyond the state-of-the-art, the idea of building active optical atomic clocks emerges. These clocks would be optical counterparts of hydrogen masers, with the emitted frequency defined by the atomic transition and therefore inherently stable against cavity instabilities. This paper discusses the latest developments and future prospects in the field of active optical atomic clocks.
Dual-species atomic interferometric sensor for simultaneous inertial measurement and clock operation
Authors: Yan Peiqiang , Jia Weichen , Wang Shengzhe , Feng Yanying
Published: November 2024

The atomic interferometer, serving as a precise measurement tool for multiple physical quantities, holds the potential to establish a fully quantum autonomous “position, navigation, and timing (PNT)” unit. This paper introduces a method for simultaneous inertial measurement and clock operation based on atom interferometry with dual-isotope atomic beams. The corresponding related experimental progress is also reported. A 87Rb Raman-Mach-Zehnder interferometer is presented with a fringe contrast of C = 0.05, providing a foundational sample for further experiments.
Time-dependent Aharonov-Bohm effect for electromagnetic and gravitational scalar potentials
Authors: Chiao RY , Inan NA , Scheibner M , Sharping J , Singleton DA , Tobar ME
Published: November 2024

In this article, we review a new approach to the scalar Aharonov-Bohm effect for both the electromagnetic and gravitational interaction. For both interactions a quantum system is placed in a time-dependent electromagnetic or gravitational potential, but with no force (spatial derivative of the potential) acting on the quantum system. Nevertheless, we show that the energy levels of the quantum system develop side bands which can be detected as the signature of this version of the scalar Aharonov-Bohm effect. We briefly look at the specific experimental setups required to detect the energy side bands.
The effect of asymmetric rolling on aluminum alloy 5XXX series with scandium
Authors: Nikitina M.A. , Pesin A.M. , Tandon P. , Pustovoytov D.O. , Pesin I.A. , Lokotunina N.M. , Biryukova O.D.
Published: November 2024

One of the directions of development of aluminum alloys is to increase strength characteristics without increasing density. Scandium is an effective additive for improving the strength characteristics of alloys with a high magnesium content. The main disadvantage of scandium-containing alloys is the high cost, the cost of ligature in Russia Al-2%Sc reaches $ 50 per kg. The high cost of semi-finished products is a deterrent to the use of aluminum-scandium alloys in various industries. In this paper, we consider the replacement of symmetric rolling with asymmetric rolling in the last passes of hot and cold rolling as one of the ways to reduce the cost in the production of semi-finished products. The research was carried out on an aluminum wrought non-heat-treatable alloy of the 5XXX series with scandium having the Russian marking 1545K. Rolled semi-finished products using symmetric rolling, as well as using asymmetric, were manufactured at the Zhilyaev Laboratory of the Nosov Magnitogorsk State Technical University using the unique laboratory industrial rolling mill 400. Asymmetric rolling is used for both hot and cold rolling. Asymmetric rolling made it possible to significantly reduce the force per pass, the pressure per pass became higher than when using standard technology. The obtained mechanical characteristics and the study of the micro-structure indicate a positive effect of asymmetric rolling. The use of this approach can significantly reduce costs in the manufacture of semi-finished products without reducing the quality of the resulting semi-finished products.
Effects of Cognitive Distraction on the Performance of Brain-Controlled Hand Exoskeleton
Authors: Liu Siyu , Liu Mengxin , Ming Zhiyuan , Zhao Yan , Liu Mengzhen , Luo Jianwei , Liu Ziyu , Chen Qiming , Ma Lingfei , Song Yifan , Zhang Jian , Yan Tianyi
Published: November 2024

Advances in brain-machine interfaces (BMIs) have greatly enhanced the control of assistive devices like hand exoskeletons, providing new rehabilitation possibilities for individuals with impaired hand function. However, the presence of cognitive distraction during device operation may negatively affect performance. This study explores the impact of cognitive interference on a brain-controlled hand exoskeleton system. Participants were required to perform hand movement tasks using the exoskeleton while engaging in a cognitive distraction task. The results showed a significant decline in task completion rate and a marked increase in response time as cognitive distraction intensified. These findings underscore the need to mitigate cognitive distraction in brain-controlled systems to enhance performance, especially in rehabilitation contexts. This study contributes valuable insights into the interaction between cognitive distraction and brain-controlled hand exoskeleton performance, laying the groundwork for improving BMI reliability and effectiveness in practical applications.
The study of the turbo-machines erosion caused by solid particles during the evacuation of combustion gases in a biomass power plant
Authors: Sangsawangmatum Thanate
Published: November 2024

Turbo-machines are recognized as a significant engineering device for transferring heat and mass, particularly solid particles in the transport medium. The biomass power plants turbo-machines, known as centrifugal fans, is normally used in the process of evacuating combustion. Due to their duty to continuously work in high concentrations of solid particles, unavoidable damage resulting from solid particle erosion must occur. This causes the system to shut down unexpectedly. To avoid system shutdown, the centrifugal impeller must be designed to withstand the solid particles from exhaust gas, which quickly deteriorate. The aims of the research paper are to study the behaviour of an erosion mechanism of the system using Computational Fluid Dynamics (CFD) verified against the various parameters obtained from actual operating data which were collected during the operating season. Steady-state turbulence modelling and discrete phase modelling (DPM) in powerful commercial software were used to predict the fluid kinetics of substances and the trajectories of individual solid particles, respectively. In the end, the study’s results not only aid users in understanding the system behaviour but also lead to engineering improvements in turbo-machinery technology.
Influence of preparation process on electromagnetic shielding and infrared properties of hydrogen-bonded bridged MXene thin films
Authors: Zhang Jinman , Liu Xinmin , Li Chuang
Published: November 2024

With the continuous development of communication technology and mobile electronic devices, the problem of electromagnetic interference is becoming more and more prominent, so the development of films with high tensile strength and excellent electromagnetic shielding and infrared camouflage properties has become an important research direction. We introduced hydrogen bonding by adding sodium alginate between the layers of two-dimensional material MXene to improve the tensile strength of the film, and compared the effects of film preparation processes such as sodium alginate concentration, vacuum-assisted filtration, and blade scraping method on the film properties. The results show that the hydrogen bonded bridged MXene films (HBMB) prepared by blade scraping method have high electrical conductivity, electromagnetic shielding performance, tensile strength, low infrared emissivity and good thermal camouflage performance.The tensile strength of HBMB films is nearly four times higher than that of vacuum-assisted filtration (HBM) films, and the electromagnetic shielding performance of the scraped films in the X-band against electromagnetic waves reaches 53.54 dB, and the absolute electromagnetic efficiency of 47,528 dB-cm2/g.
Investigation of steam-diluted hydrogen combustion in a counter-current nozzle configuration using LES
Authors: Wawrzak A , Tyliszczak A
Published: November 2024

The study concerns a co-axial counter-current jet configuration conceptualized as a wet hydrogen/air injector. Such an injector system induces a flow pattern beneficial for triggering global instability near a nozzle lip. Using high-fidelity LES, we explore how global instability alter the flame dynamics through adjustments in the strength of the counter-current flow for selected dilution level. In particular, we present regimes for lifted flames to mitigate hydrogen corrosion risk and enhance combustion efficiency.
Quantification of laminar mixing efficiency with negative index Sobolev norm
Authors: Fabisiak Jakub , Gepner Stanisław
Published: November 2024

The efficiency of stirring in the laminar mixing protocol resulting from the action by the nonstationary laminar flow through a longitudinally corrugated channel is evaluated using the negative exponent Sobolev norm of the concentration - the Mix-Norm. The Mix-norm is applied to a range of stirring velocity fields, resulting from the low Reynolds number destabilisation of the flow through a corrugated channel. The results are compared to the well-known quantifying measure, the concentration variance. The ability of the Mix-norm to include the stirring effect at the increasing Péclet number is illustrated.
Utilizing a pressure-based CFD solver for modelling wet steam flow in low-pressure turbine stages: a predictive approach to assessing flow losses
Authors: Shabani Sima , Majkut Miroslaw , Dykas Slawomir , Smolka Krystian
Published: November 2024

This research focuses on addressing a critical challenge in steam turbine operation, specifically condensation losses within the Low-Pressure (LP) section. Such losses have a significant impact on energy efficiency and operational costs in industries like power generation and manufacturing. The objective of this research is to predict condensation losses in the LP part of steam turbines. The simulation of the two-phase flow of wet steam is performed in the ANSYS CFX software. The geometry studied in this research is the actual geometry of the last stage of a steam turbine, which is modeled in three dimensions. The complexities of modeling three-dimensional flows, as well as providing relationships that can be used to calculate losses that can be generalized and used in different conditions, are distinctive features of this research.
PIV measurement of model nuclear fuel rod bundle
Authors: Duda Daniel , Yanovych Vitalii , Uruba Václav
Published: November 2024

The fuel rods are kept in their positions by using spacer grids. This grid is sometimes connected with mixing grid, which mixes the fluid between the fuel rods in order to enhance the heat transfer. One of the possible configurations is the usage of the mixing vanes, which divert the flow from the main channel (between 3 rods) to its narrower part (between 2 rods), possibly even into the neighboring channel. The technical details are top secret. Therefore, in order to test the measuring methodology, we designed and manufactured our own mixing grid. This grid is scaled to the sizes of UWB wind tunnel and its vanes have a parabolic profile. We show results of Stereo PIV (Particle Image Velocimetry) measurement. The studied plane is perpendicular to the stream-wise direction covering area behind two main channels ca 2mm behind the rod ends. Reynolds number of this experiment Re
E
≈ 7.8 · 104 (in reactor Re
R
≈ 2.6 · 105). The obtained data show focusing of the flow into the narrower part of channel, relatively fast turbulence decay and strong anizotropy of fluctuations.
Predictive uncertainty in state-estimation drives active sensing
Authors: Kaan Karagoz Osman , Kilic Aysegul , Yusuf Aydin Emin , Mert Ankarali Mustafa , Uyanik Ismail
Published: November 2024

Animals use active sensing movements to shape the spatiotemporal characteristics of sensory signals to better perceive their environment under varying conditions. However, the underlying mechanisms governing the generation of active sensing movements are not known. To address this, we investigated the role of active sensing movements in the refuge tracking behavior of Eigenmannia virescens, a species of weakly electric fish. These fish track the longitudinal movements of a refuge in which they hide by swimming back and forth in a single linear dimension. During refuge tracking, Eigenmannia exhibits stereotyped whole-body oscillations when the quality of the sensory signals degrades. We developed a closed-loop feedback control model to examine the role of these ancillary movements on the task performance. Our modeling suggests that fish may use active sensing to minimize predictive uncertainty in state estimation during refuge tracking. The proposed model generates simulated fish trajectories that are statistically indistinguishable from that of the actual fish, unlike the open-loop noise generator and stochastic resonance generator models in the literature. These findings reveal the significance of closed-loop control in active sensing behavior, offering new insights into the underlying mechanisms of dynamic sensory modulation.
Stability and agility trade-offs in spring-wing systems
Authors: Lynch James , Wold Ethan S , Gau Jeff , Sponberg Simon , Gravish Nick
Published: November 2024

Flying insects are thought to achieve energy-efficient flapping flight by storing and releasing elastic energy in their muscles, tendons, and thorax. However, ‘spring-wing’ flight systems consisting of elastic elements coupled to nonlinear, unsteady aerodynamic forces present possible challenges to generating stable and responsive wing motion. The energetic efficiency from resonance in insect flight is tied to the Weis-Fogh number (N), which is the ratio of peak inertial force to aerodynamic force. In this paper, we present experiments and modeling to study how resonance efficiency (which increases with N) influences the control responsiveness and perturbation resistance of flapping wingbeats. In our first experiments, we provide a step change in the input forcing amplitude to a series-elastic spring-wing system and observe the response time of the wing amplitude increase. In our second experiments we provide an external fluid flow directed at the flapping wing and study the perturbed steady-state wing motion. We evaluate both experiments across Weis-Fogh numbers from

1
<
N
<
10

. The results indicate that spring-wing systems designed for maximum energetic efficiency also experience trade-offs in agility and stability as the Weis-Fogh number increases. Our results demonstrate that energetic efficiency and wing maneuverability are in conflict in resonant spring-wing systems, suggesting that mechanical resonance presents tradeoffs in insect flight control and stability.
Identifying opportunities for nature-based solutions with geospatialized life cycle assessments and fine-scale socioecological data
Authors: Shirkey Gabriela , Anctil Annick , John Ranjeet , Kolluru Venkatesh , Mungai Leah , Kashongwe Herve , Cooper Lauren T , Celik Ilke , Fisher Joshua B , Chen Jiquan
Published: November 2024

As we increasingly understand the impact that land management intensification has on local and global climate, the call for nature-based solutions (NbS) in agroecosystems has expanded. Moreover, the pressing need to determine when and where NbS should be used raises challenges to socioecological data integration as we overcome spatiotemporal resolutions. Natural and working lands is an effort promoting NbS, particularly emissions reduction and carbon stock maintenance in forests. To overcome the spatiotemporal limitation, we integrated life cycle assessments (LCA), an ecological carbon stock model, and a land cover land use change model to synthesize rates of global warming potential (GWP) within a fine-scale geographic area (30 m). We scaled National Agricultural Statistic Survey land management data to National Land Cover Data cropland extents to assess GWP of cropland management over time and among management units (i.e. counties and production systems). We found that cropland extent alone was not indicative of GWP emissions; rather, rates of management intensity, such as energy and fertilizer use, are greater indicators of anthropogenic GWP. We found production processes for fuel and fertilizers contributed 51.93% of GWP, where 33.58% GWP was estimated from N2O emissions after fertilization, and only 13.31% GWP was due to energy consumption by field equipment. This demonstrates that upstream processes in LCA should be considered in NbS with the relative contribution of fertilization to GWP. Additionally, while land cover change had minimal GWP effect, urbanization will replace croplands and forests where NbS are implemented. Fine-scale landscape variations are essential for NbS to identify, as they accumulate within regional and global estimates. As such, this study demonstrates the capability to harness both LCA and fine-resolution imagery for applications in spatiotemporal and socioecological research towards identifying and monitoring NbS.
On a generating function for the isotropic basis functions and other connected results
Authors: Slepian Zachary , Chellino Jessica , Hou Jiamin , Greco Alessandro
Published: November 2024

Recently isotropic basis functions of N unit vector arguments were presented; these are of significant use in measuring the N-point correlation functions (NPCFs) of galaxy clustering. Here we develop the generating function for these basis functions—i.e. that function which, expanded in a power series, has as its angular part the isotropic functions. We show that this can be developed using basic properties of the plane wave. A main use of the generating function is as an efficient route to obtaining the Cartesian basis expressions for the isotropic functions. We show that the methods here enable computing difficult overlap integrals of multiple spherical Bessel functions, and we also give related expansions of the Dirac Delta function into the isotropic basis. Finally, we outline how the Cartesian expressions for the isotropic basis functions might be used to enable a faster NPCF algorithm on the CPU.
A metasurface integrated self-decoupled multiport tunable antenna for THz applications
Authors: Das Priyanka
Published: November 2024

A four port multiple-input multiple-output (MIMO) antenna is initially designed on silicon dioxide (quartz) substrate by arranging the antenna elements in an orthogonal configuration by using self-decoupling mechanism. Mean effective gain lower than 0.5 and radiation efficiency greater than 95% are obtained. Characteristic mode analysis of the proposed MIMO antenna has been performed using finite integration technique to validate the resonant modes. Further, a dual band self-multiplexing MIMO antenna has been constructed by loading each antenna element with a graphene constituted stub. Graphene loading in the antenna elements is done to introduce tunability in the MIMO operation in two frequency bands. The dual resonance frequencies range from 4.3–4.6 THz and 5.2–5.6 THz while the chemical potential is varied from 0.1 eV to 0.9 eV. The diversity performance of the MIMO antenna with and without graphene loading have been analyzed through numerical simulations. Envelope correlation coefficient lower than 0.0002 and diversity gain of 10 dB have been obtained. By biasing each of the antenna elements with different voltages, quadruplexing mechanism can be performed since each antenna resonates at a different frequency. Finally, a metasurface is designed on silicon dioxide (quartz) substrate to function as a reflective surface from 3.75–6.42 THz covering the resonance band of the tunable MIMO antenna for enhancing its gain to 14 dBi.
Enhanced proton acceleration using spiral-phase plasma mirrors
Authors: Shpilman Z , Amir Y , Hollinger R , Wang S , Zahedpour Anaraki S , Rocca J J , Pomerantz I
Published: November 2024

We present a method for generating intense vortex laser beams using spiral-phase plasma mirrors. These single-use micro-metric formations imprint a set amount of orbital angular momentum (OAM) to an arbitrary high power focusing beam. Using these beams, we irradiated ultrathin foils and measured the emission of ions from their back side. Utilizing a PW class laser, 5 J@45fs@2w resulting in an Intensity of 2×1020 W 

cm

−
2

at spot focus, we observed an increase in the energy and numbers of these ions, compared to shots taken with reflection off flat plasma mirrors. A 45% increase in the proton numbers and a 35% increase in cutoff energy was observed. This is a major advance since the area of interaction and intensity are reduced due to the planar shape of the generated OAM laser. We review the available data-sets on laser ion acceleration using vortex beams, and conclude with a comparison to our findings.
Prediction of grain size in TB18 titanium alloy forgings by re-crystallization and grain growth modelling
Authors: Xiang Wei , Li Qineng , Zhang Feng , Yuan Wuhua
Published: November 2024

After plastic deformation, metals and alloys will be in a thermodynamically unstable high free en-ergy state with a tendency to spontaneously return to a low free energy state. Understanding the laws of occurrence and development of these processes is of great significance in improving and controlling the microstructure and properties of TB18 titanium alloy. In this paper, the recrystalli-sation kinetics is investigated based on the Johnson–Mehl–Avrami equation, and a kinetic model for the grain growth of solid solution TB18 alloy undergoing predeformation at different solid solution temperatures and different solid solution times has been established by combining the Arrhenius formula and Beck’s equation to derive a prediction model for the grain size that includes three types of parameters, namely, T, t, and ε, during the solid solution process. Using simulation soft-ware(Deform) based on finite element analysis to simulate the grain size of forging heat treatment, validate the grown-up model, and analyse the deformation of each part of the forging and the grain size deviation of its corresponding position. The results show that the deviation of grain size pre-dicted by the TB18 grain size model for the forging after heat treatment is less than 10%. Overall, the size prediction model of the grain growth has been proven to be accurate and usable.