bluuebunny/crossref_metadata_2025 huggingface dataset:
Asymmetry and intermittency in the rheo-inertial transition to turbulence in pipe flow
Authors: Charles Antoine , Peixinho Jorge , Ribeiro Thierry , Azimi Sam , Rocher Vincent , Baudez Jean-Christophe , Bahrani S. Amir
Published: May 2024

Transition to turbulence in pipe has been extensively studied but is still not completely understood and even more for non-Newtonian fluids. We focus here on yield stress shear-thinning fluids and the mechanism leading to the transition in pipe, the so-called rheo-inertial transition to turbulence. An experimental setup has enabled us to identify flow regimes in a cylindrical pipe, using both flow visualizations and pressure drops measurements for a range of Reynolds numbers. We delimited the non-Newtonian specific regime in the laminar-turbulent transition triggered at a critical Reynolds number below the turbulent puffs onset. This pre-transition regime is associated with a velocity profile asymmetry in which its degree and position evolve as the Reynolds number increases. The origin for the stability of this rheo-inertial regime is discussed, as it could be due to a competition between the nonlinear contributions of rheological behavior and flow inertia. Beyond this regime, we quantified the intermittence of puff transit, revealing the delay to turbulence. We spotted for the first time a different rheo-inertial transitional behavior in the intermittency evolution vs Reynolds number, displaying a smoother transition on a broader range. Finally, the critical Reynolds numbers for different yield stresses are compared with previous works, and the novelty is the linear increase in the delay to turbulent puffs with the yield stress.
Phase and amplitude reconstruction by weak measurement based on metasurface
Authors: Luo Wenxian , Yang Qiang , Wang Yan , Liu Jiawei , Luo Hailu
Published: May 2024

Phase distribution is crucial for obtaining the whole information of phase object in imaging. However, due to the transparency of phase objects, the phase distribution cannot be obtained in traditional bright-field imaging. Here, we propose a phase distribution reconstruction based on the imaginary value of weak measurement, which is achieved by a Pancharatnam–Berry phase metasurface. Moreover, by adjusting the weak value to a real weak value, amplitude reconstruction can also be achieved. Different parts of weak values can be obtained by controlling the preselection and postselection states. The weak interaction is achieved by the metasurface, which is convenient to control the weak coupling and reduce the complexity of the experimental setup at the same time. Furthermore, the edge contour of objects can also be acquired by the weak measurement, and the edge sharpness is related to types of the weak values, which plays an important role in image resolution. Our method paves a way for quantitative phase imaging and unlabeled biological imaging.
The Hill function is the universal Hopfield barrier for sharpness of input–output responses
Authors: Martinez-Corral Rosa , Nam Kee-Myoung , DePace Angela H. , Gunawardena Jeremy
Published: May 2024

The Hill functions,

H
h

(
x
)

=

x
h

/

(
1
+

x
h

)

, have been widely used in biology for over a century but, with the exception of

H
1

, they have had no justification other than as a convenient fit to empirical data. Here, we show that they are the universal limit for the sharpness of any input–output response arising from a Markov process model at thermodynamic equilibrium. Models may represent arbitrary molecular complexity, with multiple ligands, internal states, conformations, coregulators, etc, under core assumptions that are detailed in the paper. The model output may be any linear combination of steady-state probabilities, with components other than the chosen input ligand held constant. This formulation generalizes most of the responses in the literature. We use a coarse-graining method in the graph-theoretic linear framework to show that two sharpness measures for input–output responses fall within an effectively bounded region of the positive quadrant,

Ω
m

⊂

(

R

+

)

2

, for any equilibrium model with

m

input binding sites.

Ω
m

exhibits a cusp which approaches, but never exceeds, the sharpness of

H
m

, but the region and the cusp can be exceeded when models are taken away from thermodynamic equilibrium. Such fundamental thermodynamic limits are called Hopfield barriers, and our results provide a biophysical justification for the Hill functions as the universal Hopfield barriers for sharpness. Our results also introduce an object,

Ω
m

, whose structure may be of mathematical interest, and suggest the importance of characterizing Hopfield barriers for other forms of cellular information processing.
Balance between asymmetric allocation and repair of somatic damage in unicellular life forms as an ancient form of r/K selection
Authors: Biba Dmitry A. , Wolf Yuri I. , Koonin Eugene V. , Rochman Nash D.
Published: May 2024

Over the course of multiple divisions, cells accumulate diverse nongenetic, somatic damage including misfolded and aggregated proteins and cell wall defects. If the rate of damage accumulation exceeds the rate of dilution through cell growth, a dedicated mitigation strategy is required to prevent eventual population collapse. Strategies for somatic damage control can be divided into two categories, asymmetric allocation and repair, which are not, in principle, mutually exclusive. We explore a mathematical model to identify the optimal strategy, maximizing the total cell number, over a wide range of environmental and physiological conditions. The optimal strategy is primarily determined by extrinsic, damage-independent mortality and the physiological model for damage accumulation that can be either independent (linear) or increasing (exponential) with respect to the prior accumulated damage. Under the linear regime, the optimal strategy is either exclusively repair or asymmetric allocation, whereas under the exponential regime, the optimal strategy is a combination of asymmetry and repair. Repair is preferred when extrinsic mortality is low, whereas at high extrinsic mortality, asymmetric damage allocation becomes the strategy of choice. We hypothesize that at an early stage of life evolution, optimization over repair and asymmetric allocation of somatic damage gave rise to
r
and
K
selection strategists.
Coordination of actin plus-end dynamics by IQGAP1, formin, and capping protein
Authors: Pimm Morgan L. , Haarer Brian K. , Nobles Alexander D. , Haney Laura M. , Marcin Alexandra G. , Alcaide Eligio Marcela , Henty-Ridilla Jessica L.
Published: May 2024

Cell processes require precise regulation of actin polymerization that is mediated by plus-end regulatory proteins. Detailed mechanisms that explain plus-end dynamics involve regulators with opposing roles, including factors that enhance assembly, e.g., the formin mDia1, and others that stop growth (capping protein, CP). We explore IQGAP1’s roles in regulating actin filament plus-ends and the consequences of perturbing its activity in cells. We confirm that IQGAP1 pauses elongation and interacts with plus ends through two residues (C756 and C781). We directly visualize the dynamic interplay between IQGAP1 and mDia1, revealing that IQGAP1 displaces the formin to influence actin assembly. Using four-color TIRF, we show that IQGAP1’s displacement activity extends to formin-CP “decision complexes,” promoting end-binding protein turnover at plus-ends. Loss of IQGAP1 or its plus-end activities disrupts morphology and migration, emphasizing its essential role. These results reveal a new role for IQGAP1 in promoting protein turnover on filament ends and provide new insights into how plus-end actin assembly is regulated in cells.
The Einstein–Hilbert action for entropically dominant causal sets
Authors: Carlip Peter , Carlip Steve , Surya Sumati
Published: May 2024

In the path integral formulation of causal set quantum gravity, the quantum partition function is a phase-weighted sum over locally finite partially ordered sets, which are viewed as discrete quantum spacetimes. It is known, however, that the number of ‘layered’ sets—a class of causal sets that look nothing like spacetime manifolds—grows superexponentially with the cardinality n, giving an entropic contribution that can potentially dominate that of the action. We show here that in any dimension, the discrete Einstein–Hilbert action for a typical K-layered causal set reduces to the simple link action to leading order in n. Combined with earlier work, this completes the proof that the layered sets, although entropically dominant, are very strongly suppressed in the path sum of causal set quantum gravity whenever the discreteness scale is greater than or equal to a (mildly dimension-dependent) order one multiple of the Planck scale.
Programmable metasurfaces with high angular stability for arbitrarily-polarized obliquely-incident waves
Authors: Xu Liang , Zhang Xin Ge , Li Qi Yang , Jiang Wei Xiang , Cui Tie Jun
Published: May 2024

Programmable metasurfaces show enormous potential in real-time electromagnetic (EM) manipulation and their stable responses to variable EM waves including incident angle and polarization changes are crucial for related applications. However, the demonstrated programmable metasurfaces are commonly considered in normal-incident waves with fixed polarization; how to achieve stable performance in more realistic scenarios of wide-angle and full-polarized wave incidences is still a challenge. Here, we propose and realize a wide-angle and full-polarization programmable metasurface, which can generate stabilized amplitude and phase responses at both transverse electric (TE) and transverse magnetic (TM) oblique incidences. These are achieved by introducing metallic walls around the metasurface element to reduce element coupling, which greatly improves the angular stability of its reflection responses. The mechanisms of angular insensitivity are analyzed comprehensively, and as a proof of concept, obliquely-incident beam steering, large-angle beam scanning and oblique vortex beam emitting are demonstrated on this programmable metasurface. Both the simulation and experimental results demonstrate that the programmable metasurface can operate well at both TE and TM wide-angle oblique incidences in the upper half space. Our work offers an actual route for improving the angular stability and polarization insensitivity of metasurfaces, which could push them one step closer towards more complicated applications.
Janus TiSi

Z

3H (

Z
=

N, P, As) monolayers with large out-of-plane piezoelectricity and high electron mobility: first-principles study
Authors: Vu Tuan V , My Bui Kieu , Hoang Khanh V , Kartamyshev A I , Ho Thi H , Lavrentyev A A , Anh Nguyen P Q , Phuc Huynh V , Hieu Nguyen N
Published: May 2024

In this paper, we propose a series of novel two-dimensional Janus structures TiSiZ
3H (

Z
=

N, P, As) and investigate their electronic, mechanical, piezoelectric, and transport properties using the density functional theory. The examined results demonstrated that Janus TiSiZ
3H monolayers are structurally stable. At the ground state, TiSiN3H, TiSiP3H, and TiSiAs3H monolayers are all semiconductors with indirect bandgaps of 2.98, 1.06, 1.0 eV at the hybrid-functional level, respectively. The absence of vertical mirror symmetry in TiSiZ
3H results in the occurrence of both in-plane and out-of-plane piezoelectricity. Interestingly, TiSiAs3H monolayer exhibits large out-of-plane piezoelectric response with coefficient d
31 up to −0.45 pm V−1, that is appropriate for use in piezoelectric devices. The calculated results demonstrate that the carrier mobility in Janus TiSiZ
3H monolayers is high and directional anisotropic. Particularly, electron mobility in TiSiP3H monolayer is observed up to 772.31 cm2 V−1 s−1. Our results not only suggest and confirm some fundamental physical characteristics of new materials but also lay important premises for experimental studies as well as their application prospects in the future.
Geometrical characterization of healthy red blood cells using digital holographic microscopy and parametric shape models for biophysical studies and diagnostic applications
Authors: Bhabhor Gaurav D , Patel Chetna , Chhillar Nishant , Anand Arun , Lad Kirit N
Published: May 2024

Modeling of the red blood cell (RBC) shape is an integral part of the experimental and computer simulation investigations of light scattering by these cells for fundamental studies as well as diagnostic applications in techniques like cytometry and quantitative phase imaging. In the present work, a comprehensive study of the geometrical characterization of healthy human RBCs using digital holographic microscopy (DHM) and six frequently employed parametric shape models is reported. It is shown that the comparison of the optical phase profiles, and the thickness profiles given by the models with the DHM results gives a better judgment of the appropriateness of the parametric shape models. It is also shown that the RBC parametric models offer a simpler solution to the refractive index-thickness decoupling problem in QPI methods. Results of geometrical characterization of 500 healthy RBCs in terms of volume, surface area (SA), and sphericity index (SI) led to the classification of the parametric models in two categories based on the nature of variation of these quantities with the cell diameter. In light of the variability of the healthy RBC shapes, our findings suggest that the parametric models exhibiting a negative correlation between the SI and the cell diameter would provide more reliable estimates of the RBC parameters in diagnostic applications. Statistical distributions and descriptive statistics of the RBC volume, SA and SI serve as a guide for the assessment of the capability of the studied parametric models to give a reliable account of the variability of the healthy RBC shape and size.
Efficient gradient heating-up approach for rapid growth of high-quality amorphous ZrO2 dielectric films
Authors: Chen Ao , Liang Zhihao , Liao Zhiying , Zhang Huiqi , Li Songju , Wang Ruihua , Li Yan , Yu Mengxia , Liu Xianzhe , Ning Honglong , Huang Aiping , Luo Jianyi
Published: May 2024

High-k oxide dielectric films are indispensable for low-power-consumption oxide thin-film transistors (TFTs) applied in advanced and portable electronics. However, high-quality oxide dielectric films prepared by solution process typically require sophisticated processes and long thermal annealing time, severely limiting both the throughput manufacturing and cost-effectiveness. In this study, the influence of different heating-up methods on the surface morphology and dielectric properties was systematically investigated. Gradient heating-up method could not only substantially improve the surface morphology and quality of high-k ZrO2 films but also efficiently shorten the annealing time. The gradient heating-up process was further designed on the basis of thermal behavior of the xerogel-like precursor, which successfully realize the preparation of high-quality ZrO2 films with an annealing time of 5 min (i.e. the efficiency of thermal treatment increased by about 89%). The ZrO2 film presented excellent dielectric properties, including a low leakage current density of ∼10−8 A cm−2 (at 2 MV cm−1 ), a large areal capacitance of 169 nF cm−2 and a high dielectric constant of 20.41 (1 MHz). Furthermore, InSnZnO TFT based on the ZrO2 gate dielectrics shows an acceptable device performances, such as a high carrier mobility of 2.82 cm2 V−1 s, a high on/off current ratio of ∼105 and a low subthreshold swing of 0.19 V decade −1 at a low operation voltage of 5 V. This work provide a highly promising approach to fabricate high-quality solution-processed high-k oxide dielectric films employed for large-scale and low-power-consumption electronics.
In-flight iron ore reduction and nanoparticle formation in an atmospheric pressure hydrogen microwave plasma
Authors: Xiong Zichang , Kumar Sachin , Held Julian , Bruggeman Peter , Kortshagen Uwe
Published: May 2024

The in-flight reduction of iron ore particles using an atmospheric pressure hydrogen plasma is investigated. Iron ore particles with a size less than 75 µm are aerosolized and carried with an argon-hydrogen (90%–10%) gas mixture through an atmospheric pressure microwave plasma. After the treatment, the collected particles are observed to follow three distinct populations: (i) fully reduced nanoparticles, (ii) partially reduced spheres, larger than the feedstock, and (iii) partially melted, partly reduced agglomerates. A model is developed to explain the possible mechanism for the origin of the three populations. The nanoparticles (i) are found to be likely formed from the previously evaporated material whereas the particles (ii) and (iii) result from the partial/complete melting of the particles and agglomerates flowing through the reactor. The gas temperature is estimated to be more than 2000 K, which enables the rapid melting, evaporation, and reduction of these particles within residence times of only a few 10 ms.
Low-frequency Raman active modes of twisted bilayer MoS2
Authors: Klein Brandon , Liang Liangbo , Meunier Vincent
Published: May 2024

We study the low-frequency Raman active modes of twisted bilayer MoS2 for several twist angles using a force-field approach and a parametrized bond polarizability model. We show that twist angles near high-symmetry stacking configurations exhibit stacking frustration that leads to significant buckling of the moiré superlattice. We find that atomic relaxation due to the twist is of prime importance. The periodic displacement of the Mo atoms shows the realization of a soliton network, and in turn, leads to the emergence of a number of frequency modes not seen in the high-symmetry stacking systems. Some of the modes are only seen in the XZ Raman polarization setup while others are seen in the XY setup. The symmetry of the normal modes, and how this affects the Raman tensors is examined in detail.
Electrostatic doping tunable magnetic transition and half-metallicity in the monolayer CrCTe3
Authors: Liu Linlin , Jiang Peng , Huang Hong-Mei , Li Yan-Ling
Published: May 2024

The electrical manipulation of the magnetic transition and spin-polarized states has attracted extensive attention in the field of spintronics. In this work, we perform a detailed study on the electronic and magnetic properties of the carrier-doped monolayer CrCTe3 by using first-principles calculation. It is found that, the magnetic transition from Néel-antiferomagnetic (nAFM) to ferromagnetic (FM) is observed in the case of the electron doping, while for hole doping a magnetic transition sequence of nAFM

→

zigzag-AFM

→

FM is observed in the monolayer CrCTe3. Interestingly, the carrier doping induced FM ground state always exhibits half-metallicity with full spin polarization. Moreover, the spin polarity of the half-metallic electronic states is opposite for electron and hole doping, meaning that the spin polarization direction can be tuned by manipulating a gate voltage. The Monte Carlo calculations show that the magnetic transition temperature of the doped FM CrCTe3 is rapidly increased with the increasing doping concentration and is extremely expected to achieve room temperature at a suitable doping concentration. These findings demonstrate that the monolayer AFM system possesses a potential application in spintronic devices with electrically tunable spin polarization.
A bearing fault diagnosis approach based on an improved neural network combined with transfer learning
Authors: Li Ruoyu , Pan Yanqiu , Fan Qi , Wang Wei , Ren Ruling
Published: May 2024

In modern industrial systems, bearing failures account for 30%–40% of industrial machinery faults. Traditional convolutional neural network suffers from gradient vanishing and overfitting, resulting in a poor diagnostic accuracy. To address the issues, a new bearing fault diagnosis approach was proposed based on an improved AlexNet neural network combined with transfer learning. After decomposition and noise-reduction, reconstructed vibration signals were transformed into 2D images, then input into the improved AlexNet for training and follow-up transfer learning. Program auto-tuning and image-enhancing techniques were employed to increase the diagnostic accuracy in this study. The approach was verified with the datasets from Case Western Reserve University (CWRU), Jiangnan University (JNU), and the Association for Mechanical Failure Prevention Technology (MFPT). The results showed that the diagnostic accuracies by normal learning were more than 97% for CWRU and JNU datasets, and 100% for MFPT dataset. After transfer learning, the accuracies all reached above 99.5%. The proposed approach was demonstrated to be able to effectively diagnose the bearing faults.
Dual-weight attention-based multi-source multi-stage alignment domain adaptation for industrial fault diagnosis
Authors: Wang Qi , Chen Qitong , Chen Liang , Shen Changqing
Published: May 2024

Cross-domain fault diagnosis is crucial for industrial applications with various and unknown operating conditions. However, due to the significant differences in the distribution of features in multiple source domains, it may lead to mutual interference of features between different domains and reduce the accuracy of diagnosis, which is a problem not considered by most current researches. In addition, most of the existing methods focus only on the extraction of low-frequency global information and cannot adequately deal with high-frequency local information. Consequently, this paper provides a multi-stage processing integrated dual-weight attention-based multi-source multi-stage aligned domain adaptation (DAMMADA) method. Global fault features that are shared by various subdomains are extracted by three domain-specific feature extractors from various domains. In a local feature extractor, the dual-weight attention module not only uses shared weights to aggregate local information, but it also uses contextual weights to improve local features. In terms of loss handling, multiple pseudo-labels are used to reduce the loss of the local maximum mean discrepancy in order to learn the domain-invariant characteristics after improving the high-frequency and low-frequency information extraction. To modify the classification boundaries, the pseudo-labels’ mean square errors are combined. Comprehensive experiments were carried out on two platforms for fault diagnosis of SCARA robots and bearings respectively, and the results demonstrated that DAMMADA is superior to other methods in terms of accuracy and its ability to suppress negative transfer for cross-domain tasks.
An enhanced meta-learning network with sensitivity penalty for cross-domain few-shot fault diagnosis
Authors: Mu Mingzhe , Jiang Hongkai , Jiang Wenxin , Dong Yutong , Wu Zhenghong
Published: May 2024

Big data-driven rotating machine intelligent diagnostic technology has gained widespread applications. In practice, however, fault data are limited as well as inconsistencies in fault categories among different domains are widespread. These make developing robust intelligent diagnostic models a challenge. To this end, this paper develops an enhanced meta-learning network with a sensitivity penalization mechanism (EMLN-SP) for few-shot fault diagnosis in severe domain bias. First, lightweight channel attention is introduced to establish an enhanced feature encoder under meta-learning framework, which elevates the key feature expression to facilitate the extraction of generalized diagnostic knowledge within limited samples. Second, a boundary-enhanced loss calculation method is designed, which boosts the focus for decision boundary information to prevent the model from the overfitting dilemma in the case of few-shot. Finally, a sensitivity penalty mechanism is constructed to adjust the optimization direction, which prevents the model from falling into a local optimum, to boost the generalization of the model performance. The effectiveness of EMLN-SP is validated by three cross-domain diagnostic cases with diverse domain offsets.
High-impact dynamic loading method for calibration of triaxial acceleration sensors
Authors: Wei Jian , Ma Shaojie , Shi Huifa
Published: May 2024

In this study, a high-impact dynamic loading device was designed to generate a three-dimensional pulse excitation signal with high intensity shock acceleration and achieve triaxial synchronous calibration of a triaxial acceleration sensor. A light-gas gun interior ballistic model and a sensor mechanical response model were developed, and the relationships between the bullet impact velocity, barrel length, and initial chamber pressure were obtained. Additionally, the transformation relationship of the sensor’s triaxial acceleration in different coordinate systems was derived. Based on the stress wave theory and the finite element method, the influence of the bullet impact velocity on the variation pulse, and different slope and deflection angles on the triaxial acceleration were analyzed. By optimizing the parameter design, machining the prototype, and conducting high-impact dynamic loading tests, the results showed that the deviation between theoretical and measured values of the generated triaxial acceleration signal was small, and the maximum deviation was less than 4%. This indicated that the proposed high-impact dynamic loading device satisfied the calibration requirements for calibrating triaxial acceleration sensors, which can generate a three-dimensional acceleration with a peak value of not less than 700 000 m s−2.
Mechanism of acoustic pressure spectrum shifting toward lower frequencies in applied current thermoacoustic imaging
Authors: Zhang Wenwei , Xia Hui , Li Xiaonan , Li Yuanyuan , Li Shiqiang , Liu Guoqiang
Published: May 2024

Objective. Thermoacoustic tomography (TAT) is a promising imaging technique used for early cancer diagnosis, tumor therapy, animal study and brain imaging. Although it is widely known that the TAT frequency response depends on the pulse width of the source and the size of the object, a thorough comprehension of the quantitative frequency modulation in TAT and the mechanism governing the shift in the thermoacoustic pressure spectrum towards lower frequencies with respect to the excitation source is still lacking. This study aims to understand why the acoustic pressure spectrum and the final voltage signals shift towards lower frequencies in TAT. Approach. We employed a linear time-invariant model. In the proposed model, the applied current thermoacoustic imaging (ACTAI) process is divided into the thermoacoustic stage and the acoustoelectric stage. These two stages are characterized by the thermoacoustic transfer function(TATF) and the transducer transfer function (TDTF), respectively. We confirmed the effectiveness of our model through a rigorous examination involving both simulations and experiments. Main results. Simulation results indicate that the TATF behaves as a low-pass filter. The inherent low-pass nature induces a shift towards low frequencies in the acoustic pressure spectrum. Experiments further confirm this behavior, demonstrating that the final electrical voltage also shifts towards low frequencies. Notably, employing the proposed model, there is a remarkable consistency between the main frequency bands of the synthesized and measured final voltage spectrum. Significance. The proposed model thoroughly explains how the TATF causes shifts to low frequencies in both the acoustic pressure spectrum and the final voltage spectrum in TAT. These insights deepen our understanding of optimizing TAT systems in the frequency domain, including aspects like filter design and transducer selection. Furthermore, we underscore the potential significance of this discovery for medical applications, particularly in the context of cancer diagnosis.
Effects of prepulse on hot electron emission from mesoscopic particles
Authors: Sabui Ratul , Kumar Rakesh , S V Rahul , Mondal Angana , Gopal Ram , Sharma Vandana , Krishnamurthy M
Published: May 2024

In this paper we make an attempt to study the effect of a nanosecond prepulse on electron acceleration from microscopic solid particles. While standard scaling laws predict temperatures of

∼

50

keV, our investigations showed an anomalous enhancement (

∼

200

keV) in electron temperatures from microscopic solids subjected to intense laser fields. Conventional isotropic expansion of the plasma target as a result of pre-pulse interaction is unable to explain the enhancement, prompting an experimental inquiry into the expansion form. Tentacle-like structures emerging from the spherical plasma are detected as an outcome of the pre-pulse interaction, with the region between the tentacles being targeted by the main laser pulse. We resort to PIC simulations to understand and predict the exact plasma condition that exists in this region. In this paper, we study a series of approximate pre-plasma conditions, particle shapes, and electron densities, examining them for their role in electron acceleration from this extended over-critical plasma target.
Generation of low-energy abundant electron energy probability functions using a magnetized plasma source
Authors: Lee Minkeun , Park Junbeom , Nam Jiseong , Kim June Young , Chung Kyoung-Jae
Published: May 2024

The generation of low-energy electrons is essential for the plasma source of the charge neutralizer system within the ion implanter process of semiconductors and displays, owing to their exceptional capability of being effectively transported along their ion beams. In this study, we propose a method to produce non-Maxwellian electron energy probability functions (eepfs) characterized by low-energy-abundant electrons, specifically below 5 eV, across an electron extraction system. In the electron transport region with an axial magnetic field under conditions of high discharge voltage and gas flow rate, we observed a significant increase in low-energy electrons in eepfs. The simple global model proposed to analyze these results demonstrated that the wall loss of electrons can be reduced by an elevated plasma potential, which is influenced by the ionization rate in the transport region. These results are consistent with the experimentally measured plasma potential and electron density. Additionally, the reduction in wall losses and increased ionization rate within the transport region resulted in the relaxation of the plasma potential gradient. This phenomenon effectively inhibited the cutting of low-energy electrons within the eepfs, thereby facilitating their consequential transport to the target. This study emphasizes the significance of increasing the ionization rate and minimizing the potential gradient for the dual purposes of generating low-energy electrons and directing them towards the target.
Investigation of the forward gate leakage current in pGaN/AlGaN/GaN HEMTs through TCAD simulations
Authors: Sarkar Arghyadeep
Published: May 2024

In this study, we examined the gate leakage characteristics of normally off pGaN/AlGaN/GaN HEMTs through a simulation study. The Fowler Nordheim Tunneling (FNT) mechanism mainly contributes to the gate leakage process as indicated by the Technology Computer-Aided Design (TCAD) simulation. However, at low bias, the FNT undercalculates the leakage current since the electric field is low in this region. This extra leakage current component at this low bias region can be attributed to the presence of surface traps. Trap-assisted tunneling current along with the FNT current can explain forward leakage characteristics of the pGaN HEMTs. Our TCAD simulations were matched with the experimental data for five devices from four different research groups to support this claim. Using TCAD simulations, we have been able to analyze several device parameters including the various potential drops inside the gate stack structure. We were able to identify some of the trap levels and compare them to the dominant defects expected to be present in the pGaN cap layer. Furthermore, we studied the effects of different device parameters on the gate leakage process in the pGaN HEMT.
The investigation of the energy harvesting performance using electrospun PTFE/PVDF based on a triboelectric assembly
Authors: White Pattarinee , Pankaew Piyapong , Bavykin Dmitry , Moshrefi-Torbati M , Beeby Stephen
Published: May 2024

This work presents an investigation into the energy harvesting performance of a combination of polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) materials prepared using a one-step electrospinning technique. Before electrospinning, different percentages of the 1 micron PTFE powder were added to a PVDF precursor. The surface morphology of the electrospun PTFE/PVDF fibre was investigated using a scanning electron microscope and tunnelling electron microscope. The structure was investigated using Fourier-transform infrared spectroscopy and x-ray diffraction analysis (XRD). A highly porous structure was observed with a mix of the α- and β-phase PVDF. The amount of β-phase was found to reduce when increasing the percentage of PTFE. The maximum amount of PTFE that could be added and still be successfully electrospun was 20%. This percentage showed the highest energy harvesting performance of the different PTFE/PVDF combinations. Electrospun fibres with different percentages of PTFE were deployed in a triboelectric energy harvester operating in the contact separation mode and the open circuit voltage and short circuit current were obtained at frequencies of 4–9 Hz. The 20% PTFE fibre showed 4 (51–202 V) and 7 times (1.3–9.04 µA) the voltage and current output respectively when compared with the 100% PVDF fibre. The V
oc and I
sc were measured for different load resistances from 1 kΩ to 6 GΩ and achieved a maximum power density of 348.5 mW m−2 with a 10 MΩ resistance. The energy stored in capacitors 0.1, 0.47, 1, and 10 µF from a book shaped PTFE/PVDF energy harvester were 1.0, 16.7, 41.2 and 136.8 µJ, respectively. The electrospun fibre is compatible with wearable and e-textile applications as it is breathable and flexible. The electrospun PTFE/PVDF was assembled into shoe insoles to demonstrate energy harvesting performance in a practical application.
Quantum tricriticality in a generalized quantum Rabi system
Authors: Lu You-Qi , Zhang Yu-Yu
Published: May 2024

Quantum tricriticality, a unique form of high-order criticality, is expected to exhibit fascinating features including unconventional critical exponents and universal scaling laws. However, a quantum tricritical point (QTCP) is much harder to access, and the corresponding phenomena at tricriticality have rarely been investigated. In this study, we explore a tricritical quantum Rabi model, which incorporates a non-trivial parameter to adjust the coupling ratio between a cavity and a three-level atom. The QTCP emerges at the intersection of first- and second-order superradiant phase transitions according to Landau theory. By using finite-frequency scaling analysis on quantum fluctuations and the average photon number, universal critical exponents differentiate the QTCP from the second-order critical point. Our results indicate that the phase transition at the tricritical point goes beyond the conventional second-order phase transition. Our work explores an interesting direction in the generalization of the well-known Rabi model for the study of higher-order critical points due to its high control and tunability.
LOCC convertibility of entangled states in infinite-dimensional systems
Authors: Massri César , Bellomo Guido , Freytes Hector , Giuntini Roberto , Sergioli Giuseppe , Bosyk Gustavo M
Published: May 2024

We advance on the conversion of bipartite quantum states via local operations and classical communication (LOCC) for infinite-dimensional systems. We introduce δ-LOCC convertibility based on the observation that any pure state can be approximated by a state with finite-support Schmidt coefficients. We show that δ-LOCC convertibility of bipartite states is fully characterized by a majorization relation between the sequences of squared Schmidt coefficients, providing a novel extension of Nielsen’s theorem for infinite-dimensional systems. Hence, our definition is equivalent to the one of ε-LOCC convertibility (Owari et al 2008 Quantum Inf. Comput.
8 0030), but deals with states having finitely supported sequences of Schmidt coefficients. Additionally, we discuss the notions of optimal common resource and optimal common product in this scenario. The optimal common product always exists, whereas the optimal common resource depends on the existence of a common resource. This highlights a distinction between the resource-theoretic aspects of finite versus infinite-dimensional systems. Our results rely on the order-theoretic properties of majorization for infinite sequences, applicable beyond the LOCC convertibility problem.
Lattice polaron in a Bose–Einstein condensate of hard-core bosons
Authors: Santiago-García Moroni , Castillo-López Shunashi G , Camacho-Guardian Arturo
Published: May 2024

Lattice polarons, quasiparticles arising from the interaction between an impurity and its surrounding bosonic environment confined to a lattice system, have emerged as a platform for generating complex few-body states, probing many-body phenomena, and addressing long-standing problems in physics. In this study, we employ a variational ansatz to investigate the quasiparticle and spectral properties of an impurity coupled to a condensate gas of hard-core bosons in a two-dimensional optical lattice. Our findings demonstrate that the polaron features can be tuned by adjusting the filling factor of the bath, revealing intriguing polaron characteristics in the strongly interacting regime. These results offer valuable insights for lattice polaron experiments with ultracold gases and can serve as a guide for new experiments in emergent quantum devices, such as moiré materials, where optical excitations can be described in terms of hard-core bosons.
Fusion and fission phenomena in a (2+1)-dimensional Sawada-Kotera type system
Authors: Wang Jianyong , Yang Yunqing , Tang Xiaoyan , Chen Yong
Published: May 2024

In this study, we extend the generalized multilinear variable separation approach to a fifth-order nonlinear evolution equation. By performing asymptotic analysis on the variable separation solution, which is composed of three lower-dimensional functions, we identify a resonant regime governing dromion-dromion/solitoff interactions. In the case of two-dromion interactions, elastic, inelastic, and completely inelastic collisions are possible, while for the dromion-solitoff interaction only inelastic and completely inelastic collisions are permitted. Furthermore, we derive two types of semi-rational solutions from the quadratic function ansatz. In particular, in the scenario of a completely resonant collision between a lump and a line-soliton pair, the lump separates from one line soliton and exists briefly before merging with the other soliton, forming a localized lump in both time and space dimensions. The fusion or fission phenomena between the dromion-dromion/solitoff interaction and the lump-line soliton interaction are shown graphically.
Improved dual-threshold quantum image segmentation algorithm and simulation*
Authors: Dong Yumin , Yan Rui , Mou Dingkang , Li Feifei
Published: May 2024

Quantum image segmentation algorithm is crucial for quantum image processing. In this paper, a dual-threshold quantum image segmentation algorithm is designed and simulated in IBM Quantum Experience (IBM Q) platform, which can segment a complex image into three parts using fewer quantum bits. In our algorithm, given a high threshold and a low threshold, grayscale values larger than the high threshold are set to the high threshold and grayscale values smaller than the low threshold are set to the low threshold, with no change for the part between the two thresholds. Then we use a low-cost quantum comparator and design a complete and scalable quantum image segmentation circuit. Analysis of the circuit cost shows that the quantum gates required for the circuit are only related to the grayscale range q and are independent of the image size. The feasibility of the algorithm and the correctness of the quantum circuit are verified by simulation in IBM Q platform, and finally the MSE, PSNR AND SSIM value of the image is analyzed to prove the effectiveness of the segmentation algorithm.
Tunable broadband absorption and broadband linear polarization converter based on vanadium dioxide
Authors: Niu Junhao , Hui Qiang , Mo Wei , Tian Renfang , Zhu Aijun
Published: May 2024

A composite dielectric metamaterial based on vanadium dioxide (VO2) is proposed to achieve flexible switching between two functions, broadband absorption, and polarization conversion, by adjusting the VO2 conductivity. The designed metamaterial functions as a broadband absorber when VO2 is in the metal phase. The absorber consists of a VO2 top structure, a silicon dioxide (SiO2) dielectric layer, and a VO2 thin film. Numerical simulation ns show that the absorber can absorb up to more than 90% in the frequency range of 3.22 ∼ 8.51 THz, and due to the symmetry of the structure, the absorber is characterized by polarization-insensitive properties and good absorption over a wider incidence angle. When VO2 is in the insulator phase, the designed metamaterial has a cross-polarization conversion function. The linear polarization converter primarily comprises an I-beam metal, a SiO2 dielectric layer, and a gold substrate layer. Numerical simulations demonstrate that the linear polarization converter accomplishes a line polarization conversion rate (PCR) greater than 90% within the 1.40 ∼ 4.11 THz frequency range, attains a close to 100% cross-polarization conversion rate (PCR) at 1.46, 1.95, 3.0, and 3.97 THz. To confirm the wave absorption mechanism of the absorber, we utilize the impedance matching theory to analyze it. The proposed switchable bifunctional metamaterials present significant potential for broader applications in future terahertz communication, imaging, stealth technology, and related fields.
Robustness analysis and prediction of topological edge states in topological elastic waveguides
Authors: Tong Shiqi , Sun Wenjun , Xu Jiawen , Li Huijun
Published: May 2024

Topological elastic waveguides constructed using acoustic topological insulators have garnered significant attention due to their exceptional wave modulation properties. While the existence of these edge states is guaranteed by topology, their robustness to defects is unclear. In this paper, topological edge states based on the acoustic pseudo-spin Hall effect are constructed, and the robustness of the topological edge states is quantitatively studied by analyzing displacement fields of phononic crystal (PnC) plates with various defects. Our robustness assessment considers nearly all possible defect scenarios, focusing on the influence of defects on three primary indicators: transmittance, maximum displacement and its specific location on the PnC plate. The results indicate that the topological edge states formed by this structure are highly robust to defects with varying rotation angles, but exhibit limited robustness to defects of different dimensions or positions. Furthermore, a Light Gradient Boosting Machine (LightGBM) model is employed to predict the displacement along the wave transmission path in the presence of diverse lattice defects. The model emerges as an accurate predictor of displacement distribution changes, and thus can provide potential optimization strategies for topologically elastic waveguide-based energy harvesting systems and self-powered sensors.
Graphene oxide microstrip antenna-based sensor for oxygen gas sensing in medical applications
Authors: do Carmo Felipe Felix , Sales Antonio Jefferson Mangueira , Nascimento João Paulo Costa do , da Costa Júnior Antonio Eufrazio , da Silva Clemente Claudenilson , Mazzetto Selma Elaine , Maia Saulo Macedo , Frutuoso Rômulo Lopes , da Silveira Cavalcante Tarique , Cavalcante Cleidson , Vieira Júlio Daniel Siqueira , Buffalo Biz Jose Alvaro , Ribeiro de Carvalho Carlos Roberto , Sombra Antonio Sergio Bezerra
Published: May 2024

In this work, we report the development of a new graphene oxide (GO) sensor based on a microstrip antenna for detecting and measuring O2 concentration. GO was prepared from natural graphite powder using a modified Hummers procedure and then deposited upon a phenolic substrate to act as the sensing element of the designed device. Detection tests employing the sensor to evaluate oxygen gas (O2) in higher concentrations were performed, whereas it was observed that the two operating frequencies of the device was displaced to higher values as the concentration oxygen gas increased. The effect of relative humidity (RH) in the response sensor too was observed, whereas the 9.704 GHz mode demonstrating to be the most sensitive to O2 variation after sensitivity values have been corrected, presenting limit of detection (LOD) equal to 0.38%O2. Evaluating the results, it is possible to note that the device studied could be used as sensor in medical equipment operating at elevated oxygen concentrations, such as ventilators, O2 concentrators, and other medical equipment. Moreover, evaluated sensor would be a promisor candidate for healthcare monitoring applications for the reason that this device could act as both an O2 sensor and antenna, and thus transmitting their information to other devices.
Experimental study on effect of deformation temperature on mechanical and biological activities of Ti-6Al-7Nb titanium alloy
Authors: Munisamy Raju , Rajendran Ramadoss
Published: May 2024

Titanium alloy plays a crucial role in biomedical applications, particularly in the field of medical implants. One of the most significant advantages of titanium alloy is its excellent biocompatibility. Eventhough, it offered excellent behaviour, at elevated temperature, titanium alloys may experience softening, which limits their application in environment with higher operating temperatures. In this investigation, hot tensile and biological behaviour of the Ti-6Al-7Nb under different operating temperatures (300 °C, 400 °C, 500 °C and 600 °C) is studied. The biological behaviour of the deformed Ti-6Al-7Nb titanium alloy treated with simulated body fluid is studied. The microstructure and phase transformation of deformed titanium alloy is evaluated using scanning electron microscope (SEM) and x-ray diffraction (XRD) respectively. It was revealed that at temperature of 600 °C, the mobility of molecules at the interface between the solid and liquid phases increases. This enhanced mobility can lead to better wetting of the solid surface by the liquid, resulting in a decrease in the contact angle. The elevated temperature facilitates improved grain development, recrystallization and mobility. The coarser grains could result from deformation at temperature higher than 600 °C. It was concluded that the Ti-6Al-7Nb titanium alloy deformed with 600 °C showed the improvement in contact angle of 42 ± 2° and biocompatibility.
Numerical simulation of fractional-order Duffing system with extended Mittag-Leffler derivatives
Authors: Odibat Zaid
Published: May 2024

In this paper, we studied the dynamics of a nonlinear fractional-order Duffing system combined with Mittag-Leffler derivatives in order to provide dynamic behaviors different from existing ones. The Mittag-Leffler derivative is a generalized version of the exponential kernel derivative. To achieve this goal, we introduced a modified extension to higher-order Mittag-Leffler derivatives to overcome the initialization problem. Moreover, we discussed some properties and relationships of the studied derivatives. Then we presented numerical schemes to handle fractional extensions of the considered oscillatory system including the Mittag-Leffler and the Caputo derivatives. Numerical simulations are carried out and the resulting simulation dynamics of the studied fractional oscillatory system are compared.