bluuebunny/crossref_metadata_2025 huggingface dataset:
An extension of the 16th Hilbert problem for continuous piecewise linear–quadratic centers separated by a non-regular line
Authors: Esteban M. , Llibre J. , Valls C.
Published: December 2023

In the last few decades, there has been much interest in studying piecewise differential systems. This is mainly due to the fact that these differential systems allow us to modelize many natural phenomena. In order to describe the dynamics of a differential system, we need to control its periodic orbits and, especially, its limit cycles. In particular, providing an upper bound for the maximum number of limit cycles that such differential systems can exhibit would be desirable, that is solving the extended 16th Hilbert problem. In general, this is an unsolved problem. In this paper, we give an upper bound for the maximum number of limit cycles that a class of continuous piecewise differential systems formed by an arbitrary linear center and an arbitrary quadratic center separated by a non-regular line can exhibit. So for this class of continuous piecewise differential systems, we have solved the extended 16th Hilbert problem, and the upper bound found is seven. The question whether this upper bound is sharp remains open.
Hydrogen-bond network in an equimolar acetic acid–water mixture as studied by neutron scattering and density functional theory
Authors: Trabelsi Sahbi , Tlili Mouadh , Hammami Férid , Nasr Salah , Bellissent-Funel Marie-Claire , Darpentigny Jacques
Published: December 2023

The present study explores the hydrogen-bond network in an equimolar mixture of acetic acid and water (AA–W). The investigation was conducted using a combination of neutron scattering and Density Functional Theory (DFT). New neutron scattering data at large scattering wave vectors were analyzed to determine the total structure factor SM(q) and the molecular form factor F1(q) of the system. DFT calculations using the 6-311++G(d, p) basis set were performed to optimize the monomers and various AA–W H-bonded clusters, including one acetic acid (AA) molecule connected to one, two, and three water molecules. Consequently, three dimers, three trimers, and one tetramer have been considered in order to describe the local order in the mixture. In addition, this study focused on the H-bond interactions in the most probable clusters in the solution, using the natural bond orbital and the atoms in molecules analyses. Our analysis particularly shows that stronger H-bond interactions occur in the ring structures.
A study of gas transport mechanisms in shale's confined nanopores: Examining irregularity, adsorption effects, and stresses
Authors: Ding Yunna , Li Bobo , Li Jianhua , Duan Shulei , Song Haosheng , Zeng Xingyi
Published: December 2023

Many difficulties and challenges have been encountered during the exploration and development of shale gas, among which high flexibility of the reservoir structure and low permeability have been the most notable problems that have restricted the efficient development of shale gas. In this paper, we have developed a fractal apparent permeability model for shale based on fractal theory that has taken into account the confinement effects. Also considering the effect of pore deformation on porosity, the defining equation of pore size under the combined effect of multiple factors is obtained, which, in turn, leads to the defining equation of dynamic fractal dimension. Due to the significant confinement effect due to the development of nanopores in shale reservoirs, the Peng–Robinson equation of state is modified using the adsorption effect, and the influence of the confinement effect on the critical properties and each permeability parameter is considered. Based on this, a shale fractal apparent permeability model coupled with slip flow, Knudsen diffusion, and surface diffusion was developed, and the model was validated with experimental data. The results revealed that the developed model was in relatively better agreement with the measured data. Furthermore, the confinement effect performed a positive role in shale's apparent permeability, with the calculated values of model permeability that considered the confinement effect was greater than the calculated values of model permeability, without the confinement effects being considered.
Stall and stability enhancement mechanisms of transonic compressor with inlet total temperature distortion
Authors: Qiu Jia-Hui , Zhao Hong-Liang , Du Juan , Zhang Min , Zhang Wen-Qiang , Fan Zhong-Gang
Published: December 2023

Inlet total temperature distortion refers to the nonuniform distribution of the total temperature at the inlet of the aero-engine, which is one of the external destabilizing factors that have the most remarkable impact on the stability of an aero-engine. In this study, the stalling process of the Darmstadt transonic compressor is investigated under the total temperature distortion of 180 deg circumferential extent and 500 K intensity by full-annulus unsteady numerical simulation. The analysis shows the addition of inlet total temperature distortion deteriorates the compressor stall margin from 22.7% to 17.0% with a considerable decrease in the pressure ratio. The type of compressor stall inception under temperature distortion conditions remains spike. Pressure perturbations and radial vortex formation are first clearly detected when the rotor rotates into the high temperature distortion region. The circumferential propagation of the stall cells under the total temperature distortion is 66% of the rotor speed, which is faster than that under uniform condition whose value is 44% of the rotor speed. The optimized casing treatment (CT) has extended the stall margin of the rotor without producing efficiency loss under uniform condition. The anti-distortion ability of CT is first verified despite its negative impact on efficiency under total temperature distortion. The adoption of CT could obviously push the shock wave into the blade passage under total temperature distortion condition. In addition, it can reduce the tip blade loading, thus removing the low Mach number area in the tip region, while increasing the blade loading below 80% span.
A novel fabrication of microfluidic device for generation of multiple emulsions
Authors: Khalilnezhad Ali , Sahraei Eghbal , Cortes Farid B. , Riazi Masoud
Published: December 2023

Due to extensive applications of microfluidic devices, manufacturing of these apparatus has recently been noticed. Production of multiple emulsions is one of the main goals of manufacturing microfluidic devices. Design and fabrication of microfluidics are functions of the size of emulsion droplets, properties of fluids applied for emulsification, and considered stability for emulsions. In this article, we have manufactured a novel microfluidic device using simple fabrication and accessible materials. Capillary tubes, PTFE (polytetrafluoroethylene) chassis, a medical needle of gauge 32, and O-rings are the primary materials used to produce this device. The production procedure is explained completely, and all the drawings are represented. Concerning probable interactions between glues and flowing fluids, we tried to fabricate and seal the device without applying chemical agents. The device is tested by n-heptane and deionized water to produce multiple water-in-oil-in-water (W/O/W) emulsions. A sensitivity analysis on the rate of injection is performed. Considering the HLB (hydrophilic–lipophilic balance) as an important property of emulsifiers, the effects of two different types of emulsifiers (sodium dodecyl sulfate with HLB of 40 and glycerol monostearate with HLB of 3.8) at various concentrations are investigated. Due to the results, the injection rate of the mediate phase should be less than half of the outer phase for the formation of emulsions. Consequently, the rate of injection for the inner phase should be less than half of that for the mediate phase. The simplicity of production and accessible raw materials could be considered as the strengths of our microfluidic device.
Local probing of eddy current correlated with magnetic properties
Authors: Kang Jinho , Sun Changhyo , Kim Jungi , You Jinyoung , Jang Min-Sun , Jeong Jae Won , Heo Yooun , Kim Yunseok
Published: December 2023

Recently, the development of long-range electric vehicles with effective electric motors has drawn considerable attention. The key to achieving such electric vehicles development is power saving, which has served as an essential motive for development of new magnetic materials. In this regard, further improvement of magnetic materials requires deep insight into the existence of eddy currents, which are primary contributors toward power loss in practical applications. Therefore, exploring the key effects of eddy currents on overall magnetic properties is essential. Here, we demonstrate clearly distinguished eddy current distributions being influenced by local magnetic properties via multidimensional magnetic force microscopy. Using our model systems, we explored the key role of an insulation layer and magnetic domains on eddy current dependent magnetic properties. In particular, we visualized the correlation between the eddy current and magnetic domain/domain wall. Therefore, our approach provides detailed characterization of eddy current, particularly related to the underlying contributions of local magnetic properties, offering crucial insights for improvement of electric motors.
Analytical model for the power production of a yaw-misaligned wind turbine
Authors: Lu Jianfeng , Li Chao , Li Xiang , Liu Haoyang , Zhang Gengsheng , Liu Nansheng , Liu Luoqin
Published: December 2023

Wake steering has proven to be effective in enhancing the power output of a wind farm. However, this approach still highly relies on empirical formulas to predict the power production of yawed turbines, limiting its potential in practical applications. In this study, an analytical model is proposed to predict the power production of a yaw-misaligned turbine under uniform inflow conditions. The model is based on the combination of the blade element theory and the momentum theory, with a modification in the latter to account for the disturbance on the spanwise velocity caused by the yawed turbine. A series of large eddy simulations were performed using a utility-scale wind turbine operating at yaw angles |γ|≤30° and tip-speed ratios λ=5–8. The validity of the proposed model is confirmed by the good agreement between the theoretical predictions and the simulation data. Furthermore, the well-known cosine model is shown to describe well the power production of the yawed turbine within the studied parameter range. However, the power-yaw loss exponent is not a constant, but rather a function of the tip-speed ratio. These findings may be useful in yaw optimization and control strategies in wind farms.
Half-valley semimetal and largest inverse topological caloric effect at topological quantum criticality in the chiral-symmetric AIII class
Authors: Ding Linjie , Zhong Yuan
Published: December 2023

Half-valley semimetal (HVSM) and single-valley states are the hallmark of valleytronics in two-dimensional honeycomb lattice materials, but their quasi-one-dimensional analog that takes advantage of quantum manipulation has not yet been realized. We propose a double-helical ladder model described by a coupled double Su–Schrieffer–Heeger chain, wherein the interchain coupling controlled by magnetic flux induces time-reversal and particle-hole symmetry breaking and preserves only the chiral symmetry, which is classified into the AIII symmetry class. It realizes valley polarization, single-valley topological insulator, and HVSM as the topological quantum criticality (TQC), signaling well valley filter or valve effects. Furthermore, the TQC produces the largest inverse topological caloric effect accompanied by a T-linear relation of isothermal entropy change at ultra-low temperatures. Our findings not only open alternative perspectives for multifunctional quantum devices in valleytronics but also shed light on the thermodynamic characterization of TQC and promote the rapid development of topological quantum refrigeration technology.
Magnetic field-enhanced orifice traversal of droplets: Minimizing surface adhesion for improved efficiency
Authors: Wang Ya-Ping , Zhou Jin-Xiang , Li Jia-Qing , Khan Adnan , Niu Xiao-Dong , Chen Mu-Feng , Yang Liming
Published: December 2023

In this article, we propose the feasibility of replacing traditional materials with ferrofluid droplets to actively regulate their behavior as they traverse an orifice in the presence of an external magnetic field. The traversal behavior of the droplet is investigated using both rectangular and curved orifice boundaries. We employed a simplified multiphase lattice Boltzmann method (SMLBM) to simulate the flow field and interface, which considerably improves computational efficiency. For magnetic field generation, a self-correction procedure is coupled with SMLBM. For curved boundaries, we used our recently developed immersed boundary approach, which can specify wetting boundary conditions for both stationary and moving boundaries, in the same way as flat boundaries are handled. To check the validity of our methods, we first simulated three benchmark phenomena and compared our results with experimental and numerical findings. This research includes orifice geometries, including straight and curved boundaries, and investigates the dynamic behavior of droplets traversing through narrow opening, increased orifice thicknesses, and large diameter droplets passing through confined and multiple orifices. All simulations are initially carried out without the use of magnetic fields, then the experiments are repeated and compared with the addition of a uniform magnetic field. It is found that, in the absence of a magnetic field, the droplets can successfully pass only through wide orifices. However, for narrow or thick orifices, a significant portion of droplet volume adheres to the orifice walls, causing an apparent decrease in falling velocity. In contrast, the addition of a magnetic field enables the droplet to efficiently traverse through even narrower and thicker orifices, attaining faster speeds and reduced mass loss. Furthermore, the influence of Reynold number and magnetic field strengths on the droplet velocity, its wetting dynamics, and relative shedding area are also discussed in detail.
Non-axisymmetric modes in ultrathin annular liquid films coating a cylindrical fiber
Authors: Moreno-Boza D. , Sevilla A.
Published: December 2023

This paper presents a detailed analysis of the three-dimensional stability properties of an annular liquid film coating a cylindrical fiber in the presence of van der Waals (vdW) interactions, whose influence depends on the wettability of the solid by the liquid. Under wetting conditions, vdW interactions can stabilize a uniform annular film when its thickness is smaller than a critical value that depends only on the fiber radius, the Hamaker constant, and the surface tension coefficient [Quéré et al., Science 249(4974), 1256–1260 (1990)]. In contrast, under non-wetting conditions, both surface tension and vdW forces contribute to destabilize the interface, and non-axisymmetric modes may become dominant depending on the thickness of the film and the relative strength of the surface tension and vdW forces. We perform temporal stability analyses of both the Stokes and lubrication equations of motion, allowing us to reveal the dominant azimuthal mode, as well as the optimal axial wavenumber and the corresponding temporal growth rate, as a function of the relevant governing parameters.
Numerical simulation of supersonic sea-skimming flight based on discontinuous Galerkin method with adaptive mesh refinement framework
Authors: Kong Qi , Liu Yun-Long , Ma Shan , Zhang A-Man
Published: December 2023

The multi-medium fluid flow around a supersonic sea-skimming flight is featured by the detached/attached shock wave, separation shock wave, and the reflected wave from the free surface. The complex wave structure and high nonlinearity pose a great challenge in accurate and stable numerical simulation. In this paper, a numerical model based on the high-order Runge–Kutta discontinuous Galerkin method is established to resolve the above problem. Based on the fact that the dimensionless vertical velocity is small, the air–water interface is linearized and a modified flux scheme is proposed to simplify the treatment of the multi-medium problem. A block-based adaptive mesh refinement scheme is adopted to capture the complex wave structure with the new nodes projected on the curved boundary. Finally, the numerical simulation of supersonic sea-skimming flight of the National Advisory Committee for Aeronautics 0012 airfoil is carried out by using the above-mentioned simplified numerical model based on the scheme of partition solution. The results show that the model can perform high-resolution simulations for the shock wave structure in various scenes. Meanwhile, the Mach number and distance between the airfoil and free surface are important factors affecting the structural characteristics of the shock wave systems and the airfoil loading characteristics. When the reflected shock wave acts on the airfoil's lower boundary, there will be a positive moment effect to make the airfoil dive, and the occurrence of this dangerous scene should be avoided. The relevant conclusions obtained can provide a reference for further research and engineering design.
Acoustic far field of a propeller working in the wake of a hydrofoil
Authors: Posa A. , Felli M. , Broglia R.
Published: December 2023

The Ffowcs-Williams & Hawkings (FWH) acoustic analogy is adopted to reconstruct the acoustic far field of a system consisting of an upstream hydrofoil and a downstream propeller, considering the former at incidence angles of 0°, 10°, and 20°. Also comparisons against the same propeller working in isolated conditions are reported. Fluid dynamic data from earlier high-fidelity, Large-Eddy Simulations (LES) on a grid consisting of 1.7 × 109 points are utilized. The analysis demonstrates that, with some exceptions at the smallest frequencies, the acoustic far field is dominated by the loading sound coming from the propeller, achieving its highest values of acoustic pressure in the upstream and downstream directions. In contrast, the lowest values occur on the propeller plane, whose minima are aligned with the spanwise direction of the hydrofoil. A strong dependence on the incidence angle of the hydrofoil is found, although decreasing toward higher frequencies. Interestingly, while at the shaft and at the blade frequencies the acoustic pressure coming from the hydrofoil-propeller system is always higher than that from the open-water propeller working alone, as expected, at higher harmonics of the blade frequency this is not the case. This may be due to phenomena of destructive interactions across the acoustic sources on the surface of the propeller or the result of a shift of the acoustic signature toward even higher frequencies, beyond the range covered by the database available to the present study.
Propagation of magnetogasdynamics spherical shock wave in a gravitating gas with radiation heat flux
Authors: Vats Vidit Kumar , Singh Dheerendra Bahadur , Amin Danish
Published: December 2023

This article presents a mathematical model for characterizing the dynamic behavior of spherical shock waves in a self-gravitating, radiating ideal gas with the presence of an azimuthal magnetic field, emphasizing adiabatic conditions. The analysis assumes that the environment just ahead of the shock wave is stationary, and it accounts for variations in density, magnetic field, and fluid velocity within the disturbed medium just behind the shock front. Furthermore, the impact of thermal radiation within the context of an optically thin limit is incorporated into the energy equation of the governing system. Employing the Lie invariance method, the set of partial differential equations governing the flow within this medium is transformed into a system of nonlinear ordinary differential equations through the use of similarity variables. Four distinct cases of similarity solutions are derived by selecting different values for the arbitrary constants associated with the generators. Among these four cases, only two yield similarity solutions, one assuming a power-law shock path and the other an exponential-law shock path. In the case of a power-law shock path, the resulting set of nonlinear ordinary differential equations is numerically solved using the 4th-order Runge-Kutta method in MATLAB software. The article thoroughly discusses the influence of various parameters, including γ (adiabatic index of the gas), Ma−2 (Alfvén–Mach number), ϕ (ambient density exponent), and G0 (gravitational parameter), on the flow properties. The findings are presented graphically to provide a comprehensive understanding of the effects of these parameters.
Wideband tunable absorber breaking the trade-off between absorption efficiency and tuning range
Authors: Zhao Wenbo , Fan Chenxi , Zhao Junming , Jiang Tian , Chen Ke , Feng Yijun
Published: December 2023

Tunable absorbers have attracted much attention due to their smart control of electromagnetic wave absorption. Despite much effort to enhance their performance, the absorption performance remains restricted by the conflict between absorption efficiency and tuning range. In this study, a wideband tunable absorber breaking the trade-off between the absorption efficiency and the tuning range is presented and investigated. First, an improved frequency-dependent resistance model is proposed and analyzed, in which the real part of input impedance varies with frequency. Subsequently, based on the frequency-dependent resistance circuit, a frequency tunable absorber (FTA) with a wide frequency tuning range is constructed by loading voltage-controlled varactors, which exhibits wide tuning bandwidth from 0.613 to 1.816 GHz with reflection coefficients below −10 dB. Additionally, by changing the location of varactor, a varactor-controlled amplitude tunable absorber (ATA) is further explored and designed. The prototypes of FTA and ATA are fabricated and measured, respectively, and good agreements between the simulated and measured results are observed.
Planar memristor and artificial synaptic simulating based on two-dimensional layered tungsten oxychloride WO2Cl2
Authors: Zhou Shuang , Xing Yu , Xu Qingxu , Yan Qingyu , Liu Ping , Wei Lujun , Niu Wei , Li Feng , You Lu , Pu Yong
Published: December 2023

Two-dimensional van der Waals ferroelectrics with in-plane polarization are less vulnerable to the depolarization field effect, making them practically more favorable in device applications. Herein, symmetric planar memristor based on two-dimensional van der Waals WO2Cl2 was fabricated and electrically characterized, showing significant memory effect with a current ON/OFF ratio up to 104 and stable switching cycles. Both short-term plasticity and long-term potentiation were observed in synaptic simulations by applying consecutive positive and negative pulses, respectively, which demonstrates the potential capability of this WO2Cl2 memristor in neuro-morphic computing as an artificial synapse.
Δ-based composite models for calculating x-ray absorption and emission energies
Authors: Zamani Abdulrahman Y. , Hratchian Hrant P.
Published: December 2023

A practical ab initio composite method for modeling x-ray absorption and non-resonant x-ray emission is presented. Vertical K-edge excitation and emission energies are obtained from core-electron binding energies calculated with spin-projected ΔHF/ΔMP and outer-core ionization potentials/electron affinities calculated with electron propagator theory. An assessment of the combined methodologies against experiment is performed for a set of small molecules containing second-row elements.
Deformation dynamics of rear concave droplet enclosed by nanoparticle surfactants in a capillary
Authors: He Long , Wang Saipin , Yuan Yuejin
Published: December 2023

In oil reservoirs with high water-cut, residual oil droplets are dominant and noticeable rear concave deformed when mobilizing in capillaries. The “solid-like” interface was exhibited by nanoparticle surfactants (NPSs) adsorbed in nanoparticles flooding. Related specific interfaces (i.e., phospholipid bilayer and nanoparticles adsorbed interface) have demonstrated their influences on droplet dynamics, e.g., elastic modulus related breathing, and Marangoni stress induced deformation. However, the constitutive mechanical characteristics of the NPSs adsorbed interface still differ from them, resulting in that the deformation dynamics of rear concave droplets enclosed by NPSs is not fully understood. A Neo-Hookean model was employed to simulate the elastic interface adsorbed by NPSs. The effects of the elastic interface on the droplet deformation dynamics were examined on three typical rear concave droplets. The results indicate that the elastic interface exerts a great inhibitory effect on the rear concave droplet deformation: for droplets with rear jet penetration, the inhibitory effect is only significant at droplet tail; for droplets with shear-induced tail breakup, the inhibitory effect appears both at droplet tail and head; and for droplets with steady rear concave, only droplet head deformation is inhibited. As viscosity ratio increased, the inhibitory effect of elastic interface on droplet deformation shifts from droplets tail to head. These findings significantly contribute to our understanding of droplet deformation dynamics within reservoir pores and hold great importance for optimizing nanoparticles flooding processes.
Self-interaction correction schemes for non-collinear spin-density-functional theory
Authors: Tancogne-Dejean Nicolas , Lüders Martin , Ullrich Carsten A.
Published: December 2023

We extend some of the well-established self-interaction correction (SIC) schemes of density-functional theory—the Perdew–Zunger SIC and the average-density SIC—to the case of systems with noncollinear magnetism. Our proposed SIC schemes are tested on a set of molecules and metallic clusters in combination with the widely used local spin-density approximation. As expected from the collinear SIC, we show that the averaged-density SIC works well for improving ionization energies but fails to improve more subtle quantities like the dipole moments of polar molecules. We investigate the exchange-correlation magnetic field produced by our extension of the Perdew–Zunger SIC, showing that it is not aligned with the local total magnetization, thus producing an exchange-correlation torque.
Cavitation cloud of waterjet under double excitation
Authors: Cai Tengfei , Wang Zibin , Chamorro Leonardo P. , Zheng Lifang , Ma Fei
Published: December 2023

This study experimentally explores the interplay of active and passive excitation on double-excited cavitating waterjet clouds. High-speed imaging and high-frequency pressure sensors are used to characterize the impact of piezoelectric transducers for active excitation and nozzle lip geometries for strong, moderate, and weak passive excitation conditions. The analysis of pressure fluctuations revealed that under active excitation, the waterjet exhibited forced oscillations characterized by an amplitude amplification exceeding that of single passive excitation by an order of magnitude. High-speed imaging, combined with proper orthogonal decomposition, allowed us to observe an expansion in the volume, size, and effective standoff distance of cavitation clouds upon introducing active excitation across all passive excitation scenarios. The synergy between strong passive excitation and harmonized frequency with active excitation resulted in the most robust cavitation cloud development, characterized by the highest intensity.
Evolution of interfacial mechanics of lung surfactant mimics progression of acute respiratory distress syndrome
Authors: Ciutara Clara O. , Iasella Steven V. , Huang Boxun , Barman Sourav , Zasadzinski Joseph A.
Published: December 2023

How acute respiratory distress syndrome progresses from underlying disease or trauma is poorly understood, and there are no generally accepted treatments resulting in a 40% mortality rate. However, during the inflammation that accompanies this disease, the phospholipase A
2
concentration increases in the alveolar fluids leading to the hydrolysis of bacterial, viral, and lung surfactant phospholipids into soluble lysolipids. We show that if the lysolipid concentration in the subphase reaches or exceeds its critical micelle concentration, the surface tension, γ, of dipalmitoyl phosphatidylcholine (DPPC) or Curosurf monolayers increases and the dilatational modulus,

E

∗

ω

, decreases to that of a pure lysolipid interface. This is consistent with DPPC being solubilized in lysolipid micelles and being replaced by lysolipid at the interface. These changes lead to

2

E

∗

-
γ
<
0
,

which is the criterion for the Laplace instability that can lead to mechanical instabilities during lung inflation, potentially causing alveolar collapse. These findings provide a mechanism behind the alveolar collapse and uneven lung inflation during ARDS.
Antigen exposure reshapes chromatin architecture in central memory CD8+T cells and imprints enhanced recall capacity
Authors: Zhu Shaoqi , Liu Jia , Patel Vanita , Zhao Xiuyi , Peng Weiqun , Xue Hai-Hui
Published: December 2023

CD62L+central memory CD8+T (TCM) cells provide enhanced protection than naive cells; however, the underlying mechanism, especially the contribution of higher-order genomic organization, remains unclear. Systematic Hi-C analyses reveal that antigen-experienced CD8+T cells undergo extensive rewiring of chromatin interactions (ChrInt), with TCMcells harboring specific interaction hubs compared with naive CD8+T cells, as observed at cytotoxic effector genes such asIfngandTbx21. TCMcells also acquire de novo CTCF (CCCTC-binding factor) binding sites, which are not only strongly associated with TCM-specific hubs but also linked to increased activities of local gene promoters and enhancers. Specific ablation of CTCF in TCMcells impairs rapid induction of genes in cytotoxic program, energy supplies, transcription, and translation by recall stimulation. Therefore, acquisition of CTCF binding and ChrInt hubs by TCMcells serves as a chromatin architectural basis for their transcriptomic dynamics in primary response and for imprinting the code of “recall readiness” against secondary challenge.
Conceptualizing achromaticity
Authors: Hatakka Veera
Published: December 2023

The word for grey has been studied in different languages as part of the definition of basic colour terms, and in
historical linguistics some studies have addressed grey as their main focus. The Finnish basic colour term harmaa
(‘grey’) has been addressed before in data from early to mid-twentieth century and as a basic colour term, but in contemporary language
harmaa has not been analysed with corpus methods before. This study presents the semantics of
harmaa in written communicational use of language, internet conversation, in the framework of Cognitive
Grammar and access semantics, using qualitative corpus analysis. The study results show that the shade or set of shades that
harmaa profiles in different contexts vary, and surface textures, mood, or evaluative aspects can also be
profiled. However, more studies are needed to reveal the semantics of harmaa in different interactional
situations.
Crystallite growth limits in amorphous oxides
Authors: Linker Seth , Ausbeck Christopher , DeSalvo Riccardo , Granata Veronica , Larsen Brecken , LeBohec Tugdual , Liu Yangyang , Miller Akilah , Mondin Marina , Neilson Joshua , Themann Harry
Published: December 2023

Post deposition thermal annealing of amorphous coatings improves optical properties of dielectric mirrors. However, excessive temperatures cause crystallization, resulting in a degradation of mechanical and optical properties. Therefore, annealing is limited to temperatures ‘below’ the crystallization threshold. The threshold is determined by x-ray diffraction (XRD) measurement which requires a significant amount of crystallized material for detection, yet it has been shown that a population of crystallites may exist in otherwise amorphous coatings below the threshold temperature. In this study XRD measurements show crystallites that grow during annealing within amorphous oxide coatings to a limited and predictable size predicated on the difference in density between the crystal and the surrounding amorphous phase and the average material’s Young’s modulus. These crystallites may be the point-like, extremely weak scatterers revealed in the LIGO test masses when imaged off-axis.
Determining a parabolic system by boundary observation of its non-negative solutions with biological applications
Authors: Liu Hongyu , Lo Catharine W K
Published: December 2023

In this paper, we consider the inverse problem of determining some coefficients within a coupled nonlinear parabolic system, through boundary observation of its non-negative solutions. In the physical setup, the non-negative solutions represent certain probability densities in different contexts. We innovate the successive linearisation method by further developing a high-order variation scheme which can both ensure the positivity of the solutions and effectively tackle the nonlinear inverse problem. This enables us to establish several novel unique identifiability results for the inverse problem in a rather general setup. For a theoretical perspective, our study addresses an important topic in partial differential equation (PDE) analysis on how to characterise the function spaces generated by the products of non-positive solutions of parabolic PDEs. As a typical and practically interesting application, we apply our general results to inverse problems for ecological population models, where the positive solutions signify the population densities.
Solution of the EEG inverse problem by random dipole sampling
Authors: Della Cioppa L , Tartaglione M , Pascarella A , Pitolli F
Published: December 2023

Electroencephalography (EEG) source imaging aims to reconstruct brain activity maps from the neuroelectric potential difference measured on the skull. To obtain the brain activity map, we need to solve an ill-posed and ill-conditioned inverse problem that requires regularization techniques to make the solution viable. When dealing with real-time applications, dimensionality reduction techniques can be used to reduce the computational load required to evaluate the numerical solution of the EEG inverse problem. To this end, in this paper we use the random dipole sampling method, in which a Monte Carlo technique is used to reduce the number of neural sources. This is equivalent to reducing the number of the unknowns in the inverse problem and can be seen as a first regularization step. Then, we solve the reduced EEG inverse problem with two popular inversion methods, the weighted Minimum Norm Estimate (wMNE) and the standardized LOw Resolution brain Electromagnetic TomogrAphy (sLORETA). The main result of this paper is the error estimates of the reconstructed activity map obtained with the randomized version of wMNE and sLORETA. Numerical experiments on synthetic EEG data demonstrate the effectiveness of the random dipole sampling method.
Wideband phased array design using hairpin ring resonator (HRR) and DGS for double band-notched performance
Authors: Qi Huanhuan , Liu Haiwen
Published: December 2023

In this paper, a wideband Vivaldi phased array with double band-notched performance for radio astronomy is proposed. To address the issues of radio frequency interference from 5 G mobile communication (4.8–5 GHz) and C-band satellite communication (5.9–6.5 GHz) in radio astronomy system, the hairpin ring resonator (HRR), defected ground structure and λ/2 shorted-circuit stub are utilized together to realize the double notched bands with different bandwidth. The resonate mechanism of the proposed HRR is widely investigated, which exhibits independent and controllable resonances. Meanwhile, λ/2 shorted-circuited stub is adopted for the band notched performance. As the current on the stub is induced along the shorted via to the ground, without participating in radiation, thus the notched frequency is not affected by the scan angle. With these novel and dedicated design, the proposed phased array performs double band-notched performance with high skirt selectivity and deep suppression, within the notched band the maximum rejection level is better than 22.7 dB. This is the first work to implement double notched bands in phased array to the authors’ best knowledge. Finally, a prototype composed of 8 × 9 elements is fabricated and measured. The measurements agree well with the simulated ones.
Ion flux measurements using a Mach-Langmuir probe in the ITER prototype neutral beam injection ion source
Authors: Zielke D , Wimmer C , Fantz U
Published: December 2023

Neutral beam injection systems as foreseen for ITER use radio-frequency (RF) ion sources at low pressure, where negative hydrogen ions are mainly produced via surface conversion of neutral atoms and positive ions at a plasma facing grid (PG). Up to now there is only limited knowledge about how fluxes and directed velocities of the positive ions are affected by external parameters such as power, pressure and the horizontal magnetic filter field which causes plasma drifts and vertical asymmetries in the vicinity of the PG. For this reason a combined Mach-Langmuir-probe diagnostic is used at multiple positions in the expansion and close to the extraction system in the prototype RF ion source (1/8 of the full ITER ion source size) to measure the positive ions directed velocity and flux as well as the plasma parameters simultaneously. With increasing RF power the flux towards the PG is found to increase linearly, its magnitude being controlled by the plasma density. Towards ITER-relevant pressures the ion flux decreases, in contrast to the directed velocity, which increases non-linearly, reaching around 5 km s−1 at a pressure of 0.3 Pa. The magnetic filter field is discovered to strongly bent down the ion flow in front of the PG. As a result, the ions at the lower half of the PG flow almost exclusively parallel to it, wherefore the flux which impinges onto the lower PG half is reduced by around one order of magnitude.
Field-view model for triboelectric nanogenerator motion superposition analysis
Authors: Zheng Hao , Yu Haiyang , Wu Cui , Wang Yunfei , Zhao Yiming , Wang Zhonglai
Published: December 2023

The precise value of the triboelectric nanogenerators’ (TENGs) energy output is hard to predict under coupled three-dimensional spatial motions in practical situations. In addition, motion monitoring based on TENGs in engineering applications requires in-depth support from basic theories. Herein, we introduce the applied field-view motion superposition output model (MSOM) of TENGs to address these challenges. Firstly, a comprehensive model for the field portrait and output prediction of the TENG with spatial motions based on basic physical and electrical theory is established through superposed motion decoupling. Secondly, a triboelectric signal spectrum model is provided to reveal the mechanisms of the TENG’s self-powered spatial motion frequency monitoring. The model validation experiments indicate a high degree of uniformity in practical measurements of the proposed MSOM model predictions. Likewise, the spectrum analysis of the TENG’s signals is verified to be an effective method for frequency monitoring and confirms a reliable observing error, which is less than 1.8%. When the TENG is equipped with three-dimensional motion traits, the MSOM model dramatically expands its physical theories for output prediction, conversion efficiency calculation, and motion monitoring.
An innovative and low-cost system for in situ and real-time cure monitoring using electrical impedancemetry for thermoset and CFRP laminate
Authors: Bao Huikangyue , Marguerès Philippe , Olivier Philippe
Published: December 2023

This paper is divided into five sections. The first one introduces the context of our study dealing with the monitoring of the cure of structural composites made of carbon fibers and thermoset matrix (CFRPs). The second one presents a brief state of the art. The third one deals with the materials characterized in this study, and the design and the production of a new bench dedicated to electrical impedance (EI) and thermal measurements. The fourth one compares the results obtained on CFRP and unreinforced matrix samples using conventional differential scanning calorimetry and EI measurements. A conclusion and some prospectives close the paper. In a recent previous work, we studied phases transitions in CFRP during their curing by EI showing that changes in the electrical complex impedance Z can easily be related to those of conventional parameters such as the thermoset matrix degree of cure (DOC) α. This work was carried out using a commercial single-channel impedance analyzer: HIOKI. In addition to its high acquisition cost, this device presented certain limitations in terms of measurement channels (only one) and data acquisition rate (60 s for a frequency sweep). These facts led us to develop a new EI measurement bench for monitoring the impedance changes in CFRP part for aeronautical applications (airframe structures). The innovative new multi-channel (8) bench we designed and manufactured is based on the Digilent PmodIA module (never used previously for this purpose) and an analog-front-end developed for EI measurements. It costs only 15% of the HIOKI analyzer and has a data acquisition rate 48 times higher (1,23 s versus 60 s). All this while maintaining an equivalent impedance measurement range: 100 mΩ to 1 MΩ. The proposed approach makes it possible not only to monitor the DOC α, but also to detect potential cure cycle issues. This latter demonstration was carried out on a new composite material (vacuum-bag oven-cured), NC66/1808NA (supplied by CTMI), which, to our knowledge, had never been characterized in the literature. Compared with preliminary results, similar behavior is obtained on two different CFRPs using two different benches. This clearly underlines the value and quality of the study. Experimental validation of our approach will contribute to CFRP structural health monitoring.
Vision-aided intelligent and adaptive vehicle pose estimation during GNSS outages
Authors: Xu Qimin , Tian Yuan , Ruan Guoxing , Chang Bin
Published: December 2023

In this paper, a novel multi-information fusion methodology is proposed for vehicle pose estimation. The purpose is to improve the pose estimation accuracy during global navigation satellite system (GNSS) outages, mainly from two aspects: (1) extra observations of accurate velocities and angular rates without cumulative errors; (2) adaptive and intelligent fusion. Firstly, a multidimensional motion perception network (MMPN) is designed in order to estimate the velocities and angular rates. At the same time, the motion state is also output. The inputs of the network are two consecutive images. Thus, the estimated velocities and angular rates are not affected by cumulative errors. Besides, because the corresponding velocities and angular rates measured by high-quality inertial measurement unit (IMU) with low noise and drift are used as the training samples, the accuracy of the estimated velocities and angular rates are guaranteed. Further, an unscented Kalman filter with federal structure (UKF-F) with different motion models is designed for pose estimation. The local filters of UKF-F use the current probabilities of belonging to the motion patterns output by the MMPN as the information-sharing factors. Thus, the fusion is adaptive to the actual vehicle motion state. In addition, a gate recurrent unit (GRU)-based error compensation module is introduced to further reduce the position errors during GNSS outages. The GRU-based module is trained offline with the input of MMPN and IMU observations. Due to the advantages of time series forecasting, the GRU-based module can accurately predict the position error of IMU/MMPN integration online. The KITTI dataset with different driving scenarios is used to confirm the feasibility of the proposed methodology. The results of the experiments verify that the proposed methodology can achieve precise vehicle pose estimation during GNSS outages.
BOF steelmaking endpoint carbon content and temperature soft sensor based on supervised dual-branch DBN
Authors: Lu Zongxu , Liu Hui , Chen Fugang , Li Heng , Xue XiaoJun
Published: December 2023

Accurate prediction of endpoint carbon content and temperature is critical in the basic oxygen furnace (BOF) steelmaking process. Although deep learning soft sensor approaches have the capacity to extract abstract features from high-dimensional nonlinear steelmaking data, they confront the challenge of a low correlation between acquired features and labels. This work presents a BOF steelmaking soft sensor model based on supervised dual-branch deep belief network (SD-DBN) to address this issue. The SD-DBN model incorporates label information into the feature extraction process and fuses crucial feature information to complete the feature extraction in order to extract features that are closely connected to the target variables. First, the supervised Restricted Boltzmann Machine (RBM) is improved by using a pruning strategy to extract features that are highly correlated with quality information, and then the autocorrelation key feature extraction module is spliced and fused to form a dual-branch feature extraction module to improve key information extraction. Second, stacking the supervised dual-branch RBM modules to build a deep feature extraction network enhances the deep extraction capabilities of data features. This deep network stacking not only increases the impact of essential target data in hierarchical training, but it also acquires characteristics associated with the target variables.
Irradiation-induced enhancement of Fe and Al magnetic polarizations in Fe60Al40 films
Authors: Smekhova A , Szyjka Th , La Torre E , Ollefs K , Eggert B , Cöster B , Wilhelm F , Bali R , Lindner J , Rogalev A , Többens D , Weschke E , Luo C , Chen K , Radu F , Schmitz-Antoniak C , Wende H
Published: December 2023

The rise of Fe magnetic moment, changes in Al electronic structure and a variation of Al magnetic polarization in thin films of transition metal aluminide Fe60Al40 have been probed through the order-disorder phase transition by soft x-ray absorption spectroscopy and x-ray resonant magnetic reflectivity in the extreme ultraviolet regime. In a course of the transition induced by 20 keV Ne+ irradiation with low fluences (∼1014 ions cm−2), x-ray magnetic circular dichroism spectra taken at the Fe L

2
,
3

absorption edges at room and low temperatures revealed a pronounced increase of Fe

3

d

states spin-polarization. X-ray resonant magnetic reflectivity applied to the Al L

2
,
3

and Fe M

2
,
3

edges allowed to detect the magnetic polarization of Al atoms in the films. The changes in Al electronic structure have been seen by alteration of Al K edge x-ray absorption near edge structure. A difference in anisotropy fields for films before and after irradiation has been observed by element-specific hysteresis loops recorded at low temperatures in absorption and reflection geometries at the Fe L

2
,
3

and M

2
,
3

edges, respectively. An attempt to reduce the top oxide layer by an inductively coupled hydrogen plasma has shown a possibility to recover the chemically ordered phase.