bluuebunny/crossref_metadata_2025 huggingface dataset:
Imprint from ferromagnetic skyrmions in an antiferromagnet via exchange bias
Authors: Rana Kumari Gaurav , Lopes Seeger Rafael , Ruiz-Gómez Sandra , Juge Roméo , Zhang Qiang , Bairagi Kaushik , Pham Van Tuong , Belmeguenai Mohamed , Auffret Stéphane , Foerster Michael , Aballe Lucia , Gaudin Gilles , Baltz Vincent , Boulle Olivier
Published: November 2021

Magnetic skyrmions are topological spin textures holding great potential as nanoscale information carriers. Recently, skyrmions have been predicted in antiferromagnets, with key advantages in terms of stability, size, and dynamical properties over their ferromagnetic analogs. However, their experimental demonstration is still lacking. Here, we show the imprint from ferromagnetic skyrmions into a thin film of an IrMn antiferromagnet, at room temperature and zero external magnetic field, using exchange-bias. Using high-spatial-resolution x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM), we observed the imprinted spin textures within the IrMn from the XMCD signal of the uncompensated Mn spins at the interface with the ferromagnet. This result opens up a path for logic and memory devices based on skyrmion manipulation in antiferromagnets.
Heteroatom-doped Clar's goblet: Tunable magnetic order and programmable spin logic gate
Authors: Kang Dawei , Zhang Shuai , Ju Weiwei , Zuo Zheng-wei , Wang Zhaowu
Published: November 2021

Nanographene exhibits manifold magnetic orders depending on its topology. The Clar's goblet, envisioned 50 years ago and synthesized recently, is an emblematic nanographene with an antiferromagnetic ground state induced by topological frustration. Inspired by the significant interest in the designer magnetic order of nanographene, we studied the tunable magnetic order in heteroatom-doped Clar's goblet. Interestingly, the antiferromagnetic to ferromagnetic transition is found in doped Clar's goblet by varying the doping positions. A large exchange-coupling strength of 77 meV is realized in a Clar's goblet doped by two nitrogen atoms. The spin directions and distribution at the connecting atoms determine the magnetic order and exchange-coupling strength. Moreover, the spin logic gate based on Clar's goblet can be converted from XOR (XAND) gate into OR (AND) gate by doping the outer units with nitrogen atoms. The heteroatom-doped nanographene with tunable magnetic order provides a platform for spintronic devices with controllable functions.
Coherent spin transport in a natural metalloprotein molecule
Authors: Matsuura Yukihito
Published: November 2021

Recently, the long-range spin-selective transport in chiral molecules has been investigated for bio-spintronics. The experimental results for a natural metalloprotein molecule suggested a high spin selectivity. I performed first-principle calculations of electron spin transport in a natural metalloprotein molecule based on the Landauer formula. A gold–metalloprotein–gold device model was used to confirm the high spin polarization. There was a relatively large spin density at some amide groups in the helical peptide structures. Furthermore, a large spin density of iron atoms enhanced the spin density of the neighboring coordinated atoms, resulting in spin polarization in the whole molecule.
Training algorithm matters for the performance of neural network potential: A case study of Adam and the Kalman filter optimizers
Authors: Shao Yunqi , Dietrich Florian M. , Nettelblad Carl , Zhang Chao
Published: November 2021

One hidden yet important issue for developing neural network potentials (NNPs) is the choice of training algorithm. In this article, we compare the performance of two popular training algorithms, the adaptive moment estimation algorithm (Adam) and the extended Kalman filter algorithm (EKF), using the Behler–Parrinello neural network and two publicly accessible datasets of liquid water [Morawietz et al., Proc. Natl. Acad. Sci. U. S. A. 113, 8368–8373, (2016) and Cheng et al., Proc. Natl. Acad. Sci. U. S. A. 116, 1110–1115, (2019)]. This is achieved by implementing EKF in TensorFlow. It is found that NNPs trained with EKF are more transferable and less sensitive to the value of the learning rate, as compared to Adam. In both cases, error metrics of the validation set do not always serve as a good indicator for the actual performance of NNPs. Instead, we show that their performance correlates well with a Fisher information based similarity measure.
Terahertz spectroscopy of antiferromagnetic resonances in YFe1−xMnxO3 ≤x≤0.4 across a spin reorientation transition
Authors: Lee Howon , Jung Taek Sun , Shin Hyun Jun , Oh Sang Hyup , Sim Kyung Ik , Ha Taewoo , Choi Young Jai , Kim Jae Hoon
Published: November 2021

We have conducted a terahertz spectroscopic study of antiferromagnetic resonances in bulk orthoferrite YFe1−xMnxO3 0≤x≤0.4. Both the quasi-ferromagnetic resonance mode and the quasi-antiferromagnetic resonance mode in the weak ferromagnetic Γ4 phase disappear near the spin reorientation temperature, TSR, for the onset of the collinear antiferromagnetic Γ1 phase (x ≥ 0.1). Below TSR, an antiferromagnetic resonance mode emerges and exhibits a large blueshift with decreasing temperature. However, below 50 K, this mode softens considerably, and this tendency becomes stronger with Mn doping. We provide a deeper understanding of such behaviors of the antiferromagnetic resonance modes in terms of the influence of the Mn3+ ions on the magnetocrystalline anisotropy. Our results show that terahertz time-domain spectroscopy is a useful, complementary tool in tracking magnetic transitions and probing the interaction between disparate magnetic subsystems in antiferromagnetic materials with multiple ionic species.
Data-efficient iterative training of Gaussian approximation potentials: Application to surface structure determination of rutile IrO2 and RuO2
Authors: Timmermann Jakob , Lee Yonghyuk , Staacke Carsten G. , Margraf Johannes T. , Scheurer Christoph , Reuter Karsten
Published: November 2021

Machine-learning interatomic potentials, such as Gaussian Approximation Potentials (GAPs), constitute a powerful class of surrogate models to computationally involved first-principles calculations. At a similar predictive quality but significantly reduced cost, they could leverage otherwise barely tractable extensive sampling as in global surface structure determination (SSD). This efficiency is jeopardized though, if an a priori unknown structural and chemical search space as in SSD requires an excessive number of first-principles data for the GAP training. To this end, we present a general and data-efficient iterative training protocol that blends the creation of new training data with the actual surface exploration process. Demonstrating this protocol with the SSD of low-index facets of rutile IrO2 and RuO2, the involved simulated annealing on the basis of the refining GAP identifies a number of unknown terminations even in the restricted sub-space of (1 × 1) surface unit cells. Particularly in an O-poor environment, some of these, then metal-rich terminations, are thermodynamically most stable and are reminiscent of complexions as discussed for complex ceramic materials.
Deep image restoration for infrared photothermal heterodyne imaging
Authors: Zhang Shuang , Kniazev Kirill , Pavlovetc Ilia M. , Zhang Shubin , Stevenson Robert L. , Kuno Masaru
Published: November 2021

Infrared photothermal heterodyne imaging (IR-PHI) is an all-optical table top approach that enables super-resolution mid-infrared microscopy and spectroscopy. The underlying principle behind IR-PHI is the detection of photothermal changes to specimens induced by their absorption of infrared radiation. Because detection of resulting refractive index and scattering cross section changes is done using a visible (probe) laser, IR-PHI exhibits a spatial resolution of ∼300 nm. This is significantly below the mid-infrared diffraction limit and is unlike conventional infrared absorption microscopy where spatial resolution is of order ∼5μm. Despite having achieved mid-infrared super-resolution, IR-PHI’s spatial resolution is ultimately limited by the visible probe laser’s diffraction limit. This hinders immediate application to studying samples residing in spatially congested environments. To circumvent this, we demonstrate further enhancements to IR-PHI’s spatial resolution using a deep learning network that addresses the Abbe diffraction limit as well as background artifacts, introduced by experimental raster scanning. What results is a twofold improvement in feature resolution from 300 to ∼150 nm.
AFM-IR and s-SNOM-IR measurements of chemically addressable monolayers on Au nanoparticles
Authors: Rikanati Lihi , Dery Shahar , Gross Elad
Published: November 2021

The performance of catalysts depends on their nanoscale properties, and local variations in structure and composition can have a dramatic impact on the catalytic reactivity. Therefore, probing the localized reactivity of catalytic surfaces using high spatial resolution vibrational spectroscopy, such as infrared (IR) nanospectroscopy and tip-enhanced Raman spectroscopy, is essential for mapping their reactivity pattern. Two fundamentally different scanning probe IR nanospectroscopy techniques, namely, scattering-type scanning near-field optical microscopy (s-SNOM) and atomic force microscopy-infrared spectroscopy (AFM-IR), provide the capabilities for mapping the reactivity pattern of catalytic surfaces with a spatial resolution of ∼20 nm. Herein, we compare these two techniques with regard to their applicability for probing the vibrational signature of reactive molecules on catalytic nanoparticles. For this purpose, we use chemically addressable self-assembled molecules on Au nanoparticles as model systems. We identified significant spectral differences depending on the measurement technique, which originate from the fundamentally different working principles of the applied methods. While AFM-IR spectra provided information from all the molecules that were positioned underneath the tip, the s-SNOM spectra were more orientation-sensitive. Due to its field-enhancement factor, the s-SNOM spectra showed higher vibrational signals for dipoles that were perpendicularly oriented to the surface. The s-SNOM sensitivity to the molecular orientation influenced the amplitude, position, and signal-to-noise ratio of the collected spectra. Ensemble-based IR measurements verified that differences in the localized IR spectra stem from the enhanced sensitivity of s-SNOM measurements to the adsorption geometry of the probed molecules.
Kinetics of nonisothermal phase change with arbitrary temperature–time history and initial transformed phase distributions
Authors: Kangas Joseph , Bischof John C. , Hogan Christopher J.
Published: November 2021

This paper describes the extension of the classic Avrami equation to nonisothermal systems with arbitrary temperature–time history and arbitrary initial distributions of transformed phase. We start by showing that through examination of phase change in Fourier space, we can decouple the nucleation rate, growth rate, and transformed fraction, leading to the derivation of a nonlinear differential equation relating these three properties. We then consider a population balance partial differential equation (PDE) on the phase size distribution and solve it analytically. Then, by relating this PDE solution to the transformed fraction of phase, we are able to derive initial conditions to the differential equation relating nucleation rate, growth rate, and transformed fraction.
Compacting the density matrix in quantum dynamics: Singular value decomposition of the surprisal and the dominant constraints for anharmonic systems
Authors: Komarova K. , Remacle Francoise , Levine R. D.
Published: November 2021

We introduce a practical method for compacting the time evolution of the quantum state of a closed physical system. The density matrix is specified as a function of a few time-independent observables where their coefficients are time-dependent. The key mathematical step is the vectorization of the surprisal, the logarithm of the density matrix, at each time point of interest. The time span used depends on the required spectral resolution. The entire course of the system evolution is represented as a matrix where each column is the vectorized surprisal at the given time point. Using the singular value decomposition (SVD) of this matrix, we generate realistic approximations for the time-independent observables and their respective time-dependent coefficients. This allows for a simplification of the algebraic procedure for determining the dominant constraints (the time-independent observables) in the sense of the maximal entropy approach. A non-stationary coherent initial state of a Morse oscillator is used to introduce the approach. We derive the analytical exact expression for the surprisal as a function of time, and this offers a benchmark for comparison with the accurate but approximate SVD results. We discuss two examples of a Morse potential of different anharmonicities, H2 and I2 molecules. We further demonstrate the approach for a two-coupled electronic state problem, the well-studied non-radiative decay of pyrazine from its bright state. Five constraints are found to be enough to capture the ultrafast electronic population exchange and to recover the dynamics of the wave packet in both electronic states.
The Sociopragmatics of Stance
Authors: Grund Peter J.
Published: November 2021

Anchored in historical pragmatics, historical sociolinguistics, and corpus linguistics, this book weaves together a powerful narrative of the significance of stance marking in the history of English. Focusing on the community of practice that developed during the witch trials in Salem (Massachusetts) in 1692–1693, it showcases how witnesses and the recorders of their ca. 450 depositions deployed linguistic features to signal the evaluation of experiences with alleged witchcraft, the intensification of those experiences, and the sources of the witnesses’ knowledge. The resulting stance profiles for groups of depositions, witnesses, and recorders highlight varying strategies of claiming, supporting, and boosting the importance of the evidence and the role of the witnesses within the community of practice. With its innovative focus on sociopragmatic variation in a historical community, the book demonstrates the essential contribution of synchronic-historical research to the analysis, description, and theorization of stance and historical English more broadly.
Category-building lists between grammar and interaction
Authors: Goria Eugenio , Masini Francesca
Published: November 2021

Lists are one of the most common devices that are
used in interaction to refer to a category. Yet, there are only few
studies that analyze the relationship between lists and
categorization. Our paper aims at advancing our knowledge of this
relationship, and of lists in general. From a theoretical point of
view, we discuss the benefits of integrating the Construction Grammar
approach to lists adopted in Masini et al. (2018) with some of the basic assumptions
of Interactional Linguistics. From an empirical point of view, we
offer a qualitative analysis of lists based on data from two corpora
of spoken Italian: the LIP corpus (De Mauro et al. 1993) and the KIParla corpus (Mauri et al. 2019a). In
particular, we discuss a case study on the use of the Italian
discourse marker insomma within list constructions:
while it serves as a reformulation marker in most of its uses,
insomma also proves to be used (more marginally)
as a category introducer within category-building lists. Our findings
provide useful insight to ultimately bridge the gap between denotation
lists as a reference-oriented phenomenon and other types of mechanisms
that are relevant at the discourse level, including conversational
repair.
Making the implicit explicit
Authors: Paul Christine
Published: November 2021

Semantic underdeterminacy in the form of
unformulated syntactic slots is a widely-discussed research theme,
even though opinions differ about whether the interpretation is a
result of pragmatic processes of free enrichment (e.g., Carston 2004; Recanati 2002, 2004; Sperber & Wilson 1986/1995) or of
obligatory processes of the linguistic structure (Stanley 2007). Using a
conversation analytic approach, a corpus of narrative interviews can
show that interlocutors use a wide range of turns to deal with these
forms of semantic underdeterminacy. In narrative interviews,
prototypically the communicative functions of these turns (e.g.
repair, gaining time or developing the topic) are in relation to the
accessibility of possible candidates within the given context. The
empirical findings support the relevance theory account of free
enrichment.
French type-noun constructions based on
genre
Authors: Mihatsch Wiltrud
Published: November 2021

Colloquial French genre is highly
polysemous with a variety of functions such as comparison,
approximation and the fully pragmaticalized functions as a mitigator,
a quotative marker, an exemplifier, a marker of narrative progression,
explanation and focussing. So far, the focus has been on the various
discourse functions, however, several studies also point out possible
paths of pragmaticalization. The aim of this paper is to analyse in
greater detail the construction at the root of all these functions,
i.e. “X of the same type as Y”, a construction originally used for
construing ad hoc categories. This rather learned construction became
established in the 19th century for French and transformed into a
backgrounded instruction for sloppy categorization and the other
derived colloquial functions listed above.
Piezo1 helps bile on the pressure
Authors: Short Ben
Published: November 2021

JGP study shows that a mechanosensitive complex containing Piezo1 and Pannexin1 couples osmotic pressure to ATP secretion in bile duct cholangiocytes.
Highly responsive screen-printed asymmetric pressure sensor based on laser-induced graphene
Authors: Zhao Jiang , Gui Jiahao , Luo Jinsong , Gao Jing , Zheng Caidong , Xu Rongqing
Published: November 2021

Graphene-based pressure sensors have received extensive attention in wearable devices. However, reliable, low-cost, and large-scale preparation of structurally stable graphene electrodes for flexible pressure sensors is still a challenge. Herein, for the first time, laser-induced graphene (LIG) powder are prepared into screen printing ink, and shape-controllable LIG patterned electrodes can be obtained on various substrates using a facile screen printing process, and a novel asymmetric pressure sensor composed of the resulting screen-printed LIG electrodes has been developed. Benefit from the 3D porous structure of LIG, the as-prepared flexible LIG screen-printed asymmetric pressure sensor has super sensing properties with a high sensitivity of 1.86 kPa−1, low detection limit of about 3.4 Pa, short response time, and long cycle durability. Such excellent sensing performances give our flexible asymmetric LIG screen-printed pressure sensor the ability to realize real-time detection of tiny body physiological movements (such as wrist pulse and pronunciation action). Besides, the integrated sensor array has a multi-touch function. This work could stimulate an appropriate approach to designing shape-controllable LIG screen-printed patterned electrodes on various flexible substrates to adapt the specific needs of fulfilling compatibility and modular integration for potential application prospects in wearable electronics.
Dual-band metamaterial absorber with stable absorption performance based on fractal structure
Authors: Fang Shuguang , Deng Lianwen , Zhang Pin , Qiu Leilei , Xie Haipeng , Du Junsa , Wang Haiyue , Zhao Haonan
Published: November 2021

In this paper, two kinds of dual-band metamaterial absorbers (MMAs) with stable absorption performance based on fractal structures are proposed. As the key feature, with the increase in fractal order, the fractal MMAs can reduce the weight while keeping the absorption performance. The multi-band absorption property is analyzed by multiple L-C resonances generated by the fractal structure. By virtue of good impedance matching characteristics and the synergy of the circuit and electromagnetic resonance, effective and stable microwave absorption is readily achieved. Finally, two prototypes are fabricated for demonstration, and the measurement result is consistent well with the simulation one. As expected, the proposed fractal MMAs have the advantage of low-cost, light-weight, and dual-effective absorption bands, and have great potential in the application of multi-band radar stealth.
Numerical simulation of high-current pulsed arc discharge in air
Authors: Bocharov A N , Mareev E A , Popov N A
Published: November 2021

A computational model of high-current pulsed arc discharge in air is proposed. This is, in general, a 2D model which takes into account the gas dynamics of the discharge channel, real air thermodynamics in a wide range of pressures and temperatures, the electrodynamics of the discharge including the pinch effect, and radiation. The 1D version of the model is tested and verified on several numerical and experimental works reported recently. It is concluded that low and moderate current discharges are satisfactorily described with the model. The model was then applied to simulate the electric discharge in air for the currents 1–250 kA and characteristic rise times in 13–25 µs, and the results of the calculations were compared with experimental ones. It was concluded that most characteristics of the discharge are predicted well. Namely, the arc column radius and shock wave position agree well with experimental data for all the current amplitudes and rise times considered. Radial distributions of temperature and electron density also satisfactorily agree with experimental data. It was found that the pinch effect should be considered for currents higher than 100 kA.
The interplay of transverse degrees of freedom and axial-vector mesons with short-distance constraints in g
− 2
Authors: Masjuan Pere , Roig Pablo , Sanchez-Puertas Pablo
Published: November 2021

We revisit well-known short-distance constraints relating the hadronic light-by light Green’s function to the ⟨VVA⟩ one, that have been a subject of debate over the past years in the context of the muon (g − 2). Specifically, we identify a relation among the longitudinal and transverse degrees of freedom that is enforced by the axial anomaly that, by contrast, has not received attention in the past. Such relation allows, among other things, to overcome the problem of basis ambiguities when describing axial-vector mesons transition form factors, but further applications are discussed as well, with special focus on the role of axial-vector mesons in the HLbL contribution to the muon (g − 2). Our results should also contribute to a better understanding of the, so far, controversial interplay among short-distance constraints with longitudinal and transverse degrees of freedom, such as axial-vector mesons. This is key to confront the theoretical and experimental result for the muon (g − 2) that, currently, exhibits a 4.2σ tension.
Anisotropic thermal conductivity and corrugated patterns in single-layer black phosphorus nanoribbon subjected to shear loading: a molecular dynamics study
Authors: Mahnama Maryam , Meshkinghalam Mostafa , Ozmaian Masoumeh
Published: November 2021

Single-layer black phosphorus (SLBP) also known as phosphorene is a recently introduced two-dimensional material with unique structure and promising physical properties that has drawn considerable attention in the field of nanodevices. This structure demonstrates a high anisotropy in mechanical and thermal behavior along zigzag (ZZ) and armchair (AC) principal in-plane directions. Here in this study, it is shown that implementing shear strain on 10 nm × 50 nm SLBP nanoribbons (SLBPNRs) along ZZ and AC directions, the anisotropy leads to different corrugated patterns on the pristine structure. Applying non-equilibrium molecular dynamics under a parameterized Stillinger–Weber potential for modelling SLBP, thermal conductivity (TC) behavior of the sheared SLBPNRs with corrugated patterns are examined. The results show a higher amplitude and wavelength of the corregations on the ZZ-aligned SLBPNRs, which is around two times higher than that of AC-aligned counterparts. Although, it is also shown that unlike some other 2D materials, such as graphene, the wrinkling does not have such a significant effect on TC of SLBP. The phonon density of states results obtained in this work as well as phonon dispersion curves by first-principle calculations in other works concrete this finding. The results show small frequency shifts in both high- and low-frequency phonons, which are not strong enough to affect TC in SLBPNRs. This interesting thermal property of SLBP under shear strain suggests the great potential application of these corrugated structures in nanodevices without any loss of TC abilities.
Magnetic properties and phase diagram of quasi-two-dimensional Na2Co2TeO6 single crystal under high magnetic field
Authors: Xiao Guiling , Xia Zhengcai , Song Yujie , Xiao Lixia
Published: November 2021

We investigated the magnetic characteristics of Na2Co2TeO6 at different temperatures and magnetic field. The experimental results indicated that the magnetic field can disturb the antiferromagnetic interaction and lead to the disorder. Magnetization curves measured with different angles θ (θ is between the magnetic field direction and c axis) express the magnetocrystalline anisotropy in this system. When the angle θ = 0 (magnetic field parallel to c axis), two continuous magnetic phase transitions at critical temperature T
N1 and T
N3 were observed. As θ changes, T
N1 is almost independent on θ, indicating the magnetic ordering at T
N1 was a spontaneous behavior with a robust AFM characteristic. On the other hand, as θ increases from 0 to 180, T
N3 presents extreme value at θ = 90 (magnetic field perpendicular to c axis). It indicates that T
N3 were sensitive to temperature and magnetic fields. At some angles closing to ab plane, an additional phase transition was observed at T
N2. This phase transition at T
N2 may mainly result from the long range antiferromagnetic ordering within ab-plane. Furthermore, the magnetization measurement up to 50 T revealed the strong antiferromagnetic coupling in the system, and in which the magnetic coupling within the honeycomb layers is strong and the magnetic coupling interaction between honeycomb layers is weaker. Based on the experimental results, we have obtained the complete magnetic phase diagram.
A fault diagnosis method based on low signal to noise ratio vibration measurement for use in casing cutters
Authors: Zhang Pu , Liu Shuyao , Tao Aihua , Cheng Jingjing , Gao Peng
Published: November 2021

In this paper, a method for fault diagnosis in casing cutters is proposed. A vibration signal acquisition circuit for use in a high-temperature environment was designed, and a casing cutter measurement model was established, including a model of the casing cutter in a trouble-free state and two other common fault states. The vibration characteristics of the model were analyzed. A fault feature enhancement model based on enhancement of the signal to noise ratio and sparse representation, which effectively solves the fault diagnosis problem caused by the limited installation location and the limited performance of the vibration measurement at high temperature, was also designed. The MobileNet-V3-Small convolutional neural network (CNN) model was improved by reducing the basic blocks of the continuous homogeneous structure in the original model, and the Squeeze and Excitation structure expanded to the global level to obtain a lightweight CNN fault recognition model. The effectiveness and efficiency of the proposed method were validated by various experiments.
Nanopatterning of oxide 2-dimensional electron systems using low-temperature ion milling
Authors: D’Antuono M , Kalaboukhov A , Caruso R , Wissberg S , Weitz Sobelman S , Kalisky B , Ausanio G , Salluzzo M , Stornaiuolo D
Published: November 2021

We present a ‘top-down’ patterning technique based on ion milling performed at low-temperature, for the realization of oxide two-dimensional electron system devices with dimensions down to 160 nm. Using electrical transport and scanning Superconducting QUantum Interference Device measurements we demonstrate that the low-temperature ion milling process does not damage the 2DES properties nor creates oxygen vacancies-related conducting paths in the STO substrate. As opposed to other procedures used to realize oxide 2DES devices, the one we propose gives lateral access to the 2DES along the in-plane directions, finally opening the way to coupling with other materials, including superconductors.
Electrical impedance sensing of organic pollutants with ultrathin graphitic membranes
Authors: Baah Marian , Rahman Afifa , Sibilia Sarah , Trezza Gianmarco , Ferrigno Luigi , Micheli Laura , Maffucci Antonio , Soboleva Ekaterina , Svirko Yuri , Kuzhir Polina
Published: November 2021

In this paper we propose an original approach for the real-time detection of industrial organic pollutants in water. It is based on the monitoring of the time evolution of the electrical impedance of low-cost graphitic nanomembranes. The developed approach exploits the high sensitivity of the impedance of 2D graphene-related materials to the adsorbents. We examined sensitivity of the nanomembranes based on pyrolyzed photoresist, pyrolytic carbon (PyC), and multilayer graphene films. In order to realize a prototype of a sensor capable of monitoring the pollutants in water, the membranes were integrated into an ad hoc printed circuit board. We demonstrated the correlation between the sensitivity of the electric impedance to adsorbents and the structure of the nanomembranes, and revealed that the amorphous PyC, being most homogeneous and adhesive to the SiO2 substrate, is the most promising in terms of integration into industrial pollutants sensors.
Insights of an AI agent via analysis of prediction errors: a case study of fluence map prediction for radiation therapy planning
Authors: Li Xinyi , Wu Q Jackie , Wu Qiuwen , Wang Chunhao , Sheng Yang , Wang Wentao , Stephens Hunter , Yin Fang-Fang , Ge Yaorong
Published: November 2021

Purpose. We have previously reported an artificial intelligence (AI) agent that automatically generates intensity-modulated radiation therapy (IMRT) plans via fluence map prediction, by-passing inverse planning. This AI agent achieved clinically comparable quality for prostate cases, but its performance on head-and-neck patients leaves room for improvement. This study aims to collect insights of the deep-learning-based (DL-based) fluence map prediction model by systematically analyzing its prediction errors. Methods. From the modeling perspective, the DL model’s output is the fluence maps of IMRT plans. However, from the clinical planning perspective, the plan quality evaluation should be based on the clinical dosimetric criteria such as dose-volume histograms. To account for the complex and non-intuitive relationships between fluence map prediction errors and the corresponding dose distribution changes, we propose a novel error analysis approach that systematically examines plan dosimetric changes that are induced by varying amounts of fluence prediction errors. We investigated four decomposition modes of model prediction errors. The two spatial domain decompositions are based on fluence intensity and fluence gradient. The two frequency domain decompositions are based on Fourier-space banded frequency rings and Fourier-space truncated low-frequency disks. The decomposed error was analyzed for its impact on the resulting plans’ dosimetric metrics. The analysis was conducted on 15 test cases spared from the 200 training and 16 validation cases used to train the model. Results. Most planning target volume metrics were significantly correlated with most error decompositions. The Fourier space disk radii had the largest Spearman’s coefficients. The low-frequency region within a disk of ∼20% Fourier space contained most of errors that impact overall plan quality. Conclusions. This study demonstrates the feasibility of using fluence map prediction error analysis to understand the AI agent’s performance. Such insights will help fine-tune the DL models in architecture design and loss function selection.
On the magnetoelectric performance of multiferroic particulate composite materials
Authors: Newacheck Scott , Singh Anil , Youssef George
Published: November 2021

In the current work, quantitative analysis of magnetoelectric particulate composite material system explicated the main mechanisms responsible for the below-optimal performance of this class of materials. We considered compliant particulate composite materials, with constituents relevant to technological and scientific interest, leading to 0–3 Terfenol-D/PVDF–TrFE composite samples. To this objective, thick Terfenol-D/PVDF–TrFE films (10–15 µm) were fabricated and analyzed for chemical, mechanical, and magnetic properties to demonstrate their suitability for energy applications in harsh environmental conditions. The vigorous experimental characterization of the composite exemplified the multifunctional properties, quantifying the interrelationship between the composition and performance. We observed that the addition of magnetic particles to the electroactive copolymer matrix resulted in improvement in the mechanical and electrical properties since the particles acted as pinning sites, hindering the deformation of the chains and enhancing polarization. The effective modulus model was amended to account for the crystallization-induced change in material stiffness. We also measured and computed the magnetic particles motion to explicate the detrimental effect of mobility and migration on the overall magnetoelectric coupling performance of the composite. Thereby, we derived an analytical model based on the magnetic force due to the co-presence of alternating and constant magnetic fields, and the viscous drag force due to the viscoelastic properties of the electroactive copolymer matrix. We demonstrated that the mobility of the particles plays a crucial role in the short and long term performance of magnetoelectric coupling in multiferroic particulate composites, uncovering the underpinnings of the dichotomy in performance between experimentally measured and analytically predicted coupling coefficients, thus allowing for the proposal of new approaches to realize the scientific potential of magnetoelectric particulate composites in energy applications.
Realizing pure shear mode of dielectric elastomers by tuning biaxial prestress of a deformation controller
Authors: Tang Liling , Ding Yuxi , Liu Lei , Zhang Junshi
Published: November 2021

In this article, we propose a method to realize the pure shear deformation mode of dielectric elastomer (DE) membranes by tuning two in-plane prestresses. With utilization of carbon grease electrodes, VHB 4905 membranes are prestretched and attached into a retractable device, forming a pure-shear deformation controller. Experimental results demonstrate that, accurate pure shear deformation mode of DEs can be realized by tuning the mechanical loads in the two directions of the deformation controller. Furthermore, large deformation in the direction of free state can be achieved without electromechanical instabilities. The designed deformation controller accurately realizes the specific pure shear deformation mode of DEs and can be utilized to help design the practical soft actuators.
100 s negative ion accelerations for the JT-60SA negative-ion-based neutral beam injector
Authors: Kashiwagi M. , Hiratsuka J. , Ichikawa M. , Saquilayan G. Q. , Kojima A. , Tobari H. , Umeda N. , Watanabe K. , Yoshida M. , Grisham L.
Published: November 2021

In the negative-ion-based neutral beam injector (N-NBI) of JT-60SA, a hydrogen negative ion beam with energy of 500 keV and a current density of 154 A m−2 for 118 s has been successfully demonstrated. This achievement exceeds the requirements (500 keV, 130 A m−2, 100 s) for the first time. To maintain stable negative ion production for a long pulse, the optimal temperatures of the chamber wall and plasma grid were analytically examined and were experimentally demonstrated. It was confirmed that the temperature during the beam pulse should be <50 °C for the chamber wall and >200 °C for the plasma grid. Damage to the filament cathode due to an abnormal discharge, so-called arcing, has been mitigated by developing a fast cut-off system of the arc current for around 100 μs after the arcing. To maintain sufficient voltage holding capability and to reduce the grid heat load due to the beam in the accelerator, techniques developed for the beam acceleration have been applied to this test. As a result of the integration of these techniques, a stable beam over 100 s has been demonstrated successfully. This is the first achievement over a 100 s stable beam with intensity of >75 MW m−2, which is the required practical level in the N-NBI. These results contribute to the coming NBI system for ITER and DEMO.
Applying the Heaviside step function to simulate the changes of temperature in automotive batteries
Authors: Zakharov N S , Sapozhenkov N O , Tyan R V , Nazarov V P
Published: November 2021

Discharged batteries do not provide the specified voltage in the car’s power supply system during parking, which can cause malfunctions of electrical equipment and an increase in the quiescent current in the on-board network, due to incorrect operation of electronic control units responsible for the operation of self-diagnosis systems, anti-theft alarm, multi-media, maintaining a thermal state, etc. Therefore, to ensure a reliable start of the ICE and the proper operation of the electrical equipment of a car at low temperatures, it is required to maintain the battery in a charged state. Vehicle generator is selected taking into account the nominal capacity of the battery, power and operating modes of electrical consumers, which excludes the battery operation with a low level of charge. However, when operating cars in large cities in winter, the battery charge level decreases. Deterioration of the battery charging characteristics, increased power consumption of additional equipment and low speed of movement of cars in the city with frequent stops at intersections are the reasons for the decrease in the efficiency of the battery charge. In such conditions, the battery can be discharged not only by starting the ICE and turning on consumers in the parking lot, but also when the ICE is idling and at low crankshaft speeds while driving on city routes and during rush hours. Considering that the operational characteristics of the battery change significantly with decreasing temperature, studies aimed at establishing and predicting the battery temperature during operation are relevant.
Investigation of the operation of a ship’s synchronous generator based on a numerical model
Authors: Grinek AV , Boychuk IP , Fishenko A M , Savosteenko NV , Gerasimenko O N
Published: November 2021

The article presents the results of modeling a ship’s synchronous generator. Based on preliminary design calculations, a geometric model of the generator was built. The static and overclocking processes of the generator are investigated. For static modes, the frequency response of the process is obtained. A numerical model was used to identify a mechanical defect. On the example of a simulated defect of an electrical machine - the eccentricity of the generator rotor, the signature of the defect signal is obtained. The study revealed that the presence of rotor eccentricity leads to the appearance of a harmonic component in the spectrum of the force of large amplitude with a maximum value at a low frequency. Transient analysis was carried out using wavelet transformations. The results of the study of dynamics show how the rotor speed increases. The simulation revealed three frequency regions of the signal under study: the region of the increase in speed, the achievement of the critical speed (between the second and third seconds), and the exit to the steady-state. A diagram of a system for diagnosing defects in an electrical machine using a digital twin - a numerical model is proposed. Generator defects (mechanical and electromechanical) can be identified based on model data. Databases of defect signatures in a static mode and a diagnostic model, which contains algorithms for deciding on the presence of a defect, can serve as the basis of information for an operator to decide.
Development, features and prospects of application of AMP / cold ironing marine power systems
Authors: Ignatenko A V , Migel D V , Deruzhinsky G V , Kravchenko N A
Published: November 2021

The evolution and current state of the technology for supplying ships from the shore under high voltage - alternative power from the shore (APS), known as “Alternative Maritime Power® (AMP®), cold ironing (CI) and high voltage shore connection (HVSC) are described. The structure of the system and existing methods of implementation, mandatory components, depending on the system version are considered. The need for national adaptations of the international versons, the unification of existing technical solutions and their development trends, taking into account high-voltage technologies is emphasized. Advantages and challenges of environmental impacts, expected phased tightening of environmental regulations, including the maritime legislation (the MARPOL convention), as well as promising initiatives in the context of global decarbonization trends are described. The need to take into account purposes and cargo capacity and regions of operation of ships, to develop the port infrastructure, and make clean electricity available is emphasized.
Monitoring and charging level alignment system for a vehicle hybrid power unit battery pack
Authors: Bakhmutov S V , Kuznetsov A V , Sizov Y A , Chernokozov V V
Published: November 2021

The article is devoted to the actual problem of developing effective means of control and charging level alignment of the vehicle hybrid power unit (HPU) accumulators. A description of the automatic control and charging level alignment system of the battery pack for hybrid power unit developed by the authors, while simultaneously controlling the temperature of each battery, the originality of which is protected by patents of the Russian Federation, is provided.The device is distinguished by the simplicity of the circuit design, its own low energy consumption and potentially low cost. To check the efficiency of the proposed device the computer simulation and experimental study were carried out. As a result of the provided multifactorial experiment, a regression function was obtained, which allows, by the value of the obtained coefficients, to reveal the degree of inhomogeneity of the monitored batteries in terms of electrical parameters and the temperature of influence, as well as to take into account the effects of pair and quadratic interactions.
Dependence of the increase in the power reserve of an electric vehicle on the season when using a non-flat battery of photovoltaic converters
Authors: Kozlov V N , Kolbasov A F , Karpukhin K E , Katanaev N T
Published: November 2021

Due to the fight against CO2 emissions and other harmful substances, the world’s leading vendors of motor vehicles (MV) come back to development of electric vehicles (EV) as the most environmentally friendly transport. But EV has inadequate power reserve from one accumulators charge. One of the ways to increase it is to use additional environmentally friendly electrical energy sources, e.g., photovoltaic converter (PVC) batteries due to the increase in their efficiency. In order to improve aerodynamic, design and consumer properties, the world’s leading EV manufacturers pass from flat PVC battery to non-flat. Non-flat PVC batteries compared with flat have insufficient energy efficiency, which can be increased in several ways, including PVC battery segmentation. In scientific publications, there are no methods for calculating non-flat PVC batteries, which indicates the actuality of the research being conducted. Mathematical modeling of the EV power reserve depending on the season allows us to justify the actuality of segmenting the non-flat PVC batteries installed on the EV. Materials for the mathematical modeling of nonlinear interaction are obtained experimentally, the method of conducting experimental research is scientifically justified. As a result of the mathematical modeling, the dependences of EV power reserve on the season at different standard test cycles were obtained. The obtained dependences of the EV power reserve on the season allow us to assume the feasibility of segmenting the PVC batteries installed on the EV to increase the energy output and EV power reserve from one accumulators charge.
Development and validation of vehicle wheel load scaling method for formation of durability testing loading cycle
Authors: Bokarev A I , Kulagin V A , Nazarkov I A
Published: November 2021

For a vehicle durability study, performed with simulation or laboratory testing, impact on the object should be described as set of time-domain load signals, which reflects accelerated service modes of a vehicle operation. For a newly developed vehicle these load signals can be based on previously prepared loading cycle of a similar vehicle with use of the load scaling theory. Importance and certainty of the load scaling theory is approved by active use among foreign car makers and engineering centers. However, mathematical description of the theory and scaling procedure are strictly classified, despite of being based on fundamentals of vehicle dynamics. In this paper the method of scaling of time-domain wheel and driveline loads is suggested; the method is based on proportions of size and mass properties of the original and the new vehicles. Assumed that previously recorded loading cycle corresponds to the service life of a vehicle. It is worth noting that level of loading and damage accumulation, shown with scaled loading cycle and after first prototypes testing on a proving ground, will be different because of impact of chassis stiffness and damping properties. Suggested scaling theory is being studied in FSUE “NAMI” and is on the validation and verification stage. First completed experiments showed that a multiaxial test rig could perform the vehicle suspension loading cycle, obtained with the theory, with a satisfactory accuracy. This makes utilization of the theory limited to early stages of vehicle development.
Method of formation of loading cycles for performing forced bench tests of suspension elements at the stage of technical design
Authors: Nazarkov I , Bokarev A , Plotnikov A , Bakhmutov S V
Published: November 2021

Ensuring the required vehicle service life is one of the most important and topical global engineering challenges. Automobile manufacturers and research engineers around the world are actively working to improve safety and durability testing methods of vehicles, their components and systems. This article touches upon the main issues of comparing the modes of vehicle road operation and the method of forming an adequate program for extreme testing of suspension elements. The developed method has been actively applied in FSUE “NAMI” in the field of research on durability of vehicle components and systems, in particular, of hub units, with the use of mathematical modeling tools and the test base capacities and capabilities.