bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shockwaves evolving on nanosecond timescales around individual micro-discharge filaments in deionised water
Authors: Hoffer Petr , Prukner Václav , Schmidt Jiří , Šimek Milan 
Published: April 2021

Abstract
In this study, we present an analysis of the pressure fields developing around nanosecond discharges produced in deionised water by positive high-voltage pulses (+130 and +170 kV) with a fast rise time on a tungsten anode pin. Shockwaves and their associated pressure characteristics were investigated by laser interferometry with a very high spatial resolution of 0.8 μm utilising the concept of a picosecond Mach–Zehnder interferometer based on a Nd:YAG laser (532 nm, 30 ps). Shifts of the fringes in interference patterns due to variations in the refractive index of liquid water produced in the vicinity of the tungsten anode were projected by the interferometer and analysed as a function of the pressure. High spatial resolution combined with the picosecond laser pulse allowed for the examination of frozen interferometric characteristics of cylindrical shockwaves. Consequently, unique results characterising the shockwaves developing around individual discharge filaments were obtained. For easier comparison, the shockwave pressures were normalised to a radius of 0.4 μm, which was found as the most probable maximum of initial radius of primary dark filament. At this radius, the most probable shock pressure was 1.5 GPa, whereas the highest obtained shock pressure reached 11 GPa. We showed that the modified Gaussian distribution fits the obtained results well. Finally, we observed that most of those extraordinary strong shock-fronts were associated with the dark filaments containing strong residual plasma-induced emission. This observation likely provides an indirect evidence of the electrostriction-assisted discharge onset mechanism.
Aluminum and lithium sulfur batteries: a review of recent progress and future directions
Authors: Akgenc Berna , Sarikurt Sevil , Yagmurcukardes Mehmet , Ersan Fatih 
Published: April 2021

Abstract
Advanced materials with various micro-/nanostructures have attracted plenty of attention for decades in energy storage devices such as rechargeable batteries (ion- or sulfur based batteries) and supercapacitors. To improve the electrochemical performance of batteries, it is uttermost important to develop advanced electrode materials. Moreover, the cathode material is also important that it restricts the efficiency and practical application of aluminum-ion batteries. Among the potential cathode materials, sulfur has become an important candidate material for aluminum-ion batteries cause of its considerable specific capacity. Two-dimensional materials are currently potential candidates as electrodes from lab-scale experiments to possible pragmatic theoretical studies. In this review, the fundamental principles, historical progress, latest developments, and major problems in Li–S and Al–S batteries are reviewed. Finally, future directions in terms of the experimental and theoretical applications have prospected.
Matching and reassignment based time-frequency enhancement for rotating machinery fault diagnosis under nonstationary speed operations
Authors: Hua Zehui , Shi Juanjuan , Jiang Xingxing , Luo Yang , Zhu Zhongkui 
Published: April 2021

Abstract
Time-frequency (TF) analysis (TFA) to nonstationary signals can reveal the nonlinearly changing instantaneous frequencies (IFs) of signals; it is, therefore, widely used for rotating machinery fault diagnosis under time-varying speed conditions. However, the traditional TFA methods may only reveal the outline of IFs due to the extra TF diffusion caused by limited TF resolution, hindering the fault diagnosis of rotating machinery. To enhance the readability of the time-frequency representation (TFR) of the signals with IF trajectories linearly time-varying, linear chirplet transform has been proved effective. To effectively tackle the signal with nonlinearly changing IFs, a string of chirp-rates is preferred, where the final TFR is obtained by superposition of each corresponding sub-TFR at each TF point. However, the extra cross-term interferences resulted from a string of chirp-rates cannot be neglected on TFRs. Aiming at alleviating the cross-terms from the TFR, matching and reassignment based TF enhancement strategy is proposed, where only the appropriate chirp-rate and its corresponding TFR slice is retained at each time instant. The appropriate chirp-rate is adaptively selected by the index—spectral kurtosis. To further increase the readability of the resulting TFR, a reassignment technique synchrosqueezing transform is integrated with the proposed matching strategy. By iteratively employing reassignments, TFR with the enhanced energy and sharp IF ridges can be generated. The effectiveness of the proposed method is validated by both simulated and experimental analyses. It is shown that the proposed method is effective in processing time-varying signals and can provide more accurate IF estimation, which paves the way for rotating machinery fault diagnosis under nonstationary speed conditions.
Structural evolution of Si-based anode materials during the lithiation reaction
Authors: Wang Zuozhang , Li Feng , Ding Wenyu , Tang Xianqiong , Xu Fu , Ding Yanhuai 
Published: April 2021

Abstract
Si-based materials have been intensively investigated as anode materials for Li-ion batteries. However, the structural evolution of the materials during the lithiation reaction is still unrevealed. In this paper, the structural parameters and mechanical properties of Si, SiO
x
(0 < x < 2) and SiO2 during the lithiation reaction are studied by first-principle calculation based on density functional theory. The relationship between the Li number and expansion coefficient, elastic constant, modulus, and Poisson’s ratio is systematically calculated.
Gas-solid interfacial charge transfer in volatile organic compound detection by CuCrO2 nanoparticles
Authors: Xu Sifan , Zhao Tingting , Kong Lingwei , Zhu Wenhuan , Bo Maolin , Huang Yizhong , Liu Hai 
Published: April 2021

Abstract
Nanostructured metal oxide semiconductors have received great attention used as the chemiresistive layer of gas sensor to detect the volatile organic compound recently. As indispensable complementary parts for dominative n-type semiconductors, the p-type metal oxides based gas sensors fail to be studied sufficiently, which hampers their practical applications. In this work, the p-type delafossite CuCrO2 nanoparticles were synthesized, characterized, and tested for gas sensing, followed by the first principles calculations to simulate the generation of chemiresistive signal. The hydrothermal synthesis time of CuCrO2 nanoparticles is optimized as 24 h with a higher proportion of oxygen vacancies but a smaller size, which is confirmed by the microscopy and spectrum characterization and allows for a prevailing gas sensitivity. Meanwhile, this CuCrO2 gas sensor is proven to perform a higher selectivity to n-propanol and a low detection limit of 1 ppm. The adsorption sites and charge variations of dehydrogenation at the gas-solid interface predicted by the theoretical analysis are claimed to be crucial to such selectivity. It is an innovative approach to understand the chemiresistive gas sensing by evaluating the preference of charge transfer between the sensor and target gaseous molecule, which provides a new route to precisely design and develop the advanced sensing devices for the diverse applications.
Reducing metal/graphene contact resistance via N, N-dimethylacetamide-assisted clean fabrication process
Authors: Zhu Chao-yi , Peng Song-ang , Zhang Xiao-rui , Yao Yao , Huang Xin-nan , Yan Yun-peng , Zhang Da-yong , Shi Jing-yuan , Jin Zhi 
Published: April 2021

Abstract
Contact resistance (R

C
) is of great importance for radio frequency (RF) applications of graphene, especially graphene field effect transistors (FETs) with short channel. FETs and transmission line model test structures based on chemical vapor deposition grown graphene are fabricated. The effects of employing traditional lithography solvent (Acetone) and strong solvents for photo resist, such as N, N-Dimethylacetamide (ZDMAC) and N-Methyl pyrrolidone (NMP), are systematically investigated. It was found that ZDMAC and NMP have more proficiency than acetone to remove the photo-resist residues and contaminations attached on graphene surface, enabling clean surface of graphene. However, strong solvents are found to destroy the lattice structure of graphene channel and induce defects in graphene lattice. Clean surface contributes to a significant reduction in the R

C
between graphene channel and metal electrode, and the defects introduced on graphene surface underneath metal electrodes also contribute the reduction of R

C
. But defects and deformation of lattice will increase the resistance in graphene channel and lead to the compromise of device performance. To address this problem, a mix wet-chemical approach employing both acetone and ZDMAC was developed in our study to realize a 19.07% reduction of R

C
, without an unacceptable mass production of defects.
On the origins of Riemann–Hilbert problems in mathematics*
Authors: Bothner Thomas 
Published: April 2021

Abstract
This article is firstly a historic review of the theory of Riemann–Hilbert problems with particular emphasis placed on their original appearance in the context of Hilbert’s 21st problem and Plemelj’s work associated with it. The secondary purpose of this note is to invite a new generation of mathematicians to the fascinating world of Riemann–Hilbert techniques and their modern appearances in nonlinear mathematical physics. We set out to achieve this goal with six examples, including a new proof of the integro-differential Painlevé-II formula of Amir et al (2011 Commun. Pure Appl. Math.
64 466–537) that enters in the description of the Kardar–Parisi–Zhang crossover distribution. Parts of this text are based on the author’s Szegő prize lecture at the 15th International Symposium on Orthogonal Polynomials, Special Functions and Applications (OPSFA) in Hagenberg, Austria.
Optimising use of 4D-CT phase information for radiomics analysis in lung cancer patients treated with stereotactic body radiotherapy
Authors: Davey Angela , van Herk Marcel , Faivre-Finn Corinne , Brown Sean , McWilliam Alan 
Published: April 2021

Abstract

Purpose. 4D-CT is routine imaging for lung cancer patients treated with stereotactic body radiotherapy. No studies have investigated optimal 4D phase selection for radiomics. We aim to determine how phase data should be used to identify prognostic biomarkers for distant failure, and test whether stability assessment is required. A phase selection approach will be developed to aid studies with different 4D protocols and account for patient differences. Methods. 186 features were extracted from the tumour and peritumour on all phases for 258 patients. Feature values were selected from phase features using four methods: (A) mean across phases, (B) median across phases, (C) 50% phase, and (D) the most stable phase (closest in value to two neighbours), coined personalised selection. Four levels of stability assessment were also analysed, with inclusion of: (1) all features, (2) stable features across all phases, (3) stable features across phase and neighbour phases, and (4) features averaged over neighbour phases. Clinical-radiomics models were built for twelve combinations of feature type and assessment method. Model performance was assessed by concordance index (c-index) and fraction of new information from radiomic features. Results. The most stable phase spanned the whole range but was most often near exhale. All radiomic signatures provided new information for distant failure prediction. The personalised model had the highest c-index (0.77), and 58% of new information was provided by radiomic features when no stability assessment was performed. Conclusion. The most stable phase varies per-patient and selecting this improves model performance compared to standard methods. We advise the single most stable phase should be determined by minimising feature differences to neighbour phases. Stability assessment over all phases decreases performance by excessively removing features. Instead, averaging of neighbour phases should be used when stability is of concern. The models suggest that higher peritumoural intensity predicts distant failure.
Display-pixel performances driven by contact-limited switching transistors
Authors: Lee Seunghyuk , Kim Chang-Hyun 
Published: April 2021

Abstract
In this paper, a direct link between contact properties of the transistor and electrical behaviors of the display system is established. Employing a liquid-crystal display driven by organic thin-film transistors as a model platform, systematic simulation of the image pixel circuit is performed to investigate this critical relationship. An elevated contact resistance at the transistor level is found to have a profound impact on charging dynamics of cell capacitors, revealing the importance of rendering such effects in designing advanced display electronics.
Influence of a compressive strain on the high-temperature thermoelectric properties of europium orthoferrite
Authors: Carlos III Baldo , Rajan P Iyyappa , Mahalakshmi S , Ramalingam R Jothi 
Published: April 2021

Abstract
Promising high temperature thermoelectric (TE) potential of europium orthoferrite (EuFeO3) is methodically investigated in this work, wherein the focus is on the influence of a −3% compressive strain on scattering rates and on transport properties. Using Boltzmann transport theory, transport properties such as Seebeck coefficient S, electrical conductivity σ, electronic thermal conductivity κ
e and power factor (PF) are obtained with appropriate regard to the prevailing scattering mechanisms present in the materials that affect its electronic transport. Here, we find that polar optical phonon (POP) scattering is the dominant scattering potential affecting the TE properties of EuFeO3 for temperatures from 900 K to 1500 K. The incorporation of a −3% compressive strain suppresses the POP scattering, as evidenced by the decrease in its scattering rates. This result consequently enhances the lattice thermal conductivity κ
L—which then has negative impact to the TE efficiency. Nevertheless, we find that the strain largely improves the σ of EuFeO3, and the PF as well. Unstrained p-type EuFeO3 registers remarkable values of PF equal to 167 μW m−1 K−2 at 900 K and 97.7 μW m−1K−2 at 1500 K for when the hole concentration is 1021 cm−3. Under a −3% compressive strain, the PF rises to almost double at 294 μW m−1 K−2 for 900 K and 170 μW m−1 K−2 for 1500 K for the same doping value. Finally, we believe that the methodology and discussions presented in this work well deliver a template relevant in modeling materials fit for high-temperature TE applications.
Jerky active matter: a phase field crystal model with translational and orientational memory
Authors: te Vrugt Michael , Jeggle Julian , Wittkowski Raphael 
Published: April 2021

Abstract
Most field theories for active matter neglect effects of memory and inertia. However, recent experiments have found inertial delay to be important for the motion of self-propelled particles. A major challenge in the theoretical description of these effects, which makes the application of standard methods very difficult, is the fact that orientable particles have both translational and orientational degrees of freedom which do not necessarily relax on the same time scale. In this work, we derive the general mathematical form of a field theory for soft matter systems with two different time scales. This allows to obtain a phase field crystal model for active particles with translational and orientational memory. Notably, this theory is of third order in temporal derivatives and can thus be seen as a spatiotemporal jerky dynamics. We obtain the phase diagram of this model, which shows that, unlike in the passive case, the linear stability of the liquid state depends on the damping coefficients. Moreover, we investigate sound waves in active matter. It is found that, in active fluids, there are two different mechanisms for sound propagation. For certain parameter values and sufficiently high frequencies, sound mediated by polarization waves experiences less damping than usual passive sound mediated by pressure waves of the same frequency. By combining the different modes, acoustic frequency filters based on active fluids could be realized.
Insights on magnon topology and valley-polarization in 2D bilayer quantum magnets
Authors: Ghader Doried 
Published: April 2021

Abstract
The rich and unconventional physics in layered 2D magnets can open new avenues for topological magnonics and magnon valleytronics. In particular, two-dimensional (2D) bilayer quantum magnets are gaining increasing attention due to their intriguing stacking-dependent magnetism, controllable ground states, and topological excitations induced by magnetic spin–orbit couplings (SOCs). Despite the substantial research on these materials, their topological features remain widely unexplored to date. The present study comprehensively investigates the magnon topology and magnon valley-polarization in honeycomb bilayers with collinear magnetic order. We elucidate the separate and combined effects of the SOC, magnetic ground-states, stacking order, and inversion symmetry breaking on the topological phases, magnon valley transport, and the Hall and Nernst effects. The comprehensive analysis suggests clues to determine the SOC’s nature and predicts unconventional Hall and Nernst conductivities in topologically trivial phases. We further report on novel bandgap closures in layered antiferromagnets and detail their topological implications. We believe the present study provides important insights into the fundamental physics and technological potentials of topological 2D magnons.
Orbital Solutions of the New Low-mass Eclipsing Binary TIC 157376469 with Spotted Activities
Authors: Pan Yang , Fu Jian-Ning , Zhang Xiaobin , Wang Jiaxin , Zong Weikai , Li Chunqian , Zhang Bo 
Published: April 2021

Abstract
We carried out a photometric and spectroscopic analysis for the eclipsing binary TIC 157376469 using the TESS and LAMOST data. A new linear ephemeris is given. By fitting the light curves and radial velocity curves with the Wilson–Devinney code, it apperas that the binary is composed of two K-type main-sequence stars. The orbit of the binary is slightly eccentric (

e
≈
0.0017

) and the primary is a spotted active star. The masses and radii of the two components are determined to be

M

1

=
0.704
±
0.028

M

⊙

,

R

1

=
0.754
±
0.010

R

⊙

,

M

2

=
0.539
±
0.021

M

⊙

,

R

2

=
0.543
±
0.007

R

⊙

, respectively. The temperature ratio (

T

2

/

T

1

) is determined to be ∼0.879. Under a assumption that the primary temperature is

T

1

=
4740
K

, comparisons to the PARSEC v1.2 isochrones show that for the primary the radius is oversized of ∼16%, and the effective temperature is cooler of

∼
300
K

(∼6%). While, the properties of the secondary are almost in agreement with the predictions of the model.
Stable self-pulsing regime in a Brillouin ring fiber laser cavity
Authors: Silva Luís C B , Marques Carlos A F , Segatto Marcelo E V , Pontes Maria J 
Published: April 2021

Abstract
This study reports that when solving by full integration a set of coupled ordinary differential equations that describe the spatial evolution of the guided pump and Stokes powers caused by stimulated Brillouin scattering in the regime of pump depletion, a structure of regular pulses emerge from the output of a Brillouin laser cavity characterized as a stable self-pulsing regime. The dependence of this self-pulsing mechanism on the laser cavity length, the coupling factor, and the pump power is investigated revealing the existence of three regimes: no lasing, continuous, and self-pulsing. When compared to records in the scientific literature, this is the first time, to the best of the author’s knowledge, that a stable self-pulsing regime is reported theoretically. Furthermore, we also demonstrated the pumping depletion during the formation of the self-pulsing regime. These results provide not only a better understanding of the dynamics of self-pulsing regimes in a fiber laser cavity but also the possibility of unlocking the mechanisms responsible for the formation of stable pulse trains in a Brillouin fiber-ring laser.
Multiform description of the AKNS hierarchy and classical r-matrix
Authors: Caudrelier Vincent , Stoppato Matteo 
Published: April 2021

Abstract
In recent years, new properties of space-time duality in the Hamiltonian formalism of certain integrable classical field theories have been discovered and have led to their reformulation using ideas from covariant Hamiltonian field theory: in this sense, the covariant nature of their classical r-matrix structure was unravelled. Here, we solve the open question of extending these results to a whole hierarchy. We choose the Ablowitz–Kaup–Newell–Segur (AKNS) hierarchy. To do so, we introduce for the first time a Lagrangian multiform for the entire AKNS hierarchy. We use it to construct explicitly the necessary objects introduced previously by us: a symplectic multiform, a multi-time Poisson bracket and a Hamiltonian multiform. Equipped with these, we prove the following results: (i) the Lax form containing the whole sequence of Lax matrices of the hierarchy possesses the rational classical r-matrix structure; (ii) the zero curvature equations of the AKNS hierarchy are multiform Hamilton equations associated to our Hamiltonian multiform and multi-time Poisson bracket; (iii) the Hamiltonian multiform provides a way to characterise the infinite set of conservation laws of the hierarchy reminiscent of the familiar criterion {I, H} = 0 for a first integral I.
Passive amplitude-phase modulations and sensing based on Mach–Zehnder interferometer of spoof surface plasmon polaritons
Authors: Cui Wen Yi , Zhang Jingjing , Gao Xinxin , Zhang Xuanru , Cui Tie Jun 
Published: April 2021

Abstract
We numerically and experimentally demonstrate an ultrathin and compact Mach–Zehnder interferometer (MZI) for sensing and amplitude/phase modulations of spoof surface plasmon polariton (SSPP) waves. For a specific frequency, the magnitude and phase of the far-field transmission are modulated when a dielectric sample is loaded on one of the MZI arms. The phase difference between the SSPP waves propagating along the sensing and reference arms causes the outputs from both arms to interfere, allowing small perturbations in the sensing arm to be detected. Our study shows that the sensitivity of the proposed SSPP MZI is significantly higher than that of the single-armed SSPP waveguide, and also better than that of the conventional MZI formed with the traditional microstrip lines. The dependence of the sensitivity on the structural parameters such as geometrical parameters of the detected material and the arm length of MZI is discussed, revealing the possibility of realizing miniaturized MZI with high sensitivity.