bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic dielectric function and phonon self-energy from electrons strongly correlated with acoustic phonons in 2D Dirac crystals
Authors: Kazemian Sina , Fanchini Giovanni 
Published: April 2023

Abstract
The unique structure of two-dimensional (2D) Dirac crystals, with electronic bands linear in the proximity of the Brillouin-zone boundary and the Fermi energy, creates anomalous situations where small Fermi-energy perturbations critically affect the electron-related lattice properties of the system. The Fermi-surface nesting (FSN) conditions determining such effects via electron–phonon interaction require accurate estimates of the crystal’s response function

(
χ
)

as a function of the phonon wavevector q for any values of temperature, as well as realistic hypotheses on the nature of the phonons involved. Numerous analytical estimates of

χ
(

q

)

for 2D Dirac crystals beyond the Thomas–Fermi approximation have been so far carried out only in terms of dielectric response function

χ
(
q
,
ω
)

, for photon and optical-phonon perturbations, due to relative ease of incorporating a q-independent oscillation frequency

(
ω
)

in calculation. Models accounting for Dirac-electron interaction with acoustic phonons, for which ω is linear to q and is therefore dispersive, are essential to understand many critical crystal properties, including electrical and thermal transport. The lack of such models has often led to the assumption that the dielectric response function

χ
(
q
)

in these systems can be understood from free-electron behavior. Here, we show that, different from free-electron systems,

χ
(
q
)

calculated for acoustic phonons in 2D Dirac crystals using the Lindhard model, exhibits a cuspidal point at the FSN condition. Strong variability of

∂
χ

∂
q

persists also at finite temperatures, while

χ
(
q
)

tend to infinity in the dynamic case where the speed of sound is small, albeit non negligible, over the Dirac-electron Fermi velocity. The implications of our findings for electron-acoustic phonon interaction and transport properties such as the phonon line width derived from the phonon self-energy will also be discussed.
A single-turn rotating coil magnetic center calibration system designed for high energy photon source
Authors: Zhang Luyan , Han Yuanying , Dong Lan , Wang Tong , Ke Zhiyong , Wang Xiaolong , Men Lingling , Yan Luping , Lu Shang , Liu Xiaoyang , Yan Haoyue 
Published: April 2023

Abstract
To ensure high-precision alignment of large quantities of magnets in Chinese high energy photon source, a high magnetic center measurement efficiency is required. To achieve this, a unique single-turn rotating coil magnetic center calibration system was designed, which simplifies the traditional multi-turn compensated coil with two sets of windings that can be connected. This design reduces measurement time significantly while increasing precision by incorporating a three-coordinate measuring machine. The study presents the system’s general design, mathematical theory, and test results. Tests replacing the coil and magnets and realigning them demonstrated that the precision and measurement efficiency meet the design requirements. The displacement between the magnetic and mechanical axes was within 20 μm, indicating good performance of the well-fabricated and tested ultra-high gradient quadrupole magnet. The optimized rotating coil system design reduces the entire procedure, including magnet installation and alignment, magnetic axis measurement, and magnetic center extraction to fixed points on the magnet, to only a few hours. Several magnets participating in pre-alignment were measured, and tests and practical operation resulted in small magnetic center displacements.
Slow entropy of some combinatorial constructions
Authors: Banerjee Shilpak , Kunde Philipp , Wei Daren 
Published: April 2023

Abstract
Measure-theoretic slow entropy is a more refined invariant than the classical measure-theoretic entropy to characterize the complexity of dynamical systems with subexponential growth rates of distinguishable orbit types. In this paper we prove flexibility results for the values of upper and lower polynomial slow entropy of rigid transformations as well as maps admitting a good cyclic approximation. Moreover, we show that there cannot exist a general upper bound on the lower measure-theoretic slow entropy for systems of finite rank.
A novel non-contact heart rate measurement method based on EEMD combined with FastICA
Authors: Shi Yingli , Qiu Jian , Peng Li , Han Peng , Luo Kaiqing , Liu Dongmei 
Published: April 2023

Abstract

Objective. The imaging photoplethysmography (IPPG), which is applied to heart rate measurement, is susceptible to interference caused by illumination variations during photography. To improve the accuracy, robustness, and real-time performance of IPPG, a new method combined with modified ensemble empirical mode decomposition (EEMD) and fast independent component analysis (FastICA) was proposed. Approach. On the modified EEMD, to reduce the error caused by the residual white noise of the algorithm, it was characterized by recurrently updating zero-mean white noise for ensemble averaging based on the standard deviation of the input signal. On the modified FastICA, its constructed nonlinear function was superseded by Huber’s approximation function to improve the robustness and running speed. Main results. Comparison experiments were conducted between the MAHNOB-HCI database and own collected data. In the hybrid natural light and computer screen light scenario, the mean absolute error (MAE) of heart rate amounted to 0.93 beats per minute and the correlation coefficient

r

reached 0.85. In the experiments of MAHNOB-HCI database, the MAE amounted to 6.03 beats per minute and the correlation coefficient

r

reached 0.75. Furthermore, the modified method decreased the running time by approximately ten times compared to the original algorithms. Significance. Various experimental results demonstrated that the proposed method significantly improves the accuracy, timeliness, and interference resistance.
Model-independent radiative symmetry breaking and gravitational waves
Authors: Salvio Alberto 
Published: April 2023

Abstract
Models where symmetries are predominantly broken (and masses are then generated) through radiative corrections typically produce strong first-order phase transitions with a period of supercooling, when the temperature dropped by several orders of magnitude. Here it is shown that a model-independent description of these phenomena and the consequent production of potentially observable gravitational waves is possible in terms of few parameters (which are computable once the model is specified) if enough supercooling occurred. It is explicitly found how large the supercooling should be in terms of those parameters, in order for the model-independent description to be valid. It is also explained how to systematically improve the accuracy of such description by computing higher-order corrections in an expansion in powers of a small quantity, which is a function of the above-mentioned parameters. Furthermore, the corresponding gravitational wave spectrum is compared with the existing experimental results from the latest observing run of LIGO and VIRGO and the expected sensitivities of future gravitational wave experiments to find regions of the parameter space that are either ruled out or can lead to a future detection.
One-parameter dynamical dark-energy from the generalized Chaplygin gas
Authors: von Marttens Rodrigo , Barbosa Dinorah , Alcaniz Jailson 
Published: April 2023

Abstract
The fact that Einstein's equations connect the space-time geometry to the total matter content of the cosmic substratum, but not to individual contributions of the matter species, can be translated into a degeneracy in the cosmological dark sector. Such degeneracy makes it impossible to distinguish cases where dark energy (DE) interacts with dark matter (DM) from a dynamical non-interacting scenario using observational data based only on time or distance measurements. In this paper, based on the non-adiabatic generalized Chaplygin gas (gCg) model, we derive and study some cosmological consequences of a varying one-parameter dynamical DE parameterization, which does not allow phantom crossing.
We perform a parameter selection using the most recent publicly available data, such as the data from Planck 2018, eBOSS DR16, Pantheon and KiDS-1000. In light of this analysis, we assess how our model responds to the S
8 tension. We find that CMB data impose strong constraints on the model and conclude that the S
8 tension can be alleviated only for values of the model parameters very close to the ΛCDM cosmology.
i-SPin: an integrator for multicomponent Schrödinger-Poisson systems with self-interactions
Authors: Jain Mudit , Amin Mustafa A. 
Published: April 2023

Abstract
We provide an algorithm and a publicly available code to numerically evolve multicomponent Schrödinger-Poisson (SP) systems with a SO(n) symmetry, including attractive or repulsive self-interactions in addition to gravity. Focusing on the case where the SP system represents the non-relativistic limit of a massive vector field, non-gravitational self-interactions (in particular spin-spin interactions) introduce complexities related to mass and spin conservation which are not present in purely gravitational systems. We address them with an analytical solution for the `kick' step in the algorithm, where we are able to decouple the multicomponent system completely. Equipped with this analytical solution, the full field evolution is second order accurate, preserves spin and mass to machine precision, and is reversible. Our algorithm allows for an expanding universe relevant for cosmology, and the inclusion of external potentials relevant for laboratory settings.
Precision cosmology with primordial GW backgrounds in presence of astrophysical foregrounds
Authors: Racco D. , Poletti D. 
Published: April 2023

Abstract
The era of Gravitational-Wave (GW) astronomy will grant the detection of the astrophysical
GW background from unresolved mergers of binary black holes, and the prospect of probing the
presence of primordial GW backgrounds. In particular, the low-frequency tail of the GW spectrum
for causally-generated primordial signals (like a phase transition) offers an excellent
opportunity to measure unambiguously cosmological parameters as the equation of state of the
universe, or free-streaming particles at epochs well before recombination. We discuss whether
this programme is jeopardised by the uncertainties on the astrophysical GW foregrounds that
coexist with a primordial background. We detail the motivated assumptions under which the
astrophysical foregrounds can be assumed to be known in shape, and only uncertain in their
normalisation. In this case, the sensitivity to a primordial signal can be computed by a simple
and numerically agile procedure, where the optimal filter function subtracts the components of the
astrophysical foreground that are close in spectral shape to the signal. We show that the
degradation of the sensitivity to the signal in presence of astrophysical foregrounds is limited
to a factor of a few, and only around the frequencies where the signal is closer to the
foregrounds. Our results highlight the importance of modelling the contributions of eccentric or
intermediate-mass black hole binaries to the GW background, to consolidate the prospects to
perform precision cosmology with primordial GW backgrounds.
Firing-rate-modulated spike detection and neural decoding co-design
Authors: Zhang Zheng , Constandinou Timothy G 
Published: April 2023

Abstract

Objective. Translational efforts on spike-signal-based implantable brain-machine interfaces (BMIs) are increasingly aiming to minimise bandwidth while maintaining decoding performance. Developing these BMIs requires advances in neuroscience and electronic technology, as well as using low-complexity spike detection algorithms and high-performance machine learning models. While some state-of-the-art BMI systems jointly design spike detection algorithms and machine learning models, it remains unclear how the detection performance affects decoding. Approach. We propose the co-design of the neural decoder with an ultra-low complexity spike detection algorithm. The detection algorithm is designed to attain a target firing rate, which the decoder uses to modulate the input features preserving statistical invariance in long term (over several months). Main results. We demonstrate a multiplication-free fixed-point spike detection algorithm with an average detection accuracy of 97% across different noise levels on a synthetic dataset and the lowest hardware complexity among studies we have seen. By co-designing the system to incorporate statistically invariant features, we observe significantly improved long-term stability, with decoding accuracy degrading by less than 10% after 80 days of operation. Our analysis also reveals a nonlinear relationship between spike detection and decoding performance. Increasing the detection sensitivity improves decoding accuracy and long-term stability, which means the activity of more neurons is beneficial despite the detection of more noise. Reducing the spike detection sensitivity still provides acceptable decoding accuracy whilst reducing the bandwidth by at least 30%. Significance. Our findings regarding the relationship between spike detection and decoding performance can provide guidance on setting the threshold for spike detection rather than relying on training or trial-and-error. The trade-off between data bandwidth and decoding performance can be effectively managed using appropriate spike detection settings. We demonstrate improved decoding performance by maintaining statistical invariance of input features. We believe this approach can motivate further research focused on improving decoding performance through the manipulation of data itself (based on a hypothesis) rather than using more complex decoding models.
Two-dimensional diffusive epidemic process in the presence of quasiperiodic and quenched disorder
Authors: Alencar D S M , Alves T F A , Alves G A , Lima F W S , Macedo-Filho A , Ferreira R S 
Published: April 2023

Abstract
This work considers the diffusive epidemic process model coupled to the square lattice, the Penrose quasiperiodic lattice, and the Voronoi–Delaunay random lattice. The main objective is to verify if spatial disorder influences critical behavior. According to the Harris–Barghathi–Vojta criterion, quenched or quasiperiodic disorder can change the critical behavior of the system, depending on the disorder decay exponent of the lattice. We employed extensive Monte Carlo simulations of the relevant quantities. Furthermore, we estimate the critical exponent ratios. Our results suggest that the disorder does not change the critical behavior when comparing the critical exponent ratios for the three studied lattice structures. In addition, the critical exponents depend on the three possible diffusion regimes: (1) where diffusion is dominated by susceptible individuals, (2) where infected and susceptible individuals have the same diffusion constant, and (3) where diffusion is dominated by the infected individuals.
New duality relation for the discrete Gaussian SOS model on a torus
Authors: Cornu F , Hilhorst H J , Bauer M 
Published: April 2023

Abstract
We construct a new duality for two-dimensional discrete Gaussian models. It is based on a known one-dimensional duality and on a mapping, implied by the Chinese remainder theorem, between the sites of an N × M torus and those of a ring of NM sites. The duality holds for an arbitrary translation-invariant interaction potential

v
(

r

)

between the height variables on the torus. It leads to pairs

(
v
,

v
˜

)

of mutually dual potentials and to a temperature inversion according to

β
˜

=

π
2

/

β

. When

v
(

r

)

is isotropic, duality renders an anisotropic

v
˜

. This is the case, in particular, for the potential that is dual to an isotropic nearest-neighbor potential. In the thermodynamic limit, this dual potential is shown to decay with distance according to an inverse square law with a quadrupolar angular dependence. There is a single pair of self-dual potentials

v
⋆

=

v
⋆

˜

. At the self-dual temperature

β
⋆

=

β
⋆

˜

=
π

the height–height correlation can be calculated explicitly; it is anisotropic and diverges logarithmically with distance.
A magnetoelectric heterostructure employing a magnetic levitation mechanism for harvesting low-frequency vibration energy
Authors: He Wei , Liu Shuanghua 
Published: April 2023

Abstract
A magnetoelectric (ME) heterostructure using shear-mode ME transducers to extract ambient low-frequency vibration energy is proposed. The demand for the traditional mechanical spring is eliminated by utilizing a magnetic levitation mechanism. When the suspending magnet moves relative to the ME transducers, the piezoelectric plates deform in shear mode owing to the magnetostriction of the magnetostrictive plates, and large shear piezoelectric effect is induced. Consequently, larger voltages can be produced by the presented device. The kinetic equation of the energy harvesting system is derived and solved, and the maximum output power is obtained based on the vibration rule and the variation of the sensed magnetic field. The feasibility of the heterostructure is experimentally verified. The maximum load power increases with acceleration. A maximum output power of 1.46mW is generated across a 1.25MΩ resistive load at the acceleration of 0.7g. The generated energy of the heterostructure is sufficient to drive a low-power electronic device. Improvements are feasible, which allow an obvious increase of the maximum output powers by employing a Halbach array with a particular arrangement of the magnets.
Analysis of Dynamic Operation Characteristics of the Integrated Energy System
Authors: Zhai Jiang , Yang Jing , Dang Yanyang , Wang Xiang , Zhang xingliang 
Published: April 2023

Abstract
Gas turbines make the coupling between the natural gas system(NGS) and the power system tighter. So Natural gas systems and power systems are interdependent in security and stability, and only paying attention to the security of the power system itself can not guarantee the security and stability of the system. To meet the problem and challenge, in this paper, a technical route based on the method of characteristic (MOC) is proposed to analyze the interaction of integrated energy systems (IES). It can calculate the transient process of the active and reactive power output of GT after the fluctuation of the NGS. Then, according to the dynamic math model of the natural gas in the pipeline(line-pack), the dynamic change of the line-pack is calculated, and the maximum interruption time of the gas source can be calculated according to the line-pack calculation result. Because of the intrinsic mechanism advantages of the MOC, the time step in the simulation calculation can be very small, which does not affect the calculation efficiency. It can calculate the dynamic change of GT output power, identify weak links in the operation of the system, and provide an important decision-making basis for taking safety control measures. Finally, based on an IES case, it is verified that the method proposed in this paper is of great value to analyze the security and stability of the IES.
Research on the application and benefit of energy storage technology
Authors: Sun Xiaoguang , Geng Jianyu , Liu Kai , Wang Yuanzhi , Wang Zhipeng 
Published: April 2023

Abstract
The randomness, volatility and un-dispatch ability of large-scale new energy connected to the grid have caused a series of problems with the stable operation of the grid and great difficulties with power dispatch. The configuration of the energy storage power station and substation is studied through the metering and reliable capacity planning method of energy storage power station and substation capacity planning. This will improve the level of utilization of grid assets and promote the coordinated development of new energy, energy storage and the grid.
Optimization of Ultrasonic Welding Parameters Based on Response Surface Methodology
Authors: Yao Zhen , Liu Kaijie , Ding Rongjie , Luo Zilun , He Jian 
Published: April 2023

Abstract
In this paper, the optimal process parameters for ultrasonic welding of copper wire and aluminum plates are studied using the response surface method. The effect of various welding parameters on the welding effect is experimentally tested. The results are analyzed using the Box-Behnken design to establish a regression model to optimize the welding parameters. The model uses the welding height, welding energy and welding pressure as influencing factors and the welding strength and welding time as response values. The results show that optimal welding of copper wire and aluminum plate is obtained at the height of 2.2mm, energy 1300J, amplitude 85% or 95%. The response surface method used in this paper can provide a reference for the ultrasonic welding of other materials in the study of process parameters.
Gate modulation drive and modeling of IGBT in MMC converters
Authors: Wang Kefeng , Wen Fuyue , Sun Baokui , Zhou Jianbo , Han Lei , Wang Jiangyong 
Published: April 2023

Abstract
The energy surplus caused by the alternating current (AC) system’s failure results in a severe overvoltage problem in Bai hetan-Jiangsu ±800 kV hybrid cascade direct current (DC) project. However, the insulated gate bipolar transistor’s (IGBT) off-state voltage is the crucial reason for the insufficient voltage capacity of modular multilevel converter (MMC). Therefore, analysis and suppression of the off-state overvoltage are of vital significance. The off-state model of IGBT in an MMC converter is established, and the process of IGBT’s turning off is analyzed. Then, based on the characteristics of IGBT’s off-state and traditional resistance switching strategy, the gate modulation drive strategy is proposed, and the equivalent topology of the MMC submodule with the strategy is established. Finally, MMC submodule models with gate modulation drive and resistance switching strategy, respectively, are built in simulation software, and two groups of data are compared under multiple groups of the control cycle and reference current slope given. The simulation results show that the gate modulation drive supresses the off-state overvoltage on IGBT better than the resistance switching strategy. Moreover, the shorter the control cycle and the less reference current slope, the better the overvoltage suppression.
Comparison of Power Density of Triboelectric Generators via Frequency-up-Conversion Method
Authors: Li Zhongjie , Yang Chao , Peng Yan , Shen Fan , Peng Xuzhang 
Published: April 2023

Abstract
In this paper, we experimentally compared the instantaneous volume power density and the average volume power density of the triboelectric nanogenerator (TENG) with and without a frequency-up conversion mechanism. We first proposed a double-cantilever structure TENG (DC-TENG). A conventional contact-separation TENG was also constructed as the control case for electric output comparison. A few experiments were then conducted to investigate how the cantilever’s high-frequency vibrations influence the output voltage, instantaneous power, etc., before those of the triboelectric nanogenerator without frequency conversion. The results indicate that the double-cantilever system effectively converts low-frequency linear impact into high-frequency vibration. As of the best contrast, the DC-TENG yields a maximal open-circuit voltage of 141.5 V, an instantaneous power of 0.76 mW, and an average power of 0.77 μW excited by a linear impact, which frequency is 0.6 Hz and amplitude is 8 mm. The peak and the average power density of generators with the frequency convert device are enhanced by 34 times and 13 times as high as those of the original case, respectively. This finding proves that the cantilever integrated with triboelectric nanogenerators is an effective configuration with evident performance improvement.