bluuebunny/crossref_metadata_2025 huggingface dataset:
A method and its validation for measuring the absolute time-delay of the read-out system of a space electrostatic accelerometer
Authors: Li Duo , Chang Xin , Yu Jianbo , Bai Yanzheng , Wang Chengrui , Zhou Zebing
Published: March 2023

High-precision accelerometers play an important role in satellite gravity field missions to measure the non-conservative forces acting on the satellites. To map the Earth’s gravity field, the accelerometer data must be time-tagged using the on-board global navigation satellite system time reference. For example, in the Gravity Recovery and Climate Experiment mission, the time-tag error of the accelerometers must be within 0.1 ms with respect to the satellite clock. To realize this requirement, the time delay between the actual measurement time and the nominal time of the accelerometer should be considered and corrected. This paper presents the techniques for measuring the absolute time delay of an electrostatic accelerometer on the ground, where this delay is mainly introduced by the low-noise scientific data read-out system, which is based on a Σ–Δ (sigma–delta) analog-to-digital converter (ADC). First, the time-delay sources of the system are theoretically analyzed. Then, a time-delay measurement method is proposed, and its principle and system error are presented. Finally, a prototype is built to demonstrate and investigate the feasibility of the method. Experimental results show that the absolute time delay of the read-out system is 150.80 ± 0.04 ms. This important value is the basis for the final time-tag error correction of the scientific accelerometer data. Meanwhile, the time-delay measurement method described in this paper is also useful for other data acquisition systems.
RC-FODS algorithm for solving numerical solutions of fractional order dynamical system
Authors: Lin Zi-Fei , Zhao Jia-Li , Liang Yan-Ming , Kapitaniak Tomasz
Published: March 2023

We present a new method, the solving fractional order dynamical systems using reservoir computing (RC-FODS) algorithm, for solving fractional order nonlinear dynamical systems using deep learning. The method is shown to have advantages over traditional methods, such as less calculation time and higher accuracy. This study also compares the RC-FODS algorithm with the traditional recurrent neural network and echo state network algorithms and finds that it has a higher accuracy and shorter computation time. The accuracy of the method is validated using the largest Lyapunov exponent, and the study also analyzes the advantages and disadvantages of different deep learning models. Our study concludes that the RC-FODS algorithm is a promising method for solving fractional order nonlinear dynamical systems with a high accuracy and low error rate.
Electronic transition dipole moments from time-independent excited-state density-functional tight-binding
Authors: Deshaye Megan Y. , Wrede Alex T. , Kowalczyk Tim
Published: March 2023

Computationally inspired design of organic electronic materials requires robust models of not only the ground and excited electronic states but also of transitions between these states. In this work, we introduce a strategy for obtaining electronic transition dipole moments for the lowest-lying singlet–singlet transition in organic chromophores from time-independent excited-state density-functional tight-binding (ΔDFTB) calculations. Through small-molecule benchmarks and applications to larger chromophores, we explore the accuracy, potential, and limitations of this semiempirical strategy. While more accurate methods are recommended for small systems, we find some evidence for the method’s potential in high-throughput molecular screening applications and in the analysis of molecular dynamics simulations.
Fast aerodynamics prediction of laminar airfoils based on deep attention network
Authors: Zuo Kuijun , Ye Zhengyin , Zhang Weiwei , Yuan Xianxu , Zhu Linyang
Published: March 2023

The traditional method for obtaining aerodynamic parameters of airfoils by solving Navier–Stokes equations is a time-consuming computing task. In this article, a novel data-driven deep attention network (DAN) is proposed for reconstruction of incompressible steady flow fields around airfoils. To extract the geometric representation of the input airfoils, the grayscale image of the airfoil is divided into a set of patches, and these are input into the transformer encoder by embedding. The geometric parameters extracted from the transformer encoder, together with the Reynolds number, angle of attack, flow field coordinates, and distance field, are input into a multilayer perceptron to predict the flow field of the airfoil. Through analysis of a large number of qualitative and quantitative experimental results, it is concluded that the proposed DAN can improve the interpretability of the model while obtaining good prediction accuracy and generalization capability for different airfoils and flow-field states.
Impacts of salt concentration on nucleate pool boiling of NaCl solution
Authors: Liu Qi , Zhao Yanwei , Wu Yuxin , Qin Guangyu , Li Guangde , Lyu Junfu
Published: March 2023

Salt solution pool boiling is of great significance in thermal engineering equipment, such as boilers and heat exchangers. Few researchers have been able to draw on systematic research into the impacts of salt concentration on boiling heat transfer coefficients. This experimental work is aimed to understand the role of dissolved salts on pool boiling performance, which is affected by surface wettability and bubble dynamics. Pool boiling experiment was conducted within a broad range of salt concentration. The results show two different tendencies for the two heating surfaces. The heat transfer coefficient is enhanced in the pin–fin heating surface while deteriorated in the bare heating surface as the salt concentration increased. It is indicated that salt solution promotes bubble diameter and nucleate density for ∼13% and 9%, respectively, by strengthening the hydrophobicity of the pin–fin heating surface. Hence, the boiling heat transfer is strengthened.
Effect of surface roughness and blade material on the performance of a stationary Savonius wind turbine under different operating conditions
Authors: Mat Yazik Muhamad Hasfanizam , Chang Wei Shyang , Ishak Mohammad Hafifi Hafiz , Fatahian Esmaeel , Ismail Farzad
Published: March 2023

The Savonius wind turbine is a vertical-axis wind turbine invented in 1930s consisting of a cylindrical drum with semi-circular blades attached to the drum. It is popular for its simple design, low costs, and self-starting ability, making it feasible for rural areas. As a rotating device, the blade is considered an important component of the Savonius turbine because it captures energy from an omni-directional wind flow and converts it into mechanical/electrical energy. Blade corrosion can cause a surface degradation which affects the blade's aerodynamic and structural performance. The relation between surface roughness and turbine performance has been addressed in various studies; however, most of these studies focused on horizontal-axis wind turbine. This study analyzed the performance of a static Savonius turbine using a three-dimensional (3D) computer simulation at different blade angle positions through a one-way fluid–structure interaction in terms of static coefficients, von Mises stresses, and deformation with different surface roughness at different wind velocities. The simulation reveals that the position with highest static torque coefficient is when the turbine is resting at 15° with respect to the flow direction. The flow velocity increases the performance; however, the surface roughness deteriorates the flow and decreases the static coefficient. The simulation herein predicts no structural failure, but different materials exhibit different maximum stress and deformation showing the importance of material selection in the turbine blade development. The findings from this study helps to identify a suitable material for the development of the Savonius turbine from a material point of view to minimize turbine downtime and potentially save cost.
Ion filling of a one-dimensional nanofluidic channel in the interaction confinement regime
Authors: Robin Paul , Delahais Adrien , Bocquet Lydéric , Kavokine Nikita
Published: March 2023

Ion transport measurements are widely used as an indirect probe for various properties of confined electrolytes. It is generally assumed that the ion concentration in a nanoscale channel is equal to the ion concentration in the macroscopic reservoirs it connects to, with deviations arising only in the presence of surface charges on the channel walls. Here, we show that this assumption may break down even in a neutral channel due to electrostatic correlations between the ions arising in the regime of interaction confinement, where Coulomb interactions are reinforced due to the presence of the channel walls. We focus on a one-dimensional channel geometry, where an exact evaluation of the electrolyte’s partition function is possible with a transfer operator approach. Our exact solution reveals that in nanometer-scale channels, the ion concentration is generally lower than in reservoirs and depends continuously on the bulk salt concentration, in contrast to the conventional mean-field theory that predicts an abrupt filling transition. We develop a modified mean-field theory taking into account the presence of ion pairs that agrees quantitatively with the exact solution and provides predictions for experimentally relevant observables, such as the ionic conductivity. Our results will guide the interpretation of nanoscale ion transport measurements.
A “moment-conserving” reformulation of GW theory
Authors: Scott Charles J. C. , Backhouse Oliver J. , Booth George H.
Published: March 2023

We show how to construct an effective Hamiltonian whose dimension scales linearly with system size, and whose eigenvalues systematically approximate the excitation energies of GW theory. This is achieved by rigorously expanding the self-energy in order to exactly conserve a desired number of frequency-independent moments of the self-energy dynamics. Recasting GW in this way admits a low-scaling O[N4] approach to build and solve this Hamiltonian, with a proposal to reduce this further to O[N3]. This relies on exposing a novel recursive framework for the density response moments of the random phase approximation, where the efficient calculation of its starting point mirrors the low-scaling approaches to compute RPA correlation energies. The frequency integration of GW, which distinguishes so many different GW variants, can be performed without approximation directly in this moment representation. Furthermore, the solution to the Dyson equation can be performed exactly, avoiding analytic continuation, diagonal approximations, or iterative solutions to the quasiparticle equation, with the full-frequency spectrum obtained from the complete solution of this effective static Hamiltonian. We show how this approach converges rapidly with respect to the order of the conserved self-energy moments and is applied across the GW100 benchmark dataset to obtain accurate GW spectra in comparison to traditional implementations. We also show the ability to systematically converge all-electron full-frequency spectra and high-energy features beyond frontier excitations, as well as avoiding discontinuities in the spectrum, which afflict many other GW approaches.
Double-layer magnetic recording with multilayer perceptron decoder for single-reader/two-track reading in BPMR systems
Authors: Rueangnetr N. , Koonkarnkhai S. , Kovintavewat P. , Warisarn C.
Published: March 2023

To expand an areal density of hard disk drives, bit-patterned magnetic recording (BPMR) using a patterned medium instead of a granular medium as employed in perpendicular magnetic recording is attracting much attention as the next-generation recording technology. To further increase the storage capacity of BPMR, multi-layer magnetic recording can be combined with BPMR. Therefore, this paper considers double-layer magnetic recording with a single-reader/two-track reading technique for the staggered BPMR system, which is performed together with a rate-3/5 modulation code. This paper proposes to utilize a multilayer perceptron decoder to decode and estimate the log-likelihood ratio value of the recorded bit sequence that is obtained from the equalized channel. Simulation results show that at a bit-error rate of 10−4, the proposed system with a double-layer recording medium can achieve an improvement gain of about 1.2 decibel if compared to that with a regular single-layer recording medium, even in the presence of media noise.
Physics-based modelling of junction fires: parametric study
Authors: Hassan Ahmad , Accary Gilbert , Sutherland Duncan , Moinuddin Khalid
Published: March 2023

Background Junction fires occur when two fire fronts merge. The rate of spread (ROS) and heat release rate (HRR) of the junction increase more quickly than that of each fire front, this effect exacerbated by slopes. Aims Numerical modelling of junction fires and an interpretation of their behaviour are given examining the key influencing factors. Methods Twenty physics-based simulations of laboratory-scale junction fires were performed for a shrub fuel bed using FIRESTAR3D, varying slope (0°–40°) and junction angles (15°–90°). Key results Accelerative and decelerative behaviours were observed for junction angles lower than 45°, but above this, deceleration was absent. The behaviour was firmly related to junction angle evolution, which controlled the flame and interactions between fire fronts. HRR followed similar trends; maximum HRR increased with increasing junction angle. Convection was the primary heat transfer mode in the initial propagation phase. In no-slope cases, radiation was the dominant method of heat transfer, but convection dominated fires on slopes. Conclusions The physics-based model provided great insight into junction fire behaviour. The junction angle was critical for determining ROS and fire behaviour. Implications The research helped to assess the effects of some topographical parameters in extreme fires. Situational awareness, operational predictions and firefighter safety will consequently improve.
RNA recruitment switches the fate of protein condensates from autophagic degradation to accumulation
Authors: Zheng Hui , Peng Kangfu , Gou Xiaomeng , Ju Chen , Zhang Hong
Published: March 2023

Protein condensates can evade autophagic degradation under stress or pathological conditions. However, the underlying mechanisms are unclear. Here, we demonstrate that RNAs switch the fate of condensates in Caenorhabditis elegans. PGL granules undergo autophagic degradation in embryos laid under normal conditions and accumulate in embryos laid under heat stress conditions to confer stress adaptation. In heat-stressed embryos, mRNAs and RNA control factors partition into PGL granules. Depleting proteins involved in mRNA biogenesis and stability suppresses PGL granule accumulation and triggers their autophagic degradation, while loss of activity of proteins involved in RNA turnover facilitates accumulation. RNAs facilitate LLPS of PGL granules, enhance their liquidity, and also inhibit recruitment of the gelation-promoting scaffold protein EPG-2 to PGL granules. Thus, RNAs are important for controlling the susceptibility of phase-separated protein condensates to autophagic degradation. Our work provides insights into the accumulation of ribonucleoprotein aggregates associated with the pathogenesis of various diseases.
Dark Contributions to h → μ
+
μ
– in the Presence of a μ-Flavored Vector-Like Lepton
Authors: De Bibhabasu
Published: March 2023

A simple extension of the standard model (SM) with a μ-flavored vector-like lepton (VLL) doublet and a real singlet scalar can have an interesting implication to the h → μ
+
μ
– decay while offering the simplest possible explanation for the dark matter (DM) phenomenology. Assuming the real singlet scalar to be a viable DM candidate, it has been shown that the muon Yukawa coupling can have a negative contribution at the one-loop order if the 2nd generation SM leptons are allowed to couple with the VLL doublet. The stringent direct detection bounds corresponding to a real singlet scalar DM can easily be relaxed if the SM quark sector was augmented with a dimension-6 operator at some new physics (NP) scale Λ
NP. Thus, this model presents a significant phenomenological study where the muon Yukawa coupling can be corrected within a real singlet scalar DM framework. The considered parameter space can be tested/constrained through the high luminosity run of the LHC (HL-LHC) and future direct detection experiments.
On the non-minimal coupling of magnetic fields with gravity in Schwarzschild spacetime
Authors: Ravi Kumar , Pavlović Petar , Saveliev Andrey
Published: March 2023

In this work we study the effects of non-minimal coupling between electromagnetism and gravity, which are motivated by quantum effects such as vacuum polarization. We investigate the modification of both asymptotically dipole and uniform magnetic fields around a Schwarzschild black hole that come as the result of non-minimal coupling. While in both cases the magnetic field gets enhanced or suppressed with respect to the case of minimal coupling, depending on the sign of non-minimal coupling parameter, in the case of a background uniform magnetic field the direction of the magnetic field also alters in the vicinity of the black hole horizon. We have discussed the possible astrophysical and cosmological sources for which the vacuum polarization may be at play, while also discussing the observational effects, in particular the possibility of synchrotron radiation from the vicinity of a black hole. We conclude that such observations could be used to constrain the value of the non-minimal coupling parameter.
The classical Aharonov–Bohm interaction as a relativity paradox
Authors: Boyer Timothy H
Published: March 2023

The situation of a charged particle passing down the symmetry axis through a magnetic toroid presents a relativity paradox; different inertial frames suggest different forces on the charge and on the toroid due to the unperturbed systems. We review the charge-toroid interaction and suggest that the magnetic Aharonov–Bohm situation is misunderstood because of unfamiliarity with the acceleration fields following from the Darwin Lagrangian, which go unmentioned in recent textbooks of classical electromagnetism.
Various methods for solving the pursuit problem with two objects on a plane
Authors: Mančev Ivan , Kostić Ljiljana
Published: March 2023

We shall consider the classical problem of pursuit which can be described as follows. If object A (the pursued) moves along a known trajectory, then object B (the pursuer) which has a higher speed describes a pursuit trajectory (the chase trajectory) if B is always directed towards A. This article examines only the simplest two-dimensional case where the pursued moves rectilinearly, both the pursuer and the pursued have constant velocities, and the speed of the pursuer is γ times greater than that of the pursued. The different methods for solving the pursuit problem on a plane presented in this article require various levels of knowledge in mathematics as well as basic principles of two-dimensional kinematics. By learning pursuit problem, undergraduate students will be trained to solve the more complicated problems associated with this. On the other hand, the pursuit problem is convenient for Problem Based Learning as well as opportunity for animation of pursuit curves.
Minimally driven Kapitza oscillator: a pedagogical perspective from Newtonian mechanics and geometry
Authors: Pal Mainak
Published: March 2023

The unstable top-equilibrium point of a simple pendulum turns stable when its pivot point is given a fast and strong enough vertical vibration. Known as the Kapitza oscillator, it has four symmetrically spaced points of equilibrium in absence of gravity, out of which two are stable and two are unstable. This article, completely based on a geometric argument and an elementary intuition in Newtonian mechanics, is a visual and pedagogical exposition of (a) why the oscillator has four symmetrically spaced equilibrium points in absence of gravity, (b) which of them are stable or unstable, (c) why they are so and (d) how the stability, position and number of the equilibrium points change when gravity is turned on gradually along the line of vibration of the pivot of the oscillator. A minimal impulsive drive of the pivot is sufficient to illustrate the bare bones of the phenomenon. I propose a construction that can sustain the minimal drive passively in absence of dissipative forces, or actively if all dissipative forces cannot be eliminated. In either of the cases, the discussed arguments apply.
Effect of porous heat transfer model on different equivalent thermal dose methods considering an experiment-based nanoparticle distribution during magnetic hyperthermia
Authors: Tang Yundong , Wang Yuesheng , Flesch Rodolfo C C , Jin Tao
Published: March 2023

Magnetic fluid hyperthermia damages malignant cells by keeping the therapeutic temperature within a specific range after magnetic nanoparticles (MNPs) are exposed to an alternating magnetic field. The temperature distribution inside bio-tissue is usually predicted by a classic Pennes bio-heat transfer equation, which considers a heat source due to a homogeneous distribution for MNPs. Aiming at this problem, this study compares the Pennes model to a porous heat transfer model, named local thermal non-equilibrium equation, by considering an experiment-based MNPs distribution, and evaluates the thermal damage degree for malignant tissue by two different thermal dose methods. In addition, this study evaluates the effect of porosity and different blood perfusion rates on both effective treatment temperature and equivalent thermal dose. Simulation results demonstrate that different bio-heat transfer models can result in significant differences in both the treatment temperature profile and the thermal damage degree for tumor region under the same power dissipation of MNPs. Furthermore, scenarios considering a temperature-dependent blood perfusion rate or a lower porosity can have a positive effect on the temperature distribution inside tumor, while having a lower value in the maximum equivalent thermal dose in both thermal dose evaluation methods.
Effect of Y-doping on switching mechanisms and impedance spectroscopy of HfO
x
-based RRAM devices
Authors: Bai Jiao , Xie Weiwei , Qu Dehao , Wei Shengsheng , Li Yue , Qin Fuwen , Ji Min , Wang Dejun
Published: March 2023

Y-doping can effectively improve the performance of HfO
x
-based resistive random-access memory (RRAM) devices, but the underlying physical mechanism of Y-doping affecting the performance of HfO
x
-based memristors is still missing and unclear. Although impedance spectroscopy (IS) has been widely used to investigate impedance characteristics and switching mechanisms of RRAM devices, there is less IS analysis on Y-doped HfO
x
-based RRAM devices as well as devices at different temperatures. Here, the effect of Y-doping on the switching mechanism of HfO
x
-based RRAM devices with a Ti/HfO
x
/Pt structure were reported using current–voltage characteristics and IS. The results indicated that doping Y into HfO
x
films could decrease the forming/operate voltage and improve the RS uniform. Both doped and undoped HfO
x
-based RRAM devices obeyed the oxygen vacancies (V
O) conductive filament model along the grain boundary (GB). Additionally, the GB resistive activation energy of the Y-doped device was inferior to that of the undoped device. It exhibited a shift of the V
O trap level towards the conduction band bottom after Y-doping in the HfO
x
film, which was the main reason for the improved RS performance.
Investigation of ultrafast demagnetization and Gilbert damping and their correlation in different ferromagnetic thin films grown under identical conditions
Authors: Mukhopadhyay Suchetana , Majumder Sudip , Narayan Panda Surya , Barman Anjan
Published: March 2023

Following the demonstration of laser-induced ultrafast demagnetization in ferromagnetic nickel, several theoretical and phenomenological propositions have sought to uncover its underlying physics. In this work we revisit the three temperature model (3TM) and the microscopic three temperature model (M3TM) to perform a comparative analysis of ultrafast demagnetization in 20 nm thick cobalt, nickel and permalloy thin films measured using an all-optical pump-probe technique. In addition to the ultrafast dynamics at the femtosecond timescales, the nanosecond magnetization precession and damping are recorded at various pump excitation fluences revealing a fluence-dependent enhancement in both the demagnetization times and the damping factors. We confirm that the Curie temperature to magnetic moment ratio of a given system acts as a figure of merit for the demagnetization time, while the demagnetization times and damping factors show an apparent sensitivity to the density of states at the Fermi level for a given system. Further, from numerical simulations of the ultrafast demagnetization based on both the 3TM and the M3TM, we extract the reservoir coupling parameters that best reproduce the experimental data and estimate the value of the spin flip scattering probability for each system. We discuss how the fluence-dependence of inter-reservoir coupling parameters so extracted may reflect a role played by nonthermal electrons in the magnetization dynamics at low laser fluences.
Recent advances in highly accelerated 3D MRI
Authors: Zhou Yihang , Wang Haifeng , Liu Congcong , Liao Binyu , Li Ye , Zhu Yanjie , Hu Zhangqi , Liao Jianxiang , Liang Dong
Published: March 2023

Three-dimensional MRI has gained increasing popularity in various clinical applications due to its improved through-plane spatial resolution, which enhances the detection of subtle abnormalities and provides valuable clinical information. However, the long data acquisition time and high computational cost pose significant challenges for 3D MRI. In this comprehensive review article, we aim to summarize the latest advancements in accelerated 3D MR techniques. Covering over 200 remarkable research studies conducted over the past 20 years, we explore the development of MR signal excitation and encoding, advancements in reconstruction algorithms, and potential clinical applications. We hope that this survey serves as a valuable resource, providing insights into the current state of the field and serving as a guide for future research in accelerated 3D MRI.
Foundations of machine learning for low-temperature plasmas: methods and case studies
Authors: Bonzanini Angelo D , Shao Ketong , Graves David B , Hamaguchi Satoshi , Mesbah Ali
Published: March 2023

Machine learning (ML) and artificial intelligence have proven to be an invaluable tool in tackling a vast array of scientific, engineering, and societal problems. The main drivers behind the recent proliferation of ML in practically all aspects of science and technology can be attributed to: (a) improved data acquisition and inexpensive data storage; (b) exponential growth in computing power; and (c) availability of open-source software and resources that have made the use of state-of-the-art ML algorithms widely accessible. The impact of ML on the field of low-temperature plasmas (LTPs) could be particularly significant in the emerging applications that involve plasma treatment of complex interfaces in areas ranging from the manufacture of microelectronics and processing of quantum materials, to the LTP-driven electrification of the chemical industry, and to medicine and biotechnology. This is primarily due to the complex and poorly-understood nature of the plasma-surface interactions in these applications that pose unique challenges to the modeling, diagnostics, and predictive control of LTPs. As the use of ML is becoming more prevalent, it is increasingly paramount for the LTP community to be able to critically analyze and assess the concepts and techniques behind data-driven approaches. To this end, the goal of this paper is to provide a tutorial overview of some of the widely-used ML methods that can be useful, amongst others, for discovering and correlating patterns in the data that may be otherwise impractical to decipher by human intuition alone, for learning multivariable nonlinear data-driven prediction models that are capable of describing the complex behavior of plasma interacting with interfaces, and for guiding the design of experiments to explore the parameter space of plasma-assisted processes in a systematic and resource-efficient manner. We illustrate the utility of various supervised, unsupervised and active learning methods using LTP datasets consisting of commonly-available, information-rich measurements (e.g. optical emission spectra, current–voltage characteristics, scanning electron microscope images, infrared surface temperature measurements, Fourier transform infrared spectra). All the ML demonstrations presented in this paper are carried out using open-source software; the datasets and codes are made publicly available. The FAIR guiding principles for scientific data management and stewardship can accelerate the adoption and development of ML in the LTP community.
Low temperature atomic hydrogen annealing of InGaAs MOSFETs
Authors: Olausson Patrik , Yadav Rohit , Timm Rainer , Lind Erik
Published: March 2023

Recent work showing a strong quality improvement of the Si/SiO2 material system by low temperature atomic hydrogen annealing (AHA), and the fact that III–V semiconductors outperform Si in many applications makes the investigation of AHA on III–V/high-k interfaces to a very interesting topic. In this work, the potential of AHA as a low temperature annealing treatment of InGaAs metal–oxide–semiconductor field-effect transistors is presented and compared to conventional annealing in a rapid thermal process (RTP) system using forming gas. It is found that post metal annealing in atomic hydrogen greatly enhances the quality of the metal–oxide–semiconductor structure in terms of effective mobility, minimum subthreshold swing, and reliability. The device performance is comparable to RTP annealing but can be performed at a lower temperature, which opens up for integration of more temperature-sensitive materials in the device stack.
Rational and semi-rational solution to the (3+1)-dimensional Kadomtsev-Petviashvili-Boussinesq-like equation
Authors: Ma Hongcai , Chen Xiaoyu , Deng Aiping
Published: March 2023

In the paper, we take the (3+1)-dimensional KP-Boussinesq-like equation as an instance and utilize long wave limit approach to generate rational solution and semi-rational solution from the N-order soliton solution. For N = 2, 3, with specific parametric constraints, we have constructed rational solutions which can be presented as first order line rogue wave and single breather from two-soliton solution, and semi-rational solution is classified as first order kink-shaped rogue wave and a hybrid of breather and one soliton from three-soliton solution. For N = 4, the rational solution includes second order line rogue wave, double breather, interaction between two breathers and a hybrid of breather and line rogue wave. The semi-rational solution contains second order kink-shaped rogue wave and interaction between breather, soliton and line rogue wave. In addition, we give mathematical expressions for higher N-order rational solution.
Influence of spontaneously generated coherence on absorption, dispersion, and group index in a five-level cascade atomic system
Authors: Mai Anh Le Nguyen , Bang Nguyen Huy , Van Phu Nguyen , Khoa Dinh Xuan , Thi Ngan Nguyen , Huyen Bui Thu , Doai Le Van
Published: March 2023

By solving the density matrix equations in the steady state, we have derived analytical expressions for the absorption, dispersion, and group index of a five-level cascade-type atomic system as functions of laser intensity and frequency, spontaneously generated coherence (SGC), and relative phase of applied fields. The influences of SGC and relative phase on absorption, dispersion, and group index of this system under electromagnetically induced transparency (EIT) are studied. It is shown that the three EIT windows of system become deeper and narrower as the strength of SGC increases. These lead to an increase in the slope and the amplitude of the dispersion curves at three EIT windows. As a result, the amplitude of the group index at these three EIT windows also becomes larger when the strength of SGC increases. In particular, the group index can easily be switched between negative and positive values i.e., the light propagation can easily be converted between superluminal to subluminal modes by adjusting the strength of SGC, relative phase or the coupling laser intensity.
Noether symmetries in f(T, TG) cosmology
Authors: Kadam S A , Mishra B , Levi Said Jackson
Published: March 2023

All degrees of freedom related to the torsion scalar can be explored by analysing, thef(T,TG) gravity formalism where,Tis a torsion scalar andTGis the teleparallel counterpart of the Gauss-Bonnet topological invariant term. The well-known Noether symmetry approach is a useful tool for selecting models that are motivated at a fundamental level and determining the exact solution to a given Lagrangian, hence we explore Noether symmetry approach inf(T,TG) gravity formalism with three different forms off(T,TG) and study how to establish nontrivial Noether vector form for each one of them. We extend the analysis made in S Capozziello, M De Laurentis, and K F Dialektopoulos 2016, “Noether symmetries in gauss–bonnet-teleparallel cosmology,”Eur. Phys. J. C76, 629. for the formf(T,TG)=b0TGk+t0Tmand discussed the symmetry for this model with linear teleparallel equivalent of the Gauss-Bonnet term, followed by the study of two models containing exponential form of the teleparallel equivalent of the Gauss-Bonnet term. We have shown that all three cases will allow us to obtain non-trivial Noether vector which will play an important role to obtain the exact solutions for the cosmological equations.
Estimation of electron temperature dynamics in warm dense gold using measured and DFT-calculated plasma frequency
Authors: Shikne Rakesh , Yoneda Hitoki , Chaurasia Shivanand
Published: March 2023

In this study, we report the temperature evolution of electron density of states (DOS) along with the thermophysical and optical properties of gold calculated by means of density functional theory (DFT). To corroborate the effects due to temperature-dependent electron density of states, we performed ellipsometric pump-probe experiments with broadband white-light continuum probe pulse that covered both the intraband and the interband region of the dielectric permittivity of gold. The intraband part was analyzed to give plasma frequency and collision rate as a function of the pump-probe delay. The electron temperature evolution of warm dense gold is determined by comparing the experimental plasma frequency dynamics with the DFT-calculations. The study also emphasizes the essential role of temperature-dependent modifications to the electron DOS and the thermophysical properties in order to model the non-equilibrium states of matter.
Quantum chaos and thermalization in the two-mode Dicke model
Authors: Kirkova Aleksandrina V , Ivanov Peter A
Published: March 2023

We discuss the onset of quantum chaos and thermalization in the two-mode Dicke model, which describes the dipolar interaction between an ensemble of spins and two bosonic modes. The two-mode Dicke model exhibits normal to superradiant quantum phase transition with spontaneous breaking either of a discrete or continuous symmetry. We study the behaviour of the fidelity out-of-time-order correlator (FOTOC) derived from the Loschmidt echo signal in the quantum phases of the model. We show that the exponential growth of the FOTOC in the beginning of the time evolution cannot be related to a classical unstable point in the general case. Furthermore, we find that the collective spin observable in the two-mode Dicke model quickly saturates to its long-time average value, and shows very good agreement between its diagonal ensemble average and microcanonical average even for a small number of spins. We show that the temporal fluctuations of the expectation value of the collective spin observable around its average are small and decrease with the effective system size, which leads to thermalization of the spin system.
Study of optoelectronic and thermoelectric properties of double perovskites X2HfI6 (X = Ga, In, Tl) for renewable energy
Authors: Kattan Nessrin A , Rouf Syed Awais , Mahmood Q , AL-Anazy Murefah Mana , Amin Mohammed A , Hegazy H H , Morsi Manal , Alotaibi Nouf H , Somaily H H
Published: March 2023

The double perovskites (DPs) are outstanding materials for renewable energy and other optoelectronic applications. Here in this paper, the thermoelectric and optical behavior of X2HfI6 (X = Ga, In, Tl) have been explained systematically by DFT. The structural stability has been certified using ionic radii in terms of tolerance factor, and dynamic stability has been confirmed by positive phonon dispersion frequencies in acoustic modes. The band structure findings show the direct band gaps for (Ga, In, Tl) based DPs. The optical properties have been investigated by dispersion, absorption, refection, and related other optical characteristics. The absorption bands are existing in ultraviolet region and shifted to higher energy (blue shift). The reflection and optical loss of light are noted less than 0.3 which increases their potential for optoelectronic devices. The high Seebeck coefficient and electrical conductivity along with ultralow lattice thermal conductivity confirm the high figure of merit at and below the room temperature.
Estimation of carbon dust particle lifetime in a radio-frequency thermal plasma
Authors: Long J M , Ou Jing , Huang Yueheng
Published: March 2023

A carbon dust particle in a collisionless thermal plasma is studied under the assumption of the drifting Maxwellian distribution with a time varying velocity caused by the oscillatory radio-frequency (RF) field. The dust particle potential decreases while its fluctuation increases with the increasing RF field strength or the decreasing frequency even taken into account the thermionic current. As the thermionic current is increased by changing the dust particle surface temperature, the resultant increasing dust particle potential can vary from negative to positive, and the fluctuation of the dust particle potential increases first and then decreases. When the dust particle heating and mass loss processes are considered, it is found that the fluctuation of the total energy flux to the dust particle is mainly determined by the electron energy flux, which causes the stair-like increase of the dust particle surface temperature in heating process and the stair-like decrease of the dust particle radius in the mass loss process. With the increasing RF field strength or decreasing frequency, the increase of the total energy flux to the dust particle leads to the decrease of the dust particle lifetime. The results mean that the presence of the RF field can shorten the dust particle lifetime or reduce the dust particle survivability in RF plasma, by compared with in the absence of the RF field.
On numerical stationary distribution of overdamped Langevin equation in harmonic system
Authors: Li De-Zhang , Yang Xiao-Bao
Published: March 2023

Efficient numerical algorithm for stochastic differential equation has been an important object in the research of statistical physics and mathematics for a long time. In this work we study the highly accurate numerical algorithm for the overdamped Langevin equation. In particular, our interest is in the behaviour of the numerical schemes for solving the overdamped Langevin equation in the harmonic system. Based on the large friction limit of the underdamped Langevin dynamic scheme, three algorithms for overdamped Langevin equation are obtained. We derive the explicit expression of the stationary distribution of each algorithm by analysing the discrete time trajectory for both one-dimensional case and multi-dimensional case. The accuracy of the stationary distribution of each algorithm is illustrated by comparing with the exact Boltzmann distribution. Our results demonstrate that the “BAOA-limit” algorithm generates an accurate distribution of the harmonic system in a canonical ensemble, within a stable range of time interval. The other algorithms do not produce the exact distribution of the harmonic system.
Optically pumped wavelength-tunable lasing from a GaN beam cavity with an integrated Joule heater pivoted on Si
Authors: Qin Feifei , Sun Yang , Yang Ying , Li Xin , Wang Xu , Lu Junfeng , Wang Yongjin , Zhu Gangyi
Published: March 2023

Dynamically tunable laser sources are highly promising for realizing visionary concepts of integrated photonic circuits and other applications. In this paper, a GaN-based laser with an integrated PN junction heater on Si is fabricated. The photoluminescence properties of the GaN beam cavity are controlled by temperature, and the Joule heater provides electrically driven regulation of temperature. These two features of the cavity make it possible to realize convenient tuning of the lasing properties. The multi-functional GaN beam cavity achieves optically pumped lasing with a single mode near 362.4 nm with a high Q-factor of 1394. The temperature of this device increases by 0–5 °C under the Joule heating effect. Then, electrical control of the lasing mode is demonstrated. The lasing resonant peak shows a continuous redshift of about 0.5 nm and the device also exhibits dynamic switching of its lasing mode. The lasing modulation can be ascribed to temperature-induced reduction of the bandgap. Our work may be of benefit for external optical modulation in future chip-based optoelectronic devices.
Polyvinyl alcohol/polyacrylamide double-network hydrogel-based semi-dry electrodes for robust electroencephalography recording at hairy scalp for noninvasive brain–computer interfaces
Authors: Li Guangli , Liu Ying , Chen Yuwei , Li Mingzhe , Song Jian , Li Kanghua , Zhang Youmei , Hu Le , Qi Xiaoman , Wan Xuan , Liu Jun , He Quanguo , Zhou Haihan
Published: March 2023

Objective. Reliable and user-friendly electrodes can continuously and real-time capture the electroencephalography (EEG) signals, which is essential for real-life brain–computer interfaces (BCIs). This study develops a flexible, durable, and low-contact-impedance polyvinyl alcohol/polyacrylamide double-network hydrogel (PVA/PAM DNH)-based semi-dry electrode for robust EEG recording at hairy scalp. Approach. The PVA/PAM DNHs are developed using a cyclic freeze-thaw strategy and used as a saline reservoir for semi-dry electrodes. The PVA/PAM DNHs steadily deliver trace amounts of saline onto the scalp, enabling low and stable electrode-scalp impedance. The hydrogel also conforms well to the wet scalp, stabilizing the electrode-scalp interface. The feasibility of the real-life BCIs is validated by conducting four classic BCI paradigms on 16 participants. Main results. The results show that the PVA/PAM DNHs with 7.5 wt% PVA achieve a satisfactory trade-off between the saline load-unloading capacity and the compressive strength. The proposed semi-dry electrode exhibits a low contact impedance (18 ± 8.9 kΩ at 10 Hz), a small offset potential (0.46 mV), and negligible potential drift (1.5 ± 0.4 μV min−1). The temporal cross-correlation between the semi-dry and wet electrodes is 0.91, and the spectral coherence is higher than 0.90 at frequencies below 45 Hz. Furthermore, no significant differences are present in BCI classification accuracy between these two typical electrodes. Significance. Based on the durability, rapid setup, wear-comfort, and robust signals of the developed hydrogel, PVA/PAM DNH-based semi-dry electrodes are a promising alternative to wet electrodes in real-life BCIs.
Predictive JET current ramp-up modelling using QuaLiKiz-neural-network
Authors: Ho A. , Citrin J. , Challis C.D. , Bourdelle C. , Casson F.J. , Garcia J. , Hobirk J. , Kappatou A. , Keeling D.L. , King D.B. , Koechl F. , Lerche E. , Maggi C.F. , Mailloux J.
Published: March 2023

This work applies the coupled JINTRAC and QuaLiKiz-neural-network (QLKNN) model on the ohmic current ramp-up phase of a JET D discharge. The chosen scenario exhibits a hollow

T

e

profile attributed to core impurity accumulation, which is observed to worsen with the increasing fuel ion mass from D to T. A dynamic D simulation was validated, evolving j,

n

e

,

T

e

,

T

i

, n
Be, n
Ni, and n
W for 7.25 s along with self-consistent equilibrium calculations, and was consequently extended to simulate a pure T plasma in a predict-first exercise. The light impurity (Be) accounted for Z
eff while the heavy impurities (Ni, W) accounted for P
rad. This study reveals the role of transport on the

T

e

hollowing, which originates from the isotope effect on the electron-ion energy exchange affecting

T

i

. This exercise successfully affirmed isotopic trends from previous H experiments and provided engineering targets used to recreate the D q-profile in T experiments, demonstrating the potential of neural network surrogates for fast routine analysis and discharge design. However, discrepancies were found between the impurity transport behaviour of QuaLiKiz and QLKNN, which lead to notable

T

e

hollowing differences. Further investigation into the turbulent component of heavy impurity transport is recommended.
Testing a prediction model for the H-mode density pedestal against JET-ILW pedestals
Authors: Saarelma S. , Connor J.W. , Bilkova P. , Bohm P. , Field A.R. , Frassinetti L. , Fridstrom R. , Kirk A.
Published: March 2023

The neutral ionisation model proposed by Groebner et al (2002 Phys. Plasmas
9 2134) to determine the plasma density profile in the H-mode pedestal, is extended to include charge exchange processes in the pedestal stimulated by the ideas of Mahdavi et al (2003 Phys. Plasmas
10 3984). The model is then tested against JET H-mode pedestal data, both in a ‘standalone’ version using experimental temperature profiles and also by incorporating it in the Europed version of EPED. The model is able to predict the density pedestal over a wide range of conditions with good accuracy. It is also able to predict the experimentally observed isotope effect on the density pedestal that eludes simpler neutral ionization models.
Remote tropical central Pacific influence on driving sea surface temperature variability in the Northeast Pacific
Authors: Hong Hao-Jhe , Hsu Huang-Hsiung
Published: March 2023

The Northeast Pacific (NEP) had two record-breaking marine heatwave events in the winters of 2013–2015 and summer of 2019, which had a detrimental impact on the fisheries, marine ecosystems, and climate in North America. Here, we investigated the cause of sea surface temperature (SST) variability in NEP during late spring–summer of 1981–2020. The regression circulation anomalies to the principal component of leading empirical orthogonal function mode suggested that the warm NEP SST were characterized by a cyclonic circulation anomaly in the midlatitude North Pacific and a warming SST center in the Gulf of Alaska. We noted that this cyclonic circulation anomaly, attributable to a barotropic atmospheric wave originating from the tropical central Pacific (CP) in the preceding spring, reduced the surface heat flux loss from the ocean to the atmosphere in the NEP and led to the warm SST anomalies in summer. This finding was confirmed by not only empirical diagnosis but also long-term numerical simulations forced by the observed SST perturbations in the tropical CP. Our results highlight the role of the tropical CP SST in driving the summertime North Pacific SST variability through the atmospheric bridge in recent decades.