bluuebunny/crossref_metadata_2025 huggingface dataset:
l1‐ATSXKF‐based state and bias estimation for non‐linear systems with non‐Gaussian process noise
Authors: Yang Boyu , Chen Xueqin , Wu Fan , Liu Ming
Published: January 2025

To solve the problem of state and bias estimation for the non‐linear system with non‐Gaussian noise terms, a series of exogenous Kalman filters (XKF)‐based state and bias estimation algorithms are proposed. First, a non‐linear system model with bias and non‐Gaussian process noise is established. Second, the l1 norm is incorporated into the two‐stage exogenous Kalman filter (TSXKF) algorithm, known as the l1‐TSXKF, to mitigate the effect of non‐Gaussian process noise. Considering the uncertainty in the system transition model, adaptive factors are introduced into the Kalman filter, known as the adaptive Kalman filter algorithm, to enhance the estimation accuracy by modifying the predicted state covariance. Then, the l1 norm adaptive two‐stage exogenous Kalman filter (l1‐ATSXKF) algorithm is designed by combining the advantages of the l1 norm, adaptive factors and XKF in dealing with non‐Gaussian process noise, model uncertainty and state/bias simultaneous estimation, respectively. Finally, the simulation results show that the proposed algorithms can reduce the influence of the non‐Gaussian characteristics of the system and obtain high‐precision attitude and bias estimation results quickly in the process of satellite attitude manoeuvre, which is conducive to the application of satellite in orbit.
Electrical properties of ScN thin films controlled by defect engineering using oxygen ion implantation
Authors: Poterie Charlotte , Bouteiller Hugo , Burcea Razvan , Dubois Sylvain , Eklund Per , Le Febvrier Arnaud , Cabioc’h Thierry , Barbot Jean-François
Published: January 2025

Defects tend to modify significantly the properties of semiconductors, such as transport properties, by increasing the scattering of electrons and phonons, or optical properties, by modifying the band structure and the Fermi level. The high interest of ScN thin films for thermoelectric applications results from the incorporation of oxygen, which is well known to be the source for their degenerate n-type state and their significant power factor. Indeed, oxygen acts as a donor defect when substituted to nitrogen. In this study, oxygen ion implantation was performed at a high damage level as a way to modify electrical properties through defect engineering. Hence, we measured the changes in electrical properties induced by oxygen implantation at room temperature. Two types of defects have been identified as being responsible for the change in resistivity, carrier concentration, mobility, and Seebeck coefficient. At first, the point-like defects, recombining from 440 K and onward, introduce localized states near the Fermi level, inducing a change in the conduction mode from a metallic-like to a hopping mechanism. The relationship between Mott's temperature and defect concentration has been clearly demonstrated through in situ resistivity measurements in the 80–750 K temperature range. Furthermore, these measurements highlight that oxygen induced defects result not only from ballistic effects, but also from chemical effects that are involved. Second, the complex-like defects introduce deep acceptor levels into the bandgap and act as scattering centers that modify the Debye temperature as well as the electron–phonon interactions. These complexes, likely between scandium vacancies and oxygen atoms (VSc-yO, y ≤ 4), are primarily responsible for the increase of the Seebeck coefficient and the reduced mobility. The concentration of such defects can qualitatively be assessed as their formation introduces an additional term, independent of temperature, in the variation of resistivity, mobility, and also the Seebeck coefficient. The recovery of the complex-like defects takes place at a minimum temperature of 750 K. Results show that the effectiveness of oxygen in creating defects exceeds that of noble gases in terms of concentration, demonstrating the promise of this approach to control the electrical properties of ScN.
Design of a C-band lightweight, high-efficiency relativistic backward wave oscillator with permanent magnetic package
Authors: Jin Zhenxing , Lei Yifan , Zhang Dian , Yang Kaiqi , Zhou Fugui , Xiang Yujie , Zhang Jun
Published: January 2025

The paper presents a design for a C-band lightweight, high-efficiency relativistic backward wave oscillator with compact permanent magnet (PM) packaging. The study addresses the following several key aspects, including the efficient electromagnetic structures, the design of lightweight and compact permanent magnet, and the particle-in-cell (PIC) simulation integrated with the multi-objective particle swarm optimization algorithms. The PIC simulations indicate an output microwave power of approximately 2.4 GW with a frequency of 4.28 GHz, achieving a conversion efficiency of up to 48%. Additionally, the magnetic field strength is around 0.28 T, generated by a PM weighing only about 63.5 kg.
Interface instabilities in hafnium hydride entrained iron metal matrix composites
Authors: Dunkin Mikaela R. , Shawon Mirza A. , Ouyang Mingxi , Gentile Jonathan M. , Pattammattel Ajith , Trelewicz Jason R. , Snead Lance L. , Sprouster David J.
Published: January 2025

The chemical interactions in Fe–HfH2 metal matrix composites (MMCs) are studied across multiple length scales to elucidate the decomposition of the parent phases and corresponding reaction zone physics during direct current sintering. Fe–HfH2 composites were synthesized with increasing as-mixed hydride contents of Fe–25% HfH2, Fe–40% HfH2, Fe–55% HfH2, and Fe–70% HfH2 (all in vol. %) to demonstrate the ability to achieve sintered MMCs with target hydride contents. Samples were probed across multiple length scales through a multi-modal workflow employing x-ray diffraction, scanning electron microscopy and segmentation analysis, and synchrotron techniques including hard x-ray fluorescence mapping and nanoprobe x-ray absorption near-edge structure measurements. Under the selected sintering temperature and pressure conditions, hydrogen evolution is seen to evolve through parallel paths: thermal decomposition from during the transformation of HfH2 to HfHx<2 and through subsequent reaction with the Fe matrix leading to intermetallic phase formation. Specifically, HfFe and HfFe2 intermetallic formation accelerates the release of hydrogen with a subsequent HfO2 phase forming at grain boundaries. For this MMC, the consumption or loss of hydrogen can be considerable in compacts with initial hydride loading of 25%–40% HfH2 approaching 83% hydrogen loss for the lower volume fraction composites. Increasing the volume fraction of HfH2 to 70% enhanced the retained hydrogen content to 53% and attributed to the reduced interfacial area intrinsic to the increased HfH2 loading in this MMC.
Simulating anharmonic vibrational polaritons beyond the long wavelength approximation
Authors: Jasrasaria Dipti , Mandal Arkajit , Reichman David R. , Berkelbach Timothy C.
Published: January 2025

In this work, we investigate anharmonic vibrational polaritons formed due to strong light–matter interactions in an optical cavity between radiation modes and anharmonic vibrations beyond the long-wavelength limit. We introduce a conceptually simple description of light–matter interactions, where spatially localized cavity radiation modes couple to localized vibrations. Within this theoretical framework, we employ self-consistent phonon theory and vibrational dynamical mean-field theory to efficiently simulate momentum-resolved vibrational-polariton spectra, including effects of anharmonicity. Numerical simulations in model systems demonstrate the accuracy and applicability of our approach.
Frictional heating in cyclotrimethylene trinitramine during nanoscratching: Plasticity and localized melting
Authors: Hu Jianqiao , Yao Haiyang , Song Huajie
Published: January 2025

Frictional heating in cyclotrimethylene trinitramine (RDX) can generate hotspots, which are local regions of elevated temperature that may trigger explosion. In this study, we quantified the characteristic size of the hotspot to be approximately 20 Å based on the width of the nanoscale shear band in shock loading simulations and further examined the temperature rise in RDX crystals during high-speed nanoscratching using molecular dynamics simulations. These simulations were performed under varying sliding velocities, normal loads, and sliding directions to explore the relationship between friction coefficient, shear stress, and localized hotspots. Our results revealed that, despite the anisotropic friction properties, the temperature rise exhibited a consistent dependence on shear stress, with a critical shear stress identified above which the hotspots experienced a sharp increase in the temperature. This temperature transition correlates with localized melting, as demonstrated by the analysis of atomic temperature and bond-length changes. These findings enhance our understanding of the mechanical and thermal stability of energetic materials.
Modulating the resonance transport of edge states in topological insulator junction
Authors: Yang Jia-En , Lü Xiao-Long , Xie Hang , Chen Kai-Rang
Published: January 2025

This work investigates how the width (Ny) of zigzag silicene-like nanoribbons, along with defect size and position, affect the resonance transmission of a topological insulator junction with anisotropic chiral and helical edge states. Despite changes in the resonance peak with Ny below the critical value, neither a proportional nor inverse formula can adequately express the relationship between the resonance period (T) and Ny. The energy band calculations indicate that the change mechanism is attributed to the size effect on the band structure. We also examine the influence of the defect size and position on resonance and provide a detailed explanation by calculating the local bond current. It is found that specific defect size and position greatly impact the resonance peak, indicating the potential of modulating resonance using these two variables. These findings provide theoretical insights for controlling resonance.
4780 nm ultra-broadband entangled biphotons from a chirped PPLN
Authors: Zhu Wen-Xin , Jin Rui-Bo
Published: January 2025

Ultra-broadband frequency entangled biphotons have exceptionally short temporal duration and can achieve narrow Hong–Ou–Mandel (HOM) interference patterns, making them vital for quantum metrology applications. However, the bandwidth of previously demonstrated biphotons used for HOM interference has been limited to less than 400 nm, which is not wide enough to achieve ultra-high precision in quantum metrology. In order to push the precision to its limit, we have theoretically designed a 20-mm-long chirped periodically poled lithium niobate (CPPLN) crystal with type-II phase matching. Pumped by a 405 nm laser, the down-converted signal and idler photons can cover the wavelength range from 420 to 5200 nm, approaching the transparent upper bound of the LN crystal. In the simulated Hong–Ou–Mandel (HOM) interference, the full-width at half-maximum of the interference pattern is 965 attoseconds, with a visibility of 99.44%. Following a similar approach, we also designed a type-0 CPPLN crystal to achieve higher brightness. These ultra-broadband biphoton sources can generate ultra-narrow quantum interference patterns, which have the potential for attosecond-level high-precision quantum metrology.
Torsion-induced rapid switching and tunability of multistable state ferroelectric polarization
Authors: Zuo Boyu , Lou Xuhui , Chen Yu , Jiang Wentao , Wang Qingyuan , Fan Haidong , Qiao Chuan , Tian Xiaobao
Published: January 2025

The pulse-based rapid domain structure switching method in ferroelectric memristors has stability and other issues, limiting its applications. In this study, we perform atomic simulations to investigate the polarization domain switching behavior of ferroelectric materials under non-pulse torsional loading. During torsion, uniformly distributed spontaneous polarization transitions to predominantly in-plane polarization and finally evolves to predominantly out-of-plane polarization. The out-of-plane polarization remains stable during torsion and can be adjusted through mechanical and electric fields to achieve multistability. This evolution behavior is attributed to the rapid increase in initial normal stress and continuous cyclic variation of shear stress during torsion. The non-pulse control method developed in this study lays the foundation for further research and utilization of polarization regulation in ferroelectric materials, potentially advancing the application of ferroelectric memristors.
All-optical vector magnetometry based on fine and hyperfine interactions in spin-32 centers in silicon carbide
Authors: Likhachev Kirill V. , Uchaev Maxim V. , Veyshtort Igor P. , Batueva Anastasia V. , Gurin Aleksandr S. , Babunts Roman A. , Baranov Pavel G.
Published: January 2025

The possibility of using axial spin centers with S=3/2 in silicon carbide for all-optical measurement of the projection Bz of the external magnetic field onto the c-axis of the SiC crystal, as well as the polar and azimuthal angles of the magnetic field relative to the direction of the c-axis, at room and significantly higher temperatures is shown. Spin centers in SiC, where optically induced spin alignment occurs, have a unique system of spin levels in a magnetic field, caused by the interaction of the fine structure and hyperfine interaction with the 29Si nuclei. There is a wide range of level anticrossings (LACs) resulting in an extremely strong change in the photoluminescence intensity at LAC. The dependence of the LAC spectrum on the orientation of the external magnetic field is also observed. The proposed magnetometer is based on the compensation of the external magnetic field at the position of the optical excitation spot of the confocal microscope. The sensitivity to a constant magnetic field for the z-component of the magnetic field (Bz) is better than 0.1μT/Hz in the confocal volume at room temperature. The sensitivity of polar and azimuthal angle determination depends on the sensitivity of the perpendicular component of the magnetic field, which is better than ∼0.01mT/Hz in the range from −0.4 to 0.4 mT.
Strain-controllable electronic, magnetic properties, and magnetic anisotropy energy in a 2D ferromagnetic half-metallic MGT monolayer
Authors: Lv Linhui , Zhang Fangyu , Qi Diancong , Xu Zihao , Wang Weiyi , Su Ya , Jiang Yanyan , Guan Zhaoyong
Published: January 2025

The investigation of two-dimensional (2D) intrinsic ferromagnetic material is important in the field of spintronics. In this study, the Mn2Ge2Te6 monolayer (ML) with intrinsic ferromagnetism was fabricated by using the density functional theory (DFT). The Mn2Ge2Te6 ML is a half metal (HM) with a spin-β bandgap of 1.462 eV. Biaxial strain could be applied to tune the electronic and magnetic properties of Mn2Ge2Te6. The magnetic moment (MM), magnetic exchange parameter (J), band structures, and magnetic anisotropy energy (MAE) could be effectively controlled by the biaxial strains (ε). This modulation originates that the states near the Fermi level mainly come from the contribution of in-plane atomic orbitals. The MM of Mn monotonously increases as the tensile strains increase. The energy difference between different magnetic orders (ΔE) and J also change with the strains. The antiferromagnetic-stripy order always has the lowest energy under the strains. As the strains change, ΔE and J monotonously change as the direct exchange and super-exchange interactions between Mn atoms vary. As the tensile strain decreases and compressive strain increases (−2.1%<ε<8%), the gap of spin-β electrons monotonously decreases. The Mn2Ge2Te6 ML changes from a HM to a normal spin-unpolarized metal under larger compressive strains (ε>−2.1%). When the tensile strains are applied, the MAE monotonously increases to the largest value of −22.3 meV (ε=12%). As the compressive strains increase, the MAE monotonously decreases. Last, the Mn2Ge2Te6 ML changes from an in-plane magnetic anisotropy into a perpendicular magnetic anisotropy under a larger compressive strain (−11%). The change of MAE direction origins that the contribution of hybridization between Te's py and pz orbitals is changed when the strain changes. Our results offer crucial insights into the potential of strain modulation in a 2D Mn2Ge2Te6 ML, paving the way for future advancements in this field.
Flexible 3ω sensors on submicron-thick parylene substrates for thermal conductivity measurements of liquids and soft materials
Authors: Yamasaki Ryuto , Matsunaga Yuki , Akura Yuki , Shimofuri Masaki , Banerjee Amit , Tsuchiya Toshiyuki , Hirotani Jun
Published: January 2025

Measurement of thermal conductivity in liquids and soft materials is pivotal across various sectors, from designing cooling systems for electronic devices to monitoring biological parameters via medical devices and studying the thermal properties of tissues. Accurate thermal conductivity measurements require high sensitivity, and a flexible measurement device is advantageous to adapt to the shape of the sample. The 3ω method stands out as an ideal technique that meets these criteria, offering a simple and sensitive approach to assess the thermal properties of materials. In this study, we introduce a 3ω sensor fabricated on submicron-thick parylene substrates. The parylene substrate not only provides the necessary flexibility but also acts as an insulating layer, essential for the measurement of conductive materials. The sensor's sensitivity was enhanced by reducing the thickness of the parylene substrate. A thermal peeling film was utilized as a supporting substrate during the fabrication of the 3ω sensor with a thin parylene substrate, which has a thickness of 0.77 μm. The performance of the sensor was evaluated by measuring the thermal conductivities of water, isopropyl alcohol, and their mixtures, achieving results within 15% of previously reported values.
Monte Carlo and micromagnetic study on constructing biskyrmion-like spin textures in bilayer magnetic films
Authors: Wang Wenyan , Pan Sheng , Yu Jie-Xiang
Published: January 2025

Biskyrmion, a novel topological magnetic structure, has its unique physical properties and potential application value. In this study, we proposed a mechanism for constructing biskyrmions in a bilayer centrosymmetric magnetic thin film with the broken inversion symmetry for each layer. By using Monte Carlo and micromagnetic simulation methods, we found that biskyrmion-like spin textures can be stabilized under the opposite Dzyaloshinskii–Moriya interactions and finite magnetic fields applied. In addition, we also provided insights into the dynamic property of a biskyrmion with the spin polarized current applied to the system. After the current density reaches a certain threshold, the biskyrmion moves forward in a bound state and exhibits a behavior similar to the skyrmion Hall effect. Our findings have provided a theoretical basis for the application of biskyrmions in spintronics.
6 kV GaN p–n diode fabricated by hybrid epitaxial growth with regrowth interface treated by CF4 plasma
Authors: Ohta Hiroshi , Narita Yoshinobu , Kaneki Shota , Kitamura Toshio , Horikiri Fumimasa , Fujikura Hajime , Takatani Shinichiro , Mishima Tomoyoshi
Published: January 2025

A high breakdown voltage was achieved for a p–n junction diode grown by a hybrid epitaxial growth. Using a quartz-free hydride vapor-phase epitaxy, a thick and extremely high-purity n−-GaN drift layer was grown on a GaN substrate. A p-GaN layer was grown on the n−-GaN drift layer using metal-organic vapor-phase epitaxy (MOVPE). Before the MOVPE growth, inductively coupled plasma dry etching treatment using CF4 gas was performed on the regrowth surface to reduce the effect of Si contamination. The device with a reduced effective donor sheet concentration at the regrowth interface obtained by the CF4 treatment achieved a high breakdown voltage of 6.23 kV with good diode characteristics. A clear correlation was found between the breakdown voltage and the effective donor concentration at the p–n junction determined by C–V measurements. It is predicted that a breakdown voltage as high as 8 kV can be obtained if the effective donor concentration at the p–n junction is reduced to 1 × 1012 cm−2 or lower.
Temperature dependent thermoelectric transport in PEDOT–PSS conducting polymer: The effect of additives
Authors: Rohmer Anthony , Lansac Yves , Hee Jang Yun , Limelette Patrice
Published: January 2025

We report on both the electrical and thermoelectric transport properties as a function of temperature in poly(3,4-ethylene dioxythiophene) (PEDOT)–poly(styrene sulfonate) conducting polymers for a wide range of dimethyl sulfoxide (DMSO) additives. Whereas an insulating-like electrical behavior is found over the whole temperature range, a metallic-like thermopower is mainly observed. We show that the resistivity appears to be governed by a three-dimensional variable range hopping mechanism due to disordered regions with a decreasing localization temperature T0 and an increasing scaling factor ρ0 as a function of the DMSO ratio. The correlation between T0 and ρ0 demonstrates that they are both controlled by the localization length ξ0, which is strongly enhanced by the DMSO in agreement with the morphological evolution of the PEDOT chains with the additive. On the other hand, the high-T positive metallic-like thermopower seems rather unaffected by the additive in contrast to its low-T counterpart, which appears negative below a characteristic temperature Tswitch. By showing that the latter is closely related to the localization temperature, we propose to ascribe this sign switch to the thermoelectric contribution originating from disordered regions, which competes with the metallic ones due to ordered domains. While still controlled by the localization temperature, this negative contribution appears to be consistent with a phonon-drag component with a scaling behavior as T0T−3. These analyses allow us to discuss the overall temperature dependent thermoelectric properties in a consistent way by considering a heterogeneous structure with both ordered and disordered domains. By relating explicitly the electrical resistivity to the thermopower, our results do not only reconcile these transport coefficients, but they also provide a unified picture of the properties of the conducting polymers.
Giant electrostriction in textured La2Ce2O7 ceramics: A promising lead-free alternative for electromechanical conversion
Authors: Talanov Mikhail V. , Marakhovsky Mikhail A. , Lakshya Annu Kumar , Chowdhury Anirban
Published: January 2025

The search for high-performance, lead-free materials with tailored electromechanical properties is crucial for the advancement of energy harvesting and actuator technologies. While piezoelectric materials offer promising solutions, balancing high piezoelectric response with low dielectric permittivity remains a significant challenge. Recent research has highlighted the potential of “giant” electrostriction as an alternative approach, offering substantial electromechanical responses with more favorable electrical properties. This work investigates the electrostrictive and dielectric properties of non-textured and textured La2Ce2O7 ceramics. Our findings reveal a substantial electrostrictive coefficient [M33 ≈ 10−18 (m/V)2, exceeding conventional electrostrictive materials], coupled with a high effective piezoelectric response (d33eff = 40 pm/V at E = 100 kV/cm) and a high effective piezoelectric voltage coefficient (g33eff = 146–205 × 10−3 Vm/N). Notably, [111]-texturing of La2Ce2O7 significantly reduces dielectric losses, further enhancing its suitability for energy harvesting and actuator applications. The combination of electromechanical and dielectric properties creates conditions for high energy-harvesting performance, comparable to lead-containing ceramics and far superior to lead-free alternatives. Combined with temperature stability and compatibility with Si-based microfabrication, La2Ce2O7 emerges as a promising lead-free alternative for high-performance electromechanical energy conversion applications.
Photoluminescence dynamics and ligand exchange in PbS/CdS core/shell nanocrystal films
Authors: Islam R. , Wu X. , Lockwood D. J. , Ko D.-K. , Tsybeskov L.
Published: January 2025

Photoluminescence studies in PbS/CdS core/shell nanocrystal thin films reveal that the length of organic ligands at the nanocrystal surface controls the photoluminescence rise time and the short-lived decay component. The long-lived photoluminescence does not depend on the ligand length but strongly depends on the detection wavelength and temperature. We conclude that the observed complex photoluminescence dynamics are governed by a combination of energy transfer and exciton recombination and propose a method to separate these processes.
Evidence for the geomagnetic gradient induced current in the ionosphere around the South Atlantic Anomaly
Authors: Yi Siqi , Xu Xiaojun , Jiang Yi , Wang Xing , Yan Qing , Li Hui
Published: January 2025

The geomagnetic gradient induced current (GGIC) should exist as a result of the electron and ion drift motions due to the geomagnetic field gradient in the Earth's ionosphere. GGICs exhibit a westward flow near the magnetic equator, whereas around the southern boundary of the South Atlantic Anomaly (SAA), they shift to an eastward direction. These GGICs contribute to the strongest radially outward magnetic field near the center of the SAA. This GGIC-induced magnetic field is easily contaminated by the solar quiet (Sq) currents and equatorial electrojet, so that it usually cannot be directly verified from the magnetic field measurements. By subtracting the CHAMP, Ørsted, and SAC-C model of Earth's magnetic field from Swarm satellites' magnetic field measurements, the magnetic fields produced by the ionospheric currents are illustrated. To eliminate the influence of other currents, we calculate the radial magnetic field differences between the summer and winter seasons in the southern hemisphere using data from all three Swarm satellites. This differential magnetic signature, which points radially outward, can only be attributed to the GGIC. Despite the limited measurements, the existence of GGIC can be also verified in the radial magnetic field data collected by the Macao Science Satellite-1. Our results reveal a universal phenomenon that occurs in the dayside ionospheres of the magnetized planets.
Million-atom heat transport simulations of polycrystalline graphene approaching first-principles accuracy enabled by neuroevolution potential on desktop GPUs
Authors: Zhou Xiaoye , Liu Yuqi , Tang Benrui , Wang Junyuan , Dong Haikuan , Xiu Xiaoming , Chen Shunda , Fan Zheyong
Published: January 2025

First-principles molecular dynamics simulations of heat transport in systems with large-scale structural features are challenging due to their high computational cost. Here, using polycrystalline graphene as a case study, we demonstrate the feasibility of simulating heat transport with near first-principles accuracy in systems containing over 1.4×106 atoms, achievable even with consumer desktop GPUs. This is enabled by the highly efficient neuroevolution potential (NEP) approach, as implemented in the open-source GPUMD package. Leveraging the NEP model’s accuracy and efficiency, we quantify the reduction in thermal conductivity of polycrystalline graphene due to grain boundaries with varying grain sizes, resolving contributions from in-plane and out-of-plane (flexural) phonon modes. Additionally, we find that grain boundaries can lead to finite thermal conductivity even under significant tensile strain, in contrast to the divergent behavior observed in pristine graphene under similar conditions, indicating that grain boundaries may play a crucial role in thermal transport in low-dimensional momentum-conserving systems. These findings could offer insights into interpreting experimental observations, given the widespread presence of both large-scale grain boundaries and external strains in real materials. The demonstrated ability to simulate millions of atoms with near-first-principles accuracy on consumer desktop GPUs using the NEP approach will help make large-scale high-fidelity atomistic simulations more accessible to the broader research community.
Experiments on scalar interface in plane turbulent wall jet: Statistics and fractality
Authors: Sood Pranav , Bhatt Shibani , Choudhary Harish , Gupta Abhishek , Raghuvanshi Neetesh Singh , Sapkal Prajyot , Prabhakaran Thara , Dixit Shivsai Ajit
Published: January 2025

Statistical and fractal properties of the scalar interface in a plane turbulent wall jet of air are investigated experimentally. Seeding is introduced for only the jet flow. These seed particles do not diffuse or evaporate quickly, in contrast to smoke that is commonly used in air flows. Three cameras are placed one above the other and operated in a single-frame mode to image the instantaneous scalar interface between the seeded jet and unseeded ambient fluid with sub-Kolmogorov spatial resolution and an unprecedented dynamic range (large-to-small scale ratio) of 2450. The interface in each image is marked by a simple thresholding technique. A well-converged probability density function (p.d.f.) of the interface height from the wall is obtained from an ensemble of 2945 usable images. The p.d.f. is found to be Gaussian to an excellent approximation, with the most probable location at 1.57 times the outer length scale of the wall jet (marking half the maximum velocity). Fractal dimension of the interface in each usable image is computed using the box counting algorithm and compensated plots for an objective determination. The mean fractal dimension over all usable images is 1.361 ± 0.002, which agrees very well with the near-universal value reported by Sreenivasan and coworkers for a variety of turbulent flows.
Sorption of gases by disordered materials: A model based on the glass transition effect
Authors: Kocherbitov Vitaly
Published: January 2025

Disordered materials in the glassy state show different gas sorption properties compared to same materials in the liquid or rubbery state. The sorption enthalpy becomes more exothermic, and the absorbed amount is greater compared to the liquid or rubbery state. The sorption data are often treated in the literature using the dual-mode theory—a three-parameter sorption model. This work presents another approach where a gas sorption isotherm model for glassy materials is derived from thermodynamic consideration of glass transition properties. The model is particularly applicable for describing sorption data that obey Henry's law in the limit of the liquid or rubbery state. The model parameters correspond to physically meaningful characteristics of the system's glass transition. We demonstrate that experimental gas sorption data, when plotted as ln(P/C) vs C, exhibit linear behavior in both the rubbery and glassy states, enabling accurate determination of the glass transition point from isothermal data. Additionally, gas sorption in glassy disordered materials can be effectively described using a two-parameter function based on the Lambert W function.
Temperature characteristics of a photoinduced blackbody in intense light fields
Authors: Cui Hao , Qin Weiping
Published: January 2025

A “whitebody” can transform into a “blackbody” under intense light exposure, and the temperature of photoinduced blackbodies deviates significantly from Planck's law. This discovery necessitates the consideration of light excitation's impact on the radiation spectrum of a blackbody when applying Planck's formula. Under the adiabatic approximation, this paper theoretically derives the relationship between the temperature of photoinduced blackbodies and the intensity of excitation light field. The actual temperature of a photoinduced blackbody is directly proportional to the fourth root of the excitation light power. Experimental data demonstrate that this relationship can more accurately describe the temperature characteristics of a photoinduced blackbody in intense light fields. These results provide a theoretical foundation for further investigation into photoinduced blackbody radiation, contribute to an enhanced comprehension of the underlying physical mechanism behind this phenomenon, and may have significant implications for celestial temperature measurements based on Planck's law.
Two-color strong-field terahertz amplification in the non-identical focusing condition
Authors: Zhao Jingjing , Zhang Yizhu , Gao Yanjun , Chen Ahai , Jiang Yuhai
Published: January 2025

High optical-to-terahertz (THz) conversion efficiency is crucial for generating THz waves. Strong-field ionization using a bi-focal bi-chromatic geometry produces cascading plasmas, leading to amplified THz generation and extended THz bandwidth. We investigate the effect of focal length in this bi-focal geometry on THz intensity. The results show that the THz intensity produced with non-identical focal lengths of the bi-chromatic fields is 25% higher than that of identical focal lengths, and 15 times higher than traditional bi-chromatic THz generation. The electro-optic sampling measurements reveal that the THz-electric-field intensity generated by the bi-focal bi-chromatic field exhibits periodic oscillations, which results from the modulation of the photoelectron's asymptotic velocity by the relative phase of the bi-chromatic pulses, and are consistent with the photocurrent model. The photocurrent simulations indicate that the self-compression of the second harmonic pulse significantly enhances THz amplification and extends the THz bandwidth. These findings deepen understanding of the THz generation mechanism and suggest potential avenues for optimizing THz sources.
Multihyperuniformity in high-entropy MXenes
Authors: Liu Yu , Chen Mohan
Published: January 2025

MXenes are a large family of two-dimensional transition metal carbides and nitrides that possess excellent electrical conductivity, high volumetric capacitance, great mechanical properties, and hydrophilicity. In this work, we generalize the concept of multihyperuniformity, an exotic state that can exist in a disordered multi-component system, to MXenes. Disordered hyperuniform systems possess an isotropic local structure that lacks traditional translational and orientational order, yet they completely suppress infinite-wavelength density fluctuations as in perfect crystals and, in this sense, possess a hidden long-range order. In particular, we evaluate the static structure factor of the individual components present in the high-entropy (HE) MXene experimental sample TiVCMoCr based on high-resolution scanning electron microscope imaging data, which suggests that this HE MXene system is at least effectively multihyperuniform (MH). We then devise a packing algorithm to generate MH models of HE MXene systems. The MH HE MXenes are predicted to be energetically more stable compared to the prevailing (quasi)random models of the HE MXenes due to the hidden long-range order. Moreover, the MH structure exhibits a distinctly smaller lattice distortion, which has a vital effect on the electronic properties of HE MXenes, such as the density of states and charge distribution. This systematic study of HE MXenes strengthens our fundamental understanding of these systems and suggests possible exotic physical properties, as endowed by the multihyperuniformity.
Aerodynamic optimization design of high-load counter-rotating compressor based on vorticity dynamic parameter distribution
Authors: Yan Tingsong , Chen Huanlong , Yan Peigang
Published: January 2025

This paper proposes a supersonic cascade aerodynamic design method based on the unique inlet angle theory and applies it to the design of a supersonic cascade with a Mach number of 1.75. The superiority of this cascade design method and the accuracy of the simulation method are verified by jointly using the vorticity dynamics flow field diagnosis method and the planar cascade pressure measurement experiment. Based on this achievement, the aerodynamic design of high-load counter-rotating compressors has been carried out. For the first time, numerical optimization techniques are used to optimize the three-dimensional blade geometry with the boundary vorticity flux (BVF) on the suction surface as the optimization target. After optimization, the integral value of BVF on the blade surface significantly decreased, and the distribution of vorticity dynamics parameters, such as radial vorticity and enstrophy, was significantly improved. The efficiency of the compressor increased by 2.08%, the total pressure ratio increased by 2.80%, and the aerodynamic performance at off-design points was also significantly improved.
Beyond despair: Leveraging ecosystem restoration for psychosocial resilience
Authors: Smith Carter S. , DeMattia Elizabeth A. , Albright Elizabeth , Bromberger Abigail F. , Hayward Olivia G. , Mackinson India J. , Mantell Sydney A. , McAdoo Brian G. , McAfee Dominic , McCollum Aurora , Paxton Avery B. , Roderer Anne , Stevenson Kathryn , Vidra Rebecca L. , Zhao Zixin
Published: January 2025

Ecosystem restoration has historically been viewed as an ecological endeavor, but restoration possesses significant, yet largely untapped, potential as a catalyst for personal and social transformation. We highlight the opportunity for restoration to enhance community resilience by increasing agency and collective action and countering the pervasive perception that we are powerless witnesses to environmental decline. In this perspective, we take a “bright spots” approach and highlight successful examples of ecosystem restoration that have helped to nurture a sense of place, foster optimism, and cultivate stronger and more diverse social networks. These three individual- and community-level capacities have the potential to lead to increased psychosocial resilience, which is a key component of community resilience. Our aim is to spark discussion and research to better understand how we can transform restoration from a largely technical endeavor to a practice and process through which human–nature relationships are infused with deliberate meaning and human well-being is improved. With current calls to upscale and technologize restoration to meet sustainable development goals, we cannot lose sight of the value of community-engaged ecosystem restoration as a strategy with great potential for psychosocial benefits.
SGD-SLAM: a visual SLAM system with a dynamic feature rejection strategy combining semantic and geometric information for dynamic environments
Authors: Chen Yuqian , Lu Tongwei
Published: January 2025

Simultaneous localization and mapping (SLAM) is a key technology for mobile robots to perform localization and navigation in unknown environments. The majority of existing visual SLAM systems are predicated on the assumption of a static scene, which can result in suboptimal performance, reduced accuracy, and diminished system robustness in complex dynamic environments. In this paper, we propose SGD-SLAM, an improved SLAM system developed on the ORB-SLAM2 framework, designed for complex dynamic scenes. The system proffers a newly devised methodology that integrates semantic data with geometric data to address challenges to dynamic scenes. First, real-time instance segmentation algorithms are used to obtain semantic information about the surrounding environment and identify prior dynamic objects. Then, epipolar constraints are employed to find potential dynamic points, while the density-based spatial clustering of applications with noise clustering algorithm is used to group dynamic points into different clusters and compute the centers of these clusters to obtain geometric information. Finally, a dynamic feature rejection strategy is implemented, combining both semantic and geometric information, to exclude dynamic feature points. The system is tested and evaluated using the TUM dataset. The outcomes illustrate that, in dynamic scenes, the SGD-SLAM system outperforms existing algorithms with respect to enhanced accuracy and robustness.
The evolution of ChatGPT for programming: a comparative study
Authors: Jain Rushabh , Thanvi Jyoti , Subasinghe Akila
Published: January 2025

The introduction of Transformer models has significantly advanced natural language processing, with the development of Large Language Models (LLMs) like GPT-4 and Gemini revolutionizing industries by automating programming tasks. However, challenges remain regarding their ability to fully replace human programmers, especially in terms of efficiency and handling complex problems. This study aims to evaluate the performance of GPT models in solving algorithmic problems across three programming languages—Python, Java, and C++. It focuses on assessing runtime and memory efficiency to provide insights into the capabilities and limitations of LLMs in practical programming tasks. We selected 15 LeetCode problems categorized by difficulty and instructed GPT-3.5, GPT-4, and GPT-4o to generate solutions in Python, Java, and C++. Code was generated and executed 10 times for each problem, measuring runtime and memory usage. Statistical analyses, including two-way ANOVA and post hoc Tukey’s HSD tests, were conducted to evaluate the results. The findings indicate that programming language has a significant effect on memory and runtime efficiency, with C++ outperforming Python and Java. However, there were no statistically significant differences in performance between GPT-3.5, GPT-4, and GPT-4o across most tasks. Python was found to be significantly slower and more memory-intensive compared to C++ and Java. While GPT models show promise in assisting with programming tasks, their practical utility remains limited, particularly for complex problems. Improvements in newer GPT models do not always translate into significant performance gains. The choice of programming language plays a crucial role in optimizing LLM-generated code, suggesting that LLMs are better suited for augmenting human programmers rather than replacing them in critical tasks.
Hilbert meets Ramanujan: Singularity theory and integer partitions
Authors: Mourtada Hussein
Published: January 2025

What can singularities of algebraic varieties say about the decompositions of a positive integer into a sum of positive integers?
Chaucer’s Ethical Philosophy
Authors: Ashe Laura
Published: January 2025

Chaucer’s Ethical Philosophy reads Chaucer in new ways, revealing his deep engagement with the most urgent questions of modern political and ethical philosophy. The book offers original readings of Troilus and Criseyde, the Canterbury Tales, and the Book of the Duchess, placing Chaucer in close dialogue not only with medieval philosophy and theology, and his great European literary sources (Boccaccio, Dante, Guillaume de Machaut), but also with some major figures and concepts of modern philosophical thought (Hegel, Levinas, Wittgenstein, Butler; recognition, subjectivity, gender). It thereby illuminates his use of distinctively medieval forms and structures of narrative to explore ideas and develop philosophies that we have been conditioned to think of as exclusively modern. Chaucer’s fictional experiments are shown to be as philosophically complex and ethically powerful as anything in current thought.
Facial Emotion Recognition and its Associations With Psychological Well-Being Across Four Schizotypal Dimensions: a Cross-Sectional Study
Authors: Karamaouna Penny , Zouraraki Chrysoula , Economou Elias , Bitsios Panos , Giakoumaki Stella G
Published: January 2025

Objective

The present study aimed to examine facial emotion recognition in a sample from the general population with elevated schizotypal traits, as defined by the four-factor model of schizotypy, and the association of facial emotion recognition and the schizotypal dimensions with psychological well-being.

Method

Two hundred and thirty-eight participants were allocated into four schizotypal groups and one control group. Following a cross-sectional study design, facial emotion recognition was assessed with a computerized task that included images from the Radboud Faces Database, schizotypal traits were measured with the Schizotypal Personality Questionnaire, and psychological well-being was evaluated with the Flourishing scale.

Results

The results revealed distinct patterns of performance across the schizotypal groups and the application of a dimensional approach that included all participants as one group indicated specific associations between the four schizotypal dimensions and psychological well-being. Specifically, (a) negative schizotypes showed poor identification of sadness and fear potentially due to the activation of coping mechanisms, (b) disorganized schizotypes inaccurately recognized surprise, possibly reflecting the effects of disorganized thought on distinguishing this ambiguous emotion, and (c) psychological well-being was predicted by high cognitive-perceptual along with low negative and disorganized schizotypy as well as the accurate recognition of specific emotional states that are common in daily social interactions.

Conclusions

In conclusion, the study findings further advance the identification of emotion-processing difficulties in schizophrenia-vulnerable individuals and further highlight the need for highly personalized early intervention strategies.
Structured feature ranking for genomic marker identification accommodating multiple types of networks
Authors: Ge Yeheng , Li Tao , Feng Xingdong , Wu Mengyun , Liu Hailong
Published: January 2025

Numerous statistical methods have been developed to search for genomic markers associated with the development, progression, and response to treatment of complex diseases. Among them, feature ranking plays a vital role due to its intuitive formulation and computational efficiency. However, most of the existing methods are based on the marginal importance of molecular predictors and share the limitation that the dependence (network) structures among predictors are not well accommodated, where a disease phenotype usually reflects various biological processes that interact in a complex network. In this paper, we propose a structured feature ranking method for identifying genomic markers, where such network structures are effectively accommodated using Laplacian regularization. The proposed method innovatively investigates multiple network scenarios, where the networks can be known a priori and data-dependently estimated. In addition, we rigorously explore the noise and uncertainty in the networks and control their impacts with proper selection of tuning parameters. These characteristics make the proposed method enjoy especially broad applicability. Theoretical result of our proposal is rigorously established. Compared to the original marginal measure, the proposed network structured measure can achieve sure screening properties with a faster convergence rate under mild conditions. Extensive simulations and analysis of The Cancer Genome Atlas melanoma data demonstrate the improvement of finite sample performance and practical usefulness of the proposed method.