bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantification method of tubing defects based on machine learning algorithm and magnetic flux leakage signals
Authors: Shi Mingjiang , Ni Mao , Qin Liansheng , Liang Yanbing , Huang Zhiqiang
Published: January 2023

Tubing is the pipeline that transports crude oil and natural gas from the oil and gas layer to the surface of the earth. Due to the harsh operating environment, the tubing will suffer from etch pits, scratches, cracks, perforations, and even direct fractures of different degrees of defective conditions. If tubing defects are not detected and quantified in a timely manner, the continued use of tubing will result in tubing leakage and failure. Magnetic flux leakage (MFL) testing as a nondestructive testing method enables the identification and quantitative analysis of defects in metal tubing. To improve the quantification accuracy of defects in the wellhead MFL testing of tubing defects during workover operations, this paper proposes a multi-output least-squares support vector regression machine (MLSSVR) model optimized based on the simulated annealing algorithm. The size of tubing defects can be quantified by establishing the mapping between the characteristic quantity of MFL signals and the defect size. The experimental results of MFL testing of tubing defects show that the root mean square error (RMSE) of the diameter of tubing defects of the simulated annealing algorithm optimized multi-output least-squares support vector regression (SA-MLSSVR) machine model proposed in this paper is 0.4562 mm, and the RMSE of the depth of tubing defects is 0.1504 mm. Compared with the non-optimized MLSSVR model, the overall RMSE of tubing defects is reduced by 36.48%. The SA-MLSSVR model only needs one-ninth of the time to achieve the same quantification accuracy as the particle swarm optimized multi-output least-squares support vector regression machine model.
Homogeneous nucleation of crystalline methane hydrate in molecular dynamics transition paths sampled under realistic conditions
Authors: Arjun A. , Bolhuis Peter G.
Published: January 2023

Methane hydrates are important from a scientific and industrial perspective, and form by nucleation and growth from a supersaturated aqueous solution of methane. Molecular simulation is able to shed light on the process of homogeneous nucleation of hydrates, using straightforward molecular dynamics or rare event enhanced sampling techniques with atomistic and coarse grained force fields. In our previous work [Arjun, T. A. Berendsen, and P. G. Bolhuis, Proc. Natl. Acad. Sci. U. S. A. 116, 19305 (2019)], we performed transition path sampling (TPS) simulations using all atom force fields under moderate driving forces at high pressure, which enabled unbiased atomistic insight into the formation of methane hydrates. The supersaturation in these simulations was influenced by the Laplace pressure induced by the spherical gas reservoir. Here, we investigate the effect of removing this influence. Focusing on the supercooled, supersaturated regime to keep the system size tractable, our TPS simulations indicate that nuclei form amorphous structures below roughly 260 K and crystalline sI structures above 260 K. For these temperatures, the average transition path lengths are significantly longer than in our previous study, pushing the boundaries of what can be achieved with TPS. The temperature to observe a critical nucleus of certain size was roughly 20 K lower compared to a spherical reservoir due to the lower concentration of methane in the solution, yielding a reduced driving force. We analyze the TPS results using a model based on classical nucleation theory. The corresponding free energy barriers are estimated and found to be consistent with previous predictions, thus adding to the overall picture of the hydrate formation process.
Planar tunneling spectroscopy on van der Waals superconductors with AlOx junction grown by atomic layer deposition
Authors: Ji Yu , Wang Hao , Dong Zehao , Ye Shusen , Li Qingyang , Gao Zhiting , Gu G. D. , Hao Zhenqi , Wang Yayu
Published: January 2023

We demonstrate a method for fabricating a high-quality AlOx-based planar tunnel junction using atomic layer deposition, integrated with the exfoliation and transfer techniques for van der Waals (vdW) materials. The tunneling spectroscopy results on exfoliated Bi2Sr2CaCu2O8+δ and 2H-NbSe2 vdW superconductors are highly consistent with that obtained by ultrahigh vacuum scanning tunneling spectroscopy on atomically clean surfaces. The planar tunneling devices enable high-precision spectroscopy over a wide range of temperatures and magnetic fields and reveal novel features and stark contrast between high-TC cuprates and conventional superconductors. This method represents a universally applicable technique for probing the electronic structure of various two-dimensional vdW materials.
Characterizing gas–liquid two-phase flow behavior using complex network and deep learning
Authors: Li Meng-Yu , Wang Rui-Qi , Zhang Jian-Bo , Gao Zhong-Ke
Published: January 2023

Gas–liquid two-phase flow is polymorphic and unstable, and characterizing its flow behavior is a major challenge in the study of multiphase flow. We first conduct dynamic experiments on gas–liquid two-phase flow in a vertical tube and obtain multi-channel signals using a self-designed four-sector distributed conductivity sensor. In order to characterize the evolution of gas–liquid two-phase flow, we transform the obtained signals using the adaptive optimal kernel time-frequency representation and build a complex network based on the time-frequency energy distribution. As quantitative indicators, global clustering coefficients of the complex network at various sparsity levels are computed to analyze the dynamic behavior of various flow structures. The results demonstrate that the proposed approach enables effective analysis of multi-channel measurement information for revealing the evolutionary mechanisms of gas–liquid two-phase flow. Furthermore, for the purpose of flow structure recognition, we propose a temporal-spatio convolutional neural network and achieve a classification accuracy of 95.83%.
Strain-mediated electric-field control of the electronic transport properties of 5d iridate thin films of SrIrO3
Authors: Li Shuang-Shuang , Zhang Ying , Ying Jing-Shi , Wang Zao-Cai , Yan Jian-Min , Gao Guan-Yin , Ye Mao , Zheng Ren-Kui
Published: January 2023

SrIrO3 (SIO) thin films were epitaxially grown on (001)-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single-crystal substrates. Upon applying electric fields to the piezoelectric PMN-PT along the thickness direction, the electronic transport properties of SIO films can be in situ tuned and modulated by non-180° ferroelectric domain rotation-induced strain, piezoelectric strain, and rhombohedral-to-tetragonal structural phase transition-induced strain in the PMN-PT layer, respectively. Moreover, the weak negative magnetoresistance (MR) of the 60-nm SIO films could be modified by applying an electric field to the PMN-PT layer. At T = 2 K, upon the application of E = 4 kV/cm to the PMN-PT, MR at H = 9 T is reduced by 14.2% as compared to that under zero electric field, indicating in-plane compressive strain-induced suppression of the influence of quantum corrections to the conductivity in the SIO film. These results demonstrate that the electric-field controllable lattice strain is a simple approach to get insight into the strain-property relationships of 5d iridate thin films.
A coupled awareness—epidemic model on a multi-layer time-varying network
Authors: Xu Haidong , Xie Weijie , Han Dun
Published: January 2023

Social interactions have become more complicated and changeable under the influence of information technology revolution. We, thereby, propose a multi-layer activity-driven network with attractiveness considering the heterogeneity of activated individual edge numbers, which aims to explore the role of heterogeneous behaviors in the time-varying network. Specifically, three types of individual behaviors are introduced: (i) self-quarantine of infected individuals, (ii) safe social distancing between infected and susceptible individuals, and (iii) information spreading of aware individuals. Epidemic threshold is theoretically derived in terms of the microscopic Markov chain approach and the mean-field approach. The results demonstrate that performing self-quarantine and maintaining safe social distance can effectively raise the epidemic threshold and suppress the spread of diseases. Interestingly, individuals’ activity and individuals’ attractiveness have an equivalent effect on epidemic threshold under the same condition. In addition, a similar result can be obtained regardless of the activated individual edge numbers. The epidemic outbreak earlier in a situation of the stronger heterogeneity of activated individual edge numbers.
Large eddy simulation of ship airflow control with steady Coanda effect
Authors: Xu Kewei , Su Xinchao , Bensow Rickard , Krajnovic Sinisa
Published: January 2023

This paper numerically studies the steady Coanda effect for drag reduction and airwake manipulations on the Chalmers ship model (CSM) using large eddy simulation with wall-adapting local-eddy viscosity model. Numerical methods are validated by experimental data acquired from the baseline CSM. In creating the flow control model, the hanger base of the baseline CSM is modified with Coanda surfaces and injection slots along its roof edge and two side edges. Four representative cases are studied: a no-jet case and three cases with the same momentum coefficient of the jet flow activated at different locations (roof, sides, and combined). The results show that the four cases have various performances in drag reduction and vortex structures on the deck. They are also different in mean and turbulent quantities as well as POD (proper orthogonal decomposition) modes in their airwake. It is found that the roof-jet has a stronger Coanda effect and is more vectored toward the low-speed area (LSA) on the deck than the side-jets that detach earlier from the Coanda surface. The energization process is, therefore, different where the roof-jet is more effective that directly brings high momentum to LSA and side-jets manipulate shear layers for mixing enhancement. The cases with roof-jet achieve better mitigation of flow re-circulation and higher recovery of streamwise velocity with lower turbulent fluctuation in the airwake. POD analysis suggests that the roof-jet can stabilize the wake.
Extending multi-layer energy-based fragment method for excited-state calculations of large covalently bonded fragment systems
Authors: Chen Wen-Kai , Fang Wei-Hai , Cui Ganglong
Published: January 2023

Recently, we developed a low-scaling Multi-Layer Energy-Based Fragment (MLEBF) method for accurate excited-state calculations and nonadiabatic dynamics simulations of nonbonded fragment systems. In this work, we extend the MLEBF method to treat covalently bonded fragment ones. The main idea is cutting a target system into many fragments according to chemical properties. Fragments with dangling bonds are first saturated by chemical groups; then, saturated fragments, together with the original fragments without dangling bonds, are grouped into different layers. The accurate total energy expression is formulated with the many-body energy expansion theory, in combination with the inclusion–exclusion principle that is used to delete the contribution of chemical groups introduced to saturate dangling bonds. Specifically, in a two-layer MLEBF model, the photochemically active and inert layers are calculated with high-level and efficient electronic structure methods, respectively. Intralayer and interlayer energies can be truncated at the two- or three-body interaction level. Subsequently, through several systems, including neutral and charged covalently bonded fragment systems, we demonstrate that MLEBF can provide accurate ground- and excited-state energies and gradients. Finally, we realize the structure, conical intersection, and path optimizations by combining our MLEBF program with commercial and free packages, e.g., ASE and SciPy. These developments make MLEBF a practical and reliable tool for studying complex photochemical and photophysical processes of large nonbonded and bonded fragment systems.
Strain-induced exciton localized states in quantum well
Authors: Wang Jian , Huang Junhui , Li Yuanhe , Ding Kun , Jiang Desheng , Dou Xiuming , Sun Baoquan
Published: January 2023

We use AlAs sacrificial layer etching technology to peel a film of In0.15Ga0.85As/GaAs single quantum wells (QWs) from a GaAs substrate and transfer the film to a Si wafer covered with randomly distributed Au nanoparticles. In this way, local strains are introduced into the QW film, which leads to the formation of the exciton confinement potential. From them, we have observed very sharp emission lines in photoluminescence (PL) spectra and local PL bright spots in space. The PL is proved to be from localized exciton emission in a potential energy funnel. We can also introduce the localized strain in the QW film using a micropillar array of an electron beam resist and observe similar narrow emission lines. The method to achieve localized exciton states is a controllable way and it will further expand the application of traditional semiconductor QWs in optical quantum devices.
Electronic heat generation in semiconductors: Non-equilibrium excitation and evolution of zone-edge phonons via electron–phonon scattering in photo-excited germanium
Authors: Murphy-Armando F. , Murray É. D. , Savić I. , Trigo M. , Reis D. A. , Fahy S.
Published: January 2023

We investigate experimentally and using first-principles theory the generation of phonons and the relaxation of carriers on picosecond timescales across the Brillouin zone of photo-excited Ge by inter-valley electron–phonon scattering. The phonons generated are typical of those generated in semiconductor devices, contributing to the accumulation of heat within the material. We simulate the time-evolution of phonon populations, based on first-principles band structure and electron–phonon and phonon–phonon matrix elements, and compare them to data from time-resolved x-ray diffuse scattering experiments, performed at the Linac Coherent Light Source x-ray free-electron laser facility, following photo-excitation by a 50 fs near-infrared optical pulse. We show that the intensity of the non-thermal x-ray diffuse scattering signal, which is observed to grow substantially near the L-point of the Brillouin zone over 3–5 ps, is due to phonons generated by scattering of carriers between the Δ and L valleys. These phonons have low group velocities, resulting in a heat bottleneck. With the inclusion of phonon decay through 3-phonon processes, the simulations also account for other non-thermal features observed in the x-ray diffuse scattering intensity, which are due to anharmonic phonon–phonon scattering of the phonons initially generated by electron–phonon scattering.
Ionic environment effects on collagen type II persistence length and assembly
Authors: Wilcox Kathryn G. , Kemerer Grace M. , Morozova Svetlana
Published: January 2023

Collagen type II is a main structural protein in cartilage and forms fibrils. The radius of the fibrils ranges from 50 nm to a few hundred nm, and previous theoretical studies point to electrostatics and collagen elasticity (measured as the persistence length, lp) as the main origin for the self-limiting size scales. In this study, we have investigated the collagen triple helical structure and fibril size scales in pH 2 solutions with varying NaCl concentrations from 10−4 to 100 mM, at which collagen is positively charged, and in pH 7.4 solutions, with varying ionic strengths from 100 to 250 mM, at which collagen is both positively and negatively charged. Using static and dynamic light scattering, the radius of gyration (Rg), hydrodynamic radius (Rh), and second virial coefficient (A2) of collagen triple helices are determined, and lp is calculated. With increasing ionic strength, triple helical lp decreases in pH 2 solutions and increases in pH 7.4 solutions. The value ranges from 60 to 100 nm depending on the ionic environment, but at the salt concentration at which A2 is near zero, there are no net backbone interactions in solution, and the intrinsic collagen triple helix lp is determined to be 90–95 nm. Electron microscopy is used to determine the diameter of fibrils assembled in pH 7.4 conditions, and we compare lp of the collagen triple helices and fibril diameter using recent theory on fibril assembly. By better understanding collagen lp and fibril assembly, we can further understand mechanisms of biomacromolecule self-assembly.
Transmission-based charge modulation microscopy on conjugated polymer blend field-effect transistors
Authors: Zhang Yansheng , Nguyen Malgorzata , Schnedermann Christoph , Keene Scott T. , Jacobs Ian , Rao Akshay , Sirringhaus Henning
Published: January 2023

Charge modulation microscopy (CMM) is an electro-optical method that is capable of mapping the spatial distribution of induced charges in an organic field-effect transistor (OFET). Here, we report a new (and simple) implementation of CMM in transmission geometry with camera-based imaging. A significant improvement in data acquisition speed (by at least an order of magnitude) has been achieved while preserving the spatial and spectral resolution. To demonstrate the capability of the system, we measured the spatial distribution of the induced charges in an OFET with a polymer blend of indacenodithiophene-co-benzothiadiazole and poly-vinylcarbazole that shows micrometer-scale phase separation. We were able to resolve spatial variations in the accumulated charge density on a length scale of 500 nm. We demonstrated through a careful spectral analysis that the measured signal is a genuine charge accumulation signal that is not dominated by optical artifacts.
A turbulent crosswind simulation method at high-speed railway tunnel entrance: Based on field test and geometric turbulence generator
Authors: Deng E , Yue Huan , Ni Yi-Qing , Wang You-Wu , He Xu-Hui , Chen Zheng-Wei
Published: January 2023

It is common for high-speed trains (HSTs) to abruptly switch between a tunnel and a flat ground along high-speed rail lines. When encountering strong crosswinds, the safety of HSTs in such running scenarios will be severely threatened. The simulation of the turbulent component of an incoming crosswind is very important to restore the real aerodynamic environment of HSTs in tunnel-flat ground-tunnel (TFT) running scenario. The purpose of the present study is to determine which of the two geometric turbulence generators, the spire and the fence, is more suitable for computational fluid dynamics (CFD) simulation of a fluctuating crosswind field in the TFT scene. First, the wind field characteristics in the TFT scene are analyzed based on the field test. Then, the tunnel-flat ground-spire/fence CFD model was established based on the “mosaic” mesh technology. Finally, the difference of wind field fluctuating characteristics under two turbulence generator conditions based on improved delayed detached eddy simulation (IDDES) is discussed. The main results show that the average wind speed of the windward and leeward lines in the fence case are 60% and 43.75% higher than the corresponding values in the spire case, respectively. The main conclusions show that the turbulent crosswind generated by the spire is more consistent with the spectrum characteristics of the natural wind field.
Sequence-specific binding behavior of coralyne toward triplex DNA: An ultrafast time-resolved fluorescence spectroscopy study
Authors: Jiao Zeqing , Yang Chunfan , Zhou Qian , Hu Zheng , Jie Jialong , Zhang Xianwang , Su Hongmei
Published: January 2023

Triplex DNA structure has potential therapeutic application in inhibiting the expression of genes involved in cancer and other diseases. As a DNA-targeting antitumor and antibiotic drug, coralyne shows a remarkable binding propensity to triplex over canonical duplex and thus can modulate the stability of triplex structure, providing a prospective gene targeting strategy. Much less is known, however, about coralyne-binding interactions with triplex. By combining multiple steady-state spectroscopy with ultrafast fluorescence spectroscopy, we have investigated the binding behaviors of coralyne with typical triplexes. Upon binding with a G-containing triplex, the fluorescence of coralyne is markedly quenched owing to the photoinduced electron transfer (PET) of coralyne with the G base. Systematic studies show that the PET rates are sensitive to the binding configuration and local microenvironment, from which the coexisting binding modes of monomeric (full and partial) intercalation and aggregate stacking along the sugar-phosphate backbone are distinguished and their respective contributions are determined. It shows that coralyne has preferences for monomeric intercalation within CGG triplex and pure TAT triplex, whereas CGC+ triplex adopts mainly backbone binding of coralyne aggregates due to charge repulsion, revealing the sequence-specific binding selectivity. The triplex-DNA-induced aggregation of coralyne could be used as a probe for recognizing the water content in local DNA structures. The strong π–π stacking of intercalated coralyne monomer with base-triplets plays an important role in stabilizing the triplex structure. These results provide mechanistic insights for understanding the remarkable propensity of coralyne in selective binding to triplex DNA and shed light on the prospective applications of coralyne-triplex targeted anti-gene therapeutics.
High-order optimal mode decomposition analysis of the ground effect on flow past two tandem inclined plates
Authors: Zhou Lei , Zhang Hongfu , Li Wenhui , Tse K. T. , Ai Yifeng , Hu Gang
Published: January 2023

Two-dimensional flow past two tandem near-ground plates with inclination angles of 25° at the Reynolds number of 150 is numerically simulated via the high-order spectral element method. Plate-to-ground gap is varied from G = 0.2L to 1.6L with intervals of 0.2L at two representative inter-plate spacings (i.e., X = 2.5L and 6L). The ground effect on the fluid force, power spectral density, asymmetric gap flow, and wake structure of plates is systematically evaluated. Then, the high-order optimal mode decomposition (HOOMD) method is proposed to synchronously analyze the velocity and pressure fields. The results show that the fluid force and flow structure are closely dependent on G. The presence of the ground inhibits vortex shedding when G < 0.6L; as the gap increases from 0.6 L to 1.4 L, the fluctuating forces are continuously enhanced until the ground effect basically disappears at G > 1.4L. The ground effect exacerbates the asymmetry of the vortex structure near the upper and lower parts of the inclined plates, consequently changing the fluid force. The downstream plate is more sensitive to the ground effect because of impingement from the upward-biased jet flow generated in the narrow gap between the upstream plate and ground. The HOOMD method well captures the spatial morphology and temporal evolution features of different dominant modes at the transition or vortex shedding flow regime. Mode analysis affords a correspondence between the coherent vortex structure and fluid force of plates. Furthermore, the ground effect can simultaneously change the global mode energy and local pressure mode shape, subsequently influencing the fluid force. However, the global mode energy plays the determinant role in the variation of the fluid force of plates with the plate-to-ground distance herein.
Wide-angle and broadband nonreciprocal thermal emitter with cascaded dielectric and Weyl semimetal grating structure
Authors: Wu Jun , Qing Ye Ming
Published: January 2023

The recent review [Phys. Rev. Appl. 18, 027001 (2022)] has considered that the existing schemes of nonreciprocal radiation are greatly limited by the narrow-operated bandwidth and small angular range. To address these key challenges, here, the wide-angle and broadband nonreciprocal radiation based on cascaded dielectric and Weyl semimetal (WS) grating atop a thick continuous metal film is investigated. It is shown that strong nonreciprocal radiation with nonreciprocity larger than 0.9 is achieved in the spectral range of 14.77–16.175 μm for the angle of 59°. The physical origin behind this broadband nonreciprocal radiation is revealed through investigating the magnetic field distributions at several selected wavelengths and is also confirmed by the impedance matching theory. In addition, the broadband nonreciprocal radiation performance remains stably in a wide parameter space. Furthermore, it is found that the broadband spectral nonreciprocity can be maintained well in a wide angular range, in particular, above 0.7 nonreciprocity can be realized in the wavelength range of 14.5–16.5 μm for the angle between 36° and 64.5°. Both features make the proposed scheme very attractive for real production. Finally, the broadband spectral nonreciprocity can be flexibly controlled through change in the axial vector of the WS. We believe that the conclusions will pave the way for designing energy harvesting and conversion devices with improved efficiency.
Sonomaglev: Combining acoustic and diamagnetic levitation
Authors: Hunter-Brown George , Sampara Naresh , Scase Matthew M. , Hill Richard J. A.
Published: January 2023

Acoustic levitation and diamagnetic levitation are experimental methods that enable the contact-free study of both liquid droplets and solid particles. Here, we combine both the techniques into a single system that takes advantage of the strengths of each, allowing for the manipulation of levitated spherical water droplets (30 nl–14 μl) under conditions akin to weightlessness, in the laboratory, using a superconducting magnet fitted with two low-power ultrasonic transducers. We show that multiple droplets, arranged horizontally along a line, can be stably levitated with this system and demonstrate controlled contactless coalescence of two droplets. Numerical simulation of the magnetogravitational and acoustic potential reproduces the multiple stable equilibrium points observed in our experiments.
Investigation on the adsorption properties and adsorption layer thickness during CH4 flow driven by pressure gradient in nano-slits
Authors: Deng Jia , Zhang Qi , Zhang Lan , Lyu Zijian , Rong Yan , Song Hongqing
Published: January 2023

In shale gas exploration, gas adsorbed on the surface of porous medium results in a change in pore size, which is closely relevant to permeability, flow rate, and production capacity of shale gas reservoirs, especially for the reservoir containing large numbers of pores and slits. Thus, the present work investigates the adsorption mechanism and adsorption layer thickness during CH4 flow driven by the pressure gradient in nano-slits by using molecular dynamics simulation. Herein, a slit-pore model in terms of gas storage and grapheme pore is developed, implemented, and verified. The effects of the pressure, temperature, pressure gradient, and pore size on adsorption properties and adsorption layer thickness of CH4 are also examined. Results show that the relative adsorption capacity is positively correlated with the pressure gradient and pore size and negatively correlated with the system pressure, whereas unaffected by temperature. Moreover, the adsorption layer thickness decreases with the pressure and is almost unaffected by the pore size under the small pore size, whereas increasing with the pressure gradient and temperature. The descending order of sensibility to the adsorption layer thickness is temperature, pressure gradient, pore size, and system pressure. Hence, based on those findings, a new formula for calculating the adsorption layer thickness is proposed for the quantitative determination of the effective pore size of porous medium when gas flows in slits, thereby contributing to shale gas high-efficient exploration.
Atomistic insight into the effects of electrostatic fields on hydrocarbon reaction kinetics
Authors: Kritikos Efstratios M. , Lele Aditya , van Duin Adri C. T. , Giusti Andrea
Published: January 2023

Reactive Molecular Dynamics (MD) and Density Functional Theory (DFT) computations are performed to provide insight into the effects of external electrostatic fields on hydrocarbon reaction kinetics. By comparing the results from MD and DFT, the suitability of the MD method in modeling electrodynamics is first assessed. Results show that the electric field-induced polarization predicted by the MD charge equilibration method is in good agreement with various DFT charge partitioning schemes. Then, the effects of oriented external electric fields on the transition pathways of non-redox reactions are investigated. Results on the minimum energy path suggest that electric fields can cause catalysis or inhibition of oxidation reactions, whereas pyrolysis reactions are not affected due to the weaker electronegativity of the hydrogen and carbon atoms. MD simulations of isolated reactions show that the reaction kinetics is also affected by applied external Lorentz forces and interatomic Coulomb forces since they can increase or decrease the energy of collision depending on the molecular conformation. In addition, electric fields can affect the kinetics of polar species and force them to align in the direction of field lines. These effects are attributed to energy transfer via intermolecular collisions and stabilization under the external Lorentz force. The kinetics of apolar species is not significantly affected mainly due to the weak induced dipole moment even under strong electric fields. The dynamics and reaction rates of species are studied by means of large-scale combustion simulations of n-dodecane and oxygen mixtures. Results show that under strong electric fields, the fuel, oxidizer, and most product molecules experience translational and rotational acceleration mainly due to close charge transfer along with a reduction in their vibrational energy due to stabilization. This study will serve as a basis to improve the current methods used in MD and to develop novel methodologies for the modeling of macroscale reacting flows under external electrostatic fields.
Dense random packing with a power-law size distribution: The structure factor, mass–radius relation, and pair distribution function
Authors: Cherny Alexander Yu. , Anitas Eugen M. , Osipov Vladimir A.
Published: January 2023

We consider a dense random packing of disks with a power-law distribution of radii and investigate their correlation properties. We study the corresponding structure factor, mass–radius relation, and pair distribution function of the disk centers. A toy model of dense segments in one dimension (1D) is solved exactly. It is shown theoretically in 1D and numerically in 1D and 2D that such a packing exhibits fractal properties. It is found that the exponent of the power-law distribution and the fractal dimension coincide. An approximate relation for the structure factor in arbitrary dimensions is derived, which can be used as a fitting formula in small-angle scattering. These findings can be useful for understanding the microstructural properties of various systems such as ultra-high performance concrete, high-internal-phase-ratio emulsions, or biological systems.
Universality and scaling in complex networks from periods of Chinese history
Authors: Pan Yi-Ru , Hsiao Pang , Chang Chen-Yu , Ma Wen-Jong , Hsiao Hsiang , Lin Pei-Jung , Wang Shih-Chieh , Yang Hui-Jie , Chi Ting-Ting , Hu Chin-Kun
Published: January 2023

Critical physical systems with large numbers of molecules can show universal and scaling behaviors. It is of interest to know whether human societies with large numbers of people can show the same behaviors. Here, we use network theory to analyze Chinese history in periods 209 BCE–23 CE and 515–618 CE) related to the Western Han–Xin Dynasty and the late Northern Wei–Sui Dynasty, respectively. Two persons are connected when they appear in the same historical event. We find that the historical networks from two periods separated about 500 years have interesting universal and scaling behaviors, and they are small-world networks; their average cluster coefficients as a function of degree are similar to the network of movie stars. In the historical networks, the persons with larger degrees prefer to connect with persons with a small degree; however, in the network of movie stars, the persons with larger degrees prefer to connect with persons with large degrees. We also find an interesting similar mechanism for the decline or collapse of historical Chinese dynasties. The collapses of the Xin dynasty (9–23 CE) and the Sui dynasty (581–618 CE) were initiated from their arrogant attitude toward neighboring states.
Effect of particle anisotropy on the thermodynamics and kinetics of ordering transitions in hard faceted particles
Authors: Sharma Abhishek K. , Escobedo Fernando A.
Published: January 2023

Monte Carlo simulations were used to study the influence of particle aspect ratio on the kinetics and phase behavior of hard gyrobifastigia (GBF). First, the formation of a highly anisotropic nucleus shape in the isotropic-to-crystal transition in regular GBF is explained by the differences in interfacial free energies of various crystal planes and the nucleus geometry predicted by the Wulff construction. GBF-related shapes with various aspect ratios were then studied, mapping their equations of state, determining phase coexistence conditions via interfacial pinning, and computing nucleation free-energy barriers via umbrella sampling using suitable order parameters. Our simulations reveal a reduction of the kinetic barrier for isotropic–crystal transition upon an increase in aspect ratio, and that for highly oblate and prolate aspect ratios, an intermediate nematic phase is stabilized. Our results and observations also support two conjectures for the formation of the crystalline state from the isotropic phase: that low phase free energies at the ordering phase transition correlate with low transition barriers and that the emergence of a mesophase provides a steppingstone that expedites crystallization.
Analytical solutions for vortex flow at the tangential inlet of a vertical dropshaft
Authors: Wei Wangru , Chang Lu
Published: January 2023

Vertical dropshafts with tangential intake structures are often used in urban drainage systems to route surface flow into underground systems. Vortex flow driven by a tangential inlet is the typical flow pattern in the vertical dropshaft. However, analytical solutions of the key hydraulic transition from chute flow to vortex flow have not been investigated, and theoretical guidelines of the vortex dropshaft are not available. In the present study, a series of theoretical analytical solutions are proposed to determine the circumferential flow generated at the vertical dropshaft inlet. The contraction ratio of the tapering chute, dropshaft size, and flow depth at the joint section determines the vortex flow performance in the vertical dropshaft. Based on the free surface drop height, theoretical criteria are proposed to describe the spiral movement intensity in the vertical dropshaft. Systemic experiments for different vortex dropshaft models are tested, and the experimental observations agree with the theoretical analysis. The present investigation provides a general reference for a tangential dropshaft inlet design that can smoothly route rotational flow down a vertical dropshaft.
Information-processing dynamics in neural networks of macaque cerebral cortex reflect cognitive state and behavior
Authors: Varley Thomas F. , Sporns Olaf , Schaffelhofer Stefan , Scherberger Hansjörg , Dann Benjamin
Published: January 2023

One of the essential functions of biological neural networks is the processing of information. This includes everything from processing sensory information to perceive the environment, up to processing motor information to interact with the environment. Due to methodological limitations, it has been historically unclear how information processing changes during different cognitive or behavioral states and to what extent information is processed within or between the network of neurons in different brain areas. In this study, we leverage recent advances in the calculation of information dynamics to explore neural-level processing within and between the frontoparietal areas AIP, F5, and M1 during a delayed grasping task performed by three macaque monkeys. While information processing was high within all areas during all cognitive and behavioral states of the task, interareal processing varied widely: During visuomotor transformation, AIP and F5 formed a reciprocally connected processing unit, while no processing was present between areas during the memory period. Movement execution was processed globally across all areas with predominance of processing in the feedback direction. Furthermore, the fine-scale network structure reconfigured at the neuron level in response to different grasping conditions, despite no differences in the overall amount of information present. These results suggest that areas dynamically form higher-order processing units according to the cognitive or behavioral demand and that the information-processing network is hierarchically organized at the neuron level, with the coarse network structure determining the behavioral state and finer changes reflecting different conditions.
Similar evolutionary trajectories in an environmental
Cryptococcus neoformans
isolate after human and murine infection
Authors: Sephton-Clark Poppy , McConnell Scott A. , Grossman Nina , Baker Rosanna P. , Dragotakes Quigly , Fan Yunfan , Fu Man Shun , Gerbig Gracen , Greengo Seth , Hardwick J. Marie , Kulkarni Madhura , Levitz Stuart M. , Nosanchuk Joshua D. , Shoham Shmuel , Smith Daniel F. Q. , Stempinski Piotr , Timp Winston , Wear Maggie P. , Cuomo Christina A. , Casadevall Arturo
Published: January 2023

A pet cockatoo was the suspected source of
Cryptococcus neoformans
recovered from an immunocompromised patient with cryptococcosis based on molecular analyses available in 2000. Here, we report whole genome sequence analysis of the clinical and cockatoo strains. Both are closely related MATα strains belonging to the VNII lineage, confirming that the human infection likely originated from pet bird exposure. The two strains differ by 61 single nucleotide polymorphisms, including eight nonsynonymous changes involving seven genes. To ascertain whether changes in these genes are selected for during mammalian infection, we passaged the cockatoo strain in mice. Remarkably, isolates obtained from mouse tissue possess a frameshift mutation in one of the seven genes altered in the human sample (LQVO5_000317), a gene predicted to encode an SWI–SNF chromatin-remodeling complex protein. In addition, both cockatoo and patient strains as well as mouse-passaged isolates obtained from brain tissue had a premature stop codon in a homologue of ZFC3 (LQVO5_004463), a predicted single-zinc finger containing protein, which is associated with larger capsules when deleted and reverted to a full-length protein in the mouse-passaged isolates obtained from lung tissue. The patient strain and mouse-passaged isolates show variability in virulence factors, with differences in capsule size, melanization, rates of nonlytic expulsion from macrophages, and amoeba predation resistance. Our results establish that environmental strains undergo genomic and phenotypic changes during mammalian passage, suggesting that animal virulence can be a mechanism for genetic change and that the genomes of clinical isolates may provide a readout of mutations acquired during infection.
The cationic interstitials induced resistive switching: A case study on Mn-doped SnO2
Authors: Xu Zhemi , Ji Tianhao , Zhang Shule , Guan Peiyuan , Elliott Joshua , Wan Tao , Cazorla Claudio , Chu Dewei
Published: January 2023

This work has explored the possible defects in Mn-doped SnO2 and compared the effects of interstitial Mn and oxygen vacancies on the electronic structure of SnO2. Combining the DFT calculations and experimental measurements, we found that when the Mn-doped SnO2 is synthesised under Sn-rich or O-poor conditions, the defect pair of Mn substitution and interstitial rather than oxygen vacancy will be formed, which induces energy band across the Fermi level and significantly affects the electronic structure of SnO2. With the Mn interstitials, stable intrinsic multi-level resistive states and optical SET can be achieved in the Mn-doped SnO2 memristors. This result can provide guidance in the fabrications of defective metal oxides and promote the investigations on cationic interstitial triggered multi-level resistive switching and optoelectronic memristors.
Axion-Photon Conversion of LHAASO Multi-TeV and PeV Photons
Authors: Zhang Guangshuai , Ma Bo-Qiang
Published: January 2023

The Large High Altitude Air Shower Observatory (LHAASO) has reported the detection of a large number of multi-TeV-scale photon events also including several PeV-scale gamma-ray-photon events with energy as high as 1.4 PeV. The possibility that some of these events may have extragalactic origins is not yet excluded. Here we propose a mechanism for the traveling of very-high-energy and ultra-high-energy photons based upon the axion-photon conversion scenario, which allows extragalactic above-threshold photons to be detected by observers on the Earth. We show that the axion-photon conversation can serve as an alternative mechanism, besides the threshold anomaly due to Lorentz invariance violation, for the very-high-energy features of the newly observed gamma ray burst GRB 221009A.
Short-range forces due to Lorentz-symmetry violation
Authors: Bailey Quentin G , James Jennifer L , Slone Janessa R , O’Neal-Ault Kellie
Published: January 2023

Complementing previous theoretical and experimental work, we explore new types of short-range modifications to Newtonian gravity arising from spacetime-symmetry breaking. The first non-perturbative, i.e. to all orders in coefficients for Lorentz-symmetry breaking, are constructed in the Newtonian limit. We make use of the generic symmetry-breaking terms modifying the gravity sector and examine the isotropic coefficient limit. The results show new kinds of force law corrections, going beyond the standard Yukawa parameterization. Further, there are ranges of the values of the coefficients that could make the resulting forces large compared to the Newtonian prediction at short distances. Experimental signals are discussed for typical test mass arrangements.
Mode stability results for the Teukolsky equations on Kerr–anti-de Sitter spacetimes
Authors: Graf Olivier , Holzegel Gustav
Published: January 2023

We prove that there are no non-stationary (with respect to the Hawking vectorfield), real mode solutions to the Teukolsky equations on all

(
3
+
1
)

-dimensional subextremal Kerr–anti-de Sitter spacetimes. We further prove that stationary solutions do not exist if the black hole parameters satisfy the Hawking–Reall bound and

a

−
Λ

<

3

20

. We conclude with the statement of mode stability which preludes boundedness and decay estimates for general solutions which will be proven in a separate paper. Our boundary conditions are the standard ones which follow from fixing the conformal class of the metric at infinity and lead to a coupling of the two Teukolsky equations. The proof relies on combining the Teukolsky–Starobinsky identities with the coupled boundary conditions. In the stationary case the proof exploits elliptic estimates which fail if the Hawking–Reall bound is violated. This is consistent with the superradiant instabilities expected in that regime.
Phonon dispersion curves in the type-I crystalline and molten clathrate compound Eu8Ga16Ge30
Authors: Hasegawa Takumi , Inui Masanori , Onimaru Takahiro , Kajihara Yukio , Hosokawa Shinya , Nakajima Yoichi , Matsuda Kazuhiro , Takabatake Toshiro , Hiroi Satoshi , Uchiyama Hiroshi , Tsutsui Satoshi
Published: January 2023

The dynamic structure factor

S
(
Q
,
E
)

, where Q and E are momentum and energy transfer, respectively, has been measured for liquid Eu8Ga16Ge30 (EGG), using inelastic x-ray scattering. The excitation energy of the longitudinal acoustic mode in the liquid was scaled to that in liquid Ba8Ga16Sn30 (BGS) with the effective mass. This result means that the local structure in both liquids are similar. The longitudinal acoustic excitation energy of type-I clathrate compound EGG disperses faster than that in the liquid, suggesting that the interatomic force is weakened on melting. The lower energy excitation was observed in both liquid EGG and liquid BGS. In comparison with the longitudinal phonon dispersion in crystalline clathrate compound EGG obtained by density functional theory-based calculations, the lower energy in the liquid was found to be near the optical mode energy. The result indicates that the lower energy mode arises from the relative motion between Eu and (Ga, Ge) atoms.
UK audit of variation in nuclear medicine occupational exposure calculations in 2021
Authors: Murray Anthony W , Memmott Matthew
Published: January 2023

It is a core requirement of UK ionising radiations regulations 2017 (IRR17) compliance for radiation risk assessments and the investigation of accidental exposure scenarios that the magnitude of doses likely to be encountered are evaluated. A novel national audit was undertaken to investigate the variation in dose estimations for a range of foreseeable accidental exposure scenarios in nuclear medicine (NM). Participants were asked to estimate the levels of exposure in 15 foreseeable scenarios; covering whole-body and extremity exposures from external sources, internal exposure and exposures from skin (surface contamination and needle-stick injury) and eye contamination. Questions were intentionally simplified to reduce variation from assumptions made by the participants and to focus more on the underlying gross systematic variation. Twenty-seven centres participated. There was generally a very wide variation in the estimated exposures across all the categories of exposures, apart from internal exposure estimates. Whilst there was no ground truth for each individual question, the variation in results itself often exceeded the relevant threshold for classification and annual dose limits. The majority of variation was due to differences in methods, models and assumptions used by each participant. This audit raises questions around how IRR17 compliance can be universally demonstrated with such wide national variation. It evidences the need for a more standardised practice in NM radionuclide exposure estimates through national consensus guidelines or standards etc.
Improved YOLOv3 model with feature map cropping for multi-scale road object detection
Authors: Shen Lingzhi , Tao Hongfeng , Ni Yuanzhi , Wang Yue , Stojanovic Vladimir
Published: January 2023

Road object detection is an essential and imperative step for driving intelligent vehicles. Generally, road objects, such as vehicles and pedestrians, present the characteristic of multi-scale and uncertain distribution which puts a high demand on the detection algorithm. Therefore, this paper proposes a YOLOv3 (You Only Look Once v3)-based method aimed at enhancing the capability of cross-scale detection and focusing on the valuable area. The proposed method fills an urgent need for multi-scale detection, and its individual components will be useful in road object detection. The K-means-GIoU algorithm is designed to generate a priori boxes whose shapes are close to real boxes. This greatly reduces the complexity of training, paving the way for fast convergence. Then, a detection branch is added to detect small targets, and a feature map cropping module is introduced into the newly added detection branch to remove the areas with high probability of background targets and easy-to-detect targets, and the cropped areas of the feature map are filled with a value of 0. Further, a channel attention module and spatial attention module are added to strengthen the network’s attention to major regions. The experiment results on the KITTI dataset show that the proposed method maintains a fast detection speed and increases the mAP (mean average precision) value by as much as 2.86

%

compared with YOLOv3-ultralytics, and especially improves the detection performance for small-scale objects.