Field Parameters Research Articles

Quantum Mechanics-Calibrated Classical Simulation of Earth-Abundant Divalent Metal Bis(trifluoromethanesulfonyl)imide Molar Conductivity in Organic Cosolvents with Onsager Transport Formalism.

Molar conductivities are one of the fundamental transport properties of electrolytes that reflect the complex and dynamic interactions between ions and solvents comprehensively. The quantitative accuracy of experimental input-free simulations of molar conductivities is strongly influenced by the underlying interaction parameters employed in the model. When validated with experimental molar conductivities, the developed model could be used to reveal further atomistic level details about the solvation structures and correlated ion pair formation, providing in-depth knowledge about solution physical chemistry and shedding light on electrolyte-solvent system design rules. Divalent cations are more challenging to model than monovalent cations due to their higher charge densities and stronger interactions with the environment. Yet, they started attracting significant attention for next-generation energy storage purposes. In this work, we focus on two earth-abundant divalent cation electrolytes, Mg(TFSI)2 and Ca(TFSI)2 in a dimethylacetamide-tetrahydrofuran (DMA-THF) cosolvent system. We used quantum mechanical cluster models to optimize the force field parameters (including the pairwise nonbonded interaction parameters and atomic charges) to be applied in classical simulations. With the reliable force field model, we discussed the importance of including ion correlation explicitly in predicting the molar conductivities via the Onsager formalism and showed that the conventional Nernst-Einstein formula overestimates ionic mobilities due to its intrinsic independent and uncorrelated particle assumption. Further, we investigated the solvation structures and ion pair formations. We concluded that the suitability of the interaction potentials utilized in a classical model for particular systems needs to be assessed not solely by directly comparing the simulated molar conductivities with the measured ones but, more importantly, by using the correct formalism (Onsager) to deduce the simulated result from dynamics trajectories.

Radiative properties and QPOs around charged black hole in Kalb–Ramond gravity

Studies of accretion disc luminosities and quasiperiodic oscillations around black holes may help us understand the gravitational properties of black hole spacetime. This work is devoted to studying the radiation properties of the accretion disk around the black holes in Kalb–Ramond gravity. We investigate the event horizon of the black hole spacetime and calculate the effective gravitational mass of the spacetime. Also, we analyze the circular motion of test particles in the black hole spacetime. The effects of the black hole charge and KR parameters on the particles’ effective mass, energy, and angular momentum at circular orbits and innermost stable circular orbits are studied. The frequency of Keplerian orbits and the radial and vertical oscillations of the particles along stable orbits are calculated and applied to analyze the existence of QPO in relativistic precession, warped disc, and epicyclic resonance models. QPO orbits’ locations with ratios of upper and lower frequencies of twin-peaked QPOs 3:2, 4:3, and 5:4 are analyzed compared to ISCO. We also obtain constrain values for the black hole mass, charge, KR field parameter, and QPO orbits found using Markovian chain Monte Carlo (MCMC) simulations for stellar mass (XTE J1550, GRS 1915+105), intermediate mass (M82-X1), and supermassive black holes (Sgr A*). Finally, we explore the radiative properties of the accretion disk around the charged black hole in KR gravity, such as the total radiation flux, accretion disc temperature, and differential luminosity.

Solar Flare Forecasting Using Hybrid Neural Networks

Abstract Solar flares are one of the most intense solar activities, the result of a sudden large-scale release of magnetic energy in the form of electromagnetic radiation and energetic particles. Intense solar flares can severely threaten communication and navigation systems, oil pipelines, and power grids on Earth. Therefore, it is crucial to establish highly accurate solar flare prediction models to enable humans to anticipate solar flare eruptions in advance, thereby reducing human and economic losses. In this paper, we utilized the solar active region (AR) magnetogram provided by the Solar Dynamics Observatory’s Helioseismic and Magnetic Imager and the associated feature parameters of the magnetic field; specifically, the feature vectors of the magnetic field’s spatial structure characteristics and the magnetic field feature parameters are fused to predict solar flares. We built two solar flare prediction models based on a combination of convolutional neural networks (CNN) and a temporal convolutional network (TCN), called CNN-TCN, and predicted whether a ≥C- or ≥M-class flare event would erupt in ARs in the next 24 hr, respectively. Then, after training and testing our model, we focused on the true skill statistic (TSS). Through the model superiority discussion, the model obtained high average TSS values, with the ≥C and ≥M models achieving TSS scores of 0.798 ± 0.032 and 0.850 ± 0.074, respectively, suggesting that our models have good forecasting performance. We speculate that some key features automatically extracted by our model may not have been previously identified, and these features could provide important clues for studying the mechanisms of flares.

Investigating the optical properties of cylindrical core/shell/shell quantum dots (CCSSQDs) with and without hydrogenic impurity: Role of spatial factors, magnetic field, dielectric matrices and Rashba parameter

Investigating the optical properties of cylindrical core/shell/shell quantum dots (CCSSQDs) with and without hydrogenic impurity: Role of spatial factors, magnetic field, dielectric matrices and Rashba parameter

Synthesis and Characterization of K2Ba3(P2O7)2:VO2+ Nanopowder: Reddish-Orange Emission for LED Applications.

Solid-state reaction method is employed to prepare K2Ba3(P2O7)2:VO2+ nanopowder and studied by using powder x-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, optical absorption spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and photoluminescence (PL) spectroscopy. XRD studies revealed VO2+ ion doped K2Ba3(P2O7)2 nanopowder have 21 nm crystallite size, orthorhombic phase, and Pmn21 space group. From Williamson-Hall analysis, crystallite size is found as 24 nm. SEM morphology recorded the presence of irregular-sized and round-shaped agglomerates. FT-IR and Raman spectra reveal characteristic bands of phosphate groups. Three characteristic peaks are observed at 848, 695, and 452 nm in optical absorption spectrum. Also, crystal and tetragonal field parameters are calculated as Dq = 1439, Ds = -2789, and Dt = 3422 cm-1. In addition, bandgap energy is found as 3.97 eV. Optical and EPR analyses led to understand the incorporation of vanadyl ions into host lattice. Spin Hamiltonian parameters are evaluated. Basing PL spectrum, Commission Internationale de l'Éclairage's (CIE) chromaticity coordinates are calculated, which are present in reddish-orange region with good color correlated temperature (CCT) and color rendering index (CRI) values facilitating the use in lighting applications and LEDs.

Relationship between outer retinal tubulation, retinal volume, and visual field in Bietti crystalline dystrophy.

To investigate the presence of tubulation in the outer nuclear layer of patients with Bietti crystalline dystrophy (BCD) using optical coherence tomography (OCT) and evaluate its relationship with visual field, visual field progression, and retinal volume. This retrospective cross-sectional study included 37 patients diagnosed with BCD who underwent spectral-domain OCT examination. OCT examinations and Humphrey visual field tests (10-2 program) were conducted. We performed correlation analyses to assess the correlation of the number of tubulations with the visual field parameters and retinal volume. We also compared the number and prevalence of tubulations in groups based on median values of the parameters. The primary outcome measure was the number and prevalence of tubulations. The average age of the participants was 58.7 ± 9.6years. The mean deviation (MD) value was -25.0 ± 9.0 decibels (dB). The MD slope value during an average follow-up period of 5.9 ± 3.8years was -0.91 ± 1.02dB/year. The number of tubulations tended to increase as the MD values worsened (P = 0.055, r = -0.33). Moreover, the number (P = 0.48) and prevalence (P = 0.42) of tubulations tended to be higher in the group with lower MD values. The number of tubulations decreased with worsening logarithmic minimum angle of resolution (logMAR) (P = 0.68, r = -0.07). The prevalence of tubulations was higher in the group with poorer logMAR (P = 0.068). We observed no significant correlations between the number of tubulations and the retinal outer, inner, or center volume (P = 0.46, r = -0.13; P = 0.76, r = 0.05; P = 0.47, r = 0.12, respectively). However, the prevalence of tubulations in the group with smaller retinal center volume was lower (P = 0.054). The number of tubulations correlated with the severity of visual field loss in patients with BCD; however, it did not correlate with visual field progression or retinal volume measurements. Further studies are needed to understand the development of tubulations and their implications for retinal atrophy in BCD.

Constrained optimization approach for magnetohydrostatic equilibria on the solar atmosphere

The magnetic field plays an essential role in the evolution of structures and the description of events in the solar atmosphere. Several models have been developed to reconstruct the magnetic field, due to the impossibility of its direct measurement in the solar corona. The model proposed here extrapolates the photospheric magnetogram data up to the corona using a constrained optimization method. In the upper photosphere and chromosphere, both the magnetic and nonmagnetic forces must be taken into account, and the magnetic field reconstruction must be done considering the plasma pressure and density. This is done by applying the Lagrange multiplier technique, as the constrained optimization method, to compute the magnetic field, plasma pressure, and density in magnetohydrostatic equilibria. This approach has previously been introduced to reconstruct a nonlinear force-free magnetic field. For this work we extended it to a more realistic issue to reconstruct the magnetic field and calculate the plasma pressure and density in a magnetohydrostatic environment. Our approach was to use the constrained optimization method, which is computationally more efficient and easy to implement. The Lagrange multiplier technique is a powerful mathematical tool that has been successfully applied to many areas of physics. We sought to minimize a Lagrangian, which minimizes the divergence term subject to the constraint magnetohydrostatic equilibrium equation. The plasma parameters and magnetic field were eventually computed following the iteration scheme along with appropriate boundary data. In our previous work, we applied Lagrange multiplier techniques to reconstruct a force-free magnetic field for the solar atmosphere. For this wok, we extended the same optimization technique to extrapolate magnetic field and plasma parameters in magnetohydrostatic equilibria. The results for the magnetic field and plasma parameters were calculated and compared with those obtained by other models in the magnetohydrostatic equilibrium environment as well as the semi-analytical solution as a reference model. A force-free magnetic field and a suitable distribution for pressure and density were used as the initial input for their corresponding evolution equations. After $20,000$ iterations, the convergence of the Lagrangian in our model was slightly better than that of the comparison model. The indicators such as the relative magnetic energy and magnetic field lines were investigated, which are in agreement with the reference model compared to the comparison model.

Some Challenges of Diffused Interfaces inImplicit-Solvent Models.

The standard Poisson-Boltzmann (PB) model for molecular electrostatics assumes a sharp variation of the permittivity and salt concentration along the solute-solvent interface. The discontinuous field parameters are not only difficult numerically, but also are not a realistic physical picture, as it forces the dielectric constant and ionic strength of bulk in the near-solute region. An alternative to alleviate some of these issues is to represent the molecular surface as a diffuse interface, however, this also presents challenges. In this work we analyzed the impact of the shape of the interfacial variation of the field parameters in solvation and binding energy. However we used a hyperbolic tangent function to couple the internal and external regions, our analysis is valid for other definitions. Our methodology, restricted to the linear PB, was based on a coupled finite element (FEM) and boundary element (BEM) scheme that allowed us to have a special treatment of the permittivity and ionic strength in a bounded FEM region near the interface, while maintaining BEM elsewhere. Our results suggest that the shape of the function (represented by ) has a large impact on solvation and binding energy. We saw that high values of induce a high gradient on the interface, to the limit of recovering the sharp jump when , presenting a numerical challenge where careful meshing is key. Using the FreeSolv database to compare with molecular dynamics, our calculations indicate that an optimal value of for solvation energies was around 3. However, more challenging binding free energy tests make this conclusion more difficult, as binding showed to be very sensitive to small variations of . In that case, optimal values of ranged from 2 to 20.

Improved GIS Techniques and a Novel Physico-Chemical Risk Index for Surface Water Quality Assessment: A Case Study of the Al-Garraf Oil Field

Petroleum hydrocarbons and waste streams have polluted the environment, harmed human health, affected socioeconomic conditions, and impacted communities in oil-producing countries. The aim of the study is to identify hotspots of contaminated water, create spatial risk maps of pollution from the petroleum industry and develop a novel index to estimate ecosystem pollution named physico-chemical risk index (PRI). Ten sites in the Al-Gharraf oil field were analyzed for their water quality. The highest results of the six-month sample analysis were PH (8.7), DO (11.5mg/L), turbidity (70.3 NTU), temperature (34 C), BOD<sub>5</sub> (37.8 mg/L), COD (101 mg/L) and TSS (109 mg/L). To achieve the above objectives, different methods and techniques were used; one of them is inverse distance weighting(IDW) with GIS to create geographical maps of the measured parameters. The IDW method was used to accurately map the distribution of ecosystem parameters of the oil field. The PRI was performed to compare the threshold values for pollutant elements with the contamination of the site. The threshold value for contaminated water in Garraf oil field is 24.328 and is determined by the PRI index. The analysis is carried out at regular intervals and compared with the threshold values. This work has created an important database for the oil industry that should be used to monitor ecosystems.

Theoretical Studies on the EPR Parameters and Local Structures for the Orthorhombic and Tetragonal Cu2+ Centers in Cu1-xHxZr2(PO4)3.

The defect structures of the orthorhombical and tetragonal Cu2+ centers in Cu1-xHxZr2(PO4)3 are theoretically studied by analyzing their experimental electron paramagnetic resonance (EPR) parameters, based on the perturbation formulas of these parameters for a 3d9 ion in orthorhombically and tetragonally elongated octahedra, respectively. The above centers are attributed to the Cu2+ ions locating at M(1) site, and the crystal field parameters (CFPs) are quantitatively determined from the superposition model and the local structures of the Cu2+ sites. Based on the calculation, the parallel Cu-O bonds may undergo the relative elongations ΔZO (≈ 0.113 Å) and ΔZT (≈ 0.102 Å) for the orthorhombical and tetragonal Cu2+ centers in Cu1-xHxZr2(PO4)3 along z-axis, respectively. Meanwhile, the planar Cu-O bonds are found to experience the relative variation δr (≈ 0.056 Å) along the x- and y-axes for the orthorhombical Cu2+ center because of the Jahn-Teller (JT) effect. The theoretical EPR parameters based on the above local structures agree well with the observed values.

Parameter constraints on a black hole with Minkowski core through quasiperiodic oscillations

We investigate the geodesic motion of charged particles in the vicinity of regular black holes with a Minkowski core, embedded in a uniform magnetic field, and study the influences of magnetic field and regular black hole parameter on the radial effective potential and angular momentum of the particles’ orbits. We perturb the circular orbit and analyze the characteristic frequencies of the epicyclic oscillations, which are closely related with the quasiperiodic oscillations (QPOs) phenomena of the accretion disc surrounding the black hole. Then using the MCMC simulation, we fit our theoretical results with four observational QPOs events (GRO J1655-40, XTE J1550-564, XTE J1859+226, and GRS 1915+105) and provide constraints on the magnetic field strength B, the characteristic radius r, the mass M, and the regular black hole parameter g. In particular, since the parameter g describes the degree of deviation from the classical Schwarzschild black hole, our studies suggest that, within a certain level of confidence, the black holes in the current model can deviate from the classical singularity structure of Schwarzschild black holes, and exhibit quantum corrections near the core.

Modelling and optimization of small - scale soft magnetic robots for enhanced locomotion

Small-scale soft robots are vital in medical scenarios requiring access to confined spaces. This study explores motion optimization for such robots, emphasizing magnetically responsive materials that enable shape changes through controlled magnetic fields. These materials provide robots with versatile and agile locomotion capabilities. Using genetic algorithms, we present a novel approach to optimize magnetic field parameters and robot dimensions. In magnetic field optimization, the results validate prior experimental observations while providing new insights into determining optimal magnetic field characteristics for walking motions. Deviations from optimal magnetic field magnitudes directly affect walking velocity, revealing a non-linear relationship between magnetic fields and locomotion speed, diverging from linear modeling results. Furthermore, we find that both excessively low and high robot heights hinder walking speed lower heights reduce surface friction, while higher heights compromise agility. This comprehensive optimization strategy advances the capabilities of small-scale soft magnetic robots. Our work in motion modeling and optimization enhances the understanding of these robots' dynamics and unlocks new possibilities for deployment in complex environments. These findings reaffirm the significance of soft robots in medical and confined-space applications, offering a robust foundation for further innovations in this evolving field.

Liquid–Solid Coupled Internal Flow Field Analysis of Natural Gas Hydrate Spiral-Swirling Downhole In Situ Separator

This study aims to solve the problem of the recovery efficiency of natural gas hydrate being affected by a large amount of mud and sand in the solid fluidization mining of natural gas hydrate. Therefore, a new method for the separation of in situ sediment and natural gas hydrate in a spiral-swirling downhole is proposed, and the corresponding numerical simulation model is established to realize the analysis and verification of key flow field parameters such as flow velocity, pressure, sediment, and natural gas hydrate phase distribution. The results show that the flow velocity field of the mixed slurry presents an ‘M’-shaped symmetrical distribution, and the slurry near the wall of the separator can obtain a larger flow velocity, which is beneficial to the separation of mud–sand and natural gas hydrate. The static pressure field shows an axisymmetric distribution that decreases first and then increases, indicating that the pressure of the mixed slurry increases with the increase in the radial position, and the closer to the wall, the greater the static pressure of the mixed slurry. Near the wall of the separator, the volume fraction of the sediment phase reaches the maximum. In contrast, the volume fraction of the natural gas hydrate phase reaches the minimum, which confirms the separation effect of the sediment and the natural gas hydrate. The results show that the separation of sediments and natural gas hydrate can be realized, thereby improving the exploitation efficiency of natural gas hydrate. The designed spiral cyclone coupling separator provides a new solution to solving the problem of sand removal in natural gas hydrate exploitation.

Analysis of heat transfer of second-grade hybrid nanofluid and optimization using response surface methodology for thermal enhancement

The fluid flow and heat transfer applications in coaxial double-revolving disks are extensive and encompass multiple engineering and scientific disciplines. This study presents a comprehensive heat transfer analysis in a second-grade hybrid nanofluid. The fluid, influenced by variable thermal conductivity, is confined between two rotating disks in a magnetohydrodynamic Darcy-Forchheimer flow. The hybrid nanofluid combines titanium dioxide (TiO2) and cobalt ferrite (CoFe2O4) nanoparticles with engine oil. These issues have not been addressed in previous research. Similarity transformations make flow equations dimensionless. The resulting equations are solved using a semi-analytical approach called the homotopy analysis method (HAM). This approach provides flexibility in selecting the base function and an initial estimate. The temperature profile improved with higher values of the variable thermal conductivity parameter. Furthermore, the heat transfer rate was enhanced by increasing the variable thermal conductivity, the volume fraction concentration of TiO2, and the Reynolds number.The sensitivity analysis is performed using response surface methodology (RSM). Both the R-squared and adjusted R-squared values attain 100%. The heat transfer rate is found to have a maximum sensitivity of 0.50243 towards varying thermal conductivity parameters and a minimum sensitivity of -0.00666 towards magnetic field parameters. The research utilizes RSM to elucidate methods for improving heat transfer. This work offers practical solutions for developing more efficient thermal management systems. This research provides practical strategies for improving thermal management systems. These solutions are especially useful in rotating machinery-intensive industries. Designing biochemical and pharmaceutical microfluidic pumps and mixers requires understanding hybrid nanofluid flows between spinning disks.

Refinement of Atomic Polarizabilities for a Polarizable Gaussian Multipole Force Field with Simultaneous Considerations of Both Molecular Polarizability Tensors and In-Solution Electrostatic Potentials.

Atomic polarizabilities are considered to be fundamental parameters in polarizable molecular mechanical force fields that play pivotal roles in determining model transferability across different electrostatic environments. In an earlier work, the atomic polarizabilities were obtained by fitting them to the B3LYP/aug-cc-pvtz molecular polarizability tensors of mainly small molecules. Taking advantage of the recent PCMRESPPOL method, we refine the atomic polarizabilities for condensed-phase simulations using a polarizable Gaussian Multipole (pGM) force field. Departing from earlier works, in this work, we incorporated polarizability tensors of a large number of dimers and electrostatic potentials (ESPs) in multiple solvents. We calculated 1565 × 4 ESPs of small molecule monomers and dimers of noble gas and small molecules and 4742 × 4 ESPs of small molecule dimers in four solvents (diethyl ether, ε = 4.24, dichloroethane, ε = 10.13, acetone, ε = 20.49, and water, ε = 78.36). For the gas-phase polarizability tensors, we supplemented the molecule set that was used in our earlier work by adding both the 4252 monomer and dimer sets studied by Shaw and co-workers and the 7211 small molecule monomers listed in the QM7b database to a combined total of 13,523 molecular polarizability tensors of monomers and dimers. The QM7b polarizability set was obtained from quantum-machine.org and was calculated at the LR-CCSD/d-aug-cc-pVDZ level of theory. All other polarizability tensors and all ESPs were calculated at the ωB97X-D/aug-cc-pVTZ level of theory. The atomic polarizabilities were developed using all polarizability tensors and the 1565 × 4 ESPs of small molecule monomers and were then assessed by comparing them to the 4742 × 4 ab initio ESPs of small molecule dimers. The predicted dimer ESPs had an average relative root-mean-square error (RRMSE) of 9.30%, which was only slightly larger than the average fitting RRMSE of 9.15% of the monomer ESPs. The transferability of the polarizability set was further evaluated by comparing the ESPs calculated using parameters developed in another dielectric environment for both tetrapeptide and DES monomer data sets. It was observed that the polarizabilities of this work retained or slightly improved the transferability over the one discussed in earlier work even though the number of parameters in the present set is about half of that in the earlier set. Excluding the gas-phase data, for the DES monomer set, the average transfer RRMSEs were 16.25% and 10.83% for pGM-ind and pGM-perm methods, respectively, comparable to the average fitting RRMSEs of 16.03% and 10.54%; for tetrapeptides, the average transfer RRMSEs were 5.62% and 3.95% for pGM-ind and pGM-perm methods, respectively, slightly larger than 5.41% and 3.61% of the fitting RRMSEs. Therefore, we conclude that the pGM methods with updated polarizabilities achieved remarkable transferability from monomer to dimer and from one solvent to another.

External Flow Field and Rock Erosion Characteristics of a Coaxial Straight‐Swirling Mixed Jet

ABSTRACTRadial jet drilling is an effective technology for mining coal‐bed methane. A self‐propelled jet bit greatly affects drilling efficiency. Simulations and laboratory experiments using a coaxial straight‐swirling mixed jet (CSMJ) were performed to study the flow field and rock erosion characteristics, and analyze laws influencing key structural parameters (straight‐swirling flow ratio N, slot length–width ratio dr/ds, mixing chamber length–diameter ratio Lq/Dq, and linear segment length–diameter ratio Lf/df) on the flow field and rock erosion characteristics, and study the change law of the axial velocity of the flow field under different structural parameters and the distribution law of the three‐dimensional velocity along the radial direction at the non‐dimensional injection distance of 5.56. The CSMJ displayed characteristics of a straight jet, having a high‐velocity area near the axis. The velocity was attenuated with increasing dimensionless jet distance Ls/df. The bit also displayed characteristics of a swirling jet, with an obvious jet diffusion with increased Ls/df. N affected the distribution ratio of the straight and swirling jets, and dr/ds mainly affected CSMJ rotational shear energy. With the centerline velocity and radial distribution of the CSMJ as evaluation indices, the optimal parameters of the CSMJ suitable for self‐propelled drilling were N = 0.46, dr/ds = 3.88, Lq/Dq = 0.67, and Lf/df = 0.56. Optimal flow field parameters also optimized the erosion capability, realizing the mutual verification of experimental and simulation results. The erosion hole crushing volume was used as the evaluation sequence. The parameter's sensitivity to the rock erosion volume was Ls/df > Lq/Dq > dr/ds > N. The results provide engineering guidance for determining reasonable parameters for radial jet drilling.

Analysis of Crack‐Tip Field in Orthotropic Compact Tension Shear Specimens: The Role of Elastic Mode Mixity and T‐Stress

ABSTRACTThe analysis of mixed‐mode crack propagation mechanisms in anisotropic materials remains a pivotal research focus. Although the compact tension shear (CTS) test is a recommended laboratory method, the lack of solutions for anisotropic crack‐tip field parameters hinders accurate assessment of stress states and deformations during crack propagation. To address this gap, this study conducted a systematic finite element analysis (FEA) to compute the elastic mode mixity and T‐stress results. It is found that by adjusting the loading angle along with the initial crack length, CTS tests on orthotropic specimens can similarly achieve a broad spectrum of Me at the crack‐tip. Statistical analysis indicates that applying isotropic solutions to estimate orthotropic T‐stress can lead to average errors of 234.1%. Subsequently, crack‐tip fields were analyzed, with crack initiation angles predicted using the maximum tangential stress (MTS) criterion and plastic zone profiles determined based on Hill's yield criterion. Larger fracture process zones enhance T‐stress correction effects on crack initiation angles, with positive T intensifying crack deflection, while negative T reduces it. Additionally, T also significantly affects the plastic zone's shape and size, with patterns varying according to material orthotropy. A detailed multiparameter characterization of crack‐tip fields will enhance the use of the CTS test for assessing multiaxial strength and mixed‐mode fracture mechanisms in anisotropic materials.

Topological phase transitions and switchable edge states for the non-Hermitian Aubry-André-Harper model in photonic crystals.

The Aubry-André-Harper (AAH) model with imaginary periodic or quasiperiodic modulations could regulate the local properties of the system. In this work, we apply the non-Hermitian AAH potential field to the photonic system induced by gain and loss. It is found that the potential field with different parameters will cause the system to exhibit different local properties and induce different localized edge states under the open boundary conditions. Moreover, we investigated the influence of non-Hermitian AAH potential parameters on the edge states of the Haldane model under periodic boundary conditions. It is shown that two-dimensional magnetic photonic crystals can undergo topological transitions and switchable edge states by tuning the potential field parameters. This offers a versatile method for controlling optical flow in photonic platforms.

Minimal Basis Iterative Stockholder Decomposition with Multipole Constraints.

The minimal basis iterative Stockholder (MBIS) decomposition of molecular electron densities into atomic quantities is an attractive approach for deriving electrostatic parameters in force fields. The MBIS-derived atomic charges, however, in general tend to overestimate the molecular dipole and quadrupole moments by ∼10%. We show that it is possible to derive a constrained MBIS model where the atomic charges or a combination of atomic charges and dipoles exactly reproduce the molecular dipole and quadrupole moments for molecules. The atomic multipole moments derived by the constrained procedure are better at reproducing the molecular electrostatic potential (ESP) than the unconstrained atomic multipole moments. They are, furthermore, significantly less conformationally dependent than atomic charges obtained by fitting to the molecular electrostatic potential.

Simulation analysis of coupling mechanism between transient flow field characteristics of bubble collapse and metal deformation based on surface micromorphology

In the process of modifying titanium alloy oral implants using cavitation water jet, the collapse of bubbles releases significant energy. This phenomenon is accompanied by micro-jets and shock waves, which induce changes in the three-dimensional microscopic morphology of the implant surface. The loose and porous surface of the implant will increase the adhesion area of the cells, which is more conducive to the combination of the oral implant with the surrounding bone tissue. In order to explore the coupling mechanism between the instantaneous energy of bubble collapse and the surface deformation of titanium metal, based on different flow field and solid field model parameters, the numerical analysis software Ansys and the fluid-structure coupling simulation method are used to establish the numerical simulation model of single bubble collapse on the near curved wall. In order to explore the coupling mechanism between the instantaneous energy of bubble collapse and the surface deformation of titanium metal, the bubble growth process is ignored. Based on different flow field and solid field model parameters, this paper adopts the numerical analysis software Ansys and the fluid-structure coupling simulation method to establish the numerical simulation model of single bubble collapse on the near curved wall. The effects of flow field parameters and wall morphology on the transient flow field of bubble collapse and the effect of metal surface modification are revealed. The results show that when the initial bubble diameter is 180 μm, the instantaneous collapse high pressure reaches 7.24 GPa, and the maximum stress on the titanium surface is 689 MPa, which is 1.57 times higher than that under the bubble diameter of 60 μm. When the bubble collapses away from the wall, due to the weakened constraint of the wall, more intense energy is released, but the energy decays rapidly in the propagation process, and the energy loss when it reaches the wall is more serious. In this paper, the surface micromorphology is simplified into a near-curved shape. After the modification, the flow obstruction on the near-curved concave wall inhibits bubble collapse, resulting in an increase in bubble collapse time. The stress and deformation caused by a single bubble collapse are concentrated within a radius of 1mm and a depth of 5 μm.