Radial Coupling Research Articles

Cartesian atomic cluster expansion for machine learning interatomic potentials

Machine learning interatomic potentials are revolutionizing large-scale, accurate atomistic modeling in material science and chemistry. Many potentials use atomic cluster expansion or equivariant message-passing frameworks. Such frameworks typically use spherical harmonics as angular basis functions, followed by Clebsch-Gordan contraction to maintain rotational symmetry. We propose a mathematically equivalent and simple alternative that performs all operations in the Cartesian coordinates. This approach provides a complete set of polynormially independent features of atomic environments while maintaining interaction body orders. Additionally, we integrate low-dimensional embeddings of various chemical elements, trainable radial channel coupling, and inter-atomic message passing. The resulting potential, named Cartesian Atomic Cluster Expansion (CACE), exhibits good accuracy, stability, and generalizability. We validate its performance in diverse systems, including bulk water, small molecules, and 25-element high-entropy alloys.

Theoretical investigation of electron capture processes in slow O7+–H collisions

Aims. The total and n-, l-, and S -resolved single-electron-capture cross sections for the collisions of O7+ with atomic hydrogen are studied in the energy region from 10−3eV u−1−5keV u−1. Methods. These state-selective cross sections were calculated by employing the full quantum-mechanical molecular-orbital close-coupling (QMOCC) method. The ab initio multireference single- and double-excitation configuration interaction approach, with optimized atomic basis sets to accurately describe the highly excited states, was used to obtain the adiabatic potentials and the radial and rotational coupling matrix elements that are required in the QMOCC calculation. Results. Our results are compared with other available theoretical and experimental data. The n = 5 manifold is the dominant reaction channel for the chasrge-transfer process for this collision system over the entire energy range, and our results agree better with the experimental data than the other theoretical results in the energy region in which they overlap because we included the necessary highly excited states in the expansion basis set. These charge-exchange cross-section data are useful for understanding and modeling the X-ray emission in astrophysical environments.

Wireless Charging System with Three Arc-Transmitting Coils for Autonomous Underwater Vehicle

To enhance the misalignment tolerance of the coupling device of the autonomous underwater vehicle wireless charging system, this paper proposes a magnetic coupling device with strong misalignment tolerance. Through the Ansys Maxwell finite element analysis software, it is concluded that, under the dislocation state of the proposed magnetic coupling device, the magnetic field is mainly distributed near the shell wall of the autonomous underwater vehicle. The coupling coefficient change range under the rolling dislocation state is 0.35~0.83, the axial dislocation coupling coefficient fluctuation range is 0.79~0.83, and the radial dislocation coupling coefficient variation range is 0.48~0.83. We design and calculate the compensation network in a wireless charging system and obtain the calculation method of the compensation network. A prototype of that wireless charging system containing arc-emitting coils applied to the AUV has been made, which transfers 48 W power with an efficiency of 87.3%.

Evaluation of Joint Clearance Effects on the Shimmy of Nose Landing Gear

Through the establishment of a three-dimensional joint clearance model, the effects of joint clearances at different positions on shimmy stability are evaluated. In this paper, considering the radial, axial and coupling characteristics of joint clearance, the shimmy multibody dynamics (MBD) model is applied to different joints in the nose landing gear (NLG) transmission system. It is proposed to evaluate the influence of joint clearance on shimmy from two aspects of position factor and wear factor. The study found that different joint clearances have different effects on shimmy: the joint clearance between the NLG and fuselage has little influence on shimmy; the larger axial clearance of upper and lower torque link joint will cause the shimmy of the NLG, but the radial clearance has no effect on shimmy; while the joint clearance between turning sleeve and upper torque link, lower torque link and piston only works in the axial and radial coupling. The reasons for the different influence characteristics of each joint space are analyzed. Consequently, studying and summarizing the influence of different clearance on shimmy is of great significance for the design and maintenance of the NLG joints.

Decoupling control of radial 4 degree of freedom system of magnetic-liquid double suspension bearing based on generalized extended state observer.

As the novel suspension bearing, Magnetic-Liquid Double Suspension Bearing (MLDSB) is mainly supported by magnetic suspension and supplemented by a liquid hydrostatic bearing. Due to its great bearing capacity and stiffness, rapid response, great active control, and so on, MLDSB is suitable for medium speed heavy loads and has a large carrying capacity and high operating stability. In addition, the radial inertia coupling and gyroscopic coupling between radial 4-DOF control channels can reduce control precision, operation stability, and reliability of MLDSB. Therefore, a mathematical model of radial 4-DOF rotor-dynamics of MLDSB is established in this paper, and the inherent coupling mechanism is explored. Taking inertial coupling, gyroscopic coupling, and external disturbance loads as lumped disturbances, a decoupled controller based on Generalized Extended State Observer (GESO) is established. The influence of the GESO controller on the decoupling and control performance of radial 4-DOF control channels is simulated. The results indicate that the decoupling effect of the GESO controller is great. Under the action of step signal, the steady displacement, maximum displacement, adjustment time, and peak time of the rotor after decoupling are all reduced, among which the steady displacement and maximum displacement are the most obvious. Under the sinusoidal signal, the steady displacement and maximum displacement are reduced by 90%, which can effectively avoid the "gap-impact" fault. Under the pulse signal, the steady displacement, maximum displacement, adjustment time, and peak time are all reduced, among which the maximum displacement is the most obvious. The research in this paper can provide a theoretical reference for the stable support and decoupling control of MLDSB.

Near-field manipulation of Tamm plasmon polaritons.

Tamm plasmon polaritons (TPPs) arise from electromagnetic resonant phenomena which appear at the interface between a metallic film and a distributed Bragg reflector. They differ from surface plasmon polaritons (SPPs), since TPPs possess both cavity mode properties and surface plasmon characteristics. In this paper, the propagation properties of TPPs are carefully investigated. With the aid of nanoantenna couplers, polarization-controlled TPP waves can propagate directionally. By combining nanoantenna couplers with Fresnel zone plates, asymmetric double focusing of TPP wave is observed. Moreover, radial unidirectional coupling of the TPP wave can be achieved when the nanoantenna couplers are arranged along a circular or a spiral shape, which shows superior focusing ability compared to a single circular or spiral groove since the electric field intensity at the focal point is 4 times larger. In comparison with SPPs, TPPs possess higher excitation efficiency and lower propagation loss. The numerical investigation shows that TPP waves have great potential in integrated photonics and on-chip devices.

Effects of supporting stiffness of deep groove ball bearings with raceway misalignment on vibration behaviors of a gear-rotor system

The raceway misalignment of deep groove ball bearings is a typical engineering problem that dramatically influences the supporting stiffness and vibration behaviors of gear transmission systems. Considering the influences of meshing of the spur gear pair, the connection of the spline, and the flexibility of the shaft in the practical transmission system, a method for calculating the stiffness of bearings with raceway misalignment is proposed. The effects of misalignment angle, input torque and rotational speed on radial, axial and coupling stiffness are analyzed. Subsequently, the dynamic model of the gear-rotor-bearing system is established, and the influences of the time-varying and coupling characteristics of bearing stiffness on the vibration of the system are analyzed. The results show that the raceway misalignment enhances the radial and axial coupling characteristics of the bearing stiffness and aggravates the axial vibration of the system, which is mainly manifested in the increase of the amplitude of the axial meshing frequency. The vibration amplitude of the system is easily affected by high-order resonance in the case of raceway misalignment.

Experimental and simulation study on aluminium alloy piston based on thermal barrier coating

Thermal barrier coatings (TBCs) have low thermal conductivity, effectively reducing the temperature of the metal matrix and improving thermal performance, knock resistance, and combustion performance of the piston. In this study, an off-road high-pressure common-rail diesel engine was chosen as the research object. Combined with the test results of the piston temperature field under the rated power and maximum torque conditions, a finite element simulation model of the thermal barrier coating piston was established. This model enabled the distribution characteristics and variation laws of the temperature field, stress, and deformation of the thermal barrier coating on the piston matrix to be analysed. The results show that the maximum temperature of the TBC piston is 12.2% and 13.73% lower than that of the aluminium alloy piston under the rated power and maximum torque conditions, respectively. The thermal stresses of the TBC piston at the top of the cavity were 25.9% and 26.8% lower than those of the aluminium piston, while the thermo-mechanical coupling stress of the TBC piston was slightly higher than that of the aluminium piston—1.2 MPa and 3.7 MPa in the bottom of the combustion chamber with geometric mutation, respectively. The radial thermal deformation of the TBC piston was 0.067 mm and 0.073 mm lower than that of the aluminium piston, with the radial thermo-mechanical coupling deformation also decreasing by 0.069 mm and 0.075 mm, respectively. The radial thermal deformation of the piston in the direction parallel to the pinhole axis was greater than that in the direction perpendicular to the pinhole axis; the difference in the magnitude of the change results in uneven thermal deformation of the piston.

Tone colour in music and bifurcation control

An intrinsic characteristic of musical sounds is the qualitative evolution of their timbre (tone colour). In this paper, we interpret each qualitative change by a bifurcation. We employ spectral and temporal envelopes as two of the most salient features of tone colour. Fourier analysis of a note generates its n-leading harmonic partials and an amplitude spectral n-vectorA for n≥2. We introduce harmonic manifolds associated with amplitude spectral vectors. This is to accommodate the n-leading harmonic partials of the note. Then, harmonic partials are modelled by solutions of a radial coupling of n-tuple parametric Hopf oscillators. We use one bifurcation parameter and interpolate the qualitative evolution of temporal envelope over a set of consecutive time-intervals via bifurcation analysis and control. Bifurcation scenarios involve harmonic asymptotic sets as time-asymptotic limits of harmonic partials. Each harmonic asymptotic set is homeomorphic to a k-tori, where k≤n is the number of contributing harmonic partials. Bifurcation classification of tone colour is then drawn up by encoding the spectral geometry of acoustic signals into harmonic manifolds and harmonic asymptotic sets. For instance, we treat audio C♯4 files obtained from piano and violin. Different bifurcation scenarios distinguish temporal amplitude bifurcations of these sounds. A complete hysteresis cycle is observed within the temporal amplitude bifurcations of C♯4 note played by violin.

Temporal and Spatial Evolution of Coupling Coordination Degree of Industrial Innovation Ecosystem—From the Perspective of Green Transformation

This paper takes the industrial innovation ecosystem as the research object and the realization of green development as the goal, discussing the temporal and spatial evolution of coupling coordination degree of industrial innovation ecosystem from the perspective of system view. Based on the data of 30 provinces in China from 2010 to 2021, the spatial and temporal pattern distribution and spatial connection evolution of synergy among the three subsystems of industrial innovation ecosystem are studied by using coupling coordination degree model, trend surface model and gravity model. It is found that during the study period, the coupling relationship between the three subsystems is in a dynamic upward state. The regions with high values and rapid growth are distributed in the key areas of the national economic development strategy. At the same time, they have the characteristics of “positive U-shaped first and then inverted U-shaped” in the east-west and north-south directions; the spatial connection strength of coupling coordination degree shows that the spatial connection strength of the eastern region is significantly greater than that of the western region. With the improvement of spatial connection strength, a radial coupling network centered on Beijing Tianjin Tangshan region and the Yangtze River Delta is formed, which is of core significance to promote the coordinated development of industrial innovation ecosystem.

Semi‐circular mushroom resonator loaded substrate integrated waveguide cavity based compact triple‐band bandpass filter with high selectivity

Two cascaded semi-circular mushroom resonators (ScMRs) loaded to a circular substrate integrated waveguide (CSIW) is used to implement a triple-band bandpass filter of compact size and high selectivity with six transmission zeros (TZs). The ScMRs are coupled to each other along the linear edges of the metal patches and are loaded to the CSIW cavity. A distinctive modification in the schematic and the orientation of the loaded mushroom resonators is carried out along with the introduction of radial coupling slots into the CSIW cavity to generate the three passbands. The TM101 mode is responsible for the generation of first passband. The second and third passbands are formed due to the split odd and even modes of next higher order mode (TM201). An extracted pole is formed within the second passband that splits TM201 mode into odd and even modes. TM201 odd mode (TM201odd) and TM201 even mode (TM201even) are responsible for the generation of second and third passbands, respectively. Here, source-load coupling is employed within the proposed resonator to generate one TZ each at the lower stopband and upper stopband. Two cross-couplings of different modes between two loaded ScMRs are introduced to generate four transmission zeros (TZs) additionally to achieve high selectivity. The triple bandpass filter covering a compact volume of 0.0011 λg3 is fabricated and measured to validate the filter structure. The measured result agrees decently with the simulated one where the passband center frequencies (CFs) of first, second, and third passbands are measured at 1.9, 3.5, and 4.4 GHz with measured insertion losses of 1.5, 1.87, and 1.8 dB, respectively.

К вопросу о методе перепроекцирования для неупругих процессов в атомных столкновениях в рамках подхода Борна — Оппенгеймера

The paper provides a detailed description of the reprojection method for the exact solution of the nonadiabatic nuclear dynamics within the Born–Oppenheimer formalism. In particular, it discusses the asymptotic behaviour of a state-to-state transition probability when a nonadiabatic radial coupling for this transition has a nonzero asymptotic value—a fundamental feature of the Born–Oppenheimer approach. It is known that the conventional Born–Oppenheimer approach leads to divergency of inelastic cross sections and inelastic rate coefficients, while the reprojection method provides convergences. The article describes physical background of the reprojection method.

Mistuning parameter identification and vibration localization analysis of the integration rotor

This paper deals with the coupling vibration characteristic of the disk-blade-shaft integration rotor. First, a reduced-order model (ROM) based on an improved hybrid interface component mode synthesis method (IHISCMSM) is carried out, which takes the prestress effect into account. The frequency of the disk-blade-shaft integration rotor at different rotating speeds are calculated and the influence of selecting different mode truncation numbers is investigated. In order to quantitatively evaluate the coupling degree of blade and disk, the coupling factor is defined from the perspective of strain energy, and the influence of prestress on system’s dynamic is discussed. Then, an experimental modal analysis is performed on blades to identify the mistuning parameters, and the mode localization of the disk-blade-shaft integration rotor is analyzed with and without blade mistuning. The results indicate that there are several types of coupling modes among blade, disk and shaft of the integration rotor. After considering the prestress, the frequency increases, and the axial coupling vibration degree and radial coupling vibration degree of the integration rotor change. The mode localization of mistuned rotor is more likely to occur in the modes dominated by mistuning stage blades. There also exists a subtle mode localization phenomenon for tuned integration rotor.

A computational study of the non-adiabatic coupling among low-lying doublet states of the CN radical

First principle electronic structure calculations on low-lying doublet states of the CN radical have been performed using the multi-reference configuration interaction method and large all-electron basis sets. Beside the adiabatic interatomic potentials, the non-adiabatic spin-orbit and L-uncoupling electronic matrix elements were evaluated for the mutually perturbed (2)B2Σ+∼(1–4)2Π and (1)A2Π∼(1–3)2Σ+, (1)2Σ−, (1,2)2Δ pairs of states. The radial coupling matrix element was calculated between the X2Σ+ and B2Σ+ states. The reliability of the derived A∼X and A∼B matrix elements was confirmed by comparison with their empirical counterparts. Both local and regular perturbations in the A∼B∼X complex were found to depend mostly on spin-orbit and electronic-rotational interactions between the lowest A2Π, and B2Σ+ states. Excited states, in all their diversity, have little effect on the fine structure of the A∼B complex, except for the qA Λ-doubling function. The ab initio coupling functions can be crucial to providing a global deperturbation treatment for the A, B and X states on a spectroscopic level of accuracy.

Shaft system profile reconstruction method based on L-shaped axial four-probe method

The inability to extract spatial axis and radial multi-error coupling phenomenon exists in the process of axial profile reconstruction, which is essentially a first harmonic suppression problem as well as a multi-error decoupling problem. In this paper, a four-probe system is constructed based on an L-shaped arrangement in two adjacent planes. First, the mathematical model of the first harmonic suppression problem of the shaft system is established in the first plane, and the first harmonic component of roundness error is used as the axial reference for reconstructing the profile, and the value of the first-order harmonic component is solved by theoretical derivation, and the spatial axis of the reconstructed shaft system profile is fitted with it, which proves the correctness of the established mathematical model by the data simulation. Then, the radial mixed error detection is carried out in two adjacent planes in the axial direction, and the results measured at the two measurement positions are analyzed theoretically to obtain the tilt error decoupling formula. It breaks through the limitation that the error separation online detection cannot be performed in the standard ball measurement method. The experiment verifies that the accuracy of the spatial axis is improved by up to 0.5 μm after decoupling the tilt error, and the accuracy of the reconstructed circularity profile of a single section is improved by up to 2.657 mm. In the comparison experiment with the standard ball measurement method, the difference of the measured roundness error between the two methods does not exceed 1.2 μm, which proves that the online inspection method proposed in this paper can guarantee the accuracy of the reconstructing circularity profile.

A novel Z-shaped elastic flange structure for increasing the amplitude output of a piezoelectric ultrasonic transducer

A novel Z-shaped elastic flange structure is presented in this paper, which is used to mount the piezoelectric ultrasonic transducer (PUTs) together with the housing and increase amplitude output of the transducer. Generally, the mounting fixture of the transducer refers to the traditional flat-faced flange structure, which has the advantages of low processing cost and easy installation. However, considering its structural characteristics, the flange structure also exerts a negative influence on the coupling between the transducer and housing and accordingly suppresses the conversion of ultrasonic vibration energy inside the transducer. The novel Z-shaped elastic flange is combined with a traditional flat-faced flange structure and an elastic cylindrical sleeve, and the amplitude output of the transducer is increased by reducing the longitudinal and radial coupling effect between the transducer and the flange. Ultrasonic transducers with different flange structures are designed and manufactured. Through the combination of Finite Element Method and experimental analysis, the decoupling and amplitude increase ability of the novel elastic flange are investigated in detail. The results show that without changing the stiffness of the transducer, the proposed Z-shaped elastic flange structure could significantly increase the amplitude output of the transducer, regardless of whether the transducer was working in a resonance state. Hence, the newly proposed structure serves as a meaningful attempt and can be used as a universal structure for PUTs in different fields.

Extended Applications of Subgrid Representation in the 2D/1D Method

Recent efforts in MPACT have focused on improving the performance of the 2D/1D subplane implementation to help target computational performance goals. This paper builds on previous efforts that targeted the use of subgrid treatments to improve the accuracy of control rod representation, presenting three additional applications of subgrid treatments with the goal of reducing the computational burden of simulations. These subgrid applications include treatment of spacer grids, thermal feedback, and axial reflector material representation. With these approaches, a single method of characteristics (MOC) plane can contain several different materials axially that are represented explicitly via subgrids on the coarse mesh finite difference (CMFD) mesh but are axially homogenized on the MOC mesh. This allows for a substantial reduction in the number of MOC planes needed in the calculation through the introduction of an approximate treatment, particularly with regard to the self-shielded cross sections and MOC-informed radial current coupling coefficients in CMFD. Several test problems ranging from single rod to quarter core are used to assess the solution accuracy and performance of these various subgrid representations. Overall, the accuracy of the approximations seems very reasonable, with extremely small differences in eigenvalue observed and maximum pin power errors in the 0.5% to 1.0% range. Several cases show substantial value in the compromise between accuracy and computational performance. Others highlight the new computational hurdles that future research will aim to resolve.

Pattern design and performance analysis of a flexible spoke bionic non-pneumatic tire

Based on the characteristics of kangaroo’s lower limb structure, a 195/50R16 flexible spoke bionic non-pneumatic tire model is established through the methodology of non-pneumatic tire unit configuration. From the radial stiffness coupling model, and based on numerical and theoretical derivation, the accuracy of the radial stiffness coupling model is confirmed. By comparing a pneumatic tire with the same size, a radial stiffness comparison experiment is carried out to ensure the accuracy of numerical analysis. The radial stiffness, lateral stiffness, longitudinal stiffness, torsional stiffness, and ground pressure of the tires under different loads are studied. The results show that the flexible spoke bionic non-pneumatic tire has better performance than the pneumatic tire. This study guides the industrial production of flexible spoke bionic non-pneumatic tires. At the same time, it also provides a new idea of theory and methodology for the research of non-pneumatic tires.

Effect of Three-Dimensional Aerodynamics and Dynamic Stall on Lead–Lag Damping of an Isolated Rotor

This paper investigates three-dimensional aerodynamic effects due to radial flow on lead–lag damping of a rotor in forward flight conditions. Three-dimensional effects in this study are restricted to yawed flow aerodynamics and radial flow coupling between blade segments. These effects are included in the ONERA dynamic stall model, and lead–lag damping for an isolated torsionally stiff rotor is calculated for different forward flight conditions. This augmented aerodynamic model with three-dimensional effects and Peters–He dynamic wake model improves the correlation of lead–lag damping with experimental data at high advance ratios. The effect of modeling static lift characteristics on damping correlation is also presented. Finally, a modification to the trailing edge separation point–based static lift model for improved yawed flow modeling amenable to aeromechanical stability analysis is proposed.

Chimera states in ring–star network of Chua circuits

We investigate the emergence of amplitude and frequency chimera states in ring–star networks consisting of identical Chua circuits connected via nonlocal diffusive, bidirectional coupling. We first identify single-well chimera patterns in a ring network under nonlocal coupling schemes. When a central node is added to the network, forming a ring–star network, the central node acts as the distributor of information, increasing the chances of synchronization. Numerical simulations show that the radial coupling strength k between the central and the peripheral nodes acts as an order parameter leading from a lower- to a higher-frequency domain. The transition between the domains takes place for intermediate coupling values, $$0.5<k< 2$$ , where the frequency chimera states prevail. The transition region (width and boundaries) depends on the Chua oscillator parameters and the network specifics. Potential applications of star connectivity can be found in the control of Chua networks and in other coupled chaotic dynamical systems. By adding one central node and without further modifications to the individual network parameters, it is possible to entrain the system to lower- or higher-frequency domains as desired by the particular applications.