Numerical Simulation Results Research Articles

Dynamics of entanglement of qubits in the three-qubit Tavis — Cummings model with dipole-dipole interaction

The article studies the dynamics of pairwise entanglement of three qubits, two of which are trapped in a resonator and interact with a single-mode ideal resonator through single-photon transitions, and the third qubit is outside the resonator. This takes into account the dipole-dipole coupling between the isolated qubit and the qubit in the resonator. We have found a solution to the quantum nonstationary Schrodinger equation for the total wave function of the system for the initial separable and biseparable states of qubits and the thermal initial state of the resonator field. Using these solutions, the criterion of entanglement of qubit pairs - negativity is calculated. The results of numerical simulation of the negativity criterion have shown that the including of a small dipole-dipole coupling between an isolated and one of the trapped qubits can lead to significant entanglement of qubit pairs for all initial states. There is a transition of entanglement from one pair of atoms to other pairs of atoms during the evolution of the system. It is also shown that for some separable and biseparable states, the dipole-dipole interaction can suppress the effect of sudden death of entanglement

Dynamics of the Euler — Bernoully beam with distributed hysteresis properties

In this paper, we present a new mathematical approach to the analysis of a beam with distributed hysteresis properties. These hysteresis characteristics are described by two methods: phenomenological (Bouc — Wen model) and constructive (Prandtl — Ishlinskii model). The equations for beam are developed using the well-known Hamilton method. We investigate the dynamic response of a hysteresis beam under various external loads, including impulse, periodic and seismic loads. The results of numerical simulations show that the hysteresis beam exhibits differently to external influences as compared to the classical Euler-Bernoulli beam. In particular, under the same external loads, the vibration amplitude and energy characteristics of the hysteresis beam are lower than those of the classical one. These findings can be useful for buildings developers in the design of external load resistant buildings and structures

Enhancing output characteristics of semi-active flapping airfoil energy capture device via flexible deformation strategy

ABSTRACT A concentrated-torsion flexible airfoil model is established to enhance the output characteristics of the flapping airfoil energy capture device in this work. The effect of the damping ratio C 2*, spring ratio K 2* of the torsion spring, and mass ratio M A * of the tail airfoil on the dynamic characteristics is investigated systematically. The numerical simulation results show that compared with the rigid airfoil, the time-averaged power coefficient and output efficiency of the optimized flexible airfoil (C 2* = 4, K 2* = 0.5, and M A * = 0.7) are increased by 91.85% and 63.45%, respectively. Remarkably, the output efficiency of the optimized flexible airfoil is 32.15%. The reason for the enhanced performance is that the passive deformation can ensure the airfoil generates a stronger vortex and delays the shedding of the vortex. In addition, the experimental test results (with a 36.29% performance enhancement) further demonstrate the effectiveness of using the concentrated-torsional flexible deformation strategy in enhancing the energy output characteristics of the flapping airfoil.

Hover Flight Improvement of a Quadrotor Unmanned Aerial Vehicle Using PID Controllers with an Integral Effect Based on the Riemann–Liouville Fractional-Order Operator: A Deterministic Approach

The hovering flight of a quadrotor Unmanned Aerial Vehicle (UAV) refers to maintaining the aircraft in a fixed position in the air, without lateral, vertical, or rotational movements, using only the vehicle’s control systems to maintain proper balance in all spatial dimensions. Algorithms and control systems have been developed to continuously adjust motor speeds to counteract deviations from the desired position and achieve effective hovering flight. This paper proposes a set of PID controllers with an integral effect based on the Riemann–Liouville fractional-order approach to improve the hovering flight of a quadrotor UAV. This research innovates by introducing a set of fractional-order PID controllers for UAV hover stability, which offer better adaptability to non-linear dynamics and robustness than traditional PID controllers. Also presented is the development of new performance metrics (MSE, BQC-LR), which allow for more comprehensive control system evaluations. A thorough comparative analysis with conventional control methods demonstrates the superior performance of fractional-order control in real-world simulations. The numerical simulation results show the effectiveness of the proposed Fractional Integral Action PID Controller in the control of UAV hovering flight, while comparative analyses against a classical controller emphasize the benefits of the fractional-order approach in terms of control accuracy.

Analytical and Finite Element Analysis of the Rolling Force for the Three-Roller Cylindrical Bending Process.

In the roll bending process, the rolling force acting on the roller shafts is one of the most important parameters since, on the one hand, it determines the process settings including the pre-loading, and, on the other hand, its distribution and size may affect the integrity of both the bending system and the final product. In this study, the three-roller bending process was modeled using a two-dimensional plane-strain finite element method, and the rolling force was determined as a function of plate thickness, upper roller diameter, and yield strength for various API steel grades. Based on the numerical simulation results, a critical bending angle of 41° was identified and the rolling systems were divided into two categories, of less than or equal to, and greater than 41°, and an analytical model for predicting the maximum rolling force was developed for each category. To determine the optimal pre-tensioning force, two optimization formulations were proposed by minimizing the maximum equivalent stress and the absolute maximum displacement. The rolling forces predicted by the analytical models were found to be in good agreement with the numerical simulation results, with relative errors generally less than 10%. The predictive analytical models developed in this study capture well the complex deformation behavior that occurs during the roll bending process of steel plates, providing guidelines and predictions for industrial applications of this process.

Field test and numerical research on explosion crater in calcareous sand

The explosion in foundation poses a significant threat to people and buildings. Currently, a unified empirical prediction formula for crater in calcareous foundation has not been established. In this paper, analyzed the types and sizes of explosion crater with different scaled burial depths through field tests and numerical simulation. In field tests, revealed the influence of scaled burial depth on the type and size of explosion crater and obtained the critical scaled burial depth for three different types of explosion craters, namely ejecta-type crater, collapse-type crater and covert explosion. Through the Smooth Particle Hydrodynamic-Finite Element Method (SPH-FEM) coupling algorithm, studied the movement trajectory of sand particles around the explosive at the moment of explosion in detail. Based on the field tests and numerical simulation results, it was found that calcareous sand has a smaller specific gravity due to its own characteristics, and the size of the explosion crater is larger than that of quartz sand at the same scaled burial depth. Obtained an empirical formula for crater in calcareous sand. Which can quickly predict the size of explosion crater and provide calculation basis for explosion resistant design in calcareous sand foundations.

Design of gas control lane of 9# coal seam in Wuhushan Mine based on layer layout optimization

In order to address the issue of gas over limit in the upper corner of the working face of the 9# coal seam in Wuhushan Mine, a series of theoretical and numerical simulation analyses were conducted to evaluate the optimal configuration for the gas control lane of the 9# coal seam. In accordance with the "O" circle theory and the lithology of the overlying rock strata of the 9# coal seam, the height range of the fallout zone and fissure zone in the working face mining area was determined by employing empirical formulas. The change rule and distribution characteristics of the porosity of the fissure zone and the fall zone in the mining area were analyzed based on the characteristics of rock movement and fall. The determination method was also provided. The numerical simulation software was employed to simulate and analyze the gas concentration field in the air-mining zone under conditions of no extraction and six distinct layer positions of the gas control lane. The optimal layer position of the gas control lane in the 9# coal seam was determined and subsequently implemented in the field. The results demonstrate that the overlying rock layer in the 9# coal seam exhibits a height range of 6.86 ~ 11.26 m, while the fissure zone displays a height range of 30.11 ~ 41.31 m. When the gas control road is situated in close proximity to the working face, the gas concentration field exhibits a markedly low concentration. When the distance between the gas control lane and the return airway of the working face is 20 m and the distance from the top of the coal seam is 20 m, the gas concentration in the upper corner and the return airway is 0.35% and 0.26%, respectively. These values are close to the lowest concentration observed in the layout scheme. Additionally, the gas extraction concentration and the pure volume of the gas control lane are 23.7% and 38.3 m3 min−1, respectively. These values represent the highest concentrations observed in the various layout schemes. The application of the gas management lane in the field, based on the numerical simulation results, demonstrated a successful extraction effect, which was consistent with the numerical simulation results. This effectively managed the issue of an over-limit of gas in the upper corner of the working face of the 9# coal seam.

Dynamics and event-triggered control of rumor propagation model with saturated incidence and time delay on heterogeneous networks

Considering the impact of user’s cognitive ability in rumor propagation, this paper proposes a new susceptible infection recovery (2SIR) rumor propagation model with saturation incidence and time delay on heterogeneous networks. First, the existence of the equilibria is discussed by using mean field theory and basic reproduction number. Second, the dynamic behaviors of the rumor-free and persistent equilibria are analyzed via the local linearization method, Lyapunov stability theory and irreducible matrix properties. Furthermore, an event-triggered impulsive control strategy is proposed to control the rumor spreaders and some corresponding control conditions are given. Finally, some numerical simulation results and a practical example are presented to verify the correctness of the theoretical results and reflect the impact of cognitive ability and time delay on rumor propagation.

Stochastic Green’s Function Method Considering Non-Uniform Rise Time Distribution to Simulate 3D Broadband Ground Motion

The stochastic Green’s function method has been widely used in the field of ground motion simulation in recent years. It is generally assumed that the rise time of each subfault is the same in this method. Since the rise time significantly influences the amplitude of simulation results in the intermediate frequency band, to improve the accuracy of stochastic Green’s function method for near-fault broadband ground motion simulation, referring to the numerical simulation results of Day, the rise time is assumed to be non-uniformly distributed on the fault, and an improved approximate expression of rise time on a rectangular fault considering that the rupture starting point may be at any position and the aspect ratio may be arbitrary is proposed. Additionally, the contributions of P, SV and SH wave are considered, respectively, and an improved stochastic Green’s function method is proposed for 3D broadband ground motion simulation. Taking the 1994 Northridge earthquake in America and 2013 Lushan earthquake in China as examples, under different subfault division numbers, the synthesized source spectra are compared with the omega-squared theoretical source spectra of the large earthquake, and the simulated ground motions at observation points are compared with observed records to verify the effectiveness of the improved method. The results show that when the Northridge earthquake fault and Lushan earthquake fault are divided into 9 × 10 subfaults and 11 × 7 subfaults, respectively, the simulation results obtained using the improved method are close to the observed records in the broadband frequency range. Therefore, the improved method can effectively simulate the 3D ground motion in near-fault regions.

An 8-channel narrow linewidth multi-wavelength laser hybrid integrated by photonic wire bonding structures for DWDM systems

An 8-channel monolithically integrated narrow linewidth multi-wavelength laser array (NL-MLA) combined with the commercial 8 × 1 planar lightwave circuit (PLC) coupler by the photonic wire bonding (PWB) technique is demonstrated in this paper. A distributed feedback (DFB) laser with the high-reflection and anti-reflection coatings (HR-AR) and the tapered asymmetric corrugation-pitch-modulated (TACPM) grating structure is proposed. The TACPM grating is achieved by the reconstruction equivalent chirp (REC) technique, which is low-cost and of high wavelength accuracy. According to the numerical simulation results, under the unavoidable impact of the facet phase of the HR end, the TACPM DFB laser suppresses the longitudinal spatial hole burning (LSHB) effect significantly, while having better single-mode performance and control of wavelength compared with the conventional HR-AR DFB laser. An 8-channel HR-AR TACPM DFB NL-MLA is fabricated with the 0.8 nm wavelength spacing design. The hybrid integration between the 8-channel NL-MLA and the PLC chip is achieved using the PWB technique. Both good single-mode performance and accurate wavelength interval of 0.8 nm can be obtained when all channels work simultaneously. The laser linewidth is below 273.8 kHz with good uniformity, and the relative intensity noise is under −159.6 dB/Hz for each channel.

Numerical analysis of impact resistance mechanical properties of energy-absorbing columns under static and dynamic loads

To enhance the impact resistance of hydraulic columns, a theoretical analysis method was employed to develop a dynamic characteristic analysis model for conventional columns under impact loads. This model facilitated the derivation of key parameters such as equivalent stiffness, maximum retraction amount, and impact duration. A fluid-solid coupling model for the conventional column was constructed using finite element and coupled Eulerian-Lagrangian (CEL) methods. Subsequently, numerical simulation results were compared and analyzed against theoretical predictions. Based on this analysis, an energy-absorbing column was designed, and its fluid-solid coupling model was established to investigate its mechanical response under static and dynamic impact loads.The findings indicate that under a static load of 2000 kN, when superimposed with impact loads of 200 kJ, 400 kJ, and 800 kJ respectively, the peak impact forces on energy-absorbing columns are 89.20%, 91.72%, and 98.42% lower than those on normal columns. The yield displacements of energy-absorbing columns increase by 142.26%, 109.15%, and 108.41% compared to normal columns. Energy absorption in energy-absorbing columns is 152.11%, 171.80%, and 145.18% higher than in normal columns. Furthermore, initial velocities of energy-absorbing columns are consistently lower compared to normal columns. After reaching initial velocity, energy-absorbing columns exhibit reduced oscillations due to interactions between the energy absorber, column, and hydraulic fluid system under impact loads. Unlike normal columns, energy-absorbing columns mitigate stress concentration at the column head through interactions between the energy absorber, emulsion, and column. Additionally, the impact resistance time of energy-absorbing columns is 2.19, 1.64, and 1.85 times longer than that of normal columns.Energy-absorbing columns outperform conventional columns across six metrics: peak impact force, column yield displacement, energy absorption, column movement speed, stress distribution, and impact resistance time, demonstrating superior mechanical properties in impact resistance.

Study on the thermal storage properties of a spiral tube heat storage tank based on numerical analysis

IntroductionThe spiral tube heat storage tank is a highly efficient device designed for storing and releasing heat, utilizing a spiral tube structure. Its key advantages include efficiency, reliability, and flexibility, making it suitable for a wide range of conditions, from high temperatures and pressures to low temperatures and high vacuums.MethodsThis study aims to analyze phase change heat storage in spiral tube heat storage tanks using numerical simulation.ResultsIt explores the impact of varying water supply temperatures on heat transfer efficiency and the melting behavior of phase change materials within the tanks. Proposed enhancements, informed by numerical simulation results, seek to improve heat transfer efficiency. Simulation findings indicate that charging efficiency rises with increased temperature differentials, akin to sleeve-type heat exchangers.DiscussionCalculations suggest faster melting of phase change materials at the central position of the tank’s spiral tube, with slower melting near the vessel wall. Consequently, reducing the number of spiral tubes in the middle is suggested for future structural optimization.

KEEPING AN ELECTRON BEAM IN POTENTIAL WELL MAGNETIC SOLENOIDAL FIELD

An intense cylindrical magnetic field is considered in which potential well is created with the help of additional magnets. It is shown that the motion of electrons can be associated with model of three-dimensional oscillations in potential well. The results of numerical simulation of electron trajectories in gradient magnetic field with point secondary emission cathode located in the middle of the system are presented. The formation of the beam with energy of 55 keV in the radial and longitudinal directions during its transportation in solenoidal field with large gradient is considered. The operating modes of the gun are obtained, in which the particle experiences stable three-dimensional vibrations. The influence of the initial conditions during emission on the occurrence of oscillations is studied. It is shown that for the given electron energy and the fixed magnetic field, the parameter that determines the stability of particle motion is the polar angle of entry relative to the axis of the cylindrical magnetic field.

Investigation of a piezoelectric ultrasonic surface wave transducer that minimizes structural scattering

Abstract The Structural of ultrasonic surface wave transducers affects structural scattering. A numerical model of an ultrasonic surface wave transducer was established. Numerical simulations and dynamic acoustic analysis were performed to systematically assess, the effects of the transducer parameters, such as the front and back angles, matching layer, and front wedge shape on structural scattering. The results show that the acoustic amplitude of the transducer structure scattered waves is basically stable when the back angle of the wedge is 64° -68 °and the front angle is 65°-85°. The amplitude obtained from a transducer with orthogonal slots and a front uniform matching layer is 61% lower for the primary structure scattering, 56% lower for the secondary structure scattering.
When equipped with the upper matching layer, the amplitude of the secondary structural scattering echo is reduced by 78.2%. The experimental results show that the transducer with orthogonal slots on the wedge and a matching layer at the front and upper edges has a signal-to-noise ratio of 19.6dB when detecting the echo signal of a ϕ8 through-hole in a welded steel plate, indicating good detection capability. The experiment validates the numerical simulation results. The proposed transducer can be used for structural monitoring of welded structures and detecting flaws.

Experimental and numerical study of shear strength on the slide zone soil by the coupling of seepage and shear test

The stability of reservoir landslides is determined by the strength of the slide zone. Using both experimental and numerical techniques to analyze the strength of the slide zone has been widely used in the research of reservoir landslides. However, few models consider the strength of the coupling between seepage and shear. This paper aims to analyze the shear strength of slide zone soil combined with different stresses by using the directed shear test and particle flow code PFC2D. The results indicated that slide zone soil clearly experienced the strain-hardening without seepage. While a specific strain-softening phenomenon was observed because the introduction of seepage reduced the shear strength significantly, the internal friction angle demonstrated a higher sensitivity to seepage stress compared to cohesion as the seepage stress increased. The direction and amount of flow velocity dynamically alter during the shear process, as revealed by numerical simulation results, suggesting that the shear strength was nonlinear with increasing seepage stress and changed structure. It can be assumed that seepage deterioration in the Huangtupo landslide is a dynamic process that influences the structure, strength and permeability characteristics.

Discrete modulation continuous variable quantum key distribution under fast fading channel

After decades of development, continuous variable quantum key distribution technology still cannot meet people’s needs for secure communication over long distances. Free-space quantum communication provides a new way for secure communication over long distances. However, because the communication connected in free space is inevitably affected by atmospheric turbulence, the transmission rate of the channel changes rapidly according to the probability distribution, making it difficult for the communication personnel to determine the transmission rate of the channel. At the same time, discrete modulated continuously variable quantum key Distribution protocol (DM-CVQKD) has certain advantages over Gauss modulated continuously variable quantum key Distribution protocol (GM-CVQKD) in the communication distance. Therefore, this paper analyzes the key rate of DM-CVQKD in this case (that is, in the fast attenuation channel), proves that it can resist the collective attack, and observes the relationship between the parameters and the key rate in the fast attenuation channel by numerical simulation and control variables. Finally, through the analysis of numerical simulation results, it is found that DM-CVQKD can still maintain a high key rate under certain conditions, which proves that long-distance free space quantum communication is feasible under certain conditions. At the same time, it was found that the performance of DM-CVQKD was affected by the extreme case where Eve completely controlled the instantaneous transmittance.

Experimental method for internal deformation measurement of 3D solids with embedded cracks based on 3D printing and digital speckle techniques

Quantification of the internal deformation of fractured solids such as rock masses under external loads, especially the deformation around internal fractures, is crucial for understanding and predicting the failure of fractured solids. However, it is very difficult to achieve the goal using conventional experimental methods. In this study, we proposed a novel internal deformation measurement method based on three-dimensional (3D) printing and digital speckle techniques. The 3D printing technology was applied to fabricate a 3D transparent model with an embedded elliptical crack and to set a speckle pattern on the internal section of the transparent model. The digital image correlation (DIC) method was used to determine the internal deformation field of the 3D fractured model. The measured displacements and strains of the internal sections in the fractured model were compared with the numerical simulation results. The comparison indicates that the proposed experimental method can well determine the deformation inside the 3D model. This built-in speckle method can realize real-time observation of the internal deformation of a 3D solid model in a non-contact and non-destructive manner.

Revealing the pinning landscape and related vortex pattern evolution in granular superconducting films

Most superconducting electronics based on films exhibit granular structures. It has been suggested that grain boundaries form a network with relatively weak superconductivity, potentially acting as pinning centers. Yet, so far, detailed microscopic studies of the pinning landscape and its relation to vortex behavior remain scarce. Here, we imaged the vortex lattices (VL) in granular Nb films using magnetic force microscopy over large scanning areas at various magnetic fields. A non-monotonic evolution in the degree of vortex lattice ordering was observed with increasing vortex density, driven by a combination of vortex-vortex interactions and pinning effects. The spatial distribution of pinning potential within the film was directly mapped using a recently developed scanning quantum vortex microscope (SQVM). Instead of the network formed by grain boundaries, the pinning landscape presents a network-like structure, yet with domains significantly larger than the individual grains. The results of numerical simulations based on pinning landscape revealed by SQVM well reproduce our experiments. The pinning force per unit length at low magnetic fields was calculated. The critical current density, estimated from the relative positions of vortices, aligns well with the critical state model. Our work illustrates the relationship between the evolution of the vortex lattice with magnetic field and the structural features of granular Nb film, providing new insights into the design of high-performance superconducting electronic devices.

Statistical analysis for progressive stress accelerated life test with transmutation Weibull distribution

The Transmutation Weibull distribution is derived from the quadratic rank transmutation map of the Weibull distribution. This distribution integrates the high adaptability of the Weibull distribution in engineering and materials fields, and has great potential utility for modeling lifetime data. Therefore, the article explores the progressive stress accelerated life test model for components under the Transmutation Weibull distribution, conducts statistical analysis using the maximum likelihood estimation (MLE), Lindley’s approximation, and Markov Chain Monte Carlo (MCMC) algorithm to provide approximate estimates for the model. Finally, by comparing the results of numerical simulations, it is confirmed that the Bayesian estimation is more accurate and effective.

Characteristics of coal crack development and gas desorption in the stress affected zone of rock pillar

Coal (Rock) pillar retaining in the mining of protective layer would cause gas dynamic disaster in the protected layer. Based on the gas geological conditions of the two-layer coal seam in Jinhe Coal Mine of Yaojie Mining District, the stress evolution law of coal seam in the rock pillar affected area was studied by theoretical analysis and numerical simulation, and the crack development law of coal seam in different loading stages under conventional triaxial loading was studied by CT scanning technology. With the analysis of the stress evolution and crack development of coal in rock pillar affected area, the gas extraction effect under different stress states and the gas desorption law after pressure relief antireflection were studied on site. The results showed that the stress of coal in the rock pillar affected area is in the approximate elastic stage of the conventional triaxial stress-strain curve, and the cracks of coal are mainly closed at this stage. Meanwhile, the increase of stress leaded to the decrease of coal permeability and the poor gas extraction effect. CT scanning tests under conventional triaxial loading were carried out in the laboratory, and three-dimensional visual models of coal sample cracks were constructed at different loading stages. When loading to the linear elastic stage, the crack volume and surface area were reduced by 74% and 71% compared with the ones in initial state. At the same time, the expression between stress σ and crack density T was further established. After comprehensive control measures such as intensive drilling discharge, presplitting blasting and coal water injection were taken to the coal in rock pillar affected area, the crack density T could reach the crack development level of the conventional triaxial loading softening stage, realizing the crack development of the coal under low stress. The enclosed gas in front of the coal could desorption flow during the roadway driving. And the predict index value K1 also decreased from 0.57 mL/(g·min1/2) to 0.17 mL/(g·min1/2) continuously. The safety of coal roadway in rock pillar affected area was realized, and the accuracy of numerical simulation and laboratory test results was verified, which had certain reference significance for coal roadway excavation under this similar conditions.