Tunneling Dynamics Research Articles

Quantum tunneling dynamics with robust reciprocity of Bose-Einstein condensate in a quadruple-well potential with synthetic gauge fields

Bose-Einstein condensation (BEC) trapped in quadruple-well potential with complex coupling provides a great useful platform in theoretical and experimental researches. Utilizing analytical and numerical methods, we investigate tunneling dynamics and the reciprocity of quantum transport of BEC in quadruple-well potential formed by the laser-assisted transition. According to the investigation, the tunneling dynamics of BEC in this system is independent of dissipation and complex coupling between wells caused by Raman coupling laser. By adjusting the coupling phase, the coherent destruction of tunneling can be observed. Meanwhile, this system provides an applicable proposal for reciprocal quantum switch by using the tunneling dynamics of BEC.

Effect of ice accretion on aerodynamic characteristics of pipeline suspension bridges

Pipeline suspension bridges may confront the issue of ice accretion in areas prone to glaze ice or rime. Ice accretion is known to influence the wind-induced responses of various structures, while the effects on the wind-induced responses of pipeline suspension bridges received little attention. To this end, this paper investigated the effect of ice accretion on the aerodynamic characteristics of pipeline suspension bridges from a series of wind tunnel tests. The influences of the shape of cross-section, ice shape, ice class, and Reynolds number on mean aerodynamic force coefficients were examined through static wind tunnel tests. The galloping stability was further examined based on the quasi-steady galloping theory according to the mean aerodynamic force coefficients. Furthermore, the effects of ice class and ice shape on the aeroelastic stability and flutter derivatives of a pipeline suspension bridge were investigated through dynamic wind tunnel tests. The results comprehensively reveal how ice accretion affects the aerodynamic characteristics of the bridge. Ice accretion on the girder can increase the static aerodynamic force, probability of galloping, and leads to vortex-induced vibration. Research results can provide a basis for aerostatic and buffeting analyses and a reference for the wind-resistant design of similar bridges in cold regions.

Nonadiabatic Dynamics of Hydrogen Tunneling with Nuclear-Electronic Orbital Multistate Density Functional Theory.

Proton transfer reactions play a critical role in many chemical and biological processes. The development of computationally efficient approaches to describe the quantum dynamics of proton transfer, which often involves hydrogen tunneling, is challenging. Herein, the nuclear-electronic orbital multistate density functional theory (NEO-MSDFT) method is combined with both Ehrenfest and surface hopping nonadiabatic dynamics methods to describe hydrogen tunneling. The NEO-MSDFT method treats the transferring hydrogen nucleus quantum mechanically on the same level as the electrons and incorporates both static and dynamical correlation by mixing localized NEO-DFT solutions with a nonorthogonal configuration interaction scheme. The other nuclei are propagated on the NEO-MSDFT vibronic surfaces during the Ehrenfest or surface hopping dynamics. These methods are applied to proton transfer in malonaldehyde as a prototypical hydrogen tunneling system. The inclusion of vibronically nonadiabatic effects is found to significantly impact the proton transfer time and tunneling dynamics. This approach is applicable to a wide range of other proton transfer reactions.

An analytical solution for the dynamic tunnel–soil–shallow foundation interaction under a harmonic point load

Elastic waves excited by railway tunnels can induce excessive vibration in nearby buildings. The dynamic interaction between the tunnel, soils, and the shallow foundations of buildings can significantly affect wave transmission from the vibration source to buildings. In this study, a three-dimensional theoretical model involving structure–soil–structure interaction (SSSI) is proposed and the analytical solution is obtained. The foundation is assumed to be seated on the ground surface, and the full coupling between the soil and structures is considered through the perfect contact at the tunnel-soil and soil-foundation interfaces. The response of the foundation to an incident wave field generated by a harmonic point load in a tunnel is calculated, and the impact of the tunnel–soil–foundation interaction is evaluated. The numerical results show that the SSSI needs to be considered when the relative distance between the tunnel and the foundation is within twice the shear wavelength. The vertical compliance coefficient at the center of the foundation features a significant peak due to the existence of a tunnel at the resonance frequency of the soil-tunnel system. The existence of the foundation restrains the displacement response of the ground surface within the foundation area, while causing significant amplification of the surface displacement outside the foundation area.

Tunneling dynamics of spin-orbit coupled BECs in a one-dimensional accelerating optical lattice

We theoretically investigate the energy band structure, nonlinear Landau–Zener tunneling dynamics and tunneling probability of spin-orbit coupled Bose–Einstein condensates in a one-dimensional accelerating optical lattice by using mean-field and two-mode approximation. The critical condition for the appearance of the loop structure is obtained numerically in parameter planes. When the intraspecies atomic interaction is less than the interspecies atomic interaction, the loop only appears in the lower band. In this case, Raman coupling inhibits the appearance of loop, while spin-orbit coupling (SOC) promotes the appearance of loop. If the intraspecies atomic interaction is larger than interspecies atomic interaction, the loop can appear in either the upper band or the lower band. In this case, Raman coupling promotes the loop appearing in the lower band, while SOC suppresses the loop appearing in upper band. Interestingly, when the interspecies atomic interaction is equal to the intraspecies atomic interaction, there is a critical atomic intercation value determined by the optical lattice depth, only when the intraspecies atomic interaction is greater than the critical value, the loop will occur only in lower band. Especially, the emergence of the loop structure destroys the Bloch oscillation of the system and results in the nonlinear Landau–Zener tunneling of the system. Furthermore, the Landau–Zener tunneling probability of the system is calculated, and it is found that the nonlinear Landau–Zener dynamics and the tunneling probability can be manipulated by SOC and Raman coupling.

Dynamical change under slowly changing conditions: the quantum Kruskal–Neishtadt–Henrard theorem

Adiabatic approximations break down classically when a constant-energy contour splits into separate contours, forcing the system to choose which daughter contour to follow; the choices often represent qualitatively different behavior, so that slowly changing conditions induce a sudden and drastic change in dynamics. The Kruskal–Neishtadt–Henrard (KNH) theorem relates the probability of each choice to the rates at which the phase space areas enclosed by the different contours are changing. This represents a connection within closed-system mechanics, and without dynamical chaos, between spontaneous change and increase in phase space measure, as required by the Second Law of Thermodynamics. Quantum mechanically, in contrast, dynamical tunneling allows adiabaticity to persist, for very slow parameter change, through a classical splitting of energy contours; the classical and adiabatic limits fail to commute. Here we show that a quantum form of the KNH theorem holds nonetheless, due to unitarity.

Wind tunnel research, dynamics, and scaling for wind energy

The interaction of wind turbines with turbulent atmospheric boundary layer (ABL) flows represents a complex multi-scale problem that spans several orders of magnitudes of spatial and temporal scales. These scales range from the interactions of large wind farms with the ABL (on the order of tens of kilometers) to the small length scale of the wind turbine blade boundary layer (order of a millimeter). Detailed studies of multi-scale wind energy aerodynamics are timely and vital to maximize the efficiency of current and future wind energy projects, be they onshore, bottom-fixed offshore, or floating offshore. Among different research modalities, wind tunnel experiments have been at the forefront of research efforts in the wind energy community over the last few decades. They provide valuable insight about the aerodynamics of wind turbines and wind farms, which are important in relation to optimized performance of these machines. The major advantage of wind tunnel research is that wind turbines can be experimentally studied under fully controlled and repeatable conditions allowing for systematic research on the wind turbine interactions that extract energy from the incoming atmospheric flow. Detailed experimental data collected in the wind tunnel are also invaluable for validating and calibrating numerical models.

Chaos-assisted many-body tunnelling.

We study the interplay of chaos and tunneling between two weakly coupled Bose-Josephson junctions. The classical phase space of the composite system has a mixed structure including quasi-integrable self-trapping islands for particles and excitations, separated by a chaotic sea. We show that the many-body dynamical tunneling gap between macroscopic Schrödinger cat states supported by these islands is chaos-enhanced. The many-body tunneling rate fluctuates over several orders of magnitude with small variations of the system parameters or the particle number.

Coherent destruction of tunnelling in a symmetrical double well driven by a series of time dependent δ functions

It is analytically and numerically shown that the coherent tunnelling between the individual wells of a symmetrical double well potential can be totally suppressed when it is driven by a periodic series of δ function in time, depending on the time period and strength of the δ function. We have applied time dependent perturbation theory to have an understanding over the process. In absence of any kind of perturbation, the average position of the particle makes a sinusoidal oscillation between two wells. With the application of a periodic δ function, the amplitude and the frequency of the oscillation both get modified. In this article we have explored how the frequency and strength of the applied perturbation controls the quantum dynamics of tunnelling and finally, how these parameters drive the system towards a complete stand still situation, which is described as coherent destruction of tunnelling.

Probing Resonant Photoionization Time Delay by Self-Referenced Molecular Attoclock.

Attosecond time-resolved electron tunneling dynamics have been investigated by using attosecond angular streaking spectroscopy, where a clock reference to the laser field vector is required in atomic strong-field ionization and the situation becomes complicated in molecules. Here we reveal a resonant ionization process via a transient state by developing an electron-tunneling-site-resolved molecular attoclock in Ar-Kr^{+}. Two distinct deflection angles are observed in the photoelectron angular distribution in the molecular frame, corresponding to the direct and resonant ionization pathways. We find the electron is temporally trapped in the Coulomb potential wells of the Ar-Kr^{+} before finally releasing into the continuum when the electron tunnels through the internal barrier. By utilizing the direct tunneling ionization as a self-referenced arm of the attoclock, the time delay of the electron trapped in the resonant state is revealed to be 3.50±0.04 fs. Our results give an impetus to exploring the ultrafast electron dynamics in complex systems and also endow a semiclassical presentation of the electron trapping dynamics in a quantum resonant state.

Flexibility Regulation of Loops Surrounding the Tunnel Entrance in Cytochrome P450 Enhanced Substrate Access Substantially

In recent years, the engineering of flexible loops to improve enzyme properties has gained attention in biocatalysis. Herein, we report a loop engineering strategy to improve the stability of the substrate access tunnels, which reveals the molecular mechanism between loops and tunnels. Based on the dynamic tunnel analysis of CYP116B3, five positions (A86, T91, M108, A109, T111) in loops B-B′ and B′-C potentially affecting tunnel frequent occurrence were selected and subjected to simultaneous saturation mutagenesis. The best variant 8G8 (A86T/T91L/M108N/A109M/T111A) for the dealkylation of 7-ethoxycoumarin and the hydroxylation of naphthalene was identified with considerably increased activity (134-fold and 9-fold) through screening. Molecular dynamics simulations showed that the reduced flexibility of loops B-B′ and B′-C was responsible for increasing the stability of the studied tunnel. The redesign of loops B-B′ and B′-C surrounding the tunnel entrance provides loop engineering with a powerful and likely general method to kick on/off the substrate/product transportation.

A digital twin approach for tunnel construction safety early warning and management

Accidents tend to happen during tunnel construction due to the harsh environmental and geological conditions. Towards high safety risk during tunnel construction, a digital-twin based multi-information intelligent early warning and safety management platform is proposed in this study. At first, a communication line is built inside tunnel through multifunctional base stations. Multi-source information from tunnel construction could be collected and transmitted automatically. Then, dynamic tunnel construction information and surrounding rock conditions are virtual simulated. Meanwhile, four-level early warning and emergency response plan are built to provide judgement on the construction status. At last, application effects of the platform are validated in a deep buried tunnel project, Dongtianshan Tunnel in China, which has extreme weather, harmful gas, and bad geological conditions. A collapse accident of tunnel excavation face was successfully predicted by the platform. Early warning and appropriate emergency measures were taken in time, and the personnel safety was ensured.

The Use of a Roadheader Simulator in Research of Dynamics and Energy-Consumption of Excavating Underground Roadways and Tunnels

Boom-type roadheaders are commonly used for excavation of roadways in underground mines, tunnels, and other architectural structures using trenchless techniques, as well as sinking shafts and occasionally excavating the harder soil and softer formations in cut and cover construction. The main research and development of these machines is to offer solutions for automatic control. This refers to automation or robotization of the operation, and raises the possibility of their eventual unmanned operation. This article presents a roadheader research simulator which implements experimentally verified mathematical models describing the dynamics of a roadheader in operation and the rock cutting process. Due to very high computational requirements, a distributed system comprising several workstations connected via TCP/IP was used. Both the visualization of the roadheader in the heading face of the excavation and the graphic simulation of the course of the rock-cutting process were carried out using the Autodesk Inventor Professional 2022 graphics engine. It provided the simulator with a virtual scene environment and enabled the control of the roadheader model’s movement during the simulated cutting process, including the generation of breakout graphics in the heading face while drilling a roadway or tunnel. The presented roadheader simulator enables the determination of various time characteristics, for example, dynamic loads, power demand, efficiency, energy consumption, and others. It is still under development.

Theory of rain-wind-induced vibration of stay cables: A quasi-steady-state approximation

Rain-wind-induced vibration (RWIV) of stay cables in cable-stayed bridges is jointly induced by rainfall and incoming wind. It is a major concern to the bridge engineering community due to its very large vibration amplitude. Yet the characteristics and mechanism of RWIV have not been understood completely. In particular, a theoretical model that can well describe the RWIV is urgently needed for amplitude prediction in engineering applications. Following a recent experimental work, we propose a theoretical framework for the analytical analysis of RWIV in the present study. The moving upper rivulet, which plays a crucial role in the excitation of RWIV, is modeled with a quasi-steady-state approximation. The analytical and numerical results are first compared with the experimental data to validate the theory. Then, the effects of some key parameters, including cable mass, frequency, damping ratio, and dynamic upper rivulet, on RWIV are investigated in detail with the theoretical framework. The model in the present study provides quick and reliable evaluations of the vibration amplitude and influencing parameters of RWIV, without performing time-consuming experiments in wind tunnel or computational fluid dynamics simulations.

Excited-state resonance tunneling in strong-field ionization

We study the tunneling dynamics of a system with two bound states. We find that the system can be effectively described by a two-level leakage cavity model, with which we can reproduce the dynamics of tunneling ionization. It shows that tunneling via the excited-state resonance dominates over the ground-state tunneling within the field strength considered, where the electron prefers jumping to the excited-state resonance channel first and then tunneling out. Moreover, several key parameters of the system naturally emerge in our two-level model. Especially, one of the parameters is the physical correspondence of the tunneling time obtained from the ground-state tunneling.

Türbülans Yoğunluğunun Geçiş Yer Tahminine Etkisinin Bölgesel Korelasyon Geçiş Modeli ile İncelenmesi

Aerodynamic parameters are among the most important parameters in flight performance analyses of air/sea vehicles. Free stream turbulence intensity has significant importance on aerodynamic parameters obtained with computational fluid dynamic analyses and wind tunnel tests measurements. In this study, the effect of free stream turbulence intensity on the transition locations of spheroid geometry using with the widely accepted local correlation transition model. The computations are performed at 6.5 x 106 Reynolds number with 0 and 5 degree angle of attacks. The computations at 5 degree angle of attack are compared with an available experimental study. The effect of free stream turbulence intensity is investigated with axial force coefficient, normal force coefficient, and surface friction coefficient distributions. It is seen that axial and normal force coefficients increase with increasing free stream turbulence intensity. The differences in force coefficients obtained with the free stream intensity range used in the study shall create noteworthy effects in flight performance analyses. When surface friction coefficients are investigated, the transition model estimates the transition locations earlier while free stream turbulence intensity increases as expected. However, the transition front geometry is obtained significantly different with respect to the experimental results.

Laboratory experiments and discrete element modeling on the surface failure induced by EPB tunneling: The effects of cutterhead open ratio and relative tunneling depth

This paper presents laboratory tests and high-fidelity numerical simulations to examine the ground failure induced by Earth Pressure Balance (EPB) Shield Tunneling in granular soils. Specifically, we designed and conducted laboratory tests using a reduced-scale EPB Shield Tunnel machine, and built corresponding three-dimensional (3D) discrete-element method (DEM) models to simulate the dynamic excavation process and to gain further understandings of the mechanisms of the ground movement. The study is particularly focused on the combined influences of the cutterhead open ratio and the relative tunnel depth on the ground motions and stress perturbations during the EPB tunneling, which remain understudied in existing studies. The results show that the open ratio of the cutterhead has significant effects on the ground failure in granular soils, especially in cases of relatively shallow tunnels. The larger the open ratio of the cutterhead, the wider the surface and subsurface settlement trough and the greater the soil pressure in the chamber. The pressure distribution in the soil chamber with a larger cutterhead open ratio is significantly more non-linear than that of the case with a smaller cutterhead open ratio. For a given cover-to-diameter ratio (C/D) of the tunnel, the width parameter (k) is generally constant regardless of the depth for the case with a large cutterhead open ratio, especially in the relatively shallow tunnels, while it increases non-linearly with the depth for the case with a small cutterhead open ratio, especially in relatively deep tunnels. Furthermore, soil arching mechanisms are analyzed qualitatively with respect to different cutterhead open ratios and C/Ds. The study demonstrates quantitatively the response of ground surface to the cutterhead open ratios and C/Ds as well as the associated ground failure mechanisms through a combination of laboratory experiments and 3D DEM simulations, providing further insights into the ground behaviors during the dynamic EPB tunneling process.

Waiting time distribution and current correlations via a Majorana single-charge transistor

We investigate the electron transport and the waiting time distribution (WTD) in a topological superconducting Coulomb island system weakly coupled to two metallic leads. A pair of Majorana bound states are hosted in the island with a finite charging energy. By employing the Markovian master equation, we study the effect of interplay between Majorana energy splitting and the charging energy on the current correlations and the relevant electron WTDs. It is found that the super-Poissonian shot noise could be induced when the Majorana energy splitting is larger than the charging energy. The reason is that the degeneracy of the ground states in the island could be lifted by a finite Majorana energy splitting, which produces the asymmetry between tunneling channels and leads to the dynamical channel blockade effect. We show that the WTD for electron tunneling through two Majorana bound states is equivalent to the WTD in a single-resonant-level device. For comparison, we also discuss the WTD for electron tunneling through a non-Majorana device. It is found that the WTD sensitively depends on the length of the island and indicates oscillation behaviors in the absence of Majorana bound states. The particular behaviors of the WTDs in a Majorana island device can be useful in identifying the existence of Majorana bound states. Furthermore, we study the randomness parameter of the waiting time to describe the fluctuations of waiting times. It is shown that the randomness parameter indicates behavior similar to that indicated by the noise Fano factor, and both of them reflect the information of tunneling dynamics.

Wind Dynamic Characteristics and Wind Tunnel Simulation of Subgrade Sand Hazard in the Shannan Wide Valley of the Sichuan-Tibet Railway.

The Shannan wide valley section of the Sichuan–Tibet Railway is located in the middle reaches of the Yarlung Zangbo River, where sand hazard is severe. A wind tunnel simulation experiment was conducted by establishing a subgrade model and performing field observation to carry out research on the dynamic environment of blown sand and the sand hazard formation mechanism of subgrade in the Shannan wide valley. Observation results showed that the sand-moving wind of the Shannan wide valley was chiefly derived from the ENE direction, and the resultant sand transport direction was WSW. Wind speed, the frequency of sand-moving wind, the sand drift potential, and the maximum possible sand transport quantity were relatively high in the spring. Meanwhile, the dynamic of the wind-blown sand flow was further enhanced in the spring, particularly influenced by the flow action of the Yarlung Zangbo River. Thus, sand hazard mainly occurred in the spring. The Sichuan–Tibet Railway subgrade evidently changed the wind speed, the wind-blown sand flow field, and conditions of transport and accumulation. Within the distance of 5 times the model height in the windward direction and at the subgrade top center to 20 times the model height of the leeward direction was the wind speed deceleration zone, resulting in sand particle sediments. A wind speed acceleration zone appeared on the subgrade windward slope shoulder, resulting in wind-blown sand flow erosion. This study provides a scientific basis for sand hazard prevention and control in the Sichuan–Tibet Railway.

Development and Fidelity Assessment of Potential Flow based Framework for Aerodynamic Modeling of High Lift Devices

High lift devices play a vital role in dictating the accelerated performance of an aircraft for different flight phases such as takeoff, landing, and aerobatic maneuvers. The aerodynamic design of high lift devices for any particular aircraft is an iterative process and is achieved through extensive aerodynamic Analysis of the aircraft for various flap configurations. Computational Fluid Dynamics (CFD) and Wind tunnel testing are highly effective techniques for performing the required Analysis, yet they have high computational costs and time. To overcome this shortcoming, a robust framework based on potential flow solver (PFS) and geometry parameterization is required without compromising the fidelity of the Analysis. This research aims to develop a highly robust aerodynamic analysis framework based on the Vortex Lattice Method (VLM) coupled with Polhamus Suction Analogy and parametric modeling of high lift devices. The fidelity of the framework is validated through experimental testing and is quantified by developing a fidelity assessment matrix. It is established that the computational cost of CFD has been reduced three times with only a 10% to 20% loss in accuracy when the developed framework is used. The developed PFS framework gives results from 80% to 90%. The framework results for a reference aircraft are thoroughly compared with CFD analyses. The framework provides values that agree with corresponding CFD analyses in a fraction of the time.