Tunneling Effect Research Articles

면진층 구조를 가진 다중쉘 해저터널의 응력 저감 효과

면진층 구조를 가진 다중쉘 해저터널의 응력 저감 효과

Seismic Response Analysis of Secondary Lining Polymer Grouting Debonding Repair for Tunnel Construction Based on Parameter Inversion

The void phenomenon behind the tunnel lining has become the main cause of tunnel disease, easily triggering tunnel lining structure damage, shedding, water seepage, and other diseases that seriously threaten the normal operation of the tunnel. The void area behind the lining seriously reduces the seismic capacity of the tunnel. In this paper, the mechanical parameters of the surrounding rock are calculated by optimizing the inversion of the improved system identification sensitivity analysis method, and the numerical model of the tunnel’s dynamic response is optimized using the improved inversion results to study the repair effect and seismic capacity of the Longmenshan tunnel using polymer grouting to repair the void area behind the lining under the action of a seismic load. The results show that the displacement and stress at the top of the tunnel secondary lining void area are significantly reduced and close to normal after the repair of polymer grouting; however, the stress and displacement at the top of the secondary lining are significantly different under the action of seismic waves at the same peak at different site conditions, which indicates that the dynamic response of this tunnel model has obvious sensitivity to the seismic wave spectrum.

Tunnel effect and analysis of the survival amplitude in the nonlinear Winter’s model

In this paper we show how the nonlinearity term affects the tunnel effect and the survival amplitude in the nonlinear Winter’s model. In particular, in the case of attractive nonlinearity large enough it turns out that the tunnel effect is going to disappear. Furthermore, the difficulty in giving a rigorous and appropriate definition of quantum resonances by means of the notions already used for linear equations is also highlighted.

Resonant Tunneling Effects on the Double‐Barrier Electron Blocking Layer of a Nitride Deep‐UV Light‐Emitting Diode

The multi‐quantum‐barrier electron blocking layer (EBL) is reported to significantly improve efficiency by nearly 3 times over a single barrier in deep‐UV AlGaN light‐emitting diodes to deal with electron leakage. The improvement is usually attributed to the enhanced effective barrier height, and this article aims to explore the benefits of the tunneling effect by calculating the tunneling currents of electrons and holes through an Al0.6Ga0.4N/AlyGa1−yN double‐barrier EBL under external bias from opposite directions. The results show that the tunneling current for holes Jh is several orders of magnitude higher than that of the electrons Je as the barriers are with Al mole fraction y greater than 0.75 and thickness larger than 2 nm, which promises effective hole injection by tunneling without much electron leakage. Tunneling mechanism works better in EBL with higher and thicker barriers because the tunneling coefficients of light hole drop much slower than electrons due to its small effective mass. A proper distance between the barriers is needed to avoid electron leakage while holes tunnel through the EBL. Built‐in electric fields tilt the band to enlarge the peak‐to‐valley ratio. This work indicates that the tunneling effect substantially facilitates a multibarrier EBL to enhance carrier‐injection efficiency.

An artificial dead-layer to protect the ferroelectric thin films from electron injection

For ferroelectric (FE) thin films, working in the harsh environment of a high electric field (E) or high temperature (T) remains a great challenge. As a post-treatment approach, dead-layer engineering exhibits a certain generality and could improve the dielectric strength (Eb) via depositing a specially designed artificial “dead-layer” on most of the as-prepared FE thin films. However, physical essence of the artificial dead-layer needs further analysis. Great challenges are the abundant and complicated conduction mechanisms in the FE-based thin films and the lack of adequate research on modulating these conduction mechanisms by this artificial dead-layer. As a vital part of the conduction mechanisms, electron injection can be easily triggered under E and thermal excitation that almost appeared in all FE-based thin films. Here, the ultrathin artificial dead-layer of Ca0.2Zr0.8O1.8 (CSZ) was used to restrain multiple electron injection in low-Eb LaNiO3/Ba0.58Sr0.42TiO3 (LNO/BST) FE thin films, including thermal emission and tunneling effect, under a high E and T, even under an opposite E. It was found that the suppressing effect on the multiple electron-injection mechanisms via the artificial dead-layer mainly comes from its wall-like energy-barrier structure, which is composed of two opposite and high interface energy barriers (BST/CSZ: 2.95 eV, CSZ/Au: 3.92 eV) and a wide depletion layer. The generality of protecting the ferroelectric thin films from electron injection via the artificial dead-layer was discussed.

Thermomechanical performance of energy retaining pile influenced by surrounding utility tunnel via the regression tree model

The thermomechanical performance of energy retaining pile differs from that of axisymmetric energy pile due to utility tunnel excavation. This study presents four field tests of energy retaining pile conducted before and after utility tunnel construction. A regression tree (RT) model for predicting the thermally induced stress of energy retaining pile was established based on the measured water temperature, pile temperature and previous stage thermally induced stress to evaluate the effect of shallow buried utility tunnel on the thermomechanical performance of adjacent energy pile. The established thermally induced stress RT prediction model could acceptably predict the thermally induced stress of the future short-team. Surrounding utility tunnel excavation alters the distribution of the axial thermally induced stress. The axial thermomechanical response of the energy retaining pile after utility tunnel construction is approximately 50% that before utility tunnel construction. The asymmetrical boundary conditions cause a limited bending moment of the energy retaining pile at the top or bottom of the utility tunnel, which is not enough to threaten the pile safety. Moreover, the thermal performance of the energy retaining pile slightly increases due to the heat exchange between the pile and the air in the surrounding utility tunnel.

Real-time assessment of tunnelling-induced damage to structures within the building information modelling framework

During the initial design phases of complex multi-disciplinary systems such as urban tunnelling, the appraisal of different design alternatives can ensure optimal designs in terms of costs, construction time, and safety. To enable the evaluation of a large number of design scenarios and to find an optimal solution that minimises impact of tunnelling on existing structures, the design and assessment process must be efficient, yet provide a holistic view of soil-structure interaction effects. This paper proposes an integrated tunnel design tool for the initial design phases to predict the ground settlements induced by tunnelling and building damage using empirical and analytical solutions as well as simulation-based meta models. Furthermore, visualisation of ground settlements and building damage risk is enabled by integrating empirical and analytical models within our Building Information Modelling (BIM) framework for tunnelling. This approach allows for near real-time assessment of structural damage induced by settlements with consideration of soil-structure interaction and non-linear material behaviour. Furthermore, because this approach is implemented on a BIM platform for tunnelling, first, the design can be optimised directly in the design environment, thus eliminating errors in data exchange between designers and computational analysts. Secondly, the effect of tunnelling on existing structures can be effectively visualised within the BIM by producing risk-maps and visualising the scaled deformation field, which allows for a more intuitive understanding of design actions and for collaborative design. Having a fully parametric design model and real-time predictions therefore enables the assessment and visualisation of tunneling-induced damage for large tunnel sections and multiple structures in an effective and computationally efficient way.

Overcoming sub-threshold slope degradation by the advances of TFETSs materials

With the scaling of devices in the past few decades, a lot of problems arise include short tunnel effect and significant power consumption, in which sub-threshold slope is a considerate factor. However, Sub-threshold Slope of MOSFET is limited to 60 mV/decade at room temperature due to Boltzmann Tyranny. TFETs (Tunnelling Field Effect Transistors) are the most promising field-effect transistors candidates owing to its potential to overcome sub-threshold slope degradation. This article illustrates the main principles of TFETs and explains how TFETs can overcome sub-threshold slope degradation through tunnelling effect. Furthermore, this article introduces the advances of TFETs materials to optimize devices performances.

Wind tunnel effects on gust-interaction simulations

Wind tunnel effects on gust-interaction simulations

How Does an Extra-Long Freeway Tunnel Influence Driving Performance? A Comparative Study of Driving Simulation

Extra-long tunnels have adverse effects on driving performance since drivers will be affected by the enclosed, dimly lit, and monotonous environment for a longer time. In the context of the increasing number of extra-long tunnels, this study aims to investigate the effects of extra-long freeway tunnels with a length of 20 km on driving performance using driving simulation tests. Factors including the tunnel environment, driving time, traffic flow, and gender were considered as influencing factors. Performance indicators including the brake reaction time, standard deviation of driving speed, and standard deviation of lateral position were collected. A total of 60 drivers were recruited for the driving simulation study, and the relationships between the driving performance indicators and influencing factors were analyzed by establishing linear mixed models with random intercept. The results demonstrate that driving performance significantly degraded after 5 – 6 min of driving in the extra-long tunnel although drivers were more cautious and presented a better performance when just entering the tunnel. Moderately higher traffic flow could improve driving performance in the extra-long tunnel but not on the open road. Meanwhile, female drivers had better lateral and longitudinal stability in the extra-long tunnel, while no significant difference was witnessed in reaction ability and driving performance on the open road.

Tunneling induced swapping of orbital angular momentum in a quantum dot molecule

In this paper, we have examined the effectiveness exchange of optical vorticity via three-wave mixing (TWM) technique in a four-level quantum dot (QD) molecule by means of the electron tunneling effect. Our analytical analysis demonstrates that the TWM procedure can result in the production of a new weak signal beam that may be absorbed or amplified within the QD molecule. We have taken into account the electron tunneling as well as the relative phase of the applied lights to assess the absorption and dispersion characteristics of the newly generated light. We have discovered that the slow light propagation and signal amplification can be achieved. Our results show that the exchange of the orbital angular momentum of light can transfer from coupling optical vortex light to the new generated light in high efficiency.

Multifunctional applications of topological valley-locked elastic waves

Topological valley metamaterial in classical wave systems has shown great potential for manipulating electromagnetic, acoustic, and elastic waves due to the defect-immune and lossless energy properties. The application prospects of topological valley material on signal processing, structural damage detection, and energy harvesting are worth exploring further. In this study, we combine the valley Hall effect and the tunneling effect of local resonant metamaterials to reveal some novel coupling transport phenomena in elastic systems. Some potential applications are explored experimentally and numerically. First, we implement a low-frequency (<1 kHz) valley-locked waveguide in heterostructures based on the topological valley edge state of the local resonant metamaterial. The robustness of the topological valley-locked waveguide under wide valley-locked layers, impurities, disorder, and bends is verified. Next, we introduce tunneling phenomena into the topological valley-locked waveguide, enabling the realization of an on-off controllable heterojunction by sandwiching crystals with different Dirac cones. The difference between the transmission characteristics of valley-locked waveguides under different tunneling layers (potential barrier and well) is revealed. Finally, we explore potential applications such as signal splitters, energy concentrators, and logical gates, both numerically and experimentally. Beyond the presented applications, this research has promising application prospects for vibration signal processing and high-performance energy harvesting.

Transition from optical bistability to multistability in a tunneling quantum dot via structure hybrid light

In this paper, we proposed a new model based on the electron tunneling effect in a four-level quantum dot molecule (QDM) for studying the optical bistability (OB) and optical multistability (OM). The QDM interacts with a probe and two coupling and Laguerre–Gaussian (LG) fields. We found that by adjusting the electron tunneling effect and the parametric controlling of LG light, the transition from OB to OM or vice versa is possible. Moreover, due to the simultaneous interaction between coupling and LG lights with the same optical transition adjusting the threshold of OB and OM by orbital angular momentum (OAM) of the LG light becomes achievable. Our results show that by adjusting the simultaneous effect of electron tunneling and OAM state of the vortex light, the favorable OB and OM patterns with adjustable intensity thresholds are achievable. Our proposed model may have potential application in quantum information science based on quantum dot (QD) devices.

Device Simulation on GaN‐LED Operating in Noncarrier Injection Mode for Performance Improvement by Enhancing the Tunneling Effect in Multiquantum Wells

AbstractNoncarrier injection (NCI) operation mode is an emerging driving mode for nanoscale light‐emitting diodes (LEDs) for application in nanopixel light‐emitting displays. However, the luminescence intensity of the NCI‐LED with traditional epitaxial structure is relatively low because of the absence of external carrier injection. Therefore, improving the luminescence intensity by optimizing the epitaxial structure of the LED is an important technical measure. In this work, the tunneling behavior of the NCI‐LED under reverse bias, which plays a key role in increasing the luminescence intensity, is studied through modeling and simulation. The dynamic variation of carrier concentration in each voltage cycle is studied to explore the working process of the NCI‐LED. Results show that the luminescence output of the NCI‐LED is highly sensitive to doping concentrations, and reducing the number of multiquantum wells can increase the probability of interband tunneling so as to improve dramatically the carrier number contributing to luminescence. This simulation work can deepen the understanding of the NCI mode and serve as an important guidance for the rational design of the NCI‐LEDs.

A numerical investigation on electron runaway threshold at the initial stage of atmospheric streamer development

Pre-ionization caused by runaway electrons is an important mechanism for negative streamer development. The aim of this paper is to investigate the runaway criteria and overvoltage threshold of electrons at the initial stage of streamer development in air, with the self-developed 3D particle-in-cell with Monte Carlo Collision code. First, numerical simulations are performed with fixed number of electrons to study the runaway criteria in nonrelativistic cases. This method takes the stochastic fluctuations of collisions into account and solves the major shortcomings of theoretical approach. The simulated critical electric field is less than that of the theoretical approach, and the amplitude of the difference increases with electron energy, due to the “tunneling effect” caused by the stochastic fluctuations of collisions. Then, simulations of negative streamers at various applied voltages are performed to investigate the overvoltage threshold. A more intuitive method, searching energetic electrons in front of the negative streamer head, which corresponds to the nature of runaway electrons, is applied to determine the generation of runaway electrons. Electrons that escaped a certain distance ahead of the streamer can be observed at 30 kV. Thus, the overvoltage threshold for runaway electrons can be roughly estimated as 3.3 in our simulations, which is about three times less than the previously published one. At last, with the redefined overvoltage threshold, the figure of regions of breakdown development for various mechanisms depending upon the overvoltage in air is updated.

Improvements in reliability and radio frequency performance of junctionless tunnelling field effect transistor using p+ pocket and metal strip

AbstractIn this article, a new p+ pocket stacked gate oxide junctionless tunnelling field effect transistor (junction less tunnelling field effect transistor (JLTFET)) which has metal strip in gate oxide layer is proposed for analogue/RF circuit applications. Due to the insertion of a p+ pocket in source/channel junction and the use of metal strip in oxide layer, the following properties of the proposed JLTFET are resulted. First, the tunnelling barrier width is reduced in the source/channel junction thereby, electrons easily tunnel from the source to the channel. Second, the hole concentration (empty state) in the channel is increased, leading to higher electron contribution in the tunnelling process. These improvements are useful in achieving high drain current and steep subthreshold swing. As a result, the maximum ON current of 4.4 × 10−5 A/μm and average subthreshold swing of 40 mV/decade are obtained from simulation results. Moreover, as compared to conventional JLTFET, the proposed JLTFET provides improvements in reliability and analogue/radio frequency (RF) performance.

Tunable Sensitivity in Long Period Fiber Gratings During Mode Transition With Low Refractive Index Intermediate Layer

Double-clad fibers where the second cladding has a lower refractive index than the first cladding, prove to be ideal structures for potentiating and tuning the sensitivity in long-period fiber gratings (LPFGs) operating in mode transition. When a thin film is deposited on the optical fiber, the second cladding performs acts as a barrier that initially prevents the transition to guidance in the thin film of one of the modes guided in the first cladding. Finally, the transition to guidance occurs with a sensitivity increase, in analogy to the tunnel effect observed in semiconductors. This improvement has been demonstrated both as a function of the thin film thickness and the surrounding medium refractive index, with enhancement factors of 4 and 2, respectively. This idea reinforces the performance of LPFGs, adding a new degree of freedom to the mode transition and the dispersion turning point phenomena. Moreover, the control of the variation of the effective index of cladding modes could be applied in other structures, such as tilted-fiber gratings or evanescent wave sensors.

Tunneling via surface dislocation in W/β-Ga2O3 Schottky barrier diodes

In this work, W/β-Ga2O3 Schottky barrier diodes, prepared using a confined magnetic field-based sputtering method, were analyzed at different operation temperatures. Firstly, Schottky barrier height increased with increasing temperature from 100 to 300 K and reached 1.03 eV at room temperature. The ideality factor decreased with increasing temperature and it was higher than 2 at 100 K. This apparent high value was related to the tunneling effect. Secondly, the series and on-resistances decreased with increasing operation temperature. Finally, the interfacial dislocation was extracted from the tunneling current. A high dislocation density was found, which indicates the domination of tunneling through dislocation in the transport mechanism. These findings are evidently helpful in designing better performance devices.

Manipulating single excess electrons in monolayer transition metal dihalide

Polarons are entities of excess electrons dressed with local response of lattices, whose atomic-scale characterization is essential for understanding the many body physics arising from the electron-lattice entanglement, yet difficult to achieve. Here, using scanning tunneling microscopy and spectroscopy (STM/STS), we show the visualization and manipulation of single polarons in monolayer CoCl2, that are grown on HOPG substrate via molecular beam epitaxy. Two types of polarons are identified, both inducing upward local band bending, but exhibiting distinct appearances, lattice occupations and polaronic states. First principles calculations unveil origin of polarons that are stabilized by cooperative electron-electron and electron-phonon interactions. Both types of polarons can be created, moved, erased, and moreover interconverted individually by the STM tip, as driven by tip electric field and inelastic electron tunneling effect. This finding identifies the rich category of polarons in CoCl2 and their feasibility of precise control unprecedently, which can be generalized to other transition metal halides.

Performance-based three-level fortification goal and its application in anti-dislocation countermeasures: A case study of Shantou Submarine tunnel

The dislocation momentum is the design basis for anti-dislocation to tunnel when a tunnel crosses an active fault. The influence of different dislocation levels on tunnel performances is not clear. Thus, based on seismic activity parameters at the site of interest and probability of fault dislocation, probability fault displacement hazard analysis (PFDHA) methodology was introduced in this paper to ascertain the fault dislocation level under different exceeding probabilities (63%, 10%, and 2%–3%). Then, based on the definition of different ground motion strength and fortification goals of the tunnel, a three-level fortification goal with different performance requirements of the tunnel was proposed. The first attempt to use the proposed indexes including the maximum dislocation of the tunnel and maximum relative deformation of the tunnel was tried to evaluate deformation and failure states with an experimental approach. Subsequently, the feasibility of the three-level fortification goal was further investigated according to the self-defined qualitative description and quantitative indexes in the segmental design and sectional expansion tunnels comprehensively. The results show that the fault dislocations relying on PFDHA at the site of the Shantou Submarine Tunnel are firstly ascertained as 0.04, 1.8, and 2.4 m respectively. Taking the fault dislocation as model input values into account, the dislocation mechanism of the tunnel under the three levels was revealed. More importantly, judging from the dislocation performance requirements of the three-level fortification goal, the tunnel deformation and failure states are mitigated by adopting the countermeasures. The sectional expansion design can well meet the requirements without the restriction of a strong earthquake, while the effectiveness of the segmental tunnel can be proved under frequently occurred and fortification earthquake. The final research results are expected to provide a new fortification goal for anti-dislocation hazard evaluation on expansion design in high-intensity seismic regions and segmental design in slight and moderate-intensity seismic regions.