Magnetotransport in the quantum wires comprised of vertically stacked quantum dots

We investigate a periodic system of vertically stacked InAs/GaAs quantum dots (VSQD) subjected to a two-dimensional confining harmonic potential and a magnetic field in the symmetric gauge. Given the tiny length scales, adequate lateral confinement, and strong vertical coupling involved in the experiments, the VSQD system has become known for mimicking the standard semiconducting quantum wires. An exact analytical diagnosis of the problem allows us to show the system’s direct relevance to the physics of musical sounds, magnetization, magnetotransport, and the designing of the optical amplifiers. The results suggest making the most of the system for applications in single-electron devices and quantum state transfer in the quantum computation.

Vibration Analysis of Hub Motor Based on ANSYS

The hub motor is designed with multidirectional excitation and Halbach Array, which includes inner rotor, left and right stator, outer stator, encoder and rotary transformer. The rotor consists of an axial disk and a top ring. The rotor’s permanent magnets are affixed to the left and right sides of the disk and to the outside of the top ring. The permanent magnets on the rotor adopt a Halbach Array. The three stators have not the iron core and they are arranged outside the rotor to form a three-way closed loop. The motor has high power density, high torque density, low heating, strong adaptability and no cogging effect. It is suitable for electric car control. On this basis, the dynamic equation of the hub motor is established, the vibration mode of the rotor system is analysed, when the inner rotor’s speed is 18000rpm. By use of the solid model, the hub-rotor’s accurate dynamics solution can be obtained. In the future, the effect of vertical coupling vibration will be investigated for its ride comfort and safety.

An Ultra-Compact Design of Plasmonic Memristor with Low Loss and High Extinction Efficiency Based on Enhanced Interaction between Filament and Concentrated Plasmon

We present a numerical design of the plasmonic memristive switching device operated at the telecommunication wavelength of 1.55 μm, which consists of a triangle-shaped metal taper mounted on top of a Si waveguide, with rational doping in the area below the apex of the taper. This device can achieve optimal vertical coupling of light energy from the Si waveguide to the plasmonic region and, at the same time, focus the plasmon into the apex of the metal taper. Moreover, the area with concentrated plasmon is overlapped with that where the memristive switching occurs, due to the formation/removal of the metallic nano-filament. As a result, the highly distinct transmission induced by the switching of the plasmonic memristor can be produced because of the maximized interactions between the filament and the plasmon. Our numerical simulation shows that the device hasa compact size (610 nm), low insertion loss (~1 dB), and high extinction efficiency (4.6 dB/μm). Additionally, we point out that stabilizing the size of the filament is critical to improve the operation repeatability of the plasmonic memristive switching device.

The Intensity- and Size-Dependent Response of Tropical Cyclones to Increasing Vertical Wind Shear

This study describes a set of idealized simulations in which westerly vertical wind shear increases from 3 to 15 m s−1 at different stages in the lifecycle of an intensifying tropical cyclone (TC). The TC response to increasing shear depends on the intensity and size of the TC’s tangential wind field when shear starts to increase. For a weak tropical storm, increasing shear decouples the vortex and prevents intensification. For Category 1 and stronger storms, increasing shear causes a period of weakening during which vortex tilt increases by 10–30 km before the TCs reach a near-steady Category 1–3 intensity at the end of the simulations. TCs exposed to increasing shear during or just after rapid intensification tend to weaken the most. Backward trajectories reveal a lateral ventilation pathway between 8–11 km altitude that is capable of reducing equivalent potential temperature in the inner core of these TCs by nearly 2°C. In addition, these TCs exhibit large reductions in diabatic heating inside the radius of maximum winds (RMW) and lower-entropy air parcels entering downshear updrafts from the boundary layer, which further contributes to their substantial weakening. The TCs exposed to increasing shear after rapid intensification and an expansion of the outer wind field reach the strongest near-steady intensity long after the shear increases because of strong vertical coupling that prevents the development of large vortex tilt, resistance to lateral ventilation through a deep layer of the middle troposphere, and robust diabatic heating within the RMW.

Observations of Quasi-Periodic Electric Field Disturbances in the E Region before and during the Equatorial Plasma Bubble

Wave-like electric field disturbances in the ionosphere before the Equatorial Plasma Bubble (EPB) are the subject of numerous recent studies that address the issue of possible short-term forecasting of EPB. We report the observations of the Equatorial Quasi-Periodic-Electric field Disturbances (QP-EDs) of the Field-aligned Irregularities (FAI) in the E region before the EPB occurrence in the F region. They are observed from 30 MHz coherent scatter radar during the SpreadFEx campaign 2005 carried out in Brasil. The presently reported QP-EDs at the equatorial E region below an altitude of 110 km are undescribed so far. Though QP-EDs characteristics vary on a day-to-day basis, consistent features are their intensification before the EPB, and their simultaneous occurrence with EPBs. This study highlights the monitoring of QP-EDs in the short-term forecasting of EPBs and further reveals the robust energetics of vertical coupling between E and F regions.

Robust Design of Coupled Engineered Systems

Coupled Engineered Systems can be characterized by the inherent interactions among design decisions. These interactions define the influence that one design decision exerts over another and require appropriate method to model such interactions. Robust design enables designers to design a product or process that is relatively insensitive to uncertainties. Hence, robust design of coupled engineered systems enables designers to, (i) design engineered systems while accounting for interaction among design decisions and (ii) identifying design decisions that are relatively insensitive to uncertainties. In this paper, an appropriate method to model interactions and identify robust solution is presented. The interacting decisions are categorized into concurrent and hierarchical decisions and are respectively modeled with horizontal and vertical coupling. Based on the strength of interaction between these decisions, two types of interactions are defined, weak and strong interactions. To enable robust decisions in a coupled engineered systems, robustness metrics are defined and included as goals/constraints. The metrics considered in this work are to explore the solution space and manage uncertainty by considering the design of robust systems. The method has been tested on three design examples, that are, (i) design of a fender, (ii) design of a gearbox and (iii) design of a composite structure.

The thermodynamic structures of the planetary boundary layer dominated by synoptic circulations and the regular effect on air pollution in Beijing

To investigate the impacts of multiscale circulations on the planetary boundary layer (PBL), we have carried out the PBL thermodynamic structure field experiment with a Doppler wind profile lidar, a microwave radiometer, and a ceilometer from January 2018 to December 2019 in Beijing. We found that the direct regulatory effect of synoptic circulation worked through transporting and accumulating pollutants in front of mountains in the daytime, while the indirect effect of multiscale circulations worked through coupling mechanisms in the nighttime. The horizontal coupling of different-direction winds produced a severe pollution convergent zone. The vertical coupling of upper environmental winds and lower regional breezes regulated the mixing and diffusion of pollutants by generating dynamic wind shear and advective temperature inversion. We also found that the dominating synoptic circulations led to great differences in PBL thermodynamic structure and pollution. The cyclonic circulation resulted in a typical multilayer PBL characterized by high vertical shear (600 m), temperature inversion (900 m), and an inhomogeneous stratification. Meanwhile, strong regional breezes pushed the pollution convergent zone to the south of Beijing. The southwesterly circulation resulted in a mono-layer PBL characterized by low vertical shear (400 m) and inversion (200 m). The westerly circulation led to a hybrid-structure PBL, and the advective inversion was generated by the vertical shear of zonal winds. Strong environmental winds of southwesterly and westerly circulations pushed the severe-pollution zone to the front of mountains. There was no distinct PBL structure under the anticyclone circulation. The study systematically revealed the appreciable effects of synoptic and regional circulations on PBL structure and air quality, which enriched the prediction theory of atmospheric pollution in the complex terrain.