J. Z. Jiang

Design of a Magnetic-Geared Outer-Rotor Permanent-Magnet Brushless Motor for Electric Vehicles

This paper proposes a novel in-wheel motor, which artfully integrates a magnetic gear into a permanent-magnet brushless (PMBL) DC motor so that they can share a common PM rotor, hence offering both high efficiency and high power density. Moreover, the low-speed requirement for direct driving and the high-speed requirement for compact motor design can be achieved simultaneously. A 2-kW 600/4400-rpm magnetic-geared outer-rotor PMBL DC motor is designed and analyzed, which is particularly suitable for battery-powered electric motorcycles

A Magnetic-Geared Outer-Rotor Permanent-Magnet Brushless Machine for Wind Power Generation

This paper presents a novel permanent-magnet (PM) brushless machine for wind power generation. In this machine, an outer-rotor topology is engaged aiming at capturing wind power directly. In order to match the wind speed as well as produce electricity in a normal frequency, a conventional outer- rotor generator usually has a bulky size with a very large pole number. The purpose of this paper is to artfully integrate a high-speed PM brushless generator with a coaxial magnetic gear to achieve high power density. By using finite element method (FEM), the static characteristics are analyzed. Computer simulation for no-load and full-load operation is also conducted based on time-stepping FEM. The results are given to verify the validity of the proposed machine.

Effects of rapid thermal annealing on structure and luminescence of self-assembled InAs/GaAs quantum dots

Postgrowth rapid thermal annealing was used to modify the structural and optical properties of the self-assembled InAs quantum dots grown on GaAs substrates by molecular beam epitaxy. It is found that significant narrowing of the luminescence linewidth (from 78.9 to 20.5 meV) from the InAs dot layer occurs together with about 260 meV blueshift at annealing temperatures up to 850u2009°C. Observation of high-resolution transmission electron microscopy shows the existence of the dots under lower annealing temperatures but disappearance of the dots annealed at 850u2009°C. The excited-state-filling experiments for the samples show that the luminescence of the samples annealed at 850u2009°C exhibits quantum well-like behavior. Comparing with the reference quantum well, we demonstrate significant enhancement of the interdiffusion in the dot layer.

Comparison of Coaxial Magnetic Gears With Different Topologies

This paper quantitatively compares two coaxial magnetic gears (CMGs) with different topologies, namely, the CMG installed with radially magnetized permanent magnets (CMGRM) and the CMG installed with Halbach magnetized permanent magnets (CMGHM). By using the 3D finite element method, the end-effect and the performances of both CMGs are investigated. Analysis results show that the CMGHM can offer higher pull-out torque, lower torque ripple and lower iron losses than the CMGRM. Experimental results are also given for verification.

Characteristics of InGaAs quantum dot infrared photodetectors

A quantum dot infrared photodetector (QDIP) consisting of self-assembled InGaAs quantum dots has been demonstrated. Responsivity of 3.25 mA/W at 9.2 μm was obtained for nonpolarized incident light on the detector with a 45° angle facet at 60 K. The QDIPs exhibit some unique electro-optic characteristics such as a strong negative differential photoconductance effect and blueshift of the response peak wavelength.

Novel permanent magnet motor drives for electric vehicles

Novel permanent magnet (PM) motor drives have been successfully developed to fulfil the special requirements for electric vehicles such as high power density, high efficiency, high starting torque, and high cruising speed. These PM motors are all brushless and consist of various types, namely rectangular-fed, sinusoidal-fed, surface-magnet, buried-magnet, and hybrid. The advent of novel motor configurations lies on the unique electromagnetic topology, including the concept of multipole magnetic circuit and full slot-pitch coil span arrangements, leading to a reduction in both magnetic yoke and copper, decoupling of each phase flux path, and hence an increase in both power density and efficiency. Moreover, with the use of fractional number of slots per pole per phase, the cogging torque can be eliminated. On the other hand, by employing the claw-type rotor structure and fixing an additional field winding as the inner stator, these PM hybrid motors can further provide excellent controllability and improve efficiency map. In the PM motors, by purposely making use of the transformer EMF to prevent the current regulator from saturation, a novel control approach is developed to allow for attaining high-speed constant-power operation which is particularly essential for electric vehicles during cruising. Their design philosophy, control strategy, theoretical analysis, computer simulation, experimental tests and application to electric vehicles are described.

Dissemination, divergence and establishment of H7N9 influenza viruses in China

Since 2013 the occurrence of human infections by a novel avian H7N9 influenza virus in China has demonstrated the continuing threat posed by zoonotic pathogens. Although the first outbreak wave that was centred on eastern China was seemingly averted, human infections recurred in October 2013 (refs 3, 4, 5, 6, 7). It is unclear how the H7N9 virus re-emerged and how it will develop further; potentially it may become a long-term threat to public health. Here we show that H7N9 viruses have spread from eastern to southern China and become persistent in chickens, which has led to the establishment of multiple regionally distinct lineages with different reassortant genotypes. Repeated introductions of viruses from Zhejiang to other provinces and the presence of H7N9 viruses at live poultry markets have fuelled the recurrence of human infections. This rapid expansion of the geographical distribution and genetic diversity of the H7N9 viruses poses a direct challenge to current disease control systems. Our results also suggest that H7N9 viruses have become enzootic in China and may spread beyond the region, following the pattern previously observed with H5N1 and H9N2 influenza viruses.

A New Efficient Permanent-Magnet Vernier Machine for Wind Power Generation

This paper proposes a new outer-rotor permanent-magnet (PM) vernier machine for direct-drive wind power generation, which can offer low-speed operation to directly capture wind power, and enable high-speed rotating field design to maximize the power density. Compared with its mechanical gear counterpart, the proposed machine can eliminate the mechanical wear and tear as well as gear transmission loss, thus improving the generation reliability and efficiency. The key is to newly introduce the flux-modulation poles which can effectively modulate the high-speed rotating field of the armature windings and the low-speed rotating field of the PM outer rotor. By using the time-stepping finite-element method, the proposed machine can be accurately analyzed. Hence, its performances are quantitatively compared with other PM vernier machines, thus verifying its validity.

A Permanent-Magnet Hybrid Brushless Integrated Starter–Generator for Hybrid Electric Vehicles

A new permanent-magnet (PM) hybrid brushless (PMHB) machine is proposed and implemented as the integrated starter-generator (ISG) for hybrid electric vehicles (HEVs). It has the advantages of higher torque density than other PMHB machines and much wider speed range than other PM brushless machines. The key is to tune its dc-field winding current in such a way that three major modes of ISG system operation for HEVs, namely, engine cranking, battery charging, and torque boosting, can be achieved effectively. The finite-element method is employed to simulate its steady-state and dynamic performances. Finally, a 2-kW prototype is constructed and tested to experimentally verify the simulation results and the validity of the proposed ISG system.

Transient analysis of coaxial magnetic gears using finite element comodeling

In this paper, the transient performance of coaxial magnetic gears is firstly analyzed and discussed in literature. The key is to employ finite element comodeling in such a way that both the finite element model of the driving motor and the finite element model of the magnetic gear are coupled together to perform time-stepping finite element analysis. Hence, the dynamic interactions between the motor rotor and the gear inner rotor as well as the gear outer rotor and the external load can be taken into account. The proposed transient analysis verifies that the magnetic gear takes the definite advantage of overload self-protection, whereas reveals that it suffers from speed oscillations with significant time delays between the two rotors which are unacceptable for servomechanism.