Crustal thickness,V_(P)/V_(S) ratio,and shear wave velocity structures beneath Myanmar and their tectonic implications

The crustal structure in Myanmar can provide valuable information for the eastern margin of the ongoing IndoEurasian collision system.We successively performed H-k stacking of the receiver function and joint inversion of the receiver function and surface wave dispersion to invert the crustal thickness(H),shear wave velocity(V_(S)),and the V_(P)/V_(S) ratio(k)beneath nine permanent seismic stations in Myanmar.H was found to increase from 26 km in the south and east of the study area to 51 km in the north and west,and the V_(P)/V_(S) ratio was complex and high.Striking differences in the crust were observed for different tectonic areas.In the Indo-Burma Range,the thick crust(H~51 km)and lower velocities may be related to the accretionary wedge from the Indian Plate.In the Central Myanmar Basin,the thin crust(H=26.9-35.5 km)and complex V_(P)/V_(S) ratio and V_(S) suggest extensional tectonics.In the Eastern Shan Plateau,the relatively thick crust and normal V_(P)/V_(S) ratio are consistent with its location along the western edge of the rigid Sunda Block.

3D electromagnetic modelling for high-temperature superconducting dynamo flux pumps using T-A formulation

A high-temperature superconducting(HTS)dynamo flux pump can inject DC currents into closed-loop HTS magnets without contact.It enables the realisation of current-lead-free or even through-wall charging systems for high-field applications such as nuclear magnetic resonance/magnetic resonance imaging(MRI)magnets,fusion reactors and accelerators.Researchers have proposed many simulation models to understand the working principle of HTS dynamos,few of which are in 3D because of converging problems.Therefore,the influences of many key 3D parameters in the HTS dynamo are scarcely reported.The authors propose an efficient 3D modelling method of the HTS dynamo based on the T-A formulation.The rotating magnets are modelled by a ring-shaped permanent magnet with space-time-variant remanent flux density to avoid moving meshes.This,together with the T-A formulation,makes the 3D model efficient and universal.The accuracy of the model is verified by the experimental instantaneous and time-integrated dynamic voltages.Using this model,the authors present systematic case studies to thoroughly explore the influences of the key parameters of a dynamo flux pump on the dynamic voltage and losses.The proposed modelling method and results could significantly benefit the design and optimisation of HTS dynamos for high-field magnets.

High-accuracy optical time delay measurement in fiber link [Invited]

Optoelectronic components and subsystems such as optically controlled phased array antennas,distributed radar networks,interferometric optical fiber hydrophones,and high-speed optoelectronic chips demand highaccuracy optical time delay measurement with large measurement range and the capability for single-end and wavelength-dependent measurement.In this paper,the recent advances in the optical time delay measurement of a fiber link with high accuracy are reviewed.The general models of the typical time delay measurement technologies are established with the operational principle analyzed.The performance of these techniques is also discussed.

An 8–18 GHz power amplifier with novel gain fluctuation compensation technique in 65 nm CMOS

A wideband CMOS power amplifier with high gain and excellent gain flatness for X-Ku-band radar phased array is proposed in this paper. Excellent gain flatness is achieved with transformer based matching networks(TMNs), in which the gain fluctuation of an inter-stage matching network can be compensated by the proposed design methods. The circuit is fabricated in the TSMC 65 nm RF CMOS process. The proposed technique is verified by the measurement results, which show that the wideband PA achieves gain of 21-22.5 dB with only±0.75 dB gain fluctuation and 13-14.6 dBm flat output power between 7.5 and 15.5 GHz,and a little more ripple in the rest of the X-Ku band due to the inaccuracy of passive modelling at high frequency. The circuit delivers saturated and 1 dB-compressed output power of 14.6 and 11.3 dBm respectively at 13 GHz, for a maximal poweradded efficiency(PAE) of 23%.

Current knowledge of COVID-19:Advances,challenges and future perspectives

The pandemic of coronavirus disease 2019(COVID-19)has already evoked massive influence.The global pandemic has been ravaging the whole world for a year,with the number of confirmed human infection cases over 150 million and a death toll exceeding 3 million.Although the genomic sequence of the cognate pathogen SARS-CoV-2(severe acute respiratory syndrome coronavirus 2)has been quickly determined,there are still many unknown aspects,including the virus origin and evolution trend,and the effectiveness of current vaccines and drugs against the mutating virus.This review summarizes current knowledge and advances about COVID-19,including virus origin,transmission and infection,with the aim to improve the understanding of COVID-19 and provide a new perspective for future studies.