Equal-time kinetic equations in a rotational field

We investigate quantum kinetic theory for a massive fermion system under a rotational field. From the Dirac equation in curved space we derive the complete set of kinetic equations for the spin components of the covariant and equal-time Wigner functions. While the particles are no longer on a mass shell in general case due to the rotation-spin coupling, there are always only two independent components, which can be taken as the number and spin densities. With the help from the off-shell constraint we obtain the closed transport equations for the two independent components in classical limit and at quantum level. The classical rotation-orbital coupling controls the dynamical evolution of the number density, but the quantum rotation-spin coupling explicitly changes the spin density. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

Application of a new type of six-component seismometer for underground anomaly detection

<p>A new type of portable six-component seismometer is invented and used in the development of a seismic imaging method for shallow subsurface anomaly detection. This new six-component seismometer contains a mini-MEMS-array for acceleration and rotational velocity measurements. The self-noise for acceleration measurement is about 8 µg/√Hz, and the self-noise for rotational velocity measurement is about 5 µrad/s/√Hz. The frequency band is DC-1000 Hz. Different from the traditional seismic imaging methods that require the deployment of an array of either one-component or three-component seismometers, our imaging method is established based on the data recorded at individual six-component seismometer. Because the rotational field (i.e., the curl field) gives information about the spatial gradient of a seismic wavefield, so the translational field together with the rotational field can be used to derive the frequency-dependent velocity (i.e., dispersion) of the formation right beneath a seismic station. This single station velocity inversion approach delivers localized subsurface velocity information, making it suitable for imaging of small-scale underground anomalies. Especially, the Rayleigh wave dispersion is used in our method as Rayleigh wave is generally the dominant signal in surface seismic data. An underground velocity model can be immediately constructed by consolidating the dispersion curves derived from individual receivers. In our study, we first demonstrate the accuracy of our imaging method through numerical modeling of various scenarios of subsurface anomalies and then conduct an experiment to further verify the performance of our self-invented six-component seismometer and the field applicability of our imaging method.</p>

A Novel Rotational Field Eddy Current Planar Probe with Two-Circular Sector Pickup Coils

A new rotational field planar eddy current probe is proposed. The probe is combined with two orthogonal driver traces and a pickup coil that includes two-circular sector windings with series connection. Rotational eddy currents are induced by driver traces of the same amplitude and frequency, but fed with 90° phase different alternating exciting currents. An experimental demonstration using prototypes of the probes and artificial defects showed that the probe with a two-circular sector pickup coil is more sensitive for detecting the short defects than the probe with a circular pickup coil.