Searching for cosmic string induced stochastic gravitational wave background with the Parkes Pulsar Timing Array

We search for stochastic gravitational wave background emitted from cosmic strings using the Parkes Pulsar Timing Array data over 15 years. While we find that the common power-law excess revealed by several pulsar timing array experiments might be accounted for by the gravitational wave background from cosmic strings, the lack of the characteristic Hellings-Downs correlation cannot establish its physical origin yet. The constraints on the cosmic string model parameters are thus derived with conservative assumption that the common power-law excess is due to unknown background. Two representative cosmic string models with different loop distribution functions are considered. We obtain constraints on the dimensionless string tension parameter $G\mu<10^{-11}\sim10^{-10}$, which is more stringent by two orders of magnitude than that obtained by the high-frequency LIGO-Virgo experiment for one model, and less stringent for the other. The results provide the chance to test the Grand unified theories, with the spontaneous symmetry breaking scale of $U(1)$ being two-to-three orders of magnitude below $10^{16}$ GeV. The pulsar timing array experiments are thus quite complementary to the LIGO-Virgo experiment in probing the cosmic strings and the underlying beyond standard model physics in the early Universe.Comment: 10 pages, 8 figures, 4 tables. Comments welcom

All-optical vector cesium magnetometer

Based on power modulation of a pump laser and precessional projection detection, we present an all-optical vector magnetometer of cesium, which has a demonstrated magnitude sensitivity of 80 fT/Hz 1/2 and an orientation sensitivity of 0.1°/Hz 1/2. In the device, four main factors are measured experimentally, which are the Larmor precession frequency of a polarized magnetic moment that depends on the modulus of the measured magnetic field only, two phase shifts and amplitude ratio of the precession projection in the two probe directions relative to the magnetic field orientation. This kind of magnetometer with high sensitivity in the range of the spatial angle is suitable for solving the inverse problem and geomagnetic navigation

Mechanism interference critical characterization and autonomous demodulation method of solid filling hydraulic support

Whether the self-demodulation of mechanism interference can be realized in the self-driven execution process of filling operation is the basis for the solid filling hydraulic support to achieve intelligence. Using the theoretical analysis method, taking the ZC5 160/30/50 type solid filling hydraulic support as an example, starting from the geometric and motion constraint relationship of the filling support mechanism, the orthogonal pose control index is established: the horizontal distance and vertical distance of the tamping hinge point top beam, which realizes the pose characterization of the rear top beam of the support under any working condition; The motion characteristics of the bottom-discharge conveyor of the filling support under various working condition factors were analyzed, and the orthogonal pose control index was established: the vertical distance and horizontal distance of the top beam of the bottom-discharge conveyor, which realized the pose characterization of the bottom-discharge conveyor under any working condition; Based on the pose control index of the rear top beam and the bottom-discharge conveyor, the landing position characterization index of the filling material on the coal seam floor during the discharge process is further obtained: the discharge center distance, which realizes the landing position characterization of the filling material under any working condition; the connection relationship and easy interference position of the mechanism action and pose adjustment in each stage of the filling operation process are analyzed, based on the orthogonal pose control index, the interference critical control equation of the discharge and typical collision position under any working condition is established by using the projection method; taking the tamping mechanism rotation angle and tamping cylinder stroke as the characterization of the interference critical curve under typical working conditions, it is proposed to use the three-zone distribution characteristics of “interference zone, easy interference zone, and non-interference zone” to characterize the interference critical degree, and give the demodulation path of each interference state; based on the interference critical control equation, interference three-zone distribution characteristics and the connection relationship of mechanism action and pose adjustment in the filling operation process, an interference state autonomous identification method is proposed: using angle sensor and stroke sensor to obtain the real-time rotation angle and stroke of the tamping mechanism, substituting into the interference critical equation of each easy interference position to obtain the theoretical value and interference critical curve of the tamping mechanism rotation angle or stroke in that position, judging the position of the actual value on the interference critical curve three-zone distribution diagram can realize the autonomous discrimination of interference position and state, and autonomous demodulation can be realized according to the interference three-zone distribution curve diagram; based on the interference position and interference state autonomous identification method, the interference autonomous discrimination and demodulation algorithm is designed. The research results provide new reference indicators for the pose characterization of the filling hydraulic support mechanism, provide basic criteria for the intelligent obstacle avoidance and demodulation of mechanism interference, and provide algorithm basis for the self-driven execution of the filling operation of solid intelligent filling