Analysis and correction for systematic error of ionospheric monostatic system

Abstract

In the ionospheric monostatic system the echo is affected by systematic error. A real-time method using the special characters of direct wave existing in monostatic radar to correct systematic error is advanced. In the condition of large-amplitude direct wave, time delay of maximum amplitude of echo is considered as system time delay; in the condition of small-amplitude direct wave, the mathematical model of time delay error is built to approach after direct wave test. And a method using large-amplitude direct wave to correct phase distortion is advanced. It achieves good effect using this method in practice, which can improve the quality of sound result obviously.

Numerical Simulation of Ionospheric Disturbances Due to Rocket Plume and Its Influence on HF Radio Waves Propagation

“…In the case of a point source, the density distribution function of the release is n(x, y, z, t). Assuming that the same amount of neutral gas is released at any release point on the rocket trajectory, the approximate solution of the diffusion equation of neutral gas in the case of multi-source release can be obtained as [13]:…”

“…Affected by the effects of electron and ion density gradient, magnetic field, electric field, neutral wind, ionospheric disturbance zone collision, etc., plasma will drift, and its detailed force condition is more complicated. In the F layer of the ionosphere, the ion cyclotron frequency is much larger than the collision frequency of ion-ion and ion-neutral molecules; thus, we suppose that plasma is constrained to move along geomagnetic field lines, for the fact that its force is assumed stronger than others in the ionosphere, and ignoring the influence of magnetic deflection angle, the plasma diffusion equation can be obtained [13]:…”

The Analysis of Ionospheric TEC Anomalies Prior to the Jiuzhaigou Ms7.0 Earthquake Based on BeiDou GEO Satellite Data

“…The disturbances of ionospheric TEC have been studied extensively using BeiDou satellite data. However, the existing research mainly focuses on the effects of space weather, such as solar and geomagnetic activity [25,26]. Wu et al [27] investigated the variation characteristics of ionospheric TEC based on specified piercing points using GEO observation data.…”

Chinese grammatical error correction based on the BERT-BiLSTM-CRF model

“…However, exposure bias (EB) might affect complex semantic error models, and the seq2seq neural network inference speed is vastly inferior to that of sequence tagging. Therefore, Liang et al [2] suggested implementing sequence tagging to address CGEC problems, as Wang et al [3] proposed to split the correction of Chinese text into two stages. First, a sequence tagging model is applied to predict the location of the erroneous words and the type of errors, after which the predicted erroneous words are corrected later by implementing confusion sets and machine learning.…”