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Surface charge accumulation on insulator is one of the main restrictive factors of DC gas insulated pipeline transmission line (DC-GIL). The current research on the accumulation and dissipating mechanism of surface charge has the following deficiencies on the solid side. Firstly, the volume conductivity of insulators are usually taken as a fixed value, so the comprehensive effect of electric field intensity and temperature on this parameter is not taken full consideration. Secondly, the calculation models of current density and surface charge density on the solid side ignore the effects of dielectric relaxation, which also affects the calculation of surface charge density. So in this paper, the mathematical model of solid conductivity based on electric field and temperature has been studied, and the model of volume current density and charge density has been reestablished in combination with dielectric relaxation. When the solid side is dominant, the temperature, electric field and dielectric relaxation characteristics of surface charge accumulation and dissipation are simulated and analyzed. The results indicate that the steady state value of surface charge density increases exponentially with the increase of the initial value of electric field and temperature, and the charge saturation time also increased. The increase of the electric field intensity change rate leads to an exponential decrease of the steady state value of surface charge density and the saturation time. The saturation time increases by 3% and the steady state value of surface charge density increases by 0.9% in the influence of dielectric relaxation. Considering only the charge dissipation of the solid side, the higher the temperature, the more favorable for the dissipation of the surface charge. Moreover, the dissipation rate increases exponentially with temperature. The effect of field strength on charge dissipation depends on the initial charge density. Dielectric relaxation slows the dissipation rate by 28%.

In this paper, multiple-symbol differential detection (MSDD) is applied to the differential single-carrier frequency-division multiple access (SC-FDMA) system. Both time domain and frequency domain MSDD are investigated to compensate for the performance loss of conventional differential detection comparing with coherent detection. The decision metric of time and frequency domain MSDD for SC-FDMA are derived respectively. Simulation results demonstrate the effectiveness of MSDD in some situations.

The traditional model reference adaptive system (MRAS) is of parallel configuration. By representing the reference model as an equivalent closed-loop subsystem, these two subsystems can share a controller virtually. An embedded structure of MRAS is thereby presented. In this paper, two approaches are developed for designing the adaptive laws. The adaptive law based on Lyapunov stability theory is designed for low-order systems. The adaptive law based on the recursive least-square (RLS) algorithm is suitable for both low- and high-order systems. The RLS-based adaptive law provides a quick convergence rate for the controller adaption. MRAS with RLS-based adaptation law performs better in trajectory tracking and model following. Simulation results show the effectiveness of the proposed method.