High-precision satellite clock bias (SCB) data is a critical product for satellite navigation systems to realize accurate navigation, positioning and timing. Unlike other satellite navigation systems, the precise SCB data for the BeiDou Navigation Satellite System (BDS) are mainly determined by two methods, the Two-Way Time Transfer (TWTT) method and the Orbit Determination and Time Synchronization (ODTS) method. Awareness of the data variations obtained from different methods can be used to improve clock modeling performance, and be beneficial to higher-rate GNSS positioning and for predictions in real-time applications. We describe a comprehensive method to analyze the systematic and random characteristics of BDS SCB data obtained from TWTT and ODTS and discuss possible causes of observed variations. Some new conclusions are drawn: the data continuity of TWTT is highly related to satellite orbit types; affected by orbit error and other factors, the fitting residuals (RMS) of ODTS is 0.2 ns worse than that of TWTT on average, while the fitting precision of TWTT is 0.49 ns. There are up to 8ns periodic fluctuations in the mutual agreement between TWTT and ODTS data. The stability result shows a remarkable effect of flicker phase modulation (FLPM) noise can be seen in the period of 300-1000 s in TWTT data. All the BDS satellites display more complex, nonpower law behavior due to the effects of periodic clock variations.

There are a large number of unstable rocks whose stability are controlled by soft base layer in the mountainous areas of southwest China, and they have caused serious harm to people's lives and local economic development. Therefore, it is of great practical significance to study the stability and failure mechanism of such unstable rock. Taking the in Wulong District, Chongqing as an example, this paper analyzes the failure probability and reliability index of the unstable rock under different conditions by use of Monte Carlo method and on this basis, the sensitivity of the stability of dangerous rock mass to the main influencing factors is analyzed. The results show that the stability coefficient, failure probability and reliability index of are equal to 1.151, 26.245% and 0.642 under natural condition. However, the stability coefficient of decreases rapidly and the reliability index and failure probability increase obviously when combined with other factors such as rainfall or earthquake. The sensitivities of the influencing factors of the unstable rock are from top to bottom internal friction angle of soft layer, the horizontal seismic force, the cohesion of soft layer, the water content in the crack and the weight of soft layer. The research results can provide some reference for the stability analysis and engineering prevention of such unstable rocks.

With a high proportion of renewable energy being connected to the grid, the stable operation of the power system has been severely challenged. Conventional coal-fired power units need to take measures to compensate for random fluctuations in renewable power generation. This study introduces the battery energy storage system (BESS) to the coordinated control system (CCS) of the coal-fired units to improve the load regulation. Firstly, the dynamic models of boiler-turbine unit and BESS are set up. Furthermore, an improved coordinated control system combined with boiler, turbine, and BESS is designed. A dual controller that consists of BESS and fuel control is proposed to improve the power ramp rate. Finally, a power step simulation in a 330 MW coal-fired power unit is conducted. The simulation results show that the power ramp rate is 60 MW/min and the AGC performance index reaches 7.68 with the improved strategy.

To study the influence of the spatial configuration of two tandem ground-effect hydrofoils on the power-extraction efficiency, this paper uses the overset grid method to establish a two-dimensional numerical calculation model based on the STAR-CCM+ software. The comparison of the numerical results of the single hydrofoil verifies the validity of the method. This paper systematically analyzes the influence of ground effect on the energy extraction performance of the hydrofoil, and further studies the changes in the hydrodynamic performance and energy extraction efficiency of the hydrofoil when two ground effect hydrofoil are tandem. The results show that: compared with a single ordinary hydrofoil, the energy extraction efficiency of the ground-effect hydrofoil is slightly improved. When the hydrofoil is close to the wall, its lift will be significantly increased due to ground effect. When two ground effect hydrofoils are tandem with a phase difference of 180 deg, the vortex generated by the upstream hydrofoil will significantly increase the absolute lift of the downstream hydrofoil, but the energy extraction efficiency will be reduced significantly.

The limited regulation capacity in the integrated energy community is a key factor restricting the development of the community-based integrated (distributed) energy system. Based on this, a model for optimal sharing of day-ahead energy in multi-communities considering the matching degree of source-load curves between communities is proposed. Firstly, the relationship between energy supply and multi-energy flow is analysed concretely in a single community. A mathematical model that includes electric vehicles and multiple energy conversion equipment is built, then, an objective function minimizing the cost of energy purchase, equipment operation and maintenance, and EV battery loss is established. Secondly, the comprehensive Spearman constant and Euclidean distance matching index based on photovoltaic and load data among the communities are considered to optimize the multi-community operation efficiency with the goal of minimizing the energy interaction cost. Finally, in a 3-community simulation system simulation, results show that the multi-energy sharing mode can effectively improve the overall economy of the system and the photovoltaic consumption capacity. The introduction of matching index also improves the energy transmission efficiency, verifying the rationality of the proposed model.

Based on the revised ALONSO model, combined with the ABAQUS software platform, this paper compiled the USDFLD subroutine and obtained the stress-strain curve and the axial strain-volume deformation by simulating the triaxial shear test of the unsaturated soil to control the suction and confining pressure. The curve verifies the accuracy and reliability of the algorithm. The research results show that: (1) When the suction is the same, the higher the confining pressure is, the higher the yield point of the soil sample is. According to the comparison between experiment and simulation, the modified Alonso model can reflect the nonlinearity of the stress-strain relationship of the reshaped unsaturated soil sample and its plastic flow characteristics; (2) Compared with saturated soil, unsaturated soil has a higher yield point as a result of the suction. And the larger the suction is, the higher the yield point is, which proves that the model can simulate the influence of unsaturated soil liquid relative to the solid phase.