This article reports a statistical investigation on Chinese power grid. A new statistical parameter, averaged ratio of cycles, is suggested for describing the stratum structure of the grid. A dynamical model, which may reproduce the developing process of Chinese power grid, is also presented.
We suggest a self-adaptive model for a description of actor-collaboration. Suppose that the numbers of actors and directors increase as time progresses (with different velocity). Each of the people is randomly given a style coefficient and a famousness coefficient, which vary on time according to his achievements in every year. A director can conduct more films and an actor can be invited to perform in more films in condition they have a higher famousness coefficient. Our numerical simulation results show that the actor-collaboration network described by this model is both small-world network and scaling-free network. All the important statistical parameters obtained by the simulation are in a good agreement with the statistical results. We also suggest a new parameter, which is addressed as "degree of connexity". Its distribution shows a new power law.
The improved A * algorithm is a method of navigation path planning for articulated underground scrapers. Firstly, an environment model based on a mining Geographic Information System (GIS) map is established, and then combined with improved A * algorithm, the underground global path planning problem of the intelligent Load Haul Dump (LHD) is solved. In this paper, for the articulated structure, the method of expanding nodes by articulation angle is adopted to make expanded nodes meet the trajectory characteristics. In addition, collision threat cost is introduced in the evaluation function to avoid collisions between the LHD and the tunnel walls. As peran analysis of the simulation test to verify the effectiveness of the improved A * algorithm and a comparison with the traditional A * algorithm, the improved A * algorithm can enhance search efficiency. Acontrast of multiple sets of test parameters suggests that when the price weighted coefficient of collision is 0.2, the shortest path can be derived to avoid impact. Finally, tracking results indicate that the proposed algorithm for navigation path planning can maintain the tracking error to within 0.2 m in line with the structural characteristics of the scraper in the laboratory environment to realize the path planning of unmanned scrapers and trajectory tracking. Moreover, the algorithm can enhance the safety of scrapers and prevent roadway collisions. The feasibility and practicality of the proposed method is verified in this work.
This paper uses CFD (Computational Fluid Dynamics) numerically to simulate and calculate the axial flow pumps under different guide vane rotation angle and inlet angles and to conduct a comparative analysis of the inflow field. The results show that the influence of different guide vane rotation angles and inlet angles on the performance of the axial flow pump reflects in the operating conditions of large-discharge conditions. Adjusting the different guide vane rotation angles can significantly improve the efficiency of axial flow pumps. Moreover, the high-efficiency area of pump operation conditions is expanded nearly two times with the increase of the guide vane rotation angles under large-discharge conditions. At the same time, Under the design operating conditions, when the guide vane rotation angle is -2{degree sign}, the highest efficiency of the axial flow pump is 87.69%. However, under the linear change of the inlet angle of the guide vane, the highest efficiency of the axial flow pump can reach 87.71%. Finally, the model test verifies the reliability of the numerical simulation, and the research results are beneficial for improving the efficiency of the axial flow pump.
When the axial-flow pump is running, the blade angle is not fully adjusted or there are errors in the manufacture of the blades, which will lead to inconsistent blade placement angles during operation, and which will reduce the efficiency of the axial-flow pump. This paper uses the research methods of numerical simulation and model experiments to analyze the hydraulic performance and impeller structure characteristics of each flow components under different schemes when the angles of each blade of the S-type front shaft extension tubular pump device are inconsistent. The research phenomenon is that the guide vane greatly recovers the flow velocity circulation at the impeller outlet, reduces the hydraulic loss of guide vane, and widens the best efficiency range with an increase in guide vane blade angle. When the blade angle deviation occurs, the flow field of each blade channel affects each other, and the maximum decrease in the best efficiency is up to 7.78%, mainly due to the increased hydraulic loss in the outlet channel. The blade angle deviation will also affect the maximum equivalent stress and maximum deformation of the impeller, which is more obvious in large flow conditions. Inconsistent blade angles seriously affect the operating efficiency of the water pump and water pump device, and make the structural characteristics of the impeller worse.
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