Papers by Keyword: Stability

Abstract: There is not any calibration specification or verification regulation for the milliampere-second meter, a very important instrument for preventive maintenance and calibrating the X-ray machine [1][2], is used to measure the value of the product of tube current and exposure time. To solve the problem that the traditional method can not offer the same standard value in different times, this paper presents a method for calibrating the milliampere-second meter by using a signal generator and a digital meter. It shows that the new method has good repeatability and stability.

Abstract: A quasi static finite element method for assessing cyclic bearing capacity of semi-circular guiding dike on natural or reinforced soft clay foundation is developed by combining the concept of cyclic shear strength with D-P yield criterion. Then the proposed method is numerically implemented in the framework of the large universal finite element software. Combining with a practical engineering, the stability of semi-circular guiding dike before and after foundation reinforcement is analyzed. The results showed that the foundation bearing capacity decreases obviously when cyclic weakening effect of soft foundation was considered, so cyclic weakening effect of soft foundation under cyclic wave load should be considered in practical design. Moreover, foundation reinforcement has an obvious effect to increase foundation bearing capacity.

Abstract: The characteristics of explicit numerical integral method is without iteration, and the characteristics of inexplicit numerical integral method is unconditionally stable. The traditional CD-Newmark method has the shortcoming of the bigger upper frequency leads to a small time step, a modified combined integral method named MCD-Newmark release the fixed DOF of numerical substructure, then obtained the parameters range of stable condition of experimental substructure, and the unconditionally stable of numerical substructure is also researched,then the strict stability conditions of the traditional CD-Newmark algorithm is resolved. The study provides reference for structural seismic test.

Abstract: According to the three characteristics of deep surrounding rock: high stress, high temperature and high seepage, the three field coupling control equation of temperature-stress-seepage are established, the finite element method is used for solution. Considering stress transference of surrounding rock after creep and deformation, the finite element incremental equations is deduced. Combining the finite element method and strength reduction method, The defect of deep surrounding rock stability that never quantitatively assess before was overcome. The proposed calculation method is applied to project, the analysis results show that the proposed method is feasible.

Abstract: Single-layer lattice dome as a main form of large span space structure, its stability is the key of the research.Up to now, study on the stability of the single-layer lattice dome mainly depends on the overall stability, stability of the member buckling for single-layer lattice dome as a whole research is less. In this paper, based on the K8 single-layer lattice dome as an example, considering the node flaws and member, on the basis of the single-layer lattice dome of the joint at different location of the member to be weakened, to make it before the single-layer lattice dome of the overall instability buckling, comparative analysis of different location of single member buckling of the effect on the stability of the whole single-layer lattice dome.

Abstract: The stability of the last train connection under delays directly reflects the coordination of urban rail network. Based on the connection of scheme of last trains, this paper analyzed of the impact of the delay on the transfers and established a static evaluation index system of the impact on transit network. Furthermore, the paper evaluated a rail transit network under different last train delays. Ultimately, the evaluation results could be got by this method, which could be used to analyze the trend of the evaluation results over delay time.

Abstract: This paper investigates the problems of tracking control for switched fuzzy systems. Based on the state-dependent switching method, sufficient conditions for the solvability of the tracking control problem are given. We use single Lyapunov function technique to design a tracking control law. The controller design problem can be solved efficiently. A numerical example is given to show the effectiveness of our method.

Abstract: The effect on the stability of the analysis of time lag effect of the milling system，Reveals the root cause of the milling type regenerative chatter occurs，Milling type regenerative chatter is derived from the time-delay feedback within the system，Application of routh criterion and Fourier analysis of chatter in milling system before and after the change of rigidity and damping system, it is concluded that the limit cutting depth.

Abstract: Keeping the water-repellent stability of superhydrophobic surface is necessary in application. Based on the total reflection of Cassie interface and vacuum technique, the superhydrophobic stability of the lotus leaf and an artificial material was investigated. The results show that during the Cassie-Wenzel transition, primary wetting transition occurs at a certain pressure that in accordance with theoretical prediction. However, when the air film is entrapped between microstructures, stability of water-repellency was greatly enhanced, and part of the wetting transition can be recovered when the pressure was released. Due to the micro-and nanoscale hierarchical structures, the lotus leaf shows better water-repellent stability and dewetting property than the artificial superhydrophobic surface when the hydrostatic pressure was applied and released.

Abstract: The stability of rectangular thin wall with 3 simple supported sides and 1 free side, subjected to nonlinear distributed stress, is analyzed. Galerkin method is applied in order to study the internal relationship between the critical thickness and nonlinear stress. Under the same stress circumstance, as the a/b ratio gets larger, the critical thickness for the thin wall structure getting buckled grows too. The influence of different material properties on the critical thickness is also researched. The method proposed in this paper is applicable for more complicated distributed stress and also can provide some reference criterion for design of thin wall structure.