Papers by Keyword: Stability

Abstract: The copper catalyst was prepared by coprecipitation method and used for treating the Acid Red B wastewater with catalytic wet air oxidation method. Results showed that when (NH₄)₂CO₃ was used as precipitating agent, and the concentration was 0.6mol / L, reaction temperature was 40 °C, calcination temperature was 700 °C, the copper catalysts prepared by direct addition method showed better stability in treating the wastewater.

Abstract: In this paper the elastic load-carrying capacity of the stability columns, which provide lateral support to leaning columns, is investigated. The solution to the effective length of the columns is obtained by using of differential equations. The influences of the leaning columns on the stabilizing columns are studied and the nomo-graphs for determining effective length of the supporting columns are made for practical using. The effective length of columns can be quickly determined by using the nomo-graph, which shows intuitively the trends of the curves in the nomo-graph owing to some relevant parameters.

Abstract: The solution of 2D parabolic equations based on the alternating direction implicit scheme is one of the important methods to solve high dimension problems.A alternating direction implicit scheme is presented in this paper, the stability and convergence of the alternating direction implicit scheme is to be proved, and the scheme of the errors are analyzed. Through the numerical experiment, the result shows that the method has good stability and high precision.

Abstract: This article is devoted to the forward Euler difference method for the parabolic equation. In this paper, a forward Euler difference scheme is derived. It is shown that the forward Euler difference scheme is convergence and stability. Moreover, a numerical experiment is conducted to illustrate the theoretical results of the presented method.

Abstract: Temporal linear stability of a compressible axisymmetric swirling jet is investigated. The present work extends a previous analysis to include the effects of swirl number on the stability of flow dynamics. Results obtained show that the optimal growth rate of disturbance for azimuthal wavenumber n = -1 is larger than that for n = -2 while the corresponding frequencies for both n increases as axial wavenumber increases. As swirl number q increases, the optimal growth rate of disturbance also increases. What is more, there is an optimal swirl number for small axial wavenumbers, which is different from the situation for medium and large axial wavenumbers.

Abstract: Back propagation (BP) neural network is used to approximate the dynamic character of nonlinear discrete-time system. Considering the unmodeling dynamics of the system, the weights of neural network are updated by using a dead-zone algorithm and a robust adaptive controller based on the BP neural network is proposed. For the situation that jumping change parameters exist, multiple neural networks with multiple weights are built to cover the uncertainty of parameters, and multiple controllers based on these models are set up. At every sample time, a performance index function based on the identification error will be used to choose the optimal model and the corresponding controller. Different kinds of combinations of fixed model and adaptive model will be used for robust multiple models adaptive control (MMAC). The proof of stability and convergence of MMAC are given, and the significant efficacy of the proposed methods is tested by simulation. This paper deals with the problem of delay-dependent stability criterion of delay-difference system with multiple delays of cellular neural networks. Based on quadratic Lyapunov functional approach and free-weighting matrix approach, some linear matrix inequality criteria are found to guarantee delay-dependent asymptotical stability of these systems. And one example illustrates the exactness of the proposed criteria.

Abstract: This paper presents a modified harmony search (MHS) algorithm for solving numerical optimization problems. MHS employs a novel self-learning strategy for generating new solution vectors that enhances accuracy and convergence rate of harmony search (HS) algorithm. In the proposed MHS algorithm, the harmony memory consideration rate (HMCR) is dynamically adapted to the changing of objective function value in the current harmony memory. The other two key parameters PAR and bw adjust dynamically with generation number. Based on a large number of experiments, MHS has demonstrated stronger convergence and stability than original harmony search (HS) algorithm and its two improved algorithms (IHS and GHS).

Abstract: On the basis of Umansky box-girder torsion theory, the software of ANSYS is applied to simulate related engineering model. In considering a variety of live load conditions, the lateral stability of multi-span single-pier variable cross-section box-girder under torsion eccentric load is analyzed. Analysis results reveal that under different working conditions, the factors affecting the transverse stability of the bridge and the proportion of the value on each, such as gravity, the span ratio and the distance between support are different; When the overload ratio is 2 times larger, the bridge stability safety coefficient decreases along the curve and changes rapidly. In the future design of this kind of bridge, the overall lateral stability should be paid much more attention. Some methods and suggestions about how to prevent the emergence of security and stability problems are put forward in the end.

Abstract: Compression deformation will cause a micro-spring to buckle, and structural parameters, constraint conditions and structural forms of a micro-spring will affect its critical load and buckling mode. In order to study the influence on the micro-spring’s stability caused by structural forms and find a structure to improve its critical load in the end, this paper designs a new kind of parallel micro-springs, which consists of two same-structured S-shaped planar micro-springs. We have carried on eigenvalue buckling analysis on the parallel micro-spring by software ANSYS, and have gotten its six orders’ buckling mode. Because the critical load of the parallel micro-spring may change with the length of the beam connecting the two sub-springs, this paper studies the effect of the beam’s length on the parallel micro-spring’s critical loads and buckling mode. From comparing the analysis results between parallel micro-spring and single micro-spring with same stiffness, this paper concludes the stability’s degree of improvement.

Abstract: We conduct first-principles total-energy density functional calculations to study the ScB₂ (0001) surfaces. The optimized surface structures and electronic properties are obtained. The results show that Sc-terminated surface is thermodynamically more favorable in most of range. The relaxations indicate that it is mainly localized within top three layers and it is less relaxation for Sc-terminated surface. The surface induced features in DOS disappear slowly for the B-terminated surface but vanish rapidly for the Sc-terminated surface. For the Sc-terminated surface, it shows strong metallic property. Simultaneously, both termination surfaces are found charge accumulation relative to the idea surface. Sc-B bonds are strengthened result in the outermost interface spacing are all contracted.