To protect against the destruction of cultural relics, the artificial neural network and the toolbox of MATLAB artificial neural network (ANN) are applied to set up an intelligent model of the anchoring force prediction with consideration of the bolt diameter, the bolt length, the angle of inclination, the grouting body intensity, the aperture and the carbon fiber wrapped spacing, based on the in-situ test of the anchorage force of the CFRP (carbon fibre reinforced plastics)-bamboo bolt used in the protection of a certain earth site in Xinjiang. And by learning the samples from the in-situ test, the applicability and the feasibility of the method are checked. Based on the calculation results, the sensitivity of influencing factors on the anchorage force of the CFRP-bamboo bolt is analyzed by using L25(56) orthogonal table, which may provide a reference for similar reinforcement engineering practical applications.
An analysis method of the aperture throttle based on turbulence state is presented in this paper. Three-layer velocity distribution expressions of the fluent in the turbulence state are obtained based on the boundary layer theory. The aperture flow equation for parallel-plates is deduced using the integration theorem and is verified by the comparison with the numerical solution of the CFD. The turbulence equations of the con-centric annular aperture are deduced based on this equation, and the influences of different physical parameters on the aperture pressure difference and the flow are analyzed, which can serve as the aperture throttle equation in the turbulence state for applications in engineer designs and for the improvement of the design accuracy of the throttle valve.
With the fast development of the domestic high speed railway, the very high running velocity of the trains causes a series of aerodynamic problems, including the problems of the aerodynamic drag, the cross wind effect, the train passing effect, the tunnel effect and the aerodynamic noise. It is very important to combine various investigation technologies, such as the model testing, the real train measurements and the numerical simulation to study the aerodynamics of the high speed train. This paper reviews the domestic and overseas aerodynamics studies of the high speed train, and the development directions.
The electromagnetic hydrodynamics are widely applied in aeronautics and astronautics. The mag-netohydrodynamics (MHD) technology, especially, the technology of the MHD acceleration is a hot topic in this area. This paper analyzes the basic principle of the MHD acceleration, and then reviews its studies on three main aspects, that is, the MHD acceleration project, the hypersonic MHD wind tunnel development and the MHD propulsion explorement, including the key techniques and difficult problems. For the supersonic airflow acceleration technology based on the MHD, it is shown that the studies in the world cover a wide field, but the domestic studies lag behind, concentrating on numerical investigations; the mechanism of the MHD acceleration needs further studies; and there are still some engineering bottlenecks need to be solved.
In order to accurately assess the aerodynamic performance of high speed trains in passing each other under the crosswinds, this paper studies the effects of the uniform crosswind and the lower atmospheric boundary layer crosswind on the train operating performance by means of the computational fluid dynamics, and analyzes the flow structure, the crossing pressure pulse, and the aerodynamic forces. Numerical results show that the crossing pressure pulses under these two types of crosswinds are different, but their amplitudes show no significant difference. The aerodynamic forces under the uniform wind are greater than the corresponding numerical values under the boundary layer crosswind, which means that using the uniform wind field for the evaluation will overestimate the aerodynamic forces. This paper provides some guidances for the safety evaluation of traveling high speed train and some understanding for the complex flow field in the complex running scene.
The analytical velocity potential and the wave height of the sloshing liquid with horizontal hydro-static surface are obtained from Laplace equations. It is observed experimentally that the mode shapes of a curved hydrostatic surface in a microgravity condition do not appreciably differ from the mode shapes of a flat hydrostatic surface. To obtain sloshing characteristics in cylindrical containers in microgravity conditions, the mode shapes of a flat hydrostatic surface are used to approximate the curved hydrostatic surface. After truncating the first five modes of sloshing, the dimensionless coupling dynamics equations for the sloshing liquid and the main rigid body are derived by the Lagrange equation. The bifurcations of the sloshing modes are simulated for the amplitude and the frequency of the force variations. The effects of the system parameters, such as the Bond number, the contact angle, the contact angle hysteresis, the liquid height, the frequency ratio, and the mass ratio, and of the periodic form and the direction of the force, on the bifurcations of sloshing modes are studied.
This paper studies the variations of the freezing pressure of the freezing walls in the thick clay strata, against the temperature change by the field measured results. Combining the analysis of actual measured data with the numerical model of the ADINA FEM method, the artificial freezing stress field is simulated to provide a reference for the engineering practice.
The free vibration equation for the horizontal elastic support arch structures is established by the flexibility method. The additional inertia force of the arch foot mass is taken into account. The influence of the horizontal elastic support on the inherent characteristics of the two-hinged arch is analyzed. The natural frequency is shown to be decreased. The influence is the largest at the rise span ratio of 0.1. The horizontal elastic support affects the vibration modes. Especially for higher modes, the horizontal elastic support arch vibrates completely in accordance with the circular beam. The vibration internal force characteristics of the circular beam and the two-hinged circular arch are analyzed. The concept of the flexibility coefficient is put forward. The critical flexibility and the corresponding critical stiffness are obtained.
Due to the difference of their environments, the deep and shallow buried tunnels show different deformation patterns in the excavation. This paper simulates the deformations of the deep and shallow buried soft rock tunnels with different stress boundary conditions, rock mechanical properties and section shapes of tunnels. The calculation results might be used for the selection of the tunnel section shapes, and the excavation support of tunnels.
The in-plane stability of a deep circular arch under uniform radial pressure is studied by using the small deformation theory solutions and the numerical solutions of the finite element software ANSYS. The application examples indicate that the stability of the arch under radial pressure is superior to that under hydrostatic pressure with small central angle and is inferior to that with a large central angle.
Although the choice of shape parameters in the radial PIM (point interpolation method) is a hot issue in the numerical computation based on the element-free method and some empirical formulas of the shape parameters are proposed, but how the influence domain affects these shape parameters remains to be studied. In this paper, the effect of the MQ (multi-quadrics) radial basis function's shape parameters on the errors of the element-free method is studied. The variations of the shape function's derivative with the shape parameters and the symmetrical and unsymmetrical node distributions around the evaluation point are analyzed together with the effect of the size of the influence domain on the error, and based on the analysis, the relationship between the errors and the shape parameters and the range of the suitable influence domain are obtained.
Based on the micromechanics, a general method of determining the elastic constants of trans-versely anisotropic composites is proposed. For long-fiber reinforced composites, the Young's modulus, the two transverse elastic moduli, the shear modulus and the Poisson's ratio are determined by this method, which demonstrates the applicability and the accuracy of the present method, as an analytical approach for the esti-mation of material properties. This is a typical example for the study of composites mechanics, related with the micromechanical method.