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In order to obtain the dynamic stress of invert and its filling in the high-speed railway tunnel under the vibration load of the train, this paper uses the field measurement method to arrange the resistance strain gauge inside the invert of the Lanzhou–Urumqi high-speed railway Fuchuan tunnel. The dynamic stress of the invert and its filling was measured, and the measurement results were verified by numerical analysis, the results obtained by the two were consistent. The results show that under the action of CRH5 electric multiple units, the dynamic stress time history curve of the invert and its filling has 16 peaks, with V-shape on both sides and W-shape in the middle. When the train load speed is constant, the dynamic stress in the tunnel invert and invert filling decreases with the increase of the depth. The dynamic stress at 0.5 m below the track bed is attenuated by about 23.1% compared to 0.2 m, the dynamic stress at 2.0 m below the track bed is attenuated by 67.5% compared to 0.2 m. Tunnel invert and its filling are the main carriers of train vibration load. The dynamic stress attenuation law of the invert and its filling conforms to the exponential function distribution. Through the data fitting, the calculation formula of the dynamic stress in different depths is given. The research results provide a new method for obtaining the dynamic stress of the invert and its filling in high-speed railway tunnel. [ABSTRACT FROM AUTHOR]

Highlights • Finite element models of BBC joints were established and verified. • The uniaxial compression bearing capacity of the BBC joint was defined. • Influence factors on the ultimate load of BBC joints were studied. • Formulae of the ultimate load of BBC joints were proposed. Abstract Bolted ball-cylinder joint (BBC joint) is an innovative joint system applied in non-purlin spatial truss structures. According to the theoretical analysis, the fitting formulae of the uniaxial compression bearing capacity of the BBC joint were proposed in this paper. Experiments on 5 BBC joints were introduced briefly at first. The finite element (FE) models were established using ABAQUS and verified by the experimental results. The numerical and experimental results agreed well with each other in failure modes and load-displacement curves. Subsequently, parametric study was conducted to investigate the effects of the dimensions of hollow cylinder, rectangular tube and ribbed stiffener on the bearing capacity of the joint. Finally, the formulae to estimate the uniaxial compression bearing capacity of the BBC joint were obtained by means of regression analysis. And the increasing coefficients of bearing capacity were obtained on the basis of parametric study. The calculation results were verified against the experimental and numerical results. It is indicated that the practical calculation formulae can estimate the uniaxial compression bearing capacity accurately. [ABSTRACT FROM AUTHOR]

This paper presents a novel computing method of optical efficiency fitting formulas and its applications for parabolic trough solar collectors, by combining the Monte Carlo ray-tracing methodology with the population-based particle swarm optimization algorithm. The expressions of the optical efficiency fitting formulas are deduced by means of analyzing the Monte Carlo ray-tracing data samples with a variable reduction technique, while the fitting formula coefficients are obtained using the particle swarm optimization algorithm. The computing time of the annual optical efficiency reduces to less than 10 −7  s, from about a day as previously calculated by a once powerful Monte Carlo ray-tracing model. Thus, it makes the once time-consuming long-time average optical efficiency calculations or corresponding population-based optimizations much more feasible and efficient. A dynamic particle swarm size factor is also proposed to improve the particle swarm optimization performance, which reduces nearly 90% of the particle swarm optimization computing time. Numerical results calculated by the Monte Carlo ray-tracing model and the obtained optical efficiency fitting formulas were compared with the corresponding reference data. Good agreements were obtained, proving that the computing method and model are reliable. The obtained optical efficiency fitting formula of parabolic trough solar collectors is then applied successfully to efficiently study the characteristics of long-time average optical efficiencies under different geometrical configurations, geographical locations, tracking models and corresponding optical or geometrical optimizations. This proposed novel method offers a useful option of high potential for further applications on efficient optical efficiency related analyses and corresponding population-based optimizations for parabolic trough solar collectors. [ABSTRACT FROM AUTHOR]

The outflow of the effervescent atomization spray is simulated by a comprehensive numerical model based on the Navier-Stokes equation and the particle tracking method. The droplet mean diameter under different operating conditions and liquid properties were calculated. Based on the extensive computations, a formula relating droplet Sauter mean diameter to the operating conditions and liquid physical parameters were obtained with curve fitting technique. The results calculated from the formulae were compared with the experimental data and a good agreement was obtained. The formulae can be used to predict the droplet mean diameter for various Newtonian liquid in axisymmetric effervescent atomization spray conveniently and effectively. [ABSTRACT FROM AUTHOR]