Effect Blasting Excavation of Yujiapeng Tunnel on Stability of Nearby Giant Dangerous Rock Masses (DRM)

On the basis of the interpretation of engineering geology of the tunnel and of its adjacent dangerous rock masses (DRM), this paper presents the energy and vibration parameters of the explosion that propagates in different blasting modes according to the experimental formulas now usually employed. Then the stability checking computation of T 8-T 12 area, the most dangerous area of DRM, is conducted under the limited blasting condition and with the limited equilibrium method. The result shows that the effect on the stability is only 5.5 % and that this area also contains certain safety reserves.

A micro-kinetic model of enhanced foam stability under artificial seismic wave

To get a deeper understanding on the synergistic enhancement effect of low frequency artificial seismic wave on foam stability,a micro-kinetic model of enhanced foam stability under low frequency artificial seismic wave is established based on a vertical liquid film drainage model and elastic wave theory.The model is solved by non-dimensional transformation of the high order partial differential equations and a compound solution of implicit and explicit differences and is verified to be accurate.The foam film thickness,surfactant concentration distribution and drainage velocity under the action of low frequency artificial seismic wave are quantitatively analyzed.The research shows that low-frequency vibration can reduce the difference between the maximum and minimum concentrations of surfactant in the foam liquid film at the later stage of drainage,enhance the effect of Marangoni effect,and improve the stability of the foam liquid film.When the vibration frequency is close to the natural frequency of the foam liquid film,the vibration effect is the best,and the best vibration frequency is about 50 Hz.The higher the vibration acceleration,the faster the recovery rate of surfactant concentration in the foam liquid film is.The higher the vibration acceleration,the stronger the ability of Marangoni effect to delay the drainage of foam liquid film and the better the foam stability is.It is not the higher the vibration acceleration,the better.The best vibration acceleration is about 0.5 times of gravity acceleration.Reasonable vibration parameters would greatly enhance the effect of Marangoni effect.The smaller the initial concentration of surfactant,the better the vibration works in enhancing Marangoni effect.

Detection of apple firmness with a novel loudspeaker-based excitation device

Firmness is one of the important indices to evaluate the internal quality of fruit.In this study,a noncontact loudspeaker-based detection system was developed to evaluate apple firmness.The structural parameters of the excitation device were modified in the single-factor experiments,and the best combination of structural parameters was that the inner diameter of the gasket was 40 mm;the distance between fruit surface and loudspeaker was 95 mm.Besides,the proper posture style was that the apple was placed with its stem upward.After the modification of the Laser Doppler Vibrometer(LDV)method,the vibration response signals of 48 apples were measured to establish the firmness prediction model.The results showed that the better prediction performance of stiffness was obtained in multiple models.The Back Propagation Neural Network(BPNN)model had the best prediction performance by using parameters of elasticity index(EI),the peak value at the second resonance frequency f_(2)(A_(2)),and peak area S,with a correlation coefficient of prediction(r_(p))of 0.914;root mean square error of prediction(RMSEP)of 0.491 N/mm.Therefore,the proposed detection system is feasible to nondestructively detect apple firmness,which has the potential to be applied in online detection.