Influence of Shear Effects on the Characteristics of Axisymmetric Wave Propagation in a Buried Fluid‑Filled Pipe

The acoustic propagation characteristics of axisymmetric waves have been widely used in leak detection of fluid-filled pipes.The related acoustic methods and equipment are gradually coming to the market,but their theoretical research obviously lags behind the field practice,which seriously restricts the breakthrough and innovation of this technology.Based on the fully three-dimensional effect of the surrounding medium,a coupled motion equation of axisymmetric wave of buried liquid-filled pipes is derived in detail,a contact coefficient is used to express the coupling strength between surrounding medium and pipe,then,a general equation of motion was derived which contain the pipe soil lubrication contact,pipe soil compact contact and pipe in water and air.Finally,the corresponding numerical calculation model is established and solved used numerical method.The shear effects of the surrounding medium and the shear effects at the interface between surrounding medium and pipe are discussed in detail.The output indicates that the surrounding medium is to add mass to the pipe wall,but the shear effect is to add stiffness.With the consideration of the contact strength between the pipe and the medium,the additional mass and the pipe wall will resonate at a specific frequency,resulting in a significant increase in the radiation wave to the surrounding medium.The research contents have great guiding effect on the theory of acoustic wave propagation and the engineering application of leak detection technology in the buried pipe.

Serological Investigation into the Infected Genotypes of Patients with Japanese Encephalitis in the Coastal Provinces of China

Objective Genotypes(G)1,3,and 5 of the Japanese encephalitis virus(JEV)have been isolated in China,but the dominant genotype circulating in Chinese coastal areas remains unknown.We searched for G5 JEV-infected cases and attempted to elucidate which JEV genotype was most closely related to human Japanese encephalitis(JE)in the coastal provinces of China.Methods In this study,we collected serum specimens from patients with JE in three coastal provinces of China(Guangdong,Zhejiang,and Shandong)from 2018 to 2020 and conducted JEV cross-neutralization tests against G1,G3,and G5.Results Acute serum specimens from clinically reported JE cases were obtained for laboratory confirmation from hospitals in Shandong(92 patients),Zhejiang(192 patients),and Guangdong(77 patients),China,from 2018 to 2020.Seventy of the 361 serum specimens were laboratory-confirmed to be infected with JEV.Two cases were confirmed to be infected with G1 JEV,32 with G3 JEV,and two with G5 JEV.Conclusion G3 was the primary infection genotype among JE cases with a definite infection genotype,and the infection caused by G5 JEV was confirmed serologically in China.

Numerical simulation of particle flow behavior in a screw conveyor using the discrete element method

Particle motion in a screw conveyor was simulated w让h the discrete element method. The particle flow behavior and transport processes at different screw rotating speeds and filling levels were investigated in this study. The spatial distributions of particle velocity were predicted. The predicted mass flow rate increased w让h increasing screw rotating speed and filling level. The contact forces and granular temperatures of particles were also calculated. The simulation results showed that the translational granular particle temperatures were higher than the rotational granular particle temperatures. In add让ion, the configurational temperatures of particles were calculated from simulated instantaneous particle overlaps, and results indicated that deformation of elastic particles contributed to the rate of energy dissipation. Good agreement between the numerical simulation and experimental results was achieved in this study.

Evaluation of power regeneration in primary suspension for a railway vehicle

To improve the fuel economy of rail vehicles,this study presents the feasibility of using power regenerating dampers(PRDs)in the primary suspension systems of railway vehicles and evaluates the potential and recoverable power that can be obtained.PRDs are configured as hydraulic electromagnetic-based railway primary vertical dampers and evaluated in parallel and series modes(with and without a viscous damper).Hydraulic configuration converts the linear behavior of the track into a unidirectional rotation of the generator,and the electromagnetic configuration provides a controllable damping force to the primary suspension system.In several case studies,generic railway vehicle primary suspension systems that are configured to include a PRD in the two configuration modes are modeled using computer simulations.The simulations are performed on measured tracks with typical irregularities for a generic UK passenger route.The performance of the modified vehicle is evaluated with respect to key performance indicators,including regenerated power,ride comfort,and running safety.Results indicate that PRDs can simultaneously replace conventional primary vertical dampers,regenerate power,and exhibit desirable dynamic performance.A peak power efficiency of 79.87%is theoretically obtained in series mode on a top-quality German Intercity Express track(Track 270)at a vehicle speed of 160 mile/h(~257 km/h).