Viscoelastic plastic interaction of tunnel support and strain-softening rock mass considering longitudinal effect

A simplified two-stage method was employed to provide an explicit solution for the time-dependent tunnel-rock interaction,considering the generalized Zhang-Zhu strength criterion.Additionally,a simplified mechanical model of the yielding support structure was established.The tunnel excavation is simplified to a two-stage process:the first stage is affected by the longitudinal effect,while the second stage is affected by rheological behavior.Two cases are considered:one is that the rigid support is constructed during the first stage,and the other is that constructed at the second stage.Distinguished by the support timing at the seconde stage,different kinds of the“yield-resist combination”support method are divided into three categories:“yield before resist”support,“yield-resist”support,and“control-yield-resist”support.Results show that the support reaction of“control-yield-resist”is much higher than that of“yield before resist”if the initial geostress is not very high,but the effect is not obvious on controlling the surrounding rock deformation.So,the“yield before resist”support is much more economical and practical when the ground stress is not very high.However,under high geostress condition,through applying relatively high support reaction actively to surrounding rock at the first stage,the“control-yield-resist”support is superior in controlling the deformation rate of surrounding rock.Therefore,in the high geostress environment,it is recommended to construct prestressed yielding anchor immediately after excavation,and then construct rigid support after the surrounding rock deformation reaches the predetermined deformation.

The effects of the uneven bottom on horizontal longitudinal correlations of acoustic field in deep water

The spatial coherence of sound field in the reflection area of deep-water bottom is studied by analyzing the data of an acoustic propagation experiment conducted in the South China Sea. Some different oscillation patterns of the measured horizontal longitudinal correla- tions of acoustic field are observed for two different tracks in the flat bottom and the uneven bottom environments when the source distance ranges from 29 km to 35 km. Numerical analysis based on the ray theory is carried on to explain the causes of the differences. The experimental and mlmerical results show that the travel time differences between the one-bottom-reflection （1BR） rays, which make a major contribution to the sound field of the 1BR area in flat bottom environment, decrease gradually with increasing horizontal distance. Then the phase of the interference cyclically changes within 27r, leading to the correlations＇ periodical oscillation in deep water with flat bottom. In the uneven bottom environment, however, due to the reflection- blockage effects of the sea hill on the 1BR sound beams, the sound transmission losses （TLs） in- crease significantly in the reflection area of the sea hill. What＇s more, the horizontal-longitudinal correlations decreasing slightly in general don＇t show obvious cyclical oscillation any longer in the corresponding reflection area because of the complex interference of the relatively more eigenrays. This work is of significance to analyze the detection performance of the sonar array in deep water with the complicated bathymetry environment.

THE EFFECT OF LONGITUDINAL OSCILLATIONS ON FREE CONVECTION FROM A VERTICAL PLATE EMBEDDED IN A POROUS MEDIUM

In this paper oscillatory 2-D natural convection from a vertical isothermal wall embedded in a po- rous medium, and originating from the oscillation of longitudinal fluid flow, has been investigated both analytically and numerically. Two asymptotic solutions, valid for large and small values of dimensionless frequency γ respectively, are obtained in the closed form. In the range where the asymptotic solutions break down, numerical results to the governing equations are obtained by local similarity meth- od. Both numerical and analytical results show that pulsatory components of the flow and heat transfer depend only on the parameter γ, and the effect of longitudinal oscillation is to decrease the magnitude or' pulsatory Nusselt number with a phase lag between 0 and 90 deg. A correlation for pulsatory heat trans- fer rates is proposed in the whole range of γ within 3% accuracy compared with the numerical results.

Interruption of schistosomiasis transmission in mountainous and hilly regions with an integrated strategy:a longitudinal case study in Sichuan,China

Background:Schistosomiasis remains a major public health concern in China.Since 2004,an integrated strategy was developed to control the transmission of Schistosoma japonicum in China.However,the long-term effectiveness of this integrated strategy for the interruption of schistosomiasis transmission remains unknown in the mountainous and hilly regions of China until now.This longitudinal study aims to evaluate the effectiveness of the integrated strategy on transmission interruption of schistosomiasis in Sichuan Province from 2005 through 2014.Methods:The data regarding replacement of bovines with machines,improved sanitation,access to clean water,construction of public toilets and household latrines,snail control,chemotherapy,and health education were captured from the annual report of the schistosomiasis control programmes in Sichuan Province from 2005 to 2014,and S.japonicum infection in humans,bovines and snails were estimated to evaluate the effectiveness of the integrated strategy.Results:During the 10-year period from 2005 through 2014,a total of 536568 machines were used to replace bovines,and 3284333 household lavatories and 15523 public latrines were built.Tap water was supplied to 19116344 residents living in the endemic villages.A total of 230098 hm2 snail habitats were given molluscicide treatment,and 357233 hm2 snail habitats received environmental improvements.There were 7268138 humans and 840845 bovines given praziquantel chemotherapy.During the 10-year study period,information,education and communication(IEC)materials were provided to village officers,teachers and schoolchildren.The 10-year implementation of the integrated strategy resulted in a great reduction in S.japonicum infection in humans,bovines and snails.Since 2007,no acute infection was detected,and no schistosomiasis cases or infected bovines were identified since 2012.In addition,the snail habitats reduced by 62.39%in 2014 as compared to that in 2005,and no S.japonicum infection was identified in snails since 2007.By 2014,88.9%of the endemic counties achieved the transmission interruption of schistosomiasis and transmission control of schistosmiasis was achieved in the whole province in 2008.Conclusion:The government-directed and multi-department integrated strategy is effective for interrupting the transmission of schistosomiasis in the mountainous and hilly regions of China.

Time-varying latent model for longitudinal data with informative observation and terminal event times

Longitudinal data often occur in follow-up studies, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-up. We propose a semiparametric mixed effect model with time-varying latent effects in the analysis of longitudinal data with informative observation times and a dependent terminal event. Estimating equation approaches are developed for parameter estimation, and asymptotic properties of the resulting estimators are established. The finite sample behavior of the proposed estimators is evaluated through simulation studies, and an application to a bladder cancer study is provided.

Pseudo-rapidity distribution from a perturbative solution of viscous hydrodynamics for heavy ion collisions at RHIC and LHC

The charged-particle final state spectrum is derived from an analytic perturbative solution for relativistic viscous hydrodynamics. By taking into account the longitudinal acceleration effect in relativistic viscous hydrody namics, the pseudorapidity spectrum describes the nucleus-nucleus colliding systems at RHIC and the LHC well. Based on both the extracted longitudinal acceleration parameter λ^＊ and a phenomenological description of λ^＊, the charged-particle pseudorapidity distributions for √SNN= 5.44 TeV Xe＋Xe collisions are computed from the final state expression in a limited space-time rapidity ~/8 region.