Research and Application of Drag Reduction by Grouting the Pipe Jacking in Complex Conditions北大核心CSCD

This paper presents the technology measures, equipment selection and required grout properties and re-lated techniques for the grouting base-station arrangement of the drag reduction system of the Fuchun River pipe jacking project, which is characterized by a combined stratum, a longitudinal curve with a large falling head, a large gradient and high water pressure. Drag reduction by grouting can effectively reduce the friction coefficient in pipe jacking construction, decrease the time and frequency of the relay station, improve construction efficiency, and re-duce the grout loss along the stratum fissure while guaranteeing grouting pressure of the terminal, is favorable for sta-ble annular bentonite grouting between the stratum fissure and the segment. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Tracking a system of shared autonomous vehicles across the Austin,Texas network using agent-based simulation

This study provides a large-scale micro-simulation of transportation patterns in a metropolitan area when relying on a system of shared autonomous vehicles (SAVs). The six-county region of Austin, Texas is used for its land development patterns, demographics, networks, and trip tables. The agent-based MATSim toolkit allows modelers to track individual travelers and individual vehicles, with great temporal and spatial detail. MATSim’s algorithms help improve individual travel plans (by changing tour and trip start times, destinations, modes, and routes). Here, the SAV mode requests were simulated through a stochastic process for four possible fare levels: $0.50, $0.75, $1, and $1.25 per trip-mile. These fares resulted in mode splits of 50.9, 12.9, 10.5, and 9.2% of the region’s person-trips, respectively. Mode choice results show longer-distance travelers preferring SAVs to private, human-driven vehicles (HVs)—thanks to the reduced burden of SAV travel (since one does not have to drive the vehicle). For travelers whose households do not own an HV, SAVs (rather than transit, walking and biking) appear preferable for trips under 10 miles, which is the majority of those travelers’ trip-making. It may be difficult for traditional transit services and operators to survive once SAVs become available in regions like Austin, where dedicated rail lines and bus lanes are few. Simulation of SAV fleet operations suggest that higher fare rates allow for greater vehicle replacement (ranging from 5.6 to 7.7 HVs per SAV, assuming that the average SAV serves 17–20 person-trips per day); when fares rise, travel demands shift away from longer trip distances. Empty vehicle miles traveled by the fleet of SAVs ranged from 7.8 to 14.2%, across the scenarios in this study. Implications of mobility and sustainability benefits of SAVs are also discussed in the paper.     

Elderly travel frequencies and transport mode choices in Greater Rotterdam,the Netherlands

Demographic ageing is a key societal challenge in Europe as well as in many other western and non-western societies. A crucial dimension concerns elderly daily mobility patterns. While still partaking fewer and shorter trips than younger generations, today’s elderly have been found increasingly (auto)mobile. Although the elderly benefit from the independence, freedom of movement, and social inclusion, concerns may rise regarding the environmental and accessibility impacts of this induced mobility. The present study adds to the expanding literature on elderly mobility, an integrated analysis of the effects of socio-demographic, health, trip, spatial and weather attributes on elderly mobility. Utilizing travel diary data for Greater Rotterdam, The Netherlands, trip frequencies and transport mode choices of the elderly are analysed by means of zero-inflated negative binomial models as well as multinomial logit regression models, and contrasted to the non-elderly subpopulation to explore (dis)similarities. While the results show common determinants, the models also highlight important differences in the magnitude of the estimated coefficients and factors only influencing transport patterns for the elderly. Embedded in the context of an aging population, the empirical findings assist policy-makers and planners in several respects: For transportation plans and programs it is critical to recognize mobility needs of the elderly. As the seniors are becoming increasingly automobile, the results call for strategies to encourage older people to use more physically active and environmentally friendly transport modes such as public transport, walking and cycling.     

柔性路面车辙预估的粘弹性方法

沥青混合料的粘弹性流动导致沥青路面产生永久变形(车辙)。对于粘弹性体系,永久变形与材料的弹性参数无关,但可通过采用粘性参数的线弹性模型预估出来。为了确定沥青混合料在较大环境变化条件下的粘性,该文引入了一个新的基于常规试验数据的简单理论方法,并将根据此方法得到的车辙预估深度与法国新近的一个足尺试验数据进行对比,结果表明此线性车辙模型的适用性较好。     

A porous cell method for the simulation of fluid-solid interactions

There are many ways of describing a solid,porous or fluid region of the computational domain when solving the Navier-Stokes equations(NSE)for flow motions.Amongst these the porous cell method is one of the most flexible approaches.In this method,a parameter is defined as a ratio of the volume open to water and air in a calculation cell to its cell volume.In the calculation,the same numerical procedure is applied to every cell and no explicit boundary conditions are needed at solid boundaries.The method is used to simulate flow through porous media,around solid bodies and over a moving seabed.The results compare well with experimental data and other numerical results.In our future work the porous cell method will be applied to more complex fluid-solid interaction situations.     

THE EFFECTS OF ARGATROBAN ON THROMBIN INDUCED CEREBROVASCULAR THROMBOEMBOLISM IN RABBITS

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Dynamic Stability of Vehicle Systems via Poincaré Maps

Computer simulations of a driven vehicle are performed to assess and quantify the automobile stability. The analytical methodology is based on PoincarS maps and Floquet theory, which are commonly used to investigate the stability of periodic systems. The approach accommodates the study of the complex dynamics of vehicle locomotion under various configurations of the system. The proposed method does not require any knowledge regarding the inner structure of the vehicle model. Kinematic data is simply collected at the specific instants to conduct the analysis. It is found that this method has the potential for real time warning and control of vehicle instabilities.     

STUDY OF EFFECT OF SURFACE-OPTICAL PHONON ON BIPOLARON IN QUANTUM-WELL WIRE

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A disaggregated land use—transport model for Delhi,India

A Lowry-type land use-transport model stratified both by socio-economic group and urban sub-region is described. The parameters of this model are calibrated from a 1969 urban travel survey conducted in Delhi. Parameter magnitudes are estimated for several versions of the model and the qualities of these calibrations are reported. Applications of the calibrated models to the analysis of alternative development concepts for the Delhi urban region are described.