Analysis on Ground Surface Deformation and Influence of Construction Parameters Caused by Two Different Shield Machines in Double-tube Tunnelling北大核心CSCD

Based on a shield-driven running tunnel project of Hangzhou Metro Line 2, this paper carries out field measuring of the ground surface deformation caused by two different shield machines in double-tube tunnelling in soft soil areas, obtains the laws of the surface deformation caused by shield-driven double-tube tunnelling and verifies the applicability of the modified Peck formula to double-tube tunnelling. The results show that in soft soil areas the impacts on ground surface deformation caused by different shield construction parameters in the previously and subsequently excavated tunnels are different, while the surface deformation changes sharply before and after the shield machine passing through the cutting face, and a rebound phenomenon occurs when the shield tail passes through the cutting face due to the influence of the grouting; The cutterhead torque of the shield machine in soft soil areas can be composed of five calculation factors, and the calculation results are in good agreement with the measured values. The larger the opening rate of the shield cutterhead is, the larger the average torque value will be, the higher the percentage of large ground loss rate will be, and the larger the maximum ground surface settlement will be; The ratio of cutterhead torque T to mucking volume per ring Q is used as the control parameter for analyzing the ground surface settlement, and a certain positive correlation between the ratio and the surface settlement value is determined, the smaller the cutterhead opening rate is, the more accurate the fitting results will be. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Chaotic movement of vortices in superconductors of high-Tc superconducting maglev system at a high speed

Vortex motion in superconductors of higb-Tc superconducting maglev system is studied by a computational simulation.The vortex system is treated in a similar fashion,as a system where defects arc arrang...     

Multiaxial stress creep rupture mechanisms of AZ31 magnesium alloy

The maximum principal stresses, von Mises effective stresses and principal facet stresses at the time of creep rupture were compared in uniaxial, biaxial, and triaxial stress states for AZ31 magnesium alloy. The creep rupture of this alloy was experimentally controlled by cavitation, which was the result of a low damage tolerance, λ. Creep deformation could be correlated with the von Mises effective stress parameter. The failure-mechanism control parameter governing the stress state coincided with the experimental results of the rupture of the materials under multiaxial stress states. Finally, the theoretical prediction based on constrained cavity growth and continuous nucleation agreed with the experimental rupture data to within a factor of three.     

Implementation of discharging/charging current sensorless state-of-charge estimator reflecting cell-to-cell variations in lithium-ion series battery packs

This paper offers novel insights to the design and implementation of an innovative state-of-charge (SOC) estimator for the lithium-ion (Li-Ion) series battery pack. The most interesting feature of this approach is that it can utilize information from each filtered terminal voltage of the Li-Ion cells connected in series for SOC estimation of the battery pack. Without actual sensing each discharging/charging current (DCC) applied to the Li-Ion cells, it is possible to extract each DCC estimation from the corresponding filtered terminal voltages with an equivalent electrical circuit model (EECM) identification of all Li-Ion cells in the battery pack. There are two advantages to SOC estimation of the battery pack with this approach. First, the proposal can be implemented simply and effectively, reducing the computational steps required for SOC estimation. By reducing computational steps, the proposal is expected to be more cost-effective. Second, the approach guarantees an improved SOC performance, even if the battery pack results in inevitable cell-to-cell variation among Li-Ion cells. Accordingly, there are fewer differences to previously estimated DCCs among Li-Ion cells. Specifically, all values from the estimated DCCs are properly compensated for by simultaneous parameter modification according to each cell’s electrochemical characteristics. Experimental results clearly demonstrate that our DCC sensorless SOC estimator provides robust SOC performance for the battery pack. This approach considered an experimental battery pack (12S1P) connected in series using 2.6 Ah LiCoO2 cells produced by Samsung SDI.     

Effect of rear slant angle on vehicle crosswind stability simulation on a simplified car model

It is important to know the effect of the aerodynamic forces and moments on driving stability because it is responsible for the excitation and influences the response of the vehicle. The purpose of this paper is to study the effect of rear slant angle of a surface vehicle on crosswind sensitivity for stability analysis. The vehicle mathematical model used to conduct a dynamic simulation was based on a simple reduced order lateral dynamics of sideslip and yaw rate motion coupled with aerodynamics model. The intention here is to compare the effect of rear slant angles response to crosswind and to rank the crosswind sensitivity ratings. The aerodynamic loads are defined as the function of the aerodynamic derivatives from the static wind tunnel tests. Result shows a 20° rear slant angle demonstrates the highest rating of crosswind sensitivity, while zero degree slant exhibits the least.     

Propagating buckles in corroded pipelines

Rigid–plastic solutions for the steady-state, quasi-static buckle propagation pressure in corroded pipelines are derived and compared to finite element predictions (ABAQUS). The corroded pipeline is modeled as an infinitely long, cylindrical shell with a section of reduced thickness that is used to describe the corrosion. A five plastic hinge mechanism is used to describe plastic collapse of the corroded pipeline. Closed-form expressions are given for the buckle propagation pressure as a function of the amount of corrosion in an X77 steel pipeline. Buckles that propagate down the pipeline are caused by either global or snap-through buckling, depending on the amount of corrosion. Global buckling occurs when the angular extent of the corrosion is greater than 90°. When the angular extent is less than 90° and the corrosion is severe, snap-through buckling takes place. The buckle propagation pressure and the corresponding collapse modes also compare well to finite element predictions.     

Challenges and Prospects of Fisheries Co-Management under a Marine Extractive Reserve Framework in Northeastern Brazil

In Brazil, Marine Extractive Reserves—MERs (Reservas Extrativistas Marinhas) represent the most significant government-supported effort to protect the common property resources upon which traditional small-scale fishers depend. From an initial small-scale experience in 1992, MERs have expanded countrywide, now encompassing 30 units (9,700 km²) and nearly 60,000 fishers. Despite such escalating interest in the model, there is little research on the effectiveness of MERs. In this article, we discuss relevant parts of the history and examine the current situation of the fisheries co-management initiative in the Marine Extractive Reserve of Corumbau, which was created in 2000 as the first MER to encompass coral reefs and reef fisheries. We describe the Extractive Reserve co-management arrangement and its main policy and legislative challenges. Finally, we discuss the prospects for the use of MERs as management frameworks for traditional small-scale fisheries in Brazil.     

Damage detection in offshore structures using neural networks

This paper discusses the damage detection in offshore jacket platforms subjected to random loads using a combined method of random decrement signature and neural networks. The random decrement technique is used to extract the free decay of the structure from its online response while the structure is in service. The free decay and its time derivative are used as input for a neural network. The output of the neural network is used as an index for damage detection. It has been shown that function N is effective in damage detection in the members of an offshore structure. Experimental studies conducted on a reduced model for a real jacket structure with geometrical scale of 1:30 are used. The applied loads were random loads. Two different load spectra were used: White noise, and Pierson-Moskowitz.     

Evaluating locational accessibility to the US air transportation system

Although there are hundreds of airports that support commercial air passenger traffic in the United States (US), not all areas are equivalently served by the commercial air transportation system. Locations in the US differ with respect to their level of access to the commercial air network and their overall accessibility within the system. Given the complexity of the domestic commercial air passenger network and supporting infrastructure, past research has only been able to provide a limited assessment of locational accessibility within the United States. To address these complexities, this paper proposes a new metric that incorporates measures of access to air transport as well as accessibility within air transportation networks. Using a comprehensive dataset on scheduled airline service, the developed approach is then applied to the US domestic commercial passenger air transportation network to explore geographic differentials in accessibility. Results suggest marked differences between core-based statistical areas throughout the US.