This paper presents a torque distribution method for an individual-wheel drive vehicle, in which each wheel is controlled individually by its own electric motor. The terminal sliding mode technique is employed for the motion control so as to track the desired vehicle motion obtained by interpreting the driver’s commands. Thus, finite-time convergence of the system’s dynamic errors can be achieved on the terminal sliding manifolds, as compared to the well-used linear sliding surface. By considering nonlinear constraints of the tire adhesive limits, a simple yet effective distribution strategy is introduced to allocate the motion control efforts to each of the four wheels. Through the use of a high-fidelity CarSim full-vehicle model, vehicle stability and handling performance of the proposed controller is evaluated in both open- and closed-loop simulations.

A coupled vehicle-track dynamic model is put forward for use in investigating the safety effects of crosswinds on the operation of a high-speed railway vehicle. In this model, the vehicle is modeled as a nonlinear multi-body system, and the ballasted track is modeled as a three-layer discrete elastic support system. The steady aerodynamic forces caused by crosswinds are modeled as ramp-shaped external forces being exerted on the vehicle body. This model was used in a numerical analysis of the dynamic response and dynamic derailment mechanisms of high-speed vehicles subjected to strong crosswinds. The effects of the crosswind speeds, crosswind attack angle, and vehicle speed on the operational safety of the vehicle were examined. The operational safety boundaries of a high-speed vehicle subjected to crosswinds were determined. The numerical results obtained indicate that crosswinds at attack angles of 75° to 90° with respect to the forward direction of the vehicle have a great influence on the safety of operating high-speed railway vehicles. The wheelset unloading limit, which determines the position of the warning boundary dividing the safe operating area and the warning area, is the most conservative, i.e., the safest, criterion to use in assessing the high-speed operational safety of vehicles in crosswinds.

This paper presents a two-degree-of-freedom (2DOF) hybrid piezoelectric-electromagnetic energy harvester (P-EMEH). Such a 2DOF system is designed to achieve two close resonant frequencies. The combined piezoelectric-electromagnetic conversion mechanism is exploited to further improve the total power output of the system in comparison to a stand-alone piezoelectric or electromagnetic conversion mechanism. First, a mathematical model for the 2DOF hybrid P-EMEH is established. Subsequently, the maximal power output of the 2DOF hybrid P-EMEH is compared both experimentally and theoretically with those from the 1DOF piezoelectric energy harvester (PEH), 1DOF electromagnetic energy harvester (EMEH), 2DOF PEH, and 2DOF EMEH. Based on the validated mathematical model, the effect of the effective electromechanical coupling coefficients (EMCC) on the maximal power outputs from various harvester configurations is analyzed. The results indicate that for the 2DOF hybrid P-EMEH, although the increase of the power output from one electromechanical transducer will lead to the decrease of the power output from the other, the overall performance of the system is improved in weak and medium coupling regimes by increasing electromechanical coupling. In weak and medium coupling scenarios, the hybrid energy harvester configuration is advantageous over conventional 1DOF or 2DOF harvester configurations with a stand-alone conversion mechanism.

A reliable prediction of the characteristics of roof collapse in deep tunnels is still one of the most important and challenging tasks in tunnel engineering. To investigate the collapse mechanisms and possible shapes of the collapsing blocks in deep tunnels, an analytical solution of shape curves for collapsing blocks is derived based on the nonlinear Hoek-Brown failure criterion by using the functional catastrophe theory. The obtained formulas are extremely simple. Furthermore, a judging criterion is proposed to distinguish whether the roof collapses of deep tunnels will occur or not. The effects of rock mass parameters used in the proposed method on the collapsing block shapes of deep tunnels are also discussed. The proposed analytical solution is verified by both the empirical method and the model test.

Networks of actin filaments and bundles are ubiquitous in cellular cytoskeletons, but the elasticity of the network is not well understood. In this paper, a computational model based on form-finding analysis is proposed to investigate the stiffness of cytoskeleton networks consisting of actin filaments and bundles. The model shows that networks with parallel bundles aligned in the stretching direction are stiffer than those with randomly distributed bundles. The results provide a mechanical explanation for the experimental observation that cells primarily create parallel rather than disordered bundles during cell adhesion and cell motion. The effect of filament undulations on network stiffness is explored briefly. The results show that undulations can soften the network by increasing the bending-dominated deformations in filaments and bundles. Finally, we find that the effect of the relative density of bundles depends on their orientation. Increasing the density of randomly distributed bundles has no effect on the stiffness of cells, but softens the cytoskeleton network. In contrast, the stiffness of networks of parallel bundles first increases, then reduces as the relative density of bundles increases. The stiffest network is a mixture of actin filaments and bundles.

The aim of this study was to establish an activated sludge model and to verify its predictability for use in a pilot-scale anoxic/anaerobic/aerobic/post-anoxic (modified AAO) process. Respirometric measurements were conducted to identify the influent organic characteristics and to determine the yield coefficient (Y_H) and decay coefficient (b_H) for heterotrophic biomass (OHOs). The values obtained for Y_H and b_H were 0.72 mg COD/mg COD and 0.275 d⁻¹, respectively. Within the model’s calibration, the most influential stoichiometric and kinetic parameters were identified with the aid of sensitivity analysis. The output of the model was most sensitive to parameters associated with the growth and decay of OHOs and ammonia-oxidizing biomass (AOB) (Y_H, μ_maxH, K_s, b_H, μ_maxA, K_NH4A, and b_aeroa,A). Furthermore, all the calibrated parameters, with the exception of Y_{PAO, aerob} related to the phosphorus accumulating organisms (PAOs), could be regarded as influential. Both steady-state and dynamic simulations indicated good agreement between the simulated and measured values of the output variables. The calibrated model can be used to provide insight into the pilot-scale modified AAO process, and information needed to optimize design and operation when applied at full-scale.

Motor vehicles are the major source of urban air pollution. The abatement of air pollutant emissions is an urgent task for environmental protection. This paper simulated the abatement for carbon monoxide (CO), volatile organic compounds (VOCs), nitrogen oxides (NO_x), and particular matter (PM) emissions from vehicles under four scenarios in the year 2015 in Hangzhou, China. It was found that the emissions of CO, VOCs, NO_x, and PM from vehicles were 440.551, 23.079, 44.255, and 6.532 kt/a in 2010 in Hangzhou, respectively. The vehicle population will increase to over 1.2 million with a 60.7% growth rate until 2015 (estimated). Based on the scenario analysis, it was found that eliminating substandard vehicles and upgrading vehicle’s standards could help reduce CO and VOCs effectively, while the expected abatement of NO_x and PM would be offset by the rapid increase in the vehicle numbers. It was also found that integrated measurements, including eliminating substandard vehicles, upgrading vehicle standards, supplying low sulfur oil, and introducing alternative fuel vehicles could simultaneously reduce the four key pollutants. These integrated policies make it possible to reduce 250.197, 10.270, 1.791, and 0.335 kt/a CO, VOCs, NO_x, and PM with 56.79%, 44.50%, 4.05%, and 5.14% decrease rates in 2015, respectively, when compared to those in 2010.