Ageing transitions in a network of Rulkov neurons

The phenomenon of ageing transitions (AT) in a Erdős–Rényi network of coupled Rulkov neurons is studied with respect to parameters modelling network connectivity, coupling strength and the fractional ratio of inactive neurons in the network. A general mean field coupling is proposed to model the neuronal interactions. A standard order parameter is defined for quantifying the network dynamics. Investigations are undertaken for both the noise free network as well as stochastic networks, where the interneuronal coupling strength is assumed to be superimposed with additive noise. The existence of both smooth and explosive AT are observed in the parameter space for both the noise free and the stochastic networks. The effects of noise on AT are investigated and are found to play a constructive role in mitigating the effects of inactive neurons and reducing the parameter regime in which explosive AT is observed.

Impact of Penetrations of Connected and Automated Vehicles on Lane Utilization Ratio

Lane Utilization Ratio (LUR), affected by lane selection behavior directly, represents the traffic distribution on different lanes of road section for a single direction. The research on LUR, especially under Penetration Conditions of Connected and Automated Vehicles (PCCAV), is not comprehensive enough. Considering the difficulty in the conduction of real vehicle experiment and data collection under PPCAV, the lane selection model based on phase-field coupling and set pair logic, which considers the full-information of lanes, was used to carry out microscopic traffic simulation. From the analysis of microsimulation results, the basic relationships between Penetration of Connected and Automated Vehicles (PCAV), traffic volume, and Lane-Changing Times, also that between PCAV, traffic volume, and LUR in the basic section of the urban expressway were studied. Moreover, the influence of driving propensity on the effect of PCAVs was also studied. The research results could enrich the traffic flow theory and provide the theoretical basis for traffic management and control.

Multi-Physics Coupling Modeling and Experimental Investigation of Vibration-Assisted Blisk Channel ECM

Due to its advantages of good surface quality and not being affected by material hardness, electrochemical machining (ECM) is suitable for the machining of blisk, which is known for its hard-to-machine materials and complex shapes. However, because of the unstable processing and low machining quality, conventional linear feeding blisk ECM has difficulty in obtaining a complex structure. To settle this problem, the vibration-assisted ECM method is introduced to machine blisk channels in this paper. To analyze the influence of vibration on the process of ECM, a two-phase flow field model is established based on the RANS k-ε turbulence model, which is suitable for narrow flow field and high flow velocity. The model is coupled with the electric field, the flow field, and the temperature field to form a multi-physics field coupling model. In addition, dynamic simulation is carried out on account of the multi-physics field coupling model and comparative experiments are conducted using the self-developed ECM machine tool. While a shortcut appeared in the contrast experiment, machining with vibration-assisted channel ECM achieved fine machining stability and surface quality. The workpiece obtained by vibration-assisted channel ECM has three narrow and straight channels, with a width of less than 3 mm, an aspect ratio of more than 8, and an average surface roughness Ra in the hub of 0.327 μm. Compared with experimental data, the maximum relative errors of simulation are only 1.05% in channel width and 8.11% in machining current, which indicates that the multi-physics field coupling model is close to machining reality.

Numerical simulation method of submerged arc surfacing process of rollers

The submerged arc surfacing process involves complex behaviors such as metal heat transfer, melting, flow, phase transformation, and solidification and involves the interaction of electric field, thermal field, magnetic field, and flow field. At present, it is impossible to reveal the transient mechanism of multi-field coupling in submerged arc surfacing by experience or trial and error, which is not conducive to shorten the development cycle and save the cost. Moreover, it is difficult to measure the molten pool velocity, von Mises stress, and phase transformation zone in real-time. However, these factors are the key to obtain a high-quality surfacing layer. Therefore, a three-dimensional mathematical model of heat force flow multi-field coupling for roller submerged arc surfacing is established in this article. The distribution and variation of welding temperature, von Mises stress, molten pool flow field, and phase transformation zone are revealed by solving the model. The maximum von Mises stress of the rollers during submerged arc surfacing is 432 MPa. The depth of the phase transformation is 2.50 mm, and the width is 1.98 mm. Zeiss-IGMA HD FESEM was used to observe the welding microstructure. The results show that the main microstructure is martensite and a small amount of ferrite.

Experimental and Numerical Investigation of Temperature Development of Ohmic Heating Cured Nonmass Concrete under Subzero Temperature

In this paper, carbon fiber/carbon nanofiber strengthening nonmass concrete slab was designed, and ohmic heating (OH) curing was used to promote the strength formation of the slab under −20°C. COMSOL multiphysical field coupling program has been used to simulate the heating process of nonmass concrete slabs under different conditions. COMSOL analysis results showed that the optimal loading power density of OH cured sample under −20°C was 1000 W/m2∼1200 W/m2. Moreover, numerical analysis results were experimentally validated by the multipoint temperature measurement method. Furthermore, the mechanical properties showed that the compressive strength of the sample cured by 2 days OH curing at −20°C reached up to 48.2 MPa. SEM analysis exhibited that OH curing could improve the interfacial transition zone (ITZ) between the fiber and the matrix, leading to a denser microstructure. This study proved that COMSOL program could provide good theoretical guidance for OH cured nonmass cement concrete under subzero temperature. This work establishes an accurate guideline for electric power supplementation, laying a solid foundation of winter construction with high efficiency and low energy consumption.