Investigation on the Short-Term Aging-Resistance of Thermoplastic Polyurethane-Modified Asphalt Binders

In this reported work, thermoplastic polyurethane (TPU) was used as a reactive polymer modifying agent to prepare a modified-asphalt, using a high-speed shearing method. Physical performance tests of the TPU-modified asphalt were conducted before and after short-term aging, and the aging resistance was examined by the change in materials properties. In addition, low-temperature rheological properties, thermal properties, the high-temperature storage stability, and the aging mechanism of TPU-modified asphalt were also investigated. The results showed that the addition of TPU improved the aging resistance of base asphalt, which was evidenced by the increased penetration ratio and decreased softening point of the asphalt, after aging. Similarly, Fourier Transform infrared (FTIR) spectroscopy results verified that TPU improved the asphalt aging resistance. It was found that the TPU functional groups played a role in improving thermal properties, high-temperature storage stability, and in the dispersion of modified asphalt

A Sensitive Frequency Range Method Based on Laser Ultrasounds for Micro-Crack Depth Determination

The laser ultrasonic method using the characteristics of transmitted Rayleigh waves in the frequency domain to determine micro-crack depth is proposed. A low-pass filter model based on the interaction between Rayleigh waves and surface cracks is built and shows that the stop band, called the sensitive frequency range, is sensitive to the depth of surface cracks. The sum of transmission coefficients in the sensitive frequency range is defined as an evaluated parameter to determine crack depth. Moreover, the effects of the sensitive frequency range and measured distance on the evaluated results are analyzed by the finite-element method to validate the robustness of this depth-evaluating method. The estimated results of surface cracks with depths ranging from 0.08 mm to ~0.5 mm on the FEM models and aluminum-alloy samples demonstrate that the laser ultrasounds using the characteristics of Rayleigh waves in the frequency domain do work for quantitative crack depth

Inverse time overcurrent optimization of distribution network with DG based on improved gray wolf algorithm

Inverse time overcurrent protection can be applied to distribution networks with distributed power sources because of its superior protection characteristics, but its time limit coordination and value setting are complicated, which limits its large-scale engineering application. Therefore, this paper proposes an inverse time overcurrent protection setting strategy for distribution network(DN) based on improved gray wolf optimizer (GWO) algorithm. Firstly, the current setting optimization model and the protection operation characteristics are established considering the reliability, rapidity and selectivity. Secondly, the GWO algorithm is improved by introducing the population initialization strategy based on elite backward learning, adaptive weights and variation strategy based on the Cauchy operator for the characteristics of the traditional GWO algorithm which is easy to trap in local optimum and low convergence accuracy. The improved algorithm does not introduce new parameters and achieves a balance between global and local. Finally, the case study results represent that the improved GWO algorithm has high accuracy and stability in both two-phase short-circuit and three-phase short-circuit scenarios, and has good practical applicability

The influence of NaOH concentration on the strength and microstructure of ceramic binders prepared from coal gangue through geopolymerization

The efficient utilization of coal gangue plays an indispensable role in reducing environmental pressure, improving resource utilization efficiency and promoting green development. As a kind of solid waste rich in silicon and aluminium, coal gangue can be used to prepare ceramic materials. Therefore, a new ceramic preparation process was proposed in this study to prepare ceramic binders for grinding wheels by geopolymerization. The SiO _2 -B _2 O _3 -Al _2 O _3 -RO-R _2 O ceramic binder, a green and low-cost material, was successfully prepared using this method. The effect of the concentration of NaOH on the mechanical properties and microstructure of the ceramic binder was also studied. The strength and microstructure of different ceramic binders were characterized by XRD, TG-DTG, SEM-EDS and FT-IR. The results show that the bending strength of the geopolymer ceramic binder increases proportionately with the increase of NaOH concentration. When the concentration of sodium hydroxide is 15 M, the bending strength reaches 19 MPa. N-A-S-H gel and zeolite formed in the geopolymerization reaction and the pores formed in the sintering process have a significant effect on the bending strength of the ceramic binder. This technology can significantly stimulate the chemical activity of coal gangue and provide innovative ideas for efficient utilization of coal gangue

Social anxiety, mentalizing and social distance preference: A preliminary psychometric evaluation

Humans' ability to interact with strangers is fundamental, and an individual's mentalizing ability is closely linked to inferences and interactions with strangers. The main aim of this study is to identify the quantitative mentalizing capability with social distance preferences and interaction attitudes with individual variation. In the first two experiments, we examined association between mentalizing ability, social anxiety and conducted behavioral experiments with Virtual Social Distance (VSD, experiment 2a, N = 223) and Real Social Distance (RSD, experiment 2b, N = 45) preference tasks. In experiment 3, we induced the "social exclusion" paradigm (N = 94) and linked it to the measured dynamic characteristic of mentalization. The findings reveal that: (i) individuals with lower capability of self-perception show a greater degree of social anxiety and a diminished capacity for meta-cognition; (ii) higher degree of "social anxiety" associates more with VSD preference naturally; and (iii) participants from the "socially excluded group" show decreasing tendency in their mentalizing capability. The results provide new insights into social distance preferences and how social environment variations affect sub-clinical social anxious individuals, highlighting individual differences in social interaction preference. It may also have the potential for intervention and treatment for people with anxiety in social interactions

The short-term aging effect on the interface and surface wetting behavior of modified asphalt mixtures

In this study, the interface models and nanodroplets wetting models of base asphalt (BA), polyurethane modified asphalt (PU-MA) and polyurethane/graphene oxide composite modified asphalt (PU/GO-MA) with acidic and alkaline aggregates were constructed. The adhesion and debonding effects of modifiers on short-term aged asphalt mixtures were analyzed by molecular dynamics (MD) simulation. The moisture damage resistance of the mixture was evaluated by simulating the wetting characteristics of asphalt and water nanodroplets on the aggregate surface. The contact angle, adhesion work, debonding work and relative concentration distribution can effectively analyse the interface interaction behavior between asphalt and aggregate. The results show that the adsorption effect between aged asphalt and CaCO _3 was stronger, and short-term aging enhanced the interfacial adhesion of asphalt mixtures. Calcite was more hydrophilic, and its resistance to moisture damage was far less than quartz. The difference between the contact angle of water-aggregate and that of asphalt-aggregate can effectively analyze the water sensitivity of asphalt mixture. In addition, different components played different roles in the adsorption of asphalt and different aggregate surfaces. The synergistic analysis of the asphalt-aggregate interface and the asphalt nanodroplet-wetting aggregate surface can more comprehensively reveal the variation principle of asphalt parameters and nanoscale properties of asphalt mixtures