Search

Improving the built environment to support walking is a popular strategy to increase urban sustainability and walkability. In the past decade alone, many US cities have implemented crosswalk visibility enhancement programs as part of road safety improvements and active transportation plans. However, there are no systematic ways of measuring and monitoring the presence of key built environment attributes that influence the safety and walkability of an area, such as marked crosswalks. Furthermore, little is known about how these attributes change over time at a national scale. In this paper, we introduce an innovative approach using a deep learning-based computer vision model on Street View images to identify changes in intersection-level marked crosswalks around more than 4,000 US transit stations over a 14-year period. We found an increase in the overall number of marked crosswalks at intersections. Furthermore, high-visibility crosswalks became more common, as they replaced existing parallel-line crosswalks. We further examine crosswalks around transit stations in New York City and San Francisco to illustrate geographic variations and compare associations with other characteristics of the built environment as reported in the Smart Location Database. Areas with increases in high-visibility crosswalks focused on high density residential areas and areas with a higher percent of zero-vehicle households. However, geographic variations exist. For example, in San Francisco, transit station areas outside downtown or major corridors (South and Southwest of the city) had the lower prevalence of marked crosswalks. This analysis confirms important gaps in crosswalk visibility that call for safety enhancements and opens the door for additional research involving these data. We conclude by discussing the limitations and future research opportunities using computer vision to automatically detect large-scale transportation infrastructure changes at a relatively low cost.

Recent experiments showed that gold nanoparticle (NP)–polymer composite exhibits excellent properties such as high stretchability and electron conductivity, rendering this novel material promising for bendable and stretchable electronics and optoelectronics. Theoretical models have been proposed to investigate the conduction mechanism; however, the role of the quantum tunneling effect in electrical percolation remains unclear. Here, we used a numerical approach together with Monte Carlo sampling to investigate the percolation of the gold NP–polymer system. The effects of the electron tunneling and the inter-NP van der Waals interaction were considered in the model. A distinct two-stage electrical percolation behavior is identified because of the effect of electron tunneling at the nanoscale. Such an effect is found to be dependent on the radii of gold NPs and becomes negligible when the radius is larger than 195 nm. The observed behavior is also sensitive to the potential barrier height of the hosting pol...

Bridge pier collision avoidance system is a hot research topic. As the representative of the intelligent material, the Magnetorheological Grease has become one of the main research directions in the research of bridge pier collision due to its special mechanical properties and rheological properties. In this work, we present a bridge pier collision avoidance system using Magnetorheological Grease Material. Firstly, according to the characteristics of bridge pier collision, a series of Magnetorheological Grease Material are configured, and then the collision avoidance structure of the actual size of the bridge pier is given. The structure can be directly applied to the bridge pier collision avoidance. Secondly the experimental characteristics of the Magnetorheological Grease Material are given, and the experimental results are analyzed. The strong theoretical guidance and engineering basis were provided for the related scientific and technical workers and researchers.

In this paper, we establish the mechanical property analysis of Single-walled Carbon Nanotubes (SWCNTs) modified beam element model based on the molecular structural mechanics method. Then we study the mechanical properties of their radial direction characteristics using the finite element software Abaqus. The model simulated the different bending stiffness with rectangular section beam elements C-C chemical force field. When the graphene curled into arbitrary chirality of SWCNTs spatial structure, the adjacent beam position will change the moment of inertia of the section of the beam. Compared with the original beam element model and the calculation results, we found that the established model largely reduced the overestimate of the original model of mechanical properties on the radial direction of the SWCNTs. At the same time, compared with other methods available in the literature results and the experimental data, the results can be in good agreement.

Gold nanoparticle (AuNP)-polymer composites have emerged as promising candidates for flexible electronics due to their super-high stretchability and metal-like conductivity. Their percolation threshold is, however, much higher than that of 1D carbon nanotubes or silver nanowires. A practical and appealing solution is to assemble AuNPs into 1D quasi-nanowires via the van der Waals interaction. In this letter, electron tunneling is incorporated into the theory of traditional composites to explore the percolation of these nanocomposites. The geometries of AuNP-chains are found to play a key role in determining the effect of electron tunneling and thus the overall percolation behavior. Small and/or short AuNP-chains yield the substantial tunneling effect, leading to the rapid growth in conductivity across a transition zone where the conductivity mechanism transfers from electron tunneling to contact conductance. This unique feature agrees with experimental observation but cannot be characterized directly by existing theories.Gold nanoparticle (AuNP)-polymer composites have emerged as promising candidates for flexible electronics due to their super-high stretchability and metal-like conductivity. Their percolation threshold is, however, much higher than that of 1D carbon nanotubes or silver nanowires. A practical and appealing solution is to assemble AuNPs into 1D quasi-nanowires via the van der Waals interaction. In this letter, electron tunneling is incorporated into the theory of traditional composites to explore the percolation of these nanocomposites. The geometries of AuNP-chains are found to play a key role in determining the effect of electron tunneling and thus the overall percolation behavior. Small and/or short AuNP-chains yield the substantial tunneling effect, leading to the rapid growth in conductivity across a transition zone where the conductivity mechanism transfers from electron tunneling to contact conductance. This unique feature agrees with experimental observation but cannot be characterized directly by e...

More attentions have been paid to Magnetorheological fluid, which is a kind of new functional materials. An elegant device is designed for the test of the mechanical properties of Magnetorheological fluid, and the mechanical properties of ten samples of Magnetorheological fluid are tested with the device. In the experimental investigation, we choose ten samples of Magnetorheological fluid to analyze and obtain the material parameters with the testing device. The effects of the typical influencing factors, such as magnetic induction intensity, ferromagnetic particle volume fraction, base solutions, temperature, shear strain rate, response time, sedimentation stability, yield shear stress, viscosity and zero-field viscosity, etc, are investigated. This work proves that Magnetorheological fluid is reliable and practical through experimental results. We welcome warmly the relevant experts and scholars to exchange and guide further.

As a new intelligent material, Nano-Magnetorheological Material (Nano-MRM) gets a wide range of great concern to researchers and its application scope is very broad. For diagnosis and treatment cancer in one of the most difficult types of intracranial aneurysm, the work established the most practical model on Nano-MRM in intracranial aneurysm therapy research and analyzed quantitatively. The results are effective. Hope the work can be a strong impetus to human progress in the anti-cancer project.

With the development of society, watercraft is used more and more widely. However, the stability and vibration control of watercraft have been the bottleneck of its development. In order to reduce investment cost and the accident risk, the work presents a set of design for the vibration control of propulsion motor TJDJ-1000 on watercraft. The efficiency and reliability of the proposed method are demonstrated by experimental results. Hope the work can effectively promote the rapid development of watercraft.

The kind double-channel Magnetorheological Fluids (MRFs) testing equipment is characterized by low inertia of rotating element and ensures certain precision and economical applicability. Especially, research on and analyze the strain tensor by Finite element software Abaqus. Hope cordially the research can accelerate the study of MRFs with a rapid development.

A theoretical model of temperature change on a kind of self-decoupling magnetorheological (SDMR) damper was established based on conservation of energy, and the constraint equation for structural design parameters of the SDMR damper was improved to satisfy heat dissipation requirements in this work. According to the theoretical model and improved constraint equation, the main structure parameters of SDMR damper were obtained and the damper was tested. The temperature performance test results indicate that the rising temperature makes the damping force decline, and the main affection factors of temperature variation are excitation methods and input current. The results also show that the improved constraint equation and design method introduced are correct and efficient in the engineering.