Tribological and mechanical behaviours of resin-based friction materials based on microcrack filling

To enhance the friction performance of resin-based friction materials,five types of specimens with different polymer ether ketone(PEEK)contents were fabricated and their physiomechanical behaviours were tested and,their tribological properties were investigated using a JF150F-II constant-speed tester.It was found that the addition of PEEK had a positive influence on the properties of the friction materials,and sample FM-3(the shorthand of‘Friction Materials-3’,containing 2 wt%PEEK)exhibited improved friction performance with a fade ratio and recovery ratio of 8.6%and 101.1%respectively.Among all samples,FM-4(the shorthand of‘Friction Materials-4’,con-taining 3 wt%PEEK)had the lowest specific wear rate with a value of 0.622×10^(−7)cm^(3)(N⋅m)^(−1)at 350℃.The PEEK can fill the microcracks in the composite at a high tem-perature and can also cover the hard abrasive particles to prevent them from directly damaging the composite.The findings from this study afford a foundation for studies to further improve the properties of resin-based friction materials.

Investigation of the Potential and Mechanism of Clove for Mitigating Airborne Particulate Matter Emission from Stationary Sources

Vegetative Barriers （VB） have the potential to mitigate air pollutants emitted from area sources, including concentrated Animal Feeding Operations （AFOs）. However, the mechanism has not been fully investigated, thereby limiting the application of vegetation systems in practice. An experimental method with repeatable and controllable conditions was developed to measure the change of Particulate Matter （PM） concentrations at upwind and downwind of VB in the wind tunnel and observe accumulated PM on leaves with Scanning Electron Microscope （SEM）, thus evaluating the ability of VB in mitigating PM emitted from AFOs. Branch-scale vegetation, clove （syzygium aromaticum） was selected because its leaves are one of the major factors affecting PM dispersion. The results show that the branch-scale barriers, as porous medium have the ability to interfere with airflow and reduce PM, which could be influenced by wind speed, particle size fraction and surface area density of clove. Moreover, clove elements could adjust to the wind and the micro structure of clove （such as the hierarchical structures of leaves） affected on the PM deposition. These results indicate that the methods developed in this study may be used to evaluate the potential of vegetation in mitigating PM from stationary sources, and some characteristics of vegetation can be further studied as bionic prototype for exploring engineering application of reducing particulates.

Estimating the risk of completion total thyroidectomy using real-world data to guide initial surgical decision-making for patients with clinical low-risk papillary thyroid carcinoma

Background:Continuing controversy exists in diferent guidelines’recommendations regarding whether total thyroidectomy(TT)or lobectomy is the optimal surgery for patients with low-risk papillary thyroid carcinoma(PTC).Diverse perceptions of the risk of completion TT after lobectomy are the main debate between guidelines and institutions.Methods:Patients who underwent thyroidectomy and prophylactic central lymph node dissection for≤4 cm PTC(January 2007 to December 2020)by high-volume surgeons were included.Patients with preoperatively known highrisk characteristics or suspicious bilateral multifocality were excluded.The pathological fndings were defned as the risk stratifcations of completion TT from low to high to evaluate which initial surgical procedure could allow more patients to meet the criteria of optimal surgical extent.Results:Of 4965 consecutive patients met lobectomy criteria as the initial operation.Aggressive histological subtypes were found in 2.5%of patients,T3b disease in 1.1%,T4 disease in 3.1%,LNs involved≤5 in 29.5%,LNs involved>5 in 3.1%,and incidental bilateral multifocality in 7.9%.According to our defned risk stratifcation system,TT and lobectomy would be considered the optimal initial procedure in 12.0%and 67.2%PTC patients with a tumor≤1 cm and 28.7%and 36.6%in the 1-4 cm groups in our real-world cohort,respectively.Conclusion:Lobectomy alone,as an initial procedure,could allow more low-risk PTC patients with a tumor either≤1 cm or 1-4 cm to achieve the optimal surgical extent.Moreover,surgeons should balance the high-risk characteristics and complication risks during surgery to re-evaluate surgical decision-making.

Bio-inspired Design and Evaluation of Porous Fences for Mitigating Fugitive Dust

Fugitive dust has been recognized as an important contributor to air pollution,and artificial porous fence is one of the most effective management strategies to reduce fugitive dust in open areas.To improve the shelter effects and efficiency of Particulate Matter(PM)reduction of traditional fences,this study proposed five bionic fences and their capability was evaluated through wind tunnel tests.The results indicated that all of bionic fences presented better efficiency in reducing wind speed and PM concentrations compared with traditional fences,and they were more efficient in capturing PM10.Among the bionic fences,the non-woven cloth material with four-leave opening presented the best capability both in wind speed and PM reduction.The proposed bionic fences may be further developed and studied for future application in capturing fine PM and adapting to the wind.

Facial Fabrication of Biomimetic Water Pinning Microstructures on Polyethylene Surfaces with Robust Superhydrophobic Wetting State

Applying hot-embossing technology,a simple and cost-effective method for the fabrication of microstructured High Density Polyethylene(HDPE)surfaces with a robust superhydrophobic wetting state is proposed.Micro-meshes and micro-grooves in the flexible template are filled by the PE melt in the hot embossing process.Subsequently,a two-stage microstructure on the PE film surface is formed.This PE film exhibits a contact angle of 151.8°±2°and roll-offangle of>90~when a 5μL water droplet is dropped on its surface.Water pinning ability on the surface is figured out and roll-off angles are as a quadratic function of specified water droplet volume.Specifically,a 356μN water pinng force appears on the HDPE film due to the solid-vapor composite interface on its surface.Meanwhile,self-cleaning and immersion tests reveal that the HDPE surface with micro-pillars exhibit robust Cassie impregnating wetting state against external pressure.The proposed method for facial fabrication ofmicrostructured surfaces is an appropriate candidate for the development of droplet manipulation and functional biomimetic polymer surfaces.

Erratum to: Facile Fabrication of Biomimetic Water Pinning Microstructures on Polyethylene Surfaces with Robust Superhydrophobic Wetting State

Erratum to:J Bionic Eng(2020)17(4):644651 https://doi.org/10.1007/s42235-020-0052-1 The title was incorrect in the published paper and should be revised as"Facile Fabrication of Biomimetic Water Pinning Microstructures on Polyethylene Surfaces with Robust Superhydrophobic Wetting State".