On the Viscoelastic Parameters of Gussasphalt Mixture Based on Modified Burgers Model: Deviation and Experimental Verification

Viscoelasticity is an important characteristic of gussasphalt mixtures. The aim of this study is to find the correct viscoelastic material parameters of the novel gussasphalt applied in the 4th Yangtze River Bridge based on the modified Burgers model. This study firstly derives the explicit Prony series form of the shear relaxation modulus of viscoelastic material from Laplace transformation, to fulfill the parameter inputting requirements of commonly used finite element software suites. Secondly, a kind of uniaxial penetration creep experiment on the gussasphalt mixtures is conducted. By fitting the creep compliance, the viscoelastic parameters characterized by the modified Burgers model are obtained. And thirdly, based on the viscoelastic test data of asphalt mixtures, the Prony series formula derived in this study is verified through the finite element simulation. The comparison results of the relative errors between the finite element simulation and the theoretical calculation confirm the reliability of the Prony series formulas deduced in this research. And finally, a stress-correcting method is proposed, which can significantly improve the accuracy of model parameters identification and reduce the relative error between the finite element simulation and the experimental data

Development of a novel three degrees-of-freedom rotary vibration-assisted micropolishing system based on piezoelectric actuation

The limited degrees of freedom (DOF) and movement form of the compliant vibration-assisted processing device are inherent constraints of the polishing technique. In this paper, a concept of a 3-DOF rotary vibration-assisted micropolishing system (3D RVMS) is proposed and demonstrated. The 3-DOF means the proposed vibration-assisted polishing device (VPD) is driven by three piezo-electric (PZT) actuators. Compared with the current vibration-assisted polishing technology which generates a trajectory with orthogonal actuators or parallel actuators, a novel 3-DOF piezoelectrically actuated VPD was designed to enable the workpiece to move along the rotational direction. Meanwhile, the proposed VPD can deliver large processing stoke in mrad scale and can be operated at a flexible non-resonant mode. A matrix-based compliance modeling method was adopted for calculating the compliance and amplification ratio of the VPD. Additionally, the dynamic and static properties of the developed VPD were verified using finite element analysis. Then, the VPD was manufactured and experimentally tested to investigate its practical performance. Finally, various polished surfaces which used silicon carbide (SiC) ceramic as workpiece material were uniformly generated by the high-performance 3D RVMS. Compared with a nonvibration polishing system, surface roughness was clearly improved by introducing rotary vibration-assisted processing. Both the analysis and experiments verified the effectiveness of the present 3D RVMS for micro-machining surfaces

Vibration-Assisted Roll-Type Polishing System Based on Compliant Micro-Motion Stage

This paper aims to create a high-quality surface based on the linear contact material removal mechanism. For this paper, a piezo-driven, flexure-based micro-motion stage was developed for the vibration-assisted roll-type precision polishing system. Meanwhile, the compliance matrix method was employed to establish the amplification ratio and compliance model of the flexure mechanism. The dimensions of the mechanism were optimized using the grey wolves optimization (GWO) algorithm, aiming to maximize the natural frequencies. Using the optimal parameters, the established models for the mechanical performance evaluation of the flexure stage were verified with the finite-element method. Through closed-loop test, it was proven that the proposed micro-motion stage performs well in positioning micro motions. Finally, high quality surface using silicon carbide (SiC) ceramic with 36 nm Sa was generated by the independently developed vibration-assisted roll-type polishing machine to validate the performance of the established polishing system

Ionic liquid modified graphene for supercapacitors with high rate capability

Ionic liquids (ILs) with large electrochemical windows up to 4 V have been employed as the electrolyte to boost the energy density of graphene-based supercapacitors. However, due to the larger molecular size, lower conductivity, and higher viscosity of the IL electrolyte, graphene-based supercapacitors in IL electrolyte usually exhibit low rate capability. To make graphene-based electrodes more compatible with the IL electrolyte, we functionalized chemically reduced graphene oxide with the same IL which is also used as the electrolyte. Electrochemical test results show that the relaxation time and charge transfer resistance at electrode-electrolyte interface for IL modified electrode is one third and one fourth of that for the pristine graphene electrode, respectively, indicating the improved compatibility between the IL modified electrode and the electrolyte. Furthermore, the capacitance retention of the IL modified electrode from current density of 0.5 to 20 A g(-1) is 85%, which is much higher than that of the pristine electrode (53%). (C) 2015 Elsevier Ltd. All rights reserved

Microbial diversity and ecotoxicity of sediments 3 years after the Jiaozhou Bay oil spill

Abstract In 2013, the “Qingdao oil pipeline explosion” released an estimated 2000 tons of oil into the environment. Sediment samples were collected from ten sites in Jiaozhou Bay and Shilaoren Beach to evaluate the influence of the spilled oil on the benthic environment 3 years after the oil spill accident. The compositions of oil, bacterial diversity and biotoxicity were examined in this study. The results showed that the concentration of total petroleum hydrocarbons (TPHs) peaked near the oil leak point and gradually decreased along the coastline, ranging from 21.5 to 133.2 μg/g. The distribution of polycyclic aromatic hydrocarbons (PAHs) was correlated with TPH, and naphthalenes were dominant in the 20 detected PAHs. The bacterial diversities in seriously polluted and slightly polluted sediments were completely different. As degrading bacteria, Alcanivorax and Lutibacter were the main genera at the oil-polluted sites. The analysis of biotoxicity by the luminescent bacteria method showed great differences among the polluted sites, the control site in Jiaozhou Bay, and the non-polluted site outside of Jiaozhou Bay. The biotoxicity also peaked at the site near the oil leak point. These results indicate that the oil spill that occurred 3 years ago still affects the environment and impacts the bacterial communities in the sediments

Molecular basis of ubiquitin recognition by the autophagy receptor CALCOCO2

<p>The autophagy receptor CALCOCO2/NDP52 functions as a bridging adaptor and plays an essential role in the selective autophagic degradation of invading pathogens by specifically recognizing ubiquitin-coated intracellular pathogens and subsequently targeting them to the autophagic machinery; thereby it is required for innate immune defense against a range of infectious pathogens in mammals. However, the mechanistic basis underlying CALCOCO2-mediated specific recognition of ubiqutinated pathogens is still unknown. Here, using biochemical and structural analyses, we demonstrated that the cargo-binding region of CALCOCO2 contains a dynamic unconventional zinc finger as well as a C₂H₂-type zinc-finger, and only the C₂H₂-type zinc finger specifically recognizes mono-ubiquitin or poly-ubiquitin chains. In addition to elucidating the specific ubiquitin recognition mechanism of CALCOCO2, the structure of the CALCOCO2 C₂H₂-type zinc finger in complex with mono-ubiquitin also uncovers a unique zinc finger-binding mode for ubiquitin. Our findings provide mechanistic insight into how CALCOCO2 targets ubiquitin-decorated pathogens for autophagic degradations.</p

Drug resistance patterns of Klebsiella pneumonia strains isolated from Shaoxing City, Zhejiang Province in 2019: a multi-centre retrospective study

We retrospectively collected drug susceptibility data of Klebsiella pneumoniae from six tertiary hospitals in Shaoxing City in 2019 and performed a comparative analysis of drug resistance among different hospitals, sexes, ages, and specimens. In total, 1954 strains were identified. The antibiotic resistance rate varied from 4.42% to 36.18%. Most K. pneumoniae were still susceptible to carbapenems and tigecycline, with resistance rates of less than 10%. Drug resistance was relatively mild in Shaoxing Traditional Chinese Medicine Hospital and Shaoxing Maternal and Children Health Hospital, but most severe in Affiliated Hospital of Shaoxing University. Specimens were primarily obtained from elderly and male patients, and the resistance rate increased with age. The specimens were mostly collected from the respiratory and urinary tracts. No carbapenem-resistant strains were collected in 112 isolates from patients under 20 years of age. The ratio of carbapenem-resistant K. pneumoniae isolates was highest in blood-isolated strains (23.86%), and that of extended-spectrum beta-lactamase positive strains was highest in non-blood-sterile body fluids (37.37%). The resistance spectrum of K. pneumoniae varied between hospitals in the same area. Elderly and male patients, non-sterile body fluids, and blood source strains should be seriously considered in empirical treatment. Highlights Prevention and control should be strengthened in hospitals with high rate of drug resistance. Strengthen screening of drug-resistant bacteria in specific populations. Transferred patients should be alerted to the bacterial drug resistance status

MOESM1 of Microbial diversity and ecotoxicity of sediments 3Â years after the Jiaozhou Bay oil spill

Additional file 1: Figure S1. PCA results of the sampling sediments. Figure S2. The standard curve of the biotoxicity analysis