摘要：
A new and convenient visible-light-induced method has been developed for the synthesis of sulfonylated benzofurans via oxidative cyclization reaction of 1,6-enynes and arylsulfinic acids.This reaction was carried out under metal-free and mild conditions,in which the C-S,C-C and C=O bonds could be sequentially formed in one pot operation.
摘要：
A simple I2O5-mediated method for the construction of sulfonylated benzofurans has been developed under metal-free conditions. The present reaction can be efficiently achieved through the oxidative cyclization of 1,6-enynes and arylsulfonylhydrazides, which provides an attractive approach to a series of sulfonylated benzofurans in moderate to good yields. (C) 2019 Elsevier Ltd. All rights reserved.
摘要：
With the capacity models in the 2004 edition of the European Committee for Standardization's Standard Design of Concrete Structures, a more realistic limit state function is obtained for reinforced concrete columns with random loads eccentricity. Using this function, the applicability of the code-based design factors is discussed. Taking the wind-dominated combination as an example, the probabilistic distribution of loads eccentricity and the statistics of column resistance are analyzed for representative cases. The analysis indicates that the possible loads eccentricity is scattered over a large range, and the probabilistic model of column resistance varies from case to case, which is largely different from the resistance model assumed in previous reliability calibration. With Monte Carlo simulation, the column reliability and the contributions of both tension failure and compression failure to the total failure probability are calculated and obtained for different cases. The results show that the fixed loads eccentricity criterion underestimates differences in the reliability of columns for different loads eccentricity cases and overestimates the column reliability in some tension failure cases. Furthermore, it is found that the tension failure mode contributes most to the total failure probability for not only some columns designed to fail in tension failure but also for some columns designed to fail in compression failure. To attain a robust design, a group of optimum wind load factors varying with cases is recommended. The new calibration results prove that the recommended wind local factors can achieve a better goal.
摘要：
Currently, blockchain technology has been widely researched and is being applied to many other fields, such as financial transactions, E-government, logistics, and supply-chain system. It can be used to store and maintain transaction data through the de-centralized model. In this paper, we propose an autonomous resource request transaction framework based on blockchain in a social network, in which all kinds of resources in the social community can be traded through blockchain technology. When a user needs to acquire some resources from a community, the user may make a transaction with the members from the community through blockchain technology while the members autonomously negotiate each other to reach an agreement. The proposed framework provides an incentive mechanism to encourage community members to disseminate the resources through a smart contract.
摘要：
In this paper, the authors present a stress wave-based active sensing method to detect the crack in FRP-reinforced concrete beams. The embedded smart aggregates (SAs), which utilize Lead Zirconate Titanate (PZT) as transducers, are employed in this research to generate and sense the stress wave. Three specimens are involved in the experimental program and each is made of concrete, longitudinal distributed reinforcement, steel stirrups, main bar (FRP bar or steel bar), and four SAs. A pair of SAs installed on the lower part of the main bar and the other pair of SAs mounted on the upper part of main bar are utilized to monitor the crack occurrence and development in the three test specimens. The signals received by the SA sensors are analyzed in both time domain and frequency domain. The wavelet packet energy is used to extract damage features. The applied load-vertical displacement curves of mid-span in the specimen are obtained. Experimental results show the test specimens experience crushing failure when the concrete compression exceeds its compressive strength. Increasing the contact area between FRP bar and concrete can effectively improve the cracking load of the FRP-reinforced concrete beam and reduce the cracking speed and depth of FRP-reinforced concrete beam; on the other hand, increasing the elastic modulus of the main bar can slow down the crack development of concrete on the upper side of the main bar and decrease the displacement of reinforced concrete beam during the loading test process. The research results show that the developed piezoceramic-based active sensing method, though low-cost, can monitor the crack-induced damage and estimate the process of damage degree in real-time, and has potentials to provide an early warning of crack occurrence and development for FRP-reinforced concrete beams.
摘要：
<jats:title>Abstract</jats:title><jats:p>In terms of Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub>‐based anodes, enormous academic progress has been achieved over the past two decades; however, even with excellent half‐cell performance, the relatively high lithiation potential and unsatisfactory initial coulombic efficiency (ICE) represent two major barriers to their commercial application, at present. We propose partially phosphorized Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> (P−Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub>) with interior void spaces induced by phosphorization to enhance the Li<jats:sup>+</jats:sup> storage property of Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub>‐based anodes. P−Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> anodes offer a much higher capacity at low potential compared with bare Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> electrodes. Additionally, the well‐designed nanostructure with preferable specific surface area prevents the initial irreversible lithium loss, which contributes to a brilliant ICE (80.8 % at 100 mA g<jats:sup>−1</jats:sup>). Moreover, in‐situ X‐ray diffraction proves that the formation of the Li<jats:sub><jats:italic>x</jats:italic></jats:sub>Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> phase results from an initial intercalation process. In particular, the output voltage and energy density of P−Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> full‐cells are much greater than those of Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> full‐cells. In this work, the P−Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> full‐cell exhibits a capacity of 680 mAh g<jats:sup>−1</jats:sup> at 200 mA g<jats:sup>−1</jats:sup> as well as an excellent rate capability of 267 mAh g<jats:sup>−1</jats:sup> with a current density up to 1000 mA g<jats:sup>−1</jats:sup>. This study presents a new strategy to enhance Li<jats:sup>+</jats:sup> storage of Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> enabling low lithiation/delithiation potential and high ICE, which may offer exciting opportunities toward designing high‐performance full‐cells with commercial cathodes.</jats:p>
关键词：
Energy storage;Vanadium redox flow batteries;Carbon paper;MnO2 nanosheets;Electrochemical kinetics
摘要：
An in-situ and controllable redox deposition method has been applied to prepare binder-free MnO2 nanosheet array-decorated carbon paper as negative electrode for vanadium redox flow batteries (VRFB). Electrochemical performance of electrode depends on amount and uniform distribution of MnO2 on carbon paper, which were controlled by solution pH, KMnO4 concentration, and deposition time. Modified carbon paper (CPA-05-30) with a uniform MnO2 nanosheet coating layer was obtained in 0.05 M KMnO4 + 0.5 M H2SO4 solution for 30 min. CPA-05-30 presents the most excellent electrocatalytic performance for V3+/V2+ redox reaction. On CPA-05-30, charge transfer and diffusion processes for V3+/V2+ redox reaction are accelerated as a result of MnO2 nanosheet with high catalytic activity and excellent hydrophilcity. Therefore, loading MnO2 on carbon paper improves electrochemical activity V3+/V2+ redox reaction. Moreover, in charge-discharge test, the cell using CPA-05-30 as negative electrode shows higher discharge capacity and better capacity retention at 50 mA cm(-2) for 50 cycles in comparison with pristine cell. It indicates that MnO2 nanosheet can efficiently increase electrolyte utilization. At 100 mA cm(-2), energy efficiency of the cell using CPA-05-30 is 66.4%, which is 6.0% higher than that of pristine cell. MnO2 nanosheet decorated carbon paper shows excellent electrochemical properties for energy storage application, which evidences its potential application in VRFB. (C) 2019 Elsevier Ltd. All rights reserved.
摘要：
ZrO2 nanoparticle decorated carbon nanofibers (ZrO2/CNF) were explored by electrospinning technique with ZrOCl2 center dot 8H(2)O and polyacrilonitrile (PAN) as precursors, and were considered as negative electrode for vanadium redox flow battery (VRFB). It is found that the ZrO2 nanoparticle uniformly embedded in the CNF not only increases the disorder of CNF, but also improves the catalytic activity of CNF, further resulting in good electrochemical activity. Specially, the sample with proper content of ZrO2 (CNF-ZrO2-18) shows superior electrochemical activity for the negative couple for VRFB. Furthermore, the charge-discharge tests verify that CNF-ZrO2-18 can enhance performance of cell. At 100 mA cm(-2), the discharge capacity and energy efficiency of the cell with CNF-ZrO2-18 arrive at 91.5 mA h and 73.3%, 8.7% and 8.3% more than those of pristine cell, respectively. After charging and discharging for 50 cycles at 80 mA cm(-2), the cell exhibits outstanding stability with initial discharge capacity retention of 95.0%. The high electrochemical performance of ZrO2/CNF mainly comes from the good electrocatalytic properties of ZrO2 and in situ decoration for CNF by electrospinning technique. (C) 2019 Elsevier Ltd. All rights reserved.
