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Using microwave heating technology to assist concrete recycling have great potential for improve the quality of recycled concrete aggregate. Unfortunately, there are few studies explored on the properties of concrete incorporating microwave treated coarse aggregates. This study aims to investigate the performance of coarse aggregate after microwave treatment and to evaluate the properties of the resulting concrete incorporated microwave treatment aggregate. The water absorption and crushing value tests were carried out to study the effect of microwave heating treatment on the physical properties of coarse aggregates. Concrete incorporated aggregate with various microwave heating parameters was fabricated and tested. The results indicated that physical performance of microwave treated aggregate was within the range of specification requirement and water absorption and crushing value of coarse aggregate heated under low microwave power levels (2–3 kW) is very closed to the untreated samples, while coarse aggregates treated with high power levels showed a significant increase. It was also observed that concrete made out of low microwave power levels heated aggregates are able to achieve strength on par with natural coarse aggregate concrete. In addition, in case of similar strength, the elastic modulus of microwave treated aggregate concrete is similar to natural aggregate concrete. These results indicate that using low microwave power levels to assisted aggregates recycling can reduce the damage to coarse aggregates to some extent, which provide a further understanding for the application of microwave-assisted aggregates recycling.

Due to the potential for significant process benefit, microwave assisted concrete recycling is highlighted by many scholars and engineers over the world recently. In this paper, a multi-field model is established to simulate the microwave heating process of concrete specimen with single-particle aggregate by using of COMSOL Multiphysics. The validation of this model is verified by comparison with temperature from experiment. Mechanical properties of aggregate-mortar interface during microwave heating process was experimentally investigated. Electric, temperature, stress field evolution and moisture transformation during microwave heating process are discussed in detail. Temperature and stress gradient at mortar-aggregate interface influenced by microwave heating power, frequency and duration are analyzed and graphically presented, which are the dominant factors to achieve the interface debonding. Based on the comparison between concrete absorbed energy and temperature variation, energy efficiency for microwave heating concrete is also briefly discussed. Results of this investigation could provide a multi-field understanding for the microwave treatment on concrete.

Microwave heating is a novel and promising method to remove mortar that adheres to aggregates in recycled concrete. A systematic experiment was carried out to evaluate the heating results o...

Development of highly active and durable non-precious metal bi-functional electrocatalyst for both oxygen reduction and evolution reaction (ORR and OER) remains a significant challenge. Herein, porous mixed spinel MnCoxO4 was loaded on the N-doped multi-walled carbon nanotubes (MnCoxO4/NCNT) through a facile one-pot hydrothermal method to work as a bi-functional oxygen electrocatalyst. Physical characterizations confirm that the MnCoxO4 nanoparticles are composed of mixed spinel-type Co2MnO4 and (Co, Mn)[Mn, Co]2O4 with a diameter of 5–10 nm, which are dispersed on NCNT with secondary aggregation and resultant porous structure. Electrochemical measurements show that the MnCoxO4/NCNT catalyst exhibits high ORR catalytic activity with a dominant four-electron ORR catalytic pathway, remarkable durability, excellent methanol-tolerance, as well as superior OER catalytic activity with significantly decreased overpotential of 0.479 V in alkaline media. The multiple valence states of Co and Mn ions in MnCoxO4 coupled with the enlarged specific surface area with the help of NCNT exert crucial roles for the superior catalytic performance for both ORR and OER. Such a bi-functional oxygen electrocatalyst based on mixed spinel MnCoxO4 provides a new direction for developing low-cost, highly efficient, and robust multiple valence states transition metal-based electrocatalysts for oxygen electrode.

Hyaluronic acid (HA) is applied in a number of medical applications and HA of different molecular weight (Mw) are used in different pharmaceutical preparations. In determination of Mw by muti-angle laser light-scattering (MALS), refractive index increment (dn/dc) is an important parameter for accuracy. Herein, the influence of dn/dc on the Mw of HA in stroke-physiological saline solution is investigated by MALS in this work. Additionally, the Mw variation of HA in the manufacturing process of preparations is measured. It is shown that each HA sample corresponds to a specific value of dn/dc, which is varied from 1.38 to 1.74 L/g with the Mw increasing from 13.5 to 2840 kDa in solution. It is indicated by the results from both MALS approach and viscometry that appropriate dn/dc should be selected for Mw determination. In steam sterilization process of preparations at 121 °C, the Mw and conformation of HA can be accurately and rapidly determined by MALS. This work provides a precise method to determine the Mw of HA in the medical applications and preparation industries.

Controllable growth of uniform nanoparticles with specific morphology to obtain high active electrocatalyst is a key common problem in developing efficient energy conversion and storage devices. In this work, a tangerine peel-derived carbon (TPC) supported mixed manganese oxides (MnOx/TPC) was synthesized for oxygen reduction reaction (ORR) through a facile pyrolysis procedure. By making full use of the confinement effect of tangerine peel cells, the MnOx nanoparticles of MnOx/TPC-800 are obtained with a components of Mn(II), Mn(III) and Mn(IV) with cubic morphology of about 15 nm and evenly dispersed on the TPC surface. Electrochemistry measurements show that MnOx/TPC-800 demonstrates excellent ORR performance with a comparable half-wave potential to commercial Pt/C and a high onset potential with a dominant 4e− catalytic process, superior stability, and remarkable immunity to methanol crossover effect in alkaline media. The synergy effect between multi-oxidation states MnOx and TPC of MnOx/TPC-800 is proved to play significant factor for its high ORR performance. This study provides a valuable and rational strategy to construct morphology-controlled metal nanoparticles with unique carbon materials in developing cost-effective catalysts for fuel cells and metal air batteries.

Exploring cost-effective, high-performance and durable non-precious metal catalysts is of great significance for the acceleration of sluggish oxygen reduction reaction (ORR). Here, we report an intriguing heteroatom-doped graphitized carbon encased Fe species composite by introducing N, S and B sequentially. The experimental approach was designed ingeniously for that the FeCl3·6H2O could catalyze thiourea to synthesize N, S co-doped carbon materials which would further react with H3BO3 and NH3 (emerged at the heat-treatment process) to prepare N, S and B co-doped carbon materials (Fe-N/S/B-C). The Fe-N/S/B-C exhibits an impressive ORR activity for its half-wave potential of −0.1 V, which is 36 mV or 19 mV higher than that of the corresponding single or dual doped counterparts (Fe-N-C or Fe-N/S-C) and 31 mV positive than that of Pt/C catalyst, respectively. Further chronoamperometric measurement and accelerated aging test confirm the excellent electrochemical durability of Fe-N/S/B-C with the stable core–shell structure. The remarkable ORR performance and facile preparation method enable Fe-N/S/B-C as a potential candidate in electrochemical energy devices.

The construction of nonprecious metal catalysts for the oxygen reduction reaction (ORR) is highly desirable but remains as a key challenge for fuel cells and metal–air batteries. Herein, we designed and synthesized novel Fe2P nanoparticles embedded in an N,P co-doped mesoporous carbon catalyst (Fe2P/NPC) through direct pyrolysis of o-methylaniline in the presence of FeCl3·6H2O, H3PO4, silica nanospheres, and hexadecyltrimethyl ammonium bromide (CTAB) micelles. Transmission electron microscopy, Brunauer–Emmett–Teller (BET), X-ray diffraction and X-ray photoelectron spectroscopy measurements demonstrated that the obtained three-dimensional mesoporous Fe2P/NPC catalyst possessed a considerable specific surface area of 785 m2 g−1 with high contents of Fe2P nanoparticles, pyridinic N, and graphitic N species. Electrochemical evaluations showed that the formed Fe2P/NPC exhibited superior ORR performance to Pt/C in terms of a comparable onset potential (−0.01 V vs. Ag/AgCl electrode), about 20 mV higher half-wave potential, excellent stability and remarkable methanol tolerance in alkaline media. The synergistic effect of pyridinic N, graphitic N and Fe2P species together with its three-dimensional porous structure contribute to the impressive ORR performance. This research, most importantly, provides new clues to the rational development of cost-effective FePx-based catalysts for the ORR.

Controlled synthesis of efficient core-shell non-precious metal catalysts for oxygen reduction reaction (ORR) is undoubtedly crucial but challenging for the extensive application of fuel cells and metal-air batteries. Herein, we prepared a core-shell structured Fe/FeCx nanoparticles and porous carbon composited catalyst (Fe/FeCx@NC) via a facile two-step heat treatment strategy. The Fe/FeCx@NC-800−0.5 prepared with secondary anneal at 800 °C for 0.5 h exhibits superior ORR performance to the commercial Pt/C in terms of comparable onset potential, higher half-wave potential, and outstanding long-term durability in alkaline media. Through combining the physical and electrochemical characterizations of Fe/FeCx@NC-T−t with different anneal temperature and precursors, the outstanding ORR performance of Fe/FeCx@NC-800−0.5 is caused by the synergistic effect between Fe/FeCx core and enriched pyridinic N- and graphitic N-doped carbon shell as well as porous carbon with large specific surface area. The structure-activity relationship of core-shell structured Fe–N–C catalysts for ORR provides directions for the development of advanced nonprecious metals catalysts.

In order to solve the problem of intelligent obstacle avoidance when an unmanned surface vehicle navigates autonomously in a complex marine environment, the obstacle avoidance is divided into stationary obstacle avoidance and dynamic obstacle avoidance. Based on the ant colony algorithm, the local path planning of the simplified model of the unmanned surface vehicles is carried out to achieve the static collision avoidance. And in accordance with the Convention on the International Regulations for Preventing Collisions at Sea (COLREGS), a dynamic obstacle model is established and calculated to obtain the changes of the speed and course of the unmanned surface vehicles under different encounters. It is shown through the simulations that the proposed approach considering multiple factors can achieve the automatic collision avoidance.

Microwave assisted concrete recycling is highlighted by a large number of research groups all over the world due to its potential for significant process benefit. In this paper, systematic experiments are established to investigate the heating outcomes of mortar-aggregate under microwave irradiation. Four different aggregates are selected that widely used as aggregates in concrete. The temperature variations of mortar and aggregate under different heating times and microwave power inputs are obtained. The crack formation, propagation and material damage during the heating process are illustrated. Push-out tests are conducted after microwave heating process to investigate the interface mechanical behavior of aggregate and mortar. The physical properties of recycled aggregate, including apparent density, porosity, water absorption, toughness and adhered mortar percentage after microwave treatment methods are evaluated. The research proves that microwave irradiation could weaken the bonding between mortar and aggregate effectively, which provide a contribution and reference for the further application of microwave-assisted aggregates recycling.

This paper proposes a docking device by using only magnetic force with multi-dipole for CubeSat/micro-satellite. An innovative electromagnetic capture device was recently proposed to increase the reliability and simplify rendezvous operations. The device could be implemented in the re-configurable space structures that architect large structure or reconstruct themselves by assembling basic structural units. The joining mechanism is designed to combine in a simple way of probe-drogue configurations, through the docking ports of auto attraction capabilities, avoiding the need of a large amount of actuators usually employed in larger docking ports. The paper presents the design and control aspects of this magnetic capture device. One remarkable benefit of this device is that it does not require attitude controls for final rendezvous stage and doesn't require propulsion. The final contact is secured thanks to a current control of passive magnet. The performance of magnetic force is analyzed, and test results are presented.

Promoting the oxygen reduction reaction (ORR) catalytic activities of cost-effective catalysts is of great significance for the development of various energy conversion and storage systems. Herein, we describe the preparation of a highly active N- and S-co-doped ketjenblack (Kb) by facile pyrolysis of a mixture of thiourea and Kb in the presence of FeCl3⋅6 H2O followed by an acid-leaching process. This novel synthetic approach was rationally designed with the consideration that thiourea could easily introduce both N and S heteroatoms into the carbon matrix by a heat-treatment method by releasing plentiful reactive N- and S-containing gases, which could simultaneously optimize the porous structure of the resultant catalyst. Physical characterization revealed that N and S were homogeneously incorporated into the nanostructure of Kb and formed a hierarchical porous structure with a high specific surface area. The N/S-Kb catalyst showed impressive ORR activity, with an onset potential of 0.08 V at 0.1 mA cm−2, which is 20 mV more positive than that of commercial 20 wt. % Pt/C catalyst. This was coupled with long-term durability and superior methanol tolerance in alkaline media. The improved ORR performance can be mainly ascribed to synergistic contributions of highly efficient active sites arising from high contents of thiophene S and pyridinic N along with the high specific surface area and the favorable mass-transport properties arising from the hierarchical porous structure. The remarkable ORR performance and facile preparation method make the N/S-Kb catalyst a promising substitute for Pt in electrochemical energy devices.

Enzyme-linked immunosorbent assays (ELISA) show extensive application in immunoassays, to detect and monitor protein biomarkers in clinical diagnosis. Nevertheless, the time required and its multiple steps limit its application. We take advantage of a polyethyleneimine (PEI) gold nanoparticle (GNP) coated microwell plate to perform blocking-free ELISA, in which no nonspecific protein adsorption appears on the GNP layer. If the PEI-GNP coated microwell plate and immobilization of captured antibodies on the plate are prepared in advance, such as using an ELISA kit, the whole ELISA process can be finished in less than 2 h. Meanwhile, we have ensured that the GNP layer can preserve the precision and good linearity of ELISA without causing negative effects on the plate.