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Opposite effects of Co and Cu dopants on the catalytic activities of birnessite MnO2 catalyst for low-temperature formaldehyde oxidation
Get PDFDefect engineering is an effective strategy to enhance the activity of catalysts for various applications. Herein, it was demonstrated that in addition to enhancing surface properties via doping, the influence of dopants on the surface-intermediate interaction is a critical parameter that impacts the catalytic activity of doped catalysts for low-temperature formaldehyde (HCHO) oxidation. The incorporation of Co into the lattice structure of δ-MnO2 led to the generation of oxygen vacancies, which promoted the formation of surface active oxygen species, reduced activation energy, and enhanced catalytic activity for low-temperature oxidation of HCHO. On the contrary, Cu doping led to a drastic suppression of the catalytic activity of δ-MnO2, despite its enhanced redox properties and slight increase in the surface concentration of active oxygen species, compared to pristine δ-MnO2. Diffuse reflectance infrared Fourier transform analysis revealed that in the presence of Cu, carbonate intermediate species accumulate on the surface of the catalysts, leading to partial blockage of active sites and suppression of catalytic activity
Quasi-solid-state electrolyte for rechargeable high-temperature molten salt iron-air battery
Get PDFMolten salts are a unique type of electrolyte enabling high-temperature electrochemical energy storage (EES) with unmatched reversible electrode kinetics and high ion-conductivities, and hence impressive storage capacity and power capability. However, their high tendency to evaporate and flow at high temperatures challenges the design and fabrication of the respective EES devices in terms of manufacturing cost and cycling durability. On the other hand, most of these EES devices require lithium-containing molten salts as the electrolyte to enhance performances, which not only increases the cost but also demands a share of the already limited lithium resources. Here we report a novel quasi-solid-state (QSS) electrolyte, consisting of the molten eutectic mixture of Na2CO3-K2CO3 and nanoparticles of yttrium stabilized zirconia (YSZ) in a mass ratio of 1:1. The QSS electrolyte has relatively lower volatility in comparison with the pristine molten Na2CO3-K2CO3 eutectic, and therefore significantly suppresses the evaporation of molten salts, thanks to a strong interaction at the interface between molten salt and YSZ nanoparticles at high temperatures. The QSS electrolyte was used to construct an iron-air battery that performed excellently in charge-discharge cycling with high columbic and energy efficiencies. We also propose and confirm a redox mechanism at the three-phase interlines in the negative electrode. These findings can help establish a simpler and more efficient approach to designing low-cost and high-performance molten salt metal-air batteries with high stability and safety
The regulation of religious communities in the late middle ages: a comparative approach to Ming China and pre-reformation England
Get PDFThis article examines the regulation of religious life in the late Middle Ages (14th and 15th centuries), focusing comparatively on Catholic monastic communities in pre-Reformation England and Buddhist monasticism in early Ming China. This comparative approach to two of the most important monastic traditions across Eurasia allows us to problematize the paradigm of ideas and praxes surrounding monastic self-governance in Latin Christendom and to integrate the current scholarship on Ming regulation of religious communities by investigating the pivotal changes in imperial religious policies taking place in the early period of this dynasty. We find that monks and secular authorities at the two ends of Eurasia often shared the same concerns about the discipline of religious men and women, the administration of their properties, and the impact of these communities on society at large. Yet, the article identifies significant differences in the responses given to these concerns. Through the analysis of primary sources that have thus far been overlooked, we show how in early Ming China the imperial government imposed a strict control over the education, ordination and disciplining of Buddhist monks. This bureaucratic system was especially strengthened during the reign of Zhu Yuanzhang (r. 1368–1398), when the figure of the Monk-Official and other tools of secular regulation were introduced, and limits to property claims and economic activities of monasteries were imposed. Instead, during the same period, English monasteries benefited from the previous disentangling of the Church from secular political authorities across Europe. In fact, in late medieval England, the Benedictine tradition of self-governance and independence from the secular sphere was arguably even more marked than in the rest of the continent
Understanding environmental justice capital in China — a new framework to study environmental justice in contexts
Get PDFEnvironmental justice has drew worldwide attention since the 1982 protest in USA to against duping toxic waste. In the globalization era, worldwide scholars and environmental activists are actively engaged in related studies and social movements. However, these researches and movements usually ignore the influences of local contexts on local environmental justice configurations, including related researches in China. Whilst, evidences have been provided that different forms of capital from contexts, such as economic, social, political, natural capital and cultural capital, will affect the local concept of environmental justice. That is to say environmental justice should have different discourse from what has been researched in western countries in different contexts. Thus, this research will discuss the common ground of environmental justice study framework and promote the new conceptual framework “environmental justice capital” for having a better understanding environmental justice in contexts. Additionally, the framework of “environmental justice capital” will be put in Chinese contexts as a preliminary discussion to get an initial image of environmental justice in China
Influence of stabilisers on the unconfined compressive strength of a fine soil
Get PDFIn foundation engineering, weak subgrade soils are usually improved by adding several stabilisers to satisfy construction requirements, but the influence degree of each stabiliser on the strength of the stabilised soils is rarely studied. In this study, a series of unconfined compressive strength tests was conducted on a fine soil stabilised with various proportions of cement, lime, fly ash and gypsum. The influences of the four stabilisers were investigated through quantitative analysis and grey correlation analysis. The quantitative analysis examined the trends of the unconfined compressive strength with increasing contents of different stabilisers. It was found that there existed optimum fly ash and gypsum contents in this study. Also, the cement had the highest positive impact on the unconfined compressive strength. In the grey relational analysis, different normalisation methods were utilised, and it was found that the normalisation method and the trend of the strength with rising stabiliser content affected the order of the impact of various stabilisers. The grey relational analysis with a range-normalisation method provided a reasonable order of impact in this study
Leadership preparation in China: providers’ perspectives
Get PDFIn China, accreditation training programme has been a compulsory programme for all the aspiring and new principals, which is also a part of National Training Plan. Under such hierarchical system, leadership preparation in China is supported, implemented, evaluated, and also, constrained by different levels of administrative organisations and various professional providers. The purpose of the study was to understand the role definition and task allocation of different levels of administrations and providers, as well as how they work as a whole for leadership preparation. The study features a qualitative design that combined data from policy document analysis and semi-structured interviews of people who directly involved in this procedure. Data collected in qualitative strand were coded and analysed thematically through discourse analysis. We identified a completed, but disintegrated system for leadership preparation. The results provided important practice and policy implications. We suggest the collaboration and appropriate supervision among different providers and develop a systematic mechanism for principal preparation and development
Study on toughness improvement of a rosin-sourced epoxy matrix composite for green aerospace application
Get PDFA high temperature epoxy resin was formulated by using a rosin-sourced anhydride-type curing agent, i.e., maleopimaric acid (RAM), and a two-component epoxy consisting of an E51-type epoxy and a solid phenolic epoxy to form a bio-sourced green matrix resin. The glass transition temperature of the final resin was 238◦C Carbon fiber composite prepreg and was manufactured and laminated into composite specimens. Interleaving Toughening Technology (ITT) was applied to the laminates by using Polyamide interleaf veils. The interlaminar fracture toughness and compression after impact (CAI) strength were investigated and showed that the opening Mode I interlaminar fracture toughness GIC and the Mode II interlaminar fracture toughness GIIC of the specimens with interleaves were significantly improved from 227.51 J/m2 to 509.22 J/m2 and 1064.3 J/m2 to 1510.8 J/m2, respectively. Correspondingly, the drop-weight impact test shows that the interleaves reduced the impact damage area from 20.9% to 11.3% of the total area, and the CAI residual strength was increased from 144 MPa to 191 MPa. Meanwhile, mechanical tests showed that the in-plane properties of the interleaved laminates were slightly reduced due to carbon fiber volume fraction reduction. In conclusion, the high glass transition temperature, fracture toughness and CAI behaviour make the green resin matrix composite a potential candidate for aerospace applications
Understanding health and social challenges for aging and long-term care in China
Get PDFThe second King’s College London Symposium on Ageing and Long-term Care in China was convened from 4 to 5th July 2019 at King’s College London in London. The aim of the Symposium was to have a better understanding of health and social challenges for aging and long-term care in China. This symposium draws research insights from a wide range of disciplines, including economics, public policy, demography, gerontology, public health and sociology. A total of 20 participants from eight countries, seek to identify the key issues and research priorities in the area of aging and long-term care in China. The results published here are a synthesis of the top four research areas that represent the perspectives from some of the leading researchers in the field. © The Author(s) 2020
Large-eddy simulation of gas–liquid two-phase flow in a bubble column reactor using a modified sub-grid scale model with the consideration of bubble-eddy interaction
Get PDFThe Eulerian–Eulerian Large-eddy simulations (LES) of gas–liquid two-phase flow in a cylindrical bubble column reactor have been conducted. When considering the turbulent eddy viscosity in LES, apart from the well-accepted contributions from shear turbulence and bubble induced turbulence (BIT), the effect of the interaction between entrained bubbles and eddies with a similar turbulence length scale to the sub-grid scale (SGS) cannot be neglected. With the consideration of the bubble response to the eddies on the induced sub-grid stresses, a modified SGS model, which incorporates the Stokes number, St, was proposed. The results of LES clearly indicate that the use of the modified SGS model can effectively capture the transient bubbly flow in the cylindrical bubble column. The power turbulent kinetic energy spectrum obtained in LES indicates that a slope similar to Komogorov -5/3 scaling law and the -3 scaling law can still be identified for a critical frequency f=10.70 Hz. © 2020 The Author(s
Important considerations in optimising the structural aspect of a SDOF electromagnetic vibration energy harvester
Get PDFThis study investigates several important considerations to be made when optimising the structural aspects of a single-degree-of-freedom (SDOF) electromagnetic vibration energy harvester. Using the critically damped stress method, the damping and power output of the harvester were modelled and verified, displaying an excellent agreement with the experimental results. The SDOF harvester was structurally optimised under a certain set of constraints and it was found that under the fixed beam’s thickness condition, the harvester displayed an insignificant increase in power output as a function of volume when the device’s size was relatively larger. This highlights the importance of considering a smaller practical volume for this case. Additionally, when optimising the device using a low stress constraint and a low damping material, it was observed that considering the load resistance as an input parameter to the objective function would lead to a higher power output compared to the optimum load resistance condition. Further analysis indicated that there exists a power limit when the electromagnetic coupling coefficient approaches infinity. For the case of a high electromagnetic coupling coefficient value and a small volume constraint, it is possible to achieve approximately 80.0% of the harvester’s power limit. Finally, it was demonstrated that a high power output can be achieved for a SDOF electromagnetic harvester by considering a high-density proof mass centred at the free end of the beam
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