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1,236 results on '"Ma Chaoqun"'

1. Research progress on the methods of observation and analysis of dental bonding interfaces

Author

MA Chaoqun, LIU Meng, QIU Jun, LIAO Zixuan, ZHOU Wei, and CHEN Jihua

Subjects
dental tissues，, dental bonding，, bonding interface，, scanning electron micrographs，, transmission electron microscope，, confocal laser scanning microscopy，, raman spectroscopy，, optical coherence tomography，, atomic force microscope，, observation and analysis，, Medicine
Abstract

Dental bonding technology and materials have been used widely in dentistry because of their excellent properties. The development of novel bonding technology and materials is constantly being performed to improve the effect of dental bonding restorations. Observation and analysis of the dental bonding interface is one of the most important methods for laboratory evaluation of bonding efficiency. This paper aims to review the methods of observation and analysis of dental bonding interfaces to provide a reference for the selection of evaluation methods in dental bonding research. The features of 6 methods, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM), Raman spectroscopy (RS), optical coherence tomography (OCT) and atomic force microscopy (AFM), were described and summarized. Among these methods, SEM and TEM are used most often in the analysis of fine structures; CLSM and OCT are used for the acquisition of characteristic image signals, such as microleakage and exogenous and endogenous fluorescence; and RS and AFM can test chemical composition and mechanical properties.

Published
2021
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2. Smoke-charged vortex doubles hemispheric aerosol in the middle stratosphere and buffers ozone depletion

Author

Ma, Chaoqun, Su, Hang, Lelieveld, Jos, Randel, William, Yu, Pengfei, Andreae, Meinrat O, and Cheng, Yafang

Subjects
Earth Sciences, Atmospheric Sciences, Climate Action
Abstract

Australian mega-wildfires in the summer of 2019-2020 injected smoke into the stratosphere, causing strong ozone depletion in the lower stratosphere. Here, we model the smoke plume and reproduce its unexpected trajectory toward the middle stratosphere at ~35-kilometer altitude. We show that a smoke-charged vortex (SCV) induced and maintained by absorbing aerosols played a key role in lofting pollutants from the lower stratosphere and nearly doubled the southern hemispheric aerosol burden in the middle stratosphere. The SCV caused a redistribution of stratospheric aerosols, which boosted heterogeneous chemistry in the middle stratosphere and enhanced ozone production, compensating for up to 70% of the ozone depletion in the lower stratosphere. As global warming continues, we expect a growing frequency and importance of SCVs in promoting the impacts of wildfires on stratospheric aerosols and chemistry.

Published
2024

8. Effect of Recycled Powder on Properties of Cement Morta

Author

Zhang Yanxing, Zhang Tongheng, Liu Zhiwu, and Ma Chaoqun

Subjects
Environmental sciences, GE1-350
Abstract

The effects of two types of recycled micro-powder (concrete powder and brick powder) replacing part of cement on the mechanical properties of cement mortar were studied. The results show that the contribution of recycled concrete powder to concrete strength is slightly stronger than that of brick powder. In a certain range of dosage, the performance of recycled concrete powder is close to that of pure cement. When the content of recycled concrete powder is less than 10 %, the compressive strength and flexural strength of cement mortar will not be greatly affected: over 20% cement mortar strength will decrease significantly. When the grinding content of recycled concrete is 5 %, the strength of cement mortar is even increased by 4.5 %. The relationship between recycled brick powder content and cement mortar strength is almost linear to 20% limit. The more recycled brick powder content is, the more obvious the cement mortar strength decreases. The particle size of regenerated powder has a certain influence on its activity. After a certain time of ball milling, the activity of regenerated powder can be effectively increased, but the ball milling time is too long, resulting in very fine particles. The activity of regenerated powder increases slightly with the increase of ball milling time, but the effect gradually decreases after more than 1 h.

Published
2021
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17. A survey on the development status and application prospects of knowledge graph in smart grids

Author

Wang, Jian, Wang, Xi, Ma, Chaoqun, and Kou, Lei

Subjects
Computer Science - Artificial Intelligence, 68T30, I.2
Abstract

With the advent of the electric power big data era, semantic interoperability and interconnection of power data have received extensive attention. Knowledge graph technology is a new method describing the complex relationships between concepts and entities in the objective world, which is widely concerned because of its robust knowledge inference ability. Especially with the proliferation of measurement devices and exponential growth of electric power data empowers, electric power knowledge graph provides new opportunities to solve the contradictions between the massive power resources and the continuously increasing demands for intelligent applications. In an attempt to fulfil the potential of knowledge graph and deal with the various challenges faced, as well as to obtain insights to achieve business applications of smart grids, this work first presents a holistic study of knowledge-driven intelligent application integration. Specifically, a detailed overview of electric power knowledge mining is provided. Then, the overview of the knowledge graph in smart grids is introduced. Moreover, the architecture of the big knowledge graph platform for smart grids and critical technologies are described. Furthermore, this paper comprehensively elaborates on the application prospects leveraged by knowledge graph oriented to smart grids, power consumer service, decision-making in dispatching, and operation and maintenance of power equipment. Finally, issues and challenges are summarised., Comment: IET Generation, Transmission & Distribution

Published
2022
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21. African biomass burning affects aerosol cycling over the Amazon

Author

Holanda, Bruna A, Franco, Marco A, Walter, David, Artaxo, Paulo, Carbone, Samara, Cheng, Yafang, Chowdhury, Sourangsu, Ditas, Florian, Gysel-Beer, Martin, Klimach, Thomas, Kremper, Leslie A, Krüger, Ovid O, Lavric, Jost V, Lelieveld, Jos, Ma, Chaoqun, Machado, Luiz AT, Modini, Robin L, Morais, Fernando G, Pozzer, Andrea, Saturno, Jorge, Su, Hang, Wendisch, Manfred, Wolff, Stefan, Pöhlker, Mira L, Andreae, Meinrat O, Pöschl, Ulrich, and Pöhlker, Christopher

Subjects
Climate Action, Life on Land
Abstract

AbstractSmoke from vegetation fires affects air quality, atmospheric cycling, and the climate in the Amazon rain forest. A major unknown has remained the quantity of long-range transported smoke from Africa in relation to local and regional fire emissions. Here we quantify the abundance, seasonality, and properties of African smoke in central Amazonia. We show that it accounts for ~ 60% of the black carbon concentrations during the wet season and ~ 30% during the dry season. The African smoke influences aerosol-radiation interactions across the entire Amazon, with the strongest impact on the vulnerable eastern basin, a hot spot of climate and land use change. Our findings further suggest that the direct influence of African smoke has been historically relevant for soil fertilization, the carbon and water cycles, and, thus, the development of the Amazon forest ecosystem, even in the pre-industrial era.

Published
2023

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