Review on Applications of X-ray computed tomography for coal characterization : recent progress and perspectives

This research was funded by the National Natural Science Foundation of China (grant nos. 42130806, 41830427, 41922016 and 42102227).Peer reviewedPostprin

Microstructure Characterization Techniques for Shale Reservoirs : A Review

Funding This work was funded by the National Natural Science Foundation of China (Grant nos. U19B6003-03-01 and 42030804).Peer reviewedPublisher PD

Intelligent classification of coal structure using multinomial logistic regression, random forest and fully connected neural network with multisource geophysical logging data

Acknowledgments This research was funded by the National Natural Science Foundation of China (grant nos. 42130806, 41922016 and 41830427).Peer reviewe

Single Photon Emission from Single Perovskite Nanocrystals of Cesium Lead Bromide

The power conversion efficiency of photovoltaic devices based on semiconductor perovskites has reached ~20% after just several years of research efforts. With concomitant discoveries of other promising applications in lasers, light-emitting diodes and photodetectors, it is natural to anticipate what further excitements these exotic perovskites could bring about. Here we report on the observation of single photon emission from single CsPbBr3 perovskite nanocrystals (NCs) synthesized from a facile colloidal approach. Compared with traditional metal-chalcogenide NCs, these CsPbBr3 NCs exhibit nearly two orders of magnitude increase in their absorption cross sections at similar emission colors. Moreover, the radiative lifetime of CsPbBr3 NCs is greatly shortened at both room and cryogenic temperatures to favor an extremely fast output of single photons. The above findings have not only added a novel member to the perovskite family for the integration into current optoelectronic architectures, but also paved the way towards quantum-light applications of single perovskite NCs in various quantum information processing schemes

Ultrafast field-driven monochromatic photoemission from carbon nanotubes

Ultrafast electron pulses, combined with laser-pump and electron-probe technologies, allow for various forms of ultrafast microscopy and spectroscopy to elucidate otherwise challenging to observe physical and chemical transitions. However, the pursuit of simultaneous ultimate spatial and temporal resolution has been largely subdued by the low monochromaticity of the electron pulses and their poor phase synchronization to the optical excitation pulses. State-of-the-art photon-driven sources have good monochromaticity but poor phase synchronization. In contrast, field-driven photoemission has much higher light phase synchronization, due to the intrinsic sub-cycle emission dynamics, but poor monochromaticity. Such sources suffer from larger electron energy spreads (3 - 100 eV) attributed to the relatively low field enhancement of the conventional metal tips which necessitates long pump wavelengths (> 800 nm) in order to gain sufficient ponderomotive potential to access the field-driven regime. In this work, field-driven photoemission from ~1 nm radius carbon nanotubes excited by a femtosecond laser at a short wavelength of 410 nm has been realized. The energy spread of field-driven electrons is effectively compressed to 0.25 eV outperforming all conventional ultrafast electron sources. Our new nanotube-based ultrafast electron source opens exciting prospects for attosecond imaging and emerging light-wave electronics

Multiobjective constructal optimization of an insulating wall combining heat flow, strength and weight

a b s t r a c t For a vertical insulating wall, it is pursued in engineering design that taking the three requirements of heat insulation, mechanical strength and weight into account simultaneously, so we further develop the pioneer study of multidisciplinary constructal optimization presented in the previous paper [S. Lorente, A. Bejan, Combined 'flow and strength' geometric optimization: internal structure in a vertical insulating wall with air cavities and prescribed strength, Int. J. Heat Mass Transfer, 2002, 45(16): 3313e3320]. In this paper, thermal resistance per unit mass is introduced as the optimization objective, and a multidisciplinary and multiobjective constructal optimization is carried out based on the maximization of thermal resistance per unit mass with the global constraints, i.e. fixed external dimensions and prescribed mechanical strength. The results show that, the thermal resistance per unit mass of the insulating wall can approach its maximum with the corresponding optimal number of cavity under specified environmental condition (i.e. with specified natural convection effect). The bigger the strength is, the smaller the thermal resistance per unit mass is. For specified strength, the maximum thermal resistance per unit mass is insensitive to the change of the overall Rayleigh number group when the overall Rayleigh number group is much small; and then decreases monotonically with the increase of the overall Rayleigh number group when the overall Rayleigh number group is big, however, its decreasing amplitude decreases gradually. When heat flow, strength and weight are all taken into account, the 3-way optimization and selection (the maximization of thermal resistance per unit mass) of wall architecture requires higher degree of accuracy compared with the 2-way optimization and selection (the maximization of overall thermal resistance). This paper gives out an alternative scheme for the practical design of insulating wall, especially for the application case in which the weight of wall is limited strictly

Constructal optimization for "disc-to-point" heat conduction without the premise of optimized last-order construct

a b s t r a c t Based on constructal theory, branch-patterned disc with first-(or higher-) order assembly is optimized based on constructal minimization of maximum temperature difference without the premise that elemental sectors that assemble the perimeter of the branch-patterned disc are optimal. Results show that the optimal constructs without the premise and that with the premise are different obviously with the same conditions, maximum temperature difference of heat transfer without the premise decreases by 49.3%, and every optimal branch-patterned disc with higher-order assembly reduces to a branchpatterned disc with first-order assembly. The optimal construct obtained in this paper decreases the maximum thermal resistance greatly