Semiconducting phase is extremely rare and difficult to be realized in two-dimensional(2D)aluminum borides.Here,we for the first time report the discovery of a rarely semiconducting allotrope(labeled as AlB4-1)in 2D A...Semiconducting phase is extremely rare and difficult to be realized in two-dimensional(2D)aluminum borides.Here,we for the first time report the discovery of a rarely semiconducting allotrope(labeled as AlB4-1)in 2D AlB4 nanosheets.This semiconductor is the global minimum structure in 2D space with two layers stacked together connected by strong Al-B bonds.Systematic studies demonstrate the high thermodynamic,lattice dynamic,thermal,and mechanical stabilities of AlB4-1.More importantly,this semiconducting AlB4-1 shows fascinating properties and promising applications,such as,the optimal band gap(1.156 eV at HSE06 level),high carrier mobility(up to 3.14×103 cm2V−1s−1),substantially high solar energy conversion efficiency(21.9%)and large optical response(106 cm−1)in the visible region.Extensive studies indiate that h-BN can serve as an effective substrate to support and encapsulate AlB4-1 with minimal impact on the electronic properties of AlB4-1,laying the foundation for the real application of AlB4-1 in electronic devices.Besides this semiconducting phase,other low-lying allotropes(AlB4-2 to-11)also display high stabilities,exotic properties and diverse applications.For example,the metallic AlB4-4 shows Dirac cone near Fermi level and superconductivity with TC as high as 23.4K,which can be substantially enhanced to 34.1K at tensile strain of 11%.These allotropes with different shapes show diverse hypercoordinate motifs with unusual bonding patterns.Comprehensive studies demonstrate that 2D AlB4 nanosheets is a class of highly stable,multifunctional nanomaterials for diverse applications in electronics,optics,optoelectronics,nanodevices,solar energy conversion,superconductivity,nanomechanics,and so on.The present study will provide useful guidance in fabricating these interesting nanostructures and stimulate both experimental and computational efforts in this direction.展开更多
Minor errors in the spoil deposition process,such as placing stronger materials with higher shear strength over weaker ones,can lead to potential dump failure.Irregular deposition and inadequate compaction complicate ...Minor errors in the spoil deposition process,such as placing stronger materials with higher shear strength over weaker ones,can lead to potential dump failure.Irregular deposition and inadequate compaction complicate coal spoil behaviour,neces-sitating a robust methodology for temporal monitoring.This study explores using unmanned aerial vehicles(UAV)equipped with red-green-blue(RGB)sensors for efficient data acquisition.Despite their prevalence,raw UAV data exhibit temporal inconsistency,hindering accurate assessments of changes over time which could be attributed to radiometric errors.To this end,the study introduces an empirical line calibration with invariant targets(ELC-IT),for precise calibration across diverse scenes,particularly in the context of UAV imagery used to monitor the evolving nature of spoil dumps.To evaluate the effec-tiveness of this calibration approach,accuracy assessment of an object-based classification is conducted on both calibrated and uncalibrated data.This classification involves several steps:performing segmentation,carrying out feature extraction,and integrating the extracted features and ground truth labels collected over the time period of UAV image capture into machine learning pipelines.Calibrated RGB data exhibit a substantial performance advantage,achieving a 90.7%overall accuracy for spoil pile classification using ensemble(subspace discriminant),representing a noteworthy 7%improvement compared to classifying uncalibrated data.The study highlights the critical role of data calibration in optimising UAV effectiveness for spatio-temporal mine dump monitoring.These findings play a crucial role in informing and refining sustainable management practices within the domain of mine waste management.展开更多
基金supported by the National Natural Science Foundation of China(21873032,21903032,22073033,21673087)startup fund from Huazhong University of Science and Technology(2006013118 and 3004013105)+1 种基金the Fundamental Research Funds for the Central Universities(2019kfyRCPY116)the Innovation and Talent Recruitment Base of New Energy Chemistry and Device(B21003).
文摘Semiconducting phase is extremely rare and difficult to be realized in two-dimensional(2D)aluminum borides.Here,we for the first time report the discovery of a rarely semiconducting allotrope(labeled as AlB4-1)in 2D AlB4 nanosheets.This semiconductor is the global minimum structure in 2D space with two layers stacked together connected by strong Al-B bonds.Systematic studies demonstrate the high thermodynamic,lattice dynamic,thermal,and mechanical stabilities of AlB4-1.More importantly,this semiconducting AlB4-1 shows fascinating properties and promising applications,such as,the optimal band gap(1.156 eV at HSE06 level),high carrier mobility(up to 3.14×103 cm2V−1s−1),substantially high solar energy conversion efficiency(21.9%)and large optical response(106 cm−1)in the visible region.Extensive studies indiate that h-BN can serve as an effective substrate to support and encapsulate AlB4-1 with minimal impact on the electronic properties of AlB4-1,laying the foundation for the real application of AlB4-1 in electronic devices.Besides this semiconducting phase,other low-lying allotropes(AlB4-2 to-11)also display high stabilities,exotic properties and diverse applications.For example,the metallic AlB4-4 shows Dirac cone near Fermi level and superconductivity with TC as high as 23.4K,which can be substantially enhanced to 34.1K at tensile strain of 11%.These allotropes with different shapes show diverse hypercoordinate motifs with unusual bonding patterns.Comprehensive studies demonstrate that 2D AlB4 nanosheets is a class of highly stable,multifunctional nanomaterials for diverse applications in electronics,optics,optoelectronics,nanodevices,solar energy conversion,superconductivity,nanomechanics,and so on.The present study will provide useful guidance in fabricating these interesting nanostructures and stimulate both experimental and computational efforts in this direction.
基金supported by the Australian Coal Industry's Research Program(ACARP)(C29048).
文摘Minor errors in the spoil deposition process,such as placing stronger materials with higher shear strength over weaker ones,can lead to potential dump failure.Irregular deposition and inadequate compaction complicate coal spoil behaviour,neces-sitating a robust methodology for temporal monitoring.This study explores using unmanned aerial vehicles(UAV)equipped with red-green-blue(RGB)sensors for efficient data acquisition.Despite their prevalence,raw UAV data exhibit temporal inconsistency,hindering accurate assessments of changes over time which could be attributed to radiometric errors.To this end,the study introduces an empirical line calibration with invariant targets(ELC-IT),for precise calibration across diverse scenes,particularly in the context of UAV imagery used to monitor the evolving nature of spoil dumps.To evaluate the effec-tiveness of this calibration approach,accuracy assessment of an object-based classification is conducted on both calibrated and uncalibrated data.This classification involves several steps:performing segmentation,carrying out feature extraction,and integrating the extracted features and ground truth labels collected over the time period of UAV image capture into machine learning pipelines.Calibrated RGB data exhibit a substantial performance advantage,achieving a 90.7%overall accuracy for spoil pile classification using ensemble(subspace discriminant),representing a noteworthy 7%improvement compared to classifying uncalibrated data.The study highlights the critical role of data calibration in optimising UAV effectiveness for spatio-temporal mine dump monitoring.These findings play a crucial role in informing and refining sustainable management practices within the domain of mine waste management.
