Unmanned Aerial Vehicles(UAVs)are widely used and meet many demands in military and civilian fields.With the continuous enrichment and extensive expansion of application scenarios,the safety of UAVs is constantly bein...Unmanned Aerial Vehicles(UAVs)are widely used and meet many demands in military and civilian fields.With the continuous enrichment and extensive expansion of application scenarios,the safety of UAVs is constantly being challenged.To address this challenge,we propose algorithms to detect anomalous data collected from drones to improve drone safety.We deployed a one-class kernel extreme learning machine(OCKELM)to detect anomalies in drone data.By default,OCKELM uses the radial basis(RBF)kernel function as the kernel function of themodel.To improve the performance ofOCKELM,we choose a TriangularGlobalAlignmentKernel(TGAK)instead of anRBF Kernel and introduce the Fast Independent Component Analysis(FastICA)algorithm to reconstruct UAV data.Based on the above improvements,we create a novel anomaly detection strategy FastICA-TGAK-OCELM.The method is finally validated on the UCI dataset and detected on the Aeronautical Laboratory Failures and Anomalies(ALFA)dataset.The experimental results show that compared with other methods,the accuracy of this method is improved by more than 30%,and point anomalies are effectively detected.展开更多
Large-area gratings play a crucial role in various engineering fields.However,traditional interference lithography is limited by the size of optical component apertures,making large-area fabrication a challenging task...Large-area gratings play a crucial role in various engineering fields.However,traditional interference lithography is limited by the size of optical component apertures,making large-area fabrication a challenging task.Here,a method for fabricating laser interference lithography pattern arrays with a global alignment reference strategy is proposed.This approach enables alignment of each area of the laser interference lithography pattern arrays,including phase,period,and tilt angle.Two reference gratings are utilized:one is detached from the substrate,while the other remains fixed to it.To achieve global alignment,the exposure area is adjusted by alternating between moving the beam and the substrate.In our experiment,a 3×3 regions grating array was fabricated,and the−1st-order diffraction wavefront measured by the Fizeau interferometer exhibited good continuity.This technique enables effective and efficient alignment with high accuracy across any region in an interference lithography pattern array on large substrates.It can also serve as a common technique for fabricating various types of periodic structures by rotating the substrate.展开更多
Graphene nanoribbons(GNRs)are regarded as an ideal candidate for beyond-silicon electronics.However,synthesis of aligned GNR arrays on insulating substrates with high efficiency is challenging.In this work,we develop ...Graphene nanoribbons(GNRs)are regarded as an ideal candidate for beyond-silicon electronics.However,synthesis of aligned GNR arrays on insulating substrates with high efficiency is challenging.In this work,we develop a facile strategy,involving KOH pre-treatment and high-temperature annealing,to construct parallel steps on the two-fold symmetry a-plane sapphire substrate.Horizontal GNRs as narrow as 15.1 nm with global alignment across a region of 20 mm^(2)are then grown on the step edgeenriched substrate through plasma enhanced chemical vapor deposition(PECVD)method.GNRs align well along the atomic steps on sapphire([■]direction)with their widths and densities swiftly adjustable by step morphology modification on substrate surface.A step-edge confined growth mechanism is proposed,attributing the constraint on the nanoribbon broadening to a relatively low growth temperature in PECVD,which restrains the activation energy to suppress GNRs across step edges on sapphire and prevents detrimental nanoribbon widening.The results provide a new perspective for scalable synthesizing well aligned nanoribbons of other two-dimensional materials.展开更多
基金supported by the Natural Science Foundation of The Jiangsu Higher Education Institutions of China(Grant No.19JKB520031).
文摘Unmanned Aerial Vehicles(UAVs)are widely used and meet many demands in military and civilian fields.With the continuous enrichment and extensive expansion of application scenarios,the safety of UAVs is constantly being challenged.To address this challenge,we propose algorithms to detect anomalous data collected from drones to improve drone safety.We deployed a one-class kernel extreme learning machine(OCKELM)to detect anomalies in drone data.By default,OCKELM uses the radial basis(RBF)kernel function as the kernel function of themodel.To improve the performance ofOCKELM,we choose a TriangularGlobalAlignmentKernel(TGAK)instead of anRBF Kernel and introduce the Fast Independent Component Analysis(FastICA)algorithm to reconstruct UAV data.Based on the above improvements,we create a novel anomaly detection strategy FastICA-TGAK-OCELM.The method is finally validated on the UCI dataset and detected on the Aeronautical Laboratory Failures and Anomalies(ALFA)dataset.The experimental results show that compared with other methods,the accuracy of this method is improved by more than 30%,and point anomalies are effectively detected.
基金supported by the National Natural Science Foundation of China(no.62275142)the Shenzhen Stable Supporting Program(no.WDZC20231124201906001).
文摘Large-area gratings play a crucial role in various engineering fields.However,traditional interference lithography is limited by the size of optical component apertures,making large-area fabrication a challenging task.Here,a method for fabricating laser interference lithography pattern arrays with a global alignment reference strategy is proposed.This approach enables alignment of each area of the laser interference lithography pattern arrays,including phase,period,and tilt angle.Two reference gratings are utilized:one is detached from the substrate,while the other remains fixed to it.To achieve global alignment,the exposure area is adjusted by alternating between moving the beam and the substrate.In our experiment,a 3×3 regions grating array was fabricated,and the−1st-order diffraction wavefront measured by the Fizeau interferometer exhibited good continuity.This technique enables effective and efficient alignment with high accuracy across any region in an interference lithography pattern array on large substrates.It can also serve as a common technique for fabricating various types of periodic structures by rotating the substrate.
基金This work was financially supported by the Ministry of Science and Technology of China(Nos.2016YFA0200100 and 2018YFA0703502)the National Natural Science Foundation of China(Nos.52021006,51720105003,21790052,and 21974004)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36030100)the Beijing National Laboratory for Molecular Sciences(No.BNLMS-CXTD-202001).
文摘Graphene nanoribbons(GNRs)are regarded as an ideal candidate for beyond-silicon electronics.However,synthesis of aligned GNR arrays on insulating substrates with high efficiency is challenging.In this work,we develop a facile strategy,involving KOH pre-treatment and high-temperature annealing,to construct parallel steps on the two-fold symmetry a-plane sapphire substrate.Horizontal GNRs as narrow as 15.1 nm with global alignment across a region of 20 mm^(2)are then grown on the step edgeenriched substrate through plasma enhanced chemical vapor deposition(PECVD)method.GNRs align well along the atomic steps on sapphire([■]direction)with their widths and densities swiftly adjustable by step morphology modification on substrate surface.A step-edge confined growth mechanism is proposed,attributing the constraint on the nanoribbon broadening to a relatively low growth temperature in PECVD,which restrains the activation energy to suppress GNRs across step edges on sapphire and prevents detrimental nanoribbon widening.The results provide a new perspective for scalable synthesizing well aligned nanoribbons of other two-dimensional materials.
