As a manufacturing method that is focused on end-users,3D printing has gained a lot of attention in recent years due to its unique advantages in fabricating complex three-dimensional structures.Various new micro-nano ...As a manufacturing method that is focused on end-users,3D printing has gained a lot of attention in recent years due to its unique advantages in fabricating complex three-dimensional structures.Various new micro-nano 3D printing methods have been developed to meet the demand for high-precision and high-yield manufacturing1-9.Among them,multi-photon-photon lithography(MPL) is a promising 3D nanofabrication technology due to its capability of true 3D digital processing and nanoscale processing resolution beyond the diffraction limit.It has been widely used to fabricate microoptics10,11,photonic crystals12,microfluidics13,meta-surfaces14,and mechanical metamaterials15.展开更多
Optical reflection anisotropy microscopy mappings of micropipe defects on the surface of a 4H-SiC single crystal are studied by the scanning anisotropy microscopy(SAM)system.The reflection anisotropy(RA)image with a...Optical reflection anisotropy microscopy mappings of micropipe defects on the surface of a 4H-SiC single crystal are studied by the scanning anisotropy microscopy(SAM)system.The reflection anisotropy(RA)image with a'butterfly pattern'is obtained around the micropipes by SAM.The RA image of the edge dislocations is theoretically simulated based on dislocation theory and the photoelastic principle.By comparing with the Raman spectrum,it is verified that the micropipes consist of edge dislocations.The different patterns of the RA images are due to the different orientations of the Burgers vectors.Besides,the strain distribution of the micropipes is also deduced.One can identify the dislocation type,the direction of the Burgers vector and the optical anisotropy from the RA image by using SAM.Therefore,SAM is an ideal tool to measure the optical anisotropy induced by the strain field around a defect.展开更多
In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiat...In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiation area is required for the extracted ion beams,which is crucial because it directly affects the experimental precision and therapeutic effect.Specifically,ultra-large-area and high-uniformity scanning are crucial requirements for spacecraft radiation effects assessment and serve as core specification for beamline terminal design.In the 300 MeV proton and heavy ion accelerator complex at the Space Environment Simulation and Research Infrastructure(SESRI),proton and heavy ion beams will be accelerated and ultimately delivered to three irradiation terminals.In order to achieve the required large irradiation area of 320 mm×320 mm,horizontal and vertical scanning magnets are used in the extraction beam line.However,considering the various requirements for beam species and energies,the tracking accuracy of power supplies(PSs),the eddy current effect of scanning magnets,and the fluctuation of ion bunch structure will reduce the irradiation uniformity.To mitigate these effects,a beam uniformity optimization method based on the measured beam distribution was proposed and applied in the accelerator complex at SESRI.In the experiment,the uniformity is successfully optimized from 75%to over 90%after five iterations of adjustment to the PS waveforms.In this paper,the method and experimental results were introduced.展开更多
To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Ach...To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Achieving optimal energy efficiency and cost competitiveness in these systems requires the strategic design of electrocatalysts,coupled with a thorough comprehension of the underlying mechanisms and degradation behavior occurring during the electrocatalysis processes.Scanning electrochemical microscopy(SECM),an analytical technique for studying surface electrochemically,stands out as a powerful tool offering electrochemical insights.It possesses remarkable spatiotemporal resolution,enabling the visualization of the localized electrochemical activity and surface topography.This review compiles crucial research findings and recent breakthroughs in electrocatalytic processes utilizing the SECM methodology,specifically focusing on applications in electrolysis,fuel cells,and metal–oxygen batteries within the realm of energy conversion and storage systems.Commencing with an overview of each energy system,the review introduces the fundamental principles of SECM,and aiming to provide new perspectives and broadening the scope of applied research by describing the major research categories within SECM.展开更多
To investigate the macroscopic fatigue properties and the mesoscopic pore evolution characteristics of salt rock under cyclic loading,fatigue tests under different upper-limit stresses were carried out on salt rock,an...To investigate the macroscopic fatigue properties and the mesoscopic pore evolution characteristics of salt rock under cyclic loading,fatigue tests under different upper-limit stresses were carried out on salt rock,and the mesoscopic pore structures of salt rock before and after fatigue tests and under different cycle numbers were measured using CT scanning instrument.Based on the test results,the effects of the cycle number and the upper-limit stress on the evolution of cracks,pore morphology,pore number,pore volume,pore size,plane porosity,and volume porosity of salt rock were analyzed.The failure path of salt rock specimens under cyclic loading was analyzed using the distribution law of plane porosity.The damage variable of salt rock under cyclic loading was defined on basis of the variation of volume porosity with cycle number.In order to describe the fatigue deformation behavior of salt rock under cyclic loading,the nonlinear Burgers damage constitutive model was further established.The results show that the model established can better reflect the whole development process of fatigue deformation of salt rock under cyclic loading.展开更多
AIM:To propose an algorithm for automatic detection of diabetic retinopathy(DR)lesions based on ultra-widefield scanning laser ophthalmoscopy(SLO).METHODS:The algorithm utilized the FasterRCNN(Faster Regions with CNN ...AIM:To propose an algorithm for automatic detection of diabetic retinopathy(DR)lesions based on ultra-widefield scanning laser ophthalmoscopy(SLO).METHODS:The algorithm utilized the FasterRCNN(Faster Regions with CNN features)+ResNet50(Residua Network 50)+FPN(Feature Pyramid Networks)method for detecting hemorrhagic spots,cotton wool spots,exudates,and microaneurysms in DR ultra-widefield SLO.Subimage segmentation combined with a deeper residual network FasterRCNN+ResNet50 was employed for feature extraction to enhance intelligent learning rate.Feature fusion was carried out by the feature pyramid network FPN,which significantly improved lesion detection rates in SLO fundus images.RESULTS:By analyzing 1076 ultra-widefield SLO images provided by our hospital,with a resolution of 2600×2048 dpi,the accuracy rates for hemorrhagic spots,cotton wool spots,exudates,and microaneurysms were found to be 87.23%,83.57%,86.75%,and 54.94%,respectively.CONCLUSION:The proposed algorithm demonstrates intelligent detection of DR lesions in ultra-widefield SLO,providing significant advantages over traditional fundus color imaging intelligent diagnosis algorithms.展开更多
Optical endoscopy has become an essential diagnostic and therapeutic approach in modern biomedicine for directly observing organs and tissues deep inside the human body,enabling non-invasive,rapid diagnosis and treatm...Optical endoscopy has become an essential diagnostic and therapeutic approach in modern biomedicine for directly observing organs and tissues deep inside the human body,enabling non-invasive,rapid diagnosis and treatment.Optical fiber endoscopy is highly competitive among various endoscopic imaging techniques due to its high flexibility,compact structure,excellent resolution,and resistance to electromagnetic interference.Over the past decade,endoscopes based on a single multimode optical fiber(MMF)have attracted widespread research interest due to their potential to significantly reduce the footprint of optical fiber endoscopes and enhance imaging capabilities.In comparison with other imaging principles of MMF endoscopes,the scanning imaging method based on the wavefront shaping technique is highly developed and provides benefits including excellent imaging contrast,broad applicability to complex imaging scenarios,and good compatibility with various well-established scanning imaging modalities.In this review,various technical routes to achieve light focusing through MMF and procedures to conduct the scanning imaging of MMF endoscopes are introduced.The advancements in imaging performance enhancements,integrations of various imaging modalities with MMF scanning endoscopes,and applications are summarized.Challenges specific to this endoscopic imaging technology are analyzed,and potential remedies and avenues for future developments are discussed.展开更多
The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory e...The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.展开更多
The dissolution kinetics of Al_(2)O_(3) in CaO-Al_(2)O_(3) SiOslags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K.The results show that the controlling step during the Al_(2...The dissolution kinetics of Al_(2)O_(3) in CaO-Al_(2)O_(3) SiOslags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K.The results show that the controlling step during the Al_(2)O_(3) dissolution was the diffusionin molten slag.It was found that the dissolution curves of Al_(2)O_(3) particles were hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al_(2)O_(3) ratio of slag.A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al_(2)O_(3) in slag.Diffusion coefficients of Al_(2)O_(3) in slag were calculated as 2.8×10to 4.1×10m~2/s at the temperature of 1773-1873 K.The dissolution rate of Al_(2)O_(3) increased with higher temperature,CaO/Al_(2)O_(3),and particle size.A new model was shown to be v_(Al_(2)O_(3))=0.16×r_(0)^(1.58)×x^(3.52)×(T-T_(mp))^(1.11)to predict the dissolution rate and the total dissolution time of Al_(2)O_(3) inclusions with various sizes,where vAl_(2)O_(3) is the dissolution rate of Al_(2)O_(3) in volume,μm^(3)/s;x is the value of CaO/Al_(2)O_(3) mass ratio;R_(0) is the initial radius of Al_(2)O_(3),μm;T is the temperature,K;T_(mp) is the melting point of slag,K.展开更多
Nano-3D printing has obtained widespread attention owing to its capacity to manufacture end-use components with nano-scale features in recent years.Multiphoton lithography(MPL)is one of the most promising 3D nanomanuf...Nano-3D printing has obtained widespread attention owing to its capacity to manufacture end-use components with nano-scale features in recent years.Multiphoton lithography(MPL)is one of the most promising 3D nanomanufacturing technologies,which has been widely used in manufacturing micro-optics,photonic crystals,microfluidics,meta-surface,and mechanical metamaterials.Despite of tremendous potential of MPL in laboratorial and industrial applications,simultaneous achievement of high throughput,high accuracy,high design freedom,and a broad range of material structuring capabilities remains a long-pending challenge.To address the issue,we propose an acousto-optic scanning with spatial-switching multispots(AOSS)method.Inertia-free acousto-optic scanning and nonlinear swept techniques have been developed for achieving ultrahigh-speed and aberration-free scanning.Moreover,a spatial optical switch concept has been implemented to significantly boost the lithography throughput while maintaining high resolution and high design freedom.An eight-foci AOSS system has demonstrated a record-high 3D printing rate of 7.6×10^(7)voxel s^(-1),which is nearly one order of magnitude higher than earlier scanning MPL,exhibiting its promise for future scalable 3D nanomanufacturing.展开更多
Local geometric information and discontinuity features are key aspects of the analysis of the evolution and failure mechanisms of unstable rock blocks in rock tunnels.This study demonstrates the integration of terrest...Local geometric information and discontinuity features are key aspects of the analysis of the evolution and failure mechanisms of unstable rock blocks in rock tunnels.This study demonstrates the integration of terrestrial laser scanning(TLS)with distinct element method for rock mass characterization and stability analysis in tunnels.TLS records detailed geometric information of the surrounding rock mass by scanning and collecting the positions of millions of rock surface points without contact.By conducting a fuzzy K-means method,a discontinuity automatic identification algorithm was developed,and a method for obtaining the geometric parameters of discontinuities was proposed.This method permits the user to visually identify each discontinuity and acquire its spatial distribution features(e.g.occurrences,spac-ings,trace lengths)in great detail.Compared with hand mapping in conventional geotechnical surveys,the geometric information of discontinuities obtained by this approach is more accurate and the iden-tification is more efficient.Then,a discrete fracture network with the same statistical characteristics as the actual discontinuities was generated with the distinct element method,and a representative nu-merical model of the jointed surrounding rock mass was established.By means of numerical simulation,potential unstable rock blocks were assessed,and failure mechanisms were analyzed.This method was applied to detection and assessment of unstable rock blocks in the spillway and sand flushing tunnel of the Hongshiyan hydropower project after a collapse.The results show that the noncontact detection of blocks was more labor-saving with lower safety risks compared with manual surveys,and the stability assessment was more reliable since the numerical model built by this method was more consistent with the distribution characteristics of actual joints.This study can provide a reference for geological survey and unstable rock block hazard mitigation in tunnels subjected to complex geology and active rockfalls.展开更多
Objective: To evaluate the lung CT scan as a possible predictive diagnostic method for COVID-19 in the Cameroonian context. Methods: We designed a cross sectional study. Suspected cases of COVID-19 during the first wa...Objective: To evaluate the lung CT scan as a possible predictive diagnostic method for COVID-19 in the Cameroonian context. Methods: We designed a cross sectional study. Suspected cases of COVID-19 during the first wave at the national social insurance fund (NSIF) hospital were screened with both COVID-19 with lung CT scan and a PCR test. Univariate analysis was performed for sample description and multivariate analysis to assess the correlation between positive results for the PCR and other parameters. We estimated the optimum threshold of sensitivity/specificity, and area under curve using the empirical method and package. Results: A total of 62 suspected COVID-19 cases were recorded, predominantly males (Sex Ratio = 2.2) with a median age of 58.5 (IQR = 19.7). Among our 62 patients, 29 (46.8%) were confirmed COVID-19 cases with positive PCR results. All the patients had a thorax CT scan with a median impairment of 40% (IQR = 20%). The optimum threshold estimate for CT scan for COVID-19 infection diagnosis was 60% (95% CI = 25% - 80%). Overall, the sensitivity and specificity estimates were 0.30 (95% CI = 0.15 - 0.49) and 0.87 (95% CI = 0.70 - 0.96), respectively, leading to an Area Under Curve (AUC) estimate of 0.59 (95% CI = 0.46, 0.71). Conclusion: In this setting, lung CT scan was neither sensitive nor specific to predict COVID-19 disease.展开更多
Introduction: A scanning acoustic microscope (SAM) is an apparatus for imaging acoustic properties. This apparatus can non-invasively and rapidly evaluate the hardness of materials in the elastic region. This device s...Introduction: A scanning acoustic microscope (SAM) is an apparatus for imaging acoustic properties. This apparatus can non-invasively and rapidly evaluate the hardness of materials in the elastic region. This device shows great potential for the diagnosis of dental caries in the clinical setting. However, since the tissue elastic modulus measured using a SAM is a property of the elastic region and the Knoop hardness is a property of the plastic region, the hardness properties differ completely. Therefore, we investigated whether the acoustic impedance measured using a SAM is related to the Knoop hardness, which is used as the standard for removal of carious dentin. Method: Polished sections were prepared from 20 extracted carious wisdom teeth. The acoustic impedance and Knoop hardness were measured for each section. In addition to comparing carious and healthy dentin in SAM images, we evaluated the difference between the carious and healthy dentin in terms of the acoustic impedance and Knoop hardness. We also evaluated the correlation between the Knoop hardness and acoustic impedance. Results: The SAM images were visualized as two-dimensional color images based on the acoustic impedance values. The mean acoustic impedance of carious dentin was significantly lower than that of healthy dentin, showing a similar trend as Knoop hardness. A strong correlation was observed between the two. Discussion: The acoustic impedance values obtained through acoustic microscopy differed significantly between carious and sound dentin. Both types of dentins were visualized using two-dimensional color images. A strong correlation was observed between the acoustic impedance value, which indicates the hardness of the elastic region, and the Knoop hardness, which indicates the hardness of the plastic region. The results of the present study indicate that acoustic impedance accurately reflects the hardness of dentin.展开更多
Leaf area index (LAI) is a key parameter for studying global terrestrial ecology and environment and has great ecological significance. How to accurately measure and calculate structural parameters of trees has become...Leaf area index (LAI) is a key parameter for studying global terrestrial ecology and environment and has great ecological significance. How to accurately measure and calculate structural parameters of trees has become an urgent matter. This paper reports the use of terrestrial laser scanning (TLS) as a measurement tool to achieve accurate LAI estimation through point cloud preprocessing measures, the LeWos algorithm, and voxel methods. The accuracy and feasibility of this indirect measurement method were explored. It is found that the single wood structure parameters extracted from TLS have a good linear relationship with manual measurement, and the extraction errors meet the requirements of real-scene conversion. The study also found when the voxel size is consistent with the minimum distance of the point cloud set by TLS instrument, it has a strong correlation with the measured value of canopy analyser. These results lay the foundation for conveniently and quickly obtaining structural parameters of trees, tree growth state detection, and canopy ecological benefit assessment.展开更多
The microwave-induced thermoacoustic imaging(TAI)technology has both the advantages of high contrast of microwave imaging and high resolution of ultrasound imaging(UI),so it has carried out exploratory application res...The microwave-induced thermoacoustic imaging(TAI)technology has both the advantages of high contrast of microwave imaging and high resolution of ultrasound imaging(UI),so it has carried out exploratory application research in various areas,such as the early detection of breast tumors and cerebrovascular diseases.However,the microwave generator used in the traditional TAI technology is huge and expensive,and the temporal resolution is also too low due to the single-element scanning mechanism.Thus,it is difficult to meet the needs of clinical applications.In this paper,the iterative process and the analysis of related application scenarios from single-element scanning to portable and array-based TAI,such as the miniaturized microwave generator,handheld antenna,multi-channel data acquisition,and UI/TAIdual-modality imaging,are reviewed,and the future trends of this technology are discussed.This review helps researchers in the field of TAI learn the technological development process and future trends.It also deepens clinicians’understanding of TAI so as to put forward more application requirements.展开更多
Ferroelectric polymer nanocomposites possess exceptional electric properties with respect to the two otherwise uniform phases,which is commonly attributed to the critical role of the matrix-particle interfacial region...Ferroelectric polymer nanocomposites possess exceptional electric properties with respect to the two otherwise uniform phases,which is commonly attributed to the critical role of the matrix-particle interfacial region.However,the structure-property correlation of the interface remains unestablished,and thus,the design of ferroelectric polymer nanocompos-ite has largely relied on the trial-and-error method.Here,a strategy that combines multi-mode scanning probe microscopy-based electrical charac-terization and nano-infrared spectroscopy is developed to unveil the local structure-property correlation of the interface in ferroelectric polymer nano-composites.The results show that the type of surface modifiers decorated on the nanoparticles can significantly influence the local polar-phase content and the piezoelectric effect of the polymer matrix surrounding the nano-particles.The strongly coupled polar-phase content and piezoelectric effect measured directly in the interfacial region as well as the computed bonding energy suggest that the property enhancement originates from the formation of hydrogen bond between the surface modifiers and the ferroelectric polymer.It is also directly detected that the local domain size of the ferroelectric polymer can impact the energy level and distribution of charge traps in the interfacial region and eventually influence the local dielectric strength.展开更多
The advanced integrated circuits have been widely used in various situations including the Internet of Things,wireless communication,etc.But its manufacturing process exists unreliability,so cryptographic chips must b...The advanced integrated circuits have been widely used in various situations including the Internet of Things,wireless communication,etc.But its manufacturing process exists unreliability,so cryptographic chips must be rigorously tested.Due to scan testing provides high test coverage,it is applied to the testing of cryptographic integrated circuits.However,while providing good controllability and observability,it also provides attackers with a backdoor to steal keys.In the text,a novel protection scheme is put forward to resist scan-based attacks,in which we first use the responses generated by a strong physical unclonable function circuit to solidify fuseantifuse structures in a non-linear shift register(NLSR),then determine the scan input code according to the configuration of the fuse-antifuse structures and the styles of connection between the NLSR cells and the scan cells.If the key is right,the chip can be tested normally;otherwise,the data in the scan chain cannot be propagated normally,it is also impossible for illegal users to derive the desired scan data.The proposed technique not only enhances the security of cryptographic chips,but also incurs acceptable overhead.展开更多
The temperature field in laser line scanning thermography is investigated comprehensively in this work,including analytical calculation and experiment.Firstly,the principle of laser line scanning thermography is analy...The temperature field in laser line scanning thermography is investigated comprehensively in this work,including analytical calculation and experiment.Firstly,the principle of laser line scanning thermography is analyzed.On this basis,a physical laser line scanning model is proposed.Afterwards,based on Fourier transform(FT)and segregation variablemethod(SVM),the heat conduction differential equation in laser line scanning thermography is derived in detail.The temperature field of the composite-based coatings model with defects is simulated numerically.The results show that the laser line scanning thermography can effectively detect the defects in the model.The correctness of the analytical calculation is verified by comparing the surface temperature distribution obtained by analytical calculation and numerical simulation.Additionally,an experiment is carried out and the changeable surface temperature obtained by analytical calculation is compared with the experimental results.It shows that the error of maximum temperature obtained by analytical calculation and by experiment is 8%with high accuracy,which proves the correctness of analytical calculation and enriches the theoretical foundation of laser line scanning thermography.展开更多
文摘As a manufacturing method that is focused on end-users,3D printing has gained a lot of attention in recent years due to its unique advantages in fabricating complex three-dimensional structures.Various new micro-nano 3D printing methods have been developed to meet the demand for high-precision and high-yield manufacturing1-9.Among them,multi-photon-photon lithography(MPL) is a promising 3D nanofabrication technology due to its capability of true 3D digital processing and nanoscale processing resolution beyond the diffraction limit.It has been widely used to fabricate microoptics10,11,photonic crystals12,microfluidics13,meta-surfaces14,and mechanical metamaterials15.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2018YFE0204001,2018YFA0209103,2016YFB0400101,and 2016YFB0402303)the National Natural Science Foundation of China(Grant Nos.61627822,61704121,61991430,and 62074036)Postdoctoral Research Program of Jiangsu Province(Grant No.2021K599C).
文摘Optical reflection anisotropy microscopy mappings of micropipe defects on the surface of a 4H-SiC single crystal are studied by the scanning anisotropy microscopy(SAM)system.The reflection anisotropy(RA)image with a'butterfly pattern'is obtained around the micropipes by SAM.The RA image of the edge dislocations is theoretically simulated based on dislocation theory and the photoelastic principle.By comparing with the Raman spectrum,it is verified that the micropipes consist of edge dislocations.The different patterns of the RA images are due to the different orientations of the Burgers vectors.Besides,the strain distribution of the micropipes is also deduced.One can identify the dislocation type,the direction of the Burgers vector and the optical anisotropy from the RA image by using SAM.Therefore,SAM is an ideal tool to measure the optical anisotropy induced by the strain field around a defect.
基金Supported by National Key R&D Program of China(2019YFA0405400)。
文摘In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiation area is required for the extracted ion beams,which is crucial because it directly affects the experimental precision and therapeutic effect.Specifically,ultra-large-area and high-uniformity scanning are crucial requirements for spacecraft radiation effects assessment and serve as core specification for beamline terminal design.In the 300 MeV proton and heavy ion accelerator complex at the Space Environment Simulation and Research Infrastructure(SESRI),proton and heavy ion beams will be accelerated and ultimately delivered to three irradiation terminals.In order to achieve the required large irradiation area of 320 mm×320 mm,horizontal and vertical scanning magnets are used in the extraction beam line.However,considering the various requirements for beam species and energies,the tracking accuracy of power supplies(PSs),the eddy current effect of scanning magnets,and the fluctuation of ion bunch structure will reduce the irradiation uniformity.To mitigate these effects,a beam uniformity optimization method based on the measured beam distribution was proposed and applied in the accelerator complex at SESRI.In the experiment,the uniformity is successfully optimized from 75%to over 90%after five iterations of adjustment to the PS waveforms.In this paper,the method and experimental results were introduced.
基金supported by a characterization platform for advanced materials funded by the Korea Research Institute of Standards and Science(KRISS-2023-GP2023-0014)the KRISS(Korea Research Institute of Standards and Science)MPI Lab.program。
文摘To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Achieving optimal energy efficiency and cost competitiveness in these systems requires the strategic design of electrocatalysts,coupled with a thorough comprehension of the underlying mechanisms and degradation behavior occurring during the electrocatalysis processes.Scanning electrochemical microscopy(SECM),an analytical technique for studying surface electrochemically,stands out as a powerful tool offering electrochemical insights.It possesses remarkable spatiotemporal resolution,enabling the visualization of the localized electrochemical activity and surface topography.This review compiles crucial research findings and recent breakthroughs in electrocatalytic processes utilizing the SECM methodology,specifically focusing on applications in electrolysis,fuel cells,and metal–oxygen batteries within the realm of energy conversion and storage systems.Commencing with an overview of each energy system,the review introduces the fundamental principles of SECM,and aiming to provide new perspectives and broadening the scope of applied research by describing the major research categories within SECM.
基金supported by the National Natural Science Foundation of China(No.52178354).
文摘To investigate the macroscopic fatigue properties and the mesoscopic pore evolution characteristics of salt rock under cyclic loading,fatigue tests under different upper-limit stresses were carried out on salt rock,and the mesoscopic pore structures of salt rock before and after fatigue tests and under different cycle numbers were measured using CT scanning instrument.Based on the test results,the effects of the cycle number and the upper-limit stress on the evolution of cracks,pore morphology,pore number,pore volume,pore size,plane porosity,and volume porosity of salt rock were analyzed.The failure path of salt rock specimens under cyclic loading was analyzed using the distribution law of plane porosity.The damage variable of salt rock under cyclic loading was defined on basis of the variation of volume porosity with cycle number.In order to describe the fatigue deformation behavior of salt rock under cyclic loading,the nonlinear Burgers damage constitutive model was further established.The results show that the model established can better reflect the whole development process of fatigue deformation of salt rock under cyclic loading.
基金Supported by Hunan Provincial Science and Technology Department Clinical Medical Technology Innovation Guidance Project(No.2021SK50103)。
文摘AIM:To propose an algorithm for automatic detection of diabetic retinopathy(DR)lesions based on ultra-widefield scanning laser ophthalmoscopy(SLO).METHODS:The algorithm utilized the FasterRCNN(Faster Regions with CNN features)+ResNet50(Residua Network 50)+FPN(Feature Pyramid Networks)method for detecting hemorrhagic spots,cotton wool spots,exudates,and microaneurysms in DR ultra-widefield SLO.Subimage segmentation combined with a deeper residual network FasterRCNN+ResNet50 was employed for feature extraction to enhance intelligent learning rate.Feature fusion was carried out by the feature pyramid network FPN,which significantly improved lesion detection rates in SLO fundus images.RESULTS:By analyzing 1076 ultra-widefield SLO images provided by our hospital,with a resolution of 2600×2048 dpi,the accuracy rates for hemorrhagic spots,cotton wool spots,exudates,and microaneurysms were found to be 87.23%,83.57%,86.75%,and 54.94%,respectively.CONCLUSION:The proposed algorithm demonstrates intelligent detection of DR lesions in ultra-widefield SLO,providing significant advantages over traditional fundus color imaging intelligent diagnosis algorithms.
基金supported by National Natural Science Foundation of China(62135007 and 61925502).
文摘Optical endoscopy has become an essential diagnostic and therapeutic approach in modern biomedicine for directly observing organs and tissues deep inside the human body,enabling non-invasive,rapid diagnosis and treatment.Optical fiber endoscopy is highly competitive among various endoscopic imaging techniques due to its high flexibility,compact structure,excellent resolution,and resistance to electromagnetic interference.Over the past decade,endoscopes based on a single multimode optical fiber(MMF)have attracted widespread research interest due to their potential to significantly reduce the footprint of optical fiber endoscopes and enhance imaging capabilities.In comparison with other imaging principles of MMF endoscopes,the scanning imaging method based on the wavefront shaping technique is highly developed and provides benefits including excellent imaging contrast,broad applicability to complex imaging scenarios,and good compatibility with various well-established scanning imaging modalities.In this review,various technical routes to achieve light focusing through MMF and procedures to conduct the scanning imaging of MMF endoscopes are introduced.The advancements in imaging performance enhancements,integrations of various imaging modalities with MMF scanning endoscopes,and applications are summarized.Challenges specific to this endoscopic imaging technology are analyzed,and potential remedies and avenues for future developments are discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.42277150,41977219)Henan Provincial Science and Technology Research Project(Grant No.222102320271).
文摘The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.
基金financially supported by the National Nature Science Foundation of China(Nos.U1860206,51725402)the Science and Technology Program of Hebei,China(Nos.20311006D,20591001D)。
文摘The dissolution kinetics of Al_(2)O_(3) in CaO-Al_(2)O_(3) SiOslags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K.The results show that the controlling step during the Al_(2)O_(3) dissolution was the diffusionin molten slag.It was found that the dissolution curves of Al_(2)O_(3) particles were hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al_(2)O_(3) ratio of slag.A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al_(2)O_(3) in slag.Diffusion coefficients of Al_(2)O_(3) in slag were calculated as 2.8×10to 4.1×10m~2/s at the temperature of 1773-1873 K.The dissolution rate of Al_(2)O_(3) increased with higher temperature,CaO/Al_(2)O_(3),and particle size.A new model was shown to be v_(Al_(2)O_(3))=0.16×r_(0)^(1.58)×x^(3.52)×(T-T_(mp))^(1.11)to predict the dissolution rate and the total dissolution time of Al_(2)O_(3) inclusions with various sizes,where vAl_(2)O_(3) is the dissolution rate of Al_(2)O_(3) in volume,μm^(3)/s;x is the value of CaO/Al_(2)O_(3) mass ratio;R_(0) is the initial radius of Al_(2)O_(3),μm;T is the temperature,K;T_(mp) is the melting point of slag,K.
基金National Key Research and Development Program of China(2021YFF0502700)National Natural Science Foundation of China(52275429,62205117)+4 种基金Innovation project of Optics Valley Laboratory(OVL2021ZD002)Hubei Provincial Natural Science Foundation of China(2022CFB792)Young Elite Scientists Sponsorship Program by CAST(2022QNRC001)West Light Foundation of the Chinese Academy of Sciences(xbzg-zdsys-202206)Knowledge Innovation Program of Wuhan-Shuguang。
文摘Nano-3D printing has obtained widespread attention owing to its capacity to manufacture end-use components with nano-scale features in recent years.Multiphoton lithography(MPL)is one of the most promising 3D nanomanufacturing technologies,which has been widely used in manufacturing micro-optics,photonic crystals,microfluidics,meta-surface,and mechanical metamaterials.Despite of tremendous potential of MPL in laboratorial and industrial applications,simultaneous achievement of high throughput,high accuracy,high design freedom,and a broad range of material structuring capabilities remains a long-pending challenge.To address the issue,we propose an acousto-optic scanning with spatial-switching multispots(AOSS)method.Inertia-free acousto-optic scanning and nonlinear swept techniques have been developed for achieving ultrahigh-speed and aberration-free scanning.Moreover,a spatial optical switch concept has been implemented to significantly boost the lithography throughput while maintaining high resolution and high design freedom.An eight-foci AOSS system has demonstrated a record-high 3D printing rate of 7.6×10^(7)voxel s^(-1),which is nearly one order of magnitude higher than earlier scanning MPL,exhibiting its promise for future scalable 3D nanomanufacturing.
基金support of the National Natural Science Foundation of China(Grant No.42102316)the Open Project of the Technology Innovation Center for Geological Environment Monitoring of Ministry of Natural Resources of China(Grant No.2022KFK1212005).
文摘Local geometric information and discontinuity features are key aspects of the analysis of the evolution and failure mechanisms of unstable rock blocks in rock tunnels.This study demonstrates the integration of terrestrial laser scanning(TLS)with distinct element method for rock mass characterization and stability analysis in tunnels.TLS records detailed geometric information of the surrounding rock mass by scanning and collecting the positions of millions of rock surface points without contact.By conducting a fuzzy K-means method,a discontinuity automatic identification algorithm was developed,and a method for obtaining the geometric parameters of discontinuities was proposed.This method permits the user to visually identify each discontinuity and acquire its spatial distribution features(e.g.occurrences,spac-ings,trace lengths)in great detail.Compared with hand mapping in conventional geotechnical surveys,the geometric information of discontinuities obtained by this approach is more accurate and the iden-tification is more efficient.Then,a discrete fracture network with the same statistical characteristics as the actual discontinuities was generated with the distinct element method,and a representative nu-merical model of the jointed surrounding rock mass was established.By means of numerical simulation,potential unstable rock blocks were assessed,and failure mechanisms were analyzed.This method was applied to detection and assessment of unstable rock blocks in the spillway and sand flushing tunnel of the Hongshiyan hydropower project after a collapse.The results show that the noncontact detection of blocks was more labor-saving with lower safety risks compared with manual surveys,and the stability assessment was more reliable since the numerical model built by this method was more consistent with the distribution characteristics of actual joints.This study can provide a reference for geological survey and unstable rock block hazard mitigation in tunnels subjected to complex geology and active rockfalls.
文摘Objective: To evaluate the lung CT scan as a possible predictive diagnostic method for COVID-19 in the Cameroonian context. Methods: We designed a cross sectional study. Suspected cases of COVID-19 during the first wave at the national social insurance fund (NSIF) hospital were screened with both COVID-19 with lung CT scan and a PCR test. Univariate analysis was performed for sample description and multivariate analysis to assess the correlation between positive results for the PCR and other parameters. We estimated the optimum threshold of sensitivity/specificity, and area under curve using the empirical method and package. Results: A total of 62 suspected COVID-19 cases were recorded, predominantly males (Sex Ratio = 2.2) with a median age of 58.5 (IQR = 19.7). Among our 62 patients, 29 (46.8%) were confirmed COVID-19 cases with positive PCR results. All the patients had a thorax CT scan with a median impairment of 40% (IQR = 20%). The optimum threshold estimate for CT scan for COVID-19 infection diagnosis was 60% (95% CI = 25% - 80%). Overall, the sensitivity and specificity estimates were 0.30 (95% CI = 0.15 - 0.49) and 0.87 (95% CI = 0.70 - 0.96), respectively, leading to an Area Under Curve (AUC) estimate of 0.59 (95% CI = 0.46, 0.71). Conclusion: In this setting, lung CT scan was neither sensitive nor specific to predict COVID-19 disease.
文摘Introduction: A scanning acoustic microscope (SAM) is an apparatus for imaging acoustic properties. This apparatus can non-invasively and rapidly evaluate the hardness of materials in the elastic region. This device shows great potential for the diagnosis of dental caries in the clinical setting. However, since the tissue elastic modulus measured using a SAM is a property of the elastic region and the Knoop hardness is a property of the plastic region, the hardness properties differ completely. Therefore, we investigated whether the acoustic impedance measured using a SAM is related to the Knoop hardness, which is used as the standard for removal of carious dentin. Method: Polished sections were prepared from 20 extracted carious wisdom teeth. The acoustic impedance and Knoop hardness were measured for each section. In addition to comparing carious and healthy dentin in SAM images, we evaluated the difference between the carious and healthy dentin in terms of the acoustic impedance and Knoop hardness. We also evaluated the correlation between the Knoop hardness and acoustic impedance. Results: The SAM images were visualized as two-dimensional color images based on the acoustic impedance values. The mean acoustic impedance of carious dentin was significantly lower than that of healthy dentin, showing a similar trend as Knoop hardness. A strong correlation was observed between the two. Discussion: The acoustic impedance values obtained through acoustic microscopy differed significantly between carious and sound dentin. Both types of dentins were visualized using two-dimensional color images. A strong correlation was observed between the acoustic impedance value, which indicates the hardness of the elastic region, and the Knoop hardness, which indicates the hardness of the plastic region. The results of the present study indicate that acoustic impedance accurately reflects the hardness of dentin.
文摘Leaf area index (LAI) is a key parameter for studying global terrestrial ecology and environment and has great ecological significance. How to accurately measure and calculate structural parameters of trees has become an urgent matter. This paper reports the use of terrestrial laser scanning (TLS) as a measurement tool to achieve accurate LAI estimation through point cloud preprocessing measures, the LeWos algorithm, and voxel methods. The accuracy and feasibility of this indirect measurement method were explored. It is found that the single wood structure parameters extracted from TLS have a good linear relationship with manual measurement, and the extraction errors meet the requirements of real-scene conversion. The study also found when the voxel size is consistent with the minimum distance of the point cloud set by TLS instrument, it has a strong correlation with the measured value of canopy analyser. These results lay the foundation for conveniently and quickly obtaining structural parameters of trees, tree growth state detection, and canopy ecological benefit assessment.
基金supported in part by the National Key Research and Development Program of China under Grant No.2018YFB1801503National Natural Science Foundation of China under Grants No.61931006,No.82071940,No.62101111,No.U20A20212,No.61921002,and No.U1930127+1 种基金Fundamental Research Funds for the Central Universities under Grants No.ZYGX2020ZB011 and No.ZYGX2019J013Medico-Engineering Cooperation Funds from University of Electronic Science and Technology of China under Grants No.ZYGX2021YGLH205 and No.ZYGX2021YGLH216.
文摘The microwave-induced thermoacoustic imaging(TAI)technology has both the advantages of high contrast of microwave imaging and high resolution of ultrasound imaging(UI),so it has carried out exploratory application research in various areas,such as the early detection of breast tumors and cerebrovascular diseases.However,the microwave generator used in the traditional TAI technology is huge and expensive,and the temporal resolution is also too low due to the single-element scanning mechanism.Thus,it is difficult to meet the needs of clinical applications.In this paper,the iterative process and the analysis of related application scenarios from single-element scanning to portable and array-based TAI,such as the miniaturized microwave generator,handheld antenna,multi-channel data acquisition,and UI/TAIdual-modality imaging,are reviewed,and the future trends of this technology are discussed.This review helps researchers in the field of TAI learn the technological development process and future trends.It also deepens clinicians’understanding of TAI so as to put forward more application requirements.
基金supported by the National Natural Science Foundation of China(Nos.51922056 and 51921005).
文摘Ferroelectric polymer nanocomposites possess exceptional electric properties with respect to the two otherwise uniform phases,which is commonly attributed to the critical role of the matrix-particle interfacial region.However,the structure-property correlation of the interface remains unestablished,and thus,the design of ferroelectric polymer nanocompos-ite has largely relied on the trial-and-error method.Here,a strategy that combines multi-mode scanning probe microscopy-based electrical charac-terization and nano-infrared spectroscopy is developed to unveil the local structure-property correlation of the interface in ferroelectric polymer nano-composites.The results show that the type of surface modifiers decorated on the nanoparticles can significantly influence the local polar-phase content and the piezoelectric effect of the polymer matrix surrounding the nano-particles.The strongly coupled polar-phase content and piezoelectric effect measured directly in the interfacial region as well as the computed bonding energy suggest that the property enhancement originates from the formation of hydrogen bond between the surface modifiers and the ferroelectric polymer.It is also directly detected that the local domain size of the ferroelectric polymer can impact the energy level and distribution of charge traps in the interfacial region and eventually influence the local dielectric strength.
基金This work was funded by the Researchers Supporting Project No.(RSP2022R509)King Saud University,Riyadh,Saudi Arabia.In additionthe Natural Science Foundation of Hunan Province under Grant no.2020JJ5604,2022JJ2029 and 2020JJ4622the National Natural Science Foundation of China under Grant no.62172058.
文摘The advanced integrated circuits have been widely used in various situations including the Internet of Things,wireless communication,etc.But its manufacturing process exists unreliability,so cryptographic chips must be rigorously tested.Due to scan testing provides high test coverage,it is applied to the testing of cryptographic integrated circuits.However,while providing good controllability and observability,it also provides attackers with a backdoor to steal keys.In the text,a novel protection scheme is put forward to resist scan-based attacks,in which we first use the responses generated by a strong physical unclonable function circuit to solidify fuseantifuse structures in a non-linear shift register(NLSR),then determine the scan input code according to the configuration of the fuse-antifuse structures and the styles of connection between the NLSR cells and the scan cells.If the key is right,the chip can be tested normally;otherwise,the data in the scan chain cannot be propagated normally,it is also impossible for illegal users to derive the desired scan data.The proposed technique not only enhances the security of cryptographic chips,but also incurs acceptable overhead.
基金supported by the National Natural Science Foundation of China(Grant No.52005495).
文摘The temperature field in laser line scanning thermography is investigated comprehensively in this work,including analytical calculation and experiment.Firstly,the principle of laser line scanning thermography is analyzed.On this basis,a physical laser line scanning model is proposed.Afterwards,based on Fourier transform(FT)and segregation variablemethod(SVM),the heat conduction differential equation in laser line scanning thermography is derived in detail.The temperature field of the composite-based coatings model with defects is simulated numerically.The results show that the laser line scanning thermography can effectively detect the defects in the model.The correctness of the analytical calculation is verified by comparing the surface temperature distribution obtained by analytical calculation and numerical simulation.Additionally,an experiment is carried out and the changeable surface temperature obtained by analytical calculation is compared with the experimental results.It shows that the error of maximum temperature obtained by analytical calculation and by experiment is 8%with high accuracy,which proves the correctness of analytical calculation and enriches the theoretical foundation of laser line scanning thermography.