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- 摘要
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- 实验方案
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A greyscale voxel model for airborne lidar data applied to building detection
摘要： The existing binary voxel model algorithm for 3D building detection (3BD) from airborne lidar cannot distinguish between connected buildings and non-buildings. As a result, a greyscale voxel structure model, using the discretised mean intensity of lidar points, is presented to support subsequent building detection in areas where buildings are adjacent to non-buildings but with different greyscales. The resulting 3BD algorithm first detects a building roof by selecting voxels characterised by a jump in elevation as seeds, labelling them and their 3D connected regions as rooftop voxels. Then voxels which fall into buffers and possess similar greyscales to that of the corresponding building outline are assigned as building facades. The results for detected buildings are evaluated using lidar data with different densities and demonstrate a high rate of success.
关键词： lidar,greyscale,voxel,building detection,point cloud,intensity
更新于2025-09-23 15:22:29
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Systematic λ/21 resolution achieved in nanofabrication by two-photon-absorption induced polymerization
摘要： Photopolymerization, based on two-photon absorption in resins, has been recognized as one of the enabling technologies to fabricate three-dimensional micro/nanostructures with a sub-diffraction-limit resolution. This work focuses on improving the spatial resolution using femtosecond laser, λ=780 nm, with a systematic nanofabrication process which we developed. We discuss the factors influencing the spatial resolution, including the laser intensity, the exposure time, and the scanning speed by fabricating polymerized-voxels, nano-lines, and suspended nano-fibers in a photoresist based on a methyl-methacrylate monomer. We show that a resolution of ~36 nm, corresponding to ~λ/21, is achieved. Stable 3D microstructures can be fabricated by using our custom made set up.
关键词： Voxel,Resolution,Two Photon Polymerization,Micro/Nanostructures,Femtosecond Laser,Suspended Polymerized Fibers
更新于2025-09-23 15:22:29
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[IEEE 2018 International Multi-Conference on Industrial Engineering and Modern Technologies (FarEastCon) - Vladivostok, Russia (2018.10.3-2018.10.4)] 2018 International Multi-Conference on Industrial Engineering and Modern Technologies (FarEastCon) - Numerical Simulation of Low-Coherence Radiation Propagation in Turbid Media and Structural Image Reconstruction in Endoscopic Optical Coherence Tomography with Allowance for Speckle Fluctuations
摘要： A method of Monte Carlo simulation of low-coherence radiation propagation in turbid media with consideration of speckle noise (the result of mutual interference of secondary spherical waves) is described. The process of photon propagation within investigated object, such as biological tissue, includes the following steps: the photon injection, mean free path determination, the verification of the fulfillment of the boundary condition, the absorption and scattering. Structural image reconstruction in optical coherence tomography (OCT) with consideration of speckle fluctuations is made by summation the statistical weight of the beam coming out of the investigated object inside the detector area with the intensity of a series of pixels of the current A-scan. The key feature of the presented method is the description of the investigated object geometry. Three-dimensional array of voxels combined into parallelograms, and the border cross checking is carried out by using an improved Smith algorithm. The described method can be used to obtain high-quality endoscopic structural OCT images of body cavities and tracts (diagnosis of the respiratory tract, cardiovascular system, gastrointestinal tract, genitourinary system, etc.).
关键词： coherence probing depth,Monte Carlo simulation,optical coherence tomography,voxel based model,speckle fluctuations,structural image
更新于2025-09-23 15:22:29
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Automated and efficient powerline extraction from laser scanning data using a voxel-based subsampling with hierarchical approach
摘要： For periodic monitoring of power utilities, there has been keen interest by utility companies to extract the powerlines from laser scanning data. However, challenges arise when utilizing large point clouds as well as avoiding false positives or other errors in the extraction due to noise from objects in close proximity to the powerlines. In this study, we propose an efficient and robust approach to overcome these challenges through two main steps: candidate powerline point extraction and refinement. In the candidate powerline point extraction step, a voxel-based subsampling structure temporarily substitutes the original scan points with regularly spaced subsampled points that still preserve key details present within the point cloud but significantly reduce the dataset size. After removing the ground surface and adjacent objects, candidate powerline points are efficiently extracted through a hierarchical, feature-based filtering process. In the refinement step, the link between the subsampled candidate powerline points and original scan point cloud enable the original points to be segmented and grouped into clusters. By fitting mathematical models, an individual powerline is re-clustered and used to reconstruct the broken sections in the powerlines. The proposed approach is evaluated on 30 unique datasets with different powerline configurations acquired at five different sites by either a terrestrial or mobile laser scanning system. The parameters are optimized through a sensitivity analysis with pointwise comparison between the extracted powerlines and ground truth using 10 diverse datasets, demonstrating that only one requisite parameter varied as a function of resolution while the remaining parameters were generally consistent across the datasets. With optimized parameters, the proposed approach achieved F1 scores of 88.87–95.47% with high efficiency ranging from 0.81 and 1.46 million points/sec when tested on 30 datasets.
关键词： Lidar,Powerlines,Voxel-based subsampling,Laser scanning,Point cloud
更新于2025-09-23 15:21:01
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Laser direct printing of solder paste
摘要： We experimentally demonstrated a laser-based approach for the maskless printing of solder paste with a predefined size and position. In this work, a 532 nm laser marking system is used to induce the formation of a solder paste bridge between the donor and acceptor substrate. After the donor is removed vertically, the bridge will rupture and a high aspect ratio voxel can be obtained on the acceptor substrate. The width and height of transferred voxels can be controlled by modifying the laser fluence. In order to find out the specific conditions for the solder paste bridge formation, we carried out transfer experiments at different gap distances and found out a bridge formation threshold. Solder paste bridges can be produced only when the gap distance is smaller than the threshold. Furthermore, the threshold can be affected by the film thickness and spot size. In this condition, a solder paste array with an average size of 100 μm and a pitch of 200 μm has been successfully transferred. Compared to conventional printing methods, the method proposed in this paper can effectively improve the transfer accuracy and reduce the production cost.
关键词： laser direct printing,laser-induced forward transfer,solder paste,high aspect ratio voxel,maskless printing
更新于2025-09-12 10:27:22
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Building Point Detection from Vehicle-Borne LiDAR Data Based on Voxel Group and Horizontal Hollow Analysis
摘要： Information extraction and three-dimensional (3D) reconstruction of buildings using the vehicle-borne laser scanning (VLS) system is significant for many applications. Extracting LiDAR points, from VLS, belonging to various types of building in large-scale complex urban environments still retains some problems. In this paper, a new technical framework for automatic and efficient building point extraction is proposed, including three main steps: (1) voxel group-based shape recognition; (2) category-oriented merging; and (3) building point identification by horizontal hollow ratio analysis. This article proposes a concept of “voxel group” based on the voxelization of VLS points: each voxel group is composed of several voxels that belong to one single real-world object. Then the shapes of point clouds in each voxel group are recognized and this shape information is utilized to merge voxel group. This article puts forward a characteristic nature of vehicle-borne LiDAR building points, called “horizontal hollow ratio”, for efficient extraction. Experiments are analyzed from two aspects: (1) building-based evaluation for overall experimental area; and (2) point-based evaluation for individual building using the completeness and correctness. The experimental results indicate that the proposed framework is effective for the extraction of LiDAR points belonging to various types of buildings in large-scale complex urban environments.
关键词： horizontal hollow analysis,vehicle-borne LiDAR,building point extraction,voxel group
更新于2025-09-10 09:29:36
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Disturbed interhemispheric functional connectivity in visual pathway in individuals with unilateral retinal detachment: A resting state fMRI study
摘要： Previous neuroimaging studies demonstrated that retinal detachment (RD) subjects were associated with abnormal spontaneous brain activities; however, whether the altered interhemispheric functional connectivity (FC) occurred in RD patients remains unknown. The current study tried to explore the alternations of interhemispheric FC of the whole brain in unilateral RD patients using the voxel-mirrored homotopic connectivity (VMHC) method and their connections to clinical features. Methods: We recruited 30 patients with RD (16 males and 14 females) and 30 healthy controls (HCs) (16 males and 14 females) whose age and sex were closely matched. All subjects underwent the rs-fMRI scans. The VMHC method was applied to directly assess the hemispheres’ functional interaction. The VMHC in these brain areas, which could be used as biomarkers to differentiate RD from HC, was identified by the receiver operating characteristic (ROC) curve analyses. The relations between these patients’ clinical features and their mean VMHC signal values in multiple brain regions were calculated by Pearson correlation analysis. Results: RD patients had significantly lower VMHC values than HCs in the bilateral occipital lobe (Brodmann areas, BA 18), bilateral superior temporal gyrus (BA 39), and bilateral cuneus (BA 19). Moreover, the mean VMHC signal values of the bilateral cuneus were in positive correlation with the duration of the RD (r = 0.446, P = 0.013). Conclusion: Our results provided an evidence of disturbed interhemispheric FC in the visual area occurred in RD patients, which might provide some useful information to understand the neural mechanism of RD patients with acute vision loss. Furthermore, the VMHC values might indicate the progress of the RD.
关键词： Retinal detachment,Functional magnetic resonance imaging,Static condition,Voxel-mirrored homotopic connectivity
更新于2025-09-10 09:29:36
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Estimation of Voxel-Based Above-Ground Biomass Using Airborne LiDAR Data in an Intact Tropical Rain Forest, Brunei
摘要： The advancement of LiDAR technology has enabled more detailed evaluations of forest structures. The so-called “Volumetric pixel (voxel)” has emerged as a new comprehensive approach. The purpose of this study was to estimate plot-level above-ground biomass (AGB) in different plot sizes of 20 m × 20 m and 30 m × 30 m, and to develop a regression model for AGB prediction. Both point cloud-based (PCB) and voxel-based (VB) metrics were used to maximize the efficiency of low-density LiDAR data within a dense forest. Multiple regression model AGB prediction performance was found to be greatest in the 30 m × 30 m plots, with R2, adjusted R2, and standard deviation values of 0.92, 0.87, and 35.13 Mg·ha?1, respectively. Five out of the eight selected independent variables were derived from VB metrics and the other three were derived from PCB metrics. Validation of accuracy yielded RMSE and NRMSE values of 27.8 Mg·ha?1 and 9.2%, respectively, which is a reasonable estimate for this structurally complex intact forest that has shown high NRMSE values in previous studies. This voxel-based approach enables a greater understanding of complex forest structure and is expected to contribute to the advancement of forest carbon quantification techniques.
关键词： LiDAR,voxel,REDD+,volumetric pixel,forest biomass,forest carbon stock,climate change
更新于2025-09-04 15:30:14