- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
High Precision Individual Tree Diameter and Perimeter Estimation from Close-Range Photogrammetry
摘要： Close-range photogrammetry (CRP) can be used to provide precise and detailed three-dimensional data of objects. For several years, CRP has been a subject of research in forestry. Several studies have focused on tree reconstruction at the forest stand, plot, and tree levels. In our study, we focused on the reconstruction of trees separately within the forest stand. We investigated the influence of camera lens, tree species, and height of diameter on the accuracy of the tree perimeter and diameter estimation. Furthermore, we investigated the variance of the perimeter and diameter reference measurements. We chose four tree species (Fagus sylvatica L., Quercus petraea (Matt.) Liebl., Picea abies (L.) H. Karst. and Abies alba Mill.). The perimeters and diameters were measured at three height levels (0.8 m, 1.3 m, and 1.8 m) and two types of lenses were used. The data acquisition followed a circle around the tree at a 3 m radius. The highest accuracy of the perimeter estimation was achieved when a fisheye lens was used at a height of 1.3 m for Fagus sylvatica (root mean square error of 0.25 cm). Alternatively, the worst accuracy was achieved when a non-fisheye lens was used at 1.3 m for Quercus petraea (root mean square error of 1.27 cm). The tree species affected the estimation accuracy for both diameters and perimeters.
关键词： close-range photogrammetry,fisheye lens,trunk perimeter,circle fitting,trunk diameter,convex hull,point cloud
更新于2025-09-09 09:28:46
-
Heterogeneity governs diameter-dependent toughness and strength in SiC nanowires
摘要： Using a combination of density functional theory and molecular dynamics simulations, this paper reveals the atomistic origin of diameter-dependent extreme mechanical behavior of [111] 3C-SiC nanowires obtained from an energy-based framework. Our results suggest that heterogeneity in atomic stress and variations in diameter-dependent potential-energy density have a profound impact on extreme mechanical properties in the nanowires. The heterogeneity in stress evolves from the nonuniform bond lengths mediated by low coordinated surface atoms—and it penetrates the entire cross section in thinner nanowires and constitutes the atomistic basis for their large reduction in fracture strain, toughness, and strength. Although stress heterogeneity is substantially higher in ultrathin nanowires, its intensity drops and saturates rapidly in larger nanowires following a nonlinear dependence on diameter. The maximum stress heterogeneity in a cross section localizes crack nucleation at the core in ultrathin nanowires but near the surface in larger nanowires. Moreover results show that stiffness, toughness, strength, and fracture strain of the nanowires increase nonlinearly with increasing diameter and saturate at a lower value compared to bulk SiC. In addition to resolving wide discrepancies in the reported values of the ?rst-order elastic modulus in SiC nanowires, the ?ndings highlight heterogeneity as a critical factor for inducing diameter-dependent extreme mechanical behavior in brittle nanowires.
关键词： heterogeneity,atomic stress,strength,toughness,potential-energy density,fracture strain,SiC nanowires,diameter-dependent,mechanical properties
更新于2025-09-09 09:28:46
-
A blue fluorescent labeling technique utilizing micro- and nanoparticles for tracking in LIVE/DEAD® stained pathogenic biofilms of Staphylococcus aureus and Burkholderia cepacia
摘要： Strategies that target and treat biofilms are widely applied to bacterial cultures using popular live/dead staining techniques with mostly red or green fluorescent markers (eg, with SYTO? 9, propidium iodide, fluorescein). Therefore, visualizing drugs or micro- and nanoparticulate delivery systems to analyze their distribution and effects in biofilms requires a third fluorescent dye that does not interfere with the properties of the live/dead markers. The present study establishes and evaluates a model for tracking polymeric particles in fluorescently stained biological material. To this end, poly(d,l-lactide-co-glycolide) (PLGA)-based micro- and nanoparticles were used as well-established model systems, which, because of their favorable safety profiles, are expected to play important future roles with regard to drug delivery via inhalation. PLGA was covalently and stably labeled with 7-amino-4-methyl-3-coumarinylacetic acid (AMCA), after which blue fluorescent poly(ethylene glycol)-block-PLGA (PEG-PLGA) particles were prepared using a mixture of fluorescent AMCA-PLGA and PEG-PLGA. Because chitosan is known to reduce negative surface charge, blue fluorescent PEG-PLGA-particles with chitosan were also prepared. These micro- and nanoparticles were physicochemically characterized and could be clearly distinguished from live/dead stained bacteria in biofilms using confocal laser scanning microscopy.
关键词： 7-amino-4-methyl-3-coumarinylacetic acid,cystic fibrosis,PEG,PLGA,chitosan,hydrodynamic diameter,confocal laser scanning microscopy
更新于2025-09-09 09:28:46
-
Application of confocal X-ray fluorescence based on capillary X-ray optics in nondestructively measuring the inner diameter of monocapillary optics
摘要： The inner diameter is an important parameter in the design and fabrication of monocapillary X-ray optics which is widely used in X-ray technology. The confocal X-ray fluorescence(CXRF) based on X-ray capillary optics was proposed to nondestructively measure the inner diameter of the monocapillary. The zinc chlorine solutions were filled into monocapillary in order to measure its inner diameter with the CXRF. With a scan of the edge of zinc solutions in a monocapillary optic through the confocal volume of the CXRF, the inner diameter could be obtained directly and nondestructively. The mean of relative errors of this method for measuring the inner diameter were approximately 4.1%. This proposed method of determining the inner diameter of monocapillary optics plays a significant role in design, fabrication and application of the monocapillary X-ray optics.
关键词： Confocal X-ray fluorescence,Nondestructive,Measurement of inner diameter of monocapillary
更新于2025-09-09 09:28:46
-
A Remote Free-head Pupillometry Based on Deep Learning and Binocular System
摘要： Objective. Pupillometer plays a key role in a variety of research areas, including disease diagnosis, human-machine interaction, and education. Here we set out to leverage the deep learning theory to develop a remote binocular vision system for pupil diameter estimation. Approach. The system consists of three parts: eye detection, eye tracking, and pupil diameter estimation. We ?rst train a convolutional neural network based on YOLO V2 to perform eye detection, leading to high accuracy and robustness under ambient light interference. By exploring the similarity of binocular camera images, we then propose a master-slave structure for eye tracking, surpassing the traditional parallel structure in tracking speed while keeping considerable accuracy. Furthermore, we develop a pupil diameter estimation algorithm based on binocular vision, avoiding the personal calibration procedure and reducing the measurement distortion error. Main results. Experimental results on real datasets reveal that our system exhibits state-of-the-art performance with high eye detection accuracy (90.6%), fast eye tracking speed (< 11 ms per frame), low pupil diameter estimation error ((0.022 ± 0.017) mm mean absolute error and (0.6 ± 0.7)% percentage of the mean absolute error) and excellent ?exibility. Signi?cance. In contrast with previous pupillometers, which lead to pupil diameter measurement distortion error through a 2D projection image on a single camera, our system measures pupil diameter in 3D space without distortion in?uence, thus improving its robustness to head angle variation and making it more practical for real applications.
关键词： pupil detection,binocular vision,eye tracking,deep learning,eye detection,master-slave structure,Pupil diameter (PD)
更新于2025-09-04 15:30:14
-
Design and engineering of dispersion and loss in photonic crystal fiber 1?×?4 power splitter (PCFPS) based on hole size alteration and optofluidic infiltration
摘要： We have presented a technique based on optofluidic infiltration and air-holes diameter variation together to design a 1 × 4 photonic crystal fiber power splitter (PCFPS) which have very low dispersion (D): (0 ≤ D ≤ 2.5 (ps/nm/km) and very low loss (L): 0 ≤ L ≤ 0.025(dB/cm) in a wide range of wavelengths (1100–1700 nm). This approach allows us to control the dispersion of the fundamental mode in a PCF beam splitter by choosing appropriate refractive indices for liquids and suitable diameters for air-holes in PCF power splitter. In fact, the techniques, used in this paper are complementary of each other and give us more excellent results which are better than other reported results in researchers’ works so far. In this work, a new design of 1 × 4 photonic crystal fiber power splitter is proposed by using beam propagation method. An optical Gaussian signal at a wavelength of third communication window range (1550 nm) is inserted into the central core and equally is divided into four core (25% of the total input power interred to each core). In addition, the physical behavior of coupling characteristics is obtained by using coupled mode analysis. Numerical simulations show that input optical signal can be equally divided in photonic crystal fiber structure with low dispersion and low loss. The total size of proposed PCFPS is 30 μm × 30 μm × 1.2 mm, too.
关键词： Third communication window range,Optofluidic infiltration,Air-holes diameter variation,PCFPS
更新于2025-09-04 15:30:14