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Table S2: spore settling velocities v set and sizes estimated from acquired high-speed camera images, and derived theoretical v set and aerodynamic diameter D a for the selected sporophytes and spores.
Figure S1: SEM photographs of ten individual spores per species. Nine video sequences illustrating, for each investigated species, one of the source materials used to build the database Table S2. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account.
Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Article Contents Abstract. Measuring spore settling velocity for an improved assessment of dispersal rates in mosses. E-mail f. To determine settling velocity of soil, the R-programming language is used to analyze the digital image set.
An original image is cropped in order to remove unnecessary parts for DIP. The procedure of calculation of settling velocity by DIP is as follows. First, select a digital image set of the settling particle.
The digital image set has N frames of the digital image. Second, perform binarization to segmentation of target soil particle and background. After binarization, the soil particle in the digital image is converted to a set of white pixels. To determine the position of the soil particle in each image, calculate centroid of white pixels in each image.
Finally, settling velocity is calculated by dividing the displacement into time difference. The procedure of acquisition of settling velocity is summarized in Figure 4. The size of a soil particle could be given by 3-dimensional as the shape of particle is commonly nonspherical.
The major A , intermediate B , and minor C axes of the particle are measured by a Vernier caliper, and each particle is classified by the shape classification table [ 31 ]. The shape classification table is plotted in Figure 5 a.
The shapes of nonspherical soil are classified into 4 groups such as sphere, short rod, thick plate, and ellipsoid Figure 5 b. The other shape groups such as plate, blade, and needle are an extreme case in natural soil particles. Therefore, the soil particles used in this study represent almost all shapes of soil in nature. The shape properties of nonspherical soil such as diameter maximum, mean, and minimum , area, perimeter, roundness, and aspect ratio are measured by digital image processing.
The statistic properties of shape properties are shown in Table 3. The mean diameter of soil particles is 8. The maximum diameter and minimum diameter are 5.
The area of soil particles is The roundness is distributed between 0. Sampled soil particles are classified to well-rounded particles. The aspect ratio is 2. It means that the shape of soil particles is elongated vertically. Figure 7 shows relationship of settling velocity and particle mean diameter measured by the digital image processing method. Settling velocity of soil particle has a large variation even though the mean diameter of particles is similar to each other.
This means that settling velocity of soil particles is affected by the particle shape, even when particles have the same mean diameter. Therefore, particle shape classification by the shape classification table well explains variation of settling velocity through a difference in the particle shape. But particle shape classification by the shape classification table has a poor applicability because it needs 3-dimensional size of every single particle.
As the settling velocity is related with particle diameter and shape, to analysis relationship between settling velocity and particle shape, the relationship between settling velocity and mean diameter of the particle should be excluded. For this reason, the residual of settling velocity versus mean diameter Figure 8 is calculated with the regression curve of settling velocity and mean diameter. The correlation coefficient between shape factors and residual is shown in Figure 9.
The aspect ratio has a high negative correlation with residual, and its correlation coefficient is —0. In common with the result using the shape classification table Figure 7 , settling velocity is affected by the particle shape in case of each particle having a same mean diameter.
It means that the settling velocity can be explained with shape properties which acquired by a 2-dimensional digital image instead of using the 3-dimensional shape classification method. Especially, DIP has a higher applicability than the shape classification table because it can measure a number of particles at once. The settling velocity of soil particles is a function of diameter and aspect ratio.
The prediction formula for settling velocity 1 is an empirical formula derived with multiple nonlinear regression by Microsoft Excel Solver. The form of the formula was determined in the simplest form by trial and error. The formula was developed for nonspherical soil particles with an average particle size range of 1. The coefficient of determination is 0. This function has a high applicability because it needs only two parameters mean diameter and aspect ratio derived from DIP.
To verify the prediction function for settling velocity, soil particles are sampled. Compared with other researches [ 1 , 6 , 15 , 18 ], the prediction formula of settling velocity by DIP is much simpler and has a higher accuracy Figure In this study, the digital image processing method has been used as an alternative measure to predict settling velocity of soil particles. The following conclusions were obtained. The shapes of nonspherical soil are classified into 4 groups such as sphere, short rod, thick plate, and ellipsoid.
Measurement method of soil shape properties and settling velocity by digital image processing is evaluated as a simple, faster alternative rather than using the shape classification table. The settling velocity of the soil particle has a large variation even though the mean diameter of particles is similar to each other.
In case particles have a same mean diameter, sphere shape particles have higher settling velocity than that of other shape particles. The settling velocity is affected by mean diameter and aspect ratio measured by digital image processing. The prediction formula for settling velocity is derived with multiple nonlinear regression, and it is simple and accurate compared to results of previous researches.
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Journal overview. Special Issues. Academic Editor: Giuseppe Oliveto. Received 29 Aug Accepted 06 Nov Published 09 Dec
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