Particle morphology is an important factor affecting the mechanical properties of granular materials. However, it is difficult to quantify the morphology characteristics of the complex concave particle. Fortunately, complex particle can be segmented by convex decomposition, so a new shape index named convex decomposition coefficient (CDC) related to the number of segmentations is proposed. First, the pocket concavity was introduced to simplify the morphology hierarchically. Second, the cut weight linked to concavity was defined and convex decomposition was linearly optimised by maximizing the total cut weights. Third, the CDC was defined as the minimum block number where the block area ratio cumulatively exceeded 0.9 in descending order. Finally, the proposed index was used to quantify the particle morphology of coral sand. The results demonstrate that the CDC of coral sands mainly ranges from 2 to 6, with a positively skewed distribution. Furthermore, CDC correlates well with three shape indices: sphericity, particle size, and convexity. Larger CDC is associated with smaller sphericity, larger particle size, and smaller convexity. The index has certain scientific research value and practical significance.

The identification of phytoparasitic nematodes, which is essential for the implementation of management strategies is required. The objective of this work was to identify, at the genus level, the phytoparasites and free-living nematodes associated with the cultivation of sweet granadilla ( Passiflora ligularis Juss.) in the valley of Sandia, region Puno, Peru. For the study, 165 soil samples were evaluated, coming from eight communities from the district of Sandia, during the agricultural season 2018-2019. The samples were processed by the method of centrifugal flotation in sucrose solution, and later identified on the basis of morphological characteristics. The results showed the presence of seven genera of phytoparasitic nematodes: Meloidogyne , Pratylenchus , Helicotylenchus , Mesocriconema , Xiphinema , Tylenchus, and Hemicycliophora , and two genera of free-living nematodes, Aphelenchus and Dorylaimus. The most harmful genera were Meloidogyne and Pratylenchus because they cause damage to other crops. In the nematode community, there was variability in the density and frequency of phytoparasitic and freeliving individuals in the evaluated localities.