Micro-PIXE elemental mapping for ionome studies of crop plants

In order to maintain homeostasis and consequent optimal cell functioning and integrity and/or to avoid toxicity, proper allocation of elements at organ, tissue, cellular and subcellular level is needed. Studies of element localization are therefore crucial to reveal the mechanisms of element trafficking and also tolerance and toxicity. Moreover, studies of localization and speciation of trace elements in grains of staple crops are also of high applicative value, allowing one to determine major and trace element concentrations in different grain tissues without possible contamination. In the last decade, a remarkable progress has been made in the development and application of different 2D imaging techniques in complex biological systems, especially in the sense of improved lateral resolution and sensitivity. The superiority of micro-PIXE over other 2D imaging techniques lies in its wide elemental range (from sodium (Na) to uranium (U)), high elemental sensitivity below micron spatial resolution and fully quantitative element concentration analysis. The aim of this review is to summarize the latest development of micro-PIXE for imaging of the distribution of major and trace elements in crop plants with emphasis on sample preparation methodologies and post-imaging analysis. Case studies of element localization in the grains of major crop plants are also presented.

Venation-Inspired Growth Technique for Stiffener Layout Design of Plate and Shell Structures

A novel design method for stiffener layout of plate and shell structures is proposed in this paper. The method is inspired by the morphogenesis mechanism of dicotyledonous venation which is featured by hierarchy and functional adaptivity. It is expected that a optimal stiffener layout can be gradually achieved if the stiffeners extend by obeying a similar growth rule as the venation. Starting from the so called “seeds”, the stiffeners grow and branch off towards the direction that optimizes the structural performance. And the stiffeners with the minimum effectiveness to the structural performance are degenerated simultaneously. During the design process, the relative density of each element is treated as the design variable. The growth and degeneration of the stiffeners are determined by the nodal and elemental sensitivity numbers respectively. The design algorithm is programmed in Python and integrated with Abaqus software which is used as the FEA preprocessor and solver. To validate the effectiveness of the proposed method, it is applied to design the stiffener layouts of some typical structures with the objective of maximizing the overall stiffness with a volume constraint.

Research on Evolutionary Topology Optimization in ANSYS

Topology optimization function in ANSYS software is inefficient with the limitation of element types. By using the secondary developing language APDL and UIDL, the secondary development of bi-directional evolutionary structural optimization (BESO) method with volume constraint and stiffness maximization is completed in ANSYS. To suppress the checkerboard patterns, the elemental sensitivity numbers are recalculated by a filter method. To ensure the convergence of the optimization method in ANSYS, the elemental sensitivity numbers are updated by adding in their historical information. Two classic numerical examples are calculated to obtain the best topology structure. The numerical results indicate that the secondary method can solve the 2D and 3D problems effectively, which makes up for the deficiency of topology optimization part in ANSYS and broadens the application scope of the evolutionary optimization method.