Isogeometric Analysis and Shape Optimization of Holed Structures via the Patch Removing Technique

In this study,a patch removing based Isogeometric analysis(PR-IGA)method is proposed to conduct the holed structural analysis with only one parametric domain,in which there are also no trimmed elements.The theoretical foundation of this novel patch removing approach is that any holed structure can be obtained by removing sub-patches(i.e.,the holes)from an intact base patch.Since the parametric domains of these patches are all meshed by rectangular grids,the elements in the resulted holed structural parametric domain could all be untrimmed rectangles under certain mapping conditions.To achieve the special condition,a systematic technique consisting of T-spline local refinement and control points substitution/adjustment is provided.Due to the intactness of parametric elements,the analysis procedure of holed structures based on the proposed PRIGA is quite simplified and efficient compared to traditional multi-patch and trimming schemes.Moreover,after the deduction of analytical sensitivities related to structural mass and mechanical responses,the PR-IGA is directly employed in the holed structural shape optimization to successfully eliminate the need for model transformation during modeling,analysis and optimization processes.Numerical examples involving analysis and shape optimization of complex holed structures are presented to demonstrate the effectiveness of the proposed method.

A novel method for identifying influential nodes in complex networks based on gravity model

How to identify influential nodes in complex networks is an essential issue in the study of network characteristics.A number of methods have been proposed to address this problem,but most of them focus on only one aspect.Based on the gravity model,a novel method is proposed for identifying influential nodes in terms of the local topology and the global location.This method comprehensively examines the structural hole characteristics and K-shell centrality of nodes,replaces the shortest distance with a probabilistically motivated effective distance,and fully considers the influence of nodes and their neighbors from the aspect of gravity.On eight real-world networks from different fields,the monotonicity index,susceptible-infected-recovered(SIR)model,and Kendall’s tau coefficient are used as evaluation criteria to evaluate the performance of the proposed method compared with several existing methods.The experimental results show that the proposed method is more efficient and accurate in identifying the influence of nodes and can significantly discriminate the influence of different nodes.

Structural optimization of uniaxial symmetry non-circular bolt clearance hole on turbine disk

This study proposes a parameterized model of a uniaxial symmetry non-circular hole, to improve conventional circular bolt clearance holes on turbine disks. The profile of the model consists of eight smoothly connected arcs, the radiuses of which are determined by 5 design variables.By changing the design variables, the profile of the non-circular hole can be transformed to accommodate different load ratios, thereby improving the stress concentration of the area near the hole and that of the turbine disk. The uniaxial symmetry non-circular hole is optimized based on finite element method（FEM）, in which the maximum first principal stress is taken as the objective function. After optimization, the stress concentration is evidently relieved; the maximum first principal stress and the maximum von Mises stress on the critical area are reduced by 30.39% and 25.34%respectively, showing that the uniaxial symmetry non-circular hole is capable of reducing the stress level of bolt clearance holes on the turbine disk.

ENTREPRENEURIAL OPPORTUNITY,VALUE EVOLUTION,AND ORGANIZATIONAL INTEGRATION OF PROFESSIONAL FARMER ENTREPRENEURSHIP:A MULTI-CASE COMPARISON IN CHINA

A comparative multi-case analysis of professional farmer entrepreneurship cases in China was performed by applying the structural hole theory.The results confirmed four views.(1)Choosing the modern agriculture project entrepreneurship is rational for professional farmers,who return from urban,to reduce the interference from non-market factors.The success of this project stems from its ability to successfully occupy the structural hole of the market trading network.(2)In economically developed areas,professional farmers start their businesses and reduce transaction costs with factors by occupying‘self-benefit’or‘mutual-benefit’structural holes in market networks.(3)In traditional agricultural areas,for reducing factor transaction costs,professional farmers occupy the organizational-governance structural hole of rural social relationship networks and the mutual-benefit structural hole of market networks to start their businesses.(4)The embedding order of these two structural holes will change depending on the differences in the local resource endowment.This article proposes some suggestions to encourage professional farmers to develop featured agricultural projects,build a close benefit-linked mechanism with smallholders through the provision of socialized services,and participate in the governance of rural communities.

Recent advances in the design of dopant-free hole transporting materials for highly efficient perovskite solar cells

Continuous success has been achieved for solution-processed inorganic-organic hybrid perovskite solar cells（PVSCs） in the past several years, in which organic charge transporting materials play an important role. At present, most of the commonly used hole-transporting materials（HTMs） such as spiro-OMeTAD derivatives for PVSCs require additional chemical doping process to ensure sufficient conductivity and shift the Fermi level towards the HOMO level for efficient hole transport and collection. However, this doping process not only increases the complexity and cost of device fabrication, but also decreases the device stability. Thus development of efficient dopant-free HTMs for PVSCs is highly desirable and remains as a major challenge in this field. In this review, we will summarize the recent advances in the molecular design of dopant-free HTMs for PVSCs.

Design of a Photonic-Crystal Channel-Drop Filter Based on the Two-Dimensional Triangular-Lattice Hole Structure

A channel-drop filter has been designed based on the two-dimensional triangular-lattice hole photonic-crystal structure, which consists of two line defects and two point defects, by a two-dimensional finite-difference time-domain simulation.