Multiscale Isogeometric Topology Optimization with Unified Structural Skeleton

This paper proposes a multiscale isogeometric topology optimization(ITO)method where the configuration and layout of microstructures are optimized simultaneously.At micro scale,a shape deformation method is presented to transform a prototype microstructure(PM)for obtaining a series of graded microstructures(GMs),where microstructural skeleton based on the level set framework is applied to retain more topology features and improve the connectability.For the macro scale calculation,the effective mechanical properties can be estimated by means of the numerical homogenization method.By adopting identical non-uniform rational basis splines(NURBS)as basis functions for both parameterized level set model and isogeometric calculation model,the isogeometric analysis(IGA)is integrated into the level set method,which contributes to improving the accuracy and efficiency.Numerical examples demonstrate that,the proposed method is effective in improving the performance and manufacturability.

Method for pests detecting in stored grain based on spectral residual saliency edge detection

Pests detecting is an important research subject in grain storage field.In the past decades,many edge detection methods have been applied to the edge detection of stored grain pests.Although some of them can realize the stored grain pests detecting,precision and robustness are not good enough.Spectral residual(SR)saliency edge detection defines the logarithmic spectrumof image as novelty part of the image information.The remaining spectrumis converted to the airspace to obtain edge detection results.SR algorithm is completely based on frequency domain processing.It not only can effectively simplify the target detection algorithm,but also can improve the effectiveness of target recognition.The experimental results show that the edge results of stored grain pests detected by SR method are effective and stable.

An XBi-CFAO Method for the Optimization of Multi-Layered Variable Stiffness Composites Using Isogeometric Analysis

This paper presents an effective fiber angle optimization method for two and multi-layered variable stiffness composites.A gradient-based fiber angle optimization method is developed based on isogeometric analysis(IGA).Firstly,the element densities and fiber angles for two and multi-layered composites are synchronously optimized using an extended Bi-layered continuous fiber angle optimization method(XBi-CFAO).The densities and fiber angles in the base layer are attached to the control points.The structure response and sensitivity analysis are accomplished using the non-uniform rational B-spline(NURBS)based IGA.By the benefit of the B-spline space,this method is free from checkerboards,and no additional filtering is needed to smooth the sensitivity numbers.Then the curved fiber paths are generated using the streamline method and the discontinuous fiber paths are smoothed using a partitioned selection process.The proposed method in the paper can alleviate the phenomenon of fiber discontinuity,enhance information retention for the optimized fiber angles of the singular points and save calculating resources effectively.

A New Finite Element Model with Manufactured Error for Additive Manufacturing

Additive manufacturing(AM),adding materials layer by layer,can be used to produce objects of almost any shape or geometry.However,AM techniques cannot accurately build parts with large overhangs,especially for the large features close to horizontal,hanging over the void.The overhangs will make the manufactured model deviate from the design model,which will result in the performance of the manufactured model that cannot satisfy the design requirements.In this paper,we will propose a new finite element(FE)analysis model that includes the manufacturing errors by mimicking the AM layer by layer construction process.In such FE model,an overhang coefficient is introduced to each FE,which is defined by the support elements in the lower layer.By mimicking the AM process from the bottom layer to the top layer,all the FE properties are updated based on their overhang coefficients,which makes the computational model be able to predict the manufactured model with manufacturing errors.The proposed model can be used to predict the performance of the AM objects in the design stage,which will help the designers to improve their design by the simulation results.

IGA Based Bi-Layer Fiber Angle Optimization Method for Variable Stiffness Composites

This paper presents a topology optimization method for variable stiffness composite panels with varying fiber orientation and curvilinear fiber path.Non-uniform rational B-Splines(NURBS)based Isogeometric analysis(IGA)is utilized for the numerical computation of the general minimum compliance problem.The sensitivity analysis of the structure compliance function for the density and bi-layer orientation is conducted.The bi-layer fiber paths in the design domain are generated using streamline method and updated by divided pieces reselection method after the optimization process.Several common examples are tested to demonstrate the effectiveness of the method.The results show that the proposed method can generate more manufacturable fiber paths than some typical topology optimization methods.

Drosophila Homolog of FMRP Maintains Genome Integrity by Interacting with Piwi

Fragile X syndrome （FraX）, the most common form of inherited mental retardation, is caused by the absence of the evolutionally conserved fragile X mental retardation protein （FMRP）. While neuronal functions of FMRP have been intensively studied for the last two decades, its role in non-neuronal cells remains poorly understood. Piwi, a key component of the Piwi-interacting RNA （piRNA） pathway, plays an essential role in germline development. In the present study, we report that similar to piwi, dfmrl, the Drosophila homolog of human FMR1, is required for transposon suppression in the germlines. Genetic analyses showed that dfmrl and piwi act synergistically in heterochromatic silencing, and in inhibiting the differentiation of primordial germline cells and transposon expression. Northern analyses showed that roo piRNA expression levels are reduced in dfmrl mutant ovaries, suggesting a role of dfmrl in piRNA biogenesis. Biochemical analysis demonstrated a physical interaction between dFMRP and Piwi via their N-termini. Taken together, we propose that dFMRP cooperates with Piwi in maintaining genome integrity by regulating heterochromatic silencing in somatic cells and suppressing transposon activity via the piRNA pathway in germlines.