Stationary solution of the ring-spinning balloon in zero air drag using a RBFN based mesh-free method

A technique for numerical analysis of the dynamics of the ring-spinning balloon based on the Radial Basis Function Networks (RBFNs) is presented in this paper. This method uses a 'universal approximator' based on neural network methodology to solve the differential governing equations which are derived from the conditions of the dynamic equilibrium of the yarn to determine the shape of balloon yarn. The method needs only a coarse finite collocation points without any finite element-type discretisation of the domain and its boundary for numerical solution of the governing differential equations. This paper will report a first assessment of the validity and efficiency of the present mesh-less method in predicting the balloon shape across a wide range of spinning conditions

Improving the tensile strength of carbon nanotube spun yarns using a modified spinning process

A modified process for the dry spinning of carbon nanotube (CNT) yarn is reported. The approach gives an improved structure of CNT bundles in the web drawn from the CNT forest and in the yarn produced from the twisted web leading to improved mechanical properties of the yarn. The process enables many different mechanical and physical treatments to be applied to the individual stages of the pure CNT spinning system, and may allow potential for the development of complex spinning processes such as polymer–CNT-based composite yarns. The tensile strength and yarn/web structure of yarn spun using this approach have been investigated and evaluated using standard tensile testing methods along with scanning electron microscopy. The experimental results show that the tensile properties were significantly improved. The effect of heat treatments and other yarn constructions on the tensile properties are also reported

Simulation of several CNT based macrostructures using slip-link model and discrete element method

The CNT macrostructures including membranes start by forming web on which CNT fibers are oriented along the web axis, some of them are parallel and others are poorly aligned or coiled. Since the CNT web impacts on the properties of derived macrostructures, the simulation of CNT membranes attracted significant attentions. The scanning electron microscopy analysis of CNT webs showed that CNT fibers entangle together. This entanglement is a key factor for the formation of CNT macrostructures because it allows the array of parallel fibers to unfold continuously into CNT networks. The work focuses on modelling the interconnection between CNT fibers within membranes and also other macro-structures and then analyzing mechanical properties of them

Simulation of non‑dilute fibre suspensions using RBF‑based macro–micro multiscale method

The multiscale stochastic simulation method based on the marriage of the Brownian Configuration Field (BCF) and the Radial Basis Function mesh-free approximation for dilute fibre suspensions by our group, is further developed to simulate non-dilute fibre suspensions. For the present approach, the macro and micro processes proceeded at each time step are linked to each other by a fibre contributed stress formula associated with the used kinetic model. Due to the feature of non-dilute fibre suspensions, the interaction between fibres is introduced into the evolution equation to determine fibre configurations using the BCF method. The fibre stresses are then determined based on the fibre configuration fields using the Phan–Thien–Graham model. The efficiency of the simulation method is demonstrated by the analysis of the two challenging problems, the axisymmetric contraction and expansion flows, for a range of the fibre concentration from semi-dilute to concentrated regimes. Results evidenced by numerical experiments show that the present method would be potential in analysing and simulating various suspensions in food and medical industries

Vortex flow generator utilizing synthetic jets by diaphragm vibration

This paper develops a millimeter scale fully packaged device in which a vortex flow of high velocity is generated inside a chamber. Under the actuation by a lead zirconate titanate (PZT) diaphragm, a flow circulates with increasing velocity after each actuating circle to form a vortex in a cavity named as the vortex chamber. At each cycle, the vibration of the PZT diaphragm creates a small net air flow through a rectifying nozzle, generates a synthetic jet which propagates by a gradual circulation toward the vortex chamber and then backward the feedback chamber. The design of such device is firstly conducted by a numerical analysis whose results are considered as the base of our experimental set-up. A vortex flow generated in the votex chamber was observed by a high-speed camera. The present approach which was illustrated by both the simulation and experiment is potential in various applications related to the inertial sensing, fluidic amplifier and micro/nano particle trapping and mixing

Computation of limit and shakedown using the NS-FEM and second-order cone programming

This paper presents a novel numerical procedure for computation of limit and shakedown using node-based smoothed finite element method (NS-FEM) in combination with second-order cone programming (SOCP). The obtained discretization formulation is then cast in a form which involves second-order cone constraints, ensuring that the underlying optimization problem can be solved by highly efficient primal-dual interior point algorithm. Furthermore, in the NS-FEM, the system stiffness matrix is computed using the smoothed strains over the smoothing domains associated with nodes. This ensures that the size of the resulting optimization problem is kept to a minimum. The efficiency of the present approach is illustrated by examining several numerical examples

An XFEM based kinematic limit analysis formulation for plane strain cracked structures using SOCP

This paper extends a numerical procedure for limit analysis based on extended finite element method (XFEM) and second-order cone programming (SOCP) to plane strain cracked structures. The cracked structures are easily modelled and simulated using XFEM because it allows discontinuities across elements, and these discontinuities are recognized by means of level set method. The resulting discretization formulation is then cast in a form which involves second-order cone constraints, ensuring that the underlying optimization problem can be solved by highly efficient primal-dual interior point algorithm. The efficiency of the present approach is illustrated by examing several numerical examples

Linear Query Approximation Algorithms for Non-monotone Submodular Maximization under Knapsack Constraint

This work, for the first time, introduces two constant factor approximation algorithms with linear query complexity for non-monotone submodular maximization over a ground set of size $n$ subject to a knapsack constraint, $\mathsf{DLA}$ and $\mathsf{RLA}$. $\mathsf{DLA}$ is a deterministic algorithm that provides an approximation factor of $6+\epsilon$ while $\mathsf{RLA}$ is a randomized algorithm with an approximation factor of $4+\epsilon$. Both run in $O(n \log(1/\epsilon)/\epsilon)$ query complexity. The key idea to obtain a constant approximation ratio with linear query lies in: (1) dividing the ground set into two appropriate subsets to find the near-optimal solution over these subsets with linear queries, and (2) combining a threshold greedy with properties of two disjoint sets or a random selection process to improve solution quality. In addition to the theoretical analysis, we have evaluated our proposed solutions with three applications: Revenue Maximization, Image Summarization, and Maximum Weighted Cut, showing that our algorithms not only return comparative results to state-of-the-art algorithms but also require significantly fewer queries