Xcast6 Treemap Islands - Revisiting Multicast Model

International audienceDue to the complexity and poor scalability, IP Multicast has not been used on the Internet. Recently, Xcast6 - a complementary protocol of IP Multicast has been proposed. However, the key limitation of Xcast6 is that it only supports small multicast sessions. To overcome this, we propose Xcast6 Treemap islands (X6Ti) - a hybrid model of Overlay Multicast and Xcast6. In summary, X6Ti has many advantages: support large multicast groups, simple and easy to deploy on the Internet, no router configuration, no restriction on the number of groups, no multicast routing protocol and no group management protocol. Based on simulation, we compare X6Ti with IP Multicast and NICE protocols to show the benefits of our new model

New temperature jump boundary condition in high-speed rarefied gas flow simulations

The effect of the sliding friction has been important in calculating the heat flux of gas flow from the surface since there is some slip over the surface. There has not been any the temperature jump condition including the sliding friction part so far. In this paper, we will propose a new temperature jump condition that includes the sliding friction. Our new temperature jump condition will be evaluated for NACA0012 micro-airfoil in high-speed rarefied gas flow simulations using the CFD method, which solves the Navier-Stokes equations within the OpenFOAM framework with working gas as air. The airfoil case is simulated with various Knudsen numbers from 0.026 to 0.26, and the angles-of-attack (AOAs) from 0-deg to 20-deg. The surface gas temperatures predicting by our new temperature jump condition give good agreements with the DSMC data, especially the NACA0012 micro-airfoil cases with the high Knudsen numbers, Kn = 0.1, and Kn = 0.26 with AOA = 20-deg. for the lower surface

An Optimal Design Method for Compliant Mechanisms

Compliant mechanisms are crucial parts in precise engineering but modeling techniques are restricted by a high complexity of their mechanical behaviors. Therefore, this paper devotes an optimal design method for compliant mechanisms. The integration method is a hybridization of statistics, finite element method, artificial intelligence, and metaheuristics. In order to demonstrate the superiority of the method, one degree of freedom is considered as a study object. Firstly, numerical datasets are achieved by the finite element method. Subsequently, the main design parameters of the mechanism are identified via analysis of variance. Desirability of both displacement and frequency of the mechanism is determined, and then, they are embedded inside a fuzzy logic system to combine into a single fitness function. Then, the relationship between the fine design variables and the fitness function is modeled using the adaptive network-based fuzzy inference system. Next, the single fitness function is maximized via moth-flame optimization algorithm. The optimal results determined that the frequency is 79.517 Hz and displacement is 1.897 mm. In terms of determining the global optimum solution, the current method is compared with the Taguchi, desirability, and Taguchi-integrated fuzzy methods. The results showed that the current method is better than those methods. Additionally, the devoted method outperforms the other metaheuristic algorithms such as TLBO, Jaya, PSOGSA, SCA, ALO, and LAPO in terms of faster convergence. The result of this study will be considered to apply for multiple-degrees-of-freedom compliant mechanisms in future work

Behavior Analysis of a Flexure Hinge Array

Compliant mechanisms have been well designed to reach an ultra-high accuracy in positioning systems. However, the displacement of compliant mechanisms is still a major problem that restricts practical applications. Hence, a new flexure hinge array (FHA) is proposed to improve its displacement in this article. This paper is aimed to design and optimize the FHA. The structure of FHA is constructed by series-parallel array. Analytical calculations of the FHA are derived so as to analyze the stiffness and deformation. The displacement of the FHA is optimized by moth-flame optimization algorithm. The results determined that optimal parameters are found at Lt1 of 20.58 mm, wt1 of 1.92 mm, and wt2 of 2.29 mm. Besides, the optimal displacement is about 27.02 mm. Through Kruskal–Wallis test, the results verified that the proposed MFO outperforms other optimization algorithms in terms of searching the largest displacement. Validations of the analytical models are verified through simulations and experiments. The theoretical results are close to the experimental results. Additionally, the displacement of the FHA is superior that of existing joints. The displacement in the z-direction is approximately 32 mm according to a displacement of 12 mm in the x-direction

Design and Performance Analysis of a TLET-Type Flexure Hinge

In order to permit a large deflection, three lamina emergent torsional flexure hinges are reconfigured to create a new triple LET-type flexure hinge (TLET) in this paper. The TLET consists of flexure hinges in a series coupled with others in parallel configuration. This arrangement is aimed to enhance the displacement of the joint. The proposed joint is capable of generating a large displacement and a large capacity of load within safety working conditions. The closed-form models are derived to calculate the equivalent spring constant, rotation angle, and displacement of the proposed joint. Failure analysis of the TLET joint with different materials is conducted by finite element analysis. The closed-form models are validated by simulations and experimentations. The validated results are well coincided each other. The result found that the joint achieves a maximum large displacement of 16.97 mm in the x-axis with respect to a maximum load of 20 N. When the joint slides a maximum displacement of 16.97 mm along the x-axis, the output displacement emerges out the z-axis up to 23.12 mm, respectively. The joint can achieve an angle displacement of 38.92°. The displacement of the TLET joint is 2.4 times greater than that of the traditional LET joint. The proposed joint is considered for engineering applications where a large working stroke and a large capacity of load are expected

Prediction of Fatigue Life for a New 2-DOF Compliant Mechanism by Clustering-Based ANFIS Approach

Two-degree-of-freedom (2-DOF) compliant mechanism has some outstanding characteristics in accurate positioning systems. Studying the fatigue life for the 2-DOF compliant mechanism is a meaningful task to ensure a long working. However, a study for fatigue life prediction of this mechanism has not been conducted so far. In this article, a method for fatigue life prediction of 2-DOF compliant mechanism is developed for the first time. This method is the combining of the differential evolution algorithm and the adaptive neuro-fuzzy inference system (ANFIS) with subtractive clustering. The numerical results on two case studies consisting of material steel A-36 and the material AL 6061-T6 show that the accuracy of the proposed method is very high. Compared to the actual fatigue life, the root mean square error of the proposed method lies in the range [1.7, 3.97] cycles for Case 1 and [2.03, 10.38] cycles for Case 2. The statistical test also indicates that the proposed method outperforms the traditional method using triangular membership function, bell-shape, and Gaussian membership function, with the significance level from 0.05 to 0.1. These results demonstrate the feasibility of the proposed approach in fatigue life prediction of 2-DOF compliant mechanism