Political Optimizer Based Feedforward Neural Network for Classification and Function Approximation

Neural Processing Letters - Political optimizer (PO) is a recently proposed human-behavior inspired meta-heuristic, which has shown tremendous performance on complex multimodal functions as well as...     

Tensile behavior change depending on the varying tungsten content of W–Ni–Fe alloys

Tungsten heavy alloys (WHAs) are metal–metal composites consisting of nearly pure spherical tungsten particles embedded in a Ni–Fe–W or Ni–Co–W or Ni–Cu–W ductile matrix. In this dual phase alloy, there are several complicated relations between the ductile matrix and hard tungsten particles. The aim of this research was to examine the effect of varying tungsten content on the microstructure and mechanical properties of tungsten heavy alloys. The microstructural parameters (grain size, connectivity, contiguity and solid volume fraction) were measured and were found to have a significant effect on the mechanical properties of tungsten-based heavy alloys. The result shows that the binding strength between the W and the matrix phase has a major influence on the ductility of tungsten-based alloys. The larger this binding force is, the better the ductility is.     

微/纳米复合多层金刚石自支撑膜的制备及应力研究

利用大功率DC Arc Plasma Jet CVD装置,采用Ar-H2-CH4混合气体为气源,通过优化工艺参数,在多晶钼衬底上制备出了多层复合金刚石自支撑膜.利用扫描电镜(SEM)、X射线衍射(XRD)、激光拉曼谱(Raman)对膜体进行表征,结果显示,多层膜体的组织结构体现了微米金刚石与纳米金刚石的典型特征;复合金刚石自支撑膜具有光滑的表面,微米层与纳米层间呈相互嵌套式的界面;此外,利用激光拉曼谱分析了多层膜中的内应力状态,研究发现,多层膜中各层膜体具有不同的内应力状态,内应力沿膜体生长方向有明显变化,呈现出从压应力到拉应力的变化过程.     

The synthesis of nano-sized ZSM-5 zeolite by dry gel conversion method and investigating the effects of experimental parameters by Taguchi experimental design

In this study ZSM-5 Nano particles with high crystallinity were synthesized using a dry gel conversion technique. An L9 orthogonal array of the Taguchi method was applied to investigate the effect of synthesis parameters, such as crystallization time, gel drying temperature, molar composition of template (TPAOH) and water content in the crystallization stage on crystallinity and particle size of the ZSM-5 catalyst. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Beside short crystallization time, the particle sizes were considerably smaller in comparison with those prepared using the hydrothermal method. The results showed that the particle size and crystallinity increased with increasing water content and crystallization time. The effects of gel drying temperature and molar composition of template were found to be more complex, however. Comparing to hydrothermal method, ZSM-5 samples synthesized with the dry gel conversion exhibited higher selectivity to gasoline than other hydrocarbons.     

Adaptive robust control of uncertain systems with state and input delay

In this paper, adaptive robust control of uncertain systems with multiple time delays in states and input is considered. It is assumed that the parameter uncertainties are time varying norm-bounded whose bounds are unknown but their functional properties are known. To overcome the effect of input delay on the closed loop system stability, new Lyapunov Krasovskii functional will be introduced. It is shown that the proposed adaptive robust controller guarantees globally uniformly exponentially convergence of all system solutions to a ball with any certain convergence rate. Moreover, if there is no disturbance in the system, asymptotic stability of the closed loop system will be established. The proposed design condition is formulated in terms of linear matrix inequality (LMI) which can be easily solved by LMI Toolbox in Matlab. Finally, an illustrative example is included to show the effectiveness of results developed in this paper.     

Adaptive neural dynamic surface control of MIMO stochastic nonlinear systems with unknown control directions

In this paper, an adaptive neural output‐feedback control approach is considered for a class of uncertain multi‐input and multi‐output (MIMO) stochastic nonlinear systems with unknown control directions. Neural networks (NNs) are applied to approximate unknown nonlinearities, and K‐filter observer is designed to estimate unavailable system's states. Due to utilization of Nussbaum gain function technique in the proposed approach, the singularity problem and requirement to prior knowledge about signs of high‐frequency gains are removed, simultaneously. Razumikhin functional method is employed to deal with unknown state time‐varying delays, so that the offered control approach is free of common assumptions on derivative of time‐varying delays. Also, an adaptive neural dynamic surface control is developed; hence, explosion of complexity in conventional backstepping method is eliminated, effectively. The boundedness of all the resulting closed‐loop signals is guaranteed in probability; meanwhile, convergence of the tracking errors to adjustable compact set in the sense of mean quartic value is also proved. Finally, simulation results are shown to verify and clarify efficiency of the offered approach. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of silver nanoparticles by gelcasting using a low toxic monomer and optimization of gelation time using the Taguchi method

Silver nanoparticles were synthesized using a gelcasting process, which includes using in situ polymerization for forming the samples followed by calcination. Methacrylamide (MAM) was used as a monomer and N,N′-methylene-bis-acrylamide (MBAM) was used as a cross-linker to form a cross-linked polymer network. The effects of monomer content, cross-linker to monomer ratio, and silver salt to monomer ratio on gelation time were investigated using the Taguchi experimental design method. A set of 16 experiments was conducted at a constant temperature and agitation speed. The results from the Minitab design of experiments (DOE) analysis indicate that the cross-linker to monomer ratio had the greatest effect on gelation time. Finally, silver nanoparticles were synthesized by burning out a gel sample in a furnace. Scanning electron microscopy (SEM) analysis showed that the average size of the silver nanoparticles was approximately 42 nm.     

Influence of case hardening on wear resistance of a sintered low alloy steel

PM technique has been applied for some products in the autoindustries due to unique functions and cost saving. The wear resistance of PM steel parts is one of the most significant surface properties. Nitriding and carburizing processes consist of exposing metallic materials to nitrogen and carbon to improve their surface hardness and wear resistance. In this research, the partially diffusion prealloyed powders, Ultrapac LE, containing Fe-4Ni-1.5Cu-0.5Mo with 0.2% graphite and two different densities were sintered at 1120 °C for 30 min. Depending on the applied pressures during cold pressing, two different porosities of 14.11 and 10.26 vol.% were obtained. Some specimens were carburized and some others were nitrided in cyanate liquid salt bath. The pin-on-disc wear test and hardness test were used to evaluate the surface behavior of specimens. The results showed that the wear resistance increased by nitriding and carburizing processes and the effect of nitriding is more than carburizing on wear resistance. In the case of materials studied, except for 4 h nitrided specimens, other specimens with higher porosity level showed better wear resistance. In these specimens, large pores entrapped the wear debris and created a densified layer. It prevented the formation of large abrasive agglomerates. For the carburized specimens, wear mechanisms were affected by the brittle fracture caused by abrasive wear. So, wear resistance did not increase significantly. In this investigation, abrasive, plastic deformation and oxidation wear were observed as wear mechanisms.