Wear behavior of Al–Cu and Al–Cu/SiC components produced by powder metallurgy

In the present study, the dry sliding wear behavior of some powder metallurgy (P/M) Al–Mg–Cu alloys with different weight percentage of Cu (0, 1, 2, 3, 4, and 5 wt%) and corresponding metal matrix composites reinforced with 5 or 10 vol% silicon carbide particles (SiC) have been carried using pin-on-disk apparatus. The tested specimens were tested against hardened steel disk as a counter face at room conditions (∼20 °C and ∼50% relative humidity). The normal load was 40 N and sliding velocity of counter face disk was 150 rpm (0.393 m/s) and total testing time of 60 min, which corresponds to a distance of 1414 m. Generally, both hardness and wear resistance were enhanced by the addition of Cu and/or SiC to the Al-4 wt% Mg alloy. The formations of mechanically mixed layer (MML) as a result of material transfer from counter face disk to the samples and vice versa were observed in all tested specimens.     

Compressibility and compactibility studies of chitosan,xanthan gum,and their mixtures

The compressibility and compactibility studies of binary mixtures containing chitosan (CS) and xanthan gum (XG) were highlighted in this article. The compressibility of the examined powders was studied according to Heckel and Gurnham equations. Results indicated that CS exhibits more ductile character than XG. Moreover, in this study percolation theory has been applied to the tensile strength of different compacts obtained from CS–XG mixtures. The obtained percolation thresholds showed that higher pressures must be applied to form compacts with a specific strength as the mass fraction of XG was increased. Additionally, the values of the maximum tensile strength showed that the percolation threshold of CS occurs at equal mass fraction of the two polymers. Scanning electron microscope, light microscope techniques, and molecular mechanical calculations were also conducted in order to study the interactions between CS and XG. The obtained results revealed that 1:1 ratio (by weight) represents the maximum interactions between the two polymers.     

Prediction of density,porosity and hardness in aluminum–copper-based composite materials using artificial neural network

The potential of using feed forward backpropagation neural network in prediction of some physical properties and hardness of aluminium–copper/silicon carbide composites synthesized by compocasting method has been studied in the present work. Two input vectors were used in the construction of proposed network; namely weight percentage of the copper and volume fraction of the reinforced particles. Density, porosity and hardness were the three outputs developed from the proposed network. Effects of addition of copper as alloying element and silicon carbide as reinforcement particles to Al–4 wt.% Mg metal matrix have been investigated by using artificial neural networks. The maximum absolute relative error for predicted values does not exceed 5.99%. Therefore, by using ANN outputs, satisfactory results can be estimated rather than measured and hence reduce testing time and cost.     

On transient error surfaces of output error IIR adaptive filtering

Addresses the convergence of IIR output error adaptive algorithms. We argue that convergence to global or local optimum is simultaneously determined by the shape of the transient error surface and the convergence speed of the algorithm. This argument is confirmed by simulation examples comparing the convergence of LMS-based and LS-based algorithms     

Polyphenol-Induced Adhesive Liquid Metal Inks for Substrate-Independent Direct Pen Writing

Surface patterning of liquid metals (LMs) is a key processing step for LM-based functional systems. Current patterning methods are substrate specific and largely suffer from undesired imperfections—restricting their widespread applications. Inspired by the universal catechol adhesion chemistry observed in nature, LM inks stabilized by the assembly of a naturally abundant polyphenol, tannic acid, has been developed. The intrinsic adhesive properties of tannic acid containing multiple catechol/gallol groups, allow the inks to be applied to a variety of substrates ranging from flexible to rigid, metallic to plastics and flat to curved, even using a ballpoint pen. This method can be further extended from hand-written texts to complex conductive patterns using an automated setup. In addition, capacitive touch and hazardous heavy metal ion sensors have been patterned, leveraging from the synergistic combination of polyphenols and LMs. Overall, this strategy provides a unique platform to manipulate LMs from hand-written pattern to complex designs onto the substrate of choice, that has remained challenging to achieve otherwise.     

Wear behavior of Al-Mg-Cu-based composites containing SiC particles

The friction and wear behavior of Al-Mg-Cu alloys and Al-Mg-Cu-based composites containing SiC particles were investigated at room conditions at a pressure of 3.18 MPa and a sliding speed of 0.393 m/s using a pin-on-disk wear testing machine. This study is an attempt to investigate the effects of adding copper as alloying element and silicon carbide as reinforcement particles to Al-4 wt% Mg metal matrix. The wear loss of the copper containing alloys was less than that for the copper free alloys. It was observed that the volume losses in wear test of Al-Mg-Cu alloy decrease continuously up to 5%. Also it was found that the silicon carbide particles play a significant role in improving wear resistance of the Al-Mg-Cu alloying system. The formation of mechanically mixed layer (MML) due to the transfer of Fe from counterface disk to the pin was observed in both Al-Mg-Cu alloys and Al-Mg-Cu/SiC composites.     

Evaluation of a functional food preparation based on chitosan as a meal replacement diet

The ability of chitosan to entrap large amounts of water when dispersed in an oily phase was utilized to formulate a novel meal replacement functional food. Furthermore, the proposed preparation can be fortified with nutrients. The purpose of this formulation was to produce an edible low calorie pseudo-fatty rich meal that can enhance the feeling of satiety when ingested. Different concentrations of chitosan and pectin were tested to find out a stable preparation with acceptable physical characteristics. It was found that a preparation containing 1% chitosan and 6% pectin is suitable to be consumed as a meal replacement diet. The safety of such preparation was assessed by repeated dose administration to rats. A set of other in vivo experiments was performed to assess the ability of this preparation to enhance satiety. The ingestion of chitosan preparation resulted in reduced body weight, food and water intake, and reduced faecal excretion in the emulsion administered rats (p < 0.05). Furthermore, serum lipids of tested rats were not essentially changed. Accordingly, the investigated chitosan emulsion could be introduced as a low calorie, relatively stable and a safe functional food preparation for enhancing satiety when ingested as a meal replacement diet.     

A New Variable Step Size Control Method for the Transform Domain LMS Adaptive Algorithm

This paper develops a new adaptive step size control method for the transform domain least mean-square (TDLMS) adaptive algorithm. The time-varying step size is an efficient approximation of an optimal step size based on a proposed cost function, therefore leading to significant improvements in the performance characteristics of the TDLMS algorithm. Mean-square analysis is provided, and an expression for the steady-state excess mean-squared error (MSE) is derived. Simulation experiments confirm the algorithm's enhanced convergence properties and verify the theoretical steady-state MSE results.