Modeling,analysis and multi-objective optimization of twist extrusion process using predictive models and meta-heuristic approaches,based on finite element results

Recently, twist extrusion has found extensive applications as a novel method of severe plastic deformation for grain refining of materials. In this paper, two prominent predictive models, response surface method and artificial neural network (ANN) are employed together with results of finite element simulation to model twist extrusion process. Twist angle, friction factor and ram speed are selected as input variables and imposed effective plastic strain, strain homogeneity and maximum punch force are considered as output parameters. Comparison between results shows that ANN outperforms response surface method in modeling twist extrusion process. In addition, statistical analysis of response surface shows that twist extrusion and friction factor have the most and ram speed has the least effect on output parameters at room temperature. Also, optimization of twist extrusion process was carried out by a combination of neural network model and multi-objective meta-heuristic optimization algorithms. For this reason, three prominent multi-objective algorithms, non-dominated sorting genetic algorithm, strength pareto evolutionary algorithm and multi-objective particle swarm optimization (MOPSO) were utilized. Results showed that MOPSO algorithm has relative superiority over other algorithms to find the optimal points.     

Security of Internet of Things using RC4 and ECC Algorithms (Case Study: Smart Irrigation Systems)

Internet of Things (IoT) deploys a wide range of technologies including wireless sensor networks, machine-to-machine communication, robots, internet technologies, and smart devices. IoT is a novel phenomenon in the IT world wherein objects can transmit data, and interact through the internet or intranet networks. But the most important and crucial issue on the IoT is privacy and data security. The objective of this paper is to create a new encryption model for data storage servers in an IoT-based irrigation systems. Thus, a hybrid encryption algorithm based on Elliptic Curve Cryptography (ECC), RC4, and SHA-256 is proposed to protect sensitive data of IoT-based irrigation systems. The proposed model uses ECC to improve RC4. In RC4, XOR operation is performed using a key encrypted by ECC and shift-right, and then the resulting data are transformed to SHA-256 to ensure security. Simulation results indicate that encryption and decryption time in the proposed model are shorter than other models like XXTEA & ECC, XXTEA & RSA, ECC&3DES&SHA-256, RC4&3DES&SHA-256, AES&RC4&SHA-256, AES&3DES &SHA-256, RC4&AES&SHA-256, RC2&3DES&SHA-256, and ECC&RC2&SHA-256 with, 43.39%, 66.03%, 45.28%, 54.71%, 50.94%, 33.96%, 33.62%, 24.52%, and, 15.09% respectively.

     

Exploring Energy Efficient Architectures for RLWE Lattice-Based Cryptography

Journal of Signal Processing Systems - Quantum computers are imminent threat to secure signal processing because they can break the contemporary public-key cryptography schemes in polynomial time....     

Highly Tunable Nanostructures in a Doubly pH-Responsive Pentablock Terpolymer in Solution and in Thin Films

Multiblock copolymers with charged blocks are complex systems that show great potential for enhancing the structural control of block copolymers. A pentablock terpolymer PMMA-b-PDMAEMA-b-P2VP-b-PDMAEMA-b-PMMA is investigated. It contains two types of midblocks, which are weak cationic polyelectrolytes, namely poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(2-vinylpyridine) (P2VP). Furthermore, these are end-capped with short hydrophobic poly(methyl methacrylate) (PMMA) blocks in dilute aqueous solution and thin films. The self-assembly behavior depends on the degrees of ionization α of the P2VP and PDMAEMA blocks, which are altered in a wide range by varying the pH value. High degrees of ionization of both blocks prevent structure formation, whereas microphase-separated nanostructures form for a partially charged and uncharged state. While in solutions, the nanostructure formation is governed by the dependence of the P2VP block solubility of the and the flexibility of the PDMAEMA blocks on α, in thin films, the dependence of the segregation strength on α is key. Furthermore, the solution state plays a crucial role in the film formation during spin-coating. Overall, both the mixing behavior of the 3 types of blocks and the block sequence, governing the bridging behavior, result in strong variations of the nanostructures and their repeat distances.     

Developing electrically conductive polypropylene/polyamide6/carbon black composites with microfibrillar morphology

We have established that the PP/PA6/CB composite with 3D microfibrillar conducting network can be prepared in situ using melt spinning process. CB particles preferably were localized at the interface between polypropylene as the matrix and PA6 microfibrils, which act as the conducting paths inside the matrix. The percolation threshold of the system reduced when aspect ratio of the conducting phase was increased by developing microfibrillar morphology. The effect of annealing process on the conductivity of PP/PA6/CB composite with co‐ continuous and microfibrillar morphologies was studied. It was observed that, annealing process forces CB particles towards the interface (2D space) of PP and PA6 co‐continuous phases, and percolation threshold and critical exponent of classical percolation theory will be decreased, while the conductivity of conducting composite with microfibrillar morphology was not affected considerably by annealing process at temperatures either higher or lower than the melting point of the PA6 microfibrils. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Chitosan hydrogel loaded with Aloe vera gel and tetrasodium ethylenediaminetetraacetic acid (EDTA) as the wound healing material: in vitro and in vivo study

The main aim of the current study was to develop a chitosan hydrogel containing Aloe vera gel and Ethylenediaminetetraacetic acid (EDTA) as the wound healing materials. Chitosan with the concentration of (2% w/v) was prepared in AA (0.5%, v/v) and Tetrasodium EDTA (0.01% w/w) and AV (0.5% v/v) were added to the prepared polymer solution. As prepared solution was cross-linked by β-GP with the weight ratio of 1/6 w/w (1 chitosan and 6 β-GP). The characterization of the hydrogels showed that the hydrogels have porous structures and interconnected pores with the pores size range from 41.5 ± 14 to 48.3 ± 11 μm. The swelling and weight loss measurements of the hydrogels showed that the hydrogels could swell up to 240% of their initial weight during 8 h and loss 79.7 ± 3.5% of the initial weight during 14 days. The antibacterial studies depicted that the prepared Cs/tEDTA/AV hydrogel inhibited the growth of Staphylococcus aureus (the minimum inhibition concentration, MIC of 73 ± 4.8) and Pseudomonas aeruginosa (the MIC of 40 ± 7.9). Moreover, the prepared hydrogels were hemocompatible (Cs/tEDTA/AV: OD of 0.24 ± 0.30) and biocompatible (Cs/tEDTA/AV: OD of 0.38 ± 0.01). At the final stage, the wound healing assessments in the animal model revealed that the application of the prepared hydrogels effectively enhanced the wound healing process. In conclusion, the results confirmed the efficacy of the prepared hydrogels as the wound healing materials.     

Numerical prediction of elastic properties for carbon nanotubes reinforced composites using a multi-scale method

The main aim of this research was to investigate longitudinal elastic and effective modulus of composites reinforced with zigzag and armchair single-walled (CNT) and multi-walled carbon nanotubes (MWCNT) with different volume fractions and aspect ratios via finite element simulation. A three-phased volume element was adopted for the modeling of nanocomposite behavior and nonlinear spring elements were used to model interphase part joints and the effective force between nanotubes and resin were determined based on Lennard-Jones potential. After the evaluation and validation of the model, elastic modulus and Poisson’s ratio of composites reinforced with zigzag and armchair CNTs with different volume fractions and aspect ratios were extracted. It was found that by increasing volume fraction and aspect ratio, elastic modulus of representative volume element of composite was increased and its Poisson’s ratio was decreased. At similar aspect ratio and volume fraction, the elastic modulus of composites reinforced with armchair CNTs and Poisson’s ratio of those reinforced with zigzag CNTs were higher. Also, results showed that elastic modulus of composite was independent from elastic modulus of interphase.

     

Study of the effect of electric field and electroneutrality on transport of biomolecules in microreactors

In this article, the effect of electrophoresis on the transport of a sample (like biomolecules) in active microreactors is numerically investigated. Navier–Stokes equations are solved along with the equations of electrostatics, species mass transport in the buffer, and chemical reaction kinetics at reactive surfaces. Unlike previous studies, in which the effect of the charge of the sample molecules on the electric field has been neglected (i.e., the assumption of electroneutrality), here the space charge density is assumed to be nonzero and a function of biomolecule concentration. As a result, the governing equations become fully coupled. The validity of the assumption is examined against experimental results. Then, the effect of electroneutrality on the efficiency of the microreactor device is analyzed for the parallel plate open channel geometry, commonly used in biomolecule separation. It is shown that the electroneutrality assumption can drastically influence the final adsorbed concentration depending on the device configuration. Average adsorbed surface concentration and capture efficiency are compared as measures of the performance of the device for a wide range of physiochemical parameters. The sensitivity of the simulation with respect to the ionic concentration of the buffer is investigated. It is also discussed how the electric field and nonzero space charge density alter the bulk concentration profile and the velocity field inside the microreactor.     

Security of internet of things based on cryptographic algorithms: a survey

Wireless Networks - Internet of Things (IoT) is a new concept in Information and Communications Technology and its structure is based on smart objects communications. It contributes to controlling,...     

Erratum to: Prediction of Surface Flow by Forcing of Climate Forecast System Reanalysis Data

Water Resources Management -