In‐plane functionalizing graphene nanolayers with polystyrene by atom transfer radical polymerization: Grafting from hydroxyl groups

Graphene oxide (GO) was prepared from the oxidation of graphite and then it was functionalized with (3‐aminopropyl)triethoxysilane (APTES) from hydroxyl groups by a coupling reaction. Subsequently, alpha‐bromoisobutyryl bromide (BiBB) was attached to the APTES groups to yield initiator anchored graphene nanolayers (GOHBr). Then, GOHBr was used in different amounts as the precursor for atom transfer radical polymerization of styrene to evaluate the effect of graphene loading along with the graft density on the properties of final product. Successful in‐plain attachment of APTES, BiBB, and polystyrene to GO was evaluated by Fourier transform infrared spectroscopy. Graphene interlayers expansion by oxidation and functionalization processes was evaluated using X‐ray diffraction. The ordered and disordered crystal structures of carbon were evaluated by Raman spectroscopy. Morphology of graphene nanolayers was studied by scanning electron microscopy and also transmission electron microscopy. POLYM. COMPOS., 35:386–395, 2014. © 2013 Society of Plastics Engineers     

High‐performance doubly fed induction machine drive system using predictive direct torque control drive system fed by indirect matrix converters

This paper presents a novel predictive direct torque control for doubly fed induction machine based on indirect matrix converter (IMC), which is characterized by its simple structure, minimal‐torque ripple, and constant switching frequency. Nowadays, the control strategies based on predictive methods have proved their efficiency to improve drive systems capabilities. So, in this paper, one of the best predictive methods that have recently been suggested for doubly fed induction machine drive systems is applied to IMC. The purpose of this combination is to modify the control parameters and size/volume reduction of drive system structure, which is difficult to achieve in conventional systems based on voltage source inverters. The good tracking behavior with reduced torque and flux ripple for both motoring and generating modes as well as removing bulky electrolytic capacitor from the DC link of a converter resulted by using three vectors, two active vectors together with one zero vector per switching period, and applying these vectors to the inverter stage of IMC. To improve the motor drive system performance and reduce losses caused by snubber circuits, the rectifier four‐step commutation method in rectifier bridge is used. In the inverter stage, the predictive direct torque control method is employed. The simulation results of the proposed model confirm its effectiveness and accuracy. Copyright © 2013 John Wiley & Sons, Ltd.     

Spatial Based Pilot Allocation (SBPA) in Crowded Massive MIMO Systems

Nowadays, the internet of things (IoT) has gained significant research attention. It is becoming critically imperative to protect IoT devices against cyberattacks with the phenomenal intensification. The malicious users or attackers might take control of the devices and serious things will be at stake apart from privacy violation. Therefore, it is important to identify and prevent novel attacks in the IoT context. This paper proposes a novel attack detection system by interlinking the development and operations framework. This proposed detection model includes two stages such as proposed feature extraction and classification. The preliminary phase is feature extraction, the data from every application are processed by integrating the statistical and higher-order statistical features together with the extant features. Based on these extracted features the classification process is evolved for this, an optimized deep convolutional neural network (DCNN) model is utilized. Besides, the count of filters and filter size in the convolution layer, as well as the activation function, are optimized using a new modified algorithm of the innovative gunner (MAIG), which is the enhanced version of the AIG algorithm. Finally, the proposed work is compared and proved over other traditional works concerning positive and negative measures as well. The experimental outcomes show that the proposed MAIG algorithm for application 1 under the GAF-GYT attack achieves higher accuracy of 64.52, 2.38 and 3.76% when compared over the methods like DCNN, AIG and FAE-GWO-DBN, respectively.

     

Multi-walled carbon nanotube-supported Ni@Pd core–shell electrocatalyst for direct formate fuel cells

Journal of Applied Electrochemistry - In the present work, Ni@Pd core–shell nanoparticles are successfully deposited on multi-walled carbon nanotubes as support and investigated their...     

Assessment of offshore platforms under extreme waves by probabilistic incremental wave analysis

In this study, a novel probabilistic framework named Probabilistic Incremental Wave Analysis (PIWA) is established in order to assess the performance of jacket offshore platforms under extreme waves. The PIWA can take into account the uncertainties in three main elements consisting of sea state parameters, structural response and collapse capacity. The main advantage of the PIWA approach is reflected in decoupling of the wave hazard and structural analyses via an intermediate variable known as the wave height intensity measure. Despite the fact that most of the uncertainties associated with structural response are concentrated in wave hazard, this will enable the PIWA to estimate the probability of failure accurately. Moreover, both static and dynamic wave analyses can be utilized in the PIWA procedure. In this approach, multiple incremental wave analyses are employed to estimate the distribution of structural demand for a wide range of wave height intensities. Subsequently, the mean annual frequency of exceeding a structural limit state is calculated for which this research addresses two different methodologies including demand-based and wave height-based approaches. Furthermore, a new probabilistic-based Reserve Strength Ratio (RSR) is proposed and the probability of exceeding various levels of RSR is provided. To reduce the large number of simulations and hence improving the computational effort in the PIWA procedure, a combination of Latin Hypercube Sampling and Simulated Annealing optimization technique is utilized as an efficient sampling scheme. The PIWA procedure is employed in probabilistic assessment of an existing jacket offshore platform located in the Persian Gulf as well.     

Novel isocyanate-based matrix resins for high temperature composite applications

Polyoxazolidone composites were prepared from polymeric isocyanate (PAPI 901) and epoxides (Epon 828 and DEN 431) in the presence of an oxazolidone-forming catalyst, triphenylantimony iodide. The effects of isocyanate to epoxide equivalent ratio, type of epoxide, and amount of fiberglass reinforcement on the composite properties were studied as well as the effects of post-curing temperature and time. Increasing the fiberglass content of the polyoxazolidone composites resulted in an improvement of the thermal and mechanical strength properties. The heat deflection temperature of all polyoxazolidones was > 250°C. The retention of the tensile strength at 150°C was excellent, ∼90% or higher. Polyoxazolidone composites based on DEN 431 at 1.2 isocyanate to epoxide equivalent ratio with 70 wt.% of fiberglass and post-cured at 150°C for 48 h exhibited the best properties. According to the results of DMA, TMA and DSC, the maximum operating temperature for polyoxazolidone composites is around 200°C. The TGA data showed that the decomposition temperature was ∼330°C.     

Combination of acid‐demineralization and enzymatic desizing of cotton fabrics by using industrial acid stable glucoamylases and α‐amylases

In this study, the possibility of simultaneous acid‐demineralization and enzymatic desizing of cotton fabric in acidic conditions (pH 2) by using industrial acid stable enzymes has been investigated. Acid‐demineralization is necessary to remove undesired cationic metals and earth alkalis. Our experiments showed that by use of a mixture of two appropriate enzymes, a glucoamylase (Multifect GA 10L) and an α‐amylase (Optisize Next) in a solution of citric acid and presence of a chelating agent, enzymatic desizing, and acid‐demineralization can be successfully carried out at the same time. Therefore, two processes of pretreatment were integrated into a single process, which can effectively reduce time and costs for textile industry.