Determination of mechanical properties of glass‐epoxy composites in high temperatures

The objective of this study is to determine the tensile, compressive, and shear properties of unidirectional glass/epoxy composite plates under room (∼20°C) and high (40, 60, 80, and 100°C) temperatures. Mechanical properties were determined according to the ASTM standards. A hot lamination press was used for fabrication of composite plates. For curing process, laminated plates were retained at a constant pressure (250 kPa) and 120°C during 2 h. And then, composite plate is cooled to room temperature at the same pressure. The fiber volume fraction of laminated composite plate is measured as 65%. Experimental results show that the mechanical properties (except for the transverse tensile strength) of glass/epoxy composites are reduced by increasing temperature. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Fabrication of Mo-modified carbon felt as candidate substrate for electrolysis: Optimization of pH,current and metal amount

Mo was electrochemically deposited over a carbon felt (C) support in order to enhance hydrogen evolution activity of the support and make it a candidate for further modifications. For this aim, the effects of pH of deposition bath solution, deposition current and amount of deposited Mo were studied and optimized. Hydrogen evolution activity of the electrodes was evaluated in 1 M KOH solution with the help of electrochemical techniques. Surface structures of the electrodes were examined by scanning electron microscopy (SEM). It was found that 1 g Mo/g C modified electrode at pH 6 and 50 mA current exhibits the best hydrogen releasing performance. The enhanced current density at this electrode under ?1.60 V(Ag/AgCl) was 59.6% with respect to the bare support, which demonstrates that modifying the support by a thin Mo layer favors the hydrogen evolution reaction (HER) and reduces the energy requirement. The high hydrogen evolution performance of this modified substrate was assigned to its excellent structure, large surface area as well as high intrinsic catalytic activity of Mo. According to experimental findings, the Mo-modified C substrate was suggested for preparation of further modified electrode materials, especially with trace amounts of precious metals.     

A conceptual model for data management and distribution in peer-to-peer systems

While Peer-to-Peer (P2P) model gains significant attention in distributed computing, it is also expected to be a powerful model for information sharing. P2P systems are expected to provide exhaustive reliable computational resources and scalable accessibility. The data management and distribution in such systems requires storage, replication, data modeling, indexing, querying, retrieval, streaming, and topology management. While a lot of data management strategies have been proposed through the last years, these strategies have not been investigated with respect to a common model for P2P systems. However, since the services provided by the P2P systems are so diverse, it is very challenging to come up with a common layer-based model for all P2P systems. In this paper, we firstly propose a conceptual model for P2P systems, and then provide a classification and summary of data management and distribution strategies by referring to this model. The horizontal layers of the model correspond to modules of a P2P system whereas the columns are related to the services provided. The modules include base P2P service, storage, indexing, logical, service, and application modules. The services include security, querying, publish, join/leave, collaboration, and streaming. The paper concludes by providing a comprehensive list of data management and distribution strategies used in the existing P2P systems.     

Neural network aided design of Pt-Co-Ce/Al2O3 catalyst for selective CO oxidation in hydrogen-rich streams

In this study, the design of Pt-Co-Ce/Al₂O₃ catalyst for the low temperature CO oxidation in hydrogen streams was modeled using artificial neural networks. The effects of five design parameters, namely Pt wt.%, Co wt.%, Ce wt.%, calcination temperature and calcination time, on CO conversion were investigated by modeling the experimental data obtained in our laboratory for 30 catalysts. Although 30 points data set can be considered as small for the neural network modeling, the results were quite satisfactory apparently due to the fact that the experimental data generated with response surface method were well balanced over the experimental region and it was very suitable for neural network modeling. The success of neural network modeling was more apparent when the number of data points was increased to 120 by using the time on stream as another input parameter. It was then concluded that the neural network modeling can be very helpful to improve the experimental works in catalyst design and it may be combined with the statistical experimental design techniques so that the successful models can be constructed using relatively small number of data points.     

Dynamical adaptive integral backstepping variable structure controller design for uncertain systems and experimental application

In this study, a dynamical adaptive integral backstepping variable structure control (DAIBVSC) system based on the Lyapunov stability theorem is proposed for the trajectory tracking control of a nonlinear uncertain mechatronic system with disturbances. In this control scheme, no prior knowledge is required on the uncertain parameters and disturbances because it is estimated by two types of dynamical adaptive laws. These adaptive laws are integrated into the dynamical adaptive integral backstepping control and variable structure control (VSC) parts of the DAIBVSC. The dynamical adaptive law in the dynamical adaptive integral backstepping control part updates parametric uncertainties, while the other in the VSC part adapts upper bounds of non‐parametric uncertainties and disturbances. In order to achieve a more robust output tracking and better parameter adaptation, the control system is extended by one integrator and sliding surface is augmented by an integral action. Experimental evaluation of the DAIBVSC is conducted with respect to performance and robustness to parametric uncertainties. Experimental results of the DAIBVSC are compared with those of a traditional VSC. The proposed DAIBVSC exhibits satisfactory output tracking performance, good estimation of the uncertain parameters and can reject disturbances with a chattering free control law. Copyright © 2017 John Wiley & Sons, Ltd.     

Sliding mode PI control with backstepping approach for MIMO nonlinear cross‐coupled tank systems

The control of tank systems in industrial applications is an important issue for monitoring the chemical processes involved in the manufacture and delivery of product. The most important reason to control the tank systems is to keep the liquid level in the tanks constant and at the desired level for a specified period of time. In this study, the sliding mode control (SMC) with a repetitive approach called backstepping that is insensitive to uncertainties in system parameters and input disturbances is proposed and experimentally applied to a quadruple, cross‐coupled, uncertain, nonlinear, and multiple‐input/multiple‐output tank system. A proportional‐integral (PI) control is used to reduce the steady‐state error caused by the parameter variations and external noises. The traditional way of introducing PI usually leads to sliding surfaces. In this paper, the PI action is introduced to the control signal. The proposed backstepping sliding mode PI control (BSMPIC) is applied to such a complex tank system for the first time. The experimental results are compared with those of the SMC, sliding mode PI control, and backstepping sliding mode control to see the effect of the proposed BSMPIC on the system. As a result of the comparison, it is observed that less overshoot and tracking error, better tracking performance, and faster rise time in the transient regime is obtained by the BSMPIC.     

Hydrogenolysis and hydrocracking of the carbonoxygen bond. 3. Thermolysis in tetralin of substituted anisoles

Mild pyrolysis and hydrogenolysis products of coal contain substantial amounts of pyrocatechol and resorcinol and their homologues whereas hydroquinone and its homologues are absent or present in only low amounts. In the present work the model compounds anisole and methyl-, methoxy- or hydroxy-substituted anisoles were studied to elucidate substituent effects on the carbon—oxygen bond cleavage in the presence of tetralin. The experiments were carried out at 618 K and 6 MPa (H₂). The major reaction is demethylation to the corresponding phenols. A steric effect can be seen in the ortho compounds and an electronic effect when the substituent is a strongly electron-releasing group. In compounds with oxygen substituents para to each other little or no hydroquinone can be isolated whereas the ortho and meta compounds, respectively, give pyrocatechol and resorcinol. It is suggested that the low yield or absence of hydroquinone in this work and in coal pyrolysis is due to the high reactivity of the intermediate p-hydroxyphenoxy radical, which gives rise to adducts and other compounds of high molar mass. The ortho radical is sterically hindered and the meta radical has a lower reactivity and are hence abstracting hydrogen from the hydrogen donor or coal.     

Multi‐scroll chaotic attractors from a generalized time‐delay sampled‐data system

In this paper, the first generalization for time‐delay sampled‐data chaotic system in order to generate multi‐scroll attractor is introduced with its circuit implementation. An efficient delay‐line with binary priority encoding, parallel shifting, and binary decoding is also suggested and implemented to overcome the delay line realization drawback in such systems. The proposed system enhances the complexity of chaotic behavior by means of multi‐scroll feature and exemplifies the simplification of chaotic systems for better realizations. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of functionalized PET fibers by grafting and modification and their application for Cr(VI) ion removal

A new fiber adsorbent for removing Cr(VI) ions from aqueous solution was prepared by grafting and modification. The grafted fiber and modified fiber were characterized by SEM, FTIR, and TGA. FTIR analysis indicated that acrylonitrile monomer was grafted onto the PET surface and that new groups were present on the surface after the modification. Scanning electron microscopy showed that the PET fiber was wider after grafting and especially modification. The TGA results showed that the degradation steps and the thermal behavior of the PET fiber changed after modification. The effects of the pH, ion concentration, and temperature on the amount of Cr(VI) adsorbed were investigated. The fiber showed its maximum adsorption capacity in acidic medium. Isotherm studies indicated that the experimental results were best fitted to the Langmuir isotherm. The adsorption capacity of the modified fiber was found to be 25.77, 38.17, and 44.84 mg/g fiber at 25, 35, and 45 °C, respectively. Kinetic results indicated that the adsorption of Cr(VI) onto the modified fiber followed a pseudo-second-order kinetic model. Calculated thermodynamic parameters demonstrated that the adsorption of Cr(VI) ions on the modified fiber is an endothermic, feasible, and spontaneous process.