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.     

Investigating the thermal,mechanical, and electrochemical properties of PVdF/PVP nanofibrous membranes for supercapacitor applications

Polyvinylidene fluoride and polyvinylpyrrolidone polymers incorporated with carbon black nanoparticles (50 nm) were electrospun to fabricate nanofibrous membranes for supercapacitor separators. Different weight percentages (0, 0.25, 0.5, 1, 2, and 4 wt %) of carbon black nanoparticles were dispersed in N,N‐dimethylacetamide and acetone prior to the electrospinning processes at various voltage, pump speed, and tip‐to‐collector distances. The morphology, thermal, mechanical, hydrophobic, and electrochemical characterization of nanofibrous membrane were analyzed using different techniques, such as scanning electron microscopy, differential scanning calorimetry, capacitance bridge, thermogravimetric analysis, dynamic mechanical analyzer, and water contact angle. Effects of annealing and UV irradiation exposures on the nanofibrous membranes were investigated in detail. Test results revealed that the physical properties of the nanocomposite separators were significantly enhanced as a function of carbon black inclusions in the polymeric structures, which may be useful for the applications of supercapacitor separators and other energy storage devices. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43707.     

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.     

Design and implementation of an Internet based effective controlling and monitoring system with wireless fieldbus communications technologies for process automation--an experimental study

The network requirements of control systems in industrial applications increase day by day. The Internet based control system and various fieldbus systems have been designed in order to meet these requirements. This paper describes an Internet based control system with wireless fieldbus communication designed for distributed processes. The system was implemented as an experimental setup in a laboratory. In industrial facilities, the process control layer and the distance connection of the distributed control devices in the lowest levels of the industrial production environment are provided with fieldbus networks. In this paper, the Internet based control system that will be able to meet the system requirements with a new-generation communication structure, which is called wired/wireless hybrid system, has been designed on field level and carried out to cover all sectors of distributed automation, from process control, to distributed input/output (I/O). The system has been accomplished by hardware structure with a programmable logic controller (PLC), a communication processor (CP) module, two industrial wireless modules and a distributed I/O module, Motor Protection Package (MPP) and software structure with WinCC flexible program used for the screen of Scada (Supervisory Control And Data Acquisition), SIMATIC MANAGER package program ("STEP7") used for the hardware and network configuration and also for downloading control program to PLC.     

Effects of moisture ingression on polymeric laminate composites and its prevention via highly robust barrier films

Three different fiber-reinforced composite test laminates were laid up using carbon-, glass-, and Kevlar-reinforced epoxy prepregs, and then four different hydrophobic barrier films were placed as the out-of-most ply (last ply) on top of the test laminates. The prepared samples were co-cured through an autoclave per recommended cure cycles. These hydrophobic barrier films included polyether ether ketone or PEEK (12.7- and 25.4-μm thicknesses), polytetrafluoroethylene or Teflon (25.4 μm), and polyvinyl fluoride (PVF) or Tedlar (25.4 μm). Tedlar films have been the only source used for moisture prevention in Aerospace composites, so the purpose of the present study was to determine other alternatives and their moisture ingression prevention characteristics. The tape adhesion tests conducted on the barrier films of the composite panels indicated that PEEK and Tedlar films were well bonded on the composite surfaces, while Teflon films failed the tape adhesion tests. The laminate composites that were co-bonded with barrier films were immersed in water up to 29 days, and then 3-point bend tests were conducted on each sample before and after immersion. Test results show that 25.4-μm thick PEEK and Tedlar films on the carbon, glass, and Kevlar laminate composites provided similar mechanical properties. Also, the laminates incorporated with barrier films exhibited significantly higher mechanical properties when compared to the same laminates without any barrier films. This study indicated that these barrier films considerably reduced moisture ingression into the laminate composite structures, which may be useful for applications in composite aircraft and wind turbines.     

Spectrophotometric determination of low levels arsenic species in beverages after ion-pairing vortex-assisted cloud-point extraction with acridine red

A new, low-cost, micellar-sensitive and selective spectrophotometric method was developed for the determination of inorganic arsenic (As) species in beverage samples. Vortex-assisted cloud-point extraction (VA-CPE) was used for the efficient pre-concentration of As(V) in the selected samples. The method is based on selective and sensitive ion-pairing of As(V) with acridine red (ARH⁺) in the presence of pyrogallol and sequential extraction into the micellar phase of Triton X-45 at pH 6.0. Under the optimised conditions, the calibration curve was highly linear in the range of 0.8–280 µg l^?1 for As(V). The limits of detection and quantification of the method were 0.25 and 0.83 µg l^?1, respectively. The method was successfully applied to the determination of trace As in the pre-treated and digested samples under microwave and ultrasonic power. As(V) and total As levels in the samples were spectrophotometrically determined after pre-concentration with VA-CPE at 494 nm before and after oxidation with acidic KMnO₄. The As(III) levels were calculated from the difference between As(V) and total As levels. The accuracy of the method was demonstrated by analysis of two certified reference materials (CRMs) where the measured values for As were statistically within the 95% confidence limit for the certified values.     

Fabrication of hydrophobic PLA filaments for additive manufacturing

Journal of Materials Science - There is an ever-greater need for self-cleaning and water-repelling properties of hydrophobic materials at this time in history, mainly due to the coronavirus disease...     

Stability Analysis of MIMO Microgrid Systems in d–q Axis Platform with Constant Power Loads Based on Popov Absolute Stability Criterion

Microgrid has several advantages over the conventional utility grid system, thus naturally being the gateway to implement the renewable energy resources. Now it is considered as the primary solution to solve the next generation power demand. However, in practice, it is very challenging to retain the microgrid operational stability due to the dense presence of constant power loads in the system. In this article, we considered a technique of compensating the load side to mitigate the instability issues introduced by CPL. Adopting this technique, a stability analysis was presented here for MIMO (multiple input, multiple output) AC microgrid system in dq axis platform by Popov Absolute Stability Criterion using the sector conditions and Popov plots. Besides the recent researches regarding the microgrid stability techniques and the previous analysis using Popov Absolute Stability Criterion, the modeling of the energy storage-based load side compensated microgrid system is also provided in this article. All the cases and results are rigorously scrutinized in virtual platform such as MATLAB/Simulink and verified through experimental results as well.