Investigations of the Failure in Boilers Economizer Tubes Used in Power Plants

In this study, failure of a high pressure economizer tube of a boiler used in gas-Mazut combined cycle power plants was studied. Failure analysis of the tube was accomplished by taking into account visual inspection, thickness measurement, and hardness testing as well as microstructural observations using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Optical microscopy images indicate that there is no phase transformation during service, and ferrite-pearlite remained. The results of XRD also revealed Iron sulfate (FeSO₄) and Iron hydroxide sulfate (FeOH(SO₄)) phases formed on the steel surface. A considerable amount of Sulfur was also detected on the outer surface of the tube by EDS analysis. Dew-point corrosion was found to be the principal reason for the failure of the examined tube while it has been left out-of-service.     

Application of Fractal Theory for Prediction of Shrinkage of Dried Kiwifruit Using Artificial Neural Network and Genetic Algorithm

In current research, fractal theory has been applied for estimation of shrinkage of osmotically dehydrated and air-dried kiwifruit using a combination of neural network and genetic algorithm. Kiwifruits were dehydrated at different conditions and digital images of final dried products were taken. Kiwifruit-background interface lines were detected using a threshold combined with an edge detection approach and their corresponding fractal dimensions were calculated based on a box counting method. A neural network was constructed using fractal dimension and moisture content as inputs to predict shrinkage of dried kiwifruit and a genetic algorithm was applied for optimization of the neural network's parameters. The results indicated good accuracy of optimal model (correlation coefficient of 0.95) and high potential application of fractal theory and described intelligent model for shrinkage estimation of dried kiwifruit.     

Synthesis of highly isotactic poly 1-hexene using Fe-doped Mg(OEt)2/TiCl4/ED Ziegler–Natta catalytic system

In this article, polymerization of 1-hexene with FeCl_3-doped Mg(OET)₂/TiCl₄/electron donor (ED) catalytic system is presented. For this purpose, first a number of TiCl₄ catalysts supported on Mg(OEt)₂ and Fe-doped Mg(OEt)₂ supports were prepared with ethylbenzoate or dibutylphthalate as the internal EDs. After successive catalysts synthesis, they were employed in 1-hexene polymerization using cyclohexyl methyl dimethoxysilane as external ED as well as without it. The catalysts activity and molecular weight distribution (MWD) of poly 1-hexenes (PHs) were influenced strongly by both FeCl₃ doping and donor presence so that a remarkable increase in the catalyst activity was seen in doped catalysts. Deconvolution of MWD curves revealed that increase in the type of active centers by introducing FeCl₃ into the support should be responsible for the broadening of MWD of PHs. ¹³CNMR analysis indicated that while isotacticity does not change considerably by Fe doping, EDs increase its amount as high as 8–21%. Second, the stereoselective behavior of active Ti species in doped and undoped catalysts was fully explored by molecular modeling using density functional theory (DFT) method. Finally, with the aid of rheological measurements, the processability of polymers were evaluated and then the gel permeation chromatography (GPC) results were approved through the values obtained from model fitting as well as changes in moduli crossover modulus.     

Hydrophilic antioxidants of virgin olive oil. Part 2: Biosynthesis and biotransformation of phenolic compounds in virgin olive oil as affected by agronomic and processing factors

The biosynthesis of the phenolic fraction of olive fruits during ripening and the transformations occurring in this moiety during virgin olive oil (VOO) extraction are discussed in this paper. The influence of agronomical factors that can significantly affect the phenolic profile of VOO is also discussed. Particularly, it is worth emphasizing the role of genetic factors, cultivation and climatic conditions such as water availability, atmospheric temperature, altitude, health status of the fruits, alternate bearing in the olive, and some processing factors such as crushing, malaxation time and temperature or volume of water added during milling. Among these parameters, special attention has been paid to genetic factors due to the high variability observed among Olea europaea genotypes for all recorded traits. In this context, interesting experimental results have been obtained with cultivated and wild olive trees, and also with segregating populations resulting from olive breeding programs. To the authors' knowledge, reviews evaluating the influence of the main factors that contribute to the profile of hydrophilic phenols have not been previously published. The discussion concerning olive breeding programs is a major and novel aspect to be emphasized considering recent trends to obtain new olive cultivars that confer better organoleptic properties and better quality to VOO.     

Microfluidic study of surfactant flooding of heavy oil in layered porous media containing fractures

Surfactant injection is a promising method for enhanced oil recovery (EOR) due to its effective micro-displacement mechanisms. However, understanding the interaction of a surfactant solution with heavy oil in porous media is neither straightforward nor well understood, particularly in heterogeneous systems. By enabling in-situ real-time monitoring of flow transport, microfluidic studies have provided novel insights into the underlying multiphase physics of flow at the pore scale. This paper examines the two-phase displacement efficiency of a new surfactant in layered–fractured porous microfluidic patterns, a topic seldom discussed in the literature. To evaluate the performance of the proposed surfactant, we considered several heterogeneous media with varying layer and fracture geometrical characteristics, quantifying displacement efficiency for each case. Based on the analysis of pore-scale snapshots, it was inferred that the primary mechanisms responsible for EOR during surfactant flooding into heavy oil include pore wall transportation, emulsifications, the deformation of residual oil, inter-pore or intra-pore bridging, and wettability alteration. Macroscopic displacement experiments revealed that the width of the swept area from surfactant injection significantly exceeded that of water injection, resulting in a substantially higher oil recovery. Furthermore, it was demonstrated that the direction of fluid flow in relation to fracture orientation plays a critical role in the dynamics of surfactant solution movement and, consequently, the ultimate oil production.     

A Taguchi analysis on structural properties of polypropylene microcellular nanocomposite foams containing Fe2O3 nanoparticles in batch process

Polypropylene (PP) as a thermoplastic polymer has been foamed using batch foaming process. CO₂ is used as the blowing agent of the foaming. Ferrous oxide nanoparticles (nano Fe₂O₃) are also added as reinforcement. Effect of different parameters including nanoparticle weight percentage, foaming temperature and time on the structural properties of PP/nano Fe₂O₃ nanocomposites is investigated using Taguchi approach. Scanning electron microscope results depict that an appropriate microcellular structure is obtained with the cell density of 10⁹ cells/cm³ and almost 1 μm of cell size. Analysis of variance results indicated that foaming temperature is the most significant parameter on the structural properties. Cell density and expansion ratio are decreased by increasing foaming temperature. This phenomenon could be due to the reducing melt strength of polymer/gas mixture. It was also inferred that adding 2 wt% of nanoparticles leads to 80% improvement in cell density while cell size and expansion ratio was decreased.     

Fabrication and characterization of novel nanofibers from cress seed mucilage for food applications

Cress seed mucilage (CSM) as a new source of biomacromolecule has gained attraction in food science due to its biodegradability and biocompatibility. In this research CSM–poly(vinyl alcohol) (PVA) nanofibers were produced under different conditions by electrospinning technique. Viscosity and electrical conductivity of the produced biopolymers were analyzed. The effect of CSM to PVA volume ratio and applied electrical field were evaluated on nanofiber morphology by scanning electron spectroscopy. The optimum nanofibers showed smooth and uniform surfaces with diameter size range of 95–278 nm. The results of Fourier transform infrared spectroscopy of CSM–PVA nanofiber with volume ratio of 60:40 showed characteristic peaks of CSM and PVA. X‐ray diffractometer data clearly revealed the amorphous structure of the electrospun nanofibers. Thermogravimetric and derivative thermogravimetric analysis indicated that thermal stability of electrospun nanofibers increased in comparison to CSM and PVA. The results of this study indicated that CSM can be applied as a new source of biopolymer for production of nanofibers that could be used for different applications such as delivery systems and packaging film fabrication. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45811.     

Catalytic desulphurization of benzothiophene in an emulsion via in situ generated H2

Catalytic desulphurization of benzothiophene (BTH) in a water/toluene emulsion, a model system for heavy oil emulsions, was achieved at 340°C using a water-soluble phosphomolybdic acid (PMA), a precursor for dispersed Mo catalyst. This process is based on the activation of H₂O to generate H₂ in situ via the water gas shift reaction (WGSR) for hydrodesulphurization (HDS). At 340°C with an initial CO loading of 4.14 MPa, essentially complete sulphur removal was obtained. Kinetic expressions for the WGSR and HDS of BTH with in situ generated H₂ and externally supplied H₂ were developed and verified experimentally. The kinetic analysis indicates that WGSR is rate-determining and desulphurization with in situ generated H₂ is a relatively fast step. Apparently, in situ H₂ is about seven times more active than externally supplied H₂ for the hydrogenation of BTH. A mechanism for desulphurization involving initial hydrogenation of BTH to dihydrobenzothiophene (DHBTH) followed by hydrogenolysis to give ethylbenzene (EB) and H₂S is proposed.     

Conservative laparoscopic management of a large cornual ectopic pregnancy

Cornual pregnancy traditionally has been treated with laparotomy and either cornual resection or hysterectomy. Recently, more conservative operations have been developed, and operative laparoscopy has provided yet another management option. This report describes the conservative management of a large cornual ectopic pregnancy and reviews the techniques and outcomes of conservative repair that have been described in the literature.     

Will smartwatches last? factors contributing to intention to keep using smart wearable technology

This study aims to deepen our understanding of the underlying factors affecting the intention to continue using increasingly popular wearable technology. A new theoretical model is developed and validated to extend traditional technology acceptance theories by identifying several value drivers of the continuous intention and actual usage of wearable devices. Hypotheses were tested using partial least squares path modeling on data collected from 383 actual smartwatch users. The results provide wearable device manufacturers with practical guidance for optimizing competition strategies. They also offer policy-making insights for practitioners to promote better wearable devices on the market, especially during the early stages of adoption.