Prediction of carbon dioxide separation from gas mixtures in petroleum industries using the Levenberg–Marquardt algorithm

In this study, two mathematical models for hydrate formation process to separate carbon dioxide by a combination of two different kinds of organic and surfactant promoters are presented. Promoters such as sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and dodecyl trimethyl ammonium chloride as surfactant promoters; also, tetrahydrofuran, cyclopentane, 1,3-dioxolane, and 2-methyl tetrahydrofuran as organic promoters have been used in recent years. The results showed that a combination of 3000 ppm of surfactant promoters and 4 wt% organic promoters had the highest separation rate of carbon dioxide and; consequently, the investigated models were based on this optimum condition. As a matter of fact, by using these simulations the hydrate formation behavior was predicted with high accuracy; moreover, conducting consuming experiments is not essential anymore. To sum up, in the present research both Vandermonde matrix model and Levenberg-Marquardt algorithm were applied to predict the hydrate formation behavior; in addition, their results were precisely considered and validated with experimental data.     

Characterization of vanadyl phthalocyanine based surface-type capacitive humidity sensors

This study presents the fabrication and characterization of novel surface-type capacitive humidity sensors using vanadyl phthalocyanine (VOPc) as the active material. The devices, which comprise three different thicknesses,have been fabricated using the thermal evaporation technique. A thin film of VOPc is deposited on thoroughly cleaned glass substrates with pre-pattemed Ag electrodes. The capacitive effect of the samples under humidity has been in-vestigated. Comparison of the samples with different thicknesses shows that the thinnest device seems more sensitive towards humidity. The humidity dependent capacitance properties of the sensor make it beneficial for use in commercial hygrometers.     

Effect of amino acids as capping agent on the size and morphology of pure TmVO<Subscript>4</Subscript> nanoparticles and their photocatalyst properties

In this paper, thulium vanadate (TmVO₄) nanoparticles were synthesized via a simple precipitation method based on the reaction between thulium nitrate hexahydrate and ammonium metavanadate in water. Besides, three capping agent such as alanine, valine, and glycine were used to investigate their effects on the morphology and particle size of thulium vanadate nanoparticles. According to the vibrating sample magnetometer, thulium vanadate nanoparticles indicated a paramagnetic behavior at room temperature. In addition, the photocatalyst activity of as-prepared thulium vanadate nanoparticles was evaluated by degradation of methyl orange under ultraviolet light irradiation. The structural, morphological, and optical properties of as-obtained products were characterized by techniques such as XRD, SEM, EDX, and UV–Vis spectroscopy.     

Production and characterization of polypropylene fiber upon addition of selective peroxide during melt spinning and comparison with conventional polypropylene fibers

In the present work, effect of selective peroxide on reactor grade polypropylene (PP) (known as V30S) during melt spinning process on the physical and thermal properties of as‐spun resultant multifilament yarn was studied. Attempts have also been made to compare this yarn sample with other fiber samples produced from reactor and controlled rheology grades polypropylene. The results show that the multifilament yarn spun from V30S/Peroxide sample shows higher birefringence and tensile strength and also lower modulus, elongation at break, and shrinkage compared with that of spun from pure V30S granule. Density and thermal behavior studies show low variations compared with original sample. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Prediction of hydrate equilibrium conditions using k-nearest neighbor algorithm to CO2 capture

Gas or clathrate hydrates are an important issue when they form in the oil and gas pipelines. Since the determination of the hydrate formation temperature and pressure is very difficult experimentally for every gas system and it is impossible in terms of cost and time approximately, mathematical models can be useful tools to overcome these difficulties. In this study, k-nearest neighbor model was used to predict the equilibrium conditions of hydrate formation in absorption and separation of carbon dioxide from flue gas mixture, containing carbon dioxide and nitrogen. At the training phase, temperature and composition data of nitrogen and carbon dioxide in the flue gas mixture at equilibrium conditions and the equilibrium pressures of hydrate formation were used as input and output, respectively. The error percentage less than 0.38% indicates the high accuracy of the proposed model. In this study, 80%, 85%, and 90% of the training data are examined for three numbers of nearest. For three numbers of used nearest (k = 1, k = 2 and k = 3), the value of k = 1 leads to the lowest error; so, it is selected as the best nearest in the presented model.     

Use of D‐optimal design to model and the analysis of the effect of the draw ratio on some physical properties of hot multistage drawn nylon 6 fibers

In this article, we present an experimental design methodology for studying the effect of the draw ratio on the physical properties of nylon 6 fibers on hot multistage drawing. A response surface methodology involving D‐optimal design was used for the modeling and optimization. According to the analysis of variance results, the proposed models could be used to navigate the design space. We found that the responses of the tenacity and initial modulus were very sensitive to the factor of the second‐stage draw ratio, and the shrinkage response was governed by the factor of the third‐stage draw ratio. The results show a good agreement between the experimental and model predictions with high correlation coefficients. The operation conditions for obtaining the drawn yarn with the highest tenacity and initial modulus and low shrinkage are proposed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1337‐1344, 2013     

Preparation of nickel ferrite nanoparticles via a new route and study of their photocatalytic properties

Pure nickel ferrite (NiFe₂O₄) were prepared via sol-gel route in presence of different amino acids as a capping agent. The effect of different amino acids such as leucine, asparagine, and cysteine on the size, and morphology of NiFe₂O₄ nanoparticles were investigated. The magnetic properties of the samples were investigated using VSM analyze. We found that the NiFe₂O₄ nanoparticles synthesized at temperature of 800 °C exhibit a ferromagnetic behavior with a saturation magnetization of 34 emu/g and a coercivity of 100 Oe. Furthermore, the photocatalytic properties of as synthesized NiFe₂O₄ were evaluated by degradation of methyl orange as water contaminant. XRD, SEM, EDS, and UV–Vis spectroscopy were employed to characterize structural, morphological, and optical properties of NiFe₂O₄ nanoparticles.