Quantitative Microstructural Analysis of Formability Enhancement in Dual Phase Steels Subject to Electrohydraulic Forming

Under certain conditions, strain rate sensitive materials such as dual phase steels, show formability improvement under high strain rate forming which is known as hyperplasticity. In this research, two commercial dual phase steel sheets, DP500 and DP780, were formed under quasi-static conditions using the Nakazima test and under high strain rate conditions by electrohydraulic forming (EHF) into a conical die. Macro-strains, measured from electro-etched circle grids with an FMTI analyzer, showed remarkable formability improvement in EHF specimens. Micro-strains, i.e., the strains in the ferrite and the martensite, were calculated by quantitative metallography of more than 7000 ferrite grains and 10,500 martensite islands. The goal was to investigate the deformation improvement of the constituents under EHF. Around 20 and 100% deformation improvements were observed in ferrite and martensite, respectively. Furthermore, as a micro-mechanical modeling technique, correlation of the micro-strains with the macro-strains was investigated by applying the mixture rule. Results showed a reasonable correlation between the macro and micro-scale strains; however in banded microstructures, the strain in the martensite should be determined precisely for more accuracy.     

Rapid Separating and Enrichment of 4,4′-Dimethylsterols of Vegetable Oils by Solid-Phase Extraction

Phytosterols are separated into three classes: 4-desmethylsterols, 4-monomethylsterols and 4,4′-dimethylsterols. 4,4′-Dimethylsterols are used to detect vegetable oil adulteration and some compounds from this class can have anti-inflammatory and anticancer properties. There are methods such as thin layer chromatography (TLC) and solid phase extraction (SPE) used to separate phytosterol classes from each other. However, in some cases, separation of all three classes is not required. In addition, TLC has some drawbacks such as low recovery and it is time consuming. An SPE method has previously been used, but it was necessary to use high volume of solvents with this method to avoid coelution of phytosterol classes. In this study, an SPE (silica, 1 g) method was developed to separate and enrich only 4,4′-dimethylsterols from unsaponifiables of vegetable oil samples using 25 mL n-hexane and diethyl ether (95:5, v:v). This method was applied to hazelnut and olive oils and results were compared with those of TLC and the previously developed SPE method. Recovery of 4,4′-dimethylsterols was two times higher with the new SPE method compared with the TLC method. The newly developed SPE method generally gave a similar recovery compared with the previously developed SPE method. Moreover, the SPE method developed in this study has the advantage of using a 3.5 times lower volume of solvent than previously developed SPE methods. Because the newly developed SPE method has a single step requiring a low volume of solvents, it is rapid and simple, and can easily be used to detect olive oil adulteration with hazelnut oil and to analyze and quantify effective nutritional compounds in the 4,4′-dimethylsterols class.     

Mathematical modeling and genetic algorithm optimization of clove oil extraction with supercritical carbon dioxide

In the present study, a mathematical modeling for extraction of oil from clove buds using supercritical carbon dioxide was performed. Mass transfer is based on local equilibrium between solvent and solid. The model was solved numerically, and model estimation was validated using experimental data. For optimization, the clove oil equilibrium constant between solid and supercritical phase was determined by a theoretical method using fugacity concept, consequently the genetic algorithm for obtaining optimal operational conditions was used. The optimal conditions which obtained the highest amount of clove oil were pressure of 10 MPa and temperature of 304.2 K.     

A Comprehensive Review on Chemotaxonomic and Phytochemical Aspects of Homoisoflavonoids,as Rare Flavonoid Derivatives

Homoisoflavonoids (3-benzylidene-4-chromanones) are considered as an infrequent flavonoid class, possessing multi-beneficial bioactivities. The present study gives an overview on phytochemical aspects of homoisoflavonoids, including utilized plant species, parts, extracts, and separation techniques. Overall, these compounds have mainly been isolated and identified from bulbs and rhizomes of the plants belonging to Asparagaceae and Fabaceae families, particularly the genera of Ophiopogon, Dracaena, Scilla, Polygonatum, and Caesalpinia.     

Theoretical and experimental analyses of rheological,compatibility and mechanical properties of PVMQ/XNBR-g GMA/XNBR/GO ternary hybrid nanocomposites

Iranian Polymer Journal - Effects of graphene oxide (GO) on various properties of rubber hybrid nanocomposites based on PVMQ/XNBR-g-GMA/XNBR (phenyl-vinyl-methyl-polysiloxane/carboxylated nitrile...     

Multi- Objective Optimal Design of on- Demand Pressurized Irrigation Networks

In the context of water as an economic good, from the use of water, one can derive a value, which can be affected by the reliability of supply. On-demand irrigation systems provide valuable water to skilled farmers who have the capacity to maximize economic value of water. In this study, simultaneous optimization of on-demand irrigation network layout and pipe sizes is considered taking into account both investment and annual energy costs. The optimization problem is formulated as a problem of searching for the upstream head value, which minimizes the total cost (investment and energy costs) of the system. The investment and annual energy costs are obtained in two separate phases. Max–Min ant system (MMAS) algorithm is used to obtain the minimum cost design considering layout and pipe diameters of the network simultaneously. Clement methodology is used to determine flow rates of pipelines at the peak period of irrigation requirements. The applicability of the proposed method is showed by re-designing a real world example from literature.     

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.     

Aspen plus simulation of heavy oil gasification in a fluidized bed gasifier

Gasification is a clean technology to convert fuels to high-quality syngas in presence of a gasifying agent. In this study, an Aspen Plus model of heavy oil gasification was developed to produce the hydrogen rich syngas. Effect of some parameters such as gasification temperature and steam/fuel ratio on the hydrogen yield and was investigated. Results showed that the temperature plays a major role in the process; higher temperatures produce the higher hydrogen content. It was also found that the operation under high steam/fuel ratio can cause a significant increase in the hydrogen yield. The modeling results were compared with the experimental data available in the literature and found to be in good agreement.     

First-principles study of H2 adsorption on the pristine and oxidized (8,0) carbon nanotube

The effect of oxygen, hydrogen, and (oxygen + hydrogen) molecules adsorption on the structural and electrical properties of (8,0) carbon nanotube (CNT) are investigated through density functional theory. The obtained results indicate endothermical chemisorption of O₂ on the nanotube surface with a large binding energy of about 598 meV and a significant charge transfer of about 0.43 e per molecule. It is discussed that the O₂ chemisorption creates hole carries in the (8,0) carbon nanotube and thus increases the work function of the system. In the case of hydrogen molecule, a weak physisorption on the surface of CNT (∼−5 meV) is identified. The adsorption of H₂ on CNT is also accompanied by hole doping and increment of the work function of the CNT, while the charge transfer between CNT and H₂ is negligible. The band offsets in the H₂-CNT junction are calculated to examine and describe the observed hole doping in this system. The effect of oxygenation of CNT on hydrogen adsorption is also investigated and the most favorable adsorption configuration is found and the related adsorption energy is calculated. It is argued that the oxygenation of CNT enhances the physisorption of hydrogen molecules. It is shown that hydrogen molecule adsorption on the oxidized CNT cancels hole doping and hence decreases the work function of the system.