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In general, temporary well plugging is essential for repairing of oil and gas wells due to their long life time. One of the newest methods used for this purpose is gel polymer plugging. The strength of the gel in the well conditions is one of the most important challenges in the application of gel polymer in the temporary well plugging in work over operation. In this study, silica nanoparticles were used to improve the strength of polymer hydrogels. The bottle and rheological tests were used to determine the gel strength in desired well conditions (high temperature and high salinity). Also, the gel strength properties and swelling behavior were studied in various conditions such as distilled water, formation water, tap water and oil. It was observed that the strength of the gel increased from 520Pa to about 36kPa (5000% increase) by adding nanoparticles. Also, the gel swelling in the aqueous solution has been significantly reduced. Based on the results obtained in this study, a polymer gel containing 9 wt.% of silica nanoparticles with structural strength and thermal stability at 90 °C was introduced for field studies.

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In this study, the effects of drying temperature and mechanical pressure on the surface structure and dynamical properties of polyaniline (PAni) were studied. PAni was synthesized through the aniline polymerization process in the presence of ammonium persulfate in acidic medium and normal methyl-2-pyrrolidine solution. The obtained solution was dipped on a substrate of quartz glass. Atomic force microscopy (AFM) analysis based on nano-indentation tests were used to determine the values of hardness, Young’s modulus and Poisson’s ratio of the films. The results of the analysis of the scanning electron microscope demonstrated that the surface morphology of the film is changed from a fiber-to-interconnected cross-linked networkby increasing the drying temperature. The transmission electron microscope analysis showed that the diameter of the fibers on the surfaces dried at 318 K and 418 K was 18 and 30 nm, respectively. AFM results showed that the mean surface roughness of PAni film at 318 K without mechanical pressure was 63 nm, while for the film pressed at 5 MPa was less than 35 nm. Thermo-mechanical analysis showed that the glass transition temperature of the PAni film prepared without mechanical pressure and the film pressed at 5 MPa were 386 K and 378 K, respectively. Investigating the temperature dependence and applied pressure on the film surface in determining the viscoelastic properties of the PAni nanostructured film can provide readers with appropriate information about the storage and loss modulus of the film and the activation energy of the polymer layer during the thermal decomposition process.

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Abstract:
Research subject: In water injection process, part of the surface active agents that are naturally present in oil can be dissolved in injected water. The presence of these substances affects the surface phenomena of the three phase water-oil-rock system. The effect of these substances on modification of the ionic composition of injected water has been less investigated in previous studies.
Research approach: In this paper, first, the effects of acidic compounds in crude oil and connate water composition on initial wettability of carbonate rock were investigated. Then to investigate the wettability changes of oil-wet calcite rock, single-salt aqueous solutions of MgCl₂, CaCl₂, KCl, and Na₂SO₄ having concentrations of 0.1 to 1 molar were used.
Oil–water interfacial tension (IFT) for distilled water and salt waters in various concentrations were measured and compared. Variations of calcite rock surface properties were investigated by contact angle measurement after aging of thin sections in oil and salt waters.
Main results: Results indicated that by increasing ion concentration and ionic strength of salt waters, IFT decreases due to dissolution of acidic compounds of oil at the interface of oil and water. Moreover, for high content of acidic compounds in the oil, Magnesium ion has the most impact on reducing IFT and altering the rock wettability. So that by increasing the concentration up to 1 molar, IFT and contact angle decrease to 1 mN/m and 42 degrees, respectively.
Contact angle measurements revealed that the composition of connate water is effective in changing the initial wettability of the rock, and formation of ionic-organic layer adjacent to the rock surface is one of the most important factors in wettability alteration. The presence of Magnesium ion in connate water decreases the contact angle to 145 degrees and causes the rock surface to become more water wet.
Also, increasing solubility of oil-soluble acidic compounds in the aqueous phase has a significant effect on the rock wettability. The experimental results showed that the interaction between ions in the aqueous phase, especially the divalent ions, and surface active agents (carboxylic acid) determine the surface behavior of water in contact with oil and rock.
 
Keywords: Wettability, IFT, Acidic oil, Divalent ions, Ionic-organic layer

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In this paper, the effect of processing temperature on the elastic and viscoelastic properties including storage modulus, loss modulus and damping value of PVC/plain weave fiberglass composites laminates was investigated. For this, composite samples with [0/90]10 lay ups were produced in three different temperatures including 160 ᵒC, 200 ᵒC and 230 ᵒC using film stacking procedure. Firstly, the flexural strength and modulus of the samples were measured using three points bending test according to ASTM D790-07 standard. Then, viscoelastic properties of the samples were measured in the temperature range of 25 ᵒC up to 220 ᵒC using Dynamic Mechanical Thermal Analysis (DMTA) and the effect of temperature on the viscoelastic properties was studied. Also, the effect of fiber/ matrix impregnation quality on the thermal and dynamic properties of the samples was evaluated using optical microscope images. It was concluded that the temperature of 230 ᵒC is proper to achieve high quality impregnation, according to both DMTA and three points bending test. Also, it was seen that increase of processing temperature up to 230 ᵒC increases the storage modulus; however, processing temperature doesn’t affect the glass transition temperature of the samples.

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Due to the polar functional groups of PVC thermoplastic and its good adhesiveness to the metals, production and roll forming of PVC/ aluminuim/ glass fiber FMLs were investigated in this research. At the first, flexural strength and bonding quality between PVC matrix and aluminuim layer in the FMLs were studied by doing three point bending tests according to ASTM D790 standard. In the following, FMLs with dimension of 12×80 cm and two layups including [0/90, 0/90, Al]s and [45/-45, 45/-45, Al]s were produced using film stacking and hot pressing procedure. The FMLs were rollformed into 30, 45 and 60º channel section profiles at 160ᵒC using a single stand rollforming process and geometrical decects including profile bowing, edge wrinkling, spring back and also aluminuim/composite layers delamination of the resulted profiles were evaluated. The FMLs also were roll formed into 86º channel section profiles using a multi stand roll forming process and the effects of multi stand roll forming on the defects stacking were evaluated. Finally, it was concluded that more than 45º bend angle increase in a rollforming stand results in composite/ aluminum delamination. Also, placement of the reinforcing fibers in the longitudinal direction of the profiles reduces the profile bowing and edge wrinkling defects significantly.

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Yazdi cake is one of the indigenous snacks of Iran that by adding some ingredients can improve its nutritional and textural properties. Green tea extract is high in antioxidants and have a health role. The aim of this study was to investigate the effect of green tea extract on physicochemical and sensory properties of Yazdi cake. In this study, green tea extract was added to Yazdi cake formulation at 0, 2.5, 5 and 10% levels. Then the physicochemical properties (moisture, protein, fat, ash, fiber, carbohydrate, Specific weight for cake dough, cake volume, density, porosity, weight loss) and sensory analyze during storage at 2, 4 and 6 days intervals after baking, it was performed according to standard methods. All the prepared cakes containing different concentrations of extract had significant physico-chemical and sensory characteristics and were within the standard range. Observations showed that the addition of green tea extract in cake formulation decreased weight loss, moisture, porosity, density, brightness, ash and sensory scores and increased volume, fiber, fat, protein, carbohydrate and specific gravity. High levels of 5% green tea extract had a negative effect on the quality of the cake. Therefore, the addition of green tea extract at levels of 2.5 and 5% produced an acceptable product cake. Finally, optimization of Yazdi cake formulation to produce a useful product using the investigated characteristics and limits indicated that 2/5% of green tea extract is the most suitable enrichment for Yazdi cake, in which the percent extract there was no adverse change in the physicochemical and sensory properties of the cake.

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 The inhibitory activity of Pistacia eurycarpa Yalt. Essential Oil (EO) toward Aspergillus flavus (PTCC: 5004) was evaluated by agar dilution method and vapor phase method. For the first method, the EO was added to agar medium to obtain concentrations of 0, 5,000, 6,000, 7,000, 8,000, 9,000, and 10,000 µL L^-1. For the vapor contact assays, uncovered inoculated potato dextrose agar plates and maize plates were placed inside airtight containers whose headspace was saturated by EO vapor. The results showed that at agar dilution test, the EO completely inhibited the growth of the tested mold at ≥ 10,000 µL L^-1. In vapor contact method, mycelia growth was inhibited 60.87% in PDA plates and no growth was observed within twenty days of incubation in maize plates.