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Abstract
Research subject: Due to the drought and lack of water resources, many efforts have been made to store water properly recently. Using of multilayer polyethylene tanks is an efficient measure in order to solve this problem and it has received considerable attention. Proper manufacturing conditions will greatly improve the strength of these tanks and their applications.
Research approach: In this study, the effect of cooling process on the final properties of polyethylene tanks prepared by rotational molding method is investigated. Three different cooling methods comprised of cooling with water, cooling by air, and quiescent cooling is selected and their mechanical and thermal properties were investigated.
Main results: The results of the tensile test show that as the tank is cooled faster, the elongation at break will be higher. It is also demonstrated that the air cooling method results in the lower elongation at break. The results of the thermal properties show that higher cooling rate creates thicker crystals in the fragment which requires higher energy to overcome these thick crystals. According to the results of the thermal properties and using the softening temperature test it is found that by increasing the cooling rate, the softening temperature will be increased as well which will improve the application of the tank in high temperature conditions. Melt flow rate and density tests are also performed to confirm the results of mechanical and thermal properties, respectively. Charpy impact test is performed at ambient temperature to confirm mechanical behavior induced by crystal structure. All in all, cooling by water performs better than other methods in terms of mechanical and thermal properties.

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Today, biodegradable packaging materials have received a great deal of attention due to growing concerns about non-degradable materials; Therefore, the aim of this study was to investigate the effect of betanine pigment on surfaces (0, 2/5, 5 W/V%) and CuO nanoparticles on surfaces (0, 2, 4 W/V%) in nanocomposite film based on whey protein isolated / pectin in the form of a central composite design on the mechanical properties and physicochemical properties of the film is produced. The results showed that with increasing the percentage of betanine pigment and CuO nanoparticles, the thickness and moisture of the samples increased and the solubility decreased (P­<0.05). Also, by adding high levels of betanin pigment, redness (a) increased and brightness (L) and yellowing (b) of the samples decreased. Addition of nanoparticles decreased b value while it had no significant effect on a value of the samples. Also, by adding pigments and nanoparticles, tensile strength and elongation of film samples increased significantly (P <0.05). According to all the results, the use of CuO nanoparticles and betanine pigment in nanocomposite film leads to the production of a film suitable for food packaging with desirable physicochemical and mechanical properties.

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Abstract:
Concrete is the most widely made construction material in the structural engineering world. Advantages such as high compressive strength, availability of raw materials, and low preparation cost make concrete one of the most important used construction materials. Under harsh environmental conditions, aggressive agents such as sulfates and chlorides penetrate the concrete through these cracks to damage the concrete. While concrete cracks are not only expensive to repair, they are often hard to detect as well. It is now identified that the strength of concrete alone is not sufficient, the degree of harshness of the environmental condition to which concrete is exposed over its entire life is very important. Self-healing concrete is a type of concrete that has the ability to repair itself without the need for an external agent during cracking. Concrete containing microorganisms has self-healing properties. The self-healing agent contains a specific concentration of bacteria with a nutrient in the concrete that produces calcium carbonate while the water and environmental conditions are suitable for the concrete. In this research, four different specimens of concrete have been made. Concrete containing microorganisms is made in two different concentrations of bacterium bacillus pasteurization (10⁷,10⁹ cells/ml) and calcium lactate nutrients and is compared with concrete containing silica fume, concrete containing latex and control concrete. In all four specimens, the same mix design was used with a water/cement ratio of 0.48 and containing silica fume, latex polymer, and calcium lactate, which replaced cement in different percentages. Specimens were subjected to compressive, flexural, and tensile strength tests at 7 and 28 days of operation, and the results were compared. The results showed that the best performance among all specimens for concrete containing silica fume and self-repair agent (bacteria and brain material) increased compressive strength and reduced tensile and flexural strengths compared to the controlled specimens. The use of a self-healing agent in concrete increases the compressive strength of concrete, but this increase is not as great as the increase in silica fume. Bacteria with a higher concentration have a negative effect on the compressive strength of concrete so that more use of bacteria in concrete increases the compressive strength to such an extent that it even reduces the compressive strength compared to the concrete strength of the control specimens. The self-healing agent reduces the flexural and tensile strength of concrete, as opposed to silica fume but they are better than latex and produce better results.

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In present study, an improved severe plastic deformation process named improved tube cyclic expansion extrusion process has been introduced. The idea of this process is taken from the conventional tube cyclic expansion extrusion process, and in this novel process, it is tried to solve some important problems of the conventional process. Improved tube cyclic expansion extrusion process is capable of severe plastic deforming and improving microstructure and mechanical properties of tubular components. Also, this process can be considered for producing relatively long tubes. For this purpose, the improved tube cyclic expansion extrusion process was successfully performed on AZ91 magnesium alloy tubes, up to two passes. Then, the microstructure evolution and the mechanical properties improvement were scrutinized. The results showed that the microstructure and mechanical properties were improved considerably. In this way, after two passes of this process, an ultrafine grained (UFG) microstructure was formed, and the values of ultimate strength (UTS), hardness (Hv) and ductility (EL%) became 3.6, 1.83 and 1.8 times higher, respectively. Also, the comparison of the results of the improved tube cyclic expansion extrusion process with those of the conventional tube cyclic expansion extrusion process indicated that ultimate strength and hardness of the improved process were near to those of the conventional process, but the value of elongation to failure of the improved process is considerably higher than the value of the conventional process. This can be considered as one of the important advantages of the improved process over the conventional process.