نشریه تحقیقات در علوم مهندسی سطح و نانو مواد
سال دوم شماره 1 (پیاپی 5، بهار 1402)

Cardiovascular diseases, including ischemic heart disease and stroke, are responsible for nearly 25% of all deaths worldwide. Globally, their prevalence continues to increase, despite enormous progress in cardiovascular diagnostics and therapy. For therapeutic and regenerative purposes, biomaterials promise solutions with multiple advantages over synthetic materials. Furthermore, their easy availability as nanoformulations recommends their application as drug carriers or protective nanoshells improving the biocompatibility of imaging agents. For example, compared to traditional drug delivery methods, nano-drug delivery introduces different ligands into corresponding nanocarriers according to pathological mechanisms and different therapeutic strategies to directly target the lesion site. This strategy more effectively targets the atherosclerotic plaque area and increases drug concentration to improve myocardial blood flow.

Nanotechnology deals with the production and use of materials with nanoscale dimensions in various fields of science. Due to their nanoscale dimensions, nanomaterials have a high surface-to-volume ratio, which gives them very unique and special properties compared to their macro components. Nanotechnology affects several aspects of the food industry, from how food is grown to how it is packaged. Companies are developing nanomaterials that make a difference in food taste and safety, health benefits, and packaging type and shelf life. Nano products for food packaging are currently being developed. Nanosensors in plastic packaging can detect gases released from food as it spoils and change the color of the packaging to warn you that the food has spoiled. Plastic films are being developed that allow food to stay fresher for longer. Packaging is an important part of the product, and a perfect packaging material must have good strength, barrier and performance characteristics. Nano-based packaging has several advantages over conventional packaging methods and offers better packaging materials with better strength and barrier. Nanotechnology offers tremendous opportunities for innovative developments in food packaging. The use of nanotechnology brings the benefits of improved performance in terms of barriers, mechanical and physicochemical properties of packaging, which leads to safe transportation of food and increased shelf life. However, more research needs to be done in this area as many applications are in their infancy. In addition, toxicology and migration studies should also be conducted extensively to ensure food safety.

An experimental study was carried out in order to find out the effects of ZnO Nano fluid with a mean diameter of 30nm on heat transfer, pressure drop and termal performance of a double tube heat exchanger, where the volume fraction of nanoparticles in the base fluid is less than 1% (low concentration). Ethylene glycol and Nano fluid with particle volume fraction of 0.5%, 0.7% and 1% are used as working fluid. The experiments are carried out in the fully developed turbulent regime. The results indicate that addition of low value of nanoparticles to the base fluid motivates the heat transfer to increase remarkably. The Nano fluid also show that the pressure drop of Nano fluid is slightly higher than that of the base fluid and does not increase with increasing the nanoparticles volume fraction. In this paper, experimental results have been compared with the existing correlations for Nano fluid convective heat transfer coefficient in turbulent regime. Also Nusselt number and friction factor were considered in definition of thermal performance factor for all cases are greater than unity which indicate that this Nano fluid enhances the heat transfer without huge penalty in pumping power. Thermal performance factor maximum is obtained 1.32% by 1% volume fraction and between 1.03%~1.20% by 0.5% volume fraction. Also, for Reynolds about 6300, nusselt number have increased by 0.7% volume fraction, about 19.8 percent. Hence, applying the methods studied here could be considered as a good choice in particle application.

In this paper, the structural and electronic properties of MoS2 and MoS2 compounds doped with cobalt in two nonmagnetic and magnetic states are investigated in the framework of the density functional theory with the Espresso quantum computing code in two exchange approximations of the generalized slope correlation and the local density of the constant charge type. The lattice constants were calculated and compared and were consistent with the results. The band structure and density of states for the MoS2 compound showed semiconducting properties. The band structure and density of states for the cobalt-doped MoS2 compound in the non-magnetic state showed metallic properties. The band structure and density of states for the cobalt-doped MoS2 composite in the magnetic state with cobalt showed weak ferromagnetism and metallic nature. The density of partial states for the composition of MoS2 shows the role of d orbital of molybdenum atom and p orbital of sulfur atom, and for MoS2 doped with cobalt, it shows the role of d orbital of cobalt atom, d orbital of molybdenum atom and p orbital of sulfur atom, which is consistent with the results of others. To compare the structural properties of the two structures, the MoS2 compound changes from the hexagonal structure to the tetragonal structure after doping with cobalt. The results are consistent with previous works.

Tubes with diameters in micro and nano dimensions with long length, while having a special manufacturing technology, have wide applications in the field of biosensors, atomic microscopes, actuators, tanks for fluid transfer in drug delivery, etc. The reason for the wide application of micropipes is their hollow geometry and very good mechanical properties. In this research, while comparing and using the classical theory of continuous medium mechanics and the non-classical theory of strain gradient based on the classical Euler-Bernoulli beam model and von-Carman nonlinear geometry, the mathematical equations are expressed in terms of three longitudinal parameters, then to investigate the vibrations of the micropipe under the influence Velocity and temperature fields are discussed. For this purpose, the frequencies and vibration amplitudes have been calculated by the integral solution of the governing differential equations using the point interpolation numerical meshless method of the displacement field, and the effect of temperature and diameter on the linear and non-linear behaviors in the micropipe has been studied. The findings of the research, while showing the effectiveness of the point interpolation numerical meshless method with base functions developed for the mentioned analysis, state that; by reducing the diameter of the micropipe, the natural frequency and critical speed increase and whit the temperature increases, resulting in a decrease in the basic frequency and an increase in the amplitude and becomes the nonlinear behavior of micropipe.

The measurement and removal of residual stresses using the ultrasonic method is being developed. In this paper, the capability of ultrasonic method using longitudinal wave with critical refraction angle or LCR wave in measuring and removing residual stress caused by welding has been investigated. Two plates of 2024-T351 alloy are welded together. To measure their residual stress field, the acoustoelastic property is used, and the changes in the speed of propagation of ultrasonic elastic waves when passing through the residual stress field are investigated. Then, the relationships of the effective stress intensity factor and the fatigue crack growth rate in the case where the welded parts have residual stress and are subjected to cyclic loading have been obtained. Finally, in order to eliminate tensile residual stress, a package of ultrasonic waves has been used again, and the modified relationships of stress intensity factor and fatigue crack growth rate have been introduced in this regard.