علی اکبر عظمتی

With the continuous improvement of integrated circuit technology and micro/nano electromechanical system technology, the development of small generator devices has become an inevitable trend in the development of microelectromechanical systems. Since the volume of electronic devices will be smaller and smaller on a daily basis, the demand for energy will be smaller and smaller, as a result, the energy needed by micro-devices can be easily supplied by using wind energy piezoelectric generators. In this research, while analyzing the behavior of piezoelectric transducers with the help of Abaqus finite element software, a method to increase the power extracted from wind generators has also been presented using auxetic structures. For this purpose, three different types of auxetic structures have been used and the effect of the type and thickness of the auxetic layer on the behavior of the structure has been analyzed. Examining the obtained results shows an acceptable increase in the output voltage of the piezoelectric layer by using auxetic structures, so that a 100% increase in output can be achieved by using this type of structure. Also, a drastic increase in the electric potential obtained with the help of similar-shaped auxetic structures made of steel compared to aluminum structures was observed, which confirms the effect of the geometric shape and material of these structures on the output power of the generator.

This paper has investigated a simulation and numerical study of the flow field and temperature distribution in a room with inorganic insulation with a floor heating system. The air in the room is considered incompressible, and the modeling turbulent flow and radiation heat transfer are modeled by disturbance k-ε (RNG) and DO radiation models, respectively. Piso algorithm is used for solving the governing equations. The results indicate that the best position for insulation in the floor heating system is in the external walls of the building. It has been found that paint with ceramic coatings can lead to 18% savings in energy consumption in the winter than the conventional paint. Also, the impact of external wall insulation with floor heating system in different climates has been investigated. It has also been found that hot and humid, hot and dry and humid temperate climates provide better thermal comfort conditions for the residents and that the lowest energy consumption is related to the hot and humid climate.

 Due to the high use of polystyrene in food and medicine industries, it is particularly important to have antibacterial properties for these types of polymers. In this study, composite samples of polystyrene and titanium dioxide were prepared by using a twin-screw extruder.

 The samples were prepared by injection moulding process for mechanical and anti-bacterial testing. It was observed that adding TiO2 would improve the mechanical and thermal properties of polystyrene.

 According to the results of the natural weathering test, TiO2 as a semi-conductor photo-catalyst has an active role in the determination of antibacterial properties of polymer matrix.

  Micro and nano-scale of TiO2 improved impact strength, tensile strength, Vicat softening temperature and melt flow index of all samples. Moreover, the prepared mixture showed appropriate antibacterial properties against E.Coli and S.Aureus. It was concluded that the antibacterial properties of the nanocomposite sample are better than those of the composite sample because of smaller size and larger surface area of Nano particles.

Introduction and AimLimited resources and the need for energy conservation have made the use of energy loss preventive thermal insulations, like the paints containing micro mineral particles, an economic option in different industries and buildings. The aim of the current study is to investigate the effect of modern insulation, such as paints with ceramic micro-particle in internal walls of a room with radiative cooling panels, on energy consumption.
MethodIn the present study, to investigate the flow field and temperature distribution in a room with a wall of radiation cooling, a three-dimensional cavity has been simulated with different boundary conditions. The effect of coating with a paint containing ceramic micro-particles, ordinary acrylic paints and no paint in different states of changing the boundary conditions, such as changes in wall temperature and absorption coefficient on a room with wall cooling radiation has been studied and the results were compared.
FindingsUsing the computer code, the interior surface temperature is obtained for different boundary conditions and used as a boundary condition for simulation. In case of using wall radiative cooling panels, room temperature is in the comfort zone in all cases, and the lowest temperature occurs when using paints with ceramic micro-particles in the interior surfaces of the room.
DiscussionIt was observed that the coating containing ceramic micro-particles acted as a thermal insulation and reduced energy consumption by about 22% .

Iranian crude oil with high sulfur content should be desulfurized before applicatiom. Because of high percentage of sulfur in crude oil, sulfur gases are produced and polluted the environment and ultimately can cause problems during processing. Therefore, in this study the ultrasound process has been applied for the removal of sulfur from sour crude oil of Darkhovein. This method is actually a combination of oxidation and applying ultrasonic waves to achieve very low sulfur content in crude oil. In this paper, the influence of ultrasonic radiation duration, oxidant materials, type of solvent in extraction process, and type of organic acids were examined. At condition of ultrasound of 24 KHz/400 W with amplitude of 70% by using of acetic acid and hydrogen peroxide, and extraction with methanol, the sulfur removal efficiency reached to 93% in 20 minutes.