نشریه مهندسی مکانیک و ارتعاشات
سال چهارم شماره 2 (پیاپی 11، تابستان 1392)

Carbon has several allotropes. One of the newest carbon allotrope is graphene nanobud. It isn’t available in laboratory. Graphene nanobud is formed by connecting fullerene and graphene sheet. Molecular dynamic simulation is used for calculating mechanical properties of graphene nanobuds. Influence of temperature, neck length and size of graphene sheet are estimated in this study. The results shows that Young’s modulus has a little changes with temperature arrises. In another word, with increasing temperature the Young’s modulus doesn’t change very much and just alittle decrease. Also seen that in constant temperature with increasing the size of graphene sheet, the Young’s modulus arises. Our simulation findings afford not only a molecular level understanding of graphene nanobud but also may be instructive to mechanical engineers and scientists who attempt to develop effective mechanical properties.

One of the most important issues in various industries, including electronics, is Components thermal management. In order to have more powerful, integrated and smaller electronic products, it is necessary to use higher level of Heat Dissipation Technology. This requires the use of extended surfaces (fins) resolves. Many studies have been conducted to find the optimal shape of the fins. Different methods are used to optimize and increase the efficiency of the fins and heat sinks which can be noted to optimize the geometry, shape and dimensions, change the fins distance, the use of different materials in the manufacture of fins, the use of porous media with high thermal conductivity to improve fins thermal characteristics. . In this study is mentioned review of some previous researches that has been done in this context.

This paper examines the opportunities and potential use of renewable energy resources in Iran's.The energy necessary for economic development , social and quality of life and continuous energy, and sustainable economic growth is necessary for any development .Iran has considerable natural resources to modernize energy supply and the transition to a sustainable energy system is .For the use of wind energy , geothermal energy , hydroelectric power development and use of solar thermal energy is ideal context forIn addition, this study is based on a case study on renewable energy and solar thermal energy and its use in the air conditioning to reduce the use of fossil fuels and the greenhouse effect is taken into consideration .

The aim of the present study is to investigate the effects of shear rate on dynamic viscosity of MWCNT-ZnO/engine oil hybrid nanofluid. Using two-step method and without using any surfactant, the studied nanofluid has been produced in different solid concentration (0.125, 0.5, and 1%) as the experimental sample. All the experiments were conducted in the temperatures ranging from 5 to 55°C and shear rates ranging from 50 to 1000 RPM. Based on the experimental results, although the base fluid showed Newtonian behavior in all the studied temperatures and shear rates, in the temperatures of 5 and 15°C, the studied nanofluid shows Non-Newtonian behavior while it shows Newtonian behavior in the temperatures of 25, 35, 45, and 55°C.

This invention has been designed in conjunction with spot welding machines, which is widely used in various industries including the automotive industry. The spot-welding electrodes made of copper alloy welding operations are performed. The electrodes after a certain number of limited time to work and boiling point, Pleated and deformed and lose its original state. Therefore, no performance is required and Quality welded joint is severely drop. And in the case of product safety will be extremely low. This feature provides a portable electrode milling machine Copper electrodes of the device is opened without boiling point just in- line They shaved and re- forming. Thus, in addition to quality assurance and Strength boiling points, the shelf life of up to 10 times will be added.

One of the new ideas to deal with the irritation caused by wind or earthquake Is the idea of controlling structures. The use of dampers in retrofitting structures is one of the most applicable and effective approach to control the imposed force and its induced energy dissipation increase.Dampers can be selected based on the period of structure,type of site, material of structure, type of bracing system, lateral force of structure, site and geographical position of structure, distance of structure from the fault or epicenter and other effective factors. The performance of tuned mass damper is basically according to dampers mass vacillation energy dissipation and developing mass inertia force in opposite phase of the imposed load on structure.

In this study has been investigated the natural heat transfer for F-shaped geometry with laminar flow and under certain conditions. The top walls are isolated, and right wall has a hot boundary condition and left walls are cold. Momentum and energy equations written and SIMPLE algorithm was used to solve for the equations. For geometry modeling prepare a program in FORTRAN and for checking of accuracy of written code it was checked with one adapted articles. In this paper, the influence of factors such as Raily number, Hartman number, aspect ratio and the ratio of silver nano-particles on the heat transfer is investigated. The results show that by increasing the Raily number increases of heat transfer. The horizontal and vertical speed decreases with increasing aspect ratio compartment. Increasing Railey number will increase the effect of the influence of Hartmann number and heat transfer. By proportion of aspect ratio equal 0.4 that warm wall temperature too close to the cold wall, heat transfer was increased. Keywords