نشریه مهندسی مکانیک و ارتعاشات
سال چهارم شماره 4 (پیاپی 13، زمستان 1392)

In this paper, the main purpose is the calculation of mass transfer due to road roughness in different maneuvers including of the vehicle accelerating and braking. To achieve this goal, the damping model of a full car for 10 degrees of freedom, based on the vibrations in MATLAB software was Simulated. Vertical displacement of the wheels on uneven roads based on ISO classification at a constant speed of 70 km per hour and the general direction of the vehicle was 1,000 meters. The following, using inverse dynamics analysis in MATLAB Simulink, the forces acting on each wheel of the vehicle during various maneuvers was obtained. Finally, using of force histories resulting in the wheels of to cross the road roughness, as well as accelerating and braking, rate of mass transfer from back to front in the braking maneuver and rate of mass transfer from the front to the rear of the vehicle in the accelerating maneuvers was obtained.

In this paper we investigate the Casimir energy for systems with Anti-Periodic Boundary Conditions (BCs) in one spatial dimension by Box Subtraction Scheme (BSS). The BSS is a slight modification of Boyer's subtraction method to remove divergences from expressions in the Casimir energy calculation. The more routine method which involves many regularization and analytic continuation procedures has some ambiguities. These ambiguities have been described recently in some papers. However, in this paper we shall investigate some of them and also we describe the main ingredient of the BSS in the subtraction of two comparable configurations for our problem. Usually, two approaches in the Leading order Casimir energy are yield identical results but the latter regularization has more manifest way to remove divergences from expressions. So it could be the best instrument for us to remove complicated divergences which appear in the higher order radiative corrections to the Casimir energy. Extracting and obtaining of finite results from complicated divergent expressions without resorting to any analytic continuation techniques is also the other privilege of the BSS. In this paper we use this regularization method to obtain the Casimir energy and in final we compare our results with those reported in the literature, which are obtained from other regularization techniques.

Ionic liquids are nonvolatile, non-toxic and non-flammable liquids with high thermal and chemical stability. Therefore they are suggested as a solvent in absorption refrigeration cycle. For modeling of cycle operating should be specified thermodynamics properties. One thermodynamics model is used for one effect absorption refrigeration cycle. Thermodynamics properties of refrigerant-solvent mixture are modeled by equation of state. [hmim][Tf2N], [emim][Tf2N] and [hmim][BF4] are used as solvents and R134a is used as a refrigerant. Results compare with other common refrigerant-solvents. Coefficient of performance of these systems are lower than common cycle like LiBr-water and water-NH3 but specific properties of ionic liquids such as nonvolatile, non corrosive, non-flammable and eco-friendly, cause very research perform to get proper refrigerant and ionic liquid as a solvent

One of the most important issues that is widely industry, monitoring the situation. To work with this system defects before he could create serious problem and known to tackle it. Damage in two ways: existent malicious and nondestructive and from where the solution with less cost, so this method is more. One of the methods of identifying damage nondestructive ,methodology Modal parameters structure in this way is to investigate the changes Modal parameters, such as the natural frequencies and modes form before and after the damage to seek the site and levels of damage in are structures and damage to find with a wide range of response so a lot of research hit optimization techniques used in solving the problem for considering the dynamic parameters and changes in the structure that objective functions is considered to be optimized for them , and the amount of damage to the desired effectively The study by using the method of genetic algorithm to examine the structural damage, with regard to the presence of various target functions, first as a single point, and the accuracy of the response to the parameters for change in the algorithm sensitivity analysis, and then paid using various target functions and optimized genetic algorithm multi-purpose of the appropriate response is obtained.

Heat transfer is one of the most important phenomena in nature. According to the principle of heat transfer, the best way to increase the exchange of heat from a surface,is expanding the cross section. Using porous media for increasing the cross section can be a new approach for better heat transfer. Since heat transfer by natural method has less capacity to transfer heat, using porous media in this case is more important. Due to the widespread usage of heatsinks and fins in Industry and Laboratory, designing high efficient optimized system Has been become interesting for researchers and scientist. In this study review of previous researchs in solid and porous fins and heat sinks has been conducted.

Natural gas is extracted from wells and after purification, it reaches to consumption stages by transmission and distribution network. Energy losses in this section is vital and must be calculated appropriately. In this study, the network of distribution with low working pressure is examined. A network sample of natural gas is investigated using analitical solution of a steady flow of natural gas. Flow equations initially provided for a tube considering all parameters. Then, using the existing rules in pipe networks the network sample is analyzed. Effect of tube material as an important factor on network performance are evaluated and analyzed And finally, the rate of entropy generation in steel and polyethylene pipes were compared. The results show that by increasing the diameter or decreasing the gas flow rate, the tube material and friction coefficient is less effective on entropy generation in practice. Furthermore, the gas flow in lower diameters cause more entropy production using steel pipes in compare with polyethylene pipes.

In the common practice design of structures, one of the most important design parameters is design spectrum. design spectrum can divided to two category. first linear design spectrum and second nonlinear design spectrum. Exact determination of nonlinear design spectrum needs to nonlinear dynamic Analysis of single degree of freedom system. Because of time consuming of such analysis previous researchers determine many relation for estimating of nonlinear spectrum from elastic spectrum. In this Article Three relations of previous study have been selected and then twenty records of earthquake for soil types have been extracted from earthquake database of PEER database. for each record linear and nonlinear exact dynamic time history carried out and maximum displacement and acceleration is drawn versus elastic period of single degrees of freedom system. After this, linear spectrum is estimated based on elastic exact analysis and nonlinear spectrum is estimated based on relations of previous researchers. Comparison of exact and approximate results are carried out for displacement and acceleration response of nonlinear spectrum. Assessing the result revealed that relation based on Miranda and Krawinkler are matching better than Bazan with respect to exact nonlinear dynamic analysis