Sharif Digital Repository

The main popuse of this Thesis is investigating of the different wagon arrangement effect on stability of the train set. So to gain this goal, one train with 10 wagons has been simulated. The model of the each wagon is Nonlinear with 40 DOF. 3 of the wagons are heavy and make 3 different kinds of arrangement by putting them at first, middle and the end of the train (HLL, LHL and LLH arrangements). Then these three arrangements have been simulated on two differen tracks and conditions, 1st Accelerating on curved track (320 R) with positive slope and 2nd decelerating on curved track with negative slope.We suppose that the contact is singular point and aslso contact equations have bben solved... 

In recent years, machine learning has been widely used to solve various computational problems. One of the most fundamental and integral type of these issues is the problem of classification, in which the data samples of different types such as image, voice, or video are classified into different categories. Since these data types are inherently sequential, the problem of classifying sequential data, is of great importance. This problem has a wide range of applications, including but not restricted to, handwriting recognition, voice recognition, malware detection, and fraud detection in financial transactions. Regarding the fact that in many cases, the length of the sequence (which could be... 

The electrospray technique involves the production of small charged droplets through the application of electrohydrodynamic forces. Under well-defined operating conditions, multiple flow modes can be observed, among which the stable jet-cone mode has received significant attention from the research community. This mode is desirable due to its uniform droplet diameter, reduction in droplet rebound when impacting hot surfaces, and potential for utilizing two-phase heat transfer for cooling purposes. In this study, a comprehensive experimental investigation was conducted to evaluate the cooling of hot surfaces through the use of electrospray in the steady cone-jet mode. The fundamental... 

The numerical modeling of engineering contact problems is one of the most difficult and demanding tasks in computational mechanics. Frictional contact can be observed in many problems; such as: crack propagation, metal forming operation, drilling pile etc. In metal forming operations the required shape changes are obtained by either of forming process, such as pressing, hammering, rolling or extruding the material between the tools which are much stiffer than shaped material. Because of large difference between deformability of the tool and material, relative movements occur in contact area. These relative movements produce the normal and tangential stresses, which have important role on... 

Growing demand on energy and limitation and consequence of fossil fuels have caused to utilize the clean and renewable energy sources. Hydrogen is a clean energy carrier which produced just water vapor during combustion. Today, methods which are usually used to produce this fuel are based on using fossil fuel compounds. Therefore, utilizing new production methods is unavoidable. One of these methods is using semiconductors such as TiO2 to spilt water and produce H2 by solar irradiation. Reducing the energy gap of these semiconductors to match the solar spectrum, specially in its visible range, modification of their structures, surfaces and stability are the main challenges in hydrogen... 

In this thesis the tow-dimensional wave propagation in a functionally graded elastic medium is considered. It is assumed that the stiffness and density of the medium vary continuously in one direction. This work presents analysis in both time and frequency domain. In time domain, a graded element is presented for static and dynamic analyses in FGMs. This element clearly simulates wave propagation in inhomogeneous materials. The most important property which an element must have to be reasonable in wave propagation analyses in FGMs is simulating reflection only from boundaries. In frequency domain a dynamic stiffness matrix is generated using stiffness and mass matrix used in time domain... 

Zinc oxide(ZnO) nanoparticles have been used in a wide-ranging of applications such as transparent UV protection, medical treatments, light emitting diodes, sensors and photovoltaic cells. Many applications of ZnO nanoparticles could be improved by changing the particle size, shape and morphology. In order to take advantage of the unique size dependent properties observed for ZnO anoparticles, knowledge of how particle growth can be controlled is required. As an alternative to transmittance electron microscopy (TEM), which is already used in the study of size and monodispersity of ZnO nanoparticles during synthesis, we proposed a simple spectrophotometric method coupled with chemometric... 

Aspect ratio dependant optical properties of silver and gold nanorods is responsible for great attention toward controlling the aspect ratio of this class of the nanostructure for their application in variety of area, such as medical diagnosis, drug delivery, biosensing and treatment. In this research, gold and silver nanorods have been synthesized using chemical reducation and growth based on seed mediated method, which is the newest and one of the best methods with less difficulty for producing silver and gold nanorods. Absorption of the visible light by gold and silver nanorods results in appearing the longitudinal and transverse Plasmon bands in their absorption spectra which is related... 

Statistics have shown an endemic worldwide increase of Autistic Spectrum Disorders (ASD) since the 1960s, Iran also faces the same problem. Autistic disorders are characterized by three major behavioral disorders: impaired social interaction, impaired communication, and impaired imagination and social creativity. The usage of robots in autism diagnosis and treatment has been increasing in recent years. In this study, our objective (as one of the pioneers in Iran) is to explore the clinical application of two interactive social humanoid robots (NAO and ALICE with the Iranian names of NIMA and MINA) as medical assistants in the treatment and education of children with autism in order to...