Sharif Digital Repository

Tungsten Inert Gas (TIG) process and different cored wires that were filled separately with nano TiC particles, micro TiC particles and graphite powders were employed to produce surface composite coating on CP-Ti substrate to improve wear resistance. At first using titanium strips, wire drawing process and different powders various cored wires were produced and then using TIG, these cored wires were coated on CP-Ti. This process was done for different current intensities and velocities. Composite coating tracks were found to be affected by the TIG heat input and the kinds of the cored wires. The microstructures of the surface composite coating showed phases of α'-Ti and primary and dendritic... 

Analog-to-digital conversion and signal processing has been increasing due to its many advantages. So that mostly we prefer to convert signal from analog area to digital samples, then they are processed and finaly put the result signal at the system output. How ever because the restriction of the sampling rate, Prevent the spread of digital processing for the high-frequency signal (RF). In recent years, ADCs sampling rate rise up to several GHz (for example ADC with 4 GSPS and 12 bits for TI) that output of the these ADCs by powerful and fast FPGAs are processed but According to Shannon theorem band width of these ADCs is not desirable.the goal of this thesis uses of the compressed sensing... 

This is common for organizations to don't move in their specified mission statement direction, because of pressures for saving themselves in reaction to environment changes. This problem can be addressed as conflict between survival and identity. In this thesis we approach this problem by synthesizing "Viable System Model" and "System Dynamics". Basic of this model shaped on viable system model structure and system dynamics modeling. In literature there is only two such models. But they are not detailed enough for providing mathematical analysis. In this research, law of requisite variety (one of the key principles in cybernetics) has been quantified. In this synthetic model, appropriate... 

Observations of cosmic microwave background (CMB) and large scale structure show that standard model of cosmology ΛCDM is consistant with observational data. The standard model is defined by cold dark matter, cosmological constant and also Gaussian inital conditions which are almost scale-invariant, adiabatic and isotropic.while this model is consistant with observational data, there exist a couple of problems namely the problems of dark energy, dark matter, missing baryon and early universe. One of the most recent methods to analyse cosmological models which is tightly ascociated with structure formation is the use of galaxy clusters distribution function and the effect of such structures... 

Space debris have increasing importance for space missions. The towing removal scheme is one of the most promising ways for active removal of these debris from LEO orbits. In this approach, an active propelled satellite captures the debris via a space tether and a tethered net which by producing a force opposite to its velocity, it will cause deorbiting and burning the debris in the dense atmosphere. One of the issues with this technique is the danger of tether rupture which for solving that two tethers instead of one can be used. In this research study of active removal of flexible space debris via double tethered towing system has been done. Dynamic modeling has been done with Newton’s and... 

In this thesis, we study the heterogeneous vehicles routing problem, which is a general-ization of the well-known travelling salesperson problem. In this problem, we are given a set of heterogeneous vehicles located in specific depots, along with a set of customers in the form of a graph. The vertices of the graph represent clients and depots, and the weight of edges represents the cost of travel between vertices of the graph. The goal is to find a subgraph for each vehicle so that the union of the subgraphs contain all customers and the total travel cost is minimized. The heterogeneity here means that the cost of traversing edges for each vehicle might be different. In this work, we briefly...