Sharif Digital Repository

Polyurethane elastomer networks were designed and synthesized based on hydroxyl terminated polybutadiene/polypropyleneoxide (HTPB/PPO) mixtures, 2,4-toluene diisocyanate and 1,4-butanediol. Various networks with different molar ratio of HTPB to PPO (0/100, 25/75, 50/50, 75/25 and 100/0) had been prepared. Depending on the length of soft segment, average functionality of polyol mixtures, mechanical and thermal properties of samples were varied. Our observations confirmed that final properties of the networks can be attributed to two synergistic factors: (a) formation of chemical network (crosslinking) and (b) soft segment length. An optimum composition was found. This optimum composition... 

This overview presents a tutorial introduction to the theory of magnetic plasma confinement in toroidal confinement systems with particular emphasis on axisymmetric equilibrium geometries, and tokamaks. The discussion covers three important aspects of plasma physics: Equilibrium, Stability, and Transport. The section on equilibrium will go through an introduction to ideal magnetohydrodynamics, curvilinear system of coordinates, flux coordinates, extensions to axisymmetric equilibrium, Grad-Shafranov Equation (GSE), Green's function formalism, as well as analytical and numerical solutions to GSE. The section on stability will address topics including Lyapunov Stability in nonlinear systems,... 

In this study, a hybrid of silica nanosphere/multiwall carbon nanotube (MWCNT) has been synthesized by wet chemical method at room temperature. The effect of MWCNTs, silica nanospheres and hybrid nanostructures (80% silica nanosphere/20% MWCNT and 50% silica nanosphere/50% MWCNT) on the thermal conductivity of distilled water has been investigated. SDBS was used as the dispersant to stabilize nanomaterials in the aqueous suspension and its concentration was 1.5 times of the concentration of nanomaterials. As results show, by increasing the concentration of nanomaterials, effective thermal conductivity of nanofluids increased. The most and the least enhancement in the effective thermal... 

This paper proposes a generalized analytical approach to evaluate the reliability of active distribution networks. The studies are implemented in the context of renewable-based energy hubs. The reliability of energy demands is determined as a function of reliability characteristics of energy hub input resources and converters as well as hub operating strategies. The framework proposed in this paper involves the main attributes of different distributed generation technologies as well as vehicle-to-grid (V2G)-capable vehicles in the reliability studies. Dealing with the uncertainty in energy services provided by the wind turbine output generation and V2G programs, efficient probabilistic... 

We have synthesized CdS nanocrystals (NCs) by a microwave activated method. CdSO4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The aqueous synthesis was based on the heat sensitivity of Na2S 2O3. In this method, microwave irradiation creates the activation energy for dissociation of Na2S2O3 and leads to the CdS NCs formation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses demonstrated hexagonal phase CdS NCs with an average size around 3 nm for sample prepared at 5 min irradiation time. A band gap range of 3.38-2.89 eV was possible only by increasing the microwave irradiation time, corresponding to a... 

In this paper, the analytical solution to a new class of nonlinear solitons is presented with cubic nonlinearity, subject to a dissipation term arising as a result of a first-order derivative with respect to time, in the weakly nonlinear regime. Exact solutions are found using the combination of the perturbation and Green's function methods up to the third order. We present an example and discuss the asymptotic behavior of the Green's function. The dissipative solitary equation is also studied in the phase space in the non-dissipative and dissipative forms. Bounded and unbounded solutions of this equation are characterized, yielding an energy conversation law for non-dissipative waves....