Sharif Digital Repository

Scaled model test in towing tank is a common method to predict the ship resistance in calm water. The scale effects are dominant in these tests because the Reynolds and Froude numbers of the model and full-scale ship cannot be equal. There is a sufficient amount of knowledge about the displacement hulls which have limited speed ranges in most cases. However, scarcity of published data on high-speed crafts is noticed. The influence of the model length on ship resistance varies in different speeds, so it should be studied in more detail. The extrapolation method of model ship resistance to full scale is studied in this paper for high-speed monohulls. Resistance model tests of semi-displacement... 

Plasmonic Sierpinski nanocarpet as back structure for a thin film Si solar cell is investigated. We demonstrate that ultra-broadband light trapping can be obtained by placing square metallic nanoridges with Sierpinski pattern on the back contact of the thin film solar cell. The multiple-scale plasmonic fractal structure allows excitation of localized surface plasmons and surface plasmon polaritons in multiple wavelengths leading to obvious absorption enhancements in a wide frequency range. Full wave simulations show that 109 % increase of the short-circuit current density for a 200 nm thick solar cell, is achievable by the proposed fractal back structure. The amount of light absorbed in the... 

In this paper, we evaluate how traffic-load dependent vehicle routing at intersections is able to improve the connectivity status of all streets. To this end, we consider a VANET scenario, comprised of several streets and intersections. Then, we focus on two vehicle routing algorithms, one based on the distance to destination, i.e., traffic-load independent (TLI) algorithm, and another one based on both distance to destination and traffic load status of the local streets, i.e., traffic-load dependent (TLD) algorithm. By employing a simple mobility model based on an open BCMP queueing network, we derive the spatial traffic distribution at two cases. Afterwards, we propose a simple algorithm... 

Enlargement of ship size in recent decades and no change in the harbors and approach channels have resulted in global attention toward navigation in shallow and confined waters. A phenomenon which restricts ship navigation in shallow waters is reduction of under-keel clearance in terms of sinkage and dynamic trim, which is called squatting. Due to the complexity of flow around the ship hull, one of the best methods for predicting the ship squat is the experimental approach based on systematic model tests in the towing tank. In this study, model tests for tanker ship model and traditional Persian Gulf and Oman Sea vessel called dhow had been performed in the towing tank and the squat of the... 

One of the phenomena restricting the tanker navigation in shallow waters is reduction of under keel clearance in the terms of sinkage and dynamic trim that is called squatting. According to the complexity of flow around ship hull, one of the best methods to predict the ship squat is experimental approach based on model tests in the towing tank. In this study model tests for tanker ship model had been held in the towing tank and squat of the model are measured and analyzed. Based on experimental results suitable formulae for prediction of these types of ship squat in fairways are obtained  

In this article, a v2f model is employed to conduct a series of computations of incompressible flow in a periodic array of square cylinders simulating a porous media. A Galerkin/least-squares finite element formulation employing equal order velocity-pressure elements is used to discretize the governing equations. The Reynolds number is varied from 1000 to 84,000 and different values of porosities are considered in the calculations. Results are compared to the available data in the literature. The v2f model exhibits superior accuracy with respect to κ - ε results and is closer to LES calculations. The macroscopic pressure gradients for all porosities studied showed a good agreement with... 

In this article a v2f model is employed to conduct a series of computations of incompressible flow in a periodic array of square cylinders simulating a porous media. Galerkin/Least-Squares finite element formulation employing equal order velocity-pressure elements is used to discretize the governing equations. The Reynolds number is varied from 1000 to 50,000 and different values of porosities are considered in the calculations. Results are compared with the available data in the literature. v2f model exhibits superior accuracy with respect to k - ε results and is closer to LES calculations. The macroscopic pressure gradients for all porosities studied, showed a good agreement with... 

Two different ternary nanocomposites, PPy/CNT/CoFe2O4 and PPy/CNT/NiFe2O4, were synthesized by in situ polymerization method. The resulting composites were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. They were evaluated with the aim of investigating microwave absorption properties. The results showed that the value of microwave reflection decreases as that of prepared nanocomposites increases. This happens with increase in the PPy content and polymerization on the surface. © 2018 Académie des sciences  

The general goal of the facility layout problem is to arrange a given number of facilities to minimize the total cost associated with the known or projected interactions between them. One of the special classes of the facility layout problem is the Single Row Facility Layout Problem (SRFLP), which consists of finding an optimal linear placement of rectangular facilities with varying dimensions on a straight line. This paper first presents and proves a theorem to find the optimal solution of a special case of SRFLP. The results obtained by this theorem prove to be very useful in reducing the computational efforts when a new algorithm based on tabu search for the SRFLP is proposed in this... 

In this paper, we have discussed the results of sensitivity analysis in a payoff matrix of the Matching Pennies game. After representing the game as a LP model, the sensitivity analysis of the elements of the payoff matrix is presented. The game value and the optimal strategies for different values of parameters are determined and compared  

In this paper, a hierarchical RVE-based continuum-atomistic multi-scale procedure is developed to model the nonlinear behavior of nano-materials. The atomistic RVE is accomplished in consonance with the underlying atomistic structure, and the inter-scale consistency principals, i.e. kinematic and energetic consistency principals, are exploited. To ensure the kinematic compatibility between the fine- and coarse-scales, the implementation of periodic boundary conditions is elucidated for the fully atomistic method. The material properties of coarse-scale are modeled with the nonlinear finite element method, in which the stress tensor and tangent modulus are computed using the Hill-Mandel...