Sharif Digital Repository

In this work, a more accurate prediction of liquid evaporation flux has been achieved. The statistical rate theory approach, which is recently introduced by Ward and Fang and exact estimation of vapor pressure in the layer adjacent to the liquid-vapor interface have been used for prediction of this flux. Firstly, the existence of an equilibrium layer adjacent to the liquid-vapor interface is considered and the vapor pressure in this layer and its thickness calculated. Subsequently, by using the Fick's second law, an appropriate vapor pressure expression for the pressure of equilibrium layer is derived and by this expression and the statistical rate theory approach, evaporation flux is... 

This paper presents an optimum pre-filter for ICA based multi-input multi-output OFDM system. In our former work, we presented a pre-filter solution for multiuser reconstruction in ICA based MIMO-OFDM systems [1,2]. Here, based on the structure of the system and former pre-filter solution, an optimization problem has been designed to give us the optimum pre-filter. The designed problem is based on minimization of the estimation error of ambiguities inherent to ICA in reconstruction of the data after separation. The optimization problem is mathematically solved and a set of optimized coefficients are obtained. Among the obtained set as optimum coefficients, optimum coefficients are acquired... 

This paper presents an Optimum pre-filter for ICA based mulit-input multi-output OFDM System. In our former work, we presented a pre-filter solution for multiuser reconstruction in ICA based MIMO-OFDM systems [1], [2]. Here, based on the structure of the system and former prefilter solution, an optimization problem has been designed to give us the optimum pre-filter. The designed problem is based on minimization of the estimation error of ambiguities inherent to ICA in reconstruction of the data after separation. The optimization problem is mathematically solved and a set of optimized coefficients are obtained. Among the obtained set as optimum coefficients, optimum coefficients are acquired... 

Effect of different conditions on shear behaviour of rock has been investigated by various researchers. As known, in larger scale the continuity of the rock material is interrupted by separated planes such as bedding planes, faults, shear zones, closure and the behaviour converts to be inelastic and anisotropic. Generally, discontinuities appear repeatedly in more than one preferential direction, creating a three dimensional structure, reducing its stiffness and shear strength as mechanical effects and increasing its transport velocity associated with discontinuity flow as hydraulic effects. They also make rock behavior more complex and different compared to the behavior of soil. According... 

Dynamic properties of soil, such as shear modulus and damping ratio, are necessary for analyzing the dynamic response of the soil in geostructures. This study investigates the effects of partially inherent anisotropy and stress-induced anisotropy on the shear stiffness of unsaturated soil through a series of dynamic hollow cylinder tests at medium strain levels. The different inherent anisotropy in tested sand specimens was introduced through different compaction water contents in the sample preparation stage while keeping the void ratio nearly constant. Moreover, the influences of the angle of maximum principal stress, α, and intermediate principal stress parameter, b = (σ2 − σ3)/(σ1 − σ3),... 

The cosmological constant term can be seen as a constant potential for a (scalar) field. In this viewpoint, at late times, the field is stopped rolling and behaves as a cosmological constant (w=-1). While at the early Universe, its kinetic term can be dominant and behaves as a stiff fluid (w=+1). This new phase lowers the cosmological sound horizon by increasing the Hubble parameter for very high redshifts. Consequently, the lower cosmological sound horizon results in the higher Hubble constant at the present time. This early phase ends before the photon decoupling, so we do not expect any new physics after the last scattering surface. We checked this model in the presence of (reduced) CMB,... 

This letter investigates the deterministic design of pilot power and pattern for sparse channel estimation in OFDM systems based on minimizing the coherence of the DFT sub-matrix. It has been suggested that the pilot pattern forming a cyclic difference set (CDS) or almost difference set (ADS) is optimal. So, we proposed a deterministic procedure that jointly optimized for pattern and power of pilots as a solution. First, pilot patterns forming CDS/ADS were gathered through a search. Then, the power was numerically allocated to the different pilots from all the patterns. Finally, the pilot pattern and power pair leading to minimum coherence was selected from the available pairs. Simulation... 

In this paper, the problem of finding the shortest path between two points in the presence of single-point visibility constraints is studied, In these types of constraint, there should be at least one point on the output path from which a fixed viewpoint is visible. The problem is studied in various domains, including simple polygons, polygonal domains and polyhedral surfaces. The method is based on partitioning the boundary of the visibility region of the viewpoint into a number of intervals. This is done from the combinatorial structure of the shortest paths from the source and destination to the points on the boundary. The result for the case of simple polygons is optimal with O(n) time... 

In this paper, we study the problem of finding the shortest path between two points inside a simple polygon such that there is at least one point on the path from which a query point is visible. We provide an algorithm which preprocesses the input in O (n2 + n K) time and space and provides logarithmic query time. The input polygon has n vertices and K is a parameter dependent on the input polygon which is O (n2) in the worst case but is much smaller for most polygons. The preprocessing algorithm sweeps an angular interval around every reflex vertex of the polygon to store the optimal contact points between the shortest paths and the windows separating the visibility polygons of the query... 

We study a constrained version of the shortest path problem in polygonal domains, in which the path must visit a given target polygon. We provide an efficient algorithm for this problem based on the wavefront propagation method and also present a method to construct a subdivision of the domain to efficiently answer queries to retrieve the constrained shortest paths from a single-source to the query point. © 2008 Springer-Verlag Berlin Heidelberg  

We study a constrained version of the shortest path problem in simple polygons, in which the path must visit a given target polygon. We provide a worst-case optimal algorithm for this problem and also present a method to construct a subdivision of the simple polygon to efficiently answer queries to retrieve the shortest polygon-meeting paths from a single-source to the query point. The algorithms are linear, both in time and space, in terms of the complexity of the two polygons. © 2004 Elsevier B.V. All rights reserved  

Computing the period of the periodic functions is the main reason of using Simon’s algorithm to attack symmetric-key cryptographic primitives. However, if the target function does not satisfy Simon’s promise completely or if the number of superposition queries of the adversary is limited, Simon’s algorithm cannot compute the actual target period, unambiguously. These problems may lead to the failure of period-finding-based quantum attacks.Our main aim in this paper is to relax Simon’s algorithm so that quantum adversaries can still carry out the mentioned attacks without any assumptions (Simon’s promise) on the target function. To that end, we use two different methods, each of which is...