Sharif Digital Repository

The subject of Secret Sharing refers to the methods that a secret information is shared (by a dealer) among a number of parties, so called participants, each having one or more shares, such that the predefined subsets of the participants, called authorized subsets, are able to regenerate the secret using their shares. A more general scheme which is called Multi Stage Secret Sharing (MSSS) is to share multiple secrets among the participants such that the authorized subsets can reconstruct the secrets in the consecutive stages; in these schemes, in addition to the individual shares, the dealer should provide the participants with a number of public values regarding the secrets. A Multi-Secret... 

All known examples of homogeneous Einstein spaces with negative scalar curvature (non compact) are isometric to standard Einstein solvmanifolds . we prove that any nilpotent Lie algebra having a codimension-one abelian ideal is the nilradical of a rank –one Einstein solvmanifold . In other words this nilpotent Lie algebra admits a rank-one solvable extension which can be endowed with an Einstein left invariant Riemannian metric . also a curve of pairwise non-isometric 8-dimensional rank-one Einstein solvmanifold is given .
 

One of the main purposes of this project is to propose an efficient and stable algorithm of a semi-discretized formulation for compositional simulation of oil reservoirs. In this algorithm, all the equations including both mass balances and equilibrium equations are solved simultaneously. The gradient terms are discretized by the Finite Volume Method (FVM). The resulting Differential Algebraic Equation, the so-called DAE, are solved by MATLAB functions. Another novel technique developed, handles each block equations set, separately. In this block-by-block scheme, there are two set of equations; the primary (mass balance) and secondary (equilibrium) equations. In the primary ones, the... 

One of the main purposes of this study is to present a robust and yet efficient semi-discretized algorithm for compositional simulation. All the equations including both the mass balance and the phase equilibrium equations are solved simultaneously which forms a Differential-Algebraic set of Equations and is solved by utilizing an efficient MATLAB solver. Furthermore, another formulation and algorithm is proposed which is consisted of two sets of equations, the primary equations (differential mass balance equations) and the secondary equations (the algebraic phase equilibrium equations). The gradient terms in the primary equations are discretized by using finite element method (Galerkin... 

The preferences of participants can have negative impacts on the efficiency and welfare of peer-to-peer energy communities. If the preferences of participants lead to suboptimal market participation and energy consumption, it can result in price fluctuations, increased costs, and reduced participation in peer-to-peer energy markets, ultimately diminishing community welfare. To demonstrate the effect of participants preferences in the peer-to-peer market, a fully decentralized peer-to-peer energy market for prosumers equipped with photovoltaic production and storage is designed and modeled. In the proposed market, prosumers are divided into buyers and sellers and can trade energy bilaterally.... 

Two-phase fluid flow physics in porous media is applied in various fields. Studies have shown that wettability and surface tension, which represent fluid-rock and fluid-fluid interactions, have a significant effect on the dynamics of the immiscible displacement. Although the effects of wettability and surface tension on the macroscopic behavior of fluid flow are known, there is less understanding of it at the micro scale. Considering the essential role of wettability and surface tension in various fields, this project seeks to investigate the effects of wettability and surface tension on the movement and distribution of fluids and the dominant displacement mechanisms within the porous media... 

This thesis develops a multi-market equilibrium framework for analyzing retail electricity markets, with a focus on the interaction between the forward and spot markets under conditions of network uncertainty and renewable integration. We explore `the role of retailers’ hedging strategies, forward contract demand, and their impact on market efficiency. By modeling the forward price and the retailer’s optimal forward position under mean-variance preferences, we derive key equilibrium conditions for the spot, forward, and retail markets. Our results show that an increase in uncertainty leads to lower hedge ratios, even in the face of higher price variance. Numerical simulations using Monte... 

Permeability is an essential parameter used for reservoir evaluation, simulation and management to optimize oil recovery. The conventional approach to estimate reservoir connectivity, conductivity, sweep efficiency and other critical information for decision-making is to build detailed geological models, which are then upscaled to a coarser grid where flow simulations are run. However, this takes many hours to be carried out even for a single realization practically. In practice, a very small number of realizations are considered and consequently the true uncertainty in the results is very poorly estimated. In this study, a statistical model of isotropic overlying sandbodies is used to... 

In this thesis, with a review on policy simulation and economic reform analysis literature, we design a suitable method to analyze the effects of monetizing energy carriers subsidy on welfare criteria of Iranian households. The selected method is limited general equilibrium that needs demand estimates of goods, services and energy. In firs step,based on 13 years of data on “Iranian Households’ Expenditures and Income” surveys, data are provided as a pseudo-panel. Demand equations are estimated using “Seemingly Unrelated Regressions” for panel data, and elasticities are calculated. In the next step, we evaluated the equivalent variation and equivalent gain measures in each price scenarios.... 

This thesis finds evidence for the presence of adverse selection in the Iranian life insurance market. We use a unique dataset including more than one million policyholders’ profile information alongside their chosen life insurance coverage from the largest Iranian insurance company. Our results not only find evidence in support of adverse selection in this market, but also consider the magnitude of adverse selection relatively notable. Moreover, we found that in addition to the coverage, the other dimensions of contract could be the potential source of adverse selection. Particularly, we focused on the insurance duration and the payment method (monthly, annually, all-in-advance).... 

In this research we have studied the changes in the technology performance in the smartphone industry, and by using theoretical models in technology management literature, we have compared this performance with coustomer’s required level of performance. The study shows that after 2011, the level of customer satisfactions depends less on the technology performance and more on the price. This observation is consistent with Christiensen’s suggested model for technology performance, in which after a certain point technology’s performance surpasses the customer’s need. In addition, we have studied the effect of modular design for smartphones on the customer’s satisfaction. We found that... 

Retrofitting of old mechanical structures by composite materials is one of the most important issues of the world.High reproducing and replacement cost of structures leads to, researchers try to retrofitting old structures and increase their capabilities and so increase their service age. Their research results leads to decreasing cost in one hand and introduce new application of composites in aviation industry in the other hand.Retrofitting mechanical structures show us the important of elements with more stress than the others. The probability of failure is more in these element than the other that we call critical element.These elements in fact are critical parts of an aerial structures... 

Michael Zimmerman in his book Living with Uncertainty has objected to two views of moral obligation, namely objective and subjective view. Two overcome these problems he suggests a third view which he calls prospective view and tells us that our moral obligation is determined by the prospection that each of our choices give us. In this thesis first I review Zimmerman’s objections to objective and subjective view. Then I try to suggest a solution for the objective view