Sharif Digital Repository

An important step in the early stages of an oilfield development is the accurate identification of the location of production and injection wells which has a significant impact on productivity and profitability of the reservoir. Recently, operation companies in petroleum industry focus on production optimization, recovery enhancement and cost reduction; as a result, application of non-conventional wells (NCW) or non-vertical wells have dramatically increased. Well placement optimization is a complicated task as it is a function of several contributing factors including reservoir heterogeneities and economic constraints. The complexity of this task increases when it is considered as a... 

Economics have been thought about market, trade and money in many eras. During years, several issues regarding markets and making economic decisions have become more complicated, due to population growth and changes in market structure.we are going to discuss the classic model of Cournot in social networks in two competence companies which both produce identical products. Each individual considers a value for each product. lf friend it an individual buy a product then it can effect the individual's value of product. In this model, each company decides on quantity of its products and the selling price of products is calculated based on the amount of all productions. In Cournot model, at the... 

In  this  dissertation,  we  investigate  the  frequency  hopped  spread  spectrum  systems  which are extensively used in many communication systems. We derive the capacity region  of  Synchronous  Frequency  Hopped  Multiple  Access  (FHMA)  channels  (for  any  kind of noisy or nonselective fading environment) by using the side information which exists in the multi‐user detection. We assume that random hopping patterns are used by all the transmitters, and the common receiver knows the hopping patterns. We also compute  the  capacities  of  FHMA  with  and  without  power  control  for  AWGN  and  noiseless MFSK (in particular BFSK) modulated systems and compare the ... 

Regarding to the emergence of quantum computers and advances in the large scale implementation of them, exploiting hard problems of coding theory is of great importance.This family of problems, like those of lattices, has an acceptable resistance against classic and quantum attacks. Thus, they can be replaced with hard problems in number theory and algebra. Increasing dominance of cyberspace made us highly dependent to it. Consequently, preparing tools and methods to mitigate future threats is necessary. Digital signatures constitute an important family of cryptographic primitives. Code-based digital signatures are mostly suffering from two main drawbacks: large public key and long time of... 

“Decode and Forward” is one of coding strategies used in relay channel and networks in which each relay in the network decodes the transmitted message by the sender and other relays in the network and then re-encode and transmit it to the other relays and the receiver in the network. This process results in the cooperation between the relays and the sender to remove the uncertainty of the receiver about the transmitted message. “irregular encoding-successive decoding”, “regular encoding-backward decoding” and “regular encoding-sliding window decoding” are different methods usually used in “Decode and Forward” strategy. “partial decode and forward” is a generalized form of “decode and... 

In this thesis the problem of simultaneously generating multiple keys among multiple terminals is investigated. After providing a survey on the related works and exploiting the problem of sharing a common secret key and a private key among three terminals, we introduce a new source model which we call it the Four-Terminal model. We consider the problem of generating three kinds of keys among legitimate terminals and investigate the problem under two different scenarios, Backward and Forward scenarios, which depend on the kind of restrictions imposed on the usage of the public channel. We derive an achievable region for the backward scenario, using the combination of superposition coding and... 

In order to utilize cooperative resources of a network, we have to investigate cooperative networks and strategies. Information theory, by introducing different concepts such as coordination and common information, gives us a suitable tool to study cooperative networks and using their resources. In this thesis, we investigate coordination and secret key agreement in cooperative networks. Our study consists of two parts. In the first part, we consider coordination and its applications in cooperative networks. For this purpose, we introduce the triangular multiterminal network as a proper model for studying empirical coordination in multiterminal networks and establish an inner and outer... 

In this thesis, the problem of secret key agreement in the channel model with side information is studiedx. In order to investigate the problem, we consider three models according to the different ways of side information availability which are the state-dependent broadcast channel; the state-dependent broadcast channel in presence of public channel and the state-dependent wiretap channel with degraded versions of the channel state information.For the problem of secret key agreement in broadcast channels, two models, the state-dependent wiretap channel and state-dependent three receivers broadcast channel, are considered. We obtain inner and outer bounds of the secret key capacity region for...