Sharif Digital Repository

The rapid adoption of the Internet of Things (IoT) has led to significant advancements in healthcare digitization and modernization. However, given the sensitive nature of medical data, security and privacy of such data have always posed major challenges. Moreover, resource constraints of IoT devices have necessitated the use of cloud resources for handling massive amounts of data in traditional approaches, introducing issues like single points of failure, processing delays, and security vulnerabilities. In this context, blockchain technology shows promise for enhancing security, decentralization, and returning data ownership. A robust solution should maintain confidentiality, enable access... 

Energy of graphs first defined by Ivan Gutman in 1978[1]. Let G be a graph with (0,1)-adjacency matrix A and let λ_1≥⋯≥λ_n be eigenvalues of A. Grap h energy is defined as the sum of absolute values of the eigenvalues of A and is shown by ɛ(G). let H_1,…,H_k be the vertex-disjoint induced subgraphs of graph G, it is proved that energy of G is at least equal to the sum of energy of H_i subgraphs, where the summation is over i. Also by partitioning edges of G to L_1,…,L_k subgraphs, energy of G is at most equal to sum of energy of L_i subgraphs , where the summation is over i. In this thesi s we study energy of graphs, specially... 

In recent years, the use of mesoporous silica nanoparticles as carriers of biological agents has increased. The use of nanometer dimensions in intra-body applications not only hides the particles from the view of macrophages and the body's immune system, but also causes the particles to enter the cells more easily through endocytosis. Template removal method is the most common method in the synthesis of mesoporous silica. In this method, the orderly arrangement of pattern-forming molecules is used to form pores. Until now, various types of organic materials have been used as pattern materials. The main goal is the synthesis of nanoparticles with the largest size of holes and the largest... 

In this project, for hydrodynamic simulation of RIPI experimental bubble column with concerning chemical reaction, first only hydrodynamic simulation and then hydrodynamic with reaction was done. For complete knowledge about bubble columns hydrodynamic, all common flow regimes were studied. First of all a rectangular semi-batch bubble column with bubbly flow regime and gas flow of 0.26 m3/h was simulated with commercial CFD software, FLUENT v. 14.5. Euler-Euler approach in 2D and 3D was used and because of bubbly flow regime a mean constant diameter was assumed for dispersed gas phase. Effect of interfacial forces (e. g drag, lift and virtual mass) was studied and compared with experimental... 

Membrane bioreactors (MBRs) which are commonly understood as the combination of membrane filtration and biological treatment using activated sludge have several advantages, but membrane fouling reduces the membrane efficiency, permeability and lifetime. An alternative is replacing a moving bed biofilm reactor (MBBR) with the activated sludge system which may reduce the effect of membrane fouling. The sludge produced in MBBRs has poor settling characteristics, therefore, their efficiency is limited by the sedimentation tank performance and they require a larger settling surface. The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of... 

Fischer-Tropsch synthesis (FTS) is the main part of a Gas to Liquid (GTL) process. In this reaction which shall be done based upon iron or cobalt catalysts, H2 and CO molecules (namely Syngas) transform to long hydrocarbon chains. Regarding all of the advantages of cobalt catalysts in comparison with iron counterparts, Research Institute of Petroleum Industry (RIPI) began investigations since two decade ago. The present catalyst comprised of cobalt as active metal, ruthenium as activity promiter and lanthanum as support (gamma alumina) modifier. By the way, still some areas such as its lifetime duration and deactivation needs to be improved by complimentary researches. The present... 

Value at risk of an asset, is the asset’s expected maximum loss for a certain period of time and at a specified confidence level. Value-at-Risk can be calculated in the bank with its inter-nal method or standardized method. when a method have more violation number then bank need to keep more daily capital requirements. under the Basel 2 agreement if the violation of method more than 10 times in year, the Bank uses the standardized method.
There are trade off Between daily capital charge and violations. Therefore, existing methods for calculating the value at risk, usually lead to much daily capital charge or many violations. Studies show with combination of different methods to calculate... 

Journals and conferences in computer science are the major venue for publishing new achievement in the field. It is an expert opinion that a number of top conferences in computer science are even more important than journals. In this work we aim at studying this in terms of citation analysis. To this end, we took 100 top journals and 63 top conferences and extracted their citation graph through Scopus dataset. We then constructed the citation graph in which the nodes were the journals and conferences and the links corresponded to the citations of the papers. We used various measures to rank the nodes in the graph. The ranking methods included Prestige, PageRank, Eigenfactor, HITS and SALSA.... 

The long term evolution (LTE) standard is introduced and developed by the 3rd generation partnership project (3GPP) based on orthogonal frequency division multiplexing (OFDM). OFDM systems, in spite of having many advantages such high performance in bandwidth usage, are very sensitive to inter carrier interference (ICI) as a drawback. In order to prevent ICI, the frequency offset, mainly caused by the miss-match between oscillators' frequency and also between the sampling frequency of the transmitter and the receiver, should be estimated and compensated. Frequency synchronization is a part of the tasks of a synchronizer. In this thesis, main tasks of a synchronizer are illustrated and... 

Value-at-Risk (VaR) is the most commontool for risk management. This tool is used to measure market risk and also used as a basis in determining financial standards for international financial institutions. VaR is the maximum loss of the asset portfolio at the specified confidence level and certain time horizon. Many parametric, nonparametric and semi parametric methods have been invented for VaR estimation. Each one of these methods has its advantages and disadvantages and different methods may perform better in differnet situations.When estimating VaR, we can choose one of these methods or we can combine the VaRs estimated by different methods. There are few researches conducted on VaR...