Sharif Digital Repository

Hyperledger Fabric is an open-source modular platform to launch permissioned-blockchains for use cases like banking and supply chains. This system uses the elliptic curve digital signature algorithm to authenticate transactions. The advent and progress of quantum computers have threatened the security of classical cryptographic schemes; therefore, the process of re- placing these schemes with post-quantum alternatives has gained considerable importance.This research intends to replace the elliptic curve digital signature algorithm with post-quantum digital signatures by using the algorithms passed to the third round of the National Institute of Science and Technologies (NIST) post- quantum... 

This thesis aims to create an electronic health system for transferring, verifying, and monitoring patient data. Blockchain technology is used in this system. In this system, the patient can communicate with the relevant hospital via an authentication protocol and transmit his data to the hospital. The hospital levels the patient's data creates the patient's treatment prescription and shares it with the pharmacy and insurance company to facilitate the patient's effective treatment. Blockchain technology has been used in a variety of electronic health systems. There are several problems with these systems, including the incorrect use of blockchain, a lack of comprehensiveness, a lack of... 

The electronic health system plays a crucial role in modern healthcare, facilitating efficient data management, secure information exchange, and improved patient care. However, existing systems often face challenges related to security, privacy, scalability, and interoperability. The primary objectives of this study are proposing a system that ensures data security, patient and peer privacy, scalability, data integrity, deniability, traceability, secure data sharing, access control, transparency, real-time monitoring, and security in the drug supply chain. To achieve these objectives, we have proposed a system that encompasses a wide range of requirements of healthcare system. To enhance... 

In this thesis, we first briefly review the basic concepts of stochastic processes. After reviewing and studying the dynamic equation that can explain a stochastic process, we show how one can find on a data-driven basis, the first-, second- and higher-order interactions between different subunits of a complex system by disentangling the dynamics of multivariate time series into stochastic and deterministic parts. Our data-driven approach is to detect different degrees of interactions obtained using conditional moments of Kramers-Moyal coefficients from unconditioned correlation functions and statistical moments of multivariate N-dimensional multivariate time series. Finally, we study the... 

Tipping points occur in diverse systems in various disciplines such as ecology, climate science, economy, sociology, and engineering. Critical thresholds in system parameters or state variables at which a tiny perturbation can lead to a qualitative change in the system exist in many subsystems in complex systems. These thresholds are called tipping points, and these subsystems are called tipping elements. Additionally, many systems with tipping points can be modeled as networks of coupled multistable subsystems. Domino-like tippings are called tipping cascades. Considering that these tipping cascades are primarily unprecedented, it is essential to study the dynamics and control of these... 

The aim of this thesis is to review the theory of deep learning with an experimental approach. In this thesis, we review researches that examine the impact of input selection on outputs in deep learning systems; Inputs we can control (samples, architecture, model size, optimizer, etc.) and outputs we can observe (the performance of the neural network, its test error, its parameters, etc.). Among the reviewed cases are the generalizability of deep learning systems, the effect of model components on its accuracy, interpolation and hyperparameters, as well as new phenomena in this field for which new frameworks have been defined  

One of the issues in the design and synthesis of the state or output feedback controller is the issue of fragility as the existence of disturbance in the coefficients of the designed controller causes instability in the controlled closed-loop system or leads to deterioration of its performance. The need to consider this point results in some novel approaches for designing the non-fragile controllers. Accordingly, defining criteria for measuring fragility is crucial.As well, due to the considered practical problems in the implementation of ordinary designed robust and optimal controllers, non-reachability of all the states of dynamical systems, and the boundedness for the quantity of the... 

Strongly Rayleigh measures are an important class of negatively dependent (repulsive) probability measures. These measures are defined via a geometric condition, called “real stability”, on their generating polynomials, and have interesting probabilistic properties. On one important property of negatively dependent measures is their rigid dependence structure. In other words, the it is impossible for these measures to have strong overall dependencies. In this thesis, we study two manifestations if this phenomenon: (1) paving property and (2) tail triviality. Informally, the paving property states that it is possible to partition the set of the components of every strongly Rayleigh random... 

Stochastic block models are the most common statistical models for simulating graphs with block structures. These models have been studied extensively for community detection problem and evaluating the performance of algorithms for community detection. Commu- nity detection has various applications in the study of social networks, protein networks, image processing, and natural language processing. In the classical setting, community detection is studied when only one graph is available. In 2021, a model for correlated stochastic block graphs was introduced, in which multiple edge-correlated graphs with the same block structure are observed. In this model, node labels are not available,... 

When we talk about the large-scale structure of the cosmos and the cosmic web, one of the important issues is to examine the location of the structures formed. We use statistical characteristics to check the cosmic web. Nearest neighbor distribution, two-point correlation, count in cell, etc. are some of the parameters that help us in this way. Our main problem in this project is to examine these statistical parameters in large scale structure for two different time periods. First, in the time period near the present age(z ≈ 0), we want to check these parameters for the dark matter halos that have formed the structure, and secondly, for the initial conditions and transition to high... 

In local transportation service companies, there is a need for estimation of arrival times (ETA) for customers. These companies not having the sufficient number of active online users, they are not able to obtain a proper estimation for ETA from that data. However, there are some overseas companies that have the established user base, and provide access to necessary data with a service fee. It is possible to solve this problem using the data which they provide.In this thesis, the problem of learning a hidden graph for the purpose of aiding local companies is explained and different aspects of it are introduced. In order to tackle this problem, first we define the idea of vertex separators,... 

Cells in their surrounding environment subjected to biochemical and biomechanical stimuli and respond to this signals. The mechanism by which cells transduce external mechanical signals into responses is called Mechanotransduction and cell use this mechanism to sense and respond to extracellular signals. Cells control processes like migration and division by mechanosensing. Cell migration is one of the most important responses to Cell-ECM interaction. This migration underlies many biological processes including embryogenesis, wound healing, tumorogenesis, morphogenesis and immune defense, so the study of cell migration is of particular importance. If there are external signals in cells... 

Few-shot learning methods have achieved notable performance in recent years. However, fewshot learning in large-scale settings with hundreds of classes is still challenging. In this dissertation, we tackle the problems of large-scale few-shot learning by taking advantage of pre-trained foundation models. We recast the original problem in two levels with different granularity. At the coarse-grained level, we introduce a novel object recognition approach with robustness to sub-population shifts. At the fine-grained level, generative experts are designed for few-shot learning, specialized for different superclasses. A Bayesian schema is considered to combine coarse-grained information with... 

Since the amount of data is increasing, it is important to reduce the size of components and circuits. For instance, bus routing problem, rectangle scape problem, and minimizing number of layers are important problems in printed circuit boards. Rectangle scape problem can be used as an estimation for minimizing number of layers problem. To minimize number of layers in this problem, we are given some axis-parallel rectangles inside a axis-parallel rectangular region. The objective is to extend one of the four boundaries of each rectangle in a certain direction such that all rectangles can be placed without any conflict in minimum number of layers. In this thesis, we analyze a common greedy... 

With the increase of competition in the world of business and the advent of modern technologies, many companies in the world have turned into integration. The need for flexibility, reduction of costs, establishing close and broad connection among suppliers, producers, and distributors has caused companies to integrate their own systems and organizations so as to survive and keep going in today’s competitive, ever changing environment and finally gain competitive advantage. Supply chain management as a support for essential and operational processes of the organization is not an exception from this integration rule. Despite many views on the integrity of the supply chain, yet there is no... 

Managing the supply chain is a competitive necessity in today's global marketplace where differentiation between products and services means providing a total value package that can compete for an increasingly discerning and empowered customer. Today's view is one of integration. Supply chain management is the integrated management of business links, of information flows and of people. This research is based on a study conducted to introduce a reference model for Supply Chain integration. In that study, 10 drivers are introduced as keys for integrity in Supply Chain. The objective of this article is to discuss a method which has been developed to measure objectively and quantify the level of... 

The integration of pricing and production planning decisions has attracted many researchers and industry professionals, as these decisions directly affect the highest and lowest levels of a company. In this thesis, an integrated production-price problem for two complementary products is studied. Regarding the negative correlation of the two products, different sales strategies, including unbundling, pure bundling and mixed bundling, are used and three distinct models are proposed for each one. In the models, real and important assumptions such as production capacity limitation, shared resources, and the cost of preparation are considered. The goal of solving these models is to determine the... 

On-board hydrogen storage systems (as a substitute for fossil fuels) employing high-pressure metal hydrides, promise advantages including high volumetric capacities and cold start capability. In this project, we discuss the development of a system simulation model in Matlab/Simulink platform. Transient equations for mass balance and energy balance are presented. During driving, the bed requires external heat source, which is planned to be supplied by rejected heat from proton-exchange membrane (PEM) fuel cell. Therefore, this study develops a system-level dynamic model of a PEM fuel cell that is capable of characterizing the mixed effects of temperature, gas flow and capacitance, with... 

In this thesis, variable order operators as a generalization for fractional operators are introduced and their characteristics are investigated. Then fractional variable order systems are defined whose their corresponding differential equations are stated by variable order operators. Most of this research delineate some beneficial control characteristics of fractional variable order systems. The first is type number subject. In this section two important theorems are stated which are useful in determining type number in an intensive range of systems. The other important subject is norm of functions. In this part a useful theorem is presented that states a sufficient and necessary condition... 

As an essential laboratory instrument in aerospace engineering, wind tunnels need to be calibrated. Therefore, this thesis takes into account the calibration of the subsonic wind tunnel at the Sharif University of Technology, with the test section dimensions of 90 × 42 × 30 cm3. It is necessary to accurately and correctly determine the effective parameters for the wind tunnel results to be reliable. A pitot-static tube, a standard wing, pressure sensors, a force balance, a turbulence sphere, rake, yawhead, a digital level, a protractor, and a data acquisition system were used for this experiment. For calibration, variables including flow uniformity, flow Angularity, turbulence intensity,...