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Results on Clustering of Imprecise Points and Higher Order Voronoi Tessellations
, Ph.D. Dissertation Sharif University of Technology ; Haji Mirsadeghi, Mir Omid (Supervisor) ; Abam, Mohammad Ali (Supervisor)
Abstract
We study the problem of preclustering a set $B$ of imprecise points in~$\Reals^d$: we wish to cluster the regions specifying the potential locations of the points such that, no matter where the points are located within their regions, the resulting clustering approximates the optimal clustering for those locations. We consider $k$-center, $k$-median, and $k$-means clustering, and obtain the various results. Then we study the higher order Voronoi Tessellations as an important concept in clustering area. Generalizing Lee’s inductive argument for counting the cells of higher order Voronoi tessellations in $\Reals^2$ to $\Reals^3$, we get precise relations in terms of Morse theoretic quantities...
Adversarial Robustness Against Perceptual and Unforeseen Attacks in Deep Neural Networks in Images
, M.Sc. Thesis Sharif University of Technology ; Rohban, Mohammad Hossein (Supervisor)
Abstract
Improvements in deep neural networks and their widespread use in research and practical application have raised significant concerns about the robustness of these networks against adversarial examples designed to deceive a deep network in calcu- lating the correct output with a slight change in input. Since this is an essential issue in highly sensitive applications, it is necessary to use a training method that reduces the model’s sensitivity to these changes but still preserves the accuracy. The common method for this goal is training the model with adversarial examples. In other words, adversarial examples are generated during the training, and the model is trained with them. This allows...
Optimal Architecture for Vertical Take-off and Landing Vehicle
, M.Sc. Thesis Sharif University of Technology ; Malaek, Mohammad Bagher (Supervisor)
Abstract
This work investigates the characteristics of a typical Urban Air-taxi Network (UrAN) in terms of critical parameters, such as aircraft speed and capacity. With the help of a Multi-agent virtual environment (in this case, “Net-Logo”), we were able to show the relationship among key parameters affecting passenger displacement capacity in a simple network with two stations. The critical parameters include the aircraft (EVTOL) speed and its passenger capacity, together with the available number of take-off and landing pads at each station as well as the distance between the two immediate stations.The results of 400 simulations show that the capacity of passenger displacement in a simple UrAN...
Probabilistic Stability Analysis of a Railway Embankment on Dispersive Strata Subjected to Periodic Rainfall Conditions with Various Patterns
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor)
Abstract
The importance of rainfall pattern in assessing embankment stability and deformation is widely known. However, many studies have examined an embankment with simple rainfall patterns or used average and maximum ones. The importance of diverse rainfall patterns has also been overlooked in the study of divergent soil stability in the previous study. Therefore, the hydraulic properties of a natural soil with and without salinity potential and the stability analysis of the railway embankment located on this type of soil under various rainfall patterns are investigated. The study area is part of the Zahedan Chabahar National Railway Project, which is located on divergent soil and has high...
Correlated Stochastic Block Models and Graph Matching
, M.Sc. Thesis Sharif University of Technology ; Yassaee, Mohammad Hossein (Supervisor)
Abstract
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,...
Geochemical Simulation of Acidizing Sandstone Core Samples
, M.Sc. Thesis Sharif University of Technology ; Bazargan, Mohammad (Supervisor)
Abstract
Acidizing is one of the widely used practices of formation damage remediation. The success of this rather expensive job depends on the precise design and operation. Though, improper execution of an acid job, not only does not improve the formation damage but also can contribute to even more damage itself. For this purpose, it is critically important to thoroughly design an acidizing job conducting extensive lab experiments and utilizing numerical tools before operation in order for a successful acidizing. Unlike, carbonate acidizing, the chemistry of sandstone acidizing is very complex and challenging because of the wide variety of minerals and aqueous species present in the system. Hence, a...
Biosensor Fabrication for Fast Detection of Stroke Biomarkers
, Ph.D. Dissertation Sharif University of Technology ; Mousavi, Abbas (Supervisor) ; Abdekhodaie, Mohammad Jafar (Co-Supervisor)
Abstract
Stroke is the second most frequent cause of death and the leading cause of disability in the world. Some effective drugs have been developed for ischemic stroke, while the golden time of use is three hours. Therefore, if stroke is diagnosed quickly, its side effects can be greatly avoided. However, it is not possible to use conventional diagnostic methods in many cases at a short time. In this work, S100β, MMP-9 and D-Dimer biomarkers were selected for rapid diagnosis of stroke based on previous studies.For this purpose, electrochemical immunosensors were developed with advantages such as low cost, ease of use, the possibility to automating the device, suitable sensitivity, reproducibility,...
Towards Robust Anomaly Detectors by Fake Data Generation
, M.Sc. Thesis Sharif University of Technology ; Rohban, Mohammad Hossein (Supervisor)
Abstract
Detecting out-of-distribution (OOD) input samples at the inference time is a key element in the trustworthy deployment of intelligent models. While there has been a tremendous improvement in various flavors of OOD detection in recent years, the detection performance under adversarial settings lags far behind the performance in the standard setting. In order to bridge this gap, we introduce RODEO in this paper, a data-centric approach that generates effective outliers for robust OOD detection. More specifically, we first show that targeting the classification of adversarially perturbed in- and out-of-distribution samples through outlier exposure (OE) could be an effective strategy for the...
Estimation of Gasoline Demand Elasticity in Iran
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor) ; Vesal, Mohammad ($item.subfieldsMap.e)
Abstract
The price elasticity of gasoline demand is a key parameter in evaluation of various policy options. However, most of the literature uses aggregate data to identify this elasticity. Temporal and spatial aggregation make elasticity estimates unreliable. We employ a unique dataset of all gasoline transactions in Iran during a four-month period around an unexpected exogenous price change to identify price elasticity. After controlling for date and individual fixed effects we estimate a robust significant price elasticity of -0.127. Aggregation of the same data by week, month, and city yields an estimate of -0.3 indicating a significant bias in earlier studies. We also identify a significant...
Urban Traffic Analysis Using Limited Queries from a Predicting Source
, M.Sc. Thesis Sharif University of Technology ; Abam, Mohammad Ali (Supervisor)
Abstract
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,...
A Study in Genome Editing with Clustered Regularly Interspaced Short Palindromic Repeats
, M.Sc. Thesis Sharif University of Technology ; Sharifi Tabar, Mohsen (Supervisor) ; Rabiee, Hamid Reza (Co-Supervisor) ; Rohban, Mohammad Hossein (Co-Supervisor)
Abstract
Clustered Regularly Interspaced Short Palindromic Repeats, or in short, CRISPR is a relatively new technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding, or altering parts of the DNA. Initially found in the genomes of prokaryotic organisms such as bacteria and archaea, this technology can cure many illnesses such as blindness and cancer. A significant issue for a practical application of CRISPR systems is accurately predicting the single guide RNA (sgRNA) on-target efficacy and off-target sensitivity. While some methods classify these designs, most algorithms are on separate data with different genes and cells. The lack of...
Optimal Scheduling in Wirelessly-powered Communication Networks
, Ph.D. Dissertation Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor)
Abstract
In this thesis, we study optimal scheduling in a multi-hop wirelessly-powered network. We propose an online control policy for energy transfer from the energy access point to the wireless nodes and for data transfer among the nodes. With our proposed control policy, all data queues of the nodes are stable, while the average energy consumption of the network is shown to be within a bounded gap of the minimum energy required for stabilizing the network. Our proposed policy is designed using a quadratic Lyapunov function to capture the limitations on the energy consumption of the nodes imposed by their bachery levels. We show that under the proposed control policy, the bachlog level in the data...
Statistical Analysis of Dark Matter Halos in the Non-Linear Regime and Peaks of the Density Field in the Initial Conditions of the Cosmic Web
, M.Sc. Thesis Sharif University of Technology ; Baghram, Shant (Supervisor)
Abstract
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...
Persian Query Corrector Based on Deep Learning Networks (with Emphasis on Spatial Queries)
, M.Sc. Thesis Sharif University of Technology ; Izadi, Mohammad (Supervisor)
Abstract
The main spectrum of a location search engine is retrieving the locations that are most relevant to the user query. Geographic and spatial queries usually consist of a series of keywords that express the user's needs. The geographic search engine should retrieve the locations associated with the user request and then rank the retrieved results according to their relevance to the user request. In some cases, user requests may contain spelling errors that can greatly affect the results retrieved. Spell correction is automatic in the back spectrum recovery system. Spelling correction is the task of automatically recovering the intended text from a misspelled text. Therefore, spelling correction...
Tipping Cascades in Complex Networks: Dynamics and Control
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
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...
Data-driven Control of Complex Systems
,
M.Sc. Thesis
Sharif University of Technology
;
Rahimi Tabar, Mohammad Reza
(Supervisor)
Abstract
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...
Covering Orthogonal Art Galleries with Sliding k-transmitters
, Ph.D. Dissertation Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
The problem of guarding orthogonal art galleries with sliding cameras is a special case of the well-known art gallery problem when the goal is to minimize the number of guards. Each guard is considered as a point, which can guard all points that are in its visibility area. In the sliding camera model, each guard is specified by an orthogonal line segment which is completely inside the polygon. The visibility area of each sliding camera is defined by its line segment.Inspired by advancements in wireless technologies and the need to offer wireless ser- vices to clients, a new variant of the problems for covering the regions has been studied. In this problem, a guard is modeled as an...
Implementing a Variant of Hyperledger Fabric with Post-Quantum Digital Signature
, M.Sc. Thesis Sharif University of Technology ; Bayat Sarmadi, Siavash (Supervisor)
Abstract
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...
Incorporating Three Echelon Location, Routing and Inventory Decisions in Supply Chain Network Design with Heterogeneous Vehicle
, M.Sc. Thesis Sharif University of Technology ; Shadrokh, Shahram (Supervisor)
Abstract
A key driver of the overall productivity and profitability of a supply chain is its distribution network which can be used to achieve a variety of the supply chain objectives ranging from low cost to high responsiveness. Designing a distribution network consists of three subproblems: location–allocation problem, vehicle routing problem, and inventory control problem. Because of high dependency among these problems, in the literature there are several papers integrating two of the above problems: location–routing problems, inventory–routing problems, and location–inventory problems.
The three echelon location routing inventori problem (LRIP) is raised by the design of transportation...
The three echelon location routing inventori problem (LRIP) is raised by the design of transportation...
Integration of Production-inventory-routing Problem with Simultaneous Pickup and Delivery and Robust Optimization Approach
, M.Sc. Thesis Sharif University of Technology ; Akbari Jokar, Mohammad Reza (Supervisor)
Abstract
PRP is a combination of two classic problems. First one is the lot-sizing and the second one is vehicle’s routing which have been studied for more than fifty years. The prp is solved in attempt to jointly optimize production, inventory, distribution, routing decision and as a result, it is a inventory-routing problem as a whole. Despite the fact that prp involves a complex instructor, both universities and industries have been so eager to this problem since last decade. In this thesis an integrated assessment of PRP and various technics for solving the problem have been discussed. Moreover, taking into account the structure, hypothesis, and the constraints of the problem, a...