Sharif Digital Repository

Let R be a ring with unity, M be a unitary left R-module and I(M)* be the set of all non-trivial submodules of M. The intersection graph of submodules of M, denoted by G(M), is a graph with the vertex set I(M)* and two distinct vertices N and K are adjacent if and only if N\K ̸= 0. We investigate the interplay between the module-theoretic properties of M and the graph-theoretic properties of G(M). We characterize all modules for which the intersection graph of submodules is connected. Also the diameter and the girth of G(M) are determined. We study the clique number and the chromatic number of G(M). Among other results, it is shown that if G(M) is a bipartite graph, then G(M) is a star... 

The purpose of this thesis is to find upper bounds for the eigenvalues of natural operators acting on functions on a compact Riemannian man-ifold (M, g) such as the Laplace–Beltrami operator and Laplace-type operators. In the case of the Laplace–Beltrami operator, two aspects are investigated:
The first aspect is to study relationships between the intrinsic geometry and eigenvalues of the Laplace–Beltrami operator. In this regard, we obtain upper bounds depending only on the dimension and a conformal invariant called min-conformal volume. Asymptotically, these bounds are consistent with the Weyl law. They improve previous results by Korevaar and Yang and Yau. The proof relies on the... 

Raising number of vehicles and increasing tendency of people to possess their own cars have posed a lot of expenses on users. One of the most significant of them is the time it takes to travel between origin and destination. Several researches have been conducted so far in order to evenly distribute travel times among transportation network users. A variable that has been neglected in many of these studies is travel time variability. Users, obviously, need to know not only the travel time, but also the probability of varying this time. In this research, an analytical model has been developed on a geometrical basis that includes both traffic conditions and intersection characteristics to... 

The so-called intersection problem has been considered for many different combinatorial structures, including Latin squares. This intersection problem basically takes a pair of structures, with the same parameters and based on the same underlying set, and determines the possible number of common sub-objects (such as blocks, entries, etc.) which they may have. The intersection problem has also been extended from consideration of pairs of combinatorial structures to sets of three, or even sets of , where may be larger than 3. In this thesis, we study the related problem of determining, for all orders n, the set of integers k for which there exists = 4 Latin squares of order n having... 

A moduli spase consists in classifying geometric objects up tp equivalence relations and its point are in 1-1 corrospondence with equivalence classes. One of the most important moduli spaces in algebraic geometry is «moduli space of stable n-pointed curves of genus zero» which has many applications in mathematics and theoretical physics.In [10] Knudsen shows that for every n 3 there is a smooth projective variety Xn that is a moduli space for stable n-pointed curves of genus zero.In this thesis we study moduli spaces and introduce Xn and its relation with cross ratios. This way we show Xn is smooth projective variety and a fine moduli space. [5] After that we study a paper by Sean Keel. [9]... 

In recent years, different cryptographic tools have been introduced for a wide range of cloud computing applications that can be classified based on a trade-off between performance and security. In this thesis, we introduced the private set operation schemes, and at their heart, private set intersection schemes, in the cloud computing platform. These schemes are of particular importance because they can be used as basic cryptographic schemes for a wide range of functionalities in the cloud platform. Using these schemes, the user can securely store datasets on the cloud, run set queries remotely and receive the desired results. To this end, we first modeled the syntax and the security notions... 

In a discrete network design problem (DNDP), an optimal set of projects is chosen from suggested projects to expand a transportation network. The optimal set is selected by minimizing the total travel time with respect to the budget constraint. This problem is formulated as a bi-level optimization. In the current study, traffic assignment is solved at the lower level as a user equilibrium problem by considering the delay of intersections which is the major portion of total intra-city travel time. This study investigates the performance of the transportation network with more realistic assumptions compared to the previous studies in the network design problem.This study uses the branch and... 

Pedestrian accidents involve most of traffic accidents mainly happen in urban intersections (signalized or non-signalized). The present research is to identify and evaluate the factors influencing the pedestrian decision while crossing the street at signalized intersections. The data used in this study are captured by recording the behavior of 596 pedestrians while crossing 2 signalized intersections in Karaj. To better identify the variables affecting the behavior of pedestrians, such as age, education, etc., 394 people have been interviewed in person. The factors affecting the pedestrian behavior are divided into two general groups: 1- Social, demographic, economic, family, and other... 

Secure multi-party computation (MPC) enables a group of mutually distrustful parties to compute a joint and agreed upon function of their private inputs without disclosing anything but the corresponding output. One of the most important secure computation protocols is private set intersection (PSI). In PSI, often two or several parties wish to find the intersection of their sets without revealing other non-common elements. There exist some other variants of PSI protocol like PSI cardinality or threshold PSI which in the former only the cardinality of the intersection set is revealed and in the latter the intersection set is revealed if its cardinality is greater (less) than a certain value.... 

In railway transportation network, there are spots that we have to intersect with highway network. These intersections break into two branches named grade crossing and unlevel crossing depend on their structure. Grade crossings from the view of protection are grouped into protected crossings and unprotected crossings. Protected crossings depend on their traffic control devices are categorized into active crossings and passive crossings.There are many factors that influence highway-railroad grade crossing design. Some of these factors can vary widely by drivers' behavior. These factors have been developed in models by AASHTO and its publications and shaped like we have them today. In order to... 

Left-turn operation is a critical component in the safe and efficient operation of a signalized intersection. The proper type of left-turn phasing results in reduction of traffic delay and number of accidents. A review of the literature indicates that different warrants have been proposed for the installation of the protected left-turn phase; however, there is not a consensus to implement a specific warrant up to the present. In general, the warrants fall into four categories: traffic volume, operational characteristics of traffic, intersection geometrics and accident experiences. Considering the high rate of accidents resulting from left-turn movements at signalized intersections in Iran,... 

Studies show that Pedestrians are at fault in 59% of the vehicle-pedestrian accidents. The traffic crash statistics show the importance of understanding factors of pedestrian errors. If pedestrians terminate their waiting behavior during the red light period and cross the street, they would put themselves in danger. Pedestrians’ red-light violation is a type of highly dangerous behavior occurring at intersections. A total of 1130 pedestrians approaching the intersections during red light periods were observed from the videotapes data collected at 6 intersections in Tehran, Iran. Pedestrian crossing behaviors are classified into immediate crossing behavior and waiting behavior. A logit model... 

The results of the conducted research indicate that although there is a period of time for pedestrians to cross the street safely at signalized intersections, some pedestrians cross the street when they find a space between the passing cars even though their traffic light is red. This behavior has caused a great increase in the number of pedestrian accidents. Understanding pedestrians’ behavior can be helpful in reducing these types of accidents.In order to analysis the pedestrians behavior while crossing the street two types of data were collected; a field questionnaires and a concurrent video image recordings of the pedestrians crossing the streets.The 435 questionnaires collected... 

The interaction of perpendicularly tunneling beneath existing metro station is investigated. In this paper E4R7 station, in line 7 of Tehran Metro (Tehran Urban and Suburban Railway co., TUSRC); Iran has been studied. This existing station has some special specifications such as a new pre-supporting system that is called Concrete Arch Pre-supporting System (CAPS). Construction of CAPS is mainly based on an Old Iranian small water tunnels excavation method, Quanat, which is faster and more economical than other common methods. CAPS is a rib like structure consisting of concrete piles and arch beams constructed around underground space before its construction. This method has been utilized in... 

Compared to systematically signalized intersections, in the absence of any systematic instruction or signalization at unsignalized-prioritized intersections and due to lower levels of control, driver performance strongly steps in as a decisive factor of intersection traffic and geometric design. Therefore, the study of driver behavior at these intersections appears necessary. This thesis aims to study driver behavior at four prioritized intersections where the minor stream has to yield right of way to the main stream in the city of Mashhad, Iran. Following extraction of raw statistical data from extensive filming, the initial database was constructed consisting of 29 variables. Based on the... 

A large amount of travel time in urban travels, is caused by intersection delays. Considering the intersection delay in traffic assignment, leads to more accurate network travel time and equilibrium flow pattern. Most traffic assignment softwares, consider unsignalized intersection delay as a constant or as a function of traffic volume on entering link, however, unsignalized intersection delay is a function of traffic volumes on all entering links. One of the reasons for these functions rarely being used in traffic assignments is that there is a lack of multi-variable delay function in transportation literature, and that most traffic assignment algorithms can not consider these functions.... 

One of the frequent aspects of lawlessness at signalized intersections, is red-light violation (RLV). In addition to its adverse effect on intersection safety, RLV can cause delay in the startup of the vehicles in the next phase defined as “green flow”. In this research, in order to investigate the adverse effect of RLV, the required data were collected from two signalized intersections in the City of Esfahan, Iran using recording cameras. Then, using a cellular network in the intersections and the Aimsun traffic simulation software, the effects of RLV on the delay, capacity, and level of service of the intersections were evaluated. The results show that the behavior of the drivers in the... 

In this thesis we ascribe a one graph to groups and investigate the relations between groups structure and graph. Let G be a group. The prime index graph of G, denoted by π(G), is the graph whose vertex set is the set of all subgroups of G and two distinct comparable vertices H and K are adjacent if and only if the index of H in K or the index of K in H is prime.Also, The intersection graph of G denoted by Γ(G), is the graph whose vertex set is the set of all non-trivial proper subgroups of G and two distinct vertices H and K are adjacent if and only if H ⋂ K≠ {e}, where e denoted the identity element of G. We denote the complement of Γ(G) by Λ(G). In this thesis we consider the following... 

One major problem in sport match analysis and interpretation is that there are restricted viewpoints of the game. 3D reconstruction allows us to have virtual replay from any viewpoint so that the events such as penalties can be detected easily. For achieving this purpose, we use many cameras with overlapped views that cover almost all parts of the field. After some preprocessing, 3D reconstruction and texture mapping, we can enhance the viewer experience by having arbitrary viewpoint of the match. In this research, we use two different visual hull methods for 3D reconstruction. In the first method, the visual hull of an object is computed efficiently and robustly from image contours. This... 

The main interest of this study is designing a correction algorithm for intersecting trajectories of two flying robots. For this purpose, path planning algorithms were studied and Rapidly-exploring random tree (RRT) was chosen as a proper algorithm for flying robots in urban environments which is modified for the problem. It should be considered that this project focuses on path correction therefore initial path could be produced by any suitable algorithm. In addition, new paths were designed with flying robots’ performance equations. The correction was done so the paths differ as little as possible in comparison to the original path. Since there are no flight regulations available for...