Sharif Digital Repository

In this research, the instability analysis of single-walled carbon nanotubes (SWCNTs) and graphitic shells conveying fluid is investigated based on the molecular structural mechanics. Using the reduced order models for fluid and structure, the dynamic behavior of carbon nanotubes (CNTs) conveying fluid is accurately modeled via a few number of lowest flow modes and natural frequencies and mode shapes of CNTs structure. In addition, the boundary element method (BEM) is used to model the potential flow. The molecular mechanics (MM) model is applied to modal analysis and driving the natural frequencies and mode shapes of SWCNTs. The effect of chirality on flow-induced instability is taken into... 

The growing usage of nonlinear loads has resulted in increasing voltage and current harmonic levels in distribution systems. Additionally the faults occurring in the distribution system cause voltage sag at the point of customer supply. These two power quality disturbances impose considerable costs on consumers through disrupting the correct performance of sensitive loads, causing unintended outages and decreasing the devices’ useful lifetime. Besides the aforementioned power quality issues, the electric power loss has a determining role in operational costs. In this thesis, based on feeder reconfiguration and shunt passive filters, a strategy is proposed in order to reduce the average... 

With the environmental concerns and scarce supply of the crude oil, a revival in the development of bio-based and compostable materials is coming. They are in general being called the ''green'' materials, among which poly(lactic acid) (PLA) got the most extensive attention due to its good combined properties, including the renewable feedstock, the compostability, and its good mechanical properties, especially the young's modulus and stiffness. PLA has found numerous applications. It is considered having the highest potential to replace some regular petroleum based plastics. However PLA has its own shortcomings, its brittleness, low heat distortion temperature and relatively high cost witch... 

The purpose of the study was four-fold: first to investigate the predictive adequacy of the Task-Induced Involvement Load Hypothesis which contends that higher-load inducing tasks yield better retention rates in incidental learning situations, second, to examine whether type of dictionary search could affect vocabulary retention, third, to investigate the effect of translation direction on retention rate, and finally to determine the most effective tasks. To meet these ends, six groups of EFL learners - all male, aging 19-25, majoring in various fields of engineering sciences were assigned to the study. Each one of the groups performed distinct tasks which were as follow: reading... 

In recent years, quantum sensing based on spin defects in solid-state materials, particularly nitrogen vacancy defects in diamond, has been a significant research topic in the field of quantum technologies. Its applications have been demonstrated in various areas such as biology, microelectronics chips, and condensed matter physics. The aim of this research is to construct a magnetic imaging microscope based on an ensemble of diamond crystals using the continuous wave optically detected magnetic resonance method (CW-ODMR). By constructing an epifluorescence microscope and simultaneously exciting the diamond sample with green light and microwave radiation, it is possible to obtain information... 

In recent years, dust pollution has become a worldwide issue due to the creation of serious environmental problems and the effects it has on human health. In this research, an environmentally friendly soil stabilizer has been synthesized, and its performance has been investigated. Acrylamide monomers were grafted onto sodium lignosulfonate chains, utilizing solution polymerization. The soil of the Ahvaz deserts was used in the analyses. Using EDX and DLS analyses, the components of this soil and the particle size distribution of the used soil were obtained. Characterization of the functional groups and the structure of the graft copolymer were done by FTIR and H-NMR analysis, respectively,... 

In this thesis, we introduce limited-sharing multi-party computation; in which there is a network of workers (processors) and a set of sources, each having access to a massive matrix as a private input. These sources aim to offload the task of computing a polynomial function of the matrices to the workers, while preserving the privacy of data. We also assume that the load of the link between each source and each worker is upper bounded by a fraction of each input. The objective is to minimize the number of workers needed to perform the computation, such that even if an arbitrary subset of t 1 workers, for some t 2 N, collude, they cannot gain any information about the input matrices. This... 

In this project the effect of rolling temperature on mechanical properties and microstructure evolution of a low carbon steel was studied. The steel was rolled up to a nominal strain of 67% at three different temperatures consisted of room, blue brittleness, and subzero temperature. Micreohardnessand tensile tests were used to characterize the recrystallization kinetics. Optical and scanning electron microscopic examinations were carried out to evaluate the mechanical, grain size, and the kinetics of static recrystallization by the Avrami equation. The results indicated that the volume fraction of static recrystallization increases with the increase in annealing period. The Avrami exponent... 

In this dissertation we aim to survey the concepts and results concerning Total Domination Set. Consider graph G = (V;E). Let S be a subset of V . S is Total Domination Set in G if every vertex in V is adjacent to at least one vertex in S.Furthermore, we call S a k-Total Domination Set if every vertex in V is adjacent to at least k vertices in S. The size of the smallest Total Domination and k-Total Domination Set in a graph G is respectively called the Total Domination and k-Total Domination Number of G.Now, if there is a sequence of subsets of V like S = V0; V1; V2; : : : ; Vl = V so that for each i, every vertex in Vi is connected to at least k vertices in Vi1, S is a Dynamical k-Total... 

The use of polyether ether ketone (PEEK) in bone implants is limited due to a lack of cell adhesion and proliferation. Therefore, in this study, we modified the surface of PEEK with a nanocomposite coating containing piezoelectric and bioactive properties. Sulfonated PEEK with suitable mechanical and hydrophilic properties along with polyvinylidene fluoride was used as a biocompatible polymer with piezoelectric properties for coating. Also, nanohydroxyapatite was used as a bioactive material, and carbon nanofibers with significant mechanical and electrical properties were used in the nanocomposite. The surface was sulfonated as an intermediate layer to improve the connection between the...