Sharif Digital Repository

This research examines the impact of road transport fleet renewal on the transportation behavior of vehicles in Iran. The study identifies different effects of fleet renewal in different years. The method of fixed effects estimation is used to analyze the dataset of Iran's domestic bills of lading between 1394 and 1400, which contains information on over 200 million bills of lading issued for shipments of more than 490 thousand road transport vehicles. The findings indicate that vehicles with a lifetime of less than one year (≤1) move about 1.4 fewer cargoes per month on average compared to those with a lifetime of more than 35 years (≥35). Per trip, they carry 1.9 tons less, travel 100 km... 

Nonlinear dynamic procedure (NDP) can in general provide more realistic results than nonlinear static procedures (NSPs). That is due to consideration of higher modes effects and the shifts in inertia load patterns as the structural system experiences nonlinear behavior. Therefore, the simplified NSPs based on constant load patterns are inadequate to determine the inelastic seismic demands especially for top stories of tall buildings. The conventional procedures that have been implemented in design codes and guidelines such as ATC-40, FEMA356, FEMA440 and ASCE41-06, apply invariant load patterns such as inverse triangular, equal lateral force (ELF), first mode shape, uniform and SRSS modal... 

The dynamic response of the structural systems are influenced by various parameters such as the effect of higher and torsional modes, the change in frequency or inertial loads caused by the structural softening, frequency content of earthquake records, etc.. Therefore, any method that is only based on static procedure without considering the dynamic characteristics of the structural system may lead to erroneous output. The enhanced pushover procedures have been developed to minimize the inaccuracies of the nonlinear static analyses in predicting the real nonlinear response of structures while maintaining their simplicity. In this research the innovative methods are proposed individually for... 

High-quality online services demand reliable and fast packet delivery at the network layer. However, clear evidence documents the existence of compromised routers in the ISP and enterprise networks, threatening network availability and reliability. A compromised router can stealthily drop, modify, inject, or delay packets in the forwarding path to launch Denial-of-Service, surveillance, man-in-the-middle attacks, etc. So researches tried to create intrusion detection methods to identify adversarial routers and switches. To this end, data-plane fault localization (FL) aims to identify faulty links and is an effective means of achieving high network availability. FL protocols use... 

Confining nematic liquid crystal between two curved boundary conditions while the nematic molecules have a degenerate planar anchoring leads to complex and beautiful textures of molecular disparagement(defect) in the bulk and on the surfaces. Such the liquid crystal shells are made with double-emulsion techniques in microfluidic devices have provided applications for micro-scale colloidal linkers.In this work, we have numerically minimized the elastic energy in one-constant approximation in present of Fournier’s degenerate surface potential with finite element method. The nematic shell is confined between two spherical surfaces that we have studied the final energies and their related... 

A liquid crystal is a state of matter composed of highly anisotropic building blocks. When liquid crystals are exposed to surfaces with given shapes and anchoring conditions, the orientation of their molecules gets spatially disordered and topological defects may form in the system. The interplay between liquid crystals and the geometry and topology of the colloidal particles has motivated extensive recent studies.In this thesis, we present the numerical modeling results for two faceted colloidal particles in a thermotropic nematic liquid crystal. To obtain the equilibrium nematic field with a finiteelement method, we numerically minimize the free energy of the system that based on the... 

Providing high bandwidth network infrastructures for ever increasing need of data transport is of great importance. The underling infrastructure for many communication services such as GSM/3G/4G mobile networks and Internet services is Synchronous Digital Hierarchy (SDH) optical transport systems. SDH are standardized protocols that multiplex multiple lower rate digital bit streams, such as E1 and Ethernet, and transfer them synchronously over optical fiber using lasers or LEDs. In addition to high data transfer rates, flexible network management and protection mechanisms have great importance, hence are part of SDH standards. In order to obtain flexible network architecture and protected... 

Development of Smart Grid and deployment of smart meters in large scale has raised a lot of concerns regarding customers’ privacy. Consequently, several schemes have been proposed to overcome the above mentioned issue. These schemes mainly rely on data aggregation as a method of protecting users’ privacy from the grid operators. However, the main problem with most of these schemes is the fact that they require a large amount of processing power at the meter side. This, together with the fact that smart meters don’t usually have a powerful processor, can cause the unavailability of smart meter data at the required time for operators of the grid, and at the same time disables smart meters from... 

Secure routing is a major key to service maintenance in wireless ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. Wormhole attack is one of the most severe active attacks to mobile ad hoc networks. Noting the resource limitations in such networks, nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a... 

Deciding for the future is one of the key tasks that project managers must carry out. Accurate Estimate at Completion helps them make the right decision. Numeruse novel methods have been proposed for calculation of estimate at completion which most of them are based on Earned Value Management. The question is whether considering the resources, as the essential elements of activities and therefoe the project, would result in a more accurate Estimation. In this Thesis, we propose a method that uses resource performance and activity structure to calculate the Estimate at Completion. The method also forecasts future resource usage. To evaluate the proposed method, we generated fictitious... 

With the rapid development of mico-nano propulsion systems in micro-spacecrafts and micro-sattelites, precise investigation of flow field in these devices has become necessary. Micro propulsion systems usually have a thrust in order of mili Newton, and they can be used for maneuvers of spacecrafts with mass of less than 10 kg. Micro propulsion systems are usually classified according to their thrust generation mechanism to different classes like cold gas, and chemical propulsion systems. Cold gas micro propulsion systems obtain their energy from thermodynamic expansion of gas and not by combustion. If the flow fiel dimensionare comparable to mean free path, rarefaction effects are observed... 

Dynamic spectrum access with the aid of cognitive radio (CR) technology is a viable solution to spectrum scarcity. There are many military and emergency applications that require the use of cognitive radio ad-hoc networks (CRAHNs). In these net- works, nodes must first find each other in a wide spectrum and then exchange their desired data. The process of finding each other in a multichannel environment is a challenging task and is usually known as rendezvous. Since rendezvous is the first step in communication, disrupting will disable the nodes from establishing proper communication sessions. That results in a drastic degrade in the performance of the network. Therefore, it is important to...