Sharif Digital Repository

The quality of service in Wireless Multimedia Sensor Networks (WMSNs) is related to packet loss rate. Recently dierent studies have been done on developing ecient protocols in the transport layer for controlling packet loss in WMSNs. However, all of these protocols are independent of the characteristics of the multimedia content. In this thesis, a novel transport layer protocol, called User Datagram Dispatcher Protocol (UDDP), is proposed to minimize the packet loss ratio in WMSNs by considering trac characteristics, the inter-arrival pattern of packets and packet priority. UDDP is a new cross-layer transport layer that uses information of MAC and application layers to distribute packet... 

In this study, free vibration analysis of moderately thick rectangular FG plates with general boundary conditions is investigated. Governing equations of motion are obtained based on the Mindlin plate theory. A semi analytical solution is presented for the governing equations using extended Kantorovich method (EKM). Results are compared and validated with available results in the literature. Effects of different parameters such as boundary conditions, material and geometrical parameters on natural frequencies of the FG plates are investigated  

Electrical impedance tomography is considered as medical and industrial imaging methods which is inexpensive and safer than other imaging methods, but has low quality results. The purpose of this study is providing a practical method to increase its quality. Image reconstruction in EIT always is encountered with both direct and inverse problem. In the forward problem electric potential distribution is achieved from known distribution of electrical impedance and currents, but in the inverse problem, identifying of electrical impedance distribution is the target which is achieved by known electric potential and current distribution. In fact, solving inverse problem results the image... 

We investigate heat transfer between parallel plates separated by liquid argon using three-dimensional molecular dynamics (MD) simulations incorporating with 6-12 Lennard-Jones potential between molecule pairs. We use thermal walls constructed from the oscillating molecules, which are connected to their original positions using linear spring forces. Channel walls are maintained at specific temperatures using a recently developed interactive thermal wall model. This approach is much more effective than the one which uses a fixed lattice wall modeling to simulate the heat transfer between wall and fluid. Heat flux and temperature distribution in nanochannels are calculated for channel height... 

Jean-Pierre Serre in 1955, in his famous article “Faisceaux Algébriques Cohérents” asked if there is any finitely generated projective module on polynomial rings which is not free. Or equivalently: is there any non-trivial algebraic vector bundle over an affine space? The negative answer to this question is known as Serre’s conjecture and it was an open problem in algebra and affine algebraic geometry until 1976, when it was proved independently by Quillen and Suslin. The challenge of solving this question and its consequences led to a vast amount of research in commutative algebra, homological algebra and algebraic K-theory and inspired generalizations and similar questions. In this thesis... 

In recent years, eLoran system has been introduced as backup to global navigation systems like GPS, because of their vulnerability. eLoran is a low frequency (100 kHz) system. Its long wavelength allows indoor positioning.
Main eLoran advantages rather than Loran-C are: better accuracy (near 10m), using 9th pulse positioning modulation (PPM) as loran data channel (LDC) and all-in-view receivers
In this thesis, eLoran pulses are simulated in GRI. Also, a new analoge-digital circuit for faster pulse detection is developed.
Also, it is proved that an oscillator with same frequency and phase as enterance signal, responses faster than a band pass filter and envelope detector. So, a... 

Traffic density estimation is one of the most challenging problems in Intelligent Transportation Systems. One of the important traffic information that is broadcasted to drivers is Traffic Density information. In many traffic control centers; human operators are responsible for estimating traffic density from captured video data. Increasing traffic cameras and constraint number of operators introduce an updating delay to broadcasted information. So it is important to have an automatic traffic density estimation system. In this thesis, machine vision is used to solve this problem. Supervised Image classification is our approach. In supervised Image classification, images are classified to... 

Slosh phenomenon is described as the motion of the fluid’s free surface in a tank or partially-filled container. This motion can induce undesired forces that can change the path of a vehicle. In some liquid carrying vehicles these undesired changes is sensed by the driver or control system and can lead to instability. Some examples of this phenomenon are aircrafts, rockets, ships and fuel carrier trucks.
In this project, a coupling between the dynamics of the vehicle and the contained fluid is implemented for in depth understanding of the interactions. This is done by Co-Simulation. With the help of Co-Simulation, corrective control actions can be taken and the design of more powerful...