Sharif Digital Repository

Due to safety critical applications of the embedded systems, reliability is one of the most important properties of these systems. Wireless networks also have error prone data transmission channels and limited power consumption. Therefore reliability and power conservation are two vital characteristics of the wireless network especially in embedded applications. Since achieving to a desirable level of data reliability is power consuming, we must consider a trade-off between power consumption and data reliability. In wireless networks power consumption can be categorized into: power consumption in wireless devices and power consumption in data transmission. For decrement of wireless devices... 

In this project, investigation of C-N internal rotation in ethyl tetrahydro-1(2H)-pyridine carbdithioate and ethyl 1-pyrrolidine carbodithioate were investigated by dynamic nuclear magnetic resonance spectroscopy. The 1HNMR and 13CNMR spectra were taken at the variable tempratures around the coalescence temprature. Thermodynamic parameters were calculated by analysing the spectra and the outcomes were compared by the theoretical results. For ethyl tetrahydro-1(2H)-pyridine carbdithioate ∆G‡ was 14.3 (kcal/mol) and for ethyl 1-pyrrolidine carbodithioate ∆G‡ was 17.0 (kcal/mol) which were in accordance with the theoretical results. The analysis were done by the Spinworks program which... 

Yttrium Aluminum Garnet powders possessing controlled size distribution has found applications in production of transparent ceramics, phosphors, laser host materials and composites. Sol-Gel Combustion process is one of the versatile methods to produce nanometeric garnet powders. This procedure is based on combustion of a concentrated gel of metal salts and fuel in an exothermic reaction which leads to nanoparticles formation. pH value of solution and employed fuel system strongly affect production quality and single phase nanopowder can be synthesized by well monitoring these parameters. In this study nanocrystalline Yttrium Aluminum Garnet powders was Synthesized via sol-gel combustion... 

In this work, the effect of Active Screen Plasma Nitriding (ASPN) treatment on structural, mechanical, electrical and magnetic properties of nanocrystalline Finemet-type alloys with the composition of Fe73.5Si13.5B9Nb3Cu1 and Fe77Si11B9Nb2.4Cu0.6 was investigated. The samples were prepared by vacuum arc melting of high purity constitution in order to obtain a nanocrystalline structure. The rapidly solidified samples on a chilling wheel, were subjected to the ASPN treatment in different temperatures ranging from 410 °C to 560 °C for 3 h and in two gas mixtures of 75% N2-25% H2 and 25% N2-75% H2 at 5 mbar atmosphere. The amorphous ribbons were then annealed under vacuum with the same... 

Goal of this project is to present a method for dynamic transmission planning in restructured environment by system regulator. Congestion, fair competition in power market, stakeholders’ desires in transmission expansion, transmission investment traits, creating incentive for investment and transcos revenue are considered in this work. Presentation of methodology for reliability evaluation is necessary because of increasing uncertainties due to restructuring. Remedial action method is suggested for uncertainties analysis and reliability index presented for measuring degree of reliability. The method has been applied to the IEEE 14-bus system. ... 

Vortex Tube is a mechanical device without any moving parts. It separates a compressed gas stream into a low and a high temperature region (temperature or energy separation effect). Advantages of VT are existence of no moving parts, no external power (electricity or flames) required to operate, tiny and lightweight, inexpensive tube & parts material, convenience and pollution free. Heating, cooling, cleaning and drying gases, separating gas mixtures, gas liquefaction, natural gas pressure reduction and dehydration are the applications of vortex tube. The main Objectives in this research are investigation of various types of gas streams including pure gas or mixture of gases in vortex tube... 

In the present investigation, the mechanical alloying (MA) technique was employed to produce nanocrystalline Al-Ti Powder mixtures. Elemental Al and Ti powders were mixed with different compositions (0, 5, 10, and 20 wt.% Ti) and then, milled in a vibratory mill up to 7 hr. The variations of powder morphology and particle size, apparent and tap densities, microstructure, grain size, lattice strain, and microhardness were studied with increasing the milling time. While dissolution of Ti in the Al matrix resulted to the formation of supersaturated Al-Ti solid solution in the samples containing 5 and 10 wt.% Ti, the specimen with 20 wt.% Ti, eventually, led to nanocomposite powder with... 

State estimation is a process in which values of unknown system state variables is obtained by considering measurements in such a system. State estimators’ output data are applied in control centers of power systems. Nowadays, using of phasor measurement unit (PMU) in WAMS (Wide Area Measurement Systems) and SCADA have significantly extended. PMUs increase the accuracy proportion compared with traditional measurement units, improve the power networks observability as well as detect and correct bad data. Since the possibility of removing the traditional measurement devices and replacing them with full PMU ones does not exist in the near future it is mandatory to find out an efficient and... 

Nowadays, modeling the behavior of materials during forming processes is so important. The role of most of them is to investigate and predict the evolutions of microstructure and mechanical properties of materials during plastic deformation. Previous researches have demonstrated that the best parameter to investigate these evolutions is the dislocation density of materials. In this study, first, the dislocation-based models, which investigate the material parameters evolutions during plastic deformation, were investigated and it was revealed that among all presented models, only the two internal variables models can investigate the behavior of materials during severe plastic deformation. ... 

In this research, the effect of political system on economic performance of resource abundant countries is studied. We use political economy litreture to develop a theoritical model in this issue. Here, the politcal systems are divided to democracy and dictatory and in each of them other institutional variable will be introduced. Policy indicator is based on the difference between social welfare in each situation and its optimal amount when maximized. We show that if democracy does not come with high accountability it reduces social welfare more than dictatory. Also, if politician are myopic, democracy aggravates economic performance in those countries. In addition, easy access to income... 

Milk is One of the most important source s of protein in the world. during the process of cheese the most of these protein remain in whey. There are different methods to separate these protein from whey. The one of advanced method is ultrafiltartion, this method is based on a permeable membranes, with different pore size. There are many research works in this field. In this project we have tried to study the effect ofpressure, temperature, concentration and resistance time on membrane porosity. In order to design the experiment and analyze the results tagochi L 16 methods is used. The PVC membranes were prepaid by gas anti solvent method, experiment showed that changes of temperature and... 

Network coding is realized to have great potential for improving the performance of uncoordinated distributed networked storage, and also cooperative content distribution networks (Peer-to-Peer networks). In these kinds of systems, file is stored or dispensed in blocks which can be the coded version of the original blocks of the file. The existing network coding scheme in P2P networks (Avalanche) finds coding opportunities and uses them in forwarding en-coded blocks through the network. This scheme uses the swarming technique and network coding together, in a single transmission, and consequently, it achieves several fold increase in the throughput of P2P networks. In this thesis, we have... 

High power, broadband amplifiers at microwave and millimeter wave frequencies are needed for military and civilian applications. High power, broadband, high linearity, low noise, high efficiency and graceful degradation on failure are among the most important features in amplifier design. Solid state and vacuum tube devices have many disadvantages. A promising solution has been spatial power combining technique. Spatial power combining is a method of coherently combining the power of many amplifying devices using free space as the power dividing/combining medium within a guided wave structure in contrast to traditional circuit based amplifiers. This thesis presents the design and fabrication... 

A biocompatible ferrofluid have been prepared by co-precipitation of FeCl2.4H2O and FeCl3.6H2O under ultrasonic irradiation and with NaOH as alkaline agent. Also cystein was used as capping agent in the solution. Magnetic properties of the produced ferrofluid then determined by VSM test and magnetite nanoparticles were characterized by XRD and TEM techniques. Results indicate the presence of a biocompatible superparamagnetic ferrofluid including magnetite nanoparticles with particle size ranging under 15 nm. The effect of ultrasonic irradiation on presence of a sharp particle size distribution then denoted by comparing the condition with production without ultrasonic irradiation  

In the present investigation, the mechanical alloying (MA) technique was employed to produce nanocrystalline Al-Ti alloys. Elemental Al and Ti powders were mixed with different compositions (0, 5, 10, and 20 wt.% Ti) and then, milled in a planetary ball-mill up to 40 h. The variations of powder morphology and particle size, apparent and tap densities, microstructure, grain size, lattice strain, and microhardness were studied with increasing the milling time. While dissolution of Ti in the Al matrix resulted to the formation of supersaturated Al-Ti solid solution in the samples containing 5 and 10 wt.% Ti, the specimen with 20 wt.% Ti, eventually, led to nanocomposite powder with different... 

Future of the Karkheh River Basin and its people’s livelihoods clearly depends on natural resources like water, soil, vegetation and livestock. As water is the most limiting natural resource in this basin, any increase in water productivity will almost certainly benefit rural livelihoods. To ensure the sustainability of the improvements in water productivity, assessment of the possible impacts of climate change on hydrology and water resources in the basin is necessary. In this study the potential impacts of climate change on hydrology in the Karkheh River Basin were assessed using a macroscale hydrology model driven by 21st century simulations of temperature and precipitation downscaled... 

Humanoid robots are robots that are similar in appearance and performance to humans. Designing and controlling a humanoid robot to perform such supposedly ordinary tasks as walking, running, writing, talking, driving, riding bikes, and the like is such a difficult task from the control point of view that it seems to be quite ambitious and inaccessible. In this thesis, the previous efforts of scientists and researchers are presented using different intelligent controllers. Additionally, the dynamic analysis of selective biped (seven-link biped robot) is illustrated. In this research, we present a method to control the walking of the biped robot while retaining stability. In this method the... 

Biosorption capacity of zinc (II) by biomasses produced from four species of microorganism including two kinds of bacteria (Pseudomonas putida and Streptomyces rimosus) and two kinds of fungi ( Aspergillus niger and Phanerochate chrysosporium) in batch case were investigated and compared. In all cases dried original bio mass and dried pretreated bio mass with NaOH were used. In all cases biosorption capacity of pretreated biomasses were much higher than non-treated biuomasses to the ratio of 3.8 – 1.4 times. Freundlich and Langmuir equilibrium isotherms were used to match with experimental results of this research. Except S.rimosus, all others were completely matched with Langmuir... 

Most broadcast stations insert their logos to claim video content ownership and/or for business purposes.This process reduces picture quality in the logo region and also causes visual discomfort to viewers. Logo detection has a variety of applications; such as automatic TV commercial removal, broadcast surveillance, and video content understanding. Video logos can be considered as a form of visible watermark. Stations may also overlay their logos over the original logo when rebroadcasting a program produced by another station. Also, most comapnies keep a giant archive of their broadcasted programs which are going to be used in their future programs. Here, we have presented an efficient... 

Microstructure and mechanical properties developments of X80 weld metal by addition of different amounts of alloying elements such as: Nickel and Manganese in coated electrodes were investigated. For this reason samples were welded by electrodes that Ni value has been changed between 0.8%- 3.2% in tow critical amounts of Mn: 0.7 and 1.6. The weld quality was evaluated using nondestructive testing methods (NDT), such as visual inspection and radiography. Tensile test, Charpy impact test and microhardness results indicated the suitable range of Ni and Mn for achieving acceptable mechanical properties. In addition, optical microscopy and scanning electron microscopy (SEM) were applied to link...