Sharif Digital Repository

In this thesis, the simulation of HEMT for high frequency applications has been explored. It has been tried to examine the changes such as: gate recess, T-shaped gate, changing the channel length and doping of buffer layer on the performance of the proposed device. Simulation results show that the best way to improve the device performance, in particular its cut-off frequency, is increase in buffer layer doping density. Because it significantly increase the saturation current, electron mobility inside the channel, the transconductance and the cut-off frequency. If we need to lower the noise, the T-shaped gate can also be used. Also, by change in doping of donor layer, amount of 1017 cm-3 is... 

The exponential increase in power density within a chip due to higher frequency of operation in recent years (Moor's law) is a major limiting factor for designers. Increasing the number of parallel cores instead of increasing the frequency of operation is a possible solution. The design of connections within the cores can be followed by the old process but the global interconnectsbetween the cores instead of point to point can be replaced byNetwork-on-Chip (NoC). In this thesis, The dimensions of global interconnects in many-core chips are optimized for maximum bandwidth density and minimum delay taking into account network-on-chip router latency and size effects of coppe. The optimal... 

catalyzed oxidation of organic compounds such as olefins, sulfides, benzylics alcohols and phenolics. Cyanide-catalyzed aldimine coupling was employed to senthesize compounds with a-imineamine structural motifs : 2,3-di-(2-hydroxyphenyl)-1,2-dihydroquinoxaline, that way for synthesized NONO tetra-dentate Schiff-base ligands. With attention to solid geometry these ligands are possible to synthesize homo and hetronuclear mixed-ligand complexes. we are also synthesized homonuclear mixed-ligand Mn(III) and hetronuclear Mn(III)-Fe(III) with tetradentate Schiff-base ligand quinoxaline and acetyl acetone ligand. These complexes and ligands are characterized by FT-IR, 1H NMR, 13C NMR, UV and... 

In this thesis we propose a two-layer hybrid fuzzy genetic algorithm for designing anomaly based an Intrusion Detection System. Our proposed algorithm is based on two basic Genetic Based Machine Learning Styles (i.e. Pittsburgh and Michigan). The Algorithm supports multiple attack classifications; it means that the algorithm is able to detect five classes of network patterns consisting of Denial of Service, Remote to Local, User to Root, Probing and Normal class.
Our proposed algorithm has two approaches. In the first approach we choose Pittsburgh style as the base of the algorithm that provides a global search. Then combine it with Michigan style to support local search. In this... 

The daily increase of fuel prices, decrease of fuel resources and the need for controlling environmental pollution, reflect the importance of optimizing the heat recovery in different industries. In the past 20 years, Pinch technology has been considered as a powerful tool used for, recovering wasted energies, optimizing the energy transfer between hot and cold streams and reducing the need for additional services. In this thesis, Pinch technology is used to optimize the process of wafer and chocolate production in one of the KitKat’s factories and different retrofits for the increase of the heat recovery are proposed. urthermore, the data collected at this factory is used to investigate the... 

Thermal barrier coatings (TBCs) are used for increasing the efficiency and reducing pollutants of internal combustion engines (ICEs). In this paper, an optimization framework is developed in order to obtain the optimal dimensions for conventional coat, and the optimal dimensions and material property for functionally graded (FG) coat of a partially coated piston. A thermo mechanical analysis is investigated for Nano coat by finite element method. The conventional and Nano coats are made of MgZrO_3 as the insulating ceramic overlay and NiCrAl as the metallic bond-coat. The properties of the FG coat is assumed to vary according to power law through the thickness. For all tree conventional, FG... 

Applying of seismic waves and analysing of its reflections is of effective ways in exploration of the internal structur of the Earth. In this method the Earth is considered as a elastic body that seismic waves are propagated in it. In this thesis the how of creation and propagation of seismic waves is modeld at first and then the inverse problem, exploration of the internal structure of the Earth from observed data, is considered  

Since interconnects are playing a very important role in today’s IC technology, introducing new models and approximations is vital to IC designers. In this dissertation, maxwell equations are introduced as they are the main equations governing transmission lines. Different methods to model interconnects are also presented. Moreover, because of the importance of the step response of a system, available methods for finding the step response of interconnects are briefly discussed. Some approximations are also described, which result in faster but not very accurate responses. Delay and noise in integrated circuit connections have been the subject of several investigations for a long time. Since... 

Due to the growth of information volume and increment in the speed of processor units, it is critical to achieve higher speed in data transaction systems. This necessity could be recognized in all fields, from digital data transactions on a chip and among its building blocks to data transactions among electronic boards and computerized systems in huge control constructions.
Methods of data transmission have been improved both in terms of speed and simplicity for different applications in today’s enormous consumer electronics market. One possible option is to use conventional wires as physical channel of transmission system.
The most important drawback of the wires is their relative... 

Due to the negative effects of conventional plastics on the environment, especially in the packaging sector, extensive efforts have been put to replace these polymers with biodegradable polymers. Starch is one of the biodegradable polymers which has attracted a lot of attentions because of low cost and good process ability. Native starch has the form of granule and can be processed to a continuous phase after gelatinization in the presence of a plasticizer. The resulting material is a biodegradable plastic-like material called thermoplastic starch (TPS) which is processed using conventional technologies, but suffers from low mechanical properties and high hydrophilicity. Addition of... 

Studing the Scattering Amplitudes has a crucial importance in Quantum Field Theory; and nowadays; there have been many progress in computing these observables: Scattering amplitudes respect the symmetries of a theory: However; it is possible for them to have more symmetries than ones can be seen from the lagrangian of the theory: On the other hand; Feynman diagrams which manifest the locality and unitarity of the theory are not applicable in these kind of theories; since for computing the easiest scattering amplitudes thousends of these diagrams must be computed: In this work; we are going to see using BCFW recursion relation and onshell diagrams how it is easy to compute the scattering... 

In the most cosmological models which already have putted forth, metric has a spherical symmetry; however, according to the galaxy’s shape is not a real approximation. In order to build a more acqurate model, by applying a particular conformal transformation on the static vacuum solution, we introduce a new metric which is axially symmetric and also it approaches to FLRW metric at space infinity. The cosmological model according to this metric has especial features;The solution we have found represent a spacetime which is axially symmetric although it leads to a spherically symmetric Einstein tensor. Therefore, we have found a solution of Einstein equations representing a spherically... 

Searching for images of the same object or scene in a large number of images is a major problem in computer vision. It has many applications specially in the search engines.For the goal of efficient image search, we need descriptors that are not only discriminative, but also short and need small amount of memory.In this thesis we analyze the image search methods in two categories: The first methods are based on converting the existed descriptors such as gist into a compact binary code. The second methods are based on building short descriptors, especially by some modifications in the framework of bag of features descriptor.Finally we will introduce a novel descriptor "bag of codes" which... 

One of the important branches in machine learning is finding patterns and hidden features, which is useful for prediction and decision making in many cases. Finding patterns and features of financial data and particularly stock market data may play an important role in guidance, development and proper decision making related to such data sets. In this thesis, we focus on discovering and collecting appropriate methods in machine learning which can be helpful for gathering proper information from financial data and applying them on actual data  

Delay of Interconnects in modern digital ICs is several times greater than delay of gates. One proper measure for this problem is to shorten interconnects length by using three dimensional structures instead of conventional two dimensional structures. In these structures TSVs (Through Silicon Vias) make connection between stratums. Power integrity in 3D ICs necessitates power distribution networks to have minimum IR drop and Ldi/dt noise. In this dissertation we design power distribution network considering IR drop and Ldi/dt noise margin. We expand a mathematical model which represents differential equation of power distribution in the surface of each stratum. Using this expanded model we... 

This project aimed to fabricate the bone scaffolds with applying thermoplastic starch-based nano-biocomposites. The starting materials for this scaffold are as follows: thermoplastic starch, ethylene vinyl alcohol as the polymer matrix and nanoforsterite as the ceramic reinforcing phase. Furthermore, vitamin E was used as antioxidant for preserving starch against thermo-mechanical degradations. Likewise, 3D pore structure was developed using azo-dicarbonamide and water in injection moulding process. With blending thermoplastic starch and ethylene vinyl alcohol, some thermoplastic starch’s properties including degradation rate and water absorption were modified. In addition, having... 

As the transistors’ dimensions in integrated circuits shrink, according to Moore’s law, a number of challenges emerges that can decrease the benefits of scaling. One of the main challenges in deep submicron CMOS technologies is the delay in interconnects. In recent years, researchers have been looking into different methods to minimize the delay in interconnects. International Technology Roadmap for Semiconductors (ITRS) predicts that the input capacitance of a buffer will become in the order of 10s of aFs with technology scaling. This will give us the opportunity to transmit the data in electrical interconnects near the speed of light.In this thesis, a novel buffer is designed in which the... 

Two new dioxomolybdenum(VI) complexes have been synthesized by the reaction of N,N'-bis(5-chlorosalicylidene)-2,2'-dimethyl-1,3-propanediamine and N,N'-bis(5-bromosalicylidene)-2,2'-dimethyl-1,3-propanediamine as Schiff base ligands with [Mo(O)2(acac)2] in methanolic solution.and their electronic structures have been investigaged theoretically. The Schiff base ligands H2L1 and H2L2 were prepared by reaction of 5-Chlorosalicylaldehyde and 5-Bromosalicylaldehyde with 2,2'-dimethyl-1,3-propanediamine, respectively. The result of these reactions, was two complexes of Mo(O)2L1 and Mo(O)2L2 .The compounds were characterized by elemental analyses (CHN), and 1HNMR and IR spectroscopic techniques.... 

Several advantages and problems associated with technology scaling. One of the most important problems facing technology scaling is interconnects. As technology scales down wire delay becomes dominant. Optical interconnects has been subject of many researches for more than two decades to overcome this problem. The key idea behind near speed of light transmission (NSoLT) is that for buffers at the end of ITRS projections input capacitances could be as small as tens of atto Farads. Hence, voltage of the end of global wires could jump at the time of flight.
In this project, a global wire has been divided in to k segments in a way that data can be transferred with the speed close to the... 

Inflation is the leading paradigm for the theory of early universe and the mechanism for generating the seeds of perturbation in cosmic microwave background and large scale structure. In this thesis various aspects of primordial anisotropies and the effects of long mode during inflation are studied. There exist two powerful tools in studying the effects of super-horizon inflationary perturbations, namely, Maldacena’s consistency condition and Weinberg’s theorem. However, there are inflationary models, such as solid inflation and non-attractor inflation, which evade these theorems and in this thesis we study their consequences and features. At first we study statistical anisotropy in the...