Sharif Digital Repository

IoE devices are going to integrate with our environment. It has been predicted that there would be more than 6 connected devices per each person by 2020. Currently what obstruct this technology from continuing its evolusion path, is its dependence on Ultra Low-Power devices, and for this reason there is a huge concenteration on Radio-Frequency standards which can make devices more power efficient. Within these standards, Bluetooth Low Energy (BLE) attracted designers consentration for its similarities with conventional Bluetooth and its dominance in cellphones and other portable devices.In this project, we have attempted to design a trasmitter for BLE standard based on an All Digital Phase... 

Global Positioning System (GPS) is one of the most widely-used systems nowadays. GPS receivers are frequently integrated along with other communication systems in hand-held devices like cellular phones, tablets and etc. Therefore, implementing receivers with low power consumption (for longer battery lives) and high sensitivity (in order to detect the weak GPS signal) has attracted the attention of many researchers. With the purpose of designing such a low-power and sensitive receiver, we have studied the recently proposed low-power schemes. We have proposed a new architecture for the QLMV Cell; the circuit in which main blocks associated with RF front-end are stacked on top of each other in... 

Variation of the input driving power can cause in some varactor and BJT frequency multipliers parametric instability. If parametric oscillations are present in the circuit, output phase noise of the multiplier degrades remarkably in some specific driving levels. Phase noise of the varactor and BJT multiplier is calculated by the conversion matrix method using generalized nodal analysis. By the conversion method the phase noise degradation can be predicted precisely. In the calculation of phase noise the effect of the noise sources that are modulated by the large signal drive and the conversion of components of the internal noise sources of the device to the output spectrum due to circuit... 

Mobile technology has become Ubiquitous and common in all over the world from the first years of 21st century. Mobile has been used as a strong media in marketing and specifically in advertising due to it’s unique features and various functions. Currently (2008) mobile media is not used very aggressively in Iran. Considering the quick expansions of mobile networks in Iran and growth of subscribers, it is anticipated that Mobile will affect many businesses and consumer market very soon in Iran. This study is the first academic research in the country on Mobile advertising via SMS. The purpose of this thesis is to provide the better understanding of the Mobile advertising via SMS in high... 

Ridge gap waveguide is a new technology with low loss and high power handling capability in millimeter wave(mm-wave) frequencies. In this technology there is no need for electrical connection between the constitutive parts and using dielectric material as a substrate. This thesis focuses on the capabilities of this technology in realization of devices used in communication systems at the mm-wave frequency. Novel devices based on this technology have been designed, fabricated and tested. The main goal of the thesis is realization of the whole RF front end of a communication system in Ka band based on this technology. So at first step, a ridge gap waveguide transmission line is evaluated and a... 

Cache networks play a key role in today’s Internet. Inspired by the successful deployment of caching in content delivery networks (CDNs), pervasive caching now is a fundamental concept in storage-assisted future Internet architectures, e.g., information-centric networks (ICN), and 5G. However, despite the clear and increasing economic advantages of caching for the network operators, it does not take place efficiently due to various problems. The emergence of in-network caching has created new challenges for modeling and performance evaluation of networks. In addition, content providers (CPs), who alone have the detailed demand data required for optimal content placement, have no natural... 

Modern broadband microwave and millimeter-wave systems often struggle with excessive pass band ripple and negative gain slopes due to the loss of transmission lines such as coaxial cables, or ripples in the gain characteristic of broadband amplifiers. The common solution for this problem is using a gain equalizer to compensate for the intrinsic pass band variation with some extra loss in the band of interest in return.Designed equalizers often have a constant slope in their bandwidth. However, having ripples in pass band or in other words slope changing in some parts of the band is one of the issues that designers should deal with. In this thesis, after reviewing the previous works on the... 

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... 

In this thesis, new boundary conduction mode boost PFCs are proposed and implemented for different power levels according to the characteristics and requirements of each power level. For medium power applications, we have proposed a new zero voltage switching PFC based on a synchronous boost converter which is controllable with conventional boundary conduction mode PFC control ICs without requiring any additional timing adjustment control circuits other than a special high side driver that consists of only low voltage components. Based on mathematical calculations, we have proposed two sipmle circuit solutions to reduce the high level of line current zero crossing distortion in the proposed... 

Masonry buildings are one of the most vulnerable structures against earthquakes, and therefore their seismic response should be evaluated in order to mitigate casualties in the future. Although there are numerous experimental and analytical studies on these buildings, few have aimed on Confined Masonry (CM) buildings to simulate and predict their seismic performance. To estimate damage, assess vulnerability and choose the best retrofitting method, fragility curves can be utilized as a powerful tool. In this paper, the hysteretic behavior of two typical CM walls with and without opening is calibrated in both In-plane (IP) and Out-of-Plane (OOP) loading directions making use of OPENSEES... 

Geothermal energy is one of the most important sources of energy that is increasingly becoming more popular all over the world. In this study, the performance of deep geothermal energy as a form of geothermal energy was evaluated using a numerical modeling approach. To do so, first, the thermo-hydraulic behavior of geothermal reservoirs was studied to help achieve the most efficient arrangement for production and injection wells. The results show that to optimize production and injection wells, there are two factors to consider. Firstly, the distance between production and injection wells must be high. Secondly, the production wells must be uniformly distributed throughout the reservoir so... 

Long-term Multi-Channel Bio-Signal monitoring in a comfort way is demanding for emerging applications in everyday life. Typically, in multi-channel amplification, one amplifier per channel is employed. However, the bio-signal amplification requires lower bandwidth in comparison with the available speed of CMOS amplifiers. Therefore, it is sensible to develop a practical circuit trading the excess CMOS bandwidth with power consumption. The proposed circuit, which has three inputs, performs amplification through three stages; First, the inputs are applied to a 3 to 1 time-domain multiplexer. Second, a Current Feedback Instrumentation Amplifier (CFIA) is utilized. Finally, the amplified signal... 

In this thesis, three novel geothermal-based ORC systems are proposed to enhance efficiency and to recover the waste heat recovery. The proposed systems are modeled based on basic ORC system (concept 1), ORC system with internal heat exchanger (concept 2), and regenerative ORC system (concept 3). Accordingly, two thermoelectric generators are introduced into the systems to exploit the waste heat of the system. For this purpose, the condenser is replaced by a TEG unit, while the other TEG unit is employed to recover the waste heat of the reinjected geothermal fluid. A comprehensive numerical investigation is conducted to compare the proposed systems from thermodynamic and thermo-economic... 

Self-organized public key management scheme in mobile ad hoc networks (MANETs) is an inevitable solution to achieve different security services. The aim of such schemes is to find an efficient protocol which makes the node able to obtain the authenticated public key of another node. Public key transmission and verification is achieved using certificate chain or message authentication code, thus it needs other nodes cooperation. It is also notable that in heterogeneous MANETs which include malicious nodes, this method suffers from low throughput and spoofing attack. In this thesis, a novel certificateless, on-demand self-organized public key management scheme is proposed which is based on the... 

In this thesis, I introduce a general equilibrium model of international trade that takes into account the industry linkages between intermediate goods and consumption goods producers to quantitatively measure the countries’ welfare gains and losses from different trade policies on intermediate and consumption goods. My model extends the inter-industry trade model of Ricardo (1817), intra-industry model of Krugman (1980), and firm heterogeneous model of Melitz (2003). Reduction of tariffs affect welfare of countries through direct effects on income, cost of export, and cost of input bundles of production (labor and intermediate goods), and indirectly through changes in term of trades, and... 

LiFi is a bidirectional wireless optical networking technology that uses commercial LEDs for data transmission. In simpler terms, LiFi is considered a light-based WiFi that uses light instead of radio waves to transmit information. Using light to transmit data allows LiFi to deliver a couple of advantages, such as working in areas susceptible to electromagnetic, working across higher bandwidth while offering higher transmission speeds. Finally, the security of this technology is much more than other ways of communication since the light cannot penetrate through walls and doors, so other people who are not in the room could not access data.In this dissertation, a Li-Fi receiver that uses... 

In this work hydrometallurgical route for processing spent commercial catalysts (Co/Al2O3) are investigated for leaching the Cobalt component. The used catalysts were initially pre-oxidized at 500 °C and 5 h in order to eliminate coke and other volatile species present. Pre-oxidized catalysts were dissolved in solvents such as H2SO4, HNO3, HCl and H2O at 80-90 °C, and the remaining residues separated from the solution. These experiments were performed at different concentrations, presence and absence H2O2 solution. Also effect of reflux on leaching process investigated. The result show the yield of the pre-oxidized catalysts extracted with highly concentration of extractant is higher than... 

Interconnects in SOFC’s has oxidation problems which is Because of high temperature operation. Also Cr migration to cathode make chroumiom poisoning problems and all of this affects SOFC’s efficiency. To solve this problem researchers decided to use some protective coating on interconnect. The best group of coatings is Mn-Co Spinels. In this thesis (Mn,Co)3O4 spinels was synthesized via solid state reaction. MC reffered to Mn1.5Co1.5O4 was calcined at 850°C and then sintered at 1200°C. It’s electrical conductivity measured by 4-point probe DC method. It had the lowest ASR (17mΩ.cm2) among other stochiometries. To reduce the sintering temperature, Cu and Y was added as dopants. Among the... 

RFID systems are available in various applications for indoor and outdoor positioning. Location awareness in public environment and in stores and companies are widely in use. In indoor environment , multipath and fading changes signals specification, so it is difficult to detect the related parameters. In the other hand the necessity of fast and reliable system which support traffic and a large number of users are in demand. RFID which is based on radio frequency signals is developed for this aim.RFID system with asymmetrical link which support UWB and Narrowband signals is suggested for indoor positioning application. RFID passive tag in this system is redesigned in his thesis.... 

Nowadays, optical networks is one of the best options for ultra high speed data transmission. An optical network is either implemented using optical fibers or via free space optical links. Fiber optics has gained special popularity among all mediums of data transmission, however, builing a fiber infrastructure is not a cost or time effective solution and this is the main limitation of these networks. Free space optics has been an attractive answer to overcome the drawbacks of the fiber optic networks. On the other hand, atmospheric turbulence and scattering are the main factors affecting FSO’s availability and Reliability. As a result, Design of next generation FSO networks need high speed...