Sharif Digital Repository

The development of natural gas supply systems and its transmission networks are vitally important to achieve a natural gas economy. Development and planning of natural gas transmission networks as multidisciplinary projects have crucial impact on the economy of gas-rich countries like Iran. The nvestment costs and operation expenses of pipeline networks are so large that even small improvements in system utilization and planning can involve substantial amounts of money. A large number of technological options exist for development in conversion, distribution levels and …, which cause various pathways for supplying natural gas. In addition there are many energy recovery technologies along... 

Wireless Sensor Networks have become widespread because of their flexibility, applicability and ability to precept data with high accuracy. However, the most limiting factor in their usage is the amount of available energy in nodes since energy depletion in a node means that it is dead, therefore many efforts have been done for optimum energy management in Wireless Sensor Networks. In many cases, the key solution to prolong the network lifetime is load balancing. In this way, all the nodes will die (approximately) together and the lifetime of network will be maximized. Load balancing can be implemented in all layers from physical layer to application. It should be noted that it is not always... 

The electrical voltage, current and power output is calculated due to harmonic forced vibration of shell energy harvester. So five electromechanical equation together with Gauss equation is solved for doubly curve shell harvester in steady state condition in order to derive voltage, current and electric power output. The effect of shell curvature in cylindrical and spherical shells, the harvester series or parallel connection of layers and thickness of substrate and piezoelectric layer, is also considered in order to obtain maximum power output. The results show for small shell curvatures a high frequency load is needed to obtain maximum power and when the shell arc length is three times to... 

In this dissertation, we focus on two types of EH cooperative networks. In the first type, the source and relay nodes access a shared channel according to a random access protocol. Also, they harvest energy from non-RF environmental resources. The relay node has data and energy buffers to store the packets of the source and the harvested energy, respectively. Our main goal is to find the optimal relaying protocol at the relay node. In this regard, the first type of the EH cooperative networks are investigated in two different scenarios. In the first one, the MAC channels of the nodes are independent of the applied policy at the relay node, and thus the throughput of the network is fixed.... 

In recent years, energy harvesting from ambient sources in order to use for low-powered electronics has been considered by many researchers. Wind energy, solar energy, water energy, mechanical energy from vibrations, etc are common sources of ambient energy. In this thesis, optimization of energy harvesting from ambient vibration using magnetic shape memory alloy is presented. To this end, a clamped-clamped beam coupled with MSMA units is considered. A shock load is applied to a proof mass which is attached to the middle of the beam. As a result of beam vibration a longitudinal strain is produced in the MSMA. This strain changes magnetic flux inside the coil connected to MSMA and as a... 

Energy Harvesting is one of the techniques which can be utilized in Green Communications and increase the wireless networks lifetime. In an EH system, each resource is supplied with the energy harvested from the environment. When we confront with a situation that the users of one channel want to increase their rates and this action negatively affects the other user’s rates, the user’s cooperation problem for obtaining a fair rate will be created. In this study, at first we consider a Multiple Access Channel and we assume that the energy resources of transmitters are harvested according to a known probability. In addition, we assume that the transmitters do not know the instantaneous amount... 

Among different mechanisems for ambient energy harvesters, energy harvesting systems by means of magnetic shape memory alloys are noted due to their long life time, large strain amplitudes and the ability to operate at low frequencies. Strain change in these systems, changes the MSMA magnetization resulting change in the magnetic flux leading to inducing voltage by means of pickup coil. in the commercial systems, magnetic flux path is created by inserting an MSMA specimen in the air gap of ferromagnetic core and generation of bias magnetic field by means of the permanent magnet or electromagnet. In this proposed research, a thermodynamic based constitutive model is selected for the mdeling... 

Nowadays energy consumption becomes an important design factor in communication systems because of financial reasons and environmental concerns. There would be many equipments with large energy consumption in next generation (5G) networks, so energy efficiency will play an important rule in these networks. Two alternative techniques used for energy consumption management are energy harvesting and simultaneous wireless information and power transfer (SWIPT). A useful scenario in SWIPT is to use received energy for future transmissions. In this scenario, the design of encoder and decoder is a new open problem, because of the memory now appeared in the system. Thus to understand the interplay... 

Harvesting energy from renewable sources in nature, such as wind energy, solar energy, water energy and vibrations has always attracted researchers. There exist different ways to harvest energy from environmental vibrations. In this thesis, energy harvesting via Magnetic Shape Memory Alloys (MSMAs) has been taken into account due to important advantages of these alloys, such as their long fatigue life and good performance at high amplitudes and low frequencies.In this system, applying strain on alloy changes the magnetization and this change generates voltage in the pick-up coil around the MSMA. On the other hand, since the strain-magnetization relation is nonlinear and hysteresis,... 

In this thesis, we investigate the achievable secrecy rate in a relay channel where the source and the destination wish to keep the information confidential from an untrusted relay (potential eavesdropper). The relay has no energy supply, and harvests its required energy for relaying from its received signals. For radio-frequency (RF) Energy Harvesting (EH) at the relay,we adopt power splitting (PS) and time switching (TS) approach. We study the problem of achieving positive secrecy rates between the transmitter and the receiver while making use of an untrusted relay. Energy limitation at the relay makes the problem more interesting. Because,the relay must choose either to eavesdrop the... 

Energy crisis has always been a crucial issue faced by the development of wireless communication techniques. As a more energy-efficient network architecture, green communications and networks (GCNs) have recently attracted significant attention from academia and industry. In order to enable the technical and economical GCNs, several emerging techniques have been proposed including energy-efficient and energy harvesting techniques. Although these emerging techniques have drawn considerable attention and have been studied recently, there are still many open theoretical and practical problems to be addressed. Energy harvesting (EH) is a key technology to achieve the objectives of GCNs. This... 

Harvesting energy by magnetic shape memory alloy has many advantages against other various methods which harvested from environmental vibrations and has been considered due to high long longevity, large strain amplitude and good performance in low frequencies. These materials can display up to % recoverable strain in response to the application of a magnetic field or compressive mechanical stress. Microstructure of these materials changes under applying mechanical loading and/or magnetic field which cause magnetic vector rotating in magnetic domain. Change in magnetization of these materials, lead to harvesting energy by considering Faraday's law of induction. The model of this... 

Magnetic shape memory alloys (MSMAs) are a new kind of smart materials which are great alternatives for energy harvesting systems due to some unmatched characteristics such as reversible large strain, high cycle fatigue and fast time response. In this work, an energy harvesting system using MSMA is studied. For this goal, a 3-D thermodynamic-based MSMA model is applied for predicting magnetomechanical behavior of the MSMA sample which is used in the energy harvester system. Since demagnetization effect, which has a great influence on the model’s outputs, has been neglected in the selected MSMA model, a new approach is presented for inserting demagnetization coefficients, regarding to the... 

Device to device communication (D2D) in cellular networks is seen as a promising thechnology to assist local communication services. It offers several gains including cellular traffic offloading gain and proximity gain of devices that allows high data rate, low power consumption, low delays and the reuse gain when cellular and D2D links are allowed to utilize same radio resources simultaneously. D2D communication is one of the key enabler for fifth generation (5G) networks. Major bottleneck in the operation of D2D communication is energy. The direct D2D communication can result in energy inefficiency as the battery powered devices are required to perform energy consuming tasks on their own... 

Evolution of electrical devices and the need for wireless sensor and remote control has led to extensive research in field of energy harvesting. Regarding this approach, most studies devoted to use of piezoelectric effect in converting the dissipative vibration energy into usable electrical energy. Despite extensive progress made in this field of engineering, there were no significant growth in analytical solution and implementation of mathematical equations related to dynamic and electricity of piezoelectric harvester of beams with different geometries. The main focus of this thesis is solving constitutive and coupled electromechanical equations of piezoelectric harvester related to a... 

Vibration based energy harvesting is the process of trapping and collecting vibrational energy from ambient sources which seem unusable at first sight. The smart materials with the capability of coupling two different fields can be used in converting vibrational energy to electrical one. One of this smart material which has been taken into account recently is the Magnetic Shape Memory Alloy (MSMA) and it can couple the magnetic and mechanical fields. In MSMAs the total magnetization vector changes with the application of stress and make it possible to harvest energy from Faraday law’s of induction. An important phenomena that exist in MSMA is the dependency of magnetization-strain behavior... 

The need to supply energy of low voltage electronic circuits such as sensors and wireless systems has attracted many researchers in recent years. As a solution to this problem, the energy needed for electronic devices can be obtained from the surrounding environment. An important part of energy harvesters are the systems that use vibrating energy of mechanical devices known as vibration power generators. Most linear vibration generators are systems that operate in resonance mode. As the frequency of the environment moves away from the natural frequency of the generator, the amount of converted energy decreases significantly. For this reason, some solutions are needed to solve this problem. ... 

Ocean waves are a huge, renewable energy resource, and the potential for extracting energy from waves is high. So a lot of different systems have been designed but most of them are hydraulically and have a lot of problems and they are very complex. In this thesis, the mechanism designed is purely mechanical and very simple and innovative. It has some gears in special combination with together. The mechanism can convert any form of oscillation to rotation movement; this event has been shown in results and prototype. According to the results and discussion, Designed mechanism needs very low maintenance and has low lost. So, efficiency is between 80-95%  

Energy harvesters are used in today’s Wireless Sensor Networks (WSNs) to harvest the energy from the environment. One of the important advantages of the energy harvesting sensor networks over battery-operated sensor networks is that the use of the energy harvester prolongs the life time of the nodes, while a battery-operated node becomes useless once its energy runs out. Although an energy harvester can provide a supply source with a lifetime much greater than a battery, the amount of available energy for an energy harvesting system is a random variable and is not as predictable as the energy of a battery. This unpredictability may cause reliability problems. In order to solve the existing... 

Considering energy efficiency ways a key role in designing future wireless networks( 5G mobile networks). Moreover Spectrum efficiency is another critical issues in designing wireless networks. Cognitive radios can improve the spectrum efficiency. On the other hand, radio frequency (RF) energy harvesting has emerged as a promising technique to supply energy for wireless networks and thereby increase their energy efficiency. In this thesis, we propose a new technique for the RF-powered CRNs.To this end,We consider a cognitive radio network comprised of a primary user and a secondary user. The primary user, uses a typical frequency band for transmit data in a time slot basis and both the...