Sharif Digital Repository

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... 

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... 

Flexible thermoelectric (TE) fabrics were prepared by dip coating of a mixture solution of water base colloidal geraphen nano sheet(GNS) and carbon nano tube(CNT) and polyaniline (PANI) on polyester fabric. The phase composition and morphology of the TE fabrics were investigated by FTIR-ATR diffraction and feld emission scanning electron microscopy. The TE properties of the PANI/GNS or CNT coated fabrics with different GNS and CNT loadings were measured in the temperature range from 303 to 338 K. As the content of GNS increased from 0.5 to 10 wt% and CNT increased from 0.5 to 20 wt%, the electrical conductivity of the PANI/GNS or CNT coated polyester fabrics increased, while the Seebeck... 

All societies need energy to meet the basic needs of the people and to carry out the production processes. From 1850 onwards, the global use of fossil fuels (coal, oil and gas) for energy production increased, leading to a dramatic increase in the emission of carbon dioxide (CO2) into the atmosphere. Rising carbon dioxide and other greenhouse gases in the Earth's atmosphere and seeing adverse effects such as global warming have prompted the international community to replace fossil fuels with clean energy as much as possible. Geothermal energy as one of the clean, sustainable and extensive sources can be one of the available solutions to meet this need.Numerical modeling of geothermal... 

Internet of things (IOT) interconnects a system of low power embedded devices that each of them has a unique identifier, without human intervention. The number of devices of IOT increases every day, therefor routing in the network of IOT is an important challenge. So, Internet Engineering Task Force (IETF) propose a protocol for routing low power and lossy networks in 2012, which is named RPL. Considering the power supply limitation of devices in the network, utilizing energy-aware policies within the RPL is so important. Meanwhile, objective functions have a vital role in the consuming energy. Also, energy consumption determines the lifetime of nodes. Since many of devices are placed in... 

The purpose of this study is to investigate a flapping hydrofoil with semi-active kinematics for energy harvesting and evaluate the effect of different dynamic parameters and structures on its performance. The turbulent flow field with Re = 5 × 105 around a NACA 0015 hydrofoil is simulated by URANS method using commercial software and the dynamics of the oscillating hydrofoil is modeled as a mass-spring-damper set in combination with the fluid solver. The sliding mesh method is used for the pitching motion of the hydrofoil with a reduced frequency of 0.14 in combination with the dynamic mesh method for Transitional motion. Initially, the oscillating hydrofoil was considered as a single... 

Nowadays, energy harvesting from the sea is developing for a variety of applications, including small-scale technologies for the production of small amounts of energy, including the use of low-speed currents to power ocean floor sensors. Ocean floor sensors are currently working with batteries. The cost of replacing or recharging these batteries is high, and the technology of these conventional batteries does not keep up with the rapid development of these sensors. Using new energy harvesting technologies has made the ocean current harvesting system as an adequate replacement for the batteries. According to operating principles, energy harvester can be broadly classified into three general... 

Vortex-induced vibration is a known phenomenon in fluids flow that is being studied in different fields of engineering and usually, we want to reduce the harmful effects of this phenomenon on the subjected structures. Also, it is possible to use this phenomenon for harvesting clean energy from fluids flow. Energy harvesting from vortex-induced vibrations is based on the maximizing of flow instead of its reduction, and the utilization of these vibrations instead of their suppression. Vortex induced vibrations occur in any ranges of Reynolds numbers. Only in three transient regions cause a reduction in vortex-induced vibrations; therefore, even in streams with a velocity less than 0.2 m/s, it... 

OBS1 frame is a concentric bracing system that consists of three elements, and it provides openings for building using a y-form structure. In the present thesis, the OBS system has been accompanied by a smart damping system.The buildings in which this lateral bearing system is employed are considered as SCBF frames. According to design guidelines, seismic performance parameters are required to design these buildings, including response modification coefficient (R), over-strength factor (Ω) and displacement amplification factor (Cd). This thesis aims to quantify these parameters and evaluate their accuracy based on the method proposed by FEMA-P695. In this method, first, the required initial... 

Forward progress (response time), energy consumption, capacitor size, and correct functionality are the most important design constraints of energy harvesting embedded systems. The system needs to backup the state of the processor and memories during the execution periodically to successfully execute long-running applications on energy harvesting systems with unreliable energy sources and small capacitors. The check-pointing policy, which specifies the place, time, and the data to be backed up, has a major effect on the energy consumption, forward-progress, and correct functionality of energy harvesting systems. Furthermore, emerging non-volatile processors equipped with hybrid volatile and... 

Energy consumption is considered as one of the key constraints in the design of Embedded Systems. Exploiting abundant ambient energy offers a practical solution for designing embedded systems. In this regard, emerging trends are surging towards replacing battery-powered embedded systems in various different applications such as wearable systems, Internet of Things, and pervasive computing. Also, with the development and ommercialization of emerging Non-volatile memory technologies,the potential to reduce the static energy consumption and the ability to retain data in the absence of input energy, has become practically feasible for Embedded Systems. Consequently, recent researches have... 

In recent years, with the continuous growth and development of wireless communication systems, the demand for the use of radio spectrum has increased significantly, which has led to problems such as a shortage of spectrum. An effective solution to the spectrum shortage problem is to use cognitive radio. One of the main functions of cognitive radio networks is spectrum sensing and our focus in this study is to examine machine learning and deep learning methods to improve cooperative spectrum sensing. Since channel and noise parameters are not accurate in telecommunication systems, we need to use a method to estimate these parameters. In this regard, the structure of Bayesian with neural... 

Heat sources with temperatures less than 100 °C are available in various processes in the form of waste heat and from renewable sources such as solar energy. One of the methods of gaining benefit from these ubiquitous and abundant heat sources is using thermal harvesters that convert low-temperature heat into electrical energy without the need for the power grid. Portable harvesters can be a reliable and low-cost option for providing stable energy for low-power electronic devices such as wireless sensors. Many studies have been conducted at the global level to design and develop efficient low-temperature heat harvesting mechanisms. However, each of them is associated with fundamental...