Sharif Digital Repository

Wireless sensor networks consist of many small sensor nodes which suffer from some limitations like energy level, band width, processing ability and memory; therefore, decreasing energy consumption, increasing network lifetime and scalability are the main challenges in the area of routing in wireless sensor networks. In the field of routing in sensor networks, many algorithms have been suggested, one group of which is clusterbased hierarchical algorithms. The main goals of such algorithms are reducing energy consumption, distributing consumed energy within whole network and increasing scalability of algorithm. There are some problems in most of cluster-based routing algorithms which cause... 

According to the increasing amount of data exchanged among data centers, the need for speeding up and bandwidth and reduced power consumption has been increased. The information show that about 77% of the data is moved into the data centers. On the other hand, 10% of data center’s power consumption is used to data transmission. Improving the interconnection network of data centers can play an important role in reducing power consumption and speeding up. In recent years, optical interconnects have gained attention as a promising solution. Nevertheless, offering an all-optical and efficient architecture is an important issue. In this study, we intend to provide a multi-stage, all-optical... 

Today with the deployment of cloud computing and web applications; We need to have powerful datacenters with provisioning high bandwidth. Current data centers with electronic network interconnects, using excessive power to provisioning requisite bandwidth. Nevertheless, interconnecting networks in data centers isn’t in maximum efficiency and many components of them aren't used efficiently. So it is necessary to use an optical network with dynamic provisioning variable bandwidth and energy management. In this approach, our proposed architecture is designing topology with adopting dynamically for energy management in optical interconnect networks in data centers. To achieve this we can study... 

The purpose of this project is to identify the most suitable propulsion system for a micro-satellite in LEO for orbit, altitude, and pointing corrections. Hence, different propulsion systems are investigated by comparing the propulsion thrust, mass, volume, cost, and specific impulse. In the first chapter, an introduction is given on micro-satellite and its subsystems. The second chapter discusses first the different types of disturbances that a microsatellite might face and second the control requirements for the satellite to counterbalance these disturbances. In the third chapter, different space propulsion systems are briefly reviewed and their main performance parameters discussed. In... 

Lobe blowers are positive displacement machines (PDM) that are widely used in various industries. The efficiency of lobe blowers depends on the clearance between fixed and moving parts. If the clearance between the parts increases, backflow occurs, which means that the flow returns from the high-pressure zone of the outlet to the low-pressure zone of the inlet, and this makes the blower not have the initial efficiency and work with a lower capacity than its design. This research is carried out with the aim of checking the feasibility of backflow detection using two condition monitoring methods, including ultrasonic and thermography techniques. The sample of this research includes seven...