Sharif Digital Repository

These days, societies prefer to use systemsthat provide more utilities with rapid processing. This lead to make large volume of information to process.And also, the number of processors used in embedded systems is more than the number of them in PC. Gradually, the embedded systems own complex processor. On the other hand, according to the Moore’s law, the number of transistors on a chip doubles every eighteen months. That lead to be more complex. And also, based on predictions, the amount of software used in most of electronic devices doubles every two years.The increasing of amount of information and high-performance expecting havecaused increaseprocessing. The increasing requires more... 

Technology advances in the era of wireless communications leads to the birth of a very useful network called Wireless sensor Network which is very interesting for scientists and researchers. While these networks consist of tens to thousands of tiny sensor nodes, they consume their energy from none-rechargeable batteries. Reducing energy consumption and extend the life of network is the most challenging requirement for these kinds of networks; in some environments like military training which precision and sensitivity are critical, it might take at least K sensors to cover the whole area and these conditions leads to a vast data repetition in network and as a result energy exhaustions in... 

Temporary or permanent overload commonly occurs in soft real-time systems. In such situations,the scheduler cannot guarantee the completion of all tasks prior to their deadlines.Hence, some tasks are usually aborted before or during the execution with the aim of maximizing system utility. For this purpose, time-utility function (TUF) of tasks is used to determine how to maximize the accrual utility of the system. Tasks which can provide more utility are more preferable for execution. Previous works on utility accrual maximizing algorithms have not considered memory allocation in accruing utility of soft real time systems. In this thesis, we present an online scheme for multicore embedded... 

Energy consumption is one of the most crucial issues in embedded systems and memories are responsible for a considerable portion of it. Furthermore, leakage power is becoming the dominant part of total power consumption as the feature size of transistors is scaled down, therefore, the memory management must be improved in order to mitigate the negative effect of increased static power dissipation. In this study, a new memory architecture and a new data mapping algorithm are presented that reduce the energy consumption of multi-core embedded systems while respecting the timing constraints. We propose a novel two-level scratch-pad memory (SPM) based on STTRAM, which is a type of non-volatile... 

In this thesis, we consider the simulation and active control of a centrifugal compressor in during surge occurrence. Surge, as an aerodynamic instability in compressors, causes to severe decrease of efficiency and loss of energy and with stabilizing the compressor in this condition, efficiency and system reliability increase. Nowadays, anti surge systems are used for surge avoidance in different industrials. They recycle the compressed gas from compressor down-stream to up-stream in instability condition and cause to exit the operation point from unstable zone. In this thesis, at first compression system is modeled based on Greitzer model and governing equation of compressor shaft in surge... 

consumption is an economical and environmental concern in nowadays world. Data centers (DC) are an important and energy power hunger part of modern life infrastructure. Many researches have shown that by considering special properties of DCs (e.g. redundancy) the energy consumption can be reduced. However new advances in hardware and software technologies have made DCs equipment more power proportional, i.e. they consume power proportional to their load. Unfortunately this new feature and many previous works do not have synergy. Also the performance of the DCs is so important that no DC owner is willing to trade it for lower power bills. Therefore algorithms that don’t consider the... 

With a growing concern on the considerable energy consumed by data centers, research efforts are targeting toward green data centers with higher energy efficiency. Networks are essential to today’s highly instrumented and connected society. Currently responsible for a fraction of the energy the IT sector consumes, networks rely on equipments that often use a constant amount of power regardless of their utilization; a worsening scenario as traffic is expected to increase by a factor of three in the next few years. Datacenter networks, for instance, employ devices that consume several kilowatts of power even when idle. This work aims to improve the energy efficiency of datacenter networks by... 

Energy efficiency for Iran, which has large reserves of oil and gas but also has a high energy consumption is important because it ensures the country's energy security and saving each energy unit creates energy exports opportunity. Buildings have high energy saving potential; this sector uses about thirty percent of energy consumption (about half the gas and thirty percent of the annual electricity consumption). Households are not motivated in saving energy because government pays energy subsidy. In this research building energy consumption (in Tehran) modeled by bottom up approach. Then the effect of economic incentive tools such as subsidy, loan and tax on motivation in energy saving... 

The high rate of energy consumption in the building sector has led the designers towards the construction methods that consume less energy during construction up to serviceability. One of these methods is rammed-earth (RE) structures due to the availability of its materials, ease of preparation, considerable decrease in energy consumption and environmentally-destructive consequences. Improving the thermal characteristics besides the mechanical parameters of RE structures develops the application of this method. In the current study, the dynamic thermal parameters of RE wall specimens were experimentally measured under simulated conditions and compared to those of masonry walls. Thereby, a... 

Evaporative cooling systems are of most common cooling systems which their electricity consumption is much lower than vapor compression cooling systems. Enhancement of these system’s performance could help to propagate these systems and also decrease the electricity consumption and corresponding emissions in large scale. In this thesis, first a modified cycle is proposed for evaporative cooling. Then, in order to use evaporative cooling in humid climates, a desiccant wheel is implemented in this modified evaporative cooler. As using evaporative cooling will cause high water consumption, a novel cycle is proposed for desiccant based evaporative cooling which is able to cover system water... 

The fast development of semiconductor industry has moved the design methodology to SoC (System on Chip) design. Due to the increasing number of processing elements, In SoC, buses become the bottleneck of the system and lead to non-efficient designs. NoC (Network onChip) is an efficient solution that eliminates bus bottleneck and it had been introduced as a suitable substructure for interconnecting processing elements. The NoCs were originally built based on Interconnection Networks.They have been proposed as an efficient, scalable, modular and reliable solution to provide on chip communication in any large SoC design. The trend of market to mobile digital systems and battery-powered devices,... 

Recently, the tradeoff between low energy consumption and high fault-tolerance has attracted a lot of attention as a key issue in the design of real-time embedded systems. Dynamic Voltage Scaling (DVS) is known as one of the most effective low energy techniques for real-time systems. Control-theoretic DVS techniques, which have been exploited recently for DVS-enabled systems, are able to adapt well to dynamic workload. In this thesis, we have combined the above two important issues i.e., the control-theoretic DVS and fault-tolerance, and investigated reducing the energy consumption of fault-tolerant hard real-time systems using feedback control theory. Our proposed feedback-based DVS method... 

Nowadays, enterprise storage systems are widely used in data centers such as databases, servers, and bank institutes. Due to mechanical activity of disk drives, these systems are one of the most power consumptive components in data centers. Prefetching and RAID, which are employed to enhance performance, are widely used in data storage systems. These two methods, however, impose significant energy overhead to the system due to the increased disk activity. In this thesis, we first elaborate shortcomings of prefetching and RAID methods. Then, we propose a new energy efficient and RAID-compatible prefetching method (LPTAP), which aims at improving performance and energy consumption. To evaluate... 

Decimal multiplication is a frequent operation with inherent complexity in implementation. Commercial and financial applications require their data to be precise while binary number system cannot ensure precision. Existing research works on parallel decimal multipliers have mainly focused on latency and area as two major factors to be improved. However, energy/power consumption is another prominent issue in today’s digital systems. Hence, in this thesis we present a comparative study of parallel decimal multipliers, considering energy/power consumption (leakage and dynamic power consumption), latency and area. Furthermore, we present two novel techniques to reduce energy/power consumption of... 

In this thesis, Optimum Counterweight and Spring Balancing of a novel kind of mechanism called a general 3-RPS parallel robot in Dynamic Motion are investigated. Balancing is explained as the set of configurations on robot inertial and dimensional parameters which, when convinced, certify that the weight of the links produce less force at the actuators for any configuration of the robot, under dynamic or static behaviors. In the references, different procedures have been suggested for balancing that consisted of counterweights, springs, and other auxiliary equipments. Study represents the essential information for having optimum spring and counterweight balancing in a new (3RPS) robot using... 

Since multi-core processors have become a primary trend in processor development, new scheduling algorithms are needed to minimize power consumption while achieving the desired timeliness guarantees for multi-core real-time embedded systems. Although various power/energy efficient scheduling algorithms have recently been proposed, existing studies may have degraded run-time performance in terms of power/energy efficiency and real-time guarantees when applied to real-time embedded systems with uncertain execution time. Moreover, these algorithms are only provided for a specific set of tasks, while many industrial applications with real-time demands are composed of mixed sets of tasks with a... 

Data generation rate is far more than the technology scaling rate in a way that there will be a 40x gap between the data generation rate and the technology scaling rate in 2020. On one hand, unlike traditional HPC clusters, processors in data centers are not fully utilized and on the other hand, unlike traditional embedded processors, they are not idle most of the time. Therefore, energy consumption of such processors is an important issue; otherwise dealing with a huge volume of data will be problematic in the near future. In this dissertation, we will show that while first level data cache encounters high miss rate, traditional approaches such as data prefetching, which were efficient for... 

RT-level techniques are one of the most important categories of techniques employed for decreasing power consumption in digital systems. These techniques are usually applied in the HDL description of the system, however some of them are applicable automatically by the synthesis tools. Some of the most commonly used RT-level techniques include Operand isolation, Clock gating, Concurrency & Redundancy, Pre-computation and Pipeline for low power. However these techniques have been mostly employed in ASIC designs, and FPGAs have scarcely been addressed. Application of these techniques on FPGAs might need special considerations, since resources on FPGAs are inherently different than their ASIC... 

Energy consumption is one of the most important design constraints in embedded systems and a considerable fraction of the energy is consumed in memories. Memories play an important role in the systems since they occupy a large portion of the die area and they have a substantial impact on the performance of the systems. Therefore, managing their energy is of great importance. Moreover, as the technology scales down, the static energy becomes more important. For instance, in conventional memories like SRAM, the static energy becomes a considerable part of the total energy. Non-volatile memories (NVMs) have been proposed as a promising candidate for conventional memories. NVMs have appealing... 

With the proliferation of data centers, their ever-growing energy consumption has gained lots of attention from both academy and industry . Two primary parts that use majority of energy in data centers are IT equipment and cooling system or Computing Room Air Conditioning (CRAC) unit. Energy consumption of cooling system strongly relies on thermal performance of data center. Therefore, applying thermal management techniques for decreasing energy consumption of CRAC is a common practice. Moreover, the energy consumption of IT equipment affects the energy consumption of CRAC directly. Demand for more computing resources in data centers and their physical limits has, motivated the use of FPGAs ...