Sharif Digital Repository

Dynamic Random Access Memory (DRAM) has been the leading main memory technology during the last four decades. In deep sub-micron regime, however, scaling DRAM comes with several challenges caused by charge leakage and imprecise charge placement. Phase Change Memory (PCM) technology is known as one of the most promising technologies to replace DRAM. Compared to competitive non-volatile memories, PCM benefits from best attributes of fast random access, negligible leakage energy, superior scalability, high density, and operating in both Single-level Cell (SLC) and Multi-level Cell (MLC) storage levels without imposing large storage overhead. Unfortunately, density advantage of MLC PCM devices... 

Despite the advantages of shrinking transistors’ dimensions, e.g. decrease in power consumption and fabrication cost and increase in their switching speed, it has an adverse impact on some characteristics of nano-scale (less than 130nm) transistors that can reduce the system lifetime. Bias Temperature Instability (BTI) and Hot Carrier Injection (HCI) are amongst the most important adverse effects of transistor shrinkage. These two effects, are known as transistor aging, decrease the switching speed of the transistors by increasing the threshold voltage and decreasing the charge carriers’ mobility in the channel of transistors. Temperature, operating voltage, and the size of transistors have... 

Nowadays, due to the need of high performance systems, embedded systems have been redirected to multicore architectures. As energy consumption is one of the most important issues in embedded systems, careful considerations must be taken during the design of embedded systems to achieve low energy consumption. In this thesis, we propose the use of hybrid scratchpad memories to achieve low energy consumption. The hybrid memory uses both SRAM and STT-RAM memory. While STT-RAM has very low static energy consumption it suffers from high latency and energy consumption during write activities. In order to tackle this problem, we have devised a genetic algorithm that exploits architecture information... 

Reliability is an important concern in safety-critical applications. Hardware and software redundancies are used to include reliability in such systems. Software approaches benefit from high flexibility and low cost. Moreover, they do not impose any hardware modifications to the design. The most important challenges of software approaches are performance and code size overheads. Some of software reliability approaches duplicate all of the program’s instructions which impose high performance overhead to the designs. Some other approaches only apply the redaduncies to critical instructions in the programs. While these approaches impose the the performance overhead but they suffer from fault... 

The development of embedded systems in safety critical applications leads to using fault tolerant methods to improve their dependability. Among the various fault tolerant methods, recently, software based methods are more appealing during to the following reasons: 1) They are applicable to the Commercial-Off-The Shelf (COTS) processors and lead to reduction in cost and time to market, 2) Unlike the traditional hardware based internal error detection methods, software based methods fault coverage are more promising, and 3)Software-based methods are cheaper, quicker and do not require any hardware modifications. The technology scaling trend in recent years, made system more vulnerable to... 

Nowadays, improvement in operational condition of distribution networks considering daily growth in electrical energy usage with financial limits appears as a huge challenge for network operators. Under these kind of circumstances, operators need to have efficient and inexpensive plans more than ever. Considering high share of power losses in overall pro-duced power, utilities always tried to minimize losses in Iran and other points of world. In addition, numerous equipment in distribution networks compared with the transmission level, impose high costs to reliability plans. Therefore, reliability improvement plans have been paid low attention by distribution network operators. This lower... 

Capacitor setting and reconfiguration are of main means of loss reduction and voltage profile improvement in distribution system operation. Cooperation between these two strategies can effectively minimize power losses in distribution system automation. Also, from the medium and long term viewpoint, capacitor placement and reconfiguration can be used for loss reduction and reliability enhancement. In this section, the sum of losses cost, capacitor investment cost and reliability cost should be minimized. Regarding the need to solve two non-linear combinatorial optimization problems simultaneously, metaheuristic algorithms are used in this thesis. Specifically, Elitist Genetic Algorithm,...