Sharif Digital Repository

In this paper we discuss and analyze an enhanced media access control (MAC) layer protocol which uses the signaling method benefits of physical layer in order to provide different quality of service (QoS) levels in optical code-division multiple-access (OCDMA) packet networks. In the proposed network architecture the users are categorized into the high and low classes of service. Users of each class transmit at the same power level and different from the other classes' users. Also, the MAC of each user estimates the amount of interference on the channel and adjusts the packet transmission's time to improve network performance. Through simulation it is shown that the combination of... 

In this paper, we introduce a novel algorithm for rate allocation in media streaming P2P networks where multimedia contents are distributed among network members and streamed toward any requesting peer. The proposed algorithm is based on ant-colony optimization. It is capable of handling network dynamism, which is an inherent property of unstructured P2P networks. Another advantage of our algorithm is its ability to get over uncertainties in network state information, particularly the rate of supplying peers that could happen due to lack of accurate measurements. In addition, the suggested method does not rely on any information about the topology of the network. We have investigated both... 

Within-die process variation is increasing in nanometer-scale process technologies. We observe that the same SRAM cell leaks differently under within-die process variations when storing 0 compared to 1; this difference can be up to 3 orders of magnitude at 60mV variation of threshold voltage (V th). Thus, leakage can be reduced if most often the values that dissipate less leakage are stored in the cache SRAM cells. We take advantage of this fact to reduce instruction-cache leakage by presenting three binary-optimization and software-level techniques: we (i) reorder instructions within basic-blocks so that their bits better match the less-leaky state of their corresponding cache cells, (ii)... 

In this study, the effects of ferrofluids on the forced convective heat transfer in a tube with a round cross section under constant heat flux in the laminar flow regime are investigated experimentally. For this purpose, an experimental setup was designed and built. Furthermore, the effects of an external magnetic field on the forced convective heat transfer were examined for various Reynolds numbers and volume concentrations. The parameters of magnetic field strength, magnetic field arrangement, the constancy or oscillation of the magnetic field and also its oscillatory mode were examined. As a result of the experimental studies, in the absence of a magnetic field enhancement in convective... 

A table-based application-specific data prefetching mechanism is presented in this paper. This mechanism is proposed to improve the performance of the application specific instruction-set processors (ASIP) we develop customized to an object-oriented application. In this approach, we divide the data accesses of a class method into two conditional and unconditional parts. We supply the prefetch engine with the static information about each part to prefetch all data fields of an object required by a class method when the class method is invoked. Effective management of memory access patterns by dividing them based on the method to which they belong and storing the access information of nested... 

Signal compression is an important element encountered in data storage applications. Over the years various techniques for data reductions have been proposed. In this paper we introduce an effective method for compressing semi-periodic signals. Although the approach is applicable to any semi-periodic signal, our attention is focused on the compression of electrocardiogram (ECG) signals. An ECG signal is composed of many similar beats which makes it to behave semi-periodic This paper deals with beat variation periods and exploits the correlation between cycles (inter-beat) and correlation within each cycle (intra-beat) for compression. For efficient compression a 2-dimensional array is... 

An ECG signal is composed of many similar beats which makes it to behave semi-periodic. This paper deals with beat variation periods and exploits the correlation between cycles (inter-beat) and correlation within each cycle (intra-beat) for compression. For efficient compression a 2-dimensional array is constructed from the one dimensional ECG signal using decimation and interpolation in the discrete cosine transform (DCT) domain. Since reasonable results in image compression have been achieved by means of set partitioning in hierarchical trees (SPIHT) algorithm, we use SPIHT algorithm to code the 2-D wavelet transform of the ECG signals. Experimental results on selected records of ECG from... 

Sludge handling is a common issue in all biological wastewater treatment methods. In this study, sonication technique as a state-of-the-art technology has been applied to a continuous MBBR system with the aim of sludge reduction. A novel configuration of MBBR with an additional recycle stream of sonicated sludge was used as the experimental setup. Based on exposed energy and sludge disruption performance, optimized sonication density and exposure time were obtained 1.5 W/mL and 15 min, respectively. This condition provided 42.2% increase in soluble COD as a result of sludge disintegration. Our results revealed that the performance of MBBR and excess sludge reduction were affected by... 

The main purpose of this study is to evaluate the effect of intravenous irradiation of different low-level laser wavelengths on the activity of lecithin-cholesterol acyltransferase (LCAT), paraoxonase (PON1), catalase, and ferric reducing ability of plasma (FRAP) in diabetic rats. First, diabetes was induced in rats using streptozotocin (STZ). Enzymes’ activity was measured in the blood samples and compared before and after intravenous laser blood irradiation. We used four continuous-wave lasers—IR (λ = 808 nm), Red (λ = 638 nm), Green (λ = 532 nm), and Blue (λ = 450 nm)—to compare the wavelength’s effect on different enzymes’ activity. Laser power was fixed at 0.01 mW and laser energy was... 

In this paper we integrate a verification methodology with our object-oriented system-level synthesis methodology to address the problem of HW/SW co-verification after system synthesis. We have defined a set of system-level assertions. These assertions are automatically converted to monitor hardware or monitor software during the system-level synthesis process depending on their type and also synthesis style of their corresponding functions. The synthesized assertions are functionally equivalent to their original system-level assertion, and hence, can be used to verify the system after HW/SW synthesis. This way, not only system-level assertions are reused in lower-levels of abstraction, but... 

Titanium anodes coated with noble metal oxides are widely used in chlorate industry. In fact, these anodes are dimensionally stable. In this article, the electrochemical characteristics of the ternary oxide coating created by sol-gel on titanium, which consisted of Ti, Ru and Ir, were investigated in the number of different layers. The electrochemical properties of anodes, morphology of samples, and phase analysis were investigated respectively by cyclic voltammetry and polarization measurements, Field Emission Scanning Electron Microscope (FESEM) and XRD. The result indicated that the application of the more layer number increases the rate of chlorine evolution. Also, The morphology of the... 

The ODYSSEY methodology takes an unconventional approach to designing at Electronic System Level (ESL): it expands the traditional definition of the processor instruction-set and introduces a new class of processors whose instructions correspond to the methods of an object oriented class library. These new processors, called Object-Oriented Application-Specific Instruction Processor (OO-ASIP), provide a versatile vehicle to explore the synergy between hardware and software not only when implementing an OO application for the first time, but also more significantly, when expanding an existing product for additional functionality or customization. This book provides ESL researchers and... 

In nanometer-scale process technologies, the effects of process variations are observed in Multiprocessor System-on-Chips (MPSoC) in terms of variations in frequencies and leakage powers among the processors on the same chip as well as across different chips of the same design. Traditionally, worst-case values are assumed for these parameters and then a deterministic optimization technique is applied to the MPSoC application under design. We show that such worst-case-based approaches are not optimal with the increasing variation observed at system-level, and instead, statistical approaches should be employed. We consider the problem of simultaneously choosing MPSoC architecture and task... 

Share of leakage in total power consumption of static RAM (SRAM) memories is increasing with technology scaling. Reverse body biasing increases threshold voltage (Vth), which exponentially reduces subthreshold leakage, but it increases SRAM access delay. Traditionally, when all cells of an SRAM block used to have almost the same delay, within-die variations are increasingly widening the delay distribution of cells even within a single SRAM block, and hence, most of these cells are substantially faster than the delay set for the entire block. Consequently, after the reverse body biasing and the resulting delay rise, only a small number of cells violate the original delay of the SRAM block; we... 

Titanium anodes activated by noble metal oxides possess a wide range of advantages and applications. Actually, coating of titanium anodes by highly conductive oxides of noble metals (Ru, Ir) dramatically increases the lifetime of these anodes. In this study, the binary coating consisting of Ti and Ru and the ternary coating consisting of Ti, Ru and Ir were prepared through sol–gel method. After coating of the titanium substrate, the corrosion behavior of coatings was studied by anodic polarization and cyclic voltammetry tests. The lifetime of anodes was determined using accelerated corrosion test. The morphology of coatings was examined by field emission scanning electron microscopy and... 

A model-based algorithm is proposed and tested using the simulator and operation data of a plastic pipeline prototype to locate multiple non-simultaneous leaks in the pipeline. A combination of an extended Kalman filter and obtained relations from the steady state response is used in order to tackle the problem of multi-leak localization. To achieve the mentioned relations, a real pipe with two leaks is equated to a virtual pipe with a single virtual equivalent leak  

We describe implementation of design automation tools that we have developed to automate system-level design using our ODYSSEY methodology, which advocates object-oriented (OO) modeling of the embedded system and ASIP-based implementation of it. Two flows are automated: one synthesizes an ASIP from a given C++ class library, and the other one compiles a given C++ application to run on the ASIP that corresponds to the class library used in the application. This corresponds, respectively, to hardware- and software-generation for the embedded system while hardware-software interface is also automatically synthesized. This implementation also demonstrates three other advantages: firstly, the...