Sharif Digital Repository

One of the challenging problems in real-time data-parallel processing applications is to schedule tasks to different servers aiming to increase data locality for higher efficiency or lower delay, and at the same time, doing load balancing to stabilize the system of server-queues. We target this problem, and discuss efficient real-time task scheduling algorithms aimed not only to stabilize the system when the arrival rate is in the capacity region (i.e. throughput optimality condition), but also to minimize the mean delay of all tasks in heavy traffic regime when the arrival rate approaches the capacity boundary (i.e. heavy-traffic optimality condition). In this paper, we point out the data... 

The main objective of this work is to develop a novel moving-mesh finite-volume method capable of solving the seepage problem in domains with arbitrary geometries. One major difficulty in analysing the seepage problem is the position of phreatic boundary which is unknown at the beginning of solution. In the current algorithm, we first choose an arbitrary solution domain with a hypothetical phreatic boundary and distribute the finite volumes therein. Then, we derive the conservative statement on a curvilinear co-ordinate system for each cell and implement the known boundary conditions all over the solution domain. Defining a consistency factor, the inconsistency between the hypothesis... 

Reliability and security are two important subjects in modern digital communications. A secure channel coding scheme provides both of reliability and security in one process to combat problems in an unreliable and insecure channel. In this paper, a secure block turbo coding scheme will be proposed and analyzed. Security and reliability are based on pseudo-random puncturing. Simulation results show that this scheme has superior performance and high security  

Influence of two nano-size additives oSubject:A. Suspensions. Subject:C. Electrical conductivity. Subject:Castable. Subject:E. Refractories. Subject:Castables. Subject:Electrical conductivity. Subject:Electrical property. Subject:High alumina. Subject:matrix. Subject:Mechanical strength. Subject:Nano-size. Subject:Polycarboxylate ethers. Subject:Refractory castables. Subject:Working time. Subject:Alumina. Subject:Cement additives. Subject:Electric conductivity. Subject:Ethers. Subject:Suspensions (fluids) Subject:Refractory materials. n electrical properties of suspension matrix of self-flowing low-cement high alumina refractory castable is investigated. For this purpose, castament FS 10 and... 

In this paper, we address global non-fragile control and synchronization of a new fractional order chaotic system. First we inspect the chaotic behavior of the fractional order system under study and also find the lowest order (2.49) for the introduced dynamics to remain chaotic. Then, a necessary and sufficient condition which can be easily extended to other fractional-order systems is proposed in terms of Linear Matrix Inequality (LMI) to check whether the candidate state feedback controller with parameter uncertainty can guarantee zero convergence of error or not. In addition, the proposed method provides a global zero attraction of error that guarantees stability around all existing... 

The first step to locate Partial Discharge in power transformers is to find a model that can clearly explain the behavior of the winding in high-frequency. The detailed model is one of the models used for the study of PD. One of the fundamental problems of the described model is to find its parameters. And the accuracy in calculating these parameters has significant impact on reducing the simulation error and PD locating. The current paper seeks to calculate the parameters of the detailed model 20kv distribution transformer winding by using the finite element method (FEM). Comparing the results of this model with pulse waveforms obtained from the PD to the winding in the laboratory... 

A single-degree-of-freedom model is considered for flexible exercise bars based on the lumped-element approach. By considering the side segment of a flexible bar as a cantilever beam with an equivalent mass at the free end, its free-vibration response, as well as the forced response under the excitation of the grip, are expressed parametrically. Experiments are performed on a particular flexible bar (FLEXI-BAR) in order to obtain numerical values for quantifying the model's parameters. The model is also computationally simulated to study the response of the flexible bar to various excitations. The results are imported into a multi-segment musculoskeletal software (AnyBody), where the effect... 

While the differentiation factors have been widely used to differentiate mesenchymal stem cells (MSCs) into various cell types, they can cause harm at the same time. Therefore, it is beneficial to propose methods to differentiate MSCs without factors. Herein, magnetoelectric (ME) nanofibers were synthesized as the scaffold for the growth of MSCs and their differentiation into neural cells without factors. This nanocomposite takes the advantage of the synergies of the magnetostrictive filler, CoFe 2 O 4 nanoparticles (CFO), and piezoelectric polymer, polyvinylidene difluoride (PVDF). Graphene oxide nanosheets were decorated with CFO nanoparticles for a proper dispersion in the polymer through... 

We have investigated the piezoelectric response of the hydrogenated graphene oxide (H-G-SiO2) stacks both experimentally and theoretically. The piezoresponse force microscopy method and density-functional theory (DFT) calculations were used to study the piezoresponse effect of this structure from both experimental and computational point of views. A mono-layer graphene, made by chemical vapour deposition method, is deposited on Si/SiO2 substrate and its surface is then functionalized with hydrogen atoms. The vertical piezoresponse, observed by piezoresponse force microscopy, is measured to be about 2146 pC N-1, that is comparable to the reported state of the art piezoelectric materials such... 

Design of an Ultra-Wideband 3-dB quadrature (90°) Hybrid using ADS and HFSS softwares plus Measurement report are presented. Simultaneous Use of these two softwares lead to fast and accurate design procedure. The coupler is realized in broadside stripline and with the connection of coupled regions in tandem structure. The measured data agrees well with the expected values from simulations, and shows a good ultra wide bandwidth response over the frequency range of 1-10 GHz. Measurements showed an amplitude unbalance of ±1.5 dB, a phase unbalance of 90°±7° , and an isolation and a return loss characteristics of more than 14 dB over the frequency of 1 to 10 GHz  

The Ni-base superalloy GTD-111 is employed in high-power stationary gas turbines because of its high temperature strength and oxidation resistance. The temperature dependence of the tensile behavior of GTD-111 has been studied by tensile tests in the temperature range of 25-900°C with a constant strain rate of 10-4s-1. The results showed an abnormal tensile property variation with increasing temperature. The yield strength decreased slightly with temperature up to about 650°C and then increased between 650 and 750°C. Above 750°C, a rapid decrease in the yield strength was found. The tensile strength showed a similar behavior except for its maximum that occurred at 650°C. The elongation... 

Bioinspired materials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. In this study, biomimetic micro/nanoenvironments were fabricated by cell-imprinted substrates based on mature human keratinocyte morphological templates. The data obtained from atomic force microscopy and field emission scanning electron microscopy revealed that the keratinocyte-cell-imprinted poly(dimethylsiloxane) casting procedure could imitate the surface morphology of the plasma membrane, ranging from the nanoscale to the macroscale, which may provide the required topographical cell fingerprints to induce differentiation. Gene expression levels of the genes analyzed... 

Grid computing is a type of parallel and distributed system that provides the possibility of sharing, choosing and collecting the autonomous resources (such as computer, software, databases, and equipments) that are distributed geographically. Resource discovery is one of the key subjects in distributed systems and especially Grids. We should consider that Grid consists of different applications that each of them consist of different hardware and software resources, therefore recognizing these resources is important in a Grid system. Classical approaches to Grid resource discovery are either centralized or hierarchical [1] (and will maybe prove inefficient as the scale of Grid systems... 

Recently, a renewed interest arises in the application of nanotechnology for the upstream petroleum industry. In particular, adding nanoparticles to fluids may drastically benefit enhanced oil recovery (EOR) and improve well drilling, by changing the properties of the fluid, rocks wettability alteration, advanced drag reduction, strengthening the sand consolidation, reducing the interfacial tension and increasing the mobility of the capillary trapped oil. In this study, we focus on roles of clay nano-particles on polymer viscosity. Polymer-flooding schemes for recovering residual oil have been in general less than satisfactory due to loss of chemical components by adsorption on reservoir... 

Polyurethane (PU) nanocomposites with 0, 1, 3, 5, and 7 wt-% nanoclay contents were prepared. X-ray diffraction patterns, transmission electron microscopy images, tensile test, and thermogravimetric analysis were utilised to reveal the morphological, mechanical, and thermal-resistant properties of the prepared nanocomposites. The exfoliated structure was obtained for nanoclay contents up to 3 wt-%. Incorporation of nanoclay to the PU matrix prompted the thermal stability of the polymer. A nanocomposite filled with 3 wt-% nanoclay showed the best tensile strength in the prepared nanocomposites. Subsequently, the nanocomposite with the 3 wt-% nanoclay was reinforced with carbon and glass... 

Buckling and post-buckling behaviors of geometrically imperfect annular sector plates made from nanoparticle reinforced composites have been investigated. Two types of nanoparticles are considered including graphene oxide powders (GOPs) and silicone oxide (SiO2). Nanoparticles are considered to have uniform and functionally graded distributions within the matrix and the material properties are derived using Halpin-Tsai procedure. Annular sector plate is formulated based upon thin shell theory considering geometric nonlinearity and imperfectness. After solving the governing equations via Galerkin’s technique, it is showed that the post-buckling curves of annular sector plates rely on the... 

Central nervous system (CNS) uses vision, vestibular, and somatosensory information to maintain body stability. Research has shown that there is more lumbar proprioception error among low back pain (LBP) individuals as compared to healthy people. In this study, two groups of 20 healthy people and 20 non-specific low back pain (NSLBP) participants took part in this investigation. This investigation focused on somatosensory sensors and in order to alter proprioception, a vibrator (frequency of 70 Hz, amplitude of 0.5 mm) was placed on the soleus muscle area of each leg and two vibrators were placed bilaterally across the lower back muscles. Individuals, whose vision was occluded, were placed...