Sharif Digital Repository

Synthesis of dextran-graft-poly(hydroxyethyl methacrylate) gels as a new fluoride biosorbent was considered in this work. For this propose, the Taguchi experimental design method was used for optimizing the synthetic conditions of the gels to reach high level of fluoride absorbency. The effects of three main parameters including concentrations of monomer (hydroxyethyl methacrylate), crosslinking agent (ethylene glycol dimethacrylate), and initiator (ammonium persulfate) on the final properties of the prepared gels were investigated. The proposed mechanism for grafting and chemically crosslinking reactions was proved with equilibrium water absorption, Fourier-transformed infrared, scanning... 

In this letter, we identify a class of absolutely continuous probability distributions, and show that the differential entropy is uniformly convergent over this space under the metric of total variation distance. One of the advantages of this class is that the requirements could be readily verified for a given distribution. © 1997-2012 IEEE  

Atomistic simulation was used to study the deformation and fracture mechanisms of Ni-Si interfaces under tensile and shear loads dependent on the crystal structure of interface zone. Modified embedded atom method (MEAM) potential was utilized for molecular dynamics (MD) modeling. The simulation includes analysis of common neighbors, coordination number, least-square atomic local strain, and radial distribution function. The profound effect of interface crystallography on the tensile and shear deformation is shown. The highest tensile strength is obtained for interfaces with high plane density due to lowest atomic disorder while under shear loading planes with low density exhibit a high local... 

Time-interleaved analog to digital converters (TI-ADC) offer high sampling rates by passing the input signal through C parallel low-rate ADCs. We can achieve C-times the sampling rate of a single ADC if all the shifts between the channels are identical. In practice, however, it is not possible to avoid mismatch among shifts. Besides, the samples are also subject to jitter noise. In this paper, we propose a blind method to mitigate the joint effects of sampling jitter and shift mismatch in the TI-ADC structure. We assume the input signal to be bandlimited and incorporate the jitter via a stochastic model. Next, we derive an approximate model based on a first-order Taylor series and use an... 

A TI-ADC is a circuitry to achieve high sampling rates by passing the signal and its shifted versions through a number of parallel ADCs with lower sampling rates. When the time shifts between the C channels of a TI-ADC are properly tuned, the aggregate of the obtained samples is equivalent to that of a single ADC with C-times the sampling rate. However, the performance of a TI-ADC can be seriously degraded under interchannel timing mismatch. As this non-ideality cannot be avoided in practice, we need to first estimate the mismatch value, and then, compensate it. In this paper, by adopting a stochastic bandlimited signal model we study the signal recovery problem from the samples of a TI-ADC... 

In high-speed analog-To-digital converters (ADCs), two main factors contribute to high power consumption. The first is the super linear relationship with the sampling rate; i.e., by doubling the sampling rate, the power consumption more than doubles. The second factor arises from the consumption of analog circuitry responsible to mitigate the jitter noise. By employing a multichannel sampling system, one can achieve high sampling rates by incorporating multiple low sampling-rate channels, which results in a linear scaling of power consumption with the number of channels. The main drawback of this system is the timing mismatch between the sampling channels. In this paper, we intend to jointly... 

This paper is devoted to the characterization of an extended family of continuous-time autoregressive moving average (CARMA) processes that are solutions of stochastic differential equations driven by white Lévy innovations. These are completely specified by: 1) a set of poles and zeros that fixes their correlation structure and 2) a canonical infinitely divisible probability distribution that controls their degree of sparsity (with the Gaussian model corresponding to the least sparse scenario). The generalized CARMA processes are either stationary or nonstationary, depending on the location of the poles in the complex plane. The most basic nonstationary representatives (with a single pole... 

A novel biopolymer-based superabsorbent hydrogel was synthesized through chemical crosslinking by graft copolymerization of partially neutralized acrylic acid onto the hydrolyzed collagen, in the presence of a crosslinking agent and a free radical initiator. The Taguchi method, a robust experimental design, was employed for the optimization of the synthesis reaction based on the swelling capacity of the hydrogels. This method was applied for the experiments and standard L16 orthogonal array with three factors and four levels were chosen. The critical parameters that have been selected for this study are crosslinker (N,N′-methylene bisacrylamide), initiator (potassium persulfate), and monomer... 

In this paper, we investigate the problem of designing compact-support interpolation kernels for a given class of signals. By using calculus of variations, we simplify the optimization problem from an nonlinear infinite dimensional problem to a linear finite dimensional case, and then find the optimum compact-support function that best approximates a given filter in the least square sense (ℓ 2 norm). The benefit of compact-support interpolants is the low computational complexity in the interpolation process while the optimum compact-support interpolant guarantees the highest achievable signal-to-noise ratio (SNR). Our simulation results confirm the superior performance of the proposed kernel... 

Today, cloud computing has developed as one of the important emergent technologies in communication and Internet. It offers on demand, pay per use access to infrastructure, platforms, and applications. Due to the increase in its popularity, the huge number of requests need to be handled in an efficient manner. Task scheduling as one of the challenges in the cloud computing supports the requests for assigning a particular resource so as to perform effectively. In the resource management, task scheduling is performed where there is the dependency between tasks. Many approaches and case studies have been developed for the scheduling of these tasks. Up to now, a systematic literature review... 

In the last decade, the scale of heterogeneous computing (HC) systems such as heterogeneous cloud computing environments was growing like never before. So network failures are unavoidable in such systems, which affect system reliability. Since the task scheduling algorithm in HC is challenging, we investigate a new reliability-aware task scheduling algorithm (RATSA) in this paper. RATSA is designed to schedule tasks on directed acyclic graphs (DAGs) by using the shuffled frog-leaping algorithm (SFLA) and genetic algorithm (GA) as evolutionary algorithms. The population-based SFLA-GA is applied to optimize makespan in the RATSA as an NP-complete problem. Moreover, the proposed algorithm... 

In the last decade, the scale of heterogeneous computing (HC) systems such as heterogeneous cloud computing environments was growing like never before. So network failures are unavoidable in such systems, which affect system reliability. Since the task scheduling algorithm in HC is challenging, we investigate a new reliability-aware task scheduling algorithm (RATSA) in this paper. RATSA is designed to schedule tasks on directed acyclic graphs (DAGs) by using the shuffled frog-leaping algorithm (SFLA) and genetic algorithm (GA) as evolutionary algorithms. The population-based SFLA-GA is applied to optimize makespan in the RATSA as an NP-complete problem. Moreover, the proposed algorithm... 

In this work, the effects of the surface-modified nanodiamond particles (NDs) on the barrier, rheological, mechanical and thermal properties of ethylene vinyl acetate (EVA) composites for the packaging applications were investigated. Fourier transform infrared spectroscopy, as well as thermal gravimetric analysis were employed to study the grafting of vinyltriethoxy silane (VTS) on the surface of NDs. Afterwards, EVA samples containing 0, 0.1, 0.5, 1, 1.5 and 2 wt% of surface-modified NDs were prepared by a two-stage process including the solution and injection processes. In order to evaluate the physicochemical, rheological, mechanical and thermal properties of the EVA/NDs samples, field... 

The problem of extracting low-dimensional structure from high-dimensional data arises in many applications such as machine learning, statistical pattern recognition, wireless sensor networks, and data compression. If the data is restricted to a lower dimensional subspace, then simple algorithms using linear projections can find the subspace and consequently estimate its dimensionality. However, if the data lies on a low-dimensional but nonlinear space (e.g., manifolds), then its structure may be highly nonlinear and, hence, linear methods are doomed to fail. In this paper, we introduce a new technique for dimensionality reduction based on point-wise operators. More precisely, let $ {bf A} n... 

In this paper, we focus on the heavy-tailed stochastic signals generated through continuous-time autoregressive (CAR) models excited by infinite-variance α-stable processes. Our goal is to estimate the parameters of the continuous-time model, such as the autoregressive coefficients and the distribution parameters related to the excitation process for the α-stable CAR process with 0<α>2 based on the state-space representation. Likewise, we investigate the closed form expressions for the parameters of equivalent model in the discrete-time setting via regular samples of the process. We analyze the estimator based on the Monte Carlo simulations and illustrate the estimator consistency to the... 

The binary-valued images usually represent shapes. Therefore, the recovery of binary images from samples is often linked with recovery of shapes, where certain parametric structures are assumed on the shape. In this paper, we study the recovery of shape images with the perspective of low-rank matrix recovery. The matrix of such images is not automatically low-rank. Therefore, we consider the Hankel transformation of binary images in order to apply tools in low-rank matrix recovery. We introduce an ADMM technique for the reconstruction which is numerically confirmed to yield suitable results. We also analyze the sampling requirement of this process based on the theory of random matrices. ©... 

In this letter, we consider the problem of recovering analysis-sparse signals from under-sampled measurements when some prior information about the support is available. We incorporate such information in the recovery stage by suitably tuning the weights in a weighted ℓ1-analysis optimization problem. Indeed, we try to set the weights such that the method succeeds with minimum number of measurements. For this purpose, we exploit the upper-bound on the statistical dimension of a certain cone to determine the weights. Our numerical simulations confirm that the introduced method with tuned weights outperforms the standard ℓ1-analysis technique. © 1994-2012 IEEE  

We study the problem of reconstructing a block-sparse signal from compressively sampled measurements. In certain applications, in addition to the inherent block-sparse structure of the signal, some prior information about the block support, i.e., blocks containing non-zero elements, might be available. Although many block-sparse recovery algorithms have been investigated in the Bayesian framework, it is still unclear how to incorporate the information about the probability of occurrence into regularization-based block-sparse recovery in an optimal sense. In this letter, we bridge between these fields by the aid of a new concept in conic integral geometry. Specifically, we solve a weighted... 

In present work, first, the water-stable metal–organic framework (MOF) nanocrystals, UiO-66-(F)4, were synthesized under green reaction condition and then some PES/PA thin-film nanocomposite (TFN) membranes were prepared using this synthesized nanocrystals (as modifier) and polyethersulfone (as the substrate). The obtained MOF and membranes were characterized by various characterization techniques such as FE-SEM, AFM, PXRD, contact angle measurements and FT-IR spectroscopy. Finally, the forward osmosis performance of the resultant membranes was evaluated by using different concentrations of NaCl as a draw solution and deionized water as a feed solution. Among all used membranes, the membrane... 

In this study, first, the UiO-66-NH2 metal-organic frameworks (MOFs) were modified with graphene quantum dots (GQDs) to facilitate the water attraction on MOF surface as well as improve their compatibility/affinity with the polyamide layer matrix of forward osmosis (FO) membranes. Next, to fabricate a new type of thin-film nanocomposite (TFN) membranes, the synthesized GQDs@UiO-66-NH2 composites are incorporated into the polyamide (PA) selective layer of FO membranes during the interfacial polymerization reaction of m-phenylenediamine (MPD) and trimesoyl chloride (TMC). The influence of the prepared fillers on the chemical structure, morphology, surface roughness and hydrophilicity of the PA...