Sharif Digital Repository

Cloud computing and web applications have further highlighted the need for powerful data centers with large bandwidth and low power consumption. In order to provide such a large bandwidth, today's electronic data centers require high power levels. Furthermore, communications and devices are not always used to their full potential. Optical networks can be a proper option for data centers, as they can offer large and variable bandwidth with lower power consumption compared to their electronic counterparts. In this regard, a dynamic all-optical network architecture is proposed in this paper, with bandwidth reconfiguration capability and low latency to reduce energy consumption. This proposed... 

The current coronavirus disease 2019 (COVID-19) outbreak spread rapidly worldwide. Yet, there is no identifiable antiviral treatment, so an effective drug is urgently needed. Preventive strategies and oxygen therapy are the main practical approaches to prevent and treat COVID-19. Clinical trials are in progress for the antiviral and immunomodulation agents that eventually are being developed for COVID-19 treatment. Pharmacological, immunotherapies, natural-based supplements, biologics, and combination therapies interventions have been established. The concept of drug repurposing was re-visited, and many conventional antivirals or immunosuppresses were evaluated for Efficacy against COVID-19... 

Modeling passengers' itinerary choice behavior helps in understanding the increasingly competitive airline market and in predicting air travel demand. Recently, investigation of the variation in passengers' preferences with regard to factors influencing their choice through estimation of the mixed multinomial logit model has received attention. An extended form of the model identifies sources of heterogeneity and consequently makes the choice models less restrictive in considering both systematic and random preference variation across individuals. This research investigates the existence of significant interactions between passengers' preference heterogeneity around the mean of random... 

In this paper an integrated model has been developed that is capable of considering the effects of process parameters on the thermo-mechanical behaviour of the work-roll and the strip during hot rolling operations. The commercially finite element package ABAQUS is utilized to solve the governing equations, while an elasto-viscoplastic material behaviour is utilized in the model. The model may be employed in single-pass as well as multi-pass rolling layouts. Various aspects of the hot rolling process are predicted including temperature field and thermo-mechanical stresses within the work-roll as well as temperature, strain, and residual stresses distributions within the strip. To assess the... 

Oscillatory behavior and transfer properties of relay feedback systems with a linear plant including a fractional-order integrator are studied in this paper. An expression for system response in the time domain is obtained by means of short memory principle, Poincare return map, and Mittag-Leffler functions. On the basis of this expression, the frequency of self-excited oscillations is approximated. In addition, the locus of perturbed relay system (LPRS) is derived to analyze the input-output properties of the relay system. The presented analysis is supported by a numerical example. Copyright © 2017 by ASME  

In this paper, an oscillatory condition is obtained for fractional order relay feedback systems. This condition is derived by time domain representation of the response of the fractional order relay feedback system on the basis of the Mittag-Leffler functions. Also, using an inequality, which has been recently proved for fractional derivative of convex Lyapunov functions, an invariant set is found for the under-study fractional order relay feedback system. The obtained results are validated by numerical examples  

In this paper, we try to develop and implement the HRV signal processing into a Field Programmable Gate Array (FPGA) for extracting this signals feature  

The present study is a nationwide survey of language identity among English language learners in Iran. The participants who completed the survey in this research included 1851 English language learners from different parts of the country who belonged to different genders, age groups and English language proficiency levels. The main instrument was a validated questionnaire which included 19 items and was administered online and by hand. The results of this survey revealed that Iranian English language learners had a moderate level of language identity and there was no significant difference between the language identity of male and female participants. In addition, the results indicated that... 

Carbon nanotubes (CNT) have unique electronic properties and remarkable optical properties. Despite of on layer thickness of CNTs, it has able to absorb photons from visible to far infrared and terahertz. These unique properties lets to create heterojunction devices by semiconductor/CNTs or metal/CNTs junctions e.g. photodiodes, sensor and heterojunction solar cell. The CNTs can play the role of a heterojunction component for charge separation as a high conductive network for charge transport and as a transparent electrode for light illumination and charge collection. The main objective of the present article is to establish a relation between interface recombination and the characteristics... 

Terephthalic acid is generally produced via oxidation of p-xylene. In this process, a large quantity of residue is produced containing cobalt, manganese, and bromine catalysts as well as by-products such as benzoic acid. Our purpose is to totally recover this residue. Extraction by water has been used as an efficient method to recover catalyst from this residue. In this study, the best condition for extraction was obtained at water/residue dilution ratio of 6: 1, extraction temperature of 45°C and extraction time of 40 min. Efficiency of catalyst recovery was 92 wt % at these conditions. The catalyst containing extracted solution can be reused in the oxidation process after being... 

In this work, Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) is applied for numerical simulation of impulsive wave. Properties of linear and angular momentum in WCSPH formulation are studied. Kernel gradient of viscous term in momentum equation is corrected to ensure preservation of angular momentum. Corrected WCSPH method is used to simulate solitary Scott Russell wave and applied to simulate impulsive wave generated by two-dimensional under water landslide. In each of the test cases, results of corrected WCSPH are compared with experimental results. The results of the numerical simulations and experimental works are matched and a satisfactory agreement is observed.... 

Purpose: The purpose of this paper is to provide a theoretical analysis of the fracture behavior of multiple axisymmetric interface cracks between a homogeneous isotropic layer and its functionally graded material (FGM) coating under torsional loading. Design/methodology/approach: In this paper, the authors employ the distributed dislocation technique to the stress analysis, an FGM coating-substrate system under torsional loading with multiple axisymmetric cracks consist of annular and penny-shaped cracks. First, with the aid of the Hankel transform, the stress fields in the homogeneous layer and its FGM coating are obtained. The problem is then reduced to a set of singular integral equations... 

Nowadays, many second/foreign language (L2) academic writing instruction programs place a high premium on pre-writing strategies. The current study examined the effect of software-supported concept mapping on lexical diversity (LD) of English learners' argumentative essays within a process writing framework. Additionally, the relationship between the learners' LD and their overall writing quality was investigated. To this end, 53 university English as a foreign language (EFL) undergraduates were assigned to a computer-aided concept mapping (CACM) and a traditional outlining condition over a span of seven weeks. The CACM group was instructed through the graphic organizer software... 

Textbooks provide the most serious source of knowledge construction and transmission for children at schools. This paper used a discursive and qualitative content analysis approach to extract the dominant values, ideologies and identities in four social studies textbooks taught nationwide to children in primary schools in Iran. Textual and visual analysis were applied on these textbooks and the results showed the saliency of four dominant discourses and values including pre-Islamic ethos and Iranian-Islamic identity, war and peace, social and traditional values in Iranian culture, and respect for diversity. Each of these discourses are discussed and some recommendations are made at the end... 

Textbooks provide the most serious source of knowledge construction and transmission for children at schools. This paper used a discursive and qualitative content analysis approach to extract the dominant values, ideologies and identities in four social studies textbooks taught nationwide to children in primary schools in Iran. Textual and visual analysis were applied on these textbooks and the results showed the saliency of four dominant discourses and values including pre-Islamic ethos and Iranian-Islamic identity, war and peace, social and traditional values in Iranian culture, and respect for diversity. Each of these discourses are discussed and some recommendations are made at the end... 

Low and high valence were induced in 20 male volunteers using two groups of pictures stimuli. Heart response was compared between two groups from RR series extracted from recorded ECG measurements. Mean heart rate and heart rate variability measures including time, frequency and Poincare domain were extracted. The results revealed that HRV triangular index, SDNN and SD2 were the only statistically significant parameters between groups (p<0.05). Mean heart rate and power in LF and HF bands were also different between low and high valence groups however level of significance was not reached. © 2015 CCAL  

Research in the choice behavior of air travelers has evolved to include an analytical focus on variation in the sensitivities of travelers to factors influencing itinerary choice. Some choice studies have moved beyond a focus on assumed representative, mean-level sensitivities toward a goal of representing the distribution of preferences across a sample. The mixed multinomial logit model has served as a valuable means of estimating such distributions of air travel preferences, including studies of business travelers, impacts of airport level-of-service attributes, distributions of willingness-to-pay (WTP), and information-processing strategies. Does the insight gained in previous studies,... 

The present study was an attempt to explore international English-medium publication in humanities and social sciences in Iran. In so doing, 50 PhD students from 8 humanities and social sciences disciplines, who had already published or attempted to publish in English-medium journals, were requested to write reflection guide accounts and to take part in follow-up semi-structured interviews. The reflection guide and interview data were analyzed based on the principles of grounded theory research yielding the four major themes of motivations, hurdles, strategies, and call for support. The results indicated that the Iranian PhD students in the fields of humanities and social sciences are... 

The Per Tone equalization algorithm is a novel discrete multitone (DMT) equalization method with practical applications in subscriber digital loop systems. Unlike time domain DMT equalizers (TEQ), which equalize all DMT tones in a combined fashion, the Per Tone equalizer equalizes each tone separately. In this paper, the performance and complexity of this technique is investigated and compared with that of other TEQs. Furthermore, the behavior of this technique in different simulation conditions, such as over different standard CSA loops and in the presence of additive white Gaussian noise with variable power spectral density level and near end crosstalk (NEXT), is studied and compared with... 

Time domain equalizers are used in the receiver of a discrete multitone (DMT) receiver to compensate the channel effects on the received signal. There are a lot of DMT equalization algorithms presented in the literature, but recently a novel Per Tone equalizer structure was proposed which offers some advantages over the previous traditional ones. The objective of this paper is to provide an overview of the important concepts of this technique and evaluate its initialization complexity. The performance of this technique is also compared with typical time-domain equalization algorithms in different simulation environments. © 2004IEEE