Sharif Digital Repository

In this work, Compressible Smooth Particles Hydrodynamics (C-SPH) is applied for numerical simulation of impulsive wave. Properties of linear and angular momentum in SPH formulation are studied. Kernel gradient of viscous term in momentum equation is corrected to ensure preservation of angular momentum. Corrected SPH 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 test cases, results of corrected SPH are compared with experimental results. The results of the numerical simulations and experimental works are matched and a satisfactory agreement is observed. Furthermore, vorticity... 

Extraction of the frequency response of a musical instrument is the first step to analyze its vibration characteristic. This research introduces the results of several experiments implemented on Setar, a Persian long-necked lute. Setar has a wooden, reflective sound-box which is highly coupled with its surrounding air. High level of damping in addition to the composite properties in Setar, consequences dissimilar frequency domain vibration patterns. At lower frequencies, the response exhibits very distinct modal behavior, while in higher frequencies an overall effect of close modes is demonstrated. In this paper different approaches are utilized to handle both frequency regimes; and their... 

This paper introduces a finite element model of Setar, a Persian long-necked lute. Setar is modeled as a transfer function between the imposed force on the bridge and the near-field resulted sound. Numerical modeling of stringed musical instruments is a computationally challenging task which has always been done with extreme simplifications. Phenomena such as fluid-structure interaction, composite structure, preload effect and infinite boundary are considered in this model. The cycle of Software used in here is CATIA, HyperMesh, Nastran, and HyperGraph. The frequency response between the force of string and generated sound in near field are obtained, taking into account the fluid inside and... 

This study aims to evaluate the amount of energy transfers through the bridge in Setar, a Persian long-necked lute, Stringed musical instruments are among the most complicated acoustical systems. When the string is plucked, its vibration distributes into the entire vibrating system (i.e. body, string, air enclosure) and produces sound. The resultant sound consists of three parts: the first is the string's direct sound; the second is that part of sound-box vibration being excited by string's direct sound, and the third is the part of sound-box vibration being excited by string force passing through bridge. The last part believed to have the major share and the others have minor effect. For... 

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... 

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  

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

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... 

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... 

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... 

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... 

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... 

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... 

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,...