Sharif Digital Repository

Perturbation of logarithmic conformal field theories using Zamolodchikov's method is investigated. We derive conditions for the perturbing operator, such that the perturbed model be integrable. We also consider an example where an integrable model arises out of perturbation of the c = - 2 logarithmic conformal field theory. © 2006 Elsevier B.V. All rights reserved  

MXenes have recently witnessed significant evolution and advances in terms of their applications in different areas such as flexible electronics, energy storage devices, and coatings. Here, the mechanical properties of both pristine and functionalized Tin+1CnO2 and Tin+1NnO2 (n = 1, 2) are investigated utilizing classical molecular dynamics simulations. For eight different MXene structures, the stress-strain curves are calculated including Young's modulus, strength, and fracture strain. It is found that Ti2N holds the highest Young's modulus with the value of 517 GPa while Ti3C2 has the lowest one with the amount of 133 GPa. In addition, the strongest MXene structure is Ti2N while the... 

We investigate some aspects of the c = -2 logarithmic conformal field theory (LCFT). At first, we calculate some correlators of logarithmic conformal fields which have third order singular OPE with the energymomentum tensor. Then, we argue about the fields in the c = -2 model which are associated with this kind of more general logarithmic primary fields. We go on to find fermionic representations for all the fields in the extended Kac table, in particular the untwisted sector. Moreover, we calculate the various OPEs of the fields, especially for the logarithmic energy-momentum tensor and by using these OPEs we find the exact finite transformation of this field. We briefly discuss about the... 

Nanofluids - dispersions of nanometer-sized particles in a liquid medium - have been proposed for a wide variety of thermal management applications. It is known that a solid-like nanolayer of liquid of typical thicknesses of 0.5-1 nm surrounding the colloidal nanoparticles can act as a thermal bridge between the nanoparticle and the bulk liquid. Yet, its effect on the nanofluid viscosity has not been elucidated so far. In this article, we compute the local viscosity of the nanolayer using equilibrium molecular dynamics based on the Green-Kubo formula. We first assess the validity of the method to predict the viscosity locally. We apply this methodology to the calculation of the local... 

Heat transfer through the interface between a metallic nanoparticle and an electrolyte solution has great importance in a number of applications, ranging from nanoparticle-based cancer treatments to nanofluids and solar energy conversion devices. However, the impact of the surface charge and dissolved ions on heat transfer has been scarcely explored so far. In this study, we compute the interface thermal conductance between hydrophilic and hydrophobic charged gold nanoparticles immersed in an electrolyte using equilibrium molecular dynamics simulations. Compared with an uncharged nanoparticle, we report a 3-fold increase of the Kapitza conductance for a nanoparticle surface charge of +320... 

We investigate the explicit renormalization group for fermionic field theoretic representation of two-dimensional random bond Ising model with long-range correlated disorder. We show that a new fixed point appears by introducing a long-range correlated disorder. Such as the one has been observed in previous works for the bosonic (φ 4) description. We have calculated the correlation length exponent and the anomalous scaling dimension of fermionic fields at this fixed point. Our results are in agreement with the extended Harris criterion derived by Weinrib and Halperin. © 2007 Springer Science+Business Media, LLC  

Molecular dynamics (MD) simulations were used to study the mechanical behaviour of β-SiC at nano-scale under tensile loading. Effects of loading rate and tensile temperature on the mechanical properties and failure were studied. Modified embedded-atom method (MEAM) potential and Berendsen thermostat were utilized for modelling. Periodic boundary conditions were employed and the behaviour of material was analyzed under three-axial loading condition at which the stress–strain relation was acceptably size independent. It is shown that with increasing the loading rate from 5 m/s to 70 m/s, the failure strain increases without a remarkable change in the stress–strain relationship. The MD... 

Numerous studies have investigated driving equations used to predict the slip factor in centrifugal compressors so far. Inevitably, through these studies, the ow field characteristics have been simplified and the effects of the related parameters have been neglected. The present study, experimentally and numerically, investigates the slip phenomenon in a specific centrifugal compressor with complex blade curves and splitter blades, considering the main effective parameters such as the number of blades, exit angle, etc. To this end, a three-dimensional simulation of the viscous flow field of the compressor via an appropriate turbulence method was performed. In addition, an experimental study... 

Numerous published articles focus on optimizing individual components of radial flow compressors to achieve enhanced performance. These components include the impeller, diffuser, and volute. However, there is a limited number of published papers studying the combined performance of individually optimized components working together. This article presents a hierarchy optimization approach conducted on a turbocharger compressor, composed of two or three individually optimized components including two optimized impellers, one vaned diffuser and one optimized volute, each with distinctive optimization method. The article also reports the resulting improvements in pressure ratio and overall... 

Molecular dynamics (MD) simulations were used to study the mechanical behaviour of β-SiC at nano-scale under tensile loading. Effects of loading rate and tensile temperature on the mechanical properties and failure were studied. Modified embedded-atom method (MEAM) potential and Berendsen thermostat were utilized for modelling. Periodic boundary conditions were employed and the behaviour of material was analyzed under three-axial loading condition at which the stress- strain relation was acceptably size independent. It is shown that with increasing the loading rate from 5 m/s to 70 m/s, the failure strain increases without a remarkable change in the stress-strain relationship. The MD... 

Human body stiffness plays an important role in whole body vibration analysis and also athletic performance and motor control. In recent years researchers focused on calculating lower-extremity stiffness for better monitoring vibration of whole body and also improving athletic performance and decreasing their injuries. Lower limb power, stiffness and muscular strength are often obtained from maximal vertical jump which is an important motor skill in physical activities. The stiffness can be calculated by vertical reaction force divided by vertical movement of mass centre. During running and jumping, legs can be modelled as a spring with the body mass sitting at the top. With regard to the... 

Learning a foreign language encompasses a process of trial and error that can lead to the progression of the learner's interlanguage, meaning that the learners make use of their language knowledge that receives feedback and brings about progress through diagnosis of the problems and being corrected by the teacher. Therefore, there exists a need to analyze the underlying reasons causing the students to remain taciturn with a low willingness to communicate (WTC) during a language class. There has been much work done investigating the role of the learner's stable personal characteristics (traits) along with their situational changes at a specific time (states) that influence the student's... 

Accurate system identification (SI) is essential for flight controller design of unmanned aerial vehicles and microaerial vehicles (MAVs). SI can be performed either in frequency or time domain using flight test data. As flight testing is often costly and may even lead to catastrophic events before some flight stability analysis is at hand, a low-cost 5 degree-of-freedom free motion platform (FMP) is designed and used for initial identification of MAVs via wind tunnel testing. A typical MAV is constructed as a test case and equipped with inertial sensors for testing and validation purposes. The proposed FMP allows for both rotational as well as translational motions that in turn provide for... 

Using 3-D scanned data to analyze and extract pore network plays a vital role in investigation of porous media's characteristics. In this paper, a new simple method is developed to detect pores and throats for analyzing the connectivity and permeability of the network. This automated method utilizes some of the common and well-known image processing functions which are widely accessible by researchers and this has led to an easy algorithm implementation. In this method, after polishing and quality control of images, using city-block distance function and watershed segmentation algorithm, pores and throats are detected and 3-D network is produced. This method can also be applied on 2-D images... 

In this paper, we try to recognize and distinguish different groups of arrhythmia using novel features which have been obtained from the heart rate's phase space in recent years. For this purpose, we used Triangular Phase Space Mapping (TPSM) and Parabolic Phase Space Mapping (PPSM). For recognition, we used three groups of 15 subjects using the Physionet database (Arrhythmia, Congestive Heart Failure (CHF), and Atrial Fibrillation (AF)) with Normal Sinus Rhythm (NSR). The obtained features discriminate arrhythmia from NSR by p