Sharif Digital Repository

For a given quantum field theory, provided the area of the entangling surface is fixed, what surface maximizes entanglement entropy? We analyze the answer to this question in four and higher dimensions. Surprisingly, in four dimensions the answer is related to a mathematical problem of finding surfaces that minimize the Willmore (bending) energy and eventually to the Willmore conjecture. We propose a generalization of the Willmore energy in higher dimensions and analyze its minimizers in a general class of topologies Sm×Sn and make certain observations and conjectures that may have some mathematical significance  

In practice, some differences are usually observed between computer simulation and experimental results of a chaotic circuit. In this paper, it is tried to obtain computer simulation results having more correlation with those obtained in practice by using more realistic models for chaotic circuits. This goal is achieved by considering the fractionality nature of electrical capacitors in the model of a chaotic circuit  

In odd dimensions the integrated conformal anomaly is entirely due to the boundary terms [1]. In this paper we present a detailed analysis of the anomaly in five dimensions. We give the complete list of the boundary conformal invariants that exist in five dimensions. Additionally to 8 invariants known before we find a new conformal invariant that contains the derivatives of the extrinsic curvature along the boundary. Then, for a conformal scalar field satisfying either the Dirichlet or the conformal invariant Robin boundary conditions we use the available general results for the heat kernel coefficient a5, compute the conformal anomaly and identify the corresponding values of all boundary... 

In the presence of boundaries, the quantum anomalies acquire additional boundary terms. In odd dimensions, the integrated conformal anomaly, for which the bulk contribution is known to be absent, is nontrivial due to the boundary terms. These terms became a subject of active study in the recent years. In the present paper, we continue our previous study [1,2] and compute explicitly the anomaly for fermions in dimensions d=3, 4 and 5. The calculation in dimension 5 is new. It contains both contributions of the gravitational field and the gauge fields to the anomaly. In dimensions d=3 and 4, we reproduce and clarify the derivation of the results available in the literature. Imposing the... 

Coming up with a model which matches biological observations more closely has always been one of the main challenges in the field of artificial neural networks. Lately, an ionic model of reservoir networks containing spiking neurons (ILS-based reservoir network) has been proposed which seems to replicate some of the biological processes we have observed up until now. This paper presents a local learning rule for the ILS-based reservoir inspired by the biological fact that each incoming stimulus causes the formation of new dendritic spines, producing new synapses. This property may result in a higher degree of neuroplasticity, leading to a higher learning capacity. To evaluate the proposed... 

In this note we address the discrepancy found by Hung, Myers and Smolkin between the holographic calculation of entanglement entropy (using the Jacobson-Myers functional for the holographic minimal surface) and the CFT trace anomaly calculation if one uses the Wald prescription to compute the entropy in six dimensions. As anticipated in our previous work [1] the discrepancy originates entirely from a total derivative term present in the trace anomaly in six dimensions  

This paper proposes a new method based on Particle Swarm Optimization (PSO) for feature selection in phonemes sound classification. Inspired of biologist's studies, each particle is represented by filterbank which is motivated by human hearing. Thus, we propose a technique in which PSO is used to extract audio features similar to human's ear in order to achieve better classification. We use PSO technique for optimizing particle's filterbank in order to classify sound signals accurately. Then, feature extraction is done by using particle's information. Moreover, a classification method based on nearest neighbor is used. Furthermore, by using a defined fitness function in this paper, the... 

ILS-based reservoir is a bio-inspired computational model consisting of spiking neurons which has been designed to process spatiotemporal patterns appropriately. In ILS-based reservoir, the neurons are located in an ionic environment and the connections are provided by ionic density. By using ionic diffusion as a processing operation, this model is able to consider the effects of both the preceding and current stimuli properly. Since character recognition is an important task in various applications, this paper focuses on the classification of handwritten digits using ILS-based reservoir. For this purpose, a neuromorphic handwritten digit dataset called N-MNIST dataset is used as a... 

This paper focuses on localizing acoustic source using fuzzy logic. For this purpose, an array of microphones are used as sensors. The Time Delay Estimation (TDE) is performed by correlation between received signals from each pair of microphones. In this paper, instead of assuming a crisp value as a TDOA, we introduce fuzzy number of TDOA in which the absolute value of the cross correlation function is normalized and then assumed as TDOA membership function for each pair of microphones. Truth value of presenting acoustic source is computed in region of interest based on achieved TDOA membership functions. Computing this truth value is represented in this paper based on fuzzy logic. The... 

Sound source localization has always been one of the most challenging subjects in different fields of engineering, one of the most important of which being tracking of flying objects. This article focuses on sound source localization using fuzzy fusion and a beamforming method. It proposes a new fuzzy-based algorithm for localizing a sound source using distributed sensor nodes. Eight low-cost sensor nodes have been constructed in this study each of which consists of a microphone array to capture sound waves. Each node is able to record audio signals synchronously on an SD card to evaluate different algorithms offline. However, the sensor nodes are designed to be able to estimate the location... 

RGO/Ag/TiO2-nanotubes/Ti plates with high photocatalytic activity were fabricated via electrochemical reduction of graphene oxide on Ag/TiO2-nanotubes. The loading of silver nanoparticles was carried out by electroless reduction of Ag1+ onto TiO2 nanotubes previously formed by anodizing titanium. Microstructure studies show that reduced graphene oxide (RGO) layers having high surface area have been deposited on the as-prepared Ag/TiO2-nanotubes, where nanoparticles of Ag had grown on the walls of TiO2-nanotubes. The results of photocatalytic experiments demonstrate that the RGO/Ag/TiO2-nanotubes/Ti plate exhibits significantly enhanced photocatalytic activity for the photocatalytic... 

We have presented a set of laws of entanglement thermodynamics for TT¯-deformed CFTs and in general for T2-deformed field theories. In particular, the first law of this set, states that although we are dealing with a non-trivial deformed theory, the change of the entanglement entropy is simply translated to the change of the bending energy of the entangling surface. We interpret this energy as the energy of decomposition. Probing the whole spectrum of the deformed theory, a second law also results, which suggests an inequality that the first law is derived from its saturation limit. We explain that this second law guarantees the preservation of the unitarity bound. The thermodynamical form... 

A 2-D numerical model was developed to predict the shape of weld pool in stationary GTA welding of commercial pure aluminium, without considering fluid flow in the weld pool. A Gaussian current density and heat input distribution on the surface of the workpiece were considered. The parameters of Gaussian distribution were modified by comparing calculated results with experimental ones. It was found that these distribution parameters are functions of applied current and arc length. Effects of arc length, applied current and welding time on the geometry of the weld pool were investigated. To check the validity of the model, a series of experiments were also conducted. In general, the agreement... 

One of the biggest struggles while working with artificial neural networks is being able to come up with models which closely match biological observations. Biological neural networks seem to capable of creating and pruning dendritic spines, leading to synapses being changed, which results in higher learning capability. The latter forms the basis of the present study in which a new ionic model for reservoir-like networks, consisting of spiking neurons, is introduced. High plasticity of this model makes learning possible with a fewer number of neurons. In order to study the effect of the applied stimulus in an ionic liquid space through time, a diffusion operator is used which somehow... 

A series of g-C3N4-SnO2/TiO2 nanotubes/Ti plates were fabricated via simple dipping of TiO2 nanotubes/Ti in a solution containing SnCl2 and g-C3N4 nanosheets and finally annealing of the plates. Synthesized plates were characterized by various techniques. The SEM analysis revealed that the g-C3N4-SnO2 nanosheets with high physical stability have been successfully deposited onto the surface of TiO2 nanotubes/Ti plate. Photocatalytic activity was investigated using two probe chemical reactions: oxidative decomposition of acetic acid and oxidation of 2-propanol under irradiation. Antibacterial activities for Escherichia coli (E. coli) bacteria were also investigated in dark and under UV/Vis... 

Hydrogen technology through water electrolyzer systems has attracted a great attention to overcome the energy crisis. So, rationally designed non-noble metal based-electrocatalysts with high activity and durability can lead to high performance water electrolyzer systems and high purity hydrogen generation. Herein, a facile two-step method: hydrothermal and electrodeposition, respectively, are developed to decorate highly porous three-dimensional binder-free structure NiFeO/NiO nanosheets array on Ni foam (NiFeO/NiO/NF) with robust adhesion as a high-performance electrode for Hydrogen Evolution Reaction (HER). The electrodeposition process applied after the initial hydrothermal process...