Sharif Digital Repository

The human action recognition is one of the most important concepts of computer vision in recent decades. Most of the two dimensional methods in this field are facing serious challenges such as occlusion and missing the third dimension of data. Development of depth sensors has made easy access to tracking people and 3D positions of human body joints. This Thesis proposes a new method of action recognition that utilizes the position of joints obtained by Kinect sensor. The learning stage uses Fisher Linear Discriminant Analysis (LDA) to construct discriminant feature space. Two types of distances, i.e., Euclidean and Mahalanobis, are used for recognizing the states. Also, Hidden Markov Model... 

The non-stationary nature of brain activity signals and their many inter-subject differences have created many challenges in the practical applications of emotion recognition based on electroencephalogram (EEG) signals, such as brain-computer interfaces. In such a way, the use of traditional classifiers in classifying these signals leads to a significant decrease in accuracy when applying the classifier to a new subject. Domain Adaptation methods seem to be an effective way to solve this problem by minimizing the difference between the EEG signals of different subjects. But in the basic techniques for domain adaptation, looking at all subjects' data in the same look causes the loss of a part... 

Solar heating in aqautic systems, causes tempreture increasing.This temperature difference will promote an exchange flow between the vegetation and open water. The exchange flow generated by the differential heating and cooling associated with depth variation has also been studied through laboratory experiment and modelling. Differential solar heating can result from shading by rooted emergent aquatic plants, producing a temperature difference between vegetated and unvegetated regions of a surface water body. Horizontal density difference between shaded and open water regions drives currents that carry fluxes between biologically and chemically distinct regions of an aquatic system. Such... 

Preservation and survival of ecological systems by vegetation is important. A study focusing on the hydrodynamics of these complex ecosystems could help to explain the filtering ability of vegetation in wetlands and estuaries. Wetlands assist in flood control, shoreline protection, and groundwater recharge. In addition, they play a purification role in removing sediments and contaminants from polluted waters, nutrient uptake, and oxygen production.
Laboratory experiments have been designed to study the influence of marsh vegetation on lateral dispersion in flexible vegetation that has been modelled with inclined cylinder. The flow through vegetation is modelled by a circulating flow... 

Conventionally all objects radiate most of its energy in the from of infrared waves, therefore, infrared photodetectors for detecting objects is important and more study is done on improve the detecting parameters. The proposed structures are developed from bulk to quantum well and quantum dots in recently years. In this work at reason insensitivity to incident light polarization, flexible operation wavelength, high operation temperature, inherent photovoltaic effect, low capture probability we study the structure of quantum dot infrared photodetectors and then for improve the detecting parameters structure of two layers quantum dot separated with a layer thin barrier (bilayer). And then a... 

Dirac-Weyl semimetals are new topological phases hosting the coexistence of Dirac and Weyl points in momentum space. Due to the different symmetry requirements of Weyl and Dirac semimetals, one may wonder whether these phases can coexist in real materials. Based on first principles calculations the noncentrosymmetric compounds SrHgPb and CaHgSn have band structure with the Dirac-Weyl crossings. In this thesis we introduce four band minimal lattice models which preserve n-fold rotation along z axis and break inversion symmetry. The obtained models use the minimum number of degrees of freedom, spin and orbital, and proper symmetries relevant to real materials yielding a four-band model where... 

The excitonic insulator phase is a quantum state of matter resulting from the macroscopic coherent condensation of electron-hole bound states. As such, it shares similarities with superconductivity, exhibiting superfluid-like behavior and collective Higgs and Goldstone modes. The discovery of primary excitonic candidates at cryogenic temperatures has spurred research into materials with higher critical temperatures and stable conditions. Recently, several transition metal chalcogenides have emerged as promising high-temperature excitonic insulators. However, the interplay between excitonic condensation and structural phase transitions in these materials presents a significant challenge to... 

In this project, a novel action recognition method, named Fisherposes, is proposed, which is improved by several space-time (spatio-temporal) methods afterwards. The proposed method utilizes skeleton data obtained from Kinect sensor. First, pre-processing is performed in which the scales of bodies are canceled and the skeletons become aligned in order to make the method robust to location, orientation, and scale of people. In Fisherposes method, every action is defined as a sequence of body poses. Using the training samples for the poses, a Fisher subspace is created which we name it Fisherposes. Moreover, a novel distance measuring function, named regularized Mahalanobis distance, is... 

In present study, it is tried to investigate the effect of physical properties on hydrodynamic and overall mass transfer coefficient of single drops using different experiments and then simulation of drop motion with OpenFOAM software version 1.7.1. the systems were choosen are toluene/acetone/water and n-butanol/succinic acid/water which their interfacial tensions are 36 and 1.6 mN/m respectively. Various type of nozzles have been used for produce of 1.5, 2, 3 and 4 millimeter drops. The results show that in absence of solute component, the rising velocity of toluene drops in each size is higher than rising velocity of butanol drops inside the water between 25 to 75 percent. But with... 

The researches done on legged robots can be categorized in two main groups: based on analytical methods and intelligent methods. All researched done by intelligent methods are similar in adaptation of learning methods. Robots can improve their actions with learning and there is no need to do an exact modeling of environment and system. Also this is adaptive to changes in system and environment. There are different approaches for studying intelligence in cognitive science. Embodiment approach focuses on body, its properties and connection to environment. Controller, morphology and environment effect doing the tasks in embodiment. Morphology contains sensors, shapes of elements, actuators and... 

The wind phenomenon has always caused significant damage to structures. Suffering from extensive damage and loss over the years has led researchers to establish the novel science of wind engineering. Wind engineering references introduce wind as an intricate dynamic and random phenomenon and encourage engineers to familiarize themselves with its exact effects on structures by utilizing the latest methods of structural analysis, such as time history analysis. In this research, the idea of a new method for time history analysis of tall buildings against the wind is proposed. In this method, the purpose is to determine the responses of the structure against any wind of any intensity and return... 

Human has different emotions such as happiness, sadness, anger, etc. Recognizing these emotions plays an important role in human-machine interface. Emotion recognition can be divided into approaches, physiological and non-physiological signals. Non-physiological signals include facial expressions, body gesture, and voice, and physiological signals include electroencephalograph (EEG), electrocardiograph (ECG), and functional magnetic resonance imaging (fMRI). EEG signal has been absorbed a lot of attention in emotion recognition because recording of EEG signal is easy and it is non-invasive. Analysis of connectivity and interaction between different areas of the brain can provide useful...