Sharif Digital Repository

Despite the various approaches in the literature adopted for analysing cone penetration test (CPT), determination of the initial horizontal stress and relative density of a sandy soil during this test has not been tackled yet. In order to propose a new method in this regard, a numerical study of CPT has been performed and the predicted results have been compared with several databases of comprehensive calibration chamber tests. The penetration mechanism has been then fully investigated by presenting different kinds of outputs for the surrounding soil. Finally, an innovative procedure has been suggested for estimating the initial horizontal stress and relative density during performing CPT in... 

The binding of Mg 2+, Ca 2+, Zn 2+ and Cu + metal cations to 2′-deoxyguanosine has been analyzed, using the hybrid B3LYP, Density Functional Theory (DFT) method and 6311++G(d,p) orbital basis sets. Coordination geometries, absolute metal ion affinities, and free energies for the most stable complexes formed by Mg 2+, Ca 2+, Zn 2+ and Cu + with the nucleoside, 2′-deoxyguanosine, have been determined. Furthermore, the influences of metal cationization on the strength of the N-glycosidic bond, torsion angles and angle of Pseudorotation (P) have been studied. With respect to the results, it has been found that metal binding significantly changes the values of the phase angle of Pseudorotation... 

Density functional theory (DFT) calculations were performed at the B3LYP/6-311++G(d, p) level to determine coordination geometries, absolute metal ion affinities, and free energies for all possible complexation stable products formed by monovalent metal cations including Li+, Na+, K+ with the nucleoside 2'-Deoxyguanosine. All computations indicate that the metal ion affinity (MIA) decreases on going from Li+ to Na+ and K+ for 2'-Deoxyguanosine. For example, the affinities for the metal ions described above are 75.2, 57.3, 43.4 kcal/mol, respectively. Furthermore, the influence of metal cationization and O 6 protonation on the strength of the N-glycosidic bond, torsion angles and angle of... 

We theoretically study the quasi bound state of Dirac electrons in cylindrically symmetric quantum dots with sharp boundary. According to the existing picture, due to Klein tunneling "relativistic electrons" can not be localized by any confinement potential. We show however that despite of Klein tunneling, interference effects can cause the trapping of electron in quantum dots. Considering the quasi bound state as the state with complex energy, to find the energy of this state we solve the wave-equation with outgoing boundary condition at infinity. The imaginary part of complex energy determines the trapping time of electron within the quantum dot. We show that for any finite confining... 

This paper presents a numerical investigation into the static behavior of stepped soil nail walls constructed in dry sandy soils. The finite element method was used to study influence of wall geometry and soil parameters on behavior of the walls. We analyzed walls with heights of 10, 15, and 20 m. This study shows that the wall deformation and the nail tensile forces of the stepped soil nail wall are smaller than those of the typical soil nail wall. If properties of soils such as friction angle, cohesion, and elastic modulus decrease, more decrease in the wall lateral displacement and nail tensile forces of a stepped soil nail wall would occur. Therefore, stepped soil nail walls are more... 

With the increasing share of distributed generation in electrical energy supply, the proper planning procedure for using these units, has become more vital for power system planners. In this paper, the application of multi-objective optimization techniques for siting, sizing and determination of the proper technology to be used, has been investigated in such a way that, the load demand during the planning horizon is met and the technical and environmental constraints are satisfied. Unlike the traditional optimization methods used in power system optimization, NSGA-II multi-objective optimization algorithm does not consider techno-economical and environmental parameters in the constraints of... 

Routing is a very important matter for ad hoc networks which means choosing the suitable and correct path for transferring data from a source node to a destination node. Today, the methods using several paths for routing are attended very much. In this paper, a new plan in multiple paths On-Demand Distance Vector (AODV) routing is presented which its routing is based on the distance of nodes from the center of the network. In this new routing algorithm, the number of dropped packets will be decreased and indeed this will be happened with more balancing in the network. This claim will be proved by some simulations using ns2 (network simulator)  

Interaction quality improvement in a social robotic platform can be achieved through intention detection/prediction of the user. In this research, we tried to study the effect of intention prediction during a human-robot game scenario. We used our humanoid robotic platform, RASA. Rock-Paper-Scissors was chosen as our game scenario. In the first step, a Leap Motion sensor and a Multilayer Perceptron Neural Network is used to detect the hand gesture of the human-player. On the next level, in order to study the intention prediction’s effect on our human-robot gaming platform, we implemented two different playing strategies for RASA. One of the strategies was to play randomly, while the other... 

In this study, the effects of the type and content of reactive diluents on the permeation/separation of carbon dioxide/nitrogen (CO2/N2) through acrylate-terminated polyurethane (APU)-acrylate/acrylic diluent (APUA) composite membranes was investigated. A series of APUs based on poly(ethylene glycol) (PEG)-1000 g mol−1, toluene diisocyanate, and 2-hydroxyethyl methacrylate was synthesized and then diluted with several reactive diluents. The results obtained from differential scanning calorimetry (DSC) and Fourier transform infrared analyses showed that the microphase interference of hard and soft segments increased with increasing reactive diluent content. Furthermore, with increasing alkene... 

An Al2O3/Si3N4 nanocomposite coating was successfully fabricated on commercial aluminum alloy. Hardness measurements, polarization and electrochemical impedance spectroscopy (EIS) were employed to study the mechanical and corrosion behaviors of the coatings. Field-Emission Scanning Electron Microscopy (FE-SEM) equipped with Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) were utilized to characterize the surface morphology and phase composition of the coatings. Also, coatings abrasive wear properties were evaluated with a modified ASTM G105 standard. FE-SEM image, EDS and XRD analysis revealed the presence of Si3N4 in the coating. Furthermore, the results showed hardness of... 

Varactor and bipolar junction transistor (BJT) frequency multipliers are a class of non-linear circuits that show parametric instability when the input drive is varied. If parametric oscillations are present in the circuit, output phase noise of the multiplier degrades remarkably in some specific driving levels. Phase noise analysis is performed by the conversion matrix method using generalised nodal analysis. The conversion method predicts the phase noise degradation precisely because it encompasses the effect of the noise sources that are modulated by the large signal drive. The added phase noise of a varactor and a BJT frequency doubler with subharmonic oscillation is calculated and the... 

Nowadays, content distribution is of high attention in peer to peer information systems. There are two main problems that could be mentioned in this context. The first problem is how to disseminate fragments of information efficiently and the next is to avoid missing same rare fragments towards end of download. For overcoming these problems, a new mechanism is presented in this paper which uses gossip algorithms on basis of social networks. Our mechanism maintains simplicity of gossip and has low overhead. This mechanism includes two phases for managing traffic and solving bottleneck problem: one for spreading rumors inside the social network and finding network of interests and the other... 

A nanocomposite of Ce-doped TiO2-reduced graphene oxide (CedT/RGO) was synthesized to evaluate the synergistic effects of constituents on electrical and photoelectric properties. The nanoparticles of titania and CedT were synthesized via the sol-gel method. Then, RGO was prepared using a new version derived from the Hammer's method and hydrothermal methods. Finally, CedT/RGO nanocomposite was synthesized applying hydrothermal method. The nanoparticles and nanocomposite were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy and elemental mapping. Then, diffuse reflectance and... 

The modified Claus process is characterized by several problems, namely poor instrumentation and no precise kinetic model for predicting the behaviour of the reactors. Using operational data of an industrial plant, this paper proposes a general framework for development of a plant-wide simulation model for modified Claus process based on simultaneous data reconciliation and parameter estimation (DRPE) using Genetic algorithm (GA). HYSYS as a commercial process simulator that provides a high-level of accuracy as well as redundancy which all is favoured for DRPE has been utilized in this work. Building a communication framework between HYSYS and MATLAB, data pre-processing of raw measurement... 

Efficient hardware realization of spiking neural networks is of great significance in a wide variety of applications, such as high-speed modeling and simulation of large-scale neural systems. Exploiting the key features of FPGAS, this paper presents a novel nonlinear function evaluation approach, based on an effective uniform piecewise linear segmentation method, to efficiently approximate the nonlinear terms of neuron and synaptic plasticity models targeting low-cost digital implementation. The proposed approach takes advantage of a high-speed and extremely simple segment address encoder unit regardless of the number of segments, and therefore is capable of accurately approximating a given... 

In recent years the development of Simultaneous Localization and Mapping (SLAM) techniques have enabled social robots to autonomously navigate in routine human workplaces. However, most common SLAM techniques are developed for mapping and localization in static worlds. In this paper, we have developed and analyzed a novel augmentation of the FastSLAM algorithm, including a person tracking module using 2D LiDAR sensor data. Utilizing this module, the SLAM algorithm is capable of filtering measurements coming from walking people who produce noises due to their intrinsic dynamic and unstableness. This augmentation was developed and then tested on our socially assistive mobile robot platform,... 

In this study, titania-ceria-graphene quantum dot (TC-GQD) nanocomposite was synthesized by hydrothermal method for the first time. The prepared nanomaterials were characterized by XRD, FTIR dynamic light scattering (DLS), FESEM, HRTEM, and EDX spectroscopy along with elemental mapping. The synergistic effect of the nanocomposite components was studied by diffuse reflectance spectroscopy (DRS) and electrical conductivity meter. The results showed that band gap of TC-GQD nanocomposite was shifted to visible lights relative to its components (1.3 eV), and electrical conductivity of the sample was significant increased to 89.5 μS cm−1. After chemical and physical characterization, prepared new... 

The rise of the damage to energy systems caused by both natural and man-made disruptive events and the connection between energy systems and socio-economic systems have motivated the study of energy system resilience. This paper conceptualizes and comprehensively presents a systematic review of the recent literature focused on the analytical, technical, and mathematical points from the standpoint of the energy systems facing disruptive events. To this end, five phases are developed. Firstly, the concept of the energy system resilience is presented, and then the energy resilience characters and the resilience states are introduced and connected. Thirdly, the formulation and indicators of the... 

The rise of the damage to energy systems caused by both natural and man-made disruptive events and the connection between energy systems and socio-economic systems have motivated the study of energy system resilience. This paper conceptualizes and comprehensively presents a systematic review of the recent literature focused on the analytical, technical, and mathematical points from the standpoint of the energy systems facing disruptive events. To this end, five phases are developed. Firstly, the concept of the energy system resilience is presented, and then the energy resilience characters and the resilience states are introduced and connected. Thirdly, the formulation and indicators of the... 

Nanopowders are powders with particle size less than 100 nanometer. The applications of nanopowders are in the production and processing of nanocomposites, microelectronic, industrial cathalists, coating, sintering at low temperature, lubricants, propellants, purification of aqiuos solutions, biomaterials and filtration. In this work, a reactor for production of nanopowder using IGC method was designed and manufactured. By changing the production parameters such as chamber temperature and pressure, evaporation rate, precursor and evaporation time, silver powders were produced. The characteristics of the produced powders were studied using EDX, SEM and TEM techniques. The results showed that...