Sharif Digital Repository

During an earthquake, if the seat width provided at the joint is less than the relative joint opening, the bridge’s superstructure becomes unseat which leads to potential collapse due to the lack of support. Because of the catastrophic consequences of loss of support and the perception that the damage could easily be prevented at relatively low cost, some retrofitting programs focus on preventing such failures involved the addition of longitudinal restrainer cables and bars to limit the relative movements at expansion joints. Noticing the weaknesses of usual restrainers including the transmission of excessive forces to substructures, weak capability of energy dissipation during severe... 

This thesis deals with a theoretical and experimental investigation of different approaches for reduction of electronic recombination in the semiconductor/Dye interface of dye sensitized solar cells (DSSC) including dye coverage, core-shell structures and energy level distributions. Interface of ZnO/TiO2 in the core-shell structure have been studied by density functional theory and the energy level distribution of surface atoms, recombination and Fermi level changes, open circuit voltage and surface dipole distributions have been discussed.
The presence of TiO2 shell increases the ZnO surface dipole moment, and shifts the ZnO conduction and valence bands to higher energies. Also, it... 

In this thesis, pure –known as T- and chromium doped titanium dioxide nanoparticles –known as -CTx- with different dopant atomic ratio (0.1 to 5 %at.) were synthesized using a facile, fast and efficient method. FESEM and XRD studies showed no morphologic and structural change via Cr doping of nanoparticles (size in the range of 20-30 nm). However, according to DRS analysis, Cr intrusion in TiO2 crystal structure, drastically reduced band gap energy of pure TiO2 from 3.14 eV to 1.81 eV for CT3 powder and improved absorption range of UV-Vis spectrum. Mott-Schottky plots indicated that, Cr doping, caused reduction in donor density of TiO2 and an upward shift in the conduction band edge.... 

In this work, a comprehensive dynamic model has been used for styrene emulsion polymerization in a semi-batch reactor to predict the evolution of product particle size and molecular weight distributions under non-isothermal condition. Method of moments has been applied for solving the population balance equations and the results are compared with the results obtained from finite-volume method as a precise technique. A sensitivity analysis respect to perturbation in initial values of various reagents, species and the reactor temperature has been performed to identify suitable manipulated variables for closed-loop control of the reactor. The detailed model is used to generate optimal feed... 

The probabilistic behavior and the reliability of high-temperature defective components under creep-fatigue conditions have been assessed, considering different sources of uncertainty in “material behavior”, “geometric parameters” and “operation conditions”. For this purpose, deterministic calculations of creep-fatigue crack growth have been derived based on the R5 procedure, and then these relationships have been used at the heart of the probabilistic assessments. One of the aims of this dissertation was to present a procedure for assessing the reliability of defective components operating under creep-fatigue conditions. This procedure has been implemented on a benchmark problem, i.e.... 

This research investigated the seismic performance of gravity dam in the reliability and sensitivity analysis framework under earthquake loading. The performance criteria were defined using crest displacement and tensile stress. The uncertainty due to the material properties of the dam was considered for the reliability approach, in addition to the different ground motion intensity levels for parametric analysis. The exceedance probability of the limit-state functions was computed for varying threshold values through Mean-Value Second-Moment, First-Order Reliability Method and improved Latin Hypercube sampling. Approximation methods were applied along with the sampling method for considering... 

A new strategy for enhancing the efficiency of TiO2 dye sensitized solar cells (DSSCs) doped with Ni ions with different molar percentages (i.e., 0, 0.5, 1, 5 and 10 mol%) was reported. The samples were prepared by sol-gel route and characterized by means of XRD, DRS, UV-visible, FESEM and photovoltaic measurment techniques. It was found that Ni-doped TiO2 nanoparticles had a mixture of anatase, rutile and brookite crystal structures. Moreover, the band gap energy was decreased with increasing Ni molar ratio, The highest cell efficiency of 5.4% was achieved for 1mol% Ni-doped TiO2, being 42% greater than that of pure TiO2 nanoparticles  

The development of technologies and some defects in medicine caused to emerge a new approach called precision medicine. Unlike the traditional medicine, medical experts do best treatment for each patient based on his genetic characteristics in this approach. Predicting drug response on cancer cell lines is one of the most vital challenges in this area. Various approaches have been proposed to construct predicting models while the substantial distinctions between resistant and sensitive cell lines had been neglected in them. Here, we propose a new approach for constructing the predictive model. In our approach, we utilized the distinctions between sensitive and resistant cell lines and also... 

Data envelopment Analysis is a non parametric technique which estimates the efficiency of a decision making unit in compare with others. In correspondent literature this unit’s Inputs and outputs are often assumed to be deterministic, but in recent years different approaches which viewing the data as non deterministic are presented. In this study we propose an algorithm for determining the stability region of a DMU while we assume other DMUs’ data are fixed. This algorithm is based on changing the reference set of the under investigation DMU. In fact applying these changes make the DMU move toward other DMUs’ efficient frontiers and by using this fact it is possible to determine the... 

In the present study, TiO2-reduced graphene oxide (T-RGO) nanocomposites were synthesized via various in-situ and ex-situ methods, then their photovoltaic performance was examined as photoanode and mesoporous layers in dye-sensitized Solar Cells (DSSCs) and perovskite Solar Cells (PSCs), respectively. Graphene oxide (GO) was prepared using Hummer’s method with some modifications. Both thermal and hydrothermal processes were used to reduce GO. Structural and optical characterization was analytically demonstrated by subjecting of the obtained materials by several techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, thermogravimetric analysis (TGA),... 

Servo control valves including pressure control valves and flow control valves are the main components of the hydraulic system. Since these valves are responsible for controlling the flow or pressure in hydraulic systems, are important. In the present study, we focus on modeling and sensitivity analysis of an electro-servo-hydraulic valve with two stages. The first stage mechanism is the seating type (flapper-nozzle) and the second stage mechanism is the sliding type (spool type). For simulation main components of the servo valve include torque motor, flapper, flow through the nozzle-flapper, flow through the orifice and flow through the valve spool and body separately have been modeled.... 

In recent years, dust storms have been recognized as one of the most crucial problems for people worldwide. Provided that the dust masses transport mechanisms are properly known, the main dust sources can be identified, and therefore, appropriate actions can be taken. Therefore, the main goals of the present study are estimating dust concentration, determination of dust distribution with an emphasis on Iran (especially Tehran), and finding the main dust sources which will be followed in five steps. In the first step, by analyzing the measured data during dust observations in Tehran through 2013-2016, several simple and multivariate nonlinear regression models have been established in order... 

Principal component analysis (PCA) is a conventional tool for dynamic system analysis. In this paper, a new damage diagnosis method is presented based on sensitivities of principal components obtained from PCA of Frequency response functions (FRFs). Damage identification, determination of its location and estimation of the damage severity are conducted by an innovative well established sensitivity relation of PCA results. Then, sensitivity matrix is obtained by using measured frequency of damaged structure, and comparison of PCA of the intact structure with PCA from FRFs which are measured at sensors locations. Damage location and its severity are calculated by model updating procedure. This... 

Terahertz (THz) spectroscopy has recently attracted great interest due to the special characteristics of THz waves, such as their capability of penetrating and passing through many non-polar materials, non-ionizing atoms and especially human tissues, and less scattering compared to optical waves and X rays. Also, polar molecules of some dielectric materials have vibrational or circular oscillations that create peaks in their spectral characteristics. This can be used to identify materials by spectroscopy. In this thesis, a simple THz spectroscopy system is introduced and modeled for detecting the C-4 material. First, a wideband Vivaldi antenna is designed and simulated for the frequency... 

In this research, the trends of trade and transportation for the 10 subdivisions of food products and food products as a whole product based upon Standard International Trade Classification, SITC, have been appraised during the time period covering 1965 to 2005 among 125 countries in Asia, Europe and Africa. In this respect, the data of trade for the mentioned goods was gathered and other variables including gross domestic product, population, access to the international waters and area of countries and three transportation networks comprising two multimodal transportation networks and a unimodal network, during the cited period and for 125 countries was gathered. Then, regressions of trade... 

This study presents a facile sol-gel template-assisted route to prepare CNT-TiO2 hybrid structures (CTH) for dye-sensitized solar cell (DSSC) applications. Non-covalent functionalized multi-walled carbon nanotubes (CNTs) with average diameter of 80 nm are used as the template for TiO2 deposition. The X-ray diffraction reveals that the hybrid structures are composed of primary anatase TiO2 nanoparticles with the average crystallite size of 12 nm, after heat treatment at 450°C in air atmosphere. TEM and FESEM images show that the shell thickness of the coated TiO2 on CNTs’ outmost walls varies between 60 to 120 nm, when the ratio of CNTs:TiO2 is 10wt. %. Photovoltaic measurements demonstrate... 

Different types of morphologies and phase structures of crystalline TiO2 were synthesized by hydrothermal methods. For the first time, dandelion-like rutile TiO2 powder composed of numerous single crystalline nanorods was synthesized using TiCl4 as the main precursor. TiO2 Nanoparticles were produced using TTIP and 2-propanol, as precursor and solvent, respectively. Field emission scanning electron microscopy analyses revealed that the synthesized TiO2 nanoparticles had average crystallite size in the range 21–70 nm, whereas dandelion-like TiO2 showed diameter in the range 2-10 µm. According to the significant refractive index of TiO2, in particular rutile phase, it can be used in the... 

Servo hydraulic pumps are being utilized in hydraulic circuits to prevent hydraulic oil reaching high temperatures in result of relief valve’s functions. In this study, we focus on modeling and sensitivity analysis of a pump of this kind. At first the importance of the current study and some of related studies has been discussed and some of the appropriate results has been represented. Then by employing CFD and Fluent code, the flow around servo valve of pump has been simulated, and operational curve of the valve has been calculated. This curve has been verified by results of the experimental set. At the next stage of the study, by modeling Dynamic parts of the pump in SIMULINK software and... 

The present work focuses on the sustainable development of an intelligent self-healing anticorrosion coating using nanocontainers based on the aluminium oxide nanostructure-pomegranate peel extract-Ce3+ (Ce-PPE@Cat). The Ce-PPE@Cat nanopigment was introduced into the epoxy film (Ep) to achieve a smart barrier/ self-healing anti-corrosive property. To this end, a couple of characterization tests, including FT-IR, TGA, and, BET have been carried out to investigate the Ce-PPE@Cat nanopigment structure/composition. The effectiveness of the anti-corrosion performance of the established coatings was confirmed by EIS, FE-SEM, and accelerated salt spray test. Furthermore, EIS studies revealed that... 

With the growing development of urban communities and population, the demand for water and treated sewage water has grown significantly. The environmental damage of polluted water has resulted in passing of new and strict environmental laws on wastewater discharge recently. In the present research, a hybrid system involving a power, heat and cool cogeneration and a carbon dioxide capture system has been designed for a typical wastewater treatment plant. The plant is optimized from economic and environmental criteria. The anaerobic digester is modeled using the ADM1 model. The biogas is directed into the hydrogen sulfide removal filter to remove the impurities and into the heat exchanger to...