Sharif Digital Repository

In 2009, a general equation of state (EOS-III) based on an effective near-neighbor pair interaction of an extended Lennard-Jones (3, 6, 12) type has been introduced as : , where is the compressibility factor, p and ρ stand for pressure and molar density , respectively, T is Temperature , and e, f and g are the temperature dependent coefficient of the equation of state . the Z_th and Z_in are the thermal and internal contributions of pressure in the compressibility factor, respectively. this equation of state gives a good description of all types of nano- and bulk –solid and bulk fluid at entire temperature and pressure ranges for which thee is experimental data. Investigation show that... 

The rise in carbon dioxide levels has led to the manifestation of numerous environmental challenges. Currently, the absorption and conversion of carbon dioxide into valuable fuel resources such as synthetic gas, methane, and ethylene are deemed crucial from both environmental and economic standpoints. Despite the presentation of photocatalysts such as titanium oxide and electrocatalysts such as copper, silver, and zinc, their efficiency in CO2 conversion is found to be insufficient. One potential solution to this problem is the utilization of photoelectrocatalytic CO2 recovery. In this study, the aim was to enhance the photoelectrocatalytic reduction of CO2 by designing and manufacturing... 

Preformed particle gels (PPGs) due to its advatantage over commonly used in situ gels has been successfully applied for controlling excess water production in mature oil reservoirs. Field results of using PPGs in oil fields shows that commonly used PPGs are highly sensitive to hard reservoir conditions such as high temperature and salinity and can not effectively block fractures and high permeability layers.Objects of this study are synthesis and evaluating performance of this novel polymer based hydrogel in oil reservoirs with high temperature and salinity. Central composite design ( which is a experiment design approach) was used for synthesizing thirteen gel samples and optimal sample was... 

Biological layers are one of the main problems related to water transfer with pipe lines which are formed through time in the inner surface of the pipes by the water nutrients. Hence, the inner surfaces in the pipe lines and water refineries should be made in order not to let these biological layers to be made. The reason is that when the biofilm is formed on these surfaces, the traversing water is polluted. Dredging of these pipes is not only necessary in most of the countries in the world and needs huge amounts of water but is also very complex and expensive.In this research, nanomaterials, namely ZnO, T〖iO〗_2،S〖iO〗_2 have been used to cover the surface of concrete and steel pipes (The... 

Sand production from oil reservoirs leads to various problems, such as well productivity reduction, operating equipment corrosion, and increased production costs. Therefore, controlling sand production in unconsolidated reservoirs is crucial for operating companies. Chemical injection into the formation in order to strengthen and reduce sand production is one of the most important methods of sand control. In this study, a hydrogel nanocomposite was designed and its effectiveness in sand control was investigated. Various tests were carried out to define and assess its efficacy, as follows: Morphological tests demonstrated the creation of a dense, homogeneous, and porous structure. Structural... 

In this project the energy of rotational barrier of C-N bond in 2-cyanoethyl piperidine-1-carbodithioate has been studied by using Dynamic Nuclear Magnetic Resonance spectroscopy. Spectra were taken at various temperatures in two different solvent; acetone and chloroform. For simulation of line-shape broadening SpinWorks software was used. This with two interfaces made possible simulation with two band-shape simulator programs; DNMR and MEXICO. The rate constants obtained from simulations were used for calculation of thermodynamic activation parameters (ΔG#. ΔH#. ΔS# and Ea#). The computational calculations were done by using Gaussian03 in several level and basis sets that are in good... 

The focus of this project was on gaining the knowledge of design characteristics and manufacturing of a hydraulic servo valve. Hence, in the first stage, the model of the valve was considered. After investigating the important parameters which influence the performance of the valve, the effect of each parameter on the valve's efficiency was examined. One of the most important characteristics of the valve is the amount of lapping between the spool and sleeve. Numerical analysis was done and all the characteristic curves were elicited. Equations governing the dynamics of the plant including a servo valve, servo actuator and dynamic model of the turbine and waterway were presented. Then the... 

A mathematical model was developed to assess thermomechanical behavior of work rolls during warm rolling processes of AA2017. A combined finite element analysis-slab method was first developed to determine thermal and mechanical responses of the strip being rolled under steady-state conditions; Then, the calculated roll pressure and temperature field were utilized as the governing boundary conditions for the thermomechanical problem of the work roll. Finally, the thermomechanical stresses within the work rolls were predicted by a thermoelastic finite element approach. The results indicate that, in warm strip rolling, thermal and mechanical stresses developed in the work rolls are comparable.... 

As technology develops, the need of instruments which could be used for improving the rate and accuracy of the manufacturing increases. This makes the robots inevitable to use in most industries. Among the robots, cable-driven robots have special characteristics that increase the tendency of using them.Multi-body cable-driven robots are novel type of cable-driven robots that have advantages compared to single-body ones. Capability of use in rehabilitation applications, in which the different parts of human body have to move separately, is one of the advantages of multi-body cable-driven robots.The first aim of this thesis is to extend the tensionable workspace concept for multi-body... 

Transportation systems have been impressed the humankind societies in an astonishing way. However, there are some weak points that have been accompanied with them. In order to decrease these effects, some strategies such as Transportation Demand Management (TDM) methods have been proposed in some few literatures. In this study, regarding increasing women’s role in urban trips and also some gender based differences; the effects of pricing have been applied as a management method through a Logit Model. Results show that using dummy gender based values would lead to more reliable consequences rather than some separated models with insufficient information. Moreover, it was concluded that women... 

We obtain a large deviation principle describing the small time asymptotics of the solution of a stochastic evolution equation with multiplicative noise. Our assumptions are a condition on the linear drift operator that is satisfied by generators of analytic semigroups and Lipschitz continuity of the nonlinear coefficient functions. Methods originally used by Peszat.
For the small noise asymptotics problem are adapted to solve the small time asymptotics problem. The results obtained in this way improve on some results of Zhang  

This thesis contains four chapters. In first chapter the role of water in organic reactions as a ecofriendly solvent, computational chemistry and dynamic nuclear magnetic resonance were studied. In the second chapter synthesis of new 4-hydroxy pyrrole derivatives in water were reported. For the synthesis of these compounds arylglyoxal derivatives, 1,3-dicarbonyl compounds and ammonium acetate were used. The reaction conditions are very mild. The third chapter contains the synthesis of new (4 or 5)-Aryl-2-aryloeil-(1H)-imidazole compounds in aqueous media. We also investigated the tauto-isomerisation of isomeric imidazoles during this reaction using DNMR technique. In forth chapter a... 

Increasing need for energy, non-renewable fossil resources and environmental pollution persuaded investigators to offer hydrogen as a clean alternative fuel. One of efficient methods for producing hydrogen is the ammonia catalytic cracking reaction. The present work the most to caused on the simulation of both 1D and 2D in an assisted-membrane tapered fluidized bed reactor. In 1D simulation several tubes of membrane placed inside the reactor, but in the case of 2D simulation two membrane tubes on the reactor walls were used. In 1D and 2D simulations the compartmental and Eulerian-Eulerian approach were used, respectively. The simulation results indicate that in a constant static bed height,...