Sharif Digital Repository

Generating the experimental spectrum for all gamma-ray elements is difficult and practically impossible in some industrial applications. Furthermore, in many applications such as neutron activation, it is not possible to obtain an experimental spectrum for a single isotope on account of the fact that the gamma-ray spectrum obtained from neutron activation is derived from the gamma-rays of various elements in a sample. Therefore, using computational techniques like Monte Carlo method for calculating the detector response functions seems an appropriate solution. The detector response functions for 3''×3'' NaI detectors have been simulated using MCNPX 2.7 code and Ptrac card in this project.... 

In this work 1-(2-hydroxyethyl)-3-methylimidazoliumbis{(trifluoromethyl) sulfonyl}imide ([hemim][NTf2]) and 1-benzyl-3-methylimidazoliumbis{(trifluoromethyl) sulfonyl}imide ([bzmim][NTf2]) ionic liquids were used to study the effect of introducing hydroxyl and benzyl groups to the imidazolium cation on aliphatic/aromatic separations. Toluene separation from heptanes has been investigated by extraction using ionic liquids. Finally, a realistic model for survey the data was used. The liquid-liquid equilibrium (LLE) data for the {heptane + toluene + [hemim][NTf2]}, {heptane + benzene + [hemim][NTf2]} , {heptane + toluene + [bzmim][NTf2]} systems were measured at 313.2 K and atmospheric... 

Ionic liquids (IL's) are found to be potentially suitable solvents for the chemical process industry, especially due to their negligible vapor pressure which can result in a major decrease of solvent loss and the environmental harm. One of the foreseeable industrial applications in the field of natural gas processing is the replacement of traditional organic solvents (usually alkanol amines) presently used for the absorption of H2S from sour gases, by suitable IL's. Ionic liquids have been proposed for the separation of gas mixtures. In particular, ionic liquids have been suggested for the removal of the acid gases, hydrogen sulfide, and carbon dioxide, from natural gases and refinery gases.... 

In this study thermodynamics and kinetics effects of two ionic liquids (ILs) on the formation and dissociation of methane and carbon dioxide hydrates were investigated. The ILs used in this study are 1-butyle-3-metylimidazolium tetrafluoroborate, [Bmim][BF4], and 1-butyle-3-metylimidazolium methyl sulfate, [Bmim][MS]. At the first step of experimental section, the tetrahydrofuran (THF) was used in atmospheric pressure. The structure of THF hydrate is similar to natural gas hydrate; therefore it is used as a model for studying the properties and investigation of inhibitors effects on gas hydrates. In order to consider the effects of foregoing ILs on the formation and dissociation of gas... 

Nowadays, different processes are designed in order to convert raw materials to value added products. One of these is the Bentonite sulfur production process. The most important equipment in this process are stirred tanks where mixing operation of molten sulfur with some additives such as functionalized Bentonite and oxides of iron, zinc and manganese are performed.
In this thesis, following the design and making of a laboratory scale glass baffled stirred tank, the viscosity of molten sulfur and additive suspension has been measured at different temperature (125, 130 and 135oC) and several formulations. Concentration profile of Bentonite has also been obtained by means of local sampling... 

Atmospheric corrosion as one of the most principal factors of destruction is not Climatic map of atmospheric corrosion is closely related to air and atmospheric factors among which we can point out to different types of atmospheric pollutions such as NOX, SOX gases and pendant materials as well as the rate of humidity and rain and even the rate of sun radiation. The effects of these factors beside each other cause the speed of corrosion from a climate to another climate to be changed, which is presentable in form of a map. There is a 2 method to provide this map. First build up a station to measure the corrosion data and collect them in a long period of time. This method are time consuming... 

Modern broadband microwave and millimeter-wave systems often struggle with excessive pass band ripple and negative gain slopes due to the loss of transmission lines such as coaxial cables, or ripples in the gain characteristic of broadband amplifiers. The common solution for this problem is using a gain equalizer to compensate for the intrinsic pass band variation with some extra loss in the band of interest in return.Designed equalizers often have a constant slope in their bandwidth. However, having ripples in pass band or in other words slope changing in some parts of the band is one of the issues that designers should deal with. In this thesis, after reviewing the previous works on the... 

In this study, a novel multiscale analysis is proposed to utilize atomistic properties of crystalline nano-materials as an input to continuum problems in the range of large deformation. The main purpose of presented work is investigating the capability of different hyperelasticity models based on molecular statics (MS) and molecular dynamics methods to attain proper hyperelastic strain energy density function to illustrate atomistic information under various types of deformation loadings. Also, the proficiency of hyperelastic model is investigated for nano-structure including different percentages of voids. The material parameters of hyperelastic strain energy density can be obtained from... 

This dissertation focuses on addressing electromagnetic forward and inverse scattering problems using physics-based deep learning models. A key challenge in integrating physics with data-driven models lies in the implicit nature and nonlinearity of the forward scattering operator. To address this, a novel closed-form expression is proposed for piecewise homogeneous media. By formulating the scattered field as an implicit function of the permittivity values in each homogeneous region, the computational complexity of solving the forward problem for a fixed geometry is changed from O(N^3 ) to O(NΣM_k^2), where N is the total number of meshes, and M_k refers to the meshes in the kth region. This... 

Wear of parts during service is one of the main factors of damage to the industrial parts. From among various kinds of wear, abrasive wear has the most role in damage of industrial parts. Hard surfacing is a useful and cost effective method for improving the surface properties of parts. This method is made through coherent layer sediment from the alloys resistant to abrasion, oxidation and wear by welding or spray. Determining the appropriate alloy for hard surfacing operations need knowing of working conditions of the part and the type of occurred abrasion. Ordinarily, the alloys which are prepared for hard work by welding, are in the form of cored wire or electrodes. In this research die... 

Entropy is one of the important quantities in thermodynamics. In this project has tried to make this quantity as a bridge between quantum and thermodynamics. Entropy has many definitions that the Shannon entropy is chosen in this work. By this definition of entropy, we are able to define the entropy for a electronic system in molecules. By this definition, we are seeking an answer for this question,”whether entropy has a similar application in quantum like thermodynamics or not?”. To elucidate this hypothesis, simple diatomic molecules are computed. In fact, displacement of the Shannon entropy has investigated in bond making process. The question is that whether we can use this quantity to... 

Radioisotope thermoelectric generator (RTG) is a kind of nuclear batteries, in which thermal energy resulting from the discharge of charged particles decayed of radioisotope, using thermoelectric arrays, can be converted to electrical energy. In this study, the different kinds of RTGs introduced and applications of them have been expressed. All types of radioisotopes used in RTGs have been reviewed and the most suitable of them in terms of maximum thermal power density and minimum dose rate have been selected. All types of thermoelectrics used in RTGs have been reviewed and the most suitable of them in terms of the range of temperature and maximum efficiency have been selected.
In this... 

Results showed that 9 factors of “Brand Equity”, “Product Quality”, “Service Quality”, “Service Recovery”, “Perceived Value”, “Relationship”, “Employee Satisfaction”, “Physical Environment” and “Distribution Channel” are most effective factors by researchers that have effect on customer satisfaction. Thus, the Macromodel of this research was designed based on these factors. Due to limitations and context of the research, “Service Quality”, “Service Recovery” and “Relationship” were chosen in the final model. Results of questionnaire showed that the 5 parameters of “Service Recovery Speed”, “Reliability”, “Responsiveness”, “Empathy” and “Seller-focused antecedents” was the most important... 

Bearing capacity of foundations is one of the most controversial issues in foundation engineering. In this study regarding to the previous researches which has done by the other researchers the bearing capacity factors of a footing has calculatedusing finite element method. On the next step of this study some footings has modeled on different positions near slopes with different angles and bearing capacity of them has calculated, then some strip foundation has modeled and bearing capacity of them has calculated and compared with the values of the footings in this study and strip foundations of the other researches. Furthermore some foundations have modeled on the solpe and bearing capacity... 

Deployment of demands, increase in users and new services highlight the necessity of effective frequency allocation i.e. dynamic allocation instead of fixed allocation. Cognitive radio is a proper solution for dynamic frequency allocation. Cognitive radio can scan the spectrum and use the idle bands for transmitting and receiving data. The main part of this radio which is responsible for the most pivotal task is spectrum sensing. Recently, varied methods have been proposed to sense the spectrum. The scope of this research is on designing a very high-speed spectrum sensing system. In this thesis, in order to meet the required scan rate, a tunable complex filter with 40MHz pass-band has... 

The potential future use of hydrogen as a transportation fuel must be evaluated from a supply chain perspective. However, the main challenge in motivating the hydrogen supply chain network is the lack of existing hydrogen infrastructure. Strategic decisions for planning sustainable infrastructure can be analyzed hierarchically in time-related stages (2025-2030-2035). Meanwhile, a time- and location-based design has been specifically applied to a few selected ports in southern Iran, with limited focus on a national or countrywide scale. This study proposes a mixed-integer linear programming (MILP) optimization model to logically design the hydrogen supply chain, considering primary energy... 

In this thesis, the transmission characteristics of a vertical tunneling transistors based on graphene-hBN-MoSe2 heterostructure is studied. We first obtain the tight-binding parameters required for Hamiltonian matrix and bandstructure calculations using density functional theory results. Once we have the tight-binding parameters, Hamiltonian and coupling matrices are calculated both of size 326×326. We then proceed to calulate the density of stated for source and drain contacts using the aforementioned matrices and nonequilibrium Green’s function(NEGF) formalism. We can then calculate the quantum capacitances of source and drain and acquire source/drain potentials using a capacitive circuit... 

The objective of this research is to investigate fluid flow in cracked porous media. Fluid, mass, and heat transfer in porous and cracked porous media, particularly in subsurface environments characterized by complexity and uncertainty—such as hydraulic fracturing, lowـpressure groundwater flow, and more—are of great importance in the oil and geothermal energy industries. The problem domain consists of three main sections: the saturated porous medium, the crack or channel within this porous medium, and the boundary layer between the crack and the adjacent environment. The phase field method is utilized in this study to model these discontinuities. Phase field models are similar to... 

In this study, the effect of external filter on the various parameters of image quality in digital industrial radiography by CR method for steel and aluminum piece has been investigated. The filter reduces the noise of scattered beams by absorbing the low-energy beams in the X-ray spectrum that are most likely to be scattered, but high filter thicknesses can attenuate the more energetic beams and have a negatively effect on the image quality. On the other hand, the absorption of those low-energy beams increases the average spectrum energy and thus reduce the contrast, so it is necessary to use the appropriate material and thickness of the filter. For this purpose, to examine the filter... 

In recent years, various research has been done on the severe deformation of low carbon steel sheets. One of the methods used is the pressing in the grooved die, only two passes of the pressing process in the grooved mold have been successful when applied to these sheets, but on the other hand, these two passes also lessen the sheet's ductility while increasing its strength. Due to the fact that the sheet surface produced by the pressing in the grooved die is not entirely smooth, the attempt in this project was to improve the ductility to some extent using warm rolling in addition to the smoothness of the surface using higher temperature while improving the strength or maintain it. To...