Sharif Digital Repository

Brines are one of the main resources for lithium extraction and Iran has got many high magnesium and low lithium brine resources. In order to extract lithium, it is required to carefully identify these resources and their associated compounds and then an appropriate method can be adopted to extract lithium. Among the Previous researches, Bahadori, Jandaghi and Moazeni developed methods for removal of undesirable brines elements, Deposition of lithium from refined brine and lithium adsorption anatase ion-sieves membrane respectively; in this study it has been tried to investigate the optimization of the adsorption process, onto the TiO2-B ion sieve with nanotube morphology. TiO2-B nanotubes... 

The purpose of this project is the synthesis and characterization of a group of phenolic amino acidic derivatives that are studied in both solid phases as well as their solutions. For this, new phenol derivatives of serin and isoleucine amino acids were synthesized and characterized by 1H NMR , 13C NMR, IR spectroscopy as well as elemental analysis. These ligands were utilized to prepare LSF perovskite membrane. According to their XRD patterns, it was concluded that the powdered precursor prepared by serin derivative has shown better qualification and less intermediate phase in the synthesized perovskite membrane similar to the sample prepared by applying EDTA. Furthermore, in the previous... 

Derivation and lexicalization are two critical subjects in morphology and word-formation processes. Although wide studies have been taken place about derivation, which is one of the most productive processes of word-formation along with composition, there has been no proper attention to lexicalization, which sometimes happens after derivation. One of the applications of this thesis is developing dictionaries. With regard to this issue that there is no scientific and complete method for recording lexical units in Persian dictionaries, we decided to propose a scientific method to do the mentioned activity by studying derivational processes, affixes and lexicalization phenomena and its relation... 

The progress and development in the field of Natural Language Processing (NLP) have led to the emergence of Natural Language Understanding (NLU). One of the main objectives in this field is inference, deduction, or entailment from the phrases (sentences) of a natural language. The crucial question here is whether it is possible to semantically infer a natural language hypothesis from a set of natural language premises. Since in many applications of Natural Language Inference (NLI) in the real world, it has a decisive role, this problem is of the utmost importance. Furthermore, the previously proposed approaches to tackle this problem incorporate a wide range of classic logic-based and new... 

High peak to average power ratio (PAPR) is one major drawback of OFDM system which highly affects the performance if untreated. Several methods have been proposed to overcome this problem. In all these methods reduction in PAPR is gained through a tradeoff with another system figure such as mean transmit power, bandwidth or BER. In this thesis we investigate high PAPR problem in OFDM, and we will introduce some methods proposed to alleviate it. These methods are divided into two classes; methods in the first class are based on finding a peak cancelling signal and methods in second class rely on solving a discrete optimization problem. We give a general formulaion for the methods in second... 

The aim of this thesis is experimentally and numerically investigation of annular flow between the inner rotating smooth surface and the outer stationary grooved surface with or without axial fluid flow. Mounting grooves on the surfaces is important in cooling of rotating machineries such as electric generators and rotating heat pipes. The effect of different parameters such as the air gap between the surfaces, the geometry of the grooves, axial flow and rotation speed are numerically and experimentally investigated. The experimental results with axial grooves show that the entrance length decreases up to 17% with increasing the grooves depth. The reason is enhancement of the mixing and the... 

Surface Growth processes, as critical phenomena, have long attracted physicists’ attention. In many cases, the surfaces exhibit scale-free properties and they become fractals. Based on the large scale dy- namics of each model, one can divide the different models into niversality classes. Two well-known universality classes are Edwards-Wilkinson and KPZ. the kind of noise present in the stochastic differ- ential equation describing the model, can determine the large-scale dynamics to a large extent. In this research, we have perturbed the Edwards-Wilkinson dynamics to make it suitable for describing growth processes in non-homogeneous environments, such that the noise gets stronger in higher... 

We study hydrodynamic fluctuation forces in a compressible and viscous fluid in confined geometries. First, we shall give an introduction on fluctuations and their applications in several experimental methods. Then, we shall proceed by introducing hydrodynamic equations governing the behavior of fluids and their dynamics. Assuming a compressible and viscous fluid, confined between two rigid, parallel, infinite plates, we subject one of the plates to a random force, having zero ensemble average and finite variance, while the other plate is kept fixed. We shall investigate the correlation functions of the forces acting on the boundaries and analyze the responses of the fluid film to the...