Sharif Digital Repository

Tin sulfide with an energy gap of about 1.1 ev is a semiconductor suitable for applications such as solar cells, lithium-ion batteries, photocatalysts and other semiconductor-based devices. There are several methods for synthesizing this semiconductor at the nanometer scale, among which the solvothermal method is an efficient, controllable and inexpensive method. By precisely controlling the parameters of this process, two-dimensional tin sulfide nanosheets with high purity and desirable morphology can be produced. In this research, tin sulfide has been synthesized by solvothermal / hydrothermal chemical method and its metallurgical properties have been studied. Effect of solvothermal... 

In this research, we have tried to predict the morphology of the membranes that were prepared by phase inversion method. In this research Polyvinylinedifluoride (PVDF) and dimethylacetamide (DMAc) was used as the polymer and solvent. The affect of titanium oxide (TiO2 ) and polyvinylpyrolidene (PVP) which are respectively an inorganic and an organic additive, on the morphology of the membranes was investigated. Ternary and Quadratic phase diagrams were drawn based on the Flory Huggins theory. The interaction between components was determined and the effect of interactions and molar volumes of polymer, solvent, non-solvent and additives on the binodal line was investigated. To predict... 

Machine translation has been an important subject in the field of natural language processing (NLP). In recent years, because of providing essential linguistic data resources, statistical approached have been deployed in machine translation. Although there have been several attempt to create English to Persian automatic translator, there has not been sufficient effort in the reverse direction. In this project, we reviewed previous works in machine translator for Persian and implemented a statistical machine translator from Persian to English. We needed a bilingual corpus for building the translator. For this purpose, we used a corpus of Phd and MSc abstracts in Persian and their translation... 

Human brain is one the most efficient biological neural network that is capable of performing most complicated tasks in very short time. Visual system as a part of the brain can process the visual records from the environment and perform very useful processes on them. The information provided from visual system processes play important roles in human intelligence. In this thesis we introduce and investigate one of the well-known theories about visual system called gestalt theories. These theories tried to define how a biological neural network can perform such results. Gestalt theorists developed rules of perception to explain their ideas including Law of Pragnanz, Similarity, Closure,... 

Considering the tremendous development in imaging systems’ industry, today we can afford to have imaging equipment, capable of taking multispectral images in very high resolution. One of the remarkable benefits of this technology is in the realm of arts and particularly in museums. Taking advantage of the potentials of multispectral, highquality imaging, curators will be able to probe their priceless works of art ( e.g. paintings ) without putting them in danger through invasive research. Besides, one can investigate and control the transformation of these works through time by using this new imaging method. Recently, Multispectral Imaging of paintings, in different frequency bands from... 

Syntheses of coats including nickel nano-particles by electrodeposition have been
investigated for over 10 years. A method of testing according to surface reply was chosen
to reveal the effect of each pulse parameters (including duty cycle, frequency, average
current density, off time (toff) and on time (ton)) and the effect of saccharin concentration
on electroplating cathode efficiency, nanostructure. Pulse electroplating test of nickel was
composed by 30 tests. Pulse electroplating with relatively high peak current density was
employed and saccharine was added to increase deposition and rate of nickel nucleation on
surface. According to the results of cathode... 

Vibration is one of the most important factors in design, operation and lifetime of drill strings. There for, investigation of vibrations in drill string, like every other rotary machine, is very important. The main goal of this research is developing a nonlinear model for a drill string system dynamics in an inclined well. Effects of drilling mud flow rate, weight on bit, angular velocity along with viscous damping, on the stability and vibration of a drill string are studied. Dynamic equation of the model is developed considering axial displacement and lateral bending geometric nonlinear coupling. The effect of drilling mud flow is modeled using Paidoussis formulations. Equation of motion... 

Enhancement of photocatalytic characteristics of semiconductors have been always a challenge for the researchers. Doping semiconductors for adjusting their energy gap and changing their morphology in order to increase their effective surface area and reaction sites are examples of their endeavor to overcome the challenge. In this research, nanostructured Aluminum Titanate powder was synthesized with Sol-Gel process and by altering synthesis parameters, the best synthesis condition to get the best possible band gap was discovered. Moreover, we examined the photocatalytic properties of the recently developed material “tialite”, which were not studied before and also evaluated the effect... 

In this work two shapes of silver nanostructures including silver nanowires and silver nanocubeswere synthesized by polyol method. Silver nanostructures were characterized by SEM, XRD and UV-Vis spectroscopy. Afterwards the morphology-dependent electrocatalyticperformance of these nanocrystals on the differential pulse behavior of naltrexone (NAL) was investigated. To this aim the differential pulse voltammetric behavior of NAL on a glassy carbon electrode modified with electrochemical deposited gold nanoparticles conjugated with different shapes of silver nanostructures and nafion was investigated. It was proved that silver nanowires show more effective electrocatalytic activity toward... 

Morphological analysis of words plays a fundamental role in natural language processing applications such as spell checker, POS-tagging and machine translation. Among different dialects belonging to Kurdish, Northern Kurdish (Kurmanji), Central Kurdish (Sorani) and Southern Kurdish are the closest ones to each other. The central dialect of Kurdish is the second official language in Iraq and a large volume of text content is producing daily in this dialect. In this research, designing and implementation of a two-level morphological analyzer for the central Kurdish dialect is introduced. This analyzer is designed using an open source toolkit named HFST, which is a finite state transducer... 

In this thesis, the theoretical foundation, the way of implementation and the uses of Pars Morph, a Persian morphological analyzer is introduced. Pars Morph is a rule-based Persian morphological analysis system, which analyzes the internal structure of word in Persian and determines the grammatical category and function of the word parts. Pars Morph being in link with a lexicon covering about 45000 lexemes and based on morphological rules in Persian can analyze the structure of complex lexemes and their possible inflected forms and even out-of-lexicon words.
Accuracy rate of the first version of Pars Morph is about 95% which could be enhanced to 100% by applying the regulations on... 

Coordination polymers are a wide range of metal-organic polymers that have good potential for use as extraction phase in solid phase extraction and solid phase microextraction. Also, these polymers can be synthesized in various morphologies such as nanorods, microspheres, nanofibers, etc. to demonstrate the effect of morphology on extraction efficiency.In this study, the extraction efficiency of a coordination polymer with two morphologies (nanorods and microspheres) and different nitrogen percentages was investigated in needle trap device using gas chromatography-mass spectrometry to measure polycyclic aromatic hydrocarbons as model analytes.PAHs were measured in conventional cigarette... 

polyamides have found great attractions in wide variety of applications due to their desirable mechanical and tribological properties and appropriate processability. Pure polymers are not suitable for this kind of application due to their low mechanical strength. High strength materials are needed for abrasive applications. Polytetrafluoroethylene (PTFE) is one of the most popular materials for abrasive applications. In this study the effect of PTFE and surface modification on PA/PTFE composite properties is investigated. duo to modification of PTFE powder, PTFE is exposed to sodium naphtalenide (Na/naphtha) etchant so as to deflurinate the surface for obtaining carbonyl, carboxyl and... 

Polyamides have found great attraction in the wide variety of application due to their desireable and tribological properties and appropriate processability. Due to their low mechanical strength reinforcing of these types of polymers has always been one of the important academic and industrial issues. In order to improve mechanical properties of such polymers, different kinds of reinforcement particles such as titaniom diaoxide, Nano clay, glass fibers (Short or long glass fiber), etc were used. Carbon nano tubes have high thermal and electrical conduction and mechanical properties; they are widely used as a reinforcement particle for polymer matrix. In this study, carbon nano tube and... 

Polyvinylidene fluoride is highly regarded by researchers due to its piezoelectric properties, mechanical properties, chemical and thermal stability and biocompatibility. This thermoplastic polymer has a semi-crystalline structure and, depending on the crystallization conditions, has five distinct crystalline phases α, β, γ, δ and ε. The β, γ and δ phases are electroactive, and among them, the β phase has high piezoelectric activity due to its high dipole moment. This study focuses on increasing the amount of β phase in polyvinylidene fluoride and increasing its piezoelectric property. Polyvinylidene fluoride is highly miscible with oxygen containing polymers such as polymethyl... 

Synthesis and characterization of Nafion/TiO2 membranes whit different solvent (DMF, DMAc, NMP) for proton exchange membrane fuel cell (PEMFC) were investigated in this study. Nafion/ TiO2 nanocomposite membranes have been prepared by solution casting Method. The structures of membranes were investigated by Scanning Electron Microscopy (SEM). Also water uptake, proton conductivity and ion exchange capacity (IEC) of membranes were measured and compared whit Nafion 112 in microbial fuel cell. The membrane was prepared whit DMF solvent has maximum proton conductivity and best morphology and maximum cell voltage  

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... 

The tree structure of neuron morphologies has excited neuroscientists since their discovery in the 19-th century. Many theories assign computational meaning to morphologies, but it is still hard to generate realistic looking morphologies. There are a few growth models for generating neuron morphologies that correctly reproduce some features (e.g. branching angles) of morphologies, but they tend to fall short on other features. Here we present an approach that builds a generative model by extracting a set of human-chosen features from a database of neurons by using the naïve Bayes approach. Then by starting from a neuron with a soma we use statistical sampling techniques to generate... 

Aluminum is the lightest industrial element after magnesium. As a result, aluminum alloys have many industrial usages because of their high specific strength. Semisolid casting is one of the processes that is capable of producing aluminum alloys with high mechanical properties. In this process, there are a wide variety of methods to prepare semisolid slurry, one of the best ways of which to produce globular structure is electromagnetic stirrer. In this research, the semisolid slurry of A356 aluminum alloy is fabricated by electromagnetic stirrer under different conditions of stirrer intensity current, stirring time and pouring temperature. Then the fabricated semisolid slurry is injected... 

Perovskite solar cells, with high efficiency operation, have been candidated as a cost-effective and environmentally friendly technology. Despite the great progress, there are some primarily issues remained regarding to the perovskite film and its fabrication methods. A very common perovskite cell structure is FTO/TiO2/CH3NH3PbI3/Spiro-OMeTAD/Au. Although, this structure has some advantages, lack of full surface coverage of perovskite film leads researchers to put much effort on finding other constructions. This surface inhomogeneity reduces the amount of light absorption and therefore efficiency. One way to produce a complete and uniform film is applying mixed-halide composition; such as...