Sharif Digital Repository

In this work, wool keratin/polyethylene oxide (PEO) nanofibrous scaffolds were fabricated by electrospinning method. Bacterial cellulose nanofibrils (BCNFs) were embedded in the electrospun keratin/PEO nanofibers. Incorporation of BCNFs into the nanofibers enhances their hydrophilicity, mechanical properties and cell viability, adhesion and proliferation. Water contact angle of the nanofibers decreased from 126˚ to 83˚by addition of 1 wt % BCNFs. A thermogelling hydrogel based on carboxylated pluronic (Pl-COOH) and gum tragacanth (GT) was fabricated and polymer conjugation was confirmed by FTIR and H-NMR spectroscopy. Morphological and viscoelastic properties of GT-grafted Pl-COOH hydrogels... 

Channel estimation is one of the fundamental challenges in every communication system and different algorithms have been proposed to deal with it. Obviously, type of a communication channel is an important factor in choosing the appropriate method for channel estimation. Sparse channels are one kind of them that occur in many real-world applications such as wireless communication systems. In addition, emergence of a new means in signal processing to deal with sparse signals, known as Compressed Sensing(CS), paved the way for their extensive usage in many applications including sparse channel estimation.On the other hand, one of the most fundamental problems in sparse signal recovery using CS... 

The X-ray attosecond pulses have many useful applications for studying atomic and sub-atomic scales phenomena in attosecond scale duration. Generation and optimization of high-order harmonics is an efficient way to produce such attosecond pulses which are studied in this thesis. There are several limitations in the attosecond pulse generation such as low efficiency of high-order harmonics, long duration of output pulses and the impossibility of producing an attosecond pulse with any desired wavelength in the x-ray region. Therefore, more investigations into high harmonic generation and fully control and optimization of this process is significant. In this thesis, high harmonic generation... 

Today, the use of carbon nanostructures hybridized with noble metals has attracted considerable attention for the fabrication of bio-electrochemical sensors. Since the specific surface area has an immense effect on the sensing response, three-dimensional structures of graphene have a great capability to utilize in these sensors. In this research, three-dimensional graphene was provided on the porous nickel foam by chemical vapor deposition technique. By evaluation of raman spectroscopy, the time period of 20 minutes for solving of the carbon atoms into the nickel foam was selected as the main parameter of optimized conditions for the synthesis of graphene. Afterward, production of few-layer... 

Nitrite (〖NO〗_2^-) anions are ubiquitous within the physiological, industrial, environmental, and food industries. The potential toxicity risk of these inorganic compounds has well been recognized; thus, the precise detection of these ions by developing reliable and high-throughput analytical methods is crucial for health and environment security. In this study, we present a reagentless electrochemical biosensor using cobalt-based metal-organic frameworks (ZIF-67) and gold nanoparticles (Au NPs) for determination of nitrite ions. The developed biosensor provides the advantages of MOF properties including high surface area, hierarchical porosity, and tunable functionalities along with high... 

Flow control means changing the optimal flow behavior of the fluid in accordance with the desired targets, such as decreasing drag force, increasing the lift force or lift to drag ration, as well as manipulating the separation of the flow from the surface. So far, little research has been done on increasing the airflow performance through the active control of the trailing edge flow. Gurney flap is a great tool, and its experimental results show a significant increase lift force in the airfoil. In this study, it is possible experimentally to use plasma actuators to create microtap and garney flap artificial for enhancing the aerodynamic performance of airfoil by controlling the flow field at... 

One of the features of a project is its uniqueness, if two sets of activities are the same neither of them will longer be included in the project definition. A method in two projects with the same nature may yield inverse results of each other. Therefore, it is necessary to study the parameters affecting the project carefully before any action. So far, some research has been conducted in this area and it has been tried to perform case study on qualitative and quantitative parameters of the project. By investigating a number of common factors in most civil engineering projects, especially megaprojects, the present study attempts to identify and examine exquisite and effective parameters and... 

In this study, based on Households Income and Expenditure Survey (HIES) data, we examined the socio-economic characteristics and transition of Iranian urban households in each of the three different income groups from 1997 to 2020. Moreover, factors affecting entry to poverty or persistence in poverty in Iranian urban households are discussed.The results of this study show that, contrary to popular belief, there is no evidence of accumulation of entrepreneurs and business owners in the urban middle class. Rather, middle-income households have higher-skilled jobs and pay more for social security than low-income ones, as well as pay more attention to investing in human capitals (education and...