Sharif Digital Repository

In recent years, utilization of hybrid attached and suspended growth system for modification of conventional activated sludge systems has attracted a lot of attentions. Nowadays, with development of urban areas and also introducing new emerging contaminants and as a result an increase in the influent loading of wastewater treatment facilities, the importance of upgrading and retrofitting available facilities have been highlighted. Conversion of Sequencing Batch Reactors to Sequencing Batch Biofilm Reactors is a viable solution for overcoming these problems. Eventhough several researches have been conducted on removal of different contaminants through these systems, the information about the... 

During recent years, thin-film solar cells based on chalcogenide light absorbers with CuInxGa1-xS(Se)2 compound have attracted considerable attraction due to their desirable band gaps and demonstrated high power conversion efficiencies. These solar cells are fabricated under two categories named as ‘substrate’ and ‘superstrate’, generally. The best reported energy conversion efficiency belongs to substrate type (sodalime glass/Mo/absorber layer/buffer layer/window layer) CIGS solar cells, most have been fabricated with vacuum processes. In spite of this, superstrate solar cells (transparent conducting oxide/blocking layer/buffer layer/absorber layer/back contact) provide easier and cheaper... 

In a counter current two phase flow systems that liquid flows downward due to gravity on the pipe wall and gas flows upward due to pressure gradient in the pipe core, Flooding and reversal Flooding are important phenomena. Flooding is beginning of velocity direction change of liquid from downward to upward that with zero axial velocity of liquid in interface, liquid is on verge of moving upward. When mass flow rate of liquid or gas increase, some part of liquid film are separated and enter the gas stream. With further increase in mass flow rate of liquid or gas in flooding point, reversal flooding occurs that cause to all liquid film flows upward. Flooding and reversal flooding phenomena are... 

In recent years, mobile social networks have largely been developed and gained considerable popularity. With the development of smartphones, the growth rate of users on mobile social networks has dramatically increased, with users constantly interacting and sharing their various private and public data. Such volume of information can be used for profitable purposes and may affect the users' privacy. However, due to the limitations of smartphones and the trivial and costly encryption, entrusting the encryption to the user, both for users and for the service provider will be challenging, thus, social network providers themselves take charge that can compromise the privacy. In this... 

Orbital angular momentum (OAM)and the radial quantum number (p) in infinite-dimensional Hilbert space are two degrees of freedom of light which are associated with the spatial distribution of the electromagnetic field. They are attracting a growing interest for their potential in communication applications ranging from classical communication to fundamental tests of quantum mechanics,quantum communication and quantum cryptography. However, a third party trying to eavesdrop information from communication channel and treat channel security , quantum cryptography or quantum key distribution (QKD) is the secure communication method which is based on the quantum mechanical principles can... 

Electromagnetic field modes have several degrees of freedom, including polarization, orbital angular momentum, and radial order, which can be described by orthogonal modes. By using all the degrees of freedom in communication, the channel capacity can be increased dramatically. With the aim of increasing the capacity and correcting the errors created along the optical fiber, two important issues have been addressed in this thesis. First, the states propagated in the fiber may be disrupted by many unwanted factors and may not be transmitted correctly. Therefore, measures should be taken to minimize the impact of these factors as much as possible or to compensate for their effects. In the... 

The processing of brain signals, including the electrocorticogram (ECoG) signal, is widely used in the investigation of neurological diseases. Conventionally, the ECoG signal has frequency components up to the range of 80 Hz. Studies have proven that in some conditions, such as epilepsy, the brain signal includes frequency components higher than 80 Hz, which are called high-frequency oscillations (HFO). Therefore, HFOs are recognized as a biomarker for epilepsy. The aim of this thesis is to review the previous methods of detecting HFOs and to present new methods with greater efficiency in the direction of diagnosis or treatment of epileptic patients. For this purpose, we used the ECoG data... 

In this thesis a rigorous approach toward systematic quantification of qualitative fea-tures in a three-dimensional (3D) integral imaging is proposed. Incorporating the concepts of sampling rays and sampling points, the first approach is based on geo-metrical optics and quantifies the lateral and depth resolutions of the system within the field-of-view (FOV) and depth-of-field (DOF). The obtained results are justified through experiments. In the next step, the principals of wave optics are employed to measure the lateral and depth resolutions of the system. To this end, the concept of point-spread function is generalized to three-dimensional imaging systems. Through this systematic approach the... 

Microemulsion is one of the major processing techniques to synthesize a nano, homogeneous, and almost agglomerate-free powders. Any kind of oxide ceramics such as piezoelectric ceramics can be synthesis via this method in nano scale without the formation of any intermediate phase. In this study, Lead zirconate titanate (PZT) powders with composition near the morphotropic phase boundary (MPB) have been synthesized via a microemulsion processing route. This emulsion system is a thermodynamically stable mixture of oil (cyclohexane), nonionic surfactant (Triton X100), and an aqueous solution containing specific amount of Pb2+, Zr4+ and Ti4+. The ratio of these ions was adjusted with using ICP....