Sharif Digital Repository

Synthesis, characterization and photoelectrocatalytic performance evaluation of worm-like BiVO4 porous films have been conducted in this research. An in situ combustion approach was employed to prepare BiVO4 nanolayers on glass and ITO/glass by using drop casting, spin coating, dip coating and pulsed spray pyrolysis deposition techniques. The precursor solution of vanadium and bismuth include ~0.0233g ammonium metavanadate (NH4VO3) and ~0.0970g bismuth (III) nitrate pentahydrate (Bi(NO3)3.5H2O) in 2.5 mL ethylene glycol. Different deposition parameters were investigated for each of the aforementioned deposition techniques to obtain a uniformly-deposited BiVO4 nanolayer with high adhesion to... 

For more than two decades psychologists and sociologists have been warning about the damage of new social media. in the last decade, the neurological research has been developed to provide an empirical foundation to support the above hypothesis. Much of the research has focused on teenagers and young adults as the so-called digital native and as the largest number of social media users. They hold that a significant contribution to the adolescent trend plays a significant role in the tendency of individuals toward social media, thus increasing impulsive behavior. The three parts of the brain, namely the "social cognition network," the "self-referential cognition network" and the "reward... 

Technological catchup has been one of the topics of interest for researchers and policymakers, especially in developing countries, and has been studied from various dimensions. The catchup in the renewable energy industries is important due to the possibility of benefiting from its economic dimensions along with responding to the growing energy demand in these countries, as well as accessing the sustainable sources of energy supply. In the literature, various dimensions have been studied to investigate the factors affecting the technological catchup, one of the most important of them is the technology life cycle. In answer to the question of what stages of the technological area life cycle... 

This thesis investigates methods to improve the utility of cellular spectrum to secondary users. Here, secondary users exploit the spectrum by hierarchical spectrum access. Since the information of the channels is available at the central controller, cellular networks can play an active role in spectrum use of the secondary users and increase their utility in this way. Transmitting the information available at the central controller to the secondary users and ordering the channels in use by primaries can help improve spectrum sensing. First, we consider the schemes which maximize secondary users’ utility by ordering the channel allocation process to primary users. We model the secondary... 

In this thesis, vibration analysis of multi-walled carbon nanoconesstudied by molecular mechanics approach. In this simulation, atoms of carbon and bondings of them modeled by concentrated mass and structural elements, respectively and then mode shapes and natural frequencies of these structures calculated and effects of height, apex angle, boundary conditions and number of layers on natural frequencies of carbon nanocones studied. Also, critical buckling load of multi-walled carbon nanocones due to axial and in-plane loads obtained and effects of height, apex angle and number of layers on critical buckling loads of carbon nanocones studied. These results validated by molecular dynamics and... 

In this thesis we study one of the applications of algebraic topology to computer science and define some tools to analyze concurrent programs. For this purpose a geometric space is corresponded to every concurrent program and a partial order is considered on this space, so every path on it corresponds to an execution of the program. Some of these paths which are dihomotop (homotop in partial ordered spaces) with each other induce the same execution of the program. By defining “Fundamental Category” in which objects are points of the space and morphisms are dihomotopy classes, the space that should be analyzed shrinks to a smaller one. By defining component category in the next step, without... 

Today, many organizations are active in service industry, and many others are planning to take part in. Phone call is the simplest channel between an organization and the customers, and these organizations devise call centers to acquire, retain and create value for customers. On the other hand, human resource in call center is the key element to identify problems, and improve performance. This research aims to provide a competency model for a firm which provides access to internet and has a call center for after-sales support. BEI method with a process-driven approach was used to gather information from call center employees, and related themes were extracted from the information with theme... 

Surgery theaters are one of the most important and expensive departments in hospitals. Since the operating theaters are connected with other departments, improving the efficiency in the operating theaters can affect other departments as well, so effective and efficient planning and scheduling of the operating theater It is necessary. In this research, we study and investigate the problem of planning and scheduling surgery theaters under the uncertainty of surgery duration, considering the open scheduling strategy and having the list of patients and limited resources after surgery. Let's say that the parameter of the duration of surgery is uncertain and we have little data about it. Some... 

Microbial fuel cell (MFC) has attracted a great attention in the recent years due to its advantage of simultaneous energy generation and pollution removal. However, utilization of MFC technologies a challenging issue because of the low energy output and high expenses. Generally, using ion exchange membrane in MFC contributes to a large proportion of the construction costs. Without using a membrane, oxygen intrudes to the anode chamber which will inhibit the anode reaction and decreases the coulombic efficiency. As a solution, using less expensive membranes can facilitate the commercialization of MFC technology.
In this study, soil cylinder and earthen plate were examined as low cost... 

Addition of heavy metal cations such as manganese and nickel in low zinc phosphating bath increases the corrosion resistance of coatings and provides more suitable substrates for painting (especially electrophoretic painting). In addition, due to accelerating property and low cost availability of heavy metal cations such as Mn, multi– cationic phosphating is cost effective. In the present study, chemical composition and operating parameters of zinc - calcium - manganese Tri- cationic phosphating solution were optimized. Then the effects of various parameters such as phosphating time, bath temperature and pH on properties of coating were investigated. According to the results, about 1 g/L was...