Sharif Digital Repository

High advantages of hydrometallurgy have led to its recent development in metal extraction. Many investigations have been carried out on applying hydrometallurgy processes on copper extraction. In this study, Chalcopyrite concentrate produced in Sarcheshmeh copper plant was subjected to oxidative leaching investigation by cupric ion to determine the effect of several parameters on the copper and iron dissolution, included temperature of leaching, time of holding and cupric concentration as oxidant agent in a range of 38-97°C, 1.5-8.5 hours and 0.2-0.8 M respectively. The leaching media was chloride providing with 3M HCl 37% and CuCl2. The experiments were designed by central composite... 

This paper concerns the delay margin achievable using fractional order Proportional_Integral_Derivative controllers for linear time- invariant systems subject to variable, unknown time delays. The basic issue under investigation addresses the question: What is the largest range of time delay so that there exists a single fractional order Proportional_Integral_Derivative controller to stabilize the delay plants within the entire range? Delay margin is a fundamental measure of robust stabilization against uncertain time delays and poses a fundamental, longstanding problem that remains open except in simple, isolated cases. In this research, we develop explicit expressions of the exact delay... 

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... 

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... 

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... 

In this thesis, various fractional order controllers (FOCs), e.g., FO-PID, FO-TID, CRONE and FO-Lead/Lag, are implemented using PLC. For this purpose first, several methods are used to approximate the differentiator and integral operators. Based on these methods, the equivalent rational transfer functions of the fractional order controllers are obtained. Then, using STEP7 software, the FOCs are implemented in Siemens PLC. Moreover, to facilitate the use of the implemented FOCs in the industry and to take full advantage of the controllers, WinCC software as an interface between human and machine (HMI) is used. The WinCC software enables the operator to access the PLC through a computer (PC)... 

In this study, some of robust and exact tuning methods for fractional order PD and PI controllers are investigated in order to extract their solution existence conditions. Using aforementioned methods needs solving a set of nonlinear equations to obtain desired controller parameters which satisfy the control objectives. Hence, one of the aims of this study is to find necessary and sufficient condition on tuning specifications which guarantee the applicability of the aforementioned methods. The achievable performance region of the methods is obtained through the extracted necessary and sufficient conditions. The other aim of this work is to investigate the uniqueness of the methods... 

Along with the development of electronic exchanges, accessibility to various data streams, increasing computing power, decreasing trading costs, and growing competition in financial investment industry, quantitative trading strategies or quantitative trading rules have developed rapidly in the recent decades. These strategies try to forecast the future price movements of risky assets from the historical market information in algorithmic ways or statistical ways and thus challenge the Efficient Market Hypothesis.
The increasing attention to these strategies and lack of related empirical studies in the financial markets of Iran, motivate the research in this area. Furthermore, despite its...