Sharif Digital Repository

Today, users can easily access network and Internet services from anywhere, anytime, using mobile computing devices, such as laptops, tablets, smartphones, and so forth This trend has diversified users and their need for network protocol-based services, including VoIP. VoIP is an Internet protocol for voice transmission and reception, which has become one of the biggest challenges in today's world of communications and telecommunications. Analyzing and evaluating the quality of network service (QoS) in VoIP traffic is an essential part of the process of ensuring and improving the quality of multimedia networks. Therefore, monitoring and measuring "users’ satisfaction" toward voice... 

nowadays, due to population growth, unconventional use of water resources and on the other hand, climate change, limited renewable water resources, reduction of groundwater cavities, the need for water for agricultural use and energy production are increasing. Due to the fact that each cubic meter of dirty water pollutes 40 to 60 cubic meters of clean water and the entry of polluted effluent into the receiving sources of environmental degradation leads to a lot of wastewater treatment, water consumption management and The development of wastewater treatment processes is also becoming increasingly important. At present, wastewater treatment plants face the challenges of high energy... 

Concentrated photovoltaic systems (CPVs) allow simultaneous production of electrical energy and high-temperature thermal energy. These systems consist of a concentrator for collecting solar rays onto the surface of the recipient cells. Moreover, these systems are always facing the sun using a sun tracker. The heat generated by these systems can be used in industrial processes, heating, cooling, and water desalinating. Given the concurrent generation of power and high-temperature heat, it is possible to achieve higher efficiency than that of conventional solar systems. Furthermore, the electrical efficiency is also higher than conventional systems due to the use of multi-junction solar cells... 

In this research copper oxide ores were dissolved under acidic condition. Chemical analysis (XRF) and X-Ray diffraction analysis (XRD) were used to identify the phases and determine the percentage and amount of the elements in the mineral. The results showed that the mineral contains 4.464% by weight of copper, which is malachite in mineral. The experimental design method (DOE) was used to dissolve concentrate by sulfurice acid. The parameters of temperature, time, acid concentration and solid to liquid ratio, as well as the interaction of these parameters on leaching and optimization of parameters were also done by response surface method (RSM). To determine the amount of copper dissolved,... 

The water and energy demand increase as the population grows. Increased usage of energy leads to scarcity of available resources and limited absorption capacity of environment. Development of efficient and environmentally compatible energy conversion technologies are conceived as an important option for resolving pressing challenges. Compatibility with environment requires considerable reduction in the share of fossil fuels and efficient utilization of renewable energy sources. Hence, development of high-efficiency solar energy systems is becoming an important challenge in the energy sector. The present study is involved with development an integrated solar system based on the application of... 

The study presents a comprehensive electric arc furnace model for simulation and control application to predict chemical processes, heat and mass transfer. The model consists of arc module, chemical – slag module and heat transfer sector to observe fundamental phenomena affecting on energy consumption. Two modules act independently of each other and the two module calculations apply in the heat transfer sector. Arc module predicts the amount of energy dissipated from the arcs using arc currents and arc lengths; chemical and slag module calculates chemical energy, changes of elements/compounds, slag height and slag quality; while the heat-transfer sector uses calculations of the other two... 

The objective of the present research work has been the development of a model of optimal distribution electrical energy which may include distributed generators. Electrical distribution company has the option of receiving electric power from distributed generators owned by customers (Private Companies), DGs belonging to the electrical distribution company and purchase of power from market (high voltage network). The electrical distribution company would alternatively be able to sell surplus of its generation to the power market (high voltage network). The model of distribution system depicts the flow of electricity in each hour interval. The restrictions and bounds are the flows in each... 

The purpose of this research is to monitor the health of structures using the updated finite element model, in which digital images are used to optimize the numerical model. Structural Health Monitoring (SHM) is always an important and significant issue that has attracted the attention of many researchers in recent years. In general, some researches have been conducted in this field using physical sensors that provide discrete data to the system for analysis. Using cameras to monitor the structure makes it possible to extract continuous and integrated data from the structure using digital images, which is a significant advantage compared to physical sensors.In this research, a steel... 

Aluminum Bronzes have many applications in marine environments. These alloys suffer from both hot cracking and cold cracking. In order to overcome the hot cracking and cold cracking, Semisolid Stir Joining method and a proper thermal cycle was used respectively. Effects of temperature, stirring rate, and tool type were investigated in Semisolid Stir joining method. In this method, butt joint design was used in order to place specimens, and the specimens were heated up to specific temperatures (920, 925, 930°C). A stirrer (Cylindrical and Grooved tool) with three rotational speeds (800, 1200, 1600 RPM) was introduced into the stir weld seam. Welded specimens were cooled to the 900°C... 

In order to increase the network performance, to discover network security threats, to guarantee the quality of services, to simulate networks and develop new network protocols, network designers and operators need software tools to analyze the network traffic. The first step to do this analysis is network monitoring. This can be done by using various software and hardware tools.
In this research we developed a tool which analyzes the network traffic using appropriate statistical methods. The models which are analyzed in this application are: Poisson, Self-similar and Weibull. This application analyzes the network traffic based on this statistical models and calculates their parameters.... 

The increasing number of road accidents and fatalities have yielded the introduction of several solutions by related industries such as automobile manufacture. Proposed solutions can be classified into two categories: passive, such as airbags, and active such as ABS ad ITS-based technologies. Inter vehicles communication let the communication between vehicles(V2V) or between vehicles and road infrastructure (V2I) by relying on DSRC technology and standards. Intelligent Transportation System (ITS) has three main types of applications namely safety, traffic and commercial. Safety applications are the main goal of vehicular communication, and real time guarantee in safety applications is so... 

Nowadays, one of the problems of network designers and users is the correctness of network equipment functionality. Since routers play an important role in information transfer between various networks and communicate with each other through a routing protocol, any violation of such protocol can result in the network's failure or defective transfer of data. Thus, being assured of the conformance of the implemented protocol in a router with what has been defined in the protocol's standard is of great significance. To this end, before using or exposing a router, network equipment testers should run protocol conformance tests on it and insure its correct functionality. This brings up the... 

In real-time systems, jobs that miss their deadline are considered worthless or ineffective. Nowadays, real-time applications (such as multimedia) that communicate through software-defined networks (SDN) are widely used and will continue to expand in the future. SDN is an emerging network architecture in which control plane is separated from data plane to manage it directly. In this research, we make changes to the controller and the switch used in such network to deliver real time packets or real-time flows (such as video) on time, as much as possible. As missed deadline packets are worthless and they waste bandwidth, dropping them is a solution. Moreover, the controller can drop flows that... 

Network Function Virtualization (NFV) is a new paradigm in computer networks for implementing network functions on general-purpose common-of-the-shelf processors. The revolutionized NFV architecture has shown to be a suitable replacement for hardware middleboxes. NFV is in high demand because of its lower costs, increased flexibility, and more scalability. However, the ever-growing volume of network traffic and increased data transfer speed in computer networks have made achieving high performance the major issue in this area. With thousands of processing cores and high memory bandwidth, Graphical Processing Units (GPUs) are potentially an appropriate solution to accelerate network... 

Recent advancement in wireless communications, electronics, low power design and also tendency to use high performance low cost products have led to emergence of Wireless Sensor Networks (WSNs). As the main purpose of a WSN is information gathering and it’s transmission to the sink node, the main problem is to deliver information correctly with minimum energy consumption. Besides, whereas the majority of developed applications for WSNs are event-critical applications, achieving reliable data transfer as the main factor of dependability and quality of service seems vital. However, data transmission is unreliable over multi-hop WSN due to the unreliability of wireless links and node failures. ...