Sharif Digital Repository

Due to their low volatility, negligible flammability, and high regeneration capacity, ionic liquids have attracted a lot of attention in chemical and process engineering fields. Regarding the limited access to the laboratory facilities, developing theoretical methods such as equations of state is important in this research field. Thus, data for density and viscosity of pure ionic liquids and vapor pressure data for binary mixtures of ionic liquids and acidic gas have been collected and validated from the IL Thermo website for 42 ionic liquids. By consideration of theoretical studies and comparison of the performance of different cubic equations of state in predicting the aforementioned... 

Shot peening is a cold-working process commonly used in industry to improve the fatigue performance, stress corrosion resistance and surface nano-crystallization of metallic parts. This process extends fatigue life via two mechanisms: Preventing the crack growth due to compressive residual stresses and, preventing the crack initiation because of increased material hardness. These mechanisms are the results of the bombardment of the component's surface with small spherical particles. In this research, an analytical model is developed for estimating the residual stress distribution induced by shot peening process. The modifications of the developed analytical model are related to... 

With improving of technology, using of Wireless Sensor Networks (WSN) is rapidly increasing. In some application, wireless sensor network do need to supply realtimeness. In the other hand, in many cases, sensor networks are in risky environments distributed. Therefore, security is a key factor in sensor networks to performing their works properly optimized and maximum. Hence, both security and realtimeness features are important features of sensor networks. But because of common resource use, increasing efficiency of a feature will result in decreasing efficiency of other feature. In this thesis, we indicated to study mutual effect of security and realtimeness in Wireless Sensor Networks in... 

Residual stresses are one of the influencing factors on fatigue life. These stresses may cause cracking and failure of the element even in the absence of any applied stress or any external load. For this reason they are very important, and their measurement is crucial. The methods for measuring the residual stress in spite of their name often measure the strain and by analyzing the measured strain, determine the residue stress of the element. The important problem about residual stresses is that their values in the element often remain unknown and usually no simple and non destructive method for measuring is available. Usually finite element analyzing is used for modeling the production... 

Nowadays Wireless Sensor Networks (WSNs) are found in a variety of applications such as environmental monitoring, military surveillance and medical systems. These applications interface with the real world environments and the delivery of data is subject to certain timing constraints. Most of the protocols being used in the WSNs do not satisfy real-time requirements and only deliver data in a best-effort fashion. However, real-time support in the WSNs remains an open research topic. This dissertation first studies real-time application and then real-time approaches in WSNs. Real-time applications are applications that require bounded service time. Normally in WSNs, communication delays are... 

A carrier should be used a guidance system for reaching to the point of injection in an orbit. The main purpose of guidance system in the injection process is issuance of guidance commands to achieve the final desirable velocity and position. These velocity and position indicate the purpose orbit for injection. Carrier is a dynamic system which is described by mathematical terms. In general carrier guidance systems apply pitch angle or rate of pitch angle to reach specific path over injection process. Different methods are available for carrier guidance such that preset method. In this method, the guidance system addresses specific guidance commands and control system performs these... 

Friction Stir Spot Welding (FSSW) with ability of refilling weld’s keyhole, is one of the new solid state joining processes which have gained many applications, especially in automobile industry. Considering newness of the process, first part of this study has been dedicated to design and manufacture of a FSSW machine which is done entirely by author of this study. Second part was survey on effect of parameters such as Tool rotation speed, Weld time, and Forge time for refilling the hole, on properties of an aluminum joint. After welds were made, specimens were subjected to Lap-shear tensile test, after that, studies on macro and microstructure have been carried out. Generally an increase in... 

Prolonging the lifetime of wireless sensor networks (WSN) is one of the most important goals in the sensor network research. A lot of work has been done to achieve this goal. Since sensor nodes normally have limited resources in terms of energy, bandwidth and computation capability, efficiency is a key design goal in sensor network research. Data aggregation is a very important method to conserve energy by eliminating the inherent redundancy of raw data in dense WSNs. Previous research on data aggregation has demonstrated its effectiveness in reducing traffic, easing congestion and decreasing the energy consumption. However, few are actually designed for a real world application and... 

Nowadays, in the presence of different types of computer attacks and different methods of eavesdropping on network communications, nobody can deny the importance of cryptography. Hardware Security Modules that are specifically designed for this purpose are widely used as a fast and reliable tool for encrypting data in computer networks. In this project, using the common and well-known FPGA platform and by leveraging the reconfigurability feature of this platform and also by adding a network protocol detection module to the traditional architecture of Hardware Security Modules, a novel module has been designed and implemented that can encrypt and decrypt data in a communication network, at... 

Security is an important issue in Vehicular Ad Hoc Networks (VANETs),which are mainly aimed at enhancing safety. Analysis of security mechanisms can help design and implement secure communication establishment methods in such networks. Formal verification is an analysis approach, with the purpose of proving the correctness of a system based on defined precise assumptions. Formal verification is applicable to a vast range of systems, such as time-critical reactive systems. Timed formal verification of cryptographic protocols is a subject that has gained a lot of attention in the recent two decades. The TESLA broadcast authentication protocol is on one hand an efficient, standardized method... 

Additive manufacturing (AM), also known as Rapid prototyping or D printing, is a new technology for the manufacturing of the physical parts through an additive manner. In the AM process, the orientation pattern of the part is one of the most important factors that significantly affects the product properties such as the build time, the surface roughness, the mechanical strength, the wrinkling, and the amount of support material. The build time and the surface roughness are the more imperative criteria than others that can be considered to find the optimum orientation of parts. In this research, Two method is used to optimize part build orientation (PBO). In the first method a new combined... 

Classification of Traffic Internet obtained early interest in the computer science community. Various methods have been presented for classifying the traffic of Internet to manage both security and Quality of Service (QoS). Nonetheless, traditional methods of classification including scheme of Transmission Control Protocol/Internet Protocol (TCP/IP) have not been accepted because of their complicated management. Classification method of network through learning algorithms of machine is the most popular classification method of traffic at this time. ELM was proposed as a modern algorithm of learning for the Single-hidden Layer Feed Forward Neural Networks (SLFNs). Meanwhile, learning process... 

The transportation industry has been greatly impacted by computer technologies, and utilizing AI in autonomous vehicles is one of the visions for its future. Due to the need for better perception of the surroundings through sensor sharing, fully autonomous vehicles must rely on appropriate vehicular networks. Advanced applications of vehicular networks like sensor sharing require high transmission rates and low end-to-end delay, which are addressed by mmWaves as the transmission medium. As a result of their high attenuation, mmWaves are directional and susceptible to obstacles. Packet relaying for mmWave communications can extend the communication range. When selecting relay vehicles in the... 

Shahid Kazemi reservoir is the largest, and the most strategic dam of Urmia Lake basin is located on the Zarrineh Rood River in the south of this basin. This reservoir is responsible for supplying drinking water to large cities such as Tabriz, the agricultural demands of significant plains, including the Miandoab plain, and most importantly, the environmental demands of Urmia Lake and downstream rivers. In recent years, due to increased consumption upstream of the dam and agricultural development downstream of the, Urmia Lake has faced water shortages. This study develops the first daily runoff forecast system for Shahid Kazemi reservoir in Urmia Lake basin (ULB), Iran, an important region... 

Sustainable development of the energy sector, as a resource-consuming sector with high environmental emissions, is essential. Especially in energy-intensive countries such as Iran with a sensitive environment, the sustainability considerations are more critical. The sustainability may be achieved when all pillars (economic, social, and environmental) are considered in a balanced manner. Previous economic experiences show the incapability of the market view in proper consideration of the ecosystem assets. Therefore, and in contrast to the economic view, in the physical approaches the limited capacity of the cosystem bounds the economic activities for meeting social welfare. In this view, the... 

The objective of this investigation was obtaining sound Friction Stir Welded (FSWed) Commercially Purity Titanium using suitable Tool’s Materials (for Shoulder and Pin) in order to be able to work in high temperature (>1000 ˚C) with great mechanical properties and minimum wear during process. Consequently, different materials and designs for Tool, such as High Speed Steel tool, Tungsten based tool, Tungsten Carbide (WC-Co) based tool and diverse tool geometry and designs like simple design, threaded design, fixed pin and inserted pin (adjustable pin) was used. The results demonstrated that using simple cylindrical WC-Co for pin and Tungsten for shoulder resulted in joints with the best... 

In this research, for optimization of repair welding of control valve and flange that use in East Oil& Gas Company, effect of chemical composition, microstructure, hardness and stress relive on sulfide stress cracking (SSC) investigated with select of four electrodes. All welds were prepared by shielded metal arc welding (SMAW) and investigated with optical microscope, hardness test, tensile test and SSC test. The results showed that increase of nickel content in the range of 0.032–1.58 wt. % in weld metals, decrease of acicular ferrite and increase of side plate ferrite, grain boundary ferrite and M/A micro constituent in microstructure. Ni3S2 decrease SSC resistance and (FeCu).S increase... 

There are several applications of wireless sensor networks wherein the data collected by the sensors in the network are critical and hence have to be reliably transported to the sink, example of such applications are fire detection in a forest or controlling vibration on body of dam. Reliable communication in wireless sensor networks is hard to achieve efficiently using methods in conventional systems like Internet. End-to-end retransmission is inefficient, or in some cases impossible. It is well-known that Reed-Solomon codes may be used to provide error correction for multiple failures in RAID-like systems. To the coding theorists, this technique is a straight forward extension to a basic... 

The current work is carried out to characterize welding of AISI 304 Austenitic Stainless Steel to Ductile Cast Iron. The welding method was SMAW and the welds were produced using a Nickel-Buttering by a pure Nickel electrode(ENi1) on Cast Iron side, then by 4 types of filler materials the joints were produced; Ni-base electrode(Ni1), E308 and E309 Austenitic stainless steel electrodes and E7018 electrode. The preheat temperature of Cast Iron has been selected to be 250○ and 500 ○C to avoid crack of weldments. The comparative evaluation was based on metallography, chemical composition, hardness and corrosion behavior on two different preheat temperatures. According to metallography, the best... 

Daily improvements in technology and exchanging important information via internet and connection networks make data and connection security a significant problem. Cryptology is the branch of knowledge which concerns secret communications in all of its aspects. Two major areas of cryptology are cryptography and cryptanalysis. Cryptography is a branch of cryptology concerned with protecting communications from being read by unauthorized people.
Cryptologists design and create algorithms to improve cryptography along with finding methods to crack those algorithms. Cryptanalysis is a branch of cryptology concerned with cracking the cryptographic systems used by others.
Cryptographic...