Sharif Digital Repository

In 2009, a general equation of state (EOS-III) based on an effective near-neighbor pair interaction of an extended Lennard-Jones (3, 6, 12) type has been introduced as : , where is the compressibility factor, p and ρ stand for pressure and molar density , respectively, T is Temperature , and e, f and g are the temperature dependent coefficient of the equation of state . the Z_th and Z_in are the thermal and internal contributions of pressure in the compressibility factor, respectively. this equation of state gives a good description of all types of nano- and bulk –solid and bulk fluid at entire temperature and pressure ranges for which thee is experimental data. Investigation show that... 

The rise in carbon dioxide levels has led to the manifestation of numerous environmental challenges. Currently, the absorption and conversion of carbon dioxide into valuable fuel resources such as synthetic gas, methane, and ethylene are deemed crucial from both environmental and economic standpoints. Despite the presentation of photocatalysts such as titanium oxide and electrocatalysts such as copper, silver, and zinc, their efficiency in CO2 conversion is found to be insufficient. One potential solution to this problem is the utilization of photoelectrocatalytic CO2 recovery. In this study, the aim was to enhance the photoelectrocatalytic reduction of CO2 by designing and manufacturing... 

a graph into specific subgraphs. Specially, decomposing the edges of a complete graph into cycles with determined length draws the main attention. Most of the former works in this area were studied the Alspach conjecture. In another words, Alspach conjecture states that ” Is the obvious necessary conditions for decomposing a graph into cycles (equality of the edges count with sum of cycle lengths) with specified length but not necessarily identical are also sufficient.” Different cases of Alspach conjecture have been studied and proved completely.The decomposition of a complete graph into cycles with the same length k is called k-cycle system. Steiner triple system is a 3-cycle system.... 

Switched systems as a subset of hybrid systems have both discrete and continuous behaviors and have attracted a lot of attention during the past decades. A set of subsystems or modes whose sequence is specified by a switching rule makes the switched system. Another category of systems is the fractional order system in which the order of derivatives is not limited to integers. This feature has provided a significant capacity for this type of system. On the other hand, every real system faces a set of limitations that neglecting them may reduce the quality of control or even lead to system instability. The purpose of this research is to model and control the switched system, whose subsystems... 

Biological layers are one of the main problems related to water transfer with pipe lines which are formed through time in the inner surface of the pipes by the water nutrients. Hence, the inner surfaces in the pipe lines and water refineries should be made in order not to let these biological layers to be made. The reason is that when the biofilm is formed on these surfaces, the traversing water is polluted. Dredging of these pipes is not only necessary in most of the countries in the world and needs huge amounts of water but is also very complex and expensive.In this research, nanomaterials, namely ZnO, T〖iO〗_2،S〖iO〗_2 have been used to cover the surface of concrete and steel pipes (The... 

Preformed particle gels (PPGs) due to its advatantage over commonly used in situ gels has been successfully applied for controlling excess water production in mature oil reservoirs. Field results of using PPGs in oil fields shows that commonly used PPGs are highly sensitive to hard reservoir conditions such as high temperature and salinity and can not effectively block fractures and high permeability layers.Objects of this study are synthesis and evaluating performance of this novel polymer based hydrogel in oil reservoirs with high temperature and salinity. Central composite design ( which is a experiment design approach) was used for synthesizing thirteen gel samples and optimal sample was... 

Sand production from oil reservoirs leads to various problems, such as well productivity reduction, operating equipment corrosion, and increased production costs. Therefore, controlling sand production in unconsolidated reservoirs is crucial for operating companies. Chemical injection into the formation in order to strengthen and reduce sand production is one of the most important methods of sand control. In this study, a hydrogel nanocomposite was designed and its effectiveness in sand control was investigated. Various tests were carried out to define and assess its efficacy, as follows: Morphological tests demonstrated the creation of a dense, homogeneous, and porous structure. Structural... 

Cardiovascular (CV) system is very similar to a wireless communication system in which a common input signal from the heart is fed into different arterial channels throughout different body parts. By putting multiple sensors on different peripheral body sites effects of this circulation from the heart can be recorded and be used as inputs for different multi channel blind system identification (BSI) methods for estimation of arterial channel dynamics. This Thesis is defined in order to investigate different BSI methods capability in CV characterization. To achieve this goal photoplethysmogram signals has been used as primary sensory recorded effect of heart function at three different... 

Block shear failure in the parent material is considered as a common potential failure mode in welded connections used in steel structures. However, there is only little research reported on the block shear failure of welded connections under multiaxial loading. Multiaxial loading is defined as loading not parallel or perpendicular to weld lines and in the case of in planar eccentricity results in torsional loads. In this research a nonlinear finite element model is developed to study the effect of connection geometry, weld group configuration, and eccentricity of lap splice connection on block shear capacity. The case studied concerns a 3 milimeter thick structural steel plate (CSA G40.21... 

Cloud Manufacturing is a new paradigm which under development and has been introduced as one of the promising models for providing ubiquitous, convenient, on-demand network access to a shared pool of configurable manufacturing resources (e.g, networks, servers, facilities, applications, robots, machines and services) that can be rapidly provisioned with minimal management effort and service provider’s interaction. Cloud Manufacturing is defined based on Cloud Computing. Like the Cloud Computing, Cloud Manufaturing offers a service-oriented architecture that is based on information technology (IT) in which each manufacturing resources is expressed as a service. For providing a... 

In recent years, the Internet of Things has become one of the most popular technologies that has facilitated new interactions between objects and humans to improve their quality of life. With the rapid proliferation of the Internet of Things, an ever-evolving question arises - how to control access and permissions in a space that can contain hundreds of smart devices - which ultimately address security and privacy concerns of technologies and consumers. Today, cloud computing has become an important technology for the Internet of Things and creates a cloud architecture that is used in various fields in this area. A smart city is an urban area that uses a variety of sensors and electronic... 

Supercapacitors are safe and environmentally friendly energy storage devices that have been considered for their diverse applications. One of the most important factors that control supercapacitors' capacity is the electrode material's structure and properties. Adding heteroatoms or composite materials synthesis is one way to improve electrode performance. In this study, a facile, fast, and economical hydrothermal method was used to synthesize N doped, P doped or N/P co-doped 3D reduced graphene oxide (rGO) for high-performance supercapacitor application. Nitrogen and phosphorus elements were replaced by carbon atoms simultaneously during the graphene oxide hydrothermal reduction procedure.... 

Capacitive deionization (CDI) is a suitable method for water desalination with low energy consumption and high efficiency, which does not have secondary pollution and is environmentally friendly. The hybrid capacitive deionization uses a faradaic electrode next to the carbonaceous electrode, taking advantage of both electrodes, and high capacities have also been reported. Titanium carbide Mxene is an important candidate in CDI due to its high electrical conductivity and tunable interlayer distance, but Mxene suffers from low oxidation resistance. Therefore, in this research, molybdenum disulfide (MoS2) that is an essential member of the 2D transition metal dichalcogenides family, was used as... 

The aim of this thesis is investigating the approaches proposed for controlling switched systems and designing a controller for MIMO switched systems. The system under consideration is in strict feedback form with unknown dynamics, unmodeled dynamics, state-dependent delays and disturbances and input nonlinearity (saturation, backlash, dead-zone). In this work, the unknown dynamics are estimated by an intelligent approximator. The arbitrary switching law is assumed and for control purpose the switching instances are not required. The backstepping technique has been utilize for controller design and by using a nonnegative switching function and a common lyapunov function, the closed loop... 

In recent decades, we have faced the enormous growth of data and graph volumes. This requires modern ways of computation and storage systems and algorithms. MapReduce is a known way of processing Big Data in a Parallel and primarily Distributed setting. Theoretical models (e.g., Massively Parallel Computation) for Algorithms using this paradigm commonly evaluate the number of rounds and needed communication. We study the Minimum Spanning Tree (MST) as a fundamental graph problem. This problem in MapReduce is harder for sparse graphs. We introduce an algorithm that performs well comparing previous studies, especially for sparse graphs.We present an empirical study by implementing some... 

The present study has been conducted with the purpose of investigating how to reduce behavioral biases in investors' decisions, which has become very important in the recent situation of Tehran Stock Exchange and with the entry of a large number of inexperienced investors. In this research, an attempt is made to examine the relationship between investors' trading experience and the effect of herd mentality on their investment decisions through the perspective of social cognitive theory and using financial self-efficacy. Multiple regression analysis and Bootstrap mediator relationship analysis were performed on data collected from 502 active investors in the Tehran Stock Exchange, and the...