Sharif Digital Repository

At building industry and other construction industries concrete process can be named as the most important part of making structure process, it is important because concrete is responsible of bearing compressive stress at the structure, and most of concrete quality depends on the curing after concreting. Concrete operation at the structure causes using other sciences like heat transfer science to increase the concert quality. Since freezing phenomenon causes serve decrease at concrete quality and the only way is destruction and repeating concreting which is very hard and sometimes impossible and also using chemical additive to decrease freezing point decreases quality and also is... 

Supervision is considered one of the fundamental pillars in the construction of building projects within the country's engineering system. Enhancing the supervision process for construction projects can significantly improve the quality of buildings nationwide. However, in many cases, the supervision process has not effectively fulfilled its assigned responsibilities and has encountered numerous challenges. This study aims to identify and prioritize the challenges present in the operational processes of supervisors within the engineering system. The primary objective of this research is to identify and analyze these challenges and propose solutions to enhance supervisors' performance and... 

The construction system, as a fundamental pillar of any country's development, requires meticulous oversight and the employment of qualified professionals. The introduction of qualified contractors in Iran as a measure to enhance the quality of construction projects and eliminate unqualified individuals from this field has been a valuable step. However, legal and operational shortcomings, as well as challenges in the contracts between contractors and employers, have hindered the effectiveness of this role. This study aimed to identify and prioritize the challenges in the workflows of qualified contractors and propose solutions for their improvement. Key identified challenges include... 

Despite advancements in Building Information Modeling (BIM) in the construction industry, issues such as the intangibility of building models and a lack of interaction and opinion-sharing still exist. The integration of Virtual Reality with BIM has rectified these problems. Quantity surveying, material estimation, solving design problems during modeling and preparing a building model containing information are some of the advantages of using BIM in this research. Alongside BIM, VR tools were employed as a mean to increase interaction with the user, boost marketing and pre-sales, create alternative options for building components, and estimate cost and time. Following the development of a... 

In this research the effects of cooling slope angle and the temperature of molten steel on globular structure after holding the samples at semisolid state have been investigated. The globular structure of high speed steel in the form of rolled - annealed and as cast condition, has been investigated in the semisolid state. The results showed that the grain sizes of cooling slope samples were lower than the rolled- annealed samples after holding at semisolid temperature. On the other hand, rolled-annealed solid grains had better roundness compared with cooling slope samples. Dissolution of carbides in the austenite phase at grain boundary leads to formation of globular particles in the... 

Nowadays, most of businesses are becoming computer-based. This trend causes the organizations to become more vulnerable to internal and external threats. Internal threats are done through insiders. Insiders unlike outsiders have capabilities which aid them to easily carry out their illicit activities. Unfortunately, most of research in computer security has focused on the outsider threats, whereas the most damaging is the result of insiders’ illicit activities.This dissertation addresses three primary necessities of the research in the area of insider threat: a consistent definition of insider threat, a classification of types of insider threats, and a classification of vulnerabilities which... 

When the reservoir energy is too low for the well to flow, or the production rate desired is greater than the reservoir energy can deliver, it becomes necessary to put the well on some form of artificial lift to provide the energy to bring the fluid to the surface. Continuous flow gas lift is one of the most common artificial lift methods widely used in the oil industry. In continuous gas lift, gas at high-pressure is injected in a suitable depth into the tubing, to gasify the oil column, and thus facilitate the production. Every well has an optimal gas lift operating point at which it will produce the most fluid. Ideally, if there is no restriction in the total amount of gas available,... 

This thesis describes different neural networks models and an approximation based neural network controller for autonomous underwater vehicles (AUVs). The online multilayer perceptron neural networks (OMLPNN) have been designed to perform modeling of AUVs of which the dynamics are highly nonlinear and time varying. The online recurrent multilayer perceptron neural networks (ORMLPNN) have been additionally designed to generate a memory to pervious states and increase the performance of the modeling. The designed OMLPNN and ORMLPNN with the use of backpropagation learning algorithm have advantages and robustness to model the highly nonlinear functions. The proposed neural networks architecture... 

Members of Centaurea species are common traditional medicines throughout the world. For this reason medicinal plants are the targets of intense Phytochemical studies. In this research we have investigated Centautea Golestanica which are members of this genus and endemic of Iran. In this research, One Flavonoid, two Sesquiterpenelactones and two triterpenoides were elucidated by advanced spectroscopic techniques such as IR, MS, 1H NMR, 13C NMR and 2D NMR. In continuation of this research, we have reported new and efficient methods for the synthesis of hitherto unknown indole-annulated pentacyclic indolylhydroisoquino lines and naphthooxazocines via tandem dinucleophilic addition of... 

Determining the optimized number and best locations for new wells is a challenging problem due to the nonlinearly correlation and uncertainty associated with engineering, geological and economical variables affecting reservoir performance. The proposed location and configuration for new producers and injectors is usually nontrivial because of the complexity of the fluid flow in highly heterogeneous reservoirs. It depends on reservoir and fluid properties, well and surface equipment specifications and economic criteria. Various approaches have been proposed for this problem. Among those, direct optimization using the numerical simulator as the evaluation function is the most common... 

In this study, the micro and nano particles of substituted strontium hexaferrites with nominal composition of SrFe12-xTix/2Znx/2O19 (x=0, 0.5, 1, 1.5, 2 and 2.5) were prepared by a co-precipitaion method. Ferrite-PVA composites (70:30) with thickness of 1.8mm were prepared at 220°C and 50Mpa. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometer (EDS), vibrating sample magnetometer (VSM) and vector network analyzer (VNA) were employed for characterization of synthesized powders and composites. XRD and FTIR results showed that single phase hexaferrite were obtained for almost all of the... 

Decentralized control is a typical method for the design of industrial MIMO control systems. However, in most multivariable systems, the existence of large interactions limit the achievable performance of such controllers. In the Nyquist Array design method proposed by Rosenbrock, the system interactions can be reduced using a precompensator, such that a decentralized controller may be used with acceptable performance. A well designed pre-compensator will effectively decouple the system and the multivariable systems may be considered as a set of SISO systems. It is therefore obvious that the key element in the Nyquist Array design method is the design of the pre-compensator. There are two... 

By progress of computer vision, many systems are produced for soccer analysis. These systems have been used in many applications such as 2D and 3D reconstruction in arbitrary view. In this circumstance, we need to detect and track players, referee and ball in whole matches. In a single view system there are problems such as occlusion. By having more views of game, when two objects are occluded in one view, we can detect and track them in the others. Objective of this project is multi-view detection and multi-view tracking players and ball in soccer. In recorded videos from multiple views, we track path of players and the ball.
Proposed player tracking system has two main parts. First... 

In this thesis, the individuals’ decision process to achieve consensus in complex networks is modeled. A set of experiments with volunteered participants were run, in which the person is a node in a network with 35 other nodes who behave based on a prescribed model. Each participant is tested twice, once with and once without reward. Performance of individuals in the two experiment types and the effect of structural properties of the underlying network on the results are studied. It is observed that increase in the characteristic path length, diameter, clustering coefficient and local efficiency of the network adversely affects consensus.On the other hand, global efficiency and closeness... 

Integrity of closed-loop systems with integral action control is characterized by using a series of successively more difficult to obtain conditions: Integral Stabilizable (IS), Integral Controllable (IC), Integral Controllable with Integrity (ICI), and Decentralized Integral Controllability (DIC). The IS condition requires that for a Linear Time-Invariant (LTI) finitedimensional (FD) plant, G(s), one finds a stabilizing decentralized controller with integral action. For G(s) to be IC, in addition to being IS, one should be able to reduce the gain of
all control loops by the same factor from a finite value to (but not including) zero without introducing instabilities. ICI requires that... 

Liquid storage tanks are important components of lifeline and industrial facilities. Since,many tanks have borne serious damages during past earthquakes, Forcasting seismic behavior of tanks have attracted for numerous researchers who investigated seismic behavior of liquid storage tanks. This Thesis investigates the effects of slab foundation flexibility on seismic behavior of anchored and unanchored aboveground cylindrical steel storage tanks. In this study, finite elements method by ABAQUS software is used for three tanks with height to diameter ratios (H/D) of 0.343 , 0.85, and 1.53. These tanks are excited by seven one-way and three two-way earthquake records which were scaled to Iran... 

Dams are huge structures in which safety is a very important issue because a failure will result in loss of lives and finance. Several approximate equations for the approximate analysis of arch dams already exist. These equations are usually obtained by considering the behavior of the dam as a shell. Approximate methods are much faster in comparison to the exact methods and give young design engineers who do not have the experience of designing inside view of displacements, stresses and strains. The aim of this project is to compare the results of approximate analysis of arch dams with the results of finite element models and clarify the points of dams in which approximate analysis methods... 

In this research we focus on study and fabrication of ZnO composite nanofibers by electrospinning method for photocatalytic application. The most important challenges in the field of photocatalyst are photocatalytic activity under the visible light and efficiency enhancement. ZnO is a wide band gap semiconductor and it is not active under the visible light. In Iran, we have more than 300 sunny days in a year. Therefore fabrication and application of photocatalytic material with activity under the sun light that contained 40% of visible light is so vital in our country. In the first part of this project, ZnO-CNT nanofibers were fabricated and carbon doped in the crystal lattice of the ZnO.... 

Intraction in multi input multi output (MIMO) system makes control of these systems difficult.There are two ways to control such systems; Centralized and Decentralized control. One way in which a centralized controller is designed is using a precompensator. With application of the pre-compensator, the MIMO sytem is decoupled into several SISO systems and one can control these seperatly. Almost all previews methods for the design of pre-compensator assume that the model of the plant containsno uncertainties.In this thesis a new method is proposed which takes into account model uncertaintes in the design of the pre-compensator.The form of the uncertainties considred an interval-parametric  

Atom transfer radical polymerization (ATRP) is a convenient approach to synthesis of polymer with narrow molecular weight distribution. ATRP of acrylamide (AAm) is taken into consideration because of the intrinsic properties of acrylamide such as water solubility and biocompatibility. As reported in many recent works, polymerization of acrylamide by this method didn’t provide monomodal molecular weight distributions. In best condition with strong ligands such as Me4Cyclam, polymerization was carried out in a short time with high yield but polymerization was not highly controlled. It was shown that polymerization of acrylamide under typical ATRP condition displayed a much lower ATRP...