Sharif Digital Repository

In this study, application of a Magnetic Nanofluid consisting of Magnetite as Nanoparticle and Water as base fluid in DASC systems is investigated. The DASC system is modeled theoretically and behavior of such system is predicted.In this study a comparison between magnetite Nanofluid and some other common Nanofluids is conducted. The study shows that Magnetite Nanofluid has a better performance and efficiency than Water, Al2O3 Nanofluid and SiO2 Nanofluid. Also magnetite Nanofluid and TiO2 Nanofluid function are almost similar.Also effect of external magnetic field on the performance of magnetite Nanofluid is investigated. It is showed that when the magnetic Nanofluid is subjected to an... 

Electrospray, as a novel and efficient method in jet production, utilizes a combination of hydrodynamic and electrostatic forces. In electrohydrodynamic systems, by controlling effective parameters, it is possible to achieve a wide range of fluid flow regimes. Among these, the stable cone-jet mode has attracted special attention from researchers due to its stability and controllability characteristics. The unique features of this mode include uniformity in droplet size resulting from jet breakup (which is effective in reducing temperature gradients on hot surfaces), the ability to control fluid flow characteristics through adjustable parameters such as electrical voltage, and spray... 

Today, using Radio Frequency Identification (RFID) technology is of a remarkable interest to the industry and services sectors. Application of this technology could result in higher levels of productivity and effectiveness. On the other hand, department stores are increasing in number and size in the country. Application of RFID technology could play an undeniable role in both reducing the time each customer must spend in order to complete their purchase, and accelerating the logistics operations of these stores.
Through literature review, this research studies application of RFID technology instead of other identification technologies such as Bar-Code, reveals strengths and weaknesses... 

Scientific collaboration and the resulting outputs have been always of interest to the scientific community. Specifically, drawing and understanding the elements of scientific collaboration network and identifying its determinants are important step in prescribing and implementing policies in various fields and disciplines of science. Focusing on the Iran context, this study examines the scientific collaborations of faculty members in selected Iranian universities (Sharif University of Technology, University of Tehran, Iran University of Science and Technology, Amirkabir University of Technology, Isfahan University of Technology, and Ferdowsi University of Mashhad). We have drawn the... 

let T4 = C2/ be a complex torus with induced flat Kähler metic. The quotient X = T4/Z2 (where the generator of Z2 acts by multiplication by −1) is an orbifold with 24 singularities, called a singular Kummer Surface. Locally any of the singularities are modelled on the singularity of C2/Z2. We can describe the minimal resolution X of X by resolving all of the singularities as : TCP1 ! C2/Z2.There is a well known Calabi–Yau metric on TCP1 named the Eguchi–Hanson metric, with the important property that far from the exceptional divisor −1(0) the metric is asymptotically locally Euclidean (ALE). We identify a small annulus around any singular point of X/Z2 with a large annulus over TCP1 far... 

Due to ignoring the effect of length scale and neglecting the details at nanosize, classical methods are not sufficiently accurate to determine the properties of nanostructured materials. More reliable results can be obtained, using surface elasticity theory. Lots of analytical, experimental and numerical investigations have been done on the effect of interphase on the mechanical properties of polymer nanocomposites whereas metal matrix nanocomposites are in the first stages of analytical and numerical researches and have attracted so much attention.
The main objective of this research is to investigate the effects of interphase as well as coating, on the mechanical behavior of metal... 

Long memory in assets return is important on the theoretical as well as the practical aspects and since it is a special form of nonlinear dynamics, in this study an ARFIMA model was used with the aim of considering the long memory in the return conditional average of automobile industry index. Then, due to the observation of ARCH effects, the simultaneous conditional average modeling and turbulences in the automotive industry index return using an ARFIMA-FIGARCH model was considered in the residuals of the best fitted model and results were that for modeling the returns and turbulences of automobile industry stocks which has a special long memory, FIGARCH will provide better and more... 

Identification of different hazards in a UF6 production process, and evaluation of the risk originated from these hazards is the main objective of this project. A number of hazards are present in a typical UF6 production process, such as leakage of chemical gases like HF and F2 and also radioactive UF6 gas release. In order to evaluate risk due to these hazards, probabilistic approach has been used. Due to lack of probabilistic safety criteria (PSC) for chemical releases, only for UF6 gas release risk assessment has been done. As a first step in PSA of this process eight groups of initiating events have been identified using HAZOP study, and for each initiating event, event tree analysis... 

For validation of simulation, plasma actuator was modelled on a flat plate in quiescent flow, which is result in low-speed jet near the wall. The results were compared with similar model and were showed good agreement with them. After that, blade was modelled in three-dimensional manner with MRF technique and periodic method and the results were validated in clean situation (absence of plasma). In the following, turbine was analysed with a code, which was written in MATLAB software based on BEM method and the results were compared with present CFD simulation. Then, plasma actuator was used in chordwise in parts of the blade to improve wind turbine performance. Also it was used in spanwise... 

One of the major problems encountered in artificial intelligence is environment interaction. A sensible way for around-interaction is to collect information from sensors and make proper reactions. Generally, in the real world, an intelligent agent needs to know its pose. There are several ways to know the pose of an agent. One of them is based on the fusion of the output of an inertial sensor with the information retrieved from a camera. This leads to enhance the estimation of the pose of an agent. In this research different solutions for this problem are compared. Studies are done with the goal of attitude detection for vehicles and mini-robots, moving on planar surface. For this end, we... 

It is necessary to evaluate the effect of the lifting arms of VTOL UAVs in increasing the drag of UAV and reducing the flight endurance of the cruise phase. In this study, the adverse effect of the lifting subsystem and its accessories on reducing the aerodynamic efficiency of the wing and optimizing its design for the cruise phase is studied. The base UAV is an integrated wing-body drone with a 2.12 m wing span, 7 kg maximum take-off weight and with about 65 km / h horizontal flight speed. To investigate the possibility of reducing the adverse aerodynamic effect of the arms of the lifting system, different positions are selected in terms of the geometric dimensions of the arms and their... 

The most important feature of the fifth generation of mobile telecommunications is the increase of information transfer rate and together with it the increase of the capacity of telecommunication channels in comparison with the previous generation. One solution is to increase the frequency toward millimeter-wave frequencies. Currently, the most suitable option for the millimeter-wave frequency band is the 28 GHz band, which has received a lot of attention due to its availability and the possibility of implementing cheap integrated circuits using CMOS technology in this band. In addition to the features that this frequency band has; This band has limitations such as high emission losses and... 

The purpose of this research is to design and construct a test stand for the study of the kinematic and flow pattern of bluff bodies oscillating motion due to the induction of wake vortices. An experimental investigation was conducted to explore the effect of bluff bodies cross section to optimize the amount of electrical energy withdraw by electromagnetic harvester. The tests are carried out on cylinders with square section and rectangular sections with a length to width ratio of 1/2 and 2/1 and height of 50 cm, at speeds of 5 to 35 m/s in eiffel type wind tunnel. The effect of cylinder cross-section on the amount of energy harvested showed that the amplitude of oscillation in square-shaped... 

High-quality online services demand reliable and fast packet delivery at the network layer. However, clear evidence documents the existence of compromised routers in the ISP and enterprise networks, threatening network availability and reliability. A compromised router can stealthily drop, modify, inject, or delay packets in the forwarding path to launch Denial-of-Service, surveillance, man-in-the-middle attacks, etc. So researches tried to create intrusion detection methods to identify adversarial routers and switches. To this end, data-plane fault localization (FL) aims to identify faulty links and is an effective means of achieving high network availability. FL protocols use... 

In this study production of bioethanol from corn fiber that is a lignocellulosic material is investigated. Experiments were performed in a membrane bioreactor. Bioethanol is a second generation biofuel that is considered recently because of the decrease in oil production and pollutions caused by fossil fuels.The feed was corn fiber which is considered suitable due to its low cost and availability in my country. Corn fiber is composed of cellulose, hemicellulose and lignin. We should increase cellulose fraction by pretreatment methods to get a higher conversion rate into bioethanol. We did this by acid pretreatment and the fraction was reached to 41%. In most of previous work experiments were... 

The physics of the flow around the wing in the oscillatory motion of the wing has various patterns, including the leading edge vortex, the tip vortex and trailing edge vortex escape. The interaction of these vortices forms a complex flow structure around the wing, which will have a direct effect on the aerodynamic performance of the wing. Therefore, controlling these structures can be considered as a way to improve the performance of the flapping wing. One of the passive flow control techniques that has recently been taken into consideration is a leading-edge protuberance method. Another type of passive flow control is geometric correction, using corrugation method. According to studies, two... 

Confining nematic liquid crystal between two curved boundary conditions while the nematic molecules have a degenerate planar anchoring leads to complex and beautiful textures of molecular disparagement(defect) in the bulk and on the surfaces. Such the liquid crystal shells are made with double-emulsion techniques in microfluidic devices have provided applications for micro-scale colloidal linkers.In this work, we have numerically minimized the elastic energy in one-constant approximation in present of Fournier’s degenerate surface potential with finite element method. The nematic shell is confined between two spherical surfaces that we have studied the final energies and their related... 

A liquid crystal is a state of matter composed of highly anisotropic building blocks. When liquid crystals are exposed to surfaces with given shapes and anchoring conditions, the orientation of their molecules gets spatially disordered and topological defects may form in the system. The interplay between liquid crystals and the geometry and topology of the colloidal particles has motivated extensive recent studies.In this thesis, we present the numerical modeling results for two faceted colloidal particles in a thermotropic nematic liquid crystal. To obtain the equilibrium nematic field with a finiteelement method, we numerically minimize the free energy of the system that based on the...