Sharif Digital Repository

Increasing the kinetic energy of the near-wall fluid by exciting shear layers is known as an effective method for flow separation control. So far, choosing the proper approach to apply excitations has been a challenging issue in the field of flow control. This work investigates flow control of airfoils in static stall and flutter conditions, employing shear layer excitation technique and plasma actuators. This research introduces a novel flow separation control, namely dual-point excitation of shear layers and compares its performance with the conventional single-point excitation method. Two airfoils (NACA 4415 and NACA 0015) have been considered as the baseline test-cases. In the first part... 

This thesis is devoted to deriving a port Hamiltonian control approach for different scenarios of brachiation movement by a two-link underactuated planar robot called brachiation robot. The port Hamiltonian modeling and control of this type of robot is introduced for the first time and shows promising results in the analysis and simulation as will be showed here. Animals have long inspired roboticists. Their dexterity, versatility, flexibility of motion and great variety of behaviors has made them benchmarks for robot performance. Recently things have begun to change and robots are now capable, to a limited degree, of mimicking the behavior of animals. This paper studies a type of... 

The internet of things is a network of interconnected things (people, electronic devices, mechanical machines, etc.) that are able to transfer data. The applications of internet of things in electronic health (eHealth) are becoming increasingly interested. Deployment of eHealth facilitates the access of users to healthcare services, and improves the quality of the services. Using cloud computing provides the accessibility of healthcare services, and enables a data owner to share his health data with doctors and healthcare service providers. Health data is considered sensitive. So, leakage of any information about it endangers data owner privacy. Attribute-based encryption is a cryptographic... 

The chemical vapor deposition (CVD) of graphene from methane on a copper substrate is the most promising method for production of large-area graphene films. There have been long-standing challenges in this field such as controlling the graphene coverage, film quality, the number of layers, and the nucleation density of graphene domain. These challenges can be overcome by developing a fundamental understanding of the graphene growth process. The main aim of this study is to control nucleation density of graphene domains. Chemical vapor deposition (CVD) graphene is polycrystalline, and grain boundaries in graphene film have been identified to degrade the properties of graphene as a membrane... 

Anzali wetland, in the Caspian Sea, northern Iranian province of Gilan, ranges from fresh near the tributary streams to brackish near the mouth into the harbor and the sea. Anzali wetland has faced with the serious levels of eutrophication because on the other hand, the lagoon has decreased in size during current century, to less than a quarter of its former extent and on the other hand, this wetland is faced with entering a huge amount of nutrient elements due to human activities in its watershed. Discharge of industrial wastewater, animal wastes, timber harvesting and the most important entering, rice farms irrigated wastewater are of the considerable causes of eutrophication in wetland.... 

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... 

A number of players are positioned on the vertices of a finite graph, and each is wearing a hat whose color has been randomly and equally likely selected from a finite set of colors. Player A sees Player B if and only if there is a directed edge from the vertex corresponding to A to the vertex corresponding to B. The players must agree on a specific strategy before the game begins and carry it out. Once the game begins, no communication is allowed between the players, and each player must simultaneously guess the color of their own hat. The team wins if at least one guess is correct. For a given directed graph, we define the 'guessing number' of the graph as the maximum number of colors for... 

One of the most important parts of designing turbine blades is machining (milling) process of blade root. There is some implementing problem in material removal processing by milling. Because of low heat transferring of inconel 738 in machine parts there is huge amount of heat which cause high temperature in machine and burning, which reduces the efficiency of milling.One of the common way to reduce the temperature of machine is using coolant fluids, which increases expenses and makes environmental pollution, so it is not completely efficient as an industrial work. In this paper Whit using MQL and some new lubricant had been observed more efficient condition in milling process. The main goal... 

Descriptive complexity refers to the difficulty of expressing a problem in a formal language, allowing for a complete and precise description of the problem, including output specifications for function problems. Despite the success of the descriptive approach in computational complexity, this approach has been predominantly used for decision problems. In contrast to decision problems, a counting problem can be considered as a function with the range of natural numbers. This thesis focuses on the examination of counting problems from a descriptive perspective, exploring the connection between their descriptive and computational versions. Toward this goal, weighted logic is utilized to... 

The aim of this research is to predict the backbone curve of reinforced concrete shear walls by identifying different failure modes. Failure mode identification is performed by measuring the contribution percentage of flexure, shear, and combined flexure-shear failure modes in the force-displacement response of the wall under cyclic loading. The approach used in this research is a probabilistic and data-driven method, which leads to the calculation of model uncertainty in detecting the wall's failure mode and, consequently, the prediction uncertainty of the backbone curve. The database used in this research consists of 253 reinforced concrete shear walls, obtained from a review of existing... 

Traditional tool life models and wear prediction do not take into account the variation inherent in metal cutting processes. These lead to additional manufacturing costs. This research presents a stochastic method for both tool life and tool wear prediction. In the first part, Bayesian inference is applied to estimate the two model constants of Taylor tool life prediction model using a discrete grid method. Tool wear tests are performed using an uncoated M42 HSS tool and AISI 1018 carbon steel work material. Test results are used to update initial beliefs about the constants and the updated beliefs are then used to predict tool life using a probability density function (pdf). Finally, the... 

Public key encryption (PKE) cryptography plays a big role in securing communication channels of internet. The security of every PKE scheme is usually based on a hard problem that has no polynomial time solution using any computational structure. However, widely used classic PKE schemes such as RSA or ECC, are based on hard problems that have polynomial solutions using a quantum computer. Therefore, such PKE schemes will not be secure in post-quantum era. Among quantum-resistant schemes, lattice-based cryptography and especially learning with errors (LWE) problem have gained high attention due to their low computational complexity. In this thesis, different LWE-based cryptosystems are... 

Today, the use of radar technology and its various applications in different areas of science is no secret. The developed countries are looking to increase their ability to use new radar tools. Synthetic aperture radar is one of the most modern and efficient equipment imaging of the surface. One of the major advantages of synthetic aperture radar is imaging capabilities at night and bad weather conditions if the imaging methods used in the camera have limitations in night and bad weather conditions. There are different methods for extracting the images, one of the most important algorithms is Range Doppler Algorithm which is used to obtaining images from raw data received. Because of the... 

Lameness in dairy cattle is a crucial welfare issue in dairy industry, and over the years scientists are attempting to present a detection method. In recent years it is attracting more attention to make the identification and discrimination of sounds and lames systematic and automatic. Right now, the most hopeful results have been obtained through the measurement of Ground Reaction Forces (GRF) of hooves, and analysis of load distribution between four legs, which seems applicable for wide use in dairy industry. However, the accuracy, validity, and reliability of discrimination is still far from an acceptable point, that is because of a great lack in understanding quantitative effects of the... 

In the proccess of making key slots in lock parts, broaching is necessary. The only procedure or at least the best procedure for making the slots is broaching. High speed and precision, surface quality and the ability to create complicated surfaces in one step are the advantages that make broaching suitable for this product. The cost of tool maintainance and replacement is very important to make this process efficient economically, therefore, determining the factors affecting tool life are important for industries. The purpose of this study is to increase the life of narrow broaching tools. In other words, in this study, the purpose is to design and manufacture the tool in such a way that... 

Coronary arteries often experience tortuosity under internal blood pressure and longitude axial twisting. Arterial tortuosity can enhance the stress concentration on the artery walls. Now if the coronary arteries suffer from atherosclerosis (a common disease among adults) the stress concentration on the tortuous artery plaque will be enhanced as well. Increased stress on the plaque may result in plaque rupture and its consequent damages. This study aims to investigate the stress concentration on the plaques and blood flow patterns within the coronary arteries with plaque. Moreover, the plaque growth was predicted taking into account various geometrical parameters including fibrous cap... 

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... 

Compact Objects involve White Dwarfs,Neutron Stars and Black Holes which are formed from the gravitational collapse of main sequence stars after their nuclear fuel is finished.The special characteristic of all Compact Objects is that they are high density which requires a vast knowledge of nuclear physics with strong and weak interactions ,electromagnetic and numerical methods.we need general relativistic simulation of stars because the theories are simple and some are not in agreement with observations. studying of astro physical constraints on equation of state ,stability and cooling of Neutron Stars and pulsation of gravitational waves is needed nowadays. in first part of this thesis,we... 

It is well known that the fluctuations of electromagnetic fields in vacuum or in material media depend on the boundary conditions imposed on the fields. This dependence gives rise to forces which are known as Casimir forces, acting on the boundaries. Casimir forces between similar and disjoint objects such as two conducting or dielectric bodies are known in most cases to be attractive.¬¬ These forces are sometimes viewed as the macroscopic consequence of Van der Waals and Casimir-Polder attraction between molecules. In this thesis at first, calculation of Casimir forces in simple models were demonstrated. Then Van der Waals and Casimir-Polder forces have been explained in a unified theory...