Sharif Digital Repository

Low back pain is one the most prevalent disease and major economic issue facing modern countries. Epidemiological studies suggest that maximum trunk flexion, the angular velocity of trunk and the rate of repetitive movements (such as flexion-extension), are associated with low-back disorders. From biomechanical point of view, lack of stability during dynamic repetitive movements, increases the risk of injuries. On the other hand, some researchers suggest increasing motor variability could be an intrinsic factor to intervene muscuskeletal disorders during repetitive movements. Pace of repetitive occupational tasks could affect both, motor variability and dynamic stability. The goal of this... 

One of the ways to optimize fuel consumption and improve aircraft performance can be realized by reducing drag, and a major part of this force is the lift-induced drag, which is reduced by increasing the wing span. On the other hand, increasing the wingspan has physical limitations on the allowed dimensions of the aircraft, increasing the weight and reducing the maneuverability of the aircraft, especially in the roll maneuver. Therefore, in order to benefit from the advantages of increasing the wing span and not facing the mentioned limitations, the idea of using a Folding Wing-Tip (FWT) has been proposed by aircraft manufacturing companies and experts. In this way, in normal flight such as... 

The purpose of this study is to analyze the stability and creeping behavior of rock salt in underground gas and oil reservoirs. Preparation of natural salt caverns and operating them can manipulate the initial state of previously existed stress and to produce deviatoric stresses around the cavern. New state of stress and with creeping behavior of rock salt, causes a significant decrease in cavern’s volume and damages the surrounding area. Reduction of internal minimum pressure of cavern, increases the intensity of mentioned problems. Geometrical characteristics of cavern can also be significantly effective in the magnitude of damages around the reservoir. For instance, Deflection of cavern... 

Injuries of neuro-musculoskeletal system impose large costs to the modem societies. Studying the strategies of CNS in planning and control of movements can be helpful in developing diagnoSiS, prognosis and treatment procedures in clinical view and also in designing rehabilitation system and humanoid robots. Tow important features of human movements are redundancy problem and structured variability. Previous studies solved the redundancy problem mainly with optimization methods. Also optimal feedback control theory is the only method that successfully modeled structured variability in voluntary movements. Despite the appropriate outputs this methods are not based on physiological facts... 

Lifting is considered a major risk to people's health in life, particularly to the workers. Appropriate wearable tools for measuring the individual’s kinematic and kinetic movement are required for examining and analyzing the lifting activity to prevent injury in the workplace. Different wearable systems have been developed to calculate the force applied on the foot sole to analyze movement in various areas of gait analysis, occupational biomechanics, sports, and other areas. The accuracy and precision of these systems need to be tested before application in any of these areas. In this study, 3 subjects performed five different activities of symmetrical lifting by placing Pedar insoles in... 

Turan Toad-headed Agama is a lizard (Phrynocephalus mystaceus) inhabiting in the deserts of the Middle East. In order to hide from predators, it laterally vibrates (and slightly oscillates around the dorsal axis) to descend beneath the sand. Despite its low density, toad-headed agama easily burrows beneath the sand. The purpose of this study is to initially determine 3D kinematics of the agama's burial technique (frequency, amplitude and position of critical points of the body). After determining the motion, we will figure how the motion interacts with granular media and enables the animal to burry. This includes simulating animal's motion within granular media using discrete element method... 

In this project, we use a novel mechanism to control the lumbar rotational profile and also the disc pressure of L3/L4 and L4/L5. Spine, as one of the most important parts of human musculoskeletal system, helps human beings to walk on two feet without much energy consumption. Any problem in this part may cause moving disorders or pain. To heal severe spine disorders, many different methods like surgery and implantation are adopted. To be sure of proper functionality in the human body, these methods should be tested clinically in advance. Cadaver spine testing in vitro, is accepted as a gold standard to evaluate new methods. One of the main challenges facing spine in vitro tests is how to... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by... 

In this thesis we consider the problem of distributed computation by many processors.We mainly concentrate on matrix multiplication problem in this thesis because of its importance. A distributed system consists of N worker processors and one master processor. The master processor should distribute the computation between workers and after computation in each of them, collect the results. In this thesis, we are going to mitigate the effect of straggler processors by using coding methods. Straggler processors can cause delays in the computation time.In this thesis, we firstly introduce a method to multiply any number of matrices in each other. The proposed method occurred in one shot without... 

The main goal of current investigation was partial reduction of Fe2O3 available in Hematite-rich ore to Magnetite by Fludization Bed method. The reductive gas, CO, was produced by incomplete combustion of Acetylene and Airmixed in inappropriate ratio. X-Ray Diffraction and X-Ray Florescence analyses were implemented in order to conducting qualitative analysis of present phases before and after reduction of the ore. Quantitative analysis of the same phases was also conducted by Titration. The latter analysis revealed the precise magnitude of available iron in each of the oxide containing phases. The chemical composition of the reactor gas was also determined before and after reduction... 

Abstract The problem of competetive facility location can be defined as follows: There are a number of customers in the form of points in space, and two players arrange a number of facilities in the form of points in space, given some limitations, respectively. Each customer’s connection to each facility has a cost for the customer and an advantage for the facility, and each customer wants to be connected to at most one of the facilities which has the lowest cost for him. The goal is to find the strategy of placing the facilities and determining the cost which the facility receives from the customer, in such a way that the player’s profit is maximised.In this thesis, we first sought to... 

Zero knowledge proofs allow a person (prover) to convince another person (verifier) that he has performed a specific computation on a secret data correctly, and has obtained a true answer, without having to disclose the secret data. QAP (Quadratic Arithmetic Program) based zkSNARKs (zero knowledge Succinct Non-interactive Argument of Knowledge) are a type of zero knowledge proof. They have several properties that make them attractive in practice, e.g. verifier's work is very easy. So they are used in many areas such as Blockchain and cloud computing. But yet prover's work in QAP based zkSNARKs is heavy, therefore, it may not be possible for a prover with limited processing resource to run... 

Lightweight clients are a type of blockchain users who do not store all the blocks in the blockchain due to limited resources. These users store only a small part of each block and when needed, request transactions from full nodes that store the entire blockchain. These users have no role in block validation and only want to receive transactions related to their addresses with proof of the inclusion in the block from full nodes.Since light clients rely on full nodes for receiving transactions, their privacy against full nodes is important. The current implementation of Bitcoin uses Bloom filters for privacy, but this offers very little privacy to the users.In this thesis, we study the... 

Protein multiple sequence alignment is one of important problems in biology which no polynomial time algorithms is known for it yet. Due to importance of this problem, several methods have been developed to find an approximate solution for it. Approximation algorithms, Evolutionary algorithms and Probabilistic methods are some of these methods. According to evolutionary nature of this problem, evolutionary algorithms and specifically genetic algorithms can be a potential good solution method for this problem. In this project we have a survey on using genetic algorithms for this problem and after mentioning benefits and draw backs of existing methods, we develop a method for improving one of... 

At this project we proceed to aero elastic modelling of a flapping wing using unsteady aerodynamic approach. Solving this model according to aerodynamic and structure coupling needs to simultaneously solve of aerodynamic and wing structure. Left side and right side of wing, each on divided into 18 elements. each element is interacting with sides element in terms of structural force and moment. In this modeling aerodynamic was modeling with unsteady aerodynamic approach (using modify theodersen function), also structure is flexible in to direction, bending and twisting. In the following it is proved that with change in flapping pattern better performance can be achieved. the effect of change... 

This dissertation consists of three chapters. In the first chapter, a description of formation of Darwin's theory of Evolution is expressed. After that, the process of formation of modern theory of Evolution, along with an explanation of the theory of evolution and the evidence for it was mentioned. In the second season, which is responsible for the scientific study of the theory, at some point the evidence of this theory has been reviewed. After that, some of the challenges raised against this theory have been studied. The major scientific challenges described in this chapter is based on recent advances made in biology, based on that, the mechanism of theory can’t explain the complex...