Sharif Digital Repository

Attaining accurate information about satellite attitude is one of the most important requirements in space missions in order to improve the accuracy of the satellite control and mission objectives. Many different sensors such as sun sensor, star sensor, horizon sensor, etc. are used to estimate spacecraft’s attitude. Attitude estimation using temperature sensors is a topic that has recently been addressed by some related researchers because, they need less power and budget to operate in comparison with the other sensors.Accuracy and heat model performance improvement is the main purpose of this project. To achieve a more accurate perspective of space thermal model, and the way heat transfers... 

The research methods presented in this dissertation are the result of the confrontation between medical science and engineering science. This contrast is intended to better understand the function of the middle ear system and the inner ear cochlea through modeling and finite element analysis and the effect of hearing aid use on the middle ear and cochlear function.The research began with the creation of a three-dimensional model of the middle ear using microCT imaging. Then the finite element model of the middle human ear was implemented using the same three-dimensional model. The results of the finite element model resulting from the loading on eardurm were calculated as displacement of... 

Television, radio, newspaper, magazines, and billboards are among the major channels that traditionally place ads, however, the advancement of the Internet enables users to seek information online. In display and mobile advertising, the most significant technical development in recent years is the growth of Real-Time Bidding (RTB), which facilitates a real-time auction for a display opportunity. Real-time means the auction is per impression and the process usually occurs less than 300 milliseconds before the ad is placed. RTB has fundamentally changed the landscape of the digital media market by scaling the buying process across a large number of available inventories among publishers in an... 

The problem of concurrent attitude and orbit estimation (CAOE) of satellite using its surface thermal data is studied and investigated in the present dissertation. Considering various uncertainties associated with the satellite system and its surrounding with regards to thermal issues, the dissertation subject and its application to CAOE is challenging and of importance. To this aim, the space thermal model for low Earth orbiting (LEO) satellite is initially reviewed and presented. Since the Sun and the Earth are considered as significant sources of radiation for near Earth space systems, the view factor is a key parameter for orbit observability and estimation via surface thermal data.... 

In this project, the effect of improper lubrication on vibrational behavior of rolling element bearings is investigated. Different lubrication conditions were deliberately produced using three oils with different viscosity grades on a bearing at different loads and speeds. The acceleration of bearing vibrations were measured, then analyzed by means of squared envelope analysis, a special case of cyclostationary analysis. The results and their comparison showed that decrease in lubricant’s viscosity grade can lead to an increase in magnitude of cyclic frequencies equal to cage frequency and its harmonics. This observation can be helpful in detection of lubricant degradation and in... 

Traumatic brain injury (TBI) has long been known as one of the most anonymous reasons for death around the world. This phenomenon has been under study for many years and yet it remains a question due to physiological, geometrical and computational complexity. Due to limitation in experimental study on human head, the finite element human head model with precise geometric characteristics and mechanical properties is essential. In this study, the visco-hyperelastic parameters of bovine brain extracted from experimental data and finite element simulations which validated by experimental results. Then a 3D human head including brain, skull, and the meninges is modeled using CT-scan and MRI data... 

This research describes the design and analysis of an actuating robot to manipulate the disposable Endo-wrist robotic surgery instruments. Analyzing the mechanism of common manual Endo-wrist instruments, it was found that the rotations of handle of the instrument are transferred to its wrist using a snake-like element and four connecting cables. Based on this observation, a 2DOF parallel actuating robot was designed to rotate the instrument handle, in which the degrees of freedom are controlled by two linear spindle motors. The Inverse kinematic analysis of the manual instrument was performed by minimizing the potential energy of cables. Also the inverse kinematic solution of the actuating... 

Varus-Valgus deformity increases local stress in cartilage and the other soft tissues of knee. This phenomenon may adversely influence patient’s walking pattern and also lead to worsen its existing impairments. In this situation, osteotomy is used to modify the alignment of the lower limb. Using CT-scan, radiography data, and their experiences, surgeons quantify the amount of modification. However, in many cases, the surgery does not result in desired output. It seems that the effects of soft tissues, which play an important role in this respect, should be taken into account. In order to design effectively for the osteotomy surgery, it is necessary to develop a patient-specific... 

Ethylene is considered as one of the key materials in the petrochemical industry and has a particular importance. Polymerized ethylene produces polyethylene, which is widely used in plastics and pipe-manufacturing industries. Ethylene is mainly produced by the processes of catalytic cracking or thermal cracking of heavier hydrocarbon compounds. In these processes, acetylene is produced as a by-product, which deactivates the Ziegler-Nata catalysts in the polymerization unit of ethylene. Therefore, there should be some considerations to reduce acetylene to its minimum value -around zero. For this purpose, the fixed bed catalytic reactor is used to hydrogenate acetylene to ethylene. Various... 

The purpose of this work, is to design a cantilever arm made of functionally graded materials so that the arm has maximum natural frequency and minimum mass. In this work the arm is modeled by Euler-Bernoulli beam theory and properties are assumed to be varying through the thickness. The beam is considered to be made of Aluminum and Alumina as metal and ceramic respectively and Genetic Algorithm method is used for optimization step. Finally using FGMs in atomic force microscopes is proposed as a new application of these materials  

It is well known that sulfur removal from petroleum is necessary for both industrial and environmental reasons. Sulfur in petroleum products corrodes parts of internal combustion engines and refineries due to the formation of sulfur oxyacids and causes major air pollution and acid rain due to exhaust from diesel engines and emission of sulfur oxides. Hydrodesulfurization (HDS), biodesulfurization (BDS), extraction by ionic-liquids (ILs), selective adsorption, alkylation desulfurization and oxidative desulfurization (ODS) are some methods, can be effective in removal of sulfur compounds. Among these new processes, ODS appears to be particularly promising and is currently receiving increasing... 

New technologies for three-dimensional (3D) sensing and visualization of real-world objects have been pursued by scientists and engineers for many decades. As opposed to traditional two-dimensional (2D) imaging techniques, 3D imaging technologies can potentially capture the 3D structure, range, and texture information of objects. Therefore, it can be developed for many applications, as medical imaging and diagnosis, dentistry, industrial designs, architecture and security. There are many 3D imaging technologies, such as holography, incoherent holography and integral imaging. Since holographic methods are based on the wave interferometry of two coherent beams, they demand high stability of... 

The wideband code-division multiple access (WCDMA) system has been widely used for the third-generation wireless communication system. It uses Frequency division duplexing for two-way communication by a transceiver. Although a duplexer will significantly suppress the TX leakage signal (50dB-60dB), a residual attenuated signal still remains at the receiver input and act as a strong blocker which reduces the sensitivity of the receiver. For reducing the effect of the TX leakage on the RX performance, a band pass RF SAW filter is typically inserted between the LNA and the mixer to reject the TX leakage. However, this filter increases the system cost and size. This encouraged us to propose a novel... 

Ion exchange resins are widely used in nuclear industries. These spent resins result in the production of a large amount of low and intermediate level radioactive wastes, therefore, the treatment and immobilization of spent ion exchange resins are the major problems in the development of nuclear power plants.In this research, in a laboratory scale, we tried to find the suitable procedure and formulation to immobilize a specific group of cation-exchange resins which is used in Bushehr nuclear power plant (AMBERLITE IRN-97H) in the cement matrix. The solidification matrix consists of five constituents: anti sulfate slag type portland cement, cation-exchange resins, diatomite, sodium hydroxide... 

Low Back Pain is one of the most problems in health domain which has a high treatment costs, also has high recurrence rates. Postural stability has been introduced as a health characteristic for musculoskeletal systems. Body stability is maintained with sensory feedback data such as Eyes, Vestibular and proprioception data which are sent to brain. Prior investigations have shown that proprioception data have many disorders in lumbar area of Low Back Pain patient and this data are not sent to brain encounters so many problems for muscle activation and stability of body. Researches have been indicated that Low Back Pain patients rely on Ankle proprioception more than healthy people and less... 

Magnetic shape memory alloys (MSMAs) are a new kind of smart materials which are great alternatives for energy harvesting systems due to some unmatched characteristics such as reversible large strain, high cycle fatigue and fast time response. In this work, an energy harvesting system using MSMA is studied. For this goal, a 3-D thermodynamic-based MSMA model is applied for predicting magnetomechanical behavior of the MSMA sample which is used in the energy harvester system. Since demagnetization effect, which has a great influence on the model’s outputs, has been neglected in the selected MSMA model, a new approach is presented for inserting demagnetization coefficients, regarding to the... 

Almost all of the country's industrial enzyme needs are met through imports. In this regard, much attention has been paid to industrial production of detergent enzymes such as protease, lipase, amylase and cellulase. Proteases, are the most important industrial enzymes with 60% of the world's enzyme market. Extracellular alkaline proteases of microbial origin are most widely used in the laundry detergent industry to help clear protein stains on clothing caused by blood, milk, eggs, and meat. In this study, bacterial alkaline protease enzyme produced by Bacillus subtilis ATCC6633 was used as a model of functional enzymes in detergent industries.Enzyme immobilization-drying operations are one... 

Since the first observed case in December 2019, millions of people have been infected by Coronavirus disease 2019 (COVID-¬19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS¬-CoV-¬2). Located on the viral membrane, trimeric spike glycoprotein is one of the most crucial parts of the virus’ structure as it is responsible for the attachment and entry of the virus to host cells. The spike glycoprotein undergoes hinge-like conformational movements and its receptor¬binding domains (RBD) can be in either an accessible (up) state or an inaccessible (down) state to the host cell receptors, such as ACE2. Having performed Molecular Dynamics Simulations and Targeted Molecular...