Sharif Digital Repository

The frequency divider is one of the components of a frequency synthesizer. Regenerative frequency divider is one of the frequency division methods and is used in narrow band applications. In this thesis, the process of designing & fabricating Ka band and Ku band regenerative frequency dividers is reported. A bandwidth of 550MHz for the Ka band divider and 400MHz for the Ku band divider have been achieved. Multiple passive structures such as microstrip filters, Wilkinson power dividers and a waveguide-to-microstrip transition have been designed during the fabrication of the mentioned frequency dividers. According to the results of the simulations, the bandwidth of the waveguide-to-microstrip... 

In this thesis first of all we investigate phase noise and it's generation factors. Then we design and implement an ultra low phase noise oscillator. To do this, an ultra low phase noise oscillator which is tunable in 1-2GHz with 100MHz steps will be designed. The outline of the circuit is as follows: at the first we design a VCO which is ultra low phase noise and mechanically tunable in 1-2GHz by means of rotation of a handle. Then a phase locked loop will be built with the help of an ultra low phase noise OCXO at 100MHz and one SPD1 which generates harmonics of OCXO's output frequency. For the next, design and implementation of a 1.6GHz oscillator with fixed output frequency has been done.... 

Enzymes are an important part of detergents, they reduce the activation energy of the reaction and thus increase the efficiency of the process. Protease enzyme is one of the most common enzymes in detergents. Bacillus strain is the most important strain in the production of this enzyme and among the species of Bacillus, Bacillus subtilis is the most used. Bacillus subtilis is a gram-positive, rod-shaped bacterium. This bacterium is considered a non-pathogenic cell that has the ability to form spores and prevent death and damage in harsh conditions. In this study, CRISPR system was used to modify the genome of Bacillus subtilis ATCC 6633 in order to increase alkaline protease. To increase the... 

Genetic engineering of cells has been one of the most effective ways to increase protein production in wild strains. Among the various genetic engineering techniques, the CRISPR/Cas9 system that directly edits the cell chromosome, yielding greater efficiency and easier operation. In this study, we used this system to modify the genome of Bacillus subtilis ATCC 6633 to increase the production of extracellular alkaline protease enzyme. Alkaline protease enzyme has many applications in different industries, but in this study, the application of this enzyme in the detergent industry has been considered. To increase the production of this enzyme, we disrupted and prevented the gene responsible... 

Because of the importance of gas-solid fluidized beds in industrial plants, many efforts have been done for predicting their behavior up to now. Generally, there are two major attitudes for describing and simulating the hydrodynamics of fluidized beds, Eulerian-Eulerian methods and Eulerian-Lagrangian metods. Both of these approaches have their own advantages and disadvantages and a lot of studies have been done to understand the nature of gas-solid fluidized beds with aid of these models. Due to fewer presumptions in the basic structure of Eulerian-Lagrangian methods such as DEM in comparison with Eulerian-Eulerian methods like TFM, these models can predict the hydrodynamics of fluidized... 

Industrial enzymes can generally be classified into three groups: carbohydrases, proteases and lipases, which account for a major part of the global enzyme trade. Proteases, in particular, have always been extensively studied and investigated due to their widespread use in various industries, such as food, pharmaceutical, chemical, and agricultural sectors. Proteases are a group of proteolytic enzymes that break down proteins and peptides into their constituent amino acids by hydrolyzing peptide bonds. Among the family of proteases, alkaline serine proteases have special biocatalytic abilities in both aqueous and organic environments. Their suitable resistance in alkaline environments and... 

Today, by emerging wearable technologies and digital health, it is possible to constantly monitor vital signals of people without time-consuming and costly referrals to medical centers. Applications of wearable sensors for health monitoring include electrocardiograms (ECG), blood pressure measurement, and blood sugar measurement, etc. One of the important fields of health monitoring is cardiac arrhythmia detection. Cardiac arrhythmia is any kind of anomalies in heart beat rhythm that can lead to serious damage to vital organs of the body. It is estimated that between 750 thousand to 1.5 million people are facing cardiac arrhythmia in Iran. Therefore, early detection of cardiac arrhythmia is... 

Since the early 90s, nanotechnology has contributed to several developments in a wide range of Science and industry such as medicine, Physics, Chemistry, Aerospace, electronics and Biology. In recent years, nanotechnology has also made development in the oil and gas industry. The drilling fluid is already one of the most important parts in drilling operation.The physical properties of a mud, rheological properties and minimize fluid invasion into the formation with perfect mudcake are important to assist in optimizing results. Nano-materials as one of the achievements of recent years are effective in achieving these purposes. To obtain the above properties, a variety of polymers as... 

The main goal of this thesis is the design and development of a rehabilitation device for helping patients “to improve blood circulation” & retain and recover their abilities if possible that were lost during the stroke or a accident like that (my research in karaj/iran shows that it is possible by just movement of the specific body part). The focus is on hand in this thesis because Injuries to the hand are common and can be very debilitating since our hands are our primary means for interacting with our world. For rehabilitation in case of human hand there are several practices that should be done for patients either in home or in a rehabilitation center, time and money that is supposed to... 

In the past few decades, shaking tables are widely used to evaluate system response of structures under seismic excitations. These devices are used without any fundamental research performed on a shaking table system as an entity model. In most of these studies for simplicity, it is assumed that there exist no considerable vibration and displacement around the shaking tables, and no attention is paid to the peripheral substances such as soil settled under the foundation.
In this thesis, result of ambient vibration test on shaking table system (solid deck, concrete foundation and soil layer) has been presented. Precise sensors known as low frequency and high accuracy accelerometers have... 

Out of several ground improvement techniques available, stone columns have been widely used. This technique has been successfully applied to increase the bearing capacity and to reduce the settlement for foundation of structures like liquid storage tanks, earthen embankments, raft foundations, etc., where a relatively large settlement is permissible. This technique has, generally, been proven successful in increasing the stiffness of weak soils, upgrading their safe bearing capacity, and reducing their total and differential settlements, as well as speeding up their consolidation process. The beneficial effects of stone column installation in weak deposits is manifested in the form of... 

In the present study, a new version of haptic devices is presented in which user’s hand is in contact with the device just while collision with virtual surface. In this system, the position of user’s finger can be traced by using a camera and the haptic device follows user’s finger at the distance of about two centimeters. While the haptic device approaches to the virtual surface, gradually reduces its speed and stops about two centimeters distant of virtual plane. Then user’s hand collides with the haptic device which is static. Greater fidelity, transparency, more stability and also no need to large actuators are of the advantages of this system. In this project, first we present a new... 

Laminar forced convection flow through a channel partially filled with a porous material was numerically studied in this thesis. The Navier-Stokes and Brinkman-Forchheimer equations were used to model the fluid flow in the free and porous regions, respectively. Coupling of the pressure and velocity fields was resolved using the SIMPLEC algorithm. The local thermal equilibrium was adopted in the energy equation. The effects of the thermal conductivity ratio, Darcy number, porosity, Reynolds number and height of the porous insert on velocity and temperature field were investigated. The results show that the flow behavior and its associated heat transfer are susceptible to the variation of the...