Sharif Digital Repository

Nowadays, millimeter-wave imaging is widely used in security and medical applications. The growing threat from terrorist attacks is driven research on novel ways to enhance security inspection systems. Millimeter-wave imaging not only is an effective option of penetrating into dielectric materials including cloth, but also provides suitable imaging resolution. Moreover, millimeter-wave imaging is capable of identifying different materials making it a promising option for concealed weapon detection. In spite of X-ray, millimeter-wave imaging is non-ionizing, allowing for non-invasive imaging. In this thesis, first we investigate different millimeter-wave imaging systems and reconstruction... 

One of the most important alternative technologies in the field of security monitoring is millimeter-wave imaging technology, which is a good alternative both for performance and cost-effectiveness. Conventional security monitoring techniques use optical images or metal detectors to control people in crowded, sensitive places, but with the help of electromagnetic waves, these technologies can be obtained. This way, metal and non-metallic objects hidden inside clothing, bags or shoes can also be detected that are not identifiable by conventional security-control methods. This thesis examines the implementation of an improved algorithm for automatic detection of objects in millimeter-wave... 

Terahertz (THz) spectroscopy has recently attracted great interest due to the special characteristics of THz waves, such as their capability of penetrating and passing through many non-polar materials, non-ionizing atoms and especially human tissues, and less scattering compared to optical waves and X rays. Also, polar molecules of some dielectric materials have vibrational or circular oscillations that create peaks in their spectral characteristics. This can be used to identify materials by spectroscopy. In this thesis, a simple THz spectroscopy system is introduced and modeled for detecting the C-4 material. First, a wideband Vivaldi antenna is designed and simulated for the frequency... 

One of the major environmental problems in recent years is the presence of micropollutants that cause many problems for the environment and living organisms. The micropollutant bisphenol A and the drug diclofenac are one of the pollutants and endocrine disruptors. Usually, conventional biological and physico-chemical methods do not have a high ability to remove such pollutants. Also, advanced oxidation methods usually lead to the production of highly toxic products. Using enzymes is an attractive method to remove these micropollutants. Laccase enzyme is one of the most famous enzymes in the field of biotherapy because it can remove a wider range of pollutants and it is one of the... 

Food spoilage cased by food-borne pathogens and microorganisms is a serious problem in the food and packaging industry. Then, the demand for antibacterial agents in food packaging is growing. The antibacterial efficacy of some nanocomposites has been recognized and exploited in various industries, including the packaging industry. Also, metal organic frameworks due to their porous structure, are used in various fields such as food packaging. The purpose of this work, is synthesize hybrid nanocomposite that have promising antibacterial activity for preparation of food packaging films. Carboxymethyl cellulose is a derivative of cellulose fiber. The use of carboxymethyl cellulose as... 

Increasing advances in millimeter-wave imaging have given the new technology a special place in military and civilian activities. A very important advantage of this imaging system, which has led to its rapid development and growth, is that unlike methods such as X-ray imaging, the millimeter-wave signal is completely harmless to the human body. Because millimeter-wave imaging is non-ionizing, allowing for non- invasive imaging. Also, the millimeter-wave easily passes through human clothing and is reflected when it hits the human body, metal and ceramic objects, and some other objects. As a result, it can be used to photograph underwear, insensitive and safe places such as airports. In this... 

Nowadays, micropollutants present in aquatic environments posses a significant threat to the well-being and health of human beings. Various physicochemical and advanced approaches have been proposed to confront these hazards. In recent years, biological treatment methods have gained great interest for their green approach. One of these biological treatment options is the treatment of polluted waters by enzymes. Enzymatic treatment of micropollutants can be achieved by oxidoreductase enzymes. One of the most important and widely used oxidoreductase enzymes employed for water treatment is Laccase. However, enzyme immobilization is employed to counter the drawbacks of using enzymes, such as... 

Millimeter waves provide an effective opportunity to improve vision and imaging in addition to systems based on visible light, X-rays, and infrared, and researchers have paid special attention to the field of millimeter waves to develop imaging. The spectrum of millimeter waves is in the frequency between 30GHz and 300GHz, which is equivalent to the wavelength in free space, between 1 and 10mm. The advantage of millimeter waves is that it works well in different weather conditions. Also, these millimeter waves have the ability to pass through clothing and provide a suitable level of resolution in reconstructed images and provide a suitable ability to separate different materials from each... 

Micropollutants, like Bisphenol A (BPA) and diclofenac, pose a growing threat to human health and the environment. Traditional wastewater treatment struggles to remove these contaminants. While physicochemical methods often fall short, advanced oxidation processes can generate harmful byproducts. Enzymatic degradation offers a promising, new solution. This research explores the potential of laccase, a versatile pollutant-degrading enzyme, immobilized on a chitosan-aminated graphene oxide aerogel. Laccase from Trametes sp. was covalently bonded to the aerogel for enhanced stability and reusability. The optimized removal of BPA and diclofenac was investigated under specific conditions (pH 5,... 

Acoustic-resolution photoacoustic microscopy (AR-PAM) system can provide 3-D images of facial tissues. The lateral resolution of AR-PAM depends on the numerical aperture (NA) of the acoustic lens and the central frequency of the ultrasonic transducer. There is a trade-off between resolution enhancement and imaging depth. The acoustic beam is tight in the acoustic focal plane but expands in the out-of-focus regions, deteriorating the resolution. High-NA AR-PAM has depth-variant resolution. Synthetic aperture focusing technique (SAFT) based on a virtual detector (VD) concept can compensate for the beam shape and improve the lateral resolution via beamforming. Although, beamforming can enhance... 

Millimeter wave imaging has been used in many applications including security screening and medical imaging. Millimeter wave screening systems are considered a reliable option in the design of surveillance systems, because they feature enough penetration in dielectric materials including clothes, low health- risk and decent resolution. The first generation of such systems are based on mono-static arrays and mechanical scanning. Large mono-static arrays are challenging and expensive to implement, because they require high number of antenna elements to satisfy the Nyquist sampling rate. Moreover, the minimum sampling rate imposes limitations on design and size of antenna elements. So,... 

One of the actions taken to mitigate the climate change is research, development and demonstration (RD&D) investments in renewable energy technology. In addition to domestic R&D spending, the importation of foreign technologies, as a main channel of technology transfer, is another option to obtain renewable energy technologies in order to achieve climate objectives. In this study, a panel dataset of 28 OECD member countries from 2011 to 2020 is analysed, using the OLS, fixed-effects, and two-system system GMM methods, to assess the impacts of public spending on renewable energy RD&D and the import of renewable energy technologies on the energy-related CO2 emissions. To fully capture the the... 

Radio waves can penetrate through walls and various scattering environments, allowing us to communicate with mobile phones within buildings or use wireless waves to transfer data from one room to another despite physical obstacles. Radio signals, especially at lower frequencies, are highly effective in traversing such environments. However, the ability to penetrate walls does not imply the ability to "see through" them. In this thesis, we focus on examining the development and improvement of imaging techniques in the presence of walls. The aim is to present the concept of imaging through walls in a comprehensible manner for researchers and enthusiasts, facilitating the development and... 

One of the most important factors that make breast cancer such a dangerous and deadly disease is its hidden. One of the most important methods of revealing this disease is imaging. There are different types of imaging to reveal cancerous tissues (tumors), such as ultrasound, mammography, X-ray, etc. Ultrasound imaging is a cheap, convenient and accessible imaging. The aim of this project is to provide a breast cancer detection system that uses the images taken with this method according to the characteristics of ultrasonic imaging. Regarding cancer diagnosis, doctors identify the tumor with the help of their personal experience, which is based on the characteristics of the tumor image. In... 

Cardio Vascular Diseases (CVD) is currently the most important cause of mortality in the world. Coronary artery disease (CAD-with 3 major epicardial vessels) is one of the significant CVD. Coronary angiography remains the gold standard for identifying the presence and absence of stenosis due to CAD. It is performed by inserting a catheter into the coronary artery, directly injecting radiopaque contrast material there and recording radiographic images in different view of arteries. Images of this invasive way show severity and area of stenosis.
A sign of CAD is endothelial dysfunction (inner artery layer) in peripheral arteries like the brachial artery. Due to a significant correlation... 

Once damaged, articular cartilage has very little capacity for spontaneous healing because of the avascular nature of the tissue. Although many repair techniques have been proposed over the past decades, none has successfully regenerated long-lasting tissue to replace damaged cartilage. Tissue engineering have recently demonstrated tremendous approaches for regeneration of cartilage tissue lesions. Tissue engineering is based on three principles: cells, scaffolds for cell adhesion and growth factors. Three-dimensional biodegradable scaffolds play an important role in tissue engineering. In this study, novel cross-linked hybrid chitosan/ECM scaffolds were prepared for articular cartilage... 

For policy and decision makers, controlling pollution emissions are a real challenge. The best way to collect fiscal resources, optimal distribution of them to developing businesses in optimal energy production and reducing emissions, are important issues to be decided. Finding a monetary value emissions imposing to community is a key point to find out how they are affecting the whole economy and this will help decision makers to conduct better road maps and policies. Many different approaches and methodologies are used in literature to find appropriate answers to above mentioned questions and phenomena, in this research, integrated assessment modeling methodology is used, an economical... 

Power system operators are facing with imperative challenges to integrate high penetration of renewable power plants. The main challenge is required investment cost for accommodating the grid with uncertainties of renewable resources. In addition, intermittency and fluctuations of renewable resources are another challenges of system operators. Therefore, choosing a proper control procedure to respond the grid disturbances is a crucial task. However, the strategic behaviours of generation companies lead to a competition between them which affects the control performance. In this thesis, an integrated mechanism is proposed that consider both dynamic and strategic behaviours of generation... 

In this thesis, no-load and full-load performance of Permanent Magnet Vernier Generators (PMVGs) is investigated in fully-aligned condition and under different types of mechanical faults. The studied mechanical faults are Static Eccentricity (SE), Dynamic Eccentricity (DE), Inclined Rotor (IR), and Run-out (RO). Furthermore, an analytical model is also developed to calculate the permeance of the air-gap and the induced voltages in the health machine and under studied mechanical faults. Then, 2-D and 3-D non-linear, time stepping finite element method is utilized for performance evaluation of the generator in no-load and full-load (with resistive, inductive and capacitive loads). In continue,... 

In petroleum related drilling, Barite particles settling and Barite sag as major problems in drilling wells can potentially impose significant operational issues. In this study, a computational fluid dynamics (CFD) and experimental investigation of Barite settlement in annular space were conducted in both static and dynamic conditions. The Euler-Euler approach was used to model the multiphase flow of solid Barite particles and drilling fluid. In this approach, the momentum lost between phases has been taken into account by means of particle-particle and particle-fluid exchange coefficients. The governing equations were numerically solved using finite volume method by CFD software package...