Sharif Digital Repository

One of the most vital aspects of understanding the traffic phenomenon is scrutinizing the traffic transition status, such as the transition from free flow to congestion. The Percolation Theory is a renowned theory focusing on analyzing various network types to detect the critical zones, which are the zones including links that are important to control to improve stability. By calculating the quality indices of network links, the Percolation Theory can simulate the traffic percolation propagation in the network and determine possible critical zones for further analysis. Most studies in this field assume access to data of several traffic parameters for the entire transportation network, such... 

In recent years, optical biomedical imaging techniques show great potential in noninvasive imaging. Although these methods have many advantages over other biomedical imaging methods (such as Computerized Tomography (CT), Magnetic Resonance Imaging (MRI) and etc.), these techniques confront with some problems such as optical scattering, light absorption and etc. For in vivo imaging, the short-wavelength infrared region (SWIR; 1,000–2,000 nm) provides several advantages over the visible and near-infrared regions: general lack of auto-fluorescence, low light absorption by blood and tissue, and reduced scattering. In this thesis we want to analyze the traditional IR imaging techniques and... 

Strain imaging is a non-invasive ultrasound modality for assessing cardiac function in echocardiography systems. In this thesis, we implemented a fully automated strain imaging system containing 5 steps: 1) echocardiographic view recognition, 2) cardiac cycle phase detection, i.e., the events of end-diastole (ED) and end-systole (ES), 3) segmentation of left ventricular (LV) myocardium, 4) motion estimation of this wall and 5) strain calculation. In this work, we propose a novel deep learning-based framework for phase detection of cardiac cycle by the use of echocardiographic images in multibeat videos. Further, by applying the augmentation technique, the model has been able to detect events... 

Resolvers, due to their robust structure, are widely used in automation systems. Among the types of resolvers, the accuracy of the Wound Rotor (WR) resolver in the occurrence of common mechanical errors is higher than other types of resolvers. therefore, in this thesis, an AFWRR is studied to improve the performance. Increasing the number of poles in WR resolvers is a good solution for increasing the accuracy of these electromagnetic position sensors. However, high-speed WR resolvers due to employing fractional slot windings suffer from rich sub-harmonics in the induced voltages. A common solution for suppressing the undesirable sub-harmonics is using multi-layer winding with appropriate... 

Using visual information of an environment is the immediate way of detecting and identifying an unknown environment. These information maybe obtained using straight visibility detecting sensors. One of the formal models of these visual information is the visibility graph which have a vertex for each vertex (corner point) of the environment and two vertices have an edge whenever their corresponding corners see each other. Then, the problem is to characterize such a graph and reconstruct the target environment with equivalent visibility graph. Despite existence of plenty of research results, these are open problems in computational geometry and rigid results exist only for limited special... 

Housing is among the most primary fundamental needs of the household ,which consumes a high Proportion of the household expenditure and therefore it remains An important topic in macro economical analysis. Estimating and determining housing prices in different urban , areas is also important for planning .Estimations are also use in many decision making and process for the urban , regional , public, privet and organizational policy making. Due to the heterogeneity housing prices and the fact that it’s prices are affected by it’s characteristics , in this research housing prices of a few regions in tehran metropoly are assessed by the hedonic price model using macro and micro... 

Linear position sensors are widely used in linear motion-control systems. In this thesis, the design, optimization, performance analysis, and prototyping of a linear variable reluctance, variable air-gap length resolver are discussed. The accurate modelling of the studied sensor needs three-dimensional (3-D) time stepping finite element analysis (TSFEA) that is computationally expensive and unsuitable for co-usage with optimization algorithms. Therefore, the aim of this thesis is to establish an accurate, yet computationally fast, model suitable for optimal design of linear variable reluctance resolvers. The proposed mathematical model is presented based on modified winding function method. ... 

Computerized tomography (CT) imaging is a powerful tool among the existing bio-imaging techniques for capturing bio-images. In a CT scan procedure, linear sensors receive x-ray radiations, passed through the patient’s body and the reconstruction algorithms provide the required image for physicians from the captured data. In spite of its great advantages, due to the use of x-ray radiations and its ionization effect, it will raise the risk of cancer in long times. Therefore, to take benefit from several advantages of CT such as low-cost and high speed, solving this problem is aimed by many physicians and scientists. A new compressed sensing-based algorithm in order to reduce the number of... 

Position sensors are inseparable parts of motion control systems. The variable reluctance resolvers, as position sensors, are widely used in the drive of permanent magnet motors due to their simple and reliable strucutre. One of the most possible installation faults in these sensors is rotor and stator eccentricities that deteriorate the accuracy of the resolver. Therefore, axial flux variable reluctance (AFVR) resolvers have been proposed to decrease the influence of eccentricities on the output accuracy. Hence, optimizing the AFVR resolver structure is necessary for improving its commercial usage. However, its accurate modelling needs three-dimensional (3-D) time stepping finite element... 

Frequency-scan millimeter-wave imaging systems are of high interest due to their low cost and acceptable performance in many applications such as concealed-weapon-detection. In recent years, the performance of this system in view of imaging time, image quality and cost has been improved via its implementation based on metamaterial apertures. These structures take advantage from the famous theory of single pixel imaging in optics. Through using the compressive sensing principle, the number of required imaging modes for obtaining diffraction limited resolution is reduced which in turn lessens the imaging time and more importantly the required bandwidth. Still, the image quality and resolution... 

Linear position sensors are widely used in linear motion-control drives. In this thesis, the design, optimization, performance analysis, and prototyping of a linear variable reluctance, variable area resolver is discussed. To test the new design approach of the studied sensor, three-dimensional time-stepping finite element analysis (3-D TSFEA) is crucial. However, the 3D TSFEA is a very time-consuming method which leads to an inappropriate choice for co-using with optimization algorithms. Hence, an accurate analytical model based on a winding function (WF) method presented in favor of calculating the inductances, air-gap flux density, induced voltages precisely and yet is a very fast method,... 

Spatial-temporal duality is considered vastly as a powerful technic to process optical signal fast. Band-width and sampling rate are bottlenecks in real time capturing and processing of optical signals by analog to digital converters. There have been tremendous efforts in the field of optical processing in order to enhance the speed of processing or quality of optical beams. Another successful method in high speed processing of optical signals is the improvement of time-bandwidth product by applying group delay engineering. In this research I did my best to overcome the inherent restriction of band-width of imaging systems exploiting concepts of time lens and time prism in such a way that... 

A resolver is a position sensor that converts the angular position information of a mechanical shaft to electrical signals. Due to their machine-like structure, resolvers have been preferred to other position sensors like optical encoders for working in harsh environments with wide temperature variations, high vibrations, moisture, and dust. Besides, the resolution of a resolver is infinite, and it can provide absolute position information. A multi-turn resolver is a type of resolver that has been developed to provide absolute position information with very high precision. Conventional multi-turn resolver consists of two individual resolvers in a common frame. One of them determines... 

Photoacoustic imaging is one of the nascent imaging methods that has received a lot of attention in the last two decades. There are two major imaging challenges with this method, including the finite size of the transducer element and the limited view angles of the photoacoustic tomography arrangement. To compensate for the effects of finite transducer size, we have proposed a multi-angle detection method for circular photoacoustic imaging systems based on the synthetic aperture techniques, in the proposed method, each transducer, in addition to rotating around the scan center, also has a rotation in the around its center. This rotation depends on the cut-off frequency, the diameter of the... 

The fast-growing development of engineering and medical sciences leads to the diagnosis and treatment of diseases with higher accuracy and in the early stages of the disease. Medical imaging systems are considered as a crucial and effective tool in this field that based on the principle of technology used, are able to image various tissues with high quality. In recent years, photoacoustic imaging has attracted the attention of many researchers and engineers, because it able to image different tissues with good resolution and penetration depth non-invasively and without the use of ionizing radiation. The photoacoustic system response is a low-pass filter that passes only low-frequency... 

Nowadays, various policies are adopted by transportation managers and planners. These policies aim to improve system performance, reduce user costs, control and reduce air pollution, reduce noise pollution, and ultimately reduce congestion. A set of these policies in the form of transportation demand management is presented in the literature. A common way to find the effect of a policy on user behavior is to use questionnaires. Other causal inference models have been proposed in disciplines such as statistics, political science, marketing science, epidemiology, and psychology. The purpose of these models is to find the causal effect of an intervention (treatment) on a system. These studies... 

Position sensors are an integral part of electric machine control systems. There are different ways to determine the position. The most common methods are using resolvers or optical encoders. Resolver is the recommended in harsh environments where there is wide temperature variation, vibration, and dust. Despite their good features, resolvers face challenges such as eccentricity, short circuit fault, single-phase disconnection, and non-ideal signal voltage. The Resolver chosen in this research is the variable reluctance resolver with variable air gap length. Although this type of resolvers is cheaper than wound rotor resolvers, but its position error is high under electrical and mechanical... 

Measuring the speed and position of the rotating part and using the speed and position information in the closed loop control of electric machines is very important. Various sensors are available for this purpose, including resistive sensors, capacitive sensors, encoders, synchros, resolvers, Halleffect sensors, and etc. Common encoders include optical and magnetic types. There are two main problems in using an encoder as a sensor: determining/maintaining accuracy during change of rotational direction and determining the absolute position. Both of the mentioned challenges have been investigated in the case of optical encoders and some solutions have been provided to overcome them. Although... 

Position sensors are an inevitable part of motion control mechanisms with inverter-driven electric machines. Encoders and resolvers are two common types of position sensors. Resolvers are preferred over encoders due to their superior performance in polluted and noisy environments with wide temperature variation or high vibration. Conventional resolvers are synchronous generators whose excitation winding is fed by an AC instead of a DC voltage. There are different types of resolvers for determining position in linear or rotational motions. However, increasing usage of two-degree of freedom (2-DOF) motors for simultaneous rotational and linear motion leads to request for helical motion...