Sharif Digital Repository

Lorentz reciprocity theorem is one of the most fundamental concepts in electromagnetism. Although, in specific conditions, for example in nonlinear systems or systems with broken time-reversal symmetry it can be violated. In recent years, many interests have been attracted towards such systems. With a proper design, they can support nonreciprocal or at specific conditions unidirectional propagation behavior. For example, despite ordinary dielectrics, in ferrite layers, the propagation constant of surface waves on ferrite edge, depends on the direction of propagation with respect to magnetization direction. Furthermore, in the specific interval of frequencies, ferrite structures allow... 

The definition of human action recognition is classification of input visual elements based on the action which is done by a person in the scene. One of the most important topics in the filed which has lots of applications is human action recognition in videos. Some of these applications are surveillance, video retrieval, human computer interaction and smart houses. Due to increments in number of alone elderly people, surveillance of them is one of the important applications of human action recognition. The challenges of the task are, camera movement, differences of environment and differences in acting by different actors.The goal of the project is proposing a deep convolutional neural... 

Image registration is an important preprocessing step in analysis of medical images. Detection, Treatment plan, disease grows process analysis and assistance in surgical applications are some of medical images applications. We need to be able to compare different modalities in medical images such as X-ray, PET, MRI, and CT... , or sometimes doctors need to take images of a patient in a same modality but in different times and directions. In which in order to be able to do theses comparisons we need to first align these images by using image registration methods. Image registration is an image processing method in which tries to find a geometrical transformation that would map different... 

Medical imaging is of interest because of information that will provide for doctors and registration is inevitable when we need to compare two or more images, taken from a subject at different times or with different sensors or when comparing two or more subjects together. Registration methods can be categorized in two major groups; methods based on feature and methods based on intensity. Methods in first group have three steps in common: feature extraction, finding matches and transform estimation. In second group it’s important to define a similarity measure and find the transform that minimizes this measure.
Manifold learning algorithms are mostly used as a dimensionality reduction... 

The most popular system for quantification of the facial behaviors and expressions is the Facial Action Coding System (FACS). FACS provides a description of all possible and visually detectable facial variations in terms of 33 Action Units (AUs). The activation of each AU leads to a slight variation in the facial appearance, and any facial expression can be modeled by a single AU or a combination of AUs. Definition of AUs is such that they are sparse in multiple domains. The goal of this dissertation is utilizing these sparsity properties to develop an effective algorithm for automatic intensity estimation of AUs. One of the sparsity domains of AUs is the spatial domain that means the... 

Converting analog signal to digital one is one of the most important issues in signal processing which can be done by using analog to digital converter (A/D). In the first part of this thesis, sigma delta converters based on minimum support filter are investigated. Then, we will show that iterative algorithm can be used in order to improve the performance of the overall system significantly. Asynchronous converters can be utilized for the sake of decreasing power in the process of analog to digital converting. In these converters, a few numbers of samples will be taken from the regions which signal has high autocorrelation. In other words, samples in the asynchronous converters have more... 

Wireless communications often requires accurate knowledge of the underlying channel be­ tween transmitter and receiver which leads to channel estimation problem. Wireless chan­ nels are mostly multipath channels and have sparse impulse responses in time domain. One popular method in this field is to estimate the channel using training symbols. Also, Orthog­ onal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output OFDM (MIMO-OFDM) systems are two popular and widely used systems. Since in training-based channel estimation methods some resources which can be utilized for data transmission is used for the channel estimation process, decreasing the number of pilots or... 

In this thesis, detection problem in CDMA systems in overloaded regim is investigated. To thid end, both wireless and optical CDMA systems are considered. In overloaded CDMA systems, if the spreading matrix is invertible and channel is ideal and noiseless, then in the receiver the information of users can be detected without any error. Previusely, it was proven that for limited information symbols space, there are some matrices which are invertible or detecting. However, optimal receiver in these systems is comlex and infeasible. The only case that the optimal receiver can be implemented in a fesible way, is when the spreading matrix is constructed using kronecker technique. Therefore, in... 

One of the most effective and robust algorithms in watermarking are additive and multiplicative methods. Although the detector of additive watermarking methods are easier than the multiplicative one, they do not gain from human visual or auditory systems. This is the main drawback of additive watermarking techniques. On the other hand, the most advantage of multiplicative watermarking methods is that the power of the watermark is proportional to the power of the host signal. In this thesis, we have introduced a new multiplicative watermarking technique for audio and image signals. For the audio signal, the embedding is performed on the wavelet coefficients. We used Maximum likelihood rule... 

The remote sensing is the knowledge of gaining information about an event without having direct access to it, and synthetic aperture radars (SAR) have gained spectacular attention in this filed due to their wide applications and high efficiency. The performance of SAR, which are classified in the space-borne or space-borne radars is similar to that of pulse radars. The transmitted signals in SAR are generally chirp signals, and the received signal is two-dimensional which is scattered in two dimensions of range and azimuth called as raw data. Due to relative movement between the radar base and the target point, the distance between the radar base and the target point would not be fixed along... 

Optical Coherence Tomography (OCT) has a great potential to elicit clinically useful information from tissues due to its high axial and transversal resolution. In practice, an OCT setup cannot reach to its theoretical resolution due to imperfections of its components, which make its images blurry. The blurriness is different alongside regions of image, thus they cannot be modeled by a unique point spread function (PSF). In this paper, we investigate the use of solid phantoms to estimate the PSF of each sub-region of imaging system. We then utilize Lucy-Richardson, steepest descent (SD) and total variation (TV) based iterative deconvolution methods for mitigating occurred spatially variant... 

On one hand Code Devision Multiple Access (CDMA) as an efficient spread spectrum multiple access solution was under consideration in recent years. On the other hand one of the main challenges in cellular networks was near-far effect and fading effect which cause different received powers from different users.
In this thesis we are going to investigate near-far effects in overloaded CDMA systems from different aspects. Firstly we will investigate on the robust systems over near-far effect, propose near-far resistance codes and a very low complexity ML decoder for a subclass of these codes. Secondly we deal evaluation of the sum capacity of finite dimensional CDMA systems. These systems... 

Predicting the Amino Acids that have a catalytic effect in the enzymes, is a big step in appointing the activity of the enzymes and classifying them. This is a very challenging job, because an Amino Acid can appear in a variety of active sites.The biological activity of a protein usually depends on the existence of a small number of Amino Acids. Detecting these Amino Acids from the sequence of Amino Acids has many applications. Usually, the Amino Acids that are preserved are known as the Amino Acids that build up the active site, but the algorithms for finding the preserved Amino Acids are much more complex. There are a lot of algorithms for predicting the active sites of Amino Acids, but... 

Methodology has always one of important issues in philosophy of science; especially in social sciences lots of challenges arise from this field. Each of positivistic and relativistic different schools, on their own ontology about human and society, had suggested different methods of social studies. Roy Bhaskar, as the others, offers a model for scientific method, on the base of his own critical realistic ontological principles; and tries to secure his model from the objections on previous models of scientific method. In this model, hi suppose empirical survey as an obvious and undoubted activity in science. Then, he transcendentally derives his ontological principles from this antecedent,... 

The philosophers of social sciences, in addition to epistemological questions-the questions about our knowledge of the social world- implicitly or explicitly, consider ontological issues: the questions about the nature of social world (society, structures and relations, people and actions). In Critical Realism, ontology and epistemology are linked. It means that what it is awarded, it is crucial that knowledge can be gained from it. This school, with a critique of Positivism and Hermeneutics, tries to authenticate ontological arguments and by reconstruction of concepts like causality, necessity, structure and stratification reality, forms the realist ontology and offers a novel solution to... 

Memory and recalling process has always been a basic question. Decoding the Long-Term_Memory is one of the first steps in answering this question. Since various experiments in the field of human long-term memory, was conducted. This research is motivated by a trial that in which, the Mgntvansfalvgram (MEG) has been recorded while recalling the color and orientation of a grading which is associated with an object, after the object has been shown. High accuracy in Decoding the mentioned color and direction, will be decoding the long-term memory. In order to enhance memory decoding, the research studies different classifiers such as sparse based classifiers and other popular one. It has also... 

Considering the tremendous development in imaging systems’ industry, today we can afford to have imaging equipment, capable of taking multispectral images in very high resolution. One of the remarkable benefits of this technology is in the realm of arts and particularly in museums. Taking advantage of the potentials of multispectral, highquality imaging, curators will be able to probe their priceless works of art ( e.g. paintings ) without putting them in danger through invasive research. Besides, one can investigate and control the transformation of these works through time by using this new imaging method. Recently, Multispectral Imaging of paintings, in different frequency bands from... 

Super-resolution means increasing the resolution so that the quality improves. This is defined for both image and video. In this regard, machine-learning based methods, especially convolutional neural networks, have shown great potential in recent years. Finding the right structure that can deliver high speed and accuracy is the key to solving the super-resolution problem.Despite the myriad of methods for image super-resolution, less attention has been paid to its generalization to video. This generalization should be such that more detail is created in the output using adjacent frames.In this dissertation, the existing methods for image and video super-resolution are reviewed, and then a... 

In recent years there has been a great effort to enhance the computer-aided diagnosis systems, Since expertise elicited from past resolved cases plays an important role in medical applications, and images acquired from various cases have a great contribution to diagnosis of the abnormalities, Content based medical image retrieval has become an active research area for many scientists. In this project we proposed a new framework to retrieve visually similar images from a large database, in which visual similarity is regarded as much as the semantic category relevance, we used optimized wavelet transform as the multi-resolution analysis of the images and extracted various statistical SGLDM... 

Breast cancer is considered as the most common type of cancer in women worldwide and mammography is currently utilized as the principal method for screening the breast cancer. Breast Magnetic resonance imaging (MRI) can be used as a complementary imaging technique besides mammography. MRI technique involves scanning a patient before and repeatedly after the injection of the contrast agent (DCE-BMRI). This examination often takes 7-10 minutes and any movement of the patient’s breasts due to breath, heartbeat or deliberate movement, made in this relatively long acquisition period, leads to a distortion in images called motion artifact. This problem makes the quantitative analysis of the images...