Sharif Digital Repository

The integration of radar and communication functionalities into a unified Joint Radar-Communication (JRC) system offers enhanced spectral efficiency and reduced hardware complexity. Recognized as a key enabler for next-generation wireless networks, JRC systems require a careful balance between radar and communication demands, where waveform design plays a pivotal role in achieving this equilibrium. Although waveform design has been extensively studied separately in radar and communication domains, the requirements of modern networks necessitate a unified approach that simultaneously addresses the needs of both systems. This thesis advances waveform design methodologies for JRC systems,... 

Today, the global environmental restrictions as well as; energy problems have directed researchers toward developing ideas of producing a clean liquid fuel from coal or natural gas as a major research topic. In this regard, a special attention is paid to the dimethyl ether (DME) as a clean material containing 34.8% oxygen possessing enough positive potential to replace the diesel and LPG fuels. One of the most economic routes for producing the DME is known to be the direct conversion of the synthesis gases and carbon dioxide first to the methanol and then its dehydration to the DME. Moreover, the DME is not limited to a particular country or resource area since small reservoirs of natural... 

The synthetic aperture radar (SAR) is a microwave imaging radar that achieves high resolution while taking advantage of pulse compression technology and the Doppler effect. In typical radar systems, in order to obtain a good azimuth resolution, one should use an antenna with big aperture. However this is not possible in many cases. SAR has overcome this problem by moving the antenna and so making a synthetic aperture. In inverse SAR (ISAR) the radar antenna is static and synthetic aperture is created by the movement of target. Typical SAR imaging aims at the static targets and when the target is moving, it does not operate well. When detecting moving targets by SAR, both radar and target are... 

In this dissertation, the application of frequency and space diversities in radar target parameter estimation are investigated. On this basis, multi-frequency signal is used to improve the range resolution, array structure is used to increase the angle estimation accuracy and the merger of the multi-frequency signal and array structure are used to increase the maximum number of targets that can be uniquely identified.Considering the desirable properties of multi-frequency signals such as high bandwidth efficiency, high range resolution achievement without chip length decrease and …, there has been increased interest in the vast area of research on the design of such signals that has... 

Target recognition techniques based on micro Doppler phenomenon are popular because they are applicable even on low resolution radars, in contrast to other techniques such as High Resolution Range Profile (HRRP) which need high resolution in range or angle. Usually, main purpose of such techniques is generating robust features against target initial state, velocity, aspect angle, etc. rather than features which exactly identify a target. Main approaches in the literature are based on time-frequency transforms (TFT) such as spectrogram in order to generate features to classify targets, but in this thesis, we propose a totally different method using Recurrence Plot for generating features... 

In this research with Finite Element Methods in ABAQUS, numerical modeling has done in three-dimensions, which can be used to determine the effect of different factors on the surface settlement. Also, various factors such as geotechnical conditions, tunnel diameter,tunnel depth, the impact of the thickness of the segments and the amount of eccentricity of the structure relative to the longitudinal axis of the tunnel considered in this study. Face Pressure Supports, and Grout Injection Pressures are taken into account, too.Tunnel drilling causes a change in the displacement area and creates a changing zone around the tunnel. In this regard, not only adjacent buildings will be affected by... 

Proton precession magnetometers are one of the most sensitive scalar magnetic sensors. Their function is based on Zeeman effect and also nuclear magnetic resonance phenomena. In this project we have designed and implemented needed coils, swithching and signal detection circuits. Because of extremely high sensitivity of this sensor to induced noises and also gradient of earth’s magnetic fileld, detection of precession signal needs design of low noise electronic circuits with special EMC considerations. The implemented system in this project contains different blocks, such as switching circuit and its related control unit, amplifier, filter and frequency meter. Using this system, the obtained... 

Effective field theory is a practical method for model building and explaining experimental/observational data. These theories are constructed based on knowing low energy degrees of freedom and symmetries (accidental or fundamental). By construction, these theories are applicable up to a cut-off scale and their predictions beyond that are not reliable. For applications to higher energies a UV completion is needed through which modifications are applied or new heavy degrees of freedom are introduced. In order to complete a theory in a Wilsonian approach, scattering amplitudes must satisfy some constraints. These constraints are derived from basic assumptions like Lorentz invariance,... 

Numerous structures which are involved in seismic soil-pile-structure interaction have been destroyed. Considering complexities which exist in soil-pile interaction problems and lack of precise methods without imperfect bases, it is necessary to use numerical methods for analyzing soil-pile interaction problems. In this research, three-dimensional modeling and studying the effect of changing soil and pile parameters on the behavior of pile under earthquake loading is performed using finite difference software, FLAC3D. The soil in this model has a softening behavior. Real earthquake spectrum has been applied into the model as the acceleration time history at the bedrock level. The results of... 

This thesis presents several methods time-frequency based approach for classifying the vibration signals of rotatery machine. It uses the features extracted from the time-frequency distribution (TFD) of the vibration signal segments. Results of applying the method to a database of real signals reveal that, for the given classification task, the selected features consistently exhibit a high degree of discrimination between the vibration signals collected from healthy and fault machine. A comparison between the performances of the features extracted from several TFDs shows that the STFT slightly outperforms other reduced interference TFDs.


 

A group of vehicles are contributed to follow static or dynamic targets in a cooperative target tracking problem. The vehicles estimate the future location of dynamic targets based on the information they receive from other vehicles and targets. Noting to these estimations, the vehicles are able to decide the best movement toward the targets. Various control methods have been presented to solve different problems of target tracking which the majority of them proposed optimal control solutions. A new approach to the problem of tracking dynamic targets via cooperative multi-vehicle systems under the receding horizon control of the vehicles is proposed in this dissertation. A receding horizon... 

In this Thesis, a new algorithm is presented to cooperatively guide a set of robots, modeled as dynamic vehicles, toward a moving object while their heading angles variation are limited and collision avoidance is also required. The trajectory of object has unknown behavior, such that, at each moment in time, during the mission period, the available information about the object's trajectory is merely its position and instantaneous velocity. Due to this situation, vehicles are supposed to determine their movements, based on the predicted object's trajectory. To meet the goals of the algorithm, a time-decreasing reward is associated with the object, such that vehicles can collect the reward... 

Nowadays, economical extraction of oil and gas, and their products is an important issue for many countries. Up to now, vertical wells have been used for oil extraction but some wells exist that they cannot be reached by using vertical drilling; for example the wells under a sea. Therefore, this makes the governments and scientists determined to find a new way to reach them. Horizontal drilling is one of the new ways to reach such worthy wells. In this project, dynamics of the horizontal drill string is studied. Then, according to the forces that affect the dynamics of drilling, its vibration is analyzed. After finding the boundary conditions and normal modes of the system with using mode... 

Prescribing and consuming drugs more than necessary is considered polypharmacy, which is both wasteful and harmful. In this study, an innovative data mining framework is developed for analyzing prescriptions regarding polypharmacy. The approach consists of three main steps: pre-modeling, modeling, and post-modeling. In the first step, after collecting and cleaning the raw data, several novel features are extracted for physicians and patients. In the modeling step, decision trees are applied to generate a set of If-Then rules to detect and describe physicians’ features or patients’ features associated with polypharmacy. A novel approach based on the response surface methodology (RSM) is... 

Thyroid gland is one of the important internal organs of the body that is responsible for T3 and T4 hormones secretion. Concentration of these hormones directly influences growth of body, thus measurement concentration of thyroid hormones is one of the most common experiments all of the world, specially in our country that Hypothyroidism is common among people. Secretion of hormones in thyroid gland controlled by TSH (thyroid Stimulating Hormone) that released from Pituitary gland. TSH concentration is opposite of level of thyroid secretion. Because of interconnected relationship between these three hormones, measurement of each of them is so important. Many researches for developing... 

In this Thesis, the necessary steps to implement near-optimal atmospheric flights in order to create micro and partial gravity condition has specified. This documentary has been prepared in a comprehensive way. The goal of this project is to reach the optimal throttle and elevator inputs and consequently optimal paths to perform the maneuver with maximum time. The basis of my work is to integrate two methods of tabu search and continuous ant colony system in order to find the best match for inputs. As a result, the aircraft’s proper inputs as a function of time can be accommodated. The constraints here refers to the safety of the flight, which are maximum operating speed, stall angle of... 

The visibility is one of the most important problems in computational geometry. Two points are said to be visible to each other, if the line segment that joins them does not intersect any obstacles. The art gallery problem is a well-studied visibility problem in computational geometry. It originates from a real-world problem of guarding an art gallery with the minimum number of guards who together can observe the whole gallery. In many of applications, the “guards” are “landmarks” deployed in an environment to help provide navigation and localization service to mobile robots. The mobile device communicates with these landmarks through wireless, or other “line-of-sight” signaling... 

Air conditioning systems are one of the main parts of buildings, and their performance is very important, especially during the peak heat and cold days, both in terms of providing comfort area for the people and in terms of energy consumption. These systems control the temperature and humidity inside one or more target zones using heating, cooling, humidification, and dehumidification processes. One of the most common solutions to optimize the performance of air conditioning systems is the use of control systems. In this study, a nonlinear multi input-multi output dynamic model of a two-zone variable air volume & temperature air handling unit is considered for operation in the summer season.... 

Heat sources with temperatures less than 100 °C are available in various processes in the form of waste heat and from renewable sources such as solar energy. One of the methods of gaining benefit from these ubiquitous and abundant heat sources is using thermal harvesters that convert low-temperature heat into electrical energy without the need for the power grid. Portable harvesters can be a reliable and low-cost option for providing stable energy for low-power electronic devices such as wireless sensors. Many studies have been conducted at the global level to design and develop efficient low-temperature heat harvesting mechanisms. However, each of them is associated with fundamental... 

Nowadays, machine learning is used to solve various problems, and different machine learning models have increasingly become a part of our daily lives. This raises the importance of a more detailed examination of the models' outputs. In sensitive areas such as medical uses, this issue becomes even more critical, and using these models without having a framework to quantify the uncertainty of the outputs can lead to significant challenges and hinder their broader application. Conformal prediction is one of the frameworks that can help quantify the uncertainty of outputs. This framework is model-agnostic, meaning that we can use it for any model, including black-box models. The outputs of this...