Sürdürülebilir Yeşil Kampüs Koleksiyonu / Sustainable Green Campus Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7755
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Master Thesis Distance Estimation in Tabletop Molecular Communication(Izmir Institute of Technology, 2019) Uzun, Emrehan; Atakan, BarışAlthough existing communication technologies based on electrical and electromagnetic signals are applicable for a variety of applications, these technologies are insufficient in some applications. Especially, developments in nanotechnology and biotechnology require an alternative communication paradigm. Molecular communication (MC) paradigm is a promising solution needed to fill the gap in both nano- and macroscale. It is one of the oldest communication paradigm in which molecules are used as information carrier. Its mechanism provides a basis for all living organisms from unicellular bacteria to humankind to continue their existence. For instance, the information transfer among nerve cells is accomplished via MC. These kind of biological activities inspire a base for communication between nanomachines. The realization of MC occurs by sending and receiving molecules between nanomachines. The information about distance between transmitter (Tx) and receiver (Rx) is one of the critical points to enable an efficient performance in terms of clock synchronization, transmission rate, etc. in the design of MC system. However, most of the existing works on MC are based on the assumption distance is pre-known. In addition, the proposed theoretical methods are validated using an ideal simulation environment. Furthermore, there is a limited number of studies about macroscale practical applications. In this thesis, an end-to-end tabletop MC testbed is established to transmit chemical signals from a Tx to Rx. This testbed allows us to provide an estimate about the distance using molecular information received by the Rx. In the development of the estimation algorithms, the principles of molecular random walk are used. We propose three novel approaches that are called as peak time, correlation based and relative entropy based approaches to estimate the distance between Tx and Rx for a practical MC system. The performance of the proposed estimation methods is evaluated in the tabletop MC testbed. The experimental results shows that our proposed methods present a satisfactory performance in terms of estimation error and the methods can be used to develop new potential macro-scale MC applications.Master Thesis Correction of Errors Due To Radial Run-Out in Absolute Rotary Encoders(Izmir Institute of Technology, 2018) Cirit, Mehmet Onur; Özdemirel, BarbarosThis thesis proposes a novel, general purpose correction algorithm for analog absolute rotary encoders to eliminate errors due to radial run-out of the shaft. Unlike traditional quadrature encoders, four sensors were employed that produce four quadrature signals instead of two. The radial variation of the field intensity was exploited to identify the direction and extent of radial run-out and correction was applied to poorly identified position values accordingly. A simulation environment was created from the scratch to simulate encoder signals under the influence of shaft run-out in order to verify the performance of the algorithm. The numerical results were collected in each milestone of the development and results were presented both for overall performance and for a number of special cases. The issues occurring in the first iterations of the algorithm, such as error mismatch and singularities, were identified and resolved in a stepwise manner. The final version of the algorithm has shown significant improvement and successfully reduced the mean error in angular position down to 12% of the initial value.Master Thesis Nonlinear Controller Design for High Speed Dynamic Atomic Force Microscope System(Izmir Institute of Technology, 2018) Coşar, Alper; Balantekin, MüjdatIn this study, the performances of conventionally used PI controller and a nonlinear H∞ controller, are compared in the state-of-the-art High-Speed Dynamic Atomic Force Microscope (HS-AFM). The state-of-the-art HS-AFM system is modeled via MATLAB/ SIMULINK for four different cantilevers, i.e., small high-frequency and regular lowfrequency cantilevers used in air and liquid environments. For the modeled system, PI and H∞ controllers are designed and implemented by using both analytical methods and toolboxes available in MATLAB. Simulations are performed in ideal condition, and under exogenous effects such as noise, disturbance and parametric uncertainty. In ideal condition, achieved maximum frame rate, and the percentage of topography acquisition error with two controllers are calculated for each cantilever. Also, performances of controllers in the system are tested under exogenous effects. It is observed that with the H∞ controller, the topography of the selected sample can be obtained with up to 2 times less acquisition error. It is also observed that PI controller is better in disturbance rejection, but H∞ controller is more robust under the effect of noise. For each cantilever, similar results to the ideal condition is obtained in case of uncertainty. Most distinctive results are obtained with high-frequency cantilevers, as H∞ controller enables a 2 times higher frame rate (14.3 fps) compared to the PI controller (7.1 fps) with the same level of acquisition error in the state-of-the-art HS-AFM operated in liquid environment.Master Thesis Metamaterial antenna design for 5.8 GHz Doppler radar(Izmir Institute of Technology, 2018) Yılmaz, Hasan Önder; Yaman, FatihThis thesis presents mainly simulation and measurement results of metamaterial based transmitter and receiver antennas for a Doppler radar system operating at 5.8 GHz and indoor, outdoor and through-wall performances of the Doppler radar system after the integration of field and the realized transmitter and receiver antennas. Firstly, the antennas are modeled via 3D electromagnetic simulation program CST:Microwave Studio and related parameters are calculated. Afterwards, in order to observe antenna performances, radiation pattern and gain characteristics of realized antennas are measured in laboratory environment including anechoic chamber. Another essential objective of this thesis is to examine and analyze applicability and effectiveness of the metamaterial based antennas for a 5.8 GHz Doppler radar system. For this reason, a double negative index metamaterial structure is integrated to a patch antenna for the transmitter. For the receiver antenna, a near-zero index medium is designed to locate over patch antenna. Accordingly, significant improvements in size and bandwidth for the transmitter and in gain and directivity for the receiver in addition to improvement of its psychical size are obtained. It is shown that return loss, radiation pattern and gain measurement results of the designed antennas agree well with the simulations for a desired frequency band. According to the experimental data, the realized transmitter antenna has a higher directivity value as compared to the simulated one, therefore it radiates most of the power into narrower area. Additionally, the measured one has a wider bandwidth. The measurement results of receiver antenna are consistent with simulation in terms of bandwidth, return-loss, radiation pattern of horizontal direction and gain value. The last part of the thesis is devoted to expressing the application of the designed antennas to the low-power, short-range Doppler radar system, which is designed to detect the speed of the human or moving target in the indoor/outdoor environment or behind the wall. Improvements on the performance of the radar system integrated with metamaterial antennas are discussed and performances results are commented.Master Thesis Analysis of Cantilevers for High-Speed Atomic Force Microscopy(Izmir Institute of Technology, 2018) Brar, Harpreet Singh; Balantekin, MüjdatIn life sciences, High-Speed Atomic Force Microscopy (HS-AFM) is now widely accepted as a dynamic event visualizer for numerous biological samples such as live cells, membrane lipids, ATP-proteins, enzymatic reactions, DNA-protein interactions, etc. HSAFM’s unique ability to observe surface topography of the samples with height data and with a resolution of up-to a single atom makes it a prominent tool in Nano measurements. HS-AFM Imaging technique’s speed and response is limited by various factors including cantilever probes, operating environment, scanning techniques etc. Cantilevers are indispensable and integral part of HS-AFM Systems, thereby necessitating their own critical evaluations. Therefore, evaluation of various parameters like resonance frequency, stiffness and Q-factor of cantilevers is an active area of research. The simulated research work mimics the experimental conditions of HS-AFM operation in air and liquid environment. The damping mechanisms such as viscous and acoustic damping of the medium, squeeze film damping, and damping due to viscoelasticity of the material are included in the finite element simulations. High frequency soft cantilevers suitable for HS-AFM with the stiffness of ~1 N/m and with the first flexural eigenmode resonance frequency of ~1.5 MHz (in liquid) and ~5 MHz (in air) are studied. Numerous small rectangular and modified cantilevers of Silicon and Polymer (SU-8) materials with the length of ~5 to 10 μm, width of ~1 to 2.5 μm and thickness of ~0.1 to 0.6 μm are analyzed. Our aim in this research is to identify appropriate cantilever geometries and materials for HS-AFM applications.Master Thesis Cell Selection Algorithms for Conventional Narrow Band Wireless Systems(Izmir Institute of Technology, 2017) Yılmaz, Saadet Simay; Özbek, BernaPublic safety organizations provide a stable and secure environment for the society. Wireless communication between public safety officers is very important to transmit voice or data during an emergency crisis. When the public communication networks can not provide service during crisis, disaster and high traffic cases, Professional Mobile Radio systems (PMR) such as conventional Association of Public Safety Communications Officials (APCO25) and trunked Digital Mobile Radio (DMR) systems are needed to improve the service quality and to provide uninterrupted service provided to the users. While providing continuous voice and data service, it is very important to efficiently select the base station to be served and to ensure that a mobile user can seamlessly attach from one base station to another base station while moving within a cell. In this sense, it is critical to determine the base station to be served by efficient cell selection algorithms. Cell selection is the process of deciding the base station which provides services to the users. Cell selection plays an important role in balancing the system load and thus overall system performance. By means of efficient cell selection algorithms, it is aimed to reduce the waiting time and to connect a base station as soon as possible while establishing reliable transmission link for PMR systems in emergencies.Master Thesis Learning Control of Robot Manipulators With Telerobotic Applications(Izmir Institute of Technology, 2016) Doğan, Kadriye Merve; Tatlıcıoğlu, EnverLearning control of teleoperation systems that can be utilized in telerehabilition applications is investigated in this thesis. Specifically, considering the fact that in rehabilitation the patient is required to perform a task over and over again, learning controllers are considered as the most feasible solution, in which desired trajectories are periodic with a known period. Since control of teleoperation systems are directly related with the control of robots that are included to the system, learning control of joint space and task space of these robots are simulated in the first part of this study. Joint space learning controller is designed under the restrictions that the robot dynamic model being uncertain and that joint velocities are unmeasurable. Then, a task–space learning controller is designed by considering the fact that the most desired tasks are defined in the end–effector space. Via Lyapunov based stability analysis methods, asymptotic tracking is ensured for both controllers. Numerical simulation results and experimental studies are utilized to illustrate the performance of the designed controllers. In the second part of this thesis, performance of the direct teleoperation and model mediated teleoperation methods under time delays in the communication cahannel are examined in a comparative manner. In direct teleoperation, the information between master and slave systems are exchanged directly, while the model of the environment of the slave system is learnt and integrated at the master side as proxy dynamics in model mediated teleoperation. Experimental studies are realized to evaluate the performance of both of mentioned methods.Master Thesis Accelerometer Based Handwritten Character Recognition Using Dynamic Time Warping(Izmir Institute of Technology, 2016) Tunçer, Esra; Ünlü, Mehmet ZübeyirCharacter and gesture recognition are one of the most studied topics in recent years. Character recognition studies are generally based on image processing. Only a few studies can be found about character recognition as gesture recognition. Gesture recognition is making the computers understand human body movements by using different kind of knowledge of the environment. This knowledge can be obtained by image or sensor-based efforts. Accelerometer is the most used sensor in gesture recognition, so in this study a 3-axis accelerometer is used. In this thesis, English alphabet‟s lowercase characters are used. A ring-like device which contains accelerometer in it is used. After obtaining the acceleration data of each character with 20 repetitions, we apply filtering, segmentation and normalization preprocessing steps for each signal. Since there are different accelerations and decelerations between each repetitions, Dynamic Time Warping (DTW) algorithm has been chosen to determine the similarities between signals. DTW is an algorithm that uses the amplitude values of the signals, so it is weak to amplitudes that shift in time domain. To overcome this shortcoming, the method called Derivative Dynamic Time Warping (DDTW) has been applied to the acceleration signals. DTW and DDTW methods have been compared and we have found that even we remove the normalization step; DDTW gives better results than DTW. By comparison of linear alignment and DTW, the results show that DTW gives better recognition rates for signals with different accelerations and decelerations. DTW also gives better result for the different length signals.Master Thesis Interference Management Techniques for Femtocell Networks(Izmir Institute of Technology, 2015) Bayrak, Uğur; Özbek, BernaThe need for high capacity and data rate increases with the growing demand for wireless communication. In order to meet this demand, one of the most effective ways of improving capacity and data rate is deployment of femtocell networks which are considered to be a promising technique for future wireless networks. However, mass deployment of these low-power base stations brings many challenges. Interference management will be one of the major challenges for the dense deployment scenarios of femtocells in coverage of the macro base stations. To cope with interference problem, there are many interference management techniques. In this thesis, power control and beamforming techniques are implemented separately and jointly in order to deal with cross-tier downlink interference which occurs between macro base station and users of femtocell. In this two-tier network system involving femtocell and macrocell layers, power control problem, first, is investigated. Feasible transmission power region for femtocell is determined with respect to the user locations so that targeted signal-to-interference-plus-noise-ratio (SINR) values are satisfied. Secondly, beamforming technique is applied using partial zero-forcing method. In this method, beamforming vectors are designed to remove cross-tier interference. It is observed that SINR of macro base station’s user does not undergoes any degradation in the nearfield region of femtocell. Finally, we apply these two techniques jointly. Since both interference suppression and power-efficiency is provided, joint technique seems to be a viable and environment-friendly solution for femtocell networks.Master Thesis Analysis of Stochastic Dynamical Systems(Izmir Institute of Technology, 2007) Güngör, Mesut; Savacı, Ferit Acar; Savacı, Ferit Acar; Savacı, Ferit AcarIn this thesis, analysis of stochastic dynamical systems have been considered in the sense of stochastic differential equations (SDEs). Brownian motion, which can be considered as a first example of stochastic dynamical systems, its derivation and its properties have been investigated, then the analytic and numerical solution methods of SDE have been studied with the examples from the physical world. In order to construct a random variable in a computer environment, random number generation algorithms have also been investigated. Finally a Matlab-Simulink block for numerical solutions of linear SDEs has been newly developed.