Elektrik - Elektronik Mühendisliği Bölümü Tez Koleksiyonuhttps://hdl.handle.net/11655/4242024-03-28T11:44:15Z2024-03-28T11:44:15ZInvestigation of Multisensory Behavioral Control in Zebrafish During Target TrackingKoç, Orhunhttps://hdl.handle.net/11655/343712023-12-29T07:59:41Z2023-10-11T00:00:00ZInvestigation of Multisensory Behavioral Control in Zebrafish During Target Tracking
Koç, Orhun
Animals capture several signals of different speeds and propagation patterns from their environment, such as light, sound, and pressure, through various sensory organs and interpret these signals in their central nervous systems (CNS) to represent a sensory expression of their environments. In addition, the same source can stimulate different sensory organs simultaneously. In such cases, multisensory integration is employed to accelerate information processing, increase the accuracy of perception, and reduce noise. Consequently, animals perform their behavior in the presence of feedback signals by generating the necessary motor signals. The main objective of this thesis is to design and build a novel experimental setup and stimuli system that allows the investigation of multisensory integration in animals during their instinctive behavior. In this study, we used free-swimming (unconstrained) Danio rerio (zebrafish), which exhibits swimming behavior against the water flow called positive rheotaxis and is referred to as a model organism in the literature. Rheotaxis is an instinctive behavior to station keeping by spending minimal energy to avoid drifting in the water flow, and zebrafish use both visual and mechanosensory cue signals to perform this behavior. Our new experimental setup based on the purpose of rheotaxis is a kind of virtual reality environment in the form of a speed-controlled laminar flow tunnel for the fish. First of all, to induce instinctive rheotaxis behavior in the zebrafish, we place it in our experimental setup where we obtain laminar flow. A low-gradient regime occurs behind it when we place an obstacle in the water. The fish can perceive this regime, and it tends to stay in this regime in accordance with the low energy cost purpose of rheotaxis. After that, when we move the obstacle perpendicular to the water flow and horizontally according to the fish's perspective, the low-gradient regime also moves, and, more importantly, the zebrafish follows this regime. Zebrafish detect the low-gradient regime behind the obstacle by combining mechanosensory and visual information simultaneously for target tracking behavior. The new experimental setup and the two-actuator stimulation system we built aim to decouple the multisensory integration that the zebrafish performs for target tracking during rheotaxis and allow us to understand how the zebrafish integrate the signals. In this context, we placed a D-shaped semi-cylindrical transparent plexiglass tube in the water flow and placed a blue neon strip LED inside this tube, which can move completely independently of the transparent tube to stimulate the zebrafish. The transparent D-shaped plexiglass tube is invisible in the water due to light refraction, stimulating only the zebrafish's lateral line organ. The neon strip LED inside the tube does not induce vibration in the water as it is surrounded by the tube and only provides visual cues to the zebrafish. We can provide mechanosensory and visual stimuli to the fish both synchronously and asynchronously, thanks to our unique high-resolution two-actuator stimulation system. We evaluate the closed-loop sensory-motor control processes of zebrafish during target tracking behavior with our determined sensor conflict scenarios. In our study, we repeated target tracking experiments for N=5 zebrafish and estimated the frequency responses of multisensory integration dynamics. Using our unique experimental setup, the two-actuator stimulation system, and the protocol, we found that mechanosensory stimuli dominate over visual stimuli, and visual cues alone are not sufficient to trigger the fish's tracking behavior when contrasted with mechanosensory cues, but zebrafish can integrate mechanosensory signals with visual signals to improve target tracking performance. Our results suggest that the dynamics of sensory integration cannot be explained by simple superposition methods.
120E054 Numaralı TÜBİTAK Projesi
2023-10-11T00:00:00ZTekil Değer Ayrışımı ile 2-B Toplam Elektron İçeriği Yeniden YapılandırılmasıArdıç, Furkanhttps://hdl.handle.net/11655/343632023-12-21T06:33:56Z2023-01-01T00:00:00ZTekil Değer Ayrışımı ile 2-B Toplam Elektron İçeriği Yeniden Yapılandırılması
Ardıç, Furkan
Ionosphere affects the performance of shortwave communication, satellite communications,
space-based navigation and positioning systems. To enhance the performance of these systems, understanding the structure of the Ionosphere is crucial. The Ionosphere has inhomogeneous, anisotropic, space and time varying, spatio-temporal dispersive behaviour. Total Electron Content (TEC) is an important parameter of Ionosphere for understanding the structure of ionosphere. TEC can be estimated at limited number of points in space. Therefore, there is a need for accurate, reliable, and robust TEC mapping methods. In this study, Singular Value Decomposition (SVD) and Least Square methods are employed to perform 2-D reconstruction of the European mid-latitude Ionosphere. The SVD provides an expansion onto physical basis vectors. The output contains the minimum basis vector with maximum energy. In this study, the 'Model Matrices',on which the SVD is applied, are generated based on the 11-yearly and monthly cycles of the Sun and the geomagnetic indices of the Earth. The structure of these model matrices is one of the factors contributing to the high performance of the basis vectors obtained through SVD in ionospheric reconstruction. The Least Squares is used for 2-D TEC reconstruction by measurement TEC values and the basis vectors obtained through SVD. 99.9952% of there constructed 145,152 TEC values has less than 3 TECU difference with JPL-TECs. Probability Density Function (PDF) is estimated for this TEC differences, between JPL-TEC and the reconstructed maps. The TEC difference pdfs are shown to be Laplace Distributed. The mean of this distribution indicates no bias in TEC reconstructions. The developed reconstruction algorithm and proposed application can compute the TEC maps in closed form, without any computational complexity. High performance can be achieved by using small number of basis vectors in signal subspace. All of these features make the algorithm reliable, accurate, and robust. The algorithm developed in this thesis can be applied to all Ionosphere states for regional and global TEC mapping. In application, the signal subspace can be determined based on the estimated PDF parameters obtained in this thesis. This reconstruction algorithm can be used for near-real time estimation and near-real time prediction of TEC maps.
2023-01-01T00:00:00ZİHA Haberleşmesi İçin Havadan Havaya Kanal Modellerinin İncelenmesiYılmaz, Atakanhttps://hdl.handle.net/11655/343592023-12-25T12:59:38Z2023-01-01T00:00:00ZİHA Haberleşmesi İçin Havadan Havaya Kanal Modellerinin İncelenmesi
Yılmaz, Atakan
Unmanned Aerial Vehicles (UAVs), due to their continuously advancing technologies and features such as low cost, small size, light weight, high maneuverability and quick deployment, have begun to find extensive use in military, civilian, and commercial fields such as transportation, logistics, agriculture, telecommunications, healthcare, media, and entertainment, both in single and multiple (swarm) applications. In order to establish reliable communication links between ground control stations and UAVs or between UAVs themselves, the characteristic properties of the communication channel need to be identified, and the necessary parameters for communication should be selected based on these characteristics.
In this thesis, the analysis of the air-to-air channel for different scenarios of UAVs in the field of communication is conducted using the "Two-Ray Model" based on ray tracing method. The communication channel characterization is carried out for the specified scenarios by analizing the line-of-sight signal received by the receiver and signals that are propagated from different paths and reach the receiver through ground reflections. Various scenarios with different UAV altitudes, inter-UAV distances, antenna types, environmental factors, etc. are considered to analyze the communication channel.
In addition to the theoretical results of channel characterizations obtained by using the model for different flight scenarios, this study discusses the preliminary stages of field measurement studies conducted in various scenarios for communication between two identical UAVs, by introducing the platforms used in the research. The obtained field measurement results are interpreted and compared with the theoretical results.
2023-01-01T00:00:00ZNanokompozit Tabanlı Esnek Dokunsal SensörlerŞekertekin, Yeterhttps://hdl.handle.net/11655/343552023-12-26T12:32:31Z2023-01-01T00:00:00ZNanokompozit Tabanlı Esnek Dokunsal Sensörler
Şekertekin, Yeter
The use of smart devices and applications that require more interaction between human and machine has increased significantly in many areas since flexible electronic devices starting to find more place in the traditional electronics world. Tactile sensors, which are an important part of flexible electronics with the function of converting an external mechanical effect into electrical signals, are used especially in the biomedical field to diagnose and treat diseases by monitoring electrophysiological signals and to increase the functionality of prosthetic devices. Besides, tactile sensors are the most fundemental component in robotic systems developed for commercial or educational purposes and in the development of next–generation touch screens as well as in various applications where artificial intelligence is integrated. For this reason, the developments and improvements have a very important place as they directly affect the efficiency and performance of devices and applications that have the potential to use flexible tactile sensors. The variety of materials used in the production of flexible tactile sensors, different production methods and working mechanisms of the sensors offer a wide range of research opportunities.
In this thesis, polymer nanocomposites consisting of polymer and conductive fillers were used in the sensing layers of sensors that are fabricated on flexible substrates. Polyvinyl alcohol (PVA) and sodium alginate (SA) were preferred as polymers, especially because they are biocompatible and easy to use. Carbon black (CB), carbon nanotubes (CNTs), graphene nanoplatelets (GnPs) and silver nanoparticles (Ag NPs) were used as conductive fillers. Different nanocomposites were produced so that each nanocomposite consists of a polymer and a filler, the nanocomposites were characterized and used to produce nanocomposites–based sensors with different sensor designs. The obtained flexible tactile sensors are based on PVA–CB, PVA–CNT, PVA–GnP, PVA–Ag NP, SA–CB and SA–CNT nanocomposites. In addition to tactile sensors produced by screen–printing on paper, melt–blown and cotton fabrics, there are also sensors produced without using any substrate. Produced sensors were tested via electromechanical measurements under different pressure values. PVA–fCNT, PVA–GnP and PVA–Ag NP nanocomposites–based sensors fabricated with the same structural design have shown that the phase angle change versus applied force can be used in touch sensing. Also, the PVA–Ag NP nanocomposite–based sensor mounted on a glove was tested in an application consisting of holding and lifting a full bottle, with measurements taken over an impedance analyzer circuit. The concept of determining the point where force is applied and the magnitude of the force are demonstrated using the SA–CB nanocomposite–based sensor. In addition, the frequency responses of the sensors produced without any substrate were examined in certain frequency ranges and their equivalent circuits were created.
The obtained data show that polymer nanocomposite–based flexible tactile sensors perform the sensing function effectively. In addition, taking impedance measurements for the analysis of sensors in different designs gave the opportunity to evaluate both the capacitive and piezoresistive properties of the sensor at the same time. It has been shown that sensors in different frequency ranges can have different operating mechanisms and equivalent circuits can be determined accordingly. It has been demonstrated that the change in resistance and capacitance can be used for touch sensing, as is usually the case, and depending on the design, the phase angle change can be used for the same purpose.
2023-01-01T00:00:00Z