Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Experimental Investigation of Refractive Index Measurement of Common Solvents and Aqueous Solutions in the Infrared Wavelengths(2018) Yüksel, K.; İde, CWe proposed and experimentally demonstrated a fast and simple technique to measure refractive index of liquids. A commercial Optical Time-Domain Reflectometer (OTDR) was implemented for interrogating sensor tips from a remote location. The system uses Fresnel reflected light from standard single mode fiber tips as sensing points without requiring any chemical coating, delicate fiber components, and/or sophisticated architecture at the sensor head. We reported new measurements of refractive indices of common solvents and solutions at both 1550 nm and 1625 nm. The precision of the proposed measurement system was found to be in the order of 10-4. The experimental results have been validated by the way of theoretical calculations.Article Sensory and Sensorimotor Gating in Children With Subclinical Hypothyroidism(2023) Kocaaslan Atlı, Sibel; Olgaç Dündar, Nihal; Erdoğan, Uğraş; Evirgen Esin, Nur; Bayazıt, Turan Onur; Kahya, Mehmet Cemal; Çatlı, Gönül; Gençpınar, Pınar; Dündar, Bumin NuriObjective: Attention and learning problems have been reported in children diagnosed with subclinic hypothyroidism (SH). Sensory gating is an automatic phenomenon that is related to attentional processes. It is known that an impairment in sensory/sensorimotor gating negatively affects the signal processing mechanism and hence attention and learning processes. The aim of the present study was to evaluate the effect of SH on sensory gating processes via P50 suppression and prepulse inhibition (PPI) in children. Methods: Fifteen children aged 8-16 years, diagnosed with SH, and 15 healthy children were included in the study. Auditory P50 suppression and PPI paradigms were applied during the recordings. P50 suppression was examined via auditory brain potentials recorded by electroencephalography. PPI was evaluated via electromyography, in which the blink reflex was recorded by oculomotor muscle activity. Results: No statistical difference was found in P50 suppression and PPI processes between children in the SH and control groups. These findings indicate that the sensory gating processes children with SH are not affected. Conclusion: The findings of this study show that the sensory gating processes of SH children are not affected. However, considering that brain maturation continues until the age of 20s, it may be more useful to scrutinize these processes with a wider age range and a larger number of participants to reveal more clearly how sensory gating is affected by SH.Article Citation - WoS: 1Citation - Scopus: 1Resting Electroencephalography Differences Between Eyes-Closed and Eyes-Open Conditions in Children With Subclinical Hypothyroidism(AVES, 2023) Bayazıt, Onur; Kahya, Mehmet Cemal; Çatlı, Gönül; Kocaaslan Atlı, Sibel; Olgaç Dündar, Nihal; Erdoğan, Uğraş; Evirgen Esin, NurObjective: Electroencephalography changes that occur during the transition from eyes-closed to the eyes-open state in resting condition are related to the early phase of sensory processing and are defined as activation. The present study aimed to reveal the potential deteriorations that may occur in the initial period of sensory processing in resting electroencephalography between children with subclinical hypothyroidism and a control group. Materials and Methods: Electroencephalographies of 15 children with subclinical hypothy-roidism and 15 healthy children aged 10 to 17 years were recorded for 2 minutes for EC and 2 minutes for eyes-open conditions in resting state. Absolute electroencephalography band powers (μV2) within the delta, theta, alpha, and beta frequency bands were calculated in Fz, Cz, Pz, and Oz electrodes, respectively, for eyes-closed and eyes-open conditions. Results: The results show that, although there was no noteworthy difference between the powers of the electroencephalography frequency bands of children with subclinical hypothyroidism and healthy children during the eyes-open condition, the alpha powers of the control group were significantly higher in all electrodes during the eyes-closed condition. Furthermore, the powers of all frequency bands were observed to decrease in the eyes-open condition in the control group. However, the same net decrease was not observed in the frequency powers of children with subclinical hypothyroidism. Conclusion: According to the results of this study, children with subclinical hypothyroidism may experience information processing impairments starting in the early stages of sensory processing. © 2023, AVES. All rights reserved.Article Model-free output feedback controller design for twin rotor systems(Muğla Sıtkı Koçman Üniversitesi, 2020) Deniz, Meryem; Tatlıcıoğlu, Enver; Bayrak, AlperIn this work, tracking control of twin rotor systems is aimed. The control problem is restricted by the lack ofmathematical model of the twin rotor and further complicated by the unavailability of the angular velocitymeasurements. A model–free controller in conjunction with a high gain observer is designed. Experiments performed on atwin rotor system demonstrates the viability of the controller–observer couple.Article Synthesis and Characterization of Pollen Extract Mediated Gold Nanostructures(Bingöl Üniversitesi Fen Bilimleri Enstitüsü, 2020) Bakar, Fatma; Sönmez, Hamide; Evecen, Senanur; Turan, Buse; Demir, Mehmet; Gümüş, Abdurrahman; Çeter, Talip; Yazgan, İdrisThere is an increasing demand in the synthesis of shape and size-controlled gold nanostructures (Au NSs) with greener methods. Therefore, we aimed to synthesize differently shaped and sized Au NSs using a greener technique under ambient conditions. In this study, we utilized pollen extracts of Corylus avellana, Juniperus oxycedrus and Pinus nigra species (collected from Kastamonu region of Turkey) for the synthesis. The extraction was performed in water in order to recover water soluble content from the pollen grains. The extracts were used to stabilize, and shape/size direct the HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer synthesized Au NSs. UV-vis, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) characterizations proved synthesis of spherical, anisotropic and large Au NSs with this benign approach. The obtained Au NSs were possible to separate small and large Au NSs through centrifugation. Chemistry of pollen extracts played key role on morphology and stability of the Au NSs. The findings, for the first time, is revealing the synthesis of large Au nanorod bundles (>300 nm) along with hexagonal and spherical Au NSs under ambient conditions using pollen grain extracts, whose maturation took 24h.Article Citation - WoS: 5Citation - Scopus: 7Fast Texture Classification of Denoised Sar Image Patches Using Glcm on Spark(Türkiye Klinikleri Journal of Medical Sciences, 2020) Özcan, Caner; Ersoy, Okan; Oğul, İskender ÜlgenClassification of a synthetic aperture radar (SAR) image is an essential process for SAR image analysis and interpretation. Recent advances in imaging technologies have allowed data sizes to grow, and a large number of applications in many areas have been generated. However, analysis of high-resolution SAR images, such as classification, is a time-consuming process and high-speed algorithms are needed. In this study, classification of high-speed denoised SAR image patches by using Apache Spark clustering framework is presented. Spark is preferred due to its powerful open-source cluster-computing framework with fast, easy-to-use, and in-memory analytics. Classification of SAR images is realized on patch level by using the supervised learning algorithms embedded in the Spark machine learning library. The feature vectors used as the classifier input are obtained using gray-level cooccurrence matrix which is chosen to quantitatively evaluate textural parameters and representations. SAR image patches used to construct the feature vectors are first applied to the noise reduction algorithm to obtain a more accurate classification accuracy. Experimental studies were carried out using naive Bayes, decision tree, and random forest algorithms to provide comparative results, and significant accuracies were achieved. The results were also compared with a state-of-the-art deep learning method. TerraSAR-X images of high-resolution real-world SAR images were used as data.Article Implementation of Long-Perıod Fiber Gratings for Refractive Index Measurement of Liquids(Eskişehir Teknik Üniversitesi, 2018) İde, Cansu; Aldoğan, Kıvılcım YükselRefractive index (RI) is one of the optical parameters that is of paramount interest in characterizing liquid solutions and solvents. Increased public awareness and legal requirements for quality standards in different sectors have created a need for reliable, fast, automated, remote and/or portable refractive index sensors with multi-measurement capability. The fiber-based RI sensors are very good candidates in providing attractive solutions in such application areas and have been attracting a growing interest by the scientific community. In this work, a fiber optic refractive index sensor has been investigated. It uses a long-period fiber grating (LPFG) and an Optical Spectrum Analyzer (OSA), as sensor head and interrogator unit, respectively. New measurements of refractive indices of common solvents and solutions at the low-loss telecom wavelength band have been successfully demonstrated by using the proposed sensor. The reported measurement results are in excellent agreement with our simulation results and reference measurements realized by conventional measurement techniques.Article Citation - Scopus: 1Reconstruction of Geometrical and Reflection Properties of Surfaces by Using Structured Light Imaging Technique(Türkiye Klinikleri Journal of Medical Sciences, 2018) Ozan, Şükrü; Gümüştekin, ŞevketWhen a robust and dense surface reconstruction is aimed, structured light imaging techniques are usually much appreciated. In this paper we propose a method to reconstruct both geometrical and reflective properties of surfaces by using structured light imaging. We use a technique where a camera and a projector are both treated as viewing devices. They are calibrated in the same manner. Each visible point can be correctly located on both image planes without solving a correspondence problem; hence, a dense reconstruction can be obtained. Since both the camera and the projector are explicitly calibrated, lighting and viewing directions can be identified for each surface point. It is also possible to measure reflected radiance by using high dynamic range (HDR) images for each surface point. The lighting and viewing directions that are known after calibration are combined with the reflected radiance and the incoming irradiance measurements to determine the bidirectional reflectance distribution function (BRDF) values of the material at the reconstructed surface points. We illustrate the reconstruction of surface reflection properties of sample surfaces by fitting the Phong BRDF model to the BRDF measurements.Article Citation - WoS: 2Citation - Scopus: 2Quantification of Resistive Wall Instability for Particle Accelerator Machines(Türkiye Klinikleri Journal of Medical Sciences, 2019) Yaman, FatihThe aim of this study is to quantify longitudinal resistive wall impedances, corresponding wake functions, and wake potentials for different accelerator machines of interest. Accurate calculations of wake potentials by particle-in-cell codes are extremely difficult for the investigated parameters; therefore, we use an analytical approach and consider large domains with fine discretization for the required numerical integrations. The semianalytical wake potential computations are benchmarked against numerical general purpose 2D/3D Maxwell solver software codes and a different analytical approach for a certain set of parameters. We report examples to illustrate limitations of wake potential estimations from coupling impedances, and computations for the machines using realistic beam parameters and machine conditions. A numerical example where the aim is to find the wake potential of the machine from the 5% noisy impedance data is given.Article Development of a Phase-Otdr Interrogator Based on Coherent Detection Scheme(Uludağ Üniversitesi, 2018) Yüksel, Kıvılcım; Jason, Johan; Wuilpart, MarcWe present in this work, the experimental demonstration of a phase-sensitive Optical Time- Domain Reflectometer (phase-OTDR) having coherent detection scheme. An analysis algorithm has also been developed to calculate amplitude and phase evolution of the experimental phase-OTDR traces. The efficiency of the analysis algorithm to determine the position of the applied vibration has been verified for a single and two simultaneous vibrations. The slow-time analysis results show a good agreement with the mathematical calculations discussed in the paper. This work could have a technological implication in many fields such as distributed vibration sensor for railway monitoring applications.