Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/11

Browse

Filters

Settings

Scopus Q: search.filters.scopusQuartile.N/A

Search Results

Now showing 1 - 10 of 228
  • Article
    Experimental Investigation of Refractive Index Measurement of Common Solvents and Aqueous Solutions in the Infrared Wavelengths
    (2018) Yüksel, K.; İde, C
    We 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.
  • Conference Object
    Carrier Frequency Offset Based Shared Randomness for Secure Transmission in M-Psk Noma
    (IEEE, 2023) Göztepe, Caner; Karabulut Kurt, Güneş; Özbek, Berna
    Power domain non-orthogonal multiple access (NOMA) enhances spectral efficiency by superposing multiple users in the same time-frequency resource block at the expense of exposing the users' data. However, current approaches to improve the secrecy levels of users are limited to rate reduction. This paper proposes a secure NOMA system based on the shared randomness extracted from the reciprocal carrier frequency offsets (CFOs) between the transmitter-receiver pairs for M-ary phase-shift keying. As multiple users will have physically separated oscillators, it will result in independent CFOs among users. This randomness is used to introduce a constellation rotation in the transmitted symbols. We show that under ideal CFO estimates, the proposed approach achieves perfect secrecy among all NOMA users without introducing any rate reduction. We also demonstrate the practical applicability of the proposed approach by using a software-defined radio-based test bed. © 2023 IEEE.
  • Conference Object
    Detection Scheme for Pnc-Based Cell-Free Mimo Systems
    (IEEE, 2023) Cumali, Irem; Ozbek, Berna; Kurt, Gunes Karabulut
    Cell-free multiple-input multiple-output (cell-free MIMO) is a promising concept to overcome inter-cell interference and avoid non-uniform data rates among users by combining the best features of ultra-dense networks and MIMO. Hence, cell-free MIMO can fulfill the increasing demand on data rate with uniformly good coverage for the sixth-generation (6G) wireless communications. In addition to that, physical-layer network coding (PNC) reduces the transmission delay since it requires only two time slots instead of four time slots to exchange information between two users. In this paper, we propose a novel scheme called PNC-based cell-free MIMO to improve reliability further while reducing the transmission delay. We demonstrate the effectiveness of the proposed scheme regarding the bit error rate in different system configurations. The proposed PNC-based cell-free MIMO achieves significantly lower error probability than the conventional cell-free MIMO.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 1
    Görgül kip ayrıştırması kullanılarak optik faz kırınımında hassasiyet iyileştirilmesi
    (IEEE, 2023) Ataç, Enes; Dinleyici, Mehmet Salih
    Phase diffraction is a potent property used in transparent dielectric film characterization. The measured diffraction pattern on the camera is evaluated by matching numerically computed diffraction patterns to determine the optical properties of the ultra-thin films (refractive index, thickness, etc.). However, the obtained diffraction data is not only a nonlinear and non-stationary signal but also exhibits micron-scale variations, thus limiting the measurement accuracy. Therefore, it is challenging to identify shifts in minima and deviations in amplitude on diffraction data to extract information about the optical properties of phase objects. In this study, it is aimed to improve the thickness sensitivity of the system by applying Empirical Mode Decomposition (EMD) to plane wave-based near-field phase diffraction data. Since EMD is very sensitive to abrupt changes in the signal due to the spatial frequency components, the nanoscale variations in the film thickness become more observable and detectable. Experimental outputs and numerical simulations show that the decomposition increases the thickness sensitivity comparing the classical matching technique.
  • Conference Object
    Citation - Scopus: 2
    Parkinson hastalığı sınıflandırmasına yönelik ivmeölçer tabanlı zamanlama analizi
    (IEEE, 2023) Karaçalı, Bilge; Onay, Fatih
    Parkinson's disease is a neurodegenerative disorder caused by dopamine deficiency in the basal ganglia, resulting in cognitive and motor impairments. In this study, accelerometer signals were used to estimate the delay time between the command to start pedaling and the actual movement onset in three groups: healthy individuals (n=13), Parkinson's disease patients (n=13), and patients with freezing of gait symptoms (n=13). Features were extracted from the delay time distributions for each participant and subjected to a triple classification. Linear support vector machine achieved a classification accuracy of 69.2% for all participants. Notably, the average time to start pedaling was found to be significantly different among the three groups, and accelerometer-based timing analysis could be used as a diagnostic tool to assist clinical tests.
  • Conference Object
    Dalgacık gürültü giderme yöntemiyle mikrodalga bileşen karakterizasyonunun iyileştirilmesi
    (IEEE, 2023) Karatay, Anıl; Olcay, Bilal Orkan; Yaman, Fatih
    In this study, an efficient approach is presented to improve the characterization of various microwave components commonly used in communication and radar applications, such as antennas and power dividers. The components were initially simulated and then fabricated using the Computer Simulation Technology (CST) software. Vector Network Analyzer (VNA) measurements of the fabricated components were performed using a low-cost but noisy coaxial cable, and the measurement results were processed using a wavelet-based noise reduction method. For comparison purposes, the Haar and Daubechies-4 (DB4) wavelet functions were applied separately, and the results were examined. It was observed that the correlation and root mean square error between the ideal and measurement results improved in a positive direction with the noise reduction application. This approach provides significant cost and labor advantages, particularly when expensive elements such as gold and silver are used in coaxial cables that are physically free from noise. The experimental and numerical results show good agreement between the ideal simulation results and the filtered measurement results.
  • Conference Object
    Algıda gecikme ve kısa-ömürlü senkronizasyon temelli yeni bir hayali motor aktivite tanıma yaklaşımı
    (IEEE, 2023) Olcay, B. Orkan; Karaçalı, Bilge
    This study proposes a novel approach for investigating a brain-computer interface that considers the temporal organization of brain activity, explicitly accounting for perception latency. To this end, we aligned the onset of task periods with the concurrence of left parietal and parieto-occipital electrodes to obtain the timings of perception latencies. Then, activity-specific synchronization timings between channel pairs were calculated using the time-aligned task periods. The perception latency and activity-specific synchronization timings were subsequently used for feature extraction and classification. The proposed approach achieved significantly better performance when comparing the proposed approach with the method that did not account for the perception latency
  • Conference Object
    A Framework for Physical Layer Network Coding With Multiple Antennas for Bpsk
    (IEEE, 2023) İlgüy, Mert; Özbek, Berna
    Physical layer network coding (PNC) is combined with multiple antennas to increase the spectral efficiency of wireless communication systems. In this work, we present a PNC framework including both uplink and downlink for binary phase shift keying (BPSK). In the uplink, we propose a scheme for detecting network-coded symbol (NCS) with reduced complexity. For the downlink, we propose a transmission scheme of NCS through maximum ratio transmission (MRT) by defining the precoding vector as an average of users' channels. The bit-error-rate (BER) performances and the comparison results with the conventional scheme in both downlink and uplink are provided for the proposed low-complexity PNC framework.
  • 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 Nuri
    Objective: 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.
  • Research Project
    Bağımsız bileşen analizinin iletişim, imge işleme ve jeofizikteki uygulamaları
    (TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2006) Sankur, Bülent; Gençağa, Deniz; Kalkan, Olcay; Altınkaya, Mustafa Aziz
    Bu projede literatürde kaynak ayrıştırma olarak bilinen istatistiksel işaret işleme yöntemleri hem kuramsal açıdan, hem de uygulamaları açısından ele alınmıştır. Kuramsal çalışmalarda, kaynakların uzamda ve zamanda birbirlerinden bağımsız olmadıkları düşüncesiyle parçacık süzgeçleri yöntemi ele alınmıştır. Bu yaklaşımda süreç hakkında elimizde varolan önsel bilgilerin algoritmaya ağdırılması mümkün olmuştur. Ayrıca durağan olmayan süreçlerin de ayrıştırılma problemi ele alınmış, farklı yeniden örnekleme ve önem fonksiyonları seçerek literatürdeki teknikleri aşan sonuçlar bulunmuştur. Uygulamaya dönük çalışmalarda ise, jeofizik işaret işlemede klimatolojik verilere bakılmış ve gerek Kuzey Atlantik Salınımı diye adlandırılan olgu irdelenmiştir. Ancak topografık etkiler istenen sonuca ulaşılmasına engel olmuştur. Öte yandan sıcaklık verileri faktör analizi ile incelenmiş ve volkanik hareketlerin etkisi ortaya çıkarılmaya çalışılmıştır. Beyin-işaretleri konusunda özellikle prefrontal korteks bölgesinden bilişsel süreçlerle ilgili araştırmalar yapılmıştır. Deneklerin biliş esnasında beyindeki kan dengesinin, oksi- ve deoksi hemoglobinin değişimleri yakalanmaya çalışılmıştır. Bağımsız bileşen analizinin bu türlü dalga biçimlerini ortaya çıkarmakta çok etkili bir araç olduğu gösterilmiştir. Biyometri alanında, bağımsız bileşenler analizi hem yüz imgelerine hem de el imgelerine uygulanmıştır. Bağımsız-bileşenlerin deneklerin kimlik bilgilerini taşıyan ve bozucu etkilere karşı en dayanıklı öznitelikler olduğu görülmüştür. Nihayet bağımsız bileşen analizi CDMA: kod bölüşümlü çoklu erişim işaretlerine uygulanmış ve sönümlü kanallardaki alıcının performansını iyileştirici tasarımlar irdelenmiştir.