Elektrik-Elektronik Mühendisliği Bölümü / Department of Electrical and Electronics Engineering

Permanent URI for this collectionhttps://hdl.handle.net/11413/6818

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Open Access
Akciğer Basınçlarının İnvasiv Olmayan Yöntemler ile Kestirilmesi Amacıyla Akciğer Basınçları Ve Akciğer Sesleri Arasındaki İlişkinin Modellenmesi
(TÜBİTAK EEEAG Proje, 2020) SAATÇI, ESRA; Öztürk, Ayşe Bilge; SAATÇI, ERTUĞRUL; Akan, aydın
Solunum fonksiyon testleri solunum hastalıklarının teshis ve tedavisinin izlenmesinde kullanılırlar. Hastane ortamında yapılan bu testler pahalı cihazlara ve hastalar tarafından yapılan çesitli solunum manevralarına ihtiyaç duyarlar. Bu projenin amacı klinikte kullanılan solunum fonksiyon testlerinin yerine basit yöntemler ile solunum parametrelerinin bulunmasıdır. Bu amacı gerçeklestirmek için akciger basınçlarının girisimsel olmayan yöntemler ile kestirilmesi gerekmektedir. Basit mikrofonlar ile ölçülen akciger seslerinin ve havayolu gaz akıs hızı, sıcaklıgı ve nemi gibi çesitli solunum sinyallerinin istatistiksel ve fraktal sinyal isleme yöntemleri ile islenmesi bu projede önerilen temel yöntemdir. Solunum parametrelerinin kestiriminde bazı sinyal isleme yaklasımları önerilmis olsa bile solunum sesleriyle beraber istatistiksel ve fraktal sinyal isleme yöntemleri kombinasyonunun kullanılması bu projenin yenilikçi kısmıdır. Yapılan analizler sonucunda derin ve normal solunumların birlikte kullanıldıgı bronsial solunum sesinden elde edilen Hurst üstelinin agız içi basıncının kestiriminde en basarılı sonuçları verdigi görülmüstür. Ayrıca viskoelastik modelin yardımıyla kestirilen akciger basınçlarının gücü en iyi spirometrik testlerde FEV1 ve FVC parametreleriyle IOS testinde R5 parametresi ile ilişkilidir.
Open Access
A Broadband, Polarization Insensitive, Wide Incidence-Angle-Slotted Ring/Lumped Resistor-Based Metamaterial Absorber for K-u-Band Applications
(Istanbul University - Cerrahpaşa, 2021) AKŞİMŞEK, HÜSEYİN SİNAN
A broadband-slotted ring/lumped resistor-based metamaterial absorber (MA) is presented in this study for K-u-band microwave applications. Numerical results of the MA indicate that it can achieve a broadband absorption ratio of more than 85% in the frequency range of 12.4-17.6 GHz and has active polarization insensitivity and wide incidence-angle response over the entire operation band between 12.4-17.6 GHz. The designed MA is ultrathin around lambda/14.7 in terms of wavelength at its lowest operation frequency, corresponding to 1.7 mm. The proposed unit-cell structure of the MA is novel, consisting of a slotted ring with eight symmetrically-located lumped resistors, FR-4 material, and a metallic ground, which is compatible with low-cost PCB fabrication; therefore, the MA is suitable for practical microwave applications in the K-u-band.
Open Access
Design of 24-28 GHz band 5G Antenna Based on Symmetrically Located Circular Gaps
(Osman Sağdıç, 2020) ÖZPINAR, HÜRREM; AKŞİMŞEK, HÜSEYİN SİNAN
5G (fifth generation) cellular system is expected to work in a wide frequency range to meet the demand for mobile services and applications. Antennas will be addressed to the future 5G applications should pose superior characteristics, such as high gain and ultra-large bandwidth response by considering atmospheric absorption/free-space path loss on planned millimeter-wave frequency range of 5G communications. Therefore, antenna design for the future 5G applications is a challenging process. In this article we present a high-gain, broadband mm-Wave antenna based on a circular patch structure with a ground plane and resonator gaps. The designed antenna is analyzed using a widely used full-wave electromagnetic solver. The major antenna figure-of-merits including reflection coefficient, VSWR (voltage-standing wave ratio), antenna patterns in E- and H-planes, surface current distribution, antenna directivity and maximum gain, are obtained. The simulation results show that the gapped circular patch based design has the S11 response less than −10 dB in the frequency range of 21.6-28.8 GHz, which includes 24-28 GHz band of 5G cellular systems. Moreover, it is observed that the symmetrically located circular gaps on both top and bottom layers decrease the side lobe level under −10 dB value, and enhance the gain. We attribute the improvement in the antenna performance to the created current regions due to gaps hosting large vortex current distributions. With 10 mm × 13mm surface area, the proposed antenna demonstrates the peak gain of 9.44 dBi and the radiation efficiency of over 85%. High gain and compact size make this antenna suitable for coming 5G devices.
Open Access
Determination of Respiratory Parameters by Means of Hurst Exponents of the Respiratory Sounds and Stochastic Processing Methods
(IEEE-Institute of Electrical and Electronics Engineers Inc., 2021) SAATÇI, ESRA; SAATÇI, ERTUĞRUL
Objectives: System approach to the human respiratory system and input/output signals which characterize the system properties were not explored in detail in the literature. The aim of this study is to propose a combination of methods to investigate the indirect relationship between the fractal properties of Respiratory Signals (RS) and Respiratory Sound Signals (RSS) and the clinically measured respiratory parameters. Methods: We used Hurst exponent to reveal the fractal properties of RS and RSS and to estimate the pressures in the respiratory system. The combination of well-known statistical signal processing methods and optimization were applied to the experimentally acquired 23 records. Pearson correlation coefficient and Bland-Altman analysis were the chosen validation methods. Results: Considerable amounts of Hurst exponent values of RSS were found to be between 0.5 and 1, which means increasing trend or decreasing trend can be seen in RSS with fractional Gaussian process properties. Results of the pressure estimator revealed that internal pressure due to tissue viscoelasticity is higher than the pressure due to static elasticity. Feature power and skewness also provided distinctive results for all recordings. Conclusion: Hurst exponent values of the RSS are fruitful representation of the signals which bring the underlaying system characteristics into the surface. We illustrated that required number of sensors can be reduced in the feature calculation to ease implementation effort on the hardware of the handheld devices. Significance: Bland-Altman plots were very successful to demonstrate the connection between the sets of measured respiratory parameters and calculated features.
Open Access
IoT-Based Fire Detection: A Comparative Study of Machine Learning Techniques
(Niğde Ömer Halisdemir Üniversitesi, 2024) AYRANCI, AHMET AYTUĞ; Erkmen, Burcu
Fires that cannot be detected quickly become uncontrollable. The fires that start to spread uncontrollably pose a significant danger to humans and natural life. Especially in public and crowded areas, fires can lead to possible loss of life and massive property damage. Because of this, it is necessary to detect fires as accurately and quickly as possible. Smoke detectors used with Internet of Things (IoT) technology can exchange data with each other. In this study, data collected from two different types of IoT-based smoke detectors were processed using machine learning algorithms. The k-Nearest Neighbor (k-NN), Multilayer Perceptron (MLP), Radial Basis Function (RBF) Network, Naïve Bayes (NB), Decision Tree (DT), Random Forest (RF), and Logistic Model Tree (LMT) algorithms were used. The data obtained from the smoke detectors were processed using machine learning algorithms to create a highly successful model design. The aim of the study is to design an artificial intelligence-based system that enables the early detection of fires occurring both indoors and outdoors.
Open Access
Multifractal Behaviour of Respiratory Signals
(AVES Yayıncılık, İstanbul Üniversitesi-Cerrahpaşa, 2020) SAATÇI, ERTUĞRUL; SAATÇI, ESRA
In this study, to analyze the biomedical signals emerging from fractal structures in the human body, fractal analysis was used. Respiratory signals, such as airflow, mouth pressure, and lung volume, comprise a complex relationship that has not been inspected to date. Furthermore, the mechanism for which it is linked to the lung’s fractal structure has not been scrutinized to date. Thus, using a well-known method, known as multifractal detrended fluctuation analysis (MF-DFA), this study aims to determine both mono- and multi-fractal property of respiratory signals ,. The real signals were analyzed using the MF-DFA algorithm. Moreover, for different scales, generalized Hurst exponent values were calculated. The results demonstrated that respiratory signals are fractional Brown motion-type signals, whereas fractal properties demonstrate less intersubject change. Moreover, in addition to both airflow and lung volume, respiratory signals and sounds are multifractal signals. In conclusion, the presence of the lung’s long-memory property is the primary reason of multifractality.
Restricted
An Open-Source User Interface Development for Widely Used Low-cost Spectrometer Designs
(Istanbul Univ., 2020) GÜRKAN, GÜRAY
In this paper, the development and test stages of an open-source user interface are presented. The developed user interface is compatible with most of the low-cost camera-based spectrometer designs in the literature. The spectrum image of the light source that is acquired with the camera is cropped and analyzed in a real-time thread after interactive calibration which is a special feature of the user interface. Camera controls (such as brightness, contrast, saturation, exposure and etc.) are also available through the user interface. For user interface testing, a common spectrometer design that is composed of a light-guide tube with a narrow entrance slit in one end and an image sensor on the other is constructed. Various compact fluorescent lamps and light emitting diodes are applied as light source and the results are presented. Developed cross-platform user interface can be used with lowcost spectrometer designs especially involving a web camera.
Open Access
Speaker Accent Recognition Using MFCC Feature Extraction and Machine Learning Algorithms
(Marmara Üniversitesi, Fen Bilimleri Enstitüsü, 2021) AYRANCI, AHMET AYTUĞ; Atay, Sergen; Yıldırım, Tülay
Speech and speaker recognition systems aim to analyze parametric information contained in the human voice and recognize it at the highest possible rate. One of the most important features in the audio signal for the speaker to be recognized successfully by the system is the speaker's accent. Speaker accent recognition systems are based on the analysis of patterns such as the way the speaker speaks and the word choice he uses while speaking. In this study, the data obtained by the MFCC feature extraction technique from voice signals of 367 speakers with 7 different accents were used. The data of 330 speakers in the data set were taken from the "Speaker Accent Recognition" data set in the UC Irvine Machine Learning (ML) open data source. The data of the other 37 speakers were obtained by converting the voice recordings in the "Speaker Accent Archive" data set created by George Mason University into data using the MFCC feature extraction technique. 9 ML classification algorithms were used for the designed speaker accent recognition system. Also, the k-fold cross-validation technique was used to test the data set independently. In this way, the performance of ML algorithms is shown when the data set is divided into a k number of parts. Information about the classification algorithms used in the designed system and the hyperparameter optimizations made in these algorithms are also given. The success performances of the classification algorithms are shown with performance metrics.
Open Access
Sub-Block Aided OFDM with Index Modulation
(Bajece (İstanbul Teknik Üniversitesi), 2019) ACAR, YUSUF
Recently, orthogonal frequency division multiplexing (OFDM) with index modulation (IM) has been appeared as a novel method for future wireless communication systems. However, such a mechanism has low spectral efficiency since some sub-carriers are not activated in order to implicitly convey information. In this paper, a subblock dependent approach, called sub-block aided OFDMIM (SA-OFDM-IM) technique, is proposed for spectral efficiency enhancement of the OFDM-IM method with lower complexity. The simulation results illustrate that the proposed SA-OFDM-IM and well known OFDM-IM have same bit error rate (BER) performance while SA-OFDMIM has 40% more spectral efficiency with low complexity.

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