Onur, Tuğba Özge | Hacıoğlu, Rıfat

Proceedings | 2017 | 2017 25th Signal Processing and Communications Applications Conference, SIU 2017

Reverberation and multipath propagation afîect the accuracy of time of flight (TOF) estimation in confined underwater medium. In this paper, time delay has been estimated by obtaining the transmitted signal and first echo signal from measured signal acquised by using a wideband transducer with 5 MHz central frequency. Cross-correlation (CC) and generalized cross-correlation (GCC) methods have been applied to the obtained signals and their performances have been compared. The results show that GCC method has better performance for time delay estimation in confined underwater medium where multipath propagation and reverberation are se . . .vere. © 2017 IEEE Daha fazlası Daha az

Onur, Tuğba Özge | Hacıoğlu, Rıfat

Proceedings | 2016 | 2016 24th Signal Processing and Communication Application Conference, SIU 2016 - Proceedings , pp.821 - 824

In this paper, two different methods are suggested in order to provide image enhancement in ultrasonic B-mode imaging. By obtaining RF data from two different phantom used to form B-mode image, their spectral characteristics were observed. Then by forming RF envelope from obtained data, conversion of envelope to color image is provided. Logarithmic compression and histogram equalization methods found in literature are used to improve image quality. From the results obtained, it is observed that both algorithms are effective based on the intended use when they are applied individually. © 2016 IEEE.

Onur, Tuğba Özge | Carlson, Johan E. | Svanström, Erika | Hacıoğlu, Rıfat

Article | 2017 | Erzincan Üniversitesi Fen Bilimleri Enstitüsü Dergisi10 ( 1 ) , pp.138 - 147

Elastik dalgalar, sadece gaz ve sıvılarda değil aynı zamanda katılarda da yayılırlar. Katılar, sıvı ve gazlarda olmayan form elastisitesine sahip olduğundan, katıların elastik özellikleri farklıdır. Bu nedenle, sadece boylamsal dalgalar değil aynı zamanda diğer dalgalar da katılarda yayılabilir. Katı içinde yayılan dalgalar kullanılarak hedefin konumu hakkında bilgi edinilebilir. Bu çalışmada ince düzlemlerde tek transdüktör kullanılarak ultrasonik dalga yayılımının modellenmesi yapılarak, uyarlamalı algoritma ile hedef uzaklığı kestirilmektedir. Elde edilen sonuçlarda, modellenen dalga yayılımında ultrasonik dalganın hızı ile birli . . .kte zaman gecikmesi uyartım noktasının sensöre olan uzaklığı ile ilintili olduğu için, uyarlamalı algoritma ile darbe cevabı başlangıç noktası belirlenerek hedef konumunun tespit edilebildiği görülmektedir. Elastic waves propagate not only in gases and liquids but also in solids. The elastic properties of solids are different since they have form elasticity which liquids and gases don't have. Because of this reason, not only longitudinal waves but also other waves can propagate in solids. Waves propagating in solids can be used to get information about target location. In this paper, modelling of ultrasonic wave propagation in thin plates is investigated by using a single transducer and target distance is estimated with adaptive algorithm. According to the obtained results, it can be seen that target location can be estimated by detecting the starting point of the impulse response with adaptive algorithm since the delay along with the velocity of ultrasound wave in the modelled wave propagation is related to the distance between the excitation point and sensor Daha fazlası Daha az

Onur, Tuğba Özge | Carlson, Johan E | Svanström, Erika | Hacıoğlu, Rıfat

Article | 2019 | Iranian Journal of Science and Technology - Transactions of Electrical Engineering43 ( 3 ) , pp.405 - 413

This paper demonstrates how flexural wave propagation in a thin plate can be modeled by estimating the combined effect of the excitation source signal and the impulse response of the ultrasonic sensor. The wave propagation in the plate is modeled using the wave equation for the flexural wave mode. A theoretical model for flexural wave propagation in thin plates has been derived, and it has been compared with measurements excited by tapping gently on the surface. The combined effects of the excitation source signal and the impulse response of the low-cost piezoelectric sensor are modeled using finite-impulse response and/or infinite- . . .impulse response filters. Thereafter, the performances of the selected filters are compared on estimating the wave propagation in a thin quartz glass plate. Results indicate that the most accurate estimation of wave propagation has been obtained using a linear phase filter which attributes all dispersions to the flexural wave. © 2018, Shiraz University Daha fazlası Daha az

Onur, Tuğba Özge | Hacıoğlu, Rıfat

Article | 2017 | Turkish Journal of Electrical Engineering and Computer Sciences25 ( 2 ) , pp.939 - 949

We investigated adaptive algorithms for a Hammerstein block structure in which a static nonlinear block and dynamic linear block are cascaded. The approach considered here is to use generalized orthonormal basis functions in a Hammerstein block structure by using xed pole lter banks. We applied the normalized least mean square approach to the developed adaptive algorithm in order to acquire Hammerstein block structure parameters. Performance comparison of the proposed approach was investigated considering convergence speed and parametric complexity for acoustic echo cancellation application. The results indicated that in the develop . . .ed algorithm along with appropriate selection of xed poles, the algorithm convergences faster and less parametric complexity is provided when compared to direct adaptive Hammerstein algorithms with IIR and FIR linear blocks. We investigated adaptive algorithms for a Hammerstein block structure in which a static nonlinear block and dynamic linear block are cascaded. The approach considered here is to use generalized orthonormal basis functions in a Hammerstein block structure by using xed pole lter banks. We applied the normalized least mean square approach to the developed adaptive algorithm in order to acquire Hammerstein block structure parameters. Performance comparison of the proposed approach was investigated considering convergence speed and parametric complexity for acoustic echo cancellation application. The results indicated that in the developed algorithm along with appropriate selection of xed poles, the algorithm convergences faster and less parametric complexity is provided when compared to direct adaptive Hammerstein algorithms with IIR and FIR linear blocks Daha fazlası Daha az

Onur, Tuğba Özge | Hacıoğlu, Rıfat

Proceedings | 2013 | 2013 21ST SIGNAL PROCESSING AND COMMUNICATIONS APPLICATIONS CONFERENCE (SIU) , pp.939 - 949

The speech signals are formed with echo caused by the reflections and also noise caused by engine, tyres, wind, etc during using hands-free voice communication in automobiles. In this paper, it has been focused on the adaptive filtering algorithms that based on eliminating purpose of not only noise removal but also separation in speech signals with echo and noise. It has been evaluated that the speech signals separation performance by comparing adaptive filtering methods that made with Least Mean Squares (LMS) and Recursive Least Squares (RLS) algorithms. Signals belong to near and far end speakers will be decomposed with each while . . . near-end and far-end speakers' signals affected by noise are decomposing from noise with the proposed adaptive algorithms. Furthermore, convergency and error analyses are performed by comparing the performances of LMS and RLS algorithms Daha fazlası Daha az

Onur, Tuğba Özge | Hacıoğlu, Rıfat

Proceedings | 2014 | 2014 22nd Signal Processing and Communications Applications Conference, SIU 2014 - Proceedings , pp.1323 - 1326

Time delay estimation has been used as a research area of significant practical important in many fields such as especially military system like localization, targeting, course acquisition also sonar, seismology, hands-free communications etc. In these applications, it is important to detect the delay and arrival times of ultrasonic echoes comprised in the medium for ultrasonic signals. Here, it is aimed to determine the time delay between the signals arrived from a signal source in order to detect the location. Hence, a system is suggested that uses a multi-surfaced waveguide with only one receiver instead of using receiver arrays. . . . By using this structure, time delay estimation is compared for different signal-to-noise ratios with Cross-Correlation, Maximum Likelihood and Phase Transform methods. © 2014 IEEE Daha fazlası Daha az

Onur, Tuğba Özge | Hacıoğlu, Rıfat

Proceedings | 2016 | 2016 24th Signal Processing and Communication Application Conference, SIU 2016 - Proceedings , pp.825 - 828

The spatially limited plane (SLP) wave can be created by exciting the ring transducer elements with different amplitudes and at different times. Although the ring transducer initially worked well, many transducer elements have become inoperative, due probably to service life and material life. The result of these bad elements is artifacts in the resulting spatially limited plane waves. In this study, the effects of bad elements of ring transducer system (RTS) which is used to obtain high quality images by using inverse scattering techniques in formation of the SLP wave are investigated. Also, the weighting of operative elements is e . . .xamined in order to compensate the bad ones. Results show that loses in the generated SLP wave can be compensated with correcting the artifacts of bad elements by using elements adjacent to the inoperative ones. © 2016 IEEE Daha fazlası Daha az