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In this paper, a fiber optic based acoustic sensing system (FOTAS) is presented. Utilizing such cables as hundreds of acoustic movement detectors has become a novel approach for many security applications. Developed for securing critical infrastructures via utilizing both buried and fence-mounted cables, phase OTDR system FOTAS’s requirements, design, development, test and analysis modules are outlined. The detected movement type, location, magnitude are conveyed to the user via a user-friendly interface. Associated hardware, software, and utilized fiber optic network characteristics are presented. Detailed information about developed novel signal processing and artificial intelligencebased movement detection studies are provided. Real world data indicate that preliminary threat detection performance is more than 90%.

APCO Project 25 (P25) digital radios became widespread for either government or personal communication in the last two decades. Since the P25 standards are quite old, performance of its voice services is not satisfactory when compared to today's standards. Although 7200 bps Improved Multi-band Excitation vocoder used in P25 incorporates a decent rate of forward error correction, it does not provide fine error correction for noisy communication channels. In order to improve performance of P25 radios, we proposed a better forward error correction scheme which consists of 11/18 punctured convolutional coder and Viterbi decoder. The proposed forward error correction scheme provides 4.82 dB coding gain hence increases the performance of P25 radios.

Afet yönetim birimleri, güvenlik güçleri ve üniformalı çalışanların mobil telsiz haberleşme ihtiyaçları arttıkça, çift yönlü karasal mobil telsiz sistemleri analogdan sayısala doğru evrilmiştir. Sayısal telsizler analog telsizlere göre daha iyi ses kalitesi sunsa da konuşma kodlayıcı gerçekleme hataları ve yüksek çerçeve hata oranı durumlarında sesin anlaşılırlık ve kalitesi düşmektedir. Bu çalışmada ETSI TS 102 361 sayısal mobil telsiz standardı üzerinde çalışmalar yapılarak, sayısal mobil telsizlerin ses kalitesini arttırma amacına yönelik iki optimizasyon önerilmiştir. Bunlardan ilki; bit ve çerçeve hata oranlarını düşürecek nitelikte ve AMBE 3600 bps kodlayıcıda yer alandan daha iyi bir hata düzeltme planının kullanılmasıdır. İkincil öneri ise; ses şiddeti optimizasyonudur. Ses şiddeti optimizasyonu ile kodlayıcı çerçeveleri analiz edilerek, kodlayıcı ses şiddetini doyuma ulaştıran ve bozan etkiler azaltılmış veya tamamen ortadan kaldırılmıştır. Sayısal mobil telsizler için önerilen optimizasyonlar, sadece ses kodlayıcı üzerinde uygulanmış, sayısal mobil telsiz standardında herhangi bir değişiklik yapılmamıştır. Bu sebeple, optimizasyonların uygulanabilirliği oldukça basit ve düşük maliyetlidir. Sonuç olarak, önerilen hata düzeltme planının uygulaması sayesinde 2,95 dB kodlama kazancı sağlanmıştır. Kodlama kazancı ses şiddeti optimizasyonu ile birleştirilerek iletilen sesin kalitesi ve anlaşılabilirliği arttırılmıştır.

IEEE International Ultrasonics Symposium (IUS) (2014 : Chicago, IL), In CMUT based ultrasound catheter ablation systems, transducer arrays and their drivers are to be kept as small as possible due to size restrictions, while maintaining a reasonable number of channels for proper beamforming. In addition, these systems should be highly integrated with minimal power consumption for flexibility and functionality. Despite the size restrictions on these systems, such problems can be overcome by ASICs. In this work, we present a simple 8 channel high-frequency, high-voltage driver, together with its beamforming and control circuitry designed with AMS's H35 high voltage process.

IEEE International Ultrasonics Symposium (IUS) (2014 : Chicago, IL), In high intensity focused ultrasound (HIFU) the choice of transducer frequency depends on the target depth and tissue type. At high frequencies attenuation does not permit enough acoustical power to be transmitted to the target whereas at low frequencies the transmitted power is not absorbed efficiently. Hence, there exists an optimum frequency at which the power deposited at the target is maximum. In this study, we verified this relation experimentally using MR compatible focused transducers, ex-vivo tissue samples and magnetic resonance (MR) thermometry.

IEEE International Ultrasonics Symposium (IUS) (2017 : Washington, DC), High-intensity focused ultrasound (HIFU) have been an attractive research topic for some time now. HIFU studies have started with single-element transducers, but using arrays provide the opportunity to scan the focal point electronically. Modular and scalable driving systems that can be used with custom-made transducer elements to drive these arrays are needed and at the present time there are few such systems. In this work, a modular and scalable driver system was designed and manufactured to be used in various HIFU applications. Acoustic power output characteristics were examined with a hydrophone and scanning system. Heating tests were performed on ex vivo chicken breast tissue using a 16-channel annular array transducer and temperature increases were examined by using MR thermometry., National Magnetic Resonance Research Center (UMRAM)