Uçan, Osman N. | Osman, Onur | Gümüş, Aykal

Article | 2001 | Istanbul University Journal of Electrical and Electronics Engineering1 ( 2 ) , pp.149 - 168

In this paper, the performance of turbo coded signals are investigated over a new channel model, denoted as 1 ± Dn / Partial Response Fading Channels (PRFC) with imperfect phase reference. The combined effects of the 1 ± Dn /PRFC and nonideal coherent receiver on the phase of the received amplitude and of a noisy carrier reference are considered, each modelled by the Rician and Tikhonov distributions respectively. As an example, the jitter performance of turbo coded signals are evaluated over 1D / PRSC channel with different fading parameter K, effective signalto-noise ratio in the carrier tracking loop a, iteration nu . . .mber and data block size N. The numerical results clearly demonstrate the error performance degradation due to both amplitude fading and phase noise process Daha fazlası Daha az

Uçan, Osman N. | Osman, Onur | Osman, Onur

Article | 2001 | Istanbul University Journal of Electrical and Electronics Engineering1 ( 1 ) , pp.1 - 5

Bu makalede Turbo Kafes Kodlamalı (TKK) sistemlerin AWGN ve Rician ortamlarda faz bozulması durumunda hata başarımı elde edilmiştir. TKK yapısı ikili Turbo modülasyonu gibidir ancak TKK çok boyutludur. Turbo kodlamanın Kafes Kodlama ile birlikte kulanımı kodlayıcı yapısının değişimini gerektirir. Alıcıda ise ikili kodlayıcılarda olduğu gibi iteratif kod çözücü yapısı vardır. Burada 8PSK modülasyonda TKK farklı Rician katsayısı K, faz bozulma katsayısı a için benzetim sonuçları elde edilmiştir. Elde edilen sonuçlar hem genlikte hem de faz daki bozulmayı içermektedir. In this paper, we investigate the performance of Turbo Trellis Code . . .d Modulation (TTCM) over AWGN, and Rician channels and assume that phase disturbance is available. As we know Turbo Trellis Coded Modulation (TTCM) is similer to binary turbo codes, but employs Trellis Coded Modulation (TCM) codes which include multi-dimensional codes. The combination of turbo codes with trellis codes leads to a strigthforward encoder structure, and allows iterative decoding as binary turbo decoder. However, iterative Turbo Decoder needs to be adapted to the decoding of TCM codes. Here, we investigate TTCM for 8PSK for several Rician parameter K and effective signal-to-noise ratio in the cafrier tracking loop a. Thus, our results will reflect the degredations both due to the effects of the fading on the amplitude of the received signal and of a noisy carrier reference Daha fazlası Daha az

Çekiç, Yalçın | Şenay, Seda | Akan, Aydın | Chaparro, Luis F.

Article | 2005 | Istanbul University Journal of Electrical and Electronics Engineering5 ( 2 ) , pp.1411 - 1417

Multi-carrier spread spectrum (MCSS) communication systems are able to mitigate the effects of fading, interferences and Doppler frequency shifts as well as to support multiple access schemes. It is possible to get optimum performance from MCSS systems by carefully choosing the spreading sequences. However, due to inter-user interferences, performance degrades as the number of users increases unless the transmission channels are modeled and estimated. In this paper, we present a new spreading sequence obtained from a complex quadratic sequence multiplied by a pseudo random noise sequence, thus exploiting the properties of constant e . . .nvelope and statistical independence. Our approach is based on the time-frequency characterization of the wireless communication channel by means of discrete evolutionary transform. The properties of the new spreading sequence enables us to estimate the parameters of multi-user channels, both for uplink and downlink transmission cases, and design a receiver that is robust to channel noise, inter-user interference and intentional jammers. The performance of the proposed system is illustrated by simulations Daha fazlası Daha az

Şafak, Koray Kadir

Article | 2014 | Turkish Journal of Electrical Engineering and Computer Sciences22 ( 6 ) , pp.1611 - 1624

In this paper, methods to achieve actively powered walking on level ground using a simple 2-dimensional walking model (compass-gait walker) are explored. The walker consists of 2 massless legs connected at the hip joint, a point mass at the hip, and an infinitesimal point mass at the feet. The walker is actuated either by applying equal joint torques at the hip and ankle, by an impulse applied at the toe off, immediately before the heel strike, or by the combination of both. It is shown that actuating the walker by equal joint torques at the hip and ankle on level ground is equivalent to the dynamics of the passive walker on a downh . . .ill slope. The gait cycle for the simplified walker model is determined analytically for a given initial stance angle. Stability of the gait cycle by an analytical approximation to the Jacobian of the walking map is calculated. The results indicate that the short-period cycle always has an unstable eigenvalue, whereas stability of the long-period cycle depends on selection of the initial stance angle. The effect of the torso mass by adding a third link attached at the hip joint is investigated. The torso link is kept in the vertical position by controlling the torque applied to it. The proportional-derivative control law is utilized to regulate the angular position error of the torso link. Using linearized dynamics for this walker, active control is applied to the ankle, which reduces the dynamics of the walker to the passive walker without the torso. The proposed walker is capable of producing stable walking while keeping the torso in an upright positio Daha fazlası Daha az

Köksal, Meriç Akkoc | Yarım, Mine Yüksel | Durmaz, İrem | Çetin, Rengül Atalay

Article | 2012 | Turkish Journal of Chemistry36 ( 4 ) , pp.503 - 514

A series of 3-[(4-substitutedpiperazin-1-yl)methyl]-1H -indole derivatives were synthesized, and their structures were confirmed by spectral analysis. All the compounds were tested for their cytotoxic activity in vitro against 3 human tumor cell lines: human liver (HUH7), breast (MCF7), and colon (HCT116). Among the designed derivatives, most of the compounds showed significant cytotoxicity against liver and colon cancer cell lines with lower IC50 concentrations than the standard drug 5-fluorouracil. Compound 3s, with 3,4-dichlorophenyl substituent on the piperazine ring, was the most active in suppressing the growth of all screened . . . cancer cells Daha fazlası Daha az

Erdal, Cevat | Toker, Ali | Acar, Cevdet

Article | 2001 | Istanbul University Journal of Electrical and Electronics Engineering1 ( 2 ) , pp.267 - 273

Süreç kontrol endüstrisinde, orantı-türev-integral (PID) tip kontrolörler en önemli kontrol elemanlarından biridir. Uygulamada, analog kontrolörlerde genellikle işlemsel kuvvetlendiriciler kullanılmaktadır. Öte yandan ikinci nesil akım tasıyıcı ve akım geri beslemeli işlemsel kuvvetlendiriciler gibi akım çıkıslı olarak çalısan devreler, islemsel kuvvetlendiricilerle karşılaştırıldıklarında daha geniş bir frekans bandına, daha düşük güç tüketimi ile çalışma, ve daha iyi doğrusallık ve kararlılık özelliklerine sahip olduklarından, son zamanlarda oldukça çok dikkat çekmektedirler. Bu çalışmanın amacı akım tasıyıcılar (CCII) kullanarak . . .bir analog kontrolör gerçeklemek için gerekli tasarım yöntemini vermektir. Tasarımı yapılan PID devresi için optimum parametre toleransları hesaplanmıştır. Bu toleranslar önerilen PID kontrol edicinin duyarlık davranışlarının iyileştirilmesi ve kontrol edilmesinde kullanılabilirler. In process control industry, the proportional-integral-derivative (PID) controllers are one of the most important control elements. In practice, operational amplifiers are generally used in analog controllers. On the other hand, current-mode (CM) circuits such as second-generation current conveyors (CCII) and current feedback operational amplifiers (CFOA) have considerable attention due to their wider frequency band, lower power consumption, better linearity and stability properties compared to their voltage-mode counterparts, operational amplifiers. The purpose of this study is to present a synthesis procedure for the realization of analog PID controller by the use of CCIIs. For the designed PID circuit, the optimum parameter tolerances are determined. These tolerances can be used to improve and to control the sensitivity performance of the proposed PID controller Daha fazlası Daha az

Sak, Haşim | Güngör, Tunga | Safkan, Yaşar

Article | 2006 | Turkish Journal of Electrical Engineering and Computer Sciences14 ( 2 ) , pp.209 - 223

Speech synthesis is the process of converting written text into machine-generated synthetic speech. Concatenative speech synthesis systems form utterances by concatenating pre-recorded speech units. Corpus-based methods use a large inventory to select the units to be concatenated. In this paper, we design and develop an intelligible and natural sounding corpus-based concatenative speech synthesis system for the Turkish language. The implemented system contains a front-end comprised of text analysis, ,phonetic analysis, and optional use of transplanted prosody. The unit selection algorithm is based on commonly used Viterbi decoding a . . .lgorithm of the best-path in the network of the speech units using spectral discontinuity and prosodic mismatch objective cost measures. The back-end is the speech waveform generation based on the harmonic coding of speech and overlap-and-add mechanism. Harmonic coding enabled us to compress the unit inventory size by a factor of three. In this study, a Turkish phoneme set has been designed and a pronunciation lexicon for root words has been constructed. The importance of prosody in unit selection has been investigated by using transplanted prosody. A Turkish Diagnostic Rhyme Test (DRT) word list that can be used to evaluate the intelligibility of Turkish Text-to-Speech (TTS) systems has been compiled. Several experiments have been performed to evaluate the quality of the synthesized speech and we obtained 4-2 Mean Opinion Score (MOS) in the listening tests for our system, which is the first unit selection based system published for Turkish Daha fazlası Daha az

Ovant, Burak Sezin | Güney, Isa Ahmet | Savaş, Muhammed Emin | Küçük, Gürhan

Article | 2018 | Turkish Journal of Electrical Engineering and Computer Sciences26 ( 1 ) , pp.220 - 233

http://www.trdizin.gov.tr/publication/paper/detail/TWpVMU5qSXlNZz09 https://hdl.handle.net/20.500.11831/5334

Develi, Ahmet Çağrı | Olcay, Ali Bahadır

Article | 2017 | Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi21 ( 5 ) , pp.1081 - 1087

There have been developments on surface texturing methods providing benefit in a great many engineering applications.Especially, influence on surface texturing in lubrication applications related to frictional properties have been cause of concern.In the present study, it was aimed to work on the computational fluid dynamics (CFD) study of the lubrication system consistingof two parallel plates. While one of the plates was sliding, the other one was stationary and an incompressible two-dimensionalsingle phase flow was assumed between those plates. The scope of the CFD analysis was to determine the relationship betweendrag force and . . .operating fluid properties (i.e., oil types), rotational speed and the amount of the cavities. It was realized that SAE0W-30 was found to be the best fluid among the seven studied oil types providing optimal conditions such as high drag reductionand less drag force. It was noticed that the drag coefficient thus, drag force appeared to be increasing as the rotating disk speedrose. The influence of the number of the cavities along the textured surface was also investigated in the present study and it wasfound that drag reduction was not associated with the number of cavities because 0, 1, 2 and 3 cavities nearly gave the same dragforce values. Yüzey dokusu yöntemlerinde gelişmeler yaşanırken bu gelişmelerden birçok mühendislik uygulamaları fayda sağlayabilir.Özellikle sürtünme özellikleri ile ilgili yağlama uygulamalarında yüzey dokusu etkisi önemli bir etkiye sahiptir. Bu çalışmakapsamında iki paralel plakadan oluşan yağlama sisteminin hesaplamalı akışkanlar dinamiği çalışmasıyla incelenmesihedeflenmiştir. Plakalardan birisi hareket ederken, diğer plaka sabittir ve plakalar arasındaki akış, sıkıştırılamaz, iki boyutlu vetek fazlı olarak kabul edildi. Hesaplamalı akışkanlar dinamiği analizinin amacı direnç kuvvetindeki azalmanın, çalışan akışkanözellikleri (yani yağ çeşidi), açısal hız ve boşluk miktarı ile nasıl ilişkili olduğunu belirlemektir. Bu çalışmada SAE 0W-30 tipiyağın, çalışılan yedi yağ arasında en yüksek direnç düşüşü ve daha az direnç kuvveti sağladığı için en uygun koşulları sağlayanakışkan olduğu belirlenmiştir. Direnç katsayısının ve dolayısıyla direnç kuvvetinin açısal hızın artmasıyla arttığı fark edilmiştir.Boşluk sayısının yüzey dokusuna etkisi de bu çalışma kapsamında araştırılmıştır ve dirençteki azalmanın boşluk sayısı ile ilişkiliolmadığı bulunmuştur. Bunun nedeni 0, 1, 2 ve 3 boşluk yerleştirildiğinde neredeyse aynı direnç kuvvetleri elde edilmiştir Daha fazlası Daha az

Ertaş, Gökhan | Gültekin, Nida

Article | 2018 | Süleyman Demirel Üniversitesi Fen Bilimleri Enstitüsü Dergisi22 ( 1 ) , pp.32 - 37

The respiration pattern represents the volume of air in the lungs as afunction of time during human respiration process. Abnormal changes in thispattern can be signs of several diseases or conditions. There exit severalrespiration pattern detection methods. Among them, an easy technique relies onsensing the movements of thoracic and (or) abdominal regions. In this study, adevice based on thoracic motion tracking with complementary filtering has beendeveloped to detect the respiration pattern. The device is equipped with a motionsensor placed in a flexible belt housing a three-axis accelerometer and a three-axisgyroscope and a UART-t . . .o-USB converter providing computer connectivity. Thedevice is operated by a microcontroller that controls the operation of the motionsensor, applies complementary filtering to the motion data acquired and transfersthe results to a personal computer. The device is powered from the computer it isconnected to. Experiments with using the device during continues inhaling andexhaling, deep inhaling followed by breath-hold and deep exhaling followed bybreath-hold respiration activities in standing, lying and seated postures show thatthoracic motion tracking with complementary filtering may provide quite wellrespiration pattern detections. Solunum motifi, insan solunum işlemi sırasında zamanın bir fonksiyonuolarak akciğerlerdeki hava hacmini temsil eder. Bu desendeki anormaldeğişiklikler birtakım hastalıkların veya durumların belirtileri olabilir. Solunummotifinin tespitinde birçok yöntem bulunmaktadır. Bunlar arasında kolay birteknik göğüs ve (veya) karın bölgelerinin hareketlerinin algılanmasınadayanmaktadır. Bu çalışmada, tamamlayıcı filtreleme ile göğüs hareket izlemeyedayalı bir solunum deseni tespit cihazı geliştirilmiş bulunmaktadır. Cihaz esnek birkemer içine yerleştirilmiş üç eksenli bir ivmeölçer ve üç eksenli bir jiroskopbarındıran bir hareket algılayıcısı ve bilgisayar bağlantısı sağlayan bir UART-USBdönüştürücüsü ile donatılmıştır. Cihaz hareket algılayıcısının çalışmasını kontroleden, elde edilen hareket verilerine tamamlayıcı filtreleme uygulayan ve sonuçlarıkişisel bir bilgisayara aktaran bir mikrodenetleyici tarafından işletilmektedir.Cihaz bağlı olduğu bilgisayardan beslenmektedir. Ayakta durma, yatma ve oturmapozisyonlarında; sürekli nefes alma ve verme, derin nefes almayı takiben nefestutma ve derin nefes vermeyi takiben nefes tutma solunum aktiviteleri süresincecihaz kullanarak gerçekleştirilen deneyler tamamlayıcı filtreleme ile göğüshareketi izlemenin oldukça iyi solunum deseni tespitlerine imkân tanıyabildiğinigöstermektedir Daha fazlası Daha az