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

Utku, Feride Şermin | Özdemir, Ozan Enver | Bakay, Melahat Sevgül

Article | 2018 | Electrica18 ( 1 ) , pp.39 - 44

A molecularly imprinted polymer (MIP)-based impedimetric biosensor was developed for the electrochemical analysis of low-weight biological molecules. Synthetic polymeric matrices with specific and selective recognition sites, which are complementary to the shapes and sizes of the functional groups of analytes, can be prepared using the molecular imprinting method. In this study, a small molecule, tris(hydroxymethyl)aminomethane (TRIS), was used to coat a graphite pencil tip with a TRIS-containing polyacrylamide gel to fabricate a working electrode. The electrode modification and performance were evaluated using cyclic voltammetry an . . .d electrochemical impedance spectroscopy. The electrochemical properties of the modified electrodes were observed using an electrochemical cell comprising a Ag/AgCl reference electrode, a Pt wire as the counter electrode, and a pencil graphite tip as the working electrode using a redox-phosphate buffer solution with different concentrations of TRIS and Ethylenediaminetetraacetic acid (EDTA). The I–V and impedance performance of the chemically modified graphite pencil-tip electrodes exhibited decreased conductance and increased impedance correlating with the increase in TRIS concentration. Thus, MIP-based small-molecule biosensor prototypes can be promising economical replacements over other expensive sensors Daha fazlası Daha az

Aybar, İlknur Kuşbeyzi

Article | 2019 | Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi23 ( 5 ) , pp.1005 - 1011

In this study, we perform the stability and Hopf bifurcation analysis for two population modelswith Allee effect. The population models within the scope of this study are the one prey-twopredator model with Allee growth in the prey and the two prey-one predator model with Alleegrowth in the preys. Our procedure for investigating each model is as follows. First, weinvestigate the singular points where the system is stable. We provide the necessary parameterconditions for the system to be stable at the singular points. Then, we look for Hopf bifurcationat each singular point where a family of limit cycles cycle or oscillate. We provid . . .e the parameterconditions for Hopf bifurcation to occur. We apply the algebraic invariants method to fullyexamine the system. We investigate the algebraic properties of the system by finding allalgebraic invariants of degree two and three. We give the conditions for the system to have afirst integral Daha fazlası Daha az

Ertaş, Gökhan

Article | 2018 | Electrica18 ( 2 ) , pp.242 - 248

Melanocytic lesions are the main cause of death from skin cancer, and early diagnosis is the key to decreasing the mortality rate. This studyassesses the role of input-vector encoding in neural network-based classification of melanocytic lesions in dermoscopy. Twelve dermoscopicmeasures from 200 melanocytic lesions are encoded by compact encoding, ACD encoding, 1-of-N encoding, normalized encoding, and rawencoding, resulting in five different input-vector sets. Feed-forward neural networks with one hidden layer and one output layer are designedwith several neurons in the hidden layer, ranging from two to twenty-two for each type of . . .input-vector set, to classify a melanocytic lesion intocommon nevus, atypical nevus, and melanoma. Accordingly, 105 networks are designed and trained using supervised learning and then testedby performing a 10-fold cross validation. All the neural networks achieve high sensitivities, specificities, and accuracies in classification. However,the network with seven neurons in the hidden layer and raw encoded dermoscopic measures as the input vector realizes the highest sensitivity(97.0%), specificity (98.1%), and accuracy (98.0%). The practical use of the network can facilitate lesion classification by retaining the neededexpertise and minimizing diagnostic variability among dermatologists Daha fazlası Daha az

İnce, Ahmet T. | Snook, Richard D. | Dawson, John B.

Other | 2000 | Turkish Journal of Chemistry24 ( 1 ) , pp.43 - 58

A study of inherent noise sources present in a purpose built flame atomic magneto-optic rotation (AMOR) spectrometer system was carried out with a view to identifying their sources. Two different optical configurations were employed, a crossed polariser and a 45° offset polariser configuration. The offset polariser configuration was operated in both an AMOR and atomic absorption (AA) mode for the noise measurements. Two main interference frequencies were found to occur in all the optical measurement modes. An interference flame feature frequency (15.5 Hz -39.0 Hz) which arose from an "organ-pipe" effect in the gas flow . . . through the flame cooling sheets. The second interference frequency (at 100 Hz) was thought, to arise due to modulation of the analytes magneto-optic properties due to ripple on the electromagnet d.c. power supply. Photon noise and fluctuation noise were found to be present as background noise. The fluctuation noise was dominant at. higher analyte concentrations. The characteristics and origins of fluctuation noise are discussed and investigated for each measurement mode. The noise spectra of the conventional AA measurements were compared with those of the contemporary AMOR measurements, to ascertain any differences in noise power spectra which may affect, the signal-to-noise ratio 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

Yeğin, Korkut

Article | 2014 | Turkish Journal of Electrical Engineering and Computer Sciences22 ( 2 ) , pp.371 - 379

Wire antennas can be made wideband if the antenna is loaded with passive elements and connected to a lossless matching network. However, realization of the load component values and matching network can easily become impractical. In this study, using only a surface mount and standard component values, antenna loads and a matching network are optimized using genetic algorithms. The optimized design achieves a 25:1 bandwidth ratio, from 20 MHz to 500 MHz, with a maximum voltage standing wave ratio (VSWR) of 3.5 and minimum system gain of --5 dBi. The antenna system gain at azimuth is taken as the objective function and an exact penalt . . .y function is formulated to take into account the VSWR over the design frequency band. A loaded antenna is built and measured to corroborate the simulations results. The realized antenna is only 0.14 lambda long at 20 MHz Daha fazlası Daha az

Saatçı, Gökhan Erkin | Tahralı, Necati

Other | 2003 | Havacılık ve Uzay Teknolojileri Dergisi1 ( 1 ) , pp.21 - 30

Malzemelerde oluşan yorulma hasarının incelenip önceden saptanabilmesi, yorulma kırılmalarını önleyebilmek için çok büyük önem kazanmaktadır. Yorulma konusundaki en önemli konu ise çeşitli değişken gerilmelere maruz kalan malzemelerin gösterdikleri birikimli hasarlardır. Bu çalışmada, çeşitli araştırmacılar tarafından ortaya konmuş birikimli hasar metotları sunulmuş ve bu metotlar 1013. Ord. Ana. Tam. Fabrikasında üretilen GTD model 4X4 askeri aracın çeşitli değişken gerilmeler altında çalışan aktarma elemanına uygulanmıştır. Her metodun kendine özgü kuralları bulunduğundan herbiri farklı sonuçlar vermiştir. Çalışmadaki amaç, pratik . . .te karşılaşılan çeşitli birikimli hasar durumlarında bulunan metotlardan hangisinin kullanılması gerektiğini saptamaktır. Formüllerde kullanılan çentik, yüzey düzgünlük, boyut faktörleri, gerilmelerin uygulanma yüzdeleri ve malzemenin mukavemet özellikleri, örnek gösterilen aracın aktarma organları üzerinde uygulanmış başka bir çalışmadan elde edilen sonuçlara göre alınmıştır. The prediction of fatigue failure in the materials has great importance in preventing of fatigue cracks. The most important thing in fatigue topic is the cumulative damage that can be seen in the materials subjected to several variable stresses. In this study, the cumulative fatigue failure methods that are created by several researchers, are represented and these methods are applied to the transmission component of "GTD model 4X4 military vehicle" that is being produced in "1013. Ord. Ana. Tam. Fabrikası" which is working under several variable stresses. Because of having special characteristics, each method gave different solutions. This study is aimed at the problem that is encountered in practice which is the choice of the method for the several different cumulative failure conditions. Notch, surface quality, dimension factors, stresses' applying percents and the material's strength properties that are used in the equations are taken from another study that is applied on this example vehicle's transmission elements Daha fazlası Daha az

Akgün, Hülya | Berk, Barkın | Erol, Demir Dilek | Mercanoğlu, Güldem | Bayrak, Faruk Ömer | Çağlayan, Berrak | Kurnaz, Aksan Işıl

Article | 2009 | Turkish Journal of Chemistry33 ( 1 ) , pp.107 - 121

New series of [(2-chloroethyl)ureido] benzoic acids (compounds 3-8) and nitric oxide releasing derivatives of [(2-chloroethyl)ureido] benzoic acid esters (compounds 9-14) were synthesized as potential anti-cancer agents. These compounds were screened for their anti-proliferative activities on A549 (human lung carcinoma) cells and for their cytotoxic effects on L929 (mouse fibroblast) cells. The compounds 3-8 exhibited mild cytotoxic effects on L929 cells (cell viability from 100% to 85% – 90% only) whereas they had very little antiproliferative activities towards A549 lung carcinoma cells. On the other hand, compounds 10, . . .11, and 13 had some growth inhibition activity in A549 (human lung carcinoma) cells. Among them, compounds 11 and 13 exhibited better anti-proliferative activities towards A549 cells, but also appeared to be cytotoxic towards L929 cells. In this group, the compound 10 with (1-(2-nitrooxyethyl)-3-[(2-chloroethyl)ureido]benzoate) structure appeared to have very weak anti-neoplastic activity towards A549 cells, with very little cytotoxic activity towards fibroblasts at physiological concentrations. Therefore, this compound is a better candidate for a potential anti-cancer therapy for non-small cell lung carcinomas. However, further studies are required in order to show applicability and effectiveness in animal models for this type of cancer 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

Gökhan, Nesrin | Köksal, Meriç | Küpeli, Esra | Yeşilada, Erdem | Erdoğan, Hakkı

Article | 2005 | Turkish Journal of Chemistry29 ( 4 ) , pp.445 - 454

The synthesis of a novel series of Mannich bases of 5-methyl-3-substituted piperazinomethyl-2-benzoxazolinones is described. The structures attributed to compounds 3c, 3d and 3f-3n were elucidated using IR and 1H NMR spectroscopic techniques as well as elemental analysis. The compounds were examined for their in vivo anti-inflammatory and analgesic activities in 2 different bioassays, namely, carrageenan-induced hind paw edema and p-benzoquinone-induced abdominal constriction tests in mice, respectively. In addition, the ulcerogenic effects of the compounds were determined. Among the derivatives tested the most promising results wer . . .e obtained for the compounds bearing electron-withdrawing substituents (F, Cl, COCH_3) in the para position of the phenyl nucleus on the piperazine ring at the 3 position of benzoxazolinone moiety (3a, 3c, 3i). The analgesic activities of all compounds are higher than their anti-inflammatory activities and therefore these high analgesic activities indicated that the compounds could a show central effect Daha fazlası Daha az

Özkaya, Mert

Other | 2018 | Havacılık ve Uzay Teknolojileri Dergisi11 ( 2 ) , pp.119 - 133

In this paper, the existing 31 different UML-based software modelling languages have been analysed for anumber of requirements that are believed to be highly important for practitioners. These requirements areformal semantics, multiple viewpoints modelling, model analysis, code-generation, and modelling toolset.According to the analysis results, only the UWE, TTool, Pi-ADL languages support all those requirements. While21% of the languages offer general-purpose notation set, the rest offer domain-specific notation set and the topdomains of interest are the multi-agent, embedded, and real-time systems. 38% of the languages use UML’sp . . .rofiling mechanism for extending UML, 18% of the languages extend UML’s class diagram, and 13% of thelanguages extend UML’s state and sequence diagrams. 41% of the languages support the logical viewpoint and36% support the behaviour viewpoint – the rest of the viewpoints are rarely used. 58% of the languages aredefined formally and many of them are based on formal verification languages. 44% of the languages ignoremodel analysis. Among the rest, 25% of the languages support the exhaustive model checking and 14% supportthe analysis for well-formedness. Generating software code from software models and the modelling toolsupport are the least supported requirements by the UML-based languages. Bu makalede, mevcut 31 farklı UML-tabanlı yazılım modelleme dili yazılımcılar için önemli olan bir takımgereksinimler bakımından analiz edilmiştir. Bu gereksinimler, biçimsel semantik, çoklu bakış-açısı ilemodelleme, modellerin analizi, modellerden kod üretme, ve modelleme araçları desteği olarak belirlenmiştir.Analiz sonuçlarına göre, 31 farklı UML-tabanlı modelleme dili arasından sadece UWE, TTool, ve Pi-ADLdillerinin tüm belirtilen gereksinimleri karşılayabildiği gözlemlenmiştir. UML-tabanlı dillerin 21%’i genelamaçlı diller olarak belirlenmişken, geri kalanı ise alana özgü dillerdir ve en yaygın olan alanlar ise gömülüsistemler, çok etmenli sistemler, ve gerçek zamanlı sistemlerdir. UML-tabanlı dillerin 38%’i UML’in profilmekanizmasını kullanarak UML’i genişletirken, 18%’i UML’in sınıf diyagramını ve 13%’ü UML’in durum vesıra diyagramlarını genişletmektedirler. UML-tabanlı dillerin 41%’i mantıksal bakış açısını desteklerken,36%’sı da davranış bakış açısını desteklemektedir. Diğer bakış açıları (aynı anda kullanım, fiziksel, dağıtım, veoperasyonel gibi) pek destek görememektedir. UML-tabanlı dillerin 58%’inin semantiği biçimsel metotlarkullanılarak tanımlandığı belirlenmiştir. Dillerin 44%’ü modellerin analizini desteklememektedir. Geri kalanının25%’i ise kapsamlı model sınaması ile modellerin analizini desteklerken, 14%’ü ise dillerin biçim kurallarınagöre analizini desteklemektedirler. Yazılım modellerinin koda dönüştürülmesi hemen hemen hiçbir UML-tabanlıdil tarafından destek görmemektedir. Yine aynı şekilde, dillerin hemen hemen hiçbiri modelleme araçları iledesteklenmemektedir Daha fazlası Daha az