Wyniki wyszukiwania - BazTech

1

Application of higher order Hamiltonian approach to nonlinear vibrating systems

Askari H., Nia Z. S., Yildirim A., Yazdi M. K., Khan Y.

Journal of Theoretical and Applied Mechanics

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2013

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Vol. 51 nr 2

287--296

EN

The higher order Hamiltonian approach is utilized to elicit approximate solutions for two nonlinear oscillation systems. Frequency-amplitude relationships and the model of buc kling of a column and mass-spring system are scrutinized in this paper. First, second and third approximate solutions of examples are achieved, and the frequency responses of the systems are verified by exact numerical solutions. According to the numerical results, we can conclude that the Hamiltonian approach is an applicable method for solving the nonlinear equations, and the accuracy of this method in the second and third approximates is very high and reliable. The achieved results of this paper demonstrate that this method is powerful and uncomplicated for solving of sophisticated nonlinear problems.

PL

W pracy przedstawiono zastosowanie metody Hamiltona wyższego rzędu do wyznaczania przybliżonych rozwiązań analitycznych dla dwóch nieliniowych układów drgających. Szczegółowej analizie poddano charakterystyki amplitudowo-częstościowe modelu ściskanej belki oraz dyskretnego układu sprężysto-inercyjnego. Otrzymano przybliżone rozwiązania pierwszego, drugiego i trzeciego rzędu, a odpowiedzi częstościowe układów porównano z dokładnymi rezultatami symulacji numerycznych. Na ich podstawie oceniono, że metoda Hamiltona jest stosowalna dla układów nieliniowych, a przybliżenia drugiego i trzeciego rzędu stanowią rozwiązania analityczne o wysokiej dokładności. Uzyskane w pracy wyniki przekonują, że zaproponowana metoda jest prostym i jednocześnie bardzo skutecznym narzędziem rozwiązywania nieliniowych problemów układów mechanicznych o dużym stopniu złożoności.

2

Patterns of fish communities along a mountain river : the Upper Coruh river (Turkey)

Yildirim A., Arslan M., Pegg M.

Polish Journal of Ecology

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2008

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Vol. 56, nr 4

731-736

EN

Distribution of fish communities along the submountain river (upper Coruh River, Northeastern of Turkey) was assessed to evaluate course of the longitudinal pattern in fish species diversity. The watershed area of Coruh Basin is 21.000 km[^2], river length 376 km and it flows into Black Sea in northeastern Turkey at average discharge of 149 m[^3] s[^-1] (range: 45.2.1215 m[^3] s[^-1]). Fixed-site electrofishing sampling at five sites located 15.210 km from river source at 2100-950 m a.s.l (Q values ranged 5.200 m[^3] s[^-1]) was conducted from March 2001 to March 2002. A total of 12 species were collected. Number of species (8-10) did not differ among sites suggesting no longitudinal changes, but Shannon-Wiener biodiversity index (H') increased downstream from 1.23 to 1.82. Two distinct fish assemblages were identified. Most abundant species were Leuciscus cephalus and Alburnoides bipunctatus. Both Oncorhynchus mykiss and Cyprinus carpio collected rarely are exotic fishes for Coruh River.

3

Determination of ciprofloxacin In human gingival crevicular fluid by high-performance liquid chromatography

Dincel A., Yildirim A., Caglayan F., Bozkurt A.

Acta Chromatographica

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2005

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No. 15

306-314

EN

A simple and selective high-performance liquid chromatographic (HPLC) method has been developed for determination of ciprofloxacin in human gingival crevicular fluid (GCF). GCF samples were collected with paper strips. Ciprofloxacin was extracted from the pooled strips with me-thanol–water, 50:50 (v/v), and separated on a cartridge column (Radial-pak C18, 100 mm × 8 mm, 10 žm) with acetonitrile–sodium dihydrogen phos-phate, 2:8 (v/v), as mobile phase at a flow rate of 2 mL min-1. The effluent was monitored with a fluorescence detector at 280 nm (excitation) and 455 nm (emission). The retention times of ciprofloxacin and internal standard quinine sulphate were 4.55 and 13.25 min, respectively. The within-day and day-to-day precision were less than 9% for ciprofloxacin at 0.05, 0.1 and 0.4 µg mL-1 (n = 6), the within-day and day-to-day accuracy values were in the range 96.33–102.67% for ciprofloxacin at the concentrations given above and the detection limit corresponding to a signal-to-noise ratio of 3:1 was 3 ng mL-1. This method was suitable and selective for determi-nation of ciprofloxacin levels in human GCF.