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171.
K. Huseyin 《International Journal of Non》1973,8(5):431-443
A special perturbation technique, employing several independent perturbation parameters, is outlined in general terms. The procedure is then illustrated with reference to multiple-parameter non-linear stability problems of a conservative structural field. Successive approximations to the associated stability boundary are obtained in parametric form. This is equivalent to the general mathematical problem of locating the points on a non-linear surface at which points the Hessian of a potential function vanishes. Such a problem can arise in relation to other branches of mechanics and applied mathematics and the technique described in this paper is readily applicable. A shallow circular arch subjected to combined uniform pressure and concentrated load at the apex is analysed for illustration. 相似文献
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173.
Gumus Ilkay Solmaz Ummuhan Binzet Gun Keskin Ebru Arslan Birdal Arslan Hakan 《Research on Chemical Intermediates》2019,45(2):169-198
Research on Chemical Intermediates - We synthesized and characterized a series of four closely related thiourea derivatives (1–4) obtained by reaction of 4-R-benzoyl chloride (R: H, Cl, CH3,... 相似文献
174.
Huseyin Serencam Mehmet Tufekci Ali Gundogdu Celal Duran Sibel Hamza 《International journal of environmental analytical chemistry》2013,93(14):1484-1499
A simple separation/pre-concentration method was developed for extraction of Pd(II) in various environmental samples, based on its adsorption of 4–phenyl–5–{[(4–phenyl–5–pyridin–4–yl–4H–1,2,4–triazole–3–yl)thio]methyl}–4H–1,2,4–triazole–3–thyol (PPTTMET) complex on Amberlite XAD–2010 resin in a mini column. The ligand has high affinity for Pd(II) among many other metals that are taken into consideration. The flame atomic absorption spectrometry is employed to determine the concentration of Pd(II). The optimum working conditions which were determined are as follows: 0.05?mol?L?1 HNO3 as working medium, 1.0?mol?L?1 HCI in acetone as elution solvent, 0.75?mg of PPTTMET amount and 750?mL of sample volume. The system was independent from the flow rates between 3.1 and 23.1?mL?min?1. The Pd(II) adsorption capacity of Amberlite XAD–2010 resin was found to be 12.8?mg?g?1 and the enrichment factor was calculated as 375. The method was successfully applied for the determination of Pd(II) in motorway dust samples, anodic sludge, gold ore, industrial electronic waste materials and various water samples. 相似文献
175.
176.
Cuneyt Sevim Asil Oztekin Ozkan Bali Serkan Gumus Erkam Guresen 《European Journal of Operational Research》2014
The purpose of this paper is to develop an early warning system to predict currency crises. In this study, a data set covering the period of January 1992–December 2011 of Turkish economy is used, and an early warning system is developed with artificial neural networks (ANN), decision trees, and logistic regression models. Financial Pressure Index (FPI) is an aggregated value, composed of the percentage changes in dollar exchange rate, gross foreign exchange reserves of the Central Bank, and overnight interest rate. In this study, FPI is the dependent variable, and thirty-two macroeconomic indicators are the independent variables. Three models, which are tested in Turkish crisis cases, have given clear signals that predicted the 1994 and 2001 crises 12 months earlier. Considering all three prediction model results, Turkey’s economy is not expected to have a currency crisis (ceteris paribus) until the end of 2012. This study presents uniqueness in that decision support model developed in this study uses basic macroeconomic indicators to predict crises up to a year before they actually happened with an accuracy rate of approximately 95%. It also ranks the leading factors of currency crisis with regard to their importance in predicting the crisis. 相似文献
177.
An NH2-MIL-53(Al)-DES(ChCl-Urea) nanocomposite was synthesized for extraction and determination of Rhodamine (Rh) 6G from environmental and cosmetic samples. The deep eutectic solvent (DES) was prepared by mixing choline chloride and urea in a mole ratio of 1:2. NH2-MIL-53(Al)-DES(ChCl-Urea) nanocomposite was synthesized using the impregnation method at a ratio of 60:40 (w/w). The optimum conditions were determined after NH2-MIL-53(Al)-DES(ChCl-Urea) characterization was performed. The optimum conditions were determined as pH 8, adsorbent amount of 15 mg, total adsorption-desorption time of 6 min, and enrichment factor of 20. The recovery values of the solid-phase extraction method for water and cosmetic samples under optimum conditions were between 95% and 106%. NH2-MIL-53(Al)-DES(ChCl-Urea) nanocomposite was an economically advantageous adsorbent because of its reusability of 15 times. All analyses were performed using the ultraviolet-visible spectrophotometer. The linear range, limit of detection, and limit of quantification of the method were 100–1000, 9.80, and 32.68 μg/L, respectively. The obtained results showed that the synthesized nanocomposite is a suitable adsorbent for the determination of Rh 6G in water and cosmetic samples. The real sample applications were verified with the high-performance liquid chromatography system. 相似文献
178.
Hamide Filiz Ayyildiz Fakhar N. Memon Irfan Ali Mangi Huseyin Kara 《Journal of separation science》2023,46(14):2200914
Multimode chromatographic separations are highly desirable in pharmaceutical and environmental sciences. Current study deals with the application of newly developed mixed-mode end capped-immobilized humic acid onto an aminopropyl silica based chromatographic column for separation and identification of six drugs belonging to different therapeutic groups for its applicability in pharmaceutical industries. For this, central composite design was used to evaluate the separation and resolution by optimization of three most effective parameters (acetonitrile%, flow rate, and pH of mobile phase). Second-order quadratic model was used to evaluate their effect on resolution of peaks; the probability value (<0.05) obtained from analysis of variance suggested the best applicability of the model. Desirability function was applied to calculate optimum conditions (44.8% acetonitrile, 1.75 mL/min of flow rate, and 7.5 pH) required to achieve maximum separation with good resolution within 11 min. The method was validated for linearity, precision accuracy, selectivity, and sensitivity. The results revealed a highly precise (coefficient of variance > 1%), linear (R2 = 0.99), and highly selective method. Moreover, the limit of detection/quantification values revealed acceptable sensitivity of the method. The developed column was compared for its efficiency with a commercially available column and found to be highly applicable for industrial applications. 相似文献