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排序方式: 共有115条查询结果,搜索用时 23 毫秒
21.
Periodica Mathematica Hungarica - In this paper, we define the localization operator associated with the Riemann–Liouville operator, and show that it is not only bounded, but it is also in... 相似文献
22.
Hammami Asma Assaker Ibtissem Ben Chtourou Radhouane 《Journal of Solid State Electrochemistry》2022,26(1):211-218
Journal of Solid State Electrochemistry - In this work, we investigate the properties of manganese dioxide (MnO2) and graphene oxide (GO) to develop a new photoelectrochemical (PEC) sensor-based... 相似文献
23.
We introduce a generalized coercivity type condition for setvalued maps defined on topological spaces endowed with a generalized
convex structure and we extend Fan’s matching theorem. 相似文献
24.
25.
Alaa A. Hassan Aboul‐Fetouh E. Mourad Kamal M. El‐Shaieb Ashraf H. Abou‐Zied 《Journal of heterocyclic chemistry》2006,43(2):471-475
26.
Zied Hassen 《Journal of fluorine chemistry》2003,121(2):177-183
Ten phosphorylated β-hydrazones of structure R2P(O)C(NNHRF)CHR2′ were prepared in 54-91% yield by heating the allenes R2P(O)CHCCR2′ with fluorinated hydrazines H2NNHRF in chloroform or methanol [R=Ph, OCH2C(Me)2CH2O or OCH2C(Me)(Pr)CH2O, R′=H or Me and RF=CH2CF3 or C6F5]. Two cyclohexyl derivatives were prepared similarly from R2P(O)CHCCy. The triphenyl derivatives Ph2P(O)CH2C(NNHCH2CF3)Ph and Ph2P(O)CH2C(NNHC6F5)Ph were made in 91 and 68% yield by heating the ketones Ph2P(O)CH2C(O)Ph with an ethanol solution of the corresponding hydrazines. The stereochemistry of the hydrazones was determined by multinuclear NMR experiments. Compounds with C(NNHRF)Me groups exist as a mixture of Z and E isomers, with the Z form predominating (fluorinated group syn to phosphorus). Those with C(NNHRF)CHMe2, C(NNHRF)Cy or C(NNHRF)Ph groups were formed selectively, the Z isomers being the only products. The results are explained by steric hindrance, the bulkier isopropyl, cyclohexyl or phenyl group disfavouring the E configuration. , , , NMR data, coupling constants and IR data are reported. 相似文献
27.
F. De Corte L. Moens K. Sordo-El Hammami A. Simonits J. Hoste 《Journal of Radioanalytical and Nuclear Chemistry》1979,52(2):305-317
Some methods described in the literature for the determination of α in the 1/E1+α epithermal neutron spectrum are critically reviewed with respect to their accuracy. The multi resonance—detector method with
Cd-covered irradiations, as used by SCHUMANN and ALBERT, is generalized by subtracting the epithermal 1/v-tail and by introducing
the effective resonance energy, as defined by RYVES. The two-detector method of RYVES is modified by using Cd-ratio measurements,
thus eliminating the introduction of systematic errors due to the inaccuracy of absolute nuclear data. The adapted methods
are applied in channel 15 of the Thetis reactor (Gent).
Research Associate of the “Nationaal Fonds voor Wetenschappelijk Onderzoek” 相似文献
28.
We consider the classical limit of the Nelson model, a system of stable nucleons interacting with a meson field. We prove convergence of the quantum dynamics towards the evolution of the coupled Klein–Gordon–Schrödinger equation. Also, we show that the ground state energy level of \(N\) nucleons, when \(N\) is large and the meson field approaches its classical value, is given by the infimum of the classical energy functional at a fixed density of particles. Our study relies on a recently elaborated approach for mean field theory and uses Wigner measures. 相似文献
29.
Suppliers network in the global context under price discounts and uncertain fluctuations of currency exchange rates have become critical in today’s world economy. We study the problem of suppliers’ selection in the presence of uncertain fluctuations of currency exchange rates and price discounts. We specifically consider a buyer with multiple sites sourcing a product from heterogeneous suppliers and address both the supplier selection and purchased quantity decision. Suppliers are located worldwide and pricing is offered in suppliers’ local currencies. Exchange rates from the local currencies of suppliers to the standard currency of the buyer are subject to uncertain fluctuations overtime. In addition, suppliers offer discounts as a function of the total quantity bought by the different customer’ sites over the time horizon irrespective of the quantity purchased by each site. 相似文献
30.
A simple, fast and efficient liquid-liquid extraction (LLE) technique using headspace solid-phase microextraction (HS-SPME), in conjunction with gas chromatography-electron capture detection (GC-ECD) has been developed for the determination of haloacetic acids (HAAs) in tap water. The analytical procedure involves LLE, evaporation of extraction solvent to dryness, derivatization of HAAs into their methyl esters with acidic methanol, HS-SPME using 100-μm polydimethylsiloxane (PDMS) fiber, and GC-ECD determination. The derivatization process was optimized in dry conditions to achieve maximum sensitivity using the following conditions: esterification for 10 min at 55°C in 50 μL methanol, 30 μL sulphuric acid and 0.1 g anhydrous sodium sulphate. The HS-SPME conditions were also optimized and good sensitivity was obtained at a sampling temperature of 25°C, an absorption time of 10 min and a desorption time of 2 min. The linear calibration curves were observed for the concentration ranging from 0.1 to 200 μg/L with the correlation coefficients (R 2) greater than 0.993 and the relative standard deviation (RSD) less than 12%. The method detection limits of all analytes ranging from 0.02 to 0.7 μg/L were obtained. The proposed method is compared directly to standard EPA method 552.2 in drinking water, and significant advantage in terms of selectivity was observed. Finally the optimized procedure was applied to the analysis of HAAs in Bizerte drinking water. The studied HAA were detected in all the water samples and the concentration of total HAA5 ranged from 17.8 to 70.3 μg/L. 相似文献