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81.
We show that any k-fold covering using translates of an arbitrary convex polygon can be decomposed into Ω(k) covers. Such a decomposition can be computed using an efficient (polynomial-time) algorithm. 相似文献
82.
Chaofeng Zhang Matt Quince Zhixin Chen Zaiping Guo Huakun Liu 《Journal of Solid State Electrochemistry》2011,15(11-12):2645-2652
In this work, the potential of using coconut shell, which is very cheap and readily available, for the production of graphitic nanocarbon three-dimensional networks is investigated. The three-dimensional carbon has been produced via the wet-impregnation of coconut shell powder with a transition metal catalyst. The novel process employed offers low costs and environmental advantages, with biological waste used in place of carbonaceous precursor as the feedstock. Nanocarbon/tin oxide composites were prepared via wet-impregnation and the solvothermal method, using tin chloride solution with the activated nanocarbon. The electrochemical performances of the three-dimensional nanocarbon doped with tin oxide and of activated nanocarbon alone as anode materials were investigated in rechargeable lithium ion batteries. One composite made by using the solvothermal method shows stable cyclic retention up to 100 cycles and delivers a high reversible capacity of about 405?mAh g?1. 相似文献
83.
Mohammad Reza Yaftian Saeed Rayati Daryoush Emadi Dominique Matt 《Analytical sciences》2006,22(8):1075-1078
The preparation of a lead-selective electrode based on 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-(diphenylphosphinoylmethoxy)calix[4]arene (1) as an ionophore is reported. The plasticized PVC membrane containing 30% PVC, 57% ortho-nitrophenyloctylether (NPOE), 4% sodium tetraphenylborate (NaTPB) and 9% ionophore 1 was directly coated on a graphite electrode. It exhibits a nearly Nernstian slope of 28.0 +/- 0.2 mV decade(-1) over a concentration range of 1 x 10(-5) - 1 x 10(-2) mol dm(-3) with a detection limit of 1.4 x 10(-6) mol dm(-3). The response time of the electrode was found to be ca. 17 s. The potential of the sensor was independent of the pH variation in the range 3.5 - 5.0. The selectivity of the electrode performance towards lead ions over Th4+, La3+, Sm3+, Dy3+, Y3+, Ca2+, Sr2+, Cd2+, Mn2+, Zn2+, Ni2+, Co2+, NH4+ Ag+, Li+, Na+ and K+ ions was investigated. The prepared electrode was used successfully as an indicator electrode for a potentiometric titration of a lead solution using a standard solution of EDTA. The applicability of the sensor for Pb2+ measurements in various synthetic water samples spiked with lead nitrate was also checked. 相似文献
84.
We discuss smoothness of theWeyl functional calculus and use it to prove that every C*-algebra is a confined Banach space.
Received: 17 August 2005 相似文献
85.
Matt J. Kipper Soenke Seifert P. Thiyagarajan Balaji Narasimhan 《Journal of Polymer Science.Polymer Physics》2005,43(5):463-477
Synchrotron small‐angle X‐ray scattering (SAXS) was used to study the isothermal crystallization kinetics of a family of polyanhydride copolymers consisting of 1,6‐bis(p‐carboxyphenoxy)hexane and sebacic acid monomers. In situ SAXS experiments permitted the direct observation of the crystallization kinetics. The structural parameters (the long period, lamellar thickness, and degree of crystallinity) were obtained from Lorentz‐corrected intensity profiles, one‐dimensional correlation functions, and interface distribution functions to form a comprehensive picture of the crystal morphology. The combination of these three analyses provided information not only on the lamellar dimensions but also on the polydispersity (nonuniformity) of these dimensions. Where possible, the crystallization kinetics were interpreted with a modified version of the Avrami equation. The results can be used to perform the rational design of controlled‐drug‐release formulations because crystallinity affects drug‐release kinetics. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 463–477, 2005 相似文献
86.
87.
NAA characterization of the new Bovine Liver SRM 总被引:2,自引:1,他引:1
R. Zeisler W. D. James E. A. Mackey R. O. Spatz R. R. Greenberg 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(3):783-787
The National Institute of Standards and Technology (NIST) is preparing a freeze-dried powdered bovine liver tissue Standard
Reference Material (SRM) to replace SRM 1577b Bovine Liver as the stock of this material was exhausted during 2006. Like the
original SRM 1577 issued in 1972, this renewal focuses on the key elements for diagnostic, nutritional, and toxicological
measurements that are important to medical, veterinary, and environmental sciences investigations. NIST’s approach for value
assignment included extensive characterization by neutron activation analysis (NAA). Difficulties in the determination of
some elements present at very low levels were overcome by use of radiochemical separations. Twentyone elements were characterized
in SRM 1577c by NAA. The previous materials, SRM 1577 and 1577b, served as quality control. 相似文献
88.
Ne KLL Auger satellite lines are measured with an energy resolution of 0.02% FWHM. The relative intensities of initial 2p vacancy satellite lines are observed to be four times larger with He+ than with H+ bombardment. The He+ beam also produces new satellite lines which are assigned to double initial 2p vacancies. 相似文献
89.
90.