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711.
A microscopic laser-induced breakdown spectrometer was used to evaluate the analytical matrix effect commonly observed in the analysis of geological materials. Samples were analyzed in either the powder or pressed pellet forms. Calibration curves of a number of iron and aluminum compounds showed a linear relationship between the elemental concentration and peak intensity. A direct determination of elemental content can thus be made from extrapolation on these calibration curves. To investigate matrix effects, synthetic model samples were prepared from various iron and aluminum compounds spiked with SiO2 and CaCO3. The addition of these matrices had a pronounced analytical effect on those compounds prepared as pressed pellets. However, results indicated the absence of matrix effects when the samples were presented to the laser as loose powders on tape and results were compared to certified values, indicating the reliability of this approach for accurate analysis, provided the sample particle diameters are greater than ≈100 μm. Finally, the simultaneous analysis of two different elements was demonstrated using powders on tape. 相似文献
712.
Dominic Walsh 《Angewandte Chemie (International ed. in English)》2009,48(25):4474-4474
John Wiley & Sons, Hoboken 2008. 400 pp., hardcover € 129.00.—ISBN 978‐1405167826
713.
本文研究了三种物资同时段需求的EOQ模型,从理论以及实例均说明了该模型相对单一物资的EOQ模型,能够缩小这三种物资对仓库的占用空间,该模型在实际问题中要求需求和采购价格均随着时间的变化而变化,通过算法计算得到了满足三种物资同时段需求的最佳采购次数,最后得出了所要建立满足需求的最小仓库容量. 相似文献
714.
Yoshimasa Tani Kazunori Sato Hiroshi Katayama-Yoshida 《Physica B: Condensed Matter》2012,407(15):3056-3058
Based on ab initio electronic structure calculations by self-interaction-corrected local-density-approximation (SIC-LDA) with the Korringa–Kohn–Rostoker coherent potential approximation (KKR-CPA), we propose a materials design for high efficiency photovoltaic solar cells (PVSCs). It is shown that (i) the concentration dependence of the mixing energy of CuIn1−xGaxSe2 shows upward convexity, thus this system favors phase separation. Due to the type II band alignment between CuInSe2 and CuGaSe2, efficient electron–hole separation is realized in decomposed phase of this system. (ii) CuIn1−xZn0.5xSn0.5xSe2 has a direct band gap and no impurity state appears in the gap. Therefore, cost reduction is possible by using Zn and Sn instead of In. (iii) n-type CuAl1−xSnxS2 and p-type Cu1−xVCuxAlS2 have negative activation energy for doped impurities and are expected to be low-resistive transparent conducting sulfides, which should be useful for CuInSe2-based PVSCs. 相似文献
715.
Sangita Dhara Nand Lal Misra Uday Kumar Thakur Dipti Shah R. M. Sawant K. L. Ramakumar Suresh K. Aggarwal 《X射线光谱测定》2012,41(5):316-320
A total reflection X‐ray fluorescence (TXRF) method for the determination of chlorine at trace levels in nuclear fuel samples is described. Chlorine present in trace concentrations in nuclear fuel materials such as U3O8, (U,Pu)C, PuO2 and Pu‐alloys was first separated from the solid matrix by pyrohydrolysis as HCl and was collected in 5 mM NaOH solution. This solution was analyzed for chlorine by TXRF spectrometry using Cl Kα analytical line excited by W Lα. Cobalt was used as internal standard. The precision for such chlorine determination was found to be within 27% (n = 4) when the analysis was carried out in air atmosphere. This could be improved to 8% by making TXRF measurement in flowing helium atmosphere. The results obtained from TXRF determinations were also compared with those obtained from ion chromatography (IC) and were in good agreement. The collection of distillate during pyrohydrolysis in NaOH helped in counterchecking loss of chlorine during TXRF sample preparation. The average deviation of TXRF‐determined values in helium‐purged TXRF measurements with IC determined values (as chloride) was 15% at a chlorine concentration level in the range of 1–70 µg/mL. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
716.
717.
We present the results of tests performed in a reverberation room measuring reverberation time with different acoustic absorbent materials in different layouts, compared to those results where the same material was placed as a single piece. With the analysis of the obtained data, a regression model is established in order to predict, for certain frequencies, the improvement produced in the reverberation time of a room, using the same amount of material by placing it in pieces separated from each other, instead of in one piece. The analysis also prove the sturdiness of the model. 相似文献
718.
Markus Grandl Thomas Kaese Anke Krautsieder Dr. Yu Sun Dr. Frank Pammer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14373-14382
Ladder‐type organoboranes featuring intramolecular N→B coordination have been prepared through hydroboration of a 2‐(ortho‐styryl)pyridine ( PhPy ) with a series of hydroboranes, including 9H‐9‐borabicyclo[3.3.1]nonyl (9H‐BBN), BH3 ? THF, HBCl2 ? SMe2, HB(C6F5)2, and a 9H‐9‐borafluorene derivative. The hydroboration reaction results in highly regioselective borylation under mild conditions and gives the products in good to excellent yields. The molecular structure and electronic properties of the obtained boranes have been experimentally investigated in detail, and complemented with DFT calculations to further elucidate the origin of differences in optical and electronic properties. The electron affinity of the conjugated system can be controlled through variation of the borane, while the optical properties are likewise directly linked to the type and molecular structure of the substituents on boron. The broad substrate range shows that this preparative approach is widely applicable to introduce chemically diverse boryl groups into conjugated systems. 相似文献
719.
Fuel pins from the UK's Advanced Gas-cooled Reactors (AGR) consist of ceramic UO2 fuel encased in a 20/25/Nb stainless steel cladding. Spent AGR fuel is currently reprocessed, but the option of direct disposal of spent fuel in a sealed, underground Geological Disposal Facility (GDF) is now under examination. It is assumed that over several thousand years groundwater from the environment will penetrate these barriers and come into contact with the fuel surface and steel cladding.Electrochemical studies on unsensitised samples of 20/25/Nb steel in simulant groundwater electrolytes have been performed, and show low corrosion currents, typically of the order μA/cm2, at the oxidative potential stresses found in such repositories. Whilst the cladding may therefore be considered to be passive short time periods, the very long timescales involved in a GDF project mean that these currents are sufficient to cause corrosion of the full thickness of the clad in a matter of decades.Furthermore, an increase in electrochemical potential from that expected of less than 50 mV is sufficient to initiate severe pitting corrosion in a matter of hours. It can therefore be assumed that there is a risk of cladding corrosion in a repository environment, and the corrosion products created may have implications for the chemistry of the spent fuel ceramic. 相似文献
720.
《Comptes Rendus Chimie》2015,18(4):379-384
In this report, fructose-derived carbonaceous spheres were utilized as sacrificial templates for the fabrication of metal oxide hollow spheres (MOHSs) by a facile hydrothermal approach. Hollow spheres of a series of crystalline metal oxides (α-Fe2O3, Cr2O3, Co3O4, NiO, and ZnO) have been fabricated, utilizing the metal chloride as the oxide precursors. Heating of an aqueous solution of the metal chloride and fructose to moderate temperature in an autoclave affords a spherical composite consisting of a metal precursor shell sheathing a carbonaceous core. Subsequent removal of the interior carbonaceous cores by thermal treatment through oxidation in air produces free-standing crystalline oxides hollow spheres. The MOHSs were characterized by means of SEM, TEM, XRD, IR spectroscopy, energy dispersive X-ray (EDX) and sorption measurements. The results show convincingly that using fructose as a sacrificial template after application of a hydrothermal synthesis route could be a favourable sacrificial template for the fabrication of various MOHSs. 相似文献