排序方式: 共有74条查询结果,搜索用时 265 毫秒
21.
Calvo Nati; Durany Jose; Munoz Ana I.; Schiavi Emanuele; Vazquez Carlos 《IMA Journal of Applied Mathematics》2006,71(1):62-91
** Email: nati{at}dma.uvigo.es*** Email: durany{at}dma.uvigo.es**** Email: anaisabel.munoz{at}urjc.es***** Email: emanuele.schiavi{at}urjc.es****** Email: carlosv{at}udc.es This paper deals with the numerical solution of a non-linearmodel describing a free-boundary problem arising in modern glaciology.Considering a shallow, viscous ice sheet flow along a soft,deformable bed, a coupled non-linear system of differentialequations can be obtained. Particularly, an obstacle problemis then deduced and solved in the framework of its complementarityformulation. We present the numerical solution of the resultingmultivalued system modelling the ice sheet non-Newtonian dynamicsdriven by the underlying drainage system. Our numerical resultsshow the existence of fast ice streams when positive wave-likeinitial conditions are considered. The solutions are numericallycomputed with a decoupling iterative method and finite-elementtechnique. A duality algorithm and a projected GaussSeidelmethod are the alternatives used to cope with the resultingvariational inequality while the explicit treatment, Newtonmethod or a duality method are proposed to deal with the non-linearsource term. Finally, the numerical solutions are physicallyinterpreted and some comparisons among the numerical methodsare then discussed. 相似文献
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We investigate the weight distribution of random binary linear codes. For 0 < λ < 1 and n→∞ pick uniformly at random λn vectors in and let be the orthogonal complement of their span. Given 0 < γ < 1/2 with 0 < λ < h(γ) let X be the random variable that counts the number of words in C of Hamming weight γn. In this paper we determine the asymptotics of the moments of X of all orders . 相似文献
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Determination of pharmaceutical compounds in sewage sludge using a standard addition method approach
Aida Garcia-Rodríguez Ester Sagristà Clàudia Fontàs Manuela Hidalgo Victòria Salvadó 《International journal of environmental analytical chemistry》2013,93(12):1199-1209
An analytical method for the simultaneous determination of eight pharmaceutical compounds in biosolids from urban wastewater treatment plants (WWTPs) was developed and validated. The compounds evaluated were non-steroidal anti-inflammatory drugs (naproxen, diclofenac, and ibuprofen), lipid regulators (clofibric acid), and antibiotics (sulfathiazole, sulfapyridine, sulfamethazine, and sulfamethoxazole). Ultrasound assisted extraction with a water–methanol solvent mixture (1:1, v:v) was performed and the compounds were then determined by liquid chromatography coupled with tandem mass spectrometry. The design of the method was based on the application of the standard addition calibration methodology to reduce matrix interferences. Validation procedures were conducted with rabbit excrements as blank samples. Recoveries of the target analytes ranged from 76 to 131% in spiked samples at 50, 200 or 1000 ng g?1 dry weight (dw). The relative standard deviations were in the range of 5–15% and the method detection limits ranged from 2 to 12 ng g?1dw. The method was applied to monitor pharmaceutical concentrations in biosolids from different WWTPs over an eight-month period (May to December 2011). Diclofenac, sulfapyridine and ibuprofen were detected in most of the samples whereas sulfamethazine and ibuprofen were the pharmaceuticals found in the highest concentrations (>200 ng g?1 dw on average). 相似文献
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Natić Maja M. Baošić Rada M. Milojković-Opsenica Dušanka M. Tešić Živoslav Lj. 《平面色谱法杂志一现代薄层色谱法》2005,18(5):344-348
JPC – Journal of Planar Chromatography – Modern TLC - Experimental RM values for two series of ß-diketonato complexes, M(acac)3-n(phacphac)n and M(acac)3-n(phSacphSac)n, where M... 相似文献
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Let r; s≥2 be integers. Suppose that the number of blue r-cliques in a red/blue coloring of the edges of the complete graph K n is known and fixed. What is the largest possible number of red s-cliques under this assumption? The well known Kruskal-Katona theorem answers this question for r = 2 or s = 2. Using the shifting technique from extremal set theory together with some analytical arguments, we resolve this problem in general and prove that in the extremal coloring either the blue edges or the red edges form a clique. 相似文献
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An optical sensor is described for the sensitive and selective determination of the Cr(VI) ion in aqueous solutions. The optode membrane is prepared by incorporating Aliquat 336 as an ionophore and a chromoionophore (4',5'-dibromofluorescein octadecyl ester) in a poly(vinyl chloride) (PVC) membrane containing ortho-nitrophenyloctyl ether (o-NPOE) as a plasticizer. The response to Cr(VI) is indicated by co-extraction of the target species and of hydrogen ions into the bulk of the membrane yielding large absorbance changes which can easily be measured in the visible spectral range. The optode membrane shows a reversible response in the concentration range of 1.1x10(-5)-1.0x10(-3) M and has been shown to be more selective towards the HCrO4(-) ion than other anions with a selectivity pattern HCrO4(-) > SCN- approximately = ClO4(-) > NO3(-) approximately = I- approximately = NO2(-) > H2PO4(-) approximately = Cl- approximately = SO4(2-). The sensing method developed has successfully been applied to the determination of Cr(VI) in spiked river water as well as in electroplating rinse waters. 相似文献
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In this paper we consider four previously known parameters of sign matrices from a complexity-theoretic perspective. The main
technical contributions are tight (or nearly tight) inequalities that we establish among these parameters. Several new open
problems are raised as well.
Supported by the ISF.
Supported by the ARC. 相似文献
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