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991.
Fred T. Tracy 《PAMM》2007,7(1):2020025-2020026
Lumping of the mass matrix for transient problems is the state of the practice for finite element groundwater programs. This improves nonlinear convergence where there is unsaturated flow, but the discovery was made that the accuracy of the results is reduced significantly for a test problem. This paper compares results from a recently derived transient three-dimensional (3-D) analytical solution for a given unsaturated flow test problem with those obtained from a standard parallel Galerkin 3-D finite element groundwater program with the mass matrix lumping option turned both on and off. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
992.
993.
994.
Jeanette Adams Fred H. Strobel Alex Reiter M. Cameron Sullards 《Journal of the American Society for Mass Spectrometry》1996,7(1):30-41
The occurrence of charge-separation reactions in tandem mass spectrometry of doubly protonated angiotensin II is demonstrated by the use of mass-analyzed ion kinetic energy spectrometry (MIKES) and kinetic energy release distributions (KERDs). Linked scans at a constant B/E severely discriminate against product ions formed by charge-separation reactions. Although the products are significantly more abundant in MIKES experiments, instrumental discrimination still makes quantitation of relative product ion abundances highly inaccurate. The most probable KERs (T m. p.) and the average KERs (T ave.) of the reactions are determined from the KERDs, and these values are compared to the KERs determined from the peak widths at half-height (T 0. 5). The measurement of T 0. 5 is a poor approximation to T m. p. and T ave.. The T m. p. is used to calculate a most probable intercharge distance, which is compared to results from molecular dynamics calculations. The results provide evidence with regard to the mechanisms of fragmentation of multiply charged ions and the location of the charge site in relation to the decomposition reactions. 相似文献
995.
996.
Large eddy simulation (LES) results are reported for temporally developing solid–solid and solid–rigid-lid juncture flows. A MacCormack-type scheme that is second-order in time, and fourth-order in space for the convective terms and second-order in space for the viscous terms, is used. The simulations are obtained for a low subsonic Mach number. The subgrid-scale stresses (SGS) are modeled using the dynamic modeling procedure. The turbulent flow field generated on a flat-plate boundary layer is used to initialize the juncture flow simulations. The results of the flat-plate boundary layer simulations are validated with experimental and direct numerical simulations (DNS) data. In juncture flow simulations, the presence of an adjacent solid-wall/rigid-lid boundary altered the mean and the turbulent field, setting up gradients in the anisotropy of normal Reynolds stresses resulting in the formation of turbulence-induced secondary vortices. The relative size of these secondary vortices and the distribution of mean and turbulent quantities are in qualitative agreement with the experimental observations for the solid–solid juncture. The overall distribution of the mean and turbulence quantities showed close resemblance between the solid–solid and the solid–rigid-lid junctures; except for the absence of a second vortical region near the rigid-lid boundary. In agreement with the experimental observations, it was found that the normalized anisotropy term exhibited similarity when plotted against the distance from the boundary, regardless of the type of boundary, i.e. solid-wall or rigid-lid. The turbulent kinetic energy increased near the rigid-lid boundary. While the surface normal velocity fluctuations decreased to zero at the rigid-lid boundary, the other two velocity components showed an increase in their energy, which is also consistent with the experimental observations. © 1998 John Wiley & Sons, Ltd. 相似文献
997.
Prof. Qichun Zhang Dr. Jinchong Xiao Dr. Zongyou Yin Dr. Hieu M. Duong Fen Qiao Prof. Freddy Boey Prof. Xiao Hu Prof. Hua Zhang Prof. Fred Wudl 《化学:亚洲杂志》2011,6(3):856-862
We report the synthesis and characterization of a novel, stable and blue heteroacene, 2‐methyl‐1,4,6,7,8,9‐hexaphenylbenz(g)isoquinolin‐3(2H)‐one (BIQ 3 ). BIQ 3 , with its relatively small π framework, has an absorption λmax at 620 nm, which is larger than that of pentacene (λmax=582 nm), but BIQ 3 is more stable. The solutions of BIQ 3 are observed without any noticeable photobleaching on the order of days. In the solid state, it is very stable at ambient conditions and can be stored indefinitely. Owing to its pyridone end unit, BIQ 3 can display different resonance structures in different solvents (aprotic and protic) or Lewis acids to give different colors. The attractive stability exhibited by BIQ 3 is very desirable in organic semiconductor devices. Herein, we investigated a simple heterojunction photovoltaic device based on BIQ 3 as an electron donor and [6,6]‐phenyl‐C61 butyric methyl ester as an electron acceptor. Our results show that this type of heteroacene could be a good candidate as a charge‐transport material in organic semiconductor devices. 相似文献
998.
Goldstein Irving S. Bayat-Makooi Fred Sabharwal H. S. Singh T. M. 《Applied biochemistry and biotechnology》1989,(1):95-106
Satisfactory separation of either hydrochloric or sulfuric acid from sugars in wood hydrolyzates by application of membrane
technology is technically feasible. The permeability of disaccharides is less than 1% that of the acids. Acid flux in diffusion
dialysis is only 6% of acid flux at optimum current density in electrodialysis. Critical parameters for economic feasibility
are acid to wood ratio in hydrolysis, current efficiency, and membrane service life. Best case estimates project total costs
for sulfuric acid recovery and loss of about $0.02 per pound of glucose produced. 相似文献
999.
The mass spectrometry of cardenolides is briefly reviewed. Recent developments in the characterization of the cardiac glycosides by a combination of electron impact and field ionization methods are discussed, with emphasis on the information obtained regarding the sequence of monosaccharide residues in the case of oligosaccharide glycosides. Recent efforts to understand the detailed fragmentation behaviour of cardenolide aglycones in terms of their structure and substitution pattern are also discussed. 相似文献
1000.
The syntheses and crystal structures of the first cyanide, sulfur mixed ligand copper(I) complexes are reported. The first complex of the family was discovered when (CuCN)(3)(C(6)H(12)N(4))(2) (1) (C(6)H(12)N(4) = hexamethylenetetramine) was treated with aqueous thiourea. The sulfur ligands include thiourea (tu), 1,3-dimethyl-2-thiourea (dmtu), 1,3-diethyl-2-thiourea (detu), 1,1,3,3-tetramethyl-2-thiourea (tmtu), and 2-imidazolidinethione (N,N'-ethylenethiourea, etu). Synthesis was effected by adding the ligand to a solution of CuCN in aqueous sodium thiosulfate. Complex 2, (CuCN)(2)(tu)(3)(H(2)O), crystallizes in the triclinic space group P&onemacr;with unit cell dimensions a = 7.696(5) ?, b = 9.346(2) ?, c = 10.772(2) ?, alpha = 106.53(2) degrees, beta = 91.11(4) degrees, gamma = 98.42(3) degrees, and Z = 2. Complex 3, (CuCN)(3)(dmtu)(2), crystallizes in the monoclinic space group Cc with unit cell dimensions a = 10.082(3) ?, b = 14.984(5) ?, c = 11.413(3) ?, beta = 104.50(2) degrees, and Z = 4. Complex 4, (CuCN)(2)(detu)(H(2)O), crystallizes in the monoclinic space group P2(1)/n with unit cell dimensions a = 7.969(5) ?, b = 11.559(4) ?, c = 13.736(5) ?, beta = 100.48(4) degrees, and Z = 4. Complex 5, (CuCN)(tmtu) (polymorph a), crystallizes in the orthorhombic space group P2(1)2(1)2(1) with unit cell dimensions a = 8.653(1) ?, b = 9.426(1) ?, c = 11.620(3) ?, and Z = 4. Complex 6, (CuCN)(tmtu) (polymorph b), which has the same connectivity as 5, crystallizes in the triclinic space group P&onemacr; with unit cell dimensions a = 9.660(4) ?, b = 14.202(4) ?, c = 16.03(1) ?, alpha = 101.68(5) degrees, beta = 107.08(6) degrees, gamma = 70.07(2) degrees, and Z = 8. The difference between the polymorphs is that 5 has a zig-zag chain with a repeat unit of two while 6 has a 4-fold helix. Complex 7, (CuCN)(2)(etu), crystallizes in the monoclinic space group P2(1)( )()with unit cell dimensions a = 3.994(2) ?, b = 13.886(3) ?, c = 7.556(1) ?, beta = 97.07(2) degrees, and Z = 2. 相似文献