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71.
We discuss a C1-continuous time integration method based on piecewise cubic Hermite approximation. This method, denoted as p2-scheme, belongs to a class of one-step integration methods derived recently [1]. It exhibits a convergence rate of order four and shows properties similar to variational integrators, such as an excellent long-term energy preservation. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
72.
Sina Ober-Blöbaum 《PAMM》2016,16(1):821-822
Higher order variational integrators are analyzed and applied to optimal control problems posed with mechanical systems. First, we derive two different kinds of high order variational integrators based on different dimensions of the underlying approximation space. While the first well-known integrator is equivalent to a symplectic partitioned Runge-Kutta method, the second integrator, denoted as symplectic Galerkin integrator, yields a method which in general, cannot be written as a standard symplectic Runge-Kutta scheme [1]. Furthermore, we use these integrators for the discretization of optimal control problems. By analyzing the adjoint systems of the optimal control problem and its discretized counterpart, we prove that for these particular integrators optimization and discretization commute [2]. This property guarantees that the accuracy is preserved for the adjoint system which is also referred to as the Covector Mapping Principle. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
73.
Aliakbar Dehno Khalaji Gholamhossein GrivaniMorteza Rezaei Karla FejfarovaMichal Dusek 《Polyhedron》2011,30(17):2790-2794
Three mercury(II) complexes, [Hg((23-MeO-ba)2en)X2] (X = I (1), Br (2) and Cl(3)), and the ligand (23-MeO-ba)2en ((23-MeO-ba)2en = N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane) have been synthesized and characterized by elemental analyses, FT-IR and 1H NMR spectroscopy. The crystal and molecular structures of 1 and 2 were determined by X-ray crystallography from single-crystal data. The metal-to-ligand ratio was found to be 1:1. The mercury(II) center in 1 and 2 has a distorted tetrahedral geometry with HgN2I2 and HgN2Br2 chromophores, respectively. The Schiff base ligand (23-MeO-ba)2en acts as a chelating ligand, coordinating via the two nitrogen atoms to the mercury(II) center, and it adopts an E,E conformation. The coordination sphere of the mercury(II) center in 1 and 2 is completed by the two I and Br atoms, respectively. In complex 1 an inter-molecular non-classical hydrogen bond of the type C-H?O was found, while in complex 2 inter- and intra-molecular non-classical hydrogen bonds of the type C-H?X (X = O and Br) were found. The 1H NMR spectra of the complexes exhibit downfield as well as upfield shifts of the free ligand resonances, reflecting changes in the ligand’s geometry during its coordination. 相似文献
74.
Mahdi Rezaei Sameti 《中国化学》2011,29(2):237-242
13C NMR chemical shifts have been calculated for structures of some substituted 3‐anilino‐2‐nitrobenzo‐[b]thiophenes ( 2 o) and 2‐anilino‐3‐nitrobenzo[b]thiophenes ( 3 o) derivatives containing OH, NH2, OMe, Me, Et, H, F, Cl and Br. The molecular structures were fully optimized using B3LYP/6‐31G(d,p). The calculation of the 13C shielding tensors employed the GAUSSIAN 03 implementation of the gauge‐including atomic orbital (GIAO) and continuous set of gauge transformations (CSGT) by using 6‐311++G(d,p) basis set at density functional levels of theories (DFT). The isotropic and the anisotropy parameters of chemical shielding for all compounds are calculated. The predicted 13C chemical shifts are derived from equation δ=δ0+δ where δ is the chemical shift, δ is the absolute shielding, and δ0 is the absolute shielding of the standard TMS. Excellent linear relationships have been observed between experimental and calculated 13C NMR chemical shifts for all derivatives 相似文献
75.
Gholamabbas Chehardoli Mohammad Ali Zolfigol Seyedeh Bahareh Azimi Ebadollah Alizadeh 《中国化学快报》2011,22(7):827-830
Melamine and poly vinylpyrrolidone(PVP) reacted with neat sulfuric acid readily to form two new organic solid acids namely melamine-(H2SO4)3 and PVP-(H2SO4)n.These solid acids were used for the first nitration of bisphenol A as well as other phenols in the presence of NH4NO3.Mono- and di-nitro bisphenol A have been characterized with IR and 1H NMR techniques. 相似文献
76.
Ali Ramazani Morteza Rouhani Aram Rezaei Nahid Shajari Ali Souldozi 《Helvetica chimica acta》2011,94(2):282-288
Reactions of biacetyl (=butane‐2,3‐dione) with (N‐isocyanimino)triphenylphosphorane in the presence of aromatic carboxylic acids proceed smoothly at room temperature and under neutral conditions to afford 3‐(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)‐3‐hydroxybutan‐2‐one derivatives in high yields. 相似文献
77.
We describe the catalytic activity of the first chimeric ligase containing a foldameric sequence of β- and γ-amino acids. The chimeric backbone provides for the spatial arrangement of all functional groups involved in the formation of the catalytic site to allow efficient catalysis to take place. Our finding indicates significant progress in the field of functionally active artificial motifs. 相似文献
78.
Rezaei M Norooz Oliaee J Moazzen-Ahmadi N McKellar AR 《Physical chemistry chemical physics : PCCP》2011,13(27):12635-12639
Infrared spectra of a carbon disulfide trimer formed in a pulsed supersonic slit-jet expansion are obtained via direct absorption of a tuneable diode laser in the region of the CS(2)ν(3) fundamental (~1535 cm(-1)). This is the first high-resolution spectroscopic observation of (CS(2))(3). Two bands sharing the same lower state are assigned to ((12)C(32)S(2))(3). These correspond to the two infrared active trimer vibrations (a parallel and a perpendicular band) of the constituent CS(2) monomer asymmetric stretches. The weaker perpendicular band is centered at 1524.613 cm(-1), shifted by -10.74 cm(-1) with respect to the free CS(2) monomer. The parallel band is centered at 1545.669 cm(-1), a vibrational shift of +10.31 cm(-1). Transitions with K≠ 3n and those with K = 0, J = odd in the ground state are absent, establishing that this trimer has D(3) symmetry. The two parameters required to define this structure are determined to be 3.811 ? for the C-C bond distance and 61.8° for the angle between a monomer axis and the plane containing the C atoms. In addition, a parallel band arising from trimers with a single (34)S substitution is observed around 1544.46 cm(-1). Together with the recently observed cross-shaped CS(2) dimer, these results indicate a tendency for CS(2) to form highly symmetric clusters. 相似文献
79.
The impact of fractional wettability on the production characteristics of a VAPEX process at the macroscale was investigated.
Conventional VAPEX experiments were conducted in a 220 Darcy random packing of glass beads in a rectangular physical model
and n-pentane was used to recover the Cold Lake bitumen from the oil-saturated model in the absence of connate water. The composition
of oil-wet beads in the packed bed was altered from completely water-wet beads to completely oil-wet beads at different proportions
of oil-wet beads mixed with water-wet beads. A substantial increase (about 40%) in the production rate of live oil was observed
during the VAPEX process when the wettability of the porous packing was entirely oil-wet beads. A critical oil-wet fraction
of 0.66 was found for the heterogeneous packing of water-wet and oil-wet beads of similar size distribution. Above this critical
composition, the live oil production rate was not affected by further increase in the proportion of the oil-wet beads. It
is believed that above this critical composition of the oil-wet beads, the crevice flow process is dominated by the continuity
of higher conductivity live oil films between particles through the oil-wet regions. Below this critical composition, the
live oil production rate increased linearly with the fraction of the oil-wet beads in the packing. The oil-wet regions favor
the live oil drainage compared to that of the water-wet regions as they enhance the rate of imbibition of the live oil from
the oil-filled pores to the vacated pores near the nominal VAPEX interface. These two factors enhance the live oil production
rate during the VAPEX process. The solvent content of the live oil, the solvent-to-oil ratio (SOR), and the residual oil saturation
did not correlate strongly with the proportion of the oil-wet beads in the packing. The average solvent content of the live
oil and the residual oil saturation were measured to be 48% by weight and 7% by volume respectively. 相似文献
80.