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31.
Complex [Zn2(bimb)2(mal)2(H2O)2]·4H2O (1) (mal=−OCOCH2COO−) was obtained by reaction of bidentate ligand 4,4′-bis(imidazole-1-ylmethyl)biphenyl (bimb) with zinc(II) salt of malonate, while the reaction of the same metal salt with 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (titmb) gives another novel complex [Zn2(titmb)2(mal)][mal]·12H2O (2). The structures of these complexes were determined by X-ray crystallography. The results revealed that 1 is a cyclic dinuclear complex in which the malonate groups act as terminators and prevent further aggregation, while 2 is a 2D honeycomb network in which each independent 2D sheet contains two sub-layers bridged by the malonate groups and complex 2 also contains free malonate as a counteranion connected to the 2D layer by C-H?O hydrogen bonds. The entirely different structure and topology of complexes 1 and 2, on the one hand, indicates that the nature of organic ligands affected the structures of assemblies greatly, and on the other, reveals the versatility of the malonate which can act as a bridging and/or blocking ligand. 相似文献
32.
《Journal of Coordination Chemistry》2012,65(16):2852-2861
Three cadmium(II) coordination polymers, [CdBr2(L1)] n (1), [CdI2(L2)] n (2), and Cd2Br4(L3)2 (3), where L1?=?1,3-bis(5,6-dimethylbenzimidazole)propane, L2?=?1,4-bis(5,6-dimethylbenzimidazole)butane, and L3?=?1,6-bis(5,6-dimethylbenzimidazole)hexane, have been synthesized by hydrothermal methods and characterized by elemental analyses, IR spectra, TGA, PXRD, and X-ray crystallographic diffraction. Complex 1 contains a 1-D helical chain in which CdBr2 units are linked by L1. For 2, each CdI2 is connected by two different conformations of L2 to form a 1-D zigzag chain. For 3, each CdBr2 is linked by L3 bridges to afford a binuclear structure. These results indicate that the spacer length of the ligands play important roles in assembly of Cd(II) coordination polymers. Thermogravimetric analyses and solid-state luminescent properties of the complexes have also been investigated. 相似文献
33.
《Journal of Coordination Chemistry》2012,65(2):218-225
By using the flexible bis(triazole) ligand 1,2-bis(1,2,4-triazol-1-yl)ethane (bte), a polyoxometalate-templated compound, [Zn2(bte)4(SiW12O40)]·2H2O (1), was synthesized under hydrothermal conditions. The compound was characterized by single-crystal X-ray diffraction, elemental analyses, IR spectroscopy, photoluminescence spectroscopy, and cyclic voltammetry. Compound 1 is constructed from two motifs: the [SiW12O40]4? polyanion and a bi-nuclear metal-organic circle [Zn2(bte)2]4+. The polyanion exerts a template role, inducing the formation of the bi-nuclear circle. The circles build a 1-D circle connecting circle chain through sharing the same Zn ions. Adjacent circles in the chain are vertical with each other. The template polyanion is surrounded by four circles from four different 1-D chains, forming a 3-D supramolecular structure. 相似文献
34.
X.S. Zhou C. Zhao R. Hou J. Zhang K.J. Kirk D. Hutson Y.J. Guo P.A. Hu S.M. Peng X.T. Zu Y.Q. Fu 《Ultrasonics》2014
Nanocrystalline ZnO films with both C-axis vertical grown and inclined angled grown were sputter-deposited onto aluminium foils (50 μm thick) and characterised for using as flexible ultrasonic transducers. As-deposited C-axis grown ZnO films were annealed at different temperatures up to 600 °C to enhance film crystallinity and reduce film stress. The C-axis grown ZnO film on the Al foil were bonded onto steel plates, and the pulse-echo tests verified a good performance (with dominant longitudinal waves) of the ultrasonic transducers made from both as-deposited and post-annealed films. Inclined angled ZnO films on the Al foil glued onto steel plates generated mixed shear and longitudinal waves in the pulse-echo test. 相似文献
35.
We consider two-stage tandem queueing systems attended by two specialized and one flexible server, where all servers have time varying rates. Assuming exponential processing times and linear holding costs, we derive properties of server allocation policies that minimize expected costs over an infinite time horizon. 相似文献
36.
I.M. KrishnakumarBeena Mathew 《European Polymer Journal》2002,38(9):1745-1752
To correlate the coupling difficulty and nature of the support in solid-phase peptide synthesis, a set of difficult peptides were built under identical conditions on rigid and hydrophobic divinyl benzene-crosslinked polystyrene (DVB-PS) and flexible and polar 1,4-butanediol dimethacrylate-crosslinked polystyrene (BDDMA-PS) resins of same functional capacity (∼2 mmol/g). The difficult coupling stages observed on each support were identified by monitoring the acylation time, coupling yield and deprotection efficiency. The yield and purity of the peptides prepared on BDDMA-PS were higher than when DVB-PS support was used. 相似文献
37.
38.
One of the most well-known situations in which nonlinear effects must be taken into account to obtain realistic results is
the rotating beam problem. This problem has been extensively studied in the literature and has even become a benchmark problem
for the validation of nonlinear formulations. Among other approaches, the substructuring technique was proven to be a valid
strategy to account for this problem. Later, the similarities between the absolute nodal coordinate formulation and the substructuring
technique were demonstrated. At the same time, it was found the existence of a critical angular velocity, beyond which the
system becomes unstable that was dependent on the number of substructures. Since the dependence of the critical velocity was
not so far clear, this paper tries to shed some light on it. Moreover, previous studies were focused on a constant angular
velocity analysis where the effects of Coriolis forces were neglected. In this paper, the influence of the Coriolis force
term is not neglected. The influence of the reference conditions of the element frame are also investigated in this paper. 相似文献
39.
Tsuyoshi Katayama 《Queueing Systems》2007,57(4):169-178
We consider a multi-class priority queueing system with a non-preemptive time-limited service controlled by an exponential
timer and multiple (or single) vacations. By reducing the service discipline to the Bernoulli schedule, we obtain an expression
for the Laplace-Stieltjes transform (LST) of the waiting time distribution via an iteration procedure, and a recursive scheme
to calculate the first two moments. It is noted that we have to select embedded Markov points based on the service beginning
epochs instead of the service completion epochs adopted for most of M/G/1 queueing analyses. Through the queue-length analysis, we obtain a decomposition form for the LST of the waiting time in
each queue having the exhaustive service.
相似文献
40.
The flexible Ag/TiO2/ITO/PET resistive switching memory is prepared by low-temperature sol-gel method with UV irradiation, and the simple method that combined the advantages of sol-gel method and low temperature can be applied to fabricate high-quality film. The flexible Ag/TiO2/ITO/PET memory device displays good resistive behavior, for instance, the narrow distributions of switching voltages, good cycle endurance, and long retention time. Meanwhile, the multilevel resistance states of the device can be realized by controlling the compliance current or reset voltages, showing the potential of applications in neural networks and high-density storge. In addition, flexibility of the Ag/TiO2/ITO/PET is studied, which exhibit good endurance and retention properties under bending condition. The I–V curves are replotted and fitted for analyzing the conductive mechanism of the device. The fitting results show that SCLC and Ohmic mechanism are main mechanisms of high resistance state and low resistance state respectively. The electrochemical and thermochemical modes are adopted to explain resistive switching behavior. Our results indicate the Ag/TiO2/ITO/PET memory has potential application in wearable and foldable electronics. 相似文献