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991.
Y. Zhou Md. Mahbub Alam H.X. YangH. Guo D.H. Wood 《International Journal of Heat and Fluid Flow》2011,32(1):329-339
This paper presents the measurements of mean and fluctuating forces on an NACA0012 airfoil over a large range of angle (α) of attack (0-90°) and low to small chord Reynolds numbers (Rec), 5.3 × 103-5.1 × 104, which is of both fundamental and practical importance. The forces, measured using a load cell, display good agreement with the estimate from the LDA-measured cross-flow distributions of velocities in the wake based on the momentum conservation. The dependence of the forces on both α and Rec is determined and discussed in detail. It has been found that the stall of an airfoil, characterized by a drop in the lift force and a jump in the drag force, occurs at Rec ? 1.05 × 104 but is absent at Rec = 5.3 × 103. A theoretical analysis is developed to predict and explain the observed dependence of the mean lift and drag on α. 相似文献
992.
Oxidation of primary aliphatic aldehydes with p-trifluoromethylphenyl(difluoro)-λ(3)-bromane in dichloromethane at 0 °C afforded acid fluorides selectively in good yields, while that of aromatic aldehydes in chloroform at room temperature produced aryl difluoromethyl ethers. A larger migratory aptitude of aryl groups compared to primary alkyl groups during a 1,2-shift from carbon to an electron-deficient oxygen atom in bromane(III) Criegee-type intermediates will result in these differences in the reaction courses. 相似文献
993.
Mariano Pracella Cristiano Pancrazi Md. Minhaz-Ul Haque Aldo D’Alessio 《Journal of Thermal Analysis and Calorimetry》2011,103(1):95-101
Composites of polystyrene (PS) with cellulose microfibres and oat particles, obtained by melt mixing, were examined. The compatibilization
of the composites was carried out by addition of maleic anhydride-functionalized copolymers (SEBS-g-MA, PS-co-MA) and poly(ethylene glycol) to improve the fibre–matrix interfacial interactions. The plain components and their composites
were characterised by FT-IR, DSC, TGA, SEM microscopy and mechanical tests. The properties of the various systems were analysed
as a function of both fibre and compatibilizer amount. The compatibilized PS composites showed enhanced fibre dispersion and
interfacial adhesion as a consequence of chemical interactions between the anhydride groups on the polymer chains and the
hydroxyl groups on the fibres, as demonstrated by FT-IR spectroscopy. DSC analysis pointed out a neat increase of T
g of composites on addition of SEBS-g-MA, as compared to PS-co-MA. The thermal stability of composites was also influenced
by the type and amount of fibres, as well as by the structure and concentration of compatibilizer. The effect of the reactive
copolymers on the composites properties was accounted for on the basis of the polymer–polymer miscibility and chemical interactions
at the matrix/filler interface. 相似文献
994.
Alam MM Chattopadhyaya M Chakrabarti S 《Physical chemistry chemical physics : PCCP》2011,13(20):9285-9292
In the present work, we have studied the two-photon absorption (TPA) properties of some selective molecules containing triarylborane and 1-naphthylphenylamine as the acceptor and donor moiety, respectively. The calculations are performed by using the state-of-the-art linear and quadratic response theory in the framework of the time dependent density functional theoretical method. The TPA parameters are calculated with CAMB3LYP functional and the cc-pVDZ basis set. The one-photon results indicate that both the electronic transitions (S(0)-S(1) and S(0)-S(2)) are associated with the charge transfer interaction between the donor and acceptor moieties along with the reorganization of the π-electron density. All these chromophores are found to have very strong two-photon active modes. In order to find out the origin of large TP transition probability of these molecules, we have performed two-state model (TSM) and sum-over-states (SOS) calculations. We have found that the TSM failed to reproduce the correct trend of the TP transition probability of the molecules obtained from the response theory, while SOS is quite successful in doing so. The whole study indicates that the transition moments between the excited states play a pivotal role in controlling the TP transition probabilities of these molecules. The role of solvent in the TP transition probability of these molecules has meticulously been scrutinized within the polarized continuum model (PCM). Further more, we have benchmarked our theoretical findings by calculating the TPA cross-section of a boron and nitrogen containing a charge transfer molecule for which the experimental result is available and we found that our theoretical result is in good agreement with the experimental one which definitely demonstrates the potential of all these light-emitting diode molecules as TP active materials too. 相似文献
995.
Miran MS Kinoshita H Yasuda T Susan MA Watanabe M 《Chemical communications (Cambridge, England)》2011,47(47):12676-12678
The temperature dependence of the N-H proton chemical shift in protic ionic liquids (PILs) and FT-IR spectra of the N-H bonds indicated the presence of strong hydrogen bonds between the protonated cation and the anion, depending on the ΔpK(a) of the constituent acid and base, and their successive breaking with temperature, which may explain the characteristic properties of PILs such as relatively low ionicity and its decrease with temperature. 相似文献
996.
Islam MM Valiyev F Lu HF Kuo MY Chao I Tao YT 《Chemical communications (Cambridge, England)》2011,47(7):2008-2010
A novel p-channel semiconductor pyreno[4,5-a]coronene has been synthesized and characterized. The highly fused π-conjugated framework has a twisted geometry with an excellent on-top cofacial π-π stacking in the crystal structure and with a centroid-to-centroid distance of 3.808 ?. Single-crystal field effect transistors based on the molecule exhibit a high mobility of ~0.89 cm(2) V(-1) s(-1) and an on/off ratio of ~6 × 10(4). 相似文献
997.
Zhirong L Azhar Uddin M Zhanxue S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):1013-1016
Na-bentonite has been studied extensively because of its strong adsorption capacity and complexation ability. In this work, surface area, total pore volume, mean pore diameter, TG, DTA, FT-IR and XRD were carried out in order to reveal the characteristics of natural Na-bentonite. XRD and FT-IR of natural Na-bentonite (China) and Cu-loaded Na-bentonite as a function of Na-bentonite dosage and temperature using batch technique were characterized in detail, respectively. 相似文献
998.
Shishir Ghosh Md. Kamal Hossain Daniel T. Haworth Sergey V. Lindeman Shariff E. Kabir 《Journal of organometallic chemistry》2010,695(8):1146-2942
The readily prepared [Re2(CO)6(μ-S2NC7H4)2] (1) reacts with Group 8 trimetallic carbonyl clusters to yield new mixed-metal tri- and tetranuclear clusters. With [Os3(CO)10(NCMe)2] at 80 °C the tetranuclear mixed-metal cluster [Os3Re(CO)13(μ3-C7H4NS2)] (2) is the only isolated product. With Ru3(CO)12 products are dependent upon the reaction temperature. At 80 °C, a mixture of tetranuclear mixed-metal [Ru3Re(CO)13(μ3-C7H4NS2)] (5) and the triruthenium complex [Ru3(CO)9(μ-H)(μ3-C7H4NS2)] (4) results, while at 110 °C a second tetranuclear mixed-metal cluster, [Re2Ru2(CO)12(μ4-S)(μ-C7H4NS)(μ-C7H4NS2)] (3), resulting from carbon-sulfur bond scission, is the major product. Reaction of 1 With Fe3(CO)12 at 80 °C furnishes the trinuclear mixed-metal cluster [Fe2Re(CO)8(μ-CO)2(μ3-C7H4NS2)] (6). The reactivity of 6 has been probed with the aim of identifying any metal-based selectivity for carbonyl substitution. Addition of PPh3 in presence of Me3NO at 25 °C gives both the mono- and bis(phosphine)-substituted derivatives [Os3Re(CO)12(PPh3)(μ3-C7H4NS2)] (7) and [Os3Re(CO)11(PPh3)2(μ3-C7H4NS2)] (8). In 7 the PPh3 ligand occupies an axial site on wingtip osmium, while in 8 one PPh3 ligand is equatorially coordinated to wingtip osmium and the other is bonded to a hinge osmium. New complexes have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction studies. 相似文献
999.
A novel hybrid plasma bonding (HPB) that combines sequential plasma activation (reactive ion etching followed by microwave radicals) with anodic bonding has been developed to achieve void-free and strong silicon/glass bonding at low temperature. The interfacial voids were observed at the silicon/glass interface both in the anodic bonding and in the plasma activated anodic bonding, but the voids were completely disappeared in the HPB method at 200 °C. The bonding strength of the silicon/glass in the HPB was as high as 30 MPa at 200 °C, which was higher than that in the individual treatment of anodic and plasma activated bonding methods. The improved characteristic behavior of the interface in the HPB is attributed to the higher hydrophilicity and smooth surfaces of silicon and glass after sequential plasma activation. These highly reactive and clean surfaces enhance the mobility of alkaline cations from the glass surface across the interface toward the bulk of glass in the HPB. This transportation resulted in a ∼353 nm thick alkaline depletion layer in the glass and enlarged the amorphous SiO2 across the interface. The void-free strong bonding is attributed to the clean hydrophilic surfaces and the amorphous SiO2 layer across the interface. 相似文献
1000.
Reaction of thiomaleic anhydride with triphenylphosphine gives the title compound, which undergoes reaction with a variety of aldehydes to give a range of alkylidene thiomaleic anhydrides (substituted monothioitaconic anhydrides). Subsequent treatment with tert-butoxycarbonylamino-substituted thiols, or under radical conditions with tert-butoxycarbonylamino-substituted alkyl halides results in a series of substituted monothiomaleic anhydrides, that on exposure to trifluoroacetic acid and then base lead to thiocarboxyl substituted 1,4-thiazepin-5-ones and piperidinones, respectively, that are ultimately trapped by reaction with 2,4-dinitrobenzenesulfonamides to give the corresponding amides. 相似文献