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71.
A novel high temperature thermosetting resin system based on the addition polymerization of bis (4-maleimidophenyl)methane and o, o′-diallyl-bisphenol A is presented in this paper. This system offers the combination of easy solventless processing and the high temperature and toughness performance characteristics demanded for the fabrication of C-fibre laminates. The mechanism of the polyaddition reaction is unusual. In a first step an ENE addition reaction of the maleimide to the allyl group occurs to give a 1:1 adduct with a propenyl phenol type of structure. This is then followed by a Diels-Alder addition reaction of another maleimide functional group to the ENE adduct (by the so-called Wagner-Jauregg reaction) to give a densely crosslinked polymer with glass transition temperatures well over 280°C. 相似文献
72.
Ruppa P. Kamalesh Babu Setharampattu S. Krishnamurthy Munirathinam Nethaji 《Heteroatom Chemistry》1991,2(4):477-485
Two new diphosphazane ligands, PriN(PPh2)(PO2C6H4) ( 1 ) and PriN{P(O2C6H4)}2 ( 3 ), have been synthesized and characterized by spectroscopic data. The structure of 1 has been confirmed by single crystal X-ray diffraction. Crystal data: Monoclinic, C2/c, Z = 16, a = 34.149(5) Å, b = 9.717(6) Å, c = 29.439(5) Å, β = 125.11(2)°, V = 7991 Å3, R = 0.058, Rw = 0.061. This compound shows two different P–N bond lengths (1.654 (4) and 1.743(4) Å) and a P–N–P angle of 120.7(2)°. Variable temperature 31P NMR measurements for 1 and 3 throw light on the nature of the conformers present in solution. 相似文献
73.
Mangesh Chaudhari Gunjan Verma Bhalchandra Puranik Amit Agrawal 《Experimental Thermal and Fluid Science》2009,33(3):439-448
A synthetic jet results from periodic oscillations of a diaphragm in a cavity. We present the results of a detailed experimental investigation wherein the effect of excitation frequency on the synthetic jet flow is studied for cavities of different depths and for orifices of different diameters. The exit velocity averaged over an excitation cycle indicates a lower and an upper bound on the frequency for the formation of a jet, and shows resonance at two frequencies. The resonant frequencies have been identified as being close to the diaphragm and the Helmholtz frequencies, with the former being more important in the present set of experiments. We discuss approaches to manipulate these frequencies from the point of view of cavity design. Interestingly, the input power is found to be at a minimum at the diaphragm frequency. Our measurements over a relatively large parameter domain suggest that the turbulence intensity in the near field is independent of the cavity depth and excitation frequency, but depends on the orifice diameter. These results are expected to be useful for designing synthetic jet cavity. 相似文献
74.
We present a generalized convolution theorem in the fractional Fourier domains that preserves the convolution theorem of the conventional Fourier transform. The Papoulis-like generalized sampling expansions in the fractional Fourier domains using this generalized convolution theorem are also derived and it is shown that the classical generalized Papoulis sampling expansion is a special case of it. Its application in the context of the image superresolution is also discussed. 相似文献
75.
B. Schröder W. Grobman W.L. Johnson C.C. Tsuei P. Chaudhari 《Solid State Communications》1978,28(8):631-633
Ultraviolet photoemission measurements at two photon energies are carried out, to understand the strong enhancement of the superconducting transition temperature Tc in the nitrogen stabilized amorphous molybdenum films. The rise of Tc can be attributed to a 40% increase of the electronic density of states at the Fermi level N(EF) and a 15% softening of the phonon spectrum. 相似文献
76.
77.
The reaction of [Pd2Cl2(μ-Cl)2(PR3)2] with triarylbismuth in dichloromethane at room temperature afforded chloro-bridged arylpalladium complexes, [Pd2Ar2(μ-Cl)2(PR3)2] (Ar = Ph or 4-MeC6H4 (tol)) in 85–90% yield as a yellow crystalline powder. These complexes were characterized by elemental analysis and NMR spectroscopy. Molecular structures of [Pd2tol2(μ-Cl)2(PEt3)2] and [Pd2Ph2(μ-Cl)2(PMePh2)2] were established by single crystal X-ray crystallography. These complexes are centrosymmetric dimers with trans configuration. The C–C coupling reaction between triarylbismuth and an arylhalide in the presence of a base is catalyzed by [Pd2Cl2(μ-Cl)2(PR3)2]. The reactions proceed via an arylpalladium complex formed by transmetallation reaction between [Pd2Cl2(μ-Cl)2(PR3)2] and Ar3Bi. Probable reaction routes for C–C coupling have been discussed. 相似文献
78.
Nita H. Shah Mrudul Y. Jani Urmila Chaudhari 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2018,24(1):1-11
In competitive edge, the proffer of delay payment is of great consequence tool to boost the market demand by exerting influence of more customers. In opposition to, merchandiser may be asked to pay some per cent of purchasing cost before receiving products to reduce the risk of cancellation of order. In this article, optimal replenishment time for merchandiser under partial upstream prepayment and partial downstream overdue payment is presented under quadratic demand with three different models: (1) without deterioration, (2) with constant deterioration and (3) maximum fixed-lifetime deterioration as loss of utility is the real situation of products like fruits, vegetables, juices, etc., and to reduce deterioration of the product, merchandiser spends capital on preservation technology to preserve the item. Quadratic demand is suitable for the products for which demand increases initially and afterward it starts to decrease. The decision policies are analysed for the merchandiser. The objective is to minimize merchandiser’s total cost with respect to decision variables. The models are supported with numerical examples. Sensitivity analysis is carried out to derive insights for decision maker. 相似文献
79.
K. A. Dubey Y. K. Bhardwaj C. V. Chaudhari N. K. Goel S. Sabharwal K. Rajkumar S. K. Chakraborty 《先进技术聚合物》2011,22(12):1888-1897
Varying compositions of styrene–butadiene rubber (SBR) and ethylene–propylene diene monomer (EPDM) 50:50 blend containing multiple walled carbon nanotube (MWNT) as nanoparticulate filler (0.5–5%) were prepared and their efficacy for radiation vulcanization was analyzed by gel‐content, Charlesby‐Pinner parameter, and crosslinking density measurements. Radiation sensitivity of the nanocomposites increased with increase in the MWNT fraction and radiation dose in the dose range studied. The elastic modulus, tensile strength increased with the radiation dose, while elongation at break exhibited downward trend. The extent of reinforcement as assessed using Kraus equation suggested high reinforcement of blend on MWNT addition. The reinforcing mechanism of nanocomposites was studied by various micromechanics models which predicted higher modulus than the experimentally observed results, indicating agglomeration in the nanocomposites. The thermal stability of the composites increased with increase in MWNT loading has been attributed to the antioxidancy induced by nanotubes and higher crosslinking extent of the nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
80.
Experimental Techniques - The method presented in this paper has a good practical application, which may be used in all cases of oblique-incidence measurements in reflection photoelasticity. The... 相似文献