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81.
The polyesterification and isomerization reaction of 1,6-hexane diol and maleic anydride in a melt without catalyst was studied by 13C and 1H n.m.r. spectroscopy. The structure and concentration of oligoester species during the polyesterification and isomerization were determined depending on the reaction temperature and time. According to the number and configuration of repeating units determined from 1H n.m.r. spectra kinetics of both reactions were also considered. The degree of isomerization is continuously increasing in the investigated reaction range. 相似文献
82.
An experimental study has been made of temperature profiles incident within a zeolite adsorbent particle in the course of adsorption of n-heptan. Using thermocouple wires 0.1 mm in diameter it has been possible to measure simultaneously the temperatures of the surface and in the centre. It was observed that temperature differences between center of the pellet and ambient stagnant gas may be more than 20°C. The results of this work indicate that the overheating of an adsorbent particle is a very rapid process which is followed by a slow cooling of the hot particle. Experimental data are compared with predictions calculated from the theoretical model. 相似文献
83.
A model employing the correction factors of Marek and Standart, but using a concentration-dependent liquid phase association factor of Jenkins—Robinson, has been used to model vapour—liquid equilibrium data for mixtures of acetic acid with benzene, toluene, o-xylene and p-xylene. With the aim to use systems of acetic acid—benzene and acetic acid—toluene as the test mixtures for distillation columns, the examination of the systems of acetic acid—aromatic hydrocarbons was undertaken. The model promises to be useful in modelling isobaric and isothermal data of acetic acid—benzine, acetic acid—toluene, acetic acid-p-xylene and acetic acid-o-xylene systems. Deviation plots show that the isothermal and isobaric data are represented well. 相似文献
84.
Summary
2,5-Dihydro-2,5-dimethoxyfuran (DHMF) was polymerized via constant current electrolysis (CCE), in CH3CN-NaClO4 solvent-electrolyte couple. Poly(DHMF) was obtained from the anolyte. The effect of current density, temperature, monomer and electrolyte concentrations on the polymer yield have been examined. The apparent activation energy for CCE of DHMF was found to be 37.2 kj/mol. The FTIR and 1H-NMR analyses show that DHMF polymerizes by a ring opening. Molecular weight of poly(DHMF) was found by using cryoscopy. 相似文献
85.
Hae Jin Kim Jin Bae Lee Young-Min Kim Myung-Hwa Jung Z. Jagličić P. Umek J. Dolinšek 《Nanoscale research letters》2007,2(2):81-86
We present synthesis, structure and magnetic properties of structurally well-ordered single-crystalline β-MnO2 nanorods of 50–100 nm diameter and several μm length. Thorough structural characterization shows that the basic β-MnO2 material is covered by a thin surface layer (∼2.5 nm) of α-Mn2O3 phase with a reduced Mn valence that adds its own magnetic signal to the total magnetization of the β-MnO2 nanorods. The relatively complicated temperature-dependent magnetism of the nanorods can be explained in terms of a superposition
of bulk magnetic properties of spatially segregated β-MnO2 and α-Mn2O3 constituent phases and the soft ferromagnetism of the thin interface layer between these two phases. 相似文献
86.
Polymer Bulletin - Solutions of syndiotactic (s) poly (methyl methacrylate) (PMMA) and samples of solid s-PMMA prepared from these solutions were studied by NMR and infrared (IR) spectroscopy and... 相似文献
87.
Sintered negative electrodes for nickel-cadmium secondary cells were studied. Model electrodes prepared by means of three different impregnation methods were evaluated. It was demonstrated that the impregnation procedure may affect properties of active mass and the service life of electrodes in a significant way. 相似文献
88.
The underpotential deposition of Bi on Au has been investigated by specular reflectance spectroscopy and linear sweep voltammetry. The spectral dependance of ΔR/R caused by Bi adatoms has been determined and compared with the calculated spectrum. A satisfactory agreement between experimental and calculated spectra was found. ΔR/R values have been used to determine the surface concentration of Biad which then has been used to calculate the electrosorption valence of Biad. It has been found that γBi = 2.6. The optical evidence of interaction of Bi ions with gold oxide has been obtained. 相似文献
89.
The rotational mobility of stable nitroxide radicals in PS, PMMA, PVC, PP and PE has been studied over a wide temperature range by the e.s.r. method. At temperatures T lower than Tg, spin probes act as kinetically independent particles, the rotational frequency of which is deter mined mainly by the micropore dimensions of the polymer and depends indirectly on the mobility of segments or side groups. 相似文献
90.
Irena Orović Milica Orlandić Srdjan Stanković 《Multimedia Tools and Applications》2014,70(3):1503-1519
An image watermarking technique based on the concept of JPEG2000 algorithm is proposed. Biorthogonal wavelet 9/7 transform is used to provide a set of coefficients suitable for watermark embedding. The statistical properties of different subbands are analyzed in order to choose the number of decomposition levels and position of subbands, which will assure the best compromise between the watermark transparency and robustness. The JPEG2000 quantization is applied to avoid insignificant wavelet coefficients, while the remaining ones are used for watermarking. The optimal and blind watermark detection is based on the nonlinear score function and appropriate model of coefficients distribution. The performance of the proposed procedure is tested on examples with various images, showing robustness under different attacks, while maintaining high image quality. 相似文献