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991.
The solubilities of 2-methyl-6-acetylnaphthalene (2,6-MAN) and 2-methyl-7-acetylnaphthalene (2,7-MAN) in n-heptane, n-octane, and n-dodecane were measured, respectively, from 273.15 to 319.15 K using an analytical method. On the basis of the thermodynamics theory of solid-liquid equilibrium, a model was derived to relate the solubilities with temperature. Using the least square method, the parameters of the model, the fusion enthalpies △fusH and the Margules equation coefficients A12 and A21 of 2,6-MAN and 2,7-MAN in n-heptane, n-octane, and n-dodecane-were obtained by regressing the experimental data. The average deviation of the model was 1.70%. 相似文献
992.
Faliang Zhang Yongchun Luo Anqiang Deng Zhaohui Tang Long Kang Jianhong Chen 《Electrochimica acta》2006,52(1):24-32
(La, Ce, Pr, Nd)2MgNi9 hydrogen storage alloys were prepared through induction melting followed by a long annealing treatment. The structure and electrochemical properties of annealed alloys have been investigated by orthogonal design experiments. Both the individual effects of each substituting element and their interaction in alloys were studied systemically. It has been shown that the structure of main phase in alloys belongs to PuNi3-type with a space group R-3m. Substituting rare-earth elements have a significant effect on both the phase structure of alloys and microstructure. The anisotropic change in the crystal structure of alloys can cause the acceleration of pulverization of alloy particles and result in the deterioration of the cyclic stability of alloy electrodes. Misch metals can raise the plateau pressure of hydrogen absorption/desorption. The discharge capacity of alloy ranges from 342.97 to 380.68 mAh g−1 depending on the sort and content of substituting elements. Both cerium and neodymium can obviously reduce the discharge capacity of alloy electrodes. When compared to the La2MgNi9 alloy electrode, mish metals can significantly improve the high rate dischargeability of alloy electrodes. The improvement of the kinetic characteristic of alloy electrodes mainly results from the increase of the hydrogen diffusion rate in alloy bulk. 相似文献
993.
Jia Bing Dai Xing Yuan Zhang Jing Chao Chen Yan Bai 《Journal of Coatings Technology and Research》2007,4(3):283-288
A novel core–shell type fluorinated acrylic and siliconated polyurethane (FSiPUA) hybrid emulsion was prepared by seeded emulsion
polymerization using siliconated polyurethane (SiPU) as a seed and forming the structure with SiPU as a shell and the copolymer
of butyl acrylate (BA) with 2,2,2-trifluoroethylmethacrylate (TFEMA) as a core. SiPU was synthesized using isophorone diisocyanate
(IPDI), polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), dihydroxybutyl-terminated polydimethylsiloxane
(PDMS), dimethylol propionic acid (DMPA), 1,6-hexanediol (HDO) and triethylamine (TEA). The contents of siloxane and fluorine
were determined according to the feed ratio. Fourier transform infrared spectroscopy (FTIR) was used to identify the chain
structure of SiPU and FSiPUA. Investigation of transmission electron microscopy (TEM) confirmed the core–shell structure of
FSiPUA emulsion and gave the particle size at about 50 nm. The measurement results of water contact angles and the solvent
absorptions in water and n-octane for cured films showed that the water and the oil repellency for FSiPUA had been improved significantly with a suitable
content of fluorine and siloxane. 相似文献
994.
Summary Polysilanes with an optically active alkoxy group, i.e., (S)-(+)-2-butoxy, (R)-(-)-2-butoxy, (S)-(-)-2-methyl-1-butoxy, and (S)-(+)-3,7-dimethyl-1-octoxy, at the terminal positions, the chiral carbon centers of which were located at the α, β, and γ
positions relative to the oxygen, respectively, were prepared, and the effect of the position of chiral center of the terminal
optically active group on the induction of optical activity in polysilanes was investigated. The circular dichroism (CD) spectra
of these polymers showed positive Cotton signals around 340 nm at temperatures below -20 °C, but the intensities were small,
indicating that the optically active groups at the terminal positions have some ability, albeit small, to induce optical activity
to the polysilanes. Further, the optically active (S)-(+)-2-butoxy and (R)-(-)-2-butoxy groups did not control the helical sense direction of the polymers, despite the different chiral stimuli from
the 2-butoxy groups introduced to the terminal positions. To control the helical structure of polysilanes by the use of optically
active terminal groups, appropriate optically active groups are required. 相似文献
995.
Elisée Ouédraogo Leo Stroosnijder Abdoulaye Mando Lijbert Brussaard Robert Zougmoré 《Nutrient Cycling in Agroecosystems》2007,77(3):245-256
A field experiment was conducted in Gampela (Burkina Faso) in 2000 and 2001 to assess the impact of organic and mineral sources
of nutrients and combinations thereof in optimising crop production in till and no-till systems and to assess the economic
benefit of these options. The study showed that under conditions of rainfall deficiency, the use of a single organic resource
at an equivalent dose of 40 kg N ha−1 better secured crop yield than the application of an equivalent amount as urea-N, while a combination of organic resources
and fertiliser was better in increasing crop yield than the application of the same N amount in the form of urea. In a year
of rainfall deficiency, a mix of organic resources and fertiliser in both till and no-till systems increased crop water use
efficiency, with the result that the farmer was able to purchase only half of the normal quantity of N fertiliser to obtain
a higher yield that he would have done when all of the N was supplied in the form of urea. Under conditions where soil N is
deficient, an economic benefit was achieved when urea was combined with easily decomposable organic material (e.g. sheep dung);
mixing the urea at a dose of 40 kg N ha−1 with maize straw was not sufficient in alleviating the negative interaction due to the enhanced N immobilisation. The results
demonstrate that the use of N fertiliser alone was risky and that a higher yield, with the accompanying economic benefit,
was scarcely achieved under the prevailing rainfall conditions. The application of soil and water conservation measures can
contribute greatly to increasing the economic benefit of mineral, organic or combined organic and mineral-derived nutrient
application under semi-arid conditions. 相似文献
996.
Polyelectrolyte complexes (PECs) composed of chitosan and hyaluronic acid (HA) were prepared in various pH regions and at different weight ratios. At low pHs, there was a strong ionic interaction between NH groups in chitosan and both COO? and COOH groups in HA due to the deprotonation of HA, whereas weak linkages were formed at high pHs because only the carboxyl groups of HA could interact with NH groups in chitosan. The formation of PECs resulted in a decrease in the crystallinity and thermal stability caused by the interactions between polyions. With variations in the degree of ionization of polyions at various pH conditions, novel PEC sponges were prepared by the freeze drying of PEC solutions. Furthermore, for the evaluation of the wound‐healing effect of PEC sponges with or without an antimicrobial agent (silver sulfadiazine), they were applied to a full‐skin defect of a Wistar rat in vivo. The histology and computerized morphometric analysis of the epidermal healing confirmed the proliferation of fibroblasts in the wound bed and a distinct reduction in infectious agents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 925–932, 2003 相似文献
997.
膜生物反应器(MBR)是膜分离与生物反应器相结合的新型水处理技术。焦化污水是一种高浓度、难降解的工业污水,应用传统的生化方法处理焦化污水存在费用大、效率低的缺点。作者采用一体浸没式膜生物反应器处理焦化污水,调整合适的操作参数,污水中主要污染物COD、NH2-N的去除率分别达到80%、98%以上,操作简单,出水水质稳定,且远好于国家一级排放标准,取得了良好的效果,有一定的推广意义。 相似文献
998.
Solutions of rare earth modifier (RES) and epoxy chloropropane (ECP) grafting modification method were used for the surface treatment of aramid fiber. Tensile properties of both the aramid/epoxy composites and single fibers were tested. The effects of RES concentration on tensile properties of aramid/epoxy composites were investigated in detail to explore an optimum amount of rare earth elements in solution for modifying aramid fiber. The fracture surface morphologies of tensile specimens were observed and analyzed with the aid of SEM. The experimental results show that rare earth treatment is superior to ECP grafting treatment in promoting interfacial adhesion between the aramid fiber and epoxy matrix. Meanwhile, the tensile strengths of single fibers were almost not affected by RES treatment. The optimum performance is obtained when the content of rare earth elements is 0.5 wt %. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1037–1041, 2004 相似文献
999.
In this paper, we will extend the strict maximum principle preserving flux limiting technique developed for one dimensional scalar hyperbolic conservation laws to the two-dimensional scalar problems. The parametrized flux limiters and their determination from decoupling maximum principle preserving constraint is presented in a compact way for two-dimensional problems. With the compact fashion that the decoupling is carried out, the technique can be easily applied to high order finite difference and finite volume schemes for multi-dimensional scalar hyperbolic problems. For the two-dimensional problem, the successively defined flux limiters are developed for the multi-stage total-variation-diminishing Runge–Kutta time-discretization to improve the efficiency of computation. The high order schemes with successive flux limiters provide high order approximation and maintain strict maximum principle with mild Courant-Friedrichs-Lewy constraint. Two dimensional numerical evidence is given to demonstrate the capability of the proposed approach. 相似文献
1000.