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991.
《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(7):1301-1309
Four samples of paper and board (P/B) of a type used for packaging dry foods were subjected to migration tests using mushrooms, apples, potatoes and bananas, and using the polymeric powder Tenax? as a food simulant. The P/B samples contained only low levels of diisopropylnaphthalene (DiPN) and diisobutyl phthalate (DiBP) and so the experiments were conducted after impregnating the P/B with added model substances. These were o-xylene, acetophenone, dodecane, benzophenone, DiPN and DiBP. Migration levels depended strongly on the nature of the substance and on the nature of the food and much less on the characteristics of the P/B, except insofar as they affected the contact area – flexible papers giving more extensive contact with the food than thick rigid board. Migration into Tenax? was at least a factor of 10 higher than migration into the fresh fruit and vegetables. The food samples were placed in contact with the P/B and then overwrapped loosely with aluminium foil and so this correction factor will tend to be conservative compared with a more open storage of the packed foods. Washing, peeling or cooking the fruits and vegetables after contact with the P/B had a surprisingly small effect on contaminant levels in general, and no one processing step was effective in giving a significant reduction of all the types of chemicals studied. This was because either they had penetrated into the food (so resisting peeling), or were not freely water-soluble (so resisting washing) or were not particularly volatile (so resisting loss by evaporation during cooking). 相似文献
992.
Michihiro Asakawa Sadayuki Kaneko Reiji Hattori 《Journal of the Society for Information Display》2011,19(10):693-699
Abstract— A shrunk multiline addressing method (SMLA) in a passive‐matrix‐driven liquid powder display will be discussed. An algorithm to generate SMLA data that effectively reduces the number of scanning lines has been devised. The update time is reduced by 44.5% on average, and this reduction is maintained despite increased sizes of the images. The SMLA data generated by this algorithm is applied to e‐paper panels, thereby confirming the reduction in update time and that the image quality of the panels driven by SMLA is equal to that of conventionally driven ones. 相似文献
993.
994.
多媒体技术和网络技术的出现使计算机辅助教学取得了飞速的发展。文章首先解释了什么是Authorware,然后利用Authorware中的Quiz知识对象设计制作出一份考试试卷并详细讲解了其制作操作过程。 相似文献
995.
Paper membranes made from vulcanized cellulose were used for the pervaporation (PV) of aqueous solutions containing methanol, ethanol, and isopropanol. It was noted that the vulcanized cellulose paper membranes (VCPM) could effectively separate alcohol and water from the mixture solutions. To observe the effect of the separation of alcohol aqueous mixtures, the permeation behavior of water and alcohol was examined by means of the separation factor and the permeation flux. The values of the permeation flux in the ethanol/water mixtures were found to vary from 6.2 kg/m2h to 2.1 kg/m2h, as the concentration of ethanol increased from 8 to 87 wt %, and the separation factor (α) changed from α = 2.6 to 6.6, respectively. This showed that the VCPM enhanced the separation of water and alcohol. The highest value observed for the permeation flux was 11 kg/m2h at 87 wt % of methanol concentration and the separation factor at this condition was 4.1. It was shown also that an efficient separation was obtained in the isopropanol/water mixture with a separation factor of 16.6. The contact angles of alcohol/water droplets on the VCPM were measured as well as the wettability of the membrane. There was a tendency of decrease for the contact angle, as the alcohol concentration decreased. This suggested that the solvent wettability decreased in high alcohol concentrations. It was concluded that a high permeabilitty of water through the VCPM resulted in the separation of alcohols and water in the PV process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
996.
997.
Inexpensive synthesis of diamine, 1,4-bis(4-nitrophenoxy)-2-(6-oxido-6H-dibenz <c,e> <1,2> oxaphosphorin-6-yl) phenylene was revealed in this work. Based on the diamine, a series of organosoluble polyamides were prepared by direct polycondensation of the diamine with various aromatic diacids using triphenyl phosphite and pyridine as condensing agents. The number-average molecular weights of the resulting polyamides range from 4.2 × 104 to 10.5 × 104 g/mol, and the weight-average molecular weights are in the range of 7.5-28.2 × 104 g/mol. The Tgs of these polyamides range from 210 to 255 °C by dynamic mechanical analysis. The resulting polyamides are tough and flexible with tensile strength, elongation at break and moduli range from 84 to 101 MPa, 4.8-7.0%, and 2.36-3.22 GPa, respectively. The degradation temperatures (Td 5%) and char yields at 800 °C in nitrogen range from 460 to 486 °C and 59-68 wt%, respectively. The cutoff wavelength of these polyamides falls in the range of 345-366 nm, showing a very light color characteristic. In addition, these polyamides display good oxygen plasma resistance. 相似文献
998.
《Petroleum Science and Technology》2013,31(5-6):641-650
In this paper the aging processes of two penetration-grade paving asphalt which conform to the standard of Esson Company have been studied by rotation thin film oven (RTFO). The first order aging kinetic model has been established and some kinetics parameters were calculated. The relationship between pavement properties of asphalt and aging course was revealed. The intervention of oxygen in high temperature caused oxidation reactions, which changed the composition and structure of asphalt, the aging resistant performance of asphalt was weak, and the service performance went to bad. 相似文献
999.
Xiao Wei et al. 《工程抗震与加固改造》2001,(3)
通过对比计算分析 ,结合同类型结构 1 3比例模型试验及课题研究 ,提出了相应的计算机分析方法 ,并编制出电算程序。引入墙板单元分析抗震墙 ,对于地震倾覆力矩的分配及底部框架梁承担竖向荷载合理取值等采用新的研究成果。本方法可以作为相应课题研究的配套技术 ,在这类房屋的抗震设计中应用。 相似文献
1000.
简要介绍涂布运行性主要问题、影响运行性主要因素、涂料固化对涂布的影响,重点介绍了涂料保水性能、高剪切性能、原纸吸收性能测试方法的新进展。 相似文献