共查询到20条相似文献,搜索用时 46 毫秒
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以中间体聚琥珀酰亚胺(PSI)为原料,己二胺为交联剂,通过在乙醇和水的混合介质中水解,合成了环境友好型的聚天冬氨酸高吸水性树脂。研究了乙醇和水的体积比对水解过程和产物性能的影响。结果表明,当乙醇和水的体积比为7∶3时,树脂分散均匀,体系无粘结,且水解产物吸水性能最好。通过正交实验考察了在最佳乙醇用量的水解介质中进行水解时,PSI相对分子质量、水解温度、体系pH值和水解时间对吸水性树脂吸水性能的影响,得到了合成高吸水性树脂的最佳工艺条件为:PSI分子量为88500、水解温度35℃、pH值9.5~10.0、水解时间4h。在此最优条件下所制备的吸水性树脂的吸水率达1021倍。对产物进行TG测试结果表明,所制备的吸水树脂具有良好的热稳定性。 相似文献
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以羧甲基纤维素(CMC),丙烯酸(AA),2-丙烯酰胺2甲基丙磺酸(AMPS)为原料,过硫酸钾为引发剂,N,N'-亚甲基双丙烯酰胺为交联剂,经接枝共聚制备高吸水性树脂;为提高高吸水性树脂的耐热性能,使用分子筛对高吸水性树脂进行改性,探讨了分子筛种类和用量对高吸水性树脂性能的影响,测定了改性后高吸水性树脂的吸水倍率、吸水速率、再生性能和耐热性能,通过对其性能进行比较得出:添加0.5g的13X分子筛改性高吸水性树脂效果最佳,所得产物吸水倍率为675g·g-1,吸水速率、再生性能和耐热性能也比改性前有显著提高. 相似文献
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李本刚范玉曼张严丹曹绪芝罗振扬 《高分子材料科学与工程》2018,(7):156-161
先用铈(Ⅳ)盐引发丙烯酰胺(AM)在纳米纤维素晶体(NCC)表面接枝聚合,接枝产物NCC-g-PAM可稳定地分散在丙烯酸钠/丙烯酸混合单体水溶液中,然后以N,N-亚甲基双丙烯酰胺作交联剂通过原位光聚合制得聚丙烯酸钠(PAANa)/NCC-g-PAM复合高吸水性树脂。用红外光谱、X射线衍射、元素分析等方法对NCC-g-PAM进行了表征,通过红外光谱、扫描电镜、溶胀实验考察了NCC-g-PAM的添加对高吸水性树脂结构、形貌和吸水性能的影响。结果表明,NCC-g-PAM中NCC的晶态结构未改变,聚丙烯酰胺(PAM)的含量为59.54%。PAANa/NCC-g-PAM复合高吸水性树脂具有丰富的网孔结构,NCC-g-PAM中的PAM链与PAANa基体间形成了氢键。与PAANa高吸水性树脂相比,PAANa/NCC-g-PAM复合高吸水性树脂的吸水倍率和吸水速率均有所增加,吸水倍率最高可达3000 g/g,是PAANa的3.2倍,吸生理盐水倍率最高可达139 g/g,是PAANa的2.5倍。 相似文献
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A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling. 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue. 相似文献
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An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a
rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate
agreement is demonstrated between the derived relations and experimental data. 相似文献
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Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995. 相似文献
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由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。 相似文献
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M. M. Gadenin 《Inorganic Materials》2013,49(15):1352-1356
It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle. 相似文献
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V. T. Kornienko 《Strength of Materials》1991,23(7):760-765
The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991. 相似文献
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水三相点是开尔文热力学温度的唯一基准点,也是ITS-90国际温标重要的定义固定点。因此,水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来,中国计量科学研究院研制出一系列高质量的水三相点容器,加强了水三相点的研究,为不确定度的分析提供了更为可靠的实验依据。同时,不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此,根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明,其扩展不确定度为0.16mK(k=2.69,P=0.99)。 相似文献