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71.
通过对湿法PU合成革用聚氨酯(PU)树脂浆料配方的改进,降低了浆料的生产成本,浆料的后期加工性能提高,并且PU膜的性能也有所改善。 相似文献
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Strong polyelectrolytes, known as superplasticizers, improve the initial fluidity of concentrated cement suspensions through electrostatic stabilization. These polyelectrolytes do not maintain the initial fluidity, however, primarily due to an increase in the ionic strength of the cementitious suspension. Consequently, non-ionic polymers are often used in conjunction with polyelectrolytes to provide steric stabilization and hence to sustain the desired fluidity over a longer time, and this has lead to the development of copolymers with both electrostatic and steric (electrosteric) functionalities. To design such polymers, it is necessary to optimize the balance between electrostatic and steric stabilization to maximize suspension fluidity. We have quantified the effects of a strong anionic polyelectrolyte, melamine formaldehyde sulfonate (MFS), and a non-ionic polymer, hydroxypropylmethylcellulose (HPMC), on the zeta potential of cement particles and the steady shear and low-amplitude rheological properties of concentrated cement suspensions. While the adsorption of MFS onto the cement particle surfaces leads to a sign inversion in the zeta potential, the adsorption of the non-ionic HPMC has no significant effect on the potential. The addition of HPMC to the suspensions substantially reduces the steady shear viscosity and the storage modulus at constant MFS concentration; in addition, there exists an intermediate HPMC concentration that minimizes fluidity. The resulting suspension fluidity is also maintained over a longer time than in the absence of HPMC. This improvement in the stability and fluidity of cement suspensions is attributed to “complementary electrosteric dispersion/stabilization”, and provides insight to the design of polymers with electrosteric functionality. 相似文献
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75.
Fresh leaves and volatile oil of the important weed Ageratum conyzoides in south China were highly inhibitory to seedling growth of various cultivated crops, especially in an adverse habitat. The constituents of the volatile oil were analyzed by GC-MS. Eleven components were identified and six main components, precocene I, precocene II, 3,3-dimethyl-5-tert-butylindone, -caryophyllene, -bisabolene, and fenchyl acetate, were isolated by means of column chromatography. Precocene I, precocene II, -caryophyllene, and 3,3-dimethyl-5-tert-butylindone inhibited seedling growth of acceptor plants. Inhibitory activity of the volatile oil was more intense than that of the pure components. Fenchyl acetate and -bisabolene have no inhibitory activity, but when mixed with precocene II, they increased the inhibitory activity to growth of acceptor seedling plants. Experiments show that allelopathic synergism exists among allelochemicals of Ageratum conyzoides. 相似文献
76.
基于现阶段条件下的混凝土热力学参数及温控措施,考虑气温、混凝土性能随龄期的变化及MgO的膨胀性等因素,采用三维有限元法对鱼粮水库拱坝的温度场进行仿真计算分析,计算结果表明,坝体混凝土在自然入仓、冬季保温的情况下,无需采取其它温控措施,通过对比不分缝方案及分缝方案,说明设置诱导缝可改善坝体应力分布情况。通过改变缝的位置更加有利于释放大坝温度应力,且各部位应力均能满足规范要求。 相似文献
77.
介绍了企业在面临国际陶瓷市场竞争激烈的形势下,努力转变发展思路,拓宽市场,强化质量意识。根据市场变化,生产适销对路搞档优质陶瓷产品,增强产品的市场能力,提高了企业的经济效益。 相似文献
78.
This paper presents a segment-based probabilistic approach to robustly recognize continuous sign language sentences. The recognition strategy is based on a two-layer conditional random field (CRF) model, where the lower layer processes the component channels and provides outputs to the upper layer for sign recognition. The continuously signed sentences are first segmented, and the sub-segments are labeled SIGN or ME (movement epenthesis) by a Bayesian network (BN) which fuses the outputs of independent CRF and support vector machine (SVM) classifiers. The sub-segments labeled as ME are discarded and the remaining SIGN sub-segments are merged and recognized by the two-layer CRF classifier; for this we have proposed a new algorithm based on the semi-Markov CRF decoding scheme. With eight signers, we obtained a recall rate of 95.7% and a precision of 96.6% for unseen samples from seen signers, and a recall rate of 86.6% and a precision of 89.9% for unseen signers. 相似文献
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80.