Durability of sheet molding compounds: Influence of hydrothermal aging on morphology and molecular mobility at microscopic scale

The physicochemical aging for parts of Sheet Molding Compound should be considered for their lifetime management and reusability. This material has a complex morphology and contains porosity due to the process and to shrinkage compensation. This SMC study has two complementary approaches. One describes the morphological consequences of water uptake, showing the decrease in the total amount and the fractal dimension of micro-voids by scanning electron microscopy and image processing. The other shows, by mechanical spectrometry, the effect of water on physical or chemical bonds. In both cases, the “low profile agent” in SMC plays an important role. The molecular mobility was taken as a sensor parameter for the structural changes at the molecular scale, highlighting and quantifying the first steps of the aging. The loss factor level increases, and the activation energies are modified, even for the first aging days. The analysis shows recovery for the material near the relaxation peak of the low profile agent, since the curve recovers its initial shape.     

近红外光谱分析在农业领域应用中的几个问题

分析近红外在农业领域应用的特殊性,分析近红外分析过程中影响模型性能的若干因素,讨论近红外分析准确度的评价方法,预测标准差SEP不宜作为近红外分析性能的指标性参数,提出近红外分析在农业应用中值得重视的研究方向。     

Diffusion of electrolytes in hydrolyzable glassy polymers: Acetic acid in poly(vinyl acetate), poly(vinyl alcohol), and polyesters

Engineering materials containing poly(vinyl acetate) (PVAc) as the key component undergo hydrolytic degradation, which must be minimized or, at least, controlled. To characterize PVAc hydrolysis quantitatively, the diffusion of acetic acid (HAc) in PVAc, poly(vinyl alcohol) (PVA), unsaturated polyester (UPE), and a UPE/PVAc blend was studied in detail. The permeability cell earlier developed by the authors was modified here to reduce experimental error. As the diffusion and solubility coefficients of water and HAc in the above materials were measured at different temperatures, a mathematical model was developed, which takes proper account of the combined water and HAc diffusion in PVAc undergoing partial hydrolysis. The model was further validated by the experimental data obtained at 70°C for UPE/PVAc film, simulating a matrix of sheet‐molding compounds composite materials. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1157–1166, 2002     

不同成膜温度对高粱秸秆粉/纳米ZnO/聚乙烯醇纳米复合膜理化性能和微观结构的影响

为提高农林废弃物的利用率及促进新型生物质材料的产业化生产,本文以高粱秸秆粉(Sorghum straw powder,SSP)、纳米ZnO、聚乙烯醇(Polyvinyl alcohol,PVA)等为主要成膜基材,采用共混流延法制备出高粱秸秆粉/纳米ZnO/聚乙烯醇(SSP/Nano-ZnO/PVA,SNP)纳米复合膜,研究SSP的加入及不同成膜温度(75、80、85、90、95℃)对SNP纳米复合膜厚度、抗拉强度(Tensile strength,TS)、阻隔性能、微观结构、光谱特性和热性能的影响。结果表明:SSP的加入能提高SNP纳米复合膜TS、阻隔性能及热性能;随着成膜温度的升高,SNP纳米复合膜TS和阻隔性能先变好后变差,当成膜为85℃时,SNP纳米复合膜性能最好(TS=31.22 MPa最大,水蒸气透过系数=1.32×10^-12 g/(cm·s·Pa)、水溶性=36.41%、溶胀度=238.41%最小),并通过SEM、AFM、FT-IR、TG分析表明该温度下SNP纳米复合膜表面光滑,截面致密,各基质间具有良好的相容性且热稳定性较好,综合性能优于其他成膜温度...     

命题逻辑公式模糊软集语义及其在决策分析中的应用

基于论域公式引入软命题逻辑公式概念,给出软命题逻辑公式的模糊软语义解释.将决策模糊信息系统转化为决策模糊软集,软决策规则表示为包含有蕴含联结词的软命题逻辑公式.引入软命题逻辑公式的基本真度、条件真度、绝对真度等指标,从充分性、必要性等方面评价软决策规则的有效性、合理性.提出基于决策软集的典型软决策规则提取算法和基于软决策分析的推荐算法,并通过实例和数值实验证明算法的有效性.     

基于DBN的电子战指挥决策辅助方法研究

现代战争中的电子战指挥相较于传统作战方式需要考虑的因素更多、更复杂.借助动态贝叶斯网络(DBN)的动态可推理性建立了一种电子战指挥决策定量辅助决策模型,将传统作战决策中的一维定量分析转化为动态多维定量推理分析.利用影响电子战作战效果的各类因素进行每个作战时刻的贝叶斯网络(BN)构建,结合节点之间的条件概率矩阵,使用隐马尔可夫(HMM)模型推理算法实现了电子战辅助决策的动态推理.对实际演习算例进行模型仿真和分析,得出对电子战指挥员切实有效的指挥决策建议,表明了模型的有效性.