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81.
82.
Emilio Marengo Valentina Longo Elisa Robotti Marco Bobba Fabio Gosetti Orfeo Zerbinati Silvana Di Martino 《应用聚合物科学杂志》2008,109(6):3975-3982
Principal component regression (PCR), partial least squares (PLS), StepWise ordinary least squares regression (OLS), and back‐propagation artificial neural network (BP‐ANN) are applied here for the determination of the propylene concentration of a set of 83 production samples of ethylene–propylene copolymers from their infrared spectra. The set of available samples was split into (a) a training set, for models calculation; (b) a test set, for selecting the correct number of latent variables in PCR and PLS and the end point of the training phase of BP‐ANN; (c) a production set, for evaluating the predictive ability of the models. The predictive ability of the models is thus evaluated by genuine predictions. The model obtained by StepWise OLS turned out to be the best one, both in fitting and prediction. The study of the breakdown number of samples to be included in the training set showed that at least 52 experiments are necessary to build a reliable and predictive calibration model. It can be concluded that FTIR spectroscopy and OLS can be properly employed for monitoring the synthesis or the final product of ethylene–propylene copolymers, by predicting the concentration of propylene directly along the process line. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
83.
Xin Song Xiaoyu Qi Bin Hao Yinbo Qu 《European Journal of Lipid Science and Technology》2008,110(12):1095-1101
Although lipases are widely applied in a wide variety of reactions, available information on the factors that are responsible for the substrate specificities of lipases from different sources is scarce. In this paper, nine lipase‐producing microorganism strains were isolated from oil‐containing samples. The properties of these enzymes, including pH optima, temperature optima, thermal stability, and pH stability, vary significantly with the different sources from which these lipases were isolated. The substrate specificities of the nine lipases, including fatty acid and positional specificities, were also studied. The fatty acid specificities of the nine lipases were observably different toward 15 substrates with different carbon chain lengths, different saturation degrees and different side chains. The lipases from S3 Penicillium citrinum (PCL), MJ1 Aspergillus niger (ANL), MJ2 Aspergillus oryzae (AOL), YM Bacillus coughing (BCL), S9 Geotrichum candidum (GCL), and S11 Candida lypolytica (CLL) showed the strongest specificities to short‐chain esters, and the other lipases showed strong selectivity for medium‐ or long‐chain and branched esters. The positional specificities were examined by analyzing the hydrolytic products of triolein catalyzed by the nine lipases, using TLC. The lipases can be mainly classified into two groups by their specificities for the ester bond at position 2 of triglycerides; one group can selectively hydrolyze the ester bond at position 2 of the triglycerides, the other group cannot. All these nine lipases were divided into four groups by hierarchical clustering analysis on the basis of the results of fatty acid and positional specificities. 相似文献
84.
卸荷裂隙在水利水电工程建设中的危害 总被引:3,自引:0,他引:3
卸荷裂隙是对水工建筑物稳定最不利的软弱结构面之一。文中较系统地介绍了这种结构面的特点、分布规律、形成的力学机理、对工程的危害、勘查方法及处理措施。 相似文献
85.
86.
This paper introduces a novel methodology for clustering of symbolic objects by making use of Genetic Algorithms (GAs). GAs
are a family of computational models inspired by evolution. These algorithms encode potential solutions to specific problems
on simple chromosome-like data structures and apply recombination operators to these structures so as to preserve critical
information. A new type of representation for chromosome structure is presented here along with a new method for mutation.
The efficacy of the proposed method is examined by application to numeric data of known number of classes and also to assertion
type of symbolic objects drawn from the domain of fat oil, microcomputers, microprocessors and botany. The validity of the
clusters obtained is examined. 相似文献
87.
激光实际大气传输湍流效应相位校正一些实验结果 总被引:8,自引:0,他引:8
进行了近地面水平大气中激光传输湍流效应及其自适应光学相位校正实验,对光束振幅起伏、到达角起伏及其远场Strehl比进行了测量分析。实验结果表明,光束到达角起伏功率谱在低频段(f<0.4υ/d)近似地满足-2/3次幂关系,而在高频段(f>0.4υ/d)则近似满足-8/3次幂关系。在较弱湍流效应情况下时数振幅起伏方差小于0.3),相位补偿是有效的,而在较强湍流效应树数振福起伏饱和)时,自适应光学系统常常不能实现稳定闭环。由于传输场景地形复杂,湍流效应及其相位校正效果定量规律的描述还需进一步研究。 相似文献
88.
根据波速计算多相土石地基压实度的理论模型 总被引:2,自引:0,他引:2
本文基于多相复合介质的波动传播特性,导出介质内纵、横波速的理论计算公式。通过对影响因素分析,建立了横波波速与土石复合介质的干密度之间的近似理论关系。在此基础上,推导出土石地基压实度的波速计算理论模型的近似表达式。最后进行了现场地基的波速测试和灌砂法测试,通过理论计算和灌砂法测试结果的对比分析,表明该近似模型是可行的,并且其在对非均匀土石复合地基的压实质量评价中优越于传统的密度法。 相似文献
89.
Chaosuan Kanchanomai Yukio Miyashita Yoshiharu Mutoh 《Journal of Electronic Materials》2002,31(5):456-465
Low-cycle fatigue (LCF) tests on as-cast Sn-3.5Ag, Sn-3Ag-0.5Cu, Sn-3Ag-0.5Cu-1Bi, and Sn-3Ag-0.5Cu-3Bi solders was carried
out using a noncontact strain-controlled system at 20°C with a constant frequency of 0.1 Hz. The addition of Cu does not significantly
affect the fatigue life of eutectic Sn-Ag solder. However, the fatigue life was significantly reduced with the addition of
Bi. The LCF behavior of all solders followed the Coffin-Manson relationship. The fatigue life of the present solders is dominated
by the fracture ductility and can be described by the ductility-modified Coffin-Manson’s relationship. Steps at the boundaries
of dendrite phases were the initiation sites for microcracks for Sn-3.5Ag, Sn-3Ag-0.5Cu, and Sn-3Ag-0.5Cu-1Bi solders, while
for Sn-3Ag-0.5Cu-3Bi solder, cracks initiated along both the dendrite boundaries and subgrain boundaries in the dendrite phases.
The linking of these cracks and the propagation of cracks inside the specimen occurred both transgranularly through eutectic
phases and intergranularly along dendrite boundaries or subgrain boundaries. 相似文献
90.
Numerical simulations of acoustic scattering in the frequency domain based on hybrid methods coupling finite elements and boundary elements are the most suited for dealing with problems involving wave propagation in inhomogeneous media. Furthermore, it is necessary to resort to high performance computing to effectively solve the large size problems. However, the direct coupling yields a linear system with a matrix which is partly dense and partly sparse and thus not adapted to high performance computing. To avoid this difficulty, we present a new iterative method constructed from a non overlapping domain decomposition technique. 相似文献