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51.
为了有效求解多目标优化问题,找到分布宽广、均匀的Pareto解集,提出了一个基于空间网格划分的进化算法。将目标空间网格化,利用网格的位置,删除大量被支配个体。在杂交算子中利用了单个目标最优的个体信息,以增加非劣解的宽广性。利用一种新设计的基于最大距离排序的方法删除非劣解集中多余个体。数值实验表明提出的算法是可行有效的。 相似文献
52.
We employ self-consistent mean-field (SCMF) theory in studying the body-centered cubic (bcc) spheres of block copolymers in the presence of a neutral solvent. First we examine the accuracy of the dilution approximation then analyze the dependence of the bcc structural sizes with copolymer volume fraction ?, the interaction parameter χAB, and degree of copolymerization N. Our results reveal that both distribution of each component and the micro-structural length scales are greatly influenced by each parameter ?, χAB, and N. As expected, with decreasing ?, more solvent distributes non-uniformally in the segregated domains, therefore deviation from the dilution approximation increases. This also suggests that when the effective segregation parameter ?χABN is fixed, a larger deviation is expected as χABN increases (i.e. ? decreases). Although when both χABN and ? are fixed, decreasing N (i.e. increasing χAB) enlarges the deviation from the dilution approximation. Furthermore, this solvent non-uniformity behavior is so significant that it even affects the dependence of the domain spacing L* and the matrix length Λ* with respect to (χAB)effN=?χABN near the ODT. When the systems are in molten state and/or in the concentrated regime, both L* and Λ* exhibit a sharp increase behavior as ODT is approached, due to many of the minority blocks being pulled from the spherical domains and swelling the matrix. With increasing solvent amount and/or χABN, we observe that the increase of the degree for the minority blocks pulled from the spheres into the matrix near the ODT is not as significant as that in the melt. As such, the sharp increase behavior in L* as well as Λ* near the ODT smoothens and even disappears. 相似文献
53.
54.
C. Kapseu G. J. Kayem D. Balesdent L. Schuffenecker 《Journal of the American Oil Chemists' Society》1991,68(2):128-130
Cold fractionation of cottonseed oil is made difficult by the high viscosity of the oil. This study was aimed at demonstrating
the effect of solvents on the viscosity of mixtures between 0°C and 25°C with a view to facilitating the fractionation of
refined cottonseed oil. The solvents used were acetone, methylethylketone, methylisobutylketone, hexane and heptane. Measurements
of viscosity were carried out by means of a capillary viscometer. The ratio of the viscosity of cottonseed oil to that of
pure solvents is of the order of 300. The viscosities of solutions of various ratios of solvent to oil (1/3, 1/1, 3/1) are
between those of cottonseed oil and the pure solvents. The effect of the solvent/oil ratio overrides that of solvent nature.
The effect of solvent in reducing the viscosity of cottonseed oil is by descending order: acetone, hexane, methylethylketone,
heptane, methylisobutylketone. 相似文献
55.
Do-Kyun Kwon Clive A. Randall Thomas R. Shrout Michael T. Lanagan 《Journal of the American Ceramic Society》2004,87(6):1088-1092
The dielectric properties and frequency dispersion associated with a dielectric relaxation were evaluated within the perovskite (1− x )BiScO3 – x Ba(Mg1/3 Nb2/3 )O3 solid solution systems (0.7 ≤ x ≤ 1). With increasing BiScO3 , the room-temperature dielectric permittivity at low frequency (100 Hz) increased up to 115 at x = 0.7, and a dielectric relaxation phenomenon was evident. Relaxation parameters were analyzed using several Arrhenius-type equations, and the microwave dielectric property measurement using rectangular wave-guide method enabled confirmation of the extrapolated value of the Arrhenius plot. The result of the microwave dielectric property measurement was also checked with J -function fitting based on the frequency-dependent Gaussian distribution of the associated dielectric loss data at low frequency. 相似文献
56.
近年来,安防监控系统技术发展迅速,安防产品已形成一个较为成熟的产业。本文通过详细描述平安校园安防监控系统的各个环节的设备特点、选型要求、设计理念等方面,从南通大学平安校园安防监控系统的建设实践出发,总结平安校园安防监控系统建设中的经验与创新。 相似文献
57.
In this paper, the theory on the translation of a measured chord length distribution (CLD) into its particle size distribution (PSD), which was developed in the first part of this study [Li and Wilkinson, 2005. Determination of non-spherical particle size distribution from chord length measurements. Part 1: theoretical analysis. Chemical Engineering Science 60, 3251-3265], has been validated using experimental results. CLDs were measured using the Lasentec focused beam reflectance measurement (FBRM) with three different materials, spherical ceramic beads and non-spherical plasma aluminium and zinc dust particles. Meanwhile, the particle shape and PSD of each material were also investigated by image analysis (IA). Comparison of the retrieved PSDs with the measured PSDs by IA shows that the PSD can be retrieved from a measured CLD successfully using the proposed iterative nonnegative least squares (NNLS) method based on the PSD-CLD model. 相似文献
58.
Fred J. Parker 《Journal of the American Ceramic Society》1990,73(4):929-932
The characterization and properties of ceramic composites containing the phases Al2 TiO5 , ZrTiO4 , and ZrO2 are described. The range of compositions investigated gives very low average thermal expansions (α24–1000°C as low as −2.0 × 10−6 °C−1 ) and excellent high-temperature stability. The low thermal expansions are apparently due to a combination of microcracking by the titanate phases and a contractive phase transformation by the ZrO2 . The crystal chemistry and microstructure of the product are processing dependent. Although the composites represent a complex microcracking system, the low thermal expansions and high-temperature stability make them potential candidates for commercial applications requiring thermal shock resistance. 相似文献
59.
60.
Yoshiyuki Abe Kazuyuki Kakegawa Yoshinori Sasaki 《Journal of the American Ceramic Society》1992,75(1):234-236
A complex perovskite of Sr(Cu x Zn1- x )1/2 W1/2 O3 (SCZW) is synthesized by a new combination of wet and dry processess. Mixed oxides containing Cu2+ and Zn2+ (CZ) are prepared by the wet process (coprecipitate method). SCZW is obtained by the dry process (mixed-oxide method) from a mixture of CZ, SrCO3 , and WO3 . SCZW has practically no compositional, unlike solid solutions prepared by the conventional dry method. The wet–dry process method is useful because the wet process is applied to only B-site cations having the same valence. 相似文献