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41.
We consider the optimization of quadratic functions on the set of permutations in Rn. Extremal properties of these functions are studied. Branch-and-bound methods are proposed for the solution of these optimization problems.Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 97–104, July–August, 1991. 相似文献
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A gene encoding the centromere binding factor 1 (Cbf1p) of the human pathogenic yeast Candida albicans was cloned and characterized. An open reading-frame was detected which encoded a 223 amino acid protein with a calculated molecular weight of 25.8 kDa and a relative isoelectric point of 5.55. It shares 39% overall amino acid sequence identity with Saccharomyces cerevisiae Cbf1p. We localized the CaCBF1 gene on chromosome 4. Southern analysis indicated that CaCBF1 is probably present as a single copy gene per haploid genome. The CaCBF1 gene under the control of its own promoter was able to complement the methionine auxotrophic growth, the increased mitotic instability of CEN plasmids and the slow growth of a Saccharomyces cerevisiae cbf1Delta mutant strain. 相似文献
44.
G. Tomandl M. Mangler D. Stoyan A. Tscheschel Tu Bergakademie Freiberg J. Goebbels G. Weidemann 《Journal of Materials Science》2006,41(13):4143-4151
In this paper the characterisation of functionally graded materials is elucidated by several different methods. These methods
described here are used for the quantitative analysis of materials with a local dependence of microstructure parameters. Using
X-ray microscopy (computed tomography) for 3D-measurements and optical microscopy on polished sections for 1D and 2D measurements
on the same sample, a ceramic filter consisting of sintered spherical particles, various mathematical evaluation methods are
described and compared. 相似文献
45.
The modelling of the geometrical structure of a special kind of concrete is discussed. It is a matter of self-flowing refractory castables with spherical grains. The system of hard spheres is compared to several well-established models of spatial statistics and statistical physics as well as to a model used by concrete engineers. It turns out that the structure can be well described by the latter model and a further newly developed model, which is similar to a marked Gibbs process. The result is based on the comparison of common summary statistics like the pair correlation function and the spherical contact distribution function. 相似文献
46.
Nikola Drenchev Tony Spassov Stoyan Bliznakov 《Journal of Alloys and Compounds》2008,450(1-2):288-292
Mg2−xSnxNi (x = 0, 0.1, 0.3) alloys were synthesized by reactive ball milling under protective Ar atmosphere and liquid n-heptane. The microstructure and the morphology of the powders were determined by X-ray diffraction and scanning electron microscopy. The as-milled alloys consist of Mg2Ni nanocrystals with an average grain size in the range 3–7 nm, depending on the alloy composition. Sn containing phases were not detected even in the Sn-rich alloy. Obviously, Sn is dissolved in the Mg2Ni intermetallic compound. Gas phase sorption of hydrogen was not observed in the alloys containing Sn (Mg2−xSnxNi; x = 0.1, 0.3). It was suggested that Sn impedes the process of hydrogen molecules decomposition. The as-milled alloys absorbed reversibly hydrogen electrochemically. Mg2Ni alloy showed the highest discharge capacity of 300 mAh/g. The capacity of Mg1.9Sn0.1Ni and Mg1.7Sn0.3Ni was about 260 mAh/g. It was found that Sn improved the cycle life of the electrode. 相似文献
47.
The Weibull theory of material strength and fracture assumes that the Weibull modulus m is a material parameter, which does not depend on shape and size of the loaded object. Based on large data sets from single-particle
fracture experiments with brittle materials (glass, clinker cement, limestone), the authors show that the Weibull modulus
of nearly spherical particles seems to decrease with increasing particle diameter. A possible explanation is that the inner
structure of the particles depends on their size so that small particles are much stronger than large ones.
Received: 9 December 1999 相似文献
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ABSTRACT: The effect of warm water dip in combination with irradiation on quality of fresh-cut green onions was studied. Fresh-cut green onions were treated with and without warm water (50°C for 20 s) and packaged prior to irradiation at 0, 0.5, 1.0, and 1.5 kGy, then stored at 4°C for 14 d. Color, texture, decay percentage, electrolyte leakage, sensory qualities, and total aerobic count (TAC) were measured at 1,4,8, and 14 d of storage. The warm water treatment reduced the TAC by 0.9 log initially but the beneficial effect disappeared during storage. With the test conditions used in this study, the warm water treatment did not provide added benefits for quality improvements. Irradiation at all tested doses reduced TAC and the development of decay and off-odor, improved visual quality, and preserved green color. 相似文献
50.
A technique for mathematical modeling of a state of a distributed-parameter dynamic system with incomplete data about their initial boundary conditions is proposed in the paper. Modeling accuracy and uniqueness conditions are formulated. An algorithm is proposed for recalculation of modeling results for different numbers of discrete observations of the initial boundary state of the system with point modeling effects. 相似文献