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81.
82.
We derive a simple analytical correction of a well-known standard formulation of the gravity wave height produced in a prismatic channel due to a sudden discharge stoppage at the downstream end of the channel. The proposed analytical correction considers the vertical growth of the wave and, as a result, takes into account the effect of the channel bed slope on the wave height. This simple correction is useful to be considered in preliminary designs of relatively long channels subject to unsteady flow conditions. 相似文献
83.
Pablo A. Corzo-Valladares Álvaro Fernández-Cuesta José M. Fernández-Martínez Leonardo Velasco 《Journal of the American Oil Chemists' Society》2013,90(11):1713-1718
Jatropha curcas L. has great potential for biofuel and phytosterol production. The objective of this research was to evaluate G × E variability for kernel phytosterol content and composition in Jatropha germplasm. Freshly matured seeds from 21 accessions grown in Málaga, Spain were collected at two stages of development. Significant genetic variation was detected for total kernel phytosterol content, which ranged from 2,246 to 2,883 mg kg?1; and stigmasterol concentration, which ranged from 7.6 to 11.5 % of the total phytosterols. An accession with 9.2 % Δ5‐avenasterol was also identified. The coefficient of variation for kernel phytosterol content and stigmasterol concentration was 6.2 and 14.0 % respectively between accessions and 7.2 and 10.2 % respectively within accessions. Accordingly, evaluation of plant to plant variation is advisable. The existence of variability for kernel phytosterol content and composition in Jatropha will enable breeding for enhanced levels of these compounds. 相似文献
84.
Leonardo I. Farfán-Cabrera Cesar D. Reséndiz-Calderón Cesar Sedano de la Rosa 《摩擦学汇刊》2018,61(4):640-647
This article aims to investigate the degradation of physical and tribological properties (friction coefficients and wear resistance) of a dynamic sealing material (silicone rubber [VMQ]) exposed to Jatropha oil (JO), engine mineral oil (EMO), and a blend (B20; 80% EMO–20% JO), separately. JO has demonstrated better lubricating properties than EMO in various mechanical applications; however, the degradation of elastomers by using this oil has not been studied yet, nor have its effect on their tribological properties. The physical degradation was evaluated by conducting static immersion tests (670 h at 25 °C) based on ASTM-D471 and ASTM-D7216 methods. Hence, the changes in mass, volume, tensile and tear strengths, and hardness of VMQ were measured. In addition, creep compliance tests were conducted to determine the changes in viscoelastic properties and the changes in morphology and topography were measured by scanning electron microscopy (SEM) and optical profilometry, respectively. In addition, the compositional changes were determined by Fourier transform infrared (FTIR) analyses to complement the degradation examination. Changes in the friction coefficients were determined by ball-on-disk tests and changes in wear resistance were obtained by accelerated wear tests (microabrasion tests). Finally, VMQ exhibited no significant physical and compositional degradation due to immersion in the three lubricants. However, considerable changes in the friction coefficients and wear resistance were observed; the change in the friction coefficients was minimal using JO. In addition, the coefficients using JO were 50% lower than those for EMO and the changes in wear resistance were lowest after immersion in JO. 相似文献
85.
86.
Jichun Ye Leonardo Ajdelsztajn Julie M. Schoenung 《Metallurgical and Materials Transactions A》2006,37(8):2569-2579
Dense, bulk nanocrystalline aluminum 5083 alloy was fabricatedvia a combined technique: cryomilling (mechanical milling at cryogenic temperature) to achieve the nanocrystalline Al 5083 powder
and spark plasma sintering (SPS) to consolidate the cryomilled powder. The results of X-ray diffraction analysis indicate
that the average grain size in the SPS consolidated material is 51 nm, one of the smallest grain sizes ever reported in bulk
Al alloys produced by powder metallurgy derived methods. In contrast, transmission electron microscopy (TEM) analysis revealed
a bimodal grain size distribution, with an average grain size of 47 nm in the fine-grained regions and approximately 300 nm
in the coarse-grained regions. Nanoindentation was used to evaluate the mechanical properties and the uniformity of the consolidated
nanocrystalline Al 5083. The hardness of the material is greatly improved over that of the conventional equivalent, due to
the fine grain size. The mechanisms for spark plasma sintering and the microstructural evolution are discussed on the basis
of the experimental findings. 相似文献
87.
Estevez, L., Kehtarnavaz, N., and Wendt, R. III, Interactive Selective and Adaptive Clustering for Detection of Microcalcifications in Mammograms,Digital Signal Processing6(1996), 224–232.This paper presents a clustering algorithm, called interactive selective and adaptive clustering (Isaac), to assist radiologists in looking for small clusters of microcalcifications in mammograms. Isaac is developed to identify suspicious microcalcification regions which are missed by other classification techniques due to false positive samples in the feature space. It comprises two parts: (i) selective clustering and (ii) interactive adaptation. The first part reduces the number of false positives by identifying the microcalcification subspace or domains in the feature space. The second part allows the radiologist to improve results by interactively identifying additional false positive or true negative samples. Clinical evaluations of mammograms indicate the potential of using this algorithm as an effective tool to bring microcalcification areas to the attention of the radiologist during a routine reading session of mammograms. 相似文献
88.
n-Heptane, 2- and 3-methylhexane, ethylcyclopentane, and cycloheptane were passed in the presence of hydrogen at 500 °C over “nonacidic” platinum-alumina catalyst containing 3% by weight of platinum. The conversion ranged between 12 and 26%, depending on the interval of time the product was removed for analysis. In the case of cycloheptane, however, the conversion amounted to 98% during the first 30 min on stream and with time, during the approximate period between 2 and 3 h, it decreased to 69%. The products from the reaction contained besides toluene, also hydrocarbons resulting from a skeletal isomerization and dehydrocyclization of the original hydrocarbons, and to a smaller extent from a bond shift process, and a repetitive 1,5-ring closure followed by hydrogenolysis. Using 1,1-dimethylcyclohexane as a model compound, it was shown that the skeletal isomerization accompanying the aromatization of the seven-carbon hydrocarbons does not proceed through cationic intermediates. A survey of the literature relating to the mechanism of aromatization of hydrocarbon over “nonacidic” chromia-alumina and platinum-alumina catalysts is presented, and the differences between the two mechanisms are discussed. 相似文献
89.
Guido?BoellaEmail author Leonardo?Lesmo Rossana?Damiano 《Artificial Intelligence and Law》2004,12(4):317-357
This article describes an ontological model of norms. The basic assumption is that a substantial part of a legal system is
grounded on the concept of agency. Since a legal system aims at regulating a society, then its goal can be achieved only by affecting the behaviour of the
members of the society. We assume that a society is made up of agents (which can be individuals, institutions, software programs, etc.), that agents have beliefs, goals and preferences, and that
they commit to intentions in order to choose a line of behaviour. The role of norms, within a legal system, is to specify
how and when the chosen behaviour agrees with the basic principles of the legal system. In this article, we show how a model
based on plans can be the basis for the ontological representation of norms, which are expressed as constraints on the possible
plans an agent may choose to guide its behaviour. Moreover, the paper describes how the proposed model can be linked to the
upper level of a philosophically well-founded ontology (DOLCE); in this way, the model is set in a wider perspective, which
opens the way to further developments. 相似文献
90.
Surface-enhanced Raman scattering substrate based on a self-assembled monolayer for use in gene diagnostics 总被引:3,自引:0,他引:3
The development of surface-enhanced Raman scattering (SERS)-active substrates for cancer gene detection is described. The detection method uses Raman active dye-labeled DNA gene probes, self-assembled monolayers, and nanostructured metallic substrates as SERS-active platforms. The mercaptohexane-labeled single-stranded DNA (SH-(CH(2))(6)-ssDNA)/6-mercapto-1-hexanol system formed on a silver surface is characterized by atomic force microscopy. The surface-enhanced Raman gene (SERGen) probes developed in this study can be used to detect DNA targets via hybridization to complementary DNA probes. The probes do not require the use of radioactive labels and have a great potential to provide both sensitivity and selectivity. The effectiveness of this approach and its application in cancer gene diagnostics (BRCA1 breast cancer gene) are investigated. 相似文献