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排序方式: 共有398条查询结果,搜索用时 62 毫秒
1.
Napoli Maria Lia Barbero Monica Scavia Claudio 《Bulletin of Engineering Geology and the Environment》2021,80(10):7457-7466
Bulletin of Engineering Geology and the Environment - A wide range of heterogeneous geological units composed of strong rock blocks enclosed in a bonded matrix of fine texture exists worldwide.... 相似文献
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Charles A. White John F. Kennedy Anna Lombard Valeria Rossetti 《Polymer International》1985,17(4):327-329
The oligosaccharide component compositions of a series of non-reducing oligosaccharides extracted from the roots of Arnica montana L. has been determined by gel permeation chromatography (g.p.c.). The range of oligosaccharides present was found to extend beyond the octasaccharide previously reported. with 16% to 19% of the oligosaccharides having a degree of polymerisation of between 11 and 19 and almost 3% having a degree of polymerisation greater than 20. The chromatographic behaviour of this series of oligosaccharides is compared with that observed for series of D-gluco-oligosaccharides. 相似文献
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A kinetic analysis of the isothermal nitridation of high-purity oxide-free silicon powder is described. The kinetic analysis suggests that the and polymorphs of Si3N4 are formed by separate and parallel reaction paths. This analysis provides for the decoupling and quantitative kinetic interpretation of- and-Si3N4 formation reactions. Consistent with existing microstructural and thermodynamic evidence, the-forming reaction is shown to obey a first-order rate law, whereas a phase-boundary controlled rate law describes the-forming reaction. A kinetic model employing these rate laws is developed and is used to predict the/ phase ratio as a function of isothermal reaction temperature and extent of reaction. The/ phase ratios so obtained are shown to be in good agreement with experimental observations made under a variety of reaction conditions. 相似文献
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Felice Strollo Lia Pecorelli Giovanna Strollo Massimo Morè Giuseppe Riondino Maria Angela Masini Bianca Maria Uva 《Microgravity science and technology》2006,18(3-4):226-229
A significant reversible decrease in testosterone (T) has been associated with microgravity in male rodents and humans. Urinary T excretion increases in primates under hypergravity. Hypogonadism is somehow related to abnormally high levels of leptin (L), a hormone produced by the adipose tissue which has been found to increase under microgravity simulation conditions like head down bed rest (HDBR). The aim of this study was to assess hemodynamic and pituitary-adrenal and -gonadal adaptation to an acute HDBR test to be eventually used on a routine basis to get better prepared to next space flights. The Authors performed a 1 hour ?12° HDBR in 6 male and 6 female volunteers who underwent heart rate and blood pressure measurement together with a blood draw three times at 30 min intervals from the start to the end of the test for L, T, estradiol (E2), LH, androstenedione (A), cortisol (F), ACTH. 12 age- and sexmatched control subjects followed the same protocol except for keeping the sitting position all the time. According to the ANOVA for repeated measures, no changes occurred in L, T, E2 or LH whereas A, F and ACTH significantly decreased independently of gender. During HDBR systolic blood pressure decreased in both genders, diastolic blood pressure decreased significantly only in men and HR showed a more clear-cut decrease in women than in men. As a conclusion, such an acute steep-slope HDBR protocol may be efficiently used to testing immediate individual haemodynamic or adrenal response to microgravity but is not suitable for studies concerning gonadal adaptation. 相似文献
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对收集到的7种国内外铜带轧制润滑剂进行了基础性能测试,并对其工艺使用性能进行了评价研究,其结果将为有关工厂润滑剂的选用与研制提供一些依据。 相似文献
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Lia Toledo Moreira Mota Alexandre Assis Mota 《International Journal of Electrical Power & Energy Systems》2004,26(10):805-811
This paper is focused on electric power distribution substations load modeling using dynamic load parameters estimation. The load parameters are estimated using two models: the exponential and the ZIP load models. Since the load bus voltage and parameters are known one can determine the active and reactive power injections of this bus and include these pseudo-measurements in the state estimation in order to improve observability and estimation accuracy. The dynamic parameter estimation is developed using the weighted least squares method in a recursive form and the tests are carried out based on actual measurements. It is shown that the estimated parameters (for both load models) at a distribution substation are valid, since the obtained active and reactive power residuals are very close to zero. 相似文献
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A direct carbon fuel cell (DCFC) is a variation of the molten carbonate fuel cell (MCFC) which converts the chemical energy of carbon directly into electrical energy. Thus, the energy conversion efficiency is very high and correspondingly CO2 emission is very low for given power output. DCFC as a high temperature fuel cell performs better at elevated temperatures (>800 °C) but because of the corrosive nature of the molten carbonates at elevated temperatures the degradation of cell components becomes an issue when DCFC is operated for an extended period of time.We explored the DCFC performance at lower temperatures (at 700 °C and less) using different sources of carbon, different compositions of electrolytes and some additives on the cathode surface to increase catalytic activity. Experiments showed that with petroleum coke as a fuel at low temperatures the ternary eutectic (43.4 mol % Li2CO3 - 31.2 mol% Na2CO3 - 25.4 mol % K2CO3) spiked by 20 wt % Cs2CO3 performed better than any binary or ternary eutectics described in the published work by other researchers. Maximum power output achieved at 700 °C was 49 mW/cm2 at a current density of 78 mA/cm2 when modified cathode was fed with O2/CO2 gases. 相似文献
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This case study uncovers a turning point in the production of play space in Amsterdam. Whereas over the first half of the twentieth century the creation of play spaces used to be the primary responsibility of the Amsterdam civil society, this situation started to change after the Second World War. Between 1947 and 1970, the Amsterdam Urban Planning Department created over 700 public play spaces. These spaces were little niches in the urban public domain, specifically designed and constructed to enable city children's play. This remarkable change from a predominantly private to a public intervention, is explained through a rapid increase of the number of children (the post-war baby-boom), the existence of the General Extension Plan (AUP) with its detailed age specific approach and the fruitful collaboration between powerful urban planners and politically dominant socialist politicians. 相似文献