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91.
《Carbon》2014
Fluorine and oxygen co-doped graphene with controllable element coverage was effectively synthesized through simultaneously fluorinating and reducing graphene oxide by pyrolysis of fluorinated graphite. Morphology investigation indicates that the doped graphene is of few-layered thickness, and the prepared films exhibit layered structure through cross-section. Chemical composition analysis confirms that fluorine has been grafted onto graphene scaffold through CF covalent bond, and the doping level can be readily manipulated just by adjusting the reaction temperature. The structural changes of graphene induced by the controllable doping thus facilitate the tunable electrical property, which can be tuned over several orders of magnitude. These results indicate our method is not only potentially useful to tailor the chemical surface and electronic structure of graphene, but also can find applications in novel electronic devices based on graphene co-doped with different dopants. 相似文献
92.
Sacha inchi (Plukenetia volubilis L., Euphorbiaceae) seed oil is rich in α-linolenic acid, a kind of n-3 fatty acids with many health benefits. To discover the mechanism underlying α-linolenic acid accumulation in sacha inchi seeds, preliminary research on sacha inchi seed development was carried out from one week after fertilization until maturity, focusing on phenology, oil content, and lipid profiles. The results suggested that the development of sacha inchi seeds from pollination to mature seed could be divided into three periods. In addition, investigations on the effect of temperature on sacha inchi seeds showed that total oil content decreased in the cool season, while unsaturated fatty acid and linolenic acid concentrations increased. In parallel, expression profiles of 17 unsaturated fatty acid related genes were characterized during seed development and the relationships between gene expression and lipid/unsaturated fatty acid accumulation were discussed. 相似文献
93.
《Journal of the European Ceramic Society》2014,34(3):841-848
A unique combination of high-energy ball-milling, annealing, and spark-plasma sintering has been used to process superhard B4C ceramics with ultrafine-grained, dense microstructures from commercially available powders, without sintering additives. It was found that the ultrafine powder prepared by high-energy ball-milling is hardly at all sinterable, but that B2O3 removal by gentle annealing in Ar provides the desired sinterability. A parametric study was also conducted to elucidate the role of the temperature (1600–1800 °C), time (1–9 min), and heating ramp (100 or 200 °C/min) in the densification and grain growth, and thus to identify optimal spark-plasma sintering conditions (i.e., 1700 °C for 3 min with 100 °C/min) to densify completely (>98.5%) the B4C ceramics with retention of ultrafine grains (∼370 nm). Super-high hardness of ∼38 GPa without relevant loss of toughness (∼3 MPa m1/2) was thus achieved, attributable to the smaller grain size and to the transgranular fracture mode of the B4C ceramics. 相似文献
94.
《Journal of the European Ceramic Society》2014,34(15):3635-3640
Laminated HfC–SiC/BN ceramics were successfully fabricated by tape casting and hot pressing. Fully dense HfC–SiC ultra-high temperature ceramics with homogeneous structure were obtained. The introduction of the weak BN layer resulted in a slight decrease of the flexural strength but significantly improved the fracture toughness compared with monolithic HfC–SiC ceramics. The fracture toughness of laminated HfC–SiC/BN ceramics in the parallel direction peaked at 8.06 ± 0.46 MPa m1/2, which increased by 115% than that of monolithic HfC–SiC ceramics. The composites showed non-catastrophic fracture behaviors in both parallel and perpendicular directions. It indicates that laminated structure design is a promising approach to obtain full density HfC–SiC ceramics with high fracture toughness. 相似文献
95.
《Acta Metallurgica》1987,35(3):735-739
An Al-0.58 m% Fe billet was cast by semicontinuous method (melt temperature: 685°C, casting speed: 80 mm/min). The intermetallic AlFe phases formed during casting and subsequent heat treatments were investigated by Mössbauer spectroscopy. The Mössbauer parameters of the iron-containing species (i.e. dissolved iron, Al6Fe and Al3Fe) occurring in the specimens were determined by the measurement of samples specially prepared for that purpose. Possible problems of phase analysis such as the apparent orientation of Al6Fe crystallites were also considered and discussed. The Mössbauer spectra indicated that initially the cast alloy contained only Al6Fe besides Al(Fe) solid solution. Heat treatments performed at 450 and 530°C caused only some broadening in the spectrum lines of Al6Fe, but at 620°C Al6Fe transformed completely to Al3Fe after 10–15 h. 相似文献
96.
《Fuel》1987,66(11):1540-1543
The relationship between the rate of secondary quinoline insoluble (QI) formation in coal-tar pitches and variations in their chemical composition is examined. Production of significant concentrations of secondary QI is shown to be accompanied by mesophase formation, the significance of which is discussed in terms of electrode binder performance. 相似文献
97.
《Fuel》1987,66(5):627-631
The effect of coal rank on the product distribution pattern was investigated in Ar at 1037 K with a Curie-point pyrolyser, using seventeen coals ranging from lignite to anthracite. The yields of inorganic gases, hydrocarbon gases, light hydrocarbon liquids and tar were determined and correlated with the structural parameters of the coals. The yields of CO2 were found to have a linear relationship with the carboxylic group content of the coals. The amounts of light hydrocarbon gases correlated well with the aliphatic hydrocarbon content of the coals. 相似文献
98.
99.
一种抗遮挡的运动目标跟踪算法 总被引:16,自引:4,他引:12
提出了一种基于彩色特征的抗遮挡目标跟踪算法。利用mean shift递推寻找当前帧目标的位置,并通过Kalman滤波估计目标状态。选用对目标部分遮挡具有鲁棒性的加权量化彩色直方图作为目标特征的概率分布,用Bhattacharyya系数作为特征相似性度量。提出一种目标遮挡因子,作为目标被遮挡程度的判断根据。当目标严重遮挡后,观测位置不再满足Kalman滤波的条件,采用目标状态量外推取代Kalman状态更新来预测目标当前的位置。实验结果表明,此方法对于部分遮挡以及全遮挡有较好的鲁棒性。 相似文献
100.
TDI-CCD图像传感器的噪声分析与处理 总被引:8,自引:2,他引:6
为提高TDI-CCD的工作性能,根据TDI-CCD器件的工作原理,较完整地分析了TDI-CCD图像的噪声组成,给出了其噪声的详细分类。TDI-CCD 的噪声主要来自两个方面,一个是TDI-CCD器件本身所固有的噪声,如霰粒噪声、非均匀性噪声、暗电流噪声、固定图形噪声、转移噪声等,另一个是TDI-CCD工作过程中的各种噪声干扰,如复位噪声和1/f噪声等。根据各种噪声的特点,提出了相应的噪声处理技术,并针对KTC噪声,给出了双相关采样电路处理方式,提高了器件的信噪比,输出信噪比达到53.8 dB。 相似文献