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41.
The interaction of alkali metal with surfaces has been of great interest to the community of catalysis since alkali metal can play an important role as a promoter. On alkali-doped MoS2, such a promotion effect of alkali metal has been exemplified in the direct synthesis of linear alcohols from CO and H2, where the alkali-doping switches the catalyst selectivity from methanation to alcohol synthesis. This paper reviews recent high-resolution X-ray photoelectron spectroscopy experiments that have provided direct
observation of electron transfer from alkali metals to a model single crystal MoS2 and the capture of the supra-valence electrons in the subsequent oxidation reactions. 相似文献
42.
用射频分子束外延技术研制出了室温迁移率为1035cm2/(V·s),二维电子气浓度为1.0×1013cm-2,77K迁移率为2653cm2/(V·s),二维电子气浓度为9.6×1012cm-2的AlGaN/GaN高电子迁移率晶体管材料.用此材料研制的器件(栅长为1μm,栅宽为80μm,源-漏间距为4μm)的室温非本征跨导为186mS/mm,最大漏极饱和电流密度为925mA/mm,特征频率为18.8GHz. 相似文献
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45.
Real-time palmprint acquisition system design 总被引:1,自引:0,他引:1
Wong M. Zhang D. Kong W.-K. Lu G. 《Vision, Image and Signal Processing, IEE Proceedings -》2005,152(5):527-534
Capturing high quality palmprint images in a very short time period is a fundamental step in palmprint research. While a palmprint scanner capable of this function is especially important for developing a real-time online palmprint identification system, limited research effort has been put into designing and implementing palmprint acquisition systems. A novel palmprint acquisition system is presented, which is designed for various civilian applications such as access control, ATM, etc. The novel contactless design on the user interface prevents the distortion of the palm skin introduced by the traditional glass plate of a palm scanner. The system is designed to have the best performance at reasonable price. It has a resolution of 150 dpi that is able to obtain palmprint features, including the principal lines, wrinkles and ridge texture. The proposed system provides an important step for implementing a personal identification system using palmprint. Over 9,400 palmprint images were collected by the proposed system. An online palmprint identification system was then developed based on the proposed acquisition system. 相似文献
46.
氨合成塔出口氨含量偏低原因分析及对策 总被引:1,自引:0,他引:1
阐述UHDE合成塔运行现状 ,分析氨净值达不到设计值的原因 ,提出相应的解决措施 相似文献
47.
Shumin Zhai Jing Kong Xiangshi Ren 《International journal of human-computer studies》2004,61(6):823-856
Pointing tasks in human–computer interaction obey certain speed–accuracy tradeoff rules. In general, the more accurate the task to be accomplished, the longer it takes and vice versa. Fitts’ law models the speed–accuracy tradeoff effect in pointing as imposed by the task parameters, through Fitts’ index of difficulty (Id) based on the ratio of the nominal movement distance and the size of the target. Operating with different speed or accuracy biases, performers may utilize more or less area than the target specifies, introducing another subjective layer of speed–accuracy tradeoff relative to the task specification. A conventional approach to overcome the impact of the subjective layer of speed–accuracy tradeoff is to use the a posteriori “effective” pointing precision We in lieu of the nominal target width W. Such an approach has lacked a theoretical or empirical foundation. This study investigates the nature and the relationship of the two layers of speed–accuracy tradeoff by systematically controlling both Id and the index of target utilization Iu in a set of four experiments. Their results show that the impacts of the two layers of speed–accuracy tradeoff are not fundamentally equivalent. The use of We could indeed compensate for the difference in target utilization, but not completely. More logical Fitts’ law parameter estimates can be obtained by the We adjustment, although its use also lowers the correlation between pointing time and the index of difficulty. The study also shows the complex interaction effect between Id and Iu, suggesting that a simple and complete model accommodating both layers of speed–accuracy tradeoff may not exist. 相似文献
48.
49.
Flame retardant and the degradation mechanism of high impact polystyrene/Fe-montmorillonite nanocomposites 总被引:1,自引:1,他引:0
High impact polystyrene/Fe-montmorillonite (HIPS/Fe-MMT) nanocomposites were successfully prepared by melting intercalation.
The nanostructures of HIPS/Fe-MMT were testified by X-ray diffraction (XRD) and transmission electron microscope (TEM). Corresponding
to pure HIPS, the thermal stability of HIPS/Fe-MMT nanocomposites was notably improved. The peaks of heat release rate (PHRR)
and the mass loss rate (MLR) were significantly reduced after the formation of the HIPS/Fe-MMT nanocomposites from cone calorimetry.
And nanocomposites PHRR was further lower with the increase of Fe-MMT content in the range of 1 to 5 wt%. The degradation
mechanism of HIPS and HIPS/Fe-MMT nanocomposites was conducted by pyrolysis gas chromatography mass spectrometry (Py-GC-MS).
And the reason of the enhancement of thermal stability maybe is that structural iron is the operative site for radical trapping
in the Fe-MMT and the nanostructure enhances the interaction of the chains of the HIPS. 相似文献
50.
通过对大别山北缘火山岩大量的样品分析认为,本火区山岩主量元素的地球化学特征属碱钙性,稀土元素表现轻稀土富集的地球化学特征。在此基础上,进一步研究火山岩成分与其形成构造环境之间的关系,认为本区火山岩形成于板块俯冲碰撞期后,与造山带根部拆沉相联系的构造环境。 相似文献