Replacement of methane from quartz sand-bearing hydrate with carbon dioxide-in-water emulsion

The replacement of CH4 from its hydrate in quartz sand with 90:10, 70:30, and 50:50 (W-CO2:W-H2O) carbon dioxide-in-water (C/W) emulsions and liquid CO2 has been performed in a cell with size of empty set 36 x 200 mm. The above emulsions were formed in a new emulsifier, in which the temperature and pressure were 285.2 K and 30 MPa, respectively, and the emulsions were stable for 7-12 h. The results of replacing showed that 13.1-27.1%, 14.1-25.5%, and 14.6-24.3% of CH4 had been displaced from its hydrate with the above emulsions after 24-96 It of replacement, corresponding to about 1.5 times the CH4 replaced with high-pressure liquid CO2. The results also showed that the replacement rate of CH4 with the above emulsions and liquid CO2 decreased from 0.543, 0.587, 0.608, and 0.348 1/h to 0.083, 0.077, 0.069, and 0.063 1/h with the replacement time increased from 24 to 96 h. It has been indicated by this study that the use of CO2 emulsions is advantageous compared to the use of liquid CO2 in replacing CH4 from its hydrate.

我国南海珊瑚礁区现代沉积底栖有孔虫的生态特征研究综述

综述了南海的海南岛和南海诸岛各珊瑚礁区现代沉积底栖有孔虫研究成果，区

FPGA中专用可重构乘法器的设计

提出了一种新的嵌入在FPGA中可重构的流水线乘法器设计.该设计采用了改进的波茨编码算法,可以实现18×18有符号乘法或17×17无符号乘法.还提出了一种新的电路优化方法来减少部分积的数目,并且提出了一种新的乘法器版图布局,以便适应tilebased FPGA芯片设计所加的约束.该乘法器可以配置成同步或异步模式,也町以配置成带流水线的模式以满足高频操作.该设计很容易扩展成不同的输入和输出位宽.同时提出了一种新的超前进位加法器电路来产生最后的结果.采用了传输门逻辑来实现整个乘法器.乘法器采用了中芯国际0.13μm CMOS工艺来实现,完成18×18的乘法操作需要4.1ns.全部使用2级的流水线时,时钟周期可以达到2.5ns.这比商用乘法器快29.1%,比其他乘法器快17.5%.与传统的基于查找表的乘法器相比,该乘法器的面积为传统乘法器面积的1/32.

ZnO单晶的缺陷及其对材料性质的影响

利用X射线衍射技术、荧光光谱、霍尔效应和光学显微等方法分别研究了ZnO单晶的品格完整性、深能级缺陷、电学性质、位错和生长极性．通过比较ZnO单晶材料在退火前后的测试结果，分析了材料的缺陷属性和缺陷对材料性质、晶体完整性的影响．

微重力细胞生物学实验地面模拟技术研究

<正>微重力对细胞的影响是空间生命科学研究的重要环节,(哺乳动物)细胞感受重力变化的机制是其中的一个基本问题。由于空间实验机会稀少且成本昂贵,必须辅助以相关的地面微重力效应模拟方法。旋转培养器在微重力细胞生物学实验中一直是模拟微重力效应的主要手段,其前提假设是,旋转可以"迷惑"细胞对固定重力方向的感知,并且重力方向改变的速度快于细胞对重力方向感知的响应时间阈值。严格上说旋

长白山北坡植被垂直带群落交错区的定量判定

以海拔梯度上的群落重要值和二元数据为指标 ,采用游动分割窗技术辨析了长白山北坡各植被带群落交错区的位置和宽度 .结果表明 ,采用平方欧氏距离 (SED)和Bray Curtis距离函数 (PD)计算的游动分割窗的峰值和峰宽有较好的重合性 ,其中基于灌木和草本物种重要值的平方欧氏距离更能准确地反映交错带植被的变异 .依据游动分割窗的分析 ,判定阔叶红松林和暗针叶林的交错区为渐变类型 ,位于海拔 112 0m ,宽度为 2 0 0m ,暗针叶林和岳桦交错区为急变类型 ,位于海拔 1790m ,宽度为 5 0m ,林线为急变类型 ,位于海拔 2 0 0 0m ,宽度为 4 0m .

Mass resolved MPI spectra of methyl iodide in the 430-490 nm region

The mass resolved multiphoton ionization (MPI) spectra of methyl iodide were obtained in the 430-490 nm region using a time-of-flight (TOF) mass spectrometer. They have the same vibrational structure, which testifies that the fragment species, in the wavelength region under study, are from the photodissociation of multiphoton ionized molecular parent ions. Some features in the spectra are identified as three-photon excitations to 6p and 7s Rydberg states of methyl iodide. Two new vibrational structures of some Rydberg states are observed. The mechanism of ionization and dissociation is also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.