一种容错计算机体系结构在惯性系统中的应用

容错技术已成为提高计算机系统可靠性的必要手段.通过对冗余模式及级别进行选择,本文提出了一种面向任务的双机并联体系结构,运用双机数据比较实现容错.文中给出了此系统的功能、结构及原理,并给出了部分实现方案.     

2p2阶3度点传递图

一个图称为点传递图,如果它的全自同构群在它的顶点集合上作用传递.本文证明了一个2p～2（p为素数）阶连通3度点传递图或者是Calyley图,或者同构于广义Petersen图P（p～2,t）,这里t～2≡-1（modp～2）.     

介孔SiO2孔道内Gemini分子有序自组装构筑正相胶束辅助传递OH-离子

利用Gemini型阳离子表面活性剂(顺丁烯二酸二乙酯撑基双[辛烷基二甲基氯/溴化铵], G_8-2-8)在有机反离子水杨酸根(Sal^-)的诱导作用下, 于介孔SiO₂孔道内有序组装, 构筑表面带有季铵基团的正相蠕虫胶束. 胶束外表面有序排布的季铵基团与介孔SiO₂孔道内壁布满的硅羟基共同作用形成环形保水腔室, 即构筑了OH^-传递的有序通道. 通过对G_8-2-8/NaSal 胶束体系的流变学性质研究, 结果表明, 胶束网络结构已经形成. 将G_8-2-8/NaSal胶束网络形成过程引入聚砜(PSF)体系中, 制备出有序OH^-迁移通道的高耐碱性的阴离子导电膜. 相关性能测定结果表明, 随着G_8-2-8质量分数的增加, 电导率、 含水率及离子交换量均呈现上升趋势, 特别是在离子交换量和含水率均较低的情况下, OH^-的迁移效率得到明显提升. 经过400 h的耐碱性测试, 结果表明, 该系列膜的电导率降幅仅为1.5%左右, 且外观形貌无明显变化, 表现出优异的耐碱稳定性.     

Cu-supported carbon networks containing SnO<Subscript>2</Subscript> as three-dimensional anodes for lithium-ion batteries

Cu-supported SnO₂@C composite coatings constructed by interconnected carbon-based porous branches were fabricated by annealing Cu foils with films formed by knife coating DMF solution containing SnCl₂, polyacrylonitrile (PAN), and poly(methyl methacrylate) (PMMA) on their surface in vacuum. The carbon-based porous branches consist of amorphous carbon matrices, SnO₂ nanoparticles with a size of 30–100 nm mainly encapsulated inside, and many micropores with a size of 1–5 nm. The three-dimensional (3D) porous network structures of the SnO₂@C composite were achieved by volatilization of PMMA and pyrolysis of SnCl₂. The SnO₂@C composite coatings demonstrate good cyclic performance with a high reversible capacity of 642 mA h g^?1 after 100 cycles at a current density of 50 mA g^?1 without apparent capacity fading during cycling and excellent rate performance with a capacity of 276 mA h g^?1 at a high current density up to 10 A g^?1.     

AFM characterization of dendrimer-stabilized platinum nanoparticles

This work describes the use of atomic force microscopy (AFM) to measure the size of dendrimer-stabilized Pt nanoparticles (Pt DNs) deposited from aqueous solutions onto mica surfaces. Despite considerable previous work in this area, we do not fully understand the mechanisms by which PAMAM dendrimers template the formation of Pt DNs. In particular, Pt DN sizes measured by high-resolution transmission electron microscopy (HRTEM) are reported to be larger than expected if one assumes that each PAMAM molecule templates one spherical Pt nanoparticle. AFM provides a vertical height measurement that complements the lateral dimension measurement from HRTEM. We show that AFM height measurements can distinguish between "empty" PAMAM and Pt DNs. If the complexation of Pt precursor with PAMAM is prematurely terminated, AFM images and feature height distributions show evidence of arrested precipitation of Pt colloids. In contrast, sufficient Pt-PAMAM complexation time leads to AFM images and height distributions that have relatively narrow, normal distributions with mean values that increase with the nominal Pt:PAMAM ratio. The surface density of features in AFM images suggest that these Pt DNs reside on the mica surface as two-dimensional surface aggregates. These observations are consistent with an intradendrimer templating mechanism for Pt DNs. However, we cannot determine if the mechanism obeys a fixed loading law because we do not have definitive information about Pt DN shape. A second peak in the Pt DN height distribution appears when the Pt loading exceeds about 66% of PAMAM's theoretical capacity for Pt. Excluding these secondary particles, the dependence of mean feature height on the Pt:PAMAM ratio follows a power-law relationship. Also considering the magnitudes of the measured mean height values, the data suggest that Pt DNs exist as ramified, noncompact aggregates of Pt atoms interspersed within the PAMAM framework.     

Fe2O3-MWNTs Composite with Reinforced Concrete Structure as High-performance Anode Material for Lithium-ion Batteries

AFe₂O₃-MWNTs(multi-walled carbon nanotubes) composite with a reinforced concrete structure was fabricated employing a two-step method, which involves a sol-gel process followed by high-temperature in situ sintering. This Fe₂O₃-MWNTs composite, intended to be used as an anode material for lithium-ion batteries, maintained a reversible capacity as high as 896.3 mA·h/g after 100 cycles at a current density of 100 mA/g and the initial coulombic efficiency reached 75.5%. The rate capabilities of the Fe₂O₃-MWNTs composite, evaluated using the ratios of capacity at 100, 200, 500, 1000, 2000 and 100 mA/g after every 10 cycles, were determined to be 904.7, 852.1, 759.0, 653.8, 566.8 and 866.3 mA·h/g, respectively. Such a superior electrochemical performance of the Fe₂O₃-MWNTs composite is mainly attributed to the reinforced concrete construction, in which the MWNTs function as the skeleton and conductive network. Such a structure contributes to shortening the transport pathways for both Li⁺ and electrons, enhancing conductivity and accommodating volume expansion during prolonged cycling. This Fe₂O₃-MWNTs composite with the designed structure is a promising anode material for high-performance lithium-ion batteries.     

Construction of a Recombinant <Emphasis Type="Italic">S. cerevisiae</Emphasis> Expressing a Fusion Protein and Study on the Effect of Converting Xylose and Glucose to Ethanol

Gene XYL1 from Candida shehatae and gene XYL2 from Pichia stipitis were amplified by polymerase chain reaction (PCR), and the two genes were both placed under the strong promoter of alcohol dehydrogenase (ADH) of plasmid pAD2 to produce the recombinant expression vector pAD2-P12. Because the amplified XYL1 fragment lacks the stop codon UAA, the polypeptide expressed in yeast cells should be a fusion protein, which is a fusion of xylose reductase and xylitol dehydrogenase. Subsequently, the pAD2-P12 vector was transformed into Saccharomyces cerevisiae YS58 to produce a recombinant S. cerevisiae YS58-12. It was indicated that S. cerevisiae YS58-12 has the ability of metabolizing xylose to produce ethanol by fermentation experiment. The result of cofermentation of glucose and xylose by using this recombinant S. cerevisiae YS58-12 showed a relatively satisfactory result. The highest percentage of xylose consumption rate reached 81.3% and the ethanol yield was equal to 67.14% of the ideal value.     

Novel 2N bit bipolar photonic digital-to-analog converter based on optical DQPSK modulation coupled with differential detection

A novel 2N bit bipolar photonic digital-to-analog converter (PDAC) scenario based on the optical differential quadrature phase shift keying (ODQPSK) modulation coupled with differential detection is proposed. Compared with other proposed schemes, this bipolar PDAC has a greater dynamic range and a larger noise margin with good scalabilities both in speed and resolution. We demonstrate a 4 bit PDAC in a proof-of-principle experiment at a sampling rate of 2.5 GS/s.     

石墨炉法测定牛黄解毒片等中药的As、Hg、Mo

从牛黄解毒片等复方中成药中Ａｓ、Ｈｇ、Ｍｏ元素分析测定研究入手,测定了Ａｓ、Ｈｇ、Ｍｏ元素的含量,讨论了这些元素与药效的关系。     

Characteristics investigation of Yb3+:YAG crystals for optical refrigeration

Yb³⁺:YAG crystal is one excellent material for developing high-power radiation-balanced lasers (RBLs). An experimental study of the laser cooling performances of YAG crystals with various doping Yb³⁺ concentrations, especially for application of RBLs, is reported here. With improved Yb³⁺ doping concentration in YAG crystal, though the resonance absorption coefficient increases, the corresponding external quantum efficiency has been found to decrease with the average fluorescence wavelength being red shifted, which is detrimental to anti-Stokes fluorescence (ASF) cooling. The decrease of the external quantum efficiency can cause the first zero crossing wavelength to red shift, which is not conducive to RBLs. Based on the comprehensive study of the cooling characteristics of the series of Yb³⁺-doped YAG crystals, the optimal Yb³⁺ doping concentration for ASF cooling has been suggested.