利用双光栅Lau效应测量透镜焦距

根据计量光栅的特点，可以利用双光栅效应测量透镜焦距．本文简述了利用双光栅Lau效应测量透镜焦距的实验原理、实验装置及测量方法，并计算了测量结果的不确定度．     

抑制孔径间距误差影响的相干场成像质量提升方法研究

相干场成像基于激光发射孔径间距相等、频谱相等的基本假设, 迭代计算频谱重建高分辨图像, 实际应用中不可避免的激光发射孔径间距误差是影响成像质量的重要因素. 针对发射孔径间距误差造成的成像质量下降问题, 提出一种抑制孔径间距误差影响的成像质量提升方法. 首先分析了孔径间距误差对激光回波频谱和成像质量的影响机理; 推导得到了频谱误差迭代模型; 理论上构建了孔径间距误差对信号频谱和成像质量的零影响条件方程; 提出一种线性规划方法求解成像质量零影响条件方程, 得到孔径间距误差最优化分布矩阵; 实际应用中基于该最优化误差矩阵合理分配各孔径间距误差, 就可抑制孔径误差对成像质量的影响. 实验验证了该方法的正确性和有效性. 结果表明: 该方法可提升成像质量评价指标斯特列尔比近1倍; 所提方法可便捷有效地抑制孔径误差对成像质量的影响. 该研究为实际相干场系统成像质量的提升和发射阵列孔径间距精度设计提供了理论指导.     

能谱涨落统计特征分析在Logistic混沌序列上的应用

混沌现象普遍存在于现实生活中,混沌时间序列的分析是非线性系统研究的主要内容.基于Anderson 模型,提出了一种新的混沌序列的分析方法.通过对Logistic序列的分析,使用能谱涨落分析方法,发现能级斥力的大小能与最大lyapunov指数相对应.结果表明,该方法能较好的预测混沌序列,而且具有较强的抗噪声的能力,不受初值敏感性的影响.     

In silico identification and structure function analysis of a putative coclaurine N-methyltransferase from Aristolochia fimbriata

In this study we isolated and performed in silico analysis of a putative coclaurine N-methyltransferase (CNMT) from the basal angiosperm Aristolochia fimbriata. The Aristolochiaceae plant family produces alkaloids similar to the Papavaraceae family, and CNMTs are central enzymes in biosynthesis pathways producing compounds of ethnopharmacological interest. We used bioinformatics and computational tools to predict a three-dimensional homology model and to investigate the putative function of the protein and its mechanism for methylation. The putative CNMT is a unique (S)-adenosyl-L-methionine (SAM)-dependent N-methyltransferase, catalyzing transfer of a methyl group from SAM to the amino group of coclaurine. The model revealed a mixed α/β structure comprising seven twisted β-strands surrounded by twelve α-helices. Sequence comparisons and the model indicate an N-terminal catalytic Core domain and a C-terminal domain, of which the latter forms a pocket for coclaurine. An additional binding pocket for SAM is connected to the coclaurine binding pocket by a small opening. CNMT activity is proposed to follow an S_N2-type mechanism as observed for a similarly conformed enzyme. Residues predicted for the methyl transfer reaction are Tyr79 and Glu96, which are conserved in the sequence from A. fimbriata and in homologous N-methyltransferases. The isolated CNMT is the first to be investigated from any basal angiosperm.     

Tuning the Interlayer Spacings in Dry Graphene Oxide Membranes via Ions

We show the experimental achievement of dry GO membranes with interlayer spacings in the range from 7.09 Å to 8.72 Å, tuned and fixed by salts. We found that the interlayer spacings were dominated by the anions or the groups with negative charges in between the GO membranes. Density functional theory (DFT) calculations reveal that the highly efficient tuning of the interlayer spacing in dry GO membranes is due to ion‐π interactions on the graphene sheets, together with the steric effects of anions in between the GO sheets. The findings are helpful for extending their potential applications including chemical sensors, nanomaterial devices preparation, chemical catalysis and synthesis, and gas separation.     

微米尺寸二硫化钼层间化合物的电化学制备及其储镁性能

采用一种简便的电化学方法制备了有机阳离子(1-丁基-3-甲基咪唑阳离子,BMIM~+)插层的微米尺寸MoS_2层间化合物,并将其用作镁离子电池正极材料。所制备的MoS_2层间化合物(MoS_2-BMIM~+)具有扩大的层间距(0.98 nm),能有效降低Mg~(2+)的嵌入/脱出势垒,为存储Mg~(2+)提供了更多的活性位点,从而表现出显著提高的充电比容量和良好的倍率性能。MoS_2-BMIM~+在20 mA·g~(-1)电流密度下的充电比容量可达101.93 mAh·g~(-1)(约4倍于初始体相MoS_2)。我们进一步证明了这一方法同样适用于插层1-丁基-1-甲基吡咯烷双阳离子(Pyr~+_(14)),所得化合物的层间距为1.04 nm。     

激光快速凝固条件下Cu-31.4%Mn合金的微观组织特征

利用连续波CO2激光器对Cu 314%Mn进行了系列表面熔凝实验，对该合金的组织形态和胞晶间距选择规律进行了研究.结果表明：随着生长速度的提高，组织形态由低速平界面向展宽胞晶、规则胞晶、展宽胞晶、类平面晶和高速绝对稳定平界面转变.在快速凝固条件下，Cu 314%Mn合金的胞晶间距存在一个选择范围，最大、最小和平均胞晶间距与生长速度的关系分别为λmax=682v-033s，λmin=289v-028s和=435v-031s，实验结果与Hunt Lu模型的预测结果相吻合.     

Periodic cracking of films supported on compliant substrates

When a tensile strain is applied to a film supported on a compliant substrate, a pattern of parallel cracks can channel through both the film and substrate. A linear-elastic fracture-mechanics model for the phenomenon is presented to extend earlier analyses in which cracking was limited to the film. It is shown how failure of the substrate reduces the critical strain required to initiate fracture of the film. This effect is more pronounced for relatively tough films. However, there is a critical ratio of the film to substrate toughness above which stable cracks do not form in response to an applied load. Instead, catastrophic failure of the substrate occurs simultaneously with the propagation of a single channel crack. This critical toughness ratio increases with the modulus mismatch between the film and the substrate, so that periodic crack patterns are more likely to be observed with relatively stiff films. With relatively low values of modulus mismatch, even a film that is more brittle than the substrate can cause catastrophic failure of the substrate. Below the critical toughness ratio, there is a regime in which stable crack arrays can be formed in the film and substrate. The depth of these arrays increases, while the spacing decreases, as the strain is increased. Eventually, the crack array can become deep enough to cause substrate failure.     

采用元胞自动机法模拟二元规则共晶生长

基于元胞自动机方法,建立了二元规则共晶生长的数值模拟模型.该模型耦合宏观温度场,考虑了溶质扩散、成分过冷以及曲率过冷等重要因素,实现了二元规则共晶的稳态层片生长.以共晶模型合金为对象,研究了定向凝固条件下不同过冷度、初始层片间距、温度梯度及凝固速率对共晶两相生长形貌及层片间距的影响,再现了两相在溶质扩散及界面能的相互作用下通过形核、分岔、湮没及合并等机理实现共晶层片间距的调整.模拟得到的结果与Jackson-Hunt模型及前人实验结果规律一致.将模型扩展到三维系统,验证了二元规则共晶生长三维模拟的可行性. 关键词： 规则共晶 生长形貌 层片间距 CA方法     

磁性量子元胞自动机逻辑电路的转换特性研究

本文研究了磁性量子元胞自动机反相器和择多逻辑门等基本逻辑电路在不同纳磁体厚度和间距下的转换特性.采用单畴近似LLG方程对纳磁体以及电路进行了建模和仿真,结果表明更厚的纳磁体需要更大的转换磁脉冲,大厚度纳磁体逻辑电路表现出较慢的转换;相同厚度和间距下,择多逻辑门比反相器的转换时间略长.此外,模拟结果还表明纳磁体间距对反相器的转换过程影响明显,而对择多逻辑门则影响较小. 关键词： 磁性量子元胞自动机 转换特性 厚度和间距 逻辑电路