Design of high T g Zr-based metallic glasses using atomistic simulation and experiment

In this paper, we systematically investigate local atomic structures of Zr_100?x Al _x (0???x???72) alloys using molecular dynamics simulations. Radial distribution functions of Zr-Al configurations at 300 K indicate that Zr-Al metallic glasses form only when the Al atomic concentration is larger than 32%. Voronoi polyhedral analysis shows that Zr₄₀Al₆₀ has the highest fraction of ?0,0,12,0? icosahedra around Al atoms, which are characteristic of amorphous microstructures. Variations of thermal expansion coefficient and heat capacity of Zr_100?x Al _x (40???x???72) metallic glasses as a function of temperature from 1100 to 800?K reveal that Zr₄₀Al₆₀ has the highest transition temperature of 1008?K. To confirm the simulation results, Zr-Al metallic glasses were fabricated using co-sputtering deposition; differential scanning calorimetry testing suggests the highest crystallisation-onset temperature of above 920?K is within Zr_100?x Al _x where 43?<?x?<?61. The experimental finding is in a good agreement with the simulation predictions.     

不同结构毛细管网辐射板供冷性能实验研究

对两种不同结构毛细管网辐射板的性能进行了实验研究,分析了在不同供水温度下,该两种辐射板在表面温度分布、供冷能力、安装辐射板房间温度变化情况之间的差异,为今后毛细管网辐射供冷空调系统辐射末端的设计应用及运行控制提供依据。     

量子密钥分发私密放大的实现

在量子密钥分发系统中,私密放大是合法通信双方提取共享安全密钥的一个必不可少的环节.本文主要介绍了实现私密放大的两种加速算法,采用将两种加速算法进行有效组合的方法,既可以保证私密放大的安全性,同时又有效地减少了运算的操作次数.在连续变量量子密钥分发实验系统中,采用上述组合加速算法,实现了安全密钥的提取.     

非均匀多孔介质有效热导率分析

本文采用控制容积法,界面调和平均导热系数值以及图形处理方法对典型非均匀多孔介质硬质聚氨酯泡沫材料的导热过程进行了分析与模拟计算。结果表明:多孔介质的内部结构是影响温度分布和热量传递的主要的因素,其影响程度与骨架和孔隙的导热系数,孔隙的大小和分布有关;计算得到的有效热导率值与文献中实验测量结果吻合较好。本文的研究结果可以推广到更为复杂的非均匀多孔介质的场合,从而可以进一步认识非均匀多孔介质中的导热规律,为工程计算提供更精确的计算方法。     

Mössbauer Study of Thin Iron Film Beryllization

Beryllium coating of the iron foil is made by means of magnetron sputtering. Mössbauer studies are performed by means of two registration techniques: conversion electron Mössbauer spectroscopy (CEMS) and the γ-ray technique in absorption geometry. Performed investigations confirm the original thermodynamic approach to creation of thermally stable multi-layer materials.

     

Nanopowder Characterization: Challenges and Future Directions

This article summarizes the conclusions of a workshop organized at the National Institute of Standards and nobreak Technology (NIST), Gaithersburg, October 4–5, 2001. The workshop was focused on the strengths and limitations of the techniques currently used for creating stable dispersions of nanoparticles and measuring the size distribution of powders in the nanosize range. Several emerging and alternative techniques with potential for use in particle size measurement in the nanometer range were advanced. Future needs for procedural and instrumental techniques and standards were identified.     

On the phase space approach to complexity

We elaborate in some detail on a new phase space approach to complexity, due to Y.-C. Zhang. We show in particular that the connection between maximal complexity and power law noise or correlations can be derived from a simple variational principle. For a 1D signal we find 1/f noise, in accordance with Zhang.     

Opinion dynamics in networks with heterogeneous confidence and influence

We propose a discrete-time model of opinion dynamics. The neighborhood relationship is decided by confidence radius and influence radius of each agent. We investigate the influence of heterogeneity in confidence/influence distribution on the behavior of the network. The simulations suggest that the heterogeneity of single confidence or influence networks can promote the opinions to achieve consensus. It is shown that the heterogeneous influence radius systems converge in fewer time steps and more often in finite time than the heterogeneous confidence radius systems. We find that heterogeneity does not always promote consensus, and there is an optimal heterogeneity so that the relative size of the largest consensus cluster reaches maximum in heterogeneous confidence and influence networks.     

The variation of Mn-dopant distribution state with x and its effect on the magnetic coupling mechanism in Znl-xMnxO nanocrystals

Zn1-xMnxO （x = 0.0005, 0.001, 0.005, 0.01, 0.02） nanocrystals are synthesized by using a wet chemical process. The coordination environment of Mn is characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, and its X-ray absorption fine structure. It is found that the solubility of substitutional Mn in a ZnO lattice is very low, which is less than 0.4%. Mn ions first dissolve into the substitutional sites in the ZnO lattice, thereby forming Mn2＋O4 tetrahedral coordination when x ≤ 0.001, then entering into the interstitial sites and forming Mn3＋O6 octahedral coordination when x ≥ 0.005. All the samples exhibit paramagnetic behaviors at room temperature, and antiferromagnetic coupling can be observed below 100 K.     

A practical method of investigating the stray light in laser Raman spectrophotometer

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