Dynamic behavior of a Zr-based metallic glass at cryogenic temperature

The dynamic behavior of a Zr-based bulk metallic glass at cryogenic temperature is investigated by a miniaturized split Hopkinson pressure bar apparatus. As that at room temperature, the failure stress decreases suddenly and then tends to hold steady along with increasing strain rate at cryogenic temperature, but the strain rate regime corresponding to the sudden decrease of the failure stress moves up. The failure stress also increases along with decreasing temperature, whereas there is no obvious change for the plasticity.     

In situ continuously monitoring the early age microstructure evolution of cementitious materials using ultrasonic measurement

The early age microstructure evolution was continuously monitored by using a specially improved ultrasonic monitoring apparatus. The influence of water-to-binder ratios, mineral admixtures, aggregates and temperature were systematically investigated. The experimental results show that concrete can be clearly classified into four stages, while only the three stages can be observed without coarse aggregates. In addition, pre-percolation threshold, percolation threshold and full connectivity of the solid phase were identified. The microstructure formation is promoted with the reduced water-to-binder ratios, increased temperature, silica fume and aggregates addition, while the reverse phenomenon is observed when fly ash and slag are incorporated.     

光影诗篇——墨西哥建筑艺术中的地域智慧与启迪

强烈的光照作为墨西哥一个十分突出的地域特征,对墨西哥的气候、文化乃至民众的生活习惯都产生了巨大的影响。墨西哥建筑师敏锐地捕捉到这一特征,融入自己的理解和想象,在光影与空间的交织、变化中呈现出丰富的情感色彩,使得建筑与人之间建立起直触心灵的对话。随着时代的变迁和文化的发展,建筑所要实现的功能、表达的情感在不断改变,而建筑师们对于光影的处理手段也趋于多元化,从而产生了越来越多极具特色的建筑形式。通过对墨西哥不同历史时期建筑的分析,来研究墨西哥建筑师运用光影塑造不同情感空间的多种手法和传承关系。     

W-based versus latent variables spatial autoregressive models: evidence from Monte Carlo simulations

In this paper, we compare by means of Monte Carlo simulations two approaches to take spatial autocorrelation into account: the classical spatial autoregressive model and the structural equations model with latent variables. The former accounts for spatial dependence and spillover effects in georeferenced data by means of a spatial weights matrix W. The latter represents spatial dependence and spillover effects by means of a latent variable in the structural (regression) model while the observed spatially lagged variables are related to the latent spatial dependence variable in the measurement model. The simulation results based on Anselin’s Columbus, Ohio, crime data set show that the misspecified latent variables approach slightly trails the correctly specified classical approach in terms of bias and root mean squared error of the coefficient estimators.     

从种子产业的形势看大豆种业的发展

介绍了我国大豆种业发展的概况,讨论了当前形势下我国大豆种业存在的问题,提出了加快大豆种业发展的建议.     

建筑业农民工夜校的法制教育探讨

开办农民工夜校是提升农民工素质的有效途径.分析了建筑业农民工夜校开展法制教育的意义,阐述了建筑业农民工夜校法制课程教学应遵循的原则、教学内容的安排和教学手段、方法的选择.     

A Novel Method for Calculation of Eigenmodes of Gyrotron Resonators

A new method for calculating the eigenmodes of gyrotron resonators is presented. With this method, the resonant frequency, Q-factor and field profiles of the eigenmodes are determined through finding the minimum value of a function of two variables, namely the resonant frequency and the Q-factor. Compared with the traditional calculation method, the new method predicts a significantly higher Q-factor of the eigenmodes.     

Growth of hydrophobic TiO2 on wood surface using a hydrothermal method

Hydrophobic titanium dioxide (TiO₂) was successfully grown on a wood surface using a hydrothermal method. Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and water contact angle (WCA) were employed to characterize the features of grown TiO₂ and its hydrophobicity. EDS, XRD, and FTIR proved that anatase TiO₂ chemically bonded to the wood surface through the combination of hydrogen groups during the hydrothermal process. The values of WCAs manifested that the hydrophobicity of the treated wood was mainly dependent on specific reaction conditions, especially on reaction pH value and hydrothermal temperature. The highest WCA reached 154° when the hydrothermal temperature was 130 °C. The treated wood thus possessed a superhydrophobic surface.