Exploring dynamic surface processes during silicate mineral (wollastonite) dissolution with liquid cell TEM

Most liquid cell transmission electron microscopy (LC TEM) studies focus on nanoparticles or nanowires, in large part because the preparation and study of materials in this size range is straightforward. By contrast, this is not true for samples in the micrometre size range, in large part because of the difficulties associated with sample preparation starting from a ‘bulk’ material. There are also many advantages inherent to the study of micrometre‐sized samples compared to their nanometre‐sized counterparts. Here, we present a liquid cell transmission electron study that employed an innovative sample preparation technique using focused ion beam (FIB) milling to fabricate micrometre‐sized electron transparent lamellae that were then welded to the liquid cell substrate. This technique, for which we have described in detail all of the fabrication steps, allows for samples having dimensions of several square micrometres to be observed by TEM in situ in a liquid. We applied this technique to test whether we could observe and measure in situ dissolution of a crystalline material called wollastonite, a calcium silicate mineral. More specifically, this study was used to observe and record surface dynamics associated with step and terrace edge movement, which are ultimately linked to the overall rate of dissolution. The wollastonite lamella underwent chemical reactions in pure deionized water at ambient temperature in a liquid cell with a 5‐m‐spacer thickness. The movement of surface steps and terraces was measured periodically over a period of almost 5 h. Quite unexpectedly, the one‐dimensional rates of retreat of these surface features were not constant, but changed over time. In addition, there were noticeable quantitative differences in retreat rates as a function crystallographic orientation, indicating that surface retreat is anisotropic. Several bulk rates of dissolution were also determined (1.6–4.2 ? 10^?7 mol m^?2 s^?1) using the rates of retreat of representative terraces and steps, and were found to be within one order of magnitude of dissolution rates in the literature based on aqueous chemistry data.     

新疆阿合奇县牙尔巴西沟泥石流特征与防治

以2010年9月19日新疆阿合奇县牙尔巴西沟泥石流为例,通过现场勘查和室内计算,分析了该泥石流特征并对其形成机理进行了研究。针对该区域的泥石流物源特征和下游沟道淤积的特点,提出了"拦挡+停淤"的治理方案,主要包括修建拦砂坝和停淤场等防护措施。研究结果可为新疆南麓区域泥石流的分析与防治提供参考。     

无人机影像与地形指数结合的梯田信息提取

目前,通过卫星遥感、低空遥感影像自动,半自动化解译梯田信息有一定的研究进展,但是受数据获取成本、精度、解译方法单一等限制,只限于大面积提取梯田区域。低成本地进行梯田的田面精准提取以及面积统计仍需进一步研究。本文基于面向对象方法分别对0.5m分辨率的无人机正射影像和地形指数,及两种数据的结合进行梯田区域分割、提取及面积统计。结果表明,将正射影像数据与地形指数结合的梯田的田面提取结果优于基于单一数据源。     

船载双惯导系统动态加速度计零位研究

为提高船用惯性导航系统动态工作可靠性,通过在动态情况下比对2套惯导姿态角差值来判断惯性平台是否水平;然后再通过加速度计零位与平台倾斜角度的关系来修正加速度计零位,以解决因更换加速度计而要求船舶必须进厂的矛盾;同时也提供了一种判断船用惯性导航系统加速度计工作状态好坏的方法。     

广西龙脊梯田景区生态旅游开发的生态环境保护

龙脊梯田景区是大桂林旅游圈的重要组成部分，其自然资源和人文资源丰富，景观独特，宜于发展生态旅游。但基础设施建设、耕地及人口素质成为旅游开发的主要限制因素，此外，资源优化配置、生态建设、环境保护和传统文化继承等问题，也迫切需要得到有效解决。     

构建市级电子政务安全平台

随着信息化建设的逐步推进,电子政务系统对其安全运行的依赖性越来越强。为了给市级电子政务系统的运行提供必要的安全保障,文中在基于PKI技术的安全平台建设的基础上,又增加了为系统防范网络内部的行为滥用和网络外部的恶意攻击而提供的安全辅助支撑平台,从而构建了市级电子政务系统全方位的安全平台。     

高校共建电子商务专业综合实验实训平台的探讨

本文论述了在企业商务电子化普遍应用的大趋势下,高校电子商务专业实践教学环境的建设已成为开设此类专业高等院校的重大课题。各高校尤其是同类别院校共同携手,以合作联盟的方式建立综合实验实训平台,力图实现技术共享、信息共享、资源共享、成果共享。合作共建避免了低水平的重复建设,低投入,高产出,有效地解决了资金及人力资源不足问题。     

振冲密实法单桩加固范围的变化规律

本文根据标贯检测资料,经统计分析,得出松散砂土地基上振冲单桩加固范围的立体形状为一圆台,并据此提出振冲密实法桩设计的新设想.     

PKPM在工业装置结构地坪及沉降计算中的应用

介绍了工业装置结构地坪的做法,分析了主梁和承台连接构造在PKPM模型中的实现方法,比较了多种计算模型的结果,解决了主梁计算跨度与实际跨度相差较大的问题,结合实际工程,分析并解决了工业项目中构筑物基础和大型储罐基础沉降的整体计算问题。     

对广州、中山几条步行街改造的思考

针对当前商业步行街改造多而不精的现象,深入分析了步行街产生及其意义,并以广州市、中山市的几条主要步行街为例,进行理性的对比分析,指出存在的问题,从城市的角度提出将步行街扩大为步行街区的构想,并分析其可行性。