Drying of salt-contaminated masonry: MRI laboratory monitoring

Drying of masonry specimens was monitored by means of a two-dimensional (2D) magnetic resonance imaging (MRI) technique. The external surfaces stayed wet for longer if NaCl was present instead of pure water only. This corroborates many practical observations that salts aggravate dampness in masonry. A slower evaporation process and not hygroscopicity was the cause. That suggests that salt-induced dampness may, in general, arise simply from changes in the drying process of masonry materials. That also implies that the height and depth at which crystallization occurs in walls may depend on the relative equilibrium humidity (RHeq) and other properties of salts that influence drying of porous materials. Evaporation rates of free surfaces of pure water and saturated NaCl solution were measured by a gravimetric technique. The results indicate that slow drying of salt-contaminated materials is not due only to the lower RHeq of salt solutions. The effective surface of evaporation is likely to be reduced perhaps due to blocking of pores by salt crystals. Final salt-distribution maps of the specimens show that: (a) salts may affect the inner materials of the masonry, even in evaporation-induced processes that lead crystallization to occur predominantly on the external surface; (b) distinct internal distribution patterns occur if masonry composition varies. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

核磁共振方法在致密砂岩储层孔隙结构中的应用--以鄂尔多斯大牛地气田上古生界石盒子组3段为例

采用低场核磁共振实验的方法研究了鄂尔多斯盆地大牛地气田上古生界石盒子组3段岩芯样品的核磁共振弛豫时间T2分布与由压汞毛管压力曲线所获得的孔喉半径分布之间的对应关系和转换方法,建立了T2几何平均值与毛管压力曲线孔喉结构参数之间的统计关系.研究结果表明,致密砂岩储层的核磁共振T2分布与由毛管压力曲线所获得的孔径分布之间存在密切的相关性,二者都反映了岩石的孔隙结构,利用核磁共振技术来评价致密砂岩储层的孔喉结构是有效的,同时也为利用核磁共振测井技术开展致密砂岩储层评价提供了实验基础.     

氢质子弛豫过程

论述了原子核系统磁化强度的的弛豫原理,分析了含水地层中氢质子磁化强度的弛豫过程,推导出磁化强度的布洛赫方程,从而给出接受线圈中感应电动势的衰减规律,通过计算得到磁化强度各分量随时间的衰减过程以及感应电动势的衰减曲线,分析了纵向弛豫和横向弛豫时间常数与磁化强度各分量和感应电动势的关系。     

基于低压核磁共振(LF-NMR)技术对东海带鱼(Trichiurus lepturus)保鲜品质及水分迁移特性的研究

为探究东海带鱼(Trichiurus lepturus)在低压核磁共振(LF-NMR)技术下的品质变化及水分迁移特性,以挥发性盐基氮(TVB-N)含量、pH、水分含量为指标,并分析NMR横向弛豫时间T₂反演谱图和MRI成像,研究不同电场强度(DY₁~DY₄分别为0,2,2.5,3kV/m)对带鱼内部水分迁移及品质的影响。分析TVB-N数据发现,DY₃(E=2.5kV/m)、DY₄(E=3kV/m)在贮藏后期表现出更佳的保鲜优势。在0~40d贮藏期内,不同电场强度条件下的带鱼pH值均呈先降后升趋势。电场的添加能降低自由水的流动性,抑制微生物生长,减少带鱼体内水分流失。分析NMR横向弛豫时间T₂反演谱图发现,T₂₁、T₂₂、T₂₃峰面积均有不同程度减小,其中T₂₂信号幅度变化最大,表明电场的添加能改变带鱼体内水分迁移路径,维持较高的水分含量,增加带鱼持水性和保水性。MRI成像图表明在贮藏期间,电场处理后带鱼水分保有率得到了提升,保鲜效果优于未施加电场带鱼,且电场强度越大,体外迁移水分越少。实验表明低压核磁共振(LF-NMR)技术对东海带鱼具有良好的保鲜效果,对低压核磁共振(LF-NMR)技术的保鲜应用提供一定的理论指导作用。<     

三疣梭子蟹(Portunus trituberculatus)的保活参数优化及其代谢响应

为延长三疣梭子蟹(Portunus trituberculatus)在捕捞后的存活时间,在优化保活温度和充氧量的基础上,再采用基于核磁共振(NMR)的代谢组学技术,比较分析了三疣梭子蟹前鳃代谢谱在充氧和不充氧保活过程中的变化。结果发现, 12 ℃下的三疣梭子蟹存活率最高, 80%的三疣梭子蟹能存活3.5 d。加大充氧量能提高三疣梭子蟹的存活率, 3.6 L氧气可满足一只三疣梭子蟹成蟹存活到3 d以上。因此,保活三疣梭子蟹的适宜温度和充氧量分别是12 ℃和3.6 L。不充氧保活会导致三疣梭子蟹前鳃中乳酸、丙氨酸和葡萄糖等代谢物的快速积累,但充氧保活可抑制这些代谢物的变化,表明氧气通过缓解三疣梭子蟹前鳃的缺氧和渗透压失衡,从而有效延长三疣梭子蟹的存活时间。研究结果为三疣梭子蟹的保活运输提供可借鉴的方法和理论参考。     

相同尺度地形与背景流共振生成内孤立波机制

为研究内孤立波的地形和背景流共振机制,用地形和背景流共振机制计算了3个潜标观测的内孤立波(不同模态、不同波长)的流速和传播速度,并与观测到的内孤立波进行比较。潜标观测的第一模态内孤立波(波长分别为6.4和3.3km)都是下凹型内孤立波,2个内孤立波的传播速度约为1.4m/s、最大振幅约为48m,水平流向结构都是上层西北向、下层东南向,波长3.3km 的内孤立波波峰前后有更明显的下降流和上升流。用共振机制计算出的第一模态和第二模态纬向流速的垂向结构与观测相同,最大纬向流速出现的深度与观测一致,分别相差5和12m。用共振机制计算出的内孤立波传播速度与用 KdV 方程计算的传播速度相当,共振机制计算波速为0.66~1.21m/s,KdV 方程计算波速为0.79~1.40m/s。     

吸积盘随机振荡光度功率谱密度中低频准周期振荡现象的研究

采用含有频率涨落噪声和指数形式关联随机力作用的广义朗之万(Langevin)方程模型描述黑洞吸积盘的垂向振荡,推导出吸积盘随机振荡光度功率谱密度的解析表达式,并讨论了系统参数对功率谱密度中低频准周期振荡(Low Frequency Quasi-Periodic Oscillations,LFQPOs)现象的影响。研究结果发现选取合适的系统参数时,功率谱密度曲线上出现了一个基频和一个二次谐频的共振双峰低频准周期振荡,基频峰对应的中心频率为吸积盘振荡的特征频率;随机力关联时间决定了基频峰的高度和宽度,频率噪声强度和粘滞阻尼只对二次谐频峰产生影响。结果说明吸积盘的随机振荡模型可以作为低频准周期振荡起源的一种解释。     

Reservoir parameter classification of a Miocene formation using a fractal approach to well logging,porosimetry and nuclear magnetic resonance

A methodology for rock classification is presented that considers lithology and reservoir parameters on the basis of a combined fractal analysis of well logs and mercury porosimetry results with nuclear magnetic resonance outcomes. A sandy‐shaly thinly‐bedded Miocene gas bearing formation in the Carpathian Foredeep is investigated. Fractal correlation dimensions D₂ calculated for standard logs are used to distinguish sandstone as the most homogeneous lithological group with the highest porosity. The fractal analysis also confirmed observations of gas accumulations in sandstone, shaly sandstone and sandy claystone as rocks of high porosity. The results of two laboratory methods are combined to improve reservoir properties assessment and evaluate movable media in pore space; this technique was based on the similarity of mercury porosimetry results plotted as cumulative intrusion volume versus pressure or pore diameter and also the curves of cumulative porosity and transverse relaxation time distributions using nuclear magnetic resonance. Close values of porosity from logs, recorded in situ and in laboratory measurements, provide the link between fractal analysis and porosimetry and nuclear magnetic resonance measurements.     

地面核磁共振方法在阳台滑坡中的应用

根据核磁共振找水原理,选择一个典型滑坡——安徽阳台滑坡,利用核磁共振直接找水仪测试结果,划分该滑坡的地下水含水层,确定滑动面,并运用钻探资料进行验证,证明了该方法在滑坡探测中的有效性和实用性。