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71.
水硬性石灰在欧洲石质文物修复和加固中获得了很大成功。我国的石质文物主要是砂岩,水硬性石灰的修复效果不好。为满足我国石质文物修复和加固的需求,本文以石灰石和黏土为原料,在950℃煅烧不同时间,制备出水硬性石,对试样的成分、微观形貌、收缩率、抗拉强度和拉破坏过程等进行了研究。结果表明:(1)试样中含有水硬性成分2CaO·SiO2(C2S);煅烧8h时,成分与欧洲水硬性石灰NHL5接近;1.5CaO·SiO2·xH2O(C-S-H)和CaCO3的含量随龄期的增加逐渐增加。(2)龄期1~3d,收缩率较小;龄期4~6d,收缩率以线性规律增加;7d以后,收缩率趋于稳定。(3)局部变形区随拉应力的增加而变大,邻近局部变形区逐渐合并,形成面积更大的应变局部化带;载荷超过峰值后,产生微裂隙;随载荷进一步增加,微裂隙扩展,贯穿整个试件,发展成宏观裂隙,使试件破坏。(4)抗拉强度随龄期的增加而增加,水硬性石灰中C-S-H、CaCO3等相互交织,构成空间致密体,使试件力学强度提高。合成的水硬性石灰物理力学性能与欧洲水硬性石灰NHL5相近,并且成分均匀、可控,在石质文物修复和加固工程中具有良好应用前景。 相似文献
72.
离心泵在启动阶段的水力特性研究 总被引:4,自引:0,他引:4
针对工作的离心泵,分析了其内部流体的流动情况,建立了在非稳定工况下操作的理论扬程公式,非稳态理论扬程包括旋转加速附加扬程和水流加速消耗扬程以及由于流动速度变化引起泵壳中的附加压力而产生的扬程。在离心泵的启动阶段,对其在不同阀门开度下的水力性能进行了试验研究。测量了瞬时转速、流量、扬程随时间的变化关系,并把试验结果进行修正。由于启动时一部分扬程用来提供流体加速,压力传感器测量不到,因此必须把试验扬程加以修正。将理论计算与修正的试验结果进行了比较分析,两者基本吻合。 相似文献
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Ronald V. Emmons Tiffany Liden Kevin A. Schug Emanuela Gionfriddo 《Journal of separation science》2020,43(9-10):1915-1924
The continued rise in the extraction of unconventional oil and gas across the globe poses many questions about how to manage these relatively new waste‐streams. Produced water, the primary waste by‐product, contains a diverse number of anthropogenic additives together with the numerous hydrocarbons extracted from the well. Due to potential environmental hazards, it is critical to characterize the chemical composition of this type of waste before proper disposal or remediation/reuse. In this work, a thin film solid phase microextraction approach was developed and optimized to characterize produced water. The thin film device consisted of hydrophilic‐lipophilic balance particles embedded in polydimethylsiloxane and immobilized on a carbon mesh surface. These devices were chosen to provide broad extraction coverage and high reusability. Various parameters were evaluated to ensure reproducible results while minimizing analyte loss. This optimized protocol, consisting of a 15 min extraction followed by a short (3 s) rinsing step, enabled the reproducible analysis of produced water without any sample pretreatment. Extraction efficiency was suitable for both produced water additives and hydrocarbons. The developed approach was able to tentatively identify a total of 201 compounds from produced water samples, by using one‐dimensional gas chromatography hyphenated to mass spectrometry and data deconvolution. 相似文献
76.
在水利工程管理当中,从前期决策、勘察设计、建造到运营维护的全过程,引入全过程协同管理,可以产生和助力发挥协同效应.以都江堰工程为例,运用物理-事理-人理方法论(Wuli-Shili-Renli System Approach,以下简称WSR方法论),从物理、事理、人理角度,对协同管理进行系统分析,通过构建基于WSR系统的协同管理三维分析模型、协同管理分析矩阵和协同管理分析框架,为水利工程的协同管理提供启示和借鉴,助力于发挥水利工程协同管理全过程的协同效应. 相似文献
77.
The belite material produced from limestone and waste silica was the subject of numerous investigations. In order to improve the hydraulic activity, some amount of barite was added to the raw mixture. The properties of belite phase were studied by use of differential thermal analysis, calorimetry and other methods. The influence of barium on the hydraulic activity of belite has been thus confirmed. The hydraulic activity increase in the presence of barium depends on the stabilizing action of additive accompanied by the proper thermal treatment in the α′-Ca2SiO4 stability range. 相似文献
78.
Discharge estimation under uncertainty using variational methods with application to the full Saint‐Venant hydraulic network model 下载免费PDF全文
Estimating river discharge from in situ and/or remote sensing data is a key issue for evaluation of water balance at local and global scales and for water management. Variational data assimilation (DA) is a powerful approach used in operational weather and ocean forecasting, which can also be used in this context. A distinctive feature of the river discharge estimation problem is the likely presence of significant uncertainty in principal parameters of a hydraulic model, such as bathymetry and friction, which have to be included into the control vector alongside the discharge. However, the conventional variational DA method being used for solving such extended problems often fails. This happens because the control vector iterates (i.e., approximations arising in the course of minimization) result into hydraulic states not supported by the model. In this paper, we suggest a novel version of the variational DA method specially designed for solving estimation‐under‐uncertainty problems, which is based on the ideas of iterative regularization. The method is implemented with SIC2, which is a full Saint‐Venant based 1D‐network model. The SIC2 software is widely used by research, consultant and industrial communities for modeling river, irrigation canal, and drainage network behavior. The adjoint model required for variational DA is obtained by means of automatic differentiation. This is likely to be the first stable consistent adjoint of the 1D‐network model of a commercial status in existence. The DA problems considered in this paper are offtake/tributary estimation under uncertainty in the cross‐device parameters and inflow discharge estimation under uncertainty in the bathymetry defining parameters and the friction coefficient. Numerical tests have been designed to understand identifiability of discharge given uncertainty in bathymetry and friction. The developed methodology, and software seems useful in the context of the future Surface Water and Ocean Topography satellite mission. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
79.
从分析气体分子的悬浮和静水中Brown微粒的悬浮之机理出发,论述了重力场中粒子(分子、微粒等)的悬浮不一定需要其它外力,粒子本身的任何形式的无规则运动,达到一定强度后都能使粒子弥散悬浮.河流中的泥沙颗粒和气(水)力输送管道中的颗粒的悬浮也主要靠颗粒物的无规则运动.作用于颗粒的升力和其它力可改变颗粒悬浮沿高度的分布,但仅用这些力(若无任何无规则运动)无法解释颗粒的弥散悬浮状态.讨论了颗粒对流动阻力的双重作用:支持颗粒悬浮的湍流脉动因引入颗粒而削弱,这是颗粒的减阻作用;颗粒增阻的一个主要机制是,流体给予颗粒的水平动量在颗粒一壁面碰撞中不断地损失.用悬浮动概念解释颗粒引起的增阻是不正确的. 相似文献
80.
复杂水力计算中的高次方程问题 总被引:1,自引:0,他引:1
将实际工程中的复杂水力计算问题归纳为对高次方程的求解,并提出快速、正确解决这类问题的数值方法——中点迭代法,对解决实际工程问题具有指导意义. 相似文献