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我国北亚热带白浆化土壤粘化过程的主组元分析 被引量:3
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作者 傅桦 丁瑞兴 《热带亚热带土壤科学》 CSCD 1996年第4期187-192,共6页
运用主组元分析方法,研究了白浆化土壤的粘化过程.认为粘粒的化学组成与粘粒的矿物组成相一致;在淋溶过程中,矿物分解可形成蒙脱石和高岭石,粘淀层是土体脱硅富铁铝化过程和粘粘形成、淋溶、淀积的结果.
关键词 北亚热带 白浆土壤 粘化过程 主组元分析
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Evolution of distribution and content of water in cement paste by low field nuclear magnetic resonance 被引量:11
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作者 佘安明 姚武 袁万城 《Journal of Central South University》 SCIE EI CAS 2013年第4期1109-1114,共6页
The low field nuclear magnetic resonance (NMR), as a nondestructive and noninvasive technique, was employed to investigate the water distribution and content in cement paste with different water-to-cement ratio (w/c r... The low field nuclear magnetic resonance (NMR), as a nondestructive and noninvasive technique, was employed to investigate the water distribution and content in cement paste with different water-to-cement ratio (w/c ratio) during early and later hydration stages. From the water distribution spectrum deduced from relaxation time distribution in paste, it is suggested that the water fills in the capillary pores at initial period, and then diffuses to the mesopores and gel pores in hydration products with the hydration proceeding. The decrease of peak area in water distribution spectrum reflects the transformation from physically bound water to chemically bound water. In addition, based on the connection between relaxation time and pore size, the relative content changes of water in various states and constrained in different types of pores were also measured. The results demonstrate that it is influenced by the formation of pore system and the original water-to-cement ratio in the paste. Consequently, the relative content of capillary water is dropped to less than 2% in the paste with low w/c ratio of 0.3 when being hydrated for 1 d, while the contents are still 16% and 36% in the pastes with w/c ratios of 0.4 and 0.5, respectively. 展开更多
关键词 cement water DISTRIBUTION water-to-cement ratio PORE nuclear magnetic resonance
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Process Intensification of VOC Removal from High Viscous Media by Rotating Packed Bed 被引量:9
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作者 李沃源 毋伟 +3 位作者 邹海魁 初广文 邵磊 陈建峰 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2009年第3期389-393,共5页
The removal of a volatile organic compound (VOC) from high viscous liquid was carried out in a rotat-ing packed bed (RPB) in this study. The mixed liquid of syrup and acetone was used as simulated high viscous polymer... The removal of a volatile organic compound (VOC) from high viscous liquid was carried out in a rotat-ing packed bed (RPB) in this study. The mixed liquid of syrup and acetone was used as simulated high viscous polymer solution with acetone as the volatile compound. The influence of the rotating speed of RPB, liquid viscos-ity, liquid flow rate, vacuum degree, and initial acetone content in the liquid on acetone removal efficiency was in-vestigated. The experimental results indicated that the removal efficiency increased with increasing rotating speed and initial acetone content in the viscous liquid and decreased with increasing liquid viscosity and flow rate. It was also observed that acetone removal efficiency increased with an increasing vacuum degree and reached 58% at a vacuum degree of 0.1 MPa. By the comparison with a flash tank devolatilizer, it was found that acetone removal ef-ficiency in RPB increased by about 67%. 展开更多
关键词 polymer devolatilization rotating packed bed high viscosity mass transfer volatile organic compound
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Degradation of bond between steel bar and freeze-thaw concrete after electrochemical chloride extraction 被引量:6
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作者 郭育霞 贡金鑫 《Journal of Central South University》 SCIE EI CAS 2010年第2期388-393,共6页
The effect of electrochemical chloride extraction (ECE) on bond strength between steel bar and freeze-thaw concrete contaminated by chloride was experimentally investigated for beam specimens with dimensions of 100 ... The effect of electrochemical chloride extraction (ECE) on bond strength between steel bar and freeze-thaw concrete contaminated by chloride was experimentally investigated for beam specimens with dimensions of 100 mm × 100 mm × 400 ram. During the experiment, 3% NaC1 (vs mass of cement, mass fraction) was mixed into concrete to simulate chloride contamination, and the specimens experienced 0, 25, 50, 75 freeze-thaw cycles before ECE. In the process of ECE, different current densities and durations were adopted. It is indicated that the bond strength between reinforcement and concrete decreases with the increase of freeze-thaw cycles; the more the current and the electric quantity of ECE are, the more the loss of bond strength is; and the largest loss is up to 58.7%. So, it is important to choose proper parameters of ECE for the reinforced concrete structures contaminated by chloride and subjected to freeze-thaw cycles. 展开更多
关键词 CONCRETE bond strength DEGRADATION electrochemical chloride extraction freeze-thaw cycles
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北京低山与山前地带土壤发生过程及不同分类系统的对比 被引量:4
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作者 张凤荣 王数 孙鲁平 《土壤通报》 CAS CSCD 北大核心 1999年第4期145-148,共4页
本文论述了北京低山和山前地带7个土壤剖面的主要发生过程,即粘化过程和碳酸钙淋溶淀积过程。残积粒化过程不仅仅表现在土体中部,在各个层次均存在,是土壤中普遍存在的发生学过程。本文认为钙积层存在与否取决于母质类型。并对比了... 本文论述了北京低山和山前地带7个土壤剖面的主要发生过程,即粘化过程和碳酸钙淋溶淀积过程。残积粒化过程不仅仅表现在土体中部,在各个层次均存在,是土壤中普遍存在的发生学过程。本文认为钙积层存在与否取决于母质类型。并对比了7个研究剖面在不同土壤分类系统中的地位。 展开更多
关键词 粘化过程 钙积过程 土壤分类 北京
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Turbulence and mixing in a freshwater-influenced tidal bay: Observations and numerical modeling 被引量:1
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作者 LIAN Qiang LIU ZhiYu 《Science China Earth Sciences》 SCIE EI CAS CSCD 2015年第11期2049-2058,共10页
In situ observations and numerical simulations of turbulence are essential to understanding vertical mixing processes and their dynamical controls on both physical and biogeochemical processes in coastal embayments. U... In situ observations and numerical simulations of turbulence are essential to understanding vertical mixing processes and their dynamical controls on both physical and biogeochemical processes in coastal embayments. Using in situ data collected by bottom-mounted acoustic Doppler current profilers(ADCPs) and a free-falling microstructure profiler, as well as numerical simulations with a second-moment turbulence closure model, we studied turbulence and mixing in the Xiamen Bay, a freshwater-influenced tidal bay located at the west coast of the Taiwan Strait. Dynamically, the bay is driven predominantly by the M2 tide, and it is under a significant influence of the freshwater discharged from the Jiulong River. It is found that turbulence quantities such as the production and dissipation rates of the turbulent kinetic energy(TKE) were all subject to significant tidal variations, with a pronounced ebb-flood asymmetry. Turbulence was stronger during flood than ebb. During the flooding period, the whole water column was nearly well mixed with the depth-averaged TKE production rate and vertical eddy viscosity being up to 5?10?6 W kg?1 and 2?10?2 m2 s?1, respectively. In contrast, during the ebb strong turbulence was confined only to a 5?8 m thick bottom boundary layer, where turbulence intensity generally decreases with distance from the seafloor. Diagnosis of the potential energy anomaly showed that the ebb-flood asymmetry in turbulent dissipation and mixing was due mainly to tidal straining process as a result of the interaction between vertically shared tidal currents and horizontal density gradients. The role of vertical mixing in generating the asymmetry was secondary. A direct comparison of the modeled and observed turbulence quantities confirmed the applicability of the second-moment turbulence closure scheme in modeling turbulent processes in this weakly stratified tidally energetic environment, but also pointed out the necessity of further refinements of the model. 展开更多
关键词 tidal bay turbulent mixing second-moment turbulence closure model turbulent kinetic energy dissipation rate vertical eddy viscosity
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