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Shanghai, China

Yu Y.,Tongji University | Sun Z.,Tongji University | Pang M.,Tongji University | Yang P.,Shanghai Niumag Corporation
Journal Wuhan University of Technology, Materials Science Edition | Year: 2013

Development of microstructure of early cement paste (0-6 h) was investigated with 1H low-field NMR. It was found that T 2 (transverse relaxation time) distributions of fresh cement paste were bimodal and two peaks were 'long component' and 'short component'. Separation degree of two peaks was a sign of exchange of water within flocculation and outside flocculation. Factors such as water cement ratio, specific surface area and dosage of superplasticizer had influences on the separation degree: the separation degree increased with the water cement ratio; the separation degree of cement paste prepared with cement with a high specific surface area was zero; dosage of superplasticizer will decrease separation degree. Results also suggested that T 2 distribution gradually moved to the left and T 2 of long component and initial fluidity were linearly correlated. © 2013 Wuhan University of Technology and Springer-Verlag Berlin Heidelberg.

Zhenping S.,Tongji University | Qi L.,Tongji University | Yang Y.,Tongji University | Peiqiang Y.,Shanghai Niumag Corporation
Key Engineering Materials | Year: 2013

Early cement paste (0h-6h) made with cement of different Blain specific surface area was investigated with 23MHz 1H low-field NMR. T2 distribution, T2 against age and T2 distributions against age were obtain. Results showed: 1) T2 distribution of fresh cement paste made with cement of common Blain specific surface area has two peaks and corresponded to water within flocculation and among flocculation; 2)T2 against age could reflect a stage-like behavior of cement hydration; 3) T2 distributions against age showed evolution of microstructure in early cement paste. © (2013) Trans Tech Publications, Switzerland.

Di Q.,Shanghai University | Hua S.,Shanghai University | Gu C.,Shanghai University | Ye F.,Shanghai University | And 3 more authors.
Shiyan Liuti Lixue/Journal of Experiments in Fluid Mechanics | Year: 2016

Core micro flow visualization is an important method to study the microcosmic mechanism of the chemical flooding.The latest results of core micro flow visualization by MRI technology in our research group was introduced in detail. Some questions on low field MRI core displacement system (MRICDS) were put forward, and improvement and optimization were made from the two aspects of hardware and software to eliminate interference factors. The experiments of fluid image test during water-flooding process were successfully carried out using the improved MRICDS. The real-time signals of NMR and MRI of the oil-water distribution during the flow test were collected, and NMR-T2 spectrums and oil or water distribution images were obtained in different stages. The images with high resolution can meet the request of visually analyzing the fluid distribution in the core. Experimental results show that residual oil decreases with PV increasing. The trendline of oil distribution drops rapidly first and then slowly. Images also show the phenomenon of residual oil gathering in the end area in core flow tests and its influence range is about 4mm from the end. A new method of oil saturation by the oil-water distribution map of MRI was introduced, and its results are consistent with that of the traditional method and the error is within 10%. This also shows that the reliability of the oil-water distribution map. This provides a new method for the study of oil saturation. Especially the other advantage of the method is that it can analyze the oil-water saturation at any local position. The results also indicate that the new method of MRI is worthy of further development for fluid distribution visualization during core micro flow. © 2016, Editorial Department of JOURNAL OF EXPERIMENTS IN FLUID MECHANICS. All right reserved.

Li Z.-M.,Guangdong University of Technology | Zeng W.-X.,Guangdong University of Technology | Gao M.-L.,Shanghai Niumag Corporation | Luo Z.-B.,Guangdong University of Technology
Wuli Xuebao/Acta Physica Sinica | Year: 2014

Several typical loads are applied to muck specimens to simulate muck ground treatment conditions. Then tests of pore structural distribution of the soil are performed by the method of nuclear magnetic resonance (NMR), for seeking variation of their internal structure under the typical load level and rate, and thus to further determine the muck ground reinforcement mechanism and responses in micro-structure aspect. The results suggest that: (1) the max-pore decreases under a certain load, and the reduction increases with load level; nevertheless, when the impact load reaches a considerable level, both the max-pore and small-pore decrease; (2) the confining stiffness effect of constraint samples induces a decrease in the proportion of large-pore; (3) at a certain load level (680 kPa or less), the loading rate is the key factor determining the relative proportion of maximum void ratio: smaller lading rate will make the void ratio increase, larger lading rate will make the void ratio reduced, and its boundary value is between >0.8 MPa/s and ≤1.6 MPa/s; (4) with a certain load level and rate, an the number of impact times increses, namely as the total energy is enhanced, the large-pore as well as the max-pore considerably decreases; however, this effect will be reduced when the interval time is short and as the number of impact times increases further. i.e. the large-pore effectively decreases. There exists a suitable value of the number of impact times for the muck specimens. These results reflect the rule of different loading effects in the micro of micro fine structure and provide a basis for the design and construction optimization for muck ground improvement. © 2014 Chinese Physical Society.

Li T.,Nanjing Agricultural University | Tu C.,Nanjing Agricultural University | Rui X.,Nanjing Agricultural University | Gao Y.,Shanghai Niumag Corporation | And 4 more authors.
Journal of Agricultural and Food Chemistry | Year: 2015

Solid-state fermentation (SSF) of starchy grain is a traditional technique for food and alcoholic beverage production in East Asia. In the present study, low-field nuclear magnetic resonance (LF-NMR) was introduced for the elucidation of water dynamics and microstructure alternations during the soaking, steaming, and SSF of glutinous rice as a rapid real-time monitoring method. Three different proton fractions with different mobilities were identified based on the degree of interaction between biopolymers and water. Soaking and steaming significantly changed the proton distribution of the sample. The different phases of SSF were reflected by the T2 parameters. In addition, the variations in the T2 parameters were explained by the microstructure changes of rice induced by SSF. The fermentation time and T2 parameters were sigmoidally correlated. Thus, LF-NMR may be an effective real-time monitoring method for SSF in starch systems. © 2015 American Chemical Society.

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