Nanjing Center

Nanjing, China

Nanjing Center

Nanjing, China
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Huang Y.,Tongji University | Yang Y.,Nanjing Center | Wang L.,Tongji University
Bulletin of Engineering Geology and the Environment | Year: 2017

This research examines the foundation of a 7-year-old reservoir dam. No anti-liquefaction reinforcement treatment was applied before or during dam construction because the designers believed that the overburden load of the levee improved the soil liquefaction resistance. Here, we reassess the anti-liquefaction performance of the foundation and evaluate the reinforcement effect of the levee overburden load. Standard penetration tests and cone penetration tests were conducted to assess and compare the liquefaction potential of the foundation soils before and after the dam construction to reveal the evolution of anti-liquefaction performance. The confining pressure and relative density of the liquefiable soils were obtained before and after dam construction. Laboratory resonant column tests and dynamic triaxial tests were conducted under different confining pressures to obtain the dynamic properties of the soils before and after dam construction and the evolution mechanism of the anti-liquefaction performance of the foundation soils. © 2017 Springer-Verlag GmbH Germany

Yin A.,Jiangsu Academy of Agricultural Sciences | Yin A.,Nanjing University | Gao C.,Nanjing University | Zhang M.,Nanjing Center | And 2 more authors.
Geoderma | Year: 2017

Phosphorus (P) plays a key role in the global biogeochemical cycle. The dynamics of P in soils is of considerable importance to the management of soil fertility. However, little is known about P dynamics in reclaimed land at the centennial scale during the initial stage of soil development, when the ambient conditions undergo substantial changes. In this study, conducted in Eastern China, we used a sequential extraction method to analyze the changes in P species in sediments and soils in a coastal reclaimed area representing a sequence of soil ages. Significant accumulation of total P accompanied by organic matter enrichment, desalination, and decalcification were observed in the initial pedogenesis of reclaimed tidal flat sediments. A rapid change in top soil P species within a century of pedogenesis was revealed, which was characterized by a marked decline in P contained within primary minerals (DeP) and an increase in loosely absorbed P, Fe-bound P, authigenic P (CaP), and organic P. DeP decreased from 67.3% to 25.3% of total P, whereas CaP increased from 8.4% to 32.9% along the reclamation gradient. Dissolution of primary minerals and a high rate of fertilization were identified as the major causes of this P trajectory. A key factor controlling the evolution of soil P speciation is the marked change in ambient conditions following land conversion, resulting in a shift in anaerobic conditions, a decrease in pH, accumulation of organic matter, and depletion of carbonates. Under the strong interference of human activities, the P dynamics in soils derived from tidal flat sediments differ from those predicted by the Walker and Syers model. Our results indicate that current nutrient management practices in the studied area can not only avert soil P depletion but also increase P availability. © 2017

Wei L.,Nanjing Center | Cheng X.,CAS Chengdu Institute of Mountain Hazards and Environment | Cai Y.,Nanjing University
Hydrological Processes | Year: 2013

Understanding the influence of complex interactions among hydrological factors, soil characteristics and biogeochemical functions on nutrient dynamics in overland flow is important for efficiently managing agricultural nonpoint pollution. Experiments were conducted to assess nutrient export from Ultisol soils in the Sunjia catchment, Jiangxi province, southern China, between 2003 and 2005. Four plots were divided into two groups: two peanut plots and two agroforestry (peanut intercropped with citrus) plots. During the study period, we collected water samples for chemical analyses after each rainfall event that generated overland flow to assess nutrient export dynamics. The concentrations of potassium (K) and nitrate-N (NO3 --N) in overland flow were higher during the wetting season (winter and early spring). This reflects the solubility of K and NO3 --N, the accumulation of NO3 --N during the dry season and an increase in desorption processes and mixing with pre-event water caused by prolonged contact with soil in areas with long-duration, low-intensity rainfall. In contrast, concentrations of total nitrogen (TN) and total phosphorus (TP) were higher during the wet season (late March to early July) and during the dry season (mid-July to the end of September or early October). This was due to the interaction between specific hydrological regimes, the properties of the Ultisol and particulate transport processes. Variations in nutrient concentrations during storm events further identified that event water was the dominant source of total nitrogen and total phosphorus, and pre-event water was the dominant source of NO3 --N. In addition, the results obtained for the different land uses suggest that agroforestry practices reduce nutrient loss via overland flow. © 2012 John Wiley & Sons, Ltd.

Huang X.,Nanjing University of Information Science and Technology | Huang X.,Georgia Institute of Technology | Zhang J.,Nanjing Center | Rao W.,Nanjing University of Information Science and Technology | And 3 more authors.
Journal of Alloys and Compounds | Year: 2016

In this study, the flaky graphite/cobalt zinc ferrite composites were synthesized by the coprecipitation method. The XRD results showed that the flaky graphite/cobalt zinc ferrite composites can be obtained and there is no impurity when the graphite weight ratio is less than 20 wt%. The FE-SEM results exhibited that the flaky graphite/cobalt zinc ferrite composites possessed flake-like shape with high aspect ratio. Moreover, the electromagnetic properties could be tuned by varying the graphite weight ratio. In the series of as-prepared flaky graphite/cobalt zinc ferrite composites, the sample with 10 wt% graphite possessed excellent impedance matching performance. As a result, the it exhibited the best microwave absorption properties. The reflection loss was less than -10 dB in frequency range of 10.3-13.5 GHz and the maximum reflection loss was reach to -33.85 dB at 11.7 GHz when the coating thickness was 2.5 mm. Moreover, the electromagnetic analysis demonstrated that the electromagnetic loss properties and the electromagnetic impedance matching performance should be both satisfied to obtain the excellent microwave absorption properties. This study was meaningful to design the ferrite/carbon composites based microwave absorbers. © 2015 Elsevier B.V. All rights reserved.

Huang X.,Nanjing University of Information Science and Technology | Zhang J.,Nanjing Center | Lai M.,Nanjing University of Information Science and Technology | Sang T.,University of California at Davis
Journal of Alloys and Compounds | Year: 2015

In this paper, the NixZn(1- x )Fe2O4 (x = 0.2, 0.4, 0.5, 0.6, 0.8) ferrite nanofibers were synthesized by electrospinning method. The microstructure, electromagnetic properties and microwave absorption mechanisms were analyzed (in detail). The results indicated that the nanofiber diameter, the saturation magnetization, the coercivity and the electromagnetic properties could be optimized by tuning the Ni2+ content. The Ni0.5Zn0.5Fe2O4 ferrite nanofiber finally performed the excellent microwave absorption properties. The reflection loss was less than -10 dB in the whole X-band frequencies. The analysis of microwave absorption mechanism indicated that the microwave absorption bandwidth was mainly depended on the input impedance matching, the enhanced electromagnetic loss properties ensured that the entering wave could be mostly absorbed, and the frequency appearing the reflection loss peak was determined by the absorber thickness. © 2015 Published by Elsevier B.V.

Huang X.,Nanjing University of Information Science and Technology | Chen Y.,Nanjing University of Information Science and Technology | Yu J.,Nanjing University of Information Science and Technology | Zhang J.,Nanjing Center | And 3 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2015

The Fe3O4 nanofibers were prepared by electrospinning method. The phase composition and morphology were analyzed by XRD and FE-SEM. The results indicated that the pure Fe3O4 nanofibers were obtained and exhibited evident shape anisotropy. The magnetic study via VSM showed that the Fe3O4 nanofibers possessed ferrimagnetic properties. The saturation magnetization was around 58.4 emu/g and the coercivity was approximate 186.7 Oe. In addition, the electromagnetic loss properties were detailed investigated by network analyzer. The dispersion relaxation phenomenon was observed in the frequency range of 2–18 GHz. The dielectric loss was caused by the interface polarization and the magnetic loss was owing to the exchange resonance. The as-prepared Fe3O4 nanofibers showed excellent electromagnetic loss properties and could be potentially applied as the lightweight microwave absorption materials. © 2015, Springer Science+Business Media New York.

Huang X.,Nanjing University of Information Science and Technology | Zhang J.,Nanjing Center | Xiao S.,Nanjing University of Information Science and Technology | Sang T.,Nanjing University of Science and Technology | Chen G.,Nanjing University of Information Science and Technology
Materials Letters | Year: 2014

The ZnFe2O4 ferrite nanoparticle and nanofiber were synthesized by electrospinning method. The phase composition, morphology, magnetic and electromagnetic properties were analyzed. The results showed that both the samples exhibited a pure phase of spinel type ferrite. The ZnFe 2O4 ferrite nanoparticle was aggregated, while the ZnFe2O4 ferrite nanofiber performed the homogeneous nano-fibrous shape as well as single-particle-chain structure. The magnetic analysis indicated that the ZnFe2O4 ferrite nanofiber showed ferromagnetic behaviour. Moreover, the dielectric loss and magnetic loss properties of ZnFe2O4 ferrite nanofiber were both enhanced due to its better dipole polarization, interfacial polarization and shape anisotropy. © 2014 Elsevier B.V.

Zhang S.,Wuhan University | Shi H.,Nanjing Center | Hao H.,Wuhan University | Li D.,Wuhan University | And 2 more authors.
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2014

Risong rocks and Jiawei acid rock veins are located at Bangong Lake ophiolite mélange belt, western Tibetan Plateau. The lithology is tonalite, corcovadite and granodiorite, displaying a transition from medium-K calc-alkaline series to high-K calc-alkaline series. Rocks show geochemical characteristics of adakites, having high content of SiO2 (63.05%~70.72%), Al2O3(≥15%), Sr (380.4×10-6-625.0×10-6), Sr/Y ratio(>35) and low content of MgO (0.97%-2.33%)<3%, HREE, Y(5.64×10-6-13.80×10-6) and Yb(0.46×10-6-1.25×10-6). The differentiation is obvious between HREE and LREE (17.09<(La/Yb)N<48.51). Risong granodiorite is dated to 82.0±1.1 Ma by zircon U-Pb dating method; east-west trend granodiorite and south-north trend corcovadite are dated to 90.7±1.2 Ma, 82.9±1.2 Ma respectively. Risong and Jiawei adakitic rocks are enriched in K and depleted in Na, and have low Cr, Ni, Sr/Y and high Th, Th/La, Th/U, Rb/Sr and Mg#(43.09-54.35). These characteristics indicate that they were formed by partial melting of thickened lower crust which was caused by basaltic magma underplating. 91-82 Ma adakites were formed in the early stage after the collision as the product of both interplates thermal upwelling extension and crust-mantle interaction after the closure of Meso-Tethys. Outcropping of adakites in this period can mark the transition from the plate tectonic system to intraplate tectonic system.

Zhou X.,Hubei University | Zhou X.,Nanjing Center | Zhu C.-F.,Nanjing Center
Acta Geoscientica Sinica | Year: 2014

The content of nitrate in groundwater not only influences water quality but also significantly affects the groundwater hydrochemical classification. An analysis of nitrate content characteristics of shallow groundwater in Jinjiang City shows that nitrate absolute content of groundwater is high and the anion percentage of MEQ proportion has exceeded the sulfate, which has a significant impact on groundwater chemical types. Samples with higher NO3 - relative content often have the characteristics of low salinity, low pH, and high r(Na+)/r(Cl-), and belong to chloride water type. r(NO3 -)/r(Cl-) can be used as a criterion to judge the water concentration effect or dilution effect under natural conditions, and can also be used to confirm the artificial pollution or concentration effect under the natural hydrodynamic conditions in combination with the change of absolute content of target pollutants.

Wang M.,Wuhan University | Wang M.,TU Bergakademie Freiberg | Guo X.,Wuhan University | Michalak P.P.,TU Bergakademie Freiberg | And 4 more authors.
Ore Geology Reviews | Year: 2015

This study documents the geochemistry of sulfide ores of the Tudun Cu-Ni sulfide deposit, located at the western end of theHuangshan-Jing'erquan ore belt in the northern part of eastern Tianshan. The ores have been classified as (1) disseminated sulfide ores, (2) net-textured sulfide ores, and (3) massive sulfide ores. The geochemistry of barren rocks shows Ni and Cu contents ranged 889-1330 ppm and 145-253 ppm, respectively. The rocks generally contained ~0.10 ppb Rh, Ir, Ru and Os, and ~1 ppb Pt and Pd, as well as high Cu/Pd ratios (133-246). The contents of Cu, Ni and PGEs in sulfide oreswere calculated on a 100% sulfide basis. Total PGEs on a 100% sulfide basis ranged from13.2 ppb to 443 ppb (average=144 ppb),whichwere lower than the values in the Huangshandong deposit (average = 186 ppb) in the eastern Tianshan ore belt, one order of magnitude lower than the Jinchuan deposit, and twoorders of magnitude lower than theNoril'sk-Talnakh deposit. The R factor value ranged from168 to 1810 in sulfide ores of the Tudun deposit, indicating Cu andNi enrichment, although PGEs enrichment did not reach recoverable grades. In the Tudun deposit, the Pd/Ir ratio of sulfide ores was less than 100, showing weak hydrothermal fluid alteration. The massive sulfide ores exhibited less primitive mantle-normalized PGEs patterns, which are depleted in PPGEs and different from PPGEs-rich intrusions, as well as disseminated and net-textured sulfide ores. In addition, the massive sulfide ores exhibit a strong negative Pt anomaly. This may be due to fractionation of Pt-Fe alloys in the magma batches prior to its intrusion into the staging chamber. It could also be caused by selective Pt leaching from the sulfides by hydrothermal fluids during remobilization within the Tudun chamber. © 2014 Elsevier B.V.

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