ISSN 0253-2778

CN 34-1054/N

2017 Vol. 47, No. 5

Display Method:
Original Paper
Insight into fine structures of LiFexMn1-xO2 by synchrotron radiation-based X-ray absorption spectroscopy
WU Guixian, ZHAO Haifeng, HUANG Weifeng, TAO Shi, ZHANG Lingming, YU Zhen, CHU Wangsheng, WEI Shiqing
2017, 47(5): 369-376. doi: 10.3969/j.issn.0253-2778.2017.05.001
LiFexMn1-xO2 (0≤x≤1) compounds were synthesized by the co-precipitation method. Electrochemical tests show that the LiFe0.25Mn0.75O2 composite has a maximum reversible capacity of 180 mAh/g at 0.1 C(1 C=140 mA/g). These as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS). XRD and XAS results show that the LiFexMn1-xO2 (0<x<1) samples actually have multiple crystal phases, especially the spinel phase (LiMn2O4), Li-rich phase (Li2MnO3) and layered phase (LiFeO2). Moreover, XAS reveals that the Mn-phase and the Fe-phase are randomly stacked in the samples. The work shows the doping of Fe influences the crystal phase and local structure of the Mn-phase upon the samples and then adjusts the electrochemical performances of the cathode materials, giving an optimal proportion (x=0.25) of the spinel and Li-rich and layered phase.
Ir-ReOx/SiO2 combined with HZSM-5 as catalyst to convert biomass into C5/C6 alkane
WU Hao, LI Wenzhi, XU Zhiping, DU Zhijie, LIU Qiyu
2017, 47(5): 377-384. doi: 10.3969/j.issn.0253-2778.2017.05.002
Ir-ReOx/SiO2 combined with HZSM-5 was used as catalyst for biogasoline production in the biphasic system. The effects of various parameters such as reaction time, temperature and hydrogen pressure on the yield of biogasoline were investigated. The experiment results show that, when using biomass as substrate, a maximum C5/C6 alkane yield is obtained under the optimal conditions with the reaction temperature being 170 ℃ and hydrogen pressure 7 MPa. In addition, It is found that dehydration reaction is the control step in the experiment. Compared with other catalysts, HZSM-5 has suitable Lewis acid and Bronsted acid, and it has a channel architecture which can increase substrate concentration and thus shows better catalytic activity.
Preparation and electrochemical performance of porous NiO nanoparticles for lithium ion batteries
HUANG Tao, LI Xiaona, YANG Zeheng
2017, 47(5): 385-391. doi: 10.3969/j.issn.0253-2778.2017.05.003
Porous NiO nanoparticles were synthesized via a facile thermal decomposition method by only using a simple compound precursor. The as-prepared NiO samples are composed of nanoparticles with large pore volume. The electrochemical properties of the porous NiO nanoparticles were examined by cyclic voltammetry and galvanostatic charge-discharge studies. The results demonstrate that the as-prepared NiO nanoparticles are excellent electrode materials in LIBs(lithium ion batteries) with high specific capacity, good retention and rate performance. The porous NiO nanoparticles can retain a reversible capacity of 835 mAh/g after 120 cycles at a high current density of 500 mA/g. The introduction of porous structure into the NiO electrodes offers a large contact area between the electrode and electrolyte, and provides space for buffering the strain during cycling, thus leading to enhanced lithium-storage properties.
Ensemble forecast and verification of the Western Pacific Subtropical High based on multi-model data from TIGGE
YAN Yan, ZHOU Renjun, KE Zongjian, LIU Changzheng, DU Liangmin, SU Qihua
2017, 47(5): 392-402. doi: 10.3969/j.issn.0253-2778.2017.05.004
The skill of a set of control and ensemble forecasts of Western Pacific Subtropical High was evaluated based on the 500 hPa geopotential height information from the THORPEX Interactive Grand Global Ensemble (TIGGE) datasets, which consist of model outputs from CMA, JMA, ECMWF, UKMO and NCEP. Three methods were adopted, i.e., Ensemble Mean (EMN), Bias-Removed Ensemble Mean (BREM) and running Training Period Superensemble (R_SUP), to integrate the data from different sources, and the metrics for performance evaluation include Talagrand distribution, correlation coefficient, Root Mean Square Error (RMSE), and Brier Skill Score (BSS). A comparison of the outputs of these models shows significant variation in forecast performance. The results indicate that the UKMO model has the best forecast skill for the 500 hPa geopotential height among all control forecasts, while the ECMWF model ranks on the top of all ensemble forecasts. From the improvement of RMSE, both BREM and R_SUP can significantly reduce the RMSE of the integrated forecast results compared to the original control forecasts in TIGGE, but EMN does not show similar improvement. However, none of the three integration methods shows discernable improvement of ensemble forecast of the 500 hPa geopotential height, with all having less skills than ECMWF single model ensemble forecast.
Characteristics of lightning activity and its relationship with the atmospheric environment parameters in Southeast China
WANG Jixin, ZHU Baoyou, MA Ming
2017, 47(5): 403-412. doi: 10.3969/j.issn.0253-2778.2017.05.005
Based on space-borne lightning observation data from Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD), and reanalysis data of National Center for Environmental Protection/National Center for Atmospheric Research (NCEP/NCAR) and ERA-Interim in an 18-year period from 1997 to 2013, the lightning activity over southeastern China (17.5~30°N, 100~122.5°E) and its associations with atmospheric environmental factors were investigated. The results indicate that the lightning activities show strong seasonal variabilities with high frequency of lightning events in the spring and summer. On the inter-annual time scale, the El Nio-Southern Oscillation (ENSO ) has a significant impact on lightning variability. The El Nio events can significantly intensify the lightning activity in winter and spring. The high frequency of lightning events in southeastern China is associated with the increase of thermodynamic parameters, such as surface air temperature, 700~400 hPa averaged relative humidity and 850 hPa potential temperature. The atmospheric stability parameters are also closely related to lightning activity, and a larger unstable atmospheric layer is associated with a stronger lightning activity. Furthermore, multivariate step linear regression is applied to establish the relationship between predictor variables (e.g., surface air temperature, convective available potential energy, Bowen ratio, lifted index and Showalter index) and prediction (averaged lightning activity concentration). The multiple stepwise linear regression equation is beneficial for regional lightning activity forecast.
Distribution and ecological risk assessment of 6 typical trace elements in mining soils in Huainan coalfield
WEI Yong, ZHOU Chuncai, WANG Jie, FAN Zhijian, LIU Guijian
2017, 47(5): 413-420. doi: 10.3969/j.issn.0253-2778.2017.05.006
Accumulation of coal gangue can release trace elements into the surroundings, causing severe soil pollution. To access the soil deterioration and environmental contamination by trace elements under the coal mining activities, soil and coal gangue samples were collected from 3 different mines (Xinzhuangzi, Panyi, Guqiao) in Huainan city, Anhui Province, China. Concentrations of trace elements (Cd, Cr, Cu, Ni, Pb and Zn) were determined using an inductively coupled plasma atomic emission spectrometry (ICP-AES). The results show that Cd is the only one element that exceeded the soil background of Huainan. There are no obvious characteristics for horizontal trace metal distributions. The oldest mine presented the worst contamination for the time effect (old mine> middle aged mine> new mine). The soil pollution assessment using individual pollution index suggests that Cd presents light pollution in Xinzhuangzi Mine, and minor pollution in Panyi and Guqiao Mine. The three mines all present moderate pollution risk evaluated using superimposed indices. Potential ecological risk index indicates that Cd element poses a considerable potential ecological risk, and the soil of the three mining areas has medium ecological risk.
Non-Fickian model and experimental study of solute transport in porous media
QIAN Jiazhong, ZHOU Yang, LI Fulin, LIU Yong
2017, 47(5): 421-425. doi: 10.3969/j.issn.0253-2778.2017.05.007
To quantify the non-Fickian transport in porous media, a linear function was employed to characterize the relationship between the dispersivity and migration distance, a mathematical model LAF(Linear-Asymptotic Function) was presented, solute transport tests in one-dimensional glass column were carried out, and the accuracy of LAF was contrasted with the traditional ADE (advection-dispersion equation) models according to experimental data. The results show that, although the flow satisfies Darcy’s law, there are some differences between the experimental values and the fitted values obtained from the ADE model treating the dispersivity as a constant(the maximal error value being 1.57 g/L).#br##br##br##br#The simulation accuracy is enhanced when the dispersivity is treated as a linear function of LAF:#br##br# the maximal error value is 0.62 g/L. It can better simulate solute transport in the homogeneous finite column. These conclusions have been obtained in homogeneous media. The situation is more complicated in heterogeneous porous media, and the mechanism needs further research.
Heavy metal pollution characteristics and ecological risk assessment for soil in northern Chaohu Lake
QIN Xianyan, PENG Miaozhi, HU Bo, WU Jianxiong, SUN Yue
2017, 47(5): 426-434. doi: 10.3969/j.issn.0253-2778.2017.05.008
The surface soil in the north of Chaohu was studied and a total of 165 samples were collected and the concentrations and pollution characteristics of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were analyzed. The heavy metal concentrations in this area were compared with those of other areas. Then, pollution index and potential ecological risk index were used respectively for assessing the pollution status and ecological risk of soil heavy metals in this area. Results suggest that the average concentrations of eight heavy metals rank as follows: Cr>Zn>Ni>Pb>Cu>As>Cd>Hg. The coefficent variations of Cd and Hg are higher than the other six heavy metals. Furthermore, higher enrichment coefficients occur also in Cd and Hg when compared with the deep soils. Single factor pollution index indicates that eight heavy metals in the soils of this area are all at a clear level, and the pollution degree is in the following order: Pb>Cr>As=Ni>Cu>Cd>Zn>Hg. Accordingly, a clear level in this area is shown by Nemerow integrated pollution index. Calculation of the potential ecological risk index shows that, among the eight tested heavy metals, Cd and Hg are the main potential ecological risk factors, and their contribution is 19.40% and 72.87%, respectively.
LES of uniform flow over tandem circular disks
YAO Mengyun, GU Hailin, ZHAO Pu, HUANG Hongjie, LI Xinlong, LIU Minghou
2017, 47(5): 435-442. doi: 10.3969/j.issn.0253-2778.2017.05.009
A large eddy simulation(LES) was conducted to investigate the uniform flow over tandem disks at low Reynolds number,mainly focusing on the influence of separation distance on wake structure.The results show that the Hopf bifurcation of flow field is delayed compared with that of a single disk when the distance between the two disks is small enough.The research was performed at Re=200 with distances l/d=1,1.5,2,3 and 6, respectively. It is concluded that the wake is stable and plane-symmetrical at l/d=1 and unstable but plane-symmetrical at  l/d=1.5. At l/d=2, the plane-symmetrical structure is broken.The upstream wake resumes plane-symmetry at l/d=3 while the wake of both disks resume plane-symmetry at l/d=6.
Influence of glass microspheres content on underwater explosion energy of emulsion explosives
GONG Yue, WANG Xuguang, HE Jie
2017, 47(5): 443-447. doi: 10.3969/j.issn.0253-2778.2017.05.010
To study the influence of glass microsphere content on underwater explosion energy of emulsion explosives, emulsion matrix was mixed with 2%,3%,4%,5% and 6% glass microspheres respectively to make five kinds of emulsion explosives, and underwater explosions were tested under the same experimental conditions. Results show that glass microsphere content has a great influence on underwater explosion energy of emulsion explosives, and that the energy parameters of underwater explosion rise with the increase of glass microsphere content within a certain range. When the mass fraction of glass microspheres is 4%, underwater explosion energy output of emulsion explosives reaches maximum, and underwater explosion energy decreases when the glass microspheres content further increases.
Using RGD-containing peptide to enhance cell uptake for the detection of furin activity in cells
WANG Yuwei, LIANG Gaolin
2017, 47(5): 448-454. doi: 10.3969/j.issn.0253-2778.2017.05.011
A new self-assembled nano fluorescence probe was designed and synthesized.The new biocompatible CBT-Cys click reaction was used to cyclize RGD peptide in synthesis method. Using RGD peptide sequence, this probe can targetαvβ3 integrin of cancer cells and react with furin enzyme in cells, resulting in fluorescence“Off-On”.Thus it achieves the ability to target tumor cells for fluorescence imaging.