Yinchuan, China
Yinchuan, China

Ningxia University is a regional comprehensive university, co-administrated by Ningxia Hui Autonomous Region and Ministry of Education of the People's Republic of China.The school was founded in 1958. In the end of 1997, Ningxia Institute of Technology and Yinchuan Normal College were merged into the University. In February 2002, it was merged with Ningxia Agricultural College, and formed the new Ningxia University.It currently comprises three campuses. It consists of more than 2,600 teachers and staff, over 50% of them are formal instructors. More than half of the instructors hold intermediate to senior titles, 52% of them with masters or doctors degrees. 15 teachers receives special subsidies of the State Council, and 17 were elected into "National Hundreds, Thousands, Tens of Thousands Experts Project". It enrolls more than 15,000 undergraduates and over 1,300 graduates. More than 600 are minority preparatory students. Wikipedia.

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Zheng Q.-Z.,Ningxia University | Zheng Q.-Z.,Peking University | Jiao N.,Peking University
Tetrahedron Letters | Year: 2014

In the past 20 years, organic chemists have made significant contributions to the development of transition-metal-catalyzed ketone-directed ortho-C-H functionalization. These include Ru, Rh, Pd, and Ir-catalyzed ketone-directed C-C and C-heteroatom (O, N, Cl, Br, I) bond forming reactions. This article summarizes the developments of Ru, Rh, Pd, and Ir-catalyzed ketone-directed ortho-C-H functionalization reactions in the past two decades. © 2014 Elsevier Ltd. All rights reserved.

Tian X.,Ningxia University
International Journal of Advancements in Computing Technology | Year: 2012

In this paper, the improved version of Prewitt operator edge detection algorithm proposed which is based on the soft-threshold wavelet de-noising is aimed at processing the image with Gaussian white noise. A number of experiments show that this algorithm adds some advantages of wavelet de-noising, such as that the differential nature of the wavelet function can highlight the discontinuous edge of the image, The multi-resolution of wavelet transform overcome the contradiction between reduction of noise and the precision of edge positioning in the field of neighborhood selection. At the same time the wavelet transformation has the function of band-pass filter, and it can extraction the different levels of information. The improvement of algorithm combined by soft-thresholding wavelet de-noise and the conventional prewitt operator is a much better method than the conventional edge detection operator when it detects the edge of the image with White Gauss Noise.

Ding L.-H.,Ningxia University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

The stability of slope is influenced by multiple factors. It is one important subject to evaluate and predict the stability reasonably in the research of slope. Based on the approved grey correlation analysis and analytic hierarchy process (AHP), the comprehensive method is proposed to analyze the slope stability. According to the principle of grey correlation analysis, associate degree of slope stability is estimated and the slope grade is appraised by maximum correlation law. This method avoids the disadvantage that interval of the grade standards is not taken into account in traditional grey correlation analysis. The AHP of scale 3 is used to discuss the index weights; and precision of grey correlation analysis is improved. Case study shows that this method is reasonable and feasible to estimate slope stability.

Wen Z.,Nanjing University | Wen Z.,Ningxia University | Li C.,Nanjing University | Wu D.,Nanjing University | And 2 more authors.
Nature Materials | Year: 2013

Ferroelectric tunnel junctions (FTJs), composed of two metal electrodes separated by an ultrathin ferroelectric barrier, have attracted much attention as promising candidates for non-volatile resistive memories. Theoretical and experimental works have revealed that the tunnelling resistance switching in FTJs originates mainly from a ferroelectric modulation on the barrier height. However, in these devices, modulation on the barrier width is very limited, although the tunnelling transmittance depends on it exponentially as well. Here we propose a novel tunnelling heterostructure by replacing one of the metal electrodes in a normal FTJ with a heavily doped semiconductor. In these metal/ferroelectric/semiconductor FTJs, not only the height but also the width of the barrier can be electrically modulated as a result of a ferroelectric field effect, leading to a greatly enhanced tunnelling electroresistance. This idea is implemented in Pt/BaTiO3/Nb:SrTiO3 heterostructures, in which an ON/OFF conductance ratio above 104, about one to two orders greater than those reported in normal FTJs, can be achieved at room temperature. The giant tunnelling electroresistance, reliable switching reproducibility and long data retention observed in these metal/ferroelectric/semiconductor FTJs suggest their great potential in non-destructive readout non-volatile memories. © 2013 Macmillan Publishers Limited. All rights reserved.

Li H.,Ningxia University | Liang S.,Ningxia University | Li J.,Ningxia University | He L.,Ningxia University
Journal of Materials Chemistry A | Year: 2013

In this work, a carbon nanotubes (CNTs) and reduced graphene oxide (RGO) composite (CNTs-RGO) has been synthesized by a facile chemical approach for capacitive removal of salty ions from synthetic salty water. The as-prepared RGO-CNTs composite exhibits a network structure and strong hydrophilicity which are favourable for electrosorption. Cyclic voltammetry results illustrate that CNTs with 10 wt% RGO (CNTs-RGO-10) have the highest electrochemical capacity among all CNTs-RGO samples, implying the high capacitive deionization (CDI) performance. Meanwhile, it is found that the interfacial electron transfer resistance derived from the electrochemical impedance spectra for CNTs-RGO-10 in 1 M NaCl solution is 0.58 Ω which is much lower than that of either pure CNTs or RGO, implying that the introduced CNTs inhibit the aggregation and increase the conductivity by forming a network structure. Furthermore, the CDI performance of CNTs-RGO-10 is demonstrated through a batch mode desalination experiment in a given NaCl solution. The results reveal that the electrosorptive capacity of CNTs-RGO-10 is higher than that of pure CNTs regardless of the applied voltage when the experiment is conducted in NaCl solution with an initial conductivity of 100 μS cm-1. This is due to the optimized synergistic effect. In addition, the electrosorption rate constant as well as charge efficiency of the CNTs-RGO-10 electrode is found to be proportional to the electrical voltage and higher than that of the pure CNTs electrode at each electrical voltage, confirming the enhanced conductivity in the CNTs-RGO-10 electrode. Besides, the result of charge efficiency also demonstrates that CDI is envisioned to be a very energy efficient water desalination technology when the ionic content is relatively low. Finally, the repeatability of the CNTs-RGO-10 electrode is investigated, demonstrating that the CNTs-RGO composite electrode could be regenerated very well without any decay after several cycles. This journal is © The Royal Society of Chemistry 2013.

Liu C.,Ningxia University | Ren Y.,Ningxia University | Wang Y.,Ningxia University
Journal of Chemical and Engineering Data | Year: 2014

The equilibrium data of quaternary system phosphoric acid + sodium chloride + water + tri-n-butyl phosphate (TBP) was discussed at 298.15 K and atmospheric pressure. It was investigated experimentally in the mass concentration range 0-15% of NaCl and 4-24% of H3PO4 in the initial aqueous phase. The experimental results show that the separation factor of H 2O and the distribution coefficient of H3PO4 increase when the content of H3PO4 increases. The separation factor of NaCl decreases after an increase to a maximum value. Moreover, it was found out that the mass ratio of ternary system H 3PO4-NaCl-H2O to the saturation point. It would separate easily when the mass percent of NaCl occupies more than 12% in the system. The experimental tie-line data was correlated with the nonrandom two-liquid activity coefficient model. © 2013 American Chemical Society.

Zhao H.-L.,Chinese Academy of Sciences | Liu R.-T.,Ningxia University
Catena | Year: 2013

In the moving sand dune of Horqin Sand Land (Inner Mongolia), the diversity of the soil macro-arthropod communities beneath the canopies of two shrub species (Caragana microphylla and Salix gordejevii) and in open areas was investigated in order to determine the effect of shrubs on these soil communities. The results showed that the shrubs facilitated the aggregation of soil macro-arthropods, resulting in significantly higher diversity and individual density of macro-arthropods in the soil beneath the shrub canopy compared to the open areas. This is known as the "bug island" effect. Although the dominant families in these three soil macro-arthropod communities were the same beneath the shrub canopy compared to open areas, many new macro-arthropod families also occurred in the shrub canopy communities, resulting in significant changes in the composition and structure of these soil communities. The "bug island" effect of the shrubs resulted from the "fertile island" effect generated by these shrubs, i.e., reduced wind velocity, retained dust and sand, increased soil litter biomass and soil moisture, improved soil texture and soil fertility. Between the two shrub species investigated C. microphylla had a greater "bug island" effect than S. gordejevii, as C. microphylla had a higher "fertile island" effect than S. gordejevii. © 2013 Elsevier B.V.

Huang X.-F.,Lanzhou University | Ma J.-X.,Ningxia University | Liu W.-S.,Lanzhou University
Inorganic Chemistry | Year: 2014

On the basis of lanthanide metalloligands, [Ln(ODA)3] 3- (H2ODA = oxydiacetic acid), three series of d-f heterometallic metal-organic frameworks, {[Co(H2O) 6]·[Ln2(ODA)6Co2] ·6H2O}n [1; Ln = Gd (1a), Dy (1b), and Er (1c)], {[Ln2(ODA)6Cd3(H2O) 6]·mH2O}n [2; Ln = Pr (2a), Nd (2b), Sm (2c), Eu (2d), and Dy (2e), m = 9, 6, or 3], and {[Cd(H2O) 6]·[Ln2(ODA)6Cd2] ·mH2O}n [3; Ln = Dy (3a), Ho (3b), Er (3c), Tm (3d), and Lu (3e), m = 6 or 12], were designed and synthesized by a solvent volatilization and hydrothermal method. Magnetic investigation of 1 reveals the ferromagnetic interactions between the metal ions. In 2, LnIII ions occupied the inversion centers, which are confirmed by the fact that the emission intensity ratio of 5D0 → 7F 1 to 5D0 → 7F2 of the EuIII ion is much more than 3 in 2d. It is worth noting that, in 2d, the intensity ratio I(5D0→7F 1)/I(5D0→7F2) could decrease significantly upon the introduction of different hydrophilic guest molecules, which implies that the luminescent properties of 2d have a strong dependence on the geometry of the first coordination sphere of the Eu III ion. © 2014 American Chemical Society.

A fourth-order compact difference discretization scheme with unequal meshsizes in different coordinate directions is employed to solve a three-dimensional (3D) Poisson equation on a cubic domain. Two multgrid methods are developed to solve the resulting sparse linear systems. One is to use the full-coarsening multigrid method with plane Gauss-Seidel relaxation, which uses line Gauss-Seidel relaxation to compute each planewise solution. The other is to construct a partial semi-coarsening multigrid method with the traditional point or plane Gauss-Seidel relaxations. Numerical experiments are conducted to test the computed accuracy of the fourth-order compact difference scheme and the computational efficiency of the multigrid methods with the fourth-order compact difference scheme. © 2010 Elsevier Inc.

Ma W.-T.,Ningxia University
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

Based on the displacement sequence of slope, the stability of slope could be judged effectively by forecasting the displacement of slope in the future. Through analyzing advantages and disadvantages of grey forecasting methods and least square support vector machines(LSSVM) respectively , a new forecasting model of grey least square support vector machine was proposed. The new model not only developed the advantages of accumulation generation of the grey forecasting method, weakened the effect of stochastic-disturbing factors in original sequence and strengthened the regularity of data, but also used the quickly solving speed and the excellent characteristics of least square support vector machines for nonlinear relationship and avoided the theoretical defects existing in the grey forecasting model. At the same time, the genetic algorithms were used to optimize the parameters of new model. At last, two engineering examples are given to testify the effectiveness of the grey least square support vector machine method to forecast displacements of slope; the results show that the new model has higher precision.

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