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Search Results: 1 - 10 of 328260 matches for " Z. J. Gu "
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Dynamic Monitoring of Plant Cover and Soil Erosion Using Remote Sensing, Mathematical Modeling, Computer Simulation and GIS Techniques  [PDF]
Z. Y. Zeng, J. Z. Cao, Z. J. Gu, Z. L. Zhang, W. Zheng, Y. Q. Cao, H. Y. Peng
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.47180
Abstract:

Dynamic monitoring of plant cover and soil erosion often uses remote sensing data, especially for estimating the plant cover rate (vegetation coverage) by vegetation index. However, the latter is influenced by atmospheric effects and methods for correcting them are still imperfect and disputed. This research supposed and practiced an indirect, fast, and operational method to conduct atmospheric correction of images for getting comparable vegetation index values in different times. It tries to find a variable free from atmospheric effects, e.g., the mean vegetation coverage value of the whole study area, as a basis to reduce atmospheric correction parameters by establishing mathematical models and conducting simulation calculations. Using these parameters, the images can be atmospherically corrected. And then, the vegetation index and corresponding vegetation coverage values for all pixels, the vegetation coverage maps and coverage grade maps for different years were calculated, i.e., the plant cover monitoring was realized. Using the vegetation coverage grade maps and the ground slope grade map from a DEM to generate soil erosion grade maps for different years, the soil erosion monitoring was also realized. The results show that in the study area the vegetation coverage was the lowest in 1976, much better in 1989, but a bit worse again in 2001. Towards the soil erosion, it had been mitigated continuously from 1976 to 1989 and then to 2001. It is interesting that a little decrease of vegetation coverage from 1989 to 2001 did not lead to increase of soil erosion. The reason is that the decrease of vegetation coverage was chiefly caused by urbanization and thus mainly occurred in very gentle terrains, where soil erosion was naturally slight. The results clearly indicate the details of plant cover and soil erosion change in 25 years and also offer a scientific foundation for plant and soil conservation.

Anisotropy of magnetic susceptibility of rocks induced by experimental deformation
J. Hao,Z. Gu,J. Zhou
Annals of Geophysics , 1997, DOI: 10.4401/ag-3923
Abstract: In the present paper, the influence of the rheological process on the Anisotropy of Magnetic Susceptibility (AMS) of rocks is studied experimentally. The cylindrical samples of quartz-magnetite rock undergo a process under the confining stress of 300 MPa, temperature of 500-800 °C and strain rate of 5 ′ 10-5 - 1 ′ 10-4/s. The residual deformation after the above process ranges 9-42%, depending on the experimental condition. It is found that the magnetic susceptibilities and the shapes of magnetic grains in these samples are almost isotropic before deformation. After being deformed, these samples show certain amounts of anisotropy of magnetic susceptibility and the axes of maximum principal susceptibilities deviate from the original ones more or less. Furthermore, the grains become oblate-ellipsoidal and a certain preferred orientation occurs. The grain shape anisotropy seems to be the main reason for AMS formation. It appears that there is a limitation of the piezomagnetic theory in explaining some tectonomagnetic phenomena. The results obtained in this study imply that ductile deformation at high temperature and pressure in depth during a long time-process may result in another kind of response in rock magnetism, which could be a new mechanism of tectonomagnetic variation.
Decay out of a Superdeformed Band
J. Z. Gu,H. A. Weidenmueller
Physics , 1999, DOI: 10.1016/S0375-9474(99)00362-0
Abstract: Using a statistical model for the normally deformed states and for their coupling to a member of the superdeformed band, we calculate the ensemble average and the fluctuations of the intensity for decay out of the superdeformed band and of the intraband decay intensity. We show that both intensities depend on two dimensionless variables: The ratio $\Gamma^{\downarrow}/\Gamma_S$ and the ratio $\Gamma_N/d$. Here, $\Gamma^{\downarrow}$ is the spreading width for the mixing of the superdeformed and the normally deformed states, $d$ is the mean level spacing of the latter, and $\Gamma_S$ ($\Gamma_N$) is the width for gamma decay of the superdeformed state (of the normally deformed states, respectively). This parametric dependence differs from the one predicted by the approach of Vigezzi et al. where the relevant dimensionless variables are $\Gamma_N/\Gamma_S$ and $\Gamma^{\downarrow}/d$. We give analytical and numerical results for the decay intensities as functions of the dimensionless variables, including an estimate of the error incurred by performing the ensemble average, and we present fit formulas useful for the analysis of experimental data. We compare our results with the approach of Vigezzi et al. and establish the conditions under which this approach constitutes a valid approximation.
Bosonization study of quantum phase transitions in the one-dimensional asymmetric Hubbard model
Z. G. Wang,Y. G. Chen,S. J. Gu
Physics , 2007, DOI: 10.1103/PhysRevB.75.165111
Abstract: The quantum phase transitions in the one-dimensional asymmetric Hubbard model are investigated with the bosonization approach. The conditions for the phase transition from density wave to phase separation, the correlation functions and their exponents are obtained analytically. Our results show that the difference between the hopping integrals for up- and down-spin electrons is crucial for the happening of the phase separation. When the difference is large enough, the phase separation will appear even if the on-site interaction is small.
Ab initio Studies on Magnetism of 3d Transition Metal Dimers
Ab initio STUDIES ON MAGNETISM OF 3d TRANSITION METAL DIMERS

JH Gu,ZL Zhu,
J.H.
,Gu,Z.L.,Zhu

金属学报(英文版) , 2007,
Abstract: Ab initio calculations with the self-consistent full-potential linearized augmented-plane-wave method (FLAPW), under generalized gradient approximation, have been carried out to describe the electronic and magnetic properties of 3d transition metal dimers. It predicted the antiferromagneticity of Cr2 and ferromagneticity of other species. The Mn2 dimer was shown to be ferromagnetic coupling with a local magnetic moment of 5μB. Retaining the value of its free atom state. The V2 and Ni2 exhibited low spin-polarization with local magnetic moment of only 1μB per atom. On the other hand, Fe2 and Co2 were highly spin-polarized with local magnetic moments of 3 and 2μB.
Correlation between muonic levels and nuclear structure in muonic atoms
J. M. Dong,W. Zuo,H. F. Zhang,W. Scheid,J. Z. Gu,Y. Z. Wang
Physics , 2011, DOI: 10.1016/j.physletb.2011.09.057
Abstract: A method that deals with the nucleons and the muon unitedly is employed to investigate the muonic lead, with which the correlation between the muon and nucleus can be studied distinctly. A "kink" appears in the muonic isotope shift at a neutron magic number where the nuclear shell structure plays a key role. This behavior may have very important implications for the experimentally probing the shell structure of the nuclei far away from the $\beta$-stable line. We investigate the variations of the nuclear structure due to the interaction with the muon in the muonic atom and find that the nuclear structure remains basically unaltered. Therefore, the muon is a clean and reliable probe for studying the nuclear structure. In addition, a correction that the muon-induced slight change in the proton density distribution in turn shifts the muonic levels is investigated. This correction to muonic level is as important as the Lamb shift and high order vacuum polarization correction, but is larger than anomalous magnetic moment and electron shielding correction.
Effects of tensor interaction on pseudospin energy splitting and shell correction
J. M. Dong,W. Zuo,J. Z. Gu,Y. Z. Wang,L. G. Cao,X. Z. Zhang
Physics , 2011, DOI: 10.1103/PhysRevC.84.014303
Abstract: In the framework of a Skyrme-Hartree-Fock approach combined with BCS method, the role of the tensor force on the pseudospin energy splitting for tin isotope chain is investigated. The tensor force turns out to obviously affect the pseudospin energy splitting of the spin-unsaturated nuclei. Since the tensor force shifts the single-particle levels, it modifies the single-particle level density and the shell correction energy thereof. The influence of the tensor interaction on shell correction energy is considerable according to our analysis taking a magic nucleus $^{132}$Sn as well as a superheavy nucleus $^{298}114$ as examples. This modification of the shell correction energy due to the tensor component affects the stability of the superheavy nuclei.
Large magnetoresistance in La2/3Ca1/3MnO3 thin films induced by metal masked ion damage technique
M. J. Zhang,J. Li,Z. H. Peng,D. N. Zheng,A. Z. Jin,C. Z. Gu
Physics , 2006, DOI: 10.1063/1.2200883
Abstract: e have developed a simple process to obtain large magnetoresistance (MR) in perovskite manganite thin films by a combination of focused ion beam (FIB) milling and 120 keV H$_{2}^{+}$ ion implantation. Metal slits about 70 nm in width were printed by 30 kV focused Ga ion beam nanolithography on a 4 mm track, and the materials in these slits are then irradiated by the accelerated H$_{2}^{+}$ ions. Using this method, in a magnetic field of 5 T we can get a MR${>}$60% over a 230 K temperature scope, with a maximum value of 95% at around 70 K. This technique is very promising in terms of its simplicity and flexibility of fabrication and has potential for high-density integration.
Dependence of superconductivity in CuxBi2Se3 on quenching conditions
J. A. Schneeloch,R. D. Zhong,Z. J. Xu,G. D. Gu,J. M. Tranquada
Physics , 2015, DOI: 10.1103/PhysRevB.91.144506
Abstract: Topological superconductivity, implying gapless protected surface states, has recently been proposed to exist in the compound CuxBi2Se3. Unfortunately, low diamagnetic shielding fractions and considerable inhomogeneity have been reported in this compound. In an attempt to understand and improve on the finite superconducting volume fractions, we have investigated the effects of various growth and post-annealing conditions. With a melt-growth (MG) method, diamagnetic shielding fractions of up to 56% in Cu0.3Bi2Se3 have been obtained, the highest value reported for this method. We investigate the efficacy of various quenching and annealing conditions, finding that quenching from temperatures above 560C is essential for superconductivity, whereas quenching from lower temperatures or not quenching at all is detrimental. A modified floating zone (FZ) method yielded large single crystals but little superconductivity. Even after annealing and quenching, FZ-grown samples had much less chance of being superconducting than MG-grown samples. From the low shielding fractions in FZ-grown samples and the quenching dependence, we suggest that a metastable secondary phase having a small volume fraction in most of the samples may be responsible for the superconductivity.
F06296$+$5743 : A Very Massive Starburster ?
J. H. Huang,Q. S. Gu,H. J. Su,Z. H. Shang
Physics , 1996,
Abstract: We have observed an object having strong Balmer absorption lines and blue continuum. The inference about the nuclear stellar population drawn from the line ratios is basically coincident with that drawn from the continuum color, both indicating the dominant fraction of early A type population in the nucleus. This might be expected only if there has been a very massive starburst, burst strength of $>$ 10\% at least.
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