oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

4 ( 1 )

2019 ( 112 )

2018 ( 354 )

2017 ( 314 )

Custom range...

Search Results: 1 - 10 of 86183 matches for " Z. Y. Zeng "
All listed articles are free for downloading (OA Articles)
Page 1 /86183
Display every page Item
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.

Research on the Software of Track Reconstruction in Vertex Chamber of BESII
Y. Zeng,Z. P. Mao
Physics , 2003,
Abstract: The software of track reconstruction of the vertex chamber of BESII-VCJULI was studied when it was transplanted from the HP-Unix platform to PC-Linux. The problems of distinct dictionary storage and precision treatment in these two different platforms were found and settled in the modified software. Then the obvious differences of the candidate track number in an event and some track parameters caused by them were reduced from 74% to 0.02% and from 5% to 0.5%, respectively. As a result, the quality of the track finding was greatly improved and the CPU time saved.
Delocalization and conductance quantization in one-dimensional systems
Z. Y. Zeng,F. Claro
Physics , 2001, DOI: 10.1103/PhysRevB.65.193405
Abstract: We investigate the delocalization and conductance quantization in finite one-dimensional chains with only off-diagonal disorder coupled to leads. It is shown that the appearence of delocalized states at the middle of the band under correlated disorder is strongly dependent upon the even-odd parity of the number of sites in the system. In samples with inversion symmetry the conductance equals $2e^{2}/h$ for odd samples, and is smaller for even parity. This result suggests that this even-odd behaviour found previously in the presence of electron correlations may be unrelated to charging effects in the sample.
Comment on: "Even-odd behavior of conductance in monatomic sodium wires"
Z. Y. Zeng,F. Claro
Physics , 2001,
Abstract: In this comment, we give a simple analytical proof for the even-odd behavior of the conductance of atomic wires.
Landauer-Büttiker-type current formula for hybrid mesoscopic systems
Z. Y. Zeng,F. Claro
Physics , 2001,
Abstract: A general Landauer-B\"uttiker-type current formula is derived, which can be applied to the ferromagnet (F)/Normal metal (N)/superconductor (S), F/N/N, N/N/S and N/N/N systems in the presence of various kinds of interactions in the central region.
Self-similarity and novel sample-length-dependence of conductance in quasiperiodic lateral magnetic superlattices
Z. Y. Zeng,F. Claro
Physics , 2001, DOI: 10.1103/PhysRevB.65.064207
Abstract: We study the transport of electrons in a Fibonacci magnetic superlattice produced on a two-dimensional electron gas modulated by parallel magnetic field stripes arranged in a Fibonacci sequence. Both the transmission coefficient and conductance exhibit self-similarity and the six-circle property. The presence of extended states yields a finite conductivity at infinite length, that may be detected as an abrupt change in the conductance as the Fermi energy is varied, much as a metal-insulator transition. This is a unique feature of transport in this new kind of structure, arising from its inherent two-dimensional nature.
Electronic Transport in Hybrid Mesoscopic Structures: A Nonequilibrium Green Function Approach
Z. Y. Zeng,Baowen Li,F. Claro
Physics , 2003, DOI: 10.1103/PhysRevB.68.115319
Abstract: We present a unified transport theory of hybrid structures, in which a confined normal state ($N$) sample is sandwiched between two leads each of which can be either a ferromagnet ($F$) or a superconductor ($S$) via tunnel barriers. By introducing a four-dimensional Nambu-spinor space, a general current formula is derived within the Keldysh nonequilibrium Green function formalism, which can be applied to various kinds of hybrid mesoscopic systems with strong correlations even in the nonequilibrium situation. Such a formula is gauge invariant. We also demonstrate analytically for some quantities, such as the difference between chemical potentials, superconductor order parameter phases and ferromagnetic magnetization orientations, that only their relative value appears explicitly in the current expression. When applied to specific structures, the formula becomes of the Meir-Wingreen-type favoring strong correlation effects, and reduces to the Landauer-B\"uttiker-type in noninteracting systems such as the double-barrier resonant structures, which we study in detail beyond the wide-band approximation.
Electron transport in interacting hybrid mesoscopic systems
Z. Y. Zeng,Baowen Li,F. Claro
Physics , 2002, DOI: 10.1140/epjb/e2003-00115-6
Abstract: A unified theory for the current through a nanoscale region of interacting electrons connected to two leads which can be either ferromagnet or superconductor is presented, yielding Meir-Wingreen-type formulas when applied to specific circumstances. In such a formulation, the requirement of gauge invariance for the current is satisfied automatically. Moreover, one can judge unambiguously what quantities can be measured in the transport experiment.
Diurnal pattern of the drying front in the desert and its application for determining the effective infiltration
Y. Zeng,Z. Su,L. Wan,Z. Yang
Hydrology and Earth System Sciences Discussions , 2009,
Abstract: Located in western Inner Mongolia, the Badain Jaran Desert is the second largest desert in China and consists of a regular series of stable megadunes, among which over 70 permanent lakes exist. The unexpected lakes in desert attracted research interests on exploring the hydrological process under this particular landscape; however, a very few literatures exist on the diurnal and spatial variation of the drying front in this area, which is the main issue in the desert hydrological process to characterize the movement of water in soil. In order to understand the drying front in the Badain Jaran Desert, a field campaign was conducted by the observations of soil physical parameters and micrometeorological parameters. With the field data, the performance of a vadose zone soil water balance model, the HYDRUS, was verified and calibrated. Then, the HYDRUS was used to produce the spatial and temporal information of coupled water, water vapour and heat transport in sand to characterize the variation pattern of the drying front before, during and after the rainfall. Finally, the deepest drying front was applied to determine the effective infiltration, which is defined as the amount of soil water captured by the sand beneath the deepest drying front by infiltrating water of an incident rainfall event.
Quantum Cable as transport spectroscopy of 1D DOS of cylindrical quantum wires
Z. Y. Zeng,Y. Xiang,L. D. Zhang
Physics , 2001, DOI: 10.1063/1.1313247
Abstract: We considered the proposed Quantum Cable as a kind of transport spectroscopy of one-dimensional (1D) density of states (DOS) of cylindrical quantum wires. By simultaneously detecting the direct current through the cylindrical quantum wire and the leaked tunneling current into the neighboring wire at desired temperatures, one can obtain detailed information about 1D DOS and subband structure of cylindrical quantum wires.
Page 1 /86183
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.