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Search Results: 1 - 10 of 265765 matches for " Wang H "
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Use of phosphorus to alleviate stress induced by cadmium and zinc in two submerged macrophytes
H Wang, PF Wang, H Zhang
African Journal of Biotechnology , 2009,
Abstract: The potential mechanism by which P antagonizes the toxicity of Zn and Cd was investigated in Elodea nuttallii and Hydrilla verticillata to understand the interactions between P, Cd and Zn pollutants. The two submerged macrophytes were treated with a combination of Cd (0.25 mg L-1) and Zn (1.0 mg L-1) and various concentrations of P (0, 0.05 and 5 mg L-1) for different exposure times (0.5, 1, 2, 4 and 7 days). The toxic effects and oxidative stress caused by the Cd and Zn resulted in a reduction of the total chlorophyll (chlorophyll a and b) and an increase in the content of glutathione (GSH). The activity of catalase (CAT) and the contents of malondialdehyde (MDA) both increased in the 1st day, and then reduced during the following 6 days. However, the activity of guaiacol peroxidase (POD) and the contents of soluble protein both decreased in the first day then increased from the 2nd to 7th days. Each index in the plants treated with Cd and Zn containing P showed similar changing trends to those treated with only Cd and Zn during the 7 days. However, different indices had different response times. At the best response time in each index, the result showed that using P can protect plants from the toxicity and oxidative stress caused by Cd and Zn, which suggested that P can produce an antagonistic response with Cd and Zn to mitigate the oxidative stress to plants. Also, these results suggested that Cd and Zn exerted their toxic effects on the growth of E. nuttallii and H. verticillata, at least in part, by the induction of oxidative stress and inhibition of photosynthesis. Through comparing the response of the two plants to oxidative stress caused by Cd and Zn, it was found that E. nuttallii was more sensitive than H. verticillata. E. nuttallii can be regarded as an indicative plant for Cd and Zn polluted waters.
Quantitative analysis on the ecological impact of large-scale water transfer project on water resource area in a changing environment
D. H. Yan,H. Wang,H. H. Li,G. Wang
Hydrology and Earth System Sciences Discussions , 2011, DOI: 10.5194/hessd-8-10465-2011
Abstract: The interbasin long-distance water transfer project is a key support for the reasonable allocation of water resources in a large-scale area, which can optimize the spatiotemporal change of water resources to reinforce the guarantee of the access of water resources. And large-scale water transfer projects have a deep influence on ecosystems; besides, global climate change causes the uncertainty and additive effect of the ecological impact of water transfer projects. Therefore, how to assess the ecological and environmental impact of large-scale water transfer projects in both construction and operation has triggered a lot of attention. The water-output area of the western route of China's South-North Water Transfer Project was taken as the study area of the present article. According to relevant evaluation principles and on the basis of background analysis on the eco-environment of the study area, the influence factors were identified and evaluation indexes were established. The climate-hydrology-ecology coupled simulation model was used to imitate the laws of ecological and environmental change of the water resource area in a changing climate. The emphasis of influence analysis and quantitative evaluation was placed on the reservoir construction and operation scheduling, representative river corridors and wetlands, natural reserves and the water environment of river basins below the dam sites. In the end, an overall influence evaluation of the impact of the project on the water circulation and ecological evolution of the water resource area was conducted. The research results were as follows: the environmental impacts of the western route project in the water resource area were concentrated on two aspects, i.e. the permanent destruction of vegetation during the phase of dam construction and river impoundment, and the significant influence on the hydrological situation of natural river corridor after the implementation of water transfer. Its impact on local climate, vegetation ecology, typical wetlands, natural reserves and the water environment of river basins below the dam sites was small.
The efficiency of mechanisms driving Subauroral Polarization Streams (SAPS)
H. Wang,H. Lühr
Annales Geophysicae (ANGEO) , 2011,
Abstract: We have investigated the seasonal and diurnal variation of SAPS (Subauroral Polarization Streams) occurrence based on 3663 SAPS events identified in DMSP ion drift observations in the Northern Hemisphere during July 2001 and June 2003. Their relationships with high latitude convection electric field, substorm, and ionospheric conductivity have been addressed. SAPS occurrences show a clear seasonal and diurnal variation with the occurrence rates varying by a factor of 5. It is found that the convection electric field might play a dominant role in association with SAPS occurrence. Peak convection electric fields mark the occurrence maximum of SAPS. Substorm might play a secondary role related to SAPS occurrence. It account for the secondary maximum in SAPS occurrence rate during December solstice. Our work demonstrates that the substorm induced electric field can develop SAPS during relatively low global convection. Somewhat low fluxtube-integrated conductivity is favorable for SAPS to develop. Another topic is the temporal relationship between SAPS and substorm phases. SAPS can occur at substorm onset, substorm expansion and recovery phases. Most probably SAPS tend to occur 60 min/45 min after substorm onset during quiet/more disturbed geomagnetic activity, respectively. This indicates that enhanced global convection helps SAPS to develop quicker during substorms. The peak plasma velocity of SAPS is increased on average only by 5–10 % by the substorm process.
Numerical Stability Test of Neutral Delay Differential Equations
Z. H. Wang
Mathematical Problems in Engineering , 2008, DOI: 10.1155/2008/698043
Abstract: The stability of a delay differential equation can be investigated on the basis of the root location of the characteristic function. Though a number of stability criteria are available, they usually do not provide any information about the characteristic root with maximal real part, which is useful in justifying the stability and in understanding the system performances. Because the characteristic function is a transcendental function that has an infinite number of roots with no closed form, the roots can be found out numerically only. While some iterative methods work effectively in finding a root of a nonlinear equation for a properly chosen initial guess, they do not work in finding the rightmost root directly from the characteristic function. On the basis of Lambert W function, this paper presents an effective iterative algorithm for the calculation of the rightmost roots of neutral delay differential equations so that the stability of the delay equations can be determined directly, illustrated with two examples.
Discrimination of Xihulongjing tea grade using an electronic tongue
H Xiao, J Wang
African Journal of Biotechnology , 2009,
Abstract: Five grades of Xihulongjing tea (grade: AAA, AA, A, B and C, from the same region and processed with the same processing method) were discriminated using -Astree II electronic tongue (e-tongue) coupled with pattern recognition methods including principal component analysis (PCA), canonical discriminant analysis (CDA) and back-propagation neural networks (BPNN). Results of PCA and CDA showed that the grades of the samples were discriminated with the exception of a few overlap samples between grade AA and grade A. The discrimination of accuracy of the training sample set and the predicted sample set was 95.7 and 97.5%, respectively, by the analysis of BPNN. 92.9% of all the crossvalidated training sample set and 100% of the predicted sample set were exactly grouped by CDA. The sensory evaluation of the samples was consistent with the evaluation based on the e-tongue. The results show that the e-tongue is a potential tool to identify the tea quality.
Hardware implementation of smart antenna systems
H. Wang,M. Glesner
Advances in Radio Science : Kleinheubacher Berichte , 2006,
Abstract: Smart antenna systems attract a lot attentions now and believably more in the future, as it can increase the capacity of mobile communication systems dramatically. Design of smart antenna systems combines the technologies of antenna design, signal processing, and hardware implementation. In this paper, a propose of smart antenna structure, as well as some function blocks that have been already implemented in hardware will be presented.
OCLC CJK Automated Library Information Network
  Andrew H. Wang
Journal of Library and Information Science , 1985,
Abstract: 頁次:143-153
Hypervelocity impact properties of graphene armor via molecular dynamics simulations
Shang H.,Wang W.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122604027
Abstract: Hypervelocity impact properties of two different graphene armor systems are investigated using molecular dynamics simulations. One system is the so-called spaced armor which consists of a number of graphene plates spaced certain distance apart. Its response under normal impact of a spherical projectile is studied, focusing on the effect of the number of graphene monolayers per plate (denoted by n) on the penetration resistance of the armor. We find that under normal impact by a spherical projectile the penetration resistance increases with decreasing number of monolayers per plate (n), and the best penetration resistance is achieved in the system with one graphene layer for each plate. Note that the monolayers in all the simulated multilayer graphene plates were AB-stacked. The second system being studied is the laminated copper/graphene composites with the graphene layers inside copper, on impact or back surface, or on both the impact and back surfaces. The simulation results show that under normal impact by a spherical projectile the laminated copper/graphene composite has much higher penetration resistance than the monolithic copper plate. The best efficiency is achieved when the graphene layers are on both the impact and back surfaces.
Towards conformal loop quantum gravity
Charles H. -T. Wang
Physics , 2005, DOI: 10.1088/1742-6596/33/1/032
Abstract: A discussion is given of recent developments in canonical gravity that assimilates the conformal analysis of gravitational degrees of freedom. The work is motivated by the problem of time in quantum gravity and is carried out at the metric and the triad levels. At the metric level, it is shown that by extending the Arnowitt-Deser-Misner (ADM) phase space of general relativity (GR), a conformal form of geometrodynamics can be constructed. In addition to the Hamiltonian and diffeomorphism constraints, an extra first class constraint is introduced to generate conformal transformations. This phase space consists of York's mean extrinsic curvature time, conformal three-metric and their momenta. At the triad level, the phase space of GR is further enlarged by incorporating spin-gauge as well as conformal symmetries. This leads to a canonical formulation of GR using a new set of real spin connection variables. The resulting gravitational constraints are first class, consisting of the Hamiltonian constraint and the canonical generators for spin-gauge and conformorphism transformations. The formulation has a remarkable feature of being parameter-free. Indeed, it is shown that a conformal parameter of the Barbero-Immirzi type can be absorbed by the conformal symmetry of the extended phase space. This gives rise to an alternative approach to loop quantum gravity that addresses both the conceptual problem of time and the technical problem of functional calculus in quantum gravity.
Unambiguous spin-gauge formulation of canonical general relativity with conformorphism invariance
Charles H. -T. Wang
Physics , 2005, DOI: 10.1103/PhysRevD.72.087501
Abstract: We present a parameter-free gauge formulation of general relativity in terms of a new set of real spin connection variables. The theory is constructed by extending the phase space of the recently formulated conformal geometrodynamics for canonical gravity to accommodate a spin gauge description. This leads to a further enlarged set of first class gravitational constraints consisting of a reduced Hamiltonian constraint and the canonical generators for spin gauge and conformorphism transformations. Owing to the incorporated conformal symmetry, the new theory is shown to be free from an ambiguity of the Barbero-Immirzi type.
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