oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

4 ( 1 )

2020 ( 36 )

2019 ( 352 )

2018 ( 700 )

Custom range...

Search Results: 1 - 10 of 200965 matches for " H. Z. MA "
All listed articles are free for downloading (OA Articles)
Page 1 /200965
Display every page Item
Fault Diagnosis Based on ANN for Turn-to-Turn Short Circuit of Synchronous Generator Rotor Windings  [PDF]
H. Z. MA, L. PU
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2009, DOI: 10.4236/jemaa.2009.13028
Abstract: Rotor winding turn-to-turn short circuit is a common electrical fault in steam turbines. When turn-to-turn short circuit fault happens to rotor winding of the generator, the generator terminal parameters will change. According to these parameters, the conditions of the rotor winding can be reflected. However, it is hard to express the relations between fault information and generator terminal parameters in accurate mathematical formula. The satisfactory results in fault diagnosis can be obtained by the application of neural network. In general, the information about the severity level of the generator faults can be acquired directly when the faulty samples are found in the training samples of neural network. However, the faulty samples are difficult to acquire in practice. In this paper, the relations among active power, reactive power and excitation current are discovered by analyzing the generator mmf with terminal voltage constant. Depending on these relations, a novel diagnosis method of generator rotor winding turn-to-turn short circuit fault is proposed by using ANN method to obtain the fault samples directly, without destructive tests.
A meshless method for compressible flows with the HLLC Riemann solver
Z. H. Ma,H. Wang,L. Qian
Physics , 2014,
Abstract: The HLLC Riemann solver, which resolves both the shock waves and contact discontinuities, is popular to the computational fluid dynamics community studying compressible flow problems with mesh methods. Although it was reported to be used in meshless methods, the crucial information and procedure to realise this scheme within the framework of meshless methods were not clarified fully. Moreover, the capability of the meshless HLLC solver to deal with compressible liquid flows is not completely clear yet as very few related studies have been reported. Therefore, a comprehensive investigation of a dimensional non-split HLLC Riemann solver for the least-square meshless method is carried out in this study. The stiffened gas equation of state is adopted to capacitate the proposed method to deal with single-phase gases and/or liquids effectively, whilst direct applying the perfect gas equation of state for compressible liquid flows might encounter great difficulties in correlating the state variables. The spatial derivatives of the Euler equations are computed by a least-square approximation and the flux terms are calculated by the HLLC scheme in a dimensional non-split pattern. Simulations of gas and liquid shock tubes, moving shock passing a cylinder, internal supersonic flows in channels and external transonic flows over aerofoils are accomplished. The current approach is verified by extensive comparisons of the produced numerical outcomes with various available data such as the exact solutions, finite volume mesh method results, experimental measurements or other reference results.
Partonic State and Single Transverse Spin Asymmetries in Semi Inclusive DIS
Ma, J. P.;Sang, H. Z.
High Energy Physics - Phenomenology , 2008,
Abstract: Using partonic states we verify the transverse momentum dependent factorization for single transverse spin asymmetries in semi inclusive DIS at leading but nontrivial order of alpha_s. The factorization has been previously derived in a formal way by using diagram expansion at hadron level. We find with our partonic results that two relevant structure functions satisfy the factorization. Our results also satisfy the collinear factorization but with the perturbative coefficient different than that derived formally.
Partonic State and Single Transverse Spin Asymmetry in Drell-Yan Process
Ma, J. P.;Sang, H. Z.
High Energy Physics - Phenomenology , 2008, DOI: 10.1088/1126-6708/2008/11/090
Abstract: Single transverse-spin asymmetries have been studied intensively both in experiment and theory. Theoretically, two factorization approaches have been proposed. One is by using transverse-momentum-dependent factorization and the asymmetry comes from the so called Sivers function. Another is by using collinear factorization where the nonperturbative effect is parameterized by a twist-3 hadronic matrix element. However, the factorized formulas for the asymmetries in the two approaches are derived at hadron level formally by diagram expansion, where one works with various parton density matrices of hadrons. If the two factorizations hold, they should also hold at parton level. We examine this for Drell-Yan processes by replacing hadrons with partons. By calculating the asymmetry, Sivers function and the twist-3 matrix element at nontrivial leading order of $\alpha_s$, we find that we can reproduce the result of the transverse-momentum-dependent factorization. But we can only verify the result of the collinear factorization partly. Two formally derived relations between Sivers function and the twist-3 matrix element are also examined with negative results.
Estimating surface fluxes over middle and upper streams of the Heihe River Basin with ASTER imagery
W. Ma, Y. Ma, Z. Hu, Z. Su, J. Wang,H. Ishikawa
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2011,
Abstract: Land surface heat fluxes are essential measures of the strengths of land-atmosphere interactions involving energy, heat and water. Correct parameterization of these fluxes in climate models is critical. Despite their importance, state-of-the-art observation techniques cannot provide representative areal averages of these fluxes comparable to the model grid. Alternative methods of estimation are thus required. These alternative approaches use (satellite) observables of the land surface conditions. In this study, the Surface Energy Balance System (SEBS) algorithm was evaluated in a cold and arid environment, using land surface parameters derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. Field observations and estimates from SEBS were compared in terms of net radiation flux (Rn), soil heat flux (G0), sensible heat flux (H) and latent heat flux (λE) over a heterogeneous land surface. As a case study, this methodology was applied to the experimental area of the Watershed Allied Telemetry Experimental Research (WATER) project, located on the mid-to-upstream sections of the Heihe River in northwest China. ASTER data acquired between 3 May and 4 June 2008, under clear-sky conditions were used to determine the surface fluxes. Ground-based measurements of land surface heat fluxes were compared with values derived from the ASTER data. The results show that the derived surface variables and the land surface heat fluxes furnished by SEBS in different months over the study area are in good agreement with the observed land surface status under the limited cases (some cases looks poor results). So SEBS can be used to estimate turbulent heat fluxes with acceptable accuracy in areas where there is partial vegetation cover in exceptive conditions. It is very important to perform calculations using ground-based observational data for parameterization in SEBS in the future. Nevertheless, the remote-sensing results can provide improved explanations of land surface fluxes over varying land coverage at greater spatial scales.
SOIL GLYCOSIDASE ACTIVITIES AND WATER SOLUBLE ORGANIC CARBON UNDER DIFFERENT LAND USE TYPES
X. Z Ma,L. J Chen,Z. H Chen,Z.J Wu
Revista de la Ciencia del Suelo y Nutrición Vegetal , 2010,
Abstract: The purpose of this study was to measure the effects of different land uses on soil glycosidase activities (a- and (β-glucosidase, α- and (β-galactosidase), water soluble organic carbon (WSOC) and their relationships. Glycosidase activities showed significant differences under different land use types, the highest one was woodland. (β-glucosidase had the highest activity among the four glycosidases. The activities of these glycosidases decreased with increasing soil depth, being all significantly affected by change of soil depth. Except grassland, the four glycosidase activities intercorrelated each other. Woodland had the highest content of WSOC in the soil depth of 0-20 cm and at increasing soil depth, WSOC content decreased sharply under woodland and grassland. Glycosidase activities had positive and significant relationships with WSOC. Glycosidase activities and WSOC all had significant correlations with soil total organic carbon (TOC) and pH, which were sensitive to different land use types. We found that glycosidase activity indirectly impacts on nutrient recycling and energy flow in soil under different land use types.
Snow distribution over the Namco lake area of the Tibetan Plateau
M. Li, Y. Ma, Z. Hu, H. Ishikawa,Y. Oku
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2009,
Abstract: The mesoscale snow distribution over the Namco lake area of the Tibetan Plateau on October 2005 has been investigated in this paper. The base and revised experiments were conducted using the Weather Research Model (WRF) with three nested grids that included a 1 km finest grid centered on the Namco station. Our simulation ran from 6 October through to 10 October 2005, which was concurrent with long term meteorological observations. Evaluation against boundary layer meteorological tower measurements and flux observations showed that the model captured the observed 2 m temperature and 10 m winds reasonably well in the revised experiment. The results suggest that output snow depth maximum amounts from two simulated experiments were centered downwind of the Namco lakeshore. Modified surface state variable, for example, surface skin temperature on the lake help to increase simulated credibility.
Management of corneal bee sting
Razmjoo H, Abtahi MA, Roomizadeh P, Mohammadi Z, Abtahi SH
Clinical Ophthalmology , 2011, DOI: http://dx.doi.org/10.2147/OPTH.S26919
Abstract: nagement of corneal bee sting Case report (3904) Total Article Views Authors: Razmjoo H, Abtahi MA, Roomizadeh P, Mohammadi Z, Abtahi SH Video abstract presented by H Abtahi and P Roomizadeh Views: 235 Published Date December 2011 Volume 2011:5 Pages 1697 - 1700 DOI: http://dx.doi.org/10.2147/OPTH.S26919 Hassan Razmjoo1,2, Mohammad-Ali Abtahi1,2,4, Peyman Roomizadeh1,3, Zahra Mohammadi1,2, Seyed-Hossein Abtahi1,3,4 1Medical School, Isfahan University of Medical Sciences (IUMS); 2Ophthalmology Ward, Feiz Hospital, IUMS; 3Isfahan Medical Students Research Center (IMSRC), IUMS; 4Isfahan Ophthalmology Research Center (IORC), Feiz Hospital, IUMS, Isfahan, Iran Abstract: Corneal bee sting is an uncommon environmental eye injury that can result in various ocular complications with an etiology of penetrating, immunologic, and toxic effects of the stinger and its injected venom. In this study we present our experience in the management of a middle-aged male with a right-sided deep corneal bee sting. On arrival, the patient was complaining of severe pain, blurry vision with acuity of 160/200, and tearing, which he had experienced soon after the injury. Firstly, we administered conventional drugs for eye injuries, including topical antibiotic, corticosteroid, and cycloplegic agents. After 2 days, corneal stromal infiltration and edema developed around the site of the sting, and visual acuity decreased to 100/200. These conditions led us to remove the stinger surgically. Within 25 days of follow-up, the corneal infiltration decreased gradually, and visual acuity improved to 180/200. We suggest a two-stage management approach for cases of corneal sting. For the first stage, if the stinger is readily accessible or primary dramatic reactions, including infiltration, especially on the visual axis, exist, manual or surgical removal would be indicated. Otherwise, we recommend conventional treatments for eye injuries. Given this situation, patients should be closely monitored for detection of any worsening. If the condition does not resolve or even deteriorates, for the second stage, surgical removal of the stinger under local or generalized anesthesia is indicated.
Snow distribution over the Namco lake area of the Tibetan Plateau
M. Li,Y. Ma,Z. Hu,H. Ishikawa
Hydrology and Earth System Sciences Discussions , 2009,
Abstract: The mesoscale snow distribution over the Namco lake area of the Tibetan Plateau on October 2005 has been investigated in this paper. The control and sensitive experiments were conducted using Weather Research Model (WRF) with three nested grids that included a 1 km finest grid centered on the Namco station. Our simulation ran from 6 October through 10 October 2005, which was concurrent with long term meteorological observations. Evaluation against boundary layer meteorological tower measurements and flux observations showed that the model captured the observed 2 m temperature and 10 m winds reasonably well in the sensitive experiment. The results suggested that output snow depth maximum amounts from two simulated experiments were centered downwind shore of Namco lake. Modified surface parameters for example surface skin temperature on the lake help to increase simulated credibility.
Analyzing influence of spatial resolution on the estimated evapotranspiration by using remote sensing data over an oasis area in Northwestern China
H. Tian,J. Wen,Z. B. Su,Y. M. Ma
Hydrology and Earth System Sciences Discussions , 2009,
Abstract: In this paper, the influence of spatial resolution on the precision of estimates was analyzed through evapotranspiration (ET hereafter) modeling over a typical oasis in northwestern China by using the Landsat-TM and MODIS data. A relatively high consistency was observed between the TM-based latent heat flux and daily ET estimates and in-situ measurements, with relative errors of 9.7% and 8.8%, respectively. Despite lower precision of the relative errors of 22.4% and 17.0%, respectively, the MODIS-based latent heat flux and ET estimates can effectively depict the basic trend of the spatial distribution of the land surface processes. When the visible and near-infrared information of 250 m resolution was syncretized into MODIS LST retrieval algorithm, the precision of latent heat flux prediction was improved evidently. Additionally, the diurnal variation of the reference ET fraction shows that the temporal upscaling method of ET is suitable for the study area. In spite of suffering the influence of the heterogeneity of land surface, the moderate resolution MODIS data, combined with the parameterization model of land surface energy flux applied in this investigation, are suitable for the ET mapping at large scale while high-resolution data can serve as an important supplement.
Page 1 /200965
Display every page Item


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