检索结果-南通市图书馆

harmonic aspects of wind power integration

在线全文

学校读者我要写书评

暂无评论

journal of Modern Power Systems and Clean Energy 2013年第1期1卷 14-21页

作者： Math h.j.BOLLEN Kai YANG Electric Power Engineering Lulea University of Technology93187 SkellefteaSweden

This paper discusses a number of ways in which wind power installations can impact the harmonic levels in the power *** turbines are an additional source of harmonic emission,especially when it concerns"non-characteristic harmonics."Parallel resonances can amplify the emission from individual turbines.A mathematical model is developed to quantify this *** resonances can result in high currents,driven by the background voltage distortion in the transmission grid,flowing into thewind *** of the transmission grid will increase lower order harmonics but reduce higher order harmonics.

关键词： Power quality Power system harmonics Wind power

Research on the Influence of Steam Curing on Properties of C50 Shield Segment Concrete

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

武汉理工大学学报 2010年第17期32卷 137-140页

作者： LI j h Wuhan harbour Engineering Design & Research Co. Ltd.Wuhan 430071China Key Lab of Large-span Bridge Construction Technology Ministry of CommunicationsWuhan 430071China School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China

The effects of steam curing on mechanical properties,drying shrinkage,cracking sensitivity,anti-permeability,and carbonation resistance of C50 shield segment concrete were investigated,which were compared with the standard curing conditions. The results indicated that steam curing could increase early strength of concrete and reduce its drying shrinkage. however,steam curing reduced later strength of concrete,increased its crack sensitivity and deteriorated its anti-permeability and carbonation resistance. Moreover,the incorporation of fly ash could improve the durability of steam-cured concrete.

关键词： shield segment concrete steam curing properties influence

Trace element characteristics of partial melts produced by melting of metabasalts at high pressures: Constraints on the formation condition of adakitic melts

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2006年第9期49卷 915-925页

作者： j. Adam T.h. Green GEMOC National Key Centre Department of Earth and Planetary Sciences Macquarie University Sydney NSW 2109 Australia GEMOC National Key Centre Department of Earth and Planetary Sciences Macquarie University Sydney NSW 2109 Australia

Experiments were conducted on a natural basalt (with 5 wt.% added h2O) at 1.0―2.5 GPa and 900―1100℃. Experimental products include partial melts (quenched glasses) + residual mineral assemblages of amphibolite or eclogite. Electron microprobe and LAM-ICP-MS were used to determine major and trace element compositions of these quenched melts, respectively. Major ele- ment compositions of all the melts are tonalitic- trondhjemitic, similar to adakite. Their trace element characteristics are controlled by coexisting residual minerals. Signatures of adakite such as high Sr/Y, low hREE and negative Nb-Ta anomaly, etc. are present only in the melts coexisting with residual assemblages containing rutile and garnet (rutile-bearing eclogite or rutile-bearing amphibole-eclogite). Garnet leads to hREE depletion in melts, whereas rutile controls Nb and Ta partitioning during the partial melting and causes negative Nb-Ta anomaly in melts. Therefore, in addition to garnet, rutile is also a necessary residual phase during the generation of adakite or TTG magmas to account for the negative Nb-Ta anomaly of the magmas. The depth for the generation of adakite/TTG magmas via melting of metabasalt must be more than about 50 km based on the approximate 1.5 GPa mini- mum-pressure for rutile stability in the partial melting field of hydrous basalt.

关键词： trace element adakite/TTG magmas partial melting of metabasalt negativeNb-Ta anomaly rutile

Spatial Prediction of Soil Aggregate Stability and Aggregate-Associated Organic Carbon Content at the Catchment Scale Using Geostatistical Techniques

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2011年第3期21卷 389-399页

作者： j.MOhAMMADI M.h.MOTAGhIAN Department of Soil Science Agriculture CollegeShahrekord University

The association of organic carbon with secondary particles （aggregates） results in its storage and retention in soil. A study was carried out at a catchment covering about 92 km2 to predict spatial variability of soil water-stable aggregates （WSA）, mean weight diameter （MWD） of aggregates and organic carbon （OC） content in macro.- （〉 2 mm）, meso- （1-2 mm）, and micro-aggregate （〈 1 mm） fractions, using geostatistical methods. One hundred and eleven soil samples were eSlleeted at the 0 10cm depth and fractionated into macro-, meso-, and mlcro-aggregates by wet sieving. The OC content was determined for each fraction. A greater percentage of water-stable aggregates was found for micro-aggregates, followed by meso-aggregates. Aggregate OC content was greatest in meso-aggregates （9 g kg-1）, followed by micro-aggregates （7 g kg-1）, while the least OC content was found in macro-aggregates （3 g kg-1）. Although a significant effect （P = 0.000） of aggregate size on aggregate OC content was found, however, our findings did not support the model of aggregate hierarchy. Land use had a significant effect （P = 0.073） on aggregate OC content. The coefficients of variation （CVs） for OC contents associated with each aggregate fraction indicated macro-aggregates as the most variable （CV = 71%）. Among the aggregate fractions, the micro-aggregate fraction had a lower CV value of 27%. macro-aggregates to 84% for micro-aggregates. Geostatistical analysis differences in their spatial patterns in both magnitude and space at variance for most aggregate-associated properties was lower than 45%. The mean content of WSA ranged from 15% for showed that the measured soil variables exhibited each aggregate size fraction. The relative nugget The range value for the variogram of water-stable aggregates was almost similar （about 3 km） for the three studied aggregate size classes. The range value for the variogram of aggregate-associated OC contents ranged from about 3 km for macro-aggregates to about

关键词： kriging organic matter variogram water-stable aggregates

Spatial Estimation of Saturated hydraulic Conductivity from Terrain Attributes Using Regression,Kriging,and Artificial Neural Networks

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2011年第2期21卷 170-177页

作者： h.R.MOTAGhIAN j.MOhAMMADI Department of Soil Science Agriculture CollegeShahrekord UniversityShahrekord (Iran)

Several methods,including stepwise regression,ordinary kriging,cokriging,kriging with external drift,kriging with varying local means,regression-kriging,ordinary artificial neural networks,and kriging combined with artificial neural networks,were compared to predict spatial variation of saturated hydraulic conductivity from environmental *** methods except ordinary kriging allow for inclusion of secondary *** secondary spatial information used was terrain attributes including elevation,slope gradient,slope aspect,profile curvature and contour curvature.A multiple jackknifing procedure was used as a validation *** mean square error (RMSE) and mean absolute error (MAE) were used as the validation indices,with the mean RMSE and mean MAE used to judge the prediction *** performance by ordinary kriging was poor,indicating that prediction of saturated hydraulic conductivity can be improved by incorporating ancillary data such as terrain *** combined with artificial neural networks performed *** prediction models made better use of ancillary information in predicting saturated hydraulic conductivity compared with the competing *** combination of geostatistical predictors with neural computing techniques offers more capability for incorporating ancillary information in predictive soil *** is great potential for further research and development of hybrid methods for digital soil mapping.

关键词： digital elevation model geostatistics soil hydraulic properties spatial mapping

Order Environments of Topological Spaces

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2004年第5期20卷 943-948页

作者： j.h.LIANG K.KEIMEL Department of Mathematics Sichuan Univ.Chengdu 610064P.R.China Department of Mathematics Darmstadt Univ.Germany

In this paper it is proved that a space may be realized as the set of the maximal elementsin a continuous poset if and only if it is Tychonoff.

关键词： Domain environment Weakly complete Tychonoff space

hIGh-TEMPERATURE TENSILE FRACTURE BEhAVIOR OF DIRECTIONALLY SOLIDIFIED Ni,Cr,Al-TaC EUTECTIC SUPERALLOY

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2004年第4期17卷 455-459页

作者： j.Zhang j.j.Yu h.Z.Fu State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi'an 710072ChinaInstitute of Metal Research Chinese Academy of Sciences Shenyang 110016 ChinaState Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi'an 710072China

The high-temperature tensile fracture behavior of the Ni, Cr, Al-TaC eutectic superal-loy directionally solidified under high temperature gradient is investigated. The high-temperature tensile fracture of this in situ composite has ductile character with lots of ductile nests whose diameters decrease with the increasing solidification rates. The maximum σb and δ are respectively 668.5MPa and 19.6%. There is α TaC whisker in the center of each nest, and the deformation of γ' and TaC is uneven. The high-temperature tensile behavior cannot be explained by the rule of mixtures but is decided by the formation of the plastic deformation band. The crack extension model is given.

关键词： Ni Cr Al-TaC eutectic superalloy directional solidification,in situ composite high-temperature tenslie fracture

Generalizing plant–water relations to landscapes

在线全文

学校读者我要写书评

暂无评论

journal of Plant Ecology 2011年第1期4卷 101-113页

作者： R.h.Waring j.j.Landsberg College of Forestry Oregon State UniversityCorvallisOR 97331USA Withycombe Church LaneMt WilsonNSW 2786Australia

Aims Changing climate and land use patterns make it increasingly important that the hydrology of catchments and ecosystems can be reliably *** aim of this paper is to identify the biophysical factors that determine the rates of water vapor loss from different types of vegetation,and to seek,from an array of currently available satelliteborne sensors,those that might be used to initialize and drive landscape-level hydrologic *** Findings Spatial variation in the mean heights,crowd widths,and leaf area indices(LAI)of plant communities are important structural variables that affect the hydrology of *** stomatal conductance(G)imposes physiological limitation on transpiration by *** maximum value of G(Gmax)is closely linked to canopy photosynthetic capacity,which can be estimated via remote sensing of foliar chlorophyll or nitrogen *** be modeled as a nonlinear multipliable function of:(i)leaf–air vapor pressure deficit,(ii)water potential gradient between soil and leaves,(iii)photosynthetically active radiation absorbed by the canopy,(iv)plant nutrition,(v)temperature and(vi)the CO_(2) concentration of the *** surveys with Light Detection and Ranging(LiDAR)and interferometric RADAR,along with high-resolution spectral coverage in the visible,near-infrared,and thermal infrared bands,provide,along with meteorological data gathered from weather satellites,the kind of information required to model seasonal and interannual variation in transpiration and evaporation from landscapes with diverse and dynamic vegetation.

关键词： canopy stomatal conductance plant water relations process-based models remote sensing

Quintessence Cosmology with an Effective Λ-Term in Lyra Manifold

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics Letters 2015年第10期32卷 174-177页

作者： KhurshudyanM. Pasqua A Sadeghi j. Farahani h Chair of Theoretical Physics and Physics Teaching Methods Armenian State Pedagogical University Yerevan 375010 Republic of Armenia Department of Physics University of Trieste Trieste 234127 Italy Department of Physics University of Mazandaran Babolsar 47416-95447 Iran

We study quintessence cosmology with an effective A-term in Lyra manifold. We consider three different models by choosing variable A depending on time, the hubble parameter and the energy density of dark matter and dark energy. Dark energy is assumed as quintessence which interacts with the dark matter. Using numerical analysis we investigate the behavior of cosmological parameters in three different models and compare our results with observational data. State-finder diagnostic is also performed for all models.

关键词： Quintessence Cosmology with an Effective Term in Lyra Manifold