Agriculture,community, river eutrophication and the Water Framework Directive     

Colin Neal  Helen P. Jarvie 《水文研究》2005,19(9):1895-1901

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Recombination induced softening and reheating of the cosmic plasma     

P. K. Leung  C. W. Chan  M.-C. Chu 《Monthly notices of the Royal Astronomical Society》2004,349(2):632-640

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EXPLORING SPATIAL FAMILIARITY*     

Nathan Gale  Reginald G. Golledge  William C. Halperin  Helen Couclelis 《The Professional geographer》1990,42(3):299-313

Spatial familiarity is a natural language concept that has no well-defined technical interpretation. We explore here some possible dimensions of the concept, provide subjective measurements of the dimensions, and evaluate their independence. The four dimensions examined are locational knowledge, visual recognition, name identification, and interaction frequency. We suggest that both cognitive and behavioral dimensions are embedded in the concept of spatial familiarity and must be part of the meaning of the concept and of any attempt to make it operational.  相似文献   

Improved Visualization Using a Fusion Technique Based on KNN Matting of Remotely Sensed Images     

Ablin Rajathurai  Helen Sulochana Chellakkon 《Journal of the Indian Society of Remote Sensing》2018,46(2):179-187

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High-order Taylor series expansion methods for error propagation in geographic information systems   总被引：2，自引：1，他引：1  

Jie Xue  Yee Leung  Jiang-Hong Ma 《Journal of Geographical Systems》2015,17(2):187-206

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Estimation of Facies Boundaries Using Categorical Indicators with P-Field Simulation and Ensemble Kalman Filter (EnKF)     

Siavash Nejadi  Japan Trivedi  Juliana Y. Leung 《Natural Resources Research》2015,24(2):121-138

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An experimental study of partial melting and fractional crystallization on the HED parent body          下载免费PDF全文

Helen O. Ashcroft  Bernard J. Wood 《Meteoritics & planetary science》2015,50(11):1912-1924

We have performed an experimental and modeling study of the partial melting behavior of the HED parent body and of the fractional crystallization of liquids derived from its mantle. We estimated the mantle composition by assuming chondritic ratios of refractory lithophile elements, adjusting the Mg# and core size to match the density and moment of inertia of Vesta, and the compositions of Mg‐rich olivines found in diogenites. The liquidus of a mantle with Mg# (=100*[Mg/(Mg+Fe)]) 80 is ~1625 °C and, under equilibrium conditions, the melt crystallizes olivine alone until it is joined by orthopyroxene at 1350 °C. We synthesized the melt from our 1350 °C experiment and simulated its fractional crystallization path. Orthopyroxene crystallizes until it is replaced by pigeonite at 1200 °C. Liquids become eucritic and crystal assemblages resemble diogenites below 1250 °C. MELTS correctly predicts the olivine liquidus but overestimates the orthopyroxene liquidus by ~70 °C. Predicted melt compositions are in reasonable agreement with those generated experimentally. We used MELTS to determine that the range of mantle compositions that can produce eucritic liquids and diogenitic solids in a magma ocean model is Mg# 75–80 (with chondritic ratios of refractory elements). A mantle with Mg# ~ 70 can produce eucrites and diogenites through sequential partial melting.  相似文献   

Climate change projections of the North American Regional Climate Change Assessment Program (NARCCAP)   总被引：2，自引：1，他引：1  

L. O. Mearns  S. Sain  L. R. Leung  M. S. Bukovsky  S. McGinnis  S. Biner  D. Caya  R. W. Arritt  W. Gutowski  E. Takle  M. Snyder  R. G. Jones  A. M. B. Nunes  S. Tucker  D. Herzmann  L. McDaniel  L. Sloan 《Climatic change》2013,120(4):965-975

We investigate major results of the NARCCAP multiple regional climate model (RCM) experiments driven by multiple global climate models (GCMs) regarding climate change for seasonal temperature and precipitation over North America. We focus on two major questions: How do the RCM simulated climate changes differ from those of the parent GCMs and thus affect our perception of climate change over North America, and how important are the relative contributions of RCMs and GCMs to the uncertainty (variance explained) for different seasons and variables? The RCMs tend to produce stronger climate changes for precipitation: larger increases in the northern part of the domain in winter and greater decreases across a swath of the central part in summer, compared to the four GCMs driving the regional models as well as to the full set of CMIP3 GCM results. We pose some possible process-level mechanisms for the difference in intensity of change, particularly for summer. Detailed process-level studies will be necessary to establish mechanisms and credibility of these results. The GCMs explain more variance for winter temperature and the RCMs for summer temperature. The same is true for precipitation patterns. Thus, we recommend that future RCM-GCM experiments over this region include a balanced number of GCMs and RCMs.  相似文献   

A Relationship Between Transition Region Brightenings,Abundances, and Magnetic Topology     

Fletcher  Lyndsay  López Fuentes  Marcelo C.  Mandrini  Cristina H.  Schmieder  Brigitte  Démoulin  Pascal  Mason  Helen E.  Young  Peter R.  Nitta  Nariaki 《Solar physics》2001,203(2):255-287

We present multi-instrument observations of active region (AR) 8048, made between 3 June and 5 June 1997, as part of the SOHO Joint Observing Program 33. This AR has a sigmoid-like global shape and undergoes transient brightenings in both soft X-rays and transition region (TR) lines. We compute a magneto-hydrostatic model of the AR magnetic field, using as boundary condition the photospheric observations of SOHO/MDI. The computed large-scale magnetic field lines show that the large-scale sigmoid is formed by two sets of coronal loops. Shorter loops, associated with the core of the SXT emission, coincide with the loops observed in the hotter CDS lines. These loops reveal a gradient of temperature, from 2 MK at the top to 1 MK at the ends. The field lines most closely matching these hot loops extend along the quasi-separatrix layers (QSLs) of the computed coronal field. The TR brightenings observed with SOHO/CDS can also be associated with the magnetic field topology, both QSL intersections with the photosphere, and places where separatrices issuing from bald patches (sites where field lines coming from the corona are tangent to the photosphere) intersect the photosphere. There are, furthermore, suggestions that the element abundances measured in the TR may depend on the type of topological structure present. Typically, the TR brightenings associated with QSLs have coronal abundances, while those associated with BP separatrices have abundances closer to photospheric values. We suggest that this difference is due to the location and manner in which magnetic reconnection occurs in two different topological structures. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1013302317042  相似文献   

Special features of cyclotron radiation in anisotropic plasmas     

P. C. W. Fung  P. L. Leung 《Astrophysics and Space Science》1987,137(1):33-62

We analyze the special features of cyclotron radiation in four different modes radiated by a mildly relativistic electron current in an anisotropic plasma, taking into consideration that the radiation is transmitted along the group velocity, rather than the wave normal direction. A systematic series of numerical analysis is carried out, to demonstrate the characteristics of the focussing effect and Doppler effect of the radiation, arising from anisotropy. The parameters used pertain to plasmas and radiators of the types encountered in the terrestrial upper atmosphere and the solar corona.  相似文献