The relationship between reference canopy conductance and simplified hydraulic architecture     

Kimberly Novick  Ram Oren  Paul Stoy  Jehn-Yih Juang  Mario Siqueira  Gabriel Katul 《Advances in water resources》2009

Terrestrial ecosystems are dominated by vascular plants that form a mosaic of hydraulic conduits to water movement from the soil to the atmosphere. Together with canopy leaf area, canopy stomatal conductance regulates plant water use and thereby photosynthesis and growth. Although stomatal conductance is coordinated with plant hydraulic conductance, governing relationships across species has not yet been formulated at a practical level that can be employed in large-scale models. Here, combinations of published conductance measurements obtained with several methodologies across boreal to tropical climates were used to explore relationships between canopy conductance rates and hydraulic constraints. A parsimonious hydraulic model requiring sapwood-to-leaf area ratio and canopy height generated acceptable agreement with measurements across a range of biomes (r²=0.75)$(r^2=0.75)$. The results suggest that, at long time scales, the functional convergence among ecosystems in the relationship between water-use and hydraulic architecture eclipses inter-specific variation in physiology and anatomy of the transport system. Prognostic applicability of this model requires independent knowledge of sapwood-to-leaf area. In this study, we did not find a strong relationship between sapwood-to-leaf area and physical or climatic variables that are readily determinable at coarse scales, though the results suggest that climate may have a mediating influence on the relationship between sapwood-to-leaf area and height. Within temperate forests, canopy height alone explained a large amount of the variance in reference canopy conductance (r²=0.68)$(r^2=0.68)$ and this relationship may be more immediately applicable in the terrestrial ecosystem models.  相似文献   

Plane-symmetric mesonic viscous fluid cosmological model     

J. K. Singh  Shri Ram 《Astrophysics and Space Science》1996,236(2):277-284

Exact nonstatic solutions to Einstein field equations are obtained for the plane symmetric spacetime filled with viscous perfect fluid in the presence of attractive scalar fields. Some physical and geometrical properties of the model are studied. The solutions characterize strong interaction of elementary particles.  相似文献   

LRS Bianchi type V vacuum cosmological solution in Brans-Dicke theory     

Shri Ram  D. K. Singh 《Astrophysics and Space Science》1984,98(1):193-196

In this note a new solution of the BD field equations, for a Bianchi type V space-time, is obtained. The solution has its general relativistic analogue. Some properties of the solution are also discussed.  相似文献   

Exact Bianchi type VI0 cosmological solutions with matter in Brans-Dicke theory     

Shri Ram  D. K. Singh 《Astrophysics and Space Science》1984,103(1):21-26

We present an exact solution of the Brans-Dicke equations for cosmological models of Bianchi type VI₀ with stiff matter. The solution represents anisotropic universe which has its analogy in Einstein's theory. The corresponding result for a plane symmetry Bianchi type I model is obtained as a special case.  相似文献   

SS 433: results of a recent multiwavelength campaign     

Sandip K. Chakrabarti  B. G. Anandarao  S. Pal  Soumen Mondal  A. Nandi  A. Bhattacharyya  Samir Mandal  Ram Sagar  J. C. Pandey  A. Pati  S. K. Saha 《Monthly notices of the Royal Astronomical Society》2005,362(3):957-965

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Thermal and mass diffusion on MHD natural convective flow of a rarefied gas along vertical porous plate     

P. C. Ram  R. Nath  A. K. Agrawal 《Astrophysics and Space Science》1984,98(1):81-99

The flow of an electrically conducting incompressible rarefied gas due to the combined buoyancy effects of thermal and mass diffusion past an infinite vertical porous plate with constant suction has been studied in the presence of uniform transverse magnetic field. The problem has been solved for velocity, temperature, and concentration fields. It has been observed that mean velocity and the mean temperature are affected by the Grashof numbersG ₁ andG ₂, the slip parameterh ₁, temperature jump coefficienth ₂, concentration jump coefficienth ₃ and magnetic field parameterM. The amplitude and the phase of skin-friction and the rate of heat transfer are affected by frequency in addition to the above parameters. They are shown graphically. The numerical values of the mean skin-friction and the mean rate of heat transfer are also tabulated.  相似文献   

Heat and mass transfer on MHD heat generating flow through a porous medium in a rotating fluid     

P. C. Ram 《Astrophysics and Space Science》1990,172(2):273-277

The problem of the free-convection flow of a viscous heat generating fluid through porous media in a rotating frame of reference is considered for the case when a strong magnetic field is imposed in a direction which is perpendicular to the free-stream and makes an angle to the vertical direction. Analytical expressions for the velocity field and temperature are given, and the influences of the various parameters on the velocity field are discussed.  相似文献   

On steady plane rotating hydromagnetic flows     

Chandreshwar Thakur  Ram Babu Mishra 《Astrophysics and Space Science》1988,146(1):89-97

We consider the steady plane rotating, constantly inclined magnetohydrodynamic flows of a viscous incompressible fluid when the velocity magnitude is constant on each individual stream line. Hodograph transformation is employed and resulting partial differential equations are used to obtain the solution and the geometries for these flows whenJ0 andJ=0.  相似文献   

A formal framework for the representation of stack-based terrains     

Alejandro Graciano  Antonio Jesús Rueda  Francisco Ramón Feito 《International journal of geographical information science》2018,32(10):1999-2022

This paper presents a formal framework for the representation of three-dimensional geospatial data and the definition of common geographic information system (GIS) spatial operations. We use the compact stack-based representation of terrains (SBRT) in order to model geological volumetric data, both at the surface and subsurface levels, thus preventing the large storage requirements of regular voxel models. The main contribution of this paper is fitting the SBRT into the geo-atom theory in a seamless way, providing it with a sound formal geographic foundation. In addition we have defined a set of common spatial operations on this representation using the tools provided by map algebra. More complex geoprocessing operations or geophysical simulations using the SBRT as representation can be implemented as a composition of these fundamental operations. Finally a data model and an implementation extending the coverage concept provided by the Geography Markup Language standard are suggested. Geoscientists and GIS professionals can take advantage of this model to exchange and reuse geoinformation within a well-specified framework.  相似文献   

Tree-ring analysis of teak (Tectona grandis L.F.) in central India and its relationship with rainfall and moisture index     

Somaru Ram  H. P. Borgaonkar  A. B. Sikder 《Journal of Earth System Science》2008,117(5):637-645

Tree-ring-width index chronologies of teak (Tectona grandis L.F.) from three sites in central India have been studied for their dendroclimatic potential. The existence of good correlation among the three site chronologies indicates the influence of common forcing factor to the tree growth of the region. Tree growth and climate relationship based on correlation analysis revealed the important contribution of moisture index and rainfall rather than the direct influence of the temperature on tree growth during different seasons. Significant positive relationship of moisture index and rainfall during the monsoon months as well as on the annual scale with tree-ring width variations over the region indicates the important role of moisture availability at the root zone. The results suggest that the teak tree-ring chronologies can be used as high resolution proxy for past precipitation and moisture level in the environment.  相似文献