A study of the transport and loss of ions in the earth's quiet time ring current, in which the standard radial diffusion model developed for the high-energy radiation belt particles is compared with the measurements of the lower-energy ring current ions, is presented. The data set provides ionic composition information in an energy range that includes the bulk of the ring current energy density, 1-300 keV/e. Protons are found to dominate the quiet time energy density at all altitudes, peaking near L of about 4 at 60 keV/cu cm, with much smaller contributions from O(+) (1-10 percent), He(+) (1-5 percent), and He(2+) (less than 1 percent). A minimization procedure is used to fit the amplitudes of the standard electric radial diffusion coefficient, yielding 5.8 x 10 exp -11 R(E-squared)/s. Fluctuation ionospheric electric fields are suggested as the source of the additional diffusion detected.

Ion transport and loss in the Earth's quiet ring current: 1. Data and standard model

A framework for visual tracking of contours is presented, based on a synthesis of elastic models, stochastic filtering, and geometric invariance. Flexibly coupled curve templates implement soft prior assumptions about shape. Affine invariance, built into the flexible coupling, ensures that the affine deformations that arise naturally from image projection are favored. The stochastic basis of the framework is shown to result naturally in an automatic mechanism for the control of spatiotemporal scale. >

Affine-invariant contour tracking with automatic control of spatiotemporal scale

An analytic charge sheet capacitance model for short-channel MOSFETs is derived and implemented in SPICE. It is based on a surface potential formulation which computes the approximate surface potential without iterations. The DC current, charges, and their first and second derivatives are continuous under all operating regions. Equations for node charges are derived to guarantee charge conservation. Short-channel effects such as velocity saturation, channel-length modulation, and channel-side-fringing-field capacitances are included in the model equations. The model shows good agreement with the measured gate capacitance for long- and short-channel MOSFETs. The SPICE simulation of a ring oscillator using this model shows the significant variation of circuit performance due to the short-channel effects on capacitances. >

A charge sheet capacitance model of short channel MOSFETs for SPICE

The diverse functions of roots set requirements on specific root system architecture (RSA) Investigation on RSA holds potentials for studying the adaptation of plants to environmental stresses and to interspecific competitions Ground-penetrating radar (GPR) has provided a non-invasive method for studying in situ RSA However, previous GPR method relied on manually connecting root points detected between radargrams to restore each root branch, resulting in limited accuracy and efficiency of reconstructing RSA The objective of this study is to improve the effectiveness of 3D RSA reconstruction using GPR root detection data A total of 213 coarse root sections (with diameter >05 cm) were extracted from a distribution map of a reference shrub (Arctostaphylos pungens) root system to simulate the coarse roots identified by GPR An automatic method was established to trace each root point to its optimum growing source point Connections between discrete root points recovered the topology of the reference RSA A spline curve smoothing method was applied to restore the 3D morphology of the reference RSA The proposed protocol was then tested to rebuild the 3D RSA of a shrub (Caragana microphylla) growing in the sandy soils after in situ GPR survey The accuracy of RSA reconstruction was quantitatively evaluated by a relationship matrix method and qualitatively assessed by direct comparisons between the reconstructed and the actual RSAs after in situ excavation For both simulated and field collected GPR detection datasets, the reconstructed RSAs strongly corresponded to the real topology of the actual root systems When adapting the best strategy, 186 of the 213 (8732 %) root points on the reference root system of A pungens were interlinked with correct topology, and the relationship matrix method detected an overall similarity of 8275 % between the reconstructed and the actual RSAs The proposed automatic RSA reconstruction method greatly enhances the interpretation of GPR detection data regarding coarse roots, making in situ non-invasive and long-term mapping and monitoring of RSA possible

Ground-penetrating radar-based automatic reconstruction of three-dimensional coarse root system architecture

Some observations are made concerning the source and nature of shape parameters. It is then described how Bezier curve segments can be stitched together with G/sup 1/ or G/sup 2/ continuity, using geometric constructions. These constructions lead to the development of geometric constructions for quadratic G/sup 1/ and cubic G/sup 2/ Beta-splines. A geometrically continuous subclass of Catmull-Rom splines based on geometric continuity and possessing shape parameters is discussed. >

Geometric continuity of parametric curves: constructions of geometrically continuous splines

This volume discusses the use of splines from the point of view of the computer scientist. Assuming only a background in beginning calculus, the authors present the material using many examples and illustrations, including 16 color plates, with the goal of building the reader's intuition. The book includes the most recent advances in computer-aided geometric modeling and design to make spline modeling techniques generally accessible to the computer graphics and geometric modeling communities.

An introduction to the use of splines in computer graphics and geometric modeling

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An introduction to the use of splines in computer graphics and geometric modeling