Data management for JGOFS: Theory and design

The Joint Global Ocean Flux Study (JGOFS), currently being organized under the auspices of the Scientific Committee for Ocean Research (SCOR), is intended to be a decade long internationally coordinated program. The main goal of JGOFS is to determine and understand on a global scale the processes controlling the time-varying fluxes of carbon and associated biogenic elements in the ocean and to evaluate the related exchanges with the atmosphere, sea floor and continental boundaries. 'A long-term goal of JGOFS will be to establish strategies for observing, on long time scales, changes in ocean biogeochemical cycles in relation to climate change'. Participation from a large number of U.S. and foreign institutions is expected. JGOFS investigators have begun a set of time-series measurements and global surveys of a wide variety of biological, chemical and physical quantities, detailed process-oriented studies, satellite observations of ocean color and wind stress and modeling of the bio-geochemical processes. These experiments will generate data in amounts unprecedented in the biological and chemical communities; rapid and effortless exchange of these data will be important to the success of JGOFS

Generalized Kirchhoff Vortices

A family of exact solutions of the Euler equations is presented: they are generalizations of the Kirchhoff vortex to N confocal ellipses. Special attention is given to the case N=2, for which the stability is analyzed with a method similar to the one used by Love [Proc. London Math. Soc. 1, XXV 18 (1893)] for the Kirchhoff vortex. The results are compared with those for the corresponding circular problem

Video Coding with Lifted Wavelet Transforms and Frame-Adaptive Motion Compensation

This paper investigates video coding with wavelet transforms applied in the temporal direction of a video sequence. The wavelets are implemented with the lifting scheme in order to permit motion compensation between successive pictures. We generalize the coding scheme and permit motion compensation from any even picture in the GOP by maintaining the invertibility of the inter-frame transform. We show experimentally, that frame-adaptive motion compensation improves the compression efficiency of the Haar and 5/3 wavelet

Cultivating Motivation: The importance of autonomy, competence & relatedness for instruction involving digital archives and objects

What motivates students to learn? More specifically, how can instruction involving primary sources, digital archives, or museum collections become more engaging and meaningful for students? Purdue librarians and instructional developers have found success in addressing issues of motivation by focusing on three aspects of Self-Determination Theory (SDT): autonomy, competence, and relatedness. Autonomy is defined as feelings of volition and choice, students’ ownership of their own learning processes, and endorsement of behaviors requested by an instructor. Competence refers to the degree to which students believe they can perform academically, and relatedness is concerned with student perceptions of feeling connected to other students, the instructor, and the course content. Student perceptions of these three interdependent psychological needs play an important role in fostering or impeding motivation, engagement, and knowledge-transfer. Incorporating principles of SDT in instruction provides specific and measurable goals for fostering student motivation across a variety of instructional contexts. Purdue Librarians gained exposure to the concepts of autonomy, competence, and relatedness in the IMPACT (Instruction Matters: Purdue Academic Course Transformation) program. IMPACT is a program through which faculty redesign foundational courses with the goal of creating learning-centered environments. Librarians, instructional developers, and educational technologists form teams with faculty through a 13-week instructional design process. This panel will apply lessons learned about student motivation to examine how learning experiences which involve digital objects and archives can be structured in ways that motivate students and allow instructors to assess student motivation to influence learning

Filamentation of Unstable Vortex Structures via Separatrix Crossing: A Quantitative Estimate of Onset Time

The onset of filamentation for compact vortex structures in two-dimensional incompressible flows is elucidated. An estimate is presented for the filamentation time of an unstably perturbed Kirchhoff ellipse, obtained from a linear analysis of the geometry of the instantaneous corotating streamfunction

Filamentation of Unstable Vortex Structures via Separatrix Crossing: A Quantitative Estimate of Onset Time

The onset of filamentation for compact vortex structures in two-dimensional incompressible flows is elucidated. An estimate is presented for the filamentation time of an unstably perturbed Kirchhoff ellipse, obtained from a linear analysis of the geometry of the instantaneous corotating streamfunction

Two-Layer Geostrophic Vortex Dynamics. Part 1. Upper-Layer V-States and Merger

We generalize the methods of two-dimensional contour dynamics to study a two-layer rotating fluid that obeys the quasi-geostrophic equations. We consider here only the case of a constant-potential-vorticity lower layer. We derive equilibrium solutions for monopolar (rotating) and dipolar (translating) geostrophic vortices in the upper layer, and compare them with the Euler case. We show that the equivalent barotropic (infinite lower layer) case is a singular limit of the two-layer system. We also investigate the effect of a finite lower layer on the merger of two regions of equal-sign potential vorticity in the upper layer. We discuss our results in the light of the recent laboratory experiments of Griffiths and Hopfinger (1986). The process of filamentation is found to be greatly suppressed for equivalent barotropic dynamics on scales larger than the radius of deformation. We show that the variation of the critical initial distance for merger as a function of the radius of deformation and the ratio of the layers at rest is closely related to the existence of vortex-pair equilibria and their geometrical properties

Inter-Resolution Transform for Spatially Scalable Video Coding

Spatial scalability of video signals can be achieved with critically sampled spatial wavelet schemes but also with an overcomplete spatial representation. Critically sampled schemes struggle with the problem that critically sampled high-bands are shift-variant. Therefore, efficient motion compensation is challenging. On the other hand, overcomplete representations can be shift-invariant, thus permitting efficient motion compensation in the spatial subbands, but they have to be designed carefully to achieve high compression efficiency. This paper discusses an orthonormal transform for decomposing two different spatial scales of the same image. The transform is such that it minimizes the impact of the quantization noise on the reconstructed video signal at the decoder. Further, we investigate the decorrelation property of the transform. Finally, we compare to the compression efficiency of a Laplacian pyramid, a conventional scheme for an overcomplete representation of images, and observe coding gains up to 1 dB