Invertible Carnot Groups

We characterize Carnot groups admitting a 1-quasiconformal metric inversion as the Lie groups of Heisenberg type whose Lie algebras satisfy the $J^2$-condition, thus characterizing a special case of inversion invariant bi-Lipschitz homogeneity. A more general characterization of inversion invariant bi-Lipschitz homogeneity for certain non-fractal metric spaces is also provided.Comment: 10 pages. Revised version in which the proof of Theorem 1.1 is clarifie

Transitive bi-Lipschitz group actions and bi-Lipschitz parameterizations

We prove that Ahlfors 2-regular quasisymmetric images of the Euclidean plane are bi-Lipschitz images of the plane if and only if they are uniformly bi-Lipschitz homogeneous with respect to a group. We also prove that certain geodesic spaces are bi-Lipschitz images of Carnot groups if they are inversion invariant bi-Lipschitz homogeneous with respect to a group.Comment: To appear in the Indiana University Mathematics Journa

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.This paper describes two irrigation systems in Nepal that have undergone rehabilitation - Sursia-Dudhaura and Bangeri. The experience of farmer-irrigators and their interaction with authorities of the Department of Irrigation is compared and analyzed according to criteria drawn from the literature of common property resource and collective goods theory. The analysis specifies organizational attributes hypothesized to make for successful and sustainable irrigation system rehabilitation, compares the two cases with regard to them, and notes implications. Bangeri is found to have much greater success with its rehabilitation than Sursia-Dudhaura, and the Bangeri irrigation community also possesses the organizational attributes advanced as important to effective local organization whereas Sursia-Dudhaura does not. The operation of local organizations are a most critical part of any canal rehabilitation

Image Representation of Digital Remote Sensing Data: A Perspective

Remote sensing data is the main component for determining answers to numerous fundamental questions regarding the earth\u27s environment and resources. Throughout the history of man, he has answered many of these questions with his own human remote sensors. Primary to these sensors are the images obtained by his eyes and interpreted by his brain. Universally, humans guide much of their activity based on images obtained by their eyes. Today, satellites with multispectral scanners take synoptic views of the earth\u27s surface. While computers aid modern interpretation of these reconstructed digital images, humans still obtain much meaningful interpretation by visual inspection combined with numerical analysis to produce useful information. The use of images to portray the results obtained from remote sensing information is natural to human interpretation. All to often, however, images are used without proper background for proper usage. In fact some results are merely passed over as modern computer art rather than sound scientific results obtained from rigourous analysis of remotely sensed data. This paper will define parameters of image display which provide effective guidance for proper presentation and use of images of remotely sensed data. Image representation of remotely sensed data may occur in several forms during the analysis process. One form of images may be the reconstructed image. This image represents the original data. An enhanced image in contrast represents data which may have had either or both radiometric or geometric preprocessing applied. Finally, there is the classification image which represents the themes of information obtained via analysis of the remotely sensed data. This last form is one of the most commonly misunderstood images. The key to proper understanding of results oriented images may be aided by asking the following key questions. Who will use the images? How and where will the images be used? What should the viewer of the image learn from the image? This last question only helps to focus on the fact that there are parameters for data display. The first parameter is when to use an image and in what form. Images are used before, during and after analysis. As noted earlier, the respective form of image tends to be reconstructed, enhanced and classification image. second, geographic considerations must be taken in to account. Such geographic considerations include the size of the area to be represented, the application of spatial corrections and the use locations indicators. Third, the amount of detail to be shown may be determined on two levels. The first level of detail is in the form of spatial resolution while the second is image display information level more commonly referred to as classification to level I, II or III. A fourth parameter is image display format: black and white versus color. The number of gray levels or colors respectively used may directly affect the amount of information transfer possible with a given image. Scale of the image affects the land area which may be depicted within a given physical size of image. Physical size may be 35 mm or topo map size. Finally, the medium of display may be softcopy and temporary as a digital display CRT, or hardcopy as paper and film products. While these outputs may be produced by different methods and equipment, the overriding tempering factor to all the parameters is likely to be cost. Cost of image output must be in perspective however, as images represent the ultimate and likely cost effective information transfer vehicle for results obtained from analysis of remotely sensed data

Creating Better River Basin Governance: A Comment

3 pages

Designing Local Irrigation Organizations for Democratic, Equitable, and Ecologically Sustainable Social Development: Theory and Two Cases in Nepal [abstract]

1 page

Designing Local Irrigation Organizations for Democratic, Equitable, and Ecologically Sustainable Social Development: Theory and Two Cases in Nepal [abstract]

1 page