The Visvalingam algorithm: metrics, measures and heuristics

This paper provides the background necessary for a clear understanding of forthcoming papers relating to the Visvalingam algorithm for line generalisation, for example on the testing and usage of its implementations. It distinguishes the algorithm from implementation-specific issues to explain why it is possible to get inconsistent but equally valid output from different implementations. By tracing relevant developments within the now-disbanded Cartographic Information Systems Research Group (CISRG) of the University of Hull, it explains why a) a partial metric-driven implementation was, and still is, sufficient for many projects but not for others; b) why the Effective Area (EA) is a measure derived from a metric; c) why this measure (EA) may serve as a heuristic indicator for in-line feature segmentation and model-based generalisation; and, d) how metrics may be combined to change the order of point elimination. The issues discussed in this paper also apply to the use of other metrics. It is hoped that the background and guidance provided in this paper will enable others to participate in further research based on the algorithm

Quasiclassical theory of charge transport in disordered interacting electron systems

We consider the corrections to the Boltzmann theory of electrical transport arising from the Coulomb interaction in disordered conductors. In this article the theory is formulated in terms of quasiclassical Green's functions. We demonstrate that the formalism is equivalent to the conventional diagrammatic technique by deriving the well-known Altshuler-Aronov corrections to the conductivity. Compared to the conventional approach, the quasiclassical theory has the advantage of being closer to the Boltzmann theory, and also allows description of interaction effects in the transport across interfaces, as well as non-equilibrium phenomena in the same theoretical framework. As an example, by applying the Zaitsev boundary conditions which were originally developed for superconductors, we obtain the $P(E)$-theory of the Coulomb blockade in tunnel junctions. Furthermore we summarize recent results obtained for the non-equilibrium transport in thin films, wires and fully coherent conductors.Comment: 46 pages; review articl

User Interface Management Systems: A Survey and a Proposed Design

The growth of interactive computing has resulted in increasingly more complex styles of interaction between user and computer. To facilitate the creation of highly interactive systems, the concept of the User Interface Management System (UIMS) has been developed. Following the definition of the term 'UIMS' and a consideration of the putative advantages of the UIMS approach, a number of User Interface Management Systems are examined. This examination focuses in turn on the run-time execution system, the specification notation and the design environment, with a view to establishing the features which an "ideal" UIMS should possess. On the basis of this examination, a proposal for the design of a new UIMS is presented, and progress reported towards the implementation of a prototype based on this design

Computer graphics standards for man modelling

The human being is arguably one of the most nonstandard and unpredictable components of all systems. Thus, in many application areas of computer-aided design, there is a need to model the physical aspects of humans alongside models of workplace and equipment. The paper briefly describes the Sammie systems, a long-established and succesful computer-aided design system that has fulfilled this requirement across a wide range of application areas. Recently, much development work has been aimed at incorporating a range of graphics and data-exchange standards into the Sammie software. These experiences are described, together with observations on their apparent limitations and advantages. In particular, the Programmer's Hierarchical Interactive Graphics System (Phigs), its extension to Phigs-Plus, the Computer Graphics Metafile (CGM), the Initial Graphics Exchange Specification (iges), and X-Windows with the Phigs extension (Pex) are considered

An Overview of Computer Graphics Industry Standards.

This paper presents the status of the family of computer graphics standards that have been under development in recent years. In order to take advantage of the graphics standards, the industrial communities should be aware of what standards exist, and the relationship of the standards to each other. Since it is also beneficial to understand the process for the development of standards, the role of organizations in the standards-making field and the standardization process is presented. This discussion will provide an introduction and reference source for the computer graphics standards for those who have a need to understand the emerging standards, but have no technical involvement in their development. A level of understanding is provided which will assist in determining whether or not a particular standard would be appropriate for an intended application, and if further research into the standard might be required

The Computer Graphics Scene in the United States

We briefly survey the major thrusts of computer graphics activities, examining trends and topics rather than offering a comprehensive survey of all that is happening. The directions of professional activities, hardware, software, and algorithms are outlined. Within hardware we examine workstations, personal graphics systems, high performance systems, and low level VLSI chips; within software, standards and interactive system design; within algorithms, visible surface rendering and shading, three-dimensional modeling techniques, and animation. Note: This paper was presented at Eurographics\u2784 in Copenhagen, Denmark

Nonempirical Range-separated Hybrid Functionals for Solids and Molecules

Dielectric-dependent hybrid (DDH) functionals were recently shown to yield accurate energy gaps and dielectric constants for a wide variety of solids, at a computational cost considerably less than that of GW calculations. The fraction of exact exchange included in the definition of DDH functionals depends (self-consistently) on the dielectric constant of the material. Here we introduce a range-separated (RS) version of DDH functionals where short and long-range components are matched using system dependent, non-empirical parameters. We show that RS DDHs yield accurate electronic properties of inorganic and organic solids, including energy gaps and absolute ionization potentials. Furthermore we show that these functionals may be generalized to finite systems.Comment: In press. 13 pages, 7 figures, 8 tables, Physical Review B 201

Cartography, geographical information systems and maps in perspective

CISRG discussion paper ;