6816342
SkipNet: A Scalable Overlay Network with Practical Locality Properties
Scalable overlay networks such as Chord, CAN, Pastry, and Tapestry have recently emerged as flexible infrastructure for building large peer-to-peer systems. In practice, such systems have two disadvantages: They provide no control over where data is stored and no guarantee that routing paths remain within an administrative domain whenever possible. SkipNet is a scalable overlay network that provides controlled data placement and guaranteed routing locality by organizing data primarily by string names. SkipNet allows for both fine-grained and coarse-grained control over data placement: Content can be placed either on a pre-determined node or distributed uniformly across the nodes of a hierarchical naming sub-tree. An additional useful consequence of SkipNet's locality properties is that partition failures, in which an entire organization disconnects from the rest of the system, can result in two disjoint, but well-connected overlay networks.
9636203
Two case studies in predictable application scheduling using Rialto/NT
This paper analyzes the results of two case studies in applying the Rialto/NT scheduler to real Windows 2000 applications. The first study is of a soft modem-a modem whose signal processing work is performed on the host CPU, rather than on a dedicated signal processing chip. The second is of an audio player application. Both of these are frequently used real-time applications-ones running on systems that were not designed to support predictable real-time execution. To function correctly, both applications require that ongoing computations be performed in a timely manner. In both cases, we first measured an original version designed to run on Windows 2000, and then modified the application to take advantage of ongoing CPU reservations provided by the Rialto/NT scheduler. We report on the benefits and problems observed when using reservations in these real-world scenarios. In both cases, we found that a real-time scheduler can provide the needed predictability for the application in the presence of competing applications, while also providing other benefits, such as minimizing the soft modem's impact on the scheduling predictability of other computations in the system. We also describe the methodologies we used to analyze the real-time behavior of the operating system and applications during these studies, including the use of instrumented kernels to produce execution traces.
18996618
The Production of Volume Data from Triangular Meshes Using Voxelisation
Voxelisation is the term given to the process of converting data from one source type into a three dimensional volume of data values. The techniques known collectively as volume visualisation can then be applied to the data in order to produce a graphical representation of the object. This paper gives a practical approach to the voxelisation of data in the form of triangular meshes, and demonstrates the use of the method on various datasets. Visualisation is achieved by a method also described in the paper.
29581932
Internal waves caused by the interaction of three harmonics under no restoring forces
The physical system under consideration consists of two fluids in uniform horizontal laminar motion parallel to their interface. All external restoring forces are absent. We find that nevertheless, three-wave interaction between different harmonics of the motion can take place. Attention is focused on the situation when this resonance is among the lowest three harmonics. Using the method of strained coordinates, a system of three coupled nonlinear partial differential equations is derived. These model the propagation of the interface, correct to second order. Solutions are found whose stability is briefly considered.
14632058
First-class polymorphism with type inference
Languages like ML and Haskell encourage the view of values as first-class entities that can be passed as arguments or results of functions, or stored as components of data structures. The same languages offer parametric polymorphism, which allows the use of values that behave uniformly over a range of different types. But the combination of these features is not supported-- polymorphic values are not first-class. This restriction is sometimes attributed to the dependence of such languages on type inference, in contrast to more expressive, explicitly typed languages, like System F, that do support first-class polymorphism.This paper uses relationships between types and logic to develop a type system, FCP, that supports first-class polymorphism, type inference, and also first-class abstract datatypes. The immediate result is a more expressive language, but there are also long term implications for language design.
14775203
Supporting Information Structuring in a Digital Library
In this paper we present Garnet, a spatial hypertext interface to a digital library. Spatial hypertext systems support information structuring the organisation of documents performed by a user to complement their information seeking. In the past, spatial hypertext systems have suffered from poor connectivity with information sources such as digital libraries. Conversely, digital libraries have provided strong support for document retrieval whilst offering little support for information structuring over the retrieved documents. Garnet provides an integrated environment for both seeking and organising information. We report on the results of a user study that elicits the response of users to a combined seeking and structuring environment. The feasibility of exploiting the information structuring of users to identify the interests of users is also investigated.
3315511
Sorting Out Searching on Small Screen Devices
Small handheld devices - mobile phones, PDAs etc - are increasingly being used to access the Web. Search engines are the most used Web services and are an important user support. Recently, Google? (and other search engine providers) have started to offer their services on the small screen. This paper presents a detailed evaluation of the how easy to use such services are in these new contexts. An experiment was carried out to compare users' abilities to complete realistic tourist orientated search tasks using a WAP, PDA-sized and conventional, desktop interface to the full Google? index. With all three interfaces, when users succeed in completing a task, they do so quickly (within 2 to 3 minutes) and using few interactions with the search engine. When they fail, though, they fail badly. The paper examines the causes of failures in small screen searching and proposes guidelines for improving these interfaces.