32875582
Invariant object recognition by shape space analysis
This paper describes a new approach to invariant object recognition. In this approach, an object is represented by a set of key points called landmarks. All possible translation, scaling, and rotation of the object are placed into an equivalent class and associated to a single point in a complex projective space called the shape space. Object recognition is then achieved by distance calculations in this shape space. This approach is invariant to object translation, scaling, and rotation, and is computationally simple. Our experimental results also indicate that it is insensitive to noise and moderate occlusions.
37073864
Object representation and recognition in shape spaces
In this paper, we describe a shape space based approach for invariant object representation and recognition. In this approach, an object and all its similarity transformed versions are identified with a single point in a high-dimensional manifold called the shape space. Object recognition is achieved by measuring the geodesic distance between an observed object and a model in the shape space. This approach produced promising results in 2D object recognition experiments: it is invariant to similarity transformations and is relatively insensitive to noise and occlusion. Potentially, it can also be used for 3D object recognition.
43537984
A performance analysis of a discrete-time queueing system with server interruption for modeling wireless ATM multiplexer
In this paper, we study the effect of channel errors on wireless ATM. The salient characteristic of the wireless channel is that it is time varying. This variability is modeled by a Markov chain with two states corresponding to high and low error states, respectively. The channel is modeled as being synchronous with the basic time unit being the slot. The transitions from high to low error states, and vice versa occur at the slot boundaries. It is assumed that no transmission over the channel is possible during the high-error state.The information source feeding into the channel is modeled as the superposition of independent sources. Each source is controlled by a two-state Markov chain which operates in synchronism with, but statistically independent of the channel. In the source Off state, no data is emitted while, in the On state, the source generates a random number of packets in a slot each of which fits into a channel slot.It is assumed that the traffic generated by all the sources will form a single global queue which will be served by the two-state Markov channel. A discrete-time queuing analysis derives the probability generating function (PGF) of the queue length under the assumption of an infinite buffer. From the PGF, we determine mean queue length and mean delay. Finally, numerical results are presented to demonstrate the effect of wireless channel error characteristics on performance.
36022002
Version Augmented URIs for Reference Permanence via an Apache Module Design
The World Wide Web is perhaps the most convenient library resource ever to exist. Yet it also suffers from a critical flaw: WWW document citations existing as clickable links and as standard references in printed documents are quite unreliable. This arises from the ease with which these documents may be altered. Alteration of cited WWW documents may lead to the citations themselves becoming invalid or inaccurate. Printed documents are less prone to such problems due to the greater difficulty in altering or eradicating them. As a consequence of the alterability of WWW documents, the whole traditional system of new work building upon an archive of unchangeable previous work ceases to be valid. For the first time in history, documents are being built upon a shifting foundation to an extent of ever increasing and serious proportions. This work investigates a system aimed at encouraging the stability of WWW documents. In doing so it helps to preserve the accuracy of citations over time. The system presented extends a document's URI (Universal Resource Identifier) to include date or revision information thus allowing document providers to permit users to refer accurately to a particular document version. This paper both describes the system and demonstrates its use. The system is implemented as an Apache WWW server module. The module processes and retrieves documents referenced with extended URIs. It provides a model public domain system for alleviating the problem of content stable WWW documents.
37372418
Automatic image-to-site model registration
Image-to-site model registration is critical to model supported exploitation of aerial and satellite imagery. This paper presents a fully-automatic registration method. This method uses a multi-resolution image-to-image registration process assuming both affine and projective transformations to determine and refine the locations of 3D control points in the new image. Camera resection is subsequently accomplished. Registration results obtained on real imagery show good performance.
15371796
ACTIVE: agile coordinator testbed integrated virtual environment
This paper describes the specification, design and development of ACTIVE, a testbed for the testing and simulation of large-scale agent-based systems. ACTIVE is being developed as part of DARPA's Coordinators program. The goal of the ACTIVE testbed is to support the simulation of large collections of distributed cooperating agents in solving constrained scheduling problems.
119805904
Distorted-wave born approximation for the ionisation of hydrogen by electrons
Matrix elements for ionisation play an important part in electron-atom scattering calculations. Two methods for describing ionisation that can be incorporated into a scattering calculation are tested here against coplanar asymmetric experimental differential cross sections at 150 and 250 eV. They are the distorted-wave Born approximation and the coupled pseudostates methods. A method that incorporates the exact boundary conditions for three charged bodies describes the data significantly better and shows an important direction for improvement of scattering calculations