Middleware for managing a large, heterogeneous programmable network

The links between BTexact Technologies and the Department of Computing Science at University College London are becomingincreasingly beneficial for the development of the middleware area for the management of programmable networks. This paperdescribes the work that has been done to date, and outlines the plans for future research

Requirements of a middleware for managing a large, heterogeneous programmable network

Programmable networking is an increasingly popular area of research in both industry and academia. Although most programmable network research projects seem to focus on the router architecture rather than on issues relating to the management of programmable networks, there are numerous research groups that have incorporated management middleware into the programmable network router software. However, none seem to be concerned with the effective management of a large heterogeneous programmable network. The requirements of such a middleware are outlined in this paper. There are a number of fundamental middleware principles that are addressed in this paper; these include management paradigms, configuration delivery, scalability and transactions. Security, fault tolerance and usability are also examined—although these are not essential parts of the middleware, they must be addressed if the programmable network management middleware is to be accepted by industry and adopted by other research projects

Trust but verify: The case for astrophysical black holes

This article is based on a pair of lectures given at the 2005 SLAC Summer Institute. Our goal is to motivate why most physicists and astrophysicists accept the hypothesis that the most massive, compact objects seen in many astrophysical systems are described by the black hole solutions of general relativity. We describe the nature of the most important black hole solutions, the Schwarzschild and the Kerr solutions. We discuss gravitational collapse and stability in order to motivate why such objects are the most likely outcome of realistic astrophysical collapse processes. Finally, we discuss some of the observations which -- so far at least -- are totally consistent with this viewpoint, and describe planned tests and observations which have the potential to falsify the black hole hypothesis, or sharpen still further the consistency of data with theory.Comment: Based on invited lectures at the 2005 SLAC Summer Institute (SSI05-L006). 22 pages, 5 eps figures. Very embarrassing typo in third paragraph fixed; numerous minor typos throughout paper fixe

A brief survey of LISA sources and science

LISA is a planned space-based gravitational-wave (GW) detector that would be sensitive to waves from low-frequency sources, in the band of roughly $(0.03 - 0.1) {\rm mHz} \lesssim f \lesssim 0.1 {\rm Hz}$. This is expected to be an extremely rich chunk of the GW spectrum -- observing these waves will provide a unique view of dynamical processes in astrophysics. Here we give a quick survey of some key LISA sources and what GWs can uniquely teach us about these sources. Particularly noteworthy science which is highlighted here is the potential for LISA to track the moderate to high redshift evolution of black hole masses and spins through the measurement of GWs generated from massive black hole binaries (which in turn form by the merger of galaxies and protogalaxies). Measurement of these binary black hole waves has the potential to determine the masses and spins of the constituent black holes with percent-level accuracy or better, providing a unique high-precision probe of an aspect of early structure growth. This article is based on the ``Astrophysics Tutorial'' talk given by the author at the Sixth International LISA Symposium.Comment: 8 pages, 2 figures, for the Proceedings of the Sixth International LISA Symposium. Particularly silly typo in one equation fixe

Probing strong-field gravity and black holes with gravitational waves

Gravitational wave observations will be excellent tools for making precise measurements of processes that occur in very strong-field regions of spacetime. Extreme mass ratio systems, formed by the capture of a stellar mass body compact by a massive black hole, will be targets for planned space-based interferometers such as LISA and DECIGO. These systems will be especially powerful tools for testing the spacetime nature of black hole candidates. In this writeup of the talk I gave at JGRG19, I describe how the properties of black holes are imprinted on their waveforms, and how measurements can be used to study these properties and thereby learn about the astrophysics of black holes and about strong-field gravity.Comment: 19 pages, 5 figures, for the Proceedings of the 19th Workshop on General Relativity and Gravitation in Japan. Content very similar to recent reviews by the autho

The influence of project complexity on estimating accuracy

With the rapid development in technology over recent years, construction, in common with many areas of industry, has become increasingly complex. It would, therefore, seem to be important to develop and extend the understanding of complexity so that industry in general and in this case the construction industry can work with greater accuracy and efficiency to provide clients with a better service. This paper aims to generate a definition of complexity and a method for its measurement in order to assess its influence upon the accuracy of the quantity surveying profession in UK new build office construction. Quantitative data came from an analysis of twenty projects of varying size and value and qualitative data came from interviews with professional quantity surveyors. The findings highlight the difficulty in defining and measuring project complexity. The correlation between accuracy and complexity was not straightforward, being subjected to many extraneous variables, particularly the impact of project size. Further research is required to develop a better measure of complexity. This is in order to improve the response of quantity surveyors, so that an appropriate level of effort can be applied to individual projects, permitting greater accuracy and enabling better resource planning within the profession

Repeat and first time visitation in an experience specific context: The Valley of the Giants Tree Top Walk.

Communication with the public is a primary consideration in the design of natural area tourist attractions (Manfredo & Bright,1991; Roggenbuck, 1992; Vogt & Stewart, 1998). In a management context, communication is essential in ensuring a relevant and enjoyable experience on the part of the visiting tourists (Magill, 1995). Communication also serves as an important management aid in reminding visitors of appropriate behaviour while ensuring continued visitor interest in the attraction (Moscardo, 1998; Moscardo & Woods,2001). This paper presents the results of a .survey examining motivations and attitudes of repeat and first time visitors to the Tree Top Walk site in the context of the communication strategy used at the site

A Polarized HERA Collider

A brief review is given of the status of nucleon spin structure functions as determined from polarized deep inelastic lepton-nucleon scatttering, including current outstanding problems. The characteristics of a polarized HERA collider, some of the particle physics topics it could address, and the accelerator physics challenges it must meet are discussed.Comment: 5 Pages, 6 Figures, To be published in the Proceedings of the DIS99 Conference April 1999, DESY Zeuthen, German

Impact of trail-side interpretive signs on visitor knowledge

Interpretive signs provide an important tool for enhancing visitor knowledge and understanding during a natural area experience. The Tree Top Walk (TTW) site in Western Australia adopted a minimal approach to interpretive signs to reduce distractions and allow the site to speak for itself. A 1999 pilot visitor survey indicated that many visitors were frustrated at this approach and wanted more signs installed along the walk trails despite the presence of information displays around the visitor kiosk. An interpretive sign trial was carried out in 2001 to assess the impact on visitor knowledge of the natural aspects of the site. While the trail-side interpretive signs provided no additional improvement in visitor knowledge, there appeared to be a positive increase in the perception of the site as providing a learning experience. The addition of trail-side interpretive signs also provided a point of interest for repeat visitors already familiar with the unique experience of the Tree Top Walk