A cost comparison of distributed and centralized approaches tovideo-on-demand

With video-on-demand (VoD) regarded as one of the drivers for the deployment of broadband integrated service digital networks (B-ISDNs), an important issue is how to provide wide area VoD services most efficiently. A large contributor to the cost of a VoD system is storage. The nature of the service requires massive amounts of storage and bandwidth to be supplied from a video server located within the network. We examine the costs of storage in such servers and develop an efficient allocation scheme designed to minimize this cost. Using this scheme, centralized and distributed approaches to VoD are compared. We conclude that a distributed approach to storage costs no more than a centralized approach and offers considerable advantages in terms of bandwidth requirements and service quality     

Zero location for discrete-time linear system polynomials with respect to an orthogonal basis

The problem is considered of a discrete-time constant linear system whose characteristic polynomial is expressed in terms of an arbitrary basis of orthogonal polynomials. It is shown how the Jury-Marden tabular array can be generalized to determine the location of the zeros with respect to the unit circle, without conversion of the polynomial into power form.     

A new approach to testing the flammability characteristics of surface coatings

This paper describes the background information which led to the development of a technique specifically designed to test the flammability performance of coatings applied to metal substrates. Design parameters for the new test are discussed and the prototype apparatus is described in detail. The mode of operation is explained and some results are tabulated for a range of typical coating materials. Conclusions based on the behaviour of the coatings tested are drawn in the text. These conclusions are, however, biased towards the Naval environment and application, and may not be universally applicable. The main implications of this work so far are that it is possible to improve the performance of existing fire retardant paint systems by: (1) ensuring that only the minimum thickness is applied to non-flammable substrates; (2) that adequate time is allowed for solvent elimination before deliberate exposure to risk; (3) using a white coating if possible; (4) increasing the durability of the coating to reduce the need for cosmetic overcoating, (i.e. re-coating purely to improve appearance), e.g. by using a thermosetting resinous binder in place of the conventionally used alkyd resin.     

Understanding and using the medical subject headings (MeSH) vocabulary to perform literature searches

The United States National Library of Medicine's (NLM) MEDLINE database is the largest and most widely used medical bibliographic database. MEDLINE is manually indexed with NLM's Medical Subject Headings (MeSH) vocabulary. Using MeSH, a searcher can potentially create powerful and unambiguous MEDLINE queries. This article reviews the structure and use of MeSH, directed toward the nonexpert, and outlines how MeSH may help resolve a number of common difficulties encountered when searching MEDLINE. The increasing importance of the MEDLINE database as an information resource and the trend toward individuals performing their own bibliographic searches makes it crucial that health care professionals become familiar with MeSH.     

Asymptotic stability and the method of linear bounds

If x? = Ax is asymptotically stable, it is possible to find linear bounds for g(x); so that x? = Ax + g(x) is also asymptotically stable. An explicit expression is given for functions which satisfy these bounds.     

A MECHANISTIC MODEL FOR MICROBIAL UPTAKE OF HYDROCARBONS IN FLOCCULATING AND NONFLOCCULATING SYSTEMS

Hydrocarhon uptake was studied in three microbial systems with different flocculation characteristics. An integrated mechanistic model, based on different substrate sources, has been developed for both flocculating and nonflocculating hydrocarbon fermentation systems. Simulated growth kinetics were compared with experimental results. The model illustrates the role of microbial characteristics in uptake kinetics and identifies the controlling parameters to better understand microbial uptake of hydrocarbons.     

How much is control knowledge worth?: A primitive example

The most basic activity performed by an intelligent agent is deciding what to do next. Usually, the decision takes the form of selecting, from among many applicable methods, one method to try first, or opting to expand a particular node in a simple search. The most primitive case is selecting between two independent alternatives. Below, this case is examined and the value of the control knowledge that makes the decision is determined. Another result derived is the sensitivity of the expected value of control knowledge as a function of the accuracy of the parameters used to make these control decisions.