Volunteer tourism : the new ecotourism?

One of the more recent forms of tourism to emerge is what has become known as Volunteer Tourism, the practice of individuals going on a working holiday, volunteering their labour for worthy causes. While volunteering is a well-established activity, the combination with tourism is relatively new and has already changed considerably over a very short period. This paper reviews the process by which volunteer tourism has developed, focusing on its transformation from an individual altruistic endeavour to a more commercial form of conventional tourism. The paper reviews the growth in number of websites devoted to volunteer tourism, and discusses the changes that have taken place in the content and focus of these websites, the locations used as destinations and the organisations they represent over the last two decades. It is apparent that over the last two decades the organisations offering volunteer tourist vacations have increasingly focused their attention on conventional commercial tourism markets which is a similar pattern of evolution to that of ecotourism. The paper concludes that volunteer tourism is likely to become increasingly diverse in scale, distribution and focus in the future, in the same way as ecotourism has broadened its market and appeal, but in so doing, will lose more of the distinctive features that characterized its initial form

Synchronization and fault-masking in redundant real-time systems

A real time computer may fail because of massive component failures or not responding quickly enough to satisfy real time requirements. An increase in redundancy - a conventional means of improving reliability - can improve the former but can - in some cases - degrade the latter considerably due to the overhead associated with redundancy management, namely the time delay resulting from synchronization and voting/interactive consistency techniques. The implications of synchronization and voting/interactive consistency algorithms in N-modular clusters on reliability are considered. All these studies were carried out in the context of real time applications. As a demonstrative example, we have analyzed results from experiments conducted at the NASA Airlab on the Software Implemented Fault Tolerance (SIFT) computer. This analysis has indeed indicated that in most real time applications, it is better to employ hardware synchronization instead of software synchronization and not allow reconfiguration

Reliability improvements in tunable Pb1-xSnxSe diode lasers

Recent developments in the technology of Pb-salt diode lasers which have led to significant improvements in reliability and lifetime, and to improved operation at very long wavelengths are described. A combination of packaging and contacting-metallurgy improvements has led to diode lasers that are stable both in terms of temperature cycling and shelf-storage time. Lasers cycled over 500 times between 77 K and 300 K have exhibited no measurable changes in either electrical contact resistance or threshold current. Utilizing metallurgical contacting process, both lasers and experimental n-type and p-type bulk materials are shown to have electrical contact resistance values that are stable for shelf storage periods well in excess of one year. Problems and experiments which have led to devices with improved performance stability are discussed. Stable device configurations achieved for material compositions yielding lasers which operate continuously at wavelengths as long as 30.3 micrometers are described

Development of lead salt semiconductor lasers for the 9-17 micron spectral region

Improved diode lasers of Pb sub 1-x Sn sub x Se operating in the 9-17 micrometers spectral region were developed. The performance characteristics of the best lasers exceeded the contract goals of 500 microW/mode at T 30K in the 9-12 micrometers region and 200 microW/mode at T 18K in the 16-17 micrometers region. Increased reliability and device yields resulted from processing improvements which evolved from a series of diagnostic studies. By means of Auger electron spectroscopy, laser shelf storage degradation was shown to be characterized by the presence of In metal on the semiconductor crystal surfaces. Studies of various metal barrier layers between the crystals and the In metal led to the development of an improved metallurgical contacting technology which has resulted in devices with performance stability values exceeding the contract goal of a one year shelf life. Lasers cycled over 500 times between 300K and 77K were also shown to be stable. Studies on improved methods of fabricating striped geometry lasers indicated that good spectral mode characteristics resulted from lasers which stripe widths of 12 and 25 micrometers

The Mid-infrared Fine-structure Lines of Neon as an Indicator of Star For mation Rate in Galaxies

The fine-structure lines of singly ([Ne II] 12.8 micron) and doubly ([Ne III] 15.6 micron) ionized neon are among the most prominent features in the mid-infrared spectra of star-forming regions, and have the potential to be a powerful new indicator of the star formation rate in galaxies. Using a sample of star-forming galaxies with measurements of the fine-structure lines available from the literature, we show that the sum of the [Ne II] and [Ne III] luminosities obeys a tight, linear correlation with the total infrared luminosity, over 5 orders of magnitude in luminosity. We discuss the formation of the lines and their relation with the Lyman continuum luminosity. A simple calibration between star formation rate and the [Ne II]+[Ne III] luminosity is presented.Comment: To appear in ApJ. 8 page

Pipeline failure prediction in water distribution networks using weather conditions as explanatory factors

This is the author accepted manuscript. The final version is available from IWA Publishing via the DOI in this recordThis paper examines the impact of weather conditions on pipe failure in water distribution networks using artificial neural network (ANN) and evolutionary polynomial regression (EPR). A number of weather-related factors over 4 consecutive days are the input of the binary ANN model while the output is the occurrence or not of at least a failure during the following 2 days. The model is able to correctly distinguish the majority (87%) of the days with failure(s). The EPR is employed to predict the annual number of failures. Initially, the network is divided into six clusters based on pipe diameter and age. The last year of the monitoring period is used for testing while the remaining years since the beginning are retained for model development. An EPR model is developed for each cluster based on the relevant training data. The results indicate a strong relationship between the annual number of failures and frequency and intensity of low temperatures. The outputs from the EPR models are used to calculate the failures of the homogenous groups within each cluster proportionally to their length.The work reported is supported by the UK Engineering & Physical Sciences Research Council (EPSRC) project Safe & SuRe (EP/K006924/1)