Showing papers by "University of Westminster published in 2001"

The valuation of reliability for personal travel

Abstract: The paper reviews progress made towards a general theory of the traveller's valuation of travel time reliability, and give some indication of recent empirical research in this area. In the progress it brings together a large number of theoretical and empirical results, many of which are only partly in the public domain. Key theoretical results relating to the highway mode are discussed, and expanded to take in the additional complexity of scheduled public transport services. The paper also deals with the problems of collecting empirical data, and describes a recent study carried out by the authors in the context of rail travel, showing how valuations can be derived.

Managing Airports: An International Perspective

Abstract: This text provides a comprehensive in-depth study of the modern international airport industry. It analyses the trends towards privatisation and globalisation, which are fundamentally changing the nature of the industry It considers the key airport management issues related to economic performance and service provision within the context of the industry's wider developments and assesses the relationship between the airport customer and the role of airport marketing. The book also systematically considers the impacts that airports have on the surrounding community and the associated planning implications and places emphasis on the commercial and planning areas at strategic level, rather than the operational and technical aspects. In addition, it contains several airport examples and case studies from all over the world to aid understanding of the key topic areas - putting them in a practical context. Airport case studies include those from: BAA, Vienna, Aer Rianta, Amsterdam, Australia and the USA.

Understanding Agent Systems

Abstract: Mark d'Inverno and Michael Luck presenta formal approach to dealing with agents and agent systems in this second edition of Understanding Agent Systems. The Z specification language is used to establish an accessible and unified formal account of agent systems and inter-agent relationships. In particular, the framework provides precise and unambiguous meanings for common concepts and terms for agent systems, allows for the description of alternative agent models and architectures, and serves as a foundation for subsequent development of increasingly refined agent concepts. The practicability of this approach is verified by applying the formal framework to three detailed case studies. The book will appeal equally to researchers, students, and professionals in industry.

The Road to Military Humanitarianism: How the Human Rights NGOs Shaped A New Humanitarian Agenda

Abstract: This paper presents two articles taken from the Human Rights Quarterly publication. The first article written by David Chandler is concerned with the process through which the core ethics of humanitarianism have been transformed. It focuses on the shift in the politics of humanitarian interventionism as advocated by nongovernmental organizations (NGOs) during and after the Cold War. It also considers the nonpolitical approach of traditional humanitarian organizations and the development of more politicized human rights-based humanitarian NGOs it further analyzes some of the consequences of this change the retreat from the principles of neutrality and universalism and the development of "military humanitarianism". The second article by Marcella David discusses the pitfalls of marshaling security council resources to combat AIDS in Africa. David is convinced that the practical limitations on Security Council powers precludes tangible benefits and that there is a great risk of future Council abuse of the principle in expanding responsibility to cover disease and quality of life issues.

Long-term metabolic and skeletal muscle adaptations to short-sprint training: Implications for sprint training and tapering

Abstract: The adaptations of muscle to sprint training can be separated into metabolic and morphological changes. Enzyme adaptations represent a major metabolic adaptation to sprint training, with the enzymes of all three energy systems showing signs of adaptation to training and some evidence of a return to baseline levels with detraining. Myokinase and creatine phosphokinase have shown small increases as a result of short-sprint training in some studies and elite sprinters appear better able to rapidly breakdown phosphocreatine (PCr) than the sub-elite. No changes in these enzyme levels have been reported as a result of detraining. Similarly, glycolytic enzyme activity (notably lactate dehydrogenase, phosphofructokinase and glycogen phosphorylase) has been shown to increase after training consisting of either long (>10-second) or short (<10-second) sprints. Evidence suggests that these enzymes return to pre-training levels after somewhere between 7 weeks and 6 months of detraining. Mitochondrial enzyme activity also increases after sprint training, particularly when long sprints or short recovery between short sprints are used as the training stimulus. Morphological adaptations to sprint training include changes in muscle fibre type, sarcoplasmic reticulum, and fibre cross-sectional area. An appropriate sprint training programme could be expected to induce a shift toward type IIa muscle, increase muscle cross-sectional area and increase the sarcoplasmic reticulum volume to aid release of Ca2+. Training volume and/or frequency of sprint training in excess of what is optimal for an individual, however, will induce a shift toward slower muscle contractile characteristics. In contrast, detraining appears to shift the contractile characteristics towards type IIb, although muscle atrophy is also likely to occur. Muscle conduction velocity appears to be a potential non-invasive method of monitoring contractile changes in response to sprint training and detraining. In summary, adaptation to sprint training is clearly dependent on the duration of sprinting, recovery between repetitions, total volume and frequency of training bouts. These variables have profound effects on the metabolic, structural and performance adaptations from a sprint-training programme and these changes take a considerable period of time to return to baseline after a period of detraining. However, the complexity of the interaction between the aforementioned variables and training adaptation combined with individual differences is clearly disruptive to the transfer of knowledge and advice from laboratory to coach to athlete.

Interference between postural control and mental task performance in patients with vestibular disorder and healthy controls.

Abstract: Objectives—To determine whether inter- ference between postural control and mental task performance in patients with balance system impairment and healthy subjects is due to general capacity limita- tions, motor control interference, compe- tition for spatial processing resources, or a combination of these. Method—Postural stability was assessed in 48 patients with vestibular disorder and 24 healthy controls while they were stand- ing with eyes closed on (a) a stable and (b) a moving platform. Mental task perform- ance was measured by accuracy and reac- tion time on mental tasks, comprising high and low load, spatial and non-spatial tasks. Interference between balancing and performing mental tasks was assessed by comparing baseline (single task) levels of sway and mental task performance with levels while concurrently balancing and carrying out mental tasks. Results—As the balancing task increased in diYculty, reaction times on both low load mental tasks grew progressively longer and accuracy on both high load tasks declined in patients and controls. Postural sway was essentially unaVected by mental activity in patients and con- trols. Conclusions—It is unlikely that dual task interference between balancing and men- tal activity is due to competition for spatial processing resources, as levels of interference were similar in patients with vestibular disorder and healthy controls, and were also similar for spatial and non- spatial tasks. Moreover, the finding that accuracy declined on the high load tasks when balancing cannot be attributed to motor control interference, as no motor control processing is involved in main- taining accuracy of responses. Therefore, interference between mental activity and postural control can be attributed princi- pally to general capacity limitations, and is hence proportional to the attentional demands of both tasks. (J Neurol Neurosurg Psychiatry 2001;71:48-52)

Age and Participation in Vocational Education and Training

Abstract: In recent years increasing attention has been paid to the problems faced by older workers in the UK labour market. In this paper we examine the issue of older workers' participation in vocational training and education, drawing upon data from the Labour Force Survey. Our initial analysis identifies how rates of participation in workrelated education and training differ between age groups. Further exploratory analysis attempts to identify possible reasons for this, analysing the type of training undertaken by various age groups as well as the incidence of self-financed training. We then estimate an ordered-probit model for males and females separately, in an attempt to isolate the extent to which this lower incidence among older workers is due to employer or employee decision making. We find that, when compared to a reference group of prime aged individuals, those aged between 40 and 49 and 50 and 59/64 are less likely to undergo training and, also, less likely to be offered training. We conclude that the ...

Learning in multi-agent systems

Abstract: In recent years, multi-agent systems (MASs) have received increasing attention in the artificial intelligence community. Research in multi-agent systems involves the investigation of autonomous, rational and flexible behaviour of entities such as software programs or robots, and their interaction and coordination in such diverse areas as robotics (Kitano et al., 1997), information retrieval and management (Klusch, 1999), and simulation (Gilbert & Conte, 1995). When designing agent systems, it is impossible to foresee all the potential situations an agent may encounter and specify an agent behaviour optimally in advance. Agents therefore have to learn from, and adapt to, their environment, especially in a multi-agent setting.

Improvement of third-order intermodulation product of RF and microwave amplifiers by injection

Abstract: This paper discusses the improvement in the third-order intermodulation product (IM3) performance obtainable from RF and microwave amplifiers by two alternative injection techniques. The first is the addition to the amplifier input of the second harmonics of the input spectrum and the second is the addition to the amplifier input of the difference frequencies between the spectral components of the input signal. Both techniques are considered in theory, by simulation and in practice. Both techniques give useful improvements in two-tone IM3 performance. The second harmonic technique reduced the IM3 level by 43 dB in an amplifier at 835 MHz. The difference-frequency technique gave a reduction of 48 dB in an amplifier at 880 MHz. The difference-frequency technique also gives a greater improvement for complex spectra signals.

Low frequency noise "pollution" interferes with performance

Abstract: To study the possible interference of low frequency noise on performance and annoyance, subjects categorised as having a high- or low sensitivity to noise in general and low frequency noise in particular worked with different performance tasks in a noise environment with predominantly low frequency content or flat frequency content (reference noise), both at a level of 40 dBA. The effects were evaluated in terms of changes in performance and subjective reactions. The results showed that there was a larger improvement of response time over time, during work with a verbal grammatical reasoning task in the reference noise, as compared to the low frequency noise condition. The results further indicated that low frequency noise interfered with a proof-reading task by lowering the number of marks made per line read. The subjects reported a higher degree of annoyance and impaired working capacity when working under conditions of low frequency noise. The effects were more pronounced for subjects rated as high-sensitive to low frequency noise, while partly different results were obtained for subjects rated as high-sensitive to noise in general. The results suggest that the quality of work performance and perceived annoyance may be influenced by a continuous exposure to low frequency noise at commonly occurring noise levels. Subjects categorised as high-sensitive to low frequency noise may be at highest risk.

Differential effects of Ecstasy and cannabis on self-reports of memory ability: a web-based study.

Abstract: Given the legal status of MDMA (3,4-methylenedioxymethamphetamine), or Ecstasy, face-to-face access to participants is sometimes difficult. The number of participants in studies of cognitive performance amongst Ecstasy users is variable, with the average being around 30. Access to a larger number of participants is clearly desirable. The present investigation accessed a larger sample size using a web-based design. A website was developed and used for data collection. Prospective memory ability was assessed using the Prospective Memory Questionnaire. Self-report of day-to-day memory performance was investigated using the Everyday Memory Questionnaire. The Drug Questionnaire assessed the use of other substances as well as Ecstasy, allowing a regression design to isolate the contribution of each substance to any variance on the cognitive measures. Preliminary findings (N = 488) indicate that there is a clear double dissociation between the impact of Ecstasy and cannabis. We found that cannabis was associated with reports of 'here-and-now' cognitive problems in short-term and internally cued prospective memory. In contrast, Ecstasy was associated with reports of long-term memory problems, which were more related to storage and retrieval difficulties. Copyright 2001 John Wiley & Sons, Ltd.

'Portfolio Workers': Autonomy and Control amongst Freelance Translators

Abstract: Recent literature has begun to disaggregate groups of the `self-employed without employees' to examine in greater detail what determines their working conditions. This article continues this trend ...

Developmental changes in the effect of inversion: using a picture book to investigate face recognition.

Abstract: A novel child-oriented procedure was used to examine the face-recognition abilities of children as young as 2 years. A recognition task was embedded in a picture book containing a story about two boys and a witch. The story and the task were designed to be entertaining for children of a wide age range. In eight trials, the children were asked to pick out one of the boys from amongst eight distractors as quickly as possible. Response-time data to both upright and inverted conditions were analysed. The results revealed that children aged 6 years onwards showed the classic inversion effect. By contrast, the youngest children, aged 2 to 4 years, were faster at recognising the target face in the inverted condition than in the upright condition. Several possible explanations for this 'inverted inversion effect' are discussed.

Virtual classroom

Abstract: The paper presents the results of the "Virtual Classroom" project sponsored by the University of Westminster, Educational Initiative Centre (EIC) for delivering lectures online. The ultimate aim was to provide a portable hardware and easy to use software toolset as well as easy to follow guidelines on how to propel the lectures from the conventional dull chalk and talk environment to the realm of all interactive computer assisted Web based electronic classroom. The additional goal was to minimise the number of staff required to give the lectures and allow them to use their valuable time for other academic duties. The proposed hardware/software setup is a fully automatic solution controllable from a single PC. It allowed full student interaction and use of multimedia in the lecture. Although the best quality was achieved by use of multicasting, the students connecting via modem can also take interactive part in the lectures.

A motion sickness maximum around the 0.2 Hz frequency range of horizontal translational oscillation

Abstract: Background: Low frequency translational oscillation can provoke motion sickness in land vehicles, ships and aircraft. Although controlled motion experiments indicate a progressive increase in nauseogenicity as frequency decreases toward 0.2 Hz, few data are available on the existence of a definite maximum nauseogenic potential of motion around 0.2 Hz, or decreased nauseogenicity below this frequency. Hypothesis: Nauseogenicity should be maximal around 0.2 Hz. Methods: We selected 12 subjects for high motion sickness susceptibility, and they were exposed to horizontal sinusoidal motion (1.0 m.s-2 peak acceleration) at 3 different frequencies (0.1, 0.2 and 0.4 Hz), at 1-wk intervals at the same time of day, according to a factorial design. Subjects were seated comfortably in the upright position with head erect. Fore-aft motion was through the body and head X-axis. Motion was stopped (motion endpoint) at moderate nausea or after 30 min. Results: The proportion of subjects experiencing moderate nausea was maximal at the intermediate frequency: 8/12 at 0.1 Hz, 12/12 at 0.2 Hz, 7/12 at 0.4 Hz. The mean time to motion endpoint was significantly (p < 0.01) shorter at the intermediate frequency: 18.0 min at 0.1 Hz; 11.2 min at 0.2 Hz; 20.2 min at 0.4 Hz. Similar frequency patterns emerged for other sickness ratings. The equivalent times to achieve moderate nausea using estimated values to correct for subjects who reached the 30 min time cut-off were: 22.7 min at 0.1 Hz; 11.2 min at 0.2 Hz; 28.1 min at 0.4 Hz. Conclusions: A maximum nauseogenic potential around 0.2 Hz was substantiated.

Atlantic, Pacific, and world-wide features in English-lexicon contact languages

Abstract: This article analyzes the earliest known attestations of 302 lexical, functional, and grammatical features in 13 English-lexicon contact languages in the Atlantic and the Pacific. The main aims are (i) to shed light on the historical relationships between the individual varieties, (ii) to learn about the mechanisms at work in their genesis and development, and (iii) to examine the significance of features common to both geographical regions. Overall, our intention is to demonstrate that a statistical feature-based approach as proposed here can yield valuable insights into the development and interrelationships between Pidgins and Creoles.

A Conceptual Framework for Agent Definition and Development

Abstract: The use of agents of many different kinds in a variety of fields of computer science and artificial intelligence is increasing rapidly and is due, in part, to their wide applicability. The richness of the agent metaphor that leads to many different uses of the term is, however, both a strength and a weakness: its strength lies in the fact that it can be applied in very many different ways in many situations for different purposes; the weakness is that the term agent is now used so frequently that there is no commonly accepted notion of what it is that constitutes an agent. This paper addresses this issue by applying formal methods to provide a defining framework for agent systems. The Z specification language is used to provide an accessible and unified formal account of agent systems, allowing us to escape from the terminological chaos that surrounds agents. In particular, the framework precisely and unambiguously provides meanings for common concepts and terms, enables alternative models of particular classes of system to be described within it, and provides a foundation for subsequent development of increasingly more refined concepts.

A simulation study of the winter bed crisis

Abstract: The winter bed crisis is a cyclical phenomenon which appears in British hospitals every year, two or three weeks after Christmas. The crisis is usually attributed to factors such as the bad weather, influenza, older people, geriatricians, lack of cash or nurse shortages. However, a possible alternative explanation could be that beds within the hospital are blocked because of lack of social services for discharge of hospital patients during the Christmas period. Adopting this explanation of why the bed crisis occurs, the problem was considered as a queuing system and discrete event simulation was employed to evaluate the model numerically. The model shows that stopping discharges of rehabilitating patients for 21 days accompanied by a cessation of planned patients for 14 days precipitate a bed crisis when the planned admissions recommence. The extensive "what-if" capabilities of such models could be proved to be crucial to the designing and implementation of possible solutions to the problem.

Multiparadigm communications in Java for grid computing

Abstract: In this article, we argue that the rapid development of Java technology now makes it possible to support, in a single object-oriented framework, the different communication and coordination structures that arise in scientific applications. We outline how this integrated approach can be achieved, reviewing in the process the state-of-the-art in communication paradigms within Java. We also present recent evaluation results indicating that this integrated approach can be achieved without compromising on performance.

Extensiometric determination of the rheological properties of the epidermis of growing tomato fruit

Abstract: This paper examines the rheological properties of the fruit epidermis of tomato (Lycopersicon esculentum L.). This research was conducted because previous work had demonstrated that the rate of tomato fruit growth is determined by the interaction of tissue pressure and epidermal properties. A constant-load (or 'creep') extensiometer was employed in these experiments and the results interpreted using a model which describes creep retardation using a limited number of rheological elements, one of which appears analogous to plant growth and is of similar magnitude to fruit growth rate in vivo. The effects of pH, applied force and boiling upon the individual components of the model have been examined and indicate that several elements are strongly pH-dependent and that this dependency is eliminated by boiling. These results suggest that enzyme activity (plausibly that of one or more expansins) reduces the viscosity of the cell wall over a wide range of time scales. Further consideration of the creep of tomato epidermis in terms of models developed to describe the behaviour of artificial polymers suggests that the types of molecular event described by each rheological element can tentatively be identified and that pH-dependent enzyme activity facilitates both conformer rotation and macromolecular movement within the plant cell wall. These interpretations ascribe considerable importance to the time scale over which creep occurs.

Non parametric VaR Techniques. Myths and Realities

Abstract: VaR (value-at-risk) estimates are currently based on two main techniques: the variance-covariance approach or simulation. Statistical and computational problems affect the reliability of these techniques. We illustrate a new technique – filtered historical simulation (FHS) – designed to remedy some of the shortcomings of the simulation approach. We compare the estimates it produces with traditional bootstrapping estimates. (J.E.L.: G19).

Transformation of 2,4,6-trichlorophenol by free and immobilized fungal laccase.

Abstract: Laccase from the white rot fungus Coriolus versicolor was immobilized on Celite R-637 by covalent binding with glutaraldehyde. After a sharp primary decline in activity (up to 50%), the retained enzyme activity was stable over a storage period of 33 days at 4°C. A comparative study of soluble and immobilized laccases revealed the increased resistance of immobilized enzyme to the unfavourable effects of alkaline pH, high temperature and the action of inhibitors. A combination of these properties of immobilized laccase resulted in the ability to oxidize 2,4,6-trichlorophenol (2,4,6-TCP) at 50°C at pH 7.0. The reactions of soluble and immobilized laccase with 2,4,6-TCP were examined in the presence and absence of redox mediators. 3,5-Dichlorocatechol, 2,6-dichloro-1,4-benzoquinone and 2,6-dichloro-1,4-hydroquinone were found to be the primary products of 2,4,6-TCP oxidation by laccase; oligo- and polymeric compounds were also found.

Impact of variable pricing on temporal distribution of travel demand

Abstract: Despite the potential of congestion pricing to ease the nation's ever-increasing congestion problems, there is little quantitative evidence of its ability to spread peak travel demand more efficiently over the course of the day. The objective of the present work is to assess the impact of variable pricing on the temporal distribution of demand to investigate further the role of variable pricing as a travel demand management tool. The Variable Pricing Program of Lee County, Florida, was used as the data source for the study. Because of the limited congestion experienced at the program location, the effects of travel cost changes on the temporal distribution of demand could be isolated. It was found that program implementation had a minimal impact on the overall distribution of demand. Demand for peak-period travel remained relatively unaltered, and active peak spreading was not observed. At the more disaggregate level, however, the impact of the program was more apparent, with significant temporal shifts i...

A WISE method for designing IIR filters

Abstract: The problem of designing optimal digital IIR filters with frequency responses approximating arbitrarily chosen complex functions is considered. The real-valued coefficients of the filter's transfer function are obtained by numerical minimization of carefully formulated cost, which is referred here to as the weighted integral of the squared error (WISE) criterion. The WISE criterion linearly combines the WLS criterion that is used in the weighted least squares approach toward filter design and some time-domain components. The WLS part of WISE enforces the quality of the frequency response of the designed filter, while the time-domain part of the WISE criterion restricts the positions of the filter's poles to the interior of an origin-centred circle with arbitrary radius. This allows one not only to achieve stability of the filter but also to maintain some safety margins. A great advantage of the proposed approach is that it does not impose any constraints on the optimization problem and the optimal filter can be sought using off-the-shelf optimization procedures. The power of the proposed approach is illustrated with filter design examples that compare favorably with results published in research literature.