Enabledness and termination in refinement algebra

Refinement algebras are abstract algebras for reasoning about programs in a total correctness framework. We extend a reduct of von Wright’s demonic refinement algebra with two operators for modelling enabledness and termination of programs. We show how the operators can be used for expressing relations between programs and apply the algebra to reasoning about action systems.     

One-sided multiple comparisons for treatment means with a control mean

We study comparisons of several treatments with a common control when it is believed a priori that the treatment means, μ_i, are at least as large as the control mean, μ₀. In this setting, which is called a tree ordering, we study multiple comparisons that determine whether μ_i>μ₀ or μ_i=μ₀ for each treatment. The classical procedure by Dunnett (1955) and the step-down and step-up techniques by [Dunnett and Tamhane, 1991] and [Dunnett and Tamhane, 1992] are well known. The results in Marcus and Talpaz (1992) provide multiple comparisons based on the maximum likelihood estimates restricted by the tree ordering. We also study two-stage procedures that consist of the likelihood ratio test of homogeneity with the alternative constrained by the tree ordering followed by two-sample t comparisons with possibly different critical values for the two-sample comparisons. Marcus et al. (1976) discuss the use of closed tests in such situations and propose using a closed version of the restricted likelihood ratio test. We describe step-down versions of the Marcus-Talpaz, the two-stage, and the likelihood ratio procedures, as well as a closed version of the Marcus-Talpaz multiple comparison procedure. Using Monte Carlo techniques, we study the familywise errors and powers of these procedures and make some recommendations concerning techniques that perform well for all tree ordered mean vectors.     

Assessing the Impact of Security Education Initiatives on Critical Infrastructure Protection

The need to protect US critical infrastructures has been the primary motivation behind two of the US Federal Government’s security education initiatives: the National Security Agency’s Centers of Academic Excellence in Information Assurance Education (CAE/IAE) programme, and the National Science Foundation’s Federal Cyber Service: Scholarship for Service (SFS) programme. This article assesses the strength of these education programmes with respect to improving the level of critical infrastructure security.     

The experience of enchantment in human–computer interaction

Improving user experience is becoming something of a rallying call in human–computer interaction but experience is not a unitary thing. There are varieties of experiences, good and bad, and we need to characterise these varieties if we are to improve user experience. In this paper we argue that enchantment is a useful concept to facilitate closer relationships between people and technology. But enchantment is a complex concept in need of some clarification. So we explore how enchantment has been used in the discussions of technology and examine experiences of film and cell phones to see how enchantment with technology is possible. Based on these cases, we identify the sensibilities that help designers design for enchantment, including the specific sensuousness of a thing, senses of play, paradox and openness, and the potential for transformation. We use these to analyse digital jewellery in order to suggest how it can be made more enchanting. We conclude by relating enchantment to varieties of experience.An earlier version of this paper was presented at Chi’2004 Fringe.     

Fine structure of defects in polyethylene used for power cable insulation observed by fluorescence microscopy

The growth of defects called watertrees in cross-linked polyethylene power-insulated cables is poorly understood. We characterized the watertree structure on artificially aged samples. The resolution of the observations was improved by contrasting watertrees with rhodamine, a fluorescent probe and using epifluorescence microscopy. Both video-enhanced microscopy and confocal laser scanning microscopy provided evidence that watertrees are constituted of continuous microchannels. Their diameter is irregular and ranges between 0.6 and 0.2 m, and maybe less. They form a complex three-dimensional array that is accurately depicted.     

Confidential Incident Reporting on the UK Railways: The ‘CIRAS’ System

The paper describes CIRAS (Confidential Incident Reporting and Analysis System), a confidential reporting system developed by the authors in collaboration with ScotRail, the Health and Safety Executive, Railtrack and the (now defunct) British Rail Board. After a two-year pilot/developmental study with ScotRail during 1995–97, the system is now subscribed to by all but one of the major train operating companies, rail infrastructure and maintenance companies with a presence in Scotland; plus a developing profile in the rest of the UK.  CIRAS gathers data in three ways: (i) from an initial report form or telephone call, (ii) from a structured follow-up telephone questionnaire, and (iii) from an in-depth interview with a researcher (telephone or face-to-face, according to priority). The interviews bring to light details of personal motive, and of intended/unintended actions, which are not commonly found on company-run databases because of their association with disciplinary procedures. Information is processed through a human factors model and fed back to the companies involved, in disidentified form, to take corrective action.  The basic structure of the human-factors model is described; data are presented on reports received to date which have been processed through this model. The system has recently been recommended by a UK Parliamentary Committee and by Railtrack Safety and Standards Directorate for extension to the UK network as a whole.     

Using online pickup site inclusion policies to manage demand in retail/E-tail organizations

A major development in online retailing is the significant increase in the number of traditional “offline” retailers extending their brands online. Many of these retail/e-tail firms are attempting to leverage channel synergies by allowing customers to purchase products over the internet and then pick their orders up at one of the firm's local stores. This paper proposes that the firm presents only a subset of its stores to online customers as available pickup locations, rather than simply listing all local stores with inventory. By doing so, the firm can protect stores with critically low inventory levels and thereby reduce backorder costs. Specifically, we develop and evaluate a dynamic pickup site inclusion policy that incorporates real-time information to specify which of the firm's e-fulfillment locations should be presented at online checkout. Computational results indicate that managing in-store demand via such policies can decrease total cost (holding, backorder, and lost or redirected pickup sale costs) by as much as 18% over allowing customers to pick online orders up from any site with available inventory. The percentage of pickup sales and customers' sensitivity to travel are critical in determining the magnitude of the benefit.     

Internet pornography exposure and risky sexual behavior among adult males in the United States

Sexually transmitted infections (STIs) continue to pose a threat to the public health in the United States. Many sexual behaviors increase an individual’s risk of STI contraction. Chief among these are having unprotected sex, having sex with multiple partners, and either paying for sex or having sex for pay. The present study used General Social Survey (GSS) data from 2000, 2002, and 2004 to explore the association between exposure to internet pornography and these STI risk behaviors among adult US males. After controlling for demographic and individual difference covariates, internet pornography consumption was positively associated with having sex with multiple partners, engaging in paid sex, and having had extramarital sex. Internet pornography consumption was unrelated to having unprotected sex. Subsequent GSSs have not asked participants about exposure to internet pornography. As the GSS is the only ongoing, full-probability, national survey assessing social beliefs and behaviors, the present report provides unique insight into the risky sexual behavior patterns of adult male internet pornography consumers in the United States.