Communicating Mobile Processes

This paper presents a new model for mobile processes in occam-pi. A process, embedded anywhere in a dynamically evolving network, may suspend itself mid-execution, be safely disconnected from its local environment, moved (by communication along a channel), reconnected to a new environment and reactivated. Upon reactivation, the process resumes execution from the same state (i.e. data values and code positions) it held when it suspended. Its view of its environment is unchanged, since that is abstracted by its synchronisation (e.g. channels and barriers) interface and that remains constant. The environment behind that interface will (usually) be completely different. The mobile process itself may contain any number of levels of dynamic sub-network. This model is simpler and, in some ways, more powerful than our earlier proposal, which required a process to terminate before it could be moved. Its formal semantics and implementation, however, throw up extra challenges. We present details and performance of an initial implementation

A review on transit assignment modelling approaches to congested networks: a new perspective

This paper reviews a number of studies on both frequency-and schedule-based transit assignment models that have been proposed by far, wherein various behavioural assumptions on a wide range of aspects are embedded. With a reinvestigation on the relationships and homogeneity between different modelling approaches, it explores the representative veins of the models, and thereby extends a new perspective to the existing reviews under a historical context. Meanwhile, both advantages and disadvantages of these methods are presented. On the strength of the analyses and discussions of the state-of-the-art transit assignment models, further research directions are suggested

Service Quality Failure and Recovery Imperatives: Implications for Airlines Owned by South Africa

This article reports on a study that examined service quality and recovery among South African airlines. Service quality is pivotal in the airline industry as service failures could negatively affect operations. The authors created the acronym “AOSA†which stands for “airlines owned by South Africa†for the purposes of anonymity and confidentiality in order to protect the airlines’ identity. A quantitative research approach was used with a cross-sectional analysis (sample survey) conducted with passengers of South African-owned airlines. The questionnaire was designed using a Likert scale tool, adapted to the SERVQUAL model. A non-probability convenient sampling method was used to collect primary data from 684 passengers at O.R.Tambo International Airport in Johannesburg and King Shaka International Airport in Durban. The key findings were that: (1) significant statistical gaps exist between passengers’ expectations and perceptions of AOSA’s service quality and that unsatisfactory service quality is antecedent to service failure. (2) Unsatisfactory service quality is tantamount to service failure in the provision of services by AOSA. (3) A significant positive correlation exists between service quality and the dimensional variables of tangibility, reliability, responsiveness, assurance, and empathy of AOSA. In conclusion, AOSA service quality is unsatisfactory, and management should take steps to empower and train staff in service recovery techniques in other to avoid service failures

Using the Product Impact Tool for Prospective Thinking

The ever rising role of products and technologies in humans’ lives is increasing the call for ways to understand and investigate their influences, in the form of prospective analytical methods. This paper proposes one such method, based upon the Product Impact Tool. This Tool was developed to combine both philosophy of technology and design for usability perspectives. Its effects offer potential for prospective and reflective purposes, and can be used to investigate and structure ideas about the impacts of both current and future technologies. The proposed method offers an addition to existing tools within the field of prospective analysis. This added value is demonstrated through a case study of a concept for future personal transport. Through this case study, it is shown that the proposed method can help uncover information that remained hidden by conventional approaches, by inducing a critical investigation of the subject from multiple perspectives. Such information will aid analysts and strategists in their work, leading to more effective, desirable, and responsible technologies being developed and implemented

Towards Verification of Cyber-Physical Systems with UTP and Isabelle/HOL

In this paper, we outline our vision for building verification tools for Cyber-Physical Systems based on Hoare and He’s Unifying Theories of Programming (UTP) and interactive proof technology in Isabelle/HOL. We describe our mechanisation and explain some of the design decisions that we have taken to get a convenient and smooth implementation. In particular, we describe our use of lenses to encode state. We illustrate our work with an example UTP theory and describe the implementation of three foundational theories: designs, reactive processes, and the hybrid relational calculus. We conclude by reflecting on how tools are linked by unifying theories

New "Bigs" in cosmology

This paper contains a detailed discussion on new cosmic solutions describing the early and late evolution of a universe that is filled with a kind of dark energy that may or may not satisfy the energy conditions. The main distinctive property of the resulting space-times is that they make to appear twice the single singular events predicted by the corresponding quintessential (phantom) models in a manner which can be made symmetric with respect to the origin of cosmic time. Thus, big bang and big rip singularity are shown to take place twice, one on the positive branch of time and the other on the negative one. We have also considered dark energy and phantom energy accretion onto black holes and wormholes in the context of these new cosmic solutions. It is seen that the space-times of these holes would then undergo swelling processes leading to big trip and big hole events taking place on distinct epochs along the evolution of the universe. In this way, the possibility is considered that the past and future be connected in a non-paradoxical manner in the universes described by means of the new symmetric solutions.Comment: 7 figures, 13 pages, RevTe