The cross-entropy method for network reliability estimation

Consider a network of unreliable links, modelling for example a communication network. Estimating the reliability of the network-expressed as the probability that certain nodes in the network are connected-is a computationally difficult task. In this paper we study how the Cross-Entropy method can be used to obtain more efficient network reliability estimation procedures. Three techniques of estimation are considered: Crude Monte Carlo and the more sophisticated Permutation Monte Carlo and Merge Process. We show that the Cross-Entropy method yields a speed-up over all three techniques.

A beam-forming network for a circular switched-beam phased array antenna

This paper reports on the design and development of a dividing/phasing network for a compact switched-beam array antenna for Land-vehicle mobile satellite communications, The device is formed by a switched radial divider/combiner and 1-bit phase shifters and generates a sufficient number of beams for the proper satellite tracking.

Personal factors, communication and vision predict social participation in older adults

Social isolation is a predictor of morbidity and mortality in older people. Speech pathologists often consider that communication disabilities associated with normal ageing (sensory loss, language and discourse changes) contribute to social isolation. The aims of this study were to describe the functioning of older people using the International Classification of Functioning, Disability and Health (WHO, 2001) as a conceptual framework for language and sensory functioning, communicative activity, and social participation, and to explore the relationship between communication (both at an impairment level and an activity level), social participation and personal factors (demographics and emotional health). In a prospective study, 47 women and 28 men aged 62 to 98 years (mean=74 yrs) completed objective and subjective assessments of functioning and participation, and provided personal information. Assessments were individually conducted in a face- to-face interview situation with the primary researcher, who was a speech pathologist. Assessments revealed the sample had predominantly mild hearing and vision impairments, unimpaired naming ability, frequent involvement in a wide range of communication activities, and variable social network size and social activities participation. Social participation was shown to be associated with vision, communication activities, age, education and emotional health. Naming and hearing impairments were not reliable predictors of social participation. It was concluded that professionals interested in maintaining and improving social participation of older people could well consider these predictors in community-directed interventions. Speech pathologists should therefore promote older people's involvement in everyday communicative activities while also limiting the impact of communication-related impairments, so that social participation is maintained in our ageing population.

Social communication in older age: Lessons from people with aphasia

Lessons on social communication in older age are drawn from the stories and qualitative case reports of three older people who have aphasia following stroke. Descriptive accounts of participant responses to qualitative interviews and stimulated recall of natural conversations, together with information from a social network diary, provide evidence of aspects of social communication relevant to the older person with aphasia. The perspectives of individuals and common themes relating to social communication with family and friends, the experience of aphasia, and living with aphasia in older age are presented. The prominence of conversations and the role of storytelling and of humor within the daily social communication of older people are illuminated. Key words: aphasia, older people, social communication

Context-enhanced authentication for infrastructureless network environments

Infrastructureless networks are becoming more popular with the increased prevalence of wireless networking technology. A significant challenge faced by these infrastructureless networks is that of providing security. In this paper we examine the issue of authentication, a fundamental component of most security approaches, and show how it can be performed despite an absence of trusted infrastructure and limited or no existing trust relationship between network nodes. Our approach enables nodes to authenticate using a combination of contextual information, harvested from the environment, and traditional authentication factors (such as public key cryptography). Underlying our solution is a generic threshold signature scheme that enables distributed generation of digital certificates.

The interorganizational virtual organization: Defining a Weberian ideal

The concept of the virtual organization (VO) has engendered great interest in the literature, yet there is still little common understanding of the concept, as evidenced by the multitude of labels applied to VOs. In this article, we focus on a “Weberian-ideal-type” definition of the interorganizational VO, posited in our earlier work (Kasper-Fuehrer and Ashkanasy 2001). We argue, however, that this definition left unanswered critical questions relating to the nature and effects of interorganizational VOs. We answer these questions here by explicating the terms in the definition and deriving ten corollaries, or “natural consequences” of our definition. The corollaries posit that interorganizational VOs are temporary in nature, are network organizations, are independent, and are based on swift trust. We suggest further that interorganizational VOs enable small to medium enterprises to exploit market opportunities, and enable VO member organizations to create a value-adding partnership. We also identify information and communication technology (ICT) as the essential enabler of VOs. Finally, we argue that interorganizational VOs act as a single organizational unit and that they therefore constitute a uniquely distinguishable organizational form. We conclude with suggestions for further research, including trust, organizational behavior, transaction economics, virtual HRM, and business strategy.