Multichannel cross-layer routing for sensor networks

This paper proposes a new decentralised multi-channel tree building protocol with a centralised controller for the Internet of Things. The protocol alleviates the effect of interference which results in improved network efficiency and stability, and link reliability. The proposal takes into account all available channels to utilise the spectrum and aims to use the spectrum efficiently by transmitting on several channels. The protocol detects which channels suffer interference and changes away from those channels. The algorithm for channel selection is a two-hop colouring protocol that reduces the chances of nearby nodes to transmit on the same channel. All nodes are battery operated except for the low power border router (LPBR). This enables a centralised channel switching process at the LPBR. The protocol is built based on the routing protocol for low power and lossy networks (RPL). In its initial phase, the protocol uses RPL's standard topology formation to create an initial working topology and then seeks to improve this topology by switching channels. The implementation and evaluation of the protocol is performed using the Contiki framework. The experimental results demonstrate an increased resilience to interference and significantly higher throughput making better use of the total available spectrum and link stability

The outsourcing debate: Theories and findings

This paper addresses the issue of services outsourcing by looking at both theoretical and empirical arguments. Previous debates have often concentrated on the motives for adopting the practice rather than the outcomes. These various themes can be discussed under the twin concepts of the cost and efficiency argument and the fashion and isomorphism approach. Our research provides strong evidence to support the cost efficiency argument. On average, significant cost advantages were sought and delivered, as well as improvements in service levels and systems. Many organisations in the current environment in Australia look at outsourcing not only as a method of increasing efficiency but also as gaining competitive advantage through harnessing the superior specialist skills and experience of the outsourcing provider who takes someone's back office function and transforms them into their front office. A 10% net cost saving was considered necessary by an organisation before embarking on an organisational change that was disruptive and in some cases involved downside risks. Even if other efficiency gains such as service levels or systems improvements were required, so were 10%+ cost savings. A number of the organisations thought their skills in managing outsourcing had improved considerably such that they were in a position to move from a client/server relationship to a partnership model (i.e. an alliance)

Paradoxical Identity: The changing nature of architectural work and its relation to architects' identity

In this article, we explore what happens in professional formation when the locus of its meaning, as it has been formed, is increasingly contradicted by professional practice. Specifically, we explore the problematic nature of architects’ professional identity that is constituted in terms of the primacy of design aesthetics, in contexts where practice denies this identification. We highlight the tensions between identity and practices and suggest that while architects’ traditional self-identification enables perpetuation of the profession’s identity, it challenges the profession’s standing in its relations with other professions and occupations. We refer to this as a paradox of identity. Although much has been written about the profound changes occurring in professional practices and professional jurisdictions, scant attention has been given to the ways in which professionals shape their identities in the context of changing practices. We conducted a year-long ethnography of contemporary architects engaged in large and complex projects in order to examine both the architects’ and the profession’s identity. Our contributions are threefold. First, we conceptualize misalignments between professional identity and professional practice as identity paradox that has consequences for identity work among professionals. Second, we highlight how professional identity construction is organized around competing and paradoxical identification. Third, the article contributes to sociological studies of architecture by generating insights about the identity work of architects engaged in large multi-organizational projects

Professional identity and anxiety in architect-client interactions

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. Large-scale construction projects increasingly have powerful and knowledgeable clients as project owners with whom professionals, such as architects, must interact. In such contexts, clients may have a significant impact on the constitution of a coherent and stable professional identity. Based on qualitative interviews with 50 architects across four large multidisciplinary professional service firms (PSFs) located in Sydney, Australia, supplemented by ethnographic observations, this article explores how architects constitute their identity in interactions with clients. The findings led us to conceptualise professional–client interactions in terms of two overarching discursive strategies deployed by architects in attempts to manage clients that are powerful and knowledgeable: best for client and best for project. We illustrate the anxieties that architects experience and suggest that attempts to secure professional identity may result in (re)producing an enduring sense of anxiety with unintended consequences for project outcomes and organisational performance

On the Distribution of Traffic Volumes in the Internet and its Implication

Getting good statistical models of traffic on network links is a well-known, often-studied problem. A lot of attention has been given to correlation patterns and flow duration. The distribution of the amount of traffic per unit time is an equally important but less studied problem. We study a large number of traffic traces from many different networks including academic, commercial and residential networks using state-of-the-art statistical techniques. We show that the log-normal distribution is a better fit than the Gaussian distribution commonly claimed in the literature. We also investigate a second heavy-tailed distribution (the Weibull) and show that its performance is better than Gaussian but worse than log-normal. We examine anomalous traces which are a poor fit for all distributions tried and show that this is often due to traffic outages or links that hit maximum capacity. We demonstrate the utility of the log-normal distribution in two contexts: predicting the proportion of time traffic will exceed a given level (for service level agreement or link capacity estimation) and predicting 95th percentile pricing. We also show the log-normal distribution is a better predictor than Gaussian or Weibull distributions

Sulphur abundances in disk stars as determined from the forbidden 10821 A [SI] line

Aims: In this paper we aim to study the chemical evolution of sulphur in the galactic disk, using a new optimal abundance indicator: the [SI] line at 10821 A. Similar to the optimal oxygen indicators, the [OI] lines, the [SI] line has the virtues of being less sensitive to the assumed temperatures of the stars investigated and of likely being less prone to non-LTE effects than other tracers. Methods: High-resolution, near-infrared spectra of the [SI] line are recorded using the Phoenix spectrometer on the Gemini South telescope. The analysis is based on 1D, LTE model atmospheres using a homogeneous set of stellar parameters. Results: The 10821 A [SI] line is suitable for an abundance analysis of disk stars, and the sulphur abundances derived from it are consistent with abundances derived from other tracers. We corroborate that, for disk stars, the trend of sulphur-to-iron ratios with metallicity is similar to that found for other alpha elements, supporting the idea of a common nucleosynthetic origin.Comment: Accepted for publication in A&A Letter

Physical Conditions in Quasar Outflows: VLT Observations of QSO 2359-1241

We analyze the physical conditions of the outflow seen in QSO 2359-1241 (NVSS J235953-124148), based on high resolution spectroscopic VLT observations. This object was previously studied using Keck/HIRES data. The main improvement over the HIRES results is our ability to accurately determine the number density of the outflow. For the major absorption component, level population from five different Fe II excited level yields n_H=10^4.4 cm^-3 with less than 20% scatter. We find that the Fe ii absorption arises from a region with roughly constant conditions and temperature greater than 9000 K, before the ionization front where temperature and electron density drop. Further, we model the observed spectra and investigate the effects of varying gas metalicities and the spectral energy distribution of the incident ionizing radiation field. The accurately measured column densities allow us to determine the ionization parameter log(U) = -2.4 and total column density of the outflow (log(N_H) = 20.6 cm^-2). Combined with the number density finding, these are stepping stones towards determining the mass flux and kinetic luminosity of the outflow, and therefore its importance to AGN feedback processes.Comment: 21 pages, 3 figures (accepted for publication in the ApJ