Modelling and performance evaluation of the IEEE 802.11 DCF for real-time control

Popular wireless networks, such as IEEE 802.11/15/16, are not designed for real-time applications. Thus, supporting real-time quality of service (QoS) in wireless real-time control is challenging. This paper adopts the widely used IEEE 802.11, with the focus on its distributed coordination function (DCF), for soft-real-time control systems. The concept of the critical real-time traffic condition is introduced to characterize the marginal satisfaction of real-time requirements. Then, mathematical models are developed to describe the dynamics of DCF based real-time control networks with periodic traffic, a unique feature of control systems. Performance indices such as throughput and packet delay are evaluated using the developed models, particularly under the critical real-time traffic condition. Finally, the proposed modelling is applied to traffic rate control for cross-layer networked control system design.

The HarmonyGrid : music, space and performance in grid music systems

This research explores music in space, as experienced through performing and music-making with interactive systems. It explores how musical parameters may be presented spatially and displayed visually with a view to their exploration by a musician during performance. Spatial arrangements of musical components, especially pitches and harmonies, have been widely studied in the literature, but the current capabilities of interactive systems allow the improvisational exploration of these musical spaces as part of a performance practice. This research focuses on quantised spatial organisation of musical parameters that can be categorised as grid music systems (GMSs), and interactive music systems based on them. The research explores and surveys existing and historical uses of GMSs, and develops and demonstrates the use of a novel grid music system designed for whole body interaction. Grid music systems provide plotting of spatialised input to construct patterned music on a two-dimensional grid layout. GMSs are navigated to construct a sequence of parametric steps, for example a series of pitches, rhythmic values, a chord sequence, or terraced dynamic steps. While they are conceptually simple when only controlling one musical dimension, grid systems may be layered to enable complex and satisfying musical results. These systems have proved a viable, effective, accessible and engaging means of music-making for the general user as well as the musician. GMSs have been widely used in electronic and digital music technologies, where they have generally been applied to small portable devices and software systems such as step sequencers and drum machines. This research shows that by scaling up a grid music system, music-making and musical improvisation are enhanced, gaining several advantages: (1) Full body location becomes the spatial input to the grid. The system becomes a partially immersive one in four related ways: spatially, graphically, sonically and musically. (2) Detection of body location by tracking enables hands-free operation, thereby allowing the playing of a musical instrument in addition to “playing” the grid system. (3) Visual information regarding musical parameters may be enhanced so that the performer may fully engage with existing spatial knowledge of musical materials. The result is that existing spatial knowledge is overlaid on, and combined with, music-space. Music-space is a new concept produced by the research, and is similar to notions of other musical spaces including soundscape, acoustic space, Smalley's “circumspace” and “immersive space” (2007, 48-52), and Lotis's “ambiophony” (2003), but is rather more textural and “alive”—and therefore very conducive to interaction. Music-space is that space occupied by music, set within normal space, which may be perceived by a person located within, or moving around in that space. Music-space has a perceivable “texture” made of tensions and relaxations, and contains spatial patterns of these formed by musical elements such as notes, harmonies, and sounds, changing over time. The music may be performed by live musicians, created electronically, or be prerecorded. Large-scale GMSs have the capability not only to interactively display musical information as music representative space, but to allow music-space to co-exist with it. Moving around the grid, the performer may interact in real time with musical materials in music-space, as they form over squares or move in paths. Additionally he/she may sense the textural matrix of the music-space while being immersed in surround sound covering the grid. The HarmonyGrid is a new computer-based interactive performance system developed during this research that provides a generative music-making system intended to accompany, or play along with, an improvising musician. This large-scale GMS employs full-body motion tracking over a projected grid. Playing with the system creates an enhanced performance employing live interactive music, along with graphical and spatial activity. Although one other experimental system provides certain aspects of immersive music-making, currently only the HarmonyGrid provides an environment to explore and experience music-space in a GMS.

Birds of a feather get lost together : new venture team composition and performance

This study explores the relationship between new venture team composition and new venture persistence and performance over time. We examine the team characteristics of a 5-year panel study of 202 new venture teams and new venture performance. Our study makes two contributions. First, we extend earlier research concerning homophily theories of the prevalence of homogeneous teams. Using structural event analysis we demonstrate that team members’ start-up experience is important in this context. Second, we attempt to reconcile conflicting evidence concerning the influence of team homogeneity on performance by considering the element of time. We hypothesize that higher team homogeneity is positively related to short term outcomes, but is less effective in the longer term. Our results confirm a difference over time. We find that more homogeneous teams are less likely to be higher performing in the long term. However, we find no relationship between team homogeneity and short-term performance outcomes.

Global Warming : Impact on Building Design and Performance

Global warming is entailing new climatic conditions for the built environment. Such a warming climate will affect both the performance of existing building stock and the design of new buildings. In this article, the knowledge of global warming and climate change is first introduced. The cycling interaction between global warming and buildings is then presented. The impact of global warming on building energy use and thermal performance is also assessed. Finally, the potential mitigation and adaptation strategies to the global warming are discussed.

Impact of global warming on the design and performance of air-conditioned office buildings in Australia

As global warming entails new conditions for the built environment, the thermal behavior of existing air conditioned office buildings, which are typically designed based on current weather data, may also change. Through building computer simulations, this paper evaluates the impact of global warming on the design and performance of air-conditioned office buildings in Australia, including the increased cooling loads imposed by potential global warming and probable indoor temperature increases due to possible undersized air-conditioning system, as well as the possible change in energy use and CO2 emission of Australian office buildings. It is found that the existing office buildings would generally be able to adapt to the increasing warmth of 2030 year Low and High scenarios projections and 2070 year Low scenario projection. However, for the 2070 year High scenario, the study indicates that the existing office buildings, in all capital cities except for Hobart, will suffer from overheating problems. If the energy source is assumed to be the electricity, it is found that in comparison with current weather scenario, the increased energy uses would translate into the increase of CO2 emissions by 0 to 34.6 kg CO2 equivalent/m2, varying with different future weather scenarios and with different locations.

Compact arrays for mobile platforms : trade-off between size and performance for SDMA and MIMO applications

Smart antenna receiver and transmitter systems consist of multi-port arrays with an individual receiver channel (including ADC) and an individual transmitter channel (including DAC)at every of the M antenna ports, respectively. By means of digital beamforming, an unlimited number of simultaneous complex-valued vector radiation patterns with M-1 degrees of freedom can be formed. Applications of smart antennas in communication systems include space-division multiple access. If both stations of a communication link are equipped with smart antennas (multiple-input-multiple-output, MIMO). multiple independent channels can be formed in a "multi-path-rich" environment. In this article, it will be shown that under certain circumstances, the correlation between signals from adjacent ports of a dense array (M + ΔM elements) can be kept as low as the correlation between signals from adjacent ports of a conventional array (M elements and half-wavelength pacing). This attractive feature is attained by means of a novel approach which employs a RF decoupling network at the array ports in order to form new ports which are decoupled and associated with mutually orthogonal (de-correlated) radiation patterns.

The relationship between firm survival and innovation : an introduction to the literature

The rapid growth in use of the Internet as a business tool provides a new perspective in the study of the organizational challenges of new technologies. The innovation literature has grown vastly since its establishment in the 1920s, covering a broad range of disciplines (Foxall 1984) and measures a wide variety of variables (Rogers 1995). At first glance, studies that look at the relationship between innovation and firm survival appear contradictory. However, the results appear compatible when additional factors, such as industry type, organizational age, company size or the duration of the study are taken into account.

Catherine or Kate, the royal name dilemma : humour and performance in collaborative art practice

The traditional model of visual arts practice is one that privileges highly individuated reflection and research on studio based, predominately material outcomes. This archetypal approach to thinking about cultural production tends to overlook all of the conceptual and contextual collaborations that take place, both informally and formally in the process of making artworks. The aim of this practice-led research project is to creatively and critically explore the potential for actively engaging in a collaborative process for making artworks. It will focus on this approach to research and making through performance and video based works made in conjunction with Kate Woodcroft. Through doing this it aims to explore the possibilities for thinking and working beyond singular, materially based practices and develop new understandings for this as a model for generating new and unexpected creative outcomes. Key departure points for this discussion include; tertiary performance, conceptual art, and humour.

The asthmatic athlete, inhaled beta agonists, and performance

INTRODUCTION: The large increase in the number of athletes who apply to use inhaled beta agonists (IBAs) at the Olympic Games is a concern to the medical community. This review will examine the use of IBAs in the asthmatic athlete, the variability that exists between countries and sport, and outline a plan to justify the use of these medications. DATA SOURCES: Much of this article is a result of an International Olympic Committee (IOC) Medical Commission-sponsored meeting that took place in May 2001. Records of the use of IBAs at previous Olympics were reviewed. MEDLINE Searches (PubMed interface) were performed using key words to locate published work relating to asthma, elite athletes, performance, treatment, and ergogenic aids. MAIN RESULTS: Since 1984 there have been significant increases in the use of IBAs at the Olympic Games as well as marked geographical differences in the percentage of athletes requesting the use of IBAs. There are large differences in the incidence of IBA use between sports with a trend towards increased use in endurance sports. There are no ergogenic effects of any IOC-approved IBA given in a therapeutic dose. CONCLUSIONS: In many cases, the prescription of IBAs to this population has been made on empirical grounds. Beginning with the 2002 Winter Games, athletes will be required to submit to the IOC Medical Commission clinical and laboratory evidence that justifies the use of this medication. The eucapnic voluntary hyperpnea test will be used to assess individuals who have not satisfied an independent medical panel of the need to use an IBA.

Preliminary Design and Performance Estimation of Radial Inflow Turbines: An Automated Approach

A comprehensive one-dimensional meanline design approach for radial inflow turbines is described in the present work. An original code was developed in Python that takes a novel approach to the automatic selection of feasible machines based on pre-defined performance or geometry characteristics for a given application. It comprises a brute-force search algorithm that traverses the entire search space based on key non-dimensional parameters and rotational speed. In this study, an in-depth analysis and subsequent implementation of relevant loss models as well as selection criteria for radial inflow turbines is addressed. Comparison with previously published designs, as well as other available codes, showed good agreement. Sample (real and theoretical) test cases were trialed and results showed good agreement when compared to other available codes. The presented approach was found to be valid and the model was found to be a useful tool with regards to the preliminary design and performance estimation of radial inflow turbines, enabling its integration with other thermodynamic cycle analysis and three-dimensional blade design codes.

Dr. Seuss and the "Great Balancing Act" : Exploring the Ethical Places You’ll Go Within Australian Sport, Exercise, and Performance Psychology

Stories by children’s writer Dr. Seuss have often been utilised as non-traditional narrative reflections regarding the issues of ethics and morality (Greenwood, 2000). Such case studies are viewed as effective teaching and learning tools due to the associated analytical and decision-making frameworks that are represented within the texts, and focus upon the exploration of universally general virtues and approaches to ethics (Hankes, 2012). Whilst Dr. Seuss did not create a story directly related to the sport, exercise or performance domains, many of his narratives possess psychological implications that are applicable in any situation that requires ethical consideration of the thinking and choices people make. The following exploration of the ‘ethical places you’ll go’ draws upon references to his work as a guide to navigating this interesting and sometimes challenging landscape for sport, exercise, and performance psychologists (SEPP).