A study of event traffic during the shared manipulation of objects within a collaborative virtual environment

Event management must balance consistency and responsiveness above the requirements of shared object interaction within a Collaborative Virtual Environment (CVE) system. An understanding of the event traffic during collaborative tasks helps in the design of all aspects of a CVE system. The application, user activity, the display interface, and the network resources, all play a part in determining the characteristics of event management. Linked cubic displays lend themselves well to supporting natural social human communication between remote users. To allow users to communicate naturally and subconsciously, continuous and detailed tracking is necessary. This, however, is hard to balance with the real-time consistency constraints of general shared object interaction. This paper aims to explain these issues through a detailed examination of event traffic produced by a typical CVE, using both immersive and desktop displays, while supporting a variety of collaborative activities. We analyze event traffic during a highly collaborative task requiring various forms of shared object manipulation, including the concurrent manipulation of a shared object. Event sources are categorized and the influence of the form of object sharing as well as the display device interface are detailed. With the presented findings the paper wishes to aid the design of future systems

Supporting a Closely Coupled Task between a Distributed Team: Using Immersive Virtual Reality Technology

Collaboration and teamwork is important in many areas of our lives. People come together to share and discuss ideas, split and distribute work or help and support each other. The sharing of information and artefacts is a central part of collaboration. This often involves the manipulation of shared objects, both sequentially as well as concurrently. For coordinating an efficient collaboration, communication between the team members is necessary. This can happen verbally in form of speech or text and non-verbally through gesturing, pointing, gaze or facial expressions and the referencing and manipulation of shared objects. Collaborative Virtual Environments (CVE) allow remote users to come together and interact with each other and virtual objects within a computer simulated environment. Immersive display interfaces, such as a walk-in display (e.g. CAVE), that place a human physically into the synthetic environment, lend themselves well to support a natural manipulation of objects as well a set of natural non-verbal human communication, as they can both capture and display human movement. Communication of tracking data, however, can saturate the network and result in delay or loss of messages vital to the manipulation of shared objects. This paper investigates the reality of shared object manipulation between remote users collaborating through linked walk-in displays and extends our research in [27]. Various forms of shared interaction are examined through a set of structured sub tasks within a representative construction task. We report on extensive user-trials between three walk-in displays in the UK and Austria linked over the Internet using a CVE, and demonstrate such effects on a naive implementation of a benchmark application, the Gazebo building task. We then present and evaluate application-level workarounds and conclude by suggesting solutions that may be implemented within next-generation CVE infrastructures

Localisation of gamma-ray interaction points in thick monolithic CeBr3 and LaBr3:Ce scintillators

Localisation of gamma-ray interaction points in monolithic scintillator crystals can simplify the design and improve the performance of a future Compton telescope for gamma-ray astronomy. In this paper we compare the position resolution of three monolithic scintillators: a 28x28x20 mm3 (length x breadth x thickness) LaBr3:Ce crystal, a 25x25x20 mm3 CeBr3 crystal and a 25x25x10 mm3 CeBr3 crystal. Each crystal was encapsulated and coupled to an array of 4x4 silicon photomultipliers through an optical window. The measurements were conducted using 81 keV and 356 keV gamma-rays from a collimated 133Ba source. The 3D position reconstruction of interaction points was performed using artificial neural networks trained with experimental data. Although the position resolution was significantly better for the thinner crystal, the 20 mm thick CeBr3 crystal showed an acceptable resolution of about 5.4 mm FWHM for the x and y coordinates, and 7.8 mm FWHM for the z-coordinate (crystal depth) at 356 keV. These values were obtained from the full position scans of the crystal sides. The position resolution of the LaBr3:Ce crystal was found to be considerably worse, presumably due to the highly diffusive optical in- terface between the crystal and the optical window of the enclosure. The energy resolution (FWHM) measured for 662 keV gamma-rays was 4.0% for LaBr3:Ce and 5.5% for CeBr3. The same crystals equipped with a PMT (Hamamatsu R6322-100) gave an energy resolution of 3.0% and 4.7%, respectively

Oscillatory Modes of a Prominence-PCTR-Corona Slab Model

Oscillations of magnetic structures in the solar corona have often been interpreted in terms of magnetohydrodynamic waves. We study the adiabatic magnetoacoustic modes of a prominence plasma slab with a uniform longitudinal magnetic field, surrounded by a prominence-corona transition region (PCTR) and a coronal medium. Considering linear small-amplitude oscillations, the dispersion relation for the magnetoacoustic slow and fast modes is deduced assuming evanescent-like perturbations in the coronal medium. In the system without PCTR, a classification of the oscillatory modes according to the polarisation of their eigenfunctions is made in order to distinguish modes with fast-like or slow-like properties. Internal and external slow modes are governed by the prominence and coronal properties respectively, and fast modes are mostly dominated by prominence conditions for the observed wavelengths. In addition, the inclusion of an isothermal PCTR does not substantially influence the mode frequencies, but new solutions (PCTR slow modes) are present.Comment: Accepted for publication in Solar Physic

Deliberative quality and expertise:Uses of evidence in citizens’ juries on wind farms

When addressing socio-scientific wicked problems, there is a need to negotiate across and through multiple modes of evidence, particularly technical expertise and local knowledge. Democratic innovations, such as deliberative citizens’ juries, have been proposed as a means of managing these tensions and as a way of creating representative, fairer decision making. But there are questions around participatory processes, the utilization of expertise, and deliberative quality. This paper considers forms of argumentation in the 2013-2014 “Citizens’ juries on wind farm development in Scotland.” Through a critical-interpretative research methodology drawing on rhetoric and argumentation, we demonstrate that arguments relating to the topoi of the environment and health functioned as de facto reasoning, whereas arguments using social scientific evidence around economics more prominently interacted with local knowledge. The findings offer implications for process design to improve and promote deliberative quality in mini-publics and other forms of participatory engagement on socio-scientific issues

Sensitivity of Vertebrate Embryos to Heavy Metals as a Criterion of Water Quality, Phase II: Bioassay Procedures Using Developmental Stages as Test Organisms

Chick, amphibian, and fish embryos were evaluated as bioassay and bioindicator organisms. Test procedures were developed by which embryonic stages may be used 1) in bioassay systems to evaluate the toxicity of particular metallic or metal-containing trace contaminants, and 20 as bioindicators to monitor the quality of natural water resources. A bioassay technique was devised in which metallic toxicants were administered to chick embryos by needle tract injection into the yolk sac. This provided more uniform distribution of test metals throughout the yolk mass than can be obtained by conventional yolk sac injection methods, and gave more sensitivity and uniformity of test results. Metals such as arsenic, cadmium, mercury, lead and zinc are easily detectable at a level of 1 ppb. An in vitroculture technique was developed by which embryos of aquatic vertebrates may be maintained for bioassay and bioindicator purposes. Five test species were identified, suitable synthetic culture water was formulated, and culture monitoring procedures were determined. Most toxic metals (e.g., mercury) may be detected at 1ppb or less with the use of more sensitive embryonic species (e.g., trout). Early cleavage stages of the leopard frog (Rana pipiens) proved more sensitive to cadmium than older embryos, similar to results obtained in Phase I with mercury treatment of frog embryos. Early developmental stages, therefore, have proven especially important for use in bioassay and bioindicator systems

The importance of context and the effect of information and deliberation on opinion change regarding environmental issues in citizens’ juries

Citizens’ juries have become a popular method for engaging citizens in deliberation about complex public policy issues, such as climate action and sustainable development. Empirical evidence routinely indicates that jurors change their minds throughout the process. What is less clear is when and why this occurs and whether the causes are consistent across juries that consider the same topic but are situated within different contexts. We present evidence of opinion change in citizens’ juries through a natural experiment, contrasting three local contexts of onshore windfarm development in Scotland; viz. existing, planned, and absent. Jurors’ individual opinions of climate change, wind energy, and windfarms were measured through questionnaires at four time points: the start, following information-giving, reflection, and deliberation. Statistical examination of jurors’ responses, through paired sample t-tests, Wilcoxon sign-tests, and Generalised Least Squares regression, reveals to what extent substantive changes were associated with different phases and locational contexts. In all three juries, opinion change occurs throughout the process, on different topics, and to different degrees. While the information phase consistently influences jurors’ opinions the most, jury composition affects the magnitude and direction of opinion change, with outcomes contingent on contexts. Our findings are important for informing how mini-publics are designed and used to inform environmental policy-making at different scales

Resonantly damped surface and body MHD waves in a solar coronal slab with oblique propagation

The theory of magnetohydrodynamic (MHD) waves in solar coronal slabs in a zero-$\beta$ configuration and for parallel propagation of waves does not allow the existence of surface waves. When oblique propagation of perturbations is considered both surface and body waves are able to propagate. When the perpendicular wave number is larger than a certain value, the body kink mode becomes a surface wave. In addition, a sausage surface mode is found below the internal cut-off frequency. When non-uniformity in the equilibrium is included, surface and body modes are damped due to resonant absorption. In this paper, first, a normal-mode analysis is performed and the period, the damping rate, and the spatial structure of eigenfunctions are obtained. Then, the time-dependent problem is solved, and the conditions under which one or the other type of mode is excited are investigated.Comment: 19 pages, 9 figures, accepted for publication in Solar Physic