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

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

Large amplitude oscillatory motion along a solar filament

Large amplitude oscillations of solar filaments is a phenomenon known for more than half a century. Recently, a new mode of oscillations, characterized by periodical plasma motions along the filament axis, was discovered. We analyze such an event, recorded on 23 January 2002 in Big Bear Solar Observatory H$\alpha$ filtergrams, in order to infer the triggering mechanism and the nature of the restoring force. Motion along the filament axis of a distinct buldge-like feature was traced, to quantify the kinematics of the oscillatory motion. The data were fitted by a damped sine function, to estimate the basic parameters of the oscillations. In order to identify the triggering mechanism, morphological changes in the vicinity of the filament were analyzed. The observed oscillations of the plasma along the filament was characterized by an initial displacement of 24 Mm, initial velocity amplitude of 51 km/s, period of 50 min, and damping time of 115 min. We interpret the trigger in terms of poloidal magnetic flux injection by magnetic reconnection at one of the filament legs. The restoring force is caused by the magnetic pressure gradient along the filament axis. The period of oscillations, derived from the linearized equation of motion (harmonic oscillator) can be expressed as $P=\pi\sqrt{2}L/v_{A\phi}\approx4.4L/v_{A\phi}$, where $v_{A\phi} =B_{\phi0}/\sqrt{\mu_0\rho}$ represents the Alfv\'en speed based on the equilibrium poloidal field $B_{\phi0}$. Combination of our measurements with some previous observations of the same kind of oscillations shows a good agreement with the proposed interpretation.Comment: Astron. Astrophys., 2007, in pres