73 research outputs found
Scene-motion- and latency-perception thresholds for head-mounted displays
A fundamental task of an immersive virtual environment (IVE) system is to present images of the virtual world that change appropriately as the user's head moves. Current IVE systems, especially those using head-mounted displays (HMDs), often produce spatially unstable scenes, resulting in simulator sickness, degraded task performance, degraded visual acuity, and breaks in presence. In HMDs, instability resulting from latency is greater than all other causes of instability combined. The primary way users perceive latency in an HMD is by improper motion of scenes that should be stationary in the world. Whereas latency-induced scene motion is well defined mathematically, less is understood about how much scene motion and/or latency can occur without subjects noticing, and how this varies under different conditions. I built a simulated HMD system with zero effective latency---no scene motion occurs due to latency. I intentionally and artificially inserted scene motion into the virtual environment in order to determine how much scene motion and/or latency can occur without subjects noticing. I measured perceptual thresholds of scene-motion and latency under different conditions across five experiments. Based on the study of latency, head motion, scene motion, and perceptual thresholds, I developed a mathematical model of latency thresholds as an inverse function of peak head-yaw acceleration. Psychophysics studies showed that measured latency thresholds correlate with this inverse function better than with a linear function. The work reported here readily enables scientists and engineers to, under their particular conditions, measure latency thresholds as a function of head motion by using an off-the-shelf projector system. Latency requirements can thus be determined before designing HMD systems
Scene-motion thresholds during head yaw for immersive virtual environments
In order to better understand how scene motion is perceived in immersive virtual environments, we measured scene-motion thresholds under different conditions across three experiments. Thresholds were measured during quasi-sinusoidal head yaw, single left-to-right or right-to-left head yaw, different phases of head yaw, slow to fast head yaw, scene motion relative to head yaw, and two scene illumination levels. We found that across various conditions 1) thresholds are greater when the scene moves with head yaw (corresponding to gain 1:0), and 2) thresholds increase as head motion increases
The global burden of plastics in oral health: prospects for circularity, sustainable materials development and practice
Plastics are indispensable and ubiquitous materials in oral healthcare and dental applications, favored for their diversity in structure and properties, low cost, durability, chemical and water resistance, ease of processing, and shaping. However, ancillary plastics are used for short periods or even once due to hygiene concerns and convenience, and insufficient attention has been given to their unsustainable current usage and end-of-life. Thus, the amount of plastic waste generated by consumers and clinicians is staggering and projected to increase unabatedly for the foreseeable future. With recent advances in plastics recycling and sustainable polymers, it is time to consider alternatives to tackle dentistry's growing plastic waste problem. This Perspectives article highlights the sources and scale of dental plastic wastage, followed by a multi-pronged consideration of material and practical interventions for this issue. On the materials front, we discuss emerging approaches and alternative sustainable polymers to address the unsustainable end-of-life of existing petroleum-based dental plastics/polymers and enable material circularity. On the practical front, we discuss strategies for sustainable plastic usage, which must be implemented alongside complementary material approaches. These approaches highlight the abundant unrealized opportunities for developing a circular economy around dental plastics while reducing the environmental footprint of modern dentistr
Developing Resilience Online: Evaluation of Synchronous and Asynchronous Resilience Interventions for Filipino College Students
This study evaluated two forms of a resilience intervention amongst college students during the COVID-19 pandemic. Utilising a randomised controlled trial design; it examined the impact of a synchronous and asynchronous resilience interventions versus a control group that did a journaling intervention. Outcomes measured included coping behaviour; non-reactivity; wellbeing; stress; depression and anxiety. Participants consisted of Filipino college students randomly assigned to three groups: synchronous online resilience group (n = 135); asynchronous resilience group (n = 121) and control group (n = 127). Results revealed that students who went through the online synchronous resilience reported a significant reduction in depression at post-intervention compared to those who went through an asynchronous intervention. Post-intervention scores for nonreactivity were also higher in the synchronous group compared to both asynchronous and journaling groups. Effect sizes were small to moderate. This study suggests that online resilience interventions are viable means to address the mental health needs of students; especially in countries with limited mental health resources
A Gigantic, Exceptionally Complete Titanosaurian Sauropod Dinosaur from Southern Patagonia, Argentina
Titanosaurian sauropod dinosaurs were the most diverse and abundant large-bodied herbivores in the southern continents during the final 30 million years of the Mesozoic Era. Several titanosaur species are regarded as the most massive land-living animals yet discovered; nevertheless, nearly all of these giant titanosaurs are known only from very incomplete fossils, hindering a detailed understanding of their anatomy. Here we describe a new and gigantic titanosaur, Dreadnoughtus schrani, from Upper Cretaceous sediments in southern Patagonia, Argentina. Represented by approximately 70% of the postcranial skeleton, plus craniodental remains, Dreadnoughtus is the most complete giant titanosaur yet discovered, and provides new insight into the morphology and evolutionary history of these colossal animals. Furthermore, despite its estimated mass of about 59.3 metric tons, the bone histology of the Dreadnoughtus type specimen reveals that this individual was still growing at the time of death
'It's Reducing a Human Being to a Percentage'; Perceptions of Justice in Algorithmic Decisions
Data-driven decision-making consequential to individuals raises important
questions of accountability and justice. Indeed, European law provides
individuals limited rights to 'meaningful information about the logic' behind
significant, autonomous decisions such as loan approvals, insurance quotes, and
CV filtering. We undertake three experimental studies examining people's
perceptions of justice in algorithmic decision-making under different scenarios
and explanation styles. Dimensions of justice previously observed in response
to human decision-making appear similarly engaged in response to algorithmic
decisions. Qualitative analysis identified several concerns and heuristics
involved in justice perceptions including arbitrariness, generalisation, and
(in)dignity. Quantitative analysis indicates that explanation styles primarily
matter to justice perceptions only when subjects are exposed to multiple
different styles---under repeated exposure of one style, scenario effects
obscure any explanation effects. Our results suggests there may be no 'best'
approach to explaining algorithmic decisions, and that reflection on their
automated nature both implicates and mitigates justice dimensions.Comment: 14 pages, 3 figures, ACM Conference on Human Factors in Computing
Systems (CHI'18), April 21--26, Montreal, Canad
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