Affordances In The Design Of Virtual Environments

Human-computer interaction design principles largely focus on static representations and have yet to fully incorporate theories of perception appropriate for the dynamic multimodal interactions inherent to virtual environment (VE) interaction. Theories of direct perception, in particular affordance theory, may prove particularly relevant to enhancing VE interaction design. The present research constructs a conceptual model of how affordances are realized in the natural world and how lack of sensory stimuli may lead to realization failures in virtual environments. Implications of the model were empirically investigated by examining three affordances: passability, catchability, and flyability. The experimental design involved four factors for each of the three affordances and was implemented as a 2 [subscript IV] [superscript 4-1] fractional factorial design. The results demonstrated that providing affording cues led to behavior closely in-line with real-world behavior. More specifically, when given affording cues participants tended to rotate their virtual bodies when entering narrow passageways, accurately judge balls as catchable, and fly when conditions warranted it. The results support the conceptual model and demonstrate 1) that substituting designed cues via sensory stimuli in available sensory modalities for absent or impoverished modalities may enable the perception of affordances in VEs; 2) that sensory stimuli substitutions provide potential approaches for enabling the perception of affordances in a VE which in the real world are cross-modal; and 3) that affordances relating to specific action capabilities may be enabled by designed sensory stimuli. This research lays an empirical foundation for a science of VE design based on choosing and implementing design properties so as to evoke targeted user behavio

A method for approximating a specified impulsive response

Given a system\u27s time response, y(t), to a unit impulse, a method is presented by which an approximating function y*(t) may be determined. It is inherent in the method that the transform function Y*(s) is rational. The poles of the approximating function are found from the coefficients of a difference equation, which is made to fit the given data in a least mean square error sense. The zeros are determined by a procedure based on the fact that at a given time the given function and its approximate derivatives are known. Accuracy and implementation of the method are investigated primarily through the medium of example problems. Usefulness and comparison with other methods are among the topics discussed in conclusion --Abstract, page ii

Understanding the perceived value of global learning experiences for doctoral leadership students

Foreign travel occupies a role in the development of global leadership, yet the function of higher education in that process is scarcely understood. This sequential explanatory mixed-methods study explored the perceived value that select doctoral students experienced during from their short-term course-based foreign travel. The first phase of the research included fifty students, while the second used a subset of 12 from the first phase. The students participated in an online quantitative survey, followed by optional interviews where the qualitative data were obtained. Quantitative and Qualitative research methods were used to analyze the data. The findings were presented in numerical and narrative formats, respectively. The results were consistent with the literature. They also provided additional insights that advance the burgeoning field of global leadership and substantiate more recent trends in the older, more established education abroad arena. The findings suggest specific aspects of academic course-based foreign travel aid in the development of global leadership skills. Participants cited peer-learning, scheduling concerns, overall organization, intercultural contact, theory to practice opportunities, and learning experience applicability as the drivers of value in their academic foreign travel experiences. The recommendations suggest that course-based foreign travel may benefit from designs that balance participants’ exposure to their peers, contact with the local population, and structured academic instruction. Additionally, doctoral students may consider other activities to increase cultural intelligence more broadly; as the results indicate a significant, positive correlation between the value of global learning experiences and cultural intelligence levels

A method for determining transient stability in power systems

Given a three phase ac power system consisting of synchronous alternators interconnected by transmission lines and other items of electrical transmission equipment, a method is presented which determines the stability of the system when subjected to a three phase symmetrical fault, and to the subsequent clearing of the fault. It is inherent in the method that an estimation of system stability, assuming an instantaneous clearing of the fault, is available. The critical clearing time is therefore determined. The effect of a speed control loop on the system\u27s largest machine is investigated. The method is applied to two, three, four, and seven machine examples. Advantages and disadvantages of the method are discussed --Abstract, page ii

A Worldsheet Description of Large N_c Quantum Field Theory

The N_c to infinity limit of a matrix quantum field theory is equivalent to summing only planar Feynman diagrams. The possibility of interpreting this sum as some kind world-sheet theory has been in the air ever since 't Hooft's original paper. We establish here just such a world sheet description for a scalar quantum field with interaction term g\Tr\phi^3, and we indicate how the approach might be extended to more general field theories.Comment: 16 pages, 3 figures, latex, typos corrected, references added, interpretation of ghost determinant clarifie

Looking back at Social Knowledge in the Making

Sociolog

Diagnosis and Management of COVID-19 Disease

SARS-CoV-2 is a novel coronavirus that was identified in late 2019 as the causative agent of COVID-19 (aka coronavirus disease 2019). On March 11, 2020, the World Health Organization (WHO) declared the world-wide outbreak of COVID-19 a pandemic. This document summarizes the most recent knowledge regarding the biology, epidemiology, diagnosis, and management of COVID-19