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Proceedings of the Second Annual Virginia Tech Center for Human-Computer Interaction Research Experience for Undergraduates (REU) Symposium
Get PDFVirginia Tech's Center for Human-Computer Interaction presents the project abstracts for the REU ’07 symposium. The REU (Research Experience for Undergraduates) program provides undergraduate students from various universities with the opportunity to spend eight weeks at Virginia Tech, working with our faculty and graduate students on research projects using the state-of-the-art technology and laboratories assembled here. The REU program is sponsored by a National Science Foundation grant IIS-0552732
Increasing the Precision of Distant Pointing for Large High-Resolution Displays
Get PDFDistant pointing at large displays allows rapid cursor movements, but can be problematic when high levels of precision are needed, due to natural hand tremor and track-ing jitter. We present two ray-casting-based interaction techniques for large high-resolution displays – Absolute and Relative Mapping (ARM) Ray-casting and Zooming for Enhanced Large Display Acuity (ZELDA) – that ad-dress this precision problem. ZELDA enhances precision by providing a zoom window, which increases target sizes resulting in greater precision and visual acuity. ARM Ray-casting increases user control over the cursor position by allowing the user to activate and deactivate relative map-ping as the need for precise manipulation arises. The results of an empirical study show that both approaches improve performance on high-precision tasks when compared to basic ray-casting. In realistic use, however, performance of the techniques is highly dependent on user strategy
Parameter Estimation for Mechanical Systems Using an Extended Kalman Filter
Get PDFThis paper proposes a new computational approach based on the Extended Kalman Filter (EKF) in order to apply the polynomial chaos theory to the problem of parameter estimation, using direct stochastic collocation. The Kalman filter formula is used at each time step in order to update the polynomial chaos of the uncertain states and the uncertain parameters. The main advantage of this method is that the estimation comes in the form of a probability density function rather than a deterministic value, combined with the fact that simulations using polynomial chaos methods are much faster than Monte Carlo simulations. The proposed method is applied to a nonlinear four degree of freedom roll plane model of a vehicle, in which an uncertain mass with an uncertain position is added on the roll bar. A major drawback was identified: the EKF can diverge when using a high sampling frequency, which might prevent the use of enough data to obtain accurate results when a low sampling frequency is necessary. When applying the polynomial chaos theory to the EKF, numerical errors can accumulate even faster than in the general case due to the truncation in the polynomial chaos expansions, which is illustrated on a simple example. An alternative EKF approach which consists of applying the filter formula on all the observations at once usually yields better results, but can still sometimes fail to produce very accurate results. Therefore, using different sampling rates in order to verify the coherence of the results and comparing the results to a different approach is strongly recommended
Analysis of the Fitness Effect of Compensatory Mutations
Get PDFWe extend our previous work on the ï¬tness effect of the ï¬xation of deleterious mutations on a population by incorporating the effect of compensatory mutations. Compensatory mutations are important in the sense that they make the deleterious mutations less deleterious, thus reducing the genetic load of the population. The essential phenomenon underlying compensatory mutations is the nonindependence of mutations in biological systems. Therefore, it is an important phenomenon that cannot be ignored when considering the ï¬xation and ï¬tness effect of deleterious mutations. Since having compensatory mutations essentially changes the distributional shapes of deleterious mutations, we can consider the effect of compensatory mutations by comparing two distributions where one distribution reflects the reduced ï¬tness effects of deleterious mutations with the influence of compensatory mutations. We compare different distributions of deleterious mutations without compensatory mutations to those with compensatory mutations, and study the effect of population sizes, the shape of the distribution, and the mutation rates of the population on the total ï¬tness reduction of the population
Integration of VT ETD-db with Banner
Get PDFThe Electronic Thesis and Dissertation database (ETD-db) was developed at Virginia Tech by Digital Library and Archives for the VT Graduate School and the Networked Digital Library of Theses and Dissertations (NDLTD). The software is freely available and over 100 universities worldwide have implemented the ETD-db system. One drawback of the system is the dependence on user keyed data. At Virginia Tech, like most other universities, there is an administrative database that could provide much of this information. The Banner Administrative System is the central administration system at Virginia Tech. Banner’s underlying database software is from Oracle. This paper will demonstrate how the ETD-db can be seamlessly integrated with an Oracle database or more specifically the Banner Administrative System, to improve the integrity of the data for ETDs
Knowledge Reuse Through Categorical Breakdown Analysis: A Method for Collaborative Systems Evaluation
Get PDFDesigning Computer-Supported Cooperative Work (CSCW) systems that support the widely varying needs of targeted users is difficult. There is no silver bullet technology that enables users to effectively collaborate with one another in different contexts. We propose a method of collaborative systems evaluation that enables novice evaluators to make insightful observations about the systems they evaluate at a level comparable to experts in certain situations. These observations come in the form of a categorical breakdown analysis of a laboratory study. The quantity and type of breakdowns can then be connected to recommended CSCW tools and features developed and described in the related literature. We conducted a study to explore the results generated when the method was applied by both experts and novices in the field of CSCW. We observed that experts found the method to be usable, and that novices capitalized on the knowledge embodied in the breakdown categories to make categorizations similar to those of experts
Everywhere Energy-Efficient E-Computing
Get PDFThis document outlines a vision for “green computing for a clean tomorrow†[Feng06]. The first piece of the vision is a bit pedestrian – holistic energy-efficient computing “in a box†– but serves as a foundation to a more audacious (tongue-in-cheek) vision of holistic energy-efficient computing “in a world.†As recently noted by IDC in an IBM presentation at the Gartner Data Center Summit, December 2006, the annual spending for power and cooling would match the annual budget for new server spending in 2007, as shown in the figure below. In addition to cost, energy-efficient (power- aware) computing can enhance the reliability and availability of ever-increasingly dense computing systems, such as blades; it can also provide additional computational headroom when an institution has reached the limits of its power and cooling infrastructure, particularly when the infrastructure cannot be expanded any further [Feng08]
Note On The Effectiveness OF Stochastic Optimization Algorithms For Robust Design
Get PDFRobust design optimization (RDO) uses statistical decision theory and optimization techniques to optimize a design over a range of uncertainty (introduced by the manufacturing process and unintended uses). Since engineering ob jective functions tend to be costly to evaluate and prohibitively expensive to integrate (required within RDO), surrogates are introduced to allow the use of traditional optimization methods to ï¬nd solutions. This paper explores the suitability of radically different (deterministic and stochastic) optimization methods to solve prototypical robust design problems. The algorithms include a genetic algorithm using a penalty function formulation, the simultaneous perturbation stochastic approximation (SPSA) method, and two gradient-based constrained nonlinear optimizers (method of feasible directions and sequential quadratic programming). The results show that the fully deterministic standard optimization algorithms are consistently more accurate, consistently more likely to terminate at feasible points, and consistently considerably less expensive than the fully nondeterministic algorithms
Achieving Very High Order for Implicit Explicit Time Stepping: Extrapolation Methods
Get PDFIn this paper we construct extrapolated implicit-explicit time stepping methods that allow to efficiently solve problems with both stiff and non-stiff components. The proposed methods can provide very high order discretizations of ODEs, index-1 DAEs, and PDEs in the method of lines framework. These methods are simple to construct, easy to implement and parallelize. We establish the existence of perturbed asymptotic expansions of global errors, explain the convergence orders of these methods, and explore their linear stability properties. Numerical results with stiff ODEs, DAEs, and PDEs illustrate the theoretical findings and the potential of these methods to solve multiphysics multiscale problems
Collaborating on Affinity Diagrams Using Large Displays
Get PDFGathering and understanding user requirements is an
essential part of design. Techniques like affinity
diagramming are useful for gathering and
understanding user data but have shortcomings such as
the difficulty to preserve the diagram after its creation,
problems during the process such as searching for
notes, and loss of shared awareness. We propose an
early prototype that solves problems in the process of
creating an affinity diagram and enhances it using a
large screen display in combination with individual
PDAs