208047947
New Directions in 3D User Interfaces
Three-dimensional user interfaces (3D UIs) support user tasks in many non-traditional interactive systems such as virtual environments and augmented reality. Although 3D UI researchers have been successful in identifying basic user tasks and interaction metaphors, evaluating the usability of 3D interaction techniques, and improving the usability of many applications, 3D UI research now stands at a crossroads. Very few fundamentally new techniques and metaphors for 3D interaction have been discovered in recent years, yet the usability of 3D UIs in many real-world applications is still not at a desirable level. What directions should 3D UI researchers next explore to improve this situation? In this paper, we make some observations about the history of 3D UIs and the current state-of-the-art. Using this evidence, in addition to our own experience, we argue that 3D UI researchers should approach this problem using some new research approaches, which cluster around the concepts of specificity, flavors, implementation, and emerging technologies. We illustrate and discuss some of these new directions using case studies of research projects undertaken in our group. These explorations indicate the promise of these directions for further increasing our understanding of 3D interaction and 3D UI design, and for ensuring the usability of 3D UIs in future applications.
27797614
Interacting with Visible Human data using an ImmersaDesk
Interaction with medical volume data has often been difficult, due to the large memory and computational power required. By taking advantage of current high-end graphics hardware, we have developed a volumetric virtual environment that provides the ability to help people interact with the volumetric Visible Human data set. The application enables the user to explore the interior of a virtual human body in a natural and intuitive way.
35660331
An NL Hierarchy
Abstract We introduce a new nondeterministic oracle model. Our model is significantly different from all previous space-bounded oracle models, and has the following properties: First, it permits a nontrivial NL-hierarchy, which does not collapse without a similar consequence for the polynomial-time hierarchy. This is immediate from the result that ∑ k p is exactly the 2 k th level in our NL-hierarchy, for all k ⩾1. On the other hand, it still behaves very well in relativised worlds. In particular, the new model satisfies the Immerman-Szelepcsenyi theorem and Savitch's theorem in the relativized worlds for oracle sets in each level of the polynomial-time hierarchy.
31224210
The strong semantics for logic programs
Recently, the well-founded semantics of a logic programP has been strengthened to the well-founded semantics-by-case (WFC) and this in turn has been strengthened to the extended well-founded semantics (WFE). Both WFC(P) and WFE(P) have thelogical consequence property, namely, if an atomAj is true in the theory Th(P), thenAj is true in the semantics as well. However, neither WFC nor WFE has the GCWA property, i.e., if an atomAj is false in all minimal models ofP,Aj may not be false in WFC(P) (resp. WFE(P)). We extend the ideas in WFC and WFE to define a strong well-founded semantics WFS which has the GCWA property. The strong semantics WFS(P) is defined by combining GCWA with the notion ofderived rules. Here we use a new Type-III derived rules in addition to those used in WFC and WFE. The relationship between WFS and WFC is also clarified.
44957022
Separability and Topology Control of Quasi Unit Disk Graphs
A deep understanding of the structural properties of wireless networks is critical for evaluating the performance of network protocols and improving their designs. Many protocols for wireless networks - routing, topology control, information storage/retrieval and numerous other applications - have been based on the idealized unit-disk graph (UDG) network model. The significant deviation of the UDG model from many real wireless networks is substantially limiting the applicability of such protocols. A more general network model, the quasi unit-disk graph (quasi-UDG) model, captures much better the characteristics of wireless networks. However, the understanding of the properties of general quasi-UDGs has been very limited, which is impeding the designs of key network protocols and algorithms. In this paper, we present results on two important properties of quasi-UDGs: separability and the existence of power efficient spanners. Network separability is a fundamental property leading to efficient network algorithms and fast parallel computation. We prove that every quasi-UDG has a corresponding grid graph with small balanced separators that captures its connectivity properties. We also study the problem of constructing an energy-efficient backbone for a quasi-UDG. We present a distributed localized algorithm that, given a quasi-UDG, constructs a nearly planar backbone with a constant stretch factor and a bounded degree. We demonstrate the excellent performance of these auxiliary graphs through simulations and show their applications in efficient routing.
18194069
Avoiding Local Optima in Single Particle Reconstruction
In single-particle reconstruction, a 3D structure is reconstructed from a large number of randomly oriented 2D projections, using techniques related to computed tomography. Unlike in computed tomography, however, the orientations of the projections must be estimated at the same time as the 3D structure, and hence the reconstruction process can be error-prone, converging to an incorrect local optimum rather than the true 3D structure. In this paper, we discuss and further develop a maximum-likelihood approach to reconstruction, and demonstrate that this approach can help avoid incorrect local optima for both 2D and 3D reconstructions.
26523507
MeSwarm: memetic particle swarm optimization
In this paper, a novel variant of particle swarm optimization (PSO), named memetic particle swarm optimization algorithm (MeSwarm), is proposed for tackling the overshooting problem in the motion behavior of PSO. The overshooting problem is a phenomenon in PSO due to the velocity update mechanism of PSO. While the overshooting problem occurs, particles may be led to wrong or opposite directions against the direction to the global optimum. As a result, MeSwarm integrates the standard PSO with the Solis and Wets local search strategy to avoid the overshooting problem and that is based on the recent probability of success to efficiently generate a new candidate solution around the current particle. Thus, six test functions and a real-world optimization problem, the flexible protein-ligand docking problem are used to validate the performance of MeSwarm. The experimental results indicate that MeSwarm outperforms the standard PSO and several evolutionary algorithms in terms of solution quality.