Rotation moment invariants for recognition of symmetric objects.

In this paper, a new set of moment invariants with respect to rotation, translation, and scaling suitable for recognition of objects having N-fold rotation symmetry are presented. Moment invariants described earlier cannot be used for this purpose because most moments of symmetric objects vanish. The invariants proposed here are based on complex moments. Their independence and completeness are proven theoretically and their performance is demonstrated by experiments.     

投影机购机10步曲

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Tool Building Requirements for an API to First-Order Solvers

Effective formal verification tools require that robust implementations of automatic procedures for first-order logic and satisfiability modulo theories be integrated into expressive interactive frameworks for logical deduction, such as higher-order logic theorem provers. This paper states some pragmatic requirements for implementations of decision procedures that make them well-suited to integration into such frameworks. The aim is to open a dialogue with the designers of decision procedure software that will lead to greater and easier uptake of their implementations by verification users.     

Epipolar Geometry for Central Catadioptric Cameras

Central catadioptric cameras are cameras which combine lenses and mirrors to capture a very wide field of view with a central projection. In this paper we extend the classical epipolar geometry of perspective cameras to all central catadioptric cameras. Epipolar geometry is formulated as the geometry of corresponding rays in a three-dimensional space. Using the model of image formation of central catadioptric cameras, the constraint on corresponding image points is then derived. It is shown that the corresponding points lie on epipolar conics. In addition, the shape of the conics for all types of central catadioptric cameras is classified. Finally, the theory is verified by experiments with real central catadioptric cameras.     

Fast, On-Line Learning of Globally Consistent Maps

To navigate in unknown environments, mobile robots require the ability to build their own maps. A major problem for robot map building is that odometry-based dead reckoning cannot be used to assign accurate global position information to a map because of cumulative drift errors. This paper introduces a fast, on-line algorithm for learning geometrically consistent maps using only local metric information. The algorithm works by using a relaxation technique to minimize an energy function over many small steps. The approach differs from previous work in that it is computationally cheap, easy to implement and is proven to converge to a globally optimal solution. Experiments are presented in which large, complex environments were successfully mapped by a real robot.     

A Graph-Based Metamodel for Object-Oriented Software Metrics

Metrics are essential in object-oriented software engineering for several reasons, among which quality assessment and improvement of development team productivity. While the mathematical nature of metrics calls for clear definitions, frequently there exist many contradicting definitions of the same metric depending on the implementation language. We suggest to express and define metrics using a language-independent metamodel based on graphs. This graph-based approach allows for an unambiguous definition of generic object-oriented metrics and higher-order metrics. We also report on some prototype tools that implement these ideas.We thank Kim Mens, Roel Wuyts and the anonymous reviewers for their comments on drafts of this paper.     

A study of through-thickness texture gradients in rolled sheets

A method to simulate shear effects and through-thickness texture gradients in rolled sheet materials is introduced. The strain history during a rolling pass is idealized by superimposing a sine-shaped evolution of the ₁₃ shear component to a plane-strain state. These generic strain histories are enforced in a visco-plastic self-consistent (VPSC) polycrystal deformation model to simulate texture evolution as a function of through-thickness position. The VPSC scheme is deemed superior to a full constraints (FC) or relaxed constraints (RC) approach, because it allows one to fully prescribe diagonal and shear-strain-rate components while still accounting for grain-shape effects. The idealized strain states are validated by comparison with deformation histories obtained through finite-element method (FEM) calculations. The through-thickness texture gradients are accounted for by introducing a relative variation of the sine-shaped ₁₃ shear with respect to the plane-strain component. The simulation results are validated, in turn, by comparison with typical examples of through-thickness texture gradients observed experimentally in rolled plates and in sheets of fcc and bcc materials.     

Structure from Motion: Beyond the Epipolar Constraint

The classic approach to structure from motion entails a clear separation between motion estimation and structure estimation and between two-dimensional (2D) and three-dimensional (3D) information. For the recovery of the rigid transformation between different views only 2D image measurements are used. To have available enough information, most existing techniques are based on the intermediate computation of optical flow which, however, poses a problem at the locations of depth discontinuities. If we knew where depth discontinuities were, we could (using a multitude of approaches based on smoothness constraints) accurately estimate flow values for image patches corresponding to smooth scene patches; but to know the discontinuities requires solving the structure from motion problem first. This paper introduces a novel approach to structure from motion which addresses the processes of smoothing, 3D motion and structure estimation in a synergistic manner. It provides an algorithm for estimating the transformation between two views obtained by either a calibrated or uncalibrated camera. The results of the estimation are then utilized to perform a reconstruction of the scene from a short sequence of images.The technique is based on constraints on image derivatives which involve the 3D motion and shape of the scene, leading to a geometric and statistical estimation problem. The interaction between 3D motion and shape allows us to estimate the 3D motion while at the same time segmenting the scene. If we use a wrong 3D motion estimate to compute depth, we obtain a distorted version of the depth function. The distortion, however, is such that the worse the motion estimate, the more likely we are to obtain depth estimates that vary locally more than the correct ones. Since local variability of depth is due either to the existence of a discontinuity or to a wrong 3D motion estimate, being able to differentiate between these two cases provides the correct motion, which yields the least varying estimated depth as well as the image locations of scene discontinuities. We analyze the new constraints, show their relationship to the minimization of the epipolar constraint, and present experimental results using real image sequences that indicate the robustness of the method.     

Thickness measurement of thin dielectric films by evanescent total reflection fluorescence

The electric field of an evanescent wave generates fluorescence in the interface between a dielectric surface and an adjacent, fluorescing, medium of lower refractive index. The difference between the fluorescing signals from covered and noncovered surfaces enables nondestructive measurement of the film thickness to be made in the range 1-15 nm.     

Law of cumulative advantages in the evolution of scientific fields

Summary The evolution of scientific fields analyzed by co-word analysis and presented in strategic diagrams is simulated based on the law of cumulative advantages - the probability of a new tie between two keywords depends positively on the frequencies in which both keywords have taken part already. The results we get from simulations are compared with the results of real scientific field evolution. We consider the high correspondence of both to be a proof of the working of the law of cumulative advantages in the development of scientific fields and we believe that our research opens new possibilities for predictions of the development of scientific fields.