6341521
Rethinking classical internal forces for active contour models
The classical active contour model has two basic internal forces: tension and curvature. These forces are included to provide cohe sion, equal control point spacing, and locally smooth shape. These classical internal forces have undesirable attributes that are in conflict with these original desired characteristics. Tension evenly spaces the control points, but also causes the models to collapse in weak image gradients. Curvature produces locally smooth curvature, but it does so by forcing the model toward a straight line. The paper returns to the original active contour model motivations to reformulate these internal forces. The desired properties are achieved without the introduction of unwanted model behavior A new spacing force and a new constant change in curvature force are introduced and their performance characteristics are discussed. The paper includes experimental results that demonstrate the efficacy and performance of the proposed reformulations.
14452564
Eye Tracking Using Active Deformable Models
Developing a robust, non-intrusive, inexpensive eye tracker is quite a challenge in the computer vision field. This paper introduces a new eye tracking approach based on an enhanced formulation of the statistical pressure snakes. Using a head-mounted camera, to eliminate the effect of head movements, we can detect and track the eye pupil robustly. Experimental results on video sequences for normal and blinking eyes are presented with high accuracy.
2626294
Computation of shape through controlled active exploration
Accurate knowledge of depth continues to be of critical importance in robotic systems. Without accurate depth knowledge, tasks such as inspection, tracking, grasping, and collision-free motion planning prove to be difficult and often unattainable. Traditional visual depth recovery has relied upon techniques that require the solution of the correspondence problem or require known lighting conditions and Lambertian surfaces. In this paper, we present a technique for the derivation of depth from feature points on a target's surface using the controlled active vision framework. We use a single visual sensor mounted on the end-effector of a robotic manipulator to automatically select feature points and to derive depth estimates for those features using adaptive control techniques. Movements of the manipulator produce displacements that are measured using a sum-of-squared difference (SSD) optical flow. The measured displacements are fed into the controller to alter the path of the manipulator and to refine the depth estimate.<<ETX>>
5529316
Mixture models for dynamic statistical pressure snakes
This paper introduces a new approach to statistical pressure snakes. It uses statistical modeling for both object and background to obtain a more robust pressure model. The Expectation Maximization (EM) algorithm is used to model the data into a Mixture of Gaussians (MoG). Bayesian theory is then employed as a decision making mechanism. Experimental results using the traditional pressure model and the new mixture pressure model demonstrate the effectiveness of the new models.
5822992
Active Deformable Models Using Density Estimation
This paper introduces a new approach to active deformable models. The paper starts with a brief review of the relevant approaches. We then use the Expectation Maximization and Parzen Window techniques to develop a more robust formulation for pressure snakes. The generic nature of the proposed model allows it to perform well on complex colored images. We show, by several examples, the enhanced performance of the snake under the new formulation, compared to the performance of other known snake formulations.
41677043
Unknown object grasping using statistical pressure models
Grasping is one of the most fundamental and challenging tasks in robotics. Applications range from space missions (e.g., collection of rock samples) to industrial automation. In this work, we use a camera mounted on the end-effector of a manipulator to grasp an unknown object in the workspace. A novel deformable contour model is used to determine plausible grasp axes of the target object. Potential grasp point pairs are generated, ranked based upon measurements taken from the contour, and a vision-guided grasp of the object using the highest ranked grasp point pair is executed. Several experimental results are presented.
6910866
Performance Engineering Evaluation of Object Oriented Systems With SPE-ED
Although object-oriented methods have been shown to help construct software systems that are easy to understand and modify, have a high potential for reuse, and are relatively quick and easy to implement, concern over performance of object-oriented systems represents a significant barrier to its adoption. Our experience has shown that it is possible to design object-oriented systems that have adequate performance and exhibit the other qualities, such as reusability, maintainability, and modifiability, that have made OOD so successful. However, doing this requires careful attention to performance goals throughout the life cycle. This paper describes the use of SPE·ED, a performance modeling tool that supports the SPE process, for early life cycle performance evaluation of object-oriented systems. The use of SPE·ED for performance engineering of object-oriented software is illustrated with a simple example.
17917406
A Performance Model Web Service
Catalina M. Llado, Ramon Puigjaner Universitat Illes Balears Departament de Matematiques I Informatica Cra. de Valldemossa, Km 7.6 07071 Palma de Mallorca, Spain cllado@uib.es, putxi@uib.es Connie U. Smith Performance Engineering Services PO Box 2640 Santa Fe, New Mexico 87504-2640, USA www.perfeng.com
2552665
From UML models to software performance results: an SPE process based on XML interchange formats
The SPE process uses multiple performance assessment tools depending on the state of the software and the amount of performance data available. This paper describes two XML based interchange formats that facilitate using a variety of performance tools in a plug-and-play manner thus enabling the use of the tool best suited to the analysis. The Software Performance Model Interchange Format (S-PMIF) is a common representation that is used to exchange information between (UML-based) software design tools and software performance engineering tools. On the other hand, the performance model interchange format (PMIF 2.0) is a common representation for system performance model data that can be used to move models among system performance modeling tools that use a queueing network model paradigm. This paper first defines an XML based S-PMIF based on an updated SPE meta-model Then it demonstrates the feasibility of using both the S-PMIF and the PMIF 2.0 to automatically translate an architecture description in UML into both a software performance model and a system performance model to study the performance characteristics of the architecture. This required the implementation of some extensions to the XPRIT software in order to export UML models into the S-PMIF and a new function in the SPEED software to import S-PMIF models, which are also described. The SPE process and an experimental proof of concept are presented.
10134033
SPE Evaluation of a Client/Server Application
This paper presents the results of a software performance evaluation of a client/server application in an Open Systems environment. Some interesting features of the design and the graphical user interface are described and their performance characteristics are evaluated. The evaluation uses a new Software Performance Engineering (SPE) tool to create software models and evaluate design alternatives.
61607075
Performance model interchange format (PMIF 2.0): XML definition and implementation
A performance model interchange format (PMIF) provides a mechanism whereby system model information may be transferred among performance modeling tools. The PMIF allows diverse tools to exchange information and requires only that the importing and exporting tools either support the PMIF or provide an interface that reads/writes model specifications from/to a file. This paper presents a new version of the PMIF specification (PMIF 2.0) and its XML implementation. The paper also describes a prototype that was implemented to prove the concept, in which the exporting tool is SPE/spl middot/ED and the importing tool is Qnap, and it discusses the issues in this and the reverse exchange. It shows the validation of the prototype based on the solution of examples that were exported from SPE/spl middot/ED and imported by Qnap. In addition, it proposes some extensions to PMIF 2.0.