There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

CA : A Cancer Journal for Clinicians

Introduction to linear and nonlinear programming

Bilateral teleoperation: An historical survey

A novel interactive virtual needle insertion simulation is presented. The simulation models are based on measured planar tissue deformations and needle insertion forces. Since the force-displacement relationship is only of interest along the needle shaft, a condensation technique is shown to reduce the computational complexity of linear simulation models significantly. As the needle penetrates or is withdrawn from the tissue model, the boundary conditions that determine the tissue and needle motion change. Boundary condition and local material coordinate changes are facilitated by fast low-rank matrix updates. A large-strain elastic needle model is coupled to the tissue models to account for needle deflection and bending during simulated insertion. A haptic environment, based on these novel interactive simulation techniques, allows users to manipulate a three-degree-of-freedom virtual needle as it penetrates virtual tissue models, while experiencing steering torques and lateral needle forces through a planar haptic interface.

Interactive simulation of needle insertion models

A high-performance six-degree-of-freedom magnetically levitated fine-motion wrist with programmable compliance is described. Design considerations, a discussion of the major elements of the device, and issues of modeling, kinematics, dynamics, and control are presented. A prototype wrist which has been built and controlled successfully is discussed. Experimental results, including high bandwidth position control, compliant control, and the emulation of several mechanisms through software gain setting which establish the use of magnetically levitated robot wrists as an option for manipulation tasks requiring high precision and fine compliant motions, are included. >

A six-degree-of-freedom magnetically levitated variable compliance fine-motion wrist: design, modeling, and control

In this paper we introduce a new speckle tracking method that is based on the standard time-domain cross correlation strain estimation (TDE). We call this method time-domain cross-correlation with prior estimates (TDPE), because it uses prior displacement estimates of neighboring windows to speed up computation. TDPE has all the advantages of TDE, but is much faster. Simulations, as well as experiments with phantoms and tissue, indicate that TDPE is capable of reliably estimating tissue displacement and strain over a large range of displacements in real time. The computational efficiency of TDPE is compared with current time-efficient methods that have been used in real time strain imaging systems. The results show that TDPE is the most time efficient algorithm to date, and is roughly 10 times faster than the TDE. The implementation of TDPE on an Ultrasonix RP500 ultrasound machine runs at 30 fps for strain images of 16 000 pixels

Motion Estimation in Ultrasound Images Using Time Domain Cross Correlation With Prior Estimates

This technical brief addresses issues of mechanical emulation of stiff walls and stick-slip friction with a 6-DOF magnetically levitated joystick. In the case of stiff wall emulation, it is shown that the PD control implementation commonly used severely limits achievable wall damping and stiffness. It is also shown that the perceived surface stiffness can be increased without loss ofstability by applying a braking force pulse when crossing into the wall. For stick-slip friction, Karnopp's model was implemented using a PD controller within the stick friction threshold. Even though the PD controller allows some motion during the stick phase, the haptic feedback provided is remarkably similar to stick-slip friction.

On the Emulation of Stiff Walls and Static Friction With a Magnetically Levitated Input/Output Device

This paper studies the advantages of employing local force feedback for enhanced stability and performance in teleoperation systems. It also shows how a class of three-channel architecture bilateral controllers can provide perfect transparency under ideal conditions. Furthermore, the robustness of the proposed architecture to the communication channel time-delays is analytically investigated. Experimental results are also included to support the theoretical work.

Septimiu E. Salcudean

Papers

Interactive simulation of needle insertion models

A six-degree-of-freedom magnetically levitated variable compliance fine-motion wrist: design, modeling, and control

Motion Estimation in Ultrasound Images Using Time Domain Cross Correlation With Prior Estimates

On the Emulation of Stiff Walls and Static Friction With a Magnetically Levitated Input/Output Device

On the use of local force feedback for transparent teleoperation