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

The concept of teleoperation has evolved to accommodate not only manipulation at a distance but manipulation across barriers of scale and in virtual environments, with applications in many areas. Furthermore, the design of high-performance force-feedback teleoperation masters has been a significant driving force in the development of novel electromechanical or “haptic” computer-user interfaces that provide kinesthetic and tactile feedback to the computer user. Since haptic interfaces/teleoperator masters must interact with an operator and a real or virtual dynamic slave that exhibits significant dynamic uncertainty, including sometimes large and unknown delays, the control of such devices poses significant challenges. This chapter presents a survey of teleoperation control work and discusses issues of simulation and control that arise in the manipulation of virtual environments.

Control for teleoperation and haptic interfaces

A six degree-of-freedom magnetically levitated variable compliance fine motion wrist

This paper presents the development of a novel, fully-automatic tracking and segmentation system to extract the boundary of the carotid artery from ultrasound images in real-time. The center of the carotid artery is tracked using the Star algorithm. The stability of the Star algorithm has been improved by using a temporal Kalman filter. A spatial Kalman filter is used to estimate the carotid artery boundary. Since the method does not employ any numerical optimization, convergence is very fast. The stability and accuracy of the method is demonstrated by tracking the carotid artery over a 30 second sequence of ultrasound images taken during a carotid artery examination. An application of the tracking method to ultrasound image servoing is also presented.

Real-time extraction of carotid artery contours from ultrasound images

A novel yet simple approach for experimental determination of the link (mass and inertia-related) parameters and friction coefficients is developed for a typical excavator arm. The parameters are needed for indirect measurement of the external forces, compensation for the link weights in the operator's hand in a force-feedback teleoperation setup, impedance control of the arm, simulation of the manipulator dynamics, and model-based fault detection. Treating the machine arm as an open kinematic chain, its dynamic equations are presented symbolically. The static torque equations are derived from these equations and the gravitational parameters are defined accordingly. A new method for decoupled estimation of the gravitational parameters from static experiments is presented. Furthermore, the arm dynamics are expressed in a form which is linear in the inertia and friction-related parameters. The results obtained show that the identified model predicts the joint torques, in both static and dynamic conditions, with a very good accuracy.

Identification of inertial and friction parameters for excavator arms

In MR elastography (MRE), periodic tissue motion is phase encoded using motion-encoding gradients synchronized to an externally applied periodic mechanical excitation. Conventional methods result in extended scan time for quality phase images, thus limiting the broad application of MRE in the clinic. For practical scan times, researchers have been relying on one-dimensional or two-dimensional motion-encoding, low-phase sampling and a limited number of slices, and artifact-prone, single-shot, echo planar imaging (EPI) readout. Here, we introduce a rapid multislice pulse sequence capable of three-dimensional motion encoding that is also suitable for simultaneously encoding motion with multiple frequency components. This sequence is based on a gradient-recalled echo (GRE) sequence and exploits the principles of fractional encoding. This GRE MRE pulse sequence was validated as capable of acquiring full three-dimensional motion encoding of isotropic voxels in a large volume within less than a minute. This sequence is suitable for monofrequency and multifrequency MRE experiments. In homogeneous paraffin phantoms, the eXpresso sequence yielded similar storage modulus values as those obtained with conventional methods, although with markedly reduced variances (7.11 ± 0.26 kPa for GRE MRE versus 7.16 ± 1.33 kPa for the conventional spin-echo EPI sequence). The GRE MRE sequence obtained better phase-to-noise ratios than the equivalent spin-echo EPI sequence (matched for identical acquisition time) in both paraffin phantoms and in vivo data in the liver (59.62 ± 11.89 versus 27.86 ± 3.81, 61.49 ± 14.16 versus 24.78 ± 2.48 and 58.23 ± 10.39 versus 23.48 ± 2.91 in the X, Y and Z components, respectively, in the case of liver experiments). Phase-to-noise ratios were similar between GRE MRE used in monofrequency or multifrequency experiments (75.39 ± 14.93 versus 86.13 ± 18.25 at 28 Hz, 71.52 ± 24.74 versus 86.96 ± 30.53 at 56 Hz and 95.60 ± 36.96 versus 61.35 ± 26.25 at 84Hz, respectively). Copyright © 2013 John Wiley & Sons, Ltd.

Septimiu E. Salcudean

Papers

Control for teleoperation and haptic interfaces

A six degree-of-freedom magnetically levitated variable compliance fine motion wrist

Real-time extraction of carotid artery contours from ultrasound images

Identification of inertial and friction parameters for excavator arms

Rapid acquisition of multifrequency, multislice and multidirectional MR elastography data with a fractionally encoded gradient echo sequence.