Shape Morphing-Based Control of Robotic Visual Servoing

We present an approach for controlling robotic interactions with objects, using synthetic images generated by morphing shapes. In particular, we attempt the problem of positioning an eye-in-hand robotic system with respect to objects in the workspace for grasping and manipulation. In our formulation, the grasp position (and consequently the approach trajectory of the manipulator), varies with each object. The proposed solution to the problem consists of two parts. First, based on a model-based object recognition framework, images of the objects taken at the desired grasp pose are stored in a database. The recognition and identification of the grasp position for an unknown input object (selected from the family of recognizable objects) occurs by morphing its contour to the templates in the database and using the virtual energy spent during the morph as a dissimilarity measure. In the second step, the images synthesized during the morph are used to guide the eye-in-hand system and execute the grasp. The proposed method requires minimal calibration of the system. Furthermore, it conjoins techniques from shape recognition, computer graphics, and vision-based robot control in a unified engineering amework. Potential applications range from recognition and positioning with respect to partially-occluded or deformable objects to planning robotic grasping based on human demonstration.     

CLUSTERING VERY LARGE DATA SETS USING A LOW MEMORY MATRIX FACTORED REPRESENTATION

A scalable method to cluster data sets too large to fit in memory is presented. This method does not depend on random subsampling, but does scan every individual data sample in a deterministic way. The original data are represented in factored form by the product of two matrices, one or both of which is very sparse. This factored form avoids the need to multiply together these two matrices by using a variant of the Principal Direction Divisive Partitioning (PDDP) algorithm which does not depend on computing the distances between the individual samples. The resulting clustering algorithm is Piecemeal PDDP (PMPDDP), in which the original data are broken up into sections which will fit into memory and clustered. The cluster centers are used to create approximations to the original data items, and each original data item is represented by a linear combination of these centers. We evaluate the performance of PMPDDP on three real data sets, and observe that the quality of the clusters of PMPDDP is comparable to PDDP for the data sets examined.     

International Comparison of Fire Department Injuries

Firefighting remains a dangerous profession. The objective of this study was to compare injury rates among career and volunteer fire departments internationally. Methods: Injury and staffing data were collected for 2004–2009. All reported, lost-time, and activity-specific injury rates were calculated for fireground, medical, training and physical exercise activities. Injury rates were also adjusted for number of fireground and medical responses, and average annual training hours. Injury rates were generally higher in the U.S. than in Commonwealth nation and Japanese fire departments. Lost-time injury rates varied markedly among fire departments, from 0.6 (95% CI 0.4–0.9) to 23.5 (95% CI 22.4–22.7) injuries per 100 firefighters per year. The greatest pair-wise differences in lost-time injury rates were seen in the fireground and medical call activities, and these differences persisted when the rates were adjusted by the number of firefighters responding to fireground and medical incidents, respectively. Injury rates vary substantially across fire departments, suggesting that substantial improvements could result from adoption of more optimal health and safety approaches.     

Development of Best Practice Standard Operating Procedures for Prevention of Fireground Injuries

Fireground operations account for a large percentage of firefighter injuries, and injury rates vary widely among fire departments. Differences in safety and health management approaches including standard operating procedures (SOPs) for fireground operations may help explain the variation in injury rates. The purpose of this study was to identify SOP best practices in order to provide a mechanism to improve firefighter safety and health. As part of a larger study comparing fire department injury rates internationally, a panel with fire service representatives from four continents was convened to develop best practice fireground SOPs. The panel members focused on four tasks or operations with relatively high injury rates: handling charged hose; forcible entry; use of ground ladders; and overhaul, reviewed injury data and identified approaches for reducing these injuries. General agreement was reached on the need for a risk management approach to identify high risk activities and corrective actions. Within SOPs, addition of an awareness column describing specific hazards and corrective actions was also recommended. Probationary period training and incorporation of national data into the continuing review and revision of these documents were also considered best practices. Hazards and action points were also identified to guide SOP development for the selected fireground tasks and operations. The international panel identified specific safety and health management approaches associated with SOP development, which, if effectively implemented, would be expected to reduce fireground injuries.     

A modified algebraic reconstruction technique taking refraction into account with an application in terahertz tomography

Terahertz (THz) tomography is a rather novel technique for non-destructive testing that is particularly suited for the testing of plastics and ceramics. Previous publications showed a large variety of conventional algorithms adapted from computed tomography or ultrasound tomography which were directly applied to THz tomography. Conventional algorithms neglect the specific nature of THz radiation, i.e. refraction at interfaces, reflection losses and the beam profile (Gaussian beam), which results in poor reconstructions. The aim is the efficient reconstruction of the complex refractive index, since it indicates inhomogeneities in the material. A hybrid algorithm has been developed based on the algebraic reconstruction technique (ART). ART is adapted by including refraction (Snell’s law) and reflection losses (Fresnel equations). Our method uses a priori information about the interface and layer geometry of the sample. This results in the ‘Modified ART for THz tomography’, which reconstructs simultaneously the complex refractive index from transmission coefficient and travel time measurements.     

Anomalous nanosecond transient component in a GaAs MODFETtechnology

Modulation-doped field-effect transistors (MODFETs) exhibit transient responses that contain a variety of time constants. The strongest transients observed in the microsecond range are known to be caused by the DX centers. MODFETs also suffer a transient that arises from a source different from that of the DX centers. Preliminary measured characteristics of the nanosecond transient are presented, its effects on circuit performance are described, and its possible origin is inferred