Sensor explication: knowledge-based robotic plan execution throughlogical objects

Complex robot tasks are usually described as high level goals, with no details on how to achieve them. However, details must be provided to generate primitive commands to control a real robot. A sensor explication concept that makes details explicit from general commands is presented. We show how the transformation from high-level goals to primitive commands can be performed at execution time and we propose an architecture based on reconfigurable objects that contain domain knowledge and knowledge about the sensors and actuators available. Our approach is based on two premises: 1) plan execution is an information gathering process where determining what information is relevant is a great part of the process; and 2) plan execution requires that many details are made explicit. We show how our approach is used in solving the task of moving a robot to and through an unknown, and possibly narrow, doorway; where sonic range data is used to find the doorway, walls, and obstacles. We illustrate the difficulty of such a task using data from a large number of experiments we conducted with a real mobile robot. The laboratory results illustrate how the proper application of knowledge in the integration and utilization of sensors and actuators increases the robustness of plan execution.     

High-power passively mode-locked semiconductor lasers

We have developed optically pumped passively mode-locked vertical-external-cavity surface-emitting lasers. We achieved as much as 950 mW of mode-locked average power in chirped 15-ps pulses, or 530 mW in 3.9-ps pulses with moderate chirp. Both lasers operate at a repetition rate of 6 GHz and have a diffraction-limited output beam near 950 nm. In continuous-wave operation, we demonstrate an average output power as high as 2.2 W. Device designs with a low thermal impedance and a smooth gain spectrum are the key to such performance. We discuss design and fabrication of the gain structures and, particularly, their thermal properties     

Repeated auctions for robust task execution by a robot team

We present empirical results of an auction-based algorithm for dynamic allocation of tasks to robots. The results have been obtained both in simulation and using real robots. A distinctive feature of our algorithm is its robustness to uncertainties and to robot malfunctions that happen during task execution, when unexpected obstacles, loss of communication, and other delays may prevent a robot from completing its allocated tasks. Therefore tasks not yet achieved are resubmitted for bids every time a task has been completed. This provides an opportunity to improve the allocation of the remaining tasks, enabling the robots to recover from failures and reducing the overall time for task completion.     

Characterization of zirconia-thoria-urania ceramics by X-ray and electron interactions

X-ray and electron interactions with matter were used as probes to characterize the structure and chemistry of zirconia-thoria-urania ceramics. The ceramics were prepared by coprecipitation of Zr, Th and U salts. In this study, transmission electron microscopy (TEM) techniques such as energy dispersive X-ray (EDX) analysis and electron energy loss spectroscopy (EELS) complement X-ray diffraction, extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge spectroscopy (XANES), techniques to reveal the phase structure and chemistry. The results from XRD and EDX show that these ceramics separate into a Zr-based phase and an actinide-based phase with low mutual affinity of Th and Zr, as well as partial solubility of U in Zr. The comparison of EELS spectra collected for the ceramics with spectra collected for UO₂ and U₃O₈ reference materials also allow us to assess U oxidation state independently in the two separate phases.     

Trace elements total content and particle sizes distribution in the air particulate matter of a rural-residential area in north Italy investigated by instrumental neutron activation analysis

The concentrations (ng/m3) of more than 30 trace elements have been determined in the total air particulate of a rural-residential area in north Italy. By collecting the aerosols with multistage impactors the distribution of the trace elements in the different size-fractionated particles has been also investigated. The fine 'inhalable' fraction with particles of less than 10 microns in equivalent aerodynamic diameter (PM10) as well as the subsequent finest 'respirable' fractions with particles of 0-1.1 microns (alveolar), 1.1-4.6 microns (bronchial) and 4.6-9 microns (tracheo-pharynx) have been analyzed and evaluated. Apart from Pb, Cd and, in some cases, Ni and Cu which have been determined by ETAAS (electrothermal atomic absorption spectroscopy), all measurements have been carried out by instrumental neutron activation analysis (INAA).     

Logical sensor/actuator : knowledge-based robotic plan execution

Complex tasks are usually described as high-level goals, leaving out the details on how to achieve them. However, to control a robot, the task must be described in terms of primitive commands for the robot. Having the robot move itself to and through an unknown, and possibly narrow, doorway is an example of such a task. It is shown how the transformation from high-level goals to primitive commands can be performed at execution time and an architecture is proposed based on reconfigurable objects that contain domain knowledge and knowledge about the sensors and actuators available. The approach is illustrated using actual data from a real robot.     

Active multimode interferometer laser diode demonstrated via 1.48μm high power application

An active multimode interferometer (MMI) laser diode (LD) concept is presented. It has been verified via a 1.48 μm high power application. The active MMI-LDs, having a larger pumping area compared to that of regular single-stripe LDs with the same length, showed no significant degradation in slope efficiency and up to 50 mW power improvement resulting in 170 mW saturated output power     

Reliable real-time robot operation employing intelligent forward recovery

Modern computer-controlled robots typically fail at their tasks whenever they encounter an error, no matter how minor. The physical environment of a typical assembly robot is too unstructured to benefit from conventional software approaches to reliability. We present an approach which interfaces the real-time operation of the robot with an intelligent subsystem that performs error analysis and forward recovery if a failure occurs. Our approach involves a special representation of the robot's program that efficiently tracks the robot's operation in real time and is easy to modify to include automatically generated recovery procedures.     

Metabolism of small peptides in rumen fluid. Accumulation of intermediates during hydrolysis of alanine oligomers,and comparison of peptidolytic activities of bacteria and protozoa

Oligopeptides of L -alanine up to ala₅, were incubated in vitro in either strained rumen fluid or suspensions of mixed rumen bacteria. The disappearance of substrates and formation of products were measured for 40 min, by which time ala₃, ala₄ and ala₅ were almost totally hydrolysed. Ala₂ was more slowly hydrolysed, and accumulated in incubations with the other peptides. The pattern of formation of ala₂ but not ala₃ from ala₄, and ala₃ and ala₂ but not ala₄ from ala₅, suggested that the peptides were being hydrolysed by a dipeptidyl peptidase mechanism. Three different sheep receiving different diets gave similar results. Neither substrates nor products appeared to be accumulated intracellularly, except for ala₂, and then only if protozoa were present. Protozoa were more active than bacteria in ala₂ hydrolysis, whereas bacteria had greater activities with higher homologues. Similar preferences were observed with glycine peptides, although unlike alanine peptides gly₃ and gly₅ were more slowly degraded than the dimer. These experiments suggest that protozoa are of importance in the accumulation and hydrolysis of dipeptides, whereas bacteria are responsible for the breakdown of larger molecules by a dipeptidyl peptidase mechanism that does not appear to involve accumulation within the cell.