CCM‐SLAM: Robust and efficient centralized collaborative monocular simultaneous localization and mapping for robotic teams

Robotic collaboration promises increased robustness and efficiency of missions with great potential in applications, such as search‐and‐rescue and agriculture. Multiagent collaborative simultaneous localization and mapping (SLAM) is right at the core of enabling collaboration, such that each agent can colocalize in and build a map of the workspace. The key challenges at the heart of this problem, however, lie with robust communication, efficient data management, and effective sharing of information among the agents. To this end, here we present CCM‐SLAM, a centralized collaborative SLAM framework for robotic agents, each equipped with a monocular camera, a communication unit, and a small processing board. With each agent able to run visual odometry onboard, CCM‐SLAM ensures their autonomy as individuals, while a central server with potentially bigger computational capacity enables their collaboration by collecting all their experiences, merging and optimizing their maps, or disseminating information back to them, where appropriate. An in‐depth analysis on benchmarking datasets addresses the scalability and the robustness of CCM‐SLAM to information loss and communication delays commonly occurring during real missions. This reveals that in the worst case of communication loss, collaboration is affected, but not the autonomy of the agents. Finally, the practicality of the proposed framework is demonstrated with real flights of three small aircraft equipped with different sensors and computational capabilities onboard and a standard laptop as the server, collaboratively estimating their poses and the scene on the fly.     

Numerical modeling of heat exchange and unsaturated–saturated flow in porous media

We discuss the numerical modeling of heat and mass transport in unsaturated–saturated porous media. The heat is transported by infiltrated water underlying capillary and gravitation driven forces. Heat energy is governed by molecular diffusion, convection, dispersion and exchange between the infiltrated water and porous media matrix. An unsaturated–saturated flow is considered with boundary conditions reflecting the external driven forces. The presented mathematical model is motivated by analysis of hygrothermal isolation properties of facades. The main contribution is focused on the determination of model parameters including soil parameters, dispersion coefficients, thermal transmission coefficient, thermal conductivity of porous media matrix and external transmission coefficients. The used mathematical model does not include the vapor transport and its phase exchange with water due to vaporization and condensation. It will be the next step of our research. Thus, practical applications of our model are limited. The developed numerical method is a good candidate for solving corresponding inverse problems. Numerical experiments support our method.     

Communication of emotions in vocal expression and music performance: Different channels, same code?

Many authors have speculated about a close relationship between vocal expression of emotions and musical expression of emotions, but evidence bearing on this relationship has unfortunately been lacking. This review of 104 studies of vocal expression and 41 studies of music performance reveals similarities between the 2 channels concerning (a) the accuracy with which discrete emotions were communicated to listeners and (b) the emotion-specific patterns of acoustic cues used to communicate each emotion. The patterns are generally consistent with K. R. Scherer's (1986) theoretical predictions. The results can explain why music is perceived as expressive of emotion, and they are consistent with an evolutionary perspective on vocal expression of emotions. Discussion focuses on theoretical accounts and directions for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term consolidation of individual identities leads to Lag-1 sparing.

A rapid serial visual presentation (RSVP) technique was used to investigate the role of the nature of processing carried out on targets in the Lag-1 sparing phenomenon. Lag-1 sparing refers to a higher accuracy in the task associated with the 2nd target when the 2 targets are immediately successive in the RSVP stream relative to when there are 1 or 2 intervening items between the targets. In 5 experiments, 0, 1, or 2 digits were embedded with equal probability in RSVP streams of letter distractors. In 4 of the experiments, subjects identified the digits in some blocks of trials, and they counted the number of presented digits in other blocks. In a 5th experiment, the counting task was replaced with a digit-sum task. The most interesting results were those from trials with 2 digits. Lag-1 sparing was always evident when the task involved the explicit identification of the digits. In addition, Lag-1 sparing was evident when subjects were required to sum 2 digits or to count digits of a prespecified parity subclass (e.g., count only even digits). In striking contrast, Lag-1 sparing was absent when subjects were required to count the digits independent of their parity subclass. These results suggest that the occurrence of Lag-1 sparing depends on the type of mental representation that must be generated on the basis of target information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

High-pressure jet-assisted cooling: a new possibility for near net shape turning of decarburized steel

Ultra-high-pressure cooling (UHPC) in turning operations is an effective method for achieving higher productivity. Previous research has demonstrated that the introduction of a high-pressure fluid jet into the gap between the tool and chip interface can control chip form and breakage. The present work shows the effect of UHPC in the turning of near net shape (NNS) decarburized parts. The workpiece material properties are strongly influenced by the loss of carbon atoms to a depth of up to 1 mm, due to the aggressive atmosphere during forming (decarburization). The extremely soft material makes chips difficult to control. Consequently, productivity decreases since the machine must be frequently stopped in order to manually remove the chips from the working area. The results show the influence of UHPC on chip form, surface topography and tool life when turning decarburized parts close to NNS. An interesting observation was that the combination of small cutting depth (near net shape) and soft material (decarburization) allowed for the presence of built-up edge formation, even at a high cutting speed.     

Human error driving the development of a checklist for foreign material exclusion in the nuclear industry

In this article we describe an approach to develop a checklist for foreign material exclusion. Foreign material is material that should not be part of, or supplied with, the product because it can affect the performance of, for example, nuclear fuel rods of nuclear plants. The research itself was initiated by the presence of different types of human errors. Specifically in the nuclear industry, where there is zero tolerance for errors, work to continuously improve safety and quality is of major importance. Our approach should support such work. As a theoretical base, we have considered team errors as well as individual errors. The suggested practical approach is based on foreign materials that originate in or are introduced into a product or a process. © 2007 Wiley Periodicals, Inc. Hum Factors Man 17: 283–298, 2007.     

Effect of fracture path on the toughness of weld metal

The crack propagation direction may affect weld metal fracture behavior. This fracture behavior has been investigated using two sets of single edge notched bend (SENB) specimens; one with a crack propagating in the welding direction (B×2B) and the other with a crack propagating from the top in the root direction (B×B) of a welded joint. Two different weld metals were used, one with low and one with high toughness values. For Weld Metal A, two specimen types have been used (B×B and B×2B) both with deep cracks. The weld metal A (with high toughness values) has reasonably uniform properties between weld root and cap. The resulting J-R curves show little effect of the specimen type, are ductile to the extent that the toughness exceeds the maximum J_max, value allowed by validity limits and testing is in the large –scale yielding regime. In the case of weld metal B (with low toughness values) with two specimen types (B×B and B×2B) the B×B specimen has shallow cracks while the B×2B specimen has deep cracks. Both resulting J-R curves show unstable behavior despite the fact that the types of specimen and their constraints are different. The analysis has shown that crack propagation direction is most influential for a weldment with low toughness in the small scale yielding regime, whereas its influence diminishes due to ductile tearing during stable crack growth and large scale yielding. The results have shown that these effects are different in both the crack initiation phase and during stable crack growth, indicating a dependence on weld metal toughness and the microstructure of the weld metal. It can be concluded that, if resistance curves during stable crack growth do not show differences in both notch orientations, the fracture toughness values of the whole weld metal can be treated as uniform.     

On-Line Chemical Analysis of Individual Alkali-Containing Aerosol Particles by Surface Ionization Combined with Time-of-Flight Mass Spectrometry

An aerosol mass spectrometer for measurements of the alkali metal content in individual submicron aerosol particles is presented. The instrument combines surface ionization of individual particles on a hot platinum surface with orthogonal acceleration time-of-flight mass spectrometry. The instrument simultaneously provides the content of different alkali metal elements in single particles with high sensitivity. The instrument is characterized in laboratory experiments, and determination of the alkali metal content is demonstrated for particle diameters of 50–500 nm. The technique is demonstrated in ambient air measurements at an urban background site, and sea spray particles and particles originating from biomass burning are identified based on their content of sodium and potassium. Possible further improvements and applications of the technique are discussed.