Building safer robots: Safety driven control

In recent years there has been a concerted effort to address many of the safety issues associated with physical human-robot interaction (pHRI). However, a number of challenges remain. For personal robots, and those intended to operate in unstructured environments, the problem of safety is compounded. In this paper we argue that traditional system design techniques fail to capture the complexities associated with dynamic environments. We present an overview of our safety-driven control system and its implementation methodology. The methodology builds on traditional functional hazard analysis, with the addition of processes aimed at improving the safety of autonomous personal robots. This will be achieved with the use of a safety system developed during the hazard analysis stage. This safety system, called the safety protection system, will initially be used to verify that safety constraints, identified during hazard analysis, have been implemented appropriately. Subsequently it will serve as a high-level safety enforcer, by governing the actions of the robot and preventing the control layer from performing unsafe operations. To demonstrate the effectiveness of the design, a series of experiments have been conducted using a MobileRobots PeopleBot. Finally, results are presented demonstrating how faults injected into a controller can be consistently identified and handled by the safety protection system. © The Author(s) 2012

Site Characteristics as Predictors of Lonicera maackii in Second-Growth Forests of Central Kentucky, USA

Non-native invasive plants can negatively affect the abundance and survival of native plant species and alter ecosystem function. Amur honeysuckle (Lonicera maackii) is an invasive shrub that is an increasingly onerous problem for forest managers in eastern North America. We examined site-specific characteristics related to the presence and abundance of Amur honeysuckle, and other non-native invasive plants, in 15 second growth forests in central Kentucky. Individual remnants were characterized by: (1) frequency and cover of non-native invasive and native shrubs, (2) overstory tree basal area, (3) forest floor litter depth, (4) species composition of leaf litter, and (5) soil characteristics. Of the measured variables, the only statistically significant relationships we discovered were between Amur honeysuckle and characteristics of the forest floor. We found significant negative relationships between Amur honeysuckle presence and both forest floor litter depth (P = 0.01) and the percent of oak (Quercus spp.) litter on the forest floor (P = 0.004). The abundance (percent cover) of Amur honeysuckle was significantly and negatively related to forest floor litter depth (P = 0.03). These findings suggest that forest floor mass creates a barrier to invasion by exotic plants and that forests dominated by oak species may be more resistant to invasion by Amur honeysuckle. While this study did not identify a causal relationship between litter depth and oak litter and the presence of Amur honeysuckle, our findings do suggest that older forests, and those dominated by oak, may be more resistant to the invasion of Amur honeysuckle

Site Characteristics as Predictors of Lonicera maackii

Non-native invasive plants can negatively affect the abundance and survival of native plant species and alter ecosystem function. Amur honeysuckle (Lonicera maackii) is an invasive shrub that is an increasingly onerous problem for forest managers in eastern North America. We examined site-specific characteristics related to the presence and abundance of Amur honeysuckle, and other non-native invasive plants, in 15 second growth forests in central Kentucky. Individual remnants were characterized by: (1) frequency and cover of non-native invasive and native shrubs, (2) overstory tree basal area, (3) forest floor litter depth, (4) species composition of leaf litter, and (5) soil characteristics. Of the measured variables, the only statistically significant relationships we discovered were between Amur honeysuckle and characteristics of the forest floor. We found significant negative relationships between Amur honeysuckle presence and both forest floor litter depth (P = 0.01) and the percent of oak (Quercus spp.) litter on the forest floor (P = 0.004). The abundance (percent cover) of Amur honeysuckle was significantly and negatively related to forest floor litter depth (P = 0.03). These findings suggest that forest floor mass creates a barrier to invasion by exotic plants and that forests dominated by oak species may be more resistant to invasion by Amur honeysuckle. While this study did not identify a causal relationship between litter depth and oak litter and the presence of Amur honeysuckle, our findings do suggest that older forests, and those dominated by oak, may be more resistant to the invasion of Amur honeysuckle

Funerary Pithoi in Bronze Age Crete: Their Introduction and Significance at the Threshold of Minoan Palatial Society

Toward the end of the third millennium B.C.E., Minoan funerary customs changed, and people began to favor the use of clay receptacles-pithoi or larnakes-for the bodies of the dead. This article offers a comprehensive study of the funerary pithoi of the period, comprising a review of the available material and its classification, distribution, and dating, the relation of container to tomb types, and the specific use of pithoi within funerary ritual. It also assesses the importance of pithoi as an investment in terms of the material wealth that they represent and the knowledge of the complex techniques of handling dead bodies that they require. Finally, it examines the symbolic connotations of the pithos and argues that its wide adoption was part of a general turn toward the concept of the regeneration of life. This concept shifted the emphasis of the funerary realm toward the social dimension-namely, toward the reallocation of the roles and resources of the dead among the living. Such a shift helped people come to terms with contemporary social reality and shaped the agency of emerging elites, which led to the establishment of the first Minoan palaces and transformed Crete from a series of kin-based communities to a group of proto-states